[en] In the current study, pure elemental powders of Fe and S were mixed to give the desired compositions of Fe₆₇S₃₃, Fe₅₀S₅₀ and Fe₃₃S₆₇. A SPEX 8000D high-energy ball mill was used to synthesize iron sulfide powders under an Ar-filled atmosphere. The as-milled powders were examined by conventional X-ray diffraction (XRD) and synchrotron X-ray absorption spectroscopy (XAS). The experimental results showed that mechanochemical reactions occurred during the ball milling process for all the compositions investigated. The Fe_1-xS phase was observed at the end of milling. The formation time of the Fe_1-xS phase increased with increasing sulfur content. Extended X-ray absorption fine structure (EXAFS) results revealed that the nearest neighbor bond lengths of the radial distribution function for iron decreased when iron sulfides formed. X-ray absorption near-edge structure (XANES) of sulfar K-edge distinguished better the structural evolution of these iron sulfides

[en] Phase contrast radiology using unmonochromatic synchrotron X-ray successfully imaged the grain boundaries of Al and AlZn alloy without contrast agent. Combining the high penetration of X-ray and the possibility of 3D reconstruction by tomorgraphy or stereography method, this approach can be very used for nondestructive characterization of polycrystalline materials. By examine the images with 3D perspective, we were able locate the observed void-like defects which lies exclusively on the grain boundary and identify their origin from last stage of the rolling process. We studied the Ga Liquid metal diffusion in the AlZn alloy, under different temperature and stress conditions. High resolution images, ∼2 μm, of Ga liquid metal diffusion in AlZn were obtained in real time and diffusion paths alone grain boundaries and surfaces were clearly identified. Embrittled AlZn responses to the tensile stress and fractures in a drastic different manner than the pure AlZn. These results, although very much expected from the known weakening effect of the liquid metal embrittlement demonstrated, however, that this particular radiology method is fully capable of dynamic study in the micrometer scale

[en] Spectrophotometric methods for the determination of boron in the low μg/g and ng/g range in high-purity silicon and dichloro- and trichlorosilanes were investigated in detail. The procedures established involve dissolution of silicon samples and the hydrolyzed products of chlorosilane samples in hydrofluoric acid-containing reagents followed by evaporation of the silicon matrix as H₂SiF₆. The boron retained in the treated sample solution was then determined by a spectrophotometric method using carminic acid as a chromatic reagent. Special effort has been paid to the control of the analytical blank and reproducible determination of boron. The results indicate that addition of mannitol and proper control of the evaporation process are effective in preventing volatilization of boron during the evaporation of silicon matrix and can thus attain high recovery of boron and reproducible analysis. Through meticulous control of the analytical blank and experimental conditions, the limit of detection for boron determination with the established method can be as low as ng/g levels. Application of the methods to the determination of boron in various stages of purification of silicon and trichlorosilane as well as in borophosphosilicate film was conducted. (orig.)

[en] Objective: The aim of the study was to evaluate a hand held semiconductor gamma camera in measurement of thyroid uptake, Methods: A hand held (CdZnTe) semiconductor gamma camera (eZ-SCOPE, Anzai Medical Co., Japan) without collimator was used for study. About 20uCi of I-131 solution was inserted into a capillary tube as a point source. Twenty-four patients, 11 euthyroid and 13 hyperthyroid, were studied. The radioactivity counts of the neck and thigh were measured at 24 hr after administration of 100uCi of I-131 by eZ-SCOPE with a 12 cm distance from the surface of anterior neck and thigh. Measurement was also performed by using thyroid uptake probe (Atomlab 950, Biodex Medical Systems, USA). Thyroid uptake values were calculated described previously. The uptake values were compared by paired t-test. Results: The count rates from a 100uCi of I-131 capsule obtained by eZ-SCOPE were lower than by uptake probe (40,000 cpm vs 110,000 cpm). However, the 24-hr thyroid uptake determined by these two methods was comparable. In 11 euthyroid cases, RAIU measured by probe and eZ-SCOPE were 26.7±2.7 % and 21.6±2.3%, respectively (mean ± S.D., p<0.005, paired t-test). In 13 hyperthyroid cases, RAIU measured by probe was 54.0±14.3%, which was not significantly different from 50.3± 6.6 % measured by eZ-SCOPE (p<0.005). Conclusion: The hand held (Cd Zn Te) semiconductor gamma camera is as reliable as thyroid uptake_probe for measurement of I-131 thyroid uptake. (authors)

[en] According to the ionizing radiation safety regulation approved by the ROC Atomic Energy Council (AEC), personnel dosimeter processors shall be qualified by the Chinese National Laboratory Accreditation (CNLA) program before offering dosimeter services and shall be requalified every two years. The Institute of Nuclear Energy Research (INER) was entrusted by CNLA as the central laboratory to perform the proficiency test of personnel dosimeters for laboratory accreditation in December 1990. Such proficiency tests, based on ANSI N13.11 (1983), have been conducted three times, in 1991, 1993 and 1995, to accommodate for dosimeter processors' need for requalification every two years. The results of the latest proficiency test showed that, among the nine participants, six participants tested with eight categories all passed the test. Of other three participants tested with six categories, two passed the test and one failed this test in two categories. The central laboratory will adopt the new version of HPS N13.11 (1993) to replace ANSI N13.11 (1983) as new criteria for the next proficiency test to be conducted in 1998

[en] The specific structure and morphology often play a critical role in governing the excellent intrinsic properties of the compound semiconductor. Herein, meso structured ZnO with excellent methanol-sensing properties was prepared by a structure replication procedure through the incipient wetness technique. The investigation on the crystal structure and morphology of the resultant material shows that the product consists of hexagonally arranged meso pores and crystalline walls, and its structure is an ideal replication of CMK-3 template. Consequently, meso structured ZnO was fabricated as a gas sensor for methanol. The excellent methanol-sensing performance was achieved at a relatively low operating temperature of 120°C. In comparison with the non porous ZnO prepared through conventional coprecipitation approach, meso structured ZnO material shows the higher sensitivity and stability. Furthermore, it shows the discrimination between methanol and ethanol sensitivity, which makes it a good candidate in fabricating selective methanol sensor in practice

[en] Accurate density values of N,N-dimethylformamide (DMF) with diethyl ether (DEE), dipropyl ether (DPE), diisopropyl ether (DisoPE), dibutyl ether (DBE) or dipentyl ether (DPeE), were measured over the whole composition range at temperatures ranging from (298.15 to 358.15) K under atmospheric pressure by an Anton Paar densimeter. To gain some insight into the several aggregations of molecular interactions present in these mixtures, we calculated the excess molar volumes, V ^E, of the mixtures from density data over the entire experimental conditions. The qualitative analysis of the excess molar volumes was made by taking into consideration of the molecular size of ethers and the nature of DMF. Negative excess volumes were observed in all these mixtures except for the high mole fraction of DMF in the system of DMF + DPeE at T 298.15 K. It was found that the V ^E values of these systems are increased with increasing the temperature. The experimental V ^E data were correlated accurately with the Redlich-Kister type equation

[en] Optical photoluminescence studies are performed in self-ion (Ga⁺)-implanted nominally doped n-GaN nanowires. A 50 keV Ga⁺ focused ion beam in the fluence range of 1x10¹⁴-2x10¹⁶ ions cm^-2 is used for the irradiation process. A blueshift is observed for the yellow luminescence (YL) band with increasing fluence. Donor-acceptor pair model with emission involving shallow donor introduced by point-defect clusters related to nitrogen vacancies and probable deep acceptor created by gallium interstitial clusters is responsible for the shift. High-temperature annealing in nitrogen ambient restores the peak position of YL band by removing nitrogen vacancies

[en] An in situ synthesis of ZnS and CdS quantum dots (QDs) in an aqueous solution of sodium hyaluronate (Hyal) produced foils emitting light on excitation with a UV light. The wavelength of emission was only slightly QDs size and more QDs concentration dependent and reached up to ∼320 nm in the case of ZnS and ∼400-450 nm in the case of CdS. Nanoparticles remained as non-agglomerated 10-20 nm nanoclusters. CdS/Hyal and ZnS/Hyal-QDs biocomposites were characterized using photoluminescence (PL), IR spectrometric techniques, and Transmission Electron Microscopy (TEM). The absolute molecular weights, radii of gyration, R_g, and thermodynamic properties of the obtained foils are given. Electric resistivity studies performed for the hyaluronic foil in the 100-1000 V range have revealed that the hyaluronate foil has very weak conducting properties and QDs only insignificantly affect those properties as QDs practically did not interact with the foil. Size exclusion chromatography showed a decrease in the molecular weight of the hyaluronate after generation of QDs in its solution, particularly in the lower molecular fraction of the hyaluronate. The generation of CdS QDs was more destructive for the polysaccharide matrix.