Applications of SOI-based optical MEMS

After microelectromechanical systems (MEMS) devices have been well established, components of higher complexity are now developed. Particularly, the combination with optical components has been very successful and have led to optical MEMS. The technology of choice for us is the silicon-on-insulator (SOI) technology, which has also been successfully used by other groups. The applications presented here give an overview over what is possible with this technology. In particular, we demonstrate four completely different devices: a) a 2 × 2 optical cross connector (OXC) with an insertion loss of about 0.4 dB at a switching time of 500 μs and its extension to a 4 × 4 OXC, b) a variable optical attenuators (VOA), which has an attenuation range of more than 50 dB, c) a Fourier transform spectrometer (FTS) with a spectral resolution of 6 nm in the visible, and d) an accelerometer with optical readout that achieves a linear dynamic range of 40 dB over ±6 g. Except for the FTS, all the applications utilized optical fibers, which are held and self-aligned within the MEMS component by U-grooves and small leaf springs. All devices show high reliability and a very low power consumption

A school-based physical activity program to improve health and fitness in children aged 6–13 years ("Kinder-Sportstudie KISS"): study design of a randomized controlled trial [ISRCTN15360785]

BACKGROUND: Childhood obesity is the result of a long lasting imbalance between energy intake and energy expenditure. A major contributing factor is physical inactivity which is closely linked to bone health, cardiovascular disease risk, fitness and psychological factors. The school seems to provide an excellent setting to enhance levels of physical activity (PA). However, there is insufficient data from previous school-based intervention trials on how to enhance overall PA. It is also unknown whether an intervention aimed at increasing PA is effective in improving the children's health. The purpose of this paper is to outline the design of a school-based randomized, controlled trial (RCT) aiming to increase overall PA and to improve fitness and health in 6- to 13-year-old children. METHODS/DESIGN: 15 schools were randomized to the intervention (n = 9) or the control (n = 6) group, stratified by geographic region (urban vs. rural) and by age (1(st )and 5(th )grade). Participation was given for all children in the intervention group since in this group the intervention was part of the normal school curriculum. The intervention during one academic year consisted of: 1. two additional physical education classes per week given by trained physical education teachers adding up to a total of five PA classes per week, 2. short PA breaks (2–5 min each) during academic lessons, 3. PA home work, and 4. adaptation of recreational areas around the school. All children underwent anthropometric measurements, blood pressure assessment, fitness testing, measurement of PA and they filled out questionnaires. At least 70% of all children agreed to blood sampling and measurements of body composition and bone mineral measurements by dual energy x-ray absorptiometry. The primary endpoints of the study after one year were an increase in total PA by accelerometry, an increase in aerobic fitness measured by the 20 m shuttle run, a decrease in percent body fat derived from skinfold measurements and an increase in quality of life as assessed by the child health questionnaire in the intervention group compared to the control group. Secondary outcomes were overall fitness, differences in body composition including body fat distribution, cardiovascular risk factors, psychosocial health, bone mineral content and density of femur, lumbar spine and total body and food intake. DISCUSSION: Our preliminary data suggest that the children were representative of Swiss children with respect to sex, socio-demographic status, and body mass index. Short-term results can be expected by the beginning of 2007. We hypothesized that our intervention will lead to an increase in PA, fitness and overall health. Based on our data, we aim to provide important information regarding the influence of such an intervention on these outcome measures in school-aged children and to provide nationwide guidelines to improve PA in children

Stochastic and differential activation of σB and PrfA in Listeria monocytogenes at the single cell level under different environmental stress conditions

During host infection, the foodborne pathogen Listeria monocytogenes must sense and respond to rapidly changing environmental conditions. Two transcriptional regulators, the alternative sigma factor B (σB) and the Positive Regulatory Factor A (PrfA), are key contributors to the transcriptomic responses that enable bacterial survival in the host gastrointestinal tract and invasion of host duodenal cells. Increases in temperature and osmolarity induce activity of these proteins; such conditions may be encountered in food matrices as well as within the host gastrointestinal tract. Differences in PrfA and σB activity between individual cells might affect the fate of a cell during host invasion, therefore, we hypothesized that PrfA and σB activities differ among individual cells under heat and salt stress. We used fluorescent reporter fusions to determine the relative proportions of cells with active σB or PrfA following exposure to 45°C heat or 4% NaCl. Activities of both PrfA and σB were induced stochastically, with fluorescence levels ranging from below detection to high among individual cells. The proportion of cells with active PrfA was significantly higher than the proportion with active σB under all tested conditions; under some conditions, nearly all cells had active PrfA. Our findings further support the growing body of evidence illustrating the stochastic nature of bacterial gene expression under conditions that are relevant for host invasion via food-borne, oral infection

Cold-Shock Domain Family Proteins (Csps) Are Involved in Regulation of Virulence, Cellular Aggregation, and Flagella-Based Motility in Listeria monocytogenes

Cold shock-domain family proteins (Csps) are highly conserved nucleic acid binding proteins regulating the expression of various genes including those involved in stress resistance and virulence in bacteria. We show here that Csps are involved in virulence, cell aggregation and flagella-based extracellular motility of Listeria monocytogenes. A L. monocytogenes mutant deleted in all three csp genes (ΔcspABD) is attenuated with respect to human macrophage infection as well as virulence in a zebrafish infection model. Moreover, this mutant is incapable of aggregation and fails to express surface flagella or exhibit swarming motility. An evaluation of double csp gene deletion mutant (ΔcspBD, ΔcspAD and ΔcspAB) strains that produce single csp genes showed that there is redundancy as well as functional differences among the three L. monocytogenes Csps in their contributions to virulence, cellular aggregation, flagella production, and swarming motility. Protein and mRNA expression analysis further showed impaired expression of key virulence and motility genes in the csp mutants. Our observations at protein and mRNA level suggest Csp-dependent expression regulation of these genes at transcriptional and post-transcriptional levels. In a mutant lacking all csp genes (ΔcspABD) as well as those possessing single csp genes (ΔcspBD, ΔcspAD, and ΔcspAB) we detected reduced levels of proteins or activity as well as transcripts from the prfA, hly, mpl, and plcA genes suggesting a Csp-dependent transcriptional regulation of these genes. These csp mutants also had reduced or completely lacked ActA proteins and cell surface flagella but contained elevated actA and flaA mRNA levels compared to the parental wild type strain suggesting Csp involvement in post-transcriptional regulation of these genes. Overall, our results suggest that Csps contribute to the expression regulation of virulence and flagella-associated genes thereby promoting host pathogenicity, cell aggregation and flagella-based motility processes in L. monocytogenes

Event-related GARCH: the impact of stock dividends in Turkey

Cash dividends and rights issues on the Istanbul Stock Exchange are commonly accompanied by large stock dividend payments. This paper tests the proposition that stock dividends have no effect on company value, using a novel GARCH process with event-related intercept terms to capture induced changes in the volatility of stock prices. Returns rise in advance of stock dividend payments, but this effect becomes statistically insignificant when proper allowance is made for heteroscedasticity. Volatility rises after stock dividend payments, and this is attributed to persistence following exceptionally large price movements around the ex-dividend day, rather than to any transitory rise in the unconditional returns variance. The study does document some irrationality in responses to cash dividends, with prices rising/falling after increased/decreased dividend payments, rather than after the much earlier dividend announcements.