6,525 research outputs found
Evidence for Two Distinct Morphological Classes of Gamma-Ray Bursts from their Short Timescale Variability
We have analyzed the 241 bursts for which peak counts \C exist in the
publicly available Burst and Transient Source Experiment (BATSE) catalog.
Introducing peak counts in 1024 ms as a measure of burst brightness \B and
the ratio of peak counts in 64 and 1024 ms as a measure of short timescale
variability \V, we find a statistically significant correlation between the
brightness and the short timescale variability of \g-ray bursts. The bursts
which are smoother on short timescales are both faint and bright, while the
bursts which are variable on short timescales are faint only, suggesting the
existence of two distinct morphological classes of bursts.Comment: 9 pages + 2 Postscript figures available upon request; LATEX v. 2.0
STOCHASTIC DYNAMICS OF LARGE-SCALE INFLATION IN DE~SITTER SPACE
In this paper we derive exact quantum Langevin equations for stochastic
dynamics of large-scale inflation in de~Sitter space. These quantum Langevin
equations are the equivalent of the Wigner equation and are described by a
system of stochastic differential equations. We present a formula for the
calculation of the expectation value of a quantum operator whose Weyl symbol is
a function of the large-scale inflation scalar field and its time derivative.
The unique solution is obtained for the Cauchy problem for the Wigner equation
for large-scale inflation. The stationary solution for the Wigner equation is
found for an arbitrary potential. It is shown that the large-scale inflation
scalar field in de Sitter space behaves as a quantum one-dimensional
dissipative system, which supports the earlier results. But the analogy with a
one-dimensional model of the quantum linearly damped anharmonic oscillator is
not complete: the difference arises from the new time dependent commutation
relation for the large-scale field and its time derivative. It is found that,
for the large-scale inflation scalar field the large time asymptotics is equal
to the `classical limit'. For the large time limit the quantum Langevin
equations are just the classical stochastic Langevin equations (only the
stationary state is defined by the quantum field theory).Comment: 21 pages RevTex preprint styl
The Nutraceutical Properties of “Pizza Napoletana Marinara TSG” a Traditional Food Rich in Bioaccessible Antioxidants
: Italian gastronomy experiences have ever-enhancing fame around the world. It is due to
the linkage between taste and salubriousness commonly related to Mediterranean foods. The market
proposes many types of pizza to suit all palates. The antioxidant potential of the “Pizza Napoletana
marinara” included in the register of traditional specialties guaranteed (TSG) was determined
in this work. ABTS (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) method evaluated the
antioxidant activity of the pizza homogenized. In vitro digestion models estimated the intestinal
and gastric bioaccessibility of the main antioxidant compounds (lycopene and phenolics). To our
knowledge, this is the first study to provide the content, antioxidant potential, and bioaccessibility
of the antioxidants (polyphenols and lycopene) contained in the traditional pizza “marinara TSG”.
Our results showed that the “Pizza Napoletana marinara” had polyphenols concentration, lycopene
level, antioxidant activity, and bioaccessibility of phenolic compounds and lycopene better than other
similar pizzas. They confirmed the nutritional importance of traditional preparations and established
the nutraceutical potential of “pizza marinara TSG” as a food rich in bio-accessible antioxidants
An Application of Gaussian Process Modeling for High-order Accurate Adaptive Mesh Refinement Prolongation
We present a new polynomial-free prolongation scheme for Adaptive Mesh
Refinement (AMR) simulations of compressible and incompressible computational
fluid dynamics. The new method is constructed using a multi-dimensional
kernel-based Gaussian Process (GP) prolongation model. The formulation for this
scheme was inspired by the GP methods introduced by A. Reyes et al. (A New
Class of High-Order Methods for Fluid Dynamics Simulation using Gaussian
Process Modeling, Journal of Scientific Computing, 76 (2017), 443-480; A
variable high-order shock-capturing finite difference method with GP-WENO,
Journal of Computational Physics, 381 (2019), 189-217). In this paper, we
extend the previous GP interpolations and reconstructions to a new GP-based AMR
prolongation method that delivers a high-order accurate prolongation of data
from coarse to fine grids on AMR grid hierarchies. In compressible flow
simulations special care is necessary to handle shocks and discontinuities in a
stable manner. To meet this, we utilize the shock handling strategy using the
GP-based smoothness indicators developed in the previous GP work by A. Reyes et
al. We demonstrate the efficacy of the GP-AMR method in a series of testsuite
problems using the AMReX library, in which the GP-AMR method has been
implemented
Carcinoma cells activate AMP-activated protein kinase-dependent autophagy as survival response to kaempferol-mediated energetic impairment.
Kaempferol, a dietary cancer chemopreventive polyphenol, has been reported to trigger apoptosis in several tumor histotypes, but the mechanism underlying this phenomenon is not fully understood. Here, we demonstrate that in HeLa cells, kaempferol induces energetic failure due to inhibition of both glucose uptake and Complex I of the mitochondrial respiratory chain. As adaptive response, cells activate autophagy, the occurrence of which was established cytofluorometrically, upon acridine orange staining, and immunochemically, by following the increase of the autolysosome-associated form of the microtubule-associated protein light chain 3 (LC3-II). Autophagy is an early and reversible process occurring as survival mechanisms against apoptosis. Indeed, chemical inhibition of autophagy, by incubations with monensin, wortmannin, 3-methyladenine, or by silencing Atg5, significantly increases the extent of apoptosis, which takes place via the mitochondrial pathway, and shortens the time in which the apoptotic markers are detectable. We also demonstrate that autophagy depends on the early activation of the AMP-activated protein kinase (AMPK)/mTOR-mediated pathway. The overexpression of dominant negative AMPK results in a decrease of autophagic cells, a decrement of LC3-II levels, and a significant increase of apoptosis. Experiments performed with another carcinoma cell line yielded the same results, suggesting for kaempferol a unique mechanism of action
Unstable states in QED of strong magnetic fields
We question the use of stable asymptotic scattering states in QED of strong
magnetic fields. To correctly describe excited Landau states and photons above
the pair creation threshold the asymptotic fields are chosen as generalized
Licht fields. In this way the off-shell behavior of unstable particles is
automatically taken into account, and the resonant divergences that occur in
scattering cross sections in the presence of a strong external magnetic field
are avoided. While in a limiting case the conventional electron propagator with
Breit-Wigner form is obtained, in this formalism it is also possible to
calculate -matrix elements with external unstable particles.Comment: Revtex, 7 pages. To appear in Phys. Rev. D53(2
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