4,220 research outputs found
Advanced ablation strategies for management of post-surgical atrial arrhythmias.
Post-surgical arrhythmias include a wide range of arrhythmias occurring late after cardiac surgery and represent a complex substrate for catheter ablation either because of extended scar and remodeling or because of limited access to the area of interest. Novel image integration and ablation tools have made the catheter ablation in this population both feasible and successful. We review a structured approach to catheter ablation of post-surgical atrial arrhythmias in various patient cohorts including the most common congenital heart defects
Flavor Gauge Models Below the Fermi Scale
The mass and weak interaction eigenstates for the quarks of the third
generation are very well aligned, an empirical fact for which the Standard
Model offers no explanation. We explore the possibility that this alignment is
due to an additional gauge symmetry in the third generation. Specifically, we
construct and analyze an explicit, renormalizable model with a gauge boson,
, corresponding to the symmetry of the third family. Having a
relatively light (in the MeV to multi-GeV range), flavor-nonuniversal gauge
boson results in a variety of constraints from different sources. By
systematically analyzing 20 different constraints, we identify the most
sensitive probes: kaon, , and Upsilon decays, mixing,
atomic parity violation, and neutrino scattering and oscillations. For the new
gauge coupling in the range the model is shown to
be consistent with the data. Possible ways of testing the model in physics,
top and decays, direct collider production and neutrino oscillation
experiments, where one can observe nonstandard matter effects, are outlined.
The choice of leptons to carry the new force is ambiguous, resulting in
additional phenomenological implications, such as non-universality in
semileptonic bottom decays. The proposed framework provides interesting
connections between neutrino oscillations, flavor and collider physics.Comment: 44 pages, 7 figures, 3 tables; B physics constraints and references
added, conclusions unchange
Eliminating the d=5 proton decay operators from SUSY GUTs
A general analysis is made of the question whether the d=5 proton decay
operators coming from exchange of colored Higgsinos can be completely
eliminated in a natural way in supersymmetric grand unified models. It is shown
that they can indeed be in SO(10) while at the same time naturally solving the
doublet-triplet splitting problem, having only two light Higgs doublets, and
using no more than a single adjoint Higgs field. Accomplishing all of this
requires that the vacuum expectation value of the adjoint Higgs field be
proportional to the generator I_{3R} rather than to B-L, as is usually assumed.
It is shown that such models can give realistic quark and lepton masses. We
also point out a new mechanism for solving the \mu problem in the context of
SO(10) SUSY GUTs.Comment: 24 pages in LaTeX, with 3 figure
Getting the Supersymmetric Unification Scale from Quantum Confinement with Chiral Symmetry Breaking
Two models which generate the supersymmetric Grand Unification Scale from the
strong dynamics of an additional gauge group are presented. The particle
content is chosen such that this group confines with chiral symmetry breaking.
Fields that are usually introduced to break the Grand Unified group appear
instead as composite degrees of freedom and can acquire vacuum expectation
values due to the confining dynamics. The models implement known solutions to
the doublet-triplet splitting problem. The SO(10) model only requires one
higher dimensional representation, an adjoint. The dangerous coloured
Higgsino-mediated proton decay operator is naturally suppressed in this model
to a phenomenologically interesting level. Neither model requires the presence
of gauge singlets. Both models are only technically natural.Comment: LaTex, 23 page
SN1987A - a Testing Ground for the KARMEN Anomaly
We show, that SN1987A can serve as an astrophysical laboratory for testing
the viability of the assertion that a new massive neutral fermion is implied by
the KARMEN data. We show that a wide range of the parameters characterizing the
proposed particle is ruled out by the above constraints making this
interpretation very unlikely.Comment: 12 pages, 1 eps figure embedded, to appear in Phys. Lett.
Missing Partner Mechanism in SO(10) Grand Unification
We present a new possibility for achieving doublet-triplet splitting naturally in supersymmetric SO(10) grand unified theories. It is based on a missing partner mechanism which is realized with the 126 + 126-bar Higgs superfields. These Higgs fields, which are also needed for generating Majorana right-handed neutrino masses, contain a pair of color triplets in excess of weak doublets. This feature enables us to remove the color triplets from the low energy spectrum without fine-tuning. We give all the needed ingredients for a successful implementation of the missing partner mechanism in SO(10) and present explicit models wherein the Higgs doublet mass is protected against possible non-renormalizable corrections to all orders. We also show how realistic fermion masses can be generated in this context
Constraining Proton Lifetime in SO(10) with Stabilized Doublet-Triplet Splitting
We present a class of realistic unified models based on supersymmetric SO(10)
wherein issues related to natural doublet-triplet (DT) splitting are fully
resolved. Using a minimal set of low dimensional Higgs fields which includes a
single adjoint, we show that the Dimopoulos--Wilzcek mechanism for DT splitting
can be made stable in the presence of all higher order operators without having
pseudo-Goldstone bosons and flat directions. The \mu term of order TeV is found
to be naturally induced. A Z_2-assisted anomalous U(1)_A gauge symmetry plays a
crucial role in achieving these results. The threshold corrections to
alpha_3(M_Z), somewhat surprisingly, are found to be controlled by only a few
effective parameters. This leads to a very predictive scenario for proton
decay. As a novel feature, we find an interesting correlation between the d=6
(p\to e^+\pi^0) and d=5 (p\to \nu-bar K+) decay amplitudes which allows us to
derive a constrained upper limit on the inverse rate of the e^+\pi^0 mode. Our
results show that both modes should be observed with an improvement in the
current sensitivity by about a factor of five to ten.Comment: 21 pages LaTeX, 2 figures, Few explanatory sentences and three new
references added, minor typos corrected
Involving users in OPAC interface design: Perspective from a UK study
This is the post-print versoin of the Article. The official published version can be accessed from the link below - Copyright @ 2007 SpringerThe purpose of this study was to determine user suggestions for a typical OPAC (Online Public Library Catalogue) applicationâs functionality and features. An experiment was undertaken to find out the type of interactions features that users prefer to have in an OPAC. The study revealed that regardless of usersâ Information Technology (IT) backgrounds, their functionality expectations of OPACs are the same. However, based on usersâ previous experiences with OPACs, their requirements with respect to specific features may change. Users should be involved early in the OPAC development cycle process in order to ensure usable and functional interface
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