3,411 research outputs found

    The Radio Afterglow and the Host Galaxy of the X-Ray Rich GRB 981226

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    We report the discovery of a radio transient VLA 232937.2-235553, coincident with the proposed X-ray afterglow for the gamma-ray burst GRB 981226. This GRB has the highest ratio of X-ray to gamma-ray fluence of all the GRBs detected by BeppoSAX so far and yet no corresponding optical transient was detected. The radio light curve of VLA 232937.2-235553 is qualitatively similar to that of several other radio afterglows. At the sub-arcsecond position provided by the radio detection, optical imaging reveals an extended R=24.9 mag object, which we identify as the host galaxy of GRB 981226. Afterglow models which invoke a jet-like geometry for the outflow or require an ambient medium with a radial density dependence, such as that produced by a wind from a massive star, are both consistent with the radio data. Furthermore, we show that the observed properties of the radio afterglow can explain the absence of an optical transient without the need for large extinction local to the GRB.Comment: Accepted for publication in the Astrophysical Journal Letters. Thirteen pages. Three Postscript figure

    Non-dipole recollision-gated double ionization and observable effects

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    Using a three-dimensional semiclassical model, we study double ionization for strongly-driven He fully accounting for magnetic field effects. For linearly and slightly elliptically polarized laser fields, we show that recollisions and the magnetic field combined act as a gate. This gate favors more transverse - with respect to the electric field - initial momenta of the tunneling electron that are opposite to the propagation direction of the laser field. In the absence of non-dipole effects, the transverse initial momentum is symmetric with respect to zero. We find that this asymmetry in the transverse initial momentum gives rise to an asymmetry in a double ionization observable. Finally, we show that this asymmetry in the transverse initial momentum of the tunneling electron accounts for a recently-reported unexpectedly large average sum of the electron momenta parallel to the propagation direction of the laser field.Comment: Amended the focus of the paper and discussion. 9 pages, 7 figure

    Apollo Lightcraft Project

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    This second year of the NASA/USRA-sponsored Advanced Aeronautical Design effort focused on systems integration and analysis of the Apollo Lightcraft. This beam-powered, single-stage-to-orbit vehicle is envisioned as the shuttlecraft of the 21st century. The five person vehicle was inspired largely by the Apollo Command Module, then reconfigured to include a new front seat with dual cockpit controls for the pilot and co-pilot, while still retaining the 3-abreast crew accommodations in the rear seat. The gross liftoff mass is 5550 kg, of which 500 kg is the payload and 300 kg is the LH2 propellant. The round trip cost to orbit is projected to be three orders of magnitude lower than the current space shuttle orbiter. The advanced laser-driven 5-speed combined-cycle engine has shiftpoints at Mach 1, 5, 11 and 25+. The Apollo Lightcraft can climb into low Earth orbit in three minutes, or fly to any spot on the globe in less than 45 minutes. Detailed investigations of the Apollo Lightcraft Project this second year further evolved the propulsion system design, while focusing on the following areas: (1) man/machine interface; (2) flight control systems; (3) power beaming system architecture; (4) re-entry aerodynamics; (5) shroud structural dynamics; and (6) optimal trajectory analysis. The principal new findings are documented. Advanced design efforts for the next academic year (1988/1989) will center on a one meter+ diameter spacecraft: the Lightcraft Technology Demonstrator (LTD). Detailed engineering design and analyses, as well as critical proof-of-concept experiments, will be carried out on this small, near-term machine. As presently conceived, the LTD could be constructed using state of the art components derived from existing liquid chemical rocket engine technology, advanced composite materials, and high power laser optics

    CBT for people with intellectual disabilities : emerging evidence, cognitive ability and IQ effects

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    Historically people with intellectual disabilities have not been offered or received cognitive behavioural interventions that have been shown to be effective for mental health and emotional problems experienced by those without such disabilities. This is despite many people with intellectual disabilities having life experiences that potentially result in them having an increased risk to such problems. This paper discusses whether such therapeutic disdain is justified based on the evidence that is available and emerging concerning the application of cognitive behavioural interventions for this population. Issues concerning access to services, the ability of people with intellectual disabilities to engage in and benefit from the cognitive components of CBT, and the effect of cognitive abilities and IQ level on treatment effectiveness are explored in relation to this question

    Emergent nanoscale superparamagnetism at oxide interfaces

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    Atomically sharp oxide heterostructures exhibit a range of novel physical phenomena that do not occur in the parent bulk compounds. The most prominent example is the appearance of highly conducting and superconducting states at the interface between the band insulators LaAlO3 and SrTiO3. Here we report a new emergent phenomenon at the LaMnO3/SrTiO3 interface in which an antiferromagnetic insulator abruptly transforms into a magnetic state that exhibits unexpected nanoscale superparamagnetic dynamics. Upon increasing the thickness of LaMnO3 above five unit cells, our scanning nanoSQUID-on-tip microscopy shows spontaneous formation of isolated magnetic islands of 10 to 50 nm diameter, which display random moment reversals by thermal activation or in response to an in-plane magnetic field. Our charge reconstruction model of the polar LaMnO3/SrTiO3 heterostructure describes the sharp emergence of thermodynamic phase separation leading to nucleation of metallic ferromagnetic islands in an insulating antiferromagnetic matrix. The model further suggests that the nearby superparamagnetic-ferromagnetic transition can be gate tuned, holding potential for applications in magnetic storage and spintronics

    P092 improving postgraduate psychology students’ sleep and insomnia knowledge with a sleep education workshop

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    Abstract Introduction Trainee psychologists receive limited sleep and insomnia education during postgraduate study. This study examined the delivery of a sleep psychology training workshop for postgraduate psychology students and examined changes in sleep knowledge from pre- to post-workshop. Methods A 6-hour Sleep Psychology Workshop was delivered to postgraduate psychology students around Victoria. Online pre- and post-workshop questionnaires were used to evaluate changes in sleep psychology knowledge and collect feedback on the workshop. Results The participants were 187 students (82% female, M age = 32), most of whom were in their 5th year of psychology training (69%) and had not received any sleep education during their postgraduate studies at the date of the intervention (77%). Students’ sleep knowledge significantly improved after workshop completion (pre: 56% vs. post: 80% correct), t(107)= -21.41, p < .001. Students provided positive feedback about the workshop, with 96% rating the workshop as excellent/very good and 86% reporting that they would recommend the workshop to other postgraduate students. Overall, 94% of students agreed/strongly agreed that the sleep psychology workshop improved their confidence to manage sleep disturbances in their future psychology practice. Discussion Postgraduate psychology students require sleep and insomnia education. This study demonstrates that students’ sleep psychology knowledge can improve after a 6-hour sleep education and training workshop and provides initial positive feedback about the benefits of sleep and insomnia education for postgraduate students

    Tidal Stabilization of Rigidly Rotating, Fully Relativistic Neutron Stars

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    It is shown analytically that an external tidal gravitational field increases the secular stability of a fully general relativistic, rigidly rotating neutron star that is near marginal stability, protecting it against gravitational collapse. This stabilization is shown to result from the simple fact that the energy δM(Q,R)\delta M(Q,R) required to raise a tide on such a star, divided by the square of the tide's quadrupole moment QQ, is a decreasing function of the star's radius RR, (d/dR)[δM(Q,R)/Q2]<0(d/dR)[\delta M(Q,R)/Q^2]<0 (where, as RR changes, the star's structure is changed in accord with the star's fundamental mode of radial oscillation). If (d/dR)[δM(Q,R)/Q2](d/dR)[\delta M(Q,R)/Q^2] were positive, the tidal coupling would destabilize the star. As an application, a rigidly rotating, marginally secularly stable neutron star in an inspiraling binary system will be protected against secular collapse, and against dynamical collapse, by tidal interaction with its companion. The ``local-asymptotic-rest-frame'' tools used in the analysis are somewhat unusual and may be powerful in other studies of neutron stars and black holes interacting with an external environment. As a byproduct of the analysis, in an appendix the influence of tidal interactions on mass-energy conservation is elucidated.Comment: Revtex, 10 pages, 2 figures; accepted for publication in Physical Review D. Revisions: Appendix rewritten to clarify how, in Newtonian gravitation theory, ambiguity in localization of energy makes interaction energy ambiguous but leaves work done on star by tidal gravity unambiguous. New footnote 1 and Refs. [11] and [19

    The effects of weather and climate change on dengue

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    There is much uncertainty about the future impact of climate change on vector-borne diseases. Such uncertainty reflects the difficulties in modelling the complex interactions between disease, climatic and socioeconomic determinants. We used a comprehensive panel dataset from Mexico covering 23 years of province-specific dengue reports across nine climatic regions to estimate the impact of weather on dengue, accounting for the effects of non-climatic factors
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