994 resultados para Reaction diffusion


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Les méthodes de recherche qualitative en psychologie connaissent une diffusion de plus en plus importante, soutenue notamment par le développement phénoménal des réseaux de l'Internet. Nos investigations mettent en lumière diverses catégories de sites liés à la recherche qualitative, pour la plupart issues de grandes institutions nord-américaines. Cependant, la présence d'autant d'informa- tions sur le Web pose la question de la crédibilité des sites disponibles et de leur visibilité : en effet, si une certaine qualité peut être attendue des sites émanant d'institutions officielles, en termes de qualité d'information et de facilité d'accès, en revanche, il s'avère plus difficile d'évaluer certaines pages se réclamant pourtant de la recherche scientifique. Dans cet article, nous présentons quelques sites et liens Internet susceptibles de séduire les chercheurs intéressés par les méthodes qualitatives en psychologie.

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This article studies the diffusion of the main institutional feature of regulatory capitalism, namely, independent regulatory agencies. While only a few such authorities existed in Europe in the early 1980s, by the end of the twentieth century they had spread impressively across countries and sectors. The analysis finds that three classes of factors (bottom-up, top-down, and horizontal) explain this trend. First, the establishment of independent regulatory agencies was an attempt to improve credible commitment capacity when liberalizing and privatizing utilities and to alleviate the political uncertainty problem, namely, the risk to a government that its policies will be changed when it loses power. Second, Europeanization favored the creation of independent regulators. Third, individual decisions were interdependent, as governments were influenced by the decisions of others in an emulation process where the symbolic properties of independent regulators mattered more than the functions they performed.

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The Epstein-Barr virus (EBV) is the etiological agent of oral hairy leukoplakia (OHL), an oral lesion with important diagnostic and prognostic value in acquired immunodeficiency disease syndrome. The two EBV genotypes, EBV-1 and EBV-2, can be distinguished by divergent gene sequences encoding the EBNA-2, 3A, 3B, and 3C proteins. The purpose of this study was to identify the EBV genotype prevalent in 53 samples of scrapings from the lateral border of the tongue of HIV-1 seropositive patients, with and without OHL, and to correlate the genotypes with presence of clinical or subclinical OHL with the clinic data collected. EBV-1 and EBV-2 were identified through PCR and Nested-PCR based on sequence differences of the EBNA-2 gene. EBV-1 was identified in the 31 samples (15 without OHL, 7 with clinical OHL and 9 with subclinical OHL), EBV-2 in 12 samples (10 without OHL, 1 with clinical and 1 subclinical OHL), and a mixed infection in 10 samples (2 without OHL, 3 with clinical and 5 with subclinical OHL). The presence of EBV-1 was higher in women, but a significant statistical result relating one the EBV genotypes to the development of OHL was not found. We conclude that the oral epithelium in HIV-1 seropositive patients can be infected by EBV-1, EBV-2 or by a mixed viral population.

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Comparison of the use of indirect immunofluorescence assay (IFA), immunochromatography assay (ICA-BD) and reverse transcription-polymerase chain reaction (RT-PCR) for detecting human respiratory syncytial virus (HRSV) in 306 nasopharyngeal aspirates samples (NPA) was performed in order to assess their analytical performance. By comparing the results obtained using ICA-BD with those using IFA, we found relative indices of 85.0% for sensitivity and 91.2% for specificity, and the positive (PPV) and negative (NPV) predictive values were 85.0% and 91.2%, respectively. The relative indices for sensitivity and specificity as well as the PPV and NPV for RT-PCR were 98.0%, 89.0%, 84.0% and 99.0%, respectively, when compared to the results of IFA. In addition, comparison of the results of ICA-BD and those of RT-PCR yielded relative indices of 79.5% for sensitivity and 95.4% for specificity, as well as PPV and NPV of 92.9% and 86.0%, respectively. Although RT-PCR has shown the best performance, the substantial agreement between the ICA-BD and IFA results suggests that ICA-BD, also in addition to being a rapid and facile assay, could be suitable as an alternative diagnostic screening for HRSV infection in children.

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Les prioritats per als museus canvien. La missió de la nova museologia és convertir els museus en llocs per a gaudir i aprendre, cosa que fa que hagin de dur a terme una gestió financera molt semblant a la d'una empresa social que competeixi en el sector del lleure. Amb el pas del temps, els museus han d'establir i aplicar els criteris necessaris per a la supervivència, aplanant el terreny perquè altres institucions públiques siguin més obertes en els seus esforços per comunicar i difondre el seu patrimoni. Ja podem començar a parlar d'algunes conclusions comunament acceptades sobre el comportament dels visitants, que són necessàries per a planificar exposicions futures que vegin l'aprenentatge com un procés constructiu, les col·leccions com a objectes amb significat i les mateixes exposicions com a mitjans de comunicació que haurien de transformar la manera de pensar de l'espectador i que estan al servei del mateix missatge. Sembla que internet representa un mitjà efectiu per a assolir aquests objectius, ja que és capaç (a) d'adaptar-se als interessos i les característiques intel·lectuals d'un públic divers; (b) de redescobrir els significats dels objectes i adquirir un reconeixement sociocultural del seu valor per mitjà del seu potencial interactiu, i (c) de fer ús d'elements atractius i estimulants perquè tothom en gaudeixi. Per a aquest propòsit, és bàsic fer-nos les preguntes següents: quins criteris ha de seguir un museu virtual per a optimar la difusió del seu patrimoni?; quins elements estimulen els usuaris a quedar-se en una pàgina web i fer visites virtuals que els siguin satisfactòries?; quin paper té la usabilitat de l'aplicació en tot això?

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The present study investigated the diagnostic value of polymerase chain reaction (PCR) performed in parallel to conventional methods at an American tegumentary leishmaniasis (ATL) referral centre for diagnosis. Accuracy parameters for PCR were calculated using 130 patients with confirmed ATL (ATL group), 15 patients established with other diseases and 23 patients with a lesion suggestive of ATL, but without parasitological confirmation (NDEF group). PCR showed 92.3% sensitivity, 93.3% specificity, a 99.2% positive predictive value and a 13.84 positive likelihood ratio. In the NDEF group, PCR confirmed ATL in 13 of the 23 patients, seven of whom responded to leishmaniasis treatment and six who presented spontaneous healing of the lesion. PCR should be included in the routine diagnostic procedures for ATL, especially for cases found to be negative by conventional methods.

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The diagnosis of visceral leishmaniasis (VL) generally requires the use of invasive tests for the collection of infected tissue (aspirates of bone marrow, spleen, liver or lymph nodes). This difficulty has led to the search for safer and less painful techniques to confirm the occurrence of the disease in children. Polymerase chain reaction (PCR) is a method that is advantageous in that it allows the use of peripheral blood samples for diagnosis. This paper reports the utilisation of PCR on peripheral blood samples to diagnose VL in 45 children in Mato Grosso do Sul, Brazil. This technique is compared with methods carried out using tissue collected by invasive procedures, including direct microscopy, culture and detection of Leishmania DNA by PCR in bone marrow aspirates. The results show that PCR of peripheral blood provides great sensitivity (95.6%) that is similar to that from the PCR of bone marrow aspirates (91.1%) and higher than that achieved with microscopy (80%) or culture (26.7%) methods. PCR of peripheral blood proved to be a suitable tool for the diagnosis of VL in children because it is highly sensitive and safe, with tissue collection being less invasive than in traditional tests.

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Diffusion tensor magnetic resonance imaging, which measures directional information of water diffusion in the brain, has emerged as a powerful tool for human brain studies. In this paper, we introduce a new Monte Carlo-based fiber tracking approach to estimate brain connectivity. One of the main characteristics of this approach is that all parameters of the algorithm are automatically determined at each point using the entropy of the eigenvalues of the diffusion tensor. Experimental results show the good performance of the proposed approach

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Leptospirosis is a zoonotic disease caused by the pathogenic Leptospira spp. The clinical presentations are diverse, ranging from undifferentiated fever to fulminant disease including meningeal forms. The neurological leptospirosis forms are usually neglected. The aim of this study was to investigate leptospirosis as the cause of aseptic meningitis using different diagnostic techniques including the polymerase chain reaction (PCR). Thirty-nine cerebrospinal fluid (CSF) samples from patients presenting with meningeal abnormalities, predominance of lymphocytes and negative results by traditional microbiological tests were processed by leptospiral culture, anti-leptospiral antibody response and PCR. Leptospira spp DNA was detected in 23 (58.97%) of the CSF samples. Anti-leptospiral antibodies were found in 13 (33.33%) CSF samples. Twelve CSF samples were positive by PCR assay and negative by microscopic agglutination test (MAT) assay. Two CSF samples were positive by MAT and negative by PCR. The positive and negative agreement between both tests was 11 and 14, respectively. CSF samples from six cases of unknown diagnosis were positive by PCR assay. Eight cases showed positive results using PCR and MAT. Leptospirosis could be detected by PCR assay from the 3rd-26th day after illness onset. The sensitivity of the PCR was assessed with confirmed cases of leptospirosis (by MAT) and found to be 89.5%. All CSFs were negative by culture. PCR was found to be a powerful tool for diagnosing meningitis cases of leptospirosis. We recommend that it may be used as a supplementary diagnostic tool, especially in the early stages of the disease, when other diagnostic techniques such as serology are not sensitive.

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Recently, it has been proposed that drug permeation is essentially carrier-mediated only and that passive lipoidal diffusion is negligible. This opposes the prevailing hypothesis of drug permeation through biological membranes, which integrates the contribution of multiple permeation mechanisms, including both carrier-mediated and passive lipoidal diffusion, depending on the compound's properties, membrane properties, and solution properties. The prevailing hypothesis of drug permeation continues to be successful for application and prediction in drug development. Proponents of the carrier-mediated only concept argue against passive lipoidal diffusion. However, the arguments are not supported by broad pharmaceutics literature. The carrier-mediated only concept lacks substantial supporting evidence and successful applications in drug development.

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This work reports a survey of Leptospira spp in pampas deer (Ozotoceros bezoarticus) in the Pantanal wetlands of the state of Mato Grosso do Sul, Brazil by serology and polymerase chain reaction (PCR). Seventy pampas deer were captured in the dry season and surveyed using PCR, microscopic agglutination test (MAT) (n = 51) and by both techniques (n = 47). PCR detected infections in two pampas deer and MAT detected infections in three. Through sequencing and phylogenetic analyses, the PCR-amplified fragment detected in deer was identified as Leptospira interrogans. Serovars Pomona and Butembo were detected using MAT and the highest titre was 200 for serovar Pomona. Epidemiological aspects of the findings are discussed.

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Objectifs: Etudier l'utilité de DWI dans l'échinococcose alveolaire (EA) hépatique. Matériels et méthodes: Dix-sept patients (10 hommes, âge moyen 64.3) avec 55 lésions hépatiques ont été examinés par IRM. La sémiologie des lésions a été étudiée après classification selon Kodama. Les coefficients apparent de diffusion (ADCmax, ADCmin, ADCtot) ont été mesurés. Résultats: Trois lésions de Kodama de type 1, 13 de type 2, 15 de type 3, 3 de type 4, et 21 de type 5. L'ADCtot des lésions mesurait 1.23±0.18 x 10-3 mm2/s. L'ADCtot de Kodama type 1, 2, 3, 4 et 5 mesuraient 1.97±0.27, 1.66±0.13, 1.73±0.12, 1.15±0.27 et 1.76±0.10 x 10-3 mm2/s, respectivement. Il n'y avait pas de différence significative de l'ADCtot entre les types (p=0.25) hormis le type 4 qui représente une lésion solide (p=0.035). Conclusion: Les valeurs d'ADC des lésions d'EA ne se révèlent pas utiles pour différencier les différents types selon Kodama, hormis pour le type 4 ce qui suggère la présence d'une composante solide. Celles-ci sont relativement basses comparées à d'autres lésions kystiques hépatiques, ce qui peut aider à suggérer le diagnostic.