Effect of intimal flap motion on flow in acute type B aortic dissection by using fluid-structure interaction.

A monolithic, fully coupled fluid-structure interaction (FSI) computational framework was developed to account for dissection flap motion in acute type B aortic dissection (TBAD). Analysis of results included wall deformation, pressure, flow, wall shear stress (WSS), von. Mises stress and comparison of hemodynamics between rigid wall and FSI models. Our FSI model mimicked realistic wall deformation that resulted in maximum compression of the distal true lumen (TL) by 21.4%. The substantial movement of intimal flap mostly affected flow conditions in the false lumen (FL). Flap motion facilitated more flow entering the FL at peak systole, with the TL to FL flow split changing from 88:12 in the rigid model to 83:17 in the FSI model. There was more disturbed flow in the FL during systole (5.8% FSI vs. 5.2% rigid) and diastole (13.5% FSI vs. 9.8% rigid), via a λ2  -criterion. The flap-induced disturbed flow near the tears in the FSI model caused an increase of local WSS by up to 70.0% during diastole. This resulted in a significant reduction in the size of low time-averaged WSS (TAWSS) regions in the FL (113.11 cm2 FSI vs. 177.44 cm2 rigid). Moreover, the FSI model predicted lower systolic pressure, higher diastolic pressure, and hence lower pulse pressure. Our results provided new insights into the possible impact of flap motion on flow in aortic dissections, which are particularly important when evaluating hemodynamics of acute TBAD. This article is protected by copyright. All rights reserved

The flow structure in the wake of a fractal fence and the absence of an "inertial regime"

Recent theoretical work has highlighted the importance of multi-scale forcing of the flow for altering the nature of turbulence energy transfer and dissipation. In particular, fractal types of forcing have been studied. This is potentially of real significance in environmental fluid mechanics where multi-scale forcing is perhaps more common than the excitation of a specific mode. In this paper we report the first results studying the detail of the wake structure behind fences in a boundary layer where, for a constant porosity, we vary the average spacing of the struts and also introduce fractal fences. As expected, to first order, and in the far-wake region, in particular, the response of the fences is governed by their porosity. However, we show that there are some significant differences in the detail of the turbulent structure between the fractal and non-fractal fences and that these override differences in porosity. In the near wake, the structure of the fence dominates porosity effects and a modified wake interaction length seems to have potential for collapsing the data. With regards to the intermittency of the velocities, the fractal fences behave more similarly to homogeneous, isotropic turbulence. In addition, there is a high amount of dissipation for the fractal fences over scales that, based on the energy spectrum, should be dominated by inter-scale transfers. This latter result is consistent with numerical simulations of flow forced at multiple scales and shows that what appears to be an “inertial regime” cannot be as production and dissipation are both high

Recidiva da ingesta alcoólica em pacientes candidatos a transplante hepático: análise de fatores de risco Relapse of alcohol consumption in liver transplant candidates: risk factor analysis

RACIONAL: A recidiva do consumo do álcool após transplante representa grande preocupação nos centros transplantadores e é objeto de debate e controvérsia. OBJETIVO: Avaliar a recidiva da ingesta alcoólica e eventuais fatores a ela relacionados, em pacientes cirróticos, referidos para transplante hepático. MÉTODOS: Estudo retrospectivo de julho de 1995 a setembro de 2005 incluindo 90 pacientes adultos com cirrose hepática, listados para transplante. Os critérios de exclusão eram: ausência de 6 meses de abstinência, não liberação da equipe de psicologia. O diagnóstico da recidiva (ingesta de qualquer quantidade de bebida alcoólica) era feito com base nas informações contidas nos prontuários e fornecidas por contato telefônico. RESULTADOS: A recidiva encontrada foi de 18,9%, que correspondeu a 14,6% do número total de homens e 62,5% do número total das mulheres. A raça, média das idades, classificação de disfunção hepática, tempo de etilismo, quantidade da ingesta alcoólica e realização ou não de transplante, não mostraram correlação significativa com a recidiva da ingesta alcoólica. A comparação tempo de abstinência e recidiva guardou relação inversamente proporcional. CONCLUSÃO: A recidiva da ingesta alcoólica é baixa. Sexo feminino e tempo de abstinência inferior a 1 ano têm influência sobre a recidiva da ingesta alcoólica.<br>BACKGROUND: Alcohol relapse after transplantation is a serious concern in transplant centers and is a subject of controversy and debate. AIM: To evaluate the relapse of alcohol ingestion and the eventual associated factors in cirrhotic patients referred for liver transplantation. METHODS: A retrospective study comprised of 90 adult patients with liver cirrhosis, listed for transplant. The exclusion criteria were: not having at least 6 months of abstinence and release not approved by the psychology team. The diagnosis of relapse (ingestion of any quantity of alcohol) was done based on the information in the patients’ histories and those provided by telephone contact. RESULTS: The rate of relapse was of 18.9%. This corresponded to 14.6% of the total number of men and 62.5% of the total number of women. Race, mean age, classification of hepatic dysfunction, time of alcoholism, quantity of alcohol ingested and the execution of transplant did not show significant correlation to alcohol relapse. The comparison between time of abstinence and relapse had an inversely proportional correlation. CONCLUSION: Relapse of alcohol consumption was low. Being of the female gender and having less than 1 year of abstinence has an influence upon alcohol relapse

Toll-like receptor triggered dendritic cell maturation and IL-12 secretion are necessary to overcome T-cell inhibition by glioma-associated TGF-beta2.

Contains fulltext : 52663.pdf (publisher's version ) (Closed access)Malignant gliomas are able to secrete large amounts of immunosuppressive cytokines like transforming growth factor beta 2 (TGF-beta2) and regularly escape from immune surveillance. Many strategies have been developed to induce potent anti-glioma responses, among those the use of dendritic cells (DC) as therapeutic vaccines. Here, we report that both mature DC and IL-12 secretion are necessary to overcome T-cell inhibition by TGF-beta2. Flow cytometric analyses showed that TGF-beta2 does not suppress the upregulation of MHC (major histocompatibility complex) class II molecules and the T cell stimulatory capacity of human DC that were stimulated with a strong cytokine cocktail containing tumor necrosis factor alpha (TNF-alpha), IL-1beta, IL-6 and prostaglandin E2 (PGE2). Moreover, TGF-beta2 signaling studies revealed that these cytokine-matured DC become unresponsive to TGF-beta2. Although both mature and immature DC expressed comparable amounts of the TGF-beta receptor type II, Smad2 phosphorylation and subsequent upregulation of Smad7 was inhibited in mature DC, but not immature DC. However, further analysis revealed that mature DC alone are not sufficient to mediate full T cell activation in the presence of TGF-beta2, unless IL-12 is added to the DC/T-cell coculture. Finally, we demonstrate that MHC class II expression and IL-12 secretion by DC are not disturbed by TGF-beta2 after DC stimulation with a modified maturation cocktail containing the Toll-like receptor (TLR)-ligands Poly I:C or R848, TNF-alpha, IL-1beta and INF-gamma. These data imply that mature DC retaining their capacity to produce IL-12 are of favorable use in glioma immunotherapy and suggest that TLR triggering of DC plays an important role to elicit a strong immune response in the immunosuppressive environment of malignant gliomas