Crystal structure of troponin and the molecular mechanism of muscle regulation

Troponin plays a central role in the regulation of skeletal and cardiac muscle contraction. The protein consists of three polypeptide chains (TnT, TnI and TnC) and is located on polymerized actin together with tropomyosin, forming muscle thin filament. We have determined the molecular structures of the core domains (relative molecular mass of 46,000 and 52,000) of human cardiac troponin in the Ca2+-saturated form by X-ray crystallography. Analysis of the four structures derived from the two crystal forms reveals that the core domain is further divided into sub-domains, connected by linkers, making the entire molecule highly flexible. The structures of the troponin ternary complex suggests that the Ca2+-binding to the regulatory TnC site displaces the carboxyl-terminal portion of TnI from actin/tropomyosin, thereby altering mobility and/or flexibility of the troponin/tropomyosin strand on the actin filament. These Ca2+-dependent changes in the properties of the tropomyosin strand on the actin filament may in turn alter accessibility of myosin heads (motor protein) to the actin filament.     

收缩蛋白质分子的光学特性及其在蛋白质分子运动过程中的变化规律

本文用具有各向异性的光学晶体模拟肌肉收缩蛋白质分子，给出了描述收缩蛋白质光学特性的极化率张量表示，并讨论了在蛋白质分子运动过程中极化率张量的变化规律。基于这一理论分析，根据用光的椭圆偏振技术测得的单根青蛙肌纤维在僵直状态和松弛状态及在不同温度下的实验结果，我们认为，当肌纤维处于僵直状态时，其内部肌球蛋白分子（横桥部分）与肌动蛋白分子空间距离近，相互作用力强；而在松弛状态时，两种收缩蛋白分子空间距离远，相互作用力弱；当改变肌纤维所处溶液温度时，横桥与肌动蛋白分子的相对空间取向和相互作用力受到影响，较高温度时分子热运动会削弱肌球蛋白分子和肌动蛋白分子之间的作用，使横桥向粗肌丝骨架靠拢．     

基于S7-200PLC的机械手运动控制

基于S7-200PLC对机械手的运动进行一系列控制,这些运动包括手臂上下、左右直线运动,手腕旋转运动,手爪夹紧动作和机械手整体旋转运动等。所采用的动力机构是步进电机,能够做到精确控制。在多个行程开关传感器的保护下,保证了这些运动万无一失。     

A System for the Rapid Acquisition of Surface Potential Maps of Human Skeletal Muscle Motor Units

Inability to predict the intramusclar orientation, depth, and distribution of a motor unit's muscle fibers within a human skeletal muscle complicates unit size estimation. A data collection system is described that is suitable for systematic study of this problem.     

脂质沉积症骨骼肌纤维的电镜观察

观察脂质沉积症骨骼肌纤维的超微病理变化特征.活检肌组织取自一例16岁少女,透射电镜制样观察.镜下显示病变的肌纤维内堆积有大量脂滴,肌节模糊,肌丝紊乱,Z线断裂,线粒体嵴变态成网管状,胞质内同时伴有糖原颗粒增多,提示脂质的不正常沉积可导致肌纤维内超微结构的病理改变.     

Rich Phase Behavior in a Supramolecular Conducting Material Derived from an Organogelator

Organic conducting fiber‐like materials hold great promise for the development of nanowires that can act as connections in miniature electronic devices, as an alternative to inorganic nanometer scale structures. This article presents a conducting organic tetrathiafulvalene‐based supramolecular material which possesses a rich phase behavior with different packing of the molecules in the different forms, evidenced by electron spin resonance (ESR) spectroscopy. The distinct phases of conducting nanofibers can be easily fabricated through the temperature control of their preparation process from a xerogel by doping with iodine vapors. A total of four conducting phases have been identified conclusively using ESR spectroscopy as the key analytical tool. Three of the phases show a good long‐term stability and areas in which the I–V curves have ohmic behavior when studied by current sensing (conducting) AFM. They offer promise for applications where electrical nanometer scale connections are required.     

Temporal occurrence of immature skeletal muscle fibers in the sciatic nerve matrix regenerating within the silicone chamber after nerve transection in the normal rat

We examined by light and electron microscopy the immature skeletal muscle fibers in the rat sciatic nerve regenerating within the silicone chamber 14 days after nerve transection. Small myelinated and nonmyelinated nerve fibers associated with Schwann cells from the proximal stump began to approach the midportion of the interstump zone. In the middle segment, fibroblasts or fibroblast-like mesenchymal cells and macrophages were observed everywhere in the newly formed matrix filled with exuded erythrocytes and fibrin clots. In addition to some fibroblast-like mesenchymal cells were closely apposed to each other. However, the proximal and distal segments contained immature muscle fibers with various amount of myofilaments and one or plural centrally located nuclei, thus indicating various phases of the early differentiation of skeletal muscle fibers similar to those observed during an early stage of developing muscle fibers. However, the precise origin of these skeletal muscle fibers remains to be determined.     

Structural Evolution of Self‐Assembling Nanohybrid Thin Films from Functionalized Urea Precursors

Hybrid organic‐inorganic thin films exhibiting patterned structuring on the nanometer scale have been prepared through the controlled hydrolysis‐condensation of enantiomerically pure chiral urea‐based silyl compounds. The thin films are obtained by spin‐coating of sols obtained via acid‐ or base‐catalyzed hydrolytic condensation of these molecular precursors. A self‐templating process is demonstrated via atomic force and transmission electron microscopy, showing the formation of nanometer size aggregates consisting of interconnected spherulates under acidic condition and of assembled fibers under basic conditions.     

Discotic Liquid Crystal‐Functionalized Gold Nanorods: 2‐ and 3D Self‐Assembly and Macroscopic Alignment as well as Increased Charge Carrier Mobility in Hexagonal Columnar Liquid Crystal Hosts Affected by Molecular Packing and π–π Interactions

Gold nanorods functionalized with triphenylene‐based discotic liquid crystal (LC) motifs show striking self‐assembly behavior both on transmission electron microscopy (TEM) grids as well as in the bulk enforced by the π–π‐stacking of triphenylene groups of adjacent nanorods. TEM images confirm that these discotic LC nanorods form ribbons of parallel‐stacked nanorods several hundred nanometer long. The pursued silane conjugation approach to decorate the nanorods allows for the preparation of dispersions of the nanorods in the hexagonal columnar phases of parent discotic LCs, where the nanorods can be macroscopically aligned with almost 80% efficiency by a simple shearing protocol. Doping the parent host materials with about 1% by weight of the discotic LC‐capped nanorods also reduces the lattice parameter and the intracolumnar packing, which gives rise to enhanced charge carrier mobility in these hosts as determined by time‐of‐flight measurements.     

基于脑电和眼电的运动想象多尺度识别方法研究

基于脑电信号对同一肢体不同动作想象模式进行识别的正确率低,已成为基于脑机接口对肢体瘫痪患者进行运动想象训练监控的方法,获得临床应用前必须解决的瓶颈问题.针对该问题,本文提出一种利用运动想象时眼睛的活动状态与所想象肢体动作之间存在的耦合关系,进行运动想象多尺度识别的新方法.该方法首先在大尺度上,利用脑电信号对运动想象是否发生进行识别,再结合同一运动想象过程眼电信号协同变化模式的识别结果,基于决策融合在更精细的尺度上,对同一肢体不同动作的想象模式进行识别.实验结果表明,仅基于脑电进行右臂三种动作想象模式识别的平均正确率为63.0%,而应用所提出方法可以将其提高到91.4%.所提出方法可望有临床应用前景.     

Picosecond all-optical polarization switching in InGaAsP MQW's at1.52 μm

An all-optical switch operating at a wavelength of 1.52 μm is demonstrated. The switch makes use of electron spin polarization in a multiple-quantum-well semiconductor structure. The polarization change of a signal beam was observed to recover with a time constant of 20 ps determined by the spin relaxation time     

Manipulation of Muscle Force with Various Firing Rate and Recruitment Control Strategies

A computer-controlled, dual-channel neuromuscular stimulation system capable of manipulating skeletal muscle force with a wide range of action potential firing rates and motor-unit recruitment control strategies was designed and evaluated on the m. gastrocnemius muscle of the cat. The muscle force could be controlled with control strategies in which motor unit recruitment accounted for from 50 percent and up to 100 percent of the initial muscle force while firing rate induced the remaining force segment. The force response to linearly increasing recruitment was linear, whereas a saturation nonlinearity was evident in response to the firing rate input. Initial and terminal nonlinear force segments during 100 percent recruitment range were shown to be due to the viscoelastic components of the muscle fibers and their tendons. Recruitment of the muscle's motor units at rates that generated from 36 percent/s and up to 360 percent/s of the maximal force range was shown to correlate linearly to the input stimulus (R 0.9889). Reduction of the maximal firing rate from 55 to 40 pps showed that although minimization of fatigue at a cost of 10 percent reduction in the maximal force is possible, the correlation of the force response to the input signal remains high (R 0.9929) and linear. Some preliminary conclusions about rehabilitative applications were drawn based on the data presented in conjunction with previous studies.     

Tunable light propagation in photonic Crystal coupler filled with liquid Crystal

We propose a new photonic crystal coupler-type optical switch which consists of a triangular lattice of air holes filled with liquid crystal (LC). This switch utilizes the decoupling nature. In order to utilize a large refractive index change of LC, /spl pi/ phase-shifted larger air holes are introduced into the core region, compared to the cladding region. In our structure, all air holes are filled with LC and selective injection of LC is not required. By changing the orientation of the applied field, the coupling state changes decoupling from perfect coupling, and switching operation is realized. Switching operation of the present switch is confirmed by the two-dimensional finite-element method (FEM), and also preliminary three-dimensional calculations confirm the two-dimensional FEM results.     

Deploying Wireless Sensor Networks under Limited Mobility Constraints

In this paper, we study the issue of sensor network deployment using limited mobility sensors. By limited mobility, we mean that the maximum distance that sensors are capable of moving to is limited. Given an initial deployment of limited mobility sensors in a field clustered into multiple regions, our deployment problem is to determine a movement plan for the sensors to minimize the variance in number of sensors among the regions and simultaneously minimize the sensor movements. Our methodology to solve this problem is to transfer the nonlinear variance/movement minimization problem into a linear optimization problem through appropriate weight assignments to regions. In this methodology, the regions are assigned weights corresponding to the number of sensors needed. During sensor movements across regions, larger weight regions are given higher priority compared to smaller weight regions, while simultaneously ensuring a minimum number of sensor movements. Following the above methodology, we propose a set of algorithms to our deployment problem. Our first algorithm is the optimal maximum flow-based (OMF) centralized algorithm. Here, the optimal movement plan for sensors is obtained based on determining the minimum cost maximum weighted flow to the regions in the network. We then propose the simple peak-pit-based distributed (SPP) algorithm that uses local requests and responses for sensor movements. Using extensive simulations, we demonstrate the effectiveness of our algorithms from the perspective of variance minimization, number of sensor movements, and messaging overhead under different initial deployment scenarios.     

Micro–macro linear piezoelectric motor based on self-moving cell

This paper deals with the development of a piezoelectric linear motor that can control macro and micro movements. Concept of the motor is based on a self-moving cell, which consists of an elastic shell structure and a piezoelectric stack actuator. Three cells are connected in series and by activating piezoelectric actuators in these cells, macro movement can be achieved. Since these cells are fit into a guideway with interference, this motor can possess a high stall force and fail-safe lock. When one piezoelectric actuator is activated by open loop control with hysteresis compensation, micro movement can be obtained. Design of self-moving cell structure, fabrication, and control of the motor for macro and micro movements are explained. The maximum moving velocity of 1.05 mm/s and the maximum force of 4.3 N were observed. The possibility of nano scale movement was demonstrated by taking into account the hysteresis compensation of the piezoelectric actuator.     

ESR spectra of the triplet and singlet states of a Zn-P two-spin system in Si: Mathematical modeling and computer simulation

A computer simulation of the ESR spectra of a Zn-P two-spin system in Si is carried out, involving solving the quantum Liouville equation supplemented with a semiempirical relaxation operator (represented by a tensor of order 4). The mathematical model employed enables one to compute ESR spectra for continuous-absorption conditions as the paramagnetic-center density is increased. Two conclusions are drawn from a comparison of the simulated spectra and previously measured ones: (i) For a model of ESR spectra to be accurate it must include both the dipole-dipole interaction between the magnetic moments and isotropic and anisotropic (vector) exchange interactions. (ii) The interaction constants are comparable with one another and so cannot be neglected. The cases are covered of a triplet and a singlet state of the ion pair, the parameter values being the same; in the latter case, the system includes a spin-0 and a spin-1/2 nucleus with two valence electrons interacting by the dipole and exchange mechanisms. Satellite lines resulting from the interactions are observed in the simulated spectrum for an extremely small natural line width.     

Wearable Stretchable Dry and Self-Adhesive Strain Sensors with Conformal Contact to Skin for High-Quality Motion Monitoring

Wearable stretchable strain sensors can have important applications in many areas. However, the high noise is a big hurdle for their application to monitor body movement. The noise is mainly due to the motion artifacts related to the poor contact between the sensors and skin. Here, wearable stretchable dry and self-adhesive strain sensors that can always form conformal contact to skin even during body movement are demonstrated. They are prepared via solution coating and consist of two layers, a dry adhesive layer made of biocompatible elastomeric waterborne polyurethane and a sensing layer made of a non-adhesive composite of reduced graphene oxide and carbon nanotubes. The adhesive layer makes the sensors conformal to skin, while the sensing layer exhibits a resistance sensitive to strain. The sensors are used to accurately monitor both small- and large-scale body movements, including various joint movements and muscle movements. They can always generate high-quality signals even on curvilinear skin surface and during irregular skin deformation. The sensitivity is remarkably higher while the noise is saliently lower than the non-adhesive strain sensors. They can also be used to monitor the movements along two perpendicular directions, which cannot be achieved by the non-adhesive strain sensors.     

A study of the three-dimensional distribution of light (632.8 nm) in tissue

Effective application of photodynamic therapy requires that light dose to tissue be accurately calculated. Special fiber optic detectors have been constructed, and experimental methods developed, for determining three-dimensional flux patterns of red light instilled into tissue. These methods utilize the insertion and movement of the detecting fibers along fixed coordinates within tissue, and the measurement of light flux values at these positions. Resulting values of bovine skeletal muscle have been interpolated and mapped into two-dimensional graphical patterns. Combinations of two-dimensional patterns allow a reconstruction in three dimensions. Either calculation or geometric construction provides penetration depths. Light dispersion is spherically symmetrical, as predicted by diffusion theory. Penetration depths for bovine muscle ranged from 1.8 to 2.3 mm. Three theoretical formulations were fit to the experimental data and were found to be equally valid at depth.     

Investigation on parametric analysis of dynamic EMG signals by amuscle-structured simulation model

In the analysis of electromyographic (EMG) signals during dynamic movement, we have proposed an estimation algorithm for the time-varying parameters of an autoregressive model. The parameters correspond to less biased time-varying reflection coefficients. We determined the less biased estimation using a locally quasi-stationary model and named these parameters "k parameters." We estimated k parameters up to the fifth order for the surface EMG signals of a masseter muscle during rapid open-close movement of the lower jaw, a ballistic contraction, and fatigue. According to the results, the time courses of the k parameters displayed remarkable properties. In order to study the behavior of k parameters physiologically, we produced a muscle-structured simulation model based on anatomical and physiological data. The simulation results suggested that the behavior of the third parameter is related to the number of active motor units (MU's) at the shallow layer of a muscle. The detailed recruitment mechanism in terms of the MU's types has not yet been solved. Although further study is required, the parametric analysis using k parameters offers a new perspective for evaluation of muscle dynamics during several movements.     

Topographical map of innervation zones within single motor unitsmeasured with a grid surface electrode

A grid electrode with closely spaced contacts was developed to measure the spatial distribution of motor unit action potentials on a skin surface. This electrode was used to estimate the configuration of innervation zones. The derived action potentials showed waveforms originating from the middle length of the muscle belly and propagating bidirectionally along the muscle fibers. The position of the innervation zones was estimated from the source of the propagation. By isolating action potentials from single motor units, the innervation zones for individual motor units were defined. Studies were performed in the biceps brachii of three normal subjects. The innervation zones comprised one to four separate regions and spread over up to 20 mm along the length of muscle fibers. The number and the spreading area of innervation zones varied with the subject and with the motor unit