Corrosion of the component phases presents in high copper dental amalgams. Application of electrochemical impedance spectroscopy and electrochemical noise analysis

The corrosion resistance of three of the constituent phases in high copper dental amalgams has been investigated by electrochemical methods in 0.9% NaCl solution. Polarization curves show corrosion potentials most positive for gamma(1)-Ag2Hg3, followed by Ag-Cu, and gamma-Ag3Sn in agreement with the order of corrosion resistance deduced from the corrosion currents. Complex plane impedance plots at the open circuit potential showed distorted semicircles with diffusional components at low frequency for Ag-Hg and Ag-Cu, while for gamma-Ag3Sn a layer of corrosion products is formed, partially or completely covering the surface of the electrode. Impedance and noise spectra have been compared in the frequency domain, and show good agreement. (C) 2004 Elsevier Ltd. All rights reserved.

Community structure and comparative analysis of the woody component of a cerrado remnant in Southeastern Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Prevalence of pre-frailty for the component of gait speed in older adults

OBJETIVO: investigar a pré-fragilidade e os fatores associados a essa condição, considerando as medidas de velocidade da marcha dos idosos. MÉTODO: a seleção dos participantes ocorreu por meio de critérios de inclusão/exclusão e teste de rastreamento cognitivo. A amostra foi calculada com base na estimativa da proporção populacional e constituída por 195 idosos, usuários de uma Unidade Básica de Saúde de Curitiba, PR. Os dados foram coletados mediante questionário sociodemográfico/clínico e teste de velocidade da marcha. RESULTADOS: a pré-fragilidade para velocidade da marcha possui moderada prevalência (27,3%) e associou-se à faixa etária entre 60 e 69 anos, baixa escolaridade, não se sentir solitário, utilizar anti-hipertensivo, apresentar doença cardiovascular e sobrepeso. CONCLUSÃO: considera-se relevante identificar os idosos na condição de pré-fragilidade, pois, dessa maneira, existe a possibilidade de intervenção imediata com a finalidade de estacionamento do quadro. É significativo o déficit de estudos sobre a síndrome da fragilidade em idosos brasileiros, principalmente aqueles que se referem a um componente isolado. Visto que a enfermagem gerontológica se encontra nos primeiros passos referentes à temática, entende-se que a identificação da prevalência deve ser o ponto primordial das pesquisas sobre o tema.

Chemosystematic studies of natural compounds isolated from Asteraceae: characterization of tribes by principal component analysis

This work describes an application of principal component analysis (PCA) on a database of secondary metabolites from the Asteraceae family. The numbers of occurrences of metabolites in 11 chemical classes for the different vibes of the family were used as variables, PCA allows the identification of chemical classes that contribute most to the subgroups classification within the family. Relationships between chemical composition and botanical classification were made. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Evidence for a respiratory component, similar to mammalian respiratory sinus arrhythmia, in the heart rate variability signal from the rattlesnake, Crotalus durissus terrificus

Autonomic control of heart rate variability and the central location of vagal preganglionic neurones (VPN) were examined in the rattlesnake ( Crotalus durissus terrificus), in order to determine whether respiratory sinus arrhythmia (RSA) occurred in a similar manner to that described for mammals. Resting ECG signals were recorded in undisturbed snakes using miniature datalogging devices, and the presence of oscillations in heart rate (f(H)) was assessed by power spectral analysis (PSA). This mathematical technique provides a graphical output that enables the estimation of cardiac autonomic control by measuring periodic changes in the heart beat interval. At fH above 19 min(-1) spectra were mainly characterised by low frequency components, reflecting mainly adrenergic tonus on the heart. By contrast, at f(H) below 19 min(-1) spectra typically contained high frequency components, demonstrated to be cholinergic in origin. Snakes with a f(H) > 19 min(-1) may therefore have insufficient cholinergic tonus and/or too high an adrenergic tonus acting upon the heart for respiratory sinus arrhythmia ( RSA) to develop. A parallel study monitored f(Hd) simultaneously with the intraperitoneal pressures associated with lung inflation. Snakes with a fH < 19 min(-1) exhibited a high frequency (HF) peak in the power spectrum, which correlated with ventilation rate (f(V)). Adrenergic blockade by propranolol infusion increased the variability of the ventilation cycle, and the oscillatory component of the f(H) spectrum broadened accordingly. Infusion of atropine to effect cholinergic blockade abolished this HF component, confirming a role for vagal control of the heart in matching f(H) and f(V) in the rattlesnake. A neuroanatomical study of the brainstem revealed two locations for vagal preganglionic neurones (VPN). This is consistent with the suggestion that generation of ventilatory components in the heart rate variability (HRV) signal are dependent on spatially distinct loci for cardiac VPN. Therefore, this study has demonstrated the presence of RSA in the HRV signal and a dual location for VPN in the rattlesnake. We suggest there to be a causal relationship between these two observations.

Characterization of the cellular component of polymorphous low-grade adenocarcinoma by immunohistochemistry and electron microscopy

In order to characterize the cellular component of the polymorphous low-grade adenocarcinoma (PLGA) of the salivary gland, a morphological and immunohistochemical study was carried out. Thirty cases of PLGA were studied by light microscopy and immunohistochemistry and five cases by transmission electron microscopy (TEM). The expression of cytokeratins (CKs) 7,8,10,13,14,18,19, vimentin and muscle-specific actin (MSA) was investigated through the streptavidin-biotin method. The majority of tumor cells stained for vimentin, CKs 8,18 and 7. CK 14 was positive in most cells of the papillary and trabecular sub-types. Although the expression of CKs 8,18 and 14 varied among the tumors sub-types, a straight relationship between each histologic pattern and the CK expression could not be delineated. MSA was reactive in only three tumors while CKs 10 and 13 were not detected in any tumor studied. The absence of MSA and the expression of CKs 8,18 and 7, in most of the tumor cells, lead to the hypothesis that myoepithelial cells are not the major cellular component of the PLGA. TEM revealed cells exhibiting microvilli and variable amounts of secretory granules, some of them suggesting an excretory activity. The presence of CKs 8, 18 and 7, added to the secretory granules, indicates that PLGA originates from cells located at the acinar-intercalated duct junction. (C) 1999 Elsevier B.V. Ltd. All rights reserved.

A partial least squares and principal component regression study of quinone compounds with trypanocidal activity

A quantitative structure-activity relationship (QSAR) study of 19 quinone compounds with trypanocidal activity was performed by Partial Least Squares (PLS) and Principal Component Regression (PCR) methods with the use of leave-one-out crossvalidation procedure to build the regression models. The trypanocidal activity of the compounds is related to their first cathodic potential (Ep(c1)). The regression PLS and PCR models built in this study were also used to predict the Ep(c1) of six new quinone compounds. The PLS model was built with three principal components that described 96.50% of the total variance and present Q(2) = 0.83 and R-2 = 0.90. The results obtained with the PCR model were similar to those obtained with the PLS model. The PCR model was also built with three principal components that described 96.67% of the total variance with Q(2) = 0.83 and R-2 = 0.90. The most important descriptors for our PLS and PCR models were HOMO-1 (energy of the molecular orbital below HOMO), Q4 (atomic charge at position 4), MAXDN (maximal electrotopological negative difference), and HYF (hydrophilicity index).

Collagen type VI is a component of the extracellular matrix microfibril network of the prostatic stroma

Stroma-epithelium relationships are of great relevance in prostatic morphogenesis and physiology, However, little knowledge exists about either stromal cells or extracellular matrix composition and arrangement in this system, Ultrastructural analysis revealed the existence of a microfibrillar system which occupies large areas of the rat prostatic stroma, In this work, we have applied immunocytochemistry and an ATP treatment for the ultrastructural identification of collagen type VI microfibrils, aiming at examining its participation in the prostatic microfibrillar network. Immunocytochemistry was also extended to a human case of prostatic nodular hyperplasia, Both methods succeeded in identifying collagen type VI in the rat ventral prostate, Collagen type VI is evenly distributed throughout the stroma but mainly associated with the basal lamina, collagen fibrils, and around the stromal cells, the use of ATP treatment allowed for the discrimination between collagen type VI and elastin-associated microfibrils, and demonstrated that these two classes of microfibrils establish an extended, mixed, and open network. The same aspects of association with the basal lamina, with stromal cells (particularly with smooth muscle cells), and with fibrillar components of the stroma were observed in the human tissue, We suggest that the collagen type VI and elastin-associated microfibril system may be involved in the control of some aspects of cellular behavior and may also play a structural role, maintaining the organ integrity after the deformations occurring under smooth muscle contraction.

NUCLEAR ALIGNMENT - CLASSICAL DYNAMIC-MODEL FOR THE U-238 U-238 SYSTEM

Dynamical properties of the U-238-U-238 system at the classical turning point, specifically the distance of closest approach, the relative orientations of the nuclei, and deformations have been studied at the sub-Coulomb energy of E(lab) = 6.07 MeV/nucleon using a classical dynamical model with a variable moment of inertia. Probability of favorable alignment for anomalous positron-electron pair emission through vacuum decay is calculated. The calculated small favorable alignment probability value of 0.116 is found to be enhanced by about 16% in comparison with the results of a similar study using a fixed moment of inertia as well as the results from a semiquantal calculation reported earlier.

Competition between anchoring and reversible photo-induced alignment of a nematic liquid crystal

We investigated the alignment induced on a nematic liquid crystal (LC) by a photo-aligned polymer film with azo-dye side groups. The orientation of the LC molecules can be manipulated in a reversible manner by irradiating the film with polarized light. We analyzed the competition between the orientation induced by the main chain, through rubbing of the film and that induced by the photo-aligned polymer. Anchoring strength for the different processing conditions are reported. The changes in film morphology caused by rubbing or photo-alignment could be captured by atomic force microscopy. The reversibility of the photo-induced alignment and the competition between the two anchoring mechanisms may allow recording and erasing of information in a LC display.

Batch, sequential and hybrid approaches to spacecraft sensor alignment estimation

Two Kalman-filter formulations are presented for the estimation of spacecraft sensor misalignments from inflight data. In the first the sensor misalignments are part of the filter state variable; in the second, which we call HYLIGN, the state vector contains only dynamical variables, but the sensitivities of the filter innovations to the misalignments are calculated within the Kalman filter. This procedure permits the misalignments to be estimated in batch mode as well as a much smaller dimension for the Kalman filter state vector. This results not only in a significantly smaller computational burden but also in a smaller sensitivity of the misalignment estimates to outliers in the data. Numerical simulations of the filter performance are presented.

Human chromosome aberrations induced in vitro by Paracoccidioides brasiliensis glycoproteic component (GP 43)

The in vitro cytogenetic effects of the 43-kDa molecular mass exocellular glycoproteic component (GP 43) from Paracoccidioides brasiliensis were studied in cultures from human lymphocytes. The sample included 10 healthy, white, non-smoking, non-related males (mean age of 31.3 ± 8.2 years). Besides the control, three concentrations of GP 43 (0.125, 1.25 and 5 μg/ml) were used. In each group, around 1000 cells were examined in search of chromosome aberrations, and 30,000 metaphases were analysed for the determination of the Mitotic Index. The authors conclude that GP 43 most probably causes inhibition of the cell cycle and aneugenic and clastogenic effects.

Batch and filter approaches to spacecraft sensor alignment estimation

Two Kalman-filter formulations are presented for the estimation of spacecraft sensor misalignments from inflight data. In the first the sensor misalignments are part of the filter state variable; in the second the state vector contains only dynamical variables, but the sensitivities of the filter innovations to the misalignments are calculated within the Kalman filter. This procedure permits the misalignments to be estimated in batch mode as well as a much smaller dimension for the Kalman filter state vector. This results not only in a significantly smaller computational burden but also in a smaller sensitivity of the misalignment estimates to outliers in the data. Numerical simulations of the filter performance are presented.