Vapor pressure measurements of para-hydrogen adsorbed on exfoliated graphite

Monolayer isotherms were measured for 15, 18, and 20 K for para-hydrogen adsorbed on exfoliated graphite foam, and for the second, third, and fourth layers in the temperature interval of 8 to 20 K, using the standard volumetric method. From the data, the isosteric heat of adsorption, molar entropies and internal energies were obtained as a function of coverage. The values for coverages above the third layer were compared to those at the p-H₂ bulk triple point, showing that, within our experimental uncertainty, the results are closer to the values of bulk solid para-hydrogen. Critical temperatures for the second and third layers and the triple point temperature for the second layer, were determined, yielding values of T_c2 = (10.0±0.1) K, T_c3 = (11.0±0.5) K and T_t2 = (6.5±0.1) K respectively. Features occurring along the monolayer coverages are compared to transitions which occur in the para-hydrogen phase diagrams adsorbed on graphite, obtained from heat capacity measurements by other authors. From the isotherms, compressibilities were calculated as a function of coverage for several temperatures. Whenever possible the obtained results were compared to existing data in the literature.     

Spin waves in spin-polarized gases in the Knudsen regime

Boundary conditions are discussed for spin dynamics equations in dilute spin-polarized quantum gases. The bulk equations have the macroscopic hydrodynamic form even when mean free paths of the particles are large, and the main question is whether a supplementary hydrodynamic boundary condition is valid. Different boundary processes are considered including spin-conserving and non-conserving reflections, slip, formation of adsorbed surface layers, etc. The macroscopic boundary condition fails in the cases of very effective surface processes with violation of time-reversal symmetry (e.g. spin-lattice relaxation) or very high surface-induced diffusion rates. Otherwise, the surface processes are described by a simple boundary condition or by -type singularities in bulk equations. The meaning of different macroscopic parameters is clarified. The formation of dense adsorbed boundary layers changes the frequency shifts and linewidths of spin-wave resonances because of effective exchanges between surface and bulk particles and strong interactions within the boundary layers. Here the broadening of resonances is explained not only by additional surface dissipation (diffusion), but also by dephasing processes originating from a renormalization of the molecular field in the boundary layers. The results explain recent experiments by the Cornell group.     

The empowerment of service workers: what, why, how, and when

In recent years, businesses have rushed to adopt an empowerment approach to service delivery in which employees face customers "free of rulebooks," encouraged to do whatever is necessary to satisfy them. But that approach may not be right for everyone. Bowen and Lawler look at the benefits and costs of empowering employees, the range of management practices that empower employees to varying degrees, and key business characteristics that affect the choice of approaches. Managers need to make sure that there is a good fit between their organizational needs and their approach to frontline employees.     

Health resort treatment of eye diseases caused by ischemia]

The authors discuss the results of ophthalmodynamometric tests used for the assessment of cerebro-retinal vessels reactivity following carbon dioxide baths and "peat collars". An analysis of systemic and local blood pressure in the ophthalmic artery measured with Weigelin and Lobstein technique enables to assess changes in blood pressures following a/m balneologic procedures. It was found that blood pressure does not change parallelly due to the mechanism of cerebral autoregulation. Transient decrease in blood pressure in the ophthalmic artery is produced by the dilatation of the internal carotid artery indicating a potent vasodilating action of carbon dioxide.     

Prospects for the use of thermionic nuclear power plants for interorbital transfers of space vehicles in near space

Scientific-Production Association "Krasnaya Zvezda." Translated from Atomnaya Énergiya, Vol. 73, No. 5, pp. 346–350, November, 1992.     

Integration of different numerical techniques in shape optimization

Shape optimal design is the synthesis of structural analysis and mathematical programming (MP) combined with methods of computer aided geometric design (CAGD) and behaviour sensitivity analysis (SA). The main aspect in optimal shape design is the integration of these disciplines. At the same time an efficient and well-posed model must be formulated for the overall optimization problem. The present contribution deals with the hierarchy of the different modelling levels and numerical techniques of the design process. It will be shown for the frequency tuning of a bell how the individual disciplines can be identified step by step in the optimization procedure of the program CARAT (Computer Aided Research and Analysis Tool).Presented at NATO ASI Optimization of Large Structural Systems, Berchtesgarden, Sept. 23 – Oct. 4, 1991     

Comparison of hydrogeologic parameters evaluated by deep well testing programs to assess nuclear waste repository feasibility

Hydrogeologic parameters evaluated for rocks investigated in deep well testing projects for nuclear waste repository feasibility are transmissivity, hydraulic conductivity and storativity. Such studies have been carried out in rock formations of different geologic types, origins and ages for nuclear waste management agencies in North America and Europe. From transient pressure testing, an assessment of static pressure in selected fracture zones was measured from which a profile with depth was developed using modelling techniques. As well, temperatures of formation fluids and hence thermal gradients have also been provided. Hydrogeologic parameters are commonly used in risk analysis for repositories with respect to the possible escape of contaminants and worst case scenarios. The parameters are related to the rate of possible radionuclide migration into the biosphere. The techniques of the investigation and analysis methods of this work have been fully described in the literature. This paper is the first to date, however, to compare results from testing in differen geologic environments. High transmissivity zones have been observed in the upper few hundred metres of granite formations. Below that depth, the rock is more competent and discrete zones of higher permeability occur less frequently. Our studies show, however, that in these rocks, zones of high hydraulic conductivity do not always correspond to zones of high fracture frequency. Most formation pressure profiles have a vertical gradient of about 10 kPa/m. In discrete zones, deviations from this trend can occur due to vertical inhomogeneity in the rock. Thermal gradients vary considerably from one investigation site to another. For example, in the Canadian Shield, gradients are of the order of 1.0 degree C per 100 m, whereas in similar rock types in Europe, the gradient is up to 4.0 degrees C per 100 m.