Contribuição da densidade do PSA para predizer o câncer da próstata em pacientes com valores de PSA entre 2,6 e 10,0 ng/ml

OBJETIVO: Estudar o perfil dos pacientes submetidos a biópsia prostática, determinando possíveis padrões que, associados aos níveis de PSA entre 2,6 e 10,0 ng/ml, possam levar a uma diminuição de biópsias desnecessárias. MATERIAIS E MÉTODOS: De 2007 a 2009, foi realizado um estudo transversal com 1.282 indivíduos submetidos a biópsia prostática e que apresentavam níveis de PSA entre 2,6 e 10,0 ng/ml. RESULTADOS: A prevalência de câncer foi de 28,6%. Pacientes com câncer eram, em média, mais idosos, com valores de PSA e densidade de PSA mais altos e menor volume da próstata. Na análise da densidade de PSA, os pacientes com câncer tiveram média de 0,31 ng/ml/cc, enquanto nos pacientes com resultado negativo a média foi de 0,10 ng/ml/cc. Utilizando como critério de positividade para câncer o ponto de corte de densidade de PSA de 0,15 ng/ml/cc, obtivemos especificidade de 74% e sensibilidade de 70%. Para aumentar a sensibilidade é preciso reduzir o ponto de corte. Com o valor 0,09 ng/ml/cc, obtivemos sensibilidade de 84% (IC 95%: 80-87%) e especificidade de 75% (IC 95%: 72-78%). CONCLUSÃO: O uso sistemático da densidade de PSA na indicação de prosseguimento da investigação do paciente com biópsia poderia reduzir a quantidade de procedimentos desnecessários.

Dopplerfluxometria de artérias oftálmicas e avaliação da função endotelial nas formas precoce e tardia da pré-eclâmpsia

OBJETIVO: Avaliar possíveis diferenças entre a disfunção endotelial, avaliada pela dilatação fluxo-mediada, e hiperperfusão central, avaliada por dopplerfluxometria da artéria oftálmica, entre pacientes portadoras da forma precoce e tardia da pré-eclâmpsia. MATERIAIS E MÉTODOS: O teste de dilatação fluxo-mediada e a dopplerfluxometria da artéria oftálmica foram obtidos de 81 gestantes, sendo 56 portadoras de pré-eclâmpsia (26 na forma precoce e 30 na forma tardia) e 25 gestantes saudáveis (grupo controle). RESULTADOS: Portadoras de pré-eclâmpsia apresentaram valores menores de dilatação fluxo-mediada quando comparadas ao grupo controle, tanto na forma precoce (7,62 ± 5,42% × 14,12 ± 6,14%; p = 0,02) como na forma tardia (5,83 ± 4,12% × 14,12 ± 6,14%; p = 0,00). Não houve diferença quando foram comparadas as duas formas (7,62 ± 5,42% × 5,83 ± 4,12%; p = 0,09). A dopplerfluxometria da artéria oftálmica apresentou-se significativamente menor nas pacientes portadoras de pré-eclâmpsia quando comparadas ao grupo controle, tanto na forma precoce (0,631 ± 0,024 × 0,737 ± 0,032; p = 0,01) como na forma tardia (0,653 ± 0,019 × 0,737 ± 0,032; p = 0,03). Não houve diferença entre as duas formas de apresentação (0,631 ± 0,024 × 0,653 ± 0,019; p = 0,12). Os resultados basicamente demonstram redução nos valores de dilatação fluxo-mediada e dopplerfluxometria da artéria oftálmica nas formas tardia e precoce da pré-eclâmpsia quando comparadas ao grupo controle, sem, contudo, diferenças significativas entre as duas formas de apresentação da doença. CONCLUSÃO: Os resultados indicam a presença de disfunção endotelial e hiperperfusão central em gestantes com pré-eclâmpsia, tanto na forma precoce como na tardia.

Estudo da adsorção de hidrogênio e sulfeto na superfície de paládio: aspectos experimentais (eletroquímica) e teóricos (ab initio e Teoria do Funcional da Densidade)

The adsorption of H and S2- species on Pd (100) has been studied with ab initio, density-functional calculations and electrochemical methods. A cluster of five Pd atoms with a frozen geometry described the surface. The computational calculations were performed through the GAUSSIAN94 program, and the basis functions adapted to a pseudo-potential obtained by using the Generator Coordinate Method adapted to the this program. Using the cyclic voltammetry technique through a Model 283 Potentiostat/Galvanostat E.G.&G-PAR obtained the electrochemical results. The calculated chemisorption geometry has a Pd-H distance of 1.55Å, and the potential energy surface was calculated using the Becke3P86//(GCM/DFT/SBK) methodology. The adsorption of S2- ions on Pd surface obtained both through comparison between the experimental and theoretical results, at MP2 level, suggest a S2- absorption into the metallic cluster. The produced Pd-(S2-) system was show to be very stable under the employed experimental conditions. The paper has shows the powerful aid of computational methods to interpret adsorption experimental data.

Índices de reatividade química a partir da teoria do funcional de densidade: formalismo e perspectivas

The fundaments of the modern Density Functional Theory (DFT), its basic theorems, principles and methodology are presented. This review also discuss important and widely used concepts in chemistry but that had not been precisely defined until the development of the DFT. These concepts were proposed and used from an empirical base, but now their precise definition are well established in the DFT formalism. Concepts such as chemical potential (electronegativity), hardness, softness and Fukui function are presented and their consequences to the understanding of chemical reactivity are discussed.

Fixação de nitrogênio: estrutura, função e modelagem bioinorgânica das nitrogenases

Biological nitrogen fixation, catalyzed by nitrogenases, contributes about half of the nitrogen needed to global agriculture. For forty years synthetic chemists and theoreticians have tried to understand and model the structure and function of this important metalloenzyme. Ten years after the first report on the crystal structure of the MoFe protein, scientists still have not been able to synthesize a chemical equivalent of the FeMo cofactor nor the structure knowledge revealed the key to its catalytic activity. This paper with 104 references presents a review of the most relevant advances in chemical nitrogen fixation and their relation with the nitrogenases.

Propriedades eletrônicas e estruturais do PbTiO3: teoria do funcional de densidade aplicada a modelos periódicos

Calculations based on density functional theory at the B3LYP hybrid functional level applied to periodic models have been performed to characterize the structural and electronic properties of PbTiO3. Two different slab terminations (PbO and TiO2) have been considered to obtain and discuss the results of band structure, density of states, charge distribution on bulk and surface relaxation. It is observed that the relaxation processes are most prominent for the Ti and Pb surface atoms. The electron density maps confirm the partial covalent character of the Ti-O bonds. The calculated optical band gap and other results are in agreement with experimental data.

Transesterificação de óleos vegetais: caracterização por cromatografia em camada delgada e densidade

We studied the transesterification of two vegetable oils: soybean and waste frying oil. The main problem of transesterification is related to the measurement of the ethyl ester content. In this work we used a quick analytical method for assessing the ethyl ester fraction of the purified fuel-grade transesterification products by applying a simple correlation with density. If the ester content is higher than 85% by weight the correlation allows the determination by a single density measurement. This method is suitable for control and determines the ethyl ester quickly and simply.

Espectrofotometria de longo caminho óptico em espectrofotômetro de duplo-feixe convencional: uma alternativa simples para investigações de amostras com densidade óptica muito baixa

We describe the design and tests of a set-up mounted in a conventional double beam spectrophotometer, which allows the determination of optical density of samples confined in a long liquid core waveguide (LCW) capillary. Very long optical path length can be achieved with capillary cell, allowing measurements of samples with very low optical densities. The device uses a custom optical concentrator optically coupled to LCW (TEFLON® AF). Optical density measurements, carried out using a LCW of ~ 45 cm, were in accordance with the Beer-Lambert Law. Thus, it was possible to analyze quantitatively samples at concentrations 45 fold lower than that regularly used in spectrophotometric measurements.

Poluição e a densidade de vegetação: BTEX em algumas áreas públicas de Curitiba - PR, Brasil

The occurrence of benzene, toluene, ethylbenzene, and xylenes (BTEX) in some public areas of Curitiba-PR, Brazil, was evaluated. Their concentrations were then related to the vegetation's density in each area. Average benzene concentrations varied from 3.9 to 6.1 μg m-3, with higher values occurring in poorly dense vegetation areas. For toluene, average concentrations ranged from 6.5 to 7.2 μg m-3. The effect of such pollutants was evaluated by means of a bio indicator, Tillandsia stricta. Variation in total chlorophyll content and in stomatic density were detected in some samples and may be related to the BTEX concentrations found in the studied areas.

Uma análise do coeficiente de remoção de poluentes em função do espectro de gotas de chuva em diferentes localidades no Brasil e Alemanha

The pollutant transference among reservoirs atmosphere-hydrosphere, relevant to the atmospheric chemistry, depends upon scavenging coefficient (Λ) calculus, which depends on the raindrop size distribution as well as on the rainfall systems, both different to each locality. In this work, the Λ calculus will be evaluated to gas SO2 and particulate matter fine and coarse among five sites in Germany and two in Brazil. The results show three possible classifications in function of Λ, comparable to literature, however with a greater range due to the differences of rainfall system sites. This preliminary study supports future researches

Investigação do mecanismo de catálise ROMP do norborneno utilizando métodos de funcional de densidade

This work presents a density functional theory study of the norbornene ROMP metathesis reactions. The energies have been calculated in a Grubbs catalyst model Cl2(PH3)2Ru=CH2. The geometries and energy profile are similar to the Grubbs metilydene (Cl2(PCy3)2Ru=CH2 real model. It was found that the metathesis reaction proceeds via associative mechanism (catalyst-norbonene) followed by dissociative substitution of a phosphine ligand with norbonene, giving a monophosphine complex. The results are in reasonable agreement with the available experimental data. The dissociation energy of the phosphines is predicted to be 23.2 kcal mol-1.

Condições de equilíbrio termodinâmico: a função disponibilidade

The thermodynamic equilibrium is a state defined by conditions which depend upon some characteristics of the system. It requires thermal, mechanical, chemical and phase equilibrium. Continuum thermodynamics, its radical restriction usually called homogeneous processes thermodynamics, as well as the classical thermodynamic science of reversible processes, each of them defines equilibrium in a differing way. But these definitions lead to the same physical contents.

Determinação da densidade de corrente de corrosão em meios de baixa condutividade: uso de microeletrodos para minimizar a queda ôhmica

The gravimetric and electrochemical tests are the most common techniques used in determining the corrosion rate. However, the use of electrochemical polarization is limited to electrolytes with sufficient conductivity for which Tafel curves are linear. In this study, we investigated a technique in which working microelectrodes of AISI 1020 steel were used to obtain the Tafel curves in diesel oil. The strategy was to reduce the electrode area and hence the ohmic drop. The diameter of the microelectrode was reduced to a value where the compensation of the Tafel curves became unnecessary. The results showed that for electrodes with diameters below 50 μm, the ohmic drop tends to a minimum and independent of the microelectrode diameter.