We revisited the well known Khosrofian and Garetz inversion algorithm [Appl. Opt.22, 3406-3410 (1983)] that was developed to analyze data obtained by the application of the traveling knife-edge technique. We have analyzed the approximated fitting function that was used for adjusting their experimental data and have found that it is not optimized to work with a full range of the experimentally-measured data. We have numerically calculated a new set of coefficients, which makes the approximated function suitable for a full experimental range, considerably improving the accuracy of the measurement of a radius of a focused Gaussian laser beam.

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There has been growing interest in scattering media in recent years, due to their potential applications as solar collectors, photocatalyzers, random lasers and other novel optical devices. Here, we have introduced a novel core-shell scattering medium for a random laser composed of TiO2@Silica nanoparticles. Higher efficiency, lower laser threshold and long photobleaching lifetime in random lasers were demonstrated. This has introduced a new method or parameter (fraction of absorbed pumping), which opens a new avenue to characterize and study the scattering media. Optical chemical and colloidal stabilities were combined by coating a suitable silica shell onto TiO2 nanoparticles.

In recent years, there has been dramatic progress in the photonics field in disordered media, ranging from applications in solar collectors, photocatalyzers, random lasing, and other novel photonic functions, to investigations into fundamental topics, such as light confinement and other phenomena involving photon interactions. This paper reports several pieces of experimental evidence of localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO2@silica) in ethanol solution. We demonstrate the crossover from a diffusive transport to a localization transition regime as the nanoparticle concentration is increased, and that an enhanced absorption effect arises at localization transition.

Many studies have described the adherence of Candida albicans to epithelial cells but little is known about Candida parapsilosis adhesion and its role in host cell surface recognition. This study was designed to evaluate the correlation between the adherence of 20 C. albicans and 12 C. parapsilosis strains to human buccal epithelial cells and the expression of fungal cell surface carbohydrates using lectin histochemistry. Adherence assays were carried out by incubating epithelial cells in yeast suspensions (10(7) cells ml(-1) ) and peroxidase conjugated lectins (Con A, WGA, UEA I and PNA at 25 μg ml(-1) ) were used for lectin histochemistry. The results showed that adherence was overall greater for C. albicans than for C. parapsilosis (P < 0.01) and that the individual strain differences correlated with a high content of cell surface α-l-fucose residues as indicated by the UEA I staining pattern. Based on the saccharide specificity of the lectins used, these results suggest that l-fucose residues on cell surface glycoconjugates may represent recognition molecules for interactions between the yeast strain studied and the host (r = 0.6985, P = 0.0045). In addition, our results indicated the presence of α-d-glucose/α-d-mannose, N-acetyl-D-glucosamine/N-acetylneuraminic acid and D-galactose/N-acetyl-D-galactosamine in fungal cell wall.

RESUMO:Com o objetivo de caracterizar as alterações microclimáticas provocadas pelo uso de tela plástica na agricultura, foi desenvolvido um experimento com alface, em área de cultivo agrícola, em Alegre -ES (latitude 20º45'S, longitude 41º28'W e altitude 150 m), no período de setembro a dezembro de 1996. Foram utilizados sombreamentos de 0; 30; 50, e 70%, segundo especificação comercial. Os resultados mostraram que a tela com especificação comercial de 50% de sombreamento provocou uma atenuação média de 41% na radiação solar global, ocorrendo, no entanto, uma flutuação significativa ao longo do dia em função do movimento aparente do sol. A cobertura com a tela plástica não provocou alterações significativas da temperatura e umidade relativa do ar. Em relação à temperatura do solo, foi possível verificar uma atenuação com o aumento do sombreamento. PALAVRAS-CHAVE:microclima, tela plástica, sombreamento. MICROCLIMATOLOGICAL ALTERATIONS CAUSED BY PLASTIC SCREEN USES SUMMARY:The objective of this study was to determine the micrometeorological alterations caused by plastic screen uses in agriculture. The experiment with lettuce was carried out in Alegre (20º45'S, 41º28'W -150 m), Espírito Santo State, Brazil, during September to December, 1996. Measurements were done under plastic screen with 0; 30; 50, and 70% of solar radiation reduction (attenuation) according to commercial specification. Results showed that attenuation was less than commercial specification and there was a diurnal fluctuation as a function of solar zenital angle. A reduction in soil temperature under shading was also observed.KEYWORDS: microclimate, plastic screen, shading. INTRODUÇÃOEm algumas regiões do Brasil, tem crescido o uso de tela plástica na agricultura com o objetivo de atenuar a densidade de fluxo de radiação solar, possibilitando o cultivo, principalmente de olerícolas, em épocas com alta disponibilidade energética. A caracterização dessa atenuação da radiação solar é importante, pois afeta os outros componentes do balanço de energia, como os fluxos de calor sensível e latente, além do processo fotossintético.Diversos trabalhos têm mostrado que o uso de sombreamento artificial através de ripados ou telas plásticas causa uma modificação no balanço de energia radiante, propiciando características mais adequadas às espécies de baixo ponto de saturação luminosa (SEDYAMA & PRATES, 1986). SALVATIERRA et al. (1991), BURIOL et al. (1994) e SOUZA et al. (1995 mostram que o uso de tela de polietileno provoca uma redução da radiação fotossinteticamente ativa, bem como na porção do infravermelho próximo, além de alterar a temperatura do ar e do solo.

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