Effect of ionizing radiation on the extraction of Am(III) with <Emphasis Type="Italic">p-tert</Emphasis>-butylthiacalix[4]arene from alkaline carbonate solutions

The effect of γ-irradiation of tert-butylthiacalix[4]arene (TCA) solutions in m-nitrobenzotrifluoride (NBTF) and tetrachloroethylene (TCE) on the extraction of ²⁴¹Am from alkaline carbonate solutions was studied. TCA itself remains stable upon γ-irradiation of its solutions in NBTF to a dose of 200 kGy, but the diluent undergoes strong degradation. The radiation resistance of TCA in TCE is considerably lower: A dose of 70 kGy causes complete degradation of TCA. In the TCA–TCE–aqueous phase system, sulfate ions appear upon γ-irradiation as the final product of the extractant radiolysis. A large number of γ-radiolysis products of TCE and TCA were detected by HPLC and GCMS. The products of radiolysis of TCA in TCE, compared to the initial extractant, have lower molecular mass and higher polarity. The results show that chlorinated diluents are not promising diluents for thiacalixarene in extraction processing of alkaline high-level waste.     

Energy metabolism and fuel mobilization: from the perioperative period to recovery

PURPOSE: Previous studies of monochromatic visual evoked potentials confirm the strong suppression of (the cortical representation of) paracentral retinal areas of functionally amblyopic eyes, by a flat response to a blue stimulus. A clinical trial stimulating these areas with blue light was encouraging, and justified a prospective comparison of this treatment with conventional classic treatment. SUBJECTS AND METHODS: In 50 strabismic children with amblyopia, the blue filter treatment protocol (flash stimulation with, and the wearing of, a blue filter during occlusion of the better eye for one hour daily) was compared with the classical treatment (full time total occlusion by patch) in a prospective matched and randomized study. Patients 3 to 7 years old without previous treatment and a visual acuity up to 0.3 were admitted to the study. Visual acuity and fixation behavior were used as the parameters of comparison. Visual Evoked Potentials by monochromatic flashes were also studied. Results of treatment were compared after 6 months. RESULTS: The visual acuity outcome for the blue filter treatment was "statistically significantly" better (p=0.005). The greatest improvement was seen in the subgroup of children with eccentric fixation (p=0.01). Fixation behavior also showed a better outcome from the blue filter treatment (p=0.05) favoring especially children between 3 and 5 years. In children of this age with a visual acuity better than 0.1 we found a very "statistically significant" difference between the two treatments (p=0.004). In children 3 to 5 years old with poorer visual acuity we also found a "statistically significant" difference in the two treatments (p=0.04). The interocular difference of amplitude on the Visual Evoked Potentials also demonstrated more improvement in children treated with the blue filter. This treatment improved especially the cortical response to blue flash stimulation, correlating to paracentral retinal areas. CONCLUSIONS: The blue filter treatment protocol provided better results for treating amblyopia than the conventional classic occlusion treatment method. We propose that stimulation of these paracentral retinal areas triggers a better disinhibition of a functionally amblyopic eye.     

Synthesis of the nitrogen-fixing enzyme system in oligonitrophilic bacteria

Oligonitrophilic bacteria were cultivated on a medium containing only 2.5--10.0 mg/litre of nitrogen compounds. They assimilated elementary nitrogen only after utilization of these nitrogen compounds during growth and formation of nitrogen-fixing enzyme system. Their cells grown on a medium containing high concentrations of bound nitrogen did not fix nitrogen during further incubation in the atmosphere of 15N; therefore, the enzymes involved in nitrogen fixation were induced. These organisms are characterized by diauxia during their growth on media containing "start" doses of nitrogen. Enzymes catalysing nitrogen fixation in azotobacter are also induced. But, contrary to oligonitrophilic bacteria, the azotobacter does not require nitrogen compounds in the medium in order to adapt to molecular nitrogen, and its growth curve is not of a biphasal character. These data and the evidence of other authors suggest that all nitrogen-fixing microorganisms are characterized by the induced, not constitutive, enzymes involved in reduction of molecular nitrogen.     

Some problems of the moral and psychological training of medical service personnel

The authors' experience with 45 papillosphincterotomies, performed for diseases of bile passages and chronic pancreatitis, is reported. The details of the operative technic, employed by the authors, are described. The technic of papillosphincterotomy on a conus-shape sound by means of a "laser scalpel" proved to be the most perfect one. Careful observation of the surgical technic made it possible to gain favourable results--only 1 of 45 operated patients died. Papillosphincterotomy is largely advocated in stenoses and concretions in the large duodenal papilla, strictures of choledocho-duodenoanastomoses, care should be taken not to overwiden indications to the operation concerned.     

Multichannel Strain-Gauging System Equipped with Microprocessor for Strength Measurements of Structures

The structure of a 64-channel microprocessor strain-measuring system designed for operation with strain gauges and thermal transducers is discussed. The system measures strain and temperature during strength and thermal-strength tests of structures of machines and buildings. The computer codes have been designed in the Borland C++ Builder medium for operations with isolated transducers (1/4-bridge mode), and in the modes 1/2-bridge, bridge, and thermal transducer. The system has been certified. The paper describes examples of its practical utilization in strength tests of struts of the Tupolev-154B airliner and of the undercarriage foreleg of an aerobatic airplane.     

Monitoring of welding aerosol compositions (a review)

Physicochemical properties inherent in the solid component of welding aerosols (SCWA) are characterized. The features of SCWA sampling are considered. Methods are indicated which are most commonly used for the analysis of SCWA in Russian and foreign analytical practice. Destructive and nondestructive methods of SCWA analysis are compared, and their advantages and disadvantages are noted. By particular examples, it is shown that because of the complexity of phase and chemical composition of SCWA samples, rather frequently, one observes a loss of monitored elements in the course of the decomposition of exposed filters. Techniques for making synthetic calibration samples are considered for both classes of methods. In the case of using the X-ray fluorescence method, it is difficult to prepare calibration samples adequate to real SCWA samples collected on a filter. The comparative variant of neutron activation analysis involves synthetic mixtures for the calculation of the content of analytes containing one or two components. Metrological characteristics are presented for SCWA analysis techniques.     

Catalytically active composite materials with porous aluminum oxide matrix modified by γ-MnO<Subscript>2</Subscript> nanoparticles

Manganese dioxide has been deposited on the surface of an aluminum foil anodized in 3% solution of oxalic acid using the methods of thermal decomposition of manganese nitrate and potassium permanganate, as well as chemical synthesis, in the same solutions with intermediate drying and subsequent annealing. It has been demonstrated that the method of thermal decomposition of potassium permanganate is the most suitable for producing thermally stable “ultradispersed γ-MnO₂/nanostructured Al₂O₃/Al” composites. The produced composites are active in the reaction of oxidation of CO into CO₂ at temperatures above 180°C. Studies by means of the methods of scanning electron and atomic force microscopies have shown that the concentration and surface distribution of γ-MnO₂ particles depend on the morphological structure of aluminum oxide that is determined by conditions of the metal surface pretreatment and application of the pore broadening operation.