Results 1 - 10 of 61701
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[en] Physicochemical properties of systems referred to the type Tc/carrier, Tc-M/carrier (M = Pt, Pd, Rh, Ru, Ni; carrier = γ-Al2O3, SiO2, MgO, rare earths, TiO2, ZrO2, C) were studied using the methods of spectroscopy, X-ray diffraction and electron microscopy. It was ascertained that ionic forms of Tc, products of technetium interaction with sublayer are present on the carriers surface besides metallic Tc; the presence of second metal gives rise to formation of TcxMy clusters. Catalytic properties of mono- and bimetallic systems in reactions of different types were studied. It is shown that Tc activity is similar to Pt activity. In bimetallic systems synergetic effect was discovered, i.e. nonadditive increase in catalytic activity compared to monometallic catalysts
[ru]С использованием методов спектроскопии, рентгенографии и электронной микроскопии изучены физико-химические свойства систем типа Тс/носитель, Тс-М/носитель (M = Pt, Pd, Rh, Ru, Ni; носитель = γ-Al2O3, SiO2, MgO, редкие земли, TiO2, ZrO2, C). Установлено, что на поверхности носителей кроме металлического Тс присутствуют ионные формы Тс, продукты взаимодействия технеция с подложкой; при наличии второго металла образуются кластеры ТсxМy. Исследованы каталитические свойства моно- и биметаллических систем в реакциях разного типа. Показано, что активность Тс близка к активности Pt. В биметаллических системах обнаружен синергетический эффект - неаддитивное повышение каталитической активности по сравнению с монометаллическими катализаторами
[en] Experimental-theoretical and applied investigations of complex processing of sulphide concentrates of molybdenum are carried out, as a result of which, roasted molybdenum concentrate accordingly with a content of copper and sulphur not more than 0,08 and 0,09%; disulphide of molybdenum with high purity for preparing lubricants; disilicide of molybdenum with a method of direct synthesis from sulphide concentrates of molybdenum; lead molybdate with high purity and stoichiometric composition for growing single crystals; ligature materials for alloying steel with molybdenum; sulphides of silicon for the flotation of copper-molybdenum ores are obtained
[en] We have observed vortex penetration into Nb thin films with square arrays of square holes with variable sizes and lattice constants. We find that when the lattice spacing is large and the width of superconducting line is narrow, vortices penetrate diagonally rather than parallel to the nearest neighbor direction. This phenomenon is also confirmed in NbTiN samples with the same geometry. We also confirm that the direction of edge relative to that of hole array is not relevant. Possible origin of such a preferential penetration is proposed.
[en] The purpose of this study is to determine the technetium-99m pertechnetate ("9"9"mTcO_4) intercellular uptake by different types of cell lines. HeLa, human fetal osteoblast (hFOB), glial and glioma cell lines grown in 6-wells culture plates were incubated with "9"9"mTcO_4 of activity of 200, 400, 600, 800 and 1000 μCi for 30 minutes at 37 degree Celsius and 5 % CO_2 humidified atmosphere. After incubation, the cells were washed 3 times with phosphate buffer saline to remove the extracellular traces of "9"9"mTcO_4. Measurement of the intercellular "9"9"mTcO_4 into the cells was calculated. The intercellular uptake of "9"9"mTcO_4 was found to be inversely correlate to the radioactivity. HHeLa cell shows the highest uptake followed by hFOB, glial and glioma cell lines. Comparison of uptake between normal and cancer cells present indistinguishable results. The findings of this study suggest that the intercellular uptake of "9"9"mTcO_4 is highly dependent on the type of cells despite no significant different of uptake was found between normal and cancer cell lines. The level of radioactivity is also an important determinant factor that influence the uptake of "9"9"mTcO_4 into the cell. The study will be the first precedent toward understanding the cellular characteristics and pharmacokinetic of non-invasive imaging tracer for future molecular imaging and therapy. (author)
[en] Activated carbons impregnated with compounds of chromium, copper and silver (Cr-Cu-Ag) are widely used for removing toxic substances from air, mainly in respiratory protection for industrial and military applications. Toxicological and epidemiological studies have shown chromium (especially hexavalent Cr) to have carcinogenic properties. Hence, research has been launched to develop a new adsorption-catalytic complex without chromium, which is intended to replace the activated carbon-catalyst (Cr-Cu-Ag) system. In this work activated carbon obtained from plum stones as carrier and molybdenum, copper and silver salts as impregnates were studied. The porous structure of the carbon carrier was investigated using low temperature nitrogen adsorption. Cyanogen chloride breakthrough dynamics was analyzed in order to characterize the protection properties. Studies on the substitution of chromium by non-carcinogenic metals will be continued
[en] Spherical powders with good flowability and high stacking density are mandatory for powder bed additive manufacturing. Nevertheless, the preparation of spherical refractory tungsten and tungsten alloy powders is a formidable task. In this paper, spherical refractory metal powders processed by high-energy stir ball milling and RF inductively coupled plasma were investigated. By utilizing the technical route, pure spherical tungsten powders were prepared successfully, the flowability increased from 10.7 s/50 g to 5.5 s/50 g and apparent density increased from 6.916 g cm−3 to 11.041 g cm−3. Alloying element tantalum can reduce the tendency to micro-crack during tungsten laser melting and rapid solidification process. Spherical W-6Ta (%wt) powders were prepared in this way, homogeneous dispersion of tantalum in a tungsten matrix occurred but a small amount of flake-like shape particles appeared after high-energy stir ball milling. The flake-like shape particles can hardly be spheroidized in subsequent RF inductively coupled plasma process, might result from the unique suspended state of flaky particles under complex electric and magnetic fields as well as plasma-particle heat exchange was different under various turbulence models. As a result, the flake-like shape particles cannot pass through the high-temperature area of thermal plasma torch and cannot be spheroidized properly. (paper)
[en] The composition and temperature dependences of site occupation for Al, Cr, W, and Nb in MoSi_2 are investigated by using a thermodynamics model and first principles calculations. A simple parameter measuring the substitution energy difference between Si and Mo sites reflects the nature of site occupancy. At 0 K, these elements prefer Si sites in Mo-rich and Mo sites in Si-rich, and show no site preference in stoichiometric MoSi_2. At elevated temperature, the site occupation behaviors show strong dependence on both composition and temperature. Some calculated results have been certified in previous experiments. (paper)
[en] This study is intended for developing a rapid, sensitive, selective, and accurate analytical procedure for determining traces of Zirconium (Zr) in the presence of Molybdenum (Mo) and Aluminum (Al) inevitably eluted as chemical and/or radiochemical impurities along with the isotonic solution of Technitium - 99m using saline (0.9% NaCl solution) in a solvent extraction 99mTc-generation process utilizing Zirconium polymolybdates [99Mo] as a reactor irradiation target to be subject to extraction on a bed of Aluminum Oxide (or Alumina Al2O3) as a protective layer absorbing [99Mo] and mitagating its undesired breakthrough As the whole study has been planned; so as each of these elements can individually be investigated, this first portion is solely devoted to the spectrophotometric determination of (Zr) as a Xylenol - Orange complex; with the objective primarily being the analytical evaluation of this procedure and determining its integrity as an analytical method capable of achieving the purpose of properly assaying the eluates. The study of the xylenol- orange complex of zirconium has shown that the absorption is maximum at the (534nm) wavelength when, and only when the acidity of the work-media is 0.2N H2SO4. It was also found; using two different methods (Mole-ratios and Continuous variations), that the composition ratio of the complex is [1:1], and the stability constant of the complex is (1.59 x 106). Furthermore, several other investigations were also carried out to determine the response of the procedure parameters to the influence of various factors such as acidity of the working media, amount of complexing reagent, order-of-addition of reagents, time dependence, and interferences.