Effect of the Surface Nonuniformity of Dispersed Diabase on Properties of Composites

Adsorption of acid-base (Hammett) indicators and Fe(III) hydroxo complexes on the surface of dispersed diabase containing 45-52% silica, which is a promising polymer filler, was studied. Changes in the energy-related characteristics of the surface in the course of grinding and chemical modification of diabase with carbon from a mixture of CCl₄ and CH₄ were analyzed.     

Preparation of ion-exchange fiber from polypropylene waste with grafted polyacrylic acid

A procedure was developed for preparing weakly acidic cation exchanger from polypropylene fiber wastes by grafting of acrylic acid to the preoxidized surface of the fiber in an aqueous solution.     

A model of active acid-base surface sites for zinc sulfide electroluminescent phosphors

Results of studies into surface properties of ZnS: Cu,Al and ZnS: Cu electroluminescent phosphors by the indicator method were summarized. The surface and electrooptical properties of these phosphors were examined in relation to the reaction batch composition and synthesis atmosphere, as well as to heat-treatment and electron-beam-induced modification regimes. On this basis, the structure of the surface active sites having different acid powers was established, and a surface model for zinc sulfide electroluminescent phosphors was proposed.     

Estimation of the permittivity of polymeric composite dielectrics from the surface characteristics of the filler using a thermodynamic model

A linear correlation between the permittivity of a composite dielectric based on polyvinyl alcohol cyanate and the content of active surface sites in its filler (dispersed barium titanate) was established. This correlation, in combination with a thermodynamic model of composite dielectrics, allows estimation of their permittivity from the surface characteristics of the filler.     

Optimal Loan Management

Optimal loan repayment is posed as a linear programming problem. Reduction of problem size is achieved by decomposition and introduction of additional constraints.     

Feasibility of isotopic exchange in the system [125I] iodide - undecahydro-iodo-closo-dodecaborate(2-) anion

Derivatives of the closo-dodecaborate dianion are routinely used or proposed for use in boron neutron capture therapy of cancer. The use of radioactive label on closo-dodecaborate might facilitate pharmacokinetic studies. The use of nucleophilic reactions might be of advantage if derivatives of closo-dodecaborate were oxidation sensitive. The aim of this study was to estimate the feasibility of isotopic exchange in radioiodide - iodo-undecahydro-closo-dodecaborate system. We demonstrated that copper-catalyzed isotope exchange in this system in molten acetamide provides a labeling yield of 78.4±1.1% after 30 minutes at 170 °C. The influence of the ratio between amounts of substrate and catalyst, temperature and time on the labeling yield was studied.     

Critical behavior of the heat capacity of the manganite La<Subscript>0.87</Subscript>K<Subscript>0.13</Subscript>MnO<Subscript>3</Subscript>

The heat capacity of the manganite La_0.87K_0.13MnO₃ has been measured in the temperature range 80–350 K. The nature of the ferromagnetic phase transition and the critical properties of heat capacity near the Curie temperature have been studied. The regularities of variations in the universal critical parameters near the phase transition point have been established. The calculated critical exponent and amplitudes of the heat capacity with allowance for corrections on the scaling (α = −0.13 and A ⁺/A ⁻ = 1.178) correspond to the critical behavior of the 3D Heizenberg model.     

Production of high yield [13N] ammonia by proton irradiation from pressurized aqueous solutions

The method of direct production of large quantities of [¹³N]ammonia in the cyclotron water target for clinical cardiac studies by PET or synthetic uses was considered. Two main approaches based on the proton irradiation either of dilute aqueous ethanol solution under helium pressure or pure water pressurized by hydrogen were evaluated. Using ethanol as a target additive at the relatively low helium pressure of 400 KPa up to 22.2 GBq (600 mCi, EOB) of final product can be produced with radiochemical purity of more than 98%. Under comparable conditions the water target pressurized by hydrogen was about two times less effective for production of [¹³N]NH₃ because of the formation of considerable amounts of [¹³N]N₂. A possible mechanism of labelled nitrogen production was discussed.