A Cut‐Cell Geometric Multigrid Poisson Solver for Fluid Simulation

We present a novel multigrid scheme based on a cut‐cell formulation on regular staggered grids which generates compatible systems of linear equations on all levels of the multigrid hierarchy. This geometrically motivated formulation is derived from a finite volume approach and exhibits an improved rate of convergence compared to previous methods. Existing fluid solvers with voxelized domains can directly benefit from this approach by only modifying the representation of the non‐fluid domain. The necessary building blocks are fully parallelizable and can therefore benefit from multi‐ and many‐core architectures.     

Ammonia Released by <Emphasis Type="Italic">Streptomyces aburaviensis</Emphasis> Induces Droplet Formation in <Emphasis Type="Italic">Streptomyces violaceoruber</Emphasis>

Streptomyces violaceoruber grown in co-culture with Streptomyces aburaviensis produces an about 17-fold higher volume of droplets on its aerial mycelium than in single-culture. Physical separation of the Streptomyces strains by either a plastic barrier or by a dialysis membrane, which allowed communication only by the exchange of volatile compounds or diffusible compounds in the medium, respectively, still resulted in enhanced droplet formation. The application of molecular sieves to bioassays resulted in the attenuation of the droplet-inducing effect of S. aburaviensis indicating the absorption of the compound. ¹H-NMR analysis of molecular-sieve extracts and the selective indophenol-blue reaction revealed that the volatile droplet-inducing compound is ammonia. The external supply of ammonia in biologically relevant concentrations of ≥8 mM enhanced droplet formation in S. violaceoruber in a similar way to S. aburaviensis. Ammonia appears to trigger droplet production in many Streptomyces strains because four out of six Streptomyces strains exposed to ammonia exhibited induced droplet production.     

A Curvature and Density‐based Generative Representation of Shapes

This paper introduces a generative model for 3D surfaces based on a representation of shapes with mean curvature and metric, which are invariant under rigid transformation. Hence, compared with existing 3D machine learning frameworks, our model substantially reduces the influence of translation and rotation. In addition, the local structure of shapes will be more precisely captured, since the curvature is explicitly encoded in our model. Specifically, every surface is first conformally mapped to a canonical domain, such as a unit disk or a unit sphere. Then, it is represented by two functions: the mean curvature half‐density and the vertex density, over this canonical domain. Assuming that input shapes follow a certain distribution in a latent space, we use the variational autoencoder to learn the latent space representation. After the learning, we can generate variations of shapes by randomly sampling the distribution in the latent space. Surfaces with triangular meshes can be reconstructed from the generated data by applying isotropic remeshing and spin transformation, which is given by Dirac equation. We demonstrate the effectiveness of our model on datasets of man‐made and biological shapes and compare the results with other methods.     

Polychlorierte Biphenyle (PCB) in Fischen aus Teichwirtschaften und Nachkl?rteichen

Zusammenfassung Das Muskelgewebe von 58 Fischen aus Teichwirtschaften und 17 Fischen aus Nachklärteichen wurde auf seinen Gehalt an den sechs in der Schadstoff-Höchstmengenverordnung aufgeführten polychlorierten Biphenyl-(PCB)-Kongeneren sowie 2,2,4,5-Tetrachlorbiphenyl (PCB Nr. 49) untersucht. Die Tiere wurden in den Jahren 1986 und 1987 den Gewässern entnommen. Sie waren mit hoch und auch mit niedrig chlorierten Biphenylen belastet. Die Konzentrationen derniedrig chlorierten Kongeneren Nr. 28, 49 und 52 lagen deutlich unter denen der hoch chlorierten. Dennoch belegen die Ergebnisse den Eintrag von Komponenten des niedrig chlorierten technischen Gemisches Clophen C in Umwelt und Nahrungsketten. Verglichen mit den 1980/81 durchgeführten Untersuchungen an Fischen aus Teichwirtschaften war—bezogen auf das hoch chlorierte technische Gemisch Clophen A 60—ein Rückgang der PCB-Belastung des Muskelgewebes erkennbar. Dies steht mit den kürzlich von der hiesigen Arbeitsgruppe an Füchsen und Lebensmitteln erhaltenen Befunden in Übereinstimmung. Die Konzentrationen aller untersuchten PCB-Kongenere waren im Muskelgewebe von Fischen aus Nachklärteichen statistisch signifikant höher als bei den Tieren aus Teichwirtschaften. Die PCB-Gehalte sind somit vom Kontaminationsgrad der verschiedenen Lebensräume abhängig. Demnach können Fische als Bioindikator für den Eintrag hoch und niedrig chlorierter PCB-Kongenere in aquatische Ökosysteme dienen.

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Polychlorinated biphenyls in fish from fish hatcheries and settle ponds

Summary The concentrations of six selected single polychlorinated biphenyl (PCB) congeners, for which legal tolerance levels became valid in 1988, and the congener no. 49 (2,2,4,5-tetrachlorobiphenyl) were determined in the muscle tissue of 58 fishes from fish hatcheries and in 17 fishes from settle ponds. The fish were taken from flowing waters in the years 1986 and 1987. High and low chlorinated biphenyls were present in each sample, but the concentration of the low chlorinated biphenyls was distinctly lower than that of the higher chlorinated ones. Nevertheless these results demonstrate the intake of components of low chlorinated technical PCB mixtures in the environment and food chains. Compared with the investigations carried out in 1980/81 in fishes from fish hatcheries, a decrease of PCB contamination in the muscle tissues with regard to the technical mixture Clophen A 60 was observed. This is in accordance with the results our team obtained a short time previously in muscle tissue from foxes and in food-stuffs. The concentration of all PCB congeners determined in the muscle tissue from fish of settle ponds was significantly higher than in the tissue from fish taken from hatcheries. Thus, the PCB content depends on the PCB load in different environments. Therefore, fishes can be useful as bioindicators for the intake of low and high chlorinated PCB congeners in aquatic ecosystems.

     

Suspensions of plant cells in microgravity

Electrofusion of evacuolated with vacuolated mesophyll protoplasts of Nicotiana spec. was performed as part of the German Sounding Rocket Program (TEXUS). The results indicate a significant increase not only in the yield of 1:1 fusion products, but also in homo- and multifusion products. Heterokaryons obtained under microgravity have been shown to be viable to a higher degree with respect to their ability for light-dependent oxygen evolution (independent of other substrates than bicarbonate). Furthermore we were able to regenerate hybrid plants from suspensions of vacuolated and evacuolated protoplasts which were pulse-treated under microgravity. These expressed characteristics intermediate to those of the parental plants (Nicotiana tabacum (cv. Samsun), evacuolated; N. rustica, vacuolated).     

Periodical operation of chemical processes and evaluation of conversion improvements

The periodical operation of chemical processes and the possibility of conversion improvements have been studied. Especially, methods are discussed which allow to evaluate the result of dynamic control of inlet-concentrations. A tank reaktor with CSTR behaviours has been regarded. The isothermal balance of the reaction encloses dynamic steps at the surface of the catalyst. The derivated evaluations have been checked by numerical simulations and confirmed in many cases.     

Phase I trial of the thioether phospholipid analogue BM 41.440 in cancer patients

The online version of the original article can be found at