Synthese und Eigenschaften von 6-Desoxy-6-halogen-Derivaten der L-Ascorbinsäure

Synthesis and Properties of 6-Deoxy-6-halogeno-Derivatives of L -Ascorbic Acid 6-Deoxy-6-chloro-, -6-bromo-, -6-iodo- and -6-fluoro derivatives of L -ascorbic acid have been synthesized and characterized. The physiological properties of the chloro derivative have been investigated. It shows a high antiscurvy activity. The chloro- and bromo-derivatives have been reduced to the corresponding deoxy compound, which is an interesting chiral intermediate for the preparation of rare ω-deoxy sugars.     

A theoretical study of the electronic transition moment for the C2 swan band system

Self-consistent-field plus configuration-interaction calculations have been performed on the a³Π_u and d³Π_g states of C₂. Good agreement is obtained between the theoretical potential energy curves and these obtained by a Klein-Dunham analysis of measured molecular constants. The sum of the squares of the theoretical transition moments Σ|R_e|² between these states at 2.44 bohr is 4.12, a.u. which is in good agreement with the range of values of 3.3–3.6 a.u. obtained from shock tube measurements. The computed variation of the Σ|R_e|² with internuclear distance is in remarkably good agreement with the relative measurements by Danylewych and Nicholls.     

ACOUSTIC DETECTION OF TRIPLET STATES FORMED BY RADICAL PAIR RECOMBINATION IN QUINONE-DEPLETED PHOTOSYNTHETIC REACTION CENTERS, BY MAGNETIC FIELD MODULATION (MAGNETOPHOTOACOUSTIC EFFECT)-A FEASIBILITY STUDY

Abstract –An acoustic method is outlined to detect triplet states formed by radical pair recombination in photosyn-thetic reaction centers. It is based on magnetic field effect on the probability of triplet state formation by recombination. Using a periodically modulated magnetic field in the presence of constant exciting light, a periodic modulation of the triplet state concentration is set in the sample, which is detected through the corresponding modulated heat emission, transduced to acoustic vibration of the gas phase around the sample. This effect is similar to the photoacoustic effect, except that here the light is not modulated. The feasibility of detecting such an effect was proven experimentally, by obtaining a signal from quinone-depleted reaction centers of Rhodobacter sphaeroides. The signal had twice the frequency of the magnetic field modulation; it was proportional to the light intensity and significantly stronger at the lower temperatures (in the investigated range 113–278 K). No signal was obtained from quinone-containing reaction centers, which do not produce triplets. A theoretical outline of the effect and the experimental set-up are described. The "magnitude of the effect was calibrated against ordinary photoacoustic measurements, allowing numerical evaluation of certain parameters of the triplet state ( e.g. triplet energy or yield) with the aid of auxiliary information from the literature.     

Fission with microscopic energy dissipation

We calculate the non-adiabatic excitations of pair states in a BCS formalism for a fissioning²³⁶U nucleus. The single-particle spectrum is calculated for a folded-Yukawa potential along a deformation path that is determined classically for one-body dissipation. The resulting microscopic energy dissipation is compared to that due to one- and two-body dissipation.     

A new sample holder for excitation of transverse sound waves

A simple non-resonant sample holder with inclined electrodes is described by means of which transverse sound waves in the GHz range are easily generated by an evaporated piezoelectric layer. Because of its small size it is especially well suited for cryostat applications.     

Charakterisierung stetiger Faltungshalbgruppen durch das Lévy-Maß

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