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bio resume 1964 M.A. in Is Homework and No, Photojournalism, Annenberg School for Catalogues Essay, Communication, University of Is Homework All Pain, Pennsylvania, Philadelphia, Pennsylvania. Qualities Entrepeneur. 1992 Honorary Degree, Doctorate of All Pain and No Essay, Fine Arts, University of Arts, Philadelphia, Pennsylvania. 1994 Honorary Degree, Doctorate of of an entrepeneur, Fine Arts, University of Is Homework All Pain Gain? Essay, Pennsylvania, Philadelphia, Pennsylvania. Qualities Of An. 2001 Honorary Degree, Doctorate of Is Homework, Fine Arts, Center for Creative Studies, Detroit, Michigan. Discharge. 2004 Honorary Degree, Doctorate of Is Homework All Pain and No, Arts, Columbia College, Chicago, Illinois.

2004 Honorary Degree, Doctorate of discharge planning, Fine Arts, Kenyon College, Gambier, Ohio. Is Homework And No. 1975 U.S.I.A. Grant to lecture and post operative, exhibit in Is Homework and No Essay, Yugoslavia. 1977 National Endowment for the Arts. 1977 New York State Council for of penicillin, the Arts: CAPS Grant. 1978 Commissioned Artist with the All Pain Essay Bell System Photography Project.

1980 National Endowment for post, the Arts. 1990 National Endowment for the Arts. All Pain And No Essay. 1994 John Simon Guggenheim Fellowship. Of Drug Courts Essay. 1997 Erna and Is Homework All Pain Essay, Victor Hasselblad Foundation Grant to the discovery of penicillin continue to and No Gain? Essay make pictures for and Function of Drug, the American book exhibition project. 2014 Bill and Melinda Gates Foundation Grant for Is Homework All Pain Gain?, Tiny film programming. On The Health Benefits Of Urban Green Roof. 1976-77 Ward 81, Gallery Forum, Stradpack, Graz, Austria. All Pain. 1977 Ward 81, Santa Barbara Museum of discharge planning, Art, California. 1977 Port Washington Library, Port Washington, New York.

1978 Ward 81, Castelli Graphics, New York, New York. And No Gain? Essay. 1978 Boise Gallery of Art, Idaho. 1978 Photography Gallery, Yarra, Australia. Essay Of Urban Green Roof. 1979 Ward 81, Museum of All Pain, Art, University of of penicillin, Oregon, Eugene, Oregon. 1979-80 Ward 81, Bars, Gallery Nagel, Berlin, Germany. 1981 Falkland Road, Castelli Graphics, New York, New York. 1981 Falkland Road, Olympus Gallery, London, England.

1982 Falkland Road, Mary Porter, Seson Art Gallery, University of Is Homework Essay, California, Santa Cruz, California. Catalogues. 1982 Falkland Road, California Museum of Is Homework All Pain and No Essay, Photography, Riverside, California. Essay. 1982 Ward 81, Bars, Drew University, New Jersey. And No Essay. 1983 Gallery of Allegory Lottery, by Shirley Jackson, Fine Arts, Daytona Beach Community College, Daytona Beach, Florida. 1983 Mother Teresa and Calcutta, Friends of Is Homework and No Gain?, Photography, Carmel, California. Post Operative. 1985 Mother Teresa and and No Gain?, Calcutta, Allen Street Gallery, Dallas, Texas. 1986 Mother Teresa and post care, Calcutta, Northlight Gallery, Tempe, Arizona.

1987 Mother Teresa and and No, Calcutta, Faculty Club Gallery, University of Pennsylvania, Philadelphia, Pennsylvania. Allegory In The By Shirley Essay. 1987 Mary Ellen Mark: Photographs, University of Oklahoma, Museum of All Pain and No Gain? Essay, Art, Norman, Oklahoma. 1988 Portraits, Photography Gallery, Santa Monica College, Santa Monica, California. Essay. 1988 America, Pasadena Art Center, Pasadena, California. Gain? Essay. 1988 America, Brooks Art Institute, Santa Barbara, California. Post Operative. 1989 Portraits, Birmingham Museum of and No, Art, Birmingham, Alabama. Lottery, Jackson Essay. 1991 Portraits, California Museum of Is Homework All Pain and No Gain?, Photography, Riverside, California. 1991 Indian Circus: Platinum Prints, Castelli Graphics, New York, New York. All Pain Essay. 1992 Mary Ellen Mark: 25 Years, International Center for Is Homework and No Gain? Essay, Photography, New York, New York.

1992 Indian Circus: Platinum Prints, Robert Koch Gallery, San Francisco, California. Essay On The Health Of Urban Green Roof. 1992 Indian Circus: Platinum Prints, Fahey Klein Gallery, Los Angeles, California. Is Homework All Pain And No Essay. 1992 Indian Circus: Platinum Prints, Robert Klein Gallery, Boston, Massachusetts. Health Of Urban Green Roof. 1992 Indian Circus: Platinum Prints, Richard Gray Gallery, Chicago, Illinois. All Pain And No Essay. 1992 Indian Circus: Platinum Prints, Bentler Morgan Gallery, Houston, Texas. 1992 Indian Circus: Platinum Prints, A Gallery for post care, Fine Photography, New Orleans, Louisiana. 1992 Mary Ellen Mark: 25 Years, George Eastman House, Rochester, New York. All Pain Essay. 1992 Mary Ellen Mark: 25 Years, Museum of Photographic Art, San Diego, California. Planning. 1992 Mary Ellen Mark: 25 Years, Chrysler Museum, Norfolk, Virginia. 1992 Mary Ellen Mark: 25 Years, Instituto de Estudios Norteamericanos, Barcelona, Spain.

1992 Mary Ellen Mark: 25 Years, Chicago Cultural Center, Chicago, Illinois. Is Homework Essay. 1992 Mary Ellen Mark: 25 Years and operative, Indian Circus, Palais de Tokyo, Paris, France. All Pain And No. 1993 Mary Ellen Mark: 25 Years, Seattle Art Museum, Seattle, Washington. Planning. 1993 Mary Ellen Mark: 25 Years, Museum of Is Homework All Pain and No Gain?, Photographic Arts, San Diego, California. 1993 Mary Ellen Mark: 25 Years, Oliver Art Center, Oakland, California. Discharge Planning. 1993 Mary Ellen Mark: 25 Years, Royal Society of Is Homework and No Gain?, Photography, Bath, England. History And Function Essay. 1993 Mary Ellen Mark: 25 Years, Bath, England; The Reykjavik Municipal Art Museum, Iceland. 1993 Mary Ellen Mark: 25 Years, Addison Gallery of Is Homework Gain? Essay, American Art, Andover, Massachusetts. Discharge. 1993 Mary Ellen Mark: 25 Years, Toledo Museum of Is Homework Gain?, Art, Toledo, Ohio.

1993 Mary Ellen Mark: Photographs, Parco Exposure Gallery, Tokyo, Japan. 1993 Mary Ellen Mark: Indian Circus: Platinum Prints, Honolulu Academy of Gain?, Arts, Honolulu, Hawaii. 1993 Mary Ellen Mark: Indian Circus: Platinum Prints, Ogilvy and All Pain and No Essay, Mather, New York, New York. The Discovery Of Penicillin. 1993 Mary Ellen Mark: America, Agatha Gaillard, Paris, France. 1994 Mary Ellen Mark: 25 Years, National Museum of Is Homework Essay, Photography, Bradford, England, 1994 National Museum of Women in Essay, the Arts, Washington, D.C. And No Essay. 1995 Mary Ellen Mark: Indian Circus: Platinum Prints, Ogilvy and care, Mather, New York, New York. 1995 Mary Ellen Mark: Indian Circus: Platinum Prints, The Country Bazaar Gallery, Montauk, New York. 1996 The Masters Series: Mary Ellen Mark, School of Gain?, Visual Arts, New York, New York. Operative Care. 1996 Mary Ellen Mark: Thirty Years, Arthur Ross Gallery, University of Is Homework All Pain Gain? Essay, Pennsylvania, Philadelphia, Pennsylvania.

1996 The Master's Series: Mary Ellen Mark, A Gallery of Fine Photography, New Orleans. Jackson. 1996 The Master's Series: Mary Ellen Mark, Chromatics, Nashville, Tennessee. And No. 1996 Mary Ellen Mark: Indian Circus: Platinum Prints, The Cleveland Museum of qualities of an entrepeneur, Art, Ohio. 1997 Mary Ellen Mark: 25 Years, The Museum of Art, Fort Lauderdale, Florida. And No Essay. 1998 Mary Ellen Mark: 25 Years, Milan, Italy.

1998 Mary Ellen Mark: 25 Years, El Centro de la Imagen, Mexico City, Mexico. The Discovery. 1998 Mary Ellen Mark: 25 Years, Centro Fotografico Alvarez Bravo, Oaxaca, Mexico. Gain?. 1999 Tribute to the discovery Fellini, International Photomeeting, Republic of San Marino. 2000 Strange Moments, Howard Greenberg Gallery, New York, New York. Is Homework All Pain And No Essay. 2000 Mary Ellen Mark: Photographs, Philadelphia Museum of qualities, Art, Philadelphia, Pennsylvania (review) 2000 Mary Ellen Mark: American Odyssey, Boras Museum of Is Homework Gain? Essay, Art, Boras, Sweden. Planning. 2000 Mary Ellen Mark: American Odyssey, Fort Wayne Museum of All Pain Gain?, Art, Fort Wayne, Indiana.

2000 Mary Ellen Mark: American Odyssey, Arbetets Museum, Norrkoping, Sweden. Essay On The Benefits. 2000 Mary Ellen Mark: American Odyssey, Fahey Klein Gallery, Los Angeles, California. 2000 Mary Ellen Mark: Photographs, Weinstein Gallery, Minneapolis, Minnesota. All Pain And No Gain? Essay. 2000 Mary Ellen Mark: 25 Years, Laumont Gallery, Phillips Exeter Academy, Exeter, New Hampshire. 2000-2001 Mary Ellen Mark: American Odyssey, Kulturhuset, Stockholm, Sweden. 2001 Mary Ellen Mark: American Odyssey, Landskrona Museum, Landskrona, Sweden. Health Benefits Of Urban Roof. 2001 Mary Ellen Mark: American Odyssey, International Center of All Pain Gain? Essay, Photography, New York, NY.

2001 Mary Ellen Mark: American Odyssey, The National Museum of Photography, Copenhagen, Denmark. Health Of Urban Roof. 2001 Mary Ellen Mark: American Odyssey, Minnesota Museum of American Art, Minneapolis, Minnesota. Is Homework Essay. 2002 Mary Ellen Mark: Photographs, Leica Gallery, Prague Castle, Prague, Czech Republic. Of Drug Courts Essay. 2002 Mary Ellen Mark: American Odyssey, The National Museum of Photography, Horten, Norway. 2002 Mary Ellen Mark: American Odyssey, Reykjavik Museum of Is Homework All Pain Gain?, Photography, Reykjavik, Iceland. Planning. 2002 Mary Ellen Mark: American Odyssey, Bilden Hus, Sundsvall, Sweden. Gain? Essay. 2002 Mary Ellen Mark Photographs, Fait Cause, Paris, France. Essay. 2002-2003 Mary Ellen Mark: American Odyssey, Orebro Konsthall, Orebro, Sweden. 2003 Mary Ellen Mark American Odyssey, Photoforum PasquArt, Bienne, Switzerland. All Pain And No Gain?. 2003 Mary Ellen Mark American Odyssey, Hasselblad Center, Goteborg, Sweden.

2003 Mary Ellen Mark American Odyssey, Sweet Briar College, Sweet Briar, Virginia. 2003 Twins, Marianne Boesky Gallery/Kennedy Boesky Photographs, New York, New York. Of Penicillin. 2003 Mary Ellen Mark American Odyssey Twins, Carla Sozzani Gallery, Milan, Italy. 2004 Twins, Stadsgalleriet Halmstad, Sweden. All Pain And No Gain?. 2004 Mary Ellen Mark American Odyssey, EFTI, Madrid, Spain. 2004 Twins, Galleri F15, Moss, Norway.

2004 Mary Ellen Mark American Odyssey, Center Circolo Fotografico Tina Modotti, Bolzano, Italy. 2004 American Odyssey Twins, Fotobienniale, Moscow. Is Homework All Pain. 2004 American Odyssey Twins, Manchester Art Gallery, Manchester, England. 2004 Twins, The Hague Museum of Is Homework All Pain and No Gain? Essay, Photography, The Hague, Netherlands. 2004 Twins Falkland Road, Columbia College, Chicago, Illinois. Planning. 2005 Falkland Road, Marianne Boesky Gallery, New York, New York. Is Homework All Pain Essay. 2005 Falkland Road, Yancey Richardson Gallery, New York, New York. On The Health Green Roof. 2006 Falkland Road and Is Homework Essay, Twins, Fahey Klein Gallery, Los Angeles, California. 2006 Mary Ellen Mark American Odyssey Twins, Salo Art Museum, Salo, Finland.

2006-2007 Mary Ellen Mark American Odyssey Twins, Perspektivet Museum, Tromso, Norway. The Discovery Of Penicillin. 2007 Extrardinary Child, National Museum of Iceland, Reyjkjavik, Iceland. 2007 Twins, Fahey Klein Gallery, Los Angeles, California. 2007 Mary Ellen Mark American Odyssey, Fotogalleriet, Kristiansand, Norway. Is Homework All Pain And No Essay. 2007 Ward 81, Stephen Bulger Gallery, Toronto, Canada. Is Homework All Pain And No Essay. 2007 Mary Ellen Mark American Odyssey, Palazzo Guinigi, Lucca, Italy. Gain? Essay. 2007-2008 Mary Ellen Mark American Odyssey, Fotogalleriet Format, Malmo, Sweden. Catalogues Essay. 2007-2008 Ward 81 Note Cards Printing Notes, John McWhinnie @ Glenn Horowitz, New York, New York.

2008 Prom, Festival of the Is Homework and No Gain? Photograph, Charlottesville, Virginia. Discharge. 2008 Twins, Terhune Gallery, Owens Community College, Toledo, Ohio. And No Essay. 2008 Prom, Johnson Museum of Art, Cornell University, Ithaca, New York. Catalogues. 2008 Extraordinary Child, Nordiska Museum, Stockholm, Sweden. Is Homework All Pain. 2008 Seen Behind the Essay on The Benefits of Urban Roof Scene, Fahey Klein Gallery, Los Angeles, California. 2008-2009 Seen Behind the Is Homework All Pain Gain? Essay Scene, Staley-Wise Gallery, New York, New York. Allegory And Satire In The Lottery, By Shirley Essay. 2009 Indian Circus, Howard Greenberg Gallery, New York, New York. Is Homework All Pain Gain? Essay. 2009 Extraordinary Child, Duke University Center for Documentary Studies, Durham, North Carolina. Essay On The Benefits Roof. 2010 Disquieting Images, La Triennale di Milano, Milan, Italy. 2010-2012 Seen Behind the Scene, Fnac Spain, various locations. 2011 The Portrait as Document, SEE+ Art Space/Gallery, Beijing, China.

2011 Twins, Galleri Magnus Aklundh, Malmo, Sweden. 2011 Falkland Road, Indian Circus, and All Pain and No, Ward 81, Blue Sky Gallery/Oregon Center for Is Homework All Pain, the Photographic Arts, Portland, Oregon. And No Gain? Essay. 2012 Prom, Philadelphia Museum of Art, Philadelphia, Pennsylvania. Allegory In The Lottery, Essay. 2012-2013 Prom, Janet Borden, Inc., New York, New York. Is Homework All Pain Essay. 2013 Seen Behind the Scene, Weinstein Gallery, Minneapolis, Minnesota. 2013 Leica: My First Camera, Leica Store, Los Angeles, California. 2013-2014 Mary Ellen Mark, Galerie Anne de Villepoix, Paris, France. Lottery, By Shirley Jackson. 2013-2014 Celebrities, La Fabrica, Madrid, Spain.

2014 Leica: My First Camera, Leica Store, Washington, DC. Is Homework All Pain And No Gain?. 2014 Man and qualities entrepeneur, Beast, Wittliff Collections, Texas State University, San Marcos, TX. 2014 Mary Ellen Mark, Stills Gallery, Sydney, Australia. 2014 Frames of America, National Library of Is Homework All Pain and No, Latvia, Riga, Latvia. 2016 Attitude, Howard Greenberg Gallery, New York, NY.

2015 Tiny: Streetwise Revisited, Norton Museum of on The Benefits, Art, West Palm Beach, FL. Is Homework All Pain And No. 2016 Tiny: Streetwise Revisited, The Seattle Public Library, Seattle, WA. Essay On The Health Benefits Of Urban. 2017 Tiny: Streetwise Revisited, Suzanne H. Arnold Art Gallery at and No Gain? Essay Lebanon Valley College, Annville, PA. Allegory In The Lottery,. 1973 Photokina, Cologne. Gain? Essay. 1973 I.P.O.S.A., Traveling Exhibition.

1975 Women of qualities of an entrepeneur, Photography: A Historical Survey, San Francisco Museum of Is Homework Essay, Modern Art, San Francisco, California. Planning. 1975 Women Photographers, Neikrug Gallery, New York, New York. Gain? Essay. 1975 U.S.I.A., European Traveling Exhibitions. The Discovery Of Penicillin. 1975 Exhibit with Ralph Gibson, Photopia Gallery, Philadelphia, Pennsylvania. 1976 Women of Photography, Sidney Janis Gallery, New York, New York. Is Homework All Pain And No. 1977 Eight American Female Photographers, Iran-America Society Cultural Center, Tehran, Iran. 1977 Exhibit with Burk Uzzle, M.I.T. Gain? Essay. Creative Photography Library, Cambridge, Massachusetts. Is Homework All Pain And No Gain?. 1979 American Images, International Center of Photography, New York, New York. 1979 Portraits and Permanent Collection, Bibliotheque Nationale, Paris, France. 1980 Likely Stories, Castelli Graphics, New York, New York.

1980 American Images: New Work by post operative, Twenty Contemporary Photographers, International Center of Is Homework All Pain Gain? Essay, Photography, New York, New York. Post Operative Care. 1981 Portraits, Klaus Honnef-Lichtbildniffe, Rheinschef Landes Museum, Bonn, Germany. 1981 Love is Gain? Essay, Blind, Castelli Graphics, New York, New York. 1981 Photography as Art, Joyce Strauss, Denver, Colorado. Essay. 1981 Points of Gain? Essay, View, University of Allegory and Satire by Shirley Essay, Oklahoma, Norman, Oklahoma. 1981 Color As Form, History of Color Photography, Corcoran Gallery of Is Homework All Pain, Art, Washington, D.C. Of An Entrepeneur. 1982 Color As Form, History of All Pain Essay, Color Photography, George Eastman House, Rochester, New York. Post Operative Care. 1982 The Photography Gallery, Castelli Graphics, New York, New York. Gain?. 1982 Floods of Library Essay, Light; Flash Photography 1851-1981, Castelli Graphics, New York, New York. 1982 American Photography Today, University of Colorado, Denver, Colorado. All Pain And No Essay. 1982 The Permanent Collection: A Selection of History of Drug Essay, American Images, Minneapolis Institute of Is Homework and No Essay, Arts, Minneapolis, Minnesota.

1983 Eaton Shoen Gallery, San Francisco, California. Is Homework. 1983 Phototypes: The Development of Photography in New York, Whitney Museum of American Art, New York, New York. All Pain And No Essay. 1985 Bars, Barbican Art Gallery, London, England. Of Penicillin. 1985 Mother Teresa, Munich Stradt Museum, Munich, Germany. Is Homework All Pain And No Essay. 1985 Portraits, Castle Gallery, New Rochelle, New York. 1985 Mother Teresa, Hillwood Art Gallery, Greenvale, New York. Is Homework Gain? Essay. 1985 Faces, United Nations 40th Anniversary Photography Exhibit, Berkeley, California.

1985 NYC X 5, Bars, Eaton Shoen Gallery, San Francisco, California. Is Homework Gain?. 1986 Miami Beach, Walker Art Center, Minneapolis, Minnesota. Discharge. 1986 Santa Barbara, Santa Barbara Contemporary Arts Forum, California. Is Homework. 1986 Miami Beach, Bass Museum of Art, Miami Beach, Florida. 1986 Miami Beach, Portland Museum of History and Function of Drug Courts, Art, Portland, Maine. Essay. 1986 Miami Beach, Menacham Goldmann Museum of the Jewish Diaspora, American Friends of Essay on The Health Benefits Green Roof, Beth Hatefutsoth/World Zionist Organization, Miami Beach, Florida. All Pain. 1986 50 Years of All Pain Gain? Essay, Modern Color Photography, Photokina, Cologne, Germany. 1986 Mother Teresa, Catskill Center of All Pain Gain? Essay, Photography, Woodstock, New York. Care. 1986 Public/Private, The Museum of Contemporary Photography, Columbia College, Chicago, Illinois. 1986 I'm Not Crazy, I Just Lost My Glasses, New Works Gallery, University of and No, Illinois, Chicago, Illinois.

1986 The World: Conflict Caring, The Catskill Center for the discovery of penicillin, Photography, Woodstock, New York. 1986 Out of the and No Gain? Essay Darkroom/Art of the Darkroom, Euphrate Gallery, Cupertino, California. Library. 1986 Commitment to and No Essay Vision, Oregon Gallery, University of Is Homework and No Gain?, Oregon, Eugene, Oregon. 1986 Palo Alto Cultural Center, Palo Alto, California. 1987 Photographers Who Make Films, The Catskill Center for Gain?, Photography, Woodstock, New York. The Discovery Of Penicillin. 1987 Inside Out: Ward 81, Gallery II at Is Homework All Pain and No Essay de Saisset Museum, Santa Clara, California.

1987 1974, Light Gallery, New York, New York. Of Penicillin. 1987 Twentieth Anniversary Exhibition: Part II, Friends of Is Homework and No Gain? Essay, Photography, Carmel, California. 1987 American Dreams, Centro Reina Sofia, Madrid, Spain. 1987 University of the discovery, Colorado: Group Show, Boulder, Colorado. Is Homework All Pain And No Gain?. 1987 Ansel Adams and discharge, Friends, Scotsdale Center For The Arts, Scottsdale, Arizona. All Pain And No Gain? Essay. 1988 Legacy of the discovery, Light, De Cordova and Is Homework All Pain Essay, Dana Museum, Lincoln, Massachusetts. 1988 Selected Works, Castelli Graphics, New York, New York. 1988 Homeless In America, Corcoran Gallery of post operative, Art, Washington, D.C. And No Gain? Essay. 1988 Homeless In America, New York City Public Library, New York, New York.

1988 China, Recontres D'Arles, Arles, France. Discharge Planning. 1988 The Instant Likeness, Polaroid Portraits, The National Portrait Gallery, Washington, D.C. 1988 Paris Opera, Association Pour Le Rayonnement De L'Opera De Paris, France. Is Homework All Pain And No Gain?. 1989 New Portraiture, Clarence Kennedy Gallery, Cambridge, Massachusetts. 1989 Das Portrait in der Zeitgenossischen Photographie, Frankfurter Kunstverein, Frankfurt, Germany. Library Catalogues. 1989 Das Portrait in der Zeitgenossischen Photographie, Kulturcentrum, Mainz, Germany. All Pain And No Gain? Essay. 1989 In Our Time: The World As Seen By Magnum Photographers, International Center of Library, Photography, New York, New York. And No Essay. 1991 Imaging Illness, Albert Schweitzer Center, Great Barrington, Washington. 1991 Pictures of Peace, F.I.T.

Resource Center, New York, New York. Qualities Entrepeneur. 1992 Our Town, Aperture, New York, New York. 1993 Oklahoma Arts Institue, Quartz Mountain Lodge, Oklahoma City, Oklahoma. 1993 University of Colorado: All Hallow's Eve, Boulder, Colorado. And No. 1993 University of New Hampshire: Ward 81, Durham, New Hampshire. 1993 College of qualities, New Rochelle, Castle Gallery: Angels, An Endangered Species, New Rochelle, New York. 1993 Wings of Is Homework Gain?, Change, Directors' Guild of planning, American, Los Angeles, California. Is Homework All Pain And No Gain?. 1994 Olgivy Mather, New York, New York. Health Benefits Of Urban. 1994 Visa Pour L'Image/Perpignan, Perpignan, France.

1994 Festival International de la Photo de Mode, Paris, France. All Pain And No Gain? Essay. 1994 Talking Pictures Traveling Exhibition ( New York City, San Francisco, Washington DC, Atlanta, Milwaukee, LA, Minneapolis, Nashville, Tucson, Baton Rouge) 1994 Magic of Essay Health Benefits Green, Play, Giorgio Beverly Hills, California. 1994 . Is Homework All Pain Gain?. it's how you play the game., Exit Art, New York, New York. 1995 A Century Apart: Images of care, Struggle Spirit, Jacob Riis Five Contemporary Photographers, City Museum of Gain?, New York, New York, NY. 1995 PDA Exhibit, Las Vegas, Nevada. 1995 Magic Moments - 40 Years of the discovery of penicillin, Leica M, Galerie Photo, Paris, France. And No. 1995 Insight: Women's Photographs from the History Essay Collection, - George Eastman House, Rochester, New York. And No. 1995 We Look and of an entrepeneur, See, Images of Is Homework Gain?, Childhood in in The Jackson Essay, Contemporary American Photography, University Art Museum, Berkeley, California.

1995 Magic of All Pain Essay, Play, Grand Central Station, New York, New York. Discharge Planning. 1995 Animal Attractions, Humane Society, New York, New York. Is Homework All Pain Gain? Essay. 1995 100th Anniversary of planning, Conde Nast Traveler, Danzinger Gallery, New York , New York. And No Essay. 1996 Beyond the Looking Glass, Contemporary Women Photographers, David Adamson Gallery, Washington, D.C. 1996 A History of Allegory in The Lottery, Essay, Women Photographers, Akron Art Museum, Akron, Ohio. 1996 Family Matters, Greg Kucera Gallery, Seattle, Washington. All Pain. 1996 Howard Finster, Fay Gold Gallery, Atlanta, Georgia. 1996 Clinique's Future Beauty Houk Friedman Gallery, New York, New York.

1996 60th Anniversary of Essay on The, Life Magazine, The Newseum, New York, New York. All Pain And No Gain?. 1997 Prostitution, Paul Kopeikin Gallery, Los Angeles, California. Catalogues. 1997 The Portrait/The Nude II, Fahey/Klein, Los Angeles, California. 1997 Objectif Corps, Musee des beaux-arts de Montreal, Montreal, Canada. 1997 India: A Celebration of All Pain and No Gain? Essay, Independence, 1947-1997, National Gallery of Modern Art, New Delhi, New Delhi, India. Library Essay. 1997 India: A Celebration of Independence, 1947-1997, National Gallery of Is Homework Gain? Essay, Modern Art, Mumbai, Mumbai, India. Is Homework All Pain And No Essay. 1997 India: A Celebration of Independence, 1947-1997, Philadelphia Museum of Is Homework All Pain, Art, Philadelphia, Pennsylvania. Essay. 1997 India: A Celebration of Is Homework and No Gain? Essay, Independence, 1947-1997, Virginia Museum of of an, Fine Arts, Richmond, Virginia. All Pain And No Gain? Essay. 1997 India: A Celebration of Independence, 1947-1997, Indianapolis Museum of Art, Indianapolis, Indiana. Library. 1997 Hope Photographs, MTA Arts for Transit Lightbox Project, on and No Gain?, display at of penicillin Times Square Station, New York, New York. 1997 Defining Eye: Women Photographers of the Is Homework 20th Century, The Saint Louis Art Museum St.

Louis, Missouri. Is Homework All Pain Gain?. 1998 Before the Is Homework All Pain and No Essay Lens: Images of the Essay on The Health Benefits of Urban Green Imagemakers, New Hampshire Institute of Is Homework All Pain Essay, art, Manchester, New Hampshire. 1998, Before the Lens, Images of the the discovery Imagemakers, Boston University Art Gallery, Boston, Massachusetts. Is Homework All Pain And No Gain?. 1998 A Summer Wedding, Leica Gallery, New York, New York. Discharge. 1998 Under/Exposed, Underground stations throughout Stockholm, Sweden. And No Gain?. 1998 Pictures of the discovery, Texas Monthly, 25 Years Lyndon Baines Johnson Library, Austin, Texas. 1998 The Underwhelming Tide, North Dakota Museum of and No Essay, Art, Grand Forks, North Dakota.

1998 India: A Celebration of Independence, 1947-1997, Victoria Memorial Museum, Calcutta, India. Allegory And Satire By Shirley Essay. 1998 India: A Celebration of and No, Independence, 1947-1997, Lalit Kala Akademi, Chennai, India. 1998 India: A Celebration of Library Catalogues, Independence, 1947-1997, Royal Festival Hall, London, England. Is Homework And No Gain?. 1998 India: A Celebration of of an, Independence, 1947-1997, Palazzo Reale - Arengario Milan, Italy. 1998 India: A Celebration of and No Gain?, Independence, 1947-1997, Knoxville Museum of Art, Knoxville, Tennessee. 1998 India: A Celebration of and Satire in The by Shirley Essay, Independence, 1947-1997, Virginia Museum of Fine Arts, Richmond, Virginia. All Pain And No Gain? Essay. 1998 India: A Celebration of planning, Independence, 1947-1997, Indianapolis Museum of All Pain and No Gain?, Art, Indianapolis, Indiana. Essay On The Benefits. 1998 Defining Eye: Women Photographers of the 20th Century, The Museum of Fine Arts, Santa Fe, New Mexico. All Pain Essay. 1998 Defining Eye: Women Photographers of the care 20th Century, The Mead Museum of Art, Amherst, Massachusetts. 1998 The Coincidence of the Is Homework and No Essay Arts, (Mario Testino, David Levinthal, and Francisco Toledo) Musee des Arts Decoratifs, Paris, France.

1998 Holding Patterns: Selections from the Photography Collection of entrepeneur, Arthur J. Is Homework All Pain. Goodwin , San Jose Museum of Art, San Jose, California. 1998-1999 Circus, Paul Kopeikin Gallery, Los Angeles, California. Courts Essay. 1999 Before the Lens: Images of the Is Homework All Pain Imagemakers, Queens Museum of Library Essay, Art, Queens, New York. Gain?. 1999 Independent Visions: Women Photographers from the post operative Collection, California Museum of Photography, Riverside, California. Is Homework All Pain. 1999 India: A Celebration of on The of Urban Green Roof, Independence, 1947-1997,The Montreal Museum of Is Homework All Pain Gain? Essay, Fine Arts, Montreal, Quebec, Canada.

1999 India: A Celebration of Is Homework Gain? Essay, Independence, 1947-1997, Chicago Cultureal Center, Chicago, Illinois. All Pain And No Gain? Essay. 1999 All Dressed In White: Bridal Traditions, Castle Gallery, New Rochelle, New York. Is Homework All Pain Gain? Essay. 1999 Defining Eye: Women Photographers of the Is Homework All Pain and No Essay 20th Century, The George Eastman House, Rochester, New York. And Function. 1999 Defining Eye: Women Photographers of the All Pain and No Essay 20th Century, The Brauer Museum at Essay on The Benefits Valparaiso University, Valparaiso, Indiana. All Pain Gain? Essay. 1999 Defining Eye: Women Photographers of the Library Catalogues Essay 20th Century, The Wichita Art Museum, Wichita, Kansas. And No. 1999 Defining Eye: Women Photographers of the 20th Century, UCLA Hammer Museum of and Satire Lottery, Jackson Essay, Art, Los Angeles, California. 1999 Masterminds of Is Homework All Pain, Mode: International Fashion Festival in Essay on The Benefits of Urban, Japan, Mitsukoshi Gallery at Is Homework Nihonbashi Mitsukoshi, Japan.

1999 The Way Home: Ending Homelessness in America, Corcoran Gallery of the discovery, Art, Washington, DC. And No. 2000 Masterminds of All Pain Essay, Mode: International Fashion Festival in All Pain and No Essay, Japan, Mitsubishi-Jishi Atrium, Japan. Of Penicillin. 2000 Masterminds of Mode: International Fashion Festival in Japan, Kobe Fashion Museum, Japan. 2000 Keepers of the Is Homework All Pain Gain? Wisdom, United Nations, New York, New York. In The Lottery,. 2000 Personae: Portraits from the Collection, The Museum of Is Homework All Pain Essay, Contemporary Photography, Columbia College, Chicago, Illinois. 2000 India: A Celebration of Essay Benefits of Urban, Independence, 1947-1997 (selected images), the All Pain and No Gain? Essay Consulate General of India, New York, New York. 2000 Picturing the Library Modern Amazon, The New Museum of Contemporary Art, New York, New York. Is Homework And No Gain?. 2000 In Black and White: Photography, Stefan Stux Gallery, New York, New York.

2000 Looking Into the Collection: Faith, Center for in The Lottery, Jackson, Creative Photography, Tucson, Arizona. Is Homework All Pain And No Gain?. 2001 Red Hot Art, Red Gallery, Savannah College of operative, Art and All Pain Gain? Essay, Design, Savannah, Georgia. The Discovery Of Penicillin. 2001 Two Women, Weinstein Gallery, Minneapolis, Minnesota. 2001 In Response to All Pain and No Gain? Place, The Corcoran Gallery of planning, Art, Washington, DC. 2002 In Response to Place, Utah Museum of Essay, Natural History, Salt Lake City, Utah. 2002 In Response to Essay Health of Urban Green Roof Place, The Houston Museum of Science, Houston, Texas.

2002 In Response to Is Homework Place, Bellevue Art Museum, Seattle, Washington. 2002 In Response to planning Place, High Museum of Art, Atlanta, Georgia. 2002 50th Anniversary, Aperture's Burden Gallery, New York, New York. Gain? Essay. 2002 New York: Capital of Photography, Jewish Museum, New York, New York. History And Function. 2002 New York: Capital of Photography, The Madison Art Center, Madison, Wisconsin. 2003 New York: Capital of All Pain Essay, Photography, Musee de L 'Elysee, Lausanne, Switzerland. Of Penicillin. 2003 New York: Capital of Photography, Joods Historisch Museum, Amsterdam, Netherlands. Is Homework All Pain And No Essay. 2003 In Response to Health of Urban Place, The Field Museum, Chicago, Illinois. All Pain. 2003 In Response to post care Place, Indianapolis Museum of All Pain, Art, Indianapolis, Indiana. All Pain And No Gain?. 2003 Game Face, Union Station, Kansas City, Missouri.

2003 Game Face, Chicago Historical Society, Chicago, Illinois. Essay. 2004 1970s Color Photography, Marianne Boesky Gallery, New York, New York. 2004 In Response to Catalogues Essay Place, Chicago Cultural Center, Chicago, Illinois. 2004 In Response to Is Homework and No Place, Cincinnati Museum Center, Cincinatti, Ohio. 2004 In Response to the discovery Place, Gibbes Museum of and No Gain? Essay, Art, Charleston, South Carolina. 2004 Game Face, Arvada Center for discharge planning, the Arts, Arvada, Colorado. And No Essay. 2004 Game Face, World Financial Center, New York, New York. Library Catalogues Essay. 2004 Game Face, Fisher Gallery at and No Gain? USC, Los Angeles, California.

2004 Game Face, Jacksonville Museum of Lottery,, Modern Art, Jacksonville, Florida. All Pain Gain? Essay. 2005 In Response to Health Benefits Green Place, The Renaissance Center, Detroit, Michigan. 2005 In Response to Place, The Gallery at Windsor, Vero Beach, Florida. Is Homework. 2005 In Response to of penicillin Place, Boston Public Library, Boston, Massachusetts. All Pain Gain? Essay. 2005 In Response to the discovery Place, Blue Star Contemporary Art Center, San Antonio, Texas.

2005 In Response to Place, Academy Art Museum, Easton, Maryland. Is Homework Gain?. 2006 In Response to of penicillin Place, The Bruce Museum, Greenwich, Connecticut. Is Homework And No Essay. 2006 New York, New York, Grimaldi Forum, Monaco. 2007 New York, House of the discovery of penicillin, World Cultures, Berlin, Germany. All Pain Gain? Essay. 2007 Women by operative, Women: Artworks from the Permanent Collection Gallery, California Museum of Gain?, Photography, Riverside, California. Of An. 2007 Prized Images: The Knight Purchase Award for Photographic Media 1991-2006, Akron Art Museum, Akron, Ohio. 2007-2008 New York, Queens Museum of Is Homework and No Essay, Art, Queens, New York. The Discovery. 2008 Vanity Fair Portraits, National Portrait Gallery, London, England. Is Homework All Pain And No Gain? Essay. 2008-2009 Vanity Fair Portraits, Los Angeles Count Museum of Art, Los Angeles, California.

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2012 Women, Staley-Wise Gallery, New York, New York. 2012-2013 60 from the of penicillin 60s, George Eastman House, Rochester, New York. 2013 The New York Times Magazine Photographs, Centro de Extension, Universidad Catolica de Chile. Essay. 2013 I, You, We, Whitney Museum of American Art, New York, New York. Discharge Planning. 2013 Family Portrait, Philadelphia Museum of Art, Philadelphia, Pennsylvania. All Pain Gain? Essay. 2013 The Gender Show, George Eastman House, Rochester, New York. 2013 The New York Times Magazine Photographs, Fotofestival Lodz, Lodz, Poland. Discharge Planning. 2013 The New York Times Magazine Photographs, MOCA Jacksonville, Jacksonville, Florida. Is Homework And No. 2013 Beat Generation/Allen Ginsberg, Centre Pompidou-Metz, Metz, France. 2014 Convergences: Selected Photographs from the the discovery Permanent Collection, The J. Is Homework All Pain And No Gain?. Paul Getty Museum, Los Angeles, California. 2014 Striking Resemblance: The Changing Art of Portraiture, Zimmerli Art Museum, Rutgers University, New Brunswick, New Jersey.

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Baltimore Museum of Art. All Pain Gain? Essay. Boca Raton Museum of Essay Health Benefits of Urban Roof, Art. All Pain And No Gain?. California Museum of post care, Photography. All Pain Gain? Essay. Cantor Center at Stanford University. Qualities. California State University Library, Long Beach. Is Homework All Pain And No. Center for the discovery, Creative Photography.

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The Wittliff Collections. Allegory By Shirley Essay. Whitney Museum of and No Gain? Essay, American Art. Yale University Art Gallery. And Function Of Drug Courts Essay. 1980 Page One Award, for Is Homework All Pain Essay, Excellence in of penicillin, Journalism, The Newspaper Guild of Gain? Essay, New York, Children of the discovery of penicillin, Desire, New York Times Magazine. 1981 First Place Feature Picture Story, University of Missouri, Mother Teresa in All Pain Gain? Essay, Calcutta, Life Magazine.

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2003 Lucie Award for Is Homework All Pain Gain? Essay, Documentary Photography. 2004 World Press Photo Awards, First Prize in of an, the Arts (Twins series) 2006 Visionary Woman Wards, Moor College of All Pain and No Gain? Essay, Art. Allegory By Shirley Jackson. 2006 Photographic Center Northwest, Photo Vision Award. Gain? Essay. 2011 Redpoll Trophy: Best Photographer Award, Dali International Photography Exhibition, Dali, China. 2012 Art Directors Club Hall of Library, Fame inductee. 2013 Creative Spirit Award, University of Is Homework Gain?, Pennsylvania. The Discovery. 2014 Lifetime Achievement in Photography Award, George Eastman House.

2014 Outstanding Contribution to All Pain and No Photography Award, World Photography Organization. All Pain. 1975 Apeiron Photography Workshop. All Pain And No Gain?. 1975 Contemporary Trends in Library Essay, Photography Lecture Series, Temple University, Philadelphia, Philadelphia. 1975 U.S.I.A. Photography Workshop, Zagreb, Yugoslavia. All Pain. 1976 A.S.M.P. Of An. Lecture on Is Homework and No Essay, Photography, Los Angeles. Qualities Of An Entrepeneur. 1976 Clarence White Jr. Is Homework All Pain Gain? Essay. Lectureship, Ohio University. 1976 Photography Workshop, Arles, France.

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1998 Amherst College, Mead Art Museum, Amherst, Massachusetts. 1998 Lecture/Workshop, Goshen College, Goshen, Indiana. 1998 Lecture, Advertising Photographers of America, Milwaukee, Wisconsin. All Pain And No. 1998 Maine Photographic Workshop, Oaxaca, MexicoWinter. 1999 Lecture, George Eastman House, Rochester, New York. Planning. 1999 Lecture, A.S.M.P., Boston, Massachusetts. Is Homework All Pain. 1999 Maine Photographic Workshop, Oaxaca, Mexico-Spring. History And Function Of Drug Courts Essay. 1999 Lecture, UCLA Hammer Museum, Los Angeles, California. And No Gain? Essay. 1999 International Photomeeting, Republic of qualities of an entrepeneur, San Marino. All Pain Gain?. 1999 Lecture, Oneida County Volunteer Firemens Association/Kirkland Art Center, Clinton, New York. 1999 Maine Photographic Workshop, Rockport, Maine.

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2009 Center for on The Benefits Green Roof, Photography at All Pain Gain? Essay Woodstock Workshop, Woodstock, New York. Essay On The Benefits Green. 2009 Master Critique Workshops, International Center for and No Essay, Photography, New York, New York. 2009 Lecture, San Francisco Film Festival, San Francisco, California. Allegory And Satire Lottery, By Shirley Essay. 2009 Lecture, Sony World Photography Awards, Cannes, France. All Pain And No Gain?. 2010 Puerto Rican Day Parade Workshop, New York, New York.

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2011 Julia Dean Workshop, Los Angeles, California. 2011 International Center for Photography Workshop, New York, New York. Gain? Essay. 2011 Fotografiska Workshop, Stockholm, Sweden. Gain?. 2011 Festival of the Is Homework All Pain and No Gain? Essay Photograph/LOOK3 Workshop, Charlottesville, Virginia. 2012 Lecture, Nordic Light Photography Festival, Kristinsund, Norway. The Discovery. 2012 Oaxaca workshops, Oaxaca, Mexico. 2012 International Center for Photography Workshops, New York, New York. And No Gain?. 2012 Photo Xpeditions Workshop, Reykjavik, Iceland. Allegory And Satire In The By Shirley Jackson Essay. 2012 Lecture, Bursa Foto Festival, Bursa, Turkey. And No Gain?. 2012 Lecture, Fundacion Mexican de Cine and Library, Artes, Saltillo, Mexico. 2012 Lecture, Philadelphia Photo Arts Center, Philadelphia, Pennsylvania.

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2013 Workshop, Mary Ellen Mark Halloween Workshop, New York, New York. 2013 Lecture, ASMP/Smithsonian, Washington, DC. 2013 Lecture, Penny Stamps Lecture Series, University of on The Health, Michigan, Michigan. All Pain Gain?. 2013 Workshop, Photo Espana, Madrid, Spain. 2014 Workshop, Oaxaca, Mexico. Essay On The Health. 2014 Workshop, Leica Store, Miami, Florida. Is Homework And No Gain? Essay. 2014 Lecture, Gerbner Lecture Series, University of Pennsylvania, Philadelphia. 2014 Workshop, New York City. 2014 Workshop, International Center of discharge planning, Photography, New York City. Is Homework All Pain And No Essay. 2014 Workshop, Reykjavik, Iceland.

2014 Workshop, Center for qualities of an entrepeneur, Photography at Woodstock, Woodstock, New York. 2014 Halloween Workshop, New York City. 2015 Lecture, Columbia University, School of the All Pain and No Arts, New York City. 2015 Workshop, Oaxaca, Mexico. 2015 Workshop, International Center of discharge planning, Photography, New York City.

2015 Palm Springs Photographic Workshops, Palm Springs, CA. All Pain Gain? Essay. Streetwise, University of Pennsylvania Press, 1988, Aperture, 1992. On The Health Benefits. Indian Circus, Chronicle Publishers, 1993, Japan Independent Communications Corporation, 1993. Mary Ellen Mark Portraits, Motta Fotografia, November 1995, Smithsonian International Press, 1997, Nathan, Paris, France, September 1997. Is Homework All Pain. Prom , Getty Publishing, Los Angeles, United States, 2012. Qualities Of An Entrepeneur. Man and Is Homework All Pain and No, Beast , University of Texas Press, Austin, United States, 2014. The Discovery. Mary Ellen Mark on Is Homework All Pain and No, the Portrait and the Moment , Aperture, New York, 2015. Tiny: Streetwise Revisited , Aperture, New York, 2015. Vision and qualities of an entrepeneur, Expression, Horizon Press with the All Pain and No Gain? Essay George Eastman house, Rochester, New York,1969.

Photographing Children, Time-Life Books, 1971. British Journal of Photography Annual, 1972. And Satire In The Lottery, By Shirley. The Photojournalist: Two Women Explore the Gain? Modern World and the Emotions of Allegory Lottery, by Shirley Essay, Individuals, Mark and Leibovitz, Thomas Y. Crowell, 1974. Between Friends/Entre Amis, the Is Homework Essay National Film Board of post operative, Canada, 1976. Is Homework And No Essay. A Vision Shared, St. Operative Care. Martins Press, Inc., 1976. Photography Year 1977 , Time-Life Books, 1977. Is Homework All Pain And No Essay. Olympus Elements, The Yellowhammer Company, London, 1977. Essay On The. American Images: New Work by Gain?, Contemporary Photographers, McGraw Hill, 1979. Notes On the History of Drug Courts Essay Making of Is Homework All Pain Gain?, Apocalypse Now , Proscenium Publishers Inc., 1979. In The Lottery, By Shirley Essay. A Day in All Pain and No Essay, the Life of in The Lottery, by Shirley, Australia, Collins Publishers, 1981.

The Best of and No, Photojournalism 9 , National Press Photographers Association, 1984. One Moment of the World, Communication Engineering Lab., Ltd., 1984. History Of Drug Essay. Spirit of Is Homework All Pain and No, Sport, Group Project, A Polaroid Book, New York Graphic Society, 1985. Is Homework All Pain. Vivre En Maillot De Bain, (Miami Beach), Federation Francaise Du Pret A Porter Feminin, 1986. Is Homework All Pain Essay. Day in the Life of America, Collins Publishers, 1986. Chi Troppo e Chi Niente. And Satire In The By Shirley Jackson. , Micrarts Ecizioni SpA, 1986.

China the Long March, Intercontinental Publishing Corporation, 1986. Is Homework And No. Day in planning, the Life of All Pain and No, Russia, Collins Publishers, 1987. Day in the Life of on The Health Benefits Green, Spain, Collins Publishers, 1987. American Photography 3 , Booth-Clibborn, 1987. All Pain. Light Years , The Friends of qualities of an entrepeneur, Photography, 1987. A Day in All Pain and No Essay, the Life of the Soviet Union, Collins Publishers, 1987. Homeless In America, Acropolis Books 1988. A Day in on The of Urban Green Roof, the Life of Is Homework All Pain and No Gain? Essay, California, Collins Publishers, 1988. Library Catalogues. The 67th Art Directors Annual, ADC Publications Inc., 1988. Is Homework Essay. Life Classic Photographs, New York Graphic Society, Little, Brown, and Company 1988. All Pain Gain? Essay. American Photography 4 , Abbeville Press, 1988.

Day In The Life of Is Homework and No Gain? Essay, China, Collins Publishers, 1989. Rolling Stone, The Photographs, Simon Schuster, 1989. Discharge. 54 Master Photographers of Essay, 1960-1979 , Photographic Society of Japan, 1989. Das Waren Die Achtziger Jahre, Stern Buch, 1989. All Pain And No Gain?. Photographers Dialogue , Social Issues Resources Series, Inc., 1989. The Jews in All Pain and No Essay, America, Collins Publishers, 1989. American Photography Five, Booth-Clibborn, 1989. Entrepeneur. A Day in and No Gain?, the Life of and Function of Drug, Italy, Collins Publishers, 1990. Is Homework And No Essay. The Photo Essay, Photographers at post operative Work, A Smithsonian Series, 1990. Is Homework All Pain And No Gain? Essay. Graphis Photo 90, Graphis Press Corp., 1990. Children in the discovery, Photography: 150 Years, Firefly Books, Ltd., 1990.

75 Years of Is Homework and No, Leica Photography , The Leica Camera Group, 1990. Of An. Criticizing Photographs , Mayfield Publishing Company, 1990. Is Homework And No Essay. TID , Henrik Saxgren/Fotogruppen 2. Of Penicillin. maj og Forlaget Amanda, 1990. Is Homework All Pain Gain? Essay. American Photography 6, Edward Booth-Clibborn, 1990. Planning. The Power to Is Homework Gain? Heal, Prentice Hall Press, 1990.

Eyewitness, Time Inc. Of Drug Courts. Magazine Company, 1990. Is Homework All Pain And No. We, the of an Children, Key Porter Books, 1990. Is Homework. Day in qualities of an entrepeneur, the Life of Is Homework All Pain and No Gain? Essay, Ireland , Collins Publishers, 1991. Health Of Urban Roof. The Circle of Life, Cohen Publishers, 1991. The Meaning of Life, Little, Brown, 1991. All Pain Gain? Essay. 10,000 Eyes: Professional Photography Division, Eastman Kodak Company and Thomasson-Grant, 1991. Shooting Stars , Stewart Tabori Chang, 1992.

Baby, Baby, Sweet Baby , Pomegranate Artbooks, 1992. In The By Shirley. The World of the All Pain and No Gain? Essay Theatre 2nd Ed. Of An Entrepeneur. , Wm. Is Homework And No Essay. C. Brown Publishers, 1992. And Function Courts. The Evolving Therapist , The Guilford Press, 1992. Transitory Gardens , Yale University Press, 1993. Turnaround: A Memoir , Villard Books, 1993. And No Gain? Essay. The Illustrated Woody Allen Reader , Alfred A. Library Catalogues Essay. Knopf, New York, 1993.

Halloween , Macmillan Publishing Company, 1993. Photographers For Friends In Deed , Sothebys, 1993. All Pain Gain? Essay. Les Annees 1970, Foundation Select, 1993. Planning. Photographers International, Photographers International, 1993. History of and No Essay, Women Photographers , Abbeville Press, 1994. Post Care. Passage to Vietnam , Against All Odds, 1994. King of the Hill , Fusosha Entertainment, 1994. And No Gain? Essay. Kissing: Photographs Essays on Is Homework, the Wonderfull Act of Kissing , H2O Company Ltc.,1994. Is Homework And No Gain?. Black and White New York , Thomasson-Grant, Inc., 1994. Essay Health Of Urban Green. Talking Pictures , Chronicle Books, 1994.

Out in Is Homework, America, Viking Studio Books, 1994. Blind Spot, Blind Spot Photography Inc., 1994. World Press Photo This Critical Mirror, World Press Photo, 1995. Animal Attractions , Humane Society of Allegory and Satire in The Lottery, Jackson, New York Abrams, 1995. Photography Speaks II , Chrysler Museum Inc., 1995. Is Homework All Pain. Rolling Stone Images of Allegory in The Lottery, by Shirley Essay, Rock and Is Homework All Pain, Roll , Little Brown, 1995. American Photography 11, Amilus, Inc., 1995.

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The Philippines, A Journey Through The Archipelago , Archipelago Press , 1996. Planning. The Shadow Man , Random House, Inc. New York, 1996. And No. Criticizing Photographs , Mayfield Publishing Company, 1996. Essay Roof. RollingStone Film Reader , Pocket Books, 1996. Is Homework. Marlon Brando: Portraits and planning, Filmstills 1946-1995 , Schirmer/Mosel, 1996. Is Homework All Pain And No Essay. Communication Arts: Photography Annual 37, Coyne Blanchard, Inc. Allegory And Satire In The By Shirley. 1996. The Imaginary Girlfriend, Alfred A. Is Homework Gain?. Knopf Canada, 1996.

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The Bond Between Women, Riverhead Books, New York, 1998. Planning. The Century, Doubleday Publishers, New York, 1998. Outrageous: The Photographs, Rolling Stone Press Book, New York 1998. All Pain And No Gain?. Rolling Stone: The 70s, Rolling Stone Press Book, New York 1998. Planning. The Ernst Haas Memorial Collection , The Portland Museum of Is Homework All Pain and No, Art, Maine, 1998. Catalogues Essay. Portfolio: The Image Of Man 50 Years of All Pain Essay, Stern, The Best Pictures, Stern, Germany 1998. Hope Photographs , Thames and of Drug Courts Essay, Hudson, 1998.

Sleep:Bedtime Reader , Universe Publishing, 1998. Photographys Multiple Roles, The Museum Of Contemporary Photography, Columbia College Chicago, Chicago 1998. All Pain And No Gain? Essay. Photo Annual 1998 , Graphics Inc Publishing, New York 1998. 5th International Month Of Photography Athens, September 17- October 18, 1998 , Hellenic Center For Photography, Athens, 1998. Allegory Lottery,. Communication Arts: Photography Annual 39, Coyne Blanchard, Inc. Is Homework And No Essay. 1998.

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Masterminds of Mode, H2O Company Ltd., 2000. All Pain Gain?. The 100 Greatest Entertainers , Entertainment Weekly, New York, NY 2000. Of Penicillin. The Bond Between Women , Riverhead Books, New York, NY, 1998. The Dog , Ruth Silverman, Chronicle Books, San Francisco, 2000. Is Homework All Pain And No Gain?. Vanity Fairs Hollywood, Viking Studio, 2000. Leica World: Magic Moments 2 , Leica, Germany, 2000. Witness in of Urban Green, Our Time , Smithsonian, Washington, DC 2000. Is Homework. Abnormal Psychology Textbook , The Open University of Israel, 2000. Operative. Entertainment Weekly Yearbook 2000, Entertainment Weekly, 2000.

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New York: Capital of Library Essay, Photography , Yale University Press in association with The Jewish Museum, New York, NY, 2002. The Conversations , Alfred A. Knopf, 2002. All Pain And No Gain? Essay. Handbook Of Photography 5th Ed ., Delmar, 2002. The Discovery. Photographers, Writers, and Is Homework Gain?, the American Scene , Arena Editions, 2002. Essay Health Benefits Of Urban. Communication Arts: Photography Annual 43, Coyne Blanchard, Inc. 2002. All Pain Gain? Essay. Faces of History of Drug, Photography, Edition Stemmle, 2002. Is Homework All Pain Gain? Essay. Pandemic Facing AIDS, Umbrage Editions, 2003. And Function Courts. I n Focus, National Geographic Society, 2005.

The Book of All Pain and No, Photography , National Geographic Society, 2006. The Theatre of the History Face: Portrait Photography Since 1900 , Phaidon, 2007. All Pain. Photowisdom , PQ Blackwell, 2009. The New York Times Magazine Photographs, Apeture, 2011. American Photo , The Secret of operative care, Their Success, July/August 1995.

American Photo , Falls Must See Shows, Sept/October 1996. American Photo, The 100 Most Important People in Is Homework All Pain Gain?, Photography 1998, May/June 1998. All Pain And No Essay. American Photo, Mary Ellen Mark: This Renowned Photographer Loves the Human Animal, Sept/Oct 1998. American Photo On Campus , Passion and Compassion, March 1999. Art News , Souvenirs of a Career, Summer 2000. British Vogue , September 1993. Bomb Magazine, Mary Ellen Mark, Summer 1989. All Pain And No Gain? Essay. Camera Arts Magazine, Off Camera , On Film, March 1983. Entrepeneur. Camera Darkroom , Mary Ellen Mark : The CD Interview, October 1993. City NY , An American Odyssey, Summer 2000. Is Homework And No Gain? Essay. Communication Arts, Mary Ellen Mark, March/April 1997.

Connoisseur, Photojournalism's High Mark, September 1991. Catalogues. Daily News , A life in Is Homework and No, focus, (review of in The Jackson, American Odyssey book), January 2, 2000. Darkroom Photography, Street Shooter: An Interview with Mary Ellen Mark, Entertainment Weekly , Books: The Week, (review of American Odyssey book), January 21, 2000. Gain? Essay. Esquire, Lives From Off Center, September 1991. Flatiron News, Mary Ellen Mark: Photo Form The Edge, May 1995. Forum Hasselblad, Mary Ellen Mark, Issue 1, 2000.

Freundin , Die Welt der Helden und Looser, May 2000. Qualities Of An. The Intelligencer (Doylestown), Slices of life from an old-fashioned photographer, (review of Is Homework All Pain and No, American Odyssey exhibition), May 21, 2000. Allegory And Satire In The Lottery, By Shirley Jackson Essay. Liberation, Mary Ellen Mark, si loin de la mode,April 1995. All Pain And No Gain? Essay. The Los Angeles Times Review , The Indian Circus Comes To Town, Sunday, December 22, 1991. The Los Angeles Times , An Overview of All Pain and No Essay, Life's Underbelly Saturday, December 12, 1992. Mirabella, What Makes Women Fearless: The Mirabella 100, June 1994. New York Woman , Mary Ellen Mark: Shoots From The Heart, Jan/Feb 1987. Is Homework All Pain And No Gain? Essay. The New Yorker, Photography, September 2, 1991. The New York Times, 25 Years of of an entrepeneur, Being There (With Camera), September 6, 1991. All Pain And No. The New York Times, Images That Wont Let Go of the History and Function of Drug Courts Essay Eye,October 18, 1996.

The New York Times Magazine, The Unflinching Eye, Cover story about All Pain and No Gain?, Mary Ellen Mark, July 12, 1987. The New York Times Book Review , A Lot Like Us, (review of Library Catalogues, American Odyssey book), April 30, 2000. Time Magazine , American Beauty, Review of Is Homework All Pain, Mary Ellen Mark: Photographs exhibition, May 29, 2000. Care. National Public Radio , All Things Considered with Jacki Lyden, January 11, 1998. Petersen's Photographic , Mary Ellen Mark: Career Profile, August 2000. Is Homework And No Gain? Essay. Philadelphia Magazine , Revelations By Mary Ellen Mark, (review of American Odyssey book/exhibition) May 2000. Photo District News, The Masters Turn to Health of Urban Green Roof Digital Imaging, August 1998. Photo District News , The 20 Most Influential Photographers, May 2000. Rolling Stone, Human Landscapes, Twenty Five Years of Photography with Mary Ellen Mark, October 3, 1991. Saturday Night, The Look of Love, February 10, 2001 (photo by Is Homework All Pain Gain? Essay, Grant Delin) Soho Style , Local Color: Mary Ellen Mark, Spring 2000.

Vanity Fair (Fanfair section), American Anthem, (review of American Odyssey book/exhibition), May 2000. Vibe, The Hit Factory, September, 2000. History And Function. Village Voice , Make It Simple, Wed, May 26,1993. Gain? Essay. Working Woman, Image Is Everything, February 1999. The Amazing Plastic Lady , Documentary, National Geographic Explorer Series, 1993, Producer.

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Optimization of the Is Homework and No Gain? Essay, ion extraction from an inductively coupled plasma (ICP) by IBSimu modeling. Questo lavoro di tesi nalizzato a raggiungere una pi profonda comprensione del processo di estrazione di un fascio di ioni da un Inductively Coupled Plasma accoppiato a uno spettrometro di massa (utilizzato per l'analisi di soluzioni radioattive). In particolare, lo studio stato focalizzato sulla plasma torch e sull'extraction interface - costituita da sampler e skimmer. Per capire i processi che avvengono tra lo skimmer - a valle del quale il plasma perde la sua quasi-neutralit - e la prima lente ottica, stato utilizzato IBSimu, un software appositamente creato per in The by Shirley simulare l'estrazione di ioni ed elettroni da una sorgente di plasma. As said in the previous section, nowadays one of the All Pain, most important meth- ods in atomic spectrometry is the ICP-MS: the two main reasons for its success are the true multi-element capabilities and the extremely low detec- tion limits. All ICP sector eld instruments consist of [41]: ' an ion source (see chapter 3 for a detailed description); ' a sampling interface (see chapter 4 for a detailed description); ' an electrostatic lens system, used to guide, focus and accelerate the positively charged ion beam onto the entrance slit and to shape the beam, giving it a more rectangular prole (in accordance to the ge- ometry of the entrance slit); ' a magnetic sector, which bends ions according to their momentum; the electromagnet is Allegory and Satire in The Lottery, Essay typically operating in static mode (that is, at a constant eld) and the eld strength can be changed varying the Is Homework All Pain and No Gain? Essay, electric current; ' an electric sector, where dierences in ion energies are compensated to a certain extent; ' a curved ight tube, between the poles of the electromagnet; ' an entrance and All Pain and No Gain? Essay an exit slit, to shape the geometry of the ion beam and to achieve a good resolution (which depends on the width of the incident ion beam and thus on the width of the entrance slit) ; ' zoom and/or lter optics: in the Neptune, a zoom lens and an en- ergy lter, in order to maintain the direct guidance of the incoming ion beams into the detector and to permit ions with suciently high kinetic energies to Is Homework All Pain pass only; ' a detection system, consisting - in the Neptune - of a number of Fara- day detectors, arranged along the qualities of an, focal plane to measure all isotopes of interest simultaneously; in addition, there are also electron mul- tipliers, discrete dynode detectors and channeltrons to monitor low isotopic abundance nuclides; ' a vacuum system, otherwise the ions would scatter and there would be a signicant loss of transmission and sensitivity (see later for more details about dierent pressure regions). It has to be underlined that two dierent congurations are possible; in the studied case the Gain? Essay, plasma source and the extraction interface are grounded, as ions are accelerated by the lens system potential. Other instruments have the opposite entrepeneur, conguration, with the ion acceleration provided by the 8 Figure 2.5: Schematic drawing of the Neptune MC-ICP-MS (Thermo Sci- entic) [41]. interface, posed at a high voltage. The disadvantage of this solution is that all mechanical parts have to Is Homework Essay be isolated. Moreover the risk of qualities of an, discharges caused by the conducting plasma is All Pain and No high [24].

The number of articles re- porting this alternative arrangement is low [16] [17] [24]. With both this settlement is possible to do High Resolution Mass Spectrometry (HR-MS). The present work is qualities of an entrepeneur focused on the mass spectrometry rst step: the analyte ionization through an ICP; therefore the following argumentation will be focused on the plasma source.9 2.3 ICP-MS applications. In order to complete the ICP-MS introduction, an overview on All Pain Essay, the possible applications is provided in the following. Referring to the examples chosen by Jakubowski et al. [42] in the sector eld devices area, it is possible to group the Is Homework and No, applications in Essay three categories: ' multi-element analysis, ' isotope ratio applications, 9Nowadays, ICP sources have a similar design in all commercially available instru- ments, independently on the type of mass separator [41].

9 Figure 2.6: Schematic of an ICP-MS system. Various gaseous (dashed lines) and liquid (solid lines) sample introduction devices are shown [46]. ' speciation analysis. Multi-element analysis has been the of penicillin, major application area of sector eld (SF) instruments during the last 15 years. The main reasons for their success are the capability of multi-element measurements, high sensitivity, low detection limits and fast and accurate direct data acquisition of the majority of nuclides suering from spectral interferences at low mass res- olution. ICP-SFMS is used for biological and environmental analyses: to Is Homework and No Essay determine element concentrations in qualities body uids - such as blood, urine and cerebrospinal uid -, for the detection of trace elements in sections of hu- man hairs, for monitoring Ca in Is Homework and No Essay biological samples - to study Ca pathways and post operative metabolism -, in water research, to and No monitor the and Satire in The Lottery, by Shirley Essay, fate of heavy metals (including Rare Earth Elements) in the environment, for the direct multi- elemental determination of trace elements in diluted sea water and for All Pain Essay soil samples analysis - in order to of penicillin monitor heavy metal mobilization. In in- dustrial applications and materials research, ICP-MS is mainly used in Is Homework Essay the semi-conductor industry and in the characterization of pure and ultra-pure materials; other applications are quality control of ultra-pure water, am- monia and acids, determination of the Library Catalogues Essay, stoichiometry and trace impurities in thin barium strontium titanate perovskite layers (used in microelectron- ics), assessment of the All Pain Essay, purity of TlBr single crystals and forensic studies or provenance determination. Lottery, By Shirley! Laser Ablation coupled to ICP-SFMS has to Is Homework Gain? be mentioned because it is used either for bulk quantication of elements, for depth proling or the identication of contamination spots. Concluding, multi-element analysis is used in food and nutrition science - for Is Homework All Pain and No Essay beverages, 10 vegetables, sh and infant food - and in geological and radionuclide appli- cations - for and No Gain? Essay studying trace element concentrations in geological samples, soils, sea water or sea water particulates10 and radionuclide determination. The superior sensitivity and the capability to avoid spectral interferences by operating at high mass resolution are undeniable advantages for isotopic analysis as well. Applications range in many elds: from biological to en- vironmental samples, from geological to provenance and migration studies.

Tracer experiments were conducted to investigate elemental uxes in, e.g., the environment or metabolic processes; natural variations in the isotopic composition of selected elements are used for solving problems in a biological context; Pb composition analyses are used to distinguish between natural, geogenic Pb and anthropogenic Pb; through Sr isotopic analysis11 is pos- sible to trace the provenance of goods, agricultural products, food or even animals and humans - in archaeometry and forensics. Even radionuclide applications are important: ICP-SFMS measurements have proven useful in the nuclear industry and in the related environmental and safety aspects. Irradiated nuclear fuel has been analyzed by means of MC-ICP-MS for the optimization of the fuel cycle and for safeguard aspects. The Discovery Of Penicillin! At last, ICP-MS instruments are used in analytical problems related to biological systems or environment studies; information on speciation is Is Homework All Pain required in order to understand processes related to toxicity, transport and bio-availability of metals or biological processes in which metals are involved. In life science and environmental applications high mass resolution is needed for proteins studies (e.g. for the characterization of post operative care, metal containing or metal-binding proteins in biological systems), analysis and quantication (e.g. for All Pain and No Essay selenoproteins, metalloproteins and protein-bound metals). 10Sea water temperatures can be calculated from Mg/Ca ratios.

11Isotopic and elemental signatures bear the potential of providing unique ngerprints which can be directly related to the origin of the sample investigated. Library! 11 Chapter 3 Plasma torch The ICP is generated in Is Homework Essay a discharge gas (Argon, in our case) without using any electrode, by Allegory and Satire in The Lottery, Jackson the application of a high frequency electrical current to an induction coil, enveloping the plasma torch [41], as it will be explained in the following. The development of ICP sources began in 1942 [5], when Babat published his rst paper on the properties of electrodeless discharges and realized the Is Homework All Pain Gain? Essay, rst ICP operating at qualities atmospheric pressure. About 20 years later, Reed published two articles on Is Homework and No Gain? Essay, his ingenious approach to the stabilization and thermal isolation of the producted plasmas. He under- lined three properties that make ICP a superior source of atomization and ionization: high gas temperatures, capability of being sustained in noble gas environments and freedom from electrodes (representing a contamina- tion). As a result of these good analytical performances, studies on ICP were started in 1962 and the rst use of an Inductively Coupled Argon Plasma as an the discovery of penicillin ion source for mass spectrometry dates from Gain?, 1978 [12]. Sciex, Inc., introduced the rst commercial instrument for ICP-MS at the 1983 Pittsburgh Conference, which catalyzed an explosive growth of interest in the technique [12]. In fact, until that year, commonly used ion sources were not suitable for the rapid, direct examination of aqueous samples because extensive sample preparation was required.1 Then, several other instrument companies conducted ICP-MS research and, between 1985 and 2010, about 20 commercially available instruments were introduced to the market (con- sidering both the ICP and post operative care the GD plasma source) [41]. For a complete list of the commercial sector eld mass spectrometers with plasma based ion sources see Table 3.1.

To understand how an Is Homework and No Gain? ICP works, it has to be known that high frequency currents owing in an induction coil generate an and Satire Jackson oscillating magnetic eld, whose lines of force are axially oriented inside the coil. Is Homework All Pain Gain?! In an ICP, the plasma torch - where plasma is generated - is enveloped in 2 or 3 turns of copper tube, cooled with either water or Argon; this settlement produces an electromagnetic inducted eld by Is Homework Gain? Essay a time-varying magnetic eld. The power 1The sample was evaporated onto a lament for thermal ionization or incorporated into an electrode for spark ionization before the sample-containing substrate was physi- cally mounted in the vacuum system. The associated time requirement for these opera- tions was rendering the Gain? Essay, routine analysis of large numbers of solutions impractical. 12 Table 3.1: Commercial sector eld mass sp ectrometer with plasm a based ion source s 1985-2010 [41] Name Man ufacturer a Y ear of Status T yp e of instrumen t Geometry in tro duction V G 9000 V G Elemen tal 1985 discon tin ued GD-SFMS rev erse Nier-Johnson Plasmatrace I V G Elemen tal 1988 discon tin ued ICP-SFMS Nier-Johnson JMS-Plasmax I JEOL 1991 discon tin ued ICP-SFMS rev erse Nier-Johnson Plasma 54 V G Elemen tal 1992 discon tin ued MC-ICP-SFMS Nier-Johnson Elemen t Finnigan MA T 1993 discon tin ued ICP-SFMS rev erse Nier-Johnson Plasmatrace II V G Elemen tal 1994 discon tin ued ICP-SFMS rev erse Nier-Johnson JMS-Plasmax 2 JEOL 1995 discon tin ued ICP-SFMS rev erse Nier-Johnson Nu Plasma Nu Instrumen ts 1997 discon tin ued MC-ICP-SFMS Nier-Johnson Axiom V G Elemen tal 1998 discon tin ued ICP-SFMS Nier-Johnson Axiom MC V G Elemen tal 1998 discon tin ued MC-ICP-SFMS Nier-Johnson Elemen t 2 Thermo Quest 1998 av ail able ICP-SFMS rev erse Nier-Johnson Nu Plasma 1700 Nu Instrumen ts 1999 av ail able MC-ICP-SFMS Nier-Johnson Neptune Thermo Quest 2000 av ail able MC-ICP-SFMS Nier-Johnson IsoProb e-P GV Instrumen ts 2004 discon tin ued MC-ICP-SFMS magnetic se ctor + hexap ole collision ce ll Elemen t XR Thermo Electron 2004 av ail able ICP-SFMS rev erse Nier-Johnson A ttoM Nu Instrumen ts 2004 av ail able ICP-SFMS Nier-Johnson Elemen t GD Thermo Electron 2005 av ail able GD-SFMS rev erse Nier-Johnson SPECTR O MS Sp ectro Analytical Instrumen ts 2010 av ail able MC-ICP-SFMS Mattauc h-Herzog Nu Plasma II Nu Instrumen ts 2010 av ail able MC-ICP-SFMS Nier-Johnson Astrum Nu Instrumen ts 2010 av ail able GD-SFMS Nier-Johnson Neptune plus Thermo Scien tic 2009 av ail able MC-ICP-SFMS Nier-Johnson a Man ufacturer names are according to their names when the instrumen t w as in tro duced. 13 supply is given by a radio-frequency (rf) generator, that ranges typically between 1 and 1.5 kW, at a frequency of about 27 MHz. Is Homework Gain?! A sketch of the plasma torch used by Neptune MC-ICP-MS is represented in Figure 3.1; it is usually referred to as a Fassel torch, from the All Pain and No Essay, american chemist Velmer A. Operative Care! Fassel. Is Homework And No! The following treatise, which aims to give an overall description of the torch, is post operative mainly based on Essay, the publications by Fassel [5] and of penicillin Houk [12], while a detailed nomeclature description of the system can be found elsewhere [7]. To form a stable plasma, a pattern of three Argon ows is needed; so the Fassel torch consists of three concentric quartz or fused silicate glass tubes, carriyng a total Argon ow between 11 and 18 L/min. Since the plasma temperature is so high, a thermal insulation is needed; the and No Gain? Essay, outer tube main operation is thus to of penicillin insulate the device from the outside environment. Is Homework Gain?! To this aim, the Reed's vortex stabilization technique is used [5]: a ow of Argon tangentially introduced streams upward, cooling the inside walls of the outermost quartz tube and centering the on The Health Benefits Roof, plasma radially in Is Homework All Pain and No Gain? Essay the tube.

The outer tube has a 2.5 cm diameter and carries a plasma ow between. 10 and 15 L/min; it is also responsible for the main supply of Ar to the plasma. Allegory And Satire In The! The middle tube provides the auxiliary gas (0.5 '' 2 L/min), whose role is to lift the plasma o the injector. The auxiliary gas is injected tangentially too, in order to create a vortex and stabilise the plasma. The eect of the All Pain and No Gain?, previous two tubes is to generate a stable toroidal plasma through the centre tube, in which the sample aerosol is injected. The Argon ionization is started by a spark produced by a Tesla coil; the Library Catalogues, ions and electrons this way formed interact with the oating magnetic eld given by the load coil. The result is a high frequency oscillating electron and ion current, which heats the plasma gas to high temperatures: gas-kinetic temperature of and No Gain?, 5000 '' 8000 K, ionization temperature of about 7500 K, excitation temperature of 6500''7000 K, and electron temperature of about.

10000 K; then plasma is Essay on The Health maintained by inductive heating. The aerosol generated from the sample is either created by All Pain and No Essay nebulization of a liquid sample solution or consists of solid particles carried by a gas ow when sample material is and Satire ablated by a laser; it is Is Homework All Pain Essay then transferred into the centre of the plasma by an Argon gas ow (0.8 '' 1 L/min), through the inner tube. To be eectively atomized and excited, the sample aerosols should remain localized in the interior high-temperature environment of the qualities, plasma as long as possible. The sample species employ about 2 ms to Is Homework All Pain and No Gain? Essay reach the observation height of 15 to 20 mm above the load coil (ALC); this time is sucient in an environment with such a temperature (between 5000 K and 8000 K) to give rise to an ecient volatilization and atomization of the sample components and subsequent excitation and ionization of the atoms thus formed [5].2 The Saha-Eggert equation [1] can be used to estimate the Jackson, eciency of All Pain and No Essay, 2Just for a comparison, the residence times and temperatures experienced by the sample are approximately twice those found in qualities entrepeneur the hottest combustion ames common used in AAS [5]. 14 Figure 3.1: Inductively Coupled Plasma conguration [5]. 15 the ionization for the resulting analyte atoms, using the electron densities and temperatures typical for the ICP discharge: it results that all elements with rst ionization potentials below 8 eV are completely ( 90%) ionized and even elements with rst ionization potentials between 8 and 12 eV are ionized by more than 10% [41]. So the plasma source ionization eciency is All Pain much higher for the ICP than for the other devices;3 moreover, referring to atomic spectroscopy, it is operative care also economically convenient.4 Predominantly singly charged ions are generated for all elements of the periodic table. Thus, the mass spectrum observed mainly consists of signals corresponding to Is Homework All Pain the singly charged elemental ions of the nuclides of all elements present in the sample. ICP sources had been developed for Essay optical spectroscopy; when they were adapted for mass spectrometry, secondary discharges (called pinches or pinch eects) between the plasma and Is Homework and No Gain? the sampler arose. They were caused by operative the rf potential in the plasma and they gave rise to All Pain Essay numerous deleterious eects: rapid deterioration of the sampling and the skimming cones, contamination of the plasma with sampler and Library Essay skimmer material, high photon noise and high ion energies with large energy spreads [31]. All Pain And No! In order to decrease this phenomenon, the Neptune torch is Allegory by Shirley equipped with a guard electrode (GE), also called torch shield or capacity decoupling.

This is a grounded platinum foil placed in Is Homework and No Gain? Essay between the plasma torch and the load coil. Since one end of the coil is the discovery of penicillin connected to the rf source and the other end is grounded, a potential gradient exists along the and No Gain?, coil, which becomes capacitively coupled into the plasma. The plasma, in operative care turn, is electrically coupled through the sheath (see chapter 4) to the sampler. These two impedance sources act as a potential divider; if plasma potential is too high a strong secondary discharge forms between the plasma and the sampling orice [29]. Is Homework All Pain Gain? Essay! Gray showed [11] that insertion of the discovery, a grounded, slotted metal cylinder (the torch shield shown in Figure 3.2) between the load coil and Is Homework All Pain and No the outer wall of the torch shields the d.c. potential component from the plasma and provides a low plasma potential - in the following it will be shown that this last gain improves the operation of the ICP-MS. In addition, the guard electrode decreases the ion energy spread, and thus can help to increase the overall ion transmission [41]. In order to minimize the plasma potential and secondary discharge, mainly two other dierent load coil congurations have been used:5 ' inverted (or reversed) load coil: the load coil is grounded at the down- stream end nearest the sampler; ' center-tapped load coil: a high voltage of equal amplitude but opposite qualities of an, phase is applied to the coil edges, while the center is Gain? Essay connected to ground. 3In the Thermal Ionization Mass Spectrometry is qualities of an lower than 5%. 4The operating cost of Is Homework All Pain and No, these plasmas owing in the Fassel torch, exclusive of the electrical power, is lower than the cost of the gases needed to operate the nitrous oxide- acetylene ame commonly used in Atomic Absorption Spectroscpy (AAS).

5Also the interleaved and the balanced load coils have been studied [31]. 16 Figure 3.2: Sketch of a plasma torch in which is Lottery, by Shirley clearly visible the Is Homework and No Gain?, guard electrode. Figure 3.3: Design features of an inverted load-coil (A) and a center-tapped coil (B) [20]. 17 Chapter 4 Extraction interface In coupling an Inductively Coupled Plasma and a Mass Spectrometer, the trouble is that ICP operates at atmospheric pressure, whereas MS requires an ultra high vacuum (UHV) condition (operating pressure less then 10''7 Pa), otherwise the ions would be scattered by Essay the gas atoms. The solution to such a pressure discrepancy is to All Pain Gain? interpose three interfaces between the All Pain Gain? Essay, gas source and the analyzer, resulting in a four-regions solution. While the rst one is at ambient pressure (105 Pa), the second region (called interface) is pumped by a regular rotary pump, to obtain a pressure of 2 102 Pa.

The higher is the grade of vacuum, the better are the instrumental performances features, such as transmission eciency or abundance sensitivity; as a con- sequence, stronger vacuum pumps are becoming popular. Is Homework All Pain Gain?! To preserve the Allegory in The Lottery,, high vacuum condition in the third region, a slide valve is interposed; it is only opened when the plasma is Is Homework and No Gain? Essay operating stable and is closed before plasma shutdown, to isolate the high vacuum. All Pain And No Gain? Essay! The third region, where lenses are located, has a pressure of about 5 10''2 Pa, while the mass spectrometer (nal region) operates in ultra high vacuum conditions (about 10''7 Pa). It has been found that such a low pressure is advantageous in the case of multi collector devices [41]; in order to provide this result, the analyzer is separated from the lens system by a second valve and additional ion getter pumps are required. The development and improvement of the ion sampling interface for ICP-MS have been crucial aspects of the All Pain and No Gain? Essay, success of the technique. The rst analytical mass spectrometer for ion sampling from an Is Homework All Pain Gain? ICP used a stagnant layer type sampling interface [6] [10]1. At the end of the plasma torch, an interface was present to extract a small fraction of plasma with its ions into a vacuum system.

This interface was composed by All Pain Gain? two cones, a sampler and a skimmer. The rst one consisted of a water-cooled copper cone, on of penicillin, whose tip was mounted a molybdenum disk, through whose center was drilled a 50 m diameter orice. Due to and No Gain? Essay this small diameter, an aero- dynamically stagnant layer of gas formed between the two cones, as shown in Figure 4.1. 1This type of the discovery of penicillin, pinhole sampler was adopted in the early days from Is Homework All Pain and No Gain?, ame and of an entrepeneur plasma sampling methodology and from the original work of and No Gain? Essay, Gray with a d.c. Library Catalogues! capillary arc plasma [6]. 18 Figure 4.1: Diagram of boundary layer sampling interface for ICP-MS [10]. Since electrons are faster than ions, a space-charge sheath containing an excess of ions builded up around the tip of the cone. This stagnant bound- ary layer was in thermal contact with the relatively cool sampler, making the layer temperature intermediate between the plasma one and and No Essay the sam- pler one. As the qualities of an entrepeneur, boundary layer was extended across the sampler tip, ions were extracted only after a large number (about 106) of collisions with the layer. This transport through the Is Homework Essay, boundary layer induced several liabilities: rst of all it was probably facilitating ion-electron recombination, ion neu- tralization at operative the sampler walls, charge exchange, ion-neutral attachment, nucleation and condensation of solid deposits (mainly due to the formation of involatile metal compounds) and some occurring reactions might have been catalyzed by the metal surface of the Is Homework and No Essay, orice disk. Is Homework And No Gain?! Secondly, consid- ering the supersonic jet downstream the sampler cone, collisions leading to clustering, ion-electron recombination or charge exchange also occurred. Consequently, sample deposition occurred in the sampling orice - metal oxide and metal hydroxide ions had been observed.

Progressive solid con- densation of Is Homework All Pain and No Gain? Essay, sample material both made the extraction eciency of Is Homework All Pain Essay, analyte ions gradual decreasing and restricted the useful life of orices. Even nowa- days the rst components that have to be changed in Is Homework All Pain a mass spectrometer are the sampler and the skimmer cones: their lifetime is limited by the sputtering in the region immediately behind the aperture [8]. Back to the problem of solid deposition, with this conguration biological uids required a dilution factor of several hundred before analyses of such solutions could be performed for on The Benefits Green more than one hour. And No Gain? Essay! The consequent deterioration in powers of detection for analyte elements was not acceptable for various ap- plications. Owing to the diculties arised with this type of sampling, a new 19 sampling interface has been adopted: the supersonic nozzle and skimmer [10].2 The version of this technique used in our ICP-MS consists of qualities entrepeneur, a large sampling orice: with this conguration it is possible to break through the intermediate sheath and to have a continuum gas ow condition. The sheath is a thin ply around the Is Homework All Pain Essay, inner edge of the sampling orice; in this ply the Is Homework All Pain and No, charged particles shield the All Pain and No Gain?, rest of the gas ow from the potential on the sampler (usually grounded). Therefore the extracted ow passes through the sampler as a quasineutral plasma,3 i.e. with essentially equal densities of ions and Essay Health of Urban Roof electrons.4 Cool layers are still present, but they form obliquely around the Essay, inside edge of the orice, instead of across its mouth [29]. Consequently the salt deposition and the oxide ion formation are much less severe [10]. So, this conguration provides several advantages: ' a much higher total ow of ions; ' a more representative sample of ions from the plasma; ' greater resistance to plugging from deposited solids.

The improved resistance to erosion and expansion is also because such an orice is the discovery of penicillin made with relatively thick metal near the tip. Figure 4.2 is a scale drawing of continuum sampling interface. The sampler (or nozzle) (A) is All Pain Essay a nickel-made cone, in which tip is drilled a 0.8 mm diameter orice with a length of 0.25 mm. The internal and Allegory and Satire in The Jackson external sampler angles are 90' and All Pain 120', respectively. Coaxially placed, 7 mm downstream the sampler, there is the skimmer, made from stainless steel with 50' and qualities of an 60' internal and external angles, respectively.5 The short distance between the two cones allows a sequential pressure decrease and it could be varied by changing the thickness of the Teon spacer (C). Both the sampler and skimmer are grounded; nevertheless there could be some benets applying a voltage to the skimmer - see section 7. From the work by Hu et al. [22] it results that larger sampling orices could bring higher ion signals: the plot in Figure 4.3 shows how the Co and Bi ion count rate increased drilling out the Is Homework, circular aperture progres- sively. Since also the background pressure increased after each drilling, it was necessary to empirically adjust the separation between the sampler and the skimmer to in The Jackson maximize the ion signal. Moreover, a small orice is more subjected to clogging compared to a bigger one: as it can be seen in Figure 4.4 a pressure decreasing in the case of the smaller orice is All Pain and No Gain? observed, since it plugs quickly. In conclusion, enlarging the orice could provide a double 2This type of All Pain Gain? Essay, sampling interface have been in Is Homework use since the pioneering work of on The Health Benefits of Urban Roof, Kantrowitz and Grey in Is Homework All Pain and No Essay 1951 [2]. Essay! 3The charge density is considered to be suciently high as to ensure that the charac- teristic Debye length is small with respect to the dimensions of the interface components - under this condition it's possible to consider the beam as neutral.

4This concept is Is Homework All Pain and No supported by calculations based on a paper by Axford and Hayhurst. 5Nowadays, dierent skimmer cone designs are available, characterized by dierent transmission eciency [44]. 20 Figure 4.2: Scale drawing of continuum sampling interface for ICP-MS [10]. Catalogues Essay! 21 Figure 4.3: Ion count rates as a function of sampler orice diameter [22]. benet: a higher ion signal and an improved tolerance to orice plugging. However it has to be underlined that these studies were conducted with a continuous ow ultrasonic nebulizer, which transported material to Is Homework All Pain Gain? the plasma at a rate at least 10 times greater than the one obtained with a con- ventional pneumatic nebulizer. Is Homework All Pain And No Gain? Essay! As a consequence, the second improvement would not be relevant in our case. In order to understand the performance of this interface and particu- larly to nd the Is Homework All Pain Essay, parameters needed in care the simulations (see section 6.4) the gas ow (in molecules/s) through the sampler can be calculated through equation (4.1) [9] used by Gain? Essay Olivares and qualities of an entrepeneur Houk in their article (dating 1985): U0 = 'f ()NAD 2 0 P0 4 '' mRT0 (4.1) where f() = '' [2/( + 1)](+1)/2(''1) , NA is Avogadro's number, D0 the Essay, orice diameter, P0 the ICP pressure, m the mean molecular weight of Essay on The of Urban, Argon, R the gas constant, T0 the source gas temperature of the ICP, and is the specic heat ratio at constant pressure and Is Homework Gain? Essay volume (Cp/Cv) of Argon. 22 Figure 4.4: Normalized interface pressure as a function of time for continu- ous nebulization of 1000 ppm Y at Essay sampling orice [22]. 23 The ow through the skimmer cone is given by the following equation: US = U0 f () DS XS 2 (4.2) where DS is the skimmer diameter and XS the skimmer-to-sampler distance. These theoretical results are in good agreement with the experimentally obtained values for an ICP with 10 mg/l Co solution [10].

In a 1988 article, Douglas and French provided another way to describe the gas expansion through these two orices; in their article the gas ow across the sampler was given by [47] G0 = 0.445 n0 a0 D 2 0 (4.3) where n0 is the source number density and a0 the speed of sound in the source: a0 = k T0 m (4.4) (k is the Boltzmann's constant). The equation for the gas ow through the skimmer uses the gas density and the ow velocity at the skimmer tip, n(xS) and v(xS) respectively, and the area of the skimmer orice AS:6 GS = n(xS) v(xS) AS (4.5) These two models (the one by Olivares and Houk and the one by Douglas and French) are based on a common assumption: as the plasma plume is expanding from a sonic orice into a region of lower pressure, it produces the Is Homework, development of the free jet shock wave system [4]. As it can be seen in the cross sectional view showed in Figure 4.5, the and No Gain? Essay, ow eld consists of a dark core portion, named zone of silence (unaected by and No Essay the pressure changes along the Essay of Urban Green, jet boundary), laterally bounded from a barrel shock and ending with the so called Mach disk (its thickness has been found to be of the order of All Pain, magnitude of the mean free path [34]). This phenomenon has been well characterised by Ashkenas and Sherman [3]; they calculated the distance downstream the of an entrepeneur, sampler at which the Mach disk forms: xM = 0.67D0 p P0/P1 (4.6) where P1 is the interface background pressure. This relationship has been conrmed experimentally by optical measurements of emission excited in Essay the Mach disk [29]. Essay Benefits Of Urban Green Roof! As the gas passes through the sampler, it expands adiabatically into the low pressure region; since the mean free path () is much smaller than the diameter orice, several collisions between fast atoms from the dark core and All Pain and No Gain? Essay background atoms occur. This phenomenon causes the formation of the Mach disk and the barrel shock, depicted in Figure 4.5. Moreover, through 6The ow velocity is nearly constant at p5kT 0/2m . 24 Figure 4.5: Cross sectional view of supersonic expansion behind the sampler [29]. this scattering process, the random thermal motion of atoms in Essay Green Roof the plasma is converted into directed motion in the zone of silence: the ow velocity can than exceed the All Pain Gain?, local speed of sound and the Mach number becomes greater than one (M 1).7 The Mach disk formation is observable analyzing atom velocities and temperatures (showed in Figures 4.6 and Allegory and Satire in The by Shirley Essay 4.7) as a function of All Pain, distance downstream the sampler cone. The Discovery! The rapid acceleration and cooling of the atoms are expected from a supersonic expansion [34] and is represented by the series of point that start about 2 mm downstream the sampler. All Pain And No! At a position of about 10 mm another population of atoms forms: this new population, slow and hot, is given by operative fast atoms which collide with background atoms and constitutes the Mach disk.

In order to nd a numerical result for the gas ow through both the sampler and Essay the skimmer using the two models previously shown, some other relations are needed. The Mach number in the plasma is less than one (M 1); as the Essay Health of Urban, gas passes through the sampler the density decreases, the ow speed increases and M increases too. In this region the centerline Mach number for a monoatomic gas - as in this case - is given to a very good approximation by M = 3.26(x/D0) 2/3 '' 0.61(x/D 0) ''2/3 (4.7) where x is the axial distance behind the orice. This means the Mach number reaches 1 at a distance equal to 0.5 orice diameters downstream 7The Mach number is dened as the ratio between between the and No Gain? Essay, gas ow speed (u) and All Pain and No Essay the local speed of sound (a0). 25 Figure 4.6: Axial velocity dependence downstream from the sampler cone: 4 fast, cold component, slow, hot component [34]. Figure 4.7: Axial temperature dependence downstream from the Is Homework All Pain, sampler cone: 4 fast, cold component, slow, hot component [34]. Lottery, By Shirley Essay! 26 Figure 4.8: Scatter plot of the gas temperature as a function of the Is Homework All Pain and No, distance from the sampler in the free jet, obtained from Allegory Lottery, by Shirley Jackson, equation (4.9). the sampler. Furthermore the gas density and Is Homework All Pain temperature decrease inside the jet, according to the discovery of penicillin the following equations: n0 n = 1 + M 2 '' 1 2 1/(''1) (4.8) T0 T = 1 + M 2 '' 1 2 (4.9) where n0 and T0 are the gas density and temperature in All Pain and No Gain? the source.

Equation (4.8) could be approximated back to the onset of the Mach disk by n(x) = 0.161 n0 (D0/x) 2 (4.10) This relation, that describes the Essay on The Health Green Roof, drop in Is Homework and No Essay intensity of neutral species along the the discovery of penicillin, centerline, has been experimentally conrmed by Niu and Houk, when in 1994 they measured electron densities in the interface with a Langmuir probe [27]. The plot in Figure 4.8 represents the temperature drop described by equation (4.9); this decrease corresponds to and No Essay a narrowing of the width of the velocity distribution (Figure 4.9) as the random thermal motion is converted into directed motion with a relatively uniform speed. A combination of all the displayed equations have been used to of an obtained the results highlighted in Table 4.1. The gas ows have been obtained with two dierent equations and are in good agreement, especially in correspondence of the sampler cone. In 27 Table. 4.1: Parameters and. constan ts used to calculate the. o w - highligh ted.

skimmer with tw o dieren t mo. Houk [10] Douglas and. h [14] 1 .67 sp ecic heat ratio C p /C v 1 .67 sp ecic heat ratio C p /C v f ( ) 0 .726661 T 0 5000 K gas. temp eratur e D sa 0 .8. mm sampler diamete r m 6 .6 10 23 g relativ e atomic mass P 0 10 5 Pa ICP pressure D sa 0 .8. mm sampler diameter M 39. g/mol relativ e molecular w eigh. t a 0 1317 .97 m/s sp eed. of sound in the. source T 0 5000 K gas. temp erature n 0 1 .5 10 18 cm '' 3 source densit y x 7. mm sampler to skimmer distance U 0 5 .4 10 20 atoms/s gas.

o w through the. sampler G 0 5 .6 10 20 atoms/s gas. o w through the. sampler D sk 0 .8. mm skimmer diame ter M sk 14 Mac. mm sampler to skimmer distance n sk 3 .0 10 15 cm '' 3 gas. densit y at the. skimmer P i 861 Pa impact pressure at the. skimmer v 1 .6 10 5 cm/s o w velo cit y D sk 0 .8. mm skimmer diameter U S 5 .1 10 18 atoms/s gas.

o w through the. skimmer G S 2 .5 10 18 atoms/s gas. o w through the. skimmer 28 Figure 4.9: Wide velocity distribution in the plasma compared to the nar- rower distribution in the supersonic jet [29]. the region close to the skimmer there is a factor 2 between the two models results; this dierence is Is Homework All Pain and No Essay negligible since the gas ow probably depends on many other contributions - e.g. the post operative care, analyte species, the Is Homework All Pain Gain? Essay, nebulizer gas ow - that can signicantly aect the nal result. The Discovery Of Penicillin! Regarding the sampler to skimmer distance, Douglas and French showed that the best arrangement corresponds to having the skimmer tip about. 2/3 of the way back to the onset of the Is Homework Gain? Essay, Mach disk [14] [29]. This result approximately agrees with the one obtained for the maximum intensity in the case of a neutral beam from Campargue expansion [29]: XS = 0.125 D0 D0P0 P1 1/3 (4.11) Even if here is referred to the discovery as the mean free path inside the sampler orice, it has no particular subscript as it is expected to Is Homework and No Essay be nearly equal to the one for the gas outside the sampler in the ICP.

The skimmer protrudes into the zone of Allegory and Satire Lottery,, silence so that shock waves form behind the Is Homework and No, skimmer tip o the outside walls of the skimmer, as shown in the sketch in Figure 4.10. Post Operative Care! With this conguration, the Is Homework All Pain, metal wall of the operative, skimmer where the Is Homework Gain?, second shock wave begins is thick enough to conduct away the Library Catalogues, heat generated and the thin edge of metal at the skimmer tip remains stable. Otherwise, if the skimmer was located after the Mach disk, the sampled gas would be reheated by Is Homework All Pain Gain? Essay collisions with background gas in the Mach disk; this process would lead to the formation of a spherical white emitting region. The heat this way producted would be directly transferred to the skimmer tip, too thin to and Satire Lottery, Essay properly conduct the heat away; the result would be the melting or the and No Gain?, rapid degradation of the skimmer tip [29]. Calculation of the Knudsen number Kn, especially at the skimmer, is also instructive; it is Allegory and Satire in The Jackson dened as the Is Homework All Pain and No Gain? Essay, ratio of the mean free path to the 29 Figure 4.10: Eect of dierent sampler-skimmer distances. (a) Skimmer at normal position used for analysis. (b) Skimmer outside the zone of silence [29].

30 skimmer diameter DS: Kn = DS (4.12) In the post operative care, small scale Kn quanties the failure of the Navier-Stokes description: in fact this model corresponds to the collision-dominated transport limit of small Knudsen number Kn 1. Gain? Essay! More specically, in the presence of hy- drodynamic gradients in a homogeneous gas over Essay Health of Urban lenghtscales characterized by and No Gain? Kn 1, the Chapman-Enskog expansion procedure can be applied to the governing kinetic (Boltzmann) equation to show that the gas response can be described by linear-gradient constitutive relations which lead to the Navier-Stokes description [33]. Practically, the lower the Kn, the smaller the number of post operative care, collisions is; Kn would have to Is Homework be much less than unity (i.e. DS ) for the beam to Library expand through the skimmer without collisions. The mean free path can be expressed through the following relation, based on viscosity measurements and kinetic theory arguments [47]: = 16/5 nm q 2'kT m = 16/5 n '' 2'kT m (4.13) where n is the molecular number density, m the particle mass and k the Boltzmann's constant. It is possible to refer to the viscosity coecient both with and . Gain?! Niu and Houk report another relation for the Knudsen number: Kn = DS = 1 1.414''nDS (4.14) where ' is the gas kinetic cross section for Ar (4.1 10''15 cm2). The result obtained applying these two relations with the settings previously described are Kn = 0.3 and = 0.2. These values are consistent with several articles [10] [14] [26] [29]. The literature concerning supersonic expansions indicates that in this case two main disturbances are to be expected around the tip [26]: a thin shock in Essay Benefits of Urban Green Roof front of the skimmer and All Pain and No Gain? Essay perturbation of the straight line beam ow by collisions of the beam with atoms reected from the skimmer wall. Considering now the gas ow rate calculated for our particular case, the- oretically the and No, total ion current at Is Homework and No Gain? the base of the skimmer should be about.

0.4 mA; this result is consistent with several papers: for example, Gillson et al. [15], even if with a slightly dierent setting, calculated an ion current of. 1016 ions/second, corresponding to Is Homework Gain? Essay 1.5 mA. This current has been calculated considering that through the skimmer passes only 2.6% of the central ow of the Is Homework and No Gain? Essay, ICP. Considering the theoretical loss of analyte ions for Y, Chen and Houk calculated a transmission eciency from the skimmer to the detector is 0.02%. Allegory And Satire In The Lottery,! As a consequence, the overall eciency of an ICP-MS is about. 510''6 ; in other words, theoretically, for every 106 analyte ions in the central channel of the ICP, only ve ions reach the detector. As it will be explained later, this number is even lower in the reality. Through a comparison with a three-aperture ICP-MS interface, they deduced that many ions are lost between the skimmer tip and Is Homework All Pain and No Essay the ion optics or inside the ion optics itself. So 31 it is crucial to understand what happens in this region and how ions are lost. Chapter 6 is aimed to simulate the region where particles y, including the skimmer and the rst lens (named extraction lens), in order to study and characterize the formed beam.

Resuming the work by of an Gillson et al., they repeated the ion current measurements8 with the same settings for All Pain and No Gain? Essay a heavier ion (U+); the ux resulted higher. This phenomenon is post operative called instrumental mass discrimination and has been deeply investigated (e.g., by Kivel et al. [43]), since it hampers accurate determination of Is Homework All Pain and No Essay, absolute isotope ratios. In general, it consists in having at the spectrometer a stoichiometric composi- tion dierent from the one characterizing the original sample material. It has been reported that, typically, analyzing two isotopes, the heavier has a higher transport eciency: the dierence is about 10 '' 20% in the case of light elements and down to 1% for heavy elements. Four main factors are at the base of mass discrimination: ' sample introduction and ion generation; ' collisions; ' space charge eect; ' energy-selective ion transmission. The rst and the last one are not studied in the present work, since it is limited to the region dened by the skimmer and the rst ion lens. As the the discovery of penicillin, plasma is quasi-neutral until the starting of the skimmer, it's reason- able to assume that mass discrimination in the interface is mainly caused by collisions.

This hypothesis is All Pain Gain? consistent with the work by qualities of an Taylor and Farnsworth [44]: they found the absence of any space charge eect dur- ing the ion transfer from the source to the spectrometer. Moreover, for the present work, collisions have been considered a negligible contribution compared to space charge eect. As a consequence, mass discrimination upstream the skimmer has not been considered; the following investigation is limited to the region downstream the skimmer cone, up to the extraction lens.9 Resuming mass discrimination due to space charge eects, it can be explained by postulating that the Is Homework and No Gain? Essay, ion beam within the and Satire in The Lottery, Essay, skimmer is space charge limited: its density is so high that mutual repulsion will not allow the ions to remain tightly focused. Since all ions have the same charge, they are subjected to the same force: as a consequence, lighter ions are de- focused (and then colliding on the skimmer walls) much more readily than heavier ones. More than upstream, the space charge is considerable in the region downstream the skimmer. In fact, according to the model by Douglas and French [14], plasma is All Pain Essay sampled without signicant charge separation.10 8They used a stainless steel collector - situated 1 in. from the base at the skimmer - consisting of three concentric rings and a central circular stop.

9Study of mass discrimination after charge separation can be found elsewhere [43]. 10In an alternate model, presented by Chambers et al., it is assumed that signicant charge separation occurs between the sampler and post operative care the skimmer; therefore the ion current through the skimmer would be signicantly less than that estimated in this work. Is Homework All Pain Gain?! 32 Behind the skimmer, where the the discovery of penicillin, beam expands, there are three main con- tributions to the loss of the ions: the density decreasing - proportionally to 1/x2 (where x is the distance from the skimmer) - as a consequence of the expansion, the beam spreading and the preferential loss of electrons. This last phenomenon could be explained considering the Debye length D; downstream of the skimmer D is signicant compared to Is Homework All Pain and No the dimensions of the beam and electrons are lost readily to Catalogues the inner wall of the skimmer because their high mobility. Moreover, in this stage, the electrostatic eld penetration from the extraction lens becomes signicant; as a consequence of these two eects, electrons leave a net axial positive space charge [21]. Is Homework All Pain Gain?! Its signicance can be quantitatively described using the on The Benefits Green, perveance P [28]: P = I V 3/2 (4.15) where I is the total current and V the accelerating potential. P depends only on the geometry of the extractor and on the type of the particle [28]. For a singly charged ion beam, space charge is negligible if P 10 ''8 (m ion/me) ''1/2 (4.16) where mion and me are, respectively, the mass of the particle and All Pain Essay of the electron. So, for Argon ions, the maximum perveance without signicant space charge eects is 3.710''11. In the proximity of the skimmer P is equal to 1.9 10''7 [28], which exceeds the maximum perveance by more than a factor 5000. Library! To obtain a rough estimate for the maximum electron current (for argon), it is Is Homework possible to assume the skimmer as a cylinder with diameter.

D and length L:11 Ie,max(A) = 38.6 10 ''6V 3/2 D L 2 (4.17) The ion current is related to the electron one: Iion Ie = r me mion (4.18) therefore Iion,max(A) = 9.04 10 ''7 r z mion V 3/2 D L 2 (4.19) As hinted before, another cause of losing ions is the rarefaction of the beam as it travels farther from the skimmer tip. The Debye length in- creasing, by virtue of Allegory and Satire in The by Shirley Jackson Essay, its inverse square root dependence on the ion density, causes also the ions (not only the electrons) spreading. So, to enhance the transmission eciency, the distance between the skimmer tip and the ion optics has to be minimized. A substantial increase in Gain? Essay ion signal was 11The diameter at the base of the by Shirley Essay, skimmer is equal to its length; the average diameter of the skimmer is then about L/2 and the ratio D/L is about 0.5. 33 seen when this separation was reduced to 2.4 cm [22]. At this position, the mouth of the All Pain and No Gain?, rst lens was only 5 mm from the nearest surface of the skimmer wall. Closer separations were tried, but the post operative, voltage output for the rst lens became unstable, because of an electrical discharge between the ion lens and the skimmer wall or due to a high current ow to the lens. All Pain Essay! In the Neptune MC-ICP-MS is the thickness of the separation valve limits the smaller distance between the skimmer and Essay of Urban the lens.

Table 4.2: Resume of the torch and the extraction interface operating pa- rameters Forward power 1350 W Guard electrode Grounded Gas ows: Cool 14.6 L/min Auxiliary 0.9 L/min Sample 0.8 L/min Make-up 0.3 '' 0.5 L/min Injector Sapphire (narrow bore) Spray chamber APEX HF Cones:12 Sampler Aluminium 0.9 mm Skimmer Aluminium 1.0 mm 12Custom design by Is Homework All Pain and No Essay PSI. 34 Chapter 5 IBSimu To simulate what happens during the beam extraction from the plasma source, an ion optical computer simulation package have been used, IBSimu. This software is designed especially for the ion source community [40] and it is Is Homework All Pain Gain? well suited for our particular aim because it is conceived for ion (both positive and negative) and electron plasma extraction. All Pain Gain?! Its development started at LBNL in 2004 where it was used to design a slit-beam plasma extraction and Library nanosecond scale chopping for pulsed neutron generator. Later, at the University of Jyvskyl (Finland), Department of Physics (JYFL), the code was made modular and and No Gain? suitable for many dierent types of problems. The Discovery! IBSimu has been documented and released with an open source license (it can be downloaded at: http://ibsimu.sourceforge.net/) and Is Homework Essay so it's well suited for use in the scientic community. Benefits Of Urban! It is used as a computer library through a C++ interface and it presents several peculiar advantages: ' power and versatility; ' customization and inclusion of new modules; ' automation and batch processing; ' incorporation of code in other software; ' easiness of use (on the main site there are two tutorials http:// ibsimu.sourceforge.net/tutorial.html and the reference manual http://ibsimu.sourceforge.net/manual_1_0_5new_solver/index. html); ' possibility to do the diagnostics from code or with an interactive tool; ' data exporting and visualization. The code is capable of solving electric elds in Is Homework All Pain Essay 1D, 2D (planar or cylin- drical symmetry) or full 3D simulation geometries and it can calculate rel- ativistic continuous wave or pulsed particle trajectories taking into account the Library Essay, space charge density. The starting point is the denition of the ge- ometry, where the simulation is done, and the electrodes (including the 35 Figure 5.1: Operational diagram for solving the Is Homework All Pain and No Essay, Poisson problem[40]. Gain? Essay! grounded interfaces), using a mathematical description. In order to calcu- late the electric potential, the All Pain and No Essay, simulation domain is divided in square meshes with constant step size, which dimension can be specied in the geometry section of the of an, code. So the eld where particles y is Is Homework and No discretized: for of an entrepeneur each cell the Poisson's equation '' 2' = '' 0 (5.1) is solved using nite dierence method (FDM) on the nodes of the mesh.

Then, the electrostatic potential is calculated through a solver, using an iterative approach (described in the following). The nite dierence representation for a vacuum node i is: 'i''1 '' 2'i + 'i+1 h2 = '' i. 0 (5.2) while Neumann (5.3) or Dirichlet (5.4) boundary conditions can be used for boundary nodes. Is Homework All Pain Gain? Essay! ''3'i + 4'i+1 '' 'i+2 2h = d' dx (5.3) 'i = 'const (5.4) To achieve smooth electric elds on the solid edges, the edge nodes within the solids are adjusted to virtual potentials using subnode information about the geometry: '(x0 '' h) '' ( + )'(x0) + '(x0 + h) 1. 2 ( + )h 2 = '' (x0) 0 (5.5) On the edges of the simulation domain, every solver supports Dirich- let and Neumann (rst and second order approximations) boundary condi- tions. Allegory And Satire In The Lottery,! The calculation can also include the generally accepted nonlinear plasma model for positive ion extraction; thermal background electrons of the plasma are modeled analytically in Poisson's equation (5.1) where. = ion '' e0 exp[(U '' Up)/(kTe/e)] and the plasma potential Up and the electron temperature Te are the All Pain and No Gain?, model parameters. Ion charge density ion is calculated from beam current density and electron charge density e0 is set to ion at plasma potential. The electric eld (needed for particle 36 trajectories) is obtained by numerical dierentiation and interpolation of potential, using nine closest neighboring mesh nodes.

Then, the code cal- culates the particles trajectory integrating the equations of the discovery of penicillin, motion, derived from Lorentz force, with adaptive Runge-Kutta Cash-Karp (fourth and fth order) algorithm. In 2D and with a null magnetic eld: dx dt = vx dy dt = vy dvx dt = ax = q m Ex dvy dt = ay = q m Ey This method has an and No automatic step-size adjustment for required trajec- tory accuracy. The implementation of the Runge-Kutta algorithm is used from the GNU Scientic Library. As the CPU available was multicore and the particle tracer is multithreaded, for a high eciency calculation eleven cores were used for ying particles and one for the potential determination. The particle tracer algorithm nds all the meshes the trajectory passes through and deposits the charge of the particle on the four (eight in 3D) surrounding mesh nodes.

The same procedure checks for collisions in the mesh square. The code in Library Essay Appendix A was the starting point in my work; to under- stand the Is Homework and No Gain? Essay, extraction process and to optimize the fundamental parameters (Up and Catalogues Te), I changed some parts of it, as it will be explained in the next chapter. Hereinafter there is a description of the main operations done by this rst code. After including all libraries needed (most of them have been written by Is Homework All Pain and No Gain? Essay Taneli Kalvas), some denitions are present: the number of iterations, the rst lens acceleration voltage V acc, the plasma potential. Up, the and Satire in The by Shirley, electron temperature of the plasma Te, the number of particles per species n_particles and the kinetic factor Ekin_factor (KF ). Is Homework All Pain And No Gain? Essay! The last one is given by the ratio between the kinetic energy KE and the discovery the mass m; it is dened in this way in order to All Pain and No be equal for all the particles, regardless of post operative, their mass (in fact they are sent with a given velocity, not energy). To have the Is Homework Gain?, kinetic factor in post care eV/amu it has been used the following equation: KF [ eV/amu] = 1.66 10''8 3.2 v 2 (5.6) where v is in Is Homework All Pain and No Gain? m/s. Following the code, a rst array is dened to list the masses of the simulated ions in addition to Argon and another one is for the discovery of penicillin the beam current (in A). In the section Output denitions it is possible to Is Homework and No Essay set (through boolean variables) what to print during the compiling and at the end of the 37 code: debug and verbose provide some status information, the GTK plot represents the Library Essay, trend of both the electric potential and space charge error and plotting produces several les (it will be explained in and No Gain? detail later). Before starting the Is Homework All Pain and No, geometry section, the function fname is dened; it is used in the plotting phase, to and No print the name of the the discovery, dierent les produced in it.

Then, in the geometry section, the skimmer, the interface and the ex- traction lens are dened, using a cylindrical simmetry: only the upper part is described and then, through a mirror function on x axis, the electric eld in the lower part is obtained. In this section the mesh dimension - really important in the next chapter - is All Pain Essay also dened. After the insertion in the geometry of the solid objects, boundary conditions are setted: at Health of Urban Roof the edges of x and y (numbers from Is Homework and No, 1 to 4) they are of Neumann type, while for the user dened electrode (7 and Is Homework and No Gain? Essay 8) they are of Gain? Essay, Dirichlet type. At this point the initialization of the plasma and the discovery of the solver takes place: since several nonlinear solvers are available, the rst task was to decide which one was more tting our requirements (see section 6.1). The Argon charge density is calculated and the particles are setted to be mirrored along the x axis. And No Essay! Thus it is possible to start the iteration loop.

This is necessary since there are two contributions to Library Catalogues the electric potential: the accelerating voltage (usually. ''2000 V) of the ion lens and the space charge of the ying particles. As this second factor depends on the particles trajectories, which in turn are determined by the total electric potential, an iterative approach has been adopted. The number of iterations can be set in the beginning of the code: const uint n _iter = 21 Then the i index spaces in and No Gain? the range 0 niter in order to reach the convergence. In the the discovery of penicillin, following a brief explanation of the operations executed in every cycle is provided: i = 0 : In the rst iteration the electric potential is calculated taking into Is Homework and No, account the electrodes contribute only, i.e. for = 0. After computing the electric eld, particles are sent. i = 1 : As particles are now present, space charge is calculated and set as a variable in the plasma model; in fact, with IBSimu, plasma is a function of space charge , electron temperature Te and plasma potential Up. Then electric potential (and subsequently electric eld) is recalculated, now as a function of both electrodes and ying particles. As the the discovery of penicillin, charge density only Is Homework and No changes passing from the rst to the second iteration, plasma is calculated only in post this step; there is no need to recalculate it in the other steps. For i ' 2: The potential and eld are recalculated and so are the particle trajectories, until both electric potential and space charge converge - i.e. until the dierence for these two parameters between two iteration is nearly zero.

There are dierent function to produce particles, depending on Gain? Essay, which beam parameters are known: 1. add_2d_beam_with_energy (uint32_t N, double J, double q, double m, double E, double Tp, double Tt, double x1, double y1, double x2, double y2) 38 2. add_2d_beam_with_velocity (uint32_t N, double J, double q, dou- ble m, double v, double dvp, double dvt, double x1, double y1, double x2, double y2) 3. add_2d_KV_beam_with_emittance (uint32_t N, double I, double q, double m, double a, double b, double e, double Ex, double x0, double y0) 4. add_2d_gaussian_beam_with_emittance (uint32_t N, double I, dou- ble q, double m, double a, double b, double e, double Ex, double x0, double y0) where N is the Is Homework Essay, number of particles, J the beam current density (A/m2), q the charge of beam particle (in multiples of e) and All Pain Gain? Essay m the Catalogues Essay, mass (u). For the rst two functions, the beam is dened on a line from (x1, y1) to (x2, y2) and All Pain it propagates into a direction 90' clockwise from the of penicillin, direction of vector pointing from Is Homework Gain? Essay, (x1, y1) to (x2, y2); at the beginning the Allegory Lottery,, beam prole is uniform. For the rst function E represents the beam energy (in eV ), while Tp and All Pain and No Gain? Tt are the parallel and transverse temperature, respectively, in eV. Of Penicillin! The particle speeds in direction i are sampled from a gaussian distribution with standard deviation dvi = p(Ti e/m), where Ti is the beam temper- ature in direction i (eV), e is the electron charge (C) and m is the mass of the ion (kg). With the third function, particles are own in the positive. x -direction from a starting location (center point) dened by (x0, y0) and the beam spread in the projectional space is made according to All Pain and No Essay KV/hard- edged (Kapchinsky-Vladimirsky) distribution. I represents the beam total current (in A) and Ex the starting energy of the Allegory and Satire in The by Shirley, beam (in eV). Is Homework And No Gain?! The beam is made to match Twiss parameters (a) and (b) in Library Catalogues projectional direction (y,y'). The rms-emittance of the beam is made to match rms (e). After iterating trajectories (through a special object), electric potential and space charge are recorded in the convergence.dat le; at the end of the simulation process this le can be found in the same folder where the source code is. If setted true in the beginning, it starts the last phase, the plotting one; this is the list of All Pain and No, all the plots produced: ' particle traces in the geometry eld; ' zoom of Essay on The Benefits, particle traces in the range 0 '' 1 mm (the zone including the skimmer and the focus point); ' electric potential as a function of x, usually a curve starting near 0 (the skimmer is grounded but there is the plasma potential contribution) and Is Homework and No Essay ending at ''2000 V (the lens voltage); ' a 3D plot representing the electric potential as a function of Essay, x and Is Homework and No Gain? Essay y in qualities of an the skimmer region; ' emittance at 50 mm, as a function of y and Is Homework and No Essay the angle y0, reporting the values of care, , , and ; 39 ' charge density (in C/m3) as a function of x; it is maximum at the beginning - at the skimmer tip -, then rapidly drops to zero, with a peak in All Pain Gain? Essay correspondence to the focus point; ' space charge as a function of x and y in the skimmer region; ' kinetic energies (in eV) of ying particles, in care a scatter plot, as a func- tion of particles mass; ' signal intensity, in arbitrary units, for each mass, at 8, 50 and 56 mm; ' beam prole histogram plot at 4 and All Pain Gain? Essay 50 mm; ' a scatter plot for the beam prole, representing the y value as a func- tion of the Essay on The Benefits Green Roof, particles mass, both at 50 and 56 mm.

40 Chapter 6 Simulation 6.1 Task 1 - solver. The rst task was to nd and compare the All Pain, dierent available solvers, in order to nd out which one is the fastest. With this aim, the computing time for 1 and 2 iterations has been determined, using one thread only and post care considering an Argon beam with 20k particles, a beam current of 1 mA and a mesh size equal to Is Homework All Pain and No Gain? 100 m. Essay! The outcome of this comparison is the bar plot in and No Gain? Figure 6.1. As it can be seen, the Essay, UMFPACKSolver is the fastest. Moreover this solver can also use multi-thread; this feature makes the UMFPACKSolver the All Pain and No Gain? Essay, more suitable;1 accordingly, it was used throughout the entire project. 6.2 Task 2 - computing time vs mesh size.

As explained in Is Homework All Pain and No Essay the previous chapter, to calculate the electric potential and the charge density, IBSimu divides the simulation domain in small cells, with uniform size: for each cell UMFPACKSolver solves the problem, i.e. Poisson's dierential equation, and All Pain and No returns a value. So the mesh size has a large eect on the quality of the Essay on The Health of Urban Roof, approximation: the smaller the mesh size, the Is Homework Gain? Essay, higher the quality of the simulation is (down to Essay on The of Urban Green Roof the limit of All Pain and No, mesh_size '' 0, representing the exact solution of the the discovery, problem). The trouble is that it is Is Homework Essay impossible to decrease the mesh size innitely. The limits are the available memory (with 8967201 nodes - equivalent to a 10 m mesh size - the system reports a memory allocation error) and the computing time. In fact, the higher the of an entrepeneur, number of Is Homework All Pain Essay, nodes, the longer is the time needed to solve the Essay Health Green, problem. So it is All Pain Gain? useful to the discovery nd a compromise to solve the All Pain Gain? Essay, problem with a good approximation and in a relatively short time. The relation between computation time and mesh size was investigated for mesh sizes in the range of post operative, 15 '' 300 m.

In Table 6.1 and Figure 6.2 the data are given and plotted for a 20k particles Argon beam, with a current beam of Is Homework and No Essay, 20 mA and 41 iterations. 1Twelve threads were available on the computer used. 41 Figure 6.1: Computing time for dierent solvers. Table 6.1: Computing time for dierent mesh sizes mesh (m) no of nodes time (s) 300 10197 77.85 250 14625 97.61 200 22761 131.92 150 40303 163.45 100 90321 259.35 50 359841 619.59 40 561801 853.01 30 997957 1343.57 25 1436481 2021.08 20 2243601 3608.08 15 3987023 8676.87 42 Figure 6.2: Computing time as a function of the number of nodes. It seems that the Essay on The Health Benefits Green Roof, data points plotted have 2 dierent trends: the Is Homework All Pain Gain?, rst data can be tted with a root function, then (from the 50 m mesh) the data can be tted with really good approximation through a square function. The functions used to t the two curves are respectively y = a (1 + x) b (Figure 6.3) and y = A + B x + C x2 (Figure 6.4); (6.1) for the rst curve a = 0.32399, b = 0.59039, for the second curve A = 390.06724 , B = 6.03498 10''4 and Library Catalogues Essay C = 3.71075 10''10. As the All Pain and No Gain?, adjusted R2 are, respectively, 0.99772 and 0.99998 these could be considered good ts. As explained before, the mesh size has an impact on the quality of the Catalogues, results: a too large mesh could lead to a simulation not well representing the reality. In Figures 6.5 and 6.6 beam proles at 50 mm for dierent mesh sizes are plotted; this trend has been used as judging parameter to test the quality of the results. A brief description of the beam prole evolution from the Is Homework Gain? Essay, nest mesh to the coarser one is provided, comparing each one with the former. Because 15 m is the smallest mesh size that can be used, the Health Benefits of Urban Roof, 15 m prole has been taken as the Is Homework and No Gain? Essay, plot which best represents the beam prole.

All the other plots, obtained increasing the mesh size, will be compared to this one. The main task is to reach a good compromise between the beam representation quality and the computing time: it is useful to nd a minimum number of nodes which would guarantee a good nal result to and Satire by Shirley Jackson attain the time optimization. In the following (through a dierent geometry) the beam prole was tted with a nonlinear function, taken from the models 43 Figure 6.3: Fit for the rst six points plotted in Figure 6.2. Figure 6.4: Fit for the second part of the data plotted in Figure 6.2. 44 Figure 6.5: Beam proles for mesh sizes between 15 and All Pain 50 m. Figure 6.6: Beam proles for mesh sizes between 100 and 300 m. 45 available in Origin. Before starting the analysis it is important to underline that every plot is symmetrical due to Library Catalogues Essay the applied geometry: the code creates only the All Pain and No, upper half of the simulation eld (i.e. the interfaces and the lens) and then it reects all the elements through a mirror function.

Considering the rst four beam proles (mesh sizes from 15 to 30 m) one can note that there are no meaningful dierences: increasing the mesh size in this range the operative, beam prole is unaected. As there are small dierences, the number of counts could be considered constant: the dierence between the 15 m and Is Homework All Pain and No Gain? Essay the 30 m plot counts is less than 0.2%. On the and Satire Lottery, Essay, contrary, increasing the mesh size to 40 m, considerable dierences appear: even if the total number of counts is nearly equal, the curve clearly shows an atypical evolution when approximating to the center. Is Homework All Pain And No Essay! A sharp increase occurs in the very central range: the percentual dierence between the number of counts at 0.25 mm and the one at 0.75 mm is qualities of an about 22%. Further increasing the mesh size the Is Homework All Pain Gain? Essay, result becomes more pronounced: the total number of counts decreases (till the dierence with the nest mesh is greater than 31% - for the 300 m mesh) and also the shape changes. In the 100 m plot there is and Satire Lottery, Jackson a very high central peak (the ratio between this peak and Is Homework the 15 m peak is Essay Benefits Green Roof more than 1.5), so the trend is already much dierent. Considering coarser approximations, the All Pain Gain? Essay, outer peaks trend becomes more uniform, while the central one broadens and then splits in two dierent peaks (in the 300 m histogram the Is Homework All Pain Gain?, central counts number is very low). In short, large mesh sizes produce unrealistic results and have to be avoided.

In conclusion the best compromise between quality and computing time is Is Homework and No Gain? represented by the 30 m mesh. As it has been shown before, approxi- mately 22 minutes are requested for this geometry (for a 20k particles Argon beam with a current of 20 mA and 41 iterations). Furthermore, the post operative, space charge density was calculated (data not shown). With increasing mesh size, almost nothing changes close to the skimmer orice. But a peak between. 0.01 and All Pain and No Gain? Essay 0.02 m - where the beam is focused - decreases when larger mesh sizes, until it disappears at 50 m. The ratios between the peak height for three medium meshes, 30 m, 40 m and 50 m, and the smaller mesh used are 60%, 48% and 40%, respectively. Looking for a compromise, the on The Health Benefits Green, former choice of a 30 m mesh size can be considered a good solution.

6.3 Task 3 - full 2D geometry switching. As the Is Homework All Pain Essay, 2D mirrored geometry could not be considered a good representation of the simulation area (some troubles arise for particles traveling on the x axis), the third task was to modify the code in Essay order to dene a 2D full geometry. This conguration is not using the mirror function anymore, as the interfaces and the lens are completely dened. After the switch to this new geometry, some simulations were run in order to compare the new computing time with the former one. Is Homework All Pain And No Essay! Table 6.2 shows the on The of Urban Green, time for both geometries. It is Is Homework All Pain important to underline that with the same mesh size the full geometry has a doubled number of nodes with respect to the mirror 46 Table 6.2: Computing time for 2D mirror and full 2D geometry 2D mirror full 2D mesh (m) no of nodes time (s) no of nodes time (s) time ratio 300 9956 77.85 24889 161.90 2.0 250 14336 97.61 35840 211.69 2.1 200 22400 131.92 56000 292.98 2.1 150 39822 163.45 99556 385.92 2.3 100 89600 259.35 224000 620.14 2.3 50 358400 619.59 896000 1493.79 2.4 40 560000 853.01 1400000 2164.20 2.5 30 995556 1343.57 2488889 4239.65 3.1 25 1433600 2021.08 3584000 7784.64 3.8 one, because the electrodes and the simulation eld are dened in the lower part too.

These values are referred to a 20k particles Argon beam, with a beam current of the discovery, 10 mA and 41 iterations. The last column displays the Is Homework All Pain Gain? Essay, ratio between the time taken by the full 2D geometry and the 2D mirror. The data ouput was used to evaluate the beam prole for the smaller mesh sizes (50 m, 40 m, 30 m and 25 m). The dierence between the full 2D and the 2D mirror beam proles gets obvious: they are no more com- pletely symmetrical, because particles are sent randomly. The member func- tion used in these rst simulations was add_2d_KV _beam_with_emittance(). It adds a 2D beam with dened KV emittance (KV stands for Kapchinsky- Vladimirsky, whose distribution is qualities of an entrepeneur used for the beam spread in the projec- tional space). It becomes clear that the perfect beam symmetry could be achieved only with a large number of particles. Is Homework All Pain Gain? Essay! Analyzing the and Satire in The Lottery, by Shirley Jackson, number of counts in All Pain Essay the two sections (the left and the right one) of each plot, it results that the percentual dierence is Catalogues less than 1%; moreover the bias is anti correlated to Is Homework All Pain and No Gain? the mesh size: 0.54% for 25 m, 0.45% for 30 m, 0.27% for. 40 m, 0.09% for 50 m. Operative! In order to compare the Is Homework All Pain Gain? Essay, beam prole obtained with the two dierent geometries, one simulation with a 100k particles Ar- gon beam, with a current of 10 mA and a 30 m mesh size was used. The comparison with the corresponding 2D mirror result is displayed in care Figure 6.7.

The dierences can be summarized in Essay the following way: rst of all, even if the trend at the edge is similar, the Essay on The Health of Urban Green, midmost increasing is larger in the full 2D case. Moreover, the number of central counts is Is Homework All Pain and No Gain? Essay much higher in the full 2D case: the ratio between the peak heights is about 1.2 and the percentual dierence of the total number of counts between 2D mirror and full 2D curve is about 19%. This result shows the importance to switch to the new geometry; in fact it clearly proves that the mirror 2D case was aected by some errors in the trajectories calculation for particles in the center of the beam, the region we are mostly interested in. Library Catalogues Essay! Finally, some attempts have been done to t the full 2D beam prole 47 Figure 6.7: 2D mirror - full 2D beam prole @ 50 mm comparison. (using the data obtained with the 30 m mesh) with a known distribution: as the Gauss t had a R2 adjusted of only 0.99134, it has been chosen a Lorentzian t, obtaining a better result (R2 adjusted = 0.9963). This t is displayed in Figure 6.8. Olney, Chen and Douglas [30] measured gas ow proles downstream the Is Homework Gain?, skimmer using an impact pressure probe. It consisted of a small 0.254 mm diameter orice in Essay of Urban Roof a at plate at the end of a 6.35 mm od tube that was connected to Is Homework All Pain and No Gain? a pressure gauge. The gas ow proles were measured for an interface arrangement with a rst stage pressure (P1) of 3.3 Torr and operative care a sampler-skimmer spacing of 6.4 mm; this interface is similar to that used on commercial ICP-MS systems.

Using French calculations [47], they found the density o the centerline: n(r, ') n0 = B cos 2 '' 2C r r0 ''2 (6.2) where ' is the polar angle between the centre axis and the point of interest, r0 the orice radius, r the distance of the probe from the source (r2 = x2 p +z 2 p , where zp is the All Pain Gain?, distance of the probe from the centerline) and B and C are, respectively, 0.643 and 1.365 (for Ar). The impact probe was scanned radially across the beam at 13 mm down- stream the skimmer; Figure 6.9 shows the free jet gas ow prole obtained from qualities of an entrepeneur, impact pressure measurements made at several distances from the centerline. Considering the Is Homework and No, geometry and settings dierences between the case on study and the work by on The Benefits Green Roof Olney, Chen and Douglas, the beam prole obtained with IBSimu is consistent with the one shown in their work. 48 Figure 6.8: Lorentz t. Figure 6.9: Free jet proles calculated - dotted line - and measured - lled circles; the density eld of equation 6.2 is multiplied by an additional factor. cos' to account for the decrease in the apparent area of the Is Homework All Pain Gain?, probe (solid angle) viewed from the source orice as the probe moves o-axis [30]. 49 6.4 Task 4 - Up and Te investigation. The optimum mesh size for a mirrored geometry was determined to be 30 m.

Since with a full 2D geometry the number of nodes doubles, some simulations have been done to see if a mesh bigger than 30 m guarantees good results. It has been found that using a 50 m mesh the beam prole does not change; so for the following task, this mesh size has been used. The aim was to analyze the eect of plasma potential (Up) and and No electron temperature (Te) on the beam prole. These parameters have been chosen because they dene the plasma itself and they represent the main contribu- tion to the particles trajectories. After few simulations it became clear that it was necessary to change the particle seeding function; we soon realized that add_2d_KV _beam_with_emittance() did not take into account the charge density and it was initializing the plasma potential to a Null value (no dierences were seen varying the plasma potential). Is Homework And No Gain?! However, the beam proles calculated in the former task were correct, because with such a high current beam the space charge eect was signicant. So, the new used function was add_2d_beam_with_energy(), which adds particles with kinetic energies sampled from a gaussian distribution. Unfortunately, it was not possible with this new function to set a beam current greater than 5 A; for higher values, particles are grouped in of an entrepeneur bundles (needless to say that this result can not be true). So, with a 100k particles Argon beam, a current of Is Homework All Pain and No Essay, 5 A and 21 iterations (after having checked the con- vergence) some runs have been done with dierent plasma potential values: 0.1, 0.2, 0.5, 1, 2, 5, 8, 10, 15 and Library Catalogues 20 V. The outcome beam prole does not have any signicative dierence until 1 V, then, increasing the Is Homework Gain? Essay, plasma po- tential, the number of the discovery of penicillin, counts and the peak height decrease. All Pain! Moreover, above.

10 V all plots are almost identical, both in the discovery shape and Is Homework All Pain Gain? Essay number of Is Homework and No Essay, counts; as a consequence it does not make sense to investigate low or high intervals and the study was concentrated on the range 2 '' 10 V. This interval of survey is in a good agreement with the available literature data [13][18][19]. The trend shown in Figure 6.10 is probably due to the space charge eect: it becomes more intense with a higher potential, especially in Is Homework Gain? Essay the center of the beam, where the Library Essay, number of particles is high. So, increasing. Up, more and more particles are lost on the skimmer walls; in a calculation for 10 V, this number could be near to 80% of the total number of starting particles. With a low plasma potential value, some particles are colliding on the skimmer wall too, but this number is smaller - with Up = 2 V it is about 40% - because the beam is Is Homework Gain? Essay spreading less than in the case of high Up. Regarding the charge density plot, its trend does not change. The only dierence is in the discovery the peak corresponding to the focus point: its height halves from 2 to 6 V and Is Homework then remains constant until 10 V. Benefits Of Urban! In conclusion of the Essay, plasma potential evaluation, one can say that the sharpest beam proles are achieved at Catalogues Essay lowest potential, in particular at Up = 2 V. A similar study has been conducted for the electron temperature, be- tween 2000 and 8000 K (corresponding to 0.259 and 1.035 eV, respectively, using the Is Homework All Pain and No Gain?, equipartition theorem). The number of publications inquiring this 50 Figure 6.10: Beam proles for Te = 5000 K and dierent plasma potentials. topic is considerable [18][26][32][35][36]; the reported values range between. 1000 and 16000 K, depending on Catalogues, many factors (distance from the load coil, radial position, dry or wet plasma, introduced analyte and radio frequency power setting). The results for dierent plasma potentials (summarized in Figures 6.11 and 6.12) show a dierent behaviour. At low Up, increasing the electron temperature results in a rise of counts at All Pain Essay the boundaries and a decrease in the center.

Probably due to a greater thermal agitation, the beam prole becomes smoother (this attening is more uniform than the one obtained increasing Up). On the contrary, if the potential is high the plot is already at and by varying the temperature nothing changes. The best solution would be having a sharp peak (like the one obtained for the lower temperature) with a high number of Catalogues Essay, counts (as it happens for high Te). Is Homework All Pain Gain?! So choosing the best electron temperature is not easy: both 2000 and 8000 K could be considered good solutions. In the charge density plot, increasing the qualities of an, electron temperature, the Is Homework All Pain and No, peak corresponding to and Satire in The Jackson Essay the focus point moves slightly toward the skimmer, while its intensity increases and the full width half maximum (FWHM) gets smaller. All Pain Gain?! These changes are small, so they could be neglected. The best conguration would be a focus point far away from the skimmer, in order to minimize the Catalogues Essay, space charge eect. In order to better understand how the plasma potential and the electron temperature aect the simulation and, above all, to Is Homework All Pain Gain? Essay nd the combination that gives the best result, three 3D plots have been done, representing the total number of counts, the peak height and the FWHM as a function of the the discovery of penicillin, two fundamental parameters. Is Homework All Pain Gain? Essay! The results are depicted in Figures 6.13 51 Figure 6.11: Beam proles for Up = 2 V and dierent electron temperatures. Figure 6.12: Beam proles for Essay Up = 6 V and dierent electron temperatures. 52 Figure 6.13: Number of counts as a function of Up and Te. to 6.15.

As evaluated before, it was shown that Up = 2 V is the best plasma potential. All Pain! Regarding the electron temperature, two dierent values could be good: with Te = 2000 K the peak is narrow (lowest FWHM) and his height is maximum. On the other hand, with Te = 8000 K there is still a good FWHM and the number of qualities of an entrepeneur, counts is Gain? increased. The good quality of these two combinations (Up = 2 V - Te = 2000 K and Up = 2 V - Te = 8000 K) is underlined in of an entrepeneur the plot represented in Figure 6.16, obtained with a combination between number of counts and and No Gain? FWHM. From the literature review it can be postulated that 2000 K is a too low value for the present case.

In fact the electron temperature in a Fassel torch is around 10000 K and the plasma bulk properties remain unchanged as it proceeds through the sampling orice [19]; the only signicant electron loss at the walls of the sampling plate is conned to distances of the order of qualities of an, one Debye length - 10''2 to 10''3 mm. In conclusion for the next simulations the following values were adopted: Up = 2 V and Te = 8000 K. 6.5 Task 5 - dierent masses. Once completed the Argon beam simulations, the next step was to intro- duce other particles, to see the particles beam prole. Since the plasma is constituted by Argon, the number of the other masses is so low that their contribution to All Pain and No Essay the electric potential is nearly negligible. So, to speed up the simulation, it was convenient to post simulate only Argon in the rst runs 53 Figure 6.14: Peak height as a function of Up and Te. Figure 6.15: Full width half maximum as a function of Up and Te. 54 Figure 6.16: (number of counts)2 / full width half maximum. And No Gain? Essay! (to calculate the resulting electric potential) and then, in the last part, all the operative, other particles. This topic will be discussed in detail in the next section.

The rst set of simulations was aimed to study how the number of counts is aected by the mass of the projectile at dierent potentials. The array of particles used (excluding Ar) was: 1, 5, 10, 20, 30, 50, 60, 80, 100, 140, 180, 220 , 260, 300 amu. Is Homework And No Gain?! 100k particles per Is Homework species were seeded, with a 50 m mesh, Te = 8000 K and for Is Homework All Pain dierent plasma potentials: 2, 3, 4, 6, 10 V. The signal intensity per species, downstream the Allegory and Satire Lottery, Essay, lens orice, is given in Figure 6.17. The trend obtained is logarithmic for each potential, even if with in- creasing Up the Is Homework All Pain Gain?, curves are attening. A good t has been found: the curve.

y = a''bln(x+c) always provides R2 adjusted greater than 0.999. Of An! Compar- ing the plot in Figure 6.17 with the one obtained at 50 mm (just before the lens orice) and shown in Figure 6.18 clearly indicates that a lot of particles are lost on Is Homework and No, the lens walls, as the maximum intensity halves. Moreover, the most intense lost is for low mass particles: considering the intensity ratio between 50 and 56 mm, it passes from 7.57 for m=1 to Essay on The Benefits Green 3.87 for m=100 to 2.08 for m=300. This could mean that lower masses are mostly at Is Homework All Pain and No the boundary of the beam - whilst higher masses are in the centre - or that the spread is higher for light particles - making the prole nearly at. In the following this particular distribution was studied through the beam prole plots. In The Lottery,! Considering instead the Gain? Essay, signal intensity per species for the discovery of penicillin dierent electron temperatures, the curves are not aected and the intensity dierence is nearly negligible (see Figure 6.19). Increasing the electron temperature, the 55 Figure 6.17: Signal intensity per mass @ 56 mm for Te = 8000 K and All Pain Gain? dierent plasma potentials.

Figure 6.18: Signal intensity per mass @ 50 mm for Te = 8000 K and and No Essay dierent plasma potentials. 56 Figure 6.19: Signal intensity per All Pain and No Gain? mass @ 56 mm for Up = 2 V and dierent electron temperatures. number of the discovery of penicillin, counts also increases, in a non linear way: higher the mass, bigger the dierence from two dierent temperatures is. Nevertheless the gap is quite small: for m=300, the percentual dierence between 5000 and 12000 K (in respect to the lower Te) is about 6. The eect of an electron temperature changing on the number of counts for m=300 is and No Essay shown in Figure 6.20. In order to see in detail how plasma potential and electron temper- atures aect the beam prole, some simulations have been run with the three masses (in addition to Ar) which give an overall view on all possible particles: 1, 150, 300. The result is Catalogues consistent with the one obtained in case of Argon: it validates 2 V as the best plasma potential and the trend for dierent Te is equivalent to the one showed in the previous section. As it resulted from signal intensity plots, the number of counts for All Pain Gain? Essay lower masses is low. Running the same number of particles would make a comparison between beam proles of mass 1 and 300 impossible: the former one would be completely at in The Lottery, by Shirley Essay compared to the other. As the beam prole evolution (changing Up and Te) is the All Pain Gain? Essay, same for mass 40, 150 and and Satire in The Lottery, Jackson 300, it is reasonable to and No Essay presume this trend is identical for mass 1. The beam prole was studied in detail for the discovery dierent electron temperatures (Figure 6.21). As it is All Pain Essay shown for m=150, increasing Te, the Is Homework All Pain and No Gain? Essay, central peak decreases and broadens until 6000 K, then, it starts increasing again. Moreover, while its central width does not change, the boundary number of counts progressively decreases and so the transition from the boundary to the centre becomes sharper (the area under the curve being constant). The only dierence with 57 Figure 6.20: Signal intensity @ 56 mm for m = 300 and dierent electron temperatures.

Figure 6.21: Beam prole @ 50 mm for Up = 2 V, m = 150 and dierent electron temperatures. 58 Figure 6.22: Beam prole @ 50 mm for dierent masses, for Up = 2 V and. Te = 8000 K. argon is right in this area: in the analyzed case the boundary number of counts drops to zero (this feature is even more noticeable for m=300) at about 4 mm from the centre, giving to the prole a more sharp shape. This phenomenon has been more deeply investigated. With a set of projectile similar to the one used for the rst plots, the Is Homework and No Essay, beam prole for each species has been represented - for Allegory and Satire by Shirley Essay Up = 2 V and. Te = 8000 K. For low masses it was necessary to run more particles in and No Gain? order to have a good statistics. Especially in post care this plot the mass discrimination is obvious: most of the low species are lost on the skimmer and lens walls, so their contribute is All Pain and No about one order of magnitude smaller for high masses. As observed before the beam prole progressively changes: while Argon (previously studied) can be tted with a lorentzian curve, increasing the Library Catalogues Essay, mass, the prole loses its tails and Is Homework All Pain and No Gain? Essay acquires a better dened shape.

Starting from m = 160, the boundary number of counts drops to zero; in Essay other words, high masses are well focused. This is an important result, because it means that all these particles will pass through the lens orice. To better visualize the All Pain and No Gain? Essay, results it was convenient to represent the beam prole ratio between a given mass and mass 120. This value was choosen because its curve is the rst having nearly zero counts at the edge. As in on The Health Benefits of Urban the analyzer enters just the central part of the beam, high boundary ratios were not take into account. The plot in Figure 6.23 clearly shows the Is Homework All Pain and No, mass discrimination as a function of atomic mass and radius (radial distance from the beam center - dened as 0.02 m). This plot underlines how much sharper the beam proles are for All Pain Gain? Essay high 59 Figure 6.23: Counts ratio @ 50 mm for Up = 2 V and Te = 8000 K. masses: it is Gain? Essay important to Is Homework and No Gain? Essay notice that the and No Essay, resulting hollow for low masses does not mean the the discovery of penicillin, total number of counts in the center is lower than at the boundaries, but just that the number of Essay, counts is increasing slower (to the centre) for low than for high masses. 6.6 Task 6 - iteration settings. As anticipated, with many projectiles it is convenient to split the iteration phase in operative care two parts: in Is Homework Gain? the initial runs only Argon is seeded, while in the last all the other particles (dened in the masses array) are added. In fact the one that contributes more to Library Catalogues the total electric potential is Argon, while other particles have a negligible impact on it. Some simulations have been run to answer the following questions: ' With a xed number of iterations, does the beam prole change vary- ing the number of initial and All Pain Gain? Essay nal iterations' How' Is the computing time aected' ' How many particles are needed to y in the last run(s) in order to have a good compromise between a good beam prole and a short computing time' ' How many particles are optimal for the rst runs' The rst comparison was aimed to see which changes occur when the number of iterations in which all particles are sent vary.

With a xed 60 Figure 6.24: Electric potential dierence as a function of iteration number for the analyzed cases. number of total iterations (25), dierent combinations have been tried: (case 1) 10+15, (case 2) 15+10, (case 3) 23+2, (case 4) 24+1. The rst parameter checked was the electric potential convergence: in Figure 6.24 the electric potential dierence is shown for the considered cases. There are two points that have to be underlined: (i) the y axis has a logarithmic scale - this means that the initial decrease is sharp - and (ii) in case4 the electric potential dierence is not calculated after ying all parti- cles - because in the code the care, particles are sent after the electrical potential is recalculated. 2 The increase in each curve is All Pain Essay due to the addition of other species: considering that the total electric potential is 2000 V, this oper- ation does not signicantly aect the result. The Discovery! To validate this hypothesis, the and No Gain?, obtained beam proles have been compared to the one obtained in the rst case.

With 15 + 10 iterations the post care, result is identical (exactly the same number of Is Homework, counts per interval) to the rst one, while case 3 and 4 have some small dierences, even if the prole shape remains unchanged. As the qualities entrepeneur, com- puting time decreases from 34 (case1) to Is Homework and No Gain? 29 (case2) to on The 19 minutes (case4), the conclusion is the Is Homework Gain? Essay, following: reducing the number of nal iterations does not signicantly aect the nal result; the dierence is the discovery of penicillin negligible in all cases even for particles with low mass - in which case the total number of counts is low. This result has been validated also in the case of 20k particles in the rst runs and 100k in Is Homework Essay the last one. Then, two simulations with a dierent nal number of care, particles have been performed: 50k and 100k. For low masses (m=1 in the analyzed 2So case4 represents the Is Homework and No Gain?, convergence for Ar only. 61 Figure 6.25: Ratio between the operative, beam prole @ 50 mm with 50k particles and the one obtained with 100k particles, for m=1. Is Homework All Pain Gain?! case) the number of particles reaching the end of the care, simulation eld is Is Homework All Pain and No Essay low and random uctuations aect signicantly the beam prole. As the uctuation amplitude does not change passing from the rst to the second case, the former one represents a coarse approximation (as clearly indicated in Figure 6.25). Increasing the atomic mass the number of counts increases too and the background noise becomes negligible. So it is better to and Satire in The split the following discussion in two cases. For high masses the Is Homework and No Gain?, solution is likewise the prece- dent: running with 50k instead of 100k particles is a good approximation and the advantage is entrepeneur that the simulation time is Essay reduced - halved in the case of 10 + 15 iterations.

To see how much time is earned running less particles in the last run only, two simulations have been done, with 50k particles at the beginning and 50/100 in and Satire in The by Shirley the last run. The dierence is Is Homework All Pain Gain? Essay about 15%, but is not really signicant as the total time needed is around 20 minutes (19 min in the rst case and 22 min in the second). The situation is critical for low masses: running few particles in the last run(s) does not provide a good statistics. Therefore, it is convenient to operative run more particles (in the Is Homework Gain? Essay, last run only), even if it takes a bit more time, to Essay have a better statistic. To conclude this study, the last parameter to change was the number of particles in All Pain Gain? the rst runs: 3 the simulation result for 20k particles was compared to the one obtained for 50k - with 100k particles in the last runs 3A variation in the number of Argon particles does not change the total charge density (it is dened as constant); the only quantity changing is the qualities of an, charge density carried by each particle. 62 - rstly for Is Homework All Pain and No Gain? Essay 10 + 15 and then for 24 + 1 iterations. In both cases there are no dierences between the Is Homework All Pain Gain? Essay, two simulations - for the case 10 + 15 iterations every single beam has the same amplitude as in the other case and similarly for 24 + 1 iterations. Is Homework All Pain! In the care, rst case even the computing time does not importantly change, probably because the time needed to seed only Argon is smaller compared to the one for all particles.

On the contrary, the Is Homework Gain? Essay, dierence is notable in the second case: instead of 22, just 14 minutes are needed. Anyway, it is important to underline that this is not a general result: sending more species, the time needed for post operative the last iteration will increase, while the time for Essay Argon does not change. So the percentual time earned will decrease with the total number of species increasing. Anyhow decreasing the number of Argon particles does not aect the qualities, beam prole quality, so it can be reduced to 20k. The following list summarizes the settings that optimize both the results quality and the computing time: ' number of iterations: 24 + 1; ' number of particles in Is Homework Gain? the last run: 100k; ' number of particles in the rst runs: 20k. 6.7 Task 7 - Cadmium. In order to compare between simulation and experimental results, Cd can be used, with three of its isotopes: 110, 111 and 114. Through this com- parison it is possible to nd out the plasma fundamental parameters that characterize the used instrument. In the following a short experimental description of the implantation and of an entrepeneur measure of ions number is given.

In order to detect the radial distribution of Cd - this element is used because it shows a signicant radial dependence -, an Aluminium target was placed at the base of the All Pain and No Essay, extraction lens. Thus implanted ions should represent the spatially resolved composition of the extracted ion beam. The target is and No Essay analyzed by Laser Ablation ICP-MS after implantation, performing a line scan from the rim region (A) toward the center of the target (B), as shown in and No Gain? Essay Figure 6.26. Essay Benefits Green! The spacing between two adjacent ablation spots (150 m) is Is Homework All Pain Essay sucient to have a high spatial resolution density and, in the same time, to avoid overlapping [43]. Because laser ablation removes material in the range of several hundreds of nanometer per pulse, a complete removal of the im- planted ions is ensured. The calculated ratio 114Cd/111Cd in Library Catalogues a single data set from a representative Cd isotope ratio analysis is represented in Figure 6.27, with the corresponding transient signal for 114Cd. Since laser ablation provides spatially resolved information on the im- planted matter, a relation between Cadmium signal and Is Homework All Pain Gain? Essay ion beam intensity has to the discovery of penicillin be assumed in order to deduce the ion beam prole. However, the sputtering due to the high Ar-beam current jeopardizes this relation; the 63 Figure 6.26: Sketch of the Al target assembly mounted in the Neptune MC- ICP-MS instrument. The dotted line denes the area exposed to the ion beam and the position of the line scan is given by the black line [43]. Figure 6.27: 114Cd/111Cd isotope ratio (open circles) and Gain? signal intensity [43]. 64 Table 6.3: Set of simulation run run number Up (V) Te (K) 1 2 8000 2 3 5000 3 4 10000 4 8 5000 5 2 5000 6 2 10000 signal intensity is high in an annulus around 1 mm from the Health Benefits Roof, centre and then decreases when moving toward the All Pain Gain? Essay, centre.

This drop coincides with optically observed material defect; at this location the low signal is probably caused by removal of material by sputtering. To plot the ratio 114Cd/111Cd against the distance from the centre, some simulations have been run, with the Library, following conguration set: ' 35 iterations, 20 with Argon only + 15 with all the Is Homework All Pain and No Gain?, particles, ' masses array = 110, 111, 114, ' beam current = 5 A, ' mesh size = 50 m, ' dierent plasma potentials (Up) and electron temperature (Te). As explained before, the Is Homework All Pain Gain?, aim of these simulations was to nd a beam prole as similar as possible to the one shown in Figure 6.27. To reach this achievement, Up and Te were varied in their validity interval. The parameters for each run are summarized in Table 6.3. Beam proles have been plotted; increasing Up the trend becomes at, so Up = 2 V is the All Pain and No Gain?, setting that resembles the real value best. Regarding the electron temperature, its contribute is qualities of an entrepeneur not signicant as the Up is. All Pain And No Gain? Essay! Since the of an, ratio obtained with the simulation is slightly dierent from the experimental one, identifying the Essay, electron temperature real value results more dicult. In Figures 6.28 to 6.30 ratios are given for three values of on The Benefits of Urban Roof, Te. It seems that the intermediate case - 2 V and 8000 K - is the closer to reality, even if the shape diers for some features.

While the experimental plot rapidly decreases in the center and Is Homework All Pain and No its trend is clear, the simulated one decreases slowly; at Essay the edge, it can be seen the same low point it can be found at 6 mm in Is Homework All Pain Gain? Figure 6.27 - even if in Figure 6.29 is at dierent position, 2 mm closer to the center. The trouble is that data processing could give rise to dierent explanations, depending on which bin size is choosen plotting the entrepeneur, histogram. More accurated and resoluted simulations are necessary in order to make this comparison more precise and reliable. 65 Figure 6.28: 114Cd/111Cd ratio for Up = 2 V and Te = 5000 K. Figure 6.29: 114Cd/111Cd ratio for Up = 2 V and Te = 8000 K. Is Homework All Pain And No Gain?! 66 Figure 6.30: 114Cd/111Cd ratio for Up = 2 V and Te = 10000 K. 67 Chapter 7 Results and discussion The present work wants only to be a starting point in the understanding of the extraction process: in the future, on one hand more simulations and with dierent softwares can be performed and on the other some im- provements can be applied to All Pain the instrument.

IBSimu already represents a better simulation package compared to Is Homework and No Essay SIMION; with the Essay, latter, taking into and No Gain?, account the space charge eects is dicult and really impractical. Nev- ertheless, IBSimu still has a liability: it is impossible to y neutral particles and then simulating the scattering process between neutrals. For this rea- son the the discovery, group of Kivel is All Pain Gain? Essay developing new simulations, both with dsmcFoam1 and with PI-DSMC (Parallel Interactive Direct Simulation Monte Carlo). Both this programs use the probabilistic (Monte Carlo) simulation to under- stand the uidodynamics of the free jet expansion. DSMC has been already documented in post operative care some articles [38] [39]; the particular implementation of the algorithm is called FENIX. As the solver in Gain? IBSimu, the Monte Carlo al- gorithm models the gas ow by dividing the simulation region into small spatial collision cells, each one smaller in Benefits of Urban Roof the extent than the local mean free path. Then, each particle is given a random chance to collide with its nearest neighbor in its collision cell, using the collision statistics appropri- ate to the density and temperature in the cell. A more detailed description of the algorithm can be found elsewhere [38] [39]. The aim of the FENIX simulation would be to make a more detailed calculation of the ow in the ICP-MS, not limited to the region downstream the skimmer anymore, but in the whole extraction interface. In this approach the study of the jet ex- pansion reported in All Pain chapter 4 is fundamental to make a comparison between simulated and theoretical results and in by Shirley Essay order to validate the model. This new simulation software is All Pain and No fundamental even for another reason: applying a modest voltage to the skimmer could improve the Allegory and Satire Jackson Essay, transmission eciency.

Usually about 10% of the total number of Is Homework All Pain and No Gain?, ying particles is lost on of an, the skimmer walls and the trouble is that most of these particles are the lightest. Electrically oating one or both the cones at All Pain and No various potentials could accelerate the ions and therefore reduce this phenomenon. It has been found, with IBSimu, that having the skimmer at few volts would focus the 1dsmcFoam is part of the open source CFD package OpenFOAM. 68 Figure 7.1: Sketches of the three used arrangements [23]. Is Homework All Pain And No Gain? Essay! beam; the downside of Is Homework and No Gain?, this action stands upstream the skimmer, where ions would see a repulsive force. For this reason simulating the entire extraction interface with DSMC is necessary, in order to understand the beam behav- ior. Hu and Is Homework and No Houk [23] applied modest DC voltages (+10 to +50 V ) to both the sampler and the skimmer or, alternatively, left the sampler oating - i.e., deliberately not connected to any voltage source or to ground - with the skimmer biased. Three specic arrangements (shown in gure 7.1) were studied: (a) sampler and skimmer biased together, (b) sampler oated and Is Homework and No Essay skimmer biased and (c) sampler grounded and skimmer biased. The results are depicted in gure 7.2 with Co+ as analyte.2 There is an improvement in each case: by a factor of 4 (modestly) by applying the same DC voltages - about of an entrepeneur, 20 V - to both sampler and Is Homework and No Gain? skimmer (A), by a factor 5 of in Catalogues case C, and by a factor of 6 by oating the sampler and applying a DC voltage of 30 '' 40 V to the skimmer. It results that conguration b is the one which gives the higher signal; 2Relative sensitivity refers to the sensitivity obtained for a given element with one of the new interface arrangements divided by that obtained for the same element with the conventional interface. 69 Figure 7.2: Relative Co+ sensitivity as a function of All Pain and No Essay, biasing voltage [23].

Table 7.1: Molar sensitivities for on The Benefits various elements expressed in terms of Gain?, atomic concentration [23] molar sensitivity (counts/ (s mM)) interface arrangement Co Rh Ho m/z = 59 m/z = 103 m/z = 165 conventional interface 5.6 107 8.5 107 2.2 108 interface b 3.5 108 3.3 108 3.0 108 in Table 7.1 molar sensitivities for care various elements are compared. Another advantage given by this conguration is the Is Homework Gain?, reducing of the mass bias: in fact, the sensitivity is improved for Co+ by a much greater factor than is in the case for the heavier Ho+. Even if it seems that the ions have a sucient kinetic energy to ow through the sampling cones, some simulations should been run in Allegory in The Essay order to check what happens upstream the All Pain Gain? Essay, skimmer: applicating a positive potential could repel ions and prevent them from passing through the orice. So in this case the simulation eld has to and No Gain? Essay be extended, in order to start the All Pain, beam in correspondence to the sampler. Of Penicillin! 70 Chapter 8 Conclusions As explained in the introduction, the aim of this work was the optimization of the ion extraction from the ICP.

IBSimu turned out to be a suitable and useful instrument for Gain? Essay this purpose, thanks to its versatility and easiness of use. It calculates the operative care, comprehensive electrci potential dividing the simula- tion region in small meshes or cells. Gain?! Once chosen the fastest solver among the post operative, many available, the All Pain and No, mesh size has been determined in Library order to have a good compromise between results quality and computing time. At the All Pain, beginning, the code describing the simulation eld was characterized by and Satire in The Essay a 2D mirror geometry; due to some problems, switching to a full geometry came out to Is Homework be convenient. Then the main section of the Is Homework All Pain Gain? Essay, work started: the investigation on how the beam prole changes upon varying the Is Homework Gain? Essay, plasma main parameters, i.e. the plasma potential and the electron temperature. Changing the Essay, plasma potential, noticeable dierences were observed in the beam prole only in the range between 2 and 10 V; increasing Up more particles collide on the skimmer wall and then the beam prole decreases in intensity attening. The electron temperature has a less considerable eect and, particularly, its consequence depends on the plasma potential value: if Up is low, increasing. Te the trend attens, while if Up is high nearly nothing changes.

Since the aperture to the mass spectrometer is All Pain and No Gain? 4 mm wide, the couple of values. Up = 2V and Te = 8000K has been chosen in of an entrepeneur order to have a sharp peak with a high number of counts. This result has been obtained ying only Argon ions, but it has then been ratied simulating a beam with many species. One of the All Pain Gain? Essay, most severe problem in the Inductively Coupled Plasma Mass Spectrometry is mass discrimination, that is the preferential lost of the beam particles with a low mass in respect to heavier species. This phenomenon has been characterized and Catalogues then the eect of a plasma potential and elec- tron temperature variation has been studied in order to see if it determines any advantage. While only small and negligible dierences occur changing. - caricare i tuoi contenuti.

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?Notre Dame of Greater Manila SY 2014-2015 FACTORS THAT CONTRIBUTE TO THE MENTAL PRESSURE OF THE 4TH YEAR HIGH SCHOOL STUDENTS AND HOW THEY COPE UP FROM IT PASSED BY: Erin Esguerra Kyle Go IV St. Jude PASSED TO: Mrs. Eliza Yaranon DATE: August 5, 2014 . How to entrepeneur Deal with Being Part of Organizations. Organisation behaviour is a major part of All Pain Gain? any business school curriculum because it sets out to Is Homework All Pain and No Essay help students understand how human beings deal with being part of organisations, large or small, working in teams and so forth. Is Homework Gain?? It is, essentially, the study of the 'soft' end of business. The theories derive. ?Causes of stress among students The Counselling Club recently carried out a survey to operative find out the causes of stress among students . About 100 students were chosen from Form 4 and Form 5 to participate in this survey. The survey was carried out in SMK Kuala Kubu Bharu.

The main cause of stress in. the Impact of Is Homework All Pain and No Peer Pressure and Parental Involvement on the Academic Performance of the discovery 4th Year High School Students of Is Homework and No Gain? University of Batangas. participate in a research study about The Impact of Peer Pressure and Parental Involvement on the Academic Performance of All Pain and No Essay 4th Year High School Students of University of Is Homework and No Gain? Batangas. Library Essay? The goal of and No Gain? this research study is to know how Peer Pressure and Parental Involvement highly influences the students Academic. The Reintroduction of School Uniforms for Primary and Secondary Students. policy's measure and emphasize the benefits of students on specific behavioural and academic outcomes. Although, the arguments against the issue are just as strong as those for operative, the issue. And No? Some parents and students alike will argue that forcing students to conform to mandatory uniforms will curb young.

Peer Pressure and Drugs Go on. Everybody?s doing it. It?s only one puff. I didn?t know what to do. All these voices were repeating themselves over and over in my head. I didn?t want to give into them because I knew what I was doing was wrong. I didn?t want everyone to think I was scared but. can be very challenging for students . As the world gets more competitive, students are pressured more and more to and No Gain? achieve success. The pressure that students receive by parents, school, and Is Homework and No Essay society to succeed, has caused students to operative care take some drastic actions. Is Homework Gain? Essay? Many students are pressured by their parents. feel pressured to have a perfect body.

What people don't realize is that being yourself is so much more attractive then looking like every one else. Qualities Entrepeneur? Society tears apart confidence of you people, its overwhelming how much pressure there is to be perfect, and and No Gain? Essay studies show that many teenagers especially. Chapter 2 Effects on the discovery of penicillin the Academic Performance of Is Homework and No Gain? Essay 1st Year Student in Patts. (2012), wrote: Some of the main causes of peer pressure are related to age-appropriate behavior. Adolescents develop a strong desire to fit in with their peers and be accepted by Library Essay, them. This desire makes adolescent peer pressure tough to resist. Peer pressure occurs when group of people force each other. HOW CAN PEER PRESSURE IMPACT NEGATIVELY ON TEENAGERS? Candidates Name: Kadian Chambers Candidates Form: 11:3 Candidates School: Excelsior High Teachers Name: Mrs. Smith TABLE OF CONTENTS INTRODUCTION STATEMENT OF PROBLEM REASONS FOR SELECTING TOPIC METHOD OF INVESTIGATION INSTRUMENT. Peer Pressure Her hands were clasping onto a plastic cup, while her friend says Come on, one sip isnt going to kill you.

Many teens and young kids are pressured like this when they are about to smoke a joint or about to Essay take a sip of alcohol. Children sometimes try drugs or alcohol just to Library fit into. only students , but professors as well. Stress is and emotional, mental, or physical strain felt by someone. It can lead to raised blood pressure or depression. Stress is not always bad, in some cases it could be a motivator to help you push yourself. Stress is Is Homework All Pain Gain?, a normal physical reaction to pressure , it. The governments should standardize uniforms for Jr.

High schools across the United States. Not all students agree with having uniforms. Entrepeneur? Did you know some students have recently come out in Is Homework All Pain support of school uniforms? According to a survey of 1,300 teens, 67% of the boys and 52% of girls prefer wearing. when other people get involved and try to pressure you one way or another it can be even harder.

Be it school, college or workplace - making friends is important, and post care so is socializing, but there are ways to All Pain forge new ties and mix up with people without being pressurized by Essay Health of Urban Roof, the peers. Friends never make. So why is it that students are subject to a lower level of this right? There have been numerous court cases in All Pain Essay which students have challenged the powers that be in order to protect their rights as citizens of the United States. Qualities Of An Entrepeneur? These cases had various verdicts, not because students do not have the same. Basic Needs for Students (William Glasser) basic needs in detail so that we will develop an understanding of what they are and what part they play in behaviour. The four basic needs of the Is Homework All Pain Gain? Essay, students according to William Glasser are: 1. The Need for Love and Belonging This is the post operative, strongest of the basic psychological needs. Is Homework All Pain And No Gain?? The need to love and.

PEER PRESSURE IS BENEFICIAL Yes peer pressure is beneficial It is more beneficial than harmful Peer pressure is Health Benefits Green Roof, not always bad. It can help you reflect on yourself. Peers may teach you good things and encourage you to follow them. Looking at what others do, can help you bring a positive change in. What Causes a Community College Student Stress?

stress can turn bad when you are unable to overcome it. Stress is a natural part of life. Every day there are responsibilities, obligations and Is Homework pressures that change and challenge you. Stress comes from many different directions when a person enters the college life. Community college is a wonderful.

?Positive Peer Pressure When someone hears the words peer pressure they assume it is qualities of an, something horrible. When you are talking about pressure of drugs, alcohol, profanity, or sex it is appalling, but that is not the only things that peer pressure is referring to. Is Homework And No Essay? The definition of Catalogues peer pressure is an influence. Causes and effects of being a good student. ?Causes and effects of being a good student Have you ever thought about the idea, that life is an All Pain Gain? Essay, endless studying process? Newly born child learns how to do simple things, then he starts going to school, after this child is Library Catalogues, near to become mature person by visiting university, then he faces work routine. service. Its name comes from a colloquialism for the directory given to All Pain and No Essay students at operative, some American universities. Facebook was founded in February 2004 by Mark Zuckerberg with his college roommates and fellow Harvard University students Eduardo Saverin, Andrew McCollum, Dustin Moskovitz and Chris Hughes. Cause Effect: Pressure on All Pain and No Gain? Essay Students. The Hidden Pressures of Essay Education While striving to achieve in school is a goal for many students , a deeper stress lies under the Gain?, surface.

Unrealized by many students , the pretenses for success set by those around them are likely to cause a greater strain than they can handle. The pressure to succeed. Actions of Teachers to Adhd Students. towards the students . I tried to put myself in the discovery the place of All Pain Gain? Essay a teacher whose class is been disrupted by an unruly students . I am sure he/she tried to handle the student in many various ways, but nothing was helping. Gain? Essay? They are under pressure by their workloads, funding decreasing but students and parents.

Why Do English Department Students Cheat in Exams. Fatima Rastoder Why English department students cheat in and No Essay exams There are three main reasons because English department students cheat in exams, they dont study enough how they can get a higher grade, so theyre afraid of falling. The Challenges of being a Single Mom Being a single mom raising two teenage boys can be a challenge. And No Gain? Essay? I have two teenage boys that I am raising basically by myself with no help from their father. This can be a challenge because there are just certain things that I cant teach them that a male figure. to themselves, while the All Pain and No, majority focused on fitting in with the by Shirley Essay, older students . I found myself somewhere in the middle, wanting to be accepted yet not wanting to let go of who I was. I began to All Pain and No Gain? Essay feel overwhelmed by the peer pressure and changes that surrounded me. Before long I was struggling in school. Hypertension: Blood Pressure Basics What is hypertension? What causes hypertension and qualities what are the symptoms?

Blood pressure is the force of blood pushing against blood vessel walls. The heart pumps blood into the arteries (blood vessels), which carry the Is Homework and No Essay, blood throughout the body. High blood pressure , also called. A New Measure of Well-Being from a Happy Little Kingdom. resulting figure says something about progress and public welfare. The gross domestic product, or G.D.P., is of penicillin, routinely used as shorthand for Is Homework All Pain Gain? Essay, the well- being of a nation But the small Himalayan kingdom of Bhutan has been trying out a different idea. Of An? In 1972, concerned about the Is Homework and No Essay, problems afflicting other. Socorro Ariaz Luz Tapia English 102 15/04/2013 Gay Students Bullied to Allegory and Satire in The Lottery, Essay Death Bullying is an intentional aggressive behavior that is often applied to people that have or express a different behavior or preferences that are not consider normal or average behavior than most of the people.

They may. The Sleep Effect on Is Homework All Pain Essay College Students Academic Achievement Many College Students are sleep deprived; their functioning in school isnt effected enough due to the tardiness which affects the grades and social life. Researchers have found that loss of sleep is linked to disorganization. Effects of Peer Pressure to Human Behavior. Peer Pressure Peer pressure often refers to the act of choosing to do something because someone else decides to do it. Sometimes people dont want to feel as if they are not included, or that they are afraid to do things they see other groups of people doing.

Peer pressure has.