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Sample records for twinned cubic crystals

  1. Size effect on deformation twinning in face-centred cubic single crystals: Experiments and modelling

    International Nuclear Information System (INIS)

    Liang, Z.Y.; De Hosson, J.T.M.; Huang, M.X.

    2017-01-01

    In addition to slip by dislocation glide, deformation twinning in small-sized metallic crystals also exhibits size effect, namely the twinning stress increases with decreasing sample size. In order to understand the underpinning mechanisms responsible for such effect, systematic experiments were carried out on the small-sized single-crystalline pillars of a twinning-induced plasticity steel with a face-centred cubic structure. The flow stress increases considerably with decreasing pillar diameter from 3 to 0.5 μm, demonstrating a substantial size effect with a power exponent of 0.43. Detailed microstructural characterization reveals that the plastic deformation of the present pillars is dominant by twinning, primarily via twin growth, indicating that the size effect should be related to deformation twinning instead of slip by dislocation glide. Subsequent modelling works indicate that twinning can be accomplished by the dissociation of the ion-radiation-induced vacancy Frank loops in the damaged subsurface layer of the pillars, and the size effect is attributed to the ion-radiation-induced compressive stress in the subsurface layer, which decreases with pillar diameter.

  2. Size-dependent plastic deformation of twinned nanopillars in body-centered cubic tungsten

    Science.gov (United States)

    Xu, Shuozhi; Startt, Jacob K.; Payne, Thomas G.; Deo, Chaitanya S.; McDowell, David L.

    2017-05-01

    Compared with face-centered cubic metals, twinned nanopillars in body-centered cubic (BCC) systems are much less explored partly due to the more complicated plastic deformation behavior and a lack of reliable interatomic potentials for the latter. In this paper, the fault energies predicted by two semi-empirical interatomic potentials in BCC tungsten (W) are first benchmarked against density functional theory calculations. Then, the more accurate potential is employed in large scale molecular dynamics simulations of tensile and compressive loading of twinned nanopillars in BCC W with different cross sectional shapes and sizes. A single crystal, a twinned crystal, and single crystalline nanopillars are also studied as references. Analyses of the stress-strain response and defect nucleation reveal a strong tension-compression asymmetry and a weak pillar size dependence in the yield strength. Under both tensile and compressive loading, plastic deformation in the twinned nanopillars is dominated by dislocation slip on {110} planes that are nucleated from the intersections between the twin boundary and the pillar surface. It is also found that the cross sectional shape of nanopillars affects the strength and the initial site of defect nucleation but not the overall stress-strain response and plastic deformation behavior.

  3. Twinning of cubic diamond explains reported nanodiamond polymorphs

    Science.gov (United States)

    Németh, Péter; Garvie, Laurence A. J.; Buseck, Peter R.

    2015-12-01

    The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i-, and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin ( rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications.

  4. Twinning of cubic diamond explains reported nanodiamond polymorphs.

    Science.gov (United States)

    Németh, Péter; Garvie, Laurence A J; Buseck, Peter R

    2015-12-16

    The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i-, and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin ( rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications.

  5. Twinning of Polymer Crystals Suppressed by Entropy

    Directory of Open Access Journals (Sweden)

    Nikos Ch. Karayiannis

    2014-09-01

    Full Text Available We propose an entropic argument as partial explanation of the observed scarcity of twinned structures in crystalline samples of synthetic organic polymeric materials. Polymeric molecules possess a much larger number of conformational degrees of freedom than low molecular weight substances. The preferred conformations of polymer chains in the bulk of a single crystal are often incompatible with the conformations imposed by the symmetry of a growth twin, both at the composition surfaces and in the twin axis. We calculate the differences in conformational entropy between chains in single crystals and chains in twinned crystals, and find that the reduction in chain conformational entropy in the twin is sufficient to make the single crystal the stable thermodynamic phase. The formation of cyclic twins in molecular dynamics simulations of chains of hard spheres must thus be attributed to kinetic factors. In more realistic polymers this entropic contribution to the free energy can be canceled or dominated by nonbonded and torsional energetics.

  6. Atomic-scale processes revealing dynamic twin boundary strengthening mechanisms in face-centered cubic materials

    International Nuclear Information System (INIS)

    Yang, Z.Q.; Chisholm, M.F.; He, L.L.; Pennycook, S.J.; Ye, H.Q.

    2012-01-01

    We report experimental investigations on interactions/reactions between dislocations and twin boundaries in Al. The absorption of screw dislocations via cross-slip and the production of stair-rods via reactions with non-screw dislocations were verified by atomic resolution imaging. Importantly, the resulting partial dislocations moving along twin boundaries can produce secondary sessile defects. These immobile defects act as obstacles to other dislocations and also serve to pin the twin boundaries. These findings show the atomic-level dynamics of the dislocation–twin boundary processes and the unique strengthening mechanism of twin boundaries in face-centered cubic metals.

  7. Strong crystal size effect on deformation twinning

    DEFF Research Database (Denmark)

    Yu, Qian; Shan, Zhi-Wei; Li, Ju

    2010-01-01

    plasticity. Accompanying the transition in deformation mechanism, the maximum flow stress of the submicrometre-sized pillars was observed to saturate at a value close to titanium’s ideal strength9, 10. We develop a ‘stimulated slip’ model to explain the strong size dependence of deformation twinning......Deformation twinning1, 2, 3, 4, 5, 6 in crystals is a highly coherent inelastic shearing process that controls the mechanical behaviour of many materials, but its origin and spatio-temporal features are shrouded in mystery. Using micro-compression and in situ nano-compression experiments, here we...... find that the stress required for deformation twinning increases drastically with decreasing sample size of a titanium alloy single crystal7, 8, until the sample size is reduced to one micrometre, below which the deformation twinning is entirely replaced by less correlated, ordinary dislocation...

  8. Atomistic simulation study of deformation twinning of nanocrystalline body-centered cubic Mo

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Xiaofeng [The College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu (China); Li, Dan, E-mail: txf8378@163.com [The College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu (China); Yu, You [College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu (China); You, Zhen Jiang [Australian School of Petroleum, University of Adelaide, SA 5005 (Australia); Li, Tongye [The National Key Laboratory of Nuclear Fuel and Materials, Nuclear Power Institute of China, Chengdu (China); Ge, Liangquan [The College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu (China)

    2017-04-06

    Deformation twinning of nanocrystalline body-centered cubic Mo was studied using molecular dynamics simulations, and the effects of grain sizes and temperatures on the deformation were evaluated. With small grain size, grain rotation accompanying grain growth was found to play important role in nanocrystalline Mo during tensile deformation. Additionally, grain rotation and the deformation controlled by GB-mediated processes induce to the difficulty of creating crack. Twin was formed by successive emission of twinning partials from grain boundaries in small grain size systems. However, the twin mechanisms of GB splitting and overlapping of two extended dislocations were also found in larger size grain. Twin induced crack tips were observed in our simulation, and this confirmed the results of previous molecular dynamics simulations. At higher temperatures, GB activities can be thermally activated, resulting in suppression of twinning tendency and improvement of ductility of nanocrystalline Mo.

  9. Steps and dislocations in cubic lyotropic crystals

    International Nuclear Information System (INIS)

    Leroy, S; Pieranski, P

    2006-01-01

    It has been shown recently that lyotropic systems are convenient for studies of faceting, growth or anisotropic surface melting of crystals. All these phenomena imply the active contribution of surface steps and bulk dislocations. We show here that steps can be observed in situ and in real time by means of a new method combining hygroscopy with phase contrast. First results raise interesting issues about the consequences of bicontinuous topology on the structure and dynamical behaviour of steps and dislocations

  10. Plastic fluctuations in empty crystals formed by cubic wireframe particles

    Science.gov (United States)

    McBride, John M.; Avendaño, Carlos

    2018-05-01

    We present a computer simulation study of the phase behavior of colloidal hard cubic frames, i.e., particles with nonconvex cubic wireframe geometry interacting purely by excluded volume. Despite the propensity of cubic wireframe particles to form cubic phases akin to their convex counterparts, these particles exhibit unusual plastic fluctuations in which a random and dynamic fraction of particles rotate around their lattice positions in the crystal lattice while the remainder of the particles remains fully ordered. We argue that this unexpected effect stems from the nonconvex geometry of the particles in which the faces of a particle can be penetrated by the vertices of the nearest neighbors even at high number densities.

  11. Deformation twinning in zinc-aluminium single crystals after slip

    International Nuclear Information System (INIS)

    Lukac, P.; Kral, F.; Trojanova, Z.; Kral, R.

    1993-01-01

    Deformation twinning in Zn-Al single crystals deformed by slip in the basal system is examined. The influence of temperature and the content of aluminium in zinc on the twinning stress is investigated in the temperature range from 198 to 373 K. It is shown that the twinning stress rises with increasing temperature and increases with the concentration of Al atoms. (orig.)

  12. X-Ray Diffraction (XRD) Characterization Methods for Sigma=3 Twin Defects in Cubic Semiconductor (100) Wafers

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Kim, Hyun Jung (Inventor); Skuza, Jonathan R. (Inventor); Lee, Kunik (Inventor); King, Glen C. (Inventor); Choi, Sang Hyouk (Inventor)

    2017-01-01

    An X-ray defraction (XRD) characterization method for sigma=3 twin defects in cubic semiconductor (100) wafers includes a concentration measurement method and a wafer mapping method for any cubic tetrahedral semiconductor wafers including GaAs (100) wafers and Si (100) wafers. The methods use the cubic semiconductor's (004) pole figure in order to detect sigma=3/{111} twin defects. The XRD methods are applicable to any (100) wafers of tetrahedral cubic semiconductors in the diamond structure (Si, Ge, C) and cubic zinc-blend structure (InP, InGaAs, CdTe, ZnSe, and so on) with various growth methods such as Liquid Encapsulated Czochralski (LEC) growth, Molecular Beam Epitaxy (MBE), Organometallic Vapor Phase Epitaxy (OMVPE), Czochralski growth and Metal Organic Chemical Vapor Deposition (MOCVD) growth.

  13. THERMODYNAMIC PARAMETERS OF LEAD SULFIDE CRYSTALS IN THE CUBIC PHASE

    Directory of Open Access Journals (Sweden)

    T. O. Parashchuk

    2016-07-01

    Full Text Available Geometric and thermodynamic parameters of cubic PbS crystals were obtained using the computer calculations of the thermodynamic parameters within density functional theory method DFT. Cluster models for the calculation based on the analysis of the crystal and electronic structure. Temperature dependence of energy ΔE and enthalpy ΔH, Gibbs free energy ΔG, heat capacity at constant pressure CP and constant volume CV, entropy ΔS were determined on the basis of ab initio calculations of the crystal structure of molecular clusters. Analytical expressions of temperature dependences of thermodynamic parameters which were approximated with quantum-chemical calculation points have been presented. Experimental results compared with theoretically calculated data.

  14. Topological Characterization of Carbon Graphite and Crystal Cubic Carbon Structures.

    Science.gov (United States)

    Siddiqui, Wei Gao Muhammad Kamran; Naeem, Muhammad; Rehman, Najma Abdul

    2017-09-07

    Graph theory is used for modeling, designing, analysis and understanding chemical structures or chemical networks and their properties. The molecular graph is a graph consisting of atoms called vertices and the chemical bond between atoms called edges. In this article, we study the chemical graphs of carbon graphite and crystal structure of cubic carbon. Moreover, we compute and give closed formulas of degree based additive topological indices, namely hyper-Zagreb index, first multiple and second multiple Zagreb indices, and first and second Zagreb polynomials.

  15. Principal spectra describing magnetooptic permittivity tensor in cubic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hamrlová, Jana [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Legut, Dominik [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Veis, Martin [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Pištora, Jaromír [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Hamrle, Jaroslav, E-mail: jaroslav.hamrle@vsb.cz [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Department of Physics, VSB – Technical University of Ostrava, 17. listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic)

    2016-12-15

    We provide unified phenomenological description of magnetooptic effects being linear and quadratic in magnetization. The description is based on few principal spectra, describing elements of permittivity tensor up to the second order in magnetization. Each permittivity tensor element for any magnetization direction and any sample surface orientation is simply determined by weighted summation of the principal spectra, where weights are given by crystallographic and magnetization orientations. The number of principal spectra depends on the symmetry of the crystal. In cubic crystals owning point symmetry we need only four principal spectra. Here, the principal spectra are expressed by ab initio calculations for bcc Fe, fcc Co and fcc Ni in optical range as well as in hard and soft x-ray energy range, i.e. at the 2p- and 3p-edges. We also express principal spectra analytically using modified Kubo formula.

  16. Phase field modeling of twinning in indentation of transparent crystals

    International Nuclear Information System (INIS)

    Clayton, J D; Knap, J

    2011-01-01

    Continuum phase field theory is applied to study elastic twinning in calcite and sapphire single crystals subjected to indentation loading by wedge-shaped indenters. An order parameter is associated with the magnitude of stress-free twinning shear. Geometrically linear and nonlinear theories are implemented and compared, the latter incorporating neo-Hookean elasticity. Equilibrium configurations of deformed and twinned crystals are attained numerically via direct energy minimization. Results are in qualitative agreement with experimental observations: a long thin twin forms asymmetrically under one side of the indenter, the tip of the twin is sharp and the length of the twin increases with increasing load. Qualitatively similar results are obtained using isotropic and anisotropic elastic constants, though the difference between isotropic and anisotropic results is greater in sapphire than in calcite. Similar results are also obtained for nanometer-scale specimens and millimeter-scale specimens. Indentation forces are greater in the nonlinear model than the linear model because of the increasing tangent bulk modulus with increasing pressure in the former. Normalized relationships between twin length and indentation force are similar for linear and nonlinear theories at both nanometer and millimeter scales. Twin morphologies are similar for linear and nonlinear theories for indentation with a 90° wedge. However, in the nonlinear model, indentation with a 120° wedge produces a lamellar twin structure between the indenter and the long sharp primary twin. This complex microstructure is not predicted by the linear theory

  17. Shear response of Σ3{112} twin boundaries in face-centered-cubic metals

    Science.gov (United States)

    Wang, J.; Misra, A.; Hirth, J. P.

    2011-02-01

    Molecular statics and dynamics simulations were used to study the mechanisms of sliding and migration of Σ3{112} incoherent twin boundaries (ITBs) under applied shear acting in the boundary in the face-centered-cubic (fcc) metals, Ag, Cu, Pd, and Al, of varying stacking fault energies. These studies revealed that (i) ITBs can dissociate into two phase boundaries (PBs), bounding the hexagonal 9R phase, that contain different arrays of partial dislocations; (ii) the separation distance between the two PBs scales inversely with increasing stacking fault energy; (iii) for fcc metals with low stacking fault energy, one of the two PBs migrates through the collective glide of partials, referred to as the phase-boundary-migration (PBM) mechanism; (iv) for metals with high stacking energy, ITBs experience a coupled motion (migration and sliding) through the glide of interface disconnections, referred to as the interface-disconnection-glide (IDG) mechanism.

  18. Plastic deformation of cubic zirconia single crystals at 1400 C

    International Nuclear Information System (INIS)

    Baufeld, B.; Baither, D.; Bartsch, M.; Messerschmidt, U.

    1998-01-01

    Cubic zirconia single crystals stabilized with 11 mol% yttria were deformed in air at 1400 C and around 1200 C at different strain rates along [1 anti 12] and [100] compression directions. The strain rate sensitivity of the flow stress was determined by strain rate cycling and stress relaxation tests. The microstructure of the deformed specimens was investigated by transmission high-voltage electron microscopy, including contrast extinction analysis for determining the Burgers vectors as well as stereo pairs and wide-angle tilting experiments to find the active slip planes. At deformation along [1 anti 12], the primary and secondary slip planes are of {100} type. Previous experiments had shown that the dislocations move easily on these planes in an athermal way. During deformation along [100], mainly dislocations on {100} planes are activated, which move in a viscous way by the aid of thermal activation. The discussion of the different deformation behaviours during deformation along [1 anti 12] and [100] is based on the different dynamic properties of dislocations and the fact that recovery is an essential feature of the deformation of cubic zirconia at 1400 C. The results on the shape of the deformation curve and the strain rate sensitivity of the flow stress are partly at variance with those of previous authors. (orig.)

  19. Twinning structures in near-stoichiometric lithium niobate single crystals

    International Nuclear Information System (INIS)

    Yao, Shuhua; Chen, Yanfeng

    2010-01-01

    A near-stoichiometric lithium niobate single crystal has been grown by the Czochralski method in a hanging double crucible with a continuous powder supply system. Twins were found at one of the three characteristic growth ridges of the as-grown crystal. The twin structure was observed and analyzed by transmission synchrotron topography. The image shifts ΔX and ΔY in the transmission synchrotron topograph were calculated for the 3 anti 2 anti 12 and 0 anti 222 reflections based on results from high-resolution X-ray diffractometry. It is confirmed that one of the {01 anti 1 anti 2} m planes is the composition face of the twin and matrix crystals. The formation mechanism of these twins is discussed. (orig.)

  20. The crystal structure and twinning of neodymium gallium perovskite single crystals

    International Nuclear Information System (INIS)

    Ubizskii, S.B.; Vasylechko, L.O.; Savytskii, D.I.; Matkovskii, A.O.; Syvorotka, I.M.

    1994-01-01

    By means of X-ray structure analysis, the crystal structure of neodymium gallium perovskite (NGP) single crystals (NdGaO 3 ) being used as a substrate for HTSC film epitaxy has been refined and the position of atoms has been determined. The possibility of YBa 2 Cu 3 O 7-x film epitaxy on the plane (110) of NGP crystal as well as its advantages and pitfalls are analysed from structural data. The twinning types in the NGP crystal were established. The twinning structure of NGP substrates is found to be stable up to a temperature of 1173 K, as differentiated from the LaGaO 3 and LaAlO 3 substrates. It is intimated that the twinning in the NGP substrates oriented as (001) can result in creation of 90 degrees twin bonds in a film, and in the case of (110)-oriented plates it is possible to ignore the twinning presence in substrate completely. (author)

  1. A new spectral framework for crystal plasticity modeling of cubic and hexagonal polycrystalline metals

    Science.gov (United States)

    Knezevic, Marko

    Crystal plasticity physics-based constitutive theories are used in understanding and predicting the evolution of the underlying microstructure and the concomitant anisotropic stress-strain response in polycrystalline metals subjected to finite plastic strains. A new scheme for efficient crystal plasticity computations for both cubic and hexagonal polycrystalline metals subjected to arbitrary deformation modes has been developed in this thesis. This new computational scheme involves building material databases comprised of spectral coefficients. These spectral coefficients are computed using discrete Fourier transforms (DFTs) and allow for compact representation and fast retrieval of crystal plasticity solutions for a crystal of any orientation subjected to any deformation mode. The novel approach is able to speed up the conventional crystal plasticity computations by two orders of magnitude. Furthermore, mathematical procedures for delineation of property closures that identify the complete set of theoretically feasible combinations of macroscale effective properties has been developed for a broad set of mechanical properties. Subsequently, these constructs were used in microstructure design for identifying an optimal microstructure for selected performance criteria. And finally, hybrid processing recipes that transform a given initial microstructure into a member of the set of optimal microstructures that exhibit superior properties or performance characteristics have been described. Insights and tremendous potential of these novel materials knowledge systems are discussed and demonstrated through specific case-studies. The anisotropic stress-strain response measured in simple compression and simple tension tests in different sample directions on an annealed, strongly textured, AZ31 sheet has been studied. New insights into the mechanical response of this material were obtained by correlating the changes in the measured strain-hardening rates in the different

  2. Detwinning mechanisms for growth twins in face-centered cubic metals

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J., E-mail: wangj6@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, N.; Anderoglu, O. [Department of Mechanical Engineering, Materials Science and Engineering Program, Texas A and M University, College Station, TX 77843-3123 (United States); Zhang, X., E-mail: zhangx@tamu.edu [Department of Mechanical Engineering, Materials Science and Engineering Program, Texas A and M University, College Station, TX 77843-3123 (United States); Misra, A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Huang, J.Y. [Sandia National Laboratories, Albuquerque, NM 87185 (United States); Hirth, J.P. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2010-04-15

    Using in situ transmission electron microscopy, we studied the stability of growth twins. We observed the rapid migration of incoherent twin boundaries (ITBs), indicating that nanotwins are unstable. Topological analysis and atomistic simulations are adopted to explore detwinning mechanisms. The results show that: (i) the detwinning process is accomplished via the collective glide of multiple twinning dislocations that form an ITB; (ii) detwinning can easily occur for thin twins, and the driving force is mainly attributed to a variation of the excess energy of a coherent twin boundary; (iii) shear stresses enable ITBs to migrate easily, causing the motion of coherent twin boundaries; and (iv) the migration velocity depends on stacking fault energy. The results imply that detwinning becomes the dominant deformation mechanism for growth twins of the order of a few nanometers thick.

  3. Influence of the cone angle and crystal shape on the formation of twins in InP crystals

    International Nuclear Information System (INIS)

    Li, Xiaolan; Yang, Ruixia; Yang, Fan; Sun, Tongnian; Sun, Niefeng

    2012-01-01

    We present the investigation of twinning phenomena of LEC InP crystal growth which has been carried out in our laboratory in recent years. It is observed that the yield of twin-free single crystal InP can be grown by control the cone angle and crystal shape of a gradually increased diameter. Twin formation has been correlated to many growth factors. The influence of ingot shape on the formation of twins can be looked as the conical angle dependent twin probability of InP crystals. Twin-free InP crystals can be grown by large cone angle over 75 to 90 . (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Fishtail effect in twinned and detwinned YBCO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boudissa, M. [Universite Ferhat Abbas, Faculte des Sciences de l' Ingenieur, Setif (Algeria); Halimi, R. [Universite Mentouri, Unite de Recherche de Physique des Materiaux, Constantine (Algeria); Frikach, K.; Senoussi, S. [Universite Paris-Sud, Laboratoire de Physique des Solides, Orsay (France)

    2006-09-15

    We have studied the magnetization hysteresis loops of a twinned and detwinned single crystals in a temperature range between 4.2 and 100 K and a magnetic field (H) range between 0 and 6 T. We carried out relaxation measurements on the samples at different temperatures and magnetic fields. We investigated the twin pinning as a function of temperature (T) and the fishtail anomaly in the critical current density of the two samples. We tried in this study to confirm or infirm the different models which explain the fishtail effect by confronting them to our experimental results We found that the collective creep theory is consistent with the results of our experiment in the field region where the magnetization is at its minimum. This field marks a crossover between the small and large bundle pinning regimes. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Fishtail effect in twinned and detwinned YBCO single crystals

    International Nuclear Information System (INIS)

    Boudissa, M.; Halimi, R.; Frikach, K.; Senoussi, S.

    2006-01-01

    We have studied the magnetization hysteresis loops of a twinned and detwinned single crystals in a temperature range between 4.2 and 100 K and a magnetic field (H) range between 0 and 6 T. We carried out relaxation measurements on the samples at different temperatures and magnetic fields. We investigated the twin pinning as a function of temperature (T) and the fishtail anomaly in the critical current density of the two samples. We tried in this study to confirm or infirm the different models which explain the fishtail effect by confronting them to our experimental results We found that the collective creep theory is consistent with the results of our experiment in the field region where the magnetization is at its minimum. This field marks a crossover between the small and large bundle pinning regimes. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Crystallization and preliminary crystallographic analysis of merohedrally twinned crystals of MJ0729, a CBS-domain protein from Methanococcus jannaschii

    International Nuclear Information System (INIS)

    Fernández-Millán, Pablo; Kortazar, Danel; Lucas, María; Martínez-Chantar, María Luz; Astigarraga, Egoitz; Fernández, José Andrés; Sabas, Olatz; Albert, Armando; Mato, Jose M.; Martínez-Cruz, Luis Alfonso

    2008-01-01

    Trigonal crystals of MJ0729 showing different degrees of merohedral twinning that may vary from perfect hemihedral twinning to perfect tetartohedral twinning were obtained upon slight variation of the pH. CBS domains are small protein motifs, usually associated in tandem, that are implicated in binding to adenosyl groups. Several genetic diseases in humans have been associated with mutations in CBS sequences, which has made them very promising targets for rational drug design. Trigonal crystals of the CBS-domain protein MJ0729 from Methanococcus jannaschii were grown by the vapour-diffusion method at acidic pH. Preliminary analysis of nine X-ray diffraction data sets using Yeates statistics and Britton plots showed that slight variation in the pH as well as in the buffer used in the crystallization experiments led to crystals with different degrees of merohedral twinning that may vary from perfect hemihedral twinning to perfect tetartohedral twinning

  7. Ni-Mn-Ga single crystals with very low twinning stress

    International Nuclear Information System (INIS)

    Straka, L; Haenninen, H; Soroka, A; Sozinov, A

    2011-01-01

    Twinning stress or mechanical hysteresis associated with the twin boundary motion is one of the most essential parameters which determine the actuating performance of magnetic shape memory alloys. Recent effort at AdaptaMat Ltd. to decrease the twinning stress resulted in a consistent production of Ni-Mn-Ga magnetic shape memory single crystals with the twinning stress of about 0.1 MPa, which is much lower than previously reported. In this work, the mechanical and magnetomechanical response of the developed crystals is discussed in detail and the importance of adjustment of the twin microstructure for obtaining an optimal actuating behavior is illustrated.

  8. Dislocation structures of Σ3 {112} twin boundaries in face centered cubic metals

    Science.gov (United States)

    Wang, J.; Anderoglu, O.; Hirth, J. P.; Misra, A.; Zhang, X.

    2009-07-01

    High resolution transmission electron microscopy of nanotwinned Cu films revealed Σ3 {112} incoherent twin boundaries (ITBs), with a repeatable pattern involving units of three {111} atomic planes. Topological analysis shows that Σ3 {112} ITBs adopt two types of atomic structure with differing arrangements of Shockley partial dislocations. Atomistic simulations were performed for Cu and Al. These studies revealed the structure of the two types of ITBs, the formation mechanism and stability of the associated 9R phase, and the influence of stacking fault energies on them. The results suggest that Σ3 {112} ITBs may migrate through the collective glide of partial dislocations.

  9. Face Centered Cubic and Hexagonal Close Packed Skyrmion Crystals in Centrosymmetric Magnets

    Science.gov (United States)

    Lin, Shi-Zeng; Batista, Cristian D.

    2018-02-01

    Skyrmions are disklike objects that typically form triangular crystals in two-dimensional systems. This situation is analogous to the so-called pancake vortices of quasi-two-dimensional superconductors. The way in which Skyrmion disks or "pancake Skyrmions" pile up in layered centrosymmetric materials is dictated by the interlayer exchange. Unbiased Monte Carlo simulations and simple stabilization arguments reveal face centered cubic and hexagonal close packed Skyrmion crystals for different choices of the interlayer exchange, in addition to the conventional triangular crystal of Skyrmion lines. Moreover, an inhomogeneous current induces a sliding motion of pancake Skyrmions, indicating that they behave as effective mesoscale particles.

  10. Etching of semiconductor cubic crystals: Determination of the dissolution slowness surfaces

    Science.gov (United States)

    Tellier, C. R.

    1990-03-01

    Equations of the representative surface of dissolution slowness for cubic crystals are determined in the framework of a tensorial approach of the orientation-dependent etching process. The independent dissolution constants are deduced from symmetry considerations. Using previous data on the chemical etching of germanium and gallium arsenide crystals, some possible polar diagrams of the dissolution slowness are proposed. A numerical and graphical simulation method is used to obtain the derived dissolution shapes. The influence of extrema in the dissolution slowness on the successive dissolution shapes is also examined. A graphical construction of limiting shapes of etched crystals appears possible using the tensorial representation of the dissolution slowness.

  11. Twinning behavior in the Ti-5at.% Al single crystals during cyclic loading along [0001

    International Nuclear Information System (INIS)

    Xiao Lin

    2005-01-01

    Cyclic deformation behavior of Ti-5at.% Al single crystals subjected to pull-push cyclic load along [0001] crystallographic orientation was studied. A higher cyclic stress response was displayed in the Ti-5Al single crystal oriented for [0001] than that oriented for single prism slip. Optical microscopy and transmission electron microscopy examinations show that twinning is a dominant plastic deformation mode in the single crystals during cycling. Trace analysis of prepolished surfaces was used to identify the twin systems primarily responsible for deformation. The major twin type observed was {101-bar 2}, {112-bar 2}, {101-bar 1} and {112-bar 1}. slip was observed in the neighboring region of twins in the fatigued specimens. The activation of multiple twinning systems contributed to the higher cyclic saturation stress in Ti-5Al single crystals oriented for [0001

  12. Dual Effect of the Cubic Ag₃PO₄ Crystal on Pseudomonas syringae Growth and Plant Immunity

    Directory of Open Access Journals (Sweden)

    Mi Kyung Kim

    2016-04-01

    Full Text Available We previously found that the antibacterial activity of silver phosphate crystals on Escherichia coli depends on their structure. We here show that the cubic form of silver phosphate crystal (SPC can also be applied to inhibit the growth of a plant-pathogenic Pseudomonas syringae bacterium. SPC pretreatment resulted in reduced in planta multiplication of P. syringae. Induced expression of a plant defense marker gene PR1 by SPC alone is suggestive of its additional plant immunity-stimulating activity. Since SPC can simultaneously inhibit P. syringae growth and induce plant defense responses, it might be used as a more effective plant disease-controlling agent.

  13. Martensitic cubic → tetragonal transition

    International Nuclear Information System (INIS)

    Schumann, H.

    1983-01-01

    Indium-thallium alloys containing 14 to 30% At. Tl have a cubic face-centred beta phase wich changes into a tetragonal face-centred alpha martensite during solidification. The martensite contains twin crystals that are large enough to be seen by means of a light microscope. The phenomenological crystallographic martensite theory was used to calculate Miller's index of the habit plane, the formation of the surface relief, the orientation relations and the critical thickness ratio of the twins. In a beta monocrystal frequently only one of the 24 crystallographic possible habit planes are formed at one end of the sample and migrate through the whole crystal when the temperature drops. Externally applied tension and compression influence in different ways the direction in which the habit plane moves and can even destroy the twinned structure, i.e. they can modify the substructure of the martensite crystal. This induces superelasticity, an effect that has also been described quantitatively. (author)

  14. Visualization of membrane protein crystals in lipid cubic phase using X-ray imaging

    International Nuclear Information System (INIS)

    Warren, Anna J.; Armour, Wes; Axford, Danny; Basham, Mark; Connolley, Thomas; Hall, David R.; Horrell, Sam; McAuley, Katherine E.; Mykhaylyk, Vitaliy; Wagner, Armin; Evans, Gwyndaf

    2013-01-01

    A comparison of X-ray diffraction and radiographic techniques for the location and characterization of protein crystals is demonstrated on membrane protein crystals mounted within lipid cubic phase material. The focus in macromolecular crystallography is moving towards even more challenging target proteins that often crystallize on much smaller scales and are frequently mounted in opaque or highly refractive materials. It is therefore essential that X-ray beamline technology develops in parallel to accommodate such difficult samples. In this paper, the use of X-ray microradiography and microtomography is reported as a tool for crystal visualization, location and characterization on the macromolecular crystallography beamlines at the Diamond Light Source. The technique is particularly useful for microcrystals and for crystals mounted in opaque materials such as lipid cubic phase. X-ray diffraction raster scanning can be used in combination with radiography to allow informed decision-making at the beamline prior to diffraction data collection. It is demonstrated that the X-ray dose required for a full tomography measurement is similar to that for a diffraction grid-scan, but for sample location and shape estimation alone just a few radiographic projections may be required

  15. Visualization of membrane protein crystals in lipid cubic phase using X-ray imaging

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Anna J. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Armour, Wes [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Oxford e-Research Centre, 7 Keble Road, Oxford OX1 3QG (United Kingdom); Axford, Danny; Basham, Mark; Connolley, Thomas; Hall, David R. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Horrell, Sam [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); University of Liverpool, Liverpool L69 3BX (United Kingdom); McAuley, Katherine E.; Mykhaylyk, Vitaliy; Wagner, Armin; Evans, Gwyndaf, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom)

    2013-07-01

    A comparison of X-ray diffraction and radiographic techniques for the location and characterization of protein crystals is demonstrated on membrane protein crystals mounted within lipid cubic phase material. The focus in macromolecular crystallography is moving towards even more challenging target proteins that often crystallize on much smaller scales and are frequently mounted in opaque or highly refractive materials. It is therefore essential that X-ray beamline technology develops in parallel to accommodate such difficult samples. In this paper, the use of X-ray microradiography and microtomography is reported as a tool for crystal visualization, location and characterization on the macromolecular crystallography beamlines at the Diamond Light Source. The technique is particularly useful for microcrystals and for crystals mounted in opaque materials such as lipid cubic phase. X-ray diffraction raster scanning can be used in combination with radiography to allow informed decision-making at the beamline prior to diffraction data collection. It is demonstrated that the X-ray dose required for a full tomography measurement is similar to that for a diffraction grid-scan, but for sample location and shape estimation alone just a few radiographic projections may be required.

  16. pH-responsive lyotropic liquid crystals for the preparation of pure cubic zirconia nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    He, Wei Yan; Liu, Jin Rong; He, Zhang; Cao, Zhen Zhu; Li, Cai Hong; Gao, Yan Fang [Inner Mongolia University of Technology, School of Chemical Engineering, Hohhot (China)

    2016-07-15

    We present a lyotropic liquid crystal system consisting of SDS/Triton X-100/water at 25 C. This system is respond to pH variations with a phase switch. When pH is altered from alkaline (pH 13) to acidic (pH 2) conditions, phase change occurs from a bicontinuous hexagonal phase to a partially hexagonal phase until it disappears. The hexagonal phase under alkaline conditions is stable. Thus, this system is an ideal candidate for the preparation of pure cubic ZrO{sub 2} nanoparticles. XRD results confirm that the as-synthesized powder is composed of pure cubic ZrO{sub 2}. These nanoparticles also exhibit a thermal stability of up to 800 C. The size and morphological characteristics of the nanoparticles are greatly affected by ZrOCl{sub 2} concentration. The mechanism of zirconia nanoparticle synthesis in a lyotropic hexagonal phase was proposed. (orig.)

  17. On the magnetization process and the associated probability in anisotropic cubic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Khedr, D.M., E-mail: doaamohammed88@gmail.com [Department of Basic Science, Modern Academy of Engineering and Technology at Maadi, Cairo (Egypt); Aly, Samy H.; Shabara, Reham M. [Department of Physics, Faculty of Science at Damietta, University of Damietta, Damietta (Egypt); Yehia, Sherif [Department of Physics, Faculty of Science at Helwan, University of Helwan, Helwan (Egypt)

    2017-05-15

    We present a theoretical method to calculate specific magnetic properties, e.g. magnetization curves, magnetic susceptibility and probability landscapes along the [100], [110] and [111] crystallographic directions of a crystal of cubic symmetry. The probability landscape displays the evolution of the most probable angular orientation of the magnetization vector, for selected temperatures and magnetic fields. Our method is based on the premises of classical statistical mechanics. The energy density, used in the partition function, is the sum of magnetic anisotropy and Zeeman energies, however no other energies e.g. elastic or magnetoelastic terms are considered in the present work. Model cubic systems of diverse anisotropies are analyzed first, and subsequently material magnetic systems of cubic symmetry; namely iron, nickel and Co{sub x} Fe{sub 100−x} compounds, are discussed. We highlight a correlation between magnetization curves and the associated probability landscapes. In addition, determination of easiest axes of magnetization, using energy consideration, is done and compared with the results of the present method.

  18. Adaptive interferometry based on dynamic reflective holograms in cubic photorefractive crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kolegov, A A; Shandarov, S M; Simonova, G V; Kabanova, L A; Burimov, Nikolai I; Shmakov, S S; Bykov, V I; Kargin, Yu F

    2011-09-30

    The characteristics of a holographic interferometer, which is based on the interaction of counterpropagating light waves on reflective holograms in cubic photorefractive sillenite crystals of the (100) cut and designed for measuring surface vibration spectra from specularly reflecting objects, have been theoretically analysed and experimentally studied. The experiments showed that an interferometer of this type, based on an Bi{sub 12}TiO{sub 20} : Fe,Cu crystal, makes it possible to measure vibrations with an amplitude of 5 pm. An analysis performed with allowance for the shot and thermal noise of the photodetector showed that vibrations with an amplitude below 1 pm can be measured. A model is proposed to describe the experimentally found strong temperature dependence of the light interaction on reflection holograms in a Bi{sub 12}TiO{sub 20} : Ca crystal. This model takes into account the influence of temperature on the photoinduced charge redistribution over deep donor and shallow trap centres, as well as the drift of the interference pattern in the crystal due to the thermooptical effect and linear expansion of the crystal.

  19. Crystal twinning of human MD-2 recognizing endotoxin cores of lipopolysaccharide

    International Nuclear Information System (INIS)

    Ohto, Umeharu; Satow, Yoshinori

    2008-01-01

    Twinned crystals of humaan MD-2 are transformed into single crystals with cryoprotectant optimization. Twinning of crystals causes overlapping of two or more reciprocal lattice points, and hence structure amplitudes for a single crystalline domain are hardly obtained from X-ray diffraction intensities. MD-2 protein forms a stable complex with Toll-like receptor 4 and recognizes bacterial lipopolysaccharide (LPS). Excessive immune responses activated by LPS cause septic shocks. Saccharide-trimmed human MD-2 crystallizes in the tetragonal form with apparent Laue symmetry of 4/mmm, and diffraction intensities from these crystals indicate crystal twinning. The crystal consists of two different domains, A and B. The c A axis of domain A coincides with the c B axis of domain B with a smaller lattice, and the a A axis corresponds to the (a B + b B ) axis. This twinning severely imposes difficulty in structure determination. Through optimization of cryoprotectant, domain A was thoroughly transformed into domain B. The crystal containing only domain B is in space group P4 1 2 1 2 with one MD-2 molecule in the asymmetric unit. The structure of this form of MD-2 as well as its complex with antiendotoxic lipid IVa was successfully determined using the multiple isomorphous replacement method

  20. Orientation selection process during the early stage of cubic dendrite growth: A phase-field crystal study

    International Nuclear Information System (INIS)

    Tang Sai; Wang Zhijun; Guo Yaolin; Wang Jincheng; Yu Yanmei; Zhou Yaohe

    2012-01-01

    Using the phase-field crystal model, we investigate the orientation selection of the cubic dendrite growth at the atomic scale. Our simulation results reproduce how a face-centered cubic (fcc) octahedral nucleus and a body-centered cubic (bcc) truncated-rhombic dodecahedral nucleus choose the preferred growth direction and then evolve into the dendrite pattern. The interface energy anisotropy inherent in the fcc crystal structure leads to the fastest growth velocity in the 〈1 0 0〉 directions. New { 1 1 1} atomic layers prefer to nucleate at positions near the tips of the fcc octahedron, which leads to the directed growth of the fcc dendrite tips in the 〈1 0 0〉 directions. A similar orientation selection process is also found during the early stage of bcc dendrite growth. The orientation selection regime obtained by phase-field crystal simulation is helpful for understanding the orientation selection processes of real dendrite growth.

  1. Visualization of membrane protein crystals in lipid cubic phase using X-ray imaging.

    Science.gov (United States)

    Warren, Anna J; Armour, Wes; Axford, Danny; Basham, Mark; Connolley, Thomas; Hall, David R; Horrell, Sam; McAuley, Katherine E; Mykhaylyk, Vitaliy; Wagner, Armin; Evans, Gwyndaf

    2013-07-01

    The focus in macromolecular crystallography is moving towards even more challenging target proteins that often crystallize on much smaller scales and are frequently mounted in opaque or highly refractive materials. It is therefore essential that X-ray beamline technology develops in parallel to accommodate such difficult samples. In this paper, the use of X-ray microradiography and microtomography is reported as a tool for crystal visualization, location and characterization on the macromolecular crystallography beamlines at the Diamond Light Source. The technique is particularly useful for microcrystals and for crystals mounted in opaque materials such as lipid cubic phase. X-ray diffraction raster scanning can be used in combination with radiography to allow informed decision-making at the beamline prior to diffraction data collection. It is demonstrated that the X-ray dose required for a full tomography measurement is similar to that for a diffraction grid-scan, but for sample location and shape estimation alone just a few radiographic projections may be required.

  2. Rotation-limited growth of three-dimensional body-centered-cubic crystals.

    Science.gov (United States)

    Tarp, Jens M; Mathiesen, Joachim

    2015-07-01

    According to classical grain growth laws, grain growth is driven by the minimization of surface energy and will continue until a single grain prevails. These laws do not take into account the lattice anisotropy and the details of the microscopic rearrangement of mass between grains. Here we consider coarsening of body-centered-cubic polycrystalline materials in three dimensions using the phase field crystal model. We observe, as a function of the quenching depth, a crossover between a state where grain rotation halts and the growth stagnates and a state where grains coarsen rapidly by coalescence through rotation and alignment of the lattices of neighboring grains. We show that the grain rotation per volume change of a grain follows a power law with an exponent of -1.25. The scaling exponent is consistent with theoretical considerations based on the conservation of dislocations.

  3. Mathemimetics II. Demonstratio Mirabilis of FLT by infinitely ascending cubical crystal growth

    Science.gov (United States)

    Trell, Erik

    2012-09-01

    Emulating Nature by observation and ground-up application of its patterns, structures and processes is a classical scientific practice which under the designation of Biomimetics has now been brought to the Nanotechnology scale where even highly complex systems can be realized by continuous or cyclically reiterated assembly of the respective self-similar eigen-elements, modules and algorithms right from their infinitesimal origin. This is actually quite akin to the genuine mathematical art and can find valuable renewed use as here exemplified by the tentatively original Demonstratio Mirabilis of FLT (Fermat's Last Theorem, or, in that case, Triumph) by infinitely ascending sheet-wise cubical crystal growth leading to the binomial `magic triangle' of his close fellow Blaise Pascal.

  4. The crystal structure of (001) twinned xilingolite, Pb3Bi2S6, from Mittal-Hohtenn, Valais, Switzerland

    DEFF Research Database (Denmark)

    Berlepsch, Peter; Armbruster, Thomas; Makovicky, Emil

    2002-01-01

    geology, xilingolite, crystal structure, twinning, lillianite homologue, electron-microprobe analyses, cannizzarite, Bi-containing galena, Mittal-Hohtenn, Valais, Switzerland......geology, xilingolite, crystal structure, twinning, lillianite homologue, electron-microprobe analyses, cannizzarite, Bi-containing galena, Mittal-Hohtenn, Valais, Switzerland...

  5. The effect of deformation twinning on irradiation embrittlement in iron single crystals

    International Nuclear Information System (INIS)

    Kayano, Hideo; Tokutomi, Shoichiro; Yajima, Seishi; Takaku, Hiroshi.

    1978-01-01

    Single crystals of iron with the [100] crystal orientation were irradiated in JMTR with fast neutrons to a fluence of 8 x 10 18 n/cm 2 (E > 1 MeV). All samples were deformed in tension at temperatures from liquid nitrogen temperature to 200 0 C at different strain rates using an Instron-type tensile testing machine. Scanning electron microscopy of the fractured surfaces revealed that deformation twinning is difficult to occur in irradiated samples, and also that twins formed in both irradiated and unirradiated samples inhibit fracture nucleation and growth. From the results of tensile deformation of the irradiated samples deformed in tension a different strain rates at 159 0 K, it is conceived that twinning suppression is greater in the irradiated than in the unirradiated samples, and that the nucleation and growth of twins are not necessarily related to those of cracks. It is suggested that the irradiation-induced defects impede plastic deformation of the crystals and deformation twinning is suppressed by irradiation, thus causing the irradiation embrittlement. (auth.)

  6. SURVEY OF THE SPECTRA OF THE DIVALENT RARE EARTH IONS IN CUBIC CRYSTALS

    Energy Technology Data Exchange (ETDEWEB)

    McClure, Donald S. [Univ. of Chicago, IL (United States); Kiss, Zoltan J. [RCA Laboratories, Princeton, NJ (United States)

    1963-04-15

    The rare earth ions may exist in the divalent state in suitable host crystals such as CaF/sub 2/. All of the trivalent ions from La to Yb are reduced in situ to the divalent state in CaF/sub 2/ by gamma irradiation. The spectra of most of these ions show that the ground and first few excited states derive from f/sup n/ configurations, but the wesk absorption due to these is masked at higher energies by strong broad bands of the parity permitted f/sup n/ yields f/sup n-1/ d transitions. The excitation energy of these spectra have been calculated in a first approximation as the energy difference between the Hund Rule'' single determinant states of the configurations f/sup n -1/d and f/sup n/. This procedure satisfactorily accounts for the remarkable variations in the excitation energy in passing from one ion to the next in the series with the exception of Ge/ sup 2+/ Ce/sup 2+/, and Tb/sup 2+/, Ge/sup 2+/ probably has f/sup 7/d for its ground con figuration, while Ce/sup 2+/ and Tb/sup 2+/ are borderline cases. The spectral structure probably arises chiefly from the crystal field splitting of the d-orbital, since each ion in CaF/sub 2/ has a similar spectrum, and the spectra change drastically in sites of other than cubic symmetry. (auth)

  7. Face-centered-cubic lithium crystals formed in mesopores of carbon nanofiber electrodes.

    Science.gov (United States)

    Lee, Byoung-Sun; Seo, Jong-Hyun; Son, Seoung-Bum; Kim, Seul Cham; Choi, In-Suk; Ahn, Jae-Pyoung; Oh, Kyu Hwan; Lee, Se-Hee; Yu, Woong-Ryeol

    2013-07-23

    In the foreseeable future, there will be a sharp increase in the demand for flexible Li-ion batteries. One of the most important components of such batteries will be a freestanding electrode, because the traditional electrodes are easily damaged by repeated deformations. The mechanical sustainability of carbon-based freestanding electrodes subjected to repeated electrochemical reactions with Li ions is investigated via nanotensile tests of individual hollow carbon nanofibers (HCNFs). Surprisingly, the mechanical properties of such electrodes are improved by repeated electrochemical reactions with Li ions, which is contrary to the conventional wisdom that the mechanical sustainability of carbon-based electrodes should be degraded by repeated electrochemical reactions. Microscopic studies reveal a reinforcing mechanism behind this improvement, namely, that inserted Li ions form irreversible face-centered-cubic (FCC) crystals within HCNF cavities, which can reinforce the carbonaceous matrix as strong second-phase particles. These FCC Li crystals formed within the carbon matrix create tremendous potential for HCNFs as freestanding electrodes for flexible batteries, but they also contribute to the irreversible (and thus low) capacity of HCNFs.

  8. Optical Characterization of Light-Bending Mechanisms in Photonic Crystals with Simple Cubic Symmetry

    Science.gov (United States)

    Frey, Brian James

    For much of Earth's history, light was reputed to be an intangible, intractable, and transient quantity, but our understanding of light has since been revolutionized. The flow of electromagnetic energy through space can today be manipulated with a degree of precision and control once only dreamed of; rapidly developing technologies can create, guide, bend, and detect light to produce useful energy and information. One field where these technologies are most relevant is the field of light trapping, which concerns the harvesting of incident photons within a limited space by scattering, slowing, or otherwise prolonging and enhancing their interaction with matter. Over the past few decades, a class of materials, called photonic crystals (PCs), has emerged that is ideally suited for this task. This is because their wavelength-scale periodicity in one, two, or three dimensions can be designed to alter the dispersion relation and photonic density-of-states in a controllable manner. In this work, a TiO2 simple cubic PC with high dielectric contrast ( > 4:1) is fabricated with a lattice constant of 450 nm, and a newly discovered light-trapping mechanism is demonstrated, which bends light by 90 degrees and enhances optical absorption by one to two orders-of-magnitude over that in a reference film of the same thickness. It is shown that, for wavelengths from 450-950 nm, the achievable enhancement factor for this structure surpasses the theoretical limit of 4n2 derived under the assumption of ergodic system by multiple times. These results derive directly from the symmetry of the simple cubic lattice and are fundamental in nature, not depending on the material used or on the method of fabrication. The light trapping capability of these PCs has straight-forward applications that would be useful in a variety of areas where increased light-matter interaction is desirable, such as white-light generation, thin-film solar cells, photocatalytic pollutant degradation and hydrogen fuel

  9. How to distinguish perfect quasi-crystals from twins and other structures using diffraction experiments?

    International Nuclear Information System (INIS)

    Wolny, J.

    1992-01-01

    Performing diffraction experiments for various lengths of coherent scattering and using the scaling of peak intensities on a number of atoms one can experimentally distinguish quasi-crystals from the other structures (e.g. twins or random). For perfect quasi-crystals peak intensities scale as N 2 , for other structures this scaling depends on concentration of atoms, behaving critical for Penrose concentration. 3 figs., 8 refs. (author)

  10. Three-Dimensional Random Voronoi Tessellations: From Cubic Crystal Lattices to Poisson Point Processes

    Science.gov (United States)

    Lucarini, Valerio

    2009-01-01

    We perturb the simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC) structures with a spatial Gaussian noise whose adimensional strength is controlled by the parameter α and analyze the statistical properties of the cells of the resulting Voronoi tessellations using an ensemble approach. We concentrate on topological properties of the cells, such as the number of faces, and on metric properties of the cells, such as the area, volume and the isoperimetric quotient. The topological properties of the Voronoi tessellations of the SC and FCC crystals are unstable with respect to the introduction of noise, because the corresponding polyhedra are geometrically degenerate, whereas the tessellation of the BCC crystal is topologically stable even against noise of small but finite intensity. Whereas the average volume of the cells is the intensity parameter of the system and does not depend on the noise, the average area of the cells has a rather interesting behavior with respect to noise intensity. For weak noise, the mean area of the Voronoi tessellations corresponding to perturbed BCC and FCC perturbed increases quadratically with the noise intensity. In the case of perturbed SCC crystals, there is an optimal amount of noise that minimizes the mean area of the cells. Already for a moderate amount of noise ( α>0.5), the statistical properties of the three perturbed tessellations are indistinguishable, and for intense noise ( α>2), results converge to those of the Poisson-Voronoi tessellation. Notably, 2-parameter gamma distributions constitute an excellent model for the empirical pdf of all considered topological and metric properties. By analyzing jointly the statistical properties of the area and of the volume of the cells, we discover that also the cells shape, measured by the isoperimetric quotient, fluctuates. The Voronoi tessellations of the BCC and of the FCC structures result to be local maxima for the isoperimetric quotient among space

  11. Twinning processes in Cu-Al-Ni martensite single crystals investigated by neutron single crystal diffraction method

    International Nuclear Information System (INIS)

    Molnar, P.; Sittner, P.; Novak, V.; Lukas, P.

    2008-01-01

    A neutron single crystal diffraction method for inspecting the quality of martensite single crystals is introduced. True interface-free martensite single crystals are indispensable for, e.g. measurement of elastic constants of phases by ultrasonic techniques. The neutron diffraction method was used to detect and distinguish the presence of individual lattice correspondence variants of the 2H orthorhombic martensite phase in Cu-Al-Ni as well as to follow the activity of twinning processes during the deformation test on the martensite variant single crystals. When preparing the martensite single variant prism-shaped crystals by compression deformation method, typically a small fraction of second unwanted martensitic variant (compound twin) remains in the prism samples. Due to the very low stress (∼1 MPa) for the compound twinning in many shape memory alloys, it is quite difficult not only to deplete the martensite prisms of all internal interfaces but mainly to keep them in the martensite single variant state for a long time needed for further investigations

  12. Molecular dynamics simulation of effects of twin interfaces on Cu/Ni multilayers

    International Nuclear Information System (INIS)

    Fu, Tao; Peng, Xianghe; Weng, Shayuan; Zhao, Yinbo; Gao, Fengshan; Deng, Lijun; Wang, Zhongchang

    2016-01-01

    We perform molecular dynamics simulation of the indentation on pure Cu and Ni films and Cu/Ni multilayered films with a cylindrical indenter, aimed to investigate the effects of the cubic-on-cubic interface and hetero-twin interface on their mechanical properties. We also investigate systematically the formation of twin boundary in the pure metals and the effects of the cubic-on-cubic and hetero-twin interface on mechanical properties of the multilayers. We find that the slip of the horizontal stacking fault can release the internal stress, resulting in insignificant strengthening. The change in the crystal orientation by horizontal movement of the atoms in a layer-by-layer manner is found to initiate the movement of twin boundary, and the hetero-twin interface is beneficial to the hardening of multilayers. Moreover, we also find that increasing number of hetero-twin interfaces can harden the Cu/Ni multilayers.

  13. Preliminary X-ray analysis of twinned crystals of sarcosine dimethylglycine methyltransferase from Halorhodospira halochoris

    International Nuclear Information System (INIS)

    Kallio, Juha Pekka; Jänis, Janne; Nyyssölä, Antti; Hakulinen, Nina; Rouvinen, Juha

    2009-01-01

    The crystallization and preliminary X-ray diffraction analysis of sarcosine dimethylglycine methyltransferase from H. halochoris is reported. Sarcosine dimethylglycine methyltransferase (EC 2.1.1.157) is an enzyme from the extremely halophilic anaerobic bacterium Halorhodospira halochoris. This enzyme catalyzes the twofold methylation of sarcosine to betaine, with S-adenosylmethionine (AdoMet) as the methyl-group donor. This study presents the crystallization and preliminary X-ray analysis of recombinant sarcosine dimethylglycine methyltransferase produced in Escherichia coli. Mass spectroscopy was used to determine the purity and homogeneity of the enzyme material. Two different crystal forms, which initially appeared to be hexagonal and tetragonal, were obtained. However, on analyzing the diffraction data it was discovered that both crystal forms were pseudo-merohedrally twinned. The true crystal systems were monoclinic and orthorhombic. The monoclinic crystal diffracted to a maximum of 2.15 Å resolution and the orthorhombic crystal diffracted to 1.8 Å resolution

  14. Structural, elastic and electronic Properties of isotropic cubic crystals of carbon and silicon nanotubes : Density functional based tight binding calculations.

    Directory of Open Access Journals (Sweden)

    Alexander L. Ivanovskii

    2008-01-01

    Full Text Available Atomic models of cubic crystals (CC of carbon and graphene-like Si nanotubes are offered and their structural, cohesive, elastic and electronic properties are predicted by means of the DFTB method. Our main findings are that the isotropic crystals of carbon nanotubes adopt a very high elastic modulus B and low compressibility β, namely B = 650 GPa, β = 0.0015 1/GPa. In addition, these crystals preserve the initial conductivity type of their “building blocks”, i.e. isolated carbon and Si nanotubes. This feature may be important for design of materials with the selected conductivity type.

  15. Cross-twinning model of fcc crystal growth

    NARCIS (Netherlands)

    van de Waal, B.W.

    1995-01-01

    The theory developed in 1960 by Wagner, Hamilton and Seidensticker (WHS-theory) to explain observed crystal growth phenomena in Ge is critically reviewed and shown to be capable of explaining preservation of ABC stacking order in two dimensions in fcc crystals of effectively spherical closed shell

  16. Cubic Crystal-Structured SnTe for Superior Li- and Na-Ion Battery Anodes.

    Science.gov (United States)

    Park, Ah-Ram; Park, Cheol-Min

    2017-06-27

    A cubic crystal-structured Sn-based compound, SnTe, was easily synthesized using a solid-state synthetic process to produce a better rechargeable battery, and its possible application as a Sn-based high-capacity anode material for Li-ion batteries (LIBs) and Na-ion batteries (NIBs) was investigated. The electrochemically driven phase change mechanisms of the SnTe electrodes during Li and Na insertion/extraction were thoroughly examined utilizing various ex situ analytical techniques. During Li insertion, SnTe was converted to Li 4.25 Sn and Li 2 Te; meanwhile, during Na insertion, SnTe experienced a sequential topotactic transition to Na x SnTe (x ≤ 1.5) and conversion to Na 3.75 Sn and Na 2 Te, which recombined into the original SnTe phase after full Li and Na extraction. The distinctive phase change mechanisms provided remarkable electrochemical Li- and Na-ion storage performances, such as large reversible capacities with high Coulombic efficiencies and stable cyclabilities with fast C-rate characteristics, by preparing amorphous-C-decorated nanostructured SnTe-based composites. Therefore, SnTe, with its interesting phase change mechanisms, will be a promising alternative for the oncoming generation of anode materials for LIBs and NIBs.

  17. Twinned crystals of adeno-associated virus serotype 3b prove suitable for structural studies

    International Nuclear Information System (INIS)

    Lerch, Thomas F.; Xie, Qing; Ongley, Heather M.; Hare, Joan; Chapman, Michael S.

    2009-01-01

    Crystals of adeno-associated virus serotype 3b, a human DNA virus with promise as a vector for gene therapy, have been grown, diffract X-rays to ∼2.6 Å resolution and are suitable for structure determination in spite of twinning. Adeno-associated viruses (AAVs) are leading candidate vectors for gene-therapy applications. The AAV-3b capsid is closely related to the well characterized AAV-2 capsid (87% identity), but sequence and presumably structural differences lead to distinct cell-entry and immune-recognition properties. In an effort to understand these differences and to perhaps harness them, diffraction-quality crystals of purified infectious AAV-3b particles have been grown and several partial diffraction data sets have been recorded. The crystals displayed varying levels of merohedral twinning that in earlier times would have rendered them unsuitable for structure determination, but here is shown to be a tractable complication

  18. Quadrupolar interactions in non-cubic crystal and related extra heat capacities. Possible effects on a sapphire bolometer

    Energy Technology Data Exchange (ETDEWEB)

    Bassou, M. [Tunis Univ. (Tunisia)]|[CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Rotter, M. [Karlova Univ., Prague (Czech Republic)]|[CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Bernier, M. [CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Chapellier, M. [CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France)

    1996-02-11

    It is shown that in a non-cubic crystal, the extra heat capacity due to quadrupolar interaction of nuclear spins >1/2 could be much bigger than the phonon heat capacity when the temperature decreases. The possible coupling between quadrupolar and phonon heat reservoir via paramagnetic impurities is stressed. A NMR experiment done on sapphire is presented with an evaluation of the coupling between the two reservoirs and its consequence on the performance of the bolometer. (orig.).

  19. Quadrupolar interactions in non-cubic crystal and related extra heat capacities. Possible effects on a sapphire bolometer

    International Nuclear Information System (INIS)

    Bassou, M.; Rotter, M.; Bernier, M.; Chapellier, M.

    1996-01-01

    It is shown that in a non-cubic crystal, the extra heat capacity due to quadrupolar interaction of nuclear spins >1/2 could be much bigger than the phonon heat capacity when the temperature decreases. The possible coupling between quadrupolar and phonon heat reservoir via paramagnetic impurities is stressed. A NMR experiment done on sapphire is presented with an evaluation of the coupling between the two reservoirs and its consequence on the performance of the bolometer. (orig.)

  20. Deformed lattice states in a Zn{sub 0.9}V{sub 0.1}Se cubic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Maksimov, V. I., E-mail: kokailo@rambler.ru; Dubinin, S. F.; Surkova, T. P.; Parkhomenko, V. D. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)

    2016-01-15

    Neutron scattering patterns have been recorded for a bulk Zn{sub 0.9}V{sub 0.1}Se cubic crystal at room temperature; they are indicative of macroscopic deformation in the material and its significant inhomogeneity. Specific features of the previously found state, preceding the fcc ↔ hcp structural transformation of the sphalerite lattice upon strong destabilization induced by vanadium ions in the doped ZnSe matrix, are discussed taking into account the data obtained.

  1. The peculiar effect of forest dislocations on single twin layer development in zinc and beryllium single crystals

    International Nuclear Information System (INIS)

    Lavrentev, F.F.; Bosin, M.E.

    1978-01-01

    This is an investigation of the effect of different types of forest dislocation on the rate of twin layer broadening, Vsub(n), in zinc and beryllium crystals, and on the velocity of the twinning dislocation movement, Vsub(t), in zinc crystals under the action of a constant external shear stress. Increasing the forest basal dislocation density, rhosub(b), was found to result in increasing Vsub(n) and reducing Vsub(t), while increasing the forest pyramidal dislocation density, rhosub(p), causes Vsub(n) to decrease. An analysis in terms of crystal geometry shows that the dualism of the influence of the basal dislocations stems from the fact that they behave as twinning dislocation sources whose density, increasing with rhosub(b) leads to higher Vsub(n). The decrease in the effective stress, tausup(*), with increasing rhosub(b) is estimated. An analysis of the experimental data yielded the relation Vsub(t)(tausup(*)) and an estimate of the activation volume, which amounted to 6 x 10 -21 cm 3 . The close coincidence of the activation volumes as obtained from Vsub(t)(tausup(*)) and Vsub(n)(tau) suggests that the rate-controlling mechanism of the twin layer development in zinc crystals with large forest basal dislocation density is the twinning dislocation inhibition. In Be crystals, the increasing Vsub(n) effect is observed during untwinning. In Be twinned crystals, electron microscopy revealed twinning dislocations with a density of about 10 5 cm -1 at the twin boundaries and a large forest basal dislocation density inside the twin (ca. 10 8 cm -2 ). (Auth.)

  2. Connection between twinning and brittle fracture in Fe-Cr-Co-Mo crystals

    International Nuclear Information System (INIS)

    Kirillov, V.A.; Chumlyakov, Yu.I.; Korotaev, A.D.; Aparova, L.A.

    1989-01-01

    Plasticity dependence on crystal orientation, on deformation temperature and structure state of alloy is investigated in Fe-28 % Cr-10 % Co-2 % Mo (at. %) monocrystals. Isostructure decomposition results in increase of critical shearing stresses τ cr , in change of deformation mechanism from slipping into twinning and abrupt reduction of plasticity. Brittleness - ductility transition is detected in high-stable structure states τ cr >280 MPa. Explanation of plasticity abrupt reduction of high-stable crystals using estimation of change of deformation mechanism and of deforming stress high level is given

  3. XPS analysis for cubic boron nitride crystal synthesized under high pressure and high temperature using Li3N as catalysis

    International Nuclear Information System (INIS)

    Guo, Xiaofei; Xu, Bin; Zhang, Wen; Cai, Zhichao; Wen, Zhenxing

    2014-01-01

    Highlights: • The cBN was synthesized by Li 3 N as catalyst under high pressure and high temperature (HPHT). • The film coated on the as-grown cBN crystals was studied by XPS. • The electronic structure variation in the film was investigated. • The growth mechanism of cubic boron nitride crystal was analyzed briefly. - Abstract: Cubic boron nitride (cBN) single crystals are synthesized with lithium nitride (Li3N) as catalyst under high pressure and high temperature. The variation of electronic structures from boron nitride of different layers in coating film on the cBN single crystal has been investigated by X-ray photoelectron spectroscopy. Combining the atomic concentration analysis, it was shown that from the film/cBN crystal interface to the inner, the sp 2 fractions are decreasing, and the sp 3 fractions are increasing in the film at the same time. Moreover, by transmission electron microscopy, a lot of cBN microparticles are found in the interface. For there is no Li 3 N in the film, it is possible that Li 3 N first reacts with hexagonal boron nitride to produce Li 3 BN 2 during cBN crystals synthesis under high pressure and high temperature (HPHT). Boron and nitrogen atoms, required for cBN crystals growth, could come from the direct conversion from hexagonal boron nitride with the catalysis of Li 3 BN 2 under high pressure and high temperature, but not directly from the decomposition of Li 3 BN 2

  4. Synthesis of indium oxide cubic crystals by modified hydrothermal route for application in room temperature flexible ethanol sensors

    Energy Technology Data Exchange (ETDEWEB)

    Seetha, M., E-mail: seetha.phy@gmail.com [Department of Physics, SRM University, Kattankulathur, Kancheepuram Dt 603 203 (India); Meena, P. [Department of Physics, PSGR Krishnammal College for Women, Coimbatore 641 046 (India); Mangalaraj, D., E-mail: dmraj800@yahoo.com [DRDO-BU Centre for Life Sciences, Bharathiar University Campus, Coimbatore (India); Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 014 (India); Masuda, Yoshitake [National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan); Senthil, K. [School of Advanced Materials Science and Engineering, Sungkyunkwan University (Suwon Campus), Cheoncheon-dong 300, Jangan-gu, Suwon 440-746 (Korea, Republic of)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer For the first time HMT is used in the preparation of indium oxide. Black-Right-Pointing-Pointer HMT itself acts as base for the precursor and results in cubic indium hydroxide. Black-Right-Pointing-Pointer Modified hydrothermal route used for the preparation of cubic indium oxide crystals. Black-Right-Pointing-Pointer As a new approach a composite film synthesized with prepared indium oxide. Black-Right-Pointing-Pointer Film showed good response to ethanol vapours with quick response and recovery times. - Abstract: Indium oxide cubic crystals were prepared by using hexamethylenetetramine and indium chloride without the addition of any structure directing agents. The chemical route followed in the present work was a modified hydrothermal synthesis. The average crystallite size of the prepared cubes was found to be 40 nm. A blue emission at 418 nm was observed at room temperature when the sample was excited with a 380 nm Xenon lamp. This emission due to oxygen vacancies made the material suitable for gas sensing applications. The synthesized material was made as a composite film with polyvinyl alcohol which was more flexible than the films prepared on glass substrates. This flexible film was used as a sensing element and tested with ethanol vapours at room temperature. The film showed fast response as well as recovery to ethanol vapours with a sensor response of about 1.4 for 100 ppm of the gas.

  5. Synthesis of indium oxide cubic crystals by modified hydrothermal route for application in room temperature flexible ethanol sensors

    International Nuclear Information System (INIS)

    Seetha, M.; Meena, P.; Mangalaraj, D.; Masuda, Yoshitake; Senthil, K.

    2012-01-01

    Highlights: ► For the first time HMT is used in the preparation of indium oxide. ► HMT itself acts as base for the precursor and results in cubic indium hydroxide. ► Modified hydrothermal route used for the preparation of cubic indium oxide crystals. ► As a new approach a composite film synthesized with prepared indium oxide. ► Film showed good response to ethanol vapours with quick response and recovery times. - Abstract: Indium oxide cubic crystals were prepared by using hexamethylenetetramine and indium chloride without the addition of any structure directing agents. The chemical route followed in the present work was a modified hydrothermal synthesis. The average crystallite size of the prepared cubes was found to be 40 nm. A blue emission at 418 nm was observed at room temperature when the sample was excited with a 380 nm Xenon lamp. This emission due to oxygen vacancies made the material suitable for gas sensing applications. The synthesized material was made as a composite film with polyvinyl alcohol which was more flexible than the films prepared on glass substrates. This flexible film was used as a sensing element and tested with ethanol vapours at room temperature. The film showed fast response as well as recovery to ethanol vapours with a sensor response of about 1.4 for 100 ppm of the gas.

  6. Crystal structure of (Al,V)4(P4O12)3, archetype of double cubic ring tetraphosphate

    International Nuclear Information System (INIS)

    Yakubovich, O. V.; Biralo, G. V.; Dimitrova, O. V.

    2012-01-01

    The crystal structure of the (Al,V) 4 (P 4 O 12 ) 3 solid solution, obtained in the single-crystal form by hydrothermal synthesis in the Al(OH) 3 -VO 2 -NaCl-H 3 PO 4 -H 2 O system, has been solved by X-ray diffraction analysis (Xcalibur-S-CCD diffractometer, R = 0.0257): a = 13.7477(2) Å, sp. gr. I 4 bar 3d, Z = 4, and ρ calcd = 2.736 g/cm 3 . It is shown that the crystal structure of the parent cubic Al 4 (P 4 O 12 ) 3 modification can formally be considered an archetype for the formation of double isosymmetric tetraphosphates on its basis.

  7. Refinement of La1.5Ba1.5Cu3O7-x from a Twinned Crystal

    DEFF Research Database (Denmark)

    Hjorth, Michael

    1996-01-01

    The structure of the title compound (barium copper lanthanum oxide, Ba1.50Cu3La1.50O6.66) has been refined from a twinned crystal using single-crystal methods. The results of the present investigation show lower standard deviations than the results of earlier powder diffraction refinements...

  8. Three-dimensional Random Voronoi Tessellations: From Cubic Crystal Lattices to Poisson Point Processes

    OpenAIRE

    Lucarini, Valerio

    2008-01-01

    We perturb the SC, BCC, and FCC crystal structures with a spatial Gaussian noise whose adimensional strength is controlled by the parameter a, and analyze the topological and metrical properties of the resulting Voronoi Tessellations (VT). The topological properties of the VT of the SC and FCC crystals are unstable with respect to the introduction of noise, because the corresponding polyhedra are geometrically degenerate, whereas the tessellation of the BCC crystal is topologically stable eve...

  9. A High-Rate, Single-Crystal Model including Phase Transformations, Plastic Slip, and Twinning

    Energy Technology Data Exchange (ETDEWEB)

    Addessio, Francis L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Bronkhorst, Curt Allan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Bolme, Cynthia Anne [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Explosive Science and Shock Physics Division; Brown, Donald William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Cerreta, Ellen Kathleen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Lebensohn, Ricardo A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Lookman, Turab [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Luscher, Darby Jon [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Mayeur, Jason Rhea [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Morrow, Benjamin M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Rigg, Paulo A. [Washington State Univ., Pullman, WA (United States). Dept. of Physics. Inst. for Shock Physics

    2016-08-09

    An anisotropic, rate-­dependent, single-­crystal approach for modeling materials under the conditions of high strain rates and pressures is provided. The model includes the effects of large deformations, nonlinear elasticity, phase transformations, and plastic slip and twinning. It is envisioned that the model may be used to examine these coupled effects on the local deformation of materials that are subjected to ballistic impact or explosive loading. The model is formulated using a multiplicative decomposition of the deformation gradient. A plate impact experiment on a multi-­crystal sample of titanium was conducted. The particle velocities at the back surface of three crystal orientations relative to the direction of impact were measured. Molecular dynamics simulations were conducted to investigate the details of the high-­rate deformation and pursue issues related to the phase transformation for titanium. Simulations using the single crystal model were conducted and compared to the high-­rate experimental data for the impact loaded single crystals. The model was found to capture the features of the experiments.

  10. A comprehensive review of the lipid cubic phase or in meso method for crystallizing membrane and soluble proteins and complexes

    International Nuclear Information System (INIS)

    Caffrey, Martin

    2015-01-01

    A comprehensive and up-to-date review of the lipid cubic phase or in meso method for crystallizing membrane and soluble proteins and complexes is reported. Recent applications of the method for in situ serial crystallography at X-ray free-electron lasers and synchrotrons are described. The lipid cubic phase or in meso method is a robust approach for crystallizing membrane proteins for structure determination. The uptake of the method is such that it is experiencing what can only be described as explosive growth. This timely, comprehensive and up-to-date review introduces the reader to the practice of in meso crystallogenesis, to the associated challenges and to their solutions. A model of how crystallization comes about mechanistically is presented for a more rational approach to crystallization. The possible involvement of the lamellar and inverted hexagonal phases in crystallogenesis and the application of the method to water-soluble, monotopic and lipid-anchored proteins are addressed. How to set up trials manually and automatically with a robot is introduced with reference to open-access online videos that provide a practical guide to all aspects of the method. These range from protein reconstitution to crystal harvesting from the hosting mesophase, which is noted for its viscosity and stickiness. The sponge phase, as an alternative medium in which to perform crystallization, is described. The compatibility of the method with additive lipids, detergents, precipitant-screen components and materials carried along with the protein such as denaturants and reducing agents is considered. The powerful host and additive lipid-screening strategies are described along with how samples that have low protein concentration and cell-free expressed protein can be used. Assaying the protein reconstituted in the bilayer of the cubic phase for function is an important element of quality control and is detailed. Host lipid design for crystallization at low temperatures and for

  11. A comprehensive review of the lipid cubic phase or in meso method for crystallizing membrane and soluble proteins and complexes

    Energy Technology Data Exchange (ETDEWEB)

    Caffrey, Martin, E-mail: martin.caffrey@tcd.ie [Trinity College Dublin, Dublin (Ireland)

    2015-01-01

    A comprehensive and up-to-date review of the lipid cubic phase or in meso method for crystallizing membrane and soluble proteins and complexes is reported. Recent applications of the method for in situ serial crystallography at X-ray free-electron lasers and synchrotrons are described. The lipid cubic phase or in meso method is a robust approach for crystallizing membrane proteins for structure determination. The uptake of the method is such that it is experiencing what can only be described as explosive growth. This timely, comprehensive and up-to-date review introduces the reader to the practice of in meso crystallogenesis, to the associated challenges and to their solutions. A model of how crystallization comes about mechanistically is presented for a more rational approach to crystallization. The possible involvement of the lamellar and inverted hexagonal phases in crystallogenesis and the application of the method to water-soluble, monotopic and lipid-anchored proteins are addressed. How to set up trials manually and automatically with a robot is introduced with reference to open-access online videos that provide a practical guide to all aspects of the method. These range from protein reconstitution to crystal harvesting from the hosting mesophase, which is noted for its viscosity and stickiness. The sponge phase, as an alternative medium in which to perform crystallization, is described. The compatibility of the method with additive lipids, detergents, precipitant-screen components and materials carried along with the protein such as denaturants and reducing agents is considered. The powerful host and additive lipid-screening strategies are described along with how samples that have low protein concentration and cell-free expressed protein can be used. Assaying the protein reconstituted in the bilayer of the cubic phase for function is an important element of quality control and is detailed. Host lipid design for crystallization at low temperatures and for

  12. BDA: A novel method for identifying defects in body-centered cubic crystals.

    Science.gov (United States)

    Möller, Johannes J; Bitzek, Erik

    2016-01-01

    The accurate and fast identification of crystallographic defects plays a key role for the analysis of atomistic simulation output data. For face-centered cubic (fcc) metals, most existing structure analysis tools allow for the direct distinction of common defects, such as stacking faults or certain low-index surfaces. For body-centered cubic (bcc) metals, on the other hand, a robust way to identify such defects is currently not easily available. We therefore introduce a new method for analyzing atomistic configurations of bcc metals, the BCC Defect Analysis (BDA). It uses existing structure analysis algorithms and combines their results to uniquely distinguish between typical defects in bcc metals. In essence, the BDA method offers the following features:•Identification of typical defect structures in bcc metals.•Reduction of erroneously identified defects by iterative comparison to the defects in the atom's neighborhood.•Availability as ready-to-use Python script for the widespread visualization tool OVITO [http://ovito.org].

  13. Visualization of membrane protein crystals in lipid cubic phase using X-ray imaging

    OpenAIRE

    Warren, Anna J.; Armour, Wes; Axford, Danny; Basham, Mark; Connolley, Thomas; Hall, David R.; Horrell, Sam; McAuley, Katherine E.; Mykhaylyk, Vitaliy; Wagner, Armin; Evans, Gwyndaf

    2013-01-01

    The focus in macromolecular crystallography is moving towards even more challenging target proteins that often crystallize on much smaller scales and are frequently mounted in opaque or highly refractive materials. It is therefore essential that X-ray beamline technology develops in parallel to accommodate such difficult samples. In this paper, the use of X-ray microradiography and microtomography is reported as a tool for crystal visualization, location and characterization on the macromolec...

  14. Multiple delta doping of single crystal cubic boron nitride films heteroepitaxially grown on (001)diamonds

    Science.gov (United States)

    Yin, H.; Ziemann, P.

    2014-06-01

    Phase pure cubic boron nitride (c-BN) films have been epitaxially grown on (001) diamond substrates at 900 °C. The n-type doping of c-BN epitaxial films relies on the sequential growth of nominally undoped (p-) and Si doped (n-) layers with well-controlled thickness (down to several nanometer range) in the concept of multiple delta doping. The existence of nominally undoped c-BN overgrowth separates the Si doped layers, preventing Si dopant segregation that was observed for continuously doped epitaxial c-BN films. This strategy allows doping of c-BN films can be scaled up to multiple numbers of doped layers through atomic level control of the interface in the future electronic devices. Enhanced electronic transport properties with higher hall mobility (102 cm2/V s) have been demonstrated at room temperature as compared to the normally continuously Si doped c-BN films.

  15. Crystal structures of orthorhombic, hexagonal, and cubic compounds of the Sm(x)Yb(2−x)TiO5 series

    International Nuclear Information System (INIS)

    Aughterson, Robert D.; Lumpkin, Gregory R.; Reyes, Massey de los; Sharma, Neeraj; Ling, Christopher D.; Gault, Baptiste; Smith, Katherine L.; Avdeev, Maxim; Cairney, Julie M.

    2014-01-01

    A series of single phase compounds with nominal stoichiometry Sm (x) Yb (2−x) TiO 5 (x=2, 1.4, 1, 0.6, and 0) have been successfully fabricated to generate a range of crystal structures covering the most common polymorphs previously discovered in the Ln 2 TiO 5 series (Ln=lanthanides and yttrium). Four of the five samples have not been previously fabricated in bulk, single phase form so their crystal structures are refined and detailed using powder synchrotron and single crystal x-ray diffraction, neutron diffraction and transmission electron microscopy. Based on the phase information from diffraction data, there are four crystal structure types in this series; orthorhombic Pnma, hexagonal P6 3 /mmc, cubic (pyrochlore-like) Fd-3m and cubic (fluorite-like) Fm-3m. The cubic materials show modulated structures with variation between long and short range ordering and the variety of diffraction techniques were used to describe these complex crystal structure types. - Graphical abstract: A high resolution image of the compound Sm 0.6 Yb 1.4 TiO 5 showing contrast from lattice fringes and the corresponding fast Fourier transform (FFT) of the HREM image with pyrochlore related diffraction spots marked “P” and fluorite marked “F”. The crystal is oriented down the [1 1 0] zone axis based on the Fd-3m structure. The ideal crystal structure (no vacancies) of the cubic, pyrochlore-like (Sm 0.6 Yb 1.4 TiO 5 ). - Highlights: • First fabrication of bulk single-phase material with stoichiometry Sm 2 TiO 5 . • Systematic study of crystal structure types within Ln 2 TiO 5 series (Ln=lanthanides). • A novel technique using IFFT of HREM images to study cubic structures

  16. Acousto-optical phonon excitation in cubic piezoelectric slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Willatzen, Morten; Duggen, Lars

    2017-01-01

    In this paper we investigate theoretically the influence of piezoelectric coupling on phonon dispersion relations. Specifically we solve dispersion relations for a fully coupled zinc-blende freestanding quantum well for different orientations of the crystal unit cell. It is shown that the phonon...... mode density in GaAs can change by a factor of approximately 2–3 at qx a = 1 for different crystal-growth directions relative to the slab thickness direction. In particular, it is found that optical and acoustic phonon modes are always piezoelectrically coupled, independent of the crystal...... that the piezoelectric effect leads to a drastically enhanced coupling of acoustic and optical phonon modes and increase in the local phonon density of states near the plasma frequency where the permittivity approaches zero....

  17. Auger electron spectroscopy analysis for growth interface of cubic boron nitride single crystals synthesized under high pressure and high temperature

    Science.gov (United States)

    Lv, Meizhe; Xu, Bin; Cai, Lichao; Guo, Xiaofei; Yuan, Xingdong

    2018-05-01

    After rapid cooling, cubic boron nitride (c-BN) single crystals synthesized under high pressure and high temperature (HPHT) are wrapped in the white film powders which are defined as growth interface. In order to make clear that the transition mechanism of c-BN single crystals, the variation of B and N atomic hybrid states in the growth interface is analyzed with the help of auger electron spectroscopy in the Li-based system. It is found that the sp2 fractions of B and N atoms decreases, and their sp3 fractions increases from the outer to the inner in the growth interface. In addition, Lithium nitride (Li3N) are not found in the growth interface by X-ray diffraction (XRD) experiment. It is suggested that lithium boron nitride (Li3BN2) is produced by the reaction of hexagonal boron nitride (h-BN) and Li3N at the first step, and then B and N atoms transform from sp2 into sp3 state with the catalysis of Li3BN2 in c-BN single crystals synthesis process.

  18. Flux flow and pinning by twin boundaries in single crystal YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Kwok, W.K.; Fleshler, S.; Welp, U.; Vinokur, V.M.; Downey, J.; Crabtree, G.W.

    1993-01-01

    We present AC magnetoresistance measurements in fully oxygenated and oxygen deficient single crystals of YBa 2 Cu 3 O 7-δ . From the resistive broadening in magnetic field for H parallel ab parallel I and H parallel ab perpendicular to I, we demonstrate the existence of Lorentz force induced flux flow dissipation near T c . Using a novel crossed magnetic field technique where high angular resolution of Δθ 2 Cu 3 O 7-δ single crystals. The twin boundary pinning onset is characterized by a critical angle model and we extract a phase diagram for the onset of twin boundary pinning. We report on a strong magnetic field dependence of the critical angle for twin boundary pinning for H parallel c which is absent for H parallel ab. In addition, we find the critical angle θ * for H parallel c is greater than that observed for H parallel ab for nearly stoichiometric samples. (orig.)

  19. New orientation formation and growth during primary recrystallization in stable single crystals of three face-centred cubic metals

    International Nuclear Information System (INIS)

    Miszczyk, M.; Paul, H.; Driver, J.H.; Maurice, C.

    2015-01-01

    Graphical abstract: For Ni, Cu and Cu-2%Al and (1 1 0)[0 0 −1] and (1 1 0)[1 −1 −2] initial orientations at the initial stages of recrystallization, the appearance of a specific number of new orientation groups of new grains has been demonstrated. The orientation relations across the recrystallization front are characterized by a high proportion of angles in the range 25–35° and 45–55° around axes mostly grouped about the 〈1 2 2〉, 〈1 1 1〉, 〈1 2 3〉 and 〈1 1 2〉 directions. A local minimum was noted for the disorientation angle densities close to 40° in all cases. For a single isolated nucleus of uniform orientation, the rotation axes are usually grouped around one of the normals of all four {1 1 1} planes but do not (or only rarely) coincide with them. The orientation of the growing new grain quickly transforms through the formation of a first generation twins. The most frequent situation occurs when the normal of the twinning face plane is situated near the rotation axis, around which the crystal lattice of the ‘primary nuclei’ rotates. Based on the anisotropy of grain growth a possible mechanism of orientation generation and grain growth by thermally activation movement of dislocation families, on {1 1 1} planes is proposed. - Abstract: The early stages of recrystallization have been systematically characterized in single crystal metals of medium and low stacking fault energy. Goss {1 1 0}〈0 0 1〉 and brass {1 1 0}〈1 1 2〉 oriented samples of Ni, Cu and Cu–2 wt.% Al alloy were deformed in a channel die to a logarithmic strain of 0.51 to develop a homogeneous structure composed of two sets of symmetrical primary microbands and then lightly annealed. Scanning electron microscopy/electron backscattered diffraction analyses demonstrate a strong relation between as-deformed orientations and the limited number of recrystallized grain orientations. The disorientation angles across the recrystallization front are mostly grouped in

  20. Acoustic band gaps of the woodpile sonic crystal with the simple cubic lattice

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Liang-Yu; Chen, Lien-Wen, E-mail: chenlw@mail.ncku.edu.t [Department of Mechanical Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2011-02-02

    This study theoretically and experimentally investigates the acoustic band gap of a three-dimensional woodpile sonic crystal. Such crystals are built by blocks or rods that are orthogonally stacked together. The adjacent layers are perpendicular to each other. The woodpile structure is embedded in air background. Their band structures and transmission spectra are calculated using the finite element method with a periodic boundary condition. The dependence of the band gap on the width of the stacked rods is discussed. The deaf bands in the band structure are observed by comparing with the calculated transmission spectra. The experimental transmission spectra for the {Gamma}-X and {Gamma}-X' directions are also presented. The calculated results are compared with the experimental results.

  1. Photoresponsive Release from Azobenzene-Modified Single Cubic Crystal NaCl/Silica Particles

    Directory of Open Access Journals (Sweden)

    Xingmao Jiang

    2011-01-01

    Full Text Available Azobenzene ligands were uniformly anchored to the pore surfaces of nanoporous silica particles with single crystal NaCl using 4-(3-triethoxysilylpropylureidoazobenzene (TSUA. The functionalization delayed the release of NaCl significantly. The modified particles demonstrated a photocontrolled release by trans/cis isomerization of azobenzene moieties. The addition of amphiphilic solvents, propylene glycol (PG, propylene glycol propyl ether (PGPE, and dipropylene glycol propyl ether (DPGPE delayed the release in water, although the wetting behavior was improved and the delay is the most for the block molecules with the longest carbon chain. The speedup by UV irradiation suggests a strong dependence of diffusion on the switchable pore size. TGA, XRD, FTIR, and NMR techniques were used to characterize the structures.

  2. X-ray analysis of bilirubin oxidase from Myrothecium verrucaria at 2.3 Å resolution using a twinned crystal

    International Nuclear Information System (INIS)

    Mizutani, Kimihiko; Toyoda, Mayuko; Sagara, Kenta; Takahashi, Nobuyuki; Sato, Atsuko; Kamitaka, Yuji; Tsujimura, Seiya; Nakanishi, Yuji; Sugiura, Toshiyuki; Yamaguchi, Shotaro; Kano, Kenji; Mikami, Bunzo

    2010-01-01

    The crystal structure of bilirubin oxidase (BOD) from M. verrucaria has been determined at 2.3 Å resolution using a merohedrally twinned crystal. BOD has four copper-coordination sites that are almost identical to those of other multicopper oxidases and is also very similar to them in overall structure. Bilirubin oxidase (BOD), a multicopper oxidase found in Myrothecium verrucaria, catalyzes the oxidation of bilirubin to biliverdin. Oxygen is the electron acceptor and is reduced to water. BOD is used for diagnostic analysis of bilirubin in serum and has attracted considerable attention as an enzymatic catalyst for the cathode of biofuel cells that work under neutral conditions. Here, the crystal structure of BOD is reported for the first time. Blue bipyramid-shaped crystals of BOD obtained in 2-methyl-2,4-pentanediol (MPD) and ammonium sulfate solution were merohedrally twinned in space group P6 3 . Structure determination was achieved by the single anomalous diffraction (SAD) method using the anomalous diffraction of Cu atoms and synchrotron radiation and twin refinement was performed in the resolution range 33–2.3 Å. The overall organization of BOD is almost the same as that of other multicopper oxidases: the protein is folded into three domains and a total of four copper-binding sites are found in domains 1 and 3. Although the four copper-binding sites were almost identical to those of other multicopper oxidases, the hydrophilic Asn residue (at the same position as a hydrophobic residue such as Leu in other multicopper oxidases) very close to the type I copper might contribute to the characteristically high redox potential of BOD

  3. X-ray diffraction studies on merohedrally twinned Δ1–62NtNBCe1-A crystals of the sodium/bicarbonate cotransporter

    International Nuclear Information System (INIS)

    Gill, Harindarpal S.; Dutcher, Lauren; Boron, Walter F.; Patel, Samir; Guay-Woodford, Lisa M.

    2013-01-01

    A truncated mutant missing the first 62 residues of the N-terminal, cytoplasmic domain of the sodium-bicarbonate NBCe1-A cotransporter crystallizes in space group P3 1 with pseudo-P3 1 21 symmetry and a hemihedral twin fraction of 33.0%. Twinned fractions and twin-pair statistics over binned resolutions confirm that the calculated twin fraction is associated with hemihedral twinning and not to non-crystallographic symmetry. NBCe1-A membrane-embedded macromolecules that cotransport sodium and bicarbonate ions across the bilayer serve to maintain acid–base homeostasis throughout the body. Defects result in a number of renal and eye disorders, including type-II renal tubular acidosis and cataracts. Here, crystals of a human truncated mutant of the cytoplasmic N-terminal domain of NBCe1 (Δ1–62NtNBCe1-A) are reported that diffract X-rays to 2.4 Å resolution. The crystal symmetry of Δ1–62NtNBCe1-A is of space group P3 1 with pseudo-P3 1 21 symmetry and it has a hemihedral twin fraction of 33.0%. The crystals may provide insight into the pathogenic processes observed in a subset of patients with truncating and point mutations in the gene encoding NBCe1

  4. Temperature dependence of twinning stress – analogy between Cu–Ni–Al and Ni–Mn–Ga shape memory single crystals

    Czech Academy of Sciences Publication Activity Database

    Vronka, Marek; Seiner, Hanuš; Heczko, Oleg

    2017-01-01

    Roč. 97, č. 18 (2017), s. 1479-1497 ISSN 1478-6435 R&D Projects: GA ČR GB14-36566G; GA ČR GA15-00262S Institutional support: RVO:68378271 ; RVO:61388998 Keywords : SMA * single crystal * twinning * martensite * twinning stress * temperature dependence Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.505, year: 2016

  5. Anisotropy of creep for vortex motion along twin planes in YBa2Cu3O7-x single crystals

    International Nuclear Information System (INIS)

    Bondarenko, A.V.; Prodan, A.A.; Obolenskij, M.A.; Vovk, R.V.; Arouri, T.R.

    2001-01-01

    Anisotropy of magnetic flux creep was investigated for the flux motion along the twin boundaries. It is shown that in relatively low magnetic fields the velocity of vortex creep does not depend on magnetic field and angle α identical H, ab. It is found that the differential resistivity ρ identical dE/dJ at high transport currents tends to saturation and its value is close to the viscous friction resistivity in the Bardeen-Stephen model. In low magnetic fields for the field applied in the vicinity of the ab-plane of the crystal a lock-in transition of vortices between the superconducting CuO layers was observed

  6. Four highly pseudosymmetric and/or twinned structures of d(CGCGCG) 2 extend the repertoire of crystal structures of Z-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Zhipu; Dauter, Zbigniew; Gilski, Miroslaw

    2017-10-30

    DNA oligomer duplexes containing alternating cytosines and guanines in their sequences tend to form left-handed helices of the Z-DNA type, with the sugar and phosphate backbone in a zigzag conformation and a helical repeat of two successive nucleotides. Z-DNA duplexes usually crystallize as hexagonally arranged parallel helical tubes, with various relative orientations and translation of neighboring duplexes. Four novel high-resolution crystal structures of d(CGCGCG)2duplexes are described here. They are characterized by a high degree of pseudosymmetry and/or twinning, with three or four independent duplexes differently oriented in a monoclinicP21lattice of hexagonal metric. The various twinning criteria give somewhat conflicting indications in these complicated cases of crystal pathology. The details of molecular packing in these crystal structures are compared with other known crystal forms of Z-DNA.

  7. Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases.

    Science.gov (United States)

    Nakatani, Tomotaka; Yoshiasa, Akira; Nakatsuka, Akihiko; Hiratoko, Tatsuya; Mashimo, Tsutomu; Okube, Maki; Sasaki, Satoshi

    2016-02-01

    A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.

  8. Phase properties of elastic waves in systems constituted of adsorbed diatomic molecules on the (001) surface of a simple cubic crystal

    Science.gov (United States)

    Deymier, P. A.; Runge, K.

    2018-03-01

    A Green's function-based numerical method is developed to calculate the phase of scattered elastic waves in a harmonic model of diatomic molecules adsorbed on the (001) surface of a simple cubic crystal. The phase properties of scattered waves depend on the configuration of the molecules. The configurations of adsorbed molecules on the crystal surface such as parallel chain-like arrays coupled via kinks are used to demonstrate not only linear but also non-linear dependency of the phase on the number of kinks along the chains. Non-linear behavior arises for scattered waves with frequencies in the vicinity of a diatomic molecule resonance. In the non-linear regime, the variation in phase with the number of kinks is formulated mathematically as unitary matrix operations leading to an analogy between phase-based elastic unitary operations and quantum gates. The advantage of elastic based unitary operations is that they are easily realizable physically and measurable.

  9. Defect modes caused by twinning in one-dimensional photonic crystals

    Czech Academy of Sciences Publication Activity Database

    Němec, Hynek; Duvillaret, L.; Quemeneur, F.; Kužel, Petr

    2004-01-01

    Roč. 21, č. 3 (2004), s. 548-553 ISSN 0740-3224 Institutional research plan: CEZ:AV0Z1010914 Keywords : photonic structures * twin-defect * defect levels * tuning Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.649, year: 2004

  10. Synchrotron X-ray topography studies of twinning and the phase transition at 145deg C in LaGaO sub 3 single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yao, G.D.; Dudley, M. (Dept. of Materials Science and Engineering, State Univ. of New York, Stony Brook, NY (USA)); Wang, Y.; Liu, X.; Liebermann, R.C. (Dept. of Earth and Space Sciences, State Univ. of New York, Stony Brook, NY (USA))

    1991-02-01

    An investigation of (i) twinning in the room temperature orthorhombic phase, (ii) the orthorhombic-to-rhombohedral phase transformation occurring at 145deg C and (iii) twinning in the high temperature rhombohedral phase, all occurring in lanthanum gallate single crystals has been undertaken using white-beam synchrotron X-ray topography (WBSXRT). At room temperature, WBSXRT results obtained from the (110){sub orth} surface, orthorhombic crystals indicated the presence of ''mirror'' twinning on (1anti 12){sub orth}, (1anti 1anti 2){sub orth}, (anti 110){sub orth} and (112){sub orth} planes. Differential thermal analysis confirmed the existence of a first-order phase transformation at 145deg C. WBSXRT observations of the associated structural change (orthorhombic to rhombohedral) correlated well with the results of temperature-dependent powder diffraction results which are presented in the companion paper. WBSXRT also revealed the detailed spatial characteristics of the transition on the microstructural scale, as well as the nature of twinning in the rhombohedral phase, with the latter occurring on (110){sub rhomb} planes. In all three cases, results were consistent with the transmission electron microscopy results presented in the companion paper. The influence of both the twinning and the phase transition on the potential use of LaGaO{sub 3} single crystals as substrates for high Tc superconductor epilayers is discussed. (orig.).

  11. The microscopic twins and their crystal phase in the high Tc Y-Ba-Cu-O and Dy-Ba-Cu-O superconductive ceramics

    International Nuclear Information System (INIS)

    Zu, Z.J.; Chen, Y.L.

    1988-01-01

    Most consider that the structure of Y-Ba- Cu-O and Dy-Ba-Cu-O stable superconductive crystals with high Tc is associated with the right-angled phase. The superconductivity is closely connected with the right-angled character of the crystalline texture; the better the right- angled character, the better the superconductivity. From statistical investigations of examples the authors have discovered that most of the Y-Ba-Cu-O and Dy-Ba-Cu-O superconductivity with high Tc ceramic crystals is in the monoclinic phase, which, consists of microscopic, lamellar, single twins. The long-columnar grains consisting of lamellar twin slabs show the optical characteristics of right-angled phase. The microscopic twinning and grain morphologies are summarized in this paper

  12. Anisotropy of vortex creep in YBa2Cu3O7-x single crystals with unidirectional twin boundaries

    International Nuclear Information System (INIS)

    Bondarenko, A.V.; Revyakina, M.G.; Prodan, A.A.; Obolenskij, M.A.; Vovk, R.V.; Arouri, T.R.

    2001-01-01

    The creep of Abrikosov vortices in a YBa 2 Cu 3 O 7-x single crystal containing unidirectional twin boundaries (TB's) was investigated in a special experimental geometry: J parallel ab, J parallel TB, H perpendicular J, and α ident to angle H, ab was a variable parameter. It is shown that the TB's affect the configuration structure of vortex lines for disorientation angles θ between magnetic field vector and TB's planes up to 70: at angles θ current J cE , observed in low magnetic fields for H parallel ab, is replaced by a minimum in high magnetic fields. This behavior is explained by the change-over from the single vortex creep to a collective one with increasing magnetic field

  13. Study of 3-D stress development in parent and twin pairs of a hexagonal close-packed polycrystal: Part II – crystal plasticity finite element modeling

    International Nuclear Information System (INIS)

    Abdolvand, Hamidreza; Majkut, Marta; Oddershede, Jette; Wright, Jonathan P.; Daymond, Mark R.

    2015-01-01

    Stress heterogeneity within each individual grain of polycrystalline Zircaloy-2 is studied using a crystal plasticity finite element (CPFE) model. For this purpose, the weighted Voronoi tessellation method is used to construct 3D geometries of more than 2600 grains based on their center-of-mass positions and volumes as measured by three-dimensional X-ray diffraction (3DXRD) microscopy. The constructed microstructure is meshed with different element densities and for different numbers of grains. Then a selected group of twin and parent pairs are studied. It is shown that the measured average stress for each grain from the 3DXRD experiment is within the stress variation zone of the grain modeled in the CPFE simulation. Also, the CPFE average stress calculation for each grain is in good agreement with the measured average stress values. It is shown that upon considering the stress variations within each grain, stresses in the parent and twin are quite different if they are plotted in the global coordinate system. However, if the stress tensor is rotated into the local coordinate system of the twin habit plane, all the stress components averaged over the presented population are close, except for the shear acting on the twin plane and the transverse stress. This result is significant as it provides information needed to model such parent-twin interactions in crystal plasticity codes

  14. Twinning processes in Cu-Al-Ni martensite single crystals investigated by neutron single crystal diffraction method

    Czech Academy of Sciences Publication Activity Database

    Molnar, P.; Šittner, P.; Novák, V.; Lukáš, Petr

    2008-01-01

    Roč. 481, Sp.Iss.SI (2008), s. 513-517 ISSN 0921-5093 R&D Projects: GA AV ČR IAA100480704 Institutional research plan: CEZ:AV0Z10480505 Keywords : Cu-Al-Ni * single crystals * neutron diffraction Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.806, year: 2008

  15. Temperature dependence of the mechanical properties of equiatomic solid solution alloys with face-centered cubic crystal structures

    International Nuclear Information System (INIS)

    Wu, Z.; Bei, H.; Pharr, G.M.; George, E.P.

    2014-01-01

    Compared to decades-old theories of strengthening in dilute solid solutions, the mechanical behavior of concentrated solid solutions is relatively poorly understood. A special subset of these materials includes alloys in which the constituent elements are present in equal atomic proportions, including the high-entropy alloys of recent interest. A unique characteristic of equiatomic alloys is the absence of “solvent” and “solute” atoms, resulting in a breakdown of the textbook picture of dislocations moving through a solvent lattice and encountering discrete solute obstacles. To clarify the mechanical behavior of this interesting new class of materials, we investigate here a family of equiatomic binary, ternary and quaternary alloys based on the elements Fe, Ni, Co, Cr and Mn that were previously shown to be single-phase face-centered cubic (fcc) solid solutions. The alloys were arc-melted, drop-cast, homogenized, cold-rolled and recrystallized to produce equiaxed microstructures with comparable grain sizes. Tensile tests were performed at an engineering strain rate of 10 −3 s −1 at temperatures in the range 77–673 K. Unalloyed fcc Ni was processed similarly and tested for comparison. The flow stresses depend to varying degrees on temperature, with some (e.g. NiCoCr, NiCoCrMn and FeNiCoCr) exhibiting yield and ultimate strengths that increase strongly with decreasing temperature, while others (e.g. NiCo and Ni) exhibit very weak temperature dependencies. To better understand this behavior, the temperature dependencies of the yield strength and strain hardening were analyzed separately. Lattice friction appears to be the predominant component of the temperature-dependent yield stress, possibly because the Peierls barrier height decreases with increasing temperature due to a thermally induced increase of dislocation width. In the early stages of plastic flow (5–13% strain, depending on material), the temperature dependence of strain hardening is due

  16. Complex cubic metallides AM{sub ∝6} (A=Ca, Sr; M=Zn, Cd, Hg). Synthesis, crystal chemistry and chemical bonding

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Michael; Wendorff, Marco; Roehr, Caroline [Freiburg Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2017-09-01

    In a systematic synthetic, crystallographic and bond theoretical study, the stability ranges as well as the distribution of the isoelectronic late d-block elements Zn, Cd and Hg (M) in the polyanions of the YCd{sub 6}-type phases (Ca/Sr)Cd{sub 6} have been investigated. Starting from Ca(Cd/Hg){sub 6}, 12-30% of the M atoms can be substituted by Zn, which gradually occupies the center of the empty cubes. In all ternary compounds, smaller/less electronegative Zn/Cd atoms occupy the disordered tetrahedra explaining the lack of the YCd{sub 6}-type for pure mercurides. Along the section SrCd{sub 6}-SrHg{sub 6}, the ordered Eu{sub 4}Cd{sub 25}-type is formed (Sr{sub 4}Cd{sub 16.1}Hg{sub 8.9}: cF1392, Fd anti 3, a=3191.93(5) pm, R1=0.0404). Besides, two new complex cubic Ca phases appear at increased Zn proportion: Ca{sub 2}Zn{sub 5.1}Cd{sub 5.8}, which exhibits a nearly complete site preference of Zn and Cd, crystallizes in the rare cubic Mg{sub 2}Zn{sub 11}-type structure (cP39-δ, Pm anti 3, a=918.1(1) pm, R1=0.0349). In the Ca-Hg system, an increased Zn proportion yielded the new compound CaZn{sub 1.31}Hg{sub 3.69} (cF480, F anti 43m, a=2145.43(9) pm, R1=0.0572), with a complex cubic structure closely related to Ba{sub 20}Hg{sub 103}. All structures, which are commonly described using nested polyhedra around high-symmetric sites, are alternatively described in accordance with the calculated electron densities and charge distribution: building blocks are face-sharing [M{sub 4}] tetrahedra (star polyhedra such as TS, IS, OS), each with a cage-critical point in its center, and [M{sub 8}] cubes (deformed TS), which are either empty, distorted or filled. The M element distribution in the anion is determined by size criteria and the difference in electronegativity, which induces a preferred formation of heteroatomic polar bonds.

  17. Crystallographic relations between face- and body-centred cubic crystals formed under near-equilibrium conditions: Observations from the Gibeon meteorite

    International Nuclear Information System (INIS)

    He Youliang; Godet, Stephane; Jacques, Pascal J.; Jonas, John J.

    2006-01-01

    The orientations of the kamacite lamellae formed from a single prior-taenite grain were measured by analysing the electron backscatter diffraction patterns obtained using scanning electron microscopy. These are shown to be close to the Kurdjumov-Sachs and Nishiyama-Wassermann relations and their intermediate, i.e., the Greninger-Troiano relation. The orientations of the α grains in the plessite regions were also measured and these were found to be continuously distributed around the Bain circles formed by the variants of the common correspondence relationships, including the Pitsch one in this case. The local misorientations between individual face- and body-centred cubic crystals along their common interfaces were measured. These can be characterized by the orientation relationships mentioned above as long as a certain amount of tolerance is allowed. Orientation variations within individual kamacite lamellae were also analysed. The crystallographic data support the view that somewhat different mechanisms are involved in the formation of Widmanstaetten structures and of the plessite in meteorites

  18. Single crystal growth and characterization of the intermetallic cubic cage system YCo1.82Mn0.18Zn20

    Science.gov (United States)

    Cabrera-Baez, M.; Finatti, B. F.; Rettori, C.; Avila, M. A.

    2018-05-01

    We report on the growth of YCo2-xMnxZn20 cubic single crystals (0 ≤ x ≤ 0.18) and their characterization through elemental analysis, x-ray diffraction, magnetization and heat capacity. Mn intermediate and/or mixed-valence-like behavior was observed in the magnetic response of YCo1.82Mn0.18Zn20 (and all other samples) at temperatures between 100 K and 200 K, and a spin-glass state is established at low temperatures. Specific heat results for x = 0.18 show an increased Sommerfeld coefficient of γ ≈ 100 mJ / mol .K2 compared to that of the undoped compound (18 mJ / mol .K2) suggesting an enhancement of the quasiparticle effective mass ignoring spin-glass effects at very low temperatures. The combination of different experimental data provides a better understanding of the Mn2+ effects in the weakly correlated electron compound of YCo2Zn20, the first case in this family of compounds where local magnetic moments come exclusively from the transition metal.

  19. The crystal structure of gustavite, PbAgBi3S6. Analysis of twinning and polytypism using the OD approach

    DEFF Research Database (Denmark)

    Makovicky, Emil; Topa, Dan

    2011-01-01

    ) of the opposite species; the latter is explained by a presence of twin lamellae or antiphase domains in the crystal. In accordance with its frequently observed twinning, gustavite is an OD (order-disorder) structure that can be described by zig-zag unit layers with layer symmetry P(2/n) 21/c 2/m...... and the interlayer symmetry elements {(22/n1,1/2) 21/n1/2,2 21/2/ a2}. An alternative OD description uses planar unit layers with the layer symmetry P(2/ b) 21/c 21/m and the interlayer elements 22/n1,–1/2 21/n1/2,2 21/2/a2. The former description adheres closely to the details of coordination of bismuth observed...

  20. Crystal substructures of the rotation-twinned T (Al20Cu2Mn3) phase in 2024 aluminum alloy

    International Nuclear Information System (INIS)

    Feng, Z.Q.; Yang, Y.Q.; Huang, B.; Li, M.H.; Chen, Y.X.; Ru, J.G.

    2014-01-01

    Highlights: • The substructures in rotation-twinned T (Al 20 Cu 2 Mn 3 ) particles were investigated. • A flattened hexagonal structural subunit with 20 atomic columns was proposed. • The stacking mode of these subunits at APB and TB were revealed. • The transition structures at twin domain junctions were unraveled. -- Abstract: The substructures in rotation-twinned T (Al 20 Cu 2 Mn 3 ) particles were investigated by means of high resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) in the present work. A flattened hexagonal structural subunit with 20 atomic columns was proposed. The stacking mode of these subunits in non-defective T phase was proved to be tessellation of many flattened hexagonal subunits with the same orientations, while the stacking modes near anti-phase boundary (APB) and twin boundary (TB) were tessellations of two differently oriented flattened hexagonal subunits. The transition region at twin domain junctions has hybrid structure and perfect or imperfect pentagram structure. Centered with the perfect pentagram transition structure, a rotation twin with ten fan-shaped domains and constituted by five twin variants can be deduced

  1. X-ray diffraction studies on merohedrally twinned Δ1-62NtNBCe1-A crystals of the sodium/bicarbonate cotransporter.

    Science.gov (United States)

    Gill, Harindarpal S; Dutcher, Lauren; Boron, Walter F; Patel, Samir; Guay-Woodford, Lisa M

    2013-07-01

    NBCe1-A membrane-embedded macromolecules that cotransport sodium and bicarbonate ions across the bilayer serve to maintain acid-base homeostasis throughout the body. Defects result in a number of renal and eye disorders, including type-II renal tubular acidosis and cataracts. Here, crystals of a human truncated mutant of the cytoplasmic N-terminal domain of NBCe1 (Δ1-62NtNBCe1-A) are reported that diffract X-rays to 2.4 Å resolution. The crystal symmetry of Δ1-62NtNBCe1-A is of space group P31 with pseudo-P3121 symmetry and it has a hemihedral twin fraction of 33.0%. The crystals may provide insight into the pathogenic processes observed in a subset of patients with truncating and point mutations in the gene encoding NBCe1.

  2. Ferrobielastic twinning in irradiated quartz

    International Nuclear Information System (INIS)

    Shiau, S.M.

    1986-01-01

    Cultured quartz is usually free from electrical twinning; however, it may occur if the seed crystal is twinned or if undue applied forces are exerted on the crystal. Ferrobielastic twinning was studied optically (photoelastic effect) and electrically (piezoelectric effect). At room temperature, twins were perceptible at stresses of about 2.l5 x 10 8 N/m 2 , and crystals switched from their original states to the alternative twin states at stresses about 5.0 x 10 8 N/m 2 (called coercive stress). The decrease in coercive stress with increasing temperature was observed, and these coercive stresses become very low as temperatures reach to 300 0 C. The effects of irradiation on the twinning in quartz were also studied. The presence of defects produced by irradiation was utilized to pin the domain wall motion. Both neutrons and gamma rays were employed. The stress required to nucleate an appreciable volume of twins is about twice as high for irradiated crystals than for those unirradiated. This result demonstrated that the irradiated crystals can tolerate higher stresses. However, the coercive stress for complete switch-over was not much different for irradiated and unirradiated crystals. It appears that the defects caused by irradiation eliminate the initial twinning events but do not affect switch-over

  3. Investigation on pseudosymmetry, twinning and disorder in crystal structure determinations: Ba(H2O)M2III[PO3(OH)]4 (M=Fe, V) as examples

    International Nuclear Information System (INIS)

    Sun Wei; Huang Yaxi; Pan Yuanming; Mi Jinxiao

    2012-01-01

    Twinning commonly occurs in monoclinic crystals with dimensionally similar a and c axes and results in pseudo-orthorhombic symmetries with overlapping diffractions. For example, twinning in the new synthetic compound Ba(H 2 O)Fe 2 [PO 3 (OH)] 4 , which varies in space group from P2 1 to P2 1 /c with approximately equal a and c axial lengths, gives rise to a pseudosymmetry of C222 1 . Similarly, the related compound Ba(H 2 O)V 2 [PO 3 (OH)] 4 is commonly twinned and varies in space groups as well, arising from ordered to disordered distributions of the barium cations and water molecules in the cavities. Moreover, analyses of these and other twinned structures show that the small average standard uncertainty of bond distances is a sensitive criterion for structure determinations, especially for those involving crystal twinning as well as order–disorder. A proper structure determination leads to small standard uncertainties of the atomic displacement parameters, which further result in the small standard uncertainties of bond distances. - Graphical abstract: Ba(H 2 O)M 2 III [PO 3 (OH)] 4 (M=Fe, V) varies in space group from P2 1 to P2 1 /c, arising from ordered to disordered distributions of Ba 2+ and H 2 O in the cavities. Highlights: ► Twinning commonly occurs in monoclinic crystals with a≈c. ► Overlapping diffractions from twin domains hamper with the determination of real space groups. ► Conventional criteria for evaluating the real space groups are not effective in this case. ► Small standard uncertainty of bond distances is proposed as a sensitive criterion. ► Using this criterion we determined the order–disorder structures of Ba(H 2 O)M 2 III [PO 3 (OH)] 4 (M=Fe, V) from twinned crystals.

  4. [Adult twins].

    Science.gov (United States)

    Charlemaine, Christiane

    2006-12-31

    This paper explores the deep roots of closeness that twins share in their youngest age and their effect on their destiny at the adult age. Psychologists believe the bond between twins begins in utero and develops throughout the twins' lives. The four patterns of twinship described show that the twin bond is determined by the quality of parenting that twins receive in their infancy and early childhood. Common problems of adult twins bring about difficulties to adapt in a non-twin world. The nature versus nurture controversy has taken on new life focusing on inter-twin differences and the importance of parent-child interaction as fundamental to the growth and development of personality.

  5. Twin RSA

    OpenAIRE

    Lenstra, Arjen K.; Weger, De; Benjamin, M. M.

    2005-01-01

    We introduce Twin RSA, pairs of RSA moduli (n, n+ 2), and formulate several questions related to it. Our main questions are: is Twin RSA secure, and what is it good for? © Springer-Verlag Berlin Heidelberg 2005.

  6. HRTEM studies of dislocations in cubic BN

    International Nuclear Information System (INIS)

    Nistor, L.C.; Tendeloo, G. van; Dinca, G.

    2004-01-01

    The atomic structure of dislocations in cubic boron nitride has been investigated by high resolution transmission electron microscopy. Most of the perfect dislocations, screw and 60 edge, are dissociated. A 60 dislocation which was undissociated has been analysed. Computer simulation is performed in an attempt to characterise the core structure. Twinning dislocations and dislocations resulting from the intersection of stacking faults are also revealed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. HRTEM studies of dislocations in cubic BN

    Energy Technology Data Exchange (ETDEWEB)

    Nistor, L.C. [National Institute for Materials Physics, P.O. Box MG-7 Magurele, 077125 Bucharest (Romania); Tendeloo, G. van [University of Antwerp, EMAT, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Dinca, G. [Dacia Synthetic Diamond Factory, Timisoara av. 5, P.O. Box 58-52, 077350 Bucharest (Romania)

    2004-09-01

    The atomic structure of dislocations in cubic boron nitride has been investigated by high resolution transmission electron microscopy. Most of the perfect dislocations, screw and 60 edge, are dissociated. A 60 dislocation which was undissociated has been analysed. Computer simulation is performed in an attempt to characterise the core structure. Twinning dislocations and dislocations resulting from the intersection of stacking faults are also revealed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Preliminary X-ray analysis of twinned crystals of the Q88Y25-Lacpl esterase from Lactobacillus plantarum WCFS1

    International Nuclear Information System (INIS)

    Álvarez, Yanaisis; Esteban-Torres, María; Acebrón, Iván; Rivas, Blanca de las; Muñoz, Rosario; Martínez-Ripoll, Martín; Mancheño, José M.

    2011-01-01

    The Q88Y25-Lacpl esterase from L. plantarum WCFS1 has been recombinantly expressed, purified and crystallized. A native diffraction data set has been collected to 2.24 Å resolution. Q88Y25-Lacpl is an esterase produced by the lactic acid bacterium Lactobacillus plantarum WCFS1 that shows amino-acid sequence similarity to carboxylesterases from the hormone-sensitive lipase family, in particular the AFEST esterase from the archaeon Archaeoglobus fulgidus and the hyperthermophilic esterase EstEI isolated from a metagenomic library. N-terminally His 6 -tagged Q88Y25-Lacpl has been overexpressed in Escherichia coli BL21 (DE3) cells, purified and crystallized at 291 K using the hanging-drop vapour-diffusion method. Mass spectrometry was used to determine the purity and homogeneity of the enzyme. Crystals of His 6 -tagged Q88Y25-Lacpl were prepared in a solution containing 2.8 M sodium acetate trihydrate pH 7.0. X-ray diffraction data were collected to 2.24 Å resolution on beamline ID29 at the ESRF. The apparent crystal point group was 422; however, initial global analysis of the intensity statistics (data processed with high symmetry in space group I422) and subsequent tests on data processed with low symmetry (space group I4) showed that the crystals were almost perfectly merohedrally twinned. Most probably, the true space group is I4, with unit-cell parameters a = 169.05, b = 169.05, c = 183.62 Å

  9. 16.4 W laser output at 1.34 μm with twin Nd:YVO4 crystals and double-end-pumping structure

    International Nuclear Information System (INIS)

    Lu, C; Gong, M; Liu, Q; Huang, L; He, F

    2008-01-01

    High-power high-beam-quality 1.34 μm continuous-wave laser with twin Nd:YVO 4 crystals pumped by four fiber-coupled laser diodes, which constructed a double-end-pumping structure, is reported. With total 60 W pumping power incident, the highest 16.4 W output laser power was generated, the slope efficiency and optical efficiency were measured as better than 30.0% and 27.3%, respectively. With 12 W laser output, the beam quality was measured to be better than two times diffraction-limit and the instability of laser output was determined to be better than 1% over an hour time

  10. Study of 3-D stress development in parent and twin pairs of a hexagonal close-packed polycrystal: Part II - Crystal plasticity finite element modeling

    DEFF Research Database (Denmark)

    Abdolvand, Hamidreza; Majkut, Marta; Oddershede, Jette

    2015-01-01

    for each grain from the 3DXRD experiment is within the stress variation zone of the grain modeled in the CPFE simulation. Also, the CPFE average stress calculation for each grain is in good agreement with the measured average stress values. It is shown that upon considering the stress variations within......Stress heterogeneity within each individual grain of polycrystalline Zircaloy-2 is studied using a crystal plasticity finite element (CPFE) model. For this purpose, the weighted Voronoi tessellation method is used to construct 3D geometries of more than 2600 grains based on their center......-of-mass positions and volumes as measured by three-dimensional X-ray diffraction (3DXRD) microscopy. The constructed microstructure is meshed with different element densities and for different numbers of grains. Then a selected group of twin and parent pairs are studied. It is shown that the measured average stress...

  11. Cathodoluminescence of cubic boron nitride

    International Nuclear Information System (INIS)

    Tkachev, V.D.; Shipilo, V.B.; Zaitsev, A.M.

    1985-01-01

    Three types of optically active defect were observed in single-crystal and polycrystalline cubic boron nitride (β-BN). An analysis of the temperature dependences of the intensity, half-width, and energy shift of a narrow zero-phonon line at 1.76 eV (GC-1 center) made it possible to interpret the observed cathodoluminescence spectra as an optical analog of the Moessbauer effect. A comparison of the results obtained in the present study with the available data on diamond single crystals made it possible to identify the observed GC-1 center as a nitrogen vacancy. It was concluded that optical Moessbauer-type spectra can be used to analyze structure defects in the crystal lattice of β-BN

  12. Elastic neutron diffraction study of transforming and non-transforming single crystal ZrV2

    International Nuclear Information System (INIS)

    Bostock, J.; Wong, M.; MacVicar, M.L.A.; Levinson, M.

    1980-01-01

    The mosaic spread of single crystal ZrV 2 is unusually narrow, approx. 1' from room temperature to 130K. For non-transforming perfect single crystal the mosaic gradually increases to approx. 1.86' at 4.2K; for transforming, twinned single crystal the room temperature mosaic is maintained to 110K, then increases to 2.76' at 94K when the crystal transforms to a mixed cubic (30%) and rhombohedral state (70%). The onset of the electronic instability (approx. 100K) is accompanied by an increase in diffuse scattering background which, for the twinned crystal, peaks at the structural transformation. The electronic instability coupled to the localized lattice stress appears to be the driving mechanism for the transformation

  13. Cathodoluminescence of cubic boron nitride

    International Nuclear Information System (INIS)

    Tkachev, V.D.; Shipilo, V.B.; Zajtsev, A.M.

    1985-01-01

    Three optically active defects are detected in mono- and polycrystal cubic boron nitride (β-BN). Analysis of intensity of temperature dependences, halfwidth and energy shift of 1.76 eV narrow phononless line (center GC-1) makes it possible to interprete the observed cathodoluminescence spectra an optical analog of the Moessbaner effect. Comparison of the obtained results with the known data for diamond monocrystals makes it possible to suggest that the detected center GC-1 is a nitrogen vacancy . The conclusion, concerning the Moessbauer optical spectra application, is made to analyze structural perfection of β-BN crystal lattice

  14. Twin pregnancy

    DEFF Research Database (Denmark)

    Sperling, Lene; Tabor, A

    2001-01-01

    Determination of chorionicity is one of the most important issues in the management of twin pregnancy. Modern ultrasound equipment has made it possible to accurately assess placentation already in the first trimester with the lambda sign. With regard to prenatal diagnosis, it is important to know...... for clinicians caring for twin pregnancies....

  15. First observations of stimulated emission and of stimulated Raman scattering in acentric cubic Nd3+:Bi12SiO20 crystals

    International Nuclear Information System (INIS)

    Kaminskii, Alexandr A; Bagayev, S N; Garsia, Sole J; Jaque, D; Eichler, H J; Findeisen, J; Fernandez, J; Balda, R; Agullo, Rueda F

    1999-01-01

    Laser action (in the 4 F 3/2 - 4 I 11/2 channel) and stimulated Raman scattering were excited for the first time in an Nd 3+ :Bi 12 SiO 20 single crystal at room temperature. All the observed stimulated emission and multiple Stokes and anti-Stokes lines were identified. (letters to the editor)

  16. Peak effect in twinned superconductors

    International Nuclear Information System (INIS)

    Larkin, A.I.; Marchetti, M.C.; Vinokur, V.M.

    1995-01-01

    A sharp maximum in the critical current J c as a function of temperature just below the melting point of the Abrikosov flux lattice has recently been observed in both low- and high-temperature superconductors. This peak effect is strongest in twinned crystals for fields aligned with the twin planes. We propose that this peak signals the breakdown of the collective pinning regime and the crossover to strong pinning of single vortices on the twin boundaries. This crossover is very sharp and can account for the steep drop of the differential resistivity observed in experiments. copyright 1995 The American Physical Society

  17. Crystal structure and spectroscopic behavior of synthetic novgorodovaite Ca2(C2O4)Cl2·2H2O and its twinned triclinic heptahydrate analog

    Science.gov (United States)

    Piro, Oscar E.; Echeverría, Gustavo A.; González-Baró, Ana C.; Baran, Enrique J.

    2018-02-01

    Synthetic novgorodovaite analog Ca2(C2O4)Cl2·2H2O is identical to its natural counterpart. It crystallizes in the monoclinic I2/ m space group with a = 6.9352(3), b = 7.3800(4), c = 7.4426(3) Å, β = 94.303(4)°, V = 379.85(3) Å3 and Z = 2. The heptahydrate analog, Ca2(C2O4)Cl2·7H2O, crystallizes as triclinic twins in the P \\overline{1} space group with a = 7.3928(8), b = 8.9925(4), c = 10.484(2) Å, α = 84.070(7), β = 70.95(1), γ = 88.545(7)°, V = 655.3(1) Å3 and Z = 2. The crystal packing of both calcium oxalate-chloride double salts favors the directional bonding of oxalate, C2O4 2-, ligands to calcium ions as do other related calcium oxalate minerals. The π-bonding between C and O atoms of the C2O4 2- oxalate group leaves sp 2-hydridised orbitals of the oxygen atoms available for bonding to Ca. Thus, the Ca-O bonds in both calcium oxalate-chloride double salts are directed so as to lie in the plane of the oxalate group. This behavior is reinforced by the short O···O distances between the oxygens attached to a given carbon atom, which favors them bonding to a shared Ca atom in bidentate fashion. Strong bonding in the plane of the oxalate anion and wide spacing perpendicular to that plane due to repulsion between oxalate π-electron clouds gives rise to a polymerized structural units which are common to both hydrates, explaining the nearly equal cell constants 7.4 Å which are defined by the periodicity of Ca-oxalate chains in the framework (monoclinic b ≈ triclinic a). When compared with novgorodovaite, the higher water content of Ca2(C2O4)Cl2·7H2O leads to some major differences in their structures and ensuing physical properties. While novgorodovaite has a three-dimensional framework structure, in the higher hydrate, the highly polar water molecules displace chloride ions from the calcium coordination sphere and surround them through OwH···Cl hydrogen bonds. As a result, polymerization in Ca2(C2O4)Cl2·7H2O solid is limited to the formation

  18. Twinning interactions induced amorphisation in ultrafine silicon grains

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Y. [School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Zhang, L.C., E-mail: liangchi.zhang@unsw.edu.au [School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Zhang, Y. [School of Mechatronics Engineering, Harbin Institute of Technology (China)

    2016-03-21

    Detailed transmission electron microscopy analysis on a severely deformed Al-Si composite material has revealed that partial dislocation slips and deformation twinning are the major plastic deformation carriers in ultrafine silicon grains. This resembles the deformation twinning activities and mechanisms observed in nano-crystalline face-centred-cubic metallic materials. While deformation twinning and amorphisation in Si were thought unlikely to co-exist, it is observed for the first time that excessive twinning and partial dislocation interactions can lead to localised solid state amorphisation inside ultrafine silicon grains.

  19. High-quality single crystalline NiO with twin phases grown on sapphire substrate by metalorganic vapor phase epitaxy

    Directory of Open Access Journals (Sweden)

    Kazuo Uchida

    2012-12-01

    Full Text Available High-quality single crystalline twin phase NiO grown on sapphire substrates by metalorganic vapor phase epitaxy is reported. X-ray rocking curve analysis of NiO films grown at different temperatures indicates a minimum full width at half maximum of the cubic (111 diffraction peak of 0.107° for NiO film grown at as low as 550 °C. Detailed microstructural analysis by Φ scan X-ray diffraction and transmission electron microscopy reveal that the NiO film consists of large single crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60°. These single crystal domains are divided by the twin phase boundaries.

  20. Deformation twinning: Influence of strain rate

    Energy Technology Data Exchange (ETDEWEB)

    Gray, G.T. III

    1993-11-01

    Twins in most crystal structures, including advanced materials such as intermetallics, form more readily as the temperature of deformation is decreased or the rate of deformation is increased. Both parameters lead to the suppression of thermally-activated dislocation processes which can result in stresses high enough to nucleate and grow deformation twins. Under high-strain rate or shock-loading/impact conditions deformation twinning is observed to be promoted even in high stacking fault energy FCC metals and alloys, composites, and ordered intermetallics which normally do not readily deform via twinning. Under such conditions and in particular under the extreme loading rates typical of shock wave deformation the competition between slip and deformation twinning can be examined in detail. In this paper, examples of deformation twinning in the intermetallics TiAl, Ti-48Al-lV and Ni{sub 3}A as well in the cermet Al-B{sub 4}C as a function of strain rate will be presented. Discussion includes: (1) the microstructural and experimental variables influencing twin formation in these systems and twinning topics related to high-strain-rate loading, (2) the high velocity of twin formation, and (3) the influence of deformation twinning on the constitutive response of advanced materials.

  1. Guarded Cubical Type Theory

    DEFF Research Database (Denmark)

    Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald

    2016-01-01

    This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type-checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, is conjectured to have decidable type checking, and has an implemented type-checker. Our new type theory, called guarded cubical type theory, provides a computational interpretation of extensionality for guarded recursive...

  2. Guarded Cubical Type Theory

    DEFF Research Database (Denmark)

    Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald

    2016-01-01

    This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, enjoys canonicity for the natural numbers type, and is conjectured to support decidable type-checking. Our new type theory, guarded cubical type theory (GCTT), provides a computational interpretation of extensionality...

  3. The Qingdao Twin Registry

    DEFF Research Database (Denmark)

    Duan, Haiping; Ning, Feng; Zhang, Dongfeng

    2013-01-01

    In 1998, the Qingdao Twin Registry was initiated as the main part of the Chinese National Twin Registry. By 2005, a total of 10,655 twin pairs had been recruited. Since then new twin cohorts have been sampled, with one longitudinal cohort of adolescent twins selected to explore determinants of me...

  4. Direct observation of a-b twin laminate in monoclinic five-layered martensite of Ni-Mn-Ga magnetic shape memory single crystal

    Czech Academy of Sciences Publication Activity Database

    Heczko, Oleg; Klimša, Ladislav; Kopeček, Jaromír

    2017-01-01

    Roč. 131, Apr (2017), s. 76-79 ISSN 1359-6462 R&D Projects: GA MŠk LO1409; GA MŠk LM2015088; GA ČR GA15-00262S Grant - others:FUNBIO(XE) CZ.2.16/3.1.00/21568 Institutional support: RVO:68378271 Keywords : a-b twin laminate * magnetic shape memory alloys * martensitic trans formation * twinning Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.747, year: 2016

  5. Structure and energetics of nanotwins in cubic boron nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Shijian, E-mail: sjzheng@imr.ac.cn, E-mail: zrf@buaa.edu.cn; Ma, Xiuliang [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, Ruifeng, E-mail: sjzheng@imr.ac.cn, E-mail: zrf@buaa.edu.cn [School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191 (China); Huang, Rong [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062 (China); Taniguchi, Takashi [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Ikuhara, Yuichi [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656 (Japan); Beyerlein, Irene J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-08-22

    Recently, nanotwinned cubic boron nitrides (NT c-BN) have demonstrated extraordinary leaps in hardness. However, an understanding of the underlying mechanisms that enable nanotwins to give orders of magnitude increases in material hardness is still lacking. Here, using transmission electron microscopy, we report that the defect density of twin boundaries depends on nanotwin thickness, becoming defect-free, and hence more stable, as it decreases below 5 nm. Using ab initio density functional theory calculations, we reveal that the Shockley partials, which may dominate plastic deformation in c-BNs, show a high energetic barrier. We also report that the c-BN twin boundary has an asymmetrically charged electronic structure that would resist migration of the twin boundary under stress. These results provide important insight into possible nanotwin hardening mechanisms in c-BN, as well as how to design these nanostructured materials to reach their full potential in hardness and strength.

  6. Twin and grain boundary in InP: A synchrotron radiation study

    International Nuclear Information System (INIS)

    Han, Y.; Liu, X.; Jiao, J.; Lin, L.; Jiang, J.; Wang, Z.; Tian, Y.

    1998-01-01

    Experimentally observed X-ray reflectivity curves show bi-crystal(twin) characteristics. The study revealed that there was defect segregation at the twin boundary. Stress was relaxed at the edge of the boundary. Relaxation of the stress resulted in formation of twin and other defects. As a result of formation of such defects, a defect-free and stress-free zone or low defect density and small stress zone is created around the defects. So a twin model was proposed to explain the experimental results. Stress(mainly thermal stress), chemical stoichiometry deviation and impurities nonhomogeneous distributions are the key factors that cause twins in LEC InP crystal growth. Twins on (111) face in LEC InP crystal were studied. Experimental evidence of above mentioned twin model and suggestions on how to get twin-free LEC InP single crystals will be discussed

  7. Fortuitous structure determination of ‘as-isolated’ Escherichia coli bacterioferritin in a novel crystal form

    International Nuclear Information System (INIS)

    Eerde, André van; Wolterink-van Loo, Suzanne; Oost, John van der; Dijkstra, Bauke W.

    2006-01-01

    E. coli bacterioferritin was crystallized in a novel crystal form from different conditions and the structure was solved. The crystals belonged to space group P2 1 3 and diffracted to a resolution of 2.5 Å. Escherichia coli bacterioferritin was serendipitously crystallized in a novel cubic crystal form and its structure could be determined to 2.5 Å resolution despite a high degree of merohedral twinning. This is the first report of crystallographic data on ‘as-isolated’ E. coli bacterioferritin. The ferroxidase active site contains positive difference density consistent with two metal ions that had co-purified with the protein. X-ray fluorescence studies suggest that the metal composition is different from that of previous structures and is a mix of zinc and native iron ions. The ferroxidase-centre configuration displays a similar flexibility as previously noted for other bacterioferritins

  8. Modeling acardiac twin pregnancies

    NARCIS (Netherlands)

    de Groot, Rosa; van den Wijngaard, Jeroen P. H. M.; Umur, Asli; Beek, Johan F.; Nikkels, Peter G. J.; van Gemert, Martin J. C.

    2007-01-01

    Acardiac twin pregnancies are a rare but severe complication of monochorionic twinning, where the acardiac twin lacks cardiac function but nevertheless grows during pregnancy because it is perfused by the pump twin through a set of placental arterioarterial and venovenous anastomoses. Because the

  9. Intragranular twinning, detwinning, and twinning-like lattice reorientation in magnesium alloys

    International Nuclear Information System (INIS)

    Wu, Wei; Gao, Yanfei; Li, Nan; Parish, Chad M.; Liu, Wenjun; Liaw, Peter K.; An, Ke

    2016-01-01

    Deformation twinning plays a critical role on improving metals or alloys ductility, especially for hexagonal close-packed materials with low symmetry crystal structure. A rolled Mg alloy was selected as a model system to investigate the extension twinning behaviors and characteristics of parent-twin interactions by nondestructive in situ 3D synchrotron X-ray microbeam diffraction. Besides twinning-detwinning process, the “twinning-like” lattice reorientation process was captured within an individual grain inside a bulk material during the strain reversal. The distributions of parent, twin, and reorientated grains and sub-micron level strain variation across the twin boundary are revealed. A theoretical calculation of the lattice strain confirms that the internal strain distribution in parent and twinned grains correlates with the experimental setup, grain orientation of parent, twin, and surrounding grains, as well as the strain path changes. The study suggests a novel deformation mechanism within the hexagonal close-packed structure that cannot be determined from surface-based characterization methods.

  10. Interpolation of natural cubic spline

    Directory of Open Access Journals (Sweden)

    Arun Kumar

    1992-01-01

    Full Text Available From the result in [1] it follows that there is a unique quadratic spline which bounds the same area as that of the function. The matching of the area for the cubic spline does not follow from the corresponding result proved in [2]. We obtain cubic splines which preserve the area of the function.

  11. Escherichia coli MltA : MAD phasing and refinement of a tetartohedrally twinned protein crystal structure (vol D61, pg 613, 2005)

    NARCIS (Netherlands)

    Barends, Thomas R.M.; Jong, René M. de; Straaten, Karin E. van; Thunnissen, Andy-Mark W.H.; Dijkstra, Bauke W.

    Crystals were grown of a mutant form of the bacterial cell-wall maintenance protein MltA that diffracted to 2.15 Å resolution. When phasing with molecular replacement using the native structure failed, selenium MAD was used to obtain initial phases. However, after MAD phasing the crystals were found

  12. Temperature dependence of work hardening in sparsely twinning zirconium

    International Nuclear Information System (INIS)

    Singh, Jaiveer; Mahesh, S.; Roy, Shomic; Kumar, Gulshan; Srivastava, D.; Dey, G.K.; Saibaba, N.; Samajdar, I.

    2017-01-01

    Fully recrystallized commercial Zirconium plates were subjected to uniaxial tension. Tests were conducted at different temperatures (123 K - 623 K) and along two plate directions. Both directions were nominally unfavorable for deformation twinning. The effect of the working temperature on crystallographic texture and in-grain misorientation development was insignificant. However, systematic variation in work hardening and in the area fraction and morphology of deformation twins was observed with temperature. At all temperatures, twinning was associated with significant near boundary mesoscopic shear, suggesting a possible linkage with twin nucleation. A binary tree based model of the polycrystal, which explicitly accounts for grain boundary accommodation and implements the phenomenological extended Voce hardening law, was implemented. This model could capture the measured stress-strain response and twin volume fractions accurately. Interestingly, slip and twin system hardness evolution permitted multiplicative decomposition into temperature-dependent, and accumulated strain-dependent parts. Furthermore, under conditions of relatively limited deformation twinning, the work hardening of the slip and twin systems followed two phenomenological laws proposed in the literature for non-twinning single-phase face centered cubic materials.

  13. Use of the Primitive Unit Cell in Understanding Subtle Features of the Cubic Closest-Packed Structure

    Science.gov (United States)

    Hawkins, John A.; Rittenhouse, Jeffrey L.; Soper, Linda M.; Rittenhouse, Robert C.

    2008-01-01

    One of the most important crystal structures adopted by metals is characterized by the "abcabc"...stacking of close-packed layers. This structure is commonly referred to in textbooks as the cubic close-packed (ccp) or face-centered cubic (fcc) structure, since the entire lattice can be generated by replication of a face-centered cubic unit cell…

  14. crystal

    Science.gov (United States)

    Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

    2014-07-01

    A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

  15. Temperature dependence of critical resolved shear stress for cubic metals

    International Nuclear Information System (INIS)

    Rashid, H.; Fazal-e-Aleem; Ali, M.

    1996-01-01

    The experimental measurements for critical resolved shear stress of various BCC and FCC metals have been explained by using Radiation Model. The temperature dependence of CRSS for different cubic metals is found to the first approximation, to upon the type of the crystal. A good agreement between experimental observations and predictions of the Radiation Model is found. (author)

  16. Ferromagnetic and twin domains in LCMO manganites

    International Nuclear Information System (INIS)

    Jung, G.; Markovich, V.; Mogilyanski, D.; Beek, C. van der; Mukovskii, Y.M.

    2005-01-01

    Ferromagnetic and twin domains in lightly Ca-doped La 1-x Ca x MnO 3 single crystals have been visualized and investigated by means of the magneto-optical technique. Both types of domains became visible below the Curie temperature. The dominant structures seen in applied magnetic field are associated with magneto-crystalline anisotropy and twin domains. In a marked difference to the twin domains which appear only in applied magnetic field, ferromagnetic domains show up in zero applied field and are characterized by oppositely oriented spontaneous magnetization in adjacent domains. Ferromagnetic domains take form of almost periodic, corrugated strip-like structures. The corrugation of the ferromagnetic domain pattern is enforced by the underlying twin domains

  17. A kinematical model for the plastic deformation of face-centred cubic polycrystals

    International Nuclear Information System (INIS)

    Leffers, T.

    1975-01-01

    During the plastic deformation of a polycrystalline material the deformation of the individual grain must be adjusted to the deformation of the surrounding grains so that material continuity is maintained. This continuity condition is the essential feature distinguishing polycrystal deformation from single-crystal deformation. In the present work it is attempted to explain how the continuity condition is fulfilled in face-centred cubic polycrystals. The early treatments of the plastic deformation of polycrystalline materials were aimed directly at the formulation of a ''dynamical'' theory, i.e. it was the intention to cover the magnitude of the stresses involved as well as the slip processes producing the deformation. It is argued that rolling texture is a good tool for a necessary intermediate stage of establishing a ''kinematical'' model describing the slip processes, but not the magnitude of the necessary stresses. Three aspects of rolling texture are considered: (a) the development of the rolling textures found experimentally in face-centred cubic materials can be computer-simulated on the basis of models for the plastic deformation that only involve (111) slip; (b) experimentally that the widely accepted twinning theory for the transition in f.c.c. rolling texture does not reflect the behaviour of real materials; and (c) it is shown that the texture transition is thermally activated with an activation energy corresponding to that of cross slip. An electron-microscopical investigation of the slip process operating during rolling of f.c.c. polycrystals is also included. On the basis of the computer simulation of the texture formation supplemented by the experimental results a kinematical model is developed for the plastic deformation of f.c.c. polycrystals by rolling. In the proposed model the material continuity is maintained by inhomogeneous slip processes, combined with homogeneous multiple glide when the cross-slip frequency is high. (author)

  18. Monochorionic twin pregnancies

    NARCIS (Netherlands)

    Hack, K.E.A.

    2008-01-01

    Following widespread application of assisted reproductive technology modalities and the increased age of motherhood, the incidence of twin gestations has increased markedly. Twins are either monozygotic or dizygotic. Dizygotic (i.e. fraternal) twins result from the fertilization of two different

  19. Nano-twin mediated plasticity in carbon-containing FeNiCoCrMn high entropy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996 (United States); Parish, C.M. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Bei, H., E-mail: beih@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2015-10-25

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. The effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. The materials can be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (∼70% at 77 K and ∼40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys. - Highlights: • Interstitial atom C was successfully added into FeNiCoCrMn high entropy alloys. • The strain hardening rate and strength are enhanced in the C-containing alloy. • The increased strain-hardening and strength are caused by the nano-twinning.

  20. Simulation study of two-energy X-ray fluorescence holograms reconstruction algorithm to remove twin images

    International Nuclear Information System (INIS)

    Xie Honglan; Hu Wen; Luo Hongxin; Deng Biao; Du Guohao; Xue Yanling; Chen Rongchang; Shi Shaomeng; Xiao Tiqiao

    2008-01-01

    Unlike traditional outside-source holography, X-ray fluorescence holography is carded out with fluorescent atoms in a sample as source light for holographic imaging. With the method, three-dimensional arrangement of atoms into crystals can be observed obviously. However, just like traditional outside-source holography, X-ray fluorescence holography suffers from the inherent twin-image problem, too. With a 27-Fe-atoms cubic lattice as model, we discuss in this paper influence of the photon energy of incident source in removing twin images in reconstructed atomic images by numerical simulation and reconstruction with two-energy X-ray fluorescence holography. The results indicate that incident X-rays of nearer energies have better effect of removing twin images. In the detector of X-ray holography, minimum difference of the two incident energies depends on energy resolution of the monochromator and detector, and for inside source X-ray holography, minimum difference of the two incident energies depends on difference of two neighboring fluorescent energies emitting from the element and energy resolution of detector. The spatial resolution of atomic images increases with the incident energies. This is important for experiments of X-ray fluorescence holography, which is being developed on Shanghai Synchrotron Radiation Facility. (authors)

  1. Structures and growth textures of Japanese twin boundaries in quartz

    Science.gov (United States)

    Momma, K.; Nagase, T.; Kudoh, Y.; Kuribayashi, T.

    2008-12-01

    Growth textures and atomic configurations of Japanese twin boundaries in quartz were studied by the observation of natural samples and by computational simulations. Samples used in this study are collected from Narushima, Nagasaki Prefecture, Japan. The samples were first polished, and then etched by hydrofluoric acid for several minutes. The etched figures were observed by phase-contrast reflection microscopy and scanning electron microscopy. From these observations, high concentration of Brazil twin lamellae is found near the composition plane of Japanese twin. Observations of cathode luminescence images reveal that the development of Brazil twin lamellae at {112×2} composition plane of Japanese twin is directly related to the preferential growth of Japanese twin along the composition plane. Atomic configurations at {112×2} composition planes of Japanese twin were simulated by using molecular dynamics simulations and the energy minimization method. The simulated structures proved that {112×2} or {1×1×22} composition planes are the only composition planes that do not introduce unsatisfied bonding between Si and O atoms. When the composition plane is different from these planes, some kind of defect structures, like dislocations, are inevitably introduced. In the case of Brazil twin, screw dislocations are also known to be incorporated where orientation of Brazil twin boundary changes from one orientation to another. On the other hand, in the case where Brazil twin boundaries intersect with {112×2} composition planes of Japanese twin, we found that structures are kept coherently without any unsatisfied bonding. This result means that {112×2} composition planes of Japanese twin are the crystallographic sites having more than one possible stacking structures. Observations in this study indicate that {112×2} composition plane of Japanese twin serves as a source of Brazil twin during the course of crystal growth.

  2. Anomalous jump of stress upon the variation of the rate of deformation of single crystals of the Ni3Ge alloys with L12 superstructure under the conditions of cubic slip

    International Nuclear Information System (INIS)

    Starenchenko, V.A.; Solov'eva, Yu.V.; Gettinger, M.V.; Kovalevskaya, T.A.

    2005-01-01

    Experimental results are given on variations of plastic strain rate for Ni 3 Ge alloy with L1 2 superstructure possessing anomalous temperature dependence of mechanical properties. For the first time an anomalous strain rate dependence of mechanical properties of the alloy is revealed under conditions of cubic slip. The mechanism is proposed to explain the observed form of stress jump. Using the mechanism proposed normal and anomalous constituents of stress jump are separated. Temperature dependences of stress jump, normal and anomalous constituents of stress jump are analyzed [ru

  3. Musical Interests and Talent: Twin Jazz Musicians and Twin Studies/Twin Research: Loss of a Preterm Multiple; Conjoined Twin Conception; Depression in Fathers of Twins; Twin-to-Twin Transfusion Syndrome/Twin News: High-Achieving Twins; Twin Children of a Tennis Star; Conjoined Twin Separation; Twin Delivery to a Giant Panda.

    Science.gov (United States)

    Segal, Nancy L

    2017-12-01

    Findings from twin studies of musical interests and talent are reviewed as a backdrop to the lives and careers of twin jazz musicians, Peter and Will Anderson. The Anderson twins exemplify many aspects of twin research, namely their matched musical abilities, shared musical interests, and common career. This overview is followed by reviews of studies and case reports of bereavement in families who have lost a preterm multiple birth infant, the conception of conjoined twins following in vitro fertilization (IVF), depression in fathers of twins, and twin-to-twin transfusion incidence in monochorionic-diamniotic IVF twin pairs. Twins highlighted in the media include high-achieving identical female twins with nearly identical academic standing, tennis star Roger Federer's two sets of identical twin children, surgical separation of craniopagus conjoined twins, and the rare delivery of twins to a 23-year-old giant panda.

  4. Crystallization mechanisms of acicular crystals

    Science.gov (United States)

    Puel, François; Verdurand, Elodie; Taulelle, Pascal; Bebon, Christine; Colson, Didier; Klein, Jean-Paul; Veesler, Stéphane

    2008-01-01

    In this contribution, we present an experimental investigation of the growth of four different organic molecules produced at industrial scale with a view to understand the crystallization mechanism of acicular or needle-like crystals. For all organic crystals studied in this article, layer-by-layer growth of the lateral faces is very slow and clear, as soon as the supersaturation is high enough, there is competition between growth and surface-activated secondary nucleation. This gives rise to pseudo-twinned crystals composed of several needle individuals aligned along a crystallographic axis; this is explained by regular over- and inter-growths as in the case of twinning. And when supersaturation is even higher, nucleation is fast and random. In an industrial continuous crystallization, the rapid growth of needle-like crystals is to be avoided as it leads to fragile crystals or needles, which can be partly broken or totally detached from the parent crystals especially along structural anisotropic axis corresponding to weaker chemical bonds, thus leading to slower growing faces. When an activated mechanism is involved such as a secondary surface nucleation, it is no longer possible to obtain a steady state. Therefore, the crystal number, size and habit vary significantly with time, leading to troubles in the downstream processing operations and to modifications of the final solid-specific properties. These results provide valuable information on the unique crystallization mechanisms of acicular crystals, and show that it is important to know these threshold and critical values when running a crystallizer in order to obtain easy-to-handle crystals.

  5. Cubic phase control of ultrashort laser pulses

    International Nuclear Information System (INIS)

    Mecseki, K.; Erdelyi, M.; Kovacs, A.P.; Szabo, G.

    2006-01-01

    Complete test of publication follows. The temporal shape of an ultrashort laser pulse may change upon propagating through a linear dispersive medium having a phase shift ψω. The change can be characterized by the Taylor-coefficients of the phase shift which are calculated around the central frequency ω 0 of the pulse. Measurements and independent control of the group delay dispersion (GDD, ψ'(ω 0 )) and the third order dispersion (TOD, ψ'(ω 0 )) are important in several research fields, particularly in the generation of ultrashort laser pulses by chirped pulse amplification (CPA) and pulse shaping for molecular control. The GDD and the TOD of an ideal pulse compressor are equal to the negative of the corresponding dispersion coefficients of the medium. However, in the case of prism-pair and grating-pair compressor is different from the ratio of the coefficients of the medium to be compensated for. Therefore it is necessary to develop so-called cubic compressors that are able to control the TOD of the pulse, yet, do not affect the GDD. In this paper a new cubic compressor setup is investigated theoretically and experimentally, which resembles the set-up proposed by White, however, we control the GDD and the TOD by the position of a birefringent, semi-cylinder crystal place around the focal point of an achromatic lens. For the evaluation of the phase shift introduced by the proposed cubic compressor, a ray tracing program was written. The program allows optimizing the compressor parameters, such as the radius of the crystal, magnification of the lens etc. Calcite was applied because it is a strong birefringent material. Calculations showed that there is a trajectory, along which shifting the crystal the TOD can be tuned independently of the GDD. The value of the TOD changed in a relatively wide range between -3.15 x 10 5 fs 3 and -1.67 x 10 5 fs 3 . Although the defocus also affects the angular dispersion of the pulse leaving the compressor, if does not exceed

  6. Cubic martensite in high carbon steel

    Science.gov (United States)

    Chen, Yulin; Xiao, Wenlong; Jiao, Kun; Ping, Dehai; Xu, Huibin; Zhao, Xinqing; Wang, Yunzhi

    2018-05-01

    A distinguished structural characteristic of martensite in Fe-C steels is its tetragonality originating from carbon atoms occupying only one set of the three available octahedral interstitial sites in the body-centered-cubic (bcc) Fe lattice. Such a body-centered-tetragonal (bct) structure is believed to be thermodynamically stable because of elastic interactions between the interstitial carbon atoms. For such phase stability, however, there has been a lack of direct experimental evidence despite extensive studies of phase transformations in steels over one century. In this Rapid Communication, we report that the martensite formed in a high carbon Fe-8Ni-1.26C (wt%) steel at room temperature induced by applied stress/strain has actually a bcc rather than a bct crystal structure. This finding not only challenges the existing theories on the stability of bcc vs bct martensite in high carbon steels, but also provides insights into the mechanism for martensitic transformation in ferrous alloys.

  7. Structural study on cubic-tetragonal transition of CH3NH3PbI3

    International Nuclear Information System (INIS)

    Kawamura, Yukihiko; Mashiyama, Hiroyuki; Hasebe, Katsuhiko

    2002-01-01

    The cubic-tetragonal phase transition of CH 3 NH 3 PbI 3 was investigated by single crystal X-ray diffractometry. The crystal structure was refined at five temperatures in the tetragonal phase. The PbI 6 octahedron rotates around the c-axis alternatively to construct the SrTiO 3 -type tetragonal structure. A methylammonium ion is partially ordered; 24 disordered states in the cubic phase are reduced to 8. With decreasing temperature, the rotation angle of the octahedron increases monotonically, which indicates it is an order parameter of the cubic-tetragonal transition. (author)

  8. The planar cubic Cayley graphs

    CERN Document Server

    Georgakopoulos, Agelos

    2018-01-01

    The author obtains a complete description of the planar cubic Cayley graphs, providing an explicit presentation and embedding for each of them. This turns out to be a rich class, comprising several infinite families. He obtains counterexamples to conjectures of Mohar, Bonnington and Watkins. The author's analysis makes the involved graphs accessible to computation, corroborating a conjecture of Droms.

  9. Quantitative XRD analysis of {110} twin density in biotic aragonites.

    Science.gov (United States)

    Suzuki, Michio; Kim, Hyejin; Mukai, Hiroki; Nagasawa, Hiromichi; Kogure, Toshihiro

    2012-12-01

    {110} Twin densities in biotic aragonite have been estimated quantitatively from the peak widths of specific reflections in powder X-ray diffraction (XRD) patterns, as well as direct confirmation of the twins using transmission electron microscopy (TEM). Influence of the twin density on the peak widths in the XRD pattern was simulated using DIFFaX program, regarding (110) twin as interstratification of two types of aragonite unit layers with mirrored relationship. The simulation suggested that the twin density can be estimated from the difference of the peak widths between 111 and 021, or between 221 and 211 reflections. Biotic aragonite in the crossed-lamellar microstructure (three species) and nacreous microstructure (four species) of molluscan shells, fish otoliths (two species), and a coral were investigated. The XRD analyses indicated that aragonite crystals in the crossed-lamellar microstructure of the three species contain high density of the twins, which is consistent with the TEM examination. On the other hand, aragonite in the nacre of the four species showed almost no difference of the peak widths between the paired reflections, indicating low twin densities. The results for the fish otoliths were varied between the species. Such variation of the twin density in biotic aragonites may reflect different schemes of crystal growth in biomineralization. Copyright © 2012 Elsevier Inc. All rights reserved.

  10. Zr 2Ir 6B with an eightfold superstructure of the cubic perovskite-like boride ZrIr 3B 0.5: Synthesis, crystal structure and bonding analysis

    Science.gov (United States)

    Hermus, Martin; Fokwa, Boniface P. T.

    2010-04-01

    Single phase powder samples and single crystals of Zr 2Ir 6B were successfully synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere. Superstructure reflections were observed both on powder and on single crystal diffraction data, leading to an eightfold superstructure of ZrIr 3B x phase. The new phase, which has a metallic luster, crystallizes in space group Fm3¯m (no. 225) with the lattice parameters a=7.9903(4) Å, V=510.14(4) Å 3. Its crystal structure was refined on the basis of powder as well as single crystal data. The single crystal refinement converged to R1=0.0239 and w R2=0.0624 for all 88 unique reflections and 6 parameters. Zr 2Ir 6B is isotypic to Ti 2Rh 6B and its structure can be described as a defect double perovskite, A2BB' O6, where the A site is occupied by zirconium, the B site by boron, the O site by iridium but the B' site is vacant, leading to the formation of empty and boron-filled octahedral Ir 6 clusters. According to the result of tight-binding electronic structure calculations, Ir-B and Ir-Zr interactions are mainly responsible for the structural stability of the phase. According to COHP bonding analysis, the strongest bonding occurs for the Ir-B contacts, and the Ir-Ir bonding within the empty clusters is two times stronger than that in the BIr 6 octahedra.

  11. Perinatal hepatic infarction in twin-twin transfusion.

    LENUS (Irish Health Repository)

    O'Sullivan, M J

    2012-02-03

    We report a case of a twin pregnancy which was complicated by a twin-twin transfusion in which the recipient twin was noted to have an intra-abdominal echogenic mass. This twin died at two days of age of hepatic infarction. The donor twin was healthy at birth, at thirty weeks\\' gestation, and did not have any subsequent problems. Fetal intra-abdominal echogenicity may be a marker of hepatic infarction.

  12. The Brazilian Twin Registry.

    Science.gov (United States)

    Ferreira, Paulo H; Oliveira, Vinicius C; Junqueira, Daniela R; Cisneros, Lígia C; Ferreira, Lucas C; Murphy, Kate; Ordoñana, Juan R; Hopper, John L; Teixeira-Salmela, Luci F

    2016-12-01

    The Brazilian Twin Registry (BTR) was established in 2013 and has impelled twin research in South America. The main aim of the initiative was to create a resource that would be accessible to the Brazilian scientific community as well as international researchers interested in the investigation of the contribution of genetic and environmental factors in the development of common diseases, phenotypes, and human behavior traits. The BTR is a joint effort between academic and governmental institutions from Brazil and Australia. The collaboration includes the Federal University of Minas Gerais (UFMG) in Brazil, the University of Sydney and University of Melbourne in Australia, the Australian Twin Registry, as well as the research foundations CNPq and CAPES in Brazil. The BTR is a member of the International Network of Twin Registries. Recruitment strategies used to register twins have been through participation in a longitudinal study investigating genetic and environmental factors for low back pain occurrence, and from a variety of sources including media campaigns and social networking. Currently, 291 twins are registered in the BTR, with data on demographics, zygosity, anthropometrics, and health history having been collected from 151 twins using a standardized self-reported questionnaire. Future BTR plans include the registration of thousands of Brazilian twins identified from different sources and collaborate nationally and internationally with other research groups interested on twin studies.

  13. Conjoined (Siamese) Twins in Zambia

    African Journals Online (AJOL)

    year-old Zambian multiparous mother gave birth to a set of twins with two heads ... (symmetric or mirror image) but one twin attached with an incomplete foetus is known as hetropagtrs. (asymmetrical). Thoracopagus twins (joined at the chest).

  14. Polarization Change in Face-Centered Cubic Opal Films

    Science.gov (United States)

    Wolff, Christian; Romanov, Sergei; Küchenmeister, Jens; Peschel, Ulf; Busch, Kurt

    2011-10-01

    Artificial opals are a popular platform for investigating fundamental properties of Photonic Crystals (PhC). In this work, we provide a theoretical analysis of polarization-resolved transmission experiments through thin opal films. Despite the full cubic symmetry of the PhC, this system provides a very efficient mechanism for manipulating the polarization state of light. Based on band structure calculations and Bloch mode analysis, we find that this effect closely resembles classical birefringence. Due to the cubic symmetry, however, a description using tensorial quantities is not possible. This indicates fundamental limitations of effective material models for Photonic Crystals and demonstrates the importance of accurately modelling the microscopic geometry of such systems.

  15. Hopper Growth of Salt Crystals.

    Science.gov (United States)

    Desarnaud, Julie; Derluyn, Hannelore; Carmeliet, Jan; Bonn, Daniel; Shahidzadeh, Noushine

    2018-06-07

    The growth of hopper crystals is observed for many substances, but the mechanism of their formation remains ill understood. Here we investigate their growth by performing evaporation experiments on small volumes of salt solutions. We show that sodium chloride crystals that grow very fast from a highly supersaturated solution form a peculiar form of hopper crystal consisting of a series of connected miniature versions of the original cubic crystal. The transition between cubic and such hopper growth happens at a well-defined supersaturation where the growth rate of the cubic crystal reaches a maximum (∼6.5 ± 1.8 μm/s). Above this threshold, the growth rate varies as the third power of supersaturation, showing that a new mechanism, controlled by the maximum speed of surface integration of new molecules, induces the hopper growth of cubic crystals in cascade.

  16. An Abel type cubic system

    Directory of Open Access Journals (Sweden)

    Gary R. Nicklason

    2015-07-01

    Full Text Available We consider center conditions for plane polynomial systems of Abel type consisting of a linear center perturbed by the sum of 2 homogeneous polynomials of degrees n and 2n-1 where $n \\ge 2$. Using properties of Abel equations we obtain two general systems valid for arbitrary values on n. For the cubic n=2 systems we find several sets of new center conditions, some of which show that the results in a paper by Hill, Lloyd and Pearson which were conjectured to be complete are in fact not complete. We also present a particular system which appears to be a counterexample to a conjecture by Zoladek et al. regarding rational reversibility in cubic polynomial systems.

  17. Cubication of conservative nonlinear oscillators

    International Nuclear Information System (INIS)

    Belendez, Augusto; Alvarez, Mariela L; Fernandez, Elena; Pascual, Inmaculada

    2009-01-01

    A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme.

  18. Numbers for reducible cubic scrolls

    Directory of Open Access Journals (Sweden)

    Israel Vainsencher

    2004-12-01

    Full Text Available We show how to compute the number of reducible cubic scrolls of codimension 2 in (math blackboard symbol Pn incident to the appropriate number of linear spaces.Mostramos como calcular o número de rolos cúbicos redutíveis de codimensão 2 em (math blackboard symbol Pn incidentes a espaços lineares apropriados.

  19. Twin anemia polycythemia sequence

    NARCIS (Netherlands)

    Slaghekke, Femke

    2014-01-01

    In this thesis we describe that Twin Anemia Polycythemia Sequence (TAPS) is a form of chronic feto-fetal transfusion in monochorionic (identical) twins based on a small amount of blood transfusion through very small anastomoses. For the antenatal diagnosis of TAPS, Middle Cerebral Artery – Peak

  20. The Danish Twin Registry

    DEFF Research Database (Denmark)

    Skytthe, Axel; Ohm Kyvik, Kirsten; Vilstrup Holm, Niels

    2011-01-01

    Introduction: The Danish Twin Registry is a unique source for studies of genetic, familial and environmental factors on life events, health conditions and diseases. Content: More than 85,000 twin pairs born 1870-2008 in Denmark. Validity and coverage: Four main ascertainment methods have been emp...

  1. Randomized Block Cubic Newton Method

    KAUST Repository

    Doikov, Nikita; Richtarik, Peter

    2018-01-01

    We study the problem of minimizing the sum of three convex functions: a differentiable, twice-differentiable and a non-smooth term in a high dimensional setting. To this effect we propose and analyze a randomized block cubic Newton (RBCN) method, which in each iteration builds a model of the objective function formed as the sum of the natural models of its three components: a linear model with a quadratic regularizer for the differentiable term, a quadratic model with a cubic regularizer for the twice differentiable term, and perfect (proximal) model for the nonsmooth term. Our method in each iteration minimizes the model over a random subset of blocks of the search variable. RBCN is the first algorithm with these properties, generalizing several existing methods, matching the best known bounds in all special cases. We establish ${\\cal O}(1/\\epsilon)$, ${\\cal O}(1/\\sqrt{\\epsilon})$ and ${\\cal O}(\\log (1/\\epsilon))$ rates under different assumptions on the component functions. Lastly, we show numerically that our method outperforms the state-of-the-art on a variety of machine learning problems, including cubically regularized least-squares, logistic regression with constraints, and Poisson regression.

  2. Randomized Block Cubic Newton Method

    KAUST Repository

    Doikov, Nikita

    2018-02-12

    We study the problem of minimizing the sum of three convex functions: a differentiable, twice-differentiable and a non-smooth term in a high dimensional setting. To this effect we propose and analyze a randomized block cubic Newton (RBCN) method, which in each iteration builds a model of the objective function formed as the sum of the natural models of its three components: a linear model with a quadratic regularizer for the differentiable term, a quadratic model with a cubic regularizer for the twice differentiable term, and perfect (proximal) model for the nonsmooth term. Our method in each iteration minimizes the model over a random subset of blocks of the search variable. RBCN is the first algorithm with these properties, generalizing several existing methods, matching the best known bounds in all special cases. We establish ${\\\\cal O}(1/\\\\epsilon)$, ${\\\\cal O}(1/\\\\sqrt{\\\\epsilon})$ and ${\\\\cal O}(\\\\log (1/\\\\epsilon))$ rates under different assumptions on the component functions. Lastly, we show numerically that our method outperforms the state-of-the-art on a variety of machine learning problems, including cubically regularized least-squares, logistic regression with constraints, and Poisson regression.

  3. Cubic colloids : Synthesis, functionalization and applications

    NARCIS (Netherlands)

    Castillo, S.I.R.

    2015-01-01

    This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when

  4. Twin Pregnancy with Gastroschisis in Both Twins

    Directory of Open Access Journals (Sweden)

    Hui-Fen Kao

    2007-12-01

    Conclusion: The cause of gastroschisis is unknown, although possible exogenous causes have been studied. The diagnosis of gastroschisis in twin pregnancy is always in late gestation. Therefore, maternal serum alpha feto-protein screening and a detailed prenatal ultrasound evaluation are recommended in multifetal pregnancies.

  5. Neonatal status of twins

    Directory of Open Access Journals (Sweden)

    Božinović Dragica

    2012-01-01

    Full Text Available Multiple pregnancy is a pregnancy where more than one fetus develops simultaneously in the womb, as a result of the ovulation and fertilization of more than one egg. It is relatively rare in humans and represents the rest of the phylogenetic stages. The most common are twins and they indicate the development of two fetuses in the womb. The frequency of twin pregnancies is about 1%. Multiple pregnancies belong to a group of high-risk pregnancies because of the many complications that occur during the pregnancy: higher number of premature deliveries, bleeding, early neonatal complications and higher perinatal morbidity and mortality. Such pregnancies and infants require greater supervision and monitoring. The aim of this study was to determine the percentage of baby twins born at the maternity ward of the General Hospital in Prokuplje and their morbidity and mortality. Data on the total number of deliveries, number of twins, parity and maternal age, gestational age, body weight of twins, method of delivery, Apgar score and perinatal mortality were collected and statistically analyzed by means of retrospective analysis of operative birth and neonatal protocol for 6 years (2005 of 2010. Out of 4527 mothers who gave birth 43 were pairs of twins, or 0.95% of women gave birth to twins. These babies are more likely born by Caesarean section, but delivered with slightly lower birth weight.

  6. Cubic metaplectic forms and theta functions

    CERN Document Server

    Proskurin, Nikolai

    1998-01-01

    The book is an introduction to the theory of cubic metaplectic forms on the 3-dimensional hyperbolic space and the author's research on cubic metaplectic forms on special linear and symplectic groups of rank 2. The topics include: Kubota and Bass-Milnor-Serre homomorphisms, cubic metaplectic Eisenstein series, cubic theta functions, Whittaker functions. A special method is developed and applied to find Fourier coefficients of the Eisenstein series and cubic theta functions. The book is intended for readers, with beginning graduate-level background, interested in further research in the theory of metaplectic forms and in possible applications.

  7. SUSY meets her twin

    Energy Technology Data Exchange (ETDEWEB)

    Katz, Andrey [Theory Division, CERN,CH-1211 Geneva 23 (Switzerland); Département de Physique Théorique and Center for Astroparticle Physics (CAP),Université de Genève,24 quai Ansermet, CH-1211 Genève 4 (Switzerland); Mariotti, Alberto [Theoretische Natuurkunde and IIHE/ELEM, Vrije Universiteit Brussel,and International Solvay Institutes,Pleinlaan 2, B-1050 Brussels (Belgium); Pokorski, Stefan [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw,ul. Pasteura 5, PL-02-093 Warsaw (Poland); Redigolo, Diego [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University,Tel-Aviv 69978 (Israel); Department of Particle Physics and Astrophysics, Weizmann Institute of Science,Rehovot 7610001 (Israel); Ziegler, Robert [Institute for Theoretical Particle Physics (TTP), Karlsruhe Institute of Technology,Engesserstraße 7, D-76128 Karlsruhe (Germany)

    2017-01-31

    We investigate the general structure of mirror symmetry breaking in the Twin Higgs scenario. We show, using the IR effective theory, that a significant gain in fine tuning can be achieved if the symmetry is broken hardly. We emphasize that weakly coupled UV completions can naturally accommodate this scenario. We analyze SUSY UV completions and present a simple Twin SUSY model with a tuning of around 10% and colored superpartners as heavy as 2 TeV. The collider signatures of general Twin SUSY models are discussed with a focus on the extended Higgs sectors.

  8. Growth of cubic InN on r-plane sapphire

    International Nuclear Information System (INIS)

    Cimalla, V.; Pezoldt, J.; Ecke, G.; Kosiba, R.; Ambacher, O.; Spiess, L.; Teichert, G.; Lu, H.; Schaff, W.J.

    2003-01-01

    InN has been grown directly on r-plane sapphire substrates by plasma-enhanced molecular-beam epitaxy. X-ray diffraction investigations have shown that the InN layers consist of a predominant zinc blende (cubic) structure along with a fraction of the wurtzite (hexagonal) phase which content increases with proceeding growth. The lattice constant for zinc blende InN was found to be a=4.986 A. For this unusual growth of a metastable cubic phase on a noncubic substrate an epitaxial relationship was proposed where the metastable zinc blende phase grows directly on the r-plane sapphire while the wurtzite phase arises as the special case of twinning in the cubic structure

  9. Preparing for Twins

    Science.gov (United States)

    ... Ribbon Commands Skip to main content Turn off Animations Turn on Animations Our Sponsors Log in | Register Menu Log in | ... challenges with twins. He also can suggest helpful reading material or refer you to organizations that help ...

  10. Study of Inverse Ni-based Photonic Crystal using the Microradian X-ray Diffraction

    Science.gov (United States)

    Vasilieva, A. V.; Grigoryeva, N. A.; Mistonov, A. A.; Sapoletova, N. A.; Napolskii, K. S.; Eliseev, A. A.; Lukashin, A. V.; Tretyakov, Yu D.; Petukhov, A. V.; Byelov, D.; Chernyshov, D.; Okorokov, A. I.; Bouwman, W. G.; Grigoriev, S. V.

    2010-10-01

    Inverse photonic nickel-based crystal films formed by electrocrystallization of metal inside the voids of polymer artificial opal have been studied using the microradian X-ray diffraction. Analysis of the diffraction images agrees with an face-centred cubic (FCC) structure with the lattice constant a0 = 650 ± 10 nm and indicates two types of stacking sequences coexisting in the crystal (twins of ABCABC... and ACBACB... ordering motifs), the ratio between them being 4:5 The transverse structural correlation length Ltran is 2.4 ± 0.1 μm, which corresponds to a sample thickness of 6 layers. The in-plane structural correlation length Llong is 3.4 ± 0.2 μm, and the structure mosaic is of order of 10°.

  11. Study of Inverse Ni-based Photonic Crystal using the Microradian X-ray Diffraction

    International Nuclear Information System (INIS)

    Vasilieva, A V; Okorokov, A I; Grigoriev, S V; Grigoryeva, N A; Mistonov, A A; Sapoletova, N A; Napolskii, K S; Eliseev, A A; Lukashin, A V; Tretyakov, Yu D; Petukhov, A V; Byelov, D; Chernyshov, D; Bouwman, W G

    2010-01-01

    Inverse photonic nickel-based crystal films formed by electrocrystallization of metal inside the voids of polymer artificial opal have been studied using the microradian X-ray diffraction. Analysis of the diffraction images agrees with an face-centred cubic (FCC) structure with the lattice constant a 0 = 650 ± 10 nm and indicates two types of stacking sequences coexisting in the crystal (twins of ABCABC... and ACBACB... ordering motifs), the ratio between them being 4:5 The transverse structural correlation length L tran is 2.4 ± 0.1 μm, which corresponds to a sample thickness of 6 layers. The in-plane structural correlation length L long is 3.4 ± 0.2 μm, and the structure mosaic is of order of 10 0 .

  12. Study of Inverse Ni-based Photonic Crystal using the Microradian X-ray Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Vasilieva, A V; Okorokov, A I; Grigoriev, S V [Petersburg Nuclear Physics Institute, Gatchina, 188350, St. Petersburg (Russian Federation); Grigoryeva, N A; Mistonov, A A [Department of Physics, St. Petersburg State University, 198504, St. Petersburg (Russian Federation); Sapoletova, N A; Napolskii, K S; Eliseev, A A; Lukashin, A V; Tretyakov, Yu D [Department of Materials Science, Moscow State University, 119899, Moscow (Russian Federation); Petukhov, A V; Byelov, D [Debye Institute, Utrecht University, 3584 CH Utrecht (Netherlands); Chernyshov, D [SNBL European Synchrotron Radiation Facility (ESRF), 38043 Grenoble (France); Bouwman, W G, E-mail: vasilieva@lns.pnpi.spb.r [Delft Technical University, 2629 JB Delft (Netherlands)

    2010-10-01

    Inverse photonic nickel-based crystal films formed by electrocrystallization of metal inside the voids of polymer artificial opal have been studied using the microradian X-ray diffraction. Analysis of the diffraction images agrees with an face-centred cubic (FCC) structure with the lattice constant a{sub 0} = 650 {+-} 10 nm and indicates two types of stacking sequences coexisting in the crystal (twins of ABCABC... and ACBACB... ordering motifs), the ratio between them being 4:5 The transverse structural correlation length L{sub tran} is 2.4 {+-} 0.1 {mu}m, which corresponds to a sample thickness of 6 layers. The in-plane structural correlation length L{sub long} is 3.4 {+-} 0.2 {mu}m, and the structure mosaic is of order of 10{sup 0}.

  13. The 16th International Twin Congress: Highlights from Madrid/Twin Research: Twin Study of Partner Aggression; ABO Incompatibility in Dizygotic Twins; Growth Discordance in a Monoamniotic Twin Pair; Quick Note on Twin Implantation/In the Media: Long-Lost Twins Found; NASA Twin Experiment; Twin Brothers and the Las Vegas Attack; Retired Twin Airline Pilots; Twin Film Clips.

    Science.gov (United States)

    Segal, Nancy L

    2018-02-01

    Highlights from the 16th International Twin Congress, held in Madrid, Spain from November 16-18, 2017, are presented. The Twin Congress, formerly held every three years, now takes place biennially with a single-day meeting organized during the off years. This meeting is the largest gathering of scientific twin researchers, medical personnel, and representatives of multiple birth organizations in the world. This overview is followed by reviews of recent twin research and commentary concerning partner aggression, ABO incompatibility in dizygotic twins, growth discordance in a monoamniotic twin pair and twin implantation. The article closes with summaries of timely topics in the media, namely a father's finding of his long-lost twin children, early results from the NASA twin experiment, twin brothers at the center of the October 2017 Las Vegas attack, retired twin airline pilots, and clips from recent films with twin-based themes.

  14. d and f electrons in a qp-quantized cubical field

    International Nuclear Information System (INIS)

    Kibler, M.; Sztucki, J.

    1993-03-01

    A procedure for qp-quantizing a crystal-field potential V with an arbitrary symmetry G is developed. Such a procedure is applied to the case where V involves cubic components (G=0) of the degrees 4 and 6. This case corresponds to d and f electrons in a qp-quantized cubical potential. It is shown that the qp-quantization of the considered cubical potential is equivalent to a symmetry breaking of type O→D 4 . A general conjecture about this symmetry breaking phenomenon is given. (author) 21 refs

  15. Twinning in ZnO ceramics with Sb sub 2 O sub 3 additions

    Energy Technology Data Exchange (ETDEWEB)

    Senda, T. (Ministry of Transportation, Tokyo (Japan). Ship Research Inst.); Bradt, R.C. (Univ. of Nevada-Reno, Nevada (U.S.A.). Mackay School of Mines)

    1991-09-01

    A mechanism is proposed for the nucleation of ZnO growth twins which is based on the crystallography of the wurtzite and spinel structures. In this paper, possible twin origins from either phase transformation or a result of deformation are both rejected. It is concluded that the ZnO twins are growth twins which nucleate in the early stages of sintering and grain growth of the ceramic powder compacts. Consideration of the oxygen anion stacking layer sequences in the hexagonal ZnO wurtzite structure and the cubic Zn {sub 7} Sb {sub 2} O {sub 12} spinel structure suggests that the nuclei for the twins may form as embryos consisting of a faulted region of the spinel-oxygen anion layer stacking sequence. And then, the faulted layer sequence is created by the presence of the antimony oxide and its reaction with the ZnO. Further, the fact that the wurtzite structure is polar and the ZnO twins are inversion twins explains why there is only a single twin per grain, as multiple twins would result in the unfavorable structural configuration. 24 refs., 2 figs.

  16. Application of white beam synchrotron radiation topography to the analysis of twins

    International Nuclear Information System (INIS)

    Yao, G.D.; Dudley, M.; Hou, S.Y.; DiSalvo, R.

    1991-01-01

    White beam synchrotron X-ray topography (WBSXRT) has been used to characterize room temperature twinning structures in lanthanum gallate and p-terphenyl single crystals. Both Laue and Bragg geometries are utilized to reveal the nature of twinning in LaGaO 3 . The geometric relationships between the twin related domains and the directions of the corresponding diffracted beams are used to establish the presence of reflection twins on (1anti 12) orth , (1anti 1anti 2) orth and (1anti 10) orth planes. Also described is the application of WBSXRT to reveal the twin law in the solution grown organic crystal p-terphenyl. The active twin plane was unambiguously determined to be (201) by determination of the orientation relationship between parent and twinned structures through Laue pattern analysis. Twin lamellae with the same twin plane were also observed. For both materials, no radiation damage was observed throughout the experiments. These results demonstrate the usefulness of WBSXRT for the study of twins. (orig.)

  17. Application of white beam synchrotron radiation topography to the analysis of twins

    Science.gov (United States)

    Yao, G.-D.; Dudley, M.; Hou, S.-Y.; DiSalvo, R.

    1991-05-01

    White beam synchrotron X-ray topography (WBSXRT) has been used to characterize room temperature twinning structures in lanthanum gallate and P-terphenyl single crystals. Both Laue and Bragg geometries are utilized to reveal the nature of twinning in LaGaO 3. The geometric relationships between the twin related domains and the directions of the corresponding diffracted beams are used to establish the presence of reflection twins on (11¯2) orth, (11¯2¯) orth and (11¯0) orth planes. Also described is the application of WBSXRT to reveal the twin law in the solution grown organic crystal p-terphenyl. The active twin plane was unambiguously determined to be (201) by determination of the orientation relationship between parent and twinned structures through Laue pattern analysis. Twin lamellae with the same twin plane were also observed. For both materials, no radiation damage was observed throughout the experiments. These results demonstrate the usefulness of WBSXRT for the study of twins.

  18. Application of white beam synchrotron radiation topography to the analysis of twins

    Energy Technology Data Exchange (ETDEWEB)

    Yao, G.D.; Dudley, M.; Hou, S.Y.; DiSalvo, R. (Dept. of Materials Science and Engineering, SUNY, Stony Brook, NY (USA))

    1991-05-01

    White beam synchrotron X-ray topography (WBSXRT) has been used to characterize room temperature twinning structures in lanthanum gallate and p-terphenyl single crystals. Both Laue and Bragg geometries are utilized to reveal the nature of twinning in LaGaO{sub 3}. The geometric relationships between the twin related domains and the directions of the corresponding diffracted beams are used to establish the presence of reflection twins on (1anti 12){sub orth}, (1anti 1anti 2){sub orth} and (1anti 10){sub orth} planes. Also described is the application of WBSXRT to reveal the twin law in the solution grown organic crystal p-terphenyl. The active twin plane was unambiguously determined to be (201) by determination of the orientation relationship between parent and twinned structures through Laue pattern analysis. Twin lamellae with the same twin plane were also observed. For both materials, no radiation damage was observed throughout the experiments. These results demonstrate the usefulness of WBSXRT for the study of twins. (orig.).

  19. Twinning anisotropy of tantalum during nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Goel, Saurav, E-mail: S.GOEL@qub.ac.uk [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom); Beake, Ben [Micro Materials Limited, Willow House, Yale Business Village, Ellice Way, Wrexham LL13 7YL (United Kingdom); Dalton Research Institute, Manchester Metropolitan University, Manchester, M15GD (United Kingdom); Chan, Chi-Wai [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom); Haque Faisal, Nadimul [School of Engineering, Robert Gordon University, Garthdee Road, Aberdeen AB10 7GJ (United Kingdom); Dunne, Nicholas [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom)

    2015-03-11

    Unlike other BCC metals, the plastic deformation of nanocrystalline Tantalum (Ta) during compression is regulated by deformation twinning. Whether or not this twinning exhibits anisotropy was investigated through simulation of displacement-controlled nanoindentation test using molecular dynamics (MD) simulation. MD data was found to correlate well with the experimental data in terms of surface topography and hardness measurements. The mechanism of the transport of material was identified due to the formation and motion of prismatic dislocations loops (edge dislocations) belonging to the 1/2〈111〉 type and 〈100〉 type Burgers vector family. Further analysis of crystal defects using a fully automated dislocation extraction algorithm (DXA) illuminated formation and migration of twin boundaries on the (110) and (111) orientation but not on the (010) orientation and most importantly after retraction all the dislocations disappeared on the (110) orientation suggesting twinning to dominate dislocation nucleation in driving plasticity in tantalum. A significant finding was that the maximum shear stress (critical Tresca stress) in the deformation zone exceeded the theoretical shear strength of Ta (Shear modulus/2π~10.03 GPa) on the (010) orientation but was lower than it on the (110) and the (111) orientations. In light of this, the conventional lore of assuming the maximum shear stress being 0.465 times the mean contact pressure was found to break down at atomic scale.

  20. Development of twin Ge detector for high energy photon measurement and its performance

    Energy Technology Data Exchange (ETDEWEB)

    Shigetome, Yoshiaki; Harada, Hideo [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works

    1998-03-01

    Prototype twin HPGe detector composed of two large HPGe crystals was developed to obtain better detection efficiency ({epsilon}) and P/T ratio, which was required for high energy photon spectroscopy. In this work, the performances of the twin HPGe detector were evaluated by computer simulation employing EGS4 code. (author)

  1. Crystal orientation of monoclinic β-Ga2O3 thin films formed on cubic MgO substrates with a γ-Ga2O3 interfacial layer

    Science.gov (United States)

    Nakagomi, Shinji; Kokubun, Yoshihiro

    2017-12-01

    The crystal orientation relationship between β-Ga2O3 and MgO in β-Ga2O3 thin films prepared on (1 0 0), (1 1 1), and (1 1 0) MgO substrates was investigated by X-ray diffraction measurements and cross-sectional transmission electron microscopy images. The γ-Ga2O3 interfacial layer was present between β-Ga2O3 and MgO acted as a buffer to connect β-Ga2O3 on MgO. The following conditions were satisfied under each case: β-Ga2O3 (1 0 0)||MgO (1 0 0) and β-Ga2O3 [0 0 1]||MgO 〈0 1 1〉 for the formation of β-Ga2O3 on (1 0 0) MgO, and β-Ga2O3 (2 bar 0 1)||MgO (1 1 1) for the formation of β-Ga2O3 on (1 1 1) MgO, as well as each condition of β-Ga2O3 [0 1 0] (1 0 0)||MgO [ 1 bar 1 0 ] (0 0 1), β-Ga2O3 [0 1 0] (1 0 0)||MgO [ 0 1 bar 1 ] (1 0 0), and β-Ga2O3 [0 1 0] (1 0 0)||MgO [ 1 0 1 bar ] (0 1 0). β-Ga2O3 (1 bar 0 2)||MgO(1 1 0) and β-Ga2O3 [0 1 0] ⊥ MgO [0 0 1] for β-Ga2O3 formed on (1 1 0) MgO. The β-Ga2O3 formed on (1 1 1) MgO at 800 °C exhibited a threefold structure. The β-Ga2O3 formed on (1 1 0) MgO had a twofold structure but different by 90° from the result reported previously.

  2. Possible significance of cubic water-ice, H2O-Ic, in the atmospheric water cycle of Mars

    Science.gov (United States)

    Gooding, James L.

    1988-01-01

    The possible formation and potential significance of the cubic ice polymorph on Mars is discussed. When water-ice crystallizes on Earth, the ambient conditions of temperature and pressure result in the formation of the hexagonal ice polymorph; however, on Mars, the much lower termperature and pressures may permit the crystallization of the cubic polymorph. Cubic ice has two properties of possible importance on Mars: it is an excellant nucleator of other volatiles (such as CO2), and it undergoes an exothermic transition to hexagonal ice at temperatures above 170 K. These properties may have significant implications for both martian cloud formation and the development of the seasonal polar caps.

  3. Changing the cubic ferrimagnetic domain structure in temperature region of spin flip transition

    International Nuclear Information System (INIS)

    Djuraev, D.R.; Niyazov, L.N.; Saidov, K.S.; Sokolov, B.Yu.

    2011-01-01

    The transformation of cubic ferrimagnetic Tb 0.2 Y 2.8 Fe 5 O 12 domain structure has been studied by magneto optic method in the temperature region of spontaneous spin flip phase transition (SPT). It has been found that SPT occurs in a finite temperature interval where the coexistence of low- and high- temperature magnetic phase domains has observed. A character of domain structure evolution in temperature region of spin flip essentially depends on the presence of mechanical stresses in crystal. Interpretation of experimental results has been carried out within the framework of SPT theory for a cubic crystal. (authors)

  4. Spectral intensities in cubic systems. II. The MoCl63- system in cubic elpasolite crystals

    International Nuclear Information System (INIS)

    Acevedo, R.; Meruane, T.; Poblete, V.

    1998-01-01

    The visible and near infrared luminescence spectra of MoCl 6 3- in Cs 2 NaMCl 6 (M=Sc, Y, In) and MoBr 6 3- in Cs 2 NaYBr 6 have been reported between 15000 cm -1 and 3000 cm -1 at liquid helium temperatures. It has been observed that each electronic transition shows an extensive and rich vibronic structure, which can be analysed to yield the vibrational frequencies of the MoX 6 3- ion in each electronic state. A through analysis of the spectra for these systems, show that the vibrational frequencies associated with each of the electronic transition is almost identical. This is an evidence of a weak or rather negligible Jahn-Teller distortions. The spectra though are strongly influenced by resonant interactions among the MoX 6 3- ion and the internal and lattice modes of the host lattices and there is also a noticeable variation of the relative vibronic distributions of parity forbidden transitions assisted by the odd parity normal modes of vibrations. This present work deals with the most likely intensity mechanisms and a strategy is put forward to carry out explicit calculations for both, the electronic and vibrational factors of transitions of the kind Γ 1 ↔ Γ 2 + v k for k=3, 4, and 6. Extension of this work to include the ion-phonon interaction is currently in progress in our laboratory. (Author)

  5. Twin-twin transfusion syndrome: etiology, severity and rational management

    NARCIS (Netherlands)

    van Gemert, M. J.; Umur, A.; Tijssen, J. G.; Ross, M. G.

    2001-01-01

    The twin-twin transfusion syndrome is a serious complication of monochorionic twin pregnancies. Partly as a result of an inadequate understanding of the pathophysiology of the syndrome, there is a lack of consensus in clinical management. We sought to review the available information on the etiology

  6. Anencephaly with incomplete twinning (diprosopus).

    Science.gov (United States)

    Riccardi, V M; Bergmann, C A

    1977-10-01

    A case of diprosopus with anencephaly is presented. It is suggested that such concurrence of neural tube defects and incomplete twinning corroborates the notion that a single pathogenetic mechanism may be common to both neural tube defects and monozygotic twinning.

  7. Strain rate sensitivity and evolution of dislocations and twins in a twinning-induced plasticity steel

    International Nuclear Information System (INIS)

    Liang, Z.Y.; Wang, X.; Huang, W.; Huang, M.X.

    2015-01-01

    The present work investigated the effect of strain rates (10 −3 to 10 3 s −1 ) on the deformation behaviour of a twinning-induced plasticity (TWIP) steel. The strain rate sensitivity was studied in terms of instantaneous strain rate sensitivity (ISRS) and strain rate sensitivity of work-hardening (SRSW). While ISRS concerns the instantaneous flow stress change upon strain rate jump, SRSW deals with the subsequent modification in microstructure evolution, i.e. change of work-hardening rate. The present TWIP steel demonstrates a positive ISRS which remains stable during deformation and a negative SRSW, i.e. lower work-hardening rate at higher strain rate. Synchrotron X-ray diffraction experiments indicate that the negative SRSW should be attributed to the suppression of dislocations and deformation twins at high strain rate. This unexpected finding is different to conventional face-centred cubic (fcc) metals which generally show enhanced work-hardening rate at higher strain rate. A constitutive model which is strain rate- and temperature-dependent is developed to explain the stable ISRS and the negative SRSW. The modelling results reveal that the stable ISRS should be attributed to the thermally-activated dislocation motion dominated by interstitial carbon atoms and the negative SRSW should be due to the suppression of the dislocations and deformation twins caused by the adiabatic heating associated with high strain rate deformation

  8. Topics in Cubic Special Geometry

    CERN Document Server

    Bellucci, Stefano; Roychowdhury, Raju

    2011-01-01

    We reconsider the sub-leading quantum perturbative corrections to N=2 cubic special Kaehler geometries. Imposing the invariance under axion-shifts, all such corrections (but the imaginary constant one) can be introduced or removed through suitable, lower unitriangular symplectic transformations, dubbed Peccei-Quinn (PQ) transformations. Since PQ transformations do not belong to the d=4 U-duality group G4, in symmetric cases they generally have a non-trivial action on the unique quartic invariant polynomial I4 of the charge representation R of G4. This leads to interesting phenomena in relation to theory of extremal black hole attractors; namely, the possibility to make transitions between different charge orbits of R, with corresponding change of the supersymmetry properties of the supported attractor solutions. Furthermore, a suitable action of PQ transformations can also set I4 to zero, or vice versa it can generate a non-vanishing I4: this corresponds to transitions between "large" and "small" charge orbit...

  9. Relativistic twins or sextuplets?

    International Nuclear Information System (INIS)

    Sheldon, Eric

    2003-01-01

    A recent study of the relativistic twin 'paradox' by Soni in this journal affirmed that 'A simple solution of the twin paradox also shows anomalous behaviour of rigidly connected distant clocks' but entailed a pedagogic hurdle which the present treatment aims to surmount. Two scenarios are presented: the first 'flight-plan' is akin to that depicted by Soni, with constant-velocity segments, while the second portrays an alternative mission undertaken with sustained acceleration and deceleration, illustrated quantitatively for a two-way spacecraft flight from Earth to Polaris (465.9 light years distant) and back

  10. Relativistic twins or sextuplets?

    CERN Document Server

    Sheldon, E S

    2003-01-01

    A recent study of the relativistic twin 'paradox' by Soni in this journal affirmed that 'A simple solution of the twin paradox also shows anomalous behaviour of rigidly connected distant clocks' but entailed a pedagogic hurdle which the present treatment aims to surmount. Two scenarios are presented: the first 'flight-plan' is akin to that depicted by Soni, with constant-velocity segments, while the second portrays an alternative mission undertaken with sustained acceleration and deceleration, illustrated quantitatively for a two-way spacecraft flight from Earth to Polaris (465.9 light years distant) and back.

  11. Imaging of conjoined twins

    Energy Technology Data Exchange (ETDEWEB)

    McHugh, Kieran [Great Ormond Street Hospital for Children, Department of Radiology, London (United Kingdom); Kiely, Edward M.; Spitz, Lewis [Great Ormond Street Hospital for Children, Department of Surgery, London (United Kingdom)

    2006-09-15

    The incidence of conjoined twins is estimated to be around 1 in 250,000 live births. There is a distinct female predominance. In this paper the imaging of conjoined twins both antenatally and postnatally is reviewed, in particular taking into consideration recent advances with multidetector CT. Accurate counselling of parents regarding the likely outcome of the pregnancy and the likelihood of successful separation is dependent on good prenatal imaging with ultrasound and MRI. Planning of postnatal surgical separation is aided by accurate preoperative imaging which, depending on the conjoined area, will encompass many imaging modalities, but often relies heavily on CT scanning. (orig.)

  12. Imaging of conjoined twins

    International Nuclear Information System (INIS)

    McHugh, Kieran; Kiely, Edward M.; Spitz, Lewis

    2006-01-01

    The incidence of conjoined twins is estimated to be around 1 in 250,000 live births. There is a distinct female predominance. In this paper the imaging of conjoined twins both antenatally and postnatally is reviewed, in particular taking into consideration recent advances with multidetector CT. Accurate counselling of parents regarding the likely outcome of the pregnancy and the likelihood of successful separation is dependent on good prenatal imaging with ultrasound and MRI. Planning of postnatal surgical separation is aided by accurate preoperative imaging which, depending on the conjoined area, will encompass many imaging modalities, but often relies heavily on CT scanning. (orig.)

  13. Cubical local partial orders on cubically subdivided spaces - existence and construction

    DEFF Research Database (Denmark)

    Fajstrup, Lisbeth

    The geometric models of Higher Dimensional Automata and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes, such ...... that the underlying geometry of an HDA may be quite complicated....

  14. Cubical local partial orders on cubically subdivided spaces - Existence and construction

    DEFF Research Database (Denmark)

    Fajstrup, Lisbeth

    2006-01-01

    The geometric models of higher dimensional automata (HDA) and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes...... that the underlying geometry of an HDA may be quite complicated....

  15. Dry Powder Precursors of Cubic Liquid Crystalline Nanoparticles (cubosomes)

    International Nuclear Information System (INIS)

    Spicer, Patrick T.; Small, William B.; Small, William B.; Lynch, Matthew L.; Burns, Janet L.

    2002-01-01

    Cubosomes are dispersed nanostructured particles of cubic phase liquid crystal that have stimulated significant research interest because of their potential for application in controlled-release and drug delivery. Despite the interest, cubosomes can be difficult to fabricate and stabilize with current methods. Most of the current work is limited to liquid phase processes involving high shear dispersion of bulk cubic liquid crystalline material into sub-micron particles, limiting application flexibility. In this work, two types of dry powder cubosome precursors are produced by spray-drying: (1) starch-encapsulated monoolein is produced by spray-drying a dispersion of cubic liquid crystalline particles in an aqueous starch solution and (2) dextran-encapsulated monoolein is produced by spray-drying an emulsion formed by the ethanol-dextran-monoolein-water system. The encapsulants are used to decrease powder cohesion during drying and to act as a soluble colloidal stabilizer upon hydration of the powders. Both powders are shown to form (on average) 0.6 μm colloidally-stable cubosomes upon addition to water. However, the starch powders have a broader particle size distribution than the dextran powders because of the relative ease of spraying emulsions versus dispersions. The developed processes enable the production of nanostructured cubosomes by end-users rather than just specialized researchers and allow tailoring of the surface state of the cubosomes for broader application

  16. The Placenta in Twin-to-Twin Transfusion Syndrome and Twin Anemia Polycythemia Sequence.

    Science.gov (United States)

    Couck, Isabel; Lewi, Liesbeth

    2016-06-01

    Twin-to-twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS) are complications unique to monochorionic twin pregnancies and their shared circulation. Both are the result of the transfusion imbalance in the intertwin circulation. TTTS is characterized by an amniotic fluid discordance, whereas in TAPS, there is a severe discordance in hemoglobin levels. The article gives an overview of the typical features of TTTS and TAPS placentas.

  17. Numerical analysis of twin thickening process in magnesium alloys

    Czech Academy of Sciences Publication Activity Database

    Šiška, Filip; Stratil, Luděk; Čížek, J.; Ghaderi, A.; Barnett, M.

    2017-01-01

    Roč. 124, FEB (2017), s. 9-16 ISSN 1359-6454 R&D Projects: GA ČR GJ15-21292Y Institutional support: RVO:68081723 Keywords : Magnesium alloy * Twinning * Crystal plastic ity * FEM Subject RIV: JG - Metallurgy OBOR OECD: Materials engineering Impact factor: 5.301, year: 2016

  18. Deformation Mechanism and Recrystallization Relationships in Galfenol Single Crystals: On the Origin of Goss and Cube Orientations

    Science.gov (United States)

    Na, Suok-Min; Smith, Malcolm; Flatau, Alison B.

    2018-06-01

    In this work, deformation mechanism related to recrystallization behavior in single-crystal disks of Galfenol (Fe-Ga alloy) was investigated to gain insights into the influence of crystal orientations on structural changes and selective grain growth that take place during secondary recrystallization. We started with the three kinds of single-crystal samples with (011)[100], (001)[100], and (001)[110] orientations, which were rolled and annealed to promote the formation of different grain structures and texture evolutions. The initial Goss-oriented (011)[100] crystal mostly rotated into {111} orientations with twofold symmetry and shear band structures by twinning resulted in the exposure of rolled surface along {001} orientation during rolling. In contrast, the Cube-oriented (001)[100] single crystal had no change in texture during rolling with the thickness reduction up to 50 pct. The {123} slip systems were preferentially activated in these single crystals during deformation as well as {112} slip systems that are known to play a role in primary slip of body-centered cubic (BCC) materials such as α-iron and Fe-Si alloys. After annealing, the deformed Cube-oriented single crystal had a small fraction ( orientation, associated with {123} slip systems as well. This was expected to provide potential sites of nucleation for secondary recrystallization; however, no Goss- and Cube-oriented components actually developed in this sample during secondary recrystallization. Those results illustrated how the recrystallization behavior can be influenced by deformed structure and the slip systems.

  19. Gypsum crystals in the inner shelf sediments off Maharashtra, India

    Digital Repository Service at National Institute of Oceanography (India)

    Hashimi, N.H.; Ambre, N.V.

    Gypsum crystals have been found in the inner shelf silty clay/clayey silt off the Maharashtra Coast between Vengurla and Bombay. Generally these occur as euhedral single or twinned crystals of selenite. Very often shells are found embedded within...

  20. Dialysis for twins

    DEFF Research Database (Denmark)

    Gramkow, Ann-Maria; Aarup, Michael; Andersen, L. L. T.

    2014-01-01

    A 32-year-old woman with known stage-4 chronic kidney disease due to lupus nephritis presented with twin pregnancy after in vitro fertilization at a gestational age of 24 weeks + 3 days because of imminent preterm labour. Repeated ultrasound evaluations confirmed intrauterine growth restriction...

  1. Anaesthesia for conjoined twins

    African Journals Online (AJOL)

    draw~ver patient system consisting of a paediatric. "Ambu" bag and "Paedivalven drawing oxygen-en- riched air through a halothane vaporiser. Oxygen was supplied from an electric oxygen concentrator which can give 2 litres of 95% oxygen per minute. This apparatus has been described I. Mter 3 minutes the Sa02 of Twin ...

  2. Sleep Terrors in Twins

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2008-12-01

    Full Text Available In an attempt to clarify the genetic and environmental causes of sleep terrors in childhood, reasearchers in Canada followed 390 pairs of monozygotic and dizygotic twins by assessing the frequency of sleep terrors at 18 and 30 months of age using a questionnaire administered to the biological mothers.

  3. Sleep Terrors in Twins

    OpenAIRE

    J Gordon Millichap

    2008-01-01

    In an attempt to clarify the genetic and environmental causes of sleep terrors in childhood, reasearchers in Canada followed 390 pairs of monozygotic and dizygotic twins by assessing the frequency of sleep terrors at 18 and 30 months of age using a questionnaire administered to the biological mothers.

  4. The USC Adult Twin Cohorts: International Twin Study and California Twin Program.

    Science.gov (United States)

    Cozen, Wendy; Hwang, Amie E; Cockburn, Myles G; Hamilton, Ann S; Zadnick, John; Mack, Thomas M

    2013-02-01

    The study of twin subjects permits the documentation of crude heritability and may promote the identification of specific causal alleles. We believe that at the current time, the chief research advantage of twins as subjects, especially monozygotic twins, is that the commonality of their genetic and cultural identity simplifies the interpretation of biological associations. In order to study genetic and environmental determinants of cancer and chronic diseases, we developed two twin registries, maintained at the University of Southern California: The International Twin Study (ITS) and the California Twin Program (CTP). The ITS is a volunteer registry of twins with cancer and chronic disease consisting of 17,245 twin pairs affected by cancer and chronic disease, respectively, ascertained by advertising in periodicals from 1980-1991. The CTP is a population-based registry of California-born twin pairs ascertained by linking the California birth records to the State Department of Motor Vehicles. Over 51,000 individual California twins representing 36,965 pairs completed and returned 16-page questionnaires. Cancer diagnoses in the California twins are updated by regular linkage to the California Cancer Registry. Over 5,000 cancer patients are represented in the CTP. Twins from both registries have participated extensively in studies of breast cancer, melanoma, lymphoma, multiple sclerosis, systemic lupus erythematosus, diabetes mellitus type 1, mammographic density, smoking, and other traits and conditions.

  5. Cubic forms algebra, geometry, arithmetic

    CERN Document Server

    Manin, Yu I

    1986-01-01

    Since this book was first published in English, there has been important progress in a number of related topics. The class of algebraic varieties close to the rational ones has crystallized as a natural domain for the methods developed and expounded in this volume. For this revised edition, the original text has been left intact (except for a few corrections) and has been brought up to date by the addition of an Appendix and recent references.The Appendix sketches some of the most essential new results, constructions and ideas, including the solutions of the Luroth and Zariski problems, the th

  6. Twin-twin transfusion syndrome - diagnosis and prognosis

    Directory of Open Access Journals (Sweden)

    Hajrić-Egić Amira

    2003-01-01

    Full Text Available Twin-twin transfusion syndrome is a serious complication of monozygotic, monochorionic, diamniotic twins resulting from transplacental vascular communications. In this syndrome blood is thought to be shunted from one twin - donor,who develops anaemia,growth retardation and oligoamnios, to the other twin - recipient,who becomes plethoric,macrosomic and develops polyhydroamnios. The incidence of twin-twin transfusion syndrome ranges from 5-15% of all twin pregnancies. If this condition develops in the second trimester, it is usually associated with spontaneous abortion and death of one or both fetuses before viability. Developing the syndrome in the third trimester has better perinatal outcome. Mortality rates ranging from 56%-100%, depending on gestational age and severity of the syndrome. The ultrasound criterias for diagnosis, in this study,were the presence of twins of the same sex with discordant growth, with oligohydroamnios in one twin sac and polyhydroamnios in the other one, one placenta and thin membrane between twins. The present study shows clinical course of 14 cases and value of Doppler ultrasound to analyze the usefulness of umbilical artery blood flow velocimetry for predicting the risk of twin-twin transfusion syndrome. 14 twin pregnancies with twin-twin transfusion syndrome were diagnosed during the last four years period and prospectivelly followed. 9 cases were diagnosed before the completion od 28 weeks of gestation.The mean gestational age was 21,6_+4,2 weeks at diagnosis and 23,2+_3,6 weeks at delivery. 5 cases were diagnosed after 28 weeks of gestation. The mean gestational age in this group was 29,6+_2,1 weeks at diagnosis and 33+_3,3 weeks at delivery. The survival rate in this study was 29%(8/28.9 cases ended in spontaneous abortion between 18th and 27th weeks of pregnancy (table 1 and 5 in premature labor (table 2.There were 7 intrauterine death (5 at admission and 2 few days after admission and 13 neonatal deaths

  7. Changes in copper sulfate crystal habit during cooling crystallization

    Science.gov (United States)

    Giulietti, M.; Seckler, M. M.; Derenzo, S.; Valarelli, J. V.

    1996-09-01

    The morphology of technical grade copper(II) sulfate pentahydrate crystals produced from batch cooling experiments in the temperature range of 70 to 30°C is described and correlated with the process conditions. A slow linear cooling rate (batch time of 90 min) predominantly caused the appearance of well-formed crystals. Exponential cooling (120 min) resulted in the additional formation of agglomerates and twins. The presence of seeds for both cooling modes led to round crystals, agglomerates and twins. Fast linear cooling (15 min) gave rise to a mixture of the former types. Broken crystals and adhering fragments were often found. Growth zoning was pronounced in seeded and linear cooling experiments. Fluid inclusions were always found and were more pronounced for larger particles. The occurrence of twinning, zoning and fluid inclusions was qualitatively explained in terms of fundamental principles.

  8. Lipidic cubic phase serial millisecond crystallography using synchrotron radiation

    Directory of Open Access Journals (Sweden)

    Przemyslaw Nogly

    2015-03-01

    Full Text Available Lipidic cubic phases (LCPs have emerged as successful matrixes for the crystallization of membrane proteins. Moreover, the viscous LCP also provides a highly effective delivery medium for serial femtosecond crystallography (SFX at X-ray free-electron lasers (XFELs. Here, the adaptation of this technology to perform serial millisecond crystallography (SMX at more widely available synchrotron microfocus beamlines is described. Compared with conventional microcrystallography, LCP-SMX eliminates the need for difficult handling of individual crystals and allows for data collection at room temperature. The technology is demonstrated by solving a structure of the light-driven proton-pump bacteriorhodopsin (bR at a resolution of 2.4 Å. The room-temperature structure of bR is very similar to previous cryogenic structures but shows small yet distinct differences in the retinal ligand and proton-transfer pathway.

  9. Nano- and microsized cubic gel particles from cyclodextrin metal-organic frameworks.

    Science.gov (United States)

    Furukawa, Yuki; Ishiwata, Takumi; Sugikawa, Kouta; Kokado, Kenta; Sada, Kazuki

    2012-10-15

    Sweet cube o' mine: Bottom-up control of gel particles has been regarded as a great challenge. By employing internal cross-linking of cyclodextrin metal-organic frameworks, cubic sugar gels were formed with sharp edges that reflect the shape of the crystals. This enabled the fabrication of shape- and size-controlled polymer gels from porous crystals (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Cubical sets as a classifying topos

    DEFF Research Database (Denmark)

    Spitters, Bas

    Coquand’s cubical set model for homotopy type theory provides the basis for a computational interpretation of the univalence axiom and some higher inductive types, as implemented in the cubical proof assistant. We show that the underlying cube category is the opposite of the Lawvere theory of De...... Morgan algebras. The topos of cubical sets itself classifies the theory of ‘free De Morgan algebras’. This provides us with a topos with an internal ‘interval’. Using this interval we construct a model of type theory following van den Berg and Garner. We are currently investigating the precise relation...

  11. Generalized Vaidya spacetime for cubic gravity

    Science.gov (United States)

    Ruan, Shan-Ming

    2016-03-01

    We present a kind of generalized Vaidya solution of a new cubic gravity in five dimensions whose field equations in spherically symmetric spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its spherically symmetric apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally, we present the first law and second law hold in this gravity. Although all the results are analogous to those in Lovelock gravity, we in fact introduce the contribution of a new cubic term in five dimensions where the cubic Lovelock term is just zero.

  12. Brazilian Twin Registry: A Bright Future for Twin Studies/Twin Research: Twin Study of Alcohol Consumption and Mortality; Oxygen Uptake in Adolescent Twins/In the News: Superfecundated Twins In Vietnam; Adolescent Twin Relations; Twin and Triplet Co-Workers; A Special Twin Ultrasound; Monozygotic Twins With Different Skin Color; Identical Twin Returns from Space.

    Science.gov (United States)

    Segal, Nancy L

    2016-06-01

    The establishment of the Brazilian Twin Registry for the study of genetic, social, and cultural influences on behavior is one of eleven newly funded projects in the Department of Psychology at the University of São Paulo. These 11 interrelated projects form the core of the university's Center for Applied Research on Well-Being and Human Behavior. An overview of the planned twin research and activities to date is presented. Next, two recent twin studies are reviewed, one on the relationship between alcohol consumption and mortality, and the other on factors affecting maximal oxygen uptake. Twins cited in the media include the first identified superfecundated twins in Vietnam, adolescent twin relations, twins and triplets who work together, monozygotic twins with different skin tones and a co-twin control study that addresses the effects of space travel.

  13. Localized Pd Overgrowth on Cubic Pt Nanocrystals for Enhanced Electrocatalytic Oxidation of Formic Acid

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.; Habas, S.E.; Somorjai, G.A.; Yang, P.

    2008-03-20

    Binary Pt/Pd nanoparticles were synthesized by localized overgrowth of Pd on cubic Pt seeds for the investigation of electrocatalytic formic acid oxidation. The binary particles exhibited much less self-poisoning and a lower activation energy relative to Pt nanocubes, consistent with the single crystal study.

  14. Calculated Pourbaix Diagrams of Cubic Perovskites for Water Splitting: Stability Against Corrosion

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

    2014-01-01

    We use density functional theory calculations to investigate the stability of cubic perovskites for photo-electrochemical water splitting taking both materials in their bulk crystal structure and dissolved phases into account. The method is validated through a detailed comparison of the calculated...

  15. Basic criteria for formation of growth twins in high stacking fault energy metals

    International Nuclear Information System (INIS)

    Yu, K. Y.; Zhang, X.; Bufford, D.; Chen, Y.; Liu, Y.; Wang, H.

    2013-01-01

    Nanotwinned metals received significant interest lately as twin boundaries may enable simultaneous enhancement of strength, ductility, thermal stability, and radiation tolerance. However, nanotwins have been the privilege of metals with low-to-intermediate stacking fault energy (SFE). Recent scattered studies show that nanotwins could be introduced into high SFE metals, such as Al. In this paper, we examine several sputter-deposited, (111) textured Ag/Al, Cu/Ni, and Cu/Fe multilayers, wherein growth twins were observed in Al, Ni, and face-centered cubic (fcc) Fe. The comparisons lead to two important design criteria that dictate the introduction of growth twins in high SFE metals. The validity of these criteria was then examined in Ag/Ni multilayers. Furthermore, another twin formation mechanism in high SFE metals was discovered in Ag/Ni system

  16. Cubic Pencils and Painlev\\'e Hamiltonians

    OpenAIRE

    Kajiwara, Kenji; Masuda, Tetsu; Noumi, Masatoshi; Ohta, Yasuhiro; Yamada, Yasuhiko

    2004-01-01

    We present a simple heuristic method to derive the Painlev\\'e differential equations from the corresponding geometry of rational surafces. We also give a direct relationship between the cubic pencils and Seiberg-Witten curves.

  17. Nanodefects in ultrahard crystalline cubic boron nitride

    International Nuclear Information System (INIS)

    Nistor, S. V.; Stefan, M.; Goovaerts, E.; Schoemaker, D.

    2002-01-01

    Cubic boron nitride (cBN), the second hardest known material after diamond, exhibits high thermal conductivity and an excellent ability to be n or p doped, which makes it a strong candidate for the next generation of high-temperature micro optical and micro electronic devices. According to recent studies, cBN exhibits a better resistance to radiation damage than diamond, which suggests potential applications in extreme radiation environments. Crystalline cBN powders of up to 0.5 mm linear size is obtained in a similar way as diamond, by catalytic conversion of hexagonal BN (hBN) to cBN at even higher pressures (> 5GPa) and temperatures (∼ 1900 K). Considering the essential role played by the nanodefects (point defects and impurities) in determining its physical properties, it is surprising how limited is the amount of published data concerning the properties of nanodefects in this material, especially by Electron Paramagnetic Resonance (EPR) spectroscopy, the most powerful method for identification and characterization of nanodefects in both insulators and semiconductors. This seems to be due mainly to the absence of natural cBN gems and the extreme difficulties in producing even mm 3 sized synthetic crystals. We shall present our recent EPR studies on cBN crystalline powders, performed in a broad temperature range from room temperature (RT) down to 1.2 K on several sorts of large size cBN powder grits of yellow and amber color for industrial applications. Previous multifrequency (9.3 GHz and 95 GHz) EPR studies of brown to black cBN crystallites prepared with excess of boron, resulted in the discovery of two new types of paramagnetic point defects with different spectral properties, called the D1 and D2 centers. Our X(9.3 GHz)-band EPR investigations resulted in the observation in amber cBN crystalline powders of a spectrum with a strong temperature dependence of the lineshape. It was found that for high and low temperatures, respectively, the numerical

  18. A Note on Cubic Convolution Interpolation

    OpenAIRE

    Meijering, E.; Unser, M.

    2003-01-01

    We establish a link between classical osculatory interpolation and modern convolution-based interpolation and use it to show that two well-known cubic convolution schemes are formally equivalent to two osculatory interpolation schemes proposed in the actuarial literature about a century ago. We also discuss computational differences and give examples of other cubic interpolation schemes not previously studied in signal and image processing.

  19. Cubical version of combinatorial differential forms

    DEFF Research Database (Denmark)

    Kock, Anders

    2010-01-01

    The theory of combinatorial differential forms is usually presented in simplicial terms. We present here a cubical version; it depends on the possibility of forming affine combinations of mutual neighbour points in a manifold, in the context of synthetic differential geometry.......The theory of combinatorial differential forms is usually presented in simplicial terms. We present here a cubical version; it depends on the possibility of forming affine combinations of mutual neighbour points in a manifold, in the context of synthetic differential geometry....

  20. The RG-improved Twin Higgs effective potential at NNLL

    Energy Technology Data Exchange (ETDEWEB)

    Greco, Davide; Mimouni, Kin [Institut de Théorie des Phénomènes Physiques, EPFL,Route de la Sorge, Lausanne, CH-1015 (Switzerland)

    2016-11-18

    We present the Renormalization Group improvement of the Twin Higgs effective potential at cubic order in logarithmic accuracy. We first introduce a model-independent low-energy effective Lagrangian that captures both the pseudo-Nambu-Goldstone boson nature of the Higgs field and the twin light degrees of freedom charged under a copy of the Standard Model. We then apply the background field method to systematically re-sum all the one loop diagrams contributing to the potential. We show how this technique can be efficient to implicitly renormalize the higher-dimensional operators in the twin sector without classifying all of them. A prediction for the Higgs mass in the Twin Higgs model is derived and found to be of the order of M{sub H}∼120 GeV with an ultraviolet cut-off m{sub ∗}∼10–20 TeV. Irrespective of any possible ultraviolet completion of the low-energy Lagrangian, the infrared degrees of freedom alone are therefore enough to account for the observed value of the Higgs mass through running effects.

  1. Reared-Apart Chinese Twins: Chance Discovery/Twin-Based Research: Twin Study of Media Use; Twin Relations Over the Life Span; Breast-Feeding Opposite-Sex Twins/Print and Online Media: Twins in Fashion; Second Twin Pair Born to Tennis Star; Twin Primes; Twin Pandas.

    Science.gov (United States)

    Segal, Nancy L

    2017-04-01

    A January 2017 reunion of 10-year-old reared-apart Chinese twin girls was captured live on ABC's morning talk show Good Morning America, and rebroadcast on their evening news program Nightline. The twins' similarities and differences, and their participation in ongoing research will be described. This story is followed by reviews of twin research concerning genetic and environmental influences on media use, twin relations across the lifespan and the breast-feeding of opposite-sex twins. Popular interest items include twins in fashion, the second twin pair born to an internationally renowned tennis star, twin primes and twin pandas.

  2. Thermodynamics of twinning

    International Nuclear Information System (INIS)

    Mueller, I.; Zak, G.

    1995-01-01

    The quasiplastic hysteresis occuring in shape memory alloys is associated with twinning in tension and compression, i.e. a conversion of one martensitic variant into antoher one. It shows the phenomena of internal elasticity and internal yield, heretofore studied extensively in pseudoelasticity. This paper presents experimental evidence of such phenomena and it offers partial explanation in identifying the onset of yield as an instability phenomenon due to coherency. That conjecture is motivated from a previous consideration of pseudoelasticity. (orig.)

  3. On the deformation twinning of Mg AZ31B

    DEFF Research Database (Denmark)

    Abdolvand, Hamidreza; Majkut, Marta; Oddershede, Jette

    2015-01-01

    and grain volumes are used to construct various 3D microstructures and model them with a Crystal Plasticity Finite Element (CPFE) code. It is observed that the average grain-resolved stress did not always select the highest ranked Schmid factor twin variant. In fact, the contribution of lower ranked......Crystals with a hexagonal close-packed (HCP) structure are inherently anisotropic, and have a limited number of independent slip systems, which leads to strong deformation textures and reduced formability in polycrystalline products. Tension along the c-axis of the crystal ideally activates......-ray diffraction (3DXRD) was used to map the center-of-mass positions, volumes, orientations, elastic strains, and stress tensors of over 1400 grains in-situ up to a true strain of 1.4%. More than 700 tensile twins were observed to form in the mapped volume under deformation. The measured center-of-mass positions...

  4. Monozygotic twins with discordant intestinal rotation

    International Nuclear Information System (INIS)

    Smith, Vance L.; Nwomeh, Benedict C.; Long, Frederick

    2006-01-01

    Previous case reports have suggested a strong concordance of intestinal malrotation among identical twins. This has led to the recommendation that the asymptomatic twin undergo screening when malrotation is discovered in the identical sibling. We present a case of monozygotic twins in which one twin presented with intestinal malrotation with midgut volvulus while the other twin was found to have normal gastrointestinal anatomy. (orig.)

  5. Monozygotic twins with discordant intestinal rotation

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Vance L.; Nwomeh, Benedict C. [Ohio State University College of Medicine and Public Health, Department of Pediatric Surgery, Columbus Children' s Hospital, Columbus, OH (United States); Long, Frederick [Ohio State University College of Medicine and Public Health, Department of Radiology, Columbus Children' s Hospital, Columbus, OH (United States)

    2006-04-15

    Previous case reports have suggested a strong concordance of intestinal malrotation among identical twins. This has led to the recommendation that the asymptomatic twin undergo screening when malrotation is discovered in the identical sibling. We present a case of monozygotic twins in which one twin presented with intestinal malrotation with midgut volvulus while the other twin was found to have normal gastrointestinal anatomy. (orig.)

  6. Shock wave compression of hexagonal-close-packed metal single crystals: Time-dependent, anisotropic elastic-plastic response of beryllium

    International Nuclear Information System (INIS)

    Winey, J. M.; Gupta, Y. M.

    2014-01-01

    Understanding and modeling the response of hcp metals to high stress impulsive loading is challenging because the lower crystal symmetry, compared to cubic metals, results in a significantly more complex material response. To gain insight into the inelastic deformation of hcp metals subjected to high dynamic stresses, shock wave compression of single crystals provides a useful approach because different inelastic deformation mechanisms can be examined selectively by shock compression along different crystal orientations. As a representative example, we report, here, on wave propagation simulations for beryllium (Be) single crystals shocked along the c-axis, a-axis, and several low-symmetry directions to peak stresses reaching 7 GPa. The simulations utilized a time-dependent, anisotropic material model that incorporated dislocation dynamics, deformation twinning, and shear cracking based descriptions of inelastic deformation. The simulation results showed good overall agreement with measured wave profiles for all the different crystal orientations examined [Pope and Johnson, J. Appl. Phys. 46, 720 (1975)], including features arising from wave mode coupling due to the highly anisotropic inelastic response of Be. This good agreement demonstrates that the measured profiles can be understood in terms of dislocation slip along basal, prismatic, and pyramidal planes, together with deformation twinning along (101 ¯ 2) planes. Our results show that the response of shocked Be single crystals involves the simultaneous operation of multiple, distinct inelastic deformation mechanisms for all orientations except the c-axis. For shocked c-axis Be, the measured wave profiles do not provide good discrimination between pyramidal slip and other inelastic deformation mechanisms, such as shear cracking. The findings presented here provide insight into the complex inelastic deformation response of shocked Be single crystals and are expected to be useful for other hcp crystals. More

  7. First-principles investigation on the mechanism of photocatalytic properties for cubic and orthorhombic KNbO3

    Science.gov (United States)

    Xu, Yong-Qiang; Wu, Shao-Yi; Ding, Chang-Chun; Wu, Li-Na; Zhang, Gao-Jun

    2018-03-01

    The geometric structures, band structures, density of states and optical absorption spectra are studied for cubic and orthorhombic KNbO3 (C- and O-KNO) crystals by using first-principles calculations. Based on the above calculation results, the mechanisms of photocatalytic properties for both crystals are further theoretically investigated to deepen the understandings of their photocatalytic activity from the electronic level. Calculations for the effective masses of electron and hole are carried out to make comparison in photocatalytic performance between cubic and orthorhombic phases. Optical absorption in cubic phase is found to be stronger than that in orthorhombic phase. C-KNO has smaller electron effective mass, higher mobility of photogenerated electrons, lower electron-hole recombination rate and better light absorption capacity than O-KNO. So, the photocatalytic activity of cubic phase can be higher than orthorhombic one. The present work may be beneficial to explore the series of perovskite photocatalysts.

  8. Effect of indentation size on the nucleation and propagation of tensile twinning in pure magnesium

    International Nuclear Information System (INIS)

    Sánchez-Martín, R.; Pérez-Prado, M.T.; Segurado, J.; Molina-Aldareguia, J.M.

    2015-01-01

    Tensile twinning is a key deformation mode in magnesium and its alloys, as well as in other hcp metals. However, the fundamentals of this mechanism are still not fully understood. In this research, instrumented nanoindentation and crystal plasticity finite element simulations are utilized to investigate twin formation and propagation in pure Mg. With that purpose, several nanoindentations at different indentation depths were performed in pure Mg single crystals with a wide range of crystallographic orientations. A careful analysis of the deformation profile, by atomic force microscopy, and of the microtexture, by electron backscatter diffraction, in areas around and underneath the indents, reveals that twinning is subjected to strong size effects, i.e., that the relative activity of twinning increases dramatically with the indentation depth. Furthermore, the twin volume fraction is found to be related to the pile-up or sink-in areas close to the indentations. A decrease in hardness in orientations where the twinning activity is high was confirmed both experimentally and by crystal plasticity finite element simulations. Finally, our results support the thesis that twin activation is an energetic process that demands a concentration of high stresses in a certain activation volume

  9. Illustrations of the twin paradox

    International Nuclear Information System (INIS)

    Rebhan, E.

    1985-01-01

    In order to provide a more intuitive understanding of the twin paradox, several illustrations of this are presented. In one of these, each of the twins is equipped with a lamp whose monochromatic light can be observed by the other. In other illustrations the travelling twin uses an Einstein train instead of a space ship, all the cars of the train and all stations along the route of the train being equipped with clocks. (author)

  10. Holographic twin Higgs model.

    Science.gov (United States)

    Geller, Michael; Telem, Ofri

    2015-05-15

    We present the first realization of a "twin Higgs" model as a holographic composite Higgs model. Uniquely among composite Higgs models, the Higgs potential is protected by a new standard model (SM) singlet elementary "mirror" sector at the sigma model scale f and not by the composite states at m_{KK}, naturally allowing for m_{KK} beyond the LHC reach. As a result, naturalness in our model cannot be constrained by the LHC, but may be probed by precision Higgs measurements at future lepton colliders, and by direct searches for Kaluza-Klein excitations at a 100 TeV collider.

  11. Holographic Twin Higgs Model

    Science.gov (United States)

    Geller, Michael; Telem, Ofri

    2015-05-01

    We present the first realization of a "twin Higgs" model as a holographic composite Higgs model. Uniquely among composite Higgs models, the Higgs potential is protected by a new standard model (SM) singlet elementary "mirror" sector at the sigma model scale f and not by the composite states at mKK , naturally allowing for mKK beyond the LHC reach. As a result, naturalness in our model cannot be constrained by the LHC, but may be probed by precision Higgs measurements at future lepton colliders, and by direct searches for Kaluza-Klein excitations at a 100 TeV collider.

  12. Voice similarity in identical twins.

    Science.gov (United States)

    Van Gysel, W D; Vercammen, J; Debruyne, F

    2001-01-01

    If people are asked to discriminate visually the two individuals of a monozygotic twin (MT), they mostly get into trouble. Does this problem also exist when listening to twin voices? Twenty female and 10 male MT voices were randomly assembled with one "strange" voice to get voice trios. The listeners (10 female students in Speech and Language Pathology) were asked to label the twins (voices 1-2, 1-3 or 2-3) in two conditions: two standard sentences read aloud and a 2.5-second midsection of a sustained /a/. The proportion correctly labelled twins was for female voices 82% and 63% and for male voices 74% and 52% for the sentences and the sustained /a/ respectively, both being significantly greater than chance (33%). The acoustic analysis revealed a high intra-twin correlation for the speaking fundamental frequency (SFF) of the sentences and the fundamental frequency (F0) of the sustained /a/. So the voice pitch could have been a useful characteristic in the perceptual identification of the twins. We conclude that there is a greater perceptual resemblance between the voices of identical twins than between voices without genetic relationship. The identification however is not perfect. The voice pitch possibly contributes to the correct twin identifications.

  13. Twin Studies of Atopic Dermatitis

    DEFF Research Database (Denmark)

    Elmose, Camilla; Thomsen, Simon Francis

    2015-01-01

    Aim. The aim of this study was to conduct a systematic review of population-based twin studies of (a) the concordance and heritability of AD and (b) the relationship between AD and asthma and, furthermore, to reinterpret findings from previous twin studies in the light of the emerging knowledge a...

  14. Hypertensive disorders in twin pregnancy

    NARCIS (Netherlands)

    J.G. Santema (Job); E. Koppelaar (Elin); H.C.S. Wallenburg (Henk)

    1995-01-01

    textabstractObjective: To compare the incidence and severity of pregnancy-induced hypertensive disorders in twin pregnancy and in singleton gestation. Study design: Case-control study in the setting of a University Hospital. Each pregnancy of a consecutive series of 187 twin pregnancies attending

  15. Oliver Sacks: Our Correspondence About Twins/Twin Research: Vanishing Twins Syndrome; Discordant Sex in MZ Twins; Pregnancy Outcomes in IVF and ICSI Conceived Twins/Print and Media: Superfetated Twins; Twins Discordant for Smoking; Twins in Fashion; Yale University Twin Hockey Players; Conjoined Twin-Visiting Professor.

    Science.gov (United States)

    Segal, Nancy L

    2017-08-01

    The late neurologist and author, Oliver Sacks, published an insightful 1986 review of Marjorie Wallace's book, The Silent Twins, in the New York Times. Taking exception to his assertion about Sir Francis Galton, I wrote a letter to the Times' editor. The letter was unpublished, but it brought a wonderful response from Sacks himself that is reproduced and examined. Next, brief reviews of twin research concerning the vanishing twin syndrome (VTS), discordant sex in a monozygotic (MZ) twin pair, and multiple pregnancy outcomes from assisted reproductive technology (ART) are presented. This section is followed by popular coverage of superfetated twins, smoking-discordant co-twins, twins in fashion, Yale University twin hockey players, and a visiting professor who was a conjoined twin.

  16. Magnetostriction of Tb-Dy-Fe crystals

    International Nuclear Information System (INIS)

    Mei Wu; Okane, T.; Umeda, T.

    1998-01-01

    left angle 111 right angle -oriented twin free Tb-Dy-Fe single crystals, left angle 112 right angle - and left angle 110 right angle -oriented twinned ''single'' Tb-Dy-Fe crystals were prepared using floating zone melting crystal growth methods. Magnetostrictive performances of the crystals were investigated. Better low-field properties were observed in the left angle 110 right angle twinned crystals than in the left angle 112 right angle crystals. The highest properties were achieved in the left angle 111 right angle twin free single crystals. Even though there were still oxidized particles in the present left angle 111 right angle single crystals, a large magnetostrictive jump of 1700 ppm and a very low saturation magnetic field of 500 Oe were obtained. To understand magnetization and magnetostriction of different Tb-Dy-Fe crystals, theoretical modeling was carried out based on a simplified domain rotation model. Magnetization moment rotation paths of different domains were simulated and hence the resultant magnetostriction was obtained, which could adequately account for the experimental results of different crystals. The limitation of the domain rotation model was also discussed. (orig.)

  17. Experimental evidence of body centered cubic iron in Earth's core

    Science.gov (United States)

    Hrubiak, R.; Meng, Y.; Shen, G.

    2017-12-01

    The Earth's core is mainly composed of iron. While seismic evidence has shown a liquid outer core and a solid inner core, the crystalline nature of the solid iron at the core condition remains debated, largely due to the difficulties in experimental determination of exact polymorphs at corresponding pressure-temperature conditions. We have examined crystal structures of iron up to 220 GPa and 6000 K with x-ray diffraction using a double-sided laser heating system at HPCAT, Advanced Photon Source. The iron sample is confined in a small chamber surrounded by single crystal MgO. The laser power can be modulated together with temperature measurements. The modulated heating of iron in an MgO single crystal matrix allows for microstructure analysis during heating and after the sample is quenched. We present experimental evidence of a body-centered-cubic (BCC) iron from about 100 GPa and 3000 K to at least 220 GPa and 4000 K. The observed BCC phase may be consistent with a theoretically predicted BCC phase that is dynamically stable in similar pressure-temperature conditions [1]. We will discuss the stability region of the BCC phase and the melting curve of iron and their implications in the nature of the Earth's inner core. References: A. B. Belonoshko et al., Nat. Geosci., 1-6 (2017).

  18. Purely cubic action for string field theory

    Science.gov (United States)

    Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.

    1986-01-01

    It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.

  19. Nonlinear dynamics of quadratically cubic systems

    International Nuclear Information System (INIS)

    Rudenko, O V

    2013-01-01

    We propose a modified form of the well-known nonlinear dynamic equations with quadratic relations used to model a cubic nonlinearity. We show that such quadratically cubic equations sometimes allow exact solutions and sometimes make the original problem easier to analyze qualitatively. Occasionally, exact solutions provide a useful tool for studying new phenomena. Examples considered include nonlinear ordinary differential equations and Hopf, Burgers, Korteweg–de Vries, and nonlinear Schrödinger partial differential equations. Some problems are solved exactly in the space–time and spectral representations. Unsolved problems potentially solvable by the proposed approach are listed. (methodological notes)

  20. c-axis compression twinning in an off-stoichiometric compound Ti3Al with the D019 structure

    International Nuclear Information System (INIS)

    Kishida, K.; Takahama, Y.; Inui, H.

    2005-01-01

    The characteristics of the c-axis compression twin in single crystals of a D0 19 compound Ti 3 Al with off-stoichiometric composition (Ti-36.5at.%Al) have been studied by trace analysis and transmission electron microscopy. Deformation twinning is operative only at high temperatures above 1000deg. C. All observed deformation twins are assigned to be of the type II and the twinning elements are determined as: K 1 :'{2-bar 121-bar 0-bar 3}', K 2 :{202-bar 1-bar }, η 1 : , η 2 :' ', s=0.346

  1. Defect ordering in aliovalently doped cubic zirconia from first principles

    International Nuclear Information System (INIS)

    Bogicevic, A.; Wolverton, C.; Crosbie, G.M.; Stechel, E.B.

    2001-01-01

    Defect ordering in aliovalently doped cubic-stabilized zirconia is studied using gradient corrected density-functional calculations. Intra- and intersublattice ordering interactions are investigated for both cation (Zr and dopant ions) and anion (oxygen ions and vacancies) species. For yttria-stabilized zirconia, the crystal structure of the experimentally identified, ordered compound δ-Zr 3 Y 4 O 12 is established, and we predict metastable zirconia-rich ordered phases. Anion vacancies repel each other at short separations, but show an energetic tendency to align as third-nearest neighbors along directions. Calculations with divalent (Be, Mg, Ca, Sr, Ba) and trivalent (Y, Sc, B, Al, Ga, In) oxides show that anion vacancies prefer to be close to the smaller of the cations (Zr or dopant ion). When the dopant cation is close in size to Zr, the vacancies show no particular preference, and are thus less prone to be bound preferentially to any particular cation type when the vacancies traverse such oxides. This ordering tendency offers insight into the observed high conductivity of Y 2 O 3 - and Sc 2 O 3 -stabilized zirconia, as well as recent results using, e.g., lanthanide oxides. The calculations point to In 2 O 3 as a particularly promising stabilizer for high ionic conductivity. Thus we are able to directly link (thermodynamic) defect ordering to (kinetic) ionic conductivity in cubic-stabilized zirconia using first-principles atomistic calculations

  2. Minimal mirror twin Higgs

    Energy Technology Data Exchange (ETDEWEB)

    Barbieri, Riccardo [Institute of Theoretical Studies, ETH Zurich,CH-8092 Zurich (Switzerland); Scuola Normale Superiore,Piazza dei Cavalieri 7, 56126 Pisa (Italy); Hall, Lawrence J.; Harigaya, Keisuke [Department of Physics, University of California,Berkeley, California 94720 (United States); Theoretical Physics Group, Lawrence Berkeley National Laboratory,Berkeley, California 94720 (United States)

    2016-11-29

    In a Mirror Twin World with a maximally symmetric Higgs sector the little hierarchy of the Standard Model can be significantly mitigated, perhaps displacing the cutoff scale above the LHC reach. We show that consistency with observations requires that the Z{sub 2} parity exchanging the Standard Model with its mirror be broken in the Yukawa couplings. A minimal such effective field theory, with this sole Z{sub 2} breaking, can generate the Z{sub 2} breaking in the Higgs sector necessary for the Twin Higgs mechanism. The theory has constrained and correlated signals in Higgs decays, direct Dark Matter Detection and Dark Radiation, all within reach of foreseen experiments, over a region of parameter space where the fine-tuning for the electroweak scale is 10-50%. For dark matter, both mirror neutrons and a variety of self-interacting mirror atoms are considered. Neutrino mass signals and the effects of a possible additional Z{sub 2} breaking from the vacuum expectation values of B−L breaking fields are also discussed.

  3. Tensile twin nucleation events coupled to neighboring slip observed in three dimensions

    International Nuclear Information System (INIS)

    Lind, J.; Li, S.F.; Pokharel, R.; Lienert, U.; Rollett, A.D.; Suter, R.M.

    2014-01-01

    Low-symmetry crystals and polycrystals have anisotropic mechanical properties which, given better understanding of their deformation modes, could lead to development of next generation materials. Understanding how grains in a bulk polycrystal interact will guide and improve material modeling. Here, we show that tensile twins, in hexagonal close-packed metals, form where the macroscopic stress does not generate appropriate shear stress and vice versa. We use non-destructive high-energy X-ray diffraction microscopy to map local crystal orientations in three dimensions in a series of tensile strain states in a zirconium polycrystal. Twins and intragranular orientation variations are observed and it is found that deformation-induced rotations in neighboring grains are spatially correlated with many twins. We conclude that deformation twinning involves complex multigrain interactions which must be included in polycrystal plasticity models

  4. A Computational Discriminability Analysis on Twin Fingerprints

    Science.gov (United States)

    Liu, Yu; Srihari, Sargur N.

    Sharing similar genetic traits makes the investigation of twins an important study in forensics and biometrics. Fingerprints are one of the most commonly found types of forensic evidence. The similarity between twins’ prints is critical establish to the reliability of fingerprint identification. We present a quantitative analysis of the discriminability of twin fingerprints on a new data set (227 pairs of identical twins and fraternal twins) recently collected from a twin population using both level 1 and level 2 features. Although the patterns of minutiae among twins are more similar than in the general population, the similarity of fingerprints of twins is significantly different from that between genuine prints of the same finger. Twins fingerprints are discriminable with a 1.5%~1.7% higher EER than non-twins. And identical twins can be distinguished by examine fingerprint with a slightly higher error rate than fraternal twins.

  5. Evaluation of single crystal coefficients from mechanical and x-ray elastic constants of the polycrystal

    International Nuclear Information System (INIS)

    Hauk, V.; Kockelmann, H.

    1979-01-01

    Methods of calculation are developed for determination of single crystal elastic compliance or stiffness constants of cubic and hexagonal materials from mechanical and X-ray elastic constants of polycrystals. The calculations are applied to pure, cubic iron and hexagonal WC. There are no single crystal constants in the literature for WC, because no single crystals suitable for measurement are available. (orig.) [de

  6. Laser diffraction analysis of colloidal crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sogami, Ikuo S.; Shinohara, Tadatomi; Yoshiyama, Tsuyoshi [Kyoto Sangyo Univ., Department of Physics, Kyoto (Japan)

    2001-10-01

    Laser diffraction analysis is made on crystallization in salt-free aqueous suspensions of highly-charged colloidal particles for semi-dilute specimens of concentration 0.1-10.0 vol%. Kossel diffraction patterns which represent faithfully accurate information on lattice symmetries in the suspensions enable us to investigate the time evolution of colloidal crystals. The results show that the crystallization proceeds by way of the following intermediate phase transitions: two-dimensional hcp structure {yields} random layer structure {yields} layer structure with one sliding degree of freedom {yields} stacking disorder structure {yields} stacking structure with multivariant periodicity {yields} fcc twin structure with twin plane (111) {yields} normal fcc structure {yields} bcc twin structure with twin plane (11-bar2) or (1-bar12) {yields} normal bcc structure. For concentrated suspensions (>2 vol %), the phase transition ceases to proceed at the normal fcc structure. (author)

  7. Laser diffraction analysis of colloidal crystals

    International Nuclear Information System (INIS)

    Sogami, Ikuo S.; Shinohara, Tadatomi; Yoshiyama, Tsuyoshi

    2001-01-01

    Laser diffraction analysis is made on crystallization in salt-free aqueous suspensions of highly-charged colloidal particles for semi-dilute specimens of concentration 0.1-10.0 vol%. Kossel diffraction patterns which represent faithfully accurate information on lattice symmetries in the suspensions enable us to investigate the time evolution of colloidal crystals. The results show that the crystallization proceeds by way of the following intermediate phase transitions: two-dimensional hcp structure → random layer structure → layer structure with one sliding degree of freedom → stacking disorder structure → stacking structure with multivariant periodicity → fcc twin structure with twin plane (111) → normal fcc structure → bcc twin structure with twin plane (11-bar2) or (1-bar12) → normal bcc structure. For concentrated suspensions (>2 vol %), the phase transition ceases to proceed at the normal fcc structure. (author)

  8. Therapeutic modalities of twin to twin transfusion syndrome

    Directory of Open Access Journals (Sweden)

    Šulović N.

    2015-01-01

    Full Text Available Twin to twin transfusion syndrome (TTTTS accounts for approximately 10% of monochorionic twin pregnancies and, if left untreated, is associated with high morbidity and mortality rate. A net transfusion of blood flow from one fetus (donor twin to the other (recipient twin via placental vascular anastomoses has been supposed as the major etiology of TTTTS. The donor twin becomes hypovolemic and oliguria, oligohydramnios, and a variable degree of growth restriction develop, whereas the recipient twin manifests polyuria, polyhydramnios, and hydrops in response to hypervolemia. TTTTS can be treated by either serial amniocentesis or selective fetoscopic laser coagulation of the communicating vessels. The rationale for removal of large volumes of amniotic fluid is to prevent preterm delivery secondary to polyhydramnios and to improve fetal circulation by reducing pressure on the chorionic plate. On the other hand, the goal of laser therapy is to occlude vascular anastomoses, thereby interrupting intertwin blood exchange. Although laser treatment is associated with increased survival rate and reduced neurologic complications, compared with amnioreduction, it requires highly specialized centers, whereas serial amniocentesis has the advantage of being performed worldwide. Therefore, the optimal treatment for pregnancies complicated with TTTTS is still controversial.

  9. Dipaths and dihomotopies in a cubical complex

    DEFF Research Database (Denmark)

    Fajstrup, Lisbeth

    2005-01-01

    In the geometric realization of a cubical complex without degeneracies, a $\\Box$-set, dipaths and dihomotopies may not be combinatorial, i.e., not geometric realizations of combinatorial dipaths and equivalences. When we want to use geometric/topological tools to classify dipaths on the 1-skeleton...

  10. Some elements go cubic under pressure

    Czech Academy of Sciences Publication Activity Database

    Legut, Dominik

    2007-01-01

    Roč. 60, č. 10 (2007), s. 17-17 ISSN 0031-9228 Institutional research plan: CEZ:AV0Z20410507 Keywords : ab initio * polonium * cubic structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.133, year: 2007

  11. The Exact Limit of Some Cubic Towers

    DEFF Research Database (Denmark)

    Anbar Meidl, Nurdagül; Beelen, Peter; Nguyen, Nhut

    2017-01-01

    Recently, a new explicit tower of function fields was introduced by Bassa, Beelen, Garcia and Stichtenoth (BBGS). This resulted in currently the best known lower bound for Ihara’s constant in the case of non-prime finite fields. In particular over cubic fields, the tower’s limit is at least as go...

  12. Antenatal management of twin-twin transfusion syndrome and twin anemia-polycythemia sequence.

    Science.gov (United States)

    Slaghekke, Femke; Zhao, Depeng P; Middeldorp, Johanna M; Klumper, Frans J; Haak, Monique C; Oepkes, Dick; Lopriore, Enrico

    2016-08-01

    Twin-twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS) are severe complications in monochorionic twin pregnancies associated with high mortality and morbidity risk if left untreated. Both diseases result from imbalanced inter-twin blood transfusion through placental vascular anastomoses. This review focuses on the differences in antenatal management between TTTS and TAPS. Expert commentary: The optimal management for TTTS is fetoscopic laser coagulation of the vascular anastomoses, preferably using the Solomon technique in which the whole vascular equator is coagulated. The Solomon technique is associated with a reduction of residual anastomosis and a reduction in post-operative complications. The optimal management for TAPS is not clear and includes expectant management, intra-uterine transfusion with or without partial exchange transfusion and fetoscopic laser surgery.

  13. Contraction Twinning Dominated Tensile Deformation and Subsequent Fracture in Extruded Mg-1Mn (Wt Pct) at Ambient Temperature

    Science.gov (United States)

    Chakkedath, A.; Maiti, T.; Bohlen, J.; Yi, S.; Letzig, D.; Eisenlohr, P.; Boehlert, C. J.

    2018-03-01

    Due to their excellent strength-to-weight ratio, Mg alloys are attractive for applications where weight savings are critical. However, the limited cold formability of wrought Mg alloys severely restricts their widespread usage. In order to study the role that deformation twinning might play in limiting the elongation-to-failure ({ɛ} f ), in-situ tensile tests along the extrusion axis of Mg-1Mn (wt pct) were performed at 323 K, 423 K, and 523 K. The alloy exhibited a strong basal texture such that most of the grains experienced compression along their -axis during deformation. At 323 K, fracture occurred at about 10 pct strain. Although basal, prismatic, and pyramidal slip activity was observed along with extension twinning, contraction twinning significantly influenced the deformation, and such twins evolved into {10{\\bar{1}} 1}-{10{\\bar{1}} 2} double twins. Crystal plasticity simulation showed localized shear deformation within the contraction twins and double twins due to the enhanced activity of basal slip in the reoriented twin volume. Due to this, the twin-matrix interface was identified to be a potential crack initiation site. Thus, contraction twins were considered to have led to the failure of the material at a relatively low strain, suggesting that this deformation mode is detrimental to the cold formability of Mg and its alloys. With increasing temperature, there was a significant decrease in the activity of contraction twinning as well as extension twinning, along with a decrease in the tensile strength and an increase in the {ɛ} f value. A combination of basal, prismatic, and pyramidal slips accounted for a large percentage of the observed deformation activity at 423 K and 523 K. The lack of contraction twinning was explained by the expected decrease in the critical resolved shear stress values for pyramidal slip, and the improved {ɛ} f values at elevated temperatures were attributed to the vanishing activity of contraction twinning.

  14. Contraction Twinning Dominated Tensile Deformation and Subsequent Fracture in Extruded Mg-1Mn (Wt Pct) at Ambient Temperature

    Science.gov (United States)

    Chakkedath, A.; Maiti, T.; Bohlen, J.; Yi, S.; Letzig, D.; Eisenlohr, P.; Boehlert, C. J.

    2018-06-01

    Due to their excellent strength-to-weight ratio, Mg alloys are attractive for applications where weight savings are critical. However, the limited cold formability of wrought Mg alloys severely restricts their widespread usage. In order to study the role that deformation twinning might play in limiting the elongation-to-failure ({ɛ} _{ {f}}), in-situ tensile tests along the extrusion axis of Mg-1Mn (wt pct) were performed at 323 K, 423 K, and 523 K. The alloy exhibited a strong basal texture such that most of the grains experienced compression along their -axis during deformation. At 323 K, fracture occurred at about 10 pct strain. Although basal, prismatic, and pyramidal slip activity was observed along with extension twinning, contraction twinning significantly influenced the deformation, and such twins evolved into {10{\\bar{1}}1}-{10{\\bar{1}}2} double twins. Crystal plasticity simulation showed localized shear deformation within the contraction twins and double twins due to the enhanced activity of basal slip in the reoriented twin volume. Due to this, the twin-matrix interface was identified to be a potential crack initiation site. Thus, contraction twins were considered to have led to the failure of the material at a relatively low strain, suggesting that this deformation mode is detrimental to the cold formability of Mg and its alloys. With increasing temperature, there was a significant decrease in the activity of contraction twinning as well as extension twinning, along with a decrease in the tensile strength and an increase in the {ɛ} _{ {f}} value. A combination of basal, prismatic, and pyramidal slips accounted for a large percentage of the observed deformation activity at 423 K and 523 K. The lack of contraction twinning was explained by the expected decrease in the critical resolved shear stress values for pyramidal slip, and the improved {ɛ} _{ {f}} values at elevated temperatures were attributed to the vanishing activity of contraction twinning.

  15. High Strain Rate Deformation Mechanisms of Body Centered Cubic Material Subjected to Impact Loading

    Science.gov (United States)

    Visser, William

    Low carbon steel is the most common grade of structural steel used; it has carbon content of 0.05% to 0.25% and very low content of alloying elements. It is produced in great quantities and provides material properties that are acceptable for many engineering applications, particularly in the construction industry in which low carbon steel is widely used as the strengthening phase in civil structures. The overall goal of this dissertation was to investigate the deformation response of A572 grade 50 steel when subjected to impact loading. This steel has a 0.23% by weight carbon content and has less than 2% additional alloying elements. The deformation mechanisms of this steel under shock loading conditions include both dislocation motion and twin formation. The goal of this work was achieved by performing experimental, analytical and numerical research in three integrated tasks. The first is to determine the relationship between the evolution of deformation twins and the impact pressure. Secondly, a stress criterion for twin nucleation during high strain rate loading was developed which can account for the strain history or initial dislocation density. Lastly, a method was applied for separating the effects of dislocations and twins generated by shock loading in order to determine their role in controlling the flow stress of the material. In this regard, the contents of this work have been categorically organized. First, the active mechanisms in body centered cubic (BCC) low carbon steel during shock loading have been determined as being a composed of the competing mechanisms of dislocations and deformation twins. This has been determined through a series of shock loading tests of the as-received steel. The shock loading tests were done by plate impact experiments at several impact pressures ranging from 2GPa up to 13GPa using a single stage light gas gun. A relationship between twin volume fraction and impact pressure was determined and an analytical model was

  16. Twin Higgs Asymmetric Dark Matter.

    Science.gov (United States)

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-18

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

  17. The nature of pseudo-twinning modes on the basis of a twin classification scheme

    International Nuclear Information System (INIS)

    Singh, Jung B.; Sundararaman, M.; Krishnan, M.

    2011-01-01

    Pseudo-twins can form in ordered structures under high stress conditions. These twins are defined by lattice sites that are at twin positions but are incorrectly occupied by different species of atoms. The present note discusses if it is possible to further classify pseudo-twins into different modes based on the nature of associated twinning elements.

  18. Twins and Kindergarten Separation: Divergent Beliefs of Principals, Teachers, Parents, and Twins

    Science.gov (United States)

    Gordon, Lynn Melby

    2015-01-01

    Should principals enforce mandatory separation of twins in kindergarten? Do school separation beliefs of principals differ from those of teachers, parents of twins, and twins themselves? This survey questioned 131 elementary principals, 54 kindergarten teachers, 201 parents of twins, and 112 twins. A majority of principals (71%) believed that…

  19. The classical twin study and beyond

    NARCIS (Netherlands)

    Boomsma, D.I.; Busjahn, A.; Peltonen, L.

    2002-01-01

    Twin studies have been a valuable source of information about the genetic basis of complex traits. To maximize the potential of twin studies, large, worldwide registers of data on twins and their relatives have been established. Here, we provide an overview of the current resources for twin

  20. Monochorionic twin pregnancies: a systematic approach to ...

    African Journals Online (AJOL)

    Complications unique to these pregnancies include Twin-To-Twin Transfusion Syndrome (TTTS), Twin Polycythaemia Anaemia Sequence (TAPS), Selective Intrauterine Growth Restriction (sIUGR) and death of the co-twin. Adhering to a systematic and objective approach of management, can lead to early recognition and ...

  1. Modeling the effect of neighboring grains on twin growth in HCP polycrystals

    Science.gov (United States)

    Kumar, M. Arul; Beyerlein, I. J.; Lebensohn, R. A.; Tomé, C. N.

    2017-09-01

    In this paper, we study the dependence of neighboring grain orientation on the local stress state around a deformation twin in a hexagonal close packed (HCP) crystal and its effects on the resistance against twin thickening. We use a recently developed, full-field elasto-visco-plastic formulation based on fast Fourier transforms that account for the twinning shear transformation imposed by the twin lamella. The study is applied to Mg, Zr and Ti, since these HCP metals tend to deform by activation of different types of slip modes. The analysis shows that the local stress along the twin boundary are strongly controlled by the relative orientation of the easiest deformation modes in the neighboring grain with respect to the twin lamella in the parent grain. A geometric expression that captures this parent-neighbor relationship is proposed and incorporated into a larger scale, mean-field visco-plastic self-consistent model to simulate the role of neighboring grain orientation on twin thickening. We demonstrate that the approach improves the prediction of twin area fraction distribution when compared with experimental observations.

  2. Diamond cubic phase of monoolein and water as an amphiphilic matrix for electrophoresis of oligonucleotides.

    Science.gov (United States)

    Carlsson, Nils; Winge, Ann-Sofie; Engström, Sven; Akerman, Björn

    2005-10-06

    We used a cubic liquid crystal formed by the nonionic monoglyceride monoolein and water as a porous matrix for the electrophoresis of oligonucleotides. The diamond cubic phase is thermodynamically stable when in contact with a water-rich phase, which we exploit to run the electrophoresis in the useful submarine mode. Oligonucleotides are separated according to size and secondary structure by migration through the space-filling aqueous nanometer pores of the regular liquid crystal, but the comparatively slow migration means the cubic phase will not be a replacement for the conventional DNA gels. However, our demonstration that the cubic phase can be used in submarine electrophoresis opens up the possibility for a new matrix for electrophoresis of amphiphilic molecules. From this perspective, the results on the oligonucleotides show that water-soluble particles of nanometer size, typical for the hydrophilic parts of membrane-bound proteins, may be a useful separation motif. A charged contamination in the commercial sample of monoolein, most likely oleic acid that arises from its hydrolysis, restricts useful buffer conditions to a pH below 5.6.

  3. Unusually large unit cell of lipid bicontinuous cubic phase: towards nature's length scales

    Science.gov (United States)

    Kim, Hojun; Leal, Cecilia

    Lipid bicontinuous cubic phases are of great interest for drug delivery, protein crystallization, biosensing, and templates for directing hard material assembly. Structural modulations of lipid mesophases regarding phase identity and unit cell size are often necessary to augment loading and gain pore size control. One important example is the need for unit cells large enough to guide the crystallization of bigger proteins without distortion of the templating phase. In nature, bicontinuous cubic constructs achieve unit cell dimensions as high as 300 nm. However, the largest unit cell of lipid mesophases synthesized in the lab is an order of magnitude lower. In fact, it has been predicted theoretically that lipid bicontinuous cubic phases of unit cell dimensions exceeding 30 nm could not exist, as high membrane fluctuations would damp liquid crystalline order. Here we report non-equilibrium assembly methods of synthesizing metastable bicontinuous cubic phases with unit cell dimensions as high as 70 nm. The phases are stable for very long periods and become increasingly ordered as time goes by without changes to unit cell dimensions. We acknowledge the funding source as a NIH.

  4. Computational strain gradient crystal plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2014-01-01

    A numerical method for viscous strain gradient crystal plasticity theory is presented, which incorporates both energetic and dissipative gradient effects. The underlying minimum principles are discussed as well as convergence properties of the proposed finite element procedure. Three problems...... of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically...... oriented face centered cubic crystals are developed in terms of the crystallographic slip parameters. The effect on geometrically necessary dislocation structures introduced by plastic deformation is investigated as a function of the ratio of void radius to plasticity length scale....

  5. Mesoscale models for stacking faults, deformation twins and martensitic transformations: Linking atomistics to continuum

    Science.gov (United States)

    Kibey, Sandeep A.

    We present a hierarchical approach that spans multiple length scales to describe defect formation---in particular, formation of stacking faults (SFs) and deformation twins---in fcc crystals. We link the energy pathways (calculated here via ab initio density functional theory, DFT) associated with formation of stacking faults and twins to corresponding heterogeneous defect nucleation models (described through mesoscale dislocation mechanics). Through the generalized Peieirls-Nabarro model, we first correlate the width of intrinsic SFs in fcc alloy systems to their nucleation pathways called generalized stacking fault energies (GSFE). We then establish a qualitative dependence of twinning tendency in fee metals and alloys---specifically, in pure Cu and dilute Cu-xAl (x= 5.0 and 8.3 at.%)---on their twin-energy pathways called the generalized planar fault energies (GPFE). We also link the twinning behavior of Cu-Al alloys to their electronic structure by determining the effect of solute Al on the valence charge density redistribution at the SF through ab initio DFT. Further, while several efforts have been undertaken to incorporate twinning for predicting stress-strain response of fcc materials, a fundamental law for critical twinning stress has not yet emerged. We resolve this long-standing issue by linking quantitatively the twin-energy pathways (GPFE) obtained via ab initio DFT to heterogeneous, dislocation-based twin nucleation models. We establish an analytical expression that quantitatively predicts the critical twinning stress in fcc metals in agreement with experiments without requiring any empiricism at any length scale. Our theory connects twinning stress to twin-energy pathways and predicts a monotonic relation between stress and unstable twin stacking fault energy revealing the physics of twinning. We further demonstrate that the theory holds for fcc alloys as well. Our theory inherently accounts for directional nature of twinning which available

  6. Significance of Dauphiné twins in crystallographic fabrics of quartz tectonites

    Science.gov (United States)

    Eske Sørensen, Bjørn

    2014-05-01

    Dauphine twins are commonly found in quartz tectonites, however their role in deformation processes are not completely understood. This study represents a new attempt to understand the interaction between slip systems and Dauphine twins in deforming quartz-rich rocks at different temperatures. There is no doubt that Dauphine twins are mobilized under stress as this has been shown by experiments for single crystals and in polycrystalline aggregates where distinct crystallographic fabrics develop in previously randomly oriented aggregates related to minimization of elastic energy (Tullis 1972). However in quartz tectonites the Dauphine twin process is a part of interplay between plastic deformation and recovery processes which depends on PT, strain-rate and fluid composition and availability. In quartz tectonites with Y-girdle C-axis (GBM-regime) fabrics Dauphiné twins are abundant, relating different parts of r- and z rhomb "comet" distributions. This is interpreted as completion between prism slip and Dauphiné twinning. Slip rotates grains such that CRSS is low on the prism planes, but then Dauphiné twin boundaries sweeps through the grain back to the orientation giving lower stored elastic energy. The faster recovery at higher temperatures gives subgrain walls slowing down twin movement across the mm-sized grain of the GBM regime. At lower temperatures in the SGR-regime grain-size is reduced and different rotations of the grains are happening due to the domination of rhomb and basal slip. Because recrystallization is effective relative to grain-size the grains are commonly free of internal strain and subgrain walls, allowing the favorably oriented Dauphiné twin member to sweep across the whole grain overwhelming the unfavorably oriented Dauphiné twin member. As a consequence high strain reduces the number of Dauphiné twins and quartz rhomb fabrics appear trigonal, missing the "comet" shape of the GBM regime rhomb fabrics. Since Dauphiné twinning is also

  7. Twin-to-twin transfusion syndrome : from placental anastomoses to long-term outcome

    NARCIS (Netherlands)

    Lopriore, Enrico

    2006-01-01

    Twin-to-twin transfusion syndrome (TTTS) is a severe complication of monochorionic twin pregnancies associated with high perinatal mortality and morbidity rates. Placental vascular anastomoses, almost invariably present in monochorionic placentas, are the essential anatomical substrate for the

  8. Integrable peakon equations with cubic nonlinearity

    International Nuclear Information System (INIS)

    Hone, Andrew N W; Wang, J P

    2008-01-01

    We present a new integrable partial differential equation found by Vladimir Novikov. Like the Camassa-Holm and Degasperis-Procesi equations, this new equation admits peaked soliton (peakon) solutions, but it has nonlinear terms that are cubic, rather than quadratic. We give a matrix Lax pair for V Novikov's equation, and show how it is related by a reciprocal transformation to a negative flow in the Sawada-Kotera hierarchy. Infinitely many conserved quantities are found, as well as a bi-Hamiltonian structure. The latter is used to obtain the Hamiltonian form of the finite-dimensional system for the interaction of N peakons, and the two-body dynamics (N = 2) is explicitly integrated. Finally, all of this is compared with some analogous results for another cubic peakon equation derived by Zhijun Qiao. (fast track communication)

  9. Quasiparticle Interference on Cubic Perovskite Oxide Surfaces.

    Science.gov (United States)

    Okada, Yoshinori; Shiau, Shiue-Yuan; Chang, Tay-Rong; Chang, Guoqing; Kobayashi, Masaki; Shimizu, Ryota; Jeng, Horng-Tay; Shiraki, Susumu; Kumigashira, Hiroshi; Bansil, Arun; Lin, Hsin; Hitosugi, Taro

    2017-08-25

    We report the observation of coherent surface states on cubic perovskite oxide SrVO_{3}(001) thin films through spectroscopic-imaging scanning tunneling microscopy. A direct link between the observed quasiparticle interference patterns and the formation of a d_{xy}-derived surface state is supported by first-principles calculations. We show that the apical oxygens on the topmost VO_{2} plane play a critical role in controlling the coherent surface state via modulating orbital state.

  10. Minimal knotted polygons in cubic lattices

    International Nuclear Information System (INIS)

    Van Rensburg, E J Janse; Rechnitzer, A

    2011-01-01

    In this paper we examine numerically the properties of minimal length knotted lattice polygons in the simple cubic, face-centered cubic, and body-centered cubic lattices by sieving minimal length polygons from a data stream of a Monte Carlo algorithm, implemented as described in Aragão de Carvalho and Caracciolo (1983 Phys. Rev. B 27 1635), Aragão de Carvalho et al (1983 Nucl. Phys. B 215 209) and Berg and Foester (1981 Phys. Lett. B 106 323). The entropy, mean writhe, and mean curvature of minimal length polygons are computed (in some cases exactly). While the minimal length and mean curvature are found to be lattice dependent, the mean writhe is found to be only weakly dependent on the lattice type. Comparison of our results to numerical results for the writhe obtained elsewhere (see Janse van Rensburg et al 1999 Contributed to Ideal Knots (Series on Knots and Everything vol 19) ed Stasiak, Katritch and Kauffman (Singapore: World Scientific), Portillo et al 2011 J. Phys. A: Math. Theor. 44 275004) shows that the mean writhe is also insensitive to the length of a knotted polygon. Thus, while these results for the mean writhe and mean absolute writhe at minimal length are not universal, our results demonstrate that these values are quite close the those of long polygons regardless of the underlying lattice and length

  11. Neutrosophic Cubic MCGDM Method Based on Similarity Measure

    Directory of Open Access Journals (Sweden)

    Surapati Pramanik

    2017-06-01

    Full Text Available The notion of neutrosophic cubic set is originated from the hybridization of the concept of neutrosophic set and interval valued neutrosophic set. We define similarity measure for neutrosophic cubic sets and prove some of its basic properties.

  12. Spinning solitons in cubic-quintic nonlinear media

    Indian Academy of Sciences (India)

    Spinning solitons in cubic-quintic nonlinear media ... features of families of bright vortex solitons (doughnuts, or 'spinning' solitons) in both conservative and dissipative cubic-quintic nonlinear media. ... Pramana – Journal of Physics | News.

  13. Crystal modifications and dissolution rate of piroxicam.

    Science.gov (United States)

    Lyn, Lim Yee; Sze, Huan Wen; Rajendran, Adhiyaman; Adinarayana, Gorajana; Dua, Kamal; Garg, Sanjay

    2011-12-01

    Piroxicam is a nonsteroidal anti-inflammatory drug with low aqueous solubility which exhibits polymorphism. The present study was carried out to develop polymorphs of piroxicam with enhanced solubility and dissolution rate by the crystal modification technique using different solvent mixtures prepared with PEG 4000 and PVP K30. Physicochemical characteristics of the modified crystal forms of piroxicam were investigated by X-ray powder diffractometry, FT-IR spectrophotometry and differential scanning calorimetry. Dissolution and solubility profiles of each modified crystal form were studied and compared with pure piroxicam. Solvent evaporation method (method I) produced both needle and cubic shaped crystals. Slow crystallization from ethanol with addition of PEG 4000 or PVP K30 at room temperature (method II) produced cubic crystal forms. Needle forms produced by method I improved dissolution but not solubility. Cubic crystals produced by method I had a dissolution profile similar to that of untreated piroxicam but showed better solubility than untreated piroxicam. Cubic shaped crystals produced by method II showed improved dissolution, without a significant change in solubility. Based on the XRPD results, modified piroxicam crystals obtained by method I from acetone/benzene were cube shaped, which correlates well with the FTIR spectrum; modified needle forms obtained from ethanol/methanol and ethanol/acetone showed a slight shift of FTIR peak that may be attributed to differences in the internal structure or conformation.

  14. Estimating twin concordance for bivariate competing risks twin data

    DEFF Research Database (Denmark)

    Scheike, Thomas; Holst, Klaus K.; Hjelmborg, Jacob B.

    2014-01-01

    For twin time-to-event data, we consider different concordance probabilities, such as the casewise concordance that are routinely computed as a measure of the lifetime dependence/correlation for specific diseases. The concordance probability here is the probability that both twins have experience...... events with the competing risk death. We thus aim to quantify the degree of dependence through the casewise concordance function and show a significant genetic component...... the event of interest. Under the assumption that both twins are censored at the same time, we show how to estimate this probability in the presence of right censoring, and as a consequence, we can then estimate the casewise twin concordance. In addition, we can model the magnitude of within pair dependence...... over time, and covariates may be further influential on the marginal risk and dependence structure. We establish the estimators large sample properties and suggest various tests, for example, for inferring familial influence. The method is demonstrated and motivated by specific twin data on cancer...

  15. Growth curves for twins in Slovenia.

    Science.gov (United States)

    Bricelj, Katja; Blickstein, Isaac; Bržan-Šimenc, Gabrijela; Janša, Vid; Lučovnik, Miha; Verdenik, Ivan; Trojner-Bregar, Andreja; Tul, Nataša

    2017-02-01

    Abnormalities of fetal growth are more common in twins. We introduce the growth curves for monitoring fetal growth in twin pregnancies in Slovenia. Slovenian National Perinatal Information System for the period between 2002 and 2010 was used to calculate birth weight percentiles for all live born twins for each week from 22nd to 40th week. The calculated percentiles of birth weight for all live-born twins in Slovenia served as the basis for drawing 'growth' curves. The calculated growth curves for twins will help accurately diagnose small or large twin fetuses for their gestational age in the native central European population.

  16. Molecular dynamics simulation of albite twinning and pericline twinning in low albite

    International Nuclear Information System (INIS)

    Li, Bin; Knowles, Kevin M

    2013-01-01

    Two twinning laws, the albite law and the pericline law, are the predominant growth twinning modes in triclinic plagioclase feldspars such as low albite, NaAlSi 3 O 8 , in which the aluminum and silicon atoms are in an ordered arrangement on the tetrahedral sites of the aluminosilicate framework. In the terminology used formally to describe deformation twinning in a triclinic lattice, these twin laws can be described as Type I and Type II twin laws, respectively, with the pericline twin law being conjugate to the albite twin law. In this study, twin boundaries have been constructed for low albite according to these two twinning laws and studied by molecular dynamics simulation. The results show that suitably constructed twin boundary models are quite stable for both albite twinning and pericline twinning during molecular dynamics simulation. The calculated twin boundary energy of an albite twin is significantly lower than that of a pericline twin, in accord with the experimental observation that albite twinning is the more commonly observed mode seen in plagioclase feldspars. The results of the molecular dynamics simulations also agree with conclusions from the prior work of Starkey that glide twinning in low albite is not favoured energetically. (paper)

  17. Giant narrowband twin-beam generation along the pump-energy propagation direction

    Science.gov (United States)

    Pérez, Angela M.; Spasibko, Kirill Yu; Sharapova, Polina R.; Tikhonova, Olga V.; Leuchs, Gerd; Chekhova, Maria V.

    2015-07-01

    Walk-off effects, originating from the difference between the group and phase velocities, limit the efficiency of nonlinear optical interactions. While transverse walk-off can be eliminated by proper medium engineering, longitudinal walk-off is harder to avoid. In particular, ultrafast twin-beam generation via pulsed parametric down-conversion and four-wave mixing is only possible in short crystals or fibres. Here we show that in high-gain parametric down-conversion, one can overcome the destructive role of both effects and even turn them into useful tools for shaping the emission. In our experiment, one of the twin beams is emitted along the pump Poynting vector or its group velocity matches that of the pump. The result is markedly enhanced generation of both twin beams, with the simultaneous narrowing of angular and frequency spectrum. The effect will enable efficient generation of ultrafast twin photons and beams in cavities, waveguides and whispering-gallery mode resonators.

  18. Electric quadrupole interaction in cubic BCC α-Fe

    Energy Technology Data Exchange (ETDEWEB)

    Błachowski, A.; Komędera, K. [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Ruebenbauer, K., E-mail: sfrueben@cyf-kr.edu.pl [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Cios, G.; Żukrowski, J. [AGH University of Science and Technology, Academic Center for Materials and Nanotechnology, Av. A. Mickiewicza 30, PL-30-059 Kraków (Poland); Górnicki, R. [RENON, ul. Gliniana 15/15, PL-30-732 Kraków (Poland)

    2016-07-15

    Mössbauer transmission spectra for the 14.41-keV resonant line in {sup 57}Fe have been collected at room temperature by using {sup 57}Co(Rh) commercial source and α-Fe strain-free single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γ-ray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V{sub zz} = +1.61(4) × 10{sup 19} Vm{sup −2} for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the {sup 57}Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the {sup 57}Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using as-rolled polycrystalline α-Fe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V{sub zz} = +1.92(4) × 10{sup 19} Vm{sup −2}. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter. - Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge

  19. Electric quadrupole interaction in cubic BCC α-Fe

    International Nuclear Information System (INIS)

    Błachowski, A.; Komędera, K.; Ruebenbauer, K.; Cios, G.; Żukrowski, J.; Górnicki, R.

    2016-01-01

    Mössbauer transmission spectra for the 14.41-keV resonant line in "5"7Fe have been collected at room temperature by using "5"7Co(Rh) commercial source and α-Fe strain-free single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γ-ray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V_z_z = +1.61(4) × 10"1"9 Vm"−"2 for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the "5"7Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the "5"7Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using as-rolled polycrystalline α-Fe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V_z_z = +1.92(4) × 10"1"9 Vm"−"2. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter. - Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge for ab initio calculations

  20. Low temperature electron microscopy on the cubic-tetragonal transformation of V3Si

    Science.gov (United States)

    Onozuka, T.; Ohnishi, N.; Hirabayashi, M.

    1988-04-01

    The cubic-tetragonal martensitic transition of V3Si and its precursor have been investigated in the temperature range from 13 K to 80 K using a 1 MV electron microscope with a double-tilting cold stage. Below the transition temperature Tm = 19 K, fine twin lamellae appear parallel to {110} plane traces, being connected continuously with mottled striations having the same orientation. Fine striations along {110} traces or so-called tweeds are observed below 50 K at the precursor of the structural phase transition. The image contrast of mottled striations and tweed patterns is attributed to the presence of lattice distortion owing to the softening of the shear modulus. Reversible changes of the patterns recorded with a TV-VTR system during cooling and heating processes were discussed briefly.

  1. Fermi surfaces of the pyrite-type cubic AuSb2 compared with split Fermi surfaces of the ullmannite-type cubic chiral NiSbS and PdBiSe

    Science.gov (United States)

    Nishimura, K.; Kakihana, M.; Nakamura, A.; Aoki, D.; Harima, H.; Hedo, M.; Nakama, T.; Ōnuki, Y.

    2018-05-01

    We grew high-quality single crystals of AuSb2 with the pyrite (FeS2)-type cubic structure by the Bridgman method and studied the Fermi surface properties by the de Haas-van Alphen (dHvA) experiment and the full potential LAPW band calculation. The Fermi surfaces of AuSb2 are found to be similar to those of NiSbS and PdBiSe with the ullmannite (NiSbS)-type cubic chiral structure because the crystal structures are similar each other and the number of valence electrons is the same between two different compounds. Note that each Fermi surface splits into two Fermi surfaces in NiSbS and PdBiSe, reflecting the non-centrosymmetric crystal structure.

  2. Neutron diffraction study of cubic titanium carbohydride at the homogeneity lower limit

    International Nuclear Information System (INIS)

    Khidirov, I.; Mirzaev, B.B.; Mukhtarova, N.N.

    2004-01-01

    Cubic carbohydride TiC 0.47H0.22 was prepared by means of quenching from 1200 deg.C followed by the heat treatment using special regime for preventing the hydrogen yield out the lattice. It is shown that at the lower limit of homogeneity range of the cubic carbohydride, hydrogen atoms occupy the tetrahedral interstices 8(c) of the disordered cubic structure with space group of Fm3m. It is found that carbon and hydrogen atoms are partially ordered by annealing at 900-700 deg.C. The ordered structure is face-centred cubic lattice with the parameter a ≅2a 0 , where a 0 is the lattice parameter in disordered structure. The crystal structure of the disordered phase is described within the framework of space group Fd3m, where the carbon atoms occupy mainly (70%) octahedral interstices 16(c) and another ones of carbon and all hydrogen atoms occupy the octahedral interstices 16(d). (author)

  3. Nike Twins Seven Seven: Nigerian Batik Artist.

    Science.gov (United States)

    LaDuke, Betty

    1987-01-01

    Chronicles the personal and professional life of Nike Twins Seven Seven (born 1951), a Nigerian batik artist, and her husband, Twins Seven Seven, a musician-artist, both of whom have received international acclaim. (BJV)

  4. The Fourth International Network of Twin Registries: Overview from Osaka/Research Reviews: Familial Fraternal Twinning; Twin Study of Masculine Faces; Physical Aggression and Epigenetics; Prenatal Education for Parents of Twins/Current Events: 2016 Guinness Book of World Records; Oldest Living Male Twins; Twins Reunited at Sixty-Nine; Panda Twins; Twins.com.

    Science.gov (United States)

    Segal, Nancy L

    2015-12-01

    The 4th International Network of Twin Registries (INTR) Consortium Meeting took place in Osaka, Japan, September 28-29, 2015. The venue was the Osaka Medical Center for Medical Innovation and Translational Research. An overview of presentations and other activities is provided. Next, 1930s research on familial fraternal twinning, preference for masculine faces, physical aggression and epigenetics, and a prenatal education program for parents of multiples are described. Current twin-related events include the 2016 Guinness Book of World Records (GWR), the oldest living male twins, newly reunited twins, the birth of panda twins and a controversial twin-based website.

  5. Diffusion in Coulomb crystals.

    Science.gov (United States)

    Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  6. Simulations of stress-induced twinning and de-twinning: A phase field model

    International Nuclear Information System (INIS)

    Hu Shenyang; Henager, Chuck H.; Chen Longqing

    2010-01-01

    Twinning in certain metals or under certain conditions is a major plastic deformation mode. Here we present a phase field model to describe twin formation and evolution in a polycrystalline fcc metal under loading and unloading. The model assumes that twin nucleation, growth and de-twinning is a process of partial dislocation nucleation and slip on successive habit planes. Stacking fault energies, energy pathways (γ surfaces), critical shear stresses for the formation of stacking faults and dislocation core energies are used to construct the thermodynamic model. The simulation results demonstrate that the model is able to predict the nucleation of twins and partial dislocations, as well as the morphology of the twin nuclei, and to reasonably describe twin growth and interaction. The twin microstructures at grain boundaries are in agreement with experimental observation. It was found that de-twinning occurs during unloading in the simulations, however, a strong dependence of twin structure evolution on loading history was observed.

  7. Remembering Irving I. Gottesman: Twin Research Colleague and Friend Extraordinaire/Research Studies: Face-Lift Technique Comparison in Identical Twins; Raising Preterm Twins; Fetal Behavior in Dichorionic Twin Pregnancies; Co-Bedding and Stress Reduction in Twins/Public Interest: Identical Co-Twins' Same Day Delivery; Teaching Twins in Bosnia; Twin Auctioneers; Sister, the Play.

    Science.gov (United States)

    Segal, Nancy L

    2016-12-01

    Dr Irving I. Gottesman, a colleague, friend, and long-time member of the International Society of Twin Studies passed away on June 29, 2016. His contributions to twin research and some personal reflections are presented to honor both the man and the memory. This tribute is followed by short reviews of twin research concerning differences between cosmetic surgical techniques, the rearing of preterm twins, behavioral observations of dichorionic fetal twins, and the outcomes of co-bedding twins with reference to stress reduction. Interesting and informative articles in the media describe identical co-twins who delivered infants on the same day, educational policies regarding twins in Bosnia and the United Kingdom, unusual practices of twin auctioneers, and a theatrical production, Sister, featuring identical twins in the leading roles.

  8. Mechanical twinning and texture evolution in severely deformed Ti-6Al-4V at high temperatures

    International Nuclear Information System (INIS)

    Yapici, Guney Guven; Karaman, Ibrahim; Luo Zhiping

    2006-01-01

    We have investigated the deformation behavior and texture evolution of two-phase Ti-6Al-4V subjected to severe plastic deformation using equal channel angular extrusion (ECAE) at a high temperature (∼0.55T m ). Significant deformation twinning activity was observed after one and two ECAE passes in a 90 deg, die at 800 deg. C. Twinning activity at such a high temperature is a first-time observation in this material and is attributed to the high strain and stress levels imposed during ECAE. High stress levels and the stress state can affect the separation of twinning partials considerably. Resolved shear stress magnitudes on twin partials were found to be high during the ECAE process that helps the nucleation of mechanical twinning. The twinning mode was identified as the {101-bar 1} type using electron diffraction patterns which is one of the twinning modes observed in Ti at temperatures above 350 deg. C. Although only one twinning variant was mainly evident after one pass, multiple twin variants of the same mode were observed after the second pass with a significant increase in twin volume fraction. ECAE processing aligned the basal planes of the hexagonal close-packed α phase, initially having a random texture, with the ECAE shear plane. Texture evolution during ECAE was successfully predicted using a viscoplastic self-consistent crystal plasticity framework capturing the effect of the observed twinning mode on texture. Mechanical twins formed during ECAE and grain refinement led to a noteworthy improvement in flow stresses under tension and compression at room temperature. A strong directional anisotropy in yield strengths was also evident which cannot be explained only by crystallographic texture. It was speculated that the asymmetry of critical resolved shear stresses of deformation modes and the processing-induced deformation structure should play a role. With the supporting evidence from our previous works on the severe plastic deformation of other

  9. Roentgeno-cephalometric analysis on the twin

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hi Sup; Ahn, Hyung Kyu [College of Dentistry, Seoul National University, Seoul (Korea, Republic of)

    1972-11-15

    The purpose of this investigation can be sought for studying varients between twin by the cephalometric roentgenog raphic technics. The author have applied Down's, Bjork and Sakamoto's technic and measured in various angulations and length of cephalometric points. The results are as follows; 1. No significantly different data were found between twin. 2. There was no differences between normality and twin.

  10. Postpartum Mental State of Mothers of Twins

    Science.gov (United States)

    Brantmüller, Éva; Gyúró, Mónika; Galgán, Kitti; Pakai, Annamária

    2016-01-01

    Twin birth is a relevant risk factor for postnatal depression (PND). The primary objective of our study is to reveal the prevalence of suspected cases of depression and to identify some background factors among mothers of twins. We applied convenience sampling method within a retrospective, quantitative study among mothers given birth to twins for…

  11. Epigenetic Epidemiology of Complex Diseases Using Twins

    DEFF Research Database (Denmark)

    Tan, Qihua

    2013-01-01

    through multiple epigenetic mechanisms. This paper reviews the new developments in using twins to study disease-related epigenetic alterations, links them to lifetime environmental exposure with a focus on the discordant twin design and proposes novel data-analytical approaches with the aim of promoting...... a more efficient use of twins in epigenetic studies of complex human diseases....

  12. Concordance for multiple sclerosis in Danish twins

    DEFF Research Database (Denmark)

    Hansen, T; Skytthe, Axel; Stenager, Egon

    2005-01-01

    The occurrence of multiple sclerosis (MS) in twins has not previously been studied in complete nationwide data sets. The existence of almost complete MS and twin registries in Denmark ensures that essentially unbiased samples of MS cases among twins can be obtained. In this population-based study...

  13. Sports pairs: insights on athletic talent; research reviews: twins with leukemia; parents and twins.

    Science.gov (United States)

    Segal, Nancy L

    2007-06-01

    Twin research exploring genetic and environmental influences on athletic interests and talents is reviewed. Illustrative examples of twin athletes representing a variety of sports activities are presented. This is followed by an overview of twin studies offering critical insights into the onset and progress of leukemia. In the last section, timely events involving twins and parents of twins will be described--each case provides a new look at an old question.

  14. Unusual Features of Crystal Structures of Some Simple Copper Compounds

    Science.gov (United States)

    Douglas, Bodie

    2009-01-01

    Some simple copper compounds have unusual crystal structures. Cu[subscript 3]N is cubic with N atoms at centers of octahedra formed by 6 Cu atoms. Cu[subscript 2]O (cuprite) is also cubic; O atoms are in tetrahedra formed by 4 Cu atoms. These tetrahedra are linked by sharing vertices forming two independent networks without linkages between them.…

  15. Twins and non-twin siblings: different estimates of shared environmental influence in early childhood.

    Science.gov (United States)

    Koeppen-Schomerus, Gesina; Spinath, Frank M; Plomin, Robert

    2003-04-01

    Twin studies typically indicate shared environmental influence for cognitive abilities, especially in early childhood. However, across studies, DZ twin correlations tend to be greater than non-twin sibling correlations, suggesting that twin estimates of shared environment are to some extent specific to twins. We tested this hypothesis in a sample of more than 1800 MZ and 1800 same-sex DZ pairs from the Twins Early Development Study (TEDS), a study of twins born in England and Wales in 1994 and 1995. For this analysis, we obtained comparable data from more than 130 same-sex younger siblings of the twins. Twins and their younger siblings were assessed for language, cognitive abilities and behavior problems by their parents at 2 and 3 years of age. For language and cognitive measures at both 2 and 3 years, but not for behavior problems, estimates of shared environment were more than twice as large for twins as compared to non-twin siblings. We conclude that about half of twin study estimates of shared environment for cognitive abilities in early childhood are specific to twins. Although many possibilities exist for explaining the special shared environment effect for twins, we suggest that cognitive-relevant experiences that are not shared by siblings are shared by twins because they are exactly the same age.

  16. Crystallographic computing system Jana2006: solution and refinement of twinned structures

    Czech Academy of Sciences Publication Activity Database

    Petříček, Václav; Dušek, Michal; Plášil, Jakub

    2016-01-01

    Roč. 231, č. 10 (2016), s. 583-599 ISSN 2194-4946 R&D Projects: GA ČR GA15-12653S; GA ČR(CZ) GA14-03276S Institutional support: RVO:68378271 Keywords : crystal structure analysis * Jana2006 * twinning Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.179, year: 2016

  17. The effect of chorionicity and twin-to-twin delivery time interval on short-term outcome of the second twin

    DEFF Research Database (Denmark)

    Hjortø, Sofie; Nickelsen, Carsten; Petersen, Janne

    2013-01-01

    Abstract Objectives: To investigate the effect of chorionicity and twin-to-twin delivery time interval on short-term outcome in the second twin. Additionally, to investigate predictors of adverse outcome in both twins. Methods: Data included vaginally delivered twins (≥ 36 weeks) from Copenhagen ...

  18. Polarization contrast linear spectroscopies for cubic semiconductors under stress: macro- and micro-reflectance difference spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Lastras-Martinez, L.F.; Balderas-Navarro, R.E.; Castro-Garcia, R.; Herrera-Jasso, R.; Lastras-Martinez, A. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi, S.L.P. (Mexico); Chavira-Rodriguez, M. [Departamento de Fisico Matematicas, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi, S.L.P. (Mexico)

    2011-01-15

    The technique to measure optical anisotropies (OA) in cubic semiconductors is termed either reflectance difference spectroscopy (RDS) or reflectance anisotropy spectroscopy (RAS). In this paper we report on the application of RDS/RAS to a number of cubic semiconductors. We discuss RD spectra of GaAs, Si, CdTe, GaP, InP and GaSb (001) surfaces, induced by an uniaxial stress applied along [110] crystal directions. We show that all RD spectra can be explained in terms of a phenomenological model based on a perturbative Hamiltonian. We further report on measurements of spatial-resolved RDS measurements of GaAs employing a newly developed micro-RD spectrometer with a spatial resolution of 5 {mu}m. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Nanosize stabilization of cubic and tetragonal phases in reactive plasma synthesized zirconia powders

    Energy Technology Data Exchange (ETDEWEB)

    Jayakumar, S., E-mail: sjayakumar.physics@gmail.com [Research and Development Centre, Bharathiar University, Coimbatore 641 014 (India); Department of Physics, Pollachi Institute of Engineering and Technology, Pollachi 642 205 (India); Ananthapadmanabhan, P.V.; Thiyagarajan, T.K. [Laser and Plasma Technology Division, BARC, Trombay, Mumbai 400 085 (India); Perumal, K. [Vision for Wisdom, Temple of Consciousness, Aliyar 642 101 (India); Mishra, S.C. [Department of Metallurgical and Materials Engg, National Institute of Technology, Rourkela 769 008 (India); Suresh, G. [Department of Physics, Park College of Engineering and Technology, Coimbatore 641 659 (India); Su, L.T.; Tok, A.I.Y. [School of Materials Science and Engg, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639 798 (Singapore)

    2013-06-15

    Pure zirconium oxide powders with particle size 2–33 nm are synthesized by reactive plasma processing. Transmission electron microscopy investigation of these particles revealed size dependent behavior for their phase stabilization. The monoclinic phase is found to be stable when particle size is ≥20 nm; Tetragonal is found to be stabilized in the range of 7–20 nm and as the particle size decreases to 6 nm and less, the cubic phase is stabilized. - Highlights: ► Direct conversion of micron-sized zirconium hydride powder to single crystal ZrO{sub 2} nanopowder. ► Size dependent stabilization of cubic, tetragonal and monoclinic phases in the reactive plasma synthesized ZrO{sub 2} nanopowder. ► Transmission electron microscopic investigation to identify particles of different sizes and their corresponding phase structure.

  20. Twin methodology in epigenetic studies

    DEFF Research Database (Denmark)

    Tan, Qihua; Christiansen, Lene; von Bornemann Hjelmborg, Jacob

    2015-01-01

    of diseases to molecular phenotypes in functional genomics especially in epigenetics, a thriving field of research that concerns the environmental regulation of gene expression through DNA methylation, histone modification, microRNA and long non-coding RNA expression, etc. The application of the twin method...

  1. The Danish political twin study

    DEFF Research Database (Denmark)

    Klemmensen, Robert; Hobolt, Sara B; Dinesen, Peter Thisted

    2012-01-01

    We compare a recent Danish twin survey on political attitudes and behaviors to a nationally representative survey covering similar topics. We find very similar means and variances for most of our constructed scales of political attitudes and behaviors in the two surveys, although even small...

  2. Black holes in a cubic Galileon universe

    Energy Technology Data Exchange (ETDEWEB)

    Babichev, E.; Charmousis, C.; Lehébel, A.; Moskalets, T., E-mail: eugeny.babichev@th.u-psud.fr, E-mail: christos.charmousis@th.u-psud.fr, E-mail: antoine.lehebel@th.u-psud.fr, E-mail: tetiana.moskalets@th.u-psud.fr [Laboratoire de Physique Théorique, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France)

    2016-09-01

    We find and study the properties of black hole solutions for a subclass of Horndeski theory including the cubic Galileon term. The theory under study has shift symmetry but not reflection symmetry for the scalar field. The Galileon is assumed to have linear time dependence characterized by a velocity parameter. We give analytic 3-dimensional solutions that are akin to the BTZ solutions but with a non-trivial scalar field that modifies the effective cosmological constant. We then study the 4-dimensional asymptotically flat and de Sitter solutions. The latter present three different branches according to their effective cosmological constant. For two of these branches, we find families of black hole solutions, parametrized by the velocity of the scalar field. These spherically symmetric solutions, obtained numerically, are different from GR solutions close to the black hole event horizon, while they have the same de-Sitter asymptotic behavior. The velocity parameter represents black hole primary hair.

  3. Expansion into lattice harmonics in cubic symmetries

    Science.gov (United States)

    Kontrym-Sznajd, G.

    2018-05-01

    On the example of a few sets of sampling directions in the Brillouin zone, this work shows how important the choice of the cubic harmonics is on the quality of approximation of some quantities by a series of such harmonics. These studies led to the following questions: (1) In the case that for a given l there are several independent harmonics, can one use in the expansion only one harmonic with a given l?; (2) How should harmonics be ordered: according to l or, after writing them in terms of (x4 + y4 + z4)n (x2y2z2)m, according to their degree q = n + m? To enable practical applications of such harmonics, they are constructed in terms of the associated Legendre polynomials up to l = 26. It is shown that electron momentum densities, reconstructed from experimental data for ErGa3 and InGa3, are described much better by harmonics ordered with q.

  4. Heteropagus twinning on back -- a case report.

    Science.gov (United States)

    Debnath, Bidyut; Biswas, Sumitra Kumar

    2011-07-01

    Heteropagus twins, also called parasitic twins, are malformation of the foetus where the development of one twin is incomplete. They are attached most commonly to the lower chest and upper abdomen. We report a case of heteropagus twin, where the parasite possessed well-formed limb as well as blind ending intestine. It was attached to the back of the host by a broad pedicle. We take this opportunity to classify areas of confusion prevailing regarding twinning, foetus in foetu, teratoma and caudal duplication.

  5. Quasi van der Waals epitaxy of copper thin film on single-crystal graphene monolayer buffer

    Science.gov (United States)

    Lu, Zonghuan; Sun, Xin; Washington, Morris A.; Lu, Toh-Ming

    2018-03-01

    Quasi van der Waals epitaxial growth of face-centered cubic Cu (~100 nm) thin films on single-crystal monolayer graphene is demonstrated using thermal evaporation at an elevated substrate temperature of 250 °C. The single-crystal graphene was transferred to amorphous (glass) and crystalline (quartz) SiO2 substrates for epitaxy study. Raman analysis showed that the thermal evaporation method had minimal damage to the graphene lattice during the Cu deposition. X-ray diffraction and electron backscatter diffraction analyses revealed that both Cu films are single-crystal with (1 1 1) out-of-plane orientation and in-plane Σ3 twin domains of 60° rotation. The crystallinity of the SiO2 substrates has a negligible effect on the Cu crystal orientation during the epitaxial growth, implying the strong screening effect of graphene. We also demonstrate the epitaxial growth of polycrystalline Cu on a commercial polycrystalline monolayer graphene consisting of two orientation domains offset 30° to each other. It confirms that the crystal orientation of the epitaxial Cu film follows that of graphene, i.e. the Cu film consists of two orientation domains offset 30° to each other when deposited on polycrystalline graphene. Finally, on the contrary to the report in the literature, we show that the direct current and radio frequency flip sputtering method causes significant damage to the graphene lattice during the Cu deposition process, and therefore neither is a suitable method for Cu epitaxial growth on graphene.

  6. Fetal growth disorders in twin gestations.

    LENUS (Irish Health Repository)

    Breathnach, Fionnuala M

    2012-06-01

    Twin growth is frequently mismatched. This review serves to explore the pathophysiologic mechanisms that underlie growth aberrations in twin gestations, the prenatal recognition of abnormal twin growth, and the critical importance of stratifying management of abnormal twin growth by chorionicity. Although poor in utero growth of both twins may reflect maternal factors resulting in global uteroplacental dysfunction, discordant twin growth may be attributed to differences in genetic potential between co-twins, placental dysfunction confined to one placenta only, or one placental territory within a shared placenta. In addition, twin-twin transfusion syndrome represents a distinct entity of which discordant growth is a common feature. Discordant growth is recognized as an independent risk factor for adverse perinatal outcome. Intertwin birth weight disparity of 18% or more should be considered to represent a discordance threshold, which serves as an independent risk factor for adverse perinatal outcome. At this cutoff, perinatal morbidity is found to increase both for the larger and the smaller twin within a discordant pair. There remains uncertainty surrounding the sonographic parameters that are most predictive of discordance. Although heightening of fetal surveillance in the face of discordant twin growth follows the principles applied to singleton gestations complicated by fetal growth restriction, the timing of intervention is largely influenced by chorionicity.

  7. Using Twins to Better Understand Sibling Relationships.

    Science.gov (United States)

    Mark, Katharine M; Pike, Alison; Latham, Rachel M; Oliver, Bonamy R

    2017-03-01

    We compared the nature of the sibling relationship in dyads of varying genetic relatedness, employing a behavioural genetic design to estimate the contribution that genes and the environment have on this familial bond. Two samples were used-the Sisters and Brothers Study consisted of 173 families with two target non-twin children (mean ages = 7.42 and 5.22 years respectively); and the Twins, Family and Behaviour study included 234 families with two target twin children (mean age = 4.70 years). Mothers and fathers reported on their children's relationship with each other, via a postal questionnaire (the Sisters and Brothers Study) or a telephone interview (the Twins, Family and Behaviour study). Contrary to expectations, no mean level differences emerged when monozygotic twin pairs, dizygotic twin pairs, and non-twin pairs were compared on their sibling relationship quality. Behavioural genetic analyses also revealed that the sibling bond was modestly to moderately influenced by the genetic propensities of the children within the dyad, and moderately to substantially influenced by the shared environment common to both siblings. In addition, for sibling negativity, we found evidence of twin-specific environmental influence-dizygotic twins showed more reciprocity than did non-twins. Our findings have repercussions for the broader application of results from future twin-based investigations.

  8. Solitons in quadratic nonlinear photonic crystals

    DEFF Research Database (Denmark)

    Corney, Joel Frederick; Bang, Ole

    2001-01-01

    We study solitons in one-dimensional quadratic nonlinear photonic crystals with modulation of both the linear and nonlinear susceptibilities. We derive averaged equations that include induced cubic nonlinearities, which can be defocusing, and we numerically find previously unknown soliton families....... Because of these induced cubic terms, solitons still exist even when the effective quadratic nonlinearity vanishes and conventional theory predicts that there can be no soliton. We demonstrate that both bright and dark forms of these solitons can propagate stably....

  9. Register-based research on twins

    DEFF Research Database (Denmark)

    Christensen, Kaare; Ohm Kyvik, Kirsten; Holm, Niels V

    2011-01-01

    Introduction: The Danish Twin Registry (DTR) has for more than 50 years been based on surveys and clinical investigations and over the two last decades also on register linkage. Currently these two approaches are merged within Statistics Denmark. Research topics: Here we report on three major...... groups of register-based research in the DTR that used the uniqueness of twinning. First, we focus on the ''long-term prognosis'' of being a twin compared with being a singleton and show that Danish twins have health trajectories in adulthood similar to singletons, which is a result of interest for twins...... illustrate how the co-twin control method in a register setting can be used to control for the effect of rearing environment and genetic factors in studies of the association between exposures and health. CONCLUSION: The spectrum of register-based twin studies is very wide and have changed in accordance...

  10. Spectral intensities in cubic systems. II. The MoCl{sub 6} {sup 3-} system in cubic elpasolite crystals

    Energy Technology Data Exchange (ETDEWEB)

    Acevedo, R. [Department of Basic Chemistry, Faculty of Physical and Mathematical Sciences, University of Chile. Tupper 2069. Casilla 2777, Santiago, Chile (Chile); Meruane, T. [Department of Chemistry. Universidad Metropolitana de Ciencias de la Educacion. Av. J.P. Alessandri 774, Casilla 147, C. Santiago, Chile (Chile); Poblete, V. [Department of Nuclear Materials, Lo Aguirre, Comision Chilena de Energia Nuclear. Amunategui 95, Casilla 188-D, Santiago, Chile (Chile)

    1998-12-01

    The visible and near infrared luminescence spectra of MoCl{sub 6} {sup 3-} in Cs{sub 2}NaMCl{sub 6} (M=Sc, Y, In) and MoBr{sub 6} {sup 3-} in Cs{sub 2}NaYBr{sub 6} have been reported between 15000 cm {sup -1} and 3000 cm {sup -1} at liquid helium temperatures. It has been observed that each electronic transition shows an extensive and rich vibronic structure, which can be analysed to yield the vibrational frequencies of the MoX{sub 6} {sup 3-} ion in each electronic state. A through analysis of the spectra for these systems, show that the vibrational frequencies associated with each of the electronic transition is almost identical. This is an evidence of a weak or rather negligible Jahn-Teller distortions. The spectra though are strongly influenced by resonant interactions among the MoX{sub 6} {sup 3-} ion and the internal and lattice modes of the host lattices and there is also a noticeable variation of the relative vibronic distributions of parity forbidden transitions assisted by the odd parity normal modes of vibrations. This present work deals with the most likely intensity mechanisms and a strategy is put forward to carry out explicit calculations for both, the electronic and vibrational factors of transitions of the kind {Gamma}{sub 1}{r_reversible} {Gamma}{sub 2} + v{sub k} for k=3, 4, and 6. Extension of this work to include the ion-phonon interaction is currently in progress in our laboratory. (Author)

  11. Is that me or my twin? Lack of self-face recognition advantage in identical twins.

    Directory of Open Access Journals (Sweden)

    Matteo Martini

    Full Text Available Despite the increasing interest in twin studies and the stunning amount of research on face recognition, the ability of adult identical twins to discriminate their own faces from those of their co-twins has been scarcely investigated. One's own face is the most distinctive feature of the bodily self, and people typically show a clear advantage in recognizing their own face even more than other very familiar identities. Given the very high level of resemblance of their faces, monozygotic twins represent a unique model for exploring self-face processing. Herein we examined the ability of monozygotic twins to distinguish their own face from the face of their co-twin and of a highly familiar individual. Results show that twins equally recognize their own face and their twin's face. This lack of self-face advantage was negatively predicted by how much they felt physically similar to their co-twin and by their anxious or avoidant attachment style. We speculate that in monozygotic twins, the visual representation of the self-face overlaps with that of the co-twin. Thus, to distinguish the self from the co-twin, monozygotic twins have to rely much more than control participants on the multisensory integration processes upon which the sense of bodily self is based. Moreover, in keeping with the notion that attachment style influences perception of self and significant others, we propose that the observed self/co-twin confusion may depend upon insecure attachment.

  12. Twin Research and the Arts: Interconnections / Twin Research: Twin Studies of Sexual Orientation; A Historical Biological Twin Gem; GWAS Approach to Who Has Twins / Newsworthy: Twins on College Campuses; 'Brainprint': Personal Identification by Brain Waves.

    Science.gov (United States)

    Segal, Nancy L

    2016-08-01

    The interrelatedness between twin research and the arts is explored via a new play about a famous case. In the 1960s, identical twin David Bruce Reimer was accidentally castrated as an infant during circumcision to correct a urinary problem. The decision to raise him as a girl, and the consequences of that decision, are explored in the new theatrical production of Boy. Other examples of the arts mirroring science, and vice versa, are described. Next, brief reviews and summaries of twin research on sexual orientation, 1860s' knowledge of placental arrangements and twinning mechanisms, and genes underlying multiple birth conception and fertility related measures are provided. This article concludes with a look at twins on college campuses and the identification of individuals by their brain waves. A correction and clarification regarding my article on the Brazilian Twin Registry in the last issue of THG (Segal, 2016) is also provided.

  13. Modelling the motion of {112-bar 2} twinning dislocations in the HCP metals

    International Nuclear Information System (INIS)

    Serra, A.; Bacon, D.J.

    2005-01-01

    Deformation twinning is important for plasticity of the hcp metals, but little is known about the dynamics of the mechanisms that control twin boundary motion. With the exception of the {112-bar 1} twin, atomic shuffles are required for glide of twinning dislocations and hence boundary movement is temperature-dependent. A computer method has been developed to simulate a step with dislocation character in a boundary with full periodicity in the boundary plane, i.e. along both the direction of the line of the defect and its direction of motion. It may be used to investigate the properties of such interfaces as the defects in them move over large distances. We explain the nature of the method and apply it to study the motion of twinning dislocations in the {112-bar 2} boundary as a function of applied stress and temperature. A new reaction at the boundary leading to the creation of a (c+a) crystal dislocation and a {112-bar 1} micro-twin is described

  14. Ventricular strain changes in monochorionic twins with and without twin-to-twin transfusion syndrome.

    Science.gov (United States)

    Taylor-Clarke, Marisa C; Matsui, Hikoro; Roughton, Michael; Wimalasundera, Ruwan C; Gardiner, Helena M

    2013-06-01

    The objective of the study was to investigate whether vector velocity imaging (VVI), a non-Doppler speckle tracking ultrasound technology, is feasible in twin pregnancies and can aid management of twin-twin transfusion syndrome (TTTS). Twenty-seven women pregnant with monochorionic diamniotic twins affected by TTTS and 28 monochorionic pregnancies that did not develop TTTS were included in a prospective case-control study at a fetal medicine center. Fetal echocardiograms were recorded with dummy electrocardiography to retain original frame rates when exported for offline speckle tracking analysis using Syngo-VVI software (Siemens Corp, Munich, Germany). Right and left ventricular (LV) free wall Lagrangian strain was measured from the original coordinates. Within-twin pair ventricular strain differences including relationship to Quintero staging and response to laser therapy for TTTS were analyzed by Wilcoxon signed-rank test. The VVI strain measurements could be analyzed in 182 of 200 TTTS and 96 of 112 non-TTTS control ventricles. Within-pair strain was concordant in non-TTTS controls. Recipient LV strain was reduced at all Quintero stages compared with donors (P < .01). Recipient right ventricular strain was reduced only in stages 3 and 4 (P < .01). Strain improved at a median of 2 weeks following successful laser therapy. Intertwin differences in strain were independent of weight discordance. Recipient LV strain is reduced in stages 1 and 2 TTTS. Within-pair strain discordance may distinguish early TTTS from growth discordance and guide timing of and management following treatment. Copyright © 2013 Mosby, Inc. All rights reserved.

  15. Structural defects in cubic semiconductors characterized by aberration-corrected scanning transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arroyo Rojas Dasilva, Yadira; Kozak, Roksolana; Erni, Rolf; Rossell, Marta D., E-mail: marta.rossell@empa.ch

    2017-05-15

    The development of new electro-optical devices and the realization of novel types of transistors require a profound understanding of the structural characteristics of new semiconductor heterostructures. This article provides a concise review about structural defects which occur in semiconductor heterostructures on the basis of micro-patterned Si substrates. In particular, one- and two-dimensional crystal defects are being discussed which are due to the plastic relaxation of epitaxial strain caused by the misfit of crystal lattices. Besides a few selected examples from literature, we treat in particular crystal defects occurring in GaAs/Si, Ge/Si and β-SiC/Si structures which are studied by high-resolution annular dark-field scanning transmission electron microscopy. The relevance of this article is twofold; firstly, it should provide a collection of data which are of help for the identification and characterization of defects in cubic semiconductors by means of atomic-resolution imaging, and secondly, the experimental data shall provide a basis for advancing the understanding of device characteristics with the aid of theoretical modelling by considering the defective nature of strained semiconductor heterostructures. - Highlights: • The heterogeneous integration of high-quality compound semiconductors remains a challenge. • Lattice defects cause severe degradation of the semiconductor device performances. • Aberration-corrected HAADF-STEM allows atomic-scale characterization of defects. • An overview of lattice defects found in cubic semiconductors is presented. • Theoretical modelling and calculations are needed to determine the defect properties.

  16. Fingerprint recognition with identical twin fingerprints.

    Science.gov (United States)

    Tao, Xunqiang; Chen, Xinjian; Yang, Xin; Tian, Jie

    2012-01-01

    Fingerprint recognition with identical twins is a challenging task due to the closest genetics-based relationship existing in the identical twins. Several pioneers have analyzed the similarity between twins' fingerprints. In this work we continue to investigate the topic of the similarity of identical twin fingerprints. Our study was tested based on a large identical twin fingerprint database that contains 83 twin pairs, 4 fingers per individual and six impressions per finger: 3984 (83*2*4*6) images. Compared to the previous work, our contributions are summarized as follows: (1) Two state-of-the-art fingerprint identification methods: P071 and VeriFinger 6.1 were used, rather than one fingerprint identification method in previous studies. (2) Six impressions per finger were captured, rather than just one impression, which makes the genuine distribution of matching scores more realistic. (3) A larger sample (83 pairs) was collected. (4) A novel statistical analysis, which aims at showing the probability distribution of the fingerprint types for the corresponding fingers of identical twins which have same fingerprint type, has been conducted. (5) A novel analysis, which aims at showing which finger from identical twins has higher probability of having same fingerprint type, has been conducted. Our results showed that: (a) A state-of-the-art automatic fingerprint verification system can distinguish identical twins without drastic degradation in performance. (b) The chance that the fingerprints have the same type from identical twins is 0.7440, comparing to 0.3215 from non-identical twins. (c) For the corresponding fingers of identical twins which have same fingerprint type, the probability distribution of five major fingerprint types is similar to the probability distribution for all the fingers' fingerprint type. (d) For each of four fingers of identical twins, the probability of having same fingerprint type is similar.

  17. Fingerprint recognition with identical twin fingerprints.

    Directory of Open Access Journals (Sweden)

    Xunqiang Tao

    Full Text Available Fingerprint recognition with identical twins is a challenging task due to the closest genetics-based relationship existing in the identical twins. Several pioneers have analyzed the similarity between twins' fingerprints. In this work we continue to investigate the topic of the similarity of identical twin fingerprints. Our study was tested based on a large identical twin fingerprint database that contains 83 twin pairs, 4 fingers per individual and six impressions per finger: 3984 (83*2*4*6 images. Compared to the previous work, our contributions are summarized as follows: (1 Two state-of-the-art fingerprint identification methods: P071 and VeriFinger 6.1 were used, rather than one fingerprint identification method in previous studies. (2 Six impressions per finger were captured, rather than just one impression, which makes the genuine distribution of matching scores more realistic. (3 A larger sample (83 pairs was collected. (4 A novel statistical analysis, which aims at showing the probability distribution of the fingerprint types for the corresponding fingers of identical twins which have same fingerprint type, has been conducted. (5 A novel analysis, which aims at showing which finger from identical twins has higher probability of having same fingerprint type, has been conducted. Our results showed that: (a A state-of-the-art automatic fingerprint verification system can distinguish identical twins without drastic degradation in performance. (b The chance that the fingerprints have the same type from identical twins is 0.7440, comparing to 0.3215 from non-identical twins. (c For the corresponding fingers of identical twins which have same fingerprint type, the probability distribution of five major fingerprint types is similar to the probability distribution for all the fingers' fingerprint type. (d For each of four fingers of identical twins, the probability of having same fingerprint type is similar.

  18. Nanoscale characterization of the evolution of the twin–matrix orientation in Fe–Mn–C twinning-induced plasticity steel by means of transmission electron microscopy orientation mapping

    International Nuclear Information System (INIS)

    Albou, A.; Galceran, M.; Renard, K.; Godet, S.; Jacques, P.J.

    2013-01-01

    The evolution of the orientation relationship between mechanical twins and the surrounding matrix with the degree of plastic deformation has been characterized at the nanoscale in twinning-induced plasticity steel. The recently developed automated crystal orientation mapping in transmission electron microscopy revealed that the ideal twin relationship is retained up to large levels of strain, while large orientation gradients are built up within the matrix. This particular evolution undoubtedly plays a role in the large work hardening rate of these steels.

  19. Complete three-dimensional photonic bandgap in a simple cubic structure

    International Nuclear Information System (INIS)

    Lin, Shawn-Yu; Fleming, J. G.; Lin, Robin; Sigalas, M. M.; Biswas, R.; Ho, K. M.

    2001-01-01

    The creation of a three-dimensional (3D) photonic crystal with simple cubic (sc) symmetry is important for applications in the signal routing and 3D waveguiding of light. With a simple stacking scheme and advanced silicon processing, a 3D sc structure was constructed from a 6-in. silicon wafer. The sc structure is experimentally shown to have a complete 3D photonic bandgap in the infrared wavelength. The finite size effect is also observed, accounting for a larger absolute photonic bandgap

  20. Growth of InAs Wurtzite Nanocrosses from Hexagonal and Cubic Basis

    DEFF Research Database (Denmark)

    Krizek, Filip; Kanne, Thomas; Razmadze, Davydas

    2017-01-01

    . Two methods use conventional wurtzite nanowire arrays as a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the 2-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc blende in the center of the nanocrosses. We show......Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanism...

  1. Identical twins in forensic genetics

    DEFF Research Database (Denmark)

    Tvedebrink, Torben; Morling, Niels

    2015-01-01

    The increase in the number of forensic genetic loci used for identification purposes results in infinitesimal random match probabilities. These probabilities are computed under assumptions made for rather simple population genetic models. Often, the forensic expert reports likelihood ratios, where...... published results accounting for close familial relationships. However, we revisit the discussion to increase the awareness among forensic genetic practitioners and include new information on medical and societal factors to assess the risk of not considering a monozygotic twin as the true perpetrator......, then data relevant for the Danish society suggests that the threshold of likelihood ratios should approximately be between 150,000 and 2,000,000 in order to take the risk of an unrecognised identical, monozygotic twin into consideration. In other societies, the threshold of the likelihood ratio in crime...

  2. Mesostructured germanium with cubic pore symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Armatas, G S; Kanatzidis, M G [Michigan State Univ., Michigan (United States), Dept. of Chemistry

    2006-11-15

    Regular mesoporous oxide materials have been widely studied and have a range of potential applications, such as catalysis, absorption and separation. They are not generally considered for their optical and electronic properties. Elemental semiconductors with nanopores running through them represent a different form of framework material with physical characteristics contrasting with those of the more conventional bulk, thin film and nanocrystalline forms. Here we describe cubic meso structured germanium, MSU-Ge-l, with gyroidal channels containing surfactant molecules, separated by amorphous walls that lie on the gyroid (G) minimal surface as in the mesoporous silica MCM-48. Although Ge is a high-meltin covalent semiconductor that is difficult to prepare from solution polymerization, we succeeded in assembling a continuous Ge network using a suitable precursor for Ge{sup 4-} atoms. Our results indicate that elemental semiconductors from group 14 of the periodic table can be made to adopt meso structured forms such as MSU-Ge-1, which features two three-dimensional labyrinthine tunnels obeying la3d space group symmetry and separated by a continuous germanium minimal surface that is otherwise amorphous. A consequence of this new structure for germanium, which has walls only one nanometre thick, is a wider electronic energy bandgap (1.4 eV versus 0.66 eV) than has crystalline or amorphous Ge. Controlled oxidation of MSU-Ge-1 creates a range of germanium suboxides with continuously varying Ge:O ratio and a smoothly increasing energy gap. (author)

  3. Topological Oxide Insulator in Cubic Perovskite Structure

    Science.gov (United States)

    Jin, Hosub; Rhim, Sonny H.; Im, Jino; Freeman, Arthur J.

    2013-01-01

    The emergence of topologically protected conducting states with the chiral spin texture is the most prominent feature at the surface of topological insulators. On the application side, large band gap and high resistivity to distinguish surface from bulk degrees of freedom should be guaranteed for the full usage of the surface states. Here, we suggest that the oxide cubic perovskite YBiO3, more than just an oxide, defines itself as a new three-dimensional topological insulator exhibiting both a large bulk band gap and a high resistivity. Based on first-principles calculations varying the spin-orbit coupling strength, the non-trivial band topology of YBiO3 is investigated, where the spin-orbit coupling of the Bi 6p orbital plays a crucial role. Taking the exquisite synthesis techniques in oxide electronics into account, YBiO3 can also be used to provide various interface configurations hosting exotic topological phenomena combined with other quantum phases. PMID:23575973

  4. A Diagram of the Structure Evolution of Pb(Zn1/3Nb2/3 O3-9%PbTiO3 Relaxor Ferroelectric Crystals with Excellent Piezoelectric Properties

    Directory of Open Access Journals (Sweden)

    Hua Zhou

    2017-05-01

    Full Text Available Piezoelectric properties are of significant importance to medical ultrasound, actuators, sensors, and countless other device applications. The mechanism of piezoelectric properties can be deeply understood in light of structure evolutions. In this paper, we report a diagram of the structure evolutions of Pb(Zn1/3Nb2/30.91Ti0.09O3 (PZN-9PT crystals with excellent piezoelectric properties among orthorhombic, tetragonal, and cubic phases, with a temperature increasing from room temperature to 220 °C. Through fitting the temperature-dependent XRD curves with Gauss and Lorenz functions, we obtained the evolutions of the content ratio of three kinds of phases (orthorhombic, tetragonal and cubic and the lattice parameters of the PZN-9PT system with the changes of temperature. The XRD fitting results together with Raman and dielectric spectra show that the phase transitions of PZN-9PT are a typical continuous evolution process. Additionally, resonance and anti-resonance spectra show the excellent piezoelectric properties of these crystals, which probably originate from the nano twin domains, as demonstrated by TEM images. Of particular attention is that the thickness electromechanical coupling factor kt is up to 72%.

  5. Einstein and the twin paradox

    International Nuclear Information System (INIS)

    Pesic, Peter

    2003-01-01

    Einstein was the first to discuss and resolve the 'twin paradox', which in 1905 he did not consider paradoxical and treated as a consequence of lack of simultaneity. He maintained this view until at least 1914. However, in 1918 Einstein brought forward arguments about accelerated frames of reference that tended to overshadow his initial resolution. His earlier arguments were gradually rediscovered during the subsequent controversy about this 'paradox'

  6. Ectodermal dysplasia in identical twins

    OpenAIRE

    Puttaraju, Gurkar Haraswarupa; Visveswariah, Paranjyothi Magadi

    2013-01-01

    Hereditary hypohidrotic ectodermal dysplasia (HED) is typically inherited as an X-linked recessive trait, characterized by deformity of at least two or more of the ectodermal structures - hair, teeth, nails and sweat glands. Two cases of hereditary HED involving identical male twins, is being documented for the rarity of its occurrence with special attention given to genetics, pathophysiology, clinical, intraoral manifestations and to the methods to improve the masticatory function, the facia...

  7. Nonsymmorphic cubic Dirac point and crossed nodal rings across the ferroelectric phase transition in LiOsO3

    Science.gov (United States)

    Yu, Wing Chi; Zhou, Xiaoting; Chuang, Feng-Chuan; Yang, Shengyuan A.; Lin, Hsin; Bansil, Arun

    2018-05-01

    Crystalline symmetries can generate exotic band-crossing features, which can lead to unconventional fermionic excitations with interesting physical properties. We show how a cubic Dirac point—a fourfold-degenerate band-crossing point with cubic dispersion in a plane and a linear dispersion in the third direction—can be stabilized through the presence of a nonsymmorphic glide mirror symmetry in the space group of the crystal. Notably, the cubic Dirac point in our case appears on a threefold axis, even though it has been believed previously that such a point can only appear on a sixfold axis. We show that a cubic Dirac point involving a threefold axis can be realized close to the Fermi level in the nonferroelectric phase of LiOsO3. Upon lowering temperature, LiOsO3 has been shown experimentally to undergo a structural phase transition from the nonferroelectric phase to the ferroelectric phase with spontaneously broken inversion symmetry. Remarkably, we find that the broken symmetry transforms the cubic Dirac point into three mutually crossed nodal rings. There also exist several linear Dirac points in the low-energy band structure of LiOsO3, each of which is transformed into a single nodal ring across the phase transition.

  8. Bifurcation of limit cycles for cubic reversible systems

    Directory of Open Access Journals (Sweden)

    Yi Shao

    2014-04-01

    Full Text Available This article is concerned with the bifurcation of limit cycles of a class of cubic reversible system having a center at the origin. We prove that this system has at least four limit cycles produced by the period annulus around the center under cubic perturbations

  9. Kinks in systems with cubic and quartic anharmonicity

    International Nuclear Information System (INIS)

    Kashcheev, V.N.

    1988-01-01

    For a classical system of interacting particles with on-site cubic or quartic anharmonicity explicit analytic solutions of the d'Alembert equation are obtained in the form of kinks in the presence of dissipation (viscous or Rayleigh) and a constant force. These kinks will be asymptotically stable in the case of quartic anharmonicity and unstable in the case cubic anharmonicity

  10. Two-energy twin image removal in atomic-resolution x-ray holography

    International Nuclear Information System (INIS)

    Nishino, Y.; Ishikawa, T.; Hayashi, K.; Takahashi, Y.; Matsubara, E.

    2002-01-01

    We propose a two-energy twin image removal algorithm for atomic-resolution x-ray holography. The validity of the algorithm is shown in a theoretical simulation and in an experiment of internal detector x-ray holography using a ZnSe single crystal. The algorithm, compared to the widely used multiple-energy algorithm, allows efficient measurement of holograms, and is especially important when the available x-ray energies are fixed. It enables twin image free holography using characteristic x rays from laboratory generators and x-ray pulses of free-electron lasers

  11. The Spread of Substance Use and Delinquency between Adolescent Twins

    Science.gov (United States)

    Laursen, Brett; Hartl, Amy C.; Vitaro, Frank; Brendgen, Mara; Dionne, Ginette; Boivin, Michel

    2017-01-01

    This investigation examines the spread of problem behaviors (substance use and delinquency) between twin siblings. A sample of 628 twins (151 male twin pairs and 163 female twin pairs) drawn from the Quebec Newborn Twin Study completed inventories describing delinquency and substance use at ages 13, 14, and 15. A 3-wave longitudinal actor-partner…

  12. A Powerful Twin Arrives

    Science.gov (United States)

    1999-11-01

    First Images from FORS2 at VLT KUEYEN on Paranal The first, major astronomical instrument to be installed at the ESO Very Large Telescope (VLT) was FORS1 ( FO cal R educer and S pectrograph) in September 1998. Immediately after being attached to the Cassegrain focus of the first 8.2-m Unit Telescope, ANTU , it produced a series of spectacular images, cf. ESO PR 14/98. Many important observations have since been made with this outstanding facility. Now FORS2 , its powerful twin, has been installed at the second VLT Unit Telescope, KUEYEN . It is the fourth major instrument at the VLT after FORS1 , ISAAC and UVES.. The FORS2 Commissioning Team that is busy installing and testing this large and complex instrument reports that "First Light" was successfully achieved already on October 29, 1999, only two days after FORS2 was first mounted at the Cassegrain focus. Since then, various observation modes have been carefully tested, including normal and high-resolution imaging, echelle and multi-object spectroscopy, as well as fast photometry with millisecond time resolution. A number of fine images were obtained during this work, some of which are made available with the present Press Release. The FORS instruments ESO PR Photo 40a/99 ESO PR Photo 40a/99 [Preview - JPEG: 400 x 345 pix - 203k] [Normal - JPEG: 800 x 689 pix - 563kb] [Full-Res - JPEG: 1280 x 1103 pix - 666kb] Caption to PR Photo 40a/99: This digital photo shows the twin instruments, FORS2 at KUEYEN (in the foreground) and FORS1 at ANTU, seen in the background through the open ventilation doors in the two telescope enclosures. Although they look alike, the two instruments have specific functions, as described in the text. FORS1 and FORS2 are the products of one of the most thorough and advanced technological studies ever made of a ground-based astronomical instrument. They have been specifically designed to investigate the faintest and most remote objects in the universe. They are "multi-mode instruments" that

  13. Twin-Telescope Wettzell (TTW)

    Science.gov (United States)

    Hase, H.; Dassing, R.; Kronschnabl, G.; Schlüter, W.; Schwarz, W.; Lauber, P.; Kilger, R.

    2007-07-01

    Following the recommendations made by the VLBI2010 vision report of the IVS, a proposal has been made to construct a Twin Telescope for the Fundamental Station Wettzell in order to meet the future requirements of the next VLBI generation. The Twin Telescope consists of two identical radiotelescopes. It is a project of the Federal Agency for Cartography and Geodesy (BKG). This article summarizes the project and some design ideas for the Twin-Telescope. %ZALMA (2005). Technical Specification for Design, Manufacturing, Transport and Integration on Site of the ALMA ANTENNAS, Doc. ALMA-34.00.00.00.006-BSPE. Behrend, D. (2006). VLBI2010 Antenna Specs, Data sheet. DeBoer, D. (2001). The ATA Offset Gregorian Antenna, ATA Memo #16, February 10. Imbriale, W.A. (2006). Design of a Wideband Radio Telescope, Jet Propulsion Laboratory and S. Weinreb and H. Mandi, California Institute of Technology. Kilger, R. (2007). TWIN-Design studies, Presentation for the IVS board members (internal document),Wettzell. Kronschnabl, G. (2006). Subject: Memo from Bill Petrachenko, E-mail to the Twin-Working Group (in German), July. Lindgren, ETS-Lindgren (2005). The Model 3164-05 Open Boundary Quadridge Horn, Data Sheet. Niell, A., A. Whitney, W. Petrachenko, W. Schlüter, N. Vandenberg, H.Hase, Y. Koyama, C. Ma, H. Schuh, G. Tucari (2006). in: IVS Annual Report 2005, pg. 13-40, NASA/TP-2006-214136, April. Olsson, R., Kildal, P.-S., and Weinreb, S. (2006). IEEE Transactions on Antennas and Propagation, Vol. 54, No. 2, February. Petrachenko, B. (2006). The Case For and Against Multiple Antennas at a Site, IVS Memorandum, 2006-019v01. Petrachenko, B. (2006). IVS Memorandum, 2006-016v01. RFSpin (2004). Double Ridged Waveguide Horn-Model DRH20, Antenna Specifications, Data Sheet. Rohde&Schwarz (2004). SHF Antennas Crossed Log- Periodic Antennas HL024A1/S1, Data Sheet. Rohde&Schwarz (2004). SHF Antennas Log-Periodic Antennas HL050/HL050S1, Data Sheet. Rogers, A.E.E. (2006). Simulations of broadband

  14. Anaesthesia for the separation of conjoined twins

    Directory of Open Access Journals (Sweden)

    Jaya Lalwani

    2011-01-01

    Full Text Available Thoraco-omphalopagus is one of the most common type of conjoint twins accounting for 74% cases of conjoint twins. We report the anaesthetic management for successful separation of thoraco-omphalopagus conjoint twins, both of them surviving till date. We highlight the responsibility of anaesthesia team in anaesthetising the two individual patients simultaneously, need of careful monitoring and anticipation of complications like massive blood loss, hypotension, hypokalemia, hypoxia and hypercabia. Detailed description of successful management is reported.

  15. Gene-Environment Interplay in Twin Models

    OpenAIRE

    Verhulst, Brad; Hatemi, Peter K.

    2013-01-01

    In this article, we respond to Shultziner’s critique that argues that identical twins are more alike not because of genetic similarity, but because they select into more similar environments and respond to stimuli in comparable ways, and that these effects bias twin model estimates to such an extent that they are invalid. The essay further argues that the theory and methods that undergird twin models, as well as the empirical studies which rely upon them, are unaware of these potential biases...

  16. Exotic quarks in Twin Higgs models

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Hsin-Chia [Department of Physics, University of California, Davis,One Shields Avenue, Davis, CA 95616 (United States); Jung, Sunghoon [School of Physics, Korea Institute for Advanced Study,85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); SLAC National Accelerator Laboratory,2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Salvioni, Ennio [Department of Physics, University of California, Davis,One Shields Avenue, Davis, CA 95616 (United States); Tsai, Yuhsin [Department of Physics, University of California, Davis,One Shields Avenue, Davis, CA 95616 (United States); Maryland Center for Fundamental Physics,Department of Physics, University of Maryland,College Park, MD 20742 (United States)

    2016-03-14

    The Twin Higgs model provides a natural theory for the electroweak symmetry breaking without the need of new particles carrying the standard model gauge charges below a few TeV. In the low energy theory, the only probe comes from the mixing of the Higgs fields in the standard model and twin sectors. However, an ultraviolet completion is required below ∼ 10 TeV to remove residual logarithmic divergences. In non-supersymmetric completions, new exotic fermions charged under both the standard model and twin gauge symmetries have to be present to accompany the top quark, thus providing a high energy probe of the model. Some of them carry standard model color, and may therefore be copiously produced at current or future hadron colliders. Once produced, these exotic quarks can decay into a top together with twin sector particles. If the twin sector particles escape the detection, we have the irreducible stop-like signals. On the other hand, some twin sector particles may decay back into the standard model particles with long lifetimes, giving spectacular displaced vertex signals in combination with the prompt top quarks. This happens in the Fraternal Twin Higgs scenario with typical parameters, and sometimes is even necessary for cosmological reasons. We study the potential displaced vertex signals from the decays of the twin bottomonia, twin glueballs, and twin leptons in the Fraternal Twin Higgs scenario. Depending on the details of the twin sector, the exotic quarks may be probed up to ∼ 2.5 TeV at the LHC and beyond 10 TeV at a future 100 TeV collider, providing a strong test of this class of ultraviolet completions.

  17. Numerical Simulation of Twin Nozzle Injectors

    OpenAIRE

    Milak, Dino

    2015-01-01

    Fuel injectors for marine applications have traditionally utilized nozzles with symmetric equispaced orifice configuration. But in light of the new marine emission legislations the twin nozzle concept has arisen. The twin nozzle differs from the conventional configuration by utilizing two closely spaced orifices to substitute each orifice in the conventional nozzle. Injector manufacturers regard twin nozzle injectors as a promising approach to facilitate stable spray patterns independent of t...

  18. Bilateral Norrie's disease in identical twins.

    OpenAIRE

    Sukumaran, K

    1991-01-01

    A case of Norrie's disease in an identical twins is reported. No positive family history was obtained. The couple had no other children. The older of the twins died at the age of 9 months of uncertain cause. To the best of my knowledge this is the first case of Norrie's disease reported in Malaysia. And its occurrence in an identical twins is very rare.

  19. Dental twinning anomalies: the nomenclature enigma.

    Science.gov (United States)

    Killian, C M; Croll, T P

    1990-07-01

    Dental twinning results from abnormal events in the embryologic development of teeth. This paper describes the impossibility of assigning precise diagnostic terms, such as germination, fusion, macrodontia, and concrescence, to dental twinning anomalies because the entire course of odontogenesis cannot be witnessed. Traditional nomenclature is reviewed and seven cases that exemplify the principle are presented. Modification of nomenclature to describe dental twinning defects is suggested.

  20. Optical characterisation of cubic silicon carbide

    International Nuclear Information System (INIS)

    Jackson, S.M.

    1998-09-01

    The varied properties of Silicon Carbide (SiC) are helping to launch the material into many new applications, particularly in the field of novel semiconductor devices. In this work, the cubic form of SiC is of interest as a basis for developing integrated optical components. Here, the formation of a suitable SiO 2 buried cladding layer has been achieved by high dose oxygen ion implantation. This layer is necessary for the optical confinement of propagating light, and hence optical waveguide fabrication. Results have shown that optical propagation losses of the order of 20 dB/cm are obtainable. Much of this loss can be attributed to mode leakage and volume scattering. Mode leakage is a function of the effective oxide thickness, and volume scattering related to the surface layer damage. These parameters have been shown to be controllable and so suggests that further reduction in the waveguide loss is feasible. Analysis of the layer growth mechanism by RBS, XTEM and XPS proves that SiO 2 is formed, and that the extent, of formation depends on implant dose and temperature. The excess carbon generated is believed to exit the oxide layer by a number of varying mechanisms. The result of this appears to be a number of stable Si-C-O intermediaries that, form regions to either depth extreme of the SiO 2 layer. Early furnace tests suggest a need to anneal at, temperatures approaching the melting point of the silicon substrate, and that the quality of the virgin material is crucial in controlling the resulting oxide growth. (author)

  1. Neutron Dose Measurement Using a Cubic Moderator

    International Nuclear Information System (INIS)

    Sheinfeld, M.; Mazor, T.; Cohen, Y.; Kadmon, Y.; Orion, I.

    2014-01-01

    The Bonner Sphere Spectrometer (BSS), introduced In July 1960 by a research group from Rice University, Texas, is a major approach to neutron spectrum estimation. The BSS, also known as multi-sphere spectrometer, consists of a set of a different diameters polyethylene spheres, carrying a small LiI(Eu) scintillator in their center. What makes this spectrometry method such widely used, is its almost isotropic response, covering an extraordinary wide range of energies, from thermal up to even hundreds of MeVs. One of the most interesting and useful consequences of the above study is the 12'' sphere characteristics, as it turned out that the response curve of its energy dependence, have a similar shape compared with the neutron's dose equivalent as a function of energy. This inexplicable and happy circumstance makes it virtually the only monitoring device capable providing realistic neutron dose estimates over such a wide energy range. However, since the detection mechanism is not strictly related to radiation dose, one can expect substantial errors when applied to widely different source conditions. Although the original design of the BSS included a small 4mmx4mmO 6LiI(Eu) scintillator, other thermal neutron detectors has been used over the years: track detectors, activation foils, BF3 filled proportional counters, etc. In this study we chose a Boron loaded scintillator, EJ-254, as the thermal neutron detector. The neutron capture reaction on the boron has a Q value of 2.78 MeV of which 2.34 MeV is shared by the alpha and lithium particles. The high manufacturing costs, the encasement issue, the installation efficiency and the fabrication complexity, led us to the idea of replacing the sphere with a cubic moderator. This article describes the considerations, as well as the Monte-Carlo simulations done in order to examine the applicability of this idea

  2. Twin Loss: Implications for Counselors Working with Surviving Twins.(practice & Theory)

    Science.gov (United States)

    Withrow, Rebecca; Schwiebert, Valerie L.

    2005-01-01

    Multiple births are becoming increasingly prevalent due to the use of fertility drugs and women choosing to wait until later life to conceive. With the growth in the twin population, little research has been done to investigate the effects on the grief process when 1 twin dies. Counselors must understand the unique experience of twins to formulate…

  3. Photonic crystal fiber design for broadband directional coupling

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Bang, Ole; Bjarklev, Anders Overgaard

    2004-01-01

    A novel design for a broadband directional coupler based on a photonic crystal fiber is investigated numerically. It is shown that suitable index-depressing doping of the core regions in an index-guiding twin-core photonic crystal fiber can stabilize the coupling coefficient between the cores over...

  4. Crystallographic cut that maximizes of the birefringence in photorefractive crystals

    OpenAIRE

    Rueda-Parada, Jorge Enrique

    2017-01-01

    The electro-optical birefringence effect depends on the crystal type, cut crystal, applied electric field and the incidence direction of light on the principal crystal faces. It is presented a study of maximizing the birefringence in photorefractive crystals of cubic crystallographic symmetry, in terms of these three parameters. General analytical expressions for the birefringence were obtained, from which birefringence can be established for any type of cut. A new crystallographic cut was en...

  5. Problem in twin pregnancy: Findings of prenatal sonography and autopsy

    International Nuclear Information System (INIS)

    Kim, Jeong Ah; Cho, Jeong Yeon; Song, Mi Jin; Min, Jee Yeon; Lee, Young Ho; Lee, Hak Jong; Chun, Yi Kyeong; Kim, Yee Jeong; Hong, Sung Ran

    2001-01-01

    Multifetal gestations are high risk pregnancies with higher perinatal morbidity and mortality. Multifetal gestations are subject to unique complications including conjoined twins, twin-to-twin transfusion syndrome (TTTS), acardiac twins, twin embization of co-twin demise and heterotopic pregnancies. Prenatal sonographic diagnosis of types and complications of multifetal gestations is important for antenatal care and prediction of fetal outcome. This study was performed to present the prenatal ultrasonographic findings and pathologic findings of the unique complications of twin pregnancy. Acardia is a lethal anomaly occurring in 1% of monozygotic twin. The acardiac twin has a parasitic existence and depends on the donor (pump) twin for its blood supply via placental anastomoses and retrograde perfusion of umbilical cord. This twin reversed arterial perfusion (TRAP) sequence is a most extreme manifestation on the TTTS. Doppler verification reversed flow in umbilical cord of the acardiac twin confirms the diagnosis.

  6. Shape Preserving Interpolation Using C2 Rational Cubic Spline

    Directory of Open Access Journals (Sweden)

    Samsul Ariffin Abdul Karim

    2016-01-01

    Full Text Available This paper discusses the construction of new C2 rational cubic spline interpolant with cubic numerator and quadratic denominator. The idea has been extended to shape preserving interpolation for positive data using the constructed rational cubic spline interpolation. The rational cubic spline has three parameters αi, βi, and γi. The sufficient conditions for the positivity are derived on one parameter γi while the other two parameters αi and βi are free parameters that can be used to change the final shape of the resulting interpolating curves. This will enable the user to produce many varieties of the positive interpolating curves. Cubic spline interpolation with C2 continuity is not able to preserve the shape of the positive data. Notably our scheme is easy to use and does not require knots insertion and C2 continuity can be achieved by solving tridiagonal systems of linear equations for the unknown first derivatives di, i=1,…,n-1. Comparisons with existing schemes also have been done in detail. From all presented numerical results the new C2 rational cubic spline gives very smooth interpolating curves compared to some established rational cubic schemes. An error analysis when the function to be interpolated is ft∈C3t0,tn is also investigated in detail.

  7. First-principles study of nitrogen doping in cubic and amorphous Ge2Sb2Te5

    Science.gov (United States)

    Caravati, S.; Colleoni, D.; Mazzarello, R.; Kühne, T. D.; Krack, M.; Bernasconi, M.; Parrinello, M.

    2011-07-01

    We investigated the structural, electronic and vibrational properties of amorphous and cubic Ge2Sb2Te5 doped with N at 4.2 at.% by means of large scale ab initio simulations. Nitrogen can be incorporated in molecular form in both the crystalline and amorphous phases at a moderate energy cost. In contrast, insertion of N in the atomic form is very energetically costly in the crystalline phase, though it is still possible in the amorphous phase. These results support the suggestion that N segregates at the grain boundaries during the crystallization of the amorphous phase, resulting in a reduction in size of the crystalline grains and an increased crystallization temperature.

  8. 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.

  9. Tensile deformation behavior and deformation twinning of an equimolar CoCrFeMnNi high-entropy alloy

    Energy Technology Data Exchange (ETDEWEB)

    Joo, S.-H.; Kato, H. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Jang, M.J.; Moon, J. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of); Tsai, C.W.; Yeh, J.W. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Kim, H.S., E-mail: hskim@postech.ac.kr [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of); Center for High Entropy Alloys, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of)

    2017-03-24

    The tensile deformation and strain hardening behaviors of an equimolar CoCrFeMnNi high-entropy alloy (HEA) were investigated and compared with low and medium entropy equiatomic alloys (LEA and MEA). The HEA had a lower yield strength than the MEA because the addition of Mn weakens solid solution hardening in the HEA. However, deformation twinning induced the multiple stage strain hardening behavior of the HEA and enhanced strength and elongation. Using tensile-interrupted electron backscatter diffraction analysis, geometrically necessary dislocations were observed as plume-shaped features in grain interior, and a considerable texture was characterized, which is typical of face centered cubic metals. Moreover, the relationship between favorably oriented grains and twinning in the HEA bore a clear resemblance to the same tendency in TWIP steels. The thickness of the twin bundles was less than 100 nm. A high density of stacking defects was found in the nanotwins. Nano twinning and stacking faults were found to contribute to the remarkable mechanical properties. Deformation induced twinning not only demonstrated the dynamic Hall-Petch effect but also changed dislocation cell substructures into microband structures.

  10. On q-power cycles in cubic graphs

    DEFF Research Database (Denmark)

    Bensmail, Julien

    2017-01-01

    In the context of a conjecture of Erdos and Gyárfás, we consider, for any q ≥ 2, the existence of q-power cycles (i.e. with length a power of q) in cubic graphs. We exhibit constructions showing that, for every q ≥ 3, there exist arbitrarily large cubic graphs with no q-power cycles. Concerning...... the remaining case q = 2 (which corresponds to the conjecture of Erdos and Gyárfás), we show that there exist arbitrarily large cubic graphs whose only 2-power cycles have length 4 only, or 8 only....

  11. Stability of cubic zirconia in a granitic system under high pressure and temperature

    International Nuclear Information System (INIS)

    Gibb, F. G. F.; Burakov, B. E.; Taylor, K. J.; Domracheva, Y.

    2008-01-01

    Cubic zirconia is a well known, highly durable material with potential uses as an actinide host phase in ceramic waste forms and inert matrix fuels and in containers for very deep borehole disposal of some highly radioactive wastes. To investigate the behaviour of this material under the conditions of possible use, a cube of ∼2.5 mm edge was made from a single crystal of Yttria stabilized cubic zirconia doped with 0.3 wt.% CeO 2 . The cube was enclosed in powdered granite within a gold capsule and a small amount of H 2 O added before sealing. The sealed capsule was held for 4 months in a cold-seal pressure vessel at a temperature of 780 deg. C and a pressure 150 MPa, simulating both the conditions of a deep borehole disposal involving partial melting of the host rock and the conditions under which the actinide waste form might be encapsulated in granite prior to disposal. At the end of the experiment the quenched, largely glassy, sample was cut into thin slices and studied by optical microscopy, EMPA, SEM and cathodoluminescence methods. The results show that no corrosion of the zirconia crystal or reaction with the granite melt occurred and that no detectable diffusion of elements, including Ce, in or out of the zirconia took place on the timescale of the experiment. Consequently, it appears that cubic zirconia could perform most satisfactorily as both an actinide host waste form for encapsulation in solid granite for very deep disposal and as a container material for deep borehole disposal of highly radioactive wastes (HLW), including spent fuel. (authors)

  12. Morphology control and negative thermal expansion in cubic ZrWMoO8 powders

    International Nuclear Information System (INIS)

    Liu, Qinqin; Yang, Juan; Sun, Xiujuan; Cheng, Xiaonong

    2008-01-01

    Cubic ZrWMoO 8 powders with rod-like aggregate and thin fasciculus-like and flower-like rod cluster morphologies have been successfully fabricated with different amounts of (NH 4 ) 2 HPO 4 as surfactant using a hydrothermal method. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry were utilized to investigate the influence of the addition of (NH 4 ) 2 HPO 4 on the crystallization process and crystal morphology of the resulting products. The results show that the purity and the thermal expansion property of the resulting products are not influenced by the addition of (NH 4 ) 2 HPO 4 . The cubic ZrWMoO 8 powders with both rod-like aggregate and flower-like rod cluster morphologies show a positive thermal expansion property in the temperature range from room temperature to 120 C, while they show a negative thermal expansion property in the temperature range from 120 C to 700 C. The abnormal thermal expansion property of cubic ZrWMoO 8 below 120 C is caused by the presence of water molecules. Investigations also show that the essence of the different morphologies of the ZrWMoO 8 particles obtained is the result of the different aggregation modes of the nanorods, which act as nuclei, and the corresponding aggregation process is dominated by the addition of (NH 4 ) 2 HPO 4 and its amount. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Twin-Foucault imaging method

    Science.gov (United States)

    Harada, Ken

    2012-02-01

    A method of Lorentz electron microscopy, which enables observation two Foucault images simultaneously by using an electron biprism instead of an objective aperture, was developed. The electron biprism is installed between two electron beams deflected by 180° magnetic domains. Potential applied to the biprism deflects the two electron beams further, and two Foucault images with reversed contrast are then obtained in one visual field. The twin Foucault images are able to extract the magnetic domain structures and to reconstruct an ordinary electron micrograph. The developed Foucault method was demonstrated with a 180° domain structure of manganite La0.825Sr0.175MnO3.

  14. Ectodermal dysplasia in identical twins

    Directory of Open Access Journals (Sweden)

    Gurkar Haraswarupa Puttaraju

    2013-01-01

    Full Text Available Hereditary hypohidrotic ectodermal dysplasia (HED is typically inherited as an X-linked recessive trait, characterized by deformity of at least two or more of the ectodermal structures - hair, teeth, nails and sweat glands. Two cases of hereditary HED involving identical male twins, is being documented for the rarity of its occurrence with special attention given to genetics, pathophysiology, clinical, intraoral manifestations and to the methods to improve the masticatory function, the facial esthetics and psychology of patients affected by this disease.

  15. Risk of Oral Clefts in Twins

    DEFF Research Database (Denmark)

    Grosen, Dorthe; Bille, Camilla; Petersen, Inge

    2011-01-01

    and heritability. Twins (207 affected/130,710) and singletons (7766 affected/4,798,526) born from 1936 through 2004 in Denmark were ascertained by linkage among the Danish Facial Cleft Database, the Danish Twin Registry, and the Civil Registration System. We computed oral cleft prevalence and prevalence proportion...

  16. Fatique life and twinning in alphazirconium

    DEFF Research Database (Denmark)

    Warren, M.R.; Beevers, C.J.

    1970-01-01

    stress for {11−21} twinning of ~0.5 kg mm−2 in zirconium containing 0.003 wt pct O. During observations confined to internal grains it was found that increasing grain size and decreasing oxygen content favored the formation of fatigue damage in association with these {11−21} twins. In external grains...

  17. Gestation period and twinning in chimpanzees.

    Science.gov (United States)

    PEACOCK, L J; ROGERS, C M

    1959-04-10

    The length of the gestation period in 118 births in a colony of chimpanzees was found to be 226.8 days, with a standard deviation of 13.3 and a range of 196 to 260 days. Six pairs of twins were born in 120 parturitions; thus the apparent twinning rate is higher than that in man.

  18. Fetal behavior in normal dichorionic twin pregnancy

    NARCIS (Netherlands)

    Mulder, E. J. H.; Derks, J. B.; de Laat, M. W. M.; Visser, G. H. A.

    2012-01-01

    Objectives: A prospective study was performed to compare fetal behavioral development in healthy dichorionic twins and singletons, and identify twin intra-pair associations (synchrony) of fetal movements and rest-activity cycles using different criteria to define synchrony. Subjects and methods:

  19. Pressure-induced melting of micellar crystal

    DEFF Research Database (Denmark)

    Mortensen, K.; Schwahn, D.; Janssen, S.

    1993-01-01

    that pressure improves the solvent quality of water, thus resulting in decomposition of the micelles and consequent melting of the micellar crystal. The combined pressure and temperature dependence reveals that in spite of the apparent increase of order on the 100 angstrom length scale upon increasing......Aqueous solutions of triblock copolymers of poly(ethylene oxide) and poly(propylene oxide) aggregate at elevated temperatures into micelles which for polymer concentrations greater-than-or-equal-to 20% make a hard sphere crystallization to a cubic micellar crystal. Structural studies show...... temperature (decreasing pressure) the overall entropy increases through the inverted micellar crystallization characteristic....

  20. Commensurability oscillations in NdBa2Cu3Oy single crystals

    Indian Academy of Sciences (India)

    Postfach 3640, 76021 Karlsruhe, Germany. 2Technical ... the vortices are placed between the CuO2 layers, but the energy necessary for the elastic ... Two Nd123 crystals from the same batch were investigated: FK, twinned, transition tem-.

  1. ZnO twin-cones: synthesis, photoluminescence, and catalytic decomposition of ammonium perchlorate.

    Science.gov (United States)

    Sun, Xuefei; Qiu, Xiaoqing; Li, Liping; Li, Guangshe

    2008-05-19

    ZnO twin-cones, a new member to the ZnO family, were prepared directly by a solvothermal method using a mixed solution of zinc nitrate and ethanol. The reaction and growth mechanisms of ZnO twin-cones were investigated by X-ray diffraction, UV-visible spectra, infrared and ion trap mass spectra, and transmission electron microscopy. All as-prepared ZnO cones consisted of tiny single crystals with lengths of several micrometers. With prolonging of the reaction time from 1.5 h to 7 days, the twin-cone shape did not change at all, while the lattice parameters increased slightly and the emission peak of photoluminescence shifted from the green region to the near orange region. ZnO twin-cones are also explored as an additive to promote the thermal decomposition of ammonium perchlorate. The variations of photoluminescence spectra and catalytic roles in ammonium perchlorate decomposition were discussed in terms of the defect structure of ZnO twin-cones.

  2. Structure and motion of junctions between coherent and incoherent twin boundaries in copper

    Energy Technology Data Exchange (ETDEWEB)

    Brown, J.A. [Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States); Ghoniem, N.M., E-mail: ghoniem@ucla.edu [Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States)

    2009-09-15

    The atomic mechanisms of twin boundary migration in copper under externally applied mechanical loads and during thermal annealing are investigated utilizing molecular dynamics computer simulations. The migration dynamics of the incoherent {Sigma}=3[110](112) twin boundary (ITB), pinned between two {Sigma}=3[110](111) twin boundaries, is determined. A three-dimensional structural model is described for the junction between intersecting coherent and incoherent twin boundaries, and migration velocities are calculated under thermal annealing conditions. It is shown that the coherent twin boundary (CTB)/ITB junction results in breaking the crystal symmetry by creation of either an edge dislocation or a mixed (edge/screw) at the intersection. These two types of defects can lead to pronounced differences in the observed migration (and hence annealing) rates of ICT/CTB junctions. The annealing rate resulting from the migration of ITBs with a mixed dislocation is found to be more than twice that of the edge dislocation. The mechanism of ITB motion is shown to be governed by successive kink-like motion of neighboring atomic columns, each of which is shifted by 1/4[1 1 0], followed by structural relaxation to accommodate boundary motion.

  3. Structure and motion of junctions between coherent and incoherent twin boundaries in copper

    International Nuclear Information System (INIS)

    Brown, J.A.; Ghoniem, N.M.

    2009-01-01

    The atomic mechanisms of twin boundary migration in copper under externally applied mechanical loads and during thermal annealing are investigated utilizing molecular dynamics computer simulations. The migration dynamics of the incoherent Σ=3[110](112) twin boundary (ITB), pinned between two Σ=3[110](111) twin boundaries, is determined. A three-dimensional structural model is described for the junction between intersecting coherent and incoherent twin boundaries, and migration velocities are calculated under thermal annealing conditions. It is shown that the coherent twin boundary (CTB)/ITB junction results in breaking the crystal symmetry by creation of either an edge dislocation or a mixed (edge/screw) at the intersection. These two types of defects can lead to pronounced differences in the observed migration (and hence annealing) rates of ICT/CTB junctions. The annealing rate resulting from the migration of ITBs with a mixed dislocation is found to be more than twice that of the edge dislocation. The mechanism of ITB motion is shown to be governed by successive kink-like motion of neighboring atomic columns, each of which is shifted by 1/4[1 1 0], followed by structural relaxation to accommodate boundary motion.

  4. Bicontinuous cubic liquid crystalline nanoparticles for oral delivery of Doxorubicin

    DEFF Research Database (Denmark)

    Swarnakar, Nitin K; Thanki, Kaushik; Jain, Sanyog

    2014-01-01

    PURPOSE: The present study explores the potential of bicontinous cubic liquid crystalline nanoparticles (LCNPs) for improving therapeutic potential of doxorubicin. METHODS: Phytantriol based Dox-LCNPs were prepared using hydrotrope method, optimized for various formulation components, process...

  5. Urticaria in monozygotic and dizygotic twins

    DEFF Research Database (Denmark)

    Thomsen, Simon Francis; van der Sluis, Sophie; Kyvik, Kirsten Ohm

    2012-01-01

    Aim. To identify risk factors for urticaria, to determine the relative proportion of the susceptibility to urticaria that is due to genetic factors in an adult clinical twin sample, and to further determine whether the genetic susceptibility to urticaria overlaps with the genetic susceptibility...... to atopic diseases. Methods. A total of 256 complete twin pairs and 63 single twins, who were selected from sibships with self-reported asthma via a questionnaire survey of 21,162 adult twins from the Danish Twin Registry, were clinically interviewed about a history of urticaria and examined for atopic...... diseases. Data were analysed with Cox proportional hazards regression and variance components models. Results. A total of 151 individuals (26%) had a history of urticaria, whereas 24 (4%) had had symptoms within the past year. Female sex, HR = 2.09 (1.46-2.99), P = 0.000; hay fever, HR = 1.92 (1...

  6. Twins in Ancient Greece: a synopsis.

    Science.gov (United States)

    Malamitsi-Puchner, Ariadne

    2016-01-01

    This brief outline associates twins with several aspects of life in Ancient Greece. In Greek mythology twins caused ambivalent reactions and were believed to have ambivalent feelings for each other. Very often, they were viewed as the representatives of the dualistic nature of the universe. Heteropaternal superfecundation, which dominates in ancient myths, explains on one hand, the god-like qualities and, on the other hand, the mortal nature of many twins. An assumption is presented that legends referring to twins might reflect the territorial expansions of Ancient Greeks in Northern Mediterranean, around the Black Sea, in Asia Minor, as well as North East Africa. In conclusion, in Greek antiquity, twins have been used as transitional figures between myth and reality.

  7. 'Biracial'-Looking Twins: A New Twin Type?/Twin Research: Twins with Cystic Teratomas; Sleep Quality and Body Mass Index; Previable Membrane Rupture/Print and Online Reports: Twins Born to a Sister Surrogate; NASA Twin Study; African-Cosmopolitan Twin Fashion Inspirations; Triplet Hockey Stars.

    Science.gov (United States)

    Segal, Nancy L

    2017-06-01

    Dizygotic (DZ) co-twins born to mothers and fathers from different racial or ethnic backgrounds often resemble one parent much more than the other. As such, these pairs comprise a unique subset of twins for investigating how others' responses to their different looks may affect their personalities and self-esteem. This article describes some of these twin pairs and some challenges of raising them, and suggests ways they may be used in research. Next, recent twin research on cystic teratomas, relations between sleep quality and body mass index, and previable membrane rupture is described. The final section concerns twins, twin studies, and related events in the media, namely: twins born to a sister surrogate, the NASA twin investigation, inspiring African-Cosmopolitan twins in fashion, and triplet Hockey Stars.

  8. Spinor bose gases in cubic optical lattice

    International Nuclear Information System (INIS)

    Mobarak, Mohamed Saidan Sayed Mohamed

    2014-01-01

    In recent years the quantum simulation of condensed-matter physics problems has resulted from exciting experimental progress in the realm of ultracold atoms and molecules in optical lattices. In this thesis we analyze theoretically a spinor Bose gas loaded into a three-dimensional cubic optical lattice. In order to account for different superfluid phases of spin-1 bosons with a linear Zeeman effect, we work out a Ginzburg-Landau theory for the underlying spin-1 Bose-Hubbard model. To this end we add artificial symmetry-breaking currents to the spin-1 Bose-Hubbard Hamiltonian in order to break the global U (1) symmetry. With this we determine a diagrammatic expansion of the grand-canonical free energy up to fourth order in the symmetry-breaking currents and up to the leading non-trivial order in the hopping strength which is of first order. As a cross-check we demonstrate that the resulting grand-canonical free energy allows to recover the mean-field theory. Applying a Legendre transformation to the grand-canonical free energy, where the symmetry-breaking currents are transformed to order parameters, we obtain the effective Ginzburg-Landau action. With this we calculate in detail at zero temperature the Mott insulator-superfluid quantum phase boundary as well as condensate and particle number density in the superfluid phase. We find that both mean-field and Ginzburg-Landau theory yield the same quantum phase transition between the Mott insulator and superfluid phases, but the range of validity of the mean-field theory turns out to be smaller than that of the Ginzburg-Landau theory. Due to this finding we expect that the Ginzburg-Landau theory gives better results for the superfluid phase and, thus, we restrict ourselves to extremize only the effective Ginzburg-Landau action with respect to the order parameters. Without external magnetic field the superfluid phase is a polar (ferromagnetic) state for anti-ferromagnetic (ferromagnetic) interactions, i.e. only the

  9. The Combinatorial Rigidity Conjecture is False for Cubic Polynomials

    DEFF Research Database (Denmark)

    Henriksen, Christian

    2003-01-01

    We show that there exist two cubic polynomials with connected Julia sets which are combinatorially equivalent but not topologically conjugate on their Julia sets. This disproves a conjecture by McMullen from 1995.......We show that there exist two cubic polynomials with connected Julia sets which are combinatorially equivalent but not topologically conjugate on their Julia sets. This disproves a conjecture by McMullen from 1995....

  10. Interaction of dispersed cubic phases with blood components

    DEFF Research Database (Denmark)

    Bode, J C; Kuntsche, Judith; Funari, S S

    2013-01-01

    The interaction of aqueous nanoparticle dispersions, e.g. based on monoolein/poloxamer 407, with blood components is an important topic concerning especially the parenteral way of administration. Therefore, the influence of human and porcine plasma on dispersed cubic phases was investigated. Part...... activity of cubic phases based on monoolein and poloxamer 188, on soy phosphatidylcholine, glycerol dioleate and polysorbate 80 or the parenteral fat emulsion Lipofundin MCT 20%....

  11. Highlights from the 15th International Congress of Twin Studies/Twin Research: Differentiating MZ Co-twins Via SNPs; Mistaken Infant Twin-Singleton Hospital Registration; Narcolepsy With Cataplexy; Hearing Loss and Language Learning/Media Mentions: Broadway Musical Recalls Conjoined Hilton Twins; High Fashion Pair; Twins Turn 102; Insights From a Conjoined Twin Survivor.

    Science.gov (United States)

    Segal, Nancy L

    2015-02-01

    Highlights from the 15th International Congress of Twin Studies are presented. The congress was held November 16-19, 2014 in Budapest, Hungary. This report is followed by summaries of research addressing the differentiation of MZ co-twins by single nucleotide polymorphisms (SNPs), an unusual error in infant twin-singleton hospital registration, twins with childhood-onset narcolepsy with cataplexy, and the parenting effects of hearing loss in one co-twin. Media interest in twins covers a new Broadway musical based on the conjoined twins Violet and Daisy Hilton, male twins becoming famous in fashion, twins who turned 102 and unique insights from a conjoined twin survivor. This article is dedicated to the memory of Elizabeth (Liz) Hamel, DZA twin who met her co-twin for the first time at age seventy-eight years. Liz and her co-twin, Ann Hunt, are listed in the 2015 Guinness Book of Records as the longest separated twins in the world.

  12. Transdermal delivery of paeonol using cubic gel and microemulsion gel

    Science.gov (United States)

    Luo, Maofu; Shen, Qi; Chen, Jinjin

    2011-01-01

    Background The aim of this study was to develop new systems for transdermal delivery of paeonol, in particular microemulsion gel and cubic gel formulations. Methods Various microemulsion vehicles were prepared using isopropyl myristate as an oil phase, polyoxyethylated castor oil (Cremophor® EL) as a surfactant, and polyethylene glycol 400 as a cosurfactant. In the optimum microemulsion gel formulation, carbomer 940 was selected as the gel matrix, and consisted of 1% paeonol, 4% isopropyl myristate, 28% Cremophor EL/polyethylene glycol 400 (1:1), and 67% water. The cubic gel was prepared containing 3% paeonol, 30% water, and 67% glyceryl monooleate. Results A skin permeability test using excised rat skins indicated that both the cubic gel and microemulsion gel formulations had higher permeability than did the paeonol solution. An in vivo pharmacokinetic study done in rats showed that the relative bioavailability of the cubic gel and microemulsion gel was enhanced by about 1.51-fold and 1.28-fold, respectively, compared with orally administered paeonol suspension. Conclusion Both the cubic gel and microemulsion gel formulations are promising delivery systems to enhance the skin permeability of paeonol, in particular the cubic gel. PMID:21904450

  13. Size effects on negative thermal expansion in cubic ScF{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Yang, C.; Guo, X. G.; Zhang, K. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Tong, P., E-mail: tongpeng@issp.ac.cn; Lin, J. C.; Wang, M.; Wu, Y.; Lin, S.; Xu, W.; Song, W. H. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Huang, P. C. [University of Science and Technology of China, Hefei 230026 (China); High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Sun, Y. P., E-mail: ypsun@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2016-07-11

    Scandium trifluoride (ScF{sub 3}), adopting a cubic ReO{sub 3}-type structure at ambient pressure, undergoes a pronounced negative thermal expansion (NTE) over a wide range of temperatures (10 K–1100 K). Here, we report the size effects on the NTE properties of ScF{sub 3}. The magnitude of NTE is reduced with diminishing the crystal size. As revealed by the specific heat measurement, the low-energy phonon vibrations which account for the NTE behavior are stiffened as the crystal size decreases. With decreasing the crystal size, the peaks in high-energy X-ray pair distribution function (PDF) become broad, which cannot be illuminated by local symmetry breaking. Instead, the broadened PDF peaks are strongly indicative of enhanced atomic displacements which are suggested to be responsible for the stiffening of NTE-related lattice vibrations. The present study suggests that the NTE properties of ReO{sub 3}-type and other open-framework materials can be effectively adjusted by controlling the crystal size.

  14. Commensurability oscillations in NdBa2Cu3Oy single crystals

    Indian Academy of Sciences (India)

    gated by angular dependent magnetization in very pure twinned and twin-free NdBa2 Cu3 Oy single ... The layered structure and the c-axis coherence length, ξc ≈ 4 ˚A, smaller than the lattice ... The high quality of both crystals is demonstrated by ... Commensurability oscillations in NdBa2Cu3Oy single crystals. 2. 3. 4. 5. 6.

  15. The utility of twins in developmental cognitive neuroscience research: How twins strengthen the ABCD research design.

    Science.gov (United States)

    Iacono, William G; Heath, Andrew C; Hewitt, John K; Neale, Michael C; Banich, Marie T; Luciana, Monica M; Madden, Pamela A; Barch, Deanna M; Bjork, James M

    2018-08-01

    The ABCD twin study will elucidate the genetic and environmental contributions to a wide range of mental and physical health outcomes in children, including substance use, brain and behavioral development, and their interrelationship. Comparisons within and between monozygotic and dizygotic twin pairs, further powered by multiple assessments, provide information about genetic and environmental contributions to developmental associations, and enable stronger tests of causal hypotheses, than do comparisons involving unrelated children. Thus a sub-study of 800 pairs of same-sex twins was embedded within the overall Adolescent Brain and Cognitive Development (ABCD) design. The ABCD Twin Hub comprises four leading centers for twin research in Minnesota, Colorado, Virginia, and Missouri. Each site is enrolling 200 twin pairs, as well as singletons. The twins are recruited from registries of all twin births in each State during 2006-2008. Singletons at each site are recruited following the same school-based procedures as the rest of the ABCD study. This paper describes the background and rationale for the ABCD twin study, the ascertainment of twin pairs and implementation strategy at each site, and the details of the proposed analytic strategies to quantify genetic and environmental influences and test hypotheses critical to the aims of the ABCD study. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  16. The mobility of growth twins synthesized by sputtering: Tailoring the twin thickness

    International Nuclear Information System (INIS)

    Velasco, Leonardo; Hodge, Andrea M.

    2016-01-01

    The current work presents a protean twin thickness contour zone map that illustrates how the nucleation and the mobility of twin boundaries affects the twin thickness of sputtered films. The twin thickness contour zone map can be used as a versatile guide to synthesize fully nanotwinned films with tailored twin thicknesses in materials with a wide range of stacking fault energies. The nucleation and mobility of twin boundaries was studied in four Cu alloys of different compositions (Cu-6wt.%Al, Cu-4wt.%Al, Cu-2wt.%Al, and Cu-10wt.%Ni), having stacking fault energies ranging from 6 mJ/m 2 to 60 mJ/m 2 . The films were synthesized by magnetron sputtering and characterized by transmission electron microscopy, where the twin thickness varied from 2 nm to 35 nm. Our experimental results show that it is possible to control the twin thickness. Three main mechanisms are explained to describe twin nucleation and twin boundary mobility, which are correlated to the interplay of specific sputtering conditions and the deposition temperature.

  17. Anomalous Doppler effects in bulk phononic crystal

    International Nuclear Information System (INIS)

    Cai Feiyan; He Zhaojian; Zhang Anqi; Ding Yiqun; Liu Zhengyou

    2010-01-01

    Doppler effects in simple cubic phononic crystal are studied theoretically and numerically. In addition to observing Doppler shifts from a moving source's frequencies inside the gap, we find that Doppler shifts can be multi-order, anisotropic, and the dominant order of shift depends on the band index that the source's frequency is in.

  18. Effect of co-twin gender on neurodevelopmental symptoms: a twin register study.

    Science.gov (United States)

    Eriksson, Jonna Maria; Lundström, Sebastian; Lichtenstein, Paul; Bejerot, Susanne; Eriksson, Elias

    2016-01-01

    Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are neurodevelopmental disorders thought to have both genetic and environmental causes. It has been hypothesized that exposure to elevated levels of prenatal testosterone is associated with elevated traits of ASD and ADHD. Assuming that testosterone levels from a dizygotic male twin fetus may lead to enhanced testosterone exposure of its co-twins, we aimed to test the prenatal testosterone hypothesis by comparing same-sex with opposite-sex dizygotic twins with respect to neurodevelopmental symptoms. Neuropsychiatric traits were assessed in a population-based twin cohort from the Child and Adolescent Twin Study in Sweden (CATSS). Parental interviews were conducted for 16,312 dizygotic twins, 9 and 12 years old, with the Autism-Tics, ADHD, and other Comorbidities inventory (A-TAC). Girls with a female co-twin had an increased risk of reaching the cut-off score for ADHD compared with girls with a male co-twin. Both boys and girls with a female co-twin displayed a larger number of traits related to attention deficit and repetitive and stereotyped behaviors than those with a male twin. In girls, this also extended to social interaction and the combined measures for ASD and ADHD, however, with small effect sizes. Our results are reverse to what would have been expected from the prenatal testosterone hypothesis but consistent with a previous study of ASD and ADHD traits in dizygotic twins. The seemingly protective effect for girls of having a twin brother may be an effect of parent report bias, but may also be an unexpected effect of sharing the intrauterine environment with a male co-twin.

  19. Protein-crystal growth experiment (planned)

    Science.gov (United States)

    Fujita, S.; Asano, K.; Hashitani, T.; Kitakohji, T.; Nemoto, H.; Kitamura, S.

    1988-01-01

    To evaluate the effectiveness of a microgravity environment on protein crystal growth, a system was developed using 5 cubic feet Get Away Special payload canister. In the experiment, protein (myoglobin) will be simultaneously crystallized from an aqueous solution in 16 crystallization units using three types of crystallization methods, i.e., batch, vapor diffusion, and free interface diffusion. Each unit has two compartments: one for the protein solution and the other for the ammonium sulfate solution. Compartments are separated by thick acrylic or thin stainless steel plates. Crystallization will be started by sliding out the plates, then will be periodically recorded up to 120 hours by a still camera. The temperature will be passively controlled by a phase transition thermal storage component and recorded in IC memory throughout the experiment. Microgravity environment can then be evaluated for protein crystal growth by comparing crystallization in space with that on Earth.

  20. Hydrothermal synthesis and white light emission of cubic ZrO2:Eu3+ nanocrystals

    International Nuclear Information System (INIS)

    Meetei, Sanoujam Dhiren; Singh, Shougaijam Dorendrajit

    2014-01-01

    Highlights: • White light emitting cubic ZrO 2 :Eu 3+ nanocrystal is synthesized by hydrothermal technique. • Eu 3+ is used to stabilize crystalline phase and to get red counterpart of the white light. • Defect emission and Eu 3+ emission combined to give white light. • The white light emitted from this nanocrystal resembles vertical daylight of the Sun. • Lifetime corresponding to red counterpart of the sample is far longer than conventional white light emitters. -- Abstract: Production of white light has been a promising area of luminescence studies. In this work, white light emitting nanocrystals of cubic zirconia doped with Eu 3+ are synthesized by hydrothermal technique. The dopant Eu 3+ is used to stabilize crystalline phase to cubic and at the same time to get red counterpart of the white light. The synthesis procedure is simple and precursor required no further annealing for crystallization. X-ray diffraction patterns show the crystalline phase of ZrO 2 :Eu 3+ to be cubic and it is confirmed by Fourier Transform Infrared spectroscopy. From transmission electron microscopy images, size of the crystals is found to be ∼5 nm. Photoluminescence emission spectrum of the sample, on monitoring excitation at O 2− –Eu 3+ charge transfer state shows broad peak due to O 2− of the zirconia and that of Eu 3+ emission. Commission Internationale de l’éclairage co-ordinate of this nanocrystal (0.32, 0.34) is closed to that of the ideal white light (0.33, 0.33). Correlated color temperature of the white light (5894 K) is within the range of vertical daylight. Lifetime (1.32 ms) corresponding to 5 D 0 energy level of the Eu 3+ is found to be far longer than conventional red counterparts of white light emitters. It suggests that the ZrO 2 :Eu 3+ nanocrystals synthesized by hydrothermal technique may find applications in simulating the vertical daylight of the Sun

  1. Plastic crystal phases of simple water models

    International Nuclear Information System (INIS)

    Aragones, J. L.; Vega, C.

    2009-01-01

    We report the appearance of two plastic crystal phases of water at high pressure and temperature using computer simulations. In one of them the oxygen atoms form a body centered cubic structure (bcc) and in the other they form a face centered cubic structure (fcc). In both cases the water molecules were able to rotate almost freely. We have found that the bcc plastic crystal transformed into a fcc plastic crystal via a Martensitic phase transition when heated at constant pressure. We have performed the characterization and localization in the phase diagram of these plastic crystal phases for the SPC/E, TIP4P, and TIP4P/2005 water potential models. For TIP4P/2005 model free energy calculations were carried out for the bcc plastic crystal and fcc plastic crystal using a new method (which is a slight variation of the Einstein crystal method) proposed for these types of solid. The initial coexistence points for the SPC/E and TIP4P models were obtained using Hamiltonian Gibbs–Duhem integration. For all of these models these two plastic crystal phases appear in the high pressure and temperature region of the phase diagram. It would be of interest to study if such plastic crystal phases do indeed exist for real water. This would shed some light on the question of whether these models can describe satisfactorily the high pressure part of the phase diagram of water, and if not, where and why they fail.

  2. Hypothesis test for synchronization: twin surrogates revisited.

    Science.gov (United States)

    Romano, M Carmen; Thiel, Marco; Kurths, Jürgen; Mergenthaler, Konstantin; Engbert, Ralf

    2009-03-01

    The method of twin surrogates has been introduced to test for phase synchronization of complex systems in the case of passive experiments. In this paper we derive new analytical expressions for the number of twins depending on the size of the neighborhood, as well as on the length of the trajectory. This allows us to determine the optimal parameters for the generation of twin surrogates. Furthermore, we determine the quality of the twin surrogates with respect to several linear and nonlinear statistics depending on the parameters of the method. In the second part of the paper we perform a hypothesis test for phase synchronization in the case of experimental data from fixational eye movements. These miniature eye movements have been shown to play a central role in neural information processing underlying the perception of static visual scenes. The high number of data sets (21 subjects and 30 trials per person) allows us to compare the generated twin surrogates with the "natural" surrogates that correspond to the different trials. We show that the generated twin surrogates reproduce very well all linear and nonlinear characteristics of the underlying experimental system. The synchronization analysis of fixational eye movements by means of twin surrogates reveals that the synchronization between the left and right eye is significant, indicating that either the centers in the brain stem generating fixational eye movements are closely linked, or, alternatively that there is only one center controlling both eyes.

  3. Establishing a Twin Registry in Guinea-Bissau

    DEFF Research Database (Denmark)

    Bjerregaard-Andersen, Morten; Gomes, Margarida A; Joaquím, Luis C

    2013-01-01

    represent a powerful tool. Though twin studies have been carried out by the Bandim Health Project for more than 30 years, the renewed registry described here was officially established in 2009 and includes both a cohort of newborn twins and a cohort of young and adult twins. Currently more than 1,500 twins...

  4. Twin Delivery: Comparison of Incidence and Foetal Outcome in two ...

    African Journals Online (AJOL)

    Background: The incidence of twin delivery in Nigeria may have changed, in view of the worldwide increase in the rates of twinning attributed to increasing maternal age and use of fertility therapies. Objective: To determine the current incidence of twin delivery in Benin City and document the foetal outcome in twins.

  5. CERN: Ten-Tesla twin

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    An important step in the development of the high field superconducting magnets for CERN's proposed LHC proton collider came on 21 October when a 1 metre-long model of the proposed twin-dipole magnet produced a field of 10 Tesla in its two o beam apertures at the design temperature of 1.8K. The LHC designers have to plan for proton beams approaching 8 TeV to attain the right conditions for the quarks and gluons hidden deep inside protons to produce new physics. To contain these very high energy protons in the tight track of the 27-kilometre LEP tunnel would need the strongest magnetic bending power ever used in a full storage ring

  6. Median mental sinus in twins.

    Science.gov (United States)

    Ong, S T; Ngeow, W C

    1999-05-01

    Sinus on the chin can be the result of a chronic apical abscess due to pulp necrosis of a mandibular anterior tooth. The tooth is usually asymptomatic, and a dental cause is therefore not apparent to the patient or the unsuspecting clinician. Not infrequently, the patient may seek treatment from a dermatologist or general surgeon instead of a dentist. Excision and repair of the fistula may be carried out with subsequent breakdown because the dental pathology is not removed. This paper reports the presence of median mental sinus of dental origin in twins. One case healed following root canal therapy while the other required both root canal therapy and surgery to eliminate the infection.

  7. Longitudinal sound velocities, elastic anisotropy, and phase transition of high-pressure cubic H2O ice to 82 GPa

    Science.gov (United States)

    Kuriakose, Maju; Raetz, Samuel; Hu, Qing Miao; Nikitin, Sergey M.; Chigarev, Nikolay; Tournat, Vincent; Bulou, Alain; Lomonosov, Alexey; Djemia, Philippe; Gusev, Vitalyi E.; Zerr, Andreas

    2017-10-01

    Water ice is a molecular solid whose behavior under compression reveals the interplay of covalent bonding in molecules and forces acting between them. This interplay determines high-pressure phase transitions, the elastic and plastic behavior of H2O ice, which are the properties needed for modeling the convection and internal structure of the giant planets and moons of the solar system as well as H2O -rich exoplanets. We investigated experimentally and theoretically elastic properties and phase transitions of cubic H2O ice at room temperature and high pressures between 10 and 82 GPa. The time-domain Brillouin scattering (TDBS) technique was used to measure longitudinal sound velocities (VL) in polycrystalline ice samples compressed in a diamond anvil cell. The high spatial resolution of the TDBS technique revealed variations of VL caused by elastic anisotropy, allowing us to reliably determine the fastest and the slowest sound velocity in a single crystal of cubic H2O ice and thus to evaluate existing equations of state. Pressure dependencies of the single-crystal elastic moduli Ci j(P ) of cubic H2O ice to 82 GPa have been obtained which indicate its hardness and brittleness. These results were compared with ab initio calculations. It is suggested that the transition from molecular ice VII to ionic ice X occurs at much higher pressures than proposed earlier, probably above 80 GPa.

  8. Undiagnosed xiphopagus twins: a perinatal malady

    Directory of Open Access Journals (Sweden)

    Gowri Dorairajan

    2012-02-01

    Full Text Available Conjoined twins are a very rare entity. It is associated with poor survival rate in the presence of vital organ sharing. The entity can be diagnosed as early as the first trimester. A conjoined twin diagnosed late in labor is a malady with high perinatal mortality and maternal morbidity. We present one such case of xiphopagus twins. The management of a case diagnosed late in labor can be very challenging. Such obstetric challenges can be avoided by a meticulous early scan with a high index of suspicion, especially in the absence of separating membrane while scanning multiple pregnancies.

  9. Attractiveness Differences Between Twins Predicts Evaluations of Self and Co-Twin

    Science.gov (United States)

    Principe, Connor P.; Rosen, Lisa H.; Taylor-Partridge, Teresa; Langlois, Judith H.

    2012-01-01

    One of the most consistent findings in psychology shows that people prefer and make positive attributions about attractive compared with unattractive people. The goal of the current study was to determine the power of attractiveness effects by testing whether these social judgments are made where attractiveness differences are smallest: between twins. Differences in facial attractiveness predicted twins’ evaluations of self and their co-twin (n = 158; 54 male). In twin pairs, the more attractive twin judged their less attractive sibling as less physically attractive, athletic, socially competent, and emotionally stable. The less attractive twin did the reverse. Given that even negligible differences in facial attractiveness predicted self and co-twin attitudes, these results provide the strongest test yet of appearance-based stereotypes. PMID:23467329

  10. Marital status and twins' health and behavior: an analysis of middle-aged Danish twins

    DEFF Research Database (Denmark)

    Osler, Merete; McGue, Matt; Lund, Rikke

    2008-01-01

    mass index (BMI), depression symptoms, self-rated health, cognitive function, physical activity, smoking, and alcohol intake. RESULTS: Among all 2350 individual twins, men who were divorced/widowed or never married had higher depression scores, lower cognitive test scores, lower physical activity....../widowed twin had higher average depression scores and was more likely to be a smoker. Never married twins had lower physical activity scores and never married male twins had higher BMI and higher depression scores than their married co-twin. CONCLUSION: This study suggests that the relationships of adult...... divorce with depression and smoking in Danish twins are due to the stressful effects of marital dissolution, but that marital differences in other health and behavioral outcomes are most consistent with selection effects related to genetic or rearing environmental factors....

  11. Molecular dynamics simulation of deformation twin in rocksalt vanadium nitride

    International Nuclear Information System (INIS)

    Fu, Tao; Peng, Xianghe; Zhao, Yinbo; Li, Tengfei; Li, Qibin; Wang, Zhongchang

    2016-01-01

    We perform molecular dynamics simulation of nano-indentation with a cylindrical indenter to investigate the formation mechanism of deformation twin in vanadium nitride (VN) with a rocksalt structure. We find that the deformation twins occur during the loading stage, and subsequently conduct a systematic analysis of nucleation, propagation and thickening of a deformation twin. We find that the nucleation of a partial dislocation and its propagation to form a stacking fault are premise of deformation twin formation. The sequential nucleation and propagation of partial dislocation on adjacent parallel {111} planes are found to cause the thickening of the deformation twin. Moreover, the deformation twins can exist in VN at room temperature. - Highlights: • MD simulations of indentation are performed to study the deformation twin in VN. • The deformation twins can occur in VN during the loading stage. • The nucleation, propagation and thickening of a deformation twin are analyzed. • The deformation twins can exist in VN at room temperature.

  12. Cohort Profile : The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry)

    NARCIS (Netherlands)

    Gatz, Margaret; Harris, Jennifer R.; Kaprio, Jaakko; McGue, Matt; Smith, Nicholas L.; Snieder, Harold; Spiro, Avron; Butler, David A.

    The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry) is a comprehensive registry of White male twin pairs born in the USA between 1917 and 1927, both of the twins having served in the military. The purpose was medical research and ultimately improved

  13. /sup 87/Rb NMR study at the cubic to tetragonal phase transition in RbCaF/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Bulou, A [Angers Univ., 72 - Le Mans (France). Centre Universitaire; Theveneau, H; Trokiner, A; Papon, P [Ecole Superieure de Physique et Chimie Industrielles, 75 - Paris (France)

    1979-07-01

    The /sup 87/Rb nuclear magnetic resonance spectrum, in perovskite single crystal of RbCaF/sub 3/, is studied above and below the cubic-to-tetragonal phase transition occurring at 198 K. In the high-temperature cubic phase, the temperature dependence of the resonance line amplitude deviates from the Curie law and this can be attributed to the existence of tetragonal domains. In the low temperature tetragonal phase, a second-order quadrupole shift of the central line is observed, from which the CaF/sub 6/ tilt angle (order parameter) is derived. The order parameter temperature dependence is described by a power law with a cross over from exponent 0.5 to exponent 0.32 at 150 K. The tilt angle PHI is compared to the values obtained from X-ray and neutron powder diffraction data.

  14. The time-dependence of the defective nature of ice Ic (cubic ice) and its implications for atmospheric science

    Science.gov (United States)

    Sippel, Christian; Koza, Michael M.; Hansen, Thomas C.; Kuhs, Werner F.

    2010-05-01

    The possible atmospheric implication of ice Ic (cubic ice) has already been suggested some time ago in the context of snow crystal formation [1]. New findings from air-borne measurements in cirrus clouds and contrails have put ice Ic into the focus of interest to understand the so-called "supersaturation puzzle" [2,3,4]. Our recent microstructural work on ice Ic [5,6] appears to be highly relevant in this context. We have found that ice Ic is characterized by a complex stacking fault pattern, which changes as a function of temperature as well as time. Indeed, from our own [7] and other group's work [8] one knows that (in contrast to earlier believe) ice Ic can form up to temperatures at least as high as 240K - thus in the relevant range for cirrus clouds. We have good preliminary evidence that the "cubicity" (which can be related to stacking fault probabilities) as well as the particle size of ice Ic are the relevant parameters for this correlation. The "cubicity" of stacking faulty ice Ic (established by diffraction) correlates nicely with the increased supersaturation at decreasing temperatures observed in cirrus clouds and contrails, a fact, which may be considered as further evidence for the presence of ice Ic. Recently, we have studied the time-dependency of the changes in both "cubicity" and particle size at various temperatures of relevance for cirrus clouds and contrails by in-situ neutron powder diffraction. The timescales over which changes occur (several to many hours) are similar to the life-time of cirrus clouds and contrails and suggest that the supersaturation situation may change within this time span in the natural environment too. Some accompanying results obtained by cryo-SEM (scanning electron microscopy) work will also be presented and suggest that stacking-faulty ice Ic has kinky surfaces providing many more active centres for heterogeneous reactions on the surface than in the usually assumed stable hexagonal form of ice Ih with its rather

  15. Twin Cities Metro Hybrid Landcover 2000 (Raster)

    Data.gov (United States)

    Minnesota Department of Natural Resources — The Hybrid Landcover is an attempt to clean up the University of Minnesota Remote Sensing Lab's 2000 LandSat Land Cover for the Twin Cities 7-county metropolitan...

  16. Twin Screw Mixer/Fine Grind Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The 40-mm Twin-Screw Mixer/Extruder (TSE) pilot plant is a continuous, remotely operated, flexible facility that can significantly enhance safety and environmental...

  17. Prevention of preterm delivery in twin pregnancy

    DEFF Research Database (Denmark)

    Rode, Line; Tabor, Ann

    2014-01-01

    The incidence of twin gestation has increased markedly over the past decades, mostly because of increased use of assisted reproductive technologies. Twin pregnancies are at increased risk of preterm delivery (i.e. birth before 37 weeks of gestation). Multiple gestations therefore account for 2...... sequelae such as abnormal neurophysiological development in early childhood and underachievement in school. Several treatment modalities have been proposed in singleton high-risk pregnancies. The mechanism of initiating labour may, however, be different in singleton and twin gestations. Therefore......, it is mandatory to evaluate the proposed treatments in randomised trials of multiple gestations. In this chapter, we describe the results of trials to prevent preterm delivery in twin pregnancies....

  18. Having Twins? How to Stay Healthy

    Science.gov (United States)

    ... at night between bathroom breaks. Proper nutrition and hydration is important for your twin pregnancy, as is ... Pregnancy to Preschool (Copyright © 2010 American Academy of Pediatrics) The information contained on this Web site should ...

  19. Micromechanics of twinning in a TWIP steel

    International Nuclear Information System (INIS)

    Rahman, K.M.; Jones, N.G.; Dye, D.

    2015-01-01

    The deformation behaviour of a TWinning Induced Plasticity (TWIP) steel was studied at quasi-static strain rates using synchrotron X-ray diffraction. A {111} RD and {200} RD texture developed from the earliest stages of deformation, which could be reproduced using an elasto-plastic self consistent (EPSC) model. Evidence is found from multiple sources to suggest that twinning was occurring before macroscopic yielding. This included small deviations in the lattice strains, {111} intensity changes and peak width broadening all occurring below the macroscopic yield point. The accumulation of permanent deformation on sub-yield mechanical cycling of the material was found, which further supports the diffraction data. TEM revealed that fine deformation twins similar to those observed in heavily deformed samples formed during sub-yield cycling. It is concluded that twinning had occurred before macroscopic plastic deformation began, unlike the behaviour traditionally expected from hexagonal metals such as Mg

  20. Micromechanics of twinning in a TWIP steel

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, K.M., E-mail: khandaker.rahman05@imperial.ac.uk [Department of Materials, Royal School of Mines, Imperial College London, Prince Consort Road, London SW7 2BP (United Kingdom); Jones, N.G. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Dye, D. [Department of Materials, Royal School of Mines, Imperial College London, Prince Consort Road, London SW7 2BP (United Kingdom)

    2015-05-21

    The deformation behaviour of a TWinning Induced Plasticity (TWIP) steel was studied at quasi-static strain rates using synchrotron X-ray diffraction. A {111} RD and {200} RD texture developed from the earliest stages of deformation, which could be reproduced using an elasto-plastic self consistent (EPSC) model. Evidence is found from multiple sources to suggest that twinning was occurring before macroscopic yielding. This included small deviations in the lattice strains, {111} intensity changes and peak width broadening all occurring below the macroscopic yield point. The accumulation of permanent deformation on sub-yield mechanical cycling of the material was found, which further supports the diffraction data. TEM revealed that fine deformation twins similar to those observed in heavily deformed samples formed during sub-yield cycling. It is concluded that twinning had occurred before macroscopic plastic deformation began, unlike the behaviour traditionally expected from hexagonal metals such as Mg.

  1. Cooperative Research Twin Trawl Sweep Comparison Study

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The "Twin-Trawl Sweep Efficiency Study" was intended to compare the sweep efficiency and selectivity of the NEFSC standardized bottom trawl to that of a standardized...

  2. Diabetes and Menopause: A Twin Challenge

    Science.gov (United States)

    Diabetes and menopause: A twin challenge Diabetes and menopause may team up for varied effects on your body. Here's what to ... to stay in control. By Mayo Clinic Staff Menopause — and the years leading up to it — may ...

  3. Infantile Perineal Protrusion in Two Monochorionic Twins

    Directory of Open Access Journals (Sweden)

    Paola Cavicchioli

    2014-11-01

    Full Text Available Case Report - Two female monochorionic-monoamniotic twins showed the same kind of infantile perineal protrusion (IPP at birth. Lesions in both twins progressively healed until resolution in 6 weeks' time; none of the twins have manifested, till date, alvus disturbances. Discussion and Literature Review - A literature review numbers approximately 100 reports of IPP. This condition has been classically classified into three categories: congenital/familiar (i.e., female sex, positive parental history of IPP, acquired (mainly due to constipation, and associated with lichen sclerosus et atrophicus. Conclusions and Final Remarks - This case report describes, for the first time, the presence of IPP in monochorionic-monoamniotic twins, supporting the existence of hereditary/genetic factors in the developing of this condition.

  4. [Multimodal medical image registration using cubic spline interpolation method].

    Science.gov (United States)

    He, Yuanlie; Tian, Lianfang; Chen, Ping; Wang, Lifei; Ye, Guangchun; Mao, Zongyuan

    2007-12-01

    Based on the characteristic of the PET-CT multimodal image series, a novel image registration and fusion method is proposed, in which the cubic spline interpolation method is applied to realize the interpolation of PET-CT image series, then registration is carried out by using mutual information algorithm and finally the improved principal component analysis method is used for the fusion of PET-CT multimodal images to enhance the visual effect of PET image, thus satisfied registration and fusion results are obtained. The cubic spline interpolation method is used for reconstruction to restore the missed information between image slices, which can compensate for the shortage of previous registration methods, improve the accuracy of the registration, and make the fused multimodal images more similar to the real image. Finally, the cubic spline interpolation method has been successfully applied in developing 3D-CRT (3D Conformal Radiation Therapy) system.

  5. Deformation of the cubic open string field theory

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Taejin, E-mail: taejin@kangwon.ac.kr

    2017-05-10

    We study a consistent deformation of the cubic open bosonic string theory in such a way that the non-planar world sheet diagrams of the perturbative string theory are mapped onto their equivalent planar diagrams of the light-cone string field theory with some length parameters fixed. An explicit evaluation of the cubic string vertex in the zero-slope limit yields the correct relationship between the string coupling constant and the Yang–Mills coupling constant. The deformed cubic open string field theory is shown to produce the non-Abelian Yang–Mills action in the zero-slope limit if it is defined on multiple D-branes. Applying the consistent deformation systematically to multi-string world sheet diagrams, we may be able to calculate scattering amplitudes with an arbitrary number of external open strings.

  6. Deformation of the cubic open string field theory

    Directory of Open Access Journals (Sweden)

    Taejin Lee

    2017-05-01

    Full Text Available We study a consistent deformation of the cubic open bosonic string theory in such a way that the non-planar world sheet diagrams of the perturbative string theory are mapped onto their equivalent planar diagrams of the light-cone string field theory with some length parameters fixed. An explicit evaluation of the cubic string vertex in the zero-slope limit yields the correct relationship between the string coupling constant and the Yang–Mills coupling constant. The deformed cubic open string field theory is shown to produce the non-Abelian Yang–Mills action in the zero-slope limit if it is defined on multiple D-branes. Applying the consistent deformation systematically to multi-string world sheet diagrams, we may be able to calculate scattering amplitudes with an arbitrary number of external open strings.

  7. Cubic interactions of Maxwell-like higher spins

    Energy Technology Data Exchange (ETDEWEB)

    Francia, Dario [Scuola Normale Superiore and INFN,Piazza dei Cavalieri, 7 I-56126 Pisa (Italy); Monaco, Gabriele Lo [Dipartimento di Fisica, Università di Pisa,Piazza Fibonacci, 3, I-56126, Pisa (Italy); Dipartimento di Fisica, Università di Milano-Bicocca,Piazza della Scienza 3, I-20126 Milano (Italy); Mkrtchyan, Karapet [Max Planck Institut für Gravitationsphysik,Am Mühlenberg 1, Potsdam 14476 (Germany)

    2017-04-12

    We study the cubic vertices for Maxwell-like higher-spins in flat and (A)dS background spaces of any dimension. Reducibility of their free spectra implies that a single cubic vertex involving any three fields subsumes a number of couplings among different particles of various spins. The resulting vertices do not involve traces of the fields and in this sense are simpler than their Fronsdal counterparts. We propose an extension of both the free theory and of its cubic deformation to a more general class of partially reducible systems, that one can obtain from the original theory upon imposing trace constraints of various orders. The key to our results is a version of the Noether procedure allowing to systematically account for the deformations of the transversality conditions to be imposed on the gauge parameters at the free level.

  8. Deformation of the cubic open string field theory

    International Nuclear Information System (INIS)

    Lee, Taejin

    2017-01-01

    We study a consistent deformation of the cubic open bosonic string theory in such a way that the non-planar world sheet diagrams of the perturbative string theory are mapped onto their equivalent planar diagrams of the light-cone string field theory with some length parameters fixed. An explicit evaluation of the cubic string vertex in the zero-slope limit yields the correct relationship between the string coupling constant and the Yang–Mills coupling constant. The deformed cubic open string field theory is shown to produce the non-Abelian Yang–Mills action in the zero-slope limit if it is defined on multiple D-branes. Applying the consistent deformation systematically to multi-string world sheet diagrams, we may be able to calculate scattering amplitudes with an arbitrary number of external open strings.

  9. Crystals from China Exhibition Science Bringing Nations Together

    CERN Multimedia

    2000-01-01

    L3 aimed to specialize in measuring electrons, positrons, and photons emerging at small angles to LEP's colliding beams with the best possible precision. To achieve this, special crystals made from Bismuth Germanate, BGO, were chosen. Such crystals had previously only been made in small quantities, a few cubic centimetres, and never with the purity required by L3. The experiment would need a massive 12 tons of BGO crystals.

  10. Buoyant Helical Twin-Axial Wire Antenna

    Science.gov (United States)

    2016-11-15

    February 2017 The below identified patent application is available for licensing. Requests for information should be addressed to...300169 1 of 9 BUOYANT HELICAL TWIN-AXIAL WIRE ANTENNA CROSS REFERENCE TO OTHER PATENT APPLICATIONS [0001] This application is a divisional...application and claims the benefit of the filing date of United States Patent Application No. 14/280,889; filed on May 19, 2014; and entitled “Twin-Axial

  11. Magnetic resonance in multiple sclerose twins

    International Nuclear Information System (INIS)

    Polman, C.H.; UitdeHaag, B.M.J.; Koetsier, C.J.; Valk, J.; Lucas, C.J.

    1989-01-01

    Magnetic resonance imaging (MR) examinations were performed in a series of 7 twin sets (4 monozygotic and 3 dizygotic) and one triplet set who were clinically discordant for multiple sclerosis (MS). MRI abnormalities were detected in a number of the unaffected members of the nonzygotic twin pairs. The authors discuss the possible implications of their findings for the present view on the aetiology of MS. (author). 3 refs.; 1 fig.; 1 tab

  12. Screening and Invasive Testing in Twins

    Directory of Open Access Journals (Sweden)

    Giovanni Monni

    2014-07-01

    Full Text Available Prenatal screening and testing for trisomy 21 in twin pregnancies poses a number of challenges: the exact estimate of the a priori risk of trisomy 21, the choice of prenatal screening test and/or invasive techniques to employ for the diagnosis and the impact of the result on the options of treatment in case of discordant results within a twin pair or among multiples. These different aspects are discussed below while recognizing that many issues remain unresolved.

  13. Laying the ghost of twin paradox

    Directory of Open Access Journals (Sweden)

    Popović Marko

    2009-01-01

    Full Text Available Someone's true age is not written in his ID, but in his biomarkers. Aging process is not caused by time passing, but by thermodynamically laws. Entropy, extent of metabolic reaction, and temperature are Lorentz invariant, so these facts make twin paradox impossible because there is no way for one twin to age slower than the other even if the time in his frame is dilated. Entropy is the function of state, not time. So as much as standard thermodynamics concerns, the path between two points in space is equivalent to the path between two states. Whether the point B is reached by moving faster using the longer way (with time dilatation, or slower by using shortcut (without time dilatation, the state of the system after completing the road should be the same. This is supported by the fact that when two twins reach the same space-time point (point B in which the state parameters are the same. If we use entropy as an age parameter, then both twins have the same entropy value and are exactly the same biological age. Therefore, the twin paradox is a logical mistake based on wrong first premise. Bergson symmetry is not necessary any more to explain the impossibility of twin paradox.

  14. Imperfect twinning: a clinical and ethical dilemma.

    Science.gov (United States)

    Denardin, Daniela; Telles, Jorge Alberto B; Betat, Rosilene da Silveira; Fell, Paulo Renato K; Cunha, André Campos da; Targa, Luciano Vieira; Zen, Paulo Ricardo G; Rosa, Rafael Fabiano M

    2013-09-01

    OBJECTIVE To review the history, epidemiology, etiology, gestational aspects, diagnosis and prognosis of imperfect twinning. DATA SOURCES Scientific articles were searched in PubMed, SciELO and Lilacs databases, using the descriptors "conjoined twins", "multiple pregnancy", "ultrasound", "magnetic resonance imaging" and "prognosis". The research was not delimited to a specific period of time and was supplemented with bibliographic data from books. The description of conjoined twins is legendary. The estimated frequency is 1/45,000-200,000 births. These twins are monozygotic, monochorionic and usually monoamniotic. They can be classified by the most prominent fusion site, by the symmetry between the conjoined twins or by the sharing structure. The diagnosis can be performed in the prenatal period or after birth by different techniques, such as ultrasound, magnetic resonance imaging and echocardiography. These tests are of paramount importance for understanding the anatomy of both fetuses/children, as well as for prognosis and surgical plan determination. CONCLUSIONS Although imperfect twinning is a rare condition, the prenatal diagnosis is very important in order to evaluate the fusion site and its complexity. Hence, the evaluation of these children should be multidisciplinary, involving mainly obstetricians, pediatricians and pediatric surgeons. However, some decisions may constitute real ethical dilemmas, in which different points should be discussed and analyzed with the health team and the family.

  15. The Mid-Atlantic Twin Registry, revisited.

    Science.gov (United States)

    Lilley, Emily C H; Silberg, Judy L

    2013-02-01

    The Mid-Atlantic Twin Registry (MATR) is a population-based registry of more than 56,000 twins primarily born or living in Virginia, North Carolina, and South Carolina. The MATR employs several methods of ascertaining twins, and devotes considerable resources to tracking and maintaining communication with MATR participants. Researchers may utilize the MATR for administration of research services including study recruitment, collection of DNA, archival data set creation, as well as data collection through mailed, phone, or online surveys. In addition, the MATR houses the MATR Repository, with over 1,200 blood samples available for researchers interested in DNA genotyping. For over 35 years MATR twins have participated in research studies with investigators from diverse scientific disciplines and various institutions. These studies, which have resulted in numerous publications, have covered a range of topics, including the human microbiome, developmental psychopathology, depression, anxiety, substance use, epigenetics of aging, children of twins, pre-term birth, social attitudes, seizures, eating disorders, as well as sleep homeostasis. Researchers interested in utilizing twins are encouraged to contact the MATR to discuss potential research opportunities.

  16. Microstructure and spectroscopy studies on cubic boron nitride synthesized under high-pressure conditions

    International Nuclear Information System (INIS)

    Nistor, L C; Nistor, S V; Dinca, G; Georgeoni, P; Landuyt, J van; Manfredotti, C; Vittone, E

    2002-01-01

    High-resolution electron microscopy (HREM) studies of the microstructure and specific defects in hexagonal boron nitride (h-BN) precursors and cubic boron nitride (c-BN) crystals made under high-pressure high-temperature conditions revealed the presence of half-nanotubes at the edges of the h-BN particles. Their sp 3 bonding tendency could strongly influence the nucleation rates of c-BN. The atomic resolution at extended dislocations was insufficient to allow us to determine the stacking fault energy in the c-BN crystals. Its mean value of 191 pm, 15 mJ m -2 is of the same order of magnitude as that of diamond. High-frequency (94 GHz) electron paramagnetic resonance studies on c-BN single crystals have produced new data on the D1 centres associated with the boron species. Ion-beam-induced luminescence measurements have indicated that c-BN is a very interesting luminescent material, which is characterized by four luminescence bands and exhibits a better resistance to ionizing radiation than CVD diamond

  17. Microstructure and spectroscopy studies on cubic boron nitride synthesized under high-pressure conditions

    Energy Technology Data Exchange (ETDEWEB)

    Nistor, L C [National Institute for Materials Physics, Bucharest (Romania); Nistor, S V [National Institute for Materials Physics, Bucharest (Romania); Dinca, G [Dacia Synthetic Diamonds Factory, Bucharest (Romania); Georgeoni, P [Dacia Synthetic Diamonds Factory, Bucharest (Romania); Landuyt, J van [University of Antwerpen - RUCA, EMAT, Antwerpen (Belgium); Manfredotti, C [Experimental Physics Department, University of Turin, Turin (Italy); Vittone, E [Experimental Physics Department, University of Turin, Turin (Italy)

    2002-11-11

    High-resolution electron microscopy (HREM) studies of the microstructure and specific defects in hexagonal boron nitride (h-BN) precursors and cubic boron nitride (c-BN) crystals made under high-pressure high-temperature conditions revealed the presence of half-nanotubes at the edges of the h-BN particles. Their sp{sup 3} bonding tendency could strongly influence the nucleation rates of c-BN. The atomic resolution at extended dislocations was insufficient to allow us to determine the stacking fault energy in the c-BN crystals. Its mean value of 191 pm, 15 mJ m{sup -2} is of the same order of magnitude as that of diamond. High-frequency (94 GHz) electron paramagnetic resonance studies on c-BN single crystals have produced new data on the D1 centres associated with the boron species. Ion-beam-induced luminescence measurements have indicated that c-BN is a very interesting luminescent material, which is characterized by four luminescence bands and exhibits a better resistance to ionizing radiation than CVD diamond.

  18. Generalized Born-Infeld actions and projective cubic curves

    Energy Technology Data Exchange (ETDEWEB)

    Ferrara, S. [Department of Physics, CERN Theory Division, CH - 1211 Geneva 23 (Switzerland); INFN - Laboratori Nazionali di Frascati, Via Enrico Fermi 40, I-00044, Frascati (Italy); Porrati, M. [CCPP, Department of Physics, NYU, 4 Washington Pl., New York, NY, 10003 (United States); Sagnotti, A. [Department of Physics, CERN Theory Division, CH - 1211 Geneva 23 (Switzerland); Stora, R. [Department of Physics, CERN Theory Division, CH - 1211 Geneva 23 (Switzerland); Laboratoire d' Annecy-le-Vieux de Physique Theorique (LAPTH), F-74941, Annecy-le-Vieux, Cedex (France); Yeranyan, A. [INFN - Laboratori Nazionali di Frascati, Via Enrico Fermi 40, I-00044, Frascati (Italy); Centro Studi e Ricerche Enrico Fermi, Via Panisperna 89A, 00184, Roma (Italy)

    2015-04-01

    We investigate U(1){sup n} supersymmetric Born-Infeld Lagrangians with a second non-linearly realized supersymmetry. The resulting non-linear structure is more complex than the square root present in the standard Born-Infeld action, and nonetheless the quadratic constraints determining these models can be solved exactly in all cases containing three vector multiplets. The corresponding models are classified by cubic holomorphic prepotentials. Their symmetry structures are associated to projective cubic varieties. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. 3D confocal imaging in CUBIC-cleared mouse heart

    Energy Technology Data Exchange (ETDEWEB)

    Nehrhoff, I.; Bocancea, D.; Vaquero, J.; Vaquero, J.J.; Lorrio, M.T.; Ripoll, J.; Desco, M.; Gomez-Gaviro, M.V.

    2016-07-01

    Acquiring high resolution 3D images of the heart enables the ability to study heart diseases more in detail. Here, the CUBIC (clear, unobstructed brain imaging cocktails and computational analysis) clearing protocol was adapted for thick mouse heart sections to increase the penetration depth of the confocal microscope lasers into the tissue. The adapted CUBIC clearing of the heart lets the antibody penetrate deeper into the tissue by a factor of five. The here shown protocol enables deep 3D highresolution image acquisition in the heart. This allows a much more accurate assessment of the cellular and structural changes that underlie heart diseases. (Author)

  20. Eisenstein Series Identities Involving the Borweins' Cubic Theta Functions

    Directory of Open Access Journals (Sweden)

    Ernest X. W. Xia

    2012-01-01

    Full Text Available Based on the theories of Ramanujan's elliptic functions and the (p, k-parametrization of theta functions due to Alaca et al. (2006, 2007, 2006 we derive certain Eisenstein series identities involving the Borweins' cubic theta functions with the help of the computer. Some of these identities were proved by Liu based on the fundamental theory of elliptic functions and some of them may be new. One side of each identity involves Eisenstein series, the other products of the Borweins' cubic theta functions. As applications, we evaluate some convolution sums. These evaluations are different from the formulas given by Alaca et al.

  1. Regularizing cubic open Neveu-Schwarz string field theory

    International Nuclear Information System (INIS)

    Berkovits, Nathan; Siegel, Warren

    2009-01-01

    After introducing non-minimal variables, the midpoint insertion of Y Y-bar in cubic open Neveu-Schwarz string field theory can be replaced with an operator N ρ depending on a constant parameter ρ. As in cubic open superstring field theory using the pure spinor formalism, the operator N ρ is invertible and is equal to 1 up to a BRST-trivial quantity. So unlike the linearized equation of motion Y Y-bar QV = 0 which requires truncation of the Hilbert space in order to imply QV = 0, the linearized equation N ρ QV = 0 directly implies QV = 0.

  2. 3D confocal imaging in CUBIC-cleared mouse heart

    International Nuclear Information System (INIS)

    Nehrhoff, I.; Bocancea, D.; Vaquero, J.; Vaquero, J.J.; Lorrio, M.T.; Ripoll, J.; Desco, M.; Gomez-Gaviro, M.V.

    2016-01-01

    Acquiring high resolution 3D images of the heart enables the ability to study heart diseases more in detail. Here, the CUBIC (clear, unobstructed brain imaging cocktails and computational analysis) clearing protocol was adapted for thick mouse heart sections to increase the penetration depth of the confocal microscope lasers into the tissue. The adapted CUBIC clearing of the heart lets the antibody penetrate deeper into the tissue by a factor of five. The here shown protocol enables deep 3D highresolution image acquisition in the heart. This allows a much more accurate assessment of the cellular and structural changes that underlie heart diseases. (Author)

  3. Total Positivity of the Cubic Trigonometric Bézier Basis

    Directory of Open Access Journals (Sweden)

    Xuli Han

    2014-01-01

    Full Text Available Within the general framework of Quasi Extended Chebyshev space, we prove that the cubic trigonometric Bézier basis with two shape parameters λ and μ given in Han et al. (2009 forms an optimal normalized totally positive basis for λ,μ∈(-2,1]. Moreover, we show that for λ=-2 or μ=-2 the basis is not suited for curve design from the blossom point of view. In order to compute the corresponding cubic trigonometric Bézier curves stably and efficiently, we also develop a new corner cutting algorithm.

  4. Twin birth order, birthweight and birthweight discordance: any relationship

    Directory of Open Access Journals (Sweden)

    Onyiriuka A.N.

    2010-12-01

    Full Text Available Background: It is widely believed that in twin pairs, at birth, the first-born weigh more than the second-born but this concept has been challenged. Objective: To assess the truthfulness of this common concept that first-born twins are usually heavier than their second-born siblings at birth. Methods: In a series of 104 sets of live-born twins, the birth weights of first-born twins were compared with those of their second-born siblings, after controlling for gender. Their intra-pair birthweight differences were determined and twin pairs whose birthweight difference was 15% or more were designated as discordant. Results: Twin I was heavier than Twin II in 61.5% of cases while Twin II was heavier than Twin I in 28.9% of cases. Twins I and II had equal birthweights in 9.6% of cases. Comparing the mean birthweight of the first-born-male twin with that of second-born- male twin, it was 2515+427g (95% Confidence Interval, CI=2402-2628 versus 2432 +435g (95% CI=2321-2543 p>0.05. The mean birthweight of first-born-female twin was 2326+445g (95% CI=2214-2439 while that of the second-born-female twin was 2325+501g (95% CI=2197-2453 p>0.05. When the birthweight difference exceeded 750g, the probability that Twin I will be heavier than Twin II was 83.3% (5 of 6. Conclusion: Although the first-born twin was more often heavier than their second-born siblings, either could weigh more or less at birth. The larger the birthweight difference between growth-discordant twin pair, the greater the probability that the heavier twin would be delivered first

  5. Radiation effects in cubic zirconia: A model system for ceramic oxides

    Science.gov (United States)

    Thomé, L.; Moll, S.; Sattonnay, G.; Vincent, L.; Garrido, F.; Jagielski, J.

    2009-06-01

    Ceramics are key engineering materials for electronic, space and nuclear industry. Some of them are promising matrices for the immobilization and/or transmutation of radioactive waste. Cubic zirconia is a model system for the study of radiation effects in ceramic oxides. Ion beams are very efficient tools for the simulation of the radiations produced in nuclear reactors or in storage form. In this article, we summarize the work made by combining advanced techniques (RBS/C, XRD, TEM, AFM) to study the structural modifications produced in ion-irradiated cubic zirconia single crystals. Ions with energies in the MeV-GeV range allow exploring the nuclear collision and electronic excitation regimes. At low energy, where ballistic effects dominate, the damage exhibits a peak around the ion projected range; it accumulates with a double-step process by the formation of a dislocation network. At high energy, where electronic excitations are favored, the damage profiles are rather flat up to several micrometers; the damage accumulation is monotonous (one step) and occurs through the creation and overlap of ion tracks. These results may be generalized to many nuclear ceramics.

  6. Self-oriented Ag-based polycrystalline cubic nanostructures through polymer stabilization

    Science.gov (United States)

    Alonso, Amanda; Vigués, Núria; Rodríguez-Rodríguez, Rosalía; Borrisé, Xavier; Muñoz, María; Muraviev, Dmitri N.; Mas, Jordi; Muñoz-Berbel, Xavier

    2016-10-01

    This paper presents the study of the dynamics of the formation of polymer-assisted highly-orientated polycrystalline cubic structures (CS) by a fractal-mediated mechanism. This mechanism involves the formation of seed Ag@Co nanoparticles by InterMatrix Synthesis and subsequent overgrowth after incubation at a low temperature in chloride and phosphate solutions. These ions promote the dissolution and recrystallization in an ordered configuration of pre-synthetized nanoparticles initially embedded in negatively-charged polymeric matrices. During recrystallization, silver ions aggregate in AgCl@Co fractal-like structures, then evolve into regular polycrystalline solid nanostructures (e.g. CS) in a single crystallization step on specific regions of the ion exchange resin (IER) which maintain the integrity of polycrystalline nanocubes. Here, we study the essential role of the IER in the formation of these CS for the maintenance of their integrity and stability. Thus, this synthesis protocol may be easily expanded to the composition of other nanoparticles providing an interesting, cheap and simple alternative for cubic structure formation and isolation.

  7. Rapid hydrothermal route to synthesize cubic-phase gadolinium oxide nanorods

    International Nuclear Information System (INIS)

    Hazarika, Samiran; Paul, Nibedita; Mohanta, Dambarudhar

    2014-01-01

    An inexpensive fabrication route and growth mechanism is being reported for obtaining quality gadolinium oxide ( Gd 2 O 3 ) nanoscale rods. The elongated nanoscale systems, as produced via a hydrothermal process, were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), optical absorption spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and magnetic hysteresis measurements. XRD patterns of the nanorods, as-prepared from independent precursors of different pH, depict a cubic crystal phase and an average crystallite size of 5-6.5 nm. As revealed from HRTEM micrographs, diameter of the nanorods prepared at pH = 13.3 (∼7 nm) was much smaller than the rods prepared at pH = 10.8 (∼19 nm). However, the aspect ratio was more than double in the former case than the latter case. PL response was found to be dominated by defect mediated emissions, whereas Raman spectrum of a given specimen (pH = 10.8) has revealed characteristic F g + A g modes of cubic phase of Gd 2 O 3 nanorods, apart from other independent modes. Furthermore, M ∼ H plot of the nanorod system (pH = 10.8) exhibited slight departure from the ideal superparamagnetic behaviour, with low remanence and coercive field values. The exploitation of one-dimensional Gd 2 O 3 nanorods have immense potential in the production of advanced contrast agents, smart drives and also in making novel ferrofluids of technological relevance. (author)

  8. Change of Energy of the Cubic Subnanocluster of Iron Under Influence of Interstitial and Substitutional Atoms.

    Science.gov (United States)

    Nedolya, Anatoliy V; Bondarenko, Natalya V

    2016-12-01

    Energy change of an iron face-centred cubic subnanocluster was evaluated using molecular mechanics method depending on the position of a carbon interstitial atom and substitutional atoms of nickel. Calculations of all possible positions of impurity atoms show that the energy change of the system are discrete and at certain positions of the atoms are close to continuous.In terms of energy, when all impurity atoms are on the same edge of an atomic cluster, their positions are more advantageous. The presence of nickel atoms on the edge of a cubic cluster resulted in decrease of potential barrier for a carbon atom and decrease in energy in the whole cluster. A similar drift of a carbon atom from central octahedral interstitial site to the surface in the direction occurred under the influence of surface factors.Such configuration corresponds to decreasing symmetry and increasing the number of possible energy states of a subnanocluster, and it corresponds to the condition of spontaneous crystallization process in an isolated system.Taking into account accidental positions of the nickel atom in the iron cluster, such behaviour of the carbon atom can explain the mechanism of growth of a new phase and formation of new clusters in the presence of other kind of atoms because of surface influence.

  9. Dicyanamide Salts that Adopt Smectic, Columnar, or Bicontinuous Cubic Liquid-Crystalline Mesophases.

    Science.gov (United States)

    Park, Geonhui; Goossens, Karel; Shin, Tae Joo; Bielawski, Christopher W

    2018-04-25

    Although dicyanamide (i.e., [N(CN) 2 ] - ) has been commonly used to obtain low-viscosity, halogen-free, room-temperature ionic liquids, liquid-crystalline salts containing such anions have remained virtually unexplored. Here we report a series of amphiphilic dicyanamide salts that, depending on their structures and compositions, adopt smectic, columnar, or bicontinuous cubic thermotropic liquid-crystalline mesophases, even at room temperature in some cases. Their thermal properties were explored by polarized light optical microscopy, differential scanning calorimetry, thermogravimetric analysis (including evolved gas analysis), and variable-temperature synchrotron X-ray diffraction. Comparison of the thermal phase characteristics of these new liquid-crystalline salts featuring "V-shaped" [N(CN) 2 ] - anions with those of structural analogues containing [SCN] - , [BF 4 ] - , [PF 6 ] - , or [CF 3 SO 3 ] - anions indicated that not only the size of the counterion but also its shape should be considered in the development of mesomorphic salts. Collectively, these discoveries may be expected to facilitate the design of thermotropic ionic liquid crystals that form inverted-type bicontinuous cubic and other sophisticated liquid-crystalline phases. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Microscopy evidence of the face-centered cubic arrangement of monodisperse polystyrene nanospheres

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Hui [School of Science, Beijing Jiaotong University, Beijing 100044 (China)]. E-mail: zhanghui14305@sohu.com; Duan Renguan [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li Fan [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Tang Qing [Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080 (China); Li Wenchao [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2007-07-01

    This paper reports a scanning electron microscopy (SEM) investigation of polystyrene artificial opal achieved through self-assembly of monodisperse polystyrene nanospheres with a diameter of 250 nm from colloidal suspension after being ambient dried. A detailed analysis of the SEM images verifies that the face-centered cubic (fcc) phase is the most stable one for the polystyrene opal prepared. This finding provides a strong support for, by using polystyrene opal as template, fabricating a photonic crystal with inverse fcc structure of full band gap if the refractive index contrast is higher than 2.8 and the filling fraction of the high index materials is between 0.2 and 0.3.

  11. Microscopy evidence of the face-centered cubic arrangement of monodisperse polystyrene nanospheres

    International Nuclear Information System (INIS)

    Zhang Hui; Duan Renguan; Li Fan; Tang Qing; Li Wenchao

    2007-01-01

    This paper reports a scanning electron microscopy (SEM) investigation of polystyrene artificial opal achieved through self-assembly of monodisperse polystyrene nanospheres with a diameter of 250 nm from colloidal suspension after being ambient dried. A detailed analysis of the SEM images verifies that the face-centered cubic (fcc) phase is the most stable one for the polystyrene opal prepared. This finding provides a strong support for, by using polystyrene opal as template, fabricating a photonic crystal with inverse fcc structure of full band gap if the refractive index contrast is higher than 2.8 and the filling fraction of the high index materials is between 0.2 and 0.3

  12. Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics

    International Nuclear Information System (INIS)

    Li, Yiming; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua; Zhao, Lijuan

    2016-01-01

    Tm 3+ ions doped β-PbF 2 nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm 3+ doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an O h to D 4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm 3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field

  13. The quantitative representation of fiber-and sheet-texture in metals of cubic system

    International Nuclear Information System (INIS)

    Kim, H.J.; Kim, S.C.; Chun, B.C.; Lee, C.Y.

    1983-01-01

    This is the first article of a series dealing with studies on the quantitative representation of fiber-and sheet-type textures in metals of cubic crystal system. Texture measurements by neutron diffraction method are analyzed using Bunge's series expansion method and the effect of series truncation is studied for samples of various texture sharpness. The present article describes two computer programs, TXFIB and TXSHT, develped for the analysis of the respective fiber-and sheet-type texture. Using these computer programs, the orientation distribution function can be expanded in the series of generalized spherical harmonics up to 58th term from 6 experimental pole figures as input. Estimations of various errors involved in the texture analysis and texture sharpness index are also included in the programs. (Author)

  14. Spectral intensities in cubic systems. I. Progressions based upon parity vibrational modes

    International Nuclear Information System (INIS)

    Acevedo, R.; Vasquez, S.O.; Meruane, T.; Poblete, V.; Pozo, J.

    1998-01-01

    The well-resolved emission and absorption spectra of centrosymmetric coordination compounds of the transition metal ions have been used widely to provide the experimental data against which to test theoretical models of vibronic intensities. With reference to the 2 E g → 4 A 2g luminescence transition, at a perfect octahedral site in Cs 2 SiF 6 , over than one hundred vibronic lines are observed with line widths of a few wavenumber spread over some 3000 cm -1 . This paper reports a through examination of both the electronic and vibrational factors, which influences the observed vibronic intensities of the various assigned and identified lines in the spectra of the MnF 6 2- complex ion in the Cs 2 SiF 6 cubic lattice. The origin and nature of higher order vibronic interactions are analysed on the basis of a symmetrized vibronic crystal field-ligand polarization model. (Author)

  15. Cubic boron nitride (cBN) - A new material for advanced optoelectronic devices. Properties and perspectives

    International Nuclear Information System (INIS)

    Nistor, S.V.; Nistor, L.C.; Dinca, G.

    2001-01-01

    Cubic boron nitride (cBN) exhibits, besides exceptional thermal and mechanical properties similar to diamond, an excellent ability to be n or p doped, which makes it a strong candidate for advanced, high - temperature optical and microelectronic devices. Despite its outstanding characteristics, there are quite a few reports concerning the physical properties of cBN. This is partly due to the absence of natural cBN gems and the extreme difficulties in producing enough large (mm 3 sized) single crystals, or single phase thin films, for physical characterization. The state of the art knowledge concerning the basic properties of crystalline cBN, as well as our recent results of microstructure and defect properties studies will be presented. (authors)

  16. Shear-induced anisotropic plastic flow from body-centred-cubic tantalum before melting

    Science.gov (United States)

    Wu, Christine J.; Söderlind, Per; Glosli, James N.; Klepeis, John E.

    2009-03-01

    There are many structural and optical similarities between a liquid and a plastic flow. Thus, it is non-trivial to distinguish between them at high pressures and temperatures, and a detailed description of the transformation between these phenomena is crucial to our understanding of the melting of metals at high pressures. Here we report a shear-induced, partially disordered viscous plastic flow from body-centred-cubic tantalum under heating before it melts into a liquid. This thermally activated structural transformation produces a unique, one-dimensional structure analogous to a liquid crystal with the rheological characteristics of Bingham plastics. This mechanism is not specific to Ta and is expected to hold more generally for other metals. Remarkably, this transition is fully consistent with the previously reported anomalously low-temperature melting curve and thus offers a plausible resolution to a long-standing controversy about melting of metals under high pressures.

  17. Familial aggregation of atrial fibrillation: a study in Danish twins

    DEFF Research Database (Denmark)

    Christophersen, Ingrid Elisabeth; Ravn, Lasse Steen; Budtz-Joergensen, Esben

    2009-01-01

    BACKGROUND: Heritability may play a role in nonfamilial atrial fibrillation (AF). We hypothesized that a monozygotic (MZ) twin whose co-twin was diagnosed with AF would have an increased risk of the disease compared with a dizygotic (DZ) twin in the same situation. METHODS AND RESULTS: A sample......-free survival times, we compared the time span between occurrences of disease in MZ and DZ twins. The unaffected twin was included when his or her twin-sibling (the index twin) was diagnosed with AF. After adjustment for age at entry, MZ twins had a significantly shorter event-free survival time (hazard ratio......, 2.0; 95% CI, 1.3 to 3.0), thereby indicating a genetic component. Using biometric models, we estimated the heritability of AF to be 62% (55% to 68%), due to additive genetics. There were no significant differences across sexes. CONCLUSIONS: All the analyses of twin similarities in the present study...

  18. Crystallization kinetics in Si-1 at%Sn during rapid solidification in undercooled melt

    Science.gov (United States)

    Kuribayashi, K.; Ozawa, S.; Nagayama, K.; Inatomi, Y.

    2017-06-01

    In order to elucidate the cause of the morphological transition of crystals growing in an undercooled melt of semiconducting materials, we carried out the containerless solidification of undoped Si and Si-1 at%Sn using a CO2 laser-equipped electromagnetic levitator (EML). The crystallization of these materials was successfully achieved under controlled undercooling. The relation between the shape of growing crystals and the degree of undercooling in Si-1 at%Sn was similar to that in undoped Si; that is, plate-like needle crystals were observed at low undercooling, whereas at medium and high undercooling the shape of growing crystals changed to massive dendrites. The grain-size of as-solidified samples of Si-1 at%Sn was remarkably small compared with that of undoped Si. The surface morphologies of samples solidified by dropping the melt onto a chill plate of mirror-polished silicon consisted of typical twin-related dendrites. On the other hand, samples that were dropped from the undercooled state consisted of twin-free dendrites. The nucleation rate of two-dimensional nuclei calculated on the basis of two mechanisms, which are the twin-plane re-entrant edge mechanism and the twin-free mechanism, suggested that the morphological transition to twin-free dendrites from twin-related dendrites occurs when the degree of undercooling becomes larger than the critical value. These results indicate that the cause of the morphological transition of Si growing in the undercooled melt is not the roughening transition of the crystal-melt interface but the transition of the nucleation kinetics to the twin-free mechanism from the twin-related mechanism.

  19. Purification and crystallization of Phd, the antitoxin of the phd/doc operon

    International Nuclear Information System (INIS)

    Garcia-Pino, Abel; Sterckx, Yann; Vandenbussche, Guy; Loris, Remy

    2010-01-01

    The antitoxin Phd from the phd/doc operon of bacteriophage P1 was crystallized in two distinct crystal forms. The antitoxin Phd from the phd/doc module of bacteriophage P1 was crystallized in two distinct crystal forms. Crystals of His-tagged Phd contain a C-terminally truncated version of the protein and diffract to 2.20 Å resolution. Crystals of untagged Phd purified from the Phd–Doc complex diffract to 2.25 Å resolution. These crystals are partially merohedrally twinned and contain the full-length version of the protein

  20. Twin probes for space geodesy

    International Nuclear Information System (INIS)

    Bertotti, B.

    1978-01-01

    The twin probe method, proposed by Bertotti and Colombo (1972) to get rid of nongravitational forces in interplanetary space, can be applied to a near-Earth orbit to eliminate the atmospheric drag. Two equal pairs of probes, each pair consisting of two passive, small and dense spheres of equal surface and different masses, are flown on a circular orbit at an altitude of about 300 km. Each pair determines the motion of an ideal point which feels only the gravitational forces. They are separated by a distance d of (100/200) km and are tracked from a spacecraft or the Space Shuttle, flying at the same altitude. The relative motion of the two ideal points is reconstructed and yields a measurement of the fine structure of the Earth gravitational field, corresponding to a harmonic order l approximately a/d (a is the radius of the Earth). The tracking can be done by laser ranging to the four spheres, covered by corner reflectors; Doppler ranging is more convenient for higher values of l and can also be used. The accuracy in the compensation of the non-gravitational forces and in the measurements one needs for a given l are discussed in detail. (author)

  1. Effect of maternal smoking on birth weight of twins: a study from the Dutch Twin Register

    NARCIS (Netherlands)

    Orlebeke, J.F.; Boomsma, D.I.; van Baal, G.C.M.; Bleker, O.P.

    1994-01-01

    Since twins weigh about 20% less than singletons at birth, maternal smoking may be a more severe risk for them than for singletons. Therefore, the effect of maternal smoking during pregnancy on birth weight was investigated in a group of 5376 twins. All necessary information was collected by a

  2. Art for twins: Yorùbá artists and their statues/twin research studies: twins' education and conceptions; diurnal preference; inherited eye diseases; ultrasound counseling when twins are conjoined/popular twin reports: twin sisters (the film); rare pregnancy; diet test; French twins reared apart and reunited.

    Science.gov (United States)

    Segal, Nancy L

    2014-06-01

    The Yorùbá of Nigeria are well known for their high twinning rate and the statues they create to commemorate deceased twins. An impressive collection of this artwork was displayed at the University of California's Fowler Museum in Los Angeles between October 13, 2013 and March 2, 2014. An overview of this exhibit is provided. Next, twin research on maternal education and conception, diurnal preference, inherited eye diseases, and ultrasound counseling for couples with conjoined twins are briefly summarized. This article concludes with a discussion of media-based items related to twins. The topics include an award-winning twin film, a rare pregnancy, a diet test, and the separation and chance reunion of monozygotic female twins.

  3. Specific heat of the simple-cubic Ising model

    NARCIS (Netherlands)

    Feng, X.; Blöte, H.W.J.

    2010-01-01

    We provide an expression quantitatively describing the specific heat of the Ising model on the simple-cubic lattice in the critical region. This expression is based on finite-size scaling of numerical results obtained by means of a Monte Carlo method. It agrees satisfactorily with series expansions

  4. Higher-Order Approximation of Cubic-Quintic Duffing Model

    DEFF Research Database (Denmark)

    Ganji, S. S.; Barari, Amin; Babazadeh, H.

    2011-01-01

    We apply an Artificial Parameter Lindstedt-Poincaré Method (APL-PM) to find improved approximate solutions for strongly nonlinear Duffing oscillations with cubic-quintic nonlinear restoring force. This approach yields simple linear algebraic equations instead of nonlinear algebraic equations...

  5. C2-rational cubic spline involving tension parameters

    Indian Academy of Sciences (India)

    preferred which preserves some of the characteristics of the function to be interpolated. In order to tackle such ... Shape preserving properties of the rational (cubic/quadratic) spline interpolant have been studied ... tension parameters which is used to interpolate the given monotonic data is described in. [6]. Shape preserving ...

  6. Initial post dynamic buckling of a quadratic-cubic column ...

    African Journals Online (AJOL)

    In this investigation, we determine the dynamic buckling load of an imperfect finite column resting on a mixed quadratic-cubic nonlinear elastic foundation trapped by an explicitly time dependent sinusoidally slowly varying dynamic load .The resultant coefficients are dynamically slowly varying and the formulation contains ...

  7. Phonons in face-centred cubic calcium and strontium

    International Nuclear Information System (INIS)

    Singh, S.P.; Rathore, R.P.S.

    1984-01-01

    The axially symmetric and unpaired forces are employed to analyse the phonon dispersion and elastic behaviour of face centred cubic calcium and strontium which have so far not been studied adequately. The model with three parameters predicts the results which agree marvellously with the recently measured data. (author)

  8. One billion cubic meters of gas produced in Kikinda area

    Energy Technology Data Exchange (ETDEWEB)

    Vicicevic, M; Duric, N

    1969-10-01

    The Kikinda gas reservoir has just passed a milestone in producing one billion cubic meters of natural gas. The reservoir was discovered in 1962, and its present production amounts to 26 million cu m. One of the biggest problems was formation of hydrates, which has successfully been solved by using methanol. Four tables show production statistics by years and productive formations.

  9. Physical vapor deposition of cubic boron nitride thin films

    International Nuclear Information System (INIS)

    Kester, D.J.

    1991-01-01

    Cubic boron nitride was successfully deposited using physical vapor-deposition methods. RF-sputtering, magnetron sputtering, dual-ion-beam deposition, and ion-beam-assisted evaporation were all used. The ion-assisted evaporation, using boron evaporation and bombardment by nitrogen and argon ions, led to successful cubic boron nitride growth over the widest and most controllable range of conditions. It was found that two factors were important for c-BN growth: bombardment of the growing film and the presence of argon. A systematic study of the deposition conditions was carried out. It was found that the value of momentum transferred into the growing from by the bombarding ions was critical. There was a very narrow transition range in which mixed cubic and hexagonal phase films were prepared. Momentum-per-atom value took into account all the variables involved in ion-assisted deposition: deposition rate, ion energy, ion flux, and ion species. No other factor led to the same control of the process. The role of temperature was also studied; it was found that at low temperatures only mixed cubic and hexagonal material are deposited

  10. Particle Creation in Oscillating Cavities with Cubic and Cylindrical Geometry

    Science.gov (United States)

    Setare, M. R.; Dinani, H. T.

    2008-04-01

    In the present paper we study the creation of massless scalar particles from the quantum vacuum due to the dynamical Casimir effect by oscillating cavities with cubic and cylindrical geometry. To the first order of the amplitude we derive the expressions for the number of the created particles.

  11. Global Well-Posedness for Cubic NLS with Nonlinear Damping

    KAUST Repository

    Antonelli, Paolo

    2010-11-04

    We study the Cauchy problem for the cubic nonlinear Schrödinger equation, perturbed by (higher order) dissipative nonlinearities. We prove global in-time existence of solutions for general initial data in the energy space. In particular we treat the energy-critical case of a quintic dissipation in three space dimensions. © Taylor & Francis Group, LLC.

  12. Influence of strontium on the cubic to ordered hexagonal phase

    Indian Academy of Sciences (India)

    ... Refresher Courses · Symposia · Live Streaming. Home; Journals; Bulletin of Materials Science; Volume 23; Issue 6. Influence of strontium on the cubic to ordered hexagonal phase transformation in barium magnesium niobate. M Thirumal A K Ganguli. Phase Transitions Volume 23 Issue 6 December 2000 pp 495-498 ...

  13. Exact solutions for the cubic-quintic nonlinear Schroedinger equation

    International Nuclear Information System (INIS)

    Zhu Jiamin; Ma Zhengyi

    2007-01-01

    In this paper, the cubic-quintic nonlinear Schroedinger equation is solved through the extended elliptic sub-equation method. As a consequence, many types of exact travelling wave solutions are obtained which including bell and kink profile solitary wave solutions, triangular periodic wave solutions and singular solutions

  14. Estimating the board foot to cubic foot ratio

    Science.gov (United States)

    Steve P. Verrill; Victoria L. Herian; Henry N. Spelter

    2004-01-01

    Certain issues in recent softwood lumber trade negotiations have centered on the method for converting estimates of timber volumes reported in cubic meters to board feet. Such conversions depend on many factors; three of the most important of these are log length, diameter, and taper. Average log diameters vary by region and have declined in the western United States...

  15. A Unified Approach to Teaching Quadratic and Cubic Equations.

    Science.gov (United States)

    Ward, A. J. B.

    2003-01-01

    Presents a simple method for teaching the algebraic solution of cubic equations via completion of the cube. Shows that this method is readily accepted by students already familiar with completion of the square as a method for quadratic equations. (Author/KHR)

  16. Tangent Lines without Derivatives for Quadratic and Cubic Equations

    Science.gov (United States)

    Carroll, William J.

    2009-01-01

    In the quadratic equation, y = ax[superscript 2] + bx + c, the equation y = bx + c is identified as the equation of the line tangent to the parabola at its y-intercept. This is extended to give a convenient method of graphing tangent lines at any point on the graph of a quadratic or a cubic equation. (Contains 5 figures.)

  17. Hardness and thermal stability of cubic silicon nitride

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Kragh, Flemming; Frost, D. J.

    2001-01-01

    The hardness and thermal stability of cubic spinel silicon nitride (c-Si3N4), synthesized under high-pressure and high-temperature conditions, have been studied by microindentation measurements, and x-ray powder diffraction and scanning electron microscopy, respectively The phase at ambient...

  18. Attachment to the Romantic Partner and Sibling: Attachment Hierarchies of Twins and Non-Twin Siblings

    Directory of Open Access Journals (Sweden)

    Sascha Schwarz

    2015-12-01

    Full Text Available Previous studies have shown that romantic partners and siblings are important attachment figures. This study compares the attachment to the romantic partner with the attachment to the sibling as a function of the participant’s sibling type among monozygotic (MZ twins, dizygotic (DZ twins, and non-twin (NT siblings. The results show that MZ twins prefer their sibling to their romantic partner whereas DZ twins are equally attached to their sibling and romantic partner. In contrast, NT siblings are more attached to their romantic partner compared to their sibling. These results indicate that genetic relatedness has profound impact on a person’s attachment hierarchy and the relative rank of the romantic partner and the sibling.

  19. Relationship between refractive error and ocular biometrics in twin children: the Guangzhou Twin Eye Study.

    Science.gov (United States)

    Wang, Decai; Liu, Bin; Huang, Shengsong; Huang, Wenyong; He, Mingguang

    2014-09-01

    A cross-sectional study was conducted to explore the relationship between refractive error and ocular biometrics in children from the Guangzhou twin eye study. Twin participants aged 7-15 years were selected from Guangzhou Twin Eye Study. Ocular examinations included visual acuity measurement, ocular motility evaluation, autorefraction under cycloplegia, and anterior segment, media, and fundus examination. Axial length (AL), anterior chamber depth (ACD), and corneal curvature radius were measured using partial coherence laser interferometry. A multivariate linear regression model was used for statistical analysis. Twin children from Guangzhou city showed a decreased spherical equivalent with age, whereas both AL and ACD were increased and corneal curvature radius remained unchanged. When adjusted by age and gender, the data from 77% of twins presenting with spherical equivalent changes indicated that these were caused by predictable variables (R2 = 0.77, P biometrics. Refractive status is largely determined by axial length as the major factor.

  20. Indigenous Manufacturing realization of TWIN Source

    Science.gov (United States)

    Pandey, R.; Bandyopadhyay, M.; Parmar, D.; Yadav, R.; Tyagi, H.; Soni, J.; Shishangiya, H.; Sudhir Kumar, D.; Shah, S.; Bansal, G.; Pandya, K.; Parmar, K.; Vuppugalla, M.; Gahlaut, A.; Chakraborty, A.

    2017-04-01

    TWIN source is two RF driver based negative ion source that has been planned to bridge the gap between single driver based ROBIN source (currently operational) and eight river based DNB source (to be operated under IN-TF test facility). TWIN source experiments have been planned at IPR keeping the objective of long term domestic fusion programme to gain operational experiences on vacuum immersed multi driver RF based negative ion source. High vacuum compatible components of twin source are designed at IPR keeping an aim on indigenous built in attempt. These components of TWIN source are mainly stainless steel and OFC-Cu. Being high heat flux receiving components, one of the major functional requirements is continuous heat removal via water as cooling medium. Hence for the purpose stainless steel parts are provided with externally milled cooling lines and that shall be covered with a layer of OFC-cu which would be on the receiving side of high heat flux. Manufacturability of twin source components requires joining of these dissimilar materials via process like electrode position, electron beam welding and vacuum brazing. Any of these manufacturing processes shall give a vacuum tight joint having proper joint strength at operating temperature and pressure. Taking the indigenous development effort vacuum brazing (in non-nuclear environment) has been opted for joining of dissimilar materials of twin source being one of the most reliable joining techniques and commercially feasible across the suppliers of country. Manufacturing design improvisation for the components has been done to suit the vacuum brazing process requirement and to ease some of the machining without comprising over the functional and operational requirements. This paper illustrates the details on the indigenous development effort, design improvisation to suits manufacturability, vacuum brazing basics and its procedures for twin source components.

  1. Monozygotic twins discordant for ROHHAD phenotype.

    Science.gov (United States)

    Patwari, Pallavi P; Rand, Casey M; Berry-Kravis, Elizabeth M; Ize-Ludlow, Diego; Weese-Mayer, Debra E

    2011-09-01

    Rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation (ROHHAD) falls within a group of pediatric disorders with both respiratory control and autonomic nervous system dysregulation. Children with ROHHAD typically present after 1.5 years of age with rapid weight gain as the initial sign. Subsequently, they develop alveolar hypoventilation, autonomic nervous system dysregulation, and, if untreated, cardiorespiratory arrest. To our knowledge, this is the first report of discordant presentation of ROHHAD in monozygotic twins. Twin girls, born at term, had concordant growth and development until 8 years of age. From 8 to 12 years of age, the affected twin developed features characteristic of ROHHAD including obesity, alveolar hypoventilation, scoliosis, hypothalamic dysfunction (central diabetes insipidus, hypothyroidism, premature pubarche, and growth hormone deficiency), right paraspinal/thoracic ganglioneuroblastoma, seizures, and autonomic dysregulation including altered pain perception, large and sluggishly reactive pupils, hypothermia, and profound bradycardia that required a cardiac pacemaker. Results of genetic testing for PHOX2B (congenital central hypoventilation syndrome disease-defining gene) mutations were negative. With early recognition and conservative management, the affected twin had excellent neurocognitive outcome that matched that of the unaffected twin. The unaffected twin demonstrated rapid weight gain later in age but not development of signs/symptoms consistent with ROHHAD. This discordant twin pair demonstrates key features of ROHHAD including the importance of early recognition (especially hypoventilation), complexity of signs/symptoms and clinical course, and importance of initiating comprehensive, multispecialty care. These cases confound the hypothesis of a monogenic etiology for ROHHAD and indicate alternative etiologies including autoimmune or epigenetic phenomenon or a combination of genetic

  2. The Project TALENT Twin and Sibling Study.

    Science.gov (United States)

    Prescott, Carol A; Achorn, Deanna Lyter; Kaiser, Ashley; Mitchell, Lindsey; McArdle, John J; Lapham, Susan J

    2013-02-01

    Project TALENT is a US national longitudinal study of about 377,000 individuals born in 1942-1946, first assessed in 1960. Students in about 1,200 schools participated in a 2-day battery covering aptitudes, abilities, interests, and individual and family characteristics (Flanagan, 1962; www.projectTALENT.org). Follow-up assessments 1, 5, and 11 years later assessed educational and occupational outcomes. The sample includes approximately 92,000 siblings from 40,000 families, including 2,500 twin pairs and 1,200 other siblings of twins. Until recently, almost no behavior genetic research has been conducted with the sample. In the original data collection information was not collected with the intent to link family members. Recently, we developed algorithms using names, addresses, birthdates, and information about family structure to link siblings and identify twins. We are testing several methods to determine zygosity, including use of yearbook photographs. In this paper, we summarize the design and measures in Project TALENT, describe the Twin and Sibling sample, and present our twin-sib-classmate model. In most twin and family designs, the 'shared environment' includes factors specific to the family combined with between-family differences associated with macro-level variables such as socioeconomic status. The school-based sampling design used in Project TALENT provides a unique opportunity to partition the shared environment into variation shared by siblings, specific to twins, and associated with school- and community-level factors. The availability of many measured characteristics on the family, schools, and neighborhoods enhances the ability to study the impact of specific factors on behavioral variation.

  3. Diabetes and perinatal mortality in twin pregnancies.

    Directory of Open Access Journals (Sweden)

    Zhong-Cheng Luo

    Full Text Available BACKGROUND: Diabetes in pregnancy has been associated with a paradoxically reduced risk of neonatal death in twin pregnancies. Risk "shift" may be a concern in that the reduction in neonatal deaths may be due to an increase in fetal deaths (stillbirths. This study aimed to clarify the impact of diabetes on the risk of perinatal death (neonatal death plus stillbirth in twin pregnancies. METHODS: This was a retrospective cohort study of twin births using the largest available dataset on twin births (the U.S. matched multiple birth data 1995-2000; 19,676 neonates from diabetic pregnancies, 541,481 from non-diabetic pregnancies. Cox proportional hazard models were applied to estimate the adjusted hazard ratios (aHR of perinatal death accounting for twin cluster-level dependence. RESULTS: Comparing diabetic versus non-diabetic twin pregnancies, overall perinatal mortality rate was counterintuitively lower [2.1% versus 3.3%, aHR 0.70 (95% confidence intervals 0.63-0.78]. Individually, both stillbirth and neonatal mortality rates were lower in diabetic pregnancies, but we identified significant differences by gestational age and birth weight. Diabetes was associated with a survival benefit in pregnancies completed before 32 weeks [aHR 0.55 (0.48-0.63] or with birth weight =2500 g [aHR 2.20 (1.55-3.13]. CONCLUSIONS: Diabetes in pregnancy appears to be "protective" against perinatal death in twin pregnancies ending in very preterm or very low birth weight births. Prospective studies are required to clarify whether these patterns of risk are real, or they are artifacts of unmeasured confounders. Additional data correlating these outcomes with the types of diabetes in pregnancy are also needed to distinguish the effects of pre-gestational vs. gestational diabetes.

  4. Sonographic monitoring of complications and anomalies in twin gestations

    International Nuclear Information System (INIS)

    Coleman, B.G.; Grumbach, K.; Arger, P.H.; Mintz, M.C.; Arenson, R.L.; Mennuti, M.T.; Gabbe, S.G.

    1986-01-01

    One hundred sixty-eight twin gestations were evaluated to assess the role of US in the diagnosis of obstetric complications and anomalies. US revealed the following complications: symptomatic polyhydramnios (eight cases), myomas (seven), placenta previa (three), and abruption (five). Fetal anomalies included twin-twin transfusion syndrome (two), acardiac anomaly (two), chromosomal abnormality (two), anencephaly (one), hydrocephaly (one), and conjoined twins (two). In 26 gestations intrauterine fetal demise or neonatal death involved one or both twins for a total of 42 deaths, constituting a mortality of 12.5%. No maternal deaths occurred. The impact of sonographic monitoring on the obstetric management of twin gestations is emphasized

  5. Twin pregnancy possibly associated with high semen quality

    DEFF Research Database (Denmark)

    Asklund, Camilla; Jensen, Tina Kold; Jørgensen, Niels

    2007-01-01

    BACKGROUND: Recent studies found an association between a long waiting time to pregnancy (TTP) and reduced probability of twinning and a reduced dizygotic (DZ) twinning rate in subfertile men. However, it remains unsolved whether semen quality is associated with twin offspring. We therefore studied...... the semen quality in a group of fathers of naturally conceived twins. METHODS: In this study, 37 fathers of DZ twins and 15 fathers of monozygotic (MZ) twins participated, and 349 normal fertile men served as a reference group. All men delivered a semen sample, underwent a physical examination and completed...... points higher than the reference group (P semen quality than the reference group, which supports...

  6. Energy landscape of defects in body-centered cubic metals

    International Nuclear Information System (INIS)

    Alexander, Rebecca

    2016-01-01

    The structural materials in nuclear reactors are subjected to severe irradiation conditions, leading to changes in their mechanical properties. The aging of these materials raises important issues such as those related to the safety of existing plants and future reactors. In many cases, materials with body-centered cubic bcc crystal structure are used with iron, tungsten, vanadium and tantalum as base metal. Collisions between irradiating particles and atoms constituting materials generate point defects whose migration leads to the formation of clusters responsible for aging. In this thesis, we studied the energetic properties of point defects in the bcc metals mentioned above at the atomic scale. Modeling point defects at the atomic scale can be achieved with different methods that differ only in the quality of the description of the interaction between atoms. Studies using accurate atomic interactions such ab initio calculations are computationally costly making it impossible to directly study clusters of large sizes. The modeling of atomic interactions using semi-empirical potentials reduces the reliability of predictive calculations but allow calculations for large-sized clusters. In this thesis we have developed a unique energy model for dislocation loops as well as for three-dimensional interstitial cluster of type C15. The resulting model has no size limit and can be set entirely by ab initio calculations. To test its robustness for large sizes of clusters we also set this model with semi-empirical potentials calculations and compared the predictions of the model to atomic simulations. With our development we have determined: (i) The relative stability of interstitial dislocation loops according to their Burgers vectors. (ii) The stability of the clusters C15 compared to the type of cluster loop. We showed that the C15 type clusters are more stable when they involve less than 41 interstitials in iron. (iii) In Ta we were able to show the same stability till

  7. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...... element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles. Some plane deformation problems relevant for certain specific orientations of a face centered cubic crystal under plane loading conditions are studied, and effective in......-plane parameters are developed based on the crystallographic properties of the material. The problem of cyclic shear of a single crystal between rigid platens is studied as well as void growth of a cylindrical void....

  8. Cationic Phospholipids Forming Cubic Phases: Lipoplex Structure and Transfection Efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Koynova, Rumiana; Wang, Li; MacDonald, Robert C. (NWU)

    2008-10-29

    The transfection activity and the phase behavior of two novel cationic O-alkyl-phosphatidylcholines, 1,2-dioleoyl-sn-glycero-3-hexylphosphocholine (C6-DOPC) and 1,2-dierucoyl-sn-glycero-3-ethylphosphocholine (di22:1-EPC), have been examined with the aim of more completely understanding the mechanism of lipid-mediated DNA delivery. Both lipids form cubic phases: C6-DOPC in the entire temperature range from -10 to 90 C, while di22:1-EPC exhibits an irreversible lamellar-cubic transition between 50 and 70 C on heating. The lipoplexes formed by C6-DOPC arrange into hexagonal phase, while the lipoplexes of di22:1-EPC are lamellar. Both lipids exhibit lower transfection activity than the lamellar-forming 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (EDOPC). Thus, for the studied cationic phospholipid-DNA systems, the lipoplex phase state is a factor that does not seem to correlate with transfection activity. The parameter that exhibits better correlation with the transfection activity within the present data set is the phase state of the lipid dispersion prior to the addition of DNA. Thus, the lamellar lipid dispersion (EDOPC) produces more efficient lipoplexes than the dispersion with coexisting lamellar and cubic aggregates (diC22:1-EPC), which is even more efficient than the purely cubic dispersions (C6-DOPC; diC22:1-EPC after heating). It could be inferred from these data and from previous research that cubic phase lipid aggregates are unlikely to be beneficial to transfection. The lack of correlation between the phase state of lipoplexes and their transfection activity observed within the present data set does not mean that lipid phase state is generally unimportant for lipofection: a viewpoint now emerging from our previous studies 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.

  9. Cationic phospholipids forming cubic phases: lipoplex structure and transfection efficiency.

    Science.gov (United States)

    Koynova, Rumiana; Wang, Li; Macdonald, Robert C

    2008-01-01

    The transfection activity and the phase behavior of two novel cationic O-alkyl-phosphatidylcholines, 1,2-dioleoyl- sn-glycero-3-hexylphosphocholine (C6-DOPC) and 1,2-dierucoyl- sn-glycero-3-ethylphosphocholine (di22:1-EPC), have been examined with the aim of more completely understanding the mechanism of lipid-mediated DNA delivery. Both lipids form cubic phases: C6-DOPC in the entire temperature range from -10 to 90 degrees C, while di22:1-EPC exhibits an irreversible lamellar-cubic transition between 50 and 70 degrees C on heating. The lipoplexes formed by C6-DOPC arrange into hexagonal phase, while the lipoplexes of di22:1-EPC are lamellar. Both lipids exhibit lower transfection activity than the lamellar-forming 1,2-dioleoyl- sn-glycero-3-ethylphosphocholine (EDOPC). Thus, for the studied cationic phospholipid-DNA systems, the lipoplex phase state is a factor that does not seem to correlate with transfection activity. The parameter that exhibits better correlation with the transfection activity within the present data set is the phase state of the lipid dispersion prior to the addition of DNA. Thus, the lamellar lipid dispersion (EDOPC) produces more efficient lipoplexes than the dispersion with coexisting lamellar and cubic aggregates (diC22:1-EPC), which is even more efficient than the purely cubic dispersions (C6-DOPC; diC22:1-EPC after heating). It could be inferred from these data and from previous research that cubic phase lipid aggregates are unlikely to be beneficial to transfection. The lack of correlation between the phase state of lipoplexes and their transfection activity observed within the present data set does not mean that lipid phase state is generally unimportant for lipofection: a viewpoint now emerging from our previous studies 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.

  10. INVESTIGATION OF CURVES SET BY CUBIC DISTRIBUTION OF CURVATURE

    Directory of Open Access Journals (Sweden)

    S. A. Ustenko

    2014-03-01

    Full Text Available Purpose. Further development of the geometric modeling of curvelinear contours of different objects based on the specified cubic curvature distribution and setpoints of curvature in the boundary points. Methodology. We investigate the flat section of the curvilinear contour generating under condition that cubic curvature distribution is set. Curve begins and ends at the given points, where angles of tangent slope and curvature are also determined. It was obtained the curvature equation of this curve, depending on the section length and coefficient c of cubic curvature distribution. The analysis of obtained equation was carried out. As well as, it was investigated the conditions, in which the inflection points of the curve are appearing. One should find such an interval of parameter change (depending on the input data and the section length, in order to place the inflection point of the curvature graph outside the curve section borders. It was determined the dependence of tangent slope of angle to the curve at its arbitrary point, as well as it was given the recommendations to solve a system of integral equations that allow finding the length of the curve section and the coefficient c of curvature cubic distribution. Findings. As the result of curves research, it is found that the criterion for their selection one can consider the absence of inflection points of the curvature on the observed section. Influence analysis of the parameter c on the graph of tangent slope angle to the curve showed that regardless of its value, it is provided the same rate of angle increase of tangent slope to the curve. Originality. It is improved the approach to geometric modeling of curves based on cubic curvature distribution with its given values at the boundary points by eliminating the inflection points from the observed section of curvilinear contours. Practical value. Curves obtained using the proposed method can be used for geometric modeling of curvilinear

  11. Synthesis of Ag2O nanocrystals with systematic shape evolution from cubic to hexapod structures and their surface properties.

    Science.gov (United States)

    Lyu, Lian-Ming; Wang, Wei-Ching; Huang, Michael H

    2010-12-17

    We report the development of a facile method for the synthesis of Ag(2)O crystals with systematic shape evolution from cubic to edge- and corner-truncated cubic, rhombicuboctahedral, edge- and corner-truncated octahedral, octahedral, and hexapod structures by mixing AgNO(3), NH(4)NO(3), and NaOH at molar ratios of 1:2:11.8. A sufficient volume of NaOH solution was first added to a mixture of AgNO(3) and NH(4)NO(3) solution to promote the formation of Ag(NH(3))(2)(+) complex ions and the growth of Ag(2)O nanocrystals with good morphological control. The crystals are mostly submicrometer-sized. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy characterization has been performed to determine the crystalline surface facets. A band gap value of approximately 1.45 eV has been found for the octahedral Ag(2)O crystals. By changing the molar ratios of AgNO(3)/NH(4)NO(3)/NaOH to 1:2:41.8, corner-depressed rhombicuboctahedra and elongated hexapods were obtained as a result of enhanced crystal growth along the [100] directions. Smaller nanocubes with average sizes of approximately 200 and 300 nm and octapods can also be prepared by adjusting the reagent molar ratios and their added volumes. Both the octahedra and hexapods with largely silver atom-terminated {111} surface facets responded repulsively and moved to the surface of the solution when dispersing in a solution of positively charged methylene blue, but can be suspended in a negatively charged methyl orange solution. The cubes and octapods, bounded by the {100} faces, were insensitive to the molecular charges in solution. The dramatic facet-dependent surface properties of Ag(2)O crystals have been demonstrated.

  12. The influence of high hydrostatic pressure on lattice parameters of a single crystal of BaTiO3

    International Nuclear Information System (INIS)

    Malinowski, M.; Lukaszewicz, K.; Asbrink, S.

    1986-01-01

    The lattice parameters of a single crystal of BaTiO 3 have been measured under high hydrostatic pressure up to 5 GPa using a diamond-anvil high-pressure cell of a new design. The lattice becomes cubic at 2.08(8) GPa and stays cubic at higher pressures. The pressure dependence of the tetragonal-cubic transition temperature is estimated to be -46 K GPa -1 . (orig.)

  13. A twin study of body dysmorphic concerns.

    Science.gov (United States)

    Monzani, B; Rijsdijk, F; Anson, M; Iervolino, A C; Cherkas, L; Spector, T; Mataix-Cols, D

    2012-09-01

    Dysmorphic concern refers to an excessive preoccupation with a perceived or slight defect in physical appearance. It lies on a continuum of severity from no or minimal concerns to severe concerns over one's appearance. The present study examined the heritability of dysmorphic concerns in a large sample of twins. Twins from the St Thomas UK twin registry completed a valid and reliable self-report measure of dysmorphic concerns, which also includes questions about perceived body odour and malfunction. Twin modelling methods (female twins only, n=3544) were employed to decompose the variance in the liability to dysmorphic concerns into additive genetic, shared and non-shared environmental factors. Model-fitting analyses showed that genetic factors accounted for approximately 44% [95% confidence intervals (CI) 36-50%] of the variance in dysmorphic concerns, with non-shared environmental factors and measurement error accounting for the remaining variance (56%; 95% CI 50-63%). Shared environmental factors were negligible. The results remained unchanged when excluding individuals reporting an objective medical condition/injury accounting for their concern in physical appearance. Over-concern with a perceived or slight defect in physical appearance is a heritable trait, with non-shared environmental factors also playing an important role in its causation. The results are relevant for various psychiatric disorders characterized by excessive concerns in body appearance, odour or function, including but not limited to body dysmorphic disorder.

  14. Characterization of Gastric Microbiota in Twins.

    Science.gov (United States)

    Dong, Quanjiang; Xin, Yongning; Wang, Lili; Meng, Xinying; Yu, Xinjuan; Lu, Linlin; Xuan, Shiying

    2017-02-01

    Contribution of host genetic backgrounds in the development of gastric microbiota has not been clearly defined. This study was aimed to characterize the biodiversity, structure and composition of gastric microbiota among twins. A total of four pairs of twins and eight unrelated individuals were enrolled in the study. Antral biopsies were obtained during endoscopy. The bacterial 16S rRNA gene was amplified and pyrosequenced. Sequences were analyzed for the composition, structure, and α and β diversities of gastric microbiota. Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Fusobacteria were the most predominant phyla of gastric microbiota. Each individual, twins as well as unrelated individuals, harbored a microbiota of distinct composition. There was no evidence of additional similarity in the richness and evenness of gastric microbiota among co-twins as compared to unrelated individuals. Calculations of θ YC and PCoA demonstrated that the structure similarity of gastric microbial community between co-twins did not increase compared to unrelated individuals. In contrast, the structure of microbiota was altered enormously by Helicobacter pylori infection. These results suggest that host genetic backgrounds had little effect in shaping the gastric microbiota. This property of gastric microbiota could facilitate the studies discerning the role of microbiota from genetic grounds in the pathogenesis.

  15. Yoruba customs and beliefs pertaining to twins.

    Science.gov (United States)

    Leroy, Fernand; Olaleye-Oruene, Taiwo; Koeppen-Schomerus, Gesina; Bryan, Elizabeth

    2002-04-01

    The Yoruba are an important ethnic group mainly occupying Southwestern Nigeria. Mainly for genetic reasons, this very large tribe happens to present the highest dizygotic twinning rate in the world (4.4 % of all maternities). The high perinatal mortality rate associated with such pregnancies has contributed to the integration of a special twin belief system within the African traditional religion of this tribe. The latter is based on the concept of a supreme deity called Olodumare or Olorun, assisted by a series of secondary gods (Orisha) while Yoruba religion also involves immortality and reincarnation of the soul based on the animistic cult of ancestors. Twins are therefore given special names and believed to detain special preternatural powers. In keeping with their refined artistic tradition, the Yoruba have produced numerous wooden statuettes called Ibejis that represent the souls of deceased newborn twins and are involved in elaborate rituals. Among Yoruba traditional beliefs and lore some twin-related themes are represented which are also found in other parts of the world. Basic features of the original Yoruba beliefs have found their way into the religious traditions of descendants of African slaves imported in the West Indies and in South America.

  16. Separation surgery for total vertical craniopagus twins.

    Science.gov (United States)

    Goh, Keith Y C

    2004-08-01

    A pair of conjoined twins aged 11 months underwent investigations, followed by surgical separation in Singapore General Hospital in April 2001. They were joined at the skull vertex and facing in opposite directions. Radiological investigations including cerebral angiography, magnetic resonance imaging and computerized tomographic scans were performed, leading to the diagnosis of total vertical craniopagus. There were two separate brains, with separate arterial circulations, but with a common superior sagittal sinus. Tissue expanders were inserted in the subgaleal space for 6 months of scalp expansion prior to surgery. Pre-operative planning involved the use of virtual reality equipment and life-sized polymer models of the conjoined skulls and brains. Surgical separation of the twins was achieved after approximately 100 h of operating time, using intraoperative image guidance, microsurgical techniques and intraoperative neurophysiologic monitoring. Reconstruction of the dura, calvarium and scalp was performed with artificial dura, absorbable plates and split skin grafts. Postoperative complications included focal cortical infarction, meningitis, and hydrocephalus. Despite these complications, the twins recovered satisfactorily and were discharged to their home country within 6 months. The 3-month outcome was minor disability in one twin and severe developmental delays in the other. Separation surgery is possible for complex cranially-conjoined twins but requires detailed planning and extensive surgical management.

  17. A Possible Twin: The 1960s Twin Study Revisited/Twin Research: Twin-to-Twin Heart Transplantation; Distinguishing Monozygotic Twins; Twin Conceptions via Oocyte Donation; Factors Affecting Craniofacial Traits/In the Media: Triplet Delivery in the UK; Conjoined Twins and the Concept of Self; Colombian Twin Trainers; Skin Grafting to Save an Identical Co-Twin; Lack of Physical Flaws in Dolly the Cloned Sheep; Possible Conjoined Twins of Opposite-Sex; Passing of the Remaining Twin From the World's Longest Separated Pair.

    Science.gov (United States)

    Segal, Nancy L

    2018-04-01

    This article begins with the story of a 51-year-old Los Angeles, California man, Justin Goldberg, whose daughter caught a glimpse of his striking look-alike at a popular market. Many people have so-called doppelgängers, but this occurrence is especially intriguing - the individual in question, born in New York City in the mid-1960s to an unwed mother, was an adoptee placed by the Louise Wise Adoption Agency. This agency, under the guidance of a prominent psychiatrist, decided to place twins in separate homes. Some of these twin children were part of a controversial child development study that was hidden from them and their parents. Next, recent and current twin research on heart transplantation, distinguishing monozygotic co-twins, twin conceptions via oocyte donation and factors affecting craniofacial traits are summarized. The article concludes with highlights on twins in the media, specifically, a triplet delivery in the United Kingdom, self-concept and consciousness in conjoined twins, Colombian twin trainers, skin grafting to save an identical co-twin, lack of physical flaws in Dolly the cloned sheep, possible opposite-sex conjoined twins, and the passing of the remaining twin from the world's longest separated pair.

  18. A popular metastable omega phase in body-centered cubic steels

    Energy Technology Data Exchange (ETDEWEB)

    Ping, D.H., E-mail: ping.de-hai@nims.go.jp [National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047 (Japan); Geng, W.T., E-mail: geng@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2013-05-15

    Steel remains to be one of the most common structural materials in the world as human civilization advances from the Iron Age to the ongoing Silicon Age. Our knowledge of its microstructure evolution and structure–performance relationship is nevertheless still incomplete. We report the observation and characterization of a long ignored metastable phase formed in steels with body-centered cubic (bcc) structure using both transmission electron microscopy and density functional theory calculations. This ω phase has a hexagonal structure and coherent interface with the matrix: a{sub ω} = √2 × a{sub bcc} and c{sub ω} = √3/2 × a{sub bcc}. It is 3.6% smaller in volume and 0.18 eV higher in energy than bcc-Fe, with atoms in alternating close- and loose-packed layers couple anti-ferromagnetically. Carbon plays a crucial role in promoting bcc to ω transformation. At a concentration higher than 4 at.% they tend to segregate from the bcc matrix to the ω-phase; at about 14 at.%, they can induce bcc to ω transformation; and finally at 25 at.%, they stabilize the ω phase as ω-Fe{sub 3}C. The ω phase in bcc Fe can serve as sinks for vacancies, H, and He atoms, leading to improved resistance of martensitic steels to irradiation damage. - Highlights: ► A long-ignored metastable ω phase in body-centered cubic (bcc) steel. ► The ω phase has hexagonal structure with lattice parameters a{sub ω} = √2 × a{sub bcc} and c{sub ω} = √3/2 × a{sub bcc}. ► Carbon enrichment is found to play a crucial role on the bcc-to-ω phase transformation. ► The ω phase is strongly related to the martensitic transformation and twinning structure. ► The ω phase in bcc Fe can serve as sinks for vacancies, H, and He atoms.

  19. Crystallization of carbohydrate oxidase from Microdochium nivale

    International Nuclear Information System (INIS)

    Dušková, Jarmila; Dohnálek, Jan; Skálová, Tereza; Østergaard, Lars Henrik; Fuglsang, Claus Crone; Kolenko, Petr; Štěpánková, Andrea; Hašek, Jindřich

    2009-01-01

    Industrially used carbohydrate oxidase was successfully crystallized in several forms, diffraction data suitable for structural analysis were collected. Microdochium nivale carbohydrate oxidase was produced by heterologous recombinant expression in Aspergillus oryzae, purified and crystallized. The enzyme crystallizes with varying crystal morphologies depending on the crystallization conditions. Several different crystal forms were obtained using the hanging-drop vapour-diffusion method, two of which were used for diffraction measurements. Hexagon-shaped crystals (form I) diffracted to 2.66 Å resolution, with unit-cell parameters a = b = 55.7, c = 610.4 Å and apparent space group P6 2 22. Analysis of the data quality showed almost perfect twinning of the crystals. Attempts to solve the structure by molecular replacement did not give satisfactory results. Recently, clusters of rod-shaped crystals (form II) were grown in a solution containing PEG MME 550. These crystals belonged to the monoclinic system C2, with unit-cell parameters a = 132.9, b = 56.6, c = 86.5 Å, β = 95.7°. Data sets were collected to a resolution of 2.4 Å. The structure was solved by the molecular-replacement method. Model refinement is currently in progress

  20. Low twinning rate and seasonal effects on twinning in a fertile population, the Hutterites

    Science.gov (United States)

    Nonaka, K.; Miura, T.; Peter, K.

    1993-09-01

    This paper analyzes from the mid 18th century to 1987 the birth records of the “Dariusleut,” one of the three subgroups of the Hutterite population. The aim of this study is to describe several aspects of the twinning rate in a fertile population. The overall rate of twinning was 0.90%:103 twins among all 11492 maternities. The rate peaked at the 7th birth order and at the maternal age of 40 years and over. Until the mid 19th century when the Hutterites lived in Russia, the twinning rate was higher (1.5%), and it decreased during the migration period in the second half of the 19th century (0.7%). After the group had settled in the USA and Canada, the population maintained a twinning rate of 1.0% until 1965. After 1965 the rate decreased to 0.7%, partly due to a decline in fertility among women aged 30 years and over. There was a significant seasonal variation: the twinning rate decreased to 0.5% in May July compared to 1.2% for the other three seasons during the years up to 1965 ( P<0.01), while more recent mothers did not show such a seasonal variation. The incidence of twin births in this population seems to have been influenced by environmental factors, which would change their effect seasonally and secularly.

  1. Vitrification and Crystallization of Phase-Separated Metallic Liquid

    Directory of Open Access Journals (Sweden)

    Yun Cheng

    2017-02-01

    Full Text Available The liquid–liquid phase separation (LLPS behavior of Fe50Cu50 melt from 3500 K to 300 K with different rapid quenching is investigated by molecular dynamics (MD simulation based on the embedded atom method (EAM. The liquid undergoes metastable phase separation by spinodal decomposition in the undercooled regime and subsequently solidifies into three different Fe-rich microstructures: the interconnected-type structure is kept in the glass and crystal at a higher cooling rate, while the Fe-rich droplets are found to crystalize at a lower cooling rate. During the crystallization process, only Fe-rich clusters can act as the solid nuclei. The twinning planes can be observed in the crystal and only the homogeneous atomic stacking shows mirror symmetry along the twinning boundary. Our present work provides atomic-scale understanding of LLPS melt during the cooling process.

  2. Effect of cubic Dresselhaus interaction on the longitudinal optical conductivity of a spin-orbit coupled system

    Science.gov (United States)

    Cruz, Elmer; López-Bastidas, Catalina; Maytorena, Jesús A.

    2018-03-01

    We investigate the effect of the oft-neglected cubic terms of the Dresselhaus spin-orbit coupling on the longitudinal current response of a two-dimensional electron gas with both Rashba and linear Dresselhaus interactions. For a quantum well grown in the [001] direction, the changes caused by these nonlinear-in-momentum terms on the absorption spectrum become more notable under SU(2) symmetry conditions, when the Rashba and linear Dresselhaus coupling strengths are tuned to be equal. The longitudinal optical response no longer vanishes then and shows a strong dependence on the direction of the externally applied electric field, giving a signature of the relative size of several spin-orbit contributions. This anisotropic response arises from the nonisotropic splitting of the spin states induced by the interplay of Rashba and Dresselhaus couplings. However, the presence of cubic terms introduces characteristic spectral features and can modify the overall shape of the spectra for some values of the relative sizes of the spin-orbit parameters. We compare this behavior to the case of a sample with [110] crystal orientation which, under conditions of spin-preserving symmetry, has a collinear spin-orbit vector field that leads to vanishing conductivity, even in the presence of cubic terms. In addition to the control through the driven frequency or electrical gating, such a directional aspect of the current response suggests new ways of manipulation and supports the use of interband optics as a sensitive probe of spin-orbit mechanisms in semiconductor spintronics.

  3. Increased risk of abortion after genetic amniocentesis in twin pregnancies

    DEFF Research Database (Denmark)

    Palle, C; Andersen, J W; Tabor, A

    1983-01-01

    Forty-seven twin pregnancies among 3676 patients who had a genetic amniocentesis between 1973 and 1979, are reported. The detection rate of twins at the time of amniocentesis was 62 per cent. Five (17 per cent) of the 29 women with detected twin pregnancy aborted spontaneously, these are compared...... in at least one sac aborted, while 3 of 20 twin pregnancies with one puncture in each sac aborted (15 per cent). One of 18 (6 per cent) twin pregnancies, where only one sac was punctured, because the twin pregnancies were undetected, aborted. Amniocentesis of both sacs in twin pregnancies seems associated...... with an increased risk of spontaneous abortion. The indications for amniocentesis in twin pregnancies should be critically evaluated....

  4. Aging and communication in the twin paradox

    International Nuclear Information System (INIS)

    De Wolf, David A

    2016-01-01

    The twin paradox of the special theory of relativity has given rize to a large body of literature discussing its implications. In its standard form, the traveler changes velocity only at the destination of the trip, so that he appears to perceive an improbably instantaneous and non-continuous change in age of the stationary twin. In this work, a smooth velocity/acceleration profile is used that allows the abrupt velocity-change case as a limit. All gravitational effects are ignored in this treatment. Aside from mutual perception of simultaneous clock times in an accelerating frame, constant communication of clock times between the twins by means of (digital) light signals is shown to be possible, in principle if not in practice. (paper)

  5. On the theory of twinning plane superconductivity

    International Nuclear Information System (INIS)

    Mishonov, T.M.

    1988-01-01

    The thermodynamic potential of the superconducting layer in the twinning plane (TP) vicinity for the type I superconductors is found. The corrections to the surface tension in powers of the Ginsburg-Landau parameter κ are obtained. The corresponding states law for the supercooling field for the type I twinning plane superconductivity (TPS) is obtained, as well as the critical field law for the type II TPS. A review of experimental and theoretical works on TPS and some similar systems is given. The conditions for the Berezinski-Kosterlitz-Thouless transition for the proximity effect are discussed, as well as the possible mechanisms for the conducting phase transition TPS in Nb and the pinning forces close to the twinning plane. The obtained order parameter distribution can be used for description of the superlattices from normal and superconducting metals as well. 6 figs., 44 refs

  6. Upgrades for TwinSol facility

    Energy Technology Data Exchange (ETDEWEB)

    O’Malley, P.D.; Bardayan, D.W.; Kolata, J.J.; Hall, M.R.; Hall, O.; Allen, J. [Physics Department, University of Notre Dame, Notre Dame, IN 46556 (United States); Becchetti, F.D. [Physics Department, U. Michigan, Ann Arbor MI 48109 (United States)

    2016-06-01

    TwinSol, a pair of coupled, superconducting solenoids, was one of the first devices capable of producing beams of radioactive nuclei at energies near the Coulomb barrier. A primary beam from University of Notre Dame (UND) tandem accelerator is used to bombard a primary target producing a secondary beam in flight. TwinSol is used to gather, separate, and focus the recoils. Since it was commissioned at the UND in 1997, at least 58 publications have reported data from its use and there have been hundreds of collaborators from many different countries that use this device. Currently, plans are in place at the UND to provide several upgrades to TwinSol, including a multi-cell gas production target and the possible addition of a third solenoid. Upgrades currently in progress will be discussed along with future plans.

  7. Early prenatal diagnosis of ischiopagus conjoined twins

    Directory of Open Access Journals (Sweden)

    Ahmet Mete Ergenoğlu

    2014-03-01

    Full Text Available Introduction: Conjoined twins are very rare and the incidence of them vary about 1/50,000 and 1/100,000. They are named according to the joint parts. Embryos are conjoined at the level of ischium in ischiopagus. A case of ischiopagus will be presented in this article. Case: A twenty-seven year old women who is 9-10 weeks pregnant with a history of 1 abortus applied to the Ege University Department of Obstetrics and Gynecology for routine follow-up. Ultrasonography revealed a twin pregnancy but the embryos were attached at the pelvic region. 3D Doppler sonography confirmed the diagnosis of ischiopagus tetrapus. The patient's decision of termination of pregnancy is concluded at Perinatology Council of the clinic. Conclusion: Ischiopagus conjoined twins are very rare. Early prenatal diagnosis will prevent the maternal complications during the termination of the pregnancy.

  8. Morphology of growth of Bi2Sr2CaCu2O8 single crystals

    Science.gov (United States)

    Indenbom, M. V.; van der Beek, C. J.; Berseth, V.; Wolf, Th.; Berger, H.; Benoit, W.

    1996-12-01

    A good correlation of twins on the basal surface of flux-grown Bi2Sr2CaCu2Ox (BSCCO) single crystals with surface. growth steps is observed, the b-axis being perpendicular to the steps and, thus, parallel to the growth direction. It is found that mono-twin BSCCO single crystals produced by the travelling solvent floating zone method also grow preferentially along b, i.e. nearly perpendicularly to the boule axis, contrary to the common belief. This new understanding of the morphology of growth explains the nature of major defects in these crystals, which considerably change their measured superconducting properties, in a different way.

  9. Crystal shapes on striped surface domains

    International Nuclear Information System (INIS)

    Valencia, Antoni

    2004-01-01

    The equilibrium shapes of a simple cubic crystal in contact with a planar chemically patterned substrate are studied theoretically using an effective interface model. The substrate is primarily made of lyophobic material and is patterned with a lyophilic (easily wettable) stripe domain. Three regimes can be distinguished for the equilibrium shapes of the crystal. The transitions between these regimes as the volume of the crystal is changed are continuous or discontinuous depending on the strength of the couplings between the crystal and the lyophilic and lyophobic surface domains. If the crystal grows through a series of states close to equilibrium, the discontinuous transitions correspond to growth instabilities. These transitions are compared with similar results that have been obtained for a volume of liquid wetting a lyophilic stripe domain

  10. Conjoined twins detected in the first trimester: A review

    Directory of Open Access Journals (Sweden)

    Chih-Ping Chen

    2011-12-01

    Full Text Available Conjoined twinning occurs in 1 in 100 sets of monozygotic twins, 1 in 50,000 gestations or 1 in 250,000 live births. With the advent of ultrasound technology, prenatal diagnosis of conjoined twins is possible. This article provides a comprehensive review of conjoined twins detected in the first trimester including fetal gender, maternal age, parity, types of fusion, related ultrasound abnormalities, perinatal outcome and association with assisted reproduction.

  11. Dichorionic Diamniotic Twin Pregnancy Discordant for Bladder Exstrophy

    Directory of Open Access Journals (Sweden)

    William Tu

    2009-01-01

    Full Text Available A 38 year-old woman presented with a dichorionic diamniotic twin pregnancy at gestational age of 32 weeks concerning for an abdominal wall mass in one of the twins. Initial ultrasound evaluation was suspicious for an omphalocele, but the affected twin was found to have bladder exstrophy at birth. This illustrates the difficulties of accurate prenatal diagnosis of bladder exstrophy in a twin pregnancy at a late gestation.

  12. A note on twin-singleton differences in asthma

    DEFF Research Database (Denmark)

    Thomsen, Simon Francis; Kyvik, Kirsten Ohm; Backer, Vibeke

    2008-01-01

    Twins constitute a valuable resource for genetic studies of asthma. However, critics argue that twins are 'special' in terms of prenatal environment and upbringing and therefore nonrepresentative. In respect to asthma a small range of studies report differential morbidity in twins compared...... with singletons. We review some of the possible explanations for these findings and conclude that results from twin studies of asthma can be extrapolated to the general population....

  13. Testicular cancer in twins: a meta-analysis.

    Science.gov (United States)

    Neale, R E; Carrière, P; Murphy, M F G; Baade, P D

    2008-01-15

    In a meta-analysis of testicular cancer in twins, twins had a 30% increased risk (estimate 1.31, 95% CI 1.1-1.6), providing indirect support for the hypothesis that in utero hormone variations influence risk of testicular cancer. The summary-estimate for dizygotic twins was 1.3 (1.0-1.7) and for monozygotic or same sex twins 1.4 (1.2-1.8).

  14. Needle twins and right-angled twins in minerals: comparison between experiment and theory

    Science.gov (United States)

    Salje, E.K.H.; Buckley, A.; Van Tendeloo, G.; Ishibashi, Y.; Nord, G.L.

    1998-01-01

    Transformation twinning in minerals forms isolated twin walls, intesecting walls with corner junctions, and wedge-shaped twins as elements of hierarchical patterns. When cut perpendicular to the twin walls, the twins have characteristic shapes, right-angled and needle-shaped wall traces, which can be observed by transmission electron microscopy or by optical microscopy. Theoretical geometries of wall shapes recently derived for strain-related systems should hold for most displacive and order-disorder type phase transitions: 1) right-angled twins show curved junctions; 2) needle-shaped twins contain flat wall segments near the needle tip if the elastic behaviour of the mineral is dominated by its anisotroyp; 3) additional bending forces and pinning effects lead to curved walls near the junction that make the needle tip appear more blunt. Bent right-angled twins were analyzed in Gd2(MoO4)3. Linear needle tips were found in WO3, [N(CH3)4]2.ZnBr4 CrAl, BiVO4, GdBa2Cu3O7, and PbZrO. Parabolic tips occur in K2Ba(NO2)4, and GeTe whereas exponential curvatures appear in BaTiO3, KSCN, Pb3(PO4)2, CaTiO3, alkali feldspars, YBa2Cu3O7, and MnAl. The size and shape of the twin microstructure relates to its formation during the phase transition and the subsequent annealing history. The mobility of the twin walls after formation depends not only on the thermal activation but also on the structure of the wall, which may be pinned to impurities on a favorable structural site. Depinnign energies are often large compared with thermal energies for diffusion. This leads to kinetic time scales for twin coarsening that are comparable to geological time scales. Therefore, transformation twins that exhibit needle domains not only indicate that the mineral underwent a structural phase transition but also contain information about its subsequent geological history.

  15. Cord entanglement in monoamniotic twin pregnancies

    DEFF Research Database (Denmark)

    Lyndrup, J; Schouenborg, Lars Øland

    1987-01-01

    Monoamniotic twin pregnancy involves a heavy risk of fatal umbilical cord entanglement. Two cases are reported. In the first case, both twins were found dead in the 36th week, and the monoamnionicity was recognized at birth. In the second case, the monoamnionicity was discovered during an ultraso...... an ultrasound examination, and cord entanglement was suspected in the 35th week on the basis of a non-stress test (NST) with variable decelerations. Cesarean section was performed and two healthy children were delivered....

  16. Conjoined twins: scientific cinema and Pavlovian physiology.

    Science.gov (United States)

    Krementsov, Nikolai

    2015-01-01

    Through the lens of a 1957 documentary film, "Neural and humoral factors in the regulation of bodily functions (research on conjoined twins)," produced by the USSR Academy of Medical Sciences, this essay traces the entwined histories of Soviet physiology, studies of conjoined twins and scientific cinema. It examines the role of Ivan Pavlov and his students, including Leonid Voskresenkii, Dmitrii Fursikov and Petr Anokhin, in the development of "scientific film" as a particular cinematographic genre in Soviet Russia and explores numerous puzzles hidden behind the film's striking visuals. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  17. Conjoined twins: implications for blastogenesis.

    Science.gov (United States)

    Machin, G A

    1993-01-01

    fail to develop (interaction aplasia) because of conflicting migrational pathways or abnormal concentrations of morphogens in and around the neoaxes. 8. Where the cardiovascular system is discordantly expressed in dicephalus and thoracopagus twins, the right heart is more severely malformed, depending on the degree of interaction of the two embryonic septa transversa. 9. The septum transversum provides mesenchymal components to the heawrt and liver; the epithelial components (derived fro the foregut[s]) may vary in number from the number of mesenchymal septa transversa contributing to the liver of the CT embryo.(ABSTRACT TRUNCATED AT 400 WORDS)

  18. Plasma simulation with the Differential Algebraic Cubic Interpolated Propagation scheme

    Energy Technology Data Exchange (ETDEWEB)

    Utsumi, Takayuki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    A computer code based on the Differential Algebraic Cubic Interpolated Propagation scheme has been developed for the numerical solution of the Boltzmann equation for a one-dimensional plasma with immobile ions. The scheme advects the distribution function and its first derivatives in the phase space for one time step by using a numerical integration method for ordinary differential equations, and reconstructs the profile in phase space by using a cubic polynomial within a grid cell. The method gives stable and accurate results, and is efficient. It is successfully applied to a number of equations; the Vlasov equation, the Boltzmann equation with the Fokker-Planck or the Bhatnagar-Gross-Krook (BGK) collision term and the relativistic Vlasov equation. The method can be generalized in a straightforward way to treat cases such as problems with nonperiodic boundary conditions and higher dimensional problems. (author)

  19. Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure

    KAUST Repository

    Suteewong, Teeraporn

    2011-01-19

    Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.

  20. Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure

    KAUST Repository

    Suteewong, Teeraporn; Sai, Hiroaki; Cohen, Roy; Wang, Suntao; Bradbury, Michelle; Baird, Barbara; Gruner, Sol M.; Wiesner, Ulrich

    2011-01-01

    Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.