Monolayer physical adsorption in narrow pores. Apparent surface dimension

Monolayer physical adsorption has been considered, taking into consideration the intrinsic volume of the adsorbate molecules. Since an adsorbed molecule occupies not only the site on the surface but also some of the neighboring volume, it creates steric difficulties for the adsorption of other molecules and leads to underestimation of the measured surface area. As a result, this value depends on the size of the adsorbate molecules and the apparent surface dimension can be introduced, even if the surface of narrow pores has no irregularities of atomic scale size. This effect was shown by simulation of adsorption on the surface of Menger sponge. Experimental data for measuring D-values on silica gels with different pore size distributions are in line with this effect.     

On integrability in elementary functions of certain classes of complex nonautonomous equations

This work is devoted to the search for integrability cases of a certain class of complex, linear second-order, nonautonomous ordinary differential equations.     

Distribution of Subdominant Eigenvalues of Random Matrices

We mainly investigate the behavior of the subdominant eigenvalue of matrices B= (b _i,j)^n,n whose entries are independent random variables with an expectation Eb _i,j=1/n and with a variance n c/n ² for some constant c 0. For such matrices we show that for large n, the subdominant eigenvalue is, with great probability, in a small neighborhood of 0. We also show that for large n, the spectral radius of such matrices is, with great probability, in a small neighborhood of 1.     

Possibility of Improving the Parameters of VVER Reactors by Using Metal-Ceramic Fuel Based on Metallic Uranium Nanopowder

Physics of Atomic Nuclei - The first results of the initial stage of studying the possibility of using the pellet oxide fuel with the addition of metallic uranium nanopowder in VVER reactors are...     

Preparation of pure monodisperse calcium carbonate particles

The non-template synthesis of monodisperse spherical particles of calcium carbonate is reported. Particles of a 3.5–4.5 μm size were produced by precipitation of calcium carbonate from alcohol solution at subzero temperatures.     

Thermodynamic Analysis of the New Adsorption Cycle “HeCol” for Ambient Heat Upgrading: Ideal Heat Transfer

Thermodynamic analysis of a new adsorption cycle recently suggested for upgrading ambient heat (the so-called “Heat from Cold” or HeCol cycle) was performed. The energy and entropy balances at each cycle stage and in each converter component were calculated for the methanol–AC-35.4 activated carbon working pair under conditions of ideal heat transfer. It is shown that useful heat can be obtained only if the ambient temperature is below a threshold temperature. The threshold temperature was calculated based on the Polanyi principle of temperature invariance and was experimentally validated. The specific useful heat can reach 200–300 J/(g adsorbent), which is of practical interest. The use of adsorbents with an abrupt change in the adsorption uptake between boundary isosters of the cycle may lead to further enhancement of the useful heat. For the HeCol cycle, the exergy losses under the conditions of ideal heat transfer are small. At low ambient temperature, the losses in the evaporator, condenser, and adsorber are comparable, whereas at higher ambient temperature the main exergy losses originate from the adsorber heating and cooling.     

Radiation catalysis: Defect transport towards a fractally rough surface

Using a self-similar model of rough surface, equations were obtained which describe the probabilityP of radiation defects generated in the near-surface volume to reach the surface. The influence of surface irregularity was analyzed in the case when the ionization depthl ₀ and the escape depthR ₀ are within the lowera and upperb cut-offs of surface fractality. It was shown that a surface roughening and an increase of the ratiol ₀/R ₀ result in a marked raise of probabilityP. Taking the effect into consideration may be of importance for quantitative analysis of radiation catalytic processes on real surfaces.