Microfabricated differential mobility spectrometry with pyrolysis gas chromatography for chemical characterization of bacteria

A microfabricated drift tube for differential mobility spectrometry (DMS) was used with pyrolysis-gas chromatography (py-GC) to chemically characterize bacteria through three-dimensional plots of ion intensity, compensation voltage from differential mobility spectra, and chromatographic retention time. The DMS analyzer provided chemical information for positive and negative ions simultaneously from chemical reactions between pyrolysis products in the GC effluent and reactant ions of H+(H2O)n and O2-(H2O)n in air at ambient pressure. Authentic standards for chemicals formed in the pyrolysis of bacteria showed favorable matches with plots from py-GC/DMS analysis and were supported by py-GC/MS results. These and other yet-unidentified constituents provided a means to distinguish Escherichia coli from Micrococcus luteus. A Gram-positive spore former (Bacillus megaterium) was distinguished by an abundant peak for crotonic acid evident in positive and negative ions and not observed with M. luteus. In contrast, plots from py-GC/DMS of lipid A and lipoteichoic acid showed poor matches to plots for a Gram-negative (E. coli) bacterium and a Gram-positive (M. luteus) bacterium and the differences were attributed to differences in genus sources of the biopolymers. A significant percentage of the chemical information available in py-GC/DMS is unidentified, and the analytical utility must be established. Precision in the chemical measurement was determined as +/- 0.2 V, 10% relative standard deviation (RSD), and +/- 0.05 min for compensation voltage, peak intensity, and retention time, respectively. The minimum number of total bacteria (cell forming units) detected was 6000 though detection limits and resolution could be varied by the magnitude of the separation voltage in the differential mobility spectrometer.     

Hygrothermische Beanspruchung und Lebensdauer von Wärmedämm‐Verbundsystemen

Hygrothermal loads and service life of external wall insulation systems. Service life and aging behaviour of external wall systems depend on their hygrothermal loads. Apart from the fluctuating climatic conditions temperature, solar radiation and humidity there are often additional exterior or interior sources of moisture, e.g. driving rain, construction moisture or surface condensation acting on facades. External wall insulation systems (ETICS = E xternal T hermal I nsulation C omposite S ystems) are especially affected due to their low mass. However, the long‐term observation by repeated inspections of the same objects over a period of 30 years proves that ETICS show not more damage than traditional facades. Apart from minor esthetical problems due to soiling or microbial growth their long‐term behaviour is very encouraging. Maintained at normal intervals ETICS are as durable as traditionally rendered masonry walls.     

Experiences in autotuning matrix multiplication for energy minimization on GPUs

In this paper, we report extensive results and analysis of autotuning the computationally intensive graphics processing units kernel for dense matrix–matrix multiplication in double precision. In contrast to traditional autotuning and/or optimization for runtime performance only, we also take the energy efficiency into account. For kernels achieving equal performance, we show significant differences in their energy balance. We also identify the memory throughput as the most influential metric that trades off performance and energy efficiency. As a result, the performance optimal case ends up not being the most efficient kernel in overall resource use. Copyright © 2015 John Wiley & Sons, Ltd.     

Detection of 2-alkylcyclobutanones,markers for irradiated foods,in adipose tissues of animals fed with these substances

Laboratory rats received a freshly prepared drinking fluid containing 0.005% 2-tetradecyl- or 2-tetradecenyl-cyclobutanones daily for 4 months. These two compounds were recovered in the adipose tissues of the animals that consumed them. Less than 1% of the 2-alkylcyclobutanones ingested daily were excreted in the feces. In addition, our data indicate that 2-alkylcyclobutanones are able to cross the intestinal barrier, to enter into the bloodstream, and to be stored in the adipose tissue of an animal. However, the amounts of these substances detected in the adipose tissues and in the feces were much smaller than the amounts ingested.