Automorphism groups of polycyclic-by-finite groups and arithmetic groups

We show that the outer automorphism group of a polycyclic-by-finite group is an arithmetic group. This result follows from a detailed structural analysis of the automorphism groups of such groups. We use an extended version of the theory of the algebraic hull functor initiated by Mostow. We thus make applicable refined methods from the theory of algebraic and arithmetic groups. We also construct examples of polycyclic-by-finite groups which have an automorphism group which does not contain an arithmetic group of finite index. Finally we discuss applications of our results to the groups of homotopy self-equivalences of K(\Gamma, 1)-spaces and obtain an extension of arithmeticity results of Sullivan in rational homotopy theory

The biochemical characterization of a novel non-haem-iron hydroxylamine oxidase from Paracoccus denitrificans GB17

The characterization of the hydroxylamine oxidase from the heterotrophic nitrifier Paracoccus denitrificans GB17 indicates the enzyme to be entirely distinct from the hydroxylamine oxidase from the autotrophic nitrifier Nitrosomonas europaea. Hydroxylamine oxidase from P. denitrificans contains three to five non-haem, non-iron-sulphur iron atoms as prosthetic groups, predominantly co-ordinated by carboxylate ligands. The interaction of the enzyme with the electron-accepting proteins cytochrome C556 and pseudoazurin is mainly hydrophobic. The catalytic mechanism of hydroxylamine oxidase from P. denitrificans is different from the enzyme from N. europaea because the production of nitrite by the former requires molecular oxygen. Under anaerobic conditions the enzyme makes nitrous oxide as a sole product

Purification of hydroxylamine oxidase from Thiosphaera pantotropha Identification of electron acceptors that couple heterotrophic nitrification to aerobic denitrification

AbstractThiosphaera pantotropha, a Gram-negative heterotrophic nitrifying bacterium, expresses a soluble 20 kDa monomeric periplasmic hydroxylamine oxidase that differs markedly from the hydroxylamine oxidase found in autotrophic bacteria. This enzyme can use the periplasmic redox proteins, cytochrome C551 and pseudoazurin as electron acceptors, both of which can also donate electrons to denitrification enzymes. A model of electron transfer is proposed, that suggests a coupling of nitrification to denitrification and provides a mechanism by which nitrification can play a role in dissipating reductant

Groups with infinite homology

No abstract available

Structure based modification of Bluetongue virus helicase protein VP6 to produce a viable VP6-truncated BTV.

Bluetongue virus core protein VP6 is an ATP hydrolysis dependent RNA helicase. However, despite much study, the precise role of VP6 within the viral capsid and its structure remain unclear. To investigate the requirement of VP6 in BTV replication, we initiated a structural and biological study. Multinuclear nuclear magnetic resonance spectra were assigned on his-tagged full-length VP6 (329 amino acid residues) as well as several truncated VP6 variants. The analysis revealed a large structured domain with two large loop regions that exhibit significant conformational exchange. One of the loops (amino acid position 34-130) could be removed without affecting the overall fold of the protein. Moreover, using a BTV reverse genetics system, it was possible to demonstrate that the VP6-truncated BTV was viable in BHK cells in the absence of any helper VP6 protein, suggesting that a large portion of this loop region is not absolutely required for BTV replication

Key characteristics impacting survival of COVID-19 extracorporeal membrane oxygenation

Background Severe COVID-19 induced acute respiratory distress syndrome (ARDS) often requires extracorporeal membrane oxygenation (ECMO). Recent German health insurance data revealed low ICU survival rates. Patient characteristics and experience of the ECMO center may determine intensive care unit (ICU) survival. The current study aimed to identify factors affecting ICU survival of COVID-19 ECMO patients. Methods 673 COVID-19 ARDS ECMO patients treated in 26 centers between January 1st 2020 and March 22nd 2021 were included. Data on clinical characteristics, adjunct therapies, complications, and outcome were documented. Block wise logistic regression analysis was applied to identify variables associated with ICU-survival. Results Most patients were between 50 and 70 years of age. PaO2/FiO2 ratio prior to ECMO was 72 mmHg (IQR: 58–99). ICU survival was 31.4%. Survival was significantly lower during the 2nd wave of the COVID-19 pandemic. A subgroup of 284 (42%) patients fulfilling modified EOLIA criteria had a higher survival (38%) (p = 0.0014, OR 0.64 (CI 0.41–0.99)). Survival differed between low, intermediate, and high-volume centers with 20%, 30%, and 38%, respectively (p = 0.0024). Treatment in high volume centers resulted in an odds ratio of 0.55 (CI 0.28–1.02) compared to low volume centers. Additional factors associated with survival were younger age, shorter time between intubation and ECMO initiation, BMI > 35 (compared to < 25), absence of renal replacement therapy or major bleeding/thromboembolic events. Conclusions Structural and patient-related factors, including age, comorbidities and ECMO case volume, determined the survival of COVID-19 ECMO. These factors combined with a more liberal ECMO indication during the 2nd wave may explain the reasonably overall low survival rate. Careful selection of patients and treatment in high volume ECMO centers was associated with higher odds of ICU survival

Large-eddy simulation on the effect of injection pressure and density on fuel jet mixing in gas engines

Direct injection (DI) natural gas engines are modern engine concepts providing clean combustion and high fuel efficiency. Even at high injection pressures, such engines operate at heterogeneous/stratified fuel/air mixture conditions due to the relatively short mixing time of the fuel jet. The sub-optimal fuel-air mixture results in emissions of unburnt hydrocarbon (UHC). In particular, one of the most severe UHC emission is the release of the unburnt greenhouse gas methane (CH4) into the atmosphere (methane slip). To better understand the origin of methane slip, in-depth knowledge of the turbulent mixture formation process is required. It is therefore critical to model the turbulent fuel jet using state-of-the-art computational fluid dynamics (CFD) methods with high time and space accuracy. In the present study, the penetration and mixing of non-reacting methane and nitrogen jets are simulated and compared. Nozzle pressure ratios between 4.5 and 10.5 are investigated with respective Reynolds numbers of the order 100,000. Based on these results, novel information is provided in terms of: (1) demonstration of the influence of the fuel molecular mass, and the injection pressure on turbulent mixture formation in highly underexpanded jets, and (2) understanding of the fuel air mixing dynamics for transient injection. The results indicate that, typically, the CH4 jet mixes faster than the heavier N-2 jet. Investigation of the average density distribution explains the mixing differences. (C) 2014 Elsevier Ltd. All rights reserved