The energetics of flow through a rapidly oscillating tube with slowly varying amplitude

Motivated by the problem of self-excited oscillations in fluid-filled collapsible tubes, we examine the flow structure and energy budget of flow through an elastic-walled tube. Specifically, we consider the case in which a background axial flow is perturbed by prescribed small-amplitude high-frequency long-wavelength oscillations of the tube wall, with a slowly growing or decaying amplitude. We use a multiple-scale analysis to show that, at leading order, we recover the constant-amplitude equations derived by Whittaker et al. (Whittaker et al. 2010 J. Fluid Mech. 648, 83-121. (doi:10.1017/S0022112009992904)) with the effects of growth or decay entering only at first order. We also quantify the effects on the flow structure and energy budget. Finally, we discuss how our results are needed to understand and predict an instability that can lead to self-excited oscillations in collapsible-tube systems.     

A pilot study on voucher-based incentives to promote abstinence from cigarette smoking during pregnancy and postpartum.

We report results from a pilot study examining the use of vouchers redeemable for retail items as incentives for smoking cessation during pregnancy and postpartum. Of 100 study-eligible women who were still smoking upon entering prenatal care, 58 were recruited from university-based and community obstetric practices to participate in a smoking cessation study. Participants were assigned to either contingent or noncontingent voucher conditions. Vouchers were available during pregnancy and for 12 weeks postpartum. In the contingent condition, vouchers were earned for biochemically verified smoking abstinence. In the noncontingent condition, vouchers were earned independent of smoking status. Abstinence monitoring and associated voucher delivery was conducted daily during the initial 5 days of the cessation effort, gradually decreased to every other week antepartum, increased to once weekly during the initial 4 weeks postpartum, and then decreased again to every other week for the remaining 8 weeks of the postpartum intervention period. Contingent vouchers increased 7-day point-prevalence abstinence at the end-of-pregnancy (37% vs. 9%) and 12-week postpartum (33% vs. 0%) assessments. That effect was sustained through the 24-week postpartum assessment (27% vs. 0%), which was 12 weeks after discontinuation of the voucher program. Total mean voucher earnings across antepartum and postpartum were 397 US dollars (SD=414 US dollars) and 313 US dollars (SD=142 dollars) in the contingent and noncontingent conditions, respectively. The magnitude of these treatment effects exceed levels typically observed with pregnant and recently postpartum smokers, and the maintenance of effects through 24 weeks postpartum extends the duration beyond those reported previously.     

A rotation aftereffect changes both the speed and the preferred direction of mental rotation.

Three experiments are reported that replicate and extend the finding of M. C. Corballis and R. McLaren (1982) regarding the interaction between mental rotation and the rotation aftereffect. In Experiment 1, participants saw tilted characters and made the usual parity judgment. In Experiment 2, participants were explicitly instructed to rotate the characters mentally into one direction or the other. In Experiment 3, participants had to report the direction into which they had mentally rotated. In all experiments, the function relating RT to the rotational angle was influenced by the aftereffect. RT was accelerated if the mental rotation was congruent with the aftereffect and decelerated if it was incongruent. A strategic change of direction of the mental rotation accounted only for some portion of this effect. The major portion has to be attributed to a direct interaction of two movements. The data suggest that the speed of the aftereffect combines with the speed of the mental rotation and, therefore, that imagery and perception share 1 representational medium. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microbiological oxidation of 2-methylbutanol of differing enantiomeric ratios by Gluconobacter species

 2-Methylbutanoic acid, an aroma compound of high economic interest, was synthesised using Gluconobacter species for bioconversion. The main focus was on enantioselective effects during metabolism. A preference for the (S)-enantiomer was observed when the microorganisms were fed with 2-methylbutanol of known enantiomeric ratios. Received: 15 December 1997     

世界上最小的集成电路钻头——ALPHA 4 PLUS Micro

所有的东西都一直在变得越来越小.手机的尺寸几乎不比火柴盒大,而便携式摄像机现在却小至两包烟盒的尺寸大小.当然是电子产品使得这些设备越来越小.但是电子产品不是一切.例如,在便携式摄像机中,还有大量机械装置.用于驱动胶带、自动聚焦以及镜头盖自动打开等装置.     

“aspect” – a new spectrometer for the measurement of the angular correlation coefficient a in neutron beta decay

The combination of the coefficient a of the antineutrino/electron angular correlation with the beta asymmetry of the neutron provides a sensitive test for scalar and tensor contributions to the electroweak Lagrangian, as well as for right-handed currents. A method is given for measuring a with high sensitivity from the proton recoil spectrum. The method is based on a magnetic spectrometer with electrostatic retardation potentials such as used for searches of the neutrino mass in tritium beta decay. The spectrometer can also be used for similar studies using radioactive nuclei.