WorldWideScience

Sample records for range order structure

  1. Magnetic structures of vanadium iodide (VI2): long- and short-range order and Moessbauer spectroscopy.

    NARCIS (Netherlands)

    Kuindersma, S. R.; Sanchez, J. P.; Haas, C.

    1980-01-01

    Neutron diffraction data of VI2 show a magnetic phase transition at 14 K from a 120° magnetic structure to a collinear structure. The collinear structure is compatible with low-temp. Moessbauer spectra. The 120° structure is not a magnetic phase with long-range order but rather a paramagnetic phase

  2. Local Structure and Short-Range Order in a NiCoCr Solid Solution Alloy

    Science.gov (United States)

    Zhang, F. X.; Zhao, Shijun; Jin, Ke; Xue, H.; Velisa, G.; Bei, H.; Huang, R.; Ko, J. Y. P.; Pagan, D. C.; Neuefeind, J. C.; Weber, W. J.; Zhang, Yanwen

    2017-05-01

    Multielement solid solution alloys are intrinsically disordered on the atomic scale, and many of their advanced properties originate from the local structural characteristics. The local structure of a NiCoCr solid solution alloy is measured with x-ray or neutron total scattering and extended x-ray absorption fine structure (EXAFS) techniques. The atomic pair distribution function analysis does not exhibit an observable structural distortion. However, an EXAFS analysis suggests that the Cr atoms are favorably bonded with Ni and Co in the solid solution alloys. This short-range order (SRO) may make an important contribution to the low values of the electrical and thermal conductivities of the Cr-alloyed solid solutions. In addition, an EXAFS analysis of Ni ion irradiated samples reveals that the degree of SRO in NiCoCr alloys is enhanced after irradiation.

  3. Short-range order structure and effective pair-interaction energy in Ni-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, Takumi [Department of Applied Physics, Graduate School of Engineering, Hokkaido University, Kita-ku, Sapporo 060-8628 (Japan); Hitachi, Ltd., Shinmachi Ome-shi, Tokyo 198-8512 (Japan); Osaka, Keiichi [Department of Applied Physics, Graduate School of Engineering, Hokkaido University, Kita-ku, Sapporo 060-8628 (Japan); Industrial Application Division, Japan Synchrotron Radiation Research Institute (JASRI), 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)], E-mail: k-osaka@spring8.or.jp; Takama, Toshihiko [Department of Applied Physics, Graduate School of Engineering, Hokkaido University, Kita-ku, Sapporo 060-8628 (Japan); Chen, Haydn [Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong (China)

    2007-09-15

    The diffuse X-ray scattering from single crystals of Ni - 11.3 at.% Si and 12.3 at.% Si, both aged at 1293 K followed by a water quench, was measured at room temperature. The measured diffuse intensities were analyzed to determine the Warren-Cowley atomic short-range order (SRO) parameters {alpha}{sub lmn}. The 17 values of {alpha}{sub lmn} obtained were fitted in a 5 x 10{sup 5} atom model crystal to simulate the SRO. It was found that the C16 and the C17 configurations are significantly enhanced in comparison to a random crystal. The pair-interaction energies V{sub lmn} were obtained using an inverse Monte Carlo method from the {alpha}{sub lmn} parameters. Assuming that V{sub lmn} are independent of temperature, the {alpha}{sub lmn} were calculated as a function of temperature on the basis of the Monte Carlo simulation. The curves of {alpha}{sub lmn} for 11.3 at.% Si showed a knee point at 1262 (19) K and for 12.3 at.% Si at 1325 (11) K. Both temperatures are higher by about 100 K than those of the (fcc/fcc + L1{sub 2}) phase boundary in an equilibrium phase diagram.

  4. Photoluminescence polarization anisotropy for studying long-range structural ordering within semiconductor multi-atomic alloys and organic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Prutskij, T.; Percino, J. [Instituto de Ciencias, BUAP, Privada 17 Norte, No 3417, col. San Miguel Huyeotlipan, 72050, Puebla, Pue. (Mexico); Orlova, T. [Department of Chemical and Biochemical Engineering, University of Notre Dame, Notre Dame, IN (United States); Vavilova, L. [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya, St Petersburg 194021, Russian Federation (Russian Federation)

    2013-12-04

    Long-range structural ordering within multi-component semiconductor alloys and organic crystals leads to significant optical anisotropy and, in particular, to anisotropy of the photoluminescence (PL) emission. The PL emission of ternary and quaternary semiconductor alloys is polarized if there is some amount of the atomic ordering within the crystal structure. We analyze the polarization of the PL emission from the quaternary GaInAsP semiconductor alloy grown by Liquid Phase Epitaxy (LPE) and conclude that it could be caused by low degree atomic ordering within the crystal structure together with the thermal biaxial strain due to difference between the thermal expansion coefficients of the layer and the substrate. We also study the state of polarization of the PL from organic crystals in order to identify different features of the crystal PL spectrum.

  5. Special Quasi-ordered Structures: role of short-range order in the semiconductor alloy (GaN)$_{1-x}$(ZnO)$_x$

    CERN Document Server

    Liu, Jian; Allen, Philip B

    2016-01-01

    This paper studies short-range order (SRO) in the semiconductor alloy (GaN)$_{1-x}$(ZnO)$_x$. Monte Carlo simulations performed on a density functional theory (DFT)-based cluster expansion model show that the heterovalent alloys exhibit strong SRO because of the energetic preference for the valence-matched nearest-neighbor Ga-N and Zn-O pairs. To represent the SRO-related structural correlations, we introduce the concept of Special Quasi-ordered Structure (SQoS). Subsequent DFT calculations reveal dramatic influence of SRO on the atomic, electronic and vibrational properties of the (GaN)$_{1-x}$(ZnO)$_x$ alloy. Due to the enhanced statistical presence of the energetically unfavored Zn-N bonds with the strong Zn3$d$-N2$p$ repulsion, the disordered alloys exhibit much larger lattice bowing and band-gap reduction than those of the short-range ordered alloys. Inclusion of lattice vibrations stabilizes the disordered alloy.

  6. Heredity of medium-range order structure from melts to the microstructure of Ni-Cr-W superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhongtang; Hu, Rui; Wang, Jun; Li, Jinshan [Northwestern Polytechnical University, State Key Laboratory of Solidification Processing, Xi' an (China)

    2015-07-15

    The structure factor S(Q), intensities and pair distribution function g(r) of liquid Ni-Cr-W superalloy at different temperatures have been measured by a high-temperature X-ray diffractometer. Coordination N{sub min}, correlation radius r{sub c}, the nearest atomic distance r{sub 1}, solidification microstructure and compression performance have been studied. The results show that a pre-peak exists on the structure factor curve at the liquidus temperature, and a fine structure of equiaxed, globular and non-dendritic primary grains can be achieved by casting the alloy at liquidus temperature. Liquid structure feature of Ni-Cr-W superalloy is found to depend on temperature. During the solidification, some structural information carried by the medium-range order (MRO) structure is inherited from the melt to the microstructure, which is beneficial for grain refinement. The maximum yield strength measured from typical microstructure of the equiaxed and non-dendritic grains at 1400 C is 543 MPa. The results show that refinement and non-dendritic grain is beneficial to the improvement of the yield strength. (orig.)

  7. New clues to the local atomic structure of short-range ordered ferric arsenate from extended X-ray absorption fine structure spectroscopy.

    Science.gov (United States)

    Mikutta, Christian; Mandaliev, Petar N; Kretzschmar, Ruben

    2013-04-02

    Short-range ordered ferric arsenate (FeAsO4 · xH2O) is a secondary As precipitate frequently encountered in acid mine waste environments. Two distinct structural models have recently been proposed for this phase. The first model is based on the structure of scorodite (FeAsO4 · 2H2O) where isolated FeO6 octahedra share corners with four adjacent arsenate (AsO4) tetrahedra in a three-dimensional framework (framework model). The second model consists of single chains of corner-sharing FeO6 octahedra being bridged by AsO4 bound in a monodentate binuclear (2)C complex (chain model). In order to rigorously test the accuracy of both structural models, we synthesized ferric arsenates and analyzed their local (absorption fine structure (EXAFS) spectroscopy. We found that both As and Fe K-edge EXAFS spectra were most compatible with isolated FeO6 octahedra being bridged by AsO4 tetrahedra (RFe-As = 3.33 ± 0.01 Å). Our shell-fit results further indicated a lack of evidence for single corner-sharing FeO6 linkages in ferric arsenate. Wavelet-transform analyses of the Fe K-edge EXAFS spectra of ferric arsenates complemented by shell fitting confirmed Fe atoms at an average distance of ∼5.3 Å, consistent with crystallographic data of scorodite and in disagreement with the chain model. A scorodite-type local structure of short-range ordered ferric arsenates provides a plausible explanation for their rapid transformation into scorodite in acid mining environments.

  8. Transmission electron microscopy and electron diffraction study of the short-range ordering structure of alpha-LiFeO2.

    Science.gov (United States)

    Mitome, Masanori; Kohiki, Shigemi; Murakawa, Yusuke; Hori, Kyoko; Kurashima, Keiji; Bando, Yoshio

    2004-12-01

    The basic structure of alpha-LiFeO2, lithium iron oxide, is a cubic NaCl-type structure with a lattice constant of 0.42 nm; some short-range ordering characterized by octahedral clusters exists. The local structure of the short-range ordering was investigated by transmission electron microscopy and electron diffraction. A new short-range ordering structure was found in local areas. The local structure has a cubic lattice with a doubled lattice constant. The occupation factors of cations on Wyckoff sites 4(a) and 4(b) are different from those on 24(d) sites, but the stoichiometric composition in cubic clusters is the same as the macroscopic composition. The number of pairs in which iron cations exist in nearest-neighbor sites and next nearest-neighbor sites is reduced in the structure. This means that a magnetic interaction between the iron cations is reduced by cation ordering even without spin ordering at room temperature.

  9. Short-range magnetic ordering in the geometrically frustrated layered compound YBaCo4O7 with an extended Kagomé structure

    Science.gov (United States)

    Bera, A. K.; Yusuf, S. M.; Banerjee, S.

    2013-02-01

    Structural and magnetic properties of the geometrically frustrated layered compound YBaCo4O7 have been studied by magnetization and neutron diffraction. A layered type crystal structure, with alternating tetrahedral layers of Kagomé and triangular types, along the c axis (hexagonal symmetry, space group P63mc) has been found. The oxygen content of the present compound was determined by iodometric titration to be 7.00 ± 0.01. Presence of a short-range antiferromagnetic ordering (below TN ˜ 110 K) has been concluded from the appearance of an addition broad magnetic peak (at Q ˜ 1.35 Å-1) in the neutron diffraction pattern. A staggered chiral type (√{3}×√{3}) spin structure in the Kagomé layers has been found. Presence of a significant magneto-structural coupling is concluded from the changes in lattice parameters across the magnetic ordering temperature TN ˜ 110 K.

  10. Extended-range order in glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ellison, A.J.G.; Price, D.L.; Saboungi, M.L. [Argonne National Lab., IL (United States); Egami, T.; Hu, Rui-Zhong [Pennsylvania Univ., Philadelphia, PA (United States); Howells, W.S. [Rutherford Appleton Lab., Chilton (United Kingdom)

    1994-03-01

    A new type of order is identified in complex glasses, characterized by diffraction peaks at values of the wave vector below those typical of intermediate-range order. Combined neutron and anomalous x-ray diffraction studies of one glass exhibiting this behavior, vitreous rubidium germanate, indicate it to be associated with chemical ordering of the two cations with respect to each other.

  11. Reduced-order computational model in nonlinear structural dynamics for structures having numerous local elastic modes in the low-frequency range. Application to fuel assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Batou, A., E-mail: anas.batou@univ-paris-est.fr [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallee (France); Soize, C., E-mail: christian.soize@univ-paris-est.fr [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallee (France); Brie, N., E-mail: nicolas.brie@edf.fr [EDF R and D, Département AMA, 1 avenue du général De Gaulle, 92140 Clamart (France)

    2013-09-15

    Highlights: • A ROM of a nonlinear dynamical structure is built with a global displacements basis. • The reduced order model of fuel assemblies is accurate and of very small size. • The shocks between grids of a row of seven fuel assemblies are computed. -- Abstract: We are interested in the construction of a reduced-order computational model for nonlinear complex dynamical structures which are characterized by the presence of numerous local elastic modes in the low-frequency band. This high modal density makes the use of the classical modal analysis method not suitable. Therefore the reduced-order computational model is constructed using a basis of a space of global displacements, which is constructed a priori and which allows the nonlinear dynamical response of the structure observed on the stiff part to be predicted with a good accuracy. The methodology is applied to a complex industrial structure which is made up of a row of seven fuel assemblies with possibility of collisions between grids and which is submitted to a seismic loading.

  12. Long-Range Order in β Brass

    DEFF Research Database (Denmark)

    Norvell, J.C.; Als-Nielsen, Jens Aage

    1970-01-01

    The long-range order parameter M of β brass has been determined from measurements of the intensity of superlattice reflections of Bragg-scattered neutrons. Over the whole temperature range T=300 °K to T=Tc=736 °K, the data are in remarkable agreement with the prediction for the compressible Ising...... bcc lattice with only nearest-neighbor interactions. © 1970 The American Physical Society...

  13. Long-range order in canary song.

    Science.gov (United States)

    Markowitz, Jeffrey E; Ivie, Elizabeth; Kligler, Laura; Gardner, Timothy J

    2013-01-01

    Bird songs range in form from the simple notes of a Chipping Sparrow to the rich performance of the nightingale. Non-adjacent correlations can be found in the syntax of some birdsongs, indicating that the choice of what to sing next is determined not only by the current syllable, but also by previous syllables sung. Here we examine the song of the domesticated canary, a complex singer whose song consists of syllables, grouped into phrases that are arranged in flexible sequences. Phrases are defined by a fundamental time-scale that is independent of the underlying syllable duration. We show that the ordering of phrases is governed by long-range rules: the choice of what phrase to sing next in a given context depends on the history of the song, and for some syllables, highly specific rules produce correlations in song over timescales of up to ten seconds. The neural basis of these long-range correlations may provide insight into how complex behaviors are assembled from more elementary, stereotyped modules.

  14. Structure of short-range-ordered iron(III)-precipitates formed by iron(II) oxidation in water containing phosphate, silicate, and calcium

    Science.gov (United States)

    Voegelin, A.; Frommer, J.; Vantelon, D.; Kaegi, R.; Hug, S. J.

    2009-04-01

    , depending on water composition, Fe(II) oxidation in natural waters leads to different types of short-range-ordered Fe(III)-phases. Since these phases are expected to differ in their effect on contaminant and nutrient dynamics, their specific physical and chemical properties warrant further research. Methodologically, this work demonstrated the usefulness of investigating the local structure of short-range-ordered precipitates along compositional gradients and by combining the element-selective information from different X-ray absorption edges.

  15. Computer simulation of CaSiO3 glass under compression: correlation between Si-Si pair radial distribution function and intermediate range order structure

    Science.gov (United States)

    Lan, Mai Thi; Thuy Duong, Tran; Iitaka, Toshiaki; Van Hong, Nguyen

    2017-06-01

    The structural organization of CaSiO3 glass at 600 K and under pressure of 0-100 GPa is investigated by molecular dynamics simulation (MDS). Results show that the atomic structure of CaSiO3 comprises SiO n and CaO m units considered as basic structural polyhedra. At low pressure, most of the basic structural polyhedra are SiO4, CaO5, CaO6 and CaO7. At high pressure most of the basic structural polyhedra are SiO5, SiO6 and CaO9, CaO10 and CaO11. The distribution of basic structural polyhedra is not uniform resulting in formation of Ca-rich and Si-rich regions. The distribution of SiO4, SiO5 and SiO6 polyhedra is also not uniform, but it tends to form SiO4-, SiO5-, and SiO6-clusters. For the Si-O network, under compression there is a gradual transition from the tetrahedral network (SiO4) to the octahedral network (SiO6) via SiO5 polyhedra. The SiO5-clusters are the same as immediate-phase in the transformation process. The size and shape of SiO4 tetrahedra change strongly under compression. While the size of SiO5 and SiO6 has also changed significantly, but the shape is almost unchanged under compression. The SiO n polyhedra can connect to each other via one common oxygen ion (corner-sharing bond), two common oxygen ions (edge-sharing bond) or three common oxygen ions (face-sharing bond). The Si-Si bond length in corner-sharing bonds is much longer than the ones in edge-sharing and face-sharing bonds. The change of intermediate range order (IRO) structure under compression relating to edge- and face-sharing bonds amongst SiO n at high pressure is the origin of the first peak splitting of the radial distribution functions of Si-Si pair. Under compression, the number of non-bridging oxygen (NBO) decreases. This makes the Si-O network more polymerized. At low pressure, most of the Ca2+ ions incorporate into the Si-O network via NBOs. At high pressure, the amount of NBO decreases, Ca2+ ions mainly incorporate into the Si-O network via bridging oxygen (BO) that

  16. Short range order in elemental liquids of column IV.

    Science.gov (United States)

    Mayo, M; Shor, S; Yahel, E; Makov, G

    2015-05-21

    The short range order (SRO) in liquid elements of column IV is analysed within the quasi-crystalline model across a wide range of temperatures. It is found that l-Si, Ge, and Sn are well described with a beta-tin like SRO. In contrast, Pb retains a bcc-like SRO similar to other simple elemental liquids. However, a distinction is found between the SRO in Si and Ge and that in Sn, where the latter has a more rigid structure. This difference persists across the entire temperature range examined but is overcome in Si at pressures above 8 GPa, where the liquid structure evolves towards that of Sn.

  17. Quasicrystals as alloys with short-range order

    Energy Technology Data Exchange (ETDEWEB)

    Sulston, K.W., E-mail: sulston@upei.c [Department of Mathematics and Statistics, University of Prince Edward Island, Charlottetown, PE, C1A 4P3 (Canada); Burrows, B.L. [Mathematics Section, Faculty of Computing, Engineering and Technology, Staffordshire University, Beaconside, Stafford ST18 0DG (United Kingdom)

    2010-09-15

    The electronic structure of quasiperiodic lattices is studied. An alloy theory, including short-range order effects, is used to approximate Fibonacci and Thue-Morse lattices. Short-range order is treated by embedding small clusters in an alloy that itself incorporates a two-site approximation, and the probabilities of these clusters are used to construct an efficient procedure for the calculation of electronic properties. This approach allows easy identification of the contributions of particular clusters to the electronic density of states. As the short-range order is increased via the number of clusters, the density of states can be clearly seen to transition from that of an alloy to that of a quasicrystal. It is shown that the techniques may be applied to other lattices defined by substitution rules.

  18. Dynamic range majority data structures

    DEFF Research Database (Denmark)

    Elmasry, Amr Ahmed Abd Elmoneim; He, Meng; Munro, J. Ian

    2011-01-01

    data structure for answering range α-majority queries on a dynamic set of points, where α ε (0,1). Our data structure uses O(n) space, supports queries in O((lg n)/α) time, and updates in O((lg n)/α) amortized time. If the coordinates of the points are integers, then the query time can be improved to O......((lg n/(α lglg n)). For constant values of α, this improved query time matches an existing lower bound, for any data structure with polylogarithmic update time. We also generalize our data structure to handle sets of points in d-dimensions, for d ≥ 2, as well as dynamic arrays, in which each entry...

  19. Atomistic microstructures in short-range ordered alloys

    CERN Document Server

    Hata, S

    2002-01-01

    Short-range order (SRO) in Ni-Mo alloys and their relatives has been controversial for decades, since it causes clearly diffraction intensity maxima at positions which do not coincide with the superlattice reflections in the long-range order (LRO) state. This paper gives an overview of recent studies on the structure of SRO and the transition from SRO to LRO in Ni-Mo alloys, including our results obtained in atomic level by combination of kinetic Monte Carlo simulation and semi-quantitative high-resolution transmission electron microscopy. It is rationalized in our results that the SRO state is set up by local ordering of A sub 4 B, A sub 3 B and A sub 2 B types in sub-unit cell scale. The dispersed mixture of the sub-unit cell clusters gives diffraction intensity maxima at the particular positions. An LRO state is formed by selected growth of the A sub 4 B, A sub 3 B and A sub 2 B type clusters into LRO domains depending on alloy-composition.

  20. Short-range order in undercooled metallic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Holland-Moritz, D.; Schenk, T.; Simonet, V.; Bellissent, R.; Convert, P.; Hansen, T.; Herlach, D.M

    2004-07-15

    The containerless processing technique of electromagnetic levitation was combined with elastic neutron scattering in order to study the short-range order (SRO) of stable and deeply undercooled liquids of the pure elements Ni, Fe and Zr and of the quasicrystal-forming alloy Al{sub 65}Cu{sub 25}Co{sub 10}. The results deliver experimental evidence for an icosahedral short-range order (ISRO) prevailing in the investigated metallic melts.

  1. Order and disorder in the local and long-range structure of the spin-glass pyrochlore, Tb{sub 2}Mo{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yu; Huq, Ashfia; Booth, Corwin H.; Ehlers, Georg; Greedan, John E.; Gardner, Jason S.

    2011-02-11

    To understand the origin of the spin-glass state in molybdate pyrochlores, the structure of Tb{sub 2}Mo{sub 2}O{sub 7} is investigated using two techniques: the long-range lattice structure was measured using neutron powder diffraction (NPD), and local structure information was obtained from the extended x-ray absorption fine structure (EXAFS) technique. While the long-range structure appears generally well ordered, enhanced mean-squared site displacements on the O(1) site and the lack of temperature dependence of the strongly anisotropic displacement parameters for both the Mo and O(1) sites indicate some disorder exists. Likewise, the local structure measurements indicate some Mo-Mo and Tb-O(1) nearest-neighbor disorder exists, similar to that found in the related spin-glass pyrochlore, Y{sub 2}Mo{sub 2}O{sub 7}. Although the freezing temperature in Tb{sub 2}Mo{sub 2}O{sub 7}, 25 K, is slightly higher than in Y{sub 2}Mo{sub 2}O{sub 7}, 22 K, the degree of local pair distance disorder is actually less in Tb{sub 2}Mo{sub 2}O{sub 7}. This apparent contradiction is considered in light of the interactions involved in the freezing process.

  2. Barium Titanate Nanoparticles: Short-range Lattice Distortions with Long-range Cubic Order

    Science.gov (United States)

    Haskell, Richard C.; Shi, Chenyang; Billinge, Simon J. L.; Puma, Eric; Bang, Sun Hwi; Bean, Nathaniel J. H.; de Sugny, Jean-Claude; Gambee, Robert G.; Hightower, Adrian; Monson, Todd C.

    Small barium titanate (BTO) nanoparticles (atomic pair distribution functions (PDFs). Fits to PDFs at temperatures of 20° to 220°C suggest that Ti atom displacements from the center of the unit cell are comparable to or even greater than those in the bulk material and persist at temperatures well above 120°C where the tetragonal to pseudo-cubic phase transition occurs in the bulk. Raman spectra acquired over a temperature range of 20° to 220°C confirm that small BTO nanoparticles exhibit a distorted unit cell even above 120°C. On the other hand, small BTO nanoparticles exhibit a long-range order consistent with a cubic lattice as recorded by laboratory XRD Bragg reflections at temperatures of 20° to 150°C. We have reconciled these seemingly contradictory data sets by fitting the PDFs over their full range of 6 nm to reveal a long-range structure with a reduced lattice distortion that still manages to support tetragonal Raman lines but is sufficiently close to cubic to yield apparent Bragg peak singlets. US DOE NNSA contract DE-AC04-94AL85000 and US DOE Office of Science contract DE-SC00112704.

  3. Packing defects into ordered structures

    DEFF Research Database (Denmark)

    Bechstein, R.; Kristoffersen, Henrik Høgh; Vilhelmsen, L.B.

    2012-01-01

    We have studied vicinal TiO2(110) surfaces by high-resolution scanning tunneling microscopy and density functional theory calculations. On TiO2 surfaces characterized by a high density of ⟨11̅ 1⟩ steps, scanning tunneling microscopy reveals a high density of oxygen-deficient strandlike adstructures....... With the help of density functional theory calculations we develop a complete structural model for the entire strand and demonstrate these adstructures to be more stable than an equivalent amount of bulk defects such as Ti interstitials. We argue that strands can form particularly easy on stepped surfaces...... because building material is available at step sites. The strands on TiO2(110) represent point defects that are densely packed into ordered adstructures....

  4. Chemical short range order obtained from the atomic pair distribution function

    OpenAIRE

    Proffen, Th.; Petkov, V.; Billinge, S. J. L.; Vogt, T.

    2002-01-01

    Many crystalline materials show chemical short range order and relaxation of neighboring atoms. Local structural information can be obtained by analyzing the atomic pair distribution function (PDF) obtained from powder diffraction data. In this paper, we present the successful extraction of chemical short range order parameters from the x-ray PDF of a quenched Cu_3Au sample.

  5. Unitarity corrections to short-range order long-range rapidity correlations

    CERN Document Server

    Capella, A

    1978-01-01

    Although the effective hadronic forces have short range in rapidity space, one nevertheless expects long-range dynamical correlations induced by unitarity constraints. This paper contains a thorough discussion of long-range rapidity correlations in high-multiplicity events. In particular, the authors analyze in detail the forward- backward multiplicity correlations, measured recently in the whole CERN ISR energy range. They find from these data that the normalized variance of the number n of exchanged cut Pomerons, ((n/(n)-1)/sup 2/) , is most probably in the range 0.32 to 0.36. They show that such a number is obtained from Reggeon theory in the eikonal approximation. The authors also predict a very specific violation of local compensation of charge in multiparticle events: The violation should appear in the fourth-order zone correlation function and is absent in the second-order correlation function, the only one measured until now. (48 refs).

  6. Ordering structured populations in multiplayer cooperation games

    Science.gov (United States)

    Peña, Jorge; Wu, Bin; Traulsen, Arne

    2016-01-01

    Spatial structure greatly affects the evolution of cooperation. While in two-player games the condition for cooperation to evolve depends on a single structure coefficient, in multiplayer games the condition might depend on several structure coefficients, making it difficult to compare different population structures. We propose a solution to this issue by introducing two simple ways of ordering population structures: the containment order and the volume order. If population structure is greater than population structure in the containment or the volume order, then can be considered a stronger promoter of cooperation. We provide conditions for establishing the containment order, give general results on the volume order, and illustrate our theory by comparing different models of spatial games and associated update rules. Our results hold for a large class of population structures and can be easily applied to specific cases once the structure coefficients have been calculated or estimated. PMID:26819335

  7. Ordering structured populations in multiplayer cooperation games.

    Science.gov (United States)

    Peña, Jorge; Wu, Bin; Traulsen, Arne

    2016-01-01

    Spatial structure greatly affects the evolution of cooperation. While in two-player games the condition for cooperation to evolve depends on a single structure coefficient, in multiplayer games the condition might depend on several structure coefficients, making it difficult to compare different population structures. We propose a solution to this issue by introducing two simple ways of ordering population structures: the containment order and the volume order. If population structure S1 is greater than population structure S1 in the containment or the volume order, then S1 can be considered a stronger promoter of cooperation. We provide conditions for establishing the containment order, give general results on the volume order, and illustrate our theory by comparing different models of spatial games and associated update rules. Our results hold for a large class of population structures and can be easily applied to specific cases once the structure coefficients have been calculated or estimated. © 2016 The Authors.

  8. Study of the effect of short ranged ordering on the magnetism in FeCr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jena, Ambika Prasad, E-mail: apjena@bose.res.in [Department of Condensed Matter and Materials Science, S N Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700098 (India); Sanyal, Biplab, E-mail: biplab.sanyal@physics.uu.se [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Mookerjee, Abhijit, E-mail: abhijit.mookerjee61@gmail.com [Department of Condensed Matter and Materials Science, S N Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700098 (India)

    2014-01-15

    For the study of magnetism in systems where the local environment plays an important role, we propose a marriage between the Monte Carlo simulation and Zunger's special quasi-random structures. We apply this technique on disordered FeCr alloys and show that our estimates of the transition temperature is in good agreement with earlier experiments. - Highlights: • The magnetism in FeCr is sensitively depended on the ordering of the atoms : disordered or with short ranged ordering. • This work uses the SQS technique suggested by Zunger has been used to generate various degrees of short range ordering in FeCr. • The electronic structure and pair energies have been obatined from first principles ASR and Lichtenstein methods. • The effect of chemical ordering on magnetic ordering is studied in detail. • Only those situations where the chemical ordering is complete have been studied.

  9. Ordered Algebraic Structures : the 1991 Conrad Conference

    CERN Document Server

    Holland, C

    1993-01-01

    This volume contains a selection of papers presented at the 1991 Conrad Conference, held in Gainesville, Florida, USA, in December, 1991. Together, these give an overview of some recent advances in the area of ordered algebraic structures. The first part of the book is devoted to ordered permutation groups and universal, as well as model-theoretic, aspects. The second part deals with material variously connected to general topology and functional analysis. Collectively, the contents of the book demonstrate the wide applicability of order-theoretic methods, and how ordered algebraic structures have connections with many research disciplines. For researchers and graduate students whose work involves ordered algebraic structures.

  10. Compressed Data Structures for Range Searching

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Vind, Søren Juhl

    2015-01-01

    matrices and web graphs. Our contribution is twofold. First, we show how to compress geometric repetitions that may appear in standard range searching data structures (such as K-D trees, Quad trees, Range trees, R-trees, Priority R-trees, and K-D-B trees), and how to implement subsequent range queries......We study the orthogonal range searching problem on points that have a significant number of geometric repetitions, that is, subsets of points that are identical under translation. Such repetitions occur in scenarios such as image compression, GIS applications and in compactly representing sparse...... that supports range searching....

  11. On the structure of order domains

    DEFF Research Database (Denmark)

    Geil, Olav; Pellikaan, Ruud

    2002-01-01

    The notion of an order domain is generalized. The behaviour of an order domain by taking a subalgebra, the extension of scalars, and the tensor product is studied. The relation of an order domain with valuation theory, Gröbner algebras, and graded structures is given. The theory of Gröbner bases...

  12. Higher order Hessian structures on manifolds

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    + Xψ. D2F · Sϕ. (9). If Sϕ = Yϕ Zϕ, we write Rϕ(Xϕ,Yϕ,Zϕ) = Rϕ(Xϕ,Yϕ Zϕ) and similarly for Cϕ. 4. Third-order Hessian structures. Let K be a third-order Hessian structure on M (the case n = 3 of Definition 2.1). In what follows we state that the following lemma and the proof is easy and hence left to the reader. Lemma 4.1.

  13. Variable ordering structures in vector optimization

    CERN Document Server

    Eichfelder, Gabriele

    2014-01-01

    This book provides an introduction to vector optimization with variable ordering structures, i.e., to optimization problems with a vector-valued objective function where the elements in the objective space are compared based on a variable ordering structure: instead of a partial ordering defined by a convex cone, we see a whole family of convex cones, one attached to each element of the objective space. The book starts by presenting several applications that have recently sparked new interest in these optimization problems, and goes on to discuss fundamentals and important results on a wide ra

  14. Electric field induced short range to long range structural ordering and its influence on the Eu{sup +3} photoluminescence in the lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kalaskar, Abhijeet; Rao, Badari Narayana; Ranjan, Rajeev, E-mail: rajeev@materials.iisc.ernet.in [Department of Materials Engineering, Indian Institute of Science Bangalore, Bangalore 560012 (India); Thomas, Tiju, E-mail: tijuthomas@iitm.ac.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu (India)

    2015-06-28

    Eu{sup +3} was incorporated into the lattice of a lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} (NBT) as per the nominal formula Na{sub 0.5}Bi{sub 0.5−x}Eu{sub x}TiO{sub 3}. This system was investigated with regard to the Eu{sup +3} photoluminescence (PL) and structural behaviour as a function of composition and electric field. Electric field was found to irreversibly change the features in the PL spectra and also in the x-ray diffraction patterns below the critical composition x = 0.025. Detailed analysis revealed that below the critical composition, electric field irreversibly suppresses the structural heterogeneity inherent of the host matrix NBT and brings about a long range ferroelectric state with rhombohedral (R3c) distortion. It is shown that the structural disorder on the nano-scale opens a new channel for radiative transition which manifests as a new emission line branching off from the main {sup 5}D{sub 0}→{sup 7}F{sub 0} line along with a concomitant change in the relative intensity of the other crystal field induced Stark lines with different J values. The study suggests that Eu{sup +3} luminescence can be used to probe the relative degree of field induced structural ordering in relaxor ferroelectrics and also in high performance piezoelectric alloys where electric field couples very strongly with the lattice and structural degrees of freedom.

  15. Long-range ordered nanodomains of grafted electroactive molecules.

    Science.gov (United States)

    Breitwieser, R; Marsault, M; Repain, V; Lagoute, J; Chacon, C; Girard, Y; Rousset, S; Qin, Z; Battaglini, N; Zrig, S; Lang, P

    2013-11-28

    We demonstrate the capability to build zero and one-dimensional electroactive molecular nanostructures ordered over a macroscopic scale and stable under ambient conditions. To realize these arrays, we use the selective grafting of functionalized thiols (juglon and terthiophene based) on a self-organized metallic template. The nanoscale patterning of the molecular conductance is demonstrated and analyzed by scanning tunneling spectroscopy. Finally, the influence of the nanostructuring on electro-chemical properties is measured, paving the way to an all-bottom-up fabrication of nanostructured templates for nanosciences.

  16. Short range ordering and microstructure property relationship in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shariq, A.

    2006-07-01

    A novel algorithm, ''Next Neighbourhood Evaluation (NNE)'', is enunciated during the course of this work, to elucidate the next neighbourhood atomic vicinity from the data, analysed using tomographic atom probe (TAP) that allows specifying atom positions and chemical identities of the next neighbouring atoms for multicomponent amorphous materials in real space. The NNE of the Pd{sub 55}Cu{sub 23}P{sub 22} bulk amorphous alloy reveals that the Pd atoms have the highest probability to be the next neighbours to each other. Moreover, P-P correlation corroborates earlier investigations with scattering techniques that P is not a direct next neighbour to another P atom. Analogous investigations on the Fe{sub 40}Ni{sub 40}B{sub 20} metallic glass ribbons, in the as quenched state and for a state heat treated at 350 C for 1 hour insinuate a pronounced elemental inhomogeneity for the annealed state, though, it also depicts glimpse of a slight inhomogeneity for B distribution even for the as quenched sample. Moreover, a comprehensive microstructural investigation has been carried out on the Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy system. TEM and TAP investigations evince that the as cast bulk samples constitutes a composite structure of an amorphous phase and crystalline phase(s). The crystallization is essentially triggered at the mould walls due to heterogeneous nucleation. The three dimensional atomic reconstruction maps of the volume analysed by TAP reveal a complex stereological interconnected network of two phases. The phase that is rich in Zr and Al concentration is depleted in Co concentration while the phase that is rich in Co concentration is depleted both in Zr and Al. Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy splat samples exhibit a single exothermic crystallization peak contrary to the as cast bulk sample with a different T{sub g} temperature. A single homogeneous amorphous phase revealed by TEM investigations depicts that the faster cooling

  17. Ordered mesoporous silica materials with complicated structures

    KAUST Repository

    Han, Yu

    2012-05-01

    Periodically ordered mesoporous silicas constitute one of the most important branches of porous materials that are extensively employed in various chemical engineering applications including adsorption, separation and catalysis. This short review gives an introduction to recently developed mesoporous silicas with emphasis on their complicated structures and synthesis mechanisms. In addition, two powerful techniques for solving complex mesoporous structures, electron crystallography and electron tomography, are compared to elucidate their respective strength and limitations. Some critical issues and challenges regarding the development of novel mesoporous structures as well as their applications are also discussed. © 2011 Elsevier Ltd.

  18. Short- and medium-range order in Zr[subscript 80]Pt[subscript 20] liquids

    Energy Technology Data Exchange (ETDEWEB)

    Mauro, N.A.; Wessels, V.; Bendert, J.C.; Klein, S.; Gangopadhyay, A.K.; Kramer, M.J.; Hao, S.G.; Rustan, G.E.; Kreyssig, A.; Goldman, A.I.; Kelton, K.F. (WU); (ETH Zurich); (Iowa State); (IMW-Germany)

    2011-12-09

    The atomic structures in equilibrium and supercooled liquids of Zr{sub 80}Pt{sub 20} were determined as a function of temperature by in situ high-energy synchrotron diffraction studies of the levitated liquids (containerless processing) using the beamline electrostatic levitation (BESL) technique. The presence of a pronounced pre-peak at q - 1.7 {angstrom}{sup -1} in the static structure factor indicates medium-range order (MRO) in the liquid. The position and intensity of the pre-peak remain constant with cooling, indicating that the MRO is already present in the liquid above its melting temperature. An analysis of the liquid atomic structures obtained using the Reverse Monte Carlo method utilizing both the structure factor S(q) from x-ray diffraction experiments and the partial pair-correlation functions from ab initio molecular dynamics simulations show that the pre-peak arises from a Pt-Pt correlation that can be identified with icosahedral short-range order around the Pt atoms. The local atomic ordering is dominated by icosahedral-like structures, raising the nucleation barrier between the liquid and these phases, thus assisting glass formation.

  19. Long-range dipolar order and dispersion forces in polar liquids.

    Science.gov (United States)

    Besford, Quinn Alexander; Christofferson, Andrew Joseph; Liu, Maoyuan; Yarovsky, Irene

    2017-11-21

    Complex solvation phenomena, such as specific ion effects, occur in polar liquids. Interpretation of these effects in terms of structure and dispersion forces will lead to a greater understanding of solvation. Herein, using molecular dynamics, we probe the structure of polar liquids through specific dipolar pair correlation functions that contribute to the potential of mean force that is "felt" between thermally rotating dipole moments. It is shown that unique dipolar order exists at separations at least up to 20 Å for all liquids studied. When the structural order is compared with a dipolar dispersion force that arises from local co-operative enhancement of dipole moments, a strong agreement is found. Lifshitz theory of dispersion forces was compared with the structural order, where the theory is validated for all liquids that do not have significant local dipole correlations. For liquids that do have significant local dipole correlations, specifically liquid water, Lifshitz theory underestimates the dispersion force by a factor of 5-10, demonstrating that the force that leads to the increased structure in liquid water is missed by Lifshitz theory of van der Waals forces. We apply similar correlation functions to an ionic aqueous system, where long-range order between water's dipole moment and a single chloride ion is found to exist at 20 Å of separation, revealing a long-range perturbation of water's structure by an ion. Furthermore, we found that waters within the 1st, 2nd, and 3rd solvation shells of a chloride ion exhibit significantly enhanced dipolar interactions, particularly with waters at larger distances of separation. Our results provide a link between structures, dispersion forces, and specific ion effects, which may lead to a more robust understanding of solvation.

  20. Long-range dipolar order and dispersion forces in polar liquids

    Science.gov (United States)

    Besford, Quinn Alexander; Christofferson, Andrew Joseph; Liu, Maoyuan; Yarovsky, Irene

    2017-11-01

    Complex solvation phenomena, such as specific ion effects, occur in polar liquids. Interpretation of these effects in terms of structure and dispersion forces will lead to a greater understanding of solvation. Herein, using molecular dynamics, we probe the structure of polar liquids through specific dipolar pair correlation functions that contribute to the potential of mean force that is "felt" between thermally rotating dipole moments. It is shown that unique dipolar order exists at separations at least up to 20 Å for all liquids studied. When the structural order is compared with a dipolar dispersion force that arises from local co-operative enhancement of dipole moments, a strong agreement is found. Lifshitz theory of dispersion forces was compared with the structural order, where the theory is validated for all liquids that do not have significant local dipole correlations. For liquids that do have significant local dipole correlations, specifically liquid water, Lifshitz theory underestimates the dispersion force by a factor of 5-10, demonstrating that the force that leads to the increased structure in liquid water is missed by Lifshitz theory of van der Waals forces. We apply similar correlation functions to an ionic aqueous system, where long-range order between water's dipole moment and a single chloride ion is found to exist at 20 Å of separation, revealing a long-range perturbation of water's structure by an ion. Furthermore, we found that waters within the 1st, 2nd, and 3rd solvation shells of a chloride ion exhibit significantly enhanced dipolar interactions, particularly with waters at larger distances of separation. Our results provide a link between structures, dispersion forces, and specific ion effects, which may lead to a more robust understanding of solvation.

  1. Spatially resolved distribution function and the medium-range order in metallic liquid and glass

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Xiaowei; Wang, Cai-Zhuang; Hao, Shaogang; Kramer, Matthew; Yao, Yongxin; Mendelev, Mikhail; Napolitano, Ralph; Ho, Kai-Ming

    2011-12-23

    The structural description of disordered systems has been a longstanding challenge in physical science. We propose an atomic cluster alignment method to reveal the development of three-dimensional topological ordering in a metallic liquid as it undercools to form a glass. By analyzing molecular dynamic (MD) simulation trajectories of a Cu{sub 64.5}Zr{sub 35.5} alloy, we show that medium-range order (MRO) develops in the liquid as it approaches the glass transition. Specifically, around Cu sites, we observe 'Bergman triacontahedron' packing (icosahedron, dodecahedron and icosahedron) that extends out to the fourth shell, forming an interpenetrating backbone network in the glass. The discovery of Bergman-type MRO from our order-mining technique provides unique insights into the topological ordering near the glass transition and the relationship between metallic glasses and quasicrystals.

  2. Spatially resolved distribution function and the medium-range order in metallic liquid and glass.

    Science.gov (United States)

    Fang, X W; Wang, C Z; Hao, S G; Kramer, M J; Yao, Y X; Mendelev, M I; Ding, Z J; Napolitano, R E; Ho, K M

    2011-01-01

    The structural description of disordered systems has been a longstanding challenge in physical science. We propose an atomic cluster alignment method to reveal the development of three-dimensional topological ordering in a metallic liquid as it undercools to form a glass. By analyzing molecular dynamic (MD) simulation trajectories of a Cu(64.5)Zr(35.5) alloy, we show that medium-range order (MRO) develops in the liquid as it approaches the glass transition. Specifically, around Cu sites, we observe "Bergman triacontahedron" packing (icosahedron, dodecahedron and icosahedron) that extends out to the fourth shell, forming an interpenetrating backbone network in the glass. The discovery of Bergman-type MRO from our order-mining technique provides unique insights into the topological ordering near the glass transition and the relationship between metallic glasses and quasicrystals.

  3. Distinct Short-Range Order Is Inherent to Small Amorphous Calcium Carbonate Clusters (<2 nm)

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Shengtong [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany; School of Chemical Engineering, State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, East China University of Science and Technology, 130 Meilong Road Shanghai 200237 P.R. China; Chevrier, Daniel M. [Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax Nova Scotia B3H 4R2 Canada; Zhang, Peng [Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax Nova Scotia B3H 4R2 Canada; Gebauer, Denis [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany; Cölfen, Helmut [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany

    2016-09-09

    Amorphous intermediate phases are vital precursors in the crystallization of many biogenic minerals. While inherent short-range orders have been found in amorphous calcium carbonates (ACCs) relating to different crystalline forms, it has never been clarified experimentally whether such orders already exist in very small clusters less than 2 nm in size. Here, we studied the stability and structure of 10,12-pentacosadiynoic acid (PCDA) protected ACC clusters with a core size of ca. 1.4 nm consisting of only seven CaCO3 units. Ligand concentration and structure are shown to be key factors in stabilizing the ACC clusters. More importantly, even in such small CaCO3 entities, a proto-calcite short-range order can be identified but with a relatively high degree of disorder that arises from the very small size of the CaCO3 core. Our findings support the notion of a structural link between prenucleation clusters, amorphous intermediates, and final crystalline polymorphs, which appears central to the understanding of polymorph selection.

  4. Distortion-triggered loss of long-range order in solids with bonding energy hierarchy.

    Science.gov (United States)

    Kolobov, A V; Krbal, M; Fons, P; Tominaga, J; Uruga, T

    2011-04-01

    An amorphous-to-crystal transition in phase-change materials like Ge-Sb-Te is widely used for data storage. The basic principle is to take advantage of the property contrast between the crystalline and amorphous states to encode information; amorphization is believed to be caused by melting the materials with an intense laser or electrical pulse and subsequently quenching the melt. Here, we demonstrate that distortions in the crystalline phase may trigger a collapse of long-range order, generating the amorphous phase without going through the liquid state. We further show that the principal change in optical properties occurs during the distortion of the still crystalline structure, upsetting yet another commonly held belief that attributes the change in properties to the loss of long-range order. Furthermore, our results suggest a way to lower energy consumption by condensing phase change inducing energy into shorter pulses or through the use of coherent phonon excitation.

  5. Short- and medium-range orders in Cu46Zr54 metallic glasses under shock compression

    Science.gov (United States)

    Jian, W. R.; Yao, X. H.; Wang, L.; Tang, X. C.; Luo, S. N.

    2015-07-01

    We investigate short- and medium-range orders in Cu46Zr54 metallic glasses, as represented by icosahedra and icosahedron networks, respectively, under shock compression with molecular dynamics simulations. Complementary isothermal compression and isobaric heating simulations reveal that compression below 60 GPa gives rise to increased coordination and thus high-coordination-number Voronoi polyhedra, such as icosahedra; however, pressure-induced collapse or thermal disintegration of icosahedra (and subsequently, icosahedron networks) occurs at pressures above 60 GPa or at melting, accompanied by free volume increase. The evolutions of the short- and medium-range orders upon shock loading are the effects of compression combined with shock-induced melting. The structural changes are partially reversible for weak shocks without melting (below 60 GPa) and irreversible for strong shocks. Crystallization does not occur under isothermal or shock compression at molecular dynamics scales.

  6. Intermediate-range chemical ordering of cations in molten RbCl-AgCl

    Science.gov (United States)

    Tahara, S.; Kawakita, Y.; Shimakura, H.; Ohara, K.; Fukami, T.; Takeda, S.

    2015-07-01

    A first sharp diffraction peak (FSDP) is observed in the X-ray total structure factor of a molten mixture of RbCl-AgCl, while both pure melts of RbCl and AgCl do not exhibit FSDP individually. Molecular dynamics simulations were performed to investigate the origin of the FSDP with the polarizable ion model (PIM). Coexistence of covalent Ag-Cl and ionic Rb-Cl bonds leads the system to evolve intermediate range ordering, which is simulated by introducing the induced polarization in different ways between Ag-Cl with fully polarizable treatment based on Vashishta-Raman potential and Rb-Cl with suppression over-polarization in the nearest neighbor contribution based on Born-Meyer potential. The partial structure factors for both the Ag-Ag and Rb-Rb correlations, SAgAg(Q) and SRbRb(Q), show a positive contribution to the FSDP, while SAgRb(Q) for the Ag-Rb correlation exhibits a negative contribution, indicating that Ag and Rb ions are distributed in an alternating manner within the intermediate-range length scale. The origin of the intermediate-range chemical ordering of cations can be ascribed to the preferred direction of the dipole moments of anions in the PIM.

  7. Intermediate-range chemical ordering of cations in molten RbCl-AgCl

    Energy Technology Data Exchange (ETDEWEB)

    Tahara, S. [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, Okinawa 903-0213 (Japan); Research and Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8), Hyogo 679-5198 (Japan); Kawakita, Y. [J-PARC Center, Japan Atomic Energy Agency (JAEA), Ibaraki 319-1195 (Japan); Shimakura, H. [Faculty of Pharmacy, Niigata University of Pharmacy and Applied Life Sciences, Niigata 956-8603 (Japan); Ohara, K. [Research and Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8), Hyogo 679-5198 (Japan); Fukami, T. [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, Okinawa 903-0213 (Japan); Takeda, S. [Department of Physics, Faculty of Sciences, Kyushu University, Fukuoka 812-8581 (Japan)

    2015-07-28

    A first sharp diffraction peak (FSDP) is observed in the X-ray total structure factor of a molten mixture of RbCl-AgCl, while both pure melts of RbCl and AgCl do not exhibit FSDP individually. Molecular dynamics simulations were performed to investigate the origin of the FSDP with the polarizable ion model (PIM). Coexistence of covalent Ag–Cl and ionic Rb–Cl bonds leads the system to evolve intermediate range ordering, which is simulated by introducing the induced polarization in different ways between Ag–Cl with fully polarizable treatment based on Vashishta-Raman potential and Rb–Cl with suppression over-polarization in the nearest neighbor contribution based on Born-Meyer potential. The partial structure factors for both the Ag–Ag and Rb–Rb correlations, S{sub AgAg}(Q) and S{sub RbRb}(Q), show a positive contribution to the FSDP, while S{sub AgRb}(Q) for the Ag–Rb correlation exhibits a negative contribution, indicating that Ag and Rb ions are distributed in an alternating manner within the intermediate-range length scale. The origin of the intermediate-range chemical ordering of cations can be ascribed to the preferred direction of the dipole moments of anions in the PIM.

  8. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2..sqrt..3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (..sqrt..3 x ..sqrt..3) reconstruction on the (111) face of the ..cap alpha..-CuAl alloy has been determined.

  9. New data structures for orthogonal range searching

    DEFF Research Database (Denmark)

    Alstrup, Stephen; Brodal, Gerth Stølting; Rauhe, Theis

    2000-01-01

    We present new general techniques for static orthogonal range searching problems in two and higher dimensions. For the general range reporting problem in R3, we achieve query time O(log n+k) using space O(n log1+ε n), where n denotes the number of stored points and k the number of points to be re...

  10. Neutron diffraction study of the magnetic long-range order in Tb

    DEFF Research Database (Denmark)

    Dietrich, O.W.; Als-Nielsen, Jens Aage

    1967-01-01

    and implies no change in the long-range order. In the close vicinity of the Neacuteel temperature TN = 226deg K the spiral magnetic long-range order varies as (TN-T)0.25plusmn 0.01, whereas the total order within a wider temperature range roughly follows (TN-T)1/3. The turn angle per layer varies from 16.5deg...

  11. Communication: Anomalous temperature dependence of the intermediate range order in phosphonium ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Hettige, Jeevapani J.; Kashyap, Hemant K.; Margulis, Claudio J., E-mail: claudio-margulis@uiowa.edu [Department of Chemistry, University of Iowa, Iowa City, Iowa 52242 (United States)

    2014-03-21

    In a recent article by the Castner and Margulis groups [Faraday Discuss. 154, 133 (2012)], we described in detail the structure of the tetradecyltrihexylphosphonium bis(trifluoromethylsulfonyl)-amide ionic liquid as a function of temperature using X-ray scattering, and theoretical partitions of the computationally derived structure function. Interestingly, and as opposed to the case in most other ionic-liquids, the first sharp diffraction peak or prepeak appears to increase in intensity as temperature is increased. This phenomenon is counter intuitive as one would expect that intermediate range order fades as temperature increases. This Communication shows that a loss of hydrophobic tail organization at higher temperatures is counterbalanced by better organization of polar components giving rise to the increase in intensity of the prepeak.

  12. Natural gels: crystal-chemistry of short range ordered components in Al, Fe, and Si systems

    Energy Technology Data Exchange (ETDEWEB)

    Ildefonse, Ph.; Calas, G. [Paris-6 et 7 Univ. and IPGP, Lab. de Mineralogie-Cristallographie, UA CNRS 09, 75 (France)

    1997-07-01

    In this review, the most important inorganic natural gels are presented: opal, aluminosilicate (allophanes) and hydrous iron oxides and silicates. It is demonstrated that natural gels are ordered at the atomic scale. In allophanes, Al is distributed between octahedral and tetrahedral sites. The amount of Al increases as Al/Si ratio decreases. Si-rich allophane have a local structure around Al and Si very different of that is known in kaolinite or halloysite. Transformation of Si-rich allophanes to crystallized minerals implies dissolution-recrystallization processes. On the contrary, in iron silicate with Fe/Si = 0.72, Si and Fe environments are close to those found in nontronite. The gel transformation to Fe-smectite may occur by long range ordering during ageing. In ferric silicate gels, the similarity of local structure around Fe in poorly ordered precursors and what is known in crystallized minerals suggests a solid transformation during ageing. This difference between iron and aluminium is mainly due to the ability of Al to enter both tetrahedral and octahedral sites, while the affinity of iron for octahedral sites is higher at low temperature.

  13. Ordering of carbon atoms in boron carbide structure

    Energy Technology Data Exchange (ETDEWEB)

    Ponomarev, V. I., E-mail: i2212@yandex.ru; Kovalev, I. D.; Konovalikhin, S. V.; Vershinnikov, V. I. [Russian Academy of Sciences, Institute of Structural Macrokinetics and Materials Science (Russian Federation)

    2013-05-15

    Boron carbide crystals have been obtained in the entire compositional range according to the phase diagram by self-propagating high-temperature synthesis (SHS). Based on the results of X-ray diffraction investigations, the samples were characterized by the unit-cell metric and reflection half-width in the entire range of carbon concentrations. A significant spread in the boron carbide unit-cell parameters for the same carbon content is found in the data in the literature; this spread contradicts the structural concepts for covalent compounds. The SHS samples have not revealed any significant spread in the unit-cell parameters. Structural analysis suggests that the spread of parameters in the literary data is related to the unique process of ordering of carbon atoms in the boron carbide structure.

  14. Swellable Model POPC/POPG/DHPC Membrane with a Lamellar Long-Range Order

    Science.gov (United States)

    Li, Ming; Nieh, Mu-Ping

    2012-02-01

    A physiological relevant biomimetic model membrane is of great necessity for the structural characterization of membrane protein. This presentation will report a small-angle neutron scattering (SANS) result on two lipid bicellar series composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine(POPC)/1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) and POPC/DHPC/1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG). Instead of the multi-lamellae vesicle (MLV) structure observed in zwitterionic POPC/DHPC mixture, the perforated lamellae (PL) structure is found in POPC/POPG/DHPC upon addition of small amount of charged lipid, POPG R=[POPG]/([POPC]+[POPG])=0.01. The PL phase exists from 10 to 60 degree C and the interlamellar spacing (d-spacing) varies from 12.9 to 49.0 nm as the lipid concentration changes from 25 to 7.5% wt where the lamellae still indicate long-range order. The effect of temperature and charge density (R) on structural variation will be discussed in this presentation.

  15. Charge ordering and long-range interactions in layered transition metal oxides

    OpenAIRE

    Stojkovic, Branko P.; Yu, Z. G.; Bishop, A. R.; Neto, A. H. Castro; Gronbech-Jensen, Niels

    1998-01-01

    We study the competition between long-range and short-range interactions among holes within the spin density wave picture of layered transition metal oxides. We focus on the problem of charge ordering and the charge phase diagram. We show that the main interactions are the long-range Coulomb interaction and a dipolar short-range interaction generated by the short-range antiferromagnetic fluctuations. We find four different phases depending on the strength of the dipolar interaction and the de...

  16. Loss of long-range magnetic order in a nanoparticle assembly due to random anisotropy

    Science.gov (United States)

    Binns, C.; Howes, P. B.; Baker, S. H.; Marchetto, H.; Potenza, A.; Steadman, P.; Dhesi, S. S.; Roy, M.; Everard, M. J.; Rushforth, A.

    2008-02-01

    We have used soft x-ray photoemission electron microscopy (XPEEM) combined with x-ray magnetic circular dichroism (XMCD) and DC SQUID (superconducting quantum interference device) magnetometry to probe the magnetic ground state in Fe thin films produced by depositing size-selected gas-phase Fe nanoparticles with a diameter of 1.7 nm (~200 atoms) onto Si substrates. The depositions were carried out in ultrahigh vacuum conditions and thicknesses of the deposited film in the range 5-50 nm were studied. The magnetometry data are consistent with the film forming a correlated super-spin glass with a magnetic correlation length ~5 nm. The XPEEM magnetic maps from the cluster-assembled films were compared to those for a conventional thin Fe film with a thickness of 20 nm produced by a molecular beam epitaxy (MBE) source. Whereas a normal magnetic domain structure is observed in the conventional MBE thin film, no domain structure could be observed in any of the nanoparticle films down to the resolution limit of the XMCD based XPEEM (100 nm) confirming the ground state indicated by the magnetometry measurements. This observation is consistent with the theoretical prediction that an arbitrarily weak random anisotropy field will destroy long-range magnetic order.

  17. Investigating the medium range order in amorphous Ta2O5 coatings

    Science.gov (United States)

    Bassiri, Riccardo; Hart, Martin; Byer, Robert L.; Borisenko, Konstantin B.; Evans, Keith; Fejer, Martin M.; Lin, Angie C.; MacLaren, Ian; Markosyan, Ashot S.; Martin, Iain W.; Route, Roger K.; Rowan, Sheila

    2014-06-01

    Ion-beam sputtered amorphous heavy metal oxides, such as Ta2O5, are widely used as the high refractive index layer of highly reflective dielectric coatings. Such coatings are used in the ground based Laser Interferometer Gravitational-wave Observatory (LIGO), in which mechanical loss, directly related to Brownian thermal noise, from the coatings forms an important limit to the sensitivity of the LIGO detector. It has previously been shown that heat-treatment and TiO2 doping of amorphous Ta2O5 coatings causes significant changes to the levels of mechanical loss measured and is thought to result from changes in the atomic structure. This work aims to find ways to reduce the levels of mechanical loss in the coatings by understanding the atomic structure properties that are responsible for it, and thus helping to increase the LIGO detector sensitivity. Using a combination of Reduced Density Functions (RDFs) from electron diffraction and Fluctuation Electron Microscopy (FEM), we probe the medium range order (in the 2-3 nm range) of these amorphous coatings.

  18. Loss of long-range magnetic order in a nanoparticle assembly due to random anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Binns, C [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Howes, P B [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Baker, S H [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Marchetto, H [Diamond Light Source Ltd, Harwell Science and Innovation Campus, Diamond House, Chilton, Didcot, Oxfordshire OX11 0DE (United Kingdom); Potenza, A [Diamond Light Source Ltd, Harwell Science and Innovation Campus, Diamond House, Chilton, Didcot, Oxfordshire OX11 0DE (United Kingdom); Steadman, P [Diamond Light Source Ltd, Harwell Science and Innovation Campus, Diamond House, Chilton, Didcot, Oxfordshire OX11 0DE (United Kingdom); Dhesi, S S [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Roy, M [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Everard, M J [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Rushforth, A [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2008-02-06

    We have used soft x-ray photoemission electron microscopy (XPEEM) combined with x-ray magnetic circular dichroism (XMCD) and DC SQUID (superconducting quantum interference device) magnetometry to probe the magnetic ground state in Fe thin films produced by depositing size-selected gas-phase Fe nanoparticles with a diameter of 1.7 nm ({approx}200 atoms) onto Si substrates. The depositions were carried out in ultrahigh vacuum conditions and thicknesses of the deposited film in the range 5-50 nm were studied. The magnetometry data are consistent with the film forming a correlated super-spin glass with a magnetic correlation length {approx}5 nm. The XPEEM magnetic maps from the cluster-assembled films were compared to those for a conventional thin Fe film with a thickness of 20 nm produced by a molecular beam epitaxy (MBE) source. Whereas a normal magnetic domain structure is observed in the conventional MBE thin film, no domain structure could be observed in any of the nanoparticle films down to the resolution limit of the XMCD based XPEEM (100 nm) confirming the ground state indicated by the magnetometry measurements. This observation is consistent with the theoretical prediction that an arbitrarily weak random anisotropy field will destroy long-range magnetic order.

  19. kinetics and mechanism of long-range pore ordering in anodic films on aluminium

    NARCIS (Netherlands)

    Napolskii, K.S.; Roslyakov, I. V.; Eliseev, A.A.; Byelov, D.|info:eu-repo/dai/nl/298392720; Petukhov, A.V.|info:eu-repo/dai/nl/304829196; Grigoryeva, N.A.; Bouwman, W.G.; Lukashin, A.V.; Chumakov, A. P.; Grigoriev, S.V.

    2011-01-01

    Anodic aluminum oxide has unique and highly attractive properties, including self-ordering of porous structure during anodization. Although anodization regimes leading to formation of highly ordered porous structures had been found experimentally, many aspects of the self-organization mechanism

  20. Molecular dynamics studies of short to medium range order in Cu{sub 64}Zr{sub 36} metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Sha, Z.D., E-mail: shaz@ihpc.a-star.edu.sg [Institute of High Performance Computing, 1 Fusionopolis Way, Singapore 138632 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Zhang, Y.W. [Institute of High Performance Computing, 1 Fusionopolis Way, Singapore 138632 (Singapore); Feng, Y.P. [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Li, Y. [Department of Materials Science and Engineering, National University of Singapore, Engineering Drive 1, Singapore 117576 (Singapore)

    2011-08-18

    Highlights: > Short- and medium-range orders in Cu{sub 64}Zr{sub 36} metallic glass were investigated. > We employed the concept of core-shell rather than cluster packing. > The basic atomic structure has the characteristics of an icosahedral shell structure. > This finding applies to short- and medium-range orders in the optimum glass former. - Abstract: For metallic glasses, the cluster packing scheme addresses mainly the low solute concentration regime and it breaks down beyond a length scale of a few clusters. In the present work, from the viewpoint of core-shell structure rather than cluster packing, short- and medium-range orders in Cu{sub 64}Zr{sub 36} metallic glass were investigated using the large-scale atomic/molecular massively parallel simulator. In the first three coordination shells, the total number of atoms within the nth coordination shell is 13, 61, and 169. And the number of atoms on the nth coordination shell is 12n{sup 2}. Besides, the basic atomic structure could be obtained from a central icosahedron surrounded by a shell of 12n{sup 2} atoms. From the fourth coordination shell on, the total number of atoms is 307, 561, and 924, respectively, consistent with that in an icosahedral shell structure. Our finding suggests that for the optimum glass former in the Cu-Zr binary system, the basic atomic structures over both short- and medium-range length scales have the characteristics of an icosahedral shell structure.

  1. Structural short-range forces between solid-melt interfaces

    Science.gov (United States)

    Spatschek, R.; Adland, A.; Karma, A.

    2013-01-01

    We predict the structural interaction of crystalline solid-melt interfaces using amplitude equations which are derived from classical density functional theory or phase field crystal modeling. The solid ordering decays exponentially on the scale of the interface thickness at solid-melt interfaces; the overlap of two such profiles leads to a short-range interaction, which is mainly carried by the longest-range density waves, which can facilitate grain boundary premelting. We calculate the tail of these interactions, depending on the relative translation of the two crystals, fully analytically and predict the interaction potential, and compare it to numerical simulations. For grain boundaries the interaction is predicted to decay twice as fast as for two crystals without misorientation.

  2. Application of long-range order to predict unfolding rates of two-state proteins.

    Science.gov (United States)

    Harihar, B; Selvaraj, S

    2011-03-01

    Predicting the experimental unfolding rates of two-state proteins and models describing the unfolding rates of these proteins is quite limited because of the complexity present in the unfolding mechanism and the lack of experimental unfolding data compared with folding data. In this work, 25 two-state proteins characterized by Maxwell et al. (Protein Sci 2005;14:602–616) using a consensus set of experimental conditions were taken, and the parameter long-range order (LRO) derived from their three-dimensional structures were related with their experimental unfolding rates ln(k(u)). From the total data set of 30 proteins used by Maxwell et al. (Protein Sci 2005;14:602–616), five slow-unfolding proteins with very low unfolding rates were considered to be outliers and were not included in our data set. Except all beta structural class, LRO of both the all-alpha and mixed-class proteins showed a strong inverse correlation of r = -0.99 and -0.88, respectively, with experimental ln(k(u)). LRO shows a correlation of -0.62 with experimental ln(k(u)) for all-beta proteins. For predicting the unfolding rates, a simple statistical method has been used and linear regression equations were developed for individual structural classes of proteins using LRO, and the results obtained showed a better agreement with experimental results. Copyright © 2010 Wiley-Liss, Inc.

  3. Long-range magnetic order and spin-lattice coupling in the delafossite CuFeO2

    OpenAIRE

    Eyert, Volker; Fresard, Raymond; Maignan, Antoine

    2008-01-01

    The electronic and magnetic properties of the delafossite CuFeO2 are investigated by means of electronic structure calculations. They are performed using density functional theory in the generalized gradient approximation as well as the new full-potential augmented spherical wave method. The calculations reveal three different spin states at the iron sites. Taking into account the correct crystal structure, we find long-range antiferromagnetic ordering in agreement with experiment. Contrastin...

  4. Higher order structure in a complex plasma

    Science.gov (United States)

    Donkó, Z.; Hartmann, P.; Magyar, P.; Kalman, G. J.; Golden, K. I.

    2017-10-01

    The direct experimental determination of the 3-point static structure function S(3)(k1, k2, k0) of a 2-dimensional dusty plasma liquid is presented. The measurements are complemented by molecular dynamics simulations of the system, using parameters (dust charge, plasma frequency, coupling and screening coefficients), which are derived from the experimentally obtained 2-point static structure function S(2), as well as the dynamic structure function and current-current fluctuation spectra. The experimental results of S(3) are in good agreement with those of the simulations, including the (low wavenumber) domain, where S(3) acquires negative values. The "Convolution Approximation" (giving S(3) in a factorized form of S(2) functions) clearly breaks down in this domain; however, it is found to be a useful aid for explaining the main features of the S(3)(k1, k2, k0) functions, for which (experimental and simulation) maps are presented at selected values of one of its arguments.

  5. Long-range ferromagnetic order in LaCoO3 -δ epitaxial films due to the interplay of epitaxial strain and oxygen vacancy ordering

    Science.gov (United States)

    Mehta, V. V.; Biskup, N.; Jenkins, C.; Arenholz, E.; Varela, M.; Suzuki, Y.

    2015-04-01

    We demonstrate that a combination of electronic structure modification and oxygen vacancy ordering can stabilize a long-range ferromagnetic ground state in epitaxial LaCoO3 thin films. Highest saturation magnetization values are found in the thin films in tension on SrTiO3 and (La ,Sr )(Al ,Ta )O3 substrates and the lowest values are found in thin films in compression on LaAlO3. Electron microscopy reveals oxygen vacancy ordering to varying degrees in all samples, although samples with the highest magnetization are the most defective. Element-specific x-ray absorption techniques reveal the presence of high spin Co2 + and Co3 + as well as low spin Co3 + in different proportions depending on the strain state. The interactions among the high spin Co ions and the oxygen vacancy superstructure are correlated with the stabilization of the long-range ferromagnetic order.

  6. Nurses' opinions on appropriate administration of PRN range opioid analgesic orders for acute pain.

    Science.gov (United States)

    Gordon, Debra B; Pellino, Teresa A; Higgins, Gerry Ann; Pasero, Chris; Murphy-Ende, Kathleen

    2008-09-01

    The use of "as needed" or "pro re nata" (PRN) range opioid analgesic orders is a common clinical practice in the management of acute pain, designed to provide flexibility in dosing to meet an individual's unique needs. Range orders enable necessary adjustments in doses based on individual response to treatment. However, PRN range opioid orders have recently come under scrutiny as a source of confusion and as a medication management safety issue. How nurses administer range orders may vary based on their interpretation of the intent of an order, inadequate knowledge of analgesic titration, or exaggerated concerns about opioid safety. The purpose of this study was to investigate nurses' opinions of the appropriate implementation of range orders. Six hundred two nurses from one large academic medical center and one multihospital system completed an online survey using theoretic clinical vignettes to examine their opinions of appropriate analgesic administration practices. The majority of participants chose appropriate responses to the vignettes; however, there was a great deal of variability in responses. Those who had attended pain management courses were more likely to have a higher percentage of appropriate responses than those who had not attended courses. Years in practice and educational level were not significantly related to percentage of appropriate responses; however, there was a trend for nurses with a master's degree to have a higher percentage than nurses with other educational preparation. Consideration of opioid pharmacokinetics can provide logic to develop a new paradigm where range orders are replaced with orders that provide more explicit instructions to titrate an opioid to the most effective dose.

  7. First order properties on nowhere dense structures

    OpenAIRE

    Nešetřil, Jaroslav; Ossona de Mendez, Patrice

    2010-01-01

    A set A of vertices of a graph G is called d-scattered in G if no two d-neighborhoods of (distinct) vertices of A intersect. In other words, A is d-scattered if no two distinct vertices of A have distance at most 2d. This notion was isolated in the context of finite model theory by Ajtai and Gurevich and recently it played a prominent role in the study of homomorphism preservation theorems for special classes of structures (such as minor closed classes). This in turn led ...

  8. Hidden long-range order in a two-dimensional spin-orbit coupled Bose gas

    CERN Document Server

    Su, Shih-Wei; Gou, Shih-Chuan; Liao, Renyuan; Fialko, Oleksandr; Brand, Joachim

    2016-01-01

    A two-dimensional spin-orbit coupled Bose gas is shown to simultaneously possess quasi and true long-range orders in the total and relative phases, respectively. The total phase undergoes a conventional Berenzinskii- Kosterlitz-Thouless transition, where an quasi long-range order is expected. Additionally, the relative phase undergoes an Ising-type transition building up true long-range order, which is induced by the anisotropic spin- orbit coupling. Based on the Bogoliubov approach, expressions for the total- and relative-phase fluctuations are derived analytically for the low temperature regime. Numerical simulations of the stochastic projected Gross- Pitaevskii equation give a good agreement with the analytical predictions.

  9. Long-Range Charge Order in the Extended Holstein-Hubbard Model

    Science.gov (United States)

    Miyao, Tadahiro

    2016-10-01

    This study investigated the extended Holstein-Hubbard model at half-filling as a model for describing the interplay of electron-electron and electron-phonon couplings. When the electron-phonon and nearest-neighbor electron-electron interactions are strong, we prove the existence of long-range charge order in three or more dimensions at a sufficiently low temperature. As a result, we rigorously justify the phase competition between the antiferromagnetism and charge orders.

  10. Sex differences in spatial ability: a test of the range size hypothesis in the order Carnivora.

    Science.gov (United States)

    Perdue, Bonnie M; Snyder, Rebecca J; Zhihe, Zhang; Marr, M Jackson; Maple, Terry L

    2011-06-23

    Sex differences in spatial cognition have been reported for many species ranging from voles to humans. The range size hypothesis predicts that sex differences in spatial ability will only occur in species in which the mating system selects for differential range size. Consistent with this prediction, we observed sex differences in spatial ability in giant pandas, a promiscuous species in which males inhabit larger ranges than females, but did not observe sex differences in Asian small-clawed otters, a related monogamous species in which males and females share home ranges. These results provide the first evidence of sex differences in spatial ability in the order Carnivora, and are consistent with the range size hypothesis.

  11. Longe-Range Order in beta-Brass Studied by Neutron Diffraction

    DEFF Research Database (Denmark)

    Rathmann, Ole; Als-Nielsen, Jens Aage

    1974-01-01

    The long-range order, M(T), in β-brass has been measured by neutron diffraction from a small extinction-free crystal. The results agree with those obtained recently by x-ray diffraction. Near Tc our data are in accordance with a power law M(T)=D(1-T/Tc)β with the critical exponent β=0...

  12. Charge Ordering and Long-Range Interactions in Layered Transition Metal Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Stojkovic, B.P.; Yu, Z.G.; Bishop, A.R.; Gro/nbech-Jensen, N. [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Neto, A.H. [Department of Physics, University of California, Riverside, California 92521 (United States)

    1999-06-01

    We study the competition between long-range and short-range interactions among holes within a continuum formulation of the spin density wave picture of layered transition metal oxides. We focus on the problem of charge ordering and the charge phase diagram. The main interactions are the long-range Coulomb interaction and a magnetic dipolar short-range interaction generated by short-range antiferromagnetic fluctuations. Four different phases depending on the strength of the dipolar interaction and the density of holes exist: Wigner crystal, diagonal stripes, horizontal-vertical stripes (loops). and a glassy-clumped phase. The effect of temperature, disorder, and lattice effects on these phases are discussed. {copyright} {ital 1999} {ital The American Physical Society}

  13. Long-range order between the planets in the Solar system

    DEFF Research Database (Denmark)

    Bohr, Jakob; Olsen, Kasper

    2010-01-01

    The Solar System is investigated for positional correlations between the planets using a logarithmic distance scale. The pair correlation function for the logarithm of the semimajor axis shows a regular distribution with 5-7 consecutive peaks, and the Fourier transform hereof shows reciprocal peaks...... of first and second order. A procedure involving random permutations for the shuffling of the inter--logarithmic distances is employed to check for the significance of the presence of order of longer range than neighbor planets correlations. The use of permutations is a particular helpful analysis when...... the number of data points is small. The pair correlation function of the permutated planets lacks the sequence of equidistant peaks and its Fourier transform has no second order peak. This analysis demonstrates the existence of longer ranged correlations in the Solar System....

  14. Short-Range Correlation Models in Electronic Structure Theory

    Science.gov (United States)

    Goldey, Matthew Bryant

    Correlation methods within electronic structure theory focus on recovering the exact electron-electron interaction from the mean-field reference. For most chemical systems, including dynamic correlation, the correlation of the movement of electrons proves to be sufficient, yet exact methods for capturing dynamic correlation inherently scale polynomially with system size despite the locality of the electron cusp. This work explores a new family of methods for enhancing the locality of dynamic correlation methodologies with an aim toward improving accuracy and scalability. The introduction of range-separation into ab initio wavefunction methods produces short-range correlation methodologies, which can be supplemented with much faster approximate methods for long-range interactions. First, I examine attenuation of second-order Moller-Plesset perturbation theory (MP2) in the aug-cc-pVDZ basis. MP2 treats electron correlation at low computational cost, but suffers from basis set superposition error (BSSE) and fundamental inaccuracies in long-range contributions. The cost differential between complete basis set (CBS) and small basis MP2 restricts system sizes where BSSE can be removed. Range-separation of MP2 could yield more tractable and/or accurate forms for short- and long-range correlation. Retaining only short-range contributions proves to be effective for MP2 in the small aug-cc-pVDZ (aDZ) basis. Using one range-separation parameter within either the complementary error function (erfc) or a sum of two error functions (terfc), superior behavior is obtained versus both MP2/aDZ and MP2/CBS for inter- and intra-molecular test sets. Attenuation of the long-range helps to cancel both BSSE and intrinsic MP2 errors. Direct scaling of the MP2 correlation energy (SMP2) proves useful as well. The resulting SMP2/aDZ, MP2(erfc, aDZ), and MP2(terfc, aDZ) methods perform far better than MP2/aDZ across systems with hydrogen-bonding, dispersion, and mixed interactions at a

  15. Polariton Chimeras: Bose-Einstein Condensates with Intrinsic Chaoticity and Spontaneous Long-Range Ordering

    Science.gov (United States)

    Gavrilov, S. S.

    2018-01-01

    The system of cavity polaritons driven by a plane electromagnetic wave is found to undergo the spontaneous breaking of spatial symmetry, which results in a lifted phase locking with respect to the driving field and, consequently, in the possibility of internal ordering. In particular, periodic spin and intensity patterns arise in polariton wires; they exhibit strong long-range order and can serve as media for signal transmission. Such patterns have the properties of dynamical chimeras: they are formed spontaneously in perfectly homogeneous media and can be partially chaotic. The reported new mechanism of chimera formation requires neither time-delayed feedback loops nor nonlocal interactions.

  16. Long-range nematic order and anomalous fluctuations in suspensions of swimming filamentous bacteria

    Science.gov (United States)

    Nishiguchi, Daiki; Nagai, Ken H.; Chaté, Hugues; Sano, Masaki

    2017-02-01

    We study the collective dynamics of elongated swimmers in a very thin fluid layer by devising long filamentous nontumbling bacteria. The strong confinement induces weak nematic alignment upon collision, which, for large enough density of cells, gives rise to global nematic order. This homogeneous but fluctuating phase, observed on the largest experimentally accessible scale of millimeters, exhibits the properties predicted by standard models for flocking, such as the Vicsek-style model of polar particles with nematic alignment: true long-range nematic order and nontrivial giant number fluctuations.

  17. Efficient external memory structures for range-aggregate queries

    DEFF Research Database (Denmark)

    Agarwal, P.K.; Yang, J.; Arge, L.

    2013-01-01

    We present external memory data structures for efficiently answering range-aggregate queries. The range-aggregate problem is defined as follows: Given a set of weighted points in Rd, compute the aggregate of the weights of the points that lie inside a d-dimensional orthogonal query rectangle. The...

  18. Controlling flexible structures with second order actuator dynamics

    Science.gov (United States)

    Inman, Daniel J.; Umland, Jeffrey W.; Bellos, John

    1989-01-01

    The control of flexible structures for those systems with actuators that are modeled by second order dynamics is examined. Two modeling approaches are investigated. First a stability and performance analysis is performed using a low order finite dimensional model of the structure. Secondly, a continuum model of the flexible structure to be controlled, coupled with lumped parameter second order dynamic models of the actuators performing the control is used. This model is appropriate in the modeling of the control of a flexible panel by proof-mass actuators as well as other beam, plate and shell like structural numbers. The model is verified with experimental measurements.

  19. Local structural ordering in surface-confined liquid crystals

    Science.gov (United States)

    Śliwa, I.; Jeżewski, W.; Zakharov, A. V.

    2017-06-01

    The effect of the interplay between attractive nonlocal surface interactions and attractive pair long-range intermolecular couplings on molecular structures of liquid crystals confined in thin cells with flat solid surfaces has been studied. Extending the McMillan mean field theory to include finite systems, it has been shown that confining surfaces can induce complex orientational and translational ordering of molecules. Typically, local smectic A, nematic, and isotropic phases have been shown to coexist in certain temperature ranges, provided that confining cells are sufficiently thick, albeit finite. Due to the nonlocality of surface interactions, the spatial arrangement of these local phases can display, in general, an unexpected complexity along the surface normal direction. In particular, molecules located in the vicinity of surfaces can still be organized in smectic layers, even though nematic and/or isotropic order can simultaneously appear in the interior of cells. The resulting surface freezing of smectic layers has been confirmed to occur even for rather weak surface interactions. The surface interactions cannot, however, prevent smectic layers from melting relatively close to system boundaries, even when molecules are still arranged in layers within the central region of the system. The internal interfaces, separating individual liquid-crystal phases, are demonstrated here to form fronts of local finite-size transitions that move across cells under temperature changes. Although the complex molecular ordering in surface confined liquid-crystal systems can essentially be controlled by temperature variations, specific thermal properties of these systems, especially the nature of the local transitions, are argued to be strongly conditioned to the degree of molecular packing.

  20. Long-range magnetic order and spin-lattice coupling in delafossite CuFeO2

    Science.gov (United States)

    Eyert, Volker; Frésard, Raymond; Maignan, Antoine

    2008-08-01

    The electronic and magnetic properties of the delafossite CuFeO2 are investigated by means of electronic structure calculations. They are performed using density functional theory in the generalized gradient approximation, as well as the new full-potential augmented spherical wave method. The calculations reveal three different spin states at the iron sites. Using for the first time the experimentally determined low-temperature crystal structure, we find long-range antiferromagnetic ordering in agreement with experiment. In addition, our calculations show that nonlocal interactions as covered by the generalized gradient approximation lead to a semiconducting ground state.

  1. Extending the range and physical accuracy of coarse-grained models: Order parameter dependent interactions

    Science.gov (United States)

    Wagner, Jacob W.; Dannenhoffer-Lafage, Thomas; Jin, Jaehyeok; Voth, Gregory A.

    2017-07-01

    Order parameters (i.e., collective variables) are often used to describe the behavior of systems as they capture different features of the free energy surface. Yet, most coarse-grained (CG) models only employ two- or three-body non-bonded interactions between the CG particles. In situations where these interactions are insufficient for the CG model to reproduce the structural distributions of the underlying fine-grained (FG) model, additional interactions must be included. In this paper, we introduce an approach to expand the basis sets available in the multiscale coarse-graining (MS-CG) methodology by including order parameters. Then, we investigate the ability of an additive local order parameter (e.g., density) and an additive global order parameter (i.e., distance from a hard wall) to improve the description of CG models in interfacial systems. Specifically, we study methanol liquid-vapor coexistence, acetonitrile liquid-vapor coexistence, and acetonitrile liquid confined by hard-wall plates, all using single site CG models. We find that the use of order parameters dramatically improves the reproduction of structural properties of interfacial CG systems relative to the FG reference as compared with pairwise CG interactions alone.

  2. Charge ordering and long-range interactions in layered transitionmetal oxides: a quasiclassical continuum study

    Energy Technology Data Exchange (ETDEWEB)

    Stojkovic, Branko P.; Yu, Z.G.; Chernyshev, A.L.; Bishop, A.R.; Neto, A.H. Castro; Gronbech-Jensen, Niels

    1999-12-01

    The competition between long-range and short-range interactions among holes moving in an antiferromagnet (AF), is studied within a model derived from the spin density wave picture of layered transition metal oxides. A novel numerical approach is developed which allows one to solve the problem at finite hole densities in very large systems (of order hundreds of lattice spacings), albeit in a quasiclassical limit, and to correctly incorporate the long-range part of the Coulomb interaction. The focus is on the problem of charge ordering and the charge-phase diagram: at low temperatures four different phases are found, depending on the strength of the magnetic (dipolar) interaction generated by the spin-wave exchange, and the density of holes. The four phases are the Wigner crystal, diagonal shapes, a grid phase (horizontal-vertical stripe loops) and a glassy-clumped phase. In the presence of both in-plane and out-of-plane charged impurities the stripe ordering is suppressed, although finite stripe segments persist.At finite temperatures multiscale (intermittency) dynamics is found, reminiscent of that in glasses. The dynamics of stripe melting and its implications for experiments is discussed.

  3. Charge ordering and long-range interactions in layered transition metal oxides: A quasiclassical continuum study

    Energy Technology Data Exchange (ETDEWEB)

    Stojkovic, Branko P. [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Yu, Z. G. [Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States); Chernyshev, A. L. [Department of Physics, University of California, Riverside, California 92521 (United States); Bishop, A. R. [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Castro Neto, A. H. [Department of Physics, University of California, Riverside, California 92521 (United States); Groenbech-Jensen, Niels [Department of Applied Science, University of California, Davis, California 95616 and NERSC, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)

    2000-08-15

    The competition between long-range and short-range interactions among holes moving in an antiferromagnet (AF) is studied within a model derived from the spin-density-wave picture of layered transition metal oxides.A novel numerical approach is developed that allows one to solve the problem at finite hole densities in very large systems (of the order of hundreds of lattice spacings), albeit in a quasiclassical limit, and to correctly incorporate the long-range part of the Coulomb interaction. The focus is on the problem of charge ordering and the charge phase diagram: at low temperatures four different phases are found, depending on the strength of the magnetic (dipolar) interaction generated by the spin-wave exchange and the density of holes. The four phases are the Wigner crystal, diagonal stripes, a grid phase (horizontal-vertical stripe loops), and a glassy-clumped phase. In the presence of both in-plane and out-of-plane charged impurities the stripe ordering is suppressed, although finite stripe segments persist. At finite temperatures multiscale (intermittency) dynamics is found, reminiscent of that in glasses. The dynamics of stripe melting and its implications for experiments is discussed. (c) 2000 The American Physical Society.

  4. Chemical short range order and magnetic correction in liquid manganese–gallium zero alloy

    Energy Technology Data Exchange (ETDEWEB)

    Grosdidier, B. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France); Ben Abdellah, A. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France); Innovation and Management of Industrial Systems, Abdelmalek Essaadi University, College of Sciences and Techniques of Tangier , P.O. Box 416, Postal code 90000, Tangier (Morocco); Université Internationale de Rabat, Parc Technopolis Rabat-Shore, 11100 Sala El Jadida (Morocco); Osman, S.M., E-mail: osm@squ.edu.om [Physics Department, College of Science, Sultan Qaboos University, P.O. Box 36, Postal Code 123, Al-Khod, Muscat (Oman); Ataati, J. [Innovation and Management of Industrial Systems, Abdelmalek Essaadi University, College of Sciences and Techniques of Tangier, P.O. Box 416, Postal code 90000, Tangier (Morocco); Gasser, J.G. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France)

    2015-12-15

    The Mn{sub 66}Ga{sub 34} alloy at this particular composition is known to be zero alloy in which the linear combination of the two neutron scattering lengths weighted by the atomic compositions vanish. Thus for this specific concentration, the effect of the partial structure factors S{sub NN} and S{sub NC} is cancelled by a weighted term, which value is zero. Then the measured total structure factor S(q) gives directly the concentration–concentration structure factor S{sub CC}(q). We present here the first experimental results of neutron diffraction on the Mn{sub 66}Ga{sub 34} “null matrix alloy” at 1050 °C. The main peak of the experimental S{sub CC}(q) gives a strong evidence of a hetero-atomic chemical order in this coordinated alloy. This order also appears in real space radial distribution function which is calculated by the Fourier transform of the structure factor. The degree of hetero-coordination is discussed together with other manganese-polyvalent alloys. However manganese also shows abnormal magnetic scattering in the alloy structure factor which must be corrected. This correction gives an experimental information on the mean effective spin of manganese in this liquid alloy. We present the first critical theoretical calculations of the magnetic correction factor in Mn–Ga zero-alloy based on our accurate experimental measurements of S{sub CC}(q).

  5. Monadic Second Order Logic on Tree-like Structures

    DEFF Research Database (Denmark)

    Walukiewicz, Igor

    2002-01-01

    An operation M* which constructs from a given structure M a tree-like structure whose domain consists of the finite sequences of elements of M is considered. A notion of automata running on such tree-like structures is defined. It is shown that automata of this kind characterise expressive power...... of monadic second-order logic (MSOL) over tree-like structures. Using this characterisation it is proved that MSOL theory of a tree-like structure is effectively reducible to that of the original structure. As another application of the characterisation it is shown that MSOL on trees of arbitrary degree...

  6. Shiga toxin induces membrane reorganization and formation of long range lipid order

    DEFF Research Database (Denmark)

    Solovyeva, Vita; Johannes, Ludger; Simonsen, Adam Cohen

    2015-01-01

    microscopy. A content of 1% of glycosphingolipid globotriaosylceramide (Gb3) receptor lipids in a bilayer was used to bind the Shiga toxin B-subunit to the surface of gel domains. Binding of the Shiga toxin B-subunit to lipids led to the modulation of orientational membrane texture in gel domains and induced...... membrane reordering. When Shiga toxin was added above the lipid chain melting temperature, the toxin interaction with the membrane induced rearrangement and clustering of Gb3 lipids that resulted in the long range order and alignment of lipids in gel domains. The toxin induced redistribution of Gb3 lipids...

  7. Higher-order structure and epidemic dynamics in clustered networks.

    Science.gov (United States)

    Ritchie, Martin; Berthouze, Luc; House, Thomas; Kiss, Istvan Z

    2014-05-07

    Clustering is typically measured by the ratio of triangles to all triples regardless of whether open or closed. Generating clustered networks, and how clustering affects dynamics on networks, is reasonably well understood for certain classes of networks (Volz et al., 2011; Karrer and Newman, 2010), e.g. networks composed of lines and non-overlapping triangles. In this paper we show that it is possible to generate networks which, despite having the same degree distribution and equal clustering, exhibit different higher-order structure, specifically, overlapping triangles and other order-four (a closed network motif composed of four nodes) structures. To distinguish and quantify these additional structural features, we develop a new network metric capable of measuring order-four structure which, when used alongside traditional network metrics, allows us to more accurately describe a network׳s topology. Three network generation algorithms are considered: a modified configuration model and two rewiring algorithms. By generating homogeneous networks with equal clustering we study and quantify their structural differences, and using SIS (Susceptible-Infected-Susceptible) and SIR (Susceptible-Infected-Recovered) dynamics we investigate computationally how differences in higher-order structure impact on epidemic threshold, final epidemic or prevalence levels and time evolution of epidemics. Our results suggest that characterising and measuring higher-order network structure is needed to advance our understanding of the impact of network topology on dynamics unfolding on the networks. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  8. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    Science.gov (United States)

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-08-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50-100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.

  9. Formation and transformation of a short range ordered iron carbonate precursor

    DEFF Research Database (Denmark)

    Dideriksen, Knud; Frandsen, Cathrine; Bovet, Nicolas

    2015-01-01

    Fe(II)-carbonates, such as siderite, form in environments where O2 is scarce, e.g., during marine sediment diagenesis, corrosion and possibly CO2 sequestration, but little is known about their formation pathways. We show that early precipitates from carbonate solutions containing 0.1M Fe...... formed. Its coherent scattering domains determined from PDF analysis are slightly larger than for amorphous calcium carbonate, suggesting that the precursor could be nanocrystalline. Replica exchange molecular dynamics simulations of Fe-carbonate polynuclear complexes yield PDF peak positions that agree...... structural order. Moreover, PDF peak positions differ from those for known iron carbonates and hydroxides. Mössbauer spectra also deviate from those expected for known iron carbonates and suggest a less crystalline structure. These data show that a previously unidentified iron carbonate precursor phase...

  10. Short-range second order screened exchange correction to RPA correlation energies

    Science.gov (United States)

    Beuerle, Matthias; Ochsenfeld, Christian

    2017-11-01

    Direct random phase approximation (RPA) correlation energies have become increasingly popular as a post-Kohn-Sham correction, due to significant improvements over DFT calculations for properties such as long-range dispersion effects, which are problematic in conventional density functional theory. On the other hand, RPA still has various weaknesses, such as unsatisfactory results for non-isogyric processes. This can in parts be attributed to the self-correlation present in RPA correlation energies, leading to significant self-interaction errors. Therefore a variety of schemes have been devised to include exchange in the calculation of RPA correlation energies in order to correct this shortcoming. One of the most popular RPA plus exchange schemes is the second order screened exchange (SOSEX) correction. RPA + SOSEX delivers more accurate absolute correlation energies and also improves upon RPA for non-isogyric processes. On the other hand, RPA + SOSEX barrier heights are worse than those obtained from plain RPA calculations. To combine the benefits of RPA correlation energies and the SOSEX correction, we introduce a short-range RPA + SOSEX correction. Proof of concept calculations and benchmarks showing the advantages of our method are presented.

  11. Tensor Spectral Clustering for Partitioning Higher-order Network Structures.

    Science.gov (United States)

    Benson, Austin R; Gleich, David F; Leskovec, Jure

    2015-01-01

    Spectral graph theory-based methods represent an important class of tools for studying the structure of networks. Spectral methods are based on a first-order Markov chain derived from a random walk on the graph and thus they cannot take advantage of important higher-order network substructures such as triangles, cycles, and feed-forward loops. Here we propose a Tensor Spectral Clustering (TSC) algorithm that allows for modeling higher-order network structures in a graph partitioning framework. Our TSC algorithm allows the user to specify which higher-order network structures (cycles, feed-forward loops, etc.) should be preserved by the network clustering. Higher-order network structures of interest are represented using a tensor, which we then partition by developing a multilinear spectral method. Our framework can be applied to discovering layered flows in networks as well as graph anomaly detection, which we illustrate on synthetic networks. In directed networks, a higher-order structure of particular interest is the directed 3-cycle, which captures feedback loops in networks. We demonstrate that our TSC algorithm produces large partitions that cut fewer directed 3-cycles than standard spectral clustering algorithms.

  12. The encoding complexity of two dimensional range minimum data structures

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Brodnik, Andrej; Davoodi, Pooya

    2013-01-01

    of the encoding variant of the problem where queries have access to the constructed data structure but can not access the input matrix A, i.e. all information must be encoded in the data structure. Previously it was known how to solve the problem with space O(mn min {m,logn}) bits (and with constant query time......In the two-dimensional range minimum query problem an input matrix A of dimension m ×n, m ≤ n, has to be preprocessed into a data structure such that given a query rectangle within the matrix, the position of a minimum element within the query range can be reported. We consider the space complexity...

  13. Diverse Structure Synchronization of Fractional Order Hyper-Chaotic Systems

    Science.gov (United States)

    Wang, Xing-Yuan; Zhao, Guo-Bin; Yang, Yu-Hong

    2013-04-01

    This paper studied the dynamic behavior of the fractional order hyper-chaotic Lorenz system and the fractional order hyper-chaotic Rössler system, then numerical analysis of the different fractional orders hyper-chaotic systems are carried out under the predictor-corrector method. We proved the two systems are in hyper-chaos when the maximum and the second largest Lyapunov exponential are calculated. Also the smallest orders of the systems are proved when they are in hyper-chaos. The diverse structure synchronization of the fractional order hyper-chaotic Lorenz system and the fractional order hyper-chaotic Rössler system is realized using active control method. Numerical simulations indicated that the scheme was always effective and efficient.

  14. Near-Optimal Range Reporting Structures for Categorical

    DEFF Research Database (Denmark)

    Larsen, Kasper Green; Walderveen, Freek van

    2013-01-01

    Range reporting on categorical (or colored) data is a well-studied generalization of the classical range reporting problem in which each of the N input points has an associated color (category). A query then asks to report the set of colors of the points in a given rectangular query range, which...... may be far smaller than the set of all points in the query range. We study two-dimensional categorical range reporting in both the word-RAM and I/O-model. For the I/O-model, we present two alternative data structures for three-sided queries. The first answers queries in optimal O(lgB N + K/B) I....../Os using O(N lg*N) space, where K is the number of distinct colors in the output, B is the disk block size, and lg*N is the iterated logarithm of N. Our second data structure uses linear space and answers queries in O(lg B N + lg(h) N + K/B) I/Os for any constant integer h ≥ 1. Here lg(1) N = lg N and lg...

  15. The interplay of long-range magnetic order and single-ion anisotropy in rare earth nickel germanides

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Z.

    1999-05-10

    This dissertation is concerned with the interplay of long-range order and anisotropy in the tetragonal RNi{sub 2}Ge{sub 2} (R = rare earth) family of compounds. Microscopic magnetic structures were studied using both neutron and x-ray resonant exchange scattering (XRES) techniques. The magnetic structures of Tb, Dy, Eu and Gd members have been determined using high-quality single-crystal samples. This work has correlated a strong Fermi surface nesting to the magnetic ordering in the RNi{sub 2}Ge{sub 2} compounds. Generalized susceptibility, {chi}{sub 0}(q), calculations found nesting to be responsible for both incommensurate ordering wave vector in GdNi{sub 2}Ge{sub 2}, and the commensurate structure in EuNi{sub 2}Ge{sub 2}. A continuous transition from incommensurate to commensurate magnetic structures via band filling is predicted. The surprisingly higher T{sub N} in EuNi{sub 2}Ge{sub 2} than that in GdNi{sub 2}Ge{sub 2} is also explained. Next, all the metamagnetic phases in TbNi{sub 2}Ge{sub 2} with an applied field along the c axis have been characterized with neutron diffraction measurements. A mixed phase model for the first metamagnetic structure consisting of fully-saturated as well as reduced-moment Tb ions is presented. The moment reduction may be due to moment instability which is possible if the exchange is comparable to the low-lying CEF level splitting and the ground state is a singlet. In such a case, certain Tb sites may experience a local field below the critical value needed to reach saturation.

  16. Predicting Short-Range Order in Multicomponent Alloys from an Improved Mean-Field Theory

    Science.gov (United States)

    Ong, Zhun-Yong; Johnson, Duane

    2007-03-01

    In alloys the atomic short-range order (SRO) indicates the nascent ordering to which the disordered alloy is tending at high temperatures. Direct first-principles prediction based upon KKR-CPA and mean-field thermodynamics have been successful in predicting system-specific SRO [1], if, at a minimum, corrections are included to satisfy the diffuse scattering sum rule in k-space. However, such models do not account for k-dependence of the corrections. Here, we present an analytic generalization to multicomponent alloys that includes ``cyclic diagrams'' [2,3] for composition, temperature, and k-dependent corrections to SRO. We first explore the improvement to SRO in model fcc ternary alloys via the generalized Ising model. We find that there is much better agreement to Monte Carlo simulations than with standard Bragg-Williams with(out) Onsager corrections. Then we implement this within the KKR-CPA linear-response theory of SRO.Work was supported by DOE (Award DEFG02-03ER46026 and NSF (DMR-0325939). [1] J.B. Staunton, D.D. Johnson, and F.J. Pinski, Phys. Rev. Lett. 65, 1259 (1990); Phys. Rev. B 50, 1450 (1994); ibid, 57, 15177 (1998). [2] R. Brout, Phys. Rev. 115, 824-835 (1959). [3] R.V. Chepulski, et al, Phys. Rev. 65, 064201-7 (2002).

  17. Transversely isotropic higher-order averaged structure tensors

    Science.gov (United States)

    Hashlamoun, Kotaybah; Federico, Salvatore

    2017-08-01

    For composites or biological tissues reinforced by statistically oriented fibres, a probability distribution function is often used to describe the orientation of the fibres. The overall effect of the fibres on the material response is accounted for by evaluating averaging integrals over all possible directions in space. The directional average of the structure tensor (tensor product of the unit vector describing the fibre direction by itself) is of high significance. Higher-order averaged structure tensors feature in several models and carry similarly important information. However, their evaluation has a quite high computational cost. This work proposes to introduce mathematical techniques to minimise the computational cost associated with the evaluation of higher-order averaged structure tensors, for the case of a transversely isotropic probability distribution of orientation. A component expression is first introduced, using which a general tensor expression is obtained, in terms of an orthonormal basis in which one of the vectors coincides with the axis of symmetry of transverse isotropy. Then, a higher-order transversely isotropic averaged structure tensor is written in an appropriate basis, constructed starting from the basis of the space of second-order transversely isotropic tensors, which is constituted by the structure tensor and its complement to the identity.

  18. First and second order convex approximation strategies in structural optimization

    Science.gov (United States)

    Fleury, C.

    1989-01-01

    In this paper, various methods based on convex approximation schemes are discussed that have demonstrated strong potential for efficient solution of structural optimization problems. First, the convex linearization method (Conlin) is briefly described, as well as one of its recent generalizations, the method of moving asymptotes (MMA). Both Conlin and MMA can be interpreted as first-order convex approximation methods that attempt to estimate the curvature of the problem functions on the basis of semiempirical rules. Attention is next directed toward methods that use diagonal second derivatives in order to provide a sound basis for building up high-quality explicit approximations of the behavior constraints. In particular, it is shown how second-order information can be effectively used without demanding a prohibitive computational cost. Various first-order and second-order approaches are compared by applying them to simple problems that have a closed form solution.

  19. Order parameter and density of states in superconducting structures

    Energy Technology Data Exchange (ETDEWEB)

    Stojkovic, B.P. (Center for the Science and Application of Superconductivity, School of Physics and Astronomy, Univ. of Minnesota, Minneapolis, MN (United States)); Valls, O.T. (Center for the Science and Application of Superconductivity, School of Physics and Astronomy, Univ. of Minnesota, Minneapolis, MN (United States))

    1994-02-01

    We study superconducting films and layered superconducting-normal metal structures using a purely microscopic, Gor'kov equations based method. We emphasize the case where the coherence length is short. We obtain self-consistent results for the order parameter and the density of states as a function of temperature and geometry. (orig.)

  20. Reduction of Second-Order Network Systems with Structure Preservation

    NARCIS (Netherlands)

    Cheng, Xiaodong; Kawano, Yu; Scherpen, Jacquelien M.A.

    2017-01-01

    This paper proposes a general framework for structure-preserving model reduction of a second-order network system based on graph clustering. In this approach, vertex dynamics are captured by the transfer functions from inputs to individual states, and the dissimilarities of vertices are quantified

  1. First order magneto-structural transition in functional magnetic ...

    Indian Academy of Sciences (India)

    First order magneto-structural transition plays an important role in the functionality of various magnetic materials of current interest like manganese oxide systems showing colossal magnetoresistance, Gd5(Ge, Si)4 alloys showing giant magnetocaloric effects and magnetic shape memory alloys. The key features of this ...

  2. Robust stability of fractional order polynomials with complicated uncertainty structure

    Science.gov (United States)

    Şenol, Bilal; Pekař, Libor

    2017-01-01

    The main aim of this article is to present a graphical approach to robust stability analysis for families of fractional order (quasi-)polynomials with complicated uncertainty structure. More specifically, the work emphasizes the multilinear, polynomial and general structures of uncertainty and, moreover, the retarded quasi-polynomials with parametric uncertainty are studied. Since the families with these complex uncertainty structures suffer from the lack of analytical tools, their robust stability is investigated by numerical calculation and depiction of the value sets and subsequent application of the zero exclusion condition. PMID:28662173

  3. Structural architecture of the central Brooks Range foothills, Alaska

    Science.gov (United States)

    Moore, Thomas E.; Potter, Christopher J.; O'Sullivan, Paul B.

    2002-01-01

    Five structural levels underlie the Brooks Range foothills, from lowest to highest: (1) autochthon, at a depth of ~9 km; (2) Endicott Mountains allochthon (EMA), thickest under the northern Brooks Range (>15 km) and wedging out northward above the autochthon; (3) higher allochthons (HA), with a composite thickness of 1.5+ km, wedging out northward at or beyond the termination of EMA; (4) Aptian-Albian Fortress Mountain Formation (FM), deposited unconformably on deformed EMA and HA and thickening northward into a >7-km-thick succession of deformed turbidites (Torok Formation); (5) gently folded Albian-Cenomanian deltaic deposits (Nanushuk Group). The dominant faulting pattern in levels 2-3 is thin-skinned thrusting and thrust-related folds formed before deposition of Cretaceous strata. These structures are cut by younger steeply south-dipping reverse faults that truncate and juxtapose structural levels 1-4 and expose progressively deeper structural levels to the south. Structural levels 4-5 are juxtaposed along a north-dipping zone of south-vergent folds and thrusts. Stratigraphic and fission-track age data suggest a kinematic model wherein the foothills belt was formed first, by thrusting of HA and EMA as deformational wedges onto the regionally south-dipping authochon at 140-120Ma. After deposition of FM and Torok during mid-Cretaceous hinterland extension and uplift, a second episode of contractional deformation at 60 Ma shortened the older allochthonous deformational wedges (EMA, HA) and overlying strata on north-vergent reverse faults. To the north, where the allochthons wedge out, shortening caused duplexing in the Torok and development of a triangle zone south of the Tuktu escarpment.

  4. Data Structures: Sequence Problems, Range Queries, and Fault Tolerance

    DEFF Research Database (Denmark)

    Jørgensen, Allan Grønlund

    The focus of this dissertation is on algorithms, in particular data structures that give provably ecient solutions for sequence analysis problems, range queries, and fault tolerant computing. The work presented in this dissertation is divided into three parts. In Part I we consider algorithms for...... to assume that the algorithms themselves are in charge for dealing with memory faults. We investigate searching, sorting and counting algorithms and data structures that provably returns sensible information in spite of memory corruptions.......The focus of this dissertation is on algorithms, in particular data structures that give provably ecient solutions for sequence analysis problems, range queries, and fault tolerant computing. The work presented in this dissertation is divided into three parts. In Part I we consider algorithms...... by the constraints. Many variants and similar problems have been proposed leading to several dierent approaches and algorithms. We consider problems where the function is the sum of the elements in the sequence and the constraints only bound the length of the subsequences considered. We give optimal algorithms...

  5. On Space Efficient Two Dimensional Range Minimum Data Structures

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Davoodi, Pooya; Rao, S. Srinivasa

    2012-01-01

    The two dimensional range minimum query problem is to preprocess a static m by n matrix (two dimensional array) A of size N=m⋅n, such that subsequent queries, asking for the position of the minimum element in a rectangular range within A, can be answered efficiently. We study the trade-off betwee...... structure of optimal size O(N) bits. For the case where queries can not probe A, we give a data structure of size O(N⋅min {m,log n}) bits with O(1) query time, assuming m≤n. This leaves a gap to the space lower bound of Ω(Nlog m) bits for this version of the problem...... the space and query time of the problem. We show that every algorithm enabled to access A during the query and using a data structure of size O(N/c) bits requires Ω(c) query time, for any c where 1≤c≤N. This lower bound holds for arrays of any dimension. In particular, for the one dimensional version...

  6. Dynamic magnetic susceptibility of systems with long-range magnetic order

    Energy Technology Data Exchange (ETDEWEB)

    Vannette, Matthew Dano [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    The utility of the TDR as an instrument in the study of magnetically ordered materials has been expanded beyond the simple demonstration purposes. Results of static applied magnetic field dependent measurements of the dynamic magnetic susceptibility, χ, of various ferromagnetic (FM) and antiferromagnetic (AFM) materials showing a range of transition temperatures (1-800 K) are presented. Data was collected primarily with a tunnel diode resonator (TDR) at different radio-frequencies (~10-30 MHz). In the vicinity of TC local moment ferromagnets show a very sharp, narrow peak in χ which is suppressed in amplitude and shifted to higher temperatures as the static bias field is increased. Unexpectedly, critical scaling analysis fails for these data. It is seen that these data are frequency dependent, however there is no simple method whereby measurement frequency can be changed in a controllable fashion. In contrast, itinerant ferromagnets show a broad maximum in χ well below TC which is suppressed and shifts to lower temperatures as the dc bias field is increased. The data on itinerant ferromagnets is fitted to a semi-phenomenological model that suggests the sample response is dominated by the uncompensated minority spins in the conduction band. Concluding remarks suggest possible scenarios to achieve frequency resolved data using the TDR as well as other fields in which the apparatus may be exploited.

  7. Recent studies of short-range order in alloys: The Cowley theory revisited

    Energy Technology Data Exchange (ETDEWEB)

    Reinhard, L. [Lawrence Livermore National Lab., CA (United States); Moss, S.C. [Houston Univ., TX (United States). Dept. of Physics

    1993-02-08

    We present comparisons of various statistical theories for effective pair interactions (EPI) in alloys. We then evaluate these EPI`s using the Cowley theory, the Krivoglaz-Clapp-Moss (KCM) approximation, the {gamma}-expansion method (GEM) of Tokar, Masanskii and coworkers, and the exact inverse Monte Carlo (IMC) method, introduced by Gerold and Kern. Via a series of model calculations on a hypothetical bcc alloy with a single nearest-neighbor interaction we show that the Cowley theory is successful in evaluating the EPI`s in more dilute alloys but tends to overestimate the magnitude of the nearest neighbor energy at higher concentrations, whereas the KCM expression becomes increasingly inaccurate at lower concentrations. In general, however, the approximate mean field theories are most accurate at higher concentrations and higher temperatures. Recent studies of short-range order in single crystals are discussed in which these EPI`s have been evaluated using the IMC, KCM, GEM and Cowley theories. Examples include the bcc alloy Fe{sub 0.53}Cr{sub 0.47} and the fcc alloys Cu{sub 3} Au, CU{sub 0.69}Zn{sub 0.31} and Ni{sub 0.89}BgCr{sub 0.11}. In all cases the approximate expressions do quite well, especially the GEM.

  8. Proof of long range order in 4-d SU(N) lattice gauge theory

    CERN Document Server

    Grady, Michael

    2013-01-01

    An extended version of 4-d SU(2) lattice gauge theory is considered in which different inverse coupling parameters are used, $\\beta_H=4/g_{H}^2$ for plaquettes which are purely spacelike, and $\\beta_V$ for those which involve the Euclidean timelike direction. It is shown that when $\\beta_H = \\infty$ the partition function becomes, in the Coulomb Gauge, exactly that of a set of non-interacting 3-d O(4) classical Heisenberg models. Long range order at low temperatures (weak coupling) has been rigorously proven for this model. It is shown that the correlation function demonstrating spontaneous magnetization in the ferromagnetic phase is a continuous function of $g_H$ at $g_H =0$ and therefore that the spontaneously broken phase enters the ($\\beta_H$, $\\beta_V$) phase plane (no step discontinuity at the edge). Once the phase transition line has entered, it can only exit at another identified edge, which requires the SU(2) gauge theory within also to have a phase transition at finite $\\beta$. A phase exhibiting sp...

  9. Electronic structure of ordered and disordered Fe sub 3 Pt

    CERN Document Server

    Major, Z; Jarlborg, T; Bruno, E; Ginatempo, B; Staunton, J B; Poulter, J

    2003-01-01

    The electronic structure of invar alloys (i.e. materials in which the near absence of thermal expansion is observed) has been the focus of much study, owing both to the technological applications of these materials and interest in the fundamental mechanism that is responsible for the effect. Here, calculations of the magnetic Compton profiles are presented for ordered and disordered Fe sub 3 Pt alloys. Using linear muffin-tin orbital and KKR methods, the latter incorporating the coherent potential approximation to describe the substitutional disorder, the electronic band structure and measurable quantities such as the Fermi surface topology are presented.

  10. Out-of-order event processing in kinetic data structures

    DEFF Research Database (Denmark)

    Abam, Mohammad; de Berg, Mark; Agrawal, Pankaj

    2011-01-01

    We study the problem of designing kinetic data structures (KDS’s for short) when event times cannot be computed exactly and events may be processed in a wrong order. In traditional KDS’s this can lead to major inconsistencies from which the KDS cannot recover. We present more robust KDS......’s for the maintenance of several fundamental structures such as kinetic sorting and kinetic tournament trees, which overcome the difficulty by employing a refined event scheduling and processing technique. We prove that the new event scheduling mechanism leads to a KDS that is correct except for finitely many short...

  11. A ring graph method for approximating atomic short-range order in disordered multi-component systems

    Science.gov (United States)

    Ong, Zhun-Yong

    2007-03-01

    The atomic short-range order (ASRO) in an alloy provides valuable information on the atomic structure to which the disordered alloy is tending. Mean field models with Onsager corrections have been used to calculate the ASRO in lattice models of disordered multi-component alloys. The Onsager correction is composition and temperature dependent and corrects for the over-correlation inherent to mean-field methods so that ASRO calculated satisfies the sum rule. However, it is does not take into account the k-dependence of the corrections. We present an analytical method based on ring graphs which provides for a k-dependent correction to the mean field. The ASRO in a simple ternary Ising model in a FCC lattice with nearest neighbor interactions is calculated using our method and compared to the results obtained from a Monte Carlo simulation. We find that, above the transition temperature, the analytical results are in good agreement with those obtained from simulations.

  12. Short-range order in ab initio computer generated amorphous and liquid Cu–Zr alloys: A new approach

    Energy Technology Data Exchange (ETDEWEB)

    Galván-Colín, Jonathan, E-mail: jgcolin@ciencias.unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México, D.F. 04510, México (Mexico); Valladares, Ariel A., E-mail: valladar@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México, D.F. 04510, México (Mexico); Valladares, Renela M.; Valladares, Alexander [Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-542, México, D.F. 04510, México (Mexico)

    2015-10-15

    Using ab initio molecular dynamics and a new approach based on the undermelt-quench method we generated amorphous and liquid samples of Cu{sub x}Zr{sub 100−x} (x=64, 50, 36) alloys. We characterized the topology of our resulting structures by means of the pair distribution function and the bond-angle distribution; a coordination number distribution was also calculated. Our results for both amorphous and liquids agree well with experiment. Dependence of short-range order with the concentration is reported. We found that icosahedron-like geometry plays a major role whenever the alloys are Cu-rich or Zr-rich disregarding if the samples are amorphous or liquid. The validation of these results, in turn would let us calculate other properties so far disregarded in the literature.

  13. Short-range order in ab initio computer generated amorphous and liquid Cu-Zr alloys: A new approach

    Science.gov (United States)

    Galván-Colín, Jonathan; Valladares, Ariel A.; Valladares, Renela M.; Valladares, Alexander

    2015-10-01

    Using ab initio molecular dynamics and a new approach based on the undermelt-quench method we generated amorphous and liquid samples of CuxZr100-x (x=64, 50, 36) alloys. We characterized the topology of our resulting structures by means of the pair distribution function and the bond-angle distribution; a coordination number distribution was also calculated. Our results for both amorphous and liquids agree well with experiment. Dependence of short-range order with the concentration is reported. We found that icosahedron-like geometry plays a major role whenever the alloys are Cu-rich or Zr-rich disregarding if the samples are amorphous or liquid. The validation of these results, in turn would let us calculate other properties so far disregarded in the literature.

  14. Sex differences in spatial ability: a test of the range size hypothesis in the order Carnivora

    OpenAIRE

    Perdue, Bonnie M.; Snyder, Rebecca J.; Zhihe, Zhang; Marr, M. Jackson; Maple, Terry L

    2011-01-01

    Sex differences in spatial cognition have been reported for many species ranging from voles to humans. The range size hypothesis predicts that sex differences in spatial ability will only occur in species in which the mating system selects for differential range size. Consistent with this prediction, we observed sex differences in spatial ability in giant pandas, a promiscuous species in which males inhabit larger ranges than females, but did not observe sex differences in Asian small-clawed ...

  15. Filtering of higher-order laser modes using plasma structures

    Science.gov (United States)

    Djordjevic, Blagoje; Benedetti, Carlo; Schroeder, Carl; Esarey, Eric; Leemans, Wim

    2017-10-01

    Plasma structures based on leaky channels are proposed to filter higher-order laser mode content. The evolution and propagation of non-Gaussian laser pulses in leaky channels is studied, and it is shown that, for appropriate laser-plasma parameters, the higher-order laser mode content may be removed while the fundamental mode remains well-guided. The behavior of the multi-mode laser pulse is described analytically, including the derivation of the leakage coefficients, and compared to numerical calculations. Gaussian laser pulse propagation, without higher-order mode content, improves guiding in parabolic plasma channels, enabling extended interaction lengths for laser-plasma accelerator applications. This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  16. Analysis of long-range wakefields in CLIC main Linac Accelerating Structures with Damping Loads

    CERN Document Server

    De Michele, G

    2012-01-01

    The baseline design of the CLIC accelerating structure foresees a moderate detuning and heavy damping of high order modes (HOMs), which are the source of long-range transverse wakefields. Such unwanted fields produce bunch-to-bunch instabilities so the HOMs must be suppressed. In order to damp these modes, the CLIC RF structure is equipped with lossy material inserted into four rectangular waveguides coupled to each accelerating cell. The lossy material absorbs EM (electromagnetic) wave energy with little reflection back to the accelerating cells. In the past, computations of the long-range wake of CLIC accelerating modes have been done using perfectly absorbing boundaries to terminate the damping waveguides. In this paper, 3D EM simulations of CLIC baseline accelerating structure with HOMs damping loads will be presented. A comparison between different EM codes (GdfidL, CST PARTICLE STUDIO®) will be discussed as well as the analysis of different types of absorbing materials with respect to the wakefields da...

  17. Short Range-Ordered Minerals: Insight into Aqueous Alteration Processes on Mars

    Science.gov (United States)

    Ming, D. W.; Morris, R. V.; Golden, D. C.

    2011-12-01

    Short range-ordered (SRO) aluminosilicates (e.g., allophane) and nanophase ferric oxides (npOx) are common SRO minerals derived during aqueous alteration of basaltic materials. NpOx refers to poorly crystalline or amorphous alteration products that can be any combination of superparamagnetic hematite and/or goethite, akaganeite, schwertmannite, ferrihydrite, iddingsite, and nanometer-sized ferric oxide particles that pigment palagonitic tephra. Nearly 30 years ago, SRO phases were suggested as alteration phases on Mars based on similar spectral properties for altered basaltic tephra on the slopes of Mauna Kea in Hawaii and Martian bright regions measured by Earth-based telescopes. Detailed characterization of altered basaltic tephra on Mauna Kea have identified a variety of alteration phases including allophane, npOx, hisingerite, jarosite, alunite, hematite, goethite, ferrihydrite, halloysite, kaolinite, smectite, and zeolites. The presence of npOx and other Fe-bearing minerals (jarosite, hematite, goethite) was confirmed by the Mössbauer Spectrometer onboard the Mars Exploration Rovers. Although the presence of allophane has not been definitely identified on Mars robotic missions, chemical analysis by the Spirit and Opportunity rovers and thermal infrared spectral orbital measurements suggest the presence of allophane or allophane-like phases on Mars. SRO phases form under a variety of environmental conditions on Earth ranging from cold and arid to warm and humid, including hydrothermal conditions. The formation of SRO aluminosilicates such as allophane (and crystalline halloysite) from basaltic material is controlled by several key factors including activity of water, extent of leaching, Si activity in solution, and available Al. Generally, a low leaching index (e.g., wet-dry cycles) and slightly acidic to alkaline conditions are necessary. NpOx generally form under aqueous oxidative weathering conditions, although thermal oxidative alteration may occasional be

  18. Short Range-Ordered Minerals: Insight into Aqueous Alteration Processes on Mars

    Science.gov (United States)

    Ming, Douglas W.; Morris, R. V.; Golden, D. C.

    2011-01-01

    Short range-ordered (SRO) aluminosilicates (e.g., allophane) and nanophase ferric oxides (npOx) are common SRO minerals derived during aqueous alteration of basaltic materials. NpOx refers to poorly crystalline or amorphous alteration products that can be any combination of superparamagnetic hematite and/or goethite, akaganeite, schwertmannite, ferrihydrite, iddingsite, and nanometer-sized ferric oxide particles that pigment palagonitic tephra. Nearly 30 years ago, SRO phases were suggested as alteration phases on Mars based on similar spectral properties for altered basaltic tephra on the slopes of Mauna Kea in Hawaii and Martian bright regions measured by Earth-based telescopes. Detailed characterization of altered basaltic tephra on Mauna Kea have identified a variety of alteration phases including allophane, npOx, hisingerite, jarosite, alunite, hematite, goethite, ferrihydrite, halloysite, kaolinite, smectite, and zeolites. The presence of npOx and other Fe-bearing minerals (jarosite, hematite, goethite) was confirmed by the M ssbauer Spectrometer onboard the Mars Exploration Rovers. Although the presence of allophane has not been definitely identified on Mars robotic missions, chemical analysis by the Spirit and Opportunity rovers and thermal infrared spectral orbital measurements suggest the presence of allophane or allophane-like phases on Mars. SRO phases form under a variety of environmental conditions on Earth ranging from cold and arid to warm and humid, including hydrothermal conditions. The formation of SRO aluminosilicates such as allophane (and crystalline halloysite) from basaltic material is controlled by several key factors including activity of water, extent of leaching, Si activity in solution, and available Al. Generally, a low leaching index (e.g., wet-dry cycles) and slightly acidic to alkaline conditions are necessary. NpOx generally form under aqueous oxidative weathering conditions, although thermal oxidative alteration may occasional be

  19. Neutron scattering studies on chromatin higher-order structure

    Energy Technology Data Exchange (ETDEWEB)

    Graziano, V.; Gerchman, S.E.; Schneider, D.K.; Ramakrishnan, V. [Brookhaven National Laboratory, Upton, NY (United States)

    1994-12-31

    We have been engaged in studies of the structure and condensation of chromatin into the 30nm filament using small-angle neutron scattering. We have also used deuterated histone H1 to determine its location in the chromatin 30nm filament. Our studies indicate that chromatin condenses with increasing ionic strength to a limiting structure that has a mass per unit length of 6-7 nucleosomes/11 nm. They also show that the linker histone H1/H5 is located in the interior of the chromatin filament, in a position compatible with its binding to the inner face of the nucleosome. Analysis of the mass per unit length as a function of H5 stoichiometry suggests that 5-7 contiguous nucleosomes need to have H5 bound before a stable higher order structure can exist.

  20. Scaling Properties of the D-Short Range Order in PdDx for Higher D Concentrations

    DEFF Research Database (Denmark)

    Krexner, G.; Ernst, G; Fratzl, P.

    1984-01-01

    New measurements of D-short range order (SRO) in PdDx and Pd1−yAgyDx−y are presented. A scaling behaviour of the complicated SRO- features with temperature and electronic concentration is proposed and discussed with respect to the Clapp-Moss-de Fontaine theory of ordering.......New measurements of D-short range order (SRO) in PdDx and Pd1−yAgyDx−y are presented. A scaling behaviour of the complicated SRO- features with temperature and electronic concentration is proposed and discussed with respect to the Clapp-Moss-de Fontaine theory of ordering....

  1. On Space Efficient Two Dimensional Range Minimum Data Structures

    DEFF Research Database (Denmark)

    Davoodi, Pooya; Brodal, Gerth Stølting; Rao, S. Srinivasa

    2010-01-01

    The two dimensional range minimum query problem is to preprocess a static two dimensional m by n array A of size N = m · n, such that subsequent queries, asking for the position of the minimum element in a rectangular range within A, can be answered efficiently. We study the trade-off between the...... optimal O(N) bits additional space. For the case where queries can not probe A, we give a data structure of size O(N· min {m,logn}) bits with O(1) query time, assuming m ≤ n. This leaves a gap to the lower bound of Ω(Nlogm) bits for this version of the problem....... the space and query time of the problem. We show that every algorithm enabled to access A during the query and using O(N/c) bits additional space requires Ω(c) query time, for any c where 1 ≤ c ≤ N. This lower bound holds for any dimension. In particular, for the one dimensional version of the problem......, the lower bound is tight up to a constant factor. In two dimensions, we complement the lower bound with an indexing data structure of size O(N/c) bits additional space which can be preprocessed in O(N) time and achieves O(clog2 c) query time. For c = O(1), this is the first O(1) query time algorithm using...

  2. Reduced order modeling of fluid/structure interaction.

    Energy Technology Data Exchange (ETDEWEB)

    Barone, Matthew Franklin; Kalashnikova, Irina; Segalman, Daniel Joseph; Brake, Matthew Robert

    2009-11-01

    This report describes work performed from October 2007 through September 2009 under the Sandia Laboratory Directed Research and Development project titled 'Reduced Order Modeling of Fluid/Structure Interaction.' This project addresses fundamental aspects of techniques for construction of predictive Reduced Order Models (ROMs). A ROM is defined as a model, derived from a sequence of high-fidelity simulations, that preserves the essential physics and predictive capability of the original simulations but at a much lower computational cost. Techniques are developed for construction of provably stable linear Galerkin projection ROMs for compressible fluid flow, including a method for enforcing boundary conditions that preserves numerical stability. A convergence proof and error estimates are given for this class of ROM, and the method is demonstrated on a series of model problems. A reduced order method, based on the method of quadratic components, for solving the von Karman nonlinear plate equations is developed and tested. This method is applied to the problem of nonlinear limit cycle oscillations encountered when the plate interacts with an adjacent supersonic flow. A stability-preserving method for coupling the linear fluid ROM with the structural dynamics model for the elastic plate is constructed and tested. Methods for constructing efficient ROMs for nonlinear fluid equations are developed and tested on a one-dimensional convection-diffusion-reaction equation. These methods are combined with a symmetrization approach to construct a ROM technique for application to the compressible Navier-Stokes equations.

  3. Modification of modulated plasma plumes for the quasi-phase-matching of high-order harmonics in different spectral ranges

    Energy Technology Data Exchange (ETDEWEB)

    Ganeev, R. A., E-mail: rashid-ganeev@mail.ru [Institute of Ion-Plasma and Laser Technologies, 33 Dormon Yoli Street, Tashkent 100125 (Uzbekistan); Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495 (Japan); Boltaev, G. S.; Sobirov, B.; Reyimbaev, S.; Sherniyozov, H.; Usmanov, T. [Institute of Ion-Plasma and Laser Technologies, 33 Dormon Yoli Street, Tashkent 100125 (Uzbekistan); Suzuki, M.; Yoneya, S.; Kuroda, H. [Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495 (Japan)

    2015-01-15

    We demonstrate the technique allowing the fine tuning of the distance between the laser-produced plasma plumes on the surfaces of different materials, as well as the variation of the sizes of these plumes. The modification of plasma formations is based on the tilting of the multi-slit mask placed between the heating laser beam and target surface, as well as the positioning of this mask in the telescope placed on the path of heating radiation. The modulated plasma plumes with the sizes of single plume ranging between 0.1 and 1 mm were produced on the manganese and silver targets. Modification of the geometrical parameters of plasma plumes proved to be useful for the fine tuning of the quasi-phase-matched high-order harmonics generated in such structures during propagation of the ultrashort laser pulses. We show the enhancement of some groups of harmonics along the plateau range and the tuning of maximally enhanced harmonic by variable modulation of the plasma.

  4. Rational synthesis of organic thin films with exceptional long-range structural integrity

    Science.gov (United States)

    Seiki, Noriya; Shoji, Yoshiaki; Kajitani, Takashi; Ishiwari, Fumitaka; Kosaka, Atsuko; Hikima, Takaaki; Takata, Masaki; Someya, Takao; Fukushima, Takanori

    2015-06-01

    Highly oriented, domain-boundary-free organic thin films could find use in various high-performance organic materials and devices. However, even with state-of-the-art supramolecular chemistry, it is difficult to construct organic thin films with structural integrity in a size regime beyond the micrometer length scale. We show that a space-filling design, relying on the two-dimensional (2D) nested hexagonal packing of a particular type of triptycene, enables the formation of large-area molecular films with long-range 2D structural integrity up to the centimeter length scale by vacuum evaporation, spin-coating, and cooling from the isotropic liquid of the triptycene. X-ray diffraction analysis and microscopic observations reveal that triptycene molecules form a completely oriented 2D (hexagonal triptycene array) + 1D (layer stacking) structure, which is key for the long-range propagation of structural order.

  5. Higher-order Brunnian structures and possible physical realizations

    DEFF Research Database (Denmark)

    A. Baas, Nils; V. Fedorov, D.; S. Jensen, A.

    2014-01-01

    We consider few-body bound state systems and provide precise definitions of Borromean and Brunnian systems. The initial concepts are more than a hundred years old and originated in mathematical knot-theory as purely geometric considerations. About thirty years ago they were generalized and applied...... to the binding of systems in nature. It now appears that recent generalization to higher order Brunnian structures may potentially be realized as laboratory made or naturally occurring systems. With the binding energy as measure, we discuss possibilities of physical realization in nuclei, cold atoms...

  6. Effect of dispersal at range edges on the structure of species ranges

    Science.gov (United States)

    Bahn, V.; O'Connor, R.J.; Krohn, W.B.

    2006-01-01

    Range edges are of particular interest to ecology because they hold key insights into the limits of the realized niche and associated population dynamics. A recent feature of Oikos summarized the state of the art on range edge ecology. While the typical question is what causes range edges, another important question is how range edges influence the distribution of abundances across a species geographic range when dispersal is present. We used a single species population dynamics model on a coupled-lattice to determine the effects of dispersal on peripheral populations as compared to populations at the core of the range. In the absence of resource gradients, the reduced neighborhood and thus lower connectivity or higher isolation among populations at the range edge alone led to significantly lower population sizes in the periphery of the range than in the core. Lower population sizes mean higher extinction risks and lower adaptability at the range edge, which could inhibit or slow range expansions, and thus effectively stabilize range edges. The strength of this effect depended on the potential population growth rate and the maximum dispersal distance. Lower potential population growth rates led to a stronger effect of dispersal resulting in a higher difference in population sizes between the two areas. The differential effect of dispersal on population sizes at the core and periphery of the range in the absence of resource gradients implies that traditional, habitat-based distribution models could result in misleading conclusions about the habitat quality in the periphery. Lower population sizes at the periphery are also relevant to conservation, because habitat removal not only eliminates populations but also creates new edges. Populations bordering these new edges may experience declines, due to their increased isolation. ?? OIKOS.

  7. Geometric design of a multisensor structured light range digitizer

    Science.gov (United States)

    Commean, Paul K.; Smith, Kirk E.; Bhatia, Gulab H.; Vannier, Michael W.

    1994-04-01

    An optical noncontact 3-D range digitizer based on projection of 2-D structured light patterns and multiplexed charge injection device (CID) camera sensors has been developed. The system acquires digitized data in 0.75 s and allows 360-deg examination of the subject's head and facial surface features in less than 1 s, making it suitable for digitizing children as well as adults. The resultant 3-D surface data is suitable for computer graphics display and manipulation, numerically controlled replication, and further processing such as surface measurement extraction. The digitizer uses a set of six stationary sensors positioned about the subject. A sensor consists of a pattern projector and a solid state video camera. This device allows quantitative volume measurements and employs no harmful ionizing radiation. The cost of a scan with this technology is substantially less than that of alternative means of collecting 3-D surface data sets, such as by stereometric, moiré fringe, and single-point digitization. This system was geometrically designed such that any surface of the head or facial area was independently digitized by a minimum of two sensors and to capture areas normally occluded with other techniques. The dimensions of the structure were derived to satisfy physical constraints placed on its overall size. The camera and projector orientations in space, the distance from the lens centers to the center of the digitizing volume, and the lens focal lengths were determined analytically. To reduce cost, a standard lens nearest the analytical value was used. Based on the standard size lens, the field of view was calculated.

  8. Understanding Local Structure versus Long-Range Structure: The Case of UO2.

    Science.gov (United States)

    Desgranges, Lionel; Ma, Yue; Garcia, Philippe; Baldinozzi, Gianguido; Siméone, David; Fischer, Henry E

    2018-02-09

    A recent trend in the development of new optimized materials makes use of crystalline domains having nanometer sizes for which characterization methods at the atomic scale are mandatory. Amongst them is pair-distribution function analysis (PDF-analysis), a diffraction technique that has already shown that a short-range or "local" atomic structure of a given domain, having a lower symmetry than the average long-range structure, often exists in many compounds having valuable properties for industrial applications, such as pyrochlores, spinels, and doped ceria among others. However, the manner by which these domains are arranged to produce the average long-range structure is still an open question. Herein, the first structural model that accounts for both the local structure (inside a given domain) and the long-range structure (averaged over all domains) that is observed in the PDF of uranium dioxide is presented. The structural model describes domain walls in such a way as to preserve the uranium coordination polyhedron and to obey the needed symmetry rules. The proper description of domain walls is an important step in the understanding and the modelling of nanostructured materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Controlled Ordering of Long-range Perpendicular Lamellae by Block Copolymer Self-assembly

    Science.gov (United States)

    Ryu, Du Yeol; Kim, Kyunginn; Park, Sungmin; Kim, Yeongsik; Yonsei Univ Team

    We introduce a simple approach to fabricating highly stable, perpendicularly oriented lamellae through the self-assembly of high-molecular-weight polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA). The desired morphology was achieved over a narrow annealing period (5 10 min) under solvent vapor, since the SVA process need to terminate immediately before the saturated BCP films begin to dewet the substrate. This narrow processing period impeded practical applications to continuous industrial processes. A controlled SVA process at a selected temperature gap was found to show the excellent long-term stability, at which highly ordered line-arrays of perpendicularly oriented lamellae were confined to topographic line patterns.

  10. Multimodal nonlinear optical polarizing microscopy of long-range molecular order in liquid crystals.

    Science.gov (United States)

    Lee, Taewoo; Trivedi, Rahul P; Smalyukh, Ivan I

    2010-10-15

    We demonstrate orientation-sensitive multimodal nonlinear optical polarizing microscopy capable of probing orientational, polar, and biaxial features of mesomorphic ordering in soft matter. This technique achieves simultaneous imaging in broadband coherent anti-Stokes Raman scattering, multiphoton excitation fluorescence, and multiharmonic generation polarizing microscopy modes and is based on the use of a single femtosecond laser and a photonic crystal fiber as sources of the probing light. We show the viability of this technique for mapping of three-dimensional patterns of molecular orientations and show that images obtained in different microscopy modes are consistent with each other.

  11. Structural Orders of Wheat Starch Do Not Determine the In Vitro Enzymatic Digestibility.

    Science.gov (United States)

    Wang, Shujun; Wang, Shaokang; Liu, Lu; Wang, Shuo; Copeland, Les

    2017-03-01

    In this study, we elucidated the underlying mechanisms that are responsible for the rate-limiting step for wheat starch digestion. Wheat starch samples with a degree of gelatinization (DG) ranging from 0 to 100% were prepared. As DG increased, the ordered structures of the starch were disrupted increasingly. In contrast, almost all of the increase in the rate and extent of in vitro enzymatic digestion coincided with a DG of only 6% and a minor loss of structural order. As DG increased beyond 6%, digestibility of the starch increased only slightly. We propose that the access and binding of enzymes to starch is greatly increased with only a small DG, which is followed by the simultaneous hydrolysis of crystalline and amorphous areas in gelatinized starch. In vitro enzymatic digestibility of starch was determined predominantly by enzyme binding to starch rather than the ordered structures of starch.

  12. Medium-Range Order in Amorphous Silicon Measured by Fluctuation Electron Microscopy: Final Report, 23 June 1999--23 August 2002

    Energy Technology Data Exchange (ETDEWEB)

    Voyles, P. M.; Abelson, J. R.

    2003-10-01

    Despite occasional experimental hints, medium-range structural order in covalently bonded amorphous semiconductors had largely escaped detection until the advent of fluctuation electron microscopy (FEM) in 1996. Using FEM, we find that every sample of amorphous silicon and germanium we have investigated, regardless of deposition method or hydrogen content, is rich in medium-range order. The paracrystalline structural model, which consists of small, topologically ordered grains in an amorphous matrix, is consistent with the FEM data; but due to strain effects, materials with a paracrystalline structure appear to be amorphous in diffraction measurements. We present measurements on hydrogenated amorphous silicon deposited by different methods, some of which are reported to have greater stability against the Staebler-Wronski effect. FEM reveals that the matrix material of these samples is relatively similar, but the order changes in different ways upon both light soaking and thermal annealing. Some materials are inhomogeneous, with either nanocrystalline inclusions or large area-to-area variation in the medium-range order. We cite recent calculations that electronic states in the conduction band tail are preferentially located around the boundaries of the nm-scale paracrystalline regions that we have identified. This is new evidence in support of spatially inhomogeneous conduction mechanisms in a-Si. The key discovery in our work is that all samples of amorphous silicon must be described as having nm-scale topological crystalline order. This strongly modifies the long-standing model of a covalent random network. Our new understanding of medium-range order must be considered in all future models of electronic properties and the Staebler-Wronski effect.

  13. Higher-order Brunnian structures and possible physical realizations

    Science.gov (United States)

    Baas, N. A.; Fedorov, D. V.; Jensen, A. S.; Riisager, K.; Volosniev, A. G.; Zinner, N. T.

    2014-03-01

    We consider few-body bound state systems and provide precise definitions of Borromean and Brunnian systems. The initial concepts are more than a hundred years old and originated in mathematical knot-theory as purely geometric considerations. About thirty years ago they were generalized and applied to the binding of systems in nature. It now appears that recent generalization to higher-order Brunnian structures may potentially be realized as laboratory-made or naturally occurring systems. With the binding energy as measure, we discuss possibilities of physical realization in nuclei, cold atoms, and condensedmatter systems. Appearance is not excluded. However, both the form and the strengths of the interactions must be rather special. The most promising subfields for present searches would be in cold atoms because of external control of effective interactions, or perhaps in condensed-matter systems with nonlocal interactions. In nuclei, it would only be by sheer luck due to a lack of tunability.

  14. First Order Reliability Application and Verification Methods for Semistatic Structures

    Science.gov (United States)

    Verderaime, Vincent

    1994-01-01

    Escalating risks of aerostructures stimulated by increasing size, complexity, and cost should no longer be ignored by conventional deterministic safety design methods. The deterministic pass-fail concept is incompatible with probability and risk assessments, its stress audits are shown to be arbitrary and incomplete, and it compromises high strength materials performance. A reliability method is proposed which combines first order reliability principles with deterministic design variables and conventional test technique to surmount current deterministic stress design and audit deficiencies. Accumulative and propagation design uncertainty errors are defined and appropriately implemented into the classical safety index expression. The application is reduced to solving for a factor that satisfies the specified reliability and compensates for uncertainty errors, and then using this factor as, and instead of, the conventional safety factor in stress analyses. The resulting method is consistent with current analytical skills and verification practices, the culture of most designers, and with the pace of semistatic structural designs.

  15. Structural partitioning of complex structures in the medium-frequency range. An application to an automotive vehicle

    Science.gov (United States)

    Kassem, M.; Soize, C.; Gagliardini, L.

    2011-02-01

    In a recent work [ Journal of Sound and Vibration 323 (2009) 849-863] the authors presented an energy-density field approach for the vibroacoustic analysis of complex structures in the low and medium frequency ranges. In this approach, a local vibroacoustic energy model as well as a simplification of this model were constructed. In this paper, firstly an extension of the previous theory is performed in order to include the case of general input forces and secondly, a structural partitioning methodology is presented along with a set of tools used for the construction of a partitioning. Finally, an application is presented for an automotive vehicle.

  16. Effect of Jahn-Teller distortion on the short range magnetic order in copper ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Abdellatif, M.H., E-mail: Mohamed.abdellatif@iit.it [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Innocenti, Claudia [INSTM—Department of Chemistry, University of Florence, via della Lastruccia 3, I-50019 Sesto Fiorentino, FI (Italy); Liakos, Ioannis [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Scarpellini, Alice; Marras, Sergio [Nanochemistry Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Salerno, Marco [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy)

    2017-02-15

    Copper ferrite of spinel crystal structure was synthesized in the form of nano-particles using citrate-gel auto-combustion method. The sample morphology and composition were identified using scanning electron microscopy, X-ray diffraction, and X-ray spectroscopy. The latter technique reveals an inverse spinel structure with Jahn-Teller tetragonal distortion. The static magnetization was measured using vibrating sample magnetometer. Magnetic force microscopy was used in combination with the magnetization data to demonstrate the finite size effect of the magnetic spins and their casting behavior due to the introduction of copper ions in the tetrahedral magnetic sub-lattices, which results in tetragonal distorting the spinel structure of the copper ferrite. The magnetic properties of materials are a result of the collective behavior of the magnetic spins, and magnetic force microscopy can probe the collective behavior of the magnetic spins in copper ferrite, yet providing a sufficient resolution to map the effects below the micrometer size scale, such as the magnetic spin canting. A theoretical study was done to clarify the finite size effect of Jahn-Teller distortion on the magnetic properties of the material. When the particles are in the nano-scale, below the single domain size, their magnetic properties are very sensitive to their size change. - Highlights: • The spin canting due to Jahn-Teller distortion in Copper ferrite can be detected using magnetic force microscope. • The contrast in the magnetic AFM image can be analyzed to give information not only about the surface spins but also about the canting of the core spins inside the aggregated cluster of magnetic nanoparticle.

  17. Long-range order in V/sub 2/H near the. beta. -epsilon phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Schoenfeld, B.; Moss, S.C.; Kjaer, K.

    1987-10-01

    The integrated intensity I of h/2 0 h/2-bar superstructure reflections has been measured with x rays for a single crystal of V/sub 2/H. Just below the critical temperature T/sub c/ of the ..beta..-epsilon phase transition, I varies as (1-T/T/sub c/)/sup 2//sup ..beta../ with ..beta.. = 0.153 +- 0.007, increasing to ..beta.. = 0.17 and 0.20 when referred to a rigid volume and c lattice parameter, respectively, through a lattice-expansion correction. By comparing heating and cooling runs the second-order character of this phase transition has been demonstrated. A shift of T/sub c/, however, was observed when data were taken without first thermally cycling the crystal close to T/sub c/.

  18. Tuning anomalous Hall conductivity in L1[sub 0] FePt films by long range chemical ordering

    KAUST Repository

    Chen, M.

    2011-02-24

    For L10 FePt films, the anomalous Hall conductivity σ xy=-a σxx-b, where a=a0f(T), b=b 0f(T), and f (T) is the temperature dependence factor of the spontaneous magnetization. With increasing chemical long range ordering S, a0 changes its sign accompanied by a reduction of its magnitude and b0 increases monotonically. The spin-orbit coupling strength is suggested to increase with increasing S. As an approach, the long range chemical ordering can be used to control the anomalous Hall effect in ferromagnetic alloy films. © 2011 American Institute of Physics.

  19. Photonic bandgap structures for long-range surface plasmon polaritons

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Boltasseva, Alexandra; Søndergaard, Thomas

    2005-01-01

    Propagation of long-range surface plasmon polaritons (LR-SPPs) along periodically thickness-modulated metal stripes embedded in dielectric is studied both theoretically and experimentally for light wavelengths in the telecom range. We demonstrate that symmetric (with respect to the film surface) nm...... of achieving a full bandgap (in the surface plane) for LR-SPPs are also discussed....

  20. Desirable forest structures for a restored Front Range

    Science.gov (United States)

    Yvette L. Dickinson; Rob Addington; Greg Aplet; Mike Babler; Mike Battaglia; Peter Brown; Tony Cheng; Casey Cooley; Dick Edwards; Jonas Feinstein; Paula Fornwalt; Hal Gibbs; Megan Matonis; Kristen Pelz; Claudia Regan

    2014-01-01

    As part of the federal Collaborative Forest Landscape Restoration Program administered by the US Forest Service, the Colorado Front Range Collaborative Forest Landscape Restoration Project (FR-CFLRP, a collaborative effort of the Front Range Roundtable1 and the US Forest Service) is required to define desired conditions for lower montane ponderosa pine (Pinus ponderosa...

  1. Pressure effect on the long-range order in CeB{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Sera, M. [ADSM, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan)]. E-mail: sera@sci.hiroshima-u.ac.jp; Ikeda, S. [ADSM, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan); Iwakubo, H. [ADSM, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan); Uwatoko, Y. [Institute for Solid State Physics, University of Tokyo (Japan); Hane, S. [Institute for Solid State Physics, University of Tokyo (Japan); Kosaka, M. [Department of Physics, Saitama University, Urawa 338-8570 (Japan); Kunii, S. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan)

    2006-08-15

    The pressure effect of CeB{sub 6} was investigated. The pressure dependence of the Neel temperature, T{sub N} and the critical field from the antiferro-magnetic phase III to antiferro-quadrupolar phase II, H{sub c}{sup III-II} of CeB{sub 6} exhibits the unusual pressure dependence that the suppression rate of H{sub c}{sup III-II} is much larger than that of T{sub N}. In order to explain this unusual result, we have performed the mean field calculation for the 4-sublattice model assuming that the pressure dependence of T{sub N}, the antiferro-octupolar and quadrupolar temperatures, T{sub oct} and T{sub Q} as follows; dT{sub N}/dP<0, dT{sub oct}/dP>dT{sub Q}/dP>0 and could explain the unusual pressure dependence of T{sub N} and H{sub c}{sup III-II}.

  2. How Noniridescent Colors Are Generated by Quasi-ordered Structures of Bird Feathers

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Mochrie, Simon G.J.; Prum, Richard O.; Dufresne, Eric R.; Cao, Hui (Yale)

    2012-03-26

    We investigate the mechanism of structural coloration by quasi-ordered nanostructures in bird feather barbs. Small-angle X-ray scattering (SAXS) data reveal the structures are isotropic and have short-range order on length scales comparable to optical wavelengths. We perform angle-resolved reflection and scattering spectrometry to fully characterize the colors under directional and omni-directional illumination of white light. Under directional lighting, the colors change with the angle between the directions of illumination and observation. The angular dispersion of the primary peaks in the scattering/reflection spectra can be well explained by constructive interference of light that is scattered only once in the quasi-ordered structures. Using the Fourier power spectra of structure from the SAXS data we calculate optical scattering spectra and explain why the light scattering peak is the highest in the backscattering direction. Under omni-directional lighting, colors from the quasi-ordered structures are invariant with the viewing angle. The non-iridescent coloration results from the isotropic nature of structures instead of strong backscattering.

  3. How noniridescent colors are generated by quasi-ordered structures of bird feathers.

    Science.gov (United States)

    Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Mochrie, Simon G J; Prum, Richard O; Dufresne, Eric R; Cao, Hui

    2010-07-20

    We investigate the mechanism of structural coloration by quasi-ordered nanostructures in bird feather barbs. Small-angle X-ray scattering (SAXS) data reveal the structures are isotropic and have short-range order on length scales comparable to optical wavelengths. We perform angle-resolved reflection and scattering spectrometry to fully characterize the colors under directional and omni-directional illumination of white light. Under directional lighting, the colors change with the angle between the directions of illumination and observation. The angular dispersion of the primary peaks in the scattering/reflection spectra can be well explained by constructive interference of light that is scattered only once in the quasi-ordered structures. Using the Fourier power spectra of structure from the SAXS data we calculate optical scattering spectra and explain why the light scattering peak is the highest in the backscattering direction. Under omni-directional lighting, colors from the quasi-ordered structures are invariant with the viewing angle. The non-iridescent coloration results from the isotropic nature of structures instead of strong backscattering.

  4. Short-range order of undercooled melts of PdZr 2 intermetallic compound studied by X-ray and neutron scattering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Klein, S.; Holland-Moritz, D.; Herlach, D. M.; Mauro, N. A.; Kelton, K. F.

    2013-05-01

    The short-range order in undercooled melts of the intermetallic Zr2Pd glass-forming alloy is investigated by combining electrostatic levitation (ESL) with high-energy X-ray diffraction and neutron diffraction. Experimentally determined structure factors are measured and analyzed with respect to various structures of short-range order. The comparative X-ray and neutron scattering experiments allow for investigations of topological and chemical short-range order. Based on these studies, no preference of a specific short-range order is found for the liquid Zr2Pd glass-forming alloy, even in the metastable state of the deeply undercooled melt. This is in agreement with an earlier report from X-ray diffraction and molecular-dynamics studies of a Zr75.5Pd24.5 liquid, which showed a broad distribution of cluster types. The results for the Zr2Pd liquid are discussed with respect to the glass-forming ability of this melt.

  5. USSOUTHCOM: Aligning Organizational Structure to the Range of Military Operations

    Science.gov (United States)

    2011-05-04

    Secretary of Defense-transitioned to a new model of headquarters organizational structure . A functional directorate system replaced traditional J-codes...operations. Upon transition and re-deployment, the command would return to functional directorates. Such an arrangement is best described as an alternating or interchangeable organizational structure .

  6. On the effect of impurities on resistivity recovery, short-range ordering, and defect migration in electron-irradiated concentrated Fe-Cr alloys

    CERN Document Server

    Nikolaev, A L; Davletshin, A E

    1997-01-01

    The resistivity recovery of pure and impurity-doped (0.2-1.5% Si, 0.15% C+N) concentrated ferritic Fe-Cr alloys after electron irradiation at 50-60 K has been investigated over the temperature range 110-390 K. A fine recovery spectrum structure consisting of five peaks has been observed over the range 135-230 K. Short-range ordering starts with the onset of vacancy long-range migration. Doping with both types of impurity suppresses the recovery spectrum structure over the range 160-220 K in a similar manner. Additional effects of impurity doping on the resistivity recovery caused by deviation from Matthiessen's rule have been analysed. A stage III peak is found at 210 K, and two peaks - at 175 K and 195 K - are interpreted as being due to the vacancy short-range migration. It is supposed that such a manifestation of short-range vacancy migration is due to a strong immobilization of self-interstitial atoms, and suppression of short-range and long-range defect annealing processes in stage I, according to a conf...

  7. Controlled evaporative self-assembly of confined microfluids: A route to complex ordered structures

    Science.gov (United States)

    Byun, Myunghwan

    The evaporative self-assembly of nonvolatile solutes such as polymers, nanocrystals, and carbon nanotubes has been widely recognized as a non-lithographic means of producing a diverse range of intriguing complex structures. Due to the spatial variation of evaporative flux and possible convection, however, these non-equilibrium dissipative structures (e.g., fingering patterns and polygonal network structures) are often irregularly and stochastically organized. Yet for many applications in microelectronics, data storage devices, and biotechnology, it is highly desirable to achieve surface patterns having a well-controlled spatial arrangement. To date, only a few elegant studies have centered on precise control over the evaporation process to produce ordered structures. In a remarked comparison with conventional lithography techniques, surface patterning by controlled solvent evaporation is simple and cost-effective, offering a lithography- and external field-free means to organize nonvolatile materials into ordered microscopic structures over large surface areas. The ability to engineer an evaporative self-assembly process that yields a wide range of complex, self-organizing structures over large areas offers tremendous potential for applications in electronics, optoelectronics, and bio- or chemical sensors. We developed a facile, robust tool for evaporating polymer, nanoparticle, or DNA solutions in curve-on-flat geometries to create versatile, highly regular microstructures, including hierarchically structured polymer blend rings, conjugated polymer "snake-skins", block copolymer stripes, and punch-hole-like meshes, biomolecular microring arrays, etc. The mechanism of structure formation was elucidated both experimentally and theoretically. Our method further enhances current fabrication approaches to creating highly ordered structures in a simple and cost-effective manner, envisioning the potential to be tailored for use in photonics, optoelectronics, microfluidic

  8. Long-Range Order and Critical Scattering of Neutrons below the Transition Temperature in β-Brass

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Dietrich, O.W.

    1967-01-01

    The temperature dependence of long-range order langPrang has been determined from the temperature variation of a superlattice Bragg reflection. The results fitted a power law langPrang prop (Tc-T)beta with Tc the critical temperature and beta = 0.305plusmn0.005, in agreement with the theoretical ...

  9. Nonlinear wave-structure interactions with a high-order Boussinesq model

    DEFF Research Database (Denmark)

    Fuhrman, David R.; Bingham, Harry; Madsen, Per A.

    2005-01-01

    on a structurally divided domain, and it is shown that exterior corner points pose potential stability problems, as well as other numerical difficulties. These are mainly due to the discretization of high-order mixed-derivative terms near these points, where the flow is theoretically singular. Fortunately......, and highly nonlinear deep water wave run-up on a vertical plate. These cases demonstrate the applicability of the model over a wide range of water depth and nonlinearity....

  10. Biphasic Chromatin Structure and FISH Signals Reflect Intranuclear Order

    Directory of Open Access Journals (Sweden)

    Jyoti P. Chaudhuri

    2005-01-01

    Full Text Available Background and Aim: One of the two parental allelic genes may selectively be expressed, regulated by imprinting, X-inactivation or by other less known mechanisms. This study aims to reflect on such genetic mechanisms. Materials and Methods: Slides from short term cultures or direct smears of blood, bone marrow and amniotic fluids were hybridized with FISH probes singly, combined or sequentially. Two to three hundred cells were examined from each preparation. Results and Aignificance: A small number of cells (up to about 5%, more frequent in leukemia cases, showed the twin features: (1 nuclei with biphasic chromatin, one part decondensed and the other condensed; and (2 homologous FISH signals distributed equitably in those two regions. The biphasic chromatin structure with equitable distribution of the homologous FISH signals may correspond to the two sets of chromosomes, supporting observations on ploidywise intranuclear order. The decondensed chromatin may relate to enhanced transcriptions or advanced replications. Conclusions: Transcriptions of only one of the two parental genomes cause allelic exclusion. Genomes may switch with alternating monoallelic expression of biallelic genes as an efficient genetic mechanism. If genomes fail to switch, allelic exclusion may lead to malignancy. Similarly, a genome-wide monoallelic replication may tilt the balance of heterozygosity resulting in aneusomy, initiating early events in malignant transformation and in predicting cancer mortality.

  11. Long-Range Epistasis Mediated by Structural Change in a Model of Ligand Binding Proteins.

    Directory of Open Access Journals (Sweden)

    Erik D Nelson

    Full Text Available Recent analyses of amino acid mutations in proteins reveal that mutations at many pairs of sites are epistatic-i.e., their effects on fitness are non-additive-the combined effect of two mutations being significantly larger or smaller than the sum of their effects considered independently. Interestingly, epistatic sites are not necessarily near each other in the folded structure of a protein, and may even be located on opposite sides of a molecule. However, the mechanistic reasons for long-range epistasis remain obscure. Here, we study long-range epistasis in proteins using a previously developed model in which off-lattice polymers are evolved under ligand binding constraints. Epistatic effects in the model are qualitatively similar to those recently reported for small proteins, and many are long-range. We find that a major reason for long-range epistasis is conformational change-a recurrent theme in both positive and negative epistasis being the transfer, or exchange of material between the ordered nucleus, which supports the binding site, and the liquid-like surface of a folded molecule. These local transitions in phase and folded structure are largely responsible for long-range epistasis in our model.

  12. Long-Range Epistasis Mediated by Structural Change in a Model of Ligand Binding Proteins.

    Science.gov (United States)

    Nelson, Erik D; Grishin, Nick V

    2016-01-01

    Recent analyses of amino acid mutations in proteins reveal that mutations at many pairs of sites are epistatic-i.e., their effects on fitness are non-additive-the combined effect of two mutations being significantly larger or smaller than the sum of their effects considered independently. Interestingly, epistatic sites are not necessarily near each other in the folded structure of a protein, and may even be located on opposite sides of a molecule. However, the mechanistic reasons for long-range epistasis remain obscure. Here, we study long-range epistasis in proteins using a previously developed model in which off-lattice polymers are evolved under ligand binding constraints. Epistatic effects in the model are qualitatively similar to those recently reported for small proteins, and many are long-range. We find that a major reason for long-range epistasis is conformational change-a recurrent theme in both positive and negative epistasis being the transfer, or exchange of material between the ordered nucleus, which supports the binding site, and the liquid-like surface of a folded molecule. These local transitions in phase and folded structure are largely responsible for long-range epistasis in our model.

  13. Accuracy Enhanced Stability and Structure Preserving Model Reduction Technique for Dynamical Systems with Second Order Structure

    DEFF Research Database (Denmark)

    Tahavori, Maryamsadat; Shaker, Hamid Reza

    A method for model reduction of dynamical systems with the second order structure is proposed in this paper. The proposed technique preserves the second order structure of the system, and also preserves the stability of the original systems. The method uses the controllability and observability...... gramians within the time interval to build the appropriate Petrov-Galerkin projection for dynamical systems within the time interval of interest. The bound on approximation error is also derived. The numerical results are compared with the counterparts from other techniques. The results confirm...

  14. Long-range ordered self-assembled InAs quantum dots epitaxially grown on (110) GaAs

    Science.gov (United States)

    Bauer, J.; Schuh, D.; Uccelli, E.; Schulz, R.; Kress, A.; Hofbauer, F.; Finley, J. J.; Abstreiter, G.

    2004-11-01

    We report on a promising approach for positioning of self-assembled InAs quantum dots on (110) GaAs with nanometer precision. By combining self-assembly of quantum dots with molecular beam epitaxy on previously grown and in situ cleaved substrates (cleaved-edge overgrowth), arrays of long-range ordered InAs quantum dots have been fabricated. Both atomic force microscopy and micro-photoluminescence measurements demonstrate the ability to control size, position, and ordering of the quantum dots. Furthermore, single dot photoluminescence investigations confirm the high optical quality of the quantum dots fabricated.

  15. External Memory Graph Algorithms and Range Searching Data Structures

    DEFF Research Database (Denmark)

    Walderveen, Freek van

    Every day larger amounts of data are generated that describe our world in terms of networks or graphs. Think for example about maps of roads or rivers, social networks, or the internet (either as a network of computers or as a network of hyperlinks). Besides this, also surface models, such as hei......Every day larger amounts of data are generated that describe our world in terms of networks or graphs. Think for example about maps of roads or rivers, social networks, or the internet (either as a network of computers or as a network of hyperlinks). Besides this, also surface models......). In order to present (for example geographic) data to a user, it is often necessary to select only a relatively small part of a dataset|such as all post oces in the region visible on the user's screen|and return some statictic about this part|such as the distance between the two furthest post oces...

  16. A novel 2nd-order bandpass MFSS filter with miniaturized structure

    Directory of Open Access Journals (Sweden)

    C. Y. Fang

    2015-08-01

    Full Text Available In order to effectively obtain a miniaturized structure and good filtering properties, we propose a novel 2nd-order bandpass metamaterial frequency selective surface (MFSS filter which contains two capacitive layers and one inductive layer, where there are multi-loop metallic patches as shunt capacitor C and planar wire grids as series inductor L respectively. Unlike the traditional operation way—the tuned elements used in resonant surface approximately equal to one wavelength in circumference and the structure thickness with a spacing of a quarter wavelength apart, by changing the value of L and C and matching multilayer dielectric to adjust the LC coupling resonance and the resonance impedance respectively, the proposed MFSS filter can achieves a miniatured structure with ideal bandpass properties. Measurement results of the fabricated prototype of the bandpass filter (BPF indicate that the dimension of the tuned element on resonant surface is approximately 0.025 wavelength, i.e., 0.025λ. At the same time, the filter has the stable center frequency of f0 = 1.53GHz and the transmittance of T ⩾ 96.3% and high Q-value for the TE/TM wave polarization at various incidence angles. The novel 2nd-order bandpass MFSS filter with miniaturized structure not only can decrease structure dimension, but also has a wide range of applications to microwave and infrared band.

  17. Order convergence structure on C(X) | Anguelov | Quaestiones ...

    African Journals Online (AJOL)

    This paper brings together three concepts which have not been related so far, namely, the concept of order convergence, the concept of convergence space and the concept of Hausdorff continuous functions. The order convergence on a poset P, which is generally not a topological convergence, can be studied through the ...

  18. Controlled Bulk Properties of Composite Polymeric Solutions for Extensive Structural Order of Honeycomb Polysulfone Membranes

    Directory of Open Access Journals (Sweden)

    Annarosa Gugliuzza

    2016-05-01

    Full Text Available This work provides additional insights into the identification of operating conditions necessary to overcome a current limitation to the scale-up of the breath figure method, which is regarded as an outstanding manufacturing approach for structurally ordered porous films. The major restriction concerns, indeed, uncontrolled touching droplets at the boundary. Herein, the bulk of polymeric solutions are properly managed to generate honeycomb membranes with a long-range structurally ordered texture. Water uptake and dynamics are explored as chemical environments are changed with the intent to modify the hydrophilic/hydrophobic balance and local water floatation. In this context, a model surfactant such as the polyoxyethylene sorbitan monolaurate is used in combination with alcohols at different chain length extents and a traditional polymer such as the polyethersufone. Changes in the interfacial tension and kinematic viscosity taking place in the bulk of composite solutions are explored and examined in relation to competitive droplet nucleation and growth rate. As a result, extensive structurally ordered honeycomb textures are obtained with the rising content of the surfactant while a broad range of well-sized pores is targeted as a function of the hydrophilic-hydrophobic balance and viscosity of the composite polymeric mixture. The experimental findings confirm the consistency of the approach and are expected to give propulsion to the commercially production of breath figures films shortly.

  19. 29Si NMR study of structural ordering in aluminosilicate geopolymer gels.

    Science.gov (United States)

    Duxson, Peter; Provis, John L; Lukey, Grant C; Separovic, Frances; van Deventer, Jannie S J

    2005-03-29

    A systematic series of aluminosilicate geopolymer gels was synthesized and then analyzed using 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) in combination with Gaussian peak deconvolution to characterize the short-range ordering in terms of T-O-T bonds (where T is Al or Si). The effect of nominal Na2O/(Na2O + K2O) and Si/Al ratios on short-range network ordering was quantified by deconvolution of the 29Si MAS NMR spectra into individual Gaussian peaks representing different Q4(mAl) silicon centers. The deconvolution procedure developed in this work is applicable to other aluminosilicate gel systems. The short-range ordering observed here indicates that Loewenstein's Rule of perfect aluminum avoidance may not apply strictly to geopolymeric gels, although further analyses are required to quantify the degree of aluminum avoidance. Potassium geopolymers appeared to exhibit a more random Si/Al distribution compared to that of mixed-alkali and sodium systems. This work provides a quantitative account of the silicon and aluminum ordering in geopolymers, which is essential for extending our understanding of the mechanical strength, chemical and thermal stability, and fundamental structure of these systems.

  20. Structure, stability, and formation pathways of colloidal gels in systems with short-range attraction and long-range repulsion.

    Science.gov (United States)

    van Schooneveld, Matti M; de Villeneuve, Volkert W A; Dullens, Roel P A; Aarts, Dirk G A L; Leunissen, Mirjam E; Kegel, Willem K

    2009-04-09

    We study colloidal gels formed upon centrifugation of dilute suspensions of spherical colloids (radius 446 nm) that interact through a long-range electrostatic repulsion (Debye length approximately 850 nm) and a short-range depletion attraction (approximately 12.5 nm), by means of confocal scanning laser microscopy (CSLM). In these systems, at low colloid densities, colloidal clusters are stable. Upon increasing the density by centrifugation, at different stages of cluster formation, we show that colloidal gels are formed that significantly differ in structure. While significant single-particle displacements do not occur on the hour time scale, the different gels slowly evolve within several weeks to a similar structure that is at least stable for over a year. Furthermore, while reference systems without long-range repulsion collapse into dense glassy states, the repulsive colloidal gels are able to support external stress in the form of a centrifugal field of at least 9g.

  1. Self-assembly of hierarchically ordered structures in DNA nanotube systems

    Science.gov (United States)

    Glaser, Martin; Schnauß, Jörg; Tschirner, Teresa; Schmidt, B. U. Sebastian; Moebius-Winkler, Maximilian; Käs, Josef A.; Smith, David M.

    2016-05-01

    The self-assembly of molecular and macromolecular building blocks into organized patterns is a complex process found in diverse systems over a wide range of size and time scales. The formation of star- or aster-like configurations, for example, is a common characteristic in solutions of polymers or other molecules containing multi-scaled, hierarchical assembly processes. This is a recurring phenomenon in numerous pattern-forming systems ranging from cellular constructs to solutions of ferromagnetic colloids or synthetic plastics. To date, however, it has not been possible to systematically parameterize structural properties of the constituent components in order to study their influence on assembled states. Here, we circumvent this limitation by using DNA nanotubes with programmable mechanical properties as our basic building blocks. A small set of DNA oligonucleotides can be chosen to hybridize into micron-length DNA nanotubes with a well-defined circumference and stiffness. The self-assembly of these nanotubes to hierarchically ordered structures is driven by depletion forces caused by the presence of polyethylene glycol. This trait allowed us to investigate self-assembly effects while maintaining a complete decoupling of density, self-association or bundling strength, and stiffness of the nanotubes. Our findings show diverse ranges of emerging structures including heterogeneous networks, aster-like structures, and densely bundled needle-like structures, which compare to configurations found in many other systems. These show a strong dependence not only on concentration and bundling strength, but also on the underlying mechanical properties of the nanotubes. Similar network architectures to those caused by depletion forces in the low-density regime are obtained when an alternative hybridization-based bundling mechanism is employed to induce self-assembly in an isotropic network of pre-formed DNA nanotubes. This emphasizes the universal effect inevitable

  2. Short range order and stability of amorphous Ge(x)Te(100-x) alloys (12 ≤ x ≤ 44.6).

    Science.gov (United States)

    Jóvári, P; Piarristeguy, A; Escalier, R; Kaban, I; Bednarčik, J; Pradel, A

    2013-05-15

    Amorphous Ge(x)Te(100-x) alloys were obtained over a broad composition range (12 ≤ x ≤ 44.6) by thermal co-evaporation. Their structure was investigated by x-ray diffraction and extended x-ray absorption fine structure measurements. Experimental datasets were fitted simultaneously by the reverse Monte Carlo simulation technique. It is concluded that Te is mostly twofold coordinated and the majority of Ge atoms have four neighbours. The number of Ge-Ge and Te-Te bonds evolves monotonically with composition. Ge-Ge bonding can be observed already at x = 24 while Te-Te bonds can be found even in Ge44.6Te55.4. The models obtained by simulation show that the structure of compositions with x > 24 should be considered as a random covalent network but there is chemical ordering for x ≤ 24, exactly in the composition range where glasses can be obtained from the melt by fast quenching. The composition dependences of some physical properties also point to the connection between chemical short range order and the stability of the amorphous phase: while the glass transition temperature and microhardness increase monotonically with the composition, the thermal stability of the amorphous films goes through a maximum around x = 20-24.

  3. Order of arrival structures arbuscular mycorrhizal colonization of plants

    NARCIS (Netherlands)

    Werner, G.D.A.; Kiers, E.T.

    2015-01-01

    Priority effects - the impact of a species' arrival on subsequent community development - have been shown to influence species composition in many organisms. Whether priority effects among arbuscular mycorrhizal fungi (AMF) structure fungal root communities is not well understood. Here, we

  4. Magnetic anisotropy and chemical long-range order in epitaxial ferrimagnetic CrPt sub 3 films

    CERN Document Server

    Maret, M; Köhler, J; Poinsot, R; Ulhaq-Bouillet, C; Tonnerre, J M; Berar, J F; Bucher, E

    2000-01-01

    Thin films of CrPt sub 3 were prepared by molecular beam epitaxy on both Al sub 2 O sub 3 (0 0 0 1) and MgO(0 0 1) substrates, either directly by co-deposition of Cr and Pt at high temperatures or after in situ annealing of superlattices [Cr(2 A)/Pt(7 A)]. In situ RHEED observations and X-ray diffraction measurements have allowed us to check the single-crystal quality of CrPt sub 3 films and to determine the degree of L1 sub 2 -type long-range order (LRO). In films co-deposited between 850 deg. C and 950 deg. C a nearly perfect LRO has been observed. As in bulk alloys, such ordering yields a ferrimagnetic order, while the disordered films are non-magnetic. In contrast with the ferromagnetic L1 sub 2 -type ordered CoPt sub 3 (1 1 1) films, the ferrimagnetic CrPt sub 3 (1 1 1) films exhibit perpendicular magnetic anisotropy with quality factors, K sub u /K sub d , as large as 5 and large coercivities around 450 kA/m. Such anisotropy could be related to the arrangement of Cr atoms, which owing to their large mag...

  5. First-order vs. second-order structural validity of the Health Literacy Scale in patients with diabetes.

    Science.gov (United States)

    Lee, Eun-Hyun; Lee, Young Whee

    2017-08-03

    The purpose of this study was to determine the structural validity of the Health Literacy Scale (HLS) in Korean patients with diabetes based on the previously reported first-order three-factor and two-factor models and a newly proposed second-order model, to identify which model best represents the structure of the Korean version of the HLS (HLS-K). The HLS was translated from Japanese into Korean using a translation and back-translation technique. A secondary data analysis was used to validate the structure of the HLS. Data were obtained from a cross-sectional survey involving 459 adults with diabetes recruited from outpatient clinics at two university hospitals in South Korea. The structural validity was examined using confirmatory factor analysis. Additionally, the known-groups validity by education level and internal consistency validity were assessed. The second-order three-factor model of the HLS-K exhibited a good fit to the data, as indicated by χ2 /df = 3.891, SRMR = 0.042, GFI = 0.924, RMSEA = 0.079 (90% CI = 0.069-0.090), and CFI = 0.962. The second-order three-factor model empirically demonstrated that both communicative and critical factors explained the variance in the overall health literacy better than did the functional factor. The HLS-K mean score was significantly lower for patients with only elementary school education than for those with higher education levels, implying the presence of known-groups validity. Cronbach's alpha for the total scale was 0.90. This study found that the second-order three-factor model of the HLS-K is better than that the original first-order three-factor and first-order two-factor models. Further validation studies are needed to generalise the underlying structure of the instrument in diabetes populations across various cultures. © 2017 Nordic College of Caring Science.

  6. Bipartite stripe-like order of magneto-crystalline structure in Fe-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yazdani, A., E-mail: Yazdania@modares.ac.ir; Hesani, M.

    2017-01-01

    Emergence of superconductivity in the iron-based superconductor of “LaFeAsO” is a consequence of the characteristic behavior of antiferromagnetic structure at different triplet critical points. Here, we studied x{sub 2}{sup c} (highest concentration bound) = 0.5. A new second antiferromagnetic (AFM) structure was found that is developed for three different geometrical arrangements of O/H, resulting in three different antiferromagnetic structures at x{sub 2}{sup c} = 0.5. Both crystal and magnetic orderings are a consequence of the stripe-like ordering in the stripe configuration of “H” and “O”. Moreover, in our calculation a strong correlation was obtained between the magnetic and geometrical structures, resulting in the non-uniform magnetic moments of ∼1.30 μβ (AFM1-1) and ∼1.66 μβ (AFM1-3). This phenomenon results in the Jahn-Teller distortion, reflected in the non-uniformity of spin-induced distribution, in the range of 1.07 μβ close to “H” and 1.53 μβ close to “O”, in order to stabilize the ground state of the magneto-crystalline structure. This newly found second antiferromagnetic ordering behaves as the ground state with a lower cohesive energy, resulting in a lower magnetic moment. The effects are more pronounced in the displacement of atomic positions, reflecting in the repulsion of intra-layer La atoms from each other and the attraction of inter-layer Fe atoms toward each other, in direction to induce the anisotropy variable of η ≈ 0.78. - Highlights: • A new second antiferromagnetic structure was found. • Both crystal and magnetic orderings are a consequence of stripe-like ordering. • A strong correlation between the magnetic and geometrical structures was obtained. • Decrease of asymmetrical magnetic moment in direction to the decreased energy. • The effects are more pronounced on the displacement of topological atomic position.

  7. On Monadic Second-Order Theories of Multidominance Structures

    Science.gov (United States)

    Kepser, Stephan

    Multidominance structures were introduced by Kracht [4] to provide a data structure for the formalisation of various aspects of GB-Theory. Kracht studied the PDL-theory of MDSes and showed that this theory is decidable in [5], actually 2EXPTIME-complete. He continues to conjecture that thus the MSO-theory of MDSes should be decidable, too. We show here the contrary. Actually, both the MSO-theory over vertices only and the MSO-theory over vertices and edges turn out to be undecidable.

  8. Two-dimensional magnetic ordering in a multilayer structure

    Indian Academy of Sciences (India)

    mm min−1. The silicon substrates were cleaned and hydrophilized according to. RCA cleaning procedure. Grazing incidence X-ray reflectivity measurements were performed using a rotating anode X-ray set-up (ENRAF, Nonius), to characterize the structure of the deposited LB films [24]. In figure 1 we have shown the model.

  9. Higher Order Structure and Binding of Peptide Nucleic Acids

    DEFF Research Database (Denmark)

    2004-01-01

    Peptide nucleic acids and analogues of peptide nucleic acids are used to form duplex, triplex, and other structures with nucleic acids and to modify nucleic acids. The peptide nucleic acids and analogues thereof also are used to modulate protein activity through, for example, transcription arrest......, transcription initiation, and site specific cleavage of nucleic acids....

  10. Re-Ordering Structural Dimensions for Nigerian Organizations ...

    African Journals Online (AJOL)

    Findings reveal that available researches conducted in organizations, especially in western organizations, so far reflect structural properties of OS in place as well as a variety of determinants, which, in turn, reflects the model adopted. Besides, environmental and cultural factors are found to be major determinants of the ...

  11. The effect of Pd on the isothermal relaxation of short-range order in Au(Ag)-based ternary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ziya, A.B. [Institute of Materials Science, University of Tsukuba, Tsukuba 305-8573 (Japan) and Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan)]. E-mail: dr.a.b.ziya@bzumail.edu.pk; Ohshima, K. [Institute of Materials Science, University of Tsukuba, Tsukuba 305-8573 (Japan)

    2005-08-01

    The effect of Pd on the isothermal relaxation of short-range order (SRO) was studied in Au{sub x}Ag{sub x}Pd{sub 100-2x} (x=25, 40at%) alloys, using the residual resistometry at 77K. The short-range ordering resulted in an increase of electrical resistivity. The equilibrium values of this property characterizing the SRO-equilibrium states exhibit a linear dependence on the reciprocal of temperature. The analysis of the resistivity data using the fundamental laws of SRO-kinetics shows that the resistivity behavior can be satisfactorily explained by the two-exponentials law and leads to the determination of characteristic time constants and the activation enthalpies for the two processes. Further, it is found that both the equilibrium and kinetic behavior of these alloys are highly dependent on the concentration of Pd. The presence of Pd reduces the atomic mobility which results from a decrease in the vacancy mobility linked to the positive size effect of Pd in these alloys.

  12. Ordered Dissipative Structures in Exciton Systems in Semiconductor Quantum Wells

    Directory of Open Access Journals (Sweden)

    Andrey A. Chernyuk

    2006-02-01

    Full Text Available A phenomenological theory of exciton condensation in conditions of inhomogeneous excitation is proposed. The theory is applied to the study of the development of an exciton luminescence ring and the ring fragmentation at macroscopical distances from the central excitation spot in coupled quantum wells. The transition between the fragmented and the continuous ring is considered. With assumption of a defect in the structure, a possibility of a localized island of the condensed phase in a fixed position is shown. Exciton density distribution is also analyzed in the case of two spatially separated spots of the laser excitation.

  13. Photonic bandgap structures for guiding of long-range surface plasmon polaritons

    DEFF Research Database (Denmark)

    Leosson, K.; Nikolajsen, T.; Boltasseva, Alexandra

    2003-01-01

    We present the first observations of long-range plasmon polariton guiding in photonic bandgap structures. The transmission of waveguide structures is characterized at telecommunication wavelengths and a propagation loss below 4 dB/mm is determined.......We present the first observations of long-range plasmon polariton guiding in photonic bandgap structures. The transmission of waveguide structures is characterized at telecommunication wavelengths and a propagation loss below 4 dB/mm is determined....

  14. Structure and Sensor Properties of Thin Ordered Solid Films

    Directory of Open Access Journals (Sweden)

    Jadwiga Sołoducho

    2009-09-01

    Full Text Available Miniaturized gas sensors and biosensors based on nanostructured sensing elements have attracted considerable interest because these nanostructured materials can be used to significantly improve sensor sensitivity and the response time. We report here on a generic, reversible sensing platform based on hybrid nanofilms. Thin ordered Langmuir-Blodgett (LB films built of fluorene derivatives were used as effective gas sensors for both oxidative and reductive analytes. A novel immobilization method based on thin LB films as a matrix has been developed for construction of sensing protein layers. Biomolecules can often be incorporated into and immobilized on Langmuir-Blodgett films using adsorption methods or by covalent immobilization of proteins. The sensor sensitisation was achieved by an amphiphilic N-alkyl-bis(thiophenearylenes admixed into the film. The interlaced derivative was expected to facilitate the electron transfer, thereby enhancing the sensor sensitivity. The results suggest that this may be very promising approach for exploring the interactions between proteins and high throughput detection of phenol derivatives in wastewater.

  15. High order magnetic optics for high dynamic range proton radiography at a kinetic energy of 800 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Sjue, S. K. L., E-mail: sjue@lanl.gov; Mariam, F. G.; Merrill, F. E.; Morris, C. L.; Saunders, A. [Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-01-15

    Flash radiography with 800 MeV kinetic energy protons at Los Alamos National Laboratory is an important experimental tool for investigations of dynamic material behavior driven by high explosives or pulsed power. The extraction of quantitative information about density fields in a dynamic experiment from proton generated images requires a high fidelity model of the proton imaging process. It is shown that accurate calculations of the transmission through the magnetic lens system require terms beyond second order for protons far from the tune energy. The approach used integrates the correlated multiple Coulomb scattering distribution simultaneously over the collimator and the image plane. Comparison with a series of static calibration images demonstrates the model’s accurate reproduction of both the transmission and blur over a wide range of tune energies in an inverse identity lens that consists of four quadrupole electromagnets.

  16. Electrolytes induce long-range orientational order and free energy changes in the H-bond network of bulk water.

    Science.gov (United States)

    Chen, Yixing; Okur, Halil I; Gomopoulos, Nikolaos; Macias-Romero, Carlos; Cremer, Paul S; Petersen, Poul B; Tocci, Gabriele; Wilkins, David M; Liang, Chungwen; Ceriotti, Michele; Roke, Sylvie

    2016-04-01

    Electrolytes interact with water in many ways: changing dipole orientation, inducing charge transfer, and distorting the hydrogen-bond network in the bulk and at interfaces. Numerous experiments and computations have detected short-range perturbations that extend up to three hydration shells around individual ions. We report a multiscale investigation of the bulk and surface of aqueous electrolyte solutions that extends from the atomic scale (using atomistic modeling) to nanoscopic length scales (using bulk and interfacial femtosecond second harmonic measurements) to the macroscopic scale (using surface tension experiments). Electrolytes induce orientational order at concentrations starting at 10 μM that causes nonspecific changes in the surface tension of dilute electrolyte solutions. Aside from ion-dipole interactions, collective hydrogen-bond interactions are crucial and explain the observed difference of a factor of 6 between light water and heavy water.

  17. On-demand weighing of single dry biological particles over a 5-order-of-magnitude dynamic range.

    Science.gov (United States)

    Chan, Bin-Da; Icoz, Kutay; Huang, Wanfeng; Chang, Chun-Li; Savran, Cagri A

    2014-11-07

    We report a simple and highly versatile system to select and weigh individual dry biological particles. The system is composed of a microtweezer to pick and place individual particles and a cantilever-based resonator to weigh them. The system can weigh entities that vary from a red blood cell (~10(-11) g) to the eye-brain complex of an insect (~10(-6) g), covering a 5-order-of-magnitude mass range. Due to its versatility and ease of use, this weighing method is highly compatible with established laboratory practices. The system can provide complementary mass information for a wide variety of individual particles imaged using scanning electron microscopy and determine comparative weights of individual biological entities that are attached to microparticles as well as weigh fractions of individual biological entities that have been subjected to focused ion beam milling.

  18. Population Structure, Diversity and Reproductive Mode of the Grape Phylloxera (Daktulosphaira vitifoliae across Its Native Range.

    Directory of Open Access Journals (Sweden)

    Karl T Lund

    Full Text Available Grape Phylloxera, Daktulosphaira vitifoliae, is a gall-forming insect that feeds on the leaves and roots of many Vitis species. The roots of the cultivated V. vinifera cultivars and hybrids are highly susceptible to grape phylloxera feeding damage. The native range of this insect covers most of North America, and it is particularly abundant in the eastern and central United States. Phylloxera was introduced from North America to almost all grape-growing regions across five of the temperate zone continents. It devastated vineyards in each of these regions causing large-scale disruptions to grape growers, wine makers and national economies. In order to understand the population diversity of grape phylloxera in its native range, more than 500 samples from 19 States and 34 samples from the introduced range (northern California, Europe and South America were genotyped with 32 simple sequence repeat markers. STRUCTURE, a model based clustering method identified five populations within these samples. The five populations were confirmed by a neighbor-joining tree and principal coordinate analysis (PCoA. These populations were distinguished by their Vitis species hosts and their geographic locations. Samples collected from California, Europe and South America traced back to phylloxera sampled in the northeastern United States on V. riparia, with some influence from phylloxera collected along the Atlantic Coast and Central Plains on V. vulpina. Reproductive statistics conclusively confirmed that sexual reproduction is common in the native range and is combined with cyclical parthenogenesis. Native grape phylloxera populations were identified to be under Hardy-Weinberg equilibrium. The identification of admixed samples between many of these populations indicates that shared environments facilitate sexual reproduction between different host associated populations to create new genotypes of phylloxera. This study also found that assortative mating might

  19. Associative structure of second-order conditioning in humans.

    Science.gov (United States)

    Craddock, Paul; Wasserman, Jessica S; Polack, Cody W; Kosinski, Thierry; Renaux, Charlotte; Miller, Ralph R

    2017-11-03

    Second-order conditioning (SOC; i.e., conditioned responding to S2 as a result of S1-US pairings followed by S2-S1 pairings) is generally explained by either a direct S2→US association or by an associative chain (i.e., S2→S1→US). Previous research found that differences in responses to S2 after S1 was extinguished often depended on the nature of the S2-S1 pairings (i.e., sequential or simultaneous). In two experiments with human participants, we examined the possibility that such differences result from S1 evoking S2 during extinction of S1 following simultaneous but not sequential S2-S1 pairings. This evocation of S2 by S1 following simultaneous pairings may have paired the evoked representation of S2 with absence of the outcome, thereby facilitating mediated extinction of S2. Using sequential S2-S1 pairings, both Experiments 1 and 2 failed to support this account of how extinction of S1 reduced responding to S2. Experiment 1 found that extinguishing S1 reduced responding to S2, while extinguishing S2 had little effect on responses to S1, although forward evocation of S1 during extinction of S2 paired the evoked representation of S1 with absence of the outcome. In Experiment 2, evocation of S2 during S1 nonreinforced trials was prevented because S2-S1 pairings followed (rather than proceeded) S1-alone exposures. Nevertheless, responding to S2 at test mimicked S1 responding. Responding to S2 was high in the context in which S1 had been reinforced and low in the context in which S1 had been nonreinforced. Collectively, these experiments provide additional support for the associative-chain account of SOC.

  20. Understanding the Cu-Zn brass alloys using a short-range-order cluster model: significance of specific compositions of industrial alloys

    Science.gov (United States)

    Hong, H. L.; Wang, Q.; Dong, C.; Liaw, Peter K.

    2014-11-01

    Metallic alloys show complex chemistries that are not yet understood so far. It has been widely accepted that behind the composition selection lies a short-range-order mechanism for solid solutions. The present paper addresses this fundamental question by examining the face-centered-cubic Cu-Zn α-brasses. A new structural approach, the cluster-plus-glue-atom model, is introduced, which suits specifically for the description of short-range-order structures in disordered systems. Two types of formulas are pointed out, [Zn-Cu12]Zn1~6 and [Zn-Cu12](Zn,Cu)6, which explain the α-brasses listed in the American Society for Testing and Materials (ASTM) specifications. In these formulas, the bracketed parts represent the 1st-neighbor cluster, and each cluster is matched with one to six 2nd-neighbor Zn atoms or with six mixed (Zn,Cu) atoms. Such a cluster-based formulism describes the 1st- and 2nd-neighbor local atomic units where the solute and solvent interactions are ideally satisfied. The Cu-Ni industrial alloys are also explained, thus proving the universality of the cluster-formula approach in understanding the alloy selections. The revelation of the composition formulas for the Cu-(Zn,Ni) industrial alloys points to the common existence of simple composition rules behind seemingly complex chemistries of industrial alloys, thus offering a fundamental and practical method towards composition interpretations of all kinds of alloys.

  1. Synthesis, electrochemistry, STM investigation of oligothiophene self-assemblies with superior structural order and electronic properties

    Science.gov (United States)

    Kuo, Cheng-Yu; Liu, Yinghao; Yarotski, Dmitry; Li, Hao; Xu, Ping; Yen, Hung-Ju; Tretiak, Sergei; Wang, Hsing-Lin

    2016-12-01

    Three oligothiophene (terthiophene, tetrathiophene and pentathiophene) derivatives are synthesized and their monolayer self-assemblies on gold (Au) are prepared via Au-S covalent bond. Our UV-Vis experimental characterization of solution reveals the dependence of the optical properties on the conjugation length of the oligothiophenes, which compares well with Time-Dependent Density Functional Theory (TDDFT) simulations of spectra of individual chromophores. Photoluminescent spectra of thin films show pronounced red shifts compared to that of solutions, suggesting strong inter-oligomer interactions. The comparative studies of cyclic voltammograms of tetrathiophene from solution, cast film and self-assembled monolayer (SAM) indicate presence of one, two, and three oxidized species in these samples, respectively, suggesting a very strong electronic coupling between tetrathiophene molecules in the SAM. Scanning tunneling microscopy (STM) imaging of SAMs of the tetrathiophene on an atomically flat Au surface exhibits formation of monolayer assemblies with molecular order, and the molecular packing appears to show an overlay of oligothiophene molecules on top of another one. In contrast, the trimer and pentamer images show only aggregated species lacking long-range order on the molecular level. Such trends in going from disordered-ordered-disordered monolayer assemblies are mainly due to a delicate balance between inter-chromophore π-π couplings, hydrophobic interaction and the propensity to form Au-S covalent bond. Such hypothesis has been validated by our computational results suggesting different interaction patterns of oligothiophenes with odd numbered and even numbered thiophene repeat units placed in a dimer configuration. Observed correlations between oligomer geometry and structural order of monolayer assembly elucidate important structure-property relationships and have implications for these molecular structures in organic optoelectronic devices and energy

  2. Beam-based measurements of long-range transverse wakefields in the Compact Linear Collider main-linac accelerating structure

    Directory of Open Access Journals (Sweden)

    Hao Zha

    2016-01-01

    Full Text Available The baseline design of CLIC (Compact Linear Collider uses X-band accelerating structures for its main linacs. In order to maintain beam stability in multibunch operation, long-range transverse wakefields must be suppressed by 2 orders of magnitude between successive bunches, which are separated in time by 0.5 ns. Such strong wakefield suppression is achieved by equipping every accelerating structure cell with four damping waveguides terminated with individual rf loads. A beam-based experiment to directly measure the effectiveness of this long-range transverse wakefield and benchmark simulations was made in the FACET test facility at SLAC using a prototype CLIC accelerating structure. The experiment showed good agreement with the simulations and a strong suppression of the wakefields with an unprecedented minimum resolution of 0.1  V/(pC mm m.

  3. Deep crustal structure of the Cascade Range and surrounding regions from seismic refraction and magnetotelluric data

    Science.gov (United States)

    Stanley, W.D.; Mooney, W.D.; Fuis, G.S.

    1990-01-01

    Several regional seismic refraction and magnetotelluric (MT) profiles have been completed across the Cascade Range and surrounding geologic provinces in California, Oregon, and Washington. Analysis of three MT and two seismic refraction profiles in Oregon and a coincident MT and refraction profile in northern California show a high degree of correlation between resistivity and velocity models. The main feature that is evident in both data sets is a highly conductive (2-20 ohm m) zone that occurs at depths of 6-20 km and largely within a midcrustal velocity layer of 6.4-6.6 km/s, overlying a lower crust with velocities of 7.0-7.4 km/s. Accretionary structures in the southern Washington Cascades have been shown to be related to stress release in the area of Mount St. Helens. In order to explain the similar structures in the MT and refraction models for Oregon and California, a model is proposed involving the effects of metamorphic zonation to produce the velocity structure, combined with metamorphically produced fluids and partial melt to produce the deep conductor. -from Authors

  4. Short-range order and its effect on the electronic structure of binary ...

    Indian Academy of Sciences (India)

    Author Affiliations. Abhijit Mookerjee1 2 Kartick Tarafder3 Atisdipankar Chakrabarti3 4 Kamal Krishna Saha5. Department of Physics, Indian Institute of Technology, Kanpur 208 016, India; On sabbatical leave from: S.N. Bose National Center for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700 098, India; S.N. ...

  5. Short-range order and its effect on the electronic structure of binary ...

    Indian Academy of Sciences (India)

    06120. Halle (Saale), Germany. 4On sabbatical leave from: S.N. Bose National Center for Basic Sciences, JD Block,. Sector III, Salt Lake City, Kolkata 700 098, India. 5Permanent address: Ramakrishna Mission Vivekananda Centenary College ...

  6. Density dependence of hydrogen bonding and the translational-orientational structural order in supercritical water: a molecular dynamics study.

    Science.gov (United States)

    Ma, Haibo; Ma, Jing

    2011-08-07

    Molecular dynamics simulation have been performed with a wide range of densities along a near critical isotherm of supercritical water (SCW) in order to study the density dependence of the structure order and hydrogen bonding (HB). It is revealed that the translational structure order is nearly invariant while the orientational tetrahedral structure order is very sensitive to the bulk density under supercritical conditions. Meanwhile, some energetically unfavorable intermediate water dimer structures are found to appear under supercritical conditions due to the reduced energy difference and the enhanced energy fluctuation. As a consequence, a general geometrical criterion or the inclusion of a energy-based criterion instead of currently widely adopted pure r(OH)-based geometric criterion is suggested to be used in the HB statistics under supercritical conditions. It is found that the average HB number per H(2)O molecule (n(HB)) reduces with the decreasing SCW bulk density although a given pair of H(2)O molecules are shown to have a stronger ability to form a hydrogen bond under lower SCW bulk densities. Accordingly, the orientational tetrahedral structure order q decreases with the reducing bulk density under supercritical conditions. However, when the fluid is dilute with ρ ≤ 0.19ρ(c) (ρ(c) = 0.322 g/cm(3)), the energy fluctuation increases sharply and the short-range order is destroyed, signifying the supercritical fluid (SCF)-gas state transition. Accordingly, the orientational tetrahedral structure order q gets reversal around ρ = 0.19ρ(c) and approaches zero under very dilute conditions. The sensitivity of the orientational order to the density implies the microscopic origin of the significant dependence of SCF's physicochemical properties on the pressure.

  7. The Higher Order Structure of Environmental Attitudes: A Cross-Cultural Examination

    Directory of Open Access Journals (Sweden)

    Taciano L. Milfont

    2010-01-01

    Full Text Available Past research has suggested that Preservation and Utilization are the two higher order dimensions forming the hierarchical structure of environmental attitudes. This means that these two higher order dimensions could group all kinds of perceptions or beliefs regarding the natural environment people have. A crosscultural study was conducted in Brazil, New Zealand, and South Africa to test this hierarchical structure of environmental attitudes. Results from single- and multi-group confirmatory factor analyses demonstrated that environmental attitudes are a multidimensional construct, and that their first-order factors associate to each other to form a vertical structure. However, the question whether the vertical structure comprise a single higher order factor or two higher order factors still remains unanswered. These results are discussed and directions for future research trying to demonstrate that Preservation and Utilization, taken as distinct second-order environmental attitudes factors, are more empirically meaningful than a single and generalised environmental attitudes higher order factor are presented.

  8. Optically Tunable Chiral Plasmonic Guest-Host Cellulose Films Weaved with Long-range Ordered Silver Nanowires.

    Science.gov (United States)

    Chu, Guang; Wang, Xuesi; Chen, Tianrui; Gao, Jianxiong; Gai, Fangyuan; Wang, Yu; Xu, Yan

    2015-06-10

    Plasmonic materials with large chiroptical activity at visible wavelength have attracted considerable attention due to their potential applications in metamaterials. Here we demonstrate a novel guest-host chiral nematic liquid crystal film composed of bulk self-co-assembly of the dispersed plasmonic silver nanowires (AgNWs) and cellulose nanocrystals (CNCs). The AgNWs-CNCs composite films show strong plasmonic optical activities, that are dependent on the chiral photonic properties of the CNCs host medium and orientation of the guest AgNWs. Tunable chiral distribution of the aligned anisotropic AgNWs with long-range order is obtained through the CNCs liquid crystal mediated realignment. The chiral plasmonic optical activity of the AgNWs-CNCs composite films can be tuned by changing the interparticle electrostatic repulsion between the CNCs nanorods and AgNWs. We also observe an electromagnetic energy transfer phenomena among the plasmonic bands of AgNWs, due to the modulation of the photonic band gap of the CNCs host matrix. This facile approach for fabricating chiral macrostructured plasmonic materials with optically tunable property is of interest for a variety of advanced optics applications.

  9. Atomic long-range order effects on Curie temperature and adiabatic spin-wave dynamics in strained Fe-Co alloy films

    Science.gov (United States)

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

    2016-08-01

    The strained Fe-Co alloy in body-centered tetragonal (bct) structure has raised considerable interest due to its giant uniaxial magnetocrystalline anisotropy energy. On the basis of the classical Heisenberg Hamiltonian with ab initio interatomic exchange interactions, we perform a theoretical study of fundamental finite temperature magnetic properties of Fe1 -xCox alloy films as a function of three variables: chemical composition 0.3 ≤x ≤0.8 , bct geometry [a ,c (a )] arising from in-plane strain and associated out-of-plane relaxation, and atomic long-range order (ALRO). The Curie temperatures TC(x ,a ) obtained from Monte Carlo simulations display a competition between a pronounced dependence on tetragonality, strong ferromagnetism in the Co-rich alloy, and the beginning instability of ferromagnetic order in the Fe-rich alloy when c /a →√{2 } . Atomic ordering enhances TC and arises mainly due to different distributions of atoms in neighboring coordination shells rather than altering exchange interactions significantly. We investigate the ordering effect on the shape of the adiabatic spin-wave spectrum for selected pairs (x ,a ) . Our results indicate that long-wavelength acoustic spin-wave excitations show dependencies on x , a , and ALRO similar to those of TC. The directional anisotropy of the spin-wave stiffness d (x ,a ) peaks in narrow ranges of composition and tetragonality. ALRO exhibits a strong effect on d for near equiconcentration Fe-Co. We also discuss our findings in the context of employing Fe-Co as perpendicular magnetic recording medium.

  10. Self-supporting hierarchically-structured hollow ordered porous carbon spheres from spatially tangent compression.

    Science.gov (United States)

    Wu, Xiao-Feng; Cui, Yan-Bin; Liao, Yu-Chao; Chen, Yun-Fa

    2013-02-01

    Self-supporting hierarchically-structured hollow ordered porous carbon spheres (HOPCSs) have been synthesized successfully using hollow ordered mesoporous silica spheres (HOMSSs) with MCM-41 pore structure within shells as templates. The SEM and TEM observations show that the final HOPCS product presents spherical morphology with hollow interiors. The results of HRTEM, small angle X-ray Diffraction (SAXRD) and N2 adsorption-desorption isotherms confirm that the HOPCS inversely replicate the MCM41 hexagonally-stacked ordered microstructures within shells and possess the ordered porosity. Furthermore, the formation of ordered porous structures within HOPCSs is due to the two aspects below: (i) the inverse carbonaceous replicas filling in hexagonally-stacked mesopores in HOMSSs are compacted tangentially due to curvature difference along the radial direction, self-supporting ordered porous structures after removing silica template; (ii) the additional carbon deposition layers exist on the outside surface of the replicas, cooperatively cementing the carbon fillers.

  11. Local Order-Disorder Transition Driving by Structural Heterogeneity in a Benzyl Functionalized Ionic Liquid.

    Science.gov (United States)

    Faria, Luiz F O; Paschoal, Vitor H; Lima, Thamires A; Ferreira, Fabio F; Freitas, Rafael S; Ribeiro, Mauro C C

    2017-10-26

    A local order-disorder transition has been disclosed in the thermophysical behavior of the ionic liquid 1-benzyl-3-methylimidazolium dicyanamide, [Bzmim][N(CN)2], and its microscopic nature revealed by spectroscopic techniques. Differential scanning calorimetry and specific heat measurements show a thermal event of small enthalpy variation taking place in the range 250-260 K, which is not due to crystallization or melting. Molecular dynamic simulations and X-ray diffraction measurements have been used to discuss the segregation of domains in the liquid structure of [Bzmim][N(CN)2]. Raman and NMR spectroscopy measurements as a function of temperature indicate that the microscopic origin of the event observed in the calorimetric measurements comes from structural rearrangement involving the benzyl group. The results indicate that the characteristic structural heterogeneity allow for rearrangements within local domains implying the good glass-forming ability for the low viscosity ionic liquid [Bzmim][N(CN)2]. This work sheds light on our understanding of the microscopic origin behind complex thermal behavior of ionic liquids.

  12. What makes an analogy difficult? The effects of order and causal structure on analogical mapping.

    Science.gov (United States)

    Keane, M T

    1997-07-01

    In 4 experiments, the author tested 2 factors that affect the difficulty of analogies: order of presentation of information and causal structure. Experiments 1, 2, and 4 showed robust order effects for the positioning of sentences-sentence pairs in a variety of mapping problems. Experiments 2, 3, and 4 revealed the effects of causal structure in these analogies. Experiment 3 showed that the beneficial effects of causal structure are most marked in thematic, mapping problems presented in a casual question-answering context. Experiment 4 dealt with the interaction between order and causal structure and showed that order effects occur only in the presence of causal structure. Of all the analogy models in the literature, the incremental analogy machine is the best predictor of these results.

  13. V-structures of ethylene glycol and monoethanolamine in the temperature range of the liquid phase

    Science.gov (United States)

    Balabaev, N. K.; Rodnikova, M. N.; Solonina, I. A.; Shirokova, E. V.; Sirotkin, D. A.

    2017-01-01

    Vibration-averaged V-structures for liquid ethylene glycol (EG) and monoethanolamine (MEA) are found in the temperature range of the solvents' liquid phase by means of molecular dynamics. The obtained V-structures' characteristics are compared to X-ray diffraction data on the crystalline phases of these compounds. Good agreement between theoretical and experimental data is observed. The V-structures are compared to that of water.

  14. A New Technique to Compute Long-Range Wakefields in Accelerating Structures

    CERN Document Server

    Raguin, J Y; Wuensch, Walter

    2002-01-01

    A new technique is proposed to compute the coupling impedances and the long-range wakefields based on a scattering-matrix formalism which relies heavily upon post-processed data from the commercial finite-element code HFSS. To illustrate the speed of this technique, the procedures to compute the long-range wakefields of conventional constant-impedance structures and of structures damped with waveguides are presented. The efficiency and accuracy of the technique is achieved because the characteristics of periodic structures can be computed using single-cell data. Damping and synchronism effects are determined from such a computation.

  15. Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, Satoshi; Ranjan, Mukesh; Heinig, Karl-Heinz; Facsko, Stefan; Smith, Roger, E-mail: s.numazawa@hzdr.de [Helmholtz-Zentrum Dresden Rossendorf (HZDR), Institut fuer Ionenstrahlphysik und Materialforschung, PO Box 510119, 01314 Dresden (Germany)

    2011-06-08

    Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO{sub 2} surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and {approx}1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns. (fast track communication)

  16. Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO2.

    Science.gov (United States)

    Numazawa, Satoshi; Ranjan, Mukesh; Heinig, Karl-Heinz; Facsko, Stefan; Smith, Roger

    2011-06-08

    Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO(2) surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and ≈1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns.

  17. Pore Structure Control of Ordered Mesoporous Silica Film Using Mixed Surfactants

    Directory of Open Access Journals (Sweden)

    Tae-Jung Ha

    2011-01-01

    Full Text Available Materials with nanosized and well-arranged pores have been researched actively in order to be applied to new technology fields. Especially, mesoporous material containing various pore structures is expected to have different pore structure. To form a mixed pore structure, ordered mesoporous silica films were prepared with a mixture of surfactant; Brij-76 and P-123 block copolymer. In mixed surfactant system, mixed pore structure was observed in the region of P-123/(Brij-76 + P-123 with about 50.0 wt.% while a single pore structure was observed in regions which have large difference in ratio between Brij-76 and P-123 through the X-ray diffraction analysis. Regardless of surfactant ratio, porosity was retained almost the same. It is expected that ordered mesoporous silica film with mixed pore structure can be one of the new materials which has distinctive properties.

  18. Experimental Verification of Van Vleck Nature of Long-Range Ferromagnetic Order in Vanadium-Doped Three-Dimensional Topological Insulator Sb2Te3

    Science.gov (United States)

    2015-01-01

    Experimental Verification of Van Vleck Nature of Long-Range Ferromagnetic Order in Vanadium-Doped Three-Dimensional Topological Insulator Sb2Te3...spectroscopy (EELS) measurements that the long range ferromagnetic (FM) order in vanadium (V)-doped topological insulator Sb2Te3 has the nature of van...Vleck-type ferromagnetism . The positions and the relative amplitudes of two core-level peaks (L3 and L2) of the V EELS spectrum show unambiguous change

  19. Range-separated time-dependent density-functional theory with a frequency-dependent second-order Bethe-Salpeter correlation kernel

    CERN Document Server

    Rebolini, Elisa

    2015-01-01

    We present a range-separated linear-response time-dependent density-functional theory (TDDFT) which combines a density-functional approximation for the short-range response kernel and a frequency-dependent second-order Bethe-Salpeter approximation for the long-range response kernel. This approach goes beyond the adiabatic approximation usually used in linear-response TDDFT and aims at improving the accuracy of calculations of electronic excitation energies of molecular systems. A detailed derivation of the frequency-dependent second-order Bethe-Salpeter correlation kernel is given using many-body Green-function theory. Preliminary tests of this range-separated TDDFT method are presented for the calculation of excitation energies of four small molecules: N2, CO2, H2CO, and C2H4. The results suggest that the addition of the long-range second-order Bethe-Salpeter correlation kernel overall slightly improves the excitation energies.

  20. Fe2+-Ti4+ vs. Fe2+-Fe3+ charge-transfer and short-range order in single chains of face-sharing octahedra: ellenbergerite and dumortierite

    Science.gov (United States)

    Chopin, C.; Langer, K.; Khomenko, V.

    2009-04-01

    In zoned pyrope megacrysts from the Dora-Maira UHP terrane, new, dark-violet colour varieties of the hexagonal, high-pressure silicate ellenbergerite extend the range of known Fe contents for this mineral from 0-0.1 to 0-0.4 atom pfu, for Ti contents commonly in the range 0.2-0.4 pfu. The new varieties show an extremely intense pleochroism, colourless for E perpendicular to c to deep Prussian blue for E//c, as compared to colourless to lilac or reddish purple for classical Fe-poor ellenbergerite. These features were the incentive for an electronic absorption spectroscopic study and a reappraisal of the interpretation of the charge transfers (CT), colour and ordering schemes in this group and the structurally related borosilicate dumortierite. Both structures are characterized by the presence of infinite single chains of face-sharing, partly vacant octahedra along the 6-fold screw axis and pseudo-hexad axis, respectively, in which the Fe and Ti atoms are partitioned. In the spectra of Fe-poor ellenbergerite, the presence of a single Fe2+-Ti4+ CT band near 19000 cm˘1 was taken as evidence for complete short-range ordering of Mg(Fe), Ti and vacancies in the octahedral single chain [1]. The E//c spectra of Fe-rich ellenbergerite show the same absorption band near 19000 cm˘1 but consistently flanked by another CT band near 14000 cm˘1 , the intensity of which increases with total Fe content. The latter is similar to the 12400 cm˘1 CT band observed as the single feature in E//c spectra of the isotructural (Ti-free and Fe-bearing) phosphoellenbergerite, and clearly assigned to Fe2+-Fe3+ CT in the octahedral single chain [1]. The same colour pattern occurs in the dumortierite group, with red Fe-poor, Ti-rich crystals showing a single CT band near 20000 cm˘1, blue Ti-poor crystals showing a single CT band near 16500 cm˘1, and violet Fe- and Ti-rich crystals showing a combination of the two bands [2]. In the light of the new data, we reinterpret the dumortierite colour

  1. Identification of fractional-order systems with unknown initial values and structure

    Science.gov (United States)

    Du, Wei; Miao, Qingying; Tong, Le; Tang, Yang

    2017-06-01

    In this paper, the identification problem of fractional-order chaotic systems is proposed and investigated via an evolutionary optimization approach. Different with other studies to date, this research focuses on the identification of fractional-order chaotic systems with not only unknown orders and parameters, but also unknown initial values and structure. A group of fractional-order chaotic systems, i.e., Lorenz, Lü, Chen, Rössler, Arneodo and Volta chaotic systems, are set as the system candidate pool. The identification problem of fractional-order chaotic systems in this research belongs to mixed integer nonlinear optimization in essence. A powerful evolutionary algorithm called composite differential evolution (CoDE) is introduced for the identification problem presented in this paper. Extensive experiments are carried out to show that the fractional-order chaotic systems with unknown initial values and structure can be successfully identified by means of CoDE.

  2. Higher-order structure of the 30-nm chromatin fiber revealed by cryo-EM.

    Science.gov (United States)

    Zhu, Ping; Li, Guohong

    2016-11-01

    Genomic DNA is hierarchically packaged into chromatin in eukaryotes. As a central-level chromatin structure between nucleosomal arrays and higher order organizations, 30 nm chromatin fiber, and its dynamics play a crucial role in regulating DNA accessibility for gene transcription. However, despite extensive efforts over three decades, the higher-order structure of the 30 nm chromatin fiber remains unresolved and controversial. We have recently reconstituted the 30 nm chromatin fibers from 12 nucleosomal arrays in vitro in the presence of linker histone H1, and determined their cryo-EM structures at resolution of 11 Å (Song et al., Science 344, 376-380). Here, we briefly reviewed the higher-order structure studies of chromatin fibers, mainly focusing on the insights from the cryo-EM structures we recently solved. © 2016 IUBMB Life, 68(11):873-878, 2016. © 2016 International Union of Biochemistry and Molecular Biology.

  3. Fractal Dimension Analysis of Higher-Order Mode Shapes for Damage Identification of Beam Structures

    OpenAIRE

    Bai, Runbo; Cao, Maosen; Su, Zhongqing; Ostachowicz, Wieslaw; Xu, Hao

    2012-01-01

    Fractal dimension analysis is an emerging method for vibration-based structural damage identification. An unresolved problem in this method is its incapability of identifying damage by higher-order mode shapes. The natural inflexions of higher-order mode shapes may cause false peaks of high-magnitude estimates of fractal dimension, largely masking any signature of damage. In the situation of a scanning laser vibrometer (SLV) providing a chance to reliably acquire higher-order (around tenth-or...

  4. Examination of Short- and Long-Range Atomic Order Nanocrystalline SiC and Diamond by Powder Diffraction Methods

    Science.gov (United States)

    Palosz, B.; Grzanka, E.; Stelmakh, S.; Gierlotka, S.; Weber, H.-P.; Proffen, T.; Palosz, W.

    2002-01-01

    The real atomic structure of nanocrystals determines unique, key properties of the materials. Determination of the structure presents a challenge due to inherent limitations of standard powder diffraction techniques when applied to nanocrystals. Alternate methodology of the structural analysis of nanocrystals (several nanometers in size) based on Bragg-like scattering and called the "apparent lattice parameter" (alp) is proposed. Application of the alp methodology to examination of the core-shell model of nanocrystals will be presented. The results of application of the alp method to structural analysis of several nanopowders were complemented by those obtained by determination of the Atomic Pair Distribution Function, PDF. Based on synchrotron and neutron diffraction data measured in a large diffraction vector of up to Q = 25 Angstroms(exp -1), the surface stresses in nanocrystalline diamond and SiC were evaluated.

  5. Surfing in tortoises? Empirical signs of genetic structuring owing to range expansion

    Science.gov (United States)

    Graciá, Eva; Botella, Francisco; Anadón, José Daniel; Edelaar, Pim; Harris, D. James; Giménez, Andrés

    2013-01-01

    Much of our current knowledge about the genetic dynamics in range expansions originates from models, simulations and microcosm experiments that need to be corroborated by field data. Here, we report a neutral genetic pattern that matches the predictions of the genetic surfing theory. Genetic surfing occurs when repeated founding events and genetic drift act on the wave of advance of an expanding population, promoting strong spatial structure. In the range expansion of the tortoise Testudo graeca from North Africa to southeastern Spain, we found several genetic signatures consistent with surfing: a decrease of genetic diversity with distance from the initial founder area, clinal patterns in allele frequencies, rare African alleles which have become common at distal sites in the Spanish range, and stronger spatial differentiation in the expanded range than in the original one. Our results provide support for the theory that genetic drift can be an important force in shaping the genetic structure of expanding populations. PMID:23554278

  6. Detection and characterization of symmetry-broken long-range orders in the spin-1/2 triangular Heisenberg model

    Science.gov (United States)

    Saadatmand, S. N.; McCulloch, I. P.

    2017-08-01

    We present new numerical tools to analyze symmetry-broken phases in the context of SU (2 ) -symmetric translation-invariant matrix product states (MPS) and density-matrix renormalization-group (DMRG) methods for infinite cylinders, and determine the phase diagram of the geometrically frustrated triangular Heisenberg model with nearest- and next-nearest-neighbor (NN and NNN) interactions. The appearance of Nambu-Goldstone modes in the excitation spectrum is characterized by "tower of states" levels in the momentum-resolved entanglement spectrum. Symmetry-breaking phase transitions are detected by a combination of the correlation lengths and second and fourth cumulants of the magnetic order parameters (which we call the Binder ratio), even though symmetry implies that the order parameter itself is strictly zero. Using this approach, we have identified a 120∘ order, a columnar order, and an algebraic spin liquid (specific to width-6 systems), alongside the previously studied topological spin liquid phase. For the latter, we also demonstrate robustness against chiral perturbations.

  7. Exact equations for structure functions and equations for source terms up to the sixth order

    CERN Document Server

    Peters, Norbert; Gauding, Michael; Göbbert, Jens Henrik; Pitsch, Heinz

    2015-01-01

    We derive equations for the source terms appearing in structure function equations for the fourth and sixth order under the assumption of homogeneity and isotropy. The source terms can be divided into two classes, namely those stemming from the viscous term and those from the pressure term in the structure function equations. Both kinds are unclosed.

  8. Representing Block-structured Process Models as Order Matrices: Basic Concepts, Formal Properties, Algorithms

    NARCIS (Netherlands)

    Li, C.; Reichert, M.U.; Wombacher, Andreas

    2009-01-01

    In various cases we need to transform a process model into a matrix representation for further analysis. In this paper, we introduce the notion of Order Matrix, which enables unique representation of block-structured process models. We present algorithms for transforming a block-structured process

  9. Crystal structure of a small heat-shock protein from Xylella fastidiosa reveals a distinct high-order structure.

    Science.gov (United States)

    Fonseca, Emanuella Maria Barreto; Scorsato, Valéria; Dos Santos, Marcelo Leite; Júnior, Atilio Tomazini; Tada, Susely Ferraz Siqueira; Dos Santos, Clelton Aparecido; de Toledo, Marcelo Augusto Szymanski; de Souza, Anete Pereira; Polikarpov, Igor; Aparicio, Ricardo

    2017-04-01

    Citrus variegated chlorosis is a disease that attacks economically important citrus plantations and is caused by the plant-pathogenic bacterium Xylella fastidiosa. In this work, the structure of a small heat-shock protein from X. fastidiosa (XfsHSP17.9) is reported. The high-order structures of small heat-shock proteins from other organisms are arranged in the forms of double-disc, hollow-sphere or spherical assemblies. Unexpectedly, the structure reported here reveals a high-order architecture forming a nearly square cavity.

  10. Effect of short-range order on magnetic and transport properties of Fe2MnGa Heusler alloy films

    Science.gov (United States)

    Kudryavtsev, Y. V.; Melnyk, A. K.; Trachevskyi, V. V.; Gościańska, I.; Dubowik, J.

    2017-11-01

    Fe56Mn20Ga24, Fe46Mn35Ga19 and Fe39Mn25Ga36 Heusler alloy (HA) films are investigated. It is shown that as-deposited Fe-Mn-Ga films are fine crystalline with a body-centered cubic (BCC) structure. Annealing of the films leads to the formation of a face-centered cubic (FCC) structure. The BCC to FCC transformation results in a drastic increase in the magnetization, the Curie temperature as well as in a change of the sign of temperature coefficient of resistivity from negative to positive. These effects are discussed in terms of band structures of L21 and L12 phases of stoichiometric Fe2MnGa HA.

  11. Atomic Resolution Imaging of Nanoscale Structural Ordering in a Complex Metal Oxide Catalyst

    KAUST Repository

    Zhu, Yihan

    2012-08-28

    The determination of the atomic structure of a functional material is crucial to understanding its "structure-to-property" relationship (e.g., the active sites in a catalyst), which is however challenging if the structure possesses complex inhomogeneities. Here, we report an atomic structure study of an important MoVTeO complex metal oxide catalyst that is potentially useful for the industrially relevant propane-based BP/SOHIO process. We combined aberration-corrected scanning transmission electron microscopy with synchrotron powder X-ray crystallography to explore the structure at both nanoscopic and macroscopic scales. At the nanoscopic scale, this material exhibits structural and compositional order within nanosized "domains", while the domains show disordered distribution at the macroscopic scale. We proposed that the intradomain compositional ordering and the interdomain electric dipolar interaction synergistically induce the displacement of Te atoms in the Mo-V-O channels, which determines the geometry of the multifunctional metal oxo-active sites.

  12. Synthesis, electrochemistry, STM investigation of oligothiophene self-assemblies with superior structural order and electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Cheng-Yu [C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Liu, Yinghao; Yarotski, Dmitry [Center of Integrated Nanotechnologies, Materials Physics and Application Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, Hao [Theory Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Xu, Ping; Yen, Hung-Ju [C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Tretiak, Sergei, E-mail: serg@lanl.gov [Theory Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Wang, Hsing-Lin, E-mail: hwang@lanl.gov [C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2016-12-20

    Graphical abstract: STM imaging reveals differently oriented domains of self-assembled tetrathiophene molecules. - Highlights: • Optical and redox properties of oligothiophene derivatives are studied. • Packing pattern of self-assembly monolayer depends on the conjugation length. • Strong electronic coupling and three redox couples in cyclic voltamogram are observed in the hierarchical self-assembly. - Abstract: Three oligothiophene (terthiophene, tetrathiophene and pentathiophene) derivatives are synthesized and their monolayer self-assemblies on gold (Au) are prepared via Au–S covalent bond. Our UV–Vis experimental characterization of solution reveals the dependence of the optical properties on the conjugation length of the oligothiophenes, which compares well with Time-Dependent Density Functional Theory (TDDFT) simulations of spectra of individual chromophores. Photoluminescent spectra of thin films show pronounced red shifts compared to that of solutions, suggesting strong inter-oligomer interactions. The comparative studies of cyclic voltammograms of tetrathiophene from solution, cast film and self-assembled monolayer (SAM) indicate presence of one, two, and three oxidized species in these samples, respectively, suggesting a very strong electronic coupling between tetrathiophene molecules in the SAM. Scanning tunneling microscopy (STM) imaging of SAMs of the tetrathiophene on an atomically flat Au surface exhibits formation of monolayer assemblies with molecular order, and the molecular packing appears to show an overlay of oligothiophene molecules on top of another one. In contrast, the trimer and pentamer images show only aggregated species lacking long-range order on the molecular level. Such trends in going from disordered–ordered–disordered monolayer assemblies are mainly due to a delicate balance between inter-chromophore π–π couplings, hydrophobic interaction and the propensity to form Au–S covalent bond. Such hypothesis has been

  13. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    OpenAIRE

    Badri Shyam; Stone, Kevin H.; Riccardo Bassiri; Martin M. Fejer; Toney, Michael F.; Apurva Mehta

    2016-01-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50?100?nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next g...

  14. Natural nano-structures on insects—possible functions of ordered arrays characterized by atomic force microscopy

    Science.gov (United States)

    Watson, G. S.; Watson, J. A.

    2004-07-01

    Naturally occurring nano-structures is a much-neglected, but potentially rich, source of products that meet specifications imposed by natural selection. While the pharmaceutical industry has long recognized the value of natural compounds, the emerging industries based on nanotechnology have so far made little use of 'free' technology that has been 'invented' over evolutionary time-scales and driven by the imperatives of species survival. Ordered hexagonal packed array structures on cicada (e.g., Pflatoda claripennis) and termite (e.g., family Rhinotermitidae) wings have been investigated in this study. The spacings range from 200 to 1000 nm. The structures tend to have a rounded shape at the apex and protrude some 150-350 nm out from the surface plane. Wing structures with spacings at the lower end of the range are most likely optimized to serve as an anti-reflective coating (natural 'stealth technology') but may also act as a self-cleaning coating (the Lotus effect). Structures with spacings at the upper end of the range may provide mechanical strength to prevent load failure under flight and/or aid in the aerodynamic efficiency of the insect. This study demonstrates the multi-purpose design of natural structures.

  15. Broadband high-efficiency zero-order surface grating coupler for the near- and mid-infrared wavelength ranges

    Science.gov (United States)

    Sánchez-Postigo, Alejandro; Wangüemert-Pérez, J. Gonzalo; Luque-González, José Manuel; Molina-Fernández, Íñigo; Cheben, Pavel; Alonso-Ramos, Carlos A.; Halir, Robert; Schmid, Jens H.; Ortega-Moñux, Alejandro

    2017-05-01

    Efficient coupling of light from a chip into an optical fiber is a major issue in silicon photonics, as the dimensions of high-index-contrast photonic integrated waveguides are much smaller than conventional fiber diameters. Surface grating couplers address the coupling problem by radiating the optical power from a waveguide through the surface of the chip to the optical fiber, or vice versa. However, since the grating radiation angle substantially varies with the wavelength, conventional surface grating couplers cannot offer high coupling efficiency and broad bandwidth simultaneously. To overcome this limitation, for the near-infrared band we have recently proposed SOI-based zero-order grating couplers, which, making use of a subwavelength-engineered waveguide and a high-index prism, suppress the explicit dependence between the radiation angle and the wavelength, achieving a 1-dB bandwidth of 126 nm at λ = 1.55 μm. However, in the near-infrared, the bandwidth enhancement of zero-order grating couplers is limited by the effective index wavelength dispersion of the grating. In the mid-infrared spectral region, the waveguide dispersion is lower, alleviating the bandwidth limitation. Here we demonstrate numerically our zero-order grating coupler concept in the mid-infrared at λ = 3.8 μm. Several couplers for the silicon-on-insulator and the germanium-on-silicon nitride platforms are designed and compared, with subdecibel coupling efficiencies and 1-dB bandwidths up to 680 nm.

  16. Order reduction for models of space structures using modal cost analysis

    Science.gov (United States)

    Skelton, R. E.; Hughes, P. C.; Hablani, H. B.

    1982-01-01

    Modal cost analysis furnishes a promising methodology for developing dynamical models of space structures for use in control systems analysis. Economy and accuracy can be attained by only retaining vibration modes that contribute significantly to an appropriately defined cost function. Expressions for modal costs (especially simple for 'lightly damped' structures) are derived for attitude control, vibration suppression, and shape control. These techniques are illustrated through application to a high-order finite element model of a large platform-type structure.

  17. Identification of fractional-order systems with unknown initial values and structure

    Energy Technology Data Exchange (ETDEWEB)

    Du, Wei, E-mail: duwei0203@gmail.com [Key Laboratory of Advanced Control and Optimization for Chemical Processes, Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); Miao, Qingying, E-mail: qymiao@sjtu.edu.cn [School of Continuing Education, Shanghai Jiao Tong University, Shanghai 200030 (China); Tong, Le, E-mail: tongle0328@gmail.com [Faculty of Applied Science and Textiles, The Hong Kong Polytechnic University, Hong Kong (China); Tang, Yang [Key Laboratory of Advanced Control and Optimization for Chemical Processes, Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China)

    2017-06-21

    In this paper, the identification problem of fractional-order chaotic systems is proposed and investigated via an evolutionary optimization approach. Different with other studies to date, this research focuses on the identification of fractional-order chaotic systems with not only unknown orders and parameters, but also unknown initial values and structure. A group of fractional-order chaotic systems, i.e., Lorenz, Lü, Chen, Rössler, Arneodo and Volta chaotic systems, are set as the system candidate pool. The identification problem of fractional-order chaotic systems in this research belongs to mixed integer nonlinear optimization in essence. A powerful evolutionary algorithm called composite differential evolution (CoDE) is introduced for the identification problem presented in this paper. Extensive experiments are carried out to show that the fractional-order chaotic systems with unknown initial values and structure can be successfully identified by means of CoDE. - Highlights: • Unknown initial values and structure are introduced in the identification of fractional-order chaotic systems; • Only a series of output is utilized in the identification of fractional-order chaotic systems; • CoDE is used for the identification problem and the results are satisfactory when compared with other DE variants.

  18. Supramolecular order and structural dynamics: A STM study of 2H-tetraphenylporphycene on Cu(111)

    Science.gov (United States)

    Stark, Michael; Träg, Johannes; Ditze, Stefanie; Brenner, Wolfgang; Jux, Norbert; Steinrück, Hans-Peter; Marbach, Hubertus

    2015-03-01

    The adsorption of 2H-tetraphenylporphycene (2HTPPc) on Cu(111) was investigated by scanning tunneling microscopy (STM). At medium coverages, supramolecular ordered islands are observed. The individual 2HTPPc molecules appear as two pairs of intense protrusions which are separated by an elongated depression. In the islands, the molecules are organized in rows oriented along one of the close packed Cu(111) substrate rows; the structure is stabilized by T-type interactions of the phenyl substituents of neighboring molecules. Two types of rows are observed, namely, highly ordered rows in which all molecules exhibit the same orientation, and less ordered rows in which the molecules exhibit two perpendicular orientations. Altogether, three different azimuthal orientations of 2HTPPc are observed within one domain, all of them rotated by 15° ± 1° relative to one closed packed Cu direction. The highly ordered rows are always separated by either one or two less ordered rows, with the latter structure being the thermodynamically more stable one. The situation in the islands is highly dynamic, such that molecules in the less ordered rows occasionally change orientation, also complete highly ordered rows can move. The supramolecular order and structural dynamics are discussed on the basis of the specific molecule-substrate and molecule-molecule interactions.

  19. HIGHER ORDER FACTOR STRUCTURE OF THE WISC-IV IN A CLINICAL NEUROPSYCHOLOGICAL SAMPLE

    Science.gov (United States)

    Bodin, Doug; Pardini, Dustin A.; Burns, Thomas G.; Stevens, Abigail B.

    2010-01-01

    A confirmatory factor analysis was conducted examining the higher order factor structure of the WISC-IV scores for 344 children who participated in neuropsychological evaluations at a large children’s hospital. The WISC-IV factor structure mirrored that of the standardization sample. The second order general intelligence factor (g) accounted for the largest proportion of variance in the first-order latent factors and in the individual subtests, especially for the working memory index. The first-order processing speed factor exhibited the most unique variance beyond the influence of g. The results suggest that clinicians should not ignore the contribution of g when interpreting the first-order factors. PMID:19132580

  20. Strengthening of polymer ordered porous materials based on a layered nanocomposite internal structure.

    Science.gov (United States)

    Heng, Liping; Guo, Xieyou; Guo, Tianqi; Wang, Bin; Jiang, Lei

    2016-07-21

    Ordered porous polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered porous polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on.

  1. Structural Architecturing of the Western Khisor Range, North of Saiyiduwali: Implications for Hydrocarbon Prospects, KPK, Pakistan

    Directory of Open Access Journals (Sweden)

    Iftikhar Alam

    2015-12-01

    Full Text Available Western Khisor Range segment of the Trans-Indus ranges is a south-vergent, east-west trending foldthrust belt that protrudes southward into Himalayan foreland deep. The frontal flanks of range are characterized by east-west trending parallel to enechelon, plunging local anticlines and synclines structures. General structural style of folds was observed asymmetric to overturn and dominantly south vergent. The frontal outskirts of the study area is demarcated by a youngest partly emergent thrust fault named as Khisor Thrust. Outcrops projection to subsurface of the structural features suggests a thin-skinned tectonic mechanism for growth of the western Khisor Range where gliding surface for the frontal thrust sheet being located within the Cambrian rocks of Jhelum Group at a maximum depth of 4km. The structural evolution of the western Khisor Range is generally ascribed to southward directed thrust transferral system along the basal décollement being observed at base of the Cambrian Khewra Sandstone. Along this detachment horizon the Khewra Sandstone emplaced over the Recent alluvium and boulder bed deposits. The Khisor Thrust fault bulldozed the fore limb of the Saiyiduwali Anticline and demarcates the north-western proximity of the Punjab Foredeep. The Khisor Thrust sheet is predominantly comprised of the shallow marine rocks of Paleozoic to Mesozoic, laterally extended along the range. The stratigraphic framework of the western Khisor Range is considerably related and correlative to the eastern Trans-Indus and Salt ranges. Cambrian strata of the western Khisor Range comprise of Jhelum Group where its apex is underlain by the Permian Nilawahan and Zaluch groups rocks, consists of the Sardhai and Amb formations. The Sardhai Formation was observed 50m thick and consists of dark gray to blackish gray and black carbonaceous shale while the lower constituents of the Amb Formation contains dark gray carbonaceous and calcareous shale up to 30m thick

  2. Valence electronic structure of cobalt phthalocyanine from an optimally tuned range-separated hybrid functional

    Science.gov (United States)

    Brumboiu, Iulia Emilia; Prokopiou, Georgia; Kronik, Leeor; Brena, Barbara

    2017-07-01

    We analyse the valence electronic structure of cobalt phthalocyanine (CoPc) by means of optimally tuning a range-separated hybrid functional. The tuning is performed by modifying both the amount of short-range exact exchange (α ) included in the hybrid functional and the range-separation parameter (γ ), with two strategies employed for finding the optimal γ for each α . The influence of these two parameters on the structural, electronic, and magnetic properties of CoPc is thoroughly investigated. The electronic structure is found to be very sensitive to the amount and range in which the exact exchange is included. The electronic structure obtained using the optimal parameters is compared to gas-phase photo-electron data and GW calculations, with the unoccupied states additionally compared with inverse photo-electron spectroscopy measurements. The calculated spectrum with tuned γ , determined for the optimal value of α = 0.1 , yields a very good agreement with both experimental results and with GW calculations that well-reproduce the experimental data.

  3. Environmental constraints shaping constituent order in emerging communication systems: Structural iconicity, interactive alignment and conventionalization.

    Science.gov (United States)

    Christensen, Peer; Fusaroli, Riccardo; Tylén, Kristian

    2016-01-01

    Where does linguistic structure come from? Recent gesture elicitation studies have indicated that constituent order (corresponding to for instance subject-verb-object, or SVO in English) may be heavily influenced by human cognitive biases constraining gesture production and transmission. Here we explore the alternative hypothesis that syntactic patterns are motivated by multiple environmental and social-interactional constraints that are external to the cognitive domain. In three experiments, we systematically investigate different motivations for structure in the gestural communication of simple transitive events. The first experiment indicates that, if participants communicate about different types of events, manipulation events (e.g. someone throwing a cake) and construction events (e.g. someone baking a cake), they spontaneously and systematically produce different constituent orders, SOV and SVO respectively, thus following the principle of structural iconicity. The second experiment shows that participants' choice of constituent order is also reliably influenced by social-interactional forces of interactive alignment, that is, the tendency to re-use an interlocutor's previous choice of constituent order, thus potentially overriding affordances for iconicity. Lastly, the third experiment finds that the relative frequency distribution of referent event types motivates the stabilization and conventionalization of a single constituent order for the communication of different types of events. Together, our results demonstrate that constituent order in emerging gestural communication systems is shaped and stabilized in response to multiple external environmental and social factors: structural iconicity, interactive alignment and distributional frequency. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Beyond pairs: definition and interpretation of third-order structure in spatial point patterns.

    Science.gov (United States)

    Kaito, Chiho; Dieckmann, Ulf; Sasaki, Akira; Takasu, Fugo

    2015-05-07

    Spatial distributions of biological species are an important source of information for understanding local interactions at the scale of individuals. Technological advances have made it easier to measure these distributions as spatial point patterns, specifying the locations of individuals. Extensive attention has been devoted to analyzing the second-order structure of such point patterns by focusing on pairs of individuals, and it is well known that the local crowdedness of individuals can thus be quantified. Statistical measures such as a point pattern׳s pair correlation function or Ripley׳s K function show whether a given point pattern is clustered (excess of short-distance pairs) or overdispersed (shortage of short-distance pairs). These notions are naturally defined in comparison with control patterns exhibiting complete spatial randomness, i.e., an absence of any spatial structure. However, there is no rational reason why the analysis of point patterns should stop at the second order. In this paper, we focus on triplets of individuals in an attempt to quantify and interpret the third-order structure of a point pattern. We demonstrate that point patterns with "bandedness", in which individuals are primarily distributed within bands, can be detected by an excess of thinner triplets at a characteristic spatial scale linked to the band׳s width. In this context, we show how the generation of control patterns as a reference for gauging a test pattern׳s triplet frequencies is critical for defining and interpreting the third-order structure of point patterns. Since perfect information on a point pattern׳s second-order structure typically suffices for its unique reconstruction (up to translation, rotation, and reflection), we conjecture that it is essential to minimally coarse-grain such second-order information before using it to generate control patterns for identifying a point pattern׳s third-order structure. We recommend the further exploration of this

  5. AFM study of excimer laser patterning of block-copolymer: Creation of ordered hierarchical, hybrid, or recessed structures

    Energy Technology Data Exchange (ETDEWEB)

    Švanda, Jan; Siegel, Jakub; Švorčík, Vaclav; Lyutakov, Oleksiy, E-mail: lyutakoo@vscht.cz

    2016-05-15

    Highlights: • Combination of bottom-up (BCP separation) and top-down (laser patterning) technologies allows obtaining hierarchical structures. • Surface morphologies were determined by the order of patterning steps (laser modification, annealing, surface reconstruction). • Tuning the order of steps enables the reorientation of BCP domain at large scale, fabrication of hierarchical, hybrid or recessed structures. • The obtained structures can find potential applications in nanotechnology, plasmonics, information storage, sensors and smart surfaces. - Abstract: We report fabrication of the varied range of hierarchical structures by combining bottom-up self-assembly of block copolymer poly(styrene-block-vinylpyridine) (PS-b-P4VP) with top-down excimer laser patterning method. Different procedures were tested, where laser treatment was applied before phase separation and after phase separation or phase separation and surface reconstruction. Laser treatment was performed using either polarized laser light with the aim to create periodical pattern on polymer surface or non-polarized light for preferential removing of polystyrene (PS) part from PS-b-P4VP. Additionally, dye was introduced into one part of block copolymer (P4VP) with the aim to modify its response to laser light. Resulting structures were analyzed by XPS, UV–vis and AFM techniques. Application of polarized laser light leads to creation of structures with hierarchical, recessed or hybrid geometries. Non-polarized laser beam allows pronouncing the block copolymer phase separated structure. Tuning the order of steps or individual step conditions enables the efficient reorientation of block-copolymer domain at large scale, fabrication of hierarchical, hybrid or recessed structures. The obtained structures can find potential applications in nanotechnology, photonics, plasmonics, information storage, optical devices, sensors and smart surfaces.

  6. Ordered water structure at hydrophobic graphite interfaces observed by 4D, ultrafast electron crystallography

    Science.gov (United States)

    Yang, Ding-Shyue; Zewail, Ahmed H.

    2009-01-01

    Interfacial water has unique properties in various functions. Here, using 4-dimensional (4D), ultrafast electron crystallography with atomic-scale spatial and temporal resolution, we report study of structure and dynamics of interfacial water assembly on a hydrophobic surface. Structurally, vertically stacked bilayers on highly oriented pyrolytic graphite surface were determined to be ordered, contrary to the expectation that the strong hydrogen bonding of water on hydrophobic surfaces would dominate with suppressed interfacial order. Because of its terrace morphology, graphite plays the role of a template. The dynamics is also surprising. After the excitation of graphite by an ultrafast infrared pulse, the interfacial ice structure undergoes nonequilibrium “phase transformation” identified in the hydrogen-bond network through the observation of structural isosbestic point. We provide the time scales involved, the nature of ice-graphite structural dynamics, and relevance to properties related to confined water. PMID:19246378

  7. Protein Ordered Sequences are Formed by Random Joining of Amino Acids in Protein 0th-Order Structure, Followed by Evolutionary Process

    Science.gov (United States)

    Ikehara, Kenji

    2014-12-01

    Only random processes should occur on the primitive Earth. In contrast, many ordered sequences are synthesized according to genetic information on the present Earth. In this communication, I have proposed an idea that protein 0th-order structures or specific amino acid compositions would mediate the transfer from random process to formation of ordered sequences, after formation of double-stranded genes.

  8. Structural ordering of coal char during heat treatment and its impact on reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Feng, B.; Bhatia, S.K.; Barry, J.C.

    2002-07-01

    The effect of heat treatment on the structure of an Australian semi-anthracite char was studied between 850-1150{sup o}C using XRD, HRTEM, and electrical resistivity techniques. It was found that the carbon crystallite size in the char does not change during heat treatment, for both the raw coal and its ash-free derivative obtained by acid treatment. However, the fraction of the organized carbon in the raw coal chars, determined by XRD, increased with increase of heat treatment time and temperature, while that for the ash-free coal chars remained unchanged. This suggests the occurrence of catalytic ordering during heat treatment. Electrical resistivity of the raw coal chars decreased with heat treatment, while that of the ash-free coal chars did not vary. High resolution transmission electron micrographs depicted well-organized carbon layers surrounding iron particles. The fraction of organized carbon attains an apparent equilibrium value that increases with increase in temperature. Good temperature-independent correlation was found between the electrical resistivity and the organized carbon fraction, indicating that electrical resistivity is structure sensitive. These results suggest that the thermal deactivation is the result of a crystallite-perfecting process, which is effectively catalyzed by the inorganic matter in the coal char. It is concluded that the process is diffusion controlled, most likely involving transport of iron in the inter-crystallite nanospaces in the temperature range studied. The activation energy of this transport process is found to be low, which is corroborated by model-free correlation of the temporal variation of organized carbon fraction as well as electrical resistivity data using the superposition method, and is suggestive of surface transport of iron.

  9. Cooling rate and size effects on the medium-range structure of multicomponent oxide glasses simulated by molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Tilocca, Antonio [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

    2013-09-21

    A set of molecular dynamics simulations were performed to investigate the effect of cooling rate and system size on the medium-range structure of melt-derived multicomponent silicate glasses, represented by the quaternary 45S5 Bioglass composition. Given the significant impact of the glass degradation on applications of these materials in biomedicine and nuclear waste disposal, bulk structural features which directly affect the glass dissolution process are of particular interest. Connectivity of the silicate matrix, ion clustering and nanosegregation, distribution of ring and chain structural patterns represent critical features in this context, which can be directly extracted from the models. A key issue is represented by the effect of the computational approach on the corresponding glass models, especially in light of recent indications questioning the suitability of conventional MD approaches (that is, involving melt-and-quench of systems containing ∼10{sup 3} atoms at cooling rates of 5-10 K/ps) when applied to model these glasses. The analysis presented here compares MD models obtained with conventional and nonconventional cooling rates and system sizes, highlighting the trend and range of convergence of specific structural features in the medium range. The present results show that time-consuming computational approaches involving much lower cooling rates and/or significantly larger system sizes are in most cases not necessary in order to obtain a reliable description of the medium-range structure of multicomponent glasses. We identify the convergence range for specific properties and use them to discuss models of several glass compositions for which a possible influence of cooling-rate or size effects had been previously hypothesized. The trends highlighted here represent an important reference to obtain reliable models of multicomponent glasses and extract converged medium-range structural features which affect the glass degradation and thus their

  10. Crystal fields, disorder, and antiferromagnetic short-range order in (Yb{sub 0.24}Sn{sub 0.76})Ru

    Energy Technology Data Exchange (ETDEWEB)

    Klimczuk, T; Wang, C H; Lawrence, J M; Xu, Q; Durakiewicz, T; Ronning, F; Llobet, A; Trouw, F; Kurita, N; Tokiwa, Y; Lee, Han-oh; Booth, C H; Gardner, J S; Bauer, E D; Joyce, J J; Zandbergen, H W; Movshovich, R; Cava, R J; Thompson, J D

    2011-07-18

    We report extensive measurements on a new compound (Yb{sub 0.24}Sn{sub 0.76})Ru that crystallizes in the cubic CsCl structure. Valence band photoemission and L{sub 3} x-ray absorption show no divalent component in the 4f configuration of Yb. Inelastic neutron scattering (INS) indicates that the eight-fold degenerate J-multiplet of Yb{sup 3+} is split by the crystalline electric field (CEF) into a Γ{sub 7} doublet ground state and a Γ{sub 8} quartet at an excitation energy 20 meV. The magnetic susceptibility can be fit very well by this CEF scheme under the assumption that a Γ{sub 6} excited state resides at 32 meV; however, the Γ{sub 8}/Γ{sub 6} transition expected at 12 meV was not observed in the INS. The resistivity follows a Bloch-Grüneisen law shunted by a parallel resistor, as is typical of systems subject to phonon scattering with no apparent magnetic scattering. All of these properties can be understood as representing simple local moment behavior of the trivalent Yb ion. At 1 K, there is a peak in specific heat that is too broad to represent a magnetic phase transition, consistent with absence of magnetic reflections in neutron diffraction. On the other hand, this peak also is too narrow to represent the Kondo effect in the Γ{sub 7} ground state doublet. On the basis of the field-dependence of the specific heat, we argue that antiferromagnetic shortrange order (possibly co-existing with Kondo physics) occurs at low temperatures. The long-range magnetic order is suppressed because the Yb site occupancy is below the percolation threshold for this disordered compound.

  11. Vacancies in ordered and disordered titanium monoxide: Mechanism of B1 structure stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Kostenko, M.G. [Institute of Solid State Chemistry, The Ural Branch of the Russian Academy of Sciences, Pervomayskaya 91, Ekaterinburg 620990 (Russian Federation); Lukoyanov, A.V. [Institute of Metal Physics, The Ural Branch of the Russian Academy of Sciences, S. Kovalevskoy 18, Ekaterinburg 620990 (Russian Federation); Ural Federal University named after First President of Russia B.N. Yeltsin, Mira 19, Ekaterinburg 620002 (Russian Federation); Zhukov, V.P. [Institute of Solid State Chemistry, The Ural Branch of the Russian Academy of Sciences, Pervomayskaya 91, Ekaterinburg 620990 (Russian Federation); Rempel, A.A., E-mail: rempel@ihim.uran.ru [Institute of Solid State Chemistry, The Ural Branch of the Russian Academy of Sciences, Pervomayskaya 91, Ekaterinburg 620990 (Russian Federation); Ural Federal University named after First President of Russia B.N. Yeltsin, Mira 19, Ekaterinburg 620002 (Russian Federation)

    2013-08-15

    The electronic structure and stability of three phases of titanium monoxide TiO{sub y} with B1 type of the basic structure have been studied. Cubic phase without structural vacancies, TiO, and two phases with structural vacancies, monoclinic Ti{sub 5}O{sub 5} and cubic disordered TiO{sub 1.0}, was treated by means of first-principles calculations within the density functional theory with pseudo-potential approach based on the plane wave's basis. The ordered monoclinic phase Ti{sub 5}O{sub 5} was found to be the most stable and the cubic TiO without vacancies the less stable one. The role of structural vacancies in the titanium sublattice is to decrease the Fermi energy, the role of vacancies in the oxygen sublattice is to contribute to the appearance of Ti–Ti bonding interactions through these vacancies and to reinforce the Ti–Ti interactions close to them. Listed effects are significantly pronounced if the vacancies in the titanium and oxygen sublattices are associated in the so called “vacancy channels” which determine the formation of vacancy ordered structure of monoclinic Ti{sub 5}O{sub 5}-type. - Graphical abstract: Changes in total DOS of titanium monoxide when going from vacancy-free TiO to TiO with disordered structural vacancies and to TiO with ordered structural vacancies. Highlights: • Ordered monoclinic Ti{sub 5}O{sub 5} is the most stable phase of titanium monoxide. • Vacancy-free TiO is the less stable phase of the titanium monoxide. • Ordering of oxygen vacancies leads to the appearance of Ti–Ti bonding interactions. • Titanium vacancies contribute significantly to the decreasing of the Fermi energy.

  12. Functionalized 2D-MoS2-Incorporated Polymer Ternary Solar Cells: Role of Nanosheet-Induced Long-Range Ordering of Polymer Chains on Charge Transport.

    Science.gov (United States)

    Ahmad, Razi; Srivastava, Ritu; Yadav, Sushma; Chand, Suresh; Sapra, Sameer

    2017-10-04

    In this paper, we demonstrated the enhancement in power conversion efficiency (PCE) of solar cells based on poly(3-hexylthiophene-2,5-diyl) (P3HT)/[6,6]-phenyl C 71 butyric acid methyl ester (PC 71 BM) by incorporation of functionalized 2D-MoS 2 nanosheets (NSs) as an additional charge-transporting material. The enhancement in PCE of ternary solar cells arises due to the synergic enhancement in exciton dissociation and the improvement in mobility of both electrons and holes through the active layer of the solar cells. The improved hole mobility is attributed to the formation of the long-range ordered nanofibrillar structure of polymer phases and improved crystallinity in the presence of 2D-MoS 2 NSs. The improved electron mobility arises due to the highly conducting 2D network of MoS 2 NSs which provides additional electron transport channels within the active layer. The nanosheet-incorporated ternary blend solar cells exhibit 32% enhancement in PCE relative to the binary blend P3HT/PC 71 BM.

  13. First-order convex feasibility algorithms for iterative image reconstruction in limited angular-range X-ray CT

    CERN Document Server

    Sidky, Emil Y; Pan, Xiaochuan

    2012-01-01

    Iterative image reconstruction (IIR) algorithms in Computed Tomography (CT) are based on algorithms for solving a particular optimization problem. Design of the IIR algorithm, therefore, is aided by knowledge of the solution to the optimization problem on which it is based. Often times, however, it is impractical to achieve accurate solution to the optimization of interest, which complicates design of IIR algorithms. This issue is particularly acute for CT with a limited angular-range scan, which leads to poorly conditioned system matrices and difficult to solve optimization problems. In this article, we develop IIR algorithms which solve a certain type of optimization called convex feasibility. The convex feasibility approach can provide alternatives to unconstrained optimization approaches and at the same time allow for efficient algorithms for their solution -- thereby facilitating the IIR algorithm design process. An accelerated version of the Chambolle-Pock (CP) algorithm is adapted to various convex fea...

  14. Deuterium short-range order in Pd0.975Ag0.025D0.685 by diffuse neutron scattering

    DEFF Research Database (Denmark)

    Blaschko, O.; Klemencic, R.; Fratzl, P.

    1983-01-01

    By diffuse neutron scattering the D short-range order in a Pd0.975Ag0.025D0.685 crystal was investigated at 50 and 70K. The results are compared with the D ordering in the PdDx system previously investigated, and it is shown that the isointensity contours around the (1/2,1,0) point are similar to...

  15. Evaluation of Soil Loss and Erosion Control Measures on Ranges and Range Structures at Installations in Temperate Climates

    Science.gov (United States)

    2006-06-01

    classified as discontinu- ous loess on bedrock and are finely textured silty clays and silty loams (Noble et al. 1990). The first visit to Camp...challenge as vegetation reestablishment is diffi- cult on the remaining eroded nutrient -poor soil. Investigations of newly constructed embankments as in...concentrations through range monitoring. Camp Atterbury Soils The soils in this area are classified as discontinuous loess on bedrock. Soil surveys completed

  16. Structure of the ordered hydration of amino acids in proteins: analysis of crystal structures.

    Science.gov (United States)

    Biedermannová, Lada; Schneider, Bohdan

    2015-11-01

    Crystallography provides unique information about the arrangement of water molecules near protein surfaces. Using a nonredundant set of 2818 protein crystal structures with a resolution of better than 1.8 Å, the extent and structure of the hydration shell of all 20 standard amino-acid residues were analyzed as function of the residue conformation, secondary structure and solvent accessibility. The results show how hydration depends on the amino-acid conformation and the environment in which it occurs. After conformational clustering of individual residues, the density distribution of water molecules was compiled and the preferred hydration sites were determined as maxima in the pseudo-electron-density representation of water distributions. Many hydration sites interact with both main-chain and side-chain amino-acid atoms, and several occurrences of hydration sites with less canonical contacts, such as carbon-donor hydrogen bonds, OH-π interactions and off-plane interactions with aromatic heteroatoms, are also reported. Information about the location and relative importance of the empirically determined preferred hydration sites in proteins has applications in improving the current methods of hydration-site prediction in molecular replacement, ab initio protein structure prediction and the set-up of molecular-dynamics simulations.

  17. Structure of the ordered hydration of amino acids in proteins: analysis of crystal structures

    Science.gov (United States)

    Biedermannová, Lada; Schneider, Bohdan

    2015-01-01

    Crystallography provides unique information about the arrangement of water molecules near protein surfaces. Using a nonredundant set of 2818 protein crystal structures with a resolution of better than 1.8 Å, the extent and structure of the hydration shell of all 20 standard amino-acid residues were analyzed as function of the residue conformation, secondary structure and solvent accessibility. The results show how hydration depends on the amino-acid conformation and the environment in which it occurs. After conformational clustering of individual residues, the density distribution of water molecules was compiled and the preferred hydration sites were determined as maxima in the pseudo-electron-density representation of water distributions. Many hydration sites interact with both main-chain and side-chain amino-acid atoms, and several occurrences of hydration sites with less canonical contacts, such as carbon–donor hydrogen bonds, OH–π interactions and off-plane interactions with aromatic heteroatoms, are also reported. Information about the location and relative importance of the empirically determined preferred hydration sites in proteins has applications in improving the current methods of hydration-site prediction in molecular replacement, ab initio protein structure prediction and the set-up of molecular-dynamics simulations. PMID:26527137

  18. Structure-specific ribonucleases for MS-based elucidation of higher-order RNA structure.

    Science.gov (United States)

    Scalabrin, Matteo; Siu, Yik; Asare-Okai, Papa Nii; Fabris, Daniele

    2014-07-01

    Supported by high-throughput sequencing technologies, structure-specific nucleases are experiencing a renaissance as biochemical probes for genome-wide mapping of nucleic acid structure. This report explores the benefits and pitfalls of the application of Mung bean (Mb) and V1 nuclease, which attack specifically single- and double-stranded regions of nucleic acids, as possible structural probes to be employed in combination with MS detection. Both enzymes were found capable of operating in ammonium-based solutions that are preferred for high-resolution analysis by direct infusion electrospray ionization (ESI). Sequence analysis by tandem mass spectrometry (MS/MS) was performed to confirm mapping assignments and to resolve possible ambiguities arising from the concomitant formation of isobaric products with identical base composition and different sequences. The observed products grouped together into ladder-type series that facilitated their assignment to unique regions of the substrate, but revealed also a certain level of uncertainty in identifying the boundaries between paired and unpaired regions. Various experimental factors that are known to stabilize nucleic acid structure, such as higher ionic strength, presence of Mg(II), etc., increased the accuracy of cleavage information, but did not completely eliminate deviations from expected results. These observations suggest extreme caution in interpreting the results afforded by these types of reagents. Regardless of the analytical platform of choice, the results highlighted the need to repeat probing experiments under the most diverse possible conditions to recognize potential artifacts and to increase the level of confidence in the observed structural information.

  19. Adaptive - Synchronization of Fractional-Order Chaotic Systems with Nonidentical Structures

    Directory of Open Access Journals (Sweden)

    Li-xin Yang

    2013-01-01

    Full Text Available This paper investigates the adaptive - synchronization of the fractional-order chaotic systems with nonidentical structures. Based on the stability of fractional-order systems and adaptive control technique, a general formula for designing the controller and parameters update law is proposed to achieve adaptive - synchronization between two different chaotic systems with different structures. The effective scheme parameters identification and - synchronization of chaotic systems can be realized simultaneously. Furthermore, two typical illustrative numerical simulations are given to demonstrate the effectiveness of the proposed scheme, for each case, we design the controller and parameter update laws in detail. The numerical simulations are performed to verify the effectiveness of the theoretical results.

  20. Next-to leading order analysis of target mass corrections to structure functions and asymmetries

    Energy Technology Data Exchange (ETDEWEB)

    L. T. Brady, A. Accardi, T. J. Hobbs, W. Melnitchouk

    2011-10-01

    We perform a comprehensive analysis of target mass corrections (TMCs) to spin-averaged structure functions and asymmetries at next-to-leading order. Several different prescriptions for TMCs are considered, including the operator product expansion, and various approximations to it, collinear factorization, and xi-scaling. We assess the impact of each of these on a number of observables, such as the neutron to proton F{sub 2} structure function ratio, and parity-violating electron scattering asymmetries for protons and deuterons which are sensitive to gamma-Z interference effects. The corrections from higher order radiative and nuclear effects on the parity-violating deuteron asymmetry are also quantified.

  1. Orders of Magnitude Extension of the Effective Dynamic Range of TDC-Based TOFMS Data Through Maximum Likelihood Estimation

    Science.gov (United States)

    Ipsen, Andreas; Ebbels, Timothy M. D.

    2014-10-01

    In a recent article, we derived a probability distribution that was shown to closely approximate that of the data produced by liquid chromatography time-of-flight mass spectrometry (LC/TOFMS) instruments employing time-to-digital converters (TDCs) as part of their detection system. The approach of formulating detailed and highly accurate mathematical models of LC/MS data via probability distributions that are parameterized by quantities of analytical interest does not appear to have been fully explored before. However, we believe it could lead to a statistically rigorous framework for addressing many of the data analytical problems that arise in LC/MS studies. In this article, we present new procedures for correcting for TDC saturation using such an approach and demonstrate that there is potential for significant improvements in the effective dynamic range of TDC-based mass spectrometers, which could make them much more competitive with the alternative analog-to-digital converters (ADCs). The degree of improvement depends on our ability to generate mass and chromatographic peaks that conform to known mathematical functions and our ability to accurately describe the state of the detector dead time—tasks that may be best addressed through engineering efforts.

  2. Thermodynamic Aspects of Homogeneous Nucleation Enhanced by Icosahedral Short Range Order in Liquid Fcc-Type Alloys

    Science.gov (United States)

    Rappaz, Michel; Kurtuldu, Güven

    2015-08-01

    We have recently shown that minute solute element additions to liquid metallic alloys can strongly influence the nucleation of the fcc phase and act as a grain refinement method. Electron back-scattered diffraction observations revealed a concomitant increase in the percentage of nearest neighbor (nn) grains that are in a twin relationship. Furthermore, multiple-twinned (MT) nn grain configurations with a fivefold symmetry around a common direction have been identified, an occurrence that can be explained when the symmetry of the icosahedron is accounted for. It was then conjectured that a new nucleation mechanism occurs in two steps: first, the formation of small icosahedral quasicrystals in the melt, followed by heteroepitaxy of the fcc phase on facets of these quasicrystals. In the present contribution, based on thermodynamics arguments, it is proposed that the first step occurs by spinodal decomposition of the liquid, in a manner similar to Guinier-Preston zones formation in solid state precipitation, while the second step is a transformation of these quasicrystal precursors into MT-fcc nanocrystals once the driving force for this transformation is sufficient to overcome the fcc-liquid interfacial energy and the elastic strains associated with MT-fcc nanoparticles. This explanation sets up guidelines for finding solute elements and composition ranges that favor this grain refinement mechanism.

  3. Substrate stiffness-modulated registry phase correlations in cardiomyocytes map structural order to coherent beating

    Science.gov (United States)

    Dasbiswas, K.; Majkut, S.; Discher, D. E.; Safran, Samuel A.

    2015-01-01

    Recent experiments show that both striation, an indication of the structural registry in muscle fibres, as well as the contractile strains produced by beating cardiac muscle cells can be optimized by substrate stiffness. Here we show theoretically how the substrate rigidity dependence of the registry data can be mapped onto that of the strain measurements. We express the elasticity-mediated structural registry as a phase-order parameter using a statistical physics approach that takes the noise and disorder inherent in biological systems into account. By assuming that structurally registered myofibrils also tend to beat in phase, we explain the observed dependence of both striation and strain measurements of cardiomyocytes on substrate stiffness in a unified manner. The agreement of our ideas with experiment suggests that the correlated beating of heart cells may be limited by the structural order of the myofibrils, which in turn is regulated by their elastic environment.

  4. Electrohydrodynamic Direct-Write Orderly Micro/Nanofibrous Structure on Flexible Insulating Substrate

    Directory of Open Access Journals (Sweden)

    Jiang-Yi Zheng

    2014-01-01

    Full Text Available AC pulse-modulated electrohydrodynamic direct-writing (EDW was utilized to direct-write orderly micro/nanofibrous structure on the flexible insulating polyethylene terephthalate (PET substrate. During the EDW process, AC electrical field induced charges to reciprocate along the jet and decreased the charge repulsive force that applied on charged jet. Thanks to the smaller charge repulsive force, stable straight jet can be built up to direct-write orderly micro/nanofibrous structures on the insulating substrate. The minimum motion velocity required to direct-write straight line fibrous structure on insulating PET substrate was 700 mm/s. Moreover, the influences of AC voltage amplitude, frequency, and duty cycle ratio on the line width of fibrous structures were investigated. This work proposes a novel solution to overcome the inherent charge repulsion emerging on the insulating substrate, and promotes the application of EDW technology on the flexible electronics.

  5. TAR cloning: insights into gene function, long-range haplotypes and genome structure and evolution.

    Science.gov (United States)

    Kouprina, Natalay; Larionov, Vladimir

    2006-10-01

    The structural and functional analysis of mammalian genomes would benefit from the ability to isolate from multiple DNA samples any targeted chromosomal segment that is the size of an average human gene. A cloning technique that is based on transformation-associated recombination (TAR) in the yeast Saccharomyces cerevisiae satisfies this need. It is a unique tool to selectively recover chromosome segments that are up to 250 kb in length from complex genomes. In addition, TAR cloning can be used to characterize gene function and genome variation, including polymorphic structural rearrangements, mutations and the evolution of gene families, and for long-range haplotyping.

  6. Effect of dislocations on the structural order parameter in a crystal upon torsional strain

    Science.gov (United States)

    Zavorotnev, Yu. D.; Zakharov, A. Yu.; Metlov, L. S.

    2017-11-01

    The interaction of the structural subsystem with dislocations upon applying an elastic torsional strain has been studied. The consideration is performed in the terms of the Landau phenomenological theory with the refusal from the approximation that the irreducible vector magnitudes are constant. It is shown that additional spatial amplitude and frequency oscillations related to the change in the magnitudes of the structural order parameter and the dislocation density appear.

  7. Neutrino-Nucleus Interactions and the Short-Range Structure of Nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Cavanna, F. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Palamara, O. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Schiavilla, R. [Old Dominion Univ., Norfolk, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Soderberg, M. [Syracuse Univ., NY (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Wiringa, R. B. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-01-08

    Improvements in theoretical modeling of Short Range structures and phenomena, and comparisons with data, will require sustained collaboration between nuclear theorists and neutrino experimentalists. The extensive history of studying this area of nuclear physics in electron- and hadron-scattering experiments, coupled with the transformative capabilities of LArTPCs to identify neutrinos, will provide a ripe opportunity for new discoveries that will further our understanding of the nucleus.

  8. High Genetic Diversity and Structured Populations of the Oriental Fruit Moth in Its Range of Origin

    OpenAIRE

    Zheng, Yan; Peng, Xiong; Liu, Gaoming; Pan, Hongyan; Dorn, Silvia; Chen, Maohua

    2013-01-01

    The oriental fruit moth Grapholita ( = Cydia) molesta is a key fruit pest globally. Despite its economic importance, little is known about its population genetics in its putative native range that includes China. We used five polymorphic microsatellite loci and two mitochondrial gene sequences to characterize the population genetic diversity and genetic structure of G. molesta from nine sublocations in three regions of a major fruit growing area of China. Larval samples were collected through...

  9. Geographic distance and mountain ranges structure freshwater protist communities on a European scalе

    OpenAIRE

    Boenigk,Jens; Wodniok,Sabina; Bock,Christina; Beisser,Daniela; Hempel,Christopher; Grossmann,Lars; Lange,Anja; Jensen,Manfred

    2018-01-01

    Protists influence ecosystems by modulating microbial population size, diversity, metabolic outputs and gene flow. In this study we used eukaryotic ribosomal amplicon diversity from 218 European freshwater lakes sampled in August 2012 to assess the effect of mountain ranges as biogeographic barriers on spatial patterns and microbial community structure in European freshwaters. The diversity of microbial communities as reflected by amplicon clusters suggested that the eukaryotic microbial inve...

  10. Local breaking of fourfold rotational symmetry by short-range magnetic order in heavily overdoped Ba (Fe1 -xCux)2As2

    Science.gov (United States)

    Wang, Weiyi; Song, Yu; Hu, Ding; Li, Yu; Zhang, Rui; Harriger, L. W.; Tian, Wei; Cao, Huibo; Dai, Pengcheng

    2017-10-01

    We investigate Cu-doped Ba (Fe1-xCux) 2As2 with transport, magnetic susceptibility, and elastic neutron scattering measurements. In the heavily Cu-doped regime where long-range stripe-type antiferromagnetic order in BaFe2As2 is suppressed, Ba (Fe1-xCux) 2As2 (0.145 ≤x ≤0.553 ) samples exhibit spin-glass-like behavior in magnetic susceptibility and insulating-like temperature dependence in electrical transport. Using elastic neutron scattering, we find stripe-type short-range magnetic order in the spin-glass region identified by susceptibility measurements. The persistence of short-range magnetic order over a large doping range in Ba (Fe1-xCux) 2As2 likely arises from local arrangements of Fe and Cu that favor magnetic order, with Cu acting as vacancies relieving magnetic frustration and degeneracy. These results indicate locally broken fourfold rotational symmetry, suggesting that stripe-type magnetism is ubiquitous in iron pnictides.

  11. Orthogonal Range Reporting: Query Lower Bounds, Optimal Structures in 3-d, and Higher Dimensional Improvements

    DEFF Research Database (Denmark)

    Afshani, Peyman; Arge, Lars Allan; Larsen, Kasper Dalgaard

    2010-01-01

    , this is not the case in higher dimensions. In this paper we provide a space optimal pointer machine data structure for 3-d orthogonal range reporting that answers queries in O(log n + k) time. Thus we settle the complexity of the problem in 3-d. We use this result to obtain improved structures in higher dimensions...... data structure for the d-dimensional orthogonal range reporting problem in the pointer machine model of computation that uses S(n) space must spend Ω((log n/ log(S(n)/n))⌊d/2⌋--1) time to answer queries. Thus, if S(n)/n is poly-logarithmic, then the query time is at least Ω((log n/ log log n)⌊d/2......Orthogonal range reporting is the problem of storing a set of n points in d-dimensional space, such that the k points in an axis-orthogonal query box can be reported efficiently. While the 2-d version of the problem was completely characterized in the pointer machine model more than two decades ago...

  12. Linear-Space Data Structures for Range Mode Query in Arrays

    DEFF Research Database (Denmark)

    Chan, Timothy M.; Durocher, Stephane; Larsen, Kasper Green

    2012-01-01

    A mode of a multiset S is an element a in S of maximum multiplicity; that is, a occurs at least as frequently as any other element in S. Given an array A[1:n] of n elements, we consider a basic problem: constructing a static data structure that efficiently answers range mode queries on A. Each...... query consists of an input pair of indices (i, j) for which a mode of A[i:j] must be returned. The best previous data structure with linear space, by Krizanc, Morin, and Smid (ISAAC 2003), requires O(sqrt(n) loglog n) query time. We improve their result and present an O(n)-space data structure...... that supports range mode queries in O(sqrt(n / log n)) worst-case time. Furthermore, we present strong evidence that a query time significantly below sqrt(n) cannot be achieved by purely combinatorial techniques; we show that boolean matrix multiplication of two sqrt(n) by sqrt(n) matrices reduces to n range...

  13. Linear-Space Data Structures for Range Mode Query in Arrays

    DEFF Research Database (Denmark)

    Chan, Timothy M.; Durocher, Stephane; Larsen, Kasper Green

    2014-01-01

    A mode of a multiset S is an element a in S of maximum multiplicity; that is, a occurs at least as frequently as any other element in S. Given an array A[1:n] of n elements, we consider a basic problem: constructing a static data structure that efficiently answers range mode queries on A. Each...... query consists of an input pair of indices (i, j) for which a mode of A[i:j] must be returned. The best previous data structure with linear space, by Krizanc, Morin, and Smid (ISAAC 2003), requires O(sqrt(n) loglog n) query time. We improve their result and present an O(n)-space data structure...... that supports range mode queries in O(sqrt(n / log n)) worst-case time. Furthermore, we present strong evidence that a query time significantly below sqrt(n) cannot be achieved by purely combinatorial techniques; we show that boolean matrix multiplication of two sqrt(n) by sqrt(n) matrices reduces to n range...

  14. Phylogeographic structure and northward range expansion in the barnacle Chthamalus fragilis.

    Science.gov (United States)

    Govindarajan, Annette F; Bukša, Filip; Bockrath, Katherine; Wares, John P; Pineda, Jesús

    2015-01-01

    The barnacle Chthamalus fragilis is found along the US Atlantic seaboard historically from the Chesapeake Bay southward, and in the Gulf of Mexico. It appeared in New England circa 1900 coincident with warming temperatures, and is now a conspicuous member of rocky intertidal communities extending through the northern shore of Cape Cod, Massachusetts. The origin of northern C. fragilis is debated. It may have spread to New England from the northern end of its historic range through larval transport by ocean currents, possibly mediated by the construction of piers, marinas, and other anthropogenic structures that provided new hard substrate habitat. Alternatively, it may have been introduced by fouling on ships originating farther south in its historic distribution. Here we examine mitochondrial cytochrome c oxidase I sequence diversity and the distribution of mitochondrial haplotypes of C. fragilis from 11 localities ranging from Cape Cod, to Tampa Bay, Florida. We found significant genetic structure between northern and southern populations. Phylogenetic analysis revealed three well-supported reciprocally monophyletic haplogroups, including one haplogroup that is restricted to New England and Virginia populations. While the distances between clades do not suggest cryptic speciation, selection and dispersal barriers may be driving the observed structure. Our data are consistent with an expansion of C. fragilis from the northern end of its mid-19th century range into Massachusetts.

  15. Phylogeographic structure and northward range expansion in the barnacle Chthamalus fragilis

    Directory of Open Access Journals (Sweden)

    Annette F. Govindarajan

    2015-04-01

    Full Text Available The barnacle Chthamalus fragilis is found along the US Atlantic seaboard historically from the Chesapeake Bay southward, and in the Gulf of Mexico. It appeared in New England circa 1900 coincident with warming temperatures, and is now a conspicuous member of rocky intertidal communities extending through the northern shore of Cape Cod, Massachusetts. The origin of northern C. fragilis is debated. It may have spread to New England from the northern end of its historic range through larval transport by ocean currents, possibly mediated by the construction of piers, marinas, and other anthropogenic structures that provided new hard substrate habitat. Alternatively, it may have been introduced by fouling on ships originating farther south in its historic distribution. Here we examine mitochondrial cytochrome c oxidase I sequence diversity and the distribution of mitochondrial haplotypes of C. fragilis from 11 localities ranging from Cape Cod, to Tampa Bay, Florida. We found significant genetic structure between northern and southern populations. Phylogenetic analysis revealed three well-supported reciprocally monophyletic haplogroups, including one haplogroup that is restricted to New England and Virginia populations. While the distances between clades do not suggest cryptic speciation, selection and dispersal barriers may be driving the observed structure. Our data are consistent with an expansion of C. fragilis from the northern end of its mid-19th century range into Massachusetts.

  16. Second Order Nonlinear Hydroelastic Analyses of Floating Bodies - the Primary Consideration of Nonlinear Structure

    DEFF Research Database (Denmark)

    Chen, X.; Cui, W.; Jensen, Jørgen Juncher

    2003-01-01

    The theory and typical numerical results of a second order nonlinear hydroelastic analysis of floating bodies are presented in a series of papers in which only nonlinearity in fluids is considered. Under the assumption of linear fluid, the hydroelastic analysis methods of nonlinear structure...

  17. Making Ordered DNA and Protein Structures from Computer-Printed Transparency Film Cut-Outs

    Science.gov (United States)

    Jittivadhna, Karnyupha; Ruenwongsa, Pintip; Panijpan, Bhinyo

    2009-01-01

    Instructions are given for building physical scale models of ordered structures of B-form DNA, protein [alpha]-helix, and parallel and antiparallel protein [beta]-pleated sheets made from colored computer printouts designed for transparency film sheets. Cut-outs from these sheets are easily assembled. Conventional color coding for atoms are used…

  18. Band Structure and Optical Properties of Ordered AuCu3

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt; Lengkeek, H. P.

    1979-01-01

    initio band structure obtained by the relativistic linear muffin-tin orbitals method. The band calculation reveals that ordered AuCu3 has distinct copper and gold d bands positioned in and hybridizing with an s band common to copper and gold. The calculated state density is found to be in good agreement...

  19. Is Word-Order Similarity Necessary for Cross-Linguistic Structural Priming?

    Science.gov (United States)

    Chen, Baoguo; Jia, Yuefang; Wang, Zhu; Dunlap, Susan; Shin, Jeong-Ah

    2013-01-01

    This article presents two experiments employing two structural priming paradigms that investigated whether cross-linguistic syntactic priming occurred in Chinese and English passive sentences that differ in word order (production-to-production priming in Experiment 1 and comprehension-to-production priming in Experiment 2). Results revealed that…

  20. Group theory for magnetic structure determination: Recent developments and quadrupolar ordering analysis

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, W. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al.Mickiewicza 30, 30-059 Cracow (Poland)]. E-mail: sikora@novell.ftj.agh.edu.pl; Pytlik, L. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al.Mickiewicza 30, 30-059 Cracow (Poland); Bialas, F. [Nowy Sacz School of Busines-National Louis University, 33-300 Nowy Sacz (Poland); Malinowski, J. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al.Mickiewicza 30, 30-059 Cracow (Poland)

    2007-09-13

    In this paper, the recent developments in practical applications of symmetry analysis are described. The theoretical basis shortly described in Section 1 has been implemented in several computer applications, one of which is the program 'MODY-win', developed by the authors of the paper. The program calculates the so-called basis vectors of irreducible representations of a given symmetry group, which can be used for calculation of possible ordering modes. Its practical application is demonstrated on some examples, presenting the recent aspects of using the symmetry analysis to description of various types of ordering encountered in solids. The scalar-type ordering (occupation probability) is discussed shortly for occupation of interstitial sites by hydrogen atoms in inter-metallic compounds. The description of vector ordering is demonstrated on the magnetic ordering modes, with special attention focused on the freedom that is left in the structure after imposing all the symmetry constraints. In practice, the final ordering mode usually contains some free parameters that cannot be determined from the symmetry itself. The last application presented in the paper is the description of quadrupolar ordering, recently found in some compounds of 4f (5f) elements. For the latter case, an additional advantage is demonstrated by calculation of possible displacements of neighboring atoms after the establishment of non-zero quadrupolar order parameter on the central atom.

  1. Asymmetric double quantum well structure as a tunable detector in the far-infrared range

    CERN Document Server

    Shin, U; Park, M J; Lee, S J

    1999-01-01

    The eigenvalues and the wave functions of GaAs/Al sub x Ga sub 1 sub - sub x As asymmetric double quantum well structure have been calculated by using of complex energy method. Based on theoretical calculations, tuning ranges from 9 to 14 mu m are predicted for the proposed asymmetric coupled-quantum-well structure. In addition we calculated the energy eigenvalues and the wave functions of an electron in GaAs/Al sub x Ga sub 1 sub - sub x As single quantum well structure (including delta-perturbation). the variation in E sub 1 , the ground state energy eigenvalue of the electron, depends on the strength and position of the perturbation within the well.

  2. Calibration of aero-structural reduced order models using full-field experimental measurements

    Science.gov (United States)

    Perez, R.; Bartram, G.; Beberniss, T.; Wiebe, R.; Spottswood, S. M.

    2017-03-01

    The structural response of hypersonic aircraft panels is a multi-disciplinary problem, where the nonlinear structural dynamics, aerodynamics, and heat transfer models are coupled. A clear understanding of the impact of high-speed flow effects on the structural response, and the potential influence of the structure on the local environment, is needed in order to prevent the design of overly-conservative structures, a common problem in past hypersonic programs. The current work investigates these challenges from a structures perspective. To this end, the first part of this investigation looks at the modeling of the response of a rectangular panel to an external heating source (thermo-structural coupling) where the temperature effect on the structure is obtained from forward looking infrared (FLIR) measurements and the displacement via 3D-digital image correlation (DIC). The second part of the study uses data from a previous series of wind-tunnel experiments, performed to investigate the response of a compliant panel to the effects of high-speed flow, to train a pressure surrogate model. In this case, the panel aero-loading is obtained from fast-response pressure sensitive paint (PSP) measurements, both directly and from the pressure surrogate model. The result of this investigation is the use of full-field experimental measurements to update the structural model and train a computational efficient model of the loading environment. The use of reduced order models, informed by these full-field physical measurements, is a significant step toward the development of accurate simulation models of complex structures that are computationally tractable.

  3. Effect of the ordering potential on the structure of liquid alloys

    Directory of Open Access Journals (Sweden)

    Grosdidier B.

    2011-05-01

    Full Text Available The concept of “ordering or alloying potential” (J. Hafneri: from Hamiltonians to phase diagrams: Springer Berlin 1987 and R. N. Singh and F. Sommerii Rep. Prog. Phys. 60 (1997 57–150 enables the understanding of the different kind of alloys: hetero-coordinated one’s leading to compounds, homocoordinated ones leading to miscibility gap systems and substitutional alloys. The ordering potential is based on the comparison of identical atom interionic potentials (V11 and V22 and different atom interionic potential (V12 It allows the description of the demixing properties of some alloys. In order to understand the concepts, we developed our calculations by using a Lennard-Jones potential, the atomic structure being calculated by molecular dynamics simulation. We obtained surprising and unexpected results putting in evidence the time of simulation and the strength of the ordering potential.

  4. Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba2CuGe2O7 studied by neutron diffraction

    Science.gov (United States)

    Mühlbauer, S.; Brandl, G.; Mânsson, M.; Garst, M.

    2017-10-01

    Neutron diffraction on a triple-axis spectrometer and a small-angle neutron scattering instrument is used to study the magnetic phase transition in tetragonal Ba2CuGe2O7 at zero magnetic field. In addition to the incommensurate cycloidal antiferromagnetic (AFM) long-range order, we establish that weak incommensurate ferromagnetism (FM) also arises below the transition temperature TN identified by sharp Bragg peaks close to the Γ point. The intensities of both the incommensurate AFM and FM Bragg peaks vanish abruptly at TN, which is indicative of a weak first-order transition. Above TN, evidence is presented that the magnetic intensity within the tetragonal (a ,b ) plane is distributed on a ring in momentum space whose radius is determined by the incommensurate wave vector of the cycloidal order. We speculate that the associated soft fluctuations are at the origin of the weak first-order transition in the spirit of a scenario proposed by Brazovskii.

  5. Crystal structure of ZnWO{sub 4} scintillator material in the range of 3-1423 K

    Energy Technology Data Exchange (ETDEWEB)

    Trots, D M [HASYLAB at DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Senyshyn, A [Technische Universitaet Darmstadt, FB Material- und Geowissenschaften, Fachgebiet Strukturforschung, Petersenstrasse 23, D-64287 Darmstadt (Germany); Vasylechko, L [Lviv Polytechnic National University, Bandera Street 12, 79013 Lviv (Ukraine); Niewa, R [Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching bei Muenchen (Germany); Vad, T [Institut fuer Werkstoffwissenschaft, Technische Universitaet Dresden, Mommsenstrasse 13, 01062 Dresden (Germany); Mikhailik, V B; Kraus, H, E-mail: d_trots@yahoo.co, E-mail: Anatoliy.Senyshyn@frm2.tum.d [Department of Physics, University of Oxford, Oxford OX1 3RH (United Kingdom)

    2009-08-12

    The behaviour of the crystal structure of ZnWO{sub 4} was investigated by means of synchrotron and neutron powder diffraction in the range of 3-300 K. Thermal analysis showed the sample's melting around 1486 K upon heating and subsequent solidification at 1442 K upon cooling. Therefore, the structure was also investigated at 1423 K by means of neutron diffraction. It is found that the compound adopts the wolframite structure type over the whole temperature range investigated. The lattice parameters and volume of ZnWO{sub 4} at low temperatures were parametrized on the basis of the first order Grueneisen approximation and a Debye model for an internal energy. The expansivities along the a- and b-axes adopt similar values and saturate close to 8 x 10{sup -6} K{sup -1}, whereas the expansion along the c-axis is much smaller and shows no saturation up to 300 K. The minimum expansivity corresponds to the direction close to the c-axis where edge-sharing linkages of octahedra occur.

  6. Adsorbate structures and catalytic reactions studied in the torrpressure range by scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Kevin Shao-Lin [Univ. of California, Berkeley, CA (United States)

    2003-01-01

    also studied by STM on Rh(111) and Pt(111). Poisoning was found to coincide with decreased adsorbate mobility. Under ethylene hydrogenation conditions, no order is detected by STM at 300 K, as hydrogen and ethylidyne, the surface species formed by gas-phase ethylene, are too mobile. When CO is introduced, the reaction stops, and ordered structures appear on the surface. For Rh(111), the structure is predominantly a mixed c(4 x 2), though there are some areas of (2 x 2). For Pt(111), the structure is hexagonal and resembles the Moire pattern seen when Pt(111) is exposed to pure CO. From these studies it is concluded that CO poisons by stopping adsorbate mobility. This lack of adsorbate mobility prevents the adsorption of ethylene from the gas phase by hindering the creation of adsorption sites.

  7. Fractal Dimension Analysis of Higher-Order Mode Shapes for Damage Identification of Beam Structures

    Directory of Open Access Journals (Sweden)

    Runbo Bai

    2012-01-01

    Full Text Available Fractal dimension analysis is an emerging method for vibration-based structural damage identification. An unresolved problem in this method is its incapability of identifying damage by higher-order mode shapes. The natural inflexions of higher-order mode shapes may cause false peaks of high-magnitude estimates of fractal dimension, largely masking any signature of damage. In the situation of a scanning laser vibrometer (SLV providing a chance to reliably acquire higher-order (around tenth-order mode shapes, an improved fractal dimension method that is capable of treating higher-order mode shapes for damage detection is of important significance. This study proposes a sophisticated fractal dimension method with the aid of a specially designed affine transformation that is able to obviate natural inflexions of a higher-order mode shape while preserving its substantial damage information. The affine transformed mode shape facilitates the fractal dimension analysis to yield an effective damage feature: fractal dimension trajectory, in which an abruptly risking peak clearly characterizes the location and severity of the damage. This new fractal dimension method is demonstrated on multiple cracks identification in numerically simulated damage scenarios. The effectiveness of the method is experimentally validated by using a SLV to acquire higher-order mode shapes of a cracked cantilever beam.

  8. Experimental verifications of a structural damage identification technique using reduced order finite-element model

    Science.gov (United States)

    Li, Rui; Zhou, Li; Yang, Jann N.

    2010-04-01

    An objective of the structural health monitoring system is to identify the state of the structure and to detect the damage when it occurs. Analysis techniques for the damage identification of structures, based on vibration data measured from sensors, have received considerable attention. Recently, a new damage tracking technique, referred to as the adaptive quadratic sum-square error (AQSSE) technique, has been proposed, and simulation studies demonstrated that the AQSSE technique is quite effective in identifying structural damages. In this paper, the adaptive quadratic sumsquare error (AQSSE) along with the reduced-order finite-element method is proposed to identify the damages of complex structures. Experimental tests were conducted to verify the capability of the proposed damage detection approach. A series of experimental tests were performed using a scaled cantilever beam subject to the white noise and sinusoidal excitations. The capability of the proposed reduced-order finite-element based adaptive quadratic sum-square error (AQSSE) method in detecting the structural damage is demonstrated by the experimental results.

  9. The genetic structure of populations of an invading pest fruit fly, Bactrocera tryoni, at the species climatic range limit.

    Science.gov (United States)

    Gilchrist, A S; Meats, A W

    2010-08-01

    Previous population genetic studies of the Queensland fruit fly, Bactrocera tryoni Froggatt (Diptera: Tephritidae), in its central range have shown barely detectable genetic differentiation across distances of almost 3000 km (F(st)=0.003). In this study, we investigated the genetic structuring of southern border populations of B. tryoni, in the region extending from the central population to the recently colonized southern range limit. The expectation was that marginal populations would be small, fragmented population sinks, with local adaptation limited by gene flow or drift. Unexpectedly, we found that the population at the southern extreme of the range was a source population, rather than a sink, for the surrounding region. This was shown by assignment testing of recent outbreaks in an adjoining quarantine area and by indirect migration estimates. Furthermore, populations in the region had formed a latitudinal cline in microsatellite allele frequencies, spanning the region between the central population and the southern range limit. The cline has formed within 250 generations of the initial invasion and appears stable between years. We show that there is restricted gene flow in the region and that effective population sizes are of the order of 10(2)-10(3). Although the cline may result from natural selection, neutral evolutionary processes may also explain our findings.

  10. Biosonar resolving power: Echo-acoustic perception of surface structures in the submillimeter range

    Directory of Open Access Journals (Sweden)

    Ralph eSimon

    2014-02-01

    Full Text Available The minimum distance for which two points still can be separated from each other defines the resolving power of a visual system. In an echo-acoustic context, the resolving power is usually measured as the smallest perceivable distance of two reflecting surfaces on the range axis and is found to be around half a millimetre for bats employing frequency modulated echolocation calls. Only few studies measured such thresholds with physical objects, most often bats were trained on virtual echoes i.e. echoes generated and played back by a computer; moreover, bats were sitting while they received the stimuli. In these studies differences in structure depth between 200 µm and 340 µm were found. However, these low thresholds were never verified for free-flying bats and real physical objects. Here, we show behavioural evidence that the echo-acoustic resolving power for surface structures in fact can be as low as measured for computer generated echoes and even lower, sometimes below 100 µm. We found this exceptional fine discrimination ability only when one of the targets showed spectral interferences in the frequency range of the bats' echolocation call while the other target did not. This result indicates that surface structure is likely to be perceived as a spectral quality rather than being perceived strictly in the time domain. Further, it points out that sonar resolving power directly depends on the highest frequency/shortest wavelength of the signal employed.

  11. Structural provinces of the northeastern Brooks Range, Arctic National Wildlife Refuge, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, W.K.; Hanks, C.L. (Univ. of Alaska, Fairbanks (USA))

    1990-07-01

    The dominant Cenozoic structures of the northeastern Brooks Range are anticlinoria with cores of sub-Mississippian rocks, reflecting a regional north-vergent duplex with a floor thrust in the sub-Mississippian sequence and a roof thrust in the Mississippian Kayak Shale. The number of horses forming each anticlinorium and the structural style of the overlying Mississippian and younger cover sequence varies regionally, providing a basis for dividing the northeastern Brooks Range into structural provinces. In the western province, each anticlinorium contains a single horse, and shortening above the Kayak Shale was accommodated mainly by detachment folds. To the north in the Sadlerochit Mountains, the Kayak Shale is depositionally discontinuous and rocks elsewhere separated by this detachment deformed together. In the eastern province, each anticlinorium contains multiple horses, and shortening above the Kayak Shale was accommodated largely by thrust duplication of Mississippian through Triassic rocks. In the narrow central province, the Devonian Okpilak batholith was detached from its roots, internally shortened along shear zones and by penetrative strain, and transported northward. Because the Kayak Shale is locally absent, the Mississippian and younger cover sequence deformed in part penetratively along with the batholith. 13 figs.

  12. OPTICON: Pro-Matlab software for large order controlled structure design

    Science.gov (United States)

    Peterson, Lee D.

    1989-01-01

    A software package for large order controlled structure design is described and demonstrated. The primary program, called OPTICAN, uses both Pro-Matlab M-file routines and selected compiled FORTRAN routines linked into the Pro-Matlab structure. The program accepts structural model information in the form of state-space matrices and performs three basic design functions on the model: (1) open loop analyses; (2) closed loop reduced order controller synthesis; and (3) closed loop stability and performance assessment. The current controller synthesis methods which were implemented in this software are based on the Generalized Linear Quadratic Gaussian theory of Bernstein. In particular, a reduced order Optimal Projection synthesis algorithm based on a homotopy solution method was successfully applied to an experimental truss structure using a 58-state dynamic model. These results are presented and discussed. Current plans to expand the practical size of the design model to several hundred states and the intention to interface Pro-Matlab to a supercomputing environment are discussed.

  13. Fabrication Technologies of the High Gradient Accelerator Structures at 100MV/M Range

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Juwen; /SLAC; Lewandowski, James; /SLAC; Van Pelt, John; /SLAC; Yoneda, Charles; /SLAC; Gudkov, Boris; /CERN; Riddone, Germana; /CERN; Higo, Toshiyasu; /KEK, Tsukuba; Takatomi, Toshikazu; /KEK, Tsukuba

    2012-07-03

    A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of < 5 x 10{sup -7}/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed.

  14. Long-Range Correlations in Genomic DNA: A Signature of the Nucleosomal Structure

    Science.gov (United States)

    Audit, B.; Thermes, C.; Vaillant, C.; D'Aubenton-Carafa, Y.; Muzy, J. F.; Arneodo, A.

    2001-03-01

    We use the ``wavelet transform microscope'' to carry out a comparative statistical analysis of DNA bending profiles and of the corresponding DNA texts. In the three kingdoms, one reveals on both signals a characteristic scale of 100-200 bp that separates two different regimes of power-law correlations (PLC). In the small-scale regime, PLC are observed in eukaryotic, in double-strand DNA viral, and in archaeal genomes, which contrasts with their total absence in the genomes of eubacteria and their viruses. This strongly suggests that small-scale PLC are related to the mechanisms underlying the wrapping of DNA in the nucleosomal structure. We further speculate that the large scale PLC are the signature of the higher-order structure and dynamics of chromatin.

  15. Structure/Processing Relationships of Highly Ordered Lead Salt Nanocrystal Superlattices

    KAUST Repository

    Hanrath, Tobias

    2009-10-27

    We investigated the influence of processing conditions, nanocrystal/substrate interactions and solvent evaporation rate on the ordering of strongly interacting nanocrystals by synergistically combining electron microscopy and synchrotron-based small-angle X-ray scattering analysis. Spin-cast PbSe nanocrystal films exhibited submicrometer-sized supracrystals with face-centered cubic symmetry and (001)s planes aligned parallel to the substrate. The ordering of drop-cast lead salt nanocrystal films was sensitive to the nature of the substrate and solvent evaporation dynamics. Nanocrystal films drop-cast on rough indium tin oxide substrates were polycrystalline with small grain size and low degree of orientation with respect to the substrate, whereas films drop-cast on flat Si substrates formed highly ordered face-centered cubic supracrystals with close-packed (111)s planes parallel to the substrate. The spatial coherence of nanocrystal films drop-cast in the presence of saturated solvent vapor was significantly improved compared to films drop-cast in a dry environment. Solvent vapor annealing was demonstrated as a postdeposition technique to modify the ordering of nanocrystals in the thin film. Octane vapor significantly improved the long-range order and degree of orientation of initially disordered or polycrystalline nanocrystal assemblies. Exposure to 1,2-ethanedithiol vapor caused partial displacement of surface bound oleic acid ligands and drastically degraded the degree of order in the nanocrystal assembly. © 2009 American Chemical Society.

  16. Genomic mid-range inhomogeneity correlates with an abundance of RNA secondary structures

    Directory of Open Access Journals (Sweden)

    Song Jun

    2008-06-01

    Full Text Available Abstract Background Genomes possess different levels of non-randomness, in particular, an inhomogeneity in their nucleotide composition. Inhomogeneity is manifest from the short-range where neighboring nucleotides influence the choice of base at a site, to the long-range, commonly known as isochores, where a particular base composition can span millions of nucleotides. A separate genomic issue that has yet to be thoroughly elucidated is the role that RNA secondary structure (SS plays in gene expression. Results We present novel data and approaches that show that a mid-range inhomogeneity (~30 to 1000 nt not only exists in mammalian genomes but is also significantly associated with strong RNA SS. A whole-genome bioinformatics investigation of local SS in a set of 11,315 non-redundant human pre-mRNA sequences has been carried out. Four distinct components of these molecules (5'-UTRs, exons, introns and 3'-UTRs were considered separately, since they differ in overall nucleotide composition, sequence motifs and periodicities. For each pre-mRNA component, the abundance of strong local SS ( Conclusion We demonstrate that the excess of strong local SS in pre-mRNAs is linked to the little explored phenomenon of genomic mid-range inhomogeneity (MRI. MRI is an interdependence between nucleotide choice and base composition over a distance of 20–1000 nt. Additionally, we have created a public computational resource to support further study of genomic MRI.

  17. Higher order structure of short immunostimulatory oligonucleotides studied by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Dionne C.G., E-mail: dionne.c.g.klein@ntnu.no [Department of Physics, Norwegian University of Science and Technology, N-7491, Trondheim (Norway); Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7489, Trondheim (Norway); Latz, Eicke [Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7489, Trondheim (Norway); Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605 (United States); Institute of Innate Immunity, University Hospitals, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn (Germany); Espevik, Terje [Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7489, Trondheim (Norway); Stokke, Bjorn T. [Department of Physics, Norwegian University of Science and Technology, N-7491, Trondheim (Norway)

    2010-05-15

    Immunostimulatory CpG-DNA activates the innate immune system by binding to Toll-like receptor 9. Structurally different CpG-containing oligonucleotides trigger a different type of immune response while activating the same receptor. We therefore investigated the higher order structure of two different classes of immunostimulatory CpG-DNA. Class A, which contains a partly self-complementary sequence and poly-G ends, forms duplexes and nanoparticles in salt solution, while class B, which does not contain these features and is purely linear, does not form a duplex or nanoparticles. Results obtained here by high-resolution atomic force microscopy of classes A and B CpG-DNA, reflect these differences in secondary structure. Detailed structural analysis of the atomic force microscopy topographs is presented for two different sample preparation methods.

  18. Structure determination of zeolites and ordered mesoporous materials by electron crystallography.

    Science.gov (United States)

    Sun, Junliang; Zou, Xiaodong

    2010-09-28

    Structure determination of porous materials is important for understanding the materials properties and exploiting their applications. Compared to X-ray diffraction, electron crystallography has two unique advantages. Crystals that are too small to be studied by X-ray diffraction can be studied by electron crystallography. The structure factor phase information, which is lost in diffraction, can be obtained from high resolution transmission electron microscopy (HRTEM) images. Here we will present different techniques and applications of electron crystallography for structure determination of zeolites and ordered mesoporous materials, based on electron diffraction data and/or HRTEM images. Electron crystallography and X-ray diffraction are complementary in many aspects. Their combinations show great potentials for structure determination of complex porous materials.

  19. New insights into nucleosome and chromatin structure: an ordered state or a disordered affair?

    Science.gov (United States)

    Luger, Karolin; Dechassa, Mekonnen L.; Tremethick, David J.

    2012-01-01

    The compaction of genomic DNA into chromatin has profound implications for the regulation of key processes such as transcription, replication and DNA repair. Nucleosomes, the repeating building blocks of chromatin, vary in the composition of their histone protein components. This is the result of the incorporation of variant histones and post-translational modifications of histone amino acid side chains. The resulting changes in nucleosome structure, stability and dynamics affect the compaction of nucleosomal arrays into higher-order structures. It is becoming clear that chromatin structures are not nearly as uniform and regular as previously assumed. This implies that chromatin structure must also be viewed in the context of specific biological functions. PMID:22722606

  20. Structural Architecture of the Western Transverse Ranges and Potential for Large Earthquakes

    Science.gov (United States)

    Levy, Y.; Rockwell, T. K.; Driscoll, N. W.; Shaw, J. H.; Kent, G. M.; Ucarkus, G.

    2015-12-01

    Understanding the subsurface structure of the Western Transverse Ranges (WTR) is critical to assess the seismic potential of large thrust faults comprising this fold-and-thrust belt. Several models have been advanced over the years, building on new data and understandings of thrust belt architecture, but none of these efforts have incorporated the full range of data, including style and rates of late Quaternary deformation in conjunction with surface geology, sub-surface well data and offshore seismic data. In our models, we suggest that the nearly continuous backbone with continuous stratigraphy of the Santa Ynez Mountains is explained by a large anticlinorium over a deep structural ramp, and that the current thrust front is defined by the southward-vergent Pitas Point-Ventura fault. The Ventura Avenue anticline and trend is an actively deforming fault propagation fold over the partially blind Pitas Point-Ventura fault. Details of how this fault is resolved to the surface are not well constrained, but any deformation model must account for the several back-thrusts that ride in the hanging wall of the thrust sheet, as well as the localized subsidence in Carpenteria and offshore Santa Barbara. Our preliminary starting model is a modification of a recently published model that invokes ramp-flat structure, with a deep ramp under the Santa Ynez Mountains, a shallower "flat" with considerable complexity in the hanging wall and a frontal ramp comprising the San Cayetano and Pitas Point thrusts. With the inferred deep ramp under the Santa Ynez Range, this model implies that large earthquakes may extend the entire length of the anticlinorium from Point Conception to eastern Ventura Basin, suggesting that the potential for a large earthquake is significantly higher then previously assumed.

  1. Similar Endothelial Glycocalyx Structures in Microvessels from a Range of Mammalian Tissues

    DEFF Research Database (Denmark)

    Arkill, K P; Knupp, C; Michel, C C

    2011-01-01

    , with a center-to-center fiber spacing of 20 nm and a fiber width of 12 nm, which might explain the observed macromolecular filtering properties. In this study, we used electron micrographs of tissues prepared using perfusion fixation and tannic acid treatment. The digitized images were analyzed using...... lateral spacings at ~19.5 nm (possibly in a quasitetragonal lattice) and longer spacings above 100 nm. Individual glycocalyx tufts above fenestrations in the first three of these tissues and also in stomach fundus and jejunum showed evidence for similar short-range structural regularity, but with more...

  2. Herbarium specimens reveal a historical shift in phylogeographic structure of common ragweed during native range disturbance

    DEFF Research Database (Denmark)

    Martin, Michael David; Zimmer, Elizabeth A.; Olsen, Morten Tange

    2014-01-01

    Invasive plants provide ample opportunity to study evolutionary shifts that occur after introduction to novel environments. However, although genetic characters pre-dating introduction can be important determinants of later success, large-scale investigations of historical genetic structure have...... expanded rapidly as settlers deforested the landscape on a massive scale, later becoming an aggressive invasive with populations established globally. Towards a direct comparison of genetic structure now and during intense anthropogenic disturbance of the late 19th century, we sampled 45 natural...... populations of common ragweed across its native range as well as historical herbarium specimens collected up to 140 years ago. Bayesian clustering analyses of 453 modern and 473 historical samples genotyped at three chloroplast spacer regions and six nuclear microsatellite loci reveal that historical ragweed...

  3. Magnetism, structure and chemical order in small CoPd clusters: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Mokkath, Junais Habeeb, E-mail: Junais.Mokkath@kaust.edu.sa

    2014-01-15

    The structural, electronic and magnetic properties of small Co{sub m}Pd{sub n}(N=m+n=8,m=0−N) nanoalloy clusters are studied in the framework of a generalized-gradient approximation to density-functional theory. The optimized cluster structures have a clear tendency to maximize the number of nearest-neighbor CoCo pairs. The magnetic order is found to be ferromagnetic-like (FM) for all the ground-state structures. Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom μ{sup ¯}{sub N} increases approximately linearly with Co content. A remarkable enhancement of the local Co moments is observed as a result of Pd doping. This is a consequence of the increase in the number of Co d holes, due to CoPd charge transfer, combined with the reduced local coordination. The influence of spin–orbit interactions on the cluster properties is also discussed. - Highlights: • This work analyses the structural and magnetic properties of CoPd nanoclusters. • The magnetic order is found to be ferromagnetic-like for all the ground-state structures. • The average magnetic moment per atom increases approximately linearly with Co content. • The influence of spin–orbit interactions on the cluster properties is discussed.

  4. Anion ordering, magnetic structure and properties of the vacancy ordered perovskite Ba{sub 3}Fe{sub 3}O{sub 7}F

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, Oliver, E-mail: oliver.clemens@nano.tu-darmstadt.de [Technische Universität Darmstadt, Joint Research Laboratory Nanomaterials, Jovank a-Bontschits-Straße 2, 64287 Darmstadt (Germany); Karlsruher Institut für Technologie, Institut für Nanotechnologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); University of Birmingham, School of Chemistry, Birmingham B152TT (United Kingdom); Reitz, Christian; Witte, Ralf; Kruk, Robert [Karlsruher Institut für Technologie, Institut für Nanotechnologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Smith, Ronald I. [ISIS Facility, Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX (United Kingdom)

    2016-11-15

    This article describes a detailed investigation of the crystallographic and magnetic structure of perovskite type Ba{sub 3}Fe{sub 3}O{sub 7}F by a combined analysis of X-ray and neutron powder diffraction data. Complete ordering of vacancies within the perovskite lattice could be confirmed. In addition, the structure of the anion sublattice was studied by means of the valence bond method, which suggested partial ordering of the fluoride ions on two of the six crystallographically different anion sites. Moreover, the compound was found to show G-type antiferromagnetic ordering of Fe moments, in agreement with magnetometric measurements as well as previously recorded {sup 57}Fe Mössbauer spectroscopy data. - Graphical abstract: The vacancy and anion ordered structure of Ba{sub 3}Fe{sub 3}O{sub 7}F is described together with its magnetic properties. - Highlights: • Ba{sub 3}Fe{sub 3}O{sub 7}F possesses a unique vacancy order not found for other perovskite type compounds. • The valence bond method was used to locate oxide and fluoride ions. • Fluoride ions are distributed only on two of the six anion sites in Ba{sub 3}Fe{sub 3}O{sub 7}F. • The compound shows G-type antiferromagnetic ordering of magnetic moments. • The magnetic structure could be refined in one of the maximal magnetic subgroups of the nuclear structure.

  5. Robust Self-Assembly of Highly Ordered Complex Structures by Controlled Evaporation of Confined Microfluids

    Science.gov (United States)

    Lin, Zhiqun; Byun, Myunghwan; Hong, Suck Won

    2009-03-01

    We demonstrate a robust, one-step method of evaporating polymer solutions in curve-on-flat geometries to create versatile, highly regular microstructures in a precisely controlled environment, as well as offering a comprehensive study of the influence of different upper surfaces on complex structure formation via controlled evaporation. Our method further enhances current fabrication approaches to creating highly ordered structures in a simple and cost-effective manner, with the potential to be tailored for use in photonics, electronics, optoelectronics, microfluidic devices, nanotechnology, and biotechnology.

  6. Band Structure and Fermi-Surface Properties of Ordered beta-Brass

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt; Christensen, N. E.

    1973-01-01

    The band structure of ordered β-brass (β′-CuZn) has been calculated throughout the Brillouin zone by the augmented-plane-wave method. The present band model differs from previous calculations with respect to the position and width of the Cu 3d band. The derived dielectric function ε2(ω) and the p......The band structure of ordered β-brass (β′-CuZn) has been calculated throughout the Brillouin zone by the augmented-plane-wave method. The present band model differs from previous calculations with respect to the position and width of the Cu 3d band. The derived dielectric function ε2(ω...

  7. Fourth-Order Method for Numerical Integration of Age- and Size-Structured Population Models

    Energy Technology Data Exchange (ETDEWEB)

    Iannelli, M; Kostova, T; Milner, F A

    2008-01-08

    In many applications of age- and size-structured population models, there is an interest in obtaining good approximations of total population numbers rather than of their densities. Therefore, it is reasonable in such cases to solve numerically not the PDE model equations themselves, but rather their integral equivalents. For this purpose quadrature formulae are used in place of the integrals. Because quadratures can be designed with any order of accuracy, one can obtain numerical approximations of the solutions with very fast convergence. In this article, we present a general framework and a specific example of a fourth-order method based on composite Newton-Cotes quadratures for a size-structured population model.

  8. The Canonical Structure of the First Order Einstein-Hilbert Action with a Flat Background

    CERN Document Server

    Chishtie, Farrukh

    2013-01-01

    It has been shown that the canonical structure of the first order Einstein-Hilbert (1EH) action involves three generations of constraints and that these can be used to find the generator of a gauge transformation which leaves the action invariant; this transformation is a diffeomorphism with field-dependent gauge function while on shell. In this paper we examine the relationship between the canonical structure of this action and that of the first order spin-2 (1S2) action, which is the weak field limit of the Einstein-Hilbert action. We find that the weak field limit of the Possion Brackets (PB) algebra of first class constraints associated with the 1EH action is not that of the 1S2 action.

  9. Self-assembled ordered structures in thin films of HAT5 discotic liquid crystal

    Directory of Open Access Journals (Sweden)

    Piero Morales

    2010-05-01

    Full Text Available Thin films of the discotic liquid crystal hexapentyloxytriphenylene (HAT5, prepared from solution via casting or spin-coating, were investigated by atomic force microscopy and polarizing optical microscopy, revealing large-scale ordered structures substantially different from those typically observed in standard samples of the same material. Thin and very long fibrils of planar-aligned liquid crystal were found, possibly formed as a result of an intermediate lyotropic nematic state arising during the solvent evaporation process. Moreover, in sufficiently thin films the crystallization seems to be suppressed, extending the uniform order of the liquid crystal phase down to room temperature. This should be compared to the bulk situation, where the same material crystallizes into a polymorphic structure at 68 °C.

  10. Geographical structuring of genetic diversity across the whole distribution range of Narcissus longispathus, a habitat-specialist, Mediterranean narrow endemic.

    Science.gov (United States)

    Medrano, Mónica; Herrera, Carlos M

    2008-08-01

    High mountain ranges of the Mediterranean Basin harbour a large number of narrowly endemic plants. In this study an investigation is made of the levels and partitioning of genetic diversity in Narcissus longispathus, a narrow endemic of south-eastern Spanish mountains characterized by a naturally fragmented distribution due to extreme specialization on a rare habitat type. By using dense sampling of populations across the species' whole geographical range, genetic structuring at different geographical scales is also examined. Using horizontal starch-gel electrophoresis, allozyme variability was screened at 19 loci for a total of 858 individuals from 27 populations. The data were analysed by means of standard statistical approaches in order to estimate gene diversity and the genetic structure of the populations. Narcissus longispathus displayed high levels of genetic diversity and extensive diversification among populations. At the species level, the percentage of polymorphic loci was 68 %, with average values of 2.1, 0.11 and 0.14 for the number of alleles per locus, observed heterozygosity and expected heterozygosity, respectively. Southern and more isolated populations tended to have less genetic variability than northern and less-isolated populations. A strong spatial patterning of genetic diversity was found at the various spatial scales. Gene flow/drift equilibrium occurred over distances <4 km. Beyond that distance divergence was relatively more influenced by drift. The populations studied seem to derive from three panmictic units or 'gene pools', with levels of admixture being greatest in the central and south-eastern portions of the species' range. In addition to documenting a case of high genetic diversity in a narrow endemic plant with naturally fragmented populations, the results emphasize the need for dense population sampling and examination of different geographical scales for understanding population genetic structure in habitat specialists

  11. Reanalyzing the 16PF-5 Second Order Structure: Exploratory versus Confirmatory Factorial Analysis

    Science.gov (United States)

    Aluja, Anton; Blanch, Angel; Garcia, Luis F.

    2005-01-01

    In the present study, the second order structures of the 16PF-5 for 3, 4, 5 and 6 factors are analysed in a sample of 636 undergraduate students and their friends and relatives, with a mean age of 25.09 years (sd: 9.20). A two-stage analysis with Exploratory and Confirmatory Factor Analysis (EFA and CFA) was performed assigning subjects either to…

  12. Measurements of High Order Modes in High Phase Advance Damped Detuned Accelerating Structure for NLC

    CERN Document Server

    Khabiboulline, N; Carter, H

    2004-01-01

    The RF Technology Development group at Fermilab is working together with the NLC and JLC groups at SLAC and KEK on developing technology for room temperature X-band accelerating structures for a future linear collider. We have built several series of structures for high gradient tests. We have also built 150° phase advance per cell, 60 cm long, damped and detuned structures (HDDS or FXC series). Some of these structures will be used for the 8-pack test at SLAC by the end of 2004, as part of the JLC/NLC effort to demonstrate the readiness of room temperature RF technology for a linear collider. HDSS structures are very close to the final design for the linear collider, and it was very interesting to study the properties of high order modes in the structures produced by semi-industrial methods. In this study advanced RF technique and methods developed at Fermilab for structure low power testing and tuning have been used. The results of these measurements are presented in this paper.

  13. Meshing Highly Regular Structures: The Case of Super Carbon Nanotubes of Arbitrary Order

    Directory of Open Access Journals (Sweden)

    Christian Schröppel

    2015-01-01

    Full Text Available Mesh generation is an important step in many numerical methods. We present the “Hierarchical Graph Meshing” (HGM method as a novel approach to mesh generation, based on algebraic graph theory. The HGM method can be used to systematically construct configurations exhibiting multiple hierarchies and complex symmetry characteristics. The hierarchical description of structures provided by the HGM method can be exploited to increase the efficiency of multiscale and multigrid methods. In this paper, the HGM method is employed for the systematic construction of super carbon nanotubes of arbitrary order, which present a pertinent example of structurally and geometrically complex, yet highly regular, structures. The HGM algorithm is computationally efficient and exhibits good scaling characteristics. In particular, it scales linearly for super carbon nanotube structures and is working much faster than geometry-based methods employing neighborhood search algorithms. Its modular character makes it conducive to automatization. For the generation of a mesh, the information about the geometry of the structure in a given configuration is added in a way that relates geometric symmetries to structural symmetries. The intrinsically hierarchic description of the resulting mesh greatly reduces the effort of determining mesh hierarchies for multigrid and multiscale applications and helps to exploit symmetry-related methods in the mechanical analysis of complex structures.

  14. Ordered ferrimagnetic form of ferrihydrite reveals links among structure, composition, and magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Michel, F. Marc; Barrón, Vidal; Torrent, José; Morales, María P.; Serna, Carlos J.; Boily, Jean-François; Liu, Qingsong; Ambrosini, Andrea; Cismasu, A. Cristina; Brown, Jr., Gordon E. (CSIC-Spain); (Stanford); (Sandia); (Cordoba); (Umea); (Chinese Aca. Sci.)

    2010-11-19

    The natural nanomineral ferrihydrite is an important component of many environmental and soil systems and has been implicated as the inorganic core of ferritin in biological systems. Knowledge of its basic structure, composition, and extent of structural disorder is essential for understanding its reactivity, stability, and magnetic behavior, as well as changes in these properties during aging. Here we investigate compositional, structural, and magnetic changes that occur upon aging of '2-line' ferrihydrite in the presence of adsorbed citrate at elevated temperature. Whereas aging under these conditions ultimately results in the formation of hematite, analysis of the atomic pair distribution function and complementary physicochemical and magnetic data indicate formation of an intermediate ferrihydrite phase of larger particle size with few defects, more structural relaxation and electron spin ordering, and pronounced ferrimagnetism relative to its disordered ferrihydrite precursor. Our results represent an important conceptual advance in understanding the nature of structural disorder in ferrihydrite and its relation to the magnetic structure and also serve to validate a controversial, recently proposed structural model for this phase. In addition, the pathway we identify for forming ferrimagnetic ferrihydrite potentially explains the magnetic enhancement that typically precedes formation of hematite in aerobic soil and weathering environments. Such magnetic enhancement has been attributed to the formation of poorly understood, nano-sized ferrimagnets from a ferrihydrite precursor. Whereas elevated temperatures drive the transformation on timescales feasible for laboratory studies, our results also suggest that ferrimagnetic ferrihydrite could form naturally at ambient temperature given sufficient time.

  15. Cultural order and participatory local development: structure for the occupational therapist practice

    Directory of Open Access Journals (Sweden)

    Ricardo Lopes Correia

    2016-01-01

    Full Text Available The Cultural Order is understood as the expression of a game of interdependencies determinations between local and global social groups, pairs identified by productions, values and behavior that consciously guide the life projects and the expansion of a collective freedom. Based on a Social Science research and with theoretical mark of Nobert Elias and Amartya Sen, this article aims to present a theoretical-practice structure of the approach in participatory local development- PLD to the occupational therapist surround by the construction of collective life projects, in order to operationalize in the practice of the community question, understood as the strengths that singularize the participation. We discuss the use of the PLD approach to the occupational therapist in a flexible structure, aiming to guarantee its domain, the Human Occupation, and the set of interventions, technologies, sustained in the management of the activities of daily living. The approach in participatory local development presents itself as an important structural outline to the community actions, and it is the occupational therapist role to be an articulator of the Local Cultural Order dimensions, to deal with the target population their work processes of continuity in collective life projects and expansion of freedom.

  16. Silica photonic crystal fiber structure in order to simplify the process of making them

    Directory of Open Access Journals (Sweden)

    Ashkan Ghanbari

    2014-04-01

    Full Text Available In this research, a new structure of photonic crystal fibers(PCFs will be proposed,in which instead of using the aire- holes in the cladding region, the flourine(2% doped solid silica rods in order to reduce the problems associated with deformities of air-holes in the cladding region will be used.Also, in the following, a few of the propagation charactristics of the proposed Photonic Crystal Fiber with a conventional silica Photonic Crystal Fiber such as, Normalized frequency,effective refractive index,total dispersion and higher order dispersions ( Group velocity dispersion and Third Order Dispersion will be analyzed and compared. Finally it will be observed that, the proposed PCF structure is much simpler than the conventional one in the fabrication process. But they are not suitable for femtosecond solitons propagation .Also, it will be shown that, the situation of the conventional Photonic Crystal Fiber is much better than the proposed structure in the femtosecond optical solitons propagation.

  17. Reduced-order molecular-dynamics model for polystyrene by equivalent-structure coarse graining.

    Science.gov (United States)

    Srivastava, Anand; Ghosh, Somnath

    2012-02-01

    This paper develops a reduced-order equivalent-structure based model for polystyrene in a rigid body molecular dynamics framework. In general, a coarse-grained model for polymers is obtained by replacing a group of chemically connected atoms by an effective particle and deriving a coarse-grained interaction potential that reproduces the structure and dynamics at the desired length and time scale. In the current model, a detailed (~16 atoms) polystyrene monomer referred to as basic structural element (BSE) is replaced by an equivalent model with spherical backbone particles and an ellipsoidal particle that represents the styrene sidegroup. The governing principals of this homogenization is based on the mass, centroid, angular momentum, and energy equivalence between the detailed and the proposed reduced-order model. The bonded interactions parameters are readily obtained in the optimization of the equivalent structure from the detailed representation. The nonbonded interactions are treated separately. In order to capture the stereochemistry of the polystyrene molecule, an anisotropic biaxial nonbonded interaction potential function known as RE-squared (RE2) interaction has been used between pairs of ellipsoidal and/or spherical particles in the system. The required calibration of the nonbonded parameters is carried out by matching with the experimental density and the local structure using radial distribution function. This homogenization process scales up the modeling system size significantly as the higher frequency motions like -C-H- vibrations and sidegroup movements are suppressed. The accuracy of the model is established by comparing fine-scale simulation with explicit representations.

  18. Crystal Structure and Chemical Composition of a Presolar Silicate from the Queen Elizabeth Range 99177 Meteorite

    Science.gov (United States)

    Nguyen, A. N.; Keller, L. P.; Rahman, Z.; Messenger, S.

    2013-01-01

    Mineral characterization of presolar silicate grains, the most abundant stardust phase, has provided valuable information about the formation conditions in circumstellar environments and in super-nova (SN) outflows. Spectroscopic observations of dust around evolved stars suggest a majority of amor-phous, Mg-rich olivine grains, but crystalline silicates, most of which are pyroxene, have also been observed [1]. The chemical compositions of hundreds of presolar silicates have been determined by Auger spectroscopy and reveal high Fe contents and nonstoichiometric compositions intermediate to olivine and pyroxene [2-6]. The unexpectedly high Fe contents can partly be attributed to secondary alteration on the meteorite parent bodies, as some grains have Fe isotopic anomalies from their parent stellar source [7]. Only about 35 presolar silicates have been studied for their mineral structures and chemical compositions by transmission electron microscopy (TEM). These grains display a wide range of compositions and structures, including crystalline forsterite, crystalline pyroxene, nanocrystalline grains, and a majority of amorphous nonstoichiometric grains. Most of these grains were identified in the primitive Acfer 094 meteorite. Presolar silicates from this meteorite show a wide range of Fe-contents, suggestive of secondary processing on the meteorite parent body. The CR chondrite QUE 99177 has not suffered as much alteration [8] and displays the highest presolar silicate abundance to date among carbonaceous chondrites [3, 6]. However, no mineralogical studies of presolar silicates from this meteorite have been performed. Here we examine the mineralogy of a presolar silicate from QUE 99177.

  19. Coupling of structure to magnetic and superconducting orders in quasi-one-dimensional K2Cr3As3

    Science.gov (United States)

    Taddei, K. M.; Zheng, Q.; Sefat, A. S.; de la Cruz, C.

    2017-11-01

    Quasi-one-dimensional A2Cr3As3 (with A =K , Cs, Rb) is an intriguing new family of superconductors which exhibit many similar features to the cuprate and iron-based unconventional superconductor families. Yet, in contrast to these systems, no charge or magnetic ordering has been observed which could provide the electronic correlations presumed necessary for an unconventional superconducting pairing mechanism—an absence which defies predictions of first-principles models. We report the results of neutron scattering experiments on polycrystalline K2Cr3As3 (Tc˜7 K ) which probed the low-temperature dynamics near Tc. Neutron diffraction data evidence a subtle response of the nuclear lattice to the onset of superconductivity while inelastic scattering reveals a highly dispersive column of intensity at the commensurate wave vector q =(00 1/2 ) which loses intensity beneath Tc—indicative of short-range magnetic fluctuations. Using linear spin-wave theory, we model the observed scattering and suggest a possible structure to the short-range magnetic order. These observations suggest that K2Cr3As3 is in close proximity to a magnetic instability and that the incipient magnetic order both couples strongly to the lattice and competes with superconductivity, in direct analogy with the iron-based superconductors.

  20. Substitution Structures of Large Molecules and Medium Range Correlations in Quantum Chemistry Calculations

    Science.gov (United States)

    Evangelisti, Luca; Pate, Brooks

    2017-06-01

    A study of the minimally exciting topic of agreement between experimental and measured rotational constants of molecules was performed on a set of large molecules with 16-18 heavy atoms (carbon and oxygen). The molecules are: nootkatone (C_{15}H_{22}O), cedrol (C_{15}H_{26}O), ambroxide (C_{16}H_{28}O), sclareolide (C_{16}H_{22}O_{2}), and dihydroartemisinic acid (C_{15}H_{24}O_{2}). For this set of molecules we obtained 13C-subsitution structures for six molecules (this includes two conformers of nootkatone). A comparison of theoretical structures and experimental substitution structures was performed in the spirit of the recent work of Grimme and Steinmetz.[1] Our analysis focused the center-of-mass distance of the carbon atoms in the molecules. Four different computational methods were studied: standard DFT (B3LYP), dispersion corrected DFT (B3LYP-D3BJ), hybrid DFT with dispersion correction (B2PLYP-D3), and MP2. A significant difference in these theories is how they handle medium range correlation of electrons that produce dispersion forces. For larger molecules, these dispersion forces produce an overall contraction of the molecule around the center-of-mass. DFT poorly treats this effect and produces structures that are too expanded. MP2 calculations overestimate the correction and produce structures that are too compact. Both dispersion corrected DFT methods produce structures in excellent agreement with experiment. The analysis shows that the difference in computational methods can be described by a linear error in the center-of-mass distance. This makes it possible to correct poorer performing calculations with a single scale factor. We also reexamine the issue of the "Costain error" in substitution structures and show that it is significantly larger in these systems than in the smaller molecules used by Costain to establish the error limits. [1] Stefan Grimme and Marc Steinmetz, "Effects of London dispersion correction in density functional theory on

  1. Structural analysis of the Gachsar sub-zone in central Alborz range; constrain for inversion tectonics followed by the range transverse faulting

    Science.gov (United States)

    Yassaghi, A.; Naeimi, A.

    2010-04-01

    Analysis of the Gachsar structural sub-zone has been carried out to constrain structural evolution of the central Alborz range situated in the central Alpine Himalayan orogenic system. The sub-zone bounded by the northward-dipping Kandovan Fault to the north and the southward-dipping Taleghan Fault to the south is transversely cut by several sinistral faults. The Kandovan Fault that controls development of the Eocene rocks in its footwall from the Paleozoic-Mesozoic units in the fault hanging wall is interpreted as an inverted basin-bounding fault. Structural evidences include the presence of a thin-skinned imbricate thrust system propagated from a detachment zone that acts as a footwall shortcut thrust, development of large synclines in the fault footwall as well as back thrusts and pop-up structures on the fault hanging wall. Kinematics of the inverted Kandovan Fault and its accompanying structures constrain the N-S shortening direction proposed for the Alborz range until Late Miocene. The transverse sinistral faults that are in acute angle of 15° to a major magnetic lineament, which represents a basement fault, are interpreted to develop as synthetic Riedel shears on the cover sequences during reactivation of the basement fault. This overprinting of the transverse faults on the earlier inverted extensional fault occurs since the Late Miocene when the south Caspian basin block attained a SSW movement relative to the central Iran. Therefore, recent deformation in the range is a result of the basement transverse-fault reactivation.

  2. ISWI regulates higher-order chromatin structure and histone H1 assembly in vivo.

    Directory of Open Access Journals (Sweden)

    Davide F V Corona

    2007-09-01

    Full Text Available Imitation SWI (ISWI and other ATP-dependent chromatin-remodeling factors play key roles in transcription and other processes by altering the structure and positioning of nucleosomes. Recent studies have also implicated ISWI in the regulation of higher-order chromatin structure, but its role in this process remains poorly understood. To clarify the role of ISWI in vivo, we examined defects in chromosome structure and gene expression resulting from the loss of Iswi function in Drosophila. Consistent with a broad role in transcriptional regulation, the expression of a large number of genes is altered in Iswi mutant larvae. The expression of a dominant-negative form of ISWI leads to dramatic alterations in higher-order chromatin structure, including the apparent decondensation of both mitotic and polytene chromosomes. The loss of ISWI function does not cause obvious defects in nucleosome assembly, but results in a significant reduction in the level of histone H1 associated with chromatin in vivo. These findings suggest that ISWI plays a global role in chromatin compaction in vivo by promoting the association of the linker histone H1 with chromatin.

  3. High genetic diversity and structured populations of the oriental fruit moth in its range of origin.

    Science.gov (United States)

    Zheng, Yan; Peng, Xiong; Liu, Gaoming; Pan, Hongyan; Dorn, Silvia; Chen, Maohua

    2013-01-01

    The oriental fruit moth Grapholita ( = Cydia) molesta is a key fruit pest globally. Despite its economic importance, little is known about its population genetics in its putative native range that includes China. We used five polymorphic microsatellite loci and two mitochondrial gene sequences to characterize the population genetic diversity and genetic structure of G. molesta from nine sublocations in three regions of a major fruit growing area of China. Larval samples were collected throughout the season from peach, and in late season, after host switch by the moth to pome fruit, also from apple and pear. We found high numbers of microsatellite alleles and mitochondrial DNA haplotypes in all regions, together with a high number of private alleles and of haplotypes at all sublocations, providing strong evidence that the sampled area belongs to the origin of this species. Samples collected from peach at all sublocations were geographically structured, and a significant albeit weak pattern of isolation-by-distance was found among populations, likely reflecting the low flight capacity of this moth. Interestingly, populations sampled from apple and pear in the late season showed a structure differing from that of populations sampled from peach throughout the season, indicating a selective host switch of a certain part of the population only. The recently detected various olfactory genotypes in G. molesta may underly this selective host switch. These genetic data yield, for the first time, an understanding of population dynamics of G. molesta in its native range, and of a selective host switch from peach to pome fruit, which may have a broad applicability to other global fruit production areas for designing suitable pest management strategies.

  4. High genetic diversity and structured populations of the oriental fruit moth in its range of origin.

    Directory of Open Access Journals (Sweden)

    Yan Zheng

    Full Text Available The oriental fruit moth Grapholita ( = Cydia molesta is a key fruit pest globally. Despite its economic importance, little is known about its population genetics in its putative native range that includes China. We used five polymorphic microsatellite loci and two mitochondrial gene sequences to characterize the population genetic diversity and genetic structure of G. molesta from nine sublocations in three regions of a major fruit growing area of China. Larval samples were collected throughout the season from peach, and in late season, after host switch by the moth to pome fruit, also from apple and pear. We found high numbers of microsatellite alleles and mitochondrial DNA haplotypes in all regions, together with a high number of private alleles and of haplotypes at all sublocations, providing strong evidence that the sampled area belongs to the origin of this species. Samples collected from peach at all sublocations were geographically structured, and a significant albeit weak pattern of isolation-by-distance was found among populations, likely reflecting the low flight capacity of this moth. Interestingly, populations sampled from apple and pear in the late season showed a structure differing from that of populations sampled from peach throughout the season, indicating a selective host switch of a certain part of the population only. The recently detected various olfactory genotypes in G. molesta may underly this selective host switch. These genetic data yield, for the first time, an understanding of population dynamics of G. molesta in its native range, and of a selective host switch from peach to pome fruit, which may have a broad applicability to other global fruit production areas for designing suitable pest management strategies.

  5. A fractional-order controller for vibration suppression of uncertain structures.

    Science.gov (United States)

    Aghababa, Mohammad Pourmahmood

    2013-11-01

    The problem of active control of vibration structures has attracted much attention over the past decades. A general description of the control problem of vibration systems is to design an active controller to suppress the vibrations of the system induced by external disturbances such as an earthquake. In this paper, a novel fractional-order sliding mode control is introduced to attenuate the vibrations of structures with uncertainties and disturbances. After establishing a stable fractional sliding surface, a sliding mode control law is proposed. Then, the global asymptotic stability of the closed-loop system is analytically proved using fractional Lyapunov stability theorem. Finally, the robustness and applicability of the technique are verified using two examples, including a three degree of freedom structure and a two-story shear building. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

  6. Correlation between Local Structure Order and Spatial Heterogeneity in a Metallic Glass

    Science.gov (United States)

    Zhu, Fan; Hirata, Akihiko; Liu, Pan; Song, Shuangxi; Tian, Yuan; Han, Jiuhui; Fujita, Takeshi; Chen, Mingwei

    2017-11-01

    Although nanoscale spatial heterogeneity of metallic glasses has been demonstrated by extensive experimental and theoretical investigations, the nature of spatial heterogeneity remains poorly known owing to the absence of a structural depiction of the inhomogeneity from experimental insight. Here we report the experimental characterization of the spatial heterogeneity of a metallic glass by utilizing state-of-the-art angstrom-beam electron diffraction and scanning transmission electron microscopy. The subnanoscale electron diffraction reveals that the nanoscale spatial heterogeneity and corresponding density fluctuation have a close correlation with the local structure variation from icosahedronlike to tetragonal crystal-like order. The structural insights of spatial heterogeneity have important implications in understanding the properties and dynamics of metallic glasses.

  7. Cross-cultural second order factor structures of the 16PF.

    Science.gov (United States)

    Golden, C J

    1978-04-01

    Cross-cultural personality research has generated a great amount of data on individual difference patterns in diverse cultures. One of the major instruments used in this research has been Cattell's 16PF. A major question in this research is whether the underlying personality structure is equivalent for different cultures. The present study evaluated the second order factor structure of the 16PF in 101 subjects of European ancestry and 117 subjects of Japanese ancestry. The factor structure for the Japanese was significantly different from that of the caucasian group. The caucasian results did not differ from those reported by Cattell and his associates. The implications of these results for personality theory and for cross-cultural evaluation were briefly discussed.

  8. Structural ordering of Pennsylvania anthracites on heat treatment to 2000-2900{sup o}C

    Energy Technology Data Exchange (ETDEWEB)

    J.V. Atria; F. Rusinko Jr.; H.H. Schobert [Pennsylvania State University, University Park, PA (United States). Energy Institute

    2002-12-01

    Three Pennsylvania anthracites from the Penn State Coal Sample Bank and Data Base were heat-treated to temperatures to 2900{sup o}C. The products were characterized by X-ray diffraction. These anthracites clearly differ in the extent to which they transform to a graphitic structure by heat treatment at ambient pressure. Graphitizability, based on approach of interlayer spacing to the ideal value for graphite and development of crystallite height, is in the order DECS 21 {gt} PSOC 1461 {gt} PSOC 1468. By 2700{sup o}C the interlayer spacing is largely established, since improvements by increasing graphitization temperature to 2900{sup o}C are small. The crystallite stacking continues to develop; significant changes are achieved at 2900 vs 2700{sup o}C. The structural changes can be related to composition via two factors. In heat treatment to 2000{sup o}C, the structural ordering may be impeded by a 'locking' of aromatic sheets in place by cross-linkers, such as oxygen atoms. At the higher temperatures, i.e., 2700 and 2900{sup o}C, the ease of rearrangement of aromatic sheets, which is related to their size, is the dominant issue. The relative sizes of aromatic sheets can be approximated from the net hydrogen content of the anthracites. DECS-21, which has both the highest oxygen content and the highest net hydrogen value, shows the least order after heat treatment to 2000{sup o}C, but the best structural development after reaction at 2700 or 2900{sup o}C. 38 refs., 2 tabs.

  9. Assessing Local Structure Motifs Using Order Parameters for Motif Recognition, Interstitial Identification, and Diffusion Path Characterization

    Directory of Open Access Journals (Sweden)

    Nils E. R. Zimmermann

    2017-11-01

    Full Text Available Structure–property relationships form the basis of many design rules in materials science, including synthesizability and long-term stability of catalysts, control of electrical and optoelectronic behavior in semiconductors, as well as the capacity of and transport properties in cathode materials for rechargeable batteries. The immediate atomic environments (i.e., the first coordination shells of a few atomic sites are often a key factor in achieving a desired property. Some of the most frequently encountered coordination patterns are tetrahedra, octahedra, body and face-centered cubic as well as hexagonal close packed-like environments. Here, we showcase the usefulness of local order parameters to identify these basic structural motifs in inorganic solid materials by developing classification criteria. We introduce a systematic testing framework, the Einstein crystal test rig, that probes the response of order parameters to distortions in perfect motifs to validate our approach. Subsequently, we highlight three important application cases. First, we map basic crystal structure information of a large materials database in an intuitive manner by screening the Materials Project (MP database (61,422 compounds for element-specific motif distributions. Second, we use the structure-motif recognition capabilities to automatically find interstitials in metals, semiconductor, and insulator materials. Our Interstitialcy Finding Tool (InFiT facilitates high-throughput screenings of defect properties. Third, the order parameters are reliable and compact quantitative structure descriptors for characterizing diffusion hops of intercalants as our example of magnesium in MnO2-spinel indicates. Finally, the tools developed in our work are readily and freely available as software implementations in the pymatgen library, and we expect them to be further applied to machine-learning approaches for emerging applications in materials science.

  10. The Opposite Effect of Metal Ions on Short-/Long-Range Water Structure: A Multiple Characterization Study.

    Science.gov (United States)

    Ma, Kai; Zhao, Lin

    2016-04-25

    Inorganic electrolyte solutions are very important in our society as they dominate many biochemical and geochemical processes. Herein, an in-depth study was performed to illustrate the ion-induced effect on water structure by coupling NMR, viscometer, Raman and Molecular Dynamic (MD) simulations. The NMR coefficient (BNMR) and diffusion coefficient (D) from NMR, and viscosity coefficient (Bvis) from a viscometer all proved that dissolved metal ions are capable of enhancing the association degree of adjacent water molecules, and the impact on water structure decreased in the order of Cr(3+) > Fe(3+) > Cu(2+) > Zn(2+). This regularity was further evidenced by Raman analysis; however, the deconvoluted Raman spectrum indicated the decrease in high association water with salt concentration and the increase in low association water before 200 mmol·L(-1). By virtue of MD simulations, the opposite changing manner proved to be the result of the opposite effect on short-/long-range water structure induced by metal ions. Our results may help to explain specific protein denaturation induced by metal ions.

  11. Delayed avalanche breakdown of high-voltage silicon diodes: Various structures exhibit different picosecond-range switching behavior

    Science.gov (United States)

    Brylevskiy, Viktor; Smirnova, Irina; Gutkin, Andrej; Brunkov, Pavel; Rodin, Pavel; Grekhov, Igor

    2017-11-01

    We present a comparative study of silicon high-voltage diodes exhibiting the effect of delayed superfast impact-ionization breakdown. The effect manifests itself in a sustainable picosecond-range transient from the blocking to the conducting state and occurs when a steep voltage ramp is applied to the p+-n-n+ diode in the reverse direction. Nine groups of diodes with graded and abrupt pn-junctions have been specially fabricated for this study by different techniques from different Si substrates. Additionally, in two groups of these structures, the lifetime of nonequilibrium carriers was intentionally reduced by electron irradiation. All diodes have identical geometrical parameters and similar stationary breakdown voltages. Our experimental setup allows measuring both device voltage and current during the kilovolt switching with time resolution better than 50 ps. Although all devices are capable of forming a front with kilovolt amplitude and 100 ps risetime in the in-series load, the structures with graded pn-junctions have anomalously large residual voltage. The Deep Level Transient Spectroscopy study of all diode structures has been performed in order to evaluate the effect of deep centers on device performance. It was found that the presence of deep-level electron traps negatively correlates with parameters of superfast switching, whereas a large concentration of recombination centers created by electron irradiation has virtually no influence on switching characteristics.

  12. Structural damage detection using higher-order finite elements and a scanning laser vibrometer

    Science.gov (United States)

    Jin, Si

    In contrast to conventional non-destructive evaluation methods, dynamics-based damage detection methods are capable of rapid integrity evaluation of large structures and have received considerable attention from aerospace, mechanical, and civil engineering communities in recent years. However, the identifiable damage size using dynamics-based methods is determined by the number of sensors used, level of measurement noise, accuracy of structural models, and signal processing techniques. In this thesis we study dynamics of structures with damage and then derive and experimentally verify new model-independent structural damage detection methods that can locate small damage to structures. To find sensitive damage detection parameters we develop a higher-order beam element that enforces the continuity of displacements, slopes, bending moments, and shear forces at all nodes, and a higher-order rectangular plate element that enforces the continuity of displacements, slopes, and bending and twisting moments at all nodes. These two elements are used to study the dynamics of beams and plates. Results show that high-order spatial derivatives of high-frequency modes are important sensitive parameters that can locate small structural damage. Unfortunately the most powerful and popular structural modeling technique, the finite element method, is not accurate in predicting high-frequency responses. Hence, a model-independent method using dynamic responses obtained from high density measurements is concluded to be the best approach. To increase measurement density and reduce noise a Polytec PI PSV-200 scanning laser vibrometer is used to provide non-contact, dense, and accurate measurements of structural vibration velocities. To avoid the use of structural models and to extract sensitive detection parameters from experimental data, a brand-new structural damage detection method named BED (Boundary-Effect Detection) is developed for pinpointing damage locations using Operational

  13. Conformational specificity of non-canonical base pairs and higher order structures in nucleic acids: crystal structure database analysis

    Science.gov (United States)

    Mukherjee, Shayantani; Bansal, Manju; Bhattacharyya, Dhananjay

    2006-10-01

    Non-canonical base pairs contribute immensely to the structural and functional variability of RNA, which calls for a detailed characterization of their spatial conformation. Intra-base pair parameters, namely propeller, buckle, open-angle, stagger, shear and stretch describe structure of base pairs indicating planarity and proximity of association between the two bases. In order to study the conformational specificities of non-canonical base pairs occurring in RNA crystal structures, we have upgraded NUPARM software to calculate these intra-base pair parameters using a new base pairing edge specific axis system. Analysis of base pairs and base triples with the new edge specific axis system indicate the presence of specific structural signatures for different classes of non-canonical pairs and triples. Differentiating features could be identified for pairs in cis or trans orientation, as well as those involving sugar edges or C-H-mediated hydrogen bonds. It was seen that propeller for all types of base pairs in cis orientation are generally negative, while those for trans base pairs do not have any preference. Formation of a base triple is seen to reduce propeller of the associated base pair along with reduction of overall flexibility of the pairs. We noticed that base pairs involving sugar edge are generally more non-planar, with large propeller or buckle values, presumably to avoid steric clash between the bulky sugar moieties. These specific conformational signatures often provide an insight into their role in the structural and functional context of RNA.

  14. Absence of magnetic long-range order in Y2CrSbO7 : Bond-disorder-induced magnetic frustration in a ferromagnetic pyrochlore

    Science.gov (United States)

    Shen, L.; Greaves, C.; Riyat, R.; Hansen, T. C.; Blackburn, E.

    2017-09-01

    The consequences of random nonmagnetic-ion dilution for the pyrochlore family Y2(M 1 -xN x)2O7 (M = magnetic ion, N = nonmagnetic ion) have been investigated. As a first step, we experimentally examine the magnetic properties of Y2CrSbO7 (x =0.5 ), in which the magnetic sites (Cr3 +) are percolative. Although the effective Cr-Cr spin exchange is ferromagnetic, as evidenced by a positive Curie-Weiss temperature, ΘCW ≃19.5 K , our high-resolution neutron powder diffraction measurements detect no sign of magnetic long-range order down to 2 K. In order to understand our observations, we construct a lattice model to numerically study the bond disorder introduced by the ionic size mismatch between M and N , which reveals that the bond disorder percolates at xb ≃0.23 , explaining the absence of magnetic long-range order. This model could be applied to a series of frustrated magnets with a pyrochlore sublattice, for example, the spinel compound Zn (Cr1 -xGax )2O4 , wherein a Néel to spin glass phase transition occurs between x =0.2 and 0.25 [Lee et al., Phys. Rev. B 77, 014405 (2008), 10.1103/PhysRevB.77.014405]. Our study stresses the non-negligible role of bond disorder on magnetic frustration, even in ferromagnets.

  15. Influence of the precursors in the morphology, structure, vibrational order and optical gap of nano structured Zn O

    Energy Technology Data Exchange (ETDEWEB)

    Jurado, J. F.; Londono C, A.; Jurado L, F. F.; Romero S, J. D., E-mail: jfjurado@unal.edu.co [Universidad Nacional de Colombia, Laboratorio de Propiedades Termicas Dielectricas de Compositos, A. A. 127, Manizales (Colombia)

    2014-07-01

    The synthesis of Zn O by reaction in solid state from two precursor salts (zinc acetate and zinc sulfate), presented significant differences concerning morphology, structure, vibrational order and optical gap. As well as covering in the size of the compounds, a homogeneous distribution of nanoparticles of 21±3 nm and micro stars of 1.03±0.19 μm respectively. The Zn O showed a structural phase with a vibrational state of the hexagonal type (wurtzite). The variation in the morphology due to the precursor is attributed to the disorder within of lattice, which contributes to vibrational changes and is correlated to the degrees of freedom of molecules. Measurements of UV-Vis of nanoparticles displayed a band gap (E{sub g}) lower than the one reported for the bulk material. The structural characterization of the compounds was carried out by using a X-ray Bruker D8 Advance diffractometer. The vibrational order was assessed throughout micro-Raman with a monochromatic radiation source of 473 nm). (Author)

  16. PROCESSING OF UAV BASED RANGE IMAGING DATA TO GENERATE DETAILED ELEVATION MODELS OF COMPLEX NATURAL STRUCTURES

    Directory of Open Access Journals (Sweden)

    T. K. Kohoutek

    2012-07-01

    Full Text Available Unmanned Aerial Vehicles (UAVs are more and more used in civil areas like geomatics. Autonomous navigated platforms have a great flexibility in flying and manoeuvring in complex environments to collect remote sensing data. In contrast to standard technologies such as aerial manned platforms (airplanes and helicopters UAVs are able to fly closer to the object and in small-scale areas of high-risk situations such as landslides, volcano and earthquake areas and floodplains. Thus, UAVs are sometimes the only practical alternative in areas where access is difficult and where no manned aircraft is available or even no flight permission is given. Furthermore, compared to terrestrial platforms, UAVs are not limited to specific view directions and could overcome occlusions from trees, houses and terrain structures. Equipped with image sensors and/or laser scanners they are able to provide elevation models, rectified images, textured 3D-models and maps. In this paper we will describe a UAV platform, which can carry a range imaging (RIM camera including power supply and data storage for the detailed mapping and monitoring of complex structures, such as alpine riverbed areas. The UAV platform NEO from Swiss UAV was equipped with the RIM camera CamCube 2.0 by PMD Technologies GmbH to capture the surface structures. Its navigation system includes an autopilot. To validate the UAV-trajectory a 360° prism was installed and tracked by a total station. Within the paper a workflow for the processing of UAV-RIM data is proposed, which is based on the processing of differential GNSS data in combination with the acquired range images. Subsequently, the obtained results for the trajectory are compared and verified with a track of a UAV (Falcon 8, Ascending Technologies carried out with a total station simultaneously to the GNSS data acquisition. The results showed that the UAV's position using differential GNSS could be determined in the centimetre to the decimetre

  17. Short-range structure in (partially) crystalline potato starch determined with attenuated total reflectance Fourier-transform IR spectroscopy

    NARCIS (Netherlands)

    Vliegenthart, J.F.G.; Soest, J.J.G. van; Tournois, H.; Wit, D. de

    1995-01-01

    A fast and direct method, based on infrared spectroscopy, for quantitative determination of starch short-range structure has been developed. The IR spectrum of starch is sensitive to changes in short-range structure in the C—C and C—O stretching region at 1300-800 cm−1. The IR absorbance band at

  18. High order quaternary arrangement confers increased structural stability to Brucella Spp. lumazine synthase

    Energy Technology Data Exchange (ETDEWEB)

    Zylberman, V.; Craig, P.O.; Klinke, S.; Cauerhff, A.; Goldbaum, F.A. [Instituto Leloir, Buenos Aires (Argentina); Braden, B.C. [Bowie State Univ., Maryland (United States)

    2004-07-01

    The penultimate step in the pathway of riboflavin biosynthesis is catalyzed by the enzyme lumazine synthase (LS). One of the most distinctive characteristics of this enzyme is the structural quaternary divergence found in different species. The protein exists as pentameric and icosahedral forms, built from practically the same structural monomeric unit. The pentameric structure is formed by five 18 kDa monomers, each extensively contacting neighboring monomers. The icosahedral structure consists of 60 LS monomers arranged as twelve pentamers giving rise to a capsid exhibiting icosahedral 532 symmetry. In all lumazine synthases studied, the topologically equivalent active sites are located at the interfaces between adjacent subunits in the pentameric modules. The Brucella spp. lumazine synthase (BLS) sequence clearly diverges from pentameric and icosahedral enzymes. This unusual divergence prompted to further investigate on its quaternary arrangement. In the present work, we demonstrate by means of solution Light Scattering and X-ray structural analyses that BLS assembles as a very stable dimer of pentamers representing a third category of quaternary assembly for lumazine synthases. We also describe by spectroscopic studies the thermodynamic stability of this oligomeric protein, and postulate a mechanism for dissociation/unfolding of this macromolecular assembly. The higher molecular order of BLS increases its stability 20 deg C compared to pentameric lumazine synthases. The decameric arrangement described in this work highlights the importance of quaternary interactions in the stabilization of proteins. (author)

  19. Controlled fabrication of ordered structure-based ZnO films by electrochemical deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lei, J.F., E-mail: leijianfei9966@163.com [School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Wang, Z.W. [School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Li, W.S. [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China)

    2014-12-31

    Orderly structured ZnO films were fabricated by electrochemical deposition combined with a templating method. The floating-transfer technique was used to assemble polystyrene sphere (PS) templates. Hierarchical structures containing two-diameter PS were easily assembled on the surface of F–SnO{sub 2} conductive glass (FTO). When used as a working electrode, the FTO glass coated with PS templates provided arrayed cavities to accommodate ZnO crystals under potentiostatic deposition and was ultimately covered by ordered, porous ZnO films after removal of PS templates. The morphologies of the samples were examined by field-emission scanning electron microscopy and crystallographic information for the samples was obtained from X-ray powder diffraction measurements. The results indicate that ZnO films fabricated by electrochemical deposition show excellent template replication over large areas and exhibit the typical wurtzite structure. - Highlights: • PS templates with tunable layers assembled by a floating-transfer technique are presented. • ZnO films with controllable morphologies are prepared by using electrochemical deposition. • With a binary PS template, hierarchical ZnO films are obtained.

  20. Gene order data from a model amphibian (Ambystoma: new perspectives on vertebrate genome structure and evolution

    Directory of Open Access Journals (Sweden)

    Voss S Randal

    2006-08-01

    Full Text Available Abstract Background Because amphibians arise from a branch of the vertebrate evolutionary tree that is juxtaposed between fishes and amniotes, they provide important comparative perspective for reconstructing character changes that have occurred during vertebrate evolution. Here, we report the first comparative study of vertebrate genome structure that includes a representative amphibian. We used 491 transcribed sequences from a salamander (Ambystoma genetic map and whole genome assemblies for human, mouse, rat, dog, chicken, zebrafish, and the freshwater pufferfish Tetraodon nigroviridis to compare gene orders and rearrangement rates. Results Ambystoma has experienced a rate of genome rearrangement that is substantially lower than mammalian species but similar to that of chicken and fish. Overall, we found greater conservation of genome structure between Ambystoma and tetrapod vertebrates, nevertheless, 57% of Ambystoma-fish orthologs are found in conserved syntenies of four or more genes. Comparisons between Ambystoma and amniotes reveal extensive conservation of segmental homology for 57% of the presumptive Ambystoma-amniote orthologs. Conclusion Our analyses suggest relatively constant interchromosomal rearrangement rates from the euteleost ancestor to the origin of mammals and illustrate the utility of amphibian mapping data in establishing ancestral amniote and tetrapod gene orders. Comparisons between Ambystoma and amniotes reveal some of the key events that have structured the human genome since diversification of the ancestral amniote lineage.

  1. Structure Controlled Long-Range Sequential Tunneling in Carbon-Based Molecular Junctions.

    Science.gov (United States)

    Morteza Najarian, Amin; McCreery, Richard L

    2017-04-25

    Carbon-based molecular junctions consisting of aromatic oligomers between conducting sp(2) hybridized carbon electrodes exhibit structure-dependent current densities (J) when the molecular layer thickness (d) exceeds ∼5 nm. All four of the molecular structures examined exhibit an unusual, nonlinear ln J vs bias voltage (V) dependence which is not expected for conventional coherent tunneling or activated hopping mechanisms. All molecules exhibit a weak temperature dependence, with J increasing typically by a factor of 2 over the range of 200-440 K. Fluorene and anthraquinone show linear plots of ln J vs d with nearly identical J values for the range d = 3-10 nm, despite significant differences in their free-molecule orbital energy levels. The observed current densities for anthraquinone, fluorene, nitroazobenzene, and bis-thienyl benzene for d = 7-10 nm show no correlation with occupied (HOMO) or unoccupied (LUMO) molecular orbital energies, contrary to expectations for transport mechanisms based on the offset between orbital energies and the electrode Fermi level. UV-vis absorption spectroscopy of molecular layers bonded to carbon electrodes revealed internal energy levels of the chemisorbed films and also indicated limited delocalization in the film interior. The observed current densities correlate well with the observed UV-vis absorption maxima for the molecular layers, implying a transport mechanism determined by the HOMO-LUMO energy gap. We conclude that transport in carbon-based aromatic molecular junctions is consistent with multistep tunneling through a barrier defined by the HOMO-LUMO gap, and not by charge transport at the electrode interfaces. In effect, interfacial "injection" at the molecule/electrode interfaces is not rate limiting due to relatively strong electronic coupling, and transport is controlled by the "bulk" properties of the molecular layer interior.

  2. Study of Higher Order Modes in Superconducting Accelerating Structures for Linac Applications

    CERN Document Server

    Schuh, Marcel; Welsch, C P

    2011-01-01

    Higher Order Modes (HOMs) can severely limit the operation of superconducting cavities in a linear accelerator with high beam current, high duty factor and complex pulse structure. Therefore, the full HOM spectrum has to be analysed in detail to identify potentially dangerous modes already during the design phase and to define their damping requirements. For this purpose a dedicated beam dynamics simulation code, Simulation of higher order Mode Dynamics (SMD), focusing on beam-HOM interaction, has been developed in the frame of this project. SMD allows to analyse the beam behaviour under the presence of HOMs, taking into account many important effects, such as for example the HOM frequency spread, beam input jitter, different chopping patterns, as well as klystron and alignment errors. SMD is used to investigate in detail into the effects of HOMs in the Superconducting Proton Linac (SPL) at CERN and in particular their potential to drive beam instabili- ties in the longitudinal and transverse direction. Based...

  3. Efficient Model Order Reduction for the Dynamics of Nonlinear Multilayer Sheet Structures with Trial Vector Derivatives

    Directory of Open Access Journals (Sweden)

    Wolfgang Witteveen

    2014-01-01

    Full Text Available The mechanical response of multilayer sheet structures, such as leaf springs or car bodies, is largely determined by the nonlinear contact and friction forces between the sheets involved. Conventional computational approaches based on classical reduction techniques or the direct finite element approach have an inefficient balance between computational time and accuracy. In the present contribution, the method of trial vector derivatives is applied and extended in order to obtain a-priori trial vectors for the model reduction which are suitable for determining the nonlinearities in the joints of the reduced system. Findings show that the result quality in terms of displacements and contact forces is comparable to the direct finite element method but the computational effort is extremely low due to the model order reduction. Two numerical studies are presented to underline the method’s accuracy and efficiency. In conclusion, this approach is discussed with respect to the existing body of literature.

  4. Monadic structures over an ordered universal random graph and finite automata

    Energy Technology Data Exchange (ETDEWEB)

    Dudakov, Sergey M [Tver' State University, Tver' (Russian Federation)

    2011-10-31

    We continue the investigation of the expressive power of the language of predicate logic for finite algebraic systems embedded in infinite systems. This investigation stems from papers of M. A. Taitslin, M. Benedikt and L. Libkin, among others. We study the properties of a finite monadic system which can be expressed by formulae if such a system is embedded in a random graph that is totally ordered in an arbitrary way. The Buechi representation is used to connect monadic structures and formal languages. It is shown that, if one restricts attention to formulae that are <-invariant in totally ordered random graphs, then these formulae correspond to finite automata. We show that =-invariant formulae expressing the properties of the embedded system itself can express only Boolean combinations of properties of the form 'the cardinality of an intersection of one-place predicates belongs to one of finitely many fixed finite or infinite arithmetic progressions'.

  5. Extrusion induced low-order starch matrices: Enzymic hydrolysis and structure.

    Science.gov (United States)

    Zhang, Bin; Dhital, Sushil; Flanagan, Bernadine M; Luckman, Paul; Halley, Peter J; Gidley, Michael J

    2015-12-10

    Waxy, normal and highwaymen maize starches were extruded with water as sole plasticizer to achieve low-order starch matrices. Of the three starches, we found that only high-amylose extrudate showed lower digestion rate/extent than starches cooked in excess water. The ordered structure of high-amylose starches in cooked and extruded forms was similar, as judged by NMR, XRD and DSC techniques, but enzyme resistance was much greater for extruded forms. Size exclusion chromatography suggested that longer chains were involved in enzyme resistance. We propose that the local molecular density of packing of amylose chains can control the digestion kinetics rather than just crystallinity, with the principle being that density sufficient to either prevent/limit binding and/or slow down catalysis can be achieved by dense amorphous packing. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Fundamental structure of Fresnel diffraction: longitudinal uniformity with respect to fractional Fourier order.

    Science.gov (United States)

    Ozaktas, Haldun M; Arık, Sercan Ö; Coşkun, Türker

    2012-01-01

    Fresnel integrals corresponding to different distances can be interpreted as scaled fractional Fourier transformations observed on spherical reference surfaces. Transverse samples can be taken on these surfaces with separation that increases with propagation distance. Here, we are concerned with the separation of the spherical reference surfaces along the longitudinal direction. We show that these surfaces should be equally spaced with respect to the fractional Fourier transform order, rather than being equally spaced with respect to the distance of propagation along the optical axis. The spacing should be of the order of the reciprocal of the space-bandwidth product of the signals. The space-dependent longitudinal and transverse spacings define a grid that reflects the structure of Fresnel diffraction. © 2012 Optical Society of America

  7. Recursion method for the quasiparticle structure of a single vortex with induced magnetic order

    DEFF Research Database (Denmark)

    Udby, L.; Andersen, B.M.; Hedegård, P.

    2006-01-01

    . Furthermore, we study the low-energy quasiparticle structure when magnetic vortices operate as pinning centers for surrounding unidirectional spin density waves (stripes). We calculate the Fourier transformed LDOS and show how the energy dependence of relevant Fourier components can be used to determine...... the nature of the magnetic field-induced order, and predict field-induced LDOS features that can be tested by future scanning tunneling microscopy experiments.......We use a real-space recursion method to calculate the local density of states (LDOS) within a model that contains both d-wave superconducting and antiferromagnetic order. We focus on the LDOS in the superconducting phase near single vortices with either normal or antiferromagnetic cores...

  8. All-optical 1st- and 2nd-order differential equation solvers with large tuning ranges using Fabry-Pérot semiconductor optical amplifiers.

    Science.gov (United States)

    Chen, Kaisheng; Hou, Jie; Huang, Zhuyang; Cao, Tong; Zhang, Jihua; Yu, Yuan; Zhang, Xinliang

    2015-02-09

    We experimentally demonstrate an all-optical temporal computation scheme for solving 1st- and 2nd-order linear ordinary differential equations (ODEs) with tunable constant coefficients by using Fabry-Pérot semiconductor optical amplifiers (FP-SOAs). By changing the injection currents of FP-SOAs, the constant coefficients of the differential equations are practically tuned. A quite large constant coefficient tunable range from 0.0026/ps to 0.085/ps is achieved for the 1st-order differential equation. Moreover, the constant coefficient p of the 2nd-order ODE solver can be continuously tuned from 0.0216/ps to 0.158/ps, correspondingly with the constant coefficient q varying from 0.0000494/ps(2) to 0.006205/ps(2). Additionally, a theoretical model that combining the carrier density rate equation of the semiconductor optical amplifier (SOA) with the transfer function of the Fabry-Pérot (FP) cavity is exploited to analyze the solving processes. For both 1st- and 2nd-order solvers, excellent agreements between the numerical simulations and the experimental results are obtained. The FP-SOAs based all-optical differential-equation solvers can be easily integrated with other optical components based on InP/InGaAsP materials, such as laser, modulator, photodetector and waveguide, which can motivate the realization of the complicated optical computing on a single integrated chip.

  9. Pick-and-place guidance utilizing an integrated control method and structured light ranging

    Science.gov (United States)

    Riekki, Jukka P.; Roening, Juha; Silven, Olli; Pietikaeinen, Matti; Koivunen, Visa

    1992-02-01

    This paper presents a vision-guided control system for an industrial robot capable of picking up an object, moving it to a goal, and placing it there. Tasks given to the control system are based on imperfect knowledge about the environment. The control system corrects the task parameters by matching them against range information gained from the environment. The control system is part of a larger system, which includes a high-level goal-oriented planner. The planner consists of hierarchically organized planning-executing-monitoring triplets, which execute given tasks by dividing them into subtasks, by sending the subtasks either to other triplets or to the control system described in this paper, and by monitoring the execution of the subtasks. The planner sees the robot and the control system as an intelligent robot capable of executing pick-and-place tasks in a dynamic, partly unknown environment. This paper presents the results of the testing of the control system with an industrial 6-axis robot and a structured light-based range sensor. Also the principle of calibrating the robot and the sensor is presented.

  10. Structure and dielectric properties in the radio frequency range of polymer composites based on vanadium dioxide

    Directory of Open Access Journals (Sweden)

    Kolbunov V.R.

    2015-06-01

    Full Text Available Polymer composites with active fillers are recently considered to be promising materials for the design of new functional devices with controllable properties and are intensively investigated. Dielectric studies are one of the most effective methods for studying structural features and mechanisms of conductivity formation for this type of two-component systems. The paper presents research results of the dielectric characteristics in the range of radio frequency of 50 kHz — 10 MHz and temperature range of 30—60°C of polyethylene composites of vanadium dioxide with different volume fractions of filler. Two dispersion areas were found: a high-frequency area caused by the Maxwell charge separation on the boundaries of the polyethylene matrix — conductive filler of VI2 crystallites, and a low frequency area associated with the presence of the transition layer at this boundary. The relative permittivity of the composite has a tendency to a decrease in absolute value with increasing temperature. The analysis of the low-frequency dependence of the dielectric constant of the value of the filler’s volume fraction revealed that the investigated composite belongs to two-component statistical mixtures with a transition layer between the components.

  11. Ternary iron, magnesium, calcium carbonates; a thermodynamic model for dolomite as an ordered derivative of calcite-structure solutions

    National Research Council Canada - National Science Library

    Davidson, Paula M

    1994-01-01

      The simplest solution model that can account for dolomite as an ordered derivative structure of the disordered calcite structure solution, based on a ternary extension of the generalized point approximation given by C...

  12. Detecting memory and structure in human navigation patterns using Markov chain models of varying order.

    Directory of Open Access Journals (Sweden)

    Philipp Singer

    Full Text Available One of the most frequently used models for understanding human navigation on the Web is the Markov chain model, where Web pages are represented as states and hyperlinks as probabilities of navigating from one page to another. Predominantly, human navigation on the Web has been thought to satisfy the memoryless Markov property stating that the next page a user visits only depends on her current page and not on previously visited ones. This idea has found its way in numerous applications such as Google's PageRank algorithm and others. Recently, new studies suggested that human navigation may better be modeled using higher order Markov chain models, i.e., the next page depends on a longer history of past clicks. Yet, this finding is preliminary and does not account for the higher complexity of higher order Markov chain models which is why the memoryless model is still widely used. In this work we thoroughly present a diverse array of advanced inference methods for determining the appropriate Markov chain order. We highlight strengths and weaknesses of each method and apply them for investigating memory and structure of human navigation on the Web. Our experiments reveal that the complexity of higher order models grows faster than their utility, and thus we confirm that the memoryless model represents a quite practical model for human navigation on a page level. However, when we expand our analysis to a topical level, where we abstract away from specific page transitions to transitions between topics, we find that the memoryless assumption is violated and specific regularities can be observed. We report results from experiments with two types of navigational datasets (goal-oriented vs. free form and observe interesting structural differences that make a strong argument for more contextual studies of human navigation in future work.

  13. Detecting memory and structure in human navigation patterns using Markov chain models of varying order.

    Science.gov (United States)

    Singer, Philipp; Helic, Denis; Taraghi, Behnam; Strohmaier, Markus

    2014-01-01

    One of the most frequently used models for understanding human navigation on the Web is the Markov chain model, where Web pages are represented as states and hyperlinks as probabilities of navigating from one page to another. Predominantly, human navigation on the Web has been thought to satisfy the memoryless Markov property stating that the next page a user visits only depends on her current page and not on previously visited ones. This idea has found its way in numerous applications such as Google's PageRank algorithm and others. Recently, new studies suggested that human navigation may better be modeled using higher order Markov chain models, i.e., the next page depends on a longer history of past clicks. Yet, this finding is preliminary and does not account for the higher complexity of higher order Markov chain models which is why the memoryless model is still widely used. In this work we thoroughly present a diverse array of advanced inference methods for determining the appropriate Markov chain order. We highlight strengths and weaknesses of each method and apply them for investigating memory and structure of human navigation on the Web. Our experiments reveal that the complexity of higher order models grows faster than their utility, and thus we confirm that the memoryless model represents a quite practical model for human navigation on a page level. However, when we expand our analysis to a topical level, where we abstract away from specific page transitions to transitions between topics, we find that the memoryless assumption is violated and specific regularities can be observed. We report results from experiments with two types of navigational datasets (goal-oriented vs. free form) and observe interesting structural differences that make a strong argument for more contextual studies of human navigation in future work.

  14. Study of long-range orders of hard-core bosons coupled to cooperative normal modes in two-dimensional lattices

    Science.gov (United States)

    Ghosh, A.; Yarlagadda, S.

    2017-09-01

    Understanding the microscopic mechanism of coexisting long-range orders (such as lattice supersolidity) in strongly correlated systems is a subject of immense interest. We study the possible manifestations of long-range orders, including lattice-supersolid phases with differently broken symmetry, in a two-dimensional square lattice system of hard-core bosons (HCBs) coupled to archetypal cooperative/coherent normal-mode distortions such as those in perovskites. At strong HCB-phonon coupling, using a duality transformation to map the strong-coupling problem to a weak-coupling one, we obtain an effective Hamiltonian involving nearest-neighbor, next-nearest-neighbor, and next-to-next-nearest-neighbor hoppings and repulsions. Using stochastic series expansion quantum Monte Carlo, we construct the phase diagram of the system. As coupling strength is increased, we find that the system undergoes a first-order quantum phase transition from a superfluid to a checkerboard solid at half-filling and from a superfluid to a diagonal striped solid [with crystalline ordering wave vector Q ⃗=(2 π /3 ,2 π /3 ) or (2 π /3 ,4 π /3 )] at one-third filling without showing any evidence of supersolidity. On tuning the system away from these commensurate fillings, checkerboard supersolid is generated near half-filling whereas a rare diagonal striped supersolid is realized near one-third filling. Interestingly, there is an asymmetry in the extent of supersolidity about one-third filling. Within our framework, we also provide an explanation for the observed checkerboard and stripe formations in La2 -xSrxNiO4 at x =1 /2 and x =1 /3 .

  15. Small geographic range but not panmictic: how forests structure the endangered Point Arena mountain beaver (Aplodontia rufa nigra)

    Science.gov (United States)

    William J. Zielinski; Fredrick V. Schlexer; Sean A. Parks; Kristine L. Pilgrim; Michael K. Schwartz

    2012-01-01

    The landscape genetics framework is typically applied to broad regions that occupy only small portions of a species' range. Rarely is the entire range of a taxon the subject of study. We examined the landscape genetic structure of the endangered Point Arena mountain beaver (Aplodontia rufa nigra), whose isolated geographic range is found in a...

  16. Higher-Order Structure in Bacterial VapBC Toxin-Antitoxin Complexes

    DEFF Research Database (Denmark)

    Bendtsen, Kirstine L; Brodersen, Ditlev E

    2017-01-01

    Toxin-antitoxin systems are widespread in the bacterial kingdom, including in pathogenic species, where they allow rapid adaptation to changing environmental conditions through selective inhibition of key cellular processes, such as DNA replication or protein translation. Under normal growth...... that allow auto-regulation of transcription by direct binding to promoter DNA. In this chapter, we review our current understanding of the structural characteristics of type II toxin-antitoxin complexes in bacterial cells, with a special emphasis on the staggering variety of higher-order architecture...

  17. An Implementable First-Order Primal-Dual Algorithm for Structured Convex Optimization

    Directory of Open Access Journals (Sweden)

    Feng Ma

    2014-01-01

    Full Text Available Many application problems of practical interest can be posed as structured convex optimization models. In this paper, we study a new first-order primaldual algorithm. The method can be easily implementable, provided that the resolvent operators of the component objective functions are simple to evaluate. We show that the proposed method can be interpreted as a proximal point algorithm with a customized metric proximal parameter. Convergence property is established under the analytic contraction framework. Finally, we verify the efficiency of the algorithm by solving the stable principal component pursuit problem.

  18. Computational Benefits Using an Advanced Concatenation Scheme Based on Reduced Order Models for RF Structures

    CERN Document Server

    Heller, Johann; Van Rienen, Ursula; 10.1016/j.phpro.2015.11.060

    2015-01-01

    The computation of electromagnetic fields and parameters derived thereof for lossless radio frequency (RF) structures filled with isotropic media is an important task for the design and operation of particle accelerators. Unfortunately, these computations are often highly demanding with regard to computational effort. The entire computational demand of the problem can be reduced using decomposition schemes in order to solve the field problems on standard workstations. This paper presents one of the first detailed comparisons between the recently proposed state-space concatenation approach (SSC) and a direct computation for an accelerator cavity with coupler-elements that break the rotational symmetry.

  19. Observations of imposed ordered structures in a dusty plasma at high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Edward, E-mail: etjr@auburn.edu; Lynch, Brian; Konopka, Uwe [Physics Department, Auburn University, Auburn, Alabama 36849 (United States); Merlino, Robert L. [Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242 (United States); Rosenberg, Marlene [Department of Electrical and Computer Engineering, University of California–San Diego, La Jolla, California 92093 (United States)

    2015-03-15

    Dusty plasmas have been studied in argon, rf glow discharge plasmas at magnetic fields up to 2 T, where the electrons and ions are strongly magnetized. In this experiment, plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper, electrically floating electrode supports a semi-transparent, titanium mesh. We report on the formation of an ordered dusty plasma, where the dust particles form a spatial structure that is aligned to the mesh. We discuss possible mechanisms that may lead to the formation of the “dust grid” and point out potential implications and applications of these observations.

  20. Structure-based modification of a Clostridium difficile-targeting endolysin affects activity and host range.

    Science.gov (United States)

    Mayer, Melinda J; Garefalaki, Vasiliki; Spoerl, Rebecca; Narbad, Arjan; Meijers, Rob

    2011-10-01

    Endolysin CD27L causes cell lysis of the pathogen Clostridium difficile, a major cause of nosocomial infection. We report a structural and functional analysis of the catalytic activity of CD27L against C. difficile and other bacterial strains. We show that truncation of the endolysin to the N-terminal domain, CD27L1-179, gave an increased lytic activity against cells of C. difficile, while the C-terminal region, CD27L180-270, failed to produce lysis. CD27L1-179 also has increased activity against other bacterial species that are targeted by the full-length protein and in addition was able to lyse some CD27L-insensitive strains. However, CD27L1-179 retained a measure of specificity, failing to lyse a wide range of bacteria. The use of green fluorescent protein (GFP)-labeled proteins demonstrated that both CD27L and CD27L1-179 bound to C. difficile cell walls. The crystal structure of CD27L1-179 confirms that the enzyme is a zinc-dependent N-acetylmuramoyl-l-alanine amidase. A structure-based sequence analysis allowed us to identify four catalytic residues, a proton relay cascade, and a substrate binding pocket. A BLAST search shows that the closest-related amidases almost exclusively target Clostridia. This implied that the catalytic domain alone contained features that target a specific bacterial species. To test this hypothesis, we modified Leu 98 to a Trp residue which is found in an endolysin from a bacteriophage of Listeria monocytogenes (PlyPSA). This mutation in CD27L resulted in an increased activity against selected serotypes of L. monocytogenes, demonstrating the potential to tune the species specificity of the catalytic domain of an endolysin.

  1. Nonlinear Acoustic Response of an Aircraft Fuselage Sidewall Structure by a Reduced-Order Analysis

    Science.gov (United States)

    Przekop, Adam; Rizzi, Stephen A.; Groen, David S.

    2006-01-01

    A reduced-order nonlinear analysis of a structurally complex aircraft fuselage sidewall panel is undertaken to explore issues associated with application of such analyses to practical structures. Of primary interest is the trade-off between computational efficiency and accuracy. An approach to modal basis selection is offered based upon the modal participation in the linear regime. The nonlinear static response to a uniform pressure loading and nonlinear random response to a uniformly distributed acoustic loading are computed. Comparisons of the static response with a nonlinear static solution in physical degrees-of-freedom demonstrate the efficacy of the approach taken for modal basis selection. Changes in the modal participation as a function of static and random loading levels suggest a means for improvement in the basis selection.

  2. Stability and electronic structure of ordered Si0.75Ge0.25C alloy

    Science.gov (United States)

    Chen, Z. W.; Lv, M. Y.; Liu, R. P.

    2005-11-01

    Calculations are performed on the stability and electronic structure of an ordered Si0.75Ge0.25C alloy within the generalized gradient approximation using the first-principles method. The alloy is stable at zero pressure and temperature, with its lattice constant 4.34 A˚ close to that of cubic SiC and bulk modulus 223 GPa. An analysis of the band structure and density of states shows the cubic alloy to be an indirect semiconductor with a wider band gap compared to SiC and therefore is a candidate material that can function in heterostructure applications. When combined with cubic SiC to form heterostructure bipolar transistors, an enhancement coefficient 2×104 for current gain β would be expected relative to the SiC homojunction bipolar junction transistors at room temperature.

  3. Higher-Order Spectral Analysis to Identify Quadratic Nonlinearities in Fluid-Structure Interaction

    Directory of Open Access Journals (Sweden)

    Imran Akhtar

    2018-01-01

    Full Text Available Hydrodynamic forces on a structure are the manifestation of fluid-structure interaction. Since this interaction is nonlinear, these forces consist of various frequencies: fundamental, harmonics, excitation, sum, and difference of these frequencies. To analyze this phenomenon, we perform numerical simulations of the flow past stationary and oscillating cylinders at low Reynolds numbers. We compute the pressure, integrate it over the surface, and obtain the lift and drag coefficients for the two configurations: stationary and transversely oscillating cylinders. Higher-order spectral analysis is performed to investigate the nonlinear interaction between the forces. We confirmed and investigated the quadratic coupling between the lift and drag coefficients and their phase relationship. We identify additional frequencies and their corresponding energy present in the flow field that appear as the manifestation of quadratic nonlinear interaction.

  4. Efficient Analysis of Structures with Rotatable Elements Using Model Order Reduction

    Directory of Open Access Journals (Sweden)

    G. Fotyga

    2016-04-01

    Full Text Available This paper presents a novel full-wave technique which allows for a fast 3D finite element analysis of waveguide structures containing rotatable tuning elements of arbitrary shapes. Rotation of these elements changes the resonant frequencies of the structure, which can be used in the tuning process to obtain the S-characteristics desired for the device. For fast commutations of the response as the tuning elements are rotated, the 3D finite element method is supported by multilevel model-order reduction, orthogonal projection at the boundaries of macromodels and the operation called macromodels cloning. All the time-consuming steps are performed only once in the preparatory stage. In the tuning stage, only small parts of the domain are updated, by means of a special meshing technique. In effect, the tuning process is performed extremely rapidly. The results of the numerical experiments confirm the efficiency and validity of the proposed method.

  5. Spin dynamics, short range order and spin freezing in Y0.5Ca0.5BaCo4O7

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, John Ross [ISIS Facility, Rutherford Appleton Laboratory; Ehlers, Georg [ORNL; Fouquet, Peter [Institut Laue-Langevin (ILL); Mutka, Hannu [Institut Laue-Langevin (ILL); Payen, Christophe [Institut des Materiaux Jean Rouxel (IMN), Universite de Nantes-CNRS; Lortz, Rolf [University of Geneva

    2011-01-01

    Y0.5Ca0.5BaCo4O7 was recently introduced as a possible candidate for capturing some of the predicted classical spin kagome ground-state features. Stimulated by this conjecture, we have taken up a more complete study of the spin correlations in this compound with neutron scattering methods on a powder sample characterized with high-resolution neutron diffraction and the temperature dependence of magnetic susceptibility and specific heat. We have found that the frustrated near-neighbor magnetic correlations involve not only the kagome planes but concern the full Co sublattice, as evidenced by the analysis of the wave-vector dependence of the short-range order. We conclude from our results that the magnetic moments are located on the Co sublattice as a whole and that correlations extend beyond the two-dimensional kagome planes. We identify intriguing dynamical properties, observing high-frequency fluctuations with a Lorentzian linewidth G?20 meV at ambient temperature. On cooling a low-frequency ({approx}1 meV) dynamical component develops alongside the high-frequency fluctuations, which eventually becomes static at temperatures below T {approx} 50 K. The high-frequency response with an overall linewidth of {approx}10 meV prevails at T?2 K, coincident with a fully elastic short-range-ordered contribution.

  6. Uncertainty Aware Structural Topology Optimization Via a Stochastic Reduced Order Model Approach

    Science.gov (United States)

    Aguilo, Miguel A.; Warner, James E.

    2017-01-01

    This work presents a stochastic reduced order modeling strategy for the quantification and propagation of uncertainties in topology optimization. Uncertainty aware optimization problems can be computationally complex due to the substantial number of model evaluations that are necessary to accurately quantify and propagate uncertainties. This computational complexity is greatly magnified if a high-fidelity, physics-based numerical model is used for the topology optimization calculations. Stochastic reduced order model (SROM) methods are applied here to effectively 1) alleviate the prohibitive computational cost associated with an uncertainty aware topology optimization problem; and 2) quantify and propagate the inherent uncertainties due to design imperfections. A generic SROM framework that transforms the uncertainty aware, stochastic topology optimization problem into a deterministic optimization problem that relies only on independent calls to a deterministic numerical model is presented. This approach facilitates the use of existing optimization and modeling tools to accurately solve the uncertainty aware topology optimization problems in a fraction of the computational demand required by Monte Carlo methods. Finally, an example in structural topology optimization is presented to demonstrate the effectiveness of the proposed uncertainty aware structural topology optimization approach.

  7. The Ordering and Electronic Structure of Multilayer Epitaxial Graphene on SiC

    Science.gov (United States)

    Conrad, Edward

    2011-03-01

    The structural definition of graphene as a single sheet of hexagonal carbon limits how we view this material. It is the electronic properties of a single isolated graphene sheet that actually defines and motivates current graphene research. Remarkably, the best example of the idealized band structure of graphene comes does not come from a single graphene layer but from multilayer films grown on SiC. Multilayer epitaxial graphene (MEG) not only shows all the 2D properties expected for an isolated graphene sheet, but it the scalability to large scale integrated carbon circuits. I will show that the reason for this remarkable property, i.e. that a multilayer graphene films behaving like a single graphene sheet, is due to MEG's unique stacking. MEG films have a quasi-ordered rotational stacking that breaks the Bernal stacking symmetry associated with graphite. Angle resolved photoemission spectroscopy (ARPES) data demonstrates that the bands are linear at the K-point of these films. We can also show that the rotated stacking is highly ordered and that less than 20% of the graphene sheets in the film are Bernal stacked. I will also show that ARPES measurements on MEG films demonstrate serious inadequacies with both tight binding and ab initio formalisms. In particular the data shows no reductions in the Fermi velocity or the formation of Van Hove singularity that have been consistently predicted for this material. I wish to acknowledge funding from the NSF under Grants No. DMR-0820382 and DMR-1005880.

  8. LDA+DMFT approach to ordering phenomena and the structural stability of correlated materials

    Science.gov (United States)

    Kuneš, J.; Leonov, I.; Augustinský, P.; Křápek, V.; Kollar, M.; Vollhardt, D.

    2017-07-01

    Materials with correlated electrons often respond very strongly to external or internal influences, leading to instabilities and states of matter with broken symmetry. This behavior can be studied theoretically either by evaluating the linear response characteristics, or by simulating the ordered phases of the materials under investigation. We developed the necessary tools within the dynamical mean-field theory (DMFT) to search for electronic instabilities in materials close to spin-state crossovers and to analyze the properties of the corresponding ordered states. This investigation, motivated by the physics of LaCoO3, led to a discovery of condensation of spinful excitons in the two-orbital Hubbard model with a surprisingly rich phase diagram. The results are reviewed in the first part of the article. Electronic correlations can also be the driving force behind structural transformations of materials. To be able to investigate correlation-induced phase instabilities we developed and implemented a formalism for the computation of total energies and forces within a fully charge self-consistent combination of density functional theory and DMFT. Applications of this scheme to the study of structural instabilities of selected correlated electron materials such as Fe and FeSe are reviewed in the second part of the paper.

  9. Higher-order structure in the trajectories of depression and anxiety following sudden involuntary unemployment.

    Science.gov (United States)

    Howe, George W; Hornberger, Anna P; Weihs, Karen; Moreno, Francisco; Neiderhiser, Jenae M

    2012-05-01

    Recent work on comorbidity finds evidence for hierarchical structure of mood and anxiety disorders and symptoms. This study tests whether a higher-order internalizing factor accounts for variation in depression and anxiety symptom severity and change over time in a sample experiencing a period of major life stress. Data on symptoms of depression, chronic worry, and social anxiety were collected five times across seven months from 426 individuals who had recently lost jobs. Growth models for each type of symptom found significant variation in individual trajectories. Slopes were highly correlated across symptom type, as were intercepts. Multilevel confirmatory factor analyses found evidence for a higher-order internalizing factor for both slopes and intercepts, reflective of comorbidity of depression and anxiety, with the internalizing factor accounting for 54% to 91% of the variance in slopes and intercepts of specific symptom sets, providing evidence for both a general common factor and domain-specific factors characterizing level and change in symptoms. Loadings on the higher order factors differed modestly for men and women, and when comparing African American and White participants, but did not differ by age, education, or history of depression. More distal factors including gender and history of depression were strongly associated with internalizing in the early weeks after job loss, but rates of change in internalizing were associated most strongly with reemployment. Findings suggest that stressors may contribute in different ways to the common internalizing factor as compared to variance in anxiety and depression that is independent of that factor.

  10. Growth and structure of L1 sub 0 ordered FePt films on GaAs(001)

    CERN Document Server

    Nefedov, A; Theis-Broehl, K; Zabel, H; Doi, M; Schuster, E; Keune, W

    2002-01-01

    The structural properties of epitaxial L1 sub 0 ordered FePt(001) films, grown by molecular beam epitaxy (alternating deposition of Fe and Pt atomic layers) on buffer-Pt/seed-Fe/GaAs(001) have been studied by in situ reflection high-energy electron diffraction and by ex situ x-ray scattering as a function of the growth conditions. Reflection high-energy electron diffraction intensity oscillations measured during FePt layer growth provide evidence for island growth at T sub s = 200 deg. C and quasi layer-by-layer growth at T sub s = 350 deg. C. From small-angle and wide-angle x-ray scattering it was found that the degree of epitaxy depends critically on morphology of the seed layer and the substrate roughness. X-ray diffraction analysis showed that the long-range order parameter increases from near zero for films grown at 200 deg. C to 0.65 for films grown at 350 deg. C. This confirms the fact that the order parameter is mainly determined by the surface mobility of the atoms which is controlled experimentally ...

  11. Acceleration Data Reveal Highly Individually Structured Energetic Landscapes in Free-Ranging Fishers (Pekania pennanti).

    Science.gov (United States)

    Scharf, Anne K; LaPoint, Scott; Wikelski, Martin; Safi, Kamran

    2016-01-01

    Investigating animal energy expenditure across space and time may provide more detailed insight into how animals interact with their environment. This insight should improve our understanding of how changes in the environment affect animal energy budgets and is particularly relevant for animals living near or within human altered environments where habitat change can occur rapidly. We modeled fisher (Pekania pennanti) energy expenditure within their home ranges and investigated the potential environmental and spatial drivers of the predicted spatial patterns. As a proxy for energy expenditure we used overall dynamic body acceleration (ODBA) that we quantified from tri-axial accelerometer data during the active phases of 12 individuals. We used a generalized additive model (GAM) to investigate the spatial distribution of ODBA by associating the acceleration data to the animals' GPS-recorded locations. We related the spatial patterns of ODBA to the utilization distributions and habitat suitability estimates across individuals. The ODBA of fishers appears highly structured in space and was related to individual utilization distribution and habitat suitability estimates. However, we were not able to predict ODBA using the environmental data we selected. Our results suggest an unexpected complexity in the space use of animals that was only captured partially by re-location data-based concepts of home range and habitat suitability. We suggest future studies recognize the limits of ODBA that arise from the fact that acceleration is often collected at much finer spatio-temporal scales than the environmental data and that ODBA lacks a behavioral correspondence. Overcoming these limits would improve the interpretation of energy expenditure in relation to the environment.

  12. Hydrated goethite (alpha-FeOOH) (100) interface structure: Ordered water and surface functional groups.

    Energy Technology Data Exchange (ETDEWEB)

    Ghose, S.K.; Waychunas, G.A.; Trainor, T.P.; Eng, P.J.

    2009-12-15

    Goethite({alpha}-FeOOH), an abundant and highly reactive iron oxyhydroxide mineral, has been the subject of numerous stud-ies of environmental interface reactivity. However, such studies have been hampered by the lack of experimental constraints on aqueous interface structure, and especially of the surface water molecular arrangements. Structural information of this type is crucial because reactivity is dictated by the nature of the surface functional groups and the structure or distribution of water and electrolyte at the solid-solution interface. In this study we have investigated the goethite(100) surface using surface diffraction techniques, and have determined the relaxed surface structure, the surface functional groups, and the three dimensional nature of two distinct sorbed water layers. The crystal truncation rod (CTR) results show that the interface structure consists of a double hydroxyl, double water terminated interface with significant atom relaxations. Further, the double hydroxyl terminated surface dominates with an 89% contribution having a chiral subdomain structure on the(100) cleavage faces. The proposed interface stoichiometry is ((H{sub 2}O)-(H{sub 2}O)-OH{sub 2}-OH-Fe-O-O-Fe-R) with two types of terminal hydroxyls; a bidentate (B-type) hydroxo group and a monodentate (A-type) aquo group. Using the bond-valence approach the protonation states of the terminal hydroxyls are predicted to be OH type (bidentate hydroxyl with oxygen coupled to two Fe{sup 3+} ions) and OH{sub 2} type (monodentate hydroxyl with oxygen tied to only one Fe{sup 3+}). A double layer three dimensional ordered water structure at the interface was determined from refinement of fits to the experimental data. Application of bond-valence constraints to the terminal hydroxyls with appropriate rotation of the water dipole moments allowed a plausible dipole orientation model as predicted. The structural results are discussed in terms of protonation and H-bonding at the interface

  13. Monolithic integration of InGaN segments emitting in the blue, green, and red spectral range in single ordered nanocolumns

    Energy Technology Data Exchange (ETDEWEB)

    Albert, S.; Bengoechea-Encabo, A.; Sanchez-Garcia, M. A.; Calleja, E. [ISOM and Dept. Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Kong, X.; Trampert, A. [Paul-Drude-Institut fuer Festkoeperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2013-05-06

    This work reports on the selective area growth by plasma-assisted molecular beam epitaxy and characterization of InGaN/GaN nanocolumnar heterostructures. The optimization of the In/Ga and total III/V ratios, as well as the growth temperature, provides control on the emission wavelength, either in the blue, green, or red spectral range. An adequate structure tailoring and monolithic integration in a single nanocolumnar heterostructure of three InGaN portions emitting in the red-green-blue colors lead to white light emission.

  14. A bioinformatics approach to the structure, function, and evolution of the nucleoprotein of the order mononegavirales.

    Directory of Open Access Journals (Sweden)

    Sean B Cleveland

    Full Text Available The goal of this Bioinformatic study is to investigate sequence conservation in relation to evolutionary function/structure of the nucleoprotein of the order Mononegavirales. In the combined analysis of 63 representative nucleoprotein (N sequences from four viral families (Bornaviridae, Filoviridae, Rhabdoviridae, and Paramyxoviridae we predict the regions of protein disorder, intra-residue contact and co-evolving residues. Correlations between location and conservation of predicted regions illustrate a strong division between families while high- lighting conservation within individual families. These results suggest the conserved regions among the nucleoproteins, specifically within Rhabdoviridae and Paramyxoviradae, but also generally among all members of the order, reflect an evolutionary advantage in maintaining these sites for the viral nucleoprotein as part of the transcription/replication machinery. Results indicate conservation for disorder in the C-terminus region of the representative proteins that is important for interacting with the phosphoprotein and the large subunit polymerase during transcription and replication. Additionally, the C-terminus region of the protein preceding the disordered region, is predicted to be important for interacting with the encapsidated genome. Portions of the N-terminus are responsible for N∶N stability and interactions identified by the presence or lack of co-evolving intra-protein contact predictions. The validation of these prediction results by current structural information illustrates the benefits of the Disorder, Intra-residue contact and Compensatory mutation Correlator (DisICC pipeline as a method for quickly characterizing proteins and providing the most likely residues and regions necessary to target for disruption in viruses that have little structural information available.

  15. Excitation of a double corrugation slow-wave structure in terahertz range

    DEFF Research Database (Denmark)

    Zhurbenko, Vitaliy; Krozer, Viktor; Kotiranta, Mikko

    2011-01-01

    problem of a terahertz double corrugation slow-wave structure is considered and practical realization of the structure using currently available technological processes is discussed. The parameters of the realized excitation structure are optimized for vacuum electronics applications while taking...

  16. Ordered and isomorphic mapping of periodic structures in the parametrically forced logistic map

    Energy Technology Data Exchange (ETDEWEB)

    Maranhão, Dariel M., E-mail: dariel@ifsp.edu.br [Departamento de Ciências e Matemática, Instituto Federal de Educação, Ciência e Tecnologia de São Paulo, São Paulo (Brazil); Diretoria de Informática, Universidade Nove de Julho, São Paulo (Brazil)

    2016-09-23

    Highlights: • A direct description of the internal structure of a periodic window in terms of winding numbers is proposed. • Periodic structures in parameter spaces are mapped in a recurrent and isomorphic way. • Sequences of winding numbers show global and local organization of periodic domains. - Abstract: We investigate the periodic domains found in the parametrically forced logistic map, the classical logistic map when its control parameter changes dynamically. Phase diagrams in two-parameter spaces reveal intricate periodic structures composed of patterns of intersecting superstable orbits curves, defining the cell of a periodic window. Cells appear multifoliated and ordered, and they are isomorphically mapped when one changes the map parameters. Also, we identify the characteristics of simplest cell and apply them to other more complex, discussing how the topography on parameter space is affected. By use of the winding number as defined in periodically forced oscillators, we show that the hierarchical organization of the periodic domains is manifested in global and local scales.

  17. Magnetism, structure and chemical order in small CoPd clusters: A first-principles study

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-01-01

    The structural, electronic and magnetic properties of small ComPdn (N=m+n=8,m=0-N) nanoalloy clusters are studied in the framework of a generalized-gradient approximation to density-functional theory. The optimized cluster structures have a clear tendency to maximize the number of nearest-neighbor CoCo pairs. The magnetic order is found to be ferromagnetic-like (FM) for all the ground-state structures. Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom μ̄N increases approximately linearly with Co content. A remarkable enhancement of the local Co moments is observed as a result of Pd doping. This is a consequence of the increase in the number of Co d holes, due to CoPd charge transfer, combined with the reduced local coordination. The influence of spin-orbit interactions on the cluster properties is also discussed. © 2013 Elsevier B.V.

  18. Electronic structure and dynamics of ordered clusters with ME or RE ions on oxide surface

    Energy Technology Data Exchange (ETDEWEB)

    Kulagin, N.A., E-mail: nkulagin@bestnet.kharkov.u [Kharkiv National University for Radio Electronics, Avenue Shakespeare 6-48, 61045 Kharkiv (Ukraine)

    2011-03-15

    Selected data of ab initio simulation of the electronic structure and spectral properties of either cluster with ions of iron, rare earth or actinium group elements have been presented here. Appearance of doped Cr{sup +4} ions in oxides, Cu{sup +2} in HTSC, Nd{sup +2} in solids has been discussed. Analysis of experimental data for plasma created ordered structures of crystallites with size of about 10{sup -9} m on surface of separate oxides are given, too. Change in the spectroscopic properties of clusters and nano-structures on surface of strontium titanate crystals discussed shortly using the X-ray line spectroscopy experimental results. - Research highlights: External influence and variation of technology induce changes in valence of nl ions in compounds. Wave function of cluster presented as anti-symmetrical set of ions wave functions. The main equation describes the self-consistent field depending on state of all electrons of cluster. Level scheme of Cr{sup 4+} ions in octo- and tetra-site corresponds to doped oxides spectra after treatment. Plasma treatment effects in appearance of systems of unit crystallites with size of about 10{sup -6}-10{sup -9} m.

  19. Evidence of structural order recovery in LDPE based copolymers prepared by gamma irradiation

    Science.gov (United States)

    Ferreira, L. M.; Leal, J. P.; Casimiro, M. H.; Cruz, C.; Lancastre, J. J. H.; Falcão, A. N.

    2014-01-01

    PE-g-HEMA films prepared by the mutual gamma irradiation method were prepared to be used as catalyst support in catalytic membrane reactors (CMR). These copolymeric films showed good structural stability, even the high grafted ones, with a consistent correlation between their grafting degree and crystallinity. However, it was observed that above a certain radiation dose threshold, the structural changes induced in polyethylene (PE) backbone do not depend only on the extend of poly(HEMA) graft but also in what seems to be the reorganization of the amorphous regions in the PE matrix. The recovery of some crystallinity (up to 8%) in the copolymeric films was attested by DSC data. FTIR analysis confirmed this observation, revealing a slight increase in intensity and definition of the characteristic peak indicator of high crystalline regions in PE. This process seems to result from a radiation protective effect on copolymers matrix carried out by grafted poly(HEMA) which give to PE the ability to recover some of the lost structural order.

  20. Getting in (and out of the loop: regulating higher order telomere structures

    Directory of Open Access Journals (Sweden)

    Sarah eLuke-Glaser

    2012-11-01

    Full Text Available The DNA at the ends of linear chromosomes (the telomere folds back onto itself and forms an intramolecular lariat-like structure. Although the telomere loop has been implicated in the protection of chromosome ends from nuclease-mediated resection and unscheduled DNA repair activities, it potentially poses an obstacle to the DNA replication machinery during S phase. Therefore, the coordinated regulation of telomere loop formation, maintenance and resolution is required in order to establish a balance between protecting the chromosome ends and promoting their duplication prior to cell division. Until recently, the only factor know to influence telomere looping in human cells was TRF2, a component of the shelterin complex. Recent work in yeast and mouse cells has uncovered additional regulatory factors that affect the loop structure at telomeres. In the following perspective we will outline what is known about telomere looping and highlight the latest results regarding the regulation of this chromosome end structure. We will speculate about how the manipulation of the telomere loop may have therapeutic implications in terms of diseases associated with telomere dysfunction and uncontrolled proliferation.

  1. Quantifying Long-Range Interactions and Coherent Structure in Multi-Agent Dynamics.

    Science.gov (United States)

    Cliff, Oliver M; Lizier, Joseph T; Wang, X Rosalind; Wang, Peter; Obst, Oliver; Prokopenko, Mikhail

    2017-01-01

    We develop and apply several novel methods quantifying dynamic multi-agent team interactions. These interactions are detected information-theoretically and captured in two ways: via (i) directed networks (interaction diagrams) representing significant coupled dynamics between pairs of agents, and (ii) state-space plots (coherence diagrams) showing coherent structures in Shannon information dynamics. This model-free analysis relates, on the one hand, the information transfer to responsiveness of the agents and the team, and, on the other hand, the information storage within the team to the team's rigidity and lack of tactical flexibility. The resultant interaction and coherence diagrams reveal implicit interactions, across teams, that may be spatially long-range. The analysis was verified with a statistically significant number of experiments (using simulated football games, produced during RoboCup 2D Simulation League matches), identifying the zones of the most intense competition, the extent and types of interactions, and the correlation between the strength of specific interactions and the results of the matches.

  2. Structural and metal-insulator transitions in rhenium-based double perovskites via orbital ordering

    Science.gov (United States)

    Lee, Alex Taekyung; Marianetti, Chris A.

    2018-01-01

    Re-based double perovskites (DPs) have garnered substantial attention due to their high Curie temperatures (TC) and display of complex interplay of structural and metal-insulator transitions (MIT). Here we systematically study the ground-state electronic and structural properties for a family of Re-based DPs A2B ReO6 (A =Sr, Ca and B =Cr, Fe), which are related by a common low-energy Hamiltonian, using density functional theory +U calculations. We show that the on-site interaction U of Re induces orbital ordering (denoted C-OO), with each Re site having an occupied dx y orbital and a C-type alternation among dx z/dy z , resulting in an insulating state consistent with experimentally determined insulators Sr2CrReO6 , Ca2CrReO6 , and Ca2FeReO6 . The threshold value of UR e for orbital ordering is reduced by inducing Eg octahedral distortions of the same C-type wavelength (denoted C-OD), which serves as a structural signature of the orbital ordering; octahedral tilting also reduces the threshold. The C-OO and the concomitant C-OD are a spontaneously broken symmetry for the Sr-based materials (i.e., a0a0c- tilt pattern), while not for the Ca-based systems (i.e., a-a-b+ tilt pattern). Spin-orbit coupling does not qualitatively change the physics of the C-OO/C-OD, but can induce relevant quantitative changes. We prove that a single set of UC r,UF e,UR e capture the experimentally observed metallic state in Sr2FeReO6 and insulating states in other three systems. We predict that the C-OO is the origin of the insulating state in Sr2CrReO6 , and that the concomitant C-OD may be experimentally observed at sufficiently low temperatures (i.e., space group P 42/m ) in pure samples. Additionally, given our prescribed values of U , we show that the C-OO induced insulating state in Ca2CrReO6 will survive even if the C-OD amplitude is suppressed (e.g., due to thermal fluctuations). The role of the C-OO/C-OD in the discontinuous, temperature driven MIT in Ca2FeReO6 is discussed.

  3. Intercalation synthesis of graphene-capped iron silicide atop Ni(111): Evolution of electronic structure and ferromagnetic ordering

    Energy Technology Data Exchange (ETDEWEB)

    Grebenyuk, G.S. [Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Vilkov, O.Yu.; Rybkin, A.G. [St. Petersburg State University, 199034 St. Petersburg (Russian Federation); Gomoyunova, M.V. [Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Senkovskiy, B.V. [St. Petersburg State University, 199034 St. Petersburg (Russian Federation); II. Physikalisches Institut, Universität zu Köln, D-50937 Cologne (Germany); Usachov, D.Yu. [St. Petersburg State University, 199034 St. Petersburg (Russian Federation); Vyalikh, D.V. [St. Petersburg State University, 199034 St. Petersburg (Russian Federation); Institute of Solid State Physics, Dresden University of Technology, 01062 Dresden (Germany); Molodtsov, S.L. [European XFEL GmbH, 22761 Hamburg (Germany); Institute of Experimental Physics, Technische Universität Bergakademie Freiberg, 09599 Freiberg (Germany); ITMO University, 197101 St. Petersburg (Russian Federation); Pronin, I.I., E-mail: Igor.Pronin@mail.ioffe.ru [Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); ITMO University, 197101 St. Petersburg (Russian Federation)

    2017-01-15

    Highlights: • Evolution of Graphene/Ni system due to intercalation with Fe and Si is studied. • Graphene strongly interacts with the topmost atoms of the intercalated fcc Fe film. • The in-plane ferromagnetic ordering of the film arises after intercalation of 5 ML Fe. • Fe-Si solid solution and Fe{sub 3}Si surface silicide are formed after intercalation of Si. • The capping graphene layer is weakly electronically coupled to the silicide phase. - Abstract: A new method for synthesis of graphene-protected iron silicides has been tested, which consists in formation of graphene on Ni(111) followed by two-step intercalation of the system with Fe and Si. Characterization of the samples was performed in situ by low-energy electron diffraction, angular-resolved photoelectron spectroscopy, core-level photoelectron spectroscopy with synchrotron radiation and magnetic linear dichroism in photoemission of Fe 3p electrons. It is shown, that at 400 °C the intercalation of graphene/Ni(111) with iron occurs in a range up to 14 ML. The graphene layer strongly interacts with the topmost Fe atoms and stabilizes the fcc structure of the film. The in-plane ferromagnetic ordering of the film has a threshold nature and arises after the intercalation of 5 ML Fe due to the thickness-driven spin reorientation transition. Subsequent intercalation of graphene/Fe/Ni(111) with Si leads to the formation of the inhomogeneous system consisted of intercalated and nonintercalated areas. The intercalated islands coalesce at 2 ML Si when a Fe-Si solid solution covered with the Fe{sub 3}Si surface silicide is formed. The Fe{sub 3}Si silicide is ferromagnetic and has an ordered (√3 × √3)R30° structure. The graphene layer is weakly electronically coupled to the silicide phase keeping its remarkable properties ready for use.

  4. Elucidation of the Local and Long-Range Structural Changes that Occur in Germanium Anodes in Lithium-Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hyeyoung; Allan, Phoebe K.; Hu, Yan-Yan; Borkiewicz, Olaf J.; Wang, Xiao-Liang; Han, Wei-Qiang; Du, Lin-Shu; Pickard, Chris J.; Chupas, Peter J.; Chapman, Karena W.; Morris, Andrew J.; Grey, Clare P.

    2015-02-10

    Metallic germanium is a promising anode material in secondary lithium-ion batteries (LIBs) due to its high theoretical capacity (1623 mAh/g) and low operating voltage, coupled with the high lithium-ion diffusivity and electronic conductivity of lithiated Ge. Here, the lithiation mechanism of micron-sized Ge anodes has been investigated with X-ray diffraction (XRD), pair distribution function (PDF) analysis, and in-/ex-situ high-resolution Li-7 solid-state nuclear magnetic resonance (NMR), utilizing the structural information and spectroscopic fingerprints obtained by characterizing a series of relevant Li(x)Gey model compounds. In contrast to previous work, which postulated the formation of Li9Ge4 upon initial lithiation, we show that crystalline Ge first reacts to form a mixture of amorphous and crystalline Li7Ge3 (space group P32(1)2). Although Li7Ge3 was proposed to be stable in a recent theoretical study of the Li-Ge phase diagram (Morris, A. J.; Grey, C. P.; Pickard, C. J. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90, 054111), it had not been identified in prior experimental studies. Further lithiation results in the transformation of Li7Ge3, via a series of disordered phases with related structural motifs, to form a phase that locally resembles Li7Ge2, a process that involves the gradual breakage of the Ge-Ge bonds in the Ge-Ge dimers (dumbbells) on lithiation. Crystalline Li15Ge4 then grows, with an overlithiated phase, Li15+delta Ge4, being formed at the end of discharge. This study provides comprehensive experimental evidence, by using techniques that probe short-, medium-, and long-range order, for the structural transformations that occur on electrochemical lithiation of Ge; the results are consistent with corresponding theoretical studies regarding stable lithiated LixGey phases.

  5. Base sequence and higher-order structure induce the complex excited-state dynamics in DNA.

    Science.gov (United States)

    Schwalb, Nina K; Temps, Friedrich

    2008-10-10

    The high photostability of DNA is commonly attributed to efficient radiationless electronic relaxation processes. We used femtosecond time-resolved fluorescence spectroscopy to reveal that the ensuing dynamics are strongly dependent on base sequence and are also affected by higher-order structure. Excited electronic state lifetimes in dG-doped d(A)20 single-stranded DNA and dG.dC-doped d(A)20.d(T)20 double-stranded DNA decrease sharply with the substitution of only a few bases. In duplexes containing d(AGA).d(TCT) or d(AG).d(TC) repeats, deactivation of the fluorescing states occurs on the subpicosecond time scale, but the excited-state lifetimes increase again in extended d(G) runs. The results point at more complex and molecule-specific photodynamics in native DNA than may be evident in simpler model systems.

  6. Ordered and isomorphic mapping of periodic structures in the parametrically forced logistic map

    Science.gov (United States)

    Maranhão, Dariel M.

    2016-09-01

    We investigate the periodic domains found in the parametrically forced logistic map, the classical logistic map when its control parameter changes dynamically. Phase diagrams in two-parameter spaces reveal intricate periodic structures composed of patterns of intersecting superstable orbits curves, defining the cell of a periodic window. Cells appear multifoliated and ordered, and they are isomorphically mapped when one changes the map parameters. Also, we identify the characteristics of simplest cell and apply them to other more complex, discussing how the topography on parameter space is affected. By use of the winding number as defined in periodically forced oscillators, we show that the hierarchical organization of the periodic domains is manifested in global and local scales.

  7. A Separation Algorithm for Sources with Temporal Structure Only Using Second-order Statistics

    Directory of Open Access Journals (Sweden)

    J.G. Wang

    2013-09-01

    Full Text Available Unlike conventional blind source separation (BSS deals with independent identically distributed (i.i.d. sources, this paper addresses the separation from mixtures of sources with temporal structure, such as linear autocorrelations. Many sequential extraction algorithms have been reported, resulting in inevitable cumulated errors introduced by the deflation scheme. We propose a robust separation algorithm to recover original sources simultaneously, through a joint diagonalizer of several average delayed covariance matrices at positions of the optimal time delay and its integers. The proposed algorithm is computationally simple and efficient, since it is based on the second-order statistics only. Extensive simulation results confirm the validity and high performance of the algorithm. Compared with related extraction algorithms, its separation signal-to-noise rate for a desired source can reach 20dB higher, and it seems rather insensitive to the estimation error of the time delay.

  8. Proton inelastic mean free path in a group of bioorganic compounds and water in 0.05-10 MeV range - Including higher-order corrections

    Energy Technology Data Exchange (ETDEWEB)

    Tan Zhenyu, E-mail: tzy@sdu.edu.c [School of Electrical Engineering, Shandong University, Jinan 250061, Shandong (China); Xia Yueyuan; Zhao Mingwen; Liu Xiangdong [School of Physics, Shandong University, Jinan 250100, Shandong (China)

    2010-07-15

    The systematic calculations of the inelastic mean free paths (MFP) of 0.05-10 MeV protons in a group of eleven important bioorganic compounds, i.e. DNA, five bases, three fatty acids, cellulose and {beta}-carotene, have been performed. The expressions for the calculations are derived from the Ashley's optical-data model and from the higher-order correction terms in stopping power calculations. Especially, the Bloch correction for the inelastic MFP is proposed empirically in this work. The inelastic MFPs for energetic protons in water are also evaluated and compared with other theoretical calculations. The proton inelastic MFPs for these 11 bioorganic compounds in the energy range from 0.05 to 10 MeV are presented here for the first time, and might be useful for studies of various radiation effects in these materials.

  9. 5000 groove/mm multilayer-coated blazed grating with 33percent efficiency in the 3rd order in the EUV wavelength range

    Energy Technology Data Exchange (ETDEWEB)

    Advanced Light Source; Voronov, Dmitriy L.; Anderson, Erik; Cambie, Rossana; Salmassi, Farhad; Gullikson, Eric; Yashchuk, Valeriy; Padmore, Howard; Ahn, Minseung; Chang, Chih-Hao; Heilmann, Ralf; Schattenburg, Mark

    2009-07-07

    We report on recent progress in developing diffraction gratings which can potentially provide extremely high spectral resolution of 105-106 in the EUV and soft x-ray photon energy ranges. Such a grating was fabricated by deposition of a multilayer on a substrate which consists ofa 6-degree blazed grating with a high groove density. The fabrication of the substrate gratings was based on scanning interference lithography and anisotropic wet etch of silicon single crystals. The optimized fabrication process provided precise control of the grating periodicity, and the grating groove profile, together with very short anti-blazed facets, and near atomically smooth surface blazed facets. The blazed grating coated with 20 Mo/Si bilayers demonstrated a diffraction efficiency in the third order as high as 33percent at an incidence angle of 11? and wavelength of 14.18 nm.

  10. Soil microbial community structure of range-expanding plant species differs from co-occurring natives

    NARCIS (Netherlands)

    Morriën, W.E.; Putten, van der W.H.

    2013-01-01

    1. Due to global warming and other changes in the environment, many native and exotic plant species show range expansion from lower to higher latitudes. In the new range, the (in)ability of range-expanding plants to establish associations with local soil microbes can have important consequences for

  11. Measurement of third-order elastic constants and applications to loaded structural materials.

    Science.gov (United States)

    Takahashi, Sennosuke; Motegi, Ryohei

    2015-01-01

    The objective of this study is to obtain the propagation velocity of an elastic wave in a loaded isotropic solid and to show the usefulness of the third-order elastic constant in determining properties of practical materials. As is well known, the infinitesimal elastic theory is unable to express the influence of stress on elastic wave propagating in loaded materials. To solve this problem, the authors derive an equation of motion for elastic wave in a finitely deformed state and use the Lagrangian description where the state before deformation is used as a reference, and Murnaghans finite deformation theory for the unidirectional deformed isotropic solid. Ordinary derivatives were used for the mathematical treatment and although the formulas are long the content is simple. The theory is applied to the measurement of the third-order elastic constants of common steels containing carbon of 0.22 and 0.32 wt%. Care is taken in preparing specimens to precise dimensions, in properly adhering of transducer to the surface of the specimen, and in having good temperature control during the measurements to obtain precise data. As a result, the stress at various sites in the structural materials could be estimated by measuring the elastic wave propagation times. The results obtained are graphed for illustration.

  12. Cop-like operon: Structure and organization in species of the Lactobacillale order

    Directory of Open Access Journals (Sweden)

    ANGÉLICA REYES

    2006-01-01

    Full Text Available Copper is an essential and toxic trace metal for bacteria and, therefore, must be tightly regulated in the cell. Enterococcus hirae is a broadly studied model for copper homeostasis. The intracellular copper levels in E. hirae are regulated by the cop operon, which is formed by four genes: copA and copB that encode ATPases for influx and efflux of copper, respectively; copZ that encodes a copper chaperone; and copY, a copper responsive repressor. Since the complete genome sequence for E. hirae is not available, it is possible that other genes may encode proteins involved in copper homeostasis. Here, we identified a cop-like operon in nine species of Lactobacillale order with a known genome sequence. All of them always encoded a CopY-like repressor and a copper ATPase. The alignment of the cop-like operon promoter region revealed two CopY binding sites, one of which was conserved in all strains, and the second was only present in species of Streptococcus genus and L. johnsonii. Additional proteins associated to copper metabolism, CutC and Cupredoxin, also were detected. This study allowed for the description of the structure and organization of the cop operon and discussion of a phylogenetic hypothesis based on the differences observed in this operon's organization and its regulation in Lactobacillale order.

  13. Spatial coherence in high-order-harmonic generation from periodic solid structures

    Science.gov (United States)

    Liu, Lu; Zhao, Jing; Dong, Wenpu; Liu, Jinlei; Huang, Yindong; Zhao, Zengxiu

    2017-11-01

    We theoretically investigate the high-harmonic generation (HHG) from periodical structures driven by an intense laser pulse. Including the full bands, the single electron time-dependent Schrödinger equation is numerically solved in the velocity gauge using Bloch states to obtain the emission spectra. The contributions from different crystal sites are identified using the localized Wannier functions and time-frequency analysis. It is found that the cutoff energy of harmonics is depending on the migration distance of the electron and the instantaneous laser field strength when the electron transports into the related sites. We show that the coherence among different sites during electron propagation is crucial for HHG from solids which can be taken advantage to control the individual site contribution to the certain frequency range of the total harmonic spectra.

  14. Nanoporous anodic aluminum oxide with a long-range order and tunable cell sizes by phosphoric acid anodization on pre-patterned substrates

    Science.gov (United States)

    Surawathanawises, Krissada; Cheng, Xuanhong

    2014-01-01

    Nanoporous anodic aluminum oxide (AAO) has been explored for various applications due to its regular cell arrangement and relatively easy fabrication processes. However, conventional two-step anodization based on self-organization only allows the fabrication of a few discrete cell sizes and formation of small domains of hexagonally packed pores. Recent efforts to pre-pattern aluminum followed with anodization significantly improve the regularity and available pore geometries in AAO, while systematic study of the anodization condition, especially the impact of acid composition on pore formation guided by nanoindentation is still lacking. In this work, we pre-patterned aluminium thin films using ordered monolayers of silica beads and formed porous AAO in a single-step anodization in phosphoric acid. Controllable cell sizes ranging from 280 nm to 760 nm were obtained, matching the diameters of the silica nanobead molds used. This range of cell size is significantly greater than what has been reported for AAO formed in phosphoric acid in the literature. In addition, the relationships between the acid concentration, cell size, pore size, anodization voltage and film growth rate were studied quantitatively. The results are consistent with the theory of oxide formation through an electrochemical reaction. Not only does this study provide useful operational conditions of nanoindentation induced anodization in phosphoric acid, it also generates significant information for fundamental understanding of AAO formation. PMID:24535886

  15. Structural characteristics of forest stands within home ranges of Mexican spotted owls in Arizona and New Mexico

    Science.gov (United States)

    Joseph L. Ganey; William M. Block; Steven H. Ackers

    2003-01-01

    As part of a set of studies evaluating home-range size and habitat use of radio-marked Mexican spotted owls (Strix occidentalis lucida), we sampled structural characteristics of forest stands within owl home ranges on two study areas in Arizona and New Mexico. Study areas were dominated by ponderosa pine (Pinus ponderosa)-Gambel...

  16. Drying-Mediated Self-Assembly of Highly Ordered Complex Structures: From Polymers to Nanoparticles

    Science.gov (United States)

    Lin, Zhiqun

    2009-03-01

    Drying of a sessile drop containing nonvolatile solutes readily self-assembles into a number of concentric ``coffee rings'' by repetitive ``stick-slip'' motion of the three-phase contact line. However, due mainly to lack of control over the evaporation process of the drop, the challenge remains to use evaporative self-assembly to rationally ``synthesize'' ``coffee rings'' of different shapes and sizes of high regularity and fidelity. Here, we report a facile, robust, and one-step evaporation method for producing in a precisely controllable manner versatile microstructures possessing high regularity, dispensing with the need for lithographic techniques and externally applied fields. Polymer or nanocrystal solutions are confined in a simple geometry comprised of a curved surface placed upon a flat substrate. By changing the shape of the upper surface of the imposed geometry, the controlled, evaporative self-assembly of polymer or nanocrystal solutions yields a variety of complex, intriguing, and well-ordered structures over large areas. As such, this method represents a significant advance in creating regularly organized, complex structures with potential applications in microelectronics, optoelectronics, and biotechnology, among other areas.

  17. Ferromagnetic ordering in the layer-structured Pd(HS(2)O(7))(2).

    Science.gov (United States)

    Bruns, Jörn; Niehaus, Oliver; Pöttgen, Rainer; Wickleder, Mathias S

    2014-01-13

    The reaction of (NO2 )(CF3 SO3 ) and elemental palladium in oleum (65 % SO3 ) leads to violet single crystals of Pd(HS2 O7 )2 (monoclinic, P21 /c, Z=2, a=927.80(9), b=682.58(7), c=920.84(9) pm, β=117.756(2)°, wR2 =0.0439). In the crystal structure, the Pd(2+) ions show an uncommon octahedral coordination of six oxygen atoms belonging to six HS2 O7 (-) ions. The linkage of [PdO6 ] octahedra and the hydrogendisulfate anions leads to a layer structure, and the layers are held together by hydrogen bonds. The unusual coordination of the Pd(2+) ions results in an electronic d(8) high-spin configuration, which leads to the paramagnetic behavior of the compound. Moreover, at low temperature, a ferromagnetic ordering was observed with a Curie temperature of 8 K. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. A generative spike train model with time-structured higher order correlations

    Directory of Open Access Journals (Sweden)

    James eTrousdale

    2013-07-01

    Full Text Available Emerging technologies are revealing the spiking activity in ever larger neural ensembles. Frequently, this spiking is far from independent, with correlations in the spike times of different cells. Understanding how such correlations impact the dynamics and function of neural ensembles remains an important open problem.Here we describe a new, generative model for correlated spike trains that can exhibit many of the features observed in data. Extending prior work in mathematical finance, this generalized thinning and shift (GTaS model creates marginally Poisson spike trains with diverse temporal correlation structures.We give several examples which highlight the model's flexibility and utility. For instance, we use it to examine how a neural network responds to highly structured patterns of inputs.We then show that the GTaS model is analytically tractable, and derive cumulant densities of all orders in terms of model parameters. The GTaS framework can therefore be an important tool in the experimental and theoretical exploration of neural dynamics.

  19. Development of Antibody Arrays for Monoclonal Antibody Higher Order Structure Analysis

    Directory of Open Access Journals (Sweden)

    Xing eWang

    2013-08-01

    Full Text Available Antibody arrays were developed to probe a monoclonal antibody’s three-dimensional structure (3-D structure. Peptides with overlapping regions were designed to cover the whole mAb light chain and heavy chain respectively and used to generate polyclonal antibodies after the conjugation of the peptides to a carrier protein, KLH. It was shown that good peptide specificity was achieved from the antibodies generated. Using more than 30 different polyclonal antibodies to measure the surface epitope distribution, it was shown that the mAb antibody array can detect epitope exposure as low as 0.1% of defined mAb populations. This ELISA-based analysis of mAb epitope exposure can be considered as a measurement of conformational impurity in biologics development, similar to the analysis of other product-related impurities such as different forms of glycosylation, deamidation and oxidation. This analysis of conformational impurity could provide valuable information on the mAb conformational comparability for biosimilar mAbs as well as novel mAbs, especially in the area of protein immunogenicity. Furthermore, stability studies indicated that there are several conformational hot spots in many mAbs tested, especially in the hinge region. This antibody array technology can be used for novel mAb Higher Order Structure (HOS analysis during process and formulation development. Another important area of application is for biosimilar mAb development where the innovator molecule and biosimilar molecule could be compared based on their systemic fingerprint from the 30 plus antibodies.

  20. [Research progress in the structure and fuction of Orthopoxvirus host range genes].

    Science.gov (United States)

    Liu, Zheng; Liu, Ying; Shao, Yi-Ming

    2013-06-01

    Orthopoxvirus vector has a broad prospect in recombinant vaccine research, but the rarely severe side-effect impedes its development. Vaccinia virus and Cowpox virus of Orthopoxvirus have broad host range, and they have typical host range genes as K1L, CP77 and C7L. These three genes affect host range of Vaccinia virus, disturb the cell signaling pathways, suppress immune response and are related to virulence.

  1. The influence of cross-order terms in interface mobilities for structure-borne sound source characterization: Frame-like structures

    Science.gov (United States)

    Bonhoff, H. A.; Petersson, B. A. T.

    2009-01-01

    The applicability of interface mobilities for structure-borne sound source characterization critically depends on the admissibility of neglecting the cross-order terms. Following on from a previous study [H.A. Bonhoff, B.A.T. Petersson, Journal of Sound and Vibration 311 (2008) 473-484], the influence of the cross-order terms is investigated for frame-like structures under the assumption of a uniform force-order distribution. Considering the complex power, the cross-order terms are significant from intermediate frequencies on upwards. At lower frequencies, the cross-order terms can come into play for cases where the in-phase motion of the structure along the interface is constrained. The frequency characteristics of the influence of cross-order terms for the zero-order source descriptor and coupling function are similar to those of the complex power. For non-zero source descriptor and coupling function orders, the quality of the equal-order approximation mainly depends on the presence of low-order cross-order interface mobilities. By analyzing the symmetry of an interface system, it is possible to predict which cross-order terms are equal to zero. The equal-order approximation manages to capture the main trends and overall characteristics and offers an acceptable estimate for engineering practice.

  2. Improved CO Oxidation Activity of 3DOM Pr-Doped Ceria Catalysts: Something Other Than an Ordered Macroporous Structure

    Directory of Open Access Journals (Sweden)

    Arantxa Davó-Quiñonero

    2017-02-01

    Full Text Available It is demonstrated that the synthesis procedure for preparing three-dimensionally ordered macroporous (3DOM Pr-doped ceria catalysts using a polymethylmethacrylate (PMMA template not only affects the porous structure, but also the chemistry of the ceria surface. The PMMA template does not affect the crystalline features (type of phases, crystallite size, and cell parameter of Pr-doped ceria, Ce and Pr location into the particles, and the bulk reduction of the Ce-Pr mixed oxide catalysts. On the contrary, the utilization of the PMMA template improves both the porosity and surface redox properties. 3DOM Ce-Pr mixed oxide catalysts combine micro, meso, and macropores, the most area being in the macropore range, while a reference unshaped catalyst presents poor porosity in all ranges. However, the catalyzed CO oxidation rates do not correlate with the surface area of the catalysts (neither micro nor meso/macro. The Ce-Pr-3DOM catalyst also presents improved surface reducibility with regards to the counterpart reference material prepared without the template, and improved redox behavior under reaction conditions; that is, it has a higher area and this area is reduced and reoxidized more easily. X-ray photoelectron spectroscopy analysis evidences that this is mainly attributed to praseodymium cations, which accomplish redox cycles more easily than cerium cations.

  3. Plant zero structure and further order reduction of a singular $H_\\infty$ controller

    NARCIS (Netherlands)

    Watanabe, Takao; Stoorvogel, Antonie Arij

    2002-01-01

    A new class of reduced-order controllers is obtained for the $H_\\infty$ problem. The reduced-order controller does not compromise the performance attained by the full-order controller. Algorithms for deriving reduced-order $H_\\infty$ controllers are presented in both continuous and discrete time.

  4. Photonic band gap structures for long-range surface plasmon polaritons

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Boltasseva, Alexandra; Søndergaard, Thomas

    2005-01-01

    Propagation of long-range surface plasmon polaritons (LR-SPPs) along periodically thickness-modulated metal stripes embedded in dielectric is studied both theoretically and experimentally for light wavelengths in the telecom range. We demonstrate that symmetric (with respect to the film surface) nm...... of achieving a full bandgap (in the surface plane) for LR-SPPs are also discussed....

  5. Topography, structure, and formation kinetic mechanism of carbon deposited onto nickel in the temperature range from 400 to 850°C

    Science.gov (United States)

    Chen, Zhi-yuan; Bian, Liu-zhen; Wang, Li-jun; Yu, Zi-you; Zhao, Hai-lei; Li, Fu-shen; Chou, Kuo-chih

    2017-05-01

    The carbon deposition behavior on nickel particles was observed within the temperature range from 400 to 800°C in a pure methane atmosphere. The topography, properties, and molecular structure of the deposited carbon were investigated using field-emission scanning electron microscopy (FESEM), temperature-programmed oxidation (TPO) technology, X-ray diffraction (XRD), and Raman spectroscopy. The deposited carbon is present in the form of a film at 400-450°C, as fibers at 500-600°C, and as particles at 650-800°C. In addition, the structure of the deposited carbon becomes more ordered at higher temperatures because both the TPO peak temperature of deposited carbon and the Raman shift of the G band increase with the increase in experimental temperature, whereas the intensity ratio between the D bands and the G band decreases. An interesting observation is that the carbon deposition rate is suppressed in the medium-temperature range (M-T range) and the corresponding kinetic mechanism changes. Correspondingly, the FWHM of the G and D1 bands in the Raman spectrum reaches a maximum and the intensities of the D2, D3, and D4 bands decrease to low limits in the M-T range. These results indicate that carbon structure parameters exhibit two different tendencies with respect to varying temperature. Both of the two group parameters change dramatically as a peak function with increasing reaction temperature within the M-T range.

  6. The Upper Rhine Graben revisited: Miocene transtension and transpression account for the observed first-order structures

    National Research Council Canada - National Science Library

    Rotstein, Y; Schaming, M

    2011-01-01

    [1] Although the Upper Rhine Graben (URG) has been studied extensively for years, the origin of some of its first-order structures is still under debate, particularly the relatively young uplift of the Vosges Mountains (VM...

  7. Structural and Kinetic Properties of Lumazine Synthase Isoenzymes in the Order Rhizobiales

    Energy Technology Data Exchange (ETDEWEB)

    Klinke,S.; Zylberman, V.; Bonomi, H.; Haase, I.; Guimaraes, B.; Braden, B.; Bacher, A.; Fischer, M.; Goldbaum, F.

    2007-01-01

    6, 7-Dimethyl-8-ribityllumazine synthase (lumazine synthase; LS) catalyzes the penultimate step in the biosynthesis of riboflavin in plants and microorganisms. This protein is known to exhibit different quaternary assemblies between species, existing as free pentamers, decamers (dimers of pentamers) and icosahedrally arranged dodecamers of pentamers. A phylogenetic analysis on eubacterial, fungal and plant LSs allowed us to classify them into two categories: Type I LSs (pentameric or icosahedral) and Type II LSs (decameric). The Rhizobiales represent an order of ?-proteobacteria that includes, among others, the genera Mesorhizobium, Agrobacterium and Brucella. Here, we present structural and kinetic studies on several LSs from Rhizobiales. Interestingly, Mesorhizobium and Brucella encode both a Type-I LS and a Type-II LS called RibH1 and RibH2, respectively. We show that Type II LSs appear to be almost inactive, whereas Type I LSs present a highly variable catalytic activity according to the genus. Additionally, we have solved four RibH1/RibH2 crystallographic structures from the genera Mesorhizobium and Brucella. The relationship between the active-site architecture and catalytic properties in these isoenzymes is discussed, and a model that describes the enzymatic behavior is proposed. Furthermore, sequence alignment studies allowed us to extend our results to the genus Agrobacterium. Our results suggest that the selective pressure controlling the riboflavin pathway favored the evolution of catalysts with low reaction rates, since the excess of flavins in the intracellular pool in Rhizobiales could act as a negative factor when these bacteria are exposed to oxidative or nitrosative stress.

  8. Historical (1860) forest structure in ponderosa pine forests of the northern Front Range, Colorado

    Science.gov (United States)

    Peter M. Brown; Michael A. Battaglia; Paula J. Fornwalt; Benjamin Gannon; Laurie S. Huckaby; Chad Julian; Antony S. Cheng

    2015-01-01

    Management of many dry conifer forests in western North America is focused on promoting resilience to future wildfires, climate change, and land use impacts through restoration of historical patterns of forest structure and disturbance processes. Historical structural data provide models for past resilient conditions that inform the design of silvicultural treatments...

  9. On bulk singularity structures and all order α′ contact terms of BPS string amplitudes

    Directory of Open Access Journals (Sweden)

    Ehsan Hatefi

    2016-10-01

    Full Text Available The entire form of the amplitude of three SYM (involving two transverse scalar fields, a gauge field and a potential Cn−1 Ramond–Ramond (RR form field is found out. We first derive and then start constructing an infinite number of t,s channel bulk singularity structures by means of all order α′ corrections to pull-back of brane in an Effective Field Theory (EFT. Due to presence of the complete form of S-matrix, several new contact interactions as well as new couplings are explored. It is also shown that these couplings can be verified at the level of EFT by either the combinations of Myers terms, pull-back, Taylor expanded of scalar fields or the mixed combination of the couplings of this paper as well as employed Bianchi identities. For the first time, we also derive the algebraic and the complete form of the integrations for some arbitrary combinations of Mandelstam variables and for the most general case ∫d2z|1−z|a|z|b(z−z¯c(z+z¯3 on upper half plane as well.

  10. Evolutionary Origin of Higher-Order Repeat Structure in Alpha-Satellite DNA of Primate Centromeres

    Science.gov (United States)

    Koga, Akihiko; Hirai, Yuriko; Terada, Shoko; Jahan, Israt; Baicharoen, Sudarath; Arsaithamkul, Visit; Hirai, Hirohisa

    2014-01-01

    Alpha-satellite DNA (AS) is a main DNA component of primate centromeres, consisting of tandemly repeated units of ∼170 bp. The AS of humans contains sequences organized into higher-order repeat (HOR) structures, in which a block of multiple repeat units forms a larger repeat unit and the larger units are repeated tandemly. The presence of HOR in AS is widely thought to be unique to hominids (family Hominidae; humans and great apes). Recently, we have identified an HOR-containing AS in the siamang, which is a small ape species belonging to the genus Symphalangus in the family Hylobatidae. This result supports the view that HOR in AS is an attribute of hominoids (superfamily Hominoidea) rather than hominids. A single example is, however, not sufficient for discussion of the evolutionary origin of HOR-containing AS. In the present study, we developed an efficient method for detecting signs of large-scale HOR and demonstrated HOR of AS in all the three other genera. Thus, AS organized into HOR occurs widely in hominoids. Our results indicate that (i) HOR-containing AS was present in the last common ancestor of hominoids or (ii) HOR-containing AS emerged independently in most or all basal branches of hominoids. We have also confirmed HOR occurrence in centromeric AS in the Hylobatidae family, which remained unclear in our previous study because of the existence of AS in subtelomeric regions, in addition to centromeres, of siamang chromosomes. PMID:24585002

  11. The third-order structure function in two dimensions: The Rashomon effect

    Science.gov (United States)

    Cerbus, Rory T.; Chakraborty, Pinaki

    2017-11-01

    We study the third-order longitudinal structure function, S3(r), in two-dimensional turbulence. In three dimensions, there is considerable theoretical, experimental, and numerical consensus regarding the validity of Kolmogorov's arch-famous " /4 5 th law" for S3(r). By contrast, in two dimensions, two disparate cascades, changed dissipation anomalies, a large-scale drag, and other factors conspire to create several versions of the S3(r) "law." This single quantity can vary considerably when viewed from different perspectives, reminiscent of the "Rashomon effect" in anthropology. After reviewing the history and usage of S3(r) in two-dimensional turbulence, we show that S3(r) generically embodies a mixture of energy and enstrophy fluxes. Building on this result, we derive S3(r) laws for freely decaying and forced two-dimensional turbulent flows, where we also account for the effects of a large-scale drag, an inextricable feature of quasi two-dimensional turbulence in experimental and atmospheric flows. We draw attention to the caution needed in interpreting S3(r) in two-dimensional turbulence.

  12. Structural changes and out-of-sample prediction of realized range-based variance in the stock market

    Science.gov (United States)

    Gong, Xu; Lin, Boqiang

    2018-03-01

    This paper aims to examine the effects of structural changes on forecasting the realized range-based variance in the stock market. Considering structural changes in variance in the stock market, we develop the HAR-RRV-SC model on the basis of the HAR-RRV model. Subsequently, the HAR-RRV and HAR-RRV-SC models are used to forecast the realized range-based variance of S&P 500 Index. We find that there are many structural changes in variance in the U.S. stock market, and the period after the financial crisis contains more structural change points than the period before the financial crisis. The out-of-sample results show that the HAR-RRV-SC model significantly outperforms the HAR-BV model when they are employed to forecast the 1-day, 1-week, and 1-month realized range-based variances, which means that structural changes can improve out-of-sample prediction of realized range-based variance. The out-of-sample results remain robust across the alternative rolling fixed-window, the alternative threshold value in ICSS algorithm, and the alternative benchmark models. More importantly, we believe that considering structural changes can help improve the out-of-sample performances of most of other existing HAR-RRV-type models in addition to the models used in this paper.

  13. Diffraction model of short-range longitudinal wakefields in circular and rectangular structures

    CERN Document Server

    Smirnov, A V

    2002-01-01

    Diffraction models based on the Green function technique and 'image' field concept were developed for analytical calculation of high-frequency radiation in rectangular iris-loaded structures. The models for single-cell and periodic structures were considered as an extension of the Lawson and Sessler-Vainshtein approaches and were applied to circular, infinitely wide planar and 'muffin-tin' geometry. The calculated spectral radiation losses are in good agreement with existing formulae. For a 2.5D muffin-tin structure a special semi-analytical frequency domain model was built to compare the diffraction model with the matched field technique based on eigenmodes calculations.

  14. Role of long- and short-range hydrophobic, hydrophilic and charged residues contact network in protein’s structural organization

    Directory of Open Access Journals (Sweden)

    Sengupta Dhriti

    2012-06-01

    Full Text Available Abstract Background The three-dimensional structure of a protein can be described as a graph where nodes represent residues and the strength of non-covalent interactions between them are edges. These protein contact networks can be separated into long and short-range interactions networks depending on the positions of amino acids in primary structure. Long-range interactions play a distinct role in determining the tertiary structure of a protein while short-range interactions could largely contribute to the secondary structure formations. In addition, physico chemical properties and the linear arrangement of amino acids of the primary structure of a protein determines its three dimensional structure. Here, we present an extensive analysis of protein contact subnetworks based on the London van der Waals interactions of amino acids at different length scales. We further subdivided those networks in hydrophobic, hydrophilic and charged residues networks and have tried to correlate their influence in the overall topology and organization of a protein. Results The largest connected component (LCC of long (LRN-, short (SRN- and all-range (ARN networks within proteins exhibit a transition behaviour when plotted against different interaction strengths of edges among amino acid nodes. While short-range networks having chain like structures exhibit highly cooperative transition; long- and all-range networks, which are more similar to each other, have non-chain like structures and show less cooperativity. Further, the hydrophobic residues subnetworks in long- and all-range networks have similar transition behaviours with all residues all-range networks, but the hydrophilic and charged residues networks don’t. While the nature of transitions of LCC’s sizes is same in SRNs for thermophiles and mesophiles, there exists a clear difference in LRNs. The presence of larger size of interconnected long-range interactions in thermophiles than mesophiles, even at

  15. The effect of structure directing agents on the ordering of fluoride ions in pure silica MFI zeolites.

    Science.gov (United States)

    Brace, S L; Wormald, P; Darton, R J

    2015-05-14

    The effect of different sizes of structure directing agents on the ordering of the fluoride ions in pure silica MFI zeolites has been determined using magic angle spinning solid state NMR. By synthesizing fluoride containing pure silica MFI zeolites using methyltributylammonium cations as the structure directing agent, it has been possible to change the type of ordering seen for the fluoride ions at room temperature from the previously reported dynamic to static disorder. An initial mechanism for how this fluoride ordering occurs is suggested based upon the coulombic interaction between the positive charge on the nitrogen and the negative fluoride ion, within the zeolite framework, with different sizes of tetraalkylammonium cations.

  16. Controlling sub-microdomain structure in microphase-ordered block copolymers and their nanocomposites

    Science.gov (United States)

    Bowman, Michelle Kathleen

    Block copolymers exhibit a wealth of morphologies that continue to find ubiquitous use in a diverse variety of mature and emergent (nano)technologies, such as photonic crystals, integrated circuits, pharmaceutical encapsulents, fuel cells and separation membranes. While numerous studies have explored the effects of molecular confinement on such copolymers, relatively few have examined the sub-microdomain structure that develops upon modification of copolymer molecular architecture or physical incorporation of nanoscale objects. This work will address two relevant topics in this vein: (i) bidisperse brushes formed by single block copolymer molecules and (ii) copolymer nanocomposites formed by addition of molecular or nanoscale additives. In the first case, an isomorphic series of asymmetric poly(styrene-b -isoprene-b-styrene) (S1IS2) triblock copolymers of systematically varied chain length has been synthesized from a parent SI diblock copolymer. Small-angle x-ray scattering, coupled with dynamic rheology and self-consistent field theory (SCFT), reveals that the progressively grown S2 block initially resides in the I-rich matrix and effectively reduces the copolymer incompatibility until a critical length is reached. At this length, the S2 block co-locates with the S1 block so that the two blocks generate a bidisperse brush (insofar as the S1 and S2 lengths differ). This single-molecule analog to binary block copolymer blends affords unique opportunities for materials design at sub-microdomain length scales and provides insight into the transition from diblock to triblock copolymer (and thermoplastic elastomeric nature). In the second case, I explore the distribution of molecular and nanoscale additives in microphase-ordered block copolymers and demonstrate via SCFT that an interfacial excess, which depends strongly on additive concentration, selectivity and relative size, develops. These predictions are in agreement with experimental findings. Moreover, using a

  17. Genetic diversity and structuring across the range of a widely distributed ladybird: focus on rear?edge populations phenotypically divergent

    OpenAIRE

    Lecompte, ?milie; Bouanani, Mohand?Ameziane; Magro, Alexandra; Crouau?Roy, Brigitte

    2016-01-01

    Abstract Population genetics and phenotypic structures are often predicted to vary along the geographic range of a species. This phenomenon would be accentuated for species with large range areas, with discontinuities and marginal populations. We herein compare the genetic patterns of central populations of Coccinella septempunctata L. with those of two phenotypically differentiated populations considered as rear?edge populations and subspecies based on phenotype (Algeria and Japan). Accordin...

  18. Trophic structure of fish fauna along the longitudinal gradient of a first-order rural stream

    Directory of Open Access Journals (Sweden)

    Jardel Nimet

    2015-12-01

    Full Text Available Abstract Aim: This study evaluated the trophic structure of the fish assemblage along the longitudinal gradient of a first-order rural stream. Methods Fish were sampled by electrofishing technique in December 2007, September 2008 and March 2009, at three stretch of the Itiz stream (headwater, middle and mouth. We sampled 1,255 individuals relating to 18 species. The categorization of trophic guilds was based on stomach content data of 1,096 individuals, analyzed according to the volumetric method, except for four species, which were classified according to the literature. To test the hypothesis of differences in the richness, abundance and biomass of trophic guilds along the headwater-mouth gradient, it was performed non-parametric statistical analysis of the dietary data. Was also calculated, the amplitude of trophic niche (Levins's index for each guild. To summarize the composition and abundance of the trophic guilds along the longitudinal gradient, we applied a non-metric multidimensional scaling (NMDS. Results We registered seven guilds: herbivorous, detritivorous, aquatic insectivorous, terrestrial insectivorous, invertivorous, omnivorous and piscivorous, the latter was exclusive to headwater and middle stretches. The omnivorous guild was not recorded in the headwater. Through PERMANOVA analysis it was found that the species richness of more specialized guilds (detritivorous and insectivorous terrestrial and of generalist invertivorous increased, while less specialized guilds like aquatic insectivorous and herbivorous, decrease significantly in headwater-mouth direction. Except by the non-expected increase of insectivorous terrestrial and decrease of herbivorous downstream, the non-metric multidimensional scaling (NMDS identified longitudinal variations in abundance and biomass of the guilds that agree with general patterns of fish guilds distribution along environmental gradients. Conclusion These results suggest that the influence of

  19. Propagation of long-range surface plasmon polaritons in photonic band gap structures

    DEFF Research Database (Denmark)

    Boltasseva, Alexandra; Søndergaard, Thomas; Nikolajsen, Thomas

    2005-01-01

    We study the interaction of long-range surface plasmon polaritons (LR-SPPs), excited at telecommunication wavelengths, with photonic crystals (PCs) formed by periodic arrays of gold bumps that are arranged in a triangular lattice and placed symmetrically on both sides of a thin gold fil embedded ...

  20. Structures and Technology Encouraging Discussion in Human Sexuality Courses: Strategies to Engage a Range of Students

    Science.gov (United States)

    Angera, Jeffrey J.; Latty, Christopher R.

    2015-01-01

    Human sexuality courses are common across many college/university campuses. The methods of instruction typically encourage discussion to increase knowledge and critical thinking about self, relationships, and professional pathways. However, often the pedagogical practices do not include methods to draw out students with a range of personalities,…

  1. Model Study of Wave Overtopping of Marine Structure for a Wide Range of Geometric Parameters

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter

    2000-01-01

    The objective of the study described in this paper is to enable estimation of wave overtopping rates for slopes/ramps given by a wide range of geometric parameters when subjected to varying wave conditions. To achieve this a great number of model tests are carried out in a wave tank using irregular...

  2. Analytical modeling of polarization transformation of laser radiation of various spectral ranges by birefringent structures

    Science.gov (United States)

    Motrich, A. V.; Ushenko, O. G.

    2018-01-01

    The results of statistical dependence and correlation structures of two-dimensional Mueller matrix elements in various spectral regions of laser radiation by changes in the distribution of orientations of optical axes and birefringence of protein crystals. Namely, a two-wave ("red-blue") approach - layer of biological tissues irradiated by He-Ne laser (λ1 = 0,63μm ) and He-Cd laser (λ1 = 0,41μm )was used Conducted analysis of polarimetric sensitivity was made, a state of polarization points that contain volumetric structures of biological objects to spectral region of laser radiation was detected.

  3. Conductive Oxides Trench Structures as Hyperbolic Metamaterials in Mid-infrared Range

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee

    ,2]. Moreover plasmonics for mid-infrared offer unique applications such as bio-sensing, thermal imaging and quest for novel materials and structures has been continuing [3]. In this report we show that vertical trench structures made of, for example, aluminum-doped ZnO (AZO) or other transparent conductive...... oxides can function as hyperbolic metamaterials (HMMs) for the mid-infrared wavelength region. We fabricated a probe sample by a combination of atomic layer deposition (ALD) and dry etch techniques. We templated a Si wafer with deep UV photolithography and made trenches by deep reactive ion etching...

  4. Benchmarking Close-range Structure from Motion 3D Reconstruction Software under Varying Capturing Conditions

    DEFF Research Database (Denmark)

    Nikolov, Ivan Adriyanov; Madsen, Claus B.

    2016-01-01

    Structure from Motion 3D reconstruction has become widely used in recent years in a number of fields such as industrial surface in- inspection, archeology, cultural heritage preservation and geomapping. A number of software solutions have been released using variations of this technique. In this ......Structure from Motion 3D reconstruction has become widely used in recent years in a number of fields such as industrial surface in- inspection, archeology, cultural heritage preservation and geomapping. A number of software solutions have been released using variations of this technique...

  5. Ordered Nanopillar Structured Electrodes for Depleted Bulk Heterojunction Colloidal Quantum Dot Solar Cells

    KAUST Repository

    Kramer, Illan J.

    2012-03-30

    A bulk heterojunction of ordered titania nanopillars and PbS colloidal quantum dots is developed. By using a pre-patterned template, an ordered titania nanopillar matrix with nearest neighbours 275 nm apart and height of 300 nm is fabricated and subsequently filled in with PbS colloidal quantum dots to form an ordered depleted bulk heterojunction exhibiting power conversion efficiency of 5.6%. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Object-oriented classification of forest structure from light detection and ranging data for stand mapping

    Science.gov (United States)

    Alicia A. Sullivan; Robert J. McGaughey; Hans-Erik Andersen; Peter. Schiess

    2009-01-01

    Stand delineation is an important step in the process of establishing a forest inventory and provides the spatial framework for many forest management decisions. Many methods for extracting forest structure characteristics for stand delineation and other purposes have been researched in the past, primarily focusing on high-resolution imagery and satellite data. High-...

  7. Theoretical investigation on electronic structure and second-order nonlinear optical properties of novel hexamolybdate-organoimido-(car)borane hybrid.

    Science.gov (United States)

    Ma, Nana; Yan, Likai; Guan, Wei; Qiu, Yongqing; Su, Zhongmin

    2012-04-28

    We report a theoretical study based on density functional theory (DFT) on the geometric and electronic structure, linear optical and second-order nonlinear optical properties of a series of new inorganic-organic hybrid hexamolybdate-organoimido-(car)boranes. By the incorporation of borane/carborane at the end of the phenyl ring of the organoimido segment, the studied systems show excellent nonlinear optical (NLO) response than the organoimido-substituted hexamolybdate. The computed static first hyperpolarizability β(vec) value of [Mo(6)O(18)(NC(8)H(8))(B(12)H(11))](4-) (II) is largest, -167.2 × 10(-30) esu, and a higher β(vec) value of [Mo(6)O(18)(NC(8)H(8))(C(2)B(10)H(11))](2-) (III-2p) is 58.6 × 10(-30) esu. Moreover, the time-dependent (TD)DFT calculation illustrates that the maximum absorption, which is helpful for the large NLO responses, is mainly assigned to the charge transfer (CT) from (car)borane and organoimido segment to the hexamolybdate cluster. The density of density (DOS) calculations further illustrate the excitation from valence orbitals of boron atoms to that of Mo and O atoms in hexamolybdate can be responsible for larger NLO responses. The linear and nonlinear optical properties of species III both vary with the position of the vertex on the carborane. Furthermore, the order of the β(vec) values is consistent with the bathochromic shift of the maximum absorption for our studied systems, and the studied systems show a wider transparency range extending into the entire visible and infrared (IR) region. This journal is © the Owner Societies 2012

  8. Geothermal Resource Analysis and Structure of Basin and Range Systems, Especially Dixie Valley Geothermal Field, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    David Blackwell; Kenneth Wisian; Maria Richards; Mark Leidig; Richard Smith; Jason McKenna

    2003-08-14

    Publish new thermal and drill data from the Dizie Valley Geothermal Field that affect evaluation of Basin and Range Geothermal Resources in a very major and positive way. Completed new geophysical surveys of Dizie Valley including gravity and aeromagnetics and integrated the geophysical, seismic, geological and drilling data at Dizie Valley into local and regional geologic models. Developed natural state mass and energy transport fluid flow models of generic Basin and Range systems based on Dizie Valley data that help to understand the nature of large scale constraints on the location and characteristics of the geothermal systems. Documented a relation between natural heat loss for geothermal and electrical power production potential and determined heat flow for 27 different geothermal systems. Prepared data set for generation of a new geothermal map of North American including industry data totaling over 25,000 points in the US alone.

  9. Dark matter, long-range forces, and large-scale structure

    Science.gov (United States)

    Gradwohl, Ben-Ami; Frieman, Joshua A.

    1992-01-01

    If the dark matter in galaxies and clusters is nonbaryonic, it can interact with additional long-range fields that are invisible to experimental tests of the equivalence principle. We discuss the astrophysical and cosmological implications of a long-range force coupled only to the dark matter and find rather tight constraints on its strength. If the force is repulsive (attractive), the masses of galaxy groups and clusters (and the mean density of the universe inferred from them) have been systematically underestimated (overestimated). We explore the consequent effects on the two-point correlation function, large-scale velocity flows, and microwave background anisotropies, for models with initial scale-invariant adiabatic perturbations and cold dark matter.

  10. A comparison of interest point and region detectors on structured, range and texture images

    DEFF Research Database (Denmark)

    Kazmi, Wajahat; Andersen, Hans Jørgen

    2015-01-01

    )) and corner based detectors (such as Hessian and Harris with both Affine/Laplace variants, SURF with determinant of Hessian based corners and SIFT with difference of Gaussians) acquired more than 90% mean average precision, whereas on range images, homogeneous region detector did not work well. TLR offered...... and textured images. It is also shown that in a bi-channel approach, combining surface and edge regions (MSER and TLR) boosts the overall performance. Among the descriptors, SIFT and SURF generally offer higher performance but low dimensional descriptors such as Steerable Filters follow closely.......This article presents an evaluation of the image retrieval and classification potential of local features. Several affine invariant region and scale invariant interest point detectors in combination with well known descriptors were evaluated. Tests on building, range and texture databases were...

  11. Structural and Geomorphic Controls in Altitudinal Treeline: a Case Study in the Front Ranges of the Canadian Rocky Mountains

    Science.gov (United States)

    Macias Fauria, M.; Johnson, E. A.

    2009-12-01

    Altitudinal treelines occur on mountain slopes. The geological history of mountain systems sets both the distribution of slope angles, aspects and lengths, and the physical characteristics of the bedrock and regolith on which trees have to establish and grow. We show that altitudinal treeline is largely controlled at an ecosystem level by structural and slope (i.e. gravitational) geomorphic processes operating at a range of temporal and spatial scales, which have direct influence on the hydrological properties of the substrate (affecting the trees’ water and energy budget), as well as on substrate stability, both of which affect recruitment and growth of trees. The study was conducted over a relatively large area of > 200 km2 in the Front Ranges of the Canadian Rocky Mountains, selected to contain the regional diversity of slopes and substrates, which is the result of hundreds of millions of years of sea deposition, subsequent mountain building, and deep erosion by glaciations. Very high-resolution remote sensing data (LiDAR), aerial orthophotos taken at several times since the late 1940s, and ground truthing were employed to classify the terrain into process-based geomorphic units. High resolution, landscape-scale treeline studies are able avoid potential biases in site selection (i.e. selection of sites that are not representative of the overall regional treeline), and consequently capture the coupling between trees and the environment at an ecosystem (regional) level. Moreover, explicitly accounting for slope and substrate-related processes occurring in the studied mountain region is paramount in order to understand the dynamics of trees at their altitudinal distribution limit. Presence of trees in each unit was found to be controlled by a set of parameters relevant to both hydrological and slope processes, such as contributing area, slope angle, regolith transmissivity, and aspect. Our results show no treeline advance over the last 60 years in the region, as

  12. Second-order statistics and ‘designer’ waves for violent free-surface motion around multi-column structures

    Science.gov (United States)

    Grice, J. R.; Taylor, P. H.; Taylor, R. Eatock

    2015-01-01

    Extreme wave–structure interactions are investigated using second-order diffraction theory. The statistics of surface elevation around a multi-column structure are collected using Monte Carlo-type simulations for severe sea states. Within the footprint of a realistic four-column structure, we find that the presence of the structure can give rise to extreme crest elevations greater than twice those at the same return period in the incident wave field. Much of this extra elevation is associated with the excitation of second-order near-trapped modes. A ‘designer’ incident wave can be defined at each point around the structure for a given sea state as the average input wave to produce extreme crest elevations at a given return period, and we show that this wave can be simply vertically scaled to estimate the response at other return periods. PMID:25512584

  13. Response of ground-dwelling spider assemblages to prescribed fire following stand structure manipulation in the southern Cascade Range

    Science.gov (United States)

    Nancy E. Gillette; Richard S. Vetter; Sylvia R. Mori; Carline R. Rudolph; Dessa R. Welty

    2008-01-01

    We assessed spider (Arachnida: Araneae) responses to prescribed fire following stand s tructure treatments in ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) stands in the Cascade Range of California. Stands were logged or left untreated to create three levels of structural diversity. We logged one treatment to minimize old-growth...

  14. Stratigraphic controls on lateral variations in the structural style of northeastern Brooks Range, Arctic National Wildlife Refuge, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, W.K.; Hanks, C.L.

    1988-01-01

    The structural style of the range-front region of the northeastern Brooks Range in Arctic National Wildlife Refuge (ANWR) is strongly controlled by (1) the existence of detachment horizons in both pre-Mississippian rocks and the unconformably overlying Mississippian to Lower Cretaceous cover sequence, and (2) lithology and structural competency of the pre-Mississippian rocks. These variables strongly influence lateral changes in structural style. The Brooks Range of northwestern ANWR is dominated by a series of narrow linear anticlinoria, whereas in northeastern ANWR the Brooks Range is characterized by only two broad and strongly arcuate anticlinoria. In both areas, the anticlinoria are controlled by the geometry of a duplex bounded by a floor thrust in pre-Mississippian rocks and a roof thrust in the Kayak Shale, near the base of the cover sequence. In the west, where the pre-Mississippian partially consists of structurally competent carbonates, each anticlinorium marks a single horse in the duplex. However, in the east, pre-Mississippian rocks are relatively incompetent and each anticlinorium is cored by multiple horses. In the west, shortening above the roof thrust is by detachment folding, except where the shale detachment horizon is depositionally absent. In contrast, in eastern ANWR shortening above the roof thrust is by major thrust duplication of the entire cover sequence, perhaps due to lithology and thickness changes within the detachment horizon.

  15. Efficient integral equation-based analysis of finite periodic structures in the optical frequency range.

    Science.gov (United States)

    Ozdemir, Nilufer A; Craeye, Christophe

    2013-12-01

    The optical response of dense finite arrays of nanoparticles can be efficiently analyzed with the help of macro basis functions obtained by employing the array scanning method. This is demonstrated by analyzing optical collimation in arrays of silver nanorods. The accuracy of the solution obtained with the proposed method has been validated by comparison with solutions obtained employing the Krylov subspace iterative method. The relative error in the electric field distribution on an observation plane above the finite array is of the order of -25 dB, while the number of unknowns is reduced by a factor of 32.

  16. Dynamic optimization of the complex adaptive controlling by the structure of enterprise’s product range

    Directory of Open Access Journals (Sweden)

    Andrey Fyodorovich Shorikov

    2013-06-01

    Full Text Available This paper reviews a methodical approach to solve multi-step dynamic problem of optimal integrated adaptive management of a product portfolio structure of the enterprise. For the organization of optimal adaptive terminal control of the system the recurrent algorithm, which reduces an initial multistage problem to the realization of the final sequence of problems of optimal program terminal control is offered. In turn, the decision of each problem of optimal program terminal control is reduced to the realization of the final sequence only single-step operations in the form of the problems solving of linear and convex mathematical programming. Thus, the offered approach allows to develop management solutions at current information support, which consider feedback, and which create the optimal structure of an enterprise’s product lines, contributing to optimising of profits, as well as maintenance of the desired level of profit for a long period of time

  17. Close-packed structure dynamics with finite-range interaction: computational mechanics with individual layer interaction.

    Science.gov (United States)

    Rodriguez-Horta, Edwin; Estevez-Rams, Ernesto; Lora-Serrano, Raimundo; Neder, Reinhard

    2017-09-01

    This is the second contribution in a series of papers dealing with dynamical models in equilibrium theories of polytypism. A Hamiltonian introduced by Ahmad & Khan [Phys. Status Solidi B (2000), 218, 425-430] avoids the unphysical assignment of interaction terms to fictitious entities given by spins in the Hägg coding of the stacking arrangement. In this paper an analysis of polytype generation and disorder in close-packed structures is made for such a Hamiltonian. Results are compared with a previous analysis using the Ising model. Computational mechanics is the framework under which the analysis is performed. The competing effects of disorder and structure, as given by entropy density and excess entropy, respectively, are discussed. It is argued that the Ahmad & Khan model is simpler and predicts a larger set of polytypes than previous treatments.

  18. X-ray structural studies of quinone reductase 2 nanomolar range inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Pegan, Scott D.; Sturdy, Megan; Ferry, Gilles; Delagrange, Philippe; Boutin, Jean A.; Mesecar, Andrew D. (IdRS); (Purdue); (Colorado); (UIC)

    2011-09-06

    Quinone reductase 2 (QR2) is one of two members comprising the mammalian quinone reductase family of enzymes responsible for performing FAD mediated reductions of quinone substrates. In contrast to quinone reductase 1 (QR1) which uses NAD(P)H as its co-substrate, QR2 utilizes a rare group of hydride donors, N-methyl or N-ribosyl nicotinamide. Several studies have linked QR2 to the generation of quinone free radicals, several neuronal degenerative diseases, and cancer. QR2 has been also identified as the third melatonin receptor (MT3) through in cellulo and in vitro inhibition of QR2 by traditional MT3 ligands, and through recent X-ray structures of human QR2 (hQR2) in complex with melatonin and 2-iodomelatonin. Several MT3 specific ligands have been developed that exhibit both potent in cellulo inhibition of hQR2 nanomolar, affinity for MT3. The potency of these ligands suggest their use as molecular probes for hQR2. However, no definitive correlation between traditionally obtained MT3 ligand affinity and hQR2 inhibition exists limiting our understanding of how these ligands are accommodated in the hQR2 active site. To obtain a clearer relationship between the structures of developed MT3 ligands and their inhibitory properties, in cellulo and in vitro IC{sub 50} values were determined for a representative set of MT3 ligands (MCA-NAT, 2-I-MCANAT, prazosin, S26695, S32797, and S29434). Furthermore, X-ray structures for each of these ligands in complex with hQR2 were determined allowing for a structural evaluation of the binding modes of these ligands in relation to the potency of MT3 ligands.

  19. X-ray structural studies of quinone reductase 2 nanomolar range inhibitors.

    Science.gov (United States)

    Pegan, Scott D; Sturdy, Megan; Ferry, Gilles; Delagrange, Philippe; Boutin, Jean A; Mesecar, Andrew D

    2011-07-01

    Quinone reductase 2 (QR2) is one of two members comprising the mammalian quinone reductase family of enzymes responsible for performing FAD mediated reductions of quinone substrates. In contrast to quinone reductase 1 (QR1) which uses NAD(P)H as its co-substrate, QR2 utilizes a rare group of hydride donors, N-methyl or N-ribosyl nicotinamide. Several studies have linked QR2 to the generation of quinone free radicals, several neuronal degenerative diseases, and cancer. QR2 has been also identified as the third melatonin receptor (MT3) through in cellulo and in vitro inhibition of QR2 by traditional MT3 ligands, and through recent X-ray structures of human QR2 (hQR2) in complex with melatonin and 2-iodomelatonin. Several MT3 specific ligands have been developed that exhibit both potent in cellulo inhibition of hQR2 nanomolar, affinity for MT3. The potency of these ligands suggest their use as molecular probes for hQR2. However, no definitive correlation between traditionally obtained MT3 ligand affinity and hQR2 inhibition exists limiting our understanding of how these ligands are accommodated in the hQR2 active site. To obtain a clearer relationship between the structures of developed MT3 ligands and their inhibitory properties, in cellulo and in vitro IC₅₀ values were determined for a representative set of MT3 ligands (MCA-NAT, 2-I-MCANAT, prazosin, S26695, S32797, and S29434). Furthermore, X-ray structures for each of these ligands in complex with hQR2 were determined allowing for a structural evaluation of the binding modes of these ligands in relation to the potency of MT3 ligands. Copyright © 2011 The Protein Society.

  20. Structural order in ultrathin films of the monolayer protected clusters based upon 4 nm gold nanocrystals: an experimental and theoretical study.

    Science.gov (United States)

    Bhattarai, Nabraj; Khanal, Subarna; Bahena, Daniel; Olmos-Asar, Jimena A; Ponce, Arturo; Whetten, Robert L; Mariscal, Marcelo M; Jose-Yacaman, Miguel

    2014-09-14

    The structural order in ultrathin films of monolayer protected clusters (MPCs) is important in a number of application areas but can be difficult to demonstrate by conventional methods, particularly when the metallic core dimension, d, is in the intermediate size-range, 1.5 < d < 5.0 nm. Here, improved techniques for the synthesis of monodisperse thiolate-protected gold nanoparticles have made possible the production of dodecane-thiolate saturated ∼4 ± 0.5 nm Au clusters with single-crystal core structure and morphology. An ultrathin ordered film or superlattice of these nanocrystal-core MPCs is prepared and investigated using aberration corrected scanning/transmission electron microscopy (STEM) which allowed imaging of long-range hexagonally ordered superlattices of the nanocrystals, separated by the thiolate groups. The lattice constants determined by direct imaging are in good agreement with those determined by small-angle electron diffraction. The STEM image revealed the characteristic grain boundary (GB) with sigma (Σ) 13 in the interface between two crystals. The formation and structures found are interpreted on the basis of theoretical calculations employing molecular dynamics (MD) simulations and coarse-grained (CG) approach.

  1. Structural Order in Ultrathin Films of the Monolayer Protected Clusters Based Upon 4-nm Gold Nanocrystals: An Experimental and Theoretical Study

    Science.gov (United States)

    Bhattarai, Nabraj; Khanal, Subarna; Bahena, Daniel; Olmos-Asar, Jimena A.; Ponce, Arturo; Whetten, Robert L.; Mariscal, Marcelo M.; Jose-Yacaman, Miguel

    2014-01-01

    The structural order in ultrathin films of monolayer protected clusters (MPCs) is important in a number of application areas but can be difficult to demonstrate by conventional methods, particularly when the metallic core dimension, d, is in the intermediate size-range, 1.5 < d < 5.0 nm. Here, improved techniques for the synthesis of monodisperse thiolate-protected gold nanoparticles have made possible the production of dodecane-thiolate saturated ~ 4 ± 0.5 nm Au clusters with single-crystal core structure and morphology. An ultrathin ordered film or superlattice of these nanocrystal-core MPCs is prepared and investigated using aberration corrected scanning/transmission electron microscopy (STEM) which allowed imaging of long-range hexagonally ordered superlattices of the nanocrystals, separated by the thiolate groups. The lattice constants determined by direct imaging are in good agreement with those determined by small-angle electron diffraction. The STEM image revealed the characteristic grain boundary (GB) with sigma (Σ) 13 in the interface between two crystals. The formation and structures found are interpreted on the basis of theoretical calculations employing molecular dynamics (MD) simulations and coarse-grained (CG) approach. PMID:24875295

  2. L10 ordered structures in Al-Cu-(Mg) alloys at the early stages of elevated temperature aging

    Energy Technology Data Exchange (ETDEWEB)

    Fuzhong, X.; Mingpu, W.

    2016-07-01

    This study concerns the precipitation structures of Al-3Cu and Al-3Cu-1.78Mg (wt. %) alloys at the early stages of elevated temperature aging. The Al-3Cu and Al-3Cu-1.78 Mg alloys were solution treated at 540 °C and 500 °C for 2 h, respectively, and then aged at 190 °C for 2 min. The precipitation structures in aged Al-3Cu-(1.78Mg) alloys were characterized by Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HTREM). 001 zone axis Selected area electron diffraction patterns indicate that L10 ordered structures are formed in the two aged alloys. HRTEM experiments reveal the partial dislocations on the interfaces of L10 ordered structures. From comparing experimental results with that in the literature, it is concluded that the L10 ordered structures in aged Al-3Cu alloy consist of Al and Cu atoms, and they are comprised by Al, Cu and Mg atoms together in the aged Al-3Cu-1.78Mg alloy. On the basis of precipitate growing thermodynamics, it is thought the L10 ordered structures act as nuclei for GP zones in Al-Cu-(Mg) alloys during aging. (Author)

  3. Effects of PEO-PPO diblock impurities on the cubic structure of aqueous PEO-PPO-PEO pluronics micelles: fcc and bcc ordered structures in F127

    DEFF Research Database (Denmark)

    Mortensen, Kell; Pedersen, Walther Batsberg; Hvidt, S.

    2008-01-01

    We report on structural properties of PEO-PPO-PEO type of triblock block copolymers (Pluronics F127) with special emphasis on the effect of diblock PEO-PPO impurities on the ordered gel phase. Commercial F127 polymers contain as received roughly 20% PEO-PPO diblock and 80% PEO-PPO-PEO triblock...... copolymers. Aqueous solutions of F127 copolymers used as received form fee ordered micellar structure. Copolymers depleted with respect to the diblock impurity, resulting in a pure PEO-PPO-PEO triblock copolymer system, form bcc ordered micelles within the major parts of the gel phase. However, close...

  4. Range position and climate sensitivity: The structure of among-population demographic responses to climatic variation.

    Science.gov (United States)

    Amburgey, Staci M; Miller, David A W; Campbell Grant, Evan H; Rittenhouse, Tracy A G; Benard, Michael F; Richardson, Jonathan L; Urban, Mark C; Hughson, Ward; Brand, Adrianne B; Davis, Christopher J; Hardin, Carmen R; Paton, Peter W C; Raithel, Christopher J; Relyea, Rick A; Scott, A Floyd; Skelly, David K; Skidds, Dennis E; Smith, Charles K; Werner, Earl E

    2018-01-01

    Species' distributions will respond to climate change based on the relationship between local demographic processes and climate and how this relationship varies based on range position. A rarely tested demographic prediction is that populations at the extremes of a species' climate envelope (e.g., populations in areas with the highest mean annual temperature) will be most sensitive to local shifts in climate (i.e., warming). We tested this prediction using a dynamic species distribution model linking demographic rates to variation in temperature and precipitation for wood frogs (Lithobates sylvaticus) in North America. Using long-term monitoring data from 746 populations in 27 study areas, we determined how climatic variation affected population growth rates and how these relationships varied with respect to long-term climate. Some models supported the predicted pattern, with negative effects of extreme summer temperatures in hotter areas and positive effects on recruitment for summer water availability in drier areas. We also found evidence of interacting temperature and precipitation influencing population size, such as extreme heat having less of a negative effect in wetter areas. Other results were contrary to predictions, such as positive effects of summer water availability in wetter parts of the range and positive responses to winter warming especially in milder areas. In general, we found wood frogs were more sensitive to changes in temperature or temperature interacting with precipitation than to changes in precipitation alone. Our results suggest that sensitivity to changes in climate cannot be predicted simply by knowing locations within the species' climate envelope. Many climate processes did not affect population growth rates in the predicted direction based on range position. Processes such as species-interactions, local adaptation, and interactions with the physical landscape likely affect the responses we observed. Our work highlights the need to

  5. Range position and climate sensitivity: The structure of among-population demographic responses to climatic variation

    Science.gov (United States)

    Amburgey, Staci M.; Miller, David A. W.; Grant, Evan H. Campbell; Rittenhouse, Tracy A. G.; Benard, Michael F.; Richardson, Jonathan L.; Urban, Mark C.; Hughson, Ward; Brand, Adrianne B,; Davis, Christopher J.; Hardin, Carmen R.; Paton, Peter W. C.; Raithel, Christopher J.; Relyea, Rick A.; Scott, A. Floyd; Skelly, David K.; Skidds, Dennis E.; Smith, Charles K.; Werner, Earl E.

    2018-01-01

    Species’ distributions will respond to climate change based on the relationship between local demographic processes and climate and how this relationship varies based on range position. A rarely tested demographic prediction is that populations at the extremes of a species’ climate envelope (e.g., populations in areas with the highest mean annual temperature) will be most sensitive to local shifts in climate (i.e., warming). We tested this prediction using a dynamic species distribution model linking demographic rates to variation in temperature and precipitation for wood frogs (Lithobates sylvaticus) in North America. Using long-term monitoring data from 746 populations in 27 study areas, we determined how climatic variation affected population growth rates and how these relationships varied with respect to long-term climate. Some models supported the predicted pattern, with negative effects of extreme summer temperatures in hotter areas and positive effects on recruitment for summer water availability in drier areas. We also found evidence of interacting temperature and precipitation influencing population size, such as extreme heat having less of a negative effect in wetter areas. Other results were contrary to predictions, such as positive effects of summer water availability in wetter parts of the range and positive responses to winter warming especially in milder areas. In general, we found wood frogs were more sensitive to changes in temperature or temperature interacting with precipitation than to changes in precipitation alone. Our results suggest that sensitivity to changes in climate cannot be predicted simply by knowing locations within the species’ climate envelope. Many climate processes did not affect population growth rates in the predicted direction based on range position. Processes such as species-interactions, local adaptation, and interactions with the physical landscape likely affect the responses we observed. Our work highlights the

  6. Stratigraphic controls on lateral variations in the structural style of northeastern Brooks range, Arctic National Wildlife Refuge, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, W.K.; Hanks, C.L.

    1988-02-01

    The structural style of the range-front region of the northeastern Brooks Range in Arctic National Wildlife Refuge (ANWR) is strongly controlled by (1) the existence of detachment horizons in both pre-Mississippian rocks and the unconformably overlying Mississippian to Lower Cretaceous cover sequence, and (2) lithology and structural competency of the pre-Mississippian rocks. These variables strongly influence lateral changes in structural style. The Brooks Range of northwestern ANWR is dominated by a series of narrow linear anticlinoria, whereas in northeastern ANWR the Brooks Range is characterized by only two broad and strongly arcuate anticlinoria. In both areas, the anticlinoria are controlled by the geometry of a duplex bounded by a floor thrust in pre-Mississippian rocks and a roof thrust in the Kayak Shale, near the base of the cover sequence. In the west, where the pre-Mississippian partially consists of structurally competent carbonates, each anticlinorium marks a single horse in the duplex. However, in the east, pre-Mississippian rocks are relatively incompetent and each anticlinorium is cored by multiple horses. In the west, shortening above the roof thrust is by detachment folding, except where the shale detachment horizon is depositionally absent. In contrast, in eastern ANWR shortening above the roof thrust is by major thrust duplication of the entire cover sequence, perhaps due to lithology and thickness changes within the detachment horizon. A Devonian batholith marks the boundary between the eastern and western structural provinces. The thrust-controlled range front of eastern ANWR extends north of the batholith, suggesting that the batholith itself may be underlain by a thrust fault.

  7. Comparison of soil thickness in a zero-order basin in the Oregon Coast Range using a soil probe and electrical resistivity tomography

    Science.gov (United States)

    Morse, Michael S.; Lu, Ning; Godt, Jonathan W.; Revil, André; Coe, Jeffrey A.

    2012-01-01

    Accurate estimation of the soil thickness distribution in steepland drainage basins is essential for understanding ecosystem and subsurface response to infiltration. One important aspect of this characterization is assessing the heavy and antecedent rainfall conditions that lead to shallow landsliding. In this paper, we investigate the direct current (DC) resistivity method as a tool for quickly estimating soil thickness over a steep (33–40°) zero-order basin in the Oregon Coast Range, a landslide prone region. Point measurements throughout the basin showed bedrock depths between 0.55 and 3.2 m. Resistivity of soil and bedrock samples collected from the site was measured for degrees of saturation between 40 and 92%. Resistivity of the soil was typically higher than that of the bedrock for degrees of saturation lower than 70%. Results from the laboratory measurements and point-depth measurements were used in a numerical model to evaluate the resistivity contrast at the soil-bedrock interface. A decreasing-with-depth resistivity contrast was apparent at the interface in the modeling results. At the field site, three transects were surveyed where coincident ground truth measurements of bedrock depth were available, to test the accuracy of the method. The same decreasing-with-depth resistivity trend that was apparent in the model was also present in the survey data. The resistivity contour of between 1,000 and 2,000 Ωm that marked the top of the contrast was our interpreted bedrock depth in the survey data. Kriged depth-to-bedrock maps were created from both the field-measured ground truth obtained with a soil probe and interpreted depths from the resistivity tomography, and these were compared for accuracy graphically. Depths were interpolated as far as 16.5 m laterally from the resistivity survey lines with root mean squared error (RMSE) = 27 cm between the measured and interpreted depth at those locations. Using several transects and analysis of the subsurface

  8. Broadband impedance-matched electromagnetic structured ferrite composite in the megahertz range

    Energy Technology Data Exchange (ETDEWEB)

    Parke, L.; Hibbins, A. P.; Sambles, J. R. [Electromagnetic and Acoustic Materials Group, Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, Devon EX4 4QL (United Kingdom); Youngs, I. J. [DSTL, Salisbury, Wiltshire SP4 0JQ (United Kingdom)

    2014-06-02

    A high refractive-index structured ferrite composite is designed to experimentally demonstrate broadband impedance matching to free-space. It consists of an array of ferrite cubes that are anisotropically spaced, thereby allowing for independent control of the effective complex permeability and permittivity. Despite having a refractive index of 9.5, the array gives less than 1% reflection and over 90% transmission of normally incident radiation up to 70 MHz for one of the orthogonal linear polarisations lying in a symmetry plane of the array. This result presents a route to the design of MHz-frequency ferrite composites with bespoke electromagnetic parameters for antenna miniaturisation.

  9. Climate Effects on Plant Range Distributions and Community Structure of Pacific Northwest Prairies

    Energy Technology Data Exchange (ETDEWEB)

    Bridgham, Scott D. [Univ. of Oregon, Eugene, OR (United States); Johnson, Bart [Univ. of Oregon, Eugene, OR (United States)

    2013-09-26

    Pacific Northwest (PNW) prairies are an imperiled ecosystem that contain a large number of plant species with high fidelity to this habitat. The few remaining high-quality PNW prairies harbor a number of sensitive, rare, and endangered plant species that may be further at-risk with climate change. Thus, PNW prairies are an excellent model system to examine how climate change will affect the distribution of native plant species in grassland sites. Our experimental objectives were to determine: (i) how climate change will affect the range distribution of native plant species; (ii) what life history stages are most sensitive to climate change in a group of key indicator native species; (iii) the robustness of current restoration techniques and suites of species to changing climate, and in particular, the relative competitiveness of native species versus exotic invasive species; and (iv) the effects of climate change on carbon and nutrient cycling and soil-microbial-plant feedbacks. We addressed these objectives by experimentally increasing temperature 2.5 to 3.0 ºC above ambient with overhead infrared lamps and increasing wet-season precipitation by 20% above ambient in three upland prairie sites in central-western Washington, central-western Oregon, and southwestern Oregon from fall 2010 through 2012. Additional precipitation was applied within 2 weeks of when it fell so precipitation intensity was increased, particularly during the winter rainy season but with minimal additions during the summer dry season. These three sites also represent a 520-km natural climate gradient of increasing degree of severity of Mediterranean climate from north to south. After removing the extant vegetation, we planted a diverse suite of 12 native species that have their northern range limit someplace within the PNW in each experimental plot. An additional 20 more wide-spread native species were also planted into each plot. We found that recruitment of plant species within their ranges

  10. Controlling Nano-ordered Structures by Stereocomplex Formation between Poly(L-lactide) and Poly(D-lactide) Macromolecular Chains

    OpenAIRE

    Nakajima, Maho

    2015-01-01

    Polylactides (PLAs) have been widely utilized as biomaterials for making bone implants, fixing screws, and absorbable sutures because of their excellent biocompatibility and bioabsorbability. However, their nano-order structure control is required for developing functional biomaterials that can be applied to tissue engineering and specific medical devices. Various nano-ordered morphologies have been found out thus far in various multi-component polymer blends and surface -immobilized macrom...

  11. Nonlinear AeroServoElastic Reduced Order Model for Active Structural Control Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall goal of the proposed effort is to develop and demonstrate rigorous model order reduction (MOR) technologies to automatically generate fully coupled,...

  12. Orientationally ordered ridge structures of aluminum films on hydrogen terminated silicon

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Pantleon, Karen

    2006-01-01

    > directions on the silicon substrate. The ridge structure appears when the film thickness is above 500 nm, and increasing the film thickness makes the structure more distinct. Anodic oxidation enhances the structure even further. X-ray diffraction indicates that grains in the film have mostly (110) facets......Films of aluminum deposited onto Si(100) substrates show a surface structure of parallel ridges. On films deposited on oxidized silicon substrates the direction of the ridges is arbitrary, but on films deposited on hydrogen-terminated Si(100) the ridges are oriented parallel to the

  13. Effect of addition of pore expanding agent on changes of structure characteristics of ordered mesoporous silicas

    Energy Technology Data Exchange (ETDEWEB)

    Derylo-Marczewska, A. [Faculty of Chemistry, M. Curie-Sklodowska University, M. Curie-Sklodowska Sq. 3, 20-031 Lublin (Poland)], E-mail: annad@hektor.umcs.lublin.pl; Marczewski, A.W.; Skrzypek, I.; Pikus, S. [Faculty of Chemistry, M. Curie-Sklodowska University, M. Curie-Sklodowska Sq. 3, 20-031 Lublin (Poland); Kozak, M. [Department of Macromolecular Physics, A. Mickiewicz University, 61-614 Poznan (Poland)

    2008-12-30

    A series of mesoporous silica materials were synthesized by applying two types of Pluronic copolymers as pore creating agents. Differentiation of pore structure of the obtained sorbents was attained by changing the amount of trimethylbenzene as pore expander introduced to a reacting mixture. The parameters characterizing porous structure were estimated from nitrogen adsorption/desorption isotherms. The changes of pore arrangement in the synthesized materials were investigated by using X-ray diffraction. The structural transformations were found at the TMB/polymer ratio of 0.8 and 1. Correlations between the values of structure parameters and the content of TMB were found.

  14. Dynamics and genetic structure of Argentine ant supercolonies in their native range

    DEFF Research Database (Denmark)

    Vogel, Valérie; Pedersen, Jes S; d'Ettorre, Patrizia

    2009-01-01

    analyses revealed the presence of 11 supercolonies (width 1 to 515 m) over a 3-km transect. As in the introduced range, there was always strong aggression between but never within supercolonies. The genetic data were in perfect agreement with the behavioral tests, all nests being assigned to identical......Some introduced ant populations have an extraordinary social organization, called unicoloniality, whereby individuals mix freely within large supercolonies. We investigated whether this mode of social organization also exists in native populations of the Argentine ant Linepithema humile. Behavioral...... units. Genetic and chemical distances between supercolonies were positively correlated, but there were no other significant associations between geographic, genetic, chemical, and behavioral distances. A comparison of supercolonies sampled in 1999 and 2005 revealed a very high turnover, with about one...

  15. Microscopic structure and thermodynamics of a core-softened model fluid from the second-order integral equations theory

    Directory of Open Access Journals (Sweden)

    S. Sokołowski

    2011-03-01

    Full Text Available We have studied the structure and thermodynamic properties of isotropic three-dimensional core-softened fluid by using the second-order Ornstein-Zernike integral equations completed by the hypernetted chain and Percus-Yevick closures. The radial distribution functions are compared with those from singlet integral equations and with computer simulation data. The limits of the region of density anomaly resulting from different approximate theories are established. The obtained results show that the second-order hypernetted chain approximation can be used to describe both the structure and the density anomaly of this model fluid. Moreover, we present the results of calculations of the bridge functions.

  16. Development of a Compact Range-gated Vision System to Monitor Structures in Low-visibility Environments

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Yong-Jin; Park, Seung-Kyu; Baik, Sung-Hoon; Kim, Dong-Lyul; Choi, Young-Soo; Jeong, Kyung-Min [KAERI, Daejeon (Korea, Republic of)

    2015-05-15

    Image acquisition in disaster area or radiation area of nuclear industry is an important function for safety inspection and preparing appropriate damage control plans. So, automatic vision system to monitor structures and facilities in blurred smoking environments such as the places of a fire and detonation is essential. Vision systems can't acquire an image when the illumination light is blocked by disturbance materials, such as smoke, fog and dust. To overcome the imaging distortion caused by obstacle materials, robust vision systems should have extra-functions, such as active illumination through disturbance materials. One of active vision system is a range-gated imaging system. The vision system based on the range-gated imaging system can acquire image data from the blurred and darken light environments. Range-gated imaging (RGI) is a direct active visualization technique using a highly sensitive image sensor and a high intensity illuminant. Currently, the range-gated imaging technique providing 2D and range image data is one of emerging active vision technologies. The range-gated imaging system gets vision information by summing time sliced vision images. In the RGI system, a high intensity illuminant illuminates for ultra-short time and a highly sensitive image sensor is gated by ultra-short exposure time to only get the illumination light. Here, the illuminant illuminates objects by flashing strong light through disturbance materials, such as smoke particles and dust particles. In contrast to passive conventional vision systems, the RGI active vision technology enables operation even in harsh environments like low-visibility smoky environment. In this paper, a compact range-gated vision system is developed to monitor structures in low-visibility environment. The system consists of illumination light, a range-gating camera and a control computer. Visualization experiments are carried out in low-visibility foggy environment to see imaging capability.

  17. An Efficient Framework for Analysis of Wire-Grid Shielding Structures over a Broad Frequency Range

    Directory of Open Access Journals (Sweden)

    A. Karwowski

    2016-12-01

    Full Text Available A computationally efficient MoM-based framework for broadband electromagnetic simulation of wire-grid shielding structures is presented in the paper. Broadband capability of the approach is attained through supporting MoM by an adaptive frequency sweep combined with rational interpolation of the observable implemented via Stoer-Bulirsch algorithm. The performance increase is gained by employing CUDA-enabled CPU+GPU co-processing. For large-size problems exceeding the amount of memory available on the GPU device, a hybrid out-of-GPU memory LU decomposition algorithm is employed. The demonstration examples are provided to illustrate the the accuracy and high efficiency of the approach.

  18. Group velocity effect on resonant, long-range wake-fields in slow wave structures

    CERN Document Server

    Smirnov, A V

    2002-01-01

    Synchronous wake-fields in a dispersive waveguide are derived in a general explicit form on the basis of a rigorous electro-dynamical approach using Fourier transformations. The fundamental role of group velocity in wake-field propagation, calculation of attenuation, amplitudes, form-factors and loss-factors is analyzed for single bunch radiation. Adiabatic tapering of the waveguide and bunch density variation is taken into account analytically for the time-domain fields. Effects of field 'compression/expansion' and group delays are demonstrated. The role of these effects is discussed for single bunch wake-fields, transient beam loading, BBU and HOMs. A novel waveguide structure with central rf coupling and both positive and negative velocities is proposed. It can be used effectively in both high-energy accelerators and single-section linacs.

  19. X-ray propagation through a quasi-ordered multilayered structure ...

    African Journals Online (AJOL)

    We investigate the propagation of short wavelength transverse electric x-rays through a quasiordered (Fibonacci) atomically commensurate multilayered structure using a transfer matrix model which treats each atomic plane as a diffraction unit. The reflectance spectrum has a rich structure being dominated by peaks ...

  20. Visualizing High-Dimensional Structures by Dimension Ordering and Filtering using Subspace Analysis

    NARCIS (Netherlands)

    Ferdosi, Bilkis J.; Roerdink, Jos B. T. M.

    2011-01-01

    High-dimensional data visualization is receiving increasing interest because of the growing abundance of high-dimensional datasets. To understand such datasets, visualization of the structures present in the data, such as clusters, can be an invaluable tool. Structures may be present in the full

  1. On modeling micro-structural evolution using a higher order strain gradient continuum theory

    DEFF Research Database (Denmark)

    El-Naaman, S. A.; Nielsen, K. L.; Niordson, C. F.

    2016-01-01

    the experimentally observed micro-structural behavior, within a framework based on continuous field quantities, poses obvious challenges, since the evolution of dislocation structures is inherently a discrete and discontinuous process. This challenge, in particular, motivates the present study, and the aim...

  2. Co-operative interactions between first- and second-order mechanisms in the processing of structure from motion.

    Science.gov (United States)

    Aaen-Stockdale, Craig R; Farivar, Reza; Hess, Robert F

    2010-11-11

    Structure from motion (SFM) is the ability to perceive three-dimensional structure from stimuli containing only two-dimensional motion signals and this ability seems to be a result of high-level cortical processes. It has long been thought that local motion signals defined by second-order cues only weakly contribute to perception of SFM since performance on purely second-order SFM tasks is poor, relative to first-order stimuli. We hypothesized that the mechanisms responsible for deriving SFM were insensitive to low-level stimulus attributes such as the first- or second-order nature of the dots composing the stimulus, in other words: that they were "cue-invariant", but that large differences in sensitivity to local first- and second-order motions were responsible for previous findings. By manipulating the relative strength of first-order dots in an SFM stimulus that combines first- and second-order dots, we show that the two types of motion can separately support SFM and co-operatively interact to produce vivid three-dimensional percepts. This provides strong support that the mechanisms underlying SFM are cue-invariant.

  3. The application of the mesh-free method in the numerical simulations of the higher-order continuum structures

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yuzhou, E-mail: yuzhousun@126.com; Chen, Gensheng; Li, Dongxia [School of Civil Engineering and Architecture, Zhongyuan University of Technology, Zhengzhou (China)

    2016-06-08

    This paper attempts to study the application of mesh-free method in the numerical simulations of the higher-order continuum structures. A high-order bending beam considers the effect of the third-order derivative of deflections, and can be viewed as a one-dimensional higher-order continuum structure. The moving least-squares method is used to construct the shape function with the high-order continuum property, the curvature and the third-order derivative of deflections are directly interpolated with nodal variables and the second- and third-order derivative of the shape function, and the mesh-free computational scheme is establish for beams. The coupled stress theory is introduced to describe the special constitutive response of the layered rock mass in which the bending effect of thin layer is considered. The strain and the curvature are directly interpolated with the nodal variables, and the mesh-free method is established for the layered rock mass. The good computational efficiency is achieved based on the developed mesh-free method, and some key issues are discussed.

  4. Synthesis, crystal structure, growth, optical and third order nonlinear optical studies of 8HQ2C5N single crystal - An efficient third-order nonlinear optical material

    Energy Technology Data Exchange (ETDEWEB)

    Divya Bharathi, M.; Ahila, G.; Mohana, J. [Department of Physics, Presidency College, Chennai 600005 (India); Chakkaravarthi, G. [Department of Physics, CPCL Polytechnic College, Chennai 600068 (India); Anbalagan, G., E-mail: anbu24663@yahoo.co.in [Department of Nuclear Physics, University of Madras, Chennai 600025 (India)

    2017-05-01

    A neoteric organic third order nonlinear optical material 8-hydroxyquinolinium 2-chloro-5-nitrobenzoate dihydrate (8HQ2C5N) was grown by slow cooling technique using ethanol: water (1:1) mixed solvent. The calculated low value of average etch pit solidity (4.12 × 10{sup 3} cm{sup −2}) indicated that the title crystal contain less defects. From the single crystal X-ray diffraction data, it was endowed that 8HQ2C5N crystal belongs to the monoclinic system with centrosymmetric space group P2{sub 1}/c and the cell parameters values, a = 9.6546 (4) Ǻ, b = 7.1637(3) Ǻ, c = 24.3606 (12) Ǻ, α = γ = 90°, β = 92.458(2)° and volume = 1683.29(13) Ǻ{sup 3}. The FT-IR and FT-Raman spectrum were used to affirm the functional group of the title compound. The chemical structure of 8HQ2C5N was scrutinized by {sup 13}C and {sup 1}H NMR spectral analysis and thermal stability through the differential scanning calorimetry study. Using optical studies the lower cut-off wavelength and optical band gap of 8HQ2C5N were found to be 364 nm and 3.17 eV respectively. Using the single oscillator model suggested by Wemple – Didomenico, the oscillator energy (E{sub o}), the dispersion energy (E{sub d}) and static dielectric constant (ε{sub o}) were estimated. The third-order susceptibility were determined as Im χ{sup (3)} = 2.51 × 10{sup −5} esu and Re χ{sup (3)} = 4.46 × 10{sup −7} esu. The theoretical third-order nonlinear optical susceptibility χ{sup (3)} was calculated and the results were compared with experimental value. Photoluminescence spectrum of 8HQ2C5N crystal showed the yellow emission. The crystal had the single shot laser damage threshold of 5.562 GW/cm{sup 2}. Microhardness measurement showed that 8HQ2C5N belongs to a soft material category. - Highlights: • A new organic single crystals were grown and the crystal structure was reported. • Crystal possess, good transmittance, thermal and mechanical stability. • Single shot LDT value is found to be

  5. Understanding the Functions of Long Non-Coding RNAs through Their Higher-Order Structures

    Directory of Open Access Journals (Sweden)

    Rui Li

    2016-05-01

    Full Text Available Although thousands of long non-coding RNAs (lncRNAs have been discovered in eukaryotes, very few molecular mechanisms have been characterized due to an insufficient understanding of lncRNA structure. Therefore, investigations of lncRNA structure and subsequent elucidation of the regulatory mechanisms are urgently needed. However, since lncRNA are high molecular weight molecules, which makes their crystallization difficult, obtaining information about their structure is extremely challenging, and the structures of only several lncRNAs have been determined so far. Here, we review the structure–function relationships of the widely studied lncRNAs found in the animal and plant kingdoms, focusing on the principles and applications of both in vitro and in vivo technologies for the study of RNA structures, including dimethyl sulfate-sequencing (DMS-seq, selective 2′-hydroxyl acylation analyzed by primer extension-sequencing (SHAPE-seq, parallel analysis of RNA structure (PARS, and fragmentation sequencing (FragSeq. The aim of this review is to provide a better understanding of lncRNA biological functions by studying them at the structural level.

  6. Diffraction of Laser Light as a Probe of Ordered Tissue Structure

    Science.gov (United States)

    Stewart, Cody; Forrester, Kevin; Frank, C. B.; Irvine-Halliday, David; Muldrew, Ken; Shrive, Nigel; Thompson, Robert

    2002-05-01

    Laser light transmitted through thin slices of ordered tissue, such as tendon and ligament, forms a diffraction pattern elongated in the direction perpendicular to the alignment direction of the tissue fibers. The degree of elongation provides information on the degree of order in the tissue sample and thus provides a probe of the presence of scar tissue since, when damaged, collagen fibers reform more randomly than in healthy tissue. Small Angle Light Scattering (SALS) is an established technique that utilizes the diffraction properties of ordered tissue to determine bulk properties such as angle and degree of fiber orientation. This presentation will present experimental data that appears to dispute certain basic assumptions inherent in the method, as well as a basic theoretical explanation for why these assumptions may be inadequate under some experimental conditions.

  7. Role of Short-Range Chemical Ordering in (GaN) 1–x (ZnO) x for Photodriven Oxygen Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Dennis P. [Department; Neuefeind, Joerg C. [Chemical; Koczkur, Kallum M. [Department; Bish, David L. [Department; Skrabalak, Sara E. [Department

    2017-07-21

    (GaN)1–x(ZnO)x (GZNO) is capable of visible-light driven water splitting, but its bandgap at x ≤ 0.15 (>2.7 eV) results in poor visible-light absorption. Unfortunately, methods to narrow its bandgap by incorporating higher ZnO concentrations are accompanied by extensive Urbach tailing near the absorption-edge, which is indicative of structural disorder or chemical inhomogeneities. We evaluated whether this disorder is intrinsic to the bond-length distribution in GZNO or is a result of defects introduced from the loss of Zn during nitridation. Here, the synthesis of GZNO derived from layered double hydroxide (LDH) precursors is described which minimizes Zn loss and chemical inhomogeneities and enhances visible-light absorption. The average and local atomic structures of LDH-derived GZNO were investigated using X-ray and neutron scattering and are correlated with their oxygen evolution rates. An isotope-contrasted neutron-scattering experiment was conducted in conjunction with reverse Monte Carlo (RMC) simulations. We showed that a bond-valence bias in the RMC refinements reproduces the short-range ordering (SRO) observed in structure refinements using isotope-contrasted neutron data. The findings suggest that positional disorder of cation–anion pairs in GZNO partially arises from SRO and influences local bond relaxations. Furthermore, particle-based oxygen evolution reactions (OERs) in AgNO3 solution reveal that the crystallite size of GZNO correlates more than positional disorder with oxygen evolution rate. These findings illustrate the importance of examining the local structure of multinary photocatalysts to identify dominant factors in particulate-based photodriven oxygen evolution.

  8. Second-order analysis of structured inhomogeneous spatio-temporal point processes

    DEFF Research Database (Denmark)

    Møller, Jesper; Ghorbani, Mohammad

    Statistical methodology for spatio-temporal point processes is in its infancy. We consider second-order analysis based on pair correlation functions and K-functions for first general inhomogeneous spatio-temporal point processes and second inhomogeneous spatio-temporal Cox processes. Assuming......-temporal Gaussian process. Another concerns shot-noise Cox processes with a separable spatio-temporal covariance density. We propose diagnostic procedures for checking hypotheses of second-order spatio-temporal separability, which we apply on simulated and real data (the UK 2001 epidemic foot and mouth disease data)....

  9. Local structure of ordered and disordered states of 3He-A in aerogel

    Science.gov (United States)

    Surovtsev, E. V.; Fomin, I. A.

    2017-10-01

    Random textures of the orbital part of the order parameter of superfluid 3He-A in aerogel are analyzed theoretically in the Ginzburg and Landau region both in the presence and in the absence of a global anisotropy. Correlation functions of angles, determining orientation of the order parameter, are found for relative distances which are small in comparison with the characteristic scale of the random texture. Modifications of the Larkin-Imry-Ma state in limiting cases of a relatively strong uniaxial compression and of a uniaxial stretching are analyzed, and characteristic parameters of the emerging states are found.

  10. Langmuir-Blodgett films of amylose-esters and chiral azo-dyes : structure and second order nonlinear optical behaviour

    NARCIS (Netherlands)

    Schoondorp, Monique Annette

    1992-01-01

    This thesis describes the structure and second order nonlinear optical behaviour of several Langmuir-Blodgett films. Langmuir-Blodgett (LB) films are ultra thin films produced by the Langmuir-Blodgett technique, named after their inventors (Irving Langmuir and Katharina Blodgett).

  11. Run-up on a structure due to second-order waves and current in a numerical wave tank

    DEFF Research Database (Denmark)

    Buchmann, Bjarne; Skourup, Jesper; Cheung, Kwok Fai

    1998-01-01

    order in current speed. The boundary-value problem is separated into a known incident wave field and an unknown scattered wave field, the latter being absorbed at the radiation boundaries using active wave absorption. The present paper focuses on the wave run-up on a structure in waves and current...

  12. Atomically Thin Ordered Alloys of Transition Metal Dichalcogenides: Stability and Band Structures

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2016-01-01

    We explore the possibility of modulating the electronic band edges of the transition metal dichalcogenides (TMD) via alloying of different semiconductors within the same group (intra-group alloying). The stability of the ordered alloys is assessed from the calculated mixing enthalpy which is found...

  13. Reduced order modelling techniques for mesh movement strategies as applied to fluid structure interactions

    CSIR Research Space (South Africa)

    Bogaers, Alfred EJ

    2010-01-01

    Full Text Available In this paper, we implement the method of Proper Orthogonal Decomposition (POD) to generate a reduced order model (ROM) of an optimization based mesh movement technique. In the study it is shown that POD can be used effectively to generate a ROM...

  14. Low temperature stabilization process for production of carbon fiber having structural order

    Energy Technology Data Exchange (ETDEWEB)

    Rios, Orlando; McGuire, Michael Alan; More, Karren Leslie; Tenhaeff, Wyatt Evan; Menchhofer, Paul A.; Paulauskas, Felix Leonard

    2017-08-15

    A method for producing a carbon fiber, the method comprising: (i) subjecting a continuous carbon fiber precursor having a polymeric matrix in which strength-enhancing particles are incorporated to a stabilization process during which the carbon fiber precursor is heated to within a temperature range ranging from the glass transition temperature to no less than 20.degree. C. below the glass transition temperature of the polymeric matrix, wherein the maximum temperature employed in the stabilization process is below 400.degree. C., for a processing time within said temperature range of at least 1 hour in the presence of oxygen and in the presence of a magnetic field of at least 1 Tesla, while said carbon fiber precursor is held under an applied axial tension; and (ii) subjecting the stabilized carbon fiber precursor, following step (i), to a carbonization process. The stabilized carbon fiber precursor, resulting carbon fiber, and articles made thereof are also described.

  15. The Columbia River Basalt Group in the Cascade Range: A Middle Miocene reference datum for structural analysis

    Science.gov (United States)

    Beeson, Marvin H.; Tolan, Terry L.

    1990-11-01

    The distributional patterns of individual Columbia River Basalt Group (CRBG) unite and structures recorded in the CRBG place the following constraints on Neogene tectonics of the northern Oregon Cascade Range: (1) A north-east trending topographic low of regional extent, the Columbia transarc lowland, transected the Miocene northern Oregon Cascade Range. The Columbia transarc lowland existed prior to the eruption of the CRBG and served to funnel CRBG flows across the Miocene Cascade Range. The lowland was apparently devoid of active volcanic centers from before 17 to ˜14.5 Ma. After 15 Ma, volcanic centers began to develop in the southern and central parts of the lowland. (2) Folds and associated faults of the Yakima Fold Belt extend through the western Columbia Plateau and far into the Cascade Range. These structures were active between 16.5 and S Ma and represent N-S shortening. (3) The Portland Hills-Clackamas River structural zone is a northwest trending dextral wrench fault zone that became active prior to the incursion of CRBG flows (˜16.5 Ma) and limited the distribution of some CRBG units. This structural zone appears to mark the western termination of the Yakima Fold Belt. Other similarly trending, dextral strike-slip faults are common in the northern Oregon Cascades but did not affect the distribution of CRBG flows and therefore developed in post-CRBG time. (4) Mount Hood is located near the axis of a major Yakima Fold Belt syncline in the CRBG, in the general location of earlier major andesitic volcanic activity related to the Rhododendron Formation.

  16. Structure and orbital ordering of ultrathin LaVO{sub 3} probed by atomic resolution electron microscopy and Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lindfors-Vrejoiu, Ionela; Engelmayer, Johannes; Loosdrecht, Paul H.M. van [II. Physikalisches Institut, Koeln Univ. (Germany); Jin, Lei; Jia, Chun-Lin [Peter Gruenberg Institut (PGI-5) and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Juelich GmbH (Germany); Himcinschi, Cameliu [Institut fuer Theoretische Physik, TU Bergakademie Freiberg (Germany); Hensling, Felix; Waser, Rainer; Dittmann, Regina [Peter Gruenberg Institut (PGI-7), Forschungszentrum Juelich GmbH (Germany)

    2017-03-15

    Orbital ordering has been less investigated in epitaxial thin films, due to the difficulty to evidence directly the occurrence of this phenomenon in thin film samples. Atomic resolution electron microscopy enabled us to observe the structural details of the ultrathin LaVO{sub 3} films. The transition to orbital ordering of epitaxial layers as thin as ∼4 nm was probed by temperature-dependent Raman scattering spectroscopy of multilayer samples. From the occurrence and temperature dependence of the 700 cm{sup -1} Raman active mode it can be inferred that the structural phase transition associated with orbital ordering takes place in ultrathin LaVO{sub 3} films at about 130 K. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. The Presence of Turbulent and Ordered Local Structure within the ICME Shock-sheath and Its Contribution to Forbush Decrease

    Energy Technology Data Exchange (ETDEWEB)

    Shaikh, Zubair; Bhaskar, Ankush [Indian Institute of Geomagnetism (IIG), New Panvel, Navi Mumbai-410218 (India); Raghav, Anil, E-mail: raghavanil1984@gmail.com [University Department of Physics, University of Mumbai, Vidyanagari, Santacruz (E), Mumbai-400098 (India)

    2017-08-01

    The transient interplanetary disturbances evoke short-time cosmic-ray flux decrease, which is known as Forbush decrease. The traditional model and understanding of Forbush decrease suggest that the sub-structure of an interplanetary counterpart of coronal mass ejection (ICME) independently contributes to cosmic-ray flux decrease. These sub-structures, shock-sheath, and magnetic cloud (MC) manifest as classical two-step Forbush decrease. The recent work by Raghav et al. has shown multi-step decreases and recoveries within the shock-sheath. However, this cannot be explained by the ideal shock-sheath barrier model. Furthermore, they suggested that local structures within the ICME’s sub-structure (MC and shock-sheath) could explain this deviation of the FD profile from the classical FD. Therefore, the present study attempts to investigate the cause of multi-step cosmic-ray flux decrease and respective recovery within the shock-sheath in detail. A 3D-hodogram method is utilized to obtain more details regarding the local structures within the shock-sheath. This method unambiguously suggests the formation of small-scale local structures within the ICME (shock-sheath and even in MC). Moreover, the method could differentiate the turbulent and ordered interplanetary magnetic field (IMF) regions within the sub-structures of ICME. The study explicitly suggests that the turbulent and ordered IMF regions within the shock-sheath do influence cosmic-ray variations differently.

  18. Empirical tight-binding modeling of ordered and disordered semiconductor structures; Empirische Tight-Binding-Modellierung geordneter und ungeordneter Halbleiterstrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Mourad, Daniel

    2010-11-30

    In this thesis, we investigate the electronic and optical properties of pure as well as of substitutionally alloyed II-VI and III-V bulk semiconductors and corresponding semiconductor quantum dots by means of an empirical tight-binding (TB) model. In the case of the alloyed systems of the type A{sub x}B{sub 1-x}, where A and B are the pure compound semiconductor materials, we study the influence of the disorder by means of several extensions of the TB model with different levels of sophistication. Our methods range from rather simple mean-field approaches (virtual crystal approximation, VCA) over a dynamical mean-field approach (coherent potential approximation, CPA) up to calculations where substitutional disorder is incorporated on a finite ensemble of microscopically distinct configurations. In the first part of this thesis, we cover the necessary fundamentals in order to properly introduce the TB model of our choice, the effective bond-orbital model (EBOM). In this model, one s- and three p-orbitals per spin direction are localized on the sites of the underlying Bravais lattice. The matrix elements between these orbitals are treated as free parameters in order to reproduce the properties of one conduction and three valence bands per spin direction and can then be used in supercell calculations in order to model mixed bulk materials or pure as well as mixed quantum dots. Part II of this thesis deals with unalloyed systems. Here, we use the EBOM in combination with configuration interaction calculations for the investigation of the electronic and optical properties of truncated pyramidal GaN quantum dots embedded in AlN with an underlying zincblende structure. Furthermore, we develop a parametrization of the EBOM for materials with a wurtzite structure, which allows for a fit of one conduction and three valence bands per spin direction throughout the whole Brillouin zone of the hexagonal system. In Part III, we focus on the influence of alloying on the electronic

  19. Fermi Surface and Order Parameter Driven Vortex Lattice Structure Transitions in Twin-Free YBa2Cu3O7

    DEFF Research Database (Denmark)

    White, J.S.; Hinkov, V.; Heslop, R.W.

    2009-01-01

    fields. It is separated from a low-field hexagonal phase of different orientation and distortion by a first-order transition at 2.0(2) T that is probably driven by Fermi surface effects. We argue that another first-order transition at 6.7(2) T, into a rhombic structure with a distortion of opposite sign......We report on small-angle neutron scattering studies of the intrinsic vortex lattice (VL) structure in detwinned YBa2Cu3O7 at 2 K, and in fields up to 10.8 T. Because of the suppressed pinning to twin-domain boundaries, a new distorted hexagonal VL structure phase is stabilized at intermediate...

  20. Quantum features in the spin dynamics of S=1/2 and 1 Heisenberg antiferromagnets in spite of long-range ordered phases

    DEFF Research Database (Denmark)

    Enderle, M.; Kiefer, K.; Klopperpieper, A.

    2000-01-01

    Uniform S = 1 and 1/2 Heisenberg antiferromagnetic chains have a quantum singlet ground state which is an eigenstate of the total spin with S(tot) = 0. However, the 'internal' order of these ground states is quite different, and is reflected in gapless excitations in the S = 1/2 state, while the ...

  1. Electronic structure and magnetic ordering of the unconventional antiferromagnet Yb3Pt4

    KAUST Repository

    Schwingenschlögl, Udo

    2009-12-01

    Applying density functional theory within the generalized gradient approximation, we investigate the electronic and magnetic properties of the intermetallic rare-earth system Yb3Pt4. This material recently has been put forward as host for quantum criticality, while details of the magnetic ordering could not be established (Bennett N. C.et al., J. Magn. & Magn. Mater., 321 (2009) 2021). In this context, we investigate the effect of spin-orbit coupling and compare various spin patterns from the energetic point of view, which enables us to determine the electronic ground state of Yb3Pt4. The assumption of an elementary superexchange mechanism yields a magnetic-coupling constant in good agreement with the experimental ordering temperature. Copyright © 2009 EPLA.

  2. Efficient Model Order Reduction of Structural Dynamic Systems with Local Nonlinearities under Periodic Motion

    Directory of Open Access Journals (Sweden)

    M. Mohammadali

    2014-01-01

    Full Text Available In many nonlinear structural systems, compared with the local regions with induced nonlinear effects, the main portions of the structures are linear. An exact condensation technique based on the harmonic balance method (HBM in conjunction with the modal expansion technique is employed to convert the motion equations of such a system to a set of nonlinear algebraic equations that are considerably small and adequately accurate to determine periodic responses. To demonstrate the capability of the suggested method, few case studies consisting of discrete systems with weak and essential nonlinearities are studied, and the results are compared to other methodologies results.

  3. Eruptive history, geochronology, and post-eruption structural evolution of the late Eocene Hall Creek Caldera, Toiyabe Range, Nevada

    Science.gov (United States)

    Colgan, Joseph P.; Henry, Christopher D.

    2017-02-24

    The magmatic, tectonic, and topographic evolution of what is now the northern Great Basin remains controversial, notably the temporal and spatial relation between magmatism and extensional faulting. This controversy is exemplified in the northern Toiyabe Range of central Nevada, where previous geologic mapping suggested the presence of a caldera that sourced the late Eocene (34.0 mega-annum [Ma]) tuff of Hall Creek. This region was also inferred to be the locus of large-magnitude middle Tertiary extension (more than 100 percent strain) localized along the Bernd Canyon detachment fault, and to be the approximate location of a middle Tertiary paleodivide that separated east and west-draining paleovalleys. Geologic mapping, 40Ar/39Ar dating, and geochemical analyses document the geologic history and extent of the Hall Creek caldera, define the regional paleotopography at the time it formed, and clarify the timing and kinematics of post-caldera extensional faulting. During and after late Eocene volcanism, the northern Toiyabe Range was characterized by an east-west trending ridge in the area of present-day Mount Callaghan, probably localized along a Mesozoic anticline. Andesite lava flows erupted around 35–34 Ma ponded hundreds of meters thick in the erosional low areas surrounding this structural high, particularly in the Simpson Park Mountains. The Hall Creek caldera formed ca. 34.0 Ma during eruption of the approximately 400 cubic kilometers (km3) tuff of Hall Creek, a moderately crystal-rich rhyolite (71–77 percent SiO2) ash-flow tuff. Caldera collapse was piston-like with an intact floor block, and the caldera filled with thick (approximately 2,600 meters) intracaldera tuff and interbedded breccia lenses shed from the caldera walls. The most extensive exposed megabreccia deposits are concentrated on or close to the caldera floor in the southwestern part of the caldera. Both silicic and intermediate post-caldera lavas were locally erupted within 400 thousand

  4. Characterization of carbonized polydopamine nanoparticles suggests ordered supramolecular structure of polydopamine.

    Science.gov (United States)

    Yu, Xiang; Fan, Hailong; Liu, Yang; Shi, Zujin; Jin, Zhaoxia

    2014-05-20

    Polydopamine is not only a multifunctional biopolymer with promising optoelectronic properties but it is also a versatile coating platform for different surfaces. The structure and formation of polydopamine is an active area of research. Some studies have supposed that polydopamine is composed of covalently bonded dihydroxyindole, indoledione, and dopamine units, but others proposed that noncovalent self-assembly contributes to polydopamine formation as well. However, it is difficult to directly find the details of supramolecular structure of polydopamine via self-assembly. In this study, we first report the graphite-like nanostructure observed in the carbonized polydopamine nanoparticles in nitrogen (or argon) environment at 800 °C. Raman characterization, which presents the typical D band and G band, confirmed the existence of graphite-like nanostructures. Our observation provides clear evidence for a layered-stacking supramolecular structure of polydopamine. Particularly, the size of graphite-like domains is similar to that of disk-shaped aggregates hypothesized in previous study about the polymerization of 5,6-dihydroxyindole [ Biomacromolecules 2012 , 13 , 2379 ]. Analysis of the hierarchical structure of polydopamine helps us understand its formation.

  5. An efficient second-order SQP method for structural topology optimization

    DEFF Research Database (Denmark)

    Rojas Labanda, Susana; Stolpe, Mathias

    2016-01-01

    This article presents a Sequential Quadratic Programming (SQP) solver for structural topology optimization problems named TopSQP. The implementation is based on the general SQP method proposed in Morales et al. J Numer Anal 32(2):553–579 (2010) called SQP+. The topology optimization problem is mo...

  6. Electrochemical polymerization of aniline monomers infiltrated into well-ordered truncated eggshell structures of polyelectrolyte multilayers.

    Science.gov (United States)

    Briseno, Alejandro L; Han, Shubo; Rauda, Iris E; Zhou, Feimeng; Toh, Chee-Seng; Nemanick, E Joseph; Lewis, Nathan S

    2004-01-06

    The use of nanosphere lithography to construct two-dimensional arrays of polystyrene (PS) particles coated with multilayered polyelectrolyte (PE) shells and truncated eggshell structures composed of PE thin layers is reported. The truncated eggshell PE structures were produced by extraction of the PS particle cores with toluene. The core-extraction process ruptures the apex of the PE coating and causes a slight expansion of the PE thin layers. Aniline hydrochloride was infiltrated into the PE shells and subsequently electropolymerized to yield an array of a composite containing polyaniline (PAni) and PE thin shells. Voltammetric, quartz crystal microbalance, and reflectance Fourier transform infrared spectroscopic measurements indicate that aniline monomers were confined within the thin PE shells and the electropolymerization occurred in the interior of the PE shell. The PE thickness governs the amount of infiltrated monomer and the ultimate loading of the PAni in the truncated eggshell structure. Surface-structure imaging by atomic force microscopy and scanning electron microscopy, carried out after each step of the fabrication process, shows the influence of the PE thickness on the organization and dimensions of the arrays. Thus, the PE thin shells composed of different layers can function as nanometer-sized vessels for the entrapment of charged species for further construction of composite materials and surface modifications. This approach affords a new avenue for the synthesis of new materials that combine the unique properties of conductive polymers and the controllability of template-directed surface reactions.

  7. Tensor order parameters for magnetic-structural phase transitions in crystals with strong spin-lattice coupling

    Science.gov (United States)

    Birman, Joseph L.; Izyumov, Yuri A.

    1980-02-01

    We formulate the thermodynamic theory of phase transitions in magnetically ordered systems in terms of a tensor, or coupled, order parameter. This basis is constructed by coupling atomic spin and lattice displacement. Symmetry lowering is predicted at the second-order phase transition point (tricritical points are not considered here). Lower-symmetry phases should in general be classified according to the Shubnikov symmetry space group Sh, which will reveal the total broken symmetry due to the coupled order parameter. In case the apparatus is "blind" to one portion of the order parameter: either spin or displacement, the apparent symmetry group will not be Sh, but a related space group, which will reveal "partial information." Comparing this formulation and the usual (uncoupled) theory, new results are obtained here: for example "pseudoscalar order parameters" can arise and different "symmetry-broken" groups. An illustration is given by applying the formulation to the spinel-structure space group: O7h-Fd3m. It is conjectured that for TbNi2 the tensor order parameter Γ1- may be relevant, so that the phase transition which has been identified as O7h-->Sh101166 may actually be O7h-->Sh132227, caused by a pseudoscalar.

  8. Photometric analysis of the structure evolution on the Pb-19.4%Sn melt surface in the S-L temperature range

    Directory of Open Access Journals (Sweden)

    Lyakhovitskii M.M.

    2011-05-01

    Full Text Available The structure evolution of alloys in solidification range is considered as the first-order phase transformation from the solid state to the liquid one, which occurs by the mechanism of nucleation and growth of more symmetrical phase to less symmetrical crystalline phase. The kinetic regularities of this transformation are studied by the method of the photometric analysis of structure images (PHASI, which makes it possible to establish the temperature dependence of the relationship between the solid and liquid phases and their distribution on the melt surface. The PHASI method is based on the combined analysis of the brightness spectra of the visible light reflections from the sample surface and of the distribution of its scattering centers in different intensity intervals. The data on the structure evolution of the Sn+19.4%Pb alloy upon melting and solidification were considered in parallel with the measured spectra of sound signals. It was revealed that a distinct maximum is observed in the temperature dependence of radiation energy in the temperature range of phase transformation from the liquid into the solid state and hot crack formation occurs near the transition zone in the region of the contact of the ingot with the crucible.

  9. Reduced-Order Structure-Preserving Model for Parallel-Connected Three-Phase Grid-Tied Inverters

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Brian B [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Purba, Victor [University of Minnesota; Jafarpour, Saber [University of California Santa-Barbara; Bullo, Francesco [University of California Santa-Barbara; Dhople, Sairaj V. [University of Minnesota

    2017-08-21

    Next-generation power networks will contain large numbers of grid-connected inverters satisfying a significant fraction of system load. Since each inverter model has a relatively large number of dynamic states, it is impractical to analyze complex system models where the full dynamics of each inverter are retained. To address this challenge, we derive a reduced-order structure-preserving model for parallel-connected grid-tied three-phase inverters. Here, each inverter in the system is assumed to have a full-bridge topology, LCL filter at the point of common coupling, and the control architecture for each inverter includes a current controller, a power controller, and a phase-locked loop for grid synchronization. We outline a structure-preserving reduced-order inverter model with lumped parameters for the setting where the parallel inverters are each designed such that the filter components and controller gains scale linearly with the power rating. By structure preserving, we mean that the reduced-order three-phase inverter model is also composed of an LCL filter, a power controller, current controller, and PLL. We show that the system of parallel inverters can be modeled exactly as one aggregated inverter unit and this equivalent model has the same number of dynamical states as any individual inverter in the system. Numerical simulations validate the reduced-order model.

  10. Reduced-Order Structure-Preserving Model for Parallel-Connected Three-Phase Grid-Tied Inverters: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Brian B [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Purba, Victor [University of Minnesota; Jafarpour, Saber [University of California, Santa Barbara; Bullo, Francesco [University of California, Santa Barbara; Dhople, Sairaj [University of Minnesota

    2017-08-31

    Given that next-generation infrastructures will contain large numbers of grid-connected inverters and these interfaces will be satisfying a growing fraction of system load, it is imperative to analyze the impacts of power electronics on such systems. However, since each inverter model has a relatively large number of dynamic states, it would be impractical to execute complex system models where the full dynamics of each inverter are retained. To address this challenge, we derive a reduced-order structure-preserving model for parallel-connected grid-tied three-phase inverters. Here, each inverter in the system is assumed to have a full-bridge topology, LCL filter at the point of common coupling, and the control architecture for each inverter includes a current controller, a power controller, and a phase-locked loop for grid synchronization. We outline a structure-preserving reduced-order inverter model for the setting where the parallel inverters are each designed such that the filter components and controller gains scale linearly with the power rating. By structure preserving, we mean that the reduced-order three-phase inverter model is also composed of an LCL filter, a power controller, current controller, and PLL. That is, we show that the system of parallel inverters can be modeled exactly as one aggregated inverter unit and this equivalent model has the same number of dynamical states as an individual inverter in the paralleled system. Numerical simulations validate the reduced-order models.

  11. Observation of long-range ferromagnetic order in the heavy-fermion compuound URu/sub 1. 2/Re/sub 0. 8/Si/sub 2/ by neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Torikachvili, M.S.; Rebelsky, L.; Motoya, K.; Shapiro, S.M.; Dalichaouch, Y.; Maple, M.B.

    1989-01-01

    We have performed a neutron scattering study of the heavy-fermion compound URu/sub 1.2/Re/sub 0.8/Si/sub 2/, in order to verify the occurrence of long-range ferromagnetic order. This study consisted of measurements of elastic, inelastic, and polarized neutron scattering, measurement of low-angle critical scattering, and the determination of the temperature dependence of the order parameter. We found a sharp peak in the critical scattering at /approx/ 30 K for the wavevector q = 0.08 /angstrom//sup /minus/1/; and an enhancement of the intensity at the position of the (101) nuclear Bragg reflection below the Curie temperature. These measurements suggest the occurrence of long-range magnetic order. The value of the ordered moment is estimated to be /approx/ 0.53 /mu//sub B/ at 10 K. 17 refs., 3 figs.

  12. Effects of intratidal and tidal range variability on circulation and salinity structure in the Cape Fear River Estuary, North Carolina

    Science.gov (United States)

    Becker, May Ling; Luettich, Richard A.; Seim, Harvey

    2009-04-01

    Tidal influences on circulation and the salinity structure are investigated in the largely unstudied Cape Fear River Estuary (CFRE), North Carolina, a partially mixed estuary along the southeast coast of the United States. During two different tidal conditions (high versus low tidal range) and when river flow was low, salinity and velocity data were collected over a semidiurnal tidal cycle in a 2.8 km long transect along the estuary axis. Water level data were recorded nearby. Mechanisms that influence salt transport characteristics are diagnosed from an analysis of the field data. Specifically, we investigated the relationship between tidal range and salinity through comparison of along-channel circulation characteristics, computed salt fluxes, and coefficients of vertical eddy diffusivity (Kz) based on a parameterization and on salt budget analysis. Findings indicate up-estuary tidally driven salt fluxes resulting from oscillatory salt transport are dominant near the pycnocline, while mean advective transport dominates near the bottom during both tidal range periods. Earlier research related to salt transport in estuaries with significant gravitational circulation suggests that up-estuary salt transport increases during low tidal ranges as a result of increased gravitational circulation. In the CFRE, in contrast, net (tidally averaged) near-bottom along-channel velocities are greater during higher tidal range conditions than during lower tidal range conditions. Findings indicate stronger tidal forcing and associated mixing contribute to greater near-bottom salinity gradients and, consequently, increased baroclinic circulation. Lower near-bottom salinities during the higher tidal range period are a result of a combination of increased vertical turbulent salt fluxes near the pycnocline and increased bottom-generated mixing.

  13. The Later Paleozoic granites of the Greater Caucasus Fore Range zone: geochemistry, magnetic properties and the structural and metamorphic evolution.

    Science.gov (United States)

    Kamzolkin, Vladimir; Latyshev, Anton; Ivanov, Stanislav; Vidjapin, Jury

    2017-04-01

    Clarification of the position of the granitic intrusions associated with the Blyb Metamorphic Complex is the important problem of the reconstruction of the structural evolution of the Greater Caucasus Fore Range zone. Based of the rock geochemistry we found out that the quartz diorites, granodiorites and syeno-granites of the BMC formed in suprasubduction conditions and refer to I-type granites. However, their emplacement was multistage coinciding with the various stages of the BMC evolution. We detected the mineral associations typical for the epidote-amphibolite facies in the Balkan massif, but these metamorphic features are absent in the granodiorite intrusions in the southern part of the Fore Range zone. Thus, quartz diorites of the Balkan intrusion intruded after the high-pressure metamorphism of the host rocks, but before the epidote-amphibolite stage, and the Southern granodiorite intrusions are younger. The measurements of the anisotropy of the magnetic susceptibility (AMS) in the Balkan intrusion indicated the shallow orientation of the minimal (north-eastern strike) and maximal (north-western strike) axes of the AMS ellipsoid. This result is compatible with the idea of the north-east compression fixed in the fold deformation structures of the BMC host rocks (Vidyapin, Kamzolkin, 2015). However, the macroscopic foliation in the granites dips to the east steeply. The discrepancy of the texture orientation of the granites, the host rock structure and the magnetic fabric can be explained as a result of the repeated changes of the stress field during the evolution of the Fore Range nappe structures. The reported study was partially supported by RFBR, research projects No. 16-35-00571mol_a; 16-05-01012a.

  14. Long-Range Atomic Order and Entropy Change at the Martensitic Transformation in a Ni-Mn-In-Co Metamagnetic Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Vicente Sánchez-Alarcos

    2014-05-01

    Full Text Available The influence of the atomic order on the martensitic transformation entropy change has been studied in a Ni-Mn-In-Co metamagnetic shape memory alloy through the evolution of the transformation temperatures under high-temperature quenching and post-quench annealing thermal treatments. It is confirmed that the entropy change evolves as a consequence of the variations on the degree of L21 atomic order brought by thermal treatments, though, contrary to what occurs in ternary Ni-Mn-In, post-quench aging appears to be the most effective way to modify the transformation entropy in Ni-Mn-In-Co. It is also shown that any entropy change value between around 40 and 5 J/kgK can be achieved in a controllable way for a single alloy under the appropriate aging treatment, thus bringing out the possibility of properly tune the magnetocaloric effect.

  15. APPLICATION OF THE CRAIG-BAMPTON MODEL ORDER REDUCTION METHOD TO A COMPOSITE STRUCTURE: MAC AND XOR

    Directory of Open Access Journals (Sweden)

    Humberto Peredo Fuentes

    2014-04-01

    Full Text Available The Craig-Bampton model order reduction (CBMOR method based on the Rayleigh-Ritz approach is applied to dynamic behavior simulation of a composite structure in order to verify the method’s feasibility and accuracy. The principle of this method is to represent a coupled component model based on the mass, damping and stiffness matrices. The methodology consists of a finite element model based on the classical laminate theory (CLT, a design of experiment to improve the modal assurance criteria (MAC and experimental results in order to validate the reduced model based on CBMOR method and substructures (super-elements. Experimental modal analysis has been performed using a scanner laser Doppler vibrometer (SLDV in order to assess the quality of the finite element models. The MAC and cross orthogonality MAC (XOR values are computed to verify the eigenfrequencies and eigenvectors. This approach demonstrates the feasibility of using CBMOR for composite structures. The example is prepared and solved with MSC/NASTRAN SOL103. The design of experiments (DOE method has been applied in order to identify the critical parameters and thus obtain high MAC values.

  16. Two-dimensional artificial light-harvesting antennae with predesigned high-order structure and robust photosensitising activity

    Science.gov (United States)

    Feng, Xiao; Ding, Xuesong; Chen, Long; Wu, Yang; Liu, Lili; Addicoat, Matthew; Irle, Stephan; Dong, Yuping; Jiang, Donglin

    2016-09-01

    Highly ordered discrete assemblies of chlorophylls that are found in natural light-harvesting antennae are key to photosynthesis, which converts light energy to chemical energy and is the principal producer of organic matter on Earth. Porphyrins and phthalocyanines, which are analogues of chlorophylls, exhibit a strong absorbance of visible and near-infrared light, respectively. A highly ordered porphyrin-co-phthalocyanine antennae would harvest photons over the entire solar spectrum for chemical transformation. However, such a robust antennae has not yet been synthesised. Herein, we report a strategy that merges covalent bonds and noncovalent forces to produce highly ordered two-dimensional porphyrin-co-phthalocyanine antennae. This methodology enables control over the stoichiometry and order of the porphyrin and phthalocyanine units; more importantly, this approach is compatible with various metalloporphyrin and metallophthalocyanine derivatives and thus may lead to the generation of a broad structural diversity of two-dimensional artificial antennae. These ordered porphyrin-co-phthalocyanine two-dimensional antennae exhibit unique optical properties and catalytic functions that are not available with single-component or non-structured materials. These 2D artificial antennae exhibit exceptional light-harvesting capacity over the entire solar spectrum as a result of a synergistic light-absorption effect. In addition, they exhibit outstanding photosensitising activities in using both visible and near-infrared photons for producing singlet oxygen.

  17. An Arbitrary Order Adaptive Control Structure with Application to a Hydraulic Winch Drive

    DEFF Research Database (Denmark)

    Schmidt, Lasse; Andersen, Torben O.; Pedersen, Henrik Clemmensen

    2017-01-01

    The dominant physical phenomena in hydraulic drives are generally well known, why the model equations describing the dominant dynamics may be established with a high level of certainty. To some extend, this is also the case for the model parameters when these are based on data sheet information...... involves a significant number of parameters. This paper considers a novel adaptive control algorithm, theoretically applicable to systems of arbitrary orders, and potentially only with three tuning parameters. The proposed algorithm is considered in relation to the position control of a hydraulic winch...

  18. The electronic structure and the state of compositional order in metallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gyorffy, B.L.; Johnson, D.D.; Pinski, F.J.; Nicholson, D.M.; Stocks, G.M.

    1987-01-01

    Many two-component (A,B) systems crystallize into a random solid solution. In such a state the atoms occupy a more or less regular array of lattice sites but each site can be A or B in a random fashion. Then, on lowering the temperature, the system will either phase separate or order, starting at some transition temperature T/sub c/. The aim of these lectures is to present a microscopic approach to the understanding of these scientifically interesting and technologically important processes. 64 refs., 19 figs.

  19. Release evaluation of drugs from ordered three-dimensional silica structures.

    Science.gov (United States)

    Izquierdo-Barba, Isabel; Martinez, Africa; Doadrio, Antonio L; Pérez-Pariente, Joaquin; Vallet-Regí, María

    2005-12-01

    Cubic mesoporous structures with Ia3d symmetry, such as MCM-48 and large pore Ia3d material (LP-Ia3d), which present different pore size (3.6 and 5.7nm, respectively), have been prepared, characterized and used as drug delivery systems. Ibuprofen and erythromycin have been chosen as drug models for delivery studies. The influence of the pore size at these structures has been studied and the results show that the delivery rate of drugs decreases with the pore size of the matrix. The influence of chemical nature of the pore surface on the delivery process has been also studied. In this case, the hydrophilic pore surface has been modified with hydrocarbon chains (C8 and C18 moieties) and the effect upon drug delivery of hydrophobic drugs like erythromycin has been studied. The results show a noticeable decrease of the delivery rate when the surface of the matrices is modified.

  20. Electronic structure of ordered double perovskite Ba2CoWO6

    Science.gov (United States)

    Ray, Rajyavardhan; Himanshu, A. K.; Brajesh, Kumar; Choudhary, B. K.; Bandyopadhyay, S. K.; Sen, Pintu; Kumar, Uday; Sinha, T. P.

    2014-04-01

    Ba2CoWO6 (BCoW) has been synthesized in polycrystalline form by solid state reaction at 1200 °C. Structural characterization of the compound was done through X-ray diffraction (XRD) followed by Rietveld analysis of the XRD pattern. The crystal structure is cubic, space group Fm-3m (No. 225) with the lattice parameter, a = 8.210. Optical band-gap of the present system has been calculated using the UV-Vis Spectroscopy and Kubelka-Munk function, it's value being 2.45 eV. A detailed study of the electronic properties has also been carried out using the density functional theory (DFT) techniques implemented on WIEN2k. Importance of electron-electron interaction between the Co ions leading to half-metallic behavior, crystal and exchange splitting together with the hybridization between O and Co, W has been investigated using the total and partial density of states.

  1. A Next-to-Leading Order QCD Analysis of Neutrino - Iron Structure Functions at the Tevatron

    Energy Technology Data Exchange (ETDEWEB)

    Seligman, William Glenn [Nevis Labs, Columbia U.

    1997-01-01

    Nucleon structure functions measured in neutrino-iron and antineutrinoiron charged-current interactions are presented. The data were taken in two high-energy high-statistics runs by the LAB-E detector at the Fermilab Tevatron. Structure functions are extracted from a sample of 950,000 neutrino and 170,000 antineutrino events with neutrino energies from 30 to 360 Ge V. The structure functions $F_2$ and $xF_3$ are compared with the the predictions of perturbative Quantum Chromodynamics (PQCD). The combined non-singlet and singlet evolution in the context of PQCD gives NL0(4) . 2 value of $\\Lambda^{NLO,(4)}_{\\overline MS}$ = 337 ± 28 (exp.) MeV, which corresponds to $\\alpha_s$ ($M^2_z$) = 0.119 ± 0.002 (exp.) ± 0.004 (theory), and with a gluon distribution given by $xG(x,Q^2_0 = 5 GeV^2$ ) = (2.22±0.34) x ($1-x)^{4.65 \\pm 0.68}$

  2. Order-disorder phase transition in the antiperovskite-type structure of synthetic kogarkoite, Na3SO4F

    Science.gov (United States)

    Avdontceva, Margarita S.; Zolotarev, Andrey A.; Krivovichev, Sergey V.

    2015-11-01

    High-temperature phase transition of synthetic kogarkoite, Na3SO4F, has been studied by high-temperature X-ray powder and single-crystal diffraction. The temperature of the phase transition can be estimated as 112.5±12.5 °C. The low-temperature phase, α-Na3SO4F, at 293 K, is monoclinic, P21/m, a=18.065(3), b=6.958(1), c=11.446(1) Å, β=107.711(1)°, Z=12. The structure contains thirteen symmetrically independent Na sites with coordination numbers varying from 6 to 8, and six independent S sites. The high-temperature β-phase at 423 K is rhombohedral, R-3m, a=6.94(1), c=24.58(4) Å, Z=9. The crystal structure of both polymorphs of Na3SO4F can be described as a 9R antiperovskite polytype based upon triplets of face-sharing [FNa6] octahedra linked into a three-dimensional framework by sharing corners. In the α-modification, the SO4 tetrahedra are completely ordered and located in the framework cavities. In the β-modification, there are only two symmetrically independent Na atoms in the structure. The main difference between the structures of the α- and β-phases is the degree of ordering of the SO4 tetrahedra: in the α-modification, they are completely ordered, whereas, in the β-modification, the complete disorder is observed, which is manifested in a number of low-occupied O sites around fully occupied S sites. The phase transition is therefore has an order-disorder character and is associated with the decrease of structural complexity measured as an information content per unit cell [577.528 bits for the low- (α) and 154.830 bits for the high- (β) temperature modifications].

  3. Nine orders of magnitude dynamic range: picomolar to millimolar concentration measurement in capillary electrophoresis with laser induced fluorescence detection employing cascaded avalanche photodiode photon counters.

    Science.gov (United States)

    Dada, Oluwatosin O; Essaka, David C; Hindsgaul, Ole; Palcic, Monica M; Prendergast, Jillian; Schnaar, Ronald L; Dovichi, Norman J

    2011-04-01

    The dynamic range of capillary electrophoresis analysis is ultimately limited by molecular shot noise at low concentrations and by concentration-induced band broadening at high concentrations. We report a system that approaches these fundamental limits. A laser-induced fluorescence detector is reported that employs a cascade of four fiber-optic beam splitters connected in series to generate a primary signal and four attenuated signals, each monitored by a single-photon counting avalanche photodiode. Appropriate scaling of the signals from the five photodiodes produces a linear optical calibration curve for 5-carboxyl-tetramethylrhodamine from the concentration detection limit of 1 pM to the upper limit of 1 mM. Mass detection limits are 120 yoctomoles (70 molecules) injected into the instrument. The very-wide dynamic range instrument was used to study the metabolic products of the fluorescently labeled glycosphingolipid tetramethylrhodamine labeled GM1 (GM1-TMR) produced by single cells isolated from the rat cerebellum.

  4. Formation of ordered structures in systems of charged thin cylindrical grains

    Energy Technology Data Exchange (ETDEWEB)

    Vaulina, O. S., E-mail: Irina.Lisina@mail.ru; Lisina, I. I.; Lisin, E. A. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

    2016-02-15

    Conditions for the formation of various orientational and spatial configurations of charged cylindrical particles in an external electric field are investigated both analytically and numerically. Analytical expressions allowing one to determine the tilt angle of cylinders relative to the symmetry axis/plane of the electric trap are proposed. A new algorithm for numerical modeling of the dynamics of interacting nonspherical particles is developed. Conditions for correct modeling of uniformly charged cylinders by means of “bipoles” consisting of two coupled point charges of the same sign are determined. The studies have been performed in a wide range of parameters close to those typical of laboratory experiments with dusty plasmas.

  5. Amorphous effect on the advancing of wide-range absorption and structural-phase transition in γ-In2Se3 polycrystalline layers.

    Science.gov (United States)

    Ho, Ching-Hwa

    2014-04-23

    The exploitation of potential functions in material is crucial in materials research. In this study, we demonstrate a III-VI chalcogenide, polycrystalline γ-In2Se3, which simultaneously possesses the capabilities of thickness-dependent optical gaps and wide-energy-range absorption existed in the polycrystalline layers of γ-In2Se3. Transmission electron microscopy and Raman measurement show a lot of γ-phase nanocrystals contained in the disordered and polycrystalline state of the chalcogenide with medium-range order (MRO). The MRO effects on the γ-In2Se3 layers show thickness-dependent absorption-edge shift and thickness-dependent resistivities. The amorphous effect of MRO also renders a structural-phase transition of γ → α occurred inside the γ-In2Se3 layer with a heat treatment of about 700 °C. Photo-voltage-current (Photo V-I) measurements of different-thickness γ-In2Se3 layers propose a wide-energy-range photoelectric conversion unit ranging from visible to ultraviolet (UV) may be achieved by stacking γ-In2Se3 layers in a staircase form containing dissimilar optical gaps.

  6. A 180-µW, 120-MHz, Fourth Order Low-Pass Bessel Filter Based on FVF Biquad Structure

    Science.gov (United States)

    Shin, Hundo; Ryu, Seung-Tak

    This paper proposes a new biquad structure based on a flipped voltage follower (FVF) for low-power and wide-bandwidth (BW) low pass filter. The proposed biquad structure consists of an FVF and a source follower (SF) for complex pole pair generation and zero cancellation. The presented design provides good linearity at low power consumption, owing to the voltage follower structures. A power/BW ratio (PBWR) is suggested as a performance metric to compare power efficiency to bandwidth, and the proposed biquad structure shows excellent PBWR, especially for low quality factor (Q) design. As a prototype, a fourth order Bessel filter was fabricated in 0.18µm CMOS technology. The measured BW, power consumption, IIP3, and FoM are 120MHz, 180µW, 15dBm, and 0.34fJ, respectively.

  7. Population structure as revealed by mtDNA and microsatellites in northern fur seals, Callorhinus ursinus, throughout their range.

    Directory of Open Access Journals (Sweden)

    Bobette R Dickerson

    Full Text Available BACKGROUND: The northern fur seal (Callorhinus ursinus; NFS is a widely distributed pinniped that has been shown to exhibit a high degree of philopatry to islands, breeding areas on an island, and even to specific segments of breeding areas. This level of philopatry could conceivably lead to highly genetically divergent populations. However, northern fur seals have the potential for dispersal across large distances and have experienced repeated rapid population expansions following glacial retreat and the more recent cessation of intensive harvest pressure. METHODOLOGY/PRINCIPAL FINDINGS: Using microsatellite and mitochondrial loci, we examined population structure in NFS throughout their range. We found only weak population genetic structure among breeding islands including significant F(ST and Phi(ST values between eastern and western Pacific islands. CONCLUSIONS: We conclude that insufficient time since rapid population expansion events (both post glacial and following the cessation of intense harvest pressure mixed with low levels of contemporary migration have resulted in an absence of genetic structure across the entire northern fur seal range.

  8. Adaptive variable structure hierarchical fuzzy control for a class of high-order nonlinear dynamic systems.

    Science.gov (United States)

    Mansouri, Mohammad; Teshnehlab, Mohammad; Aliyari Shoorehdeli, Mahdi

    2015-05-01

    In this paper, a novel adaptive hierarchical fuzzy control system based on the variable structure control is developed for a class of SISO canonical nonlinear systems in the presence of bounded disturbances. It is assumed that nonlinear functions of the systems be completely unknown. Switching surfaces are incorporated into the hierarchical fuzzy control scheme to ensure the system stability. A fuzzy soft switching system decides the operation area of the hierarchical fuzzy control and variable structure control systems. All the nonlinearly appeared parameters of conclusion parts of fuzzy blocks located in different layers of the hierarchical fuzzy control system are adjusted through adaptation laws deduced from the defined Lyapunov function. The proposed hierarchical fuzzy control system reduces the number of rules and consequently the number of tunable parameters with respect to the ordinary fuzzy control system. Global boundedness of the overall adaptive system and the desired precision are achieved using the proposed adaptive control system. In this study, an adaptive hierarchical fuzzy system is used for two objectives; it can be as a function approximator or a control system based on an intelligent-classic approach. Three theorems are proven to investigate the stability of the nonlinear dynamic systems. The important point about the proposed theorems is that they can be applied not only to hierarchical fuzzy controllers with different structures of hierarchical fuzzy controller, but also to ordinary fuzzy controllers. Therefore, the proposed algorithm is more general. To show the effectiveness of the proposed method four systems (two mechanical, one mathematical and one chaotic) are considered in simulations. Simulation results demonstrate the validity, efficiency and feasibility of the proposed approach to control of nonlinear dynamic systems. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

  9. Vibrational Order, Structural Properties, and Optical Gap of ZnO Nanostructures Sintered through Thermal Decomposition

    Directory of Open Access Journals (Sweden)

    Alejandra Londono-Calderon

    2014-01-01

    Full Text Available The sintering of different ZnO nanostructures by the thermal decomposition of zinc acetate is reported. Morphological changes from nanorods to nanoparticles are exhibited with the increase of the decomposition temperature from 300 to 500°C. The material showed a loss in the crystalline order with the increase in the temperature, which is correlated to the loss of oxygen due to the low heating rate used. Nanoparticles have a greater vibrational freedom than nanorods which is demonstrated in the rise of the main Raman mode E 2(high during the transformation. The energy band gap of the nanostructured material is lower than the ZnO bulk material and decreases with the rise in the temperature.

  10. Higher order structure of personality and mental health: does general affectivity matter?

    Science.gov (United States)

    Simşek, Omer Faruk

    2014-01-01

    The higher order personality model, namely the Big Two, was tested in 2 studies (Ns = 878 and 467, respectively) by controlling for the effects of both general affectivity and common method variance. Study 2 also examined the associations of the metatraits with different mental health indicators through regression analyses. The results consistently provided support for the validity of the Big Two model in the latent space, with and without the effects of general affectivity and the common method variance. Moreover, in both studies, the high correlation between stability and plasticity decreased when these 2 method effects were controlled statistically. The regression analyses also showed that the associations of plasticity and stability with the indicators of both subjective and psychological well-being, as well as psychopathology, were consistent with the theoretical arguments behind the Big Two.

  11. Coupling and electrical control of structural, orbital and magnetic orders in perovskites

    Science.gov (United States)

    Varignon, Julien; Bristowe, Nicholas C.; Bousquet, Eric; Ghosez, Philippe

    2015-10-01

    Perovskite oxides are already widely used in industry and have huge potential for novel device applications thanks to the rich physical behaviour displayed in these materials. The key to the functional electronic properties exhibited by perovskites is often the so-called Jahn-Teller distortion. For applications, an electrical control of the Jahn-Teller distortions, which is so far out of reach, would therefore be highly desirable. Based on universal symmetry arguments, we determine new lattice mode couplings that can provide exactly this paradigm, and exemplify the effect from first-principles calculations. The proposed mechanism is completely general, however for illustrative purposes, we demonstrate the concept on vanadium based perovskites where we reveal an unprecedented orbital ordering and Jahn-Teller induced ferroelectricity. Thanks to the intimate coupling between Jahn-Teller distortions and electronic degrees of freedom, the electric field control of Jahn-Teller distortions is of general relevance and may find broad interest in various functional devices.

  12. Ordered structure formation in 2D mass asymmetric electron-hole plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Filinov, V.S. [Institute for High Energy Density, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412 (Russian Federation)], E-mail: vladimir_filinov@mail.ru; Fehske, H. [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet Greifswald, Felix-Hausdorff-Str. 6, D-17489 Greifswald (Germany); Bonitz, M. [Christian-Albrechts-Universitaet zu Kiel, Institut fuer Theoretische Physik und Astrophysik, Leibnizstrasse 15, 24098 Kiel (Germany); Fortov, V.E.; Levashov, P. [Institute for High Energy Density, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412 (Russian Federation)

    2008-07-28

    We study strong Coulomb correlations in dense two-dimensional electron-hole plasmas by means of direct path integral Monte Carlo simulations. In particular, the formation and dissociation of bound states, such as excitons, bi-excitons and many particle clusters, is analyzed and the density-temperature regions of their occurrence are identified. At high density, the Mott transition to the fully ionized state (electron-hole hexatic liquid) is detected. Particular attention is paid to the influence of the hole to electron mass ratio M on the properties of the plasma. For high enough values of M we observed the formation of Coulomb hole crystal-like structures.

  13. Molecular structure, spectroscopic studies and first-order molecular hyperpolarizabilities of p-amino acetanilide.

    Science.gov (United States)

    Abraham, Jose P; Sajan, D; Joe, I Hubert; Jayakumar, V S

    2008-11-15

    The infrared absorption, Raman spectra and SERS spectra of p-amino acetanilide have been analyzed with the aid of density functional theory calculations at B3LYP/6-311G(d,p) level. The electric dipole moment (mu) and the first hyperpolarizability (beta) values of the investigated molecule have been computed using ab initio quantum mechanical calculations. The calculation results also show that the synthesized molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. Computed geometries reveal that the PAA molecule is planar, while secondary amide group is twisted with respect to the phenyl ring is found, upon hydrogen bonding. The hyperconjugation of the C=O group with adjacent C-C bond and donor-acceptor interaction associated with the secondary amide have been investigated using computed geometry. The carbonyl stretching band position is found to be influenced by the tendency of phenyl ring to withdraw nitrogen lone pair, intermolecular hydrogen bonding, conjugation and hyperconjugation. The existence of intramolecular C=O...H hydrogen bonded have been investigated by means of the natural bonding orbital (NBO) analysis. The influence of the decrease of N-H and C=O bond orders and increase of C-N bond orders due to donor-acceptor interaction has been identified in the vibrational spectra. The SERS spectral analysis reveals that the large enhancement of in-plane bending, out of plane bending and ring breathing modes in the surface-enhanced Raman scattering spectrum indicates that the molecule is adsorbed on the silver surface in a 'atleast vertical' configuration, with the ring perpendicular to the silver surface.

  14. Bromodomain Protein Brd4 Associated with Acetylated Chromatin Is Important for Maintenance of Higher-order Chromatin Structure*

    Science.gov (United States)

    Wang, Ranran; Li, Qing; Helfer, Christine M.; Jiao, Jing; You, Jianxin

    2012-01-01

    Chromatin structure organization is crucial for regulating many fundamental cellular processes. However, the molecular mechanism that regulates the assembly of higher-order chromatin structure remains poorly understood. In this study, we demonstrate that Brd4 (bromodomain-containing protein 4) protein participates in the maintenance of the higher-order chromatin structure. Brd4, a member of the BET family of proteins, has been shown to play important roles in cellular growth control, cell cycle progression, and cancer development. We apply in situ single cell chromatin imaging and micrococcal nuclease (MNase) assay to show that Brd4 depletion leads to a large scale chromatin unfolding. A dominant-negative inhibitor encoding the double bromodomains (BDI/II) of Brd4 can competitively dissociate endogenous Brd4 from chromatin to trigger severely fragmented chromatin morphology. Mechanistic studies using Brd4 truncation mutants reveal that the Brd4 C-terminal domain is crucial for maintaining normal chromatin structure. Using bimolecular fluorescence complementation technology, we demonstrate that Brd4 molecules interact intermolecularly on chromatin and that replacing Brd4 molecules by BDI/II causes abnormal nucleosome aggregation and chromatin fragmentation. These studies establish a novel structural role of Brd4 in supporting the higher chromatin architecture. PMID:22334664

  15. Short range order and Ag diffusion threshold in Ag{sub x}(Ge{sub 0.25}Se{sub 0.75}){sub 100-x} glasses

    Energy Technology Data Exchange (ETDEWEB)

    Piarristeguy, A.A.; Ribes, M.; Pradel, A. [Institut Charles Gerhardt, UMR5253 CNRS, CC1503, Universite Montpellier 2, Pl.E.Bataillon, 34095 Montpellier Cedex 5 (France); Cuello, G.J.; Cristiglio, V.; Johnson, M. [Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Fernandez-Martinez, A. [Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); ISTerre, CNRS and University of Grenoble I, 38041 Grenoble (France)

    2012-10-15

    A structural investigation of Ag{sub x}(Ge{sub 0.25}Se{sub 0.75}){sub 100-x} glasses with x = 5, 15, and 25 at.% has been carried out by neutron diffraction and ab initio molecular dynamics (AIMD) simulation. A structural model for the glasses has been proposed: the Ge(Se{sub 1/2}){sub 4} tetrahedra would remain the fundamental structural units in all samples. The introduction of Ag in the Ge{sub 0.25}Se{sub 0.75} network would lead to a decrease in homopolar Se-Se bonds and appearance of Ge-Ge bonds. A strong evolution in the Ag-Ag correlations upon introduction of Ag was observed with the Ag-Ag correlation distances changing from 4.4 A for the Ag-poor glass to 3.0A for the Ag-rich ones. Such information was used to discuss the evolution of conductivity with Ag content in these glasses. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Hydrogen/Deuterium Exchange Mass Spectrometry for Probing Higher Order Structure of Protein Therapeutics: Methodology and Applications

    Science.gov (United States)

    Wei, Hui; Mo, Jingjie; Tao, Li; Russell, Reb J.; Tymiak, Adrienne A.; Chen, Guodong; Iacob, Roxana E.; Engen, John R.

    2014-01-01

    The higher order structure of protein therapeutics can be interrogated with hydrogen/deuterium exchange mass spectrometry (HDX-MS). HDX-MS is now a widely used tool in the structural characterization of protein therapeutics. In this article, HDX-MS based workflows designed for both protein therapeutic discovery and development processes are presented, focusing on the specific applications of epitope mapping for protein/drug interactions and biopharmaceutical comparability studies. Future trends in the application of HDX-MS to protein therapeutics characterization are also described. PMID:23928097

  17. Monte Carlo approach in assessing damage in higher order structures of DNA

    Science.gov (United States)

    Chatterjee, A.; Schmidt, J. B.; Holley, W. R.

    1994-01-01

    We have developed a computer monitor of nuclear DNA in the form of chromatin fibre. The fibres are modeled as a ideal solenoid consisting of twenty helical turns with six nucleosomes per turn. The chromatin model, in combination with are Monte Carlo theory of radiation damage induces by charged particles, based on general features of tack structure and stopping power theory, has been used to evaluate the influence of DNA structure on initial damage. An interesting has emerged from our calculations. Our calculated results predict the existence of strong spatial correlations in damage sites associated with the symmetries in the solenoidal model. We have calculated spectra of short fragments of double stranded DNA produced by multiple double strand breaks induced by both high and low LET radiation. The spectra exhibit peaks at multiples of approximately 85 base pairs (the nucleosome periodicity), and approximately 1000 base pairs (solenoid periodicity). Preliminary experiments to investigate the fragment distributions from irradiated DNA, made by B. Rydberg at Lawrence Berkeley Laboratory, confirm the existence of short DNA fragments and are in substantial agreement with the predictions of our theory.

  18. Electronic structure of ordered double perovskite Ba{sub 2}CoWO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Rajyavardhan [Department of Physics, Indian Institute of Technology Kanpur, Kanpur-208016, India and Nanostructured and Advanced Material Laboratory, Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Saltlake, Kolkata-700064 (India); Himanshu, A. K., E-mail: himanshu-ak@yahoo.co.in; Bandyopadhyay, S. K.; Sen, Pintu [Nanostructured and Advanced Material Laboratory, Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Saltlake, Kolkata-700064 (India); Brajesh, Kumar [Department of Physics, Veer Kunwar Singh University, Ara-802301, Bihar (India); Choudhary, B. K. [University Department of Physics, Ranchi University, Jharkhand-834001 (India); Kumar, Uday [Department of Physical Sciences, IISER, Mohanpur Campus, Mohanpur-741252, West Bengal (India); Sinha, T. P. [Department of Physics, Bose Institute, Kolkata-700042 (India)

    2014-04-24

    Ba{sub 2}CoWO{sub 6} (BCoW) has been synthesized in polycrystalline form by solid state reaction at 1200 °C. Structural characterization of the compound was done through X-ray diffraction (XRD) followed by Rietveld analysis of the XRD pattern. The crystal structure is cubic, space group Fm-3m (No. 225) with the lattice parameter, a = 8.210. Optical band-gap of the present system has been calculated using the UV-Vis Spectroscopy and Kubelka-Munk function, it’s value being 2.45 eV. A detailed study of the electronic properties has also been carried out using the density functional theory (DFT) techniques implemented on WIEN2k. Importance of electron-electron interaction between the Co ions leading to half-metallic behavior, crystal and exchange splitting together with the hybridization between O and Co, W has been investigated using the total and partial density of states.

  19. Structurally Ordered Nanowire Formation from Co-Assembly of DNA Origami and Collagen-Mimetic Peptides

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Tao [Department; Meyer, Travis A. [Wallace; Modlin, Charles [Department; Zuo, Xiaobing [X-ray; Conticello, Vincent P. [Department; Ke, Yonggang [Wallace

    2017-10-02

    We describe the co-assembly of two different building units: collagen-mimetic peptides and DNA origami. Two peptides CP++ and sCP(++) are designed with a sequence comprising a central block (Pro-Hyp-Gly) and two positively charged domains (Pro-Arg-Gly) at both N- and C-termini. Co-assembly of peptides and DNA origami two-layer (TL) nanosheets affords the formation of one-dimensional nanowires with repeating periodicity of similar to 10 nm. Structural analyses suggest a face-to-face stacking of DNA nanosheets with peptides aligned perpendicularly to the sheet surfaces. We demonstrate the potential of selective peptide-DNA association between face-to-face and edge-to-edge packing by tailoring the size of DNA nanostructures. This study presents an attractive strategy to create hybrid biomolecular assemblies from peptide and DNA-based building blocks that takes advantage of the intrinsic chemical and physical properties of the respective components to encode structural and, potentially, functional complexity within readily accessible biomimetic materials.

  20. Noncollinear Magnetic Structure and Multipolar Order in Eu2 Ir2 O7

    Science.gov (United States)

    Wang, Yilin; Weng, Hongming; Fu, Liang; Dai, Xi

    2017-11-01

    The magnetic properties of the pyrochlore iridate material Eu2 Ir2 O7 (5 d5 ) have been studied based on first principles calculations, where the crystal field splitting Δ , spin-orbit coupling (SOC) λ , and Coulomb interaction U within Ir 5 d orbitals all play significant roles. The ground state phase diagram has been obtained with respect to the strength of SOC and Coulomb interaction U , where a stable antiferromagnetic ground state with all-in-all-out (AIAO) spin structure has been found. In addition, another antiferromagnetic state with energy close to AIAO has also been found to be stable. The calculated nonlinear magnetization of the two stable states both have the d -wave pattern but with a π /4 phase difference, which can perfectly explain the experimentally observed nonlinear magnetization pattern. Compared with the results of the nondistorted structure, it turns out that the trigonal lattice distortion is crucial for stabilizing the AIAO state in Eu2 Ir2 O7 . Furthermore, besides large dipolar moments, we also find considerable octupolar moments in the magnetic states.