Propagation behavior of SH waves in layered piezoelectric plates

In this study, the propagation of SH waves in a coupled plate consisting of a piezoelectric layer and an elastic layer is analytically investigated. The piezoelectric material is polarized in the z-axis direction and perfectly bonded to an elastic layer. The mathematical model of the SH wave propagation in this plate is based on the type of surface wave solution. Dispersion relations with respect to phase velocity are obtained for electrically open and mechanically free. Numerical examples are provided to illustrate graphically and compare the variations of the phase and group velocities versus the wave number for the different layers. The thickness ratio and the properties of the two layers have a significant effect on the propagation of SH waves. The conclusions are meaningful both theoretically and practically for the design of high-performance surface acoustic wave (SAW) devices.     

Propagation of transient out-of-plane shear waves in viscoelastic layered media

Propagation of two-dimensional transient out-of-plane shear waves in multilayered viscoelastic media is investigated. The multilayered medium consists of N different isotropic, homogeneous and linearly viscoelastic layers with more than one discrete relaxation time. The top surface of the layered medium is subjected to dynamic out-of-plane shear tractions; whereas, the lower surface is free or fixed. A numerical technique is employed to obtain the solution, which combines the Fourier transform with the method of characteristics. The numerical results are displayed in curves denoting the variations of the shear stresses with time at different locations. These curves reveal clearly the scattering effects caused by the reflections and refractions of inclined waves at the boundaries and at the interfaces of the layers. The curves also display the effects of viscous damping in the wave profiles. By suitably adjusting the material constants, the curves for the case of elastic layers are also obtained as a special case. The curves further show that the numerical technique applied in this study is capable of predicting the sharp variations at the wave fronts.     

Propagation of Rayleigh waves in a rotating orthotropic material elastic half-space under initial stress and gravity

This paper aims to investigate the influence of rotation, initial stress and gravity field on the propagation of Rayleigh waves in a homogeneous orthotropic elastic medium. The government equations and Lame??s potentials are used to obtain the frequency equation which determines the velocity of Rayleigh waves, including rotation, initial stress and gravity field, in a homogeneous, orthotropic elastic medium has been investigated. The numerical results analyzing the frequency equation are discussed and presented graphically. It is important to note that the Rayleigh wave velocity in an orthotropic elastic medium increases a considerable amount in comparison to the Rayleigh wave velocity in an isotropic material. The results indicate that the effects of rotation, initial stress and gravity field on Rayleigh wave velocity are very pronounced.     

Study of calcium signaling in non-excitable cells.

The fundamental importance of calcium signaling in the control of cellular physiology is widely recognized. A dramatic illustration of this is the fact that a Medline search for review articles containing the word "calcium" in the title reveals 4,629 hits, whereas the whole body of calcium signaling literature (approximately 2 x 10(6) pages) is more than enough to fill a decent-sized library. Most of this literature deals with calcium signaling in excitable cells types (mainly neurons and muscle cells), but non-excitable cell types are capable of calcium signaling as well. Although calcium fluxes in the latter cell types have attracted much less interest, the literature involved is still vast. Nevertheless, in this review article we hope to contribute some valuable insights to the field. First we shall discuss the experimental techniques available to the researcher interested in calcium signaling in non-excitable cell types with special attention to patch clamp electrophysiology. Subsequently, we shall review some of the results obtained with these techniques by focussing on the calcium-regulating mechanisms in non-excitable cells and discussing the importance of these mechanisms for physiology.     

Propagation of pulses of shear elastic SH-polarization waves in a solid layer in a direction orthogonal to its surfaces

The propagation of a plane shear SH-polarization wave in an elastic uniform layer with free boundaries in a direction orthogonal to its surfaces is theoretically considered. Based on the expressions we obtained, the reflected pulses of SH waves in a layer are calculated for a wide layer-thickness-to-wavelength ratio range at the working frequency (the spectrum maximum frequency of the radiated pulse). The resonance phenomena for a layer with a half-wave thickness are considered. The calculation results are confirmed experimentally.     

超声衰减法研究C15H32／TritonX-100／水三元体系的稳定性

通过改变C15H32／TritonX-100／水组分配比、制备温度和搅拌速度等条件得到多种不同的三元体系;利用超声衰减法研究各体系的声衰减参数发现,三元体系的稳定性与组分配比、振荡强度和制备温度有密切关系,并与理论计算值及类似试验有较好的符合研究表明超声衰减法可作为检测微乳液体系稳定性的可靠方法,在工业在线检测上具有较高的应用价值。     

Specific labeling of connexin43 in NRK cells using tyramide-based signal amplification and fluorescence photooxidation

Imaging of gap junction proteins, the connexins, has been performed in tissue culture cells both by labeling of connexins with immunocytochemical tags and by cloning and expressing chimeras of connexins and fluorescent proteins such as Green Fluorescent Protein. These two approaches have been used to gain information about protein localization or trafficking at light microscopic resolution. Electron microscopy provides higher resolution; however, analysis of electron micrographs of unlabeled connexins has been generally limited to recognition of gap junction structures. Immunolabeling of gap junction proteins in whole cells at the electron microscopic level has been difficult to achieve because of the fixation sensitivity of most gap junction antibodies. To obtain reasonable sensitivity, immunoperoxidase procedures are typically employed, and these suffer from relatively poor resolution. Here we describe the combination of tyramide signal amplification techniques and fluorescence photooxidation for higher resolution immunolocalization studies for correlative light and electron microscopic imaging. By using correlative microscopy, we can not only localize connexin pools or structures, but also discover what other cellular substructures interact with gap junction proteins. The use of tyramide signal amplification techniques is necessary to increase fluorescence levels that have decreased due to increased specimen fixation required to maintain cell ultrastructure. The fluorescence photooxidation technique provides a high-resolution method for staining of proteins in cells. Unlike colloidal gold-based methods, fluorescence photooxidation allows for three-dimensional localization using high-voltage electron microscopy.     

Three-dimensional shoulder kinematics in individuals with C5-C6 spinal cord injury.

The shoulder kinematics of five able-bodied subjects and those of five arms in three subjects with spinal cord injuries at C5 or C6 levels were measured as the subjects elevated their arms in three different planes: coronal, scapular and sagittal. The range of humeral elevation was significantly reduced in all spinal cord injury (SCI) subjects relative to able-bodied subjects. Over this restricted range of humeral motion, the scapula of SCI subjects tended to be medially rotated, relative to able-bodied subjects, and the protraction and spinal tilt angles of the scapula of the SCI subjects indicated scapular winging. These results are consistent with paralysis or at least with significant weakness of the serratus anterior muscle. If further study confirms this hypothesis, functional neuromuscular stimulation of the serratus anterior muscle via a nerve cuff electrode may be an effective intervention for improving shoulder function in C5-C6 SCI.     

Confocal laser scanning microscopy of calcium dynamics in living cells.

Confocal laser scanning microscopy (CLSM) is widely used to monitor intracellular calcium levels in living cells loaded with calcium-sensitive fluorophores. This review examines the basic advantages and limitations of CLSM in in vivo imaging analyses of calcium dynamics. The benefits of utilizing ratioed images and dextran-conjugated fluorophores are addressed, and practical aspects of handling confocal datasets are outlined. After considering some relatively new microscopical methods that can be used in conjunction with conventional CLSM, possible future applications of confocal techniques in analyses of intracellular calcium dynamics are discussed.     

Experimental setup for studying dynamics of the calcium interaction in cells

A calcium cell signaling system is one of the first, which were formed in the course of evolution of systems. The understanding of calcium binding–uncaging dynamics is crucial in studies of corresponding intracellular processes. By now, a great number of calcium-dependent processes have been investigated. However, works that fully consider these processes are absent. This is specified in many respects by the instrumental abilities. In this work, requirements for the experimental setup intended for comprehensive studies of calcium interaction dynamics are briefly formulated, its block diagram is described, and the results of test experiments are presented.     

Interaction of torsion waves with longitudinal cracks in tubes

A testing method, theoretical and experimental studies of velocity, damping, and reflection of a torsion wave in a tube with a modeled longitudinal crack are discussed. The considered results can be regarded as a basis for the development of effective methods and means that use torsion waves to test acoustic tubes.     

变厚度板中水平剪切波的传播特性分析

为研究超声导波在储罐壁板等变壁厚结构中的传播特性,建立了SH波在空间自由边界中的传播模型,基于各向同性弹性介质Navier-Stokes方程,推导了变厚度板中SH波的频散方程,分析了变厚度板中水平剪切波走时t与倾斜角θ间的相互作用关系;通过简谐点源的远场响应并引入板厚与传播位移的非线性关系,得出了变厚度板中SH波的远场响应方程。在此基础上,仿真分析和实验验证了水平剪切波在不同倾斜角变厚度板中的传播特性,结果表明:在变厚度板的薄端激励水平剪切波并沿结构表面传播时,无频散现象,且无波包分离现象;但随着变厚度板倾斜角θ增大,水平剪切波的走时和接收信号幅值均逐渐递减,且呈非线性关系。     

Imaging and measurement of cytosolic free calcium in plant and fungal cells

Calcium plays a central role as a second messenger in plant and fungal cells and as such is involved in controlling numerous biological processes. Direct demonstration of signal-response coupling via Ca²⁺ requires the measurement and localization of changes in cytosolic free Ca²⁺, [Ca²⁺]_i, during these processes in living cells. In recent years this has become possible with the introduction of a range of fluorescent dyes (e.g. Indo-1 Fura-2 and Fluo-3) which have a high affinity and selectivity for free Ca²⁺. When used with recently developed microscope technologies (e.g. fluorescence ratio imaging or confocal scanning laser microscopy), subcellular localization and precise quantification of [Ca²⁺]_i dynamics in single cells can be achieved. This review describes the principles of [Ca²⁺]_i imaging and measurement using fluorescent dyes, the equipment required to do it, the problems with botanical material and how they are being overcome, future developments for this approach in plant cell biology, and an entirely different strategy for the imaging and measurement of [Ca²⁺]_i involving genetic transformation with the aequorin gene.     

变截面杆中纵波传播特性的实验研究

以往的理论研究结果表明,泊松效应和剪切变形对杆件中纵波的传播特性有着不可忽略的影响,纵波的传播特性也与杆件两端横截面面积比值的大小相关。为了对理论进行验证,搭建了实验系统并进行相关实验。实验结果表明:杆件材料的泊松效应、剪切变形使杆的截止频率变大;同时,变截面杆端面面积比值越大,截止频率越高。实验结果验证了以往的理论预测结果,帮助获取真实的振源振动信号,同时也为状态监测和降噪提供依据。     

一种波浪中的船舶动力定位运动建模方法研究

船舶动力定位是在船舶低速条件下对航向和位置进行控制，控制效果受海浪干扰的影响较大。考虑具有修正PM波谱的长峰不规则浪，基于海浪幅值响应算子（RAO）研究了船舶在海浪中的六自由度运动预报模型。以船舶定点保持模式为例，采用船模实验数据，对海浪作用下的船舶纵荡、横荡和转艏运动进行了数值仿真，给出了运动RAO频率特性曲线和船舶运动时域响应曲线，验证了该方法的有效性。该方法用于船舶在波浪中的运动预报和动力定位系统设计，具有实用性和经济性。     

Implementation of sine-fitting algorithms in systems with 32-bit floating point representation

In this paper, an in-depth analysis of the implementation issues of sine-fitting algorithms in systems with 32-bit floating point representation is presented. The results obtained in 32-bit systems are compared with the ones obtained in 64-bit floating point representation systems. The four-parameter sine-fitting is an iterative algorithm and the criterion used to detect convergence is even more crucial in 32-bit systems. A modification of the traditional implementation is used to, in some situations, reduce the number of iterations required to converge without compromising the final accuracy or precision of the estimated parameters. It is shown that, as the number of samples increases, the limitations of the 32-bit systems clearly limit the use of the sine-fitting algorithms. Nevertheless, the number of samples at which this effect is detected is much higher than the number of samples usually used so far in stand-alone instrumentation systems.     

Patterns of standing waves with angled profiles in distributed objects interacting with point obstacles

The paper presents experimental results pertaining to a distributed impact element (a string) interacting with point obstacles in the course of its motion. The study is also made of dynamic effects accompanying nucleation of periodic trapezoidal standing waves characterized by angled profiles, which can be composed of straight segments.     

Localizations of intracellular calcium and Ca2+-ATPase in hamster spermatogenic cells and spermatozoa

Calcium plays a predominant role regulating many functional processes of spermatogenesis and fertilization. The purpose of the present study is to define the exact location of calcium as well as examine the role it plays during spermatogenesis and sperm capacitation. Testes and epididymides were obtained from adult healthy male hamsters. Spermatozoa were incubated with modified Tyrode's medium up to 4 h at 37 degrees Celsius for sperm capacitation in vitro. Samples of the testes and sperm cells were analyzed by cytochemical techniques to determine the location of calcium and Ca(2+)-ATPase and the percentage of acrosome reactions under light and electron microscopy. The data showed that (1) Sertoli cells exhibited numerous calcium precipitates as large, round, electron-dense bodies distributed throughout the cytoplasm and the mitochondrial matrix. Fine calcium precipitates existed in fewer numbers in the intracellular storage sites of spermatogonia and primary spermatocytes, in sharp distinction to secondary spermatocyte and spermatids, which showed an abundance of large and round calcium precipitates, especially in the mitochondrial matrix of spermatids. More calcium deposits were distributed in the plasma membrane (PM), acrosome membrane, and matrices of the acrosome and mitochondria following capacitation; (2) Ca(2+)-ATPase was found in the endoplasmic reticulum system and PM of noncapacitated spermatozoa as well as Sertoli cells. Capacitated spermatozoa showed a weak signal. These results suggest that the presence of calcium in spermatogenic cells might play a role in cell growth and differentiation during spermatogenesis. The Ca(2+)-ATPase function may be inhibited during capacitation, leading to an increase in acrosomal calcium level and triggering of acrosomal exocytosis.     

C6MW汽轮机油中进水分析及处理

我公司1#汽轮机自投产以来,长期存在油中进水问题。本文阐述了其主要原因及采取的改进措施,效果显著。