632 research outputs found
Numerical method for the mixed Volterra-Fredholm integral equations using hybrid Legendre functions
summary:A new method is proposed for the numerical solution of linear mixed Volterra-Fredholm integral equations in one space variable. The proposed numerical algorithm combines the trapezoidal rule, for the integration in time, with piecewise polynomial approximation, for the space discretization. We extend the method to nonlinear mixed Volterra-Fredholm integral equations. Finally, the method is tested on a number of problems and numerical results are given
Implications of Recent Measurements
The recent measurements of the color-suppressed modes imply non-vanishing relative final-state interaction (FSI)
phases among various decay amplitudes. Depending on whether or
not FSIs are implemented in the topological quark-diagram amplitudes, two
solutions for the parameters and are extracted from data using
various form-factor models. It is found that is not universal:
and with a relative phase
of order between and . If FSIs are not included in
quark-diagram amplitudes from the outset, and
will become smaller. The large value of compared to
or naive expectation implies the importance of
long-distance FSI contributions to color-suppressed internal -emission via
final-state rescatterings of the color-allowed tree amplitude.Comment: 17 pages. The Introduction is substantially revised and the order of
the presentation in Sec. 2 is rearranged. To appear in Phys. Re
Parthenolide: suggested drug for COVID-19
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the 2019 novel coronavirus (2019-nCoV) that causes acute respiratory distress syndrome (ARDS) which is the main reason for patients mortality. One of the effective treatments to reduce the effects of this virus is parthenolide (PN). Parthenolide is a sesquiterpene lactone found in medicinal plants. It can inhibit several pro-inflammatory signaling pathways, in particular the ATPase activity of NLRP3. Based on its ability to suppress inflammatory signal transduction and elevated level of serum IL-1β (a surrogate marker for NLRP3 activation) in COVID-19 patients, we suggest that PN could be potentiallyeffective for the treatment of COVID-19
Final-state interaction and s-quark helicity conservation in B -> J/psi K*
The Section of charm quark spin conservation is deleted since it involves
more dynamical assumptions than previously stated. A few comments are added in
view of new experimental results.Comment: To replace the earlier version of hep-ph/0106354. Minor additions and
one deletion with no change in the main argument nor the conclusio
Colour-Octet Effects in Radiative Decays
We investigate the effects of colour-octet contributions to the radiative
decay within the Bodwin, Braaten and Lepage NRQCD factorization
framework. Photons coming both from the coupling to hard processes (`direct')
and by collinear emission from light quarks (`fragmentation') are consistently
included at next-to-leading order (NLO) in . An estimate for the
non-perturbative matrix elements which enter in the final result is then
obtained. By comparing the NRQCD prediction at NLO for total decay rates with
the experimental data, it is found that the non-perturbative parameters must be
smaller than expected from the na\"\i ve scaling rules of NRQCD. Nevertheless,
colour-octet contributions to the shape of the photon spectrum turn out to be
significant.Comment: 25 pages, Latex, 8 figure
Combining CP Asymmetries in Decays
We prove an approximate relation, to leading order in dominant terms, between
CP-violating rate differences in and
. We show how data from these two processes may be
combined in order to enhance the significance of a nonzero result.Comment: 9 pages, latex, no figures, submitted to Phys. Rev. Letters, revise
Kinematic Effects in Radiative Quarkonia Decays
Non-relativistic QCD (NRQCD) predicts colour octet contributions to be
significant not only in many production processes of heavy quarkonia but also
in their radiative decays. We investigate the photon energy distributions in
these processes in the endpoint region. There the velocity expansion of NRQCD
breaks down which requires a resummation of an infinite class of colour octet
operators to so-called shape functions. We model these non-perturbative
functions by the emission of a soft gluon cluster in the initial state. We
found that the spectrum in the endpoint region is poorly understood if the
values for the colour octet matrix elements are taken as large as indicated
from NRQCD scaling rules. Therefore the endpoint region should not be taken
into account for a fit of the strong coupling constant at the scale of the
heavy quark mass.Comment: LaTeX, 17 pages, 5 figures. The complete paper is also available via
the www at http://www-ttp.physik.uni-karlsruhe.de/Preprints
Co-transplantation of Human Embryonic Stem Cell-derived Neural Progenitors and Schwann Cells in a Rat Spinal Cord Contusion Injury Model Elicits a Distinct Neurogenesis and Functional Recovery
Co-transplantation of neural progenitors (NPs) with Schwann cells (SCs) might be a way to overcome low rate of neuronal differentiation of NPs following transplantation in spinal cord injury (SCI) and the improvement of locomotor recovery. In this study, we initially generated NPs from human embryonic stem cells (hESCs) and investigated their potential for neuronal differentiation and functional recovery when co-cultured with SCs in vitro and co-transplanted in a rat acute model of contused SCI. Co-cultivation results revealed that the presence of SCs provided a consistent status for hESC-NPs and recharged their neural differentiation toward a predominantly neuronal fate. Following transplantation, a significant functional recovery was
observed in all engrafted groups (NPs, SCs, NPs+SCs) relative to the vehicle and control groups.
We also observed that animals receiving co-transplants established a better state as assessed with
the BBB functional test. Immunohistofluorescence evaluation five weeks after transplantation
showed invigorated neuronal differentiation and limited proliferation in the co-transplanted
group when compared to the individual hESC-NPs grafted group. These findings have
demonstrated that the co-transplantation of SCs with hESC-NPs could offer a synergistic effect,
promoting neuronal differentiation and functional recovery
On Large Final-State Phases in Heavy Meson Decays
An attempt is made to identify circumstances under which the weak decays of
and mesons may display large differences between eigenphases of strong
final-state interactions. There are several cases in which rescattering from
other final states appears to enhance decay rates with respect to estimates
based on the factorization hypothesis.Comment: 24 pages, latex, 4 figures, to be submitted to Phys. Rev.
End-to-end numerical modeling of the Roman Space Telescope coronagraph
The Roman Space Telescope will have the first advanced coronagraph in space,
with deformable mirrors for wavefront control, low-order wavefront sensing and
maintenance, and a photon-counting detector. It is expected to be able to
detect and characterize mature, giant exoplanets in reflected visible light.
Over the past decade the performance of the coronagraph in its flight
environment has been simulated with increasingly detailed diffraction and
structural/thermal finite element modeling. With the instrument now being
integrated in preparation for launch within the next few years, the present
state of the end-to-end modeling is described, including the measured flight
components such as deformable mirrors. The coronagraphic modes are thoroughly
described, including characteristics most readily derived from modeling. The
methods for diffraction propagation, wavefront control, and structural and
thermal finite-element modeling are detailed. The techniques and procedures
developed for the instrument will serve as a foundation for future
coronagraphic missions such as the Habitable Worlds Observatory.Comment: 113 pages, 85 figures, to be published in SPIE Journal of
Astronomical Telescopes, Instruments, and System
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