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.     

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.     

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.     

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.     

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.     

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。     

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。     

固态渗碳化硼对Ti-6Al-4V显微组织和性能的影响

研究了Ti-6Al-4V在800℃和1000C下固态渗碳化硼20h后的渗层显微组织以及对硬度等的影响。结果表明：渗层在表面为致密分布的化合物层,其成分主要为TiC、TiB以及TiB2等硬质相,而在基体内部则形成沿晶界分布的板条状或等轴状的颗粒扩散层;表面碳化硼处理可以显著提高Ti-6Al-4V的表面硬度,由359HV提高到了664HV,并且可以得到良好的表面硬、芯部软的硬度梯度;断口形貌分析发现材料由韧性断裂转变成脆性断裂。     

Generation of double-frequency shear waves in materials with different resistances to tension and compression

Equations describing the dynamic processes in materials with different resistances to tension and compression have been derived. It is shown that, when a shear wave propagates in such a material, a quadratic nonlinearity arises that leads to the possibility of generating a shear wave at the double frequency, which is “prohibited” by the equation of the classical elasticity theory. Dependences relating the amplitudes of the waves propagating at the fundamental and double frequencies to the damage parameters are found. A characteristic length is determined at which a considerable transfer of the energy contained in the fundamental wave to the energy of the second harmonic can be expected, thereby allowing assessment of the integral parameter of the material damage. A dependence between the damage parameter and plastic strain has been established on the basis of a constructed mathematical model and experiments with specimens.     

基于C++ Builder 6的串口通信程序实现方法研究

串口是计算机最重要的外设接口之一,对其通信程序实现方法进行研究有着重要的意义。叙述了在C^ Builder 6环境下串口通信程序的4种实现方法：采用直接嵌入汇编、利用Windows的API通信函数、利用VB下的ActiveX控件MSComm、利用第三方控件SPComm。同时对各种实现方法进行了比较,并给出了编程实例。     

Multiple types of calcium signals are associated with cell division in zebrafish embryo

Recent studies suggested that a Ca(2+) signal is involved in the regulation of cell division. For example, using a confocal imaging technique, we have shown that a localized Ca(2+) elevation was clearly associated with the onset of cytokinesis in zebrafish embryo [Chang and Meng (1995) J. Cell Biol. 131:1539-1545]. This finding was later confirmed in studies using aequorin as a Ca(2+) probe. Here, we used a 4-D confocal measurement technique to further characterize the properties of the Ca(2+) signal associated with cell division. We found evidence that there were three types of Ca(2+) signals associated with different stages of cell cleavage in embryonic cell. The first type was repetitive Ca(2+) spikes that emerged several minutes before the first cell cleavage began. These Ca(2+) spikes were first distributed broadly over the central region of the blastodisc and then gradually localized in the equatorial region; they appeared to play the role of determining the position of the first cleavage plane. The second type was a calcium wave that propagated along the cleavage furrow and appeared to guide the furrow extension during the progression of cytokinesis. The third type was a group of post-cleavage calcium spikes that appeared to be responsible for furrow deepening and maintenance of the contractile band. When this type of Ca(2+) transient was blocked by injecting BAPTA or heparin, cell cleavage regressed and the structure of the contractile band could no longer be maintained.