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An investigation is made of the phenomena occurring at the contact of elastic spheres, subjected to forces with varying tangential component, in one direction, with changing sign, and varying normal component. The contact law is based on the assumption, introduced by H. Hertz [3], that both bodies behave physically like elastic half-spaces. We assume constant stress directions in the slip area in order to use so-called Cattaneo-Mindlin functions to solve the tangential boundary value problem. The stress distribution of the Cattaneo-Mindlin theory [2], [8] is rotational symmetric and has a typical break at the border of the stick area at ?=a1* fora1*1, with the radiusa1* of the stick area and the radiusa1 of the contact area. The general solution of the tangential contact problem can be written as a sum of Cattaneo-Mindlin functions. The appropriate superposition of two Cattaneo-Mindlin functions yields a new Cattaneo-Mindlin function, which simplifies the calculation of the force and the displacement. We will arrive at a formula for the force-displacement relation of general load-histories, which can be reduced to the compliances of Mindlin & Deresiewicz [9] by differentiation. In contrast to Mindlin & Deresiewicz our formula depends only on the points of instantaneous adhesionPi, for 1?i?N-1, and the current displacements ?N, ?N in tangential and normal direction of the initial contact point, which simplifies the solution. It also allows a generalization for oblique load-histories with elliptical contact areas and tangential forces in varying directions [4]. Finally an algorithm is given, which determines the essential number of Cattaneo-Mindlin functions.

The dipyridodiazepinone Nevirapine is a potent and highly specific inhibitor of the reverse transcriptase (RT) from human immunodeficiency virus type 1 (HIV-1). It is a member of an important class of nonnucleoside drugs that appear to share part or all of the same binding site on the enzyme but are susceptible to a variety of spontaneous drug-resistance mutations. The co-crystal-structure of HIV-1 RT and Nevirapine has been solved previously at 3.5-A resolution and now is partially refined against data extending to 2.9-A spacing. The drug is bound in a hydrophobic pocket and in contact with some 38 protein atoms from the p66 palm and thumb subdomains. Most, but not all, nonnucleoside drug-resistance mutations map to residues in close contact with Nevirapine. The major effects of these mutations are to introduce steric clashes with the drug molecule or to remove favorable protein-drug contacts. Additionally, four residues (Phe-227, Trp-229, Leu-234, and Tyr-319) in contact with Nevirapine have not been selected as sites of drug-resistance mutations, implying that there may be limitations on the number and types of resistance mutations that yield viable virus. Strategies of inhibitor design that target interactions with these conserved residues may yield drugs that are less vulnerable to escape mutations.

We have investigated the internal vibrations of metal hydrate complexes in ionic single crystals and their interactions with the phonon system of the lattice, by observing the Raman spectra and infrared reflection spectra with polarized light at different temperatures T(2 K ≦ T ≦ 300 K). As special systems the octahedral nickel hydrate complexes in NiSnCl6 · 6 H2O, NiSnCl6·6 D2O and in NiSO4 · 6H2O. NiSO4 · 6D2O have been chosen. For NiSnCl6·6 aqu a complete interpretation of the spectra is given, starting from the assumption of isolated metal hydrate complexes and SnCl6-- -ions as structural units. The discussion of the spectra of the sulfate crystal is based on the corresponding assumption. However, here an unambiguous assignment of all lines observed was not possible.

The absorption spectra of CeCl3·7 H2O, LaCl3·7 H2O, CeCl3·7 D2O and LaCl3·7 D2O have been measured at low temperatures in the region of the 4 f→4 f infrared transitions. The energy levels of the Ce3+-ion in these compounds have been derived. The infrared phonon transitions have also been determined from the reflection spectra of these crystals measured in the region between 4000 cm−1 and 50 cm−1.

Wie in der vorstehenden Arbeit [1] werden Reflexionsspektren von einkristallinem, orthorhombischem MgSO4·7H2O und MgSO4·7D2O beschrieben. Die Spektren wurden in polarisiertem Licht bei einer Probentemperatur von 300°K, 80°K und ca. 14°K im Wellenzahlenbereich zwischen 4000 cm−1 und 400 cm−1 gemessen. Mit den Kronig-Kramers-Relationen wurden die Frequenzen der ultrarotaktiven Übergänge ermittelt. Die Spektren und ihre Temperaturabhängigkeit werden Reflexionsspektren von wasserfreiem orthorhombischem Cs2SO4 gegenübergestellt, die praktisch keine Temperaturabhängigkeit zeigen.

An einkristallinem BeSO4·4H2O und BeSO4·4D2O wurden in polarisiertem Licht Reflexionsspektren gemessen bei Probentemperaturen von 300°K und 14°K im Wellenzahlenbereich zwischen 4000 cm−1 und 300 cm−1. Mittels einer Kronig-Kramers-Analyse wurden die Frequenzen der ultrarotaktiven Übergänge bestimmt. Diese Übergänge werden inneren Schwingungen der Wassermolekeln und der Sulfationen zugeordnet, im Bereich zwischen 1000 cm−1 und 300 cm−1 außerdem noch inneren und äußeren Schwingungen der tetraedrischen Be++·4aqu-Komplexe. Die Schwingungsformen dieser Komplexe bestehen aus einer Überlagerung von Translations- und Librationsschwingungen der Wassermolekeln und Translationsbewegungen des zentralen Be++-Ions.