651 research outputs found
Generalized Analysis of Weakly-Interacting Massive Particle Searches
We perform a generalized analysis of data from WIMP search experiments for
point-like WIMPs of arbitrary spin and general Lorenz-invariant WIMP-nucleus
interaction. We show that in the non-relativistic limit only spin-independent
(SI) and spin-dependent (SD) WIMP-nucleon interactions survive, which can be
parameterized by only five independent parameters. We explore this
five-dimensional parameter space to determine whether the annual modulation
observed in the DAMA experiment can be consistent with all other experiments.
The pure SI interaction is ruled out except for very small region of parameter
space with the WIMP mass close to 50 GeV and the ratio of the WIMP-neutron to
WIMP-proton SI couplings . For the predominantly SD
interaction, we find an upper limit to the WIMP mass of about 18 GeV, which can
only be weakened if the constraint stemming from null searches for energetic
neutrinos from WIMP annihilation the Sun is evaded. None of the regions of the
parameter space that can reconcile all WIMP search results can be easily
accommodated in the minimal supersymmetric extension of the standard model.Comment: 27 pages, 3 figure
Approximate Particle Number Projection for Rotating Nuclei
Pairing correlations in rotating nuclei are discussed within the
Lipkin-Nogami method. The accuracy of the method is tested for the
Krumlinde-Szyma\'nski R(5) model. The results of calculations are compared with
those obtained from the standard mean field theory and particle-number
projection method, and with exact solutions.Comment: 15 pages, 6 figures available on request, REVTEX3.
The last integrable case of kozlov-Treshchev Birkhoff integrable potentials
We establish the integrability of the last open case in the Kozlov-Treshchev
classification of Birkhoff integrable Hamiltonian systems. The technique used
is a modification of the so called quadratic Lax pair for Toda lattice
combined with a method used by M. Ranada in proving the integrability of the
Sklyanin case.Comment: 13 page
Minimum mass of galaxies from BEC or scalar field dark matter
Many problems of cold dark matter models such as the cusp problem and the
missing satellite problem can be alleviated, if galactic halo dark matter
particles are ultra-light scalar particles and in Bose-Einstein condensate
(BEC), thanks to a characteristic length scale of the particles. We show that
this finite length scale of the dark matter can also explain the recently
observed common central mass of the Milky Way satellites ()
independent of their luminosity, if the mass of the dark matter particle is
about .Comment: 10 pages, 1 figure, accepted in JCA
How large is "large " for Nuclear matter?
We argue that a so far neglected dimensionless scale, the number of neighbors
in a closely packed system, is relevant for the convergence of the large
expansion at high chemical potential. It is only when the number of colors is
large w.r.t. this new scale (\sim \order{10}) that a convergent large
limit is reached. This provides an explanation as to why the large
expansion, qualitatively successful in in vacuum QCD, fails to describe high
baryo-chemical potential systems, such as nuclear matter. It also means that
phenomenological claims about high density matter based on large
extrapolations should be treated with caution.Comment: Proceedings of CPOD2010 conference, in Dubna. Results based on
Phys.Rev.C82, 055202 (2010), http://arxiv.org/abs/1006.247
Information for decision making from imperfect national data: tracking major changes in health care use in Kenya using geostatistics
Background: most Ministries of Health across Africa invest substantial resources in some form of health management information system (HMIS) to coordinate the routine acquisition and compilation of monthly treatment and attendance records from health facilities nationwide. Despite the expense of these systems, poor data coverage means they are rarely, if ever, used to generate reliable evidence for decision makers. One critical weakness across Africa is the current lack of capacity to effectively monitor patterns of service use through time so that the impacts ofchanges in policy or service delivery can be evaluated. Here, we present a new approach that, for the first time, allows national changes in health service use during a time of major health policy change to be tracked reliably using imperfect data from a national HMIS.Methods: monthly attendance records were obtained from the Kenyan HMIS for 1 271 government-run and 402 faith-based outpatient facilities nationwide between 1996 and 2004. Aspace-time geostatistical model was used to compensate for the large proportion of missing records caused by non-reporting health facilities, allowing robust estimation of monthly and annualuse of services by outpatients during this period.Results: we were able to reconstruct robust time series of mean levels of outpatient utilisation of health facilities at the national level and for all six major provinces in Kenya. These plots revealed reliably for the first time a period of steady nationwide decline in the use of health facilities in Kenyabetween 1996 and 2002, followed by a dramatic increase from 2003. This pattern was consistent across different causes of attendance and was observed independently in each province.Conclusion: the methodological approach presented can compensate for missing records in health information systems to provide robust estimates of national patterns of outpatient service use. This represents the first such use of HMIS data and contributes to the resurrection of these hugely expensive but underused systems as national monitoring tools. Applying this approach to Kenya has yielded output with immediate potential to enhance the capacity of decision makers in monitoring nationwide patterns of service use and assessing the impact of changes in health policy and service deliver
Solar Wakes of Dark Matter Flows
We analyze the effect of the Sun's gravitational field on a flow of cold dark
matter (CDM) through the solar system in the limit where the velocity
dispersion of the flow vanishes. The exact density and velocity distributions
are derived in the case where the Sun is a point mass. The results are extended
to the more realistic case where the Sun has a finite size spherically
symmetric mass distribution. We find that regions of infinite density, called
caustics, appear. One such region is a line caustic on the axis of symmetry,
downstream from the Sun, where the flow trajectories cross. Another is a
cone-shaped caustic surface near the trajectories of maximum scattering angle.
The trajectories forming the conical caustic pass through the Sun's interior
and probe the solar mass distribution, raising the possibility that the solar
mass distribution may some day be measured by a dark matter detector on Earth.
We generalize our results to the case of flows with continuous velocity
distributions, such as that predicted by the isothermal model of the Milky Way
halo.Comment: 30 pages, 8 figure
Effect of alirocumab on major adverse cardiovascular events according to renal function in patients with a recent acute coronary syndrome: Prespecified analysis from the ODYSSEY OUTCOMES randomized clinical trial
Aims Statins reduce cardiovascular risk in patients with acute coronary syndrome (ACS) and normal-to-moderately impaired renal function. It is not known whether proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors provide similar benefit across a range of renal function. We determined whether effects of the PCSK9 inhibitor alirocumab to reduce cardiovascular events and death after ACS are influenced by renal function. ................................................................................................................................................................................................... Methods ODYSSEY OUTCOMES compared alirocumab with placebo in patients with recent ACS and dyslipidaemia despite and results intensive statin treatment. Estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m was exclusionary. In 18 918 patients, baseline eGFR was 82.8 ± 17.6 mL/min/1.73 m , and low-density lipoprotein cholesterol (LDL-C) was 92 ± 31 mg/dL. At 36 months, alirocumab decreased LDL-C by 48.5% vs. placebo but did not affect eGFR (P = 0.65). Overall, alirocumab reduced risk of the primary outcome (coronary heart disease death, non-fatal myocardial infarction, ischaemic stroke, or unstable angina requiring hospitalization) with fewer deaths. There was no interaction between continuous eGFR and treatment on the primary outcome or death (P = 0.14 and 0.59, respectively). Alirocumab reduced primary outcomes in patients with eGFR >_90 mL/min/1.73 m (n = 7470; hazard ratio 0.784, 95% confidence interval 0.670–0.919; P = 0.003) and 60 to <90 (n = 9326; 0.833, 0.731–0.949; P = 0.006), but not in those with eGFR < 60 (n = 2122; 0.974, 0.805–1.178; P = 0.784). Adverse events other than local injection-site reactions were similar in both groups across all categories of eGFR. ................................................................................................................................................................................................... Conclusions In patients with recent ACS, alirocumab was associated with fewer cardiovascular events and deaths across the range of renal function studied, with larger relative risk reductions in those with eGFR > 60 mL/min/1.73 m 2 2 2 2The trial was funded by Sanofi and Regeneron Pharmaceuticals, Inc
Modelling interventions and contact networks to reduce the spread of carbapenem-resistant organisms between individuals in the ICU
Background: Contact precautions are widely used to prevent the transmission of carbapenem-resistant organisms (CROs) in hospital wards. However, evidence for their effectiveness in natural hospital environments is limited. Objective: To determine which contact precautions, healthcare worker (HCW)–patient interactions, and patient and ward characteristics are associated with greater risk of CRO infection or colonization. Design, setting and participants: CRO clinical and surveillance cultures from two high-acuity wards were assessed through probabilistic modelling to characterize a susceptible patient's risk of CRO infection or colonization during a ward stay. User- and time-stamped electronic health records were used to build HCW-mediated contact networks between patients. Probabilistic models were adjusted for patient (e.g. antibiotic administration) and ward (e.g. hand hygiene compliance, environmental cleaning) characteristics. The effects of risk factors were assessed by adjusted odds ratio (aOR) and 95% Bayesian credible intervals (CrI). Exposures: The degree of interaction with CRO-positive patients, stratified by whether CRO-positive patients were on contact precautions. Main outcomes and measures: The prevalence of CROs and number of new carriers (i.e. incident CRO aquisition). Results: Among 2193 ward visits, 126 (5.8%) patients became colonized or infected with CROs. Susceptible patients had 4.8 daily interactions with CRO-positive individuals on contact precautions (vs 1.9 interactions with those not on contact precautions). The use of contact precautions for CRO-positive patients was associated with a reduced rate (7.4 vs 93.5 per 1000 patient-days at risk) and odds (aOR 0.03, 95% CrI 0.01–0.17) of CRO acquisition among susceptible patients, resulting in an estimated absolute risk reduction of 9.0% (95% CrI 7.6–9.2%). Also, carbapenem administration to susceptible patients was associated with increased odds of CRO acquisition (aOR 2.38, 95% CrI 1.70–3.29). Conclusions and relevance: In this population-based cohort study, the use of contact precautions for patients colonized or infected with CROs was associated with lower risk of CRO acquisition among susceptible patients, even after adjusting for antibiotic exposure. Further studies that include organism genotyping are needed to confirm these findings
Detecting a stochastic gravitational wave background with the Laser Interferometer Space Antenna
The random superposition of many weak sources will produce a stochastic
background of gravitational waves that may dominate the response of the LISA
(Laser Interferometer Space Antenna) gravitational wave observatory. Unless
something can be done to distinguish between a stochastic background and
detector noise, the two will combine to form an effective noise floor for the
detector. Two methods have been proposed to solve this problem. The first is to
cross-correlate the output of two independent interferometers. The second is an
ingenious scheme for monitoring the instrument noise by operating LISA as a
Sagnac interferometer. Here we derive the optimal orbital alignment for
cross-correlating a pair of LISA detectors, and provide the first analytic
derivation of the Sagnac sensitivity curve.Comment: 9 pages, 11 figures. Significant changes to the noise estimate
- …