360 research outputs found
Affleck-Dine leptogenesis via multiscalar evolution in a supersymmetric seesaw model
A leptogenesis scenario in a supersymmetric standard model extended with
introducing right-handed neutrinos is reconsidered. Lepton asymmetry is
produced in the condensate of a right-handed sneutrino via the Affleck-Dine
mechanism. The LH_u direction develops large value due to a negative effective
mass induced by the right-handed sneutrino condensate through the Yukawa
coupling of the right-handed neutrino, even if the minimum during the inflation
is fixed at the origin. The lepton asymmetry is nonperturbatively transfered to
the LH_u direction by this Yukawa coupling.Comment: 19 pages, 3 figures. Revised version for publication. The model was
modified to fix some problem
Anti-prion activity of an RNA aptamer and its structural basis.
Prion proteins (PrPs) cause prion diseases, such as bovine spongiform encephalopathy. The conversion of a normal cellular form (PrP(C)) of PrP into an abnormal form (PrP(Sc)) is thought to be associated with the pathogenesis. An RNA aptamer that tightly binds to and stabilizes PrP(C) is expected to block this conversion and to thereby prevent prion diseases. Here, we show that an RNA aptamer comprising only 12 residues, r(GGAGGAGGAGGA) (R12), reduces the PrP(Sc) level in mouse neuronal cells persistently infected with the transmissible spongiform encephalopathy agent. Nuclear magnetic resonance analysis revealed that R12, folded into a unique quadruplex structure, forms a dimer and that each monomer simultaneously binds to two portions of the N-terminal half of PrP(C), resulting in tight binding. Electrostatic and stacking interactions contribute to the affinity of each portion. Our results demonstrate the therapeutic potential of an RNA aptamer as to prion diseases
Primary placement technique of jejunostomy using the entristar™ skin-level gastrostomy tube in patients with esophageal cancer
<p>Abstract</p> <p>Background</p> <p>We developed a skin-level jejunostomy tube (SLJT) procedure for patients undergoing esophagectomy using a skin-level gastrostomy tube (G-tube) (Entristar™; Tyco Healthcare, Mansfield, Mass), in order to improve their nutrition status and quality of life (QOL). We describe the procedure and the adverse effects of SLJT in patients with esophageal cancer (EC).</p> <p>Methods</p> <p>Over a 24-month period (March 2008 to March 2010), there were 16 patients (mean age: 61.8 years; age range: 49-75 years; 15 men, 1 woman) who had Stage II or III EC. Primary jejunostomy was performed under general anesthesia during esophagectomy. The technical success and the immediate and delayed complications of the procedure were recorded.</p> <p>Jejunostomy techniques</p> <p>SLJT placement using the G-tube (20Fr) was performed 20 cm from the Treitz ligament on the side opposing the jejunal mesenterium. The internal retention bolster was exteriorized through an incision in the abdominal wall. A single purse string suture using a 4-0 absorbable suture was performed. The internal retention bolster was then inserted into the jejunal lumen via the small incision. The intestine adjacent to the tube was anchored to the peritoneum using a single stitch.</p> <p>Results</p> <p>The SLJT was successfully inserted in all 16 patients. No early complications were documented. Follow-up for a median of 107 days (range, 26-320 days) revealed leakage to the skin in four patients, including superficial wound infections in two patients. There were no cases of obstruction of the tube or procedure-related death.</p> <p>Conclusions</p> <p>This SLJT placement technique using the G-tube is a safe procedure in patients with EC and allows the creation of a long-term feeding jejunostomy.</p
Cosmological perturbations in a healthy extension of Horava gravity
In Horava's theory of gravity, Lorentz symmetry is broken in exchange for
renormalizability, but the original theory has been argued to be plagued with
problems associated with a new scalar mode stemming from the very breaking of
Lorentz symmetry. Recently, Blas, Pujolas, and Sibiryakov have proposed a
healthy extension of Horava gravity, in which the behavior of the scalar mode
is improved. In this paper, we study scalar modes of cosmological perturbations
in extended Horava gravity. The evolution of metric and density perturbations
is addressed analytically and numerically. It is shown that for vanishing
non-adiabatic pressure of matter the large scale evolution of cosmological
perturbations converges to that described by a single constant, , which
is an analog of a curvature perturbation on the uniform-density slicing
commonly used in usual gravitational theories. The subsequent evolution is thus
determined completely by the value of .Comment: 10 pages, 4 figures; v2: published versio
Viable Supersymmetry and Leptogenesis with Anomaly Mediation
The seesaw mechanism that explains the small neutrino masses comes naturally
with supersymmetric (SUSY) grand unification and leptogenesis. However, the
framework suffers from the SUSY flavor and CP problems, and has a severe
cosmological gravitino problem. We propose anomaly mediation as a simple
solution to all these problems, which is viable once supplemented by the
D-terms for U(1)_Y and U(1)_{B-L}. Even though the right-handed neutrino mass
explicitly breaks U(1)_{B-L} and hence reintroduces the flavor problem, we show
that it lacks the logarithmic enhancement and poses no threat to the framework.
The thermal leptogenesis is then made easily consistent with the gravitino
constraint.Comment: 5 pages, one figure, uses Revtex4; Discussion on the upper bound on
the LSP mass added. The version published in PR
Quantum fluctuations in quantum lattice-systems with continuous symmetry
We discuss conditions for the absence of spontaneous breakdown of continuous
symmetries in quantum lattice systems at . Our analysis is based on
Pitaevskii and Stringari's idea that the uncertainty relation can be employed
to show quantum fluctuations. For the one-dimensional systems, it is shown that
the ground state is invariant under the continuous transformation if a certain
uniform susceptibility is finite. For the two- and three-dimensional systems,
it is shown that truncated correlation functions cannot decay any more rapidly
than whenever the continuous symmetry is spontaneously broken.
Both of these phenomena occur owing to quantum fluctuations. Our theorems cover
a wide class of quantum lattice-systems having not-too-long-range interactions.Comment: 14 pages. To appear in J.Stat.Phy
Testing the Nambu-Goldstone Hypothesis for Quarks and Leptons at the LHC
The hierarchy of the Yukawa couplings is an outstanding problem of the
standard model. We present a class of models in which the first and second
generation fermions are SUSY partners of pseudo-Nambu-Goldstone bosons that
parameterize a non-compact Kahler manifold, explaining the small values of
these fermion masses relative to those of the third generation. We also provide
an example of such a model. We find that various regions of the parameter space
in this scenario can give the correct dark matter abundance, and that nearly
all of these regions evade other phenomenological constraints. We show that for
gluino mass ~700 GeV, model points from these regions can be easily
distinguished from other mSUGRA points at the LHC with only 7 fb^(-1) of
integrated luminosity at 14 TeV. The most striking signatures are a dearth of
b- and tau-jets, a great number of multi-lepton events, and either an
"inverted" slepton mass hierarchy, narrowed slepton mass hierarchy, or
characteristic small-mu spectrum.Comment: Corresponds to published versio
Bulk inflaton shadows of vacuum gravity
We introduce a -dimensional vacuum description of five-dimensional
bulk inflaton models with exponential potentials that makes analysis of
cosmological perturbations simple and transparent. We show that various
solutions, including the power-law inflation model recently discovered by
Koyama and Takahashi, are generated from known -dimensional vacuum
solutions of pure gravity. We derive master equations for all types of
perturbations, and each of them becomes a second order differential equation
for one master variable supplemented by simple boundary conditions on the
brane. One exception is the case for massive modes of scalar perturbations. In
this case, there are two independent degrees of freedom, and in general it is
difficult to disentangle them into two separate sectors.Comment: 22 pages, 4 figures, revtex; v2: references adde
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