Study of the hydrolysis of TEOS-TMOS mixtures under ultrasound stimulation

Pure and mixed tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS) were hydrolyzed at 35 degrees C, using oxalic acid as a catalyst and ultrasound stimulation. The hydrolysis reaction was carried out in a specially designed device, in which a heat flow steady state, between the ultrasound source and an external thermostatic bath, was maintained, in the absence of reactions. The exothermic hydrolysis causes a time dependent thermal peak. An induction time is apparent in pure TEOS before the hydrolysis peaks starts, which has been explained by the initial immiscibility gap of the TEOS-water system. The induction time was found to be approximately of the same magnitude as in the HCl catalyzed hydrolysis, in spite of the uncertainty accompanying the peak definition. No induction period is apparent in pure TMOS, so that the hydrolysis starts with its maximum rate. Two independent thermal peaks in the mixed TMOS-TEOS samples were found, both associated to the respective hydrolyses of the pure component. The induction time for the TEOS hydrolysis is decreased as more alcohol (and silanol) is produced in the earlier TMOS hydrolysis. This effect is explained by improvement of homogenization by alcohol.

Fatigue and Fluoride Corrosion on Streptococcus mutans Adherence to Titanium-Based Implant/Component Surfaces

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The cohomology of superspace, pure spinors and invariant integrals

The superform construction of supersymmetric invariants, which consists of integrating the top component of a closed superform over spacetime, is reviewed. The cohomological methods necessary for the analysis of closed superforms are discussed and some further theoretical developments presented. The method is applied to higher-order corrections in heterotic string theory up to alpha'(3). Some partial results on N = 2, d = 10 and N = 1, d = 11 are also given.

Evaluation of solvent effect on the extraction of phenolic compounds and antioxidant capacities from the berries: application of principal component analysis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Reduction capability of soil humic substances from the Rio Negro basin, Brazil, towards Hg(II) studied by a multimethod approach and principal component analysis (PCA)

This paper characterizes humic substances (HS) extracted from soil samples collected in the Rio Negro basin in the state of Amazonas, Brazil, particularly investigating their reduction capabilities towards Hg(II) in order to elucidate potential mercury cycling/volatilization in this environment. For this reason, a multimethod approach was used, consisting of both instrumental methods (elemental analysis, EPR, solid-state NMR, FIA combined with cold-vapor AAS of Hg(0)) and statistical methods such as principal component analysis (PCA) and a central composite factorial planning method. The HS under study were divided into groups, complexing and reducing ones, owing to different distribution of their functionalities. The main functionalities (cor)related with reduction of Hg(II) were phenolic, carboxylic and amide groups, while the groups related with complexation of Hg(II) were ethers, hydroxyls, aldehydes and ketones. The HS extracted from floodable regions of the Rio Negro basin presented a greater capacity to retain (to complex, to adsorb physically and/or chemically) Hg(II), while nonfloodable regions showed a greater capacity to reduce Hg(II), indicating that HS extracted from different types of regions contribute in different ways to the biogeochemical mercury cycle in the basin of the mid-Rio Negro, AM, Brazil. (c) 2007 Published by Elsevier B.V.

Kinetics of cellular component in inflammatory response induced by different stimuli in the swim bladder of pacu, Piaractus mesopotamicus Holmberg 1887 (Characidae)

The present study assessed the kinetics of cell accumulation at the site of inflammation induced by thioglycolate, Escherichia coli lipopolysaccharide (LPS) and heat-inactivated Aeromonas hydrophila, in the pacu, Piaractus mesopotamicus (Characidae), swim bladder. A quantitative, as well as qualitative, assessment was done of all the cells present in the exudate at 6, 24, and 48 h (n = 8) after inoculation of inflammatory agents. The results show that the thioglycolate was the irritant to induce higher total inflammatory cell accumulation when compared to the control group, 6 h after insult (P < 0.05). Inoculation of heat-inactivated Aeromonas hydrophila induced progressive accumulation of total inflammatory cells, with cell number peaking after 24 h and being significantly higher than observed in the other groups (P < 0.05). Injection of LPS also induced greater cell accumulation when compared to the control group (P < 0.05), although in lower numbers than those induced by the other two irritants. All irritants injected induced significantly greater accumulation of lymphocytes and thrombocytes when compared to the control group (P < 0.05).

Variance component estimates applying random regression models for test-day milk yield in Caracu heifers (Bos taurus Artiodactyla, Bovidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

IgE antibody response to the main antigenic component of Paracoccidioides brasiliensis in patients with paracoccidioidomycosis

Paracoccidioidomycosis (PCM) has two main clinical presentations, a chronic form (CF) and an acute, more severe form (AF). The AF is associated with a more marked dysfunction of the patient's immune response, and a distinct anti-Paracoccidioides brasiliensis immunoglobulin (Ig)A and IgG antibody subclass expression, compared with that seen in the CF. In this study we investigated the presence of IgE antibodies against the main P. brasiliensis antigen (a 43-kDa molecule) in the serum of PCM patients using an enzyme-linked immunosorbent assay. We found that 100% of the AF patients (n = 16) produced IgE antibodies, mostly at high levels, whereas only 9 (27%) out of 33 CF patients produced this isotype. Interestingly, these nine patients presented higher serological titers on the counter-immunoelectrophoresis assays than did those who did not produce IgE; a finding that suggests that they had a relatively more severe disease. As IgE is a characteristic feature of the AF patients, and switching to a positive IgE response is dependent on interleukin-4, our results support the notion that the relatively more severe impairment of cellular immunity in the AF is probably related to a Th-2 pattern of immune response.

Carbon fiber non-crimp multi-axial reinforcement and epoxy mono-component system composite: fatigue behavior

Fiber reinforced polymer composites have been widely applied in the aeronautical field. However, composite processing, which uses unlocked molds, should be avoided in view of the tight requirements and also due to possible environmental contamination. To produce high performance structural frames meeting aeronautical reproducibility and low cost criteria, the Brazilian industry has shown interest to investigate the resin transfer molding process (RTM) considering being a closed-mold pressure injection system which allows faster gel and cure times. Due to the fibrous composite anisotropic and non homogeneity characteristics, the fatigue behavior is a complex phenomenon quite different from to metals materials crucial to be investigated considering the aeronautical application. Fatigue sub-scale specimens of intermediate modulus carbon fiber non-crimp multi-axial reinforcement and epoxy mono-component system composite were produced according to the ASTM 3039 D. Axial fatigue tests were carried out according to ASTM D 3479. A sinusoidal load of 10 Hz frequency and load ratio R = 0.1. It was observed a high fatigue interval obtained for NCF/RTM6 composites. Weibull statistical analysis was applied to describe the failure probability of materials under cyclic loads and fractures pattern was observed by scanning electron microscopy. (C) 2010 Published by Elsevier Ltd.

Evaluation of the fretting fatigue behaviour of commercially pure titanium

Fretting fatigue occurs when the contact surfaces of two components undergo small oscillatory movement while they are subjected to a clamping force. A cyclic external load gives rise to the early initiation of fatigue cracks, thus reducing their service life. In this paper, the fretting fatigue behaviour of commercially pure titanium flat samples (1.5 mm thick) is evaluated. A fretting device composed of a frame, load cell, and two screw-mounted cylindrical fretting pads with convex extremities was built and set to a servo-hydraulic testing machine. The fatigue tests were conducted under load control at a frequency of 10 Hz and stress ratio R = 0.1, with various contact load values applied to the fretting pads. Additional tests under inert environment allowed assessing the role of oxidation on the wear debris formation. The fracture surfaces and fretting scars were analysed via scanning electron microscopy in order to evaluate the surface damage evolution and its effect on the fatigue crack features. The effect of the fretting condition on the S-N curve of the material in the range of 10(4)-10(6) cycles is described. Fatigue crack growth calculations allowed estimating the crack initiation and propagation lives under fretting conditions. The effect of the fretting condition in fatigue life is stronger for the lower values of cyclic stress and does not seem to depend on the contact loading value.

Hydrogen embrittlement in an AISI 1045 steel component of the sugarcane industry

This paper will present a failure analysis of a chain component, manufactured with AISI 1045 steel and used for sugarcane transport. During the fabrication process, this component is submitted to induction hardening, just on one surface, before the galvanizing process. The occurrence of surface cracks, during storage, disables the usage of these components. Chemical and metallographic analyses, tensile, fracture toughness, and hardness tests, and fractography were conducted in order to determine the causes of failure. The steel chemical composition was in accordance with AISI 1045. The metallographic analyses and fractography did not exhibit the presence of zinc into the cracks; this is an indication that the cracks occurred after the galvanizing process. Tensile and fracture toughness test results are as expected. The crack surface and the fracture toughness specimen surfaces showed two different fracture micromechanisms: dimples and intergranular. The delayed fracture associated with the predominance of intergranular fracture micromechanism at the induction hardened layer and the high hardness level is a clear indication of the hydrogen embrittlement. (c) 2008 Elsevier Ltd. All rights reserved.

Sebaceous metaplasia in a canine mammary gland non-infiltrative carcinoma with myoepithelial component

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Between freedom and reclusion: Social support as a quality-of-life component in the family caregiver-dependent person binomial

This is a qualitative study which uses Grounded Theory as its methodological framework and Symbolic Interactionism as a theoretical base to understand the experience of family caregivers for Cerebrovascular Accident (CVA) patients with regard to social support during their rehabilitation process at home. The components (themes and categories) of the phenomenon assuming home care and specifically the themes assuming care with support and assuming care without support were inter-related for the purpose of comparison and analysis, in order to apprehend how the interaction between them occurred, It was observed that, in addition to the recovery of the patient's autonomy, social support is one of the intervenient components in the quality of life for the family caregiver-disabled person binomial, particularly with respect to the caregiver's freedom to resume his/her life plan.

Detection of Leptospira spp. from pure cultures and from experimentally contaminated bovine semen by polymerase chain reaction

Considerando a importância do sêmen na transmissão da leptospira bovina, foi realizado o presente estudo que teve como objetivo aplicar a reação em cadeia pela polimerase (PCR) para a detecção de leptospiras em sêmen bovino experimentalmente contaminado. A reação de PCR foi capaz de amplificar um fragmento de DNA específico de 330 pares de bases a partir de cultivos puros de 26 sorovares de Leptospira spp. A contaminação experimental de sêmen com Leptospira interrogans serovar hardjo revelou que a técnica de PCR conseguiu detectar 10 bactérias/ml, concentração sensivelmente mais baixa que as 1.000 bactérias/ml detectadas através do cultivo microbiológico. Os resultados observados revelam o grande potencial da reação de PCR para a detecção de Leptospira spp. em sêmen bovino, notadamente em centrais de inseminação artificial.