The influence of a multilayer system of inhomogeneous ultrathin films on reflection of light from dielectric materials

Optics and Spectroscopy - The influence of surface layers on reflection of light in the absence of absorption is studied. The contribution of an ultrathin N-layer film system to the light...     

Potential Energies of the Orbitally Degenerate Atmospheric Rydberg Complexes

A method was developed for calculating the vibronic potential energy surfaces (PESs) of atmospheric complexes consisting of orbitally degenerate Rydberg nitrogen and oxygen molecules and the molecules of a neutral medium in the ground electronic state. The degenerate states are formed as a result of l-mixing in the D and E layers of the atmosphere during the periods of increased solar activity. The complexes are populated in the nonequilibrium two-temperature plasma and are responsible for the incoherent additional background radiation in the decimeter (microwave) and terahertz (IR) bands at an altitude of 80–110 km from the Earth’s surface. To describe the interaction of a weakly bound electron with a singly charged molecular ion and a neutral molecule of a gas medium, the formalism of the multichannel quantum defect (MCD) theory was used. Quantum-chemical calculations of the dependences of the scattering lengths, polarizabilities, and quadrupole moments of the main atmospheric molecules N₂ and O₂ on the interatomic distance were performed. The specific features of the behavior of vibronic PESs of Rydberg complexes for large values of the principal quantum number (n ? 1) were analyzed. The vibronic PESs of orbitally degenerate states were constructed. They are necessary for determining the positions and shape of the vibronic minima of the l-mixing cross sections of the N₂ and O₂ Rydberg molecules in the D and E layers of the Earth’s atmosphere, where the delay times of satellite positioning signals should be minimum. The possibility of “quantum chaos” appearing in the Rydberg complexes at sufficiently large n values and angular momenta of the weakly bound electron was noted.     

Chemical carcinogenesis studies in nonhuman primates

This review covers chemical carcinogenesis studies in nonhuman primates performed by the National Cancer Institute, USA, to provide hitherto unavailable information on their susceptibility to compounds producing carcinogenic effects in rodents. From autopsy records of 401 breeders and untreated controls, incidences of spontaneous malignant tumors were found to be relatively low in cynomolgus (1.9%) and rhesus monkeys (3.8%), but higher in African green monkeys (8%). Various chemical compounds, and in particular 6 antineoplastic agents, 13 food-related compounds including additives and contaminants, 1 pesticide, 5 N-nitroso compounds, 3 heterocyclic amines, and 7 "classical" rodent carcinogens, were tested during the 34 years period, generally at doses 10 approximately 40 times the estimated human exposure. Results were inconclusive in many cases but unequivocal carcinogenicity was demonstrated for IQ, procarbazine, methylnitrosourea and diethylnitrosamine. Furthermore, negative findings for saccharine and cyclamate were in line with results in other species. Thus susceptibility to carcinogens is at least partly shared by nonhuman primates and rodents.     

Adsorptions- und Kontaktwinkel-Studien. II. Wasser und organische Substanzen an poliertem Polytetrafluoräthylen

Ohne Zusammenfassung     

Untersuchungen über Adsorption und Kontaltwinkel. I. Wasser an Kohle mit glatter Oberfläche,an linearem Polyäthylen und an mit Stearinsäure bedecktem Kupfer

Ohne Zusammenfassung     

A method of structure-activity correlation using Wiswesser Line Notation.

Fragment sets generated manually from Wiswesser Line Notation have been used to correlate the chemical structures of a group of 79 penicillins with their serum binding activity, using multiple regression analysis. Statistically significant correlations were found, with results in accordance with the generally accepted nature of the binding. Algorithmic methods for the generation of such fragment sets are proposed and the use of various structural representations for structure-property correlation within chemical information systems is discussed.     

Singular matrix inversion in fluid dynamics computations

In certain types of hydrodynamic calculation the solution of a field equation, after finite differencing, resolves into the inversion of a singular matrix though with a consistent source. There are no physical or mathematical objections to this in principle, but in terms of computer application round-off error can make the set inconsistent. In this case no solution would be possible and this would indeed be discovered with direct methods of matrix inversion.However, with an iterative method such as ADI well-behaved ‘solutions’ are obtained, leading to satisfactory convergence of the overall problem. This article explains why this is so: it is shown that the difference in the computed field variable from the value appropriate to a consistent source is related to the error in the source by a finite matrix multiplier. Hence if the inconsistency in the source is small, e.g. owing to round-off, the error in the computed field variable is likely to be acceptable.