Optical absorption of irradiated quartz in the near i.r.

The effects of irradiation with 10 MeV electrons on the absorption spectra in the 3 μm region of both natural and synthetic quartz were investigated in the temperature range from 12 to 300°K. Six different types of synthetic crystals were included in this study. It was found that the spectra of samples that were treated by electrodiffusion were least affected by the irradiations, whereas large changes were observed in the spectra of untreated specimens. Lines were introduced by irradiation in some synthetic samples at 3306 and 3367 cm^?1. The dependence of the spectra on radiation dose was studied up to 6700 MRad. The largest spectral changes saturated above a dose of 200 MRad. The sharp, intense lines at 12°K were observed to broaden and weaken as well as to shift to shorter wavelengths as the temperature was raised to 300°K. Some of these effects can be described in terms of a model involving charge compensation of the aluminum defect by hydrogen and alkali metal ions. It is also found that, based on the spectra of unirradiated material, one can differentiate between natural, synthetic and swept synthetic crystals.     

Food and drug administration regulation of medical device biotechnology,and food and food additive biotechnology

The Food and Drug Administration (FDA) is facing a flurry of new products coming to market over the next few years that will be based on biotechnology. The agency will have to deal with state-of-the-art drugs and devices utilizing biotechnology as the developmental base. Also, many universities and companies are exploring the potential uses of biotechnology in developing new foods and food additives. This article will examine how the FDA is presently regulating medical device, and food and food additive biotechnology and the challenges confronting the agency in these areas in the future.     

The accessibility of antigenic determinants of ribosomal protein S4 in situ.

Antibodies to Escherichia coli ribosomal protein S4 react with S4 in subribosomal particles, eg, the complex of 16S RNA with S4, S7, S8, S15, S16, S17, and S19 and the RI reconstitution intermediate, but they do not react with intact 30S subunits. Antibodies were isolated by three different methods from antisera obtained during the immunization of eight rabbits. Some of these antibody preparations, which contained contaminant antibodies directed against other ribosomal proteins, reacted with subunits, but this reaction was not affected by removal of the anti-S4 antibody population. Other antibody preparations did not react with subunits. It is concluded that the antigenic determinants of S4 are accessible in some protein deficient subribosomal particles but not in intact 30S subunits.     

Coalition formation in the triad when two are weak and one is strong

Eighteen groups of subjects each participated in five different computer-controlled superadditive 3-person characteristic function games with sidepayments, that modeled negotiable conflicts in which two of the players are weak and one is considerably stronger. Both the degree to which the strong player was powerful and the type of communication were experimentally manipulated. The 90 game outcomes rejected any solution concept that predicts a single payoff vector for a given coalition structure, but supported the recently developed single-parameter α-power model that allows range predictions. Both the degree of power and type of communication were found to affect game outcomes and to determine the predictive power of models that make point predictions in 3-person games.     

Photophysics of (1-butyl-4-(1H-inden-1-ylidene)-1,4-dihydropyridine (BIDP): an experimental test for conical intersections

Fluorescence experiments on (1-butyl-4-(1H-inden-1-ylidene)-1,4-dihydropyridine (BIDP) are reported in liquid and glassy solutions. The data indicate a fast decay in the fluid nonpolar, nonprotic solutions (decay times approximately 10(-12) s) and rapid but considerably slower decay in polar ones. In frozen solutions (polar and nonpolar), the fluorescence quantum yield is much higher (near 0.5 and around 0.1 in polar and nonpolar glasses, respectively). The rapid nonradiative transitions in fluid solutions are assigned to internal conversion in both solvent classes, as intersystem crossing is much slower and no net reaction is observed. These results are in agreement with predictions made for the closely related (in terms of electronic structure) but simpler molecule cyclopentadienyl-1,4-dihydropyridine (CPDHP) for which an S1/S0 conical intersection was recently proposed [Int. J. Quant. Chem. 2005, 102, 961]. The crossing of the two lowest singlet states is calculated to vanish in polar solvents such as methyl cyanide, leading to longer lifetime of S1 of CPDHP. As BIDP has a very similar electronic structure, the model predicts a corresponding change in this larger molecule. The strong fluorescence observed in the glassy environments is rationalized by the hindering of the internal torsion required to reach the geometry of the conical intersection.     

FTIR Emission Spectra, Molecular Constants, and Potential Curve of Ground State GeO

Extensive new high-temperature, high-resolution FTIR emission spectroscopy measurements for the five common isotopomers of GeO are combined with previous diode laser and microwave measurements in combined isotopomer analyses. New Dunham expansion parameters and an accurate analytical potential energy function are determined for the ground X1Sigma+ state. Copyright 1999 Academic Press.     

La diffraction des ondes électromagnetiques par des ondes gravitationnelles. Sur une nouvelle méthode de détection des ondes gravifiques

Summary A new method for the detection of gravitational waves is proposed. It is based on an assumed diffraction of electromagnetic waves produced by a pattern of stationary gravitational waves.

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A Dario Graffi, pour son 70-ème anniversaire

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Entrata in Redazione il 1 luglio 1975.     

Spectroscopic probes of the quasi-liquid layer on ice

Raman spectra of the water OH-stretch region were acquired at air-ice and air-water interfaces at a glancing angle, which allowed observation of surface characteristics. The shapes of the OH-stretch bands indicate that the environment at the air-ice interface is different from that at the air-water interface and from that seen in bulk water. Water spectra measured at the surface of dodecane under low relative humidity indicate that this method is sensitive to fewer than 50 monolayers of water. Changes in the local environment of the surfacial water molecules may be induced by the presence of different solute species, giving rise to changes in the shape of the band. Dissolved sodium chloride disrupts hydrogen bonding in liquid water and has the same effect at the air-ice interface. However, when either HCl or HNO(3) is adsorbed from the gas phase onto an ice surface, the opposite effect is seen: Their presence appears to increase the extent of hydrogen bonding at the ice surface. At the same time, shifts in the laser-induced fluorescence spectra of acridine, a fluorescent pH-probe present at the air-ice interface, indicate that dissociation of acids occurs there. These observations suggest that the formation of hydronium ions at the air-ice interface enhances the hydrogen bonding of surfacial water molecules.