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5 Associations Between Regional Perfusion and Locus Coeruleus MRI Contrast are Moderated by Plasma Alzheimer’s Disease Biomarkers in Older Adults
- Shubir Dutt, Shelby L Bachman, Yanrong Li, Belinda Yew, Jung Y Jang, Jean K Ho, Kaoru Nashiro, Jungwon Min, Hyun Joo Yoo, Aimee Gaubert, Amy Nguyen, Isabel J Sible, Anna E Blanken, Anisa J Marshall, Arunima Kapoor, John P Alitin, Kim Hoang, Alessandra C Martini, Elizabeth Head, Xingfeng Shao, Danny J J Wang, Mara Mather, Daniel A Nation
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 610-611
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Objective:
The locus coeruleus (LC) innervates the cerebrovasculature and plays a crucial role in optimal regulation of cerebral blood flow. However, no human studies to date have examined links between these systems with widely available neuroimaging methods. We quantified associations between LC structural integrity and regional cortical perfusion and probed whether varying levels of plasma Alzheimer’s disease (AD) biomarkers (Aß42/40 ratio and ptau181) moderated these relationships.
Participants and Methods:64 dementia-free community-dwelling older adults (ages 55-87) recruited across two studies underwent structural and functional neuroimaging on the same MRI scanner. 3D-pCASL MRI measured regional cerebral blood flow in limbic and frontal cortical regions, while T1-FSE MRI quantified rostral LC-MRI contrast, a well-established proxy measure of LC structural integrity. A subset of participants underwent fasting blood draw to measure plasma AD biomarker concentrations (Aß42/40 ratio and ptau181). Multiple linear regression models examined associations between perfusion and LC integrity, with rostral LC-MRI contrast as predictor, regional CBF as outcome, and age and study as covariates. Moderation analyses included additional terms for plasma AD biomarker concentration and plasma x LC interaction.
Results:Greater rostral LC-MRI contrast was linked to lower regional perfusion in limbic regions, such as the amygdala (ß = -0.25, p = 0.049) and entorhinal cortex (ß = -0.20, p = 0.042), but was linked to higher regional perfusion in frontal cortical regions, such as the lateral (ß = 0.28, p = 0.003) and medial (ß = 0.24, p = 0.05) orbitofrontal (OFC) cortices. Plasma amyloid levels moderated the relationship between rostral LC and amygdala CBF (Aß42/40 ratio x rostral LC interaction term ß = -0.31, p = 0.021), such that as plasma Aß42/40 ratio decreased (i.e., greater pathology), the strength of the negative relationship between rostral LC integrity and amygdala perfusion decreased. Plasma ptau181levels moderated the relationship between rostral LC and entorhinal CBF (ptau181 x rostral LC interaction term ß = 0.64, p = 0.001), such that as ptau181 increased (i.e., greater pathology), the strength of the negative relationship between rostral LC integrity and entorhinal perfusion decreased. For frontal cortical regions, ptau181 levels moderated the relationship between rostral LC and lateral OFC perfusion (ptau181 x rostral LC interaction term ß = -0.54, p = .004), as well as between rostral LC and medial OFC perfusion (ptau181 x rostral LC interaction term ß = -0.53, p = .005), such that as ptau181 increased (i.e., greater pathology), the strength of the positive relationship between rostral LC integrity and frontal perfusion decreased.
Conclusions:LC integrity is linked to regional cortical perfusion in non-demented older adults, and these relationships are moderated by plasma AD biomarker concentrations. Variable directionality of the associations between the LC and frontal versus limbic perfusion, as well as the differential moderating effects of plasma AD biomarkers, may signify a compensatory mechanism and a shifting pattern of hyperemia in the presence of aggregating AD pathology. Linking LC integrity and cerebrovascular regulation may represent an important understudied pathway of dementia risk and may help to bridge competing theories of dementia progression in preclinical AD studies.
LO22: Risk-stratification of emergency department syncope by artificial intelligence using machine learning: human, statistics or machine
- L. Grant, P. Joo, B. Eng, A. Carrington, M. Nemnom, V. Thiruganasambandamoorthy
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 22 / Issue S1 / May 2020
- Published online by Cambridge University Press:
- 13 May 2020, p. S15
- Print publication:
- May 2020
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Introduction: The Canadian Syncope Risk Score (CSRS) is a validated risk tool developed using the best practices of conventional biostatistics, for predicting 30-day serious adverse events (SAE) after an Emergency Department (ED) visit for syncope. We sought to improve on the prediction ability of the CSRS and compared it to physician judgement using artificial intelligence (AI) research with modern machine learning (ML) methods. Methods: We used the prospective multicenter cohort data collected for the CSRS derivation and validation at 11 EDs across Canada over an 8-year period. The same 43 candidate variables considered for CSRS development were used to train and validate the four classes of ML models to predict 30-day SAE (death, arrhythmias, MI, structural heart disease, pulmonary embolism, hemorrhage) after ED disposition. Physician judgement was modeled using the two variables, referral for consultation and hospitalization. We compared the area under the curve (AUC) for the three models. Results: The proportion of patients who suffered 30-day SAE in the derivation cohort (N = 4030) was 3.6% and in validation phase (N = 2290) was 3.4%. Characteristics of the both cohorts were similar with no shift. The best performing ML model, a gradient boosting tree-based model used all 43 variables as predictors as opposed to the 9 final CSRS predictors. The AUC for the three models on the validation data were: best ML model 0.91 (95% CI 0.87–0.93), CSRS 0.87 (95% CI 0.83–0.90) and physician judgment 0.79 (95% CI 0.74 - 0.84). The most important predictors in the ML model were the same as the CSRS predictors. Conclusion: A ML model developed using AI method for risk-stratification of ED syncope performed with slightly better discrimination ability though not significantly different when compared to the CSRS. Both the ML model and the CSRS were better predictors of poor outcomes after syncope than physician judgement. ML models can perform with similar discrimination abilities when compared to traditional statistical models and outperform physician judgement given their ability to use all candidate variables.
P047: Emergency department practice patterns of UTI investigation among the delirious elderly: a retrospective chart review
- R. Pinnell, P. Joo
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 22 / Issue S1 / May 2020
- Published online by Cambridge University Press:
- 13 May 2020, p. S81
- Print publication:
- May 2020
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Introduction: Delirium is a common emergency department (ED) presentation in elderly patients. Urinary tract infection (UTI) investigation and treatment are often initiated in delirious patients in the absence of specific urinary symptoms, despite a paucity of evidence to support this practice. The purpose of this study is to describe the prevalence of UTI investigation, diagnosis and treatment in delirious elderly patients in the ED. Methods: We performed a retrospective chart review of elderly patients presenting to the ED at The Ottawa Hospital between January 15-July 30, 2018 with a chief complaint of confusion or similar. Exclusion criteria were pre-existing and current UTI diagnosis, Glasgow Coma Scale <13, current indwelling catheter or nephrostomy tube, transfers between hospitals, and leaving without being seen. The primary outcome was the proportion of patients for whom urine tests (urinalysis or culture) or antibiotic treatment were ordered. Secondary outcomes were associations between patient characteristics, rates of UTI investigation, and patient outcomes. Descriptive values were reported as proportions with exact binomial confidence intervals for categorical variables and means with standard deviations for continuous variables. Comparisons were conducted with Fischer's exact test for categorical variables and t-tests for continuous variables. Results: After analysis of 1039 encounters with 961 distinct patients, 499 encounters were included. Urine tests were conducted in 324 patients (64.9% [60.6-69.1]) and antibiotics were prescribed to 176 (35.2% [31.1-39.6]). Overall 57 patients (11.4% [8.8-14.5]) were diagnosed with UTI, of which only 12 (21.1% [11.4-33.9]) had any specific urinary symptom. For those patients who had no urinary symptoms or other obvious indication for antibiotics (n = 342), 199 (58.2% [52.8-63.5]) received urine tests and 62 (18.1% [14.2-22.6]) received antibiotics. Patients who received urine tests were older (82.4 ± 8.8 vs. 78.3 ± 8.4 years, p < 0.001) but did not differ in sex distribution from those than those who did not. Additionally, patients who received antibiotics were more likely to be admitted (OR = 2.6 [1.48-4.73]) and had higher mortality at 30 days (OR = 4.2 [1.35-12.91]) and 6 months (OR = 3.2 [1.33-7.84]) than those who did not. Conclusion: Delirious patient without urinary symptoms in the ED were frequently investigated and treated for UTI despite a lack of evidence regarding whether this practice is beneficial.
LO15: Treatment of asymptomatic bacteriuria in elderly patients with delirium: a systematic review
- A. Suleman, J. Krakovsky, P. Joo
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 20 / Issue S1 / May 2018
- Published online by Cambridge University Press:
- 11 May 2018, pp. S11-S12
- Print publication:
- May 2018
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Introduction: It is typical to look for UTI in delirious elderly patients, despite a high prevalence of asymptomatic bacteriuria (ASB) in this population. A common presentation of infection is delirium, which often has a non-specific and multifactorial etiology. Therefore, when bacteriuria is present with delirium in the absence of urinary symptoms, physicians prescribe antibiotics for the suspected UTI-induced delirium. We set to determine whether antibiotic treatment in the elderly presenting with delirium in the presence of ASB resulted in resolution of delirium. Methods: Literature searches were performed in MEDLINE, EMBASE, CINAHL and Cochrane Library. Abstracts were independently reviewed by two authors for decision to include for full-text review. Inclusion criteria included female gender, >65 years of age, presenting in an acute care setting with delirium and ASB. The primary outcome was resolution of delirium. The secondary outcomes were mortality, frequency of side effects from antibiotics, length of hospital stay and readmission for delirium. Results: 930 abstracts published from 1946-2017 were screened, and 42 were included for full text review. No studies were eligible for inclusion in the systematic review, as none addressed the primary outcome. One study addressed the outcomes of poor functional recovery after delirium and the rate of improvement of delirium symptoms after presentation of delirium with ASB. Conclusion: Even though current guidelines recommend against treatment of ASB, no guideline states whether ASB should be treated in elderly patients with delirium. Little evidence exists to elucidate whether treating delirious patients with ASB results in improvement in outcomes. Future studies should focus on demonstrating the relationship between resolution of delirium with antibiotic treatment. This will clarify whether delirium is a true symptom of ASB and whether treatment results in faster resolution of delirium.
LO46: The impact of rapid antigen detection testing on antibiotic prescription for acute pharyngitis: a systematic review and meta analysis
- O. Anjum, P. Joo
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 19 / Issue S1 / May 2017
- Published online by Cambridge University Press:
- 15 May 2017, pp. S43-S44
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- May 2017
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Introduction: Acute pharyngitis is a common reason for primary care or emergency department visits, often resulting in antibiotic prescription. Rapid antigen detection tests (RADT) are routinely used to diagnose Group A Streptococcus (GAS) pharyngitis. However, due to its low sensitivity, patient pressures and conflicting guidelines, the RADT often complicates management decisions. Our aim was to assess the impact of RADT in patients presenting with acute GAS pharyngitis on the antibiotic prescription rate and appropriateness of antibiotic management. Methods: We systematically searched Medline, Embase, and Cochrane databases from 1980 to June 2016. Studies were selected according to a predefined PRISMA protocol and data extracted by two independent reviewers. Prospective and retrospective studies that evaluated the impact of RADT on antibiotic prescription for pharyngitis were included. Study quality was assessed using Cochrane Risk of Bias Tool and the Newcastle-Ottawa Scale. Our main outcome was a dichotomous measure of antibiotic prescription, with or without RADT availability. Studies were combined if there was low clinical and statistical heterogeneity (I2<30%). Bivariate Mantel-Haenszel random effects model was used to perform meta analyses using SPSS 22 and Revman 5. Results: We identified 4003 studies: 139 were selected for full text review; 10 met our inclusion criteria (N=10859 participants, median age 31 years, 56.7% female). Mean antibiotic prescription rate in the RADT and control arm was 38.2% (SD 15.6) and 55.9% (SD 16.3), respectively. The use of RADT was associated with lower antibiotic prescription rate in both adults (OR=0.60 [95% CI 0.45-0.80], I2=8%, N=1407) and pediatrics (OR=0.49 [95% CI 0.44-0.55], I2=5%, N=976). There was no overall difference (p<0.3) in antibiotic prescription rate among disease severity (Centor scores 1-4). The use of RADT did not significantly impact the appropriateness of antibiotic management (OR=1.15 95% CI 0.94-1.5). Conclusion: The use of RADT is associated with a reduction in antibiotic prescription for patients with GAS pharyngitis without an increase in appropriate antibiotic use. Despite low prevalence of the disease in the population, antibiotic prescription rates are still high. These findings suggest great potential for antibiotic stewardship and reevaluation of current guidelines for managing GAS pharyngitis.
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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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Multipoint observations of plasma phenomena made in space by Cluster
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- M. L. Goldstein, P. Escoubet, K.-Joo Hwang, D. E. Wendel, A.-F. Viñas, S. F. Fung, S. Perri, S. Servidio, J. S. Pickett, G. K. Parks, F. Sahraoui, C. Gurgiolo, W. Matthaeus, J. M. Weygand
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- Journal of Plasma Physics / Volume 81 / Issue 3 / June 2015
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- 11 March 2015, 325810301
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Plasmas are ubiquitous in nature, surround our local geospace environment, and permeate the universe. Plasma phenomena in space give rise to energetic particles, the aurora, solar flares and coronal mass ejections, as well as many energetic phenomena in interstellar space. Although plasmas can be studied in laboratory settings, it is often difficult, if not impossible, to replicate the conditions (density, temperature, magnetic and electric fields, etc.) of space. Single-point space missions too numerous to list have described many properties of near-Earth and heliospheric plasmas as measured both in situ and remotely (see http://www.nasa.gov/missions/#.U1mcVmeweRY for a list of NASA-related missions). However, a full description of our plasma environment requires three-dimensional spatial measurements. Cluster is the first, and until data begin flowing from the Magnetospheric Multiscale Mission (MMS), the only mission designed to describe the three-dimensional spatial structure of plasma phenomena in geospace. In this paper, we concentrate on some of the many plasma phenomena that have been studied using data from Cluster. To date, there have been more than 2000 refereed papers published using Cluster data but in this paper we will, of necessity, refer to only a small fraction of the published work. We have focused on a few basic plasma phenomena, but, for example, have not dealt with most of the vast body of work describing dynamical phenomena in Earth's magnetosphere, including the dynamics of current sheets in Earth's magnetotail and the morphology of the dayside high latitude cusp. Several review articles and special publications are available that describe aspects of that research in detail and interested readers are referred to them (see for example, Escoubet et al. 2005Multiscale Coupling of Sun-Earth Processes, p. 459, Keith et al. 2005Sur. Geophys.26, 307–339, Paschmann et al. 2005Outer Magnetospheric Boundaries: Cluster Results, Space Sciences Series of ISSI. Berlin: Springer, Goldstein et al. 2006Adv. Space Res.38, 21–36, Taylor et al. 2010The Cluster Mission: Space Plasma in Three Dimensions, Springer, pp. 309–330 and Escoubet et al. 2013Ann. Geophys.31, 1045–1059).
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- By Mark S. Aloia, Ellemarije Altena, Peter Anderer, Christopher L. Asplund, Nitin Bangera, Jeroen S. Benjamins, Daniela Berg, Bohdan Bybel, Vincenza Castronovo, Suk-tak Chan, Michael W. L. Chee, Pietro Cortelli, Michael Czisch, Joseph T. Daley, Thien Thanh Dang-Vu, Yazmín de la Garza-Neme, Lourdes DelRosso, Derk-Jan Dijk, Maria Engström, Thorleif Etgen, Bruce J. Fisch, Ariane Foret, Patrice Fort, Steffen Gais, Anne Germain, Jana Godau, Andrew L. Goertzen, William A. Gomes, Ronald M. Harper, Seung Bong Hong, Romy Hoque, Scott A. Huettel, Yuichi Inoue, Alex Iranzo, Mathieu Jaspar, Zayd Jedidi, Alejandro Jiménez-Genchi, Eun Yeon Joo, Gerhard Klösch, Karsten Krakow, Rajesh Kumar, Caroline Kussé, Hans-Peter Landolt, Helmut Laufs, Jeffrey David Lewine, Camilo Libedinsky, Michael L. Lipton, Mordechai Lorberboym, Cheng Luo, Pierre-Hervé Luppi, Paul M. Macey, Pierre Maquet, Laura Mascetti, Christelle Meyer, Sarah Moens, Vincenzo Muto, Shadreck Mzengeza, Eric Nofzinger, Takashi Nomura, Daniela Perani, Jennifer R. Ramautar, Bernd Saletu, Michael T. Saletu, Gerda Saletu-Zyhlarz, Christina Schmidt, Monika Schönauer, Richard J. Schwab, Sophie Schwartz, Keivan Shifteh, Sanjib Sinha, Victor I. Spoormaker, Ryan P. J. Stocker, A. Jon Stoessl, Diederick Stoffers, A. B. Taly, Robert Joseph Thomas, Michael J. Thorpy, Emily Urry, Jason Valerio, Ysbrand D. Van Der Werf, Gilles Vandewalle, Hans P. A. Van Dongen, Eus J. W. Van Someren, Vinod Venkatraman, Frederic von Wegner, Thomas C. Wetter, Dezhong Yao
- Edited by Eric Nofzinger, University of Pittsburgh, Pierre Maquet, Université de Liège, Belgium, Michael J. Thorpy
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- Neuroimaging of Sleep and Sleep Disorders
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- 05 March 2013
- Print publication:
- 07 March 2013, pp viii-xii
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- By Ashok Agarwal, Linda D. Applegarth, Nelson E. Bennett, Nancy L. Brackett, Melissa B. Brisman, Mark F. H. Brougham, Cara B. Cimmino, Owen K. Davis, Rian J. Dickstein, Michael L. Eisenberg, Mikkel Fode, Gretchen A. Gignac, Bruce R. Gilbert, Ellen R. Goldmark, Marc Goldstein, Wayne J. G. Hellstrom, Wayland Hsiao, Jack Huang, Kathleen Hwang, Ann A. Jakubowski, Keith Jarvi, Loren Jones, Hey-Joo Kang, Joanne Frankel Kelvin, Mohit Khera, Thomas F. Kolon, Kate H. Kraft, Andrew C. Kramer, Dolores J. Lamb, Andrew B. Lassman, Helen R. Levey, Larry I. Lipshultz, Charles M. Lynne, Akanksha Mehta, Marvin L. Meistrich, Gregory C. Mitchell, Mark A. Moyad, John P. Mulhall, Lauren Murray, Craig Niederberger, Ariella Noy, Robert D. Oates, Dana A. Ohl, Kutluk Oktay, Ndidiamaka Onwubalili, Fabio Firmbach Pasqualatto, Elena Pentsova, Susanne A. Quallich, Gwendolyn P. Quinn, Alex Ridgeway, Matthew T. Roberts, Kenny A. Rodriguez-Wallberg, Allison B. Rosen, Lisa Rosenzweig, Edmund S. Sabanegh, Hossein Sadeghi-Nejad, Mary K. Samplaski, Jay I. Sandlow, Peter N. Schlegel, Gunapala Shetty, Mark Sigman, Jens Sønksen, Peter J. Stahl, Eytan Stein, Doron S. Stember, Raanan Tal, Susan T. Vadaparampil, W. Hamish, B. Wallace, Leonard H. Wexler, Daniel H. Williams
- Edited by John P. Mulhall, Memorial Sloan-Kettering Cancer Center, New York
- Edited in association with Linda D. Applegarth, Robert D. Oates, Peter N. Schlegel
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- Book:
- Fertility Preservation in Male Cancer Patients
- Published online:
- 05 March 2013
- Print publication:
- 21 February 2013, pp vii-x
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- By Peter A. Alces, T. T. Arvind, Richard Austen-Baker, Jean Braucher, Curtis Bridgeman, Roger Brownsword, David Campbell, David Capper, James Devenney, Larry A. DiMatteo, Roger Halson, Martin A. Hogg, Thomas W. Joo, Mel Kenny, Nancy S. Kim, Charles L. Knapp, Juliet P. Kostritsky, Hector L. MacQueen, Zoe Ollerenshaw, Keith Rowley, Djakhongir Saidov, Séverine Saintier, Qi Zhou
- Edited by Larry A. DiMatteo, University of Florida, Qi Zhou, University of Sheffield, Severine Saintier, University of Sheffield, Keith Rowley, University of Nevada, Las Vegas
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- Book:
- Commercial Contract Law
- Published online:
- 05 February 2013
- Print publication:
- 31 January 2013, pp xxi-xxvi
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Contributors
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- By Mohamed Aboulghar, Ahmed Abou-Setta, Mary E. Abusief, G. David Adamson, R. J. Aitken, Hesham Al-Inany, Baris Ata, Hamdy Azab, Adam Balen, David H. Barad, Pedro N. Barri, C. Blockeel, Giuseppe Botta, Mark Bowman, Chris Brewer, Dominique M. Butawan, Sandra A. Carson, Hai Ying Chen, Anne Clark, Buenaventura Coroleu, S. Das, C. Dechanet, H. Déchaud, Cora de Klerk, Sheryl de Lacey, S. Deutsch-Bringer, P. Devroey, Didier Dewailly, Hakan E. Duran, Walid El Sherbiny, Tarek El-Toukhy, Johannes L. H. Evers, Cynthia Farquhar, Rodney D. Franklin, Juan A. Garcia-Velasco, David K. Gardner, Norbert Gleicher, Gedis Grudzinskas, Roger Hart, B Hédon, Colin M. Howles, Jack Yu Jen Huang, N. P. Johnson, Hey-Joo Kang, Gab Kovacs, Ben Kroon, Anver Kuliev, William H. Kutteh, Nick Macklon, Ragaa Mansour, Lamiya Mohiyiddeen, Lisa J. Moran, David Mortimer, Sharon T. Mortimer, Luciano G. Nardo, Robert J. Norman, Willem Ombelet, Luk Rombauts, Zev Rosenwaks, Francisco J. Ruiz Flores, Anthony J. Rutherford, Gavin Sacks, Denny Sakkas, M. W. Seif, Ayse Seyhan, Caroline Smith, Kate Stern, Elizabeth A. Sullivan, Sesh Kamal Sunkara, Seang Lin Tan, Mohamed Taranissi, Kelton P. Tremellen, Wendy S. Vitek, V. Vloeberghs, Bradley J. Van Voorhis, S. F. van Voorst, Amr Wahba, Yueping A. Wang, Klaus E. Wiemer
- Edited by Gab Kovacs, Monash University, Victoria
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- Book:
- How to Improve your ART Success Rates
- Published online:
- 05 July 2011
- Print publication:
- 30 June 2011, pp viii-xii
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Nano-patterned Growth of Ge Quantum Dots for Infrared Detector Applications
- Christopher Chen, Dongho Cha, Joo-young Lee, Hyung-jun Kim, Fei Liu, Song Tong, Kang L. Wang, Jia-Yu Wang, Thomas P. Russell
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- Journal:
- MRS Online Proceedings Library Archive / Volume 891 / 2005
- Published online by Cambridge University Press:
- 01 February 2011, 0891-EE06-01
- Print publication:
- 2005
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Quantum dot infrared photodetectors (QDIPs) have been studied widely for normal-incidence infrared detection. The 3D confinement provided by quantum dots allows for the elimination of gratings that are typically required for normal-incidence detection in quantum well infrared photodetectors (QWIPs). Furthermore, the growth of Ge dots on Si substrates offers the potential for integration with existing CMOS platforms. To date, however, Ge QDIPs have typically been grown epitaxially by Stranski-Krastonov growth – producing pancake-like dots with base dimensions of 50-100 nm, heights of 7-10 nm, and an aerial dot density of 109–1010 cm−2. Such dots have poor lateral confinement, causing them to have non-ideal normal-incidence absorption characteristics, similar to quantum wells. In this work, we demonstrate infrared absorption in Ge dots with base dimensions of approximately 15 nm. These dots are epitaxially grown on pre-patterned Si substrates, with an aerial dot density of approximately 1011 cm−2. The substrates are prepared by using diblock copolymers to create a nano-pattern on the substrate surface which is transferred to the substrate by dry etching. The size of this pattern determines the base dimensions of the Ge dots. After growth, these dots are then tested for their infrared absorption properties using Fourier Transform Infrared (FTIR) Spectroscopy. The normal-incidence absorption of the dots can be studied with FTIR by varying the polarization angle of the infrared light. We present FTIR absorption spectra for samples grown with various conditions (e.g., different dot doping levels, numbers of layers, and dot base dimensions) and investigate the effects of different growth conditions on infrared absorption properties. We also report on the normal-incidence absorption characteristics of these dots by presenting absorption spectra for various polarization angles of infrared light.
6Li and 7Li MAS NMR and In Situ X-ray Diffraction Studies of Lithium Manganate Cathode Materials
- Young Joo Lee, Francis Wang, Clare P. Grey, Sanjeev Mukerjee, James McBreen
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- Journal:
- MRS Online Proceedings Library Archive / Volume 548 / 1998
- Published online by Cambridge University Press:
- 10 February 2011, 197
- Print publication:
- 1998
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6Li MAS NMR spectra of lithium manganese oxides with differing manganese oxidation states (LiMn2O4, Li4Mn5O12, Li2Mn4O9, and Li2Mn2O4) are presented. Improved understanding of the lithium NMR spectra of these model compounds is used to interpret the local structure of the LixMn2O4 cathode materials following electrochemical Li+ deintercalation to various charging levels. In situ x-ray diffraction patterns of the same material during charging are also reported for comparison. Evidence for two-phase behavior for x < 0.4 (LixMn2O4) is seen by both NMR and diffraction.
Mechanical Properties of Al-Cu Films with Various Heat Treatments
- Young-Chang Joo, Peter Müllner, Shefford P. Baker, Eduard Arzt
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- Journal:
- MRS Online Proceedings Library Archive / Volume 473 / 1997
- Published online by Cambridge University Press:
- 10 February 2011, 409
- Print publication:
- 1997
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Precipitation and solid solution hardening have been studied in Al-Cu thin films with Cu content ranging from 0 to 2 wt%. We have changed the precipitate and dislocation structures of films having different Cu concentrations by varying the heat treatments prior to mechanical testing. Pure Al films showed the same values of tensile and compressive yield stresses at a given temperature during stress-temperature cycling. Al-Cu alloy films, however, showed larger stresses in tension than in compression. The compressive flow stress during heating could be changed by a factor of five by the initial heat treatment, but the differences disappeared above 250°C. Upon cooling from 480°C, solution hardening as well as precipitation hardening was observed in the Al-Cu films. Solution hardening is independent of Cu concentration, but for precipitation hardening, both the magnitude and the temperature range in which the mechanism is effective are sensitive to the Cu concentration. The microstructure was observed using transmission electron microscopy. The mechanical behavior is consistent with interactions between dislocations and precipitates which arise due to constraints on the film by the substrate.
Electromigration in Single-Crystal Aluminum Lines Pre-Damaged by Nanoindentation
- Young-Chang Joo, Shefford P. Baker, Michael P. Knaufß, Eduard Arzt
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- Journal:
- MRS Online Proceedings Library Archive / Volume 428 / 1996
- Published online by Cambridge University Press:
- 15 February 2011, 225
- Print publication:
- 1996
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Electromigration tests have been performed on single-crystal Al lines which were predamaged by rows of submicrometer-depth indentations made using a nanoindentation device. Indentations were placed close to each other so that their plastic deformation zones overlapped. During subsequent electromigration testing at 280°C and I to 2 MA/cm2, no damage was observed in non-indented single-crystal lines, while the indented lines showed electromigrationinduced voids at the cathode-side ends of the indented areas, and hillocks at the anode-side ends. The voids grew and moved away from the indentations towards the cathode. Fhe electromigration damage morphology of the indented lines indicates that the mechanical damage generates a local fast diffusion path in the single-crystal lines, which is believed to be due to dislocation core diffusion. A minimum indentation row length was observed, below which no void formed. This electromigration behavior is found to be phenomenologically similar to that of polygranular clusters in near-bamboo lines.
The Metallic State of Conducting Polymers: Microwave Dielectric Response and Optical Conductivity
- A. J. Epstein, J. Joo, R. S. Kohlman, A. G. Macdiarmid, J. M. Weisinger, Y. Min, J. P. Pouget, J. Tsukamoto
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- Journal:
- MRS Online Proceedings Library Archive / Volume 328 / 1993
- Published online by Cambridge University Press:
- 16 February 2011, 145
- Print publication:
- 1993
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Recent advances in processing of polyaniline and polyacetylene have resulted in a new generation of conducting polymers with higher dc conductivities. We present the temperature (T) dependent microwave frequency dielectric constant, dc conductivity, and Kramers-Kronig analysis of conducting polyaniline and polyacetylene. The low temperature dielectric constant, ε, increases with the square of the x-ray crystalline domain length for preparations of HCl protonated polyaniline. For the highest crystalline polyaniline samples, ε increases dramatically with increasing T, supporting formation of three-dimensional (3-D) coupled “mesoscopic” Metallic regions. A “metallic” negative ε is observed for d,1-camphor sulfonie acid doped polyaniline prepared in m-cresol. Optical studies show a linear increase in reflectivity below 7000 cm-1. Below 600 cm-1 the reflectance increases rapidly. Kramers-Kronig analysis of the ir-visible results are presented. Highly conducting polyaniline is shown to have two plasma frequencies, one at ∼ 1.1 eV involving all the conduction band electrons, and one at ∼0.015 eV (120 cm-1) that is suggested to arise from the most delocalized electrons. The concept of inhomogeneous disorder is introduced. The results for polyaniline are compared to those of highly doped polyacetylene which also show metallic negative ε demonstrating the intrinsic metallic nature of the new generation of conducting polymers.
Correlations between sintering conditions and microstructure in ceramics of composition Li0.80Mg0.20 (Ta0.80Ti0.20)O3
- J. P. Bonnet, J. Ravez, Joo GiTae, P. Hagenmuller
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- Journal:
- Journal of Materials Research / Volume 3 / Issue 2 / April 1988
- Published online by Cambridge University Press:
- 31 January 2011, pp. 387-391
- Print publication:
- April 1988
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Two quite different types of microstructures have been detected for MgTiO3-enriched LiTaO3 ceramics corresponding either to small size grains and open porosity or to large size grains with closed porosity and appearance of microcracks. The first structure appears in short sintering processes at relatively low temperature. The textural change is explained by transitory formation of a grain boundary phase that leads to quick coalescence of the small grains.