What it takes to measure a fundamental difference between dark matter and baryons: the halo velocity anisotropy

Numerous ongoing experiments aim at detecting WIMP dark matter particles from the galactic halo directly through WIMP-nucleon interactions. Once such a detection is established a confirmation of the galactic origin of the signal is needed. This requires a direction-sensitive detector. We show that such a detector can measure the velocity anisotropy beta of the galactic halo. Cosmological N-body simulations predict the dark matter anisotropy to be nonzero, beta~0.2. Baryonic matter has beta=0 and therefore a detection of a nonzero beta would be strong proof of the fundamental difference between dark and baryonic matter. We estimate the sensitivity for various detector configurations using Monte Carlo methods and we show that the strongest signal is found in the relatively few high recoil energy events. Measuring beta to the precision of ~0.03 will require detecting more than 10^4 WIMP events with nuclear recoil energies greater than 100 keV for a WIMP mass of 100 GeV and a 32S target. This number corresponds to ~10^6 events at all energies. We discuss variations with respect to input parameters and we show that our method is robust to the presence of backgrounds and discuss the possible improved sensitivity for an energy-sensitive detector.Comment: 15 pages, 8 figures, accepted by JCAP. Matches accepted versio

Reviews

Reviews: Arne Skjølsvold: Slettabøboplassen. Et bidrag til diskusjonen om forholdet mellem fangst- og bondesamfunnet i yngre steinalder og bronsealder. Stavanger 1977. (by Svend Nielsen). Klaus Ebbesen: Tragtbægerkultur i Nordjylland. Nordiske Fortidsminder. Ser. B, Vol. 5, 197 8. (by P. 0. Nielsen). Birgitta Hulthen: On Ceramic Technology during the Scanian Neolithic and Bronze Age. Stockholm 1977. (by Ulla Engberg). Renate Rolle: Totenkult der Skythen I. Das Steppengebiet. Vorgeschichtliche Forschungen 18,I, I and I,2. Berlin-N.Y. 1979. (by Ole Klindt-Jensen). Werner Haarnagel: Die Grabung Feddersen Wierde. Methode, Hausbau, Siedlungs- u. Wirtschaftsformen sowie Sozialstruktur. Wiesbaden 1979. (by Steen Hvass). U. Nasman and E. Wegraeus (eds.): Eketorp. Fortification and Settlement on Öland/Sweden. The Setting. Stockholm 1979. (by Ulla Lund Hansen). Ingrid Ulbricht: Die Geweihverarbeitung in Haithabu. Die Ausgrabungen in Haithabu, Vol. 7. Neumünster 1978 . Heid Gjöstein Resi: Die Specksteinfunde aus Haithabu. Berichte über die Ausgrabungen in Haithabu, Vol. 14. Neumünster 1979. (by Hans Jørgen Madsen)

Radiofrequency Ablation as Initial Therapy in Paroxysmal Atrial Fibrillation

Background There are limited data comparing radiofrequency catheter ablation with antiarrhythmic drug therapy as first-line treatment in patients with paroxysmal atrial fibrillation. Methods We randomly assigned 294 patients with paroxysmal atrial fibrillation and no history of antiarrhythmic drug use to an initial treatment strategy of either radiofrequency catheter ablation (146 patients) or therapy with class IC or class III antiarrhythmic agents (148 patients). Follow-up included 7-day Holter-monitor recording at 3, 6, 12, 18, and 24 months. Primary end points were the cumulative and per-visit burden of atrial fibrillation (i.e., percentage of time in atrial fibrillation on Holter-monitor recordings). Analyses were performed on an intention-to-treat basis. Results There was no significant difference between the ablation and drug-therapy groups in the cumulative burden of atrial fibrillation (90th percentile of arrhythmia burden, 13% and 19%, respectively; P = 0.10) or the burden at 3, 6, 12, or 18 months. At 24 months, the burden of atrial fibrillation was significantly lower in the ablation group than in the drug-therapy group (90th percentile, 9% vs. 18%; P = 0.007), and more patients in the ablation group were free from any atrial fibrillation (85% vs. 71%, P = 0.004) and from symptomatic atrial fibrillation (93% vs. 84%, P = 0.01). One death in the ablation group was due to a procedure-related stroke; there were three cases of cardiac tamponade in the ablation group. In the drug-therapy group, 54 patients (36%) underwent supplementary ablation. Conclusions In comparing radiofrequency ablation with antiarrhythmic drug therapy as first-line treatment in patients with paroxysmal atrial fibrillation, we found no significant difference between the treatment groups in the cumulative burden of atrial fibrillation over a period of 2 years. (Funded by the Danish Heart Foundation and others; MANTRA-PAF ClinicalTrials.gov number, NCT00133211.

A detailed statistical analysis of the mass profiles of galaxy clusters

The distribution of mass in the halos of galaxies and galaxy clusters has been probed observationally, theoretically, and in numerical simulations. Yet there is still confusion about which of several suggested parameterized models is the better representation, and whether these models are universal. We use the temperature and density profiles of the intracluster medium as measured by X-ray observations of 11 relaxed galaxy clusters to investigate mass models for the halo using a thorough Bayesian statistical analysis. We make careful comparisons between two- and three-parameter models, including the issue of a universal third parameter. We find that, of the two-parameter models, the NFW is the best representation, but we also find moderate statistical evidence that a generalized three-parameter NFW model with a freely varying inner slope is preferred, despite penalizing against the extra degree of freedom. There is a strong indication that this inner slope needs to be determined for each cluster individually, i.e. some clusters have central cores and others have steep cusps. The mass-concentration relation of our sample is in reasonable agreement with predictions based on numerical simulations.Comment: 10 pages, 5 figures, accepted by ApJ. Matches accepted versio

Discontinuation of hormone replacement therapy after myocardial infarction and short term risk of adverse cardiovascular events: nationwide cohort study

Objective To assess the risk of adverse cardiovascular events in women who discontinue hormone replacement therapy after myocardial infarction compared with those who continue

Cardiorespiratory fitness, cardiovascular workload and risk factors among cleaners; a cluster randomized worksite intervention

BACKGROUND: Prevalence of cardiovascular risk factors is unevenly distributed among occupational groups. The working environment, as well as lifestyle and socioeconomic status contribute to the disparity and variation in prevalence of these risk factors. High physical work demands have been shown to increase the risk for cardiovascular disease and mortality, contrary to leisure time physical activity. High physical work demands in combination with a low cardiorespiratory fitness infer a high relative workload and an excessive risk for cardiovascular mortality. Therefore, the aim of this study is to examine whether a worksite aerobic exercise intervention will reduce the relative workload and cardiovascular risk factors by an increased cardiorespiratory fitness. METHODS/DESIGN: A cluster-randomized controlled trial is performed to evaluate the effect of the worksite aerobic exercise intervention on cardiorespiratory fitness and cardiovascular risk factors among cleaners. Cleaners are eligible if they are employed ≥ 20 hours/week, at one of the enrolled companies. In the randomization, strata are formed according to the manager the participant reports to. The clusters will be balanced on the following criteria: Geographical work location, gender, age and seniority. Cleaners are randomized to either I) a reference group, receiving lectures concerning healthy living, or II) an intervention group, performing worksite aerobic exercise “60 min per week”. Data collection will be conducted at baseline, four months and 12 months after baseline, at the worksite during working hours. The data collection will consist of a questionnaire-based interview, physiological testing of health and capacity-related measures, and objective diurnal measures of heart rate, physical activity and blood pressure. Primary outcome is cardiorespiratory fitness. DISCUSSION: Information is lacking about whether an improved cardiorespiratory fitness will affect the cardiovascular health, and additionally decrease the objectively measured relative workload, in a population with high physical work demands. Previous intervention studies have lacked robust objective measurements of the relative workload and physical work demands. This study will monitor the relative workload and general physical activity before, during after the intervention, and contribute to the understanding of the previously observed opposing effects on cardiovascular health and mortality from occupational and leisure time physical activity. TRIAL REGISTRATION: The study is registered as ISRCTN86682076