1,471 research outputs found
The influence of structural defects on intra-granular critical currents of bulk MgB2
Bulk MgB2 samples were prepared under different synthesis conditions and
analyzed by scanning and transmission electron microscopy. The critical current
densities were determined from the magnetization versus magnetic field curves
of bulk and powder-dispersed-in-epoxy samples. Results show that through a slow
cooling process, the oxygen dissolved in bulk MgB2 at high synthesis
temperatures can segregate and form nanometer-sized coherent precipitates of
Mg(B,O)2 in the MgB2 matrix. Magnetization measurements indicate that these
precipitates act as effective flux pinning centers and therefore significantly
improve the intra-grain critical current density and its field dependence.Comment: 4 pages, 4 figures, to be published in IEE Transactions in Applied
Superconductivit
Why does the Engel method work? Food demand, economies of size and household survey methods
Estimates of household size economies are needed for the analysis of poverty and inequality. This paper shows that Engel estimates of size economies are large when household expenditures are obtained by respondent recall but small when expenditures are obtained by daily recording in diaries. Expenditure estimates from recall surveys appear to have measurement errors correlated with household size. As well as demonstrating the fragility of Engel estimates of size economies, these results help resolve a puzzle raised by Deaton and Paxson (1998) about differences between rich and poor countries in the effect of household size on food demand
Search for a T-odd, P-even Triple Correlation in Neutron Decay
Background: Time-reversal-invariance violation, or equivalently CP violation,
may explain the observed cosmological baryon asymmetry as well as signal
physics beyond the Standard Model. In the decay of polarized neutrons, the
triple correlation D\cdot(p_{e}\timesp_{\nu}) is a parity-even,
time-reversal- odd observable that is uniquely sensitive to the relative phase
of the axial-vector amplitude with respect to the vector amplitude. The triple
correlation is also sensitive to possible contributions from scalar and tensor
amplitudes. Final-state effects also contribute to D at the level of 1e-5 and
can be calculated with a precision of 1% or better. Purpose: We have improved
the sensitivity to T-odd, P-even interactions in nuclear beta decay. Methods:
We measured proton-electron coincidences from decays of longitudinally
polarized neutrons with a highly symmetric detector array designed to cancel
the time-reversal-even, parity-odd Standard-Model contributions to polarized
neutron decay. Over 300 million proton-electron coincidence events were used to
extract D and study systematic effects in a blind analysis. Results: We find D
= [-0.94\pm1.89(stat)\pm0.97(sys)]e-4. Conclusions: This is the most sensitive
measurement of D in nuclear beta decay. Our result can be interpreted as a
measurement of the phase of the ratio of the axial-vector and vector coupling
constants (CA/CV= |{\lambda}|exp(i{\phi}_AV)) with {\phi}_AV = 180.012{\deg}
\pm0.028{\deg} (68% confidence level) or to constrain time-reversal violating
scalar and tensor interactions that arise in certain extensions to the Standard
Model such as leptoquarks. This paper presents details of the experiment,
analysis, and systematic- error corrections.Comment: 21 pages, 22 figure
Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source
On 2017 August 17, the Laser Interferometer Gravitational-wave Observatory
(LIGO) and the Virgo interferometer detected gravitational waves emanating from
a binary neutron star merger, GW170817. Nearly simultaneously, the Fermi and
INTEGRAL telescopes detected a gamma-ray transient, GRB 170817A. 10.9 hours
after the gravitational wave trigger, we discovered a transient and fading
optical source, Swope Supernova Survey 2017a (SSS17a), coincident with
GW170817. SSS17a is located in NGC 4993, an S0 galaxy at a distance of 40
megaparsecs. The precise location of GW170817 provides an opportunity to probe
the nature of these cataclysmic events by combining electromagnetic and
gravitational-wave observations.Comment: 25 pages, 10 figures, 2 tables, published today in Scienc
Microstructure and high critical current of powder in tube MgB2
We report dc transport and magnetization measurements of Jc in MgB2 wires
fabricated by the powder-in-tube method, using commercial MgB2 powder with 5
%at Mg powder added as an additional source of magnesium, and stainless steel
as sheath material. By appropriate heat treatments, we have been able to
increase Jc by more than one order of magnitude from that of the as-drawn wire.
We show that one beneficial effect of the annealing is the elimination of most
of the micro-cracks, and we correlate the increase in Jc with the disappearance
of the weak-link-type behavior.Comment: 12 pages, 3 figures, submitted to AP
emiT: an apparatus to test time reversal invariance in polarized neutron decay
We describe an apparatus used to measure the triple-correlation term (\D
\hat{\sigma}_n\cdot p_e\times p_\nu) in the beta-decay of polarized neutrons.
The \D-coefficient is sensitive to possible violations of time reversal
invariance. The detector has an octagonal symmetry that optimizes
electron-proton coincidence rates and reduces systematic effects. A beam of
longitudinally polarized cold neutrons passes through the detector chamber,
where a small fraction beta-decay. The final-state protons are accelerated and
focused onto arrays of cooled semiconductor diodes, while the coincident
electrons are detected using panels of plastic scintillator. Details regarding
the design and performance of the proton detectors, beta detectors and the
electronics used in the data collection system are presented. The neutron beam
characteristics, the spin-transport magnetic fields, and polarization
measurements are also described.Comment: 15 pages, 13 figure
Lessons from the evaluation of the UK's NHS R&D Implementation Methods Programme
Background: Concern about the effective use of research was a major factor behind the creation
of the NHS R&D Programme in 1991. In 1994, an advisory group was established to identify
research priorities in research implementation. The Implementation Methods Programme (IMP)
flowed from this, and its commissioning group funded 36 projects. In 2000 responsibility for the
programme passed to the National Co-ordinating Centre for NHS Service Delivery and
Organisation R&D, which asked the Health Economics Research Group (HERG), Brunel University,
to conduct an evaluation in 2002. By then most projects had been completed. This evaluation was
intended to cover: the quality of outputs, lessons to be learnt about the communication strategy
and the commissioning process, and the benefits from the projects.
Methods: We adopted a wide range of quantitative and qualitative methods. They included:
documentary analysis, interviews with key actors, questionnaires to the funded lead researchers,
questionnaires to potential users, and desk analysis.
Results: Quantitative assessment of outputs and dissemination revealed that the IMP funded useful
research projects, some of which had considerable impact against the various categories in the
HERG payback model, such as publications, further research, research training, impact on health
policy, and clinical practice.
Qualitative findings from interviews with advisory and commissioning group members indicated
that when the IMP was established, implementation research was a relatively unexplored field. This
was reflected in the understanding brought to their roles by members of the advisory and
commissioning groups, in the way priorities for research were chosen and developed, and in how
the research projects were commissioned. The ideological and methodological debates associated
with these decisions have continued among those working in this field. The need for an effective
communication strategy for the programme as a whole was particularly important. However, such
a strategy was never developed, making it difficult to establish the general influence of the IMP as a
programme.
Conclusion: Our findings about the impact of the work funded, and the difficulties faced by those
developing the IMP, have implications for the development of strategic programmes of research in
general, as well as for the development of more effective research in this field
Measuring organisational readiness for patient engagement (MORE) : an international online Delphi consensus study
Date of Acceptance: 28/01/2015. © 2015 Oostendorp et al.; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise statedWidespread implementation of patient engagement by organisations and clinical teams is not a reality yet. The aim of this study is to develop a measure of organisational readiness for patient engagement designed to monitor and facilitate a healthcare organisation’s willingness and ability to effectively implement patient engagement in healthcarePeer reviewedFinal Published versio
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