Cytostatic activity of some essential oils against HEp-2 cells

Samples of different essential oils have been tested for their cytostatic activity. The samples of cinnamon and clove essential oils showed a strong in vitro activity against HEp-2 cells.     

Switching and linear power stages evaluation for PEM fuel cell emulation

A fuel cell‐based power systems emulator designed to test devices and loads intended to interact with real prototypes is presented. The emulator uses a digital processing device and electrical power systems, evaluating the impact of using either switching or linear power stages in the emulator capabilities. A real fuel cell prototype is emulated using a parameterized physical fuel cell model, which is computed online by a digital device. Also, several power stages not previously used specifically for this application, with different efficiencies and performances, were developed and analysed. One of the power stages was based on a two‐inductor step‐down DC/DC converter for a switching power stage instead of the classical buck structure that is more prone to duty cycle saturation in transients at low output voltages. The other ones used high‐power operational amplifiers for a linear power stage and linear regulators for a scalable linear power stage. Finally, the emulation system and the power stages were evaluated and validated using experimental data of a real fuel cell prototype. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermal decomposition of 2-methylpyridine N-oxide: Effect of temperature and influence of phosphotungstic acid as the catalyst

The thermal decomposition of 2-methylpyridine N-oxide was studied at temperatures between 190 °C and 220 °C using an Automatic Pressure Tracking Adiabatic Calorimeter. The effect of the catalyst on the decomposition was evaluated using different amounts of phosphotungstic acid. It was determined that 2-methylpyridine N-oxide decomposes faster with low amounts of catalyst and temperatures above 200 °C. Below 200 °C, the decomposition is very slow. For the cases presented here, the decomposition reaction was accompanied by substantial production of non-condensable gasses, and 2-methylpyridine and pyridine were identified as the main decomposition products.     

Resonant Meta-Surface Superstrate for Single and Multifrequency Dipole Antenna Arrays

The design of a multifrequency dipole antenna array based on a resonant meta-surface superstrate is proposed. The behavior of a single element that is closely placed to a meta-surface is experimentally investigated. The proposed meta-surface is based on resonating unit cells formed by capacitively loaded strips and split ring resonators. By tuning a dipole antenna to the pass band of the meta-surface, the physical area is effectively illuminated enhancing the radiation performance. The gain, radiation efficiency and effective area values of the whole configuration are compared to the ones obtained with a single dipole without superstrate. Radiation efficiency values for the proposed configuration of more than 80% and gain values of more than 4.5 plusmn 1 dB are obtained. Based on this configuration, simulated results of a multifrequency antenna array are presented. Distinctive features of this configuration are high isolation between elements (20 dB for a distance of lambda₀/4), and low back radiation.     

The effect of grinding on precipitated magnesium hydroxide

Magnesium hydroxide, prepared by precipitation, was ground in a vibratory ball mill for 733 h. Samples were withdrawn at intervals, and examined by thermogravimetric analysis and by X-ray diffraction (the broadening of the lines being analysed using integral breadths), and their specific surfaces were determined by adsorption of nitrogen at —183°. The results indicate that the particles initially consist of small piles of plate-like crystallites and that they become progressively fractured across their (001) faces, until they are approximately equi-dimensional. By a process of shearing and re-adhesion, the piles become increasingly turbostratic in structure, but distortion of the lattice appears only after 350 h. Water is adsorbed on the surface temporarily exposed during grinding and some, at least, of it becomes buried in the interior of the particles.     

Analysis of microbial mixtures by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Many different laboratories are currently developing mass-spectrometric techniques to analyze and identify microorganisms. However, minimal work has been done with mixtures of bacteria. To demonstrate that microbial mixtures could be analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), mixed bacterial cultures were analyzed in a double-blind fashion. Nine different bacterial species currently in our MALDI-MS fingerprint library were used to generate 50 different simulated mixed bacterial cultures similar to that done for an initial blind study previously reported (Jarman, K. H.; Cebula, S. T.; Saenz, A. J.; Petersen, C. E.; Valentine, N. B.; Kingsley, M. T.; Wahl, K. L. Anal. Chem. 2000, 72, 1217-1223). The samples were analyzed by MALDI-MS with automated data extraction and analysis algorithms developed in our laboratory. The components present in the sample were identified correctly to the species level in all but one of the samples. However, correctly eliminating closely related organisms was challenging for the current algorithms, especially in differentiating Serratia marcescens, Escherichia coli, and Yersinia enterocolitica, which have some similarities in their MALDI-MS fingerprints. Efforts to improve the specificity of the algorithms are in progress.     

Environmental risk of particulate and soluble platinum group elements released from gasoline and diesel engine catalytic converters

A comparison of platinum-group element (PGE) emission between gasoline and diesel engine catalytic converters is reported within this work. Whole raw exhaust fumes from four catalysts of three different types were examined during their useful lifetime, from fresh to 80,000 km. Two were gasoline engine catalysts (Pt-Pd-Rh and Pd-Rh), while the other two were diesel engine catalysts (Pt). Samples were collected following the 91441 EUDC driving cycle for light-duty vehicle testing, and the sample collection device used allowed differentiation between the particulate and soluble fractions, the latter being the most relevant from an environmental point of view. Analyses were performed by inductively coupled plasma-mass spectrometry (ICP-MS) (quadrupole and high resolution), and special attention was paid to the control of spectral interference, especially in the case of Pd and Rh. The results obtained show that, for fresh catalysts, the release of particulate PGE through car exhaust fumes does not follow any particular trend, with a wide range (one-two orders of magnitude) for the content of noble metals emitted. The samples collected from 30,000-80,000 km present a more homogeneous PGE release for all catalysts studied. A decrease of approximately one order of magnitude is observed with respect to the release from fresh catalysts, except in the case of the diesel engine catalyst, for which PGE emission continued to be higher than in the case of gasoline engines. The fraction of soluble PGE was found to represent less than 10% of the total amount released from fresh catalysts. For aged catalysts, the figures are significantly higher, especially for Pd and Rh. Particulate PGE can be considered as virtually biologically inert, while soluble PGE forms can represent an environmental risk due to their bioavailability, which leads them to accumulate in the environment.     

Condom use with a casual partner: What distinguishes college students' use when intoxicated?

Determining alcohol's precise role in sexual risk taking has proven to be an elusive goal. Past research has produced mixed results, depending on characteristics of individuals, their partners, and the situation, as well as how the link between alcohol consumption and sexual behavior was assessed. In this study, cross-sectional predictors of the frequency of condom use were examined for 298 heterosexual college students at a large urban university. In hierarchical multiple regression analyses that controlled for frequency of condom use when sober, alcohol expectancies regarding sexual risk taking and self-efficacy regarding condom use when intoxicated were significant predictors of frequency of condom use when intoxicated. These findings highlight the importance of targeting beliefs about alcohol's disinhibiting effects in STD- and HIV-prevention programs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)