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Sample records for induced structural phase

  1. Pressure induced structural phase transition of OsB2: First-principles calculations

    International Nuclear Information System (INIS)

    Ren Fengzhu; Wang Yuanxu; Lo, V.C.

    2010-01-01

    Orthorhombic OsB 2 was synthesized at 1000 deg. C and its compressibility was measured by using the high-pressure X-ray diffraction in a Diacell diamond anvil cell from ambient pressure to 32 GPa [R.W. Cumberland, et al. (2005)]. First-principles calculations were performed to study the possibility of the phase transition of OsB 2 . An analysis of the calculated enthalpy shows that orthorhombic OsB 2 can transfer to the hexagonal phase at 10.8 GPa. The calculated results with the quasi-harmonic approximation indicate that this phase transition pressure is little affected by the thermal effect. The calculated phonon band structure shows that the hexagonal P 6 3 /mmc structure (high-pressure phase) is stable for OsB 2 . We expect the phase transition can be further confirmed by the experimental work. - Abstract: Graphical Abstract Legend (TOC Figure): Table of Contents Figure Pressure induced structural phase transition from the orthorhombic structure to the hexagonal one for OsB 2 takes place under 10.8 GPa (0 K), 10.35 GPa (300, 1000 K) by the first-principles predictions.

  2. Theoretical potential for low energy consumption phase change memory utilizing electrostatically-induced structural phase transitions in 2D materials

    Science.gov (United States)

    Rehn, Daniel A.; Li, Yao; Pop, Eric; Reed, Evan J.

    2018-01-01

    Structural phase-change materials are of great importance for applications in information storage devices. Thermally driven structural phase transitions are employed in phase-change memory to achieve lower programming voltages and potentially lower energy consumption than mainstream nonvolatile memory technologies. However, the waste heat generated by such thermal mechanisms is often not optimized, and could present a limiting factor to widespread use. The potential for electrostatically driven structural phase transitions has recently been predicted and subsequently reported in some two-dimensional materials, providing an athermal mechanism to dynamically control properties of these materials in a nonvolatile fashion while achieving potentially lower energy consumption. In this work, we employ DFT-based calculations to make theoretical comparisons of the energy required to drive electrostatically-induced and thermally-induced phase transitions. Determining theoretical limits in monolayer MoTe2 and thin films of Ge2Sb2Te5, we find that the energy consumption per unit volume of the electrostatically driven phase transition in monolayer MoTe2 at room temperature is 9% of the adiabatic lower limit of the thermally driven phase transition in Ge2Sb2Te5. Furthermore, experimentally reported phase change energy consumption of Ge2Sb2Te5 is 100-10,000 times larger than the adiabatic lower limit due to waste heat flow out of the material, leaving the possibility for energy consumption in monolayer MoTe2-based devices to be orders of magnitude smaller than Ge2Sb2Te5-based devices.

  3. Two-phase flow induced parametric vibrations in structural systems

    International Nuclear Information System (INIS)

    Hara, Fumio

    1980-01-01

    This paper is divided into two parts concerning piping systems and a nuclear fuel pin system. The significant experimental results concerning the random vibration induced in an L-shaped pipe by air-water two-phase flow and the theoretical analysis of the vibration are described in the first part. It was clarified for the first time that the parametric excitation due to the periodic changes of system mass, centrifugal force and Coriolis force was the mechanism of exciting the vibration. Moreover, the experimental and theoretical analyses of the mechanism of exciting vibration by air-water two-phase flow in a straight, horizontal pipe were carried out, and the first natural frequency of the piping system was strongly related to the dominant frequency of void signals. The experimental results on the vibration of a nuclear fuel pin model in parallel air-water two-phase flow are reported in the latter part. The relations between vibrational strain variance and two-phase flow velocity or pressure fluctuation, and the frequency characteristics of vibrational strain variance were obtained. The theoretical analysis of the dynamic interaction between air-water two-phase flow and a fuel pin structure, and the vibrational instability of fuel pins in alternate air and water slugs or in large bubble flow are also reported. (Kako, I.)

  4. Novel X-ray phase-contrast tomography method for quantitative studies of heat induced structural changes in meat

    DEFF Research Database (Denmark)

    Miklos, Rikke; Nielsen, Mikkel Schou; Einarsdottir, Hildur

    2014-01-01

    The objective of this study was to evaluate the use of X-ray phase-contrast tomography combined with 3D image segmentation to investigate the heat induced structural changes in meat. The measurements were performed at the Swiss synchrotron radiation light source using a grating interferometric...... and separated into a water phase and a gel phase formed by the sarcoplasmic proteins in the exudate. The results show that X-ray phase contrast tomography offers unique possibilities in studies both the meat structure and the different meat component such as water, fat, connective tissue and myofibrils...

  5. Structural Changes of PVDF Membranes by Phase Separation Control

    International Nuclear Information System (INIS)

    Lee, Semin; Kim, Sung Soo

    2016-01-01

    Thermally induced phase separation (TIPS) and nonsolvent induced phase separation (NIPS) were simultaneously induced for the preparation of flat PVDF membranes. N-methyl-2-pyrrolidone (NMP) was used as a solvent and dibutyl-phthlate (DBP) was used as a diluent for PVDF. When PVDF was melt blended with NMP and DBP, crystallization temperature was lowered for TIPS and unstable region was expanded for NIPS. Ratio of solvent to diluent changed the phase separation mechanism to obtain the various membrane structures. Contact mode of dope solution with nonsolvent determined the dominant phase separation behavior. Since heat transfer rate was greater than mass transfer rate, surface structure was formed by NIPS and inner structure was by TIPS. Quenching temperature of dope solution also affected the phase separation mechanism and phase separation rate to result in the variation of structure

  6. Application of X-ray phase-contrast tomography in quantative studies of heat induced structural changes in meat

    DEFF Research Database (Denmark)

    Miklos, R.; Nielsen, M. S.; Einarsdottir, Hildur

    2013-01-01

    X-ray computed tomography is increasingly used in the studies of food structure. This paper describes the perspectives of use of phase contrast computed tomography in studies of heat induced structural changes in meat. From the data it was possible to obtain reconstructed images of the sample...... structure for visualization and qualitative studies of the sample structure. Further data segmentation allowed structural changes to be quantified....

  7. Optically induced structural phase transitions in ion Coulomb crystals

    DEFF Research Database (Denmark)

    Horak, Peter; Dantan, Aurelien Romain; Drewsen, Michael

    2012-01-01

    We investigate numerically the structural dynamics of ion Coulomb crystals confined in a three-dimensional harmonic trap when influenced by an additional one-dimensional optically induced periodical potential. We demonstrate that transitions between thermally excited crystal structures, such as b......We investigate numerically the structural dynamics of ion Coulomb crystals confined in a three-dimensional harmonic trap when influenced by an additional one-dimensional optically induced periodical potential. We demonstrate that transitions between thermally excited crystal structures...

  8. Fabrication of PVDF-based blend membrane with a thin hydrophilic deposition layer and a network structure supporting layer via the thermally induced phase separation followed by non-solvent induced phase separation process

    Science.gov (United States)

    Wu, Zhiguo; Cui, Zhenyu; Li, Tianyu; Qin, Shuhao; He, Benqiao; Han, Na; Li, Jianxin

    2017-10-01

    A simple strategy of thermally induced phase separation followed by non-solvent induced phase separation (TIPS-NIPS) is reported to fabricate poly (vinylidene fluoride) (PVDF)-based blend membrane. The dissolved poly (styrene-co-maleic anhydride) (SMA) in diluent prevents the crystallization of PVDF during the cooling process and deposites on the established PVDF matrix in the later extraction. Compared with traditional coating technique, this one-step TIPS-NIPS method can not only fabricate a supporting layer with an interconnected network structure even via solid-liquid phase separation of TIPS, but also form a uniform SMA skin layer approximately as thin as 200 nm via surface deposition of NIPS. Besides the better hydrophilicity, what's interesting is that the BSA rejection ratio increases from 48% to 94% with the increase of SMA, which indicates that the separation performance has improved. This strategy can be conveniently extended to the creation of firmly thin layer, surface functionalization and structure controllability of the membrane.

  9. Pressure-induced structural phase transformation and superconducting properties of titanium mononitride

    Science.gov (United States)

    Li, Qian; Guo, Yanan; Zhang, Miao; Ge, Xinlei

    2018-03-01

    In this work, we have systematically performed the first-principles structure search on titanium mononitride (TiN) within Crystal Structure AnaLYsis by Particle Swarm Optimization (CALYPSO) methodology at high pressures. Here, we have confirmed a phase transition from cubic rock-salt (fcc) phase to CsCl (bcc) phase of TiN at ∼348 GPa. Further simulations reveal that the bcc phase is dynamically stable, and could be synthesized experimentally in principle. The calculated elastic anisotropy decreases with the phase transformation from fcc to bcc structure under high pressures, and the material changes from ductile to brittle simultaneously. Moreover, we found that both structures are superconductive with the superconducting critical temperature of 2-12 K.

  10. A theoretical study of pressure-induced phase transitions and electronic band structure of anti-A-sesquioxide type γ-Be3N2

    International Nuclear Information System (INIS)

    Paliwal, Uttam; Joshi, Kunj Bihari

    2011-01-01

    Structural parameters and electronic band structure of anti-A-sesquioxide (aAs) type γ-Be 3 N 2 are presented following the first-principles linear combination of atomic orbitals method within the framework of a posteriori density-functional theory implemented in the CRYSTAL code. Pressure-induced phase transitions among the four polymorphs α, β, cubic-γ and aAs-γ of Be 3 N 2 are examined. Enthalpy-pressure curves do not show the possibility of pressure-induced structural phase transition to the cubic-γ phase. However, α → aAs-γ and β → aAs-γ structural phase transitions are observed at 139 GPa and 93 GPa, respectively. Band structure calculations predict that aAs-γ Be 3 N 2 is an indirect semiconductor with 4.73 eV bandgap at L point. Variation of bandgap with pressure and deformation potentials are studied for the α, β and aAs-γ polymorphs. Pressure-dependent band structure calculations reveal that, within the low-pressure limit, bandgaps of β and aAs-γ increase with pressure unlike α-Be 3 N 2 .

  11. Pressure Induced Phase Transformations in Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Reimanis, Ivar [Colorado School of Mines, Golden, CO (United States); Cioabanu, Cristian [Colorado School of Mines, Golden, CO (United States)

    2017-10-15

    The study of materials with unusual properties offers new insight into structure-property relations as well as promise for the design of novel composites. In this spirit, the PIs seek to (1) understand fundamental mechanical phenomena in ceramics that exhibit pressure-induced phase transitions, negative coefficient of thermal expansion (CTE), and negative compressibility, and (2) explore the effect of these phenomena on the mechanical behavior of composites designed with such ceramics. The broad and long-term goal is to learn how to utilize these unusual behaviors to obtain desired mechanical responses. While the results are expected to be widely applicable to many ceramics, most of the present focus is on silicates, as they exhibit remarkable diversity in structure and properties. Eucryptite, a lithium aluminum silicate (LiAlSiO4), is specifically targeted because it exhibits a pressure-induced phase transition at a sufficiently low pressure to be accessible during conventional materials processing. Thus, composites with eucryptite may be designed to exhibit a novel type of transformation toughening. The PIs have performed a combination of activities that encompass synthesis and processing to control structures, atomistic modeling to predict and understand structures, and characterization to study mechanical behavior. Several materials behavior discoveries were made. It was discovered that small amounts of Zn (as small as 0.1 percent by mol) reverse the sign of the coefficient of thermal expansion of beta-eucryptite from negative to slightly positive. The presence of Zn also significantly mitigates microcracking that occurs during thermal cycling of eucryptite. It is hypothesized that Zn disrupts the Li ordering in beta-eucryptite, thereby altering the thermal expansion behavior. A nanoindentation technique developed to characterize incipient plasticity was applied to examine the initial stages of the pressure induced phase transformation from beta to

  12. Berry's Phase and Fine Structure

    CERN Document Server

    Binder, B

    2002-01-01

    Irrational numbers can be assigned to physical entities based on iterative processes of geometric objects. It is likely that iterative round trips of vector signals include a geometric phase component. If so, this component will couple back to the round trip frequency or path length generating an non-linear feedback loop (i.e. induced by precession). In this paper such a quantum feedback mechanism is defined including generalized fine structure constants in accordance with the fundamental gravitomagnetic relation of spin-orbit coupling. Supported by measurements, the general relativistic and topological background allows to propose, that the deviation of the fine structure constant from 1/137 could be assigned to Berry's phase. The interpretation is straightforward: spacetime curvature effects can be greatly amplified by non-linear phase-locked feedback-loops adjusted to single-valued phase relationships in the quantum regime.

  13. Constitutive Model Of Graded Micro-Structure Obtained Via Strain Induced Phase Transformation

    CERN Document Server

    Ortwein, Rafał

    The literature review has been divided into three main sub-chapters. The first one is concentrated on the general information about stainless steels and their applications. It is important to perform a general overview and get an idea where the results of the present thesis could be applied. Description of all the brands of stainless steels, their microstructures and properties are important, as similar characteristics can be found in the newly created functionally graded structures. The second sub-chapter is an overview of the most important constitutive models and the experimental results for materials that undergo plastic strain induced phase transformation. Finally, the last one is devoted to functionally graded microstructures obtained via strain induced martensitic transformation – the subject of particular importance for the present thesis. As a general note, the literature review is organized mainly in a chronological order. In some cases similar publications or publications of the same Authors were...

  14. Theoretical study of orbital ordering induced structural phase transition in iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Jena, Sushree Sangita, E-mail: sushree@iopb.res.in; Rout, G. C., E-mail: gcr@iopb.res.in [Physics Enclave, Plot No-664/4825, Lane-4A, Shree Vihar, Bhubaneswar-24, Odisha (India); Panda, S. K., E-mail: skp@iopb.res.in

    2016-05-06

    We attribute the structural phase transition (SPT) in the parent compounds of the iron pnictides to orbital ordering. Due to anisotropy of the d{sub xz} and d{sub yz} orbitals in the xy plane, orbital ordering makes the orthorhombic structure more favorable and thus inducing the SPT. We consider a one band model Hamiltonian consisting of first and second-nearest-neighbor hopping of the electrons. We introduce Jahn-Tellar (JT) distortion in the system arising due to the orbital ordering present in this system. We calculate the electron Green’s function by using Zuvareb’s Green’s function technique and hence calculate an expression for the temperature dependent lattice strain which is computed numerically and self-consistently. The temperature dependent electron specific heat is calculated by minimizing the free energy of the system. The lattice strain is studied by varying the JT coupling and elastic constant of the system. The structural anomaly is studied through the electron occupation number and the specific heat by varying the physical parameters like JT coupling, lattice constant, chemical potential and hopping integrals of the system.

  15. Revealing the hidden structural phases of FeRh

    Science.gov (United States)

    Kim, Jinwoong; Ramesh, R.; Kioussis, Nicholas

    2016-11-01

    Ab initio electronic structure calculations reveal that tetragonal distortion has a dramatic effect on the relative stability of the various magnetic structures (C-, A-, G-, A'-AFM, and FM) of FeRh giving rise to a wide range of novel stable/metastable structures and magnetic phase transitions between these states. We predict that the cubic G-AFM structure, which was believed thus far to be the ground state, is metastable and that the tetragonally expanded G-AFM is the stable structure. The low energy barrier separating these states suggests phase coexistence at room temperature. We propose an A'-AFM phase to be the global ground state among all magnetic phases which arises from the strain-induced tuning of the exchange interactions. The results elucidate the underlying mechanism for the recent experimental findings of electric-field control of magnetic phase transition driven via tetragonal strain. The magnetic phase transitions open interesting prospects for exploiting strain engineering for the next-generation memory devices.

  16. Stress-Induced Cubic-to-Hexagonal Phase Transformation in Perovskite Nanothin Films.

    Science.gov (United States)

    Cao, Shi-Gu; Li, Yunsong; Wu, Hong-Hui; Wang, Jie; Huang, Baoling; Zhang, Tong-Yi

    2017-08-09

    The strong coupling between crystal structure and mechanical deformation can stabilize low-symmetry phases from high-symmetry phases or induce novel phase transformation in oxide thin films. Stress-induced structural phase transformation in oxide thin films has drawn more and more attention due to its significant influence on the functionalities of the materials. Here, we discovered experimentally a novel stress-induced cubic-to-hexagonal phase transformation in the perovskite nanothin films of barium titanate (BaTiO 3 ) with a special thermomechanical treatment (TMT), where BaTiO 3 nanothin films under various stresses are annealed at temperature of 575 °C. Both high-resolution transmission electron microscopy and Raman spectroscopy show a higher density of hexagonal phase in the perovskite thin film under higher tensile stress. Both X-ray photoelectron spectroscopy and electron energy loss spectroscopy does not detect any change in the valence state of Ti atoms, thereby excluding the mechanism of oxygen vacancy induced cubic-to-hexagonal (c-to-h) phase transformation. First-principles calculations show that the c-to-h phase transformation can be completed by lattice shear at elevated temperature, which is consistent with the experimental observation. The applied bending plus the residual tensile stress produces shear stress in the nanothin film. The thermal energy at the elevated temperature assists the shear stress to overcome the energy barriers during the c-to-h phase transformation. The stress-induced phase transformation in perovskite nanothin films with TMT provides materials scientists and engineers a novel approach to tailor nano/microstructures and properties of ferroelectric materials.

  17. Structural phase transition in monolayer MoTe2 driven by electrostatic doping

    Science.gov (United States)

    Wang, Ying; Xiao, Jun; Zhu, Hanyu; Li, Yao; Alsaid, Yousif; Fong, King Yan; Zhou, Yao; Wang, Siqi; Shi, Wu; Wang, Yuan; Zettl, Alex; Reed, Evan J.; Zhang, Xiang

    2017-10-01

    Monolayers of transition-metal dichalcogenides (TMDs) exhibit numerous crystal phases with distinct structures, symmetries and physical properties. Exploring the physics of transitions between these different structural phases in two dimensions may provide a means of switching material properties, with implications for potential applications. Structural phase transitions in TMDs have so far been induced by thermal or chemical means; purely electrostatic control over crystal phases through electrostatic doping was recently proposed as a theoretical possibility, but has not yet been realized. Here we report the experimental demonstration of an electrostatic-doping-driven phase transition between the hexagonal and monoclinic phases of monolayer molybdenum ditelluride (MoTe2). We find that the phase transition shows a hysteretic loop in Raman spectra, and can be reversed by increasing or decreasing the gate voltage. We also combine second-harmonic generation spectroscopy with polarization-resolved Raman spectroscopy to show that the induced monoclinic phase preserves the crystal orientation of the original hexagonal phase. Moreover, this structural phase transition occurs simultaneously across the whole sample. This electrostatic-doping control of structural phase transition opens up new possibilities for developing phase-change devices based on atomically thin membranes.

  18. Surface modification induced phase transformation and structure variation on the rapidly solidified recast layer of titanium

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Ming-Hung [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Haung, Chiung-Fang [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Division of Family and Operative Dentistry, Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Shyu, Shih-Shiun [Department of Dentistry, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei City 231, Taiwan (China); Chou, Yen-Ru [Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Graduate Institute of Biomedical Materials and Tissue Engineering, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Lin, Ming-Hong [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); Peng, Pei-Wen, E-mail: apon@tmu.edu.tw [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); and others

    2015-08-15

    In this study, neodymium-doped yttrium orthovanadate (Nd:YVO{sub 4}) as a laser source with different scanning speeds was used on biomedical Ti surface. The microstructural and biological properties of laser-modified samples were investigated by means of optical microscope, electron microscope, X-ray diffraction, surface roughness instrument, contact angle and cell cytotoxicity assay. After laser modification, the rough volcano-like recast layer with micro-/nanoporous structure and wave-like recast layer with nanoporous structure were generated on the surfaces of laser-modified samples, respectively. It was also found out that, an α → (α + rutile-TiO{sub 2}) phase transition occurred on the recast layers of laser-modified samples. The Ti surface becomes hydrophilic at a high speed laser scanning. Moreover, the cell cytotoxicity assay demonstrated that laser-modified samples did not influence the cell adhesion and proliferation behaviors of osteoblast (MG-63) cell. The laser with 50 mm/s scanning speed induced formation of rough volcano-like recast layer accompanied with micro-/nanoporous structure, which can promote cell adhesion and proliferation of MG-63 cell on Ti surface. The results indicated that the laser treatment was a potential technology to enhance the biocompatibility for titanium. - Highlights: • Laser induced the formation of recast layer with micro-/nanoporous structure on Ti. • An α → (α + rutile-TiO{sub 2}) phase transition was observed within the recast layer. • The Ti surface becomes hydrophilic at a high speed laser scanning. • Laser-modified samples exhibit good biocompatibility to osteoblast (MG-63) cell.

  19. Pressure induced phase transition behaviour in -electron based ...

    Indian Academy of Sciences (India)

    The present review on the high pressure phase transition behaviour of ... For instance, closing of energy gaps lead to metal–insulator transitions [4], shift in energy ... systematic study of the pressure induced structural sequences has become ...

  20. Evidence of liquid phase during laser-induced periodic surface structures formation induced by accumulative ultraviolet picosecond laser beam

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, T. T. D.; Petit, A.; Semmar, N., E-mail: nadjib.semmar@univ-orleans.fr [GREMI, UMR7344, CNRS/University of Orleans, 14 rue d' Issoudun, BP6744, 45067 Orleans Cedex 2 (France); Vayer, M. [ICMN, UMR 7374, CNRS/University of Orleans, 1b rue de la Ferollerie, CS 40059, 45071 Orleans Cedex (France); Sauldubois, A. [CME, UFR Sciences, University of Orleans, 1 Rue de Chartres, BP 6759, 45067 Orleans Cedex 2 (France)

    2015-11-09

    Laser-induced periodic surface structures (LIPSS) were formed on Cu/Si or Cu/glass thin films using Nd:YAG laser beam (40 ps, 10 Hz, and 30 mJ/cm{sup 2}). The study of ablation threshold is always achieved over melting when the variation of the number of pulses increases from 1 to 1000. But the incubation effect is leading to reduce the threshold of melting as increasing the number of laser pulse. Also, real time reflectivity signals exhibit typical behavior to stress the formation of a liquid phase during the laser-processing regime and helps to determine the threshold of soft ablation. Atomic Force Microscopy (AFM) analyses have shown the topology of the micro-crater containing regular spikes with different height. Transmission Electron Microscopy (TEM) allows finally to show three distinguished zones in the close region of isolated protrusions. The central zone is a typical crystallized area of few nanometers surrounded by a mixed poly-crystalline and amorphous area. Finally, in the region far from the protrusion zone, Cu film shows an amorphous structure. The real time reflectivity, AFM, and HR-TEM analyses evidence the formation of a liquid phase during the LIPSS formation in the picosecond regime.

  1. Pressure induced structural phase transition in solid oxidizer KClO3: A first-principles study

    Science.gov (United States)

    Yedukondalu, N.; Ghule, Vikas D.; Vaitheeswaran, G.

    2013-05-01

    High pressure behavior of potassium chlorate (KClO3) has been investigated from 0 to 10 GPa by means of first principles density functional theory calculations. The calculated ground state parameters, transition pressure, and phonon frequencies using semiempirical dispersion correction scheme are in excellent agreement with experiment. It is found that KClO3 undergoes a pressure induced first order phase transition with an associated volume collapse of 6.4% from monoclinic (P21/m) → rhombohedral (R3m) structure at 2.26 GPa, which is in good accord with experimental observation. However, the transition pressure was found to underestimate (0.11 GPa) and overestimate (3.57 GPa) using local density approximation and generalized gradient approximation functionals, respectively. Mechanical stability of both the phases is explained from the calculated single crystal elastic constants. In addition, the zone center phonon frequencies have been calculated using density functional perturbation theory at ambient as well as at high pressure and the lattice modes are found to soften under pressure between 0.6 and 1.2 GPa. The present study reveals that the observed structural phase transition leads to changes in the decomposition mechanism of KClO3 which corroborates with the experimental results.

  2. Structural phase transitions in BaMo6S8: Evidence for an incommensurate phase

    International Nuclear Information System (INIS)

    Jorgensen, J.D.; Hinks, D.G.; Hatch, D.M.; Putnam, R.M.

    1986-01-01

    The structure of BaMo 6 S 8 has been studied over the temperature range 19 K to 573 K by time-of-flight neutron powder diffraction. Below 175 K the data can be suitably refined in a triclinic, P1, cell with volume equal to the rhombohedral, R3, cell common to most Chevrel-phase structures. At temperatures immediately above 175 K, the rhombohedral, R3, Bragg peaks are broadened by satellite reflections which appear to be identical to those recently observed at low temperature in PbMo 6 S 8 and SnMo 6 S 8 . An abrupt change in the sign of the temperature dependence of the hexagonal c axis (∂c/∂T) signals the transition to an undistorted rhombohedral, R3, structure at temperatures above about 350 K. An extended Landau theory determines both continuous and discontinuous transitions from R3 induced by a single order parameter. Analysis of the order parameters inducing commensurate transitions imposes symmetry restrictions on the atomic displacements in the lower symmetry phases. The assumption of an R3 commensurate phase is not consistent with the bond lengths obtained for the distortions to the P1 (or P1) phase for any of the possible cells preserving order parameters. Thus the phase immediately above 175 K cannot be a commensurate R3 structure. This is consistent with experimental evidence. 25 refs., 11 figs., 8 tabs

  3. Development of evaluation method on flow-induced vibration and corrosion of components in two-phase flow by coupled analysis. 1. Evaluation of effects of flow-induced vibration on structural material integrity

    International Nuclear Information System (INIS)

    Naitoh, Masanori; Uchida, Shunsuke; Koshizuka, Seiichi; Ninokata, Hisashi; Anahara, Naoki; Dosaki, Koji; Katono, Kenichi; Akiyama, Minoru; Saitoh, Hiroaki

    2007-01-01

    Problems in major components and structural materials in nuclear power plants have often been caused by flow induced vibration, corrosion and their overlapping effects. In order to establish safe and reliable plant operation, it is necessary to predict future problems for structural materials based on combined analyses of flow dynamics and corrosion and to mitigate them before they become serious issues for plant operation. An innovative method for flow induced vibration of structures in two phase flow by combined analyses of three dimensional flow dynamics and structures is to be introduced. (author)

  4. On the phase space structure of IP3 induced Ca2+ signalling and concepts for predictive modeling

    Science.gov (United States)

    Falcke, Martin; Moein, Mahsa; TilÅ«naitÄ--, Agne; Thul, Rüdiger; Skupin, Alexander

    2018-04-01

    The correspondence between mathematical structures and experimental systems is the basis of the generalizability of results found with specific systems and is the basis of the predictive power of theoretical physics. While physicists have confidence in this correspondence, it is less recognized in cellular biophysics. On the one hand, the complex organization of cellular dynamics involving a plethora of interacting molecules and the basic observation of cell variability seem to question its possibility. The practical difficulties of deriving the equations describing cellular behaviour from first principles support these doubts. On the other hand, ignoring such a correspondence would severely limit the possibility of predictive quantitative theory in biophysics. Additionally, the existence of functional modules (like pathways) across cell types suggests also the existence of mathematical structures with comparable universality. Only a few cellular systems have been sufficiently investigated in a variety of cell types to follow up these basic questions. IP3 induced Ca2+signalling is one of them, and the mathematical structure corresponding to it is subject of ongoing discussion. We review the system's general properties observed in a variety of cell types. They are captured by a reaction diffusion system. We discuss the phase space structure of its local dynamics. The spiking regime corresponds to noisy excitability. Models focussing on different aspects can be derived starting from this phase space structure. We discuss how the initial assumptions on the set of stochastic variables and phase space structure shape the predictions of parameter dependencies of the mathematical models resulting from the derivation.

  5. High pressure structural phase transitions of TiO2 nanomaterials

    International Nuclear Information System (INIS)

    Li Quan-Jun; Liu Bing-Bing

    2016-01-01

    Recently, the high pressure study on the TiO 2 nanomaterials has attracted considerable attention due to the typical crystal structure and the fascinating properties of TiO 2 with nanoscale sizes. In this paper, we briefly review the recent progress in the high pressure phase transitions of TiO 2 nanomaterials. We discuss the size effects and morphology effects on the high pressure phase transitions of TiO 2 nanomaterials with different particle sizes, morphologies, and microstructures. Several typical pressure-induced structural phase transitions in TiO 2 nanomaterials are presented, including size-dependent phase transition selectivity in nanoparticles, morphology-tuned phase transition in nanowires, nanosheets, and nanoporous materials, and pressure-induced amorphization (PIA) and polyamorphism in ultrafine nanoparticles and TiO 2 -B nanoribbons. Various TiO 2 nanostructural materials with high pressure structures are prepared successfully by high pressure treatment of the corresponding crystal nanomaterials, such as amorphous TiO 2 nanoribbons, α -PbO 2 -type TiO 2 nanowires, nanosheets, and nanoporous materials. These studies suggest that the high pressure phase transitions of TiO 2 nanomaterials depend on the nanosize, morphology, interface energy, and microstructure. The diversity of high pressure behaviors of TiO 2 nanomaterials provides a new insight into the properties of nanomaterials, and paves a way for preparing new nanomaterials with novel high pressure structures and properties for various applications. (topical review)

  6. Mechanically induced atomic disorder and phase transformations. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Limei, D

    1992-11-30

    The study shows the possibilities of preparing alloys in various metastable configurations by the simple technique of ball milling. Firstly, chapter 2 gives the description of experimental techniques. In chapter 3, evidence of atomic anti-site disordering in A15-structure superconducting compounds Nb3Sn and Nb3Au during an early stage of milling is demonstrated. Chapter 4 represents the experimental results on the B2-structure magnetic compounds CoGa and CoAl upon mechanical impact. These compounds are well known for their particular type of atomic disorder, namely triple-defect disorder. Various examples of experimental evidence of phase transformations induced by mechanical grinding are presented in chapter 5. Section 5.2 gives an example of amorphization induced by mechanical attrition in the intermetallic compound Ni3Sn. Section 5.3 shows the milling experiment of the intermetallic compound V3 Ga. In section 5.4, for the first time, the observation of a phase transformation to a high-temperature phase with a complex structure will be demonstrated for the intermetallic compound Co3Sn2. In the last chapter, detailed studies on the intermetallic Nb-Au binary compounds for a variety of compositions are presented.

  7. Shear-induced structural transitions in Newtonian non-Newtonian two-phase flow

    Science.gov (United States)

    Cristobal, G.; Rouch, J.; Colin, A.; Panizza, P.

    2000-09-01

    We show the existence under shear flow of steady states in a two-phase region of a brine-surfactant system in which lyotropic dilute lamellar (non-Newtonian) and sponge (Newtonian) phases are coexisting. At high shear rates and low sponge phase-volume fractions, we report on the existence of a dynamic transition corresponding to the formation of a colloidal crystal of multilamellar vesicles (or ``onions'') immersed in the sponge matrix. As the sponge phase-volume fraction increases, this transition exhibits a hysteresis loop leading to a structural bistability of the two-phase flow. Contrary to single phase lamellar systems where it is always 100%, the onion volume fraction can be monitored continuously from 0 to 100 %.

  8. Pressure induced structural phase transition of OsB 2: First-principles calculations

    Science.gov (United States)

    Ren, Fengzhu; Wang, Yuanxu; Lo, V. C.

    2010-04-01

    Orthorhombic OsB 2 was synthesized at 1000 °C and its compressibility was measured by using the high-pressure X-ray diffraction in a Diacell diamond anvil cell from ambient pressure to 32 GPa [R.W. Cumberland, et al. (2005)]. First-principles calculations were performed to study the possibility of the phase transition of OsB 2. An analysis of the calculated enthalpy shows that orthorhombic OsB 2 can transfer to the hexagonal phase at 10.8 GPa. The calculated results with the quasi-harmonic approximation indicate that this phase transition pressure is little affected by the thermal effect. The calculated phonon band structure shows that the hexagonal P 6 3/ mmc structure (high-pressure phase) is stable for OsB 2. We expect the phase transition can be further confirmed by the experimental work.

  9. Shear-induced nano-macro structural transition in a polymeric bicontinuous microemulsion

    DEFF Research Database (Denmark)

    Krishnan, K.; Almdal, K.; Burghardt, W.R.

    2001-01-01

    structure. In situ neutron scattering shows flow-induced anisotropy in the nanometer-scale microemulsion structure at moderate shear rates, while higher rates induce bulk phase separation, with micron-size morphology, which is characterized with in situ light scattering and optical microscopy....

  10. Solid-solid phase transitions in Fe nanowires induced by axial strain

    International Nuclear Information System (INIS)

    Sandoval, Luis; Urbassek, Herbert M

    2009-01-01

    By means of classical molecular-dynamics simulations we investigate the solid-solid phase transition from a bcc to a close-packed crystal structure in cylindrical iron nanowires, induced by axial strain. The interatomic potential employed has been shown to be capable of describing the martensite-austenite phase transition in iron. We study the stress versus strain curves for different temperatures and show that for a range of temperatures it is possible to induce a solid-solid phase transition by axial strain before the elasticity is lost; these transition temperatures are below the bulk transition temperature. The two phases have different (non-linear) elastic behavior: the bcc phase softens, while the close-packed phase stiffens with temperature. We also consider the reversibility of the transformation in the elastic regimes, and the role of the strain rate on the critical strain necessary for phase transition.

  11. Pressure induced structural phase transition in SnS—An ab initio study

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The structural behaviour of SnS under pressure has been investigated by first principle density functional ... tural phase transition from orthorhombic type to monoclinic type structure around 17 GPa which is in good agreement with the ... is achieved by performing the electronic structure and total energy calculation ...

  12. Deformation-induced phase transformation in 4H–SiC nanopillars

    International Nuclear Information System (INIS)

    Chen, Bin; Wang, Jun; Zhu, Yiwei; Liao, Xiaozhou; Lu, Chunsheng; Mai, Yiu-Wing; Ringer, Simon P.; Ke, Fujiu; Shen, Yaogen

    2014-01-01

    The deformation behaviour of single-crystal SiC nanopillars was studied by a combination of in situ deformation transmission electron microscopy and molecular dynamics simulations. An unexpected deformation-induced phase transformation from the 4H hexagonal structure to the 3C face-centred cubic structure was observed in these nanopillars at room temperature. Atomistic simulations revealed that the 4H to 3C phase transformation follows a stick–slip process with initiation and end stresses of 12.1–14.0 and 7.9–9.0 GPa, respectively. The experimentally measured stress of 9–10 GPa for the phase transformation falls within the range of these theoretical upper and lower stresses. The reasons for the phase transformation are discussed. The finding sheds light on the understanding of phase transformation in polytypic materials at low temperature

  13. Pressure induced phase transitions in ceramic compounds containing tetragonal zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Sparks, R.G.; Pfeiffer, G.; Paesler, M.A.

    1988-12-01

    Stabilized tetragonal zirconia compounds exhibit a transformation toughening process in which stress applied to the material induces a crystallographic phase transition. The phase transition is accompanied by a volume expansion in the stressed region thereby dissipating stress and increasing the fracture strength of the material. The hydrostatic component of the stress required to induce the phase transition can be investigated by the use of a high pressure technique in combination with Micro-Raman spectroscopy. The intensity of Raman lines characteristic for the crystallographic phases can be used to calculate the amount of material that has undergone the transition as a function of pressure. It was found that pressures on the order of 2-5 kBar were sufficient to produce an almost complete transition from the original tetragonal to the less dense monoclinic phase; while a further increase in pressure caused a gradual reversal of the transition back to the original tetragonal structure.

  14. Pressure induced reactions amongst calcium aluminate hydrate phases

    KAUST Repository

    Moon, Ju-hyuk

    2011-06-01

    The compressibilities of two AFm phases (strätlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5 GPa by using synchrotron high-pressure X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt volume contraction regardless of the molecular size of the pressure-transmitting media. This volume discontinuity could be associated to a structural transition or to the movement of the weakly bound interlayer water molecules in the AFm structure. The experimental results seem to indicate that the pressure-induced dehydration is the dominant mechanism especially with hygroscopic pressure medium. The Birch-Murnaghan equation of state was used to compute the bulk modulus of the minerals. Due to the discontinuity in the pressure-volume diagram, a two stage bulk modulus of each AFm phase was calculated. The abnormal volume compressibility for the AFm phases caused a significant change to their bulk modulus. The reliability of this experiment is verified by comparing the bulk modulus of hydrogarnet with previous studies. © 2011 Elsevier Ltd. All rights reserved.

  15. Composition-induced structural phase transitions in the (Ba1-xLax)2In2O5+x (0=

    International Nuclear Information System (INIS)

    Tenailleau, C.; Pring, A.; Moussa, S.M.; Liu, Y.; Withers, R.L.; Tarantino, S.; Zhang, M.; Carpenter, M.A.

    2005-01-01

    Composition-induced structural phase changes across the high temperature, fast oxide ion conducting (Ba 1-x La x ) 2 In 2 O 5+x , 0= orthorhombic transition, while the cubic->tetragonal transition could be continuous. Differences between the variation with composition of spectral parameters and of macroscopic strain parameters are consistent with a substantial order/disorder component for the transitions. There is also evidence for precursor effects within the cubic structure before symmetry is broken

  16. Damping Capacity of High Manganese Austenitic Stainless Steel with a Two Phase Mixed Structure of Martensite and Austenite

    International Nuclear Information System (INIS)

    Hwang, Tae Hyun; Kang, Chang-Yong

    2013-01-01

    The damping capacity of high manganese austenitic stainless steel with a two phase mixed structure of deformation-induced martensite and reversed austenite was studied. Reversed austenite with an ultra-fine grain size of less than 0.2 μm was obtained by reversion treatment. The two phase structure of deformation-induced martensite and reversed austenite was obtained by annealing treatment at a range of 500-700 °C and various times in cold rolled high manganese austenitic stainless steel. The damping capacity increased with an increasing annealing temperature and time. In high manganese stainless steel with the two phase mixed structure of martensite and austenite, the damping capacity decreased with an increasing volume fraction of deformation-induced martensite. Thus, the damping capacity was strongly affected by deformation-induced martensite. The results confirmed that austenitic stainless steel with a good combination of strength and damping capacity was obtained from the two phase mixed structure of austenite and martensite.

  17. ATR-IR spectroscopy for the detection of induced-phase transition in Langmuir-Blodgett monolayer film

    International Nuclear Information System (INIS)

    Widayati, Suci

    1996-01-01

    The rate at which a solid substrate is transferred through the Air/Water interface in the Langmuir-Blodgett process of preparing monomolecular films influences the final structure of the transferred film. This phenomenon has been observed from the attenuated total reflectance infra-red (ATR-IR) spectra of fatty acid monolayer transferred onto germanium substrate. This transfer-induced effect is most evidence when the monolayer is transferred from an expanded region of the surface-pressure-molecular area isotherm, but has limited influence on the hydrocarbon chain conformation of film molecules transferred in the condensed phases at high surface pressure. Such a conformational ordering may due to a kinetically limited phase transition taking place in the meniscus formed between the solid substrate and aqueous sub phase. In addition, these results suggest that the structure of the amphiphilic molecules may modulate the extent and nature of the dipping-speed-induced structural changes taking place in the monomolecular L-B film. In order to use monomolecular L-B films to accurately characterize the structure, orientation and phase properties of monolayers at the Air/Water interface, the L-B transfer must be performed at transfer speeds that minimize this structural phase transition

  18. Pressure-induced phase transitions in nanocrystalline ReO3

    International Nuclear Information System (INIS)

    Biswas, Kanishka; Muthu, D V S; Sood, A K; Kruger, M B; Chen, B; Rao, C N R

    2007-01-01

    Pressure-induced phase transitions in the nanocrystals of ReO 3 with an average diameter of ∼12 nm have been investigated in detail by using synchrotron x-ray diffraction and the results compared with the literature data of bulk samples of ReO 3 . The study shows that the ambient-pressure cubic I phase (space group Pm3-barm) transforms to a monoclinic phase (space group C 2/c), then to a rhombohedral I phase (space group R3-barc), and finally to another rhombohedral phase (rhombohedral II, space group R3-barc) with increasing pressure over the 0.0-20.3 GPa range. The cubic I to monoclinic transition is associated with the largest volume change (∼5%), indicative of a reconstructive transition. The transition pressures are generally lower than those known for bulk ReO 3 . The cubic II (Im3-bar) or tetragonal (P4/mbm) phases do not occur at lower pressures. The nanocrystals are found to be more compressible than bulk ReO 3 . On decompression to ambient pressure, the structure does not revert back to the cubic I structure

  19. Hierarchical structures and phase nucleation and growth during pressure-induced crystallization of polypropylene containing dispersion of nanoclay: The impact on physical and mechanical properties

    International Nuclear Information System (INIS)

    Misra, R.D.K.; Yuan, Q.; Chen, J.; Yang, Y.

    2010-01-01

    The objective of this study is to describe the evolution of structure and phases during pressure-induced crystallization of polymers containing dispersion of nanoparticles, in the pressure range of 0.1-200 MPa. The model material for nanoparticles is nanoclay and the model polymer is polypropylene, which can potentially form several crystalline phases. While the phase selection in polypropylene is dictated by pressure and temperature, however, the introduction of nanoparticles alters the nucleation and growth of phases via nanoparticle interface driven evolution. To delineate and separate the effects of applied crystallization pressure from nanoparticle effects, a relative comparison is made between neat polypropylene and polypropylene containing dispersion of nanoclay under similar experimental conditions. The significant finding is that nanoclay interacts with the host polypropylene in a manner such that it alters the structural morphology of α- and γ-crystals of polypropylene. Furthermore, nanoclay promotes the formation of γ-phase at ambient pressure suggesting its role as structure and morphology director in the stabilization of the less accessible γ-phase, and with the possibility of epitaxial growth that enhances toughness. The equilibrium melting point measurements point to thermodynamic interaction between nanoclay and polypropylene, which is supported by the change in glass transition temperature. Thus, the two components, nanoclay and pressure, together provide a unique opportunity to tune hierarchical structures and phase evolution, which has significant implication on physico-chemical and mechanical properties.

  20. Electron-irradiation-induced phase transformation in alumina

    International Nuclear Information System (INIS)

    Chen, C.L.; Arakawa, K.; Lee, J.-G.; Mori, H.

    2010-01-01

    In this study, electron-irradiation-induced phase transformations between alumina polymorphs were investigated by high-resolution transmission electron microscopy. It was found that the electron-irradiation-induced α → κ' phase transformation occurred in the alumina under 100 keV electron irradiation. It is likely that the knock-on collision between incident electrons and Al 3+ cations is responsible for the occurrence of electron-irradiation-induced phase transformation from α-alumina to κ'-alumina.

  1. Structural phase transitions in niobium oxide nanocrystals

    Science.gov (United States)

    Yuvakkumar, R.; Hong, Sun Ig

    2015-09-01

    Niobium oxide nanocrystals were successfully synthesized employing the green synthesis method. Phase formation, microstructure and compositional properties of 1, 4 and 7 days incubation treated samples after calcinations at 450 °C were examined using X-ray diffraction, Raman, photoluminescence (PL), infrared, X-ray photoelectron spectra and transmission electron microscopic characterizations. It was observed that phase formation of Nb2O5 nanocrystals was dependent upon the incubation period required to form stable metal oxides. The characteristic results clearly revealed that with increasing incubation and aging, the transformation of cubic, orthorhombic and monoclinic phases were observed. The uniform heating at room temperature (32 °C) and the ligation of niobium atoms due to higher phenolic constituents of utilized rambutan during aging processing plays a vital role in structural phase transitions in niobium oxide nanocrystals. The defects over a period of incubation and the intensities of the PL spectra changing over a period of aging were related to the amount of the defects induced by the phase transition.

  2. Polarisation Control of DFB Fibre Laser Using UV-Induced Birefringent Phase-Shift

    DEFF Research Database (Denmark)

    Philipsen, Jacob Lundgreen; Lauridsen, Vibeke Claudia; Berendt, Martin Ole

    1998-01-01

    The polarisation properties of a distributed feedback (DFB) fibre laser are investigated experimentally. A birefringent phase-shift is induced by side illumination of the centre part of the lasing structure with ultraviolet (UV) light and it is experimentally shown that the birefringence...... of the phase-shift is the dominating effect controlling the polarisation properties of the laser....

  3. High pressure and temperature induced structural and elastic properties of lutetium chalcogenides

    Science.gov (United States)

    Shriya, S.; Kinge, R.; Khenata, R.; Varshney, Dinesh

    2018-04-01

    The high-pressure structural phase transition and pressure as well temperature induced elastic properties of rock salt to CsCl structures in semiconducting LuX (X = S, Se, and Te) chalcogenides compound have been performed using effective interionic interaction potential with emphasis on charge transfer interactions and covalent contribution. Estimated values of phase transition pressure and the volume discontinuity in pressure-volume phase diagram indicate the structural phase transition from ZnS to NaCl structure. From the investigations of elastic constants the pressure (temperature) dependent volume collapse/expansion, melting temperature TM, Hardness (HV), and young modulus (E) the LuX lattice infers mechanical stiffening, and thermal softening.

  4. Structural and phase studies of stainless wire after electroplastic drawing

    International Nuclear Information System (INIS)

    Troitskij, O.A.; Baldokhin, Yu.V.; Kir'yanchev, N.E.; Ryzhkov, V.G.; Kalugin, V.D.; Sokolov, N.V.; Klekovkin, A.A.; Klevtsur, S.A.

    1983-01-01

    Structural and phase properties of the 12Kh18N10T steel wire are studied after usual and electroplastic drawing from 0.40 up to 0.11 mm with 18-22% reduction per pass with passing 250 A/mm 2 electric current. The earlier made observation on a sharp decrease in content of deformation-induced martensite of α-phase takes place in the wire from stainless metastable austenitic steel as a result of electroplastic drawing. Distribution of the remained α-phase by the wire cross section is established

  5. Strain-induced topological quantum phase transition in phosphorene oxide

    Science.gov (United States)

    Kang, Seoung-Hun; Park, Jejune; Woo, Sungjong; Kwon, Young-Kyun

    Using ab initio density functional theory, we investigate the structural stability and electronic properties of phosphorene oxides (POx) with different oxygen compositions x. A variety of configurations are modeled and optimized geometrically to search for the equilibrium structure for each x value. Our electronic structure calculations on the equilibrium configuration obtained for each x reveal that the band gap tends to increase with the oxygen composition of x 0.5. We further explore the strain effect on the electronic structure of the fully oxidized phosphorene, PO, with x = 1. At a particular strain without spin-orbit coupling (SOC) is observed a band gap closure near the Γ point in the k space. We further find the strain in tandem with SOC induces an interesting band inversion with a reopened very small band gap (5 meV), and thus gives rise to a topological quantum phase transition from a normal insulator to a topological insulator. Such a topological phase transition is confirmed by the wave function analysis and the band topology identified by the Z2 invariant calculation.

  6. Efficient excitation of nonlinear phonons via chirped pulses: Induced structural phase transitions

    Science.gov (United States)

    Itin, A. P.; Katsnelson, M. I.

    2018-05-01

    Nonlinear phononics play important role in strong laser-solid interactions. We discuss a dynamical protocol for efficient phonon excitation, considering recent inspiring proposals: inducing ferroelectricity in paraelectric perovskites, and inducing structural deformations in cuprates [Subedi et al., Phys. Rev. B 89, 220301(R) (2014), 10.1103/PhysRevB.89.220301; Phys. Rev. B 95, 134113 (2017), 10.1103/PhysRevB.95.134113]. High-frequency phonon modes are driven by midinfrared pulses, and coupled to lower-frequency modes those indirect excitations cause structural deformations. We study in more detail the case of KTaO3 without strain, where it was not possible to excite the needed low-frequency phonon mode by resonant driving of the higher frequency one. Behavior of the system is explained using a reduced model of coupled driven nonlinear oscillators. We find a dynamical mechanism which prevents effective excitation at resonance driving. To induce ferroelectricity, we employ driving with sweeping frequency, realizing so-called capture into resonance. The method can be applied to many other related systems.

  7. X-ray diffraction study of thermally and stress-induced phase transformations in single crystalline Ni-Mn-Ga alloys

    International Nuclear Information System (INIS)

    Martynov, V.V.

    1995-01-01

    Using in-situ single crystal X-ray diffraction methods, thermally- and stress-induced crystal structure evolution was investigated in two Ni-Mn-Ga Heusler-type alloys. For the 51at.%Ni-24at.%Mn-25at.%Ga alloy it was found that application of external stress in a temperature range ∼20 C above the M s at first causes intensity changes of X-ray diffuse scattering peaks in β-phase. Further stressing results in stress-induced phase transformations and under the appropriate conditions three successive martensitic transformations (one is parent-to-martensite and two are martensite-to-martensite transformations) can be stress induced. Of these only the parent-to-martensite transformation can be thermally-induced. Two successive structural transformations (thermally-induced parent-to-martensite and stress-induced martensite-to-martensite transformations) were found in 52at.%Ni-25at.%Mn-23at.%Ga alloy. Crystal structure, lattice parameters, type of modulation, and the length of modulation period for all martensites were identified. (orig.)

  8. Imaging of artificially induced vortex structures

    International Nuclear Information System (INIS)

    Fasano, Yanina; Menghini, M.; Cruz, F. de la

    2004-01-01

    The combination of engineered pinning potentials in superconducting crystals, the detection of the liquid-solid vortex transition and the observation of the vortex structure with single vortex sensitivity allow the microscopic analysis of the response of 3D elastic systems to the presence of these potentials. In this work we review recent results obtained by a combination of those techniques studying different vortex structure induced transformations. On the one hand, we have visualized the transformation, along the vortex direction, of a bulk vortex single crystal with hexagonal symmetry into another crystal with square symmetry induced by an engineered Fe-dot lattice deposited on a surface of the vortex single crystal. On the other hand, we found an infrequent first-order phase transition where a vortex liquid under the presence of a random correlated potential (columnar defects) transforms into a vortex solid with no change of topological order

  9. Structural steady states and relaxation oscillations in a two-phase fluid under shear flow: Experiments and phenomenological model

    Science.gov (United States)

    Courbin, L.; Benayad, A.; Panizza, P.

    2006-01-01

    By means of several rheophysics techniques, we report on an extensive study of the couplings between flow and microstructures in a two-phase fluid made of lamellar (Lα) and sponge (L3) phases. Depending on the nature of the imposed dynamical parameter (stress or shear rate) and on the experimental conditions (brine salinity or temperature), we observe several different structural steady states consisting of either multilamellar droplets (with or without a long range order) or elongated (L3) phase domains. Two different astonishing phenomena, shear-induced phase inversion and relaxation oscillations, are observed. We show that (i) phase inversion is related to a shear-induced topological change between monodisperse multilamellar droplets and elongated structures and (ii) droplet size relaxation oscillations result from a shear-induced change of the surface tension between both coexisting (Lα) and (L3) phases. To explain these relaxation oscillations, we present a phenomenological model and compare its numerical predictions to our experimental results.

  10. Polymer confined in membrane phases: influences on stability, structure and dynamics

    International Nuclear Information System (INIS)

    Javierre, Isabelle

    1999-01-01

    The addition of a hydrosoluble polymer to the different structures obtained with mixtures of water/surfactant/alcohol/oil alters the thermodynamic stability of microemulsion and lamellar phases. The reverse sponge phase disappears while one can observe the occurrence of a new phase, labelled L5, at intermediate polymer concentration. In polymer-'doped' solvent lamellar phase, the polymer induces an attractive contribution to the interaction between bilayers while in polymer-'doped' bilayers lamellar phase, the polymer increases the flexibility. The L5 phase exhibits symmetric sponge properties and furthermore presents very strong symmetry fluctuations. The relaxation of these fluctuations were experimentally evidenced for the first time. This unusual dynamic behaviour was confronted to the one of other sponge phases, in a large range of concentrations. (author) [fr

  11. Phase equilibria and phase structures of polymer blends

    International Nuclear Information System (INIS)

    Chalykh, Anatolii E; Gerasimov, Vladimir K

    2004-01-01

    Experimental, methodical and theoretical studies dealing with phase equilibria and phase structures of polymer blends are generalised. The general and specific features of the change in solubility of polymers with changes in the molecular mass and copolymer composition and upon the formation of three-dimensional cross-linked networks are described. The results of the effect of the prehistory on the phase structure and the non-equilibrium state of polymer blends are considered in detail.

  12. Supercooling suppression of microencapsulated phase change materials by optimizing shell composition and structure

    International Nuclear Information System (INIS)

    Cao, Fangyu; Yang, Bao

    2014-01-01

    Highlights: • A new method for supercooling suppression of microPCMs by optimizing the structure of the microcapsule shell. • Large effective latent heat (up to 213 J/g) of the microPCMs, much higher than those using additive as nucleating agents. • Change of shell composition and structure significantly affects the phase transition processes of the encapsulated PCMs. • The latent heat of the shell-induced phase transition is maximized, reaching 83.7% of the latent heat of bulk octadecane. • Hollow spheres with porous rather than solid resin shell are also formed when the SDS concentration is very high. - Abstract: A new method for supercooling suppression of microencapsulated phase change materials (PCMs) has been developed by optimizing the composition and structure of the microcapsule resin shell. The microcapsules comprising paraffin octadecane encapsulated in melamine–formaldehyde resin shell were synthesized with the use the oil-in-water emulsion technique. These PCM microcapsules are 5–15 μm in diameter. The supercooling of these octadecane microcapsules can be as large as 13.6 °C, when the homogeneous nucleation is dominant during the melt crystallization into the thermodynamically stable triclinic phase. It is discovered that the homogeneous nucleation can be mediated by shell-induced nucleation of the triclinic phase and the metastable rotator phase when the shell composition and structure are optimized, without need of any nucleating additives. The effects of synthesis parameters, such as ratio of melamine to formaldehyde, pH of pre-polymer, and pH of emulsion, on the phase transition properties of the octadecane microcapsules have been investigated systemically. The optimum synthesis conditions have been identified in terms of minimizing the supercooling while maintaining heat capacity. Potential applications of this type of phase changeable microcapsules include high heat capacity thermal fluids, thermal management in smart buildings

  13. Pressure-induced ferroelectric to antiferroelectric phase transformation in porous PZT95/5 ceramics

    International Nuclear Information System (INIS)

    Zeng, T.; Dong, X.L.; Chen, X.F.; Yao, C.H.; He, H.L.

    2007-01-01

    The hydrostatic pressure-induced ferroelectric to antiferroelectric (FE-AFE) phase transformation of PZT95/5 ceramics was investigated as a function of porosity, pore shape and pore size. FE-AFE phase transformations were more diffuse and occurred at lower hydrostatic pressures with increasing porosity. The porous PZT95/5 ceramics with spherical pores exhibited higher transformation pressures than those with irregular pores. Moreover, FE-AFE phase transformations of porous PZT95/5 ceramics with polydisperse irregular pores were more diffuse than those of porous PZT95/5 ceramics with monodisperse irregular pores. The relation between pore structure and hydrostatic pressure-induced FE-AFE transformation was established according to stress concentration theory. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Two cloud-point phenomena in tetrabutylammonium perfluorooctanoate aqueous solutions: anomalous temperature-induced phase and structure transitions.

    Science.gov (United States)

    Yan, Peng; Huang, Jin; Lu, Run-Chao; Jin, Chen; Xiao, Jin-Xin; Chen, Yong-Ming

    2005-03-24

    This paper reported the phase behavior and aggregate structure of tetrabutylammonium perfluorooctanoate (TBPFO), determined by differential scanning calorimeter, electrical conductivity, static/dynamic light scattering, and rheology methods. We found that above a certain concentration the TBPFO solution showed anomalous temperature-dependent phase behavior and structure transitions. Such an ionic surfactant solution exhibits two cloud points. When the temperature was increased, the solution turned from a homogeneous-phase to a liquid-liquid two-phase system, then to another homogeneous-phase, and finally to another liquid-liquid two-phase system. In the first homogeneous-phase region, the aggregates of TBPFO were rodlike micelles and the solution was Newtonian fluid. While in the second homogeneous-phase region, the aggregates of TBPFO were large wormlike micelles, and the solution behaved as pseudoplastic fluid that also exhibited viscoelastic behavior. We thought that the first cloud point might be caused by the "bridge" effect of the tetrabutylammonium counterion between the micelles and the second one by the formation of the micellar network.

  15. Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms

    Science.gov (United States)

    Nobukane, Hiroyoshi; Matsuyama, Toyoki; Tanda, Satoshi

    2017-01-01

    The quantum anomaly that breaks the symmetry, for example the parity and the chirality, in the quantization leads to a physical quantity with a topological Chern invariant. We report the observation of a Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms by employing electric transport. We observed the superconductor-to-insulator transition by reducing the thickness of Sr2RuO4 single crystals. The appearance of a gap structure in the insulating phase implies local superconductivity. Fractional quantized conductance was observed without an external magnetic field. We found an anomalous induced voltage with temperature and thickness dependence, and the induced voltage exhibited switching behavior when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer. These anomalous results are related to topological invariance. The fractional axion angle Θ = π/6 was determined by observing the topological magneto-electric effect in the Bose-insulating phase of Sr2RuO4 nanofilms.

  16. Structural systematics of rare earth complexes. III. Structural characterization of lanthanoid (III) picrate hydrates: gadolinium picrate dodecahydrate - an x-ray-induced phase modifications? - and some general aspects of structural chemistry of lanthanoid picrates

    International Nuclear Information System (INIS)

    Harrowfield, J.M.; Weimin, Lu; Brian, W.S.; White, A.H.

    1994-01-01

    In the course of the previous studies (Parts I and II), an unusual result was observed in the case of the structure determination of hydrated gadolinium(III) picrate. Midway through data collection, the monoclinic P2 1 /c phase modification (X-ray-induced?) to a similar cell more nearly resembling that of the La→Pr structure type recorded previously, with no loss of crystal integrity, and with useful data sets being obtained on both forms. Redetermination of the structure with a fresh sample yielded no reproduction of the anomaly. These results are recorded and discussed, together with an overview of the consequences of the data of Parts I-III in relation to those of other literature in the field. 13 refs., 4 tabs., 1 fig

  17. Magnetic phase transition induced by electrostatic gating in two-dimensional square metal-organic frameworks

    Science.gov (United States)

    Wang, Yun-Peng; Li, Xiang-Guo; Liu, Shuang-Long; Fry, James N.; Cheng, Hai-Ping

    2018-03-01

    We investigate theoretically magnetism and magnetic phase transitions induced by electrostatic gating of two-dimensional square metal-organic framework compounds. We find that electrostatic gating can induce phase transitions between homogeneous ferromagnetic and various spin-textured antiferromagnetic states. Electronic structure and Wannier function analysis can reveal hybridizations between transition-metal d orbitals and conjugated π orbitals in the organic framework. Mn-containing compounds exhibit a strong d -π hybridization that leads to partially occupied spin-minority bands, in contrast to compounds containing transition-metal ions other than Mn, for which electronic structure around the Fermi energy is only slightly spin split due to weak d -π hybridization and the magnetic interaction is of the Ruderman-Kittel-Kasuya-Yosida type. We use a ferromagnetic Kondo lattice model to understand the phase transition in Mn-containing compounds in terms of carrier density and illuminate the complexity and the potential to control two-dimensional magnetization.

  18. Room temperature chemically oxidized La2CuO4+y: Phase separation induced by thermal treatment

    DEFF Research Database (Denmark)

    Rial,C.; Moran, E.; Alario-Franco, M.A.

    1997-01-01

    The structure of roam temperature chemically oxidized La2CuO4+y [y = 0.103(4)] has been refined from powder neutron diffraction data using the space group Bmab. The modifications induced in the CuO2 and the LaO planes by the insertion of oxygen are consistent with the high T-c measured for this m......The structure of roam temperature chemically oxidized La2CuO4+y [y = 0.103(4)] has been refined from powder neutron diffraction data using the space group Bmab. The modifications induced in the CuO2 and the LaO planes by the insertion of oxygen are consistent with the high T-c measured...... a short treatment at 433 K, La2CuO4.103(4) undergoes a phase separation into two phases: phase 1, with estimated y(1) = 0.086(4) and T-cl = 30 K, and phase 2, with estimated y(2) = 0.12(1) and T-c2 = 17 K. By increasing the annealing times, phase 2 transforms to phase I and finally disappears. Therefore...

  19. Structural relative stabilities and pressure-induced phase transitions for lanthanide trihydrides REH{sub 3} (RE=Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu)

    Energy Technology Data Exchange (ETDEWEB)

    Kong Bo, E-mail: kong79@yeah.net [National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900 (China); College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Zhang Lin, E-mail: zhanglinbox@263.net [National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900 (China); Chen Xiangrong [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Zeng Tixian [College of Physics and Electronic Information, China West Normal University, Nanchong 637002 (China); Cai Lingcang [National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900 (China)

    2012-06-15

    The structures, structural relative stabilities, pressure-induced phase transitions, and equations of state for lanthanide trihydrides REH{sub 3} (RE=Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu) are systematically studied using ab initio calculations under a core state model (CSM). The obtained ground-state parameters, such as lattice constants and bulk modulus, agree well with the available data. Among the P6{sub 3}/mm, P3-bar c1, and P6{sub 3}cm structures, the P6{sub 3}cm structure is found to be the most stable structure for lanthanide trihydride via the comparison of the calculated total energies. With the help of Birch-Murnaghan equation of state, the structural transitions from hexagonal to cubic for REH{sub 3} (RE=Sm, Gd, Ho, Er, and Lu) under pressure are affirmed; especially, the similar behavior of REH{sub 3} (RE= Tb, Dy, and Tm) is reasonably predicted for the first time by this means. For the transitions, the repulsive interactions of H-H atoms may play an important role in terms of the analysis of the structures in the vicinity of the theoretical phase transition.

  20. Laser-induced microstructural development and phase evolution in magnesium alloy

    International Nuclear Information System (INIS)

    Guan, Y.C.; Zhou, W.; Li, Z.L.; Zheng, H.Y.

    2014-01-01

    Highlights: • Secondary phase evolution caused by laser processing was firstly reported. • Microstructure development was controlled by heat flow thermodynamics and kinetics. • Solid-state transformation resulted in submicron and nano-scale precipitates. • Cluster-shaped particles in overlapped region were due to precipitation coarsening. • Properties of materials can be tailored selectively by laser processing. -- Abstract: Secondary phase plays an important role in determining microstructures and properties of magnesium alloys. This paper focuses on laser-induced microstructure development and secondary phase evolution in AZ91D Mg alloy studied by SEM, TEM and EDS analyses. Compared to bulk shape and lamellar structure of the secondary phase in as-received cast material, rapid-solidified microstructures with various morphologies including nano-precipitates were observed in laser melt zone. Formation mechanisms of microstructural evolution and effect of phase development on surface properties were further discussed

  1. Modification of electronic structure, magnetic structure, and topological phase of bismuthene by point defects

    Science.gov (United States)

    Kadioglu, Yelda; Kilic, Sevket Berkay; Demirci, Salih; Aktürk, O. Üzengi; Aktürk, Ethem; Ciraci, Salim

    2017-12-01

    This paper reveals how the electronic structure, magnetic structure, and topological phase of two-dimensional (2D), single-layer structures of bismuth are modified by point defects. We first showed that a free-standing, single-layer, hexagonal structure of bismuth, named h-bismuthene, exhibits nontrivial band topology. We then investigated interactions between single foreign adatoms and bismuthene structures, which comprise stability, bonding, electronic structure, and magnetic structures. Localized states in diverse locations of the band gap and resonant states in band continua of bismuthene are induced upon the adsorption of different adatoms, which modify electronic and magnetic properties. Specific adatoms result in reconstruction around the adsorption site. Single vacancies and divacancies can form readily in bismuthene structures and remain stable at high temperatures. Through rebondings, Stone-Whales-type defects are constructed by divacancies, which transform into a large hole at high temperature. Like adsorbed adatoms, vacancies induce also localized gap states, which can be eliminated through rebondings in divacancies. We also showed that not only the optical and magnetic properties, but also the topological features of pristine h-bismuthene can be modified by point defects. The modification of the topological features depends on the energies of localized states and also on the strength of coupling between point defects.

  2. Pressure-induced phase transitions in acentric BaHf(BO{sub 3}){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Mączka, Mirosław, E-mail: m.maczka@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław 2 (Poland); Szymborska-Małek, Katarzyna [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław 2 (Poland); Sousa Pinheiro, Gardenia de [Departamento de Física, Universidade Federal do Piauí, Teresina, PI 64049-550 (Brazil); Cavalcante Freire, Paulo Tarso [Departamento de Fisica, Universidade Federal do Ceara, Fortaleza CE-60455-970 (Brazil); Majchrowski, Andrzej [Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Street, 00-908 Warszawa (Poland)

    2015-08-15

    High-pressure Raman scattering studies revealed that BaHf(BO{sub 3}){sub 2} is more compressible than calcite-type orthoborates and calcite, aragonite or dolomite carbonates. It undergoes a first-order reversible pressure-induced phase transition in the 3.9–4.4 GPa pressure range. Second structural change is observed at 9.2 GPa. The intermediate phase is most likely trigonal. However, Raman results suggest increase in the number of distinct BO{sub 3} groups from two in the ambient pressure phase to at least three in the intermediate phase. This intermediate phase is also strongly compressible and strong pressure dependence of the lattice modes proves that the main changes under pressure occur within the layers built from BaO{sub 6} and HfO{sub 6} octahedra. The second phase transition leads most likely to lowering of the trigonal symmetry, as evidenced by significant increase of the number of observed bands. The pressure coefficients of the Raman bands of the high-pressure phase are relatively small, suggesting more dense arrangement of the metal–oxygen polyhedra and BO{sub 3} groups in this phase. It is worth noting that the high-pressure phase was not reached in the second compression experiment up to 10 GPa. This behavior can be most likely attributed to worse hydrostatic conditions of the first experiment. - Graphical abstract: Raman spectra of BaHf(BO{sub 3}){sub 2} recorded at different pressures during compression showing onset of pressure-induced phase transitions. - Highlights: • High-pressure Raman spectra were measured for BaHf(BO{sub 3}){sub 2.} • BaHf(BO{sub 3}){sub 2} undergoes a reversible first-order phase transition at 3.9–4.4 GPa into a trigonal phase. • The intermediate trigonal phase is strongly compressible second structural transformation is observed at 9.2 GPa under non-perfect hydrostatic conditions.

  3. Structural and electronic phase transitions of ThS2 from first-principles calculations

    International Nuclear Information System (INIS)

    Guo, Yongliang; Wang, Changying; Qiu, Wujie; Ke, Xuezhi

    2016-01-01

    Performed a systematic study using first-principles methods of the pressure-induced structural and electronic phase transitions in ThS_2, which may play an important role in the next generation nuclear energy fuel technology.

  4. Radiation induced nano structures

    International Nuclear Information System (INIS)

    Ibragimova, E.M.; Kalanov, M.U.; Khakimov, Z.

    2006-01-01

    Full text: Nanometer-size silicon clusters have been attracting much attention due to their technological importance, in particular, as promising building blocks for nano electronic and nano photonic systems. Particularly, silicon wires are of great of interest since they have potential for use in one-dimensional quantum wire high-speed field effect transistors and light-emitting devices with extremely low power consumption. Carbon and metal nano structures are studied very intensely due to wide possible applications. Radiation material sciences have been dealing with sub-micron objects for a long time. Under interaction of high energy particles and ionizing radiation with solids by elastic and inelastic mechanisms, at first point defects are created, then they form clusters, column defects, disordered regions (amorphous colloids) and finally precipitates of another crystal phase in the matrix. Such irradiation induced evolution of structure defects and phase transformations was observed by X-diffraction techniques in dielectric crystals of quartz and corundum, which exist in and crystal modifications. If there is no polymorphism, like in alkali halide crystals, then due to radiolysis halogen atoms are evaporated from the surface that results in non-stoichiometry or accumulated in the pores formed by metal vacancies in the sub-surface layer. Nano-pores are created by intensive high energy particles irradiation at first chaotically and then they are ordered and in part filled by inert gas. It is well-known mechanism of radiation induced swelling and embrittlement of metals and alloys, which is undesirable for construction materials for nuclear reactors. Possible solution of this problem may come from nano-structured materials, where there is neither swelling nor embrittlement at gas absorption due to very low density of the structure, while strength keeps high. This review considers experimental observations of radiation induced nano-inclusions in insulating

  5. Indirect phase transition of TiC, ZrC, and HfC crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Abavare, Eric K.K.; Dodoo, Samuel N.A. [Department of Physics, Kwame Nkrumah University of Science and Technology, Kumasi (Ghana); Uchida, Kazuyuki; Oshiyama, Atsushi [Department of Applied Physics, The University of Tokyo, Hongo, Tokyo (Japan); Nkurumah-Buandoh, George K.; Yaya, Abu [Department of Physics, University of Ghana, Legon (Ghana)

    2016-06-15

    We have performed first-principles calculations to analyze the electronic structures, static, and dynamical structural stabilities of the pressure-induced phase transformation of refractory compounds (transition-metal carbides) from NaCl-type (B1) to CsCl-type (B2) via zinc-blende phase using the plane-wave pseudopotential approach in the framework of the generalized gradient approximation (GGA) for the exchange and correlation functional. The ground-state properties, equilibrium lattice constant, bulk moduli, and band structures are determined for the stoichiometry of the compounds and compared with known experimental and theoretical values. We find that the phase-transition pressure for the indirect phase transition from B1→B2 via zinc-blende structure is about 17-fold for TiC, 12-fold for both ZrC and HfC, respectively, when compared with the direct phase transition. Calculated phonon instability exists for the CsCl-B2 phase, which can prevent the structures from forming and contrary to the zinc-blende and the NaCl-B1 phases. The band dispersion and electronic density of states for B1 and B2 crystal phases were explored and found to indicate metallic character in contrast with the zinc-blende phase, which has a pseudogap opening in the bandgap region suggesting a semiconducting property and also a frequency gap in the phonon spectrum. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Pressure-induced structural phase transition and elastic properties in rare earth CeBi and LaBi

    International Nuclear Information System (INIS)

    Mankad, Venu; Gupta, Sanjay D.; Gupta, Sanjeev K.; Jha, Prafulla

    2011-01-01

    Pressure is one of the external parameters by which the interplay of the f-electrons with the normal conduction electrons may be varied. At ambient conditions the rare-earth compounds are characterized by a fixed f n configuration of atomic-like f-electrons, but the decreased lattice spacing resulting from the application of pressure eventually leads to the destabilization of the f-shell. The theoretical description of this electronic transition remains a challenge. The present study reports a comprehensive study on structural, electronic band structures, elastic and lattice dynamical properties of rare earth monopnictides CeBi and LaBi using first principles density functional calculations within the pseudopotential approximation. Both compounds possess NaCI (B1) structure at ambient pressure and transform either to CsCI or body centered tetragonal (BCT) structure. Our results concerning equilibrium lattice parameter and bulk modulus agree well with the available experimental and previous theoretical data. The volume change at the crystallographic transition is attributed to a decrease of the cerium valence or a lowering of the p-f hybridization due to the larger interatomic distances in both high pressure phases. The equation of state for rare earth bismuth compounds are calculated and compared with available experimental results. From the total energy and relative volume one can clearly see the relative stabilities of the high pressure phases of both compounds. As the primitive tetragonal phase of both compounds. As the primitive tetragonal phase can be viewed as a CsCl structure, one may think of a transition from B1 to B2. We have also calculated band structure for both phase and here we have presented for B1 case. The narrow bands originating above the Fermi level are mainly due to Ce 'f'-like states, and the major contribution to the density of states is mainly from Ce 'd'-like states. Furthermore, in high-pressure CsCI phase, there is an appreciable

  7. Understanding Strain-Induced Phase Transformations in BiFeO3 Thin Films.

    Science.gov (United States)

    Dixit, Hemant; Beekman, Christianne; Schlepütz, Christian M; Siemons, Wolter; Yang, Yongsoo; Senabulya, Nancy; Clarke, Roy; Chi, Miaofang; Christen, Hans M; Cooper, Valentino R

    2015-08-01

    Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO 3 thin films, which comprises a tetragonal-like ( T ') and an intermediate S ' polymorph. It exhibits a relatively large piezoelectric response when switching between the coexisting phase and a uniform T ' phase. This strain-induced phase transformation is investigated through a synergistic combination of first-principles theory and experiments. The results show that the S ' phase is energetically very close to the T ' phase, but is structurally similar to the bulk rhombohedral ( R ) phase. By fully characterizing the intermediate S ' polymorph, it is demonstrated that the flat energy landscape resulting in the absence of an energy barrier between the T ' and S ' phases fosters the above-mentioned reversible phase transformation. This ability to readily transform between the S ' and T ' polymorphs, which have very different octahedral rotation patterns and c / a ratios, is crucial to the enhanced piezoelectricity in strained BiFeO 3 films. Additionally, a blueshift in the band gap when moving from R to S ' to T ' is observed. These results emphasize the importance of strain engineering for tuning electromechanical responses or, creating unique energy harvesting photonic structures, in oxide thin film architectures.

  8. Field-induced magnetic phases and electric polarization in LiNiPO4

    DEFF Research Database (Denmark)

    Jensen, Thomas Bagger Stibius; Christensen, Niels Bech; Kenzelmann, M.

    2009-01-01

    Neutron diffraction is used to probe the (H,T) phase diagram of magnetoelectric (ME) LiNiPO4 for magnetic fields along the c axis. At zero field the Ni spins order in two antiferromagnetic phases. One has commensurate (C) structures and general ordering vectors k(C)=(0,0,0); the other one...... is incommensurate (IC) with k(IC)=(0,q,0). At low temperatures the C order collapses above mu H-0=12 T and adopts an IC structure with modulation vector parallel to k(IC). We show that C order is required for the ME effect and establish how electric polarization results from a field-induced reduction in the total...

  9. Synthesizing lattice structures in phase space

    International Nuclear Information System (INIS)

    Guo, Lingzhen; Marthaler, Michael

    2016-01-01

    In one dimensional systems, it is possible to create periodic structures in phase space through driving, which is called phase space crystals (Guo et al 2013 Phys. Rev. Lett. 111 205303). This is possible even if for particles trapped in a potential without periodicity. In this paper we discuss ultracold atoms in a driven optical lattice, which is a realization of such a phase space crystals. The corresponding lattice structure in phase space is complex and contains rich physics. A phase space lattice differs fundamentally from a lattice in real space, because its coordinate system, i.e., phase space, has a noncommutative geometry, which naturally provides an artificial gauge (magnetic) field. We study the behavior of the quasienergy band structure and investigate the dissipative dynamics. Synthesizing lattice structures in phase space provides a new platform to simulate the condensed matter phenomena and study the intriguing phenomena of driven systems far away from equilibrium. (paper)

  10. Modulated phases of phospholipid bilayers induced by tocopherols.

    Science.gov (United States)

    Kamal, Md Arif; Raghunathan, V A

    2012-11-01

    The influence of α-, γ- and δ-tocopherols on the structure and phase behavior of dipalmitoyl phosphatidylcholine (DPPC) bilayers has been determined from X-ray diffraction studies on oriented multilayers. In all the three cases the main-transition temperature (T(m)) of DPPC was found to decrease with increasing tocopherol concentration up to around 25 mol%. Beyond this the main transition is suppressed in the case of γ-tocopherol, whereas T(m) becomes insensitive to composition in the other two cases. The pre-transition is found to be suppressed over a narrow tocopherol concentration range between 7.5 and 10 mol% in DPPC-γ-tocopherol and DPPC-δ-tocopherol bilayers, and the ripple phase occurs down to the lowest temperature studied. In all the three cases a modulated phase is observed above a tocopherol concentration of about 10 mol%, which is similar to the P(β) phase reported in DPPC-cholesterol bilayers. This phase is found to occur even in excess water conditions at lower tocopherol concentrations, and consists of bilayers with periodic height modulation. These results indicate the ability of tocopherols to induce local curvature in membranes, which could be important for some of their biological functions. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Ultrafast studies of shock-induced melting and phase transitions at LCLS

    Science.gov (United States)

    McMahon, Malcolm

    The study of shock-induced phase transitions, which is vital to the understanding of material response to rapid pressure changes, dates back to the 1950s, when Bankcroft et al reported a transition in iron. Since then, many transitions have been reported in a wide range of materials, but, due to the lack of sufficiently bright x-ray sources, the structural details of these new phases has been notably lacking. While the development of nanosecond in situ x-ray diffraction has meant that lattice-level studies of such phenomena have become possible, including studies of the phase transition reported 60 years ago in iron, the quality of the diffraction data from such studies is noticeably poorer than that obtained from statically-compressed samples on synchrotrons. The advent of x-ray free electron lasers (XFELs), such as the LCLS, has resulted in an unprecedented improvement in the quality of diffraction data that can be obtained from shock-compressed matter. Here I describe the results from three recent experiment at the LCLS that looked at the solid-solid and solid-liquid phase transitions in Sb, Bi and Sc using single 50 fs x-ray exposures. The results provide new insight into the structural changes and melting induced by shock compression. This work is supported by EPSRC under Grant No. EP/J017051/1. Use of the LCLS, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.

  12. Theoretical analysis of the structural phase transformation in the ZnO under high pressure

    Science.gov (United States)

    Verma, Saligram; Jain, Arvind; Nagarch, R. K.; Shah, S.; Kaurav, Netram

    2018-05-01

    We report a phenomenological model based calculation of pressure-induced structural phase transition and elastic properties of ZnO compound. Gibb's free energy is obtained as a function of pressure by applying an effective inter ionic interaction potential, which includes the long range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction upto second-neighbor ions within the Hafemeister and Flygare approach. From the present study, we predict a structural phase transition from ZnS structure (B3) to NaCl structure (B1) at 8.5 GPa. The estimated value of the phase transition pressure (Pt) and the magnitude of the discontinuity in volume at the transition pressure are consistent as compared to the reported data. The variations of elastic constants with pressure follow a systematic trend identical to that observed in others compounds of ZnS type structure family.

  13. Crystalline oxides on semiconductors: A structural transition of the interface phase

    Science.gov (United States)

    Walker, F. J.; Buongiorno-Nardelli, Marco; Billman, C. A.; McKee, R. A.

    2004-03-01

    The growth of crystalline oxides on silicon is facilitated by the preparation of a surface phase of alkaline earth silicide. We describe how the surface phase serves as a precursor of the final interface phase using reflection high energy electron diffraction (RHEED) and density functional theory (DFT). RHEED intensity oscillations of the growth of BaSrO show layer-by-layer build up of the oxide on the interface. The 2x1 symmetry of the surface precursor persists up to 3 ML BaSrO coverage at which point a 1x1 pattern characteristic of the rock-salt structure of BaSrO is observed. Prior to 3 ML growth of alkaline earth oxide, DFT calculations and RHEED show that the surface precursor persists as the interface phase and induces large displacements in the growing oxide layer away from the rock-salt structure and having a 2x1 symmetry. These distortions of the rock-salt structure are energetically unfavorable and become more unfavorable as the oxide thickness increases. At 3 ML, the stability of the rock-salt structure drives a structural transformation of the film and the interface phase to a structure that is distinct from the surface precursor. Research sponsored jointly by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory under contract DE-AC05-00OR22725 with UT-Battelle, LLC and at the University of Tennessee under contract DE-FG02-01ER45937. Calculations have been performed on CCS supercomputers at Oak Ridge National Laboratory.

  14. Ultrafast terahertz-induced response of GeSbTe phase-change materials

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Michael J. [Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Zalden, Peter [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Chen, Frank [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Weems, Ben [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); Chatzakis, Ioannis [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Xiong, Feng; Jeyasingh, Rakesh; Pop, Eric; Philip Wong, H.-S. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Hoffmann, Matthias C. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Wuttig, Matthias [I. Physikalisches Institut, RWTH Aachen University, 52056 Aachen (Germany); JARA–Fundamentals of Information Technology, RWTH Aachen University, 52056 Aachen (Germany); Lindenberg, Aaron M., E-mail: aaronl@stanford.edu [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)

    2014-06-23

    The time-resolved ultrafast electric field-driven response of crystalline and amorphous GeSbTe films has been measured all-optically, pumping with single-cycle terahertz pulses as a means of biasing phase-change materials on a sub-picosecond time-scale. Utilizing the near-band-gap transmission as a probe of the electronic and structural response below the switching threshold, we observe a field-induced heating of the carrier system and resolve the picosecond-time-scale energy relaxation processes and their dependence on the sample annealing condition in the crystalline phase. In the amorphous phase, an instantaneous electroabsorption response is observed, quadratic in the terahertz field, followed by field-driven lattice heating, with Ohmic behavior up to 200 kV/cm.

  15. Shear induced phase transitions induced in edible fats

    Science.gov (United States)

    Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.

    2003-03-01

    The food industry crystallizes fats under different conditions of temperature and shear to obtain products with desired crystalline phases. Milk fat, palm oil, cocoa butter and chocolate were crystallized from the melt in a temperature controlled Couette cell. Synchrotron x-ray diffraction studies were conducted to examine the role of shear on the phase transitions seen in edible fats. The shear forces on the crystals induced acceleration of the alpha to beta-prime phase transition with increasing shear rate in milk fat and palm oil. The increase was slow at low shear rates and became very strong above 360 s-1. In cocoa butter the acceleration between beta-prime-III and beta-V phase transition increased until a maximum of at 360 s-1, and then decreased, showing competition between enhanced heat transfer and viscous heat generation.

  16. Theory of structural phase transition in MgTi{sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Talanov, V. M., E-mail: valtalanov@mail.ru [South Russian State Polytechnical University (Russian Federation); Shirokov, V. B. [Russian Academy of Sciences, South Science Centre (Russian Federation); Ivanov, V. V. [South Russian State Polytechnical University (Russian Federation); Talanov, M. V. [South Federal University (Russian Federation)

    2015-01-15

    A theory of phase transition in MgTi{sub 2}O{sub 4} is proposed based on a study of the order-parameter symmetry, thermodynamics, and mechanisms of formation of the atomic and orbital structure of the low-symmetry MgTi{sub 2}O{sub 4} phase. The critical order parameter (which induces a phase transition) is determined. It is shown that the calculated MgTi{sub 2}O{sub 4} tetragonal structure is a result of displacements of magnesium, titanium, and oxygen atoms; ordering of oxygen atoms; and the participation of d{sub xy}, d{sub xz}, and d{sub yz} orbitals. The contribution of noncritical representations to ion displacements is proven to be insignificant. The existence of various metal clusters in the tetragonal phase has been established by calculation in correspondence with experimental data. It is shown (within the Landau theory of phase transitions) that phase states can be changed as a result of both first- and second-order phase transitions: the high-symmetry phase borders two low-symmetry phases by second-order transition lines, while the border between low-symmetry phases is a first-order transition line.

  17. Sub-nanosecond laser-induced structural changes in the phase change material Ge2Sb2Te5 measured by an optical pump/x-ray probe technique: Structural snapshots with a 500 ps shutter

    International Nuclear Information System (INIS)

    Fons, P.; Brewe, D.; Stern, E.; Kolobov, A.V.; Fukaya, T.; Suzuki, M.; Uruga, T.; Kawamura, N.; Takagaki, M.; Ohsawa, H.; Tanida, H.; Tominaga, J.

    2007-01-01

    Phase-change alloys are characterized by reversible switching between amorphous and crystalline phases either by laser irradiation or by an electric programming current; the resulting changes in material properties can be used for non-volatile data storage. Switching typically occurs on nanosecond or less time scales. Considering the conflicting requirements for high-speed switching, yet long term data storage integrity, a deeper understanding of the switching processes in these materials is essential for insightful application development. Although, high-speed optical pump/probe observations have been made of reflectivity changes during the Ge 2 Sb 2 Te 5 switching process, due to the nanosecond order time scales involved little is known about the corresponding changes in structure. In addition as the amorphous phase does not diffract, its structural analysis is not amenable to analysis by high-speed diffraction techniques. We have used synchrotron-based time-resolved x-ray absorption fine structure spectroscopy (XAFS), a technique equally suitable for amorphous and crystalline phases to elaborate details in structural changes in the phase-change process. We report on two experiments using high-speed pulsed lasers that serve as optical pumps to induced material changes followed by synchrotron produced x-ray burst that serve as a time resolved structural probe. The first experiment carried out at the Advanced Photon source focuses on changes due to heating in the amorphous phase. Our experimental results indicate that the maximum temperature reached during the re-amorphization process are less than the melting point indicated in the bulk phase diagram of Ge 2 Sb 2 Te 5 reaching a maximum temperature of 620 C and in addition, do not share the same bond length distribution of a true melt. These findings strongly suggest the possibility of non-thermal melting. In the second experiment, we have obtained near-edge x-ray absorption data for a Ge 2 Sb 2 Te 5 film in the

  18. Phase space interrogation of the empirical response modes for seismically excited structures

    Science.gov (United States)

    Paul, Bibhas; George, Riya C.; Mishra, Sudib K.

    2017-07-01

    Conventional Phase Space Interrogation (PSI) for structural damage assessment relies on exciting the structure with low dimensional chaotic waveform, thereby, significantly limiting their applicability to large structures. The PSI technique is presently extended for structure subjected to seismic excitations. The high dimensionality of the phase space for seismic response(s) are overcome by the Empirical Mode Decomposition (EMD), decomposing the responses to a number of intrinsic low dimensional oscillatory modes, referred as Intrinsic Mode Functions (IMFs). Along with their low dimensionality, a few IMFs, retain sufficient information of the system dynamics to reflect the damage induced changes. The mutually conflicting nature of low-dimensionality and the sufficiency of dynamic information are taken care by the optimal choice of the IMF(s), which is shown to be the third/fourth IMFs. The optimal IMF(s) are employed for the reconstruction of the Phase space attractor following Taken's embedding theorem. The widely referred Changes in Phase Space Topology (CPST) feature is then employed on these Phase portrait(s) to derive the damage sensitive feature, referred as the CPST of the IMFs (CPST-IMF). The legitimacy of the CPST-IMF is established as a damage sensitive feature by assessing its variation with a number of damage scenarios benchmarked in the IASC-ASCE building. The damage localization capability, remarkable tolerance to noise contamination and the robustness under different seismic excitations of the feature are demonstrated.

  19. Simulation of phase structures

    International Nuclear Information System (INIS)

    Lawson, J.

    1995-01-01

    This memo outlines a procedure developed by the author to extract information from phase measurements and produce a simulated phase structure for use in modeling optical systems, including characteristic optics for the Beamlet and NIF laser systems. The report includes an IDL program listing

  20. Ab initio molecular dynamics study of pressure-induced phase transition in ZnS

    International Nuclear Information System (INIS)

    Martinez, Israel; Durandurdu, Murat

    2006-01-01

    The pressure-induced phase transition in zinc sulfide is studied using a constant-pressure ab initio technique. The reversible phase transition from the zinc-blende structure to a rock-salt structure is successfully reproduced through the simulations. The transformation mechanism at the atomistic level is characterized and found to be due to a monoclinic modification of the simulation cell, similar to that obtained in SiC. This observation supports the universal transition state of high-pressure zinc-blende to rock-salt transition in semiconductor compounds. We also study the role of stress deviations on the transformation mechanism and find that the system follows the same transition pathway under nonhydrostatic compressions as well

  1. Structural phase transitions and Huang scattering

    International Nuclear Information System (INIS)

    Yamada, Yasusada

    1980-01-01

    The usefulness of the application of the concept of Huang scattering to the understandings of the origin of diffuse scatterings near structural phase transitions are discussed. It is pointed out that in several phase transitions, the observed diffuse scatterings can not be interpreted in terms of critical fluctuations of the order parameters associated with the structural phase transitions, and that they are rather interpreted as Huang scattering due to random distribution of individual order parameter which is 'dressed' by strain fields. Examples to show effective applications of this concept to analyze the experimental X-ray data and whence to understand microscopic mechanisms of structural phase transitions are presented. (author)

  2. Pressure-induced phase transitions and templating effect in three-dimensional organic-inorganic hybrid perovskites

    Science.gov (United States)

    Lee, Yongjae; Mitzi, David; Barnes, Paris; Vogt, Thomas

    2003-07-01

    Pressure-induced structural changes of conducting halide perovskites (CH3NH3)SnI3, (CH3NH3)0.5(NH2CH=NH2)0.5SnI3, and (NH2CH=NH2)SnI3, have been investigated using synchrotron x-ray powder diffraction. In contrast to low-temperature structural changes, no evidence of an increased ordering of the organic cations was observed under pressure. Instead, increase in pressure results first in a ReO3-type doubling of the primitive cubic unit cell, followed by a symmetry distortion, and a subsequent amorphization above 4 GPa. This process is reversible and points towards a pressure-induced templating role of the organic cation. Bulk compressions are continuous across the phase boundaries. The compressibilities identify these hybrids as the most compressible perovskite system ever reported. However, the Sn-I bond compressibility in (CH3NH3)SnI3 shows a discontinuity within the supercell phase. This is possibly due to an electronic localization.

  3. Structural Phase Transition and Compressibility of CaF2 Nanocrystals under High Pressure

    Directory of Open Access Journals (Sweden)

    Jingshu Wang

    2018-05-01

    Full Text Available The structural phase transition and compressibility of CaF2 nanocrystals with size of 23 nm under high pressure were investigated by synchrotron X-ray diffraction measurement. A pressure-induced fluorite to α-PbCl2-type phase transition starts at 9.5 GPa and completes at 20.2 GPa. The phase-transition pressure is lower than that of 8 nm CaF2 nanocrystals and closer to bulk CaF2. Upon decompression, the fluorite and α-PbCl2-type structure co-exist at the ambient pressure. The bulk modulus B0 of the 23 nm CaF2 nanocrystals for the fluorite and α-PbCl2-type phase are 103(2 and 78(2 GPa, which are both larger than those of the bulk CaF2. The CaF2 nanocrystals exhibit obviously higher incompressibility compare to bulk CaF2. Further analysis demonstrates that the defect effect in our CaF2 nanocrystals plays a dominant role in the structural stability.

  4. A Multi-Phase Based Fluid-Structure-Microfluidic interaction sensor for Aerodynamic Shear Stress

    Science.gov (United States)

    Hughes, Christopher; Dutta, Diganta; Bashirzadeh, Yashar; Ahmed, Kareem; Qian, Shizhi

    2014-11-01

    A novel innovative microfluidic shear stress sensor is developed for measuring shear stress through multi-phase fluid-structure-microfluidic interaction. The device is composed of a microfluidic cavity filled with an electrolyte liquid. Inside the cavity, two electrodes make electrochemical velocimetry measurements of the induced convection. The cavity is sealed with a flexible superhydrophobic membrane. The membrane will dynamically stretch and flex as a result of direct shear cross-flow interaction with the seal structure, forming instability wave modes and inducing fluid motion within the microfluidic cavity. The shear stress on the membrane is measured by sensing the induced convection generated by membrane deflections. The advantages of the sensor over current MEMS based shear stress sensor technology are: a simplified design with no moving parts, optimum relationship between size and sensitivity, no gaps such as those created by micromachining sensors in MEMS processes. We present the findings of a feasibility study of the proposed sensor including wind-tunnel tests, microPIV measurements, electrochemical velocimetry, and simulation data results. The study investigates the sensor in the supersonic and subsonic flow regimes. Supported by a NASA SBIR phase 1 contract.

  5. Femtosecond Laser-Induced Formation of Wurtzite Phase ZnSe Nanoparticles in Air

    Directory of Open Access Journals (Sweden)

    Hsuan I Wang

    2012-01-01

    Full Text Available We demonstrate an effective method to prepare wurtzite phase ZnSe nanoparticles from zincblende ZnSe single crystal using femtosecond pulse laser ablation. The fabricated ZnSe nanoparticles are in spherical shape and uncontaminated while synthesized under ambient environment. By controlling the laser fluences, the average size of ZnSe nanoparticles can be varied from ~16 nm to ~22 nm in diameter. In Raman spectra, the surface phonon mode becomes dominant in the smaller average particle size with uniform size distribution. The interesting phase transition from the zinc blende structure of ZnSe single crystal to wurtzite structure of ZnSe nanoparticles may have been induced by the ultrahigh ablation pressure at the local area due to the sudden injection of high energy leading to solid-solid transition.

  6. Platinum-induced structural collapse in layered oxide polycrystalline films

    International Nuclear Information System (INIS)

    Wang, Jianlin; Liu, Changhui; Huang, Haoliang; Fu, Zhengping; Peng, Ranran; Zhai, Xiaofang; Lu, Yalin

    2015-01-01

    Effect of a platinum bottom electrode on the SrBi 5 Fe 1−x Co x Ti 4 O 18 layered oxide polycrystalline films was systematically studied. The doped cobalt ions react with the platinum to form a secondary phase of PtCoO 2 , which has a typical Delafossite structure with a weak antiferromagnetism and an exceptionally high in-plane electrical conductivity. Formation of PtCoO 2 at the interface partially consumes the cobalt dopant and leads to the structural collapsing from 5 to 4 layers, which was confirmed by X-ray diffraction and high resolution transmission electron microscopy measurements. Considering the weak magnetic contribution from PtCoO 2 , the observed ferromagnetism should be intrinsic of the Aurivillius compounds. Ferroelectric properties were also indicated by the piezoresponse force microscopy. In this work, the platinum induced secondary phase at the interface was observed, which has a strong impact on Aurivillius structural configuration and thus the ferromagnetic and ferroelectric properties

  7. Low-pH-induced transformation of bilayer membrane into bicontinuous cubic phase in dioleoylphosphatidylserine/monoolein membranes.

    Science.gov (United States)

    Okamoto, Yoshihide; Masum, Shah Md; Miyazawa, Haruna; Yamazaki, Masahito

    2008-04-01

    Cubic biomembranes, nonbilayer membranes with connections in three-dimensional space that have a cubic symmetry, have been observed in various cells. Interconversion between the bilayer liquid-crystalline (L(alpha)) phase and cubic phases attracted much attention in terms of both biological and physicochemical aspects. Herein we report the pH effect on the phase and structure of dioleoylphosphatidylserine (DOPS)/monoolein (MO) membranes under a physiological ion concentration condition, which was revealed by small-angle X-ray scattering (SAXS) measurement. At neutral pH, DOPS/MO membranes containing high concentrations of DOPS were in the L(alpha) phase. First, the pH effect on the phase and structure of the multilamellar vesicles (MLVs) of the DOPS/MO membranes preformed at neutral pH was investigated by adding various low-pH buffers into the MLV suspension. For 20%-DOPS/80%-MO MLVs, at and below pH 2.9, a transition from the L(alpha) to cubic (Q(224)) phase occurred within 1 h. This phase transition was reversible; a subsequent increase in pH to a neutral one in the membrane suspension transformed the cubic phase into the original L(alpha) phase. Second, we found that a decrease in pH transformed large unilamellar vesicles of DOPS/MO membranes into the cubic phase under similar conditions. We have proposed the mechanism of the low-pH-induced phase transition and also made a quantitative analysis on the critical pH of the phase transition. This finding is the first demonstration that a change in pH can induce a reversible phase transition between the L(alpha) and cubic phases of lipid membranes within 1 h.

  8. Substrate-induced phase of a [1]benzothieno[3,2-b]benzothiophene derivative and phase evolution by aging and solvent vapor annealing.

    Science.gov (United States)

    Jones, Andrew O F; Geerts, Yves H; Karpinska, Jolanta; Kennedy, Alan R; Resel, Roland; Röthel, Christian; Ruzié, Christian; Werzer, Oliver; Sferrazza, Michele

    2015-01-28

    Substrate-induced phases (SIPs) are polymorphic phases that are found in thin films of a material and are different from the single crystal or "bulk" structure of a material. In this work, we investigate the presence of a SIP in the family of [1]benzothieno[3,2-b]benzothiophene (BTBT) organic semiconductors and the effect of aging and solvent vapor annealing on the film structure. Through extensive X-ray structural investigations of spin coated films, we find a SIP with a significantly different structure to that found in single crystals of the same material forms; the SIP has a herringbone motif while single crystals display layered π-π stacking. Over time, the structure of the film is found to slowly convert to the single crystal structure. Solvent vapor annealing initiates the same structural evolution process but at a greatly increased rate, and near complete conversion can be achieved in a short period of time. As properties such as charge transport capability are determined by the molecular structure, this work highlights the importance of understanding and controlling the structure of organic semiconductor films and presents a simple method to control the film structure by solvent vapor annealing.

  9. Phorbol-ester-induced down-regulation of protein kinase C in mouse pancreatic islets. Potentiation of phase 1 and inhibition of phase 2 of glucose-induced insulin secretion

    DEFF Research Database (Denmark)

    Thams, P; Capito, K; Hedeskov, C J

    1990-01-01

    and potentiated phase 1 of glucose-induced secretion. Furthermore, perifusion of islets in the presence of staurosporine (1 microM), an inhibitor of protein kinase C, potentiated phase 1 and inhibited phase 2 of glucose-induced secretion. In addition, down-regulation of protein kinase C potentiated phase 1...

  10. On the thermal phase structure of QCD at vanishing chemical potentials

    CERN Document Server

    Kabana, S

    2011-01-01

    The hypothesis is investigated, that the thermal structure of QCD phases at and near zero chemical potentials is determined by long range coherence, inducing the gauge boson pair condensate. The latter reflects the dynamical nature of gauge boson Bogoliubov transformations at the origin of localization of all color fields inside hadrons at low temperature in contrast to loss of such localization above a unique critical temperature.

  11. Local structure, composition, and crystallization mechanism of a model two-phase “composite nanoglass”

    Energy Technology Data Exchange (ETDEWEB)

    Chattopadhyay, Soma; Shibata, Tomohiro [CSRRI-IIT, MRCAT, Sector 10, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kelly, S. D. [EXAFS Analysis, Bolingbrook, Illinois 60440 (United States); Balasubramanian, M. [Sector 20 XOR, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Srinivasan, S. G.; Du, Jincheng; Banerjee, Rajarshi [Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76203-5017 (United States); Ayyub, Pushan, E-mail: pushan@tifr.res.in [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005 (India)

    2016-02-14

    We report a detailed study of the local composition and structure of a model, bi-phasic nanoglass with nominal stoichiometry Cu{sub 55}Nb{sub 45}. Three dimensional atom probe data suggest a nanoscale-phase-separated glassy structure having well defined Cu-rich and Nb-rich regions with a characteristic length scale of ≈3 nm. However, extended x-ray absorption fine structure analysis indicates subtle differences in the local environments of Cu and Nb. While the Cu atoms displayed a strong tendency to cluster and negligible structural order beyond the first coordination shell, the Nb atoms had a larger fraction of unlike neighbors (higher chemical order) and a distinctly better-ordered structural environment (higher topological order). This provides the first experimental indication that metallic glass formation may occur due to frustration arising from the competition between chemical ordering and clustering. These observations are complemented by classical as well as ab initio molecular dynamics simulations. Our study indicates that these nanoscale phase-separated glasses are quite distinct from the single phase nanoglasses (studied by Gleiter and others) in the following three respects: (i) they contain at least two structurally and compositionally distinct, nanodispersed, glassy phases, (ii) these phases are separated by comparatively sharp inter-phase boundaries, and (iii) thermally induced crystallization occurs via a complex, multi-step mechanism. Such materials, therefore, appear to constitute a new class of disordered systems that may be called a composite nanoglass.

  12. Locally formation of Ag nanoparticles in chalcogenide phase change thin films induced by nanosecond laser pulses

    International Nuclear Information System (INIS)

    Huang, Huan; Zhang, Lei; Wang, Yang; Han, Xiaodong; Wu, Yiqun; Zhang, Ze; Gan, Fuxi

    2012-01-01

    A simple method to optically synthesize Ag nanoparticles in Ge 2 Sb 2 Te 5 phase change matrix is described. The fine structures of the locally formed phase change chalcogenide nanocomposite are characterized by high-resolution transmission electron microscopy. The formation mechanism of the nanocomposite is discussed with temperature evolution and distribution simulations. This easy-prepared metal nano-particle-embedded phase change microstructure will have great potential in nanophotonics applications, such as for plasmonic functional structures. This also provides a generalized approach to the preparation of well-dispersed nanoparticle-embedded composite thin films in principle. -- Highlights: ► We describe a method to prepare chalcogenide microstructures with Ag nanoparticles. ► We give the fine structural images of phase change nanocomposites. ► We discuss the laser-induced fusion mechanism by temperature simulation. ► This microstructure will have great potential in nanophotonics applications.

  13. The effect of high non-hydrostatic pressure on III-V semiconductors: zinc blende to wurtzite structural phase transition and multiphase generation

    International Nuclear Information System (INIS)

    Pizani, P S; Jasinevicius, R G

    2014-01-01

    Raman scattering was employed to study structural phase transitions of InSb, GaSb and GaAs induced by highly non-hydrostatic pressures applied by mechanical impact, in which high compression/decompression rates are imposed to the sample. The results showed that is possible to produce several structural phases localized in different micrometric regions of the same sample: the zinc blende to possibly wurtzite structural phase transition and the generation of a multiphase state.

  14. Photo-induced charge-transfer phase transition of rubidium manganese hexacyanoferrate in ferromagnetic and paramagnetic states

    International Nuclear Information System (INIS)

    Tokoro, Hiroko; Hashimoto, Kazuhito; Ohkoshi, Shin-ichi

    2007-01-01

    A charge transfer phase transition with thermal hysteresis loop is observed in a series of rubidium manganese hexacyanoferrates, RbMn[Fe(China) 6 ] (1), Rb 0.88 Mn[Fe(China) 6 ] 0.96 .0.6H 2 O (2), and Rb 0.97 Mn[Fe(China) 6 ] 0.99 .0.2H 2 O (3). This phase transition is accompanied by a structural change from cubic (F4-bar 3m) to tetragonal (I4-bar m2). Its high-temperature (HT) and low-temperature (LT) phases are composed of Mn II (S=2/5)NC-Fe III (S=1/2) and Mn III (S=2)-NC-Fe II (S=0), respectively. The phase transition is caused by a metal-to-metal charge transfer from Mn II to Fe III and a Jahn-Teller distortion of the produced Mn III ion. At the ferromagnetic state in LT phase of 2, the photo-induced phase transition is observed, i.e., magnetization is quenched by the irradiation with only one shot of laser pulse. This phenomenon is caused by a photo-induced phase transition from the LT phase to the HT phase. In 3, optical switching between LT and HT phases at room temperature in paramagnetic region is observed

  15. Phase control of squeezed state in double electromagnetically induced transparency system with a loop-transition structure

    Science.gov (United States)

    Li, Yuan; Zhou, Yusheng; Wang, Yong; Ling, Qiang; Chen, Bing; Dou, Yan; Zhang, Wei; Gao, Weiqing; Guo, Zhiqiang; Zhang, Junxiang

    2018-03-01

    We theoretically study the squeezed probe light passing through a double electromagnetically induced transparency (DEIT) system, in which a microwave field and two coupling lights drive a loop transition. It is shown that the output squeezing can be maintained in both two transparency windows of DEIT, and it can also be manipulated by the relative phase of the three driving fields. The influence of the intensity of applied fields and the optical depth of atoms on the squeezing is also investigated. This study offers possibilities to manipulate the squeezing propagation in atomic media by the phase of electromagnetic fields.

  16. Morphology and phase structures of CW laser-induced oxide layers on iron surface with evolving reflectivity and colors

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Taotao, E-mail: wutaotao@nint.ac.cn; Wang, Lijun; Wei, Chenghua; Zhou, Menglian; He, Minbo; Wu, Lixiong

    2016-11-30

    Highlights: • Firstly, iron samples with different color features were obtained by continuous wave laser irradiation depending on progressive durations. The real-time reflectivity and temperature of samples were measured. The color and the reflectivity evolution were related. They were both caused by the forming oxide films. • Secondly, laser-induced oxidation process of iron was studied by microscope, X-ray diffraction and Raman spectrum. The first formed magnetite made the surface reflectivity decline rapidly and caused the “positive feedback” effect because of molecular absorption. The later formed hematite oscillated the reflectivity by interference effect. • Lastly, the laser-induced oxide films were thin, orientated and badly crystallized. The Wagner oxidation theory was incapable of describing the non-isothermal and early stage oxidation process. So we emphasized that a precise oxidation model depending on the experiment and the optical constants of the laser-induced oxides must be studied. - Abstract: Laser-induced oxidation will change the laser reflectivity and color features of metal surface. Both changes can be theoretically calculated based on the oxidation kinetics and the optical constants of oxides. For the purpose of calculation, the laser-induced oxidation process of pure polycrystalline iron was studied. Samples with various color features were obtained by continuous wave Nd:YAG fiber laser (1.06 μm) irradiation depending on progressive durations in the intensity of 1.90 W/cm{sup 2}. The real-time reflectivity and temperature were measured with integral sphere and thermocouples. The irradiated surface morphology and phase structures were characterized by microscope, X-ray diffraction and Raman spectrum. It was found that the first formed magnetite made the surface reflectivity decline rapidly and caused the “positive feedback” effect because of molecular absorption. The later formed hematite oscillated the reflectivity by

  17. Phase diagram of structure of radial electric field in helical plasmas

    International Nuclear Information System (INIS)

    Toda, S.; Itoh, K.

    2002-01-01

    A set of transport equations in toroidal helical plasmas is analyzed, including the bifurcation of the radial electric field. Multiple solutions of E r for the ambipolar condition induces domains of different electric polarities. A structure of the domain interface is analyzed and a phase diagram is obtained in the space of the external control parameters. The region of the reduction of the anomalous transport is identified. (author)

  18. Phase Diagram and Electronic Structure of Praseodymium and Plutonium

    Directory of Open Access Journals (Sweden)

    Nicola Lanatà

    2015-01-01

    Full Text Available We develop a new implementation of the Gutzwiller approximation in combination with the local density approximation, which enables us to study complex 4f and 5f systems beyond the reach of previous approaches. We calculate from first principles the zero-temperature phase diagram and electronic structure of Pr and Pu, finding good agreement with the experiments. Our study of Pr indicates that its pressure-induced volume-collapse transition would not occur without change of lattice structure—contrarily to Ce. Our study of Pu shows that the most important effect originating the differentiation between the equilibrium densities of its allotropes is the competition between the Peierls effect and the Madelung interaction and not the dependence of the electron correlations on the lattice structure.

  19. First-principles study of lattice dynamics, structural phase transition, and thermodynamic properties of barium titanate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Huai-Yong; Zhao, Ying-Qin; Lu, Qing [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Zeng, Zhao-Yi [Chongqing Normal Univ. (China). College of Physics and Electronic Engineering; Chinese Academy of Engineering Physics, Mianyang (China). National Key Laboratory for Shock Wave and Detonation Physics Research; Cheng, Yan [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Sichuan Univ., Chengdu (China). Key Laboratory of High Energy Density Physics and Technology of Ministry of Education

    2016-11-01

    Lattice dynamics, structural phase transition, and the thermodynamic properties of barium titanate (BaTiO{sub 3}) are investigated by using first-principles calculations within the density functional theory (DFT). It is found that the GGA-WC exchange-correlation functional can produce better results. The imaginary frequencies that indicate structural instability are observed for the cubic, tetragonal, and orthorhombic phases of BaTiO{sub 3} and no imaginary frequencies emerge in the rhombohedral phase. By examining the partial phonon density of states (PDOSs), we find that the main contribution to the imaginary frequencies is the distortions of the perovskite cage (Ti-O). On the basis of the site-symmetry consideration and group theory, we give the comparative phonon symmetry analysis in four phases, which is useful to analyze the role of different atomic displacements in the vibrational modes of different symmetry. The calculated optical phonon frequencies at Γ point for the four phases are in good agreement with other theoretical and experimental data. The pressure-induced phase transition of BaTiO{sub 3} among four phases and the thermodynamic properties of BaTiO{sub 3} in rhombohedral phase have been investigated within the quasi-harmonic approximation (QHA). The sequence of the pressure-induced phase transition is rhombohedral → orthorhombic → tetragonal → cubic, and the corresponding transition pressure is 5.17, 5.92, 6.65 GPa, respectively. At zero pressure, the thermal expansion coefficient α{sub V}, heat capacity C{sub V}, Grueneisen parameter γ, and bulk modulus B of the rhombohedral phase BaTiO{sub 3} are estimated from 0 K to 200 K.

  20. Structural effects of C60+ bombardment on various natural mineral samples-Application to analysis of organic phases in geological samples

    International Nuclear Information System (INIS)

    Siljestroem, S.; Lausmaa, J.; Hode, T.; Sundin, M.; Sjoevall, P.

    2011-01-01

    Organic phases trapped inside natural mineral samples are of considerable interest in astrobiology, geochemistry and geobiology. Examples of such organic phases are microfossils, kerogen and oil. Information about these phases is usually retrieved through bulk crushing of the rock which means both a risk of contamination and that the composition and spatial distribution of the organics to its host mineral is lost. An attractive of way to retrieve information about the organics in the rock is depth profiling using a focused ion beam. Recently, it was shown that it is possible to obtain detailed mass spectrometric information from oil-bearing fluid inclusions, i.e. small amounts of oil trapped inside a mineral matrix, using ToF-SIMS. Using a 10 keV C 60 + sputter beam and a 25 keV Bi 3 + analysis beam, oil-bearing inclusions in different minerals were opened and analysed individually. However, sputtering with a C 60 + beam also induced other changes to the mineral surface, such as formation of topographic features and carbon deposition. In this paper, the cause of these changes is explored and the consequences of the sputter-induced features on the analysis of organic phases in natural mineral samples (quartz, calcite and fluorite) in general and fluid inclusions in particular are discussed. The dominating topographical features that were observed when a several micrometers deep crater is sputtered with 10 keV C 60 + ions on a natural mineral surface are conical-shaped and ridge-like structures that may rise several micrometers, pointing in the direction of the incident C 60 + ion beam, on an otherwise flat crater bottom. The sputter-induced structures were found to appear at places with different chemistry than the host mineral, including other minerals phases and fluid inclusions, while structural defects in the host material, such as polishing marks or scratches, did not necessarily result in sputter-induced structures. The ridge-like structures were often covered

  1. l-Serine Enhances Light-Induced Circadian Phase Resetting in Mice and Humans.

    Science.gov (United States)

    Yasuo, Shinobu; Iwamoto, Ayaka; Lee, Sang-Il; Ochiai, Shotaro; Hitachi, Rina; Shibata, Satomi; Uotsu, Nobuo; Tarumizu, Chie; Matsuoka, Sayuri; Furuse, Mitsuhiro; Higuchi, Shigekazu

    2017-12-01

    Background: The circadian clock is modulated by the timing of ingestion or food composition, but the effects of specific nutrients are poorly understood. Objective: We aimed to identify the amino acids that modulate the circadian clock and reset the light-induced circadian phase in mice and humans. Methods: Male CBA/N mice were orally administered 1 of 20 l-amino acids, and the circadian and light-induced phase shifts of wheel-running activity were analyzed. Antagonists of several neurotransmitter pathways were injected before l-serine administration, and light-induced phase shifts were analyzed. In addition, the effect of l-serine on the light-induced phase advance was investigated in healthy male students (mean ± SD age 22.2 ± 1.8 y) by using dim-light melatonin onset (DLMO) determined by saliva samples as an index of the circadian phase. Results: l-Serine administration enhanced light-induced phase shifts in mice (1.86-fold; P light-dark cycle by 6 h, l-serine administration slightly accelerated re-entrainment to the shifted cycle. In humans, l-serine ingestion before bedtime induced significantly larger phase advances of DLMO after bright-light exposure during the morning (means ± SEMs-l-serine: 25.9 ± 6.6 min; placebo: 12.1 ± 7.0 min; P light-induced phase resetting in mice and humans, and it may be useful for treating circadian disturbances. © 2017 American Society for Nutrition.

  2. Probing peptide fragment ion structures by combining sustained off-resonance collision-induced dissociation and gas-phase H/D exchange (SORI-HDX) in Fourier transform ion-cyclotron resonance (FT-ICR) instruments.

    Science.gov (United States)

    Somogyi, Arpád

    2008-12-01

    The usefulness of gas-phase H/D exchange is demonstrated to probe heterogeneous fragment and parent ion populations. Singly and multiply protonated peptides/proteins were fragmented by using sustained off-resonance irradiation collision-induced dissociation (SORI-CID). The fragments and the surviving precursor ions then all undergo H/D exchange in the gas-phase with either D(2)O or CD(3)OD under the same experimental conditions. Usually, 10 to 60 s of reaction time is adequate to monitor characteristic differences in the H/D exchange kinetic rates. These differences are then correlated to isomeric ion structures. The SORI-HDX method can be used to rapidly test fragment ion structures and provides useful insights into peptide fragmentation mechanisms.

  3. Dielectric constant of GaAs during a subpicosecond laser-induced phase transition

    Science.gov (United States)

    Siegal, Y.; Glezer, E. N.; Mazur, E.

    1994-06-01

    We measured the time evolution of the real and imaginary parts of the dielectric constant of GaAs following femtosecond laser pulse excitation. The data show a collapse of the average optical gap, or average bonding-antibonding energy-level separation. The rate of collapse increases with pump fluence. The decrease in the gap indicates that the pump beam induces a structural transformation from a covalent, tetrahedrally coordinated crystal to a phase with metallic cohesive properties.

  4. Microscopic Mechanism of Doping-Induced Kinetically Constrained Crystallization in Phase-Change Materials.

    Science.gov (United States)

    Lee, Tae Hoon; Loke, Desmond; Elliott, Stephen R

    2015-10-07

    A comprehensive microscopic mechanism of doping-induced kinetically constrained crystallization in phase-change materials is provided by investigating structural and dynamical dopant characteristics via ab initio molecular dynamics simulations. The information gained from this study may provide a basis for a fast screening of dopant species for electronic memory devices, or for understanding the general physics involved in the crystallization of doped glasses. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Surface mechanical attrition treatment induced phase transformation behavior in NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Hu, T.; Wen, C.S.; Lu, J.; Wu, S.L.; Xin, Y.C.; Zhang, W.J.; Chu, C.L.; Chung, J.C.Y.; Yeung, K.W.K.; Kwok, D.T.K.; Chu, Paul K.

    2009-01-01

    The phase constituents and transformation behavior of the martensite B19' NiTi shape memory alloy after undergoing surface mechanical attrition treatment (SMAT) are investigated. SMAT is found to induce the formation of a parent B2 phase from the martensite B19' in the top surface layer. By removing the surface layer-by-layer, X-ray diffraction reveals that the amount of the B2 phase decreases with depth. Differential scanning calorimetry (DSC) further indicates that the deformed martensite in the sub-surface layer up to 300 μm deep exhibits the martensite stabilization effect. The graded phase structure and transformation behavior in the SMATed NiTi specimen can be attributed to the gradient change in strain with depth.

  6. Theoretical studies of the pressure-induced zinc-blende to cinnabar phase transition in CdTe and thermodynamical properties of each phase

    International Nuclear Information System (INIS)

    Brik, M.G.; Łach, P.; Karczewski, G.; Wojtowicz, T.; Kamińska, A.; Suchocki, A.

    2013-01-01

    Luminescence of CdTe quantum dots embedded in ZnTe is quenched at pressure of about 4.5 GPa in the high-pressure experiments. This pressure-induced quenching is attributed to the “zinc-blende–cinnabar” phase transition in CdTe, which was confirmed by the first-principles calculations. Theoretical analysis of the pressure at which the phase transition occurs for CdTe was performed using the CASTEP module of Materials Studio package with both generalized gradient approximation (GGA) and local density approximation (LDA). The calculated phase transition pressures are equal to about 4.4 GPa and 2.6 GPa, according to the GGA and LDA calculations, respectively, which is in a good agreement with the experimental value. Theoretically estimated value of the pressure coefficient of the band-gap luminescence in zinc-blende structure is in very good agreement with that recently measured in the QDs structures. The calculated Debye temperature, elastic constants and specific heat capacity for the zinc-blend structure agree well with the experimental data; the data for the cinnabar phase are reported here for the first time to the best of the authors' knowledge. - Highlights: • Quenching of luminescence of CdTe quantum dots embedded in ZnTe is theoretically explained. • The theoretical calculation of elastic and thermodynamic properties of CdTe by two types of ab-initio methods. • Theoretical calculations of some optical properties of CdTe under pressure in zinc-blende and cinnabar phases

  7. Time-Resolved Studies of Laser-Induced Phase Transitions in Gallium Arsenide

    Science.gov (United States)

    Siegal, Yakir

    This thesis describes a series of time-resolved experiments of the linear and nonlinear optical properties of GaAs during laser-induced phase transitions. The first set of experiments consists of a direct determination of the behavior of the linear dielectric constant at photon energies of 2.2 eV and 4.4 eV following excitation of the sample with 1.9-eV, 70-fs laser pulses spanning a fluence range from 0 to 2.5 kJ/m^2. The results from this set of experiments were used to extract the behavior of the second-order optical susceptibility from second-harmonic generation measurements made under identical excitation conditions. These experiments are unique because they provide explicit information on the behavior of intrinsic material properties--the linear and nonlinear optical susceptibilities--during laser-induced phase transitions in semiconductors without the ambiguities in interpretation that are generally inherent in reflectivity and second-harmonic generation measurements. The dielectric constant data indicate a drop in the average bonding-antibonding splitting of GaAs following the laser pulse excitation. This behavior leads to a collapse of the band-gap on a picosecond time scale for excitation at fluences near the damage threshold of 1.0 kJ/m ^2 and even faster at higher excitation fluences. The changes in the electronic band structure result from a combination of electronic screening by the excited free carriers and structural deformation of the lattice caused by the destabilization of the covalent bonds. The behavior of the second-order susceptibility shows that the material loses long-range order before the average bonding-antibonding splitting, which is more sensitive to short-range structure, changes significantly. Loss of long-range order and a drop of more than 2 eV in the average bonding-antibonding splitting are seen even at fluences below the damage threshold, a regime in which the laser-induced changes are reversible.

  8. Complexation-Induced Phase Separation: Preparation of Metal-Rich Polymeric Membranes

    KAUST Repository

    Villalobos Vazquez de la Parra, Luis Francisco

    2017-08-01

    The majority of state-of-the-art polymeric membranes for industrial or medical applications are fabricated by phase inversion. Complexation induced phase separation (CIPS)—a surprising variation of this well-known process—allows direct fabrication of hybrid membranes in existing facilities. In the CIPS process, a first step forms the thin metal-rich selective layer of the membrane, and a succeeding step the porous support. Precipitation of the selective layer takes place in the same solvent used to dissolve the polymer and is induced by a small concentration of metal ions. These ions form metal-coordination-based crosslinks leading to the formation of a solid skin floating on top of the liquid polymer film. A subsequent precipitation in a nonsolvent bath leads to the formation of the porous support structure. Forming the dense layer and porous support by different mechanisms while maintaining the simplicity of a phase inversion process, results in unprecedented control over the final structure of the membrane. The thickness and morphology of the dense layer as well as the porosity of the support can be controlled over a wide range by manipulating simple process parameters. CIPS facilitates control over (i) the thickness of the dense layer throughout several orders of magnitude—from less than 15 nm to more than 6 μm, (ii) the type and amount of metal ions loaded in the dense layer, (iii) the morphology of the membrane surface, and (iv) the porosity and structure of the support. The nature of the CIPS process facilitates a precise loading of a high concentration of metal ions that are located in only the top layer of the membrane. Moreover, these metal ions can be converted—during the membrane fabrication process—to nanoparticles or crystals. This simple method opens up fascinating possibilities for the fabrication of metal-rich polymeric membranes with a new set of properties. This dissertation describes the process in depth and explores promising

  9. Mechanism of the monoclinic-to-tetragonal phase transition induced in zirconia and hafnia by swift heavy ions

    International Nuclear Information System (INIS)

    Benyagoub, Abdenacer

    2005-01-01

    Recent results demonstrated that defect formation or amorphization are not the only structural changes induced by swift heavy ions in crystalline materials and that under certain circumstances crystalline-to-crystalline phase transitions can also occur. For instance, it was found that both zirconia and hafnia transform from the monoclinic to the tetragonal phase with a kinetics involving a double ion impact process. In order to understand the origin of this ion-beam induced phase transition, the behavior of these twin oxides was analyzed and compared. In fact, the likeness of these materials offered the unique opportunity to impose drastic constraints on the possible models proposed to explain the creation of atomic displacements in the wake of swift heavy ions. This comparison clearly suggests that the thermal spike is the most appropriate process which governs the transition from the monoclinic to the tetragonal phase in zirconia and hafnia

  10. Computing optimal interfacial structure of modulated phases

    OpenAIRE

    Xu, Jie; Wang, Chu; Shi, An-Chang; Zhang, Pingwen

    2016-01-01

    We propose a general framework of computing interfacial structures between two modulated phases. Specifically we propose to use a computational box consisting of two half spaces, each occupied by a modulated phase with given position and orientation. The boundary conditions and basis functions are chosen to be commensurate with the bulk structures. It is observed that the ordered nature of modulated structures stabilizes the interface, which enables us to obtain optimal interfacial structures...

  11. Pressure-induced phase transitions in single-crystalline Cu4Bi4S9 nanoribbons

    International Nuclear Information System (INIS)

    Hu Jing-Yu; Li Jing; Zhao Qing; Shi Li-Jie; Zou Bing-Suo; Zhang Si-Jia; Zhao Hao-Fei; Zhang Qing-Hua; Yao Yuan; Zhu Ke; Liu Yu-Long; Jin Chang-Qing; Yu Ri-Cheng; Li Yan-Chun; Li Xiao-Dong; Liu Jing

    2013-01-01

    In situ angle dispersive synchrotron X-ray diffraction and Raman scattering measurements under pressure are employed to study the structural evolution of Cu 4 Bi 4 S 9 nanoribbons, which are fabricated by using a facile solvothermal method. Both experiments show that a structural phase transition occurs near 14.5 GPa, and there is a pressure-induced reversible amorphization at about 25.6 GPa. The electrical transport property of a single Cu 4 Bi 4 S 9 nanoribbon under different pressures is also investigated

  12. Structure, elastic properties and phase stability of Cr1-xAlxN

    International Nuclear Information System (INIS)

    Mayrhofer, P.H.; Music, D.; Reeswinkel, Th.; Fuss, H.-G.; Schneider, J.M.

    2008-01-01

    The effect of composition and metal sublattice population on the phase stability, structure and elastic properties of cubic (c), hexagonal (h) and orthorhombic spin-polarized Cr 1-x Al x N was studied using ab initio calculations. Excellent correlation between ab initio and experimentally obtained lattice parameters and elastic constants was obtained. The energy of formation suggests that the cubic phase can be stabilized for x in the range 0.48-0.75, depending on the metal sublattice population. The broad range of x, which is also observed in experiments, can be understood by considering the Al distribution induced changes in the configurational contribution to the total energy

  13. Fermionic phase transition induced by the effective impurity in holography

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Li-Qing [IFSA Collaborative Innovation Center, Department of Physics and Astronomy,Shanghai Jiao Tong University, Shanghai 200240 (China); School of Physics and Electronic Information, Shangrao Normal University,Shangrao 334000 (China); Kuang, Xiao-Mei [Department of Physics, National Technical University of Athens,GR-15780 Athens (Greece); Instituto de Física, Pontificia Universidad Católica de Valparaíso,Casilla 4059, Valparaíso (Chile); Wang, Bin [IFSA Collaborative Innovation Center, Department of Physics and Astronomy,Shanghai Jiao Tong University, Shanghai 200240 (China); Wu, Jian-Pin [Institute of Gravitation and Cosmology, Department of Physics,School of Mathematics and Physics, Bohai University, Jinzhou 121013 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences, Beijing 100190 (China)

    2015-11-20

    We investigate the holographic fermionic phase transition induced by the effective impurity in holography, which is introduced by massless scalar fields in Einstein-Maxwell-massless scalar gravity. We obtain a phase diagram in (α,T) plane separating the Fermi liquid phase and the non-Fermi liquid phase.

  14. Adjoint method provides phase response functions for delay-induced oscillations.

    Science.gov (United States)

    Kotani, Kiyoshi; Yamaguchi, Ikuhiro; Ogawa, Yutaro; Jimbo, Yasuhiko; Nakao, Hiroya; Ermentrout, G Bard

    2012-07-27

    Limit-cycle oscillations induced by time delay are widely observed in various systems, but a systematic phase-reduction theory for them has yet to be developed. Here we present a practical theoretical framework to calculate the phase response function Z(θ), a fundamental quantity for the theory, of delay-induced limit cycles with infinite-dimensional phase space. We show that Z(θ) can be obtained as a zero eigenfunction of the adjoint equation associated with an appropriate bilinear form for the delay differential equations. We confirm the validity of the proposed framework for two biological oscillators and demonstrate that the derived phase equation predicts intriguing multimodal locking behavior.

  15. The dynamics of the laser-induced metal-semiconductor phase transition of samarium sulfide (SmS)

    International Nuclear Information System (INIS)

    Kaempfer, Tino

    2009-01-01

    The present thesis is dedicated to the experimental study of the metal-semiconductor phase transition of samarium sulfide (SmS): Temperature- and time-resolved experiments on the characterization of the phase transition of mixed-valence SmS samples (M-SmS) are presented. The measurement of the dynamics of the laser-induced phase transition pursues via time-resolved ultrashort-time microscopy and by X-ray diffraction with sub-picosecond time resolution. The electronic and structural processes, which follow an excitation of M-SmS with infrared femtosecond laser pulses, are physically interpreted on the base of the results obtained in this thesis and model imaginations. [de

  16. A Conceptual Model for Shear-Induced Phase Behavior in Crystallizing Cocoa Butter

    International Nuclear Information System (INIS)

    Mazzanti, G.; Guthrie, S.; Marangoni, A.; Idziak, S.

    2007-01-01

    We propose a conceptual model to explain the quantitative data from synchrotron X-ray diffraction experiments on the shear-induced phase behavior of cocoa butter, the main structural component of chocolate. We captured two-dimensional diffraction patterns from cocoa butter at crystallization temperatures of 17.5, 20.0, and 22.5 o C under shear rates from 45 to 1440 s -1 and under static conditions. From the simultaneous analysis of the integrated intensity, correlation length, lamellar thickness, and crystalline orientation, we postulate a conceptual model to provide an explanation for the distribution of phases II, IV, V, and X and the kinetics of the process. As previously proposed in the literature, we assume that the crystallites grow layer upon layer of slightly different composition. The shear rate and temperature applied define these compositions. Simultaneously, the shear and temperature define the crystalline interface area available for secondary nucleation by promoting segregation and affecting the size distribution of the crystallites. The combination of these factors (composition, area, and size distribution) favors dramatically the early onset of phase V under shear and determines the proportions of phases II, IV, V, and X after the transition. The experimental observations, the methodology used, and the proposed explanation are of fundamental and industrial interest, since the structural properties of crystalline networks are determined by their microstructure and polymorphic crystalline state. Different proportions of the phases will thus result in different characteristics of the final material

  17. Tailored optical vector fields for ultrashort-pulse laser induced complex surface plasmon structuring.

    Science.gov (United States)

    Ouyang, J; Perrie, W; Allegre, O J; Heil, T; Jin, Y; Fearon, E; Eckford, D; Edwardson, S P; Dearden, G

    2015-05-18

    Precise tailoring of optical vector beams is demonstrated, shaping their focal electric fields and used to create complex laser micro-patterning on a metal surface. A Spatial Light Modulator (SLM) and a micro-structured S-waveplate were integrated with a picosecond laser system and employed to structure the vector fields into radial and azimuthal polarizations with and without a vortex phase wavefront as well as superposition states. Imprinting Laser Induced Periodic Surface Structures (LIPSS) elucidates the detailed vector fields around the focal region. In addition to clear azimuthal and radial plasmon surface structures, unique, variable logarithmic spiral micro-structures with a pitch Λ ∼1μm, not observed previously, were imprinted on the surface, confirming unambiguously the complex 2D focal electric fields. We show clearly also how the Orbital Angular Momentum(OAM) associated with a helical wavefront induces rotation of vector fields along the optic axis of a focusing lens and confirmed by the observed surface micro-structures.

  18. Structural phase transition and elastic properties of AnAs (An= Th, U, Np, Pu) compounds at high pressure

    International Nuclear Information System (INIS)

    Aynyas, Mahendra; Arya, B.S.; Srivastava, Vipul; Sanyal, Sankar P.

    2006-01-01

    The high pressure behavior and pressure induced structural phase transition of mono arsenides (AnAs; An = Th, U, Np, Pu) have been investigated by using a three body interaction potential (TBI). This method has been found quite satisfactory in the case of other Rare-Earth compounds. The calculated compression curves of mono-arsenides obtained so have been compared with high pressure X-ray diffraction work. The theoretically predicted phase transition pressure and other structural properties for these compounds agree reasonably well with the measured values. (author)

  19. CFA Films in Amorphous Substrate: Structural Phase Induction and Magnetization Dynamics

    Science.gov (United States)

    Correa, M. A.; Bohn, F.; Escobar, V. M.

    We report a systematic study of the structural and quasi-static magnetic properties, as well as of the dynamic magnetic response through MI effect, in Co2FeAl and MgO//Co2FeAl single layers and a MgO//Co2FeAl/Ag/Co2FeAl trilayered film, all grown onto an amorphous substrate. We present a new route to induce the crystalline structure in the Co2FeAl alloy and verify that changes in the structural phase of this material leads to remarkable modifications of the magnetic anisotropy and, consequently, dynamic magnetic behavior. Considering the electrical and magnetic properties of the Co2FeAl, our results open new possibilities for technological applications of this full-Heusler alloy in rigid and flexible spintronic devices.

  20. Ultrafast optically induced ferromagnetic/anti-ferromagnetic phase transition in GdTiO3 from first principles

    Science.gov (United States)

    Khalsa, Guru; Benedek, Nicole A.

    2018-03-01

    Epitaxial strain and chemical substitution have been the workhorses of functional materials design. These static techniques have shown immense success in controlling properties in complex oxides through the tuning of subtle structural distortions. Recently, an approach based on the excitation of an infrared active phonon with intense midinfrared light has created an opportunity for dynamical control of structure through special nonlinear coupling to Raman phonons. We use first-principles techniques to show that this approach can dynamically induce a magnetic phase transition from the ferromagnetic ground state to a hidden antiferromagnetic phase in the rare earth titanate GdTiO3 for realistic experimental parameters. We show that a combination of a Jahn-Teller distortion, Gd displacement, and infrared phonon motion dominate this phase transition with little effect from the octahedral rotations, contrary to conventional wisdom.

  1. Twinning induced by the rhombohedral to orthorhombic phase transition in lanthanum gallate (LaGaO3)

    Science.gov (United States)

    Wang, W. L.; Lu, H. Y.

    2006-10-01

    Phase-transformation-induced twins in pressureless-sintered lanthanum gallate (LaGaO3) ceramics have been analysed using the transmission electron microscopy (TEM). Twins are induced by solid state phase transformation upon cooling from the rhombohedral (r, Rbar{3}c) to orthorhombic ( o, Pnma) symmetry at ˜145°C. Three types of transformation twins {101} o , {121} o , and {123} o were found in grains containing multiple domains that represent orientation variants. Three orthorhombic orientation variants were distinguished from the transformation domains converged into a triple junction. These twins are the reflection type as confirmed by tilting experiment in the microscope. Although not related by group-subgroup relation, the transformation twins generated by phase transition from rhombohedral to orthorhombic are consistent with those derived from taking cubic Pm {bar {3}}m aristotype of the lowest common supergroup symmetry as an intermediate metastable structure. The r→ o phase transition of first order in nature may have occurred by a diffusionless, martensitic-type or discontinuous nucleation and growth mechanism.

  2. Thermodynamics aspects of noise-induced phase synchronization.

    Science.gov (United States)

    Pinto, Pedro D; Oliveira, Fernando A; Penna, André L A

    2016-05-01

    In this article, we present an approach for the thermodynamics of phase oscillators induced by an internal multiplicative noise. We analytically derive the free energy, entropy, internal energy, and specific heat. In this framework, the formulation of the first law of thermodynamics requires the definition of a synchronization field acting on the phase oscillators. By introducing the synchronization field, we have consistently obtained the susceptibility and analyzed its behavior. This allows us to characterize distinct phases in the system, which we have denoted as synchronized and parasynchronized phases, in analogy with magnetism. The system also shows a rich complex behavior, exhibiting ideal gas characteristics for low temperatures and susceptibility anomalies that are similar to those present in complex fluids such as water.

  3. Thermodynamics aspects of noise-induced phase synchronization

    Science.gov (United States)

    Pinto, Pedro D.; Oliveira, Fernando A.; Penna, André L. A.

    2016-05-01

    In this article, we present an approach for the thermodynamics of phase oscillators induced by an internal multiplicative noise. We analytically derive the free energy, entropy, internal energy, and specific heat. In this framework, the formulation of the first law of thermodynamics requires the definition of a synchronization field acting on the phase oscillators. By introducing the synchronization field, we have consistently obtained the susceptibility and analyzed its behavior. This allows us to characterize distinct phases in the system, which we have denoted as synchronized and parasynchronized phases, in analogy with magnetism. The system also shows a rich complex behavior, exhibiting ideal gas characteristics for low temperatures and susceptibility anomalies that are similar to those present in complex fluids such as water.

  4. Shear-induced phase changes in mixtures

    International Nuclear Information System (INIS)

    Romig, K.D.; Hanley, H.J.M.

    1986-01-01

    A thermodynamic theory to account for the behavior of liquid mixtures exposed to a shear is developed. One consequence of the theory is that shear-induced phase changes are predicted. The theory is based on a thermodynamics that includes specifically the shear rate in the formalism and is applied to mixtures by a straightforward modification of the corresponding states, conformalsolution approach. The approach is general but is used here for a mixture of Lennard-Jones particles with a Lennard-Jones equation of state as a reference fluid. The results are discussed in the context of the Scott and Van Konynenberg phase classification. It is shown that the influence of a shear does affect substantially the type of the phase behavior. Results from the model mixture are equated loosely with those from real polymeric liquids

  5. Multi-phase-field method for surface tension induced elasticity

    Science.gov (United States)

    Schiedung, Raphael; Steinbach, Ingo; Varnik, Fathollah

    2018-01-01

    A method, based on the multi-phase-field framework, is proposed that adequately accounts for the effects of a coupling between surface free energy and elastic deformation in solids. The method is validated via a number of analytically solvable problems. In addition to stress states at mechanical equilibrium in complex geometries, the underlying multi-phase-field framework naturally allows us to account for the influence of surface energy induced stresses on phase transformation kinetics. This issue, which is of fundamental importance on the nanoscale, is demonstrated in the limit of fast diffusion for a solid sphere, which melts due to the well-known Gibbs-Thompson effect. This melting process is slowed down when coupled to surface energy induced elastic deformation.

  6. Formation of {1 0 0} textured columnar grain structure in a non-oriented electrical steel by phase transformation

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Li; Yang, Ping, E-mail: yangp@mater.ustb.edu.cn; Zhang, Ning; Zong, Cui; Xia, Dongsheng; Mao, Weimin

    2014-04-01

    This study confirms the effect of anisotropic strain energy on the formation of {1 0 0} textured columnar grain structure induced by temperature gradient during γ to α phase transformation in pure hydrogen atmosphere. Results indicate that high temperature gradient in pure hydrogen atmosphere induces a significant strain energy difference across grain boundaries during γ to α phase transformation, leading to the formation of {1 0 0} texture with columnar grains. Given its simplicity in processing and its ability to obtain good texture-related magnetic properties, the proposed approach is helpful to the development of new types of non-oriented electrical steel. - Highlights: • A strong {1 0 0} texture with columnar grains was obtained. • Good texture and magnetic properties are attributed to the anisotropic strain energy. • The anisotropy in elastic strain energy was induced by the temperature gradient. • The phase transformation rate affects columnar grain morphology.

  7. Reconstructive structural phase transitions in dense Mg

    International Nuclear Information System (INIS)

    Yao Yansun; Klug, Dennis D

    2012-01-01

    The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) → body centered cubic (bcc) or hcp → double hexagonal close-packed (dhcp) → bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp → dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp → bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp → bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied. (paper)

  8. Magnetostrictive hypersound generation by spiral magnets in the vicinity of magnetic field induced phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Bychkov, Igor V. [Chelyabinsk State University, 129 Br. Kashirinykh Str., Chelyabinsk 454001 (Russian Federation); South Ural State University (National Research University), 76 Lenin Prospekt, Chelyabinsk 454080 (Russian Federation); Kuzmin, Dmitry A., E-mail: kuzminda@csu.ru [Chelyabinsk State University, 129 Br. Kashirinykh Str., Chelyabinsk 454001 (Russian Federation); South Ural State University (National Research University), 76 Lenin Prospekt, Chelyabinsk 454080 (Russian Federation); Kamantsev, Alexander P.; Koledov, Victor V.; Shavrov, Vladimir G. [Kotelnikov Institute of Radio-engineering and Electronics of RAS, Mokhovaya Street 11-7, Moscow 125009 (Russian Federation)

    2016-11-01

    In present work we have investigated magnetostrictive ultrasound generation by spiral magnets in the vicinity of magnetic field induced phase transition from spiral to collinear state. We found that such magnets may generate transverse sound waves with the wavelength equal to the spiral period. We have examined two types of spiral magnetic structures: with inhomogeneous exchange and Dzyaloshinskii–Moriya interactions. Frequency of the waves from exchange-caused spiral magnetic structure may reach some THz, while in case of Dzyaloshinskii–Moriya interaction-caused spiral it may reach some GHz. These waves will be emitted like a sound pulses. Amplitude of the waves is strictly depends on the phase transition speed. Some aspects of microwaves to hypersound transformation by spiral magnets in the vicinity of phase transition have been investigated as well. Results of the work may be interesting for investigation of phase transition kinetics as well, as for various hypersound applications. - Highlights: • Magnetostrictive ultrasound generation by spiral magnets at phase transition (PT) is studied. • Spiral magnets during PT may generate transverse sound with wavelength equal to spiral period. • Amplitude of the sound is strictly depends on the phase transition speed. • Microwave-to-sound transformation in the vicinity of PT is investigated as well.

  9. A description of phases with induced hybridisation at finite temperatures

    Science.gov (United States)

    Golosov, D. I.

    2018-05-01

    In an extended Falicov-Kimball model, an excitonic insulator phase can be stabilised at zero temperature. With increasing temperature, the excitonic order parameter (interaction-induced hybridisation on-site, characterised by the absolute value and phase) eventually becomes disordered, which involves fluctuations of both its phase and (at higher T) its absolute value. In order to build an adequate mean field description, it is important to clarify the nature of degrees of freedom associated with the phase and absolute value of the induced hybridisation, and the corresponding phase space volume. We show that a possible description is provided by the SU(4) parametrisation on-site. In principle, this allows to describe both the lower-temperature regime where phase fluctuations destroy the long-range order, and the higher temperature crossover corresponding to a decrease of absolute value of the hybridisation relative to the fluctuations level. This picture is also expected to be relevant in other contexts, including the Kondo lattice model.

  10. Pressure-induced phase transition in KxFe2-yS2

    International Nuclear Information System (INIS)

    Tsuchiya, Yuu; Ikeda, Shugo; Kobayashi, Hisao; Zhang, Xiao-Wei; Kishimoto, Shunji; Kikegawa, Takumi; Hirao, Naohisa; Kawaguchi, Saori I.; Ohishi, Yasuo

    2017-01-01

    The structural and electronic properties of high-quality K 0.66(6) Fe 1.75(10) S 2 single crystals have been investigated by angle-resolved X-ray diffraction and 57 Fe nuclear forward scattering using synchrotron radiation under pressure at room temperature. The samples exhibit phase separation into antiferromagnetic ordered K 2 Fe 4 S 5 and nonmagnetic K x Fe 2 S 2 phases. It was found that a pressure-induced phase transition occurs at p c = 5.9(4) GPa with simultaneous suppression of the antiferromagnetic and Fe vacancy orders. >From the results of 57 Fe nuclear forward scattering, the refined magnetic hyperfine field remains unchanged with pressure below p c , suggesting that the Néel temperature does not decrease with pressure up to p c . Above p c , all Fe atoms in K 0.66 Fe 1.75 S 2 are in the same nonmagnetic state. A discontinuous increase in the center shift was observed at p c , reflecting a change in the Fe electronic state in K 0.66 Fe 1.75 S 2 . (author)

  11. Strain-induced phase transition and electron spin-polarization in graphene spirals.

    Science.gov (United States)

    Zhang, Xiaoming; Zhao, Mingwen

    2014-07-16

    Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices.

  12. Electron-beam-induced structure transformation of the quasicrystalline phases of the Al 62Cu 20Co 15Si 3 alloy

    Science.gov (United States)

    Reyes-Gasga, J.; R. Garcia, G.; Jose-Yacaman, M.

    1995-02-01

    Some details on the phase transformation experienced by the quasicrystalline phases of the Al 62Cu 20Co 15Si 3 alloy under a 400 kV electron beam are given. The transition is observed in situ with a high resolution electron microscope and recorded on video tape. The results show that the electron beam radiation produces a sequence of changes similar to the ones observed in an ion-beam-induced amorphization process. Considering electron radiation damage analysis, the results agree well with the "flip-flop" model [Coddens, Bellisent, Calvayrac and Ambroise (1991) Europhys. Lett.16, 271] where the transition from a quasicrystalline phase to a crystalline phase is produced by atomic displacements but not in a cascade way.

  13. Structure directing agents induced morphology evolution and phase transition from indium-based rho- to sod-ZMOF

    KAUST Repository

    Shi, Yanshu; Cairns, Amy; Liu, Yunling; Belmabkhout, Youssef; Cai, Xuechao; Pang, Maolin; Eddaoudi, Mohamed

    2017-01-01

    In this report, indium-based rho-and sod-ZMOFs with different morphologies and sizes were prepared. Simultaneous morphology evolution and phase transformation from porous rho-to nonporous sod-ZMOFs were reported for the first time by simply varying the concentration of structure directing agents (SDAs).

  14. Structure directing agents induced morphology evolution and phase transition from indium-based rho- to sod-ZMOF

    KAUST Repository

    Shi, Yanshu

    2017-06-23

    In this report, indium-based rho-and sod-ZMOFs with different morphologies and sizes were prepared. Simultaneous morphology evolution and phase transformation from porous rho-to nonporous sod-ZMOFs were reported for the first time by simply varying the concentration of structure directing agents (SDAs).

  15. The Physics of Structural Phase Transitions

    CERN Document Server

    Fujimoto, Minoru

    2005-01-01

    Phase transitions in which crystalline solids undergo structural changes present an interesting problem in the interplay between the crystal structure and the ordering process that is typically nonlinear. Intended for readers with prior knowledge of basic condensed-matter physics, this book emphasizes the physics behind spontaneous structural changes in crystals. Starting with the relevant thermodynamic principles, the text discusses the nature of order variables in collective motion in structural phase transitions, where a singularity in such a collective mode is responsible for lattice instability as revealed by soft phonons. In this book, critical anomalies at second-order structural transitions are first analyzed with the condensate model. Discussions on the nonlinear ordering mechanism are followed with the soliton theory, thereby interpreting the role of long-range order. Relevant details for nonlinear mathematics are therefore given for minimum necessity. The text also discusses experimental methods fo...

  16. Pressure-induced phase transformation of HfO2

    International Nuclear Information System (INIS)

    Arashi, H.

    1992-01-01

    This paper reports on the pressure dependence of the Raman spectra of HfO 2 that was measured by a micro-Raman technique using a single-crystal specimen in the pressure range from 0 to 10 GPa at room temperature. The symmetry assignment of Raman bands of the monoclinic phase was experimentally accomplished from the polarization measurements for the single crystal. With increased pressure, a phase transformation for the monoclinic phase took place at 4.3 ± 0.3 GPa. Nineteen Raman bands were observed for the high-pressure phase. The spectral structure of the Raman bands for the high-pressure phase was similar with those reported previously for ZrO 2 . The space group for the high pressure phase of HfO 2 was determined as Pbcm, which was the same as that of the high-pressure phase for ZrO 2 on the basis of the number and the spectral structure of the Raman bands

  17. Corundum-to-spinel structural phase transformation in alumina

    Energy Technology Data Exchange (ETDEWEB)

    Adachi, Shogo [Department of Materials Science and Engineering, Kyushu Institute of Technology, Fukuoka 804-8550 (Japan); Ishimaru, Manabu, E-mail: ishimaru@post.matsc.kyutech.ac.jp [Department of Materials Science and Engineering, Kyushu Institute of Technology, Fukuoka 804-8550 (Japan); Sina, Younes; McHargue, Carl J.; Sickafus, Kurt E. [Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996-2200 (United States); Alves, Eduardo [Unit of Physics and Accelerators, Ion Beam Laboratory, Instituto Superior Técnico/Instituto Tecnológico e Nuclear, EN. 10 2686-953 Sacavém (Portugal)

    2015-09-01

    Several polymorphs exist in alumina (Al{sub 2}O{sub 3}), and they transform to a stable α-phase with a hexagonal corundum structure on thermal annealing. This structural change is irreversible as a function of temperature, and transformation of corundum to another metastable crystalline phase has never been observed by heat treatments. In this study, we irradiated single crystals of Al{sub 2}O{sub 3} with Zr ions and obtained an irradiated microstructure consisting of a buried α-Al{sub 2}O{sub 3} layer surrounded on top and bottom by layers of a defect cubic spinel Al{sub 2}O{sub 3} phase. We examined the thermal stability of this microstructure using transmission electron microscopy and X-ray diffraction. We found that the corundum phase completely transforms to the spinel phase following annealing at 1173 K for 1 h: the thermodynamically stable phase transforms to the metastable phase by heat treatments. We discuss this unusual structural change within the context of our results as well as previous observations.

  18. Atomic scale insight into the amorphous structure of Cu doped GeTe phase-change material

    International Nuclear Information System (INIS)

    Zhang, Linchuan; Sa, Baisheng; Zhou, Jian; Sun, Zhimei; Song, Zhitang

    2014-01-01

    GeTe shows promising application as a recording material for phase-change nonvolatile memory due to its fast crystallization speed and extraordinary amorphous stability. To further improve the performance of GeTe, various transition metals, such as copper, have been doped in GeTe in recent works. However, the effect of the doped transition metals on the stability of amorphous GeTe is not known. Here, we shed light on this problem for the system of Cu doped GeTe by means of ab initio molecular dynamics calculations. Our results show that the doped Cu atoms tend to agglomerate in amorphous GeTe. Further, base on analyzing the pair correlation functions, coordination numbers and bond angle distributions, remarkable changes in the local structure of amorphous GeTe induced by Cu are obviously seen. The present work may provide some clues for understanding the effect of early transition metals on the local structure of amorphous phase-change compounds, and hence should be helpful for optimizing the structure and performance of phase-change materials by doping transition metals.

  19. Effect of the change in the interface structure of Pd(100)/SrTiO{sub 3} for quantum-well induced ferromagnetism

    Energy Technology Data Exchange (ETDEWEB)

    Sakuragi, Shunsuke, E-mail: sakuragi@az.appi.keio.ac.jp [Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 223-0061 (Japan); Ogawa, Tomoyuki [Department of Electronic Engineering, Graduate School of Engineering, Tohoku University, Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Sato, Tetsuya [Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 223-0061 (Japan)

    2017-02-01

    Measurements of temperature dependent magnetization of Pd(100) ultrathin films on SrTiO{sub 3}(100) substrates which shows quantum-well induced ferromagnetism were performed. We observed the jump in magnetization of Pd(100) due to the structural phase transition of SrTiO{sub 3}, and then, the disappearance of ferromagnetism after temperature-cycle repetition. X-ray reflectivity measurement revealed that the density of a few layers in the Pd film decreased near the Pd/SrTiO{sub 3} interface after temperature cycles. This suggests that the structural change affects the quantum-well induced ferromagnetism, and lowering of the crystallinity of Pd at the interface has a negative effect on quantum-well induced ferromagnetism of Pd(100) ultrathin films. - Highlights: • Interface manipulation of quantum-well induced ferromagnetism was performed. • Ferromagnetic Pd(100) ultrathin films on SrTiO{sub 3} substrate were prepared. • The structural phase transition of SrTiO{sub 3} degraded gradually the interface structure. • Change in the interface structure caused change in the magnetic moment of Pd. • Magnetic change was interpreted by modulation in the effective thickness of the film.

  20. Light-induced ultrafast phase transitions in VO2 thin film

    International Nuclear Information System (INIS)

    Lysenko, S.; Rua, A.J.; Vikhnin, V.; Jimenez, J.; Fernandez, F.; Liu, H.

    2006-01-01

    Vanadium dioxide shows a passive and reversible change from a monoclinic insulator phase to a metallic tetragonal rutile structure when the sample temperature is close to and over 68 deg. C. As a kind of functional material, VO 2 thin films deposited on fused quartz substrates were successfully prepared by the pulsed laser deposition (PLD) technique. With laser illumination at 400 nm on the obtained films, the phase transition (PT) occurred. The observed light-induced PT was as fast as the laser pulse duration of 100 fs. Using a femtosecond laser system, the relaxation processes in VO 2 were studied by optical pump-probe spectroscopy. Upon a laser excitation an instantaneous response in the transient reflectivity and transmission was observed followed by a relatively longer relaxation process. The alteration is dependent on pump power. The change in reflectance reached a maximum value at a pump pulse energy between 7 and 14 mJ/cm 2 . The observed PT is associated with the optical interband transition in VO 2 thin film. It suggests that with a pump laser illuminating on the film, excitation from the d θ,ε - state of valence band to the unoccupied excited mixed d θ,ε -π* - state of the conduction band in the insulator phase occurs, followed by a resonant transition to an unoccupied excited mixed d θ,ε -π* - state of the metallic phase band

  1. Symmetry-induced deformation and reconstructive phase transformation in metal-oxide interface: the Fe (001) example

    International Nuclear Information System (INIS)

    Lahoche, L.; Universite de Technologie de Compiegne; Lorman, V.; Roelandt, J.M.; Rochal, S.B.

    1996-01-01

    A model is proposed for the structural transformation and corresponding induced deformation in physical three-dimensional interface of the metal-oxide system. The thermodynamical and elastic state of the system is described by the Landau-Ginzbourg free energy. Calculated theoretical phase diagram shows several different types of isothermal growth processes. The model is applied to the case of the oxidation of the (001) Fe surface. (orig.)

  2. A computational study of pressure-induced structural transition in ThSb

    International Nuclear Information System (INIS)

    Trinadh, Ch.U.M.; Rajagopalan, M.; Natarajan, S.

    1997-01-01

    The pressure induced phase transition from NaCl-type to CsCl-type structure in ThSb was studied using total energy calculations by tight-binding linear muffin tin orbital (TBLMTO) method within atomic sphere approximation (ASA). The density of states (DOS) at ambient pressure was compared with resonant photoemission studies (PES). The variation in interatomic distances during the transition was found to be in agreement with high pressure x-ray diffraction (HPXRD) studies. (author)

  3. First-principles assessment of potential ultrafast laser-induced structural transition in Ni

    Energy Technology Data Exchange (ETDEWEB)

    Bévillon, E.; Colombier, J.P., E-mail: jean.philippe.colombier@univ-st-etienne.fr; Stoian, R.

    2016-06-30

    Highlights: • First-principles theory calculations in nonequilibrium conditions. • Electronic temperatures fully and consistently taken into account. • Evaluation of an ultrafast laser-induced solid-to-solid transition in Ni. • Relative energies, phonon spectra and energy path are evaluated. • Discussion on the generation of non-thermal forces in metals. - Abstract: The possibility to trigger ultrafast solid-to-solid transitions in transition metals under femtosecond laser irradiation is investigated by means of first-principles calculations. Electronic heating can drastically modify screening, charge distribution and atomic binding features, potentially determining new structural relaxation paths in the solid phase, before thermodynamic solid-to-liquid transformations set in. Consequently, we evaluate here the effect of electronic excitation on structural stability and conditions for structural transitions. Ni is chosen as a case study for the probability of a solid transition, and the stability of its FCC phase is compared to the non-standard HCP structure while accounting for the heating of the electronic subsystem. From a phonon spectra analysis, we show that the thermodynamic stability order reverses at an electronic temperature of around 10{sup 4} K. Both structures exhibit a dynamic stability, indicating they present a metastability depending on the heating. However, the general hardening of phonon modes with the increase of the electronic temperature points out that no transformation will occur, as confirmed by the study of a typical FCC to HCP diffusionless transformation path, showing an increasing energy barrier. Finally, based on electronic density of states interpretation, the tendency of different metal categories to undergo or not an ultrafast laser-induced structural transition is discussed.

  4. Complexation-Induced Phase Separation: Preparation of Metal-Rich Polymeric Membranes

    KAUST Repository

    Villalobos, Luis Francisco

    2017-01-01

    The majority of state-of-the-art polymeric membranes for industrial or medical applications are fabricated by phase inversion. Complexation induced phase separation (CIPS)—a surprising variation of this well-known process—allows direct fabrication

  5. The effect of relativity on stability of Copernicium phases, their electronic structure and mechanical properties

    Science.gov (United States)

    Čenčariková, Hana; Legut, Dominik

    2018-05-01

    The phase stability of the various crystalline structures of the super-heavy element Copernicium was determined based on the first-principles calculations with different levels of the relativistic effects. We utilized the Darwin term, mass-velocity, and spin-orbit interaction with the single electron framework of the density functional theory while treating the exchange and correlation effects using local density approximations. It is found that the spin-orbit coupling is the key component to stabilize the body-centered cubic (bcc) structure over the hexagonal closed packed (hcp) structure, which is in accord with Sol. Stat. Comm. 152 (2012) 530, but in contrast to Atta-Fynn and Ray (2015) [11], Gaston et al. (2007) [10], Papaconstantopoulos (2015) [9]. It seems that the main role here is the correct description of the semi-core relativistic 6p1/2 orbitals. The all other investigated structures, i.e. face-centered cubic (fcc) , simple cubic (sc) as well as rhombohedral (rh) structures are higher in energy. The criteria of mechanical stability were investigated based on the calculated elastic constants, identifying the phase instability of fcc and rh structures, but surprisingly confirm the stability of the energetically higher sc structure. In addition, the pressure-induced structural transition between two stable sc and bcc phases has been detected. The ground-state bcc structure exhibits the highest elastic anisotropy from single elements of the Periodic table. At last, we support the experimental findings that Copernicium is a metal.

  6. The Structural Phase Transition in Octaflournaphtalene

    DEFF Research Database (Denmark)

    Mackenzie, Gordon A.; Arthur, J. W.; Pawley, G. S.

    1977-01-01

    The phase transition in octafluoronaphthalene has been investigated by Raman scattering and neutron powder diffraction. The weight of the experimental evidence points to a unit cell doubling in the a direction, but with no change in space group symmetry. Lattice dynamics calculations support...... this evidence and indicate that the mechanism of the phase transition may well be the instability of a zone boundary acoustic mode of librational character. The structure of the low-temperature phase has been refined and the Raman spectra of the upper and lower phases are reported....

  7. Prediction of pressure induced structural phase transitions and internal mode frequency changes in solid N2+

    International Nuclear Information System (INIS)

    Etters, R.D.; Kobashi, K.; Chandrasekharan, V.

    1983-01-01

    A rhombohedral distortion of the Pm3n structure is introduced which shows that a low temperature phase transition occurs from P4 2 /mnm into the R3c calcite structure at P approx. = 19.2 kbar with a volume change of 0.125 cm 3 /mole. This transition agrees with recent Raman scattering measurements. Another transition from R3c into R3m is predicted at P approx. = 67.5 kbar, with a volume change of 0.1 cm 3 /mole. The pressure dependence of the intramolecular mode frequencies for the R3c structure is in reasonably good agreement with the two main branches observed experimentally

  8. The crystal structure and the phase transitions of pyridinium trifluoromethanesulfonate

    International Nuclear Information System (INIS)

    Jesariew, Dominik; Ilczyszyn, Maria M; Pietraszko, Adam

    2014-01-01

    The calorimetric and optical studies and the structural properties of pyridinium trifluoromethanesulfonate (abbreviated as PyHOTf) are reported. A sequence of four fully reversible solid–solid phase transitions, at 223.0, 309.0, 359.9 and 394.3 K, has been discovered. The phase transition sequence was confirmed by x-ray diffraction data. The crystal structures of three phases (V, IV and III) have been determined from the single crystal x-ray diffraction data. Structural properties of the high temperature phases are characterized using powder x-ray diffraction data measured in the 290–425 K temperature range. The structural changes triggered by the temperature change are discussed in relation to the phase transitions. Two low temperature phases (V and IV) belong to the P4 3 2 1 2 space group of the tetragonal system. The intermediate phases (III and II) are monoclinic and the prototype high temperature phase (I) is a pseudo-cubic (tetragonal) one. The low temperature phases (V and IV) are well ordered. The crystal structure of intermediate (III and II) and prototype (I) phases are characterized by high disorder of the pyridinium cations and triflate anions. (papers)

  9. Kinetics of the stress induced phase transition in quartz by real-time neutron scattering

    International Nuclear Information System (INIS)

    Gibhardt, H.; Eckold, G.; Guethoff, F.

    1999-01-01

    Complete text of publication follows. The stability regime of the incommensurate phase of quartz is influenced by uniaxial stress. Hence, the phase transition can be induced under isothermal conditions by the application of external mechanical forces. Using real-time neutron scattering the time evolution of structural changes is investigated id detail during stress variations. The time dependent behaviour of the satellite reflection is compared with that one of the fundamental Bragg reflection which - via primary extinction - gives information about the perfection of the crystal. On increasing stress the perfection of the lattice is destroyed immediately while the modulated structure is built up with a delay of about 1 s. Decreasing the stress leads to a reverse behaviour. Moreover, there is evidence that under periodical load residual non-relaxed strain fields survive leading to a different temperature dependence as compared to static conditions. This finding is compatible with pronounced hysteresis effects observed under cycling stress. It is argued that these residual strains are associated with non-relaxed topological 4-line defects, that drive the structural changes in quartz (1). (author)

  10. Out-of-phase flashing induced instabilities in CIRCUS facility

    Energy Technology Data Exchange (ETDEWEB)

    Christian Pablo Marcel; Van der Hagen, T.H.J.J. [Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)

    2005-07-01

    Full text of publication follows: Flashing-induced instabilities are very important during the startup phase of natural-circulation boiling water reactors. To study this type of instability an axial fully scaled facility named CIRCUS was constructed. Experiments at low power and low pressure (typical startup conditions) are carried out on this steam/water natural circulation loop with two parallel risers. A detailed measurement of the void-fraction profile is possible by using needle-probes and the use of glass tubes for the riser and core sections allow to use optical techniques for velocity measurements. The flashing and the mechanism of flashing-induced instabilities are analyzed paying special attention on the strong coupling effect between the two riser channels. It is clear from the experiments that the out-of-phase instability is much more susceptible to occur than the in-phase instability in a system with two parallel risers. The instability region is found as soon as the operational boundary between single-phase and two-phase operation is crossed. The relation between the period of the oscillations and the fluid transient time is also investigated. The stability map constructed using this experimental data is also discussed. (authors)

  11. Relationship between hydrogen-induced phase transformations and pitting nucleation sites in duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Liqiu; Yang, Binjie; Qin, Sixiao [University of Science and Technology Beijing (China). Corrosion and Protection Center

    2016-02-15

    This paper demonstrates the hydrogen-induced phase transformation and the associated pitting nucleation sites of 2507 duplex stainless steel using scanning Kelvin probe force microscopy and magnetic force microscopy. The low potential sites in Volta potential images, which are considered as the pitting nucleation sites, are strongly dependent on the hydrogen-induced phase transformation. They firstly initiate on the magnetic martensite laths in the austenite phase or at the ferrite/austenite boundaries, and then appear near the needle-shaped microtwins in the ferrite phase, because of the difference in physicochemical properties of hydrogen-induced phase transformation microstructures.

  12. Noise-and delay-induced phase transitions of the dimer–monomer surface reaction model

    International Nuclear Information System (INIS)

    Zeng Chunhua; Wang Hua

    2012-01-01

    Highlights: ► We study the dimer–monomer surface reaction model. ► We show that noise induces first-order irreversible phase transition (IPT). ► Combination of noise and time-delayed feedback induce first- and second-order IPT. ► First- and second-order IPT is viewed as noise-and delay-induced phase transitions. - Abstract: The effects of noise and time-delayed feedback in the dimer–monomer (DM) surface reaction model are investigated. Applying small delay approximation, we construct a stochastic delayed differential equation and its Fokker–Planck equation to describe the state evolution of the DM reaction model. We show that the noise can only induce first-order irreversible phase transition (IPT) characteristic of the DM model, however the combination of the noise and time-delayed feedback can simultaneously induce first- and second-order IPT characteristics of the DM model. Therefore, it is shown that the well-known first- and second-order IPT characteristics of the DM model may be viewed as noise-and delay-induced phase transitions.

  13. Pressure-induced irreversible metallization accompanying the phase transitions in S b2S3

    Science.gov (United States)

    Dai, Lidong; Liu, Kaixiang; Li, Heping; Wu, Lei; Hu, Haiying; Zhuang, Yukai; Yang, Linfei; Pu, Chang; Liu, Pengfei

    2018-01-01

    We have revealed S b2S3 to have two phase transitions and to undergo metallization using a diamond anvil cell at around 5.0, 15.0, and 34.0 GPa, respectively. These results were obtained on the basis of high-pressure Raman spectroscopy, temperature-dependent conductivity measurements, atomic force microscopy, high-resolution transmission electron microscopy, and first-principles calculations. The first phase transition at ˜5.0 GPa is an isostructural phase transition, which is manifested in noticeable changes in five Raman-active modes and the slope of the conductivity because of a change in the electronic structure. The second pressure-induced phase transition was characterized by a discontinuous change in the slope of conductivity and a new low-intensity Raman mode at ˜15.0 GPa . Furthermore, a semiconductor-to-metal transition was found at ˜34.0 GPa , which was accompanied by irreversible metallization, and it could be attributed to the permanently plastic deformation of the interlayer spacing. This high-pressure behavior of S b2S3 will help us to understand the universal crystal structure evolution and electrical characteristics for A2B3 -type compounds, and to facilitate their application in electronic devices.

  14. Structural response in FeCl2 (iron chloride) to pressure-induced electro-magnetic transitions

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, R D [Los Alamos National Laboratory; Rozenberg, G Kh [TEL AVIV UNIV; Pasternak, M P [TEL AVIV UNIV; Gorodetsky, P [TEL AVIV UNIV; Xu, W M [TEL AVIV UNIV; Dubrovinsky, L S [UNIV OF BAYREUTH; Le Bihan, T L [FRANCE

    2009-01-01

    High pressure (HP) synchrotron x-ray diffraction studies were carried out in FeCl{sub 2} together with resistivity (R) studies, at various temperatures and pressures to 65 GPa using diamond anvil cells. This work follows a previous HP {sup 57}Fe Mossbauer study in which two pressure-induced (PI) electronic transitions were found interpreted as: (i) quenching of the orbital-term contribution to the hyperfine field concurring with a tilting of the magnetic moment by 55 degrees and (ii) collapse of the magnetism concurring with a sharp decrease of the isomer shift (IS). The R(P,T) studies affirm that the cause the collapse of the magnetism is a PI p-d correlation breakdown, leading to an insulator-metal transition at {approx}45 GPa and is not due to a spi-Ir,crossover (S=2 {yields} S=0). The structure response to the pressure evolution of the two electronic phase transitions starting at low pressures (LP), through an intermediate phase (IP) 30-57 GPa, and culminating in a high-pressure phase (HP), P >32 GPa, can clearly be quantified. The IP-HP phases coexist through the 32-57 GPa range in which the HP abundance increases monotonically at the expense of the IP phase. At the LP-IP interface no volume change is detected, yet the c-axis increases and the a-axis shrinks by 0.21 Angstroms and 0.13 Angstroms, respectively. The fit of the equation of state of the combined LP-IP phases yields a bulk modulus K{sub 0} = 35.3(1.8) GPa. The intralayer CI-CI distances increases, but no change is observed in Fe-CI bond-length nor are there substantial changes in the interlayer spacing. The pressure-induced electronic IP-HP transition leads to a first-order structural phase transition characterized by a decrease in Fe-CI bond length and an abrupt drop in V(P) by {approx}3.5% accompanying the correlation breakdown. In this transition no symmetry change is detected,and the XRD data could be satisfactorily fitted with the CdI{sub 2} structure. The bulk modulus of the HP phase is

  15. Electron backscatter diffraction studies of focused ion beam induced phase transformation in cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Jones, H.G., E-mail: helen.jones@npl.co.uk [National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom); Day, A.P. [Aunt Daisy Scientific Ltd, Claremont House, High St, Lydney GL15 5DX (United Kingdom); Cox, D.C. [National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom); Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom)

    2016-10-15

    A focused ion beam microscope was used to induce cubic to hexagonal phase transformation in a cobalt alloy, of similar composition to that of the binder phase in a hardmetal, in a controlled manner at 0°, 45° and 80° ion incident angles. The cobalt had an average grain size of ~ 20 μm, allowing multiple orientations to be studied, exposed to a range of doses between 6 × 10{sup 7} and 2 × 10{sup 10} ions/μm{sup 2}. Electron backscatter diffraction (EBSD) was used to determine the original and induced phase orientations, and area fractions, before and after the ion beam exposure. On average, less phase transformation was observed at higher incident angles and after lower ion doses. However there was an orientation effect where grains with an orientation close to (111) planes were most susceptible to phase transformation, and (101) the least, where grains partially and fully transformed at varying ion doses. - Highlights: •Ion-induced phase change in FCC cobalt was observed at multiple incidence angles. •EBSD was used to study the relationship between grain orientation and transformation. •Custom software analysed ion dose and phase change with respect to grain orientation. •A predictive capability of ion-induced phase change in cobalt was enabled.

  16. Commensurately modulated 1/4 and 1/5 phases of deuterated betaine calcium chloride dihydrate: a neutron structural study

    International Nuclear Information System (INIS)

    Hernandez, O.; Cousson, A.; Kiat, J.M.; Ecole Centrale des Arts et Manufactures, 92 - Chatenay-Malabry; Paulus, W.; Technische Hochschule Aachen; Ezpeleta, J.M.; Zuniga, F.J.

    1999-01-01

    The structures of the commensurate 1/4 and 1/5 phases of the displacively modulated compound D-BCCD [deuterated betaine (trimethylammonioacetate) calcium chloride dihydrate, i.e. (CD 3 ) 3 NCD 2 COOCaCl 2 (D 2 O) 2 or CaCl 2 x C 5 D 11 NO 2 x 2D 2 O] have been determined by single-crystal neutron diffraction at 100 and 68 K, respectively. The structural model of the 1/4 phase is found to be quite different from that obtained previously from X-ray diffraction data of the hydrogenated compound. This discrepancy comes from the fact that X-ray irradiation induces in this compound an unusual time-dependent decrease of the intensity of high-order satellite diffraction peaks. As a consequence and due to the commensurate nature of the phases investigated, X-ray diffraction failed to detect the large anharmonicity of the structural modulation which is clearly present in the two structures determined by neutron diffraction. (orig.)

  17. Structural phase transition and elastic properties of mercury chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Shriya, S. [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria)

    2012-08-15

    Pressure induced structural transition and elastic properties of ZnS-type (B3) to NaCl-type (B1) structure in mercury chalcogenides (HgX; X = S, Se and Te) are presented. An effective interionic interaction potential (EIOP) with long-range Coulomb, as well charge transfer interactions, Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and van der Waals interactions are considered. Emphasis is on the evaluation of the pressure dependent Poisson's ratio {nu}, the ratio R{sub BT/G} of B (bulk modulus) over G (shear modulus), anisotropy parameter, Shear and Young's modulus, Lame constant, Kleinman parameter, elastic wave velocity and thermodynamical property as Debye temperature. The Poisson's ratio behavior infers that Mercury chalcogenides are brittle in nature. To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of elastic and thermodynamical properties explicitly the ductile (brittle) nature of HgX and still awaits experimental confirmations. Highlights: Black-Right-Pointing-Pointer Vast volume discontinuity in phase diagram infers transition from ZnS to NaCl structure. Black-Right-Pointing-Pointer The shear elastic constant C{sub 44} is nonzero confirms the mechanical stability. Black-Right-Pointing-Pointer Pressure dependence of {theta}{sub D} infers the softening of lattice with increasing pressure. Black-Right-Pointing-Pointer Estimated bulk, shear and tetragonal moduli satisfied elastic stability criteria. Black-Right-Pointing-Pointer In both B3 and B1 phases, C{sub 11} and C{sub 12} increase linearly with pressure.

  18. Magnetically induced crystal structure and phase stability in Fe1-cCoc

    DEFF Research Database (Denmark)

    Abrikosov, I.A.; James, P.; Eriksson, O.

    1996-01-01

    We present an ab initio determination of the crystallographic phase stability of Fe-Co alloys as a function of concentration, using the coherent potential approximation. A bcc --> hcp phase transition is found at a concentration of 85 at.% of Co, in good agreement with the experimental phase...... diagram. We demonstrate that for the Pe-rich random alloys magnetism-stabilizes the bce phase relative to the close-packed fee and hcp phases. Magnetism also favors the partially ordered alpha' phase relative to the random bce alloy. This unique relation between magnetism and phase stability for the Fe...

  19. Pressure-induced phase transformations in L-alanine crystals

    DEFF Research Database (Denmark)

    Olsen, J. Staun; Gerward, Leif; Freire, P.T.C.

    2008-01-01

    Raman scattering and synchrotron X-ray diffraction have been used to investigate the high-pressure behavior of L-alanine. This study has confirmed a structural phase transition observed by Raman scattering at 2.3 GPa and identified it as a change from orthorhombic to tetragonal structure. Another...... phase transformation from tetragonal to monoclinic structure has been observed at about 9 GPa. From the equation of state, the zero-pressure bulk modulus and its pressure derivative have been determined as (31.5 +/- 1.4) GPa and 4.4 +/- 0.4, respectively....

  20. Strain-induced alignment and phase behavior of blue phase liquid crystals confined to thin films.

    Science.gov (United States)

    Bukusoglu, Emre; Martinez-Gonzalez, Jose A; Wang, Xiaoguang; Zhou, Ye; de Pablo, Juan J; Abbott, Nicholas L

    2017-12-06

    We report on the influence of surface confinement on the phase behavior and strain-induced alignment of thin films of blue phase liquid crystals (BPs). Confining surfaces comprised of bare glass, dimethyloctadecyl [3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP)-functionalized glass, or polyvinyl alcohol (PVA)-coated glass were used with or without mechanically rubbing to influence the azimuthal anchoring of the BPs. These experiments reveal that confinement can change the phase behavior of the BP films. For example, in experiments performed with rubbed-PVA surfaces, we measured the elastic strain of the BPs to change the isotropic-BPII phase boundary, suppressing formation of BPII for film thicknesses incommensurate with the BPII lattice. In addition, we observed strain-induced alignment of the BPs to exhibit a complex dependence on both the surface chemistry and azimuthal alignment of the BPs. For example, when using bare glass surfaces causing azimuthally degenerate and planar anchoring, BPI oriented with (110) planes of the unit cell parallel to the contacting surfaces for thicknesses below 3 μm but transitioned to an orientation with (200) planes aligned parallel to the contacting surfaces for thicknesses above 4 μm. In contrast, BPI aligned with (110) planes parallel to confining surfaces for all other thicknesses and surface treatments, including bare glass with uniform azimuthal alignment. Complementary simulations based on minimization of the total free energy (Landau-de Gennes formalism) confirmed a thickness-dependent reorientation due to strain of BPI unit cells within a window of surface anchoring energies and in the absence of uniform azimuthal alignment. In contrast to BPI, BPII did not exhibit thickness-dependent orientations but did exhibit orientations that were dependent on the surface chemistry, a result that was also captured in simulations by varying the anchoring energies. Overall, the results in this paper reveal that the orientations

  1. Pressure-induced crystallization and phase transformation of amorphous selenium: Raman spectroscopy and x-ray diffraction studies

    International Nuclear Information System (INIS)

    Yang Kaifeng; Cui Qiliang; Hou Yuanyuan; Liu Bingbing; Zhou Qiang; Hu Jingzhu; Mao, H-K; Zou Guangtian

    2007-01-01

    High-pressure Raman spectroscopy studies have been carried out on amorphous Se (a-Se) at room temperature in a diamond anvil cell with an 830 nm exciting line. Raman evidence for the pressure-induced crystallization of a-Se and the coexistence of the unknown high-pressure phase with the hexagonal phase is presented for the first time. Further experimental proof of high-pressure angle-dispersive x-ray diffraction studies for a-Se indicates that the unknown high-pressure phase is also a mixture phase of the tetragonal I4 1 /acd and Se IV structure. Our Raman and x-ray diffraction results suggest that hexagonal Se I undergoes a direct transition to triclinic Se III at about 19 GPa, which is in good agreement with the theoretical prediction

  2. Cylindrical-confinement-induced phase behaviours of diblock copolymer melts

    International Nuclear Information System (INIS)

    Mei-Jiao, Liu; Shi-Ben, Li; Lin-Xi, Zhang; Xiang-Hong, Wang

    2010-01-01

    The phase behaviours of diblock copolymers under cylindrical confinement are studied in two-dimensional space by using the self-consistent field theory. Several phase parameters are adjusted to investigate the cylindrical-confinement-induced phase behaviours of diblock copolymers. A series of lamella-cylinder mixture phases, such as the mixture of broken-lamellae and cylinders and the mixture of square-lamellae and cylinders, are observed by varying the phase parameters, in which the behaviours of these mixture phases are discussed in the corresponding phase diagrams. Furthermore, the free energies of these mixture phases are investigated to illustrate their evolution processes. Our results are compared with the available observations from the experiments and simulations respectively, and they are in good agreement and provide an insight into the phase behaviours under cylindrical confinement. (cross-disciplinary physics and related areas of science and technology)

  3. Epstein-Barr virus BGLF4 kinase retards cellular S-phase progression and induces chromosomal abnormality.

    Directory of Open Access Journals (Sweden)

    Yu-Hsin Chang

    Full Text Available Epstein-Barr virus (EBV induces an uncoordinated S-phase-like cellular environment coupled with multiple prophase-like events in cells replicating the virus. The EBV encoded Ser/Thr kinase BGLF4 has been shown to induce premature chromosome condensation through activation of condensin and topoisomerase II and reorganization of the nuclear lamina to facilitate the nuclear egress of nucleocapsids in a pathway mimicking Cdk1. However, the observation that RB is hyperphosphorylated in the presence of BGLF4 raised the possibility that BGLF4 may have a Cdk2-like activity to promote S-phase progression. Here, we investigated the regulatory effects of BGLF4 on cell cycle progression and found that S-phase progression and DNA synthesis were interrupted by BGLF4 in mammalian cells. Expression of BGLF4 did not compensate Cdk1 defects for DNA replication in S. cerevisiae. Using time-lapse microscopy, we found the fate of individual HeLa cells was determined by the expression level of BGLF4. In addition to slight cell growth retardation, BGLF4 elicits abnormal chromosomal structure and micronucleus formation in 293 and NCP-TW01 cells. In Saos-2 cells, BGLF4 induced the hyperphosphorylation of co-transfected RB, while E2F1 was not released from RB-E2F1 complexes. The E2F1 regulated activities of the cyclin D1 and ZBRK1 promoters were suppressed by BGLF4 in a dose dependent manner. Detection with phosphoamino acid specific antibodies revealed that, in addition to Ser780, phosphorylation of the DNA damage-responsive Ser612 on RB was enhanced by BGLF4. Taken together, our study indicates that BGLF4 may directly or indirectly induce a DNA damage signal that eventually interferes with host DNA synthesis and delays S-phase progression.

  4. Spatial Solitons and Induced Kerr Effects in Quasi-Phase-Matched Quadratic Media

    DEFF Research Database (Denmark)

    Clausen, Carl A. Balslev; Bang, Ole; Kivshar, Yu.S.

    1997-01-01

    We show that the evolution of the average intensity of cw beams in a quasi-phase-matched quadratic (or chi((2))) medium is strongly influenced by induced Kerr effects, such as self- and cross-phase modulation. We prove the existence of rapidly oscillating solitary waves (a spatial analog of the g......We show that the evolution of the average intensity of cw beams in a quasi-phase-matched quadratic (or chi((2))) medium is strongly influenced by induced Kerr effects, such as self- and cross-phase modulation. We prove the existence of rapidly oscillating solitary waves (a spatial analog...

  5. Initial stages of ion beam-induced phase transformations in Gd2O3 and Lu2O3

    Science.gov (United States)

    Chen, Chien-Hung; Tracy, Cameron L.; Wang, Chenxu; Lang, Maik; Ewing, Rodney C.

    2018-02-01

    The atomic-scale evolution of lanthanide sesquioxides Gd2O3 and Lu2O3 irradiated with 1 MeV Kr ions at room temperature and 120 K, up to fluences of 1 × 1016 ions/cm2 (˜20 dpa), has been characterized by in situ transmission electron microscopy. At room temperature, both oxides exhibited high radiation tolerance. Irradiation did not cause any observable structural change in either material, likely due to the mobility of irradiation-induced point defects, causing efficient defect annihilation. For Gd2O3, having the larger cation ionic radius of the two materials, an irradiation-induced stacking fault structure appeared at low fluences in the low temperature irradiation. As compared with the cubic-to-monoclinic phase transformations known to result from higher energy (˜GeV) ion irradiation, Kr ions of lower energies (˜MeV) yield much lower rates of damage accumulation and thus less extensive structural modification. At a fluence of 2.5 × 1015 ions/cm2, only the initial stages of the cubic-to-monoclinic (C to B) phase transformation process, consisting of the formation and aggregation of defects, have been observed.

  6. Discontinuous structural phase transition of liquid metal and alloys (2)

    International Nuclear Information System (INIS)

    Wang, Li; Liu, Jiantong

    2004-01-01

    The diameter (d f ) of diffusion fluid cluster before and after phase transition has been calculated in terms of the paper ''Discontinuous structural phase transition of liquid metal and alloy (1)'' Physics Letters. A 326 (2004) 429-435, to verify quantitatively the discontinuity of structural phase transition; the phenomena of thermal contraction and thermal expansion during the phase transition, together with the evolution model of discontinuous structural phase transition are also discussed in this Letter to explore further the nature of structural transition; In addition, based on the viscosity experimental result mentioned in paper [Y. Waseda, The Structure of Non-Crystalline Materials--Liquids and Amorphous Solids, McGraw-Hill, New York, 1980], we present an approach to draw an embryo of the liquid-liquid (L-L) phase diagram for binary alloys above liquidus in the paper, expecting to guide metallurgy process so as to improve the properties of alloys. The idea that controls amorphous structure and its properties by means of the L-L phase diagram for alloys and by the rapid cooling technique to form the amorphous alloy has been brought forward in the end

  7. Pressure-induced phase transitions in silicon studied by neural network-based metadynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Behler, Joerg [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Lehrstuhl fuer Theoretische Chemie, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Martonak, Roman [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynska dolina F2, 84248 Bratislava (Slovakia); Donadio, Davide [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Department of Chemistry, UC Davis, One Shields Ave., Davis, CA 95616 (United States); Parrinello, Michele [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland)

    2008-12-15

    We present a combination of the metadynamics method for the investigation of pressure-induced phase transitions in solids with a neural network representation of high-dimensional density-functional theory (DFT) potential-energy surfaces. In a recent illustration of the method for the complex high-pressure phase diagram of silicon[Behler et al., Phys. Rev. Lett. 100, 185501 (2008)] we have shown that the full sequence of phases can be reconstructed by a series of subsequent simulations. In the present paper we give a detailed account of the underlying methodology and discuss the scope and limitations of the approach, which promises to be a valuable tool for the investigation of a variety of inorganic materials. The method is several orders of magnitude faster than a direct coupling of metadynamics with electronic structure calculations, while the accuracy is essentially maintained, thus providing access to extended simulations of large systems. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Electric-field-induced phase transitions in co-doped Pb(Zr1−xTixO3 at the morphotropic phase boundary

    Directory of Open Access Journals (Sweden)

    Daniel J Franzbach

    2014-02-01

    Full Text Available The strain- and polarization-electric field behavior was characterized at room temperature for Pb0.98Ba0.01(Zr1−xTix0.98Nb0.02O3, 0.40 ≤ x ≤ 0.60. The investigated compositions were located in the vicinity of the morphotropic phase boundary, giving insight into the influence of crystal structure on the hysteretic ferroelectric behavior. The remanent strain of particular compositions is shown to be larger than theoretically allowed by ferroelectric switching alone, indicating the presence of additional remanent strain mechanisms. A phenomenological free energy analysis was used to simulate the effect of an applied electric field on the initial equilibrium phase. It is shown that electric-field-induced phase transitions in polycrystalline ferroelectrics can account for the experimental observations. The experimental and simulation results are contrasted to neutron diffraction measurements performed on representative compositions in the virgin and remanent states.

  9. Structural-Phase Transformations of CuZn Alloy Under Thermal-Impact Cycling

    Science.gov (United States)

    Potekaev, A. I.; Chaplygina, A. A.; Kulagina, V. V.; Chaplygin, P. A.; Starostenkov, M. D.; Grinkevich, L. S.

    2017-02-01

    Using the Monte Carlo method, special features of structural - phase transformations in β-brass are investigated during thermal impact using thermal cycling as an example (a number of successive order - disorder and disorder - order phase transitions in the course of several heating - cooling cycles). It is shown that a unique hysteresis is observed after every heating and cooling cycle, whose presence indicates irreversibility of the processes, which suggests a difference in the structural - phase states both in the heating and cooling stages. A conclusion is drawn that the structural - phase transformations in the heating and cooling stages occur within different temperature intervals, where the thermodynamic stimuli of one or the other structural - phase state are low. This is also demonstrated both in the plots of configurational energy, long- and short-range order parameter, atomic structure variations, and structural - phase state distributions. Simultaneously, there coexist ordered and disordered phases and a certain collection of superstructure domains. This implies the presence of low - stability states in the vicinity of the order - disorder phase transition. The results of investigations demonstrate that the structural - phase transitions within two successive heating and cooling cycles at the same temperature are different in both stages. These changes, though not revolutionary, occur in every cycle and decrease with the increasing cycle number. In fact, the system undergoes training with a tendency towards a certain sequence of structural - phase states.

  10. Morphological bubble evolution induced by air diffusion on submerged hydrophobic structures

    Science.gov (United States)

    Lv, Pengyu; Xiang, Yaolei; Xue, Yahui; Lin, Hao; Duan, Huiling

    2017-03-01

    Bubbles trapped in the cavities always play important roles in the underwater applications of structured hydrophobic surfaces. Air exchange between bubbles and surrounding water has a significant influence on the morphological bubble evolution, which in turn frequently affects the functionalities of the surfaces, such as superhydrophobicity and drag reduction. In this paper, air diffusion induced bubble evolution on submerged hydrophobic micropores under reduced pressures is investigated experimentally and theoretically. The morphological behaviors of collective and single bubbles are observed using confocal microscopy. Four representative evolution phases of bubbles are captured in situ. After depressurization, bubbles will not only grow and coalesce but also shrink and split although the applied pressure remains negative. A diffusion-based model is used to analyze the evolution behavior and the results are consistent with the experimental data. A criterion for bubble growth and shrinkage is also derived along with a phase diagram, revealing that the competition of effective gas partial pressures across the two sides of the diffusion layer dominates the bubble evolution process. Strategies for controlling the bubble evolution behavior are also proposed based on the phase diagram. The current work provides a further understanding of the general behavior of bubble evolution induced by air diffusion and can be employed to better designs of functional microstructured hydrophobic surfaces.

  11. An absorbing phase transition from a structured active particle phase

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, Cristobal [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain); Ramos, Francisco [Departamento de Electromagnetismo y Fisica de la Materia and Instituto de Fisica Teorica y Computacional Carlos I, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain); Hernandez-GarcIa, Emilio [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain)

    2007-02-14

    In this work we study the absorbing state phase transition of a recently introduced model for interacting particles with neighbourhood-dependent reproduction rates. The novelty of the transition is that as soon as the active phase is reached by increasing a control parameter a periodically arranged structure of particle clusters appears. A numerical study in one and two dimensions shows that the system falls into the directed percolation universality class.

  12. Tuning of Block Copolymer Membrane Morphology through Water Induced Phase Inversion Technique

    KAUST Repository

    Madhavan, Poornima

    2016-06-01

    Isoporous membranes are attractive for the regulation and detection of transport at the molecular level. A well-defined asymmetric membranes from diblock copolymers with an ordered nanoporous membrane morphologies were fabricated by the combination of block copolymer self-assembly and non-solvent-induced phase separation (NIPS) technique. This is a straightforward and fast one step procedure to develop integrally anisotropic (“asymmetric”) membranes having isoporous top selective layer. Membranes prepared via this method exhibit an anisotropic cross section with a thin separation layer supported from underneath a macroporous support. These membrane poses cylindrical pore structure with ordered nanopores across the entire membrane surfaces with pore size in the range from 20 to 40 nm. Tuning the pore morphology of the block copolymer membranes before and after fabrication are of great interest. In this thesis, we first investigated the pore morphology tuning of asymmetric block copolymer membrane by complexing with small organic molecules. We found that the occurrence of hydrogen-bond formation between PS-b-P4VP block copolymer and –OH/ –COOH functionalized organic molecules significantly tunes the pore morphology of asymmetric nanoporous membranes. In addition, we studied the complexation behavior of ionic liquids with PS-b-P4VP block copolymer in solutions and investigated their effect on final membrane morphology during the non-solvent induced phase separation process. We found that non-protic ionic liquids facilitate the formation of hexagonal nanoporous block copolymer structure, while protic ionic liquids led to a lamella-structured membrane. Secondly, we demonstrated the catalytic activity of the gold nanoparticle-enhanced hollow fiber membranes by the reduction of nitrophenol. Also, we systematically investigated the pore morphology of isoporous PS-b-P4VP using 3D imaging technique. Thirdly, we developed well-distributed silver nanoparticles on the

  13. Microstructure and phase transformation on milled and unmilled Ti induced by water quenching

    CSIR Research Space (South Africa)

    Bolokang, AS

    2014-10-01

    Full Text Available Materials Letters Vol. 132 Microstructure and phase transformation on milled and unmilled Ti induced by water quenching A.S.Bolokang a,b,n, M.J.Phasha c, D.E.Motaung b, F.R.Cummings a,d, T.F.G.Muller a, C.J.Arendse a a Department of...Physics,UniversityoftheWesternCape,PrivateBagx17,Bellville7535,SouthAfrica bDST/CSIR Nanotechnology InnovationCentre ,National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, P.O.Box395, Pretoria 0001, SouthAfrica c Transnet Engineering, Product...

  14. Impurity Induced Phase Competition and Supersolidity

    Science.gov (United States)

    Karmakar, Madhuparna; Ganesh, R.

    2017-12-01

    Several material families show competition between superconductivity and other orders. When such competition is driven by doping, it invariably involves spatial inhomogeneities which can seed competing orders. We study impurity-induced charge order in the attractive Hubbard model, a prototypical model for competition between superconductivity and charge density wave order. We show that a single impurity induces a charge-ordered texture over a length scale set by the energy cost of the competing phase. Our results are consistent with a strong-coupling field theory proposed earlier in which superconducting and charge order parameters form components of an SO(3) vector field. To discuss the effects of multiple impurities, we focus on two cases: correlated and random distributions. In the correlated case, the CDW puddles around each impurity overlap coherently leading to a "supersolid" phase with coexisting pairing and charge order. In contrast, a random distribution of impurities does not lead to coherent CDW formation. We argue that the energy lowering from coherent ordering can have a feedback effect, driving correlations between impurities. This can be understood as arising from an RKKY-like interaction, mediated by impurity textures. We discuss implications for charge order in the cuprates and doped CDW materials such as NbSe2.

  15. Structural phase transition and electronic properties in samarium chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, Y. S., E-mail: yspanwar2011@gmail.com [Department of Physics, Govt. New Science College Dewas-455001 (India); Aynyas, Mahendra [Department of Physics, C.S.A. Govt. P.G. College, Sehore, 466001 (India); Pataiya, J.; Sanyal, Sankar P. [Department of Physics, Barkatullah University, Bhopal, 462026 (India)

    2016-05-06

    The electronic structure and high pressure properties of samarium monochalcogenides SmS, SmSe and SmTe have been reported by using tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). The total energy as a function of volume is evaluated. It is found that these monochalcogenides are stable in NaCl-type structure under ambient pressure. We predict a structural phase transition from NaCl-type (B{sub 1}-phase) structure to CsCl-type (B{sub 2}-type) structure for these compounds. Phase transition pressures were found to be 1.7, 4.4 and 6.6 GPa, for SmS, SmSe and SmTe respectively. Apart from this, the lattice parameter (a{sub 0}), bulk modulus (B{sub 0}), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed that these compounds exhibit metallic character. The calculated values of equilibrium lattice parameter and phase transition pressure are in general good agreement with available data.

  16. Phase gradients in acceleration structures

    International Nuclear Information System (INIS)

    Decker, F.J.; Jobe, R.K.

    1990-05-01

    In linear accelerators with two or more bunches the beam loading of one bunch will influence the energy and energy spread the following bunches. This can be corrected by quickly changing the phase of a travelling wave structure, so that each bunch recieves a slightly different net phase. At the SLAC Linear Collider (SLC) three bunches, two (e + ,e - ) for the high energy collisions and one (e - -scavenger) for producing positrons should sit at different phases, due to their different tasks. The two e - -bunches are extracted from the damping ring at the same cycle time about 60 ns apart. Fast phase switching of the RF to the bunch length compressor in the Ring-To-Linac (RTL) section can produce the necessary advance of the scavenger bunch (about 6 degree in phase). This allows a low energy spread of this third bunch at the e + -production region at 2/3 of the linac length, while the other bunches are not influenced. The principles and possible other applications of this fast phase switching as using it for multi-bunches, as well as the experimental layout for the actual RTL compressor are presented

  17. Stress-induced thickening of Ω phase in Al–Cu–Mg alloys containing various Ag additions

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Song [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@mail.csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Zhou, Xuanwei; Xia, Peng; Liu, Meng [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

    2014-01-01

    The thickening of Ω phase in Al–Cu–Mg alloys containing various bulk Ag contents during stress aging at 200 °C with a tensile stress of 240 MPa was investigated by a combination of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). TEM characterization confirmed preferred orientation of Ω phase in all stress-aged samples. Corresponding quantitative TEM calculations revealed the thickening kinetics of Ω phase was significantly accelerated during stress aging as compared to that during stress-free aging at 200 °C. HRTEM analysis on the α/Ω interfacial structure confirmed that the applied tensile stress facilitated the rapid nucleation of the growth ledge on the broad face of Ω phase, thereby resulting in the accelerated plate thickening during stress aging at 200 °C. Meanwhile, quantitative TEM analysis highlighted the stress-induced thickening of Ω phase at 200 °C was affected by the bulk Ag content. This was consistent with the HRTEM observation as the ledge nucleation was found to be suppressed with increasing Ag addition. Our APT analysis on different stress-aged samples further suggested the progressive enrichment of Ag atoms in the segregation layer helped to stabilize the interfacial structure and was responsible for the lowest nucleation rate of the ledge in 1.77Ag alloy as compared to that in 0.46Ag alloy.

  18. Stress-induced thickening of Ω phase in Al–Cu–Mg alloys containing various Ag additions

    International Nuclear Information System (INIS)

    Bai, Song; Liu, Zhiyi; Zhou, Xuanwei; Xia, Peng; Liu, Meng

    2014-01-01

    The thickening of Ω phase in Al–Cu–Mg alloys containing various bulk Ag contents during stress aging at 200 °C with a tensile stress of 240 MPa was investigated by a combination of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). TEM characterization confirmed preferred orientation of Ω phase in all stress-aged samples. Corresponding quantitative TEM calculations revealed the thickening kinetics of Ω phase was significantly accelerated during stress aging as compared to that during stress-free aging at 200 °C. HRTEM analysis on the α/Ω interfacial structure confirmed that the applied tensile stress facilitated the rapid nucleation of the growth ledge on the broad face of Ω phase, thereby resulting in the accelerated plate thickening during stress aging at 200 °C. Meanwhile, quantitative TEM analysis highlighted the stress-induced thickening of Ω phase at 200 °C was affected by the bulk Ag content. This was consistent with the HRTEM observation as the ledge nucleation was found to be suppressed with increasing Ag addition. Our APT analysis on different stress-aged samples further suggested the progressive enrichment of Ag atoms in the segregation layer helped to stabilize the interfacial structure and was responsible for the lowest nucleation rate of the ledge in 1.77Ag alloy as compared to that in 0.46Ag alloy

  19. Scaling of Structural and Rheological Responde of L3 Sponge Phases in the 'Sweetened' Cetylpyridinium/Hexanol/Dextrose/Brine System

    International Nuclear Information System (INIS)

    Porcar, L.; Hamilton, William A.; Butler, Paul D.; Warr, G.G.

    2003-01-01

    We report a study of the shear response of sponge phases in cetylpyridinium chloride (CPCl)/hexanol/brine/dextrose systems by parallel measurements of rheology and structure by small angle neutron scattering (SANS). Our measurements show that this dextrose added to the extensively studied CPCl/hexanol/brine system is taken up exclusively by the brine solvent, resulting in an equivalent CPCl/hexanol membrane structure and phase behavior for this modified system. Adding dextrose to the brine in these systems to volume fractions up to 0.4 allows us to increase the solvent viscosity by more than an order of magnitude. This lowers the cooperative membrane diffusion coefficient in this system as measured by dynamic light scattering by the same factor, resulting in a corresponding slowing of the Helfrich fluctuation dominated membrane dynamics. Our results show clear and consistent evidence of shear-induced sponge to lamellar phase transformations in these systems. Further, both the rheological and microstructural responses of these systems follow universal master curves when plotted against a rescaled applied shear γ η s /φ 3 , where φ is the membrane volume fraction and η s is the viscosity of the brine/dextrose solvent. This well-defined shear response is characterized by three distinct regimes. At low shear rates the sponge phases exhibit Newtonian flow behavior and no structural change is observed. For intermediate shear rates, the systems shear thin and SANS measurements show that the sponge phases are progressively transformed into lamellar phases with the CPCl/hexanol membrane normals aligned parallel to the velocity gradient. This continuous process and the absence of a stress plateau in the rheological measurements both rule out the existence of a biphasic state in this region and thus of a first-order transition between sponge and lamellar phases as is observed in equilibrium phase diagrams. At higher shear rates, the systems are apparently again Newtonian

  20. Introducing site-specific cysteines into nanobodies for mercury labelling allows de novo phasing of their crystal structures

    DEFF Research Database (Denmark)

    Hansen, Simon Boje; Laursen, Nick Stub; Andersen, Gregers Rom

    2017-01-01

    of the presence of free cysteines in the target protein could considerably facilitate the process of obtaining unbiased experimental phases. Nanobodies (single-domain antibodies) have recently been shown to promote the crystallization and structure determination of flexible proteins and complexes. To extend...... phased using single-wavelength anomalous dispersion (SAD) and single isomorphous replacement with anomalous signal (SIRAS), taking advantage of radiation-induced changes in Cys-Hg bonding. Importantly, Hg labelling influenced neither the interaction of Nb36 with its antigen complement C5 nor its...

  1. Fe-doping induced Griffiths-like phase in La0.7Ba0.3CoO3

    International Nuclear Information System (INIS)

    Wan-Guo, Huang; Xiang-Qun, Zhang; Guo-Ke, Li; Young, Sun; Qing-An, Li; Zhao-Hua, Cheng

    2009-01-01

    The effect of Fe-doping on the magnetic properties of the ABO 3 -type perovskite cobaltites La 0.7 Ba 0.3 Co 1–y Fe y O 3 (0 ≤ y ≤ 0.80) is reported. With no apparent structural change in any doped sample, the Curie temperature (T C ) and the magnetization (M) are greatly suppressed for y ≤ 0.30 samples, while a distinct increase in T C for the y = 0.40 sample is observed. With the further increase of Fe concentration, T C increases monotonically. Griffiths-like phases in 0.40 ≤ y ≤ 0.60 samples are confirmed. The formation of the Griffiths-like phase is ascribed to B-site disordering induced isolation of ferromagnetic (FM) clusters above T C . (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  2. Strain-induced structural changes and chemical reactions. 1: Thermomechanical and kinetic models

    International Nuclear Information System (INIS)

    Levitas, V.I.; Nesterenko, V.F.; Meyers, M.A.

    1998-01-01

    Strain-induced chemical reactions were observed recently (Nesterenko et al) in experiments in the shear band in both Ti-Si and Nb-Si mixtures. Reactions can start in the solid state or after melting of at least one component. One of the aims is to find theoretically whether there are possible macroscopic mechanisms of mechanical intensification of the above and other chemical reactions due to plastic shear in the solid state. Continuum thermodynamical theory of structural changes with an athermal kinetics, which includes martensitic phase transformations, plastic strain-induced chemical reactions and polymorphic transformations, is developed at finite strains. The theory includes kinematics, criterion of structural change and extremum principle for determination of all unknown variable parameters for the case with neglected elastic strains. Thermodynamically consistent kinetic theory of thermally activated structural changes is suggested. The concept of the effective temperature is introduced which takes into account that temperature can vary significantly (on 1,000 K) during the chemical reactions under consideration. The theory will be applied in Part 2 of the paper for the description of chemical reactions in the shear band

  3. Pressure-induced phase transitions of multiferroic BiFeO3

    OpenAIRE

    XiaoLi, Zhang; Ye, Wu; Qian, Zhang; JunCai, Dong; Xiang, Wu; Jing, Liu; ZiYu, Wu; DongLiang, Chen

    2013-01-01

    Pressure-induced phase transitions of multiferroic BiFeO3 have been investigated using synchrotron radiation X-ray diffraction with diamond anvil cell technique at room temperature. Present experimental data clearly show that rhombohedral (R3c) phase of BiFeO3 first transforms to monoclinic (C2/m) phase at 7 GPa, then to orthorhombic (Pnma) phase at 11 GPa, which is consistent with recent theoretical ab initio calculation. However, we observe another peak at 2{\\theta}=7{\\deg} in the pressure ...

  4. Shock-Assisted Superficial Hexagonal-to-Cubic Phase Transition in GaN/Sapphire Interface Induced by Using Ultra-violet Laser Lift-Of Techniques

    International Nuclear Information System (INIS)

    Wei-Hua, Chen; Xiao-Dong, Hu; Xiang-Ning, Kang; Xu-Rong, Zhou; Xiao-Min, Zhang; Tong-Jun, Yu; Zhi-Jian, Yang; Ke, Xu; Guo-Yi, Zhang; Xu-Dong, Shan; Li-Ping, You

    2009-01-01

    Ultra-violet (KrF excimer laser, λ = 248 nm) laser lift-of (LLO) techniques have been operated to the GaN/sapphire structure to separate GaN from the sapphire substrate. Hexagonal to cubic phase transformation induced by the ultra-violet laser lift-of (UV-LLO) has been characterized by micro-Raman spectroscopy, micro-photoluminescence, along with high-resolution transmission electron microscopy (HRTEM). HRTEM indicates that UV-LLO induced phase transition takes place above the LLO interface, without phase transition under the LLO interface. The formed cubic GaN often exists as nanocrystal grains attaching on the bulk hexagonal GaN. The half-loop-cluster-like UV-LLO interface indicates that the LLO-induced shock waves has generated and played an assistant role in the decomposition of the hexagonal GaN and in the formation of cubic GaN grains at the LLO surface

  5. Identification of dominant structures and their flow dynamics in the turbulent two-phase flow using POD technique

    Energy Technology Data Exchange (ETDEWEB)

    Munir, Shahzad; Siddiqui, Muhammad Israr; Heikal, Morgan; Aziz, Abdul Rashid Abdul [Universiti Teknologi PETRONAS, Bander Seri Iskandar (Malaysia); Sercey, Guillaume de [University of Brighton, Brighton (United Kingdom)

    2015-11-15

    The Proper orthogonal decomposition (POD) method has seen increasingly used in the last two decades and has a lot of applications for the comparison of experimental and numerically simulated data. The POD technique is often used to extract information about coherent structures dominating the flow. The two-dimensional and two-component instantaneous velocity fields of both liquid and gas phases of a slug flow were obtained by Particle image velocimetry (PIV) combined with Laser induced fluorescence (LIF). POD was applied to the velocity fields of both phases separately to identify the coherent flow structures. We focused on POD eigenmodes and their corresponding energy contents of both liquid and gas phases. The sum of first few eigenmodes that contain maximum turbulent kinetic energy of the flow represents the coherent structures. In the case of liquid phase the first eigenmode contained 42% of the total energy, while in the gas phase the decaying energy distribution was flat. The POD results showed that the coefficient of mode 1 for the liquid phase oscillated between positive and negative values and had the highest amplitude. For the visualization of coherent motion different linear combinations of eigenmodes for liquid and gas phases were used. The phenomena of turbulent bursting events associated with Q2 events (low momentum fluid moving away from the wall) and Q4 events (high momentum flow moving towards the wall) were also discussed to assess its contribution in turbulence production.

  6. Structural Phase Transitions of Mg(BH4)2 under Pressure

    International Nuclear Information System (INIS)

    George, L.; Drozd, V.; Saxena, S.; Bardaji, E.; Fichtner, M.

    2009-01-01

    The structural stability of Mg(BH4)2, a promising hydrogen storage material, under pressure has been investigated in a diamond anvil cell up to 22 GPa with combined synchrotron X-ray diffraction and Raman spectroscopy. The analyses show a structural phase transition around 2.5 GPa and again around 14.4 GPa. An ambient-pressure phase of Mg(BH4)2 has a hexagonal structure (space group P61, a = 10.047(3) A, c = 36.34(1) A, and V = 3176(1) A3 at 0.2 GPa), which agrees well with early reports. The structure of high-pressure phase is found to be different from reported theoretical predictions; it also does not match the high-temperature phase. The high-pressure polymorph of Mg(BH4)2 is found to be stable on decompression, similar to the case of the high-temperature phase. Raman spectroscopic study shows a similarity in high-pressure behavior of as-prepared Mg(BH4)2 and its high-temperature phase.

  7. A Study of the Confinement Induced Sponge to Lamellar Phase Transformation by Direct Force Measurement

    International Nuclear Information System (INIS)

    Antelmi, David

    1996-10-01

    The interactions between two macroscopic walls immersed in an isotropic symmetric sponge phase (L_3) at different volume fractions, Φ, were studied with a surface force apparatus. The purpose of these experiments was to investigate the behaviour of the sponge phase when confined between two smooth rigid surfaces. Particular attention was given to investigating this behaviour as the bulk transition to the lamellar phase (L_α) was approached. At temperatures far from the L_3/L_α bulk transition temperature, the force-distance profile showed weak oscillations with a periodicity approximately equal to twice the characteristic length, ξ, measured for the sponge phase from small angle x-ray scattering. Furthermore, the oscillations were superimposed on an exponential attractive background that decayed with an order parameter correlation length of 2-3 times ξ The attractive background was explained by the enhancement of the sponge order in the vicinity of the rigid walls. The structural oscillations observed in the force-distance profile, although not completely understood, were discussed in terms of the packing of sponge cells (cell size ξ). The significance of the observed periodicity (2ξ) may indicate the importance of the symmetric nature of the sponge phase. By moving pairs of cells in response to an applied strain, the symmetry of the sponge structure is protected. As the temperature increased towards the L_3/L_α bulk transition temperature, an abrupt change in the force-distance profile was observed at a threshold separation labelled D*_i_n. A different force regime was observed for separations below D*_i_n which oscillated with a periodicity that was twice the reticular spacing, d, for a L_α phase of similar Φ. The force oscillations were superimposed on an attractive background that was almost linear. These observations were consistent with a first order phase transition from the sponge phase to the lamellar phase, induced by the confinement, where the

  8. Hydrostatic-pressure induced phase transition of phonons in single-walled nanotubes

    International Nuclear Information System (INIS)

    Feng Peng; Meng Qingchao

    2009-01-01

    We study the effect of the hydrostatic pressure on the phonons in single-walled carbon nanotubes (SWNTs) in a magnetic field. We calculate the magnetic moments of the phonons using a functional integral technique, and find that the phonons in SWNTs undergo a pressure-induced phase transition from the paramagnetic phase to the diamagnetic phase under hydrostatic pressure 2 GPa. We explain the mechanism of generating this phase transition.

  9. Influence of heat treatment in {beta} and {gamma} phases on the microscopic structure of uranium; Influence des traitements thermiques en phases {beta} et {gamma} sur la structure micrographique de l'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Robillard, A

    1958-06-02

    A new method of microscopic examination of uranium is described. Electrolytic polishing and etching are carried out in an acetic acid-chromic acid bath. Atmospheric or anodic oxidation of the polished surface produces films which follow exactly changes in the structure of the underlying metal. This method is very sensitive to small variations of orientation in polygonized crystals. Using this method of examination of uranium, it was found that annealing U in the {gamma} phase followed by a cooling at a rate dependent of the annealing temperature, causes the formation of substructures different from those due to the polygonization of {alpha}-U. The substructures are indicated by the concentration of impurities on the dislocations induced by the stresses accompanying the allotropic transformation {gamma} {yields} {beta}. Similar treatment of the U-1.4% Cr alloy in which the {beta} phase is stabilized at room temperature, confirms this explanation. In addition to the polygonization substructures, sharp discontinuities can be observed in the network of sub- boundaries as a fine white edging. The comparison of these with the structure revealed by thermal etching in vacuum suggest that there are traces of the grain boundaries of the {gamma} phase. The method of etching followed by oxidation shows a haloed phase identified as UH{sub 3}. The conditions of appearance and disappearance of this phase are studied. The sensitivity of this method of detecting the last traces of H in U is very high. The dependence of the hydrogen content on the tensile properties of uranium metal was also studied. (author) [French] Une methode nouvelle d'examen micrographique de l'uranium a ete mise au point. Le polissage electrolytique et le 'gravage' sont effectues dans un bain acide acetique-acide chromique. L'oxydation atmospherique ou anodique de la surface polie conduit a la formation de couches epitaxiques d'oxyde. Cette methode est particulierement sensible aux faibles variations d

  10. Temperature-induced transitions between domain structures of ultrathin magnetic films

    International Nuclear Information System (INIS)

    Polyakova, T.; Zablotskii, V.

    2005-01-01

    Full text: Understanding of the influence of temperature on behavior of domain patterns of ultrathin magnetic films is of high significance for the fundamental physics of nanomagnetism as well as for technological applications. A thickness-dependent Curie temperature of ultrathin films may cause many interesting phenomena in the thermal evolution of domain structures (DS): i) nontrivial changes of the anisotropy constants as a function of the film thickness; ii) so-called inverse melting of DSs (processes where a more symmetric domain phase is found at lower temperatures than at higher temperatures - the inverse phase sequence) [1]; iii) temperature-induced transitions between domain structures. The possibility of such transitions is determined by lowering of the potential barriers separating different magnetization states as the film temperature approaches the Curie point. In this case with an increase of temperature, due to a significant decrease of the anisotropy constant, the domain wall energy is low enough and allows the system to reach equilibrium by a change of the domain wall number in the sample. This manifests itself in a transition from a metastable DS to a more stable DS which corresponds to new values of the anisotropy constant and magnetizations saturation. Thus, the temperature-induced transitions are driven by temperature changes of the magnetic parameters of the film. The key parameters controlling the DS geometry and period are the characteristic length, l c =σ/4πM S 2 (the ratio between the domain wall and demagnetization energies), and the quality factor Q =K/2πM S 2 (K is the first anisotropy constant). We show that for films with a pronounced nonmonotonic temperature dependence of l c one can expect a counter thermodynamic behavior: the inverse phase sequence and cooling-induced disordering. On changing temperature the existing domain structure should accommodate itself under new magnitudes of l c and Q. There are the two possible

  11. Phase-structure of SU(3) lattice gauge-higgs model

    International Nuclear Information System (INIS)

    Gerdt, V.P.; Mitrjushkin, V.K.; Zadorozhny, A.M.

    1985-01-01

    Phase structure is investigated of SU(3) symmetric gauge-Higgs theory with a defrost radial mode. The Higgs fields are considered in the fundamental representation of SU(3) group. It is shown that the phase structures of SU(3) and SU(2) symmetric coincide qualitatively

  12. Application of Phase-Field Techniques to Hydraulically- and Deformation-Induced Fracture.

    Energy Technology Data Exchange (ETDEWEB)

    Culp, David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Miller, Nathan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schweizer, Laura [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-08-01

    Phase-field techniques provide an alternative approach to fracture problems which mitigate some of the computational expense associated with tracking the crack interface and the coalescence of individual fractures. The technique is extended to apply to hydraulically driven fracture such as would occur during fracking or CO2 sequestration. Additionally, the technique is applied to a stainless steel specimen used in the Sandia Fracture Challenge. It was found that the phase-field model performs very well, at least qualitatively, in both deformation-induced fracture and hydraulically-induced fracture, though spurious hourglassing modes were observed during coupled hydralically-induced fracture. Future work would include performing additional quantitative benchmark tests and updating the model as needed.

  13. The Structural Phase Transition in Solid DCN

    DEFF Research Database (Denmark)

    Dietrich, O. W.; Mackenzie, Gordon A.; Pawley, G. S.

    1975-01-01

    Neutron scattering measurements on deuterated hydrogen cyanide have shown that the structural phase change from a tetragonal to an orthorhombic form at 160K is a first-order transition. A transverse acoustic phonon mode, which has the symmetry of the phase change, was observed at very low energies...

  14. Two-phase cross-flow-induced forces acting on a circular cylinder

    International Nuclear Information System (INIS)

    Hara, F.

    1982-01-01

    This paper clarifies the characteristics of unsteady flow-induced lift and drag forces acting on a circular cylinder immersed perpendicular to a two-phase bubbly air-water flow, in conjunction with Karman vortex shedding and pressure fluctuations. Experimental results presented show that Karman vortex shedding disappears over a certain value of air concentration in the two-phase flow. Related to this disappearance, flow-induced forces are rather small and periodical in low air concentration but become very large and random in higher air concentration. 7 refs

  15. Thermally induced phase transformation of pearl powder

    International Nuclear Information System (INIS)

    Zhang, Guoqing; Guo, Yili; Ao, Ju; Yang, Jing; Lv, Guanglie; Shih, Kaimin

    2013-01-01

    The polymorphic phase transformation of thermally treated pearl powder was investigated by X-ray diffraction and thermoanalytical techniques. The phase transformation was based on quantification of the calcite content at various temperatures using Rietveld refinement analysis. The results show that the phase transformation of pearl aragonite occurred within a temperature range of 360–410 °C, which is 50–100 °C lower than the range for non-biomineralized aragonite. These thermoanalytical results suggest that the phase transformation of pearl aragonite may occur immediately after the thermal decomposition of the organic matrix in the pearl powder. An important finding is that decomposition of the organic matrix may greatly facilitate such transformation by releasing additional space for an easier structural reconstruction during the phase transformation process. - Highlights: ► Providing a new method to describe the polymorphic transition of pearl powder ► The phase transition sketch was exhibited by XRD phase quantitative analysis. ► There are dozens of degrees in advance comparing to natural aragonite. ► The phase transition occurs following the thermal decomposition of organism

  16. Pressure-induced phase transitions of multiferroic BiFeO3

    International Nuclear Information System (INIS)

    Zhang Xiaoli; Dong Juncai; Liu Jing; Chen Dongliang; Wu Ye; Zhang Qian; Wu Xiang; Wu Ziyu

    2013-01-01

    Pressure-induced phase transitions of multiferroic BiFeO 3 have been investigated using synchrotron radiation X-ray diffraction with diamond anvil cell technique at room temperature. Present experimental data clearly show that rhombohedral (R3c) phase of BiFeO 3 first transforms to monoclinic (C2/m) phase at 7 GPa, then to orthorhombic (Pnma) phase at 11 GPa, which is consistent with recent theoretical ab initio calculation. However, we observe another peak at 2θ=7° in the pressure range of 5-7 GPa that has not been reported previously. Further analysis reveals that this reflection peak is attributed to the orthorhombic (Pbam) phase, indicating the coexistence of monoclinic phase with orthorhombic phase in low pressure range. (authors)

  17. Pressure-induced change of the electronic state in the tetragonal phase of CaFe2As2

    International Nuclear Information System (INIS)

    Sakaguchi, Yui; Ikeda, Shugo; Kuse, Tetsuji; Kobayashi, Hisao

    2014-01-01

    We have investigated the electronic states of single-crystal CaFe 2 As 2 under hydrostatic pressure using 57 Fe Mössbauer spectroscopy and magnetization measurements. The center shift and the quadrupole splitting were refined from observed 57 Fe Mössbauer spectra using the single-crystalline sample under pressure at room temperature. A discontinuous decrease in the pressure dependence of the refined center shift was observed at 0.33 GPa without any anomaly in the pressure dependence of the refined quadrupole splitting, indicating a purely electronic state change in CaFe 2 As 2 with a tetragonal structure. Such a change is shown to be reflected in the peak-like anomalies observed in the pressure dependences of the magnetic susceptibility at 0.26 GPa above 150 K. Our results reveal that this pressure-induced electronic state change suppresses the tetragonal-to-orthorhombic structural phase transition accompanied by an antiferromagnetic ordering. We further observed superconductivity in CaFe 2 As 2 below ∼8 K around 0.33 GPa although our sample was not in a single phase at this pressure. These findings suggest that the electronic state change observed in CaFe 2 As 2 with the tetragonal structure is relevant to the appearance of the pressure-induced superconductivity in AFe 2 As 2 . (paper)

  18. Crystal structure of the Al2CuIr phase

    International Nuclear Information System (INIS)

    Meshi, L.; Ezersky, V.; Kapush, D.; Grushko, B.

    2010-01-01

    A new ternary Al 2 CuIr phase was revealed in the Al-Cu-Ir system. It is formed below 1063 o C from the β-phase (CsCl-type structure) extending at elevated temperatures from AlIr. The crystal structure of the Al 2 CuIr phase was determined using a combination of precession electron diffraction and X-ray powder diffraction techniques. The phase has an orthorhombic C-centered unit cell with lattice parameters a = 8.1196(7) A, b = 5.0646(2) A and c = 5.18513(3) A; its crystal symmetry can be described by the Cmme (no. 67) space group (Pearson symbol oC16). The unit cell of the new phase contains 8 Al, 4 Cu and 4 Ir atoms and exhibits a new structure type. The reliability factors characterizing the Rietveld refinement procedure are: R p = 4.45%, R wp = 6.45%, R B = 3.69% and R f = 2.41%.

  19. Photo-Induced Phase Transitions to Liquid Crystal Phases: Influence of the Chain Length from C8E4 to C14E4

    Directory of Open Access Journals (Sweden)

    Simone Techert

    2009-09-01

    Full Text Available Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i with n = 8, 10, 12, 14; cyclohexane/H2O. We were interested in understanding the effect of chain length increase on the dynamics of transformation from the microemulsion phase to the liquid crystal phase. Applying light pump (pulse/x-ray probe (pulse techniques, we could demonstrate that entropy and diffusion control are the driving forces for the kind of phase transition investigated.

  20. Induced Kerr effects and self-guided beams in quasi-phase-matched quadratic media [CBC4

    DEFF Research Database (Denmark)

    Clausen, Carl A. Balslev; Bang, Ole; Kivshar, Yuri S.

    1997-01-01

    We show that quasi-phase-matching of quadratic media induces Kerr effects, such as self- and cross-phase modulation, and leads to the existence of a novel class of solitary waves, QPM-solitons......We show that quasi-phase-matching of quadratic media induces Kerr effects, such as self- and cross-phase modulation, and leads to the existence of a novel class of solitary waves, QPM-solitons...

  1. Heterophase fluctuation of omega phase and X-ray diffuse scattering from dual phase structure

    International Nuclear Information System (INIS)

    Farjami, Susan; Kubo, Hiroshi

    2003-01-01

    Heterophase fluctuation of athermal omega embryos has been analyzed by assuming a dual phase structure of omega embryos composed of omega and bcc matrix phase. The two-dimensional modulation of dual phase was suggested from the quantitative estimation of coherent free energy of omega embryos using microscopic theory of elasticity and the Landau anharmonic theory for phase transformation. The X-ray diffraction theory was developed in connection to the formation of omega embryos having the dual phase structure. The offset of the diffuse peak position from the ideal omega point in the X-ray diffraction pattern is attributed to the dual phase (incommensurate phase) of omega embryos. It was also shown that the ellipsoidal shape of the diffuse intensity tailing toward the fundamental spot of the matrix phase is originated from the equilibrium shape of the omega embryo. The quantitative estimation of elastic energy modulus (EEM) in the disordered bcc matrix and in the ordered bcc matrix indicates a difference in the deviation amount of the minimum point k(q m ) from the ideal omega point k(q ω ) and a difference in the elliptical shape of embryos

  2. Supersymmetric curvatons and phase-induced curvaton fluctuations

    International Nuclear Information System (INIS)

    McDonald, John

    2004-01-01

    We consider the curvaton scenario in the context of supersymmetry (SUSY) with gravity-mediated SUSY breaking. In the case of a large initial curvaton amplitude during inflation and a negative order H 2 correction to the mass squared term after inflation, the curvaton will be close to the minimum of its potential at the end of inflation. In this case the curvaton amplitude fluctuations will be damped due to oscillations around the effective minimum of the curvaton potential, requiring a large expansion rate during inflation in order to account for the observed energy density perturbations, in conflict with cosmic microwave background constraints. Here we introduce a new curvaton scenario, the phase-induced curvaton scenario, in which de Sitter fluctuations of the phase of a complex SUSY curvaton field induce an amplitude fluctuation that is unsuppressed even in the presence of a negative order H 2 correction and large initial curvaton amplitude. This scenario is closely related to the Affleck-Dine mechanism and a curvaton asymmetry is naturally generated in conjunction with the energy density perturbations. Cosmological energy density perturbations can be explained with an expansion rate H≅10 12 GeV during inflation

  3. Osteoblasts extracellular matrix induces vessel like structures through glycosylated collagen I

    Energy Technology Data Exchange (ETDEWEB)

    Palmieri, D. [Genetics, DIBIO, University of Genova, Corso Europa 26, 16132 Genova (Italy); Valli, M.; Viglio, S. [Department of Biochemistry, University of Pavia (Italy); Ferrari, N. [Istituto Nazionale per la ricerca sul Cancro, Genova (Italy); Ledda, B.; Volta, C. [Genetics, DIBIO, University of Genova, Corso Europa 26, 16132 Genova (Italy); Manduca, P., E-mail: man-via@unige.it [Genetics, DIBIO, University of Genova, Corso Europa 26, 16132 Genova (Italy)

    2010-03-10

    Extracellular matrix (ECM) plays a fundamental role in angiogenesis affecting endothelial cells proliferation, migration and differentiation. Vessels-like network formation in vitro is a reliable test to study the inductive effects of ECM on angiogenesis. Here we utilized matrix deposed by osteoblasts as substrate where the molecular and structural complexity of the endogenous ECM is preserved, to test if it induces vessel-like network formation by endothelial cells in vitro. ECM is more similar to the physiological substrate in vivo than other substrates previously utilized for these studies in vitro. Osteogenic ECM, prepared in vitro from mature osteoblasts at the phase of maximal deposition and glycosylation of collagen I, induces EAhy926, HUVEC, and HDMEC endothelial cells to form vessels-like structures and promotes the activation of metalloproteinase-2 (MMP-2); the functionality of the p-38/MAPK signaling pathway is required. Osteogenic ECM also induces a transient increase of CXCL12 and a decrease of the receptor CXCR4. The induction of vessel-like networks is dependent from proper glycosylation of collagens and does not occur on osteogenic ECMs if deglycosylated by -galactosidase or on less glycosylated ECMs derived from preosteoblasts and normal fibroblasts, while is sustained on ECM from osteogenesis imperfecta fibroblasts only when their mutation is associated with over-glycosylation of collagen type I. These data support that post-translational glycosylation has a role in the induction in endothelial cells in vitro of molecules conductive to self-organization in vessels-like structures.

  4. Osteoblasts extracellular matrix induces vessel like structures through glycosylated collagen I

    International Nuclear Information System (INIS)

    Palmieri, D.; Valli, M.; Viglio, S.; Ferrari, N.; Ledda, B.; Volta, C.; Manduca, P.

    2010-01-01

    Extracellular matrix (ECM) plays a fundamental role in angiogenesis affecting endothelial cells proliferation, migration and differentiation. Vessels-like network formation in vitro is a reliable test to study the inductive effects of ECM on angiogenesis. Here we utilized matrix deposed by osteoblasts as substrate where the molecular and structural complexity of the endogenous ECM is preserved, to test if it induces vessel-like network formation by endothelial cells in vitro. ECM is more similar to the physiological substrate in vivo than other substrates previously utilized for these studies in vitro. Osteogenic ECM, prepared in vitro from mature osteoblasts at the phase of maximal deposition and glycosylation of collagen I, induces EAhy926, HUVEC, and HDMEC endothelial cells to form vessels-like structures and promotes the activation of metalloproteinase-2 (MMP-2); the functionality of the p-38/MAPK signaling pathway is required. Osteogenic ECM also induces a transient increase of CXCL12 and a decrease of the receptor CXCR4. The induction of vessel-like networks is dependent from proper glycosylation of collagens and does not occur on osteogenic ECMs if deglycosylated by -galactosidase or on less glycosylated ECMs derived from preosteoblasts and normal fibroblasts, while is sustained on ECM from osteogenesis imperfecta fibroblasts only when their mutation is associated with over-glycosylation of collagen type I. These data support that post-translational glycosylation has a role in the induction in endothelial cells in vitro of molecules conductive to self-organization in vessels-like structures.

  5. Light and Electrically Induced Phase Segregation and Its Impact on the Stability of Quadruple Cation High Bandgap Perovskite Solar Cells.

    Science.gov (United States)

    Duong, The; Mulmudi, Hemant Kumar; Wu, YiLiang; Fu, Xiao; Shen, Heping; Peng, Jun; Wu, Nandi; Nguyen, Hieu T; Macdonald, Daniel; Lockrey, Mark; White, Thomas P; Weber, Klaus; Catchpole, Kylie

    2017-08-16

    Perovskite material with a bandgap of 1.7-1.8 eV is highly desirable for the top cell in a tandem configuration with a lower bandgap bottom cell, such as a silicon cell. This can be achieved by alloying iodide and bromide anions, but light-induced phase-segregation phenomena are often observed in perovskite films of this kind, with implications for solar cell efficiency. Here, we investigate light-induced phase segregation inside quadruple-cation perovskite material in a complete cell structure and find that the magnitude of this phenomenon is dependent on the operating condition of the solar cell. Under short-circuit and even maximum power point conditions, phase segregation is found to be negligible compared to the magnitude of segregation under open-circuit conditions. In accordance with the finding, perovskite cells based on quadruple-cation perovskite with 1.73 eV bandgap retain 94% of the original efficiency after 12 h operation at the maximum power point, while the cell only retains 82% of the original efficiency after 12 h operation at the open-circuit condition. This result highlights the need to have standard methods including light/dark and bias condition for testing the stability of perovskite solar cells. Additionally, phase segregation is observed when the cell was forward biased at 1.2 V in the dark, which indicates that photoexcitation is not required to induce phase segregation.

  6. Evolution of phase structure and giant strain at low driving fields in Bi-based lead-free incipient piezoelectrics

    International Nuclear Information System (INIS)

    Maqbool, Adnan; Hussain, Ali; Malik, Rizwan Ahmed; Rahman, Jamil Ur; Zaman, Arif; Song, Tae Kwon; Kim, Won-Jeong; Kim, Myong-Ho

    2015-01-01

    Graphical abstract: - Highlights: • Nb-doped BNBT–SZ ceramics were prepared by conventional solid state method. • A giant normalized strain of 825 pm/V at 4 kV/mm was achieved. • A large strain of 0.20% triggered at a relatively low field of 3 kV/mm. • Highest strain obtained in BNT-based ceramics at such a low driving field. • Ferroelectric to ergodic-relaxor phase transition occurred with Nb-doping. - Abstract: Lead-free 0.99[(Bi 0.5 Na 0.5 ) 0.935 Ba 0.065 Ti (1–x) Nb x O 3 ]–0.01SrZrO 3 (BNBTNb100x–SZ, with Nb100x = 0–1) ceramics were prepared by the conventional mixed oxide route. X-ray diffraction and Raman scattering was utilized for the structural evolution of Nb-modified BNBT–SZ ceramics at average and short-scale localized structure. Temperature dependent dielectric properties showed ferroelectric–ergodic relaxor (FE–ER) transition in Nb-modified BNBT–SZ ceramics by producing a significant disruption of the long-range FE order. A giant normalized strain of 825 pm/V at 4 kV/mm was achieved at Nb1.0. Interestingly, at a relatively low applied field of 3 kV/mm, the Nb0.75 sample displayed a large electric field-induced strain (EFIS) response of 0.20%, which is highest value obtained in non-textured lead-free BNT-based ceramics at such low driving field. The structural distortion induced by doping and electric poling is correlated with the dielectric, ferroelectric and EFIS response, and the evolution of giant strain was ascribed to reversible field induced phase transition from ER–FE phase

  7. Asymmetric induced cubic nonlinearities in homogeneous and quasi-phase-matched quadratic materials: signature and importance

    DEFF Research Database (Denmark)

    Bang, Ole; Corney, Joel Frederick

    2001-01-01

    In continuous-wave operation asymmetric induced nonlinearities induce an intensity-dependent phase mismatch that implies a nonzero so-called separatrix intensity, the crossing of which changes the one-period phase shift of the fundamental by Pi , with obvious use in switching applications.......We derived a formula for this QPM-induced separatrix intensity that corrects earlier estimates by a factor of 5.3, and we found the optimum crystal lengths for a flat phase-versus-intensity response on each side of the separatrix...

  8. Strain-induced ordered structure of titanium carbide during depositing diamond on Ti alloy substrate

    Energy Technology Data Exchange (ETDEWEB)

    Li, X.J., E-mail: lixj@alum.imr.ac.cn [College of Material Science and Engineering, Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun, 130012 (China); He, L.L., E-mail: llhe@imr.ac.cn [Shenyang National Lab of Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Li, Y.S. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon S7N 5A9, SK (Canada); Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada); Yang, Q. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon S7N 5A9, SK (Canada); Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada)

    2017-01-15

    During the deposition of diamond films on Ti alloy substrates, titanium carbide is a common precipitated phase, preferentially formed at the interfacial region. However, in this case, the precipitation of an ordered structure of titanium carbide has not been reported. In our work, a long periodic ordered structure of TiC has been observed at the deposited diamond film/Ti alloy interface by high resolution transmission electron microscopy (HRTEM). The long periodic ordered structure is identified as 6H-type. The formation mechanism is revealed by comparative studies on the different structures of TiC precipitated under different diamond deposition conditions in terms of deposition time, atmosphere and temperature. A large number of carbon vacancies in the interfacial precipitated TiC phase are verified through electron energy loss spectroscopy (EELS) quantification analysis. However, an ordered arrangement of these carbon vacancies occurs only when the interfacial stress is large enough to induce the precipitation of 6H-type TiC. The supplementary analysis by X-ray diffraction (XRD) further confirms that additional diffraction peaks presented in the XRD patterns are corresponding to the precipitation of 6H-type TiC. - Highlights: •Different structures of TiC are observed during deposited diamond on Ti alloy. •One is common NaCl structure, the other is periodic structure. •The periodic structure is identified as 6H-type by HRTEM. •Carbon vacancies are verified to always exist in the TiC phase. •The precipitation of 6H-type TiC is mainly affected by interfacial stress.

  9. Strain-induced ordered structure of titanium carbide during depositing diamond on Ti alloy substrate

    International Nuclear Information System (INIS)

    Li, X.J.; He, L.L.; Li, Y.S.; Yang, Q.; Hirose, A.

    2017-01-01

    During the deposition of diamond films on Ti alloy substrates, titanium carbide is a common precipitated phase, preferentially formed at the interfacial region. However, in this case, the precipitation of an ordered structure of titanium carbide has not been reported. In our work, a long periodic ordered structure of TiC has been observed at the deposited diamond film/Ti alloy interface by high resolution transmission electron microscopy (HRTEM). The long periodic ordered structure is identified as 6H-type. The formation mechanism is revealed by comparative studies on the different structures of TiC precipitated under different diamond deposition conditions in terms of deposition time, atmosphere and temperature. A large number of carbon vacancies in the interfacial precipitated TiC phase are verified through electron energy loss spectroscopy (EELS) quantification analysis. However, an ordered arrangement of these carbon vacancies occurs only when the interfacial stress is large enough to induce the precipitation of 6H-type TiC. The supplementary analysis by X-ray diffraction (XRD) further confirms that additional diffraction peaks presented in the XRD patterns are corresponding to the precipitation of 6H-type TiC. - Highlights: •Different structures of TiC are observed during deposited diamond on Ti alloy. •One is common NaCl structure, the other is periodic structure. •The periodic structure is identified as 6H-type by HRTEM. •Carbon vacancies are verified to always exist in the TiC phase. •The precipitation of 6H-type TiC is mainly affected by interfacial stress.

  10. Pressure-induced phase transitions in Zr-rich PbZr{sub 1-x}Ti{sub x}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Souza Filho, A.G. [Departamento de Fisica, Universidade Federal do Ceara, Fortaleza, Ceara (Brazil)]. E-mail: agsf@fisica.ufc.br; Faria, J.L.B.; Freire, P.T.C.; Ayala, A.P.; Sasaki, J.M.; Melo, F.E.A.; Mendes Filho, J. [Departamento de Fisica, Universidade Federal do Ceara, Fortaleza, Ceara (Brazil); Araujo, E.B. [Departamento de Fisica e Quimica, Universidade Estadual de Sao Paulo, Campus de Ilha Solteira, Ilha Solteira, SP (Brazil); Eiras, J.A. [Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil)

    2001-08-20

    A Raman study of structural changes in the Zr-rich PbZr{sub 1-x}Ti{sub x}O{sub 3} (PZT) system under hydrostatic pressures up to 5.0 GPa is presented. We observe that externally applied pressure induces several phase transitions in PZT ceramics among phases with orthorhombic (A{sub O}), rhombohedral low-temperature (R{sub LT}), and rhombohedral high-temperature (R{sub HT}) symmetries (all found in PZT at ambient pressure and room temperature). Each of the compositions investigated (0.02{<=}x{<=}0.14) exhibits a high-pressure phase with orthorhombic (O{sub I'}) symmetry. We further report a detailed study of the pressure dependence of Raman frequencies to elucidate the phase transitions and to provide a set of pressure coefficients for the high-pressure phases. (author)

  11. Lupeol induces S-phase arrest and mitochondria-mediated ...

    Indian Academy of Sciences (India)

    48

    Lupeol induces S-phase arrest and mitochondria-mediated apoptosis in cervical cancer cells. Nupoor Prasad1, Akash Sabarwal2, Umesh C. S. Yadav1, Rana P. Singh2,*. 1School of Life Sciences, Central University of Gujarat, Gandhinagar, Gujarat, India. 2Cancer Biology Laboratory, School of Life Sciences, Jawaharlal ...

  12. Periodic orbits and TDHF phase space structure

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Yukio; Iwasawa, Kazuo [Tsukuba Univ., Ibaraki (Japan). Inst. of Physics; Tsukuma, Hidehiko; Sakata, Fumihiko

    1998-03-01

    The collective motion of atomic nuclei is closely coupled with the motion of nucleons, therefore, it is nonlinear, and the contents of the motion change largely with the increase of its amplitude. As the framework which describes the collective motion accompanied by the change of internal structure, time-dependent Hurtley Fock (TDHF) method is suitable. At present, the authors try to make the method for studying the large region structure in quantum system by utilizing the features of the TDHF phase space. The studies made so far are briefed. In this report, the correspondence of the large region patterns appearing in the band structure chart of three-level model with the periodic orbit group in the TDHF phase space is described. The Husimi function is made, and it possesses the information on the form of respective corresponding intrinsic state. The method of making the band structure chart is explained. There are three kinds of the tendency in the intrinsic state group. The E-T charts are made for the band structure charts to quantitatively express the large region tendency. The E-T chart and the T{sub r}-T chart are drawn for a selected characteristic orbit group. It became to be known that the large region properties of the quantum intrinsic state group of three-level model can be forecast by examining the properties of the periodic orbit group in the TDHF phase space. (K.I.)

  13. Inhibition of autophagy enhances DNA damage-induced apoptosis by disrupting CHK1-dependent S phase arrest

    Energy Technology Data Exchange (ETDEWEB)

    Liou, Jong-Shian; Wu, Yi-Chen; Yen, Wen-Yen; Tang, Yu-Shuan [Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan, ROC (China); Kakadiya, Rajesh B.; Su, Tsann-Long [Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, ROC (China); Yih, Ling-Huei, E-mail: lhyih@gate.sinica.edu.tw [Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan, ROC (China)

    2014-08-01

    DNA damage has been shown to induce autophagy, but the role of autophagy in the DNA damage response and cell fate is not fully understood. BO-1012, a bifunctional alkylating derivative of 3a-aza-cyclopenta[a]indene, is a potent DNA interstrand cross-linking agent with anticancer activity. In this study, BO-1012 was found to reduce DNA synthesis, inhibit S phase progression, and induce phosphorylation of histone H2AX on serine 139 (γH2AX) exclusively in S phase cells. Both CHK1 and CHK2 were phosphorylated in response to BO-1012 treatment, but only depletion of CHK1, but not CHK2, impaired BO-1012-induced S phase arrest and facilitated the entry of γH2AX-positive cells into G2 phase. CHK1 depletion also significantly enhanced BO-1012-induced cell death and apoptosis. These results indicate that BO-1012-induced S phase arrest is a CHK1-dependent pro-survival response. BO-1012 also resulted in marked induction of acidic vesicular organelle (AVO) formation and microtubule-associated protein 1 light chain 3 (LC3) processing and redistribution, features characteristic of autophagy. Depletion of ATG7 or co-treatment of cells with BO-1012 and either 3-methyladenine or bafilomycin A1, two inhibitors of autophagy, not only reduced CHK1 phosphorylation and disrupted S phase arrest, but also increased cleavage of caspase-9 and PARP, and cell death. These results suggest that cells initiate S phase arrest and autophagy as pro-survival responses to BO-1012-induced DNA damage, and that suppression of autophagy enhances BO-1012-induced apoptosis via disruption of CHK1-dependent S phase arrest. - Highlights: • Autophagy inhibitors enhanced the cytotoxicity of a DNA alkylating agent, BO-1012. • BO-1012-induced S phase arrest was a CHK1-dependent pro-survival response. • Autophagy inhibition enhanced BO-1012 cytotoxicity via disrupting the S phase arrest.

  14. Composition-induced structural, electrical, and magnetic phase transitions in AX-type mixed-valence cobalt oxynitride epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Jumpei; Oka, Daichi [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); Hirose, Yasushi, E-mail: hirose@chem.s.u-tokyo.ac.jp; Yang, Chang; Fukumura, Tomoteru; Hasegawa, Tetsuya [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Harayama, Isao; Sekiba, Daiichiro [University of Tsukuba Tandem Accelerator Complex (UTTAC), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577 (Japan)

    2015-12-07

    Synthesis of mid- to late-transition metal oxynitrides is generally difficult by conventional thermal ammonolysis because of thermal instability. In this letter, we synthesized epitaxial thin films of AX-type phase-pure cobalt oxynitrides (CoO{sub x}N{sub y}) by using nitrogen-plasma-assisted pulsed laser deposition and investigated their structural, electrical, and magnetic properties. The CoO{sub x}N{sub y} thin films with 0 ≤ y/(x + y) ≤ 0.63 grown on MgO (100) substrates showed a structural phase transition from rock salt (RS) to zinc blend at the nitrogen content y/(x + y) ∼ 0.5. As the nitrogen content increased, the room-temperature electrical resistivity of the CoO{sub x}N{sub y} thin films monotonically decreased from the order of 10{sup 5} Ω cm to 10{sup −4} Ω cm. Furthermore, we observed an insulator-to-metal transition at y/(x + y) ∼ 0.34 in the RS-CoO{sub x}N{sub y} phase, which has not yet been reported in Co{sup 2+}/Co{sup 3+} mixed-valence cobalt oxides with octahedral coordination. The low resistivity in the RS-CoO{sub x}N{sub y} phase, on the 10{sup −3} Ω cm order, may have originated from the intermediate spin state of Co{sup 3+} stabilized by the lowered crystal field symmetry of the CoO{sub 6−n}N{sub n} octahedra (n = 1, 2,…5). Magnetization measurements suggested that a magnetic phase transition occurred in the RS-CoO{sub x}N{sub y} films during the insulator-to-metal transition. These results demonstrate that low-temperature epitaxial growth is a promising approach for exploring novel electronic functionalities in oxynitrides.

  15. Composition-induced structural, electrical, and magnetic phase transitions in AX-type mixed-valence cobalt oxynitride epitaxial thin films

    International Nuclear Information System (INIS)

    Takahashi, Jumpei; Oka, Daichi; Hirose, Yasushi; Yang, Chang; Fukumura, Tomoteru; Hasegawa, Tetsuya; Nakao, Shoichiro; Harayama, Isao; Sekiba, Daiichiro

    2015-01-01

    Synthesis of mid- to late-transition metal oxynitrides is generally difficult by conventional thermal ammonolysis because of thermal instability. In this letter, we synthesized epitaxial thin films of AX-type phase-pure cobalt oxynitrides (CoO x N y ) by using nitrogen-plasma-assisted pulsed laser deposition and investigated their structural, electrical, and magnetic properties. The CoO x N y thin films with 0 ≤ y/(x + y) ≤ 0.63 grown on MgO (100) substrates showed a structural phase transition from rock salt (RS) to zinc blend at the nitrogen content y/(x + y) ∼ 0.5. As the nitrogen content increased, the room-temperature electrical resistivity of the CoO x N y thin films monotonically decreased from the order of 10 5  Ω cm to 10 −4  Ω cm. Furthermore, we observed an insulator-to-metal transition at y/(x + y) ∼ 0.34 in the RS-CoO x N y phase, which has not yet been reported in Co 2+ /Co 3+ mixed-valence cobalt oxides with octahedral coordination. The low resistivity in the RS-CoO x N y phase, on the 10 −3  Ω cm order, may have originated from the intermediate spin state of Co 3+ stabilized by the lowered crystal field symmetry of the CoO 6−n N n octahedra (n = 1, 2,…5). Magnetization measurements suggested that a magnetic phase transition occurred in the RS-CoO x N y films during the insulator-to-metal transition. These results demonstrate that low-temperature epitaxial growth is a promising approach for exploring novel electronic functionalities in oxynitrides

  16. Gravitationally induced neutrino oscillation phases in static spacetimes

    International Nuclear Information System (INIS)

    Bhattacharya, T.; Habib, S.; Mottola, E.

    1999-01-01

    We critically examine the recent claim of a 'new effect' of gravitationally induced quantum mechanical phases in neutrino oscillations. Because this claim has generated some discussion in the literature we present here a straightforward calculation of the phase and clarify some of the conceptual issues involved, particularly in relation to the equivalence principle. When expressed in terms of the asymptotic energy of the neutrinos E and Schwarzschild radial coordinates r, the lowest order at which such a gravitational effect appears is (GMΔm 4 /ℎE 3 )ln(r B /r A ). copyright 1999 The American Physical Society

  17. S-wave kaon-nucleon phase shifts with instanton induced effects

    International Nuclear Information System (INIS)

    Lemaire, S.; Labarsouque, J.; Silvestre-Brac, B.

    2003-01-01

    The kaon-nucleon S-wave phase shifts have been calculated, for both isospin channels I=0 and I=1, in the framework of a semirelativistic quark potential model which includes an instanton induced force. The agreement with experimental phase shifts is poor essentially because of a dominant attraction coming from instantons. The low-energy behaviour of S-wave phase shifts, for I=0 and I=1 channels, obtained in the kaon-nucleon system is characteristic of a potential which can produce one loosely bound state

  18. S-wave kaon-nucleon phase shifts with instanton induced effects

    Energy Technology Data Exchange (ETDEWEB)

    Lemaire, S. E-mail: lemaire@cenbg.in2p3.fr; Labarsouque, J.; Silvestre-Brac, B

    2003-09-22

    The kaon-nucleon S-wave phase shifts have been calculated, for both isospin channels I=0 and I=1, in the framework of a semirelativistic quark potential model which includes an instanton induced force. The agreement with experimental phase shifts is poor essentially because of a dominant attraction coming from instantons. The low-energy behaviour of S-wave phase shifts, for I=0 and I=1 channels, obtained in the kaon-nucleon system is characteristic of a potential which can produce one loosely bound state.

  19. A new high-pressure phase of Fe2SiO4 and the relationship between spin and structural transitions

    Science.gov (United States)

    Yamanaka, T.; Kyono, A.; Nakamoto, Y.; Kharlamova, S. A.; Struzhkin, V. V.; Gramsch, S.; Mao, H.; Hemley, R. J.

    2013-12-01

    O4. This new high-pressure phase reversibly transforms to the spinel structure under decompression. A Martensitic transformation of spinel slabs with translation vector [1/8 1/8 1/8] generates the I-Fe2SiO4 structure. The transition is induced by atomic displacements in the spinel structure, which generates the orthorhombic distortion resulting in I-Fe2SiO4 arrangement. A topotactic relation between spinel and I-Fe2SiO4 is suggested as the origin of this phase transition: Fe2SiO4 spinel at 34.8 GPa, Fd m, z = 8, a(spinel)= 7.894 Å I-Fe2SiO4 at 54.6 GPa, Imma,, z = 4, a= 5.543(1)Å, b=6.032(4)Å, c= 7.201(5)Å a = b = d(spnel 110) = 0.707107a (spinel) c= c(spinel) Compression along the [001] direction of the spinel structure and simultaneous elongation along the [110] direction results in the I-Fe2SiO4 arrangement. This transition is induced by the 20% shrinkage of ionic radius of Fe2+in the octahedral site at the low spin state.

  20. Radiation-induced phase transformation in ferromagnetic perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Podsekin, A K; Dem' yanov, V V; Ivanova, V V; Venevtsev, Yu N [Nauchno-Issledovatel' skij Fiziko-Khimicheskij Inst., Moscow (USSR)

    1976-12-01

    An effect of neutron irradiation inducing a phase transition in ferromagnetic perovskite, Sr/sub 0.3/La/sub 0.7/MnO/sub 3/, has been discovered and studied. It is shown that a change in the Curie temperature is proportional to the dose of reactor irradiation. A decrease in the temperature of the phase transition with the concentration of radiation defects is accompanied by an increase in the electrical specific resistance and a change in the initial lattice parameters. It is shown that the radiation shift is due to at least two causes, viz. to an increase in the parameters of the elementary cell and the growth of the electrical specific resistance as a result of bounded electron states' forming on the radiation defects.

  1. X-ray diffraction study on pressure-induced phase transformations and the equation of state of ZnGa{sub 2}Te{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Errandonea, D., E-mail: daniel.errandonea@uv.es [Departamento de Física Aplicada-ICMUV, MALTA Consolider Team, Universidad de Valencia, Edificio de Investigación, C/Dr. Moliner 50, Burjassot, 46100 Valencia (Spain); Kumar, R. S. [High Pressure Science and Engineering Center, Department of Physics and Astronomy, University of Nevada Las Vegas, 4505 Maryland Parkway, Las Vegas, Nevada 89154-4002 (United States); Gomis, O. [Centro de Tecnologías Físicas: Acústica, Materiales y Astrofísica, MALTA Consolider Team, Universitat Politècnica de València, 46022 València (Spain); Manjón, F. J. [Instituto de Diseño para la Fabricación y Producción Automatizada, MALTA Consolider Team, Universitat Politècnica de València, 46022 València (Spain); Ursaki, V. V.; Tiginyanu, I. M. [Institute of Applied Physics, Academy of Sciences of Moldova, 2028 Chisinau (Moldova, Republic of)

    2013-12-21

    We report on high-pressure x-ray diffraction measurements up to 19.8 GPa in zinc digallium telluride (ZnGa{sub 2}Te{sub 4}) at room temperature. An irreversible structural phase transition takes place at pressures above 12.1 GPa and upon decompression a third polymorph of ZnGa{sub 2}Te{sub 4} was recovered as a metastable phase at pressures below 2.9 GPa. Rietveld refinements were carried out for the three detected polymorphs, being their possible crystal structures reported. The axial compressibilities for the low-pressure phase of ZnGa{sub 2}Te{sub 4} have been determined as well as the equation of state of the low- and high-pressure phases. The reported results are compared with those available in the literature for related compounds. Pressure-induced coordination changes and transition mechanisms are also discussed.

  2. Structure of vortices in superfluid 3He A-like phase in uniaxially stretched aerogel

    International Nuclear Information System (INIS)

    Aoyama, Kazushi; Ikeda, Ryusuke

    2009-01-01

    Possible vortex-core transitions in A-like phase of superfluid 3 He in uniaxially stretched aerogel are investigated. Since the global anisotropy in this system induces the polar pairing state in a narrow range close to the superfluid transition in addition to the A-like and B-like phases, the polar state may occur in the core of a vortex in the A-like phase identified with the ABM pairing state, like in the case of the bulk B phase where a core including the ABM state is realized at higher pressures. We examine the core structure of a single vortex under the boundary condition compatible with the Mermin-Ho vortex in the presence of the dipole interaction. Following Salomaa and Volovik's approach, we numerically solve the Ginzburg-Landau equation for an axially symmetric vortex and, by examining its stability against nonaxisymmetric perturbations, discuss possible vortex core states. It is found that a first order transition on core states may occur on warming from an axisymmetric vortex with a nonunitary core to a singular vortex with the polar core.

  3. Structure of vortices in superfluid 3He A-like phase in uniaxially stretched aerogel

    Science.gov (United States)

    Aoyama, Kazushi; Ikeda, Ryusuke

    2009-02-01

    Possible vortex-core transitions in A-like phase of superfluid 3He in uniaxially stretched aerogel are investigated. Since the global anisotropy in this system induces the polar pairing state in a narrow range close to the superfluid transition in addition to the A-like and B-like phases, the polar state may occur in the core of a vortex in the A-like phase identified with the ABM pairing state, like in the case of the bulk B phase where a core including the ABM state is realized at higher pressures. We examine the core structure of a single vortex under the boundary condition compatible with the Mermin-Ho vortex in the presence of the dipole interaction. Following Salomaa and Volovik's approach, we numerically solve the Ginzburg-Landau equation for an axially symmetric vortex and, by examining its stability against nonaxisymmetric perturbations, discuss possible vortex core states. It is found that a first order transition on core states may occur on warming from an axisymmetric vortex with a nonunitary core to a singular vortex with the polar core.

  4. Pasta Structures of Quark-Hadron Phase Transition in Proto-Neutron Stars

    International Nuclear Information System (INIS)

    Yasutake, Nobutoshi; Maruyama, Toshiki; Tatsumi, Toshitaka

    2011-01-01

    We study the quark-hadron mixed phase in proto-neutron stars with the finite-size effects. In the calculations of pasta structures appeared in the mixed phase, the Gibbs conditions require the pressure balance and chemical equilibrium between two phases besides the thermal equilibrium. We find that the region of the mixed phase is limited due to thermal instability. Moreover, we study the effects of neutrinos to the pasta structures. As a result, we find that the existence of neutrinos make the pasta structures unstable, too. These characteristic features of the hadron-quark mixed phase should be important for the middle stage of the evolutions of proto-neutron stars.

  5. Amplitude and phase control of trichromatic electromagnetically induced transparency

    International Nuclear Information System (INIS)

    Hu Xiangming; Zou Jinhua; Li Xing; Du Dan; Cheng Guangling

    2005-01-01

    We study the dependence of absorption and dispersion spectra on amplitudes and phases of the driving fields in multiple electromagnetically induced transparency. For this purpose we consider trichromatic excitation in a three-level Λ atomic system, in which a trichromatic control laser and a monochromatic probe laser are applied to two different transitions, respectively. We numerically calculate the absorption and dispersion spectra. Two characteristic features are found. Firstly, the central transparency can be made to appear or to disappear by utilizing the amplitudes and phases of the driving components. Secondly, so long as we fix the sum of two relative phases of two sideband excitation components to the central component, the absorption and dispersion spectra keep their own lineshapes unchanged no matter how we vary the respective relative phases

  6. Average Structure Evolution of δ-phase Pu-Ga Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Alice Iulia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Page, Katharine L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Gourdon, Olivier [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Siewenie, Joan E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Richmond, Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Saleh, Tarik A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramos, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Schwartz, Daniel S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-30

    [Full Text] Plutonium metal is a highly unusual element, exhibiting six allotropes at ambient pressure, from room temperature to its melting point. Many phases of plutonium metal are unstable with temperature, pressure, chemical additions, and time. This strongly affects structure and properties, and becomes of high importance, particularly when considering effects on structural integrity over long time periods. The fcc δ-phase deserves additional attention, not only in the context of understanding the electronic structure of Pu, but also as one of the few high-symmetry actinide phases that can be stabilized down to ambient pressure and room temperature by alloying it with trivalent elements. We will present results on recent work on aging of Pu-2at.%Ga and Pu-7at.%Ga alloys

  7. Structure analysis of turbulent liquid phase by POD and LSE techniques

    International Nuclear Information System (INIS)

    Munir, S.; Muthuvalu, M. S.; Siddiqui, M. I.; Heikal, M. R.; Aziz, A. Rashid A.

    2014-01-01

    In this paper, vortical structures and turbulence characteristics of liquid phase in both single liquid phase and two-phase slug flow in pipes were studied. Two dimensional velocity vector fields of liquid phase were obtained by Particle image velocimetry (PIV). Two cases were considered one single phase liquid flow at 80 l/m and second slug flow by introducing gas at 60 l/m while keeping liquid flow rate same. Proper orthogonal decomposition (POD) and Linear stochastic estimation techniques were used for the extraction of coherent structures and analysis of turbulence in liquid phase for both cases. POD has successfully revealed large energy containing structures. The time dependent POD spatial mode coefficients oscillate with high frequency for high mode numbers. The energy distribution of spatial modes was also achieved. LSE has pointed out the coherent structured for both cases and the reconstructed velocity fields are in well agreement with the instantaneous velocity fields

  8. Structure analysis of turbulent liquid phase by POD and LSE techniques

    Energy Technology Data Exchange (ETDEWEB)

    Munir, S., E-mail: shahzad-munir@comsats.edu.pk; Muthuvalu, M. S.; Siddiqui, M. I. [Department of Fundamental and Applied Science, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak Darul Ridzuan (Malaysia); Heikal, M. R., E-mail: morgan.heikal@petronas.com.my; Aziz, A. Rashid A., E-mail: morgan.heikal@petronas.com.my [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak Darul Ridzuan (Malaysia)

    2014-10-24

    In this paper, vortical structures and turbulence characteristics of liquid phase in both single liquid phase and two-phase slug flow in pipes were studied. Two dimensional velocity vector fields of liquid phase were obtained by Particle image velocimetry (PIV). Two cases were considered one single phase liquid flow at 80 l/m and second slug flow by introducing gas at 60 l/m while keeping liquid flow rate same. Proper orthogonal decomposition (POD) and Linear stochastic estimation techniques were used for the extraction of coherent structures and analysis of turbulence in liquid phase for both cases. POD has successfully revealed large energy containing structures. The time dependent POD spatial mode coefficients oscillate with high frequency for high mode numbers. The energy distribution of spatial modes was also achieved. LSE has pointed out the coherent structured for both cases and the reconstructed velocity fields are in well agreement with the instantaneous velocity fields.

  9. Analysis of phases in the structure determination of an icosahedral virus

    Energy Technology Data Exchange (ETDEWEB)

    Plevka, Pavel; Kaufmann, Bärbel; Rossmann, Michael G. (Purdue)

    2012-03-15

    The constraints imposed on structure-factor phases by noncrystallographic symmetry (NCS) allow phase improvement, phase extension to higher resolution and hence ab initio phase determination. The more numerous the NCS redundancy and the greater the volume used for solvent flattening, the greater the power for phase determination. In a case analyzed here the icosahedral NCS phasing appeared to have broken down, although later successful phase extension was possible when the envelope around the NCS region was tightened. The phases from the failed phase-determination attempt fell into four classes, all of which satisfied the NCS constraints. These four classes corresponded to the correct solution, opposite enantiomorph, Babinet inversion and opposite enantiomorph with Babinet inversion. These incorrect solutions can be seeded from structure factors belonging to reciprocal-space volumes that lie close to icosahedral NCS axes where the structure amplitudes tend to be large and the phases tend to be 0 or {pi}. Furthermore, the false solutions can spread more easily if there are large errors in defining the envelope designating the region in which NCS averaging is performed.

  10. Influence of heat treatment in {beta} and {gamma} phases on the microscopic structure of uranium; Influence des traitements thermiques en phases {beta} et {gamma} sur la structure micrographique de l'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Robillard, A

    1958-06-02

    A new method of microscopic examination of uranium is described. Electrolytic polishing and etching are carried out in an acetic acid-chromic acid bath. Atmospheric or anodic oxidation of the polished surface produces films which follow exactly changes in the structure of the underlying metal. This method is very sensitive to small variations of orientation in polygonized crystals. Using this method of examination of uranium, it was found that annealing U in the {gamma} phase followed by a cooling at a rate dependent of the annealing temperature, causes the formation of substructures different from those due to the polygonization of {alpha}-U. The substructures are indicated by the concentration of impurities on the dislocations induced by the stresses accompanying the allotropic transformation {gamma} {yields} {beta}. Similar treatment of the U-1.4% Cr alloy in which the {beta} phase is stabilized at room temperature, confirms this explanation. In addition to the polygonization substructures, sharp discontinuities can be observed in the network of sub- boundaries as a fine white edging. The comparison of these with the structure revealed by thermal etching in vacuum suggest that there are traces of the grain boundaries of the {gamma} phase. The method of etching followed by oxidation shows a haloed phase identified as UH{sub 3}. The conditions of appearance and disappearance of this phase are studied. The sensitivity of this method of detecting the last traces of H in U is very high. The dependence of the hydrogen content on the tensile properties of uranium metal was also studied. (author) [French] Une methode nouvelle d'examen micrographique de l'uranium a ete mise au point. Le polissage electrolytique et le 'gravage' sont effectues dans un bain acide acetique-acide chromique. L'oxydation atmospherique ou anodique de la surface polie conduit a la formation de couches epitaxiques d'oxyde. Cette methode est particulierement sensible

  11. Electric field-induced phase transitions in Li-modified Na{sub 0.5}K{sub 0.5}NbO{sub 3} at the polymorphic phase boundary

    Energy Technology Data Exchange (ETDEWEB)

    Iamsasri, Thanakorn; Jones, Jacob L., E-mail: jacobjones@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Tutuncu, Goknur [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Uthaisar, Chunmanus; Pojprapai, Soodkhet [School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, Nakorn Ratchasima 30000 (Thailand); Wongsaenmai, Supattra [Program in Materials Science, Faculty of Science, Maejo University, Chiang Mai 50290 (Thailand)

    2015-01-14

    The electric field-induced phase transitions in Li-modified Na{sub 0.5}K{sub 0.5}NbO{sub 3} at the polymorphic phase boundary (PPB) were observed using in situ X-ray diffraction. The ratio of monoclinic to tetragonal phase fraction was used as an indicator of the extent and reversibility of the phase transitions. The reversibility of the phase transition was greater in compositions further from the PPB. These results demonstrate that the field-induced phase transition is one of the origins of high piezoelectric properties in lead-free ferroelectric materials.

  12. Equivalence of electronic and mechanical stresses in structural phase stabilization: A case study of indium wires on Si(111)

    Science.gov (United States)

    Kim, Sun-Woo; Kim, Hyun-Jung; Ming, Fangfei; Jia, Yu; Zeng, Changgan; Cho, Jun-Hyung; Zhang, Zhenyu

    2015-05-01

    It was recently proposed that the stress state of a material can also be altered via electron or hole doping, a concept termed electronic stress (ES), which is different from the traditional mechanical stress (MS) due to lattice contraction or expansion. Here we demonstrate the equivalence of ES and MS in structural stabilization, using In wires on Si(111) as a prototypical example. Our systematic density-functional theory calculations reveal that, first, for the same degrees of carrier doping into the In wires, the ES of the high-temperature metallic 4 ×1 structure is only slightly compressive, while that of the low-temperature insulating 8 ×2 structure is much larger and highly anisotropic. As a consequence, the intrinsic energy difference between the two phases is significantly reduced towards electronically phase-separated ground states. Our calculations further demonstrate quantitatively that such intriguing phase tunabilities can be achieved equivalently via lattice-contraction induced MS in the absence of charge doping. We also validate the equivalence through our detailed scanning tunneling microscopy experiments. The present findings have important implications for understanding the underlying driving forces involved in various phase transitions of simple and complex systems alike.

  13. Density-functional theory study of the pressure-induced phase transition in hydronitrogen compound N{sub 4}H{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qi-Jun, E-mail: qijunliu@home.swjtu.edu.cn [Bond and Band Engineering Group, Sichuan Provincial Key Laboratory (for Universities) of High Pressure Science and Technology, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhang, Ning-Chao; Sun, Yan-Yun; Zhang, Ming-Jian; Liu, Fu-Sheng [Bond and Band Engineering Group, Sichuan Provincial Key Laboratory (for Universities) of High Pressure Science and Technology, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Liu, Zheng-Tang [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China)

    2014-03-01

    Using first-principles density-functional theory, we have investigated the pressure-induced phase transition in hydronitrogen compound N{sub 4}H{sub 4} and discussed the potential tetragonal structure. We find that tetragonal structure with P4{sub 2}/n space group is mechanically stable and ductile. The thermodynamic stability of Pmna>P1{sup ¯}>P4{sub 2}/n>P2{sub 1}/m has been obtained. With increasing pressure, the phase transition pressures of T{sub Pmna→P4{sub 2/n}}, T{sub P4{sub 2/n→Pmna}}, T{sub Pmna→P1{sup ¯}} and T{sub P1{sup ¯}→P2{sub 1/m}} are 5.6, 15.0, 30.0 and 69.2 GPa, respectively, which are in agreement with the available data. Moreover, the mechanical stability of four structures under pressure has been analyzed.

  14. Theoretical description of the properties of magnetization fluctuations in the vicinity of phase transition from paramagnetic phase to ferromagnetic phase with domain structure

    International Nuclear Information System (INIS)

    Wasilewski, W.

    1983-08-01

    This paper presents a theoretical description of the phase transition from a paramagnetic phase P to the homogeneous and domain structure ferromagnetic phases within the phenomenological theory of phase transitions

  15. Preparation and Characterization of Membranes Formed by Nonsolvent Induced Phase Separation: A Review

    KAUST Repository

    Guillen, Gregory R.

    2011-04-06

    The methods and mechanisms of nonsolvent induced phase separation have been studied for more than fifty years. Today, phase inversion membranes are widely used in numerous chemical industries, biotechnology, and environmental separation processes. The body of knowledge has grown exponentially in the past fifty years, which suggests the need for a critical review of the literature. Here we present a review of nonsolvent induced phase separation membrane preparation and characterization for many commonly used membrane polymers. The key factors in membrane preparation discussed include the solvent type, polymer type and concentration, nonsolvent system type and composition, additives to the polymer solution, and film casting conditions. A brief introduction to membrane characterization is also given, which includes membrane porosity and pore size distribution characterization, membrane physical and chemical properties characterization, and thermodynamic and kinetic evaluation of the phase inversion process. One aim of this review is to lay out the basics for selecting polymer solvent nonsolvent systems with appropriate film casting conditions to produce membranes with the desired performance, morphology, and stability, and to choose the proper way to characterize these properties of nonsolvent induced phase inversion membranes. © 2011 American Chemical Society.

  16. Ultraviolet light induced refractive index structures in germanosilica

    DEFF Research Database (Denmark)

    Svalgaard, Mikael

    1997-01-01

    The focus of the research presented in this ph.d. thesis is refractive index structures photoinduced in germanonsilica waveguides with ultra-violet (UV) radiation. The physical mechanisms involved in photosensitivity and applications of a wide range of UV induced refractive index structures in both...... application of a scanning near-field optical microscope to obtain high resolution images of UV induced refractive index structures and by monitoring the dynamics of UV induced index changes and luminescence. During part of my ph.d. project I have worked at the National Institute of Standards and Technolgy...

  17. Unraveling the nature of electric field- and stress- induced structural transformations in soft PZT by a new powder poling technique.

    Science.gov (United States)

    Kalyani, Ajay Kumar; V, Lalitha K; James, Ajit R; Fitch, Andy; Ranjan, Rajeev

    2015-02-25

    A 'powder-poling' technique was developed to study electric field induced structural transformations in ferroelectrics exhibiting a morphotropic phase boundary (MPB). The technique was employed on soft PZT exhibiting a large longitudinal piezoelectric response (d(33) ∼ 650 pC N(-1)). It was found that electric poling brings about a considerable degree of irreversible tetragonal to monoclinic transformation. The same transformation was achieved after subjecting the specimen to mechanical stress, which suggests an equivalence of stress and electric field with regard to the structural mechanism in MPB compositions. The electric field induced structural transformation was also found to be accompanied by a decrease in the spatial coherence of polarization.

  18. UV-induced structural changes in chromatin

    International Nuclear Information System (INIS)

    Lang, H.; Zimmer, C.; Vengerov, Yu.Yu.

    1985-01-01

    UV-induced structural alterations of chromatin were studied by means of CD, electron microscopic, and gel electrophoretic measurements. The results indicate that chromatin undergoes serious structural changes after irradiation even at very low fluences. In the low fluence range the structural transitions from the higher ordered chromatin structure to the unfolded state occur without detectable changes in the content of histone H1 and of the core histones. Histone H1 disappears only at fluences above 10 kJ/m 2 . Furthermore, DNA in chromatin is much more sensitive against UV-irradiation and shows a higher degree of strand scission relative to free DNA. While fragmentation in free DNA occurs at fluences above 15 kJ/m 2 , it occurs even at 5.5 kJ/m 2 in the case of chromatin. The biological meaning of the observed UV-induced structural alterations of chromatin is discussed. (author)

  19. Radiation-induced brain structural and functional abnormalities in presymptomatic phase and outcome prediction.

    Science.gov (United States)

    Ding, Zhongxiang; Zhang, Han; Lv, Xiao-Fei; Xie, Fei; Liu, Lizhi; Qiu, Shijun; Li, Li; Shen, Dinggang

    2018-01-01

    Radiation therapy, a major method of treatment for brain cancer, may cause severe brain injuries after many years. We used a rare and unique cohort of nasopharyngeal carcinoma patients with normal-appearing brains to study possible early irradiation injury in its presymptomatic phase before severe, irreversible necrosis happens. The aim is to detect any structural or functional imaging biomarker that is sensitive to early irradiation injury, and to understand the recovery and progression of irradiation injury that can shed light on outcome prediction for early clinical intervention. We found an acute increase in local brain activity that is followed by extensive reductions in such activity in the temporal lobe and significant loss of functional connectivity in a distributed, large-scale, high-level cognitive function-related brain network. Intriguingly, these radiosensitive functional alterations were found to be fully or partially recoverable. In contrast, progressive late disruptions to the integrity of the related far-end white matter structure began to be significant after one year. Importantly, early increased local brain functional activity was predictive of severe later temporal lobe necrosis. Based on these findings, we proposed a dynamic, multifactorial model for radiation injury and another preventive model for timely clinical intervention. Hum Brain Mapp 39:407-427, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  20. Laser-induced partial oxidation of cyclohexane in liquid phase

    International Nuclear Information System (INIS)

    Oshima, Y.; Wu, X.W.; Koda, S.

    1995-01-01

    A laser-induced partial oxidation of cyclohexane was studied in the liquid phase. With KrF excimer laser (248 nm) irradiation to neat liquid cyclohexane in which O 2 was dissolved, cyclohexanol and cyclohexanone were obtained with very high selectivities, together with cyclohexane as a minor product. Radical recombination reactions to produce dicyclohexyl ether and bicyclohexyl also took place, while these products were not observed in the gas phase reaction. These experimental results were considered to be due not only to higher concentration of cyclohexane but to the cage effect in the liquid phase oxidation. To clarify the reaction progress including the photoabsorption process, the effects of laser intensity and O 2 pressure on product distribution were studied. (author)

  1. Structural phase transition and dynamical properties of PbTiO3 simulated by molecular dynamics

    International Nuclear Information System (INIS)

    Costa, S C; Pizani, P S; Rino, J P; Borges, D S

    2005-01-01

    The temperature- and pressure-induced structural phase transition in PbTiO 3 is studied with the isoenthalpic-isobaric molecular-dynamics method, using an effective two-body interaction potential. The tetragonal to cubic transformation is successfully reproduced with both temperature and pressure. The behaviour of lattice parameters, vibrational density of states, and phonon anharmonicity with temperature and pressure are in very good agreement with experimental data. Two- and three-body correlations were analysed through pair distribution functions, coordination numbers and bond-angle distributions

  2. Influence of grain structure on the deformation mechanism in martensitic shear reversion-induced Fe-16Cr-10Ni model austenitic alloy with low interstitial content: Coarse-grained versus nano-grained/ultrafine-grained structure

    Energy Technology Data Exchange (ETDEWEB)

    Challa, V.S.A. [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical, Materials Engineering, and Biomedical Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States); Misra, R.D.K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical, Materials Engineering, and Biomedical Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States); Somani, M.C. [Center for Advanced Steels Research, The University of Oulu, P.O. Box 4200, 90014 Oulu (Finland); Wang, Z.D. [State Key Laboratory for Rolling and Automation, Northeastern University, 3-11 Wenhua Road, Shenyang 110819 (China)

    2016-04-20

    Nanograined/ultrafine-grained (NG/UFG) materials characterized by high strength-high ductility combination are excellent vehicles to obtain an unambiguous understanding of deformation mechanisms vis-à-vis their coarse-grained counterparts. In this context, the innovative concept of phase reversion-induced NG/UFG structure enabled achieving high strength besides comparable ductility, for instance, in metastable austenitic stainless steels. In the phase reversion process, severe deformation of austenite at room temperature (typically ~60–80%) transforms face-centered cubic austenite (γ) to body centered cubic martensite (α′). Upon annealing, martensite reverts to austenite leading to extensive grain refinement. The objective of the present study to fundamentally understand the deformation mechanisms in NG/UFG structure in relation to that of the coarse-grained (CG) structure was accomplished by combining depth-sensing nanoscale experiments on an Fe-16Cr-10Ni model austenitic alloy conducted at different strain rates, followed by the study of structural evolution in the deformed zone using transmission electron microscopy (TEM). In the high strength NG/UFG steel (YS~585 MPa), stacking faults and nanotwins contributed to the enhanced ductility (El~35%), while in the case of low strength (YS~260 MPa) coarse-grained (CG) counterpart, ductility was also high (El~40%), but chiefly due to strain-induced martensite, which points to a clear case of grain size effect (and the corresponding level of strength). The distinct change in the deformation mechanism from stacking faults and twinning-induced plasticity (TWIP) in the NG structure to transformation-induced plasticity (TRIP) in the CG structure is elucidated in terms of austenite stability-strain energy relationship. The insights on the relationship between grain structure (and strength) and deformation mechanisms are envisaged to be important in providing a new direction for the futuristic design of high strength

  3. Evidence for charge-trapping inducing polymorphic structural-phase transition in pentacene.

    Science.gov (United States)

    Ando, Masahiko; Kehoe, Tom B; Yoneya, Makoto; Ishii, Hiroyuki; Kawasaki, Masahiro; Duffy, Claudia M; Minakata, Takashi; Phillips, Richard T; Sirringhaus, Henning

    2015-01-07

    Trapped-charge-induced transformation of pentacene polymorphs is observed by using in situ Raman spectroscopy and molecular dynamics simulations reveal that the charge should be localized in pentacene molecules at the interface with static intermolecular disorder along the long axis. Quantum chemical calculations of the intermolecular transfer integrals suggest the disorder to be large enough to induce Anderson-type localization. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Self-Reports of Induced Abortion

    DEFF Research Database (Denmark)

    Rasch, V; Muhammad, H; Urassa, E

    2000-01-01

    OBJECTIVES: This study estimated the proportion of incomplete abortions that are induced in hospital-based settings in Tanzania. METHODS: A cross-sectional questionnaire study was conducted in 2 phases at 3 hospitals in Tanzania. Phase 1 included 302 patients with a diagnosis of incomplete abortion......, and phase 2 included 823 such patients. RESULTS: In phase 1, in which cases were classified by clinical criteria and information from the patient, 3.9% to 16.1% of the cases were classified as induced abortion. In phase 2, in which the structured interview was changed to an empathetic dialogue...... and previously used clinical criteria were omitted, 30.9% to 60.0% of the cases were classified as induced abortion. CONCLUSIONS: An empathetic dialogue improves the quality of data collected among women with induced abortion....

  5. Structural phase transition and erasable optically memorized effect in layered γ-In2Se3 crystals

    International Nuclear Information System (INIS)

    Ho, Ching-Hwa; Chen, Ying-Cen; Pan, Chia-Chi

    2014-01-01

    We have grown In 2 Se 3 layered-type crystals using chemical vapor transport method with ICl 3 as the transport agent. The as-grown crystals show two different color groups of black shiny for α-phase In 2 Se 3 and red to yellow for γ-phase In 2 Se 3 . High-resolution transmission electron micro scopy verifies crystalline state and structural polytype of the as-grown In 2 Se 3 . The results indicate that the α-In 2 Se 3 crystals present more crystalline states than those of the other amorphous γ-In 2 Se 3 . The amorphous effect on the advancing of optoelectronic property of γ-In 2 Se 3 shows erasable optical-memorized effect in the disordered and polycrystalline γ-In 2 Se 3 layers. Laser-induced photodarkening and annealed-recovery test verified that a reversible structural-phase transition of γ↔α can occur inside the γ-In 2 Se 3 . Thermoreflectance and Raman scattering measurements are carried out to identify the inter-phase transformation of the γ-In 2 Se 3 polycrystals using different heat treatments. Direct band gaps and Raman vibration modes for the γ- and α-In 2 Se 3 crystalline phases are, respectively, characterized and identified. The character of γ↔α inter-phase transition promotes feasible optical and optoelectronic applications of the γ-In 2 Se 3 material in optical memory, optics, and solar-energy devices

  6. Structural phase transition and erasable optically memorized effect in layered γ-In2Se3 crystals

    Science.gov (United States)

    Ho, Ching-Hwa; Chen, Ying-Cen; Pan, Chia-Chi

    2014-01-01

    We have grown In2Se3 layered-type crystals using chemical vapor transport method with ICl3 as the transport agent. The as-grown crystals show two different color groups of black shiny for α-phase In2Se3 and red to yellow for γ-phase In2Se3. High-resolution transmission electron micro scopy verifies crystalline state and structural polytype of the as-grown In2Se3. The results indicate that the α-In2Se3 crystals present more crystalline states than those of the other amorphous γ-In2Se3. The amorphous effect on the advancing of optoelectronic property of γ-In2Se3 shows erasable optical-memorized effect in the disordered and polycrystalline γ-In2Se3 layers. Laser-induced photodarkening and annealed-recovery test verified that a reversible structural-phase transition of γ↔α can occur inside the γ-In2Se3. Thermoreflectance and Raman scattering measurements are carried out to identify the inter-phase transformation of the γ-In2Se3 polycrystals using different heat treatments. Direct band gaps and Raman vibration modes for the γ- and α-In2Se3 crystalline phases are, respectively, characterized and identified. The character of γ↔α inter-phase transition promotes feasible optical and optoelectronic applications of the γ-In2Se3 material in optical memory, optics, and solar-energy devices.

  7. Specific Features of Structural-Phase State and Properties of Reactor Pressure Vessel Steel at Elevated Irradiation Temperature

    Directory of Open Access Journals (Sweden)

    E. A. Kuleshova

    2017-01-01

    Full Text Available This paper considers influence of elevated irradiation temperature on structure and properties of 15Kh2NMFAA reactor pressure vessel (RPV steel. The steel is investigated after accelerated irradiation at 300°C (operating temperature of VVER-1000-type RPV and 400°C supposed to be the operating temperature of advanced RPVs. Irradiation at 300°C leads to formation of radiation-induced precipitates and radiation defects-dislocation loops, while no carbide phase transformation is observed. Irradiation at a higher temperature (400°C neither causes formation of radiation-induced precipitates nor provides formation of dislocation loops, but it does increase the number density of the main initial hardening phase—of the carbonitrides. Increase of phosphorus concentration in grain boundaries is more pronounced for irradiation at 400°C as compared to irradiation at 300°C due to influence of thermally enhanced diffusion at a higher temperature. The structural-phase changes determine the changes of mechanical properties: at both irradiation temperatures irradiation embrittlement is mainly due to the hardening mechanism with some contribution of the nonhardening one for irradiation at 400°C. Lack of formation of radiation-induced precipitates at T = 400°C provides a small ΔTK shift (17°C. The obtained results demonstrate that the investigated 15Kh2NMFAA steel may be a promising material for advanced reactors with an elevated operating temperature.

  8. Multiple pathways in pressure-induced phase transition of coesite

    Science.gov (United States)

    Liu, Wei; Wu, Xuebang; Liu, Changsong; Miranda, Caetano R.; Scandolo, Sandro

    2017-01-01

    High-pressure single-crystal X-ray diffraction method with precise control of hydrostatic conditions, typically with helium or neon as the pressure-transmitting medium, has significantly changed our view on what happens with low-density silica phases under pressure. Coesite is a prototype material for pressure-induced amorphization. However, it was found to transform into a high-pressure octahedral (HPO) phase, or coesite-II and coesite-III. Given that the pressure is believed to be hydrostatic in two recent experiments, the different transformation pathways are striking. Based on molecular dynamic simulations with an ab initio parameterized potential, we reproduced all of the above experiments in three transformation pathways, including the one leading to an HPO phase. This octahedral phase has an oxygen hcp sublattice featuring 2 × 2 zigzag octahedral edge-sharing chains, however with some broken points (i.e., point defects). It transforms into α-PbO2 phase when it is relaxed under further compression. We show that the HPO phase forms through a continuous rearrangement of the oxygen sublattice toward hcp arrangement. The high-pressure amorphous phases can be described by an fcc and hcp sublattice mixture. PMID:29162690

  9. Ultrafast Hot Electron Induced Phase Transitions in Vanadium Dioxide

    Directory of Open Access Journals (Sweden)

    Haglund R. F.

    2013-03-01

    Full Text Available The Au/Cr/VO2/Si system was investigated in pump–probe experiments. Hot-electrons generated in the Au were found to penetrate into the underlying VO2 and couple with its lattice inducing a semiconductor-to-metal phase transition in ~2 picoseconds.

  10. Photo-induced optical activity in phase-change memory materials.

    Science.gov (United States)

    Borisenko, Konstantin B; Shanmugam, Janaki; Williams, Benjamin A O; Ewart, Paul; Gholipour, Behrad; Hewak, Daniel W; Hussain, Rohanah; Jávorfi, Tamás; Siligardi, Giuliano; Kirkland, Angus I

    2015-03-05

    We demonstrate that optical activity in amorphous isotropic thin films of pure Ge2Sb2Te5 and N-doped Ge2Sb2Te5N phase-change memory materials can be induced using rapid photo crystallisation with circularly polarised laser light. The new anisotropic phase transition has been confirmed by circular dichroism measurements. This opens up the possibility of controlled induction of optical activity at the nanosecond time scale for exploitation in a new generation of high-density optical memory, fast chiroptical switches and chiral metamaterials.

  11. Suppression of nanoindentation-induced phase transformation in crystalline silicon implanted with hydrogen

    Science.gov (United States)

    Jelenković, Emil V.; To, Suet

    2017-09-01

    In this paper the effect of hydrogen implantation in silicon on nanoindentation-induced phase transformation is investigated. Hydrogen ions were implanted in silicon through 300 nm thick oxide with double energy implantation (75 and 40 keV). For both energies implantation dose was 4 × 1016 cm-2. Some samples were thermally annealed at 400 °C. The micro-Raman spectroscopy was applied on nanoindentation imprints and the obtained results were related to the pop out/elbow appearances in nanoindentatioin unloading-displacement curves. The Raman spectroscopy revealed a suppression of Si-XII and Si-III phases and formation of a-Si in the indents of hydrogen implanted Si. The high-resolution x-ray diffraction measurements were taken to support the analysis of silicon phase formation during nanoindentation. Implantation induced strain, high hydrogen concentration, and platelets generation were found to be the factors that control suppression of c-Si phases Si-XII and Si-III, as well as a-Si phase enhancement during nanoindentation. [Figure not available: see fulltext.

  12. Visualization of Two-Phase Fluid Distribution Using Laser Induced Exciplex Fluorescence

    Science.gov (United States)

    Kim, J. U.; Darrow, J.; Schock, H.; Golding, B.; Nocera, D.; Keller, P.

    1998-03-01

    Laser-induced exciplex (excited state complex) fluorescence has been used to generate two-dimensional images of dispersed liquid and vapor phases with spectrally resolved two-color emissions. In this method, the vapor phase is tagged by the monomer fluorescence while the liquid phase is tracked by the exciplex fluorescence. A new exciplex visualization system consisting of DMA and 1,4,6-TMN in an isooctane solvent was developed.(J.U. Kim et al., Chem. Phys. Lett. 267, 323-328 (1997)) The direct ca

  13. Ion irradiation induced order-to-disorder transformations in δ-phase Sc4-xZr3+xO12+x/2

    International Nuclear Information System (INIS)

    Zhang, J.; Wang, Y.Q.; Tang, M.; Valdez, J.A.; Sickafus, K.E.

    2010-01-01

    The purpose of this study is to investigate the role of stoichiometry on crystal structure transformations in derivative fluorite compounds known as delta (δ) phase. In this study, polycrystalline δ-phase ceramic pellets were prepared with stoichiometries given by Sc 4-x Zr 3+x O 12+x/2 (x = 0, 0.77 and 1.20) . The pressed and polished pellets were then irradiated under cryogenic conditions with 200 keV Ne + ions to fluences ranging from 1-5 x 10 14 Ne/cm 2 . An order-to-disorder (O-D) transformation was observed for all compositions, as determined using grazing incidence X-ray diffraction (GIXRD). However, the transformation threshold dose was found to systematically decrease with increasing ZrO 2 content: ∼0.2, ∼0.16, and ∼0.08 dpa for Sc 4-x Zr 3+x O 12+x/2 with x = 0, 0.77, and 1.20, respectively. These irradiation-induced phase transformation results are discussed in terms of the crystal structure of the δ-phase.

  14. Phase-Field Simulations of Topological Structures and Topological Phase Transitions in Ferroelectric Oxide Heterostructures

    Science.gov (United States)

    Zijian Hong

    Ferroelectrics are materials that exhibit spontaneous electric polarization which can be switched between energy-degenerated states by external stimuli (e.g., mechanical force and electric field) that exceeds a critical value. They have wide potential applications in memories, capacitors, piezoelectric and pyroelectric sensors, and nanomechanical systems. Topological structures and topological phase transitions have been introduced to the condensed matter physics in the past few decades and have attracted broad attentions in various disciplines due to the rich physical insights and broad potential applications. Ferromagnetic topological structures such as vortex and skyrmion are known to be stabilized by the antisymmetric chiral interaction (e.g., Dzyaloshinskii-Moriya interaction). Without such interaction, ferroelectric topological structures (i.e., vortex, flux-closure, skyrmions, and merons) have been studied only recently with other designing strategies, such as reducing the dimension of the ferroelectrics. The overarching goal of this dissertation is to investigate the topological structures in ferroelectric oxide perovskites as well as the topological phase transitions under external applied forces. Pb(Zr,Ti)O3 (PZT) with morphotropic phase boundary is widely explored for high piezoelectric and dielectric properties. The domain structure of PZT tetragonal/rhombohedral (T/R) bilayer is investigated. Strong interfacial coupling is shown, with large polarization rotation to a lower symmetry phase near the T/R interface. Interlayer domain growth can also be captured, with T-domains in the R layer and R-domains in the T layer. For thin PZT bilayer with 5nm of T-layer and 20 nm of R-layer, the a1/a 2 twin domain structure is formed in the top T layer, which could be fully switched to R domains under applied bias. While a unique flux-closure pattern is observed both theoretically and experimentally in the thick bilayer film with 50 nm of thickness for both T and R

  15. Traveling wave accelerating structures with a large phase advance

    International Nuclear Information System (INIS)

    Paramonov, V.V.

    2012-01-01

    The cells RF parameters for the well known Disk Loaded Waveguide (DLW) are considered in higher pass bands of TM01 wave, providing operating phase advance between 180 o - 1230 o per cell. With an appropriate shape optimization and some additional elements proposed traveling wave structures with such large phase advance overlap the classical first band DLW in RF efficiency. Examples of proposed structures together with RF and dispersion properties are presented.

  16. Non-destructive visualization of linear explosive-induced Pyroshock using phase arrayed laser-induced shock in a space launcher composite

    International Nuclear Information System (INIS)

    Jang, Jae Kyeong; Lee, Jung Ryul

    2015-01-01

    Separation mechanism of Space launch vehicles are used in various separation systems and pyrotechnic devices. The operation of these pyrotechnic devices generates Pyroshock that can cause failures in electronic components. The prediction of high frequency structural response, especially the shock response spectrum (SRS), is important. This paper presents a non-destructive visualization and simulation of linear explosive-induced Pyroshock using phase arrayed Laser-induced shock. The proposed method includes a laser shock test based on laser beam and filtering zone conditioning to predict the SRS of Pyroshock. A ballistic test based on linear explosive and non-contact Laser Doppler Vibrometers and a nondestructive Laser shock measurement using laser excitation and several PZT sensors, are performed using a carbon composite sandwich panel. The similarity of the SRS of the conditioned laser shock to that of the real explosive Pyroshock is evaluated with the Mean Acceleration Difference. The average of MADs over the two training points was 33.64%. And, MAD at verification point was improved to 31.99%. After that, experimentally found optimal conditions are applied to any arbitrary points in laser scanning area. Finally, it is shown that linear explosive-induced real Pyroshock wave propagation can be visualized with high similarity based on the proposed laser technology. (paper)

  17. Shape Memory Alloy-Based Periodic Cellular Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I effort will develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular structures...

  18. X-ray diffraction and molecular-dynamics studies: Structural analysis of phases in diglyceride monolayers

    DEFF Research Database (Denmark)

    Peters, Günther H.J.; Larsen, Niels Bent; Bjørnholm, T.

    1998-01-01

    We report a detailed structural analysis of the phases of 1,2-sn-dipalmitoylglycerol Langmuir monolayers at room temperature. Pressure-induced transitions have been investigated by combination of molecular-dynamics simulations and grazing-incidence x-ray diffraction (XRD). The diglyceride film...... undergoes two phase transitions occurring at 38.3 and 39.8 Angstrom(2)/molecule. Simulation indicates that the first transition involves a reorientation of the headgroups while simulation and XRD show that in the second transition the order parameter is the tilt angle of the alkyl chains. A methodology......; At the lowest pressure the tilt angle reaches approximate to 14 degrees in a direction close to a nearest neighbor direction. Both arrangements of the alkyl chains are confirmed by XRD. For higher order and fractional order Bragg peaks, simulations predict higher intensities than observed with XRD. This may...

  19. Radiation-induced trioxane postpolymerization in the liquid phase

    International Nuclear Information System (INIS)

    Kapustina, I.B.; Starchenko, T.V.

    1979-01-01

    Radiation-induced trioxane postpolymerization in the presence of maleic anhydride and different solvents in the liquid phase has been studied. It has been found that addition of small quantities of different solvents inhibits the trioxane polymerization process both in the presence of maleic anhydride and in the absence of it. Trioxane postpolymerization in a solvent-nonsolvent mixture gives fibrous polyoxymethylene with high molecular mass and high yield

  20. Structural and electronic properties of high pressure phases of lead chalcogenides

    Science.gov (United States)

    Petersen, John; Scolfaro, Luisa; Myers, Thomas

    2012-10-01

    Lead chalcogenides, most notably PbTe and PbSe, have become an active area of research due to their thermoelectric properties. The high figure of merit (ZT) of these materials has brought much attention to them, due to their ability to convert waste heat into electricity. Variation in synthesis conditions gives rise to a need for analysis of structural and thermoelectric properties of these materials at different pressures. In addition to the NaCl structure at ambient conditions, lead chalcogenides have a dynamic orthorhombic (Pnma) intermediate phase and a higher pressure yet stable CsCl phase. By altering the lattice constant, we simulate the application of external pressure; this has notable effects on ground state total energy, band gap, and structural phase. Using the General Gradient Approximation (GGA) in Density Functional Theory (DFT), we calculate the phase transition pressures by finding the differences in enthalpy from total energy calculations. For each phase, elastic constants, bulk modulus, shear modulus, Young's modulus, and hardness are calculated, using two different approaches. In addition to structural properties, we analyze the band structure and density of states at varying pressures, paying special note to thermoelectric implications.

  1. Phase Structure of Strong-Field Tunneling Wave Packets from Molecules.

    Science.gov (United States)

    Liu, Ming-Ming; Li, Min; Wu, Chengyin; Gong, Qihuang; Staudte, André; Liu, Yunquan

    2016-04-22

    We study the phase structure of the tunneling wave packets from strong-field ionization of molecules and present a molecular quantum-trajectory Monte Carlo model to describe the laser-driven dynamics of photoelectron momentum distributions of molecules. Using our model, we reproduce and explain the alignment-dependent molecular frame photoelectron spectra of strong-field tunneling ionization of N_{2} reported by M. Meckel et al. [Nat. Phys. 10, 594 (2014)]. In addition to modeling the low-energy photoelectron angular distributions quantitatively, we extract the phase structure of strong-field molecular tunneling wave packets, shedding light on its physical origin. The initial phase of the tunneling wave packets at the tunnel exit depends on both the initial transverse momentum distribution and the molecular internuclear distance. We further show that the ionizing molecular orbital has a critical effect on the initial phase of the tunneling wave packets. The phase structure of the photoelectron wave packet is a key ingredient for modeling strong-field molecular photoelectron holography, high-harmonic generation, and molecular orbital imaging.

  2. Flow-Induced Vibration of Circular Cylindrical Structures

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shoei-Sheng [Argonne National Lab. (ANL), Argonne, IL (United States). Components Technology Division

    1985-06-01

    Flow-induced vibration is a term to denote those phenomena associated with the response of structures placed in or conveying fluid flow. More specifically, the terra covers those cases in which an interaction develops between fluid-dynamic forces and the inertia, damping or elastic forces in the structures. The study of these phenomena draws on three disciplines: (1) structural mechanics, (2) mechanical vibration, and (3) fluid dynamics. The vibration of circular cylinders subject to flow has been known to man since ancient times; the vibration of a wire at its natural frequency in response to vortex shedding was known in ancient Greece as aeolian tones. But systematic studies of the problem were not made until a century ago when Strouhal established the relationship between vortex shedding frequency and flow velocity for a given cylinder diameter. The early research in this area has beer summarized by Zdravkovich (1985) and Goldstein (1965). Flow-induced structural vibration has been experienced in numerous fields, including the aerospace industry, power generation/transmission (turbine blades, heat exchanger tubes, nuclear reactor components), civil engineering (bridges, building, smoke stacks), and undersea technology. The problems have usually been encountered or created accidentally through improper design. In most cases, a structural or mechanical component, designed to meet specific objectives, develops problems when the undesired effects of flow field have not been accounted for in the design. When a flow-induced vibration problem is noted in the design stage, the engineer has different options to eliminate the detrimental vibration. Unfortunately, in many situations, the problems occur after the components are already in operation; the "fix" usually is very costly. Flow-induced vibration comprises complex and diverse phenomena; subcritical vibration of nuclear fuel assemblies, galloping of transmission lines, flutter of pipes conveying fluid, and whirling

  3. Influence of heat treatment in β and γ phases on the microscopic structure of uranium

    International Nuclear Information System (INIS)

    Robillard, A.

    1958-01-01

    A new method of microscopic examination of uranium is described. Electrolytic polishing and etching are carried out in an acetic acid-chromic acid bath. Atmospheric or anodic oxidation of the polished surface produces films which follow exactly changes in the structure of the underlying metal. This method is very sensitive to small variations of orientation in polygonized crystals. Using this method of examination of uranium, it was found that annealing U in the γ phase followed by a cooling at a rate dependent of the annealing temperature, causes the formation of substructures different from those due to the polygonization of α-U. The substructures are indicated by the concentration of impurities on the dislocations induced by the stresses accompanying the allotropic transformation γ → β. Similar treatment of the U-1.4% Cr alloy in which the β phase is stabilized at room temperature, confirms this explanation. In addition to the polygonization substructures, sharp discontinuities can be observed in the network of sub- boundaries as a fine white edging. The comparison of these with the structure revealed by thermal etching in vacuum suggest that there are traces of the grain boundaries of the γ phase. The method of etching followed by oxidation shows a haloed phase identified as UH 3 . The conditions of appearance and disappearance of this phase are studied. The sensitivity of this method of detecting the last traces of H in U is very high. The dependence of the hydrogen content on the tensile properties of uranium metal was also studied. (author) [fr

  4. Phase structure of (φ4)3 field theory at finite temperature

    International Nuclear Information System (INIS)

    Efimov, G.V.

    1992-01-01

    Phase structure of φ 4 field theory in the space-time R 3 is investigated at arbitrary coupling constant and temperature. The critical values of the coupling constant and temperature, corresponding to the phase transitions in the system, are calculated by the canonical transformation method within formalism of thermo field dynamics. The Hamiltonians describing the system in each phase are obtained straightforwardly. Comparison with the two-dimensional case shows a crucial influence of higher order renormalization on the phase structure of the model. 13 refs.; 5 figs

  5. Steering Charge Kinetics of Tin Niobate Photocatalysts: Key Roles of Phase Structure and Electronic Structure.

    Science.gov (United States)

    Huang, Shushu; Wang, Chunyan; Sun, Hao; Wang, Xiaojing; Su, Yiguo

    2018-05-23

    Tin niobate photocatalysts with the phase structures of froodite (SnNb 2 O 6 ) and pyrochlore (Sn 2 Nb 2 O 7 ) were obtained by a facile solvothermal method in order to explore the impact of phase structure and electronic structure on the charge kinetics and photocatalytic performance. By employing tin niobate as a model compound, the effects of phase structure over electronic structure, photocatalytic activity toward methyl orange solution and hydrogen evolution were systematically investigated. It is found that the variation of phase structure from SnNb 2 O 6 to Sn 2 Nb 2 O 7 accompanied with modulation of particle size and band edge potentials that has great consequences on photocatalytic performance. In combination with the electrochemical impedance spectroscopy (EIS), transient photocurrent responses, transient absorption spectroscopy (TAS), and the analysis of the charge-carrier dynamics suggested that variation of electronic structure has great impacts on the charge separation and transfer rate of tin niobate photocatalysts and the subsequent photocatalytic performance. Moreover, the results of the X-ray photoelectron spectroscopy (XPS) indicated that the existent of Sn 4+ species in Sn 2 Nb 2 O 7 could result in a decrease in photocatalytic activity. Photocatalytic test demonstrated that the SnNb 2 O 6 (froodite) catalyst possesses a higher photocatalytic activity toward MO degradation and H 2 evolution compared with the sample of Sn 2 Nb 2 O 7 (pyrochlore). On the basis of spin resonance measurement and trapping experiment, it is expected that photogenerated holes, O 2 -• , and OH • active species dominate the photodegradation of methyl orange.

  6. Polyoxyethylene/styrene - a model system for studying reaction-induced phase separation (RIPS)

    International Nuclear Information System (INIS)

    Sutton, D.; Stanford, J.L.; Ryan, A.J.

    2003-01-01

    Full text: Reaction-induced, phase-separation has been studied in polymer blends. A model crystalline-amorphous system consisted of semi-crystalline polyoxyethylene (POE) dissolved in the monomer styrene, which was employed as a reactive solvent to ease processing. When the styrene was polymerised to polystyrene (PS) in the mould, phase-separation and phase-inversion are induced, and a polymer blend was formed. POE was selected with a molar mass, Mn = 8578 g mol -1 and a polydispersity of 1.19 as determined using GPC. The polymerisation of styrene was initiated using 1 wt-% benzoin methyl ether (BME) and 0.2 wt-% 2,2'-azobisisobutyronitrile (AIBN) under ultra-violet (UV) light. The polymerisation kinetics were determined by monitoring the reduction in the intensity of the C=C stretching vibration band at 1631 cm -1 in the Raman spectrum of styrene. The onset times for the liquid-solid (L-S) phase-separation and crystallisation of POE from styrene/PS were observed using simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). Onset times for L-S phase-separation determined from the SAXS data were combined with the styrene polymerisation kinetics to plot the L-S phase-separation data onto a ternary phase diagram for the reactive system POE/styrene/PS at 45 and 50 deg C

  7. Pressure-induced decoupling of the order-disorder and displacive contributions to the phase transition in diguanidinium tetrachlorostannate

    DEFF Research Database (Denmark)

    Szafranski, M.; Ståhl, Kenny

    2000-01-01

    The crystals of diguanidinium tetrachlorostannate [C(NH2)(3)](2)(+).SnCl4-2, were studied by single-crystal x-ray diffraction at various temperatures and by calorimetric and dielectric measurements at ambient and high hydrostatic pressures. At room temperature the crystal structure is orthorhombic......) cations. At ambient pressure the crystals undergo two first-order phase transitions at 354.8 and 395.4 K. The former, between two orthorhombic phases (Pbca --> Cmca), is characterized by antiphase displacement of the double sheets along the b direction of the low-temperature unit cell which is coupled...... to dynamical disordering of G(2) and transformation of its hydrogen bonding scheme. At elevated pressures the coupling between the displacive and order-disorder contributions is modified and its breaking near a triple point at 180 MPa and 270 K results in a pressure-induced phase observed between Pbca and Cmca...

  8. Photostress analysis of stress-induced martensite phase transformation in superelastic NiTi

    International Nuclear Information System (INIS)

    Katanchi, B.; Choupani, N.; Khalil-Allafi, J.; Baghani, M.

    2017-01-01

    Phase transformation in shape memory alloys is the most important factor in their unique behavior. In this paper, the formation of stress induced martensite phase transformation in a superelastic NiTi (50.8% Ni) shape memory alloy was investigated by using the photo-stress method. First, the material's fabrication procedure has been described and then the material was studied using the metallurgical tests such as differential scanning calorimetry and X-ray diffraction to characterize the material features and the mechanical tensile test to investigate the superelastic behavior. As a new method in observation of the phase transformation, photo-stress pictures showed the formation of stress induced martensite in a superelastic dog-bone specimen during loading and subsequently it's disappearing during unloading. Finally, finite element analysis was implemented using the constitutive equations derived based on the Boyd-Lagoudas phenomenological model.

  9. Photostress analysis of stress-induced martensite phase transformation in superelastic NiTi

    Energy Technology Data Exchange (ETDEWEB)

    Katanchi, B. [Mechanical Engineering Faculty, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Choupani, N., E-mail: choupani@sut.ac.ir [Mechanical Engineering Faculty, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Khalil-Allafi, J. [Research Center for Advance Materials, Faculty of Materials Engineering, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Baghani, M. [School of Mechanical Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of)

    2017-03-14

    Phase transformation in shape memory alloys is the most important factor in their unique behavior. In this paper, the formation of stress induced martensite phase transformation in a superelastic NiTi (50.8% Ni) shape memory alloy was investigated by using the photo-stress method. First, the material's fabrication procedure has been described and then the material was studied using the metallurgical tests such as differential scanning calorimetry and X-ray diffraction to characterize the material features and the mechanical tensile test to investigate the superelastic behavior. As a new method in observation of the phase transformation, photo-stress pictures showed the formation of stress induced martensite in a superelastic dog-bone specimen during loading and subsequently it's disappearing during unloading. Finally, finite element analysis was implemented using the constitutive equations derived based on the Boyd-Lagoudas phenomenological model.

  10. Atomic structure of a decagonal Al-Pd-Mn phase

    Science.gov (United States)

    Mihalkovič, Marek; Roth, Johannes; Trebin, Hans-Rainer

    2017-12-01

    We present a detailed structure solution for the 16 -Å decagonal quasicrystal in the Al-Pd-Mn system by means of cluster decoration and ab initio energy minimization. It is based on structure models of the ɛ and other approximant phases. The ɛ phases can be represented as subsets of a hexagon-boat-star (HBS) tiling. The decagonal phase comprises further HBS tiles. We have constructed several fictitious HBS approximants and optimized their structures individually. All tiles are decorated by two types of atomic clusters: the pseudo-Mackay icosahedron (PMI) and the large bicapped pentagonal prism (LBPP). It turns out that, whereas the PMI clusters can be kept essentially unchanged, the LBPP clusters must be adjusted in occupancy with Al atoms depending on their positions in the various tiles. In this way we obtain cluster decorations for all tiles of the decagonal quasicrystal. The calculations were confirmed by evaluation of an effective tile Hamiltonian.

  11. Pressure induced phase transition in HfTiO4

    International Nuclear Information System (INIS)

    Mishra, A.K.; Garg, Nandini; Sharma, Surinder M.; Panneerselvam, G.

    2012-01-01

    Hafnium titanate is a low thermal expansion ceramic with a very good absorption cross section for thermal neutrons and a high refractoriness, thus making it a desirable nuclear material. At ambient conditions it crystallizes with the orthorhombic structure (space group Pbcn). The material properties of this ceramic have been studied as a function of temperature. However, apart from a lone shock study several decades ago there is no study at static high pressure on this compound. Since this ceramic is used as control rods in nuclear reactors it is important to understand its phase stability at different thermodynamic conditions. Therefore to understand the high pressure behaviour of hafnium titanate we have carried out diamond anvil cell based X-ray diffraction studies up to ∼20 GPa. The studies on this ceramic show that its structure is stable till 11 GPa. However, at ∼11.7 GPa appearance of new diffraction peaks indicate that it undergoes a structural phase transition to a low symmetry structure

  12. Modeling quiescent phase transport of air bubbles induced by breaking waves

    Science.gov (United States)

    Shi, Fengyan; Kirby, James T.; Ma, Gangfeng

    Simultaneous modeling of both the acoustic phase and quiescent phase of breaking wave-induced air bubbles involves a large range of length scales from microns to meters and time scales from milliseconds to seconds, and thus is computational unaffordable in a surfzone-scale computational domain. In this study, we use an air bubble entrainment formula in a two-fluid model to predict air bubble evolution in the quiescent phase in a breaking wave event. The breaking wave-induced air bubble entrainment is formulated by connecting the shear production at the air-water interface and the bubble number intensity with a certain bubble size spectra observed in laboratory experiments. A two-fluid model is developed based on the partial differential equations of the gas-liquid mixture phase and the continuum bubble phase, which has multiple size bubble groups representing a polydisperse bubble population. An enhanced 2-DV VOF (Volume of Fluid) model with a k - ɛ turbulence closure is used to model the mixture phase. The bubble phase is governed by the advection-diffusion equations of the gas molar concentration and bubble intensity for groups of bubbles with different sizes. The model is used to simulate air bubble plumes measured in laboratory experiments. Numerical results indicate that, with an appropriate parameter in the air entrainment formula, the model is able to predict the main features of bubbly flows as evidenced by reasonable agreement with measured void fraction. Bubbles larger than an intermediate radius of O(1 mm) make a major contribution to void fraction in the near-crest region. Smaller bubbles tend to penetrate deeper and stay longer in the water column, resulting in significant contribution to the cross-sectional area of the bubble cloud. An underprediction of void fraction is found at the beginning of wave breaking when large air pockets take place. The core region of high void fraction predicted by the model is dislocated due to use of the shear

  13. Swift heavy ion induced phase transformation and thermoluminescence properties of zirconium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Lokesha, H.S. [Physics R & D Centre, PES Institute of Technology, BSK 3rd Stage, Bangalore 560085 (India); Nagabhushana, K.R., E-mail: bhushankr@gmail.com [Physics R & D Centre, PES Institute of Technology, BSK 3rd Stage, Bangalore 560085 (India); Department of Physics, PES University, BSK 3rd Stage, Bangalore 560085 (India); Singh, Fouran [Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110 067 (India)

    2016-07-15

    Zirconium oxide (ZrO{sub 2}) powder is synthesized by combustion technique. XRD pattern of ZrO{sub 2} shows monoclinic phase with average crystallite size 35 nm. Pellets of ZrO{sub 2} are irradiated with 100 MeV swift Si{sup 7+}, Ni{sup 7+} and 120 MeV swift Ag{sup 9+} ions in the fluence range 3 × 10{sup 10}–3 × 10{sup 13} ions cm{sup −2}. XRD pattern show the main diffraction peak correspond to monoclinic and tetragonal phase of ZrO{sub 2} in 2θ range 27–33°. Structural phase transformation is observed for Ni{sup 7+} and Ag{sup 9+} ion irradiated samples at a fluence 1 × 10{sup 13} ions cm{sup −2} and 3 × 10{sup 12} ions cm{sup −2} respectively, since the deposited electronic energy loss exceeds an effective threshold (>12 keV nm{sup −1}). Phase transition induced by Ag{sup 9+} ion is nearly 2.9 times faster than Ni{sup 7+} ion at 1 × 10{sup 13} ions cm{sup −2}. Ag{sup 9+} ion irradiation leads two ion impact processes. Thermoluminescence (TL) glow curves exhibit two glows, a well resolved peak at ∼424 K and unresolved peak at 550 K for all SHI irradiated samples. TL response is decreased with increase of ion fluence. Beyond 3 × 10{sup 12} ions cm{sup −2}, samples don’t exhibit TL due to annihilation of defects.

  14. Low-temperature structural phase transition in deuterated and protonated lithium acetate dihydrate

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, F., E-mail: schroeder@kristall.uni-frankfurt.d [Goethe-Universitaet Frankfurt am Main, Institut fuer Geowissenschaften, Abt. Kristallographie, Altenhoeferallee 1, 60438 Frankfurt am Main (Germany); Winkler, B.; Haussuehl, E. [Goethe-Universitaet Frankfurt am Main, Institut fuer Geowissenschaften, Abt. Kristallographie, Altenhoeferallee 1, 60438 Frankfurt am Main (Germany); Cong, P.T.; Wolf, B. [Goethe-Universitaet Frankfurt am Main, Physikalisches Institut, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main (Germany); Avalos-Borja, M. [Instituto Potosino de Investigacion Cientifica y Tecnologica, A.C. Camino a la Presa San Jose 2055, Col. Lomas 4 seccion CP 78216, San Luis Potosi (Mexico); Quilichini, M.; Hennion, B. [Laboratoire Leon Brillouin, CEN Saclay, 91191 Gif-sur-Yvette (France)

    2010-08-15

    Heat capacity measurements of protonated lithium acetate dihydrate show a structural phase transition at T = 12 K. This finding is in contrast to earlier work, where it was thought that only the deuterated compound undergoes a low temperature structural phase transition. This finding is confirmed by low temperature ultrasound spectroscopy, where the structural phase transition is associated with a velocity decrease of the ultrasonic waves, i.e. with an elastic softening. We compare the thermodynamic properties of the protonated and deuterated compounds and discuss two alternatives for the mechanism of the phase transition based on the thermal expansion measurements.

  15. Structural formation of aluminide phases on titanium alloy during annealing

    International Nuclear Information System (INIS)

    Mamaeva, A.A.; Romankov, S.E.; Sagdoldina, Zh.

    2006-01-01

    Full text: The aluminum layer on the surface of titanium alloy has been formed by thermal deposition. The structural formation of aluminide phases on the surface has been studied. The sequence of structural transformations at the Ti/Al interface is limited by the reaction temperature and time. The sequence of aluminide phase formation is occurred in compliance with Ti-Al equilibrium phase diagram. At the initial stages at the Ti/Al interface the Al3Ti alloy starts forming as a result of interdiffusion, and gradually the whole aluminum films is spent on the formation of this layer. The Al3Ti layer decomposes with the increase of temperature (>600C). At 800C the two-phase (Ti3Al+TiAl) layer is formed on the titanium surface. The TiAl compound is unstable and later on with the increase of the exposure time at 800C gradually transforms into the Ti3Al. The chain of these successive transformations leads to the formation of the continuous homogeneous layer consisting of the Ti3Al compound on the surface. At temperatures exceeding the allotropic transformation temperature (>900C) the Ti3Al compound starts decomposing. All structural changes taking place at the Ti/Al interface are accompanied by considerable changes in micro hardness. The structure of initial substrate influences on kinetics of phase transformation and microstructure development. (author)

  16. Microstructure and structural phase transitions in iron-based superconductors

    International Nuclear Information System (INIS)

    Wang Zhen; Cai Yao; Yang Huai-Xin; Tian Huan-Fang; Wang Zhi-Wei; Ma Chao; Chen Zhen; Li Jian-Qi

    2013-01-01

    Crystal structures and microstructural features, such as structural phase transitions, defect structures, and chemical and structural inhomogeneities, are known to have profound effects on the physical properties of superconducting materials. Recently, many studies on the structural properties of Fe-based high-T c superconductors have been published. This review article will mainly focus on the typical microstructural features in samples that have been well characterized by physical measurements. (i) Certain common structural features are discussed, in particular, the crystal structural features for different superconducting families, the local structural distortions in the Fe 2 Pn 2 (Pn = P As, Sb) or Fe 2 Ch 2 (Ch = S, Se, Te) blocks, and the structural transformations in the 122 system. (ii) In FeTe(Se) (11 family), the superconductivity, chemical and structural inhomogeneities are investigated and discussed in correlation with superconductivity. (iii) In the K 0.8 Fe 1.6+x Se 2 system, we focus on the typical compounds with emphasis on the Fe-vacancy order and phase separations. The microstructural features in other superconducting materials are also briefly discussed. (topical review - iron-based high temperature superconductors)

  17. Microstructure processes induced by phase transitions in a CuAu alloy as studied by acoustic emission and optical cinematography

    Energy Technology Data Exchange (ETDEWEB)

    Masek, P.; Chmelik, F.; Sima, V. [Charles Univ., Prague (Czech Republic). Dept. of Metal Physics; Brinck, A.; Neuhaeuser, H. [Technische Univ. Braunschweig (Germany). Inst. fuer Metallphysik und Nukleare Festkoerperphysik

    1999-01-15

    Combined acoustic emission measurements and surface cinematography observations have been applied to determine the structure evolution during thermal loading of the CuAu alloy. Thermal history and the fashion of thermal loading have been shown to affect considerably the structure response of the CuAu alloy on temperature changes. On thermal loading, intense plastic deformation occurs in certain temperature intervals due to the relaxation of internal stresses induced by phase transitions and structure anisotropy. The main mechanism is twinning taking place most probably in (110) planes. Dislocation glide and grain-boundary sliding have also been observed as minor mechanisms. A shape-restoration effect associated with the order-disorder transition is revealed. Thermal cycling with upper temperatures over 500 C may also result in structural damage.

  18. High-pressure Raman and optical absorption studies on lead pyroniobate (Pb2Nb2O7) and pressure-induced phase transitions

    International Nuclear Information System (INIS)

    Jayaraman, A.; Kourouklis, G.A.; Cooper, A.S.; Espinosa, G.P.

    1990-01-01

    High-pressure Raman scattering and optical absorption studies have been carried out on lead pyroniobate (Pb 2 Nb 2 O 7 ) up to 33 GPa, using a gasketed diamond anvil cell. The Raman study reveals the occurrence of two, possibly three, pressure-induced phase changes; a rather subtle change is indicated near 4.5 GPa. The transition near 13 GPa is attributed to a structural transition from the rhombohedral to the cubic pyrochlore structure. The third phase change occurs near 20 GPa. From the broad Raman feature that is observed at about 800 cm -1 , it is concluded that the system turns amorphous at pressures above 20 GPa. The amorphous phase recrystallizes to the original rhombohedral phase, on release of pressure. The broad Raman peaks of the recrystallized phase indicate a high degree of disorder in the material. Lead pyroniobate turns deep red near 30 GPa, from light yellow at ambient pressure. Semi quantitative absorption measurements show that the energy gap shifts red at a rate of 30 meV/GPa. This shift is attributed to the downward motion of the 5d (es) conduction band of Pb

  19. Comprehensive Peptide Ion Structure Studies Using Ion Mobility Techniques: Part 3. Relating Solution-Phase to Gas-Phase Structures.

    Science.gov (United States)

    Kondalaji, Samaneh Ghassabi; Khakinejad, Mahdiar; Valentine, Stephen J

    2018-06-01

    Molecular dynamics (MD) simulations have been utilized to study peptide ion conformer establishment during the electrospray process. An explicit water model is used for nanodroplets containing a model peptide and hydronium ions. Simulations are conducted at 300 K for two different peptide ion charge configurations and for droplets containing varying numbers of hydronium ions. For all conditions, modeling has been performed until production of the gas-phase ions and the resultant conformers have been compared to proposed gas-phase structures. The latter species were obtained from previous studies in which in silico candidate structures were filtered according to ion mobility and hydrogen-deuterium exchange (HDX) reactivity matches. Results from the present study present three key findings namely (1) the evidence from ion production modeling supports previous structure refinement studies based on mobility and HDX reactivity matching, (2) the modeling of the electrospray process is significantly improved by utilizing initial droplets existing below but close to the calculated Rayleigh limit, and (3) peptide ions in the nanodroplets sample significantly different conformers than those in the bulk solution due to altered physicochemical properties of the solvent. Graphical Abstract ᅟ.

  20. Photo-induced phase transition: from where it comes and to where it goes?

    International Nuclear Information System (INIS)

    Koshihara, Shin-ya

    2005-01-01

    It is an attractive target for materials science to find a system which shows the phase transition triggered by external stimulation of light. The purpose of our study is to review experimental evidences indicating that the photo-injected local excitation can really trigger the cooperative phenomena in solids. In this sense, this unique photo-induced effect can be named as photo-induced phase transition (PIPT). Here, I will also make brief review on the experimental research on PIPT combining with a development of ultra-fast quantum electronics technology

  1. Structural Design Optimization On Thermally Induced Vibration

    International Nuclear Information System (INIS)

    Gu, Yuanxian; Chen, Biaosong; Zhang, Hongwu; Zhao, Guozhong

    2002-01-01

    The numerical method of design optimization for structural thermally induced vibration is originally studied in this paper and implemented in application software JIFEX. The direct and adjoint methods of sensitivity analysis for thermal induced vibration coupled with both linear and nonlinear transient heat conduction is firstly proposed. Based on the finite element method, the structural linear dynamics is treated simultaneously with coupled linear and nonlinear transient heat structural linear dynamics is treated simultaneously with coupled linear and nonlinear transient heat conduction. In the thermal analysis model, the nonlinear heat conduction considered is result from the radiation and temperature-dependent materials. The sensitivity analysis of transient linear and nonlinear heat conduction is performed with the precise time integration method. And then, the sensitivity analysis of structural transient dynamics is performed by the Newmark method. Both the direct method and the adjoint method are employed to derive the sensitivity equations of thermal vibration, and there are two adjoint vectors of structure and heat conduction respectively. The coupling effect of heat conduction on thermal vibration in the sensitivity analysis is particularly investigated. With coupling sensitivity analysis, the optimization model is constructed and solved by the sequential linear programming or sequential quadratic programming algorithm. The methods proposed have been implemented in the application software JIFEX of structural design optimization, and numerical examples are given to illustrate the methods and usage of structural design optimization on thermally induced vibration

  2. Structure-phase transformations in 36NXTYu highly deformed alloy during aging

    International Nuclear Information System (INIS)

    Plotnikov, S.V.; Radashin, M.V.; Alontseva, D.L.

    2001-01-01

    The 36NXTYu alloy - containing 35.39% Ni, 12.43% Cr, 3.08% Ti, 1.22% Al, 0.93% Mn, 0.36% Si, 0.09% Cu , 0.03% C, 0.12% P, 0.09% S and the rest iron - has been examined. Under aging beginning in the alloy the Ni 3 (Al,Yi) type metastable γ'-phase release of with L12 structure is taking place, and then the stable η-phase (Ni 3 Ti, DO 24 ) is occurring. The thin foils structure and micro-diffraction analysis were observed with help of the electron microscope. Fractography has been watched on the scanning electron microscope. For study both phase content and samples texture the DRON-3 diffractometer was applied. The mechanical testing include one-axis static expansion with measurement of a strength limit, conventional fluidity limit, relational extension up to sample breakage. It is shown, that rolling deep levels in the 36NXTYu alloy, in the common case, do not change the structure-phase transformation morphology, but instead of γ'-phase the η-phase is discretely releasing

  3. Silk fibroin gelation via non-solvent induced phase separation

    Czech Academy of Sciences Publication Activity Database

    Kasoju, Naresh; Hawkins, N.; Pop-Georgievski, Ognen; Kubies, Dana; Vollrath, F.

    2016-01-01

    Roč. 4, č. 3 (2016), s. 460-473 ISSN 2047-4830 R&D Projects: GA MŠk(CZ) EE2.3.30.0029; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 Keywords : silk fibroin * non-solvent induced phase separation * desolvation Subject RIV: CE - Biochemistry Impact factor: 4.210, year: 2016

  4. UPS and DFT investigation of the electronic structure of gas-phase trimesic acid

    Energy Technology Data Exchange (ETDEWEB)

    Reisberg, L., E-mail: rebban@ut.ee [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); Pärna, R. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); MAX IV Laboratory, Lund University, Fotongatan 2, 225 94 Lund (Sweden); Kikas, A.; Kuusik, I.; Kisand, V. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); Hirsimäki, M.; Valden, M. [Surface Science Laboratory, Optoelectronics Research Centre, Tampere University of Technology, FIN-33101 Tampere (Finland); Nõmmiste, E. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia)

    2016-11-15

    Highlights: • In the current study outer valence band electronic structure of benzene-1,3,5-tricarboxylic acid was interpreted. • Experimental and calculated trimesic acid (TMA) spectrum were compared to ones of benzene and benzoic acid. • It is shown that similarities between MO energies and shapes for benzene and TMA exists. • Addition of carboxyl groups to the benzene ring clearly correlates with increasing binding energy of HOMO. - Abstract: Benzene-1,3,5-tricarboxylic acid (trimesic acid, TMA) molecules in gas-phase have been investigated by using valence band photoemission. The photoelectron spectrum in the binding energy region from 9 to 22 eV is interpreted by using density functional theory calculations. The electronic structure of TMA is compared with benzene and benzoic acid in order to demonstrate changes in molecular orbital energies induced by addition of carboxyl groups to benzene ring.

  5. Phase coexistence in ferroelectric solid solutions: Formation of monoclinic phase with enhanced piezoelectricity

    Directory of Open Access Journals (Sweden)

    Xiaoyan Lu

    2016-10-01

    Full Text Available Phase morphology and corresponding piezoelectricity in ferroelectric solid solutions were studied by using a phenomenological theory with the consideration of phase coexistence. Results have shown that phases with similar energy potentials can coexist, thus induce interfacial stresses which lead to the formation of adaptive monoclinic phases. A new tetragonal-like monoclinic to rhombohedral-like monoclinic phase transition was predicted in a shear stress state. Enhanced piezoelectricity can be achieved by manipulating the stress state close to a critical stress field. Phase coexistence is universal in ferroelectric solid solutions and may provide a way to optimize ultra-fine structures and proper stress states to achieve ultrahigh piezoelectricity.

  6. Protein and Peptide Gas-phase Structure Investigation Using Collision Cross Section Measurements and Hydrogen Deuterium Exchange

    Science.gov (United States)

    Khakinejad, Mahdiar

    measurements and gas-phase HDX studies at the amino acid residue level, for the first time a drift tube is connected to a linear ion trap (LIT) with electron transfer dissociation (ETD) capability[19, 20]. In this manner CCS and per-residue deuterium uptake measurements for a model peptide carried out successfully[19]. In this study, the gas-phase conformations of electrosprayed ions of the model peptide KKDDDDIIKIIK have been examined. Using ion structures obtained from molecular dynamics (MD) simulation and considering charge-site/exchange-site density the level of the maximum total deuterium uptake for the gas-phase ions is explained. Also a new hydrogen accessibility scoring (HAS) model that includes two distance calculations (charge site to carbonyl group and carbonyl group to exchange site) is applied to the in-silico structures to describe the expected HDX behavior for these structures. Further investigation to improve the accuracy of the model is accomplished by a "per-residue" HDX kinetics study of the model peptide [21]. In this study, the ion residence time and the deuterium uptake of each residue is measured at different partial pressures of D2O. Subsequently the contribution each residue to the overall HDX rate of the intact peptide ion is calculated. These rate contributions of the residues exhibit a better fit to HAS than their maximum deuterium uptake. Proteins and peptides with very frequent acidic residue in their sequence provide very poor signal levels when employing positive polarity ESI. Also, the comparison of protonated and deprotonated ions of these biomolecules offers the potential to provide a better structural characterization [22]. Per-residue deuterium uptake values resulting from collision-induced dissociation (CID) of the model peptide KKDDDDIIKIIK were used to investigated the degree of hydrogen deuterium scrambling for deprotonated ions [23]. Remarkably, limited isotopic scrambling was observed in this study of this small model peptide. This

  7. Phases stability of shape memory alloys Cu based under irradiation

    International Nuclear Information System (INIS)

    Zelaya, Maria Eugenia

    2006-01-01

    The effects of irradiation on the relative phase stability of phases related by a martensitic transformation in copper based shape memory alloys were studied in this work.Different kind of particles and energies were employed in the irradiation experiments.The first kind of irradiation was performed with 2,6 MeV electrons, the second one with 170 keV and 300 keV Cu ions and the third one with swift heavy ions (Kr, Xe, Au) with energies between 200 and 600 MeV.Stabilization of the 18 R martensite in Cu-Zn-Al-Ni induced by electron irradiation was studied.The results were compared to those of the stabilization induced by quenching and ageing in the same alloy, and the ones obtained by irradiation in 18 R-Cu-Zn-Al alloys.The effects of Cu irradiation over b phase were analyzed with several electron microscopy techniques including: scanning electron microscopy (S E M), high resolution electron microscopy (H R E M), micro diffraction and X-ray energy dispersive spectroscopy (E D S). Structural changes in Cu-Zn-Al b phase into a closed packed structure were induced by Cu ion implantation.The closed packed structures depend on the irradiation fluence.Based on these results, the interface between these structures (closed packed and b) and the stability of disordered phases were analyzed. It was also compared the evolution of long range order in the Cu-Zn-Al and in the Cu-Zn-Al-Ni b phase as a function of fluence.The evolution of the g phase was also compared. Both results were discussed in terms of the mobility of irradiation induced point defects.Finally, the effects induced by swift heavy ions in b phase and 18 R martensite were studied. The results of the irradiation in b phase were qualitatively similar to those produced by irradiation with lower energies. On the contrary, nano metric defects were found in the irradiated 18 R martensite.These defects were characterized by H R E M.The characteristic contrast of the defects was associated to a local change in the

  8. Structure and Phase Transformation in the Giant Magnetostriction Laves-Phase SmFe2

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaonan; Lin, Kun; Gao, Qilong; Zhu, He; Li, Qiang; Cao, Yili; Liu, Zhanning; You, Li; Chen, Jun; Ren, Yang [Argonne National Laboratory, X-Ray Science Division, Argonne, Illinois 60439, United States; Huang, Rongjin [Key Laboratory; Lapidus, Saul H. [Argonne National Laboratory, X-Ray Science Division, Argonne, Illinois 60439, United States; Xing, Xianran

    2017-10-13

    As one class of the most important intermetallic compounds, the binary Laves-phase is well-known for their abundant magnetic properties. Samarium-iron alloy system, SmFe2, is a prototypical Laves compound that shows strong negative magnetostriction but relatively weak magnetocrystalline anisotropy. SmFe2 has been identified as a cubic Fd$ \\overline{3}\\ $m structure at room temperature, however, the cubic symmetry does not match the spontaneous magnetization along the [111]cubic direction. Here we studied the crystal structure of SmFe2 by high-resolution synchrotron X-ray powder diffraction and X-ray total scattering methods. SmFe2 is found to adopt a centrosymmetric trigonal R$ \\overline{3}\\ $m structure at room temperature, which transforms to an orthorhombic Imma structure at 200 K. This transition is in agreement with the changes of easy magnetization direction from [111]cubic to [110]cubic direction, and is further evidenced by the inflexion of thermal expansion behavior, the sharp decline of the magnetic susceptibility in the FC-ZFC curve, and the anomaly in the specific heat capacity measurement. The revised structure and phase transformation of SmFe2 could be useful to understand the magnetostriction and related physical properties of other RM2-type pseudo-cubic Laves-phase intermetallic compounds.

  9. Electric-field-induced paraelectric to ferroelectric phase transformation in prototypical polycrystalline BaTiO3

    International Nuclear Information System (INIS)

    Wang, Zhiyang; Hinterstein, Manuel; Daniels, John E.; Webber, Kyle G.; Hudspeth, Jessica M.

    2014-01-01

    An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO 3 at temperatures above the Curie point (T C ) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4 °C above T C . The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above T C , while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4 kV mm −1 ) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials.

  10. Martensite shear phase reversion-induced nanograined/ultrafine-grained Fe-16Cr-10Ni alloy: The effect of interstitial alloying elements and degree of austenite stability on phase reversion

    Energy Technology Data Exchange (ETDEWEB)

    Misra, R.D.K., E-mail: dmisra@louisiana.edu [Center for Structural and Functional Materials, University of Louisiana at Lafayette, Madison Hall Room 217, P.O. Box 44130, Lafayette, LA 70504-1430 (United States); Zhang, Z.; Venkatasurya, P.K.C. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, Madison Hall Room 217, P.O. Box 44130, Lafayette, LA 70504-1430 (United States); Somani, M.C.; Karjalainen, L.P. [Department of Mechanical Engineering, University of Oulu, P.O. Box 4200, Oulu 90014 (Finland)

    2010-11-15

    Research highlights: {yields} Development of a novel process involving phase-reversion annealing process. {yields} Austensite stability strongly influences development of nanograined structure. {yields} Interstitial elements influence microstructural evolution during annealing. - Abstract: We describe here an electron microscopy study of microstructural evolution associated with martensitic shear phase reversion-induced nanograined/ultrafine-grained (NG/UFG) structure in an experimental Fe-16Cr-10Ni alloy with very low interstitial content. The primary objective is to understand and obtain fundamental insights on the influence of degree of austenite stability (Fe-16Cr-10Ni, 301LN, and 301 have different austenite stability index) and interstitial elements (carbon and nitrogen) in terms of phase reversion process, microstructural evolution during reversion annealing, and temperature-time annealing sequence. A relative comparison of Fe-16Cr-10Ni alloy with 301LN and 301 austenitic stainless steels indicated that phase reversion in Fe-16Cr-10Ni occurred by shear mechanism, which is similar to that observed for 301, but is different from the diffusional mechanism in 301LN steel. While the phase reversion in the experimental Fe-16Cr-10Ni alloy and 301 austenitic stainless steel occurred by shear mechanism, there were fundamental differences between these two alloys. The reversed strain-free austenite grains in Fe-16Cr-10Ni alloy were characterized by nearly same crystallographic orientation, where as in 301 steel there was evidence of break-up of martensite laths during reversion annealing resulting in several regions of misoriented austenite grains in 301 steel. Furthermore, a higher phase reversion annealing temperature range (800-900 deg. C) was required to obtain a fully NG/UFG structure of grain size 200-600 nm. The difference in the phase reversion and the temperature-time sequence in the three stages is explained in terms of Gibbs free energy change that

  11. Preparing poly (caprolactone) micro-particles through solvent-induced phase separation

    DEFF Research Database (Denmark)

    Li, Xiaoqiang; Kanjwal, Muzafar Ahmed; Stephansen, Karen

    2012-01-01

    Poly (caprolactone) (PCL) particles with the size distribution from 1 to 100 μm were prepared through solvent-induced phase separation, in which polyvinyl-alcohol (PVA) was used as the matrix-forming polymer to stabilize PCL particles. The cloud point data of PCL-acetone-water was determined...

  12. Current-induced massless mode of the interband phase difference in two-band superconductors

    International Nuclear Information System (INIS)

    Tanaka, Y.; Hase, I.; Yanagisawa, T.; Kato, G.; Nishio, T.; Arisawa, S.

    2015-01-01

    Highlights: • A current induces an interband phase difference in two-band superconductors. • By controlling the boundary conditions, we can trap this phase difference. • A phase difference soliton is observed after switching off the current. - Abstract: There is a current-induced massless mode of an interband phase difference in two-band superconductors. For a thin wire, the externally applied current always invokes a finite interband phase difference when the end of the wire is terminated by a natural boundary condition, i.e., where the total current is specified but the other parameters are left as free and a finite interband phase difference is allowed. This condition can be realized by the normal state region formed by the shrinking of a cross section of the wire where the critical current density is lower than that of the other region of the wire. The interband interaction in the wire cannot completely prevent the emergence of the interband phase difference, though it reduces it somewhat. Instead, boundary conditions determine the presence of the interband phase difference. By reverting the normal state into the superconducting state at the shrunken region by decreasing the current, we may trap a rotation of integral multiples of 2π radians of the interband phase difference in the wire. After switching off the current, this rotation of integral multiples of 2π radians, which continuously spreads over the whole wire, is separated into several interband phase difference solitons (i-solitons), where one i-soliton locally generates a 2π interband phase difference

  13. Finger-like voids induced by viscous fingering during phase inversion of alumina/PES/NMP suspensions

    KAUST Repository

    Wang, Bo

    2012-07-01

    The formation mechanism of phase-inversion ceramic hollow fibre membranes has not been well understood. In this paper, we report on the formation of finger-like macrovoids during non-solvent-induced phase inversion of alumina/PES/NMP suspensions. A membrane structure without such finger-like macrovoids was observed when the suspension was slowly immersed into pure ethanol or a mixture of 70. wt% NMP and 30. wt% water, whereas finger-like macrovoids occurred when the suspension was slid into the non-solvents at higher speeds. We found that the formation process of finger-like macrovoids could be fully or partially reversed when nascent membranes were taken out from water shortly after immersion, depending on the duration of the immersion. Splitting of the fingers during the formation of the macrovoids was also observed during the phase inversion of two alumina/PES/NMP suspensions. These experimental observations were not predicted by current theories of finger-like macrovoid formation in polymer membranes, but appear to mimic the well-known viscous fingering phenomenon. We therefore propose that in the phase inversion of ceramic suspensions, the viscous fingering phenomenon is an important mechanism in the formation of finger-like voids. © 2012 Elsevier B.V.

  14. Microstructure Evolution and Mechanical Behavior of a Hot-Rolled High-Manganese Dual-Phase Transformation-Induced Plasticity/Twinning-Induced Plasticity Steel

    Science.gov (United States)

    Fu, Liming; Shan, Mokun; Zhang, Daoda; Wang, Huanrong; Wang, Wei; Shan, Aidang

    2017-05-01

    The microstructures and deformation behavior were studied in a high-temperature annealed high-manganese dual-phase (28 vol pct δ-ferrite and 72 vol pct γ-austenite) transformation-induced plasticity/twinning-induced plasticity (TRIP/TWIP) steel. The results showed that the steel exhibits a special Lüders-like yielding phenomenon at room temperature (RT) and 348 K (75 °C), while it shows continuous yielding at 423 K, 573 K and 673 K (150 °C, 300 °C and 400 °C) deformation. A significant TRIP effect takes place during Lüders-like deformation at RT and 348 K (75 °C) temperatures. Semiquantitative analysis of the TRIP effect on the Lüders-like yield phenomenon proves that a softening effect of the strain energy consumption of strain-induced transformation is mainly responsible for this Lüders-like phenomenon. The TWIP mechanism dominates the 423 K (150 °C) deformation process, while the dislocation glide controls the plasticity at 573 K (300 °C) deformation. The delta-ferrite, as a hard phase in annealed dual-phase steel, greatly affects the mechanical stability of austenite due to the heterogeneous strain distribution between the two phases during deformation. A delta-ferrite-aided TRIP effect, i.e., martensite transformation induced by localized strain concentration of the hard delta-ferrite, is proposed to explain this kind of Lüders-like phenomenon. Moreover, the tensile curve at RT exhibits an upward curved behavior in the middle deformation stage, which is principally attributed to the deformation twinning of austenite retained after Lüders-like deformation. The combination of the TRIP effect during Lüders-like deformation and the subsequent TWIP effect greatly enhances the ductility in this annealed high-manganese dual-phase TRIP/TWIP steel.

  15. Phase transitions and structures of methylammonium compounds

    International Nuclear Information System (INIS)

    Yamamuro, Osamu; Onoda-Yamamuro, Noriko; Matsuo, Takasuke; Suga, Hiroshi; Kamiyama, Takashi; Asano, Hajime; Ibberson, R.M.; David, W.I.F.

    1993-01-01

    The structures of CD 3 ND 3 Cl, CD 3 ND 3 I, CD 3 ND 3 BF 4 , (CD 3 ND 3 ) 2 SnCl 6 , and CD 3 ND 3 SnBr 3 crystals were studied with time-of-flight type high-resolution powder diffractometers using spallation pulsed neutron sources. The orientations of the CD 3 ND 3 cations, including the positions of the D atoms, were determined at all the room temperature phases and at the low temperature phases of CD 3 ND 3 I and (CD 3N D 3 ) 2 SnCl 6 . The heat capacity experiments were also performed for both protonated and deuterated analogs of these compounds. From both structural and thermodynamic points of view, it was found that the transitions are mainly associated with the order-disorder change of the orientations of the CD 3 ND 3 cations. (author)

  16. Self-regulated transport in photonic crystals with phase-changing defects

    Science.gov (United States)

    Thomas, Roney; Ellis, Fred M.; Vitebskiy, Ilya; Kottos, Tsampikos

    2018-01-01

    Phase-changing materials (PCMs) are widely used for optical data recording, sensing, all-optical switching, and optical limiting. Our focus here is on the case when the change in transmission characteristics of the optical material is caused by the input light itself. Specifically, the light-induced heating triggers the phase transition in the PCM. In this paper, using a numerical example, we demonstrate that the incorporation of the PCM in a photonic structure can lead to a dramatic modification of the effects of light-induced phase transition, as compared to a stand-alone sample of the same PCM. Our focus is on short pulses. We discuss some possible applications of such phase-changing photonic structures for optical sensing and limiting.

  17. Duality, phase structures, and dilemmas in symmetric quantum games

    International Nuclear Information System (INIS)

    Ichikawa, Tsubasa; Tsutsui, Izumi

    2007-01-01

    Symmetric quantum games for 2-player, 2-qubit strategies are analyzed in detail by using a scheme in which all pure states in the 2-qubit Hilbert space are utilized for strategies. We consider two different types of symmetric games exemplified by the familiar games, the Battle of the Sexes (BoS) and the Prisoners' Dilemma (PD). These two types of symmetric games are shown to be related by a duality map, which ensures that they share common phase structures with respect to the equilibria of the strategies. We find eight distinct phase structures possible for the symmetric games, which are determined by the classical payoff matrices from which the quantum games are defined. We also discuss the possibility of resolving the dilemmas in the classical BoS, PD, and the Stag Hunt (SH) game based on the phase structures obtained in the quantum games. It is observed that quantization cannot resolve the dilemma fully for the BoS, while it generically can for the PD and SH if appropriate correlations for the strategies of the players are provided

  18. Neutron scattering studies of pretransitional phenomena in structural phase transformations

    International Nuclear Information System (INIS)

    Shapiro, S.M.

    1979-03-01

    Materials exhibiting structural phase transformations are well known to possess pretransitional phenomena. Below the transition temperature, T/sub c/, an order parameter appears and the pretransitional effects are associated with the fluctuations of the order parameter. Neutron scattering techniques have proved invaluable in studying the temporal and spatial dependence of these fluctuations. SrTiO 3 is the prototypical example of a structural phase transformation exhibiting features observable in other transformations such as martensitic and order-disorder. The experimental evolution of the understanding of the phase transformation in SrTiO 3 will be reviewed and the features observed will be shown to typify other systems

  19. Structural Integrity Inspection and Visualization System, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Based on the successful feasibility demonstration in Phase I, Physical Optics Corporation (POC) proposes to continue the development of a novel Structural Integrity...

  20. Pressure induced phase transition in Pb6Bi2S9

    DEFF Research Database (Denmark)

    Olsen, Lars Arnskov; Friese, Karen; Makovicky, Emil

    2011-01-01

    consists of two types of moduli with SnS/TlI archetype structure in which the Pb and Bi lone pairs are strongly expressed. The mechanism of the phase transition is described in detail and the results are compared to the closely related phase transition in Pb3Bi2S6 (lillianite).......The crystal structure of Pb6Bi2S9 is investigated at pressures between 0 and 5.6 GPa with X-ray diffraction on single-crystals. The pressure is applied using diamond anvil cells. Heyrovskyite (Bbmm, a = 13.719(4) Å, b = 31.393(9) Å, c = 4.1319(10) Å, Z = 4) is the stable phase of Pb6Bi2S9...... at ambient conditions and is built from distorted moduli of PbS-archetype structure with a low stereochemical activity of the Pb2+ and Bi3+ lone electron pairs. Heyrovskyite is stable until at least 3.9 GPa and a first-order phase transition occurs between 3.9 and 4.8 GPa. A single-crystal is retained after...

  1. Pressure-induced phase transition of 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6

    Science.gov (United States)

    Takekiyo, Takahiro; Hatano, Naohiro; Imai, Yusuke; Abe, Hiroshi; Yoshimura, Yukihiro

    2011-03-01

    We have investigated the pressure-induced Raman spectral change of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) using Raman spectroscopy. The relative Raman intensity at 590 cm-1 of the CH2 rocking band assigned to the gauche conformer of the NCCC dihedral angle of the butyl group in the [bmim]+ cation increases when the pressure-induced liquid-crystalline phase transition occurs, while that at 610 cm-1 assigned to the trans conformer decreases. Our results show that the high-pressure phase transition of [bmim][PF6] causes the increase of the gauche conformer of the [bmim]+ cation.

  2. Structural contributions to the third-law entropy of uranyl phases

    International Nuclear Information System (INIS)

    Chen, F.; Ewing, R.C.

    1999-01-01

    Entropies that are used in geochemical calculations are usually based on calorimetric measurements. However, because of the contributions of neglected residual entropies which cannot be determined by calorimetric measurements, the true third-law entropies for many phases may be quite different from those derived from thermal data. The residual entropies are caused by site-mixing, structural disorder and magnetic spin disorder and may result in a considerable contribution to the third-law entropy of solid phases. Magnetic spin-configurational entropy is not expected to be significant in uranyl phases. However, because most uranyl phases are based on sheet or chain structures and usually contain several molecular water groups, site-mixing, vacancies, as well as disorder in the orientation of hydrogen bonds and the polar H 2 O molecules may occur. Calculations of the ideal site-mixing configurational entropy for some uranyl phases indicate that the residual contributions that arise from substitution and vacancies to the third-law entropies of uranyl phases may be large. A brief examination of the crystal chemistry of water molecules in uranyl phases suggests that considerable residual entropy may be caused by the disorder of hydrogen bonds associated with interstitial H 2 O groups

  3. Atomic disorder, phase transformation, and phase restoration in Co3Sn2

    Science.gov (United States)

    di, L. M.; Zhou, G. F.; Bakker, H.

    1993-03-01

    The behavior of the intermetallic compound Co3Sn2 upon ball milling was studied by x-ray diffraction, high-field-magnetization measurements, and subsequently by differential scanning calorimetry. It turns out that starting from the stoichiometric-ordered compound, mechanical attrition of Co3Sn2 generates atomic disorder in the early stage of milling. The nonequilibrium phase transformation from the low-temperature phase with orthorhombic structure to the high-temperature phase with a hexagonal structure was observed in the intermediate stage of milling. It was accompanied by the creation of increasing atomic disorder. After long milling periods, the phase transformation was completed and the atomic disordering became saturated. All the physical parameters measured in the present work remained constant during this period. The above outcome was confirmed by comparison with the high-temperature phase thermally induced by quenching. The good agreement of the results obtained by different techniques proves that the ball milling generates well-defined metastable states in Co3Sn2.

  4. Upgraded phase control system for superconducting low-velocity accelerating structures

    International Nuclear Information System (INIS)

    Added, N.

    1992-01-01

    Microphonic-induced fluctuations in the RF eigenfrequency of superconducting (SC) slow-wave structures must be compensated by a fast-tuning system in order to control the RF phase. The tuning system must handle a reactive power proportional to the product of the frequency range and the RF energy content of the Rf cavity. The fast tuner for the SC resonators in the ATLAS heavy-ion linac is a voltage-controlled reactance based on an array of PIN diodes operating immersed in liquid nitrogen. This paper discusses recent upgrades to the ATLAS fast tuner which can now provide as much as 30 KVA of reactive tuning capability with a real RF power loss of less than 300 watts. The design was guided by numerical modeling of all elements of the device. Also discussed is the RF coupler which can couple 30 KW from 77 K tuner to a 42 K resonant cavity with less than 2 W of RF loss into 4.2 K

  5. Upgraded phase control system for superconducting low-velocity accelerating structures

    Energy Technology Data Exchange (ETDEWEB)

    Added, N. (Sao Paulo Univ., SP (Brazil). Dept. de Fisica Nuclear); Clifft, B.E.; Shepard, K.W. (Argonne National Lab., IL (United States))

    1992-01-01

    Microphonic-induced fluctuations in the RF eigenfrequency of superconducting (SC) slow-wave structures must be compensated by a fast-tuning system in order to control the RF phase. The tuning system must handle a reactive power proportional to the product of the frequency range and the RF energy content of the Rf cavity. The fast tuner for the SC resonators in the ATLAS heavy-ion linac is a voltage-controlled reactance based on an array of PIN diodes operating immersed in liquid nitrogen. This paper discusses recent upgrades to the ATLAS fast tuner which can now provide as much as 30 KVA of reactive tuning capability with a real RF power loss of less than 300 watts. The design was guided by numerical modeling of all elements of the device. Also discussed is the RF coupler which can couple 30 KW from 77 K tuner to a 42 K resonant cavity with less than 2 W of RF loss into 4.2 K.

  6. Upgraded phase control system for superconducting low-velocity accelerating structures

    Energy Technology Data Exchange (ETDEWEB)

    Added, N. [Sao Paulo Univ., SP (Brazil). Dept. de Fisica Nuclear; Clifft, B.E.; Shepard, K.W. [Argonne National Lab., IL (United States)

    1992-09-01

    Microphonic-induced fluctuations in the RF eigenfrequency of superconducting (SC) slow-wave structures must be compensated by a fast-tuning system in order to control the RF phase. The tuning system must handle a reactive power proportional to the product of the frequency range and the RF energy content of the Rf cavity. The fast tuner for the SC resonators in the ATLAS heavy-ion linac is a voltage-controlled reactance based on an array of PIN diodes operating immersed in liquid nitrogen. This paper discusses recent upgrades to the ATLAS fast tuner which can now provide as much as 30 KVA of reactive tuning capability with a real RF power loss of less than 300 watts. The design was guided by numerical modeling of all elements of the device. Also discussed is the RF coupler which can couple 30 KW from 77 K tuner to a 42 K resonant cavity with less than 2 W of RF loss into 4.2 K.

  7. Phase stability in wear-induced supersaturated Al-Ti solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Y.; Yokoyama, K. [Dept. of Functional Machinery Mechanics Shinshu Univ., Ueda (Japan); Hosoda, H. [Precision and Intelligence Lab., Tokyo Inst. of Tech., Nagatsuta, Midori-ku, Yokohama (Japan)

    2002-07-01

    Al-Ti supersaturated solid solutions were introduced by wear testing and the rapid quenching of an Al/Al{sub 3}Ti composite (part of an Al/Al{sub 3}Ti functionally graded material) that was fabricated using the centrifugal method. The phase stability of the supersaturated solid solution was studied through systematic annealing of the supersaturated solid solution. It was found that the Al-Ti supersaturated solid solution decomposed into Al and Al{sub 3}Ti intermetallic compound phases during the heat treatment. The Al-Ti supersaturated solid solutions fabricated were, therefore, not an equilibrium phase, and thus decomposed into the equilibrium phases during heat treatment. It was also found that heat treatment leads to a significant hardness increase for the Al-Ti supersaturated solid solution. Finally, it was concluded that formation of the wear-induced supersaturated solid solution layer was a result of severe plastic deformation. (orig.)

  8. Intragenic origins due to short G1 phases underlie oncogene-induced DNA replication stress.

    Science.gov (United States)

    Macheret, Morgane; Halazonetis, Thanos D

    2018-03-01

    Oncogene-induced DNA replication stress contributes critically to the genomic instability that is present in cancer. However, elucidating how oncogenes deregulate DNA replication has been impeded by difficulty in mapping replication initiation sites on the human genome. Here, using a sensitive assay to monitor nascent DNA synthesis in early S phase, we identified thousands of replication initiation sites in cells before and after induction of the oncogenes CCNE1 and MYC. Remarkably, both oncogenes induced firing of a novel set of DNA replication origins that mapped within highly transcribed genes. These ectopic origins were normally suppressed by transcription during G1, but precocious entry into S phase, before all genic regions had been transcribed, allowed firing of origins within genes in cells with activated oncogenes. Forks from oncogene-induced origins were prone to collapse, as a result of conflicts between replication and transcription, and were associated with DNA double-stranded break formation and chromosomal rearrangement breakpoints both in our experimental system and in a large cohort of human cancers. Thus, firing of intragenic origins caused by premature S phase entry represents a mechanism of oncogene-induced DNA replication stress that is relevant for genomic instability in human cancer.

  9. Surface-induced ordering of a liquid crystal in the isotropic phase

    International Nuclear Information System (INIS)

    Miyano, K.

    1979-01-01

    A detailed account of a measurement of order parameter of a liquid crystal at the boundary by means of the wall-induced pretransitional birefringence is given. Several surface treatments were studied including surfactants and evaporated films. Although all treatments produced good alignment in the nematic phase, the boundary order parameter (hence the strength of the aligning force) in the isotropic phase differed very much depending on the treatment, indicating the diverse nature of the alignment process

  10. Ultra-precision machining induced phase decomposition at surface of Zn-Al based alloy

    International Nuclear Information System (INIS)

    To, S.; Zhu, Y.H.; Lee, W.B.

    2006-01-01

    The microstructural changes and phase transformation of an ultra-precision machined Zn-Al based alloy were examined using X-ray diffraction and back-scattered electron microscopy techniques. Decomposition of the Zn-rich η phase and the related changes in crystal orientation was detected at the surface of the ultra-precision machined alloy specimen. The effects of the machining parameters, such as cutting speed and depth of cut, on the phase decomposition were discussed in comparison with the tensile and rolling induced microstrucutural changes and phase decomposition

  11. Direct investigations of deformation and yield induced structure transitions in polyamide 6 below glass transition temperature with WAXS and SAXS

    DEFF Research Database (Denmark)

    Guo, Huilong; Wang, Jiayi; Zhou, Chengbo

    2015-01-01

    Deformation and yield induced structure transitions of polyamide 6 (PA6) were detected with the combination of the wide- and small-angle X-ray scattering (WAXS and SAXS) at 30 degrees C below glass transition temperature (T-g) of PA6. During deformation, gamma-alpha phase transition was found...... at elastic stage. The concentrated stress in crystals at elastic stage provided adequate energy for the direct gamma-alpha phase transition under T-g. The force to promote the gamma-phase into a phase directly is insufficient at the yield stage and a transient phase as a compromise was formed. The transient...... phase was confirmed by DSC measurements and assisted the gamma-alpha phase transition indirectly. The gamma-phase slips into incomplete fragments at yield point, and the parts along tensile direction are responsible for the formation of transient phase. The gamma-fragments after yield is oriented...

  12. Atoms diffusion-induced phase engineering of platinum-gold alloy nanocrystals with high electrocatalytic performance for the formic acid oxidation reaction.

    Science.gov (United States)

    Li, Fu-Min; Kang, Yong-Qiang; Liu, Hui-Min; Zhai, Ya-Nan; Hu, Man-Cheng; Chen, Yu

    2018-03-15

    Bimetallic noble metal nanocrystals have been widely applied in many fields, which generally are synthesized by the wet-chemistry reduction method. This work presents a purposely designed atoms diffusion induced phase engineering of PtAu alloy nanocrystals on platy Au substrate (PtAu-on-Au nanostructures) through simple hydrothermal treatment. Benefitting from the synergistic effects of component and structure, PtAu-on-Au nanostructures remarkably enhance the dehydrogenation pathway of the formic acid oxidation reaction (FAOR), and thus exhibit much higher FAOR activity and durability compared with Pt nanocrystals on platy Au substrate (Pt-on-Au nanostructures) and commercial Pd black due to an excellent stability of platy Au substrate and a high oxidation resistance of PtAu alloy nanocrystals. The atoms diffusion-induced phase engineering demonstrated in this work builds a bridge between the traditional metallurgy and modern nanotechnologies, which also provides some useful insights in developing noble metals based alloyed nanostructures for the energy and environmental applications. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Multifunctional nanocomposite hollow fiber membranes by solvent transfer induced phase separation.

    Science.gov (United States)

    Haase, Martin F; Jeon, Harim; Hough, Noah; Kim, Jong Hak; Stebe, Kathleen J; Lee, Daeyeon

    2017-11-01

    The decoration of porous membranes with a dense layer of nanoparticles imparts useful functionality and can enhance membrane separation and anti-fouling properties. However, manufacturing of nanoparticle-coated membranes requires multiple steps and tedious processing. Here, we introduce a facile single-step method in which bicontinuous interfacially jammed emulsions are used to form nanoparticle-functionalized hollow fiber membranes. The resulting nanocomposite membranes prepared via solvent transfer-induced phase separation and photopolymerization have exceptionally high nanoparticle loadings (up to 50 wt% silica nanoparticles) and feature densely packed nanoparticles uniformly distributed over the entire membrane surfaces. These structurally well-defined, asymmetric membranes facilitate control over membrane flux and selectivity, enable the formation of stimuli responsive hydrogel nanocomposite membranes, and can be easily modified to introduce antifouling features. This approach forms a foundation for the formation of advanced nanocomposite membranes comprising diverse building blocks with potential applications in water treatment, industrial separations and as catalytic membrane reactors.

  14. Pressure-induced structural and semiconductor-semiconductor transitions in C o0.5M g0.5C r2O4

    Science.gov (United States)

    Rahman, S.; Saqib, Hajra; Zhang, Jinbo; Errandonea, D.; Menéndez, C.; Cazorla, C.; Samanta, Sudeshna; Li, Xiaodong; Lu, Junling; Wang, Lin

    2018-05-01

    The effect of pressure on the structural, vibrational, and electronic properties of Mg-doped Cr bearing spinel C o0.5M g0.5C r2O4 was studied up to 55 GPa at room-temperature using x-ray diffraction, Raman spectroscopy, electrical transport measurements, and ab initio calculations. We found that the ambient-pressure phase is cubic (spinel-type, F d 3 ¯m ) and underwent a pressure-induced structural transition to a tetragonal phase (space group I 4 ¯m 2 ) above 28 GPa. The ab initio calculation confirmed this first-order phase transition. The resistivity of the sample decreased at low pressures with the existence of a low-pressure (LP) phase and started to increase with the emergence of a high-pressure (HP) phase. The temperature dependent resistivity experiments at different pressures illustrated the wide band gap semiconducting nature of both the LP and HP phases with different activation energies, suggesting a semiconductor-semiconductor transition at HP. No evidence of chemical decomposition or a semiconductor-metal transition was observed in our studies.

  15. Electron-beam-irradiation-induced crystallization of amorphous solid phase change materials

    Science.gov (United States)

    Zhou, Dong; Wu, Liangcai; Wen, Lin; Ma, Liya; Zhang, Xingyao; Li, Yudong; Guo, Qi; Song, Zhitang

    2018-04-01

    The electron-beam-irradiation-induced crystallization of phase change materials in a nano sized area was studied by in situ transmission electron microscopy and selected area electron diffraction. Amorphous phase change materials changed to a polycrystalline state after being irradiated with a 200 kV electron beam for a long time. The results indicate that the crystallization temperature strongly depends on the difference in the heteronuclear bond enthalpy of the phase change materials. The selected area electron diffraction patterns reveal that Ge2Sb2Te5 is a nucleation-dominated material, when Si2Sb2Te3 and Ti0.5Sb2Te3 are growth-dominated materials.

  16. Thermally-Induced Structural Disturbances of Rigid Panel Solar Arrays

    Science.gov (United States)

    Johnston, John D.; Thornton, Earl A.

    1997-01-01

    The performance of a significant number of spacecraft has been impacted negatively by attitude disturbances resulting from thermally-induced motions of flexible structures. Recent examples of spacecraft affected by these disturbances include the Hubble Space Telescope (HST) and the Upper Atmosphere Research Satellite (UARS). Thermally-induced structural disturbances occur as the result of rapid changes in thermal loading typically initiated as a satellite exits or enters the Earth's shadow. Temperature differences in flexible appendages give rise to structural deformations, which in turn result in disturbance torques reacting back on the spacecraft. Structures which have proven susceptible to these disturbances include deployable booms and solar arrays. This paper investigates disturbances resulting from thermally-induced deformations of rigid panel solar arrays. An analytical model for the thermal-structural response of the solar array and the corresponding disturbance torque are presented. The effect of these disturbances on the attitude dynamics of a simple spacecraft is then investigated using a coupled system of governing equations which includes the effects of thermally-induced deformations. Numerical results demonstrate the effect of varying solar array geometry on the dynamic response of the system.

  17. Infield X-ray diffraction studies of field and temperature driven structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}

    Energy Technology Data Exchange (ETDEWEB)

    Shahee, Aga, E-mail: agashahee@gmail.com [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Department of Physics, IIT Bombay, Powai, Mumbai 400076 (India); Sharma, Shivani; Singh, K.; Lalla, N.P. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India)

    2017-07-15

    Highlights: • Temperature and magnetic field driven coupled magneto-structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}. • Microscopic evidence of strong spin-charge-lattice coupling. • Iso-thermal magnetic field driven structure phase transition. • Field-driven structural phase transition origin of observed 1st order type CMR effect. - Abstract: Comprehensive X-ray diffraction (XRD) studies have been performed at different temperature (T) (4.2–300 K) and magnetic field (H) (0–8 T) to understand the evolution of crystal structure of Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ} (NSMO) under non ambient conditions. The T dependent XRD results show the abrupt change in the lattice parameters without any change in lattice symmetry at ∼200 K, which is associated with the first order structural phase transition from ferromagnetic to antiferromagnetic phase. This phase transition is strongly H dependent and shifted to lower temperature (∼150 K) on the application of 8 T field with phase coexistence (high temperature phase ∼18%), even down to 4.2 K. Isothermal XRD results at 150 K under different H clearly illustrate the H induced first order structural phase transition. The critical H at which this phase transformation starts is ∼1 T, with rapid growth above 4 T with hysteretic nature during increasing and decreasing H. These results are supported with the resistivity and magnetoresistance results and affirm the strong spin-lattice coupling in NSMO. Our detail studies reveal the structural correlations to the observed colossal magnetoresistance and magnetocaloric effect in this material.

  18. Structures, phase stabilities, and electrical potentials of Li-Si battery anode materials

    KAUST Repository

    Tipton, William W.

    2013-05-28

    The Li-Si materials system holds promise for use as an anode in Li-ion battery applications. For this system, we determine the charge capacity, voltage profiles, and energy storage density solely by ab initio methods without any experimental input. We determine the energetics of the stable and metastable Li-Si phases likely to form during the charging and discharging of a battery. Ab initio molecular dynamics simulations are used to model the structure of amorphous Li-Si as a function of composition, and a genetic algorithm coupled to density-functional theory searches the Li-Si binary phase diagram for small-cell, metastable crystal structures. Calculations of the phonon densities of states using density-functional perturbation theory for selected structures determine the importance of vibrational, including zero-point, contributions to the free energies. The energetics and local structural motifs of these metastable Li-Si phases closely resemble those of the amorphous phases, making these small unit cell crystal phases good approximants of the amorphous phase for use in further studies. The charge capacity is estimated, and the electrical potential profiles and the energy density of Li-Si anodes are predicted. We find, in good agreement with experimental measurements, that the formation of amorphous Li-Si only slightly increases the anode potential. Additionally, the genetic algorithm identifies a previously unreported member of the Li-Si binary phase diagram with composition Li5Si2 which is stable at 0 K with respect to previously known phases. We discuss its relationship to the partially occupied Li7Si3 phase. © 2013 American Physical Society.

  19. Novel BCH Code Design for Mitigation of Phase Noise Induced Cycle Slips in DQPSK Systems

    DEFF Research Database (Denmark)

    Leong, M. Y.; Larsen, Knud J.; Jacobsen, G.

    2014-01-01

    We show that by proper code design, phase noise induced cycle slips causing an error floor can be mitigated for 28 Gbau d DQPSK systems. Performance of BCH codes are investigated in terms of required overhead......We show that by proper code design, phase noise induced cycle slips causing an error floor can be mitigated for 28 Gbau d DQPSK systems. Performance of BCH codes are investigated in terms of required overhead...

  20. High pressure structural phase transition of neodymium mono pnictides

    International Nuclear Information System (INIS)

    Pagare, Gitanjali; Ojha, P.; Sanyal, S.P.; Aynyas, Mahendra

    2007-01-01

    We have investigated theoretically the high-pressure structural phase transition of two neodymium mono NdX (X=As, Sb) using an interionic potential theory with necessary modification to include the effect of Coulomb screening by the delocalized f electrons of Nd ion. These compounds exhibits first order crystallographic phase transition from their NaCl (B 1 ) phase to body centered tetragonal (BCT) at 27 GPa and 15.3 GPa respectively. We also calculated the Nd-Nd distance as a function of pressure. (author)

  1. Vortex phase-induced changes of the statistical properties of a partially coherent radially polarized beam.

    Science.gov (United States)

    Guo, Lina; Chen, Yahong; Liu, Xianlong; Liu, Lin; Cai, Yangjian

    2016-06-27

    Partially coherent radially polarized (PCRP) beam was introduced and generated in recent years. In this paper, we investigate the statistical properties of a PCRP beam embedded with a vortex phase (i.e., PCRP vortex beam). We derive the analytical formula for the cross-spectral density matrix of a PCRP vortex beam propagating through a paraxial ABCD optical system and analyze the statistical properties of a PCRP vortex beam focused by a thin lens. It is found that the statistical properties of a PCRP vortex beam on propagation are much different from those of a PCRP beam. The vortex phase induces not only the rotation of the beam spot, but also the changes of the beam shape, the degree of polarization and the state of polarization. We also find that the vortex phase plays a role of resisting the coherence-induced degradation of the intensity distribution and the coherence-induced depolarization. Furthermore, we report experimental generation of a PCRP vortex beam for the first time. Our results will be useful for trapping and rotating particles, free-space optical communications and detection of phase object.

  2. Preparation of mesoporous nanofibers by vapor phase synthesis: control of mesopore structures with the aid of co-surfactants

    International Nuclear Information System (INIS)

    Min, Sa Hoon; Jang, Jyongsik; Lee, Kyung Jin; Bae, Joonwon

    2013-01-01

    Mesoporous nanofibers (MSNFs) can be fabricated in the pores of anodic aluminum oxide (AAO) membrane using diverse methods. Among them vapor phase synthesis (VPS) provides several advantages over sol–gel or evaporation-induced self-assembly (EISA) based methods. One powerful advantage is that we can employ multiple surfactants as structural directing agents (SDAs) simultaneously. By adopting diverse pairs of SDAs, we can control the mesopore structures, i.e. pore size, surface area, and even the morphology of mesostructures. Here, we used F127 as a main SDA, which is relatively robust (thus, difficult to change the mesopore structures), and added a series of cationic co-surfactants to observe the systematical changes in their mesostructure with respect to the chain length of the co-surfactant. (paper)

  3. Preparation of mesoporous nanofibers by vapor phase synthesis: control of mesopore structures with the aid of co-surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Min, Sa Hoon; Jang, Jyongsik; Lee, Kyung Jin [School of Chemical and Biological Engineering, College of Engineering, Seoul National University, Shinlimdong 56-1, Seoul, 151-742 (Korea, Republic of); Bae, Joonwon [Department of Applied Chemistry, Dongduk Women' s University, Seoul 136-714 (Korea, Republic of)

    2013-06-28

    Mesoporous nanofibers (MSNFs) can be fabricated in the pores of anodic aluminum oxide (AAO) membrane using diverse methods. Among them vapor phase synthesis (VPS) provides several advantages over sol-gel or evaporation-induced self-assembly (EISA) based methods. One powerful advantage is that we can employ multiple surfactants as structural directing agents (SDAs) simultaneously. By adopting diverse pairs of SDAs, we can control the mesopore structures, i.e. pore size, surface area, and even the morphology of mesostructures. Here, we used F127 as a main SDA, which is relatively robust (thus, difficult to change the mesopore structures), and added a series of cationic co-surfactants to observe the systematical changes in their mesostructure with respect to the chain length of the co-surfactant. (paper)

  4. Preparation of mesoporous nanofibers by vapor phase synthesis: control of mesopore structures with the aid of co-surfactants

    Science.gov (United States)

    Min, Sa Hoon; Bae, Joonwon; Jang, Jyongsik; Lee, Kyung Jin

    2013-06-01

    Mesoporous nanofibers (MSNFs) can be fabricated in the pores of anodic aluminum oxide (AAO) membrane using diverse methods. Among them vapor phase synthesis (VPS) provides several advantages over sol-gel or evaporation-induced self-assembly (EISA) based methods. One powerful advantage is that we can employ multiple surfactants as structural directing agents (SDAs) simultaneously. By adopting diverse pairs of SDAs, we can control the mesopore structures, i.e. pore size, surface area, and even the morphology of mesostructures. Here, we used F127 as a main SDA, which is relatively robust (thus, difficult to change the mesopore structures), and added a series of cationic co-surfactants to observe the systematical changes in their mesostructure with respect to the chain length of the co-surfactant.

  5. Flow-induced structure in colloidal suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Vermant, J [Department of Chemical Engineering, K U Leuven, W de Croylaan 46, B-3001 Leuven (Belgium); Solomon, M J [Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109-2136 (United States)

    2005-02-02

    We review the sequences of structural states that can be induced in colloidal suspensions by the application of flow. Structure formation during flow is strongly affected by the delicate balance among interparticle forces, Brownian motion and hydrodynamic interactions. The resulting non-equilibrium microstructure is in turn a principal determinant of the suspension rheology. Colloidal suspensions with near hard-sphere interactions develop an anisotropic, amorphous structure at low dimensionless shear rates. At high rates, clustering due to strong hydrodynamic forces leads to shear thickening rheology. Application of steady-shear flow to suspensions with repulsive interactions induces a rich sequence of transitions to one-, two-and three-dimensional order. Oscillatory-shear flow generates metastable ordering in suspensions with equilibrium liquid structure. On the other hand, short-range attractive interactions can lead to a fluid-to-gel transition under quiescent suspensions. Application of flow leads to orientation, breakup, densification and spatial reorganization of aggregates. Using a non-Newtonian suspending medium leads to additional possibilities for organization. We examine the extent to which theory and simulation have yielded mechanistic understanding of the microstructural transitions that have been observed. (topical review)

  6. Pressure induced Amorphization of Ln1/3(Nb,Ta)O3

    International Nuclear Information System (INIS)

    Melchior, A.; Noked, O.; Sterer, E.; Shuker, R.

    2014-01-01

    The research focuses on the phenomenon of pressure induced amorphization (PIA) in Ln1/3MO3, Ln - La,Pr,Nd and M-Nb,Ta. In most pressure induced phase transitions the material changes from a crystalline phase to another crystalline phase. However, if this transition is kinetically hindered, the increased free energy due to the applied pressure will result in a structural collapse to an amorphous intermediate phase. This phenomenon is known as pressure induced amorphization

  7. Dependence of stress-induced omega transition and mechanical twinning on phase stability in metastable β Ti–V alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.L.; Li, L.; Mei, W.; Wang, W.L.; Sun, J., E-mail: jsun@sjtu.edu.cn

    2015-09-15

    Tensile properties and deformation microstructures of a series of binary β Ti–16–22V alloys have been investigated. The results show that the plastic deformation mode changes from the plate-like stress-induced ω phase transformation with a special habit plane of (− 5052){sub ω}//(3 − 3 − 2){sub β} to (332)<113> type deformation twinning with increasing the content of vanadium in the β Ti–16–22 wt.% V alloys. The plate-like stress-induced ω phase has a special orientation relationship with the β phase matrix, i.e., [110]{sub β}//[− 12 − 10]{sub ω}, (3 − 3 − 2){sub β}//(− 5052){sub ω} and (− 55 − 4){sub β}//(30 − 31){sub ω}. The alloys plastically deformed by stress-induced ω phase transformation exhibit relatively higher yield strength than those deformed via (332)<113> type deformation twinning. It can be concluded that the stability of β phase plays a significant role in plastic deformation mode, i.e., stress-induced ω phase transformation or (332)<113> type deformation twinning, which governs the mechanical property of the β Ti–16–22 wt.% V alloys. - Highlights: • Tensile properties and deformed microstructures of β Ti–16–22V alloys were studied. • Stress-induced ω phase transformation and (332)<113> twinning occur in the alloys. • Stability of β phase plays a significant role in plastic deformation mode. • Plastic deformation mode governs the mechanical property of the alloys.

  8. Ab initio study of the effect of Si on the phase stability and electronic structure of γ- and α-Al2O3

    International Nuclear Information System (INIS)

    Nahif, F; Music, D; Mráz, S; To Baben, M; Schneider, J M

    2013-01-01

    Using density functional theory, the effect of Si on the stability and electronic structure of γ- and α-Al 2 O 3 has been investigated. The concentration range from 0 to 5 at.% is probed and the additive is positioned at different substitutional sites in the γ-phase. The calculations for (Al,Si) 2 O 3 predict a trend towards spontaneous decomposition into α-/γ-Al 2 O 3 and SiO 2 . Therefore, the formation of the metastable γ-(Al,Si) 2 O 3 phase can only be expected during non-equilibrium processing where the decomposition is kinetically hindered. The Si-induced changes in stability of this metastable solid solution may be understood based on the electronic structure. As the Si concentration is increased, stiff silicon–oxygen bonds are formed giving rise to the observed stabilization of the γ-phase. (paper)

  9. Effect of Large Negative Phase of Blast Loading on Structural Response of RC Elements

    Directory of Open Access Journals (Sweden)

    Syed Zubair Iman

    2016-01-01

    Full Text Available Structural response of reinforced concrete (RC elements for analysis and design are often obtained using the positive phase of the blast pressure curve disregarding the negative phase assuming insignificant contribution from the negative phase of the loading. Although, some insight on the effect of negative phase of blast pressure based on elastic single-degree-of-freedom (SDOF analysis was presented before, the influence of negative phase on different types of resistance functions of SDOF models and on realistic finite element analysis has not been explored. In this study, the effects of inclusion of pulse negative phase on structural response of RC elements from SDOF analysis and from more detailed finite element analysis have been investigated. Investigation of SDOF part has been conducted using MATLAB code that utilizes non-linear resistance functions of SDOF model. Detailed numerical investigation using finite element code DIANA was conducted on the significance of the negative phase on structural response. In the FE model, different support stiffness was used to explore the effect of support stiffness on the structural response due to blast negative phase. Results from SDOF and FE analyses present specific situations where the effect of large negative phase was found to be significant on the structural response of RC elements.

  10. Negative thermal expansion near two structural quantum phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Occhialini, Connor A.; Handunkanda, Sahan U.; Said, Ayman; Trivedi, Sudhir; Guzmán-Verri, G. G.; Hancock, Jason N.

    2017-12-01

    Recent experimental work has revealed that the unusually strong, isotropic structural negative thermal expansion in cubic perovskite ionic insulator ScF3 occurs in excited states above a ground state tuned very near a structural quantum phase transition, posing a question of fundamental interest as to whether this special circumstance is related to the anomalous behavior. To test this hypothesis, we report an elastic and inelastic x-ray scattering study of a second system Hg2I2 also tuned near a structural quantum phase transition while retaining stoichiometric composition and high crystallinity. We find similar behavior and significant negative thermal expansion below 100 K for dimensions along the body-centered-tetragonal c axis, bolstering the connection between negative thermal expansion and zero-temperature structural transitions.We identify the common traits between these systems and propose a set of materials design principles that can guide discovery of newmaterials exhibiting negative thermal expansion

  11. The gas phase structure of α -pinene, a main biogenic volatile organic compound

    Science.gov (United States)

    Neeman, Elias M.; Avilés Moreno, Juan Ramón; Huet, Thérèse R.

    2017-12-01

    The gas phase structure of the bicyclic atmospheric aerosol precursor α-pinene was investigated employing a combination of quantum chemical calculation and Fourier transform microwave spectroscopy coupled to a supersonic jet expansion. The very weak rotational spectra of the parent species and all singly substituted 13C in natural abundance have been identified, from 2 to 20 GHz, and fitted to Watson's Hamiltonian model. The rotational constants were used together with geometrical parameters from density functional theory and ab initio calculations to determine the rs, r0, and rm(1 ) structures of the skeleton, without any structural assumption in the fit concerning the heavy atoms. The double C=C bond was found to belong to a quasiplanar skeleton structure containing 6 carbon atoms. Comparison with solid phase structure is reported. The significant differences of α-pinene in gas phase and other gas phase bicyclic monoterpene structures (β-pinene, nopinone, myrtenal, and bicyclo[3.1.1]heptane) are discussed.

  12. Structural phase transition and opto-electronic properties of NaZnAs

    Energy Technology Data Exchange (ETDEWEB)

    Djied, A.; Seddik, T.; Merabiha, O. [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 (Algeria); Murtaza, G. [Materials Modeling Lab, Department of Physics, Islamia College University, Peshawar (Pakistan); Khenata, R. [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 (Algeria); Ahmed, R., E-mail: rashidahmed@utm.my [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor (Malaysia); Bin-Omran, S. [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Uğur, Ş. [Department of Physics, Faculty of Sciences, Gazi University, 06500 Teknikokullar, Ankara (Turkey); Bouhemadou, A. [Laboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, University Setif 1, 19000 Setif (Algeria)

    2015-02-15

    Highlights: • First competent characterizations of NaZnAs at the level of FP-LAPW+lo. • NaZnAs, a potential alternative candidate to III-V for photovoltaic applications. • NaZnAs, a cheaper and abundantly available direct band gap semiconductor. • Potential material for solar radiation absorber from infrared to ultraviolet. - Abstract: In this study, we predict the structural phase transitions as well as opto-electronic properties of the filled-tetrahedral (Nowotny-Juza) NaZnAs compound. Calculations employ the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) scheme. The exchange-correlation potential is treated within the generalized gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE). In addition, Tran and Blaha (TB) modified Becke-Johnson (mBJ) potential is also used to obtain more accurate optoelectronic properties. Geometry optimization is performed to obtain reliable total energies and other structural parameters for each NaZnAs phase. In our study, the sequence of the structural phase transition on compression is Cu{sub 2}Sb-type → β → α phase. NaZnAs is a direct (Γ-Γ) band gap semiconductor for all the structural phases. However, compared to PBE-GGA, the mBJ approximation reproduces better fundamental band gaps. Moreover, for insight into its potential for photovoltaic applications, different optical parameters are studied.

  13. Structural phase transition and opto-electronic properties of NaZnAs

    International Nuclear Information System (INIS)

    Djied, A.; Seddik, T.; Merabiha, O.; Murtaza, G.; Khenata, R.; Ahmed, R.; Bin-Omran, S.; Uğur, Ş.; Bouhemadou, A.

    2015-01-01

    Highlights: • First competent characterizations of NaZnAs at the level of FP-LAPW+lo. • NaZnAs, a potential alternative candidate to III-V for photovoltaic applications. • NaZnAs, a cheaper and abundantly available direct band gap semiconductor. • Potential material for solar radiation absorber from infrared to ultraviolet. - Abstract: In this study, we predict the structural phase transitions as well as opto-electronic properties of the filled-tetrahedral (Nowotny-Juza) NaZnAs compound. Calculations employ the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) scheme. The exchange-correlation potential is treated within the generalized gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE). In addition, Tran and Blaha (TB) modified Becke-Johnson (mBJ) potential is also used to obtain more accurate optoelectronic properties. Geometry optimization is performed to obtain reliable total energies and other structural parameters for each NaZnAs phase. In our study, the sequence of the structural phase transition on compression is Cu 2 Sb-type → β → α phase. NaZnAs is a direct (Γ-Γ) band gap semiconductor for all the structural phases. However, compared to PBE-GGA, the mBJ approximation reproduces better fundamental band gaps. Moreover, for insight into its potential for photovoltaic applications, different optical parameters are studied

  14. Dipolar-induced interplay between inter-level physics and macroscopic phase transitions in triple-well potentials

    International Nuclear Information System (INIS)

    Zhang Aixia; Xue Jukui

    2012-01-01

    We propose a scheme to reveal the interplay between dipole–dipole interaction (DDI), inter-level coupling and macroscopic phase transitions in dipolar condensates. By considering a macroscopic sample of dipolar bosons in triple-well potentials, DDI-induced coupling between the inter-level physics and the macroscopic phase transitions is presented. When the DDI exceeds certain thresholds, the degeneracy of the two lowest energy levels and the excitation of new eigenstates occur, respectively. Interestingly, these thresholds give the boundaries of various quantum phase transitions. That is, the quantum phase transitions are the consequence of the levels' degeneracy and the new eigenstates' excitation. Furthermore, DDI-induced long-range macroscopic Josephson oscillations are observed and long-range coherent quantum transportation is achieved. Our results give clear proof of the interplay between the multi-level physics and quantum phase transitions, and also provide a way for designing the long-range coherent quantum transportation. (paper)

  15. Diffusion in porous structures containing three fluid phases

    International Nuclear Information System (INIS)

    Galani, A.N.; Kainourgiakis, M.E.; Stubos, A.K.; Kikkinides, E.S.

    2005-01-01

    In the present study, the tracer diffusion in porous media filled by three fluid phases (a non-wetting, an intermediate wetting and a wetting phase) is investigated. The disordered porous structure of porous systems like random sphere packing and the North Sea chalk, is represented by three-dimensional binary images. The random sphere pack is generated by a standard ballistic deposition procedure, while the chalk matrix by a stochastic reconstruction technique. Physically sound spatial distributions of the three phases filling the pore space are determined by the use of a simulated annealing algorithm, where those phases are initially randomly distributed in the pore space and trial-and-error swaps are performed in order to attain the global minimum of the total interfacial energy. The acceptance rule for a trial move during the annealing is modified properly improving the efficiency of the technique. The diffusivities of the resulting domains are computed by a random walk method. A parametric study with respect to the pore volume fraction occupied by each fluid phase and the ratio of the diffusivities in the fluid phases is performed. (authors)

  16. Complexation induced phase separation: preparation of composite membranes with a nanometer thin dense skin loaded with metal ions

    KAUST Repository

    Villalobos Vazquez de la Parra, Luis Francisco; Karunakaran, Madhavan; Peinemann, Klaus-Viktor

    2015-01-01

    We present the development of a facile phase-inversion method for forming asymmetric membranes with a precise high metal ion loading capacity in only the dense layer. The approach combines the use of macromolecule-metal intermolecular complexes to form the dense layer of asymmetric membranes with nonsolvent-induced phase separation to form the porous support. This allows the independent optimization of both the dense layer and porous support while maintaining the simplicity of a phase-inversion process. Moreover, it facilitates control over (i) the thickness of the dense layer throughout several orders of magnitude—from less than 15 nm to more than 6 μm, (ii) the type and amount of metal ions loaded in the dense layer, (iii) the morphology of the membrane surface, and (iv) the porosity and structure of the support. This simple and scalable process provides a new platform for building multifunctional membranes with a high loading of well-dispersed metal ions in the dense layer.

  17. Complexation induced phase separation: preparation of composite membranes with a nanometer thin dense skin loaded with metal ions

    KAUST Repository

    Villalobos Vazquez de la Parra, Luis Francisco

    2015-04-21

    We present the development of a facile phase-inversion method for forming asymmetric membranes with a precise high metal ion loading capacity in only the dense layer. The approach combines the use of macromolecule-metal intermolecular complexes to form the dense layer of asymmetric membranes with nonsolvent-induced phase separation to form the porous support. This allows the independent optimization of both the dense layer and porous support while maintaining the simplicity of a phase-inversion process. Moreover, it facilitates control over (i) the thickness of the dense layer throughout several orders of magnitude—from less than 15 nm to more than 6 μm, (ii) the type and amount of metal ions loaded in the dense layer, (iii) the morphology of the membrane surface, and (iv) the porosity and structure of the support. This simple and scalable process provides a new platform for building multifunctional membranes with a high loading of well-dispersed metal ions in the dense layer.

  18. Simulation studies of GST phase change alloys

    Science.gov (United States)

    Martyna, Glenn

    2008-03-01

    In order to help drive post-Moore's Law technology development, switching processes involving novel materials, in particular, GeSbTe (GST) alloys are being investigated for use in memory and eFuse applications. An anneal/quench thermal process crystallizes/amorphosizes a GST alloy which then has a low/high resistance and thereby forms a readable/writeable bit; for example, a ``one'' might be the low resistance, conducting crystalline state and a ``zero'' might be the high resistance, glassy state. There are many open questions about the precise nature of the structural transitions and the coupling to electronic structure changes. Computational and experimental studies of the effect of pressure on the GST materials were initiated in order to probe the physics behind the thermal switching process. A new pathway to reversible phase change involving pressure-induced structural metal insulator transitions was discovered. In a binary GS system, a room-temperature, direct, pressure-induced transformation from the high resistance amorphous phase to the low resistance crystalline phase was observed experimentally while the reverse process under tensile load was demonstrated via ab initio MD simulations performed on IBM's Blue Gene/L enabled by massively parallel software. Pressure induced transformations of the ternary material GST-225 (Ge2Sb2Te5) were, also, examined In the talk, the behavior of the two systems will be compared and insight into the nature of the phase change given.

  19. Holographic entanglement entropy and the extended phase structure of STU black holes

    International Nuclear Information System (INIS)

    Caceres, Elena; Nguyen, Phuc H.; Pedraza, Juan F.

    2015-01-01

    We study the extended thermodynamics, obtained by considering the cosmological constant as a thermodynamic variable, of STU black holes in 4-dimensions in the fixed charge ensemble. The associated phase structure is conjectured to be dual to an RG-flow on the space of field theories. We find that for some charge configurations the phase structure resembles that of a Van der Waals gas: the system exhibits a family of first order phase transitions ending in a second order phase transition at a critical temperature. We calculate the holographic entanglement entropy for several charge configurations and show that for the cases where the gravity background exhibits Van der Waals behavior, the entanglement entropy presents a transition at the same critical temperature. To further characterize the phase transition we calculate appropriate critical exponents and show that they coincide. Thus, the entanglement entropy successfully captures the information of the extended phase structure. Finally, we discuss the physical interpretation of the extended space in terms of the boundary QFT and construct various holographic heat engines dual to STU black holes.

  20. Structure determination at room temperature and phase transition ...

    Indian Academy of Sciences (India)

    Unknown

    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India. MS received 9 May 2002 ... exhibit a ferroelectric–paraelectric phase transition at ele- ..... The pattern decomposition and peak extraction methods ...

  1. Ultrafast photo-induced hidden phases in strained manganite thin films

    Science.gov (United States)

    Zhang, Jingdi; McLeod, A. S.; Zhang, Gu-Feng; Stoica, Vladimir; Jin, Feng; Gu, Mingqiang; Gopalan, Venkatraman; Freeland, John W.; Wu, Wenbin; Rondinelli, James; Wen, Haidan; Basov, D. N.; Averitt, R. D.

    Correlated transition metal oxides (TMOs) are particularly sensitive to external control because of energy degeneracy in a complex energy landscape that promote a plethora of metastable states. However, it remains a grand challenge to actively control and fully explore the rich landscape of TMOs. Dynamic control with pulsed photons can overcome energetic barriers, enabling access to transient or metastable states that are not thermally accessible. In the past, we have demonstrated that mode-selective single-laser-pulse excitation of a strained manganite thin film La2/3Ca1/3MnO3 initiates a persistent phase transition from an emergent antiferromagnetic insulating ground state to a ferromagnetic metallic metastable state. Beyond the photo-induced insulator to metal transition, we recently discovered a new peculiar photo-induced hidden phase, identified by an experimental approach that combines ultrafast pump-probe spectroscopy, THz spectroscopy, X-ray diffraction, cryogenic near-field spectroscopy and SHG probe. This work is funded by the DOE, Office of Science, Office of Basic Energy Science under Award Numbers DE-SC0012375 and DE-SC0012592.

  2. Carbon nanotubes reinforced poly(L-lactide) scaffolds fabricated by thermally induced phase separation

    International Nuclear Information System (INIS)

    Ma, Haiyun; Xue, Li

    2015-01-01

    In tissue engineering, porous nanocomposite scaffolds can potentially mimic aspects of the nanoscale architecture of the extra-cellular matrix, as well as enhance the mechanical properties required for successful weight-bearing implants. In this paper, we demonstrate that highly porous thermoplastic poly(L-lactide) nanocomposite scaffolds containing different types of functionalized multi-walled carbon nanotubes (CNTs). The nanocomposite scaffolds were manufactured by a thermally induced phase separation method. This experiment produced an uniform distribution of CNTs throughout the scaffold without obvious aggregations for funtionalized CNTs filled scaffolds by scanning electron microscope observation. The CNTs were frequently located on the pore surface, forming rough, hairy nano-textures. The pore size was reduced with the increasing of CNT loading. Parts of PLLA matrix was induced into nanofibrous structures from solid-walled state, which reduced the crystallinity of the PLLA characterized by DSC measurement. The CNT incorporation significantly improved the compression modulus of the nanocomposite scaffolds, especially the functionalized CNTs. The capacity of protein adsorption is significantly improved when the concentration of the CNTs was higher than 1.0 wt.% and the cell attachment was also enhanced by the addition of CNTs, especially N-CNT. (paper)

  3. Element-resolved atomic structure imaging of rocksalt Ge{sub 2}Sb{sub 2}Te{sub 5} phase-change material

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bin; Chen, Yongjin; Han, Xiaodong, E-mail: wzhang0@mail.xjtu.edu.cn, E-mail: ema@jhu.edu, E-mail: xdhan@bjut.edu.cn [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Zhang, Wei, E-mail: wzhang0@mail.xjtu.edu.cn, E-mail: ema@jhu.edu, E-mail: xdhan@bjut.edu.cn [Center for Advancing Materials Performance from the Nanoscale, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); I. Institute of Physics (IA), RWTH Aachen University, 52056 Aachen (Germany); Institute for Theoretical Solid-State Physics, RWTH Aachen University, 52056 Aachen (Germany); Shen, Zhenju; Li, Jixue [Department of Materials Science and Engineering, Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Zhang, Shengbai [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Zhang, Ze [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Department of Materials Science and Engineering, Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Wuttig, Matthias [I. Institute of Physics (IA), RWTH Aachen University, 52056 Aachen (Germany); Mazzarello, Riccardo [Institute for Theoretical Solid-State Physics, RWTH Aachen University, 52056 Aachen (Germany); and others

    2016-05-09

    Disorder-induced electron localization and metal-insulator transitions (MITs) have been a very active research field starting from the seminal paper by Anderson half a century ago. However, pure Anderson insulators are very difficult to identify due to ubiquitous electron-correlation effects. Recently, an MIT has been observed in electrical transport measurements on the crystalline state of phase-change GeSbTe compounds, which appears to be exclusively disorder driven. Subsequent density functional theory simulations have identified vacancy disorder to localize electrons at the Fermi level. Here, we report a direct atomic scale chemical identification experiment on the rocksalt structure obtained upon crystallization of amorphous Ge{sub 2}Sb{sub 2}Te{sub 5}. Our results confirm the two-sublattice structure resolving the distribution of chemical species and demonstrate the existence of atomic disorder on the Ge/Sb/vacancy sublattice. Moreover, we identify a gradual vacancy ordering process upon further annealing. These findings not only provide a structural underpinning of the observed Anderson localization but also have implications for the development of novel multi-level data storage within the crystalline phases.

  4. Improving Liquid Entry Pressure of Polyvinylidene Fluoride (PVDF Membranes by Exploiting the Role of Fabrication Parameters in Vapor-Induced Phase Separation VIPS and Non-Solvent-Induced Phase Separation (NIPS Processes

    Directory of Open Access Journals (Sweden)

    Faisal Abdulla AlMarzooqi

    2017-02-01

    Full Text Available Polyvinylidene fluoride (PVDF is a popular polymer material for making membranes for several applications, including membrane distillation (MD, via the phase inversion process. Non-solvent-induced phase separation (NIPS and vapor-induced phase separation (VIPS are applied to achieve a porous PVDF membrane with low mass-transfer resistance and high contact angle (hydrophobicity. In this work, firstly, the impacts of several preparation parameters on membrane properties using VIPS and NIPS were studied. Then, the performance of the selected membrane was assessed in a lab-scale direct-contact MD (DCMD unit. The parametric study shows that decreasing PVDF concentration while increasing both relative humidity (RH and exposure time increased the contact angle and bubble-point pore size (BP. Those trends were investigated further by varying the casting thickness. At higher casting thicknesses and longer exposure time (up to 7.5 min, contact angle (CA increased but BP significantly decreased. The latter showed a dominant trend leading to liquid entry pressure (LEP increase with thickness.

  5. Rapid compression induced solidification of two amorphous phases of poly(ethylene terephthalate)

    Energy Technology Data Exchange (ETDEWEB)

    Hong, S M [Laboratory of High Pressure Physics, Southwest Jiaotong University, Chengdu, 610031 (China); Liu, X R [Laboratory of High Pressure Physics, Southwest Jiaotong University, Chengdu, 610031 (China); Su, L [Laboratory of High Pressure Physics, Southwest Jiaotong University, Chengdu, 610031 (China); Huang, D H [Laboratory of High Pressure Physics, Southwest Jiaotong University, Chengdu, 610031 (China); Li, L B [Foods Research Centre Unilever R and D, Vlaardingen Olivier van Noortlaan, 120, 3133 AT Vlaardingen (Netherlands)

    2006-08-21

    Melts of poly(ethylene terephthalate) were solidified by rapid compression to 2 GPa within 20 ms and by a series of comparative processes including natural cooling, slow compressing and rapid cooling, respectively. By combining XRD and differential scanning calorimetry data of the recovered samples, it is made clear that rapid compression induces two kinds of amorphous phases. One is relatively stable and can also be formed in the slow compression and the cooling processes. Another is metastable and transforms to crystalline phase at 371 K. This metastable amorphous phase cannot be obtained by slow compression or natural cooling, and its crystallization temperature is remarkably different from that of the metastable amorphous phase formed in the rapid cooling sample.

  6. Mechanical and structural behaviour of uranium α, β, γ phases during plastic deformation

    International Nuclear Information System (INIS)

    Prunier, C.; Collot, C.

    1981-06-01

    High temperature behaviour of rich and poor uranium alloys in α, β and γ crystalline structures is studied: dynamic recrystallization phenomena begins only in α and β phases high temperature range, high strength and brittle β phase shows a very large ductility above 700 0 C. Dynamic recrystallization in γ phase rich alloys is observed only if large energy is available. Recrystallization is a thermal actived phenomena localised at grain boundary, dependant with alloy concentration and crystalline structure. β phase activation energy and deformation rate for dynamic recrystallization beginning are the most important in relation with structure complexity; both temperature and rate deformation are dynamic recrystallization factors [fr

  7. Soft modes and structural phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Venkataraman, G [Reactor Research Centre, Kalpakkam (India)

    1979-12-01

    A survey of soft modes and their relationship to structural phase transitions is presented. After introducing the concept of a soft mode, the origin of softening is considered from a lattice-dynamical point. The Landau theory approach to structural transitions is then discussed, followed by a generalisation of the soft-mode concept through the use of the dynamic order-parameter susceptibility. The relationship of soft modes to broken symmetry is also examined. Experimental results for several classes of crystals are next presented, bringing out various features such as the co-operative Jahn-Teller effect. The survey concludes with a discussion of the central peak, touching upon both the experimental results and the theoretical speculations.

  8. Vortex-Induced Waves in Two-Phase Liquid-Liquid Flows past Bluff Body

    Science.gov (United States)

    Zainal Abidin, M. I. I.; Park, Kyeong H.; Angeli, Panagiota; Xie, Zhihua; Kahouadji, Lyes; Matar, Omar K.

    2017-11-01

    Transverse cylinders of various sizes are used to generate vortex-induced interfacial waves in two-phase oil-water flows and to influence flow pattern transitions. The vortex shedding properties at different cylinder sizes and the resulting induced waves are studied experimentally with Particle Image Velocimetry (PIV) and high-speed imaging. The system consists of a 7 m long horizontal 37 mm ID acrylic pipe and different cylinders with diameters of 2, 5 and 8 mm, located in the water phase, 460 mm after the two phases come into contact. The cylinder generates waves with frequencies similar to the von Karman vortices and changes in vortex shedding properties at different cylinder size are reflected on the resulting interfacial wave characteristics. The presence of the transverse cylinder actuates the transition from stratified to dispersed flows; the boundary between the two patterns is shifted to lower mixture velocity with increasing cylinder size. Three-dimensional numerical simulation of the system is developed to assist in designing new system. Project funded by EPSRC UK and Memphis Grant.

  9. Femtosecond laser-induced phase transformations in amorphous Cu{sub 77}Ni{sub 6}Sn{sub 10}P{sub 7} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.; Zou, G.; Wu, A.; Bai, H. [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Liu, L., E-mail: liulei@tsinghua.edu.cn [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); The State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Chen, N. [School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhou, Y. [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

    2015-01-14

    In this study, the femtosecond laser-induced crystallization of CuNiSnP amorphous ribbons was investigated by utilizing an amplified Ti:sapphire laser system. X-ray diffraction and scanning electronic microscope were applied to examine the phase and morphology changes of the amorphous ribbons. Micromachining without crystallization, surface patterning, and selective crystallization were successfully achieved by changing laser parameters. Obvious crystallization occurred under the condition that the laser fluence was smaller than the ablation threshold, indicating that the structural evolution of the material depends strongly on the laser parameters. Back cooling method was used to inhibit heat accumulation; a reversible transformation between the disordered amorphous and crystalline phases can be achieved by using this method.

  10. Phase structure of the SU(5) Coleman-Weinberg theory

    International Nuclear Information System (INIS)

    Tkachev, I.I.

    1984-01-01

    The phase structure of the SU(5) Coleman-Weinberg theory in the one-loop approximation is obtained with account of temperature and space-time curvature. We show that the most essential contribution is that from the interaction between 5 and 24 scalar fields which reflects the existence of two strongly different mass scales in the model. A stability boundary of the SU(3) x SU(2) x U(1) phase is found. It is shown that the SU(4) x U(1) phase in the Coleman-Weinberg theory is unstable. (orig.)

  11. Shear induced structures in crystallizing cocoa butter

    Science.gov (United States)

    Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

    2004-03-01

    Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

  12. Electron-irradiation induced changes in structural and magnetic properties of Fe and Co based metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Kane, S.N., E-mail: kane_sn@yahoo.com [School of Physics, D.A. University, Khandwa Road Campus, Indore 452001 (India); Satalkar, M., E-mail: satalkar.manvi@gmail.com [School of Physics, D.A. University, Khandwa Road Campus, Indore 452001 (India); Ghosh, A.; Shah, M. [School of Physics, D.A. University, Khandwa Road Campus, Indore 452001 (India); Ghodke, N. [UGC-DAE CSR, University Campus, Khandwa Road, Indore 452001 (India); Pramod, R.; Sinha, A.K.; Singh, M.N.; Dwivedi, J. [Raja Ramanna Centre for Advanced Technology, P.O. CAT, Indore 452013 (India); Coisson, M.; Celegato, F.; Vinai, F.; Tiberto, P. [INRIM, Electromagnetism Division, Strada Delle Cacce 91, I-10135 TO (Italy); Varga, L.K. [RISSPO, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary)

    2014-12-05

    Highlights: • Enhancement of Ms by low electron irradiation dose in Fe-based alloy. • Variation of magnetic properties by electron irradiation induced ordered phase. • Electron irradiation alters TM-TM distance and, magnetic properties. - Abstract: Electron-irradiation induced changes in structural and, magnetic properties of Co{sub 57.6}Fe{sub 14.4}Si{sub 4.8}B{sub 19.2}Nb{sub 4}, Fe{sub 72}Si{sub 4.8}B{sub 19.2}Nb{sub 4} and, Co{sub 72}Si{sub 4.8}B{sub 19.2}Nb{sub 4} metallic glasses were studied using magnetic hysteresis and, synchrotron X-ray diffraction measurements. Results reveal composition dependent changes of magnetic properties in electron irradiated metallic glasses. A low electron irradiation dose (15 kGy) enhances saturation magnetization (up to 62%) in Fe-based alloy (Fe{sub 72}Si{sub 4.8}B{sub 19.2}Nb{sub 4}). Synchrotron XRD measurements reveal that electron irradiation transforms the amorphous matrix to a more ordered phase, accountable for changes in magnetic properties.

  13. Phase structure of NJL model with weak renormalization group

    Science.gov (United States)

    Aoki, Ken-Ichi; Kumamoto, Shin-Ichiro; Yamada, Masatoshi

    2018-06-01

    We analyze the chiral phase structure of the Nambu-Jona-Lasinio model at finite temperature and density by using the functional renormalization group (FRG). The renormalization group (RG) equation for the fermionic effective potential V (σ ; t) is given as a partial differential equation, where σ : = ψ bar ψ and t is a dimensionless RG scale. When the dynamical chiral symmetry breaking (DχSB) occurs at a certain scale tc, V (σ ; t) has singularities originated from the phase transitions, and then one cannot follow RG flows after tc. In this study, we introduce the weak solution method to the RG equation in order to follow the RG flows after the DχSB and to evaluate the dynamical mass and the chiral condensate in low energy scales. It is shown that the weak solution of the RG equation correctly captures vacuum structures and critical phenomena within the pure fermionic system. We show the chiral phase diagram on temperature, chemical potential and the four-Fermi coupling constant.

  14. Pressure induced magneto-structural phase transitions in layered RMn2X2 compounds (invited)

    International Nuclear Information System (INIS)

    Kennedy, Shane; Wang, Jianli; Campbell, Stewart; Hofmann, Michael; Dou, Shixue

    2014-01-01

    We have studied a range of pseudo-ternaries derived from the parent compound PrMn 2 Ge 2 , substituting for each constituent element with a smaller one to contract the lattice. This enables us to observe the magneto-elastic transitions that occur as the Mn-Mn nearest neighbour distance is reduced and to assess the role of Pr on the magnetism. Here, we report on the PrMn 2 Ge 2−x Si x , Pr 1−x Y x Mn 2 Ge 2 , and PrMn 2−x Fe x Ge 2 systems. The pressure produced by chemical substitution in these pseudo-ternaries is inherently non-uniform, with local pressure variations dependent on the local atomic distribution. We find that concentrated chemical substitution on the R or X site (e.g., in Pr 0.5 Y 0.5 Mn 2 Ge 2 and PrMn 2 Ge 0.8 Si 1.2 ) can produce a separation into two distinct magnetic phases, canted ferromagnetic and canted antiferromagnetic, with a commensurate phase gap in the crystalline lattice. This phase gap is a consequence of the combination of phase separation and spontaneous magnetostriction, which is positive on transition to the canted ferromagnetic phase and negative on transition to the canted antiferromagnetic phase. Our results show that co-existence of canted ferromagnetic and antiferromagnetic phases depends on chemical pressure from the rare earth and metalloid sites, on local lattice strain distributions and on applied magnetic field. We demonstrate that the effects of chemical pressure bear close resemblance to those of mechanical pressure on the parent compound

  15. Slow and fast light in SOA-EA structures for phased-array antennas

    DEFF Research Database (Denmark)

    Sales, S.; Öhman, Filip; Bermejo, A.

    We present an SOA-EA structure for controlling the phase and amplitude of optically fed phased-array antennas. Phase shifts of 40 degrees are obtained through slow and fast light effects by changing only the reverse voltage....

  16. Effects of induced magnetic field on large scale pulsed MHD generator with two phase flow

    International Nuclear Information System (INIS)

    Ishikawa, M.; Koshiba, Y.; Matsushita, T.

    2004-01-01

    A large pulsed MHD generator 'SAKHALIN' was constructed in Russia (the former Soviet-Union) and operated with solid fuels. The 'SAKHALIN' with the channel length of 4.5 m could demonstrate the electric power output of 510 MW. The effects of induced magnetic field and two phase flow on the shock wave within the 'SAKHALIN' generator have been studied by time dependent, one dimensional analyses. It has been shown that the magnetic Reynolds number is about 0.58 for Run No. 1, and the induced magnetic flux density is about 20% at the entrance and exit of the MHD channel. The shock wave becomes stronger when the induced magnetic field is taken into account, when the operation voltage becomes low. The working gas plasma contains about 40% of liquid particles (Al 2 O 3 ) in weight, and the present analysis treats the liquid particles as another gas. In the case of mono-phase flow, the sharp shock wave is induced when the load voltage becomes small such as 500 V with larger Lorentz force, whereas in the case of two phase flow, the shock wave becomes less sharp because of the interaction with liquid particles

  17. Phase structure of hot and/or dense QCD with the Schwinger-Dyson equation

    Energy Technology Data Exchange (ETDEWEB)

    Takagi, Satoshi [Nagoya Univ., Nagoya, Aichi (Japan)

    2002-09-01

    We investigate the phase structure of the hot and/or dense QCD using the Schwinger-Dyson equation (SDE) with the improved ladder approximation in the Landau gauge. We solve the coupled SDE for the Majorana masses of the quark and antiquark (separately from the SDE for the Dirac mass) in the finite temperature and/or chemical potential region. The resultant phase structure is rather different from those by other analyses. In addition to this analysis we investigate the phase structure with the different two types of the SDE, in one of which the Majorana mass gap of the antiquark is neglected, while in the other of which the Majorana mass gap of the quark and that of the antiquark are set to be equal. The effect of the Debye mass of the gluon on the phase structure is also investigated. (author)

  18. Thermal-induced structural transition and depolarization behavior in (Bi0.5Na0.5)TiO3-BiAlO3 ceramics

    Science.gov (United States)

    Peng, Ping; Nie, Hengchang; Cheng, Guofeng; Liu, Zhen; Wang, Genshui; Dong, Xianlin

    2018-03-01

    The depolarization temperature Td determines the upper temperature limit for the application of piezoelectric materials. However, the origin of depolarization behavior for Bi-based materials still remains controversial and the mechanism is intricate for different (Bi0.5Na0.5)TiO3-based systems. In this work, the structure and depolarization behavior of (1-x)(Bi0.5Na0.5)TiO3-xBiAlO3 (BNT-BA, x = 0, 0.02, 0.04, 0.06, 0.07) ceramics were investigated using a combination of X-ray diffraction and electrical measurements. It was found that as temperature increased, the induced long-range ferroelectric phase irreversibly transformed to the relaxor phase as evidenced by the temperature-dependent ferroelectric and dielectric properties, which corresponded to a gradual structural change from the rhombohedral to the pseudocubic phase. Therefore, the thermal depolarization behavior of BNT-BA ceramics was proposed to be directly related to the rhombohedral-pseudocubic transition. Furthermore, Td (obtained from thermally stimulated depolarization currents curves) was higher than the induced ferroelectric-relaxor phase transition temperature TFR (measured from dielectric curves). The phenomenon was quite different from other reported BNT-based systems, which may suggest the formation of polar nanoregions (PNRs) within macrodomains prior to the detexturation of short-range ferroelectric domains with PNRs or nanodomains.

  19. Total energy calculations for structural phase transformations

    International Nuclear Information System (INIS)

    Ye, Y.Y.; Chan, C.T.; Ho, K.M.; Harmon, B.N.

    1990-01-01

    The structural integrity and physical properties of crystalline solids are frequently limited or enhanced by the occurrence of phase transformations. Martensitic transformations involve the collective displacement of atoms from one ordered state to another. Modern methods to determine the microscopic electronic changes as the atoms move are now accurate enough to evaluate the very small energy differences involved. Extensive first principles calculations for the prototypical martensitic transformation from body-centered cubic (bcc) to closepacked 9R structure in sodium metal are described. The minimum energy coordinate or configuration path between the bcc and 9R structures is determined as well as paths to other competing close-packed structures. The energy barriers and important anharmonic interactions are identified and general conclusions drawn. The calculational methods used to solve the Schrodinger equation include pseudopotentials, fast Fourier transforms, efficient matrix diagnonalization, and supercells with many atoms

  20. Group Lifting Structures For Multirate Filter Banks, II: Linear Phase Filter Banks

    Energy Technology Data Exchange (ETDEWEB)

    Brislawn, Christopher M [Los Alamos National Laboratory

    2008-01-01

    The theory of group lifting structures is applied to linear phase lifting factorizations for the two nontrivial classes of two-channel linear phase perfect reconstruction filter banks, the whole-and half-sample symmetric classes. Group lifting structures defined for the reversible and irreversible classes of whole-and half-sample symmetric filter banks are shown to satisfy the hypotheses of the uniqueness theorem for group lifting structures. It follows that linear phase lifting factorizations of whole-and half-sample symmetric filter banks are therefore independent of the factorization methods used to compute them. These results cover the specification of user-defined whole-sample symmetric filter banks in Part 2 of the ISO JPEG 2000 standard.

  1. Electrostatic Effects in Phase Transitions of Biomembranes between Cubic Phases and Lamellar Liquid-Crystalline (Lα) phase

    Science.gov (United States)

    Masum, Shah Md.; Li, Shu Jie; Tamba, Yukihiro; Yamashita, Yuko; Yamazaki, Masahito

    2004-04-01

    Elucidation of the mechanisms of transitions between cubic phase and liquid-crystalline (Lα) phase, and between different IPMS cubic phases, are essential for understanding of dynamics of biomembranes and topological transformation of lipid membranes. Recently, we found that electrostatic interactions due to surface charges of lipid membranes induce transition between cubic phase and Lα phase, and between different IPMS cubic phases. As electrostatic interactions increase, the most stable phase of a monoolein (MO) membrane changes: Q224 ⇒ Q229 ⇒ Lα. We also found that a de novo designed peptide partitioning into electrically neutral lipid membrane changed the phase stability of the MO membranes. As peptide-1 concentration increased, the most stable phase of a MO membrane changes: Q224 ⇒ Q229 ⇒Lα. In both cases, the increase in the electrostatic repulsive interaction greatly reduced the absolute value of spontaneous curvature of the MO monolayer membrane. We also investigated factors such as poly (L-lysine) and osmotic stress to control structure and phase stability of DOPA/MO membranes. Based on these results, we discuss the mechanism of the effect of electrostatic interactions on the stability of cubic phase.

  2. Structural phase transitions in Zn(CN)2 under high pressures

    International Nuclear Information System (INIS)

    Poswal, H.K.; Tyagi, A.K.; Lausi, Andrea; Deb, S.K.; Sharma, Surinder M.

    2009-01-01

    High pressure behavior of zinc cyanide (Zn(CN) 2 ) has been investigated with the help of synchrotron-based X-ray diffraction measurements. Our studies reveal that under pressure this compound undergoes phase transformations and the structures of the new phases depend on whether the pressure is hydrostatic or not. Under hydrostatic conditions, Zn(CN) 2 transforms from cubic to orthorhombic to cubic-II to amorphous phases. In contrast, the non-hydrostatic pressure conditions drive the ambient cubic phase to a partially disordered crystalline phase, which eventually evolves to a substantially disordered phase. The final disordered phase in the latter case is distinct from the amorphous phase observed under the hydrostatic pressures. - Graphical abstract: High pressure X-ray diffraction investigations on Zn(CN) 2 show three phase transformations i.e., cubic→orthorhombic→cubic-II→amorphous. However, the results strongly depend upon the nature of stress

  3. Pressure-induced changes in the electronic structure of solids

    International Nuclear Information System (INIS)

    McMahan, A.K.

    1985-07-01

    A variety of high-pressure metalization and metal-semimetal transitions, crystallographic phase transitions, and equation of state and lattice vibrational anomalies are reviewed in terms of the concepts of electronic transition and pressure-induced loss of covalency. 46 refs., 10 figs

  4. Two-phase modeling of DDT: Structure of the velocity-relaxation zone

    International Nuclear Information System (INIS)

    Kapila, A.K.; Son, S.F.; Bdzil, J.B.; Menikoff, R.; Stewart, D.S.

    1997-01-01

    The structure of the velocity relaxation zone in a hyperbolic, nonconservative, two-phase model is examined in the limit of large drag, and in the context of the problem of deflagration-to-detonation transition in a granular explosive. The primary motivation for the study is the desire to relate the end states across the relaxation zone, which can then be treated as a discontinuity in a reduced, equivelocity model, that is computationally more efficient than its parent. In contrast to a conservative system, where end states across thin zones of rapid variation are determined principally by algebraic statements of conservation, the nonconservative character of the present system requires an explicit consideration of the structure. Starting with the minimum admissible wave speed, the structure is mapped out as the wave speed increases. Several critical wave speeds corresponding to changes in the structure are identified. The archetypal structure is partly dispersed, monotonic, and involves conventional hydrodynamic shocks in one or both phases. The picture is reminiscent of, but more complex than, what is observed in such (simpler) two-phase media as a dusty gas. copyright 1997 American Institute of Physics

  5. Flow-induced vibrations of circular cylindrical structures

    International Nuclear Information System (INIS)

    Chen, S.

    1977-06-01

    The problems of flow-induced vibrations of circular cylindrical structures are reviewed. First, the general method of analysis and classification of structural responses are presented. Then, the presentation is broken up along the lines with stationary fluid, parallel flow, and cross flow. Finally, design considerations and future research needs are pointed out. 234 references

  6. Structural evolution of epitaxial SrCoOx films near topotactic phase transition

    Science.gov (United States)

    Jeen, Hyoungjeen; Lee, Ho Nyung

    2015-12-01

    Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx) epitaxially grown by pulsed laser epitaxy (PLE) as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO2.5 thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO3-δ). We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

  7. Structural evolution of epitaxial SrCoOx films near topotactic phase transition

    Directory of Open Access Journals (Sweden)

    Hyoungjeen Jeen

    2015-12-01

    Full Text Available Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx epitaxially grown by pulsed laser epitaxy (PLE as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO2.5 thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO3-δ. We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

  8. Formation of cubic phases from large unilamellar vesicles of dioleoylphosphatidylglycerol/monoolein membranes induced by low concentrations of Ca2+.

    Science.gov (United States)

    Awad, Tarek S; Okamoto, Yoshihide; Masum, Shah Md; Yamazaki, Masahito

    2005-12-06

    We developed a new method for the transformation of large unilamellar vesicles (LUVs) into the cubic phase. We found that the addition of low concentrations of Ca(2+) to suspensions of multilamellar vesicles (MLVs) of membranes of monoolein (MO) and dioleoylphosphatidylglycerol (DOPG) mixtures (DOPG/MO) changed their L(alpha) phase to the cubic phases. For instance, the addition of 15-25 mM Ca(2+) to 30%-DOPG/70%-MO-MLVs induced the Q(229) phase, whereas the addition of > or =28 mM Ca(2+) induced the Q(224) phase. LUVs of DOPG/MO membranes containing > or =25 mol % DOPG were prepared easily. Low concentrations of Ca(2+) transformed these LUVs in excess buffer into the Q(224) or the Q(229) phase, depending on the Ca(2+) concentration. For example, 15 and 50 mM Ca(2+) induced the Q(224) and Q(229) phase in the 30%-DOPG/70%-MO-LUVs at 25 degrees C, respectively. This finding is the first demonstration of transformation of LUVs of lipid membranes into the cubic phase under excess water condition.

  9. Thin film structures and phase stability

    International Nuclear Information System (INIS)

    Clemens, B.M.; Johnson, W.L.

    1990-01-01

    This was a two day symposium, with invited and contributed papers as well as an evening poster session. The first day concentrated on solid state reactions with invited talks by Lindsay Greer from the University of Cambridge, King Tu from IBM Yorktown Heights, and Carl Thompson from MIT. Professor Greer observed that the diffusion of Zr is 10 6 times slower than that of Ni in amorphous NiZr, confirming that Ni is the mobile species in solid state amorphization. King Tu explained the formation of metastable phases in this film diffusion couples by the concept of maximum rate of free energy change. Carl Thompson discussed the formation of amorphous phases in metal silicon systems, and discussed a two stage nucleation and growth process. The contributed papers also generated discussion on topics such as phase segregation, amorphous silicide formation, room temperature oxidation of silicon, and nucleation during ion beam irradiation. There was a lively poster session on Monday evening with papers on a wide variety of topics covering the general area of thin film science. The second day had sessions Epitaxy and Multilayer Structure I and II, with the morning focussing on epitaxial and heteroepitaxial growth of thin films. Robin Farrow of IBM Almaden led off with an invited talk where he reported on some remarkable success he and his co-workers have had in growing single crystal epitaxial thin films and superlattices of silver, iron, cobalt and platinum on GaAs. This was followed by several talks on epitaxial growth and characterization. The afternoon focused on interfaces and structure of multilayered materials. A session on possible stress origins of the supermodulus effect was highlighted by lively interaction from the audience. Most of the papers presented at the symposium are presented in this book

  10. Phase conversion for fusion lasers

    International Nuclear Information System (INIS)

    Kessler, T.; Castle, W.; Sampat, N.; Skupsky, S.; Smith, D.; Swales, S.

    1988-01-01

    An essential requirement for direct drive laser fusion is the uniform irradiation of spherical targets that are located in the quasi-far field of a laser system. A major impediment to irradiation uniformity with high-power solid-state laser systems is the presence of a hot-spot structure at the target plane. The hot-spot intensity nonuniformities are caused by spatial variations in the near-field phase front of each laser beam. Although for many tabletop applications diffraction-limited laser performance can be obtained through static phase correction, adaptive optics, or phase conjugation, such approaches are either excessively expensive, difficult to implement, or not yet available for large-aperture, high-peak-power laser beams. An alternative to phase correcting a wavefront involves modifying the laser beam's coherence properties thereby changing its focusing characteristics. The method of induced spatial incoherence (ISI) involves a reduction in both spatial and temporal coherence. Other methods are based on modifications of only the spatial coherence of a laser beam. A phase conversion technology which incorporates a distribution of near-field phases to either perform static phase correction or induce spatial incoherence offers a route toward increasingly higher levels of irradiation uniformity

  11. Upgraded phase control system for superconducting low-velocity accelerating structures

    Energy Technology Data Exchange (ETDEWEB)

    Added, N [Sao Paulo Univ., SP (Brazil); Clifft, B E; Shepard, K W [Argonne National Lab., IL (United States)

    1992-11-01

    Microphonic-induced fluctuations in the RF eigenfrequency of superconducting (SC) slow-wave structures must be compensated by a fast-tuning system in order to control the RF phase. The tuning system must handle a reactive power proportional to the product of the frequency range and the RF energy content of the RF cavity. The fast tuner for the SC resonators in the ATLAS heavy-ion linac is a voltage-controlled reactance based on an array of PIN diodes operating immersed in liquid nitrogen. This paper discusses recent upgrades to the ATLAS fast tuner which can now provide as much as 30 KVA of reactive tuning capability with a real RF power loss of less than 300 watts. The design was guided by numerical modeling of all elements of the device. Also discussed is the RF coupler which can couple 30 KW from 77 K tuner to a 4.2 K resonant cavity with less than 2 W of RF loss into 4.2 K. (Author) 6 refs., 2 figs.

  12. Upgraded phase control system for superconducting low-velocity accelerating structures

    International Nuclear Information System (INIS)

    Added, N.; Clifft, B.E.; Shepard, K.W.

    1992-01-01

    Microphonic-induced fluctuations in the RF eigenfrequency of superconducting (SC) slow-wave structures must be compensated by a fast-tuning system in order to control the RF phase. The tuning system must handle a reactive power proportional to the product of the frequency range and the RF energy content of the RF cavity. The fast tuner for the SC resonators in the ATLAS heavy-ion linac is a voltage-controlled reactance based on an array of PIN diodes operating immersed in liquid nitrogen. This paper discusses recent upgrades to the ATLAS fast tuner which can now provide as much as 30 KVA of reactive tuning capability with a real RF power loss of less than 300 watts. The design was guided by numerical modeling of all elements of the device. Also discussed is the RF coupler which can couple 30 KW from 77 K tuner to a 4.2 K resonant cavity with less than 2 W of RF loss into 4.2 K. (Author) 6 refs., 2 figs

  13. Notes on qubit phase space and discrete symplectic structures

    International Nuclear Information System (INIS)

    Livine, Etera R

    2010-01-01

    We start from Wootter's construction of discrete phase spaces and Wigner functions for qubits and more generally for finite-dimensional Hilbert spaces. We look at this framework from a non-commutative space perspective and we focus on the Moyal product and the differential calculus on these discrete phase spaces. In particular, the qubit phase space provides the simplest example of a four-point non-commutative phase space. We give an explicit expression of the Moyal bracket as a differential operator. We then compare the quantum dynamics encoded by the Moyal bracket to the classical dynamics: we show that the classical Poisson bracket does not satisfy the Jacobi identity thus leaving the Moyal bracket as the only consistent symplectic structure. We finally generalize our analysis to Hilbert spaces of prime dimensions d and their associated d x d phase spaces.

  14. Shape Memory Alloy-Based Periodic Cellular Structures, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase II effort will continue to develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular...

  15. Quantification of signal detection performance degradation induced by phase-retrieval in propagation-based x-ray phase-contrast imaging

    Science.gov (United States)

    Chou, Cheng-Ying; Anastasio, Mark A.

    2016-04-01

    In propagation-based X-ray phase-contrast (PB XPC) imaging, the measured image contains a mixture of absorption- and phase-contrast. To obtain separate images of the projected absorption and phase (i.e., refractive) properties of a sample, phase retrieval methods can be employed. It has been suggested that phase-retrieval can always improve image quality in PB XPC imaging. However, when objective (task-based) measures of image quality are employed, this is not necessarily true and phase retrieval can be detrimental. In this work, signal detection theory is utilized to quantify the performance of a Hotelling observer (HO) for detecting a known signal in a known background. Two cases are considered. In the first case, the HO acts directly on the measured intensity data. In the second case, the HO acts on either the retrieved phase or absorption image. We demonstrate that the performance of the HO is superior when acting on the measured intensity data. The loss of task-specific information induced by phase-retrieval is quantified by computing the efficiency of the HO as the ratio of the test statistic signal-to-noise ratio (SNR) for the two cases. The effect of the system geometry on this efficiency is systematically investigated. Our findings confirm that phase-retrieval can impair signal detection performance in XPC imaging.

  16. Pressure-induced structural, magnetic and transport transitions in Sr2FeO3 from first-principles

    Directory of Open Access Journals (Sweden)

    Ting Jia

    2017-05-01

    Full Text Available The serial system Srn+1FenO2n+1(n=1,2,3… with the FeO4 square planar motif exhibits abundant phase transitions under pressure. In this work, we investigate the pressure-induced structural, magnetic and transport transitions in Sr2FeO3 from first-principles. Our results show that the system undergoes a structural transition from Immm to Ammm when the volume decreases by 30%, together with a spin-state transition (SST from high-spin (S = 2 to intermediate-spin (S = 1, an antiferromagnetic-to-ferromagnetic transition and an insulator-to-metal transition (IMT. Besides, the IMT here is a bandwidth controlled transition, but little influenced by the SST.

  17. Collapsing cycloidal structures in the magnetic phase diagram of erbium

    DEFF Research Database (Denmark)

    Jehan, D.A.; McMorrow, D.F.; Simpson, J.A.

    1994-01-01

    The magnetic structure of Er with a magnetic field applied in the hexagonal basal plane has been studied using a combination of experimental techniques and mean-field modeling. From neutron-scattering and magnetization measurements, phase diagrams are constructed. At temperatures above...... approximately 20 K, the application of a field is found to favor cycloidal structures with modulation wave vectors of q(c) = (6/23)c*, (4/15)c*, and (2/7)c*. For fields above almost-equal-to 40 kOe, the (2/7) structure dominates the phase diagram. From a detailed study of this most stable cycloid, we determine...... how it distorts as the field is increased. In low fields, there is a spin reorientation, so that the plane of the cycloid becomes perpendicular to the applied field, while in larger fields, the cycloid collapses through a series of fanlike structures. At lower temperatures, as the field is increased...

  18. Phase structure of lattice QCD for general number of flavors

    International Nuclear Information System (INIS)

    Iwasaki, Y.; Kanaya, K.; Yoshie, T.; Kaya, S.; Sakai, S.

    2004-01-01

    We investigate the phase structure of lattice QCD for the general number of flavors in the parameter space of gauge coupling constant and quark mass, employing the one-plaquette gauge action and the standard Wilson quark action. Performing a series of simulations for the number of flavors N F =6-360 with degenerate-mass quarks, we find that when N F ≥7 there is a line of a bulk first order phase transition between the confined phase and a deconfined phase at a finite current quark mass in the strong coupling region and the intermediate coupling region. The massless quark line exists only in the deconfined phase. Based on these numerical results in the strong coupling limit and in the intermediate coupling region, we propose the following phase structure, depending on the number of flavors whose masses are less than Λ d which is the physical scale characterizing the phase transition in the weak coupling region: When N F ≥17, there is only a trivial IR fixed point and therefore the theory in the continuum limit is free. On the other hand, when 16≥N F ≥7, there is a nontrivial IR fixed point and therefore the theory is nontrivial with anomalous dimensions, however, without quark confinement. Theories which satisfy both quark confinement and spontaneous chiral symmetry breaking in the continuum limit exist only for N F ≤6

  19. Preparation of multishell ICF target plastic-foam cushion materials by thermally induced phase-inversion processes

    International Nuclear Information System (INIS)

    Young, A.T.; Moreno, D.K.; Marsters, R.G.

    1981-01-01

    Homogenous, low-density plastic foams for ICF targets have been prepared by thermally induced phase inversion processes. Uniform, open cell foams have been obtained by the rapid freezing of water solutions of modified cellulose polymers with densities in the range of 5 mg/cm 3 to 0.7 mg/cm 3 and respective average cell sizes of 2 to 40 micrometers. In addition, low-density, microcellular foams have been prepared from the hydrocarbon polymer poly(4-methyl-l-pentene) via a similar phase inversion process using homogenous solutions in organic solvents. These foams have densities from 2 to 5 mg/cm 3 and average cell sizes of 20 micrometers. The physical-chemical aspects of the thermally induced phase inversion process is presented

  20. Phase discrimination in CdSe structures by means of Raman scattering

    International Nuclear Information System (INIS)

    Cusco, R.; Artus, L.; Consonni, V.; Bellet-Amalric, E.; Andre, R.

    2017-01-01

    Raman spectra of epitaxial layers of CdSe grown by molecular beam epitaxy have been measured for the cubic (zincblende) and hexagonal (wurtzite) phases. The Raman spectra are examined in the light of density functional calculations for these two highly similar structures. Characteristic Raman frequencies and spectral features associated with the different symmetry are discussed and reliable criteria for phase discrimination based on Raman spectroscopy are proposed. Although LO frequencies are virtually identical in both structures and may be affected by size effects, the observation of a low energy E 2 mode at 33 cm -1 unambiguously identifies the wurtzite structure and can be used as a specific fingerprint to distinguish between these two phases in CdSe-based nanostructures. The slightly lower LO frequency measured in the zincblende epitaxial layer is ascribed to residual tensile strain. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Phase discrimination in CdSe structures by means of Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Cusco, R.; Artus, L. [Institut Jaume Almera (ICTJA-CSIC), Consejo Superior de Investigaciones Cientificas, Lluis Sole i Sabaris s.n., 08028 Barcelona (Spain); Consonni, V. [Universite Grenoble Alpes and CNRS, LMGP, 38016 Grenoble (France); Bellet-Amalric, E. [Universite Grenoble Alpes and CEA, INAC-PHEILQS, Nanophysique et Semiconducteurs Group, 38000 Grenoble (France); Andre, R. [Universite Grenoble Alpes and CNRS, Institut Neel, Nanophysique et Semiconducteurs Group, 38000 Grenoble (France)

    2017-05-15

    Raman spectra of epitaxial layers of CdSe grown by molecular beam epitaxy have been measured for the cubic (zincblende) and hexagonal (wurtzite) phases. The Raman spectra are examined in the light of density functional calculations for these two highly similar structures. Characteristic Raman frequencies and spectral features associated with the different symmetry are discussed and reliable criteria for phase discrimination based on Raman spectroscopy are proposed. Although LO frequencies are virtually identical in both structures and may be affected by size effects, the observation of a low energy E{sub 2} mode at 33 cm{sup -1} unambiguously identifies the wurtzite structure and can be used as a specific fingerprint to distinguish between these two phases in CdSe-based nanostructures. The slightly lower LO frequency measured in the zincblende epitaxial layer is ascribed to residual tensile strain. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Boron incorporation into rutile: phase equilibria and structural considerations

    Energy Technology Data Exchange (ETDEWEB)

    Grey, I.E.; Li, C.; MacRae, C.M. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), East Melbourne, VIC (Australia). Div of Minerals; Bursill, L.A. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1997-06-01

    Reduction of rutile in the presence of borate flux stabilised the rutile phase relative to reduced rutiles due to incorporation of boron from the flux. In the presence of borates the rutile phase is stabilised to oxygen fugacities that are lower by almost two orders of magnitude compared with fugacities at the limit of the single-phase rutile phase field in the pure Ti-O system. Boron incorporation is accompanied by reduction of titanium to the trivalent state, according to the charge compensation relation: 3Ti{sup 4+}{identical_to} 3 Ti{sup 3+} + B{sup 3+}. Results of powder X-ray diffraction and transmission electron microscopy studies on samples prepared in the temperature range 1100 to 1300 deg C have been used to establish a model for boron incorporation. It is proposed that at the temperatures studied, local defects in boron doped rutile result from displacement of titanium atoms to adjacent interstitial sites coupled with occupation by boron of the triangular face of the vacated octahedral sites. This atomic grouping represents a small element of the TiBO{sub 3} (calcite-type) structure. Annealing at a lower temperature results in ordering of the local defects to form (101){sub r} planar intergrowths of rutile and calcite-type structures. 14 refs., 3 tabs., 8 figs.

  3. Boron incorporation into rutile: phase equilibria and structural considerations

    International Nuclear Information System (INIS)

    Grey, I.E.; Li, C.; MacRae, C.M.; Bursill, L.A.

    1997-01-01

    Reduction of rutile in the presence of borate flux stabilised the rutile phase relative to reduced rutiles due to incorporation of boron from the flux. In the presence of borates the rutile phase is stabilised to oxygen fugacities that are lower by almost two orders of magnitude compared with fugacities at the limit of the single-phase rutile phase field in the pure Ti-O system. Boron incorporation is accompanied by reduction of titanium to the trivalent state, according to the charge compensation relation: 3Ti 4+ ≡ 3 Ti 3+ + B 3+ . Results of powder X-ray diffraction and transmission electron microscopy studies on samples prepared in the temperature range 1100 to 1300 deg C have been used to establish a model for boron incorporation. It is proposed that at the temperatures studied, local defects in boron doped rutile result from displacement of titanium atoms to adjacent interstitial sites coupled with occupation by boron of the triangular face of the vacated octahedral sites. This atomic grouping represents a small element of the TiBO 3 (calcite-type) structure. Annealing at a lower temperature results in ordering of the local defects to form (101) r planar intergrowths of rutile and calcite-type structures. 14 refs., 3 tabs., 8 figs

  4. Get phases from arsenic anomalous scattering: de novo SAD phasing of two protein structures crystallized in cacodylate buffer.

    Directory of Open Access Journals (Sweden)

    Xiang Liu

    Full Text Available The crystal structures of two proteins, a putative pyrazinamidase/nicotinamidase from the dental pathogen Streptococcus mutans (SmPncA and the human caspase-6 (Casp6, were solved by de novo arsenic single-wavelength anomalous diffraction (As-SAD phasing method. Arsenic (As, an uncommonly used element in SAD phasing, was covalently introduced into proteins by cacodylic acid, the buffering agent in the crystallization reservoirs. In SmPncA, the only cysteine was bound to dimethylarsinoyl, which is a pentavalent arsenic group (As (V. This arsenic atom and a protein-bound zinc atom both generated anomalous signals. The predominant contribution, however, was from the As anomalous signals, which were sufficient to phase the SmPncA structure alone. In Casp6, four cysteines were found to bind cacodyl, a trivalent arsenic group (As (III, in the presence of the reducing agent, dithiothreitol (DTT, and arsenic atoms were the only anomalous scatterers for SAD phasing. Analyses and discussion of these two As-SAD phasing examples and comparison of As with other traditional heavy atoms that generate anomalous signals, together with a few arsenic-based de novo phasing cases reported previously strongly suggest that As is an ideal anomalous scatterer for SAD phasing in protein crystallography.

  5. Conducting polymer networks synthesized by photopolymerization-induced phase separation

    Science.gov (United States)

    Yamashita, Yuki; Komori, Kana; Murata, Tasuku; Nakanishi, Hideyuki; Norisuye, Tomohisa; Yamao, Takeshi; Tran-Cong-Miyata, Qui

    2018-03-01

    Polymer mixtures composed of double networks of a polystyrene derivative (PSAF) and poly(methyl methacrylate) (PMMA) were alternatively synthesized by using ultraviolet (UV) and visible (Vis) light. The PSAF networks were generated by UV irradiation to photodimerize the anthracene (A) moieties labeled on the PSAF chains, whereas PMMA networks were produced by photopolymerization of methyl methacrylate (MMA) monomer and the cross-link reaction using ethylene glycol dimethacrylate (EGDMA) under Vis light irradiation. It was found that phase separation process of these networks can be independently induced and promptly controlled by using UV and Vis light. The characteristic length scale distribution of the resulting co-continuous morphology can be well regulated by the UV and Vis light intensity. In order to confirm and utilize the connectivity of the bicontinuous morphology observed by confocal microscopy, a very small amount, 0.1 wt%, of multi-walled carbon nanotubes (MWCNTs) was introduced into the mixture and the current-voltage (I-V) relationship was subsequently examined. Preliminary data show that MWCNTs are preferentially dispersed in the PSAF-rich continuous domains and the whole mixture became electrically conducting, confirming the connectivity of the observed bi-continuous morphology. The experimental data obtained in this study reveal a promising method to design various scaffolds for conducting soft matter taking advantages of photopolymerization-induced phase separation.

  6. Relation between radiation-induced whole lung functional loss and regional structural changes in partial irradiated rat lung

    International Nuclear Information System (INIS)

    Luijk, Peter van; Novakova-Jiresova, Alena; Faber, Hette; Steneker, Marloes N.J.; Kampinga, Harm H.; Meertens, Haarm; Coppes, Robert P.

    2006-01-01

    Purpose: Radiation-induced pulmonary toxicity is characterized by dose, region, and time-dependent severe changes in lung morphology and function. This study sought to determine the relation between the structural and functional changes in the irradiated rat lung at three different phases after irradiation. Materials and Methods: Six groups of animals were irradiated to 16-22 Gy to six different lung regions, each containing 50% of the total lung volume. Before and every 2 weeks after irradiation, the breathing rate (BR) was measured, and at Weeks 8, 26, and 38 CT was performed. From the computed tomography scans, the irradiated lung tissue was delineated using a computerized algorithm. A single quantitative measure for structural change was derived from changes of the mean and standard deviation of the density within the delineated lung. Subsequently, this was correlated with the BR in the corresponding phase. Results: In the mediastinal and apex region, the BR and computed tomography density changes did not correlate in any phase. After lateral irradiation, the density changes always correlated with the BR; however, in all other regions, the density changes only correlated significantly (r 2 = 0.46-0.85, p < 0.05) with the BR in Week 26. Conclusion: Changes in pulmonary function correlated with the structural changes in the absence of confounding heart irradiation

  7. Disorder-induced localization in crystalline phase-change materials.

    Science.gov (United States)

    Siegrist, T; Jost, P; Volker, H; Woda, M; Merkelbach, P; Schlockermann, C; Wuttig, M

    2011-03-01

    Localization of charge carriers in crystalline solids has been the subject of numerous investigations over more than half a century. Materials that show a metal-insulator transition without a structural change are therefore of interest. Mechanisms leading to metal-insulator transition include electron correlation (Mott transition) or disorder (Anderson localization), but a clear distinction is difficult. Here we report on a metal-insulator transition on increasing annealing temperature for a group of crystalline phase-change materials, where the metal-insulator transition is due to strong disorder usually associated only with amorphous solids. With pronounced disorder but weak electron correlation, these phase-change materials form an unparalleled quantum state of matter. Their universal electronic behaviour seems to be at the origin of the remarkable reproducibility of the resistance switching that is crucial to their applications in non-volatile-memory devices. Controlling the degree of disorder in crystalline phase-change materials might enable multilevel resistance states in upcoming storage devices.

  8. Multipodal Structure and Phase Transitions in Large Constrained Graphs

    Science.gov (United States)

    Kenyon, Richard; Radin, Charles; Ren, Kui; Sadun, Lorenzo

    2017-07-01

    We study the asymptotics of large, simple, labeled graphs constrained by the densities of two subgraphs. It was recently conjectured that for all feasible values of the densities most such graphs have a simple structure. Here we prove this in the special case where the densities are those of edges and of k-star subgraphs, k≥2 fixed. We prove that under such constraints graphs are "multipodal": asymptotically in the number of vertices there is a partition of the vertices into M < ∞ subsets V_1, V_2, \\ldots , V_M, and a set of well-defined probabilities g_{ij} of an edge between any v_i \\in V_i and v_j \\in V_j. For 2≤ k≤ 30 we determine the phase space: the combinations of edge and k-star densities achievable asymptotically. For these models there are special points on the boundary of the phase space with nonunique asymptotic (graphon) structure; for the 2-star model we prove that the nonuniqueness extends to entropy maximizers in the interior of the phase space.

  9. Deceleration of arginine kinase refolding by induced helical structures.

    Science.gov (United States)

    Li, Hai-Long; Zhou, Sheng-Mei; Park, Daeui; Jeong, Hyoung Oh; Chung, Hae Young; Yang, Jun-Mo; Meng, Fan-Guo; Hu, Wei-Jiang

    2012-04-01

    Arginine kinase (AK) is a key metabolic enzyme for keeping energy balance in invertebrates. Therefore, regulation of the enzymatic activity and the folding studies of AK from the various invertebrates have been the focus of investigation. We studied the effects of helical structures by using hexafluoroisopropanol (HFIP) on AK folding. Folding kinetic studies showed that the folding rates of the urea-denatured AKs were significantly decelerated after being induced in various concentrations of HFIP. AK lost its activity completely at concentrations greater than 60%. The results indicated that the HFIP-induced helical structures in the denatured state play a negative role in protein folding, and the helical structures induced in 5% (v/v) HFIP act as the most effective barrier against AK taking its native structure. The computational docking simulations (binding energies for -2.19 kcal/mol for AutoDock4.2 and -20.47 kcal/mol for Dock6.3) suggested that HFIP interacts with the several important residues that are predicted by both programs. The excessively pre-organized helical structures not only hampered the folding process, but also ultimately brought about changes in the three-dimensional conformation and biological function of AK.

  10. Higher Strength, Lighter Weight Aluminum Spacecraft Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I program proposes to develop a bulk processing technology for producing ultra fine grain (UFG) aluminum alloy structures. The goal is to demonstrate...

  11. Simulating Nonlinear Dynamics of Deployable Space Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — To support NASA's vital interest in developing much larger solar array structures over the next 20 years, MotionPort LLC's Phase I SBIR project will strengthen...

  12. Interfacial structures in downward two-phase bubbly flow

    International Nuclear Information System (INIS)

    Paranjape, S.S.; Kim, S.; Ishii, M.; Kelly, J.

    2003-01-01

    Downward two-phase flow was studied considering its significance in view of Light Water Reactor Accidents (LWR) such as Loss of Heat Sink (LOHS) by feed water loss or secondary pipe break. The flow studied, was an adiabatic, air-water, co-current, vertically downward two-phase flow. The experimental test sections had internal hydraulic diameters of 25.4 mm and 50.8 mm. Flow regime map was obtained using the characteristic signals obtained from an impedance void meter, employing neural network based identification methodology to minimize the subjective judgment in determining the flow regimes. A four sensor conductivity probe was used to measure the local two phase flow parameters, which characterize the interfacial structures. The local time averaged two-phase flow parameters measured were: void fraction (α), interfacial area concentration (a i ), bubble velocity (v g ), and Sauter mean diameter (D Sm ). The flow conditions were from the bubbly flow regime. The local profiles of these parameters as well as their axial development revealed the nature of the interfacial structures and the bubble interaction mechanisms occurring in the flow. Furthermore, this study provided a good database for the development of the interfacial area transport equation, which dynamically models the changes in the interfacial area along the flow field. An interfacial area transport equation was developed for downward flow based on that developed for the upward flow, with certain modifications in the bubble interaction terms. The area averaged values of the interfacial area concentration were compared with those predicted by the interfacial area transport model. (author)

  13. Phase domain structures in cylindrical magnets under conditions of a first-order magnetic phase transition

    International Nuclear Information System (INIS)

    Dzhezherya, Yu.I.; Klymuk, O.S.

    2011-01-01

    The magnetic and resonance properties of cylindrical magnets at first-order phase transition from paramagnetic to ferromagnetic state were theoretically studied. It has been shown that in the external magnetic field directed perpendicularly to the rotation axis, formation of a specific domain structure of paramagnetic and ferromagnetic layers can be energetically favorable. The parameters of cylindrical phase domains as well as their dependences on temperature, magnetic field and material characteristics have been calculated. Peculiarities of the magnetic resonance spectra appearing as a result of the phase domain formation have been considered. Dependence of the resonance field of the system of ferromagnetic domains on magnetization and temperature has been obtained. - Highlights: → Parameters of the equilibrium system of cylindrical phase domains are calculated. → The range of fields for PM and FM phases coexistence is found. → FMR field of the disk domains is found to be lower than that of the PMR field.→ The resonance field increases with the decrease of temperature lower than T || .

  14. Swift heavy ion irradiation induced phase transformation in undoped and niobium doped titanium dioxide composite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gautam, Subodh K., E-mail: subodhkgtm@gmail.com [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India); Chettah, Abdelhak [LGMM Laboratory, Université 20 Août 1955-Skikda, BP 26, 21000 Skikda (Algeria); Singh, R.G. [Department of Physics, Bhagini Nivedita College, Delhi University, Delhi 110043 (India); Ojha, Sunil; Singh, Fouran [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India)

    2016-07-15

    Study reports the effect of swift heavy ion (SHI) irradiation induced phase transformation in undoped and Niobium doped anatase TiO{sub 2} composite thin films. Investigations were carried out at different densities of electronic excitations (EEs) using 120 MeV Ag and 130 MeV Ni ions irradiations. Films were initially annealed at 900 °C and results revealed that undoped films were highly stable in anatase phase, while the Nb doped films showed the composite nature with the weak presence of Niobium penta-oxide (Nb{sub 2}O{sub 5}) phase. The effect at low density of EEs in undoped film show partial anatase to rutile phase transformation; however doped film shows only further growth of Nb{sub 2}O{sub 5} phase beside the anatase to rutile phase transformation. At higher density of EEs induced by Ag ions, registered continuous ion track of ∼3 nm in lattice which leads to nano-crystallization followed by decomposition/amorphization of rutile TiO{sub 2} and Nb{sub 2}O{sub 5} phases in undoped and doped films, respectively. However, Ni ions are only induced discontinuous sequence of ion tracks with creation of damage and disorder and do not show amorphization in the lattice. The in-elastic thermal spike calculations were carried out for anatase TiO{sub 2} phase to understand the effect of EEs on anatase to rutile phase transformation followed by amorphization in NTO films in terms of continuous and discontinuous track formation by SHI irradiation.

  15. Characteristics of the stress-induced formation of R-phase in ultrafine-grained NiTi shape memory wire

    International Nuclear Information System (INIS)

    Olbricht, J.; Yawny, A.; Pelegrina, J.L.; Eggeler, G.; Yardley, V.A.

    2013-01-01

    Highlights: •We investigated the stress-induced formation of R-phase in NiTi shape memory wires. •The R-phase related strains were isolated from the overall stress-strain-behavior. •The stress–strain characteristics of R-phase suggest a homogeneous transformation. •Thermography confirms the homogeneous R-phase formation in ultrafine-grained NiTi. -- Abstract: The transformation between the cubic B2 and monoclinic B19′ phases in ultrafine-grained pseudoelastic NiTi can occur as a two-step process involving the intermediate rhombohedral R-phase. Experimental work using differential scanning calorimetry, electrical resistance measurements and transmission electron microscopy has demonstrated the formation of this intermediate phase during thermal cycling and during mechanical loading. In the present paper, complementary mechanical and thermographic results are presented which allow to further assess the character of the stress-induced R-phase formation. The transformation from B2 to R-phase is demonstrated to occur homogeneously within the gauge length rather than via advancing Lüders-type transition regions as it is the case in the localized transformation from B2 or R-phase to B19′

  16. Transient Structures and Possible Limits of Data Recording in Phase-Change Materials.

    Science.gov (United States)

    Hu, Jianbo; Vanacore, Giovanni M; Yang, Zhe; Miao, Xiangshui; Zewail, Ahmed H

    2015-07-28

    Phase-change materials (PCMs) represent the leading candidates for universal data storage devices, which exploit the large difference in the physical properties of their transitional lattice structures. On a nanoscale, it is fundamental to determine their performance, which is ultimately controlled by the speed limit of transformation among the different structures involved. Here, we report observation with atomic-scale resolution of transient structures of nanofilms of crystalline germanium telluride, a prototypical PCM, using ultrafast electron crystallography. A nonthermal transformation from the initial rhombohedral phase to the cubic structure was found to occur in 12 ps. On a much longer time scale, hundreds of picoseconds, equilibrium heating of the nanofilm is reached, driving the system toward amorphization, provided that high excitation energy is invoked. These results elucidate the elementary steps defining the structural pathway in the transformation of crystalline-to-amorphous phase transitions and describe the essential atomic motions involved when driven by an ultrafast excitation. The establishment of the time scales of the different transient structures, as reported here, permits determination of the possible limit of performance, which is crucial for high-speed recording applications of PCMs.

  17. Study of irradiation induced defects and phase instability in β phase of Zr Excel alloy with in-situ heavy ion irradiation

    International Nuclear Information System (INIS)

    Yu, H.; Yao, Z.; Kirk, M.A.; Daymond, M.R.

    2015-01-01

    In situ heavy ion irradiation with 1 MeV Kr"2"+ was carried out to study irradiation induced phase change and atomic lattice defects in theβ phase of Zr Excel alloy. No decomposition of β-Zr was observed under irradiation at either 200 "oC or 450 "oC. However, ω-Zr particles experienced shape change and shrinkage associated enrichment of Fe in the β/ω interface at 200 "oC irradiation but not at 450 "oC. The defect evolution in the β-phase was examined with single phase Zr-20Nb alloy. It was found that dislocation loops with Burgers vector 1/2 and both present in β-Zr under room temperature irradiation. (author)

  18. Beneficial effects of benzodiazepine diazepam on chronic stress-induced impairment of hippocampal structural plasticity and depression-like behavior in mice.

    Science.gov (United States)

    Zhao, Yunan; Wang, Zhongli; Dai, Jianguo; Chen, Lin; Huang, Yufang; Zhan, Zhen

    2012-03-17

    Whether benzodiazepines (BZDs) have beneficial effects on the progress of chronic stress-induced impairment of hippocampal structural plasticity and major depression is uncertain. The present study designed four preclinical experiments to determine the effects of BZDs using chronic unpredictable stress model. In Experiment 1, several time course studies on behavior and hippocampus response to stress were conducted using the forced swim and tail suspension tests (FST and TST) as well as hippocampal structural plasticity markers. Chronic stress induced depression-like behavior in the FST and TST as well as decreased hippocampal structural plasticity that returned to normal within 3 wk. In Experiment 2, mice received p.o. administration of three diazepam dosages prior to each variate stress session for 4 wk. This treatment significantly antagonized the elevation of stress-induced corticosterone levels. Only low- (0.5mg/kg) and medium-dose (1mg/kg) diazepam blocked the detrimental effects of chronic stress. In Experiment 3, after 7 wk of stress sessions, daily p.o. diazepam administration during 1 wk recovery phase dose-dependently accelerated the recovery of stressed mice. In Experiment 4, 1 wk diazepam administration to control mice enhanced significantly hippocampal structural plasticity and induced an antidepressant-like behavioral effect, whereas 4 wk diazepam administration produced opposite effects. Hence, diazepam can slow the progress of chronic stress-induced detrimental consequences by normalizing glucocorticoid hormones. Considering the adverse effect of long-term diazepam administration on hippocampal plasticity, the preventive effects of diazepam may depend on the proper dose. Short-term diazepam treatment enhances hippocampal structural plasticity and is beneficial to recovery following chronic stress. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. Composite Structure Monitoring using Direct Write Sensors, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This NASA SBIR Phase II project seeks to develop and demonstrate a suite of sensor products to monitor the health of composite structures. Sensors will be made using...

  20. The effect of phase assemblages, grain boundaries and domain structure on the local switching behavior of rare-earth modified bismuth ferrite ceramics

    International Nuclear Information System (INIS)

    Alikin, Denis O.; Turygin, Anton P.; Walker, Julian; Bencan, Andreja; Malic, Barbara; Rojac, Tadej; Shur, Vladimir Ya.; Kholkin, Andrei L.

    2017-01-01

    Piezoelectric properties and ferroelectric/ferroelastic domain switching behavior of polycrystalline ceramics are strongly influenced by local scale (i.e. <100 nm) phenomena, such as, the phase assemblages, domain structure, and defects. The method of ceramic synthesis strongly effects the local properties and thus plays a critical role in determining the macroscopic ferroelectric and piezoelectric performance. The link between synthesis and local scale properties of ferroelectrics is, however, rarely reported, especially for the emerging lead-free materials systems. In this work, we focus on samarium modified bismuth ferrite ceramics (Bi_0_._8_8Sm_0_._1_2FeO_3, BSFO) prepared by two methods: standard solid state reaction (SSR) and mechanochemi≿ally assisted synthesis (MAS). Each ceramic possesses different properties at the local scale and we used the piezoresponse force microscopy (PFM) complemented by transmission electron microscopy (TEM) to evaluate phase distribution, domain structure and polarization switching to show that an increase in the anti-polar phase assemblages within the polar matrix leads to notable changes in the local polarization switching. SSR ceramics exhibit larger internal bias fields relative to the MAS ceramics, and the grain boundaries produce a stronger effect on the local switching response. MAS ceramics were able to nucleate domains at lower electric-fields and grow them at faster rates, reaching larger final domain sizes than the SSR ceramics. Local evidence of the electric-field induced phase transition from the anti-ferroelectric Pbam to ferroelectric R3c phase was observed together with likely evidence of the existence of head-to-head/tail-to-tail charged domain walls and domain vortex core structures. By comparing the domain structure and local switching behavior of ceramics prepared by two different methods this work brings new insights the synthesis-structure-property relationship in lead-free piezoceramics.

  1. Lamellar-lamellar phase separation of phospholipid bilayers induced by salting-in/-out effects

    Energy Technology Data Exchange (ETDEWEB)

    Hishida, Mafumi [Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8501 (Japan); Seto, Hideki, E-mail: hideki.seto@kek.jp [KENS and CMRC, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan)

    2011-01-01

    The multilamellar structure of phospholipid bilayers is stabilized by the interactions between bilayers. Although the lamellar repeat distance is uniquely determined at the balance point of interactions between bilayers, a lamellar-lamellar phase separation, where the two phases with different lamellar repeat distance coexist, has been reported in a case of adding a salt to the aqueous solution of lipids. In order to understand the physical mechanism of the lamellar-lamellar phase separation, the effects of adding monovalent salt on the lamellar structure are studied by visual observation and by small-angle X-ray scattering. Further, a theoretical model based on the mean field theory is introduced and it is concluded that the salting-in and -out effects of lipid bilayers trigger the lamellar-lamellar phase separation.

  2. Direct determination of triplet phases and enantiomorphs of non-centrosymmetric structures. Pt. 2

    International Nuclear Information System (INIS)

    Huemmer, K.; Weckert, E.; Bondza, H.

    1989-01-01

    Direct measurements of triplet phase relationships for non-centrosymmetric light-atom organic structures with medium-size unit cells are reported. The phase information can be extracted from the three-beam profiles of a Renninger ψ-scan experiment. The measurements were carried out with a special ψ-circle diffractometer installed on a rotating Cu-anode generator. The incident-beam divergence is reduced to 0.02 0 . The experimental results confirm the theoretical considerations of paper I of this work. As triplet phases of ±90 0 can be distinguished, the absolute structure can be determined unambiguously. The measurements show that the triplet-phase-dependent interference effects may be superposed on phase-independent Umweganregung or Aufhellung effects. By a comparison of the ψ-scan profiles of two centrosymmetrically related three-beam cases, the triplet phases of which have opposite signs, it is possible to evaluate the phase-independent effects and to determine the value of the triplet phase with an accuracy of at least 90 0 . (orig.)

  3. Binocular contrast-gain control for natural scenes: Image structure and phase alignment.

    Science.gov (United States)

    Huang, Pi-Chun; Dai, Yu-Ming

    2018-05-01

    In the context of natural scenes, we applied the pattern-masking paradigm to investigate how image structure and phase alignment affect contrast-gain control in binocular vision. We measured the discrimination thresholds of bandpass-filtered natural-scene images (targets) under various types of pedestals. Our first experiment had four pedestal types: bandpass-filtered pedestals, unfiltered pedestals, notch-filtered pedestals (which enabled removal of the spatial frequency), and misaligned pedestals (which involved rotation of unfiltered pedestals). Our second experiment featured six types of pedestals: bandpass-filtered, unfiltered, and notch-filtered pedestals, and the corresponding phase-scrambled pedestals. The thresholds were compared for monocular, binocular, and dichoptic viewing configurations. The bandpass-filtered pedestal and unfiltered pedestals showed classic dipper shapes; the dipper shapes of the notch-filtered, misaligned, and phase-scrambled pedestals were weak. We adopted a two-stage binocular contrast-gain control model to describe our results. We deduced that the phase-alignment information influenced the contrast-gain control mechanism before the binocular summation stage and that the phase-alignment information and structural misalignment information caused relatively strong divisive inhibition in the monocular and interocular suppression stages. When the pedestals were phase-scrambled, the elimination of the interocular suppression processing was the most convincing explanation of the results. Thus, our results indicated that both phase-alignment information and similar image structures cause strong interocular suppression. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. Probing Protein Structure and Folding in the Gas Phase by Electron Capture Dissociation

    Science.gov (United States)

    Schennach, Moritz; Breuker, Kathrin

    2015-07-01

    The established methods for the study of atom-detailed protein structure in the condensed phases, X-ray crystallography and nuclear magnetic resonance spectroscopy, have recently been complemented by new techniques by which nearly or fully desolvated protein structures are probed in gas-phase experiments. Electron capture dissociation (ECD) is unique among these as it provides residue-specific, although indirect, structural information. In this Critical Insight article, we discuss the development of ECD for the structural probing of gaseous protein ions, its potential, and limitations.

  5. Novel phases of lithium-aluminum binaries from first-principles structural search

    Energy Technology Data Exchange (ETDEWEB)

    Sarmiento-Pérez, Rafael; Cerqueira, Tiago F. T.; Botti, Silvana; Marques, Miguel A. L., E-mail: marques@tddft.org [Institut Lumière Matière (UMR5306) and ETSF, Université Lyon 1-CNRS, Université de Lyon, F-69622 Villeurbanne Cedex (France); Valencia-Jaime, Irais [Institut Lumière Matière (UMR5306) and ETSF, Université Lyon 1-CNRS, Université de Lyon, F-69622 Villeurbanne Cedex (France); Centro de Investigación y Estudios Avanzados del IPN, MX-76230 Querétaro (Mexico); Amsler, Maximilian; Goedecker, Stefan [Department of Physics, Universität Basel, Klingelbergstr. 82, 4056 Basel (Switzerland); Romero, Aldo H. [Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

    2015-01-14

    Intermetallic Li–Al compounds are on the one hand key materials for light-weight engineering, and on the other hand, they have been proposed for high-capacity electrodes for Li batteries. We determine from first-principles the phase diagram of Li–Al binary crystals using the minima hopping structural prediction method. Beside reproducing the experimentally reported phases (LiAl, Li{sub 3}Al{sub 2}, Li{sub 9}Al{sub 4}, LiAl{sub 3}, and Li{sub 2}Al), we unveil a structural variety larger than expected by discovering six unreported binary phases likely to be thermodynamically stable. Finally, we discuss the behavior of the elastic constants and of the electric potential profile of all Li–Al stable compounds as a function of their stoichiometry.

  6. Ultrafast optical manipulation of atomic motion in multilayer Ge-Sb-Te phase change materials

    Directory of Open Access Journals (Sweden)

    Fons P.

    2013-03-01

    Full Text Available Phase change random access memory devices have evolved dramatically with the recent development of superlattice structure of Ge-Sb-Te material (GST-SL in terms of its low power consumption. The phase change in GST-SL is mainly characterized by the displacement of Ge atoms. Here we examine a new phase change method, that is the manipulation of Ge-Te bonds using linearly-polarized femtosecond near-infrared optical pulses. As a result, we found that the p-polarized pump pulse is more effective in inducing the reversible and irreversible displacement of Ge atoms along [111] direction in the local structure. This structural change would be induced by the anisotropic carrier-phonon interaction along the [111] direction created by the p-polarized pulse.

  7. Neutron scattering study of the phase transformation of LaNi3 induced by hydriding

    International Nuclear Information System (INIS)

    Ruan Jinghui; Zeng Xiangxin; Niu Shiwen

    1994-01-01

    The phase transformation of LaNi 3 induced by hydriding and de-hydriding is investigated using the neutron diffraction and the neutron inelastic scattering. The results show that the hydriding sample, LaNi 3 H x , is transformed from crystalline state of the LaNi 3 into amorphous state with a microcrystalline characteristic of LaNi 5 , and the de-hydriding sample produced by LaNi 3 H x dehydrated at 600 degree C is decomposed into new crystalline states composed by LaNi 5 -and La-hydrides. The procedure of phase transformation is that the result of the transformation of LaNi 3 induced by hydriding shows the properties of LaNi 5 -H 2 system

  8. Formation of local nanocrystalline structure in a boron steel induced by electropulsing

    International Nuclear Information System (INIS)

    Ma, Bingdong; Zhao, Yuguang; Ma, Jun; Guo, Haichao; Yang, Qing

    2013-01-01

    Highlights: ► The local NC structures in the uniform size of ∼15 nm were obtained by electropulsing. ► The NC structures were made up of γ-Fe without any other phases coexisting. ► The reduction in nucleation barrier of the γ-Fe helped form the local γ-Fe NC structure. ► The steel consisting of the lath martensitic and the γ-Fe nanocrystalline structure exhibits high mechanical properties. - Abstract: Nanocrystalline γ-Fe was obtained locally in a cold-rolled boron steel as a result of transient high-energy electropulsing. The nano-grains of γ-Fe were uniformly about 15 nm in size. No phases other than γ-Fe have been found in the nanocrystalline structure. It is believed that the pulse current enhances the nucleation rate of γ-Fe phase during the phase transformation from α-Fe to γ-Fe, resulting in the formation of local nanostructure. Moreover, in this study the steel consisting of the lath martensitic and the γ-Fe nanocrystalline structure exhibits high mechanical properties.

  9. Accelerated safety analyses - structural analyses Phase I - structural sensitivity evaluation of single- and double-shell waste storage tanks

    International Nuclear Information System (INIS)

    Becker, D.L.

    1994-11-01

    Accelerated Safety Analyses - Phase I (ASA-Phase I) have been conducted to assess the appropriateness of existing tank farm operational controls and/or limits as now stipulated in the Operational Safety Requirements (OSRs) and Operating Specification Documents, and to establish a technical basis for the waste tank operating safety envelope. Structural sensitivity analyses were performed to assess the response of the different waste tank configurations to variations in loading conditions, uncertainties in loading parameters, and uncertainties in material characteristics. Extensive documentation of the sensitivity analyses conducted and results obtained are provided in the detailed ASA-Phase I report, Structural Sensitivity Evaluation of Single- and Double-Shell Waste Tanks for Accelerated Safety Analysis - Phase I. This document provides a summary of the accelerated safety analyses sensitivity evaluations and the resulting findings

  10. Biofilm structure and mass transfer in a gas phase trickle-bed biofilter.

    Science.gov (United States)

    Zhu, X; Suidan, M T; Alonso, C; Yu, T; Kim, B J; Kim, B R

    2001-01-01

    Mass transport phenomena occurring in the biofilms of gas phase trickle-bed biofilters are investigated in this study. The effect of biofilm structure on mass transfer mechanisms is examined using experimental observation from the operating of biofilters, microelectrode techniques and microscopic examination. Since the biofilms of biofilters used for waste gas treatment are not completely saturated with water, there is not a distinguishable liquid layer outside the biofilm. Results suggest that due to this characteristic, gas phase substrates (such as oxygen or volatile organic compounds) may not be limited by the aqueous phase because transport of the compound into the biofilm can occur directly through non-wetted areas. On the other hand, for substrates that are present only in the liquid phase, such as nitrate, the mass transfer limitation is more serious because of the limited liquid supply. Microscopic observations show that a layered structure with void spaces exists within the biofilm. Oxygen concentration distributions along the depth of the biofilms are examined using an oxygen microelectrode. Results indicate that there are some high dissolved oxygen zones inside the biofilm, which suggests the existence of passages for oxygen transfer into the deeper sections of the biofilm in a gas phase trickle-bed biofilter. Both the low gas-liquid mass transfer resistance and the resulting internal structure contribute to the high oxygen penetration within the biofilms in gas phase trickle-bed biofilters.

  11. Administration of Zinc plus Cyclo-(His-Pro Increases Hippocampal Neurogenesis in Rats during the Early Phase of Streptozotocin-Induced Diabetes

    Directory of Open Access Journals (Sweden)

    Bo Young Choi

    2017-01-01

    Full Text Available The effects of zinc supplementation on hippocampal neurogenesis in diabetes mellitus have not been studied. Herein, we investigated the effects of zinc plus cyclo-(His-Pro (ZC on neurogenesis occurring in the subgranular zone of dentate gyrus after streptozotocin (STZ-induced diabetes. ZC (27 mg/kg was administered by gavage once daily for one or six weeks from the third day after the STZ injection, and histological evaluation was performed at 10 (early phase or 45 (late phase days after STZ injection. We found that the proliferation of progenitor cells in STZ-induced diabetic rats showed an increase in the early phase. Additionally, ZC treatment remarkably increased the number of neural progenitor cells (NPCs and immature neurons in the early phase of STZ-induced diabetic rats. Furthermore, ZC treatment showed increased survival rate of newly generated cells but no difference in the level of neurogenesis in the late phase of STZ-induced diabetic rats. The present study demonstrates that zinc supplementation by ZC increases both NPCs proliferation and neuroblast production at the early phase of diabetes. Thus, this study suggests that zinc supplemented with a histidine/proline complex may have beneficial effects on neurogenesis in patients experiencing the early phase of Type 1 diabetes.

  12. Subsurface characterization of an oxidation-induced phase transformation and twinning in nickel-based superalloy exposed to oxy-combustion environments

    International Nuclear Information System (INIS)

    Zhu Jingxi; Holcomb, Gordon R.; Jablonski, Paul D.; Wise, Adam; Li Jia; Laughlin, David E.; Sridhar, Seetharaman

    2012-01-01

    Highlights: ►Oxidation products of Ni-based superalloy were studied in oxy-fuel combustion conditions. ► An oxidation-induced phase transformation occurred in the subsurface region. ► One of the two product phases was not in the Ni database of Thermo-Calc. ► This unknown phase is an ordered derivative of FCC structure of Ni–Ti(–Ta) system. ► This phase is likely detrimental to the mechanical integrity of the alloy in use. - Abstract: In the integration of oxy-fuel combustion to turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO 2 and O 2 . While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation. In this study, bare metal coupons of Ni-base superalloys were exposed in oxy-fuel combustion environment for up to 1000 h and the oxidation-related microstructures were examined. Phase transformation occurred in the subsurface region in Ni-based superalloy and led to twinning. The transformation product phases were analyzed through thermodynamic equilibrium calculations and various electron microscopy techniques, including scanning electron microscopy (SEM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The mechanism by which the phase transformation and the formation of the microstructure occurred was also discussed. The possible effects of the product phases on the performance of the alloy in service were discussed.

  13. Nano-phase separation and structural ordering in silica-rich mixed network former glasses.

    Science.gov (United States)

    Liu, Hao; Youngman, Randall E; Kapoor, Saurabh; Jensen, Lars R; Smedskjaer, Morten M; Yue, Yuanzheng

    2018-06-13

    We investigate the structure, phase separation, glass transition, and crystallization in a mixed network former glass series, i.e., B2O3-Al2O3-SiO2-P2O5 glasses with varying SiO2/B2O3 molar ratio. All the studied glasses exhibit two separate glassy phases: droplet phase (G1) with the size of 50-100 nm and matrix phase (G2), corresponding to a lower calorimetric glass transition temperature (Tg1) and a higher one (Tg2), respectively. Both Tg values decrease linearly with the substitution of B2O3 for SiO2, but the magnitude of the decrease is larger for Tg1. Based on nuclear magnetic resonance and Raman spectroscopy results, we infer that the G1 phase is rich in boroxol rings, while the G2 phase mainly involves the B-O-Si network. Both phases contain BPO4- and AlPO4-like units. Ordered domains occur in G2 upon isothermal and dynamic heating, driven by the structural heterogeneity in the as-prepared glasses. The structural ordering lowers the activation energy of crystal growth, thus promoting partial crystallization of G2. These findings are useful for understanding glass formation and phase separation in mixed network former oxide systems, and for tailoring their properties.

  14. Probing Photoinduced Structural Phase Transitions by Fast or Ultra-Fast Time-Resolved X-Ray Diffraction

    Science.gov (United States)

    Cailleau, Hervé Collet, Eric; Buron-Le Cointe, Marylise; Lemée-Cailleau, Marie-Hélène Koshihara, Shin-Ya

    molecules transform in an independent way each other. Actually the photoinduced phase transition with the establishment of the new electronic and structural oscopic order is preceded by precursor co-operative phenomena due to the formation of nano-scale correlated objects. These are the counterpart of pre-transitional fluctuations at thermal equilibrium which take place above the transition temperature (short range order preceding long range one). Moreover ultra-fast X-ray scattering will play a central role within the fascinating field of manipulating coherence, for instance to directly observe coherent atomic motions induced by a light pulse, such as optical phonons. In the first part of this contribution we present what experimental features are accessible by X-ray scattering to describe the physical picture for a photoinduced structural phase transition. The second part shows how a time-resolved X-ray scattering experiment can be performed with regards to the different pulsed X-ray sources. The first time-resolved X-ray diffraction experiments on photoinduced phase transitions are described and discussed in the third part. Finally some challenges for future are briefly indicated in the conclusion.

  15. Nonequilibrium phase formation in oxides prepared at low temperature: Fergusonite-related phases

    International Nuclear Information System (INIS)

    Mather, S.A.; Davies, P.K.

    1995-01-01

    Sol-gel methods have been developed to prepare YNbO 4 , YTaO 4 , and other rare-earth niobates and tantalates with fergusonite-related crystal structures. At low temperatures, all of the fergusonites, with the exception of SmTaO 4 , crystallize in a metastable tetragonal (T') structure similar to that of tetragonal zirconia. Although all of the equilibrium forms of these oxides adopt a crystal structure containing an ordered distribution of the trivalent and pentavalent cations, a random cation distribution is obtained in the metastable T' phase. Metastable phase formation is often ascribed solely to kinetically limited topotactic crystallization. However, the changes in the grain size and unit-cell volumes that accompany the metastable-to-equilibrium fergusonite conversions imply that other physical phenomena induced by small-particle synthesis, namely the Gibbs-Thompson pressure effect and the increased contribution of surface energy, cannot be ignored

  16. Routine phasing of coiled-coil protein crystal structures with AMPLE

    Directory of Open Access Journals (Sweden)

    Jens M. H. Thomas

    2015-03-01

    Full Text Available Coiled-coil protein folds are among the most abundant in nature. These folds consist of long wound α-helices and are architecturally simple, but paradoxically their crystallographic structures are notoriously difficult to solve with molecular-replacement techniques. The program AMPLE can solve crystal structures by molecular replacement using ab initio search models in the absence of an existent homologous protein structure. AMPLE has been benchmarked on a large and diverse test set of coiled-coil crystal structures and has been found to solve 80% of all cases. Successes included structures with chain lengths of up to 253 residues and resolutions down to 2.9 Å, considerably extending the limits on size and resolution that are typically tractable by ab initio methodologies. The structures of two macromolecular complexes, one including DNA, were also successfully solved using their coiled-coil components. It is demonstrated that both the ab initio modelling and the use of ensemble search models contribute to the success of AMPLE by comparison with phasing attempts using single structures or ideal polyalanine helices. These successes suggest that molecular replacement with AMPLE should be the method of choice for the crystallographic elucidation of a coiled-coil structure. Furthermore, AMPLE may be able to exploit the presence of a coiled coil in a complex to provide a convenient route for phasing.

  17. Analysis of Lipoplex Structure and Lipid Phase Changes

    Energy Technology Data Exchange (ETDEWEB)

    Koynova, Rumiana

    2012-07-18

    Efficient delivery of genetic material to cells is needed for tasks of utmost importance in the laboratory and clinic, such as gene transfection and gene silencing. Synthetic cationic lipids can be used as delivery vehicles for nucleic acids and are now considered the most promising nonviral gene carriers. They form complexes (lipoplexes) with the polyanionic nucleic acids. A critical obstacle for clinical application of the lipid-mediated DNA delivery (lipofection) is its unsatisfactory efficiency for many cell types. Understanding the mechanism of lipid-mediated DNA delivery is essential for their successful application, as well as for a rational design and synthesis of novel cationic lipoid compounds for enhanced gene delivery. A viewpoint now emerging is that the critical factor in lipid-mediated transfection is the structural evolution of lipoplexes within the cell, upon interacting and mixing with cellular lipids. In particular, recent studies showed that the phase evolution of lipoplex lipids upon interaction and mixing with membrane lipids appears to be decisive for transfection success: specifically, lamellar lipoplex formulations, which were readily susceptible to undergoing lamellar-nonlamellar phase transition upon mixing with cellular lipids and were found rather consistently associated with superior transfection potency, presumably as a result of facilitated DNA release. Thus, understanding the lipoplex structure and the phase changes upon interacting with membrane lipids is important for the successful application of the cationic lipids as gene carriers.

  18. Solid-phase synthesis of an apoptosis-inducing tetrapeptide mimicking the Smac protein

    DEFF Research Database (Denmark)

    Le Quement, Sebastian Thordal; Ishøy, Mette; Petersen, Mette Terp

    2011-01-01

    An approach for the solid-phase synthesis of apoptosis-inducing Smac peptidomimetics is presented. Using a Rink linker strategy, tetrapeptides mimicking the N-4-terminal residue of the Smac protein [(N-Me)AVPF sequence] were synthesized on PEGA resin in excellent purities and yields. Following two...

  19. G2 phase arrest of cell cycle induced by ionizing radiation

    International Nuclear Information System (INIS)

    Liu Guangwei; Gong Shouliang

    2002-01-01

    The exposure of mammalian cells to X rays results in the prolongation of the cell cycle, including the delay or the arrest in G 1 , S and G 2 phase. The major function of G 1 arrest may be to eliminate the cells containing DNA damage and only occurs in the cells with wild type p53 function whereas G 2 arrest following ionizing radiation has been shown to be important in protecting the cells from death and occurs in all cells regardless of p53 status. So the study on G 2 phase arrest of the cell cycle induced by ionizing radiation has currently become a focus at radiobiological fields

  20. Phase separation and d-wave superconductivity induced by extended electron-exciton interaction

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Ming [Department of Physics and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204 (United States)], E-mail: cheng896@hotmail.com; Su Wupei [Department of Physics and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204 (United States)

    2008-12-15

    Using an auxiliary-field quantum Monte Carlo (AFQMC) method, we have studied a two-dimensional tight-binding model in which the conduction electrons can polarize an adjacent layer of molecules through electron-electron repulsion. Calculated average conduction electron density as a function of chemical potential exhibits a clear break characteristic of phase separation. Compared to the noninteracting system, the d-wave pair-field correlation function shows significant enhancement. The simultaneous presence of phase separation and d-wave superconductivity suggests that an effective extended pairing force is induced by the electron-exciton coupling.

  1. Phase separation and d-wave superconductivity induced by extended electron-exciton interaction

    International Nuclear Information System (INIS)

    Cheng Ming; Su Wupei

    2008-01-01

    Using an auxiliary-field quantum Monte Carlo (AFQMC) method, we have studied a two-dimensional tight-binding model in which the conduction electrons can polarize an adjacent layer of molecules through electron-electron repulsion. Calculated average conduction electron density as a function of chemical potential exhibits a clear break characteristic of phase separation. Compared to the noninteracting system, the d-wave pair-field correlation function shows significant enhancement. The simultaneous presence of phase separation and d-wave superconductivity suggests that an effective extended pairing force is induced by the electron-exciton coupling

  2. Nanocrystalline Fe-Pt alloys. Phase transformations, structure and magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Lyubina, J.V.

    2006-12-21

    This work has been devoted to the study of phase transformations involving chemical ordering and magnetic properties evolution in bulk Fe-Pt alloys composed of nanometersized grains. Nanocrystalline Fe{sub 100-x}Pt{sub x} (x=40-60) alloys have been prepared by mechanical ball milling of elemental Fe and Pt powders at liquid nitrogen temperature. The as-milled Fe-Pt alloys consist of {proportional_to} 100 {mu}m sized particles constituted by randomly oriented grains having an average size in the range of 10-40 nm. Depending on the milling time, three major microstructure types have been obtained: samples with a multilayer-type structure of Fe and Pt with a thickness of 20-300 nm and a very thin (several nanometers) A1 layer at their interfaces (2 h milled), an intermediate structure, consisting of finer lamellae of Fe and Pt (below approximately 100 nm) with the A1 layer thickness reaching several tens of nanometers (4 h milled) and alloys containing a homogeneous A1 phase (7 h milled). Subsequent heat treatment at elevated temperatures is required for the formation of the L1{sub 0} FePt phase. The ordering develops via so-called combined solid state reactions. It is accompanied by grain growth and thermally assisted removal of defects introduced by milling and proceeds rapidly at moderate temperatures by nucleation and growth of the ordered phases with a high degree of the long-range order. In a two-particle interaction model elaborated in the present work, the existence of hysteresis in recoil loops has been shown to arise from insufficient coupling between the low- and the high-anisotropy particles. The model reveals the main features of magnetisation reversal processes observed experimentally in exchange-coupled systems. Neutron diffraction has been used for the investigation of the magnetic structure of ordered and partially ordered nanocrystalline Fe-Pt alloys. (orig.)

  3. Polymorphism of a lipid extract from Pseudomonas fluorescens: Structure analysis of a hexagonal phase and of a novel cubic phase of extinction symbol Fd--

    International Nuclear Information System (INIS)

    Mariani, P.; Rivas, E.; Delacroix, H.; Luzzati, V.

    1990-01-01

    The phase diagram of the Pseudomonas fluorescens lipid extract is unusual, in the sense that it displays a cubic phase straddled by a hexagonal phase. The hexagonal phase was studied over an extended concentration range, and the reflections were phased on the assumption that the structure contains circular cylinders of known radius. The cubic phase, whose extinction symbol is Fd--, was analyzed by reference to space group No. 227 (Fd3m). The phases of the reflections were determined by using a novel pattern recognition approach, based upon the notion that the average fourth power of the electron density contrast 4 > is dependent on chemical composition but not on physical structure, provided that the function Δr(r) satisfies the constraints = 0 and 2 > = 1. The authors analyzed two cubic samples of different composition: for each of them they generated all the phase combinations compatible with the X-ray scattering data and they searched for those whose 4 > best agrees with the hexagonal phase. They concluded that the chemical composition of the phases being compared must be identical, that the X-ray scattering data should not be truncated artificially, and that the apodization must be mild so that the curvature takes a value intermediate between those corresponding to the raw data of the two phases. The structure may be visualized as a 3D generalization of the lipid monolayer. The structure, moreover, does not belong to the class of the infinite periodic surfaces without intersections

  4. On the crystal structure of Z-phase Cr(V,Nb)N

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John; Grumsen, Flemming Bjerg

    2006-01-01

    The Z-phase Cr(YNb)N particles in various 9 to 12 pct Cr creep-resistant steels were investigated with electron diffraction, energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy(EELS). In addition to the well-known tetragonal crystal structure for Z phase, a cubic crystal s...

  5. A phase transition in energy-filtered RNA secondary structures

    DEFF Research Database (Denmark)

    Han, Hillary Siwei; reidys, Christian

    2012-01-01

    In this paper we study the effect of energy parameters on minimum free energy (mfe) RNA secondary structures. Employing a simplified combinatorial energy model, that is only dependent on the diagram representation and that is not sequence specific, we prove the following dichotomy result. Mfe...... this phase transition from a discrete limit to a central limit distribution and subsequently put our result into the context of quantifying the effect of sparsification of the folding of these respective mfe-structures. We show that the sparsification of realistic mfe-structures leads to a constant time...

  6. Pressure-induced chemistry in a nitrogen-hydrogen host-guest structure

    Science.gov (United States)

    Spaulding, Dylan K.; Weck, Gunnar; Loubeyre, Paul; Datchi, Fréderic; Dumas, Paul; Hanfland, Michael

    2014-12-01

    New topochemistry in simple molecular systems can be explored at high pressure. Here we examine the binary nitrogen/hydrogen system using Raman spectroscopy, synchrotron X-ray diffraction, synchrotron infrared microspectroscopy and visual observation. We find a eutectic-type binary phase diagram with two stable high-pressure van der Waals compounds, which we identify as (N2)6(H2)7 and N2(H2)2. The former represents a new type of van der Waals host-guest compound in which hydrogen molecules are contained within channels in a nitrogen lattice. This compound shows evidence for a gradual, pressure-induced change in bonding from van der Waals to ionic interactions near 50 GPa, forming an amorphous dinitrogen network containing ionized ammonia in a room-temperature analogue of the Haber-Bosch process. Hydrazine is recovered on decompression. The nitrogen-hydrogen system demonstrates the potential for new pressure-driven chemistry in high-pressure structures and the promise of tailoring molecular interactions for materials synthesis.

  7. Elucidating the vacuum structure of the Aoki phase

    International Nuclear Information System (INIS)

    Azcoiti, Vicente; Di Carlo, Giuseppe; Follana, Eduardo; Vaquero, Alejandro

    2013-01-01

    In this paper, we discuss the vacuum structure of QCD with two flavors of Wilson fermions, inside the Aoki phase. We provide numerical evidence, coming from HMC simulations in 4 4 , 6 4 and 8 4 lattices, supporting a vacuum structure for this model at strong coupling more complex than the one assumed in the standard wisdom, with new vacua where the expectation value of iψ ¯ γ 5 ψ can take non-zero values, and which can not be connected with the Aoki vacua by parity–flavor symmetry transformations

  8. Martensitic phase transformations in the nanostructured surface layers induced by mechanical attrition treatment

    International Nuclear Information System (INIS)

    Ni Zhichun; Wang Xiaowei; Wu Erdong; Liu Gang

    2005-01-01

    Conversion electron Moessbauer spectroscopy (CEMS) and x-ray diffraction (XRD) analysis have been used to investigate the relationship between characteristics of phase transformation and the treatment time in surface nanocrystallized 316L stainless steel induced by surface mechanical attrition treatment (SMAT). A similar trend of development of the martensitic phase upon the treatment time has been observed from both CEMS and XRD measurements. However, in the CEMS measurement, two types of martensite phase with different magnetic hyperfine fields are revealed. Based on a random distribution of the non-iron coordinating atoms, a three-element theoretical model is developed to illustrate the difference of two types of martensite phase. The calculated results indicate the segregation of the non-iron atoms associated with SMAT treatment

  9. Study of irradiation induced defects and phase instability in β phase of Zr Excel alloy with in-situ heavy ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yu, H.; Yao, Z., E-mail: 12hy1@queensu.ca [Queen' s University, Department of Mechanical and Materials Engineering, Kingston, ON (Canada); Kirk, M.A. [Argonne National Laboratory, Materials Science Division, Argonne, IL (United States); Daymond, M.R. [Queen' s University, Department of Mechanical and Materials Engineering, Kingston, ON (Canada)

    2015-07-01

    In situ heavy ion irradiation with 1 MeV Kr{sup 2+} was carried out to study irradiation induced phase change and atomic lattice defects in theβ phase of Zr Excel alloy. No decomposition of β-Zr was observed under irradiation at either 200 {sup o}C or 450 {sup o}C. However, ω-Zr particles experienced shape change and shrinkage associated enrichment of Fe in the β/ω interface at 200 {sup o}C irradiation but not at 450 {sup o}C. The defect evolution in the β-phase was examined with single phase Zr-20Nb alloy. It was found that dislocation loops with Burgers vector 1/2<111> and <001> both present in β-Zr under room temperature irradiation. (author)

  10. Modifying effect of 5-fluoro-2-deoxyuridine and thymidine at G1 phase on radiation and chemically induced chromosome rearrangement

    International Nuclear Information System (INIS)

    Azatyan, R.A.; Voskanyan, A.Z.; Avakyan, V.A.; Akif'ev, A.P.

    1978-01-01

    The yield of structural chromosome mutations induced in Crepis capillaris seeds by X-rays and nitrogen mustard was studied as a function of treatment (at G 1 phase) with an inhibitor of unscheduled DNA synthesis, 5-fluoro-2-deoxyuridine (FdU), and its antagonist, thymidine. Air-dry seeds were irradiated at 10 krad and immediately placed in aqueous solutions of FdU, thymidine, or FdU + thymidine. Ionizing radiation induced only chromosome exchanges in the seeds. When EdU was used, the number of chromosome exchanges was the same although the fraction of simple and isolocus deletions was significantly greater than additive. The effect of FdU was manifested only after 10-hour incubation of the cells. Thymidine alone did not appreciably alter the frequency of radiation-induced aberrations. At the same time, the FdU + thymidine combination decreased the mutation yield i.e. was protective. Frequencies of the chromosome aberration in this experiment were the same as in the control

  11. Density induced phase transitions in the Schwinger model. A study with matrix product states

    Energy Technology Data Exchange (ETDEWEB)

    Banuls, Mari Carmen; Cirac, J. Ignacio; Kuehn, Stefan [Max-Planck-Institut fuer Quantenoptik (MPQ), Garching (Germany); Cichy, Krzysztof [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Adam Mickiewicz Univ., Poznan (Poland). Faculty of Physics; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2017-02-15

    We numerically study the zero temperature phase structure of the multiflavor Schwinger model at nonzero chemical potential. Using matrix product states, we reproduce analytical results for the phase structure for two flavors in the massless case and extend the computation to the massive case, where no analytical predictions are available. Our calculations allow us to locate phase transitions in the mass-chemical potential plane with great precision and provide a concrete example of tensor networks overcoming the sign problem in a lattice gauge theory calculation.

  12. [Phase transition in polymer blends and structure of ionomers and copolymers

    Energy Technology Data Exchange (ETDEWEB)

    1993-01-01

    The main thrust of the program in the past 3 years are summarized: SAXS instrumentation development; structure and dynamics of macro- and supra-molecules, phase transitions in polymer blends and solutions, structure of ionomers, and fractals and anisotropic systems.

  13. Direct phase selection of initial phases from single-wavelength anomalous dispersion (SAD) for the improvement of electron density and ab initio structure determination

    International Nuclear Information System (INIS)

    Chen, Chung-De; Huang, Yen-Chieh; Chiang, Hsin-Lin; Hsieh, Yin-Cheng; Guan, Hong-Hsiang; Chuankhayan, Phimonphan; Chen, Chun-Jung

    2014-01-01

    A novel direct phase-selection method to select optimized phases from the ambiguous phases of a subset of reflections to replace the corresponding initial SAD phases has been developed. With the improved phases, the completeness of built residues of protein molecules is enhanced for efficient structure determination. Optimization of the initial phasing has been a decisive factor in the success of the subsequent electron-density modification, model building and structure determination of biological macromolecules using the single-wavelength anomalous dispersion (SAD) method. Two possible phase solutions (ϕ 1 and ϕ 2 ) generated from two symmetric phase triangles in the Harker construction for the SAD method cause the well known phase ambiguity. A novel direct phase-selection method utilizing the θ DS list as a criterion to select optimized phases ϕ am from ϕ 1 or ϕ 2 of a subset of reflections with a high percentage of correct phases to replace the corresponding initial SAD phases ϕ SAD has been developed. Based on this work, reflections with an angle θ DS in the range 35–145° are selected for an optimized improvement, where θ DS is the angle between the initial phase ϕ SAD and a preliminary density-modification (DM) phase ϕ DM NHL . The results show that utilizing the additional direct phase-selection step prior to simple solvent flattening without phase combination using existing DM programs, such as RESOLVE or DM from CCP4, significantly improves the final phases in terms of increased correlation coefficients of electron-density maps and diminished mean phase errors. With the improved phases and density maps from the direct phase-selection method, the completeness of residues of protein molecules built with main chains and side chains is enhanced for efficient structure determination

  14. How to detect the gravitationally induced phase shift of electromagnetic waves by optical-fiber interferometry

    International Nuclear Information System (INIS)

    Tanaka, K.

    1983-01-01

    Attention is called to a laboratory experiment of an optical-fiber interferometer which can show the gravitationally induced phase shift of optical waves. A phase shift of approx.10 -6 rad is anticipated for the Earth's gravitational potential difference of 1 m when a He-Ne laser and two multiple-turn optical-fiber loops of length 5 km are used. The phase shift can be varied by rotating the loops about an axis parallel to the Earth's surface. This order of phase shifts can be detected by current optical-fiber interferometric techniques

  15. Investigations of environmental induced effects on AlQ3 thin films by AFM phase imaging

    International Nuclear Information System (INIS)

    Shukla, Vivek Kumar; Kumar, Satyendra

    2007-01-01

    Tris(8-hydroxyquinoline) metal complex (AlQ 3 ) is a widely used light-emitting material in organic light emitting devices (OLEDs). The environmental stability is still a major problem with OLEDs and needs further improvement. In this report, an additional feature of Atomic Force Microscopy (AFM) was exploited with the aim to understand the environmental induced effects and physical phenomenon involved on AlQ 3 thin films. We have used phase imaging to identify the presence of other aggregation phases formed after annealing the thin film in different ambient and after white light exposure. An enhanced photoluminescence intensity is observed for the samples annealed in oxygen near 100 deg. C. The enhanced photoluminescence is understood in terms of formation of a new aggregation phase. The phase change and the fraction of new phase is estimated by phase images taken by atomic force microscopy (AFM). Light induced effects on AlQ 3 films exposed to white light in air and vacuum are characterized by atomic force microscopy (AFM) for surface morphology and phases present. The AFM images indicate enhanced crystallinity for the vacuum exposed samples. The phase with increased lifetime and hence enhanced crystallinity for vacuum exposed films has also been found by time correlated single photon counting (TCSPC) measurements. To the best of our knowledge, this study is applied for the first time on this material with the combination of topography and phase imaging in atomic force microscopy (AFM). The major aim was to take advantage of the additional feature of AFM-mode over the conventionally used

  16. Electric-field-induced strain contributions in morphotropic phase boundary composition of (Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-BaTiO{sub 3} during poling

    Energy Technology Data Exchange (ETDEWEB)

    Khansur, Neamul H.; Daniels, John E. [School of Materials Science and Engineering, UNSW Australia, New South Wales 2052 (Australia); Hinterstein, Manuel [School of Materials Science and Engineering, UNSW Australia, New South Wales 2052 (Australia); Institute for Applied Materials, Karlsruhe Institute for Technology, P.O. Box 3640, 76021 Karlsruhe (Germany); Wang, Zhiyang [School of Materials Science and Engineering, UNSW Australia, New South Wales 2052 (Australia); The Australian Synchrotron, Clayton, Victoria 3168 (Australia); Groh, Claudia [Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Jo, Wook [School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919 (Korea, Republic of)

    2015-12-14

    The microscopic contributions to the electric-field-induced macroscopic strain in a morphotropic 0.93(Bi{sub 1/2}Na{sub 1/2}TiO{sub 3})−0.07(BaTiO{sub 3}) with a mixed rhombohedral and tetragonal structure have been quantified using full pattern Rietveld refinement of in situ high-energy x-ray diffraction data. The analysis methodology allows a quantification of all strain mechanisms for each phase in a morphotropic composition and is applicable to use in a wide variety of piezoelectric compositions. It is shown that during the poling of this material 24%, 44%, and 32% of the total macroscopic strain is generated from lattice strain, domain switching, and phase transformation strains, respectively. The results also suggest that the tetragonal phase contributes the most to extrinsic domain switching strain, whereas the lattice strain primarily stems from the rhombohedral phase. The analysis also suggests that almost 32% of the total strain is lost or is a one-time effect due to the irreversible nature of the electric-field-induced phase transformation in the current composition. This information is relevant to on-going compositional development strategies to harness the electric-field-induced phase transformation strain of (Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-based lead-free piezoelectric materials for actuator applications.

  17. Chromatin structure influence the sensitivity of DNA to ionizing radiation induced DNA damage

    International Nuclear Information System (INIS)

    Gupta, Sanjay

    2016-01-01

    Chromatin acts as a natural hindrance in DNA-damage recognition, repair and recovery. Histone and their variants undergo differential post-translational modification(s) and regulate chromatin structure to facilitate DNA damage response (DDR). During the presentation we will discuss the importance of chromatin organization and histone modification(s) during IR-induced DNA damage response in human liver cells. Our data shows G1-phase specific decrease of H3 serine10 phosphorylation in response to DNA damage is coupled with chromatin compaction in repair phase of DDR. The loss of H3Ser10P during DNA damage shows an inverse correlation with gain of γH2AX from a same mono-nucleosome in a dose-dependent manner. The loss of H3Ser10P is a universal phenomenon as it is independent of origin of cell lines and nature of genotoxic agents in G1 phase cells. The reversible reduction of H3Ser10P is mediated by opposing activities of phosphatase, MKP1 and kinase, MSK1 of the MAP kinase pathway. The present study suggests distinct reversible histone marks are associated with G1-phase of cell cycle and plays a critical role in chromatin organization which may facilitate differential sensitivity against radiation. Thus, the study raises the possibility of combinatorial modulation of H3Ser10P and histone acetylation with specific inhibitors to target the radio-resistant cancer cells in G1-phase and thus may serve as promising targets for cancer therapy. (author)

  18. Radioimmuoassay study of antidigitoxin antibodies in liquid phase and after coupling on a solid phase

    International Nuclear Information System (INIS)

    Collignon, A.; German, A.; Scherrmann, J.M.; Bourdon, R.

    1983-01-01

    Antidigitoxin antibodies prepared by immunizing rabbits with a digitoxin-bovine serum albumin conjugate have been studied by radioimmunoassay in the native serum (homogeneous phase antibodies) and after coupling on glass beads (heterogeneous phase antibodies). Homogeneous phase antibodies present a satisfactory titer and affinity constant and react very specifically with digitoxin. Fixation of antibodies on a solid phase induce a loss of their immunoreactivity as it is showed by modification of the inhibition curves, by a greater sensitivity to the chemical structure of the tracer and by a decrease of the affinity constant. Reactionnal kinetic and sensitivity to the incubation temperature are not modified. Heterogeneous phase antibodies present a greater stability. Both antibodies types can be used for a digitoxin radioimmunoassay [fr

  19. Radiation-induced structural changes, (2)

    International Nuclear Information System (INIS)

    Ogasawara, M.; Matsuyama, T.

    1992-11-01

    This seminar is aimed at understanding both the physical and chemical aspects of the structural changes of materials induced by photons or ionizing radiation. The seminar was held on December 19th, 1991 and from February 13 to 14th, 1992 in this institute. The most active areas of the material science, in addition to the previous subjects, such as organic superconductors, silicon-based polymers, and fullerenes were included in this seminar. (J.P.N.)

  20. Precipitate-induced R-phase in martensitic transformation of as-spun and annealed Ti51Ni49 ribbons

    International Nuclear Information System (INIS)

    Wu, Ling-Mei; Chang, Shih-Hang; Wu, Shyi-Kaan

    2010-01-01

    Differential scanning calorimetry (DSC) results indicate that a two-step B2 → R → B19' martensitic transformation and a one-step B19' → B2 transformation exhibit in as-spun and in 200-600 o C annealed Ti 51 Ni 49 ribbons. Guinier-Preston (GP) zones and Ti 2 Ni precipitates are formed in ribbons annealed at ≤300 o C and ≥400 o C, respectively, and a conspicuous increase of DSC transformation peak temperature occurs in between 300 o C and 400 o C. The sizes of GP zones and Ti 2 Ni precipitates increase with increased annealing temperature. Transmission electron microscope (TEM) observations show that GP zones can induce the R-phase and both of them are formed along B2 directions. DSC and TEM tests show that Ti 2 Ni precipitates can induce the R-phase more than GP zones and the induced R-phase plates are also found along B2 directions. Experimental results show that the growing direction of R-phase plates is strongly confined by that of GP zones and Ti 2 Ni precipitates. The length of R-phase plates can reach about 2 μm in 300 o C annealed ribbon.

  1. Electron crystallography applied to the structure determination of Nb(Cu,Al,X) Laves phases.

    Science.gov (United States)

    Gigla, M; Lelatko, J; Krzelowski, M; Morawiec, H

    2006-09-01

    The presence of primary precipitates of the Laves phases considerably improves the mechanical properties and the resistance to thermal degradation of the high-temperature shape memory Cu-Al-Nb alloys. The structure analysis of the Laves phases was carried out on particles contained in the ternary and quaternary alloys as well on synthesized compounds related to the composition of the Nb(Cu,Al,X)(2) phase, where X = Ni, Co, Cr, Ti and Zr. The precise structure determination of the Laves phases was carried out by the electron crystallography method using the CRISP software.

  2. Incorporation of uranium in pyrochlore oxides and pressure-induced phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, F.X., E-mail: zhangfx@umich.edu [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Lang, M.; Tracy, C.; Ewing, R.C. [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Gregg, D.J.; Lumpkin, G.R. [Institute of Materials Engineering, ANSTO, Locked Bag 2001, Kirrawee DC 2232, NSW (Australia)

    2014-11-15

    Uranium-doped gadolinium zirconates with pyrochlore structure were studied at ambient and high-pressure conditions up to 40 GPa. The bonding environment of uranium in the structure was determined by x-ray photoelectron and Raman spectroscopies and x-ray diffraction. The uranium valence for samples prepared in air is mainly U{sup 6+}, but U{sup 4+} is present in pyrochlores fabricated in an argon atmosphere. Rietveld refinement of the XRD pattern suggests that uranium ions in pyrochlores are on the 16d site in 6-fold coordination with oxygen. At pressures greater than 22 GPa, the pyrochlore structure transformed to a cotunnite-type phase. The cotunnite high-pressure phase transformed to a defect fluorite structure on the release of pressure. - Graphical abstract: In U-bearing pyrochlore, U ions mainly occupy the 16d site and replace the smaller Zr{sup 4+}, part of the oxygen will occupy the 8b site, which is empty to most pyrochlores. At pressure of 22 GPa, the pyrochlore lattice is not stable and transforms to a cotunnite-type structure. The high-pressure structure is not stable and transform to a fluorite or back to the pyrochlore structure when pressure is released. - Highlights: • We found that U ions mainly occupy the smaller cation site in U-bearing pyrochlore. • Pyrochlore structure is not stable at pressure of more than 20 GPa. • The quenched sample has a pyrochlore or a disordered fluorite structure.

  3. Analysis and Design Tools for Fluid-Structure Interaction with Multi-Body Flexible Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall objective of this proposal (Phases I and II) is to develop a robust and accurate solver for fluid-structure interaction computations capable of...

  4. Preparation and Characterization of Membranes Formed by Nonsolvent Induced Phase Separation: A Review

    KAUST Repository

    Guillen, Gregory R.; Pan, Yinjin; Li, Minghua; Hoek, Eric M. V.

    2011-01-01

    . The body of knowledge has grown exponentially in the past fifty years, which suggests the need for a critical review of the literature. Here we present a review of nonsolvent induced phase separation membrane preparation and characterization for many

  5. Thermodynamic and fluorescence studies of the underlying factors in benzyl alcohol-induced lipid interdigitated phase.

    Science.gov (United States)

    Chen, C H; Hoye, K; Roth, L G

    1996-09-15

    To further investigate factors contributing to the action of alcohol in the solute-induced lipid interdigitation phase, thermodynamic and fluorescence polarization measurements were carried out to study the interaction of benzyl alcohol with dipalmitoyl phosphatidylcholine bilayer vesicles. The obtained results were compared with those previously reported for ethanol and cyclohexanol (L. G. Roth and C-H. Chen, Arch. Biochem. Biophys. 296, 207, 1992). Similar to ethanol, benzyl alcohol was found to exhibit a biphasic effect on the enthalpy (delta Hm) and the temperature (tm) of the lipid-phase transition and the steady-state fluorescence polarization (P) monitored by 1,6-diphenyl-1,3,5-hexatriene. At a total concentration of benzyl alcohol delta Hm and P, which were correlated with the formation of a lipid interdigitated phase, as evidenced by reported X-ray diffraction data. Combining the results with benzyl alcohol and ethanol suggested that simultaneously large changes in delta Hm and P can be used as an indication of the occurrence of a solute-induced lipid interdigitated phase. The overall interacting force in the formation of this lipid phase, as derived from the interactions of the hydroxyl portion of an alcohol with the lipid phosphate head group and the hydrophobic portion of an alcohol with the lipid hydrocarbon chains, may or may not be dominated by hydrophobic interaction. Although lipid/water partition coefficients and the contribution of hydrophobic interaction to the overall interacting force were comparable between benzyl alcohol and cyclohexanol, benzyl alcohol induced lipid interdigitated phase, but not for cyclohexanol. This was due to the ability of benzyl alcohol to be more effective than cyclohexanol in simultaneously interacting with the phosphate head group and the hydrocarbon chains of lipid.

  6. Low temperature phase transition and crystal structure of CsMgPO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Orlova, Maria, E-mail: maria.p.orlova@gmail.com [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Khainakov, Sergey [Departamento de Química Física y Analítica, Universidad de Oviedo—CINN, 33006 Oviedo (Spain); Servicios Científico Técnicos, Universidad de Oviedo, 33006 Oviedo (Spain); Michailov, Dmitriy [Department of Chemistry, University of Nizhny Novgorod, 23 Gagarin av., Nizhny Novgorod 603950 (Russian Federation); Perfler, Lukas [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Langes, Christoph [Institute of Pharmacy, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Kahlenberg, Volker [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Orlova, Albina [Department of Chemistry, University of Nizhny Novgorod, 23 Gagarin av., Nizhny Novgorod 603950 (Russian Federation)

    2015-01-15

    CsMgPO{sub 4} doped with radioisotopes is a promising compound for usage as a radioactive medical source. However, a low temperature phase transition at temperatures close to ambient conditions (∼−40 °C) was observed. Information about such kind of structural changes is important in order to understand whether it can cause any problem for medical use of this compound. The phase transition has been investigated in detail using synchrotron powder diffraction, Raman spectroscopy and DFT calculations. The structure undergoes a transformation from an orthorhombic modification, space group Pnma (RT phase) to a monoclinic polymorph, space group P2{sub 1}/n (LT phase). New LT modification adopts similar to RT but slightly distorted unit cell: a=9.58199(2) Å, b=8.95501(1) Å, c=5.50344(2) Å, β=90.68583(1)°, V=472.198(3) Å{sup 3}. CsMgPO{sub 4} belongs to the group of framework compounds and is made up of strictly alternating MgO{sub 4}- and PO{sub 4}-tetrahedra sharing vertices. The cesium counter cations are located in the resulting channel-like cavities. Upon the transformation a combined tilting of the tetrahedra is observed. A comparison with other phase transitions in ABW-type framework compounds is given. - Graphical abstract: Structural behavior of β-tridymite-type phosphate CsMgPO{sub 4}, considered as potential chemical form for radioactive Cs-source has been studied at near ambient temperatures. A phase transition at (∼−40 °C) has been found and investigated. It has been established that the known orthorhombic RT modification, space group Pnma, adopts a monoclinic cell with space group P2{sub 1}/n at low temperatures. In this paper, we present results of structural analysis of changes accompanying this phase transition and discuss its possible impact on the application properties. - Highlights: • β-Tridymite type phosphate CsMgPO{sub 4} undergoes so called translationengleiche phase transition of index 2 at −40 °C. • The structure

  7. New lipid family that forms inverted cubic phases in equilibrium with excess water: molecular structure-aqueous phase structure relationship for lipids with 5,9,13,17-tetramethyloctadecyl and 5,9,13,17-tetramethyloctadecanoyl chains.

    Science.gov (United States)

    Yamashita, Jun; Shiono, Manzo; Hato, Masakatsu

    2008-10-02

    With a view to discovering a new family of lipids that form inverted cubic phases, the aqueous phase behavior of a series of lipids with isoprenoid-type hydrophobic chains has been examined over a temperature range from -40 to 65 degrees C by using optical microscopy, DSC (differential scanning calorimetry), and SAXS (small-angle X-ray scattering) techniques. The lipids examined are those with 5,9,13,17-tetramethyloctadecyl and 5,9,13,17-tetramethyloctadecanoyl chains linked to a series of headgroups, that is, erythritol, pentaerythritol, xylose, and glucose. All of the lipid/water systems displayed a "water + liquid crystalline phase" two-phase coexistence state when sufficiently diluted. The aqueous phase structures of the most diluted liquid crystalline phases in equilibrium with excess water depend both on the lipid molecular structure and on the temperature. Given an isoprenoid chain, the preferred phase consistently follows a phase sequence of an H II (an inverted hexagonal phase) to a Q II (an inverted bicontinuous cubic phase) to an L alpha (a lamellar phase) as A* (cross-section area of the headgroup) increases. For a given lipid/water system, the phase sequence observed as the temperature increases is L alpha to Q II to H II. The present study allowed us to find four cubic phase-forming lipid species, PEOC 18+4 [mono- O-(5,9,13,17-tetramethyloctadecyl)pentaerythritol], beta-XylOC 18+4 [1- O-(5,9,13,17-tetramethyloctadecyl)-beta- d-xylopyranoside], EROCOC 17+4 [1- O-(5,9,13,17-tetramethyloctadecanoyl)erythritol], and PEOCOC 17+4 [mono- O-(5,9,13,17-tetramethyloctadecanoyl)pentaerythritol]. The values of T K (hydrated solid-liquid crystalline phase transition temperature) of the cubic phase-forming lipids are all below 0 degrees C. Quantitative analyses of the lipid molecular structure-aqueous phase structure relationship in terms of the experimentally evaluated "surfactant parameter" allow us to rationally select an optimum combination of hydrophilic

  8. An Overview of 2014 SBIR Phase I and Phase II Materials Structures for Extreme Environments

    Science.gov (United States)

    Nguyen, Hung D.; Steele, Gynelle C.; Morris, Jessica R.

    2015-01-01

    NASA's Small Business Innovation Research (SBIR) program focuses on technological innovation by investing in development of innovative concepts and technologies to help NASA mission directorates address critical research needs for Agency programs. This report highlights nine of the innovative SBIR 2014 Phase I and Phase II projects that emphasize one of NASA Glenn Research Center's six core competencies-Materials and Structures for Extreme Environments. The technologies cover a wide spectrum of applications such as high temperature environmental barrier coating systems, deployable space structures, solid oxide fuel cells, and self-lubricating hard coatings for extreme temperatures. Each featured technology describes an innovation, technical objective, and highlights NASA commercial and industrial applications. This report provides an opportunity for NASA engineers, researchers, and program managers to learn how NASA SBIR technologies could help their programs and projects, and lead to collaborations and partnerships between the small SBIR companies and NASA that would benefit both.

  9. Rapid insight into heating-induced phase transformations in the solid state of the calcium salt of atorvastatin using multivariate data analysis

    DEFF Research Database (Denmark)

    Christensen, Niels Peter Aae; Van Eerdenbrugh, Bernard; Kwok, Kaho

    2013-01-01

    To investigate the heating-induced dehydration and melting behavior of the trihydrate phase of the calcium salt of atorvastatin.......To investigate the heating-induced dehydration and melting behavior of the trihydrate phase of the calcium salt of atorvastatin....

  10. From phase-change materials to thermoelectrics?

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Matthias N.; Rosenthal, Tobias; Oeckler, Oliver [Dept. of Chemistry, Ludwig Maximilian Univ. Munich (Germany); Stiewe, Christian [German Aerospace Center, Cologne (Germany)

    2010-07-01

    Metastable tellurides play an important role as phase-change materials in data storage media and non-volatile RAM devices. The corresponding crystalline phases with very simple basic structures are not stable as bulk materials at ambient conditions, however, for a broad range of compositions they represent stable high-temperature phases. In the system Ge/Sb/Te, rocksalt-type high-temperature phases are characterized by a large number of vacancies randomly distributed over the cation position, which order as 2D vacancy layers upon cooling. Short-range order in quenched samples produces pronounced nanostructures by the formation of twin domains and finite intersecting vacancy layers. As phase-change materials are usually semimetals or small-bandgap semiconductors and efficient data storage requires low thermal conductivity, bulk materials with similar compositions and properties can be expected to exhibit promising thermoelectric characteristics. Nanostructuring by phase transitions that involve partial vacancy ordering may enhance the efficiency of such thermoelectrics. We have shown that germanium antimony tellurides with compositions close to those used as phase-change materials in rewritable Blu-Ray Discs, e.g. (GeTe){sub 12}Sb{sub 2}Te{sub 3}, exhibit thermoelectric figures of merit of up to ZT = 1.3 at 450 C if a nanodomain structure is induced by rapidly quenching the cubic high-temperature phase. Structural changes have been elucidated by X-ray diffraction and high-resolution electron microscopy. (orig.)

  11. Structural properties of the metastable state of phase change materials investigated by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Merkelbach, Philipp; Eijk, Julia van; Wuttig, Matthias [I. Phys. Institut (IA), RWTH Aachen, 52056 Aachen (Germany); Braun, Carolin [Institut fuer Anorg. Chemie, CAU Kiel, 24098 Kiel (Germany)

    2008-07-01

    Phase change alloys are among the most promising materials for novel data storage devices. Since several years Phase Change Materials based on Ge-Sb-Te- alloys have been used in optical data storage solutions like rewriteable CDs and DVDs. Recently these alloys have been explored as potential candidates for fast nonvolatile electrical data storage devices in Phase Change Random Access Memory (PCRAM). Besides attracting considerable interest from the commercial point of view phase change materials are very interesting also due to their remarkable physical properties. They have the ability to be reversibly switched within a few nanoseconds between the amorphous and the crystalline phase, while changing their physical properties such as optical reflectivity and electrical resistivity significantly. Even though the electronic properties show a drastical contrast such fast transitions can only be caused by small atomic rearrangements. This behavior calls for a deeper understanding of the structural properties of the alloys. We have performed powder diffraction measurements of the crystal phase of various GeSbTe alloys, to determine the structural similarities and differences of several alloys. Understanding the crystal structure of phase change materials is a key to a deeper insight into the properties of these promising materials.

  12. Phase Structure Of Fuzzy Field Theories And Multi trace Matrix Models

    International Nuclear Information System (INIS)

    Tekel, J.

    2015-01-01

    We review the interplay of fuzzy field theories and matrix models, with an emphasis on the phase structure of fuzzy scalar field theories. We give a self-contained introduction to these topics and give the details concerning the saddle point approach for the usual single trace and multi trace matrix models. We then review the attempts to explain the phase structure of the fuzzy field theory using a corresponding random matrix ensemble, showing the strength and weaknesses of this approach. We conclude with a list of challenges one needs to overcome and the most interesting open problems one can try to solve. (author)

  13. Electronic structure and high pressure phase transition in LaSb and CeSb

    International Nuclear Information System (INIS)

    Mathi Jaya, S.; Sanyal, S.P.

    1992-09-01

    The electronic structure and high pressure structural phase transition in cerium and lanthanum antimonides have been investigated using the tight binding LMTO method. The calculation of total energy reveals that the simple tetragonal structure is found to be stable at high pressures for both the compounds. In the case of LaSb, the calculated value of the equilibrium cell volume and the cell volume at which phase transition occurs are found to have a fairly good agreement with the experimental results. However, in the case of CeSb, the agreement is not as good as in LaSb. We also predicted the most favoured c/a value in the high pressure phase (simple tetragonal) for these compounds. Further we present the calculated results on the electronic structure of these systems at the equilibrium as well as at the reduced cell volumes. (author). 8 refs, 11 figs, 1 tab

  14. A search for the ground state structure and the phase stability of tantalum pentoxide

    International Nuclear Information System (INIS)

    Pérez-Walton, S; Valencia-Balvín, C; Padilha, A C M; Dalpian, G M; Osorio-Guillén, J M

    2016-01-01

    Tantalum pentoxide (Ta 2 O 5 ) is a wide-gap semiconductor that presents good catalytic and dielectric properties, conferring to this compound promising prospective use in a variety of technological applications. However, there is a lack of understanding regarding the relations among its crystalline phases, as some of them are not even completely characterized and there is currently no agreement about which models better explain the crystallographic data. Additionally, its phase diagram is unknown. In this work we performed first-principles density functional theory calculations to study the structural properties of the different phases and models of Ta 2 O 5 , the equation of state and the zone-centered vibrational frequencies. From our results, we conclude that the phases that are built up from only distorted octahedra instead of combinations with pentagonal and/or hexagonal bipyramids are energetically more favorable and dynamically stable. More importantly, this study establishes that, given the pressure range considered, the B-phase is the most favorable structure and there is no a crystallographic phase transition to another phase at high-pressure. Additionally, for the equilibrium volume of the B-phase and the λ-model, the description of the electronic structure and optical properties were performed using semi-local and hybrid functionals. (paper)

  15. Particle-induced pulmonary acute phase response may be the causal link between particle inhalation and cardiovascular disease

    DEFF Research Database (Denmark)

    Saber, Anne T.; Jacobsen, Nicklas R.; Jackson, Petra

    2014-01-01

    Inhalation of ambient and workplace particulate air pollution is associated with increased risk of cardiovascular disease. One proposed mechanism for this association is that pulmonary inflammation induces a hepatic acute phase response, which increases risk of cardiovascular disease. Induction...... epidemiological studies. In this review, we present and review emerging evidence that inhalation of particles (e.g., air diesel exhaust particles and nanoparticles) induces a pulmonary acute phase response, and propose that this induction constitutes the causal link between particle inhalation and risk...

  16. Ultrafast photoinduced structure phase transition in antimony single crystals

    NARCIS (Netherlands)

    Fausti, Daniele; Misochko, Oleg V.; van Loosdrecht, Paul H. M.

    2009-01-01

    Picosecond Raman scattering is used to study the photoinduced ultrafast dynamics in Peierls distorted antimony. We find evidence for an ultrafast nonthermal reversible structural phase transition. Most surprisingly, we find evidence that this transition evolves toward a lower symmetry in contrast to

  17. Phase transformation induced by swift heavy ion irradiation of pure metals

    International Nuclear Information System (INIS)

    Dammak, H.; Dunlop, A.; Lesueur, D.

    1996-01-01

    It is now unambiguously established that high electronic energy deposition (HEED), obtained by swift heavy ion irradiation, plays an important role in the damage processes of pure metallic targets: (i) annealing of the defects created by elastic collisions in Fe, Nb, Ni and Pt, and (ii) creation of additional defects in Co, Fe, Ti and Zr. For Ti, we have recently evidenced by transmission electron microscopy observations that the damage creation by HEED is very important and leads to a phase transformation. Titanium evolves from the equilibrium hcp alpha-phase to the high pressure omega-phase. We studied the influence of three parameters on this phase transformation: ion fluence, electronic stopping power and irradiation temperature. The study of Ti and the results concerning other metals (Fe, Zr, etc.) and the semi-metal Bi allow us to propose criteria to predict in which metals HEED could induce damage: those which undergo a phase transformation under high pressure. As a matter of fact, beryllium is strongly damaged when submitted to HEED and seems to behave very similarly to titanium. The fact that such phase changes from a crystalline form to another form were only observed in those metals in which high pressure phases exist in the pressure-temperature diagram, strongly supports the Coulomb explosion model in which the generation of (i) a shock wave and (ii) collective atomic movements are invoked to account for the observed damage creation. (orig.)

  18. Distortion of Local Atomic Structures in Amorphous Ge-Sb-Te Phase Change Materials

    Science.gov (United States)

    Hirata, A.; Ichitsubo, T.; Guan, P. F.; Fujita, T.; Chen, M. W.

    2018-05-01

    The local atomic structures of amorphous Ge-Sb-Te phase-change materials have yet to be clarified and the rapid crystal-amorphous phase change resulting in distinct optical contrast is not well understood. We report the direct observation of local atomic structures in amorphous Ge2Sb2Te5 using "local" reverse Monte Carlo modeling dedicated to an angstrom-beam electron diffraction analysis. The results corroborated the existence of local structures with rocksalt crystal-like topology that were greatly distorted compared to the crystal symmetry. This distortion resulted in the breaking of ideal octahedral atomic environments, thereby forming local disordered structures that basically satisfied the overall amorphous structure factor. The crystal-like distorted octahedral structures could be the main building blocks in the formation of the overall amorphous structure of Ge-Sb-Te.

  19. Kinetic and collision process effects on magnetic structures in pre-disruption phase of tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Farshi, Esmaeil [Kyushu Univ., Advanced Energy Engineering Sciences, Kasuga, Fukuoka (Japan); Goudarzi, Shervin [AEOI, Plasma Physics Department, Tehran (Iran); Amrollahi, Reza [K-N Toosi Univ. of Technology, Tehran (Iran); Sato, Kohnosuke [Kyushu Univ., Research Institute for Applied Mechanics, Kasuga, Fukuoka (Japan)

    2001-07-01

    Oscillations of the parallel and perpendicular neutral fluxes that are observed during pre-disruption stage in recent experiments, show possibility of a structure in pre-disruption phase of tokamak plasmas. This structure oscillates simultaneously with the m=2 mode until the damping of this mode. The perpendicular component of this structure is greater than the parallel one. From other side, there are a good correlation between MHD activity and behavior of charge exchange neutrals, and an enough good correlation between time behavior of charge exchange flux with high energy and OV line radiation in pre-disruption phase. These may witness possibility of a mechanism of losses-excitation of inner transition with help of heavy particles in pre-disruption phase. This mechanism plays an important role in magnetic structures in pre-disruption phase. (author)

  20. Kinetic and collision process effects on magnetic structures in pre-disruption phase of tokamak plasmas

    International Nuclear Information System (INIS)

    Farshi, Esmaeil; Goudarzi, Shervin; Amrollahi, Reza; Sato, Kohnosuke

    2001-01-01

    Oscillations of the parallel and perpendicular neutral fluxes that are observed during pre-disruption stage in recent experiments, show possibility of a structure in pre-disruption phase of tokamak plasmas. This structure oscillates simultaneously with the m=2 mode until the damping of this mode. The perpendicular component of this structure is greater than the parallel one. From other side, there are a good correlation between MHD activity and behavior of charge exchange neutrals, and an enough good correlation between time behavior of charge exchange flux with high energy and OV line radiation in pre-disruption phase. These may witness possibility of a mechanism of losses-excitation of inner transition with help of heavy particles in pre-disruption phase. This mechanism plays an important role in magnetic structures in pre-disruption phase. (author)

  1. Gas-phase structure and fragmentation pathways of singly protonated peptides with N-terminal arginine.

    Science.gov (United States)

    Bythell, Benjamin J; Csonka, István P; Suhai, Sándor; Barofsky, Douglas F; Paizs, Béla

    2010-11-25

    The gas-phase structures and fragmentation pathways of the singly protonated peptide arginylglycylaspartic acid (RGD) are investigated by means of collision-induced-dissociation (CID) and detailed molecular mechanics and density functional theory (DFT) calculations. It is demonstrated that despite the ionizing proton being strongly sequestered at the guanidine group, protonated RGD can easily be fragmented on charge directed fragmentation pathways. This is due to facile mobilization of the C-terminal or aspartic acid COOH protons thereby generating salt-bridge (SB) stabilized structures. These SB intermediates can directly fragment to generate b(2) ions or facilely rearrange to form anhydrides from which both b(2) and b(2)+H(2)O fragments can be formed. The salt-bridge stabilized and anhydride transition structures (TSs) necessary to form b(2) and b(2)+H(2)O are much lower in energy than their traditional charge solvated counterparts. These mechanisms provide compelling evidence of the role of SB and anhydride structures in protonated peptide fragmentation which complements and supports our recent findings for tryptic systems (Bythell, B. J.; Suhai, S.; Somogyi, A.; Paizs, B. J. Am. Chem. Soc. 2009, 131, 14057-14065.). In addition to these findings we also report on the mechanisms for the formation of the b(1) ion, neutral loss (H(2)O, NH(3), guanidine) fragment ions, and the d(3) ion.

  2. Commensurate and incommensurate '5M' modulated crystal structures in Ni-Mn-Ga martensitic phases

    International Nuclear Information System (INIS)

    Righi, L.; Albertini, F.; Pareti, L.; Paoluzi, A.; Calestani, G.

    2007-01-01

    It is well known that the composition of ferromagnetic shape memory Ni-Mn-Ga Heusler alloys determines both temperature of martensitic transformations and the structure type of the product phase. In the present work we focused our attention on the structural study of the so-called '5M' modulated structure. In particular, the structure of Ni 1.95 Mn 1.19 Ga 0.86 martensitic phase is analysed by powder X-ray diffraction (PXRD) and compared with that of the stoichiometric Ni 2 MnGa martensite. The study of the diffraction data reveals the occurrence of commensurate (C) structural modulation in Ni 1.95 Mn 1.19 Ga 0.86 ; this contrasts with Ni 2 MnGa, where an incommensurate (IC) structural modulation was evident. The two phases also differ in the symmetry of the fundamental martensitic lattice. In fact, the incommensurate modulation is related to an orthorhombic basic structure, while the commensurate variant presents a monoclinic symmetry. The commensurate modulated structure has been investigated by using the superspace approach already adopted to solve the structure of Ni 2 MnGa martensite. The structure has been determined by Rietveld refinement of PXRD data

  3. Ab initio molecular crystal structures, spectra, and phase diagrams.

    Science.gov (United States)

    Hirata, So; Gilliard, Kandis; He, Xiao; Li, Jinjin; Sode, Olaseni

    2014-09-16

    Conspectus Molecular crystals are chemists' solids in the sense that their structures and properties can be understood in terms of those of the constituent molecules merely perturbed by a crystalline environment. They form a large and important class of solids including ices of atmospheric species, drugs, explosives, and even some organic optoelectronic materials and supramolecular assemblies. Recently, surprisingly simple yet extremely efficient, versatile, easily implemented, and systematically accurate electronic structure methods for molecular crystals have been developed. The methods, collectively referred to as the embedded-fragment scheme, divide a crystal into monomers and overlapping dimers and apply modern molecular electronic structure methods and software to these fragments of the crystal that are embedded in a self-consistently determined crystalline electrostatic field. They enable facile applications of accurate but otherwise prohibitively expensive ab initio molecular orbital theories such as Møller-Plesset perturbation and coupled-cluster theories to a broad range of properties of solids such as internal energies, enthalpies, structures, equation of state, phonon dispersion curves and density of states, infrared and Raman spectra (including band intensities and sometimes anharmonic effects), inelastic neutron scattering spectra, heat capacities, Gibbs energies, and phase diagrams, while accounting for many-body electrostatic (namely, induction or polarization) effects as well as two-body exchange and dispersion interactions from first principles. They can fundamentally alter the role of computing in the studies of molecular crystals in the same way ab initio molecular orbital theories have transformed research practices in gas-phase physical chemistry and synthetic chemistry in the last half century. In this Account, after a brief summary of formalisms and algorithms, we discuss applications of these methods performed in our group as compelling

  4. Symmetries of nonrelativistic phase space and the structure of quark-lepton generation

    International Nuclear Information System (INIS)

    Zenczykowski, Piotr

    2009-01-01

    According to the Hamiltonian formalism, nonrelativistic phase space may be considered as an arena of physics, with momentum and position treated as independent variables. Invariance of x 2 + p 2 constitutes then a natural generalization of ordinary rotational invariance. We consider Dirac-like linearization of this form, with position and momentum satisfying standard commutation relations. This leads to the identification of a quantum-level structure from which some phase space properties might emerge. Genuine rotations and reflections in phase space are tied to the existence of new quantum numbers, unrelated to ordinary 3D space. Their properties allow their identification with the internal quantum numbers characterising the structure of a single quark-lepton generation in the Standard Model. In particular, the algebraic structure of the Harari-Shupe preon model of fundamental particles is reproduced exactly and without invoking any subparticles. Analysis of the Clifford algebra of nonrelativistic phase space singles out an element which might be associated with the concept of lepton mass. This element is transformed into a corresponding element for a single coloured quark, leading to a generalization of the concept of mass and a different starting point for the discussion of quark unobservability.

  5. Dux4 induces cell cycle arrest at G1 phase through upregulation of p21 expression

    International Nuclear Information System (INIS)

    Xu, Hongliang; Wang, Zhaoxia; Jin, Suqin; Hao, Hongjun; Zheng, Lemin; Zhou, Boda; Zhang, Wei; Lv, He; Yuan, Yun

    2014-01-01

    Highlights: • Dux4 induced TE671 cell proliferation defect and G1 phase arrest. • Dux4 upregulated p21 expression without activating p53. • Silencing p21 rescued Dux4 mediated proliferation defect and cell cycle arrest. • Sp1 binding site was required for Dux4-induced p21 promoter activation. - Abstract: It has been implicated that Dux4 plays crucial roles in development of facioscapulohumeral dystrophy. But the underlying myopathic mechanisms and related down-stream events of this retrogene were far from clear. Here, we reported that overexpression of Dux4 in a cell model TE671 reduced cell proliferation rate, and increased G1 phase accumulation. We also determined the impact of Dux4 on p53/p21 signal pathway, which controls the checkpoint in cell cycle progression. Overexpression of Dux4 increased p21 mRNA and protein level, while expression of p53, phospho-p53 remained unchanged. Silencing p21 rescued Dux4 mediated proliferation defect and cell cycle arrest. Furthermore, we demonstrated that enhanced Dux4 expression increased p21 promoter activity and elevated expression of Sp1 transcription factor. Mutation of Sp1 binding site decreased dux4 induced p21 promoter activation. Chromatin immunoprecipitation (ChIP) assays confirmed the Dux4-induced binding of Sp1 to p21 promoter in vivo. These results suggest that Dux4 might induce proliferation inhibition and G1 phase arrest through upregulation of p21

  6. Dux4 induces cell cycle arrest at G1 phase through upregulation of p21 expression

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hongliang; Wang, Zhaoxia; Jin, Suqin; Hao, Hongjun [Department of Neurology, Peking University First Hospital, Beijing 100034 (China); Zheng, Lemin [The Institute of Cardiovascular Sciences, Peking University Health Science Center, Key Laboratory of Molecular Cardiovascular Sciences of Education Ministry, Key Laboratory of Cardiovascular Molecular Biology and Regulatory Peptides of Health Ministry, Beijing 100191 (China); Zhou, Boda [The Department of Cardiology, Peking University Third Hospital, Beijing 100191 (China); Zhang, Wei; Lv, He [Department of Neurology, Peking University First Hospital, Beijing 100034 (China); Yuan, Yun, E-mail: yuanyun2002@sohu.com [Department of Neurology, Peking University First Hospital, Beijing 100034 (China)

    2014-03-28

    Highlights: • Dux4 induced TE671 cell proliferation defect and G1 phase arrest. • Dux4 upregulated p21 expression without activating p53. • Silencing p21 rescued Dux4 mediated proliferation defect and cell cycle arrest. • Sp1 binding site was required for Dux4-induced p21 promoter activation. - Abstract: It has been implicated that Dux4 plays crucial roles in development of facioscapulohumeral dystrophy. But the underlying myopathic mechanisms and related down-stream events of this retrogene were far from clear. Here, we reported that overexpression of Dux4 in a cell model TE671 reduced cell proliferation rate, and increased G1 phase accumulation. We also determined the impact of Dux4 on p53/p21 signal pathway, which controls the checkpoint in cell cycle progression. Overexpression of Dux4 increased p21 mRNA and protein level, while expression of p53, phospho-p53 remained unchanged. Silencing p21 rescued Dux4 mediated proliferation defect and cell cycle arrest. Furthermore, we demonstrated that enhanced Dux4 expression increased p21 promoter activity and elevated expression of Sp1 transcription factor. Mutation of Sp1 binding site decreased dux4 induced p21 promoter activation. Chromatin immunoprecipitation (ChIP) assays confirmed the Dux4-induced binding of Sp1 to p21 promoter in vivo. These results suggest that Dux4 might induce proliferation inhibition and G1 phase arrest through upregulation of p21.

  7. Control of magnetic relaxation by electric-field-induced ferroelectric phase transition and inhomogeneous domain switching

    Energy Technology Data Exchange (ETDEWEB)

    Nan, Tianxiang; Emori, Satoru; Wang, Xinjun; Hu, Zhongqiang; Xie, Li; Gao, Yuan; Lin, Hwaider; Sun, Nian, E-mail: n.sun@neu.edu [Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States); Peng, Bin; Liu, Ming, E-mail: mingliu@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, Xi' an Jiaotong University, Xi' an 710049 (China); Jiao, Jie; Luo, Haosu [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); Budil, David [Department of Chemistry, Northeastern University, Boston, Massachusetts 02115 (United States); Jones, John G.; Howe, Brandon M.; Brown, Gail J. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States)

    2016-01-04

    Electric-field modulation of magnetism in strain-mediated multiferroic heterostructures is considered a promising scheme for enabling memory and magnetic microwave devices with ultralow power consumption. However, it is not well understood how electric-field-induced strain influences magnetic relaxation, an important physical process for device applications. Here, we investigate resonant magnetization dynamics in ferromagnet/ferroelectric multiferroic heterostructures, FeGaB/PMN-PT and NiFe/PMN-PT, in two distinct strain states provided by electric-field-induced ferroelectric phase transition. The strain not only modifies magnetic anisotropy but also magnetic relaxation. In FeGaB/PMN-PT, we observe a nearly two-fold change in intrinsic Gilbert damping by electric field, which is attributed to strain-induced tuning of spin-orbit coupling. By contrast, a small but measurable change in extrinsic linewidth broadening is attributed to inhomogeneous ferroelastic domain switching during the phase transition of the PMN-PT substrate.

  8. Mechanical Anisotropy and Pressure Induced Structural Changes in Piroxicam Crystals Probed by In Situ Indentation and Raman Spectroscopy

    Science.gov (United States)

    Manimunda, Praveena; Hintsala, Eric; Asif, Syed; Mishra, Manish Kumar

    2017-01-01

    The ability to correlate mechanical and chemical characterization techniques in real time is both lacking and powerful tool for gaining insights into material behavior. This is demonstrated through use of a novel nanoindentation device equipped with Raman spectroscopy to explore the deformation-induced structural changes in piroxicam crystals. Mechanical anisotropy was observed in two major faces ( 0bar{1}1 ) and (011), which are correlated to changes in the interlayer interaction from in situ Raman spectra recorded during indentation. The results of this study demonstrate the considerable potential of an in situ Raman nanoindentation instrument for studying a variety of topics, including stress-induced phase transformation mechanisms, mechanochemistry, and solid state reactivity under mechanical forces that occur in molecular and pharmaceutical solids.

  9. Inducing phase decomposition and superconductivity of Bi2Sr2CaCu2Oy single crystals treated in sulphur atmosphere at low temperature

    International Nuclear Information System (INIS)

    Chen, Q.W.; China Univ. of Science and Technology, Hefei, AH; Wu, W.B.; Qian, Y.T.; China Univ. of Science and Technology, Hefei, AH; Wang, L.B.; Li, F.Q.; Zhou, G.E.; Chen, Z.Y.; Zhang, Y.H.

    1995-01-01

    As it has been pointed out, phase decomposition which may be hard to be detected in a polycrystalline system and is likely to correlate with changes in both oxygen content and microstructure, has been observed frequently in annealed single crystals especially at higher temperatures (> 500 C). This is still an open question to some degree because the mechanism of phase decomposition is very complex and is dominated by the composition of the Bi-2212 phase, the condition of heat treatment, and the atmosphere. Hence, inducing oxygen loss at low temperature to avoid the evaporation of Bi atoms and other undetected structure changes which would occur at higher temperature annealing undoubtedly provides important information about the relationship between oxygen loss and phase decomposition, as well as the relationship between oxygen content and superconductivity. In this note, we report on the results of treatments of Bi 2 Sr 2 CaCu 2 O y single crystals in sulphur atmosphere at 160 C. (orig.)

  10. EARTHQUAKE-INDUCED DEFORMATION STRUCTURES AND RELATED TO EARTHQUAKE MAGNITUDES

    Directory of Open Access Journals (Sweden)

    Savaş TOPAL

    2003-02-01

    Full Text Available Earthquake-induced deformation structures which are called seismites may helpful to clasify the paleoseismic history of a location and to estimate the magnitudes of the potention earthquakes in the future. In this paper, seismites were investigated according to the types formed in deep and shallow lake sediments. Seismites are observed forms of sand dikes, introduced and fractured gravels and pillow structures in shallow lakes and pseudonodules, mushroom-like silts protruding laminites, mixed layers, disturbed varved lamination and loop bedding in deep lake sediments. Earthquake-induced deformation structures, by benefiting from previous studies, were ordered according to their formations and earthquake magnitudes. In this order, the lowest eartquake's record is loop bedding and the highest one is introduced and fractured gravels in lacustrine deposits.

  11. Dietary compounds that induce cancer preventive phase 2 enzymes activate apoptosis at comparable doses in HT29 colon carcinoma cells.

    Science.gov (United States)

    Kirlin, W G; Cai, J; DeLong, M J; Patten, E J; Jones, D P

    1999-10-01

    Dietary agents that induce glutathione S-transferases and related detoxification systems (Phase 2 enzyme inducers) are thought to prevent cancer by enhancing elimination of chemical carcinogens. The present study shows that compounds of this group (benzyl isothiocyanate, allyl sulfide, dimethyl fumarate, butylated hydroxyanisole) activated apoptosis in human colon carcinoma (HT29) cells in culture over the same concentration ranges that elicited increases in enzyme activity (5-25, 25-100, 10-100, 15-60 micromol/L, respectively). Pretreatment of cells with sodium butyrate, an agent that induces HT29 cell differentiation, resulted in parallel increases in Phase 2 enzyme activities and induction of apoptosis in response to the inducers. Cell death characteristics included apoptotic morphological changes, appearance of cells at sub-G1 phase on flow cytometry, caspase activation, DNA fragmentation and TUNEL-positive staining. The results suggest that dietary Phase 2 inducers may protect against cancer by a mechanism distinct from and in addition to that associated with enhanced elimination of carcinogens. If this occurs in vivo, diets high in such compounds could eliminate precancerous cells by apoptosis at time points well after initial exposure to chemical mutagens and carcinogens.

  12. Wave-mixing-induced transparency with zero phase shift in atomic vapors

    Science.gov (United States)

    Zhou, F.; Zhu, C. J.; Li, Y.

    2017-12-01

    We present a wave-mixing induced transparency that can lead to a hyper-Raman gain-clamping effect. This new type of transparency is originated from a dynamic gain cancellation effect in a multiphoton process where a highly efficient light field of new frequency is generated and amplified. We further show that this novel dynamic gain cancellation effect not only makes the medium transparent to a probe light field at appropriate frequency but also eliminates the probe field propagation phase shift. This gain-cancellation-based induced transparency holds for many potential applications on optical communication and may lead to effective suppression of parasitic Raman/hyper-Raman noise field generated in high intensity optical fiber transmissions.

  13. On the phase structure of lattice SU(2) Gauge-Higgs theory

    International Nuclear Information System (INIS)

    Gerdt, V.P.; Mitryushkin, V.K.; Zadorozhnyj, A.M.; Ilchev, A.S.

    1985-01-01

    The results on the phase structure of SU(2) gauge theory coupled with radially active Higgs fields are iscussed. It is shown that obtained results are not in contradiction with the known ones. The first order phase transitions observed are confirmed by the Monte Carlo calcUlations and by the analysis of an approximate effective potential

  14. In-situ studies of stress- and magnetic-field-induced phase transformation in a polymer-bonded Ni-Co-Mn-In composite

    International Nuclear Information System (INIS)

    Liu, D.M.; Nie, Z.H.; Wang, G.; Wang, Y.D.; Brown, D.E.; Pearson, J.; Liaw, P.K.; Ren, Y.

    2010-01-01

    A polymer-bonded Ni 45 Co 5 Mn 36.6 In 13.4 ferromagnetic shape-memory composite was fabricated, having magnetic-field-driven shape recovery properties. The thermo-magnetization curves of the composite suggested that the magnetic-field-induced reverse martensitic transformation occurs in the composite. The effects of temperature, stress, and magnetic-field on the phase transformation properties were systematically investigated using an in-situ high-energy X-ray diffraction technique. A temperature-induced reversible martensitic phase transformation was confirmed within the composite, showing a broad phase transformation interval. Stress-induced highly textured martensite was observed in the composite during uniaxial compressive loading, with a residual strain after unloading. The origin of the textured martensite can be explained by the grain-orientation-dependent Bain distortion energy. A recovery strain of ∼1.76% along the compression direction was evidenced in the pre-strained composite with an applied magnetic-field of 5 T. This recovery was caused by the magnetic-field-induced reverse martensitic phase transformation. The phase transformation properties of the ferromagnetic shape-memory composite, different from its bulk alloys, can be well explained by the Clausius-Clapeyron relation. The large magnetic-field-induced strain, together with good ductility and low cost, make the polymer-bonded Ni-Co-Mn-In composites potential candidates for magnetic-field-driven actuators.

  15. Determination of the structural phase and octahedral rotation angle in halide perovskites

    Science.gov (United States)

    dos Reis, Roberto; Yang, Hao; Ophus, Colin; Ercius, Peter; Bizarri, Gregory; Perrodin, Didier; Shalapska, Tetiana; Bourret, Edith; Ciston, Jim; Dahmen, Ulrich

    2018-02-01

    A key to the unique combination of electronic and optical properties in halide perovskite materials lies in their rich structural complexity. However, their radiation sensitive nature limits nanoscale structural characterization requiring dose efficient microscopic techniques in order to determine their structures precisely. In this work, we determine the space-group and directly image the Br halide sites of CsPbBr3, a promising material for optoelectronic applications. Based on the symmetry of high-order Laue zone reflections of convergent-beam electron diffraction, we identify the tetragonal (I4/mcm) structural phase of CsPbBr3 at cryogenic temperature. Electron ptychography provides a highly sensitive phase contrast measurement of the halide positions under low electron-dose conditions, enabling imaging of the elongated Br sites originating from the out-of-phase octahedral rotation viewed along the [001] direction of I4/mcm persisting at room temperature. The measurement of these features and comparison with simulations yield an octahedral rotation angle of 6.5°(±1.5°). The approach demonstrated here opens up opportunities for understanding the atomic scale structural phenomena applying advanced characterization tools on a wide range of radiation sensitive halide-based all-inorganic and hybrid organic-inorganic perovskites.

  16. Phase stability and electronic structure of transition-metal aluminides

    International Nuclear Information System (INIS)

    Carlsson, A.E.

    1992-01-01

    This paper will describe the interplay between die electronic structure and structural energetics in simple, complex, and quasicrystalline Al-transition metal (T) intermetallics. The first example is the Ll 2 -DO 22 competition in Al 3 T compounds. Ab-initio electronic total-energy calculations reveal surprisingly large structural-energy differences, and show that the phase stability of both stoichiometric and ternary-substituted compounds correlates closely with a quasigap in the electronic density of states (DOS). Secondly, ab-initio calculations for the structural stability of the icosahedrally based Al 12 W structure reveal similar quasigap effects, and provide a simple physical explanation for the stability of the complex aluminide structures. Finally, parametrized tight-binding model calculations for the Al-Mn quasicrystal reveal a large spread in the local Mn DOS behavior, and support a two-site model for the quasicrystal's magnetic behavior

  17. Structure-retention and mobile phase-retention relationships for reversed-phase high-performance liquid chromatography of several hydroxythioxanthone derivatives in binary acetonitrile-water mixtures

    International Nuclear Information System (INIS)

    Amiri, Ali Asghar; Hemmateenejad, Bahram; Safavi, Afsaneh; Sharghi, Hashem; Beni, Ali Reza Salimi; Shamsipur, Mojtaba

    2007-01-01

    The reversed-phase high-performance liquid chromatographic (RP-HPLC) behavior of some newly synthesized hydroxythioxanthone derivatives using binary acetonitrile-water mixtures as mobile phase has been examined. First, the variation in the retention time of each molecule as a function of mobile phase properties was studied by Kamlet-Taft solvatochromic equations. Then, the influences of molecular structure of the hydroxythioxanthone derivatives on their retention time in various mobile phase mixtures were investigated by quantitative structure-property relationship (QSPR) analysis. Finally, a unified model containing both the molecular structure parameters and mobile phase properties was developed to describe the chromatographic behavior of the systems studied. Among the solvent properties, polarity/polarizability parameter (π * ) and hydrogen-bond basicity (β), and among the solute properties, the most positive local charge (MPC), the sum of positive charges on hydrogen atoms contributing in hydrogen bonding (SPCH) and lipophilicity index (log P) were identified as controlling factors in the RP-HPLC behavior of hydroxythioxanthone derivatives in actonitrile-water binary solvents

  18. Small angle neutron scattering form polymer melts: structural investigation and phase behaviour

    International Nuclear Information System (INIS)

    Ertugrul, O.

    2004-01-01

    The Small-Angle Neutron Scattering (SANS) techniques have been used to study the structural properties and phase behavior of polymer melts. A model based on Random Phase Approximation (RPA) is proposed to predict the experimental data. By fitting the model to data we could be able to obtain radius of gyration (a measure of size of a polymer) and phase transition for the sample. (author)

  19. Time-resolved imaging refractometry of microbicidal films using quantitative phase microscopy.

    Science.gov (United States)

    Rinehart, Matthew T; Drake, Tyler K; Robles, Francisco E; Rohan, Lisa C; Katz, David; Wax, Adam

    2011-12-01

    Quantitative phase microscopy is applied to image temporal changes in the refractive index (RI) distributions of solutions created by microbicidal films undergoing hydration. We present a novel method of using an engineered polydimethylsiloxane structure as a static phase reference to facilitate calibration of the absolute RI across the entire field. We present a study of dynamic structural changes in microbicidal films during hydration and subsequent dissolution. With assumptions about the smoothness of the phase changes induced by these films, we calculate absolute changes in the percentage of film in regions across the field of view.

  20. Investigation of phase transformation for ferrite–austenite structure in stainless steel thin films

    Energy Technology Data Exchange (ETDEWEB)

    Merakeb, Noureddine [Laboratory of Physical Metallurgy and Property of Materials (LM2PM), Metallurgy and Materials Engineering Department, Badji Mokhtar University, P.O. Box 12, Annaba 23000 (Algeria); Messai, Amel [Laboratoire d' Ingénierie et Sciences des Matériaux Avancés (ISMA), Institut des Sciences et Technologie, Abbès Laghrour University, Khenchela 40000 (Algeria); Ayesh, Ahmad I., E-mail: ayesh@qu.edu.qa [Department of Mathematics, Statistics and Physics, Qatar University, Doha (Qatar)

    2016-05-01

    In this work we report on phase transformation of 304 stainless steel thin films due to heat treatment. Ex-situ annealing was applied for evaporated 304 stainless steel thin films inside an ultra-high vacuum chamber with a pressure of 3 × 10{sup −7} Pa at temperatures of 500 °C and 600 °C. The structure of thin films was studied by X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS) techniques. The results revealed a transformation from α-phase that exhibits a body-centered cubic structure (BCC) to γ-phase that exhibits a face-centered cubic (FCC) due to annealing. In addition, the percentage of γ-phase structure increased with the increase of annealing temperature. Annealing thin films increased the crystal size of both phases (α and γ), however, the increase was nonlinear. The results also showed that phase transformation was produced by recrystallization of α and γ crystals with a temporal evolution at each annealing temperature. The texture degree of thin films was investigated by XRD rocking curve method, while residual stress was evaluated using curvature method. - Highlights: • Stainless steel thin films were fabricated by thermal evaporation on quartz. • Alpha to gamma phase transformation of thin films was investigated. • Annealing of thin films reduces disruption in crystal lattice. • The stress of as-grown thin films was independent on the thin film thickness. • The stress of the thin films was reduced due to annealing.

  1. CREEP-INDUCED STRUCTURAL CHANGES IN Ni-Si-B AMORPHOUS ALLOY

    NARCIS (Netherlands)

    Jurikova, A.; Miskuf, J.; Csach, K.; Ocelik, V.

    The influence of the stress annealing on the reversible structural relaxation of a Ni-Si-B amorphous ribbon was studied. Creep-induced structural changes in the amorphous structure were derived from anisothermal DSC and dilatometric experiments. It is demonstrated that considerable enthalpy and

  2. Hydro-elastic response of ship structures to slamming induced whipping

    NARCIS (Netherlands)

    Tuitman, J.T.

    2010-01-01

    Slamming induced whipping can significantly increase the structural loading of ships. Although this is well-known, the whipping contribution to the structural loading is rarely taken into account when computing the structural loading. An exception are the "dynamic loading" factors found in

  3. CFD simulations of flow erosion and flow-induced deformation of needle valve: Effects of operation, structure and fluid parameters

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Hongjun, E-mail: ticky863@126.com [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, Sichuan (China); State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, Sichuan (China); Pan, Qian; Zhang, Wenli; Feng, Guang; Li, Xue [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, Sichuan (China)

    2014-07-01

    Highlights: • A combined FSI–CFD and DPM computational method is used to investigate flow erosion and deformation of needle valve. • The numerical model is validated with the comparison of measured and predicted erosion rate. • Effects of operation, structure and fluid parameters on flow erosion and flow-induced deformation are discussed. • Particle diameter has the most significant effect on flow erosion. • Inlet rate has the most obvious effect on flow-induced deformation. - Abstract: A three-dimensional fluid–structure interaction (FSI) computational model coupling with a combined continuum and discrete model has been used to predict the flow erosion rate and flow-induced deformation of needle valve. Comparisons with measured data demonstrate good agreement with the predictions of erosion rate. The flow field distribution of gas-particle flow and the erosion rate and deformation of valve core are captured under different operating and structural conditions with different fluid parameters. The effects of inlet velocity, valve opening and inlet valve channel size, particle concentration, particle diameter and particle phase components are discussed in detail. The results indicate that valve tip has the most severe erosion and deformation, and flow field, erosion rate and deformation of valve are all sensitive to inlet condition changes, structural changes and fluid properties changes. The effect of particle diameter on erosion is the most significant, while the influence of inlet rate on deformation is the greatest one.

  4. Kinetics and mechanism of solid-phase reactions of formation of yttrium ferrite with garnet structure

    Energy Technology Data Exchange (ETDEWEB)

    Pashchenko, V P; Yakushevskaya, F T; Chalyi, V P

    1977-04-01

    The perovskite phase is formed in the process of ferrogarnet formation both from the mixture of Y and Fe oxides and from mutually precipitated carbonates. The amount of the perovskite phase decreases with increasing duration of annealing. The process of the ferritoformation in the investigated systems can be presented as isovalent cationic substitution on the basis of the crystalline structure of Y/sub 2/O/sub 3/ with the formation of the perovskite structure. When the Fe concentration in orthoferrite increases, the phase with a garnet structure is formed.

  5. Laser induced structural transformation in chalcogenide based superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Zallo, Eugenio, E-mail: zallo@pdi-berlin.de; Wang, Ruining; Bragaglia, Valeria; Calarco, Raffaella [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2016-05-30

    Superlattices made of alternating layers of nominal GeTe and Sb{sub 2}Te{sub 3} have been studied by micro-Raman spectroscopy. A structural irreversible transformation into ordered GeSbTe alloy is induced by high power laser light exposure. The intensity ratio of anti-Stokes and Stokes scattering under laser illumination gives a maximum average temperature in the sample of 177 °C. The latter is lower than the growth temperature and of 400 °C necessary by annealing to transform the structure in a GeSbTe alloy. The absence of this configuration after in situ annealing even up to 300 °C evidences an electronic excitation induced-transition which brings the system into a different and stable crystalline state.

  6. Laser induced structural transformation in chalcogenide based superlattices

    International Nuclear Information System (INIS)

    Zallo, Eugenio; Wang, Ruining; Bragaglia, Valeria; Calarco, Raffaella

    2016-01-01

    Superlattices made of alternating layers of nominal GeTe and Sb 2 Te 3 have been studied by micro-Raman spectroscopy. A structural irreversible transformation into ordered GeSbTe alloy is induced by high power laser light exposure. The intensity ratio of anti-Stokes and Stokes scattering under laser illumination gives a maximum average temperature in the sample of 177 °C. The latter is lower than the growth temperature and of 400 °C necessary by annealing to transform the structure in a GeSbTe alloy. The absence of this configuration after in situ annealing even up to 300 °C evidences an electronic excitation induced-transition which brings the system into a different and stable crystalline state.

  7. New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current.

    Science.gov (United States)

    Park, Yong-Jin; Cho, Ju-Young; Jeong, Min-Woo; Na, Sekwon; Joo, Young-Chang

    2016-02-23

    The novel discovery of a current-induced transition from insulator to metal in the crystalline phase of Ge2Sb2Te5 and GeSb4Te7 have been studied by means of a model using line-patterned samples. The resistivity of cubic phase Ge-Sb-Te compound was reduced by an electrical current (~1 MA/cm(2)), and the final resistivity was determined based on the stress current density, regardless of the initial resistivity and temperature, which indicates that the conductivity of Ge-Sb-Te compound can be modulated by an electrical current. The minimum resistivity of Ge-Sb-Te materials can be achieved at high kinetic rates by applying an electrical current, and the material properties change from insulating to metallic behavior without a phase transition. The current-induced metal transition is more effective in GeSb4Te7 than Ge2Sb2Te5, which depends on the intrinsic vacancy of materials. Electromigration, which is the migration of atoms induced by a momentum transfer from charge carriers, can easily promote the rearrangement of vacancies in the cubic phase of Ge-Sb-Te compound. This behavior differs significantly from thermal annealing, which accompanies a phase transition to the hexagonal phase. This result suggests a new pathway for modulating the electrical conductivity and material properties of chalcogenide materials by applying an electrical current.

  8. Pressure-induced structural changes and insulator-metal transition in layered bismuth triiodide, BiI3: a combined experimental and theoretical study

    International Nuclear Information System (INIS)

    Devidas, T R; Chandra Shekar, N V; Sundar, C S; Chithaiah, P; Rao, C N R; Sorb, Y A; Bhadram, V S; Chandrabhas, N; Pal, K; Waghmare, U V

    2014-01-01

    Noting that BiI 3 and the well-known topological insulator (TI) Bi 2 Se 3 have the same high symmetry parent structures, and that it is desirable to find a wide-band gap TI, we determine here the effects of pressure on the structure, phonons and electronic properties of rhombohedral BiI 3 . We report a pressure-induced insulator-metal transition near 1.5 GPa, using high pressure electrical resistivity and Raman measurements. X-ray diffraction studies, as a function of pressure, reveal a structural peculiarity of the BiI 3 crystal, with a drastic drop in c/a ratio at 1.5 GPa, and a structural phase transition from rhombohedral to monoclinic structure at 8.8 GPa. Interestingly, the metallic phase, at relatively low pressures, exhibits minimal resistivity at low temperatures, similar to that in Bi 2 Se 3 . We corroborate these findings with first-principles calculations and suggest that the drop in the resistivity of BiI 3 in the 1–3 GPa range of pressure arises possibly from the appearance of an intermediate crystal phase with a lower band-gap and hexagonal crystal structure. Calculated Born effective charges reveal the presence of metallic states in the structural vicinity of rhombohedral BiI 3 . Changes in the topology of the electronic bands of BiI 3 with pressure, and a sharp decrease in the c/a ratio below 2 GPa, are shown to give rise to changes in the slope of phonon frequencies near that pressure. (paper)

  9. The effect warming time of mechanical properties and structural phase aluminum alloy nickel

    International Nuclear Information System (INIS)

    Husna Al Hasa, M.; Anwar Muchsin

    2011-01-01

    Ferrous aluminum alloys as fuel cladding will experience the process of heat treatment above the recrystallization temperature. Temperature and time of heat treatment will affect the nature of the metal. Heating time allows will affect change in mechanical properties, thermal and structure of the metal phase. This study aims to determine the effect of time of heat treatment on mechanical properties and phase metal alloys. Testing the mechanical properties of materials, especially violence done by the method of Vickers. Observation of microstructural changes made by metallographic-optical and phase structure were analyzed Based on the x-ray diffraction patterns Elemental analysis phase alloy compounds made by EDS-SEM. Test results show the nature of violence AlFeNiMg alloy by heating at 500°C with a warm-up time 1 hour, 2 hours and 3 hours respectively decreased range 94.4 HV, 87.6 HV and 85.1 HV. The nature of violence AlFeNi alloy showed a decrease in line with the longer heating time. Metallographic-optical observations show the microstructural changes with increasing heating time. Microstructure shows the longer the heating time trend equi axial shaped grain structure of growing and the results showed a trend analyst diffraction pattern formation and phase θ α phase (FeAl3) in the alloy. (author)

  10. Induced Voltages Ratio-Based Algorithm for Fault Detection, and Faulted Phase and Winding Identification of a Three-Winding Power Transformer

    Directory of Open Access Journals (Sweden)

    Byung Eun Lee

    2014-09-01

    Full Text Available This paper proposes an algorithm for fault detection, faulted phase and winding identification of a three-winding power transformer based on the induced voltages in the electrical power system. The ratio of the induced voltages of the primary-secondary, primary-tertiary and secondary-tertiary windings is the same as the corresponding turns ratio during normal operating conditions, magnetic inrush, and over-excitation. It differs from the turns ratio during an internal fault. For a single phase and a three-phase power transformer with wye-connected windings, the induced voltages of each pair of windings are estimated. For a three-phase power transformer with delta-connected windings, the induced voltage differences are estimated to use the line currents, because the delta winding currents are practically unavailable. Six detectors are suggested for fault detection. An additional three detectors and a rule for faulted phase and winding identification are presented as well. The proposed algorithm can not only detect an internal fault, but also identify the faulted phase and winding of a three-winding power transformer. The various test results with Electromagnetic Transients Program (EMTP-generated data show that the proposed algorithm successfully discriminates internal faults from normal operating conditions including magnetic inrush and over-excitation. This paper concludes by implementing the algorithm into a prototype relay based on a digital signal processor.

  11. Structural phase transitions in boron carbide under stress

    International Nuclear Information System (INIS)

    Korotaev, P; Pokatashkin, P; Yanilkin, A

    2016-01-01

    Structural transitions in boron carbide B 4 C under stress were studied by means of first-principles molecular dynamics in the framework of density functional theory. The behavior depends strongly on degree of non-hydrostatic stress. Under hydrostatic stress continuous bending of the three-atom C–B–C chain was observed up to 70 GPa. The presence of non-hydrostatic stress activates abrupt reversible chain bending, which is displacement of the central boron atom in the chain with the formation of weak bonds between this atom and atoms in the nearby icosahedra. Such structural change can describe a possible reversible phase transition in dynamical loading experiments. High non-hydrostatic stress achieved in uniaxial loading leads to disordering of the initial structure. The formation of carbon chains is observed as one possible transition route. (paper)

  12. Exploring the coordination change of vanadium and structure transformation of metavanadate MgV2O6 under high pressure

    Science.gov (United States)

    Tang, Ruilian; Li, Yan; Xie, Shengyi; Li, Nana; Chen, Jiuhua; Gao, Chunxiao; Zhu, Pinwen; Wang, Xin

    2016-01-01

    Raman spectroscopy, synchrotron angle-dispersive X-ray diffraction (ADXRD), first-principles calculations, and electrical resistivity measurements were carried out under high pressure to investigate the structural stability and electrical transport properties of metavanadate MgV2O6. The results have revealed the coordination change of vanadium ions (from 5+1 to 6) at around 4 GPa. In addition, a pressure-induced structure transformation from the C2/m phase to the C2 phase in MgV2O6 was detected above 20 GPa, and both phases coexisted up to the highest pressure. This structural phase transition was induced by the enhanced distortions of MgO6 octahedra and VO6 octahedra under high pressure. Furthermore, the electrical resistivity decreased with pressure but exhibited different slope for these two phases, indicating that the pressure-induced structural phase transitions of MgV2O6 was also accompanied by the obvious changes in its electrical transport behavior. PMID:27924843

  13. Transformers: the changing phases of low-dimensional vanadium oxide bronzes.

    Science.gov (United States)

    Marley, Peter M; Horrocks, Gregory A; Pelcher, Kate E; Banerjee, Sarbajit

    2015-03-28

    In this feature article, we explore the electronic and structural phase transformations of ternary vanadium oxides with the composition MxV2O5 where M is an intercalated cation. The periodic arrays of intercalated cations ordered along quasi-1D tunnels or layered between 2D sheets of the V2O5 framework induce partial reduction of the framework vanadium atoms giving rise to charge ordering patterns that are specific to the metal M and stoichiometry x. This periodic charge ordering makes these materials remarkably versatile platforms for studying electron correlation and underpins the manifestation of phenomena such as colossal metal-insulator transitions, quantized charge corrals, and superconductivity. We describe current mechanistic understanding of these emergent phenomena with a particular emphasis on the benefits derived from scaling these materials to nanostructured dimensions wherein precise ordering of cations can be obtained and phase relationships can be derived that are entirely inaccessible in the bulk. In particular, structural transformations induced by intercalation are dramatically accelerated due to the shorter diffusion path lengths at nanometer-sized dimensions, which cause a dramatic reduction of kinetic barriers to phase transformations and facilitate interconversion between the different frameworks. We conclude by summarizing numerous technological applications that have become feasible due to recent advances in controlling the structural chemistry and both electronic and structural phase transitions in these versatile frameworks.

  14. Structural Properties and Thermodynamic Stability of Metastable Phases in the Zr-Nb and Ti-V Systems

    International Nuclear Information System (INIS)

    Aurelio, Gabriela

    2003-01-01

    The structural properties and relative stability of metastable phases have been studied in the Zr-Nb and Ti-V systems.The first part of this Thesis is connected to a previous work performed in our Group (G. Grad, PhD Thesis, Instituto Balseiro, Argentina, 1999).It presents a phenomenological analysis of the systematics of interatomic distances in the omega (Ω ) and bcc (β) phases of the transition metals, which concerns a parameter entering into Pauling's resonating-valence- bond-theory and the structural and bonding properties of the Ω and β phases.Neutron diffraction experiments in Zr-Nb and Ti-V alloys are reported, aimed at studying possible atomic ordering in the Ω phase and the composition dependence of its interatomic distances.An extensive neutron diffraction study was performed on a series of Zr-Nb and Ti-V alloys quenched from high temperatures, where β is the stable phase.Upon quenching, three metastable structures are formed, viz., the hcp (∝ q ) phase, the Ω q phase, and the untransformed β q phase.The structural properties of these metastable phases were determined as a function of the Nb and V contents to generate a reliable experimental database.With such data, a series of issues are discussed related to the structure, relative stability, and phase relations in the alloys and its constitutive elements.The effect of composition upon the lattice parameters of the metastable β q and Ω q phases was combined in a consistent way with a critical analysis of structural and thermophysical data on the metastable phases of Ti and Zr.The relative stability of the metastable ∝ q , Ω q and β q phases in Zr-Nb alloys, and its evolution towards thermodynamic equilibrium, were studied combining neutron thermodiffraction and analytical electron microscopy techniques.During isothermal heat treatments performed at high temperature, the structural properties of the alloys