The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform
Giovanna Morigi - One of the best experts on this subject based on the ideXlab platform.
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Structural phase transitions in low-dimensional ion Crystals
Physical Review B, 2008Co-Authors: Shmuel Fishman, Gabriele De Chiara, Tommaso Calarco, Giovanna MorigiAbstract:A chain of singly charged particles, confined by a harmonic potential, exhibits a sudden transition to a zigzag configuration when the radial potential reaches a critical value, depending on the particle number. This structural change is a phase transition of second order, whose order parameter is the Crystal Displacement from the chain axis. We study analytically the transition using Landau theory and find full agreement with numerical predictions by Schiffer [Phys. Rev. Lett. 70, 818 (1993)] and Piacente et al. [Phys. Rev. B 69, 045324 (2004)]. Our theory allows us to determine analytically the system's behavior at the transition point.
Jitladda Sakdapipanich - One of the best experts on this subject based on the ideXlab platform.
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Crystal and Crystallites Structure of Natural Rubber and Peroxide-Vulcanized Natural Rubber by a Two-Dimensional Wide-Angle X-ray Diffraction Simulation Method. II. Strain-Induced Crystallization versus Temperature-Induced Crystallization
Macromolecules, 2013Co-Authors: Justin Che, Christian Burger, Shigeyuki Toki, Lixia Rong, Benjamin S. Hsiao, Sureerut Amnuaypornsri, Jitladda SakdapipanichAbstract:New insights into the strain-induced Crystallization (SIC) and temperature-induced Crystallization (TIC) of unvulcanized natural rubber (NR) and peroxide-vulcanized natural rubber (PVNR) have been obtained by wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). The SIC samples were deformed at various temperatures (from −50 to 50 °C) to determine the effect of temperature on the Crystallite structure. In the WAXD patterns, highly oriented sharp Crystal reflections were observed for the SIC samples, whereas sharp rings without preferred orientation were observed for the TIC samples. A novel 2D method to calculate WAXD patterns was used to obtain information on the Crystallite structure. For the SIC samples, the Crystallite sizes, volume, number of chains per Crystallite, Crystallite orientation, and Crystal Displacement disorder increased with increasing temperature but with a decrease in the number of Crystals. The Crystallite sizes and volume were much larger for the TIC samples a...
Shmuel Fishman - One of the best experts on this subject based on the ideXlab platform.
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Structural phase transitions in low-dimensional ion Crystals
Physical Review B, 2008Co-Authors: Shmuel Fishman, Gabriele De Chiara, Tommaso Calarco, Giovanna MorigiAbstract:A chain of singly charged particles, confined by a harmonic potential, exhibits a sudden transition to a zigzag configuration when the radial potential reaches a critical value, depending on the particle number. This structural change is a phase transition of second order, whose order parameter is the Crystal Displacement from the chain axis. We study analytically the transition using Landau theory and find full agreement with numerical predictions by Schiffer [Phys. Rev. Lett. 70, 818 (1993)] and Piacente et al. [Phys. Rev. B 69, 045324 (2004)]. Our theory allows us to determine analytically the system's behavior at the transition point.
R. F. Lobo - One of the best experts on this subject based on the ideXlab platform.
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Micromechanical compressive response of a zeolite single Crystal
Journal of Materials Science, 2002Co-Authors: Z. Wang, J. Lambros, R. F. LoboAbstract:In this work the mechanical properties of a widely used zeolite catalyst, ZSM-5, are measured. Single Crystals of the ZSM-5, of average size 500 microns, are prepared using an organic template molecule. Testing is performed on the single Crystal size scale. An in-house microdeformation tester is designed and manufactured. Loading on the Crystal is provided by a high precision stepper motor. Both Crystal Displacement and applied load are continually monitored through a computer. The entire testing assembly is placed under an optical microscope and a CCD camera is used to obtain real time optical images of the deformation. In this way monotonic and cyclic loading compression stress strain curves are generated. The material is seen to have an average elastic modulus of 4 GPa. It is also seen to be brittle and undergo a gradual stiffness deterioration through a microcracking process. Crystal anisotropy is also investigated by performing two directional tests. However, for the [100] and [010] directions little mechanical anisotropy is observed.
Saleh Saleh - One of the best experts on this subject based on the ideXlab platform.
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Structure/function interface with sequential shortening of basal and apical components of the myocardial band.
European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery, 2006Co-Authors: Gerald D Buckberg, Manuel Castellá, Morteza Gharib, Saleh SalehAbstract:To study the sequential shortening of Torrent-Guasp's 'rope-heart model' of the muscular band, and analyze the structure-function relationship of basal loop wrapping the outer right and left ventricles, around the inner helical apical loop containing reciprocal descending and ascending spiral segments. In 24 pigs (27-82 kg), temporal shortening by sonomicrometer Crystals was recorded. The ECG evaluated rhythm, and Millar pressure transducers measured intraventricular pressure and dP/dt. The predominant shortening sequence proceeded from right to left in basal loop, then down the descending and up the ascending apical loop segments. In muscle surrounded by the basal loop, epicardial muscle predominantly shortened before endocardial muscle. Crystal location defined underlying contractile trajectory; transverse in basal versus oblique in apical loop, subendocardial in descending and subepicardial in ascending segments. Mean shortening fraction average 18+/-3%, with endocardial exceeding epicardial shortening by 5+/-1%. Ascending segment Crystal Displacement followed descending shortening by 82+/-23 ms, and finished 92+/-33 ms after descending shortening stops, causing active systolic shortening to suction venous return; isovolumetric relaxation was absent. Shortening sequence followed the rope-like myocardial band model to contradict traditional thinking. Epicardial muscle shortened before endocardial papillary muscle despite early endocardial activation, and suction filling follows active systolic unopposed ascending segment shortening during the 'isovolumetric relaxation' phase.
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Structure function interface with sequential shortening of basal and apical components of the myocardial band
European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery, 2005Co-Authors: Gerald D Buckberg, Manuel Castellá, Morteza Gharib, Saleh SalehAbstract:Objective: To mechanically test the intact cardiac structure to determine the sequence of contraction within the myocardial mass to try to explain ejection and suction. Methods: In 24 pigs (30–85kg), segment shortening at the site of sonomicrometer Crystals was continuously recorded. The ECG evaluated rhythm, and Millar pressure transducers measured intraventricular pressure and dP/dt. Results: Study of segment shortening defined a sequence of contraction within the myocardial mass, starting at the free wall of the right ventricle and on the endocardial side of the antero-septal wall of the left. Crystal location defined underlying contractile trajectory; transverse in right ventricle followed by basal posterior left ventricle, and from the endocardial anterior wall to the posterior apical segment and finally to the epicardial side of the anterior wall. Mean shortening fraction averaged 18±3%, with endocardial exceeding epicardial shortening by 5±1%. Epicardial segment Crystal Displacement followed endocardial shortening by 82±23ms in the anterior wall, and finished 92±33ms after endocardial shortening stopped, time frame that matches the interval of fast drop of ventricular pressure and the start of suction. Conclusions: Crystal shortening fraction sequence followed the rope-like myocardial band model to contradict traditional thinking, with two starting points of excitation–contraction, the right anterior free wall of the right ventricle, and the endocardial side of the anterior wall. Active suction may be due to active shortening of the epicardial fibers of the anterior wall, because relaxation was not detected when both mitral and aortic valves were closed during the interval previously termed ‘isovolumetric relaxation’.