Efficacy and acceptability of two monophasic oral contraceptives containing ethinylestradiol and either desogestrel or gestodene

In this study, we have examined the effects of authentic nitric oxide (NO), NO+ (NOBF4), glutathione (GSH), glutathione disulphide (GSSG), and S-nitrosoglutathione (GSNO) in the presence and absence of Cu2+, which thermally releases NO from S-nitrosothiols on the transport of L-arginine into the human platelet. The K(M,apparent) was unaffected by NO, NO+, GSH, and GSNO. However, Cu2+ lowered K(M,apparent) by approximately 2.85-fold. Cu2+-dependent lowering of K(M,apparent) was also observed, albeit to a smaller extent when this ion was mixed with GSH (approximately 1.9-fold lower) and GSNO (approximately 2.0-fold). GSSG also lowered K(M,apparent) by approximately 1.5-fold. The Vmax,apparent of L-arginine uptake was unaffected by NO, NO+, GSH, and Cu2+. Vmax,apparent was stimulated by to the largest extent by GSNO (approximately 2.28-fold) and GSNO plus Cu2+ (approximately 2.7-fold). GSSG and GSH plus Cu2+ also increased Vmax,apparent by approximately 1.9-fold. When these parameters are expressed in terms of transport efficiency (Vmax/K(M)) the largest effect of nearly 4.7-fold (over controls) was obtained by a combination of GSNO plus Cu2+. These results suggest that platelet L-Arg transport is not affected either by NO or NO+ but by a thiol-disulphide exchange reactions on the platelet L-Arg transporter, brought about by GSNO and GSSG. Based on these results, a GSNO/GSSG/Cu2+ dependent regulatory mechanism for the uptake of L-arginine in human platelets has been proposed.     

Techniques applied to the study of microbial impact on building materials

This paper presents various techniques for materials characterisation in relation with the question of microbial impact. Application examples of some of these techniques are described as well as the respective results obtained by researchers working in this field. Additional readings are also reported.     

A Digitally Programmable A/D Converter for Smart Sensors Applications

Nonlinear analog-to-digital conversion in smart sensor applications is an important topic since signal digitization and linearization can be performed in a single step near the transducer. In this paper a double pulsewidth modulated (PWM) scheme for nonlinear analog-to-digital conversion is presented. Calibration or auto-calibration data stored in the smart sensor's memory define the nonlinear profile characteristic of the transducer and provide the required data to obtain the inverse function of the analog-to-digital converter (ADC) transfer curve. Basically, as a function of the transducer's nonlinearity degree, the input voltage range of the ADC is segmented in a continuous set of subintervals and, for each of these subintervals, a second-order correction term based on a PWM A/D conversion is used to obtain a linear characteristic for the smart sensor. Additional advantages of this method result from its easy implementation in low-cost microcontrollers that include generally comparator inputs and PWM outputs. A flexible and programmable A/D conversion solution can be dynamically adapted to variations of the transducer's nonlinearity profile, and an increased resolution can be achieved at the expense of a lower conversion rate. Some MATLAB simulations and experimental results obtained with a square-root airflow transducer will be presented in the final part of the paper     

Performance Evaluation of (Ethylene-co-Vinyl Acetate) Copolymers as Pour Point Reducing Agents for Petroleum Middle Distillates

Petroleum, as well as its middle distillate fractions (boiling between 150-400°C), shows a tendency to crystalize paraffin molecules whenever temperature is lowered below the cloud point. Paraffin deposition may occur in storage tanks, pipelines, or conduits, this leading to the impairing of fluid pumping, even with filter plugging of diesel engines. Such drawback may be overtaken by the addition of chemical compounds aiming at inhibiting paraffin deposition. Such inhibitors are not universally effective, since they are operational for a certain molecular weight interval only. This work relates the performance evaluation of commercial poly(ethylene-co-vinyl acetate) samples of varied molecular weights resulting from mechanical shear experiments. Samples included one kind of diesel oil and three kinds of base lube oils: light neutral, medium neutral, and heavy neutral or bright stock oils. Results indicated that mechanical shear was effective only for samples containing 10% w/w of vinyl acetate. Additive performance as lube oil pour point reducing agents is a function of the copolymer composition only for samples the molecular weight of which is compatible with the molecular weight of the oil paraffins.     

Athlete''s heart in elite disabled athletes

Nineteen children with congenital upper alimentary tract malformation were studied prospectively at the Department of Paediatrics, University College Hospital (UCH), Ibadan, over a period of 12 months. There were 20 cases, grouped into six types comprising congenital hypertrophic pyloric stenosis, seven; cleft lip and/or cleft palate, five; oesophagal atresia with or without tracheo-oesophageal fistula, four; jejunal atresia two and a case each of achalasia and annular pancreas. One patient had oesophageal atresia and congenital hypertrophic pyloric stenosis. The mortality rate was 31.51% (six out of nineteen). Low mortality was recorded in cases of cleft lip and/or palate, while mortalities of over 70% were recorded among cases of jejunal atresia, and oesophageal atresia with or without tracheo-oesophageal fistul. The common causes of death were milk feed aspiration (28.6%-two cases), purulent peritonitis (14.3%-one case), and probable septicaemia (14.3%-one case). The cause of death in two cases could not be determined.     

High-temperature hydrogen sulfide corrosion on the heat-affected zone of the AISI 444 stainless steel caused by Venezuelan heavy petroleum

The aim of this study was to evaluate the effect of welding on the corrosion resistance of the heat-affected zone (HAZ) of the AISI 444 ferritic stainless steel in medium containing Venezuelan heavy oil. AISI 444 steel plates were welded through the use of three levels of welding heat input (4, 6 and 8 kJ/cm). Samples were extracted from the welded plates and thermally treated in three different temperatures (200, 300 e 400 °C), while immerged in petroleum for a period of 4 h. Optical microscopy (OM), scanning electronic microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for the analysis of the surface and transversal section of the joint. Electrochemical trials of cyclic potentiokinetic reactivation of double loop (EPR-DL) were also carried out. It has been concluded that the temperature of treatment has direct influence on the level of material corrosion and that the increase in the welding heat input contributes to a higher level of corrosion.     

Dispersion characteristics of asymmetric coupled anisotropic dielectric waveguides using FDFD

The formulation is developed in the frequency domain and the finite difference method is used for the numerical solution of the scalar wave equation, written in terms of the transverse components of the magnetic field. As a result a conventional eigenvalue problem is obtained without the presence of spurious modes due to the implicit inclusion of the divergence of the magnetic field equal to zero. The formulation is developed to include biaxial anisotropic dielectrics with an index profile varying arbitrarily in the cross section of the waveguide under analysis. This formulation is then applied to the analysis of the influence on the dispersion characteristics of the dimensions of asymmetric coupled rectangular uniaxial anisotropic dielectric waveguides. As expected, the reduction of the height or the width of one of the rectangular dielectric waveguides causes the dispersion curves to move towards higher frequencies.