29Si Hyperfine Structure of the E'_\alpha Center in Amorphous Silicon Dioxide

We report a study by electron paramagnetic resonance (EPR) on the E'_\alpha point defect in amorphous silicon dioxide (a-SiO2). Our experiments were performed on gamma-ray irradiated oxygen-deficient materials and pointed out that the 29Si hyperfine structure of the E'_alpha consists in a pair of lines split by 49 mT. On the basis of the experimental results a microscopic model is proposed for the E'_alpha center, consisting in a hole trapped in an oxygen vacancy with the unpaired electron sp3 orbital pointing away from the vacancy in a back-projected configuration and interacting with an extra oxygen atom of the a-SiO2 matrix.Comment: 4 page

Tests of Diet and Insulin-like Peptides on the Duration of the 5th Instar of Male Lubber Grasshoppers

Consuming fewer calories while maintaining adequate nutrition (i.e. calorie restriction), even if that diet is started late in life, rapidly increases longevity by slowing the aging process (Mair et al. 2003). The mechanisms underlying rapidly reduced mortality rate in response to late-onset calorie restriction are largely unknown. Calorie restriction is associated with lower insulin-like peptides (ILP) levels in many organisms (Tater et al. 2003). We have shown that calorie restriction throughout adulthood, and late-onset calorie restriction, increases longevity in female grasshoppers (Wells et al. 2005; Hatle et al. 2006). The exact role of ILP in the enhanced longevity due to late-onset calorie restriction is unclear. Consequently, there is a need for experiments in which insulin signaling is manipulated only late in life.Insulin is the hormone secreted by the pancreas of vertebrates that aids in the membrane transport of glucose from the blood into the body cells (Marieb 2005). More generally, insulin directs the absorptive state. Typically, insulin levels increase upon feeding, at which time energy is available for cells to grow. In this role, insulin acts as a growth regulator and signals cells to divide. In lower organisms like insects, ILP are present and appear to act primarily as growth regulators, with little role in glucose metabolism (Ebberink et al. 1989). Previous research on fruit flies has shown that removal of insulin-producing cells causes developmental delays and growth retardation (Rulifson et al. 2002). Hence, we sought to develop an experimental system to test the role of insulin signaling in calorie restriction. The duration of the 5th instar (the stage prior to adulthood) is affected by diet level in juvenile male lubber grasshoppers (Hatle et al. 2003). Developmental events that are affected by calorie intake likely are affected by insulin signaling. To determine whether maturation to adult molt in grasshoppers can be affected by insulin signaling, we injected grasshoppers with an antibody to human insulin (anti-insulin) and measured developmental timing

Improved spatial separation of neutral molecules

We have developed and experimentally demonstrated an improved electrostatic deflector for the spatial separation of molecules according to their dipole-moment-to-mass ratio. The device features a very open structure that allows for significantly stronger electric fields as well as for stronger deflection without molecules crashing into the device itself. We have demonstrated its performance using the prototypical OCS molecule and we discuss opportunities regarding improved quantum-state-selectivity for complex molecules and the deflection of unpolar molecules.Comment: 6 figure

Opto-Electrical Cooling of Polar Molecules

We present an opto-electrical cooling scheme for polar molecules based on a Sisyphus-type cooling cycle in suitably tailored electric trapping fields. Dissipation is provided by spontaneous vibrational decay in a closed level scheme found in symmetric-top rotors comprising six low-field-seeking rovibrational states. A generic trap design is presented. Suitable molecules are identified with vibrational decay rates on the order of 100Hz. A simulation of the cooling process shows that the molecular temperature can be reduced from 1K to 1mK in approximately 10s. The molecules remain electrically trapped during this time, indicating that the ultracold regime can be reached in an experimentally feasible scheme

Technological Innovation or Educational Evolution? A Multi-disciplinary Qualitative Inquiry into Active Learning Classrooms

In recent years, many institutions have transformed traditional classrooms (TCs) into technology-rich active learning classrooms (ALCs) to accommodate the pedagogical concept of “active learning”. In order to investigate the impact of ALCs on teaching and teaching, we observed an instructor teaching in an ALC for an entire academic year, audio/video-recorded every class and took field notes. A focus group discussion was conducted with faculty from six allied health disciplines who taught weekly classes in the ALC and an online survey was distributed to students who took those classes. Data was then analysed using a qualitative constant comparative method (CCM). Findings indicated that the ALC generated greater teaching and learning enjoyment, deepened engagement, amplified interaction, enhanced group activity efficiency and fostered the development of creative ideas.  All these features were interrelated and created a synergistic effect on student learning

Scope for Credit Risk Diversification

This paper considers a simple model of credit risk and derives the limit distribution of losses under different assumptions regarding the structure of systematic risk and the nature of exposure or firm heterogeneity. We derive fat-tailed correlated loss distributions arising from Gaussian risk factors and explore the potential for risk diversification. Where possible the results are generalised to non-Gaussian distributions. The theoretical results indicate that if the firm parameters are heterogeneous but come from a common distribution, for sufficiently large portfolios there is no scope for further risk reduction through active portfolio management. However, if the firm parameters come from different distributions, then further risk reduction is possible by changing the portfolio weights. In either case, neglecting parameter heterogeneity can lead to underestimation of expected losses. But, once expected losses are controlled for, neglecting parameter heterogeneity can lead to overestimation of risk, whether measured by unexpected loss or value-at-risk

Nur77 controls tolerance induction, terminal differentiation, and effector functions in semi-invariant natural killer T cells

Semi-invariant natural killer T (iNKT) cells are self-reactive lymphocytes, yet how this lineage attains self-tolerance remains unknown. iNKT cells constitutively express high levels of Nr4a1-encoded Nur77, a transcription factor that integrates signal strength downstream of the T cell receptor (TCR) within activated thymocytes and peripheral T cells. The function of Nur77 in iNKT cells is unknown. Here we report that sustained Nur77 overexpression (Nur77^(tg)) in mouse thymocytes abrogates iNKT cell development. Introgression of a rearranged Vα14-Jα18 TCR-α chain gene into the Nur77^(tg) (Nur77^(tg);Vα14^(tg)) mouse rescued iNKT cell development up to the early precursor stage, stage 0. iNKT cells in bone marrow chimeras that reconstituted thymic cellularity developed beyond stage 0 precursors and yielded IL-4–producing NKT2 cell subset but not IFN-γ–producing NKT1 cell subset. Nonetheless, the developing thymic iNKT cells that emerged in these chimeras expressed the exhaustion marker PD1 and responded poorly to a strong glycolipid agonist. Thus, Nur77 integrates signals emanating from the TCR to control thymic iNKT cell tolerance induction, terminal differentiation, and effector functions

Nur77 controls tolerance induction, terminal differentiation, and effector functions in semi-invariant natural killer T cells

Semi-invariant natural killer T (iNKT) cells are self-reactive lymphocytes, yet how this lineage attains self-tolerance remains unknown. iNKT cells constitutively express high levels of Nr4a1-encoded Nur77, a transcription factor that integrates signal strength downstream of the T cell receptor (TCR) within activated thymocytes and peripheral T cells. The function of Nur77 in iNKT cells is unknown. Here we report that sustained Nur77 overexpression (Nur77^(tg)) in mouse thymocytes abrogates iNKT cell development. Introgression of a rearranged Vα14-Jα18 TCR-α chain gene into the Nur77^(tg) (Nur77^(tg);Vα14^(tg)) mouse rescued iNKT cell development up to the early precursor stage, stage 0. iNKT cells in bone marrow chimeras that reconstituted thymic cellularity developed beyond stage 0 precursors and yielded IL-4–producing NKT2 cell subset but not IFN-γ–producing NKT1 cell subset. Nonetheless, the developing thymic iNKT cells that emerged in these chimeras expressed the exhaustion marker PD1 and responded poorly to a strong glycolipid agonist. Thus, Nur77 integrates signals emanating from the TCR to control thymic iNKT cell tolerance induction, terminal differentiation, and effector functions