Roche tomography of cataclysmic variables - V. A high-latitude star-spot on RU Pegasi

We present Roche tomograms of the secondary star in the dwarf nova system RU Pegasi derived from blue and red arm ISIS data taken on the 4.2-m William Herschel Telescope. We have applied the entropy landscape technique to determine the system parameters and obtained component masses of M1 = 1.06 Msun, M2 = 0.96 Msun, an orbital inclination angle of i = 43 degrees, and an optimal systemic velocity of gamma = 7 km/s. These are in good agreement with previously published values. Our Roche tomograms of the secondary star show prominent irradiation of the inner Lagrangian point due to illumination by the disc and/or bright spot, which may have been enhanced as RU Peg was in outburst at the time of our observations.We find that this irradiation pattern is axi-symmetric and confined to regions of the star which have a direct view of the accretion regions. This is in contrast to previous attempts to map RU Peg which suggested that the irradiation pattern was non-symmetric and extended beyond the terminator. We also detect additional inhomogeneities in the surface distribution of stellar atomic absorption that we ascribe to the presence of a large star-spot. This spot is centred at a latitude of about 82 degrees and covers approximately 4 per cent of the total surface area of the secondary. In keeping with the high latitude spots mapped on the cataclysmic variables AE Aqr and BV Cen, the spot on RU Peg also appears slightly shifted towards the trailing hemisphere of the star. Finally, we speculate that early mapping attempts which indicated non-symmetric irradiation patterns which extended beyond the terminator of CV donors could possibly be explained by a superposition of symmetric heating and a large spot.Comment: 14 pages, 10 figures, 3 tables Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Hierarchic Extensions in the Static and Dynamic Analysis of Elastic Beams

Approximate solutions of static and dynamic beam problems by the p-version of the finite element method are investigated. Within a hierarchy of engineering beam idealizations, rigorous formulations of the strain and kinetic energies for straight and circular beam elements are presented. These formulations include rotating coordinate system effects and geometric nonlinearities to allow for the evaluation of vertical axis wind turbines, the motivating problem for this research. Hierarchic finite element spaces, based on extensions of the polynomial orders used to approximate the displacement variables, are constructed. The developed models are implemented into a general purpose computer program for evaluation. Quality control procedures are examined for a diverse set of sample problems. These procedures include estimating discretization errors in energy norm and natural frequencies, performing static and dynamic equilibrium checks, observing convergence for qualities of interest, and comparison with more exacting theories and experimental data. It is demonstrated that p-extensions produce exponential rates of convergence in the approximation of strain energy and natural frequencies for the class of problems investigated

AlGaInN laser diode technology for GHz high-speed visible light communication through plastic optical fiber and water

AlGaInN ridge waveguide laser diodes are fabricated to achieve single-mode operation with optical powers up to 100 mW at ∼420  nm∼420  nm for visible free-space, underwater, and plastic optical fiber communication. We report high-frequency operation of AlGaInN laser diodes with data transmission up to 2.5 GHz for free-space and underwater communication and up to 1.38 GHz through 10 m of plastic optical fiber

Linear Perturbations in Brane Gas Cosmology

We consider the effect of string inhomogeneities on the time dependent background of Brane Gas Cosmology. We derive the equations governing the linear perturbations of the dilaton-gravity background in the presence of string matter sources. We focus on long wavelength fluctuations and find that there are no instabilities. Thus, the predictions of Brane Gas Cosmology are robust against the introduction of linear perturbations. In particular, we find that the stabilization of the extra dimensions (moduli) remains valid in the presence of dilaton and string perturbations.Comment: 17 pages, 1 figur

Hopeful monsters - In defense of quests to rediscover long-lost species

Wild goose chase, snipe hunt, fool’s errand—these retorts typify responses of many biologists to news that someone is searching for a species considered extinct. Although these ventures can damage reputations and may offer false hope regarding the finality of extinction, genuine conservation gains often result, even for those quests that prove unsuccessful. As well as enhanced protection for regions where rediscovered species persist and new information of direct management relevance for co-occurring species, well-planned searches for long-lost species represent valuable engagement opportunities to raise awareness in the wider community about biodiversity conservation and science generally. Indeed, we suggest that “Lazarus species” (organisms rediscovered having been presumed extinct, after Dawson et al. 2006) provide beacons of hope in an increasingly desperate scramble to conserve species, shining a light on dark diversity and reminding us that population trajectories can have exceedingly long tails

Hopeful monsters - In defense of quests to rediscover long-lost species

Wild goose chase, snipe hunt, fool’s errand—these retorts typify responses of many biologists to news that someone is searching for a species considered extinct. Although these ventures can damage reputations and may offer false hope regarding the finality of extinction, genuine conservation gains often result, even for those quests that prove unsuccessful. As well as enhanced protection for regions where rediscovered species persist and new information of direct management relevance for co-occurring species, well-planned searches for long-lost species represent valuable engagement opportunities to raise awareness in the wider community about biodiversity conservation and science generally. Indeed, we suggest that “Lazarus species” (organisms rediscovered having been presumed extinct, after Dawson et al. 2006) provide beacons of hope in an increasingly desperate scramble to conserve species, shining a light on dark diversity and reminding us that population trajectories can have exceedingly long tails

Pointer Provenance in a Capability Architecture

We design and implement a framework for tracking pointer provenance, using our CHERI fat-pointer capability architec- ture to facilitate analysis of security implications of program pointer flows in both user and privileged code, with mini- mal instrumentation. CHERI enforces pointer provenance validity at the architectural level, in the presence of complex pointer arithmetic and type casting. CHERI present new op- portunities for provenance research: we discuss use cases and highlight lessons and open questions from our work.DARPA/AFRL FA8750-10-C-0237, Google Chrome University Research Program Awar

Women World Leaders: Comparative Analysis and Gender Experiences

Research suggests that executive political office poses additional and different political challenges for women than legislative office. Yet, a few dozen women have attained their nations’ highest executive office. Surprisingly little research has been devoted to the experiences of these women world leaders. This study builds profiles of the women world leaders in the modern era and analyzes their backgrounds and political experiences in an effort to both identify commonalities among the women leaders and assess the challenges they faced on account of their sex

Stabilization of Extra Dimensions at Tree Level

By considering the effects of string winding and momentum modes on a time dependent background, we find a method by which six compact dimensions become stabilized naturally at the self-dual radius while three dimensions grow large.Comment: 15 pages, 2 figures, minor typos correcte

Contrasting alterations to synaptic and intrinsic properties in upper-cervical superficial dorsal horn neurons following acute neck muscle inflammation

Background: Acute and chronic pain in axial structures, like the back and neck, are difficult to treat, and have incidence as high as 15%. Surprisingly, most preclinical work on pain mechanisms focuses on cutaneous structures in the limbs and animal models of axial pain are not widely available. Accordingly, we developed a mouse model of acute cervical muscle inflammation and assessed the functional properties of superficial dorsal horn (SDH) neurons.<p></p> Results: Male C57/Bl6 mice (P24-P40) were deeply anaesthetised (urethane 2.2?g/kg i.p) and the rectus capitis major muscle (RCM) injected with 40??l of 2% carrageenan. Sham animals received vehicle injection and controls remained anaesthetised for 2?hrs. Mice in each group were sacrificed at 2?hrs for analysis. c-Fos staining was used to determine the location of activated neurons. c-Fos labelling in carrageenan-injected mice was concentrated within ipsilateral (87% and 63% of labelled neurons in C1 and C2 segments, respectively) and contralateral laminae I - II with some expression in lateral lamina V. c-Fos expression remained below detectable levels in control and sham animals. In additional experiments, whole cell recordings were obtained from visualised SDH neurons in transverse slices in the ipsilateral C1 and C2 spinal segments. Resting membrane potential and input resistance were not altered. Mean spontaneous EPSC amplitude was reduced by ~20% in neurons from carrageenan-injected mice versus control and sham animals (20.63???1.05 vs. 24.64???0.91 and 25.87???1.32 pA, respectively). The amplitude (238???33 vs. 494???96 and 593???167 pA) and inactivation time constant (12.9???1.5 vs. 22.1???3.6 and 15.3???1.4?ms) of the rapid A type potassium current (IAr), the dominant subthreshold current in SDH neurons, were reduced in carrageenan-injected mice.<p></p> Conclusions: Excitatory synaptic drive onto, and important intrinsic properties (i.e., IAr) within SDH neurons are reduced two hours after acute muscle inflammation. We propose this time point represents an important transition period between peripheral and central sensitisation with reduced excitatory drive providing an initial neuroprotective mechanism during the early stages of the progression towards central sensitisation