Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 16 de 16
Filtrar
Mais filtros

Tipo de documento
Intervalo de ano de publicação
1.
Lung ; 201(6): 625-634, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37987861

RESUMO

PURPOSE: Guidelines recommend considering an initial trial of continuous positive airway pressure (CPAP) to treat central sleep apnea (CSA). However, practice patterns vary widely. This study investigated predictors for an initial trial of CPAP in patients with central apneas and whether those factors predict adequate treatment response in patients receiving an initial CPAP trial. METHODS: Charts of patients receiving a diagnostic code for CSA following a sleep study during 2016-2018 at a single center were reviewed. Patient factors, initial treatment prescriptions, and subsequent changes to therapy were extracted from electronic health records. Regression models were used to estimate factors associated with an initial CPAP prescription and the likelihood of an adequate CPAP response (no subsequent therapy change and no discontinuation of therapy) among patients prescribed CPAP. RESULTS: 429/588 (73%) patients with central apneas received an initial trial of CPAP. Younger age, diagnosis by home sleep testing, non-opiate etiology of central apneas, and a lower proportion of central apneas at diagnosis were independently associated with a higher likelihood of an initial CPAP trial. A lower proportion of central apneas was associated with a higher probability of adequate response, while current smoking and opiate-related central apneas predicted an unsuccessful CPAP trial. A new finding was that older age predicted a lower likelihood of an initial CPAP prescription but did not predict an unsatisfactory response to CPAP. CONCLUSION: Clinicians may incorrectly weigh certain clinical and sleep study characteristics when deciding whether to trial CPAP for patients with central apneas.


Assuntos
Apneia do Sono Tipo Central , Humanos , Pressão Positiva Contínua nas Vias Aéreas , Polissonografia , Apneia do Sono Tipo Central/diagnóstico , Apneia do Sono Tipo Central/terapia , Ensaios Clínicos como Assunto
2.
Entropy (Basel) ; 25(6)2023 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-37372250

RESUMO

Entropy density behavior poses many problems when we study non-equilibrium situations. In particular, the local equilibrium hypothesis (LEH) has played a very important role and is taken for granted in non-equilibrium problems, no matter how extreme they are. In this paper we would like to calculate the Boltzmann entropy balance equation for a plane shock wave and show its performance for Grad's 13-moment approximation and the Navier-Stokes-Fourier equations. In fact, we calculate the correction for the LEH in Grad's case and discuss its properties.

3.
Plant Physiol ; 169(1): 793-802, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26206852

RESUMO

Many bacterial pathogens of plants and animals deliver effector proteins into host cells to promote infection. Elucidation of how pathogen effector proteins function not only is critical for understanding bacterial pathogenesis but also provides a useful tool in discovering the functions of host genes. In this study, we characterized the Pseudomonas syringae pv tomato DC3000 effector protein Avirulence Protein E (AvrE), the founding member of a widely distributed, yet functionally enigmatic, bacterial effector family. We show that AvrE is localized in the plasma membrane (PM) and PM-associated vesicle-like structures in the plant cell. AvrE contains two physically interacting domains, and the amino-terminal portion contains a PM-localization signal. Genome-wide microarray analysis indicates that AvrE, as well as the functionally redundant effector Hypersensitive response and pathogenicity-dependent Outer Protein M1, down-regulates the expression of the NONRACE-SPECIFIC DISEASE RESISTANCE1/HARPIN-INDUCED1-LIKE13 (NHL13) gene in Arabidopsis (Arabidopsis thaliana). Mutational analysis shows that NHL13 is required for plant immunity, as the nhl13 mutant plant displayed enhanced disease susceptibility. Our results defined the action site of one of the most important bacterial virulence proteins in plants and the antibacterial immunity function of the NHL13 gene.


Assuntos
Proteínas de Arabidopsis/metabolismo , Proteínas de Bactérias/metabolismo , Membrana Celular/metabolismo , Regulação para Baixo , Imunidade Vegetal , Pseudomonas syringae/patogenicidade , Antibacterianos/metabolismo , Arabidopsis , Proteínas de Arabidopsis/genética , Genes de Plantas , Folhas de Planta/citologia , Plantas Geneticamente Modificadas , Estrutura Terciária de Proteína , Transporte Proteico , Deleção de Sequência , Virulência
4.
BMC Public Health ; 16: 984, 2016 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-27633380

RESUMO

BACKGROUND: The neighbourhood environment may play an important role in diet quality. Most previous research has examined the associations between neighbourhood food environment and diet quality, and neighbourhood socioeconomic status and diet quality separately. This study investigated the independent and joint effects of neighbourhood food environment and neighbourhood socioeconomic status in relation to diet quality in Canadian adults. METHODS: We undertook a cross-sectional study with n = 446 adults in Calgary, Alberta (Canada). Individual-level data on diet and socio-demographic and health-related characteristics were captured from two self-report internet-based questionnaires, the Canadian Diet History Questionnaire II (C-DHQ II) and the Past Year Physical Activity Questionnaire (PAQ). Neighbourhood environment data were derived from dissemination area level Canadian Census data, and Geographical Information Systems (GIS) databases. Neighbourhood was defined as a 400 m network-based 'walkshed' around each participant's household. Using GIS we objectively-assessed the density, diversity, and presence of specific food destination types within the participant's walkshed. A seven variable socioeconomic deprivation index was derived from Canadian Census variables and estimated for each walkshed. The Canadian adapted Healthy Eating Index (C-HEI), used to assess diet quality was estimated from food intakes reported on C-DHQ II. Multivariable linear regression was used to test for associations between walkshed food environment variables, walkshed socioeconomic status, and diet quality (C-HEI), adjusting for individual level socio-demographic and health-related covariates. Interaction effects between walkshed socioeconomic status and walkshed food environment variables on diet quality (C-HEI) were also tested. RESULTS: After adjustment for covariates, food destination density was positively associated with the C-HEI (ß 0.06, 95 % CI 0.01-0.12, p = 0.04) though the magnitude of the association was small. Walkshed socioeconomic status was not significantly associated with the C-HEI. We found no statistically significant interactions between walkshed food environment variables and socioeconomic status in relation to the C-HEI. Self-reported physical and mental health, time spent in neighbourhood, and dog ownership were also significantly (p < .05) associated with diet quality. CONCLUSIONS: Our findings suggest that larger density of local food destinations may is associated with better diet quality in adults.


Assuntos
Dieta/normas , Meio Ambiente , Alimentos/estatística & dados numéricos , Características de Residência/estatística & dados numéricos , Classe Social , Adulto , Alberta , Animais , Canadá , Censos , Estudos Transversais , Autoavaliação Diagnóstica , Inquéritos sobre Dietas , Cães , Exercício Físico , Comportamento Alimentar , Feminino , Sistemas de Informação Geográfica , Humanos , Masculino , Pessoa de Meia-Idade , Animais de Estimação , Autorrelato , Fatores Socioeconômicos , Inquéritos e Questionários , Fatores de Tempo
5.
Res Sq ; 2023 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-37547021

RESUMO

Purpose: Guidelines recommend considering an initial trial of continuous positive airway pressure (CPAP) to treat central sleep apnea (CSA). However, practice patterns vary widely. This study investigated predictors for an initial trial of CPAP in patients with central apneas and whether those factors predict adequate treatment response in patients receiving an initial CPAP trial. Methods: Charts of patients receiving a diagnostic code for CSA following a sleep study during 2016-2018 at a single center were reviewed. Patient factors, initial treatment prescriptions, and subsequent changes to therapy were extracted from electronic health records. Regression models were used to estimate factors associated with an initial CPAP prescription and the likelihood of an adequate CPAP response (no subsequent therapy change or nonadherence) among patients prescribed CPAP. Results: 429/588 (73%) patients with central apneas received an initial trial of CPAP. Younger age, diagnosis by home sleep testing, non-opiate etiology of central apneas, and a lower proportion of central apneas at diagnosis were independently associated with a higher likelihood of an initial CPAP trial. A lower proportion of central apneas was associated with a higher probability of adequate response, while current smoking and opiate-related central apneas predicted an unsuccessful CPAP trial. A new finding was that older age predicted a lower likelihood of an initial CPAP prescription but did not predict a suboptimal response to CPAP. Conclusion: Clinicians may incorrectly weigh certain clinical and sleep study characteristics when deciding whether to trial CPAP for patients with central apneas.

6.
BMJ Open ; 10(6): e036148, 2020 06 21.
Artigo em Inglês | MEDLINE | ID: mdl-32565468

RESUMO

INTRODUCTION: Quality of reporting refers to how published articles communicate how the research was done and what was found. Gaps and imprecisions of reporting hamper the assessment of the methodological quality and internal and external validity. The CONsolidated Standards of Reporting Trials (CONSORT) are a set of evidence-based recommendations of the minimum elements to be included in the reporting of randomised controlled trials (RCTs) to ensure a complete and transparent account of what was done, how it was done and what was found. Few studies have been conducted on the impact of CONSORT on RCTs published in Latin American and Spanish journals. We aim to assess the reporting quality of RCTs of three clinical specialities published in Spanish and Latin American journals, as well as to assess changes over time and associations of quality with journal and country indicators. METHODS AND ANALYSIS: We will conduct a systematic survey of all RCTs published in Spanish-language journals in three clinical fields (dentistry, neurology and geriatrics) from 1990 to 2018. We will include RCTs from previous work that has identified all RCTs on these medical fields published in Spain and Latin America. We will update this work via handsearching of relevant journals. Assessment of quality of reporting will be conducted independently and in duplicate using the CONSORT 2010 Statement. We will also extract journal and country indicators. We will conduct descriptive statistics and secondary analyses considering the year, country, and journal of publication, among others. ETHICS AND DISSEMINATION: The Universidad de Santiago de Chile's ethics committee approved the protocol. We will disseminate the results of this work in peer-reviewed scientific journals and conference proceedings. We expect to raise awareness among researchers, journal editors and funders on the importance of training in reporting guidelines and using them from the inception of RCT protocols.


Assuntos
Publicações Periódicas como Assunto , Ensaios Clínicos Controlados Aleatórios como Assunto/normas , Revisões Sistemáticas como Assunto , Odontologia , Geriatria , Humanos , América Latina , Neurologia , Projetos de Pesquisa , Espanha
7.
Mol Plant Microbe Interact ; 22(6): 703-12, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19445595

RESUMO

The broadly conserved AvrE-family of type III effectors from gram-negative plant-pathogenic bacteria includes important virulence factors, yet little is known about the mechanisms by which these effectors function inside plant cells to promote disease. We have identified two conserved motifs in AvrE-family effectors: a WxxxE motif and a putative C-terminal endoplasmic reticulum membrane retention/retrieval signal (ERMRS). The WxxxE and ERMRS motifs are both required for the virulence activities of WtsE and AvrE, which are major virulence factors of the corn pathogen Pantoea stewartii subsp. stewartii and the tomato or Arabidopsis pathogen Pseudomonas syringae pv. tomato, respectively. The WxxxE and the predicted ERMRS motifs are also required for other biological activities of WtsE, including elicitation of the hypersensitive response in nonhost plants and suppression of defense responses in Arabidopsis. A family of type III effectors from mammalian bacterial pathogens requires WxxxE and subcellular targeting motifs for virulence functions that involve their ability to mimic activated G-proteins. The conservation of related motifs and their necessity for the function of type III effectors from plant pathogens indicates that disturbing host pathways by mimicking activated host G-proteins may be a virulence mechanism employed by plant pathogens as well.


Assuntos
Proteínas de Bactérias/fisiologia , Pantoea/patogenicidade , Pseudomonas syringae/patogenicidade , Fatores de Virulência/fisiologia , Motivos de Aminoácidos/fisiologia , Arabidopsis/metabolismo , Arabidopsis/microbiologia , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Morte Celular , Retículo Endoplasmático/metabolismo , Membranas Intracelulares , Mutação , Pantoea/genética , Pantoea/metabolismo , Filogenia , Sinais Direcionadores de Proteínas , Pseudomonas syringae/genética , Pseudomonas syringae/metabolismo , Virulência , Fatores de Virulência/química , Fatores de Virulência/genética , Zea mays/citologia , Zea mays/metabolismo , Zea mays/microbiologia
8.
BMJ Open ; 9(2): e023983, 2019 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-30798307

RESUMO

INTRODUCTION: University ranking systems and the publish-or-perish dictum, among other factors, are driving universities and researchers around the world to increase their research productivity. Authors frequently report multiple affiliations in published articles. It is not known if the reported institutional affiliations are real affiliations, which is when the universities have contributed substantially to the research conducted and to the published manuscript. This study aims to establish whether there is an empirical basis for author affiliation misrepresentation in authors with multiple institutional affiliations. METHODS AND ANALYSIS: This individual secondary data exploratory analysis on Scopus-indexed articles for 2016 will search all authors who report multiple institutional affiliations in which at least one of the affiliations is to a Chilean university. We will consider that misrepresentation of an affiliation is more likely when it is not possible to verify objectively a link between the author and the mentioned institution through institutional websites. If we cannot corroborate the author affiliation, we will consider this a finding of potential misrepresentation of the affiliation. We will summarise results with descriptive statistics. ETHICS AND DISSEMINATION: The study protocol was approved by the institutional ethics committee of Universidad de Santiago de Chile, Resolution No. 261, and dated January 15, 2018. Results will be submitted to the World Conference on Research Integrity, among other meetings on publication ethics and research integrity, and will be published in scientific, peer-reviewed journals.


Assuntos
Autoria/normas , Má Conduta Científica/ética , Chile , Humanos , Editoração/normas , Universidades
9.
Curr Biol ; 28(4): 630-639.e4, 2018 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-29398214

RESUMO

The circadian clock drives daily rhythms of many plant physiological responses, providing a competitive advantage that improves plant fitness and survival rates [1-5]. Whereas multiple environmental cues are predicted to regulate the plant clock function, most studies focused on understanding the effects of light and temperature [5-8]. Increasing evidence indicates a significant role of plant-pathogen interactions on clock regulation [9, 10], but the underlying mechanisms remain elusive. In Arabidopsis, the clock function largely relies on a transcriptional feedback loop between morning (CCA1 and LHY)- and evening (TOC1)-expressed transcription factors [6-8]. Here, we focused on these core components to investigate the Arabidopsis clock regulation using a unique biotic stress approach. We found that a single-leaf Pseudomonas syringae infection systemically lengthened the period and reduced the amplitude of circadian rhythms in distal uninfected tissues. Remarkably, the low-amplitude phenotype observed upon infection was recapitulated by a transient treatment with the defense-related phytohormone salicylic acid (SA), which also triggered a significant clock phase delay. Strikingly, despite SA-modulated circadian rhythms, we revealed that the master regulator of SA signaling, NPR1 [11, 12], antagonized clock responses triggered by both SA treatment and P. syringae. In contrast, we uncovered that the NADPH oxidase RBOHD [13] largely mediated the aforementioned clock responses after either SA treatment or the bacterial infection. Altogether, we demonstrated novel and unexpected roles for SA, NPR1, and redox signaling in clock regulation by P. syringae and revealed a previously unrecognized layer of systemic clock regulation by locally perceived environmental cues.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/fisiologia , Relógios Circadianos/fisiologia , Ritmo Circadiano/fisiologia , Regulação da Expressão Gênica de Plantas , Pseudomonas syringae/fisiologia , Fatores de Transcrição/genética , Arabidopsis/genética , Arabidopsis/microbiologia , Proteínas de Arabidopsis/metabolismo , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Folhas de Planta/fisiologia , Fatores de Transcrição/metabolismo
10.
Artigo em Inglês | MEDLINE | ID: mdl-29891778

RESUMO

Background: Environmental and policy factors can influence weight status via facilitating or discouraging physical activity and healthy diet. Despite mixed evidence, some findings suggest that the neighborhood built environment, including “walkability”, is associated with overweight and obesity. Most of these findings have measured body mass index (BMI), yet other weight status measures including waist circumference (WC) and waist-to-hip (W-H) ratio are also predictive of health outcomes, independent of BMI. Our study aim was to estimate the associations between walkability, measured using Walk Score®, and each of WC, W-H ratio, and BMI among urban Canadian adults. Methods: In 2014, n = 851 adults recruited from 12 structurally and socioeconomic diverse neighborhoods (Calgary, Alberta, Canada) provided complete data on a physical activity, health and demographic questionnaire and self-reported anthropometric measures (i.e., height and weight, WC and hip circumference). Anthropometric data were used to estimate WC, W-H ratio, and BMI which were categorized into low and high risk in relation to their potential adverse effect on health. WC and BMI were also combined to provide a proxy measure of both overall and abdominal adiposity. Multivariable logistic regression models estimated odds ratios (OR) and 95% confidence intervals (CI) for associations between each weight status outcome and Walk Score®. Results: A one-unit increase in Walk Score® was associated with lower odds of being high-risk based on WC (OR = 0.99; 95%CI 0.97⁻0.99). Notably, those residing in socioeconomically disadvantage neighborhoods had significantly higher odds of being high risk based on WC, BMI, and WC-BMI combined compared with advantaged neighborhoods. Conclusions: Interventions that promote healthy weight through the design of neighborhoods that support and enhance the effect of physical activity and diet-related interventions could have a significant population health impact.


Assuntos
Planejamento Ambiental , Promoção da Saúde , Obesidade Abdominal/epidemiologia , Características de Residência/estatística & dados numéricos , Relação Cintura-Quadril , Caminhada/estatística & dados numéricos , Adulto , Idoso , Alberta , Índice de Massa Corporal , Feminino , Humanos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Obesidade Abdominal/prevenção & controle , Classe Social , Circunferência da Cintura
11.
Rev. colomb. cir ; 36(1): 42-50, 20210000. fig, tab
Artigo em Espanhol | LILACS | ID: biblio-1148507

RESUMO

Introducción. El trauma es una de las entidades con mayor morbimortalidad en el mundo. Los equipos especializados en la atención del paciente traumatizado son llamados «equipos de trauma¼. Dichos equipos surgieron de la necesidad de brindar tratamiento oportuno multidisciplinario a individuos con heridas que condicionan gran severidad en la guerra; sin embargo, con el paso del tiempo se trasladaron al ámbito civil, generando un impacto positivo en términos de tiempos de atención, mortalidad y morbilidad. El objetivo de este estudio fue describir el proceso de desarrollo de los equipos de trauma a nivel mundial y la experiencia en nuestra institución en el suroccidente colombiano. Métodos. Se realizó una búsqueda en la base de datos PUBMED, que incluyó revisiones sistemáticas, metaanálisis, revisiones de Cochrane, ensayos clínicos y series de casos. Resultados. Se incluyeron 41 estudios para esta revisión narrativa, y se observó que el tiempo de permanencia en Emergencias, el tiempo de traslado a cirugía, la mortalidad y las complicaciones asociadas al trauma fueron menores cuando se implementan equipos de trauma. Discusión. El diseño de un sistema de atención y valoración horizontal de un paciente con traumatismos severos produce un impacto positivo en términos de tiempos de atención, mortalidad y morbilidad. Se hace necesario establecer los parámetros operativos necesarios en las instituciones de salud de alta y mediana complejidad en nuestro país para implementar dichos equipos de trabajo


Introduction. Trauma is one of the entities with the highest morbidity and mortality in the world. Teams specialized in trauma patient care are called «trauma teams¼. These teams arose from the need to provide timely multidisciplinary treatment to individuals with severe injuries in war; however, with time they moved to the civilian arena, generating a positive impact in terms of care times, mortality and morbidity. The objective of this study was to describe the process of development of trauma teams worldwide and the experience in our institution in southwestern Colombia. Methods. A search of the PUBMED database was carried out, which included systematic reviews, metaanalyses, Cochrane reviews, clinical trials, and case series.Results. Forty-one studies were included for this narrative review, and it was observed that the length of stay in the ER, the time of transfer to surgery, mortality and complications associated with trauma were lower when trauma teams are implemented. Discussion. The design of a horizontal care and assessment system for a patient with severe trauma produces a positive impact in terms of care times, mortality and morbidity. It is necessary to establish operational parameters in high and medium complexity health institutions in our country to implement such work teams


Assuntos
Humanos , Centros de Traumatologia , Equipe de Assistência ao Paciente , Ferimentos e Lesões , Índices de Gravidade do Trauma , Cuidados de Suporte Avançado de Vida no Trauma
12.
Toxicon ; 40(8): 1107-114, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12165312

RESUMO

The clinical and epidemiological features, as well as complications presented by 39 patients with Bothrops, Porthidium and Bothriechis snakebites, are described. Patients were admitted during 1 year in 25 hospitals of Antioquia and Chocó and then, they were transferred to the Hospital Universitario San Vicente de Paúl in Medellín, 30 of them because of the presence of complications, eight because of lack of antivenoms and another one because of the desire of his relatives. Thirty--one (79.5%) of the patients were male, 13 (33.3%) children, 59% of them were bitten at the lower extremities, the majority (74.4%) by Bothrops asper. Twenty-one (53.8%) of the patients were initially attended by traditional healers and sought medical attention at the local hospitals after 2h in 87.2% of the cases. Edema (100%), hemorrhage (74.4%), blistering (38.5%) and necrosis (38.5%), were the local signs of envenomation, while blood coagulation alteration (79.5%), hematuria (74.4%), gingival bleeding (43.6%), hypovolemic shock (23.1%) and oliguria (23.1%), were the systemic signs of envenomation. The final grade of envenomation was severe in 29 patients (74.4%). Thirty patients (76.9%) had one or more complications of the envenomation: acute renal failure (ARF), 15 (38.5%); soft-tissue infection, 12 (30.8%); central nervous system (CNS) hemorrhage, 5 (12.8%); compartment syndrome, 3 (7.7%); soft--tissue hematomas, 6 (15.4%); and Abruptio placentae, one (2.6%). There were four deaths (10.3%), two from ARF and two from cerebral hemorrhage. Fourteen other patients (35.9%) had sequelae. The onset of serotherapy after 2h of the bite was associated with the occurrence of ARF and CNS hemorrhage (p=0.02), as well as the risk of death and sequelae (RR=2.5).


Assuntos
Bothrops , Mordeduras de Serpentes/complicações , Mordeduras de Serpentes/epidemiologia , Viperidae , Adolescente , Adulto , Idoso , Animais , Anti-Infecciosos/efeitos adversos , Anti-Infecciosos/uso terapêutico , Antivenenos/efeitos adversos , Antivenenos/uso terapêutico , Infecções Bacterianas/etiologia , Infecções Bacterianas/microbiologia , Criança , Pré-Escolar , Colômbia/epidemiologia , Feminino , Hematoma/tratamento farmacológico , Hematoma/patologia , Hemorragia/induzido quimicamente , Hemorragia/patologia , Humanos , Lactente , Testes de Função Renal , Masculino , Medicina Tradicional , Pessoa de Meia-Idade , Mordeduras de Serpentes/patologia , Resultado do Tratamento
13.
Faraday Discuss ; 140: 347-62; discussion 417-37, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-19213326

RESUMO

According to Sergio Trasatti, "A true theory of electrocatalysis will not be available until activity can be calculated a priori from some known properties of the materials." Toward this goal, we developed intrinsic kinetic equations for the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) using as the kinetic parameters the free energies of adsorption and activation for elementary reactions. Rigorous derivation retained the intrinsic connection between the intermediates' adsorption isotherms and the kinetic equations, affording us an integrated approach for establishing the reaction mechanisms based upon various experimental and theoretical results. Using experimentally deduced free energy diagrams and activity-and-barriers plot for the ORR on Pt(111), we explained why the Tafel slope in the large overpotential region is double that in the small overpotential region. For carbon-supported Pt nanoparticles (Pt/C), the polarization curves measured with thin-film rotating disk electrodes also exhibit the double Tafel slope, albeit Pt(111) is several times more active than the Pt nanoparticles when the current is normalized by real surface area. An analytic method was presented for the polarization curves measured with H2 in proton exchange membrane fuel cells (PEMFCs). The fit to a typical iR-free polarization curve at 80 degrees C revealed that the change of the Tafel slope occurs at about 0.77 V that is the reversible potential for the transition between adsorbed O and OH on Pt/C. This is significant because it predicts that the Butler-Volmer equation can only fit the data above this potential, regardless the current density. We also predicted a decrease of the Tafel slope from 70 to 65 mV dec(-1) at 80 degrees C with increasing oxygen partial pressure, which is consistent with the observation reported in literature.


Assuntos
Fontes de Energia Elétrica , Eletroquímica/métodos , Eletrodos , Modelos Químicos , Oxigênio/química , Platina/química , Catálise , Simulação por Computador , Transporte de Elétrons , Cinética , Oxirredução , Propriedades de Superfície
14.
Rev. cient. (Maracaibo) ; 19(5): 500-505, sept.-oct. 2009. tab
Artigo em Espanhol | LILACS | ID: lil-551221

RESUMO

El objetivo del presente estudio fue evaluar la integridad acrosomal, funcionalidad bioquímica de la membrana espermática y las relaciones entre éstas en machos con y sin persistencia de gotas citoplásmicas (PGC). Se usaron 254 eyaculados de 48 cerdos reproductores entre ocho y 48 meses de edad clasificados como jóvenes (<1 año), maduros (entre uno y tres años) y viejos (>3 años). Los datos fueron evaluados mediante análisis de varianza para medidas repetidas en un mismo individuo (efecto aleatorio). Se evaluó el efecto de procedencia (efecto bloque) y grupo etáreo sobre: PGC, integridad acrosomal, funcionalidad de membrana, proporción de espermatozoides vivos y con gotas citoplásmicas (GC). Además se evaluó el efecto de PGC sobre la integridad acrosomal y la funcionalidad de membrana. La presentación de PGC fue menor en cerdos reproductores jóvenes (37 ± 6 por ciento) que en los maduros (52 ± 5 por ciento; P=0,05) y los viejos (85 ± 13 por ciento; P<0,01). La diferencia en PGC entre machos maduros y viejos fue significativa (P=0,05). Los machos viejos presentaron mayor proporción de células con GC que los jóvenes (34,6 ± 4,8 vs. 19,7 ± 2.3 por ciento, respectivamente; P=0,01), mientras que los maduros no fueron diferentes de ninguno de los dos (23,5 ± 2,1 por ciento). Los cerdos reproductores que no presentaron PGC obtuvieron mayores valores de acrosoma intacto que los que presentaron PGC (86,5 ± 1,2 vs. 80,2 ± 1,1 por ciento, respectivamente; P<0,01). Los defectos de la integridad acrosomal presentaron correlaciones significativas con defectos espermáticos asociados a GC (entre -0,20 y -0,36; P<0,05). Este estudio indica que cerdos reproductores mayores de tres años presentan con mayor frecuencia eyaculados de baja calidad espermática. Los resultados además sugieren que los defectos de membrana y morfológicos tienden a presentarse conjuntamente en un eyaculado, señalando la necesidad de construir un índice de calidad seminal multifactorial...


The goal of this study was to evaluate the acrosomal integrity, biochemical functionality of the sperm membrane, and the relationship between them in boars with and without persistence of cytoplasmic droplets (PGC). It were used 254 ejaculates from 48 boars between eight and 48 months of age that were classified as young (<1 year), mature (1 to 3 years), and old (>3 years). Data were analyzed using analysis of variance for repeated measurements in the same individual (random effect). The effect of source (block effect) and age group on PGC, acrosomal integrity, membrane function, and proportion of live and with cytoplasmic droplets sperm cells were evaluated. The effect of PGC on acrosomal integrity and membrane function was also tested. Presence of PGC was lower in young (37 ± 6 percent) than mature (52 ± 5 percent; P=0.05) and old (85 ± 13 percent; P<0.01) boars. The difference in PGC between mature and old boars was significant (P=0.05). Old boars showed a higher proportion of cells with GC than young ones (34.6 ± 4.8 vs. 19.7 ± 2.3 percent, respectively; P=0.01), while mature boars were no different from the other two groups (23.5 ± 2.1 percent). Boars that did not show PGC had a higher proportion of intact acrosomes than those with PGC (86.5 ± 1.2 vs. 80.2 ± 1.1 percent, respectively; P<0.01). Defects in acrosomal integrity were significantly correlated with sperm defects associated to GC (between -0.20 y -0.36; P<0.05). These results suggest that membrane and morphologic defects tend to occur together in the same ejaculate, pointing out the need to build a multifactor seminal quality index that can be used as decision criterion in the swine industry.


Assuntos
Animais , Acrossomo , Corpos de Inclusão , Suínos/genética , Capacitação Espermática , Sêmen/química , Medicina Veterinária
16.
Ciênc. Saúde Colet. (Impr.) ; 6(1): 209-19, 2001.
Artigo em Português | LILACS | ID: lil-288161

RESUMO

Estabelece correlaçöes entre subjetividade e gestäo organizacional a partir do paradigma da organizaçäo que aprende, de Peter Senge. Os principais eixos analíticos do mesmo säo o conceito de aprendizagem organizacional, como processo que articula a aprendizagem individual e social, através da comunicaçäo, e o conceito de liderança, visto como capacidade social de moldar o futuro que depende da disseminaçäo de qualidades e atitudes que dependem de características de natureza individual ou subjetiva.


Assuntos
Aprendizagem , Inovação Organizacional , Liderança
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA