检索结果-南通市图书馆

ON THE FINITE ELEMENT APPROXIMATION OF SYSTEMS OF REACTION-DIFFUSION EQUATIONS BY p/hp METHODS

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2010年第3期28卷 386-400页

作者： christos Xenophontos Lisa Oberbroeckling Department of Mathematics & Statistics University of Cyprus Department of Mathematical Sciences Loyola University Maryland

We consider the approximation of systems of reaction-diffusion equations, with the finite element method. The highest derivative in each equation is multiplied by a parameter ε∈ （0, 1], and as ε → 0 the solution of the system will contain boundary layers. We extend the analysis of the corresponding scalar problem from [Melenk, IMA J. Numer. Anal. 17（1997）, pp. 577-601], to construct a finite element scheme which includes elements of size O（εp） near the boundary, where p is the degree of the approximating polynomials. We show that, under the assumption of analytic input data, the method yields exponential rates of convergence, independently of ε, when the error is measured in the energy norm associated with the problem. Numerical computations supporting the theory are also presented, which also show that the method yields robust exponential convergence rates when the error in the maximum norm is used.

关键词： Reaction-diffusion system Boundary layers hp finite element method.

AN hp-FEM FOR SINGULARLY PERTURBED TRANSMISSION PROBLEMS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2017年第2期35卷 152-168页

作者： Serge Nicaise christos Xenophontos Université de Valenciennes et du Hainaut Cambrésis LAMAV FR CNRS 2956 Institut des Sciences et Techniques de Valenciennes F-59313 - Valenciennes Cedex 9 France Department of Mathematics and Statistics University of Cyprus P.O. Box 20537 Nicosia 1678 Cyprus

We perform the analysis of the hp finite element approximation for the solution to singularly perturbed transmission problems, using Spectral Boundary Layer Meshes. In [12] it was shown that this method yields robust exponential convergence, as the degree p of the approximating polynomials is increased, when the error is measured in the energy norm associated with the boundary value problem. In the present article we sharpen the result by showing that the hp-Finite Element Method （FEM） on Spectral Boundary Layer Meshes leads to robust exponential convergence in a stronger, more balanced norm. Several numerical results illustrating and extending the theory are also nresented.

关键词： Singularly perturbed transmission problem Boundary layers Interface layers,hp-FEM Balanced norm Exponential convergence.

SCHEDULING IN THE SERVICE INDUSTRIES:AN OVERVIEW

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Science and Systems Engineering 2015年第1期24卷 1-48页

作者： Michael Pinedo christos Zacharias Ning Zhu Stern Business School New York University School of Business Administration University of Miami College of Economics and Management Tianjin University

Scheduling plays an important role in many different service industries. In this paper we provide an overview of some of the more important scheduling problems that appear in the various service industries. We focus on the formulations of such problems as well as on the techniques used for solving those problems. We consider five areas of scheduling in service industries, namely （i） project scheduling, （ii） workforce scheduling, （iii） timetabling, reservations, and appointments, （iv） transportation scheduling, and （v） scheduling in entertainment. The first two areas are fairly general and have applications in many different service industries. The third, fourth and fifth areas are more related to some very specific service industries, namely the hospitality and health care industries, the transportation industries （of passengers as well as of cargo）, and the entertainment industries. In our conclusion section we discuss the similarities and the differences between the problem formulations and solution techniques used in the various different industries and we also discuss the design of the decision support systems that have been developed for scheduling in the service industries.

关键词： Artificial intelligence Decision support systems Problem solving

Risk of hepatitis B reactivation in patients treated with direct-acting antivirals for hepatitis C

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2017年第24期23卷 4317-4323页

作者： Ioanna Aggeletopoulou christos Konstantakis Spilios Manolakopoulos christos Triantos Department of Gastroenterology University Hospital of Patras 2nd Department of Internal Medicine Hippokration General Hospital of Athens

The recent introduction of direct-acting antiviral drugs(DAAs) for treatment of the hepatitis C virus(HCV) has greatly improved the management of HCV for infected patients. These viral protein inhibitors act rapidly, allowing HCV clearance and increasing the sustained virological response rates. However, hepatitis B virus(HBV) reactivation has been reported in HCV/HBV co-infected patients. Hepatitis B reactivation refers to an abrupt increase in the HBV and is welldocumented in patients with previously undetected HBV DNA due to inactive or resolved HBV infection. Reactivation can occur spontaneously, but in most cases, it is triggered by various factors. Reactivation can be transient, without clinical symptoms; however, it usually causes a hepatitis flare. HBV reactivation may occur regardless of HCV genotype and type of DAA regimen. HBV screening is strongly recommended for co-infected HCV/HBV patients before initiation and during DAA therapy regardless of HBV status, HCV genotype and class of DAAs used. HBV reactivation can be prevented with pretreatment screening and prophylactic treatment when necessary. Additional data are required to evaluate the underlying mechanisms of HBV reactivation in this setting.

关键词： Hepatitis B Hepatitis C Hepatitis B virus reactivation Direct-acting antivirals Pretreatment screening

Role of NLRP3 inflammasome in inflammatory bowel diseases

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2019年第33期25卷 4796-4804页

作者： Evanthia Tourkochristou Ioanna Aggeletopoulou christos Konstantakis christos Triantos Division of Gastroenterology Department of Internal Medicine Medical School University of Patras

Inflammasomes are multiprotein intracellular complexes which are responsible for the activation of inflammatory responses. Among various subtypes of inflammasomes, NLRP3 has been a subject of intensive investigation. NLRP3 is considered to be a sensor of microbial and other danger signals and plays a crucial role in mucosal immune responses, promoting the maturation of proinflammatory cytokines interleukin 1β(IL-1β) and IL-18. NLRP3 inflammasome has been associated with a variety of inflammatory and autoimmune conditions, including inflammatory bowel diseases(IBD). The role of NLRP3 in IBD is not yet fully elucidated as it seems to demonstrate both pathogenic and protective effects. Studies have shown a relationship between genetic variants and mutations in NLRP3 gene with IBD pathogenesis. A complex interaction between the NLRP3 inflammasome and the mucosal immune response has been reported. Activation of the inflammasome is a key function mediated by the innate immune response and in parallel the signaling through IL-1β and IL-18 is implicated in adaptive immunity. Further research is needed to delineate the precise mechanisms of NLRP3 function in regulating immune responses. Targeting NLRP3 inflammasome and its downstream signaling will provide new insights into the development of future therapeutic strategies.

关键词： NLRP3 inflammasome Inflammatory bowel diseases Mucosal immune system Interleukin 1β Interleukin 18 NLRP3 gene polymorphisms

Role of band ligation for secondary prophylaxis of variceal bleeding

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2018年第26期24卷 2902-2914页

作者： Ioanna Aggeletopoulou christos Konstantakis Spilios Manolakopoulos christos Triantos Department of Gastroenterology University Hospital of Patras 2~(nd) Department of Internal Medicine Hippokration General Hospital of Athens

AIM To summarize and critically examine the role of band ligation in secondary prophylaxis of variceal bleeding in patients with cirrhosis. METHODS A literature review was performed using the MEDLINE and PubM ed databases. The search terms consisted of the words "endoscopic band ligation" OR "variceal band ligation" OR "ligation" AND "secondary prophylaxis" OR "secondary prevention" AND "variceal bleeding" OR "variceal hemorrhage" AND "liver cirrhosis". The data collected from relevant meta-analyses and from the most recent randomized studies that were not included in these meta-analyses were used to evaluate the role of endoscopic band ligation in an effort to demonstrate the most recent advances in the treatment of esophageal varices. RESULTS This study included 11 meta-analyses published from 2002 to 2017 and 10 randomized trials published from 2010 to 2017 that evaluated the efficacy of band ligation in the secondary prophylaxis of variceal bleeding. Overall, the results proved that band ligation was superior to endoscopic sclerotherapy. Moreover, the use of β-blockers in combination with band ligation increased the treatment effectiveness, supporting the current recommendations for secondary prophylaxis of variceal bleeding. The use of transjugular intrahepatic portosystemic shunt was superior to combination therapy regarding rebleeding prophylaxis, with no difference in the survival rates; however, the results concerning the hepatic encephalopathy incidence were conflicting. Recent advances in the management of secondary prophylaxis of variceal bleeding have targeted a decrease in portal pressure based on the pathophysiological mechanisms of portal *** This review suggests that future research should be conducted to enhance current interventions and/or to develop innovative treatment options with improved clinical endpoints.

关键词： Band ligation Variceal bleeding Rebleeding Liver cirrhosis Endoscopic therapy Variceal eradication Secondary prophylaxis Esophageal varices

Comparison of blood rheological models in patient specific cardiovascular system simulations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2017年第2期29卷 293-304页

作者： Anastasios Skiadopoulos Panagiotis Neofytou christos Housiadas Thermal Hydraulics and Multiphase Flows Laboratory I.N.RA.S.T.E.SN.C.S.R.

Newtonian, Quemada and Casson blood viscosity models are implemented in order to simulate the rheological behavior of blood under pulsating flow conditions in a patient specific iliac bifurcation. The influence of the applied blood constitutive equations is monitored via the wall shear stress （WSS） distribution, magnitude and oscillations, non-Newtonian importance factors, and viscosity values according to the shear rate. The distribution of WSS on the vascular wall follows a pattern which is independent of the theological model chosen. On the other hand, the WSS magnitude and oscillations are directly related to the blood constitutive equations applied and the shear rate. It is concluded that the Newtonian approximation is satisfactory only in high shear and flow rates. Moreover, the Newtonian model seems to overestimate the possibility for the formation of atherosclerotic lesions or aneurysms at sites of the vascular wall where the WSS are oscillating.

关键词： Key words: Blood flow simulation patient specific geometries geometry reconstruction non-Newtonian models wall shear stress,pulsating flow

Improvement of gastric emptying by enhanced recovery after pancreaticoduodenectomy

在线全文

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2016年第2期15卷 198-208页

作者： Efstratios Zouros Theodoros Liakakos Anastasios Machairas Paulos Patapis christos Agalianos christos Dervenis Department of Surgery "Konstantopouleio" General Hospital First Department of Surgery Laiko University Hospital Third Department of Surgery Attikon University Hospital

BACKGROUND： Enhanced recovery after surgery（ERAS） has improved postoperative outcomes particularly in colorectal surgery. This study aimed to assess compliance with an ERAS protocol and evaluate its effect on postoperative outcomes in patients undergoing pancreaticoduodenectomy. METHODS： Fifty patients who had received conventional peri operative management from 2005 to 2009（conventional group）were compared with 75 patients who had received perioperative care with an ERAS protocol（fast-track group） from 2010 to2014. Mortality, complications, readmissions and length of hospital stay were evaluated and compared in the ***： Compliance with each element of the ERAS pro tocol ranged from 74.7% to 100%. Uneventful patients had a significant higher adherence to the ERAS protocol（87.5% vs40.7%; P〈0.001）. There were no significant differences in de mographics and perioperative characteristics between the two groups. Patients in the fast-track group had a shorter time to remove the nasogastric tube, start liquid diet and solid food pass flatus and stools, and remove drains. No difference was found in mortality, relaparotomy, readmission rates and over all morbidity. However, delayed gastric emptying and length of hospital stay were significantly reduced in the fast-track group. The independent effect of the ERAS protocol in reduc ing delayed gastric emptying and length of hospital stay was confirmed by multivariate ***： ERAS pathway was feasible and safe in improving gastric emptying, yielding an earlier postoperative recovery, and reducing the length of hospital stay.

关键词： fast-track delayed gastric emptying compliance length of hospital stay morbidity

Interleukin 12/interleukin 23 pathway: Biological basis and therapeutic effect in patients with Crohn's disease

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2018年第36期24卷 4093-4103页

作者： Ioanna Aggeletopoulou Stelios F Assimakopoulos christos Konstantakis christos Triantos Division of Gastroenterology Department of Internal MedicineMedical SchoolUniversity of Patras Department of Internal Medicine University Hospital of Patras

Considering that both innate and adaptive immune responses are involved in the pathogenesis of Crohn's disease(CD), novel therapeutic options have significantly been developed. Biological agents represent an important addition to the conventional treatments for immuno-inflammatory conditions, acting as antagonists of adhesion molecules or various inflammatory cytokines. The interleukin 12(IL-12)/IL-23 common pathway has been found to play a determinant role in the induction of inflammation in adaptive immune responses. In particular, IL-23 promotes the differentiation of na?ve T helper cells into Th17 phenotype with the concomitant secretion of several inflammatory cytokines such as IL-17 and IL-22, whereas IL-12 induces the Th1 polarization and production of critical cytokines such as interferon-γ and tumor necrosis factor. Nowadays, there is increased interest regarding the role of IL-23 as a therapeutic target of CD through the blockage of IL-23 mediated pathways. In this editorial, we focus on the role of IL-12/IL-23 pathway in the regulation of mucosal immunity and in the induction and maintenance of chronic inflammation. In parallel, we critically discuss the available data regarding the therapeutic effect of the IL-12/IL-23 inhibitors and especially of ustekinumab, a human monoclonal antibody which has been recently approved by the United States Food and Drug Administration for the management of moderateto-severe CD and its potential to be used as first-line therapy in everyday clinical practice.

关键词： Crohn’s disease Interleukin 12 Interleukin 23 Monoclonal antibodies Ustekinumab Biological agents Interleukin 12/interleukin 23 blockade