Search

Acetic acid is a fermentation product of many microorganisms, including some that inhabit the food and guts of Drosophila. Here, we investigated the effect of dietary acetic acid on oviposition and larval performance of Drosophila. At all concentrations tested (0.34–3.4%), acetic acid promoted egg deposition by mated females in no-choice assays; and females preferred to oviposit on diet with acetic acid relative to acetic acid-free diet. However, acetic acid depressed larval performance, particularly extending the development time of both larvae colonized with the bacterium Acetobacter pomorum and axenic (microbe-free) larvae. The larvae may incur an energetic cost associated with dissipating the high acid load on acetic acid-supplemented diets. This effect was compounded by suppressed population growth of A. pomorum on the 3.4% acetic acid diet, such that the gnotobiotic Drosophila on this diet displayed traits characteristic of axenic Drosophila, specifically reduced developmental rate and elevated lipid content. It is concluded that acetic acid is deleterious to larval Drosophila, and hypothesized that acetic acid may function as a reliable cue for females to oviposit in substrates bearing microbial communities that promote larval nutrition.

In the oil and gas industry hydrogen sulfide is usually associated with hydrocarbon gases. This code of practice provides a way of classifying gas streams into materials where the hydrogen sulfide is the prime health hazard (high hydrogen sulfide materials, greater than 0.4% hydrogen sulfide) and where the hydrocarbons, through their ability to intoxicate and form explosive mixtures, are the prime hazard (low hydrogen sulfide materials, less than 0.4% hydrogen sulfide). This classification is based on alerting workers to the presence of hydrogen sulfide at 20 ppm in the air, or hydrocarbons at 10 percent of the lower explosive limit. Based on this classification, the code provides guidance on what type of gas monitoring is needed; exposure and evacuation standards; training requirements; respiratory protection; and working alone. The code draws attention to the way that liquids can cause hydrogen sulfide concentrations in the head space of tanks or sumps that are much higher than in the gas enter...

It is sought to determine the suitability of fluorine based gases, i.e. 1,1,1,2-Tetrafluoroethane (R-134a), for use in a micronozzle. Several experimental thrust measurements have already been made for micronozzles using air or nitrogen. However, air and nitrogen are too prohibitive in terms of transportation in nano/pico satellites. Fluorine based gases, although not as efficient, offer a huge payoff in terms of transportability. The efficiency of R-134a was found to be about 27% lower than that of nitrogen, while being multitudes better in terms of transportability. Unsteady flow was encountered for air and nitrogen, while completely unexpected behavior was exhibited by R-134a.Copyright © 2010 by ASME

Superconducting Tl–Ca–Ba–Cu–oxide films have been prepared on yttria stabilized zirconia substrates via the reaction of Tl2O vapor with precursor Ca–Ba–Cu–oxide films prepared by the spray pyrolysis of a solution of the metal nitrates. The vapor reaction process, evaluated in both air and oxygen ambients, was carried out in a two-zone reactor which permitted the independent control of the temperatures of the sample and of a boat containing thallium oxide. Sample temperatures of 865–905 °C and boat temperatures of 775–870 °C were investigated. X-ray diffraction analysis of the best samples, which were prepared in an oxygen ambient at sample temperatures of 895–900 °C and boat temperatures of 805–810 °C, revealed the presence of a highly oriented Tl2Ca2Ba2Cu3O10+y phase with a trace of the Tl2CaBa2Cu2O8+y phase. FWHM's of ∼2°θ were obtained in x-ray rocking curve analyses of the oriented 2223 phase. Tc (0) values of 95–105 K were measured for the better samples, and a zero field critical current density of 28 800 amps/cm2 was measured at 77 K for the best sample. SEM micrographs taken of the highest Jc samples reveal a highly textured structure consisting of platelike crystals.

Aluminum corrosion in a polymer-coated circuit model was studied using in-situ microscopy coupled with time-lapse video recording. Pinholes in the polymer coating and exposure to water with bias voltage of 40V applied between adjacent aluminum tracks resulted in fast anode corrosion, accompanied by gas evolution. A mathematical model is developed that is in good agreement with the observed current-time relationship. The rate of corrosion is controlled by the resistance of a 6000A thick water film occupying the space of the corroded Al film between wafer and polymer coating. A tentative corrosion mechanism is proposed.