11 results
P.017 Convergent and contrasting modulation of saccade and pupil responses by several neurodegenerative diseases during free viewing of video clips
- HC Riek, BJ White, DC Brien, BC Coe, J Huang, A Abrahao, SE Black, M Borrie, E Finger, CE Fischer, AR Frank, M Freedman, DA Grimes, M Jog, S Kumar, D Kwan, AE Lang, JM Lawrence-Dewar, C Marras, M Masellis, SH Pasternak, BG Pollock, TK Rajji, DP Seitz, C Shoesmith, TD Steeves, B Tan, DF Tang-Wai, C Tartaglia, J Turnbull, L Zinman, ONDRI Investigators DP Munoz
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- Journal:
- Canadian Journal of Neurological Sciences / Volume 50 / Issue s2 / June 2023
- Published online by Cambridge University Press:
- 05 June 2023, p. S62
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Background: Saccade and pupil responses are potential neurodegenerative disease biomarkers due to overlap between oculomotor circuitry and disease-affected areas. Instruction-based tasks have previously been examined as biomarker sources, but are arduous for patients with limited cognitive abilities; additionally, few studies have evaluated multiple neurodegenerative pathologies concurrently. Methods: The Ontario Neurodegenerative Disease Research Initiative recruited individuals with Alzheimer’s disease (AD), mild cognitive impairment (MCI), amyotrophic lateral sclerosis (ALS), frontotemporal dementia, progressive supranuclear palsy, or Parkinson’s disease (PD). Patients (n=274, age 40-86) and healthy controls (n=101, age 55-86) viewed 10 minutes of frequently changing video clips without instruction while their eyes were tracked. We evaluated differences in saccade and pupil parameters (e.g. saccade frequency and amplitude, pupil size, responses to clip changes) between groups. Results: Preliminary data indicates low-level behavioural alterations in multiple disease cohorts: increased centre bias, lower overall saccade rate and reduced saccade amplitude. After clip changes, patient groups generally demonstrated lower saccade rate but higher microsaccade rate following clip change to varying degrees. Additionally, pupil responses were blunted (AD, MCI, ALS) or exaggerated (PD). Conclusions: This task may generate behavioural biomarkers even in cognitively impaired populations. Future work should explore the possible effects of factors such as medication and disease stage.
P.002 Saccade parameters reveal cognitive impairment and differentially associate with cognitive domains across neurodegenerative diseases
- HC Riek, BC Coe, DC Brien, J Huang, A Abrahao, S Arnott, D Beaton, M Binns, S Black, M Borrie, L Casaubon, D Dowlatshahi, E Finger, C Fischer, A Frank, M Freedman, D Grimes, A Hassan, M Jog, S Kumar, D Kwan, A Lang, J Lawrence Dewar, B Levine, W Lou, J Mandzia, C Marras, M Masellis, P McLaughlin, J Orange, S Pasternak, A Peltsch, B Pollock, T Rajji, A Roberts, D Sahlas, G Saposnik, D Seitz, C Shoesmith, T Steeves, S Strother, S Sujanthan, K Sunderland, R Swartz, B Tan, D Tang-Wai, C Tartaglia, A Troyer, J Turnbull, L Zinman, ONDRI Investigators (), DP Munoz
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- Journal:
- Canadian Journal of Neurological Sciences / Volume 49 / Issue s1 / June 2022
- Published online by Cambridge University Press:
- 24 June 2022, p. S8
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Background: Eye movements reveal neurodegenerative disease processes due to overlap between oculomotor circuitry and disease-affected areas. Characterizing oculomotor behaviour in context of cognitive function may enhance disease diagnosis and monitoring. We therefore aimed to quantify cognitive impairment in neurodegenerative disease using saccade behaviour and neuropsychology. Methods: The Ontario Neurodegenerative Disease Research Initiative recruited individuals with neurodegenerative disease: one of Alzheimer’s disease, mild cognitive impairment, amyotrophic lateral sclerosis, frontotemporal dementia, Parkinson’s disease, or cerebrovascular disease. Patients (n=450, age 40-87) and healthy controls (n=149, age 42-87) completed a randomly interleaved pro- and anti-saccade task (IPAST) while their eyes were tracked. We explored the relationships of saccade parameters (e.g. task errors, reaction times) to one another and to cognitive domain-specific neuropsychological test scores (e.g. executive function, memory). Results: Task performance worsened with cognitive impairment across multiple diseases. Subsets of saccade parameters were interrelated and also differentially related to neuropsychology-based cognitive domain scores (e.g. antisaccade errors and reaction time associated with executive function). Conclusions: IPAST detects global cognitive impairment across neurodegenerative diseases. Subsets of parameters associate with one another, suggesting disparate underlying circuitry, and with different cognitive domains. This may have implications for use of IPAST as a cognitive screening tool in neurodegenerative disease.
MP22: Guiding practice transition with a faculty mentorship program
- S. Yiu, M. Yeung, L. Fischer, J. Frank
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 21 / Issue S1 / May 2019
- Published online by Cambridge University Press:
- 02 May 2019, p. S50
- Print publication:
- May 2019
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Innovation Concept: Transition to independent practice is challenging and early career physicians are more prone to burnout and error. Despite recommendations for formal mentorship to support physicians, only 43.6% of US academic Emergency Medicine departments have such programs. We describe an innovative mentorship program designed to support these early career physicians and enhance quality of care, career longevity, and wellness. We operationalized mentorship in which experienced, highly regarded, empathic mentors guide mentees in their personal and professional development. Methods: In this program two Emergency Physician mentors were teamed with each newly hired Emergency Physician. Mentees could request their own mentors, and teams were matched on the basis of shared personal and academic interests. Mentors received academic funding and training on good mentorship practice, roles and responsibilities, and feedback. Teams had to meet formally at least twice a year, with additional contact as needed. While mentees set the meeting agenda, teams were also encouraged to address four main areas. These areas were identified from a targeted needs assessment and literature review. They include: 1) clinical process and care, 2) departmental structure and culture, 3) teaching and scholarship, and 4) physician wellness. After meetings, mentees summarized and submitted the topics discussed and reflected on action plans. An oversight committee supported the program. Curriculum, Tool or Material: All nine (9) newly hired physicians joined the program in Fall 2018. As of December 2018, six (6) teams have had formal meetings. They discussed the following areas: clinical processes and care (50%), departmental structure and culture (100%), teaching and scholarship (67%), and physician wellness (100%). Other areas discussed include: academic career, financial planning, and networking. Teams spent 20-60% of the time formulating steps to achieve mentee career goals. They spent 40-60% of the time discussing skills and resources needed. End of year program evaluation will include outcomes such as satisfaction, value, effectiveness, projects, promotions, and awards. The results will shape future program design. Conclusion: We implemented a mentorship program for newly hired Emergency Physicians. As mentorship is integral to successful transition to independent practice, this program model could be highly beneficial to other academic Emergency Medicine departments.
P142: Gaps in public preparedness to be a substitute decision maker and the acceptability of high school education on resuscitation and end-of-life care: a mixed-methods study
- M. Wong, M. Medor, K. Yelle Labre, M. Jiang, J. Frank, L. Fischer, W. Cheung
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 21 / Issue S1 / May 2019
- Published online by Cambridge University Press:
- 02 May 2019, pp. S115-S116
- Print publication:
- May 2019
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Introduction: When a patient is incapable of making medical decisions for themselves, choices are made according to the patient's previously expressed, wishes, values, and beliefs by a substitute decision maker (SDM). While interventions to engage patients in their own advance care planning exist, little is known about public readiness to act as a SDM on behalf of a loved one. This mixed-methods survey aimed to describe attitudes, enablers and barriers to preparedness to act as a SDM, and support for a population-level curriculum on the role of an SDM in end-of-life and resuscitative care. Methods: From November 2017 to June 2018, a mixed-methods street intercept survey was conducted in Ottawa, Canada. Descriptive statistics and logistic regression analysis were used to assess predictors of preparedness to be a SDM and understand support for a high school curriculum. Responses to open-ended questions were analyzed using inductive thematic analysis. Results: The 430 respondents were mostly female (56.5%) with an average age of 33.9. Although 73.0% of respondents felt prepared to be a SDM, 41.0% of those who reported preparedness never had a meaningful conversation with loved ones about their wishes in critical illness. The only predictors of SDM preparedness were the belief that one would be a future SDM (OR 2.36 95% CI 1.34-4.17), and age 50-64 compared to age 16-17 (OR 7.46 95% CI 1.25-44.51). Thematic enablers of preparedness included an understanding of a patient's wishes, the role of the SDM and strong familial relationships. Barriers included cultural norms, family conflict, and a need for time for high stakes decisions. Most respondents (71.9%) believed that 16 year olds should learn about SDMs. They noted age appropriateness, potential developmental and societal benefit, and improved decision making, while cautioning the need for a nuanced approach respectful of different maturity levels, cultures and individual experiences. Conclusion: This study reveals a concerning gap between perceived preparedness and actions taken in preparation to be an SDM for loved ones suffering critical illness. The results also highlight the potential role for high school education to address this gap. Future studies should further explore the themes identified to inform development of resources and curricula for improved health literacy in resuscitation and end-of-life care.
Contributor affiliations
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- By Frank Andrasik, Melissa R. Andrews, Ana Inés Ansaldo, Evangelos G. Antzoulatos, Lianhua Bai, Ellen Barrett, Linamara Battistella, Nicolas Bayle, Michael S. Beattie, Peter J. Beek, Serafin Beer, Heinrich Binder, Claire Bindschaedler, Sarah Blanton, Tasia Bobish, Michael L. Boninger, Joseph F. Bonner, Chadwick B. Boulay, Vanessa S. Boyce, Anna-Katharine Brem, Jacqueline C. Bresnahan, Floor E. Buma, Mary Bartlett Bunge, John H. Byrne, Jeffrey R. Capadona, Stefano F. Cappa, Diana D. Cardenas, Leeanne M. Carey, S. Thomas Carmichael, Glauco A. P. Caurin, Pablo Celnik, Kimberly M. Christian, Stephanie Clarke, Leonardo G. Cohen, Adriana B. Conforto, Rory A. Cooper, Rosemarie Cooper, Steven C. Cramer, Armin Curt, Mark D’Esposito, Matthew B. Dalva, Gavriel David, Brandon Delia, Wenbin Deng, Volker Dietz, Bruce H. Dobkin, Marco Domeniconi, Edith Durand, Tracey Vause Earland, Georg Ebersbach, Jonathan J. Evans, James W. Fawcett, Uri Feintuch, Toby A. Ferguson, Marie T. Filbin, Diasinou Fioravante, Itzhak Fischer, Agnes Floel, Herta Flor, Karim Fouad, Richard S. J. Frackowiak, Peter H. Gorman, Thomas W. Gould, Jean-Michel Gracies, Amparo Gutierrez, Kurt Haas, C.D. Hall, Hans-Peter Hartung, Zhigang He, Jordan Hecker, Susan J. Herdman, Seth Herman, Leigh R. Hochberg, Ahmet Höke, Fay B. Horak, Jared C. Horvath, Richard L. Huganir, Friedhelm C. Hummel, Beata Jarosiewicz, Frances E. Jensen, Michael Jöbges, Larry M. Jordan, Jon H. Kaas, Andres M. Kanner, Noomi Katz, Matthew S. Kayser, Annmarie Kelleher, Gerd Kempermann, Timothy E. Kennedy, Jürg Kesselring, Fary Khan, Rachel Kizony, Jeffery D. Kocsis, Boudewijn J. Kollen, Hubertus Köller, John W. Krakauer, Hermano I. Krebs, Gert Kwakkel, Bradley Lang, Catherine E. Lang, Helmar C. Lehmann, Angelo C. Lepore, Glenn S. Le Prell, Mindy F. Levin, Joel M. Levine, David A. Low, Marilyn MacKay-Lyons, Jeffrey D. Macklis, Margaret Mak, Francine Malouin, William C. Mann, Paul D. Marasco, Christopher J. Mathias, Laura McClure, Jan Mehrholz, Lorne M. Mendell, Robert H. Miller, Carol Milligan, Beth Mineo, Simon W. Moore, Jennifer Morgan, Charbel E-H. Moussa, Martin Munz, Randolph J. Nudo, Joseph J. Pancrazio, Theresa Pape, Alvaro Pascual-Leone, Kristin M. Pearson-Fuhrhop, P. Hunter Peckham, Tamara L. Pelleshi, Catherine Verrier Piersol, Thomas Platz, Marcus Pohl, Dejan B. Popović, Andrew M. Poulos, Maulik Purohit, Hui-Xin Qi, Debbie Rand, Mahendra S. Rao, Josef P. Rauschecker, Aimee Reiss, Carol L. Richards, Keith M. Robinson, Melvyn Roerdink, John C. Rosenbek, Serge Rossignol, Edward S. Ruthazer, Arash Sahraie, Krishnankutty Sathian, Marc H. Schieber, Brian J. Schmidt, Michael E. Selzer, Mijail D. Serruya, Himanshu Sharma, Michael Shifman, Jerry Silver, Thomas Sinkjær, George M. Smith, Young-Jin Son, Tim Spencer, John D. Steeves, Oswald Steward, Sheela Stuart, Austin J. Sumner, Chin Lik Tan, Robert W. Teasell, Gareth Thomas, Aiko K. Thompson, Richard F. Thompson, Wesley J. Thompson, Erika Timar, Ceri T. Trevethan, Christopher Trimby, Gary R. Turner, Mark H. Tuszynski, Erna A. van Niekerk, Ricardo Viana, Difei Wang, Anthony B. Ward, Nick S. Ward, Stephen G. Waxman, Patrice L. Weiss, Jörg Wissel, Steven L. Wolf, Jonathan R. Wolpaw, Sharon Wood-Dauphinee, Ross D. Zafonte, Binhai Zheng, Richard D. Zorowitz
- Edited by Michael Selzer, Stephanie Clarke, Leonardo Cohen, Gert Kwakkel, Robert Miller, Case Western Reserve University, Ohio
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- Book:
- Textbook of Neural Repair and Rehabilitation
- Published online:
- 05 May 2014
- Print publication:
- 24 April 2014, pp ix-xvi
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Contributor affiliations
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- By Frank Andrasik, Melissa R. Andrews, Ana Inés Ansaldo, Evangelos G. Antzoulatos, Lianhua Bai, Ellen Barrett, Linamara Battistella, Nicolas Bayle, Michael S. Beattie, Peter J. Beek, Serafin Beer, Heinrich Binder, Claire Bindschaedler, Sarah Blanton, Tasia Bobish, Michael L. Boninger, Joseph F. Bonner, Chadwick B. Boulay, Vanessa S. Boyce, Anna-Katharine Brem, Jacqueline C. Bresnahan, Floor E. Buma, Mary Bartlett Bunge, John H. Byrne, Jeffrey R. Capadona, Stefano F. Cappa, Diana D. Cardenas, Leeanne M. Carey, S. Thomas Carmichael, Glauco A. P. Caurin, Pablo Celnik, Kimberly M. Christian, Stephanie Clarke, Leonardo G. Cohen, Adriana B. Conforto, Rory A. Cooper, Rosemarie Cooper, Steven C. Cramer, Armin Curt, Mark D’Esposito, Matthew B. Dalva, Gavriel David, Brandon Delia, Wenbin Deng, Volker Dietz, Bruce H. Dobkin, Marco Domeniconi, Edith Durand, Tracey Vause Earland, Georg Ebersbach, Jonathan J. Evans, James W. Fawcett, Uri Feintuch, Toby A. Ferguson, Marie T. Filbin, Diasinou Fioravante, Itzhak Fischer, Agnes Floel, Herta Flor, Karim Fouad, Richard S. J. Frackowiak, Peter H. Gorman, Thomas W. Gould, Jean-Michel Gracies, Amparo Gutierrez, Kurt Haas, C.D. Hall, Hans-Peter Hartung, Zhigang He, Jordan Hecker, Susan J. Herdman, Seth Herman, Leigh R. Hochberg, Ahmet Höke, Fay B. Horak, Jared C. Horvath, Richard L. Huganir, Friedhelm C. Hummel, Beata Jarosiewicz, Frances E. Jensen, Michael Jöbges, Larry M. Jordan, Jon H. Kaas, Andres M. Kanner, Noomi Katz, Matthew S. Kayser, Annmarie Kelleher, Gerd Kempermann, Timothy E. Kennedy, Jürg Kesselring, Fary Khan, Rachel Kizony, Jeffery D. Kocsis, Boudewijn J. Kollen, Hubertus Köller, John W. Krakauer, Hermano I. Krebs, Gert Kwakkel, Bradley Lang, Catherine E. Lang, Helmar C. Lehmann, Angelo C. Lepore, Glenn S. Le Prell, Mindy F. Levin, Joel M. Levine, David A. Low, Marilyn MacKay-Lyons, Jeffrey D. Macklis, Margaret Mak, Francine Malouin, William C. Mann, Paul D. Marasco, Christopher J. Mathias, Laura McClure, Jan Mehrholz, Lorne M. Mendell, Robert H. Miller, Carol Milligan, Beth Mineo, Simon W. Moore, Jennifer Morgan, Charbel E-H. Moussa, Martin Munz, Randolph J. Nudo, Joseph J. Pancrazio, Theresa Pape, Alvaro Pascual-Leone, Kristin M. Pearson-Fuhrhop, P. Hunter Peckham, Tamara L. Pelleshi, Catherine Verrier Piersol, Thomas Platz, Marcus Pohl, Dejan B. Popović, Andrew M. Poulos, Maulik Purohit, Hui-Xin Qi, Debbie Rand, Mahendra S. Rao, Josef P. Rauschecker, Aimee Reiss, Carol L. Richards, Keith M. Robinson, Melvyn Roerdink, John C. Rosenbek, Serge Rossignol, Edward S. Ruthazer, Arash Sahraie, Krishnankutty Sathian, Marc H. Schieber, Brian J. Schmidt, Michael E. Selzer, Mijail D. Serruya, Himanshu Sharma, Michael Shifman, Jerry Silver, Thomas Sinkjær, George M. Smith, Young-Jin Son, Tim Spencer, John D. Steeves, Oswald Steward, Sheela Stuart, Austin J. Sumner, Chin Lik Tan, Robert W. Teasell, Gareth Thomas, Aiko K. Thompson, Richard F. Thompson, Wesley J. Thompson, Erika Timar, Ceri T. Trevethan, Christopher Trimby, Gary R. Turner, Mark H. Tuszynski, Erna A. van Niekerk, Ricardo Viana, Difei Wang, Anthony B. Ward, Nick S. Ward, Stephen G. Waxman, Patrice L. Weiss, Jörg Wissel, Steven L. Wolf, Jonathan R. Wolpaw, Sharon Wood-Dauphinee, Ross D. Zafonte, Binhai Zheng, Richard D. Zorowitz
- Edited by Michael E. Selzer, Stephanie Clarke, Leonardo G. Cohen, Gert Kwakkel, Robert H. Miller, Case Western Reserve University, Ohio
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- Book:
- Textbook of Neural Repair and Rehabilitation
- Published online:
- 05 June 2014
- Print publication:
- 24 April 2014, pp ix-xvi
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Production from dairy cows of semi-industrial quantities of milk-protein concentrate (MPC) containing efficacious anti-Candida albicans IgA antibodies
- Alison J Hodgkinson, Richard D Cannon, Ann R Holmes, Frank J Fischer, Dawn J Willix-Payne
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- Journal:
- Journal of Dairy Research / Volume 74 / Issue 3 / August 2007
- Published online by Cambridge University Press:
- 30 April 2007, pp. 269-275
- Print publication:
- August 2007
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Bovine milk antibodies directed against human pathogenic organisms have potential as prophylactic or therapeutic treatments of disorders affecting mucosal surfaces. The cow, however, does not naturally secrete high levels of IgA in milk, the predominant immunoglobulin of the mucosal immune system. We have patented an immunisation protocol that results in increased production of IgA in ruminant milk and in this study established that our protocol can be used on a scale sufficient to produce semi-industrial quantities of milk for processing. Cows were immunised with a common pathogenic yeast, Candida albicans and responded with high levels of antigen-specific IgA antibodies in their milk. The spray-dried milk-protein concentrate (85% protein) powder was shown to reduce adherence of Cand. albicans cells in in vitro adherence assays, demonstrating an ability to retain efficacy through the processing. These results suggest that this milk product may be of therapeutic value if the reduction in Cand. albicans adhesion observed in vitro translates to reduced colonisation in vivo.
Difference in the Incidence of Clostridium difficile Among Patients Infected With Human Immunodeficiency Virus Admitted to a Public Hospital and a Private Hospital
- Joseph J. Pulvirenti, Dale N. Gerding, Catherine Nathan, Irfan Hafiz, Tarun Mehra, Dayle Marsh, Frank Kocka, Thomas Rice, Staci A. Fischer, John Segreti, Robert A. Weinstein
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 23 / Issue 11 / November 2002
- Published online by Cambridge University Press:
- 02 January 2015, pp. 641-647
- Print publication:
- November 2002
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Objective:
To compare the occurrence of Clostridium difficile among inpatients infected with human immunodeficiency virus (HPV) in two different hospitals.
Design:Prospective, observational study.
Setting:Specialized HPV inpatient units.
Patients:HIV-infected inpatients at Cook County Hospital (CCH) and Rush Presbyterian St. Luke's Medical Center (RPSLMC).
Interventions:A clinical and epidemiologic assessment of patient risk factors for C. difficile was performed. C. difficile isolates found on stool, rectal, and environmental cultures were typed by pulsed-field gel electrophoresis.
Results:Twenty-seven percent of patients admitted to CCH versus 4% of patients admitted to RPSLMC had positive cultures for C. difficile (P = .001). At CCH, 14.7% of environmental cultures were positive versus 2.9% at RPSLMC (P = .002). Risk factors for C. difficile acquisition included hospitalization at CCH, more severe HrV, use of acyclovir and H2-blockers, and longer hospital stay. Patients admitted to CCH were taking more antibiotics, had longer hospital stays, and more frequently had a history of C. difficile infection. During the study, two strains (CD1A and CD4) extensively contaminated the CCH environment. However, only CD1A caused an outbreak.
Conclusions:The C. difficile acquisition rate at CCH was sevenfold higher than that at RPSLMC, and CCH had a more contaminated environment Differences in patient acquisition rates likely reflect a greater prevalence of traditional C. difficile risk factors and a concurrent outbreak at CCH. Although two strains heavily contaminated the environment at CCH, only one caused an outbreak, suggesting that factors other than the environment are important in initiating C. difficile outbreak.
Chapter 4 - Pulmonary bacterial infections
- Edited by Philip Hasleton, University of Manchester, Douglas B. Flieder, Fox Chase Cancer Center, Philadelphia
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- Spencer's Pathology of the Lung
- Published online:
- 05 June 2014
- Print publication:
- 01 January 2000, pp 146-181
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Summary
Background
“Pneumonia”, wrote Laennec, “is one of the diseases most anciently known; and before pathological anatomy . . . had investigated the true nature of diseases, it was generally regarded as one of the internal afflictions most readily recognized.”
Pneumonia occurs when the host mounts an inflammatory response, centered on the lung parenchyma, usually against a microorganism, but sometimes against another toxic agent, which has reached this normally sterile site. Bacteria are the most common causative microorganisms. The effect on the host is variable, ranging from complete absence of clinical manifestations to sudden death or a brief illness followed by sudden death. More typically the effects of the inflammatory response and the replacement of the normal gas-exchanging lung tissue cause a constellation of symptoms and signs. These are associated with, and may be diagnosed as, lung infection. Untreated, the condition progresses until the host dies or the inflammatory response overcomes the microbial threat and lysis of the toxic state is followed by gradual recovery. Recognition of the condition will usually lead to appropriate medical intervention, resulting in improved outcome in most cases.
Polymer Crystallization Studied in Confined Dimensions using Nanocomposites from Polymers and Layered Minerals
- Frank-Dieter Kuchta, Piet J. Lemstra, Andrew Keller, Lawrence F. Batenburg, Hartmut R. Fischer
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- Journal:
- MRS Online Proceedings Library Archive / Volume 628 / 2000
- Published online by Cambridge University Press:
- 01 February 2011, CC11.1
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- 2000
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Polymer-layered silicate nanocomposites from polyamide-11 (PA-11) were prepared and the morphology and properties have been investigated in order to link the fundamental research field of polymer crystallization with the technical important field of composite materials. Semi-crystalline polymers are known to crystallize in different phases (e. g. monoclinic, hexagonal) forming chain-folded lamellar crystals. Depending on experimental conditions (e. g. temperature, pressure) the crystal size (lamellar thickness) affects the stability of these phases. The incorporation of layered silicates acting as hard walls into semi-crystalline polymers opens new possibilities to: i) study polymer crystallization in confined dimensions, and ii) provide materials from commodity or engineering polymers with enhanced properties. The effect of an external confinement introduced by highly anisotropic silicate layers of organically modified clay minerals on crystal growth and nanocomposite properties has been studied. The composites are prepared by in situ polycondensation of polyamides and/or blending via melt extrusion. The nanocomposites exhibit a homogeneous distribution of individual silicate layers at low clay contents. The lamellar thickening growth is reduced in polyamide crystallization due to the external constrained of the silicate layers in the host polymer. Furthermore these nanocomposites show a slightly enhanced thermal stability, tensile modulus and an increased elastic behavior over a broader temperature range. No distinct glass transition has been observed at highest clay contents.
Materials With Improved Properties From Polymer-Ceramic Nanocomposites
- Frank-Dieter Kuchta, Piet J. Lemstra, Andrew Keller, Lawrence F. Batenburg, Hartmut R. Fischer
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- Journal:
- MRS Online Proceedings Library Archive / Volume 576 / 1999
- Published online by Cambridge University Press:
- 10 February 2011, 363
- Print publication:
- 1999
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In order to link the fundamental research field of polymer crystallization with the technical important field of composite materials polymer-layered silicate nanocomposites from polyethylene (PE) are prepared and their morphology and properties are investigated. The effect of an external confinement introduced by highly anisotropic silicate layers of organically modified clay minerals on crystal growth and nanocomposite properties has been studied. The prepared nanocomposites of organically modified clay minerals and PE exhibit not only a homogeneous distribution of individual silicate layers but also of tactoids. The isothermal crystallization rate of PE in the corresponding nanocomposite at 120 °C is increased in the composite material due to the action of the silicate layers. A significant effect on crystal phase has not been observed so far but from X-ray experiments, however the crystal size seems to be influenced. The thermal stability of the nanocomposites is significantly enhanced and the decomposition mechanism has been changed due to the presence of the layered silicates within the host polymer acting as a barrier for the diffusion of small molecules like oxygen. Due to the none permanent attachment of the polymer chains to the silicate surface the thermal-mechanical properties are only moderately enhanced at low temperature while the glass transition temperature remains unaffected.