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1.
A facility for the continuous production of iodine-123 by spallation of elemental caesium by 482 MeV protons has been in operation at a TRIUMF beam dump for about 2 years. Radioxenon from the target is efficiently trapped on alumina which is subsequently used to remove the121Te decay product. The yield is 100 mCi/h from a 20 gm/cm2 target at 10 μA. Impurities are125I<2% and121Te<0.2% at 27 hours after end of production. The123I consists mainly of iodide along with significant iodate impurity. The product is used extensively in Canadian clinics for thyroid analyses and for labelling radiopharmaceuticals.  相似文献   
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A procedure is described for the liquid extraction of ingrown201Tl from its precursor201Pb using N-benzylaniline. The yield for a double extraction averaged 95.9±3.2% for thallium; 2.9±4.2% for lead. Yields for back extraction into acetic acid averaged 93.7±1.5%.  相似文献   
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An effective temperature inferred from the slope of kinetic energy spectra of the emitted fragments is not reflected in the relative populations of excited states of the emitted nuclei. We found that the excited state populations of 6Li, 7Li and 7Be emitted near 90° in the lab from the reaction of 490 MeV 14N with Ag are significantly lower than those expected on the basis of their effective temperature.  相似文献   
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Possible causes of degradation of electro-optic systems operating in a space environment include not only the effects of radiation but also the effects of temperature, temperature cycling, atomic oxygen effects (for low-Earth orbits), micrometeoroid impacts, and contamination effects. For the majority of electro-optic components, the radiation environment in space does not present a significant problem. For a few components, or for electro-optic systems that must operate in a high radiation environment, special precautions must be observed. The effects of radiation, as well as other problems of the space environment, on electro-optic components, including recent results from the LDEF satellite experiments and some later measurements, are reviewed. Guidelines for materials and component selection shielding are presented.  相似文献   
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为扩大非电话业务,即增值服务的发展,许多移动运营商都纷纷推出手机上网服务(GPRS),以促进通过手机的数据消费业务,内容提供商也表示,通过手机的内容浏览占了他们收入的主要部分。但是新业务的推出所带来的负面影响也是不容忽视的。有媒体报道:许多手机与网络运营商“结盟”,设置了一键上网”,GPRS自动启动:无需申请,拨弄按键,手机能带领青少年用户随时上网。可是,下载的内容却良莠不齐,连孩子们最爱的手机游戏都点缀着恋爱体验”的字眼。“若3G来临,青少年手机上网问题将更为严峻.”目前,GPRS等手机网络距3G仍有“半步之遥”,在技术…  相似文献   
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Monomeric Cu(I) amido and thiolate complexes that are supported by the N-heterocyclic carbene ligand 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) catalyze the hydroamination and hydrothiolation of electron-deficient vinylarenes with reactivity patterns that are consistent with an intermolecular nucleophilic addition of the amido/thiolate ligand of (IPr)Cu(XR) (X = NH or S; R = Ph, CH2Ph) to free vinylarene.  相似文献   
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The monomeric Cu(I) complexes (IPr)Cu(Z) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, Z = NHPh, OEt, or OPh) react with YH (Y = PhNH, PhCH2NH, EtO, or PhO) to catalytically add Y-H bonds across the C=C bond of electron-deficient olefins to yield anti-Markovnikov organic products. Catalytic activity has been observed for olefins CH2C(H)(X) with X = CN, C(O)Me, or CO2Me as well as crotononitrile. Preliminary studies implicate an intermediate in which the C-Y bond forms through a nucleophilic addition pathway.  相似文献   
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