Electric field-driven coherent spin reorientation of optically generated electron spin packets in InGaAs

Full electric-field control of spin orientations is one of the key tasks in semiconductor spintronics. We demonstrate that electric field pulses can be utilized for phase-coherent +/- pi spin rotation of optically generated electron spin packets in InGaAs epilayers detected by time-resolved Faraday rotation. Through spin-orbit interaction, the electric-field pulses act as local magnetic field pulses (LMFP). By the temporal control of the LMFP, we can turn on and off electron spin precession and thereby rotate the spin direction into arbitrary orientations in a 2-dimensional plane. Furthermore, we demonstrate a spin echo-type spin drift experiment and find an unexpected partial spin rephasing, which is evident by a doubling of the spin dephasing time.Comment: 10 pages, 4 figure

The Effects of Temperature, Diet, and Other Factors on Development, Survivorship, and Oviposition of Aethina tumida (Coleoptera: Nitidulidae)

Developmental rate and survivorship of small hive beetle, Aethina tumida Murray (Coleoptera: Nitidulidae), life stages were measured across different temperatures (21, 25, 28, 32 and 35 C) and diets, which included natural and artificial pollen, honey, and bee pupae. Temperature affected hatch success, time to hatching, and larval growth. Eggs hatched in 61 h at 21 C but in 22 h at 35 C. Larvae achieved peak weight in 8 d at 35 C but needed 17 d at 21 C. Diet had comparatively little effect on larval survivorship or maximum weight, although larvae fed only bee pupae had lower survivorship. Access to soil influenced pupation success. Duration of the life stage spent in the soil, during which pupation occurs, was also affected by temperature: adults emerged after 32.7 d at 21C but after only 14.8 d at 35 C, albeit with high mortality. Minimum temperature for development was estimated at 13.5 C for eggs, and 10.0 C for larvae and pupae. Temperature influenced adult longevity and oviposition: on a honey and pollen diet average adult lifespan was 92.8 d at 24 C but only 11.6 d at 35 C. Beetles lived longer at 28 C or lower but produced the most eggs per female, regardless of diet, at 32 C. Beetle density influenced fecundity: beetles kept at three pairs per vial laid 6.7 times more eggs per female than those kept as single pairs. Overall, beetles fared best at 28-32 C with mortality of all stages highest at 35 C

Image and Video Disclosure of Substance Use on Social Media Websites

The present study examines young adults’ use of social media websites, such as MySpace, Facebook, and YouTube, to post public images and videos of themselves depicting alcohol consumption, inebriated behavior, or recreational marijuana use. A content analysis revealed that the majority of image and video representations of alcohol consumption depicted females in social gatherings while images and videos depicting marijuana use depicted solitary males. Videos typically were viewed frequently and gained positive ratings. Among a sample of college students, one-third of participants reported having posted a picture depicting substance use on a social networking site, with 97 percent aware that others engage in this phenomenon. Students’ perceptions of alcohol-related postings were generally positive or seen as a matter of individual choice while marijuana-related postings were generally viewed more negatively

Design and fabrication of a long-life Stirling cycle cooler for space application. Phase 3: Prototype model

A second-generation, Stirling-cycle cryocooler (cryogenic refrigerator) for space applications, with a cooling capacity of 5 watts at 65 K, was recently completed. The refrigerator, called the Prototype Model, was designed with a goal of 5 year life with no degradation in cooling performance. The free displacer and free piston of the refrigerator are driven directly by moving-magnet linear motors with the moving elements supported by active magnetic bearings. The use of clearance seals and the absence of outgassing material in the working volume of the refrigerator enable long-life operation with no deterioration in performance. Fiber-optic sensors detect the radial position of the shafts and provide a control signal for the magnetic bearings. The frequency, phase, stroke, and offset of the compressor and expander are controlled by signals from precision linear position sensors (LVDTs). The vibration generated by the compressor and expander is cancelled by an active counter balance which also uses a moving-magnet linear motor and magnetic bearings. The driving signal for the counter balance is derived from the compressor and expander position sensors which have wide bandwidth for suppression of harmonic vibrations. The efficiency of the three active members, which operate in a resonant mode, is enhanced by a magnetic spring in the expander and by gas springs in the compressor and counterbalance. The cooling was achieved with a total motor input power of 139 watts. The magnetic-bearing stiffness was significantly increased from the first-generation cooler to accommodate shuttle launch vibrations

Consistent Anisotropic Repulsions for Simple Molecules

We extract atom-atom potentials from the effective spherical potentials that suc cessfully model Hugoniot experiments on molecular fluids, e.g., $O_2$ and $N_2$. In the case of $O_2$ the resulting potentials compare very well with the atom-atom potentials used in studies of solid-state propertie s, while for $N_2$ they are considerably softer at short distances. Ground state (T=0K) and room temperatu re calculations performed with the new $N-N$ potential resolve the previous discrepancy between experimental and theoretical results.Comment: RevTeX, 5 figure

Strategies for Managing Large Online Classes

Online classroom instruction is an exciting technology and continues to draw the attention of students, instructors and administrators working or studying in educational settings. Large numbers of faculty are currently involved in teaching online or hybrid courses within their educational institutions. At the present time, very large online classes are usually defined as 150 students and above. Many instructors are now experimenting with making online learning options available to even larger audiences and online class sizes are increasing rapidly. This paper presents guidelines for managing large online courses. Among key elements important in meeting the needs of the distant learner through large online course design are: effective communication, use of teaching assistants and multiple sections, teaching techniques successful in large online sections and professional practice in the online classroom. This paper will discuss these elements and corresponding suggestions for the instructors of large to very large online courses

Near-Optimal Distributed Maximum Flow

We present a near-optimal distributed algorithm for $(1+o(1))$-approximation of single-commodity maximum flow in undirected weighted networks that runs in $(D+ \sqrt{n})\cdot n^{o(1)}$ communication rounds in the \Congest model. Here, $n$ and $D$ denote the number of nodes and the network diameter, respectively. This is the first improvement over the trivial bound of $O(n^2)$, and it nearly matches the $\tilde{\Omega}(D+ \sqrt{n})$ round complexity lower bound. The development of the algorithm contains two results of independent interest: (i) A $(D+\sqrt{n})\cdot n^{o(1)}$-round distributed construction of a spanning tree of average stretch $n^{o(1)}$. (ii) A $(D+\sqrt{n})\cdot n^{o(1)}$-round distributed construction of an $n^{o(1)}$-congestion approximator consisting of the cuts induced by $O(\log n)$ virtual trees. The distributed representation of the cut approximator allows for evaluation in $(D+\sqrt{n})\cdot n^{o(1)}$ rounds. All our algorithms make use of randomization and succeed with high probability

On the terms violating the custodial symmetry in multi-Higgs-doublet models

We prove that a generic multi-Higgs-doublet model (NHDM) generally must contain terms in the potential that violate the custodial symmetry. This is done by showing that the O(4) violating terms of the NHDM potential cannot be excluded by imposing a symmetry on the NHDM Lagrangian. Hence we expect higher-order corrections to necessarily introduce such terms. We also note, in the case of custodially symmetric Higgs-quark couplings, that vacuum alignment will lead to up-down mass degeneration; this is not true if the vacua are not aligned.Comment: 16 pages, 1 figure. Title and abstract are modified, conclusions remain the same. Section on Yukawa couplings is extended. Published versio