Home About us Contact
|
Home About us Contact | ||
|
|
||
Mechanical Deformation (mechanical + deformation)
Selected Abstracts3-D DYNAMIC OPTICAL TECHNIQUES TO MODEL FOOD MECHANICAL DEFORMATIONJOURNAL OF TEXTURE STUDIES, Issue 4 2010MURIEL JACQUOT ABSTRACT Finding new instrumental rheological parameters that better describe sensory textures can improve correlation between rheological and sensory measurements of food. Two optical three-dimensional (3-D) techniques commonly used in mechanical engineering field were studied. These techniques have never been used in food science. Digital image correlation and Breuckmann scanning systems were successful to distinguish gelatin gels and soft cheeses varying in firmness and viscoelastic properties. These two systems were coupled with a universal testing machine to provide information regarding 3-D displacements and surface deformation of sample. Mathematical models were developed to determine surface displacement profiles of samples from their firmness and viscoelastic properties. Three parameters were obtained to describe surface displacement profiles linked to samples textural properties. These parameters may be useful to develop models predicting accurately food sensory texture from instrumental measurements. PRACTICAL APPLICATIONS Finding new instrumental rheological parameters that better describe sensory textures to improve correlation between rheological and sensory measurements of food. [source] Mechanical Deformation of Compressible Chromatographic ColumnsBIOTECHNOLOGY PROGRESS, Issue 3 2002R. N. Keener A one-dimensional model of mechanical deformation of compressible chromatography columns is presented. The model is based on linear elasticity and continuum mechanics and is compared to a more complete two-dimensional model and one-dimensional porosity profiles measured by NMR imaging methods. The model provides a quantitative description of compression and the effects of wall support during scale-up. A simple criterion for the significance of wall support as a function of both diameter and length is also developed. Although the model accounts only for mechanical deformation, flow compression can be included, and validation presented here suggests that a more complete model may be valuable for anticipating the effects of scale and aspect ratio on pressure-flow behavior of compressible columns. [source] Single mechano-gated channels activated by mechanical deformation of acutely isolated cardiac fibroblasts from ratsACTA PHYSIOLOGICA, Issue 3 2010A. Kamkin Abstract Aim:, Mechanosensitive conductances were reported in cardiac fibroblasts, but the properties of single channels mediating their mechanosensitivity remain uncharacterized. The aim of this work was to investigate single mechano-gated channels (MGCs) activated by mechanical deformations of cardiac fibroblasts. Methods:, Currents through single MGCs and mechanosensitive whole-cell currents were recorded from isolated rat atrial fibroblasts using the cell-attached and whole-cell patch-clamp configurations respectively. Defined mechanical stress was applied via the patch pipette used for the whole-cell recordings. Results:, Under resting conditions occasional short openings of two types of single MGCs with conductances of 43 and 87 pS were observed. Both types of channels displayed a linear current,voltage relationship with the reversal potential around 0 mV. Small (1 ,m) mechanical deformations affected neither single nor whole-cell mechano-gated currents. Cell compressions (2, 3 and 4 ,m) augmented the whole-cell currents and increased the frequency and duration of single channel openings. Cell stretches (2, 3 and 4 ,m) inactivated the whole-cell currents and abolished the activity of single MGCs. Gd3+ (8 ,m) blocked the whole-cell currents within 5 min. No single channel activity was observed in the cell-attached mode when Gd3+ was added to the intrapipette solution. Cytochalasin D and colchicine (100 ,m each) completely blocked both the whole-cell and single channel currents. Conclusions:, These findings show that rat atrial fibroblasts express two types of MGCs whose activity is governed by cell deformation. We conclude that fibroblasts can sense the direction of applied stress and contribute to mechano-electrical coupling in the heart. [source] Synthesis of Zinc Glycerolate Microstacks from a ZnO Nanorod Sacrificial TemplateEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2009Róbert Rémiás Abstract We synthesized zinc glycerolate (ZnGly) microstacks bytreating ZnO with glycerol at 100 °C under reflux. We observed that the morphology of the ZnO source has a pronounced effect on the appearance of the ZnGly product. In the absence of structure-directing effects the product ZnGly is obtained as a random heap of hexagonal prisms with an average diameter and thickness of ca. 2.5 ,m and ca. 350 nm, respectively. However, bundles of nanorod-shaped ZnO obtained by the thermal decomposition of zinc oxalate nanorods could readily be transformed into 2,4 ,m long zinc glycerolate microstacks in which 6,12 hexagonal prisms are aligned face-to-face. We present evidence that the ZnGly plates in the microstacks are bound together by forces strong enough to withstand mechanical deformation exercised by a contacting AFM tip. The ZnGly microstacks appear to emerge from the ZnO nanorod bundles in an approx. 1:1 ratio in the reactive template synthesis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Tunable Colors in Opals and Inverse Opal Photonic CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Carlos I. Aguirre Abstract Colloidal photonic crystals and materials derived from colloidal crystals can exhibit distinct structural colors that result from incomplete photonic band gaps. Through rational materials design, the colors of such photonic crystals can be tuned reversibly by external physical and chemical stimuli. Such stimuli include solvent and dye infiltration, applied electric or magnetic fields, mechanical deformation, light irradiation, temperature changes, changes in pH, and specific molecular interactions. Reversible color changes result from alterations in lattice spacings, filling fractions, and refractive index of system components. This review article highlights the different systems and mechanisms for achieving tunable color based on opaline materials with close-packed or non-close-packed structural elements and inverse opal photonic crystals. Inorganic and polymeric systems, such as hydrogels, metallopolymers, and elastomers are discussed. [source] Highly Extensible Bio-Nanocomposite Films with Direction-Dependent PropertiesADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Akhilesh K. Gaharwar Abstract The structure and mechanical properties of bio-nanocomposite films made from poly(ethylene oxide) (PEO) that is physically cross-linked with silicate nanoparticles, Laponite, are investigated. Direction-dependent mechanical properties of the films are presented, and the effect of shear orientation during sample preparation on tensile strength and elongation is assessed. Repeated mechanical deformation results in highly extensible materials with preferred orientation and structuring at the nano- and micrometer scales. Additionally, in vitro biocompatibility data are reported, and NIH 3T3 fibroblasts are observed to readily adhere and proliferate on silicate cross-linked PEO while maintaining high cell viability. [source] Reversibly Deformable and Mechanically Tunable Fluidic AntennasADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Ju-Hee So Abstract This paper describes the fabrication and characterization of fluidic dipole antennas that are reconfigurable, reversibly deformable, and mechanically tunable. The antennas consist of a fluid metal alloy injected into microfluidic channels comprising a silicone elastomer. By employing soft lithographic, rapid prototyping methods, the fluidic antennas are easier to fabricate than conventional copper antennas. The fluidic dipole radiates with ,90% efficiency over a broad frequency range (1910,1990,MHz), which is equivalent to the expected efficiency for a similar dipole with solid metallic elements such as copper. The metal, eutectic gallium indium (EGaIn), is a low-viscosity liquid at room temperature and possesses a thin oxide skin that provides mechanical stability to the fluid within the elastomeric channels. Because the conductive element of the antenna is a fluid, the mechanical properties and shape of the antenna are defined by the elastomeric channels, which are composed of polydimethylsiloxane (PDMS). The antennas can withstand mechanical deformation (stretching, bending, rolling, and twisting) and return to their original state after removal of an applied stress. The ability of the fluid metal to flow during deformation of the PDMS ensures electrical continuity. The shape and thus, the function of the antenna, is reconfigurable. The resonant frequency can be tuned mechanically by elongating the antenna via stretching without any hysteresis during strain relaxation, and the measured resonant frequency as a function of strain shows excellent agreement (±0.1,0.3% error) with that predicted by theoretical finite element modeling. The antennas are therefore sensors of strain. The fluid metal also facilitates self-healing in response to sharp cuts through the antenna. [source] Soft Mechanical Sensors Through Reverse Actuation in Polypyrrole,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007Y. Wu Abstract The phenomenon of voltage generated from a soft sensor using polypyrrole in response to mechanical deformation is described and investigated. The sensor consists of two polypyrrole layers in contact with an electrolyte and operates in bending mode in air. The magnitude and sign of the induced voltage was found to depend on the type of dopant counter-ions and the nature of the surrounding electrolyte. The mechanical sensor response is shown to be a "reverse actuation", generating millivolt signals for millimeter sized deflections or ,,1000,C,m,3 charge for 1,% strain in the polypyrrole layer. A model based on ,Deformation Induced Ion Flux' has been proposed whereby the strain induced volume change in the polymer produces a shift in the Donnan equilibrium between mobile dopant ions inside the polymer and in the external electrolyte. A simple thermodynamic model provides reasonable estimates of the size of the voltage and charge produced. [source] Development of a technique for modelling clay liner desiccationINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2003Y. Zhou Abstract This paper presents a model for the analysis of clay liner desiccation in a landfill barrier system due to temperature effects. The model incorporates consideration of fully coupled heat-moisture-air flow, a non-linear constitutive relationship, the dependence of void ratio and volumetric water content on stress, capillary pressure and temperature, and the effect of mechanical deformation on all governing equations. Mass conservative numerical schemes are proposed to improve the accuracy of the finite element solution to the governing equations. The application of the model is then demonstrated by examining three test problems, including isothermal infiltration, heat conduction and non-isothermal water and heat transport. Comparisons are made with results from literature, and good agreement is observed. Copyright © 2003 John Wiley & Sons, Ltd. [source] A methodology for fast finite element modeling of electrostatically actuated MEMSINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2009Prasad S. Sumant Abstract In this paper, a methodology is proposed for expediting the coupled electro-mechanical finite element modeling of electrostatically actuated MEMS. The proposed methodology eliminates the need for repeated finite element meshing and subsequent electrostatic modeling of the device during mechanical deformation. We achieve this by using an approximation of the charge density on the movable electrode in the deformed geometry in terms of the charge density in the non-deformed geometry and displacements of the movable electrode. The electrostatic problem has to be solved only once and thus this method speeds up the coupled electro-mechanical simulation process. The proposed methodology is demonstrated through its application to the modeling of four MEMS devices with varying length-to-gap ratios, multiple dielectrics and complicated geometries. Its accuracy is assessed through comparisons of its results with results obtained using both analytical solutions and finite element solutions obtained using ANSYS. Copyright © 2008 John Wiley & Sons, Ltd. [source] Meshfree simulation of failure modes in thin cylinders subjected to combined loads of internal pressure and localized heatINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 8 2008Dong Qian Abstract This paper focuses on the non-linear responses in thin cylindrical structures subjected to combined mechanical and thermal loads. The coupling effects of mechanical deformation and temperature in the material are considered through the development of a thermo-elasto-viscoplastic constitutive model at finite strain. A meshfree Galerkin approach is used to discretize the weak forms of the energy and momentum equations. Due to the different time scales involved in thermal conduction and failure development, an explicit,implicit time integration scheme is developed to link the time scale differences between the two key mechanisms. We apply the developed approach to the analysis of the failure of cylindrical shell subjected to both heat sources and internal pressure. The numerical results show four different failure modes: dynamic fragmentation, single crack with branch, thermally induced cracks and cracks due to the combined effects of pressure and temperature. These results illustrate the important roles of thermal and mechanical loads with different time scales. Copyright © 2008 John Wiley & Sons, Ltd. [source] Optically Anisotropic Colloids of Controllable Shape,ADVANCED MATERIALS, Issue 6 2005A. Fernández-Nieves Solid spheres, disks, and ellipsoids with micrometer-scale bipolar anisotropic character respond to external electric fields by aligning their mean optical axes parallel to the field. The monodisperse, optically anisotropic colloids (see Figure) are synthesized by photopolymerization of a monodisperse liquid-crystal emulsion after mechanical deformation of the drops. [source] Polymer characterization by ultrasonic wave propagationADVANCES IN POLYMER TECHNOLOGY, Issue 2 2008Francesca Lionetto Abstract The propagation of low-intensity ultrasound in polymers, acting as a high-frequency dynamic mechanical deformation, can be successfully used to monitor changes in the modulus of polymers associated with glass transition, crystallization, cross-linking, and other chemical and physical phenomena related to changes in the viscoelastic behavior, such as gelation phenomena. The velocity of sound is related to the polymer storage modulus and density, whereas the absorption of ultrasonic waves is related to the energy dissipation in the material and, therefore, to the loss modulus. Accordingly, ultrasonic measurements have been used by several authors to monitor the evolution of the viscoelastic moduli of polymers as a function of time or temperature and, recently, become a characterization technique of its own right, generally known as ultrasonic dynamic mechanical analysis (UDMA). Often the technique is used in conjunction with rheological methods as a means of providing a better insight into the viscoelastic behavior of polymer systems. As yet UDMA is underutilized primarily because of the low operating temperatures (usually below 100,C) of commercially available ultrasonic transducers, and also due to the requirement of a coupling medium to ensure an efficient energy transfer mechanism between the transducer and the test material. Despite these limitations, this paper shows that the use of ultrasonics is potentially a powerful method for the characterization of polymers, particularly as a tool for online monitoring of events occurring during polymer processing and in the manufacture of polymer matrix composites. The aim of this paper is to review the progress made in recent years, highlighting the potential and reliability of UDMA for monitoring physical transitions in polymers such as glass transition, melting, crystallization, as well as physical changes taking place during curing of thermosetting resins. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:63,73, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20124 [source] Simulating and evaluating small-angle X-ray scattering of micro-voids in polypropylene during mechanical deformationJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2010Stefan Fischer Micro-voids that evolve during mechanical deformation in polypropylene have been characterized by small-angle X-ray scattering. Such voids can be modelled as randomly distributed cylinders which are oriented along the stretching direction, showing a log-normal size distribution. The model and simulation results are presented here. Advantages and disadvantages of the approach, the validity of the model, and important considerations for data evaluation are discussed. Data analysis of two-dimensional scattering images has been performed using a fully automated MATLAB routine by direct model fitting to scattering images. [source] Studies on , to , phase transformations in mechanically deformed PVDF filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Vijayakumar R. P. Abstract PVDF cast films were drawn at different temperatures to different draw ratios at constant draw rate to understand the mechanism of , to , phase transformation during mechanical deformation. WAXD and FTIR studies were carried out to determine the formation and content of , phase in the drawn films. Lower stretch temperatures gave higher fractions of , phase. The cast PVDF films were also drawn at suitable temperatures below the PVDF ambient melting point to the draw ratio of 6.4. The highest fraction of , phase obtained in these ultra drawn films was 0.98. SALS studies carried out for films at different stretch ratios show the change in spherulitic structure with the stretching parameters and give information for the understanding of phase transformation during stretching of PVDF films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Altered T Wave Dynamics in a Contracting Cardiac ModelJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2003NICOLAS P. SMITH Ph.D. Introduction: The implications of mechanical deformation on calculated body surface potentials are investigated using a coupled biophysically based model. Methods and Results: A cellular model of cardiac excitation-contraction is embedded in an anatomically accurate two-dimensional transverse cross-section of the cardiac ventricles and human torso. Waves of activation and contraction are induced by the application of physiologically realistic boundary conditions and solving the bidomain and finite deformation equations. Body surface potentials are calculated from these activation profiles by solving Laplace's equation in the passive surrounding tissues. The effect of cardiac deformation on electrical activity, induced by contraction, is demonstrated in both single-cell and tissue models. Action potential duration is reduced by 7 msec when the single cell model is subjected to a 10% contraction ramp applied over 400 msec. In the coupled electromechanical tissue model, the T wave of the ECG is shown to occur 18 msec earlier compared to an uncoupled excitation model. To assess the relative effects of myocardial deformation on the ECG, the activation sequence and tissue deformation are separated. The coupled and uncoupled activation sequences are mapped onto the undeforming and deforming meshes, respectively. ECGs are calculated for both mappings. Conclusion: Adding mechanical contraction to a mathematical model of the heart has been shown to shift the T wave on the ECG to the left. Although deformation of the myocardium resulting from contraction reduces the T wave amplitude, cell stretch producing altered cell membrane kinetics is the major component of this temporal shift. (J Cardiovasc Electrophysiol, Vol. 14, pp. S203-S209, October 2003, Suppl.) [source] Pressureless Sintering t -zirconia@,-Al2O3 (54 mol%) Core,Shell Nanopowders at 1120°C Provides Dense t -Zirconia-Toughened ,-Al2O3 NanocompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010Min Kim Zirconia-toughened alumina (ZTA) is of growing importance in a wide variety of fields exemplified by ZTA prosthetic implants. Unfortunately, ZTA composites are generally difficult to process because of the need to preserve the tetragonal zirconia phase in the final dense ceramic, coincident with the need to fully densify the ,-Al2O3 component. We report here that liquid-feed flame spray pyrolysis of mixtures of metalloorganic precursors of alumina and zirconia at varying compositional ratios provide access in one step to core,shell nanoparticles, wherein the shell is ,-Al2O3 and the core is a perfect single crystal of tetragonal (t -) zirconia. Pressureless sintering studies provided parameters whereby these nanopowder compacts could be sintered to full density (>99%) at temperatures just above 1100°C converting the shell component to ,-Al2O3 but preserving the t -ZrO2 without the need for any dopants. The final average grain sizes of these sintered compacts are ,200 nm. The resulting materials exhibit the expected response to mechanical deformation with the subsequent production of monoclinic ZrO2. These materials appear to offer a low-temperature, low-cost route to fine-grained ZTA with varied Al2O3:t -ZrO2 compositions. [source] Strain measurement during antral contractions by ultrasound strain rate imaging: influence of erythromycinNEUROGASTROENTEROLOGY & MOTILITY, Issue 2 2009A. B. Ahmed Abstract, Strain rate imaging (SRI) is a non-invasive ultrasound (US) modality that enables the study of mechanical deformation (strain) with high spatial and temporal resolution. A total of 244 contractions in seven healthy volunteers were studied by SRI on two separate days to characterize radial strain of antral contractions in the fasting and fed states and to assess the influence of intravenous erythromycin. Gastric accommodation and emptying were assessed by 2D ultrasonography. The perception of hunger was registered by the participants. The strain increased from early to late phase II and phase III activity by (median) 18%, 58% and 82%, respectively, P < 0.05. Erythromycin infusion in phase I induced contractions with median strain of 35%, but did not increase postprandial strain. Both fasting and postprandially, lumen-occlusive contractions with erythromycin were more frequent than in naturally occurring contractions, 69%vs 48%, P = 0.036 and 40%vs 5%, P < 0.001 respectively. All subjects had rumbling in their abdomens when intraluminal air was detected sonographically (85% of all phase III contractions) and that rumbling was perceived by the participant as maximal awareness of hunger. SRI enabled detailed strain measurement of individual antral contractions. Erythromycin initiated fasting antral contractions and increased the number of lumen-occlusive contractions. [source] Dynamic fatigue studies of ZnO nanowires by in-situ transmission electron microscopyPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7-8 2009Zhiyuan Gao Abstract The fatigue behavior of ceramic ZnO nanowires (NWs) has been investigated under resonance cyclic loading conditions using in-situ transmission electron microscopy (TEM). After mechanical deformation at the resonance frequency at a vibration angle of 5.2° for 35 billion cycles, no failure or any defect generations have been found. We believe that the dislocation-free nature of NWs and the large surface-to-volume ratio contribute to the NWs' ability to undergo deformation without fatigue or fracture, proving their durability and toughness for nanogenerators and nanopiezotronics. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Analysis of SR thermal load studied by FEAPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2007Abstract This work deals with analysis of the thermal effects and inherent mechanical deformations under absorption of the X-ray beam heat. The work is motivated by recent research concentrated on the development of optics for high-flux synchrotron radiation sources. We present the analyses of the static thermal load effects on the surface deformation field for a monocrystalline silicon target, which is the basic material for crystal X-ray optics. The surface and bulk thermal load induces the gradient of temperature and mechanical deformations of the target that are affecting the reflection and diffraction properties of the target. The paper presents the finite-element analyses (FEA) and simulation results of mechanical deformation of flat and slotted silicon targets. The hints for improved target geometry and physical limits for an actual cooling system can be obtained from the presented analyses. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mass Transport Through PDMS/Clay Nanocomposite MembranesTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2007Quan Liu Abstract Poly(dimethylsiloxane)/clay nanocomposite membranes have been synthesized and mass transport properties through those nanocomposite membranes have been investigated. The effect of mechanical deformation on the transport properties of the PDMS (nanocomposite) membranes has also been studied. With the introduction of clay particles into the polymer matrix, mass transport is reduced, likely due to the longer diffusion path, which slows the diffusion process. The effect of membrane extension on diffusion is more complicated. Under small deformation, the permeation flux decreases, but under high deformation, it shows an enhanced diffusion. As the clay particle concentration increased, the effect of external deformation is reduced, and an enhanced diffusion is observed. On a synthétisé des membranes en nano-composites de polydiméthysiloxane et d'argile dans le but d'étudier leurs propriétés de transfert de matière. L'effet de la déformation mécanique sur les propriétés de transfert de ces membranes a également été étudié. Avec l'introduction des particules d'argile dans la matrice des polymères, le transfert de matière est réduit, probablement en raison du chemin de diffusion qui est plus long, ce qui ralentit le processus de diffusion. L'effet de l'extension des membranes sur la diffusion est plus compliqué. Sous faible déformation, le flux de perméation diminue, mais sous forte déformation, la diffusion est améliorée. Lorsque la concentration de particules d'argile augmente, l'effet de la déformation externe est réduit, et une meilleure diffusion est observée. [source] Mechanical Deformation of Compressible Chromatographic ColumnsBIOTECHNOLOGY PROGRESS, Issue 3 2002R. N. Keener A one-dimensional model of mechanical deformation of compressible chromatography columns is presented. The model is based on linear elasticity and continuum mechanics and is compared to a more complete two-dimensional model and one-dimensional porosity profiles measured by NMR imaging methods. The model provides a quantitative description of compression and the effects of wall support during scale-up. A simple criterion for the significance of wall support as a function of both diameter and length is also developed. Although the model accounts only for mechanical deformation, flow compression can be included, and validation presented here suggests that a more complete model may be valuable for anticipating the effects of scale and aspect ratio on pressure-flow behavior of compressible columns. [source] Single mechano-gated channels activated by mechanical deformation of acutely isolated cardiac fibroblasts from ratsACTA PHYSIOLOGICA, Issue 3 2010A. Kamkin Abstract Aim:, Mechanosensitive conductances were reported in cardiac fibroblasts, but the properties of single channels mediating their mechanosensitivity remain uncharacterized. The aim of this work was to investigate single mechano-gated channels (MGCs) activated by mechanical deformations of cardiac fibroblasts. Methods:, Currents through single MGCs and mechanosensitive whole-cell currents were recorded from isolated rat atrial fibroblasts using the cell-attached and whole-cell patch-clamp configurations respectively. Defined mechanical stress was applied via the patch pipette used for the whole-cell recordings. Results:, Under resting conditions occasional short openings of two types of single MGCs with conductances of 43 and 87 pS were observed. Both types of channels displayed a linear current,voltage relationship with the reversal potential around 0 mV. Small (1 ,m) mechanical deformations affected neither single nor whole-cell mechano-gated currents. Cell compressions (2, 3 and 4 ,m) augmented the whole-cell currents and increased the frequency and duration of single channel openings. Cell stretches (2, 3 and 4 ,m) inactivated the whole-cell currents and abolished the activity of single MGCs. Gd3+ (8 ,m) blocked the whole-cell currents within 5 min. No single channel activity was observed in the cell-attached mode when Gd3+ was added to the intrapipette solution. Cytochalasin D and colchicine (100 ,m each) completely blocked both the whole-cell and single channel currents. Conclusions:, These findings show that rat atrial fibroblasts express two types of MGCs whose activity is governed by cell deformation. We conclude that fibroblasts can sense the direction of applied stress and contribute to mechano-electrical coupling in the heart. [source] Analysis of SR thermal load studied by FEAPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2007Abstract This work deals with analysis of the thermal effects and inherent mechanical deformations under absorption of the X-ray beam heat. The work is motivated by recent research concentrated on the development of optics for high-flux synchrotron radiation sources. We present the analyses of the static thermal load effects on the surface deformation field for a monocrystalline silicon target, which is the basic material for crystal X-ray optics. The surface and bulk thermal load induces the gradient of temperature and mechanical deformations of the target that are affecting the reflection and diffraction properties of the target. The paper presents the finite-element analyses (FEA) and simulation results of mechanical deformation of flat and slotted silicon targets. The hints for improved target geometry and physical limits for an actual cooling system can be obtained from the presented analyses. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||