Effect of turbulent fluctuations on the drag and lift forces on a towed sphere and its boundary layer

The impact of turbulent fluctuations on the forces exerted by a fluid on a towed spherical particle is investigated by means of high-resolution direct numerical simulations. The measurements are carried out using a novel scheme to integrate the two-way coupling between the particle and the incompressible surrounding fluid flow maintained in a high-Reynolds-number turbulent regime. The main idea consists in combining a Fourier pseudo-spectral method for the fluid with an immersed-boundary technique to impose the no-slip boundary condition on the surface of the particle. Benchmarking of the code shows a good agreement with experimental and numerical measurements from other groups. A study of the turbulent wake downstream the sphere is also reported. The mean velocity deficit is shown to behave as the inverse of the distance from the particle, as predicted from classical similarity analysis. This law is reinterpreted in terms of the principle of "permanence of large eddies" that relates infrared asymptotic self-similarity to the law of decay of energy in homogeneous turbulence. The developed method is then used to attack the problem of an upstream flow that is in a developed turbulent regime. It is shown that the average drag force increases as a function of the turbulent intensity and the particle Reynolds number. This increase is significantly larger than predicted by standard drag correlations based on laminar upstream flows. It is found that the relevant parameter is the ratio of the viscous boundary layer thickness to the dissipation scale of the ambient turbulent flow. The drag enhancement can be motivated by the modification of the mean velocity and pressure profile around the sphere by small scale turbulent fluctuations.Comment: 24 pages, 22 figure

Palmitate Induced IL-6 and MCP-1 Expression in Human Bladder Smooth Muscle Cells Provides a Link between Diabetes and Urinary Tract Infections

Therefore we studied the effects of the free fatty acid palmitate and bacterial lipopolysaccharide (LPS) on interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1) expression and secretion in cultured human bladder smooth muscle cells (hBSMC).Biopsies were taken from patients undergoing cystectomy due to bladder cancer. Palmitate or LPS stimulated hBSMC were analysed for the production and secretion of the IL-6, gp80, gp80soluble, gp130, MCP-1, pSTAT3, SOCS3, NF-κB and SHP2 by quantitative PCR, ELISA, Western blotting, and confocal immunofluorescence. In signal transduction inhibition experiments we evaluated the involvement of NF-κB and MEK1 in IL-6 and MCP-1 regulation. Palmitate upregulates IL-6 mRNA expression and secretion via NF-κB dependent pathways in a concentration- and time-dependent manner. MCP-1 was moderately upregulated by palmitate but was strongly upregulated by LPS involving NF-κB and MEK1 dependent pathways. Soluble IL-6 receptor (gp80soluble) was downregulated by palmitate and LPS, while membrane-bound gp80 was moderately upregulated. LPS increased SOCS3 and SHP2, whereas palmitate only induced SOCS3. Secondary finding: most of the IL-6 is secreted.Bacterial infection (LPS) or metabolic alterations (palmitate) have distinct effects on IL-6 expression in hBSMC, (i) short term LPS induced autocrine JAK/STAT signaling and (ii) long-term endocrine regulation of IL-6 by palmitate. Induction of IL-6 in human bladder smooth muscle cells by fatty acids may represent a pathogenetic factor underlying the higher frequency and persistence of urinary tract infections in patients with metabolic diseases

Travelling waves in pipe flow

A family of three-dimensional travelling waves for flow through a pipe of circular cross section is identified. The travelling waves are dominated by pairs of downstream vortices and streaks. They originate in saddle-node bifurcations at Reynolds numbers as low as 1250. All states are immediately unstable. Their dynamical significance is that they provide a skeleton for the formation of a chaotic saddle that can explain the intermittent transition to turbulence and the sensitive dependence on initial conditions in this shear flow.Comment: 4 pages, 5 figure

Software Engineering for Self-Adaptive Systems: A second Research Roadmap

The goal of this roadmap paper is to summarize the state of-the-art and identify research challenges when developing, deploying and managing self-adaptive software systems. Instead of dealing with a wide range of topics associated with the field, we focus on four essential topics of self-adaptation: design space for adaptive solutions, processes, from centralized to decentralized control, and practical run-time verification and validation. For each topic, we present an overview, suggest future directions, and focus on selected challenges. This paper complements and extends a previous roadmap on software engineering for self-adaptive systems published in 2009 covering a different set of topics, and reflecting in part on the previous paper. This roadmap is one of the many results of the Dagstuhl Seminar 10431 on Software Engineering for Self-Adaptive Systems, which took place in October 2010

Die Idee eines wissenschaftlichen Experiments für die OE nutzen : Ein Bericht zum Entwicklungsdialog Experimentelle Organisationsentwicklung

«Wir möchten in unserem Führungsteam agiler und selbstorganisierter zusammenarbeiten. Aber was, wenn das alles nicht klappt? Oder wenn das eigentlich doch keine*r will?» So ein Bereichsleiter, mit dem wir über neue Arbeitswelten sprachen. Nachdem wir den Veränderungsprozess als zeitlich begrenztes Experiment eingeführt hatten, schwanden die Bedenken spürbar. Wissenschaftliche Experimente sind zentral für unseren gesellschaftlichen und technologischen Fortschritt. Sie ermöglichen es, durch einen gezielten Versuchsaufbau (das eigentliche Experiment) Hypothesen zu überprüfen und damit neues Wissen hervorzubringen. Aber kann man diese mächtige Methode der Wissenschaft auch für die Organisationsentwicklung nutzbar machen und wenn ja, wie? Die zunehmende Verbreitung von allerlei «Labs», Reallaboren und Experimentierräumen in Organisationen und Gesellschaft legen das nahe. Inzwischen blickt das Forschungsteam der ESB Business School auf eine mehrjährige Erfahrung mit der Experimentellen Organisationsentwicklung zurück. Unter anderem in Kooperation mit dem Fraunhofer IAO sowie der Hochschule Harz wurden mehrere Experimentierräume in Organisationen begleitet und evaluiert. Dabei entstand ein ausgefeiltes Interventionsdesign. Denn auch wenn Experimente allgegenwärtig und einfach umsetzbar scheinen, brauchte es in der praktischen Umsetzung unserer Erfahrung nach ein differenziertes Vorgehensmodell, um etliche Fallstricke zu umgehen

Palmitate induced IL-6 and MCP-1 expression in human bladder smooth muscle cells provides a link between diabetes and urinary tract infections. PLoS One 5: e10882

Background: Urinary tract infections (UTI) are more frequent in type-2 diabetes mellitus patients than in subjects with normal glucose metabolism. The mechanisms underlying this higher prevalence of UTI are unknown. However, cytokine levels are altered in diabetic patients and may thus contribute to the development of UTI. Increased levels of free fatty acids (FFA), as observed in obese patients, can induce IL-6 production in various cell types. Therefore we studied the effects of the free fatty acid palmitate and bacterial lipopolysaccharide (LPS) on interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1) expression and secretion in cultured human bladder smooth muscle cells (hBSMC). Methodology/Principal Findings: Biopsies were taken from patients undergoing cystectomy due to bladder cancer. Palmitate or LPS stimulated hBSMC were analysed for the production and secretion of the IL-6, gp80, gp80soluble, gp130, MCP-1, pSTAT3, SOCS3, NF-kB and SHP2 by quantitative PCR, ELISA, Western blotting, and confocal immunofluorescence. In signal transduction inhibition experiments we evaluated the involvement of NF-kB and MEK1 in IL-6 and MCP-1 regulation. Palmitate upregulates IL-6 mRNA expression and secretion via NF-kB dependent pathways in a concentration- and timedependent manner. MCP-1 was moderately upregulated by palmitate but was strongly upregulated by LPS involving NF-kB and MEK1 dependent pathways. Soluble IL-6 receptor (gp80soluble) was downregulated by palmitate and LPS, while membrane-bound gp80 was moderately upregulated. LPS increased SOCS3 and SHP2, whereas palmitate only induce

The stoichiometry of the chloroplast ATP synthase oligomer III in Chlamydomonas reinhardtii is not affected by the metabolic state

AbstractThe chloroplast H+-ATP synthase is a key component for the energy supply of higher plants and green algae. An oligomer of identical protein subunits III is responsible for the conversion of an electrochemical proton gradient into rotational motion. It is highly controversial if the oligomer III stoichiometry is affected by the metabolic state of any organism. Here, the intact oligomer III of the ATP synthase from Chlamydomonas reinhardtii has been isolated for the first time. Due to the importance of the subunit III stoichiometry for energy conversion, a gradient gel system was established to distinguish oligomers with different stoichiometries. With this methodology, a possible alterability of the stoichiometry in respect to the metabolic state of the cells was examined. Several growth parameters, i.e., light intensity, pH value, carbon source, and CO2 concentration, were varied to determine their effects on the stoichiometry. Contrary to previous suggestions for E. coli, the oligomer III of the chloroplast H+-ATP synthase always consists of a constant number of monomers over a wide range of metabolic states. Furthermore, mass spectrometry indicates that subunit III from C. reinhardtii is not modified posttranslationally. Data suggest a subunit III stoichiometry of the algae ATP synthase divergent from higher plants