The spectrin-based skeleton at the postsynaptic membrane of the neuromuscular junction

Membrane skeletons, in particular the spectrin-based skeleton, are thought to participate in the organization of specialized membrane domains by restricting integral proteins to specific membrane sites. In the neuromuscular junction, discrete isoforms of spectrin and ankyrin, the peripheral protein that links spectrin to the membrane, colocalize with voltage-dependent sodium channels and N-CAM at the troughs of the postsynaptic membrane folds. Moreover, beta-spectrin, N-CAM, and sodium channels become clustered at the endplate during a period of time coincident with postsynaptic fold formation and synapse maturation. These observations suggest a role of the spectrin skeleton in directing and maintaining postsynaptic accumulations of sodium channels and N-CAM. In addition, the coexistence of spectrin and dystrophin at the troughs of the junctional folds raises the question of their respective functions in this membrane domain, where both cytoskeletal proteins have the potential to associate with sodium channels via ankyrin and syntrophin, respectively. Possible scenarios are discussed here with respect to accumulating evidence from studies of assembly of similar membrane domains in neurons.     

工业机器人选型智能系统的研究

本文论述了机器人选用问题的两种智能方法,一种是机器人选型智能数据库;另一种是机器人选型专家系统。     

The process of collagen biomineralization observed by AFM in a model dual membrane diffusion system

Investigation and simulation of naturally occurring mineralization can offer some new ideas in the design and fabrication of new functional materials for bone analogues. In this paper, a model dual membrane diffusion system (DMDS) was used to study the mineralization behaviour of collagen. The process of mineralization was observed by atomic force microscope (AFM). The results showed that the surface roughness and hardness of mineralized collagen fibers increased with time during the process of mineralization. The adhesion force of mineralized collagen fibers decreased with mineralization time. The micromechanical properties and microstructure changes of mineralized collagen fibers suggested that the mineralization was a step-by-step assembling process.     

工件的加工与检测集成技术研究

以加工中心在线检测技术为主体,针对目前数控机床专用化程度逐步提高的趋势,提出了针对具体工件开发专用数控加工与检测集成系统的概念。系统对工件的基本几何特征进行规划,建立了基本几何量的检测宏程序库并针对具体工件自动形成检测加工程序。     

The behaviour of the plasma membrane during plasmolysis: a study by UV microscopy

A high resolution ultraviolet (UV) bright-field microscope was used to analyse the formation of Hechtian strands and the Hechtian reticulation that remain attached to the cell wall after plasmolysis and deplasmolysis of onion inner epidermal cells. In real time video images, UV microscopy allowed a detailed investigation of the dynamic behaviour of the plasma membrane during the processes of osmotic water loss and uptake. Furthermore, the role of cytoskeletal elements as possible linkers of the plasma membrane to the cell wall was probed by application of cytoskeletal drugs during plasmolysis. Microtubules were depolymerized in oryzalin, and latrunculin B was used to destabilize actin microfilaments. The results showed no visible changes in the formation of the Hechtian reticulation or strands. Plasmolysis forms appeared to be normal, indicating stong membrane-to-wall attachments independent of cytoskeletal elements. During re-expansion of the protoplast in deplasmolysis, the plasma membrane incorporated Hechtian strands and subprotoplasts, fused with the Hechtian reticulation and finally realigned at the cell wall.     

The application of real-time confocal microscopy to the study of high-speed dental-bur-tooth-cutting interactions

A tandem scanning reflected light microscope (TSM) has been used to study the cutting interactions of dental burs with enamel. Confocal microscopy produces high-resolution images of subsurface structures in semi-transparent specimens such as teeth. The TSM has a real-time imaging ability which allows the visualization of the high-speed failure of a substrate which is being machined. This paper describes the criteria for successful imaging and their implementation in the design of a stage for controlling these cutting interactions. Examples of the results achieved are given and further applications for this technique in the field of biomaterials suggested.     

供应链网络制造系统生产计划分解模型的研究

供应链管理跨越企业界限，具有集成性和时效性，其生产计划系统具有分布性、自治性和开放性等特点，传统的生产计划方法已经不能适应供应链这种新的组织模式。这里对供应链企业生产计划系统特点进行分析，构建了供应链网络制造系统三层次模型，并在此基础上提出了网络制造系统中供应链生产计划的分解模型。     

航空产品质量评估体系与模型研究

航空产品是一个复杂的系统,其质量的影响因素多种多样.在分析航空产品质量评估特性的基础上,确定航空产品质量评估体系构建的方法与原则,提出从制造过程质量和试飞过程质量两方面来评价航空产品质量,以某型号的航空产品体系结构为例,构建航空产品质量评估体系,并建立航空产品质量评估数学模型.     

Hopf bifurcation to a short porous journal-bearing system using the Brinkman model: weakly nonlinear stability

On the basis of the Brinkman model, the weakly nonlinear stability characteristics of short porous journal-bearing systems are presented. By applying the Hopf bifurcation theory, the weakly nonlinear behaviors near the critical stability boundary are predicted. According to results, the onset of oil whirl for porous bearings is a bifurcation phenomenon; it can exhibit supercritical limit cycles or subcritical limit cycles for journal speeds in the vicinity of the bifurcation point. With a fixed permeability parameter, such supercritical limit cycles for journal speeds in excess of the threshold speed are confined to a specific region in the (ω, ε_s) plane; and outside this region subcritical limit cycles exist for journal speeds below the threshold speed. In addition, increasing the value of system parameter, S_p, may change supercritical bifurcation into the more complicated subcritical bifurcation.     

延迟膜光谱分析测试系统及应用

摘要: 本文介绍了一个可以测试延迟膜不同波长下的延迟量的方法。其在测量晶体相位延迟量1/4波片法的基础上,用分光光度计代替其中的光源,滤色片,以及光电探测器,并且对样品进行了测试,利用所得数据,对样品的延迟量进行光谱分析。根据其测试原理,光强的波动以及与光强有关的误差在此系统中可以忽略,且1/4波片对多波长测试的误差很小,故此测试系统有很高的精度和可靠性,可以测试其精度范围内的任意小延迟量。     

城市公交汽车的节能系统研究

介绍一种城市公交汽车节能系统的原理、结构及功能。并通过对该系统中的主要元件之间的参数关系进行分析，得出它们的匹配关系及一些有益的结论。     

空间机器人单关节控制器模型自适应调整

文章针对空间机器人单关节系统自身的特点,在系统辨识的基础上提出了模型参数间断性自适应调整算法.该算法在不同的工作状态和负载产生变化时,适时调整系统参数,为控制器提供准确的被控模型,达到精确控制的目的.本文提出的对空间机器人系统模型进行间断性自适应调整的方法与传统的调整控制器参数的方法相结合,改进了空间机器人的动态品质,减少了系统的计算量,缩短了响应时间,提高了控制精度.     

Electron spectroscopy imaging to study ELNES at a nanoscale

Series of energy‐filtered TEM images have been acquired with very narrow energy slit using a post‐column energy filter. This allowed us to reconstruct spectra with an energy resolution estimated to 2 eV, and a spatial resolution in the order of 0.5 nm. In that way, fine structures of the N‐K edge in AlN/GaN heterostructures have been investigated and compared to EELS spectra. The fine structure in the two nitrides is very sensitive to the local environment. Very good agreement between ESI and EELS spectra was found. Moreover, this technique allowed analysis of the AlN/GaN interface at a nanoscale. The second example is an application of the technique to construct bonding maps. In this case, maps differentiating AlN nanoprecipitates with either the cubic or the hexagonal phase were created.     

三峡工程的设备监理制

在三峡工程建设中,大型机械设备对工程建设的进度、质量和投资及经济性都具有重要影响,中国长江三峡工程开发总公司设备公司实行设备监理机制,通过三峡第一阶段建设实践,证明卓有成效.     

The role delegation authorization model of a computer-supported cooperative design system

According to the specific characteristics of a computer-supported cooperative design (CSCD) system, the characteristics of role delegation authorization (RDA) are analyzed and deduced, and a set of fitful status is arrived at. Because of the diversified characteristics of RDA features in different systems, the RDA model has multi-varying status. On the basis of the basic model of role-based access control (RBAC), some basic characteristics of RDA are summed up. Then, according to the specific characteristics of CSCD system, the characteristics of RDA are recombined to develop a RDA model that is suitable for the CSCD system. It is different from the conventional role authorization models of RBAC, that is, it adopts the decentralized authorization management instead of the centralized one in CSCD system, which makes the management more flexible. This model is verified through a specific case of CSCD system. Translated from Journal of Northeastern University (Natural Science), 2006, 27(5): 548–551 [译自: 东北大学学报 (自然科学版)]     

Cellulose microfibril deposition: coordinated activity at the plant plasma membrane

Plant cell wall production is a membrane-bound process. Cell walls are composed of cellulose microfibrils , embedded inside a matrix of other polysaccharides and glycoproteins. The cell wall matrix is extruded into the existing cell wall by exocytosis. This same process also inserts the cellulose synthase complexes into the plasma membrane. These complexes, the nanomachines that produce the cellulose microfibrils, move inside the plasma membrane leaving the cellulose microfibrils in their wake. Cellulose microfibril angle is an important determinant of cell development and of tissue properties and as such relevant for the industrial use of plant material. Here, we provide an integrated view of the events taking place in the not more than 100 nm deep area in and around the plasma membrane, correlating recent results provided by the distinct field of plant cell biology. We discuss the coordinated activities of exocytosis, endocytosis, and movement of cellulose synthase complexes while producing cellulose microfibrils and the link of these processes to the cortical microtubules.     

Cell adhesion and the immune system: a case study using earthworms

In the earthworm's immune system, cell adhesion, which occurs by putative receptors on leukocytes, is essential after recognition of self vs. non-self. Confrontation with foreign antigens is a normal event in the environment, replete with microbial pathogens that pose a threat to survival. To better understand what happens when an effector cell first recognizes a foreign target followed by its adhesion to it, isolated leukocytes, in sufficient quantities to be subjected to various analyses, have been extremely beneficial. In vitro approaches when accompanied by biochemical, immunological, and molecular technologies, have opened up new vistas concerning the immune response of earthworms and other invertebrates. The most recent discovery includes the preliminary identification of cell differentiation (CD) markers that play vital roles in recognitive and adhesive events. Certain leukocyte effectors show characteristics of natural killer (NK) cells that may act differently depending upon their source, whether autogeneic, allogeneic, xenogeneic, or expressed under normal or varying environmental conditions including exposure to xenobiotics. At the level of earthworm evolution, there is apparently a dissociation of phagocytosis from the process of killing by NK-like effectors. There are at least three future challenges. First, it is essential to determine the precise nature of the CD markers with respect to their molecular structure. Second, once their molecular and biochemical characteristics have been defined, the role of these markers in cellular and humoral mechanisms must be clarified in order to define effector cell products and resulting immune responses. Third, there is a need to differentiate between the several lytic factors that have been found in earthworms with respect to molecular structure, and biochemical and functional characterization.     

The characean internodal cell as a model system for studying wound healing

This work describes the characean internodal cell as a model system for the study of wound healing and compares wounds induced by certain chemicals and UV irradiation with wounds occurring in the natural environment. We review the existing literature and define three types of wound response: (1) cortical window formation characterised by disassembly of microtubules, transient inhibition of actin-dependent cytoplasmic streaming and chloroplast detachment, (2) fibrillar wound walls characterised by exocytosis of vesicles carrying wall polysaccharides and membrane-bound cellulose synthase complexes coupled with endocytosis of surplus membrane and (3) amorphous, callose- and membrane-containing wound walls characterised by exocytosis of vesicles and endoplasmic reticulum cisternae in the absence of membrane recycling. We hypothesize that these three wound responses reflect the extent of damage, probably Ca(2+) influx, and that the secretion of Ca(2+) -loaded endoplasmic reticulum cisternae is an emergency reaction in case of severe Ca(2+) load. Microtubules are not required for wound healing but their disassembly could have a signalling function. Transient reorganisation of the actin cytoskeleton into a meshwork of randomly oriented filaments is required for the migration of wound wall forming organelles, just as occurs in tip-growing plant cells. New data presented in this study show that during the deposition of an amorphous wound wall numerous actin rings are present, which may indicate specific ion fluxes and/or a storage form for actin. In addition, we present new evidence for the exocytosis of FM1-43-stained organelles, putative endosomes, required for plasma membrane repair during wound healing. Finally, we show that quickly growing fibrillar wound walls, even when deposited in the absence of microtubules, have a highly ordered helical structure of consistent handedness comprised of cellulose microfibrils.     

Experimental study of a model system of dynamic scene generation for testing infrared imaging systems

An experimental model of a test rig for formation of images in a computer and insertion of these images into the optical-electron path of an infrared imaging system is considered. Experiments on synthesizing images in the range of 3–5 µm and dynamic scenes are performed. Experimental estimates of the model test rig are given.