New Y(La)-M-O Binary Systems (M = Ca,Sr, or Ba): Synthesis,Physicochemical Characterization,and Application As the Supports of Ruthenium Catalysts for Ammonia Synthesis

The effect of the nature of the alkaline-earth metal on the phase composition and specific surface area of new Y(La)-M-O binary oxide compositions (M = Ca, Sr, or Ba) prepared by coprecipitation was studied. These systems were found to contain mixed compounds (M₂Y₂O₅, MY₂O₄, and MLa₂O₄), which are different in thermal stability, in addition to individual La₂O₃ or Y₂O₃ phases. The Y(La)-M-O compositions calcined at 450°C were characterized by a more developed specific surface area, as compared with that of individual La₂O₃ or Y₂O₃. An increase in the calcination temperature to 650°C was accompanied by a decrease in the specific surface area of binary compositions. Catalysts prepared by supporting K₂[Ru₄(CO)₁₃] onto the Y(La)-M-O systems were active in ammonia synthesis at 250-400°C and atmospheric pressure. The most active of these catalysts, K₂[Ru₄(CO)₁₃]/Y-Ba-O, provided a higher yield of NH₃ at 250-300°C than analogous catalysts prepared with the use of well-known supports (Sibunit, CFC-1, and C/MgO).     

Comparison of Sensitivities of Semiconductor (HPGe) and Scintillation (CeBr<Subscript>3</Subscript>) Detectors in the Measurement of Gamma Spectra Induced by Neutrons in the Model of Planetary Soil

The results of neutron-activation measurements performed using the model of planetary soil and detectors based on high-purity germanium (HPGe) and cerium bromide (CeBr₃) are reported. Gamma lines lying in the energy range from 200 keV to 8 MeV are used as indicators to compare these two types of detectors in experiments with the model irradiated by 14-MeV neutrons from a pulse neutron generator. The results will aid the design of scientific instruments for the active neutron and gamma spectroscopy of planet surfaces in future Russian and international lander missions (Luna-Glob, Luna-Resurs, and ExoMars-2020).     

Effect of dimension and type of model on statistical characteristics of scattered light

The effect of the type of the model describing a non-Gaussian relief, as well as of the problem dimension, on the statistical characteristics of scattered monochromatic light is considered. A difference in the shape of diffuse scattering indicatrices was observed for different types of surface models (with identical height distributions and autocorrelation functions). The effects revealed because more pronounced with an increase in the deviation of surface height distribution from normal and with an increase in the roughness height.     

On the minimum of several random variables

For a given sequence of real numbers , we denote the th smallest one by . Let be a class of random variables satisfying certain distribution conditions (the class contains Gaussian random variables). We show that there exist two absolute positive constants and such that for every sequence of real numbers and every , one has

-

where are independent random variables from the class . Moreover, if , then the left-hand side estimate does not require independence of the 's. We provide similar estimates for the moments of as well.

     

Calcium-modulated conformational affinity chromatography. Application to the purification of calmodulin and S100 proteins.

The purification of proteins by affinity chromatography is based on their highly specific interaction with an immobilized ligand followed by elution under conditions where their affinity towards the ligand is markedly reduced. Thus, a high-degree purification by a single chromatographic step is achieved. However, when several proteins in the crude mixture share affinity to a common immobilized ligand, they may not be resolved by affinity chromatography and subsequent "real" chromatographic purification steps may be required. It is shown that by using properly selected gradient elution conditions, the affinities of the various proteins towards the immobilized ligand may be gradually modulated and their separation may be achieved. This is exemplified by the isolation and separation of a group of Ca(2+)-activated proteins, Calmodulin, S100a and S100b, from bovine brain extract, using a melittin-Eupergit C affinity column which is developed with Ca(2+)-chelator gradients. As expected, separation of the three proteins into individual peaks, eluted in order of increasing affinity to the matrix, was obtained. Sigmoid selectivity curves calculated from the elution volumes under different elution conditions for each of the proteins were obtained, illustrating the chromatographic behaviour of the gradient affinity separation system.     

Scientific Bases for the Synthesis of Highly Dispersed Framework Zirconium Phosphate Catalysts for Paraffin Isomerization and Selective Oxidation

Results of the systematic study of the synthesis of highly dispersed framework zirconium phosphates stabilized by ammonium, lanthanum, aluminum, manganese, and cobalt cations are summarized. The synthesis involves the mechanochemical activation of a mixture of solid reactants (salts) or the sol–gel process each followed by the hydrothermal treatment (HTT) of obtained precursors in the presence of surfactants. The genesis of dispersed systems under investigation is studied by modern physical methods providing information on the state of the bulk and surface of the systems. It is found that the local structure of sol nanoparticles and zirconium phosphate crystalline nuclei arising from mechanochemical activation products depends on the nature of initial substances. This, in its turn, makes different crystallization mechanisms possible during the HTT process: the dissolution/precipitation mechanism or the mechanism of oriented mating of primary particles. The crystallization mechanism in HTT and the reaction system composition influence the nature of resulting complex zirconium phosphate phases, their thermal stability, dispersity, and porous structure parameters. The relationship between the bulk structure parameters of framework zirconium phosphates, which are controlled by varying the chemical composition and conditions of synthesis, and the surface characteristics of the systems (the strength and concentration of different Lewis and Br@nsted sites) is studied. It is shown that systems based on framework zirconium phosphates are promising catalysts for paraffin (pentane and hexane) isomerization, the selective oxidation of methane by oxygen into synthesis gas at short contact times, and the oxidative dehydrogenation of propane into propylene.     

Managing the overflow of intensive care patients

Many hospitals in the Netherlands are confronted with capacity problems at their intensive care units (ICUs) resulting in cancelling operations, overloading the staff with extra patients, or rejecting emergency patients. In practice, the last option is a common choice because for legal reasons, as well as for hospital logistics, rejecting emergency patients has minimal consequences for the hospital. As a result, emergency patients occasionally have to be transported to hospitals far away. In this work, we propose a cooperative solution for the ICU capacity problem. In our model, several hospitals in a region jointly reserve a small number of beds for regional emergency patients. We present a mathematical method for computing the number of regional beds for any given acceptance rate. The analytic approach is inspired by overflow models in telecommunication systems with multiple streams of telephone calls. Simulation studies show that our model is quite accurate. We conclude that cooperation between hospitals helps to achieve a high acceptance level with a smaller number of beds resulting in improved service for all patients.     

Structural features of self-action of laser radiation in the electromagnetic induced transparency mode

Structural features of the laser radiation self-focusing dynamics in the electromagnetic induced transparency (EIT) band are studied for an atomic system with a Λ-type energy level diagram. Effective nonlinearity of an EIT medium is manifested primarily as nonlinear dispersion (dependence of the group velocity on the wave amplitude). Qualitative analysis of the dynamics of self-action of laser pulses, which is confirmed by numerical simulation, shows that nonlinear evolution of a 3D wave packet follows the scenario of self-focusing, which serves as the background on which the envelope profile turnover and the formation of a shock wave occur at an advanced rate.