Protective and Aggravating Effects of Nlrp3 Inflammasome Activation in IBD Models: Influence of Genetic and Environmental Factors

Background: Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation due to dysregulation of the mucosal immune system. The cytokines IL-1 beta and IL-18 appear early in intestinal inflammation and their pro-forms are processed via the caspase-1-activating multiprotein complex, the Nlrp3 inflammasome. Previously, we reported that the uptake of dextran sodium sulfate (DSS) by macrophages activates the Nlrp3 inflammasome and that Nlrp3(-/-) mice are protected in the acute DSS colitis model. Of note, other groups have reported opposing effects in regards to DSS susceptibility in Nlrp3(-/-) mice. Recently, mice lacking inflammasomes were found to develop a distinct intestinal microflora. Methods: To reconcile the contradicting observations, we investigated the role of Nlrp3 deficiency in two different IBD models: acute DSS colitis and TNBS (2,4,6-trinitrobenzene sulfonic acid)-induced colitis. In addition, we in-vestigated the impact of the intestinal flora on disease severity by performing cohousing experiments of wild-type and Nlrp3(-/-) mice, as well as by antibiotic treatment. Results: Nlrp3(-/-) mice treated with either DSS or TNBS exhibited attenuated colitis and lower mortality. This protective effect correlated with an increased frequency of CD103+ lamina propria dendritic cells expressing a tolerogenic phenotype in Nlrp3(-/-) mice in steady state conditions. Interestingly, after cohousing, Nlrp3(-/-) mice were as susceptible as wild-type mice, indicating that transmission of endogenous bacterial flora between the two mouse strains might increase susceptibility of Nlrp3(-/-) mice towards DSS-induced colitis. Accordingly, treatment with antibiotics almost completely prevented colitis in the DSS model. Conclusions: The composition of the intestinal microflora significantly influences disease severity in IBD models comparing wild-type and Nlrp3(-/-) mice. This observation may - at least in part - explain contradictory results concerning the role of the inflammasome in different labs. Further studies are required to define the role of the Nlrp3 inflammasome in noninflamed mucosa under steady state conditions and in IBD. Copyright (C) 2012 S. Karger AG, Base

Simplify Reporting through Spatial Data Infrastructures -the Example of the German Marine Data Infrastructure

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Similarity solutions of a Blasius flow with variable fluid properties and viscous dissipation

An analytical model of the Blasius flow is studied including temperature-dependent fluid properties and viscous dissipation. The friction coefficient and Nusselt number at the wall are calculated from the resulting dimensionless velocity and temperature fields. The variable properties model is compared to a constant properties model to verify if and under which conditions this simplification is valid. Air, water and oil are analyzed as fluids over a representative operating regime, respectively. For air, the variable properties do not influence the friction coefficient and the Nusselt number. For water, the influence of the variable properties is present for both parameters but limited since no large temperature difference can occur in water without a phase change. New correlations for the friction coefficient and Nusselt number were derived for water and oil over a large range of operating conditions. Viscous dissipation does not significantly affect these parameters for air and water because of their relatively low Prandtl numbers. The high Prandtl number of oil in combination with a viscosity that is strongly decreasing with increasing temperature, leads to a more complex behavior. The friction coefficient as well as the Nusselt number are strongly dependent on the fluid properties. Dissipation effects cannot be neglected above an Eckert number of around 0.01. The superposition principle to evaluate wall heat flux in experiments is based on the assumption of constant fluid properties. It can be used without restrictions for air but should be thoroughly checked for all other fluids, especially liquids, using the presented methodology

Microscopic Imaging Spray Diagnostics under High Temperature Conditions: Application to Urea–Water Sprays

The quantitative investigation of droplet laden turbulent flows at high temperature conditions is of great importance for numerous applications. In this study, an experiment was set up for investigation of evaporating urea-water sprays, which are relevant for the effective reduction of nitrogen oxide emissions of diesel engines using Selective Catalytic Reduction. A shadowgraphy setup is pushed to its limits in order to detect droplet diameters as small as 4µm and droplet velocities up to 250m/s. In addition, the operating conditions of the gaseous flow of up to 873K and 0.6MPa are an additional challenge. Due to the high temperature environment, image quality is prone to be compromised by schlieren effects and astigmatism phenomena. A water-cooled window and an astigmatism correction device are installed in order to correct these problems. The results to be presented include characteristics of the turbulent gas flow as well as detailed spray characteristics at different positions downstream of the atomizer. It is demonstrated that the velocity of the gas can be approximated by the velocity of the smallest detectable droplets with sufficient accuracy. Furthermore, the statistical analysis of velocity fluctuations provides data for predicting the turbulent dispersion of the droplets

mCommerce in der Tourismusindustrie : Potenziale, Risiken und rechtliche Rahmenbedingungen

Vor dem Hintergrund der sich dramatisch verschlechternden weltpolitischen Lage, ständiger Sicherheitsgefahr durch extremistische Kräfte und zunehmender Radikalisierung der Konfliktlösung in der Welt, verschlechtern sich seit dem 11. September 2001 kontinuierlich auch die Aussichten der Reisebranche. Wie kann aber Abhilfe aussehen? Es ist denkbar, dass neben der zunehmenden Vermarktung des Urlaubs in Deutschland zusätzliche Einnahmequellen erschlossen werden können. Eine solche Quelle ist in mCommerce verbunden mit dem rasant wachsenden Mobilfunkmarkt, der Einführung neuer Datenübertragungstechnologien und der Einbindung des Internets in die mobile Kommunikationswelt zu sehen. Vor diesem Hintergrund werden in der vorliegenden Studie die Potenziale von mCommerce für den Tourismus im deutschen Quellmarkt analysiert. Die Studie gliedert sich in drei Bereiche: Im Rahmen der Studie werden Erfolgsfaktoren und Hemmnisse des mCommerce in der Tourismusbranche ermittelt, sowie Perspektiven und Trends aufgezeigt. Eine weitere Zielsetzung der Studie ist die Darstellung rechtlicher Rahmenbedingungen für mCommerce. Schließlich wird anhand einer praktischen Fallstudie demonstriert, wohin sich Trends entwickeln und wo sie bereits präsent sind

Experimental investigation of the oil jet heat transfer on meshing spur gears

Designing an adequate cooling system for a high-speed high-power gearbox of a geared turbofan requires a thorough understanding of the cooling capabilities of the utilized oil jet impingement. An experimental setup is employed to determine the heat transfer coefficient on gear teeth in various non-meshing and meshing configurations, which incorporate inclined jets with varying distances between the impingement and the meshing zones. The direction of heat transfer is inverted in the experiments to allow for a feasible setup with the rotating gears, where impinging oil jets heat the hollow instrumented gear as its inner surface is cooled via air jet impingement. Measurements with varying oil volume flow rates and rotational speeds are carried out. The losses are analyzed to enable an isolated investigation of the heat transfer between the oil and the gear via measured temperatures on the gear teeth. Heat transfer coefficients are compared at the lower rotational speed with relatively small meshing losses. The meshing in the experimental setup does not have a significant influence on the mean heat transfer coefficient. The spatial distribution of the heat transfer coefficient is slightly affected by the meshing teeth as the distribution gets more uniform with decreasing distance between the impingement and meshing zones

Experimental Investigation of the Oil Jet Heat Transfer for an Aero Engine Gearbox

Geared turbofan engines have the potential to propel future civil aircraft engines more efficiently. A planetary gearbox between the low-pressure turbine and the fan enables the operation of both components at their respective optimum rotational speeds. This makes it possible to achieve higher bypass ratios and thus a better propulsion efficiency. A crucial part of the planetary gearbox design is the cooling and lubrication of the gears. Sufficient heat removal from the gear tooth flanks is necessary to ensure reliable operation without the risk of gear failure through pitting or scoring. Fast rotating and highly loaded gears are cooled with impinging oil jets according to current design guidelines. This impingement cooling process comprises a complex, multi-phase flow with heat transfer. Previous experimental, numerical and analytical investigations have shown that the cooling process depends both on the highly unsteady liquid flow dynamics and on the heat conduction in the oil film formed on the gear tooth flank. In this study, the gear is replaced by a cylinder in order to be able to study the impingement cooling on a rotating surface without the influence of unsteady flow phenomena. A hollow cylinder is instrumented with 42 thermocouples across the surface, which are all connected to a telemetry system. A single oil jet is directed radially onto the outer cylinder surface. The measured temperatures are subsequently corrected using a new algorithm to reduce systematic measurement errors without distorting the data. The corrected temperatures are used to calculate the Nusselt number distribution across the cylinder surface by means of a finite element analysis. A parameter study is performed to identify the influence of the parameters oil flow rate, oil viscosity and rotational speed of the cylinder on the heat transfer. The fundamental results of the present study enable a better understanding of the heat transfer on impingement cooled cylinders and spur gears

CFD study of oil-jet gear interaction flow phenomena in spur gears

Oil-jet lubrication and cooling of high-speed gears is frequently employed in aeronautical systems, such as novel high-bypass civil aero engines based on the geared turbofan technology. Using such oil-jet system, practitioners aim to achieve high cooling rates on the flanks of the highly thermally loaded gears with minimum oil usage. Thus, for an optimal design, detailed knowledge about the flow processes is desired. These involve the oil exiting the nozzle, the oil impacting on the gear teeth, the oil spreading on the flanks, the subsequent oil fling-off, as well as the effect of the design parameters on the oil flow. Better understanding of these processes will improve the nozzle design phase, e.g. regarding the nozzle positioning and orientation, as well as the nozzle sizing and operation. Most related studies focus on the impingement depth to characterize the two-phase flow. However, the level of information of this scalar value is rather low for a complete description of the highly dynamic three-dimensional flow. Motivated by the advancements in numerical methods and the computational resources available nowadays, the investigation of the oil-jet gear interaction by means of computational fluid dynamics (CFD) has come into focus lately. In this work, a numerical setup based on the volume-of-fluid method is presented and employed to investigate the two-phase flow phenomena occurring in the vicinity of the gear teeth. The setup consists of a single oil-jet impinging on a single rotating spur gear. By introducing new metrics for characterizing the flow phenomena, extensive use of the possibilities of modern CFD is made, allowing a detailed transient and spatially resolved flow analysis. Thus, not only the impingement depth, but also the temporal and spatial evolution of wetted areas on the gear flanks, as well as the evolution of the oil volume in contact with the gear flanks are extracted from the simulation data and compared in a CFD study. The study consists of 21 different simulation cases, whereby the effect of varying the jet velocity, the jet inclination angle, the jet diameter, and the gear speed are examined. Consistent results compared to a simplified analytical approach for the impinging depth are obtained and the results for the newly introduced metrics are presented