Exchange processes in aqueous solutions of saccharides

The results of an experimental study of proton-exchange processes in aqueous solutions of sucrose and dextran with a molecular weight of 40 000 by the NMR technique with pulse magnetic field gradient (PMFG) are reported. The lifetimes of the proton in the state of saccharide hydroxyl groups in aqueous solutions and the probability distribution functions of this quantity in both dilute and highly concentrated solutions are determined with the use of the special NMR-PMFG procedure. It is shown that the concentration dependences of the saccharide hydroxyl proton lifetimes and the self-diffusion coefficients of water show a well-pronounced correlation

Recommendations for the creation of a program for children’s camps in Rantasalmi, Finland

The research is focused on the study of the differences in the programs of children's camps in differ-ent countries, particularly in Russia and Finland, and formulating recommendations for the creation of a program for children's camps in Rantasalmi adapted for the Russian market. As the object of study was chosen organization of children's leisure activities in children's camps in the two countries. It should be noted that the subject of the study were not specialized camps. Programs of camps, which were the subject of research, also include educational goals. Children’s camps, which are locat-ed in Russia, were analyzed with particular attention. Rantasalmi Travel aims to enter the Moscow market of tourist services. Therefore, potential buyers of tours were selected Russian citizens residing in the Moscow region. This study was divided into two parts: theoretical and practical. The theoretical chapter provides information about the differences in the organization of leisure activities for children in Russia and Finland on the basis of the analysis of the theoretical material. The practical part is devoted to the study of children's camps in Rantasalmi. The practical part pro-vides introductory information about Rantasalmi Travel and describes the methods of research. This part completes the formulation of recommendations for the creation of the program in children's camps in Rantasalmi adapted for consumers from Moscow

An Investigation of the Structure of a Porous Substance by NMR Cryodiffusometry

Cryoporosimetry and diffusometry, along with traditional techniques, are used to determine the characteristics of porous media. In real systems characterized by a pore-size distribution and a complex geometry of the pore space, the possibilities of these methods are limited. To obtain more data on the structure of the pore space, it was suggested that these approaches be combined in a unified experimental technique called cryodiffusometry. A concept of this technique lies in the investigation of self-diffusion in liquid-containing regions in the course of sequential stepwise melting of a substance precrystallized in pores. Possibilities of cryodiffusometry were demonstrated by investigating of the pore structure of gypsum stone as an example. An analysis of the data obtained showed that pores of the sample are shaped like layers characterized by an equally probable alignment in space. The layers are longer than 40 μm and vary in thickness from 200 to more than 1000 Å; in this case, regions of different thickness are randomly distributed over the layer. The thinner the layer, the more the shape of layer portions of different thicknesses deviates from spherical

Concentration dependences of self-diffusion coefficients of water molecules in dilute solutions of saccharides

The DAq(c) concentration dependences of the self-diffusion coefficients of water molecules in aqueous solutions of saccharose and dextran (molecular weight 40000) are analyzed in terms of hydration phenomena. The exponential DAq(C) dependence in dilute solutions is determined by interactions of water molecules with hydroxyls and oxygen atoms of saccharide molecules; H-bond lifetime τg is three times longer than correlation time τ0 of translational mobility of molecules in pure water

The nuclear magnetic resonance method in researches of structure of porous space in the conditions of a filtration

On the basis of experimental results obtained in Example sandstones at different fluid flow rates by PFG NMR it is shown in principle the possibility of registering and determining the relative proportion of dead or stagnant zones. The possibility to study molecular exchange between molecules diffusing into the stagnant zones, and the molecules involved in the flow

Академічна мобільність як величезна можливість для українських студентів

Rapid implementation of modern technologies, expanding of the information space and development of the channels of communication demand perfect knowledge about the functioning of the world community from the Ukrainian students. As we know, education in Ukraine quite often does not live up the expectations of young ambitious people, but not everyone can afford to study abroad. Do we have a solution of this problem? Of course, we do, because today every well-educated and diligent student has a chance to use at least one of the academic mobility programs.Швидке впровадження сучасних технологій, розширення інформаційного простору та розвиток каналів комунікації вимагають від українських студентів досконалих знань про функціонування світової спільноти. Як ми знаємо, освіта в Україні досить часто не виправдовує очікувань молодих людей, але не кожен може дозволити собі навчання за кордоном. Чи є у нас рішення цієї проблеми? Звичайно, ми це робимо, адже сьогодні кожен освічений та старанний студент має шанс скористатися хоча б однією з програм академічної мобільності

NMR study of the kinetics of butane and hexane adsorption from vapor phase by porous glasses

The kinetics of butane and hexane sorption from vapor phase by porous glasses is studied by the pulsed NMR technique. The sorption process is revealed to proceed in two stages: monomolecular adsorption and capillary condensation. The rate of adsorption is limited by the rate of adsorbate transfer to the adsorbent surface, with the latter rate being described by the classical diffusion flux. It is shown that ultramicropores are filled simultaneously with the formation of a monolayer. The relative content of molecules in such pores is estimated. At the stage of monomolecular adsorption and at the initial stage of capillary condensation, when the adsorption proceeds from the vapor phase of butane-hexane or butane-deuterated hexane mixtures, butane molecules are predominantly sorbed and followed by their partial displacement by hexane molecules. The rate of the capillary condensation of butane from the mixture is 15-18-fold lower than that from the vapor phase of butane alone which is explained by a decrease in the gradient of chemical potential. It is shown that, when adsorption occurs from a nonequilibrium butane-hexane mixture, anomalous kinetic curves are observed because the driving force of adsorption changes in the course of establishing equilibrium in the liquid phase. © 2005 Pleiades Publishing, Inc

Time dependent self-diffusion coefficient of molecules in porous media

Using Monte Carlo simulation, the time dependence of the self-diffusion coefficient D(t) in porous media was investigated. It was found to be a decaying function with a cut-off to zero at time t. The exact form of decay depended on the details of the geometry of porous space. The details of the geometry were described by the surface orientation autocorrelation function. The short-term behavior of D(t) was governed by the surface population of the molecules

Rodlike polymer gelatination as studied by PFG NMR: Fibrin polymerization in human plasma

The structure formation in rodlike polymers was investigated by the example of polymerization of fibrin rodlike molecules in native plasma. Translational mobility of fibrin molecules in anticoagulated plasma and native plasma during fibrin polymerization was studied by pulse field gradient nuclear magnetic resonance. It was shown that the diffusion decay of anticoagulated plasma can be fitted by the sum of exponents and fibrin molecules have the self-diffusion coefficient Df of 1.53·10-11 m2/s. The diffusion decay of native plasma during fibrin polymerization becomes nonexponential and is described by the lognormal distribution of fibrin self-diffusion coefficients. Qualitative and quantitative changes of the spectrum of fibrin self-diffusion coefficients (SDCs) during polymerization were investigated and analyzed. A symmetrical broadening of the spectrum at the beginning of polymerization and symmetrical narrowing at its final stages with conservation of the most probable SDC was explained on the basis of the hypothesis about the simultaneous action of fibrin polymerization and lyses

Porous media characterization by PFG and IMFG NMR

Fully and partially filled with tridecane quartz sand was studied by different NMR techniques. The set of NMR experiments was carried out to obtain information about porous media geometry and fluid localization in it in case of partially filled porous space. The study was done using three NMR approaches: pulse field gradient NMR (PFG NMR), DDif experiment and tau-scanning experiment. The possibility to use all three approaches to study porous media properties even at the high resonance frequency is shown together with complementarity of the given by them information. Thus, first two approaches give information about porous sizes and geometry, at the same time tau-scanning experiment allows us to obtain information about distribution of internal magnetic field gradients in the porous space and draw conclusions about fluid localization in it. © 2007 Elsevier Inc. All rights reserved