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A Qualitative Study Exploring the Role of Hindsight Bias in the Process of Reviewing Clinical Practice Prior to Adverse Incidents
- Irene Hadjioannou, Emily Lewis, Leo Scott, Catrin Thomas, Alberto Salmoiraghi, Rajan Nathan
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- Journal:
- BJPsych Open / Volume 8 / Issue S1 / June 2022
- Published online by Cambridge University Press:
- 20 June 2022, p. S76
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Aims
To explore the effect of hindsight bias on retrospective reviews of clinical decision making prior to adverse incidents to inform future approaches to incident investigations.
MethodsWe have undertaken focus groups with doctors of varying grades across the North West of England and North Wales. A vignette based on a real-life case from the publicly available NHS England Homicide Independent Investigation report database was presented to each group in one of three versions which differed in terms of the ending of the vignettes (i.e. suicide, homicide, no adverse incident). Using a semi-structured interview approach, the group participants were encouraged by the facilitators to reflect on issues relating to risk and risk management. All groups were provided with the same vignette which initially made no reference to the outcome and asked to comment on matters of risk and risk management. Halfway through the discussion, one of the three outcomes was disclosed, and further group discussion was held. The recorded interviews were transcribed and thematic analysis was undertaken using an adapted Framework Method.
ResultsPreliminary results (n = 10) indicate that participants identified the potential for significant harm, particularly to others, and identified evidence of key psychopathological and historical correlates to support assertive management of risk and admission to hospital.
Whilst knowledge of the outcome did not lead to participants changing their favoured management plans, it did alter how they appraised the case and led to participants constructing “narrative” explanations for the outcome given. The level of conviction participants held for their management plan reduced when their expectations about the outcome were confounded.
Participants presented with the suicide outcome vignette described their difficulties appraising risk to others and their over-sensitivity to that risk. Participants faced with the ‘no adverse outcome’ vignette perceived the original management plan far more favourably in hindsight. The groups that were presented with the homicide outcome vignette initially focused on both risks to self and others as well as the perceived need for further information. Following knowledge of the outcome, there was a tendency to highlight parts of the letter pertaining to risk to others which they previously had not given as much attention.
ConclusionThe initial analysis of our data confirms the findings from previous studies that hindsight colours the appraisal of adverse events. However, this study is novel in that it describes the nature of the thought processes underpinning the influence of hindsight on appraisals of risk.
Perceived barriers and contributors to sense of purpose in life in retirement community residents
- Nathan A. Lewis, Naomi Reesor, Patrick L. Hill
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- Journal:
- Ageing & Society / Volume 42 / Issue 6 / June 2022
- Published online by Cambridge University Press:
- 21 December 2020, pp. 1448-1464
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- June 2022
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Despite the growing use of retirement communities and ageing care facilities, little is known about how residing in retirement residences may impact aspects of older adult wellbeing. Living in these communities may hold particular influence on residents’ sense of purpose, if they feel limited in their opportunities for individual action, or could serve to promote purposefulness depending on the social connections available. The current study sought to explore contributing factors as well as barriers to purpose in older adults living in three continuing care retirement communities. Using brief semi-structured interviews, 18 older adults were asked to describe their purpose in life, community-related activities and any perceived challenges limiting their ability to pursue this purpose. Thematic analysis was used to examine themes common across interviews. Interviews presented a mixed picture of the nature of purposefulness in retirement facilities. Residents espoused several benefits of community living such as social and leisure opportunities, while also noting several obstacles to their purpose, including health concerns and the belief that purpose in life was not relevant for older adults. These findings provide insight into how older adults can derive a sense of purpose from activities within their retirement community and how facilities can better tailor programmes to promote purposefulness and support personally valued roles for residents.
Assessment of coexisting psychosis and substance misuse: complexities, challenges and causality
- Rajan Nathan, Emily Lewis
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- Journal:
- BJPsych Advances / Volume 27 / Issue 1 / January 2021
- Published online by Cambridge University Press:
- 20 July 2020, pp. 38-48
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- January 2021
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Substance misuse worsens the prognosis for people suffering psychosis and places them at risk of being denied appropriate mental health service interventions. To increase the chances of its success, the plan of management for patients with coexisting psychosis and substance misuse should be based on a valid formulation of their problems, which in turn is dependent on the clinician having (a) a thorough understanding of the bidirectional and changing ways that substance use and mental illness symptoms can interact, (b) an awareness of their own biased implicit assumptions about causality in explaining these interactions and (c) a framework for assessment and formulation. This article addresses these three areas with reference to the evidence base and to clinical experience in a way that guides mental health clinicians in the assessment of patients with coexisting psychosis and substance misuse.
The Effect of Implementation of the American Heart Association Mission Lifeline PreAct Algorithm for Prehospital Cardiac Catheterization Laboratory Activation on the Rate of “False Positive” Activations
- Juliana Tolles, Nichole Bosson, Amy H. Kaji, Timothy D. Henry, William J. French, Marianne Gausche-Hill, Kevin Andruss, Nathan McNeil, Eric C. Nakkim, Gregory S. Thomas, Michael R. Gunderson, Roger J. Lewis
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- Journal:
- Prehospital and Disaster Medicine / Volume 35 / Issue 4 / August 2020
- Published online by Cambridge University Press:
- 20 May 2020, pp. 388-396
- Print publication:
- August 2020
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Hypothesis:
Emergency Medical Services (EMS) systems have developed protocols for prehospital activation of the cardiac catheterization laboratory for patients with suspected ST-elevation myocardial infarction (STEMI) to decrease first-medical-contact-to-balloon time (FMC2B). The rate of “false positive” prehospital activations is high. In order to decrease this rate and expedite care for patients with true STEMI, the American Heart Association (AHA; Dallas, Texas USA) developed the Mission Lifeline PreAct STEMI algorithm, which was implemented in Los Angeles County (LAC; California USA) in 2015. The hypothesis of this study was that implementation of the PreAct algorithm would increase the positive predictive value (PPV) of prehospital activation.
Methods:This is an observational pre-/post-study of the effect of the implementation of the PreAct algorithm for patients with suspected STEMI transported to one of five STEMI Receiving Centers (SRCs) within the LAC Regional System. The primary outcome was the PPV of cardiac catheterization laboratory activation for percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG). The secondary outcome was FMC2B.
Results:A total of 1,877 patients were analyzed for the primary outcome in the pre-intervention period and 405 patients in the post-intervention period. There was an overall decrease in cardiac catheterization laboratory activations, from 67% in the pre-intervention period to 49% in the post-intervention period (95% CI for the difference, -14% to -22%). The overall rate of cardiac catheterization declined in post-intervention period as compared the pre-intervention period, from 34% to 30% (95% CI, for the difference -7.6% to 0.4%), but actually increased for subjects who had activation (48% versus 58%; 95% CI, 4.6%-15.0%). Implementation of the PreAct algorithm was associated with an increase in the PPV of activation for PCI or CABG from 37.9% to 48.6%. The overall odds ratio (OR) associated with the intervention was 1.4 (95% CI, 1.1-1.8). The effect of the intervention was to decrease variability between medical centers. There was no associated change in average FMC2B.
Conclusions:The implementation of the PreAct algorithm in the LAC EMS system was associated with an overall increase in the PPV of cardiac catheterization laboratory activation.
Evidence of causal effect of major depression on alcohol dependence: findings from the psychiatric genomics consortium
- Renato Polimanti, Roseann E. Peterson, Jue-Sheng Ong, Stuart MacGregor, Alexis C. Edwards, Toni-Kim Clarke, Josef Frank, Zachary Gerring, Nathan A. Gillespie, Penelope A. Lind, Hermine H. Maes, Nicholas G. Martin, Hamdi Mbarek, Sarah E. Medland, Fabian Streit, Major Depressive Disorder Working Group of the Psychiatric Genomics Consortium, Substance Use Disorder Working Group of the Psychiatric Genomics Consortium, 23andMe Research Team, Arpana Agrawal, Howard J. Edenberg, Kenneth S. Kendler, Cathryn M. Lewis, Patrick F. Sullivan, Naomi R. Wray, Joel Gelernter, Eske M. Derks
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- Journal:
- Psychological Medicine / Volume 49 / Issue 7 / May 2019
- Published online by Cambridge University Press:
- 01 April 2019, pp. 1218-1226
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Background
Despite established clinical associations among major depression (MD), alcohol dependence (AD), and alcohol consumption (AC), the nature of the causal relationship between them is not completely understood. We leveraged genome-wide data from the Psychiatric Genomics Consortium (PGC) and UK Biobank to test for the presence of shared genetic mechanisms and causal relationships among MD, AD, and AC.
MethodsLinkage disequilibrium score regression and Mendelian randomization (MR) were performed using genome-wide data from the PGC (MD: 135 458 cases and 344 901 controls; AD: 10 206 cases and 28 480 controls) and UK Biobank (AC-frequency: 438 308 individuals; AC-quantity: 307 098 individuals).
ResultsPositive genetic correlation was observed between MD and AD (rgMD−AD = + 0.47, P = 6.6 × 10−10). AC-quantity showed positive genetic correlation with both AD (rgAD−AC quantity = + 0.75, P = 1.8 × 10−14) and MD (rgMD−AC quantity = + 0.14, P = 2.9 × 10−7), while there was negative correlation of AC-frequency with MD (rgMD−AC frequency = −0.17, P = 1.5 × 10−10) and a non-significant result with AD. MR analyses confirmed the presence of pleiotropy among these four traits. However, the MD-AD results reflect a mediated-pleiotropy mechanism (i.e. causal relationship) with an effect of MD on AD (beta = 0.28, P = 1.29 × 10−6). There was no evidence for reverse causation.
ConclusionThis study supports a causal role for genetic liability of MD on AD based on genetic datasets including thousands of individuals. Understanding mechanisms underlying MD-AD comorbidity addresses important public health concerns and has the potential to facilitate prevention and intervention efforts.
Association between Sleep Disordered Breathing and Nighttime Driving Performance in Mild Cognitive Impairment
- Nathan Cross, Zoe Terpening, Shantel L. Duffy, Simon J.G. Lewis, Ron Grunstein, Keith Wong, Sharon L. Naismith
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- Journal:
- Journal of the International Neuropsychological Society / Volume 23 / Issue 6 / July 2017
- Published online by Cambridge University Press:
- 24 April 2017, pp. 502-510
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Objectives: The effect of sleep disordered breathing (SDB) on driving performance in older adults has not been extensively investigated, especially in those with mild cognitive impairment (MCI). The aim of this study was to examine the relationship between severity measures of SDB and a simulated driving task in older adults with and without MCI. Methods: Nineteen older adults (age ≥50) meeting criteria for MCI and 23 age-matched cognitively intact controls underwent neuropsychological assessment and a driving simulator task in the evening before a diagnostic sleep study. Results: There were no differences in driving simulator performance or SDB severity between the two groups. In patients with MCI, a higher oxygen desaturation index (ODI) was associated with an increased number of crashes on the simulator task, as well as other driving parameters such as steering and speed deviation. Poorer driving performance was also associated with poorer executive functioning (set-shifting) but the relationship between ODI and crashes was independent of executive ability. Conclusions: While driving ability did not differ between older adults with and without MCI, oxygen saturation dips in MCI were related to worse driving performance. These results suggest that decreased brain integrity may render those with SDB particularly vulnerable to driving accidents. In older adults, both cognition and SDB need to be considered concurrently in relation to driving ability. (JINS, 2017, 23, 502–510)
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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- The Cambridge Dictionary of Philosophy
- Published online:
- 05 August 2015
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- 27 April 2015, pp ix-xxx
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BIGHORNS - Broadband Instrument for Global HydrOgen ReioNisation Signal
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- Marcin Sokolowski, Steven E. Tremblay, Randall B. Wayth, Steven J. Tingay, Nathan Clarke, Paul Roberts, Mark Waterson, Ronald D. Ekers, Peter Hall, Morgan Lewis, Mehran Mossammaparast, Shantanu Padhi, Franz Schlagenhaufer, Adrian Sutinjo, Jonathan Tickner
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- Journal:
- Publications of the Astronomical Society of Australia / Volume 32 / 2015
- Published online by Cambridge University Press:
- 16 February 2015, e004
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The redshifted 21cm line of neutral hydrogen (Hi), potentially observable at low radio frequencies (~50–200 MHz), should be a powerful probe of the physical conditions of the inter-galactic medium during Cosmic Dawn and the Epoch of Reionisation (EoR). The sky-averaged Hi signal is expected to be extremely weak (~100 mK) in comparison to the foreground of up to 104 K at the lowest frequencies of interest. The detection of such a weak signal requires an extremely stable, well characterised system and a good understanding of the foregrounds. Development of a nearly perfectly (~mK accuracy) calibrated total power radiometer system is essential for this type of experiment. We present the BIGHORNS (Broadband Instrument for Global HydrOgen ReioNisation Signal) experiment which was designed and built to detect the sky-averaged Hi signal from the EoR at low radio frequencies. The BIGHORNS system is a mobile total power radiometer, which can be deployed in any remote location in order to collect radio frequency interference (RFI) free data. The system was deployed in remote, radio quiet locations in Western Australia and low RFI sky data have been collected. We present a description of the system, its characteristics, details of data analysis, and calibration. We have identified multiple challenges to achieving the required measurement precision, which triggered two major improvements for the future system.
Hexathiapentacene Nanowires as Chemical Vapor Sensors
- Ting Gao, Edgardo Garcia-Berrios, Alejandro L Briseno, Jian Wang, Richard McConville, Mark W Ellsworth, Ryan W Dupon, Nathan Lewis
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1253 / 2010
- Published online by Cambridge University Press:
- 01 February 2011, 1253-K05-08
- Print publication:
- 2010
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Semiconducting hexathiapentacene (HTP) single–crystal nanowires were synthesized using a simple solution-phase route. Quartz Crystal Microbalance and complex resistance measurements were employed to investigate the sensing properties of an HTP nanowire to analytes including acid, amine, and hydrocarbon vapors. Cole-Cole plots (0.01Hz-4 MHz) of measured impedance spectra, modeled using equivalent circuits, were used to resolve the effects of adsorption and charge migration.
Powering the Planet
- Nathan S. Lewis
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- Journal:
- MRS Bulletin / Volume 32 / Issue 10 / October 2007
- Published online by Cambridge University Press:
- 31 January 2011, pp. 808-820
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- October 2007
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I am humbled and honored to be here to tell you about a topic that is dear to everyone's heart—and vital to the future of our planet. My colleague, Richard Smalley, gave a presentation on this topic several years ago, at a similar MRS plenary session. Over the last few years of Dr. Smalley's life, he and I worked together, traveling across our country to deliver a message about a subject that we—like many others, both scientists and lay people— have come to believe is unequivocally the most important technological problem in the world: our global energy future. That is an incredibly powerful statement, one that during the next hour I hope to ably defend.
Controlled Passivation and Luminescence Blue Shifts of Isolated Silicon Nanocrystals
- Julie S. Biteen, Anna L. Tchebotareva, Albert Polman, Nathan S. Lewis, Harry A. Atwater
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- Journal:
- MRS Online Proceedings Library Archive / Volume 770 / 2003
- Published online by Cambridge University Press:
- 10 February 2011, I6.2
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- 2003
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We have performed a comparative study of oxide- and nonoxide-passivated silicon nanocrystals to probe the role of the silicon/oxygen interface in low coverage, non-interacting silicon nanocrystal systems. Ensembles of Si nanocrystals characterized by a narrow distribution and diameters of 2–5 nm were synthesized by ion implantation into SiO2 films followed by a high-temperature anneal in Ar. The nanocrystals were removed from the SiO2 film matrix and deposited on Si substrates using a chemical etch in HF, leaving a hydrogen-terminated surface. A natural oxide layer grows on these surfaces in air. We characterized the morphology of the samples with atomic force microscopy (AFM) and the spectroscopic properties with photoluminescence (PL) and X-Ray photoelectron spectroscopy. We found that the PL energy of Si nanocrystals can be shifted by particle size reduction and hydrogen or oxygen termination. Further, PL peak energy shifts upon etching and oxidation were consistent with the model of Wolkin et al. that proposes that for very small radii, a silicon-oxygen double bond will produce deep interface states which red shift the luminescence.
Array Based Carbon Black-Polymer Composite Vapor Detectors for Detection of DNT in Environments Containing Complex Analyte Mixtures
- Shawn M. Briglin, Michael S. Freund, Brian C. Sisk, Nathan S. Lewis
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- Journal:
- MRS Online Proceedings Library Archive / Volume 700 / 2001
- Published online by Cambridge University Press:
- 17 March 2011, S4.1
- Print publication:
- 2001
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Thin films of carbon black-organic polymer composites have been deposited across two metallic leads, with sorption of vapors producing swelling-induced resistance changes of the detector films. To identify and classify vapors, arrays of such vapor sensing elements have been constructed in which each element of the array contains a different polymer as the insulating phase and a common conductor, carbon black, as the conducting phase. The differing gas-solid partition coefficients for the various polymers of the detector array produce a pattern of differential resistance changes that is used to classify vapors and vapor mixtures. The performance of this detector array system towards 2,4-dinitrotoluene, the predominant signature in the vapor phase above land mines, in the presence high concentrations of water or of acetone (as a selected volatile organic carbon vapor), has been evaluated.
Reaction Zone Growth in Ti-Base/SiC Composites
- Ann M. Ritter, Ernest L. Hall, Nathan Lewis
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- Journal:
- MRS Online Proceedings Library Archive / Volume 194 / 1990
- Published online by Cambridge University Press:
- 21 February 2011, 413
- Print publication:
- 1990
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Reaction zone phases and kinetics over a temperature range of 650-1200°C have been characterized for Ti-14Al-21Nb/SiC and Ti-6Al-2Sn-4Zr-2Mo/SiC fibrous composites. The matrix of the Ti-1421/SiC materials was α2 with varying amounts of beta phase and transformed beta phase, and the Ti-6242 matrix consisted of alpha plus beta. The reaction zone in the as-HIP Ti-1421/SiC contained fine-grained TiC, a region of coarser-grained TiC, a carbide layer containing Ti, Al and Nb, and a region of(Ti, Nb)5(Si, Al)3. The matrix adjacent to the reaction zone was α2-Ti3Al with no beta phase. In the as-HIP Ti-6242/SiC composites, the reaction zone contained TiC near the fiber, and a layer of (Ti,Zr)5Si3 adjacent to the matrix. In heat-treated samples, the reaction zone thicknesses varied in a linear fashion with the square-root of aging time, indicating diffusion-controlled growth. Incubation periods for reaction zone growth were observed in Ti-1421/SiC samples aged at 760-1000°C. The overall kinetics for the two matrix alloys were approximately the same, and the activation energy was measured as 63-73 kcal/mole for Ti-1421/SiC and 73kcal/mole for Ti-6242/SiC.
Silicon and Silicon Dioxide Thermal Bonding
- Robert D. Black, Ernest L. Hall, Nathan Lewis, Robert S. Gilmore, Steven D. Arthur, Robert D. Lillquist
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- Journal:
- MRS Online Proceedings Library Archive / Volume 107 / 1987
- Published online by Cambridge University Press:
- 28 February 2011, 495
- Print publication:
- 1987
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The quality of the bond produced after mating oxidized and/or unoxidized silicon wafers has been studied using acoustic microscopy, infrared transmission thermographs, and transmission electron microscopy. The acoustic microscopy revealed that a significant number of unbonded regions (gaps) remain at the bond interface after bonding in oxygen, nitrogen, or high vacuum, and then annealing. These gaps could be virtually eliminated by a subsequent hyperbaric annealing step. The thermal imaging was found to have insufficient resolution to give a detailed picture of the bond quality. Transmission electron microscopy showed that an excellent bond could be produced when bonding clean silicon wafers, with only very small oxide or void bubbles present at the interface. Bonding two oxidized wafers resulted in a buried oxide layer with no detectable bond line. Mating an oxidized wafer to an unoxidized wafer produced a bonded silicon/oxide interface which was nearly indistiguishable from the wafer/thermal oxide interface.