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Structural Deformation (structural + deformation)
Selected AbstractsStructural formation of hybrid siloxane-based polymer monolith in confined spacesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10-11 2004Kazuyoshi Kanamori Abstract Structural deformation of phase-separated methylsiloxane gel under the influence of a surface has been studied. Competitive wetting of siloxane gel phase on a surface during phase formation is found to significantly affect the final morphology in a confined space. When the spinodal wavelength is sufficiently shorter than the size of the available space, a uniform bicontinuous structure forms in confined geometry. However, gel skeletons in the vicinity of a surface are elongated with decreasing size of the space, and finally when the size of the space becomes shorter than the spinodal wavelength, all the gel phase wets on a surface, showing a "wetting transition". Homogeneous bicontinuous methylsiloxane gels were successfully prepared, avoiding such structural deformation, in a long cylindrical fused silica capillary and used for capillary HPLC. The capillary gels exhibited excellent separation efficiency of nitrobenzenes and it was found that the surface character can be altered by incorporating surfactants, which will enable more advanced and extended control of surface character, depending on the analytes. [source] Synthesis and characterization of core,shell-type polymeric micelles from diblock copolymers via reversible addition,fragmentation chain transferJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006Ping Zhang Abstract A method was developed to enable the formation of nanoparticles by reversible addition,fragmentation chain transfer polymerization. The thermoresponsive behavior of polymeric micelles was modified by means of micellar inner cores and an outer shell. Polymeric micelles comprising AB block copolymers of poly(N -isopropylacrylamide) (PIPAAm) and poly(2-hydroxyethylacrylate) (PHEA) or polystyrene (PSt) were prepared. PIPAAm- b -PHEA and PIPAAm- b -PSt block copolymers formed a core,shell micellar structure after the dialysis of the block copolymer solutions in organic solvents against water at 20 °C. Upon heating above the lower critical solution temperature (LCST), PIPAAm- b -PHEA micelles exhibited an abrupt increase in polarity and an abrupt decrease in rigidity sensed by pyrene. In contrast, PIPAAm- b -PSt micelles maintained constant values with lower polarity and higher rigidity than those of PIPAAm- b -PHEA micelles over the temperature range of 20,40 °C. Structural deformations produced by the change in the outer polymer shell with temperature cycles through the LCST were proposed for the PHEA core, which possessed a lower glass-transition temperature (ca. 20 °C) than the LCST of the PIPAAm outer shell (ca. 32.5 °C), whereas the PSt core with a much higher glass-transition temperature (ca. 100 °C) retained its structure. The nature of the hydrophobic segments composing the micelle inner core offered an important control point for thermoresponsive drug release and the drug activity of the thermoresponsive polymeric micelles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3312,3320, 2006 [source] A computational NQR study on the hydrogen-bonded lattice of cytosine-5-acetic acidJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2008Mahmoud Mirzaei Abstract A computational study at the level of density functional theory (DFT) employing 6-311++G** standard basis set was carried out to evaluate nuclear quadrupole resonance (NQR) spectroscopy parameters in cytosine-5-acetic acid (C5AA). Since the electric field gradient (EFG) tensors are very sensitive to the electrostatic environment at the sites of quadruple nuclei, the most possible interacting molecules with the target one were considered in a five-molecule model system of C5AA using X-ray coordinates transforming. The hydrogen atoms positions were optimized and two model systems of original and H-optimized C5AA were considered in NQR calculations. The calculated EFG tensors at the sites of 17O, 14N, and 2H nuclei were converted to their experimentally measurable parameters, quadrupole coupling constants and asymmetry parameters. The evaluated NQR parameters reveal that the nuclei in original and H-optimized systems contribute to different hydrogen bonding (HB) interaction. The comparison of calculated parameters between optimized isolated gas-phase and crystalline monomer also shows the relationship between the structural deformation and NQR parameters in C5AA. The basis set superposition error (BSSE) calculations yielded no significant errors for employed basis set in the evaluation of NQR parameters. All the calculations were performed by Gaussian 98 package of program. © 2007 Wiley Periodicals, Inc. J Comput Chem 2008 [source] Wavelet transform analysis of ab initio molecular dynamics simulation: Application to core-excitation dynamics of BF3JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2007Takao Otsuka Abstract We propose a novel analysis method of ab initio molecular dynamics (AIMD) simulation using a continuous wavelet transform (c-WT) technique. The c-WT technique, one of the time-frequency signal analysis methods, provides a clear view of the dynamical information in time developments. Combined with the auto-correlation function of velocity by AIMD simulation, c-WT analysis enables us to well understand dynamical distribution, such as the vibrational properties following a change of electronic structure in a molecular system. As a practical application, AIMD simulation of core-excited BF3 (B1s , 2a) is illustrated. AIMD simulation leads to the change of vibrational motion as well as structural deformation by core-excitation. The c-WT analysis clarifies the relationship between structural deformation and the related significant vibrational modes in core-excitation within 50 fs. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Recent Perspective on Coronary Bifurcation Intervention: Statement of the "Bifurcation Club in KOKURA"JOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 4 2010YOSHINOBU MURASATO M.D. The treatment of coronary bifurcation lesion remains a challenging issue even in the drug-eluting stent era. Frequent restenosis and stent thrombosis have been recently shown to be related not only to geometrical gap or stent structural deformation but also to rheological disturbance. Low wall shear stress at the lateral side of the bifurcation is likely to cause atherosclerotic changes due to easy access of the macrophages that induce chemical mediators. The turbulent flow over stent metal may facilitate accumulation of platelets, which results in thrombosis. The jailed strut and excess metal overlap may increase these risks. Since dramatic changes of the coronary flow pattern at the bifurcation are closely related to the genesis of atherosclerosis, future bifurcation intervention technique should be considered to restore the original physiological state as well as the anatomical structure. This article summarizes the global consensus of the members of the Asian Bifurcation Club and European Bifurcation Club at the KOKURA meeting. It also provides a perspective of basic sciences relating to bifurcation anatomy, physiology, and pathology, in the search for a best strategy for bifurcation intervention. (J Interven Cardiol 2010;23:295,304) [source] Locomotor skills and balance strategies in children with internal rotations of the lower limbsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2008Sophie Mallau Abstract The purpose of this study was to investigate the functional effects of a structural deformation, internal rotations (IR) of the lower limbs, on upper body balance strategies used during locomotion in 5,6 year-old and 7,10 year-old children. Balance control was examined in terms of rotation around the longitudinal axis in horizontal plane (yaw) and around the sagittal axis in a frontal plane (roll). Kinematics of foot, pelvis, shoulder, and head rotations were measured with an automatic optical TV image processor and used to calculate angular dispersions and segmental stabilizations. Older children with IR showed a lower gait velocity, particularly in difficult balance conditions than typically developing (TD) children. In younger children, the effect of the local biomechanical deficit remained limited to the lower limbs and did not affect upper body coordination. By contrast, in older children with IR, the development of head stabilization in space was affected. This was demonstrated by an "en bloc" instead of an articulated mode of head-trunk unit systematically adopted by the control group. As pelvic stabilization remains the main reference frame to organize balance control in older children with IR, we conclude that the structural deformity of the legs affect and possibly delay the acquisition of the head stabilization in space strategy. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:117,125, 2008 [source] Structural formation of hybrid siloxane-based polymer monolith in confined spacesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10-11 2004Kazuyoshi Kanamori Abstract Structural deformation of phase-separated methylsiloxane gel under the influence of a surface has been studied. Competitive wetting of siloxane gel phase on a surface during phase formation is found to significantly affect the final morphology in a confined space. When the spinodal wavelength is sufficiently shorter than the size of the available space, a uniform bicontinuous structure forms in confined geometry. However, gel skeletons in the vicinity of a surface are elongated with decreasing size of the space, and finally when the size of the space becomes shorter than the spinodal wavelength, all the gel phase wets on a surface, showing a "wetting transition". Homogeneous bicontinuous methylsiloxane gels were successfully prepared, avoiding such structural deformation, in a long cylindrical fused silica capillary and used for capillary HPLC. The capillary gels exhibited excellent separation efficiency of nitrobenzenes and it was found that the surface character can be altered by incorporating surfactants, which will enable more advanced and extended control of surface character, depending on the analytes. [source] Energy-dispersive X-ray absorption spectroscopy at LNLS: investigation on strongly correlated metal oxidesJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2010Júlio C. Cezar An energy-dispersive X-ray absorption spectroscopy beamline mainly dedicated to X-ray magnetic circular dichroism (XMCD) and material science under extreme conditions has been implemented in a bending-magnet port at the Brazilian Synchrotron Light Laboratory. Here the beamline technical characteristics are described, including the most important aspects of the mechanics, optical elements and detection set-up. The beamline performance is then illustrated through two case studies on strongly correlated transition metal oxides: an XMCD insight into the modifications of the magnetic properties of Cr-doped manganites and the structural deformation in nickel perovskites under high applied pressure. [source] An effective strategy for the multibody simulation of jointed FE models in the framework of the floating frame of reference formulation.PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008Wolfgang Witteveen In multibody systems (MBS), where elastic bodies are represented in the frame work of the ,floating frame of reference formulation' (FFRF), structural deformation is usually computed by the superposition of time invariant trial vectors (commonly called ,modes'). However, the mode bases, which are discussed in the literature, do not take joints into special account at the stage of mode generation. In the presented paper we propose a problem,oriented extension of classical mode bases in order to consider the presence of joints. In the novel extension which we call ,Joint Interface Modes' (JIMs), Newton's 3rd law across the joint is taken into account at the stage of mode generation, which leads to a superior convergence at the stage of mode based computation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fabrication of lab-on chip platforms by hot embossing and photo patterningBIOTECHNOLOGY JOURNAL, Issue 11 2007Devendra K. Maurya Abstract In this paper, we review the approaches developed in our laboratory to fabricate polymer-based microfluidic devices to suit a range of applications in bio- or chemical analysis. Thermoplastic materials such as polycarbonate (PC) and poly(methyl methacrylate) (PMMA) are used to fabricate microfluidic devices via hot embossing. To emboss microchannels, we use hard stamps fabricated in silicon or soft stamps molded on poly(dimethylsiloxane) (PDMS). Hard stamps are fabricated on silicon wafers through photolithography and deep reactive ion etching (DRIE). Soft stamps are fabricated by casting PDMS prepolymer on silicon molds. To enclose the fluidic channels, direct fusion bonding was found to produce the highest bond strength with minimal structural deformation. One-step photolithographic methods have also been explored to produce via photochemical patterning microfluidic structures in photocurable materials. We use the photocurable capabilities of a PDMS copolymer, which incorporates a methacrylate crosslinker. Microfluidic channels are produced via one step-photopatterning processes by crosslinking the prepolymer mixture through a photomask. The smaller feature size attainable was 100 ,m. Structures with higher spatial resolution are fabricated through a photoimprinting process whereby a mold is pressed against the precured mixture during UV crosslinking exposure. The application of the fabricated fluidic devices in electrophoretic ion analysis is also presented. [source] Basic Types and Structural Characteristics of Uplifts: An Overview of Sedimentary Basins in ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2009Dengfa HE Abstract: The uplift is a positive structural unit of the crust It is an important window for continental dynamics owing to its abundant structural phenomena, such as fault, fold, unconformity and denudation of strata. Meanwhile, it is the very place to store important minerals like oil, natural gas, coal and uranium. Giant and large-scale oil and gas fields in China, such as the Daqing Oilfield, Lunnan-Tahe Oilfield, Penglai 19,3 Oilfield, Puguang Gas Field and Jingbian Gas Field, are developed mainly on uplifts. Therefore, it is the main target both for oil and gas exploration and for geological study. The uplift can be either a basement uplift, or one developed only in the sedimentary cover. Extension, compression and wrench or their combined forces may give rise to uplifts. The development process of uplifting, such as formation, development, dwindling and destruction, can be taken as the uplifting cycle. The uplifts on the giant Precambrian cratons are large in scale with less extensive structural deformation. The uplifts on the medium- and small-sized cratons or neo-cratons are formed in various shapes with strong structural deformation and complicated geological structure. Owing to changes in the geodynamic environment, uplift experiences a multi-stage or multi-cycle development process. Its geological structure is characterized in superposition of multi-structural layers. Based on the basement properties, mechanical stratigraphy and development sequence, uplifts can be divided into three basic types , the succession, superposition and destruction ones. The succession type is subdivided into the maintaining type and the lasting type. The superposition type can be subdivided into the composite anticlinal type, the buried-hill draped type, the faulted uplift type and the migration type according to the different scales and superimposed styles of uplifts in different cycles. The destruction type is subdivided into the tilting type and the negative inverted type. The development history of uplifts and their controlling effects on sedimentation and fluids are quite different from one another, although the uplifts with different structural types store important minerals. Uplifts and their slopes are the main areas for oil and gas accumulation. They usually become the composite oil and gas accumulation zones (belts) with multiple productive formations and various types of oil and gas reservoirs. [source] The Origin of the Halogen Effect on the Phthalocyanine Green PigmentsCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2010Uck Lee Dr. Abstract The structure and the electronic and optical properties of halogenated copper-phthalocyanine (n,,m,(Hal)-CuPc) molecules are investigated, according to the variation in the substituted halogen-atom species (Hal=Cl or Br) at the , and , positions of isoindole ring with different numbers (n and m=0, 4, 8, or 16). Our results show that the halogen effect mainly results from a structural deformation rather than caused by electronic effects. A nonplanar deformation of the phthalocyanine chromophore of the n,,m,(Hal)-CuPc molecule causes a significant change only in the HOMO and HOMO-1 levels, rather than in the LUMO levels, which leads to the appearance of a green color arising from the large red-shifts of the Soret and Q bands. The present result may serve as an important reference point for designing novel halogen-free green pigments, in accordance with the environmental regulations for the restriction of hazardous substances (RoHS) in electronic and electrical devices. [source] Structure,Property Relation of SrTiO3/LaAlO3 InterfacesADVANCED MATERIALS, Issue 17 2009Mark Huijben Abstract A large variety of transport properties have been observed at the interface between the insulating oxides SrTiO3 and LaAlO3 such as insulation, 2D interface metallicity, 3D bulk metallicity, magnetic scattering, and superconductivity. The relation between the structure and the properties of the SrTiO3/LaAlO3 interface can be explained in a meaningful way by taking into account the relative contribution of three structural aspects: oxygen vacancies, structural deformations (including cation disorder), and electronic interface reconstruction. The emerging phase diagram is much richer than for related bulk oxides due to the occurrence of interface electronic reconstruction. The observation of this interface phenomenon is a display of recent advances in thin film deposition and characterization techniques, and provides an extension to the range of exceptional electronic properties of complex oxides. [source] Thermal flutter analysis of large-scale space structures based on finite element methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2007Wei Li Abstract During the orbital day,night crossing period, the suddenly applied thermal loading is apt to introducing vibration on flexible appendages of large-scale space structures. This kind of thermally-induced vibration is a typical failure of modern spacecrafts. However, owing to the complexity of this problem, many earlier researches study only the vibration of simplified beam models, which can hardly describe the performance of practical structures. This paper aims at using the finite element method to analyse the non-linear vibration of practical thin-walled large-scale space structures subjected to suddenly applied thermal loading. In this study, the coupling effect between structural deformations and the incident normal solar heat flux is considered; the necessary condition of thermally-induced vibration is verified; and the criterion of thermal flutter is established. Copyright © 2006 John Wiley & Sons, Ltd. [source] Investigations of the bond-selective response in a piezoelectric Li2SO4·H2O crystal to an applied external electric fieldACTA CRYSTALLOGRAPHICA SECTION A, Issue 4 2009O. Schmidt Piezoelectric lithium sulfate monohydrate, Li2SO4·H2O, was analyzed with respect to the relationship between the static structural properties of the crystal and its response to an external electric field. The static electron density was determined via standard low-temperature X-ray data collection at 90,(5) K using an Enraf,Nonius CAD-4 diffractometer, Mo K, radiation and multipole model refinement. Then a synchrotron-radiation experiment using the D3 beamline at HASYLAB was conducted in order to investigate the structural deformations in Li2SO4·H2O caused by an applied external electric field. In particular, the shifts of Bragg-peak positions induced by the electric field were measured and the piezoelectric constants d211, d222, d233 and d213 of Li2SO4·H2O were obtained from the shifts. With the same experimental setup the variations of more than 100 Bragg intensities were measured under an applied electric field. The data were used to refine the corresponding displacements of individual atoms within the unit cell. The distortions of the cation,anion bond lengths in the LiO4, LiO3(H2O) and SO4 tetrahedra were evaluated and then analyzed in terms of the electron-density-related properties of the Li,O and S,O bonds. The two lithium structural units were found to be strongly deformed by the applied electric field, while the SO4 tetrahedron changed less. This is in agreement with the low bond strength of the Li,O bonds. [source] Time,accurate Modular CFD-CSD Coupling for Aeroelastic Rotor SimulationsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003A. Altmikus Dipl.-Ing. This paper addresses the timewise accuracy of different coupling approaches applied to instationary aeroelastic simulations of rotors in forward flight. Two different approaches which are widely discussed in literature are examined: the tight or strong coupling, and the fully integrated or monolithic coupling. Strong coupling means an exchange of fluid loads and structural deformations at each time step which is effectuated in a fully modular manner. We will address aspects of conservativity and time-accuracy, and will present results for a helicopter forward flight scenario. However, objections concerning the correct solution of the global non-linear three field problem , structure, grid deformation, aerodynamics , remain. These objections are normally rejected by the monolithic approach. Here, a common set of partial differential equations is derived and solved in a single code. However, a truly monolithic system of equations is only needed for stability analysis, and it can be decomposed in a three field problem respecting appropriate boundary conditions for each domain. Thus, modularity can be maintained, conceiving a quasi-monolithic procedure, when both domains are simultaneously solved in a common non-linear iteration loop on a per time-step basis. First results will be shown for a 2D flutter testcase. [source] | |||||||||||||||||||