空间微重力汽相生长CdZnTe的研究进展

微重力条件下汽相生长CdZnTe晶体可以克服浮力对流,实现“无接触”生长,获得厚度均匀、结构完整、纯度高的材料.本文综述了国内外空间汽相生长CdZnTe晶体的研究进展.     

水稻花后衰退珠心和胚乳发育初期Ca2+的超微细胞化学定位

应用焦锑酸盐沉淀技术对水稻花后衰退珠心和胚乳发育初期进行了Ca^2 的超微细胞化学定位。结果显示在初始衰退的珠心细胞中Ca^2 主要分布于液泡膜上和核内；在衰退中期的珠心细胞中，Ca^ 主要分布在核膜、液泡膜及质膜上；在严重衰退的珠心细胞，Ca^2 仅存在于液泡中。珠心降解的Ca^2 跨过胚囊壁，通过质外体向胚乳内运输；发育初期的胚乳细胞，Ca^2 主要位于胞间隙，线粒体和液泡中也有少量分布。讨论了Ca^2 与珠心PCD的关系。     

Strength of Soldered Joints Formed under Microgravity Conditions

Experiments have been carried out to compare the mechanical strength of joints soldered with Sn-Ag-Cu under different gravitational conditions. Joints soldered under microgravity (produced during a parabolic flight) have lower strength (by 32% in this case) than similar joints formed under normal gravity. Electron microscopy has shown that this is due to a larger volume of residual porosity (14%) in the joints formed in microgravity compared with <1% for joints formed in normal gravity. The residual porosity in joints formed in microgravity is mainly within the bulk of the solder, with some microporosity in the Cu₆Sn₅ intermetallic layer near the copper interfaces. The porosity not only weakens the joint, but also biases the failure path away from the intermetallic layer and into the bulk of the solder. These observations show that gravitational buoyancy is important for the expulsion of flux and flux residues from soldered joints.     

用电子探针X射线显微分析法研究肾上腺素激发的心房特殊颗粒分泌

本文研究心房特殊颗粒(ASG)中的钙释放是否能促进颗粒内容的分泌.冷冻超薄切片技术和磷钨酸-乙醇(EPTA)特殊染色技术制备大鼠心房切片.X射线显微定量分析采用Hall连续谱法,用以测量在肾上腺素处理后15、30、60和120 min时ASG中钙含量的变化.用形态计量法的数密度作为判断ASG分泌状态的指标.结果显示心房特殊颗粒在生理状态下钙浓度高达80 mmol/公斤*干重.在肾上腺素注射后ASG的数密度逐渐下降,并于注射后60 min时下降至最低;ASG中的钙含量亦逐渐减低,但于注射后30 min即达最低,由此可见ASG钙含量的下降出现早于颗粒数的下降.推想肾上腺素处理引起的钙释放可能成为一种信号,启动心房肽的分泌,因此ASG在心房心肌细胞中可能具有细胞内钙库机能.本文同时讨论了Hall连续谱法近年来在生物试样定量分析中的应用和发展.     

Small clusters of granule-containing cells at the lateral side of the posterior cricoarytenoid muscle of the young adult rat

Small clusters consisting of granule-containing cells, sustentacular cells and capillaries around them, similar in structure to the carotid body-like paraganglia, sometimes existed at the lateral side of the posterior cricoarytenoid (PCA) muscle of young adult (3 months) rats. Differing from the paraganglia, however, these cell clusters were discontinuously invested by slender cytoplasmic processes of fibroblasts. In individual granule-containing cells, granules varied in size and had a concentrically or eccentrically arranged, electron-dense material, resembling those of chromaffin cells of the adrenal medulla. A series of desmosome-like structures were frequently observed between adjacent granule-containing cells, but synapses between them were not necessarily clear. Nerve endings containing clear synaptic vesicles and occasional granulated vesicles, being possibly cholinergic in nature, sometimes formed synapses with the granule-containing cells, probably indicating that the granule-containing cells receive the efferent nerve innervation. On the other hand, the sustentacular cells lacked cytoplasmic granules and sent their cytoplasmic processes around the granule-containing cells. Capillaries in and around clustered cells were of the fenestrated type. From these findings, it is suggested that unlike the carotid body-like paraganglia, the noncapsulated cell clusters at the lateral side of the PCA muscle of the young adult rat may be identical to groups of extra-adrenal chromaffin tissues.     

单用户对双向中继系统中基于梯度下降的最大化和速率功率分配方案

针对单用户对双向中继系统中的功率分配问题,提出了一种基于梯度下降法的功率分配方案。该方案在总功率约束的条件下,以最大化和速率为目标函数,通过对中继波束成形矩阵和功率分配矩阵的反复迭代,求解出局部最优的功率分配和中继波束成形矩阵。仿真结果表明:提出方案的误码性能相比于等功率分配有明显提高,在误码率为10-2时,可获得2.5d B~3 d B的信噪比增益;同时,在中高信噪比下,相比于等功率分配,该方案可获得0.3(bit/s)/Hz~0.5(bit/s)/Hz的和速率增益。     

小麦与白粉病菌相互作用的钙调素定位

本文对白粉病菌侵染后小麦表皮细胞内钙调素的动态变化过程进行了分析。结果表明,在正常情况下钙调素主要集中分布在泡内和胞外,在细胞衰老时进入解体的细胞器如细胞核等;接种白粉病菌后,感病细胞内的钙调素含量降低;但随着细胞的衰老钙调素含量又逐渐增加。钙调素逐渐穿过吸器外膜进入吸器外基质和退化的吸器内部。病原菌侵染后,抗病细胞中的钙调素迅速增加,并随着细胞的死亡散布在这个细胞中,上述结果说明,适当的钙离子浓度梯度是白粉病菌吸器发育和行使其功能的重要条件。     

Electron probe microanalysis of heterostructures with nanolayers

A technique of the electron probe microanalysis of semiconductor heterostructures consisting of nanolayers is described. Features of the microanalysis of such structures are compared to the analysis of structures with thicker layers and of homogeneous samples. Possibilities of the method are illustrated by an example of determination of the layer composition in light-emitting diodes and laser quantum-well InGaAs and ZnCdSe heterostructures. The proposed technique allowed determination of the composition and depth of quantum-well nanosize layers in the samples under study with an accuracy of no worse than 10%. The results of the microanalysis are shown to be in good agreement with the data obtained by other methods.     

SiGe HBT功率放大器基极偏置电阻的优化

模拟了基极偏置电阻对功率放大器参数的影响.在兼顾效率、S参数、电压驻波比、功率增益及稳定性等特性的同时,得到了三阶交调信号幅度为最小值时的优化基极偏置电阻.模拟结果表明,一个优化的基极偏置电阻,不仅能使功率放大器的直流偏置点不受影响,三阶交调信号幅度最小,功率增益平坦度得到改善,而且S参数也能满足功放的要求.     

空间相机整机有限元分析

相机的结构空间是相机的重要子系统,是保证相机成像质量的关键之一。光学反射镜在重力和微重力环境变化以及热控温度范围变化综合影响下,面形误差变化量RMS和PV值是衡量相机成像质量的重要指标,结构还必须保证满足光学设计提出的各反射镜的各种公差要求,为保证相机在运输以及发射过程中能承受住恶劣的振动条件,需要整机有足够高的动态刚度和合理的模态分布。利用CAD/CAE技术对空间相机整机进行大量的工程分析,分析比较计算结果,此相机满足设计指标。CAE技术对空间相机光机结构设计起着重要的指导作用,是现代设计方法的重要手段之一。     

Characterization of Ca(2+)-inhibited potassium channels in the LNCaP human prostate cancer cell line.

Potassium plasma membrane channels have been studied in the LNCaP androgen-sensitive human prostate cancer cell line, derived from a lymph node of a subject with metastatic carcinoma of the prostate. Membrane currents were recorded by the patchclamp technique, using the cell-attached, cell-free and whole-cell mode. A voltage-dependent, non-inactivating potassium channel (delayed rectifier) was the most commonly observed ion channel in LNCaP cells. The slope conductance of K+ channels in a symmetrical 140 mM K+ gradient was 78 pS. In excised inside-out patches, the channel was inhibited by increasing the cytoplasmic Ca2+ concentration (with half-block at 0.5 microM Ca2+) over a wide range of membrane potentials. The K+ channel had a high sensitivity to tetraethylammonium (TEA), that reduced the single channel conductance with Kd of 280 +/- 27 microM. The K+ channel open probability was inhibited by alpha-dendrotoxin (DTX) (with a half-blocking concentration of approximately 5 nM) and mast cell degranulating peptide (MCDP) (with half-blocking concentration of approximately 70 nM) at all membrane potentials and with very slow reversibility. In view of the biophysical and pharmacological properties of K+ channels in LNCaP cells, it is not possible to classify these channels as one of the previously characterized types of voltage- or ligand-gated K+ channels in other cell lines.     

银杏营养贮藏蛋白质的超微结构特征及季节变化

在电子显微镜下对银杏（Ginkgo biloba L.）枝条营养贮藏蛋白质的超微结构特征及季节性变化规律进行了系统研究。结果表明：银杏营养贮藏蛋白质主要存在于韧皮薄壁细胞的液泡内。银杏韧皮薄壁细胞内的营养贮藏蛋白质在细胞质内合成，由内质网和高尔基体小泡参与贮藏蛋白质的合成和积累。液泡蛋白质主要以不定形块状、絮状或颗粒状形态存在。贮藏蛋白质在整个越冬期间一直保持高含量水平，直到翌年春季牙萌发时，贮藏蛋白质迅速转移再利用。随着新梢的生长，到了夏末秋初，又重新开始积累贮藏蛋白质。     

X-ray spectrum microanalysis of semiconductor epitaxial heterostructures on the basis of a monte carlo simulation of electron transport

Specific features of the X-ray spectrum microanalysis of semiconductor heterostructures based on III–V and II–VI alloys with thin epitaxial layers are considered. Simulation of electron transport on the basis of the Monte Carlo method is used to analyze the effect of the layer and substrate on the depth distribution of X-ray generation. Good agreement between the calculated and experimental values of the ratio between the intensities of emission from the layer and bulk sample for simulated Al_0.2Ga_0.8As structures on the GaAs substrate (with different thicknesses of the layer) is obtained. Methods allowing the performance of a correct microanalysis of the layers with thicknesses in excess of 50 nm and to determine simultaneously the composition and thickness of epitaxial layers are suggested. The methods developed can be used in the analysis of thin layers and in other systems.     

Complexation‐Induced Biomimetic Long Range Fibrous Orientation in a Rigid‐Flexible Block Copolymer Thermogel

The orientation of the organofibrous structure plays an important role not only in the biomineralization process but also in the extracellular matrix (ECM) of articular cartilage by providing cells with biomechanical cues. Here, it is reported that a long range nanofibrous orientation can be realized by a self‐assembling ionic complex between (+)‐charged amphiphilic peptide block copolymers with a rigid‐flexible block structure (polyalanine‐PLX‐polyalanine; PA‐PLX‐PA) and (‐)‐charged hyaluronic acid (HA). A biomimetic 3D culture system encapsulating chondrocytes is formed by a temperature‐sensitive sol‐to‐gel transition of the PA‐PLX‐PA/HA complex aqueous solution, which provides a compatible microenvironment for the cells. The cell proliferation and biomarker expression for articular cartilage are significantly improved in the PA‐PLX‐PA/HA complex system relative to the PA‐PLX‐PA or the commercially available Matrigel systems. In particular, noticeable cell clustering is observed in the PA‐PLX‐PA/HA complex system with the long range nanofibrous structure. This research suggests a new method for developing a nanofibrous structure using an amphiphilic peptide block copolymer and demonstrates its potential uses as a unique biomimetic cell‐culture matrix.     

空间相机全铝合金光机结构的设计与分析

提高光机结构的温度适应性对空间相机降低热控难度、提升系统稳定性具有重要意义.根据统一材料结构可以消除系统热差的原理,选用铝合金材料对某可见光波段空间相机的光机结构进行了设计,并完成了实际工况下的工程分析,达到了在20℃±15℃均匀温度变化与不同方向重力耦合状态下,像质均满足MTF(modulation transfer...     

Effect of constrained growth on defect structures in microgravity grown CdZnTe boules

In a microgravity environment obtainable in an orbiting space shuttle, it is possible to virtually eliminate gravity related effects such as buoyancy driven convection and hydrostatic forces thus providing an ideal environment for diffusion-controlled, containerless crystal growth processes. Under such conditions, it is possible to investigate the effects of gravity independent growth parameters on crystal growth. Studies of CdZnTe boules grown on space shuttle mission USML-1 revealed that regions of the boules grown with wall contact were associated with a higher defect density than regions grown with partial or no wall contact. Defect densities in certain regions grown without wall contact were as low as 5 × 10²/cm² to 1.2 × 10³/cm². More detailed studies on the effects of wall contact were sought in the USML-2 mission. Two CdZnTe boules (GCRC-1 and GCRC-2) were grown by the seeded Bridgman-Stockbarger method. Boule GCRC-1 was grown under constrained conditions to force full wall contact while boule GCRC-2 had a tapered geometry designed to minimize wall contact. Defect distributions in the boules were investigated by synchrotron white beam x-ray topography. The sample GCRC-1 was characterized by the presence of large inhomogeneous strains, numerous grains and twins, all of which are caused by effects related to wall contact. On the other hand, a part of the boule GCRC-2 that grew free from wall contact revealed minimum surface strains, the absence of twins and a very high structural uniformity. Results clearly verify that ampoule wall contact plays an important role in determining the incidence of crystal imperfections.     

Analysis of the dispersion characteristics of slow-wave structures with two microwave propagation channels

Models of rectangular and axially symmetric resonator slow-wave structures, which are built using transmission matrix for determining the characteristics of the slow-wave structures in different operation modes, are investigated. Elements of the transmission matrix are determined from the results of 3D simulation with the use of the HFSS software. In the analysis of the dispersion characteristics, slow-wave structures with two microwave propagation channels are studied and simulated using a 4×4 transmission matrix.     

The cytoplasmic surface structures of uncoated vesicles in various tissues of rat as revealed by quick-freeze, deep-etching replicas

We examined the cytoplasmic surface structures of the plasmalemmal vesicles in various tissues using quick-freeze, deep-etching replicas, and identified three types of cytoplasmic surface specializations. In addition to the baskets of clathrin-coated vesicles, stripe-surfaced and bumpy-surfaced vesicles could be identified. The striped patterns were clearly observed on the vesicles in endothelial cells and fibroblasts of various tissues, while in epithelial cells such as hepatocytes, renal proximal tubule cells, and superficial cells of the urinary bladder, instead of the striped patterns, rough-surfaced vesicles could be identified. These differences in 'uncoated' vesicles may suggest that there is the tissue specificity of the cytoplasmic surface structures of plasmalemmal vesicles.     

Ultrahigh-resolution immunofluorescence microscopy using ultrathin cryosections: subcellular distribution of caveolin-1alpha and CD31 in human placental endothelial cells

We compared the z-axis resolutions achieved by immunofluorescence (IF) microscopic imaging of tissue sections of different thicknesses (ultrathin cryosections, optical sections of cryostat sections and conventional cryostat sections). We used these images to determine the distribution of caveolin-1alpha (CAV-1alpha) and CD31 in endothelial cells of full-term, human placenta. Anti-CAV-1alpha antibody was used to visualize caveolae, which are among the smallest organelles. By using ultrathin cryosections as substrates for IF microscopy, we were able to resolve discrete caveolae that were primarily present immediately beneath the endothelial cell surface. In contrast, neither conventional nor confocal images from cryostat sections were able to resolve individual caveolae, despite dramatic reductions in the confocal image degradation that arises from out-of-focus fluorescence signals. Anti-CD31 antibody labeled the endothelial cell surface exclusively. Quantitative analysis of ultrathin cryosections showed that about 2.5 times more CD31 was expressed on the luminal surface of cells than on the abluminal surface. Our results demonstrate that ultrathin cryosections can serve as excellent substrates for ultrahigh-resolution IF microscopy.     

Effects of enamel matrix derivative on mineralized tissue formation during bone wound healing in rat parietal bone defects

Enamel matrix derivative (EMD: Emdogain) has been reported to stimulate the biosynthesis and regeneration of trabecular bone. To address whether the biological action of EMD is dependent on the local environment of osseous tissue, circular perforations were made in parietal bones and immediately filled with either EMD or its carrier, propylene glycol alginate (PGA), as control. On post-operative days 4-60, the dissected bones were examined by various histological techniques. New bone matrix, which was immunoreactive for bone sialoprotein (BSP), was formed from the periosteum at the peripheral area of perforations. Different from the findings reported in injured long bones, mineralized tissue was produced in the regenerating connective tissue within bone defects. This mineralized tissue was hardly immunostained for BSP, contained few collagen fibres, and lacked osteocytic lacunae and layers of osteoblasts and osteoid. Energy-dispersive X-ray analysis showed that Ca and P weight % and Ca/P molar ratio of this mineralized tissue were similar to or slightly higher than those in the pre-existing parietal bones. In addition, most multinucleated cells located in mineralized tissue lacked a ruffled border structure and showed weak immunoreaction for the lysosomal cysteine proteinase, cathepsin K, whereas those located in the bone matrix exhibited ruffled borders and strong cathepsin K expression. However, multinucleated cells located in both tissues were strongly stained for tartrate-resistant acid phosphatase. The volume fraction of such mineralized tissue appeared to be higher in EMD-applied bones than in PGA-applied controls. The mineralized tissue-forming stromal cells within bone defects appeared to show greater accumulation in EMD-applied bones than in PGA-applied controls. Our results suggest that the bioactive effects of EMD on bone wound healing and mineralized tissue formation depend, at least in part, on the local osseous environment where EMD has been applied.