951 resultados para Condicionamento superficial


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The entorhinal cortex (EC) controls hippocampal input and output, playing major roles in memory and spatial navigation. Different layers of the EC subserve different functions and a number of studies have compared properties of neurones across layers. We have studied synaptic inhibition and excitation in EC neurones, and we have previously compared spontaneous synaptic release of glutamate and GABA using patch clamp recordings of synaptic currents in principal neurones of layers II (L2) and V (L5). Here, we add comparative studies in layer III (L3). Such studies essentially look at neuronal activity from a presynaptic viewpoint. To correlate this with the postsynaptic consequences of spontaneous transmitter release, we have determined global postsynaptic conductances mediated by the two transmitters, using a method to estimate conductances from membrane potential fluctuations. We have previously presented some of this data for L3 and now extend to L2 and L5. Inhibition dominates excitation in all layers but the ratio follows a clear rank order (highest to lowest) of L2>L3>L5. The variance of the background conductances was markedly higher for excitation and inhibition in L2 compared to L3 or L5. We also show that induction of synchronized network epileptiform activity by blockade of GABA inhibition reveals a relative reluctance of L2 to participate in such activity. This was associated with maintenance of a dominant background inhibition in L2, whereas in L3 and L5 the absolute level of inhibition fell below that of excitation, coincident with the appearance of synchronized discharges. Further experiments identified potential roles for competition for bicuculline by ambient GABA at the GABAA receptor, and strychnine-sensitive glycine receptors in residual inhibition in L2. We discuss our results in terms of control of excitability in neuronal subpopulations of EC neurones and what these may suggest for their functional roles. © 2014 Greenhill et al.

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The diatomite is a natural material that has numerous applications due to changes in their physical and chemical properties after processing. It is currently used in the industry as a sound insulator , filter aid and industrial load . The filter material shall be inert chemical composition , which will diatomite confers a high commercial value and performance not found in other particulate materials , for this application. The diatomite surface undergoes changes after thermal treatment at high temperatures , from 800ºC , with properties that enable its application in the food , beverage , pharmaceutical , cosmetic and textiles . In this work , we developed a study on thermal treatment on natural diatomite to adapt their properties to the application as a filter aid . The heat treatments were performed in an open oven at temperatures of 800ºC , 1000ºC and 1200ºC for a time of 24 hours. Reagents were added in the constitution of the samples analyzed. The reagents used were sodium carbonate (Na2CO3 ) and sodium chloride (NaCl) . The samples were characterized by x - ray diffraction , x -ray fluorescence , scanning electron microscopy , analysis and particle size distribution , specific surface area by the BET method , and pore volume by BJH method. The results showed a reduction in porosity of the material as well as a significant increase in specific surface area after heat treatment and the reactants in the ratio of 3 wt%. The diatomaceous earth , after heat treatment , undergone changes in its coloration , varying in white, cream and beige , which directly interferes with the speed of filtration materials process. All results obtained before and after heat treatment of the material with the values obtained for samples already used industrially , Brazilian and American industry , which were characterized using the same test methods performed with the samples in the study were compared and showed promising efficiency when material studied in the region of Punaú - RN , after processing , reagent addition and heat treatment, as an element in the composition of filter .

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Adsorption is a process that has become indispensable due to pollution caused by industrial activity. More economically viable adsorbents are being tested to replace the high cost of materials used. The clays can be used as adsorbents and are low cost materials, natural properties feasible for the application in the adsorption process, structural modifications are performed with ease promoting selective adsorption in these materials. The objective of this study was to synthesize and characterize adsorbents used in the adsorption of organic compounds. The adsorbents were characterized by the techniques of XRD, SEM, FTIR and TG. The results show that the studied materials have affinity to organic compounds and can be applied as adsorbents. The materials studied are viable and can be applied in the treatment of effluents contaminated in industrial scale.

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Objective: To evaluate in vitro the surface roughness and bacterial adhesion of nanoparticle composites, after being subjected to different finishing and polishing systems. Materials and Methods: 66 specimens were prepared, and 30 with Filtek Z350 XT (3M ESPE, USA) and 30 with the resin IPS Empress Direct (Ivoclar Vivadent, USA), divided into 6 groups (n = 10 ). Six specimens were prepared for analysis in scanning electron microscopy (SEM) .Each kind of resin was subjected to finishing and polishing systems: Sof-Lex Pop-On discs (3M ESPE, USA) and AstropolTM system (Ivoclar Vivadent , USA), featuring the experimental group. The control group did not undergo any kind of finishing and polishing technique. The average roughness (Ra) in both groups was measured using a roughness in the setting of 0.25 mm (cut off) and surface images obtained with photomicrographs taken with a scanning electron microscope (SEM) magnified 500 times. Bacterial adherence was evaluated by determining the absorbance (OD) of the suspension of adhered cells by spectrophotometer at 570 nm. The results were submitted for analyzed with 2-way ANOVA at α=.05 and Tukey multiple comparison tests. Results: Statistically significant differences were found between the groups in terms of roughness and bacterial adhesion. Filtek Z350 XT for resin were no differences between the tested finishing and polishing systems, where the system of lowest surface roughness was the Sof-Lex Pop-On. To the resin IPS Empress Direct, the finishing and polishing system Astropol, had lower results of surface roughness. As for bacterial adhesion, the lowest optical density value for Filtek Z350 XT was for the group that used the finishing and polishing system Sof-Lex Pop-On and the resin IPS Empress Direct the group that used the Astropol system. In addition, there was a positive correlation between surface roughness and bacterial adhesion on polished surfaces (r = 0.612) Conclusions: surface roughness and bacterial adhesion are closely related. The finishing and polishing Sof-Lex Pop-On system is more suitable for nanoparticulate Filtek Z350 XT and the finishing and polishing system Astropol for resin nanohíbrida IPS Empress Direct.

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Urinary tract infections (UTIs) are typically caused by bacteria that colonize different regions of the urinary tract, mainly the bladder and the kidney. Approximately 25% of women that suffer from UTIs experience a recurrent infection within 6 months of the initial bout, making UTIs a serious economic burden resulting in more than 10 million hospital visits and $3.5 billion in healthcare costs in the United States alone. Type-1 fimbriated Uropathogenic E. coli (UPEC) is the major causative agent of UTIs, accounting for almost 90 % of bacterial UTIs. The unique ability of UPEC to bind and invade the superficial bladder epithelium allows the bacteria to persist inside epithelial niches and survive antibiotic treatment. Persistent, intracellular UPEC are retained in the bladder epithelium for long periods, making them a source of recurrent UTIs. Hence, the ability of UPEC to persist in the bladder is a matter of major health and economic concern, making studies exploring the underlying mechanism of UPEC persistence highly relevant.

In my thesis, I will describe how intracellular Uropathogenic E.coli (UPEC) evade host defense mechanisms in the superficial bladder epithelium. I will also describe some of the unique traits of persistent UPEC and explore strategies to induce their clearance from the bladder. I have discovered that the UPEC virulence factor Alpha-hemolysin (HlyA) plays a key role in the survival and persistence of UPEC in the superficial bladder epithelium. In-vitro and in-vivo studies comparing intracellular survival of wild type (WT) and hemolysin deficient UPEC suggested that HlyA is vital for UPEC persistence in the superficial bladder epithelium. Further in-vitro studies revealed that hemolysin helped UPEC persist intracellularly by evading the bacterial expulsion actions of the bladder cells and remarkably, this virulence factor also helped bacteria avoid t degradation in lysosomes.

To elucidate the mechanistic basis for how hemolysin promotes UPEC persistence in the urothelium, we initially focused on how hemolysin facilitates the evasion of UPEC expulsion from bladder cells. We found that upon entry, UPEC were encased in “exocytic vesicles” but as a result of HlyA expression these bacteria escaped these vesicles and entered the cytosol. Consequently, these bacteria were able to avoid expulsion by the cellular export machinery.

Since bacteria found in the cytosol of host cells are typically recognized by the cellular autophagy pathway and transported to the lysosomes where they are degraded, we explored why this was not the case here. We observed that although cytosolic HlyA expressing UPEC were recognized and encased by the autophagy system and transported to lysosomes, the bacteria appeared to avoid degradation in these normally degradative compartments. A closer examination of the bacteria containing lysosomes revealed that they lacked V-ATPase. V-ATPase is a well-known proton pump essential for the acidification of mammalian intracellular degradative compartments, allowing for the proper functioning of degradative proteases. The absence of V-ATPase appeared to be due to hemolysin mediated alteration of the bladder cell F-actin network. From these studies, it is clear that UPEC hemolysin facilitates UPEC persistence in the superficial bladder epithelium by helping bacteria avoid expulsion by the exocytic machinery of the cell and at the same time enabling the bacteria avoid degradation when the bacteria are shuttled into the lysosomes.

Interestingly even though UPEC appear to avoid elimination from the bladder cell their ability to multiple in bladder cells seem limited.. Indeed, our in-vitro and in-vivo experiments reveal that UPEC survive in superficial bladder epithelium for extended periods of time without a significantly change in CFU numbers. Indeed, we observed these bacteria appeared quiescent in nature. This observation was supported by the observation that UPEC genetically unable to enter a quiescence phase exhibited limited ability to persist in bladder cells in vitro and in vivo, in the mouse bladder.

The studies elucidated in this thesis reveal how UPEC toxin, Alpha-hemolysin plays a significant role in promoting UPEC persistence via the modulation of the vesicular compartmentalization of UPEC at two different stages of the infection in the superficial bladder epithelium. These results highlight the importance of UPEC Alpha-hemolysin as an essential determinant of UPEC persistence in the urinary bladder.

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Spectral albedo has been measured at Dome C since December 2012 in the visible and near infrared (400 - 1050 nm) at sub-hourly resolution using a home-made spectral radiometer. Superficial specific surface area (SSA) has been estimated by fitting the observed albedo spectra to the analytical Asymptotic Approximation Radiative Transfer theory (AART). The dataset includes fully-calibrated albedo and SSA that pass several quality checks as described in the companion article. Only data for solar zenith angles less than 75° have been included, which theoretically spans the period October-March. In addition, to correct for residual errors still affecting data after the calibration, especially at the solar zenith angles higher than 60°, we produced a higher quality albedo time-series as follows: In the SSA estimation process described in the companion paper, a scaling coefficient A between the observed albedo and the theoretical model predictions was introduced to cope with these errors. This coefficient thus provides a first order estimate of the residual error. By dividing the albedo by this coefficient, we produced the "scaled fully-calibrated albedo". We strongly recommend to use the latter for most applications because it generally remains in the physical range 0-1. The former albedo is provided for reference to the companion paper and because it does not depend on the SSA estimation process and its underlying assumptions.

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Para avaliar os efeitos de diferentes tempos de pré-condicionamento isquêmico (IPC) em translocação bacteriana intestinal (BT). MÉTODOS: Trinta ratos Wistar pesando 280 ± 27g foram divididos em cinco grupos. No grupo IV (n = 6), a laparotomia foi realizada e a artéria mesentérica superior foi obstruído por um microclampe atraumática durante 30 minutos. Nos quatro grupos de pré-condicionamento (n = 6 cada) antes dos 30 minutos de isquemia-reperfusão (I / R), os ratos foram submetidos a IPC para duas, cinco, dez e 15 minutos, seguido pelo mesmo momento da reperfusão. A fim de avaliar se o tempo de pré-condicionamento influenciaram o surgimento de translocação bacteriana, as amostras de nódulos linfáticos mesentéricos, fígado e baço foram colhidas em condições estéreis, 24 horas após os procedimentos para a quantificação de unidades formadoras de colónias de bactérias por grama de tecido (CFU / g). O sangue foi recolhido para a medição de citoquinas. RESULTADOS: No grupo I / R, o total de CFU / g em gânglios linfáticos mesentéricos, baço, fígado, bem como o soro de TNF-a, IL-1A e IL-6 foram significativamente mais elevados do que nos outros grupos (p <0,05). Pré-condicionamento por 15 minutos significativamente atenuada BT e citocinas séricas quando comparado a outros períodos de pré-condicionamento (p <0,05). CONCLUSÃO: Nossos dados sugerem que o pré-condicionamento como um fator chave para reduzir a translocação bacteriana intestinal em I / R. Numa escala de dois a 15 minutos, o melhor tempo de pré-condicionamento isquémico pela atenuação da translocação bacteriana foi de 15 minutos

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A resistividade elétrica superficial do concreto, nos estados fresco e endurecido, pode ser influenciada por alguns fatores, como por exemplo: grau de hidratação, relação água/aglomerante (a/ag), procedimento de cura, teor de agregado e existência de armadura. Este trabalho tem o objetivo de avaliar o desempenho e o comportamento da resistividade elétrica superficial do concreto tendo como base a influência do tempo de cura e relação a/ag. Os concretos dosados foram divididos em três grupos, onde C-0,81 representa o grupo de concretos com relação água/aglomerante de 0,81 e 20 MPa de resistência à compressão; C- 0,50 representa os concretos com relação água/aglomerante de 0,50 e 40 MPa; e C-0,35 representa os concretos com relação água/aglomerante de 0,35 e 60 MPa de resistência à compressão. Os procedimentos de cura aplicados aos três grupos foram: cura seca, cura submersa até os sete dias e cura submersa até os quatorze dias. No presente estudo, os resultados mostraram que quanto maior a relação água/aglomerante, maior será a porosidade da mistura que, por sua vez, eleva a resistividade elétrica. No que tange ao procedimento de cura, os concretos curados a seco apresentaram maiores índices de resistividade que os concretos submersos.

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El balance de agua de ecosistemas situados sobre planicies áridas y semiáridas se encuentra determinado por la precipitación (principal entrada de agua) y la evapotranspiración (principal salida de agua). La fracción de la precipitación que ingresa en el suelo y su redistribución espacial son los principales controles del funcionamiento de dichos ecosistemas, como por ejemplo de su productividad primaria neta. En esta tesis se exploró la dinámica superficial del agua en planicies semiáridas dedicadas a la ganadería extensiva, evaluando el papel de las precipitaciones y de la cobertura vegetal a distintas escalas espaciales. En el centro de Argentina, la distribución relativa de tamaño de eventos de precipitación resultó constante en el espacio (sitios dispuestos a lo largo de un gradiente de precipitación de ~1000 mm/año) y en el tiempo (50 años); encontrándose que el 10 por ciento de los eventos de precipitación de mayor tamaño explicó casi la mitad de la precipitación anual. El reemplazo de bosques secos nativos por pasturas en el Chaco Árido, por un lado, aumentó la evaporación potencial del suelo y el escurrimiento superficial a escala de parcela (~1 ha); por otro lado, redujo a la mitad la conductividad hidráulica saturada y generó una reducción de la variabilidad espacial del agua del suelo a escala de parche (0,25 m2). La intensidad de los eventos de precipitación resultó el factor determinante para explicar los procesos de redistribución de agua del suelo de los bosques secos nativos; parches menos vegetados capturaron más agua en eventos de precipitación poco intensos (mayor a 10 mm/h), mientras que parches más vegetados capturaron más agua en eventos más intensos ((menor a 20 mm/h). La cosecha de agua de lluvia en represas o tajamares representó menos del 1 por ciento de la precipitación anual, desempeñando un papel menor en el balance de agua regional (~20000 km2); sin embargo, a escala de parcela o lote (1-100 ha) puede afectar profundamente la partición de flujos de agua, por ejemplo generando recarga inducida como resultado de las pérdidas por infiltración de las represas. Los resultados obtenidos en esta tesis aportan nuevas perspectivas para entender la dinámica superficial del agua en sistemas ganaderos semiáridos, y por lo tanto, para mejorar la producción primaria y secundaria de los mismos.