3,799 research outputs found
Interpreting Dark Matter Direct Detection Independently of the Local Velocity and Density Distribution
We demonstrate precisely what particle physics information can be extracted
from a single direct detection observation of dark matter while making
absolutely no assumptions about the local velocity distribution and local
density of dark matter. Our central conclusions follow from a very simple
observation: the velocity distribution of dark matter is positive definite,
f(v) >= 0. We demonstrate the utility of this result in several ways. First, we
show a falling deconvoluted recoil spectrum (deconvoluted of the nuclear form
factor), such as from ordinary elastic scattering, can be "mocked up" by any
mass of dark matter above a kinematic minimum. As an example, we show that dark
matter much heavier than previously considered can explain the CoGeNT excess.
Specifically, m_chi < m_Ge} can be in just as good agreement as light dark
matter, while m_\chi > m_Ge depends on understanding the sensitivity of Xenon
to dark matter at very low recoil energies, E_R ~ 6 keVnr. Second, we show that
any rise in the deconvoluted recoil spectrum represents distinct particle
physics information that cannot be faked by an arbitrary f(v). As examples of
resulting non-trivial particle physics, we show that inelastic dark matter and
dark matter with a form factor can both yield such a rise
Robust Bayesian detection of unmodelled bursts
A Bayesian treatment of the problem of detecting an unmodelled gravitational
wave burst with a global network of gravitational wave observatories reveals
that several previously proposed statistics have implicit biases that render
them sub-optimal for realistic signal populations.Comment: 9 pages, 1 figure, submitted to CQG Amaldi proceedings special issu
Magnetic structures of NaLMnWO_6 perovskites (L=La,Nd,Tb)
The magnetic structures of the perovskites NaLaMnWO_6, NaNdMnWO_6, and NaTbMnWO_6, with rocksalt ordering of the Mn/W ions and layered ordering of Na and the rare-earth ions, have been determined by neutron powder diffraction. The manganese moments in NaLaMnWO_6 order below 10 K with a propagation vector of k_14=(1/2,0,1/2) and a moment of 3.99Ī¼B per Mn^2+ ion. The Mn^2+ and Nd^3+ ions order simultaneously in NaNdMnWO_6 at 11 K. The resulting magnetic structure is incommensurate with the underlying crystal structure and has the propagation vector of k_5=(0,0.48,1/2). NaTbMnWO_6 undergoes two magnetic phase transitions at 15 and 9 K. The structure determined at 11 K is based on two propagation vectors of k_14=(1/2,0,1/2) and k_5=(0,0.427,1/2). Upon cooling at 6 K the incommensurate vector is no longer present and the moments order only according to k_14. The moments of the Nd and Tb ions are found to remain within the planes of the A-site cations, and in NaTbMnWO_6 the Mn moments also lie within the xy plane. This study not only reveals magnetic structures with previously unexplored topologies but it also sheds light on the intricate coupling between the two magnetic sublattices
Measuring the difference between actual and reported food intakes in the context of energy balance under laboratory conditions
Acknowledgements The present study was funded by the Food Standards Agency, UK. The Food Standards Agency had no role in the design, analysis or writing of this article. The authorsā responsibilities were as follows: R. J. S., L. M. OāR. and G. W. H. designed the research; L. M. OāR. and Z. F. conducted the research and analysed the data; G. W. H. performed the statistical analyses; P. R. carried out the DLW analysis; R. J. S. had primary responsibility for the final content; R. J. S., L. M. OāR., Z. F., S. W. and M. B. E. L. wrote the paper.Peer reviewedPublisher PD
Incidence and severity of respiratory syncytial virus pneumonia in rural Kenyan children identified through hospital surveillance
Background.Although necessary for developing a rationale for vaccination, the burden of severe respiratory syncytial virus (RSV) disease in children in resourceāpoor settings remains poorly defined.
Methods.We conducted prospective surveillance of severe and very severe pneumonia in children aged <5 years admitted from 2002 through 2007 to Kilifi district hospital in coastal Kenya. Nasal specimens were screened for RSV antigen by immunofluorescence. Incidence rates were estimated for the wellādefined population.
Results.Of 25,149 hospital admissions, 7359 patients (29%) had severe or very severe pneumonia, of whom 6026 (82%) were enrolled. RSV prevalence was 15% (20% among infants) and 27% during epidemics (32% among infants). The proportion of case patients aged 3 months was 65%, and the proportion aged 6 months was 43%. Average annual hospitalization rates were 293 hospitalizations per 100,000 children aged <5 years (95% confidence interval, 271ā371 hospitalizations per 100,000 children aged <5 years) and 1107 hospitalizations per 100,000 infants (95% confidence interval, 1012ā1211 hospitalizations per 100,000 infants). Hospital admission rates were double in the region close to the hospital. Few patients with RSV infection had lifeāthreatening clinical features or concurrent serious illnesses, and the associated mortality was 2.2%.
Conclusions.In this lowāincome setting, rates of hospital admission with RSVāassociated pneumonia are substantial; they are comparable to estimates from the United States but considerably underestimate the burden in the full community. An effective vaccine for children aged >2 months (outside the age group of poor responders) could prevent a large portion of RSV disease. Severity data suggest that the justification for RSV vaccination will be based on the prevention of morbidity, not mortality
An unusual case of finger swelling: A case report
A 66 year old man initially presented with haemoptysis and subsequently required a pneumonectomy for a lung mass, following this he had a finger swelling which was found to be a rare leiomyosarcoma and this was a metastatic deposit. This pattern of metastasis for this type of tumour has not been described before
SN 2015U: A Rapidly Evolving and Luminous Type Ibn Supernova
Supernova (SN) 2015U (also known as PSN J07285387+3349106) was discovered in
NGC 2388 on 2015 Feb. 11. A rapidly evolving and luminous event, it showed
effectively hydrogen-free spectra dominated by relatively narrow helium P-Cygni
spectral features and it was classified as a SN Ibn. In this paper we present
photometric, spectroscopic, and spectropolarimetric observations of SN 2015U,
including a Keck/DEIMOS spectrum (resolution 5000) which fully
resolves the optical emission and absorption features. We find that SN 2015U is
best understood via models of shock breakout from extended and dense
circumstellar material (CSM), likely created by a history of mass loss from the
progenitor with an extreme outburst within 1-2 yr of core collapse (but
we do not detect any outburst in our archival imaging of NGC 2388). We argue
that the high luminosity of SN 2015U was powered not through Ni decay
but via the deposition of kinetic energy into the ejecta/CSM shock interface.
Though our analysis is hampered by strong host-galaxy dust obscuration (which
likely exhibits multiple components), our dataset makes SN 2015U one of the
best-studied Type Ibn supernovae and provides a bridge of understanding to
other rapidly fading transients, both luminous and relatively faint.Comment: 20 pages, 15 figures, 4 table
Small domain estimation of census coverage: A case study in Bayesian analysis of complex survey data
Many countries conduct a full census survey to report official population
statistics. As no census survey ever achieves 100 per cent response rate, a
post-enumeration survey (PES) is usually conducted and analysed to assess
census coverage and produce official population estimates by geographic area
and demographic attributes. Considering the usually small size of PES, direct
estimation at the desired level of disaggregation is not feasible. Design-based
estimation with sampling weight adjustment is a commonly used method but is
difficult to implement when survey non-response patterns cannot be fully
documented and population benchmarks are not available. We overcome these
limitations with a fully model-based Bayesian approach applied to the New
Zealand PES. Although theory for the Bayesian treatment of complex surveys has
been described, published applications of individual level Bayesian models for
complex survey data remain scarce. We provide such an application through a
case study of the 2018 census and PES surveys. We implement a multilevel model
that accounts for the complex design of PES. We then illustrate how mixed
posterior predictive checking and cross-validation can assist with model
building and model selection. Finally, we discuss potential methodological
improvements to the model and potential solutions to mitigate dependence
between the two surveys.Comment: 35 pages, 5 figures This is an author version of a paper accepted for
publication in the Journal of Official Statistics. Once published by the
Journal of Official Statistics use the Journal citation. This version
includes supplementary material and corrected version of Figure
Occurrence Of Atlantic Tarpon, Megalops atlanticus, Leptocephali In The Mississippi Sound Estuary
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