La Recherche

En considérant quatre bâtiments de bureaux construits dans le sud de la Suède au cours des dix dernières années, les auteurs analysent en détail les effets de la forme géométrique et de la configuration sur la consommation d'énergie. Leur conclusion est que la compacité peut réduire la consommation d'énergie mais que d'autres qualités importantes peuvent s'en trouver affectées.

Les auteurs sont architectes à la BS Konsult AB, à Stockholm.     

Degradation of poly(vinyl alcohol) in strongly alkaline solutions of hydrogen peroxide

The action of hydrogen peroxide and sodium hydroxide independently as well as in combination together with stabilizer formulation–consisting of magnesium sulphate (5 g/L), ethylenediamine tetraacetic acid (2 g/L), gluconic acid (2 g/L), and nonionic/anionic wetting agent (1.5 g/L)–on poly(vinyl alcohol) (PVA) was investigated at 30°C and 95°C. The effect of sodium hydroxide (5–25 g/L) alone was to bring about an enhancement in the viscosity of PVA most probably due to gel formation. The latter was favored at higher sodium hydroxide concentrations and longer duration (30 min) of treatment. The opposite holds true when hydrogen peroxide (35% w/v) was used alone at concentrations ranging from 2 to 20 mL/L. The viscosity of PVA decreased as the hydrogen peroxide concentration increased. Nevertheless, hydrogen peroxide alone could not cause complete dissolution of PVA even at 95°C for 30 min. On the other hand, complete dissolution of PVA could be achieved under the influence of stabilized alkaline solutions of hydrogen peroxide at 95°C in less than 10 min. It was postulated that, under the conditions used, oxidation of PVA by hydrogen peroxide prevailed over gel formation under the influence of sodium hydroxide.     

Reduction by gaseous ozone of Salmonella and microbial flora associated with fresh-cut cantaloupe

This research investigates the efficacy of gaseous ozone, applied under partial vacuum in a controlled reaction chamber, for the elimination of Salmonella inoculated on melon rind. The performance of high dose, short duration treatment with gaseous ozone, in this pilot system, on the microbial and sensory quality of fresh-cut cantaloupes was also evaluated. Gaseous ozone (10,000 ppm for 30 min under vacuum) reduced viable, recoverable Salmonella from inoculated physiologically mature non-ripe and ripe melons with a maximum reduction of 4.2 and 2.8 log CFU/rind-disk (12.6 cm(2)), respectively. The efficacy of ozone exposure was influenced by carrier matrix. Salmonella adhering to cantaloupe was more resistant to ozone treatment when suspended in skim-milk powder before aqueous inoculation to the rind. This indicated that organic matter interferes with the contact efficiency and resultant antimicrobial activity of gaseous ozone applied as a surface disinfectant. Conversely, in the absence of an organic carrier, Salmonella viability loss was greater on dry exocarp surfaces than in the wetted surfaces, during ozone treatment, achieving reductions of 2.8 and 1.4 initial log CFU/rind-disk, respectively. Gaseous ozone treatment of 5000 and 20,000 ppm for 30 min reduced total coliforms, Pseudomonas fluorescens, yeast and lactic acid bacteria recovery from fresh-cut cantaloupe. A dose Ct-value (concentration x exposure time) of 600,000 ppm min achieved maximal log CFU/melon-cube reduction, under the test conditions. Finally, fresh-cut cantaloupe treated with gaseous ozone, maintained an acceptable visual quality, aroma and firmness during 7-day storage at 5 degrees C. Conclusions derived from this study illustrate that gaseous ozone is an effective option to risk reduction and spoilage control of fresh and fresh-cut melon. Moreover, depending on the timing of contamination and post-contamination conditions, rapid drying combined with gaseous ozone exposure may be successful as combined or sequential disinfection steps to minimize persistence of Salmonella on the surface of cantaloupe melons and transference during fresh-cut processing of home preparation. Based on these results, greater efficacy would be anticipated with mature but non-ripe melons while ripe tissues reduce the efficacy of these gaseous ozone treatments, potentially by oxidative reaction with soluble refractive solids.     

The statistical fuel model, FRP

The reliability of nuclear fuel for LWR reactors is generally good, but there are still some failures caused by pellet-cladding interactions (stress corrosion). Only a very small fraction of the fuel pins in operation fail, and the nature of the failures indicates a statistical problem; therefore a statistical fuel model was developed. The statistical methods are either Monte Carlo simulation or a Taylor approximation. The statistical program utilizes a deterministic fuel performance code with a stress corrosion failure criterion, verified against experimental data.The failure probability for a power ramp was evaluated for different fuel designs and ramp conditions. It is shown that the failure probability can be quite large, even when a deterministic simulation (based on the average values for design and material data) is far from the failure criterion.     

Tuberculosis of the middle ear. A case report

A case of tuberculous otitis media in an immunocompetent 11-year-old boy is reported. The difficult diagnosis is highlighted. The bibliography was reviewed.     

A Holistic Solution to Icing by Acoustic Waves: De-Icing,Active Anti-Icing,Sensing with Piezoelectric Crystals,and Synergy with Thin Film Passive Anti-Icing Solutions

Icing has become a hot topic both in academia and in the industry given its implications in transport, wind turbines, photovoltaics, and telecommunications. Recently proposed de-icing solutions involving the propagation of acoustic waves (AWs) at suitable substrates may open the path for a sustainable alternative to standard de-icing or anti-icing procedures. Herein, the fundamental interactions are unraveled that contribute to the de-icing and/or hinder the icing on AW-activated substrates. The response toward icing of a reliable model system consisting of a piezoelectric plate activated by extended electrodes is characterized at a laboratory scale and in an icing wind tunnel under realistic conditions. Experiments show that surface modification with anti-icing functionalities provides a synergistic response when activated with AWs. A thoughtful analysis of the resonance frequency dependence on experimental variables such as temperature, ice formation, or wind velocity demonstrates the application of AW devices for real-time monitoring of icing processes.     

Short- and long-term effects of calcitonin and calcium administration on blood calcium, magnesium and inorganic phosphorus in post menopausal osteoporosis

As a consequence of the civil war that devastated Burundi in October 1993, more than 300,000 refugees settled in the neighboring country of Rwanda. We describe the outbreak of dysentery due to Shigella dysenteriae type 1 (Sd1) that developed in Nzangwa, a camp hosting some 20,000 Burundese refugees. Between November 17, 1993 and March 10, 1994, 6,122 cases of bloody diarrhea were notified by the health information system of the camp. The overall attack rate was 32.3%, and the fatality rate was 3.8%. Children under five years of age were the most affected group of the population. All dysentery cases were treated with nalidixic acid for 5 days. The compliance assessment showed that less than 50% of the ambulatory patients completed the 5-day regimen. From 35 stool samples obtained from the refugees, seven Sd1 strains were isolated, of which three were multi-resistant to nalidixic acid. These results confirmed the morbidity and mortality of Sd1 outbreaks in the displaced populations of Central Africa. We also emphasize the difficulties in implementing effective prevention measures and appropriate case management strategies in this environment. To improve the management of patients in large Sd1 outbreaks with limited resources, we devised a clinical classification of cases according to the risk of dying.     

Vortex configuration flow cell based on low-temperature cofired ceramics as a compact chemiluminescence microsystem

The integration of optical detection methods in continuous flow microsystems can highly extend their range of application, as long as some negative effects derived from their scaling down can be minimized. Downsizing affects to a greater extent the sensitivity of systems based on absorbance measurements than the sensitivity of those based on emission ones. However, a careful design of the instrumental setup is needed to maintain the analytical features in both cases. In this work, we present the construction and evaluation of a simple miniaturized optical system, which integrates a novel flow cell configuration to carry out chemiluminescence (CL) measurements using a simple photodiode. It consists of a micromixer based on a vortex structure, which has been constructed by means of the low-temperature cofired ceramics (LTCC) technology. This mixer not only efficiently promotes the CL reaction due to the generated high turbulence but also allows the detection to be carried out in the same area, avoiding intensity signal losses. As a demonstration, a flow injection system has been designed and optimized for the detection of cobalt(II) in water samples. It shows a linear response between 2 and 20 microM with a correlation of r > 0.993, a limit of detection of 1.1 microM, a repeatability of RSD = 12.4%, and an analysis time of 17 s. These results demonstrate the suitability of the proposal to the determination of compounds involved in CL reactions by means of an easily constructed versatile device based on low-cost instrumentation.     

Evaluation of the effects of a school breakfast program on attention and memory

The purpose of the study was to evaluate the impact of a school breakfast program in Sonora, Mexico. The study was conducted in four counties classified as extremely poor. Three hundred children from twelve schools pertaining to three counties under research received a school breakfast; one hundred and fifty children from four schools pertaining to a fourth county did not received school breakfast. Children were four to six years old. Attention, memory and cognition tests were applied before and after the program. Results showed an improvement for those groups receiving the breakfast program, specially on response speed and behavior executions. Group without breakfast showed better results on the pre-test, nevertheless, on the post-test, performances in both groups appear the same. At the beginning of school courses any county was different, but speed in selection and running show significatives differences for the schools. The program shows similar results on response speed, no matter social condition, nevertheless, program differentially affects the number of correct behavior executions on stimulus selection and reproduction. The breakfast program benefit children, but its effects are differentially distributed improving behavioral, repertories depending of children's group vulnerability.