Measurement of transient deformations by double-pulsed holography

Holographic interferometry is used for the determination of surface deformation of items of equipment. The material failure which caused the surface deformation can then be identified. Because a double-pulsed laser is used to plot the hologram, non-vibration stabilized holographic equipment is necessary. Thus, non-destructive testing of equipment components is also possible during plant operation. In this report, we present the experimental results of non-destructive testing of composite materials. We examined centrifugally cast pipes and filament wound pipes, which were made from glass fibre reinforced plastic and carbon fibre reinforced graphite. As a rule, the severity of failure is characterized by the apparent perturbation of its holographically stored fringe pattern. In this report, we present the experimental results which yield the relationship between the perturbation of interference fringes and the extent of the specific types of failure. Measurement results were compared with displacements calculated by the finite element method. By using the interferogram, and with the knowledge of tension stress beneath the surface, the size of the crack can be estimated. The size of the smallest detectable flaw was clearly smaller than the critical flaw size. Thus, holographic interferometry is suitable for detecting damage to cylindrical containers.     

Turbulent heat transfer and pressure drop in plain tube bundles

The influence of turbulence intensity on heat transfer and pressure drop in tube bundles was measured in an open wind tunnel. The bundles consisted of one to three rows of plain tubes with in-line and staggered tube arrangements. The vertically arranged tubes were heated by saturated steam, condensing inside, and cooled outside with air in cross-flow. The turbulence intensity behind different grids varied in the air stream between 0.8% and 25%, and the air-side Reynolds numbers ranged from 1.5 × 10⁴ to 1.5 × 10⁵. The enhancement of the heat transfer coefficients for the bundles is due to an increase in the level of turbulence and also to a decreasing number of rows. The increase in the Nusselt number is about 42% for a single row and about 14% for a tube bundle with three rows.

From the pressure drop experiments it follows that over a wide range of Reynolds numbers the drag coefficient is almost independent of the inlet turbulence intensity.

In this paper the experimental results for single rows and for bundles with three rows are presented. The influence of the transverse and longitudinal pitch to diameter ratio on heat transfer and pressure drop is discussed.     

The method of fractional steps applied to laminar flat flame calculations

The premixed, freely propagating, steady, laminar, flat flames are solved by a relaxation method. For solution of the unsteady species conservation equations, the method of fractional steps is used. In this method the differential equations for the conservation of the species are split up into two parts, a reaction part and a diffusive convective part which are solved separately and then superposed. The method is used to solve a methane-oxygen flame and compared to the solution of a standard method. In addition the time step behaviour of both the methods are examined and compared to each other. Paper presented at the Workshop “Modelling of Chemical Reaction Systems”, Heidelberg 1986.     

Structure-dependent relative toxic potencies of selected pyrrolizidine alkaloids

Pyrrolizidine alkaloids are naturally occurring secondary plant metabolites mainly found in plant families of Asteraceae, Boraginaceae, and Fabaceae. Chemically, Pas consist of a pyrrolizidine core bearing hydroxyl groups, the so-called necine base, and mono- or dicarboxylic necine acids bound to the pyrrolizidine core via ester linkages. 1,2-unsaturated PAs are hepatotoxic, genotoxic, and carcinogenic due to the highly reactive pyrrolic metabolites formed by cytochrome P450 monooxygenases (CYPs) primarily in the liver. The presence of PAs as frequent contaminants in the wide variety of food and feed products has to be considered a relevant safety issue. Based on the currently available data, the risk assessment of PAs was mainly approached using the two most toxic potent congeners, i.e., lasiocarpine and riddelliine. However, it is well recognized that toxicity is differing significantly between the congeners related to their structural features. The risk of PA-containing products is indeed overestimated, and a comprehensive risk assessment should take these differences into account. After analyzing the data of many PAs, Merz and Schrenk derived interim Relative Potency (iREP) factors to present the differences in their toxicity between the sub-groups of PA congeners concerning their structural features. The use of such iREP factors could probably provide a more scientific basis for PA risk assessment until sufficient experimental analysis of the toxicities of individual congeners is applied. To obtain a better understanding of the relationship between structure and toxicity of PA congeners and provide more evidence for further refinement of relative (toxic) potency factors, data of the in vitro cytotoxicity, genotoxicity, and mutagenicity of diverse individual PA congeners (lasiocarpine, monocrotalineφ, retrorsine, senecionine, seneciphyllineφ, echimidineφ, europineφ, heliotrineφ, indicine, and lycopsamine) has been generated in our project supported by Kooperation Phytopharmaka. Among them, lasiocarpine, retrorsine, senecionine, indicine and lycopsamine have been investigated on my part. Cytotoxicity was assessed using the Alamar blue assay in primary rat hepatocytes, HepG2 cells, and the HepG2 (CYP3A4) cell line. In HepG2 cells, none of the selected PAs exhibited cytotoxic effects, probably due to the lack of CYPs. In primary rat hepatocytes as well as in HepG2(CYP3A4) cells, a clear structure dependent cytotoxicity could be demonstrated. The role of CYP450 enzymes in metabolic activation was further confirmed using an inhibition assay. A kinetic assay analyzing 7-benzyloxyresorufin-O- dealkylation (BROD) was used for measuring the activity of CYP450 enzymes. Furthermore, the utilization of a glutathione-reductase-DTNB recycling assay indicated that glutathione might not play a critical role in PA-induced cytotoxicity. A micronucleus test was used for determining the PA-induced clastogenic genotoxicity. All selected PA congeners exhibited concentration-dependent toxicity in the HepG2 (CYP3A4) cells. The relative potencies of PA congeners estimated from Alamar blue assay and micronucleus assay are generally consistent with the following ranking: lasiocarpine > senecionine > seneciphylline > retrorsine > heliotrine (?) echimidine > europine = indicine = lycopsamine = monocrotaline. The relative toxic potencies evaluated based on our findings were not completely consistent with the iREP classification previously reported by Merz and Schrenk. Monocrotaline in both assays exhibited considerably lower toxic potency. Echimidine, however, was more toxic than expected. On the other hand, mutagenicity was measured in Ames fluctuation assay with Salmonella typhimurium strains TA98 and TA100. None of the selected PA congeners up to 300 μM showed mutagenic effects despite metabolic activation with S9-mix.     

Photolytic hydrogenation of the polyynes C6H2, C8H2, C10H2, and C12H2 in n-hexane with 253.6 nm radiation

The polyynes C₆H₂, C₈H₂, C₁₀H₂, and C₁₂H₂ in n-hexane exposed to 253.6 nm radiation “disappear” much faster in air-free solutions than in solutions in equilibrium with air. These observations suggest that the disappearance is due to reaction of the polyyne molecules in the ground state with a photolytically produced chemical species which in solutions in equilibrium with air is overwhelmingly scavenged by dissolved O₂. Although no hydrogenation products were firmly established the most likely chemical is atomic hydrogen.     

The furrows of Rhinolophidae revisited

Rhinolophidae, a family of echolocating bats, feature very baroque noseleaves that are assumed to shape their emission beam. Zhuang & Muller (Zhuang & Muller 2006 Phys. Rev. Lett. 97, 218701 (doi:10.1103/PhysRevLett.97.218701); Zhuang & Muller 2007 Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 76(Pt. 1), 051902 (doi:10.1103/PhysRevE.76.051902)) have proposed, based on finite element simulations, that the furrows present in the noseleaves of these bats act as resonance cavities. Using Rhinolophus rouxi as a model species, they reported that a resonance phenomenon causes the main beam to be elongated at a particular narrow frequency range. Virtually filling the furrows reduced the extent of the main lobe. However, the results of Zhuang & Muller are difficult to reconcile with the ecological background of R. rouxi. In this report, we replicate the study of Zhuang & Muller, and extend it in important ways: (i) we take the filtering of the moving pinnae into account, (ii) we use a model of the echolocation task faced by Rhinolophidae to estimate the effect of any alterations to the emission beam on the echolocation performance of the bat, and (iii) we validate our simulations using a physical mock-up of the morphology of R. rouxi. In contrast to Zhuang & Muller, we find the furrows to focus the emitted energy across the whole range of frequencies contained in the calls of R. rouxi (both in simulations and in measurements). Depending on the frequency, the focusing effect of the furrows has different consequences for the estimated echolocation performance. We argue that the furrows act to focus the beam in order to reduce the influence of clutter echoes.     

Destillation,Absorption, Extraktion — Gibt es noch Forschungsaufgaben?

Distillation, absorption, extraction – are there any research tasks left? Thermal separation processes have been the subject of scientific investigations for more than half a century. Knowledge and mastery of the process fundamentals and their engineering techniques have reached a stage shown by few other unit operations. Nevertheless, the engineer working on the separation of fluid mixtures may today still come across obstacles and untrodden paths, be it in phase equilibria, fluid dynamics, or mass transfer.     

ATLAS: Accelerated torus-like angular source for fusion neutronics applications

There is increasing demand for fast and accurate neutronics analysis to be conducted on specific ITER components. The ATLAS (accelerated torus-like angular source) algorithm has been developed to accelerate such neutronics calculations by approximating the 3-D plasma volume source as a surface source at the first-wall region of interest. The ATLAS routine rapidly calculates the angular distribution of the unscattered neutron flux at the chosen first wall location, on a discrete angular grid, and writes a surface source for both MCNP and Attila. This discretised source can then be used to accurately reproduce the full 3-D toroidal volume source in angle and energy, and to quickly simulate the irradiation of individual components or regions in the ITER model. While designed for ITER, the method is general in implementation and can be applied to any tokamak.