Stahl und Eisen

Ohne Zusammenfassung     

Transient Growth in Exactly Counter-Rotating Couette–Taylor Flow

Transient growth due to non-normality is investigated for the Couette-Taylor problem with counter-rotating cylinders as a function of aspect ratio η and Reynolds number Re. For all Re≤500, transient growth is enhanced by curvature, i.e. is greater for η<1 than for η=1, the plane Couette limit. For fixed Re>130, it is found that the greatest transient growth is achieved for η on the linear stability boundary. Transient growth is approximately 20% higher near the Couette-Taylor linear stability boundary at Re=310, η=0.986 than at Re=310, η=1, near the threshold observed for transition in plane Couette flow. For 106<Re<130, the greatest transient growth occurs for a value of η between the linear stability boundary and one. For Re<106, the flow is linearly stable and the greatest transient growth occurs for a value of η less than one. The energy in the optimal inputs is primarily meridional; that in the optimal outputs is primarily azimuthal. Pseudospectra are calculated for two contrasting cases. Received 5 November 2001 and accepted 29 March 2002 Published online: 2 October 2002 Communicated by H.J.S. Fernando     

1-Norbornyllithium as a Precursor for the Synthesis of Novel Organic 1-Bicyclo[2.2.1]Heptane Derivatives and for the Improved Preparation of 1-Chloro-Bicyclo[2.2.2]octane

An improved strategy for synthesis of 1-chloro-bicyclo[2.2.2]octane is described in which the key compounds 1-norborny substituted ethyl formate(3) or 1-norbornylcarbaldehyde (7) were prepared from 1-norbornyllithium(1). The latter appeared as a useful precursor for the synthesis of various organic bridgehead substituted derivatives.     

Static Properties of Plain Journal Bearing

International Applied Mechanics - The phenomenon of occurrence of a hydrodynamic oil film on the bearing system is analyzed. A theoretical model of the radial slide bearing system that takes into...     

Quasilinearization for the periodic boundary value problem for hybrid differential equation

The method of quasilinearization for a periodic boundary value problem for nonlinear hybrid differential equations is studied. It is shown that the convergence is quadratic.     

Strong Antibiotic Activity of the Myxocoumarin Scaffold in vitro and in vivo

The increasing emergence of resistances against established antibiotics is a substantial threat to human health. The discovery of new compounds with potent antibiotic activity is thus of utmost importance. Within this work, we identify strong antibiotic activity of the natural product myxocoumarin B from Stigmatella aurantiaca MYX-030 against a range of clinically relevant bacterial pathogens, including clinical isolates of MRSA. A focused library of structural analogs was synthesized to explore initial structure-activity relationships and to identify equipotent myxocoumarin derivatives devoid of the natural nitro substituent to significantly streamline synthetic access. The cytotoxicity of the myxocoumarins as well as their potential to cure bacterial infections in vivo was established using a zebrafish model system. Our results reveal the exceptional antibiotic activity of the myxocoumarin scaffold and hence its potential for the development of novel antibiotics.     

Carbohydrate moieties of molluscan Rapana venosa hemocyanin

Using Zn2+ ions as new method, several FUs have been isolated from molluscan Hc Rapana venosa without formation of non-functional proteolytic side products. N-terminal sequences of these fragments in comparison with FUS from other gastropodan Hcs show a very high degree of structural identity. Four Fus, purified from enzyme-treated structural subunits RvH1 and RvH2 (RvH1-a, RvH1-f, RvH2-a and RvH2-e) show identical N-terminal sequences compared to fragments isolated after treatment with Zn2+ ions. However, in some cases trypsin cleaves RvH chains at different positions if compared to the Zn2+ treatment. To analyze the oligosaccharide composition of two FUS from the first structural subunit of Rapana Hc, RvH1-a and RvH1-f, several techniques were applied: capillary electrophoresis, MALDI-MS, ESI-MS in combination with glycosidase digestions. On basis of these results and the determined amino acid sequence two N-linkage sites were identified in the FU RvH1-a, but only one in the FU RvH1-f.     

Multivariate statistical study of simultaneously monitored cloud water, aerosol and rainwater data from different elevation levels in an Alpine valley (Achenkirch, Tyrol, Austria)

The present paper deals with data interpretation of monitoring of various atmospheric events (cloud water, aerosol and rainwater) at three different elevation levels at Achenkirch profile in an Alpine valley, Tyrol, Austria (Christlumkopf-1758 m, Christlumalm-1280 m and Talboden-930 m a.s.l.) by the use of principal components analysis. From October 1995 to September 1996 sampling sessions for all sites from the profile and for all events were performed for the major ions NH₄⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃⁻, SO₄²⁻-44 cases with eight variables for rainwater; 117 cases with eight variables for cloud water samples and 50 cases with seven variables for aerosol (the major ions as in rain- and cloud water but without magnesium) at any of the elevations. The aim of the multivariate statistical treatment was to extract information about latent factors determining the data structure in all of the cases in order to compare and interpret similarities and dissimilarities with respect to the elevation or the type of the atmospheric event. Four latent factors seem to explain over 85% of the total variance for almost all sites and events but the factors have different identification for the different events or sites (e.g. ‘anthropogenic’, ‘crustal’, ‘neutralization’, ‘salt’). Thus, a comparison between sites and between events becomes possible. It was found that cloud water and aerosol events are much more similar with respect to data structure (relevant to emission sources or processes of formation) than the same events and rainwater. Further, the upper sites of the profile (Christlumkopf and Christlumalm) also reveal data structure similarity differing from that of the lowest site Talboden.     

Impulsive Integral Inequalities with a Deviation of the Argument

In the present work are proved linear generalizations of the classical Gronwall-Bellman's integral inequality on partially continuous functions with a constant deviation.     

New route to 3-alkylthiazolo[3,2-a]benzimidazole derivatives

3-Alkyl-thiazolo[3,2-a]benzimidazole derivatives are obtained in high yields via the corresponding 4-alkyl-N-3-(2-aminophenyl)-thiazoline-2-thiones which are easily prepared from 1,2-diaminobenzene, CS(2) and halogenoketones. This new route compares advantageously with the classical mercaptobenzimidazole routes in term of simplicity,isolated yields and availability of the starting materials.