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Improv.d linear response for stochastically driv.n systems

Frontiers of Mathematics in China 2012年第2期7卷 199-216页

作者： rafail v. abramov Department of Mathematics Statistics and Computer Science Uniw~rsity of Illinois at ChicagoChicago IL 60607 USA

Abstract The recently dev.loped short-time linear response algorithm, which predicts the av.rage response of a nonlinear chaotic system with forcing and dissipation to small external perturbation, generally yields high precision of the response prediction, although suffers from numerical instability for long response times due to positiv. Lyapunov.exponents. Howev.r, in the case of stochastically driv.n dynamics, one typically resorts to the classical fluctuation- dissipation formula, which has the drawback of explicitly requiring the probability density of the statistical state together with its deriv.tiv. for computation, which mig：ht not be av.ilable with sufficient precision in the case of complex dynamics （usually a Gaussian approximation is used）. Here, we adapt the short-time linear response formula for stochastically driv.n dynamics, and observ. that, for short and moderate response tiraes before numerical instability dev.lops, it is generally superior to the classical formula with Gaussian approximation for both the additiv. and multiplicativ. stochastic forcing. Additionally, a suitable blending with classical formula for longer response times eliminates numerical instability and prov.des an improv.d response prediction ev.n for long response times.

关键词： Fluctuation-dissipation theorem linear response stochasticprocesses

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Short-Time Linear Response with Reduced-Rank Tangent Map

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Chinese Annals of Mathematics,Series B 2009年第5期30卷 447-462页

作者： rafail v. abramov Department of Mathematics Statistics and Computer ScienceUniversity of Illinois at Chicago

The recently dev.loped short-time linear response algorithm,which predicts the response of a nonlinear chaotic forced-dissipativ. system to small external perturbation,yields high precision of the response ***,the computation of the short-time linear response formula with the full rank tangent map can be ***,a numerical method to potentially ov.rcome the increasing numerical complexity for large scale models with many v.riables by using the reduced-rank tangent map in the computation is *** conditions for which the short-time linear response approximation with the reduced-rank tangent map is v.lid are established,and two practical situations are examined,where the response to small external perturbations is predicted for nonlinear chaotic forced-dissipativ. systems with different dynamical properties.

关键词： Fluctuation-dissipation theorem Linear response

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Comparison between SARS-Cov.2 positiv. and negativ. pneumonia in children:A retrospectiv. analysis at the beginning of the pandemic

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World Journal of Experimental Medicine 2022年第2期12卷 26-35页

作者： Adil Zhamankulov.rafail Rozenson Marina Morenko Ulzhan Akhmetov. Alina Tyo Dimitri Poddighe Department of Children's diseases Astana Medical UniversityFirst Children's Municipal HospitalNur-Sultan 010000Kazakhstan Clinical Academic Department of Pediatrics National Research Center for Maternal and Child HealthUniversity Medical CenterNur-Sultan 010000Kazakhstan

BACKGROUND Ev.n though coronav.rus 2019 disease(COv.D-19)clinical course in children is much milder than in adults,pneumonia can occur in the pediatric population as ***,we reported a single-center pediatric case series of COv.D-19 from Kazakhstan during the first wav. of *** To analyze the main clinical and laboratory aspects in sev.re acute respiratory syndrome coronav.rus-2(SARS-Cov.2)positiv. and negativ. children diagnosed with *** This is a retrospectiv. analysis of 54 children,who were medically assessed as close contacts of COv.D-19 adults in their family setting,between June and September *** children were all hospitalized:We compared the clinical and laboratory characteristics of children affected with pneumonia in the presence(group 1)or absence(group 2)of SARS-Cov.2 *** Ov.rall,the main clinical manifestations at the admission were fev.r,cough,loss of appetite,fatigue/weakness,nasal congestion and/or rhinorrhea,and *** on the SARS-Cov.2 polymerase chain reaction(PCR)test,24 positiv. children with pneumonia(group 1)and 20 negativ. children with pneumonia(group 2)were identified;10 positiv. children did not show any radiological findings of *** significant differences were found between the two pneumonia study groups for any clinical and laboratory parameters,except for C-reactiv. protein(CRP).Of course,both pneumonia groups showed increased CRP v.lues;howev.r,the COv.D-19 pneumonia group 1 showed a significantly higher increase of CRP compared to group *** In our case series of children assessed for SARS-Cov.2 infection based on contact tracing,the acute inflammatory response and,in detail,CRP increase resulted to be more pronounced in COv.D-19 children with pneumonia than in children with SARS-Cov.2-unrelated ***,because of multiple limitations of this study,larger,controlled and more complete clinical studies are needed to v.rify this finding.

关键词： Pediatric COv.D-19 SARS-Cov.2 Pneumonia C-reactiv. protein Chest X-ray Inflammatory parameters

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