9,253 research outputs found
Stochastic Processes Crossing from Ballistic to Fractional Diffusion with Memory: Exact Results
We address the now classical problem of a diffusion process that crosses over
from a ballistic behavior at short times to a fractional diffusion (sub- or
super-diffusion) at longer times. Using the standard non-Markovian diffusion
equation we demonstrate how to choose the memory kernel to exactly respect the
two different asymptotics of the diffusion process. Having done so we solve for
the probability distribution function (pdf) as a continuous function which
evolves inside a ballistically expanding domain. This general solution agrees
for long times with the pdf obtained within the continuous random walk approach
but it is much superior to this solution at shorter times where the effect of
the ballistic regime is crucial
Charmonia enhancement in quark-gluon plasma with improved description of c-quarks phase-distribution
We present a dynamical model of heavy quark evolution in the quark-gluon
plasma (QGP) based on the Fokker-Planck equation. We then apply this model to
the case of central ultra-relativistic nucleus-nucleus collisions performed at
RHIC and estimate the component of production (integrated and
differential) stemming from c- pairs that are initially uncorrelated.Comment: contribution presented at SQM0
Comparison of two DEM strategies for modelling cortical meshes
This work deals with the particle-based modelling of cortical wire meshes. Such meshes are being used in many engineering applications but their modelling is particularly complex because of the common large displacement serviceability conditions, the chance of localized failures, and the intrinsic geometrical and mechanical anisotropies. The discrete element method has proved to be an excellent numerical tool for the investigation of such structures. Here, two modelling strategies are compared using a wire-node description and a wire-cylinder description: in the first the wire mesh is described by a collection of spheres at nodes linked by long-range interaction forces, in the second the wires are represented by means of interconnected cylinders. The force-displacement constitutive model of the interactions is calibrated based on specific tensile tests. The comparison is performed on results of tensile tests and punch tests on a reference mesh panel
The exact evaluation of the corner-to-corner resistance of an M x N resistor network: Asymptotic expansion
We study the corner-to-corner resistance of an M x N resistor network with
resistors r and s in the two spatial directions, and obtain an asymptotic
expansion of its exact expression for large M and N. For M = N, r = s =1, our
result is
R_{NxN} = (4/pi) log N + 0.077318 + 0.266070/N^2 - 0.534779/N^4 + O(1/N^6).Comment: 12 pages, re-arranged section
Deep learning for inferring cause of data anomalies
Daily operation of a large-scale experiment is a resource consuming task,
particularly from perspectives of routine data quality monitoring. Typically,
data comes from different sub-detectors and the global quality of data depends
on the combinatorial performance of each of them. In this paper, the problem of
identifying channels in which anomalies occurred is considered. We introduce a
generic deep learning model and prove that, under reasonable assumptions, the
model learns to identify 'channels' which are affected by an anomaly. Such
model could be used for data quality manager cross-check and assistance and
identifying good channels in anomalous data samples. The main novelty of the
method is that the model does not require ground truth labels for each channel,
only global flag is used. This effectively distinguishes the model from
classical classification methods. Being applied to CMS data collected in the
year 2010, this approach proves its ability to decompose anomaly by separate
channels.Comment: Presented at ACAT 2017 conference, Seattle, US
Oxidation of hexcacyanoferrate(II) ion by hydrogen peroxide: inhibition by polyalcohols and related compounds
The oxidation of hexacyanoferrate(ll) ion by a large excess of hydrogen peroxide, in slightly acidic aqueous media containing potassium dihydrogen phosphate (pH 5.10 ± 0.05), was followed by monitoring the increase of absorbance at 420 nm as the colorless Fe(ll) complex gradually evolved into the yellow Fe(lll) complex. The reaction was inhibited by OH-containing organic compounds, either alcohols or carbohydrates, and two different inhibition pathways were observed, an iron(III)-independent pathway (rate constant k1) and an iron(III)-mediated pathway (rate constant k2). A BASIC-language computer program was developed in order to use the fourth-order Runge-Kutta integration method to obtain the concentrations of the Fe(ll)-inhibitor complex and the Fe(lll) reaction product. Rate constant k1, whose value is determined by that of the initial rate, decreased slightly as the concentration of alcohol / carbohydrate increased, and a mechanism involving the formation of hydroxyl radicals in a Fenton-like reaction and its posterior scavenging by the organic antioxidant additive has been proposed. Of the 8 inhibiting agents that were tried, the most potent antioxidant under the experimental conditions of this study was D-mannitol. Rate constant k2, whose value is a measurement of the deviation from a pseudo-first order behavior provoked by the inhibiting agent, increased notably as the concentration of the latter increased, and a mechanism involving the complexation of the Fe(lll) product by the organic inhibitor and its posterior outer-sphere one electron reduction from hexacyanoferrate(ll) ion has also been proposed. This might result in a blockage of the regeneration of pentacyanoaquaferrate(ll) ion, an intermediate believed to be essential for the redox reaction to take place
Theory of resistor networks: The two-point resistance
The resistance between arbitrary two nodes in a resistor network is obtained
in terms of the eigenvalues and eigenfunctions of the Laplacian matrix
associated with the network. Explicit formulas for two-point resistances are
deduced for regular lattices in one, two, and three dimensions under various
boundary conditions including that of a Moebius strip and a Klein bottle. The
emphasis is on lattices of finite sizes. We also deduce summation and product
identities which can be used to analyze large-size expansions of two-and-higher
dimensional lattices.Comment: 30 pages, 5 figures now included; typos in Example 1 correcte
Лекарственный анафилактический и псевдоаллергический шок: патогенез, клиника, дифференциальная диагностика, подходы к терапии
Представлены особенности патогенеза анафилактического и псевдоаллергического шока, обусловленного лекарственными средствами, сходства и различия в клиническом их течении, субъективные и объективные признаки дифференциальной диагностики, подходы к терапии.The peculiarities of the pathogenesis of anaphylactic and pseudoallergic shock caused by medications, similarity and differences of the clinical course, subjective and objective signs of differential diagnosis, approaches to therapy are presented
Ischemia and reperfusion injury in kidney transplantation : relevant mechanisms in injury and repair
Ischemia and reperfusion injury (IRI) is a complex pathophysiological phenomenon, inevitable in kidney transplantation and one of the most important mechanisms for non- or delayed function immediately after transplantation. Long term, it is associated with acute rejection and chronic graft dysfunction due to interstitial fibrosis and tubular atrophy. Recently, more insight has been gained in the underlying molecular pathways and signalling cascades involved, which opens the door to new therapeutic opportunities aiming to reduce IRI and improve graft survival. This review systemically discusses the specific molecular pathways involved in the pathophysiology of IRI and highlights new therapeutic strategies targeting these pathways
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