512 research outputs found
Final-State Phases in Doubly-Cabibbo-Suppressed Charmed Meson Nonleptonic Decays
Cabibbo-favored nonleptonic charmed particle decays exhibit large final-state
phase differences in and but not
channels. It is of interest to know the corresponding pattern of final-state
phases in doubly-Cabibbo-suppressed decays, governed by the
subprocess. An experimental program is outlined for determining such phases via
measurements of rates for and channels,
and determination of interference between bands in Dalitz plots. Such a program
is feasible at planned high-intensity sources of charmed particles.Comment: 12 pages, LaTeX, 2 figures, to be submitted to Phys. Rev. D. Revised
versio
Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
Inhibition of cyclooxygenase (COX)-2 elicits therapeutic effects in solid tumors that are coupled with the inhibition of cell proliferation and induction of apoptosis in tumor cells. Aim: This study was designed to investigate the role of COX-2 inhibitor nimesulide in cell growth and apoptosis of the cultured human hepatocellular carcinoma HepG2 cells. Methods: We performed the MTT assay, flow cytometric analysis and cell morphology study to evaluate growth inhibition and cell apoptosis upon the action of nimesulide alone or along with doxorubicin, a common agent for the treatment of human hepatocellular carcinoma. Results: Our results showed that the treatment of HepG2 cells with more than 50 µM of nimesulide suppressed COX-2 enzyme activity because of reduced PGE2 production, and then induced growth inhibition and cell apoptosis despite no alterations of COX-2 protein expression. Importantly, the combination of 50 µM or 100 µM of nimesulide and low concentrations (5 µM to 20 µM) of doxorubicin resulted in enhanced cell growth inhibition, apoptosis induction and reduced VEGF production. Conclusion: These data suggest synergistic and/or additive effects of COX-2 inhibitors and chemotherapeutic agents, and may provide the rational for clinical studies of COX-2 inhibitors on the treatment or chemoprevention of human hepatocellular carcinoma.Угнетение циклооксигеназы-2 (ЦОГ-2) оказывает терапевтический эффект при лечении больных с солидными опухолями
и сопровождается снижением пролиферации опухолевых клеток и индукцией апоптоза. Цель: изучение роли ингибитора
ЦОГ-2 — нимесулида в процессах роста и апоптоза культивированных клеток гепатокарциномы человека HepG2.
Методы: для оценки апоптоза и угнетения роста клеток при применении нимесулида самостоятельно и в сочетании с
доксорубицином применяли MTT-анализ, проточную цитометрию и стандартные морфологические методы. Результаты:
установлено, что обработка клеток HepG2 cells нимесулидом в концентрации > 50 μM приводила к угнетению активности
ЦОГ-2 за счет снижения продукции PGE2
, после чего отмечали подавление роста и апоптоз клеток при неизмененном
уровне экспрессии ЦОГ-2. Комбинированное применение 50 μM или 100 μM нимесулида и доксорубицина в концентрации
5–20 μM обусловило усиленное угнетение роста клеток, индукции апоптоза и снижение продукции VEGF. Выводы:
полученные данные свидетельствуют о синергическом и/или аддитивном эффекте при применении ингибиторов ЦОГ-2
и химиотерапевтических препаратов
Threshold resummation for exclusive B meson decays
We argue that double logarithmic corrections need to be
resumed in perturbative QCD factorization theorem for exclusive meson
decays, when the end-point region with a momentum fraction is
important. These double logarithms, being of the collinear origin, are absorbed
into a quark jet function, which is defined by a matrix element of a quark
field attached by a Wilson line. The factorization of the jet function from the
decay is proved to all orders. Threshold resummation for
the jet function leads to a universal, {\it i.e.}, process-independent, Sudakov
factor, whose qualitative behavior is analyzed and found to smear the end-point
singularities in heavy-to-light transition form factors.Comment: 10 pages, more details are include
factorization of exclusive processes
We prove factorization theorem in perturbative QCD (PQCD) for exclusive
processes by considering and . The relevant form factors are expressed as the convolution of hard
amplitudes with two-parton meson wave functions in the impact parameter
space, being conjugate to the parton transverse momenta . The point is
that on-shell valence partons carry longitudinal momenta initially, and acquire
through collinear gluon exchanges. The -dependent two-parton wave
functions with an appropriate path for the Wilson links are gauge-invariant.
The hard amplitudes, defined as the difference between the parton-level
diagrams of on-shell external particles and their collinear approximation, are
also gauge-invariant. We compare the predictions for two-body nonleptonic
meson decays derived from factorization (the PQCD approach) and from
collinear factorization (the QCD factorization approach).Comment: 11 pages, REVTEX, 5 figure
Imaging of Low Compressibility Strips in the Quantum Hall Liquid
Using Subsurface Charge Accumulation scanning microscopy we image strips of
low compressibility corresponding to several integer Quantum Hall filling
factors. We study in detail the strips at Landau level filling factors
2 and 4. The observed strips appear significantly wider than predicted by
theory. We present a model accounting for the discrepancy by considering a
disorder-induced nonzero density of states in the cyclotron gap.Comment: 5 pages, 3 figure
Study of Bc --> J/psi pi, etac pi decays with perturbative QCD approach
The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD
approach. It is found that form factors and branching ratios are sensitive to
the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of
the charmonium wave functions for Coulomb potential and harmonic oscillator
potential, respectively, f_J/psi and f_etac are the decay constants of the
J/psi and etac mesons, respectively. The large branching ratios and the clear
signals of the final states make the Bc --> J/psi pi, etac pi decays to be the
prospective channels for measurements at the hadron collidersComment: 21 pages, revtex
Classification and nondegeneracy of Toda system with singular sources
We consider the following Toda system \Delta u_i + \D \sum_{j = 1}^n
a_{ij}e^{u_j} = 4\pi\gamma_{i}\delta_{0} \text{in}\mathbb R^2, \int_{\mathbb
R^2}e^{u_i} dx -1\delta_0a_{ij}\gamma_i=0\forall \;1\leq i\leq n\gamma_i+\gamma_{i+1}+...+\gamma_j \notin \mathbb Z1\leq i\leq
j\leq nu_i$ is \textit{radially symmetric} w.r.t. 0.
(iii) We prove that the linearized equation at any solution is
\textit{non-degenerate}. These are fundamental results in order to understand
the bubbling behavior of the Toda system.Comment: 28 page
Observation of the screening signature in the lateral photovoltage of electrons in the Quantum Hall regime
The lateral photovoltage generated in the plane of a two-dimensional electron
system (2DES) by a focused light spot, exhibits a fine-structure in the quantum
oscillations in a magnetic field near the Quantum Hall conductivity minima. A
double peak structure occurs near the minima of the longitudinal conductivity
oscillations. This is the characteristic signature of the interplay between
screening and Landau quantization.Comment: 4 pages, 4 figures, to be published in Phys. Rev.
Transition Form Factor up to within the Factorization Approach
In the paper, we apply the factorization approach to deal with the
transition form factor in the large recoil
regions. The B-meson wave functions and that include the
three-particle Fock states' contributions are adopted to give a consistent PQCD
analysis of the form factor up to . It has been found that
both the wave functions and can give sizable
contributions to the form factor and should be kept for a better understanding
of the meson decays. Then the contributions from different twist structures
of the kaon wavefunction are discussed, including the -breaking
effects. A sizable contribution from the twist-3 wave function is
found, whose model dependence is discussed by taking two group of parameters
that are determined by different distribution amplitude moments obtained in the
literature. It is also shown that and
, which are more
reasonable and consistent with the light-cone sum rule results in the large
recoil regions.Comment: 22 pages and 6 figure
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