光参量效应中低阶色散对超短高斯脉冲展宽的影响

以宽度为50fs的超短脉冲和负单轴晶体CsLiB6O10（CLBO）为例，对非线性光学晶体中低阶群速度色散（GVD）导致的超短高斯脉冲和超高斯脉冲的脉冲展宽进行了理论分析。在光参量相互作用过程中，对初始无啁啾和有啁啾调制的超短高斯脉冲的脉冲展宽机制和因素进行了数值计算，得出群速度色散导致超短脉冲的寻常光比非寻常光脉冲展宽更严重；波长越短，脉冲展宽越大；当晶体长度等于色散长度时，脉冲宽度增加为初始时的√2倍，色散长度越短，超短脉冲展宽越明显。

电子束蒸发镀膜速率控制

介绍了电子束蒸发镀膜速率控制的基本原理和方法,选取实际生产中大量使用且蒸发特性较难控制的SiO_2和HfO_2,对两者的电子束蒸发速率控制分别进行了实验研究。采用比例积分微分(PID)闭环反馈控制,通过Ziegler-Nichols工程经验公式进行原始参量整定,并在实验的基础上对控制器的原始参量进行调整以及对积分作用和微分作用进行分区处理,速率控制的实验结果表明,采用该参量整定方法并结合工艺流程的改进,能获得良好的速率控制。针对速率控制中存在的难点问题进行了分析,并提出改进措施:将速率控制和电子枪扫描控制相结合能进一步改善速率控制。

植物血红蛋白基因及植物凝集素基因转化水稻的研究

植物血红蛋白在共生固氮根瘤中主要是对固氮酶进行嫌氧保护，确保固氮酶活性，在植物根中协助氧的运输或作为感觉氧压的信号分子．豆科植物凝集素功能之一是对相应专一的根瘤菌有识别作用，并有利于根瘤菌的聚集和侵染。本论文将非豆科结瘤植物Parasponia andersonii血红蛋白基因及豌豆凝集索基因转入水稻，目的是此二基因表达后，豌豆凝集素可聚集、识别豌豆根瘤菌，并有助于它们的侵染，血红蛋白则可对根瘤菌固氮酶进行嫌氧保护，保障其发挥固氮作用，从而为实现水稻结瘤和固氮打下初步基础。 本论文将带有Parasponia血红蛋白基因的pL305质粒，带有潮霉素磷酸转移酶基因及Parasponia血红蛋白基因的农杆菌双元载体质粒pLX412-Hb用花粉管通道法转化水稻l用pLX412-Hb和带有Bar基因、豌豆凝集素基因、Parasponia血红蛋白基因的质粒pLHB用基因枪法转化水稻幼胚及愈伤组织，带有pLX412-Hb的Agrobactmum tumefaciens LBA4404转化烟草，得到如下结果： 1．用pL305质粒花粉管通道法转化水稻，运作1512朵花，得到707粒种子．将230粒种子萌发，发芽220粒;白化苗4株，成苗206株;计发芽率96%，白化苗率1.7%，成苗率90%。取120株提取DNA以Parasponia血红蛋白基因为探针进行点杂交，有6株为阳性结果，阳性率5%．再取4株DNA点杂交阳性植株DNA，以Parasponia血红蛋白基因为探针进行Southem杂交，有3株有阳性结果，阳性率为75%，照此推算转化植株约占总植株的4%．目前，这些转基因植株已开花结实。 2．用pLX412-Hb质粒花粉管通道法转化水稻，运作743朵花，得到340粒种子。将120粒种子萌发，发芽117粒，白化苗3株，成苗111株;计发芽率97. 5%，白化苗率2. 5%，成苗率92. 5%．取30株提取DNA以Parasponia血红蛋白基因为探针进行点杂交，有4株为阳性结果，阳性率13%。再取4株DNA点杂交呈阳性的植株DNA，以Parasponia血红蛋白基因为探针进行Southern杂交，有2株有阳性结果，阳性率为50%，照此推算转化植株约占总植株的7%。目前部分转基因植株巳开花结实． 3.用pLX412 - Hb质粒基因枪法转化水稻幼胚及愈伤组织，抗性筛选得到15株再生植株，以Parasponia血红蛋白基因为探针进行点杂交，有14株为阳性结果，阳性率93%．取7株DNA点杂交呈阳性的植株DNA，以Parasponia血红蛋白基因为探针进行Southern杂交，都为阳性结果，阳性率为100%，照此推算转化植株约占总植株的93%．目前，部分转基因植株已开花结实． 4．用pLX412 -Hb质粒通过Agrobacterrum tumeFaciens LBA4404转化烟草，抗性筛选得到的再生植株以Parasponia血红蛋白基因为探针进行Southern杂交，结果为阳性． 5．用pLHB基因枪法转化的愈伤组织，抗性筛选得到已分化出绿芽点的愈伤组织，以Parasponia血红蛋白基因为探针或以豌豆凝集素基因为探针进行Southern杂交，杂交结果均为阳性． 6．最近国外巳发现大麦有血红蛋白基因．本论文以大麦血红蛋白cDNA为探针对未转基因的水稻进行Southern杂交，结果有阳性带。说明水稻有与大麦血红蛋白基因高度同源序列。以Parasponia血红蛋白基因为探针时杂交结果为阴性，说明水稻血红蛋白基因与Parasponiaa血红蛋白基因核苷酸序列相差较大． 7．提取Southern杂交证明有Parasponia血红蛋白基因整合的水稻根及叶总RNA，以Parasponia血红蛋白基因cDNA为探针进行RNA点杂交，结果根总RNA为阳性，叶总RNA为阴性。初步证明Parasponia血红蛋白基因在水稻根中表达。 8．提取未转基因的水稻根及叶RNA，以大麦血红蛋白基因cDNA为探针进行RNA点杂交，结果：根总RNA为阳性结果，叶总RNA为阴性结果．初步证明水稻血红蛋白基因在水稻根中表达。 总之，本论文证明已将Parasponia血红蛋白基因整合进水稻植株染色体，将豌豆凝集素基因、Parasponia血红蛋白基因整合进水稻愈伤组织染色体，初步证明水稻有血红蛋白基因，内外源血红蛋白基因都有组织特异性表达，从而为本研究的战略设想奠定初步基础。

Novel designs for Penning ion traps

A number of alternative designs are presented for Penning ion traps suitable for quantum information processing (QIP) applications with atomic ions. The first trap design is a simple array of long straight wires, which allows easy optical access. A prototype of this trap has been built to trap Ca+ and a simple electronic detection scheme has been employed to demonstrate the operation of the trap. Another trap design consists of a conducting plate with a hole in it situated above a continuous conducting plane. The final trap design is based on an array of pad electrodes. Although this trap design lacks the open geometry of the other traps described above, the pad design may prove useful in a hybrid scheme in which information processing and qubit storage take place in different types of trap. The behaviour of the pad traps is simulated numerically and techniques for moving ions rapidly between traps are discussed. Future experiments with these various designs are discussed. All of the designs lend themselves to the construction of multiple trap arrays, as required for scalable ion trap QIP.

IgA抗体的结构、功能与调控

IgA抗体是介导机体粘膜免疫的主要因子,其在粘膜分泌物中能有效地阻止外界抗原(包括可溶性抗原、病原微生物以及存在于食物中的致癌物质)附着或侵入粘膜上皮,从而避免这些外来物给机体造成损伤,保持机体粘膜完整并避免胃肠道疾病、呼吸道疾病及泌尿生殖道各种疾病的发生。为了能有效地利用IgA抗体的免疫保护功能,解决诸多困扰人类的粘膜性疾病,前人从很多方面对IgA抗体做了大量的研究,得到很多有意义的结果。本文试图总结这些研究成果,结合最新的研究进展,对IgA抗体的结构、功能及调控等进行评述。

Structure-function relationship of three neurotoxins from the venom of Naja kaouthia: a comparison between the NMR-derived structure of NT2 with its homologues, NT1 and NT3

Three homologous short-chain neurotoxins, named NT1, NT2 and NT3, were purified from the venom of Naja kaouthia. NT1 has an identical amino acid sequence to cobrotoxin from Naja naja atra [Biochemistry 32 (1993) 2131]. NT3 shares the same sequence with cobrotoxin b [J. Biochem. (Tokyo) 122 (1997) 1252], whereas NT2 is a novel 6 1 -residue neurotoxin. Tests of their physiological functions indicate that NT1 shows a greater inhibition of muscle contraction induced by electrical stimulation of the nerve than do NT2 and NT3. Homonuclear proton two-dimensional NMR methods were utilized to study the solution tertiary structure of NT2. A homology model-building method was employed to predict the structure of NT3. Comparison of the structures of these three toxins shows that the surface conformation of NT1 facilitates the substituted base residues, Arg28, Arg30, and Arg36, to occupy the favorable spatial location in the central region of loop 11, and the cation groups of all three arginines face out of the molecular surface of NT1 This may contribute greatly to the higher binding of NT1 with AchR compared to NT2 and NT3. (C) 2002 Elsevier Science B,V. All rights reserved.

A comparison of two models for the vibration response of piled foundations to inertial and underground-railway-induced loadings

The vibration response of piled foundations due to ground-borne vibration produced by an underground railway is a largely-neglected area in the field of structural dynamics. However, this continues to be an important aspect of research as it is expected that the presence of piled foundations can have a significant influence on the propagation and transmission of the wavefield produced by the underground railway. This paper presents a comparison of two methods that can be employed in calculating the vibration response of a piled foundation: an efficient semi-analytical model, and a Boundary Element model. The semi-analytical model uses a column or an Euler beam to model the pile, and the soil is modelled as a linear, elastic continuum that has the geometry of a thick-walled cylinder with an infinite outer radius and an inner radius equal to the radius of the pile. The boundary element model uses a constant-element BEM formulation for the halfspace, and a rectangular discretisation of the circular pile-soil interface. The piles are modelled as Timoshenko beams. Pile-soil-pile interactions are inherently accounted for in the BEM equations, whereas in the semi-analytical model these are quantified using the superposition of interaction factors. Both models use the method of joining subsystems to incorporate the incident wavefield generated by the underground railway into the pile model. Results are computed for a single pile subject to an inertial loading, pile-soil-pile interactions, and a pile group subjected to excitation from an underground railway. The two models are compared in terms of accuracy, computation time, versatility and applicability, and guidelines for future vibration prediction models involving piled foundations are proposed.

甲基叔丁基醚(MTBE)的环境毒理学研究进展

甲基叔丁基醚(MTBE)作为一种新型的无铅汽油添加剂被广泛应用以减少含铅汽油对空气的污染。简要介绍了MTBE的理化性质和MTBE的急性毒性、代谢、生殖、遗传毒性,就其对环境的污染以及其防治作了综述,指出了我国开展MTBE有关研究的重要性。