WorldWideScience

Sample records for bcc lattices

  1. Quartic Box-Spline Reconstruction on the BCC Lattice.

    Science.gov (United States)

    Kim, Minho

    2013-02-01

    This paper presents an alternative box-spline filter for the body-centered cubic (BCC) lattice, the seven-direction quartic box-spline M7 that has the same approximation order as the eight-direction quintic box-spline M8 but a lower polynomial degree, smaller support, and is computationally more efficient. When applied to reconstruction with quasi-interpolation prefilters, M7 shows less aliasing, which is verified quantitatively by integral filter metrics and frequency error kernels. To visualize and analyze distributional aliasing characteristics, each spectrum is evaluated on the planes and lines with various orientations.

  2. Evaluation of Watson-like integrals for a hyper bcc antiferromagnetic lattice

    Science.gov (United States)

    Radošević, S. M.; Pantić, M. R.; Kapor, D. V.; Pavkov-Hrvojević, M. V.; Škrinjar, M. G.

    2010-04-01

    Watson-like integrals for a d-dimensional bcc antiferromagnetic lattice, I_d (\\eta ) =\\frac{1}{\\pi ^d} \\prod _{i = 1}^d \\int _0^{\\pi } \\mathrm{d}x_i \\; \\frac{ \\eta }{\\sqrt{\\eta ^2 - \\prod \

  3. Towards an unbiased comparison of CC, BCC, and FCC lattices in terms of prealiasing

    KAUST Repository

    Vad, Viktor

    2014-06-01

    In the literature on optimal regular volume sampling, the Body-Centered Cubic (BCC) lattice has been proven to be optimal for sampling spherically band-limited signals above the Nyquist limit. On the other hand, if the sampling frequency is below the Nyquist limit, the Face-Centered Cubic (FCC) lattice was demonstrated to be optimal in reducing the prealiasing effect. In this paper, we confirm that the FCC lattice is indeed optimal in this sense in a certain interval of the sampling frequency. By theoretically estimating the prealiasing error in a realistic range of the sampling frequency, we show that in other frequency intervals, the BCC lattice and even the traditional Cartesian Cubic (CC) lattice are expected to minimize the prealiasing. The BCC lattice is superior over the FCC lattice if the sampling frequency is not significantly below the Nyquist limit. Interestingly, if the original signal is drastically undersampled, the CC lattice is expected to provide the lowest prealiasing error. Additionally, we give a comprehensible clarification that the sampling efficiency of the FCC lattice is lower than that of the BCC lattice. Although this is a well-known fact, the exact percentage has been erroneously reported in the literature. Furthermore, for the sake of an unbiased comparison, we propose to rotate the Marschner-Lobb test signal such that an undue advantage is not given to either lattice. © 2014 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.

  4. LatticeLibrary and BccFccRaycaster: Software for processing and viewing 3D data on optimal sampling lattices

    Directory of Open Access Journals (Sweden)

    Elisabeth Schold Linnér

    2016-01-01

    Full Text Available In this paper, we present LatticeLibrary, a C++ library for general processing of 2D and 3D images sampled on arbitrary lattices. The current implementation supports the Cartesian Cubic (CC, Body-Centered Cubic (BCC and Face-Centered Cubic (FCC lattices, and is designed to facilitate addition of other sampling lattices. We also introduce BccFccRaycaster, a plugin for the existing volume renderer Voreen, making it possible to view CC, BCC and FCC data, using different interpolation methods, with the same application. The plugin supports nearest neighbor and trilinear interpolation at interactive frame rates. These tools will enable further studies of the possible advantages of non-Cartesian lattices in a wide range of research areas.

  5. LatticeLibrary and BccFccRaycaster: Software for processing and viewing 3D data on optimal sampling lattices

    Science.gov (United States)

    Linnér, Elisabeth Schold; Morén, Max; Smed, Karl-Oskar; Nysjö, Johan; Strand, Robin

    In this paper, we present LatticeLibrary, a C++ library for general processing of 2D and 3D images sampled on arbitrary lattices. The current implementation supports the Cartesian Cubic (CC), Body-Centered Cubic (BCC) and Face-Centered Cubic (FCC) lattices, and is designed to facilitate addition of other sampling lattices. We also introduce BccFccRaycaster, a plugin for the existing volume renderer Voreen, making it possible to view CC, BCC and FCC data, using different interpolation methods, with the same application. The plugin supports nearest neighbor and trilinear interpolation at interactive frame rates. These tools will enable further studies of the possible advantages of non-Cartesian lattices in a wide range of research areas.

  6. Evaluation of Watson-like Integrals for Hyper bcc Antiferromagnetic Lattice

    CERN Document Server

    Radosevic, S M; Kapor, D V; Pavkov-Hrvojevic, M V; Skrinjar, M G

    2010-01-01

    Watson-like integrals for a d-dimensional bcc antiferromagnetic lattice I_d(\\eta) and J_d(\\eta) and another two similar integrals are evaluated in an exact way in terms of generalized hypergeometric functions. A simple formula connecting Id and Jd+1 is given along with the differential equations for I_d(\\eta) and J_d(\\eta). An application of I_d and J_d in the theory of the Heisenberg antiferromagnet is discussed, together with possible generalizations to non-integer values of d. Corresponding integrals for sc lattices are also briefly reviewed.

  7. Superstructures formed by orientationally ordered tetrahedra in the bcc lattice: new diffusionless order-disorder transition in solids.

    Science.gov (United States)

    Tamura, Ryuji

    2015-03-04

    We investigated and clarified the superstructures formed by tetrahedra in the bcc lattice within the framework of second-order transitions. Compliance with both the Landau and Lifshitz conditions was investigated for all possible superstructures and, based on this, we demonstrate that bcc crystals that contain tetrahedra at an inversion center can exhibit a variety of second-order transitions, which are regarded as a new type of diffusionless order-disorder transition with antiferroic orientational orders. Finally, we show that the transition gives rise to a new glassy state. Breaking of the local inversion symmetry may lead to a new orientational glass, which is reminiscent of spin glasses in magnetism.

  8. Ab-initio study of high temperature lattice dynamics of BCC zirconium (β-Zr) and uranium (γ-U)

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Partha S., E-mail: parthasarathi13@gmail.com; Arya, A., E-mail: parthasarathi13@gmail.com; Dey, G. K., E-mail: parthasarathi13@gmail.com [Materials Science Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

    2014-04-24

    Using self consistent ab-initio lattice dynamics calculations, we show that bcc structures of Zr and U phases become stable at high temperature by phonon-phonon interactions. The calculated temperature dependent phonon dispersion curve (PDC) of β-Zr match excellently with experimental PDC. But the calculated PDC for γ-U shows negative phonon frequencies even at solid to liquid transition temperature. We show that this discrepancy is due to an overestimation of instability depth of bcc U phase which is removed by incorporation of spin-orbit coupling in the electronic structure calculations.

  9. Data files for ab initio calculations of the lattice parameter and elastic stiffness coefficients of bcc Fe with solutes.

    Science.gov (United States)

    Fellinger, Michael R; Hector, Louis G; Trinkle, Dallas R

    2017-02-01

    We present computed datasets on changes in the lattice parameter and elastic stiffness coefficients of bcc Fe due to substitutional Al, B, Cu, Mn, and Si solutes, and octahedral interstitial C and N solutes. The data is calculated using the methodology based on density functional theory (DFT) presented in Ref. (M.R. Fellinger, L.G. Hector Jr., D.R. Trinkle, 2017) [1]. All the DFT calculations were performed using the Vienna Ab initio Simulations Package (VASP) (G. Kresse, J. Furthmüller, 1996) [2]. The data is stored in the NIST dSpace repository (http://hdl.handle.net/11256/671).

  10. Quantum statistics in the spin-lattice dynamics simulation of formation and migration of mono-vacancy in BCC iron

    Science.gov (United States)

    Wen, Haohua; Woo, C. H.

    2016-03-01

    Contributions from the vibrational thermodynamics of phonons and magnons in the dynamic simulations of thermally activated atomic processes in crystalline materials were considered within the framework of classical statistics in conventional studies. The neglect of quantum effects produces the wrong lattice and spin dynamics and erroneous activation characteristics, sometimes leading to the incorrect results. In this paper, we consider the formation and migration of mono-vacancy in BCC iron over a large temperature range from 10 K to 1400 K, across the ferro/paramagnetic phase boundary. Entropies and enthalpies of migration and formation are calculated using quantum heat baths based on a Bose-Einstein statistical description of thermal excitations in terms of phonons and magnons. Corrections due to the use of classical heat baths are evaluated and discussed.

  11. The anisotropic quantum spin-1/2 Heisenberg antiferromagnet in the presence of a longitudinal field on a bcc lattice

    Energy Technology Data Exchange (ETDEWEB)

    Neto, Minos A., E-mail: minos@pq.cnpq.br [Departamento de Fisica, Universidade Federal do Amazonas, 3000, Japiim, Manaus, 69077-000 AM (Brazil); Roberto Viana, J., E-mail: vianafisica@bol.com.br [Departamento de Fisica, Universidade Federal do Amazonas, 3000, Japiim, Manaus, 69077-000 AM (Brazil); Ricardo de Sousa, J., E-mail: jsousa@edu.ufam.br [Departamento de Fisica, Universidade Federal do Amazonas, 3000, Japiim, Manaus, 69077-000 AM (Brazil); National Institute of Science and Technology for Complex Systems, 3000, Japiim, Manaus, 69077-000 AM (Brazil)

    2012-08-15

    In this work we study the critical behavior of the quantum spin-1/2 anisotropic Heisenberg antiferromagnet in the presence of a longitudinal field on a body centered cubic (bcc) lattice as a function of temperature, anisotropy parameter ({Delta}) and magnetic field (H), where {Delta}=0 and 1 correspond the isotropic Heisenberg and Ising models, respectively. We use the framework of the differential operator technique in the effective-field theory with finite cluster of N=4 spins (EFT-4). The staggered m{sub s}=(m{sub A}-m{sub B})/2 and total m=(m{sub A}+m{sub B})/2 magnetizations are numerically calculated, where in the limit of m{sub s}{yields}0 the critical line T{sub N}(H,{Delta}) is obtained. The phase diagram in the T-H plane is discussed as a function of the parameter {Delta} for all values of H Element-Of [0,H{sub c}({Delta})], where H{sub c}({Delta}) correspond the critical field (T{sub N}=0). Special focus is given in the low temperature region, where a reentrant behavior is observed around of H=H{sub c}({Delta}){>=}H{sub c}({Delta}=1)=8J in the Ising limit, results in accordance with Monte Carlo simulation, and also was observed for all values of {Delta} Element-Of [0,1]. This reentrant behavior increases with increase of the anisotropy parameter {Delta}. In the limit of low field, our results for the Heisenberg limit are compared with series expansion values. - Highlights: Black-Right-Pointing-Pointer In the lat decade there has been a great interest in the physics of the quantum phase transition in spins system. Black-Right-Pointing-Pointer Effective-field theory in cluster with N=4 spins is generalized to treat the quantum spin-1/2 Heisenberg model. Black-Right-Pointing-Pointer We have obtained phase diagram at finite temperature for the quantum spin-1/2 antiferromagnet Heisenberg model as a bcc lattice.

  12. A simple method for determining the lattice parameter and chemical composition in ternary bcc-Fe rich nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Moya, Javier A., E-mail: jmoya.fi.uba@gmail.com [Grupo Interdisciplinario en Materiales-IESIING, Universidad Católica de Salta, INTECIN UBA-CONICET, Salta (Argentina); Gamarra Caramella, Soledad; Marta, Leonardo J. [Grupo Interdisciplinario en Materiales-IESIING, Universidad Católica de Salta, INTECIN UBA-CONICET, Salta (Argentina); Berejnoi, Carlos [Universidad Nacional de Salta, Facultad de Ingeniería, Salta (Argentina)

    2015-05-15

    Highlights: • A method for determining composition in ternary nanocrystals is presented. • X-ray diffraction and Mössbauer spectroscopy data were employed. • We perform theoretical charts for lattice parameter of Fe-rich ternary alloys. • A linear relationship in lattice parameter for binary alloys is evaluated. • A parabolic relationship is proposed for the Fe–Co–Si alloy. - Abstract: Charts containing lattice parameters of Fe{sub 1−x}(M,N){sub x} ternary systems with M and N = Si, Al, Ge or Co, and 0 ⩽ x ⩽ ∼0.3, were developed by implementing a linear relationship between the respective binary alloys with the same solute content of the ternary one. Charts were validated with experimental data obtained from literature. For the Fe–Co–Si system, the linear relationship does not fit the experimental data. For the other systems (except the Fe–Co–Ge one where no experimental data was found), the lineal relationship constitute a very good approximation. Using these charts and the lattice parameter data obtained from X-ray diffraction technique combining with the solute content data obtained from Mössbauer spectroscopy technique it is possible to determine the chemical composition of nanograins in soft magnetic nanocomposite materials and some examples are provided.

  13. Annihilators on weakly standard BCC-algebras

    OpenAIRE

    R. Halaš; L. Plojhar

    2005-01-01

    In a recent paper the authors presented a new construction of BCC-algebras derived from posets with the top element 1. Resulting BCC-algebras, called weakly standard, are those for which every 4-element subset containing 1 is a subalgebra. In this paper we continue our investigations focusing on the properties of their lattices of congruence kernels.

  14. Properties of Zr – 12.5 % Nb and Zr – 25 % Nb Alloys with hcp and bcc Lattices: ab-initio Modeling

    Directory of Open Access Journals (Sweden)

    V.O. Kharchenko

    2012-06-01

    Full Text Available Ab-initio calculations of the electronic structure for Zr – 12.5 % Nb and Zr – 25 % Nb alloys are done using density functional theory, method of linearized augmented plane-wave approximation and generalized gradient approximation. The structural and energetic properties, such as the electron densities, densities of states, energetically and X-ray spectra in the case of the hcp and bcc lattices are calculated. Optimal values for the lattice constants are found. The most favorable structure for each studied alloy is defined.

  15. Study on lattice stability in first principles of hcp-,fcc-and bcc-Sc%hcp-,fcc-和bcc-Sc晶格稳定性的第一原理研究

    Institute of Scientific and Technical Information of China (English)

    陶辉锦; 刘玲; 陈伟民; 文杰斌; 杨巧然

    2009-01-01

    分别采用第一原理总能赝势平面波的局域密度近似LDA(Local density approximation)和广义梯度近似GGA(Generalized gradient approximation)两种近似方法计算hcp-,fcc-和bcc-Sc的晶格常数、总能和态密度,并将实验值与以上两种方法以及CALPHAD方法的计算结果进行对比研究,发现采用LDA和GGA的计算结果均为△Gbcc-hcp>△Gfcc-hcp>0,与CALPHAD方法外推的结果△Gfcc-hcp>△Gbcc-hcp>0不一致.用LDA方法计算的hcp-,fcc-和bcc-Sc的晶格常数和原子体积较GGA方法的计算结果小,但总能绝对值偏大.LDA方法与GGA方法的态密度曲线形状基本一致,但LDA得到的s和p态电子占据数比GGA方法的偏小.

  16. Angular distortive matrices of phase transitions in the fcc-bcc-hcp system

    OpenAIRE

    Cayron, Cyril

    2016-01-01

    This work generalizes the one-step model previously developed on fcc-bcc martensitic transformations to the larger family of phase transitions in the fcc-bcc-hcp system. The angular distortive matrices are calculated for the bcc-fcc, bcc-hcp and fcc-hcp transitions, and for fcc-fcc mechanical twinning. The analytical expressions of the continuous atomic displacements, lattice distortion and lattice correspondence matrices result directly from the orientation relationships; the unique assumpti...

  17. BCC-代数的不分明化理想%On Fuzzifying Ideals in BCC-algebras

    Institute of Scientific and Technical Information of China (English)

    彭家寅

    2009-01-01

    通过一元谓词和采用格值逻辑语义方法推广了不分明化BCC-代数,引入了BCC代数的不分明化BCH-子代数、不分明化BCK-理想和不分明化BCC-理想的概念,讨论了它们的性质和它们间的关系.研究了BCC-代数的不分明化BCH-子代数(不分明化BCK-理想、不分明化BCC-理想)的同态象和同态原象,讨论了BCC-代数的不分明化BCH-子代数(不分明化BCK-理想、不分明化BCC-理想)的积代数的性质.%The fuzzifying BCC-algebra is extended by a unary predicate and by adopting the semantic method of lattice valued logic, and the concepts of fuzzifying subalgebras, fuzzifying BCK-ideals and fuzzifying BCC-ideais in BCC-algebras are defined, and their properties and relations among them are discussed. How to deal with the homomorphic images and inverse images of fuzzifying subalgebras, fuzzifying BCK-ideals and fuzzifying BCC-ideals are studied. Some properties of the product of two fuzzifying subalgebras (fuzzifying BCK-ideals, fuzzifying BCC-ideals)are investigated.

  18. Electronic structure and magnetism of strained bcc phases across the fcc to bcc transition in ultrathin Fe films

    Science.gov (United States)

    Calloni, Alberto; Berti, Giulia; Bussetti, Gianlorenzo; Fratesi, Guido; Finazzi, Marco; Ciccacci, Franco; Duò, Lamberto

    2016-11-01

    We investigated the electronic structure of the bcc metastable phases involved in the fcc to bcc transition of Fe. Ultrathin Fe films were grown on a 2-monolayer (ML) Ni/W(110) substrate, where a fcc lattice is stabilized at low Fe coverages and the transition proceeds through the formation of bcc nuclei showing a specific "Kurdjumov-Sachs" orientation with the substrate. A comprehensive description of the electronic structure evolution is achieved by combining spin-resolved UV photoemission spectroscopy and ab initio calculations. According to our results, an exchange-split band structure is observed starting from 2 ML of Fe, concomitant with the formation of ferromagnetic bcc nuclei. Continuous modifications are observed in the spin-resolved photoemission spectra for increasing Fe coverage, especially for what concerns the minority states, possibly indicative of the progressive relaxation of the strained bcc phase starting from the bcc/fcc interface.

  19. Perturbation theory of solid-liquid interfacial free energies of bcc metals.

    Science.gov (United States)

    Warshavsky, Vadim B; Song, Xueyu

    2012-09-01

    A perturbation theory is used to calculate bcc solid-liquid interfacial free energies of metallic systems with embedded-atom model potentials. As a reference system for bcc crystals we used a single-occupancy cell, hard-sphere bcc system. Good agreements between the perturbation theory results and the corresponding results from simulations are found. The strategy to extract hard-sphere bcc solid-liquid interfacial free energies may have broader applications for other crystal lattices.

  20. Nonlinearities in composition dependence of structure parameters and magnetic properties of nanocrystalline fcc/bcc-mixed Co-Ni-Fe thin films

    NARCIS (Netherlands)

    Chechenin, N. G.; Khomenko, E. V.; Vainchtein, D. I.; De Hosson, J. Th. M.

    2008-01-01

    In this report, the nonlinearities are analyzed in fcc-to-bcc (fcc/bcc) population ratio, lattice parameters (a(exp)(fcc)/a(ideal)(fcc) and a(exp)(bcc)/a(ideal)(bcc)) and saturation magnetization (I(S)(obs)/I(S)(a)) of the electrodeposited thin Co-Fe-Ni films as a function of average number of elect

  1. On hyper BCC-algebras

    Directory of Open Access Journals (Sweden)

    R. A. Borzooei

    2006-01-01

    Full Text Available We study hyper BCC-algebras which are a common generalization of BCC-algebras and hyper BCK-algebras. In particular, we investigate different types of hyper BCC-ideals and describe the relationship among them. Next, we calculate all nonisomorphic 22 hyper BCC-algebras of order 3 of which only three are not hyper BCK-algebras.

  2. On hyper BCC-algebras

    OpenAIRE

    Borzooei, R. A.; Dudek, W. A.; Koohestani, N.

    2006-01-01

    We study hyper BCC-algebras which are a common generalization of BCC-algebras and hyper BCK-algebras. In particular, we investigate different types of hyper BCC-ideals and describe the relationship among them. Next, we calculate all nonisomorphic 22 hyper BCC-algebras of order 3 of which only three are not hyper BCK-algebras.

  3. Electron diffraction study of the plastic relaxation of MgO epitaxially grown on BCC FeV(001) alloys by varying the lattice mismatch

    Science.gov (United States)

    Bonell, Frédéric; Andrieu, Stéphane

    2017-02-01

    The epitaxial growth of MgO on Fe1 - xVx buffer layers with adjustable lattice parameter is studied by electron diffraction (RHEED) in real time. At the onset of plastic relaxation in the MgO layer, a clear splitting of the diffraction rods is observed in directions, as well as an increase in their length in the directions. Splitting along is also made visible through image background subtraction. These features originate from the surface strain above misfit dislocations, as previously proposed to account for satellite spots in LEED measurements. This explanation is supported by simulations of the diffraction patterns using kinematic diffraction theory. Observation of the diffraction rods splitting is shown to be a powerful way to check the presence of dislocations in MgO tunnel barriers and to accurately determine the critical thickness of plastic relaxation.

  4. Smarandache hyper BCC-algebra

    OpenAIRE

    A. Ahadpanah; Borumand Saeid, A.

    2011-01-01

    In this paper, we define the Smarandache hyper BCC-algebra, and Smarandache hyper BCC-ideals of type 1, 2, 3 and 4. We state and prove some theorems in Smarandache hyper BCC -algebras, and then we determine the relationships between these hyper ideals.

  5. DISLOCATION STRUCTURE OF FCC COPPER/BCC IRON INTERPHASE INTERFACES

    OpenAIRE

    C Forwood

    1990-01-01

    The Burgers vectors and geometry of the interfacial dislocation structure in fcc/bcc interfaces in a Cu+25 wt.% Fe alloy are analysed using TEM and the technique of image matching. The Burgers vectors are shown to be differences of the Cu and Fe lattice vectors and the interfacial structure is interpreted in terms of a CSL/DSC model.

  6. EXAFS STUDY OF THE SHORT RANGE STRUCTURE OF NANOCRYSTALLINE BCC-Fe80Cu20 SOLID SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Y.Z. Yang; X.J. Bai; T.C. Kuang; G.M. Wang; S. Q. Wei

    2002-01-01

    The structure of bcc-Fe80 Cu2o solid solution produced by mechanical alloying of theelemental bcc-Fe and fcc-Cu powders has been studied using X-ray diffraction and theextended X-ray absorption fine structure (EXAFS) techniques. The disappearance ofelemental Fe and Cu X-ray diffraction (XRD) peaks and the presence of bcc structuralXRD peaks illustrate the formation of a nanocrystalline single-phase bcc-Fe80 Gu20solid solution. From the EXAFS results, the clear observation of Cu atoms taking onbcc coordination in the solid solution and Fe atoms remaining bcc structure furtherverifies the reality of atomic alloying between Fe and Cu atoms and the lattice changeof Cu from fcc to bcc. However, the supersaturated bcc solid solution is not chemicallyuniform, i.e., some regions are rich in Fe atoms and other regions rich in Cu atoms.

  7. Structural transformation between bcc and fcc in Fe-Ni nanoparticle during heating process

    Science.gov (United States)

    Li, Guojian; Sui, Xudong; Qin, Xuesi; Ma, Yonghui; Wang, Kai; Wang, Qiang

    2016-10-01

    Phase transformation between bcc and fcc in Fe-Ni nanoparticle has been studied by using molecular dynamics simulation with an embedded atom method. The transformation has been explored by designing the nanoparticles with different initial structures, sizes and elemental distributions at various Ni concentrations. The results show that the structural transformation is strongly related to the Ni content and elemental distribution. Initial fcc structure transforms to bcc for a lower Ni content and bcc transforms to fcc for a higher Ni content. The transformation is accompanied with a sharp reduction in energy even for the nanoparticle with a large size. Furthermore, lattice distortion first occurs before the transformation. The transformation from fcc to bcc is occurred by elongating fcc (100) to bcc (110) and that from bcc to fcc by compressing bcc (110) to fcc (100). The reason is that the nanoparticle has a low energy state for bcc structure with a lower Ni content and also for fcc structure with a higher Ni content. The coexistence of bcc and fcc phases appears with the change of elemental distribution.

  8. Physical metallurgy and magnetic behavior of Cd stabilized bcc (beta)Gd alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jinke, Tang.

    1990-09-21

    As a continuation of the research on bcc Gd-Mg alloy system by Herchenroeder and Gschneidner, the metastable bcc Gd-Cd alloys were studied with the emphasis on their metallurgical and magnetic properties. An essentially single phase alloy could be retained for Cd concentrations from 15 at. % Cd to 19 at. % Cd, which is in the vicinity of the eutectoid composition of {beta}Gd in the Gd-Cd system. The lattice constants obtained for these alloys were used to determine the lattice constant of pure bcc Gd by extrapolation to 0 at. % Cd. Good agreement between this extrapolated value and that obtained from Gd-Mg alloys by using the same method suggested the validity of such extrapolation method. Thermal stability of these metastable bcc Gd-Cd alloys was examined by using differential thermal analysis (DTA).

  9. Atomic displacements in bcc dilute alloys

    Indian Academy of Sciences (India)

    Hitesh Sharma; S Prakash

    2007-04-01

    We present here a systematic investigation of the atomic displacements in bcc transition metal (TM) dilute alloys. We have calculated the atomic displacements in bcc (V, Cr, Fe, Nb, Mo, Ta and W) transition metals (TMs) due to 3d, 4d and 5d TMs at the substitutional site using the Kanzaki lattice static method. Wills and Harrison interatomic potential is used to calculate the atomic force constants, the dynamical matrix and the impurity-induced forces. We have thoroughly investigated the atomic displacements using impurities from 3d, 4d and 5d series in the same host metal and the same impurity in different hosts. We have observed a systematic pattern in the atomic displacements for Cr-, Fe-, Nb-, Mo-, Ta- and W-based dilute alloys. The atomic displacements are found to increase with increase in the number of d electrons for all alloys considered except for V dilute alloys. The 3d impurities are found to be more easily dissolved in the 3d host metals than 4d or 5d TMs whereas 4d and 5d impurities show more solubility in 4d and 5d TMs. In general, the relaxation energy calculation suggests that impurities may be easily solvable in 5d TM hosts when compared to 3d or 4d TMs.

  10. T-fuzzy multiply positive implicative BCC-ideals of BCC-algebras

    OpenAIRE

    Jianming Zhan; Zhisong Tan

    2003-01-01

    The concept of fuzzy multiply positive BCC-ideals of BCC-algebras is introduced, and then some related results are obtained. Moreover, we introduce the concept of T-fuzzy multiply positive implicative BCC-ideals of BCC-algebras and investigate T-product of T-fuzzy multiply positive implicative BCC-ideals of BCC-algebras, examining its properties. Using a t-norm T, the direct product and T-product of T-fuzzy multiply positive implicative BCC-ideals of BCC-algebras are discussed and their...

  11. On some generalizations of BCC-algebras

    CERN Document Server

    Dudek, Wieslaw A

    2012-01-01

    We describe weak BCC-algebras (also called BZ-algebras) in which the condition $(xy)z=(xz)y$ is satisfied only in the case when elements $x,y$ belong to the same branch. We also characterize branchwise commutative and branchwise implicative weak BCC-algebras satisfying this condition. We also describe connections between various types of implicative weak BCC-algebras.

  12. Lattice models of ionic systems

    Science.gov (United States)

    Kobelev, Vladimir; Kolomeisky, Anatoly B.; Fisher, Michael E.

    2002-05-01

    A theoretical analysis of Coulomb systems on lattices in general dimensions is presented. The thermodynamics is developed using Debye-Hückel theory with ion-pairing and dipole-ion solvation, specific calculations being performed for three-dimensional lattices. As for continuum electrolytes, low-density results for simple cubic (sc), body-centered cubic (bcc), and face-centered cubic (fcc) lattices indicate the existence of gas-liquid phase separation. The predicted critical densities have values comparable to those of continuum ionic systems, while the critical temperatures are 60%-70% higher. However, when the possibility of sublattice ordering as well as Debye screening is taken into account systematically, order-disorder transitions and a tricritical point are found on sc and bcc lattices, and gas-liquid coexistence is suppressed. Our results agree with recent Monte Carlo simulations of lattice electrolytes.

  13. An alternative explanation for epitaxial growth. The case of fcc(111) on bcc(110)

    DEFF Research Database (Denmark)

    Grey, F.; Bohr, J.

    1993-01-01

    Starting from basic observations concerning commensurate structures, a simple explanation is given for the existence of energetically stable states of an fcc(111) adsorbate on a bcc(110) substrate, as a function of the mismatch and relative orientation of the two lattices. Numerical simulations...

  14. COMPUTER SIMULATION OF THE STRUCTURE OF bcc/hcp AND bcc/9R MARTENSITE INTERFACES

    OpenAIRE

    Barcelo, G.; Crocker, A.

    1982-01-01

    The structures of two interfaces of martensitic transformations in Cu Zn based alloys have been investigated using computer simulation techniques. A new interatomic potential has been developed which is assumed to represent all interactions between atoms in the parent bcc phase and the product hcp and 9R phases. Stable relaxed structures of bcc/hcp and bcc/9R interfaces have been found. In both cases the interface migrates into the bcc phase during the relaxation process. The boundary in the ...

  15. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011){sub B3} single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Higuchi, Jumpei; Yabuhara, Osamu [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2011-09-30

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011){sub B3} single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar]{sub bcc} || GaAs(011)[011-bar]{sub B3}. The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{l_brace}011{r_brace} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011){sub B3} substrates.

  16. The Role of Ligand Packing Frustration in Body-Centered Cubic (bcc) Superlattices of Colloidal Nanocrystals.

    Science.gov (United States)

    Goodfellow, Brian W; Yu, Yixuan; Bosoy, Christian A; Smilgies, Detlef-M; Korgel, Brian A

    2015-07-02

    This paper addresses the assembly of body centered-cubic (bcc) superlattices of organic ligand-coated nanocrystals. First, examples of bcc superlattices of dodecanethiol-capped Au nanocrystals and oleic acid-capped PbS and PbSe nanocrystals are presented and examined by transmission electron microscopy (TEM) and grazing incidence small-angle X-ray scattering (GISAXS). These superlattices tend to orient on their densest (110) superlattice planes and exhibit a significant amount of {112} twinning. The same nanocrystals deposit as monolayers with hexagonal packing, and these thin films can coexist with thicker bcc superlattice layers, even though there is no hexagonal plane in a bcc lattice. Both the preference of bcc in bulk films over the denser face-centered cubic (fcc) superlattice structure and the transition to hexagonal monolayers can be rationalized in terms of packing frustration of the ligands. A model is presented to calculate the difference in entropy associated with capping ligand packing frustration in bcc and fcc superlattices.

  17. T-fuzzy multiply positive implicative BCC-ideals of BCC-algebras

    Directory of Open Access Journals (Sweden)

    Jianming Zhan

    2003-01-01

    of BCC-algebras, examining its properties. Using a t-norm T, the direct product and T-product of T-fuzzy multiply positive implicative BCC-ideals of BCC-algebras are discussed and their properties are investigated.

  18. Vismodegib in the treatment of advanced BCC.

    Science.gov (United States)

    O'Kane, G M; Lyons, T; McDonald, I; Mulligan, N; Moloney, F J; Murray, D; Kelly, C M

    2014-01-01

    Basal-cell carcinoma (BCC) is the most commonly diagnosed malignancy, comprising over 80 per thousand of non-melanoma skin cancers. Surgical excision is adequate treatment for most BCC's. Options are however limited for the minority of patients presenting with locally advanced inoperable or metastatic BCC. The Hedgehog signalling pathway is a critical driver in the pathogenesis of both sporadic and hereditary BCC. On 31st January 2012, based on a phase II clinical trial the US Food and Drug Administration approved Vismodegib (Erivedge, Roche) a first-in-class, small-molecule oral Hedgehog-inhibitor for the treatment of locally advanced inoperable and metastatic BCC. We present our experience treating the first Irish patient with this agent.

  19. PREDICTION OF YIELD FUNCTIONS ON BCC POLYCRYSTALS

    Institute of Scientific and Technical Information of China (English)

    Huang Mojia; Fu Mingfu; Zheng Chaomei

    2006-01-01

    By the nonlinear optimization theory, we predict the yield function of single BCC crystals in Hill's criterion form. Then we give a formula on the macroscopic yield function of a BCC polycrystal Ω under Sachs' model, where the volume average of the yield functions of all BCC crystallites in Ω is taken as the macroscopic yield function of the BCC polycrystal. In constructing the formula, we try to find the relationship among the macroscopic yield function, the orientation distribution function (ODF), and the single BCC crystal's plasticity. An expression for the yield stress of a uniaxial tensile problem is derived under Taylor's model in order to compare the expression with that of the macroscopic yield function.

  20. The BCC/B2 Morphologies in AlxNiCoFeCr High-Entropy Alloys

    Directory of Open Access Journals (Sweden)

    Yue Ma

    2017-02-01

    Full Text Available The present work primarily investigates the morphological evolution of the body-centered-cubic (BCC/B2 phases in AlxNiCoFeCr high-entropy alloys (HEAs with increasing Al content. It is found that the BCC/B2 coherent morphology is closely related to the lattice misfit between these two phases, which is sensitive to Al. There are two types of microscopic BCC/B2 morphologies in this HEA series: one is the weave-like morphology induced by the spinodal decomposition, and the other is the microstructure of a spherical disordered BCC precipitation on the ordered B2 matrix that appears in HEAs with a much higher Al content. The mechanical properties, including the compressive yielding strength and microhardness of the AlxNiCoFeCr HEAs, are also discussed in light of the concept of the valence electron concentration (VEC.

  1. BCC and Childhood Low Dose Radiation

    Directory of Open Access Journals (Sweden)

    Arash Beiraghi Toosi

    2014-10-01

    Full Text Available Skin cancer is a late complication of ionizing radiation. Two skin neoplasms prominent Basal Cell Carcinoma (BCC and Squamous Cell Carcinoma (SCC are the most famous complications of radiotherapy. Basal Cell Carcinoma (BCC is the most common human malignant neoplasm. Many genetic and environmental factors are involved in its onset. BCC is observed in sun-exposed areas of skin. Some patients with scalp BCC have had a history of scalp radiation for the treatment of tinea capitis in childhood. Evidence that ionizing radiation is carcinogenic first came from past reports of nonmelanoma skin cancers on the hands of workers using radiation devices. The total dose of radiation and irradiated site exposed to sunlight can lead to a short incubation period. It is not clear whether BCC in these cases has a more aggressive nature and requires a more aggressive resection of the lesion. The aim of this review was to evaluate the differences between BCC specification and treatment results between irradiated and nonirradiated patients.

  2. Combined molecular dynamics-spin dynamics simulations of bcc iron

    Energy Technology Data Exchange (ETDEWEB)

    Perera, Meewanage Dilina N [ORNL; Yin, Junqi [ORNL; Landau, David P [University of Georgia, Athens, GA; Nicholson, Don M [ORNL; Stocks, George Malcolm [ORNL; Eisenbach, Markus [ORNL; Brown, Greg [ORNL

    2014-01-01

    Using a classical model that treats translational and spin degrees of freedom on an equal footing, we study phonon-magnon interactions in BCC iron with combined molecular and spin dynamics methods. The atomic interactions are modeled via an empirical many-body potential while spin dependent interactions are established through a Hamiltonian of the Heisenberg form with a distance dependent magnetic exchange interaction obtained from first principles electronic structure calculations. The temporal evolution of translational and spin degrees of freedom was determined by numerically solving the coupled equations of motion, using an algorithm based on the second order Suzuki-Trotter decomposition of the exponential operators. By calculating Fourier transforms of space- and time-displaced correlation functions, we demonstrate that the the presence of lattice vibrations leads to noticeable softening and damping of spin wave modes. As a result of the interplay between lattice and spin subsystems, we also observe additional longitudinal spin wave excitations, with frequencies which coincide with that of the longitudinal lattice vibrations.

  3. Temperature dependent magnon-phonon coupling in bcc Fe from theory and experiment.

    Science.gov (United States)

    Körmann, F; Grabowski, B; Dutta, B; Hickel, T; Mauger, L; Fultz, B; Neugebauer, J

    2014-10-17

    An ab initio based framework for quantitatively assessing the phonon contribution due to magnon-phonon interactions and lattice expansion is developed. The theoretical results for bcc Fe are in very good agreement with high-quality phonon frequency measurements. For some phonon branches, the magnon-phonon interaction is an order of magnitude larger than the phonon shift due to lattice expansion, demonstrating the strong impact of magnetic short-range order even significantly above the Curie temperature. The framework closes the previous simulation gap between the ferro- and paramagnetic limits.

  4. Arsenic poisoning of magnetism in bcc cobalt

    Science.gov (United States)

    Singh, David J.

    1992-04-01

    Highly converged local spin-density approximation calculations are used to determine the effectiveness of As as a poisoning agent for the magnetism of bcc Co films grown on GaAs. To do this, supercell calculations of the magnetization were performed using an extension of the general potential linearized augmented plane-wave method for Co7As, Co15As, and Co31As. The effect of the nearest-neighbor relaxation around As impurities, calculated using total energy techniques, was included. It is found that substitutional As is moderately effective as a poisoning agent, each As atom contributes a moment of -3.8μB, and this may be important in explaining the discrepancy of 0.2-0.3μB between the calculated magnetization of bcc Co and the measured magnetization of bcc Co films on GaAs.

  5. Cascade morphology transition in bcc metals.

    Science.gov (United States)

    Setyawan, Wahyu; Selby, Aaron P; Juslin, Niklas; Stoller, Roger E; Wirth, Brian D; Kurtz, Richard J

    2015-06-10

    Energetic atom collisions in solids induce shockwaves with complex morphologies. In this paper, we establish the existence of a morphological transition in such cascades. The order parameter of the morphology is defined as the exponent, b, in the defect production curve as a function of cascade energy (N(F) ~ E(MD)(b)). Response of different bcc metals can be compared in a consistent energy domain when the energy is normalized by the transition energy, μ, between the high- and the low-energy regime. Using Cr, Fe, Mo and W data, an empirical formula of μ as a function of displacement threshold energy, E(d), is presented for bcc metals.

  6. On fuzzy BCC-ideals over a t-norm

    OpenAIRE

    Dudek, W. A.; JUN, Y. B.

    2000-01-01

    Using a t-norm T, the notion of T-fuzzy BCC-ideals of BCC-algebras is introduced, and some of their properties are investigated. Connections between different types of fuzzy BCC-ideals induced by t-norms are described.

  7. Defect Studies in bcc and fcc Iron

    OpenAIRE

    Ghorai, A.; Arjun Das

    2012-01-01

    Variation of vacancy formation energy (EF1v) with rc of Ashcroft's empty core model potential (AECMP) model for different exchange and correlation functions (ECFs) show almost independent nature but slight variation with ECF for both bcc α iron and fcc γ iron.

  8. Systemic treatments for basal cell carcinoma (BCC): the advent of dermato-oncology in BCC.

    Science.gov (United States)

    Ali, F R; Lear, J T

    2013-07-01

    Basal cell carcinoma (BCC) is the most common cancer in the U.K. and its incidence is increasing. Vismodegib, a hedgehog pathway inhibitor, has recently been licensed by the U.S. Food and Drug Administration for treatment of advanced BCC. Phase 2 trials have demonstrated efficacy in cases of locally advanced and metastatic BCC, as well as cases of hereditary basal cell naevus (Gorlin) syndrome. Side-effects are frequent and considerable and include myalgia, taste disturbance, alopecia, weight loss and fatigue. Further research is needed to investigate means of circumventing these side-effects, and longitudinal data are required to assess the long-term benefits of, and the nature of resistance to, this novel class of agents. Alternative hedgehog inhibitors are currently in clinical development. We review the current data pertaining to this novel treatment modality and discuss its likely future role in the management of BCC.

  9. 22 CFR 41.33 - Nonresident alien Canadian border crossing identification card (BCC).

    Science.gov (United States)

    2010-04-01

    ... identification card (BCC). 41.33 Section 41.33 Foreign Relations DEPARTMENT OF STATE VISAS VISAS: DOCUMENTATION... Nonresident alien Canadian border crossing identification card (BCC). (a) Validity of Canadian BCC. A Canadian BCC or the BCC portion of a Canadian B-1/B-2 Visa/BCC issued to a permanent resident of...

  10. Concentration Transitions on the Crystalline Lattices

    Directory of Open Access Journals (Sweden)

    N.A. Gorenko

    2014-07-01

    Full Text Available Results of numerical modeling of dilute 2D and 3D crystalline lattices are presented. The percolation thresholds for face-centered cubic (fcc, body-centered cubic (bcc and the simple cubic (sc lattices for the first, second and third coordination spheres are obtained by means of Monte Carlo (MC method. It is shown, that the mean value of the percolation cluster density has a minimum value at the percolation threshold.

  11. Fuzzy Ideals and Congruences in BCC-algebras%BCC-代数的模糊理想与同余

    Institute of Scientific and Technical Information of China (English)

    彭家寅

    2010-01-01

    引入BCC-代数的一种新的模糊理想,并研究了它的性质,讨论了BCC-代数中模糊BCC-子代数、模糊BCK-子代数、模糊BCC-理想、模糊BCK-理想四者间的关系,给出了BCC-代数的模糊BCC-理想与BCC-代数的积代数的模糊BCC-理想二者间的关系,揭示了BCC-代数的模糊BCC-理想与同余之间的联系,讨论了由模糊BBC-理想诱导的商BCC-代数. 最后,研究了模糊BCC-理想与模糊BCK-子代数的同态象和同态逆象,建立了模糊同态基本定理.

  12. Anisotropic strain enhanced hydrogen solubility in bcc metals: the independence on the sign of strain.

    Science.gov (United States)

    Zhou, Hong-Bo; Jin, Shuo; Zhang, Ying; Lu, Guang-Hong; Liu, Feng

    2012-09-28

    When an impurity is doped in a solid, it inevitably induces a local stress, tending to expand or contract the lattice. Consequently, strain can be applied to change the solubility of impurity in a solid. Generally, the solubility responds to strain "monotonically," increasing (decreasing) with the tensile (compressive) strain if the impurity induces a compressive stress or vice versa. Using first-principles calculations, however, we discovered that the H solubility can be enhanced by anisotropic strain in some bcc metals, almost independent of the sign of strain. This anomalous behavior is found to be caused by a continuous change of H location induced by anisotropic strain. Our finding suggests a cascading effect of H bubble formation in bcc metals: the H solution leads to H bubble formation that induces anisotropic strain that in turn enhances H solubility to further facilitate bubble growth.

  13. Atomistic simulation of fcc-bcc phase transition in single crystal A1 under uniform compression

    Institute of Scientific and Technical Information of China (English)

    Li Li; Shao Jian-Li; Li Yan-Fang; Duan Su-Qing; [ Liang Jiu-Qing

    2012-01-01

    By molecular dynamics simulations employing an embedded atom model potential,we investigate the fcc-to-bcc phase transition in single crystal Al,caused by uniform compression.Results show that the fec structure is unstable when the pressure is over 250 GPa,in reasonable agreement with the calculated value through the density functional theory.The morphology evolution of the structural transition and the corresponding transition mechanism are analysed in detail.The bec (011) planes are transited from the fcc (11(1)) plane and the (1(1)1) plane.We suggest that the transition mechanism consists mainly of compression,shear,slid and rotation of the lattice.In addition,our radial distribution function analysis explicitly indicates the phase transition of A1 from fcc phase to bcc structure.

  14. Vibrational contribution to the thermodynamics of nanosized precipitates: vacancy-copper clusters in bcc-Fe.

    Science.gov (United States)

    Talati, Mina; Posselt, Matthias; Bonny, Giovanni; Al-Motasem, Ahmed; Bergner, Frank

    2012-06-06

    The effects of lattice vibration on the thermodynamics of nanosized coherent clusters in bcc-Fe consisting of vacancies and/or copper are investigated within the harmonic approximation. A combination of on-lattice simulated annealing based on Metropolis Monte Carlo simulations and off-lattice relaxation by molecular dynamics is applied to obtain the most stable cluster configurations at T = 0 K. The most recent interatomic potential built within the framework of the embedded-atom method for the Fe-Cu system is used. The total free energy of pure bcc-Fe and fcc-Cu as well as the total formation free energy and the total binding free energy of the vacancy-copper clusters are determined for finite temperatures. Our results are compared with the available data from previous investigations performed using many-body interatomic potentials and first-principles methods. For further applications in rate theory and object kinetic Monte Carlo simulations, the vibrational effects evaluated in the present study are included in the previously developed analytical fitting formulae.

  15. Phonon-magnon interactions in BCC iron: A combined molecular and spin dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Perera, Meewanage Dilina N [ORNL; Landau, David P [University of Georgia, Athens, GA; Nicholson, Don M [ORNL; Stocks, George Malcolm [ORNL; Eisenbach, Markus [ORNL; Yin, Junqi [ORNL; Brown, Greg [ORNL

    2014-01-01

    Combining an atomistic many-body potential with a classical spin Hamiltonian pa- rameterized by first principles calculations, molecular-spin dynamics computer sim- ulations were performed to investigate phonon-magnon interactions in BCC iron. Results obtained for spin-spin and density-density dynamic structure factors show that noticeable softening and damping of magnon modes occur due to the presence of lattice vibrations. Furthermore, as a result of the phonon-magnon coupling, addi- tional longitudinal spin wave excitations are observed, with the same frequencies as the longitudinal phonon modes.

  16. Identifying patients at risk for recurrent or advanced BCC.

    Science.gov (United States)

    Hamid, Omid; Goldenberg, Gary

    2013-11-01

    Basal cell carcinoma (BCC) is a common skin cancer and its incidence is on the rise worldwide. Clinical presentation and histologic examination are used for diagnosis and to stratify BCCs as either low- or high-risk for recurrence or development of advanced disease. A number of surgical and nonsurgical options are available for BCC. BCC is most often managed with a surgical approach, but not all tumors and patients are suitable for surgery. Vismodegib is a recently approved first-in-class hedgehog pathway inhibitor that has expanded options for patients who have locally advanced or metastatic BCC.

  17. Shear induced order in SEP diblock copolymer micelles: multiple BCC slip systems

    Science.gov (United States)

    Torija, Maria A.; Choi, Soohyung; Bates, Frank S.; Lodge, Timothy P.

    2010-03-01

    Poly(styrene-b-ethylene-alt-propylene) (SEP) diblock copolymers are solvated by squalane leading to glassy poly(styrene) domains dispersed in a viscoelastic medium. For diblocks containing less than about 50% by weight poly(styrene) and at SEP concentrations greater than 6 w. % these mixtures self-assemble into glassy spherical microdomains that order on a body centered cubic (BCC) lattice. We have investigated how polycrystalline configurations respond to large amplitude oscillatory shear as a function of shear rate, strain amplitude and block copolymer composition. Structure was characterized by small-angle X-ray scattering measurements while simultaneously deforming the mixtures with an in-situ rheometer. All three slip systems associated with plastic deformation in BCC metals110,211,321, were identified with the x-ray beam oriented perpendicular to the shear plane. Higher shear rates and larger strain amplitudes produced more slip within the 211 system. These results represent one of the most comprehensive assessments of BCC structure in solvated copolymers and will be discussed within the context of the associated linear viscoelastic behavior.

  18. Phomalactone optimization and production of entomopathogenic fungi by Ophiocordyceps communis BCC 1842 and BCC 2763.

    Science.gov (United States)

    Prathumpai, W; Kocharin, K

    2016-01-01

    Phomalactone, an antibacterial, insecticidal, and herbicidal compound, was produced by insect pathogenic fungi, Ophiocordyceps communis BCC 1842 and BCC 2763, in bioreactors using different carbon and nitrogen sources. Glucose and fructose were preferable for growth and phomalactone production. The highest specific growth rate (μ) of 0.012 hr(-1), the highest biomass yield (Ysx) of 0.38 g DW g(-1) sugar, the highest volumetric sugar consumption rate (qs) of 0.036 g (L hr)(-1), the maximum phomalactone concentration ([Formula: see text]) of 93.30 mg L(-1) at 127 hr, and the highest volumetric production rate of phomalactone (qp) of 0.46 ± 0.12 mg (L d)(-1) were obtained on glucose and sodium nitrate as the sole carbon and nitrogen sources, respectively, by O. communis BCC 1842. In contrast, O. communis BCC 2763 gave lower phomalactone production. This mass phomalactone production is useful for the biological synthesis of a precursor for more broad-range potent analogs such as antitumor, antifungal, and others and for its further biological studies.

  19. Temperature dependence of enthalpies and entropies of formation and migration of mono-vacancy in BCC iron

    Science.gov (United States)

    Wen, Haohua; Woo, C. H.

    2014-12-01

    Entropies and enthalpies of vacancy formation and diffusion in BCC iron are calculated for each temperature directly from free-energies using phase-space trajectories obtained from spin-lattice dynamics simulations. Magnon contributions are found to be particularly substantial in the temperature regime near the α-β (ferro/para-magnetic) transition. Strong temperature dependence and singular behavior can be seen in this temperature regime, reflecting magnon softening effects. Temperature dependence of the lattice component in this regime is also much more significant compared to previous estimations based on Arrhenius-type fitting. Similar effects on activation processes involving other irradiation-produced defects in magnetic materials are expected.

  20. Long-Lived Metastable bcc Phase during Ordering of Micelles

    Science.gov (United States)

    Bang, Joona; Lodge, Timothy P.

    2005-03-01

    We report a metastable bcc phase that intervenes between a disordered micellar suspension and an fcc crystal in a block copolymer solution. A symmetric poly(styrene-b-isoprene) diblock copolymer in the isoprene-selective solvent squalane at a volume fraction of 0.20 was investigated using small angle x-ray scattering and rheology. Upon heating, the metastable bcc phase nucleates first, and then transforms over the course of hours to the stable fcc phase. At still higher temperatures the fcc phase transforms to an equilibrium bcc phase. The metastability of the bcc phase was confirmed by oscillatory shear and annealing using small angle x-ray scattering. These results constitute an interesting experimental manifestation of Ostwald's step rule, and also support recent theory and simulation results whereby bcc nucleates more readily from a melt of spheres.

  1. About oxide dispersion particles chemical compatibility with areas coherent dissipation/sub-grains of bcc-alloys in Fe - (Cr, V, Mo, W systems

    Directory of Open Access Journals (Sweden)

    Udovsky A.

    2016-01-01

    Full Text Available A concept of partial magnetic moments (PMM of the iron atoms located in the first ч four coordination spheres (1÷4 CS for bcc lattice have been introduced based on analysis of results obtained by quantum-mechanical calculations (QMC for volume dependence of the average magnetic moment ferromagnetic (FM Fe. The values of these moments have been calculated for pure bcc Fe and bcc - Fe-Cr alloys. This concept has been used to formulate a three sub-lattice model for binary FM alloys of the Fe-M systems (M is an alloying paramagnetic element. Physical reason for sign change dependence of the short-range order and mixing enthalpy obtained by QMCs for Fe-(Cr, V bcc phases has been found. Using this model it has been predicted that static displacements of Fe - atoms in alloy matrix increase with increasing the of CS number and result in reducing of the area of coherent dissipation (ACD size with growth of the dimension factor (DF in the Fe-(Cr, V, Mo, W systems in agreement with the X-ray experiments. It has been shown theoretically that anisotropy of spin- density in bcc lattice Fe and DF in binary Fe - (Cr, V, Mo, W systems is main factor for origins of segregations on small angle boundaries of ACD and sub-grains boundaries To prevent the coagulation of both ACD and sub-grains, and to increase the strength of alloys, it is advisable to add oxide dispersion particles into ferrite steel taking into account their chemical compatibility and coherent interfacing with the crystalline lattice of a ferrite matrix. Application of phase diagrams for binary and ternary the Fe-(Y, Zr-O systems to verify chemical compatibility of oxide dispersion particles with ferrite matrix have been discussed

  2. Comment on `Magic strains in face-centered and body-centered cubic lattices'

    NARCIS (Netherlands)

    Waal, van de Benjamin W.

    1990-01-01

    The six symmetry-related so-called magic strain tensors that transform a f.c.c. lattice (or a b.c.c. lattice) into itself, which have been reported recently by Boyer [Acta Cryst. (1989), A45, FC29-FC32] are not unique: an infinite number of displacement tensors can be constructed that transform one

  3. Diffusion simulation of Cr-Fe bcc systems at atomic level using a random walk algorithm

    Energy Technology Data Exchange (ETDEWEB)

    San Sebastian, I.; Aldazabal, J. [CEIT and Tecnun (University of Navarra), San Sebastian (Spain); Capdevila, C.; Garcia-Mateo, C. [MATERALIA Research Group, Department of Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas (CENIM-CSIC), Avda. Gregorio del Amo 8, 28040 Madrid (Spain)

    2008-06-15

    This paper proposes a model to simulate the diffusion of impurities in bcc atomic lattices. It works with three-dimensional volume, divided in small cubic elements (voxels), containing more than one atomic cell each. Once the domain is discretized, impurities jump from one voxel to another according to certain probability that takes into account the composition and geometry of the target voxel. In the present work, a model was applied to a prismatic volume and in order to deduce the relationship between the atomic jumping frequency and the temperature two different cases were studied. One consists of a Fe matrix with Cr impurities, and the other is based on a Cr matrix with Fe impurities. Results obtained from these simulations were compared with profiles obtained by Dictra software. Results for the atomic jumping frequencies were fitted to an Arrhenius type equation, as shown in following expressions: From these equations it is possible to obtain an activation energy for the atomic jumping phenomenon of {proportional_to}306 kJ/mol and {proportional_to}411 kJ/mol for the Fe-matrix and Cr-matrix systems, respectively. These energies match the empirical measured values for the diffusion of Cr and Fe impurities, 250 kJ/mol and 407 kJ/mol, respectively. Results obtained in this work assure that the proposed model is suitable for simulating the three-dimensional diffusion of substitutional impurities in Cr and Fe bcc systems. It could be easily expanded to other bcc matrix systems. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Interaction in equilibrium plasmas of charged macroparticles located in nodes of cubic lattices

    Science.gov (United States)

    Filippov, A. V.

    2016-11-01

    Interaction of two charged pointlike macroparticles located at nodes of simple cubic (sc), body-centered cubic (bcc) and face-centered cubic (fcc) lattices in an equilibrium plasma is studied within the linearized Poisson-Boltzmann model. It is shown that the boundary shape has a strong influence on the electrostatic interaction between two macroparticles, which switches from repulsion at small interparticle distances to attraction as it approaches the halflength of a computational cell. It is found that in a case of dust particles arranged in the nodes of the sc, bcc and fcc lattices, the electrostatic force acting on them is equal to zero and the nature of the interaction changes from repulsion to attraction; hence, the infinite sc, bcc and fcc lattices of charged dust particles are thermodynamically stable at rather low temperatures.

  5. The expression levels of the sirtuins in patients with BCC.

    Science.gov (United States)

    Temel, Metin; Koç, Mustafa Nihat; Ulutaş, Saffet; Göğebakan, Bülent

    2016-05-01

    Basal cell carcinoma (BCC) is the most common tumor in humans. Reduced expression of sirtuins interferes with DNA repair, which may cause mutations and genomic instability, and eventually leads to tumor development. In the present study, we investigate the expression levels of SIRT genes in non-tumoral and tumor tissues of patients with BCC. A total of 27 patients (16 males, 11 females) with BCC were included in the study; the mean age was 65.40 ± 10.74 years and mean follow-up was 2.5 ± 0.5 years. There were multiple synchronous lesions in six patients, and the remaining 21 patients had a single lesion. Tumor and non-tumoral tissue samples were collected from all patients, and mRNA expression levels of SIRT1-7 (Sirt1.1, Sirt1.2, Sirt2, Sirt3, Sirt4, Sirt5, Sirt6, and Sirt7) were examined by real-time PCR. The results showed that expressions of SIRT1.1, SIRT1.2, SIRT4, SIRT5, SIRT6, and SIRT7 mRNAs were unchanged in tumor tissues of BCC patients compared with non-tumoral tissue samples. Importantly, the expressions of SIRT2 and SIRT3 mRNAs were significantly reduced in tumor tissue samples from BCC patients compared with non-tumoral tissues (P = 0.02 and P = 0.03, respectively). In light of the previous reports that have demonstrated a link between SIRT proteins and cancer, our findings suggest that SIRT2 and SIRT3 may plan important roles in BCC pathogenesis and could be candidate prognostic biomarkers for BCC.

  6. The Physical Foundation of the Quark Model the Quark Model as an approximation of the BCC Model

    CERN Document Server

    Xu, J L

    2001-01-01

    From the Dirac sea concept, the BCC model infers that the quarks u and d constitute a body center cubic quark lattice in the vacuum; when a quark $q^*$ is excited from the vacuum, the nearest primitive cell u' and d' is accompanying excited by the quark $q^*$. Using the energy band theory, the model deduces the quantum numbers (I, S, C, b, and Q) and the masses of all quarks using a united mass formula. Then, it shows that the system of} 3 excited quarks ($q^*u'd'

  7. Ginzburg-Landau theory for the solid-liquid interface of bcc elements

    Science.gov (United States)

    Shih, W. H.; Wang, Z. Q.; Zeng, X. C.; Stroud, D.

    1987-01-01

    Consideration is given to a simple order-parameter theory for the interfacial tension of body-centered-cubic solids in which the principal order parameter is the amplitude of the density wave at the smallest nonzero reciprocal-lattice vector of the solid. The parameters included in the theory are fitted to the measured heat of fusion, melting temperature, and solid-liquid density difference, and to the liquid structure factor and its temperature derivative at freezing. Good agreement is found with experiment for Na and Fe and the calculated anisotropy of the surface tension among different crystal faces is of the order of 2 percent. On the basis of various assumptions about the universal behavior of bcc crystals at melting, the formalism predicts that the surface tension is proportional to the heat of fusion per surface atom.

  8. Influence of substitutional atoms on the Snoek peak of carbon in b.c.c. iron

    Energy Technology Data Exchange (ETDEWEB)

    Saitoh, Hajime; Yoshinaga, Naoki; Ushioda, Kohsaku

    2004-03-08

    The influence of substitutional atoms (Mn, P, Si, Al, Cr, Co) on the C Snoek peak in b.c.c. iron was investigated. In the dilute range of the substitutes, the addition of Co, Mn, Cr, Si, P and Al resulted in the decreases in Snoek peak height in this ascending order. However, the addition of Mn to the Fe-C-P alloy hardly changes Snoek peak height. There is even a case that Snoek peak height is increased by further Mn addition to this alloy. They can be explained systematically by the proposed model wherein the solute carbon present in the influence region where the lattice distortion around the substitute is greater than the threshold value cannot contribute to the Snoek peak. The strain field generated by a substitutional atom due to the difference in atomic size is concluded to be the main reason for the reduction in Snoek peak height.

  9. Indium-defect interactions in FCC and BCC metals studied using the modified embedded atom method

    Science.gov (United States)

    Zacate, M. O.

    2016-12-01

    With the aim of developing a transferable potential set capable of predicting defect formation, defect association, and diffusion properties in a wide range of intermetallic compounds, the present study was undertaken to test parameterization strategies for determining empirical pair-wise interaction parameters in the modified embedded atom method (MEAM) developed by Baskes and coworkers. This report focuses on indium-solute and indium-vacancy interactions in FCC and BCC metals, for which a large set of experimental data obtained from perturbed angular correlation measurements is available for comparison. Simulation results were found to be in good agreement with experimental values after model parameters had been adjusted to reproduce as best as possible the following two sets of quantities: (1) lattice parameters, formation enthalpies, and bulk moduli of hypothetical equiatomic compounds with the NaCl crystal structure determined using density functional theory and (2) dilute solution enthalpies in metals as predicted by Miedema's semi-empirical model.

  10. Molecular dynamics, spin dynamics study of phonon-magnon interactions in BCC iron

    Science.gov (United States)

    Perera, Dilina; Landau, David P.; Stocks, G. Malcolm; Nicholson, Don; Eisenbach, Markus; Yin, Junqi

    2013-03-01

    By combining an atomistic many-body potential (Finnis-Sinclair) with a classical Heisenberg-like spin Hamiltonian, we perform combined molecular and spin dynamics simulations to investigate phonon-magnon interactions in BCC iron. The coupling between atomic and spin degrees of freedom is established via a distance dependent exchange interaction derived from first principles electronic structure calculations. Coupled equations of motion are integrated using a second order Suzuki-Trotter decomposition of the exponential time evolution operator. To investigate the effect of lattice vibrations on spin wave spectrum, we calculate spin-spin and density-density dynamic structure factors S(q, ω), and compare that to the results obtained from pure spin dynamics simulations performed on a rigid lattice. In the presence of lattice vibrations, we observe an additional peak in the longitudinal spin-spin dynamic structure factor which coincides with the peak position in density-density dynanmic structure factor. Research sponsored by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, ''Center for Defect Physics,'' an Energy Frontier Research Center

  11. Formation of pentagonal atomic chains in BCC Fe nanowires

    Science.gov (United States)

    Sainath, G.; Choudhary, B. K.

    2016-12-01

    For the first time, we report the formation of pentagonal atomic chains during tensile deformation of ultra thin BCC Fe nanowires. Extensive molecular dynamics simulations have been performed on /{110} BCC Fe nanowires with different cross section width varying from 0.404 to 3.634 nm at temperatures ranging from 10 to 900 K. The results indicate that above certain temperature, long and stable pentagonal atomic chains form in BCC Fe nanowires with cross section width less than 2.83 nm. The temperature, above which the pentagonal chains form, increases with increase in nanowire size. The pentagonal chains have been observed to be highly stable over large plastic strains and contribute to high ductility in Fe nanowires.

  12. Theoretical elastic moduli of ferromagnetic bcc Fe alloys.

    Science.gov (United States)

    Zhang, Hualei; Punkkinen, Marko P J; Johansson, Börje; Vitos, Levente

    2010-07-14

    The polycrystalline elastic parameters of ferromagnetic Fe(1-x)M(x) (M = Al, Si, V, Cr, Mn, Co, Ni, Rh; 0 ≤ x ≤ 0.1) random alloys in the body centered cubic (bcc) crystallographic phase have been calculated using first-principles alloy theory in combination with statistical averaging methods. With a few exceptions, the agreement between the calculated and the available experimental data for the polycrystalline aggregates is satisfactory. All additions considered here decrease the bulk modulus (B) and Poisson's ratio (ν) of bcc Fe. The complex composition dependence of the C(44) single-crystal elastic constant is reflected in the polycrystalline shear modulus (G), Young's modulus (E), and Debye temperature (Θ). The polycrystalline anisotropy of bcc Fe is increased by all additions, and Al, Si, Ni, and Rh yield the largest alloying effects.

  13. Hyperfine interactions on iron nuclei in the BCC and fractally decomposed BCC/FCC mixed phase iron-gold alloys

    Energy Technology Data Exchange (ETDEWEB)

    Blachowski, A. [Moessbauer Spectroscopy Division, Institute of Physics, Pedagogical University, PL-30-084 Krakow, ul. Podchorazych 2 (Poland); Ruebenbauer, K. [Moessbauer Spectroscopy Division, Institute of Physics, Pedagogical University, PL-30-084 Krakow, ul. Podchorazych 2 (Poland)], E-mail: sfrueben@cyf-kr.edu.pl; Przewoznik, J.; Zukrowski, J. [Solid State Physics Department, Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, PL-30-059 Krakow, Al. Mickiewicza 30 (Poland)

    2008-06-30

    Iron-gold alloys for the gold concentration ranging from 1 at.% till 70 at.% were investigated by means of the {sup 57}Fe-14.4 keV Moessbauer spectroscopy, X-ray diffraction and scanning electron microscopy. Samples were prepared by arc melting of the elements, and investigated as cast and after annealing. A single BCC phase is obtained for the gold concentration up to about 3 at.%, while for the higher gold concentration one obtains mixed phase samples containing BCC and FCC phases both. The BCC phase is ferromagnetically ordered at room temperature. Contributions to the charge and spin density on iron atoms in the BCC phase due to the gold impurities were determined up to the second neighbors. The FCC phase is either magnetically ordered at room temperature or it is paramagnetic at the above temperature depending upon iron concentration, as the magnetic transition temperature is increasing with the increasing iron concentration. BCC/FCC mixed phase samples are characterized by very small crystallites (nanoparticles) of both phases. These nanoparticles form hierarchical fractal structures on the scale ranging from more than 1 mm till less than 30 nm.

  14. Invariant line and crystallography of HCP→BCC precipitation

    Institute of Scientific and Technical Information of China (English)

    肖晓玲; 罗承萍; 刘江文

    2002-01-01

    The method of calculating the invariant line in HCP→BCC precipitation based on the invariant line strain model is described.The experimentally determined crystallographic features of the lath-shaped or needle-like precipitates formed in the HCP→BCC precipitations occurring in Mg-Al and Zr-Nb alloys were found to be in excellent agreement with the predictions from the model,thus suggesting that the model is valid for predicting the crystallography of diffusion-controlled phase transformations.

  15. FCC Fe2NiSi prepared by mechanical alloying and stabilization effect of L21B disorder on BCC Heusler structure

    Science.gov (United States)

    Luo, Hongzhi; Xin, Yuepeng; Ma, Yuexing; Liu, Bohua; Meng, Fanbin; Liu, Heyan; Liu, Enke; Wu, Guangheng

    2016-12-01

    Fe2NiSi FCC phase has been prepared by ball-milling successfully, which is different from the BCC Heusler phase prepared by arc-melting in previous literatures. The FCC Fe2NiSi is a ferromagnet with a lattice constant of 3.58 Å. The phase stability of the FCC and BCC Fe2NiSi has been compared by first-principles calculations. It has been found that the FCC structure has a lower total energy compared with the highly-ordered Heusler structures XA and L21, that is the reason why the FCC phase can be prepared by ball-milling. However, the Fe (A)-Ni (C) disorder in the BCC XA structure can lower its total energy further and make it smaller than the FCC phase. So the most stable structure in Fe2NiSi is L21B, as has been observed in the arc-melting sample. This can be explained from their DOS structures. The calculated total moments for the FCC and BCC phases agree with their Ms at 5 K quite well.

  16. Fcc-bcc transition for Yukawa interactions determined by applied strain deformation

    OpenAIRE

    Hoy, Robert S.; Robbins, Mark O.

    2004-01-01

    Calculations of the work required to transform between bcc and fcc phases yield a high-precision bcc-fcc transition line for monodisperse point Yukawa (screened-Couloumb) systems. Our results agree qualitatively but not quantitatively with previously published simulations and phenomenological criteria for the bcc-fcc transition. In particular, the bcc-fcc-fluid triple point lies at a higher inverse screening length than previously reported.

  17. Superradiance Lattice

    CERN Document Server

    Wang, Da-Wei; Zhu, Shi-Yao; Scully, Marlan O

    2014-01-01

    We show that the timed Dicke states of a collection of three-level atoms can form a tight-binding lattice in the momentum space. This lattice, coined the superradiance lattice (SL), can be constructed based on an electromagnetically induced transparency (EIT) system. For a one-dimensional SL, we need the coupling field of the EIT system to be a standing wave. The detuning between the two components of the standing wave introduces an effective electric field. The quantum behaviours of electrons in lattices, such as Bloch oscillations, Wannier-Stark ladders, Bloch band collapsing and dynamic localization can be observed in the SL. The SL can be extended to two, three and even higher dimensions where no analogous real space lattices exist and new physics are waiting to be explored.

  18. The Body Center Cubic Quark Lattice Model

    CERN Document Server

    Lin Xu, Jiao

    2004-01-01

    The Standard Model while successful in many ways is incomplete; many questions remain. The origin of quark masses and hadronization of quarks are awaiting an answer. From the Dirac sea concept, we infer that two kinds of elementary quarks (u(0) and d(0)) constitute a body center cubic (BCC) quark lattice with a lattice constant a < $10^{-18}$m in the vacuum. Using energy band theory and the BCC quark lattice, we can deduce the rest masses and the intrinsic quantum numbers (I, S, C, b and Q) of quarks. With the quark spectrum, we deduce a baryon spectrum. The theoretical spectrum is in agreement well with the experimental results. Not only will this paper provide a physical basis for the Quark Model, but also it will open a door to study the more fundamental nature at distance scales <$10^{-18}$m. This paper predicts some new quarks $u_{c}$(6490) and d$_{b}$(9950), and new baryons $\\Lambda_{c}^{+}$(6500), $\\Lambda_{b}^{0}$(9960).

  19. Stronger Residual BCC-algebra and Its Normal Prime Filter Theorem%强剩余BCC-代数及其正规素滤子定理

    Institute of Scientific and Technical Information of China (English)

    张小红; 邵志清; 王永全

    2008-01-01

    作为各种非可换模糊逻辑代数的推广,引入剩余BCC-代数及强剩余BCC-代数的概念,研究了它们与psMTL-代数、pseudo-hoop等代数结构的关系.研究了剩余BCC-代数滤子的基本性质,建立了剩余BCC-代数的商代数理论;引入剩余BCC-代数的正规滤子概念,证明了强剩余BCC-代数的正规素滤子定理,从而拓广了相应逻辑代数滤子理论的已有结果.

  20. Free energy calculation of mechanically unstable but dynamically stabilized bcc titanium

    Science.gov (United States)

    Kadkhodaei, Sara; Hong, Qi-Jun; van de Walle, Axel

    2017-02-01

    The phase diagram of numerous materials of technological importance features high-symmetry high-temperature phases that exhibit phonon instabilities. Leading examples include shape-memory alloys, as well as ferroelectric, refractory, and structural materials. The thermodynamics of these phases have proven challenging to handle by atomistic computational thermodynamic techniques due to the occurrence of constant anharmonicity-driven hopping between local low-symmetry distortions, while maintaining a high-symmetry time-averaged structure. To compute the free energy in such phases, we propose to explore the system's potential-energy surface by discrete sampling of local minima by means of a lattice gas Monte Carlo approach and by continuous sampling by means of a lattice dynamics approach in the vicinity of each local minimum. Given the proximity of the local minima, it is necessary to carefully partition phase space by using a Voronoi tessellation to constrain the domain of integration of the partition function in order to avoid double counting artifacts and enable an accurate harmonic treatment near each local minima. We consider the bcc phase of titanium as a prototypical example to illustrate our approach.

  1. Identifying self-interstitials of bcc and fcc crystals in molecular dynamics

    Science.gov (United States)

    Bukkuru, S.; Bhardwaj, U.; Warrier, M.; Rao, A. D. P.; Valsakumar, M. C.

    2017-02-01

    Identification of self-interstitials in molecular dynamics (MD) simulations is of critical importance. There exist several criteria for identifying the self-interstitial. Most of the existing methods use an assumed cut-off value for the displacement of an atom from its lattice position to identify the self-interstitial. The results obtained are affected by the chosen cut-off value. Moreover, these chosen cut-off values are independent of temperature. We have developed a novel unsupervised learning algorithm called Max-Space Clustering (MSC) to identify an appropriate cut-off value and its dependence on temperature. This method is compared with some widely used methods such as effective sphere (ES) method and nearest neighbor sphere (NNS) method. The cut-off radius obtained using our method shows a linear variation with temperature. The value of cut-off radius and its temperature dependence is derived for five bcc (Cr, Fe, Mo, Nb, W) and six fcc (Ag, Au, Cu, Ni, Pd, Pt) crystals. It is seen that the ratio of the cut-off values "r" to the lattice constant "a" lies between 0.23 and 0.3 at 300 K and this ratio is on an average smaller for the fcc crystals. Collision cascade simulations are carried out for Primary knock-on Atom (PKA) energies of 5 keV in Fe (at 300 K and 1000 K) and W (at 300 K and 2500 K) and the results are compared using the various methods.

  2. Ginzburg-Landau-type multiphase field model for competing fcc and bcc nucleation.

    Science.gov (United States)

    Tóth, G I; Morris, J R; Gránásy, L

    2011-01-28

    We address crystal nucleation and fcc-bcc phase selection in alloys using a multiphase field model that relies on Ginzburg-Landau free energies of the liquid-fcc, liquid-bcc, and fcc-bcc subsystems, and determine the properties of the nuclei as a function of composition, temperature, and structure. With a realistic choice for the free energy of the fcc-bcc interface, the model predicts well the fcc-bcc phase-selection boundary in the Fe-Ni system.

  3. Elastic anharmonicity of bcc Fe and Fe-based random alloys from first-principles calculations

    Science.gov (United States)

    Li, Xiaoqing; Schönecker, Stephan; Zhao, Jijun; Vitos, Levente; Johansson, Börje

    2017-01-01

    We systematically investigate elastic anharmonic behavior in ferromagnetic body-centered cubic (bcc) Fe and Fe1 -xMx (M =Al , V, Cr, Co, or Ni) random alloys by means of density-functional simulations. To benchmark computational accuracy, three ab initio codes are used to obtain the complete set of second- and third-order elastic constants (TOECs) for bcc Fe. The TOECs of Fe1 -xMx alloys are studied employing the first-principles alloy theory formulated within the exact muffin-tin orbital method in combination with the coherent-potential approximation. It is found that the alloying effects on C111,C112 , and C123, which are governed by normal strains only, are more pronounced than those on C144,C166 , and C456, which involve shear strains. Remarkably, the magnitudes of all TOECs but C123 decrease upon alloying with Al, V, Cr, Co, or Ni. Using the computed TOECs, we study compositional effects on the pressure derivatives of the effective elastic constants (d Bi j/d P ), bulk (d K /d P ), and shear moduli (d G /d P ) and derive longitudinal acoustic nonlinearity parameters (β ). Our predictions show that the pressure derivatives of K and G decrease with x for all solute elements and reveal a strong correlation between the compositional trends on d K /d P and d G /d P arising from the fact that alloying predominantly alters d B11/d P . The sensitivity of d B11/d P to composition is attributed to intrinsic alloying effects as opposed to lattice parameter changes accompanying solute addition. For Fe and the considered Fe-based alloys, β along high-symmetry directions orders as β [111 ]>β [100 ]>β [110 ] , and alloying increases the directional anisotropy of β but reduces its magnitude.

  4. First-principles study of stability of the bcc and ω phases of a low Al concentration Nb1-xAlx alloy.

    Science.gov (United States)

    Sanati, M; Albers, R C; Lookman, T; Saxena, A

    2011-07-27

    The phase stability and site occupancy of bcc (body centered cubic) Nb(5)Al and slightly rearranged atomic structures have been examined by means of first-principles calculations. In order to use first-principles methods, a periodic cell is required and we used ordered Nb(5)Al compounds as a tractable example of a low Al concentration Nb(1 - x)Al(x) alloy (in this case, for about 17 at.% Al). The instability against an ω-structure atomic displacement was also studied, since this structure is detrimental to ductility. Mulliken population analysis was used to provide an understanding of the hybridization between the atoms and the electronic origin of the site occupancy and instability of the underlying bcc structures. By making calculations for several different configurations of the Nb-Al system we estimated the strengths of the Nb-Nb and Nb-Al bonds. It is shown that the stability of the underlying bcc phases is directly related to Nb-Nb and Nb-Al first-nearest-neighbor interactions. The first-principles calculations were extended to finite temperature by including various contributions to the free energy. In particular, the vibrational free energy was calculated within the quasiharmonic approximation, and it is shown that the contribution of the low energy modes to the lattice entropy helps to stabilize ordered bcc phases against ω-type phase transformations. Semi-quasi-random structures were employed to study the stability of the ordered and disordered bcc phases. Our study showed, in agreement with experiment, that the ω, ordered, and disordered phases can coexist in a nonequilibrium state at finite temperature.

  5. Coordination chemistry of 1,4-bis-carboxymethylcyclam, H(2)(1,4-bcc).

    Science.gov (United States)

    Tonei, Deborah M; Ware, David C; Brothers, Penelope J; Plieger, Paul G; Clark, George R

    2006-01-07

    Zinc metal reduction of the cobalt(III) complex [Co(1,4-bcc)](+) (1,4-bcc = 1,4-bis-carboxymethylcyclam) produces the corresponding cobalt(II) complex which crystallises as the coordination polymer {[Co(1,4-bcc)]ZnCl(2)}(n). A method has been developed for removal of the cobalt(III) ion from [Co(1,4-bcc)](+) and isolation of the free ligand as its hydrochloride salt, H(2)(1,4-bcc).4HCl. This has been used for the preparation of new metal complexes, and the syntheses and characterisation of the copper(ii), nickel(ii), zinc(ii) and chromium(iii) complexes containing the 1,4-bcc ligand are described. X-Ray crystal structures of {[Co(1,4-bcc)]ZnCl(2)}(n).2.5H(2)O, {[Cu(1,4-bcc)]CuCl(2)}(n).0.25MeOH.H(2)O and [Cu(1,4-bcc)H]ClO(4) show the complexes to have the trans(O) geometry of the 1,4-bcc ligand, while the structure of [Cr(1,4-bcc)H(0.5)](ClO(4))(1.5).EtOH exhibits the cis(O) configuration.

  6. Calculation of body-centered-cubic lattice sums with an application to ferromagnetism.

    Science.gov (United States)

    Wintucky, E. G.

    1972-01-01

    The lattice sums for the bcc lattice are recalculated using the method of Flax and Raich to obtain more general expressions, valid for all temperatures, in terms of a Langevin function and its derivatives. Formulas are presented which enable easy numerical evaluation. A comparison with well-known low-temperature expansions and with the results of direct numerical integration demonstrates the validity at low temperatures of the more general expressions calculated here.

  7. The effects of next-to-nearest-neighbour hopping on Bose–Einstein condensation in cubic lattices

    Indian Academy of Sciences (India)

    G K Chaudhary; R Ramakumar

    2010-01-01

    In this paper, we present results of our calculations on the effects of next-to-nearest-neighbour boson hopping (′) energy on Bose–Einstein condensation in cubic lattices. We consider both non-interacting and repulsively interacting bosons moving in the lowest Bloch band. The interacting bosons are studied using Bogoliubov method. We find that the Bose condensation temperature is enhanced by increasing ′ for bosons in a simple cubic (sc) lattice and decreases for bosons in body-centred cubic (bcc) and face-centred cubic (fcc) lattices. We also find that interaction-induced depletion of the condensate is reduced for bosons in an sc lattice while it is enhanced for bosons in bcc and fcc lattices.

  8. Cubic to tetragonal crystal lattice reconstruction during ordering or decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Byung-kl [Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering

    1992-09-01

    This thesis studied thermodynamic stability and morphology of product phases in diffusional phase transformations involving cubic-to-tetragonal crystal lattice reconstructions. Two different kinds of diffusional transformations were examined: L1{sub 0} ordering (fcc to fct lattice change) and decomposition of off-stoichiometric B2 ordering alloys accompanying bcc to fcc Bain transformation. In the first case, Fe-45 at.% Pd alloys were studied by TEM; in the second, the Bain strain relaxation during decomposition of hyper-eutectoid Cu-9.04 wt% Be alloy was studied. CuAu and InMg were also studied.

  9. Student Opinion Survey, 1976. Research Report: BCC 1-77.

    Science.gov (United States)

    Eagle, Norman

    A student opinion survey was administered to a sample of 1,100 students at Bronx Community College (BCC) in 1976. Respondent ethnicity distribution was 46.2% black, 29.1% hispanic, 17.0% white, 1.5% Oriental, and 6.3% other. More than half of the respondents were in either liberal arts and music (42.8%) or business curricula (21.8%). Results…

  10. Magnetism in bcc and fcc Fe with carbon and manganese.

    Science.gov (United States)

    Medvedeva, N I; Van Aken, D; Medvedeva, J E

    2010-08-11

    Density functional theory calculations were performed to study the structure and magnetic properties of bcc (α) and fcc (γ) Fe with 3 at.% carbon and manganese impurities. We find that all bcc-based Fe, Fe-C and Fe-Mn-C phases exhibit a ferromagnetic (FM) ground state, while the antiferromagnetic double-layer (AFMD) state is lowest in energy within the collinear spin approach in fcc Fe, Fe-C and Fe-Mn-C phases. However, the carbon and manganese impurities affect the local magnetic interactions significantly. The states with opposite manganese magnetic moments are quasi-degenerate in bcc Fe-Mn alloy, whereas octa-site carbon stabilizes ferromagnetic coupling of the nearest manganese atom with the Fe host. We demonstrate that the antiferromagnetic (AFM) fcc Fe-C and Fe-Mn-C alloys are intrinsically inhomogeneous magnetic systems. Carbon frustrates the local magnetic order by reorientation of magnetic moments of the nearest Mn and Fe atoms, and favors their ferromagnetic coupling. The competition between ferromagnetic and antiferromagnetic Fe-Fe and Fe-Mn interactions and the local magnetovolume instability near carbon may give rise to the spin-glass-like regions observed in austenitic Fe-Mn-C alloys.

  11. Magnetism in bcc and fcc Fe with carbon and manganese

    Energy Technology Data Exchange (ETDEWEB)

    Medvedeva, N I [Institute of Solid State Chemistry, Yekaterinburg 620990 (Russian Federation); Van Aken, D [Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409 (United States); Medvedeva, J E [Department of Physics, Missouri University of Science and Technology, Rolla, MO 65409 (United States)

    2010-08-11

    Density functional theory calculations were performed to study the structure and magnetic properties of bcc ({alpha}) and fcc ({gamma}) Fe with 3 at.% carbon and manganese impurities. We find that all bcc-based Fe, Fe-C and Fe-Mn-C phases exhibit a ferromagnetic (FM) ground state, while the antiferromagnetic double-layer (AFMD) state is lowest in energy within the collinear spin approach in fcc Fe, Fe-C and Fe-Mn-C phases. However, the carbon and manganese impurities affect the local magnetic interactions significantly. The states with opposite manganese magnetic moments are quasi-degenerate in bcc Fe-Mn alloy, whereas octa-site carbon stabilizes ferromagnetic coupling of the nearest manganese atom with the Fe host. We demonstrate that the antiferromagnetic (AFM) fcc Fe-C and Fe-Mn-C alloys are intrinsically inhomogeneous magnetic systems. Carbon frustrates the local magnetic order by reorientation of magnetic moments of the nearest Mn and Fe atoms, and favors their ferromagnetic coupling. The competition between ferromagnetic and antiferromagnetic Fe-Fe and Fe-Mn interactions and the local magnetovolume instability near carbon may give rise to the spin-glass-like regions observed in austenitic Fe-Mn-C alloys.

  12. Synthesis and hydrogen sorption properties of TiV{sub (2−x)}Mn{sub x} BCC alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bibienne, Thomas; Tousignant, Manuel [Hydrogen Research Institute, Université du Québec à Trois-Rivières, 3351 Boulevard des Forges, Trois-Rivières, Québec (Canada); Bobet, Jean-Louis [Institut de Chimie de la Matière Condensée de Bordeaux, 87 Avenue du Dr Schweitzer, 33600 Pessac (France); Huot, Jacques, E-mail: jacques.huot@uqtr.ca [Hydrogen Research Institute, Université du Québec à Trois-Rivières, 3351 Boulevard des Forges, Trois-Rivières, Québec (Canada)

    2015-03-05

    Highlights: • New activation process was investigated for TiV{sub 2−x}Mn{sub x} samples (0.2 ⩽ x ⩽ 0.9). • Samples crystallize with a BCC structure and turn into FCC upon hydrogenation. • Samples activated with new activation process absorb up to 3.4 wt.% of hydrogen. - Abstract: We report here the effect of activation process of TiV{sub 2−x}Mn{sub x} samples (x = 0.2, 0.4, 0.6, 0.8 , 0.9). Crystal structures are investigated for the as-cast, hydrogenated and desorbed states. The as-cast samples crystallise with a Body Centered Cubic (BCC) structure, and the lattice parameter decreases as x increases in the TiV{sub 2−x}Mn{sub x} series. Upon hydrogenation, the BCC structure expands and turns into a Body Centered Tetragonal (BCT) structure for the monohydride phase and into a Face Centered Cubic (FCC) for the dihydride phase. Pressure–Composition-Isotherms (P–C–I) measurements were performed to study the thermodynamic of TiV{sub 2−x}Mn{sub x} alloys and their hydrogen capacities. The maximum hydrogen uptake is observed for TiV{sub 1.2}Mn{sub 0.8} composition, which store 3.4 wt.% of hydrogen at 100 °C. The effect of a new activation process on the hydrogen storage capacities of these alloys is discussed.

  13. Role of lipase in Burkholderia cepacia complex (Bcc) invasion of lung epithelial cells.

    Science.gov (United States)

    Mullen, T; Markey, K; Murphy, P; McClean, S; Callaghan, M

    2007-12-01

    The Burkholderia cepacia complex (Bcc) is a group of ten closely related species associated with life-threatening infection in cystic fibrosis (CF). These bacteria are highly antibiotic resistant, with some strains transmissible, and in a subgroup of patients, they can cause a rapid and fatal necrotising pneumonia. The Bcc organisms produce a range of exoproducts with virulence potential, including exopolysaccharide, proteases and lipases. Many members of the Bcc are also capable of epithelial cell invasion, although the mechanism(s) involved are poorly understood. This study investigates a role for Bcc lipase in epithelial cell invasion by Bcc strains. Lipase activity was measured in eight species of the Bcc. Strains that produced high levels of lipase were predominantly from the B. multivorans and B. cenocepacia species. Pre-treatment of two epithelial cell lines with Bcc lipase significantly increased invasion by two B. multivorans strains and one B. cenocepacia strain and did not affect either plasma membrane or tight junction integrity. Inhibition of Bcc lipase production by the lipase inhibitor Orlistat significantly decreased invasion by both B. multivorans and B. cenocepacia strains in a concentration-dependent manner. This study demonstrates the extent of lipase production across the Bcc and establishes a potential role for lipase in Bcc epithelial cell invasion.

  14. Formation of bcc and fcc during the coalescence of free and supported Fe and Ni clusters.

    Science.gov (United States)

    Li, Guojian; Wang, Qiang; Sui, Xudong; Wang, Kai; Wu, Chun; He, Jicheng

    2015-09-07

    The formation of bcc and fcc during the coalescence of free and supported Fe and Ni clusters has been studied by molecular dynamics simulation using an embedded atom method. Structural evolution of the clusters, coalesced under varying temperature, Ni content and substrate conditions, was explored by interatomic energy, snapshots, pair distribution functions and bond order parameters. The results show that the formation of bcc and fcc is strongly related to Ni content, substrate and coalescence temperature. Free clusters coalesced at 1200 K form bcc at lower Ni contents with fcc forming at higher Ni concentrations and no observable coexistence of bcc and fcc. Differences in coalescence at 1000 K result from the coexistence of bcc and fcc within the Ni range of 50-70%. Free clusters supported on disordered Ni substrates were shown to transform from spherical morphology to islands of supported clusters with preferred epitaxial orientation. The Ni content required to form bcc and fcc coexistence on supported clusters at 1000 K decreased to 30-50% Ni. Free clusters possessing bcc and fcc generally stacked along the bcc (110) and fcc (111) facets, whereas supported clusters stacked along the (111) bcc and (100) fcc planes. Structural transformation was induced by clusters containing greater numbers of atoms. Spread over the substrate enhanced interatomic energy, order substrates affect the epitaxial growth direction and increase the melting points of the supported clusters. This study can be used to predict the nature of fcc and bcc formation in Fe-Ni films.

  15. Two synchronous periungual BCC treated with Mohs surgery. Nail polish related?

    Science.gov (United States)

    Dika, Emi; Patrizi, Annalisa; Fanti, Pier Alessandro; Alessandrini, Aurora; Sorci, Rita; Piraccini, Bianca Maria; Vaccari, Sabina; Misciali, Cosimo; Maibach, Howard I

    2013-06-01

    Basal cell carcinoma (BCC), the most frequent malignant skin tumor observed in Caucasian adults, especially males, occurs mainly in sun-exposed areas of the body. BCC in the periungual tissues, such as proximal nail fold, nail matrix, nail bed and hyponychium, is rarely reported. We report a patient with two synchronous BCC of the periungual tissue localized in the IV and V fingernail, effectively treated with Mohs micrographic surgery.

  16. Cosine-Weighted B-spline interpolation: a fast and high-quality reconstruction scheme for the Body-Centered Cubic lattice.

    Science.gov (United States)

    Csébfalvi, Balázs

    2013-09-01

    In this paper, Cosine-Weighted B-spline (CWB) filters are proposed for interpolation on the optimal Body-Centered Cubic (BCC) lattice. We demonstrate that our CWB filters can well exploit the fast trilinear texture-fetching capability of modern GPUs, and outperform the state-of-the-art box-spline filters not just in terms of efficiency, but in terms of visual quality and numerical accuracy as well. Furthermore, we rigorously show that the CWB filters are better tailored to the BCC lattice than the previously proposed quasi-interpolating BCC B-spline filters, because they form a Riesz basis; exactly reproduce the original signal at the lattice points; but still provide the same approximation order.

  17. Layer texture of hot-rolled BCC metals and its significance for stress-corrosion cracking of main gas pipelines

    Science.gov (United States)

    Perlovich, Yu. A.; Isaenkova, M. G.; Krymskaya, O. A.; Morozov, N. S.

    2016-10-01

    Based on data of X-ray texture analysis of hot-rolled BCC materials it was shown that the layerwise texture inhomogeneity of products is formed during their manufacturing. The effect can be explained by saturation with interstitial impurities of the surface layer, resulting in dynamical deformation aging (DDA). DDA prevents the dislocation slip under rolling and leads to an increase of lattice parameters in the external layer. The degree of arising inhomogeneity correlates with the tendency of hot-rolled sheets and obtained therefrom tubes to stress-corrosion cracking under exploitation, since internal layers have a compressive effect on external layers, and prevents opening of corrosion cracks at the tube surface.

  18. Cadinane sesquiterpenoids from the basidiomycete Stereum cf. sanguinolentum BCC 22926.

    Science.gov (United States)

    Bunyapaiboonsri, Taridaporn; Yoiprommarat, Seangaroon; Nopgason, Rujirek; Komwijit, Somjit; Veeranondha, Sukitaya; Puyngain, Pucharapa; Boonpratuang, Thitiya

    2014-09-01

    Stereumins Q-U, together with known stereumins A, B, K, L, and N, as well as ent-strobilols E and G were isolated from the culture of Stereum cf. sanguinolentum BCC 22926. Their structures were elucidated by extensive spectroscopic analyses. The absolute configurations of stereumins A and Q, as well as ent-strobilol E were established by application of the modified Mosher's method. Stereumin T displayed antibacterial activity against Bacilluscereus with a MIC value of 3.97μM.

  19. Melting of bcc Transition Metals and Icosahedral Clustering

    Energy Technology Data Exchange (ETDEWEB)

    Ross, M; Boehler, R; Japel, S

    2006-05-26

    In contrast to polyvalent metals, transition metals have low melting slopes(dT/dP) that are due to partially filled d-bands that allow for a lowering of liquid phase energy through s-d electron transfer and the formation of local structures. In the case of bcc transition metals we show the apparent discrepancy of DAC melting measurements with shock melting of Mo can be understood by reexamining the shock data for V and Ta and introducing the presence of an icosahedral short range order (ISRO) melt phase.

  20. Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W.

    Science.gov (United States)

    Li, Xiaojie; Schönecker, Stephan; Li, Ruihuan; Li, Xiaoqing; Wang, Yuanyuan; Zhao, Jijun; Johansson, Börje; Vitos, Levente

    2016-06-03

    To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W1-x-y  Re x  Os y (0  ⩽  x, y  ⩽  6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young's modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11, the other elastic parameters including C 12, C 44, Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W1-y  Os y than in W1-x  Re x . A strong correlation between C' and the fcc-bcc structural energy difference for W1-x-y  Re x  Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C'. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

  1. Lattice QCD on fine lattices

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Stefan [DESY (Germany). Neumann Inst. for Computing

    2016-11-01

    These configurations are currently in use in many on-going projects carried out by researchers throughout Europe. In particular this data will serve as an essential input into the computation of the coupling constant of QCD, where some of the simulations are still on-going. But also projects computing the masses of hadrons and investigating their structure are underway as well as activities in the physics of heavy quarks. As this initial project of gauge field generation has been successful, it is worthwhile to extend the currently available ensembles with further points in parameter space. These will allow to further study and control systematic effects like the ones introduced by the finite volume, the non-physical quark masses and the finite lattice spacing. In particular certain compromises have still been made in the region where pion masses and lattice spacing are both small. This is because physical pion masses require larger lattices to keep the effects of the finite volume under control. At light pion masses, a precise control of the continuum extrapolation is therefore difficult, but certainly a main goal of future simulations. To reach this goal, algorithmic developments as well as faster hardware will be needed.

  2. Solving the puzzle of interstitial loop formation in bcc Iron.

    Science.gov (United States)

    Xu, Haixuan; Stoller, Roger E; Osetsky, Yury N; Terentyev, Dmitry

    2013-06-28

    The interstitial loop is a unique signature of radiation damage in structural materials for nuclear and other advanced energy systems. Unlike other bcc metals, two types of interstitial loops, 1/2 and , are formed in bcc iron and its alloys. However, the mechanism by which interstitial dislocation loops are formed has remained undetermined since they were first observed more than fifty years ago. We describe our atomistic simulations that have provided the first direct observation of loop formation. The process was initially observed using our self-evolving atomistic kinetic Monte Carlo method, and subsequently confirmed using molecular dynamics simulations. Formation of loops involves a distinctly atomistic interaction between two 1/2 loops, and does not follow the conventional assumption of dislocation theory, which is Burgers vector conservation between the reactants and the product. The process observed is different from all previously proposed mechanisms. Thus, our observations might provide a direct link between experiments and simulations and new insights into defect formation that may provide a basis to increase the radiation resistance of these strategic materials.

  3. Bcc crystal-fluid interfacial free energy in Yukawa systems.

    Science.gov (United States)

    Heinonen, V; Mijailović, A; Achim, C V; Ala-Nissila, T; Rozas, R E; Horbach, J; Löwen, H

    2013-01-28

    We determine the orientation-resolved interfacial free energy between a body-centered-cubic (bcc) crystal and the coexisting fluid for a many-particle system interacting via a Yukawa pair potential. For two different screening strengths, we compare results from molecular dynamics computer simulations, density functional theory, and a phase-field-crystal approach. Simulations predict an almost orientationally isotropic interfacial free energy of 0.12k(B)T/a(2) (with k(B)T denoting the thermal energy and a the mean interparticle spacing), which is independent of the screening strength. This value is in reasonable agreement with our Ramakrishnan-Yussouff density functional calculations, while a high-order fitted phase-field-crystal approach gives about 2-3 times higher interfacial free energies for the Yukawa system. Both field theory approaches also give a considerable anisotropy of the interfacial free energy. Our result implies that, in the Yukawa system, bcc crystal-fluid free energies are a factor of about 3 smaller than face-centered-cubic crystal-fluid free energies.

  4. The physical and mechanical metallurgy of advanced O+BCC titanium alloys

    Science.gov (United States)

    Cowen, Christopher John

    This thesis comprises a systematic study of the microstructural evolution, phase transformation behavior, elevated-temperature creep behavior, room-temperature and elevated-temperature tensile behavior, and room-temperature fatigue behavior of advanced titanium-aluminum-niobium (Ti-Al-Nb) alloys with and without boron additions. The specific alloys studied were: Ti-5A1-45Nb (at%), Ti-15Al-33Nb (at%), Ti-15Al-33Nb-0.5B (at%), Ti-15Al-33Nb-5B (at%), Ti-21Al-29Nb (at%), Ti-22Al-26Nb (at%), and Ti-22Al-26Nb-5B (at%). The only alloy composition that had been previously studied before this thesis work began was Ti-22Al-26Nb (at%). Publication in peer-reviewed material science journals of the work performed in this thesis has made data available in the scientific literature that was previously non-existent. The knowledge gap for Ti-Al-Nb phase equilibria over the compositional range of Ti-23Al-27Nb (at%) to Ti-12Al-38Nb (at%) that existed before this work began was successfully filled. The addition of 5 at% boron to the Ti-15Al-33Nb alloy produced 5-9 volume percent boride phase needles within the microstructure. The chemical composition of the boride phase measured by electron microprobe was determined to be approximately B 2TiNb. The lattice parameters of the boride phase were simulated through density functional theory calculations by collaborators at the Air Force Research Laboratory based on the measured composition. Using the simulated lattice parameters, electron backscatter diffraction kikuchi patterns and selected area electron diffraction patterns obtained from the boride phase were successfully indexed according to the space group and site occupancies of the B27 orthorhombic crystal structure. This suggests that half the Ti (c) Wyckoff positions are occupied by Ti atoms and the other half are occupied by Nb atoms in the boride phase lattice. Creep deformation behavior is the main focus of this thesis and in particular understanding the dominant creep

  5. Evaluation of the Bilingual Curriculum Content (BCC) Pilot Project: A Three Year Study. Final Report.

    Science.gov (United States)

    Rothfarb, Sylvia H.; And Others

    A three-year longitudinal study of bilingual curriculum content (BCC) was initiated in the 1983-84 school year to assess alternative strategies for teaching curriculum content to Limited English Proficient (LEP) students in Dade County (Florida) Public Schools. The BCC strategy (in which content subjects are taught bilingually) was contrasted with…

  6. A Demographic Profile of Incoming Matriculated Students, Fall, 1977. Research Report: BCC 3-77.

    Science.gov (United States)

    Bronx Community Coll., NY.

    Demographic data were compiled on incoming fall 1977 freshmen at Bronx Community College (BCC), including sex, age, ethnic group, veteran status, satisfaction with BCC curriculum, highest expected educational level, number living in household, parental education, total household income, counseling requests, marital status, employment status, and…

  7. Vismodegib for the treatment of basal cell carcinoma: results and implications of the ERIVANCE BCC trial.

    Science.gov (United States)

    Dessinioti, Clio; Plaka, Michaela; Stratigos, Alexander J

    2014-05-01

    The need for effective treatment of patients with locally advanced or metastatic basal cell carcinoma (BCC), in conjunction with major advances in the elucidation of the molecular basis of this tumor has led to the advent of new targeted therapies - namely, hedgehog inhibitors. The rationale for their use in patients with advanced BCC is based on their inhibitory effect on the hedgehog pathway, which is aberrantly activated in BCCs due to mutations of its primary components, PTCH1 and SMO genes. Vismodegib (GDC-0449) is an orally bioavailable hedgehog pathway inhibitor that selectively inhibits SMO. The ERIVANCE BCC study is a Phase II, international, multicenter clinical trial evaluating the efficacy and safety of vismodegib 150 mg once daily in patients with locally advanced or metastatic BCC. Vismodegib has been approved for the treatment of adult patients with metastatic BCC, or with locally advanced BCC that has recurred following surgery or who are not candidates for surgery or radiation therapy. This article will outline the rationale, design and available results from the ERIVANCE BCC study and discuss the clinical implications of vismodegib in the management of patients with BCC. Challenges regarding vismodegib use include the recurrence of BCC after drug discontinuation, the development of acquired resistance, the dramatic efficacy in patients with Gorlin syndrome, and class-related drug toxicity. Ongoing clinical trials aim to explore the role of vismodegib in the neoadjuvant setting prior to surgery, the potential use of alternate dosing regimens in order to limit chronic adverse events, as well as the identification of patients with BCC that are more likely to respond to this targeted therapy based on genotypic and/or phenotypic characteristics.

  8. An Overview of BCC Climate System Model Development and Application for Climate Change Studies

    Institute of Scientific and Technical Information of China (English)

    WU Tongwen; WU Fanghua; LIU Yiming; ZHANG Fang; SHI Xueli; CHU Min; ZHANG Jie; FANG Yongjie; WANG Fang; LU Yixiong; LIU Xiangwen; SONG Lianchun; WEI Min; LIU Qianxia; ZHOU Wenyan; DONG Min; ZHAO Qigeng; JI Jinjun; Laurent LI; ZHOU Mingyu; LI Weiping; WANG Zaizhi; ZHANG Hua; XIN Xiaoge; ZHANG Yanwu; ZHANG Li; LI Jianglong

    2014-01-01

    This paper reviews recent progress in the development of the Beijing Climate Center Climate System Model (BCC-CSM) and its four component models (atmosphere, land surface, ocean, and sea ice). Two recent versions are described: BCC-CSM1.1 with coarse resolution (approximately 2.8125◦×2.8125◦) and BCC-CSM1.1(m) with moderate resolution (approximately 1.125◦×1.125◦). Both versions are fully cou-pled climate-carbon cycle models that simulate the global terrestrial and oceanic carbon cycles and include dynamic vegetation. Both models well simulate the concentration and temporal evolution of atmospheric CO2 during the 20th century with anthropogenic CO2 emissions prescribed. Simulations using these two versions of the BCC-CSM model have been contributed to the Coupled Model Intercomparison Project phase fi ve (CMIP5) in support of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5). These simulations are available for use by both national and international communities for investigating global climate change and for future climate pro jections. Simulations of the 20th century climate using BCC-CSM1.1 and BCC-CSM1.1(m) are presented and validated, with particular focus on the spatial pattern and seasonal evolution of precipitation and surface air temperature on global and continental scales. Simulations of climate during the last millennium and pro jections of climate change during the next century are also presented and discussed. Both BCC-CSM1.1 and BCC-CSM1.1(m) perform well when compared with other CMIP5 models. Preliminary analyses in-dicate that the higher resolution in BCC-CSM1.1(m) improves the simulation of mean climate relative to BCC-CSM1.1, particularly on regional scales.

  9. Coulomb crystals in the harmonic lattice approximation

    CERN Document Server

    Baiko, D A; De Witt, H E; Slattery, W L

    2000-01-01

    The dynamic structure factor ${\\tilde S}({\\bf k},\\omega)$ and the two-particle distribution function $g({\\bf r},t)$ of ions in a Coulomb crystal are obtained in a closed analytic form using the harmonic lattice (HL) approximation which takes into account all processes of multi-phonon excitation and absorption. The static radial two-particle distribution function $g(r)$ is calculated for classical ($T \\gtrsim \\hbar \\omega_p$, where $\\omega_p$ is the ion plasma frequency) and quantum ($T \\ll \\hbar \\omega_p$) body-centered cubic (bcc) crystals. The results for the classical crystal are in a very good agreement with extensive Monte Carlo (MC) calculations at $1.5 \\lesssim r/a calculated for classical and quantum bcc and face-centered cubic crystals, and anharmonic corrections are discussed. The inelastic part of the HL static structure factor $S''(k)$, averaged over orientations of wave-vector {\\bf k}, is shown to contain pronounced singularities at Bragg diffraction positions. The type of the singularities is di...

  10. Plastic anisotropy and dislocation trajectory in BCC metals

    Science.gov (United States)

    Dezerald, Lucile; Rodney, David; Clouet, Emmanuel; Ventelon, Lisa; Willaime, François

    2016-05-01

    Plasticity in body-centred cubic (BCC) metals at low temperatures is atypical, marked in particular by an anisotropic elastic limit in clear violation of the famous Schmid law applicable to most other metals. This effect is known to originate from the behaviour of the screw dislocations; however, the underlying physics has so far remained insufficiently understood to predict plastic anisotropy without adjustable parameters. Here we show that deviations from the Schmid law can be quantified from the deviations of the screw dislocation trajectory away from a straight path between equilibrium configurations, a consequence of the asymmetrical and metal-dependent potential energy landscape of the dislocation. We propose a modified parameter-free Schmid law, based on a projection of the applied stress on the curved trajectory, which compares well with experimental variations and first-principles calculations of the dislocation Peierls stress as a function of crystal orientation.

  11. Free surface damage induced by irradiation of BCC iron

    Science.gov (United States)

    Korchuganov, Aleksandr V.

    2016-11-01

    The influence of the crystallographic orientation of bcc iron samples on the character of structural changes near the free surface irradiated with ions was studied in the framework of a molecular dynamics method. Irradiation of the (111) surface leads to the formation of craters surrounded by atoms escaped on the surface (adatoms). In the case of the (110) surface irradiation, a vacancy-type dislocation loop with the Burgers vector a or a/2 was formed. The number of adatoms and survived point defects was greater in the sample with the (110) surface than in the sample with the (111) surface for the atomic displacement cascade energies lower than 20 keV. The influence of the irradiated surface orientation on the number of generated point defects decreased with the increasing atomic displacement cascade energy.

  12. Atomistic modeling of carbon Cottrell atmospheres in bcc iron

    Science.gov (United States)

    Veiga, R. G. A.; Perez, M.; Becquart, C. S.; Domain, C.

    2013-01-01

    Atomistic simulations with an EAM interatomic potential were used to evaluate carbon-dislocation binding energies in bcc iron. These binding energies were then used to calculate the occupation probability of interstitial sites in the vicinity of an edge and a screw dislocation. The saturation concentration due to carbon-carbon interactions was also estimated by atomistic simulations in the dislocation core and taken as an upper limit for carbon concentration in a Cottrell atmosphere. We obtained a maximum concentration of 10 ± 1 at.% C at T = 0 K within a radius of 1 nm from the dislocation lines. The spatial carbon distributions around the line defects revealed that the Cottrell atmosphere associated with an edge dislocation is denser than that around a screw dislocation, in contrast with the predictions of the classical model of Cochardt and colleagues. Moreover, the present Cottrell atmosphere model is in reasonable quantitative accord with the three-dimensional atom probe data available in the literature.

  13. Interplay between interstitial displacement and displacive lattice transformations

    Science.gov (United States)

    Zhang, Xie; Hickel, Tilmann; Rogal, Jutta; Neugebauer, Jörg

    2016-09-01

    Diffusionless displacive lattice rearrangements, which include martensitic transformations, are in real materials often accompanied by a displacive drag of interstitials. The interplay of both processes leads to a particular atomistic arrangement of the interstitials in the product phase, which is decisive for its performance. An archetype example is the martensitic transformation in Fe-C alloys. One of the puzzles for this system is that the deviation from the cubic symmetry (i.e., the tetragonality) in the martensite resulting from this interplay is lower than what thermodynamics dictates. In our ab initio approach, the relative motion of C in the transforming lattice is studied with the nudged elastic band method. We prove that an atomic shearlike shuffle mechanism of adjacent (11 2 ¯) Fe layers along the ±[111] bcc directions is essential to achieve a redistribution of C atoms during the fcc → bcc transition, which fully explains the abnormal behavior. Furthermore, the good agreement with experiment validates our method to treat a diffusionless redistribution of interstitials and a displacive rearrangement of the host lattice simultaneously.

  14. Genetic relationships among Italian and Mexican maize-rhizosphere Burkholderia cepacia complex (BCC populations belonging to Burkholderia cenocepacia IIIB and BCC6 group

    Directory of Open Access Journals (Sweden)

    Bevivino Annamaria

    2011-10-01

    Full Text Available Abstract Background A close association between maize roots and Burkholderia cepacia complex (BCC bacteria has been observed in different locations globally. In this study we investigated by MultiLocus Restriction Typing (MLRT the genetic diversity and relationships among Burkholderia cenocepacia IIIB and BCC6 populations associated with roots of maize plants cultivated in geographically distant countries (Italy and Mexico, in order to provide new insights into their population structure, evolution and ecology. Results The 31 B. cenocepacia IIIB and 65 BCC6 isolates gave rise to 29 and 39 different restriction types (RTs, respectively. Two pairs of isolates of B. cenocepacia IIIB and BCC6, recovered from both Italian and Mexican maize rhizospheres, were found to share the same RT. The eBURST (Based Upon Related Sequence Types analysis of MLRT data grouped all the B. cenocepacia IIIB isolates into four clonal complexes, with the RT-4-complex including the 42% of them, while the majority of the BCC6 isolates (94% were grouped into the RT-104-complex. These two main clonal complexes included RTs shared by both Italian and Mexican maize rhizospheres and a clear relationship between grouping and maize variety was also found. Grouping established by eBURST correlated well with the assessment using unweighted-pair group method with arithmetic mean (UPGMA. The standardized index of association values obtained in both B. cenocepacia IIIB and BCC6 suggests an epidemic population structure in which occasional clones emerge and spread. Conclusions Taken together our data demonstrate a wide dispersal of certain B. cenocepacia IIIB and BCC6 isolates in Mexican and Italian maize rhizospheres. Despite the clear relationship found between the geographic origin of isolates and grouping, identical RTs and closely related isolates were observed in geographically distant regions. Ecological factors and selective pressure may preferably promote some genotypes within

  15. An evaluation of prefiltered B-spline reconstruction for quasi-interpolation on the Body-Centered Cubic lattice.

    Science.gov (United States)

    Csébfalvi, Balázs

    2010-01-01

    In this paper, we demonstrate that quasi-interpolation of orders two and four can be efficiently implemented on the Body-Centered Cubic (BCC) lattice by using tensor-product B-splines combined with appropriate discrete prefilters. Unlike the nonseparable box-spline reconstruction previously proposed for the BCC lattice, the prefiltered B-spline reconstruction can utilize the fast trilinear texture-fetching capability of the recent graphics cards. Therefore, it can be applied for rendering BCC-sampled volumetric data interactively. Furthermore, we show that a separable B-spline filter can suppress the postaliasing effect much more isotropically than a nonseparable box-spline filter of the same approximation power. Although prefilters that make the B-splines interpolating on the BCC lattice do not exist, we demonstrate that quasi-interpolating prefiltered linear and cubic B-spline reconstructions can still provide similar or higher image quality than the interpolating linear box-spline and prefiltered quintic box-spline reconstructions, respectively.

  16. Lattice location of O18 in ion implanted Fe crystals by Rutherford backscattering spectrometry, channeling and nuclear reaction analysis

    Science.gov (United States)

    Vairavel, Mathayan; Sundaravel, Balakrishnan; Panigrahi, Binaykumar

    2016-09-01

    There are contradictory theoretical predictions of lattice location of oxygen interstitial atom at tetrahedral and octahedral interstices in bcc Fe. For validating these predictions, 300 keV O18 ions with fluence of 5 × 1015 ions/cm2 are implanted into bcc Fe single crystals at room temperature and annealed at 400 °C. The Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA)/channeling measurements are carried out with 850 keV protons. The lattice location of implanted O18 is analysed using the α-particles yield from O18(p,α)N15 nuclear reaction. The tilt angular scans of α-particle yield along and axial directions are performed at room temperature. Lattice location of O18 is found to be at tetrahedral interstitial site by comparing the experimental scan with simulated scans using FLUX7 software.

  17. Random-field Ising model on isometric lattices: Ground states and non-Porod scattering

    Science.gov (United States)

    Bupathy, Arunkumar; Banerjee, Varsha; Puri, Sanjay

    2016-01-01

    We use a computationally efficient graph cut method to obtain ground state morphologies of the random-field Ising model (RFIM) on (i) simple cubic (SC), (ii) body-centered cubic (BCC), and (iii) face-centered cubic (FCC) lattices. We determine the critical disorder strength Δc at zero temperature with high accuracy. For the SC lattice, our estimate (Δc=2.278 ±0.002 ) is consistent with earlier reports. For the BCC and FCC lattices, Δc=3.316 ±0.002 and 5.160 ±0.002 , respectively, which are the most accurate estimates in the literature to date. The small-r behavior of the correlation function exhibits a cusp regime characterized by a cusp exponent α signifying fractal interfaces. In the paramagnetic phase, α =0.5 ±0.01 for all three lattices. In the ferromagnetic phase, the cusp exponent shows small variations due to the lattice structure. Consequently, the interfacial energy Ei(L ) for an interface of size L is significantly different for the three lattices. This has important implications for nonequilibrium properties.

  18. Free µ-Lattices

    DEFF Research Database (Denmark)

    Santocanale, Luigi

    2002-01-01

    A μ-lattice is a lattice with the property that every unary polynomial has both a least and a greatest fix-point. In this paper we define the quasivariety of μ-lattices and, for a given partially ordered set P, we construct a μ-lattice JP whose elements are equivalence classes of games in a preor...

  19. Improving ENSO periodicity simulation by adjusting cumulus entrainment in BCC_CSMs

    Science.gov (United States)

    Lu, Bo; Ren, Hong-Li

    2016-12-01

    The simulation of El Niño-Southern Oscillation (ENSO) phenomenon is a challenging issue for coupled climate models. This study focuses on the ENSO periodicity simulated by Beijing Climate Center Climate System Models (BCC_CSM1.1 and BCC_CSM1.1m) which can reproduce reasonably well ENSO amplitude as observations. However, the major period of ENSO simulated by the BCC_CSMs is around 2.4 years, which is much shorter than that in observations. Compared with other 24 coupled models in Coupled Model Intercomparison Project Phase 5 (CMIP5), BCC_CSMs produce a very unrealistic ENSO peak period. Such a bias in simulating periodicity is suggested as a consequence of the severely underestimated air-sea coupling intensity in BCC_CSMs. To test this hypothesis, a quantitative method is developed to diagnose the linear ENSO frequency. As an effort to improve the ENSO simulation in BCC_CSMs, three experiments are performed with varying entrainment rates in the cumulus convection parameterization scheme of BCC_CSM1.1m. A more realistic ENSO period of about 3.3 years can be generated by the model with an inflated entrainment rate. When the cumulus entrainment is increased by 10%, the ENSO-related convective precipitation will enhance in the equatorial central to eastern Pacific. This anomalous convective heating induces an intensified surface westerly wind stress to the west of the anomalous convection center and as a result, the air-sea coupling intensity becomes larger, which contributes to a longer period of ENSO based on previous theories. In addition, the pronounced eastward extension of ENSO-related surface wind stress could also be the secondary factor to generate a lower frequency of ENSO in BCC_CSMs. Our study proposes a method to reduce the biases in ENSO periodicity simulation and puts more insights into the importance of adjusting atmospheric convection to reproduce ENSO properties in coupled model.

  20. Slip Model Used for Prediction of r Value of BCC Metal Sheets from ODF Coefficients

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Different slip models were used for prediction of rvalue of BCC metal sheets from ODF coefficients. According to the maximum plastic work theory developed by Bishop and Hill, it is expected that the higher of Taylor factors given by a slip model, the better predictio nobtained based on the model. From this point of view, a composed slip model of BCC metals was presented. Based on the model, the agreement of predicted rvalues for deep drawing steels with experimental ones is excellent.

  1. Calculated Pressure Induced BCC-FCC Phase Transitions in Alkali Metals

    OpenAIRE

    DAĞISTANLI, Hamdi; MUTLU, R. Haluk

    2008-01-01

    The partial occupation numbers and density of states (DOS), and the total DOS at the Fermi level are calculated as a function of reduced atomic volume for bcc and fcc alkali metals employing the linear-muffin-tin-orbital (LMTO) method. By means of the abrupt changes obtained in the partial and total DOS values at the Fermi level, good agreement with regard to experiment were found in predicting the bcc-fcc transition volumes of the alkali metals.

  2. Solid-liquid interface free energies of pure bcc metals and B2 phases.

    Science.gov (United States)

    Wilson, S R; Gunawardana, K G S H; Mendelev, M I

    2015-04-07

    The solid-liquid interface (SLI) free energy was determined from molecular dynamics (MD) simulation for several body centered cubic (bcc) metals and B2 metallic compounds (space group: Pm3̄m; prototype: CsCl). In order to include a bcc metal with a low melting temperature in our study, a semi-empirical potential was developed for Na. Two additional synthetic "Na" potentials were also developed to explore the effect of liquid structure and latent heat on the SLI free energy. The obtained MD data were compared with the empirical Turnbull, Laird, and Ewing relations. All three relations are found to predict the general trend observed in the MD data for bcc metals obtained within the present study. However, only the Laird and Ewing relations are able to predict the trend obtained within the sequence of "Na" potentials. The Laird relation provides the best prediction for our MD data and other MD data for bcc metals taken from the literature. Overall, the Laird relation also agrees well with our B2 data but requires a proportionality constant that is substantially different from the bcc case. It also fails to explain a considerable difference between the SLI free energies of some B2 phases which have nearly the same melting temperature. In contrast, this difference is satisfactorily described by the Ewing relation. Moreover, the Ewing relation obtained from the bcc dataset also provides a reasonable description of the B2 data.

  3. New integrable lattice hierarchies

    Energy Technology Data Exchange (ETDEWEB)

    Pickering, Andrew [Area de Matematica Aplicada, ESCET, Universidad Rey Juan Carlos, c/ Tulipan s/n, 28933 Mostoles, Madrid (Spain); Zhu Zuonong [Departamento de Matematicas, Universidad de Salamanca, Plaza de la Merced 1, 37008 Salamanca (Spain) and Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200030 (China)]. E-mail: znzhu2@yahoo.com.cn

    2006-01-23

    In this Letter we give a new integrable four-field lattice hierarchy, associated to a new discrete spectral problem. We obtain our hierarchy as the compatibility condition of this spectral problem and an associated equation, constructed herein, for the time-evolution of eigenfunctions. We consider reductions of our hierarchy, which also of course admit discrete zero curvature representations, in detail. We find that our hierarchy includes many well-known integrable hierarchies as special cases, including the Toda lattice hierarchy, the modified Toda lattice hierarchy, the relativistic Toda lattice hierarchy, and the Volterra lattice hierarchy. We also obtain here a new integrable two-field lattice hierarchy, to which we give the name of Suris lattice hierarchy, since the first equation of this hierarchy has previously been given by Suris. The Hamiltonian structure of the Suris lattice hierarchy is obtained by means of a trace identity formula.

  4. Ultralocality on the lattice

    CERN Document Server

    Campos, R G; Campos, Rafael G.; Tututi, Eduardo S.

    2002-01-01

    It is shown that the nonlocal Dirac operator yielded by a lattice model that preserves chiral symmetry and uniqueness of fields, approaches to an ultralocal and invariant under translations operator when the size of the lattice tends to zero.

  5. Sober Topological Molecular Lattices

    Institute of Scientific and Technical Information of China (English)

    张德学; 李永明

    2003-01-01

    A topological molecular lattice (TML) is a pair (L, T), where L is a completely distributive lattice and r is a subframe of L. There is an obvious forgetful functor from the category TML of TML's to the category Loc of locales. In this note,it is showed that this forgetful functor has a right adjoint. Then, by this adjunction,a special kind of topological molecular lattices called sober topological molecular lattices is introduced and investigated.

  6. Ginzburg-Landau theory of the bcc-liquid interface kinetic coefficient

    Science.gov (United States)

    Wu, Kuo-An; Wang, Ching-Hao; Hoyt, Jeffrey J.; Karma, Alain

    2015-01-01

    We extend the Ginzburg-Landau (GL) theory of atomically rough bcc-liquid interfaces [Wu et al., Phys. Rev. B 73, 094101 (2006), 10.1103/PhysRevB.73.094101] outside of equilibrium. We use this extension to derive an analytical expression for the kinetic coefficient, which is the proportionality constant μ (n ̂) between the interface velocity along a direction n ̂ normal to the interface and the interface undercooling. The kinetic coefficient is expressed as a spatial integral along the normal direction of a sum of gradient square terms corresponding to different nonlinear density wave profiles. Anisotropy arises naturally from the dependence of those profiles on the angles between the principal reciprocal lattice vectors K⃗i and n ̂. Values of the kinetic coefficient for the (100 ) ,(110 ) , and (111 ) interfaces are compared quantitatively to the prediction of linear Mikheev-Chernov (MC) theory [J. Cryst. Growth 112, 591 (1991), 10.1016/0022-0248(91)90340-B] and previous molecular dynamics (MD) simulation studies of crystallization kinetics for a classical model of Fe. Additional MD simulations are carried out here to compute the relaxation time of density waves in the liquid in order to make this comparison free of fit parameters. The GL theory predicts an expression for μ similar to the MC theory but yields a better agreement with MD simulations for both its magnitude and anisotropy due to a fully nonlinear description of density wave profiles across the solid-liquid interface. In particular, the overall magnitude of μ predicted by GL theory is an order of magnitude larger than predicted by the MC theory. GL theory is also used to derive an inverse relation between μ and the solid-liquid interfacial free energy. The general methodology used here to derive an expression for μ (n ̂) also applies to amplitude equations derived from the phase-field-crystal model, which only differ from GL theory by the choice of cubic and higher order nonlinearities in the

  7. Lattice Regularization and Symmetries

    CERN Document Server

    Hasenfratz, Peter; Von Allmen, R; Allmen, Reto von; Hasenfratz, Peter; Niedermayer, Ferenc

    2006-01-01

    Finding the relation between the symmetry transformations in the continuum and on the lattice might be a nontrivial task as illustrated by the history of chiral symmetry. Lattice actions induced by a renormalization group procedure inherit all symmetries of the continuum theory. We give a general procedure which gives the corresponding symmetry transformations on the lattice.

  8. Langerhans cell histiocytosis arising from a BCC: a case report and review of the literature.

    Science.gov (United States)

    Patel, Payal; Talpur, Rakhshandra; Duvic, Madeleine

    2010-06-01

    Langerhans cell histiocytosis (LCH) is a rare disease characterized by a proliferation of Langerhans cells. Several organs may be involved, including the skin, bone, and central nervous system. Adult onset of LCH and solely localized cutaneous involvement are quite uncommon. Langerhans cell histiocytosis has been found in combination with other skin lesions and systemic conditions, but no definitive conclusion exists for this phenomenon. We present a case report of a 63-year-old woman who initially presented with 3 pink papules on her forehead that had developed sequentially within 1 month, all diagnosed by biopsy as basal cell carcinoma (BCC) and appropriately treated. Concurrent with the appearance of the third BCC, the patient began developing crusted ulcerative nodules on her scalp. Biopsy of 1 scalp nodule revealed a BCC, but a repeat biopsy of the same nodule weeks later revealed LCH. Langerhans cell histiocytosis arising from a BCC is extremely rare. No absolute explanation exists regarding the transformation of a BCC into LCH, but understanding the behavior of Langerhans cells may give us better insight into how this process could occur.

  9. Spontaneous Enhancement of Packing Regularity of Spherical Microdomains in the Body-Centered Cubic Lattice upon Uniaxial Stretching of Elastomeric Triblock Copolymers

    Directory of Open Access Journals (Sweden)

    Shinichi Sakurai

    2010-12-01

    Full Text Available Block copolymers forming glassy spheres in the matrix of rubbery chains can exhibit elastomeric properties. It is well known that the spherical microdomains are arranged in the body-center cubic (bcc lattice. However, recently, we have found packing in the face-centered cubic (fcc lattice, which is easily transformed into the bcc lattice upon uniaxial stretching. In the same time, the packing regularity of the spheres in the bcc lattice was found to be enhanced for samples completely recovered from the stretched state. This reminds us that a cycle of stretching-and-releasing plays an important role from analogy of densification of the packing in granules upon shaking. In the current paper, we quantify the enhancement of packing regularity of spherical microdomains in the bcc lattice upon uniaxial stretching of the same elastomeric triblock copolymer as used in our previous work by conducting small-angle X-ray scattering (SAXS measurements using high brilliant synchrotron radiation. Isotropically circular rings of the lattice peaks observed for the unstretched sample turned into deformed ellipsoidal rings upon the uniaxial stretching, with sharpening of the peaks in the direction parallel to the stretching direction and almost disappearing of the peaks in the perpendicular direction. By quantitatively analyzing the SAXS results, it was found that the packing regularity of the spherical microdomains was enhanced in the parallel direction while it was spoiled in the perpendicular direction under the stretched state. The enhanced regularity of packing was unchanged even if the stretching load was completely removed.

  10. Lichen planopilaris after imiquimod 5% cream for multiple BCC in basal cell naevus syndrome.

    Science.gov (United States)

    Drummond, Alessandra; Pichler, Janine; Argenziano, Giuseppe; Zalaudek, Iris; Longo, Caterina; Lallas, Aimilios; Piana, Simonetta; Moscarella, Elvira

    2015-11-01

    Basal cell naevus syndrome is an inherited autosomal dominant genetic disorder characterised by multiple basal cell carcinomas (BCC), skeletal, neurological and opthalmological abnormalities. The treatment of choice of the often multiple and large BCC consists of a combined approach including surgery, liquid nitrogen and other topical treatment modalities. Imiquimod 5% cream is an immune-response-modifying drug with antiviral and anti-tumour activity. Recent reports have associated the immune-stimulant properties of imiquimod with the exacerbation of several autoimmune skin diseases, such as eczema, psoriasis, vitiligo and lichenoid dermatitis. Here we report a patient with basal cell naevus syndrome who developed a lichen planopilaris on the same site of the scalp, which had been previously treated with two cycles of imiquimod for multiple BCC.

  11. Effect of Crystal Quality on HCP-BCC Phase Transition in Solid 4He

    CERN Document Server

    Mikhin, N; Rudavskii, E; Vekhov, Y; Mikhin, Nikolay; Polev, Andrey; Rudavskii, Eduard; Vekhov, Yegor

    2006-01-01

    The kinetics of HCP-BCC structure phase transition is studied by precise pressure measurement technique in 4He crystals of different quality. An anomalous pressure behavior in bad quality crystals under constant volume conditions is detected just after HCP-BCC structure phase transition. A sharp pressure drop of 0.2 bar was observed at constant temperature. The subsequent pressure kinetics is a non-monotonic temperature function. The effect observed can be explained if we suppose that microscopic liquid droplets appear on the HCP-BCC interphase region in bad quality crystals. After the interphase region disappearance, these droplets are crystallized with pressure reduction. It is shown that this effect is absent in high quality thermal-treated crystals.

  12. On the stability of rhenium up to 1 TPa pressure against transition to the bcc structure

    Indian Academy of Sciences (India)

    A K Verma; P Ravindran; R S Rao; B K Godwal; R Jeanloz

    2003-01-01

    We have carried out electronic structure total energy calculations on rhenium in the hexagonal close packed (hcp) and body centred cubic (bcc) phases, by the full potential linear muffin–tin orbital method, in order to verify the stability of the ambient pressure hcp phase against transition to the bcc structure at high pressures. As per our results, no hcp to bcc structural transition can occur up to 1 TPa pressures. Moreover, our Bain path calculations show that face centred cubic and body centred tetragonal structures are also not energetically preferred over hcp in this pressure range. The axial ratio (/) of Re changes by less than 0.33% in the pressure range studied.

  13. Modeling of the magnetic free energy of self-diffusion in bcc Fe

    Science.gov (United States)

    Sandberg, N.; Chang, Z.; Messina, L.; Olsson, P.; Korzhavyi, P.

    2015-11-01

    A first-principles based approach to calculating self-diffusion rates in bcc Fe is discussed with particular focus on the magnetic free energy associated with diffusion activation. First, the enthalpies and entropies of vacancy formation and migration in ferromagnetic bcc Fe are calculated from standard density functional theory methods in combination with transition state theory. Next, the shift in diffusion activation energy when going from the ferromagnetic to the paramagnetic state is estimated by averaging over random spin states. Classical and quantum mechanical Monte Carlo simulations within the Heisenberg model are used to study the effect of spin disordering on the vacancy formation and migration free energy. Finally, a quasiempirical model of the magnetic contribution to the diffusion activation free energy is applied in order to connect the current first-principles results to experimental data. The importance of the zero-point magnon energy in modeling of diffusion in bcc Fe is stressed.

  14. Kinetics study of crystallization with the disorder-bcc-fcc phase transition of charged colloidal dispersions.

    Science.gov (United States)

    Zhou, Hongwei; Xu, Shenghua; Sun, Zhiwei; Du, Xuan; Liu, Lixia

    2011-06-21

    Structure transformation (disorder-bcc-fcc) in charged colloidal dispersions, as a manifestation of the Ostwald's step rule, was confirmed by means of reflection spectrum (RS) measurements in our previous study. By taking advantage of a reflection spectrum containing plenty of information about the crystallization behaviors, time-dependent changes of parameters associated with the crystal structure and composition during the disorder-bcc-fcc transition are reported by treating the data from RS in this article. In addition, Avrami's model is adopted to analyze the transition process and investigate the transition rate. On the basis of the above investigations, associated kinetic features of crystallization with the disorder-bcc-fcc transition are described.

  15. Elemental moment variation of bcc FexMn1-x on MgO(001)

    Science.gov (United States)

    Bhatkar, H.; Snow, R. J.; Arenholz, E.; Idzerda, Y. U.

    2017-02-01

    We report the growth, structural characterization, and electronic structure evolution of epitaxially grown bcc FexMn1-x on MgO(001). It is observed that the 20 nm thick FexMn1-x alloy films remained bcc from 0.65≤x≤1, much beyond the bulk stability range of 0.88≤x≤1. X-ray absorption spectroscopy and X-ray magnetic circular dichroism show that both the Fe and Mn L3 binding energies slightly increase with Mn incorporation and that the elemental moment of Fe in the 20 nm crystalline bcc alloy film remain nearly constant, then shows a dramatic collapse near x 0.84. The Mn MCD intensity is found to be small at all compositions that exhibit ferromagnetism

  16. Magnetic coupling in 3d transition-metal monolayers and bilayers on bcc (100) iron

    DEFF Research Database (Denmark)

    Mirbt, S.; Eriksson, O.; Johansson, B.;

    1995-01-01

    We have calculated the magnetization profile in the (100) surface of bcc Fe covered by a monolayer or a bilayer of 3d transition metals. The calculated trends are explained in terms of the hybridization between the 3d states of the overlayer and the Fe substrate.......We have calculated the magnetization profile in the (100) surface of bcc Fe covered by a monolayer or a bilayer of 3d transition metals. The calculated trends are explained in terms of the hybridization between the 3d states of the overlayer and the Fe substrate....

  17. Theoretical study on the lattice dynamics and electron-phonon interaction of vanadium under high pressures

    CERN Document Server

    Suzuki, N

    2002-01-01

    First-principles calculations are performed for the lattice dynamics and electron-phonon interaction of the body-centred-cubic (bcc) phase of solid vanadium. A remarkable phonon anomaly is found, i.e. frequencies of the transverse mode around a quarter of the GAMMA-H line show softening with increasing pressure and become imaginary at pressures higher than approx 130 GPa. The superconducting transition temperatures T sub c of bcc vanadium estimated as a function of pressure increases at first linearly with pressure, and then the rate of increase of T sub c is abated around 80 GPa. This calculated pressure dependence of T sub c shows qualitatively the same behaviour as the experimental result.

  18. Evaluation of the Bilingual Curriculum Content (BCC) Pilot Project: A Three-Year Study. First Interim Report.

    Science.gov (United States)

    Rothfarb, Sylvia H.; And Others

    Bilingual Curriculum Content (BCC) is an instructional component of the Transitional Bilingual Basic Skills program offered to students with limited English proficiency (LEP) in the Dade County Public Schools, Florida. In BCC instruction, students learn mathematics and combined instruction (science, social studies, and health/safety) in their…

  19. New insights on microcrack propagation in bcc iron

    Energy Technology Data Exchange (ETDEWEB)

    Borodin, V.A. [PRC Kurchatov Institute, Moscow (Russian Federation); Karlsruher Inst. fuer Technologie (KIT), Eggenstein-Leopoldshafen (Germany); Vladimirov, P.V.; Moeslang, A. [Karlsruher Inst. fuer Technologie (KIT), Eggenstein-Leopoldshafen (Germany)

    2010-07-01

    Three-dimensional molecular dynamics simulations of micro-crack propagation in alpha-iron evidence high sensitivity of lattice transformation modes at the tips of propagating cracks to the crack plane orientation and expansion direction. The crack initiation on {l_brace}001{r_brace} planes is preceded with the emission of compact slip bands from the pre-crack tips, in agreement with the earlier quasi-two-dimensional simulations. Moreover, the compact slip bands emanating from the crack tips remain an essential feature of the crack propagation on {l_brace}001{r_brace} planes. On the contrary, crack propagation on {l_brace}110{r_brace} plane is accompanied with the formation of subgrains at the crack tip and the emission of dislocations. (orig.)

  20. Jammed lattice sphere packings

    OpenAIRE

    Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore

    2013-01-01

    We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a...

  1. On Traveling Waves in Lattices: The Case of Riccati Lattices

    Science.gov (United States)

    Dimitrova, Zlatinka

    2012-09-01

    The method of simplest equation is applied for analysis of a class of lattices described by differential-difference equations that admit traveling-wave solutions constructed on the basis of the solution of the Riccati equation. We denote such lattices as Riccati lattices. We search for Riccati lattices within two classes of lattices: generalized Lotka-Volterra lattices and generalized Holling lattices. We show that from the class of generalized Lotka-Volterra lattices only the Wadati lattice belongs to the class of Riccati lattices. Opposite to this many lattices from the Holling class are Riccati lattices. We construct exact traveling wave solutions on the basis of the solution of Riccati equation for three members of the class of generalized Holling lattices.

  2. Time-resolved lattice measurements of shock-induced phase transitions in polycrystalline materials

    Science.gov (United States)

    Milathianaki, Despina

    The response of materials under extreme temperature and pressure conditions is a topic of great significance because of its relevance in astrophysics, geophysics, and inertial confinement fusion. In recent years, environments exceeding several hundred gigapascals in pressure have been produced in the laboratory via laser-based dynamic loading techniques. Shock-loading is of particular interest as the shock provides a fiducial for measuring time-dependent processes in the lattice such as phase transitions. Time-resolved x-ray diffraction is the only technique that offers an insight into these shock-induced processes at the relevant spatial (atomic) and temporal scales. In this study, nanosecond resolution x-ray diffraction techniques were developed and implemented towards the study of shock-induced phase transitions in polycrystalline materials. More specifically, the capability of a focusing x-ray diffraction geometry in high-resolution in situ lattice measurements was demonstrated by probing shock-compressed Cu and amorphous metallic glass samples. In addition, simultaneous lattice and free surface velocity measurements of shock-compressed Mg in the ambient hexagonal close packed (hcp) and shock-induced body centered cubic (bcc) phases between 12 and 45 GPa were performed. These measurements revealed x-ray diffraction signals consistent with a compressed bcc lattice above a shock pressure of 26.2+/-1.3 GPa, thus capturing for the first time direct lattice evidence of a shock-induced hcp to bcc phase transition in Mg. Our measurement of the hcp-bcc phase boundary in Mg was found to be consistent with the calculated boundary from generalized pseudopotential theory in the pressure and temperature region intersected by the principal shock Hugoniot. Furthermore, the subnanosecond timescale of the phase transition implied by the shock-loading conditions was in agreement with the kinetics of a martensitic transformation. In conclusion, we report on the progress and

  3. Cytotoxic hydroanthraquinones from the mangrove-derived fungus Paradictyoarthrinium diffractum BCC 8704.

    Science.gov (United States)

    Isaka, Masahiko; Chinthanom, Panida; Rachtawee, Pranee; Srichomthong, Kitlada; Srikitikulchai, Prasert; Kongsaeree, Palangpon; Prabpai, Samran

    2015-05-01

    Two new hydroanthraquinones, paradictyoarthrins A (1) and B (2), were isolated from the mangrove-derived fungus Paradictyoarthrinium diffractum BCC 8704. Structures of the new compounds were elucidated by analyses of the NMR spectroscopic and mass spectrometry data. The absolute configuration of 1 was determined by X-ray crystallography. These compounds exhibited cytotoxic activities.

  4. The Meson Spectrum of the BCC Quark Model (A Modification of the Quark Model)

    CERN Document Server

    Xu, J L; Xu, Jiao Lin; Yu, Xin

    2002-01-01

    Using the quark spectrum of the BCC Quark Model [1] and the phenomenological formula for the binding energies of the mesons, not only have we deduced the intrinsic quantum numbers (I, S, C, b, and Q) of all mesons as was done with the Quark Model [2], but also we deduced the meson mass spectrum in agreement with experimental results [3] that we could not deduce using the Quark Model. The experimental meson spectrum gives some evidence of the existence of the new quarks $q_S^*(1391)$, $q_S^*(2551)$ and $q_C^*(6591)$..., which are predicted by the BCC Quark Model. The meson $\\chi (1600)$ $[2^+(2^{++})]$ with I = 2 (predicted by the BCC Quark Model--T(1603)) has already been discovered [4]. If this is finally confirmed, it will provide a strong support for the BCC Quark Model. We propose a search for the mesons D(5996), $D_S (6151)$, B(9504), $B_S (9659)$, $B_C (11031)$, $\\eta (5926)$, $\\eta (17837)$, $\\psi (25596)$, $\\Upsilon (17805)$, $\\Upsilon (29597)$, T(960), T(1282), T(1603), and T(1924).

  5. Divacancy binding energy, formation energy and surface energy of BCC transition metals using MEAM potentials

    Science.gov (United States)

    Uniyal, Shweta; Chand, Manesh; Joshi, Subodh; Semalty, P. D.

    2016-05-01

    The modified embedded atom method (MEAM) potential parameters have been employed to calculate the unrelaxed divacancy formation energy, binding energy and surface energies for low index planes in bcc transition metals. The calculated results of divacancy binding energy and vacancy formation energy compare well with experimental and other available calculated results.

  6. Antitubercular Lanostane Triterpenes from Cultures of the Basidiomycete Ganoderma sp. BCC 16642.

    Science.gov (United States)

    Isaka, Masahiko; Chinthanom, Panida; Sappan, Malipan; Danwisetkanjana, Kannawat; Boonpratuang, Thitiya; Choeyklin, Rattaket

    2016-01-22

    Sixteen new lanostane triterpenoids (1-16), together with 26 known compounds (17-42), were isolated from cultures of the basidiomycete Ganoderma sp. BCC 16642. Antitubercular activities of these Ganoderma lanostanoids against Mycobacterium tuberculosis H37Ra were evaluated, and structure-activity relationships are proposed.

  7. Crystallization pathways of liquid-bcc transition for a model iron by fast quenching.

    Science.gov (United States)

    Pan, Shao-Peng; Feng, Shi-Dong; Qiao, Jun-Wei; Wang, Wei-Min; Qin, Jing-Yu

    2015-11-19

    We report simulations on the local structural evolution in the liquid-bcc transition of a model iron. Fourteen main Voronoi polyhedra are chosen as the representatives of short-range orders (SROs) and their transformations during crystallization are also investigated. Thus, the crystallization pathways for the main SROs are drawn. Our results also show that the transformations between two SROs in the crystallization pathways can be classified into two categories, first the enlargement of coordination number, second the transformation of local symmetry from five-fold to four-fold. The former reduces the potential energy while the latter increases it. It is found that the potential energy cannot decease monotonously whatever crystallization pathway is chosen to transform the icosahedral SRO to bcc SRO. Therefore, the latter transformation might provide the energy barrier of crystallization. We propose two transformation styles among SROs. All the transformations in the crystallization pathways can be achieved according to the styles. Moreover, the two transformation styles indicates that the bcc structure is more similar to liquid than other crystals. That might be the reason why the first phase nucleated during a rapid cooling process should be bcc crystal.

  8. Study of loop-loop and loop-edge dislocation interactions in bcc iron

    DEFF Research Database (Denmark)

    Osetsky, Y.N.; Bacon, D.J.; Gao, F.;

    2000-01-01

    that the evolution of heterogeneities such as dislocation decoration and rafts has serious impacts on the mechanical properties on neutron-irradiated metals. In the present work, atomic-scale computer modelling (ASCM) has been applied to study the mechanisms for the formation of such microstructure in bcc iron...

  9. Hirsutane Sesquiterpenes from Cultures of the Basidiomycete Marasmiellus sp. BCC 22389.

    Science.gov (United States)

    Isaka, Masahiko; Palasarn, Somporn; Sappan, Malipan; Supothina, Sumalee; Boonpratuang, Thitiya

    2016-10-01

    Two new hirsutane sesquiterpenes, marasmiellins A (1) and B (2), were isolated from cultures of the basidiomycete Marasmiellus sp. BCC 22389. The structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data. The absolute configuration of marasmiellin B was determined by application of the modified Mosher's method.

  10. RETORNOS DE ESCALA EM DEA: CRÍTICAS AO BCC E NOVO MODELO

    Directory of Open Access Journals (Sweden)

    Juliana Benício

    2014-09-01

    Full Text Available Tomando como base o clássico modelo DEA CCR utilizado para medir a eficiência de DMUs analisadas (Decision Making Units, o presente artigo tem como objetivo apresentar um modelo capaz de medir retornos de escala variáveis; crescentes, constantes e decrescentes. Muitos estudos já alertam para problemas na formulação do modelo DEA BCC, entre eles: eficiências negativas, eficiências por default, a invalidez do fator de escala para soluções múltiplas e a incapacidade do modelo verificar retornos crescentes de escala. Segundo é desenvolvido neste estudo, o modelo DEA BCC não vislumbra em seus resultados uma análise de escala real conforme defendida pelos autores. A fronteira eficiente exposta pelo modelo BCC sempre apresenta retornos de escala decrescentes, negligenciando retornos crescentes de escala. Para tanto apresenta-se uma interpretação dos reais significados dos resultados do modelo BCC e,posteriormente, o estudo apresenta um algoritmo que solucione tal problema.

  11. Hirsutane Sesquiterpenes from Cultures of the Basidiomycete Marasmiellus sp. BCC 22389

    Directory of Open Access Journals (Sweden)

    Masahiko Isaka

    2016-08-01

    Full Text Available Abstract Two new hirsutane sesquiterpenes, marasmiellins A (1 and B (2, were isolated from cultures of the basidiomycete Marasmiellus sp. BCC 22389. The structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data. The absolute configuration of marasmiellin B was determined by application of the modified Mosher’s method. Graphical Abstract

  12. Quantum-well states and induced magnetism in Fe/CuN/Fe bcc (001) trilayers

    DEFF Research Database (Denmark)

    Niklasson, A.M.N.; Mirbt, S.; Skriver, Hans Lomholt

    1996-01-01

    We have used a first-principles Green's function technique to investigate the formation of magnetic moments in Fe/Cu-N/Fe bcc (001) trilayers. We show that the magnetic moment in the paramagnetic spacer material to a first approximation may be described as a linear superposition of the magnetic...

  13. Nucleation of hcp and fcc phases in bcc iron under uniform compression: classical molecular dynamics simulations.

    Science.gov (United States)

    Wang, B T; Shao, J L; Zhang, G C; Li, W D; Zhang, P

    2010-11-03

    By classical molecular dynamics simulations employing an embedded atom method potential, we have simulated the bcc to hcp/fcc structural transition in single-crystal iron under uniform compression. Results showed that the transition pressure is different from uniaxial compression and shock loading. The transformation occurs on a picosecond timescale and the transition time decreases along with the increase of pressure. The nucleation and growth of the hcp and fcc phases under constant pressure and temperature are analyzed in detail. The nucleation planes, all belonging to the {110}(bcc) family and parallel to the three compression directions [100], [010], and [001], have been observed. About 20% bcc atoms have transformed to fcc phase under pressure just over the critical point, and under higher pressure the fraction of the fcc phase increases steadily to exceed that of the hcp phase. We have investigated the transition mechanism of iron from initial bcc to hcp/fcc and found that the transition mainly consists of compression, rotation, and shuffle.

  14. Comparing the structural stability of PbS nanocrystals assembled in fcc and bcc superlattice allotropes.

    Science.gov (United States)

    Bian, Kaifu; Wang, Zhongwu; Hanrath, Tobias

    2012-07-04

    We investigated the structural stability of colloidal PbS nanocrystals (NCs) self-assembled into superlattice (SL) allotropes of either face-centered cubic (fcc) or body-centered cubic (bcc) symmetry. Small-angle X-ray scattering analysis showed that the NC packing density is higher in the bcc than in the fcc SL; this is a manifestation of the cuboctahedral shape of the NC building block. Using the high-pressure rock-salt/orthorhombic phase transition as a stability indicator, we discovered that the transition pressure for NCs in a bcc SL occurs at 8.5 GPa, which is 1.5 GPa higher than the transition pressure (7.0 GPa) observed for a fcc SL. The higher structural stability in the bcc SL is attributed primarily to the effective absorption of loading force in specific SL symmetry and to a lesser extent to the surface energy of the NCs. The experimental results provide new insights into the fundamental relationship between the symmetry of the self-assembled SL and the structural stability of the constituent NCs.

  15. Mechanosynthesis of supersaturated solid solutions of Sn in near-equiatomic bcc FeCo

    Energy Technology Data Exchange (ETDEWEB)

    Loureiro, J.M. [CEMDRX, Physics Department, University of Coimbra, P-3004-516 Coimbra (Portugal); Costa, B.F.O., E-mail: benilde@ci.uc.pt [CEMDRX, Physics Department, University of Coimbra, P-3004-516 Coimbra (Portugal); Le Caeer, G. [IPR, UMR URI-CNRS 6251, Universite de Rennes I, Campus de Beaulieu, Bat 11A, F-35042 Rennes Cedex (France)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer (Fe{sub 50-x/2}Co{sub 50-x/2})Sn{sub x} mixtures are mechanically alloyed for x {<=} 33 at.%. Black-Right-Pointing-Pointer As-ground powders are studied by X-ray diffraction and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy. Black-Right-Pointing-Pointer Supersaturated solutions of Sn in disordered bcc FeCo alloys are formed in our dynamical conditions up to x {<=} 20 at.%. Black-Right-Pointing-Pointer This maximum Sn solubility found is much larger than the equilibrium solubility which is about 0.5 at.%. Black-Right-Pointing-Pointer The mean {sup 119}Sn hyperfine field in the bcc alloys is essentially constant with x and equal to 9.6 T at room temperature. - Abstract: The mechanosynthesis of Fe-Co-Sn ternary alloys from initial powder mixtures of composition (Fe{sub 50-x/2}Co{sub 50-x/2})Sn{sub x} is studied for x {<=} 33 at.%. Disordered nanocrystalline bcc solid solutions are formed in that way up to Sn contents as large as {approx}20 at.%. The dissolution of Sn in near-equiatomic bcc Fe-Co is unambiguously proven by X-ray diffraction and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy.

  16. Optical properties of bcc transition metals in the range 0-40 eV

    NARCIS (Netherlands)

    Romaniello, P; de Boeij, PL; Carbone, F; van der Marel, D

    2006-01-01

    We present a systematic analysis of the optical properties of bcc transition metals in the groups VB: V, Nb, and Ta, and VIB: paramagnetic Cr, Mo, and W. For this we use our formulation of time-dependent current-density-functional theory for the linear response of metals. The calculated dielectric a

  17. Optical properties of bcc transition metals in the range 0–40 eV

    NARCIS (Netherlands)

    Romaniello, P.; Boeij, P.L. de; Carbone, F.; Marel, D. van der

    2006-01-01

    We present a systematic analysis of the optical properties of bcc transition metals in the groups VB: V, Nb, and Ta, and VIB: paramagnetic Cr, Mo, and W. For this we use our formulation of time-dependent current-density-functional theory for the linear response of metals. The calculated dielectric a

  18. Epitaxial growth of bcc-Fe{sub x}Co{sub 100-x} thin films on MgO(1 1 0) single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Nishiyama, Tsutomu; Shikada, Kouhei [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2010-07-15

    Fe{sub x}Co{sub 100-x} (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe{sub x}Co{sub 100-x} film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe{sub x}Co{sub 100-x} crystals with very small errors less than +-0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe{sub 50}Co{sub 50}/MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.

  19. Embedded atom computer simulation of lattice distortion and dislocation core structure and mobility in Fe-Cr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D.; Schon, C.G.; Lima, M.S.F. de [Virginia Polytechnic Inst., Blacksburg, VA (United States). Dept. of Materials Science and Engineering; Goldenstein, H. [Escola Politecnica USP, Sao Paulo (Brazil). Dept. de Metalurgia

    1996-01-01

    The atomistic structure of dislocation cores of <111> screw dislocations in disordered Fe-Cr b.c.c. alloys was simulated using embedded atom method potentials and molecular statics computer simulation. The mixed Fe-Cr interatomic potentials used were derived by fitting to the thermodynamic data of the disordered system and the measured lattice parameter changes of Fe upon Cr additions. The potentials predict phase separation as the most stable configuration for the central region of the phase diagram. The next most stable situation is the disordered b.c.c. phase. The structure of the screw 1/2 <111> dislocation core was studied using atomistic computer simulation and an improved visualization method for the representation of the resulting structures. The structure of the dislocation core is different from that typical of 1/2 <111> dislocations in pure b.c.c. materials. The core structure in the alloy tends to lose the threefold symmetry seen in pure b.c.c. materials and the stress necessary to initiate dislocation motion increases with Cr content. The mobility of kinks in these screw dislocations was also simulated and it was found that while the critical stress for kink motion in pure Fe is extremely low, it increases significantly with the addition of Cr. The implications of these differences for mechanical behavior are discussed.

  20. Magnetic phase transition in coupled spin-lattice systems: A replica-exchange Wang-Landau study.

    Science.gov (United States)

    Perera, Dilina; Vogel, Thomas; Landau, David P

    2016-10-01

    Coupled, dynamical spin-lattice models provide a unique test ground for simulations investigating the finite-temperature magnetic properties of materials under the direct influence of the lattice vibrations. These models are constructed by combining a coordinate-dependent interatomic potential with a Heisenberg-like spin Hamiltonian, facilitating the treatment of both the atomic coordinates and the spins as explicit phase variables. Using a model parameterized for bcc iron, we study the magnetic phase transition in these complex systems via the recently introduced, massively parallel replica-exchange Wang-Landau Monte Carlo method. Comparison with the results obtained from rigid lattice (spin-only) simulations shows that the transition temperature as well as the amplitude of the peak in the specific heat curve is marginally affected by the lattice vibrations. Moreover, the results were found to be sensitive to the particular choice of interatomic potential.

  1. Magnetic phase transition in coupled spin-lattice systems: A replica-exchange Wang-Landau study

    Science.gov (United States)

    Perera, Dilina; Vogel, Thomas; Landau, David P.

    2016-10-01

    Coupled, dynamical spin-lattice models provide a unique test ground for simulations investigating the finite-temperature magnetic properties of materials under the direct influence of the lattice vibrations. These models are constructed by combining a coordinate-dependent interatomic potential with a Heisenberg-like spin Hamiltonian, facilitating the treatment of both the atomic coordinates and the spins as explicit phase variables. Using a model parameterized for bcc iron, we study the magnetic phase transition in these complex systems via the recently introduced, massively parallel replica-exchange Wang-Landau Monte Carlo method. Comparison with the results obtained from rigid lattice (spin-only) simulations shows that the transition temperature as well as the amplitude of the peak in the specific heat curve is marginally affected by the lattice vibrations. Moreover, the results were found to be sensitive to the particular choice of interatomic potential.

  2. Nuclear lattice simulations

    Directory of Open Access Journals (Sweden)

    Epelbaum E.

    2010-04-01

    Full Text Available We review recent progress on nuclear lattice simulations using chiral effective field theory. We discuss lattice results for dilute neutron matter at next-to-leading order, three-body forces at next-to-next-toleading order, isospin-breaking and Coulomb effects, and the binding energy of light nuclei.

  3. Characteristics of the Asian-Pacific oscillation in boreal summer simulated by BCC_CSM with different horizontal resolutions

    Science.gov (United States)

    Zhang, Yazhou; Liao, Zhijie; Zhang, Yaocun; Nie, Feng

    2016-12-01

    The summer Asian-Pacific Oscillation (APO) is a major teleconnection pattern that reflects the zonal thermal contrast between East Asia and the North Pacific in the upper troposphere. The performance of Beijing Climate Center Climate System Models (BCC_CSMs) with different horizontal resolutions, i.e., BCC_CSM1.1 and BCC_CSM1.1(m), in reproducing APO interannual variability, APO-related precipitation anomalies, and associated atmospheric circulation anomalies, is evaluated. The results show that BCC_CSM1.1(m) can successfully capture the interannual variability of the summer APO index. It is also more capable in reproducing the APO's spatial pattern, compared to BCC_CSM1.1, due to its higher horizontal resolution. Associated with a positive APO index, the northward-shifted and intensified South Asian high, strengthened extratropical westerly jet, and tropical easterly jet in the upper troposphere, as well as the southwesterly monsoonal flow over North Africa and the Indian Ocean in the lower troposphere, are realistically represented by BCC_CSM1.1(m), leading to an improvement in reproducing the increased precipitation over tropical North Africa, South Asia, and East Asia, as well as the decreased precipitation over subtropical North Africa, Japan, and North America. In contrast, these features are less consistent with observations when simulated by BCC_CSM1.1. Regression analysis further indicates that surface temperature anomalies over the North Pacific and the southern and western flanks of the Tibetan Plateau are reasonably reproduced by BCC_CSM1.1(m), which contributes to the substantial improvement in the simulation of the characteristics of summer APO compared to that of BCC_CSM1.1.

  4. Effects of in-plane magnetization orientation on magnetic and electronic properties in a Bcc Co (001)/rock salt MgO (001)/Bcc Co (001) magnetic tunnel junction system: ab initio calculations.

    Science.gov (United States)

    Yoo, Dong Su; Chae, Kisung; Chung, Yong-Chae

    2012-04-01

    Ab initio calculations were performed on a fully epitaxial bcc Co (001)/rock salt MgO (001)/bcc Co (001) magnetic tunnel junction system for two cases where the magnetization is parallel to bcc Co [100] and to bcc Co [110]. Structural optimization reveals that the two cases are equivalent systems and that the Co electrodes contract in the z-direction whereas the MgO insulating barrier expands. The magnetic moments of each monolayer vary slightly in each case; furthermore, only the magnetic moment at the surface of the Co atom shows any enhancement (12%). The layer decomposed density of states profiles reveals that the bonding character of the junction interface is derived mainly from the 2p-3d hybridization of the MgO and Co interfacial atoms.

  5. Jammed lattice sphere packings.

    Science.gov (United States)

    Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore

    2013-12-01

    We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a model for the jamming and glass transitions that enables exploration of much higher dimensions than are usually accessible.

  6. SPILADY: A parallel CPU and GPU code for spin-lattice magnetic molecular dynamics simulations

    Science.gov (United States)

    Ma, Pui-Wai; Dudarev, S. L.; Woo, C. H.

    2016-10-01

    Spin-lattice dynamics generalizes molecular dynamics to magnetic materials, where dynamic variables describing an evolving atomic system include not only coordinates and velocities of atoms but also directions and magnitudes of atomic magnetic moments (spins). Spin-lattice dynamics simulates the collective time evolution of spins and atoms, taking into account the effect of non-collinear magnetism on interatomic forces. Applications of the method include atomistic models for defects, dislocations and surfaces in magnetic materials, thermally activated diffusion of defects, magnetic phase transitions, and various magnetic and lattice relaxation phenomena. Spin-lattice dynamics retains all the capabilities of molecular dynamics, adding to them the treatment of non-collinear magnetic degrees of freedom. The spin-lattice dynamics time integration algorithm uses symplectic Suzuki-Trotter decomposition of atomic coordinate, velocity and spin evolution operators, and delivers highly accurate numerical solutions of dynamic evolution equations over extended intervals of time. The code is parallelized in coordinate and spin spaces, and is written in OpenMP C/C++ for CPU and in CUDA C/C++ for Nvidia GPU implementations. Temperatures of atoms and spins are controlled by Langevin thermostats. Conduction electrons are treated by coupling the discrete spin-lattice dynamics equations for atoms and spins to the heat transfer equation for the electrons. Worked examples include simulations of thermalization of ferromagnetic bcc iron, the dynamics of laser pulse demagnetization, and collision cascades.

  7. Analytic bond-order potentials for the bcc refractory metals Nb, Ta, Mo and W.

    Science.gov (United States)

    Čák, M; Hammerschmidt, T; Rogal, J; Vitek, V; Drautz, R

    2014-05-14

    Bond-order potentials (BOPs) are based on the tight-binding approximation for determining the energy of a system of interacting atoms. The bond energy and forces are computed analytically within the formalism of the analytic BOPs. Here we present parametrizations of the analytic BOPs for the bcc refractory metals Nb, Ta, Mo and W. The parametrizations are optimized for the equilibrium bcc structure and tested for atomic environments far from equilibrium that had not been included in the fitting procedure. These tests include structural energy differences for competing crystal structures; tetragonal, trigonal, hexagonal and orthorhombic deformation paths; formation energies of point defects as well as phonon dispersion relations. Our tests show good agreement with available experimental and theoretical data. In practice, we obtain the energetic ordering of vacancy, [1 1 1], [1 1 0], and [1 0 0] self-interstitial atom in agreement with density functional theory calculations.

  8. Twin nucleation in Fe-based bcc alloys—modeling and experiments

    Science.gov (United States)

    Ojha, A.; Sehitoglu, H.; Patriarca, L.; Maier, H. J.

    2014-10-01

    We develop an analytical expression for twin nucleation stress in bcc metal and alloys considering generalized planar fault energy and the dislocations bounding the twin nucleus. We minimize the total energy to predict the twinning stress relying only on parameters that are obtained through atomistic calculations, thus excluding the need for any empirical constants. We validate the present approach by means of precise measurements of the onset of twinning in bcc Fe-50at% Cr single crystals showing excellent agreement. The experimental observations of the three activated slip systems of symmetric configuration in relation to the twinning mechanism are demonstrated via transmission electron microscopy techniques along with digital image correlation. We then confirm the validity of the model for Fe, Fe-25at% Ni and Fe-3at% V alloys compared with experiments from the literature to show general applicability.

  9. Photocatalytic degradation of gaseous toluene over bcc-In2O3 hollow microspheres

    Science.gov (United States)

    Zhang, Qianzhe; Li, Xinyong; Zhao, Qidong; Shi, Yong; Zhang, Fei; Liu, Baojun; Ke, Jun; Wang, Lianzhou

    2015-05-01

    In this work, the body-centered cubic indium oxide (bcc-In2O3) hollow microspheres were prepared via a P123-assisted solvothermal process. The structural properties of samples were investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, UV-visible diffusive reflectance spectroscopy, and nitrogen adsorption-desorption isotherms. The photocatalytic effects of degrading gaseous toluene were evaluated by gas chromatography and in situ Fourier transform infrared (FTIR) spectra under a irradiation of a 500 W high pressure xenon lamp. The results indicated that the as-prepared bcc-In2O3 hollow microspheres exhibited a high degradation efficiency towards toluene within a short reaction time. Besides, the preliminary mechanism therein was inferred with the aid of in situ FTIR and electron spin-paramagnetic resonance techniques to understand the degradation process.

  10. Lattice Gerbe Theory

    CERN Document Server

    Lipstein, Arthur E

    2014-01-01

    We formulate the theory of a 2-form gauge field on a Euclidean spacetime lattice. In this approach, the fundamental degrees of freedom live on the faces of the lattice, and the action can be constructed from the sum over Wilson surfaces associated with each fundamental cube of the lattice. If we take the gauge group to be $U(1)$, the theory reduces to the well-known abelian gerbe theory in the continuum limit. We also propose a very simple and natural non-abelian generalization with gauge group $U(N) \\times U(N)$, which gives rise to $U(N)$ Yang-Mills theory upon dimensional reduction. Formulating the theory on a lattice has several other advantages. In particular, it is possible to compute many observables, such as the expectation value of Wilson surfaces, analytically at strong coupling and numerically for any value of the coupling.

  11. SPIN ON THE LATTICE.

    Energy Technology Data Exchange (ETDEWEB)

    ORGINOS,K.

    2003-01-07

    I review the current status of hadronic structure computations on the lattice. I describe the basic lattice techniques and difficulties and present some of the latest lattice results; in particular recent results of the RBC group using domain wall fermions are also discussed. In conclusion, lattice computations can play an important role in understanding the hadronic structure and the fundamental properties of Quantum Chromodynamics (QCD). Although some difficulties still exist, several significant steps have been made. Advances in computer technology are expected to play a significant role in pushing these computations closer to the chiral limit and in including dynamical fermions. RBC has already begun preliminary dynamical domain wall fermion computations [49] which we expect to be pushed forward with the arrival of QCD0C. In the near future, we also expect to complete the non-perturbative renormalization of the relevant derivative operators in quenched QCD.

  12. Root lattices and quasicrystals

    Science.gov (United States)

    Baake, M.; Joseph, D.; Kramer, P.; Schlottmann, M.

    1990-10-01

    It is shown that root lattices and their reciprocals might serve as the right pool for the construction of quasicrystalline structure models. All noncrystallographic symmetries observed so far are covered in minimal embedding with maximal symmetry.

  13. Superalloy Lattice Block Structures

    Science.gov (United States)

    Nathal, M. V.; Whittenberger, J. D.; Hebsur, M. G.; Kantzos, P. T.; Krause, D. L.

    2004-01-01

    Initial investigations of investment cast superalloy lattice block suggest that this technology will yield a low cost approach to utilize the high temperature strength and environmental resistance of superalloys in lightweight, damage tolerant structural configurations. Work to date has demonstrated that relatively large superalloy lattice block panels can be successfully investment cast from both IN-718 and Mar-M247. These castings exhibited mechanical properties consistent with the strength of the same superalloys measured from more conventional castings. The lattice block structure also accommodates significant deformation without failure, and is defect tolerant in fatigue. The potential of lattice block structures opens new opportunities for the use of superalloys in future generations of aircraft applications that demand strength and environmental resistance at elevated temperatures along with low weight.

  14. Enhanced production of histamine dehydrogenase by Natrinema gari BCC 24369 in a non-sterile condition.

    Science.gov (United States)

    Chaikaew, Siriporn; Powtongsook, Sorawit; Boonpayung, Somphop; Benjakul, Soottawat; Visessanguan, Wonnop

    2015-01-01

    The production of histamine dehydrogenase (HADH) by Natrinema gari BCC 24369, a halophilic archeaon isolated from fish sauce, was optimized and scaled up under a non-sterile condition. Through statistical design by Plackett-Burman design (PBD), casamino acid, NaCl, MgSO4·7H2O and FeCl2·4H2O were identified as the significant medium compositions influencing HADH production. Central composite design (CCD) was employed to identify the optimal values of individual composition yielding the maximum HADH production. The analysis indicated that the optimal medium was composed of 15 g/l casamino acid, 75 g/l MgSO4·7H2O, 273 g/l NaCl, 2.5 mg/l FeCl2·4H2O, 10 g/l yeast extract, 5 g/l sodium glutamate and 5 g/l KCl. Based on the one-factor-at-a-time (OFAT) method, the optimum initial pH of the culture medium and the incubation temperature for HADH production were 7.5 and 37 °C, respectively. The production of HADH under optimal conditions was 2.2-fold higher than that under un-optimized conditions. Owing to the halophilic nature of Nnm. gari BCC 24369, a more economical and eco-friendlier HADH production was developed under a completely non-sterile condition. In a 16-l batch cultivation of Nnm. gari BCC 24369, HADH productivity under a non-sterile condition (858 ± 12 U/g cell biomass) was comparable to that under a sterile condition (878 ± 15 U/g cell biomass). These results demonstrate the feasibility and simplicity of HADH production using Nnm. gari BCC 24369 under a non-sterile condition without compromising enzyme yield and any changes in Km value.

  15. Aromadendrane and cyclofarnesane sesquiterpenoids from cultures of the basidiomycete Inonotus sp. BCC 23706.

    Science.gov (United States)

    Isaka, Masahiko; Yangchum, Arunrat; Supothina, Sumalee; Boonpratuang, Thitiya; Choeyklin, Rattaket; Kongsaeree, Palangpon; Prabpai, Samran

    2015-10-01

    Twelve aromadendrane sesquiterpenoids, inonotins A-L, and a previously unknown cyclofarnesane, i.e., inonofarnesane, together with two known compounds, were isolated from cultures of the wood-rotting basidiomycete Inonotus sp. BCC 23706. Inonotin I is identical to a previously reported compound with an incorrect structure. Structures of the compounds were elucidated by spectroscopic analysis and X-ray crystallography. The absolute configurations of inonotin D and inonofarnesane were determined by application of the modified Mosher's method.

  16. Alliacane sesquiterpenoids from submerged cultures of the basidiomycete Inonotus sp. BCC 22670.

    Science.gov (United States)

    Isaka, Masahiko; Sappan, Malipan; Supothina, Sumalee; Srichomthong, Kitlada; Komwijit, Somjit; Boonpratuang, Thitiya

    2017-02-04

    Nine alliacane sesquiterpenoids, inonoalliacanes A-I, were isolated from culture broth of the basidiomycete Inonotus sp. BCC 22670. The structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data. The absolute configuration of inonoalliacane F was determined by application of the modified Mosher's method. Inonoalliacane A, the most abundant sesquiterpene constituent, exhibited moderate antibacterial activity against Bacillus cereus, whereas inonoalliacane B showed antiviral activity against herpes simplex virus type 1.

  17. 18-Electron Resonance Structures in the BCC Transition Metals and Their CsCl-type Derivatives.

    Science.gov (United States)

    Vinokur, Anastasiya I; Fredrickson, Daniel C

    2017-02-20

    Bonding in elemental metals and simple alloys has long been thought of as involving intense delocalization, with little connection to the localized bonds of covalent systems. In this Article, we show that the bonding in body-centered cubic (bcc) structures of the group 6 transition metals can in fact be represented, via the concepts of the 18-n rule and isolobal bonding, in terms of two balanced resonance structures. We begin with a reversed approximation Molecular Orbital (raMO) analysis of elemental Mo in its bcc structure. The raMO analysis indicates that, despite the low electron count (six valence electrons per Mo atom), nine electron pairs can be associated with any given Mo atom, corresponding to a filled 18-electron configuration. Six of these electron pairs take part in isolobal bonds along the second-nearest neighbor contacts, with the remaining three (based on the t2g d orbitals) interacting almost exclusively with first-nearest neighbors. In this way, each primitive cubic network defined by the second-nearest neighbor contacts comprises an 18-n electron system with n = 6, which essentially describes the full electronic structure of the phase. Of course, either of the two interpenetrating primitive cubic frameworks of the bcc structure can act as a basis for this discussion, leading us to write two resonance structures with equal weights for bcc-Mo. The electronic structures of CsCl-type variants with the same electron count can then be interpreted in terms of changing the relative weights of these two resonance structures, as is qualitatively confirmed with raMO analysis. This combination of raMO analysis with the resonance concept offers an avenue to extend the 18-n rule into other transition metal-rich structures.

  18. Thermal hysteresis of the thermal conductivity in isotopically impure bcc 3He

    Science.gov (United States)

    Greenberg, A. S.; Armstrong, G.

    1980-11-01

    We have measured the thermal conductivity of bcc 3He containing 10 and 500 ppm 4He for temperatures below the isotopic phase separation. We find the conductivity measured during cooling can be significantly greater, as much as an order of magnitude, than upon warming. This hysteresis depends strongly on the molar volume and 4He concentration. We interpret our results in terms of phonon scattering from the boundary of solid 4He clusters formed by quantum diffusion and nucleated by crystalline faults.

  19. Similarity and Difference of Phase Transition FCC – BCC in Calcium and Strontium

    Directory of Open Access Journals (Sweden)

    V.V. Pozhivatenko

    2016-11-01

    Full Text Available Features of polymorphism in calcium and strontium from the point of view of similarity of physical processes which occur at change of pressure and temperatures are researched. The known experimental facts are added calculated (first principal and fit by results which illustrate both similarity, and difference of structural phase transitions FCC – BCC in calcium and strontium. The increase in similarity of the effects connected with polymorphism is shown, at increase both pressure, and temperatures.

  20. Yield Functions and Plastic Potentials for BCC Metals and Possibly Other Materials

    Energy Technology Data Exchange (ETDEWEB)

    Christensen, R M

    2005-09-29

    Yield functions and plastic potentials are expressed in terms of the invariants of the stress tensor for polycrystalline metals and other isotropic materials. The plastic volume change data of Richmond is used to evaluate the embedded materials properties for some bcc metals and one polymer. A general form for the plastic potential is found that is intended to represent and cover a wide range of materials types.

  1. Technicolor on the Lattice

    CERN Document Server

    Pica, C; Lucini, B; Patella, A; Rago, A

    2009-01-01

    Technicolor theories provide an elegant mechanism for dynamical electroweak symmetry breaking. We will discuss the use of lattice simulations to study the strongly-interacting dynamics of some of the candidate theories, with matter fields in representations other than the fundamental. To be viable candidates for phenomenology, such theories need to be different from a scaled-up version of QCD, which were ruled out by LEP precision measurements, and represent a challenge for modern lattice computations.

  2. Vector Lattice Vortex Solitons

    Institute of Scientific and Technical Information of China (English)

    WANG Jian-Dong; YE Fang-Wei; DONG Liang-Wei; LI Yong-Ping

    2005-01-01

    @@ Two-dimensional vector vortex solitons in harmonic optical lattices are investigated. The stability properties of such solitons are closely connected to the lattice depth Vo. For small Vo, vector vortex solitons with the total zero-angular momentum are more stable than those with the total nonzero-angular momentum, while for large Vo, this case is inversed. If Vo is large enough, both the types of such solitons are stable.

  3. Automated Lattice Perturbation Theory

    Energy Technology Data Exchange (ETDEWEB)

    Monahan, Christopher

    2014-11-01

    I review recent developments in automated lattice perturbation theory. Starting with an overview of lattice perturbation theory, I focus on the three automation packages currently "on the market": HiPPy/HPsrc, Pastor and PhySyCAl. I highlight some recent applications of these methods, particularly in B physics. In the final section I briefly discuss the related, but distinct, approach of numerical stochastic perturbation theory.

  4. A low-surface energy carbon allotrope: the case for bcc-C6.

    Science.gov (United States)

    Yin, Wen-Jin; Chen, Yuan-Ping; Xie, Yue-E; Liu, Li-Min; Zhang, S B

    2015-06-07

    Graphite may be viewed as a low-surface-energy carbon allotrope with little layer-layer interaction. Other low-surface-energy allotropes but with much stronger layer-layer interaction may also exist. Here, we report a first-principles prediction for one of the known carbon allotropes, bcc-C6 (a body centered carbon allotrope with six atoms per primitive unit), that should have exceptionally low-surface energy and little size dependence down to only a couple layer thickness. This unique property may explain the existence of the relatively-high-energy bcc-C6 during growth. The electronic properties of the bcc-C6 thin layers can also be intriguing: the (111), (110), and (001) thin layers have direct band gap, indirect band gap, and metallic character, respectively. The refrained chemical reactivity of the thin layers does not disappear after cleaving, as lithium-doped (Li-doped) 3-layers (111) has a noticeably increased binding energy of H2 molecules with a maximum storage capacity of 10.8 wt%.

  5. Influence of reaction stresses induced by dislocation slips on the orientation evolution in bcc metals

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A plastic deformation model for bcc metals is proposed in consideration of reaction stresses. The shear strains and the corresponding reaction stresses induced by the activation of dislocations are calculated in the model, which will influence the following dislocation activation. The rolling texture in bcc metals is simulated up to 80% reduction, while the ratio of critical resolved shear stresses between the dislocations slipping on the {110} and {112} planes is chosen as 0.95. The corresponding calculation is also conducted with the activation of second dislocation, if the difference between the orientation factor of the two dislocations with maximal orientation factors is lower than 5%. It is shown that the simulated texture is closer to that of the 80% rolled interstitial free steels than other modeling. It is believed that the new model can give more attention to both of the strain and stress continuities during the plastic deformation of polycrystalline metals, and therefore approaches closer to the real deformation process in bcc metals.

  6. Coulomb interaction parameters in bcc iron: an LDA+DMFT study.

    Science.gov (United States)

    Belozerov, A S; Anisimov, V I

    2014-09-17

    We study the influence of Coulomb interaction parameters on electronic structure and magnetic properties of paramagnetic bcc Fe by means of the local density approximation plus dynamical mean-field theory approach. We consider the local Coulomb interaction in the density-density form as well as in the form with spin rotational invariance approximated by averaging over all directions of the quantization axis. Our results indicate that the magnetic properties of bcc Fe are mainly affected by the Hund's rule coupling J rather than by the Hubbard U. By employing the constrained density functional theory approach in the basis of Wannier functions of spd character, we obtain U = 4 eV and J = 0.9 eV. In spite of the widespread belief that U = 4 eV is too large for bcc Fe, our calculations with the obtained values of U and J result in a satisfactory agreement with the experiment. The correlation effects caused by U are found to be weak even for large U = 6 eV. The agreement between the calculated and experimental Curie temperatures is further improved if J is reduced to 0.8 eV. However, with the decrease of J, the effective local magnetic moment moves further away from the experimental value.

  7. Diffusion behavior of Cr diluted in bcc and fcc Fe: Classical and quantum simulation methods

    Energy Technology Data Exchange (ETDEWEB)

    Ramunni, Viviana P., E-mail: vpram@cnea.gov.ar [CONICET, Avda. Rivadavia 1917, Cdad. de Buenos Aires C.P. 1033 (Argentina); Comisión Nacional de Energía Atómica, Gerencia Materiales, Av. Del Libertador 8250, C1429BNP Ciudad de Buenos Aires (Argentina); Rivas, Alejandro M.F. [CONICET, Avda. Rivadavia 1917, Cdad. de Buenos Aires C.P. 1033 (Argentina); Comisión Nacional de Energía Atómica, Departamento de Física Teórica, Tandar, Av. Del Libertador 8250, C1429BNP Ciudad de Buenos Aires (Argentina)

    2015-07-15

    We characterize the atomic mobility behavior driven by vacancies, in bcc and fcc Fe−Cr diluted alloys, using a multi-frequency model. We calculate the full set of the Onsager coefficients and the tracer self and solute diffusion coefficients in terms of the mean jump frequencies. The involved jump frequencies are calculated using a classical molecular static (CMS) technique. For the bcc case, we also perform quantum calculations based on the density functional theory (DFT). There, we show that, in accordance with Bohr's correspondence principle, as the size of the atomic cell (total number of atoms) is increased, quantum results with DFT recover the classical ones obtained with CMS calculations. This last ones, are in perfect agreement with available experimental data for both, solute and solvent diffusion coefficients. For high temperatures, in the fcc phase where no experimental data are yet available, our CMS calculations predict the expected solute and solvent diffusion coefficients. - Graphical abstract: Display Omitted - Highlights: • Comparison of diffusion coefficients obtained from classical and quantum methods. • We perform our calculations in diluted bcc/fcc Fe–Cr alloy. • Magnetic and phonon effects must be taken into account. • Classical calculations are in perfect agreement with experimental data.

  8. Modelling plastic deformation in BCC metals: Dynamic recovery and cell formation effects

    Energy Technology Data Exchange (ETDEWEB)

    Galindo-Nava, E.I. [Department of Materials Science and Metallurgy, Pembroke Street, CB2 3QZ, University of Cambridge, Cambridge (United Kingdom); Department of Materials Science and Engineering, Mekelweg 2 2628 CD, Delft University of Technology, Delft (Netherlands); Rivera-Diaz-del-Castillo, P.E.J., E-mail: pejr2@cam.ac.uk [Department of Materials Science and Metallurgy, Pembroke Street, CB2 3QZ, University of Cambridge, Cambridge (United Kingdom)

    2012-12-15

    A recently developed model for describing plasticity in FCC metals (E.I., Galindo-Nava, P.E.J., Rivera-Diaz-del-Castillo, Mater. Sci. Eng. A 543 (2012) 110-116; E.I. Galindo-Nava, P.E.J. Rivera-Diaz-del-Castillo, Acta Mater. 60 (2012) 4370-4378) has now been applied to BCC. The core of the theory is the thermostatistical description of dislocation annihilation paths, which determines the dynamic recovery rate of the material. Input to this is the energy for the formation, migration and ordering of dislocation paths; the latter term corresponds to the statistical entropy which features strongly on the solution. The distinctions between FCC and BCC stem primarily from the possible directions and planes for dislocation slip and cross-slip, as well as from the presence of the kink-pair mechanism for dislocation migration in BCC, which are incorporated to the mathematical formulation of the model. The theory is unique in describing the stress-strain response for pure iron, molybdenum, tantalum, vanadium and tungsten employing physical parameters as input; the description is made for wide ranges of temperature and strain rate. Additionally, succinct equations to predict dislocation cell size variation with strain, strain rate and temperature are provided and validated for pure iron.

  9. Coulomb interaction parameters in bcc iron: an LDA+DMFT study

    Science.gov (United States)

    Belozerov, A. S.; Anisimov, V. I.

    2014-09-01

    We study the influence of Coulomb interaction parameters on electronic structure and magnetic properties of paramagnetic bcc Fe by means of the local density approximation plus dynamical mean-field theory approach. We consider the local Coulomb interaction in the density-density form as well as in the form with spin rotational invariance approximated by averaging over all directions of the quantization axis. Our results indicate that the magnetic properties of bcc Fe are mainly affected by the Hund's rule coupling J rather than by the Hubbard U. By employing the constrained density functional theory approach in the basis of Wannier functions of spd character, we obtain U = 4 eV and J = 0.9 eV. In spite of the widespread belief that U = 4 eV is too large for bcc Fe, our calculations with the obtained values of U and J result in a satisfactory agreement with the experiment. The correlation effects caused by U are found to be weak even for large U = 6 eV. The agreement between the calculated and experimental Curie temperatures is further improved if J is reduced to 0.8 eV. However, with the decrease of J, the effective local magnetic moment moves further away from the experimental value.

  10. A Bijection between Lattice-Valued Filters and Lattice-Valued Congruences in Residuated Lattices

    Directory of Open Access Journals (Sweden)

    Wei Wei

    2013-01-01

    Full Text Available The aim of this paper is to study relations between lattice-valued filters and lattice-valued congruences in residuated lattices. We introduce a new definition of congruences which just depends on the meet ∧ and the residuum →. Then it is shown that each of these congruences is automatically a universal-algebra-congruence. Also, lattice-valued filters and lattice-valued congruences are studied, and it is shown that there is a one-to-one correspondence between the set of all (lattice-valued filters and the set of all (lattice-valued congruences.

  11. Measuring on Lattices

    Science.gov (United States)

    Knuth, Kevin H.

    2009-12-01

    Previous derivations of the sum and product rules of probability theory relied on the algebraic properties of Boolean logic. Here they are derived within a more general framework based on lattice theory. The result is a new foundation of probability theory that encompasses and generalizes both the Cox and Kolmogorov formulations. In this picture probability is a bi-valuation defined on a lattice of statements that quantifies the degree to which one statement implies another. The sum rule is a constraint equation that ensures that valuations are assigned so as to not violate associativity of the lattice join and meet. The product rule is much more interesting in that there are actually two product rules: one is a constraint equation arises from associativity of the direct products of lattices, and the other a constraint equation derived from associativity of changes of context. The generality of this formalism enables one to derive the traditionally assumed condition of additivity in measure theory, as well introduce a general notion of product. To illustrate the generic utility of this novel lattice-theoretic foundation of measure, the sum and product rules are applied to number theory. Further application of these concepts to understand the foundation of quantum mechanics is described in a joint paper in this proceedings.

  12. Weighted distance transforms generalized to modules and their computation on point lattices

    CERN Document Server

    Fouard, Céline; Borgefors, Gunilla

    2007-01-01

    This paper presents the generalization of weighted distances to modules and their computation through the chamfer algorithm on general point lattices. The first part is dedicated to formalization of definitions and properties (distance, metric, norm) of weighted distances on modules. It resumes tools found in literature to express the weighted distance of any point of a module and to compute optimal weights in the general case to get rotation invariant distances. The second part of this paper proves that, for any point lattice, the sequential two-scan chamfer algorithm produces correct distance maps. Finally, the definitions and computation of weighted distances are applied to the face-centered cubic (FCC) and body-centered cubic (BCC) grids.

  13. The Body Center Cubic Quark Lattice Model (A Modification and Further Development of the Quark Model)

    CERN Document Server

    Xu, J L

    2002-01-01

    We assume that the u quarks and the d quarks constitute a body center cubic quark lattice in the vacuum. Using energy band theory, we deduce an excited quark spectrum (from the quark lattice). Using the accompanying excitation concept, we deduce a baryon spectrum (including S, C, b, I, Q, and mass) from the quark spectrum. With a phenomenological binding energy formula, we deduce a meson spectrum (including S, C, b, I, Q, and mass) from the quark spectrum. The baryon and meson spectra agree well with experimental results. The BCC Quark Model predicts many new quarks (u'(3), d'(6)), baryons ($\\Lambda^0(4280)$, $\\Lambda_{C}^{+}(6600)$, $\\Lambda_{b}^{0}(9960))$, and mesons (K(3597), D(5996), B(9504), $\\eta(5926)$, $\\Upsilon(17805)$, T(1603) with I=2). The quarks u'(3) and d'(6) and the meson T(1603) have already been discovered.

  14. Heavy hadrons on $N_f=2$ and $2+1$ improved clover-Wilson lattices

    CERN Document Server

    Burch, Tommy

    2015-01-01

    We present the masses of singly ($B$, $B_s$, $\\Lambda_b$, $\\Sigma_b$, etc.), doubly ($B_c$, $\\eta_b$, $\\Upsilon$, $\\Xi_{bc}$, $\\Xi_{bb}$, etc.), and triply ($\\Omega_{bcc}$, $\\Omega_{bbc}$, $\\Omega_{bbb}$, etc.) heavy hadrons arising from (QCDSF-UKQCD) lattices with improved clover-Wilson light quarks. For the bottom quark, we use an $O(a,v^4)$-improved version of lattice NRQCD. Part of the bottomonia spectrum is used to provide an alternative scale and to determine the physical quark mass and radiative corrections used in the heavy-quark action. Results for spin splittings, opposite parities, and, in some cases, excited states are presented. Higher lying states and baryons with two light quarks appear to be especially affected by the relatively small volumes of this (initially) initial study. This and other systematics are briefly discussed.

  15. Model calculations of edge dislocation defects and vacancies in {alpha}-Iron lattice

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, L; Troev, T; Nankov, N; Popov, E, E-mail: lpetrov@inrne.bas.b [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria)

    2010-01-01

    Two models of defects in perfect {alpha}-iron lattice were discussed. In the perfect bcc iron lattice 42x42x42 a{sub o} (a{sub o} = 2,87 A) an edge dislocation was created, moving the second half of the bulk on one a{sub o} distance. This action generates a little volume in the middle of the bulk witch increases of the positron lifetime (PLT) calculated using the superimposed-atom method of Puska and Nieminen [1]. The result of 118 ps PLT in simple edge dislocation's model is in a good concurrence with earlier publications and experimental data [2]. Through the dislocation line one, two and three vacancies were localized. These models give the results for PLT of 146, 157 and 167 ps respectively. The computer simulations were performed using Finnis-Sinclair (FS) N-body potential.

  16. Digital lattice gauge theories

    CERN Document Server

    Zohar, Erez; Reznik, Benni; Cirac, J Ignacio

    2016-01-01

    We propose a general scheme for a digital construction of lattice gauge theories with dynamical fermions. In this method, the four-body interactions arising in models with $2+1$ dimensions and higher, are obtained stroboscopically, through a sequence of two-body interactions with ancillary degrees of freedom. This yields stronger interactions than the ones obtained through pertubative methods, as typically done in previous proposals, and removes an important bottleneck in the road towards experimental realizations. The scheme applies to generic gauge theories with Lie or finite symmetry groups, both Abelian and non-Abelian. As a concrete example, we present the construction of a digital quantum simulator for a $\\mathbb{Z}_{3}$ lattice gauge theory with dynamical fermionic matter in $2+1$ dimensions, using ultracold atoms in optical lattices, involving three atomic species, representing the matter, gauge and auxiliary degrees of freedom, that are separated in three different layers. By moving the ancilla atoms...

  17. Improved Lattice Radial Quantization

    CERN Document Server

    Brower, Richard C; Fleming, George T

    2014-01-01

    Lattice radial quantization was proposed in a recent paper by Brower, Fleming and Neuberger[1] as a nonperturbative method especially suited to numerically solve Euclidean conformal field theories. The lessons learned from the lattice radial quantization of the 3D Ising model on a longitudinal cylinder with 2D Icosahedral cross-section suggested the need for an improved discretization. We consider here the use of the Finite Element Methods(FEM) to descretize the universally-equivalent $\\phi^4$ Lagrangian on $\\mathbb R \\times \\mathbb S^2$. It is argued that this lattice regularization will approach the exact conformal theory at the Wilson-Fisher fixed point in the continuum. Numerical tests are underway to support this conjecture.

  18. Lattice gauge theories

    Science.gov (United States)

    Weisz, Peter; Majumdar, Pushan

    2012-03-01

    Lattice gauge theory is a formulation of quantum field theory with gauge symmetries on a space-time lattice. This formulation is particularly suitable for describing hadronic phenomena. In this article we review the present status of lattice QCD. We outline some of the computational methods, discuss some phenomenological applications and a variety of non-perturbative topics. The list of references is severely incomplete, the ones we have included are text books or reviews and a few subjectively selected papers. Kronfeld and Quigg (2010) supply a reasonably comprehensive set of QCD references. We apologize for the fact that have not covered many important topics such as QCD at finite density and heavy quark effective theory adequately, and mention some of them only in the last section "In Brief". These topics should be considered in further Scholarpedia articles.

  19. Graphene antidot lattice waveguides

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Gunst, Tue; Markussen, Troels

    2012-01-01

    We introduce graphene antidot lattice waveguides: nanostructured graphene where a region of pristine graphene is sandwiched between regions of graphene antidot lattices. The band gaps in the surrounding antidot lattices enable localized states to emerge in the central waveguide region. We model...... the waveguides via a position-dependent mass term in the Dirac approximation of graphene and arrive at analytical results for the dispersion relation and spinor eigenstates of the localized waveguide modes. To include atomistic details we also use a tight-binding model, which is in excellent agreement...... with the analytical results. The waveguides resemble graphene nanoribbons, but without the particular properties of ribbons that emerge due to the details of the edge. We show that electrons can be guided through kinks without additional resistance and that transport through the waveguides is robust against...

  20. Optical Lattice Clocks

    Science.gov (United States)

    Oates, Chris

    2012-06-01

    Since they were first proposed in 2003 [1], optical lattice clocks have become one of the leading technologies for the next generation of atomic clocks, which will be used for advanced timing applications and in tests of fundamental physics [2]. These clocks are based on stabilized lasers whose frequency is ultimately referenced to an ultra-narrow neutral atom transition (natural linewidths magic'' value so as to yield a vanishing net AC Stark shift for the clock transition. As a result lattice clocks have demonstrated the capability of generating high stability clock signals with small absolute uncertainties (˜ 1 part in 10^16). In this presentation I will first give an overview of the field, which now includes three different atomic species. I will then use experiments with Yb performed in our laboratory to illustrate the key features of a lattice clock. Our research has included the development of state-of-the-art optical cavities enabling ultra-high-resolution optical spectroscopy (1 Hz linewidth). Together with the large atom number in the optical lattice, we are able to achieve very low clock instability (< 0.3 Hz in 1 s) [3]. Furthermore, I will show results from some of our recent investigations of key shifts for the Yb lattice clock, including high precision measurements of ultracold atom-atom interactions in the lattice and the dc Stark effect for the Yb clock transition (necessary for the evaluation of blackbody radiation shifts). [4pt] [1] H. Katori, M. Takamoto, V. G. Pal'chikov, and V. D. Ovsiannikov, Phys. Rev. Lett. 91, 173005 (2003). [0pt] [2] Andrei Derevianko and Hidetoshi Katori, Rev. Mod. Phys. 83, 331 (2011). [0pt] [3] Y. Y. Jiang, A. D. Ludlow, N. D. Lemke, R. W. Fox, J. A. Sherman, L.-S. Ma, and C. W. Oates, Nature Photonics 5, 158 (2011).

  1. Exact Lattice Supersymmetry

    Energy Technology Data Exchange (ETDEWEB)

    Catterall, Simon; Kaplan, David B.; Unsal, Mithat

    2009-03-31

    We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of N = 4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.

  2. Belief functions on lattices

    CERN Document Server

    Grabisch, Michel

    2008-01-01

    We extend the notion of belief function to the case where the underlying structure is no more the Boolean lattice of subsets of some universal set, but any lattice, which we will endow with a minimal set of properties according to our needs. We show that all classical constructions and definitions (e.g., mass allocation, commonality function, plausibility functions, necessity measures with nested focal elements, possibility distributions, Dempster rule of combination, decomposition w.r.t. simple support functions, etc.) remain valid in this general setting. Moreover, our proof of decomposition of belief functions into simple support functions is much simpler and general than the original one by Shafer.

  3. TEMPERATURE DEPENDENCES OF ATOM STATES AND PHYSICAL PROPERTIES OF fcc-, METASTABLE hcp- AND bcc- Cu%fcc-,亚稳hcp-和bcc-Cu的原子状态及物理性质随温度的变化关系

    Institute of Scientific and Technical Information of China (English)

    陶辉锦; 谢佑卿; 彭红建; 余方新; 刘锐锋; 李晓波

    2006-01-01

    结合纯金属单原子(OA)理论和Debye-Grüneisen模型,采用CALPHAD方法确定的晶格稳定参数,研究了SGTE纯单质数据库中fcc-,hcp-和bcc-Cu的原子状态及物理性质(原子势能、原子动能、原子体积、体弹性模量和热膨胀系数等)随温度的变化关系.结果表明:电子结构计算结果与第一原理方法非常接近.3种晶体结构的电子结构差别不大,单键半径非常接近.原子体积顺序为:Va(bcc)>Va(hcp)>Va(fcc);共价电子浓度顺序为:nc(fcc)>nc(hcp)>nc(bcc);原子势能大小顺序为:εp(fcc)<εp(hcp)<εp(bcc);晶格稳定性顺序为:△G(fcc)>△G(hcp)>△G(bcc).原子动能随温度的增加幅度约为势能的3-4倍.

  4. The atomistic mechanism of hcp-to-bcc martensitic transformation in the Ti-Nb system revealed by molecular dynamics simulations.

    Science.gov (United States)

    Li, Yang; Li, JiaHao; Liu, BaiXin

    2015-02-14

    Applying the constructed Ti-Nb potentials, molecular dynamics simulations were conducted to investigate the martensitic transformation of Ti100-xNbx alloys (x = 5, 10…25) from the α' phase (hcp) to the β phase (bcc). It is found that the transformation involved four phases, i.e. α', α'', fco (face-centered orthorhombic), and β phases. The structures of the obtained phases exhibit consistency with experimental data, verifying the validity of atomic simulations. The simulations not only revealed the processes of atomic displacements during the transformation, but also elucidated the underlying mechanism of the martensitic transformation at the atomic level. The martensitic transformation incorporates three types of coinstantaneous deformations i.e. slide, shear as well as extension, and the subsequent lattice constant relaxation. Furthermore, according to the proposed mechanism, the crystallographic correlation between the initial α' phase and the final β phase has been deduced. The simulation results provide a clear landscape on the martensitic transformation mechanism, facilitating our comprehensive understanding on the phase transition in the Ti-Nb system.

  5. An Algorithm on Generating Lattice Based on Layered Concept Lattice

    Directory of Open Access Journals (Sweden)

    Zhang Chang-sheng

    2013-08-01

    Full Text Available Concept lattice is an effective tool for data analysis and rule extraction, a bottleneck factor on impacting the applications of concept lattice is how to generate lattice efficiently. In this paper, an algorithm LCLG on generating lattice in batch processing based on layered concept lattice is developed, this algorithm is based on layered concept lattice, the lattice is generated downward layer by layer through concept nodes and provisional nodes in current layer; the concept nodes are found parent-child relationships upward layer by layer, then the Hasse diagram of inter-layer connection is generated; in the generated process of the lattice nodes in each layer, we do the pruning operations dynamically according to relevant properties, and delete some unnecessary nodes, such that the generating speed is improved greatly; the experimental results demonstrate that the proposed algorithm has good performance.

  6. Quantum lattice problems

    NARCIS (Netherlands)

    de Raedt, Hans; von der Linden, W.; Binder, K

    1995-01-01

    In this chapter we review methods currently used to perform Monte Carlo calculations for quantum lattice models. A detailed exposition is given of the formalism underlying the construction of the simulation algorithms. We discuss the fundamental and technical difficulties that are encountered and gi

  7. Lattice Multiverse Models

    OpenAIRE

    Williamson, S. Gill

    2010-01-01

    Will the cosmological multiverse, when described mathematically, have easily stated properties that are impossible to prove or disprove using mathematical physics? We explore this question by constructing lattice multiverses which exhibit such behavior even though they are much simpler mathematically than any likely cosmological multiverse.

  8. Measuring on Lattices

    CERN Document Server

    Knuth, Kevin H

    2009-01-01

    Previous derivations of the sum and product rules of probability theory relied on the algebraic properties of Boolean logic. Here they are derived within a more general framework based on lattice theory. The result is a new foundation of probability theory that encompasses and generalizes both the Cox and Kolmogorov formulations. In this picture probability is a bi-valuation defined on a lattice of statements that quantifies the degree to which one statement implies another. The sum rule is a constraint equation that ensures that valuations are assigned so as to not violate associativity of the lattice join and meet. The product rule is much more interesting in that there are actually two product rules: one is a constraint equation arises from associativity of the direct products of lattices, and the other a constraint equation derived from associativity of changes of context. The generality of this formalism enables one to derive the traditionally assumed condition of additivity in measure theory, as well in...

  9. The JKJ Lattice

    Science.gov (United States)

    Shigaki, Kenta; Noda, Fumiaki; Yamamoto, Kazami; Machida, Shinji; Molodojentsev, Alexander; Ishi, Yoshihiro

    2002-12-01

    The JKJ high-intensity proton accelerator facility consists of a 400-MeV linac, a 3-GeV 1-MW rapid-cycling synchrotron and a 50-GeV 0.75-MW synchrotron. The lattice and beam dynamics design of the two synchrotrons are reported.

  10. Phenomenology from lattice QCD

    CERN Document Server

    Lellouch, L P

    2003-01-01

    After a short presentation of lattice QCD and some of its current practical limitations, I review recent progress in applications to phenomenology. Emphasis is placed on heavy-quark masses and on hadronic weak matrix elements relevant for constraining the CKM unitarity triangle. The main numerical results are highlighted in boxes.

  11. Noetherian and Artinian Lattices

    Directory of Open Access Journals (Sweden)

    Derya Keskin Tütüncü

    2012-01-01

    Full Text Available It is proved that if L is a complete modular lattice which is compactly generated, then Rad(L/0 is Artinian if, and only if for every small element a of L, the sublattice a/0 is Artinian if, and only if L satisfies DCC on small elements.

  12. Nucleation of the BCC phase from disorder in a diblock copolymer melt: Testing approximate theories through simulation

    Science.gov (United States)

    Spencer, Russell K. W.; Curry, Paul F.; Wickham, Robert A.

    2016-10-01

    We examine nucleation of the stable body-centred-cubic (BCC) phase from the metastable uniform disordered phase in an asymmetric diblock copolymer melt. Our comprehensive, large-scale simulations of the time-dependent, mean-field Landau-Brazovskii model find that spherical droplets of the BCC phase nucleate directly from disorder. Near the order-disorder transition, the critical nucleus is large and has a classical profile, attaining the bulk BCC phase in an interior that is separated from disorder by a sharp interface. At greater undercooling, the amplitude of BCC order in the interior decreases and the nucleus interface broadens, leading to a diffuse critical nucleus. This diffuse nucleus becomes large as the simulation approaches the disordered phase spinodal. We show that our simulation follows the same nucleation pathway that Cahn and Hilliard found for an incompressible two-component fluid, across the entire metastable region. In contrast, a classical nucleation theory calculation based on the free energy of a planar interface between coexisting BCC and disordered phases agrees with simulation only in the limit of very small undercooling; we can expand this region of validity somewhat by accounting for the curvature of the droplet interface. A nucleation pathway involving a classical droplet persists, however, to deep undercooling in our simulation, but this pathway is energetically unfavourable. As a droplet grows in the simulation, its interface moves with a constant speed, and this speed is approximately proportional to the undercooling.

  13. Isolation and Characterization of a Hybrid Respiratory Supercomplex Consisting of Mycobacterium tuberculosis Cytochrome bcc and Mycobacterium smegmatis Cytochrome aa3.

    Science.gov (United States)

    Kim, Mi-Sun; Jang, Jichan; Ab Rahman, Nurlilah Binte; Pethe, Kevin; Berry, Edward A; Huang, Li-Shar

    2015-06-05

    Recently, energy production pathways have been shown to be viable antitubercular drug targets to combat multidrug-resistant tuberculosis and eliminate pathogen in the dormant state. One family of drugs currently under development, the imidazo[1,2-a]pyridine derivatives, is believed to target the pathogen's homolog of the mitochondrial bc1 complex. This complex, denoted cytochrome bcc, is highly divergent from mitochondrial Complex III both in subunit structure and inhibitor sensitivity, making it a good target for drug development. There is no soluble cytochrome c in mycobacteria to transport electrons from the bcc complex to cytochrome oxidase. Instead, the bcc complex exists in a "supercomplex" with a cytochrome aa3-type cytochrome oxidase, presumably allowing direct electron transfer. We describe here purification and initial characterization of the mycobacterial cytochrome bcc-aa3 supercomplex using a strain of M. smegmatis that has been engineered to express the M. tuberculosis cytochrome bcc. The resulting hybrid supercomplex is stable during extraction and purification in the presence of dodecyl maltoside detergent. It is hoped that this purification procedure will potentiate functional studies of the complex as well as crystallographic studies of drug binding and provide structural insight into a third class of the bc complex superfamily.

  14. Subseasonal variability and predictability of the Arctic Oscillation/North Atlantic Oscillation in BCC_AGCM2.2

    Science.gov (United States)

    Zuo, Jinqing; Ren, Hong-Li; Wu, Jie; Nie, Yu; Li, Qiaoping

    2016-09-01

    The subseasonal variability and predictability of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) is evaluated using a full set of hindcasts generated from the Beijing Climate Center Atmospheric General Circulation Model version 2.2 (BCC_AGCM2.2). It is shown that the predictability of the monthly mean AO/NAO index varies seasonally, with the highest predictability during winter (December-March) and the lowest during autumn (August-November), with respect to both observations and BCC_AGCM2.2 results. As compared with the persistence prediction skill of observations, the model skillfully predicts the monthly mean AO/NAO index with a one-pentad lead time during all winter months, and with a lead time of up to two pentads in December and January. During winter, BCC_AGCM2.2 exhibits an acceptable skill in predicting the daily AO/NAO index of ∼9 days, which is higher than the persistence prediction skill of observations of ∼4 days. Further analysis suggests that improvements in the simulation of storm track activity, synoptic eddy feedback, and troposphere-stratosphere coupling in the Northern Hemisphere could help to improve the prediction skill of subseasonal AO/NAO variability by BCC_AGCM2.2 during winter. In particular, BCC_AGCM2.2 underestimates storm track activity intensity but overestimates troposphere-stratosphere coupling, as compared with observations, thus providing a clue to further improvements in model performance.

  15. A numerical study of crack initiation in a bcc iron system based on dynamic bifurcation theory

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiantao, E-mail: xli@math.psu.edu [Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-10-28

    Crack initiation under dynamic loading conditions is studied under the framework of dynamic bifurcation theory. An atomistic model for BCC iron is considered to explicitly take into account the detailed molecular interactions. To understand the strain-rate dependence of the crack initiation process, we first obtain the bifurcation diagram from a computational procedure using continuation methods. The stability transition associated with a crack initiation, as well as the connection to the bifurcation diagram, is studied by comparing direct numerical results to the dynamic bifurcation theory [R. Haberman, SIAM J. Appl. Math. 37, 69–106 (1979)].

  16. Critical currents in A-15 structure Nb3Al converted from cold-worked bcc structure

    Science.gov (United States)

    Woollam, J. A.; Alterovitz, S. A.; Haugland, E.; Webb, G. W.

    1980-01-01

    The paper considers critical currents in A-15 structure Nb3Al converted from a cold-worked bcc structure. Nb3Al prepared in the ductile phase by quenching and mechanical working followed by conversion to the A-15 structure could carry currents above 10 to the 9th power A/sq m in fields near 20 T. These critical currents are comparable to those of Nb3Ge and V3Ga which are closest competing materials for use in high fields; further enhancement of the critical current is possible if thermal treatments are optimized.

  17. Ascochlorin derivatives from the leafhopper pathogenic fungus Microcera sp. BCC 17074.

    Science.gov (United States)

    Isaka, Masahiko; Yangchum, Arunrat; Supothina, Sumalee; Laksanacharoen, Pattiyaa; Jennifer Luangsa-Ard, J; Hywel-Jones, Nigel L

    2015-01-01

    Two new ascochlorin derivatives, nectchlorins A (1) and B (2), together with eight known compounds (3-10), were isolated from cultures of the leafhopper pathogen Microcera sp. BCC 17074. The structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data. The absolute configuration of 2 was determined by application of the modified Mosher's method. The absolute configuration of LL-Z 1272α epoxide (9), which is a plausible biosynthetic precursor of ascochlorins, was established by chemical correlations. Cytotoxic activities of these ascochlorin derivatives were evaluated.

  18. Heats of Segregation of BCC Binaries from ab Initio and Quantum Approximate Calculations

    Science.gov (United States)

    Good, Brian S.

    2004-01-01

    We compare dilute-limit heats of segregation for selected BCC transition metal binaries computed using ab initio and quantum approximate energy methods. Ab initio calculations are carried out using the CASTEP plane-wave pseudopotential computer code, while quantum approximate results are computed using the Bozzolo-Ferrante-Smith (BFS) method with the most recent LMTO-based parameters. Quantum approximate segregation energies are computed with and without atomistic relaxation, while the ab initio calculations are performed without relaxation. Results are discussed within the context of a segregation model driven by strain and bond-breaking effects. We compare our results with full-potential quantum calculations and with available experimental results.

  19. Observations on the deformation-induced beta internal friction peak in bcc metals

    Science.gov (United States)

    Dicarlo, J. A.

    1974-01-01

    During a study of the effects of electron irradiation on the tungsten alpha mechanism, internal friction data were obtained. The data indicate that the mechanism underlying the beta peak does not possess the relaxation parameters generally associated with a simple dislocation process. The significance of the experimental results in the light of beta observations in other metals is discussed. It is suggested that the beta peaks in deformed bcc metals are the anelastic result of the thermally-activated relaxation of deformation-induced imperfections.

  20. Prenylhydroquinone-Derived Secondary Metabolites from Cultures of the Basidiomycete Lentinus similis BCC 52578.

    Science.gov (United States)

    Isaka, Masahiko; Palasarn, Somporn; Sappana, Malipan; Srichomthong, Kitlada; Karunarathna, Samantha C; Hyde, Kevin D

    2015-08-01

    Two new prenylhydroquinone-derived compounds, Ientinospirol (1) and 1-(2,5-dihydroxyphenyl)-4-hydroxy-3-methyl-l-butanone (2), were isolated from cultures of the basidiomycete Lentinus similis BCC 52578, together with the known compounds panepoxydone (3), panepoxydione (4), isopanepoxydone (5), 2,2-dimethyl-6-hydroxy-2H-chromene (6), and (3R,4S)-3,4-dihydroxy-2,2-dimethyl-6-methoxychroman (7). Compounds 3 and 4 exhibited cytotoxicity against all cell-lines tested, while the other compounds were inactive.

  1. Simulation of He embrittlement at grain boundaries in bcc transition metals

    Science.gov (United States)

    Suzudo, Tomoaki; Yamaguchi, Masatake

    2015-10-01

    To investigate what atomic properties largely determine vulnerability to He embrittlement at grain boundaries (GB) of bcc metals, we introduce a computational model composed of first principles density functional theory and a He segregation rate theory model. Predictive calculations of He embrittlement at the first wall of the future DEMO fusion concept reactor indicate that variation in the He embrittlement originated not only from He production rate related to neutron irradiation, but also from the He segregation energy at the GB that has a systematic trend in the periodic table.

  2. Effects of low-temperature neutron irradiation on the mechanical properties of BCC metals

    Science.gov (United States)

    Kitajima, K.; Abe, H.; Aono, Y.; Kuramoto, E.; Takamura, S.

    1982-08-01

    Tensile properties, together with the effects of point-irradiation annealings on them, were measured on single crystals of pure iron, iron containing 200 at. ppm carbon, and pure molybdenum, which were irradiated at 5 K in reactor JRR-3 and stored at 77 K, at the test temperatures of 4.2-800 K. Their measurements were compared with those irradiated by 2.5 and 28 MeV electrons at 77 K to elucidate the characteristics of neutron irradiation. Interpretations were then presented for the mechanisms of softening and hardening based on the interactions of defects and defect clusters formed in various annealing stages with screw dislocation in bcc metals.

  3. Numerical evidence for bcc ordering at the surface of a critical fcc nucleus

    OpenAIRE

    Wolde, P.R. ten; Ruiz-Montero, M. J.; Frenkel, D.

    1995-01-01

    We report a computer-simulation study of the crystal nucleation barrier and the structure of crystal nuclei in a Lennard-Jones system at moderate supercooling. The stable structure of the Lennard-Jones solid is known to be face-centered cubic. We find that the precritical nuclei are predominantly body-centered cubic ordered. But, as the nucleus grows to its critical size, the core becomes fcc ordered. Surprisingly, however, the interface of the critical nucleus retains a high degree of bcc-li...

  4. Basis reduction for layered lattices

    NARCIS (Netherlands)

    Torreão Dassen, Erwin

    2011-01-01

    We develop the theory of layered Euclidean spaces and layered lattices. We present algorithms to compute both Gram-Schmidt and reduced bases in this generalized setting. A layered lattice can be seen as lattices where certain directions have infinite weight. It can also be interpre

  5. Spin qubits in antidot lattices

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Flindt, Christian; Mortensen, Niels Asger;

    2008-01-01

    and density of states for a periodic potential modulation, referred to as an antidot lattice, and find that localized states appear, when designed defects are introduced in the lattice. Such defect states may form the building blocks for quantum computing in a large antidot lattice, allowing for coherent...

  6. Molecular dynamics simulations of hcp/fcc nucleation and growth in bcc iron driven by uniaxial compression.

    Science.gov (United States)

    Wang, B T; Shao, J L; Zhang, G C; Li, W D; Zhang, P

    2009-12-02

    Molecular dynamics simulations have been performed to study the structural transition in bcc iron under uniaxial strain loading. We found that the transition pressures are less dependent on the crystal orientations, ∼14 GPa for [001], [011], and [111] loadings. However, the pressure interval of a mixed phase for [011] loading is much shorter than loading along other orientations. In addition, the temperature increased amplitude for [001] loading is evidently lower than other orientations. The nucleation and growth of the hcp/fcc phases, and their crystal orientation dependence, were analyzed in detail, where the atom structure was presented by the topological medium-range-order analysis. For [001] compression, the hcp structure occurs first and grows into a laminar morphology in the (011)(bcc) plane with some fcc atoms as an intermediate structure. For loading along [011] and [111] directions, both hcp and fcc structure nucleation and growth along the {110}(bcc) planes are observed; their morphology is also discussed.

  7. Co thin film with metastable bcc structure formed on GaAs(111 substrate

    Directory of Open Access Journals (Sweden)

    Minakawa Shigeyuki

    2014-07-01

    Full Text Available Co thin films are prepared on GaAs(111 substrates at temperatures ranging from room temperature to 600 ºC by radio-frequency magnetron sputtering. The growth behavior and the detailed resulting film structure are investigated by in-situ reflection high-energy electron diffraction and X-ray diffraction. In early stages of film growth at temperatures lower than 200 ºC, Co crystals with metastable A2 (bcc structure are formed, where the crystal structure is stabilized through hetero-epitaxial growth. With increasing the film thickness beyond 2 nm, the metastable structure starts to transform into more stable A1 (fcc structure through atomic displacements parallel to the A2{110} close-packed planes. The crystallographic orientation relationship between the A2 and the transformed A1 crystals is A1{111} || A2{110}. When the substrate temperature is higher than 400 ºC, Ga atoms of substrate diffuse into the Co films and a Co-Ga alloy with bcc-based ordered structure of B2 is formed.

  8. Microscopic Origin of Heisenberg and Non-Heisenberg Exchange Interactions in Ferromagnetic bcc Fe.

    Science.gov (United States)

    Kvashnin, Y O; Cardias, R; Szilva, A; Di Marco, I; Katsnelson, M I; Lichtenstein, A I; Nordström, L; Klautau, A B; Eriksson, O

    2016-05-27

    By means of first principles calculations, we investigate the nature of exchange coupling in ferromagnetic bcc Fe on a microscopic level. Analyzing the basic electronic structure reveals a drastic difference between the 3d orbitals of E_{g} and T_{2g} symmetries. The latter ones define the shape of the Fermi surface, while the former ones form weakly interacting impurity levels. We demonstrate that, as a result of this, in Fe the T_{2g} orbitals participate in exchange interactions, which are only weakly dependent on the configuration of the spin moments and thus can be classified as Heisenberg-like. These couplings are shown to be driven by Fermi surface nesting. In contrast, for the E_{g} states, the Heisenberg picture breaks down since the corresponding contribution to the exchange interactions is shown to strongly depend on the reference state they are extracted from. Our analysis of the nearest-neighbor coupling indicates that the interactions among E_{g} states are mainly proportional to the corresponding hopping integral and thus can be attributed to be of double-exchange origin. By making a comparison to other magnetic transition metals, we put the results of bcc Fe into context and argue that iron has a unique behavior when it comes to magnetic exchange interactions.

  9. Nanovoid growth in BCC α-Fe: influences of initial void geometry

    Science.gov (United States)

    Xu, Shuozhi; Su, Yanqing

    2016-12-01

    The growth of voids has a great impact on the mechanical properties of ductile materials by altering their microstructures. Exploring the process of void growth at the nanoscale helps in understanding the dynamic fracture of metals. While some very recent studies looked into the effects of the initial geometry of an elliptic void on the plastic deformation of face-centered cubic metals, a systematic study of the initial void ellipticity and orientation angle in body-centered cubic (BCC) metals is still lacking. In this paper, large scale molecular dynamics simulations with millions of atoms are conducted, investigating the void growth process during tensile loading of metallic thin films in BCC α-Fe. Our simulations elucidate the intertwined influences on void growth of the initial ellipticity and initial orientation angle of the void. It is shown that these two geometric parameters play an important role in the stress-strain response, the nucleation and evolution of defects, as well as the void size/outline evolution in α-Fe thin films. Results suggest that, together with void size, different initial void geometries should be taken into account if a continuum model is to be applied to nanoscale damage progression.

  10. Twin migration in Fe-based bcc crystals: theory and experiments

    Science.gov (United States)

    Ojha, A.; Sehitoglu, H.; Patriarca, L.; Maier, H. J.

    2014-06-01

    We establish an overall energy expression to determine the twin migration stress in bcc metals. Twin migration succeeds twin nucleation often after a load drop, and a model to establish twin migration stress is of paramount importance. We compute the planar fault energy barriers and determine the elastic energies of twinning dislocations including the role of residual dislocations (br) and twin intersection types such as ?1 1 0?, ?1 1 3? and ?2 1 0?. The energy expression derived provides the twin migration stress in relation to the twin nucleation stress with a ratio of 0.5-0.8 depending on the resultant residual burgers vector and the intersection types. Utilizing digital image correlation, it was possible to differentiate the twin nucleation and twin advancement events experimentally, and transmission electron microscopy observations provided further support to the modelling efforts. Overall, the methodology developed provides an enhanced understanding of twin progression in bcc metals, and most importantly the proposed model does not rely on empirical constants. We utilize Fe-50at.%Cr in our experiments, and subsequently predict the twin migration stress for pure Fe, and Fe-3at.%V from the literature showing excellent agreement with experiments.

  11. Cluster-based composition rule for Laves phase-related BCC solid solution hydrogen storage alloys

    Institute of Scientific and Technical Information of China (English)

    WANG Qing; CHEN Feng; WU Jiang; QIANG Jianbing; DONG Chuang; ZHANG Yao; XU Fen; SUN Lixian

    2006-01-01

    A new cluster line approach for the composition rule of Laves phase-related BCC solid solution hydrogen-storage alloys was presented. The cluster line in a ternary phase diagram refers to a straight composition line linking a specific binary cluster to the third element. In the Laves phase-related BCC solid solution alloy system such as Ti-Cr-V, Ti-Cr tends to form binary Cr2Ti Laves phase while Ti-V and Cr-V to form solid solutions. This Laves phase is characterized by a close-packing icosahedral cluster Cr7Ti6. A cluster line Cr7Ti6-V is then constructed in this system. Alloy rods with a diameter of 3 mm of compositions along this line were prepared by copper-mould suction method. The alloy structure is found to vary with the V contents. Furthermore, the P-C-T measurements indicate that the cluster-line (Cr7Ti6)1-xVx alloys have large hydrogen storage capacities.

  12. Lattice Quantum Chromodynamics

    CERN Document Server

    Sachrajda, C T

    2016-01-01

    I review the the application of the lattice formulation of QCD and large-scale numerical simulations to the evaluation of non-perturbative hadronic effects in Standard Model Phenomenology. I present an introduction to the elements of the calculations and discuss the limitations both in the range of quantities which can be studied and in the precision of the results. I focus particularly on the extraction of the QCD parameters, i.e. the quark masses and the strong coupling constant, and on important quantities in flavour physics. Lattice QCD is playing a central role in quantifying the hadronic effects necessary for the development of precision flavour physics and its use in exploring the limits of the Standard Model and in searches for inconsistencies which would signal the presence of new physics.

  13. Varieties of lattices

    CERN Document Server

    Jipsen, Peter

    1992-01-01

    The study of lattice varieties is a field that has experienced rapid growth in the last 30 years, but many of the interesting and deep results discovered in that period have so far only appeared in research papers. The aim of this monograph is to present the main results about modular and nonmodular varieties, equational bases and the amalgamation property in a uniform way. The first chapter covers preliminaries that make the material accessible to anyone who has had an introductory course in universal algebra. Each subsequent chapter begins with a short historical introduction which sites the original references and then presents the results with complete proofs (in nearly all cases). Numerous diagrams illustrate the beauty of lattice theory and aid in the visualization of many proofs. An extensive index and bibliography also make the monograph a useful reference work.

  14. Fractional lattice charge transport

    Science.gov (United States)

    Flach, Sergej; Khomeriki, Ramaz

    2017-01-01

    We consider the dynamics of noninteracting quantum particles on a square lattice in the presence of a magnetic flux α and a dc electric field E oriented along the lattice diagonal. In general, the adiabatic dynamics will be characterized by Bloch oscillations in the electrical field direction and dispersive ballistic transport in the perpendicular direction. For rational values of α and a corresponding discrete set of values of E(α) vanishing gaps in the spectrum induce a fractionalization of the charge in the perpendicular direction - while left movers are still performing dispersive ballistic transport, the complementary fraction of right movers is propagating in a dispersionless relativistic manner in the opposite direction. Generalizations and the possible probing of the effect with atomic Bose-Einstein condensates and photonic networks are discussed. Zak phase of respective band associated with gap closing regime has been computed and it is found converging to π/2 value. PMID:28102302

  15. Solitons in nonlinear lattices

    CERN Document Server

    Kartashov, Yaroslav V; Torner, Lluis

    2010-01-01

    This article offers a comprehensive survey of results obtained for solitons and complex nonlinear wave patterns supported by purely nonlinear lattices (NLs), which represent a spatially periodic modulation of the local strength and sign of the nonlinearity, and their combinations with linear lattices. A majority of the results obtained, thus far, in this field and reviewed in this article are theoretical. Nevertheless, relevant experimental settings are surveyed too, with emphasis on perspectives for implementation of the theoretical predictions in the experiment. Physical systems discussed in the review belong to the realms of nonlinear optics (including artificial optical media, such as photonic crystals, and plasmonics) and Bose-Einstein condensation (BEC). The solitons are considered in one, two, and three dimensions (1D, 2D, and 3D). Basic properties of the solitons presented in the review are their existence, stability, and mobility. Although the field is still far from completion, general conclusions c...

  16. Lattice Quantum Chromodynamics

    Science.gov (United States)

    Sachrajda, C. T.

    2016-10-01

    I review the the application of the lattice formulation of QCD and large-scale numerical simulations to the evaluation of non-perturbative hadronic effects in Standard Model Phenomenology. I present an introduction to the elements of the calculations and discuss the limitations both in the range of quantities which can be studied and in the precision of the results. I focus particularly on the extraction of the QCD parameters, i.e. the quark masses and the strong coupling constant, and on important quantities in flavour physics. Lattice QCD is playing a central role in quantifying the hadronic effects necessary for the development of precision flavour physics and its use in exploring the limits of the Standard Model and in searches for inconsistencies which would signal the presence of new physics.

  17. Introduction to lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, R.

    1998-12-31

    The goal of the lectures on lattice QCD (LQCD) is to provide an overview of both the technical issues and the progress made so far in obtaining phenomenologically useful numbers. The lectures consist of three parts. The author`s charter is to provide an introduction to LQCD and outline the scope of LQCD calculations. In the second set of lectures, Guido Martinelli will discuss the progress they have made so far in obtaining results, and their impact on Standard Model phenomenology. Finally, Martin Luescher will discuss the topical subjects of chiral symmetry, improved formulation of lattice QCD, and the impact these improvements will have on the quality of results expected from the next generation of simulations.

  18. Lattices of dielectric resonators

    CERN Document Server

    Trubin, Alexander

    2016-01-01

    This book provides the analytical theory of complex systems composed of a large number of high-Q dielectric resonators. Spherical and cylindrical dielectric resonators with inferior and also whispering gallery oscillations allocated in various lattices are considered. A new approach to S-matrix parameter calculations based on perturbation theory of Maxwell equations, developed for a number of high-Q dielectric bodies, is introduced. All physical relationships are obtained in analytical form and are suitable for further computations. Essential attention is given to a new unified formalism of the description of scattering processes. The general scattering task for coupled eigen oscillations of the whole system of dielectric resonators is described. The equations for the  expansion coefficients are explained in an applicable way. The temporal Green functions for the dielectric resonator are presented. The scattering process of short pulses in dielectric filter structures, dielectric antennas  and lattices of d...

  19. Weakly deformed soliton lattices

    Energy Technology Data Exchange (ETDEWEB)

    Dubrovin, B. (Moskovskij Gosudarstvennyj Univ., Moscow (USSR). Dept. of Mechanics and Mathematics)

    1990-12-01

    In this lecture the author discusses periodic and quasiperiodic solutions of nonlinear evolution equations of phi{sub t}=K (phi, phi{sub x},..., phi{sup (n)}), the so-called soliton lattices. After introducing the theory of integrable systems of hydrodynamic type he discusses their Hamiltonian formalism, i.e. the theory of Poisson brackets of hydrodynamic type. Then he describes the application of algebraic geometry to the effective integration of such equations. (HSI).

  20. International Lattice Data Grid

    CERN Document Server

    Davies, C T H; Kenway, R D; Maynard, C M

    2002-01-01

    We propose the co-ordination of lattice QCD grid developments in different countries to allow transparent exchange of gauge configurations in future, should participants wish to do so. We describe briefly UKQCD's XML schema for labelling and cataloguing the data. A meeting to further develop these ideas will be held in Edinburgh on 19/20 December 2002, and will be available over AccessGrid.

  1. Digital lattice gauge theories

    Science.gov (United States)

    Zohar, Erez; Farace, Alessandro; Reznik, Benni; Cirac, J. Ignacio

    2017-02-01

    We propose a general scheme for a digital construction of lattice gauge theories with dynamical fermions. In this method, the four-body interactions arising in models with 2 +1 dimensions and higher are obtained stroboscopically, through a sequence of two-body interactions with ancillary degrees of freedom. This yields stronger interactions than the ones obtained through perturbative methods, as typically done in previous proposals, and removes an important bottleneck in the road towards experimental realizations. The scheme applies to generic gauge theories with Lie or finite symmetry groups, both Abelian and non-Abelian. As a concrete example, we present the construction of a digital quantum simulator for a Z3 lattice gauge theory with dynamical fermionic matter in 2 +1 dimensions, using ultracold atoms in optical lattices, involving three atomic species, representing the matter, gauge, and auxiliary degrees of freedom, that are separated in three different layers. By moving the ancilla atoms with a proper sequence of steps, we show how we can obtain the desired evolution in a clean, controlled way.

  2. Robots and lattice automata

    CERN Document Server

    Adamatzky, Andrew

    2015-01-01

    The book gives a comprehensive overview of the state-of-the-art research and engineering in theory and application of Lattice Automata in design and control of autonomous Robots. Automata and robots share the same notional meaning. Automata (originated from the latinization of the Greek word “αυτόματον”) as self-operating autonomous machines invented from ancient years can be easily considered the first steps of robotic-like efforts. Automata are mathematical models of Robots and also they are integral parts of robotic control systems. A Lattice Automaton is a regular array or a collective of finite state machines, or automata. The Automata update their states by the same rules depending on states of their immediate neighbours. In the context of this book, Lattice Automata are used in developing modular reconfigurable robotic systems, path planning and map exploration for robots, as robot controllers, synchronisation of robot collectives, robot vision, parallel robotic actuators. All chapters are...

  3. In vivo assessment of optical properties of basal cell carcinoma and differentiation of BCC subtypes by high-definition optical coherence tomography.

    Science.gov (United States)

    Boone, Marc; Suppa, Mariano; Miyamoto, Makiko; Marneffe, Alice; Jemec, Gregor; Del Marmol, Veronique

    2016-06-01

    High-definition optical coherence tomography (HD-OCT) features of basal cell carcinoma (BCC) have recently been defined. We assessed in vivo optical properties (IV-OP) of BCC, by HD-OCT. Moreover their critical values for BCC subtype differentiation were determined. The technique of semi-log plot whereby an exponential function becomes linear has been implemented on HD-OCT signals. The relative attenuation factor (µraf ) at different skin layers could be assessed.. IV-OP of superficial BCC with high diagnostic accuracy (DA) and high negative predictive values (NPV) were (i) decreased µraf in lower part of epidermis and (ii) increased epidermal thickness (E-T). IV-OP of nodular BCC with good to high DA and NPV were (i) less negative µraf in papillary dermis compared to normal adjacent skin and (ii) significantly decreased E-T and papillary dermal thickness (PD-T). In infiltrative BCC (i) high µraf in reticular dermis compared to normal adjacent skin and (ii) presence of peaks and falls in reticular dermis had good DA and high NPV. HD-OCT seems to enable the combination of in vivo morphological analysis of cellular and 3-D micro-architectural structures with IV-OP analysis of BCC. This permits BCC sub-differentiation with higher accuracy than in vivo HD-OCT analysis of morphology alone.

  4. The Academic and Remedial Placement of Students Entering B. C. C. in September 1975 by Curriculum Group. Research Report BCC-9-75.

    Science.gov (United States)

    Bronx Community Coll., NY.

    This report describes the Bronx Community College (B.C.C.) freshmen class entering in September 1975, in terms of high school grade average and scores on reading-English and mathematics placement tests. As of the fall of 1974, B.C.C. enrolled a markedly higher proportion of students with high school averages below 70 percent than any other college…

  5. DMBA/TPA treatment is necessary for BCC formation from patched deficient epidermal cells in Ptch(flox/flox)CD4Cre(+/-) mice.

    Science.gov (United States)

    Uhmann, Anja; Heß, Ina; Frommhold, Anke; König, Simone; Zabel, Sebastian; Nitzki, Frauke; Dittmann, Kai; Lühder, Fred; Christiansen, Hans; Reifenberger, Julia; Schulz-Schaeffer, Walter; Hahn, Heidi

    2014-10-01

    The development of basal cell carcinoma (BCC), the most frequently diagnosed tumor among persons with European ancestry, is closely linked to mutations in the Hedgehog (Hh) receptor and tumor suppressor Patched1 (Ptch). Using Ptch(flox/flox)CD4Cre(+/-) mice, in which Ptch was ablated in CD4Cre-expressing cells, we demonstrate that the targeted cells can give rise to BCC after treatment with DMBA (7,12-dimethylbenz(a)anthracene)/TPA (12-O-tetradecanoylphorbol-13-acetate), but not after wounding of the skin. In addition, in this model, BCC are not caused by malfunctioning of Ptch-deficient T cells, as BCC did not develop when bone marrow (BM) of Ptch(flox/flox)CD4Cre(+/-) mice was transplanted into Ptch wild-type mice. Instead, lineage-tracing experiments and flow cytometric analyses suggest that the tumors are initiated from rare Ptch-deficient stem cell-like cells of the epidermis that express CD4. As DMBA/TPA is a prerequisite for BCC development in this model, the initiated cells need a second stimulus for expansion and tumor formation. However, in contrast to papilloma, this stimulus seems to be unrelated to alterations in the Ras signaling cascade. Together, these data suggest that biallelic loss of Ptch in CD4(+) cells does not suffice for BCC formation and that BCC formation requires a second so far unknown event, at least in the Ptch(flox/flox)CD4Cre(+/-) BCC mouse model.

  6. Kenneth Wilson and lattice QCD

    CERN Document Server

    Ukawa, Akira

    2015-01-01

    We discuss the physics and computation of lattice QCD, a space-time lattice formulation of quantum chromodynamics, and Kenneth Wilson's seminal role in its development. We start with the fundamental issue of confinement of quarks in the theory of the strong interactions, and discuss how lattice QCD provides a framework for understanding this phenomenon. A conceptual issue with lattice QCD is a conflict of space-time lattice with chiral symmetry of quarks. We discuss how this problem is resolved. Since lattice QCD is a non-linear quantum dynamical system with infinite degrees of freedom, quantities which are analytically calculable are limited. On the other hand, it provides an ideal case of massively parallel numerical computations. We review the long and distinguished history of parallel-architecture supercomputers designed and built for lattice QCD. We discuss algorithmic developments, in particular the difficulties posed by the fermionic nature of quarks, and their resolution. The triad of efforts toward b...

  7. A Mechanical Lattice Aid for Crystallography Teaching.

    Science.gov (United States)

    Amezcua-Lopez, J.; Cordero-Borboa, A. E.

    1988-01-01

    Introduces a 3-dimensional mechanical lattice with adjustable telescoping mechanisms. Discusses the crystalline state, the 14 Bravais lattices, operational principles of the mechanical lattice, construction methods, and demonstrations in classroom. Provides lattice diagrams, schemes of the lattice, and various pictures of the lattice. (YP)

  8. The Academic and Remedial Placement Profile of Students Entering B.C.C. in September, 1976 [and September 1977] by Curriculum Group. Research Report BCC 4-76 [and] 4-77.

    Science.gov (United States)

    Eagle, Norman

    Profiles of freshmen students entering Bronx Community College (BCC) in September, 1976 and September, 1977 are presented in terms of their academic and remedial placement. For both years, nearly 70% of those who took placement tests in the reading/English area and subsequently enrolled were recommended for at least one remedial course; 75% of…

  9. Experience and BCC subtypes as determinants of MAL-PDT response: preliminary results of a national Brazilian project.

    Science.gov (United States)

    Ramirez, Dora P; Kurachi, Cristina; Inada, Natalia M; Moriyama, Lilian T; Salvio, Ana G; Vollet Filho, José D; Pires, Layla; Buzzá, Hilde H; de Andrade, Cintia Teles; Greco, Clovis; Bagnato, Vanderlei S

    2014-03-01

    Non-melanoma skin cancer is the most prevalent cancer type in Brazil and worldwide. Photodynamic therapy (PDT) is a noninvasive technique with excellent cosmetic outcome and good curative results, when used for the initial stages of skin cancer. A Brazilian program was established to determine the efficacy of methyl aminolevulinate (MAL)-PDT, using Brazilian device and drug. The equipment is a dual device that combines the photodiagnosis, based on widefield fluorescence, and the treatment at 630nm. A protocol was defined for the treatment of basal cell carcinoma with 20% MAL cream application. The program also involves the training of the medical teams at different Brazilian regions, and with distinct facilities and previous PDT education. In this report we present the partial results of 27 centers with 366 treated BCC lesions in 294 patients. A complete response (CR) was observed in 76.5% (280/366). The better response was observed for superficial BCC, with CR 160 lesions (80.4%), when compared with nodular or pigmented BCC. Experienced centers presented CR of 85.8% and 90.6% for superficial and nodular BCC respectively. A high influence of the previous doctor experience on the CR values was observed, especially due to a better tumor selection.

  10. Investigation of helium at a Y2Ti2O7 nanocluster embedded in a BCC Fe matrix.

    Science.gov (United States)

    Danielson, Thomas; Tea, Eric; Hin, Celine

    2016-11-02

    Nanostructured ferritic alloys (NFAs) are prime candidates for structural and first wall components of fission and fusion reactors. The main reason for this is their ability to effectively withstand high concentrations of the transmutation product helium. A high number density of oxide nanoclusters dispersed throughout a BCC Fe matrix act as trapping sites for helium and prevent its eventual delivery to high risk nucleation sites. The current study uses density functional theory to investigate the helium trapping mechanisms at the boundary between BCC iron and Y2Ti2O7, a common stoichiometry of the oxide nanoclusters in NFAs. The investigation is carried out on a structure matched oxide nanocluster that is embedded within a BCC Fe supercell. Investigation of the electronic structure and a mapping of the potential energy landscape reveals that the localized iono-covalent bonds present within the oxides create a potential energy-well within the metallically bonded BCC Fe matrix, so that trapping of helium at the oxide nanocluster is thermodynamically and kinetically favorable.

  11. Evaluation of the biphasic calcium composite (BCC), a novel bone cement, in a minipig model of pulmonary embolism.

    Science.gov (United States)

    Qin, Yi; Ye, Jichao; Wang, Peng; Gao, Liangbin; Jiang, Jianming; Wang, Suwei; Shen, Huiyong

    2016-01-01

    Polymethylmethacrylate (PMMA) bone cement, which is used as a filler material in vertebroplasty, is one of the major sources of pulmonary embolism in patients who have undergone vertebroplasty. In the present study, we established and evaluated two animal models of pulmonary embolism by injecting PMMA or biphasic calcium composite (BCC) bone cement with a negative surface charge. A total of 12 adults and healthy Wuzhishan minipigs were randomly divided into two groups, the PMMA and BBC groups, which received injection of PMMA bone cement and BBC bone cement with a negative surface charge in the circulation system through the pulmonary trunk, respectively, to construct animal models of pulmonary embolism. The hemodynamics, arterial blood gas, and plasma coagulation were compared between these two groups. In addition, morphological changes of the lung were examined using three-dimensional computed tomography. The results showed that both PMMA and BCC injections induced pulmonary embolisms in minipigs. Compared to the PMMA group, the BCC group exhibited significantly lower levels of arterial pressure, pulmonary artery pressure, blood oxygen pressure, blood carbon dioxide pressure, blood bicarbonate, base excess, antithrombin III and D-dimer. In conclusion, BCC bone cement with a negative surface charge is a promising filler material for vertebroplasty.

  12. Equilibrium fluid-crystal interfacial free energy of bcc-crystallizing aqueous suspensions of polydisperse charged spheres.

    Science.gov (United States)

    Palberg, Thomas; Wette, Patrick; Herlach, Dieter M

    2016-02-01

    The interfacial free energy is a central quantity in crystallization from the metastable melt. In suspensions of charged colloidal spheres, nucleation and growth kinetics can be accurately measured from optical experiments. In previous work, from these data effective nonequilibrium values for the interfacial free energy between the emerging bcc nuclei and the adjacent melt in dependence on the chemical potential difference between melt phase and crystal phase were derived using classical nucleation theory (CNT). A strictly linear increase of the interfacial free energy was observed as a function of increased metastability. Here, we further analyze these data for five aqueous suspensions of charged spheres and one binary mixture. We utilize a simple extrapolation scheme and interpret our findings in view of Turnbull's empirical rule. This enables us to present the first systematic experimental estimates for a reduced interfacial free energy, σ(0,bcc), between the bcc-crystal phase and the coexisting equilibrium fluid. Values obtained for σ(0,bcc) are on the order of a few k(B)T. Their values are not correlated to any of the electrostatic interaction parameters but rather show a systematic decrease with increasing size polydispersity and a lower value for the mixture as compared to the pure components. At the same time, σ(0) also shows an approximately linear correlation to the entropy of freezing. The equilibrium interfacial free energy of strictly monodisperse charged spheres may therefore be still greater.

  13. Photocatalytic degradation of gaseous toluene over bcc-In{sub 2}O{sub 3} hollow microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qianzhe [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemicals, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Li, Xinyong, E-mail: xyli@dlut.edu.cn [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemicals, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); ARC Centre of Excellence for Functional Nanomaterials, School of Chemical Engineering, the University of Queensland, St Lucia, Brisbane, Queensland, 4092 (Australia); Zhao, Qidong; Shi, Yong; Zhang, Fei; Liu, Baojun; Ke, Jun [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemicals, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Wang, Lianzhou [ARC Centre of Excellence for Functional Nanomaterials, School of Chemical Engineering, the University of Queensland, St Lucia, Brisbane, Queensland, 4092 (Australia)

    2015-05-15

    Graphical abstract: - Highlights: • The bcc-In{sub 2}O{sub 3} hollow microspheres were synthesized as photocatalyst. • Structural and photocatalytic properties of samples are tested. • Degradation of gaseous toluene over the bcc-In{sub 2}O{sub 3} hollow microspheres. - Abstract: In this work, the body-centered cubic indium oxide (bcc-In{sub 2}O{sub 3}) hollow microspheres were prepared via a P123-assisted solvothermal process. The structural properties of samples were investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, UV–visible diffusive reflectance spectroscopy, and nitrogen adsorption-desorption isotherms. The photocatalytic effects of degrading gaseous toluene were evaluated by gas chromatography and in situ Fourier transform infrared (FTIR) spectra under a irradiation of a 500 W high pressure xenon lamp. The results indicated that the as-prepared bcc-In{sub 2}O{sub 3} hollow microspheres exhibited a high degradation efficiency towards toluene within a short reaction time. Besides, the preliminary mechanism therein was inferred with the aid of in situ FTIR and electron spin-paramagnetic resonance techniques to understand the degradation process.

  14. Strain effects in Nb3Al multifilamentary conductors prepared by phase transformation from bcc supersaturated-solid solution

    NARCIS (Netherlands)

    Takeuchi, T.; Iijima, Y.; Inoue, K.; Wada, H.; Haken, ten B.; Kate, ten H.H.J.; Fukuda, K.; Iwaki, G.; Sakai, S.; Moriai, H.

    1997-01-01

    Strain effects on critical current densities have been examined for conductors containing nearly stoichiometric Nb3Al filaments with fine grains. The Nb3Al phase in these multifilamentary conductors are prepared by phase transformation from supersaturated Nb(Al) bcc solid solution and show high-fiel

  15. Lattice Vibrations in Chlorobenzenes:

    DEFF Research Database (Denmark)

    Reynolds, P. A.; Kjems, Jørgen; White, J. W.

    1974-01-01

    Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p‐C6D4Cl2 and p‐C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K...... by consideration of electrostatic forces or by further anisotropy in the dispersion forces not described in the atom‐atom model. Anharmonic effects are shown to be large, but the dominant features in the temperature variation of frequencies are describable by a quasiharmonic model....

  16. Properties of grain boundaries in BCC iron and iron-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Terentyev, D.; He, Xinfu

    2010-08-15

    The report contains a summary of work done within the collaboration established between SCK-CEN and CIEA, performed during the internship of Xinfu He (CIAE) in the period of September 2009 to June 2010. In this work, we have carried out an atomistic study addressing the properties of grain boundaries in BCC Fe and Fe-Cr alloys. Throughout this work we report on the structural and cohesive properties of grain boundaries; thermal stability; interaction of grain boundaries with He and diffusivity of He in the core of the grain boundaries; equilibrium segregation of Cr near the grain boundary zone; cleavage fracture of grain boundaries; influence of the Cr precipitates, voids and He bubbles on the structure and strength of grain boundaries.

  17. Magnetic properties and atomic ordering of BCC Heusler alloy Fe2MnGa ribbons

    Science.gov (United States)

    Xin, Yuepeng; Ma, Yuexing; Luo, Hongzhi; Meng, Fanbin; Liu, Heyan

    2016-05-01

    The electronic structure, atomic disorder and magnetic properties of the Heusler alloy Fe2MnGa have been investigated experimentally and theoretically. BCC Fe2MnGa ribbon samples were prepared. Experimentally, a saturation magnetic moment (3.68 μB at 5 K) much larger than the theoretical value (2.04 μB) has been reported. First-principles calculations indicate that the difference is related to the Fe-Mn disorder between A, B sites, as can also be deduced from the XRD pattern. L21 type Fe2MnGa is a ferrimagnet with antiparallel Fe and Mn spin moments. However, when Fe-Mn disorder occurs, part of Mn moments will be parallel to Fe moments, and the Fe moments also clearly increase simultaneously. All this results in a total moment of 3.74 μB, close to the experimental value.

  18. The effect of hydrogen on the electronic structure of kink in bcc iron

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The electronic structures of kinks in the [100](010) and 1/2[111](-110) edge dislocations in bcc iron containing hydrogen are investigated by means of the first-principles DMol method and the discrete variational method.The effects of hydrogen on the kinks are discussed.The results show that hydro-gen forms weak bonding states with its neighboring host atoms,and since hydrogen draws charge from its neighboring host atoms,the interactions between most of the host atoms are weakened com-pared with those of the corresponding atomic pairs in the clean kinks.This indicates that the migration of kink,i.e.the motion of dislocation,is easier in the doping hydrogen kink than in the clean kink,which may be the solid solution softening effect resulting from the impurity hydrogen.

  19. Further discussion of orientation relationships, surface reliefs and FCC-BCC transformations in steels

    Energy Technology Data Exchange (ETDEWEB)

    Dahmen, U. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials and Molecular Research Division; Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering

    1981-04-01

    In response to a recent discussion in this journal concerning tent-shaped surface-relief effects and the mechanism of formation of Widmanstätten ferrite and lower bainite, it was shown that Bhadeshia's (1) explanation of surface reliefs is in error. A degeneracy of the fcc → hcp type does not exist for an fcc → bcc transformation. Based on a distinction between the symmetries of the matrix, the transformation product and the strain (5), a general rule was derived for the occurrence of the type of crystallographic degeneracies described by Bhadeshia. The present paper confirmed Aaronson's (4) contention that the transformation is not shear-like (martensitic) in nature but diffusion controlled. Finally, it was argued, however, that the formal treatment of diffusional transformations may involve a shear.

  20. Magnetic properties of bcc-Fe(001)/C₆₀ interfaces for organic spintronics.

    Science.gov (United States)

    Tran, T Lan Anh; Cakır, Deniz; Wong, P K Johnny; Preobrajenski, Alexei B; Brocks, Geert; van der Wiel, Wilfred G; de Jong, Michel P

    2013-02-01

    The magnetic structure of the interfaces between organic semiconductors and ferromagnetic contacts plays a key role in the spin injection and extraction processes in organic spintronic devices. We present a combined computational (density functional theory) and experimental (X-ray magnetic circular dichroism) study on the magnetic properties of interfaces between bcc-Fe(001) and C(60) molecules. C(60) is an interesting candidate for application in organic spintronics due to the absence of hydrogen atoms and the associated hyperfine fields. Adsorption of C(60) on Fe(001) reduces the magnetic moments on the top Fe layers by ∼6%, while inducing an antiparrallel magnetic moment of ∼-0.2 μ(B) on C(60). Adsorption of C(60) on a model ferromagnetic substrate consisting of three Fe monolayers on W(001) leads to a different structure but to very similar interface magnetic properties.

  1. Giant Magnetoresistance Effect of [bcc-Fe(M)/Cu](M=Co,Ni)Multilayers

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    GMR effect of multilayers of bcc-Fe(M)(M=Co, Ni) alloy and Cu layers has been investigated. The maximum MR ratio is found at 1.1 nm Fe(Co) and 1.3~1.4 nm Cu layer thickness in [Fe(Co)/Cu], and at 1.6 nm Fe(Ni) and 1.4 nm Cu layer thickness in [Fe(Ni)/Cu]. Under the optimum annealing condition, the MR ratio increases up to 50% and 38% for Fe(Co) and Fe(Ni) systems, respectively. The origin of the increase of GMR is discussed, taking the progress of preferred orientation of Fe(Co)[100] or Fe(Ni)[100] by annealing into account.

  2. First-principles investigation of the impurity-kink interaction in bcc iron

    Institute of Scientific and Technical Information of China (English)

    YU Tao; CHEN LiQun; WANG ChongYu; QIU ZhengChen; DU JunPing

    2008-01-01

    Using the first-principles self-consistent discrete variational method based on density functional theory, we investigated the effect of light impurities C and N on the electronic structure of kink on the [100](010) edge dislocation (ED) in bcc iron. Our energetic calculations show that the light impurities have a strong segregation tendency to enter the kink. The results of the charge distribution and the local den-sity of states indicate that the strong bonds between the impurity atoms and the neighboring Fe atoms are formed due to the hybridizations of impurity atoms 2p states and Fe 3d4s4p states. The introduction of light impurities can stabilize the kink system, and impedes the sideward motion of the kink in the [100](010) ED. This is, the light impurities induce a strong pinning effect on the [100](010) ED and may result in the solid solute hardening.

  3. Properties of FeNiB-based metallic glasses with primary BCC and FCC crystallisation products

    Energy Technology Data Exchange (ETDEWEB)

    Uriarte, J.L. E-mail: euronano@ltpcm.inpg.fr; Yavari, A.R.; Surinach, S.; Rizzi, P.; Heunen, G.; Baricco, M.; Baro, M.D.; Kvick, A

    2003-01-01

    FeSiB tapes have long been commercialised for their excellent soft-magnetic properties but do not manifest a glass transition temperature T{sub g} as crystallisation intervenes. In this work, we present the crystallisation and properties of two Fe-based glasses, which show a glass transition before crystallisation. Using Ni and Co substitution, we can design glasses that form primary FCC or BCC FeNiCo solutions in their first stage of crystallisation followed by the formation of the metastable (FeNiCo){sub 4}B (C{sub 6}Cr{sub 23}-type cF116) intermetallic phase. Thermal and structural and magnetic properties were compared during heat treatment.

  4. Localization of telomerase hTERT protein in frozen sections of basal cell carcinomas (BCC) and tumor margin tissues.

    Science.gov (United States)

    Fabricius, Eva-Maria; Kruse-Boitschenko, Ute; Khoury, Reem; Wildner, Gustav-Paul; Raguse, Jan-Dirk; Klein, Martin; Hoffmeister, Bodo

    2009-12-01

    In previous studies we demonstrated telomerase activity in frozen tissues from BCC and their tumor-free margins by the PCR ELISA. In this study we examined in the same frozen sections immunohistochemical presence of hTERT in the nucleus. After fixation in acetone and methanol followed by steaming we used for visualization the antigen-antibody reactions by APAAP. This was the best method of preparation of the frozen sections in our preliminary hTERT-study with squamous cell carcinomas. This study was supplemented with antibodies against Ki-67, nucleolin, common leucocyte antigen CD45 and mutated p53. The immunoreactive scores were determined and included the comparison with telomerase activity. The investigation of hTERT expression was performed in the tissues of 41 patients with BCC and control tissues of 14 patients without tumor. Eleven commercial antibodies were used for a nuclear staining of hTERT expression. With the anti-hTERT antibodies we looked for both satisfactory distribution and intensity of immunohistochemical labeling in the carcinomas and in the squamous epithelia of the tumor centers, of the tumor-free margins and of the control tissues. The hTERT expression in the BCC was distributed heterogeneously. The score values established by the anti-hTERT antibodies used were variably or significantly increased. In the stroma they tended to be negative, so we disregarded stroma hTERT. Proof of hTERT did not differ uniformly from telomerase activity. We compared the high with the lower median hTERT values in the Kaplan-Meier curve. Patients with lower hTERT scores in the center or tumor margin as shown by some of the antibodies suffered relapse earlier. Finally, we compared the hTERT expression in BCC tissues with the hTERT scores in HNSCC tissues from our previous study. Only one anti-hTERT antibody (our Ab 7) yielded significantly higher scores in BCC than in HNSCC.

  5. Lattice harmonics expansion revisited

    Science.gov (United States)

    Kontrym-Sznajd, G.; Holas, A.

    2017-04-01

    The main subject of the work is to provide the most effective way of determining the expansion of some quantities into orthogonal polynomials, when these quantities are known only along some limited number of sampling directions. By comparing the commonly used Houston method with the method based on the orthogonality relation, some relationships, which define the applicability and correctness of these methods, are demonstrated. They are verified for various sets of sampling directions applicable for expanding quantities having the full symmetry of the Brillouin zone of cubic and non-cubic lattices. All results clearly show that the Houston method is always better than the orthogonality-relation one. For the cubic symmetry we present a few sets of special directions (SDs) showing how their construction and, next, a proper application depend on the choice of various sets of lattice harmonics. SDs are important mainly for experimentalists who want to reconstruct anisotropic quantities from their measurements, performed at a limited number of sampling directions.

  6. Investigating the magnetovolume effect in isotropic body-centered-cubic iron using spin-lattice dynamics simulations

    Directory of Open Access Journals (Sweden)

    C. P. Chui

    2014-08-01

    Full Text Available The understanding of the magnetovolume effect lacks explicit consideration of spin-lattice coupling at the atomic level, despite abundant theoretical and experimental studies throughout the years. This research gap is filled by the recently developed spin-lattice dynamics technique implemented in this study, which investigates the magnetovolume effect of isotropic body-centered-cubic (BCC iron, a topic that has previously been subject to macroscopic analysis only. This approach demonstrates the magnetic anomaly followed by the volumetric changes associated with the effect, each characterized by the corresponding field-induced inflection temperature. The temperature of the heat capacity peaks is useful in determining the temperature for retarding the atomic volume increase. Moreover, this work shows the correlation between the effects of temperature and field strength in determining the equilibrium atomic volume of a ferromagnetic material under a magnetic field.

  7. Elimination of spurious lattice fermion solutions and noncompact lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Lee, T.D.

    1997-09-22

    It is well known that the Dirac equation on a discrete hyper-cubic lattice in D dimension has 2{sup D} degenerate solutions. The usual method of removing these spurious solutions encounters difficulties with chiral symmetry when the lattice spacing l {ne} 0, as exemplified by the persistent problem of the pion mass. On the other hand, we recall that in any crystal in nature, all the electrons do move in a lattice and satisfy the Dirac equation; yet there is not a single physical result that has ever been entangled with a spurious fermion solution. Therefore it should not be difficult to eliminate these unphysical elements. On a discrete lattice, particle hop from point to point, whereas in a real crystal the lattice structure in embedded in a continuum and electrons move continuously from lattice cell to lattice cell. In a discrete system, the lattice functions are defined only on individual points (or links as in the case of gauge fields). However, in a crystal the electron state vector is represented by the Bloch wave functions which are continuous functions in {rvec {gamma}}, and herein lies one of the essential differences.

  8. Lattice Boltzmann Model for Compressible Fluid on a Square Lattice

    Institute of Scientific and Technical Information of China (English)

    SUN Cheng-Hai

    2000-01-01

    A two-level four-direction lattice Boltzmann model is formulated on a square lattice to simulate compressible flows with a high Mach number. The particle velocities are adaptive to the mean velocity and internal energy. Therefore, the mean flow can have a high Mach number. Due to the simple form of the equilibrium distribution, the 4th order velocity tensors are not involved in the calculations. Unlike the standard lattice Boltzmann model, o special treatment is need for the homogeneity of 4th order velocity tensors on square lattices. The Navier-Stokes equations were derived by the Chapman-Enskog method from the BGK Boltzmann equation. The model can be easily extended to three-dimensional cubic lattices. Two-dimensional shock-wave propagation was simulated

  9. Entangling gates in even Euclidean lattices such as Leech lattice

    CERN Document Server

    Planat, Michel

    2010-01-01

    We point out a organic relationship between real entangling n-qubit gates of quantum computation and the group of automorphisms of even Euclidean lattices of the corresponding dimension 2n. The type of entanglement that is found in the gates/generators of Aut() depends on the lattice. In particular, we investigate Zn lattices, Barnes-Wall lattices D4, E8, 16 (associated to n = 2, 3 and 4 qubits), and the Leech lattices h24 and 24 (associated to a 3-qubit/qutrit system). Balanced tripartite entanglement is found to be a basic feature of Aut(), a nding that bears out our recent work related to the Weyl group of E8 [1, 2].

  10. Low-temperature embrittlement and fracture of metals with different crystal lattices – Dislocation mechanisms

    Directory of Open Access Journals (Sweden)

    V.M. Chernov

    2016-12-01

    Full Text Available The state of a low-temperature embrittlement (cold brittleness and dislocation mechanisms for formation of the temperature of a ductile-brittle transition and brittle fracture of metals (mono- and polycrystals with various crystal lattices (BCC, FCC, HCP are considered. The conditions for their formation connected with a stress-deformed state and strength (low temperature yield strength as well as the fracture breaking stress and mobility of dislocations in the top of a crack of the fractured metal are determined. These conditions can be met for BCC and some HCP metals in the initial state (without irradiation and after a low-temperature damaging (neutron irradiation. These conditions are not met for FCC and many HCP metals. In the process of the damaging (neutron irradiation such conditions are not met also and the state of low-temperature embrittlement of metals is absent (suppressed due to arising various radiation dynamic processes, which increase the mobility of dislocations and worsen the strength characteristics.

  11. Fast simulation of lattice systems

    DEFF Research Database (Denmark)

    Bohr, H.; Kaznelson, E.; Hansen, Frank;

    1983-01-01

    A new computer system with an entirely new processor design is described and demonstrated on a very small trial lattice. The new computer simulates systems of differential equations of the order of 104 times faster than present day computers and we describe how the machine can be applied to lattice...

  12. Dark matter on the lattice

    OpenAIRE

    Lewis, Randy

    2014-01-01

    Several collaborations have recently performed lattice calculations aimed specifically at dark matter, including work with SU(2), SU(3), SU(4) and SO(4) gauge theories to represent the dark sector. Highlights of these studies are presented here, after a reminder of how lattice calculations in QCD itself are helping with the hunt for dark matter.

  13. Introduction to lattice gauge theory

    Science.gov (United States)

    Gupta, R.

    The lattice formulation of Quantum Field Theory (QFT) can be exploited in many ways. We can derive the lattice Feynman rules and carry out weak coupling perturbation expansions. The lattice then serves as a manifestly gauge invariant regularization scheme, albeit one that is more complicated than standard continuum schemes. Strong coupling expansions: these give us useful qualitative information, but unfortunately no hard numbers. The lattice theory is amenable to numerical simulations by which one calculates the long distance properties of a strongly interacting theory from first principles. The observables are measured as a function of the bare coupling g and a gauge invariant cut-off approx. = 1/alpha, where alpha is the lattice spacing. The continuum (physical) behavior is recovered in the limit alpha yields 0, at which point the lattice artifacts go to zero. This is the more powerful use of lattice formulation, so in these lectures the author focuses on setting up the theory for the purpose of numerical simulations to get hard numbers. The numerical techniques used in Lattice Gauge Theories have their roots in statistical mechanics, so it is important to develop an intuition for the interconnection between quantum mechanics and statistical mechanics.

  14. Branes and integrable lattice models

    CERN Document Server

    Yagi, Junya

    2016-01-01

    This is a brief review of my work on the correspondence between four-dimensional $\\mathcal{N} = 1$ supersymmetric field theories realized by brane tilings and two-dimensional integrable lattice models. I explain how to construct integrable lattice models from extended operators in partially topological quantum field theories, and elucidate the correspondence as an application of this construction.

  15. Charmed baryons on the lattice

    CERN Document Server

    Padmanath, M

    2015-01-01

    We discuss the significance of charm baryon spectroscopy in hadron physics and review the recent developments of the spectra of charmed baryons in lattice calculations. Special emphasis is given on the recent studies of highly excited charm baryon states. Recent precision lattice measurements of the low lying charm and bottom baryons are also reviewed.

  16. Computation of the lattice Green function for a dislocation

    Science.gov (United States)

    Tan, Anne Marie Z.; Trinkle, Dallas R.

    2016-08-01

    Modeling isolated dislocations is challenging due to their long-ranged strain fields. Flexible boundary condition methods capture the correct long-range strain field of a defect by coupling the defect core to an infinite harmonic bulk through the lattice Green function (LGF). To improve the accuracy and efficiency of flexible boundary condition methods, we develop a numerical method to compute the LGF specifically for a dislocation geometry; in contrast to previous methods, where the LGF was computed for the perfect bulk as an approximation for the dislocation. Our approach directly accounts for the topology of a dislocation, and the errors in the LGF computation converge rapidly for edge dislocations in a simple cubic model system as well as in BCC Fe with an empirical potential. When used within the flexible boundary condition approach, the dislocation LGF relaxes dislocation core geometries in fewer iterations than when the perfect bulk LGF is used as an approximation for the dislocation, making a flexible boundary condition approach more efficient.

  17. Embedded-atom-method interatomic potentials from lattice inversion.

    Science.gov (United States)

    Yuan, Xiao-Jian; Chen, Nan-Xian; Shen, Jiang; Hu, Wangyu

    2010-09-22

    The present work develops a physically reliable procedure for building the embedded-atom-method (EAM) interatomic potentials for the metals with fcc, bcc and hcp structures. This is mainly based on Chen-Möbius lattice inversion (Chen et al 1997 Phys. Rev. E 55 R5) and first-principles calculations. Following Baskes (Baskes et al 2007 Phys. Rev. B 75 094113), this new version of the EAM eliminates all of the prior arbitrary choices in the determination of the atomic electron density and pair potential functions. Parameterizing the universal form deduced from the calculations within the density-functional scheme for homogeneous electron gas as the embedding function, the new-type EAM potentials for Cu, Fe and Ti metals have successfully been constructed by considering interatomic interactions up to the fifth neighbor, the third neighbor and the seventh neighbor, respectively. The predictions of elastic constants, structural energy difference, vacancy formation energy and migration energy, activation energy of vacancy diffusion, latent heat of melting and relative volume change on melting all satisfactorily agree with the experimental results available or first-principles calculations. The predicted surface energies for low-index crystal faces and the melting point are in agreement with the experimental data to the same extent as those calculated by other EAM-type potentials such as the FBD-EAM, 2NN MEAM and MS-EAM. In addition, the order among the predicted low-index surface energies is also consistent with the experimental information.

  18. Lattice quantum chromodynamics practical essentials

    CERN Document Server

    Knechtli, Francesco; Peardon, Michael

    2017-01-01

    This book provides an overview of the techniques central to lattice quantum chromodynamics, including modern developments. The book has four chapters. The first chapter explains the formulation of quarks and gluons on a Euclidean lattice. The second chapter introduces Monte Carlo methods and details the numerical algorithms to simulate lattice gauge fields. Chapter three explains the mathematical and numerical techniques needed to study quark fields and the computation of quark propagators. The fourth chapter is devoted to the physical observables constructed from lattice fields and explains how to measure them in simulations. The book is aimed at enabling graduate students who are new to the field to carry out explicitly the first steps and prepare them for research in lattice QCD.

  19. Lattice Induced Transparency in Metasurfaces

    CERN Document Server

    Manjappa, Manukumara; Singh, Ranjan

    2016-01-01

    Lattice modes are intrinsic to the periodic structures and their occurrence can be easily tuned and controlled by changing the lattice constant of the structural array. Previous studies have revealed excitation of sharp absorption resonances due to lattice mode coupling with the plasmonic resonances. Here, we report the first experimental observation of a lattice induced transparency (LIT) by coupling the first order lattice mode (FOLM) to the structural resonance of a metamaterial resonator at terahertz frequencies. The observed sharp transparency is a result of the destructive interference between the bright mode and the FOLM mediated dark mode. As the FOLM is swept across the metamaterial resonance, the transparency band undergoes large change in its bandwidth and resonance position. Besides controlling the transparency behaviour, LIT also shows a huge enhancement in the Q-factor and record high group delay of 28 ps, which could be pivotal in ultrasensitive sensing and slow light device applications.

  20. 基于概念格的K-Means算法研究%Research on K-Means algorithm based on concept lattice

    Institute of Scientific and Technical Information of China (English)

    李艳霞; 史一民; 李冠宇

    2011-01-01

    Aiming at the problems of the existing K-Means algorithm, such as artificial assignation of number of final clustering, random selection of initial centers, high dimension and lack of semantic information in text representation, a new K-Means algorithm called KMeansBCC is proposed. Firstly, concept lattice is generated on the basis of formal context to which texts are converted by pre-process,then K-MeansBCC expresses texts using the concepts in concept lattice, and determines K values and initial centers according to the weight of concepts, finally the formula of concept similarity between texts is designed, and clustering result by K-Means algorithm is generated. The experimental result show that this algorithm improves the efficiency and accuracy of the clustering.%针对现有的K-Means算法K值需要人工赋值、随机选取初始中心点、文本表示维度高且缺乏语义的缺陷,提出了一种基于概念格的K-Means算法--K-MeansBCC(K-means algorithm based on concept lattice).将文本集经预处理转化为形式背景,在此基础上生成概念格;利用概念格中的概念表示文本,根据文本中概念的权重确定K值、选取初始中心点.最后设计了文本间的概念相似度计算公式,并由K-Means算法产生聚类结果.实验结果表明,该算法提高了聚类的效率和准确性.

  1. Basal Cell Carcinoma on the Pubic Area: Report of a Case and Review of 19 Korean Cases of BCC from Non-sun-exposed Areas.

    Science.gov (United States)

    Park, Jin; Cho, Yong-Sun; Song, Ki-Hun; Lee, Jong-Sun; Yun, Seok-Kweon; Kim, Han-Uk

    2011-08-01

    Basal cell carcinoma (BCC) is one of the most commonly diagnosed malignant skin tumors and develops characteristically on sun-exposed areas, such as the head and neck. Ultraviolet light exposure is an important etiologic factor in BCCs, and BCCs arising from non-sun- exposed areas are, therefore, very rare. In particular, the axilla, nipple, the genital and perianal areas are not likely to be exposed to ultraviolet light; thus, if BCC develops in these areas, other predisposing factors should be considered. Herein, we report a case of BCC arising on the pubic area in a 70-year-old man. We also performed a survey of the literature and discussed the 19 cases of BCC from non-sun-exposed areas reported to date in Korea.

  2. A unified relation for the solid-liquid interface free energy of pure FCC, BCC, and HCP metals

    Science.gov (United States)

    Wilson, S. R.; Mendelev, M. I.

    2016-04-01

    We study correlations between the solid-liquid interface (SLI) free energy and bulk material properties (melting temperature, latent heat, and liquid structure) through the determination of SLI free energies for bcc and hcp metals from molecular dynamics (MD) simulation. Values obtained for the bcc metals in this study were compared to values predicted by the Turnbull, Laird, and Ewing relations on the basis of previously published MD simulation data. We found that of these three empirical relations, the Ewing relation better describes the MD simulation data. Moreover, whereas the original Ewing relation contains two constants for a particular crystal structure, we found that the first coefficient in the Ewing relation does not depend on crystal structure, taking a common value for all three phases, at least for the class of the systems described by embedded-atom method potentials (which are considered to provide a reasonable approximation for metals).

  3. The influence of the excitation pulse shape on the stress wave propagation in a bcc iron crystal

    Directory of Open Access Journals (Sweden)

    Červená O.

    2008-12-01

    Full Text Available This article presents a large-scale molecular dynamic simulations of wave propagation in a cracked bcc (body centered cubic iron crystal based on an N-body potential model which gives a good description of an anisotropic elasticity. The crystal is loaded by a stress pulse on its front face and the response is detected on its opposite face. The various shapes, amplitudes, and widths of stress pulse are considered. The simulations are performed also for a central pre-existing Griffith crack. The crack is embedded in a bcc iron crystal having a basic cubic orientation. The acquired results bring important information for further analysis oriented to new NDT nanoscale methods.

  4. A unified relation for the solid-liquid interface free energy of pure FCC, BCC, and HCP metals.

    Science.gov (United States)

    Wilson, S R; Mendelev, M I

    2016-04-14

    We study correlations between the solid-liquid interface (SLI) free energy and bulk material properties (melting temperature, latent heat, and liquid structure) through the determination of SLI free energies for bcc and hcp metals from molecular dynamics (MD) simulation. Values obtained for the bcc metals in this study were compared to values predicted by the Turnbull, Laird, and Ewing relations on the basis of previously published MD simulation data. We found that of these three empirical relations, the Ewing relation better describes the MD simulation data. Moreover, whereas the original Ewing relation contains two constants for a particular crystal structure, we found that the first coefficient in the Ewing relation does not depend on crystal structure, taking a common value for all three phases, at least for the class of the systems described by embedded-atom method potentials (which are considered to provide a reasonable approximation for metals).

  5. Observation of quasi-fast diffusion process in sup 3 He- sup 4 He solid solutions near BCC-HCP

    CERN Document Server

    Mikhin, N P; Rudavskij, E Y

    2001-01-01

    By means of pulsed NMR one investigated into diffusion processes i sup 3 He dilute solid solution in sup 4 He at the BCC-HCP phase equilibrium line and in a melting-point curve. The applied techniques of the spin echo enabled to separate contributions made by all co-existing phases. It is determined that alongside with the contributions relevant to the equilibrium phases a secondary diffusion process characterized by anomalously high value of the diffusion coefficient manifests itself. It is shown to be close to the value of diffusion coefficient for liquid helium while diffusion is a spatially restricted one. One assumes that the observed effect may be associated with occurrence of liquid drops in the BCC-HCP transition process

  6. Lattice topology dictates photon statistics

    CERN Document Server

    Kondakci, H Esat; Saleh, Bahaa E A

    2016-01-01

    Propagation of coherent light through a disordered network is accompanied by randomization and possible conversion into thermal light. Here, we show that network topology plays a decisive role in determining the statistics of the emerging field if the underlying lattice satisfies chiral symmetry. By examining one-dimensional arrays of randomly coupled waveguides arranged on linear and ring topologies, we are led to a remarkable prediction: the field circularity and the photon statistics in ring lattices are dictated by its parity -- whether the number of sites is even or odd, while the same quantities are insensitive to the parity of a linear lattice. Adding or subtracting a single lattice site can switch the photon statistics from super-thermal to sub-thermal, or vice versa. This behavior is understood by examining the real and imaginary fields on a chiral-symmetric lattice, which form two strands that interleave along the lattice sites. These strands can be fully braided around an even-sited ring lattice th...

  7. Torrubiellone E, an antimalarial N-hydroxypyridone alkaloid from the spider pathogenic fungus Torrubiella longissima BCC 2022.

    Science.gov (United States)

    Isaka, Masahiko; Haritakun, Rachada; Intereya, Kamolphan; Thanakitpipattana, Donnaya; Hywel-Jones, Nigel L

    2014-05-01

    Torrubiellone E (1), a new N-hydroxypyridone alkaloid, was isolated from the spider pathogenic fungus Torrubiella longissima BCC 2022, together with the known compounds, torrubiellones A (2) and B (3), and JBIR-130 (4). Compound 1 exhibited antimalarial activity against Plasmodium falciparum K1 with an IC5 value of 3.2 microg/mL, while it also showed weak cytotoxic activities.

  8. Spheroidization behavior of dendritic b.c.c. phase in Zr-based モ-phase composite

    Directory of Open Access Journals (Sweden)

    Sun Guoyuan

    2013-03-01

    Full Text Available The spheroidization behavior of the dendritic b.c.c. phase dispersed in a bulk metallic glass (BMG matrix was investigated through applying semi-solid isothermal processing and a subsequent rapid quenching procedure to a Zr-based モ-phase composite. The Zr-based composite with the composition of Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 was prefabricated by a water-cooled copper mold-casting method and characterized by X-ray diffraction (XRD and scanning electron microscope (SEM. The results show that the composite consists of a glassy matrix and uniformly distributed fine dendrites of the モ-Zr solid solution with the body-centered-cubic (b.c.c. structure. Based on the differential scanning calorimeter (DSC examination results, and in view of the b.c.c. モ-Zr to h.c.p. メ-Zr phase transition temperature, a semi-solid holding temperature of 900 ìC was determined. After reheating the prefabricated composite to the semi-solid temperature, followed by an isothermal holding process at this temperature for 5 min, and then quenching the semi-solid mixture into iced-water; the two-phase microstructure composed of a BMG matrix and uniformly dispersed spherical b.c.c. モ-Zr particles with a high degree of sphericity was achieved. The present spheroidization transition is a thermodynamically autonomic behavior, and essentially a diffusion process controlled by kinetic factors; and the formation of the BMG matrix should be attributed to the rapid quenching of the semi-solid mixture as well as the large glass-forming ability of the remaining melt in the semi-solid mixture.

  9. Isolation and Characterization of a Hybrid Respiratory Supercomplex Consisting of Mycobacterium tuberculosis Cytochrome bcc and Mycobacterium smegmatis Cytochrome aa 3 *

    OpenAIRE

    Kim, Mi-Sun; Jang, Jichan; AB Rahman, Nurlilah Binte; Pethe, Kevin; Berry, Edward A.; Huang, Li-Shar

    2015-01-01

    Recently, energy production pathways have been shown to be viable antitubercular drug targets to combat multidrug-resistant tuberculosis and eliminate pathogen in the dormant state. One family of drugs currently under development, the imidazo[1,2-a]pyridine derivatives, is believed to target the pathogen's homolog of the mitochondrial bc 1 complex. This complex, denoted cytochrome bcc, is highly divergent from mitochondrial Complex III both in subunit structure and inhibitor sensitivity, maki...

  10. The fcc-bcc crystallographic orientation relationship in AlxCoCrFeNi high-entropy alloys

    NARCIS (Netherlands)

    Rao, J. C.; Ocelik, V.; Vainchtein, D.; Tang, Z.; Liaw, P. K.; De Hosson, J. Th. M.

    2016-01-01

    This paper concentrates on the crystallographic-orientation relationship between the various phases in the Al-Co-Cr-Fe-Ni high-entropy alloys. Two types of orientation relationships of bcc phases (some with ordered B2 structures) and fcc matrix were observed in Al0.5CoCrFeNi and Al0.7CoCrFeNi alloys

  11. Evaluation of the summer precipitation over China simulated by BCC_CSM model with different horizontal resolutions during the recent half century

    Science.gov (United States)

    Kan, Mengyun; Huang, Anning; Zhao, Yong; Zhou, Yang; Yang, Ben; Wu, Haomin

    2015-05-01

    The performance of Beijing Climate Center climate system model with different horizontal resolutions (BCC_CSM1.1 with coarse resolution and BCC_CSM1.1 m with fine resolution) in simulating the summer precipitation over China during the recent half century is evaluated, and the possible underlying physical mechanisms related to the model biases are also further analyzed and discussed. Results show that increasing horizontal resolution does improve the summer precipitation simulation over most part of China especially in western China due to the more realistic description of the topography. However, the summer precipitation amount (PA) over eastern China characterized by monsoonal climates is much more underestimated in the finer resolution model. It is also noted that the improvement (deterioration) of the summer PA over western (eastern) China in BCC_CSM1.1 m model is mainly due to the better (worse) simulation of the moderate and heavy precipitation relative to BCC_CSM1.1 model. In addition, increasing model horizontal resolution can significantly improve the convective precipitation simulation especially over western China but shows very limited improvement in the large-scale precipitation simulation. The much more underestimated summer PA over eastern China in BCC_CSM1.1 m model relative to BCC_CSM1.1 model is due to the significantly reduced positive biases of the convective PA but few changes in the negative biases of the large-scale PA. Further mechanism analysis suggests that both the underestimated land-sea thermal contrast and the overestimated Western Pacific subtropical high result in much less northeastward water vapor transport and summer PA over eastern China in BCC_CSM1.1 m model than in BCC_CSM1.1 model.

  12. Lattice sums then and now

    CERN Document Server

    Borwein, J M; McPhedran, R C

    2013-01-01

    The study of lattice sums began when early investigators wanted to go from mechanical properties of crystals to the properties of the atoms and ions from which they were built (the literature of Madelung's constant). A parallel literature was built around the optical properties of regular lattices of atoms (initiated by Lord Rayleigh, Lorentz and Lorenz). For over a century many famous scientists and mathematicians have delved into the properties of lattices, sometimes unwittingly duplicating the work of their predecessors. Here, at last, is a comprehensive overview of the substantial body of

  13. Lattice Boltzmann model for nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Xuan Yimin; Yao Zhengping [Nanjing University of Science and Technology, School of Power Engineering, Nanjing (China)

    2005-01-01

    A nanofluid is a particle suspension that consists of base liquids and nanoparticles and has great potential for heat transfer enhancement. By accounting for the external and internal forces acting on the suspended nanoparticles and interactions among the nanoparticles and fluid particles, a lattice Boltzmann model is proposed for simulating flow and energy transport processes inside the nanofluids. First, we briefly introduce the conventional lattice Boltzmann model for multicomponent systems. Then, we discuss the irregular motion of the nanoparticles and inherent dynamic behavior of nanofluids and describe a lattice Boltzmann model for simulating nanofluids. Finally, we conduct some calculations for the distribution of the suspended nanoparticles. (orig.)

  14. Localized structures in Kagome lattices

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, Avadh B [Los Alamos National Laboratory; Bishop, Alan R [Los Alamos National Laboratory; Law, K J H [UNIV OF MASSACHUSETTS; Kevrekidis, P G [UNIV OF MASSACHUSETTS

    2009-01-01

    We investigate the existence and stability of gap vortices and multi-pole gap solitons in a Kagome lattice with a defocusing nonlinearity both in a discrete case and in a continuum one with periodic external modulation. In particular, predictions are made based on expansion around a simple and analytically tractable anti-continuum (zero coupling) limit. These predictions are then confirmed for a continuum model of an optically-induced Kagome lattice in a photorefractive crystal obtained by a continuous transformation of a honeycomb lattice.

  15. Lattice Trace Operators

    Directory of Open Access Journals (Sweden)

    Brian Jefferies

    2014-01-01

    Full Text Available A bounded linear operator T on a Hilbert space ℋ is trace class if its singular values are summable. The trace class operators on ℋ form an operator ideal and in the case that ℋ is finite-dimensional, the trace tr(T of T is given by ∑jajj for any matrix representation {aij} of T. In applications of trace class operators to scattering theory and representation theory, the subject is complicated by the fact that if k is an integral kernel of the operator T on the Hilbert space L2(μ with μ a σ-finite measure, then k(x,x may not be defined, because the diagonal {(x,x} may be a set of (μ⊗μ-measure zero. The present note describes a class of linear operators acting on a Banach function space X which forms a lattice ideal of operators on X, rather than an operator ideal, but coincides with the collection of hermitian positive trace class operators in the case of X=L2(μ.

  16. LED体三维显示BCC采样体素化%BCC Sampling Voxelization in LED 3D Display

    Institute of Scientific and Technical Information of China (English)

    林品武; 孔凡国; 魏盼盼

    2014-01-01

    In order to reduce the number of voxels and improve the accuracy in the LED 3D display ,BCC sampling methods is used . The"cow"model is taken as an example ,compared with the Cartesian sampling ,BCC sampling with the same number of samples reduces the voxels by 27 .6% .When the number of samples by BCC reduce to 70% of the Cartesian samples ,the voxels can be reduced by 43 .4% .%在L ED立方体三维显示中,为了减少体素量和提高精度,采用BCC栅格采样方法。以“牛”模型进行实验,对比笛卡尔采样, BCC采样在采样点数量相等的前提下体素量减少27.6%;将BCC栅格的采样点数量降低到笛卡尔栅格采样点数量的70%后, BCC采样得到的体素模型实际体素量要比笛卡尔采样得到的体素量减少43.4%。

  17. Adsorption, dissociation, penetration, and diffusion of N2 on and in bcc Fe: first-principles calculations.

    Science.gov (United States)

    Yeo, Sang Chul; Han, Sang Soo; Lee, Hyuck Mo

    2013-04-14

    We report first-principles calculations of adsorption, dissociation, penetration, and diffusion for the complete nitridation mechanism of nitrogen molecules on a pure Fe surface (bcc, ferrite phase). The mechanism of the definite reaction path was calculated by dividing the process into four steps. We investigated various reaction paths for each step including the energy barrier based on the climb image nudged elastic band (CI-NEB) method, and the complete reaction pathway was computed as the minimum energy path (MEP). The adsorption characteristics of nitrogen (N) and molecular nitrogen (N2) indicate that nitrogen atoms and molecules are energetically favorable at the hollow sites on pure Fe(100) and (110). The dissociation of the nitrogen molecule (N2) was theoretically supported by electronic structure calculations. The penetration of nitrogen from the surface to the sub-surface has a large energy barrier compared with the other steps. The activation energy calculated for nitrogen diffusion in pure bcc Fe was in good agreement with the experimental results. Finally, we confirmed the rate-determining step for the full nitridation reaction pathway. This study provides fundamental insight into the nitridation mechanism for nitrogen molecules in pure bcc Fe.

  18. Grain Size Dependence of Uniform Elongation in Single-Phase FCC/BCC Metals

    Science.gov (United States)

    Liu, Haiting; Shen, Yao; Ma, Jiawei; Zheng, Pengfei; Zhang, Lei

    2016-09-01

    We studied the dependence of uniform elongation on grain size in the range of submicron to millimeter for single-phase FCC/BCC metals by reviewing recent experimental results and applying crystal plasticity finite element method simulation. In the order of increasing grain size, uniform elongation can be divided into three stages, namely low elongation stage, nearly constant elongation stage, and decreased elongation with large scatters stage. Low elongation stage features a dramatic increase near the critical grain size at the end of the stage, which is primarily attributed to the emergence of dislocation cell size transition from ultrafine to mid-size grain. Other factors can be neglected due to their negligible influence on overall variation trend. In nearly constant elongation stage, uniform elongation remains unchanged at a high level in general. As grain size keeps growing, uniform elongation starts decreasing and becomes scattered upon a certain grain size, indicating the initiation of decreased elongation with large scatters stage. It is shown that the increase is not linear or smooth but rather sharp at the end of low elongation stage, leading to a wider range in nearly constant elongation stage. The grain size dependence of uniform elongation can serve as a guiding principle for designing small uniaxial tensile specimens for mechanical testing, where size effect matters in most cases.

  19. Paramagnetic atom number and paramagnetic critical pressure of the sc, bcc and fcc Ising nanolattices

    Science.gov (United States)

    Şarlı, Numan

    2015-01-01

    The effects of the magnetic atom number in the unit volume on the magnetic properties are investigated by using sc (n=8), bcc (n=9) and fcc (n=14) Ising NLs within the effective field theory with correlations. We find that the magnetic properties expand as the magnetic atom number increases in the unit volume and this expanding constitutes an elliptical path at TC. The effect of the magnetic atom number (n) in the unit volume on the magnetic properties (mp) appear as nscconstant is directly proportional with the atom number in the unit volume (C α n). Hence, by using the slopes of the paramagnetic hysteresis curves of any nanosystem, it can be predicted that the number of particles in its unit volume. Moreover, the magnetic atoms in the paramagnetic region can be considered as particles in the gas. Because of the absence of an external magnetic field, the spin orientations of these atoms are random and free to rotate. Hence, they act on individually with no mutual interaction between two nearest-neighbor magnetic atoms. Therefore, we use the statistical mechanics form of the ideal gas law in the paramagnetic region and we obtain the critical paramagnetic pressure (PC=npkBTC) of the Ising NLs at TC. We define the paramagnetic magnetic atom number in the unit volume as np=n(1-M(T)).

  20. Crystallization and preliminary crystallographic analysis of histamine dehydrogenase from Natrinema gari BCC 24369.

    Science.gov (United States)

    Zhou, Dongwen; Visessanguan, Wonnop; Chaikaew, Siriporn; Benjakul, Soottawat; Oda, Kohei; Wlodawer, Alexander

    2014-07-01

    Histamine dehydrogenase (HADH) catalyzes the oxidative deamination of histamine, resulting in the production of imidazole acetaldehyde and an ammonium ion. The enzyme isolated from the newly identified halophilic archaeon Natrinema gari BCC 24369 is significantly different from the previously described protein from Nocardioides simplex. This newly identified HADH comprises three subunits with molecular weights of 49.0, 24.7 and 23.9 kDa, respectively, and is optimally active under high-salt conditions (3.5-5 M NaCl). As a step in the exploration of the unique properties of the protein, the HADH heterotrimer was purified and crystallized. Crystals were obtained using the sitting-drop vapor-diffusion method from a solution composed of 0.2 M calcium chloride dihydrate, 0.1 M HEPES pH 7.5, 28% PEG 400. Diffraction data were collected at -173°C to a resolution limit of 2.4 Å on the Southeast Regional Collaborative Access Team (SER-CAT) beamline 22-ID at the Advanced Photon Source, Argonne National Laboratory. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a=211.9, b=58.6, c=135.4 Å, β=103.0°. The estimated Matthews coefficient is 3.21 Å3 Da(-1), corresponding to 61.7% solvent content.

  1. Heats of Segregation of BCC Metals Using Ab Initio and Quantum Approximate Methods

    Science.gov (United States)

    Good, Brian; Chaka, Anne; Bozzolo, Guillermo

    2003-01-01

    Many multicomponent alloys exhibit surface segregation, in which the composition at or near a surface may be substantially different from that of the bulk. A number of phenomenological explanations for this tendency have been suggested, involving, among other things, differences among the components' surface energies, molar volumes, and heats of solution. From a theoretical standpoint, the complexity of the problem has precluded a simple, unified explanation, thus preventing the development of computational tools that would enable the identification of the driving mechanisms for segregation. In that context, we investigate the problem of surface segregation in a variety of bcc metal alloys by computing dilute-limit heats of segregation using both the quantum-approximate energy method of Bozzolo, Ferrante and Smith (BFS), and all-electron density functional theory. In addition, the composition dependence of the heats of segregation is investigated using a BFS-based Monte Carlo procedure, and, for selected cases of interest, density functional calculations. Results are discussed in the context of a simple picture that describes segregation behavior as the result of a competition between size mismatch and alloying effects

  2. STUDY OF TEXTURE EFFECT ON STRAIN LOCALIZATION OF BCC STEEL SHEETS

    Institute of Scientific and Technical Information of China (English)

    Xie Chunlei; Eiji Nakamachi; Dong Xianghuai

    2000-01-01

    Using elastic crystalline viscoplastic finite element (FE) annlysis, the formability of BCC steel sheets was assessed. An orientation probability assignment method in the FE modeling procedure, which can be categorized as an inhomogenized material modeling, was newly proposed. In the study, the crystal orientations of three materials, mild steel, dual phase steel and the high strength steel, were obtained by X ray diffraction and orientation distribution function (ODF) analyses. The measured ODF results have revealed clearly different textures in the sheets, featured by orientation fibers, skeleton lines and selected orientations in Euler angle space, which are closely related to the plastic anisotropy. Then, the crystal orientations were assigned to FE integration points by using this ODF data, individually. The FE analyses of the standard lim iting dome height(LDH) test show how the fiber textures affect the extent of strain localization in the forming processes. It was confirmed by comparison with experimental results that this FE code could predict the ex treme strain localization and assess the sheet formability.

  3. Higher-order elastic constants and megabar pressure effects of bcc tungsten: Ab initio calculations

    Science.gov (United States)

    Vekilov, Yu. Kh.; Krasilnikov, O. M.; Lugovskoy, A. V.; Lozovik, Yu. E.

    2016-09-01

    The general method for the calculation of n th (n ≥2 ) order elastic constants of the loaded crystal is given in the framework of the nonlinear elasticity theory. For the crystals of cubic symmetry under hydrostatic compression, the two schemes of calculation of the elastic constants of second, third, and fourth order from energy-finite strain relations and stress-finite strain relations are implemented. Both techniques are applied for the calculation of elastic constants of orders from second to fourth to the bcc phase of tungsten at a 0-600 GPa pressure range. The energy and stress at the various pressures and deformations are obtained ab initio in the framework of projector augmented wave+generalized gradient approximation (PAW+GGA) method, as implemented in Vienna Ab initio Simulation Package (VASP) code. Using the obtained results, we found the pressure dependence of Grüneisen parameters for long-wave acoustic modes in this interval. The Lamé constants of second and third order were estimated for polycrystalline tungsten. The proposed method is applicable for crystals with arbitrary symmetry.

  4. AB INITIO CALCULATIONS OF ELASTIC CONSTANTS OF BCC V-NB SYSTEM AT HIGH PRESSURES

    Energy Technology Data Exchange (ETDEWEB)

    Landa, A; Klepeis, J; Soderlind, P; Naumov, I; Velikokhatnyi, O; Vitos, L; Ruban, A

    2005-05-02

    First-principles total energy calculation based on the exact muffin-tin orbital and full potential linear muffin-tin orbital methods were used to calculate the equation of state and shear elastic constants of bcc V, Nb, and the V{sub 95}Nb{sub 05} disordered alloy as a function of pressure up to 6 Mbar. We found a mechanical instability in C{sub 44} and a corresponding softening in C at pressures {approx} 2 Mbar for V. Both shear elastic constants show softening at pressures {approx} 0.5 Mbar for Nb. Substitution of 5 at. % of V with Nb removes the instability of V with respect to trigonal distortions in the vicinity of 2 Mbar pressure, but still leaves the softening of C{sub 44} in this pressure region. We argue that the pressure induced shear instability (softening) of V (Nb) originates from the electronic system and can be explained by a combination of the Fermi surface nesting, electronic topological transition, and band Jahn-Teller effect.

  5. Phonon spectrum and related thermodynamic properties of microcrack in bcc-Fe

    Institute of Scientific and Technical Information of China (English)

    Cao Li-Xia; Wang Chong-Yu

    2006-01-01

    The phonon spectrum and the related thermodynamic properties of microcracks in bcc-Fe are studied with the recursion method by using the Finnis-Sinclair (F-S) N-body potential. The initial configuration of the microcracks is established from an anisotropic linear elastic solution and relaxed to an equilibrium by molecular dynamics method.It is shown that the local vibrational density of states of the atoms near a crack tip is considerably different from the bulk phonon spectrum, which is closely associated with the local stress field around the crack tip; meanwhile, the local vibrational energies of atoms near the crack tip are higher than those of atoms in a perfect crystal. These results imply that the crack tip zone is in a complex stress state and closely related to the structure evolution of cracks. It is also found that the phonon excitation is a kind of local effect induced by microcracks. In addition, the microcrack system has a higher vibrational entropy, which reflects the character of phonon spectrum related to the stress field induced by cracks.

  6. Phonon spectrum and related thermodynamic properties of microcrack in bcc-Fe

    Science.gov (United States)

    Cao, Li-Xia; Wang, Chong-Yu

    2006-09-01

    The phonon spectrum and the related thermodynamic properties of microcracks in bcc-Fe are studied with the recursion method by using the Finnis-Sinclair (F-S) N-body potential. The initial configuration of the microcracks is established from an anisotropic linear elastic solution and relaxed to an equilibrium by molecular dynamics method. It is shown that the local vibrational density of states of the atoms near a crack tip is considerably different from the bulk phonon spectrum, which is closely associated with the local stress field around the crack tip; meanwhile, the local vibrational energies of atoms near the crack tip are higher than those of atoms in a perfect crystal. These results imply that the crack tip zone is in a complex stress state and closely related to the structure evolution of cracks. It is also found that the phonon excitation is a kind of local effect induced by microcracks. In addition, the microcrack system has a higher vibrational entropy, which reflects the character of phonon spectrum related to the stress field induced by cracks.

  7. The Snoek relaxation in bcc metals-From steel wire to meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Weller, M. [Max-Planck-Institut fuer Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart (Germany)]. E-mail: weller@mf.mpg.de

    2006-12-20

    Heavy interstitial atoms, such as O, N, or C, when dissolved in bcc metals (Fe, Nb, Ta, V), induce elastic dipoles with tetragonal symmetry. The stress induced reorientation produces anelastic relaxation and is the elementary step of interstitial diffusion. Mechanical loss spectra indicate the presence of interstitial atoms by Snoek peaks at distinct, characteristic temperatures. The magnitude of the peaks is proportional to the concentration of interstitial atoms in solution. The atomic model and theory of the Snoek relaxation for ideal interstitial solutions are presented. Experiments with single crystals allow determination of the tensor components of the dipoles. Measurements of the peak position over a wide range of frequencies (6 decades) allow determination of the interstitial diffusion coefficient as a function of temperature. Nonlinearitities in the Arrhenius plots are discussed. In concentrated alloys a broadening of the Snoek peaks is observed, which can be described by a random cooperative strain interaction (RCSI) model. Measurements of the Snoek peak height can be applied as a non-destructive analytical method. This is demonstrated for O-doped Nb wires with a wide range of concentrations (20 up to 10,000 at. ppm O) and for Ta and Nb single crystals doped with O and N. Finally various experimental studies of the carbon Snoek peak in iron are presented. These include measurements of a low carbon steel wire, a Fe-Ni meteorite, and a recently (April 2002) fallen meteorite named Neuschwanstein.

  8. Nuclear models on a lattice

    CERN Document Server

    De Soto, F; Carbonell, J; Leroy, J P; Pène, O; Roiesnel, C; Boucaud, Ph.

    2007-01-01

    We present the first results of a quantum field approach to nuclear models obtained by lattice techniques. Renormalization effects for fermion mass and coupling constant in case of scalar and pseudoscalar interaction lagrangian densities are discussed.

  9. Areas on a Square Lattice

    Science.gov (United States)

    Wilby, Brian

    1974-01-01

    As an alternative to the usual method of counting squares to find the area of a plane shape, a method of counting lattice points (determined by vertices of a unit square) is proposed. Activities using this method are suggested. (DT)

  10. Lattice Studies of Hyperon Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Richards, David G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-04-01

    I describe recent progress at studying the spectrum of hadrons containing the strange quark through lattice QCD calculations. I emphasise in particular the richness of the spectrum revealed by lattice studies, with a spectrum of states at least as rich as that of the quark model. I conclude by prospects for future calculations, including in particular the determination of the decay amplitudes for the excited states.

  11. Berry phase in lattice QCD

    CERN Document Server

    Yamamoto, Arata

    2016-01-01

    We propose the lattice QCD calculation of the Berry phase which is defined by the ground state of a single fermion. We perform the ground-state projection of a single-fermion propagator, construct the Berry link variable on a momentum-space lattice, and calculate the Berry phase. As the first application, the first Chern number of the (2+1)-dimensional Wilson fermion is calculated by the Monte Carlo simulation.

  12. Multifractal behaviour of -simplex lattic

    Indian Academy of Sciences (India)

    Sanjay Kumar; Debaprasad Giri; Sujata Krishna

    2000-06-01

    We study the asymptotic behaviour of resistance scaling and fluctuation of resistance that give rise to flicker noise in an -simplex lattice. We propose a simple method to calculate the resistance scaling and give a closed-form formula to calculate the exponent, , associated with resistance scaling, for any . Using current cumulant method we calculate the exact noise exponent for -simplex lattices.

  13. Lattice gauge theory for QCD

    Energy Technology Data Exchange (ETDEWEB)

    DeGrand, T. [Univ. of Colorado, Boulder, CO (United States). Dept. of Physics

    1997-06-01

    These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and {alpha}{sub s} (M{sub z}), and B-{anti B} mixing. 67 refs., 36 figs.

  14. Transport in Sawtooth photonic lattices

    CERN Document Server

    Weimann, Steffen; Real, Bastián; Cantillano, Camilo; Szameit, Alexander; Vicencio, Rodrigo A

    2016-01-01

    We investigate, theoretically and experimentally, a photonic realization of a Sawtooth lattice. This special lattice exhibits two spectral bands, with one of them experiencing a complete collapse to a highly degenerate flat band for a special set of inter-site coupling constants. We report the ob- servation of different transport regimes, including strong transport inhibition due to the appearance of the non-diffractive flat band. Moreover, we excite localized Shockley surfaces states, residing in the gap between the two linear bands.

  15. Lattice QCD: A Brief Introduction

    Science.gov (United States)

    Meyer, H. B.

    A general introduction to lattice QCD is given. The reader is assumed to have some basic familiarity with the path integral representation of quantum field theory. Emphasis is placed on showing that the lattice regularization provides a robust conceptual and computational framework within quantum field theory. The goal is to provide a useful overview, with many references pointing to the following chapters and to freely available lecture series for more in-depth treatments of specifics topics.

  16. Advances in Lattice Quantum Chromodynamics

    Science.gov (United States)

    McGlynn, Greg

    In this thesis we make four contributions to the state of the art in numerical lattice simulations of quantum chromodynamics (QCD). First, we present the most detailed investigation yet of the autocorrelations of topological observations in hybrid Monte Carlo simulations of QCD and of the effects of the boundary conditions on these autocorrelations. This results in a numerical criterion for deciding when open boundary conditions are useful for reducing these autocorrelations, which are a major barrier to reliable calculations at fine lattice spacings. Second, we develop a dislocation-enhancing determinant, and demonstrate that it reduces the autocorrelation time of the topological charge. This alleviates problems with slow topological tunneling at fine lattice spacings, enabling simulations on fine lattices to be completed with much less computational effort. Third, we show how to apply the recently developed zMobius technique to hybrid Monte Carlo evolutions with domain wall fermions, achieving nearly a factor of two speedup in the light quark determinant, the single most expensive part of the calculation. The dislocation-enhancing determinant and the zMobius technique have enabled us to begin simulations of fine ensembles with four flavors of dynamical domain wall quarks. Finally, we show how to include the previously-neglected G1 operator in nonperturbative renormalization of the DeltaS = 1 effective weak Hamiltonian on the lattice. This removes an important systematic error in lattice calculations of weak matrix elements, in particular the important K → pipi decay.

  17. Optimal lattice-structured materials

    Science.gov (United States)

    Messner, Mark C.

    2016-11-01

    This work describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describing the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.

  18. First-principles study on the lattice stability of elemental Co, Rh, and Ir in the ⅧB group

    Institute of Scientific and Technical Information of China (English)

    TAO Huijin; YIN Jian; YIN Zhimin; ZHANG Chuangfu; LI Jie; HUANG Boyun

    2009-01-01

    Lattice constants, total energies, and densities of state of transition metals Co, Rh, and Ir in the VIIIB group with different crystalline structures were calculated via generalized gradient approximation (GGA) of the total energy plane wave pseudopotentiai method in first-principles. The lattice stabilities of Rh and Ir are △Gbcc-hcp △Gfcc-hcp 0, agreeing well with those of the projector augmented wave method in first-principles and the CALPHAD method in spite of elemental Co. Analyses of the electronic smlctures to lattice stability show that crystalline Rh and Ir with fcc structures have the obvious characteristic of a stable phase, agreeing with the results of total energy calculations. Analyses of atomic populations show that the transition rate of electrons from the s state to the p or d state for hop, fcc, and bcc crystals of Co and Rh increases with the elemental period number to form a stronger cohesion, a higher cohesive energy, or a more stable lattice between atoms in heavier metals.

  19. The cause of anomaly of temperature dependence of electroresistance of the ordering nonstoichiometric FeCo compounds based on a b.c.c. lattice

    Energy Technology Data Exchange (ETDEWEB)

    Repetsky, S.P. [Taras Shevchenko Kyiv National University, 2 Acad. Glushkov Prosp., 03022 Kyiv (Ukraine); Melnyk, I.M. [Taras Shevchenko Kyiv National University, 2 Acad. Glushkov Prosp., 03022 Kyiv (Ukraine)], E-mail: iramel@ukr.net; Tatarenko, V.A. [Taras Shevchenko Kyiv National University, 2 Acad. Glushkov Prosp., 03022 Kyiv (Ukraine); G.V. Kurdyumov Institute for Metal Physics, N.A.S.U., 36 Acad. Vernadsky Blvd., 03142 Kyiv (Ukraine); Len, E.G. [G.V. Kurdyumov Institute for Metal Physics, N.A.S.U., 36 Acad. Vernadsky Blvd., 03142 Kyiv (Ukraine); Vyshivanaya, I.G. [Taras Shevchenko Kyiv National University, 2 Acad. Glushkov Prosp., 03022 Kyiv (Ukraine)

    2009-07-01

    A theory of energy spectrum and electrical conductivity, which takes into account the electron scattering by the potentials of ions and fluctuations of both the spin and charge densities of electrons in disordered substitutional alloys, is developed. Calculations of temperature-concentration dependence of electrical resistance were performed for b.c.c.-Fe{sub 1-c}Co{sub c} alloys. The causes of weak temperature dependence of electrical resistance of the Fe-Co alloys are governed by the presence of a quasi-gap in the electron-energy spectrum, which appears due to strong electron correlations as well as atomic and magnetic orders.

  20. Extension to order $\\beta^{23}$ of the high-temperature expansions for the spin-1/2 Ising model on the simple-cubic and the body-centered-cubic lattices

    CERN Document Server

    Butera, P

    2000-01-01

    Using a renormalized linked-cluster-expansion method, we extend to order $\\beta^{23}$ the high-temperature series for the susceptibility $\\chi$ and the second-moment correlation length $\\xi$ of the spin-1/2 Ising models on the sc and the bcc lattices. A study of these expansions yields updated direct estimates of universal parameters, such as exponents and amplitude ratios, which characterize the critical behavior of $\\chi$ and $\\xi$. Our best estimates for the inverse critical temperatures are $\\beta^{sc}_c=0.221654(1)$ and $\\beta^{bcc}_c=0.1573725(6)$. For the susceptibility exponent we get $\\gamma=1.2375(6)$ and for the correlation length exponent $\

  1. A lexicographic shellability characterization of geometric lattices

    CERN Document Server

    Davidson, Ruth

    2011-01-01

    Geometric lattices are characterized as those finite, atomic lattices such that every atom ordering induces a lexicographic shelling given by an edge labeling known as a minimal labeling. This new characterization fits into a similar paradigm as McNamara's characterization of supersolvable lattices as those lattices admitting a different type of lexicographic shelling, namely one in which each maximal chain is labeled with a permutation of {1,...,n}. Geometric lattices arise as the intersection lattices of central hyperplane arrangements and more generally as the lattices of flats for matroids.

  2. Anisotropy and roughness of the solid-liquid interface of BCC Fe.

    Science.gov (United States)

    Sun, Yongli; Wu, Yongquan; Lu, Xiuming; Li, Rong; Xiao, Junjiang

    2015-02-01

    Melting point T m and kinetic coefficient μ (a proportional constant between the interfacial velocity ν and undercooling ΔT), along with the structural roughness of the solid-liquid interface for body centered cubic (BCC) Fe were calculated by molecular dynamics (MD) simulation. All simulations applied the Sutton-Chen potential, and adopted average bond orientational order (ABOO) parameters together with Voronoi polyhedron method to characterize atomic structure and calculate atomic volume. Anisotropy of T m was found through about 20~40 K decreasing from [100] to [110] and continuously to [111]. Anisotropy of μ with three low index orientations was found as: μ s,[100] > > μ s,[110] > μ s,[111] for solidifying process and μ m,[100] > > μ m,[111] > μ m,[110] for melting process. Slight asymmetry between melting and solidifying was discovered from that the ratios of μ m/μ s are all slightly larger than 1. To explain these, interfacial roughness R int and area ratio S/S 0 (ratio of realistic interfacial area S and the ideal flat cross-sectional area S 0) were defined to verify the anisotropy of interfacial roughness under different supercoolings/superheatings. The results indicated interfacial roughness anisotropies were approximately [100] > [111] > [110]; the interface in melting process is rougher than that in solidifying process; asymmetry of interfacial roughness was larger when temperature deviation ΔT was larger. Anisotropy and asymmetry of interfacial roughness fitted the case of kinetic coefficient μ very well, which could give some explanations to the anisotropies of T m and μ.

  3. Dissolving, trapping and detrapping mechanisms of hydrogen in bcc and fcc transition metals

    Directory of Open Access Journals (Sweden)

    Yu-Wei You

    2013-01-01

    Full Text Available First-principles calculations are performed to investigate the dissolving, trapping and detrapping of H in six bcc (V, Nb, Ta, Cr, Mo, W and six fcc (Ni, Pd, Pt, Cu, Ag, Au metals. We find that the zero-point vibrations do not change the site-preference order of H at interstitial sites in these metals except Pt. One vacancy could trap a maximum of 4 H atoms in Au and Pt, 6 H atoms in V, Nb, Ta, Cr, Ni, Pd, Cu and Ag, and 12 H atoms in Mo and W. The zero-point vibrations never change the maximum number of H atoms trapped in a single vacancy in these metals. By calculating the formation energy of vacancy-H (Vac-Hn complex, the superabundant vacancy in V, Nb, Ta, Pd and Ni is demonstrated to be much more easily formed than in the other metals, which has been found in many metals including Pd, Ni and Nb experimentally. Besides, we find that it is most energetically favorable to form Vac-H1 complex in Pt, Cu, Ag and Au, Vac-H4 in Cr, Mo and W, and Vac-H6 in V, Nb, Ta, Pd and Ni. At last, we examine the detrapping behaviors of H atoms in a single vacancy and find that with the heating rate of 10 K/min a vacancy could accommodate 4, 5 and 6 H atoms in Cr, Mo and W at room temperature, respectively. The detrapping temperatures of all H atoms in a single vacancy in V, Nb, Ta, Ni, Pd, Cu and Ag are below room temperature.

  4. Lattice dislocation in Si nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Omar, M.S., E-mail: dr_m_s_omar@yahoo.co [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq); Taha, H.T. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq)

    2009-12-15

    Modified formulas were used to calculate lattice thermal expansion, specific heat and Bulk modulus for Si nanowires with diameters of 115, 56, 37 and 22 nm. From these values and Gruneisen parameter taken from reference, mean lattice volumes were found to be as 20.03 A{sup 3} for the bulk and 23.63, 29.91, 34.69 and 40.46 A{sup 3} for Si nanowire diameters mentioned above, respectively. Their mean bonding length was calculated to be as 0.235 nm for the bulk and 0.248, 0.269, 0.282 and 0.297 nm for the nanowires diameter mentioned above, respectively. By dividing the nanowires diameter on the mean bonding length, number of layers per each nanowire size was found to be as 230, 104, 65 and 37 for the diameters mentioned above, respectively. Lattice dislocations in 22 nm diameter wire were found to be from 0.00324 nm for the 1st central lattice to 0.2579 nm for the last surface lattice. Such dislocation was smaller for larger wire diameters. Dislocation concentration found to change in Si nanowires according to the proportionalities of surface thickness to nanowire radius ratios.

  5. Hadron Structure on the Lattice

    Science.gov (United States)

    Can, K. U.; Kusno, A.; Mastropas, E. V.; Zanotti, J. M.

    The aim of these lectures will be to provide an introduction to some of the concepts needed to study the structure of hadrons on the lattice. Topics covered include the electromagnetic form factors of the nucleon and pion, the nucleon's axial charge and moments of parton and generalised parton distribution functions. These are placed in a phenomenological context by describing how they can lead to insights into the distribution of charge, spin and momentum amongst a hadron's partonic constituents. We discuss the techniques required for extracting the relevant matrix elements from lattice simulations and draw attention to potential sources of systematic error. Examples of recent lattice results are presented and are compared with results from both experiment and theoretical models.

  6. Nuclear Reactions from Lattice QCD

    CERN Document Server

    Briceño, Raúl A; Luu, Thomas C

    2014-01-01

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low- energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path ...

  7. Quantum Gravity on the Lattice

    CERN Document Server

    Hamber, Herbert W

    2009-01-01

    I review the lattice approach to quantum gravity, and how it relates to the non-trivial ultraviolet fixed point scenario of the continuum theory. After a brief introduction covering the general problem of ultraviolet divergences in gravity and other non-renormalizable theories, I cover the general methods and goals of the lattice approach. An underlying theme is an attempt at establishing connections between the continuum renormalization group results, which are mainly based on diagrammatic perturbation theory, and the recent lattice results, which should apply to the strong gravity regime and are inherently non-perturbative. A second theme in this review is the ever-present natural correspondence between infrared methods of strongly coupled non-abelian gauge theories on the one hand, and the low energy approach to quantum gravity based on the renormalization group and universality of critical behavior on the other. Towards the end of the review I discuss possible observational consequences of path integral q...

  8. Lattice QCD for nuclear physics

    CERN Document Server

    Meyer, Harvey

    2015-01-01

    With ever increasing computational resources and improvements in algorithms, new opportunities are emerging for lattice gauge theory to address key questions in strongly interacting systems, such as nuclear matter. Calculations today use dynamical gauge-field ensembles with degenerate light up/down quarks and the strange quark and it is possible now to consider including charm-quark degrees of freedom in the QCD vacuum. Pion masses and other sources of systematic error, such as finite-volume and discretization effects, are beginning to be quantified systematically. Altogether, an era of precision calculation has begun, and many new observables will be calculated at the new computational facilities.  The aim of this set of lectures is to provide graduate students with a grounding in the application of lattice gauge theory methods to strongly interacting systems, and in particular to nuclear physics.  A wide variety of topics are covered, including continuum field theory, lattice discretizations, hadron spect...

  9. Algebraic Lattices in QFT Renormalization

    Science.gov (United States)

    Borinsky, Michael

    2016-07-01

    The structure of overlapping subdivergences, which appear in the perturbative expansions of quantum field theory, is analyzed using algebraic lattice theory. It is shown that for specific QFTs the sets of subdivergences of Feynman diagrams form algebraic lattices. This class of QFTs includes the standard model. In kinematic renormalization schemes, in which tadpole diagrams vanish, these lattices are semimodular. This implies that the Hopf algebra of Feynman diagrams is graded by the coradical degree or equivalently that every maximal forest has the same length in the scope of BPHZ renormalization. As an application of this framework, a formula for the counter terms in zero-dimensional QFT is given together with some examples of the enumeration of primitive or skeleton diagrams.

  10. Flavor Physics and Lattice QCD

    CERN Document Server

    Bouchard, C M

    2013-01-01

    Our ability to resolve new physics effects is, largely, limited by the precision with which we calculate. The calculation of observables in the Standard (or a new physics) Model requires knowledge of associated hadronic contributions. The precision of such calculations, and therefore our ability to leverage experiment, is typically limited by hadronic uncertainties. The only first-principles method for calculating the nonperturbative, hadronic contributions is lattice QCD. Modern lattice calculations have controlled errors, are systematically improvable, and in some cases, are pushing the sub-percent level of precision. I outline the role played by, highlight state of the art efforts in, and discuss possible future directions of lattice calculations in flavor physics.

  11. A new parameterization for ice cloud optical properties used in BCC-RAD and its radiative impact

    Science.gov (United States)

    Zhang, Hua; Chen, Qi; Xie, Bing

    2015-01-01

    A new parameterization of the solar and infrared optical properties of ice clouds that considers the multiple habits of ice particles was developed on the basis of a prescribed dataset. First, the fitting formulae of the bulk extinction coefficient, single-scatter albedo, asymmetry factor, and δ-function forward-peak factor at the given 65 wavelengths as a function of effective radius were created for common scenarios, which consider a greater number of wavelengths and are more accurate than those used previously. Then, the band-averaged volume extinction and absorption coefficients, asymmetry factor and forward-peak factor of ice cloud were derived for the BCC-RAD (Beijing Climate Center radiative transfer model) using a parameter reference table. Finally, the newly developed and the original schemes in the BCC-RAD and the commonly used Fu Scheme of ice cloud were all applied to the BCC-RAD. Their influences on radiation calculations were compared using the mid-latitude summer atmospheric profile with ice clouds under no-aerosol conditions, and produced a maximum difference of approximately 30.0 W/m2 for the radiative flux, and 4.0 K/d for the heating rate. Additionally, a sensitivity test was performed to investigate the impact of the ice crystal density on radiation calculations using the three schemes. The results showed that the maximum difference was 68.1 W/m2 for the shortwave downward radiative flux (for the case of perpendicular solar insolation), and 4.2 K/d for the longwave heating rate, indicating that the ice crystal density exerts a significant effect on radiation calculations for a cloudy atmosphere.

  12. Nucleon structure from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Dinter, Simon

    2012-11-13

    In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.

  13. Residence in biofilms allows Burkholderia cepacia complex (Bcc) bacteria to evade the antimicrobial activities of neutrophil-like dHL60 cells.

    Science.gov (United States)

    Murphy, Mark P; Caraher, Emma

    2015-11-01

    Bacteria of the Burkholderia cepacia complex (Bcc) persist in the airways of people with cystic fibrosis (CF) despite the continuous recruitment of neutrophils. Most members of Bcc are multidrug resistant and can form biofilms. As such, we sought to investigate whether biofilm formation plays a role in protecting Bcc bacteria from neutrophils. Using the neutrophil-like, differentiated cell line, dHL60, we have shown for the first time that Bcc biofilms are enhanced in the presence of these cells. Biofilm biomass was greater following culture in the presence of dHL60 cells than in their absence, likely the result of incorporating dHL60 cellular debris into the biofilm. Moreover, we have demonstrated that mature biofilms (cultured for up to 72 h) induced necrosis in the cells. Established biofilms also acted as a barrier to the migration of the cells and masked the bacteria from being recognized by the cells; dHL60 cells expressed less IL-8 mRNA and secreted significantly less IL-8 when cultured in the presence of biofilms, with respect to planktonic bacteria. Our findings provide evidence that biofilm formation can, at least partly, enable the persistence of Bcc bacteria in the CF airway and emphasize a requirement for anti-biofilm therapeutics.

  14. Residence in biofilms allows Burkholderia cepacia complex (Bcc) bacteria to evade the antimicrobial activities of neutrophil-like dHL60 cells

    Science.gov (United States)

    Murphy, Mark P.; Caraher, Emma

    2015-01-01

    Bacteria of the Burkholderia cepacia complex (Bcc) persist in the airways of people with cystic fibrosis (CF) despite the continuous recruitment of neutrophils. Most members of Bcc are multidrug resistant and can form biofilms. As such, we sought to investigate whether biofilm formation plays a role in protecting Bcc bacteria from neutrophils. Using the neutrophil-like, differentiated cell line, dHL60, we have shown for the first time that Bcc biofilms are enhanced in the presence of these cells. Biofilm biomass was greater following culture in the presence of dHL60 cells than in their absence, likely the result of incorporating dHL60 cellular debris into the biofilm. Moreover, we have demonstrated that mature biofilms (cultured for up to 72 h) induced necrosis in the cells. Established biofilms also acted as a barrier to the migration of the cells and masked the bacteria from being recognized by the cells; dHL60 cells expressed less IL-8 mRNA and secreted significantly less IL-8 when cultured in the presence of biofilms, with respect to planktonic bacteria. Our findings provide evidence that biofilm formation can, at least partly, enable the persistence of Bcc bacteria in the CF airway and emphasize a requirement for anti-biofilm therapeutics. PMID:26371179

  15. Nuclear Physics from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    William Detmold, Silas Beane, Konstantinos Orginos, Martin Savage

    2011-01-01

    We review recent progress toward establishing lattice Quantum Chromodynamics as a predictive calculational framework for nuclear physics. A survey of the current techniques that are used to extract low-energy hadronic scattering amplitudes and interactions is followed by a review of recent two-body and few-body calculations by the NPLQCD collaboration and others. An outline of the nuclear physics that is expected to be accomplished with Lattice QCD in the next decade, along with estimates of the required computational resources, is presented.

  16. Lattices, graphs, and Conway mutation

    CERN Document Server

    Greene, Joshua Evan

    2011-01-01

    The d-invariant of an integral, positive definite lattice L records the minimal norm of a characteristic covector in each equivalence class mod 2L. We prove that the 2-isomorphism type of a connected graph is determined by the d-invariant of its lattice of integral cuts (or flows). As an application, we prove that a reduced, alternating link diagram is determined up to mutation by the Heegaard Floer homology of the link's branched double-cover. Thus, alternating links with homeomorphic branched double-covers are mutants.

  17. Chiral Fermions on the Lattice

    CERN Document Server

    Bietenholz, Wolfgang

    2010-01-01

    In the last century the non-perturbative regularization of chiral fermions was a long-standing problem. We review how this problem was finally overcome by the formulation of a modified but exact form of chiral symmetry on the lattice. This also provides a sound definition of the topological charge of lattice gauge configurations. We illustrate a variety of applications to QCD in the p-, the epsilon- and the delta-regime, where simulation results can now be related to Random Matrix Theory and Chiral Perturbation Theory. The latter contains Low Energy Constants as free parameters, and we comment on their evaluation from first principles of QCD.

  18. Unconventional superconductivity in honeycomb lattice

    Directory of Open Access Journals (Sweden)

    P Sahebsara

    2013-03-01

    Full Text Available   ‎ The possibility of symmetrical s-wave superconductivity in the honeycomb lattice is studied within a strongly correlated regime, using the Hubbard model. The superconducting order parameter is defined by introducing the Green function, which is obtained by calculating the density of the electrons ‎ . In this study showed that the superconducting order parameter appears in doping interval between 0 and 0.5, and x=0.25 is the optimum doping for the s-wave superconductivity in honeycomb lattice.

  19. Graphene on graphene antidot lattices

    DEFF Research Database (Denmark)

    Gregersen, Søren Schou; Pedersen, Jesper Goor; Power, Stephen

    2015-01-01

    Graphene bilayer systems are known to exhibit a band gap when the layer symmetry is broken by applying a perpendicular electric field. The resulting band structure resembles that of a conventional semiconductor with a parabolic dispersion. Here, we introduce a bilayer graphene heterostructure......, where single-layer graphene is placed on top of another layer of graphene with a regular lattice of antidots. We dub this class of graphene systems GOAL: graphene on graphene antidot lattice. By varying the structure geometry, band-structure engineering can be performed to obtain linearly dispersing...

  20. Aproximacion por simulacion ab-initio a la fragilizacion por hidrogeno en una red de hierro bcc

    OpenAIRE

    Sánchez, Javier; Andres, P.L. de; Fullea, J., Linares, P.,; Andrade, C

    2008-01-01

    La fragilización por hidrógeno es una de las causas más frecuentes de fallo en estructuras sometidas a esfuerzos mecánicos. Los aceros de alta resistencia empleados en estas estructuras se componen de una matriz ferrítica, o lo que es lo mismo, de una estructura de hierro cúbica centrada en el cuerpo (BCC). Utilizando cálculos mecano-cuánticos de primeros principios hemos estudiado la interacción del hidrógeno con la red cúbica centrada en el cuerpo del hierro. El hidrógeno intersticial ...

  1. A Study of Diffusivity in the BCC Solid Solution of Nb-Al and Nb-Ti-Al System

    Science.gov (United States)

    1990-01-01

    A STUDY OF DIFFUSIVITY IN THE BCC SOLID SOLUTION OF Nb-Al AND Nb-Ti-Al SYSTEM P DTIC ELECTE NOV 3o01993 A- J.BY JOSE GUADALUPE LUIS RUIZ APARICIO A...analysis was employed for the evaluation of composition profiles in all the diffusion couples. Tne interdiffusion coefficient for the 0 solid solution of Nb...system suggest that Ti is the fastest element in the J0 solid solution . Qualitatively the penetration tendencies correlate with the melting point of

  2. Vibrational properties of vacancy in bcc transition metals using embedded atom method potentials

    Indian Academy of Sciences (India)

    Vandana Gairola; P D Semalty; P N Ram

    2013-06-01

    The embedded atom method (EAM) potentials, with the universal form of the embedding function along with the Morse form of pair potential, have been employed to determine the potential parameters for three bcc transition metals: Fe, Mo, and W, by fitting to Cauchy pressure $(C_{12} − C_{44})/2$, shear constants $G_{v} = (C_{11} − C_{12} + 3C_{44})/5$ and 44, cohesive energy and the vacancy formation energy. The obtained potential parameters are used to calculate the phonon dispersion spectra of these metals. Large discrepancies are found between the calculated results of phonon dispersion using the EAM and the experimental phonon dispersion results. Therefore, to overcome this inadequacy of the EAM model, we employ the modified embedded atom method (MEAM) in which a modified term along with the pair potential and embedding function is added in the total energy. The phonon dispersions calculated using potential parameters obtained from the MEAM show good agreement with experimental results compared to those obtained from the EAM. Using the calculated phonons, we evaluate the local density of states of the neighbours of vacancy using the Green’s function method. The local frequency spectrum of first neighbours of vacancy in Mo shows an increase at higher frequencies and a shift towards the lower frequencies whereas in Fe and W, the frequency spectrum shows a small decrease towards higher frequency and small shift towards lower frequency. For the second neighbours of vacancy in all the three metals, the local frequency spectrum is not much different from that of the host atom. The local density of states of the neighbours of the vacancy has been used to calculate the mean square displacements and the formation entropy of vacancy. The calculated mean square displacements of the first neighbours of vacancy are found to be higher than that of the host atom, whereas it is lower for the second neighbours. The calculated results of the formation entropy of the vacancy

  3. A GENERAL CRYSTALLOGRAPHIC MODEL OF fcc/bcc(bct) MARTENSITIC NUCLEATION AND GROWTH IN STEELS%钢中fcc/bcc(bct)马氏体形核与长大的一种晶体学模型

    Institute of Scientific and Technical Information of China (English)

    杨金波; 杨志刚; 邱冬; 张文征; 张弛; 白秉哲; 方鸿生

    2005-01-01

    将不变线理论和O点阵理论应用于fcc/bcc(bct)马氏体相变的可滑移生长界面的设计,建立了马氏体形核与长大的晶体学模型.通过模型分析表明:fcc/bcc(bct)马氏体形核与长大过程是通过(121)fcc型择优界面推移进行的,界面上的错配位错可以完成马氏体晶体学唯象理论(PTMC)要求的点阵不变变形(LID),但LID要稍滞后于界面迁移,即在马氏体形核与长大过程中推移界面新相一侧存在一未发生LID的新相薄区;当相变温度达到马氏体相变点Ms时,母相奥氏体与这一薄区的晶格常数比为√3/2,这一几何条件和Olson-Cohen形核模型中要求扩展位错层错区界面能γ≤0是等价的.

  4. Nucleon structure using lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrou, C.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Constantinou, M.; Hatziyiannakou, K. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Drach, V. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Jansen, K. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Koutsou, G.; Vaquero, A. [The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Leontiou, T. [Frederick Univ, Nicosia (Cyprus). General Dept.

    2013-03-15

    A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods applied for their study, including approaches to evaluate the disconnected contributions. Results on the spin carried by the quarks in the nucleon are also presented.

  5. Triangles in a Lattice Parabola.

    Science.gov (United States)

    Sastry, K. R. S.

    1991-01-01

    Discussed are properties possessed by polygons inscribed in the lattice parabola y=x, including the area of a triangle, triangles of minimum area, conditions for right triangles, triangles whose area is the cube of an integer, and implications of Pick's Theorem. Further directions to pursue are suggested. (MDH)

  6. Hamiltonian monodromy as lattice defect

    OpenAIRE

    Zhilinskii, B.

    2003-01-01

    The analogy between monodromy in dynamical (Hamiltonian) systems and defects in crystal lattices is used in order to formulate some general conjectures about possible types of qualitative features of quantum systems which can be interpreted as a manifestation of classical monodromy in quantum finite particle (molecular) problems.

  7. Chiral fermions on the lattice

    CERN Document Server

    Jahn, O; Jahn, Oliver; Pawlowski, Jan M.

    2002-01-01

    We discuss topological obstructions to putting chiral fermions on an even dimensional lattice. The setting includes Ginsparg-Wilson fermions, but is more general. We prove a theorem which relates the total chirality to the difference of generalised winding numbers of chiral projection operators. For an odd number of Weyl fermions this implies that particles and anti-particles live in topologically different spaces.

  8. Hybrid Charmonium from Lattice QCD

    CERN Document Server

    Luo, X Q

    2006-01-01

    We review our recent results on the JPC = 0¡¡ exotic hybrid charmonium mass and JPC = 0¡+, 1¡¡ and 1++ nonexotic hybrid charmonium spectrum from anisotropic improved lattice QCD and discuss the relevance to the recent discovery of the Y(4260) state and future experimental search for other states.

  9. Ultra-small, uniform, and single bcc-phased Fe(x)Co(1-x)/graphitic shell nanocrystals for T1 magnetic resonance imaging contrast agents.

    Science.gov (United States)

    Choi, In Ae; Li, Yan; Kim, Da Jeong; Pal, Mou; Cho, Jee-Hyun; Lee, Kyujoon; Jung, Myung-Hwa; Lee, Chulhyun; Seo, Won Seok

    2013-01-01

    We have synthesized ultra-small and uniform Fe(x)Co(1-x)/graphitic carbon shell (Fe(x)Co(1-x)/GC) nanocrystals (x=0.13, 0.36, 0.42, 0.50, 0.56, and 0.62, respectively) with average diameters of bcc FeCo structure, whereas the Fe(0.13)Co(0.87)/GC, Fe(0.36)Co(0.64)/GC, and Fe(0.42)Co(0.58)/GC nanocrystals have a mixed structure of bcc FeCo and fcc Co. The single bcc-phased Fe(x)Co(1-x)/GC nanocrystals functionalized with phospholipid-poly(ethylene glycol) (PL-PEG) in phosphate buffered saline (PBS) are demonstrated to be excellent T(1) MRI contrast agents.

  10. Orbital optical lattices with bosons

    Science.gov (United States)

    Kock, T.; Hippler, C.; Ewerbeck, A.; Hemmerich, A.

    2016-02-01

    This article provides a synopsis of our recent experimental work exploring Bose-Einstein condensation in metastable higher Bloch bands of optical lattices. Bipartite lattice geometries have allowed us to implement appropriate band structures, which meet three basic requirements: the existence of metastable excited states sufficiently protected from collisional band relaxation, a mechanism to excite the atoms initially prepared in the lowest band with moderate entropy increase, and the possibility of cross-dimensional tunneling dynamics, necessary to establish coherence along all lattice axes. A variety of bands can be selectively populated and a subsequent thermalization process leads to the formation of a condensate in the lowest energy state of the chosen band. As examples the 2nd, 4th and 7th bands in a bipartite square lattice are discussed. The geometry of the 2nd and 7th bands can be tuned such that two inequivalent energetically degenerate energy minima arise at the X ±-points at the edge of the 1st Brillouin zone. In this case even a small interaction energy is sufficient to lock the phase between the two condensation points such that a complex-valued chiral superfluid order parameter can emerge, which breaks time reversal symmetry. In the 4th band a condensate can be formed at the Γ-point in the center of the 1st Brillouin zone, which can be used to explore topologically protected band touching points. The new techniques to access orbital degrees of freedom in higher bands greatly extend the class of many-body scenarios that can be explored with bosons in optical lattices.

  11. Structure analysis of Ni thin films epitaxially grown on bcc metal underlayers formed on MgO(100 substrates

    Directory of Open Access Journals (Sweden)

    Futamoto Masaaki

    2013-01-01

    Full Text Available Ni thin films are prepared on Cr, V, and Nb underlayers with bcc structure formed on MgO(100 single-crystal substrates by molecular beam epitaxy. The growth behavior and the crystallographic properties are investigated by in-situ reflection high-energy electron diffraction and pole-figure X-ray diffraction. Cr(100 and V(100 single-crystal underlayers grow epitaxially on the substrates, whereas an Nb epitaxial_underlayer consisting of two bcc(110 variants is formed on the MgO(100 substrate. Metastable crystals nucleate on the Cr and the V underlayers, where the metastable hcp structure is stabilized through heteroepitaxial growth. With increasing the film thickness, the hcp structure starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001 close-packed plane. The resulting films are consisting of mixtures of hcp and fcc crystals. On the other hand, only the formation of fcc crystal is recognized for the Ni film grown on Nb(110 underlayer.

  12. Hadron Structure and Spectrum from the Lattice

    CERN Document Server

    Lang, C B

    2015-01-01

    Lattice calculations for hadrons are now entering the domain of resonances and scattering, necessitating a better understanding of the observed discrete energy spectrum. This is a reviewing survey about recent lattice QCD results, with some emphasis on spectrum and scattering.

  13. Turbo Lattices: Construction and Performance Analysis

    CERN Document Server

    Sakzad, Amin; Panario, Daniel

    2011-01-01

    In this paper a new class of lattices called turbo lattices is introduced and established. We use the lattice Construction $D$ to produce turbo lattices. This method needs a set of nested linear codes as its underlying structure. We benefit from turbo codes as our basis codes. Therefore, a set of nested turbo codes based on nested interleavers and nested convolutional codes is built. To this end, we employ both tail-biting and zero-tail convolutional codes. Using these codes, along with construction $D$, turbo lattices are created. Several properties of Construction $D$ lattices and fundamental characteristics of turbo lattices including the minimum distance, coding gain, kissing number and an upper bound on the probability of error under a maximum likelihood decoder over AWGN channel are investigated. Furthermore, a multi-stage turbo lattice decoding algorithm based on iterative turbo decoding algorithm is given. Finally, simulation experiments provide strong agreement with our theoretical results. More prec...

  14. Metastable bcc phase formation in 3d ferromagnetic transition metal thin films sputter-deposited on GaAs(100) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Minakawa, Shigeyuki, E-mail: s-minakawa@futamoto.elect.chuo-u.ac.jp; Ohtake, Mitsuru; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo University of the Arts, Taito-ku, Tokyo 110-8714 (Japan); Inaba, Nobuyuki [Faculty of Engineering, Yamagata University, Yonezawa, Yamagata 992-8510 (Japan)

    2015-05-07

    Co{sub 100−x}Fe{sub x} and Ni{sub 100−y}Fe{sub y} (at. %, x = 0–30, y = 0–60) films of 10 nm thickness are prepared on GaAs(100) substrates at room temperature by using a radio-frequency magnetron sputtering system. The detailed growth behavior is investigated by in-situ reflection high-energy electron diffraction. (100)-oriented Co and Ni single-crystals with metastable bcc structure are formed in the early stage of film growth, where the metastable structure is stabilized through hetero-epitaxial growth. With increasing the thickness up to 2 nm, the Co and the Ni films start to transform into more stable hcp and fcc structures through atomic displacements parallel to bcc(110) slide planes, respectively. The stability of bcc phase is improved by adding a small volume of Fe atoms into a Co film. The critical thickness of bcc phase formation is thicker than 10 nm for Co{sub 100−x}Fe{sub x} films with x ≥ 10. On the contrary, the stability of bcc phase for Ni-Fe system is less than that for Co-Fe system. The critical thicknesses for Ni{sub 100−y}Fe{sub y} films with y = 20, 40, and 60 are 1, 3, and 5 nm, respectively. The Co{sub 100−x}Fe{sub x} single-crystal films with metastable bcc structure formed on GaAs(100) substrates show in-plane uniaxial magnetic anisotropies with the easy direction along GaAs[011], similar to the case of Fe film epitaxially grown on GaAs(100) substrate. A Co{sub 100−x}Fe{sub x} film with higher Fe content shows a higher saturation magnetization and a lower coercivity.

  15. Interaction of macroparticles localized in Wigner-Seitz cells of various types of cubic lattices in an equilibrium plasma

    Science.gov (United States)

    Filippov, A. V.

    2016-10-01

    The interaction of two charged point macroparticles located in Wigner-Seitz cells of simple cubic (SC), body-centered cubic (BCC), or face-centered cubic (FCC) lattices in an equilibrium plasma has been studied within the Debye approximation or, more specifically, based on the linearized Poisson-Boltzmann model. The shape of the outer boundary is shown to exert a strong influence on the pattern of electrostatic interaction between the two macroparticles, which transforms from repulsion at small interparticle distances to attraction as the interparticle distance approaches half the length of the computational cell. The macroparticle pair interaction potential in an equilibrium plasma is shown to be nevertheless the Debye one and purely repulsive for likely charged macroparticles.

  16. 体心立方固溶体合金中的“团簇+连接原子”结构模型%Cluster-plus-glue-atom model in bcc solid solution alloys

    Institute of Scientific and Technical Information of China (English)

    郝传璞; 王清; 马仁涛; 王英敏; 羌建兵; 董闯

    2011-01-01

    In the present work we propose the cluster-plus-glue-atom model for bcc solid solutions by establishing periodic packing geometries of CN14 basic clusters in bcc lattice to reflect the idealized chemical short-range order near solute atoms.The model is expressed by cluster formula (glue)x,where the cluster center is occupied by a solute having the largest negative enthalpy,mixed with the solvent,and other solute atoms serves as glues or substitute for the solvents in cluster shell.The 1∶1 cluster model [cluster](glue atom)1 is specially emphasized that guarantees to a maximum extent the glue-cluster nearest neighbors and hence forms a most efficient configuration.This 1∶1 model is conducible to the design of a low-V hydrogen-storage [Ti7Cr8]V1 alloy and a [Mo1(Ti,Zr)14]Nb1 alloy with low Young's modulus combined with high strength.%为体现固溶体合金中的溶质原子产生的化学短程序,文章提出了配位数为14的团簇在体心立方(bcc)点阵中的堆垛模式,并建立了基于bcc结构的"团簇+连接原子"结构模型,用团簇成分式[团簇](连接原子)x表述.此模型中,与基体组元具有相对大的负混合焓的溶质原子占据团簇心部,其他原子作为连接或者替代团簇壳层基体原子.1:1结构模型[团簇](连接原子)1由于最大程度地保证了团簇与连接原子的近邻,构成了连接原子最有效的合金化方式.在两个实用bcc固溶体合金体系中,1:1模型指导设计了低V含量的储氢合金[Ti7Cr8]V1和低弹性模量高强度的[Mo(Ti,Zr)14]Nb1合金.

  17. Rough Class on a Completely Distributive Lattice

    Institute of Scientific and Technical Information of China (English)

    陈德刚; 张文修; 宋士吉

    2003-01-01

    This paper generalizes the Pawlak rough set method to a completely distributive lattice. Theconcept of a rough set has many applications in data mining. The approximation operators on a completelydistributive lattice are studied, the rough class on a completely distributive lattice is defined and theexpressional theorems of the rough class are proven. These expressional theorems are used to prove that thecollection of all rough classes is an atomic completely distributive lattice.

  18. Distributive lattice orderings and Priestley duality

    CERN Document Server

    Krebs, Michel

    2007-01-01

    The ordering relation of a bounded distributive lattice L is a (distributive) (0, 1)-sublattice of L \\times L. This construction gives rise to a functor \\Phi from the category of bounded distributive lattices to itself. We examine the interaction of \\Phi with Priestley duality and characterise those bounded distributive lattices L such that there is a bounded distributive lattice K such that \\Phi(K) is (isomorphic to) L.

  19. Three different consecutive manifestations of morphoeic BCC in the same patient: presenting first as ectropion, then entropion, and finally medial canthal dystopia with epicanthus inversus.

    Science.gov (United States)

    Baker, H E; Berry-Brincat, A; Zaki, I; Cheung, D

    2008-01-01

    Morpheaform basal cell carcinoma (BCC) can cause diagnostic difficulty due to an atypical clinical presentation. Successful treatment requires a high index of clinical suspicion together with an early confirmatory biopsy. We present the case of an 81-year-old lady with a delayed diagnosis of morphoeic BCC due to an unusual presentation of evolving lid malposition, and we highlight the limitations of a punch biopsy in diagnosing atypical lesions. An appropriate biopsy technique is vital, with consideration for repeat biopsies when necessary, especially if the clinical picture is changing over time.

  20. Modified $U(1)$ lattice gauge theory towards realistic lattice QED

    CERN Document Server

    Bornyakov, V G; Müller-Preussker, M

    1992-01-01

    We study properties of the compact $~4D~$ $U(1)$ lattice gauge theory with monopoles {\\it removed}. Employing Monte Carlo simulations we calculate correlators of scalar, vector and tensor operators at zero and nonzero momenta $~\\vec{p}~$. We confirm that the theory without monopoles has no phase transition, at least, in the interval $~0 < \\beta \\leq 2~$. There the photon becomes massless and fits the lattice free field theory dispersion relation very well. The energies of the $~0^{++}~$, $~1^{+-}~$ and $~2^{++}~$ states show a rather weak dependence on the coupling in the interval of $~\\beta~$ investigated, and their ratios are practically constant. We show also a further modification of the theory suppressing the negative plaquettes to improve drastically the overlap with the lowest states (at least, for $~J=1$).

  1. The lattice of d-structures

    DEFF Research Database (Denmark)

    Fajstrup, Lisbeth

    The set of d-structures on a topological space form a lattice and in fact a locale. There is a Galois connection between the lattice of subsets of the space and the lattice of d-structures. Variation of the d-structures induces change in the spaces of directed paths. Hence variation of d...

  2. Modal analysis of kagome-lattice structures

    Science.gov (United States)

    Perez, H.; Blakley, S.; Zheltikov, A. M.

    2015-05-01

    The first few lowest order circularly symmetric electromagnetic eigenmodes of a full kagome lattice are compared to those of a kagome lattice with a hexagonal defect. This analysis offers important insights into the physics behind the waveguiding properties of hollow-core fibers with a kagome-lattice cladding.

  3. SIMPLE LATTICE BOLTZMANN MODEL FOR TRAFFIC FLOWS

    Institute of Scientific and Technical Information of China (English)

    Yan Guangwu; Hu Shouxin

    2000-01-01

    A lattice Boltzmann model with 5-bit lattice for traffic flows is proposed.Using the Chapman-Enskog expansion and multi-scale technique,we obtain the higher-order moments of equilibrium distribution function.A simple traffic light problem is simulated by using the present lattice Boltzmann model,and the result agrees well with analytical solution.

  4. Lattice QCD and the CKM matrix

    CERN Document Server

    De Grand, T

    2001-01-01

    These lectures (given at TASI 2000) provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1 (Ch. 2) is a very vanilla introduction to lattice QCD. Lecture 2 (Ch. 3) describes examples of recent lattice calculations relevant to fixing the parameters of the CKM matrix.

  5. Lattice Boltzmann solver of Rossler equation

    Institute of Scientific and Technical Information of China (English)

    GuangwuYAN; LiRUAN

    2000-01-01

    We proposed a lattice Boltzmann model for the Rossler equation. Using a method of multiscales in the lattice Boltzmann model, we get the diffusion reaction as a special case. If the diffusion effect disappeared, we can obtain the lattice Boltzmann solution of the Rossler equation on the mesescopic scale. The numerical results show the method can be used to simulate Rossler equation.

  6. Perfect and Quasi-Perfect Lattice Actions

    CERN Document Server

    Bietenholz, W

    1998-01-01

    Perfect lattice actions are exiting with several respects: they provide new insight into conceptual questions of the lattice regularization, and quasi-perfect actions could enable a great leap forward in the non-perturbative solution of QCD. We try to transmit a flavor of them, also beyond the lattice community.

  7. The Developement of A Lattice Structured Database

    DEFF Research Database (Denmark)

    Bruun, Hans

    to a given set of inserted terms, that is the smallest lattice where the inserted terms preserve their value compared to the value in the initial algebra/lattice. The database is the dual representation of this most disjoint lattice. We develop algorithms to construct and make queries to the database....

  8. Clar sextets in square graphene antidot lattices

    DEFF Research Database (Denmark)

    Petersen, Rene; Pedersen, Thomas Garm; Jauho, Antti-Pekka

    2011-01-01

    A periodic array of holes transforms graphene from a semimetal into a semiconductor with a band gap tuneable by varying the parameters of the lattice. In earlier work only hexagonal lattices have been treated. Using atomistic models we here investigate the size of the band gap of a square lattice...

  9. Exact Chiral Symmetry on the Lattice

    CERN Document Server

    Neuberger, H

    2001-01-01

    Developments during the last eight years have refuted the folklore that chiral symmetries cannot be preserved on the lattice. The mechanism that permits chiral symmetry to coexist with the lattice is quite general and may work in Nature as well. The reconciliation between chiral symmetry and the lattice is likely to revolutionize the field of numerical QCD.

  10. Mayet-Godowski Hilbert Lattice Equations

    OpenAIRE

    Megill, Norman D.; Pavicic, Mladen

    2006-01-01

    Several new results in the field of Hilbert lattice equations based on states defined on the lattice as well as novel techniques used to arrive at these results are presented. An open problem of Mayet concerning Hilbert lattice equations based on Hilbert-space-valued states is answered.

  11. Lattice gaugefixing and other optics in lattice gauge theory

    Energy Technology Data Exchange (ETDEWEB)

    Yee, Ken

    1992-06-01

    We present results from four projects. In the first, quark and gluon propagators and effective masses and {Delta}I = 1/2 Rule operator matching coefficients are computed numerically in gaugefixed lattice QCD. In the second, the same quantities are evaluated analytically in the strong coupling, N {yields} {infinity} limit. In the third project, the Schwinger model is studied in covariant gauges, where we show that the effective electron mass varies with the gauge parameter and that longitudinal gaugefixing ambiguities affect operator product expansion coefficients (analogous to {Delta}I = 1/2 Rule matching coefficients) determined by matching gauge variant matrix elements. However, we find that matching coefficients even if shifted by the unphysical modes are {xi} invariant. In the fourth project, we show that the strong coupling parallelogram lattice Schwinger model as a different thermodynamic limit than the weak coupling continuum limit. As a function of lattice skewness angle these models span the {Delta} = {minus}1 critical line of 6-vertex models which, in turn, have been identified as c = 1 conformal field theories.

  12. Efficiency of various lattices from hard ball to soft ball: theoretical study of thermodynamic properties of dendrimer liquid crystal from atomistic simulation.

    Science.gov (United States)

    Li, Youyong; Lin, Shiang-Tai; Goddard, William A

    2004-02-18

    Self-assembled supramolecular organic liquid crystal structures at nanoscale have potential applications in molecular electronics, photonics, and porous nanomaterials. Most of these structures are formed by aggregation of soft spherical supramolecules, which have soft coronas and overlap each other in the packing process. Our main focus here is to study the possible packing mechanisms via molecular dynamics simulations at the atomistic level. We consider the relative stability of various lattices packed by the soft dendrimer balls, first synthesized and characterized by Percec et al. (J. Am. Chem. Soc. 1997, 119, 1539) with different packing methods. The dendrons, which form the soft dendrimer balls, have the character of a hard aromatic region from the point of the cone to the edge with C(12) alkane "hair". After the dendrons pack into a sphere, the core of the sphere has the hard aromatic groups, while the surface is covered with the C(12) alkane "hair". In our studies, we propose three ways to organize the hair on the balls, Smooth/Valentino balls, Sticky/Einstein balls, and Asymmetric/Punk balls, which lead to three different packing mechanisms, Slippery, Sticky, and Anisotropic, respectively. We carry out a series of molecular dynamics (MD) studies on three plausible crystal structures (A15, FCC, and BCC) as a function of density and analyze the MD based on the vibrational density of state (DoS) method to extract the enthalpy, entropy, and free energies of these systems. We find that anisotropic packed A15 is favored over FCC, BCC lattices. Our predicted X-ray intensities of the best structures are in excellent agreement with experiment. "Anisotropic ball packing" proposed here plays an intermediate role between the enthalpy-favored "disk packing" and entropy-favored "isotropic ball packing", which explains the phase transitions at different temperatures. Free energies of various lattices at different densities are essentially the same, indicating that the

  13. Quantum statistical vibrational entropy and enthalpy of formation of helium-vacancy complex in BCC W

    Science.gov (United States)

    Wen, Haohua; Woo, C. H.

    2016-12-01

    High-temperature advance-reactor design and operation require knowledge of in-reactor materials properties far from the thermal ground state. Temperature-dependence due to the effects of lattice vibrations is important to the understanding and formulation of atomic processes involved in irradiation-damage accumulation. In this paper, we concentrate on the formation of He-V complex. The free-energy change in this regard is derived via thermodynamic integration from the phase-space trajectories generated from MD simulations based on the quantum fluctuation-dissipation relation. The change of frequency distribution of vibration modes during the complex formation is properly accounted for, and the corresponding entropy change avoids the classical ln(T) divergence that violates the third law. The vibrational enthalpy and entropy of formation calculated this way have significant effects on the He kinetics during irradiation.

  14. Shear Viscosity from Lattice QCD

    CERN Document Server

    Mages, Simon W; Fodor, Zoltán; Schäfer, Andreas; Szabó, Kálmán

    2015-01-01

    Understanding of the transport properties of the the quark-gluon plasma is becoming increasingly important to describe current measurements at heavy ion collisions. This work reports on recent efforts to determine the shear viscosity h in the deconfined phase from lattice QCD. The main focus is on the integration of the Wilson flow in the analysis to get a better handle on the infrared behaviour of the spectral function which is relevant for transport. It is carried out at finite Wilson flow time, which eliminates the dependence on the lattice spacing. Eventually, a new continuum limit has to be carried out which sends the new regulator introduced by finite flow time to zero. Also the non-perturbative renormalization strategy applied for the energy momentum tensor is discussed. At the end some quenched results for temperatures up to 4 : 5 T c are presented

  15. Lattice splitting under intermittent flows

    CERN Document Server

    Schläpfer, Markus

    2010-01-01

    We study the splitting of regular square lattices subject to stochastic intermittent flows. By extensive Monte Carlo simulations we reveal how the time span until the occurence of a splitting depends on various flow patterns imposed on the lattices. Increasing the flow fluctuation frequencies shortens this time span which reaches a minimum before rising again due to inertia effects incorporated in the model. The size of the largest connected component after the splitting is rather independent of the flow fluctuations but sligthly decreases with the link capacities. Our results are relevant for assessing the robustness of real-life systems, such as electric power grids with a large share of renewable energy sources including wind turbines and photovoltaic systems.

  16. Breathers in strongly anharmonic lattices.

    Science.gov (United States)

    Rosenau, Philip; Pikovsky, Arkady

    2014-02-01

    We present and study a family of finite amplitude breathers on a genuinely anharmonic Klein-Gordon lattice embedded in a nonlinear site potential. The direct numerical simulations are supported by a quasilinear Schrodinger equation (QLS) derived by averaging out the fast oscillations assuming small, albeit finite, amplitude vibrations. The genuinely anharmonic interlattice forces induce breathers which are strongly localized with tails evanescing at a doubly exponential rate and are either close to a continuum, with discrete effects being suppressed, or close to an anticontinuum state, with discrete effects being enhanced. Whereas the D-QLS breathers appear to be always stable, in general there is a stability threshold which improves with spareness of the lattice.

  17. Lattice dynamics of strontium tungstate

    Indian Academy of Sciences (India)

    Prabhatasree Goel; R Mittal; S L Chaplot; A K Tyagi

    2008-11-01

    We report here measurements of the phonon density of states and the lattice dynamics calculations of strontium tungstate (SrWO4). At ambient conditions this compound crystallizes to a body-centred tetragonal unit cell (space group I41/a) called scheelite structure. We have developed transferable interatomic potentials to study the lattice dynamics of this class of compounds. The model parameters have been fitted with respect to the experimentally available Raman and infra-red frequencies and the equilibrium unit cell parameters. Inelastic neutron scattering measurements have been carried out in the triple-axis spectrometer at Dhruva reactor. The measured phonon density of states is in good agreement with the theoretical calculations, thus validating the inter-atomic potential developed.

  18. Entanglement scaling in lattice systems

    Energy Technology Data Exchange (ETDEWEB)

    Audenaert, K M R [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom); Cramer, M [QOLS, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); Eisert, J [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom); Plenio, M B [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom)

    2007-05-15

    We review some recent rigorous results on scaling laws of entanglement properties in quantum many body systems. More specifically, we study the entanglement of a region with its surrounding and determine its scaling behaviour with its size for systems in the ground and thermal states of bosonic and fermionic lattice systems. A theorem connecting entanglement between a region and the rest of the lattice with the surface area of the boundary between the two regions is presented for non-critical systems in arbitrary spatial dimensions. The entanglement scaling in the field limit exhibits a peculiar difference between fermionic and bosonic systems. In one-spatial dimension a logarithmic divergence is recovered for both bosonic and fermionic systems. In two spatial dimensions in the setting of half-spaces however we observe strict area scaling for bosonic systems and a multiplicative logarithmic correction to such an area scaling in fermionic systems. Similar questions may be posed and answered in classical systems.

  19. Fractional random walk lattice dynamics

    CERN Document Server

    Michelitsch, Thomas; Riascos, Alejandro Perez; Nowakowski, Andrzeij; Nicolleau, Franck

    2016-01-01

    We analyze time-discrete and continuous `fractional' random walks on undirected regular networks with special focus on cubic periodic lattices in $n=1,2,3,..$ dimensions.The fractional random walk dynamics is governed by a master equation involving {\\it fractional powers of Laplacian matrices $L^{\\frac{\\alpha}{2}}$}where $\\alpha=2$ recovers the normal walk.First we demonstrate thatthe interval $0\\textless{}\\alpha\\leq 2$ is admissible for the fractional random walk. We derive analytical expressions for fractional transition matrix and closely related the average return probabilities. We further obtain thefundamental matrix $Z^{(\\alpha)}$, and the mean relaxation time (Kemeny constant) for the fractional random walk.The representation for the fundamental matrix $Z^{(\\alpha)}$ relates fractional random walks with normal random walks.We show that the fractional transition matrix elements exihibit for large cubic $n$-dimensional lattices a power law decay of an $n$-dimensional infinite spaceRiesz fractional deriva...

  20. Innovations in Lattice QCD Algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Konstantinos Orginos

    2006-06-25

    Lattice QCD calculations demand a substantial amount of computing power in order to achieve the high precision results needed to better understand the nature of strong interactions, assist experiment to discover new physics, and predict the behavior of a diverse set of physical systems ranging from the proton itself to astrophysical objects such as neutron stars. However, computer power alone is clearly not enough to tackle the calculations we need to be doing today. A steady stream of recent algorithmic developments has made an important impact on the kinds of calculations we can currently perform. In this talk I am reviewing these algorithms and their impact on the nature of lattice QCD calculations performed today.

  1. Fungal keratitis in Lattice dystrophy

    Directory of Open Access Journals (Sweden)

    Chatterjee Samrat

    2010-01-01

    Full Text Available We report a case of fungal keratitis occurring in a patient with lattice dystrophy. A 57-year-old farmer presented with a corneal ulcer following probable entry of paddy husk in the right eye, of one month duration. Corneal scraping revealed pigmented fungal filaments while culture grew Alternaria alternata. Treatment with 5% natamycin eye drops and 1% atropine healed the infection in four weeks. We would like to draw attention to the fact that the cornea in lattice dystrophy is prone to frequent erosions and is a compromised epithelial barrier to invasion by microorganisms. Patients must be made aware of this fact and should seek attention at the earliest following any trivial trauma. Management of minor corneal abrasions in them should be directed at healing the epithelium with adequate lubricants and preventing infection with topical antibiotic prophylaxis.

  2. Graphene antidot lattice transport measurements

    DEFF Research Database (Denmark)

    Mackenzie, David; Cagliani, Alberto; Gammelgaard, Lene

    2017-01-01

    We investigate graphene devices patterned with a narrow band of holes perpendicular to the current flow, a few-row graphene antidot lattice (FR-GAL). Theoretical reports suggest that a FR-GAL can have a bandgap with a relatively small reduction of the transmission compared to what is typical...... for antidot arrays devices. Graphene devices were fabricated using 100 keV electron beam lithography (EBL) for nanopatterning as well as for defining electrical contacts. Patterns with hole diameter and neck widths of order 30 nm were produced, which is the highest reported pattern density of antidot lattices...... in graphene reported defined by EBL. Electrical measurements showed that devices with one and five rows exhibited field effect mobility of ∼100 cm2/Vs, while a larger number of rows, around 40, led to a significant reduction of field effect mobility (

  3. Lattice dynamics of lithium oxide

    Indian Academy of Sciences (India)

    Prabhatasree Goel; N Choudhury; S L Chaplot

    2004-08-01

    Li2O finds several important technological applications, as it is used in solid-state batteries, can be used as a blanket breeding material in nuclear fusion reactors, etc. Li2O exhibits a fast ion phase, characterized by a thermally induced dynamic disorder in the anionic sub-lattice of Li+, at elevated temperatures around 1200 K. We have carried out lattice-dynamical calculations of Li2O using a shell model in the quasi-harmonic approximation. The calculated phonon frequencies are in excellent agreement with the reported inelastic neutron scattering data. Thermal expansion, specific heat, elastic constants and equation of state have also been calculated which are in good agreement with the available experimental data.

  4. Lattice Embedding of Heronian Simplices

    CERN Document Server

    Lunnon, W Fred

    2012-01-01

    A rational triangle has rational edge-lengths and area; a rational tetrahedron has rational faces and volume; either is Heronian when its edge-lengths are integer, and proper when its content is nonzero. A variant proof is given, via complex number GCD, of the previously known result that any Heronian triangle may be embedded in the Cartesian lattice Z^2; it is then shown that, for a proper triangle, such an embedding is unique modulo lattice isometry; finally the method is extended via quaternion GCD to tetrahedra in Z^3, where uniqueness no longer obtains, and embeddings also exist which are unobtainable by this construction. The requisite complex and quaternionic number theoretic background is summarised beforehand. Subsequent sections engage with subsidiary implementation issues: initial rational embedding, canonical reduction, exhaustive search for embeddings additional to those yielded via GCD; and illustrative numerical examples are provided. A counter-example shows that this approach must fail in high...

  5. The Fermilab Lattice Information Repository

    CERN Document Server

    Ostiguy, Jean-Francois; McCusker-Whiting, Michele; Michelotti, Leo

    2005-01-01

    Fermilab is a large accelerator complex with six rings and sixteen transfer beamlines operating in various modes and configurations, subject to modifications, improvements and occasional major redesign. Over the years, it became increasingly obvious that a centralized lattice repository with the ability to track revisions would be of great value. To that end, we evaluated potentially suitable revision systems, either freely available or commercial, and decided that expecting infrequent users to become fully conversant with complex revision system software was neither realistic nor practical. In this paper, we discuss technical aspects of the recently introduced FNAL Accelerator Division's Lattice Repository, whose fully web-based interface hides the complexity of Subversion, a comprehensive open source revision system. In particular we emphasize how the architecture of Subversion was a key ingredient in the technical success of the repository's implementation.

  6. A Lattice-Gas Model of Microemulsions

    CERN Document Server

    Boghosian, B M; Emerton, A N; Boghosian, Bruce M.; Coveney, Peter V.; Emerton, Andrew N.

    1995-01-01

    We develop a lattice gas model for the nonequilibrium dynamics of microemulsions. Our model is based on the immiscible lattice gas of Rothman and Keller, which we reformulate using a microscopic, particulate description so as to permit generalisation to more complicated interactions, and on the prescription of Chan and Liang for introducing such interparticle interactions into lattice gas dynamics. We present the results of simulations to demonstrate that our model exhibits the correct phenomenology, and we contrast it with both equilibrium lattice models of microemulsions, and to other lattice gas models.

  7. Stable kagome lattices from group IV elements

    Science.gov (United States)

    Leenaerts, O.; Schoeters, B.; Partoens, B.

    2015-03-01

    A thorough investigation of three-dimensional kagome lattices of group IV elements is performed with first-principles calculations. The investigated kagome lattices of silicon and germanium are found to be of similar stability as the recently proposed carbon kagome lattice. Carbon and silicon kagome lattices are both direct-gap semiconductors but they have qualitatively different electronic band structures. While direct optical transitions between the valence and conduction bands are allowed in the carbon case, no such transitions can be observed for silicon. The kagome lattice of germanium exhibits semimetallic behavior but can be transformed into a semiconductor after compression.

  8. Thermal Hydraulic Performance of Tight Lattice Bundle

    Science.gov (United States)

    Yamamoto, Yasushi; Akiba, Miyuki; Morooka, Shinichi; Shirakawa, Kenetsu; Abe, Nobuaki

    Recently, the reduced moderation spectrum BWR has been studied. The fast neutron spectrum is obtained through triangular tight lattice fuel. However, there are few thermal hydraulic test data and thermal hydraulic correlation applicable to critical power prediction in such a tight lattice bundle. This study aims to enhance the database of the thermal hydraulic performance of the tight lattice bundle whose rod gap is about 1mm. Therefore, thermal hydraulic performance measurement tests of tight lattice bundles for the critical power, the pressure drop and the counter current flow limiting were performed. Moreover, the correlations to evaluate the thermal-hydraulic performance of the tight lattice bundle were developed.

  9. Scale setting in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Sommer, Rainer [DESY, Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2014-02-15

    The principles of scale setting in lattice QCD as well as the advantages and disadvantages of various commonly used scales are discussed. After listing criteria for good scales, I concentrate on the main presently used ones with an emphasis on scales derived from the Yang-Mills gradient flow. For these I discuss discretisation errors, statistical precision and mass effects. A short review on numerical results also brings me to an unpleasant disagreement which remains to be explained.

  10. Integrated optical fiber lattice accumulators

    OpenAIRE

    Atherton, Adam F

    1997-01-01

    Approved for public release; distribution is unlimited. Sigma-delta modulators track a signal by accumulating the error between an input signal and a feedback signal. The accumulated energy is amplitude analyzed by a comparator. The comparator output signal is fed back and subtracted from the input signal. This thesis is primarily concerned with designing accumulators for inclusion in an optical sigma-delta modulator. Fiber lattice structures with optical amplifiers are used to perform the...

  11. Harmonic Lattice Dynamics of Germanium

    Energy Technology Data Exchange (ETDEWEB)

    Nelin, G.

    1974-07-01

    The phonon dispersion relations of the DELTA-, LAMBDA-, and SIGMA-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field.

  12. Hadron Physics from Lattice QCD

    OpenAIRE

    2016-01-01

    We sketch the basic ideas of the lattice regularization in Quantum Field Theory, the corresponding Monte Carlo simulations, and applications to Quantum Chromodynamics (QCD). This approach enables the numerical measurement of observables at the non-perturbative level. We comment on selected results, with a focus on hadron masses and the link to Chiral Perturbation Theory. At last we address two outstanding issues: topological freezing and the sign problem.

  13. Screening in graphene antidot lattices

    DEFF Research Database (Denmark)

    Schultz, Marco Haller; Jauho, A. P.; Pedersen, T. G.

    2011-01-01

    We compute the dynamical polarization function for a graphene antidot lattice in the random-phase approximation. The computed polarization functions display a much more complicated structure than what is found for pristine graphene (even when evaluated beyond the Dirac-cone approximation...... the plasmon dispersion law and find an approximate square-root dependence with a suppressed plasmon frequency as compared to doped graphene. The plasmon dispersion is nearly isotropic and the developed approximation schemes agree well with the full calculation....

  14. Lattice engineering technology and applications

    CERN Document Server

    Wang, Shumin

    2012-01-01

    This book contains comprehensive reviews of different technologies to harness lattice mismatch in semiconductor heterostructures and their applications in electronic and optoelectronic devices. While the book is a bit focused on metamorphic epitaxial growth, it also includes other methods like compliant substrate, selective area growth, wafer bonding and heterostructure nanowires etc. Basic knowledge on dislocations in semiconductors and innovative methods to eliminate threading dislocations are provided, and successful device applications are reviewed. It covers a variety of important semicon

  15. Symplectic maps for accelerator lattices

    Energy Technology Data Exchange (ETDEWEB)

    Warnock, R.L.; Ruth, R.; Gabella, W.

    1988-05-01

    We describe a method for numerical construction of a symplectic map for particle propagation in a general accelerator lattice. The generating function of the map is obtained by integrating the Hamilton-Jacobi equation as an initial-value problem on a finite time interval. Given the generating function, the map is put in explicit form by means of a Fourier inversion technique. We give an example which suggests that the method has promise. 9 refs., 9 figs.

  16. Vertical Cloudiness over East Asia Simulated by Different BCC_AGCM Models%不同分辨率BCC_AGCM模式对东亚区域垂直云量的模拟

    Institute of Scientific and Technical Information of China (English)

    孙国荣; 李昀英; 寇雄伟; 方乐锌; 高翠翠

    2016-01-01

    The ISCCP (International Satellite Cloud Climatology Project) and NCEP (National Centers for Environmental Prediction) datasets have been exploited to investigate the vertical cloudiness over East Asia simulated by BCC_AGCM2.1 (Beijing Climate Center_Atmospheric General Circulation Model 2.1) and BCC_AGCM2.2. The sources of errors are also explored in this paper. The two models generally can well simulate the distribution of total cloud amount and vertical changes in cloudiness along the topography, however, the simulated cloudiness is less than observations. The cloud cover simulated by AGCM2.2 is less than that by AGCM2.1. Despite the better representation of complex terrain, AGCM2.2 does not show any advantages of the high resolution. The poor performance of the model in the simulation of circulation fields in eastern China leads to underestimation of cloudiness, particularly in the AGCM2.2 simulation. Meanwhile, the overestimation of relative humidity in the upper troposphere results in more simulated cloudiness than observations. The underestimation of relative humidity near the ocean surface and unrealistically small moisture content simulated by the model in Sichuan Basin and its surrounding area in the cold season lead to less cloud amount in the model result. The simulated cloudiness is sensitive to relative humidity. The response of cloudiness to vertical velocity and stability is significant but has little regional difference in both models. The coefficient in the relationship between cloudiness and relative humidity in the model needs to be adjusted and should be more conducive to the production of clouds.%基于ISCCP(International Satellite Cloud Climatology Project)和NCEP(National Centers for Environmental Prediction)资料分析了BCC_AGCM2.1(Beijing Climate Center_Atmospheric General Circulation Model 2.1)和BCC_AGCM2.2模拟的云在东亚的垂直分布特点,并探讨了误差来源。两个模式大体上模拟出了总云量的

  17. Manipulation and control of a bichromatic lattice

    Science.gov (United States)

    Thomas, Claire; Barter, Thomas; Daiss, Severin; Leung, Zephy; Stamper-Kurn, Dan

    2015-05-01

    Recent experiments with ultracold atoms in optical lattices have had great success emulating the simple models of condensed matter systems. These experiments are typically performed with a single site per unit cell. We realize a lattice with up to four sites per unit cell by overlaying an attractive triangular lattice with a repulsive one at twice the wavelength. The relative displacement of the two lattices determines the particular structure. One available configuration is the kagome lattice, which has a flat energy band. In the flat band all kinetic energy states are degenerate, so we have the opportunity to explore a regime where interactions dominate. This bichromatic lattice requires careful stabilization, but offers an opportunity to manipulate the unit cell and band structure by perturbing the lattices relative to one another. I will discuss recent progress.

  18. The Algebraic Properties of Concept Lattice

    Institute of Scientific and Technical Information of China (English)

    KaisheQu; JiyeLiang; JunhongWang; ZhongzhiShi

    2004-01-01

    Concept lattice is a powerful tool for data analysis. It has been applied widely to machine learning, knowledge discovery and software engineering and so on. Some aspects of concept lattice have been studied widely such as building lattice and rules extraction, as for its algebraic properties, there has not been discussed systematically. The paper suggests a binary operation between the elements for the set of all concepts in formal context. This turns the concept lattice in general significance into those with operators. We also proved that the concept lattice is a lattice in algebraic significance and studied its algebraic properties.These results provided theoretical foundation and a new method for further study of concept lattice.

  19. AKT1 Activation is Obligatory for Spontaneous BCC Tumor Growth in a Murine Model that Mimics Some Features of Basal Cell Nevus Syndrome.

    Science.gov (United States)

    Kim, Arianna L; Back, Jung Ho; Zhu, Yucui; Tang, Xiuwei; Yardley, Nathan P; Kim, Katherine J; Athar, Mohammad; Bickers, David R

    2016-10-01

    Patients with basal cell nevus syndrome (BCNS), also known as Gorlin syndrome, develop numerous basal cell carcinomas (BCC) due to germline mutations in the tumor suppressor PTCH1 and aberrant activation of Hedgehog (Hh) signaling. Therapies targeted at components of the Hh pathway, including the smoothened (SMO) inhibitor vismodegib, can ablate these tumors clinically, but tumors recur upon drug discontinuation. Using SKH1-Ptch1(+/-) as a model that closely mimics the spontaneous and accelerated growth pattern of BCCs in patients with BCNS, we show that AKT1, a serine/threonine protein kinase, is intrinsically activated in keratinocytes derived from the skin of newborn Ptch1(+/-) mice in the absence of carcinogenic stimuli. Introducing Akt1 haplodeficiency in Ptch1(+/-) mice (Akt1(+/-) Ptch1(+/-)) significantly abrogated BCC growth. Similarly, pharmacological inhibition of AKT with perifosine, an alkyl phospholipid AKT inhibitor, diminished the growth of spontaneous and UV-induced BCCs. Our data demonstrate an obligatory role for AKT1 in BCC growth, and targeting AKT may help reduce BCC tumor burden in BCNS patients. Cancer Prev Res; 9(10); 794-802. ©2016 AACR.

  20. An ordered bcc CuPd nanoalloy synthesised via the thermal decomposition of Pd nanoparticles covered with a metal-organic framework under hydrogen gas.

    Science.gov (United States)

    Li, Guangqin; Kobayashi, Hirokazu; Kusada, Kohei; Taylor, Jared M; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Yamamoto, Tomokazu; Matsumura, Syo; Kitagawa, Hiroshi

    2014-11-18

    Presented here is the synthesis of an ordered bcc copper-palladium nanoalloy, via the decomposition of a Pd nanoparticle@metal-organic framework composite material. In situ XRD measurements were performed in order to understand the mechanism of the decomposition process. This result gives a further perspective into the synthesis of new nanomaterials via metal-organic framework decomposition.

  1. Effects of CNTs on the hydrogen storage properties of MgH{sub 2} and MgH{sub 2}-BCC composite

    Energy Technology Data Exchange (ETDEWEB)

    Ranjbar, A.; Ismail, M. [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Guo, Z.P. [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); CSIRO National Hydrogen Materials Alliance, CSIRO Energy Centre, 10 Murray Dwyer Circuit, Steel River Estate, Mayfield West, NSW 2304 (Australia); School of Mechanical, Materials and Mechatronics Engineering, University of Wollongong, NSW 2522 (Australia); Yu, X.B. [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); CSIRO National Hydrogen Materials Alliance, CSIRO Energy Centre, 10 Murray Dwyer Circuit, Steel River Estate, Mayfield West, NSW 2304 (Australia); Department of Materials Science, Fudan University, Shanghai 200433 (China); Liu, H.K. [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); CSIRO National Hydrogen Materials Alliance, CSIRO Energy Centre, 10 Murray Dwyer Circuit, Steel River Estate, Mayfield West, NSW 2304 (Australia)

    2010-08-15

    MgH{sub 2} with 10 wt.% Ti{sub 0.4}Mn{sub 0.22}Cr{sub 0.1}V{sub 0.28} alloy (termed the BCC alloy for its body centred cubic structure) and 5 wt.% carbon nanotubes (CNTs) were prepared by planetary ball milling, and its hydrogen storage properties were compared with those of the pure MgH{sub 2} and the binary mixture of MgH{sub 2} and the BCC alloy. The sample with CNTs showed considerable improvement in hydrogen sorption properties. Its temperature of desorption was 125 C lower than for the pure sample and 59 C lower than for the binary mixture. In addition, the gravimetric capacity of the ternary sample was 6 wt.% at 300 C and 5.6 wt.% at 250 C, and it absorbed 90% of this amount at 150 s and 516 s at 300 C and 250 C, respectively. It can be hypothesised from the results that the BCC alloy assists the dissociation of hydrogen molecules into hydrogen atoms and also promotes hydrogen pumping into the Mg/BCC interfaces, while the CNTs facilitate access of H-atoms into the interior of Mg grains. (author)

  2. Interplay between intrinsic point defects and low-angle grain boundary in bcc tungsten: effects of local stress field.

    Science.gov (United States)

    Niu, Liang-Liang; Zhang, Ying; Shu, Xiaolin; Jin, Shuo; Zhou, Hong-Bo; Gao, Fei; Lu, Guang-Hong

    2015-07-01

    We have used molecular statics in conjunction with an embedded atom method to explore the interplay between native point defects (vacancies and self-interstitials (SIAs)) and a low-angle grain boundary (GB) in bcc tungsten. The low-angle GB has biased absorption of SIAs over vacancies. We emphasize the significance of phenomena such as vacancy delocalization and SIA instant absorption around the GB dislocation cores in stabilizing the defect structures. Interstitial loading into the GB can dramatically enhance the interaction strength between the point defects and the GB due to SIA clustering (SIA cloud formation) or SIA vacancy recombination. We propose that the 'maximum atom displacement' can complement the 'vacancy formation energy' in evaluating unstable vacancy sites. Calculations of point defect migration barriers in the vicinity of GB dislocation cores show that vacancies and SIAs preferentially migrate along the pathways in the planes immediately above and below the core, respectively.

  3. A New Approach to Reducing Search Space and Increasing Efficiency in Simulation Optimization Problems via the Fuzzy-DEA-BCC

    Directory of Open Access Journals (Sweden)

    Rafael de Carvalho Miranda

    2014-01-01

    Full Text Available The development of discrete-event simulation software was one of the most successful interfaces in operational research with computation. As a result, research has been focused on the development of new methods and algorithms with the purpose of increasing simulation optimization efficiency and reliability. This study aims to define optimum variation intervals for each decision variable through a proposed approach which combines the data envelopment analysis with the Fuzzy logic (Fuzzy-DEA-BCC, seeking to improve the decision-making units’ distinction in the face of uncertainty. In this study, Taguchi’s orthogonal arrays were used to generate the necessary quantity of DMUs, and the output variables were generated by the simulation. Two study objects were utilized as examples of mono- and multiobjective problems. Results confirmed the reliability and applicability of the proposed method, as it enabled a significant reduction in search space and computational demand when compared to conventional simulation optimization techniques.

  4. Beyond chemical accuracy: The pseudopotential approximation in diffusion Monte Carlo calculations of the HCP to BCC phase transition in beryllium

    CERN Document Server

    Shulenburger, Luke; Desjarlais, M P

    2015-01-01

    Motivated by the disagreement between recent diffusion Monte Carlo calculations and experiments on the phase transition pressure between the ambient and beta-Sn phases of silicon, we present a study of the HCP to BCC phase transition in beryllium. This lighter element provides an oppor- tunity for directly testing many of the approximations required for calculations on silicon and may suggest a path towards increasing the practical accuracy of diffusion Monte Carlo calculations of solids in general. We demonstrate that the single largest approximation in these calculations is the pseudopotential approximation. After removing this we find excellent agreement with experiment for the ambient HCP phase and results similar to careful calculations using density functional theory for the phase transition pressure.

  5. Interplay between intrinsic point defects and low-angle grain boundary in bcc tungsten: effects of local stress field

    Science.gov (United States)

    Niu, Liang-Liang; Zhang, Ying; Shu, Xiaolin; Jin, Shuo; Zhou, Hong-Bo; Gao, Fei; Lu, Guang-Hong

    2015-06-01

    We have used molecular statics in conjunction with an embedded atom method to explore the interplay between native point defects (vacancies and self-interstitials (SIAs)) and a low-angle grain boundary (GB) in bcc tungsten. The low-angle GB has biased absorption of SIAs over vacancies. We emphasize the significance of phenomena such as vacancy delocalization and SIA instant absorption around the GB dislocation cores in stabilizing the defect structures. Interstitial loading into the GB can dramatically enhance the interaction strength between the point defects and the GB due to SIA clustering (SIA cloud formation) or SIA vacancy recombination. We propose that the ‘maximum atom displacement’ can complement the ‘vacancy formation energy’ in evaluating unstable vacancy sites. Calculations of point defect migration barriers in the vicinity of GB dislocation cores show that vacancies and SIAs preferentially migrate along the pathways in the planes immediately above and below the core, respectively.

  6. The electronic structure and bonding of a H-H pair in the vicinity of a BCC Fe bulk vacancy

    Energy Technology Data Exchange (ETDEWEB)

    Juan, A.; Pistonesi, C.; Brizuela, G. [Universidad Nacional del Sur, Bahia Blanca (Argentina). Departamento de Fisica; Garcia, A.J. [Universidad Nacional del Sur, Bahia Blanca (Argentina). Departamento de Ciencias de la Computacion

    2003-09-01

    The H-Fe interaction near a bcc Fe vacancy is analysed using a semi-empirical theoretical method. Calculations were performed using a Fe{sub 86} cluster with a vacancy. Hydrogen atoms are positioned in their local energy minima configurations. Changes in the electronic structure of Fe atoms near a vacancy were analysed for the system without H, with one H and with two H atoms. Fe atoms surrounding the vacancy weaken their bond when hydrogen is present. This is due to the formation of H-Fe bonds. Hydrogen influences only its nearest-neighbour Fe atoms. The H-H interaction was also analysed. For H-H distance of 0.82 Angstrom an H-H association is formed, while H-Fe interaction and Fe-Fe weakening is markedly reduced, when compared with other H-H interactions. (author)

  7. A low-cost BCC alloy prepared from a FeV80 alloy with a high hydrogen storage capacity

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Yigang; Chen, Yungui; Wu, Chaoling; Tao, Mingda; Liang, Hao [School of Materials Science and Engineering, Sichuan University, Chengdu 610064 (China)

    2007-02-10

    A V{sub 30}Ti{sub 32}Cr{sub 32}Fe{sub 6} alloy prepared from a FeV80 master alloy is reported. It has a high hydrogen absorption/desorption capacity, good activation performance and kinetics. Heat-treatment at 1673 K is an effective way to increase the capacity and flatten the plateau due to the homogenization of the compositions in the alloy and the disappearance of Laves phase after heat-treatment. The heat-treated alloy can absorb 3.76 wt.%H at 298 K. It desorbs 2.35 wt.%H at 298 K and 2.56 wt.%H at 373 K. The development of this alloy could be of great significance to the application of V-based BCC hydrogen storage alloys. (author)

  8. Fermentation RS3 derived from sago and rice starch with Clostridium butyricum BCC B2571 or Eubacterium rectale DSM 17629.

    Science.gov (United States)

    Purwani, Endang Yuli; Purwadaria, Tresnawati; Suhartono, Maggy Thenawidjaja

    2012-02-01

    Resistant starch type 3 (RS3) is retrograded starch which is not digested by human starch degrading enzyme, and will thus undergo bacterial degradation in the colon. The main fermentation products are the Short Chain Fatty Acid (SCFA): acetate, propionate and butyrate. SCFA has significant benefit impact on the metabolism of the host. The objectives of this research were to study the SCFA profile produced by colonic butyrate producing bacteria grown in medium containing RS3. RS3 was made from sago or rice starch treated with amylase, pullulanase and the combination of amylase and pullulanase. Fermentation study was performed by using Clostridium butyricum BCC B2571 or Eubacterium rectale DSM 17629, which has been identified as capable of degradation of starch residue and also regarded as beneficial bacteria. Experimental result revealed that enzyme hydrolysis of retrograded sago or rice starch was beneficial to RS formation. RS3 derived from sago contained higher RS (31-38%) than those derived from rice starch (21-26%). This study indicated that C. butyricum BCC B2571 produced acetate, propionate and butyrate at molar ratio of 1.8 : 1 : 1, when the medium was supplemented with RSSA at concentration 1%. In the medium containing similar substrate, E. rectale DSM 17629 produced acetate, propionate and butyrate at molar ratio of 1.7 : 1 : 1.2. High levels of acetate, propionate and butyrate at molar ratio of 1.8 : 1 : 1.1 was also produced by E. rectale DSM 17629 in medium supplemented with RSSP at concentration 1%. The results showed that both bacteria responded differently to the RS3 supplementation. Such result provided insight into the possibility of designing RS3 as prebiotic with featured regarding SCFA released in the human colon with potential health implication.

  9. Characterizing twist grain boundaries in BCC Nb by molecular simulation: Structure and shear deformation

    Science.gov (United States)

    Liu, Zeng-Hui; Feng, Ya-Xin; Shang, Jia-Xiang

    2016-05-01

    Atomic scale modeling was used to study the structure, energy and shear behaviors of (110) twist grain boundaries (TWGBs) in body-centered cubic Nb. The relation between grain boundary energy (GBE) and the twist angle θ agrees well with the Read-Shockley equation in low-angle range. At higher angles, the GBEs show no distinct trend with the variation of the twist angle or the density of coincident lattice sites. All (110) twist boundaries can be classified into two types: low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs). LAGBs contain a hexagonal dislocation network (HDN) which is composed of 1/2 [ 111 ], 1/2 [ 1 bar 1 bar 1 ] and [001] screw dislocations. HAGBs can be classified into three sub-types further: special boundaries with low Σ, boundaries in the vicinity of special boundaries with similar structures and ordinary HAGBs consisting of periodic patterns. Besides, a dependence of grain boundary shear response vs the twist angle over the entire twist angle range is obtained. Pure sliding behavior is found at all TWGBs. When θ < 12°, the flow stress of LAGBs is found to be correlated with the HDNs and decreases with the increasing twist angle. For ordinary HAGBs, the magnitude of flow stress is around 0.8-1.0 GPa and the twist angle has little effect on the anisotropy mobility. For special grain boundaries with low Σ, the boundary structures govern the GBEs and shear motion behavior significantly.

  10. One-dimensional lattices topologically equivalent to two-dimensional lattices within the context of the lattice gas model

    Science.gov (United States)

    Costanza, E. F.; Costanza, G.

    2016-10-01

    Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a rectangular lattice. This example shows the general features that possess the procedure and extensions are also suggested in order to provide a wider insight in the present approach.

  11. Tiling Lattices with Sublattices, II

    CERN Document Server

    Feldman, David; Robins, Sinai

    2010-01-01

    Our earlier article proved that if $n > 1$ translates of sublattices of $Z^d$ tile $Z^d$, and all the sublattices are Cartesian products of arithmetic progressions, then two of the tiles must be translates of each other. We re-prove this Theorem, this time using generating functions. We also show that for $d > 1$, not every finite tiling of $Z^d$ by lattices can be obtained from the trivial tiling by the process of repeatedly subdividing a tile into sub-tiles that are translates of one another.

  12. Lattice Stern-Gerlach experiment

    CERN Document Server

    Luschevskaya, E V; Teryaev, O V

    2016-01-01

    We investigate the dependence of ground state energies of charged vector $\\rho$ and $K^{*}$ mesons on the value of magnetic field in the $SU(3)$ lattice gauge theory. It has been shown that the energy of a vector particle strongly depends on its spin projection on the field axis, and the magnetic dypole polarizability and hyperpolarizabilities give a large contribution to the meson energy at large fields. We calculate the g-factor of $\\rho^{\\pm}$ and $K^{*\\pm}$ mesons. Tensor of the dypole magnetic polarizability of the charged $\\rho$ meson at rest has been found.

  13. Fractal lattice of gelatin nanoglobules

    Science.gov (United States)

    Novikov, D. V.; Krasovskii, A. N.

    2012-11-01

    The globular structure of polymer coatings on a glass, which were obtained from micellar solutions of gelatin in the isooctane-water-sodium (bis-2-ethylhexyl) sulfosuccinate system, has been studied using electron microscopy. It has been shown that an increase in the average globule size is accompanied by the formation of a fractal lattice of nanoglobules and a periodic physical network of macromolecules in the coating. The stability of such system of the "liquid-in-a-solid" type is limited by the destruction of globules and the formation of a homogeneous network structure of the coating.

  14. Hadron structure from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Green, Jeremy [Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz (Germany)

    2016-01-22

    Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, this situation is improving. Some calculations have produced agreement with experiment for key observables such as the axial charge and electromagnetic form factors, and the improved understanding of systematic errors will help to increase confidence in predictions of unmeasured quantities. The long-omitted disconnected contributions are now seeing considerable attention and some recent calculations of them will be discussed.

  15. Hadron Structure from Lattice QCD

    CERN Document Server

    Green, Jeremy

    2014-01-01

    Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, this situation is improving. Some calculations have produced agreement with experiment for key observables such as the axial charge and electromagnetic form factors, and the improved understanding of systematic errors will help to increase confidence in predictions of unmeasured quantities. The long-omitted disconnected contributions are now seeing considerable attention and some recent calculations of them will be discussed.

  16. Working Group Report: Lattice Field Theory

    Energy Technology Data Exchange (ETDEWEB)

    Blum, T.; et al.,

    2013-10-22

    This is the report of the Computing Frontier working group on Lattice Field Theory prepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theory community and argue that continued support of the U.S. (and worldwide) lattice-QCD effort is essential to fully capitalize on the enormous investment in the high-energy physics experimental program. We first summarize the dramatic progress of numerical lattice-QCD simulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. Lattice-QCD Collaboration, and describe a broad program of lattice-QCD calculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardware and software resources needed to undertake these calculations.

  17. Triangle Lattice Green Functions for Vector Fields

    Science.gov (United States)

    Moritz, Brian; Schwalm, William

    2000-03-01

    The triangle lattice is convenient for modeling fields and fluid flows in two dimensions. Discrete vector field equations are defined through the analogy between differential forms and simplicial homology theory. The basic vector difference operators on the lattice correspond to the graph adjacency matricies of the triangle, honeycomb, and Kagomé lattices. The scalar Green functions for nearest neighbor interactions on the triangle lattice are known in closed form in terms of the complete elliptic integrals. Green functions for vector field operators are obtained explicitly in terms of the known scalar Green functions. The scalar Green functions for the Kagomé lattice are thus written in terms of the Green functions for the triangle lattice and ultimately in closed form. Thus, Green functions for a wide range of vector difference models are reduced to closed form in terms of the complete elliptic integrals.

  18. Optical Lattice Simulations of Correlated Fermions

    Science.gov (United States)

    2013-10-04

    simple-cubic optical lattice, , (06 2009): 0. doi: 09/20/2013 51.00 Tin-Lun Ho, Qi Zhou. Squeezing out the entropy of fermions in optical lattices...Convention and Exhibition Center, Hong Kong, May 12, 2009 "Reducing Entropy in Quantum Gases in optical lattices", Jason Ho, Aspen workshop on quantum...Sciences Randall Hulet: chosen as a 2010 Outstanding Referee of the Physical Review and Physical Review Letters Journals Randall Hulet: Willis E. Lamb

  19. Improved Lattice Actions with Chemical Potential

    CERN Document Server

    Bietenholz, W

    1998-01-01

    We give a prescription how to include a chemical potential \\mu into a general lattice action. This inclusion does not cause any lattice artifacts. Hence its application to an improved - or even perfect - action at \\mu =0 yields an improved resp. perfect action at arbitrary \\mu. For short-ranged improved actions, a good scaling behavior holds over a wide region, and the upper bound for the baryon density - which is known for the standard lattice actions - can be exceeded.

  20. SUPER-B LATTICE STUDIES

    Energy Technology Data Exchange (ETDEWEB)

    Biagini, M.E.; Raimondi, P.; /Frascati; Piminov, P.; Sinyatkin, S.; /Novosibirsk, IYF; Nosochkov, Y.; Wittmer, W.; /SLAC

    2010-08-25

    The SuperB asymmetric e{sup +}e{sup -} collider is designed for 10{sup 36} cm{sup -2} s{sup -1} luminosity and beam energies of 6.7 and 4.18 GeV for e{sup +} and e{sup -} respectively. The High and Low Energy Rings (HER and LER) have one Interaction Point (IP) with 66 mrad crossing angle. The 1258 m rings fit to the INFN-LNF site at Frascati. The ring emittance is minimized for the high luminosity. The Final Focus (FF) chromaticity correction is optimized for maximum transverse acceptance and energy bandwidth. Included Crab Waist sextupoles suppress betatron resonances induced in the collisions with a large Piwinski angle. The LER Spin Rotator sections provide longitudinally polarized electron beam at the IP. The lattice is flexible for tuning the machine parameters and compatible with reusing the PEP-II magnets, RF cavities and other components. Details of the lattice design are presented.

  1. Introduction to Vortex Lattice Theory

    Directory of Open Access Journals (Sweden)

    Santiago Pinzón

    2015-10-01

    Full Text Available Panel methods have been widely used in industry and are well established since the 1970s for aerodynamic analysis and computation. The Vortex Lattice Panel Method presented in this study comes across a sophisticated method that provides a quick solution time, allows rapid changes in geometry and suits well for aerodynamic analysis. The aerospace industry is highly competitive in design efficiency, and perhaps one of the most important factors on airplane design and engineering today is multidisciplinary optimization.  Any cost reduction method in the design cycle of a product becomes vital in the success of its outcome. The subsequent sections of this article will further explain in depth the theory behind the vortex lattice method, and the reason behind its selection as the method for aerodynamic analysis during preliminary design work and computation within the aerospace industry. This article is analytic in nature, and its main objective is to present a mathematical summary of this widely used computational method in aerodynamics.

  2. QCD thermodynamics on a lattice

    Science.gov (United States)

    Levkova, Ludmila A.

    Numerical simulations of full QCD on anisotropic lattices provide a convenient way to study QCD thermodynamics with fixed physics scales and reduced lattice spacing errors. We report results from calculations with two flavors of dynamical staggered fermions, where all bare parameters and the renormalized anisotropy are kept constant and the temperature is changed in small steps by varying only the number of time slices. Including results from zero-temperature scale setting simulations, which determine the Karsch coefficients, allows for the calculation of the Equation of State at finite temperatures. We also report on studies of the chiral properties of dynamical domain-wall fermions combined with the DBW2 gauge action for different gauge couplings and fermion masses. For quenched theories, the DBW2 action gives a residual chiral symmetry breaking much smaller than what was found with more traditional choices for the gauge action. Our goal is to investigate the possibilities which this and further improvements provide for the study of QCD thermodynamics and other simulations at stronger couplings.

  3. Lattice theory special topics and applications

    CERN Document Server

    Wehrung, Friedrich

    2014-01-01

    George Grätzer's Lattice Theory: Foundation is his third book on lattice theory (General Lattice Theory, 1978, second edition, 1998). In 2009, Grätzer considered updating the second edition to reflect some exciting and deep developments. He soon realized that to lay the foundation, to survey the contemporary field, to pose research problems, would require more than one volume and more than one person. So Lattice Theory: Foundation provided the foundation. Now we complete this project with Lattice Theory: Special Topics and Applications, written by a distinguished group of experts, to cover some of the vast areas not in Foundation. This first volume is divided into three parts. Part I. Topology and Lattices includes two chapters by Klaus Keimel, Jimmie Lawson and Ales Pultr, Jiri Sichler. Part II. Special Classes of Finite Lattices comprises four chapters by Gabor Czedli, George Grätzer and Joseph P. S. Kung. Part III. Congruence Lattices of Infinite Lattices and Beyond includes four chapters by Friedrich W...

  4. Cooperative Ordering in Lattices of Interacting Dipoles

    CERN Document Server

    Bettles, Robert J; Adams, Charles S

    2014-01-01

    Using classical electrodynamics simulations we investigate the cooperative behavior of regular monolayers of induced two-level dipoles, including their cooperative decays and shifts. For the particular case of the kagome lattice we observe behavior akin to EIT for lattice spacings less than the probe wavelength. Within this region the dipoles exhibit ferroelectric and anti-ferroelectric ordering. We also model how the cooperative response is manifested in the optical transmission through the kagome lattice, with sharp changes in transmission from 10% to 80% for small changes in lattice spacing.

  5. A Lattice Study of the Glueball Spectrum

    Institute of Scientific and Technical Information of China (English)

    LIU Chuan

    2001-01-01

    The glueball spectrum is studied using an improved gluonic action on asymmetric lattices in the pure SU(3) lattice gauge theory. The smallest spatial lattice spacing is about 0.08 fm which makes the extrapolation to the ontinuum limit more reliable. Converting our lattice results to physical units using the scale set by the static quark potential, we obtain the following results for the glueball masses: MG(0++) -= 1730(90) MeV for the scalarglueball and MG(2++) = 2400(95) MeV for the tensor glueball.

  6. On the lattice rotations accompanying slip

    DEFF Research Database (Denmark)

    Wronski, M.; Wierzbanowski, K.; Leffers, Torben

    2013-01-01

    of the crystal lattices, and this texture may have a strong effect on the properties of the materials. The texture is introduced by lattice rotations in the individual grains during processing. The present critical assessment deals with the lattice rotations during rolling of face centred cubic (fcc) metals...... and alloys. Sixteen years ago, a modification of the traditional procedure for the calculation of these lattice rotations was suggested, a modification that would permit a realistic modelling of the development of the brass type texture, one of the two types of texture developed during rolling of fcc...

  7. Holographic Lattices Give the Graviton a Mass

    CERN Document Server

    Blake, Mike; Vegh, David

    2014-01-01

    We discuss the DC conductivity of holographic theories with translational invariance broken by a background lattice. We show that the presence of the lattice induces an effective mass for the graviton via a gravitational version of the Higgs mechanism. This allows us to obtain, at leading order in the lattice strength, an analytic expression for the DC conductivity in terms of the size of the lattice at the horizon. In locally critical theories this leads to a power law resistivity that is in agreement with an earlier field theory analysis of Hartnoll and Hofman.

  8. One-dimensional lattices topologically equivalent to two-dimensional lattices within the context of the lattice gas model. II The triangular lattice

    Science.gov (United States)

    Costanza, E. F.; Costanza, G.

    2016-12-01

    Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a triangular lattice. This example shows the general features that possess the procedure and extensions are also suggested in order to provide a wider insight in the present approach.

  9. Light propagation in optically induced Fibonacci lattices

    CERN Document Server

    Boguslawski, Martin; Timotijevic, Dejan V; Denz, Cornelia; Savic, Dragana M Jovic

    2015-01-01

    We report on the optical induction of Fibonacci lattices in photorefractive strontium barium niobate by use of Bessel beam waveguide-wise writing techniques. Fibonacci elements A and B are used as lattice periods. We further use the induced structures to execute probing experiments with variously focused Gaussian beams in order to observe light confinement owing to the quasiperiodic character of Fibonacci word sequences. Essentially, we show that Gaussian beam expansion is just slowed down in Fibonacci lattices, as compared with appropriate periodic lattices.

  10. One-dimensional lattices topologically equivalent to two-dimensional lattices within the context of the lattice gas model, III. The hexagonal lattice

    Science.gov (United States)

    Costanza, E. F.; Costanza, G.

    2017-02-01

    Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a hexagonal lattice which has the particular feature that need four types of dynamical variables. This example shows additional features to the general procedure and some extensions are also suggested in order to provide a wider insight in the present approach.

  11. Alteration of negative lattice expansion of the La(Fe,Si)13-type phase in LaFe11.14-xCo0.66NixSi1.2 alloys

    Science.gov (United States)

    Gębara, P.; Pawlik, P.; Hasiak, M.

    2017-01-01

    Inthe present work the temperature dependence of lattice parameters and magnetic properties of the LaFe11.14-xCo0.66NixSi1.2 (where x=0.1,0.2,0.3) alloys were investigated. X-ray diffraction studies of all specimens revealed coexistence of two crystalline phases: the dominant La(Fe, Si)13-type phase and minor fraction of bcc α-Fe. Furthermore changes in negative lattice expansion with the increase of Ni content in the alloy composition were also shown. The increase of Ni content caused rise of the Curie temperature and decrease of the amplitude of magnetic entropy changes.

  12. Fuzzy Ideals and Fuzzy Distributive Lattices%Fuzzy Ideals and Fuzzy Distributive Lattices*

    Institute of Scientific and Technical Information of China (English)

    S.H.Dhanani; Y. S. Pawar

    2011-01-01

    Our main objective is to study properties of a fuzzy ideals (fuzzy dual ideals). A study of special types of fuzzy ideals (fuzzy dual ideals) is also furnished. Some properties of a fuzzy ideals (fuzzy dual ideals) are furnished. Properties of a fuzzy lattice homomorphism are discussed. Fuzzy ideal lattice of a fuzzy lattice is defined and discussed. Some results in fuzzy distributive lattice are proved.

  13. bcc-Fe空位浓度对辐照损伤影响的分子动力学模拟%Molecular Dynamics Simulation of Vacancy Concentration on Irradiation Cascades Damage Effects in bcc-Fe

    Institute of Scientific and Technical Information of China (English)

    王建伟; 尚新春; 吕国才

    2011-01-01

    中子辐照引起的位移级联能在金属中产生各种缺陷.通过三维分子动力学方法模拟了bcc-Fe在不同空位浓度下中子辐照的位移级联过程.模拟结果表明,在空位浓度0%和初始碰撞原子能量5keV的情形下,位移级联过程会出现大量空位、间隙原子团等缺陷.经过0.5ps后点缺陷数量NF达到最大值1632,之后其逐渐减少,10ps后稳定在60.预置空位的存在加速了级联过程中点缺陷的湮灭.进一步的模拟指出,预置空位浓度越高,则点缺陷复合也就越快.这些结果有助于描述核反应堆结构钢的某些微观失效机理.%The neutron irradiation on metal materials could generate various defects which are caused by displacement cascades. The displacement cascades of neutron irradiation with various vacancy concentrations in bcc-Fe are simulated by three-dimensional molecular dynamics method. The simulation results show that a large number of vacancies and self interstitial atoms (SIAs) clusters would appear for the case of 0% vacancy concentration and 5keV primary knock-on atom energy. The number of point defect NF reached to peak value 1632 after 0. 5ps. It will decrease sequently and the number of point defect will go stable value 60 after 10 ps. The existence of pre-vacancy defects would accelerate the defect annihilation in the cascade process. The further simulation indicated that the defect annihilation is the faster in the case of the higher pre-vacancy concentration. These results could be useful for describing some mechanism of microcosmic failure for structural steels components in nuclear reactors.

  14. Growth and investigation of the Slater-Pauling behavior by X-ray characterization of single crystal bcc FexMn1-x on MgO(001)

    Science.gov (United States)

    Bhatkar, Harshawardhan Ramesh

    Magnetic memory storage industry is always searching for materials that can store, read, and write data ever so faster, with lower power, with accuracy and on denser packaging. The material research was spurred with discovery and successful implementation of Giant Magnetoresistance phenomena into critical components of devices. GMR devices essentially were multilayered thin films of a set of magnetically ordered metals. Fe-Mn thin films were used to create one of its moment pinning layers. Fcc Fe-Mn thin films were studied enthusiastically for their AFM properties but very little was known about the rare bcc structured single crystals. Bcc Fe-Mn was found to be ferromagnetic in parts of phase diagram of Fe-Mn. The magnetic moment of alloys usually follows a regular linear trend based upon electronic configuration of constituent elements, known as Slater-Pauling curve. While most alloys follow the trend, bcc Fe-Mn binary alloys show a dramatic collapse in the bulk magnetic moment, as concentration of Mn is varied. In this work, we successfully fabricate bcc single crystal thin film of Fe-Mn on MgO(001) substrate by Molecular Beam Epitaxy method. We confirm using Reflection High Energy Electron Diffraction that, the bcc phase of Fe-Mn thin film is achieved, albeit being a forced structure, stable up to 35% of Mn concentration. X-ray absorption spectra of individual elements were used to confirm the compositions of Fe-Mn films and x-ray magnetic circular dichroism was used to track the elemental magnetic moment as the composition was varied. We found that the magnetic moment of Fe drops faster than expected and Mn has very small identical moment in all compositions. We also successfully created a compositionally graded Fe-Mn sample in MBE and spatially mapped its Fe moment by around the critical composition. The mechanism for collapse of magnetic moment over a spread of composition of Mn is a very complex problem yet we provide our experimental findings of

  15. Hadron physics from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Andreas [Regensburg Univ. (Germany). Inst. for Theoretical Physics

    2016-11-01

    Particle physics experiments at modern high luminosity particle accelerators achieve orders of magnitude higher count rates than what was possible ten or twenty years ago. This extremely large statistics allows to draw far reaching conclusions even from minute signals, provided that these signals are well understood by theory. This is, however, ever more difficult to achieve. Presently, technical and scientific progress in general and experimental progress in particle physics in particular, shows typically an exponential growth rate. For example, data acquisition and analysis are, among many other factor, driven by the development of ever more efficient computers and thus by Moore's law. Theory has to keep up with this development by also achieving an exponential increase in precision, which is only possible using powerful computers. This is true for both types of calculations, analytic ones as, e.g., in quantum field perturbation theory, and purely numerical ones as in Lattice QCD. As stated above such calculations are absolutely indispensable to make best use of the extremely costly large particle physics experiments. Thus, it is economically reasonable to invest a certain percentage of the cost of accelerators and experiments in related theory efforts. The basic ideas behind Lattice QCD simulations are the following: Because quarks and gluons can never be observed individually but are always ''confined'' into colorless hadrons, like the proton, all quark-gluon states can be expressed in two different systems of basis states, namely in a quark-gluon basis and the basis of hadron states. The proton, e.g., is an eigenstate of the latter, a specific quark-gluon configuration is part of the former. In the quark-gluon basis a physical hadron, like a proton, is given by an extremely complicated multi-particle wave function containing all effects of quantum fluctuations. This state is so complicated that it is basically impossible to model it

  16. Bimaterial lattices as thermal adapters and actuators

    Science.gov (United States)

    Toropova, Marina M.; Steeves, Craig A.

    2016-11-01

    The goal of this paper is to demonstrate how anisotropic biomaterial lattices can be used in thermal actuation. Compared to other lattices with tailored thermal expansion, the anisotropy of these bimaterial lattices makes them uniquely suitable for use as thermal actuators. Each individual cell, and hence lattices consisting of such cells, can be designed with widely different predetermined coefficients of thermal expansion (CTE) in different directions, enabling complex shape changes appropriate for actuation with either passive or active control. The lattices are composed of planar non-identical cells that each consist of a skewed hexagon surrounding an irregular triangle. The cells and all members of any cell are connected to each other by pins so that they have no rotational constraints and are able to expand or contract freely. In this case, the skew angles of the hexagon and the ratio of the CTEs of the two component materials determine the overall performance of the lattice. At its boundaries, the lattice is connected to substrates by pins and configured such that the CTE between two neighboring lattice vertices coincides with the CTE of the adjacent substrate. Provided the boundary behavior of the lattice is matched to the thermal properties of the substrates, temperature changes in the structure produce thermal strains without producing any corresponding stresses. Such lattices can be used in three different ways: as adaptive elements for stress-free connection of components with different CTEs; for fine tuning of structures; and as thermally driven actuators. In this paper, we demonstrate some concepts for lattice configurations that produce thermally-driven displacements that enable several actuators: a switch, a valve and tweezers.

  17. Cold atoms in a rotating optical lattice

    Science.gov (United States)

    Foot, Christopher J.

    2009-05-01

    We have demonstrated a novel experimental arrangement which can rotate a two-dimensional optical lattice at frequencies up to several kilohertz. Our arrangement also allows the periodicity of the optical lattice to be varied dynamically, producing a 2D ``accordion lattice'' [1]. The angles of the laser beams are controlled by acousto-optic deflectors and this allows smooth changes with little heating of the trapped cold (rubidium) atoms. We have loaded a BEC into lattices with periodicities ranging from 1.8μm to 18μm, observing the collapse and revival of the diffraction orders of the condensate over a large range of lattice parameters as recently reported by a group in NIST [2]. We have also imaged atoms in situ in a 2D lattice over a range of lattice periodicities. Ultracold atoms in a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, i.e. the Hamiltonian of the atoms in the rotating frame resembles that of a charged particle in a strong magnetic field. In the future, we plan to use this to investigate a range of phenomena such as the analogue of the fractional quantum Hall effect. [4pt] [1] R. A. Williams, J. D. Pillet, S. Al-Assam, B. Fletcher, M. Shotter, and C. J. Foot, ``Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms,'' Opt. Express 16, 16977-16983 (2008) [0pt] [2] J. H. Huckans, I. B. Spielman, B. Laburthe Tolra, W. D. Phillips, and J. V. Porto, Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice, arXiv:0901.1386v1

  18. GENERALIZATIONS AND CARTESIAN CLOSED SUBCATEGORIES OF SEMICONTINUOUS LATTICES

    Institute of Scientific and Technical Information of China (English)

    Li Qingguo; Wu Xiuhua

    2009-01-01

    In this article, the authors mainly study how to obtain new semicontinuous lattices from the given semicontinuous lattices and discuss the conditions under which the image of a semicontinuous projection operator is also semicontinuons. Moreover, the authors investigate the relation between semicontinuous lattices and completely distributive lattices. Finally, it is proved that the strongly sernicontinuons lattice category is a Cartesian closed category.

  19. Microstructural Characterization of Dislocation Networks During Harper-Dorn Creep of fcc, bcc, and hcp Metals and Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Przystupa, Marek A.

    2007-12-13

    Harper-Dorn (H-D) creep is observed in metals and geological materials exposed to very low stresses at temperatures close to the melting point. It is one of several types of creep processes wherein the steady-state strain rate is proportional to the applied stress, Nabarro-Herring creep and Coble creep being two other important processes. H-D creep can be somewhat insidious because the creep rates are much larger than those expected for Nabarro-Herring or Coble creep. Since the working conditions of structural components of power plants and propulsion systems, as well as the motion of the earth’s mantle all involve very low stresses, an understanding of the factors controlling H-D creep is critical in preventing failures associated with those higher-than-expected creep rates. The purpose of this investigation was to obtain missing microstructural information on the evolution of the dislocation structures during static annealing of materials with fcc, bcc and hcp structure and use obtained results to test predictive capabilities of the dislocation network theory of H-D creep. In our view the evolutionary processes during static annealing and during Harper-Dorn creep are intimately related. The materials used in this study were fcc aluminum, hcp zinc and bcc tin. All characterizations of dislocation structures, densities and dislocation link length distributions were carried out using the etch pit method. To obtain quantitative information on the evolution of the dislocation networks during annealing the pure fcc aluminum samples were pre-deformed by creep at 913 and 620 K and then annealed. The higher deformation temperature was selected to generate starting dislocation networks similar to those forming during Harper-Dorn creep and the lower, to obtain higher dislocation densities suitable for reliable estimates of the parameters of the network growth law. The measured experimental link length distribution were, after scaling, (1) the same for all annealing

  20. Surface solitons in trilete lattices

    CERN Document Server

    Stojanovic, M; Hadzievski, Lj; Malomed, B A

    2011-01-01

    Fundamental solitons pinned to the interface between three semi-infinite one-dimensional nonlinear dynamical chains, coupled at a single site, are investigated. The light propagation in the respective system with the self-attractive on-site cubic nonlinearity, which can be implemented as an array of nonlinear optical waveguides, is modeled by the system of three discrete nonlinear Schr\\"{o}dinger equations. The formation, stability and dynamics of symmetric and asymmetric fundamental solitons centered at the interface are investigated analytically by means of the variational approximation (VA) and in a numerical form. The VA predicts that two asymmetric and two antisymmetric branches exist in the entire parameter space, while four asymmetric modes and the symmetric one can be found below some critical value of the inter-lattice coupling parameter -- actually, past the symmetry-breaking bifurcation. At this bifurcation point, the symmetric branch is destabilized and two new asymmetric soliton branches appear, ...

  1. FFAG lattice without opposite bends

    Science.gov (United States)

    Trbojevic, Dejan; Courant, Ernest D.; Garren, Al

    2000-08-01

    A future "neutrino factory" or Muon Collider requires fast muon acceleration before the storage ring. Several alternatives for fast muon acceleration have previously been considered. One of them is the FFAG (Fixed Field Alternating Gradient) synchrotron. The FFAG concept was developed in 1952 by K. R. Symon (ref. 1). The advantages of this design are the fixed magnetic field, large range of particle energy, simple RF; power supplies are simple, and there is no transition energy. But a drawback is that reverse bending magnets are included in the configuration; this increases the size and cost of the ring. Recently some modified FFAG lattice designs have been described where the amount of opposite bending was significantly reduced (ref. 2, ref. 3).

  2. FFAG lattice without opposite bends

    CERN Document Server

    Trbojevic, D; Garren, A

    2000-01-01

    A future 'neutrino factory' or Muon Collider requires fast muon acceleration before the storage ring. Several alternatives for fast muon acceleration have previously been considered. One of them is the FFAG (Fixed Field Alternating Gradient) synchrotron. The FFAG concept was developed in 1952 by K. R. Symon (ref. 1). The advantages of this design are the fixed magnetic field, large range of particle energy, simple RF; power supplies are simple, and there is no transition energy. But a drawback is that reverse bending magnets are included in the configuration; this increases the size and cost of the ring. Recently some modified FFAG lattice designs have been described where the amount of opposite bending was significantly reduced (ref. 2, ref. 3).

  3. Landau Levels in Lattice QCD

    CERN Document Server

    Bruckmann, Falk; Giordano, Matteo; Katz, Sandor D; Kovacs, Tamas G; Pittler, Ferenc; Wellnhofer, Jacob

    2016-01-01

    The spectrum of the two-dimensional continuum Dirac operator in the presence of a uniform background magnetic field consists of Landau levels, which are degenerate and separated by gaps. On the lattice the Landau levels are spread out by discretization artefacts, but a remnant of their structure is clearly visible (Hofstadter butterfly). If one switches on a non-Abelian interaction, the butterfly structure will be smeared out, but the lowest Landau level (LLL) will still be separated by a gap from the rest of the spectrum. In this talk we discuss how one can define the LLL in QCD and check how well certain physical quantities are approximated by taking into account only the LLL.

  4. Thermal cascaded lattice Boltzmann method

    CERN Document Server

    Fei, Linlin

    2016-01-01

    In this paper, a thermal cascaded lattice Boltzmann method (TCLBM) is developed in combination with the double-distribution-function (DDF) approach. A density distribution function relaxed by the cascaded scheme is employed to solve the flow field, and a total energy distribution function relaxed by the BGK scheme is used to solve temperature field, where two distribution functions are coupled naturally. The forcing terms are incorporated by means of central moments, which is consistent with the previous force scheme [Premnath \\emph{et al.}, Phys. Rev. E \\textbf{80}, 036702 (2009)] but the derivation is more intelligible and the evolution process is simpler. In the method, the viscous heat dissipation and compression work are taken into account, the Prandtl number and specific-heat ratio are adjustable, the external force is considered directly without the Boussinesq assumption, and the low-Mach number compressible flows can also be simulated. The forcing scheme is tested by simulating a steady Taylor-Green f...

  5. Gluonic Transversity from Lattice QCD

    CERN Document Server

    Detmold, W

    2016-01-01

    We present an exploratory study of the gluonic structure of the $\\phi$ meson using lattice QCD (LQCD). This includes the first investigation of gluonic transversity via the leading moment of the twist-two double-helicity-flip gluonic structure function $\\Delta(x,Q^2)$. This structure function only exists for targets of spin $J\\ge1$ and does not mix with quark distributions at leading twist, thereby providing a particularly clean probe of gluonic degrees of freedom. We also explore the gluonic analogue of the Soffer bound which relates the helicity flip and non-flip gluonic distributions, finding it to be saturated at the level of 80%. This work sets the stage for more complex LQCD studies of gluonic structure in the nucleon and in light nuclei where $\\Delta(x,Q^2)$ is an 'exotic glue' observable probing gluons in a nucleus not associated with individual nucleons.

  6. Approximate common divisors via lattices

    CERN Document Server

    Cohn, Henry

    2011-01-01

    We analyze the multivariate generalization of Howgrave-Graham's algorithm for the approximate common divisor problem. In the m-variable case with modulus N and approximate common divisor of size N^beta, this improves the size of the error tolerated from N^(beta^2) to N^(beta^((m+1)/m)), under a commonly used heuristic assumption. This gives a more detailed analysis of the hardness assumption underlying the recent fully homomorphic cryptosystem of van Dijk, Gentry, Halevi, and Vaikuntanathan. While these results do not challenge the suggested parameters, a 2^sqrt(n) approximation algorithm for lattice basis reduction in n dimensions could be used to break these parameters. We have implemented our algorithm, and it performs better in practice than the theoretical analysis suggests. Our results fit into a broader context of analogies between cryptanalysis and coding theory. The multivariate approximate common divisor problem is the number-theoretic analogue of noisy multivariate polynomial interpolation, and we ...

  7. Optical Lattices with Micromechanical Mirrors

    CERN Document Server

    Hammerer, K; Genes, C; Zoller, P; Treutlein, P; Camerer, S; Hunger, D; Haensch, T W

    2010-01-01

    We investigate a setup where a cloud of atoms is trapped in an optical lattice potential of a standing wave laser field which is created by retro-reflection on a micro-membrane. The membrane vibrations itself realize a quantum mechanical degree of freedom. We show that the center of mass mode of atoms can be coupled to the vibrational mode of the membrane in free space, and predict a significant sympathetic cooling effect of the membrane when atoms are laser cooled. The controllability of the dissipation rate of the atomic motion gives a considerable advantage over typical optomechanical systems enclosed in optical cavities, in that it allows a segregation between the cooling and coherent dynamics regimes. The membrane can thereby be kept in a cryogenic environment, and the atoms at a distance in a vacuum chamber.

  8. Technicolor and Lattice Gauge Theory

    CERN Document Server

    Chivukula, R Sekhar

    2010-01-01

    Technicolor and other theories of dynamical electroweak symmetry breaking invoke chiral symmetry breaking triggered by strong gauge-dynamics, analogous to that found in QCD, to explain the observed W, Z, and fermion masses. In this talk we describe why a realistic theory of dynamical electroweak symmetry breaking must, relative to QCD, produce an enhanced fermion condensate. We quantify the degree to which the technicolor condensate must be enhanced in order to yield the observed quark masses, and still be consistent with phenomenological constraints on flavor-changing neutral-currents. Lattice studies of technicolor and related theories provide the only way to demonstrate that such enhancements are possible and, hopefully, to discover viable candidate models. We comment briefly on the current status of non-perturbative investigations of dynamical electroweak symmetry breaking, and provide a "wish-list" of phenomenologically-relevant properties that are important to calculate in these theories

  9. Lattice Models of Quantum Gravity

    CERN Document Server

    Bittner, E R; Holm, C; Janke, W; Markum, H; Riedler, J

    1998-01-01

    Standard Regge Calculus provides an interesting method to explore quantum gravity in a non-perturbative fashion but turns out to be a CPU-time demanding enterprise. One therefore seeks for suitable approximations which retain most of its universal features. The $Z_2$-Regge model could be such a desired simplification. Here the quadratic edge lengths $q$ of the simplicial complexes are restricted to only two possible values $q=1+\\epsilon\\sigma$, with Ising model. To test whether this simpler model still contains the essential qualities of the standard Regge Calculus, we study both models in two dimensions and determine several observables on the same lattice size. In order to compare expectation values, e.g. of the average curvature or the Liouville field susceptibility, we employ in both models the same functional integration measure. The phase structure is under current investigation using mean field theory and numerical simulation.

  10. Lattice mechanics of origami tessellations.

    Science.gov (United States)

    Evans, Arthur A; Silverberg, Jesse L; Santangelo, Christian D

    2015-07-01

    Origami-based design holds promise for developing materials whose mechanical properties are tuned by crease patterns introduced to thin sheets. Although there have been heuristic developments in constructing patterns with desirable qualities, the bridge between origami and physics has yet to be fully developed. To truly consider origami structures as a class of materials, methods akin to solid mechanics need to be developed to understand their long-wavelength behavior. We introduce here a lattice theory for examining the mechanics of origami tessellations in terms of the topology of their crease pattern and the relationship between the folds at each vertex. This formulation provides a general method for associating mechanical properties with periodic folded structures and allows for a concrete connection between more conventional materials and the mechanical metamaterials constructed using origami-based design.

  11. Pion structure from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Javadi Motaghi, Narjes

    2015-05-12

    In this thesis we use lattice QCD to compute the second Mellin moments of pion generalized parton distributions and pion electromagnetic form factors. For our calculations we are able to analyze a large set of gauge configurations with 2 dynamical flavours using non-perturbatively the improved Wilson-Sheikholeslami-Wohlert fermionic action pion masses ranging down to 151 MeV. By employing improved smearing we were able to suppress excited state contamination. However, our data in the physical quark mass limit show that some excited state contamination remains. We show the non-zero sink momentum is optimal for the computation of the electromagnetic form factors and generalized form factors at finite momenta.

  12. p-systems in local Noether lattices

    Directory of Open Access Journals (Sweden)

    E. W. Johnson

    1994-01-01

    Full Text Available In this paper we introduce the concept of a p-system in a local Noether lattice and obtain several characterizations of these elements. We first obtain a topological characterization and then a characterization in terms of the existence of a certain type of decreasing sequence of elements. In addition, p-systems are characterized in quotient lattices and completions.

  13. Lattice QCD simulations beyond the quenched approximation

    Energy Technology Data Exchange (ETDEWEB)

    Ukawa, A. (European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.)

    1989-07-01

    Present status of lattice QCD simulations incorporating the effects of dynamical quarks is presented. After a brief review of the formalism of lattice QCD, the dynamical fermion algorithms in use today are described. Recent attempts at the hadron mass calculation are discussed in relation to the quenched results, and current understanding on the finite temperature behavior of QCD is summarized. (orig.).

  14. Lattice Platonic Solids and their Ehrhart polynomial

    CERN Document Server

    Ionascu, Eugen J

    2011-01-01

    First, we calculate the Ehrhart polynomial associated to an arbitrary cube with integer coordinates for its vertices. Then, we use this result to derive relationships between the Ehrhart polynomials for regular lattice tetrahedrons and those for regular lattice octahedrons. These relations allow one to reduce the calculation of these polynomials to only one coefficient.

  15. Disorder solutions of lattice spin models

    Science.gov (United States)

    Batchelor, M. T.; van Leeuwen, J. M. J.

    1989-01-01

    It is shown that disorder solutions, which have been obtained by different methods, follow from a simple decimation method. The method is put in general form and new disorder solutions are constructed for the Blume-Emery-Griffiths model on a triangular lattice and for Potts and Ising models on square and fcc lattices.

  16. Lattice studies of hadrons with heavy flavors

    Energy Technology Data Exchange (ETDEWEB)

    Christopher Aubin

    2009-07-01

    I will discuss recent developments in lattice studies of hadrons composed of heavy quarks. I will mostly cover topics which are at a state of direct comparison with experiment, but will also discuss new ideas and promising techniques to aid future studies of lattice heavy quark physics.

  17. An Application of Linear Algebra over Lattices

    Directory of Open Access Journals (Sweden)

    M. Hosseinyazdi

    2008-03-01

    Full Text Available In this paper, first we consider L n as a semimodule over a complete bounded distributive lattice L. Then we define the basic concepts of module theory for L n. After that, we proved many similar theorems in linear algebra for the space L n. An application of linear algebra over lattices for solving linear systems, was given

  18. Lattice dynamics of ferromagnetic superconductor UGe2

    Indian Academy of Sciences (India)

    Satyam Shinde; Prafulla K Jha

    2008-11-01

    This paper reports the lattice dynamical study of the UGe2 using a lattice dynamical model theory based on pairwise interactions under the framework of the shell model. The calculated phonon dispersion curves and phonon density of states are in good agreement with the measured data.

  19. Lattice Studies for hadron spectroscopy and interactions

    CERN Document Server

    Aoki, Sinya

    2014-01-01

    Recent progresses of lattice QCD studies for hadron spectroscopy and interactions are briefly reviewed. Some emphasis are given on a new proposal for a method, which enable us to calculate potentials between hadrons. As an example of the method, the extraction of nuclear potential in lattice QCD is discussed in detail.

  20. Dark Solitons in FPU Lattice Chain

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on multiple scales method, we study the nonlinear properties of a new Fermi-Pasta-Ulam lattice model analytically. It is found that the lattice chain exhibits a novel nonlinear elementary excitation, i.e. a dark soliton.Moreover, the modulation depth of dark soliton is increasing as the anharmonic parameter increases.

  1. Lattice Boltzmann equation for relativistic quantum mechanics.

    Science.gov (United States)

    Succi, Sauro

    2002-03-15

    Relativistic versions of the quantum lattice Boltzmann equation are discussed. It is shown that the inclusion of nonlinear interactions requires the standard collision operator to be replaced by a pair of dynamic fields coupling to the relativistic wave function in a way which can be described by a multicomponent complex lattice Boltzmann equation.

  2. Resummation of Cactus Diagrams in Lattice QCD

    CERN Document Server

    Panagopoulos, H

    1998-01-01

    We show how to perform a resummation, to all orders in perturbation theory, of a certain class of gauge invariant diagrams in Lattice QCD. These diagrams are often largely responsible for lattice artifacts. Our resummation leads to an improved perturbative expansion. Applied to a number of cases of interest, this expansion yields results remarkably close to corresponding nonperturbative estimates.

  3. First principles analysis of lattice dynamics for Fe-based superconductors and entropically-stabilized phases

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, Steven [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    Modern calculations are becoming an essential, complementary tool to inelastic x-ray scattering studies, where x-rays are scattered inelastically to resolve meV phonons. Calculations of the inelastic structure factor for any value of Q assist in both planning the experiment and analyzing the results. Moreover, differences between the measured data and theoretical calculations help identify important new physics driving the properties of novel correlated systems. We have used such calculations to better and more e ciently measure the phonon dispersion and elastic constants of several iron pnictide superconductors. This dissertation describes calculations and measurements at room temperature in the tetragonal phase of CaFe{sub 2}As{sub 2} and LaFeAsO. In both cases, spin-polarized calculations imposing the antiferromagnetic order present in the low-temperature orthorhombic phase dramatically improves the agreement between theory and experiment. This is discussed in terms of the strong antiferromagnetic correlations that are known to persist in the tetragonal phase. In addition, we discuss a relatively new approach called self-consistent ab initio lattice dynamics (SCAILD), which goes beyond the harmonic approximation to include phonon-phonon interactions and produce a temperature-dependent phonon dispersion. We used this technique to study the HCP to BCC transition in beryllium.

  4. A classification of 2-dim Lattice Theory

    CERN Document Server

    Kieburg, Mario; Zafeiropoulos, Savvas

    2013-01-01

    A unified classification and analysis is presented of two dimensional Dirac operators of QCD-like theories in the continuum as well as in a naive lattice discretization. Thereby we consider the quenched theory in the strong coupling limit. We do not only consider the case of a lattice which has an even number of lattice sites in both directions and is thus equivalent to the case of staggered fermions. We also study lattices with one or both directions with an odd parity to understand the general mechanism of changing the universality class via a discretization. Furthermore we identify the corresponding random matrix ensembles sharing the global symmetries of these QCD-like theories. Despite the Mermin-Wagner-Coleman theorem we find good agreement of lattice data with our random matrix predictions.

  5. Lattice kinetic simulation of nonisothermal magnetohydrodynamics.

    Science.gov (United States)

    Chatterjee, Dipankar; Amiroudine, Sakir

    2010-06-01

    In this paper, a lattice kinetic algorithm is presented to simulate nonisothermal magnetohydrodynamics in the low-Mach number incompressible limit. The flow and thermal fields are described by two separate distribution functions through respective scalar kinetic equations and the magnetic field is governed by a vector distribution function through a vector kinetic equation. The distribution functions are only coupled via the macroscopic density, momentum, magnetic field, and temperature computed at the lattice points. The novelty of the work is the computation of the thermal field in conjunction with the hydromagnetic fields in the lattice Boltzmann framework. A 9-bit two-dimensional (2D) lattice scheme is used for the numerical computation of the hydrodynamic and thermal fields, whereas the magnetic field is simulated in a 5-bit 2D lattice. Simulation of Hartmann flow in a channel provides excellent agreement with corresponding analytical results.

  6. Status of the ATF2 Lattices

    Energy Technology Data Exchange (ETDEWEB)

    Marin, E.; Tomas, R.; /CERN; Bambade, P.; /Orsay, LAL; Okugi, T.; Tauchi, T.; Terunuma, N.; Urakawa, J.; /KEK, Tsukuba; Seryi, A.; /Oxford U., JAI; White, G.; Woodley, M.; /SLAC

    2011-12-09

    The current status for the ATF2 Nominal and Ultra-low {beta}* lattices are presented in this paper. New lattice designs have been obtained in order to minimise the impact of the last interpretation of multipole measurements that have been included into the model. However, the new ATF2 Ultra-low design is not able to recover the expected vertical beam size at the IP with the current magnet distribution. Therefore, different quadrupole sorting have been studied. A significant gain is evident for the ATF2 Ultra-low lattice when sorting the magnets according to the skew-sextupolar components. The ATF2 Nominal lattice is also expected to benefit from the new sorting. Tuning results of the new ATF2 Ultra-low lattice under realistic imperfections are also reported.

  7. Crystalline Scaling Geometries from Vortex Lattices

    CERN Document Server

    Bao, Ning

    2013-01-01

    We study magnetic geometries with Lifshitz and/or hyperscaling violation exponents (both with a hard wall cutoff in the IR and a smooth black brane horizon) which have a complex scalar field which couples to the magnetic field. The complex scalar is unstable to the production of a vortex lattice in the IR. The lattice is a normalizable mode which is relevant (i.e. grows into the IR.) When one considers linearized backreaction of the lattice on the metric and gauge field, the metric forms a crystalline structure. We analyze the scaling of the free energy, thermodynamic entropy, and entanglement in the lattice phase and find that in the smeared limit, the leading order correction to thermodynamic properties due to the lattice has the scaling behavior of a theory with a hyperscaling violation exponent between 0 and 1, indicating a flow to an effectively lower-dimensional theory in the deep IR.

  8. Effective Field Theories and Lattice QCD

    CERN Document Server

    Bernard, C

    2015-01-01

    I describe some of the many connections between lattice QCD and effective field theories, focusing in particular on chiral effective theory, and, to a lesser extent, Symanzik effective theory. I first discuss the ways in which effective theories have enabled and supported lattice QCD calculations. Particular attention is paid to the inclusion of discretization errors, for a variety of lattice QCD actions, into chiral effective theory. Several other examples of the usefulness of chiral perturbation theory, including the encoding of partial quenching and of twisted boundary conditions, are also described. In the second part of the talk, I turn to results from lattice QCD for the low energy constants of the two- and three-flavor chiral theories. I concentrate here on mesonic quantities, but the dependence of the nucleon mass on the pion mass is also discussed. Finally I describe some recent preliminary lattice QCD calculations by the MILC Collaboration relating to the three-flavor chiral limit.

  9. Supersymmetry on a space-time lattice

    Energy Technology Data Exchange (ETDEWEB)

    Kaestner, Tobias

    2008-10-28

    In this thesis the WZ model in one and two dimensions has been thoroughly investigated. With the help of the Nicolai map it was possible to construct supersymmetrically improved lattice actions that preserve one of several supersymmetries. For the WZ model in one dimension SLAC fermions were utilized for the first time leading to a near-perfect elimination of lattice artifacts. In addition the lattice superpotential does not get modified which in two dimensions becomes important when further (discrete) symmetries of the continuum action are considered. For Wilson fermions two new improvements have been suggested and were shown to yield far better results than standard Wilson fermions concerning lattice artifacts. In the one-dimensional theory Ward Identities were studied.However, supersymmetry violations due to broken supersymmetry could only be detected at coarse lattices and very strong couplings. For the two-dimensional models a detailed analysis of supersymmetric improvement terms was given, both for Wilson and SLAC fermions. (orig.)

  10. Lattice dynamics and phase diagram of aluminum at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Kudasov, Yu. B., E-mail: yu_kudasov@yahoo.com; Surdin, O. M.; Korshunov, A. S.; Pavlov, V. N. [National Research Nuclear University ' MEPhI,' , Sarov State Institute of Physics and Technology (Russian Federation); Frolova, N. V.; Kuzin, R. S. [Russian Federal Nuclear Center-All-Russian Research Institute of Experimental Physics (Russian Federation)

    2013-10-15

    The dispersion of phonons in the fcc, hcp, and bcc phases of aluminum is calculated at ultrahigh pressures by the method of small displacements in a supercell. The stability of the phonon subsystem is studied. The thermodynamic characteristics are calculated in the quasi-harmonic approximation, and a phase diagram of aluminum is plotted. As compared to the Debye model, the use of a phonon spectrum calculated in the quasi-harmonic approximation significantly broadens the hcp phase field and strongly shifts the phase boundary between the fcc and bcc phases. The normal isentrope is calculated at megabar pressures. It is shown to intersect the fcc-hcp and hcp-bcc phase boundaries. The sound velocity along the normal isentrope is calculated. It is shown to have a nonmonotonic character.

  11. Comparison of induced damage, range, reflection, and sputtering yield between amorphous, bcc crystalline, and bubble-containing tungsten materials under hydrogen isotope and noble gas plasma irradiations

    Science.gov (United States)

    Saito, Seiki; Nakamura, Hiroaki; Tokitani, Masayuki

    2017-01-01

    Binary-collision-approximation simulation of hydrogen isotope (i.e., hydrogen, deuterium, and tritium) and noble gas (i.e., helium, neon, and argon) injections into tungsten materials is performed. Three tungsten structures (i.e., amorphous, bcc crystalline, and helium bubble-containing structures) are prepared as target materials. Then, the trajectories of incident atoms, the distribution of recoil atoms, the penetration depth range of incident atoms, the sputtering yield, and the reflection rate are carefully investigated for these target materials.

  12. Residuation Properties and Weakly Primary Elements in Lattice Modules

    Directory of Open Access Journals (Sweden)

    C. S. Manjarekar

    2014-01-01

    Full Text Available We obtain some elementary residuation properties in lattice modules and obtain a relation between a weakly primary element in a lattice module M and weakly prime element of a multiplicative lattice L.

  13. On the Product and Factorization of Lattice Implication Algebras

    Institute of Scientific and Technical Information of China (English)

    秦克云; 宋振明; 等

    1993-01-01

    In this paper,the concepts of product and factorization of lattice implication algebra are proposed,the relation between lattice implication product algebra and its factors and some properties of lattice implication product algebras are discussed.

  14. Application of microdynamics and lattice mechanics to problems in plastic flow and fracture. Final report, 1 April 1973--31 March 1978

    Energy Technology Data Exchange (ETDEWEB)

    Bilello, J C; Liu, J M

    1978-06-21

    Progress in an investigation of the application of microdynamics and lattice mechanics to the problems in plastic flow and fracture is described. The research program consisted of both theoretical formulations and experimental measurements of a number of intrinsic material parameters in bcc metals and alloys including surface energy, phonon-dispersion curves for dislocated solids, dislocation-point defect interaction energy, slip initiation and microplastic flow behavior. The study has resulted in an improved understanding in the relationship among the experimentally determined fracture surface energy, the intrinsic cohesive energy between atomic planes, and the plastic deformation associated with the initial stages of crack propagation. The values of intrinsic surface energy of tungsten, molybdenum, niobium and niobium-molybdenum alloys, deduced from the measurements, serve as a starting point from which fracture toughness of these materials in engineering service may be intelligently discussed.

  15. Magnetic properties and atomic ordering of BCC Heusler alloy Fe{sub 2}MnGa ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Xin, Yuepeng; Ma, Yuexing; Luo, Hongzhi, E-mail: luo_hongzhi@163.com; Meng, Fanbin; Liu, Heyan

    2016-05-15

    The electronic structure, atomic disorder and magnetic properties of the Heusler alloy Fe{sub 2}MnGa have been investigated experimentally and theoretically. BCC Fe{sub 2}MnGa ribbon samples were prepared. Experimentally, a saturation magnetic moment (3.68 μ{sub B} at 5 K) much larger than the theoretical value (2.04 μ{sub B}) has been reported. First-principles calculations indicate that the difference is related to the Fe–Mn disorder between A, B sites, as can also be deduced from the XRD pattern. L2{sub 1} type Fe{sub 2}MnGa is a ferrimagnet with antiparallel Fe and Mn spin moments. However, when Fe–Mn disorder occurs, part of Mn moments will be parallel to Fe moments, and the Fe moments also clearly increase simultaneously. All this results in a total moment of 3.74 μ{sub B}, close to the experimental value.

  16. Production and Partial Characterization of α-Amylase Enzyme from Bacillus sp. BCC 01-50 and Potential Applications.

    Science.gov (United States)

    Simair, Altaf Ahmed; Qureshi, Abdul Sattar; Khushk, Imrana; Ali, Chaudhry Haider; Lashari, Safia; Bhutto, Muhammad Aqeel; Mangrio, Ghulam Sughra; Lu, Changrui

    2017-01-01

    Amylase is an industrially important enzyme and applied in many industrial processes such as saccharification of starchy materials, food, pharmaceutical, detergent, and textile industries. This research work deals with the optimization of fermentation conditions for α-amylase production from thermophilic bacterial strain Bacillus sp. BCC 01-50 and characterization of crude amylase. The time profile of bacterial growth and amylase production was investigated in synthetic medium and maximum enzyme titer was observed after 60 h. In addition, effects of different carbon sources were tested as a substrate for amylase production and molasses was found to be the best. Various organic and inorganic compounds, potassium nitrate, ammonium chloride, sodium nitrate, urea, yeast extract, tryptone, beef extract, and peptone, were used and beef extract was found to be the best among the nitrogen sources used. Temperature, pH, agitation speed, and size of inoculum were also optimized. Highest enzyme activity was obtained when the strain was cultured in molasses medium for 60 h in shaking incubator (150 rpm) at 50°C and pH 8. Crude amylase showed maximal activity at pH 9 and 65°C. Enzyme remained stable in alkaline pH range 9-10 and 60-70°C. Crude amylase showed great potential for its application in detergent industry and saccharification of starchy materials.

  17. Atomistic Monte Carlo simulations of the diffusion of P and C near grain boundaries in BCC iron

    Energy Technology Data Exchange (ETDEWEB)

    Binkele, P.; Kizler, P. [MPA, Univ. Stuttgart, Stuttgart (Germany); Schmauder, S. [IMWF, Univ. Stuttgart, Stuttgart (Germany)

    2004-07-01

    It is well known that thermal ageing of steels can be caused by the segregation of phosphorus (P) and carbon (C) to grain boundaries. Atomistic Monte Carlo simulations of the diffusion of P and C to grain boundaries in bcc iron will allow, if validated, predictions of the time-dependent segregation. Simulations of the Fe-P-C system are presented, where the diffusion of Fe and P is realized via a vacancy mechanism and the diffusion of C is realized via an interstitial mechanism. Time-dependent segregations have been simulated for different temperatures and start conditions and are found to follow Johnson-Mehl-Avrami laws. A comparison of the simulation results with available AES (Auger Electron Spectroscopy) data shows close agreement with respect to P segregation. In simulations starting with a pre-filled grain boundary in increase of P and a decrease of C in the grain boundary are found where the decrease of C proceeds significantly faster than the increase of P for any temperature. The temperature-dependent ratios of the different speeds of P- and C-segregation, due to their different diffusion mechanisms, are calculated as a result of the simulations. (orig.)

  18. Enhancement of the Co magnetic moment in bcc Co1-xMnx on MgO

    Science.gov (United States)

    Snow, Ryan; Bhatkar, Harsh; N'diaye, Alpha; Arenholz, Elke; Idzerda, Yves; Montana State University Team; Lawrence Berkeley National Laboratries Team

    Using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (MCD), we show that the elemental Co moment for MBE grown thin films of bcc Co1-xMnx grown on MgO(001) is enhanced by 40% to a maximum value of 2.1 μB at x =0.24. The net Mn moment is found to align parallel with Co for all concentrations and remains roughly constant until x =0.3, then drops steadily, up to x =0.7, where the total moment of the film abruptly collapses to zero. Using a low-concentration Mn moment of 3.0 μB, the average magnetization lies directly on the Slater-Pauling (SP) curve for concentrations up to about x =.25, where it reaches a maximum moment of 2.3 μB /atom. This peak is slightly shifted and the slope is steeper on the high-Mn concentration side of the peak relative to the standard SP curve. This is in stark contrast to the fcc CoMn and hcp CoCr bulk behavior which shows only a rapid total moment reduction with Mn concentration. This material is based upon work supported by the National Science Foundation under Grant ECCS-1542210. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Con.

  19. Production and Partial Characterization of α-Amylase Enzyme from Bacillus sp. BCC 01-50 and Potential Applications

    Directory of Open Access Journals (Sweden)

    Altaf Ahmed Simair

    2017-01-01

    Full Text Available Amylase is an industrially important enzyme and applied in many industrial processes such as saccharification of starchy materials, food, pharmaceutical, detergent, and textile industries. This research work deals with the optimization of fermentation conditions for α-amylase production from thermophilic bacterial strain Bacillus sp. BCC 01-50 and characterization of crude amylase. The time profile of bacterial growth and amylase production was investigated in synthetic medium and maximum enzyme titer was observed after 60 h. In addition, effects of different carbon sources were tested as a substrate for amylase production and molasses was found to be the best. Various organic and inorganic compounds, potassium nitrate, ammonium chloride, sodium nitrate, urea, yeast extract, tryptone, beef extract, and peptone, were used and beef extract was found to be the best among the nitrogen sources used. Temperature, pH, agitation speed, and size of inoculum were also optimized. Highest enzyme activity was obtained when the strain was cultured in molasses medium for 60 h in shaking incubator (150 rpm at 50°C and pH 8. Crude amylase showed maximal activity at pH 9 and 65°C. Enzyme remained stable in alkaline pH range 9-10 and 60–70°C. Crude amylase showed great potential for its application in detergent industry and saccharification of starchy materials.

  20. Synthesis, characterization, and nanoindentation response of single crystal Fe–Cr–Ni alloys with FCC and BCC structures

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Y.Z. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Bei, H., E-mail: beih@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Gao, Y.F., E-mail: ygao7@utk.edu [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Catoor, D. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); George, E.P. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2014-08-12

    Fe-based alloys are used extensively in many structural applications including under irradiation conditions in the nuclear industry. In this study, model Fe–Cr, Fe–Ni and Fe–Cr–Ni alloys that are the basis of many structural steels were synthesized as single crystals and characterized. The compositions investigated were Fe–15Cr, Fe–30Cr, Fe–30Ni and Fe–15Cr–15Ni (at%). Several key mechanical properties were determined which will be useful in further studies of irradiation/deformation-induced defects. Incipient plasticity and slip characteristics were investigated by nanoindentation on (001) and (1{sup ¯}10) surfaces, and hardness, modulus, pop-in behavior and theoretical strength were determined. The slip trace patterns after microindentation were imaged in a microscope. A novel slip trace analysis was developed and the underlying deformation mechanisms identified. The analysis shows that under both (001) and (1{sup ¯}10) indentations, the activated slip system for the BCC alloys is {112}〈111〉; for the FCC alloys the activated slip plane is {111}. These results were confirmed with finite element simulations using a slip-based crystal-plasticity model. Finally, the effects of heterogeneous pop-in mechanisms are discussed in the context of incipient plasticity in the four different alloys.

  1. Formation of Superlattices of Gold Nanoparticles Using Ostwald Ripening in Emulsions: Transition from fcc to bcc Structure.

    Science.gov (United States)

    Schmitt, Julien; Hajiw, Stéphanie; Lecchi, Amélie; Degrouard, Jéril; Salonen, Anniina; Impéror-Clerc, Marianne; Pansu, Brigitte

    2016-06-30

    An efficient method to form 3D superlattices of gold nanoparticles inside oil emulsion droplets is presented. We demonstrate that this method relies on Ostwald ripening, a well-known phenomenon occurring during the aging of emulsions. The key point is that the nanoparticle concentration inside the smaller droplets is increasing very slowly with time, thus inducing the crystallization of the nanoparticles into superlattices. Using oil-in-water emulsions doped with hydrophobic gold nanoparticles, we demonstrate that this method is efficient for different types of oils (toluene, cyclohexane, dodecane, and hexadecane). 3D superlattices of the nanoparticles are obtained, with dimensions reaching a hundred nanometers. The kinetics of the crystallization depends on the solubility of the oil in water but also on the initial concentration of the gold nanoparticles in oil. This method also provides an innovative way to obtain the complete phase diagram of nanoparticle suspensions with concentration. Indeed, during this slow crystallization process, a transition from a disordered suspension to a fcc structure is observed, followed by a transition toward a bcc structure. This evolution with time provides key results to understand the role played by the ligands located at the surface of the nanoparticles in order to control the type of superlattices which are formed.

  2. On Decompositions of Matrices over Distributive Lattices

    Directory of Open Access Journals (Sweden)

    Yizhi Chen

    2014-01-01

    Full Text Available Let L be a distributive lattice and Mn,q (L(Mn(L, resp. the semigroup (semiring, resp. of n × q (n × n, resp. matrices over L. In this paper, we show that if there is a subdirect embedding from distributive lattice L to the direct product ∏i=1m‍Li of distributive lattices L1,L2, …,Lm, then there will be a corresponding subdirect embedding from the matrix semigroup Mn,q(L (semiring Mn(L, resp. to semigroup ∏i=1m‍Mn,q(Li (semiring ∏i=1m‍Mn(Li, resp.. Further, it is proved that a matrix over a distributive lattice can be decomposed into the sum of matrices over some of its special subchains. This generalizes and extends the decomposition theorems of matrices over finite distributive lattices, chain semirings, fuzzy semirings, and so forth. Finally, as some applications, we present a method to calculate the indices and periods of the matrices over a distributive lattice and characterize the structures of idempotent and nilpotent matrices over it. We translate the characterizations of idempotent and nilpotent matrices over a distributive lattice into the corresponding ones of the binary Boolean cases, which also generalize the corresponding structures of idempotent and nilpotent matrices over general Boolean algebras, chain semirings, fuzzy semirings, and so forth.

  3. Measurement Based Quantum Computation on Fractal Lattices

    Directory of Open Access Journals (Sweden)

    Michal Hajdušek

    2010-06-01

    Full Text Available In this article we extend on work which establishes an analology between one-way quantum computation and thermodynamics to see how the former can be performed on fractal lattices. We find fractals lattices of arbitrary dimension greater than one which do all act as good resources for one-way quantum computation, and sets of fractal lattices with dimension greater than one all of which do not. The difference is put down to other topological factors such as ramification and connectivity. This work adds confidence to the analogy and highlights new features to what we require for universal resources for one-way quantum computation.

  4. A Lattice Study of the Glueball Spectrum

    Institute of Scientific and Technical Information of China (English)

    LIU Chuan

    2001-01-01

    Glueball spectrum is studied using an improved gluonic action on asymmetric lattices in the pure SU(3)gauge theory. The smallest spatial lattice spacing is about 0.08 fm which makes the extrapolation to the continuum limit more reliable. In particular, attention is paid to the scalar glueball mass which is known to have problems in the extrapolation. Converting our lattice results to physical units using the scale set by the static quark potential,we obtain the following results for the glueball masses: MG(0++) = 1730(90) MeV for the scalar glueball mass and MG(2++) = 2400(95) MeV for the tensor glueball.

  5. Construction of Capacity Achieving Lattice Gaussian Codes

    KAUST Repository

    Alghamdi, Wael

    2016-04-01

    We propose a new approach to proving results regarding channel coding schemes based on construction-A lattices for the Additive White Gaussian Noise (AWGN) channel that yields new characterizations of the code construction parameters, i.e., the primes and dimensions of the codes, as functions of the block-length. The approach we take introduces an averaging argument that explicitly involves the considered parameters. This averaging argument is applied to a generalized Loeliger ensemble [1] to provide a more practical proof of the existence of AWGN-good lattices, and to characterize suitable parameters for the lattice Gaussian coding scheme proposed by Ling and Belfiore [3].

  6. AN EQUIVALENT CONTINUUM METHOD OF LATTICE STRUCTURES

    Institute of Scientific and Technical Information of China (English)

    Fan Hualin; Yang Wei

    2006-01-01

    An equivalent continuum method is developed to analyze the effective stiffness of three-dimensional stretching dominated lattice materials. The strength and three-dimensional plastic yield surfaces are calculated for the equivalent continuum. A yielding model is formulated and compared with the results of other models. The bedding-in effect is considered to include the compliance of the lattice joints. The predicted stiffness and strength are in good agreement with the experimental data, validating the present model in the prediction of the mechanical properties of stretching dominated lattice structures.

  7. Investigating jet quenching on the lattice

    CERN Document Server

    Panero, Marco; Schäfer, Andreas

    2014-01-01

    Due to the dynamical, real-time, nature of the phenomenon, the study of jet quenching via lattice QCD simulations is not straightforward. In this contribution, however, we show how one can extract information about the momentum broadening of a hard parton moving in the quark-gluon plasma, from lattice calculations. After discussing the basic idea (originally proposed by Caron-Huot), we present a recent study, in which we estimated the jet quenching parameter non-perturbatively, from the lattice evaluation of a particular set of gauge-invariant operators.

  8. Lattice gauge theories and Monte Carlo simulations

    CERN Document Server

    Rebbi, Claudio

    1983-01-01

    This volume is the most up-to-date review on Lattice Gauge Theories and Monte Carlo Simulations. It consists of two parts. Part one is an introductory lecture on the lattice gauge theories in general, Monte Carlo techniques and on the results to date. Part two consists of important original papers in this field. These selected reprints involve the following: Lattice Gauge Theories, General Formalism and Expansion Techniques, Monte Carlo Simulations. Phase Structures, Observables in Pure Gauge Theories, Systems with Bosonic Matter Fields, Simulation of Systems with Fermions.

  9. Lattice distortion in disordered antiferromagnetic XY models

    Institute of Scientific and Technical Information of China (English)

    Li Peng-Fei; Cao Hai-Jing

    2012-01-01

    The behavior of lattice distortion in spin 1/2 antiferromagnetic XY models with random magnetic modulation is investigated with the consideration of spin-phonon coupling in the adiabatic limit.It is found that lattice distortion relies on the strength of the random modulation.For strong or weak enough spin-phonon couplings,the average lattice distortion may decrease or increase as the random modulation is strengthened.This may be the result of competition between the random magnetic modulation and the spin-phonon coupling.

  10. Lattice surgery translation for quantum computation

    Science.gov (United States)

    Herr, Daniel; Nori, Franco; Devitt, Simon J.

    2017-01-01

    In this paper we outline a method for a compiler to translate any non fault tolerant quantum circuit to the geometric representation of the lattice surgery error-correcting code using inherent merge and split operations. Since the efficiency of state distillation procedures has not yet been investigated in the lattice surgery model, their translation is given as an example using the proposed method. The resource requirements seem comparable or better to the defect-based state distillation process, but modularity and eventual implementability allow the lattice surgery model to be an interesting alternative to braiding.

  11. QCD Thermodynamics with an Improved Lattice Action

    CERN Document Server

    Bernard, C W; DeGrand, T A; Wingate, M; DeTar, C E; Gottlieb, S; Heller, U M; Rummukainen, K; Toussaint, D; Sugar, R L; Bernard, Claude; Hetrick, James E.; Grand, Thomas De; Wingate, Matthew; Tar, Carleton De; Gottlieb, Steven; Heller, Urs M.; Rummukainen, Kari; Toussaint, Doug; Sugar, Robert L.

    1997-01-01

    We have investigated QCD with two flavors of degenerate fermions using a Symanzik-improved lattice action for both the gauge and fermion actions. Our study focuses on the deconfinement transition on an $N_t=4$ lattice. Having located the thermal transition, we performed zero temperature simulations nearby in order to compute hadronic masses and the static quark potential. We find that the present action reduces lattice artifacts present in thermodynamics with the standard Wilson (gauge and fermion) actions. However, it does not bring studies with Wilson-type quarks to the same level as those using the Kogut--Susskind formulation.

  12. Electronic properties of graphene antidot lattices

    DEFF Research Database (Denmark)

    Fürst, Joachim Alexander; Pedersen, Jesper Goor; Flindt, C.;

    2009-01-01

    Graphene antidot lattices constitute a novel class of nano-engineered graphene devices with controllable electronic and optical properties. An antidot lattice consists of a periodic array of holes that causes a band gap to open up around the Fermi level, turning graphene from a semimetal...... into a semiconductor. We calculate the electronic band structure of graphene antidot lattices using three numerical approaches with different levels of computational complexity, efficiency and accuracy. Fast finite-element solutions of the Dirac equation capture qualitative features of the band structure, while full...

  13. New Lattice Results for Parton Distributions

    CERN Document Server

    Alexandrou, Constantia; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, Karl; Steffens, Fernanda; Wiese, Christian

    2016-01-01

    We provide a high statistics analysis of the $x$-dependence of the bare unpolarized, helicity and transversity iso-vector parton distribution functions (PDFs) from lattice calculations employing (maximally) twisted mass fermions. The $x$-dependence of the calculated PDFs resembles those of the phenomenological parameterizations, a feature that makes this approach promising despite the lack of a full renormalization program for them. Furthermore, we apply momentum smearing for the relevant matrix elements to compute the lattice PDFs and find a large improvement factor when compared to conventional Gaussian smearing. This allows us to extend the lattice computation of the distributions to higher values of the nucleon momentum.

  14. Multiphase lattice Boltzmann methods theory and application

    CERN Document Server

    Huang, Haibo; Lu, Xiyun

    2015-01-01

    Theory and Application of Multiphase Lattice Boltzmann Methods presents a comprehensive review of all popular multiphase Lattice Boltzmann Methods developed thus far and is aimed at researchers and practitioners within relevant Earth Science disciplines as well as Petroleum, Chemical, Mechanical and Geological Engineering. Clearly structured throughout, this book will be an invaluable reference  on the current state of all popular multiphase Lattice Boltzmann Methods (LBMs). The advantages and disadvantages of each model are presented in an accessible manner to enable the reader to choose the

  15. Rare Kaon Decays on the Lattice

    CERN Document Server

    Isidori, Gino; Turchetti, P; Isidori, Gino; Martinelli, Guido; Turchetti, Paolo

    2006-01-01

    We show that long distance contributions to the rare decays K -> pi nu nu-bar and K -> pi l+ l- can be computed using lattice QCD. The proposed approach requires well established methods, successfully applied in the calculations of electromagnetic and semileptonic form factors. The extra power divergences, related to the use of weak four-fermion operators, can be eliminated using only the symmetries of the lattice action without ambiguities or complicated non-perturbative subtractions. We demonstrate that this is true even when a lattice action with explicit chiral symmetry breaking is employed. Our study opens the possibility of reducing the present uncertainty in the theoretical predictions for these decays.

  16. Measures on coallocation and normal lattices

    Directory of Open Access Journals (Sweden)

    Jack-Kang Chan

    1992-01-01

    Full Text Available Let ℒ1 and ℒ2 be lattices of subsets of a nonempty set X. Suppose ℒ2 coallocates ℒ1 and ℒ1 is a subset of ℒ2. We show that any ℒ1-regular finitely additive measure on the algebra generated by ℒ1 can be uniquely extended to an ℒ2-regular measure on the algebra generated by ℒ2. The case when ℒ1 is not necessary contained in ℒ2, as well as the measure enlargement problem are considered. Furthermore, some discussions on normal lattices and separation of lattices are also given.

  17. How to Share a Lattice Trapdoor

    DEFF Research Database (Denmark)

    Bendlin, Rikke; Peikert, Chris; Krehbiel, Sara

    2013-01-01

    delegation, which is used in lattice-based hierarchical IBE schemes. Our work therefore directly transfers all these systems to the threshold setting. Our protocols provide information-theoretic (i.e., statistical) security against adaptive corruptions in the UC framework, and they are robust against up to ℓ......We develop secure threshold protocols for two important operations in lattice cryptography, namely, generating a hard lattice Λ together with a "strong" trapdoor, and sampling from a discrete Gaussian distribution over a desired coset of Λ using the trapdoor. These are the central operations...

  18. A Solvable Decorated Ising Lattice Model

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A decoratedlattice is suggested and the Ising model on it with three kinds of interactions K1, K2, and K3 is studied. Using an equivalent transformation, the square decorated Ising lattice is transformed into a regular square Ising lattice with nearest-neighbor, next-nearest-neighbor, and four-spin interactions, and the critical fixed point is found atK1 = 0.5769, K2 = -0.0671, and K3 = 0.3428, which determines the critical temperature of the system. It is also found that this system and the regular square Ising lattice, and the eight-vertex model belong to the same universality class.

  19. Shock wave structure in a lattice gas

    Science.gov (United States)

    Broadwell, James E.; Han, Donghee

    2007-05-01

    The motion and structure of shock and expansion waves in a simple particle system, a lattice gas and cellular automaton, are determined in an exact computation. Shock wave solutions, also exact, of a continuum description, a model Boltzmann equation, are compared with the lattice results. The comparison demonstrates that, as proved by Caprino et al. ["A derivation of the Broadwell equation," Commun. Math. Phys. 135, 443 (1991)] only when the lattice processes are stochastic is the model Boltzmann description accurate. In the strongest shock wave, the velocity distribution function is the bimodal function proposed by Mott-Smith.

  20. Spontaneous supersymmetry breaking on the lattice

    Energy Technology Data Exchange (ETDEWEB)

    Wenger, Urs [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland)

    2013-07-01

    We discuss various strategies for regularising supersymmetric quantum field theories on a space-time lattice. In general, simulations of lattice models with spontaneously broken supersymmetry suffer from a fermion sign problem related to the vanishing of the Witten index. We discuss a novel approach which evades this problem in low dimensions by formulating the path integral on the lattice in terms of fermion loops. Then we present exact results on the spectrum and the Witten index for N=2 supersymmetric quantum mechanics and results from simulations of the spontaneously broken N=1 Wess-Zumino model.