Nonlinear closures for scale separation in supersonic magnetohydrodynamic turbulence

Turbulence in compressible plasma plays a key role in many areas of astrophysics and engineering. The extreme plasma parameters in these environments, e.g. high Reynolds numbers, supersonic and super-Alfvenic flows, however, make direct numerical simulations computationally intractable even for the simplest treatment -- magnetohydrodynamics (MHD). To overcome this problem one can use subgrid-scale (SGS) closures -- models for the influence of unresolved, subgrid-scales on the resolved ones. In this work we propose and validate a set of constant coefficient closures for the resolved, compressible, ideal MHD equations. The subgrid-scale energies are modeled by Smagorinsky-like equilibrium closures. The turbulent stresses and the electromotive force (EMF) are described by expressions that are nonlinear in terms of large scale velocity and magnetic field gradients. To verify the closures we conduct a priori tests over 137 simulation snapshots from two different codes with varying ratios of thermal to magnetic pressure ($\beta_\mathrm{p} = 0.25, 1, 2.5, 5, 25$) and sonic Mach numbers ($M_s = 2, 2.5, 4$). Furthermore, we make a comparison to traditional, phenomenological eddy-viscosity and $\alpha-\beta-\gamma$ closures. We find only mediocre performance of the kinetic eddy-viscosity and $\alpha-\beta-\gamma$ closures, and that the magnetic eddy-viscosity closure is poorly correlated with the simulation data. Moreover, three of five coefficients of the traditional closures exhibit a significant spread in values. In contrast, our new closures demonstrate consistently high correlation and constant coefficient values over time and and over the wide range of parameters tested. Important aspects in compressible MHD turbulence such as the bi-directional energy cascade, turbulent magnetic pressure and proper alignment of the EMF are well described by our new closures.Comment: 15 pages, 6 figures; to be published in New Journal of Physic

A study on the relationship between upstream and downstream conditions in swirling two-phase flow

Inline fluid separation is a concept, which is used in the oil and gas industry. Inline fluid separators typically have a static design and hence changing inlet conditions lead to less efficient phase separation. For introducing flow control into such a device, additional information is needed about the relationship of upstream and downstream conditions. This paper introduces a study on this relationship for gas/liquid two-phase flow. The downstream gas core development was analyzed for horizontal device installation in dependence of the inlet gas and liquid flow rates. A wire-mesh sensor was used for determining two-phase flow parameters upstream and a high-speed video camera to obtain core parameters downstream the swirling device. For higher accuracy of the calculated void fraction, a novel method for wire-mesh sensor data analysis has been implemented. Experimental results have shown that void fraction data of the wire-mesh sensor can be used to predict the downstream behavior for a majority of the investigated cases. Additionally, the upstream flow pattern has an impact on the stability of the gas core downstream which was determined by means of experimental data analysis

Game laboratory studies

Prof. Dr. Jens Schröter ist Herausgeber der Reihe und die Herausgeber der einzelnen Hefte sind renommierte Wissenschaftler und -innen aus dem In- und Ausland.Um die Analyse von Computerspielen aus produktionsästhetischer Perspektive zu erproben, lehnt sich der vorliegende Band an die Akteur-Netzwerk-Theorie (ANT) an. Mit ihr geht es ihm um die Frage nach den Aktanten des Game Design – etwa: Welche Hard- und Softwarekomponenten kommen wann und wofür zum Einsatz; wie und mittels welcher Medien notieren Level-Designer ihre Ideen, und wie werden die Aufzeichnungen später von Programmierern implementiert; und welche Rolle spielt eigentlich eine Action-Figur auf dem Schreibtisch eines Textur-Artists

Incidence and risk factors for relapses in HIV-associated non-Hodgkin lymphoma as observed in the German HIV-related lymphoma cohort study

Outcome of HIV-infected patients with AIDS-related lymphomas has improved during recent years. However, data on incidence, risk factors, and outcome of relapses in AIDS-related lymphomas after achieving complete remission are still limited. This prospective observational multicenter study includes HIV-infected patients with biopsy-or cytology-proven malignant lymphomas since 2005. Data on HIV infection and lymphoma characteristics, treatment and outcome were recorded. For this analysis, AIDS-related lymphomas patients in complete remission were analyzed in terms of their relapse-free survival and potential risk factors for relapses. In total, 254 of 399 (63.7%) patients with AIDS-related lymphomas reached a complete remission with their first-line chemotherapy. After a median follow up of 4.6 years, 5-year overall survival of the 254 patients was 87.8% (Standard Error 3.1%). Twenty-nine patients relapsed (11.4%). Several factors were independently associated with a higher relapse rate, including an unclassifiable histology, a stage III or IV according to the Ann Arbor Staging System, no concomitant combined antiretroviral therapy during chemotherapy and R-CHOP-based compared to more intensive chemotherapy regimens in Burkitt lymphomas. In conclusion, complete remission and relapse rates observed in our study are similar to those reported in HIV-negative non-Hodgkin lymphomas. These data provide further evidence for the use of concomitant combined antiretroviral therapy during chemotherapy and a benefit from more intensive chemotherapy regimens in Burkitt lymphomas. Modifications to the chemotherapy regimen appear to have only a limited impact on relapse rate

Identification of regulatory variants associated with genetic susceptibility to meningococcal disease.

Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes

Biomechanical comparison of two different concepts for the "standalone" anterior fusion of the human lumbar spine

Die segmentale Instabilität bei der degenerativen Bandscheibenerkrankung wird häufig durch eine anteriore interkorporelle Spondylodese (ALIF) behandelt. Gängige Techniken erfordern einen zusätzlichen dorsalen Zugang, um eine zusätzliche Stabilisierung mittels Pedikelschrauben oder translaminären Schrauben zu erreichen. Das Testimplantat, der “SynFix-LRTM”, ist ein neuartiges Implantat, das aus einem PEEKKorpus und einer intergrierten anterioren Titanplatte besteht. Die Titanplatte kann vier divergierende winkelstabile Schrauben aufnehmen, womit das Implantat in den angrenzenden Wirbelkörpern verankert werden kann. Dadurch kann auf eine dorsale Stabilisierung verzichtet werden. Das Testimplantat wurde in einem dreidimensionalen Steifigkeitstest in humanen Kadaverpräparaten mit einem bereits im klinischen Einsatz befindlichen Implantat, dem “STALIF”, verglichen, welches ebenfalls für eine sog. “stand-alone” anteriore Spondylodese vorgesehen ist. In diesem biomechanischen Test wurde isolierte Bewegungssegmente L4/5 von 16 Spendern in zwei Testgruppen aufgeteilt. Das Bewegungsausmass (ROM), die Neutrale Zone (NZ), die Elastische Zone (EZ) und die Steifigkeit wurden in den Bewegungsrichtungen Flexion, Extension, Seitneigung links und rechts sowie axialer Rotation links und rechts bestimmt. Jedes Bewegungssegment wurde zunächst in intaktem Zustand getestet, dann wurde eine Diskektomie vorgenommen und je nach Gruppenzuordnung eines der beiden Implantate appliziert. Die Testungen ergaben eine signifikant höhere Stabilisierung durch das “SynFix”-Implantat inbesondere in Seitneigung. In den anderen Bewegungsrichtungen war die Stabilität mit SynFix ebenfalls höher, als mit STALIF, jedoch ohne Signifikanzniveau zu erreichen.Segmental instability in degenerative disc disease is often treated with anterior lumbar interbody fusion (ALIF). Current techniques require an additional posterior approach to achieve sufficient stability by inserting pedicle or translaminar screws. The test device, the “SynFix-LRTM” is a novel implant which consists of a PEEK-body and an integrated anterior titanium plate hosting four diverging locking screws. The test device avoids posterior fixation by enhancing stability via the locking screws. 4/57 The test device was compared to an already established stand-alone interbody implant, called “STALIF” in a human cadaveric three dimensional stiffness test. In the biomechanical test, the L4/5 motion segment of 16 human cadaveric lumbar spines were isolated and divided into two test groups. Tests were performed in flexion, extension, right and left lateral bending, right and left axial rotation. Each specimen was tested in native state first, then a discectomy was performed and either of the test implants was applied. The biomechanical testing revealed a greater stiffness in lateral bending for the SynFix-LRTM compared to the established implant. Both implants showed a significantly higher stiffness in all loading directions compared to the native segment. Clinical investigation of the test device seems reasonable based on the good results reported here