改性硫氧镁胶凝材料的配制及性能研究

为确定工业级轻烧氧化镁粉与七水硫酸镁溶液配制改性硫氧镁胶凝材料的最优参数,分别研究了不同氧化镁/七水硫酸镁摩尔比,硫酸镁溶液浓度及水稳剂水玻璃对硫氧镁胶凝材料工作和力学性能的影响.结果表明:随着氧化镁/硫酸镁摩尔比的提高,硫氧镁水泥的初凝时间逐渐缩短,流动性逐渐降低,抗压和抗折强度逐渐提高;随着七水硫酸镁浓度的提高,硫氧镁水泥的抗压抗折强度也呈现增长趋势,MgO:MgSO4·7H2O:H2O摩尔比为14:1:12时,硫氧镁胶凝材浆体的28d抗压和抗折强度分别达到38.3MPa和7.0MPa.耐水性研究表明,加入氧化镁质量2%的水玻璃可以很好地改善硫氧镁水泥的耐水性.     

天目铁木愈伤组织和芽苗诱导技术

以天目铁木嫩茎尖为外植体,应用均匀设计法筛选其基部愈伤组织诱导和愈伤组织再分化芽苗的最适合培养基.结果表明,最适合的嫩茎尖基部愈伤组织诱导培养基为1/2DR+TDZ 2.30 mg·L^-1+2,4-D 0.55 mg·L^-1,诱导率为93.5%;愈伤组织芽苗再分化培养基为1/2DR+TDZ 3.30 mg·L^-1+KT 0.70 mg·L^-1,分化率达99.8%以上. 成功建立了天目铁木嫩茎尖离体诱导愈伤组织和芽苗再分化体系,且再生芽苗与野生植株染色体数目相同.     

Oxygen photo-adsorption related quenching of photoluminescence in group-III nitride nanocolumns

GaN and InGaN nanocolumns of various compositions are studied by room-temperature photoluminescence (PL) under different ambient conditions. GaN nanocolumns exhibit a reversible quenching upon exposure to air under constant UV excitation, following a t^−1/2 time dependence and resulting in a total reduction of intensity by 85–90%, as compared to PL measured in vacuum, with no spectral change. This effect is not observed when exposing the samples to pure nitrogen. We attribute this effect to photoabsorption and photodesorption of oxygen that modifies the surface potential bending. InGaN nanocolumns, under the same experimental conditions do not show the same quenching features: The high-energy part of the broad PL line is not modified by exposure to air, whereas a lower-energy part, which does quench by 80–90%, can now be distinguished. We discuss the different behaviors in terms of carrier localization and possible composition or strain gradients in the InGaN nanocolumns.     

一维新型阶梯函数光子晶体透射特性

研究了阶梯型折射率n22、n11(阶梯分布高度)的大小、对应的分布厚度、不同入射角以及缺陷模对阶梯函数型光子晶体透射特性的影响.由费马原理给出光在函数光子晶体中的运动方程,再由电磁传播理论给出函数光子晶体的传输矩阵,进一步推导出函数光子晶体的透射率以及电场分布的表达式.研究表明,1)随n22,n11大小或者厚度改变,其禁带变宽;2)随光的入射角增加,其禁带变窄;3)当加入缺陷层时,随着缺陷层介质折射率增加,缺陷模强度减小且位置发生红移;4)在函数光子晶体中,缺陷层前电场分布保持不变,而在缺陷层处以及之后的电场强度都明显增强,这不同于常规光子晶体的电场分布仅在缺陷层处局域增强.     

治疗胆石症蒙药苏斯—12中多种元素的ICP-AES法测定及分析

通过分析治疗胆囊炎、胆石症的蒙药苏斯—12中微量元素含量,探讨蒙药苏斯—12的药效与微量元素含量的关系。应用高压密封微波消解、电感耦合等离子体原子发射光谱法(ICP-AES)对蒙药苏斯—12进行微量元素含量分析。在蒙药的配制及整体研究工作中发现它们含有多种氨基酸和丰富的微量元素,实验结果表明：苏斯—12中含有丰富的微量元素,尤其Ca,Al,Mg,Fe,Sr,Mn,Zn,Cu等元素的含量比较高,而Pb,Cd,As等元素含量相对低,都低于国家限定值。加标回收率在94.63%～106.40% 之间,相对标准偏差RSD≤3.35 %,检出限在≤0.009 μg·L-1。蒙药苏斯—12有效控制和治疗胆囊炎、胆石症,总有效率达91.2%和100%,蒙药苏斯—12中的微量元素与药效之间有密切的关系。     

四川泸定县泥石流灾害成因、特征与防治建议

泸定县地处川西高原与四川盆地的过渡地带,地质环境条件复杂,分布泥石流沟127条,发育密度054条·10km-2。在遥感解译和地面调查基础上,论述了泸定县泥石流灾害成因、发生特征、危害和发展趋势,提出了相关防治建议。(1)成因表现为复杂的断裂构造导致流域内松散物源丰富,较大的相对高差提供了良好势能条件,而汛期集中强降雨则提供了动能条件,且雨量条件中当日雨量与前期有效降雨量之间具有幂函数关系; (2)发生特征表现出典型的空间群发性(包括2005-06-30群发性泥石流、2005-08-11群发性泥石流和2006-07-14群发性泥石流)与时间的夜发性; (3)危害方式主要包括淤埋、冲毁、侵蚀、堵河4种,泥石流已造成74人死亡; (4)发展趋势表现为泥石流沟多处于形成期和发展期(113条,占89%),发生的年际准周期由20a缩短至不足10a,且发生条(次)由4条(次)增加至44条次(2005年); (5)泸定县泥石流防治的突出问题表现为城镇泥石流问题、泥石流堵塞主河问题、风景区泥石流问题与冲沟泥石流问题,建议通过科学规划、风险防御体系构建、土木工程治理、监测预警等措施予以防御。     

Monte Carlo模拟研究抗体-抗原复合物生长的标度行为

通过Monte Carlo模拟方法对抗体-抗原复合物在等活性和非等活性条件下生长的标度行为进行了研究. 模拟所用算法的有效性通过在等活性条件下的模拟结果与解析结果之间的一致性得以证明. 在模拟中, 主要考察了抗体-抗原复合物的数量分布函数、重均聚合度以及特征关联长度在临界点附近的标度行为, 给出相应的标度指数, 并以其检验溶胶-凝胶相变的广义标度律. 研究结果表明, 非等活性对抗体-抗原复合物的生长具有显著影响, 可为临床免疫分析提供相应的理论线索.     

Temporal behavior of a high repetition rate infrared optical parametric oscillator based on periodically poled materials

The temporal behavior of a nanosecond pulsed singly resonant periodically poled lithium niobate optical parametric oscillator has been studied both theoretically and experimentally. Taking into account the cylindrical symmetry of the system, a numerical model based on the Hankel transform has been developed. Good agreement is obtained between experiment and simulation. Moreover, the computation time is reduced roughly by a factor of 60 compared to the usual simulation software. Received: 23 April 2001 / Published online: 19 September 2001     

Stabilisation of fcc cobalt layers by 0.4 nm thick manganese layers in Co/Mn superlattices

Epitaxial Co/Mn multilayers (0.75 to 6 nm Co, 0.4 nm Mn layer thickness) have been grown on mica substrates covered by a (0002) Ru buffer layer. The structural properties of these layers have been studied using X-ray diffraction, nuclear magnetic resonance (NMR), and high resolution transmission electron microscopy (HRTEM). The Co layers, grown as face centred cubic (fcc), were found to be stabilised by the very thin Mn layers. Data obtained using X-ray diffraction and NMR were analysed and found to be in good agreement, while Monte-Carlo simulations were used to interpret the data and calculate the expected diffracted intensity and NMR spectra. The HRTEM data show that the Mn layers give rise to a large strain contrast extending, in the growth direction, over a distance which exceeds the thickness of the Mn layers. The superlattices could be described as having an fcc structure containing randomly located stacking faults with varying densities. The results verify the presence of a dominant, almost perfect phase of fcc stacking, and of a faulted hcp phase, while the number of defects increases with the Co layer thickness. Received 27 October 1999 and Received in final form 29 May 2000