374 research outputs found
Direct access valve replacement (DAVR) - are we entering a new era in cardiac surgery?
OBJECTIVE: This study validates the off-pump antegrade trans-ventricular route for ultrasound-guided direct access aortic valve replacement. Direct access aortic valve replacement using a transthoracic and valved stent-based approach offers numerous advantages over the remote access percutaneous approach and may one day provide an alternative treatment modality for aortic valve disease. METHODS: Valved stents were implanted off-pump in 17 pigs (72.10+/-8.4 kg) via the direct access transapical approach using a left-sided mini-thoracotomy and continuous ultrasonic and fluoroscopic guidance. Acute valved stent function was studied with intravascular and two-dimensional intracardiac ultrasound. The invasive valve gradient was assessed with pull-back pressure catheter. All valved stents were tested in vitro before insertion. Macroscopic analysis was performed at necropsy. RESULTS: In 11 of the 17 pigs, valved stents were delivered to the target site over the native aortic valve leaflets without interference of coronary blood flow and with good acute valve function. Three valved stents were deployed supra-annularly, two of those occluded the right coronary orifice and one the left coronary orifice, leading to fatal outcomes. Three valved stents dislodged into the left ventricle, one because of size-mismatch and two because of failure to unfold correctly. In 11 properly sized and deployed valved stents, two showed a moderate and one a severe paravalvular leak. CONCLUSIONS: Seventeen pigs underwent direct access valve replacement of the aortic valve with deployment of a valved stent into the native aorta. Eleven valves observed for an average 5-h period showed satisfactory, postimplantation valve function
Neutrino Beams From Electron Capture at High Gamma
We investigate the potential of a flavor pure high gamma electron capture
electron neutrino beam directed towards a large water cherenkov detector with
500 kt fiducial mass. The energy of the neutrinos is reconstructed by the
position measurement within the detector and superb energy resolution
capabilities could be achieved. We estimate the requirements for such a
scenario to be competitive to a neutrino/anti-neutrino running at a neutrino
factory with less accurate energy resolution. Although the requirements turn
out to be extreme, in principle such a scenario could achieve as good abilities
to resolve correlations and degeneracies in the search for sin^2(2 theta_13)
and delta_CP as a standard neutrino factory experiment.Comment: 21 pages, 7 figures, revised version, to appear in JHEP, Fig.7
extended, minnor changes, results unchange
Neutrino hierarchy from CP-blind observables with high density magnetized detectors
High density magnetized detectors are well suited to exploit the outstanding
purity and intensities of novel neutrino sources like Neutrino Factories and
Beta Beams. They can also provide independent measurements of leptonic mixing
parameters through the observation of atmospheric muon-neutrinos. In this
paper, we discuss the combination of these observables from a multi-kton iron
detector and a high energy Beta Beam; in particular, we demonstrate that even
with moderate detector granularities the neutrino mass hierarchy can be
determined for values greater than 4.Comment: 16 pages, 7 figures. Added a new section discussing systematic errors
(sec 5.2); sec.5.1 and 4 have been extended. Version to appear in EPJ
Orbital order in the low-dimensional quantum spin system TiOCl probed by ESR
We present electron spin resonance data of Ti (3) ions in single
crystals of the novel layered quantum spin magnet TiOCl. The analysis of the g
tensor yields direct evidence that the d_{xy} orbital from the t_{2g} set is
predominantly occupied and owing to the occurrence of orbital order a linear
spin chain forms along the crystallographic b axis. This result corroborates
recent theoretical LDA+U calculations of the band structure. The temperature
dependence of the parameters of the resonance signal suggests a strong coupling
between spin and lattice degrees of freedom and gives evidence for a transition
to a nonmagnetic ground state at 67 K.Comment: revised version, accepted for publication in Phys. Rev. B, Rapid Com
Optimum electrode configurations for fast ion separation in microfabricated surface ion traps
For many quantum information implementations with trapped ions, effective
shuttling operations are important. Here we discuss the efficient separation
and recombination of ions in surface ion trap geometries. The maximum speed of
separation and recombination of trapped ions for adiabatic shuttling operations
depends on the secular frequencies the trapped ion experiences in the process.
Higher secular frequencies during the transportation processes can be achieved
by optimising trap geometries. We show how two different arrangements of
segmented static potential electrodes in surface ion traps can be optimised for
fast ion separation or recombination processes. We also solve the equations of
motion for the ion dynamics during the separation process and illustrate
important considerations that need to be taken into account to make the process
adiabatic
Deviation of Atmospheric Mixing from Maximal and Structure in the Leptonic Flavor Sector
I attempt to quantify how far from maximal one should expect the atmospheric
mixing angle to be given a neutrino mass-matrix that leads, at zeroth order, to
a nu_3 mass-eigenstate that is 0% nu_e, 50% nu_mu, and 50% nu_tau. This is done
by assuming that the solar mass-squared difference is induced by an
"anarchical" first order perturbation, an approach than can naturally lead to
experimentally allowed values for all oscillation parameters. In particular,
both |cos 2theta_atm| (the measure for the deviation of atmospheric mixing from
maximal) and |U_e3| are of order sqrt(Delta m^2_sol/Delta m^2_atm) in the case
of a normal neutrino mass-hierarchy, or of order Delta m^2_sol/Delta m^2_atm in
the case of an inverted one. Hence, if any of the textures analyzed here has
anything to do with reality, next-generation neutrino experiments can see a
nonzero cos 2theta_atm in the case of a normal mass-hierarchy, while in the
case of an inverted mass-hierarchy only neutrino factories should be able to
see a deviation of sin^2 2theta_atm from 1.Comment: 12 pages, no figures, references and acknowledgments adde
Asymmetric nuclear matter:the role of the isovector scalar channel
We try to single out some qualitative new effects of the coupling to the
-isovector-scalar meson introduced in a minimal way in a
phenomenological hadronic field theory. Results for the equation of state
() and the phase diagram of asymmetric nuclear matter () are
discussed. We stress the consistency of the -coupling introduction in a
relativistic approach. New contributions to the slope and curvature of the
symmetry energy and the neutron-proton effective mass splitting appear
particularly interesting. A more repulsive for neutron matter at high
baryon densities is expected. Effects on new critical properties of warm ,
mixing of mechanical and chemical instabilities and isospin distillation, are
also presented. The influence is mostly on the {\it isovectorlike}
collective response.
The results are largely analytical and this makes the physical meaning quite
transparent. Implications for nuclear structure properties of drip-line nuclei
and for reaction dynamics with Radioactive Beams are finally pointed out.Comment: 12 pages, 10 Postscript figure
Study of Bs-> \phi l^+ l^-$ Decay in a Single Universal Extra Dimension
Utilizing form factors calculated within the light-cone sum rules, we have
evaluated the decay branching ratios of and in a single universal extra dimension model (UED), which is
viewed as one of the alternative theories beyond the standard model (SM). For
the decay , the dilepton invariant mass spectra, the
forward-backward asymmetry, and double lepton polarization are also calculated.
For each case, we compared the obtained results with predictions of the SM. In
lower values of the compactification factor 1/R, the only parameter in this
model, we see the considerable discrepancy between the UED and SM models.
However, when 1/R increases, the results of UED tend to diminish and at , two models have approximately the same predictions.
Compared with data from CDF of , the 1/R tends to be
larger than . We also note that the zero crossing point of
the forward-backward asymmetry is become smaller, which will be an important
plat to prob the contribution from the extra dimension model. The results
obtained in this work will be very useful in searching new physics beyond SM.
Moreover, the order of magnitude for branching ratios shows a possibility to
study these channels at the Large Hadron Collider (LHC), CDF and the future
super-B factory.Comment: 13 pages, 16 figure
- …