12 results
An isotopic proxy for nitrogen redistribution from Alnus acuminata to wheat intercrop
- Celestin Ukozehasi, Howard Griffiths
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- Journal:
- Experimental Agriculture / Volume 57 / Issue 5-6 / December 2021
- Published online by Cambridge University Press:
- 18 February 2022, pp. 316-323
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Direct belowground nitrogen (N) transfer has often been reported where plants with contrasting nutrients acquisition strategies (N2-fixing and non-fixing) co-occur, and there is still a gap in the knowledge of the extent of this transfer in the top soil under the field conditions. However, assessment under field conditions is challenging. We hypothesized a practical application of the analysis of natural abundance of δ15N supplemented with an isotopic mixing model ‘IsoSource’ to understand the relative direct contribution of N2-fixing Alnus acuminata to wheat intercrop (non-fixing) N isotopic signatures. A field experiment was conducted in an andic soil of high lands in northern Rwanda to quantitatively determine the proportional contribution of nitrogen by Alnus acuminata to wheat vegetative tissue isotope signatures at different distances from the trees (1 m, 3 m, 5 m, and 7 m). The study involved the measurements and analyses of natural abundance of stable isotopes δ15N and isotopic mixing modeling by IsoSource. Leaf samples were collected from twigs of 10 years old Alnus acuminata grown on the terrace-risers, along with soil samples (0–20 cm) and wheat flag leaf samples across terrace at 1 m, 3 m, 5 m, and 7 m from trees for isotopic measurement. The chlorophyll content index of wheat flag leaf at the four points across terrace was estimated by means of SPAD meter 502. The δ15N proportional contribution by Alnus acuminata to wheat was obtained through IsoSource analysis. We noted a significant (p < 0·01) gradient in depletion of wheat δ15N signatures moving further away from the tree line of Alnus acuminata. The wheat at 1 m from the trees exhibited the δ15N values closer to that of the tree, while at 7 m, the crop δ15N signature was significantly different from that of the tree. An isotopic mixing model ‘IsoSource’ indicated that the tree N may have provided 33·6 ± 4·3 % of the wheat intercrop N at 1 m distance from the trees. Therefore, this study shows that the understanding of field-based crop N and nutrient transfer in agroforestry may be enhanced by analysis of the physiological basis of stable isotopes signatures.
Variation in antibiotic use among neonatal intensive care units in the United States
- Hillary J.J. Spencer, Keerti L. Dantuluri, Cary Thurm, Hannah Griffith, Carlos G. Grijalva, Ritu Banerjee, Leigh M. Howard
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 43 / Issue 12 / December 2022
- Published online by Cambridge University Press:
- 09 September 2021, pp. 1945-1947
- Print publication:
- December 2022
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Antibiotics are widely used in neonatal intensive care units (NICUs). We conducted a cross-sectional analysis of antibiotic use across US NICUs to evaluate overall, broad-spectrum, and combination antibiotic use. Patterns of antibiotic use varied by medical versus surgical service line, hospital, and geographic location.
Considerable variability in antibiotic use among US children’s hospitals in 2017–2018
- Hannah G. Griffith, Keerti Dantuluri, Cary Thurm, Derek J. Williams, Ritu Banerjee, Leigh M. Howard, Carlos G. Grijalva
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 41 / Issue 5 / May 2020
- Published online by Cambridge University Press:
- 06 March 2020, pp. 571-578
- Print publication:
- May 2020
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Objective:
To characterize the prevalence of and seasonal and regional variation in inpatient antibiotic use among hospitalized US children in 2017–2018.
Design:We conducted a cross-sectional examination of hospitalized children. The assessments were conducted on a single day in spring (May 3, 2017), summer (August 2, 2017), fall (October 25, 2017), and winter (January 31, 2018). The main outcome of interest was receipt of an antibiotic on the study day.
Setting:The study included 51 freestanding US children’s hospitals that participate in the Pediatric Health Information System (PHIS).
Patients:This study included all patients <18 years old who were admitted to a participating PHIS hospital, excluding patients who were admitted solely for research purposes.
Results:Of 52,769 total hospitalized children, 19,174 (36.3%) received antibiotics on the study day and 6,575 of these (12.5%) received broad-spectrum antibiotics. The overall prevalence of antibiotic use varied across hospitals from 22.3% to 51.9%. Antibiotic use prevalence was 29.2% among medical patients and 47.7% among surgical patients. Although there was no significant seasonal variation in antibiotic use prevalence, regional prevalence varied, ranging from 32.7% in the Midwest to 40.2% in the West (P < .001). Among units, pediatric intensive care unit patients had the highest prevalence of both overall and broad-spectrum antibiotic use at 58.3% and 26.6%, respectively (P < .001).
Conclusions:On any given day in a national network of children’s hospitals, more than one-third of hospitalized children received an antibiotic, and 1 in 8 received a broad-spectrum antibiotic. Variation across hospitals, setting and regions identifies potential opportunities for enhanced antibiotic stewardship activities.
Evaluation of older people's knowledge, awareness, motivation and perceptions about falls and falls prevention in residential aged care homes: a tale of two cities
- Jacqueline Francis-Coad, Tessa Watts, Christopher Etherton-Beer, Gerwyn Panes, Howard Griffiths, Michelle Anderson, Tracy Williams, Beth Griffiths, Debbie Nobre, Anne-Marie Hill
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- Journal:
- Ageing & Society / Volume 39 / Issue 11 / November 2019
- Published online by Cambridge University Press:
- 27 June 2018, pp. 2541-2559
- Print publication:
- November 2019
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Falls prevention strategies can only be effective in reducing falls amongst older people if they are adopted and enacted in their daily lives. There is limited evidence identifying what older people in residential aged care (RAC) homes understand about falls and falls prevention, or what may limit or enable their adoption of strategies. This study was conducted in two countries and explored older people's knowledge and awareness of falls and their preferences, opportunities and motivation to undertake falls prevention strategies. A cross-sectional survey was administered to participants (N = 70) aged 65 years and over, living in six RAC homes in Perth, Australia and six RAC homes in Swansea, Wales, United Kingdom. Participants had limited knowledge about intrinsic falls risk factors and strategies to address these and frequently expressed self-blame regarding falling. Almost all (N = 67, 95.7%) participants felt highly motivated to maintain their current functional mobility and independence in everyday tasks. Key preferences for receiving falls prevention messages favoured a positive approach promoting wellness and independence (N = 41, 58.6%) via pictorial posters or brochures (N = 37, 52.9%) and small group discussions preferably with demonstrations (N = 18, 25.7%). Findings from this study may assist organisations and staff to more effectively engage with older people living in RAC about falls prevention and design targeted resources to address the motivations and preferences of this population.
Propagation of a viscous thin film over an elastic membrane
- Zhong Zheng, Ian M. Griffiths, Howard A. Stone
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- Journal:
- Journal of Fluid Mechanics / Volume 784 / 10 December 2015
- Published online by Cambridge University Press:
- 06 November 2015, pp. 443-464
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We study the buoyancy-driven spreading of a thin viscous film over a thin elastic membrane. Neglecting the effects of membrane bending and the membrane weight, we study the case of constant fluid injection and obtain a system of coupled partial differential equations to describe the shape of the air–liquid interface, and the deformation and radial tension of the stretched membrane. We obtain self-similar solutions to describe the dynamics. In particular, in the early-time period, the dynamics is dominated by buoyancy-driven spreading of the liquid film, and membrane stretching is a response to the buoyancy-controlled distribution of liquid weight; the location of the liquid front obeys the power-law form $r_{f}(t)\propto t^{1/2}$. However, in the late-time period, the system is quasi-steady, the air–liquid interface is flat, and membrane stretching, due to the liquid weight, causes the spreading of the liquid front; the location of the front obeys a different power-law form $r_{f}(t)\propto t^{1/4}$ before the edge effects of the membrane become significant. In addition, we report laboratory experiments for constant fluid injection using different viscous liquids and thin elastic membranes. Very good agreement is obtained between the theoretical predictions and experimental observations.
Stability of a bi-layer free film: simultaneous or individual rupture events?
- Peter S. Stewart, Jie Feng, Laura S. Kimpton, Ian M. Griffiths, Howard A. Stone
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- Journal:
- Journal of Fluid Mechanics / Volume 777 / 25 August 2015
- Published online by Cambridge University Press:
- 15 July 2015, pp. 27-49
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We consider the stability of a long free film of liquid composed of two immiscible layers of differing viscosities, where each layer experiences a van der Waals force between its interfaces. We analyse the different ways in which the system can exhibit interfacial instability when the liquid layers are sufficiently thin. For an excess of surfactant on one gas–liquid interface, the coupling between the layers is relatively weak and the instability is manifested as temporally separated rupture events in each layer. Conversely, in the absence of surfactant, the coupling between the layers is much stronger and the instability is manifested as rupture of both layers simultaneously. These features are consistent with recent experimental observations.
Contributors
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- By Mitchell Aboulafia, Frederick Adams, Marilyn McCord Adams, Robert M. Adams, Laird Addis, James W. Allard, David Allison, William P. Alston, Karl Ameriks, C. Anthony Anderson, David Leech Anderson, Lanier Anderson, Roger Ariew, David Armstrong, Denis G. Arnold, E. J. Ashworth, Margaret Atherton, Robin Attfield, Bruce Aune, Edward Wilson Averill, Jody Azzouni, Kent Bach, Andrew Bailey, Lynne Rudder Baker, Thomas R. Baldwin, Jon Barwise, George Bealer, William Bechtel, Lawrence C. Becker, Mark A. Bedau, Ernst Behler, José A. Benardete, Ermanno Bencivenga, Jan Berg, Michael Bergmann, Robert L. Bernasconi, Sven Bernecker, Bernard Berofsky, Rod Bertolet, Charles J. Beyer, Christian Beyer, Joseph Bien, Joseph Bien, Peg Birmingham, Ivan Boh, James Bohman, Daniel Bonevac, Laurence BonJour, William J. Bouwsma, Raymond D. Bradley, Myles Brand, Richard B. Brandt, Michael E. Bratman, Stephen E. Braude, Daniel Breazeale, Angela Breitenbach, Jason Bridges, David O. Brink, Gordon G. Brittan, Justin Broackes, Dan W. Brock, Aaron Bronfman, Jeffrey E. Brower, Bartosz Brozek, Anthony Brueckner, Jeffrey Bub, Lara Buchak, Otavio Bueno, Ann E. Bumpus, Robert W. Burch, John Burgess, Arthur W. Burks, Panayot Butchvarov, Robert E. Butts, Marina Bykova, Patrick Byrne, David Carr, Noël Carroll, Edward S. Casey, Victor Caston, Victor Caston, Albert Casullo, Robert L. Causey, Alan K. L. Chan, Ruth Chang, Deen K. Chatterjee, Andrew Chignell, Roderick M. Chisholm, Kelly J. Clark, E. J. Coffman, Robin Collins, Brian P. Copenhaver, John Corcoran, John Cottingham, Roger Crisp, Frederick J. Crosson, Antonio S. Cua, Phillip D. Cummins, Martin Curd, Adam Cureton, Andrew Cutrofello, Stephen Darwall, Paul Sheldon Davies, Wayne A. Davis, Timothy Joseph Day, Claudio de Almeida, Mario De Caro, Mario De Caro, John Deigh, C. F. Delaney, Daniel C. Dennett, Michael R. DePaul, Michael Detlefsen, Daniel Trent Devereux, Philip E. Devine, John M. Dillon, Martin C. Dillon, Robert DiSalle, Mary Domski, Alan Donagan, Paul Draper, Fred Dretske, Mircea Dumitru, Wilhelm Dupré, Gerald Dworkin, John Earman, Ellery Eells, Catherine Z. Elgin, Berent Enç, Ronald P. Endicott, Edward Erwin, John Etchemendy, C. Stephen Evans, Susan L. Feagin, Solomon Feferman, Richard Feldman, Arthur Fine, Maurice A. Finocchiaro, William FitzPatrick, Richard E. Flathman, Gvozden Flego, Richard Foley, Graeme Forbes, Rainer Forst, Malcolm R. Forster, Daniel Fouke, Patrick Francken, Samuel Freeman, Elizabeth Fricker, Miranda Fricker, Michael Friedman, Michael Fuerstein, Richard A. Fumerton, Alan Gabbey, Pieranna Garavaso, Daniel Garber, Jorge L. A. Garcia, Robert K. Garcia, Don Garrett, Philip Gasper, Gerald Gaus, Berys Gaut, Bernard Gert, Roger F. Gibson, Cody Gilmore, Carl Ginet, Alan H. Goldman, Alvin I. Goldman, Alfonso Gömez-Lobo, Lenn E. Goodman, Robert M. Gordon, Stefan Gosepath, Jorge J. E. Gracia, Daniel W. Graham, George A. Graham, Peter J. Graham, Richard E. Grandy, I. Grattan-Guinness, John Greco, Philip T. Grier, Nicholas Griffin, Nicholas Griffin, David A. Griffiths, Paul J. Griffiths, Stephen R. Grimm, Charles L. Griswold, Charles B. Guignon, Pete A. Y. Gunter, Dimitri Gutas, Gary Gutting, Paul Guyer, Kwame Gyekye, Oscar A. Haac, Raul Hakli, Raul Hakli, Michael Hallett, Edward C. Halper, Jean Hampton, R. James Hankinson, K. R. Hanley, Russell Hardin, Robert M. Harnish, William Harper, David Harrah, Kevin Hart, Ali Hasan, William Hasker, John Haugeland, Roger Hausheer, William Heald, Peter Heath, Richard Heck, John F. Heil, Vincent F. Hendricks, Stephen Hetherington, Francis Heylighen, Kathleen Marie Higgins, Risto Hilpinen, Harold T. Hodes, Joshua Hoffman, Alan Holland, Robert L. Holmes, Richard Holton, Brad W. Hooker, Terence E. Horgan, Tamara Horowitz, Paul Horwich, Vittorio Hösle, Paul Hoβfeld, Daniel Howard-Snyder, Frances Howard-Snyder, Anne Hudson, Deal W. Hudson, Carl A. Huffman, David L. Hull, Patricia Huntington, Thomas Hurka, Paul Hurley, Rosalind Hursthouse, Guillermo Hurtado, Ronald E. Hustwit, Sarah Hutton, Jonathan Jenkins Ichikawa, Harry A. Ide, David Ingram, Philip J. Ivanhoe, Alfred L. Ivry, Frank Jackson, Dale Jacquette, Joseph Jedwab, Richard Jeffrey, David Alan Johnson, Edward Johnson, Mark D. Jordan, Richard Joyce, Hwa Yol Jung, Robert Hillary Kane, Tomis Kapitan, Jacquelyn Ann K. Kegley, James A. Keller, Ralph Kennedy, Sergei Khoruzhii, Jaegwon Kim, Yersu Kim, Nathan L. King, Patricia Kitcher, Peter D. Klein, E. D. Klemke, Virginia Klenk, George L. Kline, Christian Klotz, Simo Knuuttila, Joseph J. Kockelmans, Konstantin Kolenda, Sebastian Tomasz Kołodziejczyk, Isaac Kramnick, Richard Kraut, Fred Kroon, Manfred Kuehn, Steven T. Kuhn, Henry E. Kyburg, John Lachs, Jennifer Lackey, Stephen E. Lahey, Andrea Lavazza, Thomas H. Leahey, Joo Heung Lee, Keith Lehrer, Dorothy Leland, Noah M. Lemos, Ernest LePore, Sarah-Jane Leslie, Isaac Levi, Andrew Levine, Alan E. Lewis, Daniel E. Little, Shu-hsien Liu, Shu-hsien Liu, Alan K. L. Chan, Brian Loar, Lawrence B. Lombard, John Longeway, Dominic McIver Lopes, Michael J. Loux, E. J. Lowe, Steven Luper, Eugene C. Luschei, William G. Lycan, David Lyons, David Macarthur, Danielle Macbeth, Scott MacDonald, Jacob L. Mackey, Louis H. Mackey, Penelope Mackie, Edward H. Madden, Penelope Maddy, G. B. Madison, Bernd Magnus, Pekka Mäkelä, Rudolf A. Makkreel, David Manley, William E. Mann (W.E.M.), Vladimir Marchenkov, Peter Markie, Jean-Pierre Marquis, Ausonio Marras, Mike W. Martin, A. P. Martinich, William L. McBride, David McCabe, Storrs McCall, Hugh J. McCann, Robert N. McCauley, John J. McDermott, Sarah McGrath, Ralph McInerny, Daniel J. McKaughan, Thomas McKay, Michael McKinsey, Brian P. McLaughlin, Ernan McMullin, Anthonie Meijers, Jack W. Meiland, William Jason Melanson, Alfred R. Mele, Joseph R. Mendola, Christopher Menzel, Michael J. Meyer, Christian B. Miller, David W. Miller, Peter Millican, Robert N. Minor, Phillip Mitsis, James A. Montmarquet, Michael S. Moore, Tim Moore, Benjamin Morison, Donald R. Morrison, Stephen J. Morse, Paul K. Moser, Alexander P. D. Mourelatos, Ian Mueller, James Bernard Murphy, Mark C. Murphy, Steven Nadler, Jan Narveson, Alan Nelson, Jerome Neu, Samuel Newlands, Kai Nielsen, Ilkka Niiniluoto, Carlos G. Noreña, Calvin G. Normore, David Fate Norton, Nikolaj Nottelmann, Donald Nute, David S. Oderberg, Steve Odin, Michael O’Rourke, Willard G. Oxtoby, Heinz Paetzold, George S. Pappas, Anthony J. Parel, Lydia Patton, R. P. Peerenboom, Francis Jeffry Pelletier, Adriaan T. Peperzak, Derk Pereboom, Jaroslav Peregrin, Glen Pettigrove, Philip Pettit, Edmund L. Pincoffs, Andrew Pinsent, Robert B. Pippin, Alvin Plantinga, Louis P. Pojman, Richard H. Popkin, John F. Post, Carl J. Posy, William J. Prior, Richard Purtill, Michael Quante, Philip L. Quinn, Philip L. Quinn, Elizabeth S. Radcliffe, Diana Raffman, Gerard Raulet, Stephen L. Read, Andrews Reath, Andrew Reisner, Nicholas Rescher, Henry S. Richardson, Robert C. Richardson, Thomas Ricketts, Wayne D. Riggs, Mark Roberts, Robert C. Roberts, Luke Robinson, Alexander Rosenberg, Gary Rosenkranz, Bernice Glatzer Rosenthal, Adina L. Roskies, William L. Rowe, T. M. Rudavsky, Michael Ruse, Bruce Russell, Lilly-Marlene Russow, Dan Ryder, R. M. Sainsbury, Joseph Salerno, Nathan Salmon, Wesley C. Salmon, Constantine Sandis, David H. Sanford, Marco Santambrogio, David Sapire, Ruth A. Saunders, Geoffrey Sayre-McCord, Charles Sayward, James P. Scanlan, Richard Schacht, Tamar Schapiro, Frederick F. Schmitt, Jerome B. Schneewind, Calvin O. Schrag, Alan D. Schrift, George F. Schumm, Jean-Loup Seban, David N. Sedley, Kenneth Seeskin, Krister Segerberg, Charlene Haddock Seigfried, Dennis M. Senchuk, James F. Sennett, William Lad Sessions, Stewart Shapiro, Tommie Shelby, Donald W. Sherburne, Christopher Shields, Roger A. Shiner, Sydney Shoemaker, Robert K. Shope, Kwong-loi Shun, Wilfried Sieg, A. John Simmons, Robert L. Simon, Marcus G. Singer, Georgette Sinkler, Walter Sinnott-Armstrong, Matti T. Sintonen, Lawrence Sklar, Brian Skyrms, Robert C. Sleigh, Michael Anthony Slote, Hans Sluga, Barry Smith, Michael Smith, Robin Smith, Robert Sokolowski, Robert C. Solomon, Marta Soniewicka, Philip Soper, Ernest Sosa, Nicholas Southwood, Paul Vincent Spade, T. L. S. Sprigge, Eric O. Springsted, George J. Stack, Rebecca Stangl, Jason Stanley, Florian Steinberger, Sören Stenlund, Christopher Stephens, James P. Sterba, Josef Stern, Matthias Steup, M. A. Stewart, Leopold Stubenberg, Edith Dudley Sulla, Frederick Suppe, Jere Paul Surber, David George Sussman, Sigrún Svavarsdóttir, Zeno G. Swijtink, Richard Swinburne, Charles C. Taliaferro, Robert B. Talisse, John Tasioulas, Paul Teller, Larry S. Temkin, Mark Textor, H. S. Thayer, Peter Thielke, Alan Thomas, Amie L. Thomasson, Katherine Thomson-Jones, Joshua C. Thurow, Vzalerie Tiberius, Terrence N. Tice, Paul Tidman, Mark C. Timmons, William Tolhurst, James E. Tomberlin, Rosemarie Tong, Lawrence Torcello, Kelly Trogdon, J. D. Trout, Robert E. Tully, Raimo Tuomela, John Turri, Martin M. Tweedale, Thomas Uebel, Jennifer Uleman, James Van Cleve, Harry van der Linden, Peter van Inwagen, Bryan W. Van Norden, René van Woudenberg, Donald Phillip Verene, Samantha Vice, Thomas Vinci, Donald Wayne Viney, Barbara Von Eckardt, Peter B. M. Vranas, Steven J. Wagner, William J. Wainwright, Paul E. Walker, Robert E. Wall, Craig Walton, Douglas Walton, Eric Watkins, Richard A. Watson, Michael V. Wedin, Rudolph H. Weingartner, Paul Weirich, Paul J. Weithman, Carl Wellman, Howard Wettstein, Samuel C. Wheeler, Stephen A. White, Jennifer Whiting, Edward R. Wierenga, Michael Williams, Fred Wilson, W. Kent Wilson, Kenneth P. Winkler, John F. Wippel, Jan Woleński, Allan B. Wolter, Nicholas P. Wolterstorff, Rega Wood, W. Jay Wood, Paul Woodruff, Alison Wylie, Gideon Yaffe, Takashi Yagisawa, Yutaka Yamamoto, Keith E. Yandell, Xiaomei Yang, Dean Zimmerman, Günter Zoller, Catherine Zuckert, Michael Zuckert, Jack A. Zupko (J.A.Z.)
- Edited by Robert Audi, University of Notre Dame, Indiana
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- Book:
- The Cambridge Dictionary of Philosophy
- Published online:
- 05 August 2015
- Print publication:
- 27 April 2015, pp ix-xxx
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Contributors
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- By Paul S. Appelbaum, Elizabeth K. Dollard, Peter Ash, Madelon V. Baranoski, Alec Buchanan, Philip J. Candilis, J. Richard Ciccone, Eric Elbogen, Graham D. Glancy, Robert P. Granacher, Ezra E. H. Griffith, Jeffrey S. Janofsky, Sally Johnson, Joshua Jones, Alyson Kuroski-Mazzei, Li-Wen Grace Lee, Gregory B. Leong, Barbara McDermott, Richard Martinez, Michael A. Norko, John O’Grady, Debra A. Pinals, Marilyn Price, Patricia Ryan Recupero, Phillip J. Resnick, Robert L. Sadoff, Charles Scott, J. Arturo Silva, Sherif Soliman, Aleksandra Stankovic, Robert Weinstock, Kenneth J. Weiss, Robert M. Wettstein, Cheryl Wills, Howard Zonana
- Edited by Alec Buchanan, Yale University, Connecticut, Michael A. Norko, Yale University, Connecticut
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- Book:
- The Psychiatric Report
- Published online:
- 07 September 2011
- Print publication:
- 07 July 2011, pp ix-xii
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Patterns of suicide by occupation in England and Wales: 2001–2005
- Howard Meltzer, Clare Griffiths, Anita Brock, Cleo Rooney, Rachel Jenkins
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- Journal:
- The British Journal of Psychiatry / Volume 193 / Issue 1 / July 2008
- Published online by Cambridge University Press:
- 02 January 2018, pp. 73-76
- Print publication:
- July 2008
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Background
Suicide rates vary by occupation but this relationship has not been frequently studied
AimsTo identify the occupations with significantly high suicide rates in England and Wales in 2001–2005 and to compare these with rates from previous decades
MethodMortality data from death registrations in England and Wales over the calendar years 2001–2005 were used to calculate proportional mortality ratios (PMRs) and standardised mortality ratios (SMRs) for both men and women aged 20–64 years by their occupation
ResultsAmong men, in 2001–2005, construction workers, and plant and machine operatives had the greatest number of suicides. The highest PMRs were for health professionals (PMR=164) and agricultural workers (PMR=133). Among women, administrative and secretarial workers had the greatest number of suicides yet the highest PMRs were found for health (PMR=232), and sport and fitness (PMR=244) occupations
ConclusionsExcess mortality from suicide remains in some occupational groups. The apparent changes in suicide patterns merits further exploration, for example examining the prevalence of depression and suicidal ideation in medical practitioners, dentists, veterinarians, agricultural workers, librarians and construction workers
The role of carbonic anhydrase in photosynthesis and the activity of the carbon-concentrating-mechanism in bryophytes of the class Anthocerotae
- ELIZABETH C. SMITH, HOWARD GRIFFITHS
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- Journal:
- The New Phytologist / Volume 145 / Issue 1 / January 2000
- Published online by Cambridge University Press:
- 01 January 2000, pp. 29-37
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- January 2000
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The role of carbonic anhydrase in the carbon-concentrating-mechanism of bryophytes of the class Anthocerotae was investigated by comparing the gas-exchange characteristics of material which had been incubated in the membrane-permeable Carbonic Anhydrase inhibitor ethoxyzolamide, with those of untreated material and material which had been incubated in buffer solution. In Phaeoceros laevis (Anthocerotae), incubation in ethoxyzolamide caused a depression in the rate of gross assimilation and a decrease in CO2 affinity beyond that which could be attributed to increased diffusion limitation. A range of liverworts and mosses, in which a carbon-concentrating-mechanism is absent, were also investigated. These showed no depression of rates of gross assimilation after incubation in ethoxyzolamide relative to those of untreated material. The CO2 compensation point and CO2 uptake characteristics of Phaeoceros laevis were significantly affected by incubation in ethoxyzolamide. Values of CO2 compensation point for Phaeoceros laevis rose from 2.5 Pa, after incubation in buffer, to 20 Pa after incubation in ethoxyzolamide. The CO2 compensation point for the liverworts Pellia epiphylla and Marchantia polymorpha was not significantly affected by incubation in ethoxyzolamide. Measurements of the release of CO2 at the end of a short (15 min) period of illumination revealed that, after suppression of carbonic anhydrase activity, the rapid release of a CO2 pool occurred in Phaeoceros laevis but not in the liverworts. There were also significant differences between values for fractionation measured in units per mil (‰), measured instantaneously, for Phaeoceros laevis incubated in ethoxyzolamide, compared with fractionation values for this species after incubation in buffer. Incubation in ethoxyzolamide caused fractionation values to rise from 12.4–22.7‰, indicating that the carbon-concentrating-mechanism of this species had been inactivated. Incubation in ethoxyzolamide had no effect on fractionation values for the liverworts. The convexity of the light saturation curves of liverworts and Phaeoceros laevis was also investigated, but there were no differences between groups before or after the two treatments. The data indicate an important role for carbonic anhydrase in the functioning of the carbon-concentrating-mechanism in the Anthocerotae.
Growth and development of Mesembryanthemum crystallinum (Aizoaceae)
- PATRICIA ADAMS, DON E. NELSON, SHIGEHIRO YAMADA, WENDY CHMARA, RICHARD G. JENSEN, HANS J. BOHNERT, HOWARD GRIFFITHS
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- Journal:
- The New Phytologist / Volume 138 / Issue 2 / February 1998
- Published online by Cambridge University Press:
- 01 February 1998, pp. 171-190
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- February 1998
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This review describes the life cycle of Mesembryantheum crystallinum L. (the common ice plant, Aizoaceae, Caryophyllales), a halophyte with a developmentally programmed switch from C3 photosynthesis to Crassulacean acid metabolism (CAM) which is accelerated by salinity and drought. Since there has been controversy regarding the interplay between genes and environmental stimuli during the development of M. crystallinum, it is timely to summarize the life cycle for a defined set of conditions. We seek to establish the framework whereby five stages of development can be described in terms of morphology, physiology, and molecular biology. Stages 1 and 2, representing germination and growth of a juvenile form, show a determinate pattern of growth. Although specific genes for salt tolerance can be induced at these stages, stress early in development prevents progression to the mature form (stages 3–5) in which the plants advance to mature growth, flowering, and seed development. Growth in stage 3 is indeterminate in the absence of stress, but development and flowering are accelerated by environmental stresses, and CAM is constitutively expressed. Depending on the severity of the stress, plants start to flower (stage 4) and then die from the roots, ultimately with only seed capsules remaining viable, with salt sequestered into large epidermal bladder cells (stage 5). We highlight responses to salinity leading to compartmentation of ions and compatible solutes, turgor maintenance, and CAM. Finally, the molecular genetics of the ice plant are characterized, emphasizing selected genes and their products. We conclude with an analysis of the multiple stages of growth as an ecological adaptation to progressive stress. The initial determinate and inflexible juvenile phase provides a critical mass of plant material which supports the indeterminate, mature phase. Depending on the degree of stress, the mature form is then propelled towards flowering and seedset.
Clover development and animal production under continuous grazing
- D. W. Howard, M. S. Griffiths, C. James
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- Journal:
- BSAP Occasional Publication / Volume 14 / January 1990
- Published online by Cambridge University Press:
- 02 September 2010, pp. 129-130
- Print publication:
- January 1990
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