Acetate reduction synthesis of Sr2Si5N8:Eu phosphor and its luminescence properties

A novel synthesis method was developed for the efficient red phosphor, Eu²⁺-activated Sr₂Si₅N₈, by employing the strontium acetate as both the reducing agent and strontium source. The phase purity of final product was strongly dependent on the heating rate of the precursors. Sr₂Si₅N₈:Eu²⁺ (2 at%) phosphor presented a broadband excitation spectrum in the range 300–500 nm, matching well with the blue emission (400/460 nm) of current InGaN light-emitting diodes (LEDs). The red emission peaking at 619 nm gave the relatively high (about 155%) intensity compared with the Y₃Al₅O₁₂ (YAG) (P46-Y3) standard phosphor. In addition, the saturated chromatic coordinates (0.638, 0.359) allowed it a promising candidate as a red phosphor in white LEDs application for illumination or display.     

含5-氟脲嘧啶齐聚物的合成

<正> 5-氟脲嘧啶是用于治疗肺癌、肾癌、乳癌、结肠癌等癌变的药物。虽然5-氟脲嘧啶具有上述疗效,但在临床应用时,尚存在恶心,呕吐,腹泻,白细胞、血小板下降等副作用。更为严重的缺点,是既对肿瘤细胞有活性,同时也作用于正常细胞,为克服此缺点,将抗癌药物与低分子化合物结合,诸如激素、磺胺,这些是已知能集聚在一定组织内药物,但利用此法,迄今也很少获得成效。     

ICP—AES分析的线性回归校准曲线

本文对ICP-AES分析中2种线性回归方法的校准曲线作了比较和讨论。对大多数元素而言,用加权法得到的校准曲线的斜率比不加权校准曲线的斜率略大,减小3校准曲线在低浓度部分的弯曲,曲线明显优于不加权校准曲线。将2种方法得到的校准曲线进行比较时,应将剩余标准偏差(或剩余变差平方和)及曲线截距等加以综合考虑。用含零标的标准系列制作校准曲线可使曲线的截距更接近原点,有利于提高在低浓度部分校准分析的准确性。     

Mechanism of enhancement of conductivity for pyrolyzed polypyrrolone film at high temperature

The effects of the pyrolytic temperature on the structure of the pyrolyzed polypyrrolone (PMDA-DAB) films were investigated. The structure of pyrolyzed PMDA-DAB film was characterized by elemental analysis, XPS spectra, x-ray diffraction, and SEM images. It suggests that the pyrolysis process of PMDA-DAB films consists of carbonization and graphitization processes, and the transitional temperature is at ca. 800°C. During carbonization process (T_p < 800°C), most oxygen is removed and the enhancement of conductivity with the pyrolytic temperature may be due to an extended conjugation of π-electron orbitals resulting in an increase of the number of charge carriers. During graphitization (T_p > 800°C), both oxygen and hydrogen are removed completely, and an increase in the mobility of charge carriers may increase conductivity with pyrolytic temperature. A graphite-like structure with heterocyclic rings containing nitrogen atoms is proposed for the PMDA-DAB film pyrolyzed at 1200°C. © 1996 John Wiley & Sons, Inc.     

铁锑氧化物表面氧的性质及氨的吸附特性

研究了Fe₂O₃和Sb₂O₄及Sb/Fe比由1/9至9/1五种复合氧化物表面氧的TPD行为。Fe₂O₃在200～450℃间有少量氧脱出,Sb₂O₄在700℃以后出现脱氧峰,而Sb/Fe复合氧化物则出现所谓α和β脱氧峰。随Sb/Fe比增加α氧的脱附活化能也增高,Sb/Fe比为3/7、5/5和7/3时分别为33、36、51kcal/mol。Fe-Sb氧化物中α氧比β氧对烯烃氧化具有更高的活性。在50—275℃范围内NH₃在Fe-Sb氧化物上的吸附等温线符合Freundlich式,同时由NH₃的TPD可明显看出Fe-Sb氧化物具有不同强度的吸附中心,它们与所含表面氧有关,但表面氧对NH₃的氧化是很弱的。讨论了烯烃选择氧化反应与表面氧强度之间的联系。     

光催化氧气还原制备H2O2

H2O2广泛应用于化工和环保领域,其分解的唯一产物是水,有利于生产与自然生态系统的协调可持续发展.工业上H2O2的合成主要是通过蒽醌法间接合成,该方法能耗大,污染环境.而直接由H2与O2混合制备H2O2,具有极大的安全风险,且需要消耗大量H2.通过光催化技术将O2和H2O转化成H2O2的方法,避免了H2与O2的直接混合...     

长链不饱和脂肪酸甲酯的臭氧化反应

长链不饱和脂肪酸甲酯的臭氧化反应;选择性     

Cosmic duality in quintom Universe

In this Letter we study the duality in two-field quintom models of dark energy. We find that an expanding Universe dominated by quintom-A field is dual to a contracting Universe with quintom-B field.     

The role of short exchange length in the magnetization processes of L10-ordered FePt perpendicular media

A three-dimensional micromagnetic model with non-uniform grain size distribution has been built up to study the magnetization process in FePt L1₀ perpendicular media. A 3D model of a single FePt magnetic grain is also set up for comparison. The high magneto-crystalline anisotropy K_u results in a short exchange length l_ex in FePt nanograins. Therefore a magnetic grain is divided into smaller grids on the order of l_ex. The simulated perpendicular and longitudinal loops are consistent with experiments, and it is explained why the measured perpendicular H_c is relatively smaller compared with the saturation field of the longitudinal loop in the FePt perpendicular medium.     

Doppler angle and flow velocity mapping by combined Doppler shift and Doppler bandwidth measurements in optical Doppler tomography

Accurate estimation of flow velocity requires measurement of Doppler angle, which is not available in general clinical applications. We describe a novel method of direct Doppler angle and flow velocity mapping that uses a conventional single-beam optical Doppler tomography system. The Doppler angle is estimated by combination of Doppler shift and Doppler bandwidth measurements, and flow velocity is calculated from the Doppler shift and the estimated Doppler angle. In vivo study of lip microvascularization demonstrates that this method is capable of providing both flow speed and flow direction information.