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1.
Artigo em Inglês | MEDLINE | ID: mdl-39228099

RESUMO

BACKGROUND: Strengths-based approaches to health care are often seen as an alternative to deficit-based approaches and are common in Aboriginal health settings. Despite this, there is little existing research that describes Aboriginal peoples' perspectives about the strengths of their communities. This paper describes cultural strengths and resources as understood by Aboriginal people living in western Sydney. METHODS: In-depth interviews were used to collect qualitative data from two communities on Dharug and Dharrawal Country in western Sydney Australia. Data come from a larger study, which focused on how cultural strengths supported sexual well-being. Fifty-two interviews were conducted with Aboriginal young people (aged 16-24 years) by trained peer interviewers. Additionally, 16 interviews with Aboriginal adults (25 years and older) were conducted by members of the research team. FINDINGS AND DISCUSSION: While opinions varied, four key areas of cultural strength were identified: (1) strong kinship relationships; (2) knowledge sharing; (3) shared experiences, identities, and values; and (4) knowing Country. Throughout these four themes, the sense of connection and belonging is viewed as an important overarching theme. CONCLUSION: Communities are not homogenous with regard to what they view as cultural strengths. Knowing Country and practising culture meant different things to different individuals while providing a similar sense of belonging, connection, and identity. SO WHAT: Health service providers, policies, and programs can use this information to understand the continuing impacts of past policies and events whilst recognising that each community has strengths that can be drawn upon to improve service engagement, knowledge sharing, and health outcomes.

2.
Palliat Support Care ; 20(1): 94-100, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-33750494

RESUMO

OBJECTIVE: End-of-life and anticipatory medications (AMs) have been widely used in various health care settings for people approaching end-of-life. Lack of access to medications at times of need may result in unnecessary hospital admissions and increased patient and family distress in managing palliative care at home. The study aimed to map the use of end-of-life and AM in a cohort of palliative care patients through the use of the Population Level Analysis and Reporting Data Space and to discuss the results through stakeholder consultation of the relevant organizations. METHODS: A retrospective observational cohort study of 799 palliative care patients in 25 Australian general practice health records with a palliative care referral was undertaken over a period of 10 years. This was followed by stakeholders' consultation with palliative care nurse practitioners and general practitioners who have palliative care patients. RESULTS: End-of-life and AM prescribing have been increasing over the recent years. Only a small percentage (13.5%) of palliative care patients received medications through general practice. Stakeholders' consultation on AM prescribing showed that there is confusion about identifying patients needing medications for end-of-life and mixed knowledge about palliative care referral pathways. SIGNIFICANCE OF RESULTS: Improved knowledge and information around referral pathways enabling access to palliative care services for general practice patients and their caregivers are needed. Similarly, the increased utility of screening tools to identify patients with palliative care needs may be useful for health care practitioners to ensure timely care is provided.


Assuntos
Medicina Geral , Assistência Terminal , Austrália , Morte , Humanos , Cuidados Paliativos/métodos , Estudos Retrospectivos , Assistência Terminal/métodos
3.
Opt Express ; 27(19): 26967-26978, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31674566

RESUMO

Lasing-based sensors have several advantages over fluorescent devices, specifically related to the high light intensity and narrow mode linewidth that can improve the speed and accuracy of the sensor performance. In this work, a microcapillary-based lasing sensor is demonstrated, in which the lasing wavelengths are sensitive to the surface binding of specific materials. In order to achieve this, we utilized lasing into the "star" and "triangle" modes of a conventional microcapillary and tracked the mode positions after the deposition of a polyelectrolyte tri-layer and the subsequent amide binding of carboxy-functionalized polystyrene microspheres. While the lasing mode spectrum becomes increasingly complicated by the addition of the surface layers, careful mode selection can be used to monitor the layer-by-layer surface binding in a mechanically and optically robust device. For polystyrene microspheres, the detection limits were 9.75 nM based upon the lasing mode shift, which compares favorably with fluorescence-based devices. The methods presented in this work could readily be extended to other surface binding schemes and lasing wavelengths, showing that capillary microlasers could be used for many potential applications that capitalize on stable lasing-based detection methods.

4.
Bull Environ Contam Toxicol ; 100(1): 155-161, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29270645

RESUMO

This study compares conventional grab sampling to incremental sampling methodology (ISM) to characterize metal contamination at a military small-arms-range. Grab sample results had large variances, positively skewed non-normal distributions, extreme outliers, and poor agreement between duplicate samples even when samples were co-located within tens of centimeters of each other. The extreme outliers strongly influenced the grab sample means for the primary contaminants lead (Pb) and antinomy (Sb). In contrast, median and mean metal concentrations were similar for the ISM samples. ISM significantly reduced measurement uncertainty of estimates of the mean, increasing data quality (e.g., for environmental risk assessments) with fewer samples (e.g., decreasing total project costs). Based on Monte Carlo resampling simulations, grab sampling resulted in highly variable means and upper confidence limits of the mean relative to ISM.


Assuntos
Monitoramento Ambiental/métodos , Metais/análise , Poluentes do Solo/análise , Solo/química , Medição de Risco
5.
Bull Environ Contam Toxicol ; 100(5): 603-608, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29532132

RESUMO

Military ranges are unlike many waste sites because the contaminants, both energetics and metals, are heterogeneously distributed in soil during explosive detonation or ballistic impact and cannot be readily characterized using conventional grab sampling. The Incremental Sampling Methodology (ISM) has been successful for characterization of energetic contamination in soils, but no published ISM processing studies for soils with small arms range metals such as Pb, Cu, Sb, and Zn exists. This study evaluated several ISM sample-processing steps: (1) field splitting to reduce the sample mass shipped to the analytical laboratory, (2) necessity of milling, and (3) processing a larger subsample mass for digestion in lieu of milling. Cone-and-quartering and rotary sectorial splitting techniques yielded poor precision and positively skewed distributions. Hence, an increase in digestion mass from 2 to 10 g was evaluated with milled and unmilled samples. Unmilled samples yielded results with the largest variability regardless of aliquot mass.


Assuntos
Monitoramento Ambiental/métodos , Metais Pesados/análise , Poluentes do Solo/análise , Militares , Solo/química , Armas
6.
Bull Environ Contam Toxicol ; 100(1): 147-154, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29299633

RESUMO

Research shows grab sampling is inadequate for evaluating military ranges contaminated with energetics because of their highly heterogeneous distribution. Similar studies assessing the heterogeneous distribution of metals at small-arms ranges (SAR) are lacking. To address this we evaluated whether grab sampling provides appropriate data for performing risk analysis at metal-contaminated SARs characterized with 30-48 grab samples. We evaluated the extractable metal content of Cu, Pb, Sb, and Zn of the field data using a Monte Carlo random resampling with replacement (bootstrapping) simulation approach. Results indicate the 95% confidence interval of the mean for Pb (432 mg/kg) at one site was 200-700 mg/kg with a data range of 5-4500 mg/kg. Considering the U.S. Environmental Protection Agency screening level for lead is 400 mg/kg, the necessity of cleanup at this site is unclear. Resampling based on populations of 7 and 15 samples, a sample size more realistic for the area yielded high false negative rates.


Assuntos
Monitoramento Ambiental/métodos , Metais Pesados/análise , Poluentes do Solo/análise , Armas , Recuperação e Remediação Ambiental , Solo
7.
Ann Hematol ; 95(2): 227-32, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26490882

RESUMO

Venous thromboembolism (VTE) is a recognised complication of sickle cell disease (SCD), long considered to be a hypercoagulable state. While there is a good understanding of arterial thrombosis in SCD, the nature of VTE in SCD is less well-characterised. In this retrospective cohort study, we found that the incidence of VTE in our patient cohort was higher than in the non-SCD black population; patients of all SCD genotypes with VTE had significantly elevated steady-state platelet counts compared to those without. Recent hospitalisation (typically with acute sickle pain) was the commonest precipitating risk factor. These findings suggest consideration of longer VTE prophylaxis for acute hospital admissions in SCD.


Assuntos
Anemia Falciforme/diagnóstico , Anemia Falciforme/epidemiologia , Tromboembolia Venosa/diagnóstico , Tromboembolia Venosa/epidemiologia , Adolescente , Adulto , Anemia Falciforme/terapia , Estudos de Coortes , Feminino , Hospitalização/tendências , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Reino Unido/epidemiologia , Tromboembolia Venosa/terapia , Adulto Jovem
8.
Eur J Dent Educ ; 20(2): 120-8, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-27525342

RESUMO

INTRODUCTION: The University of British Columbia Faculty of Dentistry developed a longitudinal curriculum pilot project to assess the usefulness of portfolios for dental students to develop reflective skills and demonstrate competency development, and to examine relationships between portfolio grades and clinical success. MATERIALS AND METHODS: Students in one dental class created portfolios with reflections on examples relevant to eight selected competency statements each year of the program. As part of our program evaluation, we set out to look at trends in portfolio grades, meta-reflection skills, student and faculty views of the project, and relationships among portfolio grades, 4th year clinical grades and faculty rankings. RESULTS: Portfolio grades improved from years 1 to 3, dropping off slightly in year 4. The highest level of internal consistency for grades within and between years occurred with Competency 42, while the lowest level occurred with Competency 4. Most students were able to demonstrate meta-reflection by 4th year. Students generally agreed with portfolios and reflection in concept, but suggested a looser structure, and they shared concerns with faculty about the workload involved. Portfolio grades did not correlate with clinical course grades (P = 0.092), but they did correlate significantly with faculty rankings except for year 1. CONCLUSION: While portfolio grades for reflections were not consistent, and they did not quite correlate with clinical course grades, they correlated strongly with faculty rankings. Future use of portfolios at UBC Dentistry will be enhanced by increasing curricular support regarding both competency development and the importance of reflection for professionals, decreasing workload by focusing on five Key Competencies, incorporating more formative and face-to-face feedback, and providing greater opportunities for peer sharing.


Assuntos
Educação em Odontologia , Currículo , Humanos , Projetos Piloto , Avaliação de Programas e Projetos de Saúde , Estudantes
9.
Diabet Med ; 32(8): 1071-6, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25982032

RESUMO

AIM: This study investigates the relationship between basal insulin regimen and glycaemic outcomes 12 months after skills-based structured education in the UK Dose Adjustment for Normal Eating (DAFNE) programme for Type 1 diabetes mellitus. METHOD: Retrospective analysis of data from 892 DAFNE participants from 11 UK centres. RESULTS: Mean HbA1c 12 months after DAFNE was lower in those using twice- rather than once-daily basal insulin after correcting for differences in baseline HbA1c , age and duration of diabetes; difference -2 (95% CI -3 to -1) mmol/mol [-0.2 (-0.3 to -0.1)%], P = 0.009. The greatest fall in HbA1c of -5 (-7 to -3) mmol/mol [-0.4 (-0.6 to -0.3)%], P < 0.001 occurred in those with less good baseline control, HbA1c  ≥ 58 mmol/mol, who switched from once- to twice-daily basal insulin. There was no difference in the 12-month HbA1c between users of glargine, detemir and NPH insulin after correcting for other variables. Relative risk of severe hypoglycaemia fell by 76% and ketoacidosis by 63% 12 months after DAFNE. The rate of severe hypoglycaemia fell from 0.82 to 0.23 events/patient year in twice-daily basal insulin users. In the group with greatest fall in HbA1c , the estimated relative risk for severe hypoglycaemia in twice-daily basal insulin users versus once daily at 12 months was 1.72 (0.88-3.36, P = 0.110). CONCLUSION: After structured education in adults with Type 1 diabetes mellitus, use of basal insulin twice rather than once daily was associated with lower HbA1c , independent of insulin type, with significant reductions in severe hypoglycaemia and ketoacidosis in all groups.


Assuntos
Diabetes Mellitus Tipo 1/tratamento farmacológico , Hipoglicemiantes/administração & dosagem , Insulina de Ação Prolongada/administração & dosagem , Educação de Pacientes como Assunto , Autocuidado , Adulto , Glicemia/metabolismo , Estudos de Coortes , Diabetes Mellitus Tipo 1/metabolismo , Cetoacidose Diabética/prevenção & controle , Feminino , Hemoglobinas Glicadas/metabolismo , Humanos , Hipoglicemia/induzido quimicamente , Hipoglicemiantes/efeitos adversos , Insulina Detemir/administração & dosagem , Insulina Detemir/efeitos adversos , Insulina Glargina/administração & dosagem , Insulina Glargina/efeitos adversos , Insulina Isófana/administração & dosagem , Insulina Isófana/efeitos adversos , Insulina de Ação Prolongada/efeitos adversos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento
10.
Eur J Dent Educ ; 18(3): 170-9, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24460682

RESUMO

BACKGROUND: Situated and sociocultural perspectives on learning indicate that the design of complex tasks supported by educational technologies holds potential for dental education in moving novices towards closer approximation of the clinical outcomes of their expert mentors. A cross-faculty-, student-centred, web-based project in operative dentistry was established within the Universitas 21 (U21) network of higher education institutions to support university goals for internationalisation in clinical learning by enabling distributed interactions across sites and institutions. This paper aims to present evaluation of one dental faculty's project experience of curriculum redesign for deeper student learning. METHODS: A mixed-method case study approach was utilised. Three cohorts of second-year students from a 5-year bachelor of dental surgery (BDS) programme were invited to participate in annual surveys and focus group interviews on project completion. Survey data were analysed for differences between years using multivariate logistical regression analysis. Thematic analysis of questionnaire open responses and interview transcripts was conducted. RESULTS: Multivariate logistic regression analysis noted significant differences across items over time indicating learning improvements, attainment of university aims and the positive influence of redesign. Students perceived the enquiry-based project as stimulating and motivating, and building confidence in operative techniques. Institutional goals for greater understanding of others and lifelong learning showed improvement over time. Despite positive scores, students indicated global citizenship and intercultural understanding were conceptually challenging. CONCLUSIONS: Establishment of online student learning communities through a blended approach to learning stimulated motivation and intellectual engagement, thereby supporting a situated approach to cognition. Sociocultural perspectives indicate that novice-expert interactions supported student development of professional identities.


Assuntos
Instrução por Computador/métodos , Educação em Odontologia/métodos , Aprendizagem , Grupo Associado , Blogging , Comportamento Cooperativo , Currículo , Avaliação Educacional , Tecnologia Educacional , Feminino , Grupos Focais , Humanos , Internacionalidade , Internet , Entrevistas como Assunto , Masculino , Estudos de Casos Organizacionais , Inovação Organizacional , Avaliação de Programas e Projetos de Saúde , Inquéritos e Questionários
11.
CJEM ; 26(5): 305-311, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38334940

RESUMO

BACKGROUND: Virtual care in Canada rapidly expanded during the COVID-19 pandemic in a low-rules environment in response to pressing needs for ongoing access to care amid public health restrictions. Emergency medicine specialists now face the challenge of advising on which virtual urgent care services ought to remain as part of comprehensive emergency care. Consideration must be given to safe, quality, and appropriate care as well as issues of equitable access, public demand, and sustainability (financial and otherwise). The aim of this project was to summarize current literature and expert opinion and formulate recommendations on the path forward for virtual care in emergency medicine. METHODS: We formed a working group of emergency medicine physicians from across Canada working in a variety of practice settings. The virtual care working group conducted a scoping review of the literature and met monthly to discuss themes and develop recommendations. The final recommendations were circulated to stakeholders for input and subsequently presented at the 2023 Canadian Association of Emergency Physicians (CAEP) Academic Symposium for discussion, feedback, and refinement. RESULTS: The working group developed and reached unanimity on nine recommendations addressing the themes of system design, equity and accessibility, quality and patient safety, education and curriculum, financial models, and sustainability of virtual urgent care services in Canada. CONCLUSION: Virtual urgent care has become an established service in the Canadian health care system. Emergency medicine specialists are uniquely suited to provide leadership and guidance on the optimal delivery of these services to enhance and complement emergency care in Canada.


RéSUMé: CONTEXTE: Les soins virtuels au Canada ont rapidement pris de l'ampleur pendant la pandémie de COVID-19 dans un environnement où les règles sont peu strictes, en réponse aux besoins urgents d'accès continu aux soins dans un contexte de restrictions en santé publique. Les spécialistes de la médecine d'urgence sont maintenant confrontés au défi de conseiller sur les services de soins d'urgence virtuels qui devraient rester dans le cadre des soins d'urgence complets. Il faut tenir compte des soins sécuritaires, de qualité et appropriés, ainsi que des questions d'accès équitable, de la demande publique et de la durabilité (financière et autre). L'objectif de ce projet était de résumer la littérature actuelle et l'opinion d'experts et de formuler des recommandations sur la voie à suivre pour les soins virtuels en médecine d'urgence. MéTHODES: Nous avons formé un groupe de travail composé de médecins urgentistes de partout au Canada qui travaillent dans divers milieux de pratique. Le groupe de travail sur les soins virtuels a effectué un examen de la portée de la documentation et s'est réuni chaque mois pour discuter des thèmes et formuler des recommandations. Les recommandations finales ont été distribuées aux intervenants pour obtenir leurs commentaires, puis présentées au symposium universitaire 2023 de l'Association canadienne des médecins d'urgence (ACMU) pour discussion, rétroaction et perfectionnement. RéSULTATS: Le groupe de travail a élaboré et atteint l'unanimité sur neuf recommandations portant sur les thèmes de la conception du système, de l'équité et de l'accessibilité, de la qualité et de la sécurité des patients, de l'éducation et des programmes, des modèles financiers et de la viabilité des services virtuels de soins d'urgence au Canada. CONCLUSION : Les soins d'urgence virtuels sont devenus un service établi dans le système de santé canadien. Les spécialistes en médecine d'urgence sont particulièrement bien placés pour fournir un leadership et des conseils sur la prestation optimale de ces services afin d'améliorer et de compléter les soins d'urgence au Canada.


Assuntos
COVID-19 , Medicina de Emergência , Humanos , COVID-19/epidemiologia , Medicina de Emergência/organização & administração , Canadá , Pandemias , Telemedicina , SARS-CoV-2 , Assistência Ambulatorial/organização & administração , Acessibilidade aos Serviços de Saúde
12.
Eur J Dent Educ ; 16(4): 208-12, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23050501

RESUMO

To stimulate and enhance student learning in the areas of global citizenship, critical reflection and e-learning, an online international peer review using a purpose-built web platform, has been developed between international dental schools. Since its inception in 2007, n = 6 dental schools from six different countries have participated with n = 384 dental students engaged in online peer review. Project development was conceptually analysed utilising Lave and Wenger's notion of a community of practice (CoP). Analysis drew on the three core components within the CoP organising framework: domain, community and practice. All three components were evident in building project identity. The domain focused on both curriculum and institutional co-operation. The community was evident for both educators and students. Finally, analysis of practice was found to be significant in terms of sustained interaction and collaboration. Empirical evaluation is recommended as the next phase of project design.


Assuntos
Educação em Odontologia , Relações Interinstitucionais , Internacionalidade , Revisão por Pares , Faculdades de Odontologia , Currículo , Educação em Odontologia/normas , Humanos , Mídias Sociais
13.
Child Care Health Dev ; 37(1): 143-9, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20854448

RESUMO

BACKGROUND: The study aimed to determine if child obesity rates have risen in the Caribbean nation of Saint Lucia, as found globally, and whether under-nutrition coexists, as in other developing nations. The average adult in Saint Lucia is overweight, thus considerable child obesity might be expected, but there are no current data. METHODS: Heights and weights were obtained from a sample (n= 425) of the 2001 birth cohort of Saint Lucian children measured during the nation-wide 2006/2007 Prior to School Entry Five-Year Assessment. Prevalence of overweight, obesity and underweight were estimated by Centers for Disease Control (CDC), Cole et al. and new World Health Organization (WHO) methods. Previously reported 1976 estimates, including children ≤60 months of age only, based on National Centre for Health Statistics curves, were adjusted to new WHO equivalents using an algorithm developed by Yang and de Onis, and compared with rates in our subsample of children ≤60 months of age (n= 99). RESULTS: Regardless of classification method, overweight and obesity rates were high: 14.4% and 9.2% (WHO); 11.3% and 12.0% (CDC); and 9.9% and 7.1% (Cole et al.), respectively. Underweight estimates also varied: 4.7% (WHO); 11.3% (CDC) and 6.6% (Cole et al.). Obesity in our young subsample (15.2%; WHO) was more than 3 times the adjusted 1976 rate (4.3%). CONCLUSIONS: Obesity among Saint Lucian pre-schoolers has tripled in 30 years. Our findings also suggest that this country, like many undergoing a 'nutrition transition', faces the dual challenge of over-nutrition and under-nutrition. Routine monitoring of overweight and underweight is needed in Saint Lucia, as is the implementation and evaluation of programmes to address these problems.


Assuntos
Índice de Massa Corporal , Sobrepeso/diagnóstico , Magreza/diagnóstico , Pré-Escolar , Estudos de Coortes , Humanos , Estado Nutricional , Sobrepeso/epidemiologia , Prevalência , Santa Lúcia/epidemiologia , Fatores Sexuais , Magreza/epidemiologia , Fatores de Tempo
14.
Physiol Int ; 107(1): 155-165, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32598331

RESUMO

PURPOSE: High central blood pressure is more predictive of cardiovascular disease (CVD) versus high peripheral blood pressure. Measures of central pressures (CPs) include, central systolic blood pressure (CSBP) and central diastolic blood pressure. Measures of central pressures augmentation (CPsA) include augmentation pressure (AP) and the augmentation index @ 75 beats·min-1 (AIx@75). Increased sympathetic tone (ST) is also associated with CVD. The low to high frequency ratio (LF/HF) is often used to determine sympatho-vagal balance. Given the association between ST, CPs, CPsA and CVD there is a need to understand the association between these predictors of CVD. The aims of this study were to examine the association between the LF/HF ratio, CPs, and CPsA in men and women collectively and based on gender. METHODS: We measured the LF/HF ratio, CSBP, AP, and AIx@75 in 102 participants (41F/61M). The LF/HF ratio was determined via power spectral density analysis. CSBP, AP, and AIx@75 were determined via applanation tonometry. RESULTS: The LF/HF ratio was inversely associated with AP (r = -0.26) and AIx @75 (r = -0.29) in the combined group of men and women. The LF/HF ratio was inversely associated with CSBP (r = -0.27), AP (r = -0.28), and AIx@75 (r = -0.32) in men, but not in women. CONCLUSION: There is an inverse association between the LF/HF ratio, AP, and AIx@75 in men and women combined. The association between the LF/HF ratio, CSBP, AP, and AIx@75, differs based on gender.


Assuntos
Pressão Sanguínea/fisiologia , Sistema Cardiovascular/fisiopatologia , Sistema Nervoso Simpático/fisiologia , Nervo Vago/fisiologia , Adulto , Pressão Arterial , Sistema Cardiovascular/diagnóstico por imagem , Eletrocardiografia/métodos , Feminino , Frequência Cardíaca , Humanos , Masculino , Caracteres Sexuais , Sistema Nervoso Simpático/diagnóstico por imagem , Adulto Jovem
15.
Science ; 269(5232): 1849-51, 1995 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-7569922

RESUMO

The oxidation of toluene by permanganate has been studied as a model for the oxidation of C-H bonds by metal reagents, metalloenzymes, and metal oxide surfaces. In water, the reaction proceeds by hydride (H-) transfer from toluene to a permanganate oxygen, whereas in toluene solution, permanganate abstracts a hydrogen atom (H.). The ability of permanganate to abstract a hydrogen atom is rationalized on the basis of the strong O-H bond formed on H. addition to permanganate. This approach allows understanding and prediction of the rates of hydrogen atom transfer from substrates to metal active sites.


Assuntos
Carbono/química , Hidrogênio/química , Permanganato de Potássio/química , Tolueno/química , Cinética , Oxirredução , Solventes , Espectrofotometria Ultravioleta , Termodinâmica
16.
Science ; 247(4941): 431-6, 1990 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-17788609

RESUMO

A detailed comparison between molecular dynamics computer simulations and the experimental characterization of molecular motion through deuterium nuclear magnetic resonance (NMR) spectroscopic methods has been carried out for the crystalline phase of nylon 66 (polyhexamethyleneadipamide) at room temperature and just below the melting point. The computer simulations agree quantitatively with the experimental results at room temperature and qualitatively near the crystalline melting point. Both methods demonstrate that individual methylene groups within the crystals exhibit librational motion, which becomes very large in amplitude near the melting point, rather than undergoing discrete conformational jumps; furthermore, the hydrogen-bonded amides are relatively immobile at all temperatures below 230 degrees Celsius. The simulations are shown to be particularly useful for exaning the cooperativity of motion and for providing insight into structural-dynamical correlations. These aspects of the simulations are exemplified by the observation of concerted counterrotation of odd-numbered bonds within the methylene segments and the entropic stabilization of the crystal structure.

17.
Science ; 262(5134): 719-21, 1993 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-17812336

RESUMO

The formation of high-quality thin films of polytetrafluoroethylene (PTFE) is important in many applications ranging from material reinforcement to molecular electronics. Laser ablation, a technique widely used to deposit a variety of inorganic materials, can also be used as a simple and highly versatile method for forming thin polymer films. The data presented show that PTFE films can be produced on various supports by the evaporation of a solid PTFE target with a pulsed ultraviolet laser. The composition of the ablation plume suggests that PTFE ablation and subsequent film formation occur by way of a laser-induced pyrolitic decomposition with subsequent repolymerization. The polymer films produced by this method are composed of amorphous and highly crystalline regions, the latter being predominantly in a chain-folded configuration with the molecular axis aligned parallel to the substrate surface.

18.
19.
J Evol Biol ; 21(3): 737-48, 2008 May.
Artigo em Inglês | MEDLINE | ID: mdl-18373589

RESUMO

We examined heritable variation for quantitative traits within and between naturally occurring mesic and xeric ecotypes of the slender wild oat (Avena barbata), and in 188 recombinant inbred lines derived from a cross between the ecotypes. We measured a suite of seedling and adult traits in the greenhouse, as well as performance-related traits in field sites native to the two ecotypes. Although the ecotypes were genetically diverged for most traits, few traits showed significant heritable variation within either ecotype. In contrast, considerable heritable variation was released in the recombinant progeny of the cross, and transgressive segregation was apparent in all traits. Heritabilities were substantially greater in the greenhouse than in the field, and this was associated with an increase in environmental variance in the field, rather than a decrease in genetic variance. Strong genetic correlations were evident among the recombinants, such that 22 measured traits could be well represented by only seven underlying factors, which accounted for 80% of the total variation. The primary axis of variation in the greenhouse described a trade-off between vegetative and reproductive allocation, mediated by the date of first flowering, and fitness was strongly correlated with this trade-off. Other factors in the greenhouse described variation in size and in seedling traits. Lack of correlation among these factors represents the release of multivariate trait variation through recombination. In the field, a separate axis of variation in overall performance was found for each year/site combination. Performance was significantly correlated across field environments, but not significantly correlated between greenhouse and field.


Assuntos
Variação Genética , Poaceae/genética , Locos de Características Quantitativas/genética , Ecossistema , Ambiente Controlado , Hibridização Genética , Poaceae/crescimento & desenvolvimento , Plântula/genética
20.
J Clin Invest ; 57(3): 796-806, 1976 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-1249210

RESUMO

Standard micropuncture and microdissection techniques were used to examine the function and structure of nephrons in rats whose kidneys were made cystic by dietary exposure to diphenylamine. Heterogeneity characterized the lesion, with dilation and frank cyst formation occurring in 5-30% of nephrons. Elevated intraluminal hydrostatic pressures, occurring in the absence of increased glomerular filtration or decreased net water reabsorption, were recorded in dilated, but not in nondilated nephrons. Structural studies demonstrated communication of dilated nephrons with cysts, concretions of debris within tubular lumens, evidence of extrinsic pressure by cysts on adjacent tubules, and apparent luminal narrowing of some proximal tubules. These observations were used to explain prolonged loop of Henle transit times and occasional failure to detect [3H]inulin excretion after microperfusion into dilated tubules. It was concluded that the elevated hydrostatic pressures in the dilated nephrons of diphenylamine-exposed kidneys were the consequence of variably severe and frequently incomplete tubular occlusion. These findings support the hypothesis that cyst formation is a consequence of partial obstruction and elevated intratubular pressure in this model and perhaps in other susceptible mammalian kidneys.


Assuntos
Compostos de Anilina , Difenilamina , Modelos Animais de Doenças , Doenças Renais Císticas/induzido quimicamente , Animais , Líquidos Corporais/metabolismo , Peso Corporal/efeitos dos fármacos , Taxa de Filtração Glomerular , Pressão Hidrostática , Inulina , Córtex Renal/patologia , Doenças Renais Císticas/patologia , Doenças Renais Císticas/fisiopatologia , Túbulos Renais/efeitos dos fármacos , Túbulos Renais/patologia , Alça do Néfron/efeitos dos fármacos , Masculino , Néfrons/efeitos dos fármacos , Néfrons/fisiopatologia , Óleos/farmacologia , Ratos
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