W/Z Bremsstrahlung as the Dominant Annihilation Channel for Dark Matter, Revisited

We revisit the calculation of electroweak bremsstrahlung contributions to dark matter annihilation. Dark matter annihilation to leptons is necessarily accompanied by electroweak radiative corrections, in which a $W$ or $Z$ boson is also radiated. Significantly, while many dark matter models feature a helicity suppressed annihilation rate to fermions, bremsstrahlung process can remove this helicity suppression such that the branching ratios Br($\ell \nu W$), Br($\ell^+\ell^-Z$), and Br($\bar\nu \nu Z$) dominate over Br($\ell^+\ell^-$) and Br($\bar\nu \nu$). We find this is most significant in the limit where the dark matter mass is nearly degenerate with the mass of the boson which mediates the annihilation process. Electroweak bremsstrahlung has important phenomenological consequences both for the magnitude of the total dark matter annihilation cross section and for the character of the astrophysical signals for indirect detection. Given that the $W$ and $Z$ gauge bosons decay dominantly via hadronic channels, it is impossible to produce final state leptons without accompanying protons, antiprotons, and gamma rays.Comment: 8 pages, 6 figures; replaced to match published versio

Constraints on neutrino masses from leptogenesis models

Upper bounds on the CP asymmetry relevant for leptogenesis are reexamined and found weaker than in previous literature, both for hierarchical and for quasi-degenerate right-handed neutrinos. Successful leptogenesis implies the usual lower bound on right-handed neutrino masses, and an upper bound on left-handed neutrino masses (which we obtain to be 0.15eV at 3sigma) only if right-handed neutrinos are assumed to be much more hierarchical than left-handed neutrinos. Otherwise both bounds can be considerably relaxed. The constraint on light neutrino masses varies assuming different interpretations of why neutrinos should be quasi-degenerate. With conservative assumptions, we find that a mild quasi-degeneracy allows neutrinos heavier than an eV compatibly with leptogenesis. We also extend computations of thermal leptogenesis to an alternative model of neutrino mass mediated by fermion triplets which was never considered so far for leptogenesis. Leptogenesis can be successful despite the effect of gauge interactions, resulting in only slightly stronger constraints on neutrino masses.Comment: 16 pages, 6 figure

The impact of the resident duty hour regulations on surgical patients’ perceptions of care

Implementation of the 2003 Accreditation Council for Graduate Medical Education (ACGME) resident duty-hour regulations and access to publicly reported patient satisfaction measures have challenged administrators and clinicians to balance resident’s educational experience, patient care quality, and patients’ satisfaction and perceptions. A pre-post retrospective study design investigated association between implementation of ACGME regulations and patient satisfaction/perceptions using multinomial logistic regressions. The sample consisted of all surgical inpatients (July 2001 – June 2005), who responded to surveys at an academic medical center. Patients gave lower ratings for physician interactions (patient-physician interaction time, clinical updates, and courtesy) following the implementation of post-duty hour regulations. While the odds of patients rating “below good” post-implementation for physician survey questions (i.e., related to time spent, kept informed, and friendliness/ courtesy) were higher (i.e., 1.25 to 1.3) as compared to odds of rating “very good”, the overall rating of quality care improved post-implementation. This difference could be due to increased interaction of patients with other hospital personnel. To improve patient satisfactions and in turn their perceptions, initiatives such as workload balancing, hand-off protocols, patient communication, and interactive training for care providers are recommended. Finally, residency programs and institutions need to develop strategies for implementation of current and future ACGME duty hour regulations so as to balance patient safety, patient perceptions, and resident well-being

Imprints of dynamical dark energy on weak-lensing measurements

We show that simple models of scalar-field dark energy leave a generic enhancement in the weak-lensing power spectrum when compared to the LCDM prediction. In particular, we calculate the linear-scale enhancement in the convergence (or cosmic-shear) power spectrum for two best-fit models of scalar-field dark energy, namely, the Ratra-Peebles and SUGRA-type quintessence. Our calculations are based on linear perturbation theory, using gauge-invariant variables with carefully defined adiabatic initial conditions. We find that geometric effects enhance the lensing power spectrum on a broad range of scales, whilst the clustering of dark energy gives rise to additional power on large scales. The dark-energy power spectrum for these models are also explicitly obtained. On degree scales, the total enhancement may be as large as 30-40% for sources at redshift ~1. We argue that there are realistic prospects for detecting such an enhancement using the next generation of large telescopes.Comment: 10 pages, 8 figures, replacement matches version published in MNRA

A step towards testing general relativity using weak gravitational lensing and redshift surveys

Using the linear theory of perturbations in General Relativity, we express a set of consistency relations that can be observationally tested with current and future large scale structure surveys. We then outline a stringent model-independent program to test gravity on cosmological scales. We illustrate the feasibility of such a program by jointly using several observables like peculiar velocities, galaxy clustering and weak gravitational lensing. After addressing possible observational or astrophysical caveats like galaxy bias and redshift uncertainties, we forecast in particular how well one can predict the lensing signal from a cosmic shear survey using an over-lapping galaxy survey. We finally discuss the specific physics probed this way and illustrate how $f(R)$ gravity models would fail such a test.Comment: 12 pages, 10 figure

The Interplay Between GUT and Flavour Symmetries in a Pati-Salam x S4 Model

Both Grand Unified symmetries and discrete flavour symmetries are appealing ways to describe apparent structures in the gauge and flavour sectors of the Standard Model. Both symmetries put constraints on the high energy behaviour of the theory. This can give rise to unexpected interplay when building models that possess both symmetries. We investigate on the possibility to combine a Pati-Salam model with the discrete flavour symmetry $S_4$ that gives rise to quark-lepton complementarity. Under appropriate assumptions at the GUT scale, the model reproduces fermion masses and mixings both in the quark and in the lepton sectors. We show that in particular the Higgs sector and the running Yukawa couplings are strongly affected by the combined constraints of the Grand Unified and family symmetries. This in turn reduces the phenomenologically viable parameter space, with high energy mass scales confined to a small region and some parameters in the neutrino sector slightly unnatural. In the allowed regions, we can reproduce the quark masses and the CKM matrix. In the lepton sector, we reproduce the charged lepton masses, including bottom-tau unification and the Georgi-Jarlskog relation as well as the two known angles of the PMNS matrix. The neutrino mass spectrum can present a normal or an inverse hierarchy, and only allowing the neutrino parameters to spread into a range of values between $\lambda^{-2}$ and $\lambda^2$, with $\lambda\simeq0.2$. Finally, our model suggests that the reactor mixing angle is close to its current experimental bound.Comment: 62 pages, 4 figures; references added, version accepted for publication in JHE

Impact of hiatal hernia on histological pattern of non-erosive reflux disease

BACKGROUND: Hiatus hernia (HH) has major pathophysiological effects favoring gastroesophageal reflux and hence contributing to esophageal mucosa injury, especially in patients with severe gastroesophageal disease. However, prospective studies investigating the impact of HH on the esophageal mucosa in non-erosive reflux disease (NERD) are lacking. This study evaluated the association between the presence of (HH) and the histological findings in symptomatic patients with NERD. METHODS: Fifty consecutive patients with gastroesophageal reflux disease (GERD) were enrolled. After conventional endoscopy, Lugol solution was applied and biopsy specimens were obtained. Histological parameters including basal zone hyperplasia, papillary length and cellular infiltration were evaluated. The chi-square test with Yates' correlation was used for comparing discrete parameters between groups. However, Fisher's exact probability test was used where the expected frequencies were lower than 5. Wilcoxon's test for unpaired samples was preferred in cases of semi-quantitative parameters. RESULTS: The presence of HH along with more severe findings (0.01 <P < 0.05) was confirmed in 18 patients. NERD was observed in 29 (58%) patients. Basal zone hyperplasia and loss of glycogen accompanied HH in all cases, and the correlation was significant in NERD (P < 0.001). The remaining histological patterns were similar between erosive reflux disease and NERD in the presence of HH. CONCLUSION: The presence of HH is correlated with more severe endoscopy findings, and predisposes for severe histological abnormality in cases of NERD

A systematic review of models to predict recruitment to multicentre clinical trials

<p>Abstract</p> <p>Background</p> <p>Less than one third of publicly funded trials managed to recruit according to their original plan often resulting in request for additional funding and/or time extensions. The aim was to identify models which might be useful to a major public funder of randomised controlled trials when estimating likely time requirements for recruiting trial participants. The requirements of a useful model were identified as usability, based on experience, able to reflect time trends, accounting for centre recruitment and contribution to a commissioning decision.</p> <p>Methods</p> <p>A systematic review of English language articles using MEDLINE and EMBASE. Search terms included: randomised controlled trial, patient, accrual, predict, enrol, models, statistical; Bayes Theorem; Decision Theory; Monte Carlo Method and Poisson. Only studies discussing prediction of recruitment to trials using a modelling approach were included. Information was extracted from articles by one author, and checked by a second, using a pre-defined form.</p> <p>Results</p> <p>Out of 326 identified abstracts, only 8 met all the inclusion criteria. Of these 8 studies examined, there are five major classes of model discussed: the unconditional model, the conditional model, the Poisson model, Bayesian models and Monte Carlo simulation of Markov models. None of these meet all the pre-identified needs of the funder.</p> <p>Conclusions</p> <p>To meet the needs of a number of research programmes, a new model is required as a matter of importance. Any model chosen should be validated against both retrospective and prospective data, to ensure the predictions it gives are superior to those currently used.</p