Untersuchung von Stossvorgängen mittels eines Laser-Interferometers

Zusammenfassung Während sich die experimentellen Untersuchungen des Stosses deformierbarer Körper bisher im wesentlichen auf den Anfangs- und den Endzustand beschränkten, untersucht die vorliegende Arbeit den zeitlichen Verlauf der Bewegung während des Stosses bei zwei zentral aufeinander treffenden Kugeln. Als Messgerät diente ein Laser-Interferometer, das räumliche Messpunktabstände von weniger als 200 Å und eine zeitliche Auflösung von weit unter einer Mikrosekunde zulässt, Es wurden als Beispiele ein elastischer und ein unelastischer Stoss vermessen, wobei der elastische Übereinstimmung mit der Hertzschen Theorie zeigte.

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Summary Hitherto, experimental studies of the collision process between deformable bodies mainly concerned the difference between the initial and the final state of the shape at the beginning and at the end of the contact interval. In comparison with this method, the present note deals with an experimental analysis of the deformation process itself during the contact period. The measuring device consists essentially of an optical Michelson type interferometer fed by a He-Ne-gas Laser. It allows a spatial resolution of the timedisplacement history of the event of less than 200 Å, whereas the time resolution is much better than one microsecond. Typical experimental results of elastic and non-elastic collision processes between spheres are discussed, leading in the former case to the conclusion of a good agreement with the classical theory of Hertz.

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Résumé Les études expérimentales de la mécanique des chocs entre des corps déformables visaient jusqu'ici à connaître essentiellement les différences entre leurs états au début et à la fin du phénomène. Par contre, la présente note concerne les variations dans le temps de la déformation de deux sphères pendant leur phase de contact lors d'un choc droit. L'installation de mesure comprenant un interféromètre du type Michelson associée à un laser à gaz fournit une solution meilleure que 200 Å dans la courbe espace-temps du déplacement relatif des deux objets. Ceci co rrespond à une solution dans le temps très inférieure à la microseconde. Comme exemple type de cette méthode, on discute les résultats obtenus pour des chocs droits élastiques et non-élastiques. Il en résulte dans le premier cas une bonne concordance avec la theorie classique de Hertz.

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Vom Ernst-Mach-Institut, Weil am Rhein, gemeinnütziges Institut der Fraunhofergesellschaft, zum ISL abgeordnet.     

Über faktorisierbare Lösungen von Riccatischen Differentialgleichungen

Ohne ZusammenfassungHerrn Hans Wittich zum 60. Geburtstag am 4. Mai 1971 gewidmet     

Ternäre Erdalkali-und Seltene Erd-Silicide und-Germanide mit AlB2-Struktur

Zusammenfassung Der AlB₂-Strukturtyp (C 32) wurde für SrGeZn, elf Verbindungen mit der ZusammensetzungRGe_1,33Cu_0,67 und vierzehn Silicide der FormelRSi_1,33Cu_0,67 aufgefunden, wobeiR ein Atom der Erdalkaligruppe oder der Seltenen Erdelemente symbolisiert. Das Auftreten von binären und ternären Vertretern dieses Strukturtyps wird in Beziehung gesetzt zu einem bestimmten Bereich der Valenzelektronenkonzentration.

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Ternary alkaline earth- and rare earth-silicides and-germanides with AlB₂-structure

The AlB₂ type structure was found with SrGeZn, eleven phases of compositionRGe_1,33Cu_0,67 and fourteen silicides of compositionRSi_1,33Cu_0,67 whereR indicates an alkaline earth or a rare earth element. The occurence of binary and ternary representatives of this structure type can be correlated with a certain range of valence electron concentration.

     

Sun-reactive Skin Type in 4912 French adults participating in the SU.VI.MAX study

Phototype classifications were initially developed in an attempt to predict the skin reactions of patients to phototherapy and are now widely used to advise individuals with regard to sun protection. A transversal study was conducted on the SU.VI.MAX cohort to estimate the frequency of sun-reactive skin features in a large, general adult population-based sample, and to describe the associations between these features. The data were collected 3 years after the beginning of the SU.VI.MAX nutritional intervention study on 4912 volunteers (2868 women aged 35-60 years and 2044 men aged 45-60 years). A multiple correspondence analysis was performed to study the associations between the features. The results showed that these features correspond to a one-dimensional phenomenon, which allowed us to establish a score to summarize skin sensitivity to sun exposure. Furthermore, we found a link between gender and phototype using the Césarini classification (phototype > or = IV: 37% of women, 47% of men). The analysis of the relationship with sun-reactive skin features and the score revealed the same trend. Phenotypic evaluation appears to be a good estimator of skin sensitivity to sun exposure for clinical screening or for use in research, and is easy to collect at a lower cost. Moreover, the sun sensitivity difference between gender should be considered in education about photoprotection.     

Tuning of redox properties for the design of ruthenium anticancer drugs: part 2. Syntheses, crystal structures, and electrochemistry of potentially antitumor [Ru III/II Cl6-n(Azole)n]z(n = 3, 4, 6) complexes

A series of mixed chloro-azole ruthenium complexes with potential antitumor activity, viz., mer-[RuIIICl3(azole)3] (B), trans-[RuIIICl2(azole)4]Cl (C), trans-[RuIICl2(azole)4] (D), and [RuII(azole)6](SO3CF3)2 (E), where azole = 1-butylimidazole (1), imidazole (2), benzimidazole (3), 1-methyl-1,2,4-triazole (4), 4-methylpyrazole (5), 1,2,4-triazole (6), pyrazole (7), and indazole (8), have been prepared as a further development of anticancer drugs with the general formula [RuCl4(azole)2]- (A). These compounds were characterized by elemental analysis, IR spectroscopy, electronic spectra, electrospray mass spectrometry, and X-ray crystallography. The electrochemical behavior has been studied in detail in DMF, DMSO, and aqueous media using cyclic voltammetry, square wave voltammetry, and controlled potential electrolysis. Compounds B and a number of C complexes exhibit one RuIII/RuII reduction, followed, at a sufficiently long time scale, by metal dechlorination on solvolysis. The redox potential values in organic media agree with those predicted by Lever's parametrization method, and the yet unknown EL parameters were estimated for 1 (EL = 0.06 V), 3 (EL = 0.10 V), 4 (EL = 0.17 V), and 5 (EL = 0.18 V). The EL values for the azole ligands 1-8 correlate linearly with their basicity (pK(a) value of the corresponding azolium acid H2L+). In addition, a logarithmic dependence between the homogeneous rate constants for the reductively induced stepwise replacement of chloro ligands by solvent molecules and the RuIII/RuII redox potentials was observed. Lower E(1/2) values (higher net electron donor character of the ligands) result in enhanced kinetic rate constants of solvolysis upon reduction. The effect of the net charge on the RuIII/RuII redox potentials in water is tentatively explained by the application of the Born equation. In addition, the pH-dependent electrochemical behavior of trans-[RuCl2(1,2,4-triazole)4]Cl is discussed.     

Implications of enzymatic, acidic and thermal hydrolysis of DNA on the occurrence of cross-linked melphalan DNA adducts

Calf thymus DNA was treated with melphalan, a nitrogen mustard, and the formation of melphalan cross-linked DNA adducts was investigated. These cross-linked adducts could not be detected either in the enzymatically or in the thermally generated DNA hydrolysates. However, a search for DNA cross-linked adducts in the hydrolysates obtained under acidic conditions revealed the presence of different types of cross-links, mainly containing an adenine moiety. These results are very important because they show that the detection of cross-links is dependent on the hydrolytic procedure used and that these cross-linked adducts are formed under totally different reaction conditions from those in in vivo situations. This can explain the very low abundance or even the absence of cross-linked adducts in nitrogen mustard treated animals. The generally accepted theory that the anti-cancer activity of bifunctional mustards such as melphalan is due to cross-linking of DNA strands remains therefore from our point of view questionable.