1,317 research outputs found
Recovering piecewise smooth functions from nonuniform Fourier measurements
In this paper, we consider the problem of reconstructing piecewise smooth
functions to high accuracy from nonuniform samples of their Fourier transform.
We use the framework of nonuniform generalized sampling (NUGS) to do this, and
to ensure high accuracy we employ reconstruction spaces consisting of splines
or (piecewise) polynomials. We analyze the relation between the dimension of
the reconstruction space and the bandwidth of the nonuniform samples, and show
that it is linear for splines and piecewise polynomials of fixed degree, and
quadratic for piecewise polynomials of varying degree
A temperature-controlled device for volumetric measurements of Helium adsorption in porous media
We describe a set-up for studying adsorption of helium in silica aerogels,
where the adsorbed amount is easily and precisely controlled by varying the
temperature of a gas reservoir between 80 K and 180 K. We present validation
experiments and a first application to aerogels. This device is well adapted to
study hysteresis, relaxation, and metastable states in the adsorption and
desorption of fluids in porous media
On the New Conditions for a Total Neutrino Conversion in a Medium
We show that the arguments forming the basis for the claim that the
conditions for total neutrino conversion derived and studied in detail in [1,2]
``are just the conditions of the parametric resonance of neutrino oscillations
supplemented by the requirement that the parametric enhancement be complete'',
given in [4] have flaws which make the claim physically questionable. We show
also that in the case of the transitions in the Earth of the
Earth-core-crossing solar and atmospheric neutrinos the peaks in the relevant
transitions probabilities , associated with the new conditions, , are of physical relevance - in contrast to what is suggested in
[4]. Actually, the enhancement of in any region of the corresponding
parameter space are essentially determined by these absolute maxima of . We comment on few other aspects of the results derived in [1,2,3] which
have been misunderstood and/or misinterpreted in [4].Comment: 8 pages, late
Evidence for a disorder driven phase transition in the condensation of 4He in aerogels
We report on thermodynamic and optical measurements of the condensation
process of He in three silica aerogels of different microstructures. For
the two base-catalysed aerogels, the temperature dependence of the shape of
adsorption isotherms and of the morphology of the condensation process show
evidence of a disorder driven transition, in agreement with recent theoretical
predictions. This transition is not observed for a neutral-catalysed aerogel,
which we interpret as due to a larger disorder in this case.Comment: 11 page
Back reaction of a long range force on a Friedmann-Robertson-Walker background
It is possible that there may exist long-range forces in addition to gravity.
In this paper we construct a simple model for such a force based on exchange of
a massless scalar field and analyze its effect on the evolution of a
homogeneous Friedmann-Robertson-Walker cosmology. The presence of such an
interaction leads to an equation of state characterized by positive pressure
and to resonant particle production similar to that observed in preheating
scenarios.Comment: 14 pages, 6 color Postscript figures, LaTe
Measurement of the solar neutrino capture rate with gallium metal
The solar neutrino capture rate measured by the Russian-American Gallium
Experiment (SAGE) on metallic gallium during the period January 1990 through
December 1997 is 67.2 (+7.2-7.0) (+3.5-3.0) SNU, where the uncertainties are
statistical and systematic, respectively. This represents only about half of
the predicted Standard Solar Model rate of 129 SNU. All the experimental
procedures, including extraction of germanium from gallium, counting of 71Ge,
and data analysis are discussed in detail.Comment: 34 pages including 14 figures, Revtex, slightly shortene
Seasonal Variations of the 7Be Solar Neutrino Flux
Measuring the 7Be solar neutrino flux is crucial towards solving the solar
neutrino puzzle. The Borexino experiment, and possibly the KamLAND experiment,
will be capable of studying the 7Be neutrinos in the near future. We discuss
(1) how the seasonal variation of the Borexino and KamLAND data can be used to
measure the 7Be solar neutrino flux in a background independent way and (2) how
anomalous seasonal variations might be used to discover vacuum neutrino
oscillations, independent of the solar model and the measurement of the
background. In particular, we find that, after three years of Borexino or
KamLAND running, vacuum neutrino oscillations can be either established or
excluded for almost all values of (sin^2 2 theta, Delta m^2) preferred by the
Homestake, GALLEX, SAGE, and Super-Kamiokande data. We also discuss how well
seasonal variations of the data can be used to measure (sin^2 2 theta, Delta
m^2) in the case of vacuum oscillations.Comment: 39 pages, 13 figures, uses psfig. Now the impact of the MSW effect on
vacuum oscillations taken into account. Conclusions unchanged. References
adde
Averages of -hadron, -hadron, and -lepton properties as of summer 2014
This article reports world averages of measurements of -hadron,
-hadron, and -lepton properties obtained by the Heavy Flavor Averaging
Group (HFAG) using results available through summer 2014. For the averaging,
common input parameters used in the various analyses are adjusted (rescaled) to
common values, and known correlations are taken into account. The averages
include branching fractions, lifetimes, neutral meson mixing parameters,
violation parameters, parameters of semileptonic decays and CKM matrix
elements.Comment: 436 pages, many figures and tables. Online updates available at
http://www.slac.stanford.edu/xorg/hfag
The General Practice Assessment Questionnaire (GPAQ) – Development and psychometric characteristics
<p>Abstract</p> <p>Background</p> <p>Continual quality improvement in primary care is an international priority. In the United Kingdom, the major initiative for improving quality of care is the Quality and Outcomes Framework (QoF) of the 2004 GP contract. Although the primary focus of the QoF is on clinical care, it is acknowledged that a comprehensive assessment of quality also requires valid and reliable measurement of the patient perspective, so financial incentives are included in the contract for general practices to survey patients' views. One questionnaire specified for use in the QoF is the General Practice Assessment Questionnaire (GPAQ). This paper describes the development of the GPAQ (with post-consultation and postal versions) and presents a preliminary examination of the psychometric properties of the questionnaire.</p> <p>Methods</p> <p>Description of scale development and preliminary analysis of psychometric characteristics (internal reliability, factor structure), based on a large dataset of routinely collected GPAQ surveys (n = 190,038 responses to the consultation version of GPAQ and 20,309 responses to the postal version) from practices in the United Kingdom during the 2005–6 contract year.</p> <p>Results</p> <p>Respondents tend to report generally favourable ratings. Responses were particularly skewed on the GP communication scale, though no more so than for other questionnaires in current use in the UK for which data were available. Factor analysis identified 2 factors that clearly relate to core concepts in primary care quality ('access' and 'interpersonal care') that were common to both version of the GPAQ. The other factors related to 'enablement' in the post-consultation version and 'nursing care' in the postal version.</p> <p>Conclusion</p> <p>This preliminary evaluation indicates that the scales of the GPAQ are internally reliable and that the items demonstrate an interpretable factor structure. Issues concerning the distributions of GPAQ responses are discussed. Potential further developments of the item content for the GPAQ are also outlined.</p
Search for decays with semileptonic tagging at Belle
We present the results of a search for the rare decays , where stands for and . The results are
obtained with pairs collected with the Belle
detector at the KEKB collider. We reconstruct one meson in a
semileptonic decay and require a single meson but nothing else on the
signal side. We observe no significant signal and set upper limits on the
branching fractions. The limits set on the , , , ,
, and channels
are the world's most stringent.Comment: Submitted to PR
- …