Flow establishment in a generic scramjet combustor

The establishment of a quasi-steady flow in a generic scramjet combustor was studied for the case of a time varying inflow to the combustor. Such transient flow is characteristic of the reflected shock tunnel and expansion tube test facilities. Several numerical simulations of hypervelocity flow through a straight duct combustor with either a side wall step fuel injector or a centrally located strut injector are presented. Comparisons were made between impulsively started but otherwise constant flow conditions (typical of the expansion tube or tailored operations of the reflected shock tunnel) and the relaxing flow produced by the 'undertailored' operations of the reflected shock tunnel. Generally the inviscid flow features, such as the shock pattern and pressure distribution, were unaffected by the time varying inlet conditions and approached steady state in approx. the times indicated by experimental correlations. However, viscous features, such as heat transfer and skin friction, were altered by the relaxing inlet flow conditions

Stress distribution during cold compression of a quartz aggregate using synchrotron X-ray diffraction: Observed yielding, damage, and grain crushing

We report new experimental results that quantify the stress distribution within a quartz aggregate during pore collapse and grain crushing. The samples were probed with synchrotron X-ray diffraction as they were compressed in a multianvil deformation apparatus at room temperature from low pressure (tens of megapascal) to pressures of a few gigapascal. In such a material, stress is likely to concentrate at grain-to-grain contacts and vanish where grains are bounded by open porosity. Therefore, internal stress is likely to vary significantly from point to point in such an aggregate, and hence, it is important to understand both the heterogeneity and anisotropy of such variation with respect to the externally applied stress. In our quartz aggregate (grain size of ~4 μm), the measured diffraction peaks broaden asymmetrically at low pressure (tens of megapascal), suggesting that open pores are still a dominant characteristic of grain boundaries. In contrast, a reference sample of novaculite (a highly dense quartz polycrystal, grain size of ~6–9 μm) showed virtually no peak broadening with increasing pressure. In the quartz aggregate, we observed significant deviation in the pressure-volume curves in the range of P = 400–600 MPa. We suggest that this marks the onset of grain crushing (generally denoted as P* in the rock mechanic literature), which is commonly reported to occur in sandstones at pressures of this order, in general agreement with a Hertzian analysis of fracturing at grain contacts

A comprehensive set of simulations studying the influence of gas expulsion on star cluster evolution

We have carried out a large set of N-body simulations studying the effect of residual-gas expulsion on the survival rate and final properties of star clusters. We have varied the star formation efficiency, gas expulsion timescale and strength of the external tidal field, obtaining a three-dimensional grid of models which can be used to predict the evolution of individual star clusters or whole star cluster systems by interpolating between our runs. The complete data of these simulations is made available on the Internet. Our simulations show that cluster sizes, bound mass fraction and velocity profile are strongly influenced by the details of the gas expulsion. Although star clusters can survive star formation efficiencies as low as 10% if the tidal field is weak and the gas is removed only slowly, our simulations indicate that most star clusters are destroyed or suffer dramatic loss of stars during the gas removal phase. Surviving clusters have typically expanded by a factor 3 or 4 due to gas removal, implying that star clusters formed more concentrated than as we see them today. Maximum expansion factors seen in our runs are around 10. If gas is removed on timescales smaller than the initial crossing time, star clusters acquire strongly radially anisotropic velocity dispersions outside their half-mass radii. Observed velocity profiles of star clusters can therefore be used as a constraint on the physics of cluster formation.Comment: 12 pages, 9 figures, MNRAS accepte

Arbeit und Ökologie: Ein neues Forschungsprogramm

Die Gewerkschaften haben im DGB-Grundsatzprogramm von 1996 die Gestaltung einer nachhaltigen Entwicklung zu einer wichtigen Aufgabe erklärt. lhre Suche nach einer sozial-ökologischen Reformstrategie steht unter der Prämisse, daß ökonomische, ökologische und soziale Nachhaltigkeitsziele gleichwertig verfolgt werden müssen, wobei erhebliche Defizite bei der Berücksichtigung der sozialen Dimension von Nachhaltigkeitskonzepten konstatiert werden. Vor diesem Hintergrund haben sich die drei Forschungsinstitute DIW, WI und WZB mit ihren jeweils spezifischen fachlichen Kompetenzbereichen zum Forschungsprojektverbund "Arbeit und Ökologie" zusammengetan. Dessen Hauptziel ist es, soziale und arbeitspolitische Aspekte in ihrer Wechselwirkung mit zentralen Elementen von unterschiedlich akzentuierten Nachhaltigkeitskonzepten zu untersuchen. Damit soll die Diskussion in Deutschland mit neuen Aspekten belebt und den Gewerkschaften eine fundierte Grundlage für ihren Strategiebildungsprozeß geboten werden. Dabei wird sich das Forschungsprojekt auf drei Leitfragestellungen konzentrieren: (1) das Verhältnis zwischen den sozialen Implikationen von Nachhaltigkeitsstrategien und gewerkschaftlichen Zielen, (2) die Bausteine einer sozial-ökologischen Reformstrategie und (3) die Rolle der deutschen Gewerkschaften in einem gesellschaftlichen Nachhaltigkeitsdiskurs. Das Projekt ist in die folgenden drei, zeitlich gestaffelten Phasen gegliedert: Querschnittsanalysen: Sie dienen der Erfassung und Klärung der vielfaltigen Wechselbeziehungen zwischen Nachhaltigkeit und Arbeit, die sich aus ökonomischer, sozialer und ökologischer Sicht ergeben. Hierbei wird es auf der Makroebene etwa um Fragen von Wirtschaftswachstum, Beschäftigungsentwicklung, sozialer Sicherheit und Ressourcenverbrauch gehen; auf der Mikroebene werden neue Arbeitsverhältnisse und Arbeitszeiten, das Verhältnis von formeller und informeller Arbeit, sowie sozialökologische Innovationspotentiale untersucht. Die Analyseergebnisse sollen Grundlagen für die Beurteilung von Szenarien schaffen und die Formulierung von Strategien unterstützen. Szenarioanalysen: Um dem Spektrum verschiedener Positionen in der Nachhaltigkeitsdiskussion gerecht zu werden, sollen zwei unterschiedliche Nachhaltigkeitsszenarien entwickelt und analysiert werden. Das sogenannte ökonomisch- soziale Szenario geht von der ökonomischen Kritik an der vorherrschenden Wirtschaftspolitik aus, während das sogenannte ökologisch-soziale Szenario auf der ökologischen Kritik vorherrschender umweltrelevanter Politikmuster basiert. Als Hintergrundfolie für die Beurteilung dieser beiden Nachhaltigkeitsszenarien dient ein sog. angebots orientiertes Kontrastszenario, das auf einer Fortschreibung bisher dominierender wirtschaftspolitischer Konzepte beruht. Erarbeitung von Strategieelementen: Die Bewertung der Szenarien nach (aus den Querschnittsanalysen gewonnenen) ökonomischen, ökologischen und sozialen Kriterien soll Zielkonflikte und - Synergien aufdecken und damit der Strategieformulierung dienen. Diese können - gemeinsam mit weiteren Strategieelementen, die aus der Analyse von Konfliktpotentialen und aus den Querschnittsanalysen gewonnen wurden - einen Beitrag für die Entwicklung einer gewerkschaftlichen sozial-ökologischen Reformstrategie liefern. -- In its Basic Programme published in 1996, the German trade union movement declared the shaping of a sustainable development to be an important task. The trade unions seek to pursue a social-ecological reform strategy that takes account of the need to strike a balance between economic, ecological and social sustainability objectives, while serious deficits in the consideration of social dimension of concepts of sustainable are being stated. Against this background, three research institutions (DIW, WI and WZB) with their complementary specialist qualifications and know-how in the relevant disciplines have joined to the Research Network Project "Work and Ecology". Their major objective is to analyse social and labour-related aspects in correlation with central elements of various sustainable development concepts in different perspectives. This aims at stimulating the German discussion with new arguments and establishing a solid base for strategybuilding-process ofthe trade unions. The research project will concentrate on three guiding questions: (I) The relationship between the social implications of sustainability strategies and trade union goals; (2) possible building blocks in a social-ecological reform strategy and (3) the role of German trade unions in a social discourse on sustainability. The project is planned to be accomplished in three main broadly successive working phases: Cross-sectional analyses: The aim of the cross-sectional analyses is to determine and specify the various linkages and interrelationships between sustainability and work seen from an economic, social and ecological perspective. This implies e. g. focussing on questions such as economic growth, the development of employment, social security and resource use on a macro-Ievel, and questions of new labour relations and working time, the relation between formal and informal work and social-ecologial innovation potentials on a micro-Ievel. The cross-sectional analyses are both to provide a basis for drawing up and evaluating the scenarios and to generate findings that can help directly in formulating social-ecological strategy elements. Scenario analyses: In order to take account of the spectrum of positions held in the debate on sustainable development concepts, the research project is to develop and analyse an economic-social and an ecological-social sustainability scenario. The so-called economic-social sustainable development scenario takes up the economic critique of the predominant one-sided orientation of economic policy to the supply side, while the socalled ecological-social sustainable development scenario is based on the critique of the prevailing policy approach regarding the environment. A supply-side scenario based on an extrapolation of the supply-side economic policy concepts, that have been predominant in German politics, will serve as the background evaluationpattern for the two sustainabilty scenarios.

Gauged N=4 supergravities

We present the gauged N=4 (half-maximal) supergravities in four and five spacetime dimensions coupled to an arbitrary number of vector multiplets. The gaugings are parameterized by a set of appropriately constrained constant tensors, which transform covariantly under the global symmetry groups SL(2) x SO(6,n) and SO(1,1) x SO(5,n), respectively. In terms of these tensors the universal Lagrangian and the Killing Spinor equations are given. The known gaugings, in particular those originating from flux compactifications, are incorporated in the formulation, but also new classes of gaugings are found. Finally, we present the embedding chain of the five dimensional into the four dimensional into the three dimensional gaugings, thereby showing how the deformation parameters organize under the respectively larger duality groups.Comment: 36 pages, v2: references added, comments added, v3: published version, references added, typos corrected, v4: sign mistakes in footnote 4 and equation (2.13) correcte

Complications After Systematic, Random and Image-guided Prostate Biopsy

CONTEXT: Prostate biopsy (PB) represents the gold standard method to confirm the presence of cancer. In addition to traditional random or systematic approaches, a magnetic resonance imaging (MRI)-guided technique has been introduced recently. OBJECTIVE: To perform a systematic review of complications after transrectal ultrasound (TRUS)-guided, transperineal, and MRI-guided PB. EVIDENCE ACQUISITION: We performed a systematic literature search of Web of Science, Embase, and Scopus databases up to October 2015, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Complications and mortality following random, systematic, and image-guided PBs were reviewed. Eighty-five references were included. EVIDENCE SYNTHESIS: The most frequent complication after PB was minor and self-limiting bleeding (hematuria and hematospermia), regardless of the biopsy approach. Occurrence of rectal bleeding was comparable for traditional TRUS-guided and image-guided PBs. Almost 25% of patients experienced lower urinary tract symptoms, but only a few had urinary retention, with higher rates after a transperineal approach. Temporary erectile dysfunction was not negligible, with a return to baseline after 1-6 mo. The incidence of infective complications is increasing, with higher rates among men with medical comorbidities and older age. Transperineal and in-bore MRI-targeted biopsy may reduce the risk of severe infectious complications. Mortality after PB is uncommon, regardless of biopsy technique. CONCLUSIONS: Complications after PB are frequent but often self-limiting. The incidence of hospitalization due to severe infections is continuously increasing. The patient's general health status, risk factors, and likelihood of antimicrobial resistance should be carefully appraised before scheduling a PB. PATIENT SUMMARY: We reviewed the variety and incidence of complications after prostate biopsy. Even if frequent, complications seldom represent a problem for the patient. The most troublesome complications are infections. To minimize this risk, the patient's medical condition should be carefully evaluated before biopsy