329 research outputs found
Mechanisms to explain the poor results of carotid artery stenting (CAS) in symptomatic patients to date and options to improve CAS outcomes
BackgroundCarotid artery stenting (CAS) is considered by many as an alternative to carotid endarterectomy (CEA) for the management of carotid artery stenosis. However, recent trials demonstrated inferior results for CAS in symptomatic patients compared with CEA. We reviewed the literature to evaluate the appropriateness of CAS for symptomatic carotid artery stenosis and to determine the pathogenetic mechanism(s) associated with stroke following the treatment of such lesions. Based on this, we propose steps to improve the results of CAS for the treatment of symptomatic carotid stenosis.MethodsPubMed/Medline was searched up to March 25, 2010 for studies investigating the efficacy of CAS for the management of symptomatic carotid stenosis. Search terms used were âcarotid artery stenting,â âsymptomatic carotid artery stenosis,â âcarotid endarterectomy,â âstroke,â ârecurrent carotid stenosis,â and âlong-term resultsâ in various combinations.ResultsCurrent data suggest that CAS is not equivalent to CEA for the treatment of symptomatic carotid stenosis. Differences in carotid plaque morphology and a higher incidence of microemboli and cerebrovascular events during and after CAS compared with CEA may account for these inferior results.ConclusionsCurrently, most symptomatic patients are inappropriate candidates for CAS. Improved CAS technology referable to stent design and embolic protection strategies may alter this conclusion in the future
Lepton Flavor Violation: Constraints from exotic muon to electron conversion
The exotic neutrinoless nuclear conversion is studied within
the conventional extensions of the standard model as well as in the minimal
supersymmetric (SUSY) models with and without R-parity conservation. The
dependence of the conversion rates on the nucleon and nuclear
structure is consistently taken into account. Using our calculated transition
matrix elements and the available experimental data on the branching ratio
for Ti and Pb as well as the expected experimental
sensitivity for Al employed as a target in the planned at Brookhaven
conversion (MECO) experiment, we extract very severe constraints
for the flavor violation parameters. We especially emphasize on the constraints
resulting for SUSY R-parity violating parameters.Comment: 14 pages, 2 figures. Based on the Invited talk given by T.S. Kosmas
at the International Conference on Non-Accelerator New Physics(NANP'99),
Dubna, Russia, 199
The Impact of Lower Extremity Venous Ulcers due to Chronic Venous Insufficiency on Quality of Life
Lower extremity venous ulcers comprise a complex medical and social issue. The conservative and/or surgical management of venous ulcers is often inadequate. In addition, the psychosocial aspect of the disease is often overlooked and most often undertreated. Common symptoms such as pain, low self-esteem and patient isolation are usually not recognized and therefore not adequately managed
Cold Dark Matter in SUSY Theories. The Role of Nuclear Form Factors and the Folding with the LSP Velocity
The momentum transfer dependence of the total cross section for elastic
scattering of cold dark matter candidates, i.e. lightest supersymmetric
particle (LSP), with nuclei is examined. The presented calculations of the
event rates refer to a number of representative nuclear targets throughout the
periodic table and have been obtained in a relatively wide phenomenologically
allowed SUSY parameter space. For the coherent cross sections it is shown that,
since the momentum transfer can be quite big for large mass of the LSP and
heavy nuclei even though the energy transfer is small (), the
total cross section can in such instances be reduced by a factor of about five.
For the spin induced cross section of odd-A nuclear targets, as is the case of
studied in this work, we found that the reduction is less
pronounced, since the high multipoles tend to enhance the cross section as the
momentum transfer increases (for LSP ) and partially cancell
the momentum retardation. The effect of the Earth's revolution around the sun
on these event rates is also studied by folding with a Maxwellian LSP-velocity
distribution which is consistent with its density in the halos. We thus found
that the convoluted event rates do not appreciably change compared to those
obtained with an average velocity. The event rates increase with A and, in the
SUSY parameter space considered, they can reach values up to 140
for Pb. The modulation effect, however, was found to be small
(less than ).Comment: 23 LATEX pages, 4 Tables, 3 PostScript Figures included. Phys. Rev.
D, to be publishe
ROTATIONAL-DYNAMICS OF SOLID C-70 - A NEUTRON-SCATTERING STUDY
PMID: 10011126PMID: 10011126 This work at the University of Sussex at supported by the Science and Engineering Research Council, U.K.PMID: 10011126 This work at the University of Sussex at supported by the Science and Engineering Research Council, U.K.PMID: 10011126 This work at the University of Sussex at supported by the Science and Engineering Research Council, U.K.We report the results of neutron-diffraction and low-energy neutron-inelastic-scattering experiments on high-purity solid C-70 between 10 and 640 K. Thermal hysteresis effects are found to accompany structural changes both on cooling and on heating. The observed diffuse scattering intensity does not change with temperature. At 10 K broad librational peaks are observed at 1.82(16) meV [full width at half maximum=1.8(5) meV]. The peaks soften and broaden further with increasing temperature. At and above room temperature, they collapse into a single quasielastic line. At 300 K, the diffusive reorientational motion appears to be somewhat anisotropic, becoming less so with increasing temperature. An isotropic rotational diffusion model, in which the motions of adjacent molecules are uncorrelated, describes well the results at 525 K. The temperature dependence of the rotational diffusion constants is consistent with a thermally activated process having an activation energy of 32(7) meV.This work at the University of Sussex at supported by the Science and Engineering Research Council, U.K
Modulation effect in the differential rate for Supersymmetric Dark Matter detection
The modulation effect in the direct detection of supersymmetric Cold Dark
Matter (CDM) particles is investigated. It is shown that, while normally the
modulation effect in the total event rate is small, , in some special
cases it becomes much larger. It also becomes more pronounced in the
differential event rate. It may thus be exploited to discriminate against
background.Comment: 17 LATEX pages, 4 Tables, 4 PostScript Figures included. Phys. Rev.
D, to be publishe
Coherent pion production in neutrino nucleus collision in the 1 GeV region
We calculate cross sections for coherent pion production in nuclei induced by
neutrinos and antineutrinos of the electron and muon type. The analogies and
differences between this process and the related ones of coherent pion
production induced by photons, or the (p,n) and reactions are
discussed. The process is one of the several ones occurring for intermediate
energy neutrinos, to be considered when detecting atmospheric neutrinos. For
this purpose the results shown here can be easily extrapolated to other
energies and other nuclei.Comment: 13 pages, LaTex, 8 post-script figures available at
[email protected]
U(1) textures and Lepton Flavor Violation
U(1) family symmetries have led to successful predictions of the fermion mass
spectrum and the mixing angles of the hadronic sector. In the context of the
supersymmetric unified theories, they further imply a non-trivial mass
structure for the scalar partners, giving rise to new sources of flavor
violation. In the present work, lepton flavor non-conserving processes are
examined in the context of the minimal supersymmetric standard model augmented
by a U(1)-family symmetry. We calculate the mixing effects on the \mu-> e\gamma
and \tau -> \mu\gamma rare decays. All supersymmetric scalar masses involved in
the processes are determined at low energies using two loop renormalization
group analysis and threshold corrections. Further, various novel effects are
considered and found to have important impact on the branching ratios. Thus, a
rather interesting result is that when the see-saw mechanism is applied in the
(12 X 12)-sneutrino mass matrix, the mixing effects of the Dirac matrix in the
effective light sneutrino sector are canceled at first order. In this class of
models and for the case that soft term mixing is already present at the GUT
scale, tau -> \mu \gamma decays are mostly expected to arise at rates
significantly smaller than the current experimental limits. On the other hand,
the \mu \ra e \gamma rare decays impose important bounds on the model
parameters, particularly on the supersymmetric scalar mass spectrum. In the
absence of soft term mixing at high energies, the predicted branching ratios
for rare decays are, as expected, well below the experimental bounds.Comment: 24p, 10 figures, version to appear in Phys. Rev.
Searching for Supersymmetric Dark Matter - The Directional Rate and the Modulation Effect Due to Caustic Rings
The detection of the theoretically expected dark matter is central to
particle physics and cosmology. Current fashionable supersymmetric models
provide a natural dark matter candidate which is the lightest supersymmetric
particle (LSP). The allowed parameter space of such models combined with fairly
well understood physics (quark substructure of the nucleon and nuclear
structure) permit the evaluation of the event rate for LSP-nucleus elastic
scattering. The thus obtained event rates, which sensitively depend on the
allowed parameter space parameters, are usually very low or even undetectable.
So, for background reduction, one would like to exploit two nice features of
the reaction, the directional rate, which depends on the sun's direction of
motion and the modulation effect, i.e. the dependence of the event rate on the
earth's annual motion. In the present paper we study these phenomena in a
specific class of non isothermal models, which take into account the late
in-fall of dark matter into our galaxy, producing flows of caustic rings. We
find that the modulation effect arising from such models is smaller than that
found previously with isothermal symmetric velocity distributions and much
smaller compared to that obtained using a realistic asymmetric distribution
with enhanced dispersion in the galactocentric direction.Comment: 31 LATEX pages, 2 tables and 1 figure included. Accepted for
publication in Physical Review
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