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121.
122.
Applications of chalcogenide glass optical fibers 总被引:2,自引:0,他引:2
Chalcogenide-glass fibers based on sulfide, selenide, telluride and their rare-earth-doped compositions are being actively pursued worldwide. Great strides have been made in reducing optical losses using improved chemical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite this, chalcogenide-glass fibers are enabling numerous applications that include laser power delivery, chemical sensing, and imaging, scanning near field microscopy/spectroscopy, IR sources/lasers, amplifiers and optical switches. 相似文献
123.
124.
一缩二甘醇酸体系荧光分析法同时测定钆和铽 总被引:3,自引:0,他引:3
本文研究了Gd^3^+,Tb^3^+与一缩二甘醇酸形成络合物的荧光性能及发光机理,探讨了Gd^3^+,Tb^3^+同时测定的最佳条件和共存离子的影响。Gd^3^+,Tb^3^+的检测限分别为160和3ng/ml。并将该法成功地应用于稀土氧化物中Gd^3^+,Tb^3^+的测定。 相似文献
125.
Nanocrystalline TiO2 samples with mesoporous structure were prepared via a solvothermal treatment of surfactant-stabilized TiO2 sols. The samples were obtained from media of different acidities including nitric acid, deionized water, and ammonia (denoted as HT-1, HT-2 and HT-3, respectively). These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2-sorption (BET surface area), micro-Raman spectroscopy, infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were tested by the self-photosensitized degradation of an azo dye, Mordant Yellow 10 (MY), in aqueous solution under visible light irradiation. The results reveal that all three samples have high surface area and are pure anatase phase. The sample prepared in nitric acid medium possesses the most ideal mesoporous structure and also exhibits a blue shift in the Raman spectrum. All three samples show much higher photocatalytic activity than the commercial P-25. The activity order of the three samples is HT-1>HT-2>HT-3. 相似文献
126.
Abstract— Skin tumors were induced in hairless mutant mice following a single exposure to ultraviolet radiation (UV). Tumors were first noted as early as 7 weeks following irradiation. The UV, emitted by FS20/40T12 fluorescent lamps, was principally in the 280–320 nm spectral region with a peak at 313 nm. Single (skin surface) doses of 3 times 104 J/m2 to 24 times 104 J/m2 were delivered in 3 h or less. The higher doses resulted in more severe acute damage as well as greater tumor yield. Most of the tumors were benign hyperplastic epithelial papillomas; 4 out of 96 tumors examined histologically proved to be squamous cell carcinomas. This appears to be the first report of experimental carcinogenesis due to a single UV exposure, not requiring exogenous chemical promotion. 相似文献
127.
Xin-hua Wan Hui-lin Tu Ying-feng Tu Dong Zhang Ling Sun Qi-feng Zhou Yu-ping Dong Mao Tang Department of Polymer Science & Engineering College of Chemistry Peking University Beijing China Department of Materials & Chemical Engineering Beijing Institute of Technology Beijing China 《高分子科学》1999,(2):189-192
The first TEMPO-mediated "living" free radical polymerization of liquid crystallinemonomer, 2, 5-bis[(4-methoxyphenyl)oxycarbonyl]styrene(MPCS), was carried out at 130℃ withBPO as an initiator. The molecular weight of the polymer can be varied from rather low values to highvalues while maintaining narrow polydispersity. It was observed that the polymerization of MPCSproceeded much faster than that of styrene. A tentative explanation for this fast polymerization wassuggested. 相似文献
128.
Song H Hecimovic S Goate A Hsu FF Bao S Vidavsky I Ramanadham S Turk J 《Journal of the American Society for Mass Spectrometry》2004,15(12):1780-1793
Dysregulation of proteolytic processing of the amyloid precursor protein (APP) contributes to the pathogenesis of Alzheimer's Disease, and the Group VIA phospholipase A(2) (iPLA(2)beta) is the dominant PLA(2) enzyme in the central nervous system and is subject to regulatory proteolytic processing. We have identified novel N-terminal variants of iPLA(2)beta and previously unrecognized proteolysis sites in APP constructs with a C-terminal 6-myc tag by automated identification of signature peptides in LC/MS/MS analyses of proteolytic digests. We have developed a Signature-Discovery (SD) program to characterize protein isoforms by identifying signature peptides that arise from proteolytic processing in vivo. This program analyzes MS/MS data from LC analyses of proteolytic digests of protein mixtures that can include incompletely resolved components in biological samples. This reduces requirements for purification and thereby minimizes artifactual modifications during sample processing. A new algorithm to generate the theoretical signature peptide set and to calculate similarity scores between predicted and observed mass spectra has been tested and optimized with model proteins. The program has been applied to the identification of variants of proteins of biological interest, including APP cleavage products and iPLA(2)beta, and such applications demonstrate the utility of this approach. 相似文献
129.
Furton KG Hong YC Hsu YL Luo T Rose S Walton J 《Journal of chromatographic science》2002,40(3):147-155
Solid-phase microextraction (SPME) combined with gas chromatography (GC) is optimized and applied to the analysis of street-cocaine samples followed by the field-testing of isolated chemicals using certified detector dogs. SPME proves to be a very sensitive and rapid method for isolating odor chemicals from street-cocaine samples. SPME-GC and activated charcoal strip (ACS)-SPME-GC signature profile methods are developed for the detection and quantitation of cocaine-odor chemicals, including the optimization of controllable variables such as fiber chemistry, extraction time, and desorption time. The volatile odor chemicals in representative illicit cocaine samples are identified and quantitated by the ACS-SPME-GC signature profile method and direct injection. Field tests with drug detector dogs show methyl benzoate to be the dominant signature odor chemical along with cocaine on U.S. currency at a threshold level of approximately 1-10 microg when spiked or when 10 ng/s methyl benzoate is diffused from polymer bottles, which is required in order to initiate an alert. No other substance studied initiated consistent responses by the drug dogs. The results indicate that the microgram levels of cocaine that have been reported on circulated U.S. currency are insufficient to signal an alert from law-enforcement trained drug detector dogs. 相似文献
130.
John T. Shaw Christine E. Brotherton Robert W. Moon Mark D. Winland Mark D. Anderson Keith S. Kyler 《Journal of heterocyclic chemistry》1980,17(1):11-16
A much improved synthesis of the heretofore difficultly obtainable 2,6-diaminopyrazine (4) was afforded by the low-pressure catalytic hydrogenation (palladium on carbon) of 2,6-diazido-pyrazine (2) ; reaction of 2,6-dichloropyrazine (1) and sodium azide gave 2 in 84% yield. The outcome of the reduction was found to be solvent dependent: 1,2-dimethoxyethane containing aqueous ammonia gave 4 in 83% yield; 1,2-dimethoxyethane alone gave 5-aminotetrazolo[1,5-a]-pyrazine (3) in 26% yield. Additional alternative syntheses of 3 and 4 are described. A number of acyl and azo derivatives of 4 were prepared. Reactions of 2 with dimethyl acetylenedicarboxylate and ethyl acetate (base catalyzed) leading to vic-triazole derivatives are also described. 相似文献