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141.
142.
Synthesis of 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) involving base hydrolysis was optimized. Fluorine-18 was isolated from irradiated water to more than 90% by sorption of [1
8F]fluoride on QMA anion-exchange resin, which was followed by elution with a 96 : 4 (by volume) acetonitrile-water mixture containing Kryptofix 2.2.2 and potassium carbonate (molar ratio 2 : 1). This composition is the best for preparing the complex [K/K2.2.2]+
18F- used in nucleophilic fluorinations. No additional azeotropic drying is required. Base hydrolysis under optimized conditions (40-45°C), followed by neutralization with HCl, removal of traces of the solvent, and purification of the final product on a combined SCX/Alumina N column, yielded [1
8F]FDG of high radiochemical (>99%) and chemical purity with minimal product loss. With an RB-86 robotic system (Anatech, Sweden), the synthesis time was 38 min. The procedure is used in the Institute of Human Brain, Russian Academy of Sciences for routine synthesis of FDG; the radiochemical yield of the product by the end of synthesis (EOS) is reproducibly high: 63±3% (n = 40). 相似文献
143.
D. C. Peets R. Liang C. Stock W. J. L. Buyers Z. Tun L. Taillefer R. J. Birgeneau D. A. Bonn W. N. Hardy 《Journal of Superconductivity and Novel Magnetism》2002,15(6):531-534
We have grown cubic centimeter-size crystals of YBa2Cu3O x suitable for neutron studies, by a top-seeded melt-growth technique. Growth conditions were optimized with an eye toward maximizing phase purity. It was found that the addition of 2% Y2BaCuO5 and 0.5% Pt (by mass) were required to prevent melt loss and to obtain the highest crystallinity. A neutron diffraction study on a mosaic of six such crystals found that the final Y2BaCuO5 concentration was 5%, while other impurity phases comprised less than 1% by volume. The oxygen content was set to x = 6.5, the crystals were detwinned, and then carefully annealed to give the well-ordered ortho-II phase. The neutron study determined that 70% of the mosaic's volume was in the majority orthorhomic domain. The neutron (006) and (110) rocking curve widths were ~1° per crystal and ~2.2° for the mosaic, and the oxygen chain correlation lengths were >100 Å in the a- and b-directions and ~50 Å in the c-direction. 相似文献
144.
The crystal structure of [NpO2{OC(NH2)2}5]ClO4·H2O and [NpO2Cl{OC(NH2)2}4] was studied by X-ray diffraction. The electronic absorption spectra of these complexes were recorded. The coordination polyhedron of Np in both complexes is a distorted pentagonal bipyramid. There is no cation-cation interaction of neptunyl cations in these complexes. 相似文献
145.
Androstenedione labeled with tritium at positions 1 and 2 was prepared. The molar radioactivity of the sample prepared using homogeneous catalysts was as high as 1.4-1.5 PBq mol-
1. [1,2-3H]Androst-4-ene-3,17-dione can be converted into the [1-3H]steroid with the molar radioactivity of 0.9 PBq mol-
1. 相似文献
146.
It is essential in the simulation of power electronics applications to model magnetic components accurately. In addition to modeling the nonlinear hysteresis behavior, eddy currents and winding losses must be included to provide a realistic model. In practice the losses in magnetic components give rise to significant temperature increases which can lead to major changes in the component behavior. In this paper a model of magnetic components is presented which integrates a nonlinear model of hysteresis, electro-magnetic windings and thermal behavior in a single model for use in circuit simulation of power electronics systems. Measurements and simulations are presented which demonstrate the accuracy of the approach for the electrical, magnetic and thermal domains across a variety of operating conditions, including static thermal conditions and dynamic self heating 相似文献
147.
Aluminum and magnesium alloys are the base structural materials in aircraft and spacecraft engineering. The main stages of the development and introduction of light alloys are described. 相似文献
148.
Determination of dislocation densities in HCP metals from X-ray diffraction line-broadening analysis
Griffiths M. Sage D. Holt R. A. Tome C. N. 《Metallurgical and Materials Transactions A》2002,33(13):859-865
X-Ray diffraction (XRD) line-broadening analysis has been performed on highly textured Zr-2.5Nb specimens which had been deformed
in tensile tests to produce well-controlled dislocation structures. An iterative deconvolution method has been applied to
extract the broadening function for the material, using as standards, a Zr single crystal and a 0 pct deformed specimen. In
both cases, for specific tensile tests, a significant contribution to the basal line braodening was observed, which was clearly
not directly related to the dislocation structure generated by the deformation, i.e., so-called c-component dislocations having a component of their Burgers vectors perpendicular to the basal plane. Calculations showed
that the extent of basal line broadening cannot be attributed to the secondary effect of strain from a-type dislocations, i.e., dislocations with Burgers vectors parallel with the basal plane. It is concluded that most of the line broadening observed
was the result of intergranular strain distributions. These distributions are most prominent for grains oriented with their
c-axes perpendicular to the tensile-deformation axis and resulted in basal-plane line broadening even when there were few,
if any, c-component dislocations present.
This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals
and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following
ASM committees: Materials Science and Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic
Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee. 相似文献
149.
150.
The kinetics of changes in the bound water content in dietetic sucrose-free sponge cakes (DC) during storage was investigated. The effect of edible films of polymyxan, pectin, xanthan, and carboxymethylcellulose upon this kinetics was also investigated. The quantitative changes in both states of water (slightly bound water and strongly bound water) were registered by combined dynamic analysis (thermogravimetry analysis, TGA, and differential thermal analysis, DTA). The moisture changes in DC crumb were analyzed by drying out to constant mass. The rate constants were determined according the equation q = qoe-kt. The values of rate constants 'k', in day-1, concerning the different edible films were as follows: for crumb moisture is (8.00 ≤ k ≤ 12.47) × 10-3, for bound water is (3.07 ≤ kw ≤ 6.26) × 10-2, for slightly bound water is (4.22 ≤ k1 ≤ 8.49) × 10-2 and for strongly bound water is (2.02 ≤ k2 ≤ 5.62) × 10-2 as compared to 18.53 × 10-3, 7.16 × 10-2, 9.04 × 10-2, and 5.36 × 10-2 in the uncovered DC, respectively. The best water-retaining effect in respect to crumb moisture during storage was ascertained in the use of polymyxan and xanthan films. The lowest rate constant values for bound water and its two states were measured for DC covered with pectin. The relation between the kinetics of both bound water states during storage and ageing of the crumb of DC covered with different edible films and the crumb microstructure was represented. By means of scanning electron microscope was read the smallest change in crumb microstructure of pectin-covered DC on the sixth day of storage. 相似文献