Exact plane-symmetric solutions of the nonlinear equations of a spinor field in the theory of gravitation

We obtain exact plane-symmetric solutions of the spinor field equations with a nonlinear term that is an arbitrary functions of the invariant and with the self-gravitational field taken into account. Conditions are formulated for which the initial system of Einstein's equation and the spinor field equations with a power-law nonlinearity have regular solutions with localized (negative) spinor field energy density: so-called soliton-like solutions. Exact solutions of the spinor field equations are also obtained in flat space—time in this case and it is shown that the initial system of equations does not have soliton-like solutions. Hence the self-gravitational field plays a crucial (regularizing) in soliton-like solutions of the nonlinear spinor field equations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 63–68, August, 1995.     

Multiple time scale analysis of two models for the peroxidase-oxidase reaction

A multiple time scale analysis of two four-variable models of the peroxidase-oxidase reaction, the DOP, and the Olsen model, is carried out. It is shown that autonomous limit cycle oscillations are exhibited by the fast subsets of these two models, but only in certain regions of parameter space, confirming the prior suggestion that the slow variable (NADH) is not essential for oscillatory behavior. However, it is found that the slow variable is essential for oscillatory behavior over other ranges of parameter values, and is always essential for complex oscillatory and chaotic behavior. This latter conclusion is based on a study involving driving the fast subset with a sinusoidally varying (NADH). This study suggests the level of coupling between fast and slow variables of an autonomous system necessary to cause the chaos observed in the DOP model. Further study of the driven system allows for the identification of a natural period of the nonoscillatory but bistable fast subsystem and a set of rules for applying a parametric driving in such a way as to generate a more complete Farey sequence from a truncated Farey sequence. These conclusions are used to compare the very similar DOP and Olsen models, which, nevertheless, exhibit quite different Farey sequences and routes to chaos. (c) 1995 American Institute of Physics.     

Reaction studies of carbon clusters

Reaction studies of carbon clustersC _n in the rangen=8–37, produced by laser vaporisation in a supersonic nozzle, have been investigated using time-of-flight mass spectrometry. Clear differences in reaction products formed on hydrogenation are detected which show that even and odd clusters behave quite differently and furthermore thatat least two different types of even cluster appear to exist. The reactivity patterns for clusters C _n withn=16, 18 and 22 are in a different class from those withn=20, 24, 26 ..., a behaviour consistent with the existence of closed cage fullerene structures for even clusters with 20 or more carbon atoms (other thann=22).     

Determination of alpha contaminated soil profiles using Nuclear Track Detectors

Nuclear Track Detectors (NTD's) are a useful option forin situ measurements of the distribution of alpha contamination as a function of soil depth. The contamination profile of alpha emitting elements, e.g. Pu, Am and U, can be determined by detecting their alpha emission at varying depths. This paper discusses a stake type device, containing strips of CR-39 (allyl diglycol carbonate) that can be inserted into the soil up to ten centimeters or more, depending on the firmness of the soil. The CR-39 is exposed directly to the contaminated soil for a few hours. The stake is then withdrawn from the soil, the plastic detectors recovered and the alpha tracks developed by chemical etching with KOH. The distribution of tracks can be used to determine the alpha contamination depth profile as well as for detecting hot spots. It has a sensitivity of less than a pCi/g of soil.Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract W-7405-ENG-48.     

A definitive method for the determination of trace amounts of cobalt in biological materials by neutron activation analysis

A new, very accurate (definitive) method for the determination of trace amounts of cobalt in biological materials has been devised. The method is based on combination of neutron irradiation with quantitative and selective post-irradiation separation of cobalt from all accompanying radionuclides followed by measurement by -ray spectrometry. Column chromatography in which owing to addition of Co carrier the course of separation can be followed visually is the key element of the separation scheme. Several criteria have been formulated which must be simultaneously fulfilled in order to acknowledge the result as obtained by a definitive method. The high accuracy of the method has been demonstrated by the analysis of several certified reference materials of widely different Co contents.     

The water rise in front of a model planing hull

It is known that the water “splashes-up” or rises above the undisturbed surface immediately in front of a planing surface. This rise is greatest in front of a flat planing plate and a number of attempts have been made to reduce the experimental measurements of this phenomenon to some kind of order. Since it was first independently proposed by both Schnitzer and Smiley in 1952, all attempts to correlate the flat plate splash-up have started with the assumption that splash is only a function of the immersed length of the plate and is independent of trim angle at least below about 20°. In part, this was because the three early studies which compared this hypothesis with experimental data omitted those portions of the data which did not support the hypothesis. The present paper concludes that this forty year old hypothesis is fallacious and that the water rise in front of any prismatic planing surface is best approximated by $$\frac{d}{{\sqrt {bl} }} = k\sin ^2 {\mathbf{\tau }}$$ whered is the vertical water rise at the water/keel intersection;b is the beam;l is the submerged length of the keel;τ is the trim angle;k: is a constant determined from experiment, approximated by,k = 2e ^?2.5β , whereβ is the deadrise angle in radians. It might be thought that this is a slight contribution, of little practical import, but for one thing. Starting in the 1950's most towing tank experimenters in the United States abandoned the difficult measurement of model draft and obtained only the “actually wetted length” from underwater photographs. But theoretical planing force calculations require a knowledge of the relationship between a hull and the undisturbed water plane. Thus if modern experimental data is to be compared with theory, it is necessary to estimate what the undefined splash-up or water rise was during each experiment, in order to estimate the model's true position in space. The paper concludes by criticizing the format of some modern reports of experiments with model planing hulls and suggests that, in addition to the usual graphical presentations, measured data should always be reported numerically. Also, that when relevant data is omitted from a plot, the facts of such omission should be clearly stated.     

Boundary layers in finite thermoelasticity

In this paper, we study inhomogeneous deformations within the context of finite thermoelasticity with a view towards highlighting the developments of boundary layer like structures. We find that such structures manifest themselves by virtue of the material's ability to shear soften or shear stiffen. When the material moduli depend both on the temperature and the stretch, their effects can either reinforce or mitigate one another, thereby leading to the accentuation or annihilation of the boundary layer structure.     

Close coupling results for inelastic collisions of NH3 and Ar. A stringent test of a spectroscopic potential

We have calculated state-to-state total cross sections for rotational excitation and inversion of NH3 by collisions with Ar using the close coupling method. The Ar-NH3 interaction potential has been obtained from a fit to the spectrum of this van der Waals molecule. The calculated cross sections agree to within about 30% with the measured values; the estimated error in the latter is 10% to 20%.