On a generalized large number hypothesis

By generalizing Dirac's large number hypothesis, we find that the cosmological constant varies witht ^–2, as expected from earlier studies.This work was first prepared while the author was at the Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL. It has been partially funded by CNPq (Brazilian Government Agency).     

Large-scale flow of interstellar gas in galactic spiral waves: Effects of thermal balance and self-gravitation

Using the recent observational data on atomic and molecular hydrogen in the Galaxy, we analyse the dynamics of the interstellar gas in a spiral density wave. Within the framework of Marochniket al.'s (1972) model of the galactic spiral structure, the gas flow is obtained, with self-gravitation and thermal processes taken into account.It is shown that: (1) the self-gravitation of gas does not practically affect the galactic shock if the dominant contribution into the gas density comes from atomic hydrogen; (2) the effects of self-gravitation could be essential for both the gas flow and the stellar spiral wave only if the density contribution of H₂ exceeded several times that ofHi, with molecular hydrogen as a continuous medium having the isothermal equation of state; (3) however, regardless of the estimates of H₂ abundance in the Galaxy, its reaction to the density wave is weak, since it forms a collisionless system not dragged by the intercloud gas.It has been found that, if we allow for thermal processes in the interstellar medium, new types of gas flow can develop alongside with a previously-known continuous flow and galactic shock. They are: (1) galactic shock with the phase transition leading to the formation of dense cold clouds; (2) a three-phase flow where hot cavities and dense cold clouds coexist with an initial, moderately dense and cold phase; (3) an accretion wave which is a specific type of nonlinear wave with an amplitude of 11/2 orders of magnitude larger than that of the isothermal galactic shock appearing under the same conditions, but without heating and cooling.     

Cosmological solution in wesson's 5D theory of gravity

Cosmological solutions that obey the perfect fluid equation of state in Wesson's gravitational theory are presented assuming that the fifth dimension subspace is also homogeneous and isotropic like the usual homogeneous isotropic cosmological model. It is shown that the scale factor scales as for the vanishing fifth component of the energy momentum tensor. The role of the fifth component as a cosmological constant is remarked, and an inflationary model is thus obtained.     

The Very Early Universe might not have been Radiation-Dominated

The equation of state of the very early Universe and the formula for the radius, are here evaluated. It is shown that the very early classical Universe might not be radiation-dominated, although we do not exclude the existence of the radiation dominated phase for the early, but not the very early Universe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ductility‐dependent intensity measure that accounts for ground‐motion spectral shape and duration

The calculated nonlinear structural responses of a building can vary greatly, even if recorded ground motions are scaled to the same spectral acceleration at a building's fundamental period. To reduce the variation in structural response at a particular ground‐motion intensity, this paper proposes an intensity measure (IM_comb) that accounts for the combined effects of spectral acceleration, ground‐motion duration, and response spectrum shape. The intensity measure includes a new measure of spectral shape that integrates the spectrum over a period range that depends on the structure's ductility. The new IM is efficient, sufficient, scalable, transparent, and versatile. These features make it suitable for evaluating the intensities of measured and simulated ground motions. The efficiency and sufficiency of the new IM is demonstrated for the following: (i) elastic‐perfectly plastic single‐degree‐of‐freedom (SDOF) oscillators with a variety of ductility demands and periods; (ii) ductile and brittle deteriorating SDOF systems with a variety of periods; and (iii) collapse analysis for 30 previously designed frames. The efficiency is attributable to the inclusion of duration and to the ductility dependence of the spectral shape measure. For each of these systems, the transparency of the intensity measure made it possible to identify the sensitivity of structural response to the various characteristics of the ground motion. Spectral shape affected all structures, but in particular, ductile structures. Duration only affected structures with cyclic deterioration. Copyright © 2015 John Wiley & Sons, Ltd.     

Formation and early evolution of galaxies: Constraints on the properties of “hot” protogalaxies

Rostov State University. Translated from Astrofizika, Vol. 30, No. 1, pp. 48–59, January–February, 1989.     

Preparation of the sea water reference material for trace metals,NASS-1

The preparation of a sea water reference material, NASS-1, is described. The sea water is an open ocean sample, salinity 35.07‰, gathered at the 1300 metre level in the North Atlantic, south-east of Bermuda. It is acidified to pH 1.6 with nitric acid and bottled in 2 1 polyethylene bottles. Reliable values are available for 11 trace metals (As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Mo, Ni and Zn). The results of a long-term sea water storage experiment are also described.