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A Modified Gas-Kinetic Scheme for Turbulent Flow

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Communications in Computational Physics 2014年第6期16卷 239-263页

作者： Marcello righi School of Engineering Zurich University of Applied SciencesTechnikumstrasse 98401 WinterthurSwitzerland.

The implementation of a turbulent gas-kinetic scheme into a finite-volume RANS solver is put forward,with two turbulent quantities,kinetic energy and dissipation,supplied by an allied turbulence *** paper shows a number of numerical simulations of flow cases including an interaction between a shock wave and a turbulent boundary layer,where the shock-turbulent boundary layer is captured in a much more convincing way than it normally is by conventional schemes based on the Navier-Stokes *** the gas-kinetic scheme,the modeling of turbulence is part of the numerical scheme,which adjusts as a function of the ratio of resolved to unresolved scales of *** so doing,the turbulent stress tensor is not constrained into a linear relation with the strain *** it is modeled on the basis of the analogy between particles and eddies,without any assumptions on the type of turbulence or flow *** schemes lack multiscale mechanisms:the ratio of unresolved to resolved scales–very much like a degree of rarefaction–is not taken into account even if it may grow to non-negligible values in flow regions such as *** is precisely in these flow regions,that the turbulent gas-kinetic scheme seems to provide more accurate predictions than conventional schemes.

关键词： Gas kinetic theory turbulence modeling compressible flow shock boundary layer interaction.

Pros and cons of liver transplantation in human immunodeficiency virus infected recipients

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World Journal of Gastroenterology 2014年第18期20卷 5353-5362页

作者： Umberto Baccarani Elda righi Gian Luigi Adani Dario Lorenzin alberto Pasqualucci Matteo Bassetti Andrea Risaliti Liver Transplant Unit Department of Medical and Biological SciencesUniversity Hospital of Udine33100 UdineItaly Division of Infectious Disease University Hospital of Udine33100 UdineItaly Department of Anaesthesiology University of Perugia33100 UdineItaly

Before the introduction of combined highly active antiretroviral therapy, a positive human immunodeficiency virus (HIV) serological status represented an absolute contraindication for solid organ transplant (SOT). The advent of highly effective combined antiretroviral therapy in 1996 largely contributed to the increased demand for SOT in HIV-positive individuals due to increased patients’ life expectancy associated with the increasing prevalence of end-stage liver disease (ESLD). Nowadays, liver failure represents a frequent cause of mortality in the HIV-infected population mainly due to coinfection with hepatitis viruses sharing the same way of transmission. Thus, liver transplantation (LT) represents a reasonable approach in HIV patients with stable infection and ESLD. Available data presently supports with good evidence the practice of LT in the HIV-positive population. Thus, the issue is no longer “whether it is correct to transplant HIV-infected patients”, but “who are the patients who can be safely transplanted” and “when is the best time to perform LT”. Indeed, the benefits of LT in HIV-infected patients, especially in terms of mid- and long-term patient and graft survivals, are strictly related to the patients’ selection and to the correct timing for transplantation, especially when hepatitis C virus coinfection is present. Aim of this article is to review the pros and cons of LT in the cohort of HIV infected recipients.

关键词： Liver transplantation Human immunodeficiency virus/hepatitis C virus coinfection Hepatocellular carcinoma Immunosuppression

Management of bacterial and fungal infections in end stage liver disease and liver transplantation: Current options and future directions

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World Journal of Gastroenterology 2018年第38期24卷 4311-4329页

作者： Elda righi Department of Infectious Diseases Santa Maria della Misericordia University Hospital

Patients with liver cirrhosis are susceptible to infections due to various mechanisms, including abnormalities of humoral and cell-mediated immunity and occurrence of bacterial translocation from the intestine. Bacterial infections are common and represent a reason for progression to liver failure and increased mortality. Fungal infections, mainly caused by Candida spp., are often associated to delayed diagnosis and high mortality rates. High level of suspicion along with prompt diagnosis and treatment of infections are warranted. Bacterial and fungal infections negatively affect the outcomes of liver transplant candidates and recipients, causing disease progression among patients on the waiting list and increasing mortality, especially in the early posttransplant period. Abdominal, biliary tract, and bloodstream infections caused by Gram-negative bacteria [e.g., Enterobacteriaceae and Pseudomonas aeruginosa(P. aeruginosa)] and Staphylococcus spp. are commonly encountered in liver transplant recipients. Due to frequent exposure to broad-spectrum antibiotics, invasive procedures, and prolonged hospitalizations, these patients are especially at risk of developing infections caused by multidrug resistant bacteria. The increase in antimicrobial resistance hampers the choice of an adequate empiric therapy and warrants the knowledge of the local microbial epidemiology and the implementation of infection control measures. The main characteristics and the management of bacterial and fungal infections in patients with liver cirrhosis and liver transplant recipients are presented.

关键词： Liver cirrhosis Liver transplant recipients Bacterial infections Fungal infections Multidrug resistant organisms Management

Extension of analytical indicial aerodynamics to generic trapezoidal wings in subsonic flow

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Chinese Journal of Aeronautics 2018年第4期31卷 617-631页

作者： Andrea DA RONCH Antonino VENTURA Marcello righi Matteo FRANCIOLINI Marco BERCI Daniel KHARLAMOV Faculty of Engineering and the Environment University of Southampton Southampton SO17 1B J UK School of Engineering Zurich University of Applied Sciences Winterthur 8401 Switzerland Dipartimento di Ingegneria Industriale e Seienze Matematiche Universita Politecnica delle Marche Ancona 1-60100 Italy School of Mechanical Engineering University of Leeds Leeds LS2 9JT UK

Analytical indicial aerodynamic functions are calculated for several trapezoidal wings in subsonic flow, with a Mach number 0.3 Ma 0.7. The formulation herein proposed extends wellknown aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to generic trapezoidal wing planforms. Firstly, a thorough study is executed to assess the accuracy and limitation of analytical predictions, using unsteady results from two state-of-the-art computational fluid dynamics solvers as cross-validated benchmarks. Indicial functions are calculated for a step change in the angle of attack and for a sharp-edge gust, each for four wing configurations and three Mach numbers. Then, analytical and computational indicial responses are used to predict dynamic derivatives and the maximum lift coefficient following an encounter with a one-minus-cosine gust. It is found that the analytical results are in excellent agreement with the computational results for all test cases. In particular, the deviation of the analytical results from the computational results is within the scatter or uncertainty in the data arising from using two computational fluid dynamics solvers. This indicates the usefulness of the developed analytical theories.

关键词： Analytical approach CFD Compressible flow Gust response Indicial aerodynamics Trapezoidal wing

High Order of Accuracy for Poisson Equation Obtained by Grouping of Repeated Richardson Extrapolation with Fourth Order Schemes

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Computer Modeling in Engineering & Sciences 2021年第8期128卷 699-715页

作者： Luciano Pereira da Silva Bruno Benato Rutyna Aline Roberta Santos righi Marcio Augusto Villela Pinto Graduate Program in Numerical Methods in Engineering Federal University of ParanaCuritiba81531-980Brazil Graduate Program in Space Sciences and Technologies Aeronautics Institute of TechnologySao Jose dos Campos12228-900Brazil Department of Mechanical Engineering Federal University of ParanaCuritiba81531-980Brazil

In this article,we improve the order of precision of the two-dimensional Poisson equation by combining extrapolation techniques with high order *** high order solutions obtained traditionally generate non-sparse matrices and the calculation time is very *** can obtain sparse matrices by applying compact *** this article,we compare compact and exponential finite difference schemes of fourth *** numerical solutions are calculated in quadruple precision(Real*16 or extended precision)in FORTRAN language,and iteratively obtained until reaching the round-off error magnitude around 1.0E−*** procedure is performed to ensure that there is no iteration *** Repeated Richardson Extrapolation(RRE)method combines numerical solutions in different grids,determining higher orders of *** main contribution of this work is based on a process that initializes with fourth order solutions combining with RRE in order to find solutions of sixth,eighth,and tenth order of *** multigrid Full Approximation Scheme(FAS)is also applied to accelerate the convergence and obtain the numerical solutions on the fine grids.

关键词： Tenth order accuracy RRE compact scheme exponential scheme multigrid finite difference

Study of the Productive Chain of Stone Facings in Contemporary Buildings in Sao Paulo, Brazil

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Journal of Civil Engineering and Architecture 2016年第11期10卷 1270-1278页

作者： Eleana Patta Flain Roberto righi Faculty of Architecture and Urbanism Mackenzie Presbyterian University Sao Paolo 01302-907 Brazil

This article presents, based on field survey and in the consulted literature, the main procedures for fixing of claddings with plates of rocks, adopted in the city of Sao Paulo for buildings and contemporary urban works. There was an increase in the quality of these claddings in the last decades due to several factors, such as the adoption of technological innovations in the extraction process of the rocky material and in the productive chain and, also, the use of most modem procedures for projects in which are incorporated new knowledge for better use of the rocky material and reduction of waste, due to greater demands of the market in the sector of omamental stones.

关键词： Stone cladding dimension stone stone veneer architecture rock.

A Case-Control Study on Leisure Time Physical Activity (LTPA) during the Last Three Months of Pregnancy and Foetal Outcomes in Italy

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Health 2016年第2期8卷 133-143页

作者： Guglielmina Fantuzzi Elena righi Gabriella Aggazzotti Department of Biomedical Metabolic and Neural Sciences University of Modena and Reggio Emilia Modena Italy

The association between Leisure Time Physical Activity (LTPA) during pregnancy and foetal outcomes has been extensively investigated. However, epidemiological studies specifically referred to LPTA in the last months of pregnancy are scarce. We evaluated the association between LPTA and the risk of both preterm delivery and small for gestational age (SGA) during the last three months of pregnancy in Italy. A nationwide case-control study was performed in nine Italian cities. A total of 299 preterm delivery, 364 SGA and 855 controls were enrolled in the study. A self-administered questionnaire was used to assess socio-demographic variables, medical and reproductive history, life-style habits and LTPA referred to the last three months of pregnancy. Univariate and multivariate regression analyses were performed in order to estimate Odds ratios and 95% CI. LTPA during the last three months of pregnancy decreases the risk of preterm delivery (adjusted OR = 0.56;95% CI 0.39 - 0.79). Among the different types of physical activity, walking, the most frequently referred activity, appears significantly protective against preterm delivery (adjusted OR = 0.53;95% CI 0.36 - 0.81). Moreover, a small protective effect of walking was evidenced against SGA (adjusted OR = 0.72;95% CI 0.51 - 1.00). In conclusion, a mild physical activity such as walking in the last three months of pregnancy seems to reduce the risk of preterm delivery and, at a lesser extent, of SGA, confirming the beneficial effects of physical activity along the whole pregnancy.

关键词： Leisure Time Physical Activity (LTPA) Preterm Delivery Small for Gestational Age Last Three Months of Pregnancy Case Control Study

Tracking of Labelled Stem Cells Using Molecular MR Imaging in a Mouse Burn Model <i>in Vivo</i>as an Approach to Regenerative Medicine

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Advances in Molecular Imaging 2021年第1期11卷 1-15页

作者： Zeba Qadri Valeria righi Shasha Li A. Aria Tzika MGH NMR Surgical Laboratory Center for Surgery Innovation and Bioengineering Department of Surgery Massachusetts General and Shriners Burn Hospitals Harvard Medical School Boston USA Athinoula A. Martinos Center of Biomedical Imaging Department of Radiology Massachusetts General Hospital Harvard Medical School Charlestown USA

Therapies based on stem cell transplants offer significant potential in the field of regenerative medicine. Monitoring the fate of the transplanted stem cells in a timely manner is considered one of the main limitations for long-standing success of stem cell transplants. Imaging methods that visualize and track stem cells in vivo non-invasively in real time are helpful towards the development of successful cell transplantation techniques. Novel molecular imaging methods which are non-invasive particularly such as MRI have been of great recent interest. Hence, mouse models which are of clinical relevance have been studied by injecting contrast agents used for labelling cells such as super-paramagnetic iron-oxide (SPIO) nanoparticles for cellular imaging. The MR techniques which can be used to generate positive contrast images have been of much relevance recently for tracking of the labelled cells. Particularly when the off-resonance region in the vicinity of the labeled cells is selectively excited while suppressing the signals from the non-labeled regions by the method of spectral dephasing. Thus, tracking of magnetically labelled cells employing positive contrast in vivo MR imaging methods in a burn mouse model in a non-invasive way has been the scope of this study. The consequences have direct implications for monitoring labeled stem cells at some stage in wound healing. We suggest that our approach can be used in clinical trials in molecular and regenerative medicine.

关键词： Burn Wounds Cell Labeling Cell Tracking Cellular Imaging Magnetic Resonance Imaging (MRI) Molecular Imaging Positive Contrast Imaging Stem Cells

Impact of new treatment options for hepatitis c virus infection in liver transplantation

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World Journal of Gastroenterology 2015年第38期21卷 10760-10775页

作者： Elda righi Angela Londero Alessia Carnelutti Umberto Baccarani Matteo Bassetti Infectious Diseases Division Santa Maria della Misericordia University Hospital Liver Transplant Unit Santa Maria della Misericordia University Hospital

Liver transplant candidates and recipients with hepatitis C virus(HCV)-related liver disease greatly benefit from an effective antiviral therapy. The achievement of a sustained virological response before transplantation can prevent the recurrence of post-transplant HCV disease that occurs universally and correlates with enhanced progression to graft cirrhosis. Previous standard-of-care regimens(e.g.,pegylated-interferon plus ribavirin with or without first generation protease inhibitors,boceprevir and telaprevir) displayed suboptimal results and poor tolerance in liver transplant recipients. A new class of potent direct-acting antiviral agents(DAA) characterized by all-oral regimens with minimal side effects has been approved and included in the recent guidelines for the treatment of liver transplant recipients with recurrent HCV disease. Association of sofosbuvir with ribavirin and/or ledipasvir is recommended in liver transplant recipients and patients with decompensated cirrhosis. Other regimens include simeprevir,daclatasvir,and combination of other DAA. Possible interactions should be monitored,especially in coinfected human immunodeficiency virus/HCV patients receiving antiretrovirals.

关键词： Hepatitis C virus Direct antiviral agents Liver tr