Radiation Induced Optical Absorption of Cubic Lead Fluoride Crystals and the Effect of Annealing

Transparent and colorless lead fluoride crystals with sizes of 20 × 20 × 20 （ram3） are irradiated with several doses of γ-rays from a ^60Co source. Their transmittance spectra before and after irradiation are measured, and a new parameter ΔT = Tb - Ta is defined to evaluate the irradiation damage. Three optical absorption bands peaking at 27Onto, 37Onto and 50Onto are found in the plots of AT versus wavelength, and their intensities increase with the irradiation dose. These optical absorption bands, except the one at 27Onto, can recover spontaneously with time. Thermal annealing treatment can enhance this recovery of the transmittance, while the optimum annealing temperature for different samples depends on the irradiation dose.     

Charge ordering modulations in a Bi_0.4Ca_0.6MnO₃ film with a thickness of 110 nm

The low temperature sample stage in a transmission electron microscope is used to investigate the charge ordering behaviours in a Bi 0.4 Ca 0.6 MnO 3 film with a thickness of 110 nm at 103 K.Six different types of superlattice structures are observed using the selected-area electron diffraction(SAED) technique,while three of them match well with the modulation stripes in high-resolution transmission electron microscopy(HRTEM) images.It is found that the modulation periodicity and direction are completely different in the region close to the Bi 0.4 Ca 0.6 MnO 3 /SrTiO 3 interface from those in the region a little further from the Bi 0.4 Ca 0.6 MnO 3 /SrTiO 3 interface,and the possible reasons for this are discussed.Based on the experimental results,structural models are proposed for these localized modulated structures.     

数学建模的教学活动对大学数学教学的影响

通过分析数学建模的特点,现行大学数学教学的现状,讨论数学建模对大学数学教学的影响。     

XeCl准分子激光器寿命的研究

XeCI准分子激光器的寿命主要取决于HCI消耗的情况。实验结果表明,在环氧树脂筒的激光器室中,补充适量而价廉的HCI气体,器件寿命就可延长。我们在一次充入Xe气和Ar气的前提下,适时补充几次HCI,已获得大于1.03×10~6个脉冲输出,即在每秒5.3次的重复率和脉冲能量约100mJ的情况下,器件连续工作54hr还能正常运转。最大输出能量160mJ,文中还讨论了HCI对激光输出性能的影响。     

复合添加剂BA1摩擦化学的FTIRM光谱法研究

采用微区红外光谱技术（ＦＴＩＲＭ）研究抗磨添加剂（简称ＢＡ１）的抗磨机理，通过改变添加剂的浓度，摩擦载荷的大小和选择不同的摩擦时间，观察摩擦前后的物性变化，分析磨痕的红外光谱图，推断其作用机理，结果表明，ＢＡ１在摩擦过程中发生氧化分解反应，最终在摩擦副基质上形成一层光滑致密的聚合物膜，致使其摩擦系数减小。     

中国发酵化学的进展——为中国化学会成立五十周年而作

中国传统发酵已有数千年的历史,发酵食品如酒、酱油、醋、豆腐乳、红麯等为广大人民所喜爱。解放后酒精发酵技术日益进步,酶制剂、有机酸、氨基酸、核酸类物质、抗生素、激素、维生素等新兴发酵工业相继研究成功,并投入生产,今日发酵工业已成为中国的重要工业之一。各省、市、区均设与发酵有关的研究机关及学     

乳腺癌患者中磁共振成像参数与E-cadherin和CA153的相关性

本研究探讨磁共振成像参数与上皮钙黏蛋白(E-cadherin)、癌抗原153(CA153)的相关性及对乳腺癌患者的诊断价值。选取113例确诊为乳腺癌的患者作为研究组,另选取同期75例体检健康的志愿者作为对照组。使用酶联免疫吸附法(ELISA)检测E-cadherin,采用LIAISON全自动化学发光免疫分析仪检测血清CA153。两组均进行磁共振成像检查,对比两组的磁共振成像参数容量转移常数(Ktrans)、速率常数(Kep)、血管外细胞外间隙容积比(Ve),分析Ktrans、Kep、Ve与E-cadherin、CA153的相关性及对乳腺癌患者的诊断价值。结果显示,乳腺癌患者E-cadherin水平降低,病情越严重E-cadherin水平越低;乳腺癌患者CA153水平升高,病情越严重CA153水平越高。E-cadherin与Ktrans、Kep、Ve呈负相关,CA153与Ktrans、Kep、Ve呈正相关(P<0.05)。Ktrans、Kep、Ve三项联合对乳腺癌患者的诊断价值较高(P<0.05)。磁共振成像对乳腺癌患者有较高的诊断价值,且乳腺癌患者血清中E-cadherin...     

飞秒激光双光子加工的极限分辨力

采用3维压电微移动台高速扫描方式控制曝光时间与高精密转台精确控制圆形渐变衰减片以控制曝光功率两种方法,曝光时间和曝光功率可分别精确控制至0.02 ms和7 pW。通过精确控制聚合阈值附近处的曝光时间和曝光功率,分别在玻璃基板上获得了35 nm和45 nm的聚合物纳米线条,分别为所使用激光波长的1/22和1/17。实验结果表明,当曝光时间或曝光功率在加工阈值附近时,曝光时间和功率的微量减少会使聚合线宽急剧下降。