Ring Homomorphisms and Finite Gorenstein Dimension

The local structure of homomorphisms of commutative noetherianrings is investigated from the point of view of dualizing complexes.A concept of finite Gorenstein dimension, which substantiallyweakens the notion of finite flat dimension, is introduced forhomomorphisms. It is shown to impose structural constraints,due to a remarkable equivalence of subcategories of the derivedcategory of all modules. An essential part of this study is the development of relativenotions of dualizing complexes and Bass numbers. It is provedthat the Bass numbers of local homomorphisms are rigid, extendinga known result for local rings. Quasi-Gorenstein homomorphismsare introduced as local homomorphisms that base-change a dualizingcomplex for the source ring into one for the target. They areshown to have the stability properties of the Gorenstein homomorphismthat they generalize. 1991 Mathematics Subject Classification:primary 13H10, 13D23, 14E40; secondary 13C15.     

Influence of a Wieghardt foundation on the dynamic stability of a fluid conveying pipe

This article considers the behaviour of a fluid conveying pipe on a partial elastic foundation. The model of the pipe is that of a Timoshenko beam; the foundation response is of Wieghardt type. Both material and environmental damping are taken into account. The critical value of the velocity of the fluid inducing dynamical instability of the system is evaluated as a function of the attachment ratio of the foundation for various values of the physical quantities involved. It is shown that this dependance is not always monotonic.     

Analysis of back contact layers for flexible CdTe/CdS photovoltaic structures

The article shows the comprehensive results of the experiments, conducted in order to select the appropriate metal layers, for back absorber contacts, to apply in flexible, thin-film photovoltaic cells based on cadmium telluride. Preliminary selection of investigated materials was made on the basis of general knowledge and physical data. Deposition techniques, as well as layer parameters, were adjusted to the specific flexible solar cell’s needs. Selected metal layers were deposited either by physical vapour deposition (PVD) or screen-printing method (SP) and tested in terms of their flexibility, thermal resistance, as well as adhesion to CdTe layer. Practical verification of selected configurations is proved by the complete construction of the device.     

A systematic investigation of the effect of sample diluent on peak shape in hydrophilic interaction liquid chromatography

The aim of this study was to evaluate the importance of sample diluents to improve peak shapes in hydrophilic interaction liquid chromatography (HILIC), using low molecular weight (<1000 Da) analytes as well as peptides (with MW ranging between 1000 and 6000 Da) as model compounds. Various solvents were tested including water, acetonitrile, methanol, ethanol, propan-2-ol, dimethyl sulfoxide, and a number of combinations of them. For the analysis of small MW compounds, best peak shapes were obtained with sample dissolved in pure ACN but, IPA or a mixture of ACN/IPA (50:50, v/v) could represent a viable alternative in the case of solubility issues with pure ACN. For drug discovery applications, DMSO can be employed but in combination with at least 80% of ACN. For peptides analysis, acetonitrile, EtOH and IPA as sample diluents, provided similar chromatographic profiles, but pure EtOH or IPA were recommended to limit denaturation and samples solubility issues. Finally, whatever the nature of the compounds, it is recommended to add the lowest amount of water to the sample diluent, to maintain suitable peak shapes.     

European polytechnic schools in nineteenth century and Karlsruhe’s exemplary case

We present a short sketch of higher technical schools in Europe at the half of nineteenth century. With the aim of making some comparisons, we have consulted original documents and present the organisation of the Polytechnic in Karlsruhe in detail as an examplary case.     

Plant delta(15)N associated with arbuscular mycorrhization, drought and nitrogen deficiency

It has long been evident that plant (15)N chiefly reflects the processes which fractionate (15)N/(14)N rather than the (15)N of plant N source(s). It has emerged recently that one of the most important fractionating processes contributing to the whole plant (15)N is the presence/absence, type or species of mycorrhiza, especially when interacting with nutrient deficiency. Ecto- and ericoid mycorrhizas are frequently associated with (15)N-depleted foliar (15)N, commonly as low as -12 per thousand. As shown by the present study, plants having no mycorrhiza, or those infected with various species of arbuscular mycorrhiza (AM)-forming fungi, interact with varying concentrations of soil nitrogen [N] and moisture to enrich plant (15)N by as much as 3.5 per thousand. Hence the lack of a mycorrhiza, or variation in the species of AM-forming fungal associations, can account for about 25% of the usually reported variations of foliar (15)N found in field situations and do so by (15)N enrichment rather than depletion. Copyright 1999 John Wiley & Sons, Ltd.     

Shakedown and limit analysis of periodic composites

The optimization of fiber distribution is analyzed in order to improve the strength performance of metal-matrix composite material, which is submitted to two variable independent loads by coupling homogenization and shakedown theories. Numerical Direct Methods are applied to acquire the shakedown domain of three-dimensional heterogeneous elastic-perfectly plastic fiber-reinforced composite for optimal design. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Einfaches Gerät zur Messung sehr kleiner Druckdifferenzen

A quadratic plate moves with very small clearance in an annular duct with a width of 1 cm². This plate is connected to a turnable spindle in the axis of the duct and can move with it against a thin spiral spring. On both sides of this plate pressures are applied, the difference of which is to be measured. Its amount can be read with a pointer on a scale. In measuring a small loss of gas will occur through the narrow slit between plate and annular duct. If this loss is not admissable, it can be avoided by using two equal instruments, of which one works as zero-instrument in a kind of compensation method. The loss of the second instrument is supplied from an additional source of gas. The instrument permits measurements with an accuracy of fractions of thousandth of a mm water column.

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Einfaches Gerät zur Messung sehr kleiner Druckdifferenzen

Zusammenfassung Eine quadratische Platte bewegt sich mit seht geringem Spiel in einem ringförmigen Kanal von l cm² Querschnitt, sie ist mit einer drehbaren Welle verbunden, die in der Achse des Kanals liegt und kann sich mit dieser gegen eine dünne Spiralfeder bewegen. Auf die beiden Seiten dieser Platte wirkt die zu messende Druckdifferenz und ihre Größe kann mit Hilfe eines Zeigers abgelesen werden. Die Messung ist mit einer geringen Menge überströmenden Gases durch den Spalt zwischen Platte und Ringkanal verbunden. Ist diese Überströmung nicht zulässig, so kann man sie durch Verwenden von zwei Geräten gleicher Art vermeiden, von denen das eine als Nullinstrument nach einer Art von Kompensationsverfahren arbeitet und der Gasverlust des anderen von einer zusätzlichen Gasquelle geliefert wird. Das Gerät erlaubt Messungen mit einer Genauigkeit von Bruchteilen eines Tausendstel mm Wassersäule.

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Prof. Dr.-Ing. U. Grigull zum 60. Geburtstag.