2,730 research outputs found
New Preshower detector for DIRAC Experiment
The Preshower (PSh) detector is a component of the DIRAC setup. It is
designed to improve rejection efficiency of e-e+ pairs background in the
{\pi}{\pi} and K{\pi} pair measurement. To increase the overall efficiency, a
new two-layer structure scintillator Preshower detector has been realized in
the region where the Nitrogen Cherenkov detector has been shortened to
introduce new detectors. The new Preshower-Cherenkov combination ensures the
electron rejection efficiency better than 99.9% in momentum region 1-7 GeV/c.Comment: to be published in NIM
Targeting T cells to treat atherosclerosis: Odyssey from bench to bedside
More than 150 years from the initial description of inflammation in atherosclerotic plaques, randomized clinical trials to test anti-inflammatory
therapies in atherosclerosis have recently been initiated. Lymphocytes and macrophages are main participants in the inflammatory response in
atherosclerosis. T lymphocytes operate mainly by exerting strong influences on the function of many cells in the immune system and beyond,
and co-ordinating their interactions. Importantly, T lymphocytes are not a homogenous population, but include several subsets with specialized
functions that can either promote or suppress inflammation. The interactions between these T-lymphocyte subsets have critical consequences
on the course and outcome of inflammation. The complexity of the inflammatory response in atherosclerosis poses significant challenges on
translating experimental findings into clinical therapies and makes the journey from bench to bedside an arduous one. Here, we summarize
recent advances on the role of CD4
+
T cells in the inflammatory process in atherosclerosis and discuss potential therapies to modulate these
lymphocytes that may provide future breakthroughs in the treatment of atherosclerosis
Spectral fluctuations of tridiagonal random matrices from the beta-Hermite ensemble
A time series delta(n), the fluctuation of the nth unfolded eigenvalue was
recently characterized for the classical Gaussian ensembles of NxN random
matrices (GOE, GUE, GSE). It is investigated here for the beta-Hermite ensemble
as a function of beta (zero or positive) by Monte Carlo simulations. The
fluctuation of delta(n) and the autocorrelation function vary logarithmically
with n for any beta>0 (1<<n<<N). The simple logarithmic behavior reported for
the higher-order moments of delta(n) for the GOE (beta=1) and the GUE (beta=2)
is valid for any positive beta and is accounted for by Gaussian distributions
whose variances depend linearly on ln(n). The 1/f noise previously demonstrated
for delta(n) series of the three Gaussian ensembles, is characterized by
wavelet analysis both as a function of beta and of N. When beta decreases from
1 to 0, for a given and large enough N, the evolution from a 1/f noise at
beta=1 to a 1/f^2 noise at beta=0 is heterogeneous with a ~1/f^2 noise at the
finest scales and a ~1/f noise at the coarsest ones. The range of scales in
which a ~1/f^2 noise predominates grows progressively when beta decreases.
Asymptotically, a 1/f^2 noise is found for beta=0 while a 1/f noise is the rule
for beta positive.Comment: 35 pages, 10 figures, corresponding author: G. Le Cae
Cell-Type Specific Changes in Glial Morphology and Glucocorticoid Expression During Stress and Aging in the Medial Prefrontal Cortex.
Repeated exposure to stressors is known to produce large-scale remodeling of neurons within the prefrontal cortex (PFC). Recent work suggests stress-related forms of structural plasticity can interact with aging to drive distinct patterns of pyramidal cell morphological changes. However, little is known about how other cellular components within PFC might be affected by these challenges. Here, we examined the effects of stress exposure and aging on medial prefrontal cortical glial subpopulations. Interestingly, we found no changes in glial morphology with stress exposure but a profound morphological change with aging. Furthermore, we found an upregulation of non-nuclear glucocorticoid receptors (GR) with aging, while nuclear levels remained largely unaffected. Both changes are selective for microglia, with no stress or aging effect found in astrocytes. Lastly, we show that the changes found within microglia inversely correlated with the density of dendritic spines on layer III pyramidal cells. These findings suggest microglia play a selective role in synaptic health within the aging brain
Rovibrationally resolved photodissociation of HeH+
Accurate photodissociation cross sections have been obtained for the A-X
electronic transition of HeH+ using ab initio potential curves and dipole
transition moments. Partial cross sections have been evaluated for all
rotational transitions from the vibrational levels v"=0-11 and over the entire
accessible wavelength range 100-1129 Angstrom. Assuming a Boltzmann
distribution of the rovibrational levels of the X state, photodissociation
cross sections are presented for temperatures between 500 and 12,000 K. A
similar set of calculations was performed for the pure rovibrational
photodissociation in the X-X electronic ground state, but covering photon
wavelengths into the far infrared. Applications of the cross sections to the
destruction of HeH+in the early Universe and in UV-irradiated environments such
as primordial halos and protoplanetary disks are briefly discussed
Recommended from our members
Regulatory CD4+T cells from patients with atherosclerosis display pro-inflammatory skewing and enhanced suppression function
Faithful and Efficient Explanations for Neural Networks via Neural Tangent Kernel Surrogate Models
A recent trend in explainable AI research has focused on surrogate modeling,
where neural networks are approximated as simpler ML algorithms such as kernel
machines. A second trend has been to utilize kernel functions in various
explain-by-example or data attribution tasks. In this work, we combine these
two trends to analyze approximate empirical neural tangent kernels (eNTK) for
data attribution. Approximation is critical for eNTK analysis due to the high
computational cost to compute the eNTK. We define new approximate eNTK and
perform novel analysis on how well the resulting kernel machine surrogate
models correlate with the underlying neural network. We introduce two new
random projection variants of approximate eNTK which allow users to tune the
time and memory complexity of their calculation. We conclude that kernel
machines using approximate neural tangent kernel as the kernel function are
effective surrogate models, with the introduced trace NTK the most consistent
performer. Open source software allowing users to efficiently calculate kernel
functions in the PyTorch framework is available
(https://github.com/pnnl/projection\_ntk).Comment: 9 pages, 2 figures, 3 tables Updated 3/11/2024 various
additions/clarifications after ICLR review. Accepted as a Spotlight paper at
ICLR 202
Fragmentation Properties of Three-membered Ring Heterocyclic Molecules by Partial Ion Yield Spectroscopy: C2H4O and C2H4S
We investigated the photofragmentation properties of two three-membered ring heterocyclic molecules, C2H4O and C2H4S, by total and partial ion yield spectroscopy. Positive and negative ions have been collected as a function of photon energy around the C 1s and O 1s ionization thresholds in C2H4O, and around the S 2p and C 1s thresholds in C2H4S. We underline similarities and differences between these two analogous systems. We present a new assignment of the spectral features around the C K-edge and the sulfur L2,3 edges in C2H4S. In both systems, we observe high fragmentation efficiency leading to positive and negative ions when exciting these molecules at resonances involving core-to-Rydberg transitions. The system, with one electron in an orbital far from the ionic core, relaxes preferentially by spectator Auger decay, and the resulting singly charged ion with two valence holes and one electron in an outer diffuse orbital can remain in excited states more susceptible to dissociation. A state-selective fragmentation pattern is analyzed in C2H4S which leads to direct production of S2+ following the decay of virtual-orbital excitations to final states above the double-ionization threshold
Asymptotic forms for hard and soft edge general conditional gap probabilities
An infinite log-gas formalism, due to Dyson, and independently Fogler and
Shklovskii, is applied to the computation of conditioned gap probabilities at
the hard and soft edges of random matrix -ensembles. The conditioning is
that there are eigenvalues in the gap, with , denoting the
end point of the gap. It is found that the entropy term in the formalism must
be replaced by a term involving the potential drop to obtain results consistent
with known asymptotic expansions in the case . With this modification made
for general , the derived expansions - which are for the logarithm of the
gap probabilities - are conjectured to be correct up to and including terms
O. They are shown to satisfy various consistency conditions,
including an asymptotic duality formula relating to .Comment: Replaces v2 which contains typographical errors arising from a
previous unpublished draf
Freezing Transition in Decaying Burgers Turbulence and Random Matrix Dualities
We reveal a phase transition with decreasing viscosity at \nu=\nu_c>0
in one-dimensional decaying Burgers turbulence with a power-law correlated
random profile of Gaussian-distributed initial velocities
\sim|x-x'|^{-2}. The low-viscosity phase exhibits non-Gaussian
one-point probability density of velocities, continuously dependent on \nu,
reflecting a spontaneous one step replica symmetry breaking (RSB) in the
associated statistical mechanics problem. We obtain the low orders cumulants
analytically. Our results, which are checked numerically, are based on
combining insights in the mechanism of the freezing transition in random
logarithmic potentials with an extension of duality relations discovered
recently in Random Matrix Theory. They are essentially non mean-field in nature
as also demonstrated by the shock size distribution computed numerically and
different from the short range correlated Kida model, itself well described by
a mean field one step RSB ansatz. We also provide some insights for the finite
viscosity behaviour of velocities in the latter model.Comment: Published version, essentially restructured & misprints corrected. 6
pages, 5 figure
- …