Polarimetric variations of binary stars. II. Numerical simulations for circular and eccentric binaries in Mie scattering envelopes

We present numerical simulations of the periodic polarimetric variations produced by a binary star placed at the center of an empty spherical cavity inside a circumbinary ellipsoidal and optically thin envelope made of dust grains. Mie single-scattering is considered along with pre- and post-scattering extinction factors which produce a time-varying optical depth and affect the morphology of the periodic variations. We are interested in the effects that various parameters will have on the average polarization, the amplitude of the polarimetric variations, and the morphology of the variability. We show that the absolute amplitudes of the variations are smaller for Mie scattering than for Thomson scattering. Among the four grain types that we have studied, the highest polarizations are produced by grains with sizes in the range 0.1-0.2 micron. In general, the variations are seen twice per orbit. In some cases, because spherical dust grains have an asymmetric scattering function, the polarimetric curves produced also show variations seen once per orbit. Circumstellar disks produce polarimetric variations of greater amplitude than circumbinary envelopes. Another goal of these simulations is to see if the 1978 BME (Brown, McLean, & Emslie, ApJ, 68, 415) formalism, which uses a Fourier analysis of the polarimetric variations to find the orbital inclination for Thomson-scattering envelopes, can still be used for Mie scattering. We find that this is the case, if the amplitude of the variations is sufficient and the true inclinations is i_true > 45 deg. For eccentric orbits, the first-order coefficients of the Fourier fit, instead of second-order ones, can be used to find almost all inclinations.Comment: 23 pages, 5 figures, to be published in Astronomical Journa

Technique for anchoring fasteners to honeycomb panels

Two-piece fastener bushing provides mounting surface for components on a three-inch thick honeycomb structure. Specially constructed starter drill and sheet metal drill permit drilling without misalignment. Tapered knife-edge cutting tool removes honeycomb core material without tearing the adjacent material

Linear-scaling algorithm for rapid computation of inelastic transitions in the presence of multiple electron scattering

Strong multiple scattering of the probe in scanning transmission electron microscopy (STEM) means image simulations are usually required for quantitative interpretation and analysis of elemental maps produced by electron energy-loss spectroscopy (EELS). These simulations require a full quantum-mechanical treatment of multiple scattering of the electron beam, both before and after a core-level inelastic transition. Current algorithms scale quadratically and can take up to a week to calculate on desktop machines even for simple crystal unit cells and do not scale well to the nanoscale heterogeneous systems that are often of interest to materials science researchers. We introduce an algorithm with linear scaling that typically results in an order of magnitude reduction in computation time for these calculations without introducing additional error and discuss approximations that further improve computational scaling for larger-scale objects with modest penalties in calculation error. We demonstrate these speedups by calculating the atomic resolution STEM-EELS map using the L-edge transition of Fe, for a nanoparticle 80 Å in diameter, in 16 hours, a calculation that would have taken at least 80 days using a conventional multislice approach

An attentional control task reduces intrusive thoughts about smoking.

INTRODUCTION: Attentional control tasks such as body scanning and following isometric exercise instructions have been shown to reduce smoking cravings, apparently by reducing stress (Ussher, M., Cropley, M., Playle, S., Mohidin, R., & West, R. [2009]. Effect of isometric exercise and body scanning on cigarette cravings and withdrawal symptoms. Addiction, 104, 1251-1257. doi:10.1111/j.1360-0443.2009.02605.x). Related work based upon elaborated intrusion theory (Kavanagh, D. J., Andrade, J., & May, J. [2005]. Imaginary relish and exquisite torture: The elaborated intrusion theory of desire. Psychological Review, 112, 446-467. doi:10.1037/0033-295X.112.2.446) has shown that similar tasks can reduce hungry participants' involuntary food-related thoughts (May, J., Andrade, J., Batey, H., Berry, L.-M., & Kavanagh, D. [2010]. Less food for thought: Impact of attentional instructions on intrusive thoughts about snack foods. Appetite, 55, 279-287. doi:10.1016/j.appet.2010.06.014). This study tests the effect of body scanning instructions upon smoking-related thoughts as well as craving. METHODS: Twenty-seven smokers took part in 2 counterbalanced sessions, on different days, having been asked to abstain from smoking for 2 hr. In each session, they followed audio instructions for three 10-min blocks during which their thoughts were probed 10 times. In the first and third blocks, they were instructed to let their mind wander; during the second block of the control session, they also let their mind wander, but in the experimental session, they followed body scanning instructions. "Smoking thought frequency" was assessed using thought probes; "Craving" was measured using Factor 1 of the Questionnaire on Smoking Urges (Tiffany, S. T., & Drobes, D. J. [1991]. The development and initial validation of a questionnaire on smoking urges. British Journal of Addiction, 86, 1467-1476. doi:10.1111/j.1360-0443.1991.tb01732.x). RESULTS: Participants reported fewer smoking-related thoughts and lower smoking cravings in the body scanning block of the experimental session, whereas they rose in the comparable mind-wandering block of the control session. The reduction in thoughts during the body scanning correlated with the corresponding reduction in craving. CONCLUSIONS: Body scanning reduces cravings and reduces the frequency or shortens the duration of smoking thoughts. Attentional control strategies may form a useful part of smoking cessation practices

Workshop in Moodle: a tool for peer critiquing

This paper will begin with a brief discussion of the benefits of peer assessment and peer critiquing. In particular, it will examine how both can be beneficial in helping to introduce, and reinforce, valuable graduate attributes in students throughout their university careers. It will then examine the tools available at the University of Glasgow and evaluate them in terms of their strengths and weaknesses. In order to explain this in detail, a real life case study from a third year class in Nursing will be presented. The paper will conclude that, while there are obvious benefits to peer critiquing tools being used with a Virtual Learning Environment (VLE), some modifications are necessary in order to make them more easily usable by staff and students

Parametric studies to determine the effect of compliant layers on metal matrix composite systems

Computational simulation studies are conducted to identify compliant layers to reduce matrix stresses which result from the coefficient of thermal expansion mismatch and the large temperature range over which the current metal matrix composites will be used. The present study includes variations of compliant layers and their properties to determine their influence on unidirectional composite and constituent response. Two simulation methods are used for these studies. The first approach is based on a three-dimensional linear finite element analysis of a 9 fiber unidirectional composite system. The second approach is a micromechanics based nonlinear computer code developed to determine the behavior of metal matrix composite system for thermal and mechanical loads. The results show that an effective compliant layer for the SCS 6 (SiC)/Ti-24Al-11Nb (Ti3Al + Nb) and SCS 6 (SiC)/Ti-15V-3Cr-3Sn-3Al (Ti-15-3) composite systems should have modulus 15 percent that of the matrix and a coefficient of thermal expansion of the compliant layer roughly equal to that of the composite system without the CL. The matrix stress in the longitudinal and the transverse tangent (loop) direction are tensile for the Ti3Al + Nb and Ti-15-3 composite systems upon cool down from fabrication. The fiber longitudinal stress is compressive from fabrication cool down. Addition of a recommended compliant layer will result in a reduction in the composite modulus