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27 Clinical Symptoms, Cognitive Functioning, and Brain Health in Agricultural Workers
- Jazmin M. Diaz, Stephen R. Kellam, Emily T. Sturm, Max Henneke, Emily Pehlke, John R. Duffy, Andrea Mendez-Colmenares, Agnieszka Z. Burzynska, Lorann Stallones, Michael L. Thomas
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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, p. 903
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Objective:
Agricultural workers are immersed in environments associated with increased risk for adverse psychiatric and neurological outcomes. Agricultural work-related risks to brain health include exposure to pesticides, heavy metals, and organic dust. Despite this, there is a gap in our understanding of the underlying brain systems impacted by these risks. This study explores clinical and cognitive domains, and functional brain activity in agricultural workers. We hypothesized that a history of agricultural work-related risks would be associated with poorer clinical and cognitive outcomes as well as changes in functional brain activity within cortico-striatal regions.
Participants and Methods:The sample comprised 17 agricultural workers and a comparison group of 45 non-agricultural workers recruited in the Northern Colorado area. All participants identified as White and non-Hispanic. The mean age of participants was 51.7 years (SD = 21.4, range 18-77), 60% identified as female, and 37% identified as male. Participants completed the National Institute of Health Toolbox (NIH Toolbox) and Montreal Cognitive Assessment (MoCA) on their first visit. During the second visit, they completed NIH Patient-Reported Outcomes Measurement Information System (PROMIS) measures and underwent functional magnetic resonance imaging (fMRI; N = 15 agriculture and N = 35 non-agriculture) while completing a working memory task (Sternberg). Blood oxygen-level dependent (BOLD) response was compared between participants. Given the small sample size, the whole brain voxel-wise group comparison threshold was set at alpha = .05, but not otherwise corrected for multiple comparisons. Cohen’s d effect sizes were estimated for all voxels.
Results:Analyses of cognitive scores showed significant deficits in episodic memory for the agricultural work group. Additionally, the agricultural work group scored higher on measures of self-reported anger, cognitive concerns, and social participation. Analyses of fMRI data showed increased BOLD activity around the orbitofrontal cortex (medium to large effects) and bilaterally in the entorhinal cortex (large effects) for the agricultural work group. The agricultural work group also showed decreased BOLD activity in the cerebellum and basal ganglia (medium to large effects).
Conclusions:To our knowledge, this study provides the first-ever evidence showing differences in brain activity associated with a history of working in agriculture. These findings of poorer memory, concerns about cognitive functioning, and increased anger suggest clinical relevance. Social participation associated with agricultural work should be explored as a potential protective factor for cognition and brain health. Brain imaging data analyses showed increased activation in areas associated with motor functioning, cognitive control, and emotion. These findings are limited by small sample size, lack of diversity in our sample, and coarsely defined risk. Despite these limitations, the results are consistent with an overall concern that risks associated with agricultural work can lead to cognitive and psychiatric harm via changes in brain health. Replications and future studies with larger sample sizes, more diverse participants, and more accurately defined risks (e.g., pesticide exposure) are needed.
98 Forging a New (Digital) Path: Designing a Strategic Pilot to Engage and Educate the Public about Clinical Research on Social Media
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- Nicki Karimipour, Suail Fabros, Andrea Diaz, Gordon Wimpress, Emily Lai
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- Journal:
- Journal of Clinical and Translational Science / Volume 7 / Issue s1 / April 2023
- Published online by Cambridge University Press:
- 24 April 2023, p. 28
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OBJECTIVES/GOALS: To conceptualize, implement and evaluate a three-pronged social media plan with goals to: 1) disseminate information about the Southern California CTSI and its activities on multiple platforms; 2) educate the public about clinical research participation; 3) use storytelling methods to spread awareness about research careers. METHODS/STUDY POPULATION: We will start by creating a logic model to identify activities, outputs, short, medium and long-term outcomes of this social media innovation project, using CTSI and community stakeholder input (focus groups). This model will guide the creation of a comprehensive strategic social media plan that includes an editorial calendar for each platform, storyboarding and an operationalized narrative strategy, as well as KPIs relating to areas like reach, engagement, conversion, and sentiment. Collecting/analyzing these metrics will yield information about how the public feels about clinical research and will assist us in refining our content strategy. After completing formative research, we will create accounts on Instagram, TikTok, LinkedIn and Meta to complement our existing Twitter presence. RESULTS/ANTICIPATED RESULTS: We hope to identify which types of content lead to greater engagement and more positive sentiment on each platform, which will help us iteratively refine our content strategy. Examples of content type can include: imparting research-related information, debunking myths, providing career information, etc. Through this process we will also gain knowledge about what methods are more appealing to our users, such as narrative storytelling. Visually, we anticipate learning about what types of multimedia content works best as a mechanism to disseminate information about clinical research (e.g. video, photo, audio, or a combination). DISCUSSION/SIGNIFICANCE: In a post-pandemic world of dis- and misinformation, it is more important than ever to disseminate trusted, vetted information about clinical research in novel and engaging ways. Through this initiative we will gather information, metrics and key lessons learned to present back to CTSA hubs to inform their short and long-term social media strategies.
The impact of the COVID-19 lockdown on human psychology and physical activity; a space analogue research perspective
- Jeroen Van Cutsem, Vera Abeln, Stefan Schneider, Nathan Keller, Ana Diaz-Artiles, Miguel A. Ramallo, Emilie Dessy, Nathalie Pattyn, Fabio Ferlazzo, Gabriel G. De La Torre
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- Journal:
- International Journal of Astrobiology / Volume 21 / Issue 1 / February 2022
- Published online by Cambridge University Press:
- 14 January 2022, pp. 32-45
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Introduction
Astronauts will encounter isolated, confined and extreme (ICE) conditions during future missions, and will have to be able to adapt. Until recently, however, few places on Earth could serve as acceptable space analogues (i.e., submarine and polar regions). The coronavirus disease-2019 (COVID-19)-related lockdowns around the globe provided a good opportunity to obtain more comprehensive datasets on the impact of prolonged isolation on human functioning in a very large sample.
MethodsSeven hundred forty-eight individuals (Belgium 442, Spain 183, Germany 50, Italy 50, US 23; Mean age ± SD: 41 ± 14 years, with an age range of 18–83 years; 66% women) filled out an online survey assessing the impact of the COVID-lockdown on psychological, exercise and general health variables a first time near the beginning of the initial lockdown (hereafter ‘T1’; 24 ± 13 days after the start of the first lockdown; i.e., 3 weeks after the start of the first lockdown) and a second time a couple of weeks thereafter (hereafter ‘T2’; 17 ± 5 days after the first online survey; i.e., 6 weeks after the start of the first lockdown).
ResultsFrom T1 to T2 an improvement of subjective sleep quality was observed (P = 0.003), that was related to an increase in subjective sleep efficiency and a decrease in sleep latency and disturbance (P ≤ 0.013). Weekly sitting time decreased, and the weekly amount of moderate and vigorous physical activity increased from T1 to T2 (P ≤ 0.049). No differences from T1 to T2 were observed in terms of mood, loneliness and state anxiety. A lower amount of sitting time was significantly correlated with improved subjective sleep quality (r = 0.096, P = 0.035) and with an increased amount of moderate (r = −0.126, P = 0.005) and vigorous (r = −0.110, P = 0.015) physical activity.
ConclusionCompared to 3 weeks into the first COVID-imposed lockdown, 6-weeks after the start of the first COVID-imposed lockdown, physical activity and subjective sleep scores were positively impacted. The present, large sample size study further confirms exercise as a worthwhile countermeasure to psycho-physiological deconditioning during confinement.
Review of Candida dubliniensis at a Pediatric Hospital
- Alejandro Diaz, Dana Danino, Amy Leber, s Hospital Huanyu Wang, Emily Klamet, Stephanie Stack-Simone, Matthew Washam
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 41 / Issue S1 / October 2020
- Published online by Cambridge University Press:
- 02 November 2020, pp. s373-s374
- Print publication:
- October 2020
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Background:Candida dubliniensis is a worldwide fungal opportunistic pathogen, closely related to C. albicans. Originally identified in patients infected with HIV in Dublin, Ireland, C. dubliniensis has emerged as a pathogen in other immunocompromised individuals, including patients receiving chemotherapy and transplant recipients. Pediatric epidemiological data for this organism are limited. Methods: We report a descriptive review of C. dubliniensis isolates recovered between January 2018 and June 2019 at a large tertiary-care pediatric institution in Columbus, Ohio. Results:C. dubliniensis was identified in 48 patients in the 18-month review period. In total, 67 positive cultures were collected in these patients with the following distribution of sources: 44 sputum (66%), 11 bronchoalveloar lavage fluid (16%), 4 blood (6%), 3 wounds (4%), 2 esophageal (3%), 2 peritoneal fluid (3%), and 1 vaginal (1%). Of the 48 patients in whom C. dubliniensis was identified, 35 (73%) were patients with cystic fibrosis. Also, 8 patients (17%) were considered to have clinical infections and received antifungal therapy: 3 patients with pneumonia, 2 patients with esophagitis, 1 patient with peritonitis, 1 patient with catheter-related bloodstream infection, and 1 patient with disseminated candidiasis. The remaining 40 patients (83%) were considered colonized. Conclusions: We report a descriptive series over 18 months of clinical isolates with C. dubliniensis recovery at a pediatric institution. Most isolates were identified as colonizing strains in patients with cystic fibrosis. C. dubliniensis was a rare cause of invasive disease in our institution, with only 8 cases identified.
Funding: None
Disclosures: None
The Implementation of Active Environmental Surveillance in a Veterinary Referral Hospital Setting
- Emily Feyes, Dixie Mollenkopf, Thomas Wittum, Dubraska Diaz-Campos, Rikki Horne
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 41 / Issue S1 / October 2020
- Published online by Cambridge University Press:
- 02 November 2020, p. s409
- Print publication:
- October 2020
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Emily Feyes, The Ohio State University College of Veterinary Medicine; Dixie Mollenkopf, The Ohio State University College of Veterinary Medicine; Thomas Wittum, The Ohio State University College of Veterinary Medicine; Dubraska Diaz-Campos, The Ohio State University College of Veterinary Medicine; Rikki Horne, The Ohio State University College of Veterinary Medicine
Background: The Ohio State University College of Veterinary Medicine (OSU-CVM) Antimicrobial Stewardship Working Group (ASWG) uses monthly environmental surveillance to understand the effectiveness of our veterinary medical center (VMC) infection control and biosecurity protocols in reducing environmental contamination with multidrug resistant organisms. Monthly surveillance allows us to monitor trends in the recovery of these resistant organisms and address issues of concern that could impact our patients, clients, staff, and students. Methods: The OSU-CVM ASWG collects samples from >100 surfaces within the companion animal, farm animal, and equine sections of our hospital each month. Sampling has been continuous since January 2018. Samples are collected from both human–animal contact and human-only contact surfaces using Swiffer electrostatic cloths. These samples are cultured for recovery of Salmonella spp, extended-spectrum cephalosporin-resistant Enterobacteriaceae, carbapenemase-producing Enterobacteriaceae (CPE), and methicillin-resistant Staphylococcus spp. Results: The recovery of these antibiotic resistant target organisms is low in the environment of our hospital. Recovery from human-only contact surfaces (19.8%) is very similar to recovery from human–animal contact surfaces (25.5%). We commonly recover Enterobacteriaceae (E.coli, Klebsiella spp, and Enterobacter spp) that are resistant to extended-spectrum cephalosporins (496 of 2,016; 24.6%) from the VMC environment. These antibiotic-resistant indicator bacteria are expected in a veterinary hospital setting where use the of β-lactam drugs is common. Recovery of both Salmonella spp and CPE has remained very low in our hospital environment over the past 19 months: 16 of 2,016 (0.7%) for Salmonella and 15 of 2,016 (0.8%) for CPE. Discussion: The active environmental surveillance component of our antimicrobial stewardship program has allowed us to reduce the threat of nosocomial infections within our hospital and address environmental contamination issues before they become a problem. Our consistently low recovery of resistant organisms indicates the effectiveness of our existing cleaning and disinfection protocols and biosecurity measures. Due to the nature of our patient population, we do expect to find resistant organisms in the patient-contact areas of the hospital environment. However, our similar rates of resistant organisms from human-only surfaces (eg, computer keyboards, door handles, telephones, and Cubex machines) indicates a need to improve our hand hygiene practices. These data are now supporting the implementation of a new hand hygiene campaign in our veterinary hospital.
Funding: None
Disclosures: None
Validation and Normalization of the Tower of London-Drexel University Test 2nd Edition in an Adult Population with Intellectual Disability
- Javier García-Alba, Susanna Esteba-Castillo, Miguel Ángel Castellanos López, Emili Rodríguez Hidalgo, Nuria Ribas Vidal, Fernando Moldenhauer Díaz, Ramón Novell-Alsina
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- Journal:
- The Spanish Journal of Psychology / Volume 20 / 2017
- Published online by Cambridge University Press:
- 20 July 2017, E32
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Despite how important it is to assess executive functioning in persons with Intellectual Disability (ID), instruments adapted and validated for this population are scarce. This study’s primary goal was to find evidence for the validity of the ID version of the Tower of London (TOLDXtm) test in persons with mild (IDMi) and moderate (IDMo) levels of ID with Down Syndrome (DS). A multicenter study was carried out. Subjects (n = 63, ≥ 39 years old) had DS with mild (n = 39) or moderate ID (n = 24) with no minor neurocognitive disorder or Alzheimer’s disease. Assessment protocol: TOLDXtm for ID, Kaufman Brief Intelligence Test Second Edition (K-BIT II), Cambridge Examination for Mental Disorders of Older People with Down’s Syndrome and Others with Intellectual Disabilities (CAMDEX-DS), Weigl’s Color-Form Sorting Test (WCFST), Barcelona Test for Intellectual Disability (BT-ID), and the Behavior Rating Inventory of Executive Function (BRIEF-P). The internal consistency (IDMi and IDMo), factor structure of the different subscales, and relationship between TOLDXtm subscales and other cognitive measures (BT-ID, WCFST, and BRIEF-P) were analyzed. A normative data table with ID population quartiles is provided. TOLDXtm for ID showed a robust one factor structure and coherentassociations with other, related neuropsychological instruments. Significant differences between IDMi and IDMo on movement-related variables like Correct (Corr; p = .002) and Moves (Mov; p = .042) were observed, along with good internal consistency values, Corr (α = .75), Mov (α = .52). Regarding internal consistency, no between-groups differences were observed (all p-value > 0.05). The TOLDXtm for ID is thus an instrument, supported by good validity evidence, to evaluate problem-solving and planning in ID. It distinguishes between individuals with mild and moderate ID, and is highly associated with other measures of executive functioning.
Lessons Learned from Twelve Years of Partnered Tobacco Cessation Research in the Dominican Republic
- Deborah J. Ossip, Sergio Díaz, Zahira Quiñones, Scott McIntosh, Ann Dozier, Nancy Chin, Emily Weber, Heather Holderness, Essie Torres, Arisleyda Bautista, Jóse Javier Sánchez, Esteban Avendaño, Timothy De Ver Dye, Paul McDonald, Eduardo Bianco
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- Journal:
- Journal of Smoking Cessation / Volume 11 / Issue 2 / June 2016
- Published online by Cambridge University Press:
- 10 May 2016, pp. 99-107
- Print publication:
- June 2016
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Engaging partners for tobacco control within low and middle income countries (LMICs) at early stages of tobacco control presents both challenges and opportunities in the global effort to avert the one billion premature tobacco caused deaths projected for this century. The Dominican Republic (DR) is one such early stage country. The current paper reports on lessons learned from 12 years of partnered United States (US)-DR tobacco cessation research conducted through two NIH trials (Proyecto Doble T, PDT1 and 2). The projects began with a grassroots approach of working with interested communities to develop and test interventions for cessation and secondhand smoke reduction that could benefit the communities, while concurrently building local capacity and providing resources, data, and models of implementation that could be used to ripple upward to expand partnerships and tobacco intervention efforts nationally. Lessons learned are discussed in four key areas: partnering for research, logistical issues in setting up the research project, disseminating and national networking, and mentoring. Effectively addressing the global tobacco epidemic will require sustained focus on supporting LMIC infrastructures for tobacco control, drawing on lessons learned across partnered trials such as those reported here, to provide feasible and innovative approaches for addressing this modifiable public health crisis.
Tobacco Cessation in Economically Disadvantaged Dominican Republic Communities: Who are the Ex-Users?
- Deborah J. Ossip, Zahíra Quiñones, Sergio Diaz, Kelly Thevenet-Morrison, Susan Fisher, Heather Holderness, Xeuya Cai, Scott McIntosh, Ann Dozier, Nancy Chin, Emily Weber, Jose Javier Sanchez, Arisleyda Bautista, Héctor Almonte
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- Journal:
- Journal of Smoking Cessation / Volume 11 / Issue 4 / December 2016
- Published online by Cambridge University Press:
- 20 February 2015, pp. 239-249
- Print publication:
- December 2016
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Introduction: Tobacco use and its harm continue to increase in low and middle income countries (LMICs) globally. Smoking cessation is the most effective means of reducing morbidity and mortality from tobacco use. Increasing the prevalence of ex-users is an indicator of population cessation.
Aims: This study provides the first examination of factors associated with ex-tobacco use status in the Dominican Republic (DR), a LMIC in the Latin America and Caribbean region.
Methods: Baseline surveillance was conducted for 1,177 randomly selected households in seven economically disadvantaged DR communities (total N = 2,680 adult household members).
Results: Ex-user prevalence was 10.6% (1.0%–18.5% across communities), 14.8% were current users (9.1–20.4), and quit ratios were 41.7% (9.7%–52.7%). Among ever users, females (OR 2.02, 95% CI 1.41, 2.90), older adults (45–64: OR 1.75, 95% CI 1.12, 2.74; 65+: OR 2.09, 95% CI 1.29, 3.39), and those who could read/write (OR 1.64, 95% CI 1.08, 2.50), had health conditions (OR 1.63, 95% CI 1.11, 2.41), and lived with ex-users (OR 1.70, 95% CI 1.12, 2.58) were over 60% to two times as likely to be ex-users. Those from remote communities (OR 0.52, 95% CI 0.36, 0.74), using chewed tobacco (OR 0.14, 95% CI 0.04, 0.48) and living with tobacco users (OR 0.55, 95% CI 0.37, 0.81) were less likely to be ex-users.
Conclusions: Ex-user prevalence and quit ratios were lower than for high income countries. Implementing broad tobacco control measures, combined with clinically targeting vulnerable groups, may increase tobacco cessation to most effectively reduce this public health crisis.
Contributors
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- By Aakash Agarwala, Linda S. Aglio, Rae M. Allain, Paul D. Allen, Houman Amirfarzan, Yasodananda Kumar Areti, Amit Asopa, Edwin G. Avery, Patricia R. Bachiller, Angela M. Bader, Rana Badr, Sibinka Bajic, David J. Baker, Sheila R. Barnett, Rena Beckerly, Lorenzo Berra, Walter Bethune, Sascha S. Beutler, Tarun Bhalla, Edward A. Bittner, Jonathan D. Bloom, Alina V. Bodas, Lina M. Bolanos-Diaz, Ruma R. Bose, Jan Boublik, John P. Broadnax, Jason C. Brookman, Meredith R. Brooks, Roland Brusseau, Ethan O. Bryson, Linda A. Bulich, Kenji Butterfield, William R. Camann, Denise M. Chan, Theresa S. Chang, Jonathan E. Charnin, Mark Chrostowski, Fred Cobey, Adam B. Collins, Mercedes A. Concepcion, Christopher W. Connor, Bronwyn Cooper, Jeffrey B. Cooper, Martha Cordoba-Amorocho, Stephen B. Corn, Darin J. Correll, Gregory J. Crosby, Lisa J. Crossley, Deborah J. Culley, Tomas Cvrk, Michael N. D'Ambra, Michael Decker, Daniel F. Dedrick, Mark Dershwitz, Francis X. Dillon, Pradeep Dinakar, Alimorad G. Djalali, D. John Doyle, Lambertus Drop, Ian F. Dunn, Theodore E. Dushane, Sunil Eappen, Thomas Edrich, Jesse M. Ehrenfeld, Jason M. Erlich, Lucinda L. Everett, Elliott S. Farber, Khaldoun Faris, Eddy M. Feliz, Massimo Ferrigno, Richard S. Field, Michael G. Fitzsimons, Hugh L. Flanagan Jr., Vladimir Formanek, Amanda A. Fox, John A. Fox, Gyorgy Frendl, Tanja S. Frey, Samuel M. Galvagno Jr., Edward R. Garcia, Jonathan D. Gates, Cosmin Gauran, Brian J. Gelfand, Simon Gelman, Alexander C. Gerhart, Peter Gerner, Omid Ghalambor, Christopher J. Gilligan, Christian D. Gonzalez, Noah E. Gordon, William B. Gormley, Thomas J. Graetz, Wendy L. Gross, Amit Gupta, James P. Hardy, Seetharaman Hariharan, Miriam Harnett, Philip M. Hartigan, Joaquim M. Havens, Bishr Haydar, Stephen O. Heard, James L. Helstrom, David L. Hepner, McCallum R. Hoyt, Robert N. Jamison, Karinne Jervis, Stephanie B. Jones, Swaminathan Karthik, Richard M. Kaufman, Shubjeet Kaur, Lee A. Kearse Jr., John C. Keel, Scott D. Kelley, Albert H. Kim, Amy L. Kim, Grace Y. Kim, Robert J. Klickovich, Robert M. Knapp, Bhavani S. Kodali, Rahul Koka, Alina Lazar, Laura H. Leduc, Stanley Leeson, Lisa R. Leffert, Scott A. LeGrand, Patricio Leyton, J. Lance Lichtor, John Lin, Alvaro A. Macias, Karan Madan, Sohail K. Mahboobi, Devi Mahendran, Christine Mai, Sayeed Malek, S. Rao Mallampati, Thomas J. Mancuso, Ramon Martin, Matthew C. Martinez, J. A. Jeevendra Martyn, Kai Matthes, Tommaso Mauri, Mary Ellen McCann, Shannon S. McKenna, Dennis J. McNicholl, Abdel-Kader Mehio, Thor C. Milland, Tonya L. K. Miller, John D. Mitchell, K. Annette Mizuguchi, Naila Moghul, David R. Moss, Ross J. Musumeci, Naveen Nathan, Ju-Mei Ng, Liem C. Nguyen, Ervant Nishanian, Martina Nowak, Ala Nozari, Michael Nurok, Arti Ori, Rafael A. Ortega, Amy J. Ortman, David Oxman, Arvind Palanisamy, Carlo Pancaro, Lisbeth Lopez Pappas, Benjamin Parish, Samuel Park, Deborah S. Pederson, Beverly K. Philip, James H. Philip, Silvia Pivi, Stephen D. Pratt, Douglas E. Raines, Stephen L. Ratcliff, James P. Rathmell, J. Taylor Reed, Elizabeth M. Rickerson, Selwyn O. Rogers Jr., Thomas M. Romanelli, William H. Rosenblatt, Carl E. Rosow, Edgar L. Ross, J. Victor Ryckman, Mônica M. Sá Rêgo, Nicholas Sadovnikoff, Warren S. Sandberg, Annette Y. Schure, B. Scott Segal, Navil F. Sethna, Swapneel K. Shah, Shaheen F. Shaikh, Fred E. Shapiro, Torin D. Shear, Prem S. Shekar, Stanton K. Shernan, Naomi Shimizu, Douglas C. Shook, Kamal K. Sikka, Pankaj K. Sikka, David A. Silver, Jeffrey H. Silverstein, Emily A. Singer, Ken Solt, Spiro G. Spanakis, Wolfgang Steudel, Matthias Stopfkuchen-Evans, Michael P. Storey, Gary R. Strichartz, Balachundhar Subramaniam, Wariya Sukhupragarn, John Summers, Shine Sun, Eswar Sundar, Sugantha Sundar, Neelakantan Sunder, Faraz Syed, Usha B. Tedrow, Nelson L. Thaemert, George P. Topulos, Lawrence C. Tsen, Richard D. Urman, Charles A. Vacanti, Francis X. Vacanti, Joshua C. Vacanti, Assia Valovska, Ivan T. Valovski, Mary Ann Vann, Susan Vassallo, Anasuya Vasudevan, Kamen V. Vlassakov, Gian Paolo Volpato, Essi M. Vulli, J. Matthias Walz, Jingping Wang, James F. Watkins, Maxwell Weinmann, Sharon L. Wetherall, Mallory Williams, Sarah H. Wiser, Zhiling Xiong, Warren M. Zapol, Jie Zhou
- Edited by Charles Vacanti, Scott Segal, Pankaj Sikka, Richard Urman
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- Essential Clinical Anesthesia
- Published online:
- 05 January 2012
- Print publication:
- 11 July 2011, pp xv-xxviii
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Absolute/convective instability dichotomy at the onset of convection in a porous layer with either horizontal or vertical solutal and inclined thermal gradients, and horizontal throughflow
- EMILIE DIAZ, LEONID BREVDO
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- Journal of Fluid Mechanics / Volume 681 / 25 August 2011
- Published online by Cambridge University Press:
- 01 July 2011, pp. 567-596
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By using the methods of the theory of two- and three-dimensional linear absolute and convective instabilities, we examine the nature of the instability at the onset of convection in a model of convection in an extended horizontal layer of a saturated porous medium with either horizontal or vertical salinity and inclined temperature gradients, and horizontal throughflow. First, normal modes are analysed and the critical values of the vertical thermal Rayleigh number, Rv, wavenumber vector, (k, l) and frequency, ω, are obtained for a variety of values of the horizontal thermal and salinity Rayleigh numbers, Rh and Sh, respectively, the vertical salinity Rayleigh number Sv and the horizontal Péclet number, Qh. In the computations, a high-precision pseudo-spectral Chebyshev-collocation method is used. In most of the cases of parameter combinations considered, the onset of convection occurs through a longitudinal mode. Most of the non-longitudinal critical modes are oscillatory. Further, it is revealed that there exists an absolute/convective instability dichotomy at the onset of three-dimensional convection in a set of the base states given by exact analytic solutions of the equations of motion in the model. This echoes the results of Brevdo (vol. 641, 2009, p. 475) for transverse modes in a model with inclined temperature gradient and vertical throughflow, but with no salinity. The dependence of the dichotomy on the inclined thermal gradient, and on the horizontal and the vertical salinity gradients is investigated, for the longitudinal modes treated both as two-dimensional as well as three-dimensional modes, and for the non-longitudinal modes. For a certain set of parameter cases, it was found that the destabilization through longitudinal modes treated as two-dimensional modes has the character of absolute instability whereas a three-dimensional analysis of these modes revealed that the instability is convective, with the group velocity vector of the emerging unstable wavepacket being parallel to the axis of the convection rolls. Since a similar effect was reported by Brevdo (vol. 641, 2009, p. 475) for a model with no salinity, we conclude that this effect is not a separate case. In most of the cases considered in which a marginally unstable base state is absolutely stable, but convectively unstable, the direction of propagation of the emerging unstable wavepacket is either parallel or perpendicular to the axis of the convection rolls. Only in the absolutely stable, but convectively unstable cases in which non-longitudinal modes are favourable, the angle, ϕ, between the group velocity vector of the unstable wavepacket and the axis of the rolls satisfies 0 < ϕ < 90°.
Contributors
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- By Farook Al-Azzawi, Wita Angrianni, Sanjay Asthana, Stephan Bandelow, Kathryn J. Bryan, Cynthia M. Carlsson, Jenna C. Carroll, Gemma Casadesus, Monique M. Cherrier, Laura H. Coker, María M. Corrada, Vita Priantina Dewi, Roberta Diaz Brinton, Mark A. Espeland, Mirjam I. Geerlings, Robert B. Gibbs, Carey E. Gleason, Victor W. Henderson, Patricia E. Hogan, Eef Hogervorst, Claudia H. Kawas, Anna Khaylis, Philip Kreager, Linda Kushandy, Donald Lehmann, Jin Li, Mary E. McAsey, Pauline M. Maki, Ralph N. Martins, Scott D. Moffat, Majon Muller, Theresia Ninuk, Annlia Paganini-Hill, George Perry, Christian J. Pike, Bevin N. Powers, Tri Budi W. Rahardjo, Natalie L. Rasgon, Susan M. Resnick, Emily R. Rosario, Sabarinah, Tony Sadjimim, Barbara B. Sherwin, Sally A. Shumaker, Mark A. Smith, Robert G. Struble, Chris Talbot, Wulf H. Utian, Giuseppe Verdile, Robert B. Wallace, Whitney Wharton, Katherine E. Williams, Oliver T. Wolf, Tonita E. Wroolie, Amina Yesufu, Yudarini, Liqin Zhao
- Edited by Eef Hogervorst, Loughborough University, Victor W. Henderson, Stanford University, California, Robert B. Gibbs, University of Pittsburgh, Roberta Diaz Brinton, University of Southern California
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- Book:
- Hormones, Cognition and Dementia
- Published online:
- 06 July 2010
- Print publication:
- 24 September 2009, pp vii-x
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