The Effect of Thermal Treatment on the Structural and Electrokinetic Properties of Porous Glass Membranes

The properties of porous glass membranes prepared by acid leaching of sodium borosilicate glasses 8B and 8V and also 8B glass containing small amounts of fluorine and phosphorus (SFP) are comprehensively studied. The effect of the composition and conditions of thermal treatment of the original and porous glasses on their structural (specific surface area, structure resistance coefficient, average pore radius, volume porosity, and filtration factor) and electrokinetic characteristics (conductivity, counterion transport numbers, and electrokinetic potential) in KCl solutions at neutral pH values is studied. It is shown that an increase in thermal treatment temperature T _TT of the porous glasses from 120 to 750°C leads to a decrease in structure resistance coefficient β of 8B membranes. For membranes prepared from SFP glass, β values, efficiency coefficients, and counterion transport numbers are virtually independent of T _TT at 120–600°C and increase at T _TT = 750°C. Specific surface area and volume porosity decrease with a rise in T _TT for all studied membranes. The observed regularities of variations in the membrane characteristics are explained by the increasing fraction of large pores because of sintering of small pores with an increase in T _TT and by the different amounts of secondary silica in the pore space of porous glasses.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 299–307.Original Russian Text Copyright © 2005 by Volkova, Ermakova, Sidorova, Antropova, Drozdova.     

Search for the Dirac monopole by means of vavilov-cherenkov radiation at the 70 Gev IHEP (Institute for High Energy Physics Serpukhov) proton synchrotron

At the proton energy of 70 GeV on the internal target of the IHEP proton synchrotron the search was made for magnetic charges over the Vavilov-Cherenkov radiation and characteristic polarization. Eight Cherenkov counters of a special construction served as detectors. Possible events were recorded with two fast five-ray oscillographs triggered by 6-fold coincidences. The efficiency of the magnetic charge recording was about 10%.The proton beam of 6.4×10¹⁴ intensity traversed the target-radiator; and not a single case of the production of the Dirac monopole with the magnetic charge from minimal one of about 2/3g _D (g _D =68.5e) up to2g _D was recorded. This means that in the conditions of our experiment the upper boundary of the cross section of the Dirac monopole production by 70 GeV protons per nucleon of Si and O nuclei for magnetic charges of masses from 3 up to 5·5m_p was found to be(95%) 10^–40 cm².On leave fromDepartment of Nuclear Physics, Comenius University, Bratislava, Czechoslovakia.The authors express their gratitude to the workers of the enterprise Dioptra (Turnov, SSR) for making of optical details for the device for SDM.     

Structural and electrokinetic characteristics of ultra-and nanoporous glasses in tetraethylammonium chloride solutions

The structural and electrokinetic characteristics of ultra-and nanoporous glasses produced from basic sodium borosilicate glass have been investigated in tetraethylammonium chloride solutions. Colloido-chemical characteristics of the membranes have been compared with those determined in sodium and potassium chloride solutions. It has been found that the regularities of variations in counterion transference numbers and efficiency coefficients are related to a decrease in tetraethylammonium cation mobility in the membranes.     

Determination of cisplatin in blood plasma by liquid chromatography with mass spectrometry detection

A method is proposed for the determination of the cytotoxic antineoplastic drug cisplatin in blood plasma by reversed-phase high-performance liquid chromatography with mass spectrometry detection. The conditions of the formation of a cisplatin derivative with sodium diethyl dithiocarbamate and its isolation from the matrix using solid-phase extraction on a hydrophilic lipophilic adsorbent Oasis HLB are optimized. The limit of the quantitative determination of cisplatin was 10 ng/mL. The method is validated in accordance to the Food and Drug Administration (FDA) requires and was appllied to the pharmacokinetical study on the isolated lung perfusion by cisplatin.     

Self-organization as the driving force for the evolution of the biosphere

Synergic parallels between the mechanisms of the spatio-temporal evolution of physic-chemical and biological systems are considered. The evolution of the biosphere is treated as self-organization in the hierarchy of the active media, which is its driving force. The superposition of selection, vertical and horizontal gene transfer, as well as the processes of divergence and convergence of species, constitutes the synergetic out-line of biological evolution.     

Adsorption of potential-determining ions on porous glasses of different compositions

The adsorption characteristics are studied for nano- and ultraporous glasses (PGs) produced from sodium borosilicate glasses and a glass containing small amounts of fluoride ions and phosphorus oxide by acid (HCl) leaching and additional alkaline (KOH) and thermal treatment. The surface charges σ₀ of PGs are determined by continuous potentiometric titration in 10⁻³−1 M NaCl, KCl, and (C₂H₅)₄NCl solutions. Only negative surface charges of PGs are observed for all investigated systems. The |σ₀| value is predetermined by the following factors: the composition of PG, the pore radius in the nanometer region (r ≤ 13 nm), the specificity of counterions, the content of secondary silica in the pore space, and the temperature of the additional thermal treatment of the membranes. The introduction of fluoride ions and phosphorus oxide into sodium borosilicate glass, an increase in the pore sizes and the amount of the secondary silica in PGs, and a rise in the specificity of counterions enhance the |σ₀| values, which decrease with a rise in the temperature of the thermal treatment due to the surface dehydration and dehydroxylation. For ultraporous glasses (r > 13 nm), the surface charge is almost independent of the pore radius.     

Photon echoes in molecular iodine vapors and nanofilms as a method of optical data processing

Properties and parameters of the photon echoes (PEs) used in optical data processing are analyzed. Physical methods for constructing functional processors and measuring devices on the basis of PE are proposed. Experiments on detecting femtosecond PEs in inorganic nanofilms at the room temperature are described.     

Limiting Behavior of Surface Measures on Spaces of Trajectories

Mathematical Notes -     

Chromatographic determination of sildenafil in blood plasma using spectrophotometric and mass-spectrometric detection

Methods for the determination of sildenafil in human blood plasma by reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) and mass-spectrometric (MS) detection have been developed. Sildenafil was isolated from blood plasma by solid-phase extraction on Sep-Pak Vac tC18 cartridges with the recovery 95 ± 4%. The limits of quantification of sildenafil were 20 and 5 ng/mL using HPLC-UV and HPLC-MS methods, respectively.     

Ultrasonic Intensification of Sample Preparation for the Spectrophotometric Determination of Arsenic in Foodstuffs

A rapid procedure has been developed for the spectrophotometric determination of arsenic in various foodstuffs. The stimulating effect of ultrasound at the sample preparation stage has been found. The best parameters of ultrasound (frequencies from 22 to 40 kHz, intensity no less than 3.43 W/cm², treatment time 3 min) for the ultrasonic stimulation of digestion of some foodstuffs have been found.