Effect of plastic deformation on hole-defect formation in MgO

Plastic deformation induces an enhancement in the concentration of paramagnetic trapped-hole defects in MgO crystals which contain hydroxyl ions, but not in crystals which are hydrogen-free. EPR, ENDOR and Infrared absorption measurements of hydrogen-containing crystals indicate that deformation stimulates the conversion of existing vacancies to their trapped-hole counterparts, the V_A1, V_OH and V_F centers. There is no evidence that new impurity-compensated or intrinsic cation vacancies are produced in any crystal by deformation.     

Experimental mechanics in Israel

Experimental mechanics in the modern sense started to come to Israel only in the late fifties of the present century. At present, there are two groups of active foci: the universities on the one hand, and the research and development groups of the defense establishment on the other hand. In contrast to the United States and most European countries, there is presently little interest and requirement for experimental mechanics within private industry and within the government agencies which do not deal with defense related activities. Because of natural and demographic reasons, the bulk of activity in the field is carried out in two geographical areas: Tel-Aviv and Haifa. There are also secondary foci in Jerusalem, Rehovoth and Beer-Sheba. For technical reasons and because of physical limitations, only some topics are mentioned and no effort is made to cover everything interesting in experimental mechanics which is going on in Israel today. In most areas, we meet with optical methods, strain-gage applications, or special pickups and instrumentation, particularly for dynamic measurements.     

The NMR spectra and conformations of cyclic compounds—VII: The conformations of β-pinene,pinocarvone and the cis- and trans-pinocarveols

The proton magnetic resonance spectra of β-pinene pinocarvone and the cis- and trans-pinocarveols have been completely assigned at 220 and 300 MHz. On the basis of the proton-proton spin-spin couplings derived, conformations have been deduced for these molecules with greater certainty than has hitherto been possible. Pinocarvone is Y-shaped, while in all the other compounds the conformation is intermediate between a Y-shape and a bridged chair, with the C₃ atom bent away from the gem dimethyl groups. These conformations are discussed in terms of the steric interactions in these systems and are compared with related molecules.     

On the enumeration of distinct fuzzy switching functions

This paper entails the development of bound equations on the number of minimized fuzzy switching functions. A triangular matrix representing the transitivity between fundamental fuzzy phrases is discussed and applied in the enumeration process. Improved upper and lower bounds have been developed by use of the transitivity matrix. In addition, an algorithm is described to calculate the number of distinct fuzzy switching functions for any number of variables.     

Rotational isomerism—XXI: The conformation of 2-amino-3-fluoropropanoic acid (2-afp) and 2-fluoro-3-aminopropanoic acid (3-afp) as the zwitterion,cation and anion,an nmr and mo study

The NMR spectra of 2-AFP And 3-AFP in neutral, acid and alkaline solutions have been obtained and completely analysed to give the ¹H, ¹⁹F and the ¹³C chemical shifts and the HH, HF and CF coupling constants. In the analysis the use of FT spectra with inversion recovery sequences enabled an unambiguous assignment of the complex proton region to be made in certain cases due to the different relaxation times of the protons. The rotamer populations and hence relative energies have been obtained from the ³J_HH couplings, using calculated rotamer couplings which explicitly include the orientation dependence of electronegative substituents. A MO investigation of the rotamer energies of the zwitterions, anions and cations is given. The inclusion of the counterion into the CNDO wave function gives calculated rotamer energies in complete agreement with those observed for 2-AFP. In 3-AFP, the counter-ion method cannot fully compensate for the larger interactions between the charged groups. Calculations on related molecules including β-alanine show this is a general effect, possibly due to the solvated water molecules.     

Quadratic effects in multiphonon transition rates in solids

In this paper we explore the contribution of quadratic impurity—phonon coupling terms on nonradiative multiphonon transition rates in solids. It is demonstrated that the quadratic terms may increase substantially the transition rate and may modify quantitatively the energy gap law. Such effects will be exhibited even when the quadratic coupling is too weak to be observable in the optical spectra.     

Die Analyse hochfluorierter Kohlenwasserstoffe, demonstriert am Beispiel fluorierter n-Hexane

Zusammenfassung Gemische von Perfluor-n-hexan und Monohydrogen-perfluor-n-hexanen sind gaschromatographisch analysiert worden. Während bei der gaschromatographischen Trennung perfluorierter Kohlenwasserstoffe Fluor-Kohlenstoff- und Fluor-Chlor-Kohlenstoffverbindungen als besonders geeignete stationäre, flüssige Phasen gelten, hat sich im vorliegenden Falle Di-n-butylmaleat gut bewährt.Es werden die Infrarotspektren von 1 H-Perfluor-n-hexan, 2 H-Perfluor-n-hexan und 3 H-Perfluor-n-hexan vorgelegt und die Massenspektren dieser Verbindungen verglichen.

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Summary Mixtures of perfluoro-n-hexane and monohydrogen-perfluoro-n-hexanes were analysed by gaschromatography.While fluorocarbons and chlorofluorocarbons are known to be especially suitable media for the separation of flourocarbons by gaschromatography, in the case considered di-n-butyl maleate as a stationary liquid phase has proved to be useful.The infrared spectra of 1 H-perfluoro-n-hexane, 2 H-perfluoro-n-hexane, and 3 H-perfluoro-n-hexane are given and the mass spectra of these compounds are compared.

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Vortragender: Dr. K. Abraham.

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Das für die Untersuchung erforderlich, gewesene Kobalttrifluorid ist uns in dankenswerter Weise von den Farbwerken Hoechst, Frankfurt/M.-Höchst, zur Verfügung gestellt worden. Herrn Dr. W. Meise, Farbenfabriken Bayer, Leverkusen, danken wir auch an dieser Stelle herzlich für die exakten IR-Messungen an unseren Präparaten.