Gravitational Waves from Axisymmetric, Rotational Stellar Core Collapse

We have carried out an extensive set of two-dimensional, axisymmetric, purely-hydrodynamic calculations of rotational stellar core collapse with a realistic, finite-temperature nuclear equation of state and realistic massive star progenitor models. For each of the total number of 72 different simulations we performed, the gravitational wave signature was extracted via the quadrupole formula in the slow-motion, weak-field approximation. We investigate the consequences of variation in the initial ratio of rotational kinetic energy to gravitational potential energy and in the initial degree of differential rotation. Furthermore, we include in our model suite progenitors from recent evolutionary calculations that take into account the effects of rotation and magnetic torques. For each model, we calculate gravitational radiation wave forms, characteristic wave strain spectra, energy spectra, final rotational profiles, and total radiated energy. In addition, we compare our model signals with the anticipated sensitivities of the 1st- and 2nd-generation LIGO detectors coming on line. We find that most of our models are detectable by LIGO from anywhere in the Milky Way.Comment: 13 pages, 22 figures, accepted for publication in ApJ (v600, Jan. 2004). Revised version: Corrected typos and minor mistakes in text and references. Minor additions to the text according to the referee's suggestions, conclusions unchange

Does adult ADHD interact with COMT val 158 met genotype to influence working memory performance?

Peer reviewedPostprin

The structure of causal sets

More often than not, recently popular structuralist interpretations of physical theories leave the central concept of a structure insufficiently precisified. The incipient causal sets approach to quantum gravity offers a paradigmatic case of a physical theory predestined to be interpreted in structuralist terms. It is shown how employing structuralism lends itself to a natural interpretation of the physical meaning of causal sets theory. Conversely, the conceptually exceptionally clear case of causal sets is used as a foil to illustrate how a mathematically informed rigorous conceptualization of structure serves to identify structures in physical theories. Furthermore, a number of technical issues infesting structuralist interpretations of physical theories such as difficulties with grounding the identity of the places of highly symmetrical physical structures in their relational profile and what may resolve these difficulties can be vividly illustrated with causal sets.Comment: 19 pages, 4 figure

Challenges of diagnosis and management of giant cell arteritis in general practice: a multimethods study

BACKGROUND: In the UK, general practitioners (GPs) are usually the first medical contact for patients with suspected giant cell arteritis (GCA). While rare, it is critical not to miss, as delayed treatment can lead to significant complications including permanent visual loss. To date, little is known about the approach and challenges to diagnosis and management of GCA by GPs. OBJECTIVE: To investigate the diagnosis and management of patients with suspected GCA in UK general practice. DESIGN AND PARTICIPANTS: A multimethods approach was taken, comprising a postal survey of 5000 randomly selected UK GPs and semistructured telephone interviews of 24 GPs from across the UK. SETTING: UK general practice. RESULTS: 1249 questionnaires were returned. 879 responders (70%) indicated that they had diagnosed and managed a patient with GCA. A variety of clinical features were used to identify GCA. 21.9% suggested that they would exclude GCA as a diagnosis if headache was absent and around one-third do not routinely initiate glucocorticoid treatment prior to referral. Significant regional variations in referral pathways were reported. Thematic analysis of interview transcripts highlighted fears relating to a missed diagnosis of GCA and the non-specific nature of early GCA presentation. Accessing specialist care was highlighted as challenging by many GPs and that a national standard fast-track pathway is lacking to support this patient group. Additionally there were significant concerns regarding potential adverse effects relating to long-term treatment with glucocorticoids. CONCLUSION: GPs appear to over-rely on headache to identify GCA and marked geographical differences in management, with conflicting referral pathways and difficulties in accessing appropriate services exist in the UK. A national standard for fast-tracking patients with suspected GCA to relevant specialists would be beneficial to improve care and outcomes for patients with GCA

Effet de différents systèmes de culture à couverture végétale sur le stockage du carbone dans un sol argileux des Hautes Terres de Madagascar

Stocker du carbone dans le sol permet d'améliorer ses propriétés physico-chimiques et de réduire les émissions de dioxyde de carbone vers l'atmosphère. L'effet des systèmes en semis direct avec couverture végétale (SCV) sur le stockage de C dans le sol est étudié sur un dispositif agronomique de longue durée (11 ans) à Antsirabe, Madagascar (16°C, 1 300 mm). Quatre systèmes sont étudiés: un système en labour conventionnel avec exportation des résidus de récolte [CT m/s, rotation maïs (Zea mays L.)-soja (Glycine max. L.)], et trois systèmes en SCV sans travail du sol, et avec restitution des résidus de récolte [NT m/s, rotation maïs-soja; NT m/m-d, rotation maïs-maïs avec une couverture végétale de Desmodium uncinatum; et NT h/s-k, rotation haricot (Phaseolus vulgaris)-soja avec une couverture végétale de Pennissetum clandestinum]. Le sol est très argileux, à faible capacité d'échange cationique mais possédant des propriétés andiques pouvant influencer les potentialités de stockage du C du sol. A 0-5 cm, les teneurs en C sont plus élevées sous SCV (NT m/s, NT m/m-d et NT his) que sous labour (CT m/s), et à 5-10 cm, elles sont plus élevées sous NT m/m-d et NT m/s que sous NT h/s-k et CT m/s. Le stockage annuel de C, à masse de sol équivalente, est de 0,69 et 1,01 mg C.ha-1.an-1, sous NT m/s et NT m/m-d pour l'horizon équivalent à 0-20 cm, alors qu'il n'y a pas d'effet SCV observé pour l'horizon équivalent à 0-40 cm. Ceci peut être dû à la fois à l'absence réelle de stockage comme à une variabilité initiale des teneurs en C dans les horizons de profondeurs, car le labour n'est effectué que jusqu'à 20 cm de profondeur. Les différences de stockage de C entre NT et CT dans la couche 0-20 cm sont essentiellement attribuées aux quantités beaucoup plus importantes de résidus organiques restituées par les systèmes NT par rapport au système labouré CT, mais on peut aussi envisager qu'une partie de cette différence soit le fait d'une perte de C par érosion sous labour. Les teneurs en macroagrégats stables (MA, 200-2 000 [mu]m) sont plus élevées sous NT m/s, NT h/s-k et NT m/m-d que sous CT m/s à 0-5 cm et à 5-10 cm. Cette teneur en MA est corrélée positivement (R = 0,408, p < 0,05, n = 24) avec la teneur en C du sol, ce qui pourrait induire (i) une amélioration de l'agrégation en fonction de l'augmentation de la teneur en C du sol et (ii) une protection du C se trouvant à l'intérieur de ces agrégats contre la minéralisation microbienne. Toutefois, la respirométrie ne montre pas une protection physique de C dans les sites de protection supérieurs à 200 [mu]m pour NT m/s et CT m/s. Dans cette étude, le C stocké dans le sol pourrait alors être protégé contre la minéralisation par d'autres processus comme l'adsorption sur les colloïdes du sol ou la recalcitrance biochimique de la matière organique du sol. (Résumé d'auteur

Infrared Properties of QCD from Dyson-Schwinger equations

I review recent results on the infrared properties of QCD from Dyson-Schwinger equations. The topics include infrared exponents of one-particle irreducible Green's functions, the fixed point behaviour of the running coupling at zero momentum, the pattern of dynamical quark mass generation and properties of light mesons.Comment: 47 pages, 19 figures, Topical Review to be published in J.Phys.G, v2: typos corrected and some references adde

Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant

Jet event rates in deep inelastic ep scattering at HERA are investigated applying the modified JADE jet algorithm. The analysis uses data taken with the H1 detector in 1994 and 1995. The data are corrected for detector and hadronization effects and then compared with perturbative QCD predictions using next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2) is determined evaluating the jet event rates. Values of alpha_S(Q^2) are extracted in four different bins of the negative squared momentum transfer~\qq in the range from 40 GeV2 to 4000 GeV2. A combined fit of the renormalization group equation to these several alpha_S(Q^2) values results in alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys. J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4

On-demand semiconductor single-photon source with near-unity indistinguishability

Single photon sources based on semiconductor quantum dots offer distinct advantages for quantum information, including a scalable solid-state platform, ultrabrightness, and interconnectivity with matter qubits. A key prerequisite for their use in optical quantum computing and solid-state networks is a high level of efficiency and indistinguishability. Pulsed resonance fluorescence (RF) has been anticipated as the optimum condition for the deterministic generation of high-quality photons with vanishing effects of dephasing. Here, we generate pulsed RF single photons on demand from a single, microcavity-embedded quantum dot under s-shell excitation with 3-ps laser pulses. The pi-pulse excited RF photons have less than 0.3% background contributions and a vanishing two-photon emission probability. Non-postselective Hong-Ou-Mandel interference between two successively emitted photons is observed with a visibility of 0.97(2), comparable to trapped atoms and ions. Two single photons are further used to implement a high-fidelity quantum controlled-NOT gate.Comment: 11 pages, 11 figure

Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA

Deep-inelastic positron-proton interactions at low values of Bjorken-x down to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons are studied with the H1 experiment at HERA. The inclusive cross section for pi^0 mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward pi^0 meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.Comment: 27 pages, 8 figures and 3 table