Berechnung des Temperaturverlaufes in einer transpirationsgekühlten Rohrwand

Zusammenfassung Die Innenwandtemperatur eines transpirationsgekühlten Rohres, das einen Plasmabogen umgibt, kann experimentell nur mit sehr großen Schwierigkeiten bestimmt werden. Sie läßt sich jedoch aus auf einfache Weise zu messenden physikalischen Größen berechnen. Das Rechenverfahren wird erläutert und Rechenergebnisse werden diskutiert.

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Calculation of temperature distribution in a transpiration cooled tube wall

Experimental determination of the inner wall temperature of a transpiration cooled tube surrounding a plasma arc is very difficult. This temperature, however, can be calculated from simply measurable physical quantities. The method is explained and results are discussed.

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Bezeichnungen A =m-Bc _pG/2(1–p) _w - A _s Strahlungszahl - B =4P/mc _pG r _p - c _pG spez. Wärme des Gases - C =B(1+A) - C _s Strahlungszahl des schwarzen Körpers - f(r) =(B _r+1/r) - g(r) =(C–1/r ²) - m-B Massenstrom des Gases bezogen auf 1 cm Rohrlänge - P Porosität - q-A _L Wärmemenge, die pro cm Rohrlänge durch Leitung durch die Rohrwand hindurch transportiert wird - r Rohrradius - r _i Innenradius - r _a Außenradius - r _e Rohrradius, an dem alle Temperaturen bekannt sind - r _p Porenradius - t Gastemperatur - t _a Gastemperatur außerhalb des Rohres - T Rohrwandtemperatur - T _a Rohrwandtemperatur an der Außenfläche - T _i Rohrwandtemperatur an der Innenfläche - Wärmeübergangszahl - _w Wärmeleitzahl der Wand - _G Wärmeleitzahl des Gases Herrn Professor E. R. G.Eckert zur Vollendung seines 65. Lebensjahres gewidmet.     

Visual spatial memory is enhanced in female rats (but inhibited in males) by dietary soy phytoestrogens

Background  

In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit superior performance to females (a difference attributed to the hormonal influence of estrogen). This study examined the influence of phytoestrogens (estrogen-like plant compounds) on VSM, utilizing radial arm-maze methods to examine varying aspects of memory. Additionally, brain phytoestrogen, calbindin (CALB), and cyclooxygenase-2 (COX-2) levels were determined.     

A spectroscopic method to estimate the binding potency of amphiphile assemblies

A fast and convenient spectroscopic methodology to determine the water uptake capacity of amphiphile assemblies studied in multilayer films is presented. This method was developed to provide a reliable but relatively simple tool for estimating the binding potency of such complex systems. The water-binding potency represents a general propensity of higher-order systems to bind or embed relevant ligands, such as various non-lipid effectors in the case of artificial lipid membranes. In this sense, the binding potency might contribute to a specific functional role of certain lipids. The essence of the new method is that the calibration of data measured by infrared (IR) spectroscopy against those directly obtained by Karl–Fischer titration (KFT) enables one to replace the expensive chemical–analytical technique by a more comfortable and efficient IR-spectroscopic protocol. This approach combines the easy handling, versatility, and availability of IR spectroscopy with the high accuracy of KFT. The usefulness of the procedure is demonstrated on an example set of six amphiphiles with a common chain length of 18 carbon atoms. Despite this similarity, the binding potency data differ tremendously in a way which can be correlated with the systematic variations introduced into the amphiphile structure. Going further beyond the methodical aspect, the scientific relevance of the data is comprehensively discussed especially in terms of the structural factors that govern the binding potency of amphiphiles. That is favored mainly by fluidity and disfavored mainly by inter-amphiphile binding networks. For phosphatidylcholine, our data are strongly in favor of a particular hydration model that involves primary water binding to phosphate as well as the formation of water semi-clathrates hosting the trimethylammonium moiety. Interestingly, stearylamine and diolein assemblies did not take up any water at all. This unexpected hydrophobicity is due to the unusual structures formed in these latter cases: rigid ammonium amide with a strong hydrogen-bonding/salt bridge network in stearylamine, and patches of inverted micelles in diolein, as revealed by molecular dynamics simulations.     

Frequency based preconditioning and smoothing for shape optimization

In this paper, we present a smoothing technique which can be understood as a Quasi-Newton method. The idea of this preconditioner is that it approximates the symbol of the inverse Hessian, which has smoothing behavior. This symbol is derived analytically for the Stokes equations and investigated numerically for a flow with a Reynolds number of 80. The resulting symbol is then approximated by differential operators, which will lead to a method similar to Sobolev Smoothing. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Automated Generation of Performance Values for Algorithmic Differentiation

The transition from simulation software to optimization software is often quite cumbersome and error prone. With Algorithmic Differentiation(AD) a semi automatic transition can be achieved, but most of the times the performance characteristics of the modified software are not clear in advance. Therefore the performance model from Griewank is tested against real world examples and an automated measurement for the performance characteristics of the hardware is proposed. This enables a more accurate calculation of the performance characteristics of the modified software. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Characteristic free, improved decidability criteria for the similarity problem

In [1], the authors derived algebraic criteria, expressible as a first order sentence in field theory, for the similarity of two matrices over a field of characteristic zero. It thus follows from a well-known result in model theory that this criteria is valid for sufficiently large characteristics, while all of our philosophy and techniques, save one, remain valid in arbitrary characteristics. The characteristic zero phenomenon is contained in the Clebsch-Gordan Theorem or rather in one of its consequences, Roth's Lemma. In order to avoid the use of Roth's Lemma, we have devised an alternate proof which also gives much more simplified criteria, valid in arbitrary characteristic and denned over nonalgebraically closed fields.     

Quadrupolar ordering of phospholipid molecules in narrow necks of phospholipid vesicles

Shapes of phospholipid vesicles that involve narrow neck(s) were studied theoretically. It is taken into account that phospholipid molecules are intrinsically anisotropic with respect to the membrane normal and that they exhibit quadrupolar orientational ordering according to the difference between the local principal membrane curvatures. Direct interactions between oriented molecules were considered within a linear approximation of the energy coupling with the deviatoric field. The equilibrium shapes of axisymmetric closed vesicles were studied by minimization of the free energy of the phospholipid bilayer membrane under relevant geometrical constraints. The variational problem was stated by a system of Euler-Lagrange differential equations that revealed a singularity in the derivative of the meridian curvature at points where the effect of the orientational ordering exactly counterbalances the effect of the isotropic bending. The system of Euler-Lagrange differential equations was solved numerically to yield consistently related equilibrium orientational distribution of the phospholipid molecules and vesicle shape. According to our estimation of the model constants the formation of the neck is promoted if direct interactions between the oriented molecules are taken into account. It was shown that the energy of the equilibrium shapes is considerably affected by the quadrupolar ordering of phospholipid molecules.