592 research outputs found
Self-Tuning Dark Energy in Brane World Cosmology
Recently, the self-tuning mechanism of cancellation of vacuum energy has been
proposed in which our universe is a flat 3-brane in a 5-dimensional spacetime.
In this letter, the self-tuning mechanism of dark energy is proposed by
considering the cosmological matter in the brane world. In our model, the bulk
scalar field takes the role of the dark energy and its value is slowly varying
in time. The claim is that even if the enormous amount of vacuum energy exists
on the brane we can adjust the present value of the dark energy to be
consistent with the current observations. In this self-tuning mechanism, the
existence of the constant of integration associated with the bulk scalar is
crucial.Comment: 11pages, LaTe
Schematic model for induced fission in a configuration-interaction approach
We model fission at barrier-top energies in a simplified model space that permits comparison of different components of the residual nucleon-nucleon interaction. The model space is built on particle-hole excitations of reference configurations. These are Slater determinants of uniformly spaced orbitals characterized only by their quantum numbers and orbital energies. The residual interaction in the Hamiltonian includes the diabatic interaction connecting similar orbitals at different deformations, the pairing interaction between like nucleons, and a schematic off-diagonal neutron-proton interaction. We find that the fission reaction probability is sensitive to the off-diagonal neutron-proton interaction much more than to the pairing and the diabatic interactions. In particular, the transmission coefficients become insensitive to the strength of the pairing interaction when the neutron-proton interaction is large. We also find that the branching ratio is insensitive to the final-state scission dynamics, as is assumed in the well-known Bohr-Wheeler theory
Role of triaxiality in deformed halo nuclei
It is known that nuclear deformation plays an important role in inducing the
halo structure in neutron-rich nuclei by mixing several angular momentum
components. While previous theoretical studies on this problem in the
literature assume axially symmetric deformation, we here consider non-axially
symmetric deformations. With triaxial deformation, the quantum number
is admixed in a single-particle wave function, where is the projection
of the single-particle angular momentum on the symmetric axis, and the halo
structure may arise even when it is absent with the axially symmetric
deformation. In this way, the area of halo nuclei may be extended when triaxial
deformation is considered. We demonstrate this idea using a deformed
Woods-Saxon potential for nuclei with neutron number N=13 and 43.Comment: 4 pages, 5 figure
Schematic model for induced fission in a configuration-interaction approach
We model fission at barrier-top energies in a simplified model space that
permits comparison of different components of the residual nucleon-nucleon
interaction. The model space is built on particle-hole excitations of reference
configurations. These are Slater determinants of uniformly spaced orbitals
characterized only by their quantum numbers and orbital energies. The residual
interaction in the Hamiltonian includes the diabatic interaction connecting
similar orbitals at different deformations, the pairing interaction between
like nucleons, and a schematic off-diagonal neutron-proton interaction. We find
that the fission reaction probability is sensitive to the off-diagonal
neutron-proton interaction much more than to the pairing and the diabatic
interactions. In particular, the transmission coefficients become insensitive
to th e strength of the pairing interaction when the neutron-proton interaction
is large. We also find that the branching ratio is insensitive to the
final-state scission dynamics, as is assumed in the well-known Bohr-Wheeler
theory.Comment: 10 pages, 6 figure
Dynamics of Alpha-Helix Formation in the CSAW Model
We study the folding dynamics of polyalanine (Ala), a protein fragment
with 20 residues whose native state is a single alpha helix. We use the CSAW
model (conditioned self-avoiding walk), which treats the protein molecule as a
chain in Brownian motion, with interactions that include hydrophobic forces and
internal hydrogen bonding. We find that large scale structures form before
small scale structures, and obtain the relevant relaxation times. We find that
helix nucleation occurs at two separate points on the protein chain. The
evolution of small and large scale structures involve different mechanisms.
While the former can be describe by rate equations governing the growth of
helical content, the latter is akin to the relaxation of an elastic solid.Comment: 18 pages, 10 figure
Long-term efficacy and safety of eculizumab in Japanese patients with generalized myasthenia gravis : a subgroup analysis of the REGAIN open-label extension study
The terminal complement inhibitor eculizumab was shown to improve myasthenia gravis-related symptoms in the 26-week, phase 3, randomized, double-blind, placebo-controlled REGAIN study (NCT01997229). In this 52-week sub-analysis of the open-label extension of REGAIN (NCT02301624), eculizumab's efficacy and safety were assessed in 11 Japanese and 88 Caucasian patients with anti-acetylcholine receptor antibody-positive refractory generalized myasthenia gravis. For patients who had received placebo during REGAIN, treatment with open-label eculizumab resulted in generally similar outcomes in the Japanese and Caucasian populations. Rapid improvements were maintained for 52 weeks, assessed by change in score from open-label extension baseline to week 52 (mean [standard error]) using the following scales (in Japanese and Caucasian patients, respectively): Myasthenia Gravis Activities of Daily Living (-2.4 [1.34] and - 3.3 [0.651); Quantitative Myasthenia Gravis (-2.9 [1.98] and - 4.3 [0.79]); Myasthenia Gravis Composite (-4.5 [2.63] and - 4.9 [1.19]); and Myasthenia Gravis Quality of Life 15-item questionnaire (-8.6 [5.68) and - 6.5 [1.93]). Overall, the safety of eculizumab was consistent with its known safety profile. In this interim sub-analysis, the efficacy and safety of eculizumab in Japanese and Caucasian patients were generally similar, and consistent with the overall REGAIN population
Moduli Instability in Warped Compactifications of the Type IIB Supergravity
We show that the conifold and deformed-conifold warped compactifications of
the ten-dimensional type IIB supergravity, including the Klebanov-Strassler
solution, are dynamically unstable in the moduli sector representing the scale
of a Calabi-Yau space, although it can be practically stable for a quite long
time in a region with a large warp factor. This instability is associated with
complete supersymmetry breaking except for a special case and produces
significant time-dependence in the structure of the four-dimensional base
spacetime as well as of the internal space.Comment: 24 pages, no figure. Typos corrected, and some arguments in section 5
are adde
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