Suitable weak solutions: from compressible viscous to incompressible inviscid fluid flows

We establish the asymptotic limit of the compressible Navier–Stokes system in the regime of low Mach and high Reynolds number on unbounded spatial domains with slip boundary condition. The result holds in the class of suitable weak solutions satisfying a relative entropy inequality.     

Influence on elemental status by hip-endoprostheses

For many clinical purposes various artificial devices are applied, which contact human tissue and can thus cause adverse reactions between prosthetic surfaces and body components. Of the many materials applied for orthopaedic joint replacements the most common are cobalt-chromium-molybdenum alloys. In these cases considerable amounts of cobalt-chromium-molybdenum wear particles are released from the prostheses which have to be regarded as a cause of long-time problems for the patient.Since these particles are dissolved in body fluids of the surrounding area they are distributed in the whole body via blood. Elevated metal concentrations have been found in blood and urine of persons with endoprostheses. Partly the metals are excreted via urine, but to some extend they accumulate in different organs.Therefore this study dealt with the development of an analytical method for the determination of seven relevant trace elements, namely Al, Co, Cr, Mo, Nb, Ni, and Ti in nine kinds of human tissue (brain, heart, kidney, liver, lung, muscle, lymphatic nodes, spleen, body fat) starting with drawing of the sample, sample work up and finally analysis by means of atomic spectrometry. The optimized method was then applied to determine the metal contents in organs of persons (post mortem) with total hip replacements with metal on metal bearing surfaces. Comparison of the data obtained with those of persons without hip-endoprostheses shows that brain and lung are the main targets for elemental accumulation in persons with hip-endoprostheses. Mo and Nb represent the elements with the highest tendency to be accumulated.     

Influence of the flow,etching time and reactor cleaning method on the etching rate and selectivity of reactive ion etching of SiO2 — Photoresist system

Reactive ion etching (RIE) in a cold plasma of fluoro- and chlorocarbons is one of the most widespread etching methods used in semiconductor industry. The repeatability of etching is influt enced by many factors like the deposition on the electrodes and reactor walls, adsorption of watevapour from air in the case of reactor bleeding, deposition during etching etc. In the presenr work we study the influence of the flow of the etching gas and of the method of reactor cleaning before etching on the etching rate and selectivity in the system SiO₂ —photoresist; the etching gas was trifluorochloromethane (Freon 23, CHF₃) and the etching method was RIE.     

Late‐Stage Peptide Diversification by Bioorthogonal Catalytic CH Arylation at 23 °C in H2O

The step‐economical late‐stage diversification of tryptophan‐containing peptides was accomplished through chemo‐ and site‐selective palladium‐catalyzed C?H arylation under exceedingly mild reaction conditions. Thus, the C?H functionalization occurred efficiently at 23 °C with a catalyst loading as low as 0.5 mol %, and/or in H₂O.     

Substituting CF2 for O4′ in Components of Nucleic Acids: Towards Systems with Reduced Propensity to Form Abasic Lesions

Intrinsic structural features and energetics of nucleotides containing variously fluorinated sugars as potential building blocks of DNA duplexes and quadruplexes are explored systematically using the modern methods of density functional theory (DFT) and quantum chemical topology (QCT). Our results suggest that fluorination at the 2′‐β or 2′‐α,β positions somewhat stabilizes in vacuo the AI relative to the BI conformations. In contrast, substitution of the CF₂ group for the O4′ atom (O4′‐CF₂ modification) leads to a preference of the BI relative to AI DNA‐like conformers. All the studied modifications result in a noticeable increase in the stability of the glycosidic bond [estimated by the relaxed force constants (RFC) approach], with particularly encouraging results for the O4′‐CF₂ derivative. Consequently, the O4′‐CF₂ modified systems are suggested and explored as promising scaffolds for the development of duplex and quadruplex structures with reduced propensity to form abasic lesions and to undergo DNA damage.     

An Organoruthenium Anticancer Agent Shows Unexpected Target Selectivity For Plectin

Organometallic metal(arene) anticancer agents require ligand exchange for their anticancer activity and this is generally believed to confer low selectivity for potential cellular targets. However, using an integrated proteomics-based target-response profiling approach as a potent hypothesis-generating procedure, we found an unexpected target selectivity of a ruthenium(arene) pyridinecarbothioamide (plecstatin) for plectin, a scaffold protein and cytolinker, which was validated in a plectin knock-out model in vitro. Plectin targeting shows potential as a strategy to inhibit tumor invasiveness as shown in cultured tumor spheroids while oral administration of plecstatin-1 to mice reduces tumor growth more efficiently in the invasive B16 melanoma than in the CT26 colon tumor model.     

Circular punch on the unstretchable Westergaard-type subgrade

Summary Horizontally unstretchable continuum of the Westergaard's type is modelled by elastic layers of finite thicknesses interconnected with very thin, flexible but unstretchable sheets. For the regular layered structure, the finite difference equations are formulated and their closed solutions is presented. The resulting formulase are used when the contact problem solution is sought in a form of series of spherical functions. The unknown series coefficients are determined via Galerkine method, the formulae for punch settlement and inclination are presented and a numerical procedure is developed and used to study the influence of the Westergaard's subgrade material parameters (subgrade reinforcement intensity) and (Poisson's ratio of the basic material).

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Kreisförmiger Stempel auf unausdehnbarer Unterlage Westergaard'schen Typs

Übersicht Horizontal unausdehnbares Kontinuum Westergaard'schen Typs wird über elastische Schichten endlicher Dicke, die mittels sehr dünner und biegsamer, aber nichtdehnbarer Membranen verbunden sind, modelliert. Für den Fall regulärer Schichtstrukturen werden die Finite-Differenzen-Gleichungen aufgestellt und die geschlossene Lösung formuliert. Diese Lösung wird dann benutzt, wenn das Kontaktproblem in der Form von sphärischen Funktionenreihen dargestellt wird; die unbekannten Koeffizienten der Reihe werden über die Galerkin-Methode bestimmt. Für den Fall einer senkrechten Belastung und einer Momentenbelastung werden die Setzung und Verdrehung bestimmt. Dafür wird ein numerisches Verfahren entwickelt und verwendet, um den Einfluß der Materialparameter und des Westergaard'schen Kontinuum zu untersuchen.

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Presented at the GAMM Seminar Kontakt fester Körper, Stuttgart 18.–19. March 1993

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Dedicated to Prof. H. Bufler upon the occasion of his 65th birthday anniversary