1,276 research outputs found
Nonleptonic two-body charmless B decays involving a tensor meson in ISGW2 model
Nonleptonic charmless B decays into a pseudoscalar (P) or a vector (V) meson
accompanying a tensor (T) meson are re-analyzed. We scrutinize the hadronic
uncertainties and ambiguities of the form factors which appear in the
literature. The Isgur-Scora-Grinstein-Wise updated model (ISGW2) is adopted to
evaluate the relevant hadronic matrix elements. We calculate the branching
ratios and CP asymmetries for various decay processes. With the
ISGW2 model, the branching ratios are enhanced by about an order of magnitude
compared to the previous estimates. We show that the ratios \calB(B\to
VT)/\calB(B\to PT) for some strangeness-changing processes are very sensitive
to the CKM angle ().Comment: 23 pages, REVTEX; minor clarifications included; to appear in Phys.
Rev.
QUANTIFICAÇÃO HISTOLÓGICA DA ESPERMATOGÊNESE DE RATOS WISTAR TRATADOS COM DIMETIL SULFÓXIDO
Avaliaram-se através de histologia testicular quantitativa os efeitos da ação do Dimetil
Sulfóxido (DMSO) na espermatogênese de 28 ratos adultos albinos da raça Wistar. Os animais foram
divididos em dois grupos - Controle e Experimental - e submetidos a dois tipos de tratamento: no
primeiro tratamento, o Grupo Experimental (10 animais) recebeu aplicações tópicas de DMSO no
jarrete, duas vezes ao dia, na dosagem de 1 g/kg-1 de peso vivo, durante sete dias consecutivos; no
segundo tratamento, o Grupo Experimental (7 animais) recebeu aplicações tópicas de DMSO no
escroto duas vezes ao dia, na dosagem de 1 g/kg-1 de peso vivo, durante 54 dias consecutivos; os
Grupos Controles (8 e 3 animais) receberam aplicações de solução salina friccionada na pele do
jarrete e do escroto duas vezes ao dia, por período equivalente ao dos tratamentos, respectivamente.
Proporções volumétricas dos componentes do parênquima testicular, diâmetro dos túbulos
seminíferos, contagem dos elementos celulares do epitélio seminífero e rendimento intrínseca da
espermatogênese não apresentaram diferença significativa entre os grupos Controles e
Experimentais. O processo espermatogênico não sofreu alteração após a aplicação do DMSO.
Histological quantification of spermatogenesis in dimethyl sulfoxide treated wistar rats
Abstract
In order to provide a more accurate analysis on the effects of dimethyl sulfoxide
(DMSO) on spermatogenesis in mammals, an experiment was carried out with albino Wistar rats. A
total of 28 rats, 78 days old and average weight of 325 g were divided in one control group and two
experimental groups - G1 and G2. Rats from G1 were treated with topic applications of DMSO in the
hock twice a day at a dosage of 1.0 g/kg of live weight for 7 consecutive days. Rats from G2 received
topic applications of DMSO at the scrotum twice a day at a dosage of 1.0 g/kg of live weight for 54
consecutive days. The control group was swabbed with saline on the hock and the scrotal skin twice a
day for the same period as the treatment of G1 and G2 groups. Volumetric proportions of the testicular
parenchyma, diameter of the somniferous tubules, counting of cell types in the somniferous epithelium
and intrinsic spermatogenesis yield showed no significant differences (
Bound state solutions of the Dirac-Rosen-Morse potential with spin and pseudospin symmetry
The energy spectra and the corresponding two- component spinor wavefunctions
of the Dirac equation for the Rosen-Morse potential with spin and pseudospin
symmetry are obtained. The wave ( state) solutions for this
problem are obtained by using the basic concept of the supersymmetric quantum
mechanics approach and function analysis (standard approach) in the
calculations. Under the spin symmetry and pseudospin symmetry, the energy
equation and the corresponding two-component spinor wavefunctions for this
potential and other special types of this potential are obtained. Extension of
this result to state is suggested.Comment: 18 page
Diffuse light and galaxy interactions in the core of nearby clusters
The kinematics of the diffuse light in the densest regions of the nearby
clusters can be unmasked using the planetary nebulae (PNs) as probes of the
stellar motions. The position-velocity diagrams around the brightest cluster
galaxies (BCGs) identify the relative contributions from the outer halos and
the intracluster light (ICL), defined as the light radiated by the stars
floating in the cluster potential. The kinematics of the ICL can then be used
to asses the dynamical status of the nearby cluster cores and to infer their
formation histories. The cores of the Virgo and Coma are observed to be far
from equilibrium, with mergers currently on-going, while the ICL properties in
the Fornax and Hydra clusters show the presence of sub-components being
accreted in their cores, but superposed to an otherwise relaxed population of
stars. Finally the comparison of the observed ICL properties with those
predicted from Lambda-CDM simulations indicates a qualitative agreement and
provides insights on the ICL formation. Both observations and simulations
indicate that BCG halos and ICL are physically distinct components, with the
``hotter" ICL dominating at large radial distances from the BCGs halos as the
latter become progressively fainter.Comment: 14 pages, 5 figures. Invited review to appear in the proceedings of
"Galaxies and their masks" eds. Block, D.L., Freeman, K.C. and Puerari, I.,
2010, Springer (New York
Twist Deformations of the Supersymmetric Quantum Mechanics
The N-extended Supersymmetric Quantum Mechanics is deformed via an abelian
twist which preserves the super-Hopf algebra structure of its Universal
Enveloping Superalgebra. Two constructions are possible. For even N one can
identify the 1D N-extended superalgebra with the fermionic Heisenberg algebra.
Alternatively, supersymmetry generators can be realized as operators belonging
to the Universal Enveloping Superalgebra of one bosonic and several fermionic
oscillators. The deformed system is described in terms of twisted operators
satisfying twist-deformed (anti)commutators. The main differences between an
abelian twist defined in terms of fermionic operators and an abelian twist
defined in terms of bosonic operators are discussed.Comment: 18 pages; two references adde
Topological doping and the stability of stripe phases
We analyze the properties of a general Ginzburg-Landau free energy with
competing order parameters, long-range interactions, and global constraints
(e.g., a fixed value of a total ``charge'') to address the physics of stripe
phases in underdoped high-Tc and related materials. For a local free energy
limited to quadratic terms of the gradient expansion, only uniform or
phase-separated configurations are thermodynamically stable. ``Stripe'' or
other non-uniform phases can be stabilized by long-range forces, but can only
have non-topological (in-phase) domain walls where the components of the
antiferromagnetic order parameter never change sign, and the periods of charge
and spin density waves coincide. The antiphase domain walls observed
experimentally require physics on an intermediate lengthscale, and they are
absent from a model that involves only long-distance physics. Dense stripe
phases can be stable even in the absence of long-range forces, but domain walls
always attract at large distances, i.e., there is a ubiquitous tendency to
phase separation at small doping. The implications for the phase diagram of
underdoped cuprates are discussed.Comment: 18 two-column pages, 2 figures, revtex+eps
Holons on a meandering stripe: quantum numbers
We attempt to access the regime of strong coupling between charge carriers
and transverse dynamics of an isolated conducting ``stripe'', such as those
found in cuprate superconductors. A stripe is modeled as a partially doped
domain wall in an antiferromagnet (AF), introduced in the context of two
different models: the t-J model with strong Ising anisotropy, and the Hubbard
model in the Hartree-Fock approximation. The domain walls with a given linear
charge density are supported artificially by boundary conditions. In both
models we find a regime of parameters where doped holes lose their spin and
become holons (charge Q=1, spin S_z=0), which can move along the stripe without
frustrating AF environment. One aspect in which the holons on the AF domain
wall differ from those in an ordinary one-dimensional electron gas is their
transverse degree of freedom: a mobile holon always resides on a transverse
kink (or antikink) of the domain wall. This gives rise to two holon flavors and
to a strong coupling between doped charges and transverse fluctuations of a
stripe.Comment: Minor revisions: references update
Geometric Phase: a Diagnostic Tool for Entanglement
Using a kinematic approach we show that the non-adiabatic, non-cyclic,
geometric phase corresponding to the radiation emitted by a three level cascade
system provides a sensitive diagnostic tool for determining the entanglement
properties of the two modes of radiation. The nonunitary, noncyclic path in the
state space may be realized through the same control parameters which control
the purity/mixedness and entanglement. We show analytically that the geometric
phase is related to concurrence in certain region of the parameter space. We
further show that the rate of change of the geometric phase reveals its
resilience to fluctuations only for pure Bell type states. Lastly, the
derivative of the geometric phase carries information on both purity/mixedness
and entanglement/separability.Comment: 13 pages 6 figure
Top Background Extrapolation for H -> WW Searches at the LHC
A leading order (LO) analysis is presented that demonstrates that key top
backgrounds to H -> W^+W^- -> l^\pm l^\mp \sla{p}_T decays in weak boson fusion
(WBF) and gluon fusion (GF) at the CERN Large Hadron Collider can be
extrapolated from experimental data with an accuracy of order 5% to 10%. If LO
scale variation is accepted as proxy for the theoretical error, parton level
results indicate that the tt~j background to the H -> WW search in WBF can be
determined with a theoretical error of about 5%, while the tt~ background to
the H -> WW search in GF can be determined with a theoretical error of better
than 1%. Uncertainties in the parton distribution functions contribute an
estimated 3% to 10% to the total error.Comment: 17 pages, 9 tables, 4 figures; LO caveat emphasized, version to be
published in Phys. Rev.
- …