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Abstract  

Physicochemical processes during thermal treatment of vanadium and phosphorus oxides mixture (1) as well as with diammonium hydrophosphate (2) in the closed system (autoclave) have been studied. In the first case, at 300 °C, the defective structure γ-VOPO4 is formed and in the second case, there was established possibility of synthesis of vanadyl hydrophosphate—the precursor of vanadyl pyrophosphate (the catalyst of n-butane oxidation to maleic anhydride). At the same time, various phases of mixed ammonium and vanadium phosphates were obtained at lower and higher temperatures.

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A horizontal DS chamber for TLC has been adapted for planar electrochromatography in closed system. A test dye mixture was separated on pre-wetted RP-8 and RP-18 chromatographic plates with acetonitrile-buffer as mobile phase. A potential of 2 kV was applied to a 10-cm plate to create the electric field. Two modes of electrochromatogram development were applied — in open and closed (pressurized) systems. The disadvantages of the open system — evaporation of the mobile phase from the plate and excessive flow of mobile phase to the surface of the adsorbent layer during development — were eliminated by use of the closed system. Highly reproducible retention was achieved during planar electrochromatography in the closed system when the adsorbent layer of the plate was pre-wetted and equilibrated with a solution of the mobile phase. Examples are presented of electrochromatograms obtained from the test dye mixture under different operating conditions. Separation efficiency in planar electrochromatography was higher than in conventional HPTLC.

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Abstract  

A procedure for preparation of a sterile closed system generator for99mTc based on conversion to zirconium molybdate of99Mo produced by neutron activation is reported. The generator is sterilized by autoclaving.99mTc is eluted using 0.9% NaCl with high yield and purity in successive elutions.

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Abstract  

The parameters of two exchange methods of preparing pure 97% labelled 17-Br-HDA in acetone and in benzene with dry NaI* in a closed system are described. In aprotic solvents the need for a phase transfer catalyst up to 50g is necessary to dissolve the dry NaI*. The use of aqueous medium in the exchange is totally prohibited. Energies of activation are calculated for both reactions.

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Abstract  

The reaction of isotope exchange between [3-(iodophenyl)methyl]guanidine, mIBG, and [131]-iodide in relatively concentrated solutions, in the presence of different ammonium salts, in a closed system, over the temperature range from 130 to 150°C, has been investigated. The reaction occurs either with (NH4)2SO4 or CH3COOH, which indicates that the reaction goes through some intermediate stages. Kinetic studies show the influence of the additives. The activation energies for the reaction with (NH4)2SO4/H2O, (NH4)2SO4/CH3COOH and CH3COOH are 121.1, 115.1 and 84.5 kJ·mol–1, respectively.

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Summary  

The influence of calcite, dolomite, pyrite and vaterite on the kinetics of uranium release from a natural rock under relevant, i.e., field conditions has been investigated. The time dependence of the U release has been studied in two different experimental procedures (open and closed systems) at laboratory temperature (21±2 °C). Performing batch experiments in tap water, the U release efficiency of a natural U-bearing rock was characterized in the presence of varying amounts of three different carbonate bearing minerals for experimental durations of up to 782 days. Another experiment was conducted for a period of 14 days in the presence of a pyrite mineral. The results demonstrate that the presence of carbonate minerals does not have any significant influence on U release in closed systems where the U concentration at saturation was ca. 54 mg/l. In contrast, in open systems, the U concentration was ca. 8 mg/l at saturation and the effects of all additives both on kinetics and saturation concentration of U were apparent.

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Abstract  

A simple method for the determination of the air–water partition coefficient (Kair/water) of radon (Rn-222) was studied using a liquid scintillation counter. In the present work, the radon activity of groundwater phase in a closed container was measured and used to calculate the partition coefficient instead of the radon activity of gaseous phase in other works. The partition coefficient was determined for four groundwater samples by using a modified equilibrium partition coefficient in closed system method. The effect of temperature on the partition coefficient was investigated at 0, 10, 20 and 30 °C. Within the temperature range, the partition coefficients were 1.72–2.03, 2.11–2.28, 2.78–3.92 and 4.93–5.61 at 0, 10, 20, and 30 °C, respectively. It was found that the effect of temperature on the air–water partition coefficient of groundwater radon was agreed well with literature values.

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Journal of Thermal Analysis and Calorimetry
Authors: Zhongliang Zhang, Xuezhong Sun, Weixia Zhou, Liqiang Zhang, Bin Li, Minggui Wang, Baozhen Yan, and Fu Tan

Abstract  

Calorimetric studies were undertaken of the heat, observed during the electrolysis of H2O in normal open and closed cell as well, employing palladium cathode. A difference in heat observed during the process between opened and closed system was found. Heat generated under different conditions was presented as a function of the working current density or voltage. Such results were briefly discussed according to general thermodynamics and electrochemistry.

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Abstract  

This study developed a modified pretinning method for labeling erythrocytes with technetium-99m in vitro using a kit which contains stannous chloride stabilized with gentisic acid (GA) in lyophilized form. This GA-kit is a sterile closed system that does not require centrifugation, washing and separation of the RBCs. The kit is simple to use and labeling takes 30 min with a typical labeling efficiency of 97.3%±1.2% for 60 determinations. Imaging studies were performed in rabbit using GA-kit in vitro labeling procedure and PYP-kit in vivo labeling. It shows that the heart-to-background ratio with GA in vitro labeling were significantly higher than with in vivo labeling. Leukocytes labeling with technetium-99m using the same GA kit also was studied. The labeling efficiency was 20–41%. Thus, the GA kit is versatile and cost-effective.

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Journal of Thermal Analysis and Calorimetry
Authors: H. -H. Emons, R. Naumann, T. Pohl, and H. Voigt

The melting and decomposition behaviour of carnallite was investigated in the closed system under dynamic heating conditions and in the open system under dynamic and quasi-isothermal and quasi-isobaric conditions in the temperature range between 20 and 300°. DTA heating and cooling cycles in the closed system illustrate the incongruent melting of carnallite and the occurrence of different magnesium chloride hydrate phases. The thermal decomposition under quasi-isothermal and quasi-isobaric conditions begins at a pressure of at least 100 kPa from the melt and under reduced pressure from the solid. In any case KCl · MgCl2 · 2 H2O is formed which is decomposed to a basic product KMgCl2.84–2.90(OH0.10–0.16.

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