MOCVD生长薄膜材料制作半导体可饱和吸收镜

介绍了当前国际上流行的用半导体可饱和吸收镜来对固体激光器、光纤激光器和半导体激光器进行被动锁模的方法,阐述了半导体可饱和吸收镜用来作为被动锁模吸收体的原理,并介绍了如何利用金属有机气相淀积(MOCVD)技术生长各种波长激光器所需要的半导体可饱和吸收镜.     

挤扩支盘桩在湿陷性黄土地基中的应用

湿陷性黄土具有遇水发生湿陷、承载力大幅度降低的性质,这种性质直接影响到基础的承载力。为了研究支盘桩在湿陷性黄土地基中的承载性状,对湿陷性黄土中的3根支盘桩进行预浸水静载荷试验,结果表明,支盘桩荷载—沉降曲线为缓变型,具有较好的承载性能,荷载传递规律与在非湿陷性黄土地基中具有相似的性质,桩身各段承载力的发挥具有明显的顺序性,其结果为挤扩支盘桩在湿陷性黄土地基中的应用提供了依据。     

液态金属离子源发射尖的制备工艺与技术

发射尖是液态金属离子源(LMIS)的关键部件之一，其性能的优劣直接影响到整个离子源的工作稳定性。通过对系统软件和硬件的设计，开发了一套发射尖自动腐蚀装置，该装置可以对发射尖腐蚀过程中的速度和深度以及腐蚀电压进行控制，实现发射尖腐蚀工艺的重复性、可靠性，从而为液态金属离子源以及聚焦离子束系统的研制、开发提供了一个有效的辅助工具。     

海杂波中基于混沌预测的目标检测方法改进

基于记忆库非线性预测的NP-CFAR方法是目前混沌海杂波背景中目标检测的一种典型而先进的方法.考虑到海杂波功率与特征的时变不稳定性,本文提出运用旋转超盒分类取代这一方法中的NP-CFAR进行目标检测,并探讨了运用盒维数特征提取进行预处理以节省运算开销的问题.仿真实验验证了本文所提改进方法的有效性.     

用于高频谐振器的PbTiO_3基压电陶瓷

传统的PZT压电陶瓷的相对介电常数较大,一般为1 000以上,用于高频谐振器不易与线路匹配;而PbTiO3基压电陶瓷的相对介电常数较小,一般仅为200左右,对于10 MHz以上频率的谐振器,用PbTiO3基压电陶瓷作为压电振子是最佳的选择。本文主要研究用于高频谐振器的MnO2和Nd2O3改性PbTiO3基压电陶瓷的性质。PbTiO3基压电陶瓷的性质的改善是与此种陶瓷的制备工艺,显微结构和电导机制紧密相关的。     

Effect of alendronate treatment on the osteoclastogenic potential of bone marrow cells in mice

The expression of cytokeratins (CK), involucrin, vimentin, CD34, and alpha-smooth-muscle actin was studied in fetal and adult hair follicles. The first stage of the developing hair follicle is characterized by palisaded, elongated epithelial cells budding from the epidermal basal layer. These cells express CK5/6, CK14, CK17, CK19, and vimentin. During the following weeks of gestation, different structures in the developing hair follicle can be identified and characterized. The matrical cells display only CK19. The keratinocytes of the outer root sheath express CK5/6, CK14, CK17, CK19, and involucrin; those of the inner root sheath, CK4, CK18, and involucrin; those of the isthmus, the same profile as the ORS. In the infundibulum, the basal-layer keratinocytes express CK5/6, CK14, CK17, and CK19, whereas in the suprabasal layers CK1, CK4, CK10, CK14, and CK17 are seen. The adult hair follicle in anagen fails to express CK19 in the matrical cells and isthmus and both CK17 and CK19 in the infundibulum. These profiles of intermediate filaments and other markers appear to be potentially useful in categorizing neoplasms with apparent follicular differentiation.     

Viral dynamics of primary viremia and antiretroviral therapy in simian immunodeficiency virus infection

Mathematical modeling of viral replication dynamics, based on sequential measurements of levels of virion-associated RNA in plasma during antiretroviral treatment, has led to fundamental new insights into human immunodeficiency virus type 1 pathogenesis. We took advantage of the simian immunodeficiency virus (SIV)-infected macaque model to perform detailed measurements and mathematical modeling during primary infection and during treatment of established infection with the antiretroviral drug (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA). The calculated clearance half-life for productively infected cells during resolution of the peak viremia of primary infection was on the order of 1 day, with slightly shorter clearance half-lives calculated during PMPA treatment. Viral reproduction rates upon discontinuation of PMPA treatment after 2 weeks were approximately twofold greater than those obtained just prior to initiation of treatment in the same animals, likely reflecting accumulation of susceptible target cells during treatment. The basic reproductive ratio (R0) for the spread of SIV infection in vivo, which represents the number of productively infected cells derived from each productively infected cell at the beginning of infection, was also estimated. This parameter quantifies the extent to which antiviral therapy or vaccination must limit the initial spread of virus to prevent establishment of chronic disseminated infection. The results thus provide an important guide for efforts to develop vaccines against SIV and, by extension, human immunodeficiency virus.     

Purification of the cardiac sarcoplasmic reticulum membrane protein phospholamban from recombinant Escherichia coli

Phospholamban (PLN) was expressed in Escherichia coli as a protein fusion with glutathione S-transferase (GST). GST-PLN was mostly present in the insoluble protein fraction and accounted for approximately 50% of total insoluble protein. Attempts to suppress inclusion body formation or to use GST as an affinity-purification tag failed. A successful purification method is based on preparative SDS/PAGE and electrodialysis. From 1 g cells we typically purified 13.5 mg fusion protein with a PLN content of 2.8 mg. We genetically inserted an enterokinase (EK) protease site just in front of the PLN sequence and demonstrated the proteolytical liberation of PLN from the carrier protein. The approach described represents a substantial advancement in PLN expression and purification.     

Estramustine and estrone analogs rapidly and reversibly inhibit deoxyribonucleic acid synthesis and alter morphology in cultured human glioblastoma cells

Estramustine is an estradiol-based agent that has been shown to accumulate in human glioma cells, resulting in a concentration-dependent alteration in cell size and shape within minutes and an inhibition of proliferation over 3 to 6 days. We evaluated human glioblastoma cultures with [3H]thymidine incorporation assays to determine estramustine's early effects on deoxyribonucleic acid synthesis in these tumors. Because estramustine shares a common structural motif with other antimicrotubule drugs, we synthesized four A-ring conjugates of estrone that contained a carbamate moiety but lacked nitrogen mustard. These analogs were examined by [3H]thymidine incorporation and compared with vinblastine. Greater than 70% inhibition of [3H]thymidine incorporation occurred within 1 hour of treatment with estramustine at 10(-5) mol/L, which increased to 80% inhibition at 4 hours. Ethyl carbamate JE208 was nearly as effective as estramustine in inhibiting deoxyribonucleic acid synthesis, and both were more effective than vinblastine. The inhibitory effects of estramustine and estrone analogs were reversible; vinblastine was not reversible. Although estramustine and JE208 induced similar antiproliferative and morphological changes in glioblastoma cells that persisted for at least 4 days, there was a modest recovery of morphology and thymidine incorporation with JE208 after prolonged treatment. The common findings with estramustine and JE208 suggest that these agents may have a similar mechanism of action and form the basis for the investigation of new agents that may rapidly and reversibly inhibit glioblastoma.