2,795 research outputs found
Cavity optomechanics with stoichiometric SiN films
We study high-stress SiN films for reaching the quantum regime with
mesoscopic oscillators connected to a room-temperature thermal bath, for which
there are stringent requirements on the oscillators' quality factors and
frequencies. Our SiN films support mechanical modes with unprecedented products
of mechanical quality factor and frequency reaching Hz. The SiN membranes exhibit a low optical absorption
characterized by Im at 935 nm, representing a 15 times
reduction for SiN membranes. We have developed an apparatus to simultaneously
cool the motion of multiple mechanical modes based on a short, high-finesse
Fabry-Perot cavity and present initial cooling results along with future
possibilities.Comment: 4 pages, 5 figure
Self-consistent treatment of the self-energy in nuclear matter
The influence of hole-hole propagation in addition to the conventional
particle-particle propagation, on the energy per nucleon and the momentum
distribution is investigated. The results are compared to the
Brueckner-Hartree-Fock (BHF) calculations with a continuous choice and
conventional choice for the single-particle spectrum. The Bethe-Goldstone
equation has been solved using realistic interactions. Also, the structure
of nucleon self-energy in nuclear matter is evaluated. All the self-energies
are calculated self-consistently. Starting from the BHF approximation without
the usual angle-average approximation, the effects of hole-hole contributions
and a self-consistent treatment within the framework of the Green function
approach are investigated. Using the self-consistent self-energy, the hole and
particle self-consistent spectral functions including the particle-particle and
hole-hole ladder contributions in nuclear matter are calculated using realistic
interactions. We found that, the difference in binding energy between both
results, i.e. BHF and self-consistent Green function, is not large. This
explains why is the BHF ignored the 2h1p contribution.Comment: Preprint 20 pages including 15 figures and one tabl
Rare Decay of the Top t -> cgg in the Standard Model
We calculate the one-loop flavor changing neutral current top quark decay t
-> cgg in the Standard Model. We demonstrate that the rate for t -> cgg exceeds
the rate for a single gluon emission t -> cg by about two orders of magnitude,
while the rate for t -> cq barq (q=u) is slightly smaller than for t -> cg.Comment: 22 pages, 4 figures and 2 tables. Typo in Eq.2.1 corrected, text
slightly modified, references added. Version to appear in Phys.Rev.
Energy and Momentum densities of cosmological models, with equation of state , in general relativity and teleparallel gravity
We calculated the energy and momentum densities of stiff fluid solutions,
using Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum complexes,
in both general relativity and teleparallel gravity. In our analysis we get
different results comparing the aforementioned complexes with each other when
calculated in the same gravitational theory, either this is in general
relativity and teleparallel gravity. However, interestingly enough, each
complex's value is the same either in general relativity or teleparallel
gravity. Our results sustain that (i) general relativity or teleparallel
gravity are equivalent theories (ii) different energy-momentum complexes do not
provide the same energy and momentum densities neither in general relativity
nor in teleparallel gravity. In the context of the theory of teleparallel
gravity, the vector and axial-vector parts of the torsion are obtained. We show
that the axial-vector torsion vanishes for the space-time under study.Comment: 15 pages, no figures, Minor typos corrected; version to appear in
International Journal of Theoretical Physic
New proposed method for traceability dissemination of capacitance measurements
Capacitance measurements at the National Institute of Standards (NIS), Egypt, are traceable to the Bureau International des Poids et Mesures (BIPM). It calibrates the main NIS standard capacitors, AH11A. In this paper, traceability of the BIPM capacitance measurements could be used to evaluate a new accurate measurement method through an Ultra-Precision Capacitance Bridge. The new method is carefully described by introducing some necessary equations and a demonstrating chart. Verification of this new method has been realized by comparing its results for the 10 pF and 100 pF capacitance standards with the results obtained by the conventional substitution method at 1 kHz and 1.592 kHz. The relative differences between the two methods are about 0.3 µF/F, which reflect the accuracy of the new measurement method. For higher capacitance ranges, the new measurement method has been applied for the capacitance measurements up to 1 μF at 1 kHz. The relative differences between the two methods are in the range of 5.5 µF/F on the average which proves the acceptable accuracy and the reliability of the new method to be used
Capacity for health economics research and practice in Jordan, Lebanon, the occupied Palestinian territories and Turkey: needs assessment and options for development
Background: Capacity for health economics analysis and research is indispensable for evidence-informed allocations of scarce health resources, however little is known about the experience and capacity strengthening preferences of academics and practitioners in the Eastern Mediterranean region. This study aimed to assess the needs for strengthening health economics capacity in Jordan, Lebanon, the occupied Palestinian territories and Turkey as part of the Research for Health in Conflict in Middle East and North Africa (R4HC-MENA) project. Methods: Bibliometric analysis of health economics outputs combined with an online survey of academic researchers and non-academic practitioners. The bibliometric analysis was based on a literature search conducted across seven databases. Included records were original studies and reviews with an explicit economic outcome related to health, disease or disability; had at least one author in Jordan, Lebanon, Palestine or Turkey; and were published between January 2014 and December 2018. Two types of analyses were conducted using VOSviewer software: keyword co-occurrence; and co-publication networks across countries and organizations. The online survey asked academic researchers, analysts and decision-makers – identified through the bibliometric analysis and regional professional networks – about previous exposure to and preference for capacity development in health economics. Results: Of 15,185 records returned by the literature search, 566 were included in the bibliometric analysis. Organizations in Turkey contributed more than 80% of records and had the broadest and most diverse network of collaborators, nationally and internationally. Only 1% (n=7) studies were collaborations between researchers in two or more different jurisdictions. Cost analysis, cost-effectiveness analysis and health system economics were the main health economics topics across the included studies. Economic evaluation, measuring the economic burden of disease and health equity were reported by survey respondents (n=80) as the most important areas to develop in. Short courses, learn-by-doing and mentoring from an experienced professional were, in aggregate, the most preferred capacity development modalities. Conclusions: Existing pockets of health economic expertise in the region can constitute the base of future capacity development efforts. Building confidence toward applying specific methods and trust toward stimulating cross-jurisdiction collaborations appear essential components for sustainably developing health economics capacity
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