12 results
2 Higher White Matter Hyperintensity Load Adversely Affects Pre-Post Proximal Cognitive Training Performance in Healthy Older Adults
- Emanuel M Boutzoukas, Andrew O’Shea, Jessica N Kraft, Cheshire Hardcastle, Nicole D Evangelista, Hanna K Hausman, Alejandro Albizu, Emily J Van Etten, Pradyumna K Bharadwaj, Samantha G Smith, Hyun Song, Eric C Porges, Alex Hishaw, Steven T DeKosky, Samuel S Wu, Michael Marsiske, Gene E Alexander, Ronald Cohen, Adam J Woods
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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. 671-672
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Objective:
Cognitive training has shown promise for improving cognition in older adults. Aging involves a variety of neuroanatomical changes that may affect response to cognitive training. White matter hyperintensities (WMH) are one common age-related brain change, as evidenced by T2-weighted and Fluid Attenuated Inversion Recovery (FLAIR) MRI. WMH are associated with older age, suggestive of cerebral small vessel disease, and reflect decreased white matter integrity. Higher WMH load associates with reduced threshold for clinical expression of cognitive impairment and dementia. The effects of WMH on response to cognitive training interventions are relatively unknown. The current study assessed (a) proximal cognitive training performance following a 3-month randomized control trial and (b) the contribution of baseline whole-brain WMH load, defined as total lesion volume (TLV), on pre-post proximal training change.
Participants and Methods:Sixty-two healthy older adults ages 65-84 completed either adaptive cognitive training (CT; n=31) or educational training control (ET; n=31) interventions. Participants assigned to CT completed 20 hours of attention/processing speed training and 20 hours of working memory training delivered through commercially-available Posit Science BrainHQ. ET participants completed 40 hours of educational videos. All participants also underwent sham or active transcranial direct current stimulation (tDCS) as an adjunctive intervention, although not a variable of interest in the current study. Multimodal MRI scans were acquired during the baseline visit. T1- and T2-weighted FLAIR images were processed using the Lesion Segmentation Tool (LST) for SPM12. The Lesion Prediction Algorithm of LST automatically segmented brain tissue and calculated lesion maps. A lesion threshold of 0.30 was applied to calculate TLV. A log transformation was applied to TLV to normalize the distribution of WMH. Repeated-measures analysis of covariance (RM-ANCOVA) assessed pre/post change in proximal composite (Total Training Composite) and sub-composite (Processing Speed Training Composite, Working Memory Training Composite) measures in the CT group compared to their ET counterparts, controlling for age, sex, years of education and tDCS group. Linear regression assessed the effect of TLV on post-intervention proximal composite and sub-composite, controlling for baseline performance, intervention assignment, age, sex, years of education, multisite scanner differences, estimated total intracranial volume, and binarized cardiovascular disease risk.
Results:RM-ANCOVA revealed two-way group*time interactions such that those assigned cognitive training demonstrated greater improvement on proximal composite (Total Training Composite) and sub-composite (Processing Speed Training Composite, Working Memory Training Composite) measures compared to their ET counterparts. Multiple linear regression showed higher baseline TLV associated with lower pre-post change on Processing Speed Training sub-composite (ß = -0.19, p = 0.04) but not other composite measures.
Conclusions:These findings demonstrate the utility of cognitive training for improving postintervention proximal performance in older adults. Additionally, pre-post proximal processing speed training change appear to be particularly sensitive to white matter hyperintensity load versus working memory training change. These data suggest that TLV may serve as an important factor for consideration when planning processing speed-based cognitive training interventions for remediation of cognitive decline in older adults.
6 Adjunctive Transcranial Direct Current Stimulation and Cognitive Training Alters Default Mode and Frontoparietal Control Network Connectivity in Older Adults
- Hanna K Hausman, Jessica N Kraft, Cheshire Hardcastle, Nicole D Evangelista, Emanuel M Boutzoukas, Andrew O’Shea, Alejandro Albizu, Emily J Van Etten, Pradyumna K Bharadwaj, Hyun Song, Samantha G Smith, Eric S Porges, Georg A Hishaw, Samuel Wu, Steven DeKosky, Gene E Alexander, Michael Marsiske, Ronald A Cohen, Adam J Woods
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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. 675-676
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Objective:
Aging is associated with disruptions in functional connectivity within the default mode (DMN), frontoparietal control (FPCN), and cingulo-opercular (CON) resting-state networks. Greater within-network connectivity predicts better cognitive performance in older adults. Therefore, strengthening network connectivity, through targeted intervention strategies, may help prevent age-related cognitive decline or progression to dementia. Small studies have demonstrated synergistic effects of combining transcranial direct current stimulation (tDCS) and cognitive training (CT) on strengthening network connectivity; however, this association has yet to be rigorously tested on a large scale. The current study leverages longitudinal data from the first-ever Phase III clinical trial for tDCS to examine the efficacy of an adjunctive tDCS and CT intervention on modulating network connectivity in older adults.
Participants and Methods:This sample included 209 older adults (mean age = 71.6) from the Augmenting Cognitive Training in Older Adults multisite trial. Participants completed 40 hours of CT over 12 weeks, which included 8 attention, processing speed, and working memory tasks. Participants were randomized into active or sham stimulation groups, and tDCS was administered during CT daily for two weeks then weekly for 10 weeks. For both stimulation groups, two electrodes in saline-soaked 5x7 cm2 sponges were placed at F3 (cathode) and F4 (anode) using the 10-20 measurement system. The active group received 2mA of current for 20 minutes. The sham group received 2mA for 30 seconds, then no current for the remaining 20 minutes.
Participants underwent resting-state fMRI at baseline and post-intervention. CONN toolbox was used to preprocess imaging data and conduct region of interest (ROI-ROI) connectivity analyses. The Artifact Detection Toolbox, using intermediate settings, identified outlier volumes. Two participants were excluded for having greater than 50% of volumes flagged as outliers. ROI-ROI analyses modeled the interaction between tDCS group (active versus sham) and occasion (baseline connectivity versus postintervention connectivity) for the DMN, FPCN, and CON controlling for age, sex, education, site, and adherence.
Results:Compared to sham, the active group demonstrated ROI-ROI increases in functional connectivity within the DMN following intervention (left temporal to right temporal [T(202) = 2.78, pFDR < 0.05] and left temporal to right dorsal medial prefrontal cortex [T(202) = 2.74, pFDR < 0.05]. In contrast, compared to sham, the active group demonstrated ROI-ROI decreases in functional connectivity within the FPCN following intervention (left dorsal prefrontal cortex to left temporal [T(202) = -2.96, pFDR < 0.05] and left dorsal prefrontal cortex to left lateral prefrontal cortex [T(202) = -2.77, pFDR < 0.05]). There were no significant interactions detected for CON regions.
Conclusions:These findings (a) demonstrate the feasibility of modulating network connectivity using tDCS and CT and (b) provide important information regarding the pattern of connectivity changes occurring at these intervention parameters in older adults. Importantly, the active stimulation group showed increases in connectivity within the DMN (a network particularly vulnerable to aging and implicated in Alzheimer’s disease) but decreases in connectivity between left frontal and temporal FPCN regions. Future analyses from this trial will evaluate the association between these changes in connectivity and cognitive performance post-intervention and at a one-year timepoint.
9 Connecting memory and functional brain networks in older adults: a resting state fMRI study
- Jori L Waner, Hanna K Hausman, Jessica N Kraft, Cheshire Hardcastle, Nicole D Evangelista, Andrew O’Shea, Alejandro Albizu, Emanuel M Boutzoukas, Emily J Van Etten, Pradyumna K Bharadwaj, Hyun Song, Samantha G Smith, Steven T DeKosky, Georg A Hishaw, Samuel S Wu, Michael Marsiske, Ronald Cohen, Gene E Alexander, Eric C Porges, Adam J Woods
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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. 527-528
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Objective:
Nonpathological aging has been linked to decline in both verbal and visuospatial memory abilities in older adults. Disruptions in resting-state functional connectivity within well-characterized, higherorder cognitive brain networks have also been coupled with poorer memory functioning in healthy older adults and in older adults with dementia. However, there is a paucity of research on the association between higherorder functional connectivity and verbal and visuospatial memory performance in the older adult population. The current study examines the association between resting-state functional connectivity within the cingulo-opercular network (CON), frontoparietal control network (FPCN), and default mode network (DMN) and verbal and visuospatial learning and memory in a large sample of healthy older adults. We hypothesized that greater within-network CON and FPCN functional connectivity would be associated with better immediate verbal and visuospatial memory recall. Additionally, we predicted that within-network DMN functional connectivity would be associated with improvements in delayed verbal and visuospatial memory recall. This study helps to glean insight into whether within-network CON, FPCN, or DMN functional connectivity is associated with verbal and visuospatial memory abilities in later life.
Participants and Methods:330 healthy older adults between 65 and 89 years old (mean age = 71.6 ± 5.2) were recruited at the University of Florida (n = 222) and the University of Arizona (n = 108). Participants underwent resting-state fMRI and completed verbal memory (Hopkins Verbal Learning Test - Revised [HVLT-R]) and visuospatial memory (Brief Visuospatial Memory Test - Revised [BVMT-R]) measures. Immediate (total) and delayed recall scores on the HVLT-R and BVMT-R were calculated using each test manual’s scoring criteria. Learning ratios on the HVLT-R and BVMT-R were quantified by dividing the number of stimuli (verbal or visuospatial) learned between the first and third trials by the number of stimuli not recalled after the first learning trial. CONN Toolbox was used to extract average within-network connectivity values for CON, FPCN, and DMN. Hierarchical regressions were conducted, controlling for sex, race, ethnicity, years of education, number of invalid scans, and scanner site.
Results:Greater CON connectivity was significantly associated with better HVLT-R immediate (total) recall (ß = 0.16, p = 0.01), HVLT-R learning ratio (ß = 0.16, p = 0.01), BVMT-R immediate (total) recall (ß = 0.14, p = 0.02), and BVMT-R delayed recall performance (ß = 0.15, p = 0.01). Greater FPCN connectivity was associated with better BVMT-R learning ratio (ß = 0.13, p = 0.04). HVLT-R delayed recall performance was not associated with connectivity in any network, and DMN connectivity was not significantly related to any measure.
Conclusions:Connectivity within CON demonstrated a robust relationship with different components of memory function as well across verbal and visuospatial domains. In contrast, FPCN only evidenced a relationship with visuospatial learning, and DMN was not significantly associated with memory measures. These data suggest that CON may be a valuable target in longitudinal studies of age-related memory changes, but also a possible target in future non-invasive interventions to attenuate memory decline in older adults.
Pharmacist gender and physician acceptance of antibiotic stewardship recommendations: An analysis of the reducing overuse of antibiotics at discharge home intervention
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- Valerie M. Vaughn, Daniel L. Giesler, Daraoun Mashrah, Adamo Brancaccio, Katie Sandison, Emily S. Spivak, Julia E. Szymczak, Chaorong Wu, Jennifer K. Horowitz, Linda Bashaw, Adam L. Hersh
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 44 / Issue 4 / April 2023
- Published online by Cambridge University Press:
- 07 June 2022, pp. 570-577
- Print publication:
- April 2023
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Objective:
To assess association of pharmacist gender with acceptance of antibiotic stewardship recommendations.
Design:A retrospective evaluation of the Reducing Overuse of Antibiotics at Discharge (ROAD) Home intervention.
Setting:The study was conducted from May to October 2019 in a single academic medical center.
Participants:The study included patients receiving antibiotics on a hospitalist service who were nearing discharge.
Methods:During the intervention, clinical pharmacists (none who had specialist postgraduate infectious disease residency training) reviewed patients on antibiotics and led an antibiotic timeout (ie, structured conversation) prior to discharge to improve discharge antibiotic prescribing. We assessed the association of pharmacist gender with acceptance of timeout recommendations by hospitalists using logistic regression controlling for patient characteristics.
Results:Over 6 months, pharmacists conducted 295 timeouts: 158 timeouts (53.6%) were conducted by 12 women, 137 (46.4%) were conducted by 8 men. Pharmacists recommended an antibiotic change in 82 timeouts (27.8%), of which 51 (62.2%) were accepted. Compared to male pharmacists, female pharmacists were less likely to recommend a discharge antibiotic change: 30 (19.0%) of 158 versus 52 (38.0%) of 137 (P < .001). Female pharmacists were also less likely to have a recommendation accepted: 10 (33.3%) of 30 versus 41 (8.8%) of 52 (P < .001). Thus, timeouts conducted by female versus male pharmacists were less likely to result in an antibiotic change: 10 (6.3%) of 158 versus 41 (29.9%) of 137 (P < .001). After adjustments, pharmacist gender remained significantly associated with whether recommended changes were accepted (adjusted odds ratio [aOR], 0.10; 95%confidence interval [CI], 0.03–0.36 for female versus male pharmacists).
Conclusions:Antibiotic stewardship recommendations made by female clinical pharmacists were less likely to be accepted by hospitalists. Gender bias may play a role in the acceptance of clinical pharmacist recommendations, which could affect patient care and outcomes.
Equivalency of the diagnostic accuracy of the PHQ-8 and PHQ-9: a systematic review and individual participant data meta-analysis – ERRATUM
- Yin Wu, Brooke Levis, Kira E. Riehm, Nazanin Saadat, Alexander W. Levis, Marleine Azar, Danielle B. Rice, Jill Boruff, Pim Cuijpers, Simon Gilbody, John P.A. Ioannidis, Lorie A. Kloda, Dean McMillan, Scott B. Patten, Ian Shrier, Roy C. Ziegelstein, Dickens H. Akena, Bruce Arroll, Liat Ayalon, Hamid R. Baradaran, Murray Baron, Charles H. Bombardier, Peter Butterworth, Gregory Carter, Marcos H. Chagas, Juliana C. N. Chan, Rushina Cholera, Yeates Conwell, Janneke M. de Manvan Ginkel, Jesse R. Fann, Felix H. Fischer, Daniel Fung, Bizu Gelaye, Felicity Goodyear-Smith, Catherine G. Greeno, Brian J. Hall, Patricia A. Harrison, Martin Härter, Ulrich Hegerl, Leanne Hides, Stevan E. Hobfoll, Marie Hudson, Thomas Hyphantis, Masatoshi Inagaki, Nathalie Jetté, Mohammad E. Khamseh, Kim M. Kiely, Yunxin Kwan, Femke Lamers, Shen-Ing Liu, Manote Lotrakul, Sonia R. Loureiro, Bernd Löwe, Anthony McGuire, Sherina Mohd-Sidik, Tiago N. Munhoz, Kumiko Muramatsu, Flávia L. Osório, Vikram Patel, Brian W. Pence, Philippe Persoons, Angelo Picardi, Katrin Reuter, Alasdair G. Rooney, Iná S. Santos, Juwita Shaaban, Abbey Sidebottom, Adam Simning, Lesley Stafford, Sharon Sung, Pei Lin Lynnette Tan, Alyna Turner, Henk C. van Weert, Jennifer White, Mary A. Whooley, Kirsty Winkley, Mitsuhiko Yamada, Andrea Benedetti, Brett D. Thombs
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- Psychological Medicine / Volume 50 / Issue 16 / December 2020
- Published online by Cambridge University Press:
- 19 August 2019, p. 2816
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Equivalency of the diagnostic accuracy of the PHQ-8 and PHQ-9: a systematic review and individual participant data meta-analysis
- Yin Wu, Brooke Levis, Kira E. Riehm, Nazanin Saadat, Alexander W. Levis, Marleine Azar, Danielle B. Rice, Jill Boruff, Pim Cuijpers, Simon Gilbody, John P.A. Ioannidis, Lorie A. Kloda, Dean McMillan, Scott B. Patten, Ian Shrier, Roy C. Ziegelstein, Dickens H. Akena, Bruce Arroll, Liat Ayalon, Hamid R. Baradaran, Murray Baron, Charles H. Bombardier, Peter Butterworth, Gregory Carter, Marcos H. Chagas, Juliana C. N. Chan, Rushina Cholera, Yeates Conwell, Janneke M. de Man-van Ginkel, Jesse R. Fann, Felix H. Fischer, Daniel Fung, Bizu Gelaye, Felicity Goodyear-Smith, Catherine G. Greeno, Brian J. Hall, Patricia A. Harrison, Martin Härter, Ulrich Hegerl, Leanne Hides, Stevan E. Hobfoll, Marie Hudson, Thomas Hyphantis, Masatoshi Inagaki, Nathalie Jetté, Mohammad E. Khamseh, Kim M. Kiely, Yunxin Kwan, Femke Lamers, Shen-Ing Liu, Manote Lotrakul, Sonia R. Loureiro, Bernd Löwe, Anthony McGuire, Sherina Mohd-Sidik, Tiago N. Munhoz, Kumiko Muramatsu, Flávia L. Osório, Vikram Patel, Brian W. Pence, Philippe Persoons, Angelo Picardi, Katrin Reuter, Alasdair G. Rooney, Iná S. Santos, Juwita Shaaban, Abbey Sidebottom, Adam Simning, Lesley Stafford, Sharon Sung, Pei Lin Lynnette Tan, Alyna Turner, Henk C. van Weert, Jennifer White, Mary A. Whooley, Kirsty Winkley, Mitsuhiko Yamada, Andrea Benedetti, Brett D. Thombs
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- Psychological Medicine / Volume 50 / Issue 8 / June 2020
- Published online by Cambridge University Press:
- 12 July 2019, pp. 1368-1380
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Background
Item 9 of the Patient Health Questionnaire-9 (PHQ-9) queries about thoughts of death and self-harm, but not suicidality. Although it is sometimes used to assess suicide risk, most positive responses are not associated with suicidality. The PHQ-8, which omits Item 9, is thus increasingly used in research. We assessed equivalency of total score correlations and the diagnostic accuracy to detect major depression of the PHQ-8 and PHQ-9.
MethodsWe conducted an individual patient data meta-analysis. We fit bivariate random-effects models to assess diagnostic accuracy.
Results16 742 participants (2097 major depression cases) from 54 studies were included. The correlation between PHQ-8 and PHQ-9 scores was 0.996 (95% confidence interval 0.996 to 0.996). The standard cutoff score of 10 for the PHQ-9 maximized sensitivity + specificity for the PHQ-8 among studies that used a semi-structured diagnostic interview reference standard (N = 27). At cutoff 10, the PHQ-8 was less sensitive by 0.02 (−0.06 to 0.00) and more specific by 0.01 (0.00 to 0.01) among those studies (N = 27), with similar results for studies that used other types of interviews (N = 27). For all 54 primary studies combined, across all cutoffs, the PHQ-8 was less sensitive than the PHQ-9 by 0.00 to 0.05 (0.03 at cutoff 10), and specificity was within 0.01 for all cutoffs (0.00 to 0.01).
ConclusionsPHQ-8 and PHQ-9 total scores were similar. Sensitivity may be minimally reduced with the PHQ-8, but specificity is similar.
Cultural Universals and Cultural Differences in Meta-Norms about Peer Punishment
- Kimmo Eriksson, Pontus Strimling, Per A. Andersson, Mark Aveyard, Markus Brauer, Vladimir Gritskov, Toko Kiyonari, David M. Kuhlman, Angela T. Maitner, Zoi Manesi, Catherine Molho, Leonard S. Peperkoorn, Muhammad Rizwan, Adam W. Stivers, Qirui Tian, Paul A. M. Van Lange, Irina Vartanova, Junhui Wu, Toshio Yamagishi
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- Management and Organization Review / Volume 13 / Issue 4 / December 2017
- Published online by Cambridge University Press:
- 10 November 2017, pp. 851-870
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Violators of cooperation norms may be informally punished by their peers. How such norm enforcement is judged by others can be regarded as a meta-norm (i.e., a second-order norm). We examined whether meta-norms about peer punishment vary across cultures by having students in eight countries judge animations in which an agent who over-harvested a common resource was punished either by a single peer or by the entire peer group. Whether the punishment was retributive or restorative varied between two studies, and findings were largely consistent across these two types of punishment. Across all countries, punishment was judged as more appropriate when implemented by the entire peer group than by an individual. Differences between countries were revealed in judgments of punishers vs. non-punishers. Specifically, appraisals of punishers were relatively negative in three Western countries and Japan, and more neutral in Pakistan, UAE, Russia, and China, consistent with the influence of individualism, power distance, and/or indulgence. Our studies constitute a first step in mapping how meta-norms vary around the globe, demonstrating both cultural universals and cultural differences.
Histopathological Examination of Intervertebral Disc Specimens: A Cost-Benefit Analysis
- Adam S. Wu, Daryl R. Fourney
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- Canadian Journal of Neurological Sciences / Volume 34 / Issue 4 / November 2007
- Published online by Cambridge University Press:
- 02 December 2014, pp. 451-455
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Object:
Routine histopathological examination of intervertebral disc specimens is commonly performed in North American hospitals, but recent studies have questioned the utility of this practice in cases where the indication for surgery is a benign process such as degenerative disc disease. In this study, we have performed a cost-benefit analysis of this practice.
Methods:We performed a cost-benefit analysis of routine histopathological examination of 1775 routine (non-neoplastic and non-infectious indications for surgery) and 70 non-routine (suspected neoplastic or infectious indications for surgery) discectomy specimens obtained over an eight-year period (1996 and 2004). Chart reviews were used to determine if any histopathology findings were clinically significant (i.e., affected subsequent patient care). Total costs were calculated. A literature review was conducted to compare our results with other published series.
Results:We found four unexpected histopathology results among 1775 specimens obtained from routine cases, one of which was clinically significant. We calculated costs of $42,165.25 per unexpected histopathological finding and $168,625 per clinically significant histopathological finding. For non-routine surgeries, the cost per abnormal pathological finding was $116.67.
Conclusions:In routine cases, histopathological examination of disc specimens is not justified. The decision to send specimens for pathological examination should be based on the surgeon's judgment.
Rogues' Gallery of Contributing Authors
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- By Ramon Abola, Rishimani Adsumelli, Syed Azim, Tazeen Beg, Helene Benveniste, Louis Chun, Ramtin Cohanim, Dominick Coleman, Joseph Conrad, Tommy Corrado, Jason Daras, Michelle DiGuglielmo, Vedan Djesevic, Andrew Drollinger, Kathleen Dubrow, Brian Durkin, Ralph Epstein, Christopher J. Gallagher, Xiaojun Guo, Sofie Hussain, Ron Jasiewicz, Anna Kogan, Ursula Landman, Rany Makaryus, Daryn Moller, Tate Montgomery, Matthew Neal, Khoa Nguyen, Marco Palmieri, Shaji Poovathor, Eric Posner, Deborah Richman, Andrew Rozbruch, Misako Sakamaki, Joy Schabel, Bharathi Scott, Peggy Seidman, Shiena Sharma, Vishal Sharma, Ellen Steinberg, Neera Tewari, Jane Yi, Jonida Zeqo, Peter Chung, John Denny, Steven H. Ginsberg, Jeremy Grayson, Jonathan Kraidin, Stephen Lemke, Tejal Patel, Salvatore Zisa, Charles Cowles, Marc Rozner, Shawn Banks, Deborah Brauer, Lebron Cooper, V. Samepathi David, Steve Gayer, Steven Gil, Eric A. Harris, Murlikrishna Kannan, Michael C. Lewis, David A. Lindley, Carlos M. Mijares, Sana Nini, Shafeena Nurani, Sujatha Pentakota, Edgar Pierre, Amy Klash Pulido, Michael Rossi, Miguel Santos, Nancy Setzer-Saade, Adam Sewell, Omair H. Toor, Ashish Udeshi, Patricia Wawroski, Lauren C. Berkow, Dan Berkowitz, Ramola Bhambhani, Kerry K. Blaha, Veronica Busso, Adam J. Carinci, Paul J. Christo, R. Blaine Easley, Ralph J. Fuchs, Samuel M. Galvagno, Nishant Gandhi, Andrew Goins, Robert S. Greenberg, Sayeh Hamzehzadeh, Theresa L. Hartsell, Eugenie Heitmiller, Jeremy M. Huff, Brijen L. Joshi, Sapna Kudchadkar, Jennifer K. Lee, Ira Lehrer, Peter Lin, Justin Lockman, Christine L. Mai, Christina Miller, Nanhi Mitter, Gillian Newman, Daniel Nyhan, Lale Odekon, Rabi Panigrahi, Melissa Pant, Alexander Papangelou, Mark Rossberg, Adam Schiavi, Steven J. Schwartz, Deborah A. Schwengel, Brandon M. Togioka, Tina Tran, Emmett Whitaker, Bradford D. Winters, Christopher Wu, Elena J. Holak, Paul S. Pagel
- Edited by Christopher J. Gallagher, State University of New York, Stony Brook, Michael C. Lewis, University of Miami School of Medicine, Deborah A. Schwengel
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- Book:
- Core Clinical Competencies in Anesthesiology
- Published online:
- 06 July 2010
- Print publication:
- 12 April 2010, pp xi-xii
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Extraction of Grain Boundary Energies from Triple Junction Geometry
- A. D. Rollett, C.-C. Yang, W. W. Mullins, B. L. Adams, C. T. Wu, C. L. Bauer, D. Kinderlehrer, S. Ta'asan, F. Manolache, C. Liu, I. Livshits, D. Mason, A. Talukder, S. Ozdemir, D. Casasent, A. Morawiec, D. Saylor, G. S. Rohrer, B. El-Dasher, W. Yang
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- Journal:
- Microscopy and Microanalysis / Volume 5 / Issue S2 / August 1999
- Published online by Cambridge University Press:
- 02 July 2020, pp. 230-231
- Print publication:
- August 1999
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Measurement of the geometry of triple junctions between grain boundaries in polycrystalline materials is used to generate large sets of dihedral angles from which maps of the grain boundary energy are extracted. A preliminary analysis has been performed for samples of magnesia and aluminum based on a three-parameter description of grain boundaries. An extended form of orientation imaging microscopy (OIM) was used to measure both triple junction geometry via image analysis in the SEM and local grain orientation via electron back scatter diffraction. Serial sectioning with registry of both in-plane images and successive sections characterizes triple junction tangents from which true dihedral angles are calculated. If there is local equilibrium at each triple junction, we may apply Herring's relation. By limiting grain boundary character to a (three parameter) specification of misorientation for the preliminary analysis, we can neglect the torque terms and apply the sine law to the three boundaries. This provides two independent relations per triple junction between grain boundary energies and dihedral angles. By discretizing the misorientation and employing multiscale statistical analysis on large data sets, (relative) grain boundary energy as a function of boundary character can be extracted from triple junction geometry. The results are discussed with respect to current understanding of grain boundary structure based on their crystallography. The results suggest that a three parameter characterization of grain boundaries (lattice disorientation) is not an adequate description of boundary character. A full analysis including torque terms and a five parameter boundary description is under development.
Mapping the Mesoscale Interface Structure in Polycrystalline Materials
- C. T. Wu, B. L. Adams, C. L. Bauer, D. Casasent, A. Morawiec, S. Ozdemir, A. Talukder
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- Journal:
- Microscopy and Microanalysis / Volume 5 / Issue S2 / August 1999
- Published online by Cambridge University Press:
- 02 July 2020, pp. 260-261
- Print publication:
- August 1999
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Using the new method known as Orientation Imaging Microscopy (OIM), characterization of mesoscale aspect of the internal structure of polycrystalline materials in the two-dimensional section plane has become routine. However, in some applications which primarily focus either on the characterization of interface types or on their connectivity, OIM is rather inefficient since only the scan points that lie adjacent to the interfaces are used to determine interface character. When the OIM grid spacing is dictated by the precision with which the interfacial in-plane inclination must be determined in the section plane, the efficiency with which conventional OIM can harvest interfacial data is rather poor.
In this paper a new approach and system of microscopy is described, called the Mesoscale Interface Mapping System (MIMS). MIMS overcomes the challenges associated with OIM by directing the beam to the vicinity of interfaces which have been identified by a microstructural contrast image.
Characteristics of conductive SrRuO3 thin films with different microstructures
- Q. X. Jia, F. Chu, C. D. Adams, X. D. Wu, M. Hawley, J. H. Cho, A. T. Findikoglu, S. R. Foltyn, J. L. Smith, T. E. Mitchell
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- Journal:
- Journal of Materials Research / Volume 11 / Issue 9 / September 1996
- Published online by Cambridge University Press:
- 31 January 2011, pp. 2263-2268
- Print publication:
- September 1996
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Conductive SrRuO3 thin films were epitaxially grown on (100) LaAlO3 substrates by pulsed laser deposition over a temperature range from 650 °C to 825 °C. Well-textured films exhibiting a strong orientation relationship to the underlying substrate could be obtained at a deposition temperature as low as 450 °C. The degree of crystallinity of the films improved with increasing deposition temperature as confirmed by x-ray diffraction, transmission electron microscopy, and scanning tunneling microscopy. Scanning electron microscopy revealed no particulates on the film surface. The resistivity of the SrRuO3 thin films was found to be a strong function of the crystallinity of the film and hence the substrate temperature during film deposition. A residual resistivity ratio (RRR = ρ300 K/ρ4.2 K) of more than 8 was obtained for the SrRuO3 thin films deposited under optimized processing conditions.