33,066 research outputs found
Global superscaling analysis of quasielastic electron scattering with relativistic effective mass
We present a global analysis of the inclusive quasielastic electron
scattering data with a superscaling approach with relativistic effective mass.
The SuSAM* model exploits the approximation of factorization of the scaling
function out of the cross section under quasifree conditions. Our
approach is based on the relativistic mean field theory of nuclear matter where
a relativistic effective mass for the nucleon encodes the dynamics of nucleons
moving in presence of scalar and vector potentials. Both the scaling variable
and the single nucleon cross sections include the effective mass as a
parameter to be fitted to the data alongside the Fermi momentum . Several
methods to extract the scaling function and its uncertainty from the data are
proposed and compared. The model predictions for the quasielastic cross section
and the theoretical error bands are presented and discussed for nuclei along
the periodic table from to : H, H, He, He,
C, Li, Be, Mg, Ni,
Y, Sn, Ta, W, Au, O, Al,
Ca, Ca, Fe, Pb, and U.
We find that more than 9000 of the total data fall within the
quasielastic theoretical bands. Predictions for Ti and Ar are
also provided for the kinematics of interest to neutrino experiments.Comment: 26 pages, 20 figures and 4 table
A Lloyd-model generalization: Conductance fluctuations in one-dimensional disordered systems
We perform a detailed numerical study of the conductance through
one-dimensional (1D) tight-binding wires with on-site disorder. The random
configurations of the on-site energies of the tight-binding
Hamiltonian are characterized by long-tailed distributions: For large
, with . Our
model serves as a generalization of 1D Lloyd's model, which corresponds to
. First, we verify that the ensemble average is proportional to the length of the wire for all values of
, providing the localization length from . Then, we show that the probability distribution
function is fully determined by the exponent and
. In contrast to 1D wires with standard
white-noise disorder, our wire model exhibits bimodal distributions of the
conductance with peaks at and . In addition, we show that
is proportional to , for , with , in
agreement to previous studies.Comment: 5 pages, 5 figure
Changes in the secretory profile of NSCLC-associated fibroblasts after ablative radiotherapy: potential impact on angiogenesis and tumor growth
In the context of radiotherapy, collateral effects of ablative ionizing radiation (AIR) on stromal components of tumors remains understudied. In this work, cancer-associated fibroblasts (CAFs) isolated from freshly resected human lung tumors were exposed to AIR (1x18Gy) and analyzed for their release of paracrine factors. Inflammatory mediators and regulators of angiogenesis and tumor growth were analyzed by multiplex protein assays in conditioned medium (CM) from irradiated and non-irradiated CAFs. Additionally, the profile of secreted proteins was examined by proteomics. In functional assays, effects of CAF-CM on proliferative and migratory capacity of lung tumor cells (H-520/H-522) and endothelial cells (HUVECs), and on the tube-forming capacity of endothelial cells was assessed. Our data show that exposure of CAFs to ablative doses of ionizing radiation results in a) down-regulated release of angiogenic factors SDF-1, angiopoietin and thrombospondin-2; b) up-regulated release of growth factor bFGF from most donors, and c) unaffected expression-levels of HGF and inflammatory mediators IL-6, IL-8, IL-1ƒÒ and TNF-£. Conditioned medium from irradiated and control CAFs did not affect differently the proliferative or migratory capacity of tumor cells (H-520/H-522), whereas migratory capacity of endothelial HUVEC cells was partially reduced in the presence of irradiated CAF conditioned medium. Overall we conclude that AIR mediates a transformation on the secretory profile of CAFs that could influence the behavior of other cells in the tumor tissue and hence guide to some extent therapeutic outcomes. The downstream consequences of the changes observed in this study merits further investigations
Log canonical thresholds of Del Pezzo Surfaces in characteristic p
The global log canonical threshold of each non-singular complex del Pezzo
surface was computed by Cheltsov. The proof used Koll\'ar-Shokurov's
connectedness principle and other results relying on vanishing theorems of
Kodaira type, not known to be true in finite characteristic.
We compute the global log canonical threshold of non-singular del Pezzo
surfaces over an algebraically closed field. We give algebraic proofs of
results previously known only in characteristic . Instead of using of the
connectedness principle we introduce a new technique based on a classification
of curves of low degree. As an application we conclude that non-singular del
Pezzo surfaces in finite characteristic of degree lower or equal than are
K-semistable.Comment: 21 pages. Thorough rewrite following referee's suggestions. To be
published in Manuscripta Mathematic
Variability in high-mass X-ray binaries
Strongly magnetized, accreting neutron stars show periodic and aperiodic
variability over a wide range of time scales. By obtaining spectral and timing
information on these different time scales, we can have a closer look into the
physics of accretion close to the neutron star and the properties of the
accreted material. One of the most prominent time scales is the strong
pulsation, i.e., the rotation period of the neutron star itself. Over one
rotation, our view of the accretion column and the X-ray producing region
changes significantly. This allows us to sample different physical conditions
within the column but at the same time requires that we have
viewing-angle-resolved models to properly describe them. In wind-fed high-mass
X-ray binaries, the main source of aperiodic variability is the clumpy stellar
wind, which leads to changes in the accretion rate (i.e., luminosity) as well
as absorption column. This variability allows us to study the behavior of the
accretion column as a function of luminosity, as well as to investigate the
structure and physical properties of the wind, which we can compare to winds in
isolated stars.Comment: 6 pages, 4 figures, accepted for publication in Astronomische
Nachrichten (proceedings of the XMM-Newton Workshop 2019
Mitochondrial exchanger NCLX plays a major role in the intracellular Ca(2+) signaling, gliotransmission, and proliferation of astrocytes
Mitochondria not only provide cells with energy, but are central to Ca(2+) signaling. Powered by the mitochondrial membrane potential, Ca(2+) enters the mitochondria and is released into the cytosol through a mitochondrial Na(+)/Ca(2+) exchanger. We established that NCLX, a newly discovered mitochondrial Na(+)/Ca(2+) exchanger, is expressed in astrocytes isolated from mice of either sex. Immunoblot analysis of organellar fractions showed that the location of NCLX is confined to mitochondria. Using pericam-based mitochondrial Ca(2+) imaging and NCLX inhibition either by siRNA or by the pharmacological blocker CGP37157, we demonstrated that NCLX is responsible for mitochondrial Ca(2+) extrusion. Suppression of NCLX function altered cytosolic Ca(2+) dynamics in astrocytes and this was mediated by a strong effect of NCLX activity on Ca(2+) influx via store-operated entry. Furthermore, Ca(2+) influx through the store-operated Ca(2+) entry triggered strong, whereas ER Ca(2+) release triggered only modest mitochondrial Ca(2+) transients, indicating that the functional cross talk between the plasma membrane and mitochondrial domains is particularly strong in astrocytes. Finally, silencing of NCLX expression significantly reduced Ca(2+)-dependent processes in astrocytes (i.e., exocytotic glutamate release, in vitro wound closure, and proliferation), whereas Ca(2+) wave propagation was not affected. Therefore, NCLX, by meditating astrocytic mitochondrial Na(+)/Ca(2+) exchange, links between mitochondria and plasma membrane Ca(2+) signaling, thereby modulating cytoplasmic Ca(2+) transients required to control a diverse array of astrocyte functions
Passenger transmission and productiveness of transit lines with high loads
Deterministic transit capacity analysis applies to planning, design and operational management of urban transit systems. The Transit Capacity and Quality of Service Manual (1) and Vuchic (2, 3) enable transit performance to be quantified and assessed using transit capacity and productive capacity. This paper further defines important productive performance measures of an individual transit service and transit line. Transit work (p-km) captures the transit task performed over distance. Passenger transmission (p-km/h) captures the passenger task delivered by service at speed. Transit productiveness (p-km/h) captures transit work performed over time. These measures are useful to operators in understanding their services’ or systems’ capabilities and passenger quality of service. This paper accounts for variability in utilized demand by passengers along a line and high passenger load conditions where passenger pass-up delay occurs. A hypothetical case study of an individual bus service’s operation demonstrates the usefulness of passenger transmission in comparing existing and growth scenarios. A hypothetical case study of a bus line’s operation during a peak hour window demonstrates the theory’s usefulness in examining the contribution of individual services to line productive performance. Scenarios may be assessed using this theory to benchmark or compare lines and segments, conditions, or consider improvements
Resonance tongues and patterns in periodically forced reaction-diffusion systems
Various resonant and near-resonant patterns form in a light-sensitive
Belousov-Zhabotinsky (BZ) reaction in response to a spatially-homogeneous
time-periodic perturbation with light. The regions (tongues) in the forcing
frequency and forcing amplitude parameter plane where resonant patterns form
are identified through analysis of the temporal response of the patterns.
Resonant and near-resonant responses are distinguished. The unforced BZ
reaction shows both spatially-uniform oscillations and rotating spiral waves,
while the forced system shows patterns such as standing-wave labyrinths and
rotating spiral waves. The patterns depend on the amplitude and frequency of
the perturbation, and also on whether the system responds to the forcing near
the uniform oscillation frequency or the spiral wave frequency. Numerical
simulations of a forced FitzHugh-Nagumo reaction-diffusion model show both
resonant and near-resonant patterns similar to the BZ chemical system
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