Sample records for crystallographic space groups

  1. Crystallographic Groups, Groupoids, and Orbifolds

    SciTech Connect

    Johnson, C.K.

    2000-09-11

    In this note, We first discuss the relationship among crystallographic lattice groups, space groups, and point groups by using a short exact sequence, then in footnotes indicate the classification of those groups. We then introduce screw and glide groupoids as an extension of point groups in a new exact sequence, and list the one-translational-dimension screw and glide groupoids, which require torus and truncated cylinder projection representations in addition to the spherical projection used for point groups. We then briefly discuss the two and three translational dimension groupoids associated with the remaining point groups. Examples of space groups and their groupoid based nomenclature, which is mainly the extended Hermana-Mauguin international crystallographic nomenclature system plus a specific type of coset decomposition, are then given. Next the crystallographic orbifolds are defined and some application problems associated with orbifolds discussed. Finally, the derivation of might be called orbifoldoids is suggested as future research.

  2. Algorithms for deriving crystallographic space-group information. II: Treatment of special positions

    SciTech Connect

    Grosse-Kunstleve, Ralf W.; Adams, Paul D.

    2001-10-05

    Algorithms for the treatment of special positions in 3-dimensional crystallographic space groups are presented. These include an algorithm for the determination of the site-symmetry group given the coordinates of a point, an algorithm for the determination of the exact location of the nearest special position, an algorithm for the assignment of a Wyckoff letter given the site-symmetry group, and an alternative algorithm for the assignment of a Wyckoff letter given the coordinates of a point directly. All algorithms are implemented in ISO C++ and are integrated into the Computational Crystallography Toolbox. The source code is freely available.

  3. Chevalley's theorem for the complex crystallographic groups

    Microsoft Academic Search

    Joseph Bernstein; Ossip Schwarzman

    2006-01-01

    We prove that, for the irreducible complex crystallographic Coxeter group W, the following conditions are equivalent: a) W is generated by reflections; b) the analytic variety X\\/W is isomorphic to a weighted projective space. The result is of interest, for example, in application to topological conformal field theory. We also discuss the status of the above statement for other types

  4. Prediction of molecular crystal structures by a crystallographic QM/MM model with full space-group symmetry.

    PubMed

    Mörschel, Philipp; Schmidt, Martin U

    2015-01-01

    A crystallographic quantum-mechanical/molecular-mechanical model (c-QM/MM model) with full space-group symmetry has been developed for molecular crystals. The lattice energy was calculated by quantum-mechanical methods for short-range interactions and force-field methods for long-range interactions. The quantum-mechanical calculations covered the interactions within the molecule and the interactions of a reference molecule with each of the surrounding 12-15 molecules. The interactions with all other molecules were treated by force-field methods. In each optimization step the energies in the QM and MM shells were calculated separately as single-point energies; after adding both energy contributions, the crystal structure (including the lattice parameters) was optimized accordingly. The space-group symmetry was maintained throughout. Crystal structures with more than one molecule per asymmetric unit, e.g. structures with Z' = 2, hydrates and solvates, have been optimized as well. Test calculations with different quantum-mechanical methods on nine small organic molecules revealed that the density functional theory methods with dispersion correction using the B97-D functional with 6-31G* basis set in combination with the DREIDING force field reproduced the experimental crystal structures with good accuracy. Subsequently the c-QM/MM method was applied to nine compounds from the CCDC blind tests resulting in good energy rankings and excellent geometric accuracies. PMID:25537386

  5. Simple crystal forms as the orbits of crystallographic symmetry groups

    NASA Astrophysics Data System (ADS)

    Ovsetsina, T. I.; Chuprunov, E. V.

    2014-07-01

    Simple crystal forms are analyzed as the orbits of point symmetry groups on a set of crystal planes of space. All known polyhedra are described and structurized based on the theory of the orbits of groups, which provided a new, more harmonious approach to this problem. The orbits of groups can be general or particular and characteristic or non-characteristic. All possible versions of all crystallographic groups are listed in the table. The problem of the equivalence of polyhedra as the orbits of point symmetry groups is considered. An analysis of this problem has shown that 32 point crystallographic symmetry groups correspond to 139 symmetrically nonequivalent polyhedra.

  6. Twisted Conjugacy for Virtually Cyclic Groups and Crystallographic Groups

    Microsoft Academic Search

    Daciberg Gonçalves; Peter Wong

    \\u000a A group is said to have the property R\\u000a ? if every automorphism has an infinite number of twisted conjugacy classes. In this paper, we classify all virtually cyclic\\u000a groups with the R\\u000a ? property. Furthermore, we determine which of the 17 crystallographic groups of rank 2 have this property.

  7. Limits of crystallographic methods for detecting space topology

    E-print Network

    Roland Lehoucq; Jean-Philippe Uzan; Jean-Pierre Luminet

    2000-05-25

    We investigate to what extent the cosmic crystallographic methods aimed to detect the topology of the universe using catalogues of cosmic objects would be damaged by various observational uncertainties. We find that the topological signature is robust in the case of Euclidean spaces, but is very fragile in the case of compact hyperbolic spaces. Comparing our results to the presently accepted range of values for the curvature parameters, the best hopes for detecting space topology rest on elliptical space models.

  8. Group actions on geodesic Ptolemy spaces

    E-print Network

    Foertsch, Thomas

    2008-01-01

    In this paper we study geodesic Ptolemy metric spaces $X$ which allow proper and cocompact isometric actions of crystallographic or, more generally, virtual polycyclic groups. We show that $X$ is equivariantly rough isometric to a Euclidean space.

  9. Homological functor of a torsion free crystallographic group of dimension five with a nonabelian point group

    NASA Astrophysics Data System (ADS)

    Ting, Tan Yee; Idrus, Nor'ashiqin Mohd.; Masri, Rohaidah; Sarmin, Nor Haniza; Hassim, Hazzirah Izzati Mat

    2014-06-01

    Torsion free crystallographic groups, called Bieberbach groups, appear as fundamental groups of compact, connected, flat Riemannian manifolds and have many interesting properties. New properties of the group can be obtained by, not limited to, exploring the groups and by computing their homological functors such as nonabelian tensor squares, the central subgroup of nonabelian tensor squares, the kernel of the mapping of nonabelian tensor squares of a group to the group and many more. In this paper, the homological functor, J(G) of a centerless torsion free crystallographic group of dimension five with a nonabelian point group which is a dihedral point group is computed using commutator calculus.

  10. Nested polytopes with non-crystallographic symmetry as projected orbits of extended Coxeter groups

    E-print Network

    Motiejus Valiunas; Emilio Zappa; Briony Thomas; Reidun Twarock

    2015-01-27

    We construct nested polytopes with non-crystallographic symmetry from the orbits of groups containing a non-crystallographic Coxeter group $W$ via projection. For this, we embed $W$ into the point group $\\mathcal{P}$ of a higher dimensional lattice, and study the orbits of the subgroups of $\\mathcal{P}$ which contain $W$. The projection of these orbits into a lower dimensional subspace invariant under $W$ consists of nested shell arrangements with non-crystallographic symmetry. We study the properties of these structures and classify them in the case of extensions of $W$, i.e. subgroups of $\\mathcal{P}$ that contain $W$ as a normal subgroup. Geometrically, the convex hulls of these orbits represent nested polytopes with non-crystallographic symmetry. These have interesting applications in physics (quasicrystals), biology (viruses) and carbon chemistry (fullerenes).

  11. Bilbao Crystallographic Server

    NSDL National Science Digital Library

    The Bilbao Crystallographic Server provides access to crystallographic programs, tools, and databases. The tools are grouped according to type: space groups retrieval; group-subgroup relations of space groups; representation theory applications; solid state theory applications; structure utilities; and subperiodic groups (layer, rod, and frieze groups retrieval tools). The Incommensurate Crystal Structure Database (ICSDB) provides access to four categories of data: general (chemical information and publication data); average structure (cell, symmetry, atom sites, and experimental data for the average structure); modulated structure (cell, symmetry, atom sites, and experimental data for the modulated structure); and modulation parameters (descriptions of the modulation, wave vectors, and atom sites modulations).

  12. Novel Kac-Moody-type affine extensions of non-crystallographic Coxeter groups

    NASA Astrophysics Data System (ADS)

    Dechant, Pierre-Philippe; Bœhm, Céline; Twarock, Reidun

    2012-07-01

    Motivated by recent results in mathematical virology, we present novel asymmetric {Z}[\\tau ]-integer-valued affine extensions of the non-crystallographic Coxeter groups H2, H3 and H4 derived in a Kac-Moody-type formalism. In particular, we show that the affine reflection planes which extend the Coxeter group H3 generate (twist) translations along two-, three- and five-fold axes of icosahedral symmetry, and we classify these translations in terms of the Fibonacci recursion relation applied to different start values. We thus provide an explanation of previous results concerning affine extensions of icosahedral symmetry in a Coxeter group context, and extend this analysis to the case of the non-crystallographic Coxeter groups H2 and H4. These results will enable new applications of group theory in physics (quasicrystals), biology (viruses) and chemistry (fullerenes).

  13. The analysis of crystallographic symmetry types in finite groups

    NASA Astrophysics Data System (ADS)

    Sani, Atikah Mohd; Sarmin, Nor Haniza; Adam, Nooraishikin; Zamri, Siti Norziahidayu Amzee

    2014-06-01

    Undeniably, it is human nature to prefer objects which are considered beautiful. Most consider beautiful as perfection, hence they try to create objects which are perfectly balance in shape and patterns. This creates a whole different kind of art, the kind that requires an object to be symmetrical. This leads to the study of symmetrical objects and pattern. Even mathematicians and ethnomathematicians are very interested with the essence of symmetry. One of these studies were conducted on the Malay traditional triaxial weaving culture. The patterns derived from this technique are symmetrical and this allows for further research. In this paper, the 17 symmetry types in a plane, known as the wallpaper groups, are studied and discussed. The wallpaper groups will then be applied to the triaxial patterns of food cover in Malaysia.

  14. The Space Science Group

    NSDL National Science Digital Library

    1997-01-01

    The Space Science Group is part of the Division of Mathematics and Sciences at Northwestern State University in Natchitoches, La. The mission of The Space Science Group is to provide activities that encourage participation in math and science, build knowledge of basic concepts, teach basic science skill, and positively influence attitudes. The mission of The Space Science Group is to develop and implement programs which use aspects of the space program to motivate students to study mathematics and science. Many Space Science Group programs are described at the URL below.

  15. Space Group Symmetry

    NSDL National Science Digital Library

    In this problem set, students are given space group symmetry diagrams for primitive (P) orthorhombic space groups. For each diagram they must write down the symmetry axis (either 2 or 21) that is parallel to each major axis, and give the symmetry plane (a, b, c, n, or m) that is normal (perpendicular)to each. They must also give the simplified Hermann-Mauguin symbol for the space group.

  16. Crystallographic topology and its applications

    SciTech Connect

    Johnson, C.K.; Burnett, M.N. [Oak Ridge National Lab., TN (United States); Dunbar, W.D. [Simon`s Rock Coll., Great Barrington, MA (United States). Div. of Natural Sciences and Mathematics

    1996-10-01

    Geometric topology and structural crystallography concepts are combined to define a new area we call Structural Crystallographic Topology, which may be of interest to both crystallographers and mathematicians. In this paper, we represent crystallographic symmetry groups by orbifolds and crystal structures by Morse - functions. The Morse function uses mildly overlapping Gaussian thermal-motion probability density functions centered on atomic sites to form a critical net with peak, pass, pale, and pit critical points joined into a graph by density gradient-flow separatrices. Critical net crystal structure drawings can be made with the ORTEP-III graphics pro- An orbifold consists of an underlying topological space with an embedded singular set that represents the Wyckoff sites of the crystallographic group. An orbifold for a point group, plane group, or space group is derived by gluing together equivalent edges or faces of a crystallographic asymmetric unit. The critical-net-on-orbifold model incorporates the classical invariant lattice complexes of crystallography and allows concise quotient-space topological illustrations to be drawn without the repetition that is characteristic of normal crystal structure drawings.

  17. International Space Exploration Coordination Group

    E-print Network

    International Space Exploration Coordination Group The Global Exploration Roadmap September 2011, and stimulating technical and commercial innovation. As more nations undertake space exploration activities agencies participating in the International Space Exploration Coordination Group (ISECG) are developing

  18. International Space Exploration Coordination Group

    E-print Network

    International Space Exploration Coordination Group The Global Exploration Roadmap September 2011 participating in the International Space Exploration Coordination Group (ISECG) are developing the Global. Agencies agree that human space exploration will be most successful as an international endeavor because

  19. International Space Exploration Coordination Group

    E-print Network

    Rathbun, Julie A.

    International Space Exploration Coordination Group The Global Exploration Roadmap August 2013 #12 The Global Exploration Roadmap is being developed by space agencies participating in the International Space for collaborative space exploration missions beginning with the International Space Station (ISS) and continuing

  20. Coset spaces for quantum groups

    NASA Astrophysics Data System (ADS)

    Skoda, Zoran

    Consideration of symmetries often simplifies problems in physics and geometry. Quantum groups are analogues of groups, and they can describe a novel kind of symmetry. We view them as objects of noncommutative geometry. They may act on algebras of noncommutative or quantum observables. We propose a theory of coset spaces for quantum groups in the language of coactions of Hopf algebras and analyse an example which should be thought as a quantum group analogue of the flag variety. In the classical case the flag variety is the coset space of the special linear group modulo its Borel subgroup of lower triangular matrices. We introduce and study a notion of localized coinvariants; the quantum group coset space is viewed as a system of algebras of localized coinvariants, equipped with a quantum version of the locally trivial principal bundle where the total space is described by the quantum special linear group and the base space is described by the system of algebras of localized coinvariants. We use quasideterminants, the commutation relations between the quantum minors and the noncommutative Gauss decomposition to formulate and prove the main results. We apply our axiomatization of quantum group fibre bundles to obtain a generalization of a concept of Perelomov coherent states to the Hopf algebra setting and obtain the corresponding resolution of unity formula.

  1. Interactive PDF files with embedded 3D designs as support material to study the 32 crystallographic point groups

    NASA Astrophysics Data System (ADS)

    Arribas, Victor; Casas, Lluís; Estop, Eugènia; Labrador, Manuel

    2014-01-01

    Crystallography and X-ray diffraction techniques are essential topics in geosciences and other solid-state sciences. Their fundamentals, which include point symmetry groups, are taught in the corresponding university courses. In-depth meaningful learning of symmetry concepts is difficult and requires capacity for abstraction and spatial vision. Traditionally, wooden crystallographic models are used as support material. In this paper, we describe a new interactive tool, freely available, inspired in such models. Thirty-two PDF files containing embedded 3D models have been created. Each file illustrates a point symmetry group and can be used to teach/learn essential symmetry concepts and the International Hermann-Mauguin notation of point symmetry groups. Most interactive computer-aided tools devoted to symmetry deal with molecular symmetry and disregard crystal symmetry so we have developed a tool that fills the existing gap.

  2. Symmetric spaces of exceptional groups

    SciTech Connect

    Boya, L. J., E-mail: luisjo@unizar.e [Universidad de Zaragoza, Departamento de Fisica Teorica (Spain)

    2010-02-15

    We address the problem of the reasons for the existence of 12 symmetric spaces with the exceptional Lie groups. The 1 + 2 cases for G{sub 2} and F{sub 4}, respectively, are easily explained from the octonionic nature of these groups. The 4 + 3 + 2 cases on the E{sub 6,7,8} series require the magic square of Freudenthal and, for the split case, an appeal to the supergravity chain in 5, 4, and 3 space-time dimensions.

  3. Rotational dynamics of methyl groups in durene: A crystallographic, spectroscopic, and molecular mechanics investigation

    NASA Astrophysics Data System (ADS)

    Neumann, M. A.; Johnson, M. R.; Radaelli, P. G.; Trommsdorff, H. P.; Parker, S. F.

    1999-01-01

    Neutron powder diffraction measurements of perdeutero durene in the temperature range from 1.5 K to 290 K have been performed. The lowest temperature structure is the starting point for calculations of the methyl group tunneling and librational dynamics. Ab initio methods and atom-atom potentials are used to determine rotational single particle and coupling potentials. Tunneling splittings and librational bands are calculated by numerical solution of Schrödinger's equation for a system of many coupled methyl groups. High-resolution inelastic neutron scattering measurements of methyl tunneling and molecular vibrations have been repeated, the tunneling results resolving an inconsistency with earlier NMR work. Quantum molecular dynamics provide a stringent test of the numerical methods and the data are ultimately well reproduced. These results are also discussed in the context of optical measurements of dye molecules in a host lattice of durene.

  4. Induced representations of the full holosymmetric double space groups based on the body-centred cubic bravais lattice

    Microsoft Academic Search

    H. Kunert; M. Suffczynski

    1982-01-01

    We introduce a modified formula for the element matrices of the induced representations of any crystallographic space group. With the help of this formula we can obtain all the induced representations of any space group. The generating matrices of the induced representations for the groups Im3m (--- O9h) and Ia3d (--- O10h) have been calculated. In particular, we have considered

  5. Crystallographic Oxide Phase Identification of Char Deposits Obtained from Space Shuttle Columbia Window Debris

    NASA Technical Reports Server (NTRS)

    Olivas, J. D.; Wright, M. C.; Christoffersen, R.; Cone, D. M.; McDanels, S. J.

    2009-01-01

    Analyzing the remains of Space Shuttle Columbia has proven technically beneficial years after the vehicle breakup. This investigation focused on charred deposits on fragments of Columbia overhead windowpanes. Results were unexpected relative to the engineering understanding of material performance in a reentry environment. The TEM analysis demonstrated that the oxides of aluminum and titanium mixed with silicon oxides to preserve a history of thermal conditions to which portions of the vehicle were exposed. The presence of Ti during the beginning of the deposition process, along with the thermodynamic phase precipitation upon cool down, indicate that temperatures well above the Ti melt point were experienced. The stratified observations implied that additional exothermic reaction, expectedly metal combustion of a Ti structure, had to be present for oxide formation. Results are significant for aerospace vehicles where thermal protection system (TPS) breaches cause substructures to be in direct path with the reentry plasma. 1

  6. Space complexity of Abelian groups

    Microsoft Academic Search

    Douglas Cenzer; Rodney G. Downey; Jeffrey B. Remmel; Zia Uddin

    2009-01-01

    We develop a theory of LOGSPACE structures and apply it to con- struct a number of examples of Abelian Groups which have LOGSPACE presentations. We show that all computable torsion Abelian groups have LOGSPACE presentations and we show that the groups Z, Z(p1), and the additive group of the rationals have LOGSPACE presentations over a standard universe such as the

  7. Crystallographic Topology 2: Overview and Work in Progress

    SciTech Connect

    Johnson, C.K.

    1999-08-01

    This overview describes an application of contemporary geometric topology and stochastic process concepts to structural crystallography. In this application, crystallographic groups become orbifolds, crystal structures become Morse functions on orbifolds, and vibrating atoms in a crystal become vector valued Gaussian measures with the Radon-Nikodym property. Intended crystallographic benefits include new methods for visualization of space groups and crystal structures, analysis of the thermal motion patterns seen in ORTEP drawings, and a classification scheme for crystal structures based on their Heegaard splitting properties.

  8. Crystallographic Analysis of Ground and Space Thermostable T1 Lipase Crystal Obtained via Counter Diffusion Method Approach

    PubMed Central

    Mohamad Aris, Sayangku Nor Ariati; Thean Chor, Adam Leow; Basri, Mahiran; Salleh, Abu Bakar; Raja Abd. Rahman, Raja Noor Zaliha

    2014-01-01

    Three-dimensional structure of thermostable lipase is much sought after nowadays as it is important for industrial application mainly found in the food, detergent, and pharmaceutical sectors. Crystallization utilizing the counter diffusion method in space was performed with the aim to obtain high resolution diffracting crystals with better internal order to improve the accuracy of the structure. Thermostable T1 lipase enzyme has been crystallized in laboratory on earth and also under microgravity condition aboard Progress spacecraft to the ISS in collaboration with JAXA (Japanese Aerospace Exploration Agency). This study is conducted with the aims of improving crystal packing and structure resolution. The diffraction data set for ground grown crystal was collected to 1.3?Å resolution and belonged to monoclinic C2 space group with unit cell parameters a = 117.40?Å, b = 80.95?Å, and c = 99.81?Å, whereas the diffraction data set for space grown crystal was collected to 1.1?Å resolution and belonged to monoclinic C2 space group with unit cell parameters a = 117.31?Å, b = 80.85?Å, and c = 99.81?Å. The major difference between the two crystal growth systems is the lack of convection and sedimentation in microgravity environment resulted in the growth of much higher quality crystals of T1 lipase. PMID:24516857

  9. Aeritalia Space Systems Group, Turin, Italy

    NASA Technical Reports Server (NTRS)

    Donlan, Vincent

    1989-01-01

    Aeritalia has been involved in European space programs since the early 1960's. Space activities grew to the point that in 1984 Aeritalia established a separate Space Systems Group (SSG), located in Turin. Today, SSG is involved in dozens of projects, some of them jointly with NASA and U.S. aerospace companies. Here, several of the major projects, such as the Tethered Satellite system, HIPPARCOS, Columbus Pressurized Module, Italian Research Interim Stage, and others are briefly described.

  10. Four-dimensional space groups for pedestrians: composite structures.

    PubMed

    Sun, Junliang; Lee, Stephen; Lin, Jianhua

    2007-10-01

    Higher-dimensional crystals have been studied for the last thirty years. However, most practicing chemists, materials scientists, and crystallographers continue to eschew the use of higher-dimensional crystallography in their work. Yet it has become increasingly clear in recent years that the number of higher-dimensional systems continues to grow from hundreds to as many as a thousand different compounds. Part of the problem has to do with the somewhat opaque language that has developed over the past decades to describe higher-dimensional systems. This language, while well-suited to the specialist, is too sophisticated for the neophyte wishing to enter the field, and as such can be an impediment. This Focus Review hopes to address this issue. The goal of this article is to show the regular chemist or materials scientist that knowledge of regular 3D crystallography is all that is really necessary to understand 4D crystal systems. To this end, we have couched higher-dimensional composite structures in the language of ordinary 3D crystals. In particular, we developed the principle of complementarity, which allows one to identify correctly 4D space groups solely from examination of the two 3D components that make up a typical 4D composite structure. PMID:17886829

  11. Quantum group gauge theory on quantum spaces

    Microsoft Academic Search

    Thomasz Brzezinski; Shahn Majid

    1993-01-01

    We construct quantum group-valued canonical connections on quantum homogeneous spaces, including aq-deformed Dirac monopole on the quantum sphere of Podles with quantum differential structure coming from the 3D calculus of Woronowicz onSUq(2). The construction is presented within the setting of a general theory of quantum principal bundles with quantum group (Hopf algebra) fibre, associated quantum vector bundles and connection one-forms.

  12. UK Space Exploration Working Group Report of the

    E-print Network

    Crowther, Paul

    UK Space Exploration Working Group Report of the UK Space Exploration Working Group 13 September 2007 #12;UK Space Exploration Working Group The UK Space Exploration Working Group Chair: Prof Frank committee to: · review current global plans for space exploration; · assess what opportunities and benefits

  13. DYNAMICS OF PLANETCROSSING ASTEROIDS Space Mechanics Group,

    E-print Network

    Milani, Andrea

    DYNAMICS OF PLANET­CROSSING ASTEROIDS A. MILANI Space Mechanics Group, Department of Mathematics, including Earth­crossing ones. The dynamics of planet­crossing asteroids/comets is strongly con­ trolled in a satisfactory way most of the dynamical behaviors found in the experiments. 1. THE ASTEROID COMPLEX, NEAR EARTH

  14. Optimal space-time constellations from groups

    Microsoft Academic Search

    Brian L. Hughes

    2003-01-01

    We consider the design of space-time constellations based on group codes for fading channels with multiple transmit and receive antennas. These codes can be viewed as multiantenna extensions of phase-shift keying (PSK), in the sense that all codewords have equal energy, all are rotations of a fixed codeword, and there is a simple differential transmission rule that allows data to

  15. World Database of Crystallographers

    NSDL National Science Digital Library

    The World Database of Crystallographers and of Other Scientists Employing Crystallographic Methods is offered by the International Union of Crystallography. The simple database can be searched by family name, title, interests, address, and various other criteria. Results include basic information such as full name, position, institution address, degrees held, key interests, and contact information. Those seeking such specific information will appreciate this unique resource.

  16. The space shuttle payload planning working groups: Executive summaries

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The findings of a space shuttle payload planning group session are presented. The purpose of the workshop is: (1) to provide guidance for the design and development of the space shuttle and the spacelab and (2) to plan a space science and applications program for the 1980 time period. Individual groups were organized to cover the various space sciences, applications, technologies, and life sciences. Summaries of the reports submitted by the working groups are provided.

  17. Mathematical aspects of molecular replacement. III. Properties of space groups preferred by proteins in the Protein Data Bank.

    PubMed

    Chirikjian, G; Sajjadi, S; Toptygin, D; Yan, Y

    2015-03-01

    The main goal of molecular replacement in macromolecular crystallography is to find the appropriate rigid-body transformations that situate identical copies of model proteins in the crystallographic unit cell. The search for such transformations can be thought of as taking place in the coset space ?\\G where ? is the Sohncke group of the macromolecular crystal and G is the continuous group of rigid-body motions in Euclidean space. This paper, the third in a series, is concerned with viewing nonsymmorphic ? in a new way. These space groups, rather than symmorphic ones, are the most common ones for protein crystals. Moreover, their properties impact the structure of the space ?\\G. In particular, nonsymmorphic space groups contain both Bieberbach subgroups and symmorphic subgroups. A number of new theorems focusing on these subgroups are proven, and it is shown that these concepts are related to the preferences that proteins have for crystallizing in different space groups, as observed in the Protein Data Bank. PMID:25727867

  18. Space station group activities habitability module study

    NASA Technical Reports Server (NTRS)

    Nixon, David

    1986-01-01

    This study explores and analyzes architectural design approaches for the interior of the Space Station Habitability Module (originally defined as Habitability Module 1 in Space Station Reference Configuration Decription, JSC-19989, August 1984). In the Research Phase, architectural program and habitability design guidelines are specified. In the Schematic Design Phase, a range of alternative concepts is described and illustrated with drawings, scale-model photographs and design analysis evaluations. Recommendations are presented on the internal architectural, configuration of the Space Station Habitability Module for such functions as the wardroom, galley, exercise facility, library and station control work station. The models show full design configurations for on-orbit performance.

  19. Unified system of Hermann-Mauguin symbols for groups of material physics. 1. Groups with decomposable lattices

    NASA Astrophysics Data System (ADS)

    Kopsky, V.

    2006-03-01

    Amendments of classical concepts of space and crystallographic groups are proposed and a unified system of Hermann-Mauguin symbols described which includes subperiodic groups and groups with semicontinuous and continuous lattices. Symbols of subperiodic groups are correlated with symbols of space groups with decomposable lattices.

  20. SPACES OF BOUNDED SPHERICAL FUNCTIONS ON HEISENBERG GROUPS: PART I

    E-print Network

    Benson, Chal

    SPACES OF BOUNDED SPHERICAL FUNCTIONS ON HEISENBERG GROUPS: PART I CHAL BENSON AND GAIL RATCLIFF hermitian vector space V . Letting K act on the associ- ated Heisenberg group HV = V Ã? R yields a Gelfand. Primary 43A90; Secondary 20G05, 43A75. 1 #12;2 C. BENSON AND G. RATCLIFF finite dimensional complex vector

  1. The International Space Life Sciences Strategic Planning Working Group

    NASA Technical Reports Server (NTRS)

    White, Ronald J.; Rabin, Robert; Lujan, Barbara F.

    1993-01-01

    Throughout the 1980s, ESA and the space agencies of Canada, Germany, France, Japan, and the U.S. have pursued cooperative projects bilaterally and multilaterally to prepare for, and to respond to, opportunities in space life sciences research previously unapproachable in scale and sophistication. To cope effectively with likely future space research opportunities, broad, multilateral, coordinated strategic planning is required. Thus, life scientists from these agencies have allied to form the International Space Life Sciences Strategic Planning Working Group. This Group is formally organized under a charter that specifies the purpose of the Working Group as the development of an international strategic plan for the space life sciences, with periodic revisions as needed to keep the plan current. The plan will be policy-, not operations-oriented. The Working Group also may establish specific implementation teams to coordinate multilateral science policy in specific areas; such teams have been established for space station utilization, and for sharing of flight equipment.

  2. Automatic space group determination using precession electron diffraction patterns

    Microsoft Academic Search

    P. Oleynikov; S. Hovmöller; X. D. Zou

    A set of algorithms for automatic High Order Laue Zone (HOLZ) indexing and possible set of space groups extraction were developed\\u000a and implemented in the “Space Group Determinator” program. The symmetry analysis is performed using Morniroli-Steeds tables\\u000a [1 and 2]. The developed program becomes extremely useful for the analysis of precession electron diffraction patterns (PEDs,\\u000a see Fig. 1) [3]. “Space

  3. Semisimple actions of mapping class groups on CAT(0) spaces

    E-print Network

    Bridson, Martin

    1 Semisimple actions of mapping class groups on CAT(0) spaces Martin R. Bridson 1 Mathematical type and let Mod() be its mapping class group. We consider actions of Mod() by semisimple isometries-Petersson metric shows that there are interesting actions of this type. Whenever the mapping class group

  4. Actuator Grouping Optimization on Flexible Space Reflectors

    NASA Technical Reports Server (NTRS)

    Hill, Jeffrey R.; Wang, K. W.; Fang, Houfei; Quijano, Ubaldo

    2011-01-01

    With the rapid advances in deployable membrane and mesh antenna technologies, the feasibility of developing large, lightweight reflectors has greatly improved. In order to achieve the required surface accuracy, precision surface control is needed on these lightweight reflectors. For this study, an analytical model is shown which combines a flexible Kapton reflector with Polyvinylidene fluoride (PVDF) actuators for surface control. Surface errors are introduced that are similar to real world scenarios, and a least squares control algorithm is developed for surface control. Experimental results on a 2.4 meter reflector show that while the analytical reflector model is generally correct, due to idiosyncrasies in the reflector it cannot be used for online control. A new method called the En Mass Elimination algorithm is used to determine the optimal grouping of actuators when the number of actuators in the system exceeds the number of power supplies available.

  5. Group theoretical construction of planar noncommutative phase spaces

    SciTech Connect

    Ngendakumana, Ancille, E-mail: nancille@yahoo.fr; Todjihoundé, Leonard, E-mail: leonardt@imsp.uac.org [Institut de Mathématiques et des Sciences Physiques (IMSP), Porto-Novo (Benin)] [Institut de Mathématiques et des Sciences Physiques (IMSP), Porto-Novo (Benin); Nzotungicimpaye, Joachim, E-mail: kimpaye@kie.ac.rw [Kigali Institute of Education (KIE), Kigali (Rwanda)] [Kigali Institute of Education (KIE), Kigali (Rwanda)

    2014-01-15

    Noncommutative phase spaces are generated and classified in the framework of centrally extended anisotropic planar kinematical Lie groups as well as in the framework of noncentrally abelian extended planar absolute time Lie groups. Through these constructions the coordinates of the phase spaces do not commute due to the presence of naturally introduced fields giving rise to minimal couplings. By symplectic realizations methods, physical interpretations of generators coming from the obtained structures are given.

  6. Linear spaces with flag-transitive automophism groups

    Microsoft Academic Search

    Francis Buekenhout; Anne Delandtsheer; Jean Doyen; Peter B. Kleidman; Martin W. Liebeck; Jan Saxl

    1990-01-01

    Our purpose here is to announce a classification of the pairs (S, G), where S is a non-trivial finite linear space and (; is a group of automorphisms acting transitively on the flags of S. Here, by a linear space S we mean a finite incidence structure of points and lines such that any two points are incident with exactly

  7. SHELXT – Integrated space-group and crystal-structure determination

    SciTech Connect

    Sheldrick, George M., E-mail: gsheldr@shelx.uni-ac.gwdg.de [Georg-August Universität Göttingen, Tammannstrasse 4, Göttingen, 37077 (Germany)

    2015-01-01

    SHELXT automates routine small-molecule structure determination starting from single-crystal reflection data, the Laue group and a reasonable guess as to which elements might be present. The new computer program SHELXT employs a novel dual-space algorithm to solve the phase problem for single-crystal reflection data expanded to the space group P1. Missing data are taken into account and the resolution extended if necessary. All space groups in the specified Laue group are tested to find which are consistent with the P1 phases. After applying the resulting origin shifts and space-group symmetry, the solutions are subject to further dual-space recycling followed by a peak search and summation of the electron density around each peak. Elements are assigned to give the best fit to the integrated peak densities and if necessary additional elements are considered. An isotropic refinement is followed for non-centrosymmetric space groups by the calculation of a Flack parameter and, if appropriate, inversion of the structure. The structure is assembled to maximize its connectivity and centred optimally in the unit cell. SHELXT has already solved many thousand structures with a high success rate, and is optimized for multiprocessor computers. It is, however, unsuitable for severely disordered and twinned structures because it is based on the assumption that the structure consists of atoms.

  8. SHELXT - integrated space-group and crystal-structure determination.

    PubMed

    Sheldrick, George M

    2015-01-01

    The new computer program SHELXT employs a novel dual-space algorithm to solve the phase problem for single-crystal reflection data expanded to the space group P1. Missing data are taken into account and the resolution extended if necessary. All space groups in the specified Laue group are tested to find which are consistent with the P1 phases. After applying the resulting origin shifts and space-group symmetry, the solutions are subject to further dual-space recycling followed by a peak search and summation of the electron density around each peak. Elements are assigned to give the best fit to the integrated peak densities and if necessary additional elements are considered. An isotropic refinement is followed for non-centrosymmetric space groups by the calculation of a Flack parameter and, if appropriate, inversion of the structure. The structure is assembled to maximize its connectivity and centred optimally in the unit cell. SHELXT has already solved many thousand structures with a high success rate, and is optimized for multiprocessor computers. It is, however, unsuitable for severely disordered and twinned structures because it is based on the assumption that the structure consists of atoms. PMID:25537383

  9. The space shuttle payload planning working groups. Volume 10: Space technology

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The findings and recommendations of the Space Technology group of the space shuttle payload planning activity are presented. The elements of the space technology program are: (1) long duration exposure facility, (2) advanced technology laboratory, (3) physics and chemistry laboratory, (4) contamination experiments, and (5) laser information/data transmission technology. The space technology mission model is presented in tabular form. The proposed experiments to be conducted by each test facility are described. Recommended approaches for user community interfacing are included.

  10. Spectroscopic and structural assignment of the absolute stereochemistry in a series of 1,2-difluorovinyl organometalloids. The first crystallographic characterization and structural series of group 14 fluorovinyl compounds.

    PubMed

    Brisdon, Alan K; Crossley, Ian R; Pritchard, Robin G; Warren, John E

    2002-09-01

    The group 14 trifluorovinyl compounds Ph(3)ECF=CF(2) (E = Ge, Sn, Pb) have been prepared in high yield by the low-temperature reaction of the triphenylelement halide with trifluorovinyllithium, generated from tetrafluoroethane (CF(3)CH(2)F, HFC-134a) and 2 equiv of n-butyllithium. The X-ray crystal structures of these materials have been obtained, so affording the first structural series for such species. Subsequent reaction of Ph(3)GeCF=CF(2) with LiAlH(4) and a range of organolithium reagents has led to preparation of the 1,2-difluorovinylgermanes Ph(3)GeCF=CFR (R = H, Me, n-Bu, t-Bu, Ph). Multinuclear NMR spectroscopic and X-ray crystallographic studies of these compounds have been undertaken and have shown unequivocally the exclusive trans-geometry of the 1,2-difluorovinyl moiety. PMID:12206700

  11. Structure of Escherichia coli ribonucleotide reductase R2 in space group P6[subscript 1]22

    SciTech Connect

    Sommerhalter, Monika; Saleh, Lana; Bollinger Jr., J. Martin; Rosenzweig, Amy C. (NWU); (Penn)

    2010-07-20

    A new crystal form of wild-type ribonucleotide reductase R2 from Escherichia coli was obtained. Crystals grow in space group P6{sub 1}22 with one R2 monomer in the asymmetric unit. A twofold crystallographic symmetry axis generates the physiological dimeric form of R2. Co-crystallization with CoCl{sub 2} or MnCl{sub 2} results in full occupancy of the dinuclear metal site. The structure of the Mn{sup II}-loaded form was determined to 2.6 {angstrom} resolution by molecular replacement. The crystallization conditions, backbone conformation, crystal-packing interactions and metal centers are compared with those of previously determined crystal forms.

  12. Every finite group is the group of self homotopy equivalences of an elliptic space

    E-print Network

    Costoya, C

    2011-01-01

    In this paper we prove that every finite group $G$ can be realized as the group of self-homotopy equivalences of infinitely many (non homotopy equivalent) rational elliptic spaces $X$. Moreover, for every $k$ positive integer, $X$ can be chosen to be $k$-connected.

  13. Real-space renormalization group approach to driven diffusive systems

    Microsoft Academic Search

    T. Hanney; R. B. Stinchcombe

    2006-01-01

    We introduce a real-space renormalization group procedure for driven diffusive systems which predicts both steady state and dynamic properties. We apply the method to the boundary driven asymmetric simple exclusion process and recover exact results for the steady state phase diagram, as well as the crossovers in the relaxation dynamics for each phase.

  14. Representations of finite groups on Riemann-Roch spaces, II

    Microsoft Academic Search

    David Joyner; Amy Ksir

    2003-01-01

    If G is a finite subgroup of the automorphism group of a projective curve X and D is a divisor on X stabilized by G, then under the assumption that D is nonspecial, we compute a simplified formula for the trace of the natural representation of G on Riemann-Roch space L(D).

  15. CONFIGURATION SPACES AND BRAID GROUPS ON GRAPHS IN ROBOTICS

    E-print Network

    Ghrist, Robert W.

    CONFIGURATION SPACES AND BRAID GROUPS ON GRAPHS IN ROBOTICS ROBERT GHRIST School of Mathematics control schemes for Automated Guided Vehicles (robots) in industrial settings. In this announcement, we filtered through the robotics community [Lat91, KR90]. Surprisingly, topologists have been generally

  16. The Lorentzian oscillator group as a geodesic orbit space

    SciTech Connect

    Batat, W. [Ecole Normale Superieure d'Enseignement Technologique d'Oran, Departement de Mathematiques et Informatique, B.P. 1523, El M'Naouar, Oran (Algeria); Gadea, P. M. [Instituto de Fisica Fundamental, CSIC, Serrano 113-bis, 28006 Madrid (Spain); Oubina, J. A. [Departamento de Xeometria e Topoloxia, Facultade de Matematicas, Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain)

    2012-10-15

    We prove that the four-dimensional oscillator group Os, endowed with any of its usual left-invariant Lorentzian metrics, is a Lorentzian geodesic (so, in particular, null-geodesic) orbit space with some of its homogeneous descriptions corresponding to certain homogeneous Lorentzian structures. Each time that Os is endowed with a suitable metric and an appropriate homogeneous Lorentzian structure, it is a candidate for constructing solutions in d-dimensional supergravity with at least 24 of the 32 possible supersymmetries.

  17. Mineralogical, chemical, and crystallographic properties of supergene jarosite-group minerals from the Xitieshan Pb-Zn sulfide deposit, northern Tibetan Plateau, China

    USGS Publications Warehouse

    Chen, Lei; Li, Jian-Wei; Rye, Robert O.; Benzel, William H.; Lowers, H.A.; He, Ming-Zhong

    2013-01-01

    Supergene jarosite-group minerals are widespread in weathering profiles overlying Pb-Zn sulfide ores at Xitieshan, northern Tibetan Plateau, China. They consist predominantly of K-deficient natrojarosite, with lesser amounts of K-rich natrojarosite and plumbojarosite. Electron microprobe (EMP) analyses, scanning electron microcopy (SEM) investigation, and X-ray mapping reveal that the jarosite-group minerals are characterized by spectacular oscillatory zoning composed of alternating growth bands of K-deficient and K-bearing natrojarosite (K2O >1 wt.%). Plumbojarosite, whenever present, occurs as an overgrowth in the outermost bands, and its composition can be best represented by K0.29Na0.19Pb0.31Fe2.66Al0.22(SO4)1.65(PO4)0.31(AsO4)0.04(OH)7.37. The substitution of monovalent for divalent cations at the A site of plumbojarosite is charge balanced by the substitution of five-valent for six-valent anions in XO,4/sub> at the X site. Thermogravimetric analysis (TGA) of representative samples reveal mass losses of 11.46 wt.% at 446.6 °C and 21.42 wt.% at 683.4 °C due to dehydroxylation and desulfidation, respectively. TGA data also indicate that the natrojarosite structure collapses at 446.6 °C, resulting in the formation of NaFe(SO4)2 and minor hematite. The decomposition products of NaFe(SO4) are hematite and Na,2SO4. Powder X-ray diffraction (XRD) analyses show that the jarosite-group minerals have mean unit-cell parameters of a=7.315 ä and c=016.598 ä. XRD and EMP data support the view that substitutions of Na for K in the A site and full Fe occupancy in the B site can considerably decrease the unit-cell parameter c, but only slightly increase a. The results from this study suggest that the observed oscillatory zoning of jarosite-group minerals at Xitieshan resulted mainly from substitutions of K for Na at the A site and P for S at the X site.

  18. Preliminary joint neutron time-of-flight and X-ray crystallographic study of human ABO(H) blood group A glycosyltransferase

    PubMed Central

    Schuman, B.; Fisher, S. Z.; Kovalevsky, A.; Borisova, S. N.; Palcic, M. M.; Coates, L.; Langan, P.; Evans, S. V.

    2011-01-01

    The biosyntheses of oligosaccharides and glycoconjugates are conducted by glycosyltransferases. These extraordinarily diverse and widespread enzymes catalyze the formation of glycosidic bonds through the transfer of a monosaccharide from a donor molecule to an acceptor molecule, with the stereochemistry about the anomeric carbon being either inverted or retained. Human ABO(H) blood group A ?-1,3-N-acetylgalactosaminyltransferase (GTA) generates the corresponding antigen by the transfer of N-acetylgalactos­amine from UDP-GalNAc to the blood group H antigen. To understand better how specific active-site-residue protons and hydrogen-bonding patterns affect substrate recognition and catalysis, neutron diffraction studies were initiated at the Protein Crystallography Station (PCS) at Los Alamos Neutron Science Center (LANSCE). A large single crystal was subjected to H/D exchange prior to data collection and time-of-flight neutron diffraction data were collected to 2.5?Å resolution at the PCS to ?85% overall completeness, with complementary X-ray diffraction data collected from a crystal from the same drop and extending to 1.85?Å resolution. Here, the first successful neutron data collection from a glycosyltransferase is reported. PMID:21301100

  19. Role of the charged groups of glutathione disulfide in the catalysis of glutathione reductase: Crystallographic and kinetic studies with synthetic analogues

    SciTech Connect

    Janes, W.; Schulz, G.E. (Institut fuer Organische Chemie und Biochemie der Universitaet (West Germany))

    1990-04-24

    Six analogues of glutathione disulfide were synthesized. All of them involved the abolishment of charges, wither by amidation of carboxylates or by removal of amino groups. Four of these analogues could be bound to crystalline oxidized glutathione reductase, and their binding modes could be established by X-ray analyses at 2.4-{angstrom} resolution. All six analogues were catalytically processed; the kinetic parameters were determined. The two analogues that did not bind in the crystals had by far the poorest catalytic efficiencies. Kinetic parameters together with X-ray data show the influence of each charged group on binding and catalytic rate. Data analysis indicates that enzyme avoids processing of incorrect substrates in two ways: First, it reduces their binding strengths and/or enforces displacement of catalytically important substrate parts. Furthermore, it forms a fragile cluster of bound substrate and catalytically competent residues, which is unbalanced by incorrect parts of the substrate such that catalysis is prevented. The study showed that it is feasible to measure these parameters as a function of substrate modification.

  20. Space station group activities habitability module study: A synopsis

    NASA Technical Reports Server (NTRS)

    Nixon, David; Glassman, Terry

    1987-01-01

    Space station habitability was studied by investigating crew activity routines, proximities, ergonomic envelopes, and group volumes. Ten alternative schematic interior designs were proposed. Preliminary conclusions include: (1) in-service interior modifications may be necessary and should be planned for; (2) design complexity will be increased if the module cluster is reduced from five to three; (3) the increased crew circulation attendant upon enhancement of space station activity may produce human traffic bottlenecks and should be planned for; (4) a single- or two-person quiet area may be desirable to provide crew members with needed solitude during waking hours; and (5) the decision to choose a two-shift or three-shift daily cycle will have a significant impact on the design configuration and operational efficiency of the human habitat.

  1. Crystallization and preliminary crystallographic characterization of the N-terminal Kunitz domain of boophilin

    PubMed Central

    Cereija, Tatiana B.; Figueiredo, Ana C.; de Sanctis, Daniele; Tanaka, Aparecida S.; Pereira, Pedro José Barbosa

    2012-01-01

    Boophilin is a tight-binding thrombin inhibitor composed of two canonical Kunitz-type domains in a tandem arrangement. Thrombin-bound boophilin can inhibit a second trypsin-like serine proteinase, most likely through the reactive loop of its N-terminal Kunitz domain. Here, the crystallization and preliminary crystallographic analysis of the isolated N-terminal domain of boophilin is reported. The crystals belonged to the orthorhombic space group P212121 and diffracted to beyond 1.8?Å resolution using a sealed-tube home source and to 0.87?Å resolution at a synchrotron source. PMID:22505414

  2. Purification, crystallization and preliminary X-ray crystallographic analysis of human CCG1-interacting factor B.

    PubMed

    Padmanabhan, B; Kuzuhara, T; Mizuno, H; Horikoshi, M

    2000-11-01

    A novel human factor CIB (CCG1-interacting factor B) has been isolated using the yeast two-hybrid system. The 22 kDa CIB protein has been expressed in Escherichia coli, purified to homogeneity and crystallized in a form suitable for crystallographic studies. The protein was crystallized in the orthogonal space group P2(1)2(1)2(1), with unit-cell parameters a = 43.60 (2), b = 44.45 (1), c = 110.70 (5) A and one molecule in the asymmetric unit. The crystal diffracted beyond 2.2 A resolution using synchrotron radiation. PMID:11053859

  3. Introduction Surface actions and mapping class group Moduli space Elementary abelian actions References Elementary Abelian Group Actions on

    E-print Network

    Broughton, S. Allen

    Introduction Surface actions and mapping class group Moduli space Elementary abelian actions, 2007 #12;Introduction Surface actions and mapping class group Moduli space Elementary abelian actions and the mapping class group - background, some geometry in this part classification of elementary abelian actions

  4. The determination of some crystallographic parameters of quartz, in the sand dunes of Ouargla, Algeria

    NASA Astrophysics Data System (ADS)

    Beddiaf, Samiha; Chihi, Smail; Leghrieb, Youcef

    2015-06-01

    In this work, the crystallographic phase, degree of crystallinity, crystal system, space group and unit cell parameters of quartz in the Ouargla region (Algeria) sand dunes have been determined using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The mid-infrared absorption spectrum showed the characteristic doublet for ?-quartz at 796 and 779 cm-1. The observed principle diffractions at the d-spacings of 3.7937, 3.3539 and 1.8204 Å confirm the presence of ?-quartz in Ouargla sand. The calculated absorption ratio (degree of crystallinity) of A796 /A779 ? 1.756 indicated that our quartz exhibits a highly crystalline nature. The crystallographic parameters of quartz in Ouargla sand have been determined through analysis of X-ray diffraction data, carried out using the simulation code DICVOL06. These parameters were found as: hexagonal crystal system, space group P3221 (154), unit cell parameters: a = b = 4.9294 Å, c = 5.4093 Å and V = 113.832 Å3.

  5. Tall tales from de Sitter space; 1, Renormalization group flows

    E-print Network

    Leblond, F; Myers, R C; Leblond, Frederic; Marolf, Donald; Myers, Robert C.

    2002-01-01

    We study solutions of Einstein gravity coupled to a positive cosmological constant and matter, which are asymptotically de Sitter and homogeneous. Regarded as perturbations of de Sitter space, a theorem of Gao and Wald implies that generically these solutions are `tall,' meaning that the perturbed universe lives through enough conformal time for an entire spherical Cauchy surface to enter any observer's past light cone. Such observers will realize that their universe is spatially compact. An interesting fact, which we demonstrate with an explicit example, is that this Cauchy surface can have arbitrarily large volume for fixed asymptotically de Sitter behavior. Our main focus is on the implications of tall universes for the proposed dS/CFT correspondence. Particular attention is given to the associated renormalization group flows, leading to a more general de Sitter `c-theorem.' We find, as expected, that a contracting phase always represents a flow towards the infrared, while an expanding phase represents a `...

  6. Regularity Properties and Pathologies of PositionSpace RenormalizationGroup

    E-print Network

    Regularity Properties and Pathologies of Position­Space Renormalization­Group Transformations.EDU October 16, 1992 Short title: Renormalization­Group Pathologies KEY WORDS: Renormalization group; position­space renormalization; real­space renormalization; decimation transformation; majority­rule transformation; Kadanoff

  7. Report of the Working Group on Space/Lunar Tradeoffs

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The group discussed the advantages and disadvantages of five locations for an optical/infrared array: low-Earth orbit (LEO), Sun-synchronous Earth-orbit, geosynchronous orbit (GEO), Lagrangian points (L4 and L5), and the lunar surface. The factors affecting an array and our assessments of them are given and briefly discussed. In the discussions, two axioms are assumed: (1) Human expansion into space and to the Moon will occur; and (2) The Space Station will be constructed and operational. The major conclusion reached is that baselines of moderate size (greater than 300 m) are best done on the Moon and that large baselines (greater than 10 km) can be done only on the Moon. Three areas needing additional research were identified as follows. (1) Studies are needed on methods to steer long-baseline systems in orbit. This involves learning how to control free-flyers. It is not clear how the difficulty of control varies with orbital elevation. (2) More work is needed on the internal metrology of array systems, both orbital and lunar-surface systems.(3) We need to understand the radiation effects on detectors and electronics and learn how to mitigate them.

  8. Classification of Quaternionic Spaces with a Transitive Solvable Group of Motions

    Microsoft Academic Search

    D. V. Alekseevskii

    1975-01-01

    A complete classification of quaternionic Riemannian spaces (that is, spaces \\\\mathcal{V}^n with the holonomy group \\\\Gamma\\\\subset Sp(1)\\\\cdot Sp(m), n=4m) which admit a transitive solvable group of motions is given. It turns out that the rank of these spaces does not exceed four and that all spaces \\\\mathcal{V}^n whose rank is less than four are symmetric. The spaces \\\\mathcal{V}^n of rank

  9. Tall tales from de Sitter space I: Renormalization group flows

    E-print Network

    Frederic Leblond; Donald Marolf; Robert C. Myers

    2002-04-09

    We study solutions of Einstein gravity coupled to a positive cosmological constant and matter, which are asymptotically de Sitter and homogeneous. Regarded as perturbations of de Sitter space, a theorem of Gao and Wald implies that generically these solutions are `tall,' meaning that the perturbed universe lives through enough conformal time for an entire spherical Cauchy surface to enter any observer's past light cone. Such observers will realize that their universe is spatially compact. An interesting fact, which we demonstrate with an explicit example, is that this Cauchy surface can have arbitrarily large volume for fixed asymptotically de Sitter behavior. Our main focus is on the implications of tall universes for the proposed dS/CFT correspondence. Particular attention is given to the associated renormalization group flows, leading to a more general de Sitter `c-theorem.' We find, as expected, that a contracting phase always represents a flow towards the infrared, while an expanding phase represents a `reverse' flow towards the ultraviolet. We also discuss the conformal diagrams for various classes of homogeneous flows.

  10. Future of the US Space Launch capability: A task group report

    NASA Astrophysics Data System (ADS)

    1992-11-01

    In July 1992, a special task group of the Space Policy Advisory Board reviewed the nation's Space Launch Strategy approved by the President in July 1991. The report contains the findings and recommendations of the Task Group. The Task Group has provided a set of recommendations from a 'national' perspective that will improve our nation's space launch capability, make us more competitive in the international marketplace, and reduce the cost of government space launch operations. The U.S. should start a single, completely new, 'Spacelifter' space launch vehicle program. The Spacelifter program would focus on the medium performance range, but be 'modular' in its performance capability. The task group also recommends a transition plan to phase out the older and expensive space launch vehicles, including the Space Shuttle. The task group further recommends that a centralized management structure be established to oversee Spacelifter and other space launch activities.

  11. ISECG ToR 6 November 2007 INTERNATIONAL SPACE EXPLORATION COORDINATION GROUP

    E-print Network

    ISECG ToR 6 November 2007 INTERNATIONAL SPACE EXPLORATION COORDINATION GROUP Terms of Reference In 2006, 14 space agencies1 began a series of discussions on global interests in space exploration, and developed a common set of key space exploration themes. This vision was articulated in `The Global

  12. Purification, crystallization and preliminary crystallographic analysis of human cystathionine ?-synthase

    PubMed Central

    Oyenarte, Iker; Majtan, Tomas; Ereño, June; Corral-Rodríguez, María Angeles; Kraus, Jan P.; Martínez-Cruz, Luis Alfonso

    2012-01-01

    Human cystathionine ?-synthase (CBS) is a pyridoxal-5?-phosphate-dependent hemeprotein, whose catalytic activity is regulated by S-adenosylmethionine. CBS catalyzes the ?-replacement reaction of homocysteine (Hcy) with serine to yield cystathionine. CBS is a key regulator of plasma levels of the thrombogenic Hcy and deficiency in CBS is the single most common cause of homocystinuria, an inherited metabolic disorder of sulfur amino acids. The properties of CBS enzymes, such as domain organization, oligomerization degree or regulatory mechanisms, are not conserved across the eukaryotes. The current body of knowledge is insufficient to understand these differences and their impact on CBS function and physiology. To overcome this deficiency, we have addressed the crystallization and preliminary crystallographic analysis of a protein construct (hCBS516–525) that contains the full-length CBS from Homo sapiens (hCBS) and just lacks amino-acid residues 516–525, which are located in a disordered loop. The human enzyme yielded crystals belonging to space group I222, with unit-cell parameters a = 124.98, b = 136.33, c = 169.83?Å and diffracting X-rays to a resolution of 3.0?Å. The crystal structure appears to contain two molecules in the asymmetric unit which presumably correspond to a dimeric form of the enzyme. PMID:23143240

  13. Differential geometry of the space of orbits of a Coxeter group

    Microsoft Academic Search

    Boris Dubrovin

    1993-01-01

    Differential-geometric structures on the space of orbits of a finite Coxeter group, determined by Groth\\\\'endieck residues, are calculated. This gives a construction of a 2D topological field theory for an arbitrary Coxeter group.

  14. Supplementary Text to accompany "Cell Groups Reveal Structure of Stimulus Space"

    E-print Network

    Logan, David

    Supplementary Text to accompany "Cell Groups Reveal Structure of Stimulus Space" Carina Curto coefficients There are many definitions of homology groups, and these can be shown to be equivalent for many

  15. Neutron Laue and X-ray diffraction study of a new crystallographic superspace phase in n-nonadecane-urea.

    PubMed

    Zerdane, S; Mariette, C; McIntyre, G J; Lemée-Cailleau, M H; Rabiller, P; Guérin, L; Ameline, J C; Toudic, B

    2015-06-01

    Aperiodic composite crystals present long-range order without translational symmetry. These materials may be described as the intersection in three dimensions of a crystal which is periodic in a higher-dimensional space. In such materials, symmetry breaking must be described as structural changes within these crystallographic superspaces. The increase in the number of superspace groups with the increase in the dimension of the superspace allows many more structural solutions. This is illustrated in n-nonadecane-urea, revealing a fifth higher-dimensional phase at low temperature. PMID:26027005

  16. Preparation, crystallization and preliminary crystallographic analysis of old yellow enzyme from Trypanosoma cruzi

    SciTech Connect

    Sugiyama, Shigeru [Maruwa Foods Co. Ltd, Tsutsui-cho 170-1, Yamatokoriyama, Nara 639-1123 (Japan); Tokuoka, Keiji [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Uchiyama, Nahoko [Department of Molecular Behavioral Biology, Osaka Bioscience Institute, Osaka 565-0874 (Japan); Okamoto, Naoki; Okano, Yousuke; Matsumura, Hiroyoshi [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Inaka, Koji [Maruwa Foods Co. Ltd, Tsutsui-cho 170-1, Yamatokoriyama, Nara 639-1123 (Japan); Urade, Yoshihiro [Department of Molecular Behavioral Biology, Osaka Bioscience Institute, Osaka 565-0874 (Japan); Inoue, Tsuyoshi, E-mail: inouet@chem.eng.osaka-u.ac.jp [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Maruwa Foods Co. Ltd, Tsutsui-cho 170-1, Yamatokoriyama, Nara 639-1123 (Japan)

    2007-10-01

    Old yellow enzyme from Trypanosoma cruzi, has been crystallized using the hanging-drop vapour-diffusion method. Old yellow enzyme (OYE) is an NADPH oxidoreductase that contains a flavin mononucleotide as a prosthetic group. The OYE from Trypanosoma cruzi, which produces prostaglandin F{sub 2?}, a potent mediator of various physiological and pathological processes, from prostaglandin H2. The protein was recombinantly expressed and purified from Escherichia coli and was crystallized using the hanging-drop vapour-diffusion method. The crystal belongs to the monoclinic space group P2{sub 1}, with unit-cell parameters a = 56.3, b = 78.8, c = 78.8 Å, ? = 93.4° and two molecules per asymmetric unit. The crystals were suitable for X-ray crystallographic studies and diffracted to 1.70 Å resolution. A Patterson search method is in progress using the structure of OYE from Pseudomonas putida as a starting model.

  17. Some Groups Having Only Elementary Actions on Metric Spaces with Hyperbolic Boundaries

    Microsoft Academic Search

    Anders Karlsson; Guennadi A. Noskov

    2004-01-01

    We study isometric actions of certain groups on metric spaces with hyperbolic-type bordifications. The class of groups considered includes SLn(Z), Artin braid groups and mapping class groups of surfaces (except the lower rank ones). We prove that in various ways such actions must be elementary. Most of our results hold for non-locally compact spaces and extend what is known for

  18. Group systems, groupoids, and moduli spaces of parabolic bundles

    Microsoft Academic Search

    K. Guruprasad; J. Huebschmann; L. Jeffrey; A. Weinstein

    1995-01-01

    Let $G$ be a Lie group, with an invariant non-degenerate symmetric bilinear form on its Lie algebra, let $\\\\pi$ be the fundamental group of an orientable (real) surface $M$ with a finite number of punctures, and let $\\\\bold C$ be a family of conjugacy classes in $G$, one for each puncture. A finite-dimensional construction used earlier to obtain a symplectic

  19. Group Action Recognition Using Space-Time Interest Points

    E-print Network

    Ling, Haibin

    in computer vision due to the large complexity induced by multiple motion patterns. This paper aims the number of people in the group action. our purpose is to distinguish the group actions, just as basketball. In fact, the system has a linear time complexity, given previously extracted features. The rest

  20. Root filtration spaces from Lie algebras and abstract root groups 1

    E-print Network

    Cohen, Arjeh M.

    Root filtration spaces from Lie algebras and abstract root groups 1 Arjeh M. Cohen a, G subgroups and simple Lie algebras generated by extremal elements lead to root filtration spaces of buildings. Here we show how to obtain the root filtration space axioms from root subgroups and classical Lie

  1. 'Seeing' atoms: the crystallographic revolution.

    PubMed

    Schwarzenbach, Dieter

    2014-01-01

    Laue's experiment in 1912 of the diffraction of X-rays by crystals led to one of the most influential discoveries in the history of science: the first determinations of crystal structures, NaCl and diamond in particular, by W. L. Bragg in 1913. For the first time, the visualisation of the structure of matter at the atomic level became possible. X-ray diffraction provided a sort of microscope with atomic resolution, atoms became observable physical objects and their relative positions in space could be seen. All branches of science concerned with matter, solid-state physics, chemistry, materials science, mineralogy and biology, could now be firmly anchored on the spatial arrangement of atoms. During the ensuing 100 years, structure determination by diffraction methods has matured into an indispensable method of chemical analysis. We trace the history of the development of 'small-structure' crystallography (excepting macromolecular structures) in Switzerland. Among the pioneers figure Peter Debye and Paul Scherrer with powder diffraction, and Paul Niggli and his Zurich School with space group symmetry and geometrical crystallography. Diffraction methods were applied early on by chemists at the Universities of Bern and Geneva. By the 1970s, X-ray crystallography was firmly established at most Swiss Universities, directed by full professors. Today, chemical analysis by structure determination is the task of service laboratories. However, the demand of diffraction methods to solve problems in all disciplines of science is still increasing and powerful radiation sources and detectors are being developed in Switzerland and worldwide. PMID:24801690

  2. An orientation for the SU(2) -representation space of knot groups

    Microsoft Academic Search

    Michael Heusener; Blaise Pascal

    2003-01-01

    The aim of this paper is to study the SU(2)-representation spaces of knot groups. For a given a knot k?S3 we denote by R(k) the space of equivalence classes of irreducible representations of the knot group ?1(S3?k) in SU(2) and we denote by Reg(k)?R(k) the space of regular representations. It is well known that Reg(k)?R(k) is a real one-dimensional manifold.The

  3. The nature and space density of fossil groups of galaxies

    E-print Network

    L. R. Jones; T. J. Ponman; A. Horton; A. Babul; H. Ebeling; D. J. Burke

    2003-04-14

    We describe the properties of a sample of galaxy groups with very unusual distributions of galaxy luminosities. The most extreme example has an X-ray luminosity similar to that of the Virgo cluster but has a very low richness, with only one galaxy brighter than L*, compared with six in Virgo. That one galaxy, however, is optically more luminous than any galaxy in Virgo and has an optical luminosity as bright as many of the central cD galaxies in rich Abell clusters. The characteristic feature of the fossil groups we study is that most of the light arises from one dominant, central galaxy. We define a fossil system and, based on this definition, construct a small X-ray selected, flux-limited sample of fossil groups with well known selection criteria. We confirm that these systems are indeed groups of galaxies, but dominated by one central luminous giant elliptical galaxy and with few, or no, L* galaxies. We find that fossil systems represent 8%-20% of all systems of the same X-ray luminosity. Fossil groups are at least as numerous as all poor and rich clusters combined, and are thus a possible site for the formation of luminous central cluster galaxies before infall into clusters occurs. The fossil systems in our sample have significantly higher X-ray luminosities than normal groups of similar total optical luminosities (or similar X-ray temperature, where the latter can be measured). These enhanced X-ray luminosities may be due to relatively cool gas in the innermost regions or due to a low central gas entropy. We interpret fossil groups as old, undisturbed systems which have avoided infall into clusters, but where galaxy merging of most of the L* galaxies has occurred. An early formation epoch, before that of most groups, could explain low central gas entropies and high X-ray luminosities.

  4. Group calls for space policies to transcend politics

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2012-06-01

    At a 22 May briefing, the American Institute of Aeronautics and Astronautics (AIAA) called on Congress to “establish space exploration policy goals which transcend partisan political differences.” AIAA president and former NASA administrator Michael Griffin said the “goal of establishing human capability to b e a space-faring species is not a short-term goal,” nor is it a goal that belongs to only one political party. “We will not reach long-term goals without a stable, coherent, sensible plan that transcends elections and leaders,” said Griffin, who has provided advice to Republican U.S. presidential candidate Mitt Romney. Griffin pointed to NASA's 2008 authorization as providing the kind of vision needed for NASA. The act called for human return to the Moon and preparation for the capability for permanent bases on the Moon, among other things, he said. “That's the kind of thing that we need. All of the goals espoused by the 2008 act were long-term, generational, strategic in scope,” Griffin said, adding that the act, which had bipartisan support, demonstrated “the kind of societal support, rather than political support, that I believe our space program deserves.”

  5. Marathons versus Spaced Groups: Skin Conductance and the Effects of Time Distribution on Encounter Group Learning.

    ERIC Educational Resources Information Center

    Loomis, Thomas P.

    1988-01-01

    Randomly assigned 41 students to 2 twice-weekly groups, which met for 3 hours eight times; 2 marathons, which met continuously for 24 hours; and nontreatment control group. Treatment groups had significant positive changes on 14 of 15 measured personality variables between pre- and post-test, and positive change on all dependent measures between…

  6. SYMPLECTORMOPHISM GROUPS OF NON-COMPACT MANIFOLDS, ORBIFOLD BALLS, AND A SPACE OF

    E-print Network

    Hind, Richard

    the contact manifold is a Lens space L(n, 1) the compactly supported symplectomorphism group Sympc(sL(n, 1 RICHARD HIND, MARTIN PINSONNAULT, WEIWEI WU Abstract. We establish connections between contact isometry groups of cer- tain contact manifolds and compactly supported symplectomorphism groups

  7. Motions and pattern analysis: harmonic analysis on motion groups and their homogeneous spaces

    Microsoft Academic Search

    Jean-Paul Gauthier; Guy Bornard; Martine Silbermann

    1991-01-01

    Fourier-like transforms that are defined on several groups of motions on the plane and on the plane itself (viewed as the homogeneous space of these motion groups) are presented. These transforms should have many applications in the area of pattern recognition, detection, and the representation of motions in pattern analysis. The method is based upon group-representation theory and abstract harmonic

  8. Polyimides Containing Pendent Phosphine Oxide Groups for Space Applications

    NASA Technical Reports Server (NTRS)

    Thompson, C. M.; Smith, J. G., Jr.; Watson, K. A.; Connell, J. W.

    2002-01-01

    As part of an ongoing materials development activity to produce high performance polymers that are durable to the space environment, phosphine oxide containing polyimides have been under investigation. A novel dianhydride was prepared from 2,5-dihydroxyphenyldiphenylphosphine oxide in good yield. The dianhydride was reacted with commercially available diamines, and a previously reported diamine was reacted with commercially available dianhydrides to prepare isomeric polyimides. The physical and mechanical properties, particularly thermal and optical properties, of the polymers were determined. One material exhibited a high glass transition temperature, high tensile properties, and low solar absorptivity. The chemistry, physical, and mechanical properties of these resins will be discussed.

  9. Distributed Space-Time Block Coded OFDM with Subcarrier Grouping

    Microsoft Academic Search

    Nam H. Vien; Ha H. Nguyen; Tho Le-ngoc

    2008-01-01

    It has been shown that relaying systems can offer spatial and multipath diversity in amplify-and-forward (AF) relay-assisted transmission over frequency-selective fading channels when trellis coded modulation (TCM) is applied as an outer code. However, the price for such advantages is the high decoding complexity. To overcome this disadvantage, the technique of subcarrier grouping is applied for orthogonal frequency division multiplexing

  10. Expression, purification, crystallization and preliminary crystallographic analysis of the proliferation-associated protein Ebp1.

    PubMed

    Kowalinski, Eva; Bange, Gert; Wild, Klemens; Sinning, Irmgard

    2007-09-01

    ErbB-3-binding protein 1 (Ebp1) is a member of the family of proliferation-associated 2G4 proteins (PA2G4s) and plays a role in cellular growth and differentiation. Ligand-induced activation of the transmembrane receptor ErbB3 leads to dissociation of Ebp1 from the receptor in a phosphorylation-dependent manner. The non-associated protein is involved in transcriptional and translational regulation in the cell. Here, the overexpression, purification, crystallization and preliminary crystallographic studies of Ebp1 from Homo sapiens are reported. Initially observed crystals were improved by serial seeding to single crystals suitable for data collection. The optimized crystals belong to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2 and diffracted to a resolution of 1.6 A. PMID:17768350

  11. Expression, purification, crystallization and preliminary crystallographic analysis of the proliferation-associated protein Ebp1

    PubMed Central

    Kowalinski, Eva; Bange, Gert; Wild, Klemens; Sinning, Irmgard

    2007-01-01

    ErbB-3-binding protein 1 (Ebp1) is a member of the family of proliferation-associated 2G4 proteins (PA2G4s) and plays a role in cellular growth and differentiation. Ligand-induced activation of the transmembrane receptor ErbB3 leads to dissociation of Ebp1 from the receptor in a phosphorylation-dependent manner. The non-associated protein is involved in transcriptional and translational regulation in the cell. Here, the overexpression, purification, crystallization and preliminary crystallographic studies of Ebp1 from Homo sapiens are reported. Initially observed crystals were improved by serial seeding to single crystals suitable for data collection. The optimized crystals belong to the tetragonal space group P41212 or P43212 and diffracted to a resolution of 1.6?Å. PMID:17768350

  12. Expression, purification, crystallization and preliminary crystallographic analysis of human Rad GTPase

    SciTech Connect

    Yanuar, Arry; Sakurai, Shigeru; Kitano, Ken [Structural Biology Laboratory, Nara Institute of Science and Technology (Japan); Hakoshima, Toshio, E-mail: hakosima@bs.naist.jp [Structural Biology Laboratory, Nara Institute of Science and Technology (Japan); CREST, Japan Science and Technology Agency, Keihanna Science City, Nara 630-0192 (Japan)

    2005-11-01

    Human Rad has been crystallized. A diffraction data set was collected to a resolution of 1.8 Å. Human Rad is a new member of the Ras GTPase superfamily and is overexpressed in human skeletal muscle of individuals with type II diabetes. The GTPase core domain was overexpressed in Escherichia coli and purified for crystallization. Crystals were obtained at 293 K by vapour diffusion using a crystallization robot. The crystals were found to belong to space group P2{sub 1}, with unit-cell parameters a = 52.2, b = 58.6, c = 53.4 Å, ? = 97.9°, and contained two Rad molecules in the crystallographic asymmetric unit. A diffraction data set was collected to a resolution of 1.8 Å using synchrotron radiation at SPring-8.

  13. Crystallization and preliminary X-ray crystallographic analysis of verotoxin-1 B-subunit.

    PubMed

    Boodhoo, A; Read, R J; Brunton, J

    1991-10-01

    The B-subunit of verotoxin-1, which is believed to form a pentamer (monomer Mr = 7691), has been crystallized by vapor diffusion over a wide range of conditions. The best crystals, obtained with polyethylene glycol 8000 as the precipitant, belong to the orthorhombic space group P2(1)2(1)2(1), with cell dimensions a = 59.2 A, b = 102.7 A, c = 56.3 A. The cell dimensions are consistent with one B-subunit pentamer per asymmetric unit, and the crystals diffract to at least 2.0 A resolution. Data collected using synchrotron radiation at a wavelength of 2.070 A may allow the structure to be solved using the anomalous signal from three sulfur atoms in the monomer, combined with averaging over the non-crystallographic symmetry. PMID:1942026

  14. Crystallographic characterization of the radixin FERM domain bound to the cytoplasmic tails of adhesion molecules CD43 and PSGL-1

    SciTech Connect

    Takai, Yumiko; Kitano, Ken; Terawaki, Shin-ichi; Maesaki, Ryoko [Structural Biology Laboratory, Nara Institute of Science and Technology, Keihanna Science City, Nara 630-0192 (Japan); Hakoshima, Toshio, E-mail: hakosima@bs.naist.jp [Structural Biology Laboratory, Nara Institute of Science and Technology, Keihanna Science City, Nara 630-0192 (Japan); CREST, Japan Science and Technology Agency, Keihanna Science City, Nara 630-0192 (Japan)

    2007-01-01

    The radixin FERM domain has been crystallized in complex with CD43 and PSGL-1 peptides. Diffraction data sets were collected from the complexes to 2.9 and 2.8 Å resolution, respectively. Radixin is a member of the ERM proteins that cross-link plasma membranes and actin filaments. The FERM domains located in the N-terminal regions of ERM proteins are responsible for membrane association through direct interaction with the cytoplasmic tails of integral membrane proteins. Here, crystals of the radixin FERM domain bound to the cytoplasmic peptides of two adhesion molecules, CD43 and PSGL-1, have been obtained. Crystals of the radixin FERM domain bound to CD43 belong to space group P4{sub 3}22, with unit-cell parameters a = b = 68.72, c = 201.39 Å, and contain one complex in the crystallographic asymmetric unit. Crystals of the radixin FERM domain bound to PSGL-1 belong to space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 80.74, b = 85.73, c = 117.75 Å, and contain two complexes in the crystallographic asymmetric unit. Intensity data sets were collected to a resolution of 2.9 Å for the FERM–CD43 complex and 2.8 Å for the FERM–PSGL-1 complex.

  15. Crystallization and preliminary crystallographic analysis of l-asparaginase from Erwinia carotovora

    SciTech Connect

    Wikman, Linnea E. K. [Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Turku 20521 (Finland); Krasotkina, Julya; Kuchumova, Anastasia; Sokolov, Nikolay N. [Institute for Biomedical Chemistry, Russian Academy of Medical Sciences, 559-B, 10 Pogodinskay St, Moscow 119121 (Russian Federation); Papageorgiou, Anastassios C., E-mail: tassos.papageorgiou@btk.fi [Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Turku 20521 (Finland)

    2005-04-01

    Er. carotovoral-asparaginase, a potential antileukaemic agent, has been crystallized. Crystals diffract to 2.6 Å using a rotating-anode source and belong to space group P2{sub 1}, with unit-cell parameters a = 78.0, b = 112.3, c = 78.7 Å, ? = 101.9° and a homotetramer in the crystallographic asymmetric unit. Bacterial l-asparaginases have been used as therapeutic agents in the treatment of acute childhood lymphoblastic leukaemia for over 30 y. However, their use is limited owing to the glutaminase activity of the administered enzymes, which results in serious side effects. In contrast, l-asparaginase from Erwinia carotovora exhibits low glutaminase activity at physiological concentrations of l-asparagine and l-glutamine in the blood. Recombinant Er. carotovoral-asparaginase was crystallized in the presence of l-glutamate by the hanging-drop vapour-diffusion method using 10 mg ml{sup ?1} purified enzyme, 16–18%(w/v) PEG 3350 and 0.2 M NaF. X-ray diffraction data were collected to 2.6 Å at 293 K using an in-house rotating-anode generator. The crystals belong to the monoclinic P2{sub 1} space group, with unit-cell parameters a = 78.0, b = 112.3, c = 78.7 Å, ? = 101.9° and a homotetramer in the crystallographic asymmetric unit. A molecular-replacement solution has been found and refinement is currently in progress. The crystal structure may provide leads towards protein-engineering efforts aimed at safer asparaginase administration in leukaemia treatment.

  16. Purification, crystallization and preliminary crystallographic analysis of 3-hydroxyacyl-CoA dehydrogenase from Caenorhabditis elegans

    PubMed Central

    Xu, Yingzhi; Sun, Fei

    2013-01-01

    3-Hydroxyacyl-CoA dehydrogenase (HAD; EC 1.1.1.35) is the enzyme that catalyzes the third step in fatty-acid ?-oxidation, oxidizing the hydroxyl group of 3-hydroxyacyl-CoA to a keto group. The 3-hydroxyacyl-CoA dehydrogenase from Caenorhabditis elegans (cHAD) was cloned, overexpressed in Escherichia coli and purified to homogeneity for crystallography. Initial crystals were obtained by the hanging-drop vapour-diffusion method. Optimization of the precipitant concentration and the pH yielded two types of well diffracting crystals with parallelepiped and cuboid shapes, respectively. Complete diffraction data sets were collected and processed from both crystal types. Preliminary crystallographic analysis indicated that the parallelepiped-shaped crystal belonged to space group P1, while the cuboid-shaped crystal belonged to space group P212121. Analyses of computed Matthews coefficient and self-rotation functions suggested that there are two cHAD molecules in one asymmetric unit in both crystals, forming identical dimers but packing in distinct manners. PMID:23695566

  17. Unitary Space-Time Constellations Based on Finite Reflection Group Codes

    E-print Network

    Nevins, Monica

    1 Unitary Space-Time Constellations Based on Finite Reflection Group Codes Terasan Niyomsataya, Ali diversity unitary space-time constellations for two transmitter antennas. Our proposed constellations unitary constellation designs in the literature. I. INTRODUCTION Consider a multiple-antenna system with M

  18. Outreach of Astronomy with emphasis to the Solar System by the Space group in Greece

    Microsoft Academic Search

    X. Moussas; K. Dialynas; G. Babasides; G. Fasoulopoulos; V. Dimitropoulou; D. Prassopoulos; S. Kouphos; E. Spandagos; J. Strikis

    2006-01-01

    We have a long tradition in Space and Solar System outreach at the University of Athens (Space Group). We have contributed with many popular science articles in encyclopaedias (a total of some 200000 words), magazines and newspapers, public lectures around Greece and radio and TV programmes. We contribute in exhibitions for the public on many occasions (e.g. The British Exploration

  19. Spacing pattern in a social group of stray cats: effects on male reproductive success

    Microsoft Academic Search

    Ludovic Say; Dominique Pontier

    2004-01-01

    Reproductive consequences of male spacing patterns have received relatively little attention in nonterritorial mammals, in particular in group-living species, where most studies have focused on the relation between social rank and reproductive success. We investigated the effects of spacing pattern on male reproductive success within a social, nonterritorial, promiscuous population of stray cats, Felis catus. Male home ranges overlapped home

  20. The Chow group of the moduli space of marked cubic surfaces

    Microsoft Academic Search

    Elisabetta Colombo; Bert van Geemen

    2004-01-01

    Naruki gave an explicit construction of the moduli space of marked cubic surfaces, starting from a toric variety and proceeding with blow-ups and contractions. Using his result, we compute the Chow groups and the Chern classes of this moduli space. As an application we relate a recent result of Freitag on the Hilbert polynomial of a certain ring of modular

  1. Yang-Mills theory as Schroedinger quantum mechanics on the space of gauge-group orbits

    SciTech Connect

    Gawedzki, K.

    1982-12-15

    Recent proposals to study Yang-Mills theory on the space of gauge-group orbits are reconsidered. In particular, it is shown that the right formal Hamiltonian is not given by -h/sup 2//2 times the Laplace-Beltrami operator plus the standard ''magnetic field'' potential, as was suggested, but has an additional potential term proportional to h/sup 2/ and is expressible in terms of the geometry not only of the space of gauge-group orbits but also of the orbits themselves as embedded in the space of gauge fields. Formal discussion of the continuum fields is substantiated by a rigorous consideration of lattice gauge theory.

  2. Crystallographic influences on pressure solution in a Quartzose Sandstone

    SciTech Connect

    Hicks, B.D.; Houseknecht, D.W.; Applin, K.R.

    1985-02-01

    The solubility of quartz differs with crystallographic direction. A universal stage was used to measure the orientations of the optic axes and contact planes of 160 pairs of quartz grains in the Bromide Formation (Simpson Group) of Oklahoma. These quartz grains exhibit long, sutured, and concave-convex contacts. Results indicate that the geometry of a pressolved contact is independent of the crystallographic orientation of opposing grains. However, given a concave-convex contact, the optic axis of the concave grain tends to lie at a higher angle to the contact plane than the optic axis of the convex grain. The authors conclude that the extent and type of pressure-solution contacts in quartzose sandstones are not significantly influenced by crystallographic orientation. Other factors, such as grain size and clay content, are probably more important in controlling the pressure-solution features. Geometric etch pits, which form at the point of emergence of crystal defects, were produced by hydrothermally etching quartz crystals, quartz sand, and quartzose sandstones. The abundance, nature, and distribution pattern of crystal defects inherited from source rocks might be more important factors in affecting pressure solution of quartz grains than differences in quartz solubilities arising solely from variations in Si-O bond strengths. The extent of etch-pit formation on quartz cement may also serve as a qualitative indicator of the dissolved silica saturation in pore fluids.

  3. The quaternionic affine group and related continuous wavelet transforms on complex and quaternionic Hilbert spaces

    NASA Astrophysics Data System (ADS)

    Ali, S. Twareque; Thirulogasanthar, K.

    2014-06-01

    By analogy with the real and complex affine groups, whose unitary irreducible representations are used to define the one- and two-dimensional continuous wavelet transforms, we study here the quaternionic affine group and construct its unitary irreducible representations. These representations are constructed both on a complex and on a quaternionic Hilbert space. As in the real and complex cases, the representations for the quaternionic group also turn out to be square-integrable. Using these representations we construct quaternionic wavelets and continuous wavelet transforms on both the complex and quaternionic Hilbert spaces.

  4. The Quaternionic Affine Group and Related Continuous Wavelet Transforms on Complex and Quaternionic Hilbert Spaces

    E-print Network

    S. Twareque Ali; K. Thirulogasanthar

    2014-02-13

    By analogy with the real and complex affine groups, whose unitary irreducible representations are used to define the one and two-dimensional continuous wavelet transforms, we study here the quaternionic affine group and construct its unitary irreducible representations. These representations are constructed both on a complex and a quaternionic Hilbert space. As in the real and complex cases, the representations for the quaternionic group also turn out to be square-integrable. Using these representations we constrct quaternionic wavelets and continuous wavelet transforms on both the complex and quaternionic Hilbert spaces.

  5. The effect of in-line spacing of two cylinder groups on the Morison force coefficients

    SciTech Connect

    Smith, D.J.; Haritos, N. [Univ. of Melbourne (Australia). Dept. of Civil and Environmental Engineering

    1996-12-31

    This paper describes some results from an experimental study undertaken in the University of Melbourne`s Michell Laboratory which has investigated the interference effect associated with closely spaced cylinder groups on the in-line Morison force coefficients. Previous experimental studies undertaken at the University of Melbourne identified that the closely spaced cylinder range, (spacing to diameter ratio less than 3), is critical to the determination of the Morison force coefficients for tandem cylinders. The current research extends the previous work conducted in the department by investigating in more detail the closely spaced cylinder regime whilst extending results into the drag dominant regime (Keulegan-Carpenter number > 20). Results presented herein are limited to the exploration of the effect of varying the spacing of two cylinder groups oriented in-line to the direction of the uni-directional waves.

  6. [6] CRYSTALLOGRAPHIC STUDIES ON RIBOSOMES 95 [6] Crystallographic and Image Reconstruction Studies

    E-print Network

    Yonath, Ada E.

    . These include the whole 70S ribosomes of Bacillus stearothermophilus and E. coli, the 30S subunits of Thermus[6] CRYSTALLOGRAPHIC STUDIES ON RIBOSOMES 95 [6] Crystallographic and Image Reconstruction Studies on Ribosomal Particles from Bacterial Sources By A. YONATHand H. G. WITTMANN Introduction Diffraction methods

  7. Current Activities and Capabilities of the Terrestrial Environment Group at NASA's Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Roberts, Barry C.; Batts, Wade

    1997-01-01

    The National Aeronautics and Space Administration (NASA) designated Marshall Space Flight Center (MSFC) the center of excellence for space transportation. The Aerospace Environments and Effects (AEE) team of the Electromagnetics and Aerospace Environments Branch (EL23) in the Systems Analysis and Integration Laboratory at MSFC, supports the center of excellence designation by providing near-Earth space, deep space, planetary, and terrestrial environments expertise to projects as required. The Terrestrial Environment (TE) group within the AEE team maintains an extensive TE data base. Statistics and models derived from this data are applied to the design and development of new aerospace vehicles, as well as performance enhancement of operational vehicles such as the Space Shuttle. The TE is defined as the Earth's atmospheric environment extending from the surface to orbital insertion altitudes (approximately 90 km).

  8. Parametric Realization of the Lorentz Transformation Group in Pseudo-Euclidean Spaces

    E-print Network

    Abraham A. Ungar

    2015-05-09

    The Lorentz transformation group $SO(m,n)$ is a group of Lorentz transformations of order $(m,n)$, that is, a group of special linear transformations in a pseudo-Euclidean space of signature $(m,n)$ that leave the pseudo-Euclidean inner product invariant. A parametrization of $SO(m,n)$ is presented, giving rise to the composition law of Lorentz transformations of order $(m,n)$ in terms of parameter composition. The parameter composition, in turn, gives rise to a novel group-like structure called a bi-gyrogroup. Bi-gyrogroups form a natural generalization of gyrogroups where the latter form a natural generalization of groups. Like the abstract gyrogroup, the abstract bi-gyrogroup can play a universal computational role which extends far beyond the domain of pseudo-Euclidean spaces.

  9. X-ray Crystallographic, Scanning Microprobe X-ray Diffraction, and Cross-Polarized/Magic Angle Spinning [superscript 13]C NMR Studies of the Structure of Cellulose III[subscript II

    SciTech Connect

    Wada, Masahisa; Heux, Laurent; Nishiyama, Yoshiharu; Langan, Paul; (U of Tokyo); (CNRS-CRMD); (LANL)

    2009-03-16

    The X-ray crystallographic structure of cellulose III{sub II} is characterized by disorder; the unit cell (space group P2{sub 1}; a = 4.45 {angstrom}, b = 7.64 {angstrom}, c = 10.36 {angstrom}, {alpha} = {beta} = 90{sup o}, {gamma} = 106.96{sup o}) is occupied by one chain that is the average of statistically disordered antiparallel chains. {sup 13}C CP/MAS NMR studies reveal the presence of three distinct molecular conformations that can be interpreted as a mixture of two different crystal forms, one equivalent to cellulose III{sub I}, and another with two independent glucosyl conformations in the asymmetric unit. Both X-ray crystallographic and {sup 13}C NMR spectroscopic results are consistent with an aggregated microdomain structure for cellulose III{sub II}. This structure can be generated from a new crystal form (space group P2{sub 1}; a = 4.45 {angstrom}, b = 14.64 {angstrom}, c = 10.36 {angstrom}, {alpha} = {beta} = 90{sup o}, {gamma} = 90.05{sup o}; two crystallographically independent and antiparallel chains; gt hydroxymethyl groups) by multiple dislocation defects. These defects produce microdomains of the new crystal form and cellulose III{sub I} that scanning microprobe diffraction studies show are distributed consistently through the cellulose III{sub II} fiber.

  10. Surface structure, crystallographic and ice-nucleating properties of cellulose

    NASA Astrophysics Data System (ADS)

    Hiranuma, Naruki; Möhler, Ottmar; Kiselev, Alexei; Saathoff, Harald; Weidler, Peter; Shutthanandan, Shuttha; Kulkarni, Gourihar; Jantsch, Evelyn; Koop, Thomas

    2015-04-01

    Increasing evidence of the high diversity and efficient freezing ability of biological ice-nucleating particles is driving a reevaluation of their impact upon climate. Despite their potential importance, little is known about their atmospheric abundance and ice nucleation efficiency, especially non-proteinaceous ones, in comparison to non-biological materials (e.g., mineral dust). Recently, microcrystalline cellulose (MCC; non-proteinaceous plant structural polymer) has been identified as a potential biological ice-nucleating particle. However, it is still uncertain if the ice-nucleating activity is specific to the MCC structure or generally relevant to all cellulose materials, such that the results of MCC can be representatively scaled up to the total cellulose content in the atmosphere to address its role in clouds and the climate system. Here we use the helium ion microscopy (HIM) imaging and the X-ray diffraction (XRD) technique to characterize the nanoscale surface structure and crystalline properties of the two different types of cellulose (MCC and fibrous cellulose extracted from natural wood pulp) as model proxies for atmospheric cellulose particles and to assess their potential accessibility for water molecules. To complement these structural characterizations, we also present the results of immersion freezing experiments using the cold stage-based droplet freezing BINARY (Bielefeld Ice Nucleation ARaY) technique. The HIM results suggest that both cellulose types have a complex porous morphology with capillary spaces between the nanoscale fibrils over the microfiber surface. These surface structures may make cellulose accessible to water. The XRD results suggest that the structural properties of both cellulose materials are in agreement (i.e., P21 space group; a=7.96 Å, b=8.35 Å, c=10.28 Å) and comparable to the crystallographic properties of general monoclinic cellulose (i.e., Cellulose I?). The results obtained from the BINARY measurements suggest that there is no significant difference of the immersion ice nucleation activity of MCC and fibrous cellulose in supercooled water. Overall, our findings support the view that MCC may be a good proxy for inferring water uptake, wettability and ice nucleating properties of various cellulose materials. In addition, we discuss the ice-nucleating efficiencies of both cellulose samples and plant debris from the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) chamber experiments in comparison to the BINARY results. The influence of the acid processing of cellulose on its ice nucleation propensity may also be discussed to further demonstrate their atmospheric relevancy. Acknowledgement: We acknowledge support by German Research Society (DFG) and Ice Nuclei research UnIT (FOR 1525 INUIT).

  11. Johnson Space Center's Risk and Reliability Analysis Group 2008 Annual Report

    NASA Technical Reports Server (NTRS)

    Valentine, Mark; Boyer, Roger; Cross, Bob; Hamlin, Teri; Roelant, Henk; Stewart, Mike; Bigler, Mark; Winter, Scott; Reistle, Bruce; Heydorn,Dick

    2009-01-01

    The Johnson Space Center (JSC) Safety & Mission Assurance (S&MA) Directorate s Risk and Reliability Analysis Group provides both mathematical and engineering analysis expertise in the areas of Probabilistic Risk Assessment (PRA), Reliability and Maintainability (R&M) analysis, and data collection and analysis. The fundamental goal of this group is to provide National Aeronautics and Space Administration (NASA) decisionmakers with the necessary information to make informed decisions when evaluating personnel, flight hardware, and public safety concerns associated with current operating systems as well as with any future systems. The Analysis Group includes a staff of statistical and reliability experts with valuable backgrounds in the statistical, reliability, and engineering fields. This group includes JSC S&MA Analysis Branch personnel as well as S&MA support services contractors, such as Science Applications International Corporation (SAIC) and SoHaR. The Analysis Group s experience base includes nuclear power (both commercial and navy), manufacturing, Department of Defense, chemical, and shipping industries, as well as significant aerospace experience specifically in the Shuttle, International Space Station (ISS), and Constellation Programs. The Analysis Group partners with project and program offices, other NASA centers, NASA contractors, and universities to provide additional resources or information to the group when performing various analysis tasks. The JSC S&MA Analysis Group is recognized as a leader in risk and reliability analysis within the NASA community. Therefore, the Analysis Group is in high demand to help the Space Shuttle Program (SSP) continue to fly safely, assist in designing the next generation spacecraft for the Constellation Program (CxP), and promote advanced analytical techniques. The Analysis Section s tasks include teaching classes and instituting personnel qualification processes to enhance the professional abilities of our analysts as well as performing major probabilistic assessments used to support flight rationale and help establish program requirements. During 2008, the Analysis Group performed more than 70 assessments. Although all these assessments were important, some were instrumental in the decisionmaking processes for the Shuttle and Constellation Programs. Two of the more significant tasks were the Space Transportation System (STS)-122 Low Level Cutoff PRA for the SSP and the Orion Pad Abort One (PA-1) PRA for the CxP. These two activities, along with the numerous other tasks the Analysis Group performed in 2008, are summarized in this report. This report also highlights several ongoing and upcoming efforts to provide crucial statistical and probabilistic assessments, such as the Extravehicular Activity (EVA) PRA for the Hubble Space Telescope service mission and the first fully integrated PRAs for the CxP's Lunar Sortie and ISS missions.

  12. Crystallographic orientation assessment by electron backscattered diffraction.

    PubMed

    Cléton, F; Jouneau, P H; Henry, S; Gäumann, M; Buffat, P A

    1999-01-01

    With an angular orientation accuracy of at least 1 , the ability of electron backscattered diffraction (EBSD) to determine and emphasise crystallographic orientation is illustrated. Using the abilities of specially developed software for computing Euler angles derived from the scanned specimen, misorientations are pointed out with acceptable flexibility and graphic output through crystallographic orientation maps or pole figures. This ability is displayed in the particular case of laser cladding of nickel-based superalloy, a process that combines the advantages of a near net-shape manufacturing and a close control of the solidification microstructure (E-LMF: epitaxial laser metal forming). PMID:10483877

  13. A Hilbert Space Operator Representation of Abelian Po-Groups of Bilinear Forms

    NASA Astrophysics Data System (ADS)

    Janda, Ji?í; Paseka, Jan

    2015-02-01

    The existence of a non-trivial singular positive bilinear form Simon (J. Funct. Analysis 28, 377-385 (1978)) yields that on an infinite-dimensional complex Hilbert space H the set of bilinear forms F(H) is richer than the set of linear operators {V}(H). We show that there exists an structure preserving embedding of partially ordered groups from the abelian po-group {S}D(H) of symmetric bilinear forms with a fixed domain D on a Hilbert space {H} into the po-group of linear symmetric operators on a dense linear subspace of an infinite dimensional complex Hilbert spacel 2(M). Moreover, if we restrict ourselves to the positive parts of the above mentioned po-groups, we can embed positive bilinear forms into corresponding positive linear operators.

  14. The Determination of the Orbit Spaces of Compact Coregular Linear Groups

    E-print Network

    Vittorino Talamini

    2015-03-26

    Some aspects of phase transitions can be more conveniently studied in the orbit space of the action of the symmetry group. After a brief review of the fundamental ideas of this approach, I shall concentrate on the mathematical aspect and more exactly on the determination of the equations defining the orbit space and its strata. I shall deal only with compact coregular linear groups. The method exposed has been worked out together with prof. G. Sartori and it is based on the solution of a matrix differential equation. Such equation is easily solved if an integrity basis of the group is known. If the integrity basis is unknown one may determine anyway for which degrees of the basic invariants there are solutions to the equation, and in all these cases also find out the explicit form of the solutions. The solutions determine completely the stratification of the orbit spaces. Such calculations have been carried out for 2, 3 and 4-dimensonal orbit spaces. The method is of general validity but the complexity of the calculations rises tremendously with the dimension $q$ of the orbit space. Some induction rules have been found as well. They allow to determine easily most of the solutions for the $(q+1)$-dimensional case once the solutions for the $q$-dimensional case are known. The method exposed is interesting because it allows to determine the orbit spaces without using any specific knowledge of group structure and integrity basis and evidences a certain hidden and yet unknown link with group theory and invariant theory.

  15. Crystallographic Data Centre Services and Publications.

    ERIC Educational Resources Information Center

    Cambridge Univ. (England). Chemical Lab.

    The Cambridge Crystallographic Data Centre is concerned with the retrieval, evaluation, synthesis, and dissemination of structural data based on diffraction methods. The source of input is almost entirely primary journals. Bibliographic information and numeric data on crystal and molecular structures are on magnetic tapes. The bibliographic file…

  16. Crystallographic R Factor Refinement by Molecular Dynamics

    Microsoft Academic Search

    Axel T. Brunger; John Kuriyan; Martin Karplus

    1987-01-01

    Molecular dynamics was used to refine macromolecular structures by incorporating the difference between the observed crystallographic structure factor amplitude and that calculated from an assumed atomic model into the total energy of the system. The method has a radius of convergence that is larger than that of conventional restrained least-squares refinement. Test cases showed that the need for manual corrections

  17. Roars of black howler monkeys (Alouatta caraya): evidence for a function in inter-group spacing

    E-print Network

    Roars of black howler monkeys (Alouatta caraya): evidence for a function in inter-group spacing) Summary Loud calls can be expected to play an important role in the lives of howler monkeys, given the specialised anatomy of howler vocal apparatus and the time and energy invested in call- ing. Here we present

  18. INFLUENCE OF SPAWNING GROUP SIZE AND SPACE ON REPRODUCTION BY SHEEPSHEAD MINNOWS, CYPRINODON VARIEGATUS

    EPA Science Inventory

    Cripe, G.M., R.L. Hemmer and L.R. Goodman. In press. Influence of Spawning Group Size and Space on Reproduction Variability of Sheepshead Minnows, Cyprinodon variegatus (Abstract). To be presented at the SETAC Fourth World Congress, 14-18 November 2004, Portland, OR. 1 p. (ERL,GB...

  19. Automorphic Representations of Adele Groups We have defined the space A(G, ) of auto-

    E-print Network

    Gan, Wee Teck

    Automorphic Representations of Adele Groups We have defined the space A(G, ) of auto- morphic forms the theory of automor- phic forms using adelic language. The reasons, among others, are: · we want a theory theory, it is clean- est to use the adelic framework, as demon- strated in Tate's thesis. 2 #12;Adeles

  20. Real-space renormalization-group approach to the multigrid method

    SciTech Connect

    Vyas, V. (Physics Department, Boston University, Boston, Massachusetts 02215 (US))

    1991-05-15

    We establish the connection between the multigrid algorithms and the real-space renormalization group. This is illustrated with the example of the two-dimensional Euclidean Klein-Gordon equation with random mass. The equation is then numerically solved using a two-level multigrid algorithm.

  1. Characterization of crystalline formate dehydrogenase H from Escherichia coli. Stabilization, EPR spectroscopy, and preliminary crystallographic analysis.

    PubMed

    Gladyshev, V N; Boyington, J C; Khangulov, S V; Grahame, D A; Stadtman, T C; Sun, P D

    1996-04-01

    The selenocysteine-containing formate dehydrogenase H (FDH) is an 80-kDa component of the Escherichia coli formate-hydrogen lyase complex. The molybdenum-coordinated selenocysteine is essential for catalytic activity of the native enzyme. FDH in dilute solutions (30 microg/ml) was rapidly inactivated at basic pH or in the presence of formate under anaerobic conditions, but at higher enzyme concentrations (>/=3 mg/ml) the enzyme was relatively stable. The formate-reduced enzyme was extremely sensitive to air inactivation under all conditions examined. Active formate-reduced FDH was crystallized under anaerobic conditions in the presence of ammonium sulfate and PEG 400. The crystals diffract to 2.6 A resolution and belong to a space group of P4(1)2(1)2 or P4(3)2(1)2 with unit cell dimensions a = b = 146.1 A and c = 82.7 A. There is one monomer of FDH per crystallographic asymmetric unit. Similar diffraction quality crystals of oxidized FDH could be obtained by oxidation of crystals of formate-reduced enzyme with benzyl viologen. By EPR spectroscopy, a signal of a single reduced FeS cluster was found in a crystal of reduced FDH, but not in a crystal of oxidized enzyme, whereas Mo(V) signal was not detected in either form of crystalline FDH. This suggests that Mo(IV)- and the reduced FeS cluster-containing form of the enzyme was crystallized and this could be converted into Mo(VI)- and oxidized FeS cluster form upon oxidation. A procedure that combines anaerobic and cryocrystallography has been developed that is generally applicable to crystallographic studies of oxygen-sensitive enzymes. These data provide the first example of crystallization of a substrate-reduced form of a Se- and Mo-containing enzyme. PMID:8626495

  2. Environmental interactions in Space Exploration: Announcement of the formation of an Environmental Interactions Working Group

    NASA Technical Reports Server (NTRS)

    Kolecki, Joseph C.; Hillard, G. Barry

    1991-01-01

    With the advent of the Space Exploration Initiative, the possibility of designing and using systems on scales not heretofore attempted presents exciting new challenges in systems design and space science. The environments addressed by the Space Exploration Initiative include the surfaces of the Moon and Mars, as well as the varied plasma and field environments which will be encountered by humans and cargo enroute to these destinations. Systems designers will need to understand environmental interactions and be able to model these mechanisms from the earliest conceptual design stages through design completion. To the end of understanding environmental interactions and establishing robotic precursor mission requirements, an Environmental Interactions Working Group has been established as part of the Robotic Missions Working Group. The current paper describes the working group and gives an update of its current activities. Working group charter and operation are reviewed, background information on the environmental interactions and their characteristics is offered, and the current status of the group's activities is presented along with anticipations for the future.

  3. Recombinant production, crystallization and X-ray crystallographic structure determination of peptidyl-tRNA hydrolase from Salmonella typhimurium.

    PubMed

    Vandavasi, Venugopal; Taylor-Creel, Kasey; McFeeters, Robert L; Coates, Leighton; McFeeters, Hana

    2014-07-01

    Peptidyl-tRNA hydrolase (Pth; EC 3.1.1.29) from the pathogenic bacterium Salmonella typhimurium has been cloned, expressed in Escherichia coli and crystallized for X-ray analysis. Crystals were grown using hanging-drop vapor diffusion against a reservoir solution consisting of 0.03?M citric acid, 0.05?M bis-tris propane, 1% glycerol, 3% sucrose, 25% PEG 6000 pH 7.6. Crystals were used to obtain the three-dimensional structure of the native protein at 1.6?Å resolution. The structure was determined by molecular replacement of the crystallographic data processed in space group P2?2?2? with unit-cell parameters a=62.1, b=64.9, c=110.5?Å, ?=?=?=90°. The asymmetric unit of the crystallographic lattice was composed of two copies of the enzyme molecule with a 51% solvent fraction, corresponding to a Matthews coefficient of 2.02?Å3?Da(-1). The structural coordinates reported serve as a foundation for computational and structure-guided efforts towards novel small-molecule Pth1 inhibitors and potential antibacterial development. PMID:25005080

  4. Definition of spacecraft standard interfaces by the NASA Space Assembly and Servicing Working Group (SASWG)

    NASA Technical Reports Server (NTRS)

    Radtke, Robert; Woolley, Charles; Arnold, Lana

    1993-01-01

    The purpose of the NASA Space Assembly and Servicing Working Group (SASWG) is to study enabling technologies for on-orbit spacecraft maintenance and servicing. One key technology required for effective space logistics activity is the development of standard spacecraft interfaces, including the 'Basic Set' defined by NASA, the U.S. Space Command, and industry panelists to be the following: (1) navigation aids; (2) grasping, berthing, and docking; and (3) utility connections for power, data, and fluids. Draft standards have been prepared and referred to professional standards organizations, including the AIAA, EIA, and SAE space standards committee. The objective of the SASWG is to support these committees with the technical expertise required to prepare standards, guidelines, and recommended practices which will be accepted by the ANSI and international standards organizations, including the ISO, IEC, and PASC.

  5. Future In-Space Operations (FISO): A Working Group and Community Engagement

    NASA Technical Reports Server (NTRS)

    Thronson, Harley; Lester, Dan

    2013-01-01

    Long-duration human capabilities beyond low Earth orbit (LEO), either in support of or as an alternative to lunar surface operations, have been assessed at least since the late 1960s. Over the next few months, we will present short histories of concepts for long-duration, free-space human habitation beyond LEO from the end of the Apollo program to the Decadal Planning Team (DPT)/NASA Exploration Team (NExT), which was active in 1999 2000 (see Forging a vision: NASA s Decadal Planning Team and the origins of the Vision for Space Exploration , The Space Review, December 19, 2005). Here we summarize the brief existence of the Future In-Space Operations (FISO) working group in 2005 2006 and its successor, a telecon-based colloquium series, which we co-moderate.

  6. Comparison of phenomenological and crystallographic models for single crystal nickel base superalloys. I. Analytical identification

    Microsoft Academic Search

    Songlin Han; Shuxin Li; David J. Smith

    2001-01-01

    The general formulations of a phenomenological model and a crystallographic model are developed. These models describe the anisotropic viscoplastic deformation of single crystal nickel base superalloys. The two models are then applied to simple uniaxial loading to identify suitable tests for determining the material constants. A group of generic equations has been identified for both models, which can be applied

  7. Preliminary X-ray crystallographic analysis of the d-­xylulose 5-phosphate phospho­ketolase from Lactococcus lactis

    PubMed Central

    Petrareanu, Georgiana; Balasu, Mihaela C.; Zander, Ulrich; Scheidig, Axel J.; Szedlacsek, Stefan E.

    2010-01-01

    Phosphoketolases are thiamine diphosphate-dependent enzymes which play a central role in the pentose-phosphate pathway of heterofermentative lactic acid bacteria. They belong to the family of aldehyde-lyases and in the presence of phosphate ion cleave the carbon–carbon bond of the specific substrate d-­xylulose 5-phosphate (or d-fructose 6-phosphate) to give acetyl phosphate and d-­glyceraldehyde 3-phosphate (or d-erythrose 4-phosphate). Structural information about phosphoketolases is particularly important in order to fully understand their mechanism as well as the steric course of phosphoketolase-catalyzed reactions. Here, the purification, preliminary crystallization and crystallographic characterization of d-xylulose 5-phosphate phosphoketolase from Lactococcus lactis are reported. The presence of thiamine diphosphate during purification was essential for the enzymatic activity of the purified protein. The crystals belonged to the monoclinic space group P21. Diffraction data were obtained to a resolution of 2.2?Å. PMID:20606278

  8. Crystallographic and magnetic properties of Pb2?xBixIr2O7?? (0 ? x ? 2)

    NASA Astrophysics Data System (ADS)

    Retuerto, M.; Sarkar, T.; Li, M.-R.; Ignatov, A.; Croft, M.; Hodges, J. P.; Thao Tran, T.; Shiv Halasyamani, P.; Greenblatt, M.

    2014-12-01

    The title series of compounds have been synthesized by solid state reaction and characterized by x-ray diffraction (PXD), neutron powder diffraction (PND), second harmonic generation (SHG), x-ray absorption spectroscopy (XAS) and magnetization measurements. The crystal structures have been refined from PND data in the centrosymmetric space group Fd\\bar{3}m with pyrochlore structure. No sign of a break of the centrosymmetry has been observed by SHG and no change of the structure to a polar space group in any component of the series, as it was previously reported for Pb2Ir2O7?? with non-centrosymmetric F\\bar{4}3m space group. We have determined by PND that the oxidation state of Ir is slightly decreasing from 5+-to-4+ in the Pb-rich to almost 4+ in the Bi-rich samples. This evolution is confirmed by XAS and also it explains the progression of the crystallographic parameters. All the samples are paramagnetic in the temperature range measured and the magnitude of the effective magnetic moment is enhanced with Bi content, correlated with the enhancement of Ir4+ compared to Ir5+; suggesting Ir5+ to be present in a trigonal antiprism crystal field splitting and therefore Ir4+ as the only magnetic cation.

  9. Phase-space shapes of clusters and rich groups of galaxies

    NASA Astrophysics Data System (ADS)

    Wojtak, Rados?aw

    2013-11-01

    Context. Clusters and groups of galaxies are highly aspherical, with shapes approximated by nearly prolate ellipsoids of revolution. An equally fundamental property is the shape of these objects in velocity space which is the anisotropy of the global velocity dispersion tensor. Although many studies address the problem of the shape in position space, there has been no attempt to measure shapes in velocity space. Aims: Here we make use of kinematical data comprising ~600 nearby clusters and rich groups of galaxies from the Sloan Digital Sky Survey to place constraints on the phase-space shapes of these objects, i.e. their shapes in both position and velocity space. Methods: We show that the line of sight velocity dispersion normalised by a mass-dependent velocity scale correlates with the apparent elongation, with circular (elongated) clusters exhibiting an excessive (decremental) normalised velocity dispersion. This correlation holds for dynamically young or old clusters and, therefore, it originates from projecting their intrinsic phase-space shapes rather than from dynamical evolution. It signifies that clusters are preferentially prolate not only in position space, but also in velocity space. This property allows us to break the degeneracy between oblate and prolate models and thus to deproject the apparent elongations and the line of sight velocity dispersions obtaining constraints on the axial ratios of the ellipsoids approximating cluster shapes in 3D position or velocity space. Results: The distribution of the axial ratios in position space is found to be well approximated by a Gaussian with a mean, ? = 0.66 ± 0.01, and a dispersion, ? = 0.07 ± 0.008. The velocity ellipsoids representing the shapes in velocity space are more spherical, with a mean axial ratio of 0.78 ± 0.03. Conclusions: The mean axial ratio of the velocity ellipsoids points to a highly anisotropic velocity distribution and, therefore, to a strong dependance of the observed velocity dispersions on the angle between the line of sight and the semi-principle axes of the clusters. This finding has important implications for mass measurements based on the line of sight velocity dispersion profiles in individual clusters. For typical axial ratios of the velocity ellipsoids in the analysed cluster sample, systematic errors on the mass estimates inferred from the line of sight velocity dispersions become comparable to statistical uncertainties for galaxy clusters with as few as 40 spectroscopic redshifts.

  10. Equivalence of model space techniques and the renormalization group for a separable model problem

    E-print Network

    S. K. Bogner; T. T. S. Kuo

    2000-12-15

    Lee-Suzuki similarity transformations and Krencigowa-Kuo folded diagrams are two common methods used to derive energy independent model space effective interactions for nuclear many-body systems. We demonstrate that these methods are equivalent to a Renormalization Group (RG) analysis of a separable potential model. The effective low-momentum potentials V_{eff} are shown to give the same scaling equation that RG arguments predict. We find the new result that the different model space techniques considered in this paper yield a unique low-momentum V_{eff} when applied to the toy model problem.

  11. Space allowance and high fiber diet impact performance and behavior of group-kept gestating sows.

    PubMed

    DeDecker, A E; Hanson, A R; Walker, P M; Salak-Johnson, J L

    2014-04-01

    Identifying and optimizing housing and management systems that improve the well-being of the gestating sow is essential to sustaining animal agriculture. Therefore, the impact of 2 floor-space allowances and a high-fiber gestation diet on dry group-housed sows were evaluated using multiple measures of well-being. Groups of 10 multiparous sows/pen (n = 221) were assigned randomly to treatments in a 2 × 2 factorial arrangement to either a corn-soybean meal diet (CTL) or corn-soybean meal diet supplemented with soybean hulls and wheat middlings (FBR), and floor-space allowance of either 1.7 or 2.3 m(2)/sow. Sow BW, backfat (BF), and body condition score (BCS) were all recorded on d 34, 65, 90, and 110 of gestation, whereas skin lesions were scored on d 34, every 2 d for the first 2-wk postmixing, and then biweekly throughout gestation. Blood sample was collected only on d 34 for cortisol (baseline), and samples were collected on d 90 of gestation for other measures including cortisol. Behavior was registered on multiple days throughout gestation. Sows fed FBR and kept at 1.7 m(2) produced heavier litter and weaning weights and greater number of piglets born alive, compared to sows fed FBR but kept at 2.3 m(2) of floor space (diet × floor space, P ? 0.04). Sows fed FBR and kept at 1.7 m(2) performed fewer oral-nasal-facial and sham-chew behaviors than sows fed CTL and kept at the same floor space (diet × floor space, P ? 0.044). Sows kept at 1.7 m(2) of floor space had a greater (P < 0.05) total lesion severity score than sows kept at 2.3 m(2)/sow, and vulva lesion scores were more (P < 0.02) severe among CTL-fed sows than FBR-fed sows. Parities 2 and 3 sows fed FBR and kept at 1.7 m(2) of floor space were heavier (P < 0.001) than sows fed the same diet but kept at 2.3 m(2). These results indicate that keeping small groups of pregnant sows at a minimum floor-space allowance of 1.7 m(2)/sow and floor feeding these sows a high-fiber diet can improve short-term sow well-being. PMID:24663162

  12. A preliminary neutron crystallographic study of thaumatin

    PubMed Central

    Teixeira, Susana C. M.; Blakeley, Matthew P.; Leal, Ricardo M. F.; Mitchell, Edward P.; Forsyth, V. Trevor

    2008-01-01

    A preliminary neutron crystallographic study of the sweet protein thaumatin is presented. Large hydrogenated crystals were prepared in deuterated crystallization buffer using the gel-acupuncture method. Data were collected to a resolution of 2?Å on the LADI-III diffractometer at the Institut Laue Langevin (ILL). The results demonstrate the feasibility of a full neutron crystallographic analysis of this structure aimed at providing relevant information on the location of H atoms, the distribution of charge on the protein surface and localized water in the structure. This information will be of interest for understanding the specificity of thaumatin–receptor interactions and will contribute to further understanding of the molecular mechanisms underlying the perception of taste. PMID:18453706

  13. Fredholm and spectral properties of Toeplitz operators on H{sup p} spaces over ordered groups

    SciTech Connect

    Mirotin, Adolf R [Gomel State University, Gomel (Belarus)

    2011-05-31

    We consider Toeplitz operators on the spaces H{sup p}(G), 1< p<{infinity}, associated with a compact connected Abelian group G whose character group is ordered and, in the case of total order, prove a theorem on the Fredholm index for those operators which have continuous symbols which generalizes the classical Gohberg-Krein theorem. The results thus obtained are applied to the spectral theory of Toeplitz operators and examples where the index is evaluated explicitly are considered. Bibliography: 22 titles.

  14. Preliminary Crystallographic Study of Hemoglobin from Buffalo (Bubalus bubalis): A Low Oxygen Affinity Species.

    PubMed

    Balasubramanian, Moovarkumudalvan; Moorthy, Ponnuraj Sathya; Neelagandan, Kamariah; Ponnuswamy, Mondikalipudur Nanjappa Gounder

    2009-01-01

    Hemoglobin is a tetrameric, iron-containing metalloprotein, which plays a vital role in the transportation of oxygen from lungs to tissues and carbon dioxide back to lungs. Though good amount of work has already been done on hemoglobins, the scarcity of data on three dimensional structures pertaining to low oxygen affinity hemoglobins from mammalian species, motivated our group to work on this problem specifically. Herein, we report the preliminary crystallographic analysis of buffalo hemoglobin, which belongs to low oxygen affinity species. The buffalo blood was collected, purified by anion exchange chromatography and crystallized with PEG 3350 using 50mM phosphate buffer at pH 6.7 as a precipitant by hanging drop vapor diffusion method. Data collection was carried out using mar345dtb image plate detector system. Buffalo hemoglobin crystallizes in orthorhombic space group P2(1)2(1)2(1) with one whole biological molecule (alpha2beta2) in the asymmetric unit with cell dimensions a=63.064A, b=74.677A, c=110.224A. PMID:19200047

  15. Crystallographic studies of gas sorption in metal–organic frameworks

    PubMed Central

    Carrington, Elliot J.; Vitórica-Yrezábal, Iñigo J.; Brammer, Lee

    2014-01-01

    Metal–organic frameworks (MOFs) are a class of porous crystalline materials of modular design. One of the primary applications of these materials is in the adsorption and separation of gases, with potential benefits to the energy, transport and medical sectors. In situ crystallography of MOFs under gas atmospheres has enabled the behaviour of the frameworks under gas loading to be investigated and has established the precise location of adsorbed gas molecules in a significant number of MOFs. This article reviews progress in such crystallographic studies, which has taken place over the past decade, but has its origins in earlier studies of zeolites, clathrates etc. The review considers studies by single-crystal or powder diffraction using either X-rays or neutrons. Features of MOFs that strongly affect gas sorption behaviour are discussed in the context of in situ crystallographic studies, specifically framework flexibility, and the presence of (organic) functional groups and unsaturated (open) metal sites within pores that can form specific interactions with gas molecules. PMID:24892587

  16. Exploiting space-group symmetry in fragment-based molecular crystal calculations.

    PubMed

    Heit, Yonaton; Beran, Gregory J O

    2014-11-15

    Recent developments in fragment-based methods make it increasingly feasible to use high-level ab initio electronic structure techniques to molecular crystals. Such studies remain computationally demanding, however. Here, we describe a straightforward algorithm for exploiting space-group symmetry in fragment-based methods which often provides computational speed-ups of several fold or more. This algorithm does not require a priori specification of the space group or symmetry operators. Rather, the symmetrically equivalent fragments are identified automatically by aligning the individual fragments along their principle axes of inertia and testing for equivalence with other fragments. The symmetry operators relating equivalent fragments can then be worked out easily. Implementation of this algorithm for computing energies, nuclear gradients with respect to both atomic coordinates and lattice parameters, and the nuclear hessian is described. PMID:25270380

  17. Range Commanders Council Meteorology Group 88th Meeting: NASA Marshall Space Flight Center Task Report, 2004

    NASA Technical Reports Server (NTRS)

    Roberts, Barry C.

    2004-01-01

    Supported Return-to-Flight activities by providing surface climate data from Kennedy Space Center used primarily for ice and dew formation studies, and upper air wind analysis primarily used for ascent loads analyses. The MSFC Environments Group's Terrestrial and Planetary Environments Team documented Space Shuttle day-of-launch support activities by publishing a document in support of SSP Return-to-Flight activities entitled "Space Shuttle Program Flight Operations Support". The team also formalized the Shuttle Natural Environments Technical Panel and chaired the first special session of the SSP Natural Environments Panel meeting at KSC, November 4-7,2003.58 participants from NASA, DOD and other government agencies from across the country attended the meeting.

  18. Planning and managing future space facility projects. [management by objectives and group dynamics

    NASA Technical Reports Server (NTRS)

    Sieber, J. E.; Wilhelm, J. A.; Tanner, T. A.; Helmreich, R. L.; Burgenbauch, S. F.

    1979-01-01

    To learn how ground-based personnel of a space project plan and organize their work and how such planning and organizing relate to work outcomes, longitudinal study of the management and execution of the Space Lab Mission Development Test 3 (SMD 3) was performed at NASA Ames Research Center. A view of the problems likely to arise in organizations and some methods of coping with these problems are presented as well as the conclusions and recommendations that pertain strictly to SMD 3 management. Emphasis is placed on the broader context of future space facility projects and additional problems that may be anticipated. A model of management that may be used to facilitate problem solving and communication - management by objectives (MBO) is presented. Some problems of communication and emotion management that MBO does not address directly are considered. Models for promoting mature, constructive and satisfying emotional relationships among group members are discussed.

  19. [Crystallographic evaluation of structural changes in water].

    PubMed

    Farashchuk, N F; Rakhmanin, Yu A; Savostikova, O N; Telenkova, O G

    2014-01-01

    The study of the structural state of tap water that has been stored for two days in the packaging materials of various type and in different conditions, was performed with the use of crystallographic method for the investigation of liquids based on a special approach for dehydration of the drop, which is a fixed thin "slice" of the examines liquid. Most organized crystallographic pattern was shown to observe in a drop of water after treatment Bioptron lamp (content of liquid-crystal associates (LCA)--6.90 ± 0.23), and stored in a silver vessel (content LCA--6.28 ± 0.17), and the least organized, almost amorphous precipitate is formed in a drop of water stored in plastic containers (content LCA--2.92 ± 0.15%). Basing on the obtained results, it can be concluded that the crystallographic method can be used for the identification of qualitative changes occurring in liquid water under the influence of various physical factors, for the identification of the rationality of the use of hereafter sophisticated quantitative techniques. PMID:25842512

  20. Report from the MPP Working Group to the NASA Associate Administrator for Space Science and Applications

    NASA Technical Reports Server (NTRS)

    Fischer, James R.; Grosch, Chester; Mcanulty, Michael; Odonnell, John; Storey, Owen

    1987-01-01

    NASA's Office of Space Science and Applications (OSSA) gave a select group of scientists the opportunity to test and implement their computational algorithms on the Massively Parallel Processor (MPP) located at Goddard Space Flight Center, beginning in late 1985. One year later, the Working Group presented its report, which addressed the following: algorithms, programming languages, architecture, programming environments, the way theory relates, and performance measured. The findings point to a number of demonstrated computational techniques for which the MPP architecture is ideally suited. For example, besides executing much faster on the MPP than on conventional computers, systolic VLSI simulation (where distances are short), lattice simulation, neural network simulation, and image problems were found to be easier to program on the MPP's architecture than on a CYBER 205 or even a VAX. The report also makes technical recommendations covering all aspects of MPP use, and recommendations concerning the future of the MPP and machines based on similar architectures, expansion of the Working Group, and study of the role of future parallel processors for space station, EOS, and the Great Observatories era.

  1. Effects of row spacing, seed rate and maturity group on late planted soybean under irrigated and dryland

    E-print Network

    Balasundaram, Balabhaskar "Baski"

    Effects of row spacing, seed rate and maturity group on late planted soybean under irrigated, seeding rate, and maturity group (MG) for late planted soybean under irrigated and dryland conditions with three replications and three variables (MG, row spacing, and seeding rate). Table 1 shows all different

  2. The Scientific Capabilities of the James Webb Space Telescope Jonathan P. Gardner and the JWST Science Working Group

    E-print Network

    Sirianni, Marco

    The Scientific Capabilities of the James Webb Space Telescope Jonathan P. Gardner and the JWST.p.gardner@nasa.gov #12;The Scientific Capabilities of the James Webb Space Telescope Jonathan P. Gardner and the JWST Science Working Group 1. Introduction The James Webb Space Tele- scope (JWST; Figure 1) is a large (25 m2

  3. A summary of activities of the US\\/Soviet-Russian joint working group on space biology and medicine

    Microsoft Academic Search

    Charles R. Doarn; Arnauld E. Nicogossian; Anatoly I. Grigoriev; Galina Tverskaya; Oleg I. Orlov; Eugene A. Ilyin; Kenneth A. Souza

    2010-01-01

    The very foundation of cooperation between the United States (US) and Russia (former Soviet Union) in space exploration is a direct result of the mutual desire for scientific understanding and the creation of a collaborative mechanism—the Joint Working Group (JWG) on Space Biology and Medicine. From the dawn of the space age, it has been the quest of humankind to

  4. A systematic method to identify the space group from PED and CBED patterns part II--practical examples.

    PubMed

    Jacob, D; Ji, G; Morniroli, J P

    2012-10-01

    Precession Electron Diffraction and Convergent-Beam Electron Diffraction are used in a complementary way to determine the space group of three known structures following the general method described in the first part of this paper. The selected structures concern a monoclinic example (coesite SiO(2) with space group C2/c) and two cubic examples (?-Al(4)Cu(9) with space group P43[combining overline]m and pyrite FeS(2) with space group Pa3[combining overline]). For each case, a minimum number of zone axis patterns are used to determine the space group without ambiguity, which illustrates the simplicity and reliability of the method. PMID:22749238

  5. Topological Entropy and Renormalization Group flow in 3-dimensional spherical spaces

    E-print Network

    M. Asorey; C. G. Beneventano; I. Cavero-Peláez; D. D'Ascanio; E. M. Santangelo

    2015-01-17

    We analyze the renormalization group (RG) flow of the temperature independent term of the entropy in the high temperature limit \\beta/atheory in 3-dimensional spherical spaces M_3 with constant curvature 6/a^2. For masses lower than 2\\pi/\\beta, this term can be identified with the free energy of the same theory on M_3 considered as a 3-dimensional Euclidean space-time. The non-extensive part of this free energy, S_hol, is generated by the holonomy of the spatial metric connection. We show that for homogeneous spherical spaces the holonomy entropy S_hol decreases monotonically when the RG scale flows to the infrared. At the conformal fixed points the values of the holonomy entropy do coincide with the genuine topological entropies recently introduced. The monotonic behavior of the RG flow leads to an inequality between the topological entropies of the conformal field theories connected by such flow, i.e. S_top^UV > S_top^IR. From a 3-dimensional viewpoint the same term arises in the 3-dimensional Euclidean effective action and has the same monotonic behavior under the RG group flow. We conjecture that such monotonic behavior is generic, which would give rise to a 3-dimensional generalization of the c-theorem, along the lines of the 2-dimensional c-theorem and the 4-dimensional a-theorem. The conjecture is related to recent formulations of the F-theorem. In particular, the holonomy entropy on lens spaces is directly related to the topological R\\'enyi entanglement entropy on disks of 2-dimensional flat spaces.

  6. Crystallographic analysis of a series of inorganic compounds

    NASA Astrophysics Data System (ADS)

    Borisov, S. V.; Magarill, S. A.; Pervukhina, N. V.

    2015-04-01

    The method of crystallographic analysis relies on the mechanical-wave concept that treats the crystalline state as the result of ordering of atomic positions by families of parallel equidistant planes. Using this method, a large set of fluoride, oxide and sulfide structures was analyzed. The pseudo-translational ordering of various atomic groups (including the presence of cation and anion sublattices) in the structures of various classes of inorganic compounds was established. The crucial role of local ordering of heavy cations (coherent assembly) in the structures comprising large cluster fragments (Keggin polyanions, polyoxoniobates, etc.) is discussed. The role of symmetry and the regular distribution of heavy atoms in the formation of stable crystal structures, which is to be taken into account in the targeted design, is considered. The universality of configurations of atomic positions in the structures of various classes of inorganic compounds resulting from the ordering mechanism organized by mechanical (elastic) forces is demonstrated. The bibliography includes 158 references.

  7. Unfolding of electronic structure through induced representations of space groups: Application to Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Tomi?, Milan; Jeschke, Harald O.; Valentí, Roser

    2014-11-01

    We revisit the problem that relevant parts of band structures for a given cell choice can reflect exact or approximate higher symmetries of subsystems in the cell and can therefore be significantly simplified by an unfolding procedure that recovers the higher symmetry. We show that band-structure unfolding can be understood as projection onto induced irreducible representations of a group obtained by extending the original group of translations with a number of additional symmetry operations. The resulting framework allows us to define a generalized unfolding procedure that includes the point group operations and can be applied to any quantity in the reciprocal space. The unfolding of the Brillouin zone follows naturally from the properties of the induced irreducible representations. In this context, we also introduce a procedure to derive tight-binding models of reduced dimensionality by making use of point group symmetries. Further, we show that careful consideration of unfolding has important consequences on the interpretation of angle-resolved photoemission experiments. Finally, we apply the unfolding procedure to various representative examples of Fe-based superconductor compounds and show that the one-iron picture arises as an irreducible representation of the glide-reflection group, and we comment on the consequences for the interpretation of one-iron versus two-iron Brillouin zone representations.

  8. Finite flat commutative group schemes over complete discrete valuation rings III: classification, tangent spaces, and semistable reduction of Abelian varieties

    Microsoft Academic Search

    M. V. Bondarko

    2004-01-01

    We classify group schemes in terms of their Cartier modules. We also prove the equivalence of different definitions of the tangent space and the dimension for these group schemes; in particular, the minimal dimension of a formal group law that contains $S$ as a closed subgroup is equal to the minimal number of generators for the affine algebra of $S$.

  9. Crystallographic relationships between diamond and its inclusions

    NASA Astrophysics Data System (ADS)

    Nimis, Paolo; Nestola, Fabrizio; Angel, Ross J.; Milani, Sula; Alvaro, Matteo; Anzolini, Chiara; Schiazza, Mariangela; Bruno, Marco; Prencipe, Mauro; Harris, Jeff W.; Hutchison, Mark T.

    2015-04-01

    The study of the crystallographic orientations of minerals included in diamonds can provide an insight into the mechanisms of their incorporation and the timing of their formation relative to the host diamond. The reported occurrence of non-trivial orientations for some minerals in some diamonds, suggesting an epitactic relationship, has long been considered to reflect contemporaneous growth of the diamond and the inclusion (= syngenesis). Correct interpretation of such orientations requires (i) a statistically significant data set, i.e. crystallographic data for single and multiple inclusions in a large number of diamonds, and (ii) a robust data-processing method, capable of removing ambiguities derived from the high symmetry of the diamond and the inclusion. We have developed software which performs such processing, starting from crystallographic orientation matrixes obtained by X-ray diffractometry. Preliminary studies indicate a wide variety of trends in the orientations of different inclusion phases in diamonds. In contrast to previous claims, olivine inclusions in lithospheric diamonds from Udachnaya do not show any preferred orientations with respect to their diamond hosts, but multiple inclusions in a single diamond often show very similar orientations within a few degrees (Nestola et al. 2014). Chromite (spinel) inclusions exhibit a strong tendency for a single (111) plane of each inclusion to be parallel to a (111) plane of their diamond host, but without any statistically significant orientation of the crystallographic axes a, b, and c. By contrast, 7 inclusions of ferropericlase studied in 2 different super deep diamonds (four inclusions in one diamond and three inclusions in the second diamond) from Brazil all exhibit the same orientation with their axes practically coincident with those of diamonds regardless of the position and the shape of the inclusions. The implications of these observations for the mechanisms of diamond growth will be explored. This work was supported by ERC starting grant 307322 to F. Nestola and Alfred P. Sloan Foundation's Deep Carbon Observatory project to P. Nimis. Nestola F., et al. (2014) Int Geol Rev, 56,1658-1667.

  10. Real-space renormalization-group study of the Z(5) model

    NASA Astrophysics Data System (ADS)

    Mizrahi, Victor; Domany, Eytan

    1981-10-01

    The phase diagram of the nearest-neighbor Z(5) model on the square and triangular lattices is investigated using techniques of the real-space renormalization group. We use the recently introduced technique of Nienhuis, Berker, Riedel, and Schick, which yields the expected first-order transition on the Potts subspace of the Z(5) model on the triangular lattice. For the general Z(5) model we obtain a line of first-order transitions which crosses over into a line of second-order transitions. The same technique when applied to the square lattice is found to show this crossover behavior only in combination with a Migdal procedure.

  11. The space shuttle payload planning working groups. Volume 4: Life sciences

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The findings of the Life Sciences working group of the space shuttle payload planning activity are presented. The objectives of the Life Sciences investigations are: (1) to continue the research directed at understanding the origin of life and the search for extraterrestrial evidence of life, (2) biomedical research to understand mechanisms and provide criteria for support of manned flight, (3) technology development for life support, protective systems, and work aids for providing environmental control, and (4) to study basic biological functions at all levels or organization influenced by gravity, radiation, and circadian rhythms. Examples of candidate experimental schedules and the experimental package functional requirements are included.

  12. Pressure and equilibrium measures for actions of amenable groups on the space of configurations

    SciTech Connect

    Bufetov, Aleksei I [M. V. Lomonosov Moscow State University, Faculty of Mechanics and Mathematics, Moscow (Russian Federation)

    2011-03-31

    The model of statistical physics on a countable amenable group G is considered. For the natural action of G on the space of configurations S{sup G}, |S|<{infinity}, and for any closed invariant set X subset of S{sup G} we prove that there exists pressure which corresponds to a potential with finite norm on X (in the sense of the limit with respect to any Foelner sequence of sets in G). The existence of an equilibrium measure is established. Bibliography: 8 titles.

  13. A Fun and Effective Exercise for Understanding Lattices and Space Groups

    NSDL National Science Digital Library

    Dexter Perkins

    This activity uses figures from Francois Brisse as Esher drawings to teach students about 2-dimensional symmetry, especially involving translation. This exercise is based on discovery learning. Students need little introduction to lattices and space groups. They can figure things out for themselves. For example, they will figure out what a glide plane is, and if you tell them ahead of time it takes away from the learning experience. The last question, which asks them to make their own symmetrical drawings, is difficult but often leads to some spectacular results.

  14. Purification, crystallization and preliminary crystallographic analysis of the catalytic core of cystathionine ?-synthase from Saccharomyces cerevisiae

    PubMed Central

    Ereño-Orbea, June; Majtan, Tomas; Oyenarte, Iker; Kraus, Jan P.; Martínez-Cruz, Luis Alfonso

    2014-01-01

    Cystathionine ?-synthase (CBS; EC 4.2.1.22) catalyzes the condensation of homocysteine and serine to form cystathionine, with the release of water. In humans, deficiency in CBS activity is the most common cause of hyperhomocysteinaemia and homocystinuria. More than 160 pathogenic mutations in the human CBS gene have been described to date. Here, the purification and preliminary crystallographic analysis of the catalytic core of CBS from Saccharomyces cerevisiae (ScCBS) is described which, in contrast to other eukaryotic CBSs, lacks the N-terminal haem-binding domain and is considered to be a useful model for investigation of the pyridoxal-5?-phosphate-mediated reactions of human CBS (hCBS). The purified protein yielded two different crystal forms belonging to space groups P41212 and P212121, with unit-cell parameters a = b = 72.390, c = 386.794?Å and a = 58.156, b = 89.988, c = 121.687?Å, respectively. Diffraction data were collected to 2.7 and 3.1?Å resolution, respectively, using synchrotron radiation. Preliminary analysis of the X-ray data suggests the presence of ScCBS homodimers in both types of crystals. PMID:24598918

  15. Purification, crystallization and preliminary crystallographic analysis of the full-length cystathionine ?-synthase from Apis mellifera

    PubMed Central

    Oyenarte, Iker; Majtan, Tomas; Ereño, June; Corral-Rodríguez, María Angeles; Klaudiny, Jaroslav; Majtan, Juraj; Kraus, Jan P.; Martínez-Cruz, Luis Alfonso

    2012-01-01

    Cystathionine ?-synthase (CBS) is a pyridoxal-5?-phosphate-dependent enzyme that catalyzes the first step of the transsulfuration pathway, namely the condensation of serine with homocysteine to form cystathionine. Mutations in the CBS gene are the single most common cause of hereditary homocystinuria, a multisystemic disease affecting to various extents the vasculature, connective tissues and central nervous system. At present, the crystal structure of CBS from Drosophila melanogaster is the only available structure of the full-length enzyme. Here we describe a cloning, overexpression, purification and preliminary crystallographic analysis of a full-length CBS from Apis mellifera (AmCBS) which maintains 51 and 46% sequence identity with its Drosophila and human homologs, respectively. The AmCBS yielded crystals belonging to space group P212121, with unit-cell parameters a = 85.90, b = 95.87, c = 180.33?Å. Diffraction data were collected to a resolution of 3.0?Å. The crystal structure contained two molecules in the asymmetric unit which presumably correspond to the dimeric species observed in solution. PMID:23143241

  16. Crystallization and preliminary crystallographic study of carnosinase CN2 from mice

    PubMed Central

    Yamashita, Tetsuo; Unno, Hideaki; Ujita, Sayuri; Otani, Hiroto; Okumura, Nobuaki; Hashida-Okumura, Akiko; Nagai, Katsuya; Kusunoki, Masami

    2006-01-01

    Mammalian tissues contain several histidine-containing dipeptides, of which l-­carnosine is the best characterized and is found in various tissues including the brain and skeletal muscles. However, the mechanism for its biosynthesis and degradation have not yet been fully elucidated. Crystallographic study of carnosinase CN2 from mouse has been undertaken in order to understand its enzymatic mechanism from a structural viewpoint. CN2 was crystallized by the hanging-drop vapour-diffusion technique using PEG 3350 as a precipitant. Crystals were obtained in complex with either Mn2+ or Zn2+. Both crystals of CN2 belong to the monoclinic space group P21 and have almost identical unit-cell parameters (a = 54.41, b = 199.77, c = 55.49?Å, ? = 118.52° for the Zn2+ complex crystals). Diffraction data were collected to 1.7 and 2.3?Å for Zn2+ and Mn2+ complex crystals, respectively, using synchrotron radiation. Structure determination is ongoing using the multiple-wavelength anomalous diffraction (MAD) method. PMID:17012794

  17. Intraspecific variation in space use, group size, and mating systems of caviomorph rodents

    PubMed Central

    Maher, Christine R.; Burger, Joseph Robert

    2012-01-01

    Intraspecific variation in social systems is widely recognized across many taxa, and specific models, including polygamy potential, resource defense, and resource dispersion, have been developed to explain the relationship between ecological variation and social organization. Although mammals from temperate North America and Eurasia have provided many insights into this relationship, rodents from the Neotropics and temperate South America have largely been ignored. In this review we focus on reports documenting intraspecific variation in spacing systems, group size, and mating systems of caviomorphs. This large group of New World hystricognath rodents occupies a diverse array of habitats; thus, members of the same species potentially exhibit different social systems in response to different ecological conditions. Spatial patterns vary in response to a diverse array of factors, including predation, food availability, population density, and soil characteristics. Changes in group size typically correlate with changes in resource availability, particularly food. Mating systems generally reflect the ability of males to control access to females, which may depend on population density or food distribution. In general, social organization in caviomorphs fits predictions of resource-based models; however, most studies have been purely observational, involving small numbers of animals over short time periods and reporting qualitative rather than quantitative levels of ecological correlates. In future studies the use of molecular techniques and controlled, experimental manipulations can increase our understanding of intraspecific variation in caviomorph social systems. This understudied group of rodents offers excellent opportunities to provide insights into the influence of ecological conditions on behavior such as social systems. PMID:22328790

  18. Space group symmetry fractionalization in a family of exactly solvable models with Z2 topological order

    E-print Network

    Hao Song; Michael Hermele

    2015-02-05

    We study square lattice space group symmetry fractionalization in a family of exactly solvable models with $\\mathbb{Z}_2$ topological order in two dimensions. In particular, we have obtained a complete understanding of which distinct types of symmetry fractionalization (symmetry classes) can be realized within this class of models, which are generalizations of Kitaev's $\\mathbb{Z}_2$ toric code to arbitrary lattices. This question is motivated by earlier work of A. M. Essin and one of us (M. H.), where the idea of symmetry classification was laid out, and which, for square lattice symmetry, produces 2080 symmetry classes consistent with the fusion rules of $\\mathbb{Z}_2$ topological order. This approach does not produce a physical model for each symmetry class, and indeed there are reasons to believe that some symmetry classes may not be realizable in strictly two-dimensional systems, thus raising the question of which classes are in fact possible. While our understanding is limited to a restricted class of models, it is complete in the sense that for each of the 2080 possible symmetry classes, we either prove rigorously that the class cannot be realized in our family of models, or we give an explicit model realizing the class. We thus find that exactly 487 symmetry classes are realized in the family of models considered. With a more restrictive type of symmetry action, where space group operations act trivially in the internal Hilbert space of each spin degree of freedom, we find that exactly 82 symmetry classes are realized. In addition, we present a single model that realizes all $2^6 = 64$ types of symmetry fractionalization allowed for a single anyon species ($\\mathbb{Z}_2$ charge excitation), as the parameters in the Hamiltonian are varied. The paper concludes with a summary and a discussion of two results pertaining to more general bosonic models.

  19. The p-adic analytic space of pseudocharacters of a profinite group and pseudorepresentations over arbitrary rings

    Microsoft Academic Search

    Gaetan Chenevier

    2008-01-01

    Let G be a profinite group which is topologically finitely generated, p a prime number and d an integer. We show that the functor from rigid analytic spaces over Q_p to sets, which associates to a rigid space Y the set of continuous d-dimensional pseudocharacters G -> O(Y), is representable by a quasi-Stein rigid analytic space X, and we study

  20. Influence and passivation of extended crystallographic defects in polycrystalline silicon

    E-print Network

    Paris-Sud XI, Université de

    637 Influence and passivation of extended crystallographic defects in polycrystalline silicon S crystallographic defects are investigated in large grained polycrystalline silicon wafers and N+ P solar cells. Introduction. The various polycrystalline silicon materials (cast ingots, ribbons) used to realize solar cells

  1. Curriculum Vitae Norma Edith Cope Duke Beamline Scientist, Protein Crystallographer

    E-print Network

    Kemner, Ken

    . The Structural Biology Center 19ID undulator beam line: Facility specifications and protein crystallographic1 Curriculum Vitae Norma Edith Cope Duke Beamline Scientist, Protein Crystallographer University.D. Science 1989 Physical Chemistry Yale University Post-Doc 1990 Protein Crystallography University

  2. Systematic prediction of new ferroelectrics in space group R3. I.

    PubMed

    Abrahams, S C

    2006-02-01

    Release 2005/1 of the Inorganic Crystal Structure Database contains 158 entries under the space group R3. The first 81 together with 15 related entries include 52 different structure types, 10 of which represent families that have two or more isostructural members. There are 18 types that satisfy the structural criteria for ferroelectricity with a confidence level that necessarily depends upon the reliability of each structural determination. Among them, (LiTaO3)9.Ta2O5 and the CsCd(NO2) family are known ferroelectrics. The remaining 16 include the high-intensity higher-order harmonic generator II-BaB2O4, not previously recognized as ferroelectric. The other predicted ferroelectrics are Te(OH)6.NaF, the MgSO3.6H2O family, Li3P3O9.3H2O, SeNbF9, Al2(H2PO4)3PO4.6H2O, [Cr(OCN2H4)6].[(Co(NH3)2(NO2)4]3.(H2O)(1.5)], NaZnBr3.5H2O, III-Ag3SI, Tl2S, the Ba3Yb4O9 family, the Fe(10.7)Ru(1.3)As5 family, Sr17Ta10S42, Pb8Sb3 and the Sc7I12C family. Six structures reported in the space group R3 most likely exhibit mirror symmetry, with three experimental confirmations. The other 19 structures are most likely nonpolar, with six experimental confirmations. The capacity for physical property prediction by the remaining ten structures is shown to be in doubt. Thus, 46% of the present 52 inorganic structure types initially determined in the space group R3 and 35% of those currently assigned to R3 more likely exhibit an additional inversion center, mirror or glide plane, strongly exceeding the recently reported error rate of approximately 11% in organic structures. PMID:16434790

  3. XTAL system of crystallographic programs: programmer's manual

    SciTech Connect

    Hall, S.R.; Stewart, J.M.; Norden, A.P.; Munn, R.J.; Freer, S.T.

    1980-02-01

    This document establishes the basis for collaborative writing of transportable computer programs for x-ray crystallography. The concepts and general-purpose utility subroutines described here can be readily adapted to other scientific calculations. The complete system of crystallographic programs and subroutines is called XTAL and replaces the XRAY (6,7,8) system of programs. The coding language for the XTAL system is RATMAC (5). The XTAL system of programs contains routines for controlling execution of application programs. In this sense it forms a suboperating system that presents the same computational environment to the user and programmer irrespective of the operating system in use at a particular installation. These control routines replace all FORTRAN I/O code, supply character reading and writing, supply binary file reading and writing, serve as a support library for applications programs, and provide for interprogram communication.

  4. Nuclear safety policy working group recommendations on nuclear propulsion safety for the space exploration initiative

    NASA Technical Reports Server (NTRS)

    Marshall, Albert C.; Lee, James H.; Mcculloch, William H.; Sawyer, J. Charles, Jr.; Bari, Robert A.; Cullingford, Hatice S.; Hardy, Alva C.; Niederauer, George F.; Remp, Kerry; Rice, John W.

    1993-01-01

    An interagency Nuclear Safety Working Group (NSPWG) was chartered to recommend nuclear safety policy, requirements, and guidelines for the Space Exploration Initiative (SEI) nuclear propulsion program. These recommendations, which are contained in this report, should facilitate the implementation of mission planning and conceptual design studies. The NSPWG has recommended a top-level policy to provide the guiding principles for the development and implementation of the SEI nuclear propulsion safety program. In addition, the NSPWG has reviewed safety issues for nuclear propulsion and recommended top-level safety requirements and guidelines to address these issues. These recommendations should be useful for the development of the program's top-level requirements for safety functions (referred to as Safety Functional Requirements). The safety requirements and guidelines address the following topics: reactor start-up, inadvertent criticality, radiological release and exposure, disposal, entry, safeguards, risk/reliability, operational safety, ground testing, and other considerations.

  5. On the Reflection Type Decomposition of the Adjoint Reduced Phase Space of a Compact Semisimple Lie group

    E-print Network

    Martin Hofmann; Gerd Rudolph; Matthias Schmidt

    2013-02-25

    We consider a system with symmetries whose configuration space is a compact Lie group, acted upon by inner automorphisms. The classical reduced phase space of this system decomposes into connected components of orbit type subsets. To investigate hypothetical quantum effects of this decomposition one has to construct the associated costratification of the Hilbert space of the quantum system in the sense of Huebschmann. In the present paper, instead of the decomposition by orbit types, we consider the related decomposition by reflection types (conjugacy classes of reflection subgroups). These two decompositions turn out to coincide e.g. for the classical groups SU(n) and Sp(n). We derive defining relations for reflection type subsets in terms of irreducible characters and discuss how to obtain from that the corresponding costratification of the Hilbert space of the system. To illustrate the method, we give explicit results for some low rank classical groups.

  6. Quantum groups, roots of unity and particles on quantized Anti-de Sitter space

    SciTech Connect

    Steinacker, H [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-05-23

    Quantum groups in general and the quantum Anti-de Sitter group U{sub q}(so(2,3)) in particular are studied from the point of view of quantum field theory. The author shows that if q is a suitable root of unity, there exist finite-dimensional, unitary representations corresponding to essentially all the classical one-particle representations with (half) integer spin, with the same structure at low energies as in the classical case. In the massless case for spin {ge} 1, {open_quotes}naive{close_quotes} representations are unitarizable only after factoring out a subspace of {open_quotes}pure gauges{close_quotes}, as classically. Unitary many-particle representations are defined, with the correct classical limit. Furthermore, the author identifies a remarkable element Q in the center of U{sub q}(g), which plays the role of a BRST operator in the case of U{sub q}(so(2,3)) at roots of unity, for any spin {ge} 1. The associated ghosts are an intrinsic part of the indecomposable representations. The author shows how to define an involution on algebras of creation and anihilation operators at roots of unity, in an example corresponding to non-identical particles. It is shown how nonabelian gauge fields appear naturally in this framework, without having to define connections on fiber bundles. Integration on Quantum Euclidean space and sphere and on Anti-de Sitter space is studied as well. The author gives a conjecture how Q can be used in general to analyze the structure of indecomposable representations, and to define a new, completely reducible associative (tensor) product of representations at roots of unity, which generalizes the standard {open_quotes}truncated{close_quotes} tensor product as well as many-particle representations.

  7. International Space Station Air Quality Assessed According to Toxicologically-Grouped Compounds

    NASA Technical Reports Server (NTRS)

    James, John T.; Limero, Tom; DeVera, Vanessa; Cheng, Patti; Hand, Jennifer; Macatangay, Ariel; Beck, Steve

    2009-01-01

    Scores of compounds are found in the International Space Station (ISS) atmospheric samples that are returned to the Johnson Space Center Toxicology Laboratory for analysis. Spacecraft Maximum Allowable Concentrations (SMACs) are set with the view that each compound is present as if there were no other compounds present. In order to apply SMACs to the interpretation of the analytical data, the toxicologist must employ some method of combining the potential effects of the aggregate of compounds found in the atmospheric samples. The simplest approach is to assume that each quantifiable compound has the potential for some effect in proportion to the applicable SMAC, and then add all the proportions. This simple paradigm disregards the fact that most compounds have potential to adversely affect only a few physiological systems, and their effects would be independent rather than additive. An improved approach to dealing with exposure to mixtures is to add the proportions only for compounds that adversely affect the same physiological system. For example, toxicants that cause respiratory irritation are separated from those that cause neurotoxicity or cardio-toxicity. Herein we analyze ISS air quality data according to toxicological groups with a view that this could be used for understanding any crew symptoms occurring at the time of the sample. In addition, this approach could be useful in post-flight longitudinal surveys where the flight surgeon may need to identify post-flight, follow-up medical studies because of on-orbit exposures that target specific physiological systems.

  8. International Space Station Air Quality Assessed According to Toxicologically-Grouped Compounds

    NASA Technical Reports Server (NTRS)

    James, John T.; Limero, Thomas F.; Beck, Steve; Cheng, Patti F.; deVera, Vanessa J.; Hand, Jennifer; Macatangay, Ariel

    2010-01-01

    Scores of compounds are found in the International Space Station (ISS) atmospheric samples that are returned to the Johnson Space Center Toxicology Laboratory for analysis. Spacecraft Maximum Allowable Concentrations (SMACs) are set with the view that each compound is present as if there were no other compounds present. In order to apply SMACs to the interpretation of the analytical data, the toxicologist must employ some method of combining the potential effects of the aggregate of compounds found in the atmospheric samples. The simplest approach is to assume that each quantifiable compound has the potential for some effect in proportion to the applicable SMAC, and then add all the proportions. This simple paradigm disregards the fact that most compounds have potential to adversely affect only a few physiological systems, and their effects would be independent rather than additive. An improved approach to dealing with exposure to mixtures is to add the proportions only for compounds that adversely affect the same physiological system. For example, toxicants that cause respiratory irritation are separated from those that cause neurotoxicity or cardio-toxicity. Herein we analyze ISS air quality data according to toxicological groups with a view that this could be used for understanding any crew symptoms occurring at the time of the sample acquisition. In addition, this approach could be useful in post-flight longitudinal surveys where the flight surgeon may need to identify post-flight, follow-up medical studies because of on-orbit exposures that target specific physiological systems.

  9. Fractal space-times under the microscope: A Renormalization Group view on Monte Carlo data

    E-print Network

    Martin Reuter; Frank Saueressig

    2011-10-24

    The emergence of fractal features in the microscopic structure of space-time is a common theme in many approaches to quantum gravity. In this work we carry out a detailed renormalization group study of the spectral dimension $d_s$ and walk dimension $d_w$ associated with the effective space-times of asymptotically safe Quantum Einstein Gravity (QEG). We discover three scaling regimes where these generalized dimensions are approximately constant for an extended range of length scales: a classical regime where $d_s = d, d_w = 2$, a semi-classical regime where $d_s = 2d/(2+d), d_w = 2+d$, and the UV-fixed point regime where $d_s = d/2, d_w = 4$. On the length scales covered by three-dimensional Monte Carlo simulations, the resulting spectral dimension is shown to be in very good agreement with the data. This comparison also provides a natural explanation for the apparent puzzle between the short distance behavior of the spectral dimension reported from Causal Dynamical Triangulations (CDT), Euclidean Dynamical Triangulations (EDT), and Asymptotic Safety.

  10. Generation of crystallographic packing candidates with fixed helical symmetry and axial advance: Application to PI-2 polyimide

    SciTech Connect

    Waller, J.M.; Eby, R.K. [Univ. of Akron, OH (United States)

    1995-12-31

    A normal coordinate approach was used to generate crystallographic packing candidates of a multitorsional polyimide synthesized from 3,3`,4,4`-benzophenonetetracarboxylic acid (BTDA) and 2,2-dimethyl-1,3-(4-aminophenoxy) propane (DMDA) (PI-2). Candidates were obtained under conditions of fixed axial advance of 24.6 {Angstrom} per monomer, and imposed 2/1 helical or 1/0 translational symmetry, consistent with the observed WAXD meridional layer line spacing. The ability of combinatorially generated torsional states to adopt the desired geometry was examined. Necessary corrections to the conformational parameter equations have been made. The procedure described allowed crystallographic conformations satisfying explicit geometric and MM3 intramolecular energy criteria to be generated for a linear multitorsional polyimide prior to the application of crystallographic screening or refinement procedures. 20 refs., 7 figs., 1 tab.

  11. Crystallographic investigations of biotin and carboxybiotin derivatives.

    PubMed

    Stallings, W; Detitta, G T

    1985-01-01

    The structures of a family of biotin and carboxybiotin derivatives have provided information on the mechanism of biotin action. The ureido moiety of the uncarboxylated cofactor is polarized and able to interact with ions and polar molecules; intermolecular interactions in the biotin derivatives suggest biochemical mechanisms resulting in nucleophilic activation to the enol tautomer. N1' carboxylation of biotin is important not only as a chemical reaction to generate the carboxyl-transferring species, carboxybiotin, but also in acting as a switch to depolarize the ureido carbonyl oxygen, and thereby facilitating interactions with non-polar molecules. The structure of an N1' methoxycarbonyl biotin derivative reveals such an interaction between the carbonyl oxygen, O2', and a neighboring methyl group. A computer-generated space-filing model of the van der Waals contacts involved in this interaction reveals that the methyl group is locked with respect to rotation and thus suggests a structural basis for the stereospecificity observed in the carboxyl-transferring half-reaction. The flexibility of the valeryl side chains in this family of structures provides translocation models in line with magnetic resonance data which indicate that the translocation events involve motions of, at most, 7 A. Our models demonstrate that such motions may be accomplished by simple, observed conformational changes in bonds of the valeryl side chain which locally adjoin the bicyclic ring system. High resolution, low temperature diffraction data will allow visualization of the bonding and lone pair electrons in biotin. These studies will serve to extend and fine-tune our description of the electronic structure of biotin which is currently based on accurate measurements of bond distances and angles. PMID:3860171

  12. High-level Expression Purification Crystallization and Preliminary X-ray Crystallographic Studies of the Receptor Binding Domain of botulinum neurotoxin Serotype D

    SciTech Connect

    Y Zhang; X Gao; G Buchko; H Robinson; S Varnum

    2011-12-31

    Botulinum neurotoxins (BoNTs) are highly toxic proteins for humans and animals that are responsible for the deadly neuroparalytic disease botulism. Here, details of the expression and purification of the receptor-binding domain (HCR) of BoNT/D in Escherichia coli are presented. Using a codon-optimized cDNA, BoNT/D{_}HCR was expressed at a high level (150-200 mg per litre of culture) in the soluble fraction. Following a three-step purification protocol, very pure (>98%) BoNT/D{_}HCR was obtained. The recombinant BoNT/D{_}HCR was crystallized and the crystals diffracted to 1.65 {angstrom} resolution. The crystals belonged to space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 60.8, b = 89.7, c = 93.9 {angstrom}. Preliminary crystallographic data analysis revealed the presence of one molecule in the asymmetric unit.

  13. High-level expression, purification, crystallization and preliminary X-ray crystallographic studies of the receptor-binding domain of botulinum neurotoxin serotype D

    SciTech Connect

    Zhang, Y.; Robinson, H.; Gao, X.; Qin, L.; Buchko, G. W.; Varnum, S. M.

    2010-12-01

    Botulinum neurotoxins (BoNTs) are highly toxic proteins for humans and animals that are responsible for the deadly neuroparalytic disease botulism. Here, details of the expression and purification of the receptor-binding domain (HCR) of BoNT/D in Escherichia coli are presented. Using a codon-optimized cDNA, BoNT/D{_}HCR was expressed at a high level (150-200 mg per litre of culture) in the soluble fraction. Following a three-step purification protocol, very pure (>98%) BoNT/D{_}HCR was obtained. The recombinant BoNT/D{_}HCR was crystallized and the crystals diffracted to 1.65 {angstrom} resolution. The crystals belonged to space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 60.8, b = 89.7, c = 93.9 {angstrom}. Preliminary crystallographic data analysis revealed the presence of one molecule in the asymmetric unit.

  14. Space station needs, attributes and architectural options study commercialization working group briefing

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The benefits for each of the following commercial areas was investigated: communications, remote sensing, materials processing in space, low Earth orbit (LEO) satellite assembly, testing, and servicing, and space tourism. In each case, where economic benefits are derived, the costs for accomplishing tasks with the Space Station are compared with the cost with the Space Transportation System only.

  15. Determination of crystallographic intensities from sparse data

    PubMed Central

    Ayyer, Kartik; Philipp, Hugh T.; Tate, Mark W.; Wierman, Jennifer L.; Elser, Veit; Gruner, Sol M.

    2015-01-01

    X-ray serial microcrystallography involves the collection and merging of frames of diffraction data from randomly oriented protein microcrystals. The number of diffracted X-rays in each frame is limited by radiation damage, and this number decreases with crystal size. The data in the frame are said to be sparse if too few X-rays are collected to determine the orientation of the microcrystal. It is commonly assumed that sparse crystal diffraction frames cannot be merged, thereby setting a lower limit to the size of microcrystals that may be merged with a given source fluence. The EMC algorithm [Loh & Elser (2009 ?), Phys. Rev. E, 80, 026705] has previously been applied to reconstruct structures from sparse noncrystalline data of objects with unknown orientations [Philipp et al. (2012 ?), Opt. Express, 20, 13129–13137; Ayyer et al. (2014 ?), Opt. Express, 22, 2403–2413]. Here, it is shown that sparse data which cannot be oriented on a per-frame basis can be used effectively as crystallographic data. As a proof-of-principle, reconstruction of the three-dimensional diffraction intensity using sparse data frames from a 1.35?kDa molecule crystal is demonstrated. The results suggest that serial microcrystallography is, in principle, not limited by the fluence of the X-ray source, and collection of complete data sets should be feasible at, for instance, storage-ring X-ray sources. PMID:25610625

  16. Group Dynamics as a Critical Component of Successful Space Exploration: Conceptual Theory and Insights from the Biosphere 2 Closure Experiment

    NASA Astrophysics Data System (ADS)

    Nelson, Mark; Allen, John P.

    As space exploration and eventually habitation achieves longer durations, successfully managing group dynamics of small, physically isolated groups will become vital. The paper summarizes important underlying research and conceptual theory and how these manifested in a well-documented example: the closure experiments of Biosphere 2. Key research breakthroughs in discerning the operation of small human groups comes from the pioneering work of W.R. Bion. He discovered two competing modalities of behavior. The first is the “task-oriented” or work group governed by shared acceptance of goals, reality-thinking in relation to time, resources and rational, and intelligent management of challenges presented. The opposing, usually unconscious, modality is what Bion called the “basic-assumption” group and alternates between three “group animal” groups: dependency/kill the leader; fight/flight and pairing. If not dealt with, these dynamics work to undermine and defeat the conscious task group’s goal achievement. The paper discusses crew training and selection, various approaches to structuring the work and hierarchy of the group, the importance of contact with a larger population through electronic communication and dealing with the “us-them” syndrome frequently observed between crew and Mission Control. The experience of the first two year closure of Biosphere 2 is drawn on in new ways to illustrate vicissitudes and management of group dynamics especially as both the inside team of biospherians and key members of Mission Control had training in working with group dynamics. Insights from that experience may help mission planning so that future groups in space cope successfully with inherent group dynamics challenges that arise.

  17. Bilateral deep neck space infection in the paediatric age group: a case report and review of the literature.

    PubMed

    Songu, M; Demiray, U; Adibelli, Z H; Adibelli, H

    2011-06-01

    Deep neck space infections can occur at any age but require more intimate management in the paediatric age group because of their rapidly progressive nature. Concurrent abscess in distinct neck spaces has rarely been reported in healthy children. Herewith, a rare case of bilateral neck abscess is reported in a 16-month-old female and the clinical presentation and management are discussed with a review of the literature. PMID:22058596

  18. Extreme Covariant Quantum Observables in the Case of an Abelian Symmetry Group and a Transitive Value Space

    E-print Network

    Erkka Haapasalo; Juha-Pekka Pellonpää

    2011-05-05

    We represent quantum observables as POVMs (normalized positive operator valued measures) and consider convex sets of observables which are covariant with respect to a unitary representation of a locally compact Abelian symmetry group $G$. The value space of such observables is a transitive $G$-space. We characterize the extreme points of covariant observables and also determine the covariant extreme points of the larger set of all quantum observables. The results are applied to position, position difference and time observables.

  19. Transformation of Air Quality Monitor Data from the International Space Station into Toxicological Effect Groups

    NASA Technical Reports Server (NTRS)

    James, John T.; Zalesak, Selina M.

    2011-01-01

    The primary reason for monitoring air quality aboard the International Space Station (ISS) is to determine whether air pollutants have collectively reached a concentration where the crew could experience adverse health effects. These effects could be near-real-time (e.g. headache, respiratory irritation) or occur late in the mission or even years later (e.g. cancer, liver toxicity). Secondary purposes for monitoring include discovery that a potentially harmful compound has leaked into the atmosphere or that air revitalization system performance has diminished. Typical ISS atmospheric trace pollutants consist of alcohols, aldehydes, aromatic compounds, halo-carbons, siloxanes, and silanols. Rarely, sulfur-containing compounds and alkanes are found at trace levels. Spacecraft Maximum Allowable Concentrations (SMACs) have been set in cooperation with a subcommittee of the National Research Council Committee on Toxicology. For each compound and time of exposure, the limiting adverse effect(s) has been identified. By factoring the analytical data from the Air Quality Monitor (AQM), which is in use as a prototype instrument aboard the ISS, through the array of compounds and SMACs, the risk of 16 specific adverse effects can be estimated. Within each adverse-effect group, we have used an additive model proportioned to each applicable 180-day SMAC to estimate risk. In the recent past this conversion has been performed using archival data, which can be delayed for months after an air sample is taken because it must be returned to earth for analysis. But with the AQM gathering in situ data each week, NASA is in a position to follow toxic-effect groups and correlate these with any reported crew symptoms. The AQM data are supplemented with data from real-time CO2 instruments aboard the ISS and from archival measurements of formaldehyde, which the AQM cannot detect.

  20. Canonical Groups for Quantization on the Two-Dimensional Sphere and One-Dimensional Complex Projective Space

    NASA Astrophysics Data System (ADS)

    A, Sumadi A. H.; H, Zainuddin

    2014-11-01

    Using Isham's group-theoretic quantization scheme, we construct the canonical groups of the systems on the two-dimensional sphere and one-dimensional complex projective space, which are homeomorphic. In the first case, we take SO(3) as the natural canonical Lie group of rotations of the two-sphere and find all the possible Hamiltonian vector fields, and followed by verifying the commutator and Poisson bracket algebra correspondences with the Lie algebra of the group. In the second case, the same technique is resumed to define the Lie group, in this case SU (2), of CP'.We show that one can simply use a coordinate transformation from S2 to CP1 to obtain all the Hamiltonian vector fields of CP1. We explicitly show that the Lie algebra structures of both canonical groups are locally homomorphic. On the other hand, globally their corresponding canonical groups are acting on different geometries, the latter of which is almost complex. Thus the canonical group for CP1 is the double-covering group of SO(3), namely SU(2). The relevance of the proposed formalism is to understand the idea of CP1 as a space of where the qubit lives which is known as a Bloch sphere.

  1. Charge Conjugation from Space-Time Inversion in Qed:. Discrete and Continuous Groups

    NASA Astrophysics Data System (ADS)

    Pérez, B. Carballo; Socolovsky, M.

    We show that the CPT groups of QED emerge naturally from the {PT} and {P} (or {T}) subgroups of the Lorentz group. We also find relationships between these discrete groups and continuous groups, like the connected Lorentz and Poincaré groups and their universal coverings.

  2. REVIEW ARTICLE Protein crystallography for aspiring crystallographers or

    E-print Network

    REVIEW ARTICLE Protein crystallography for aspiring crystallographers or how to avoid pitfalls Dauter6 and Mariusz Jaskolski7 1 Protein Structure Section, Macromolecular Crystallography Laboratory Synchrotron Radiation Research Section, Macromolecular Crystallography Laboratory, NCI, Argonne National

  3. LDEF meteoroid and debris special investigation group investigations and activities at the Johnson Space Center

    NASA Technical Reports Server (NTRS)

    See, Thomas H.; Warren, Jack L.; Zolensky, Michael E.; Sapp, Clyde A.; Bernhard, Ronald P.; Dardano, Claire B.

    1995-01-01

    Since the return of the Long Duration Exposure Facility (LDEF) in January, 1990, members of the Meteoroid and Debris Special Investigation Group (M&D SIG) at the Johnson Space Center (JSC) in Houston, Texas have been examining LDEF hardware in an effort to expand the knowledge base regarding the low-Earth orbit (LEO) particulate environment. In addition to the various investigative activities, JSC is also the location of the general Meteoroid & Debris database. This publicly accessible database contains information obtained from the various M&D SIG investigations, as well as limited data obtained by individual LDEF Principal Investigators. LDEF exposed approximately 130 m(exp 2) of surface area to the LEO particulate environment, approximately 15.4 m(exp 2) of which was occupied by structural frame components (i.e., longerons and intercoastals) of the spacecraft. The data reported here was obtained as a result of detailed scans of LDEF intercoastals, 68 of which reside at JSC. The limited amount of data presently available on the A0178 thermal control blankets was reported last year and will not be reiterated here. The data presented here are limited to measurements of crater diameters and their frequency of occurrence (i.e., flux).

  4. A systematic method to identify the space group from PED and CBED patterns part I--theory.

    PubMed

    Morniroli, J P; Ji, G; Jacob, D

    2012-10-01

    This systematic method allows the unambiguous identification of the extinction and diffraction symbols of a crystal by comparison of a few experimental Precession Electron Diffraction (PED) patterns with theoretical patterns drawn for all the extinction and diffraction symbols. The method requires the detection of the Laue class, of the kinematically forbidden reflections and of the shift and periodicity differences between the reflections located in the First-Order Laue Zone (FOLZ) with respect to the ones located in the Zero-Order Laue Zone (ZOLZ). The actual space group can be selected, among the possible space groups connected with each extinction symbol or diffraction symbol, from the identification of the point group. This point group is available from observation of the 2D symmetry of the ZOLZ on Convergent-Beam Electron Diffraction (CBED) patterns. PMID:22770661

  5. Creating Social Spaces to Tackle AIDS-Related Stigma: Reviewing the Role of Church Groups in Sub-Saharan Africa

    Microsoft Academic Search

    C. Campbell; M. Skovdal; A. Gibbs

    2011-01-01

    An expanding body of literature explores the role of African church groups in facilitating or hindering the support of people\\u000a living with AIDS and challenging or contributing to HIV\\/AIDS-related stigma. Treating church groups as social spaces in which\\u000a HIV\\/AIDS-related stigma may potentially be challenged, we systematically review this literature, identifying five themes that\\u000a highlight the complex and contradictory role of

  6. Identification of succinic semialdehyde reductases from Geobacter: expression, purification, crystallization, preliminary functional, and crystallographic analysis

    SciTech Connect

    Zhang, Yanfeng; Gao, Xiaoli; Zheng, Yi; Garavito, R. Michael (MSU)

    2012-04-30

    Succinic semialdehyde reductase (SSAR) is an important enzyme involved in {gamma}-aminobutyrate (GABA) metabolism. By converting succinic semialdehyde (SSA) to {gamma}-hydroxybutyrate (GHB), the SSAR facilitates an alternative pathway for GABA degradation. In this study, we identified SSARs from Geobacter sulfurreducens and Geobacter metallireducens (GsSSAR and GmSSAR, respectively). The enzymes were over-expressed in Escherichia coli and purified to near homogeneity. Both GsSSAR and GmSSAR showed the activity of reducing SSA using nicotinamide adenine dinucleotide phosphate as a co-factor. The oligomeric sizes of GsSSAR and GmSSAR, as determined by analytical size exclusion chromatography, suggest that the enzymes presumably exist as tetramers in solution. The recombinant GsSSAR and GmSSAR crystallized in the presence of NADP{sup +}, and the resulting crystals diffracted to 1.89 {angstrom} (GsSSAR) and 2.25 {angstrom} (GmSSAR) resolution. The GsSSAR and GmSSAR crystals belong to the space groups P2{sub 1}22{sub 1} (a = 99.61 {angstrom}, b = 147.49 {angstrom}, c = 182.47 {angstrom}) and P1 (a = 75.97 {angstrom}, b = 79.14 {angstrom}, c = 95.47 {angstrom}, {alpha} = 82.15{sup o}, {beta} = 88.80{sup o}, {gamma} = 87.66{sup o}), respectively. Preliminary crystallographic data analysis suggests the presence of eight protein monomers in the asymmetric units for both GsSSAR and GmSSAR.

  7. X:\\Capital Development Group\\Documents & Forms & Guidelines\\Policies Procedures and Guidelines\\REF-FM-025 Space Management Guidelines V4

    E-print Network

    Li, Jiuyong "John"

    X:\\Capital Development Group\\Documents & Forms & Guidelines\\Policies Procedures and Guidelines Group member. #12;X:\\Capital Development Group\\Documents & Forms & Guidelines\\Policies Procedures\\REF-FM-025 Space Management Guidelines V4 260308.doc Page 1 of 7 REF-FM-025 REFERENCE DOCUMENT: Space

  8. PRE AND POST BREAKUP MOVEMENTS AND SPACE USE OF BLACK BEAR FAMILY GROUPS IN CHEROKEE NATIONAL FOREST, TENNESSEE

    Microsoft Academic Search

    ANTHONY P. CLEVENGER; MICHAEL R. PELTON

    The movements and space use of 7 yearling black bears (Ursus americanus) (3 males, 4 females) from 3 family groups were intensively monitored concurrently with 13 adults (6 males, 7 females) in the Cherokee National Forest, Tennessee from February 1983 until December 1983. The timing of family breakup occurred in 2 families between 29 May-5 June, and 22-25 June, respectively.

  9. Encoding Curved Tetrahedra in Face Holonomies: a Phase Space of Shapes from Group-Valued Moment Maps

    E-print Network

    Haggard, Hal M; Riello, Aldo

    2015-01-01

    We present a generalization of Minkowski's classic theorem on the reconstruction of tetrahedra from algebraic data to homogeneously curved spaces. Euclidean notions such as the normal vector to a face are replaced by Levi-Civita holonomies around each of the tetrahedron's faces. This allows the reconstruction of both spherical and hyperbolic tetrahedra within a unified framework. A new type of hyperbolic simplex is introduced in order for all the sectors encoded in the algebraic data to be covered. Generalizing the phase space of shapes associated to flat tetrahedra leads to group valued moment maps and quasi-Poisson spaces. These discrete geometries provide a natural arena for considering the quantization of gravity including a cosmological constant. A concrete realization of this is provided by the relation with the spin-network states of loop quantum gravity. This work therefore provides a bottom-up justification for the emergence of deformed gauge symmetries and quantum groups in 3+1 dimensional covariant...

  10. Phase-space formulation of quantum mechanics and quantum state reconstruction for physical systems with Lie-group symmetries

    E-print Network

    C. Brif; A. Mann

    1998-09-17

    We present a detailed discussion of a general theory of phase-space distributions, introduced recently by the authors [J. Phys. A {\\bf 31}, L9 (1998)]. This theory provides a unified phase-space formulation of quantum mechanics for physical systems possessing Lie-group symmetries. The concept of generalized coherent states and the method of harmonic analysis are used to construct explicitly a family of phase-space functions which are postulated to satisfy the Stratonovich-Weyl correspondence with a generalized traciality condition. The symbol calculus for the phase-space functions is given by means of the generalized twisted product. The phase-space formalism is used to study the problem of the reconstruction of quantum states. In particular, we consider the reconstruction method based on measurements of displaced projectors, which comprises a number of recently proposed quantum-optical schemes and is also related to the standard methods of signal processing. A general group-theoretic description of this method is developed using the technique of harmonic expansions on the phase space.

  11. Regularity Properties and Pathologies of Position-Space Renormalization-Group Transformations

    E-print Network

    A. C. D. van Enter; R. Fernandez; A. D. Sokal

    1992-10-22

    We reconsider the conceptual foundations of the renormalization-group (RG) formalism, and prove some rigorous theorems on the regularity properties and possible pathologies of the RG map. Regarding regularity, we show that the RG map, defined on a suitable space of interactions (= formal Hamiltonians), is always single-valued and Lipschitz continuous on its domain of definition. This rules out a recently proposed scenario for the RG description of first-order phase transitions. On the pathological side, we make rigorous some arguments of Griffiths, Pearce and Israel, and prove in several cases that the renormalized measure is not a Gibbs measure for any reasonable interaction. This means that the RG map is ill-defined, and that the conventional RG description of first-order phase transitions is not universally valid. For decimation or Kadanoff transformations applied to the Ising model in dimension $d \\ge 3$, these pathologies occur in a full neighborhood $\\{ \\beta > \\beta_0 ,\\, |h| < \\epsilon(\\beta) \\}$ of the low-temperature part of the first-order phase-transition surface. For block-averaging transformations applied to the Ising model in dimension $d \\ge 2$, the pathologies occur at low temperatures for arbitrary magnetic-field strength. Pathologies may also occur in the critical region for Ising models in dimension $d \\ge 4$. We discuss in detail the distinction between Gibbsian and non-Gibbsian measures, and give a rather complete catalogue of the known examples. Finally, we discuss the heuristic and numerical evidence on RG pathologies in the light of our rigorous theorems.

  12. Space station needs, attributes and architectural options study costing working group briefing

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The interface between tasks and the sequence of information flow are charted. The mission model and the requirements of each mission. These requirements along with the mission model schedule resulted in a further definition of the mission payloads, the Space Station architecture and the STS requirements was developed in task 2. The information was used to estimate the cost parameters necessary to generate cost estimates for the system with the aid of cost models for the Missions, Space Station and Space Transportation.

  13. Proceedings of the Space Shuttle Sortie Workshop. Volume 2: Working group reports

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Details are presented on the mission planning progress in each of the working paper reports. The general topics covered are the following: space technology; materials processing and space manufacturing; communications and navigation; earth and ocean physics; oceanography; earth resources and surface environmental quality; meteorology and atmospheric environmental quality; life sciences; atmospheric and space physics; solar physics; high energy cosmic rays; X-ray and gamma ray astronomy; ultraviolet-optical astronomy; planetary astronomy; and infrared astronomy.

  14. REQUEST FOR LEASED SPACE 3. FROM: (REQUESTING DIVISION) 4. FOR: (USER GROUP)

    E-print Network

    . FT. SUBTOTAL 13. SPECIAL REQUIREMENTS AND SERVICES (See Attached) ATTACHMENTS A. PRIMARY OFFICE AREA Spaces (Government Vehicles) BUDGET NO. PRINT NAME AND TITLE PHONE NO. DATE 15. SIGNATURE (BUSINESS MANAGER) DATE 16. SIGNATURE (SPACE ALLOCATION MANAGER) DATE 17. FOR REAL ESTATE USE ONLY RECOMMENDED

  15. Group theory for structural analysis and lattice vibrations in phosphorene systems

    NASA Astrophysics Data System (ADS)

    Ribeiro-Soares, J.; Almeida, R. M.; Cançado, L. G.; Dresselhaus, M. S.; Jorio, A.

    2015-05-01

    Group theory analysis for two-dimensional elemental systems related to phosphorene is presented, including (i) graphene, silicene, germanene, and stanene; (ii) their dependence on the number of layers; and (iii) their two possible stacking arrangements. Departing from the most symmetric D6h 1 graphene space group, the structures are found to have a group-subgroup relation, and analysis of the irreducible representations of their lattice vibrations makes it possible to distinguish between the different allotropes. The analysis can be used to study the effect of strain, to understand structural phase transitions, to characterize the number of layers, crystallographic orientation, and nonlinear phenomena.

  16. Variations in Reactivity on Different Crystallographic Orientations of Cerium Oxide

    SciTech Connect

    Mullins, David R [ORNL] [ORNL; Albrecht, Peter M [ORNL] [ORNL; Calaza, Florencia C [ORNL] [ORNL

    2013-01-01

    Cerium oxide is a principal component in many heterogeneous catalytic processes. One of its key characteristics is the ability to provide or remove oxygen in chemical reactions. The different crystallographic faces of ceria present significantly different surface structures and compositions that may alter the catalytic reactivity. The structure and composition determine the number of coordination vacancies surrounding surface atoms, the availability of adsorption sites, the spacing between adsorption sites and the ability to remove O from the surface. To investigate the role of surface orientation on reactivity, CeO2 films were grown with two different orientations. CeO2(100) films were grown ex situ by pulsed laser deposition on Nb-doped SrTiO3(100). CeO2(111) films were grown in situ by thermal deposition of Ce metal onto Ru(0001) in an oxygen atmosphere. The chemical reactivity was characterized by the adsorption and decomposition of various molecules such as alcohols, aldehydes and organic acids. In general the CeO2(100) surface was found to be more active, i.e. molecules adsorbed more readily and reacted to form new products, especially on a fully oxidized substrate. However the CeO2(100) surface was less selective with a greater propensity to produce CO, CO2 and water as products. The differences in chemical reactivity are discussed in light of possible structural terminations of the two surfaces. Recently nanocubes and nano-octahedra have been synthesized that display CeO2(100) and CeO2(111) faces, respectively. These nanoparticles enable us to correlate reactions on high surface area model catalysts at atmospheric pressure with model single crystal films in a UHV environment.

  17. Overexpression, purification, crystallization and preliminary crystallographic studies of a hyperthermophilic adenylosuccinate synthetase from Pyrococcus horikoshii OT3

    PubMed Central

    Wang, Xiaoying; Akasaka, Ryogo; Takemoto, Chie; Morita, Satoshi; Yamaguchi, Machiko; Terada, Takaho; Shirozu, Mikako; Yokoyama, Shigeyuki; Chen, Shilin; Si, Shuyi; Xie, Yong

    2011-01-01

    Adenylosuccinate synthetase (AdSS) is a ubiquitous enzyme that catalyzes the first committed step in the conversion of inosine monophosphate (IMP) to adenosine monophosphate (AMP) in the purine-biosynthetic pathway. Although AdSS from the vast majority of organisms is 430–457 amino acids in length, AdSS sequences isolated from thermophilic archaea are 90–120 amino acids shorter. In this study, crystallographic studies of a short AdSS sequence from Pyrococcus horikoshii OT3 (PhAdSS) were performed in order to reveal the unusual structure of AdSS from thermophilic archaea. Crystals of PhAdSS were obtained by the microbatch-under-oil method and X-ray diffraction data were collected to 2.50?Å resolution. The crystal belonged to the trigonal space group P3212, with unit-cell parameters a = b = 57.2, c = 107.9?Å. There was one molecule per asymmetric unit, giving a Matthews coefficient of 2.17?Å3?Da?1 and an approximate solvent content of 43%. In contrast, the results of native polyacrylamide gel electrophoresis and analytical ultracentrifugation showed that the recombinant PhAdSS formed a dimer in solution. PMID:22139164

  18. Effect of lone-electron-pair cations on the orientation of crystallographic shear planes in anion-deficient perovskites.

    PubMed

    Batuk, Dmitry; Batuk, Maria; Abakumov, Artem M; Tsirlin, Alexander A; McCammon, Catherine; Dubrovinsky, Leonid; Hadermann, Joke

    2013-09-01

    Factors affecting the structure and orientation of the crystallographic shear (CS) planes in anion-deficient perovskites were investigated using the (Pb(1-z)Sr(z))(1-x)Fe(1+x)O(3-y) perovskites as a model system. The isovalent substitution of Sr(2+) for Pb(2+) highlights the influence of the A cation electronic structure because these cations exhibit very close ionic radii. Two compositional ranges have been identified in the system: 0.05 ? z ? 0.2, where the CS plane orientation gradually varies but stays close to (203)p, and 0.3 ? z ? 0.45 with (101)p CS planes. The incommensurately modulated structure of Pb0.792Sr0.168Fe1.040O2.529 was refined from neutron powder diffraction data using the (3 + 1)D approach (space group X2/m(?0?), X = (1/2, 1/2, 1/2, 1/2), a = 3.9512(1) Å, b = 3.9483(1) Å, c = 3.9165(1) Å, ? = 93.268(2)°, q = 0.0879(1)a* + 0.1276(1)c*, RF = 0.023, RP = 0.029, and T = 900 K). A comparison of the compounds with different CS planes indicates that the orientation of the CS planes is governed mainly by the stereochemical activity of the lone-electron-pair cations inside the perovskite blocks. PMID:23968159

  19. Crystallographic characterization of the radixin FERM domain bound to the cytoplasmic tail of adhesion molecule CD44

    SciTech Connect

    Mori, Tomoyuki; Kitano, Ken; Terawaki, Shin-ichi; Maesaki, Ryoko; Hakoshima, Toshio, E-mail: hakosima@bs.naist.jp [Structural Biology Laboratory, Nara Institute of Science and Technology, Keihanna Science City, Nara 630-0192 (Japan)

    2007-10-01

    The radixin FERM domain complexed with the CD44 cytoplasmic tail peptide has been crystallized. A diffraction data set from the complex was collected to 2.1 Å. CD44 is an important adhesion molecule that specifically binds hyaluronic acid and regulates cell–cell and cell–matrix interactions. Increasing evidence has indicated that CD44 is assembled in a regulated manner into the membrane–cytoskeletal junction, a process that is mediated by ERM (ezrin/radixin/moesin) proteins. Crystals of a complex between the radixin FERM domain and the C-terminal cytoplasmic region of CD44 have been obtained. The crystal of the radixin FERM domain bound to the CD44 cytoplasmic tail peptide belongs to space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 62.70, b = 66.18, c = 86.22 Å, and contain one complex in the crystallographic asymmetric unit. An intensity data set was collected to a resolution of 2.1 Å.

  20. Crystallographic, electronic, and magnetic studies of zeta(2)-GaM (M = Cr, Mn or Fe): trends in itinerant magnetism.

    PubMed

    Gourdon, Olivier; Bud'ko, Sergey L; Williams, Darrick; Miller, Gordon J

    2004-05-17

    This study of the crystal structure, electronic structure, and magnetic properties of the zeta(2)-GaM (M = Cr, Mn or Fe) alloys is motivated by the recent reinvestigation of the crystallographic Al(8)Cr(5) structure type of zeta(2)-GaMn. The isostructural compounds zeta(2)-GaFe and zeta(2)-GaCr have been refined using X-ray powder diffraction as well as neutron powder diffraction for zeta(2)-GaFe. Their structures have been refined using the space group Rm, with cell parameters a = 12.625(8) A and c = 7.785(10) A for zeta(2)-GaCr and a = 12.4368(11) A and c = 7.7642(10) A for zeta(2)-GaFe. Band structure calculations using the self-consistent, spin-polarized TB-LMTO method were performed to understand their electronic structure and magnetic properties. Band calculations show that from GaCr to GaFe the magnetic interactions change from weakly antiferromagnetic coupling to ferromagnetic coupling. Magnetic measurements confirm ferromagnetism for GaFe and show a weak paramagnetic response for GaCr. PMID:15132628

  1. Group classification of the Sachs equations for a radiating axisymmetric, non-rotating, vacuum space-time

    E-print Network

    Nail H. Ibragimov; Ewald J. H. Wessels; George F. R. Ellis

    2006-11-21

    We carry out a Lie group analysis of the Sachs equations for a time-dependent axisymmetric non-rotating space-time in which the Ricci tensor vanishes. These equations, which are the first two members of the set of Newman-Penrose equations, define the characteristic initial-value problem for the space-time. We find a particular form for the initial data such that these equations admit a Lie symmetry, and so defines a geometrically special class of such spacetimes. These should additionally be of particular physical interest because of this special geometric feature.

  2. Magneto-transport study in single crystals of Cd3 As2 with different space group symmetry

    NASA Astrophysics Data System (ADS)

    Guo, Shih-Ting; Sankar, Raman; Chien, Yung-Yu; Jeng, Horng-Tay; Guo, G. Y.; Chou, F. C.; Lee, Wei-Li; Institute of Physics, Academia Sinica, Taiwan Collaboration; Center of condensed matter sciences, National Taiwan University, Taiwan Collaboration; Department of Physics, National Taiwan University, Taiwan Collaboration; Department of Physics, National Tsing Hua University, Taiwan Collaboration

    2015-03-01

    The 3-D Dirac semi-metal Cd3As2 is known as a potential parent compound for several unique topological phases such as Weyl semi-metal, topological superconductor, and axion insulator. Its 3D Dirac band has recently been demonstrated by ARPES experiments. In this report, we conduct magneto-transport measurements on single crystals of Cd3As2 with three different space group symmetries of I41cd, I41/acd, and P42/nmc, which was characterized by X-ray diffraction. Large anisotropy magnetoresistance and splitting of SdH frequency were observed in all Cd3As2crystals under investigation regardless of the type of space group symmetry suggesting that defects may play an important role. Detailed magneto-transport data at various field orientations will be presented and discussed..

  3. Position-space renormalization-group approach for driven diffusive systems applied to the asymmetric exclusion model.

    PubMed

    Georgiev, Ivan T; McKay, Susan R

    2003-05-01

    This paper introduces a position-space renormalization-group approach for nonequilibrium systems and applies the method to a driven stochastic one-dimensional gas with open boundaries. The dynamics are characterized by three parameters: the probability alpha that a particle will flow into the chain to the leftmost site, the probability beta that a particle will flow out from the rightmost site, and the probability p that a particle will jump to the right if the site to the right is empty. The renormalization-group procedure is conducted within the space of these transition probabilities, which are relevant to the system's dynamics. The method yields a critical point at alpha(c)=beta(c)=1/2, in agreement with the exact values, and the critical exponent nu=2.71, as compared with the exact value nu=2.00. PMID:12786216

  4. Group dynamics in a long-term blind endeavor on Earth: An analog for space missions (Lewis & Clark Expedition group dynamic analysis)

    NASA Astrophysics Data System (ADS)

    Allner, M.; Rygalov, V.

    2008-12-01

    In 1803, President Thomas Jefferson set fourth a military expedition led by Captains M. Lewis and W. Clark (Lewis and Clark Expedition) on an exploration that would become an everlasting part of US national history and pride. Looking back at the events of this exploration, there are many similarities to the experiences future human space explorers will face as we look to colonize the Moon and travel to Mars and beyond (NASA Vision for Space Exploration, 2004): The Lewis and Clark Expedition lasted almost three years and involved a crew of 43 men traveling up the Missouri River to explore the unknown lands and a possible water route to the Pacific Ocean; The Expedition took place far away from customary comfortable environments known to European settlers in the early 18th century; The Expedition involved a remotely confined high-perceived risk environment with high levels of uncertainty providing stresses and every day challenges for the crew; Supplies brought on the mission were limited (mainly a mass/weight issue rather than cost), therefore the discovery and use of environmental resources (In-Situ Resource Utilization approach, including info-resources to mitigate uncertainty) was necessary for crew survival. The environments astronauts will encounter in space and on the Moon and Mars due to high risk and uncertainty will be in many aspects similar to what Lewis and Clark's crew experienced, as environments will be hostile and unforgiving if problems arise and aren't resolved quickly. The analysis provided in this research paper is relevant because the Lewis and Clark Expedition needed to move extensively and with minimal supplies. Polar remote settings, which were analyzed extensively, were different from this expedition due to the fact that these missions did not encompass extensive movement of crew facilities and supplies and were more like space missions orbiting the Earth. Using past space station results of performance on orbit in correlation with a suggested distinguishable mission phase model, the Lewis and Clark Expedition will be analyzed for similarities to these space findings. Factors of consideration in support of this analysis involve an understanding of the leadership qualities of Lewis and Clark (and relations established and maintained with one another), the selection and diversity of their crew, and the group dynamics that were developed and maintained so carefully during the expedition. With this knowledge and understanding one can gain enormous insights useful in the planning and preparation for future long-duration space exploratory missions with high level of autonomy, mobility, minimal primary life support supply and high dependence on material re-circulation and In-Situ Resource Utilization approach.

  5. Position-space renormalization-group approach for driven diffusive systems applied to the asymmetric exclusion model

    Microsoft Academic Search

    Ivan T. Georgiev; Susan R. McKay

    2003-01-01

    This paper introduces a position-space renormalization-group approach for\\u000anonequilibrium systems and applies the method to a driven stochastic\\u000aone-dimensional gas with open boundaries. The dynamics are characterized by\\u000athree parameters: the probability $\\\\alpha$ that a particle will flow into the\\u000achain to the leftmost site, the probability $\\\\beta$ that a particle will flow\\u000aout from the rightmost site, and the

  6. Position-space renormalization-group approach for driven diffusive systems applied to the asymmetric exclusion model

    Microsoft Academic Search

    Ivan T. Georgiev; Susan R. McKay

    2003-01-01

    This paper introduces a position-space renormalization-group approach for nonequilibrium systems and applies the method to a driven stochastic one-dimensional gas with open boundaries. The dynamics are characterized by three parameters: the probability alpha that a particle will flow into the chain to the leftmost site, the probability beta that a particle will flow out from the rightmost site, and the

  7. Forced coalescence phasing: a method for ab initio determination of crystallographic phases.

    PubMed Central

    Drendel, W B; Davé, R D; Jain, S

    1995-01-01

    A method has been developed for ab initio determination of crystallographic phases. This technique, called forced coalescence phasing (FCP), is implemented on a computer and uses an automated iterative procedure that combines real space filtering with numerically seeded Fourier transforms to solve the crystallographic phase problem. This approach is fundamentally different from that of traditional direct methods of phasing, which rely on structure invariant probabilistic phase relationships. In FCP, the process begins with an appropriate set of atoms randomly distributed throughout the unit cell. In subsequent cycles of the program, these atoms undergo continual rearrangements ultimately forming the correct molecular structure(s) consistent with the observed x-ray data. In each cycle, the molecular rearrangement is directed by an electron density (Fourier) map calculated using specially formulated numerical seed coefficients that, along with the phase angles for the map, are derived from the arrangement of atoms in the preceding cycle. The method has been tested using actual x-ray data from three organic compounds. For each data set, 100 separate phase determination trials were conducted, each trial beginning with a different set of randomly generated starting phases. Correct phase sets were successfully determined in all of the trials with most trials requiring fewer than 50 cycles of the FCP program. In addition to its effectiveness in small molecule phase determination, FCP offers unexplored potential in the application of real-space methods to ab initio phasing of proteins and other macromolecule structures. PMID:11607507

  8. Space station needs attributes and architectural options study costing working group briefing

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Individuals in the United States who understand the promise of materials processing in space and who also are senior technical personnel associated with commercial firms that process materials: (1) endorsed the concept of a space station as a desirable national asset; (2) stated that a commercial MPS research program is mandatory to extend commericalization of space for materials processing; and (3) described in general terms a national research laboratory and free flying facilities that are needed. Participants agreed that industry R&D is motivated largely by market pull rather than by technology push, that initial interest is low-g materials research; and that to farther, commercial market assurance (a salable product) is a must.

  9. REQUEST FOR LEASED SPACE 3. FROM: (REQUESTING DIVISION) 4. FOR: (USER GROUP)

    E-print Network

    ORNL-669 (Formerly OR-F-4300.16) (10-2005) Exception Print Form Oct-17-2005 Asset Management Real. FT. SUBTOTAL 13. SPECIAL REQUIREMENTS AND SERVICES (See Attached) ATTACHMENTS A. PRIMARY OFFICE AREA Spaces (Government Vehicles) BUDGET NO. PRINT NAME AND TITLE PHONE NO. DATE 15. SIGNATURE (BUSINESS

  10. PHENIX: Developing new software for automated crystallographic structure determination

    Microsoft Academic Search

    Paul D. Adams; Ralf W. Grosse-Kunstleve; Li-Wei Hung; Thomas R. Ioerger; Airlie J. McCoy; Nigel W. Moriarty; Randy J. Read; James C. Sacchettini; Nicholas K. Sautera; Thomas C. Terwilligerf

    2002-01-01

    Structural genomics seeks to expand rapidly the number of protein structures in order to extract the maximum amount of information from genomic sequence databases. The advent of several large-scale projects worldwide leads to many new challenges in the field of crystallographic macromolecular structure determination. A novel software package called PHENIX (Python-based Hierarchical ENvironment for Integrated Xtallography) is therefore being developed.

  11. Detailed insights from microarray and crystallographic studies into carbohydrate

    E-print Network

    Davis, Ben G.

    Detailed insights from microarray and crystallographic studies into carbohydrate recognition of the parasite can be explained by carbohydrate microarray screening analyses that have demonstrated the ability of TgMIC1 to 2-3- and 2-6-linked sialyl carbohydrates. Interestingly, two novel synthetic fluorinated

  12. Atomic structure of defects in anion-deficient perovskite-based ferrites with a crystallographic shear structure.

    PubMed

    Batuk, Maria; Turner, Stuart; Abakumov, Artem M; Batuk, Dmitry; Hadermann, Joke; Van Tendeloo, Gustaaf

    2014-02-17

    Crystallographic shear (CS) planes provide a new structure-generation mechanism in the anion-deficient perovskites containing lone-pair cations. Pb2Sr2Bi2Fe6O16, a new n = 6 representative of the A(n)B(n)O(3n-2) homologous series of the perovskite-based ferrites with the CS structure, has been synthesized using the solid-state technique. The structure is built of perovskite blocks with a thickness of four FeO6 octahedra spaced by double columns of FeO5 edge-sharing distorted tetragonal pyramids, forming 1/2[110](101)p CS planes (space group Pnma, a = 5.6690(2) Å, b = 3.9108(1) Å, c = 32.643(1) Å). Pb2Sr2Bi2Fe6O16 features a wealth of microstructural phenomena caused by the flexibility of the CS planes due to the variable ratio and length of the constituting fragments with {101}p and {001}p orientation. This leads to the formation of "waves", "hairpins", "?-shaped" defects, and inclusions of the hitherto unknown layered anion-deficient perovskites Bi2(Sr,Pb)Fe3O8.5 and Bi3(Sr,Pb)Fe4O11.5. Using a combination of diffraction, imaging, and spectroscopic transmission electron microscopy techniques this complex microstructure was fully characterized, including direct determination of positions, chemical composition, and coordination number of individual atomic species. The complex defect structure makes these perovskites particularly similar to the CS structures in ReO3-type oxides. The flexibility of the CS planes appears to be a specific feature of the Sr-based system, related to the geometric match between the SrO perovskite layers and the {100}p segments of the CS planes. PMID:24479580

  13. Recovery of Crystallographic Texture in Remineralized Dental Enamel

    PubMed Central

    Siddiqui, Samera; Anderson, Paul; Al-Jawad, Maisoon

    2014-01-01

    Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture) and position of the (002) Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected enamel to regain structural integrity. PMID:25360532

  14. Banach frames in coorbit spaces consisting of elements which are invariant under symmetry groups

    E-print Network

    Feichtinger, Hans Georg

    the continuous transform. As examples, the continuous wavelet transform and the short time Fourier transform function on the positive halfline R+ and it turned out in [18] that the continuous wavelet transform representation theory of locally compact groups. In this abstract setting the theory for the continuous transform

  15. Finding a Space for Professional Development: Creating Thirdspace through After-School Writing Groups

    ERIC Educational Resources Information Center

    Brooke, Robert; Coyle, Deborah; Walden, Anne; Healey, Conniem; Larson, Kim; Laughridge, Virginia; Ridder, Kim; Williams, Molly; Williams, Shawn

    2005-01-01

    This article describes a teacher study group focusing on After School Writing Circles for elementary students as a site of Thirdspace professional development. Borrowing the concept of Thirdspace from postmodern geographer Edward Soja, the authors argue that professional development works best when teachers engage in the dual work of imagining and…

  16. Learning in Large Learning Spaces: The Academic Engagement of a Diverse Group of Students

    ERIC Educational Resources Information Center

    Hunt, Clive

    2012-01-01

    Teaching larger groups of students is a growing phenomenon in HE and this brings with it its own challenges, not least for the students themselves but also for their lecturers. Demographic factors as well as the experiences that characterise us as individuals will impact upon our ability to learn. The pilot study reported here considered the…

  17. Limit points in the space of left orderings of a group University of British Columbia

    E-print Network

    Harizanov, Valentina S.

    for isolated points in LO(G); those positive cones P satisfying {P} = n i=1 Ugi , for some finite family, for a given group G, we look for isolated points in LO(G); those positive cones P satisfying {P} = n i=1 Ugi

  18. Communication constraints, indexical countermeasures, and crew configuration effects in simulated space-dwelling groups

    Microsoft Academic Search

    Robert D. Hienz; Joseph V. Brady; Steven R. Hursh; Michele J. Banner; Eric D. Gasior; Kevin R. Spence

    2007-01-01

    Previous research with groups of individually isolated crews communicating and problem-solving in a distributed interactive simulation environment has shown that the functional interchangeability of available communication channels can serve as an effective countermeasure to communication constraints. The present report extends these findings by investigating crew performance effects and psychosocial adaptation following: (1) the loss of all communication channels, and (2)

  19. Localization of the Einstein group and a nonsingular cosmological model of space-time with torsion

    Microsoft Academic Search

    V. N. Tunyak

    1986-01-01

    We consider an Einstein-invariant gauge theory of gravitation (EGT), obtained by localizing the group of motions of a homogeneous static Einstein Universe. Taking into account the cosmological term, we find exact solutions of EGT are as nonsingular homogeneous Isotropic cosmological models with both the metric and the torsion regular. It is shown that EGT satisfies the principle of correspondence with

  20. Localization of the Einstein group and a nonsingular cosmological model of space-time with torsion

    Microsoft Academic Search

    Tunyak

    1987-01-01

    The authors consider an Einstein-invariant gauge theory of gravitation (EGT), obtained by localizing the group of motions of a homogeneous static Einstein Universe. Taking into account the cosmological term, they find exact solutions of EGT are as nonsingular homogeneous isotropic cosmological models with both the metric and the torsion regular. It is shown that EGT satisfies the principle of correspondence

  1. Crystallographic orientation dependence of impurity incorporation into III-V compound semiconductors grown by metalorganic vapor phase epitaxy

    Microsoft Academic Search

    Makoto Kondo; Chikashi Anayama; Naoko Okada; Hiroshi Sekiguchi; Kay Domen; Toshiyuki Tanahashi

    1994-01-01

    This article presents a comprehensive study of the dependence of impurity incorporation on the crystallographic orientation during metalorganic phase epitaxy of III-V compound semiconductors. We performed doping experiments for group-II impurities (Zn and Mg), group-VI impurities (Se and O), and a group-IV impurity (Si form SiH4 and Si2H6). The host materials were GaAs, Ga(0.5)In(0.5)P, and (Al(0.7)Ga(0.3))(0.5)In(0.5)P grown on GaAs substrates.

  2. Real-space renormalization-group investigation of the randomly dilute q-state Potts model

    Microsoft Academic Search

    A. Bakchich; A. Benyoussef; T. Biaz; L. Laanait

    1988-01-01

    The randomly bond-diluted two-dimensional nearest-neighbor q-state Potts ferromagnet and antiferromagnet on the square lattice is studied by renormalization-group methods based on the Migdal-Kadanoff approximate recursion relations. In the bond-diluted ferromagnet Potts model, differential recursion relations yield a phase diagram which is in quantitative agreement with all known results for q<=4. In the bond-diluted antiferromagnet Potts model, the phase diagram obtained

  3. Polar space group and complex magnetism in Ni11?(HPO3)8(OH)6: towards a new multiferroic material?

    NASA Astrophysics Data System (ADS)

    Poienar, M.; Maignan, A.; Sfirloaga, P.; Malo, S.; Vlazan, P.; Guesdon, A.; Lainé, F.; Rouquette, J.; Martin, C.

    2015-01-01

    The Ni11?(HPO3)8(OH)6 phosphite was prepared using a hydrothermal method. Depending on the pressure used during the synthesis, different hierarchical superstructures were encountered, including a new original cross-shaped star. The as-obtained products were characterized by X-ray diffraction, scanning and transmission electron microscopy and magnetization. In agreement with the presence of transition metal dimers in the structure, a complex magnetic behavior is observed at low temperature. This magnetic ground-state, combined with the non-centrosymmetry of the space group, creates new opportunities for applications in this class of open framework inorganic materials.

  4. Group dynamics during the EXEMSI isolation study. Experimental Campaign for the European Manned Space Infrastructure.

    PubMed

    Cazes, C; Rosnet, E; Bachelard, C; Le Scanff, C; Rivolier, J

    1996-01-01

    The objectives of this study were to investigate the social behavior, interrelations, cohesion, efficiency and team formation of the crew during 60 days of isolation and confinement, to make a critical comparison of a variety of test methods used for this purpose and to formulate recommendations for their applications in selection, training and support for future studies of this kind. The study consisted of three phases: (1) the pre-isolation period, in which initial individual and group assessment were made to understand the motivation, characteristics, and styles of the crew members, the state of the crew, and to make a prognosis for the behavior of the group and its members, (2) the isolation period, with tests and observations to follow and analyze behavior and group dynamics of the crew, and to detect manifestations of stress, and (3) the post-isolation period with final assessment and debriefing. During these three periods individual and group tests were carried out. Direct methods, questionnaires and tests, as well as indirect methods, observations of behavior, were used. These had cognitive, affective-emotional and social components; they were quantitative, qualitative or a combination. Before isolation the crew members expressed strong confidence in the team and in their own personal capability. The leadership of the Commander seemed uncontested. Crew functioning during this period was conflict-free, but was structured in a rather rigid and defensive way (isolation of affects, denial of anxiety). Apparently, the members strongly needed to present a good image image of themselves. The relatively short period of the experiment, and the absence of real risk suggested that the crew would be able to maintain their cohesion, but in a real spaceflight situation this behavior could be inadequate and even dangerous. The pre-isolation prognosis for crew behavior during isolation was validated to a large extent. During isolation there were no clear manifestations of stress. Nevertheless, the confinement and isolation were experienced as the major stress factors. The crew members described themselves as a heterogeneous but harmonious group that was successful in their mission. In fact, the team maintained its cohesion by opposing external authority, using management as a scapegoat. Occasionally, in times of crisis, they also criticized ground crew. The Commander supported this attitude. Strongly differences in personality and behavior were noted. Analysis of the sociometric data showed that the asserted harmony was more apparent than real. It is questionable whether the group cohesion would have persisted in a life threatening crisis or even in a prolongation of the experiment. The most reliable instruments for this type of survey seem to be: group methods, non-obstructive tests, indirect instruments, and qualitative tools. The least reliable are: strictly quantitative methods, self-evaluations, standard debriefing techniques, since these reinforced in most cases subjects' defenses in an unconscious avoidance of criticism. Several recommendations were made for the organization, definition of objectives, experiment selection, crew selection, roles of external management and personnel. In particular, it is felt to be necessary to explain the aims of the mission to the subjects, to give clear and complete information, to establish confident and cooperative relations with the crew. It is essential to allow dialogue, to take opinions and suggestions of the crew seriously, and to establish clear rules of confidentiality. PMID:8814802

  5. Crystallization and preliminary crystallographic analysis of the catalytic domain of human flap endonuclease 1 in complex with a nicked DNA product: use of a DPCS kit for efficient protein–DNA complex crystallization

    SciTech Connect

    Sakurai, Shigeru; Kitano, Ken [Structural Biology Laboratory, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Morioka, Hiroshi [Department of Analytical and Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-motomachi 5-1, Kumamoto 862-0973 (Japan); Hakoshima, Toshio, E-mail: hakosima@bs.naist.jp [Structural Biology Laboratory, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan)

    2008-01-01

    Human flap endonuclease 1 complexed with nicked DNA has been crystallized. A diffraction data set was collected to a resolution of 2.75 Å. Flap endonuclease 1 (FEN1) is a structure-specific nuclease that removes the RNA/DNA primer associated with Okazaki fragments in DNA replication. Here, crystals of the complex between the catalytic domain of human FEN1 and a DNA product have been obtained. For efficient crystallization screening, a DNA–protein complex crystallization screening (DPCS) kit was designed based on commercial crystallization kits. The crystal was found to belong to space group P2{sub 1}, with unit-cell parameters a = 61.0, b = 101.3, c = 106.4 Å, ? = 106.4°. The asymmetric unit is predicted to contain two complexes in the crystallographic asymmetric unit. A diffraction data set was collected to a resolution of 2.75 Å.

  6. My Time, My Space (an arts-based group for women with postnatal depression): a project report.

    PubMed

    Morton, Alison; Forsey, Philippa

    2013-05-01

    This paper will describe an innovative method of treatment for women with postnatal depression that has been used in the south west of England since 2004 and has now been successfully piloted in other areas of the UK. My Time My Space is an arts-based group for women with postnatal depression that aims to improve mood by reducing social isolation and using creativity to improve self-esteem. Results of the programme will be shared, in addition to the ways in which the project has been implemented using collaborative working with children's centres and building community capacity by engaging local charities. The qualitative results have been collected from participants (n = 30) over the last two years using post-course evaluation forms with open questions to elicit participants' views. The quantitative results of a small pilot study (n = 8) based on pre- and post-group Edinburgh Postnatal Depression Scale scores (EPDS) are also reported. The findings suggest My Time My Space has a positive effect on women's mood and perceived social support, and provides an effective alternative or additional method of treatment for postnatal depression. PMID:23724760

  7. Electrochemical and Crystallographic Aspects of Lead Granular Growth

    NASA Astrophysics Data System (ADS)

    Nikoli?, Nebojša D.; Ivanovi?, Evica R.; Brankovi?, Goran; La?njevac, Uroš ?.; Stevanovi?, Sanja I.; Stevanovi?, Jasmina S.; Pavlovi?, Miomir G.

    2015-06-01

    Lead granules synthesized by the potentiostatic regime of electrolysis were characterized by the scanning electron microscopy technique. Effect of the different parameters of electrolysis, such as solution composition, overpotential of electrodeposition, and quantity of the electricity, on lead granular growth has been systematically investigated. Aside from the electrochemical aspects of lead granular growth, crystallographic aspects of the obtained granules were also analyzed. In the dependence of the electrodeposition conditions, granules of various shapes were obtained. The granules, such as octahedrons and hexagons, as well as many various types of twinned particles: single-twinned, multiply-twinned, lamellar-twinned, and many other complicated shapes denoted as polyparticles, were synthesized through regulation of the parameters of electrolysis. Increasing both the concentration of Pb2+ ions and overpotential of the electrodeposition favored the formation of more complicated forms. Formation of granules of specified crystallographic characteristics was also correlated with the basic principle of metal electrocrystallization.

  8. An alternative to the crystallographic reconstruction of austenite in steels

    SciTech Connect

    Bernier, Nicolas, E-mail: n.bernier@yahoo.fr [OCAS N.V., ArcelorMittal R and D Gent, Pres. J.F. Kennedylaan 3, 9060 Zelzate (Belgium); Bracke, Lieven, E-mail: lieven.bracke@arcelormittal.com [OCAS N.V., ArcelorMittal R and D Gent, Pres. J.F. Kennedylaan 3, 9060 Zelzate (Belgium); Malet, Loïc; Godet, Stéphane [Université Libre de Bruxelles, 4 MAT (Materials Engineering, Characterisation, Synthesis and Recycling), Avenue F.D. Roosevelt 50, CP 194/03, 1050 Brussels (Belgium)

    2014-03-01

    An alternative crystallographic austenite reconstruction programme written in Matlab is developed by combining the best features of the existing models: the orientation relationship refinement, the local pixel-by-pixel analysis and the nuclei identification and spreading strategy. This programme can be directly applied to experimental electron backscatter diffraction mappings. Its applicability is demonstrated on both quenching and partitioning and as-quenched lath-martensite steels. - Highlights: • An alternative crystallographic austenite reconstruction program is developed. • The method combines a local analysis and a nuclei identification/spreading strategy. • The validity of the calculated orientation relationship is verified on a Q and P steel. • The accuracy of the reconstructed microtexture is investigated on a martensite steel.

  9. The Exploration Atmospheres Working Group's Report on Space Radiation Shielding Materials

    NASA Technical Reports Server (NTRS)

    Barghouty, A. F.; Thibeault, S. A.

    2006-01-01

    This part of Exploration Atmospheres Working Group analyses focuses on the potential use of nonmetallic composites as the interior walls and structural elements exposed to the atmosphere of the spacecraft or habitat. The primary drive to consider nonmetallic, polymer-based composites as an alternative to aluminum structure is due to their superior radiation shielding properties. But as is shown in this analysis, these composites can also be made to combine superior mechanical properties with superior shielding properties. In addition, these composites can be made safe; i.e., with regard to flammability and toxicity, as well as "smart"; i.e., embedded with sensors for the continuous monitoring of material health and conditions. The analysis main conclusions are that (1) smart polymer-based composites are an enabling technology for safe and reliable exploration missions, and (2) an adaptive, synergetic systems approach is required to meet the missions requirements from structure, properties, and processes to crew health and protection for exploration missions.

  10. The classification of maps between the classifying spaces of Lie groups

    E-print Network

    Mahmud, Zafer

    1974-08-01

    this informally as "H'~ (BG,R) is the subring of Weyl group invariants in H:~ (BT ,R) " • Section 1 G2 0 From [11, page 84J we find that we can choose a maximal torus T C G2 with H*(BT,Z) ~ Z[t(1),t(2),t(3)J/I where dim t(i) = 2 and I is the ideal generated... on . ~-.~ ' r, cm, Ti<:NTS . CH 'I.PTER_l1. G 2 r-md F 4 • CHAPTER 2 : fi'lap s BSp ( 1 ) .~ BH. 47 CHAPTER 3: I'jaD s BG -+ BH . J . CHAP'r ,'B·-1: The c onje c ture A ' . Refe r enc es . In t r oduc ti C2.!}, ._ Let C be . the ca t a g or y of p a irs...

  11. Crystallographic alignment of high-density gallium nitride nanowire arrays

    Microsoft Academic Search

    Tevye Kuykendall; Peter J. Pauzauskie; Yanfeng Zhang; Joshua Goldberger; Donald Sirbuly; Jonathan Denlinger; Peidong Yang

    2004-01-01

    Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is

  12. Crystallographic growth forms of silicon on a free melt surface

    Microsoft Academic Search

    T. F. Ciszek

    1985-01-01

    Crystallographic growth forms and radial growth-rate anisotropies of point-nucleated, dislocation-free silicon sheets spreading horizontally on the free surface of a silicon melt have been measured for (100), (110), (111), and (112) sheet planes. 16 mm movie photography was used to record the growth process. Analysis of the sheet edges has lead to predicted geometries for the tip shape of unidirectional,

  13. Crystallographic characterization of the crossed lamellar structure in the bivalve Meretrix lamarckii using electron beam techniques.

    PubMed

    Hayashi, Akiko; Yokoo, Naoki; Nakamura, Toshihiro; Watanabe, Tomoaki; Nagasawa, Hiromichi; Kogure, Toshihiro

    2011-10-01

    To understand the formation mechanism of crossed lamellar structures in molluskan shells, the crystallographic structural features in the shell of a bivalve, Meretrix lamarckii, were investigated using scanning electron microscopy, electron backscattered diffraction, and transmission electron microscopy with a focused ion beam sample preparation technique. Approximately 0.5 ?m-thick lamellae (the second-order units) are piled up obliquely toward the growth direction to form the first-order unit and the obliquity is inverted between adjacent units along the shell thickness direction. The first-order units originate around the center of the shell, initially growing parallel to the shell and subsequently curving toward the inner or outer surfaces. The lamellae consist of aragonite granular and columnar layers, which group together to adopt the same crystal orientation forming crystallographic units (crystallites). Multiple {110} twins are common both in the granular and columnar layers. The crystallite c-axis is parallel to the columns and is inclined at angles 0-50° from the lamellar normal (dispersing among individual lamellae), toward the shell growth direction. Probably, the directions of the a- and b-axes are random in the lamellae, showing no specific orientation. PMID:21763427

  14. Incorporating Space Science Content Into the Undergraduate Curriculum by the NASA Education Forums' Higher Education Working Group

    NASA Astrophysics Data System (ADS)

    Gross, N. A.; Buxner, S.; Cobabe-Ammann, E. A.; Fraknoi, A.; Moldwin, M.; Peticolas, L. M.; Low, R.; Schultz, G. R.

    2013-12-01

    As part of the NASA Education Forums, the Higher Education Working Group (HEWG) strives to support undergraduate science education through a variety of activities. These activities include: providing resource that incorporate space science topics into the existing undergraduate curriculum, understanding the role that community colleges play in STEM education and preparing STEM teachers, and identifying issues in diversity related to STEM education. To assess the best way of including space science into the undergraduate curriculum, the HEWG held a series of workshops and conducted surveys of undergraduate faculty who are conducting research in space science. During this engagement, the faculty expressed a need for a centralized repository of materials that can be used as part of already existing undergraduate courses in astronomy, physics, and earth science. Such a repository has since been developed, the 'EarthSpace Higher Education Clearing House (http://www.lpi.usra.edu/earthspace/) and it is still growing. Additional community tools, such as a newsletter, are provided through this website. To better understand the role and needs of community colleges, the HEWG undertook and extensive survey of community college STEM faculty. 187 faculty responded to the survey and the results show the extensive teaching load these faculty have, as well as the diverse demographics and the extent to which STEM teachers begin their preparation at 2 year institutions. Finally, the HEWG has begun to work on understanding the issues faced in increasing the diversity of the STEM work force. Progress and results of all this work will be summarized in this presentation.

  15. A New Hubble Space Telescope Distance to NGC 1569: Starburst Properties and IC 342 Group Membership

    E-print Network

    Aaron J. Grocholski; Alessandra Aloisi; Roeland P. van der Marel; Jennifer Mack; Francesca Annibali; Luca Angeretti; Laura Greggio; Enrico V. Held; Donatella Romano; Marco Sirianni; Monica Tosi

    2008-08-01

    We present deep HST ACS/WFC photometry of the dwarf irregular galaxy NGC 1569, one of the closest and strongest nearby starburst galaxies. These data allow us, for the first time, to unequivocally detect the tip of the red giant branch and thereby determine the distance to NGC 1569. We find that this galaxy is 3.36 +/- 0.20 Mpc away, considerably farther away than the typically assumed distance of 2.2 +/- 0.6 Mpc. Previously thought to be an isolated galaxy due to its shorter distance, our new distance firmly establishes NGC 1569 as a member of the IC 342 group of galaxies. The higher density environment may help explain the starburst nature of NGC 1569, since starbursts are often triggered by galaxy interactions. On the other hand, the longer distance implies that NGC 1569 is an even more extreme starburst galaxy than previously believed. Previous estimates of the rate of star formation for stars younger than ~ 1 Gyr become stronger by more than a factor of 2. Stars older than this were not constrained by previous studies. The dynamical masses of NGC 1569's three super star clusters, which are already known as some of the most massive ever discovered, increase by ~53% to 6-7x10^5 solar masses.

  16. On some homological functors of Bieberbach group of dimension four with dihedral point group of order eight

    NASA Astrophysics Data System (ADS)

    Mohammad, Siti Afiqah; Ali, Nor Muhainiah Mohd; Sarmin, Nor Haniza; Idrus, Nor'ashiqin Mohd; Masri, Rohaidah

    2014-06-01

    A Bieberbach group is a torsion free crystallographic group, which is an extension of a free abelian group of finite rank by a finite point group, while homological functors of a group include nonabelian tensor square, exterior square and Schur Multiplier. In this paper, some homological functors of a Bieberbach group of dimension four with dihedral point group of order eight are computed.

  17. Space.

    ERIC Educational Resources Information Center

    Web Feet K-8, 2001

    2001-01-01

    This annotated subject guide to Web sites and additional resources focuses on space and astronomy. Specifies age levels for resources that include Web sites, CD-ROMS and software, videos, books, audios, and magazines; offers professional resources; and presents a relevant class activity. (LRW)

  18. Vibrational algorithms for quantitative crystallographic analyses of hydroxyapatite-based biomaterials: I, theoretical foundations.

    PubMed

    Pezzotti, Giuseppe; Zhu, Wenliang; Boffelli, Marco; Adachi, Tetsuya; Ichioka, Hiroaki; Yamamoto, Toshiro; Marunaka, Yoshinori; Kanamura, Narisato

    2015-05-01

    The Raman spectroscopic method has quantitatively been applied to the analysis of local crystallographic orientation in both single-crystal hydroxyapatite and human teeth. Raman selection rules for all the vibrational modes of the hexagonal structure were expanded into explicit functions of Euler angles in space and six Raman tensor elements (RTE). A theoretical treatment has also been put forward according to the orientation distribution function (ODF) formalism, which allows one to resolve the statistical orientation patterns of the nm-sized hydroxyapatite crystallite comprised in the Raman microprobe. Close-form solutions could be obtained for the Euler angles and their statistical distributions resolved with respect to the direction of the average texture axis. Polarized Raman spectra from single-crystalline hydroxyapatite and textured polycrystalline (teeth enamel) samples were compared, and a validation of the proposed Raman method could be obtained through confirming the agreement between RTE values obtained from different samples. PMID:25673243

  19. Crystallographic Structure of the Human Leukocyte Antigen DRA, DRB3*0101: Models of a Directional Alloimmune Respone and Autoimmunity

    SciTech Connect

    Parry,C.; Gorski, J.; Stern, L.

    2007-01-01

    We describe structural studies of the human leukocyte antigen DR52a, HLA-DRA/DRB3*0101, in complex with an N-terminal human platelet integrin {alpha}II{sub B}{beta}III glycoprotein peptide which contains a Leu/Pro dimorphism. The 33:Leu dimorphism is the epitope for the T cell directed response in neonatal alloimmune thrombocytopenia and post-transfusion purpura in individuals with the {alpha}II{sub B}{beta}III 33:Pro allele, and defines the unidirectional alloimmune response. This condition is always associated with DR52a. The crystallographic structure has been refined to 2.25 {angstrom}. There are two {alpha}{beta} heterodimers to the asymmetric unit in space group P4{sub 1}2{sub 1}2. The molecule is characterized by two prominent hydrophobic pockets at either end of the peptide binding cleft and a deep, narrower and highly charged P4 opening underneath the beta 1 chain. Further, the peptide in the second molecule displays a sharp upward turn after pocket P9. The structure reveals the role of pockets and the distinctive basic P4 pocket, shared by DR52a and DR3, in selecting their respective binding peptide repertoire. We observe an interesting switch in a residue from the canonically assigned pocket 6 seen in prior class II structures to pocket 4. This occludes the P6 pocket helping to explain the distinctive '1-4-9' peptide binding motif. A {beta}57 Asp {yields} Val substitution abrogates the salt-bridge to {alpha}76 Arg and along with a hydrophobic {beta}37 is important in shaping the P9 pocket. DRB3*0101 and DRB1*0301 belong to an ancestral haplotype and are associated with many autoimmune diseases linked to antigen presentation, but whereas DR3 is susceptible to type 1 diabetes DR52a is not. This dichotomy is explored for clues to the disease.

  20. X-ray crystallographic studies of the alanine-specific racemase from Bacillus stearothermophilus. Overproduction, crystallization, and preliminary characterization.

    PubMed

    Neidhart, D J; Distefano, M D; Tanizawa, K; Soda, K; Walsh, C T; Petsko, G A

    1987-11-15

    To facilitate large-scale purification and crystallographic study, we have subcloned the gene for the alanine racemase of Bacillus stearothermophilus from pICR401 (Inagaki, K., Tanizawa, K., Badet, B., Walsh, C. T., Tanaka, H., and Soda, K. (1986) Biochemistry 25, 3268-3274) and overproduced the enzyme in Escherichia coli W3110 lacIq using the tac promoter of PKK223-3. This system yields alanine racemase as 6% of the bacterial cytosolic protein. Purification by a modification of the procedure of Inagake et al. yielded 75 mg of homogeneous alanine racemase from 30 g of cells (wet weight). Large, well-formed crystals of alanine racemase have been grown from polyethylene glycol 8000 using vapor diffusion. These crystals have unit cell dimensions a = 85.3 A, b = 110.0 A, and c = 89.9 A. The crystals belong to space group P2(1), with beta fortuitously equal to 90 degrees within experimental error; however, they are frequently twinned by second order pseudomerohedry with twin fraction (the ratio of the volume of the smaller twin domain to the total volume of the crystal) ranging from about 0 to 0.5. Fortunately, for crystals with low twin fraction, computational methods have been developed for the analysis and correction of simple twinning (Fisher, R. G., and Sweet, R. M. (1980) Acta Crystallogr. A36, 755-760). The crystals contain two alpha 2 dimers of alanine racemase in the asymmetric unit. We have identified several potentially useful heavy atom derivatives in low resolution screening experiments and are proceeding with high resolution data collection. PMID:3680197

  1. Coordination of Advanced Solar Observatory (ASO) Science Working Group (SWG) for the study of instrument accommodation and operational requirements on space station

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    1989-01-01

    The objectives are to coordinate the activities of the Science Working Group (SWG) of the Advanced Solar Observatory (ASO) for the study of instruments accommodation and operation requirements on board space station. In order to facilitate the progress of the objective, two conferences were organized, together with two small group discussions.

  2. The Star Formation Histories of Local Group Dwarf Galaxies. I. Hubble Space Telescope/Wide Field Planetary Camera 2 Observations

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel R.; Dolphin, Andrew E.; Skillman, Evan D.; Holtzman, Jon; Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F.

    2014-07-01

    We present uniformly measured star formation histories (SFHs) of 40 Local Group (LG) dwarf galaxies based on color-magnitude diagram (CMD) analysis from archival Hubble Space Telescope imaging. We demonstrate that accurate SFHs can be recovered from CMDs that do not reach the oldest main sequence turn-off (MSTO), but emphasize that the oldest MSTO is critical for precisely constraining the earliest epochs of star formation. We find that: (1) the average lifetime SFHs of dwarf spheroidals (dSphs) can be approximated by an exponentially declining SFH with ? ~ 5 Gyr (2) lower luminosity dSphs are less likely to have extended SFHs than more luminous dSphs; (3) the average SFHs of dwarf irregulars (dIrrs), transition dwarfs, and dwarf ellipticals can be approximated by the combination of an exponentially declining SFH (? ~ 3-4 Gyr) for lookback ages >10-12 Gyr ago and a constant SFH thereafter; (4) the observed fraction of stellar mass formed prior to z = 2 ranges considerably (80% for galaxies with M < 105 M ? to 30% for galaxies with M > 107 M ?) and is largely explained by environment; (5) the distinction between "ultra-faint" and "classical" dSphs is arbitrary; (6) LG dIrrs formed a significantly higher fraction of stellar mass prior to z = 2 than the Sloan Digital Sky Survey galaxies from Leitner and the SFHs from the abundance matching models of Behroozi et al. This may indicate higher than expected star formation efficiencies at early times in low mass galaxies. Finally, we provide all the SFHs in tabulated electronic format for use by the community. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  3. The use of Fourier reverse transforms in crystallographic phase refinement

    SciTech Connect

    Ringrose, S.

    1997-10-08

    Often a crystallographer obtains an electron density map which shows only part of the structure. In such cases, the phasing of the trial model is poor enough that the electron density map may show peaks in some of the atomic positions, but other atomic positions are not visible. There may also be extraneous peaks present which are not due to atomic positions. A method for determination of crystal structures that have resisted solution through normal crystallographic methods has been developed. PHASER is a series of FORTRAN programs which aids in the structure solution of poorly phased electron density maps by refining the crystallographic phases. It facilitates the refinement of such poorly phased electron density maps for difficult structures which might otherwise not be solvable. The trial model, which serves as the starting point for the phase refinement, may be acquired by several routes such as direct methods or Patterson methods. Modifications are made to the reverse transform process based on several assumptions. First, the starting electron density map is modified based on the fact that physically the electron density map must be non-negative at all points. In practice a small positive cutoff is used. A reverse Fourier transform is computed based on the modified electron density map. Secondly, the authors assume that a better electron density map will result by using the observed magnitudes of the structure factors combined with the phases calculated in the reverse transform. After convergence has been reached, more atomic positions and less extraneous peaks are observed in the refined electron density map. The starting model need not be very large to achieve success with PHASER; successful phase refinement has been achieved with a starting model that consists of only 5% of the total scattering power of the full molecule. The second part of the thesis discusses three crystal structure determinations.

  4. Arginine Kinase. Joint Crystallographic & NMR RDC Analyses link Substrate-Associated Motions to Intrinsic Flexibility

    PubMed Central

    Niu, Xiaogang; Brüschweiler-Li, Lei; Davulcu, Omar; Skalicky, Jack J.; Brüschweiler, Rafael; Chapman, Michael S.

    2010-01-01

    The phosphagen kinase family, including creatine and arginine kinases, catalyze the reversible transfer of a “high energy” phosphate between ATP and a phospho-guanidino substrate. They have become a model for the study of both substrate-induced conformational change and intrinsic protein dynamics. Prior crystallographic studies indicated large substrate-induced domain rotations, but differences among a recent set of arginine kinase structures was interpreted as a plastic deformation. Here, the structure of Limulus substrate-free arginine kinase is refined against high resolution crystallographic data and compared quantitatively with NMR chemical shifts and residual dipolar couplings (RDCs). This demonstrates the feasibility of this type of RDC analysis of proteins that are large by NMR standards (42 kDa), and illuminates the solution structure, free from crystal-packing constraints. Detailed comparison of the 1.7 Å resolution substrate-free crystal structure against the 1.2 Å transition state analog complex shows large substrate-induced domain motions which can be broken down into movements of smaller quasi-rigid bodies. The solution state structure of substrate-free arginine kinase is most consistent with an equilibrium of substrate-free and –bound structures, with the substrate-free form dominating, but with varying displacements of the quasi-rigid groups. Rigid-group rotations evident from the crystal structures are about axes previously associated with intrinsic millisecond dynamics using NMR relaxation dispersion. Thus, “substrate-induced” motions are along modes that are intrinsically flexible in the substrate-free enzyme, and likely involve some degree of conformational selection. PMID:21075117

  5. Arginine kinase: joint crystallographic and NMR RDC analyses link substrate-associated motions to intrinsic flexibility.

    PubMed

    Niu, Xiaogang; Bruschweiler-Li, Lei; Davulcu, Omar; Skalicky, Jack J; Brüschweiler, Rafael; Chapman, Michael S

    2011-01-14

    The phosphagen kinase family, including creatine and arginine kinases (AKs), catalyzes the reversible transfer of a "high-energy" phosphate between ATP and a phosphoguanidino substrate. They have become a model for the study of both substrate-induced conformational change and intrinsic protein dynamics. Prior crystallographic studies indicated large substrate-induced domain rotations, but differences among a recent set of AK structures were interpreted as a plastic deformation. Here, the structure of Limulus substrate-free AK is refined against high-resolution crystallographic data and compared quantitatively with NMR chemical shifts and residual dipolar couplings (RDCs). This demonstrates the feasibility of this type of RDC analysis of proteins that are large by NMR standards (42 kDa) and illuminates the solution structure, free from crystal-packing constraints. Detailed comparison of the 1.7 Å resolution substrate-free crystal structure against the 1.7 Å transition-state analog complex shows large substrate-induced domain motions that can be broken down into movements of smaller quasi-rigid bodies. The solution-state structure of substrate-free AK is most consistent with an equilibrium of substrate-free and substrate-bound structures, with the substrate-free form dominating, but with varying displacements of the quasi-rigid groups. Rigid-group rotations evident from the crystal structures are about axes previously associated with intrinsic millisecond dynamics using NMR relaxation dispersion. Thus, "substrate-induced" motions are along modes that are intrinsically flexible in the substrate-free enzyme and likely involve some degree of conformational selection. PMID:21075117

  6. Crystallographic phase retrieval through image processing under constraints

    NASA Astrophysics Data System (ADS)

    Zhang, Kam Y.

    1993-11-01

    The crystallographic image processing techniques of Sayre's equation, molecular averaging, solvent flattening and histogram matching are combined in an integrated procedure for macromolecular phase retrieval. It employs the constraints of the local shape of electron density, equal molecules, solvent flatness and correct electron density distribution. These constraints on electron density image are satisfied simultaneously by solving a system of non- linear equations using fast Fourier transform. The electron density image is further filtered under the constraint of observed diffraction amplitudes. The effect of each constraint on phase retrieval is examined. The constraints are found to work synergistically in phase retrieval. Test results on 2Zn insulin are presented.

  7. Crystallization and crystallographic analysis of Bacillus subtilis xylanase C

    PubMed Central

    St John, Franz J.; Godwin, David K.; Preston, James F.; Pozharski, Edwin; Hurlbert, Jason C.

    2009-01-01

    The recent biochemical characterization of the xylanases of glycosyl hydrolase family 5 (GH 5) has identified a distinctive endo mode of action, hydrolyzing the ?-1,4 xylan chain at a specific site directed by the position of an ?-1,2-linked glucuronate moiety. Xylanase C (XynC), the GH 5 xylanase from Bacillus subtilis 168, has been cloned, overexpressed and crystallized. Initial data collection was performed and a preliminary model has been built into a low-quality 2.7?Å resolution density map. The crystals belonged to the primitive monoclinic space group P21. Further screening identified an additive that resulted in large reproducible crystals. This larger more robust crystal form belonged to space group P21212 and a resulting data set has been processed to 1.64?Å resolution. This will be the second structure to be solved from this unique xylanase family and the first from a Gram-positive bacterium. This work may help to identify the structural determinants that allow the exceptional specificity of this enzyme and the role it plays in the biological depolymerization and processing of glucuronoxylan. PMID:19407387

  8. Expression, purification and preliminary crystallographic studies of NahF, a salicylaldehyde dehydrogenase from Pseudomonas putida G7 involved in naphthalene degradation

    PubMed Central

    Coitinho, Juliana Barbosa; Costa, Débora Maria Abrantes; Guimarães, Samuel Leite; de Góes, Alfredo Miranda; Nagem, Ronaldo Alves Pinto

    2012-01-01

    Pseudomonas putida G7 is one of the most studied naphthalene-degrading species. The nah operon in P. putida, which is present on the 83?kb metabolic plasmid NAH7, codes for enzymes involved in the conversion of naphthalene to salicylate. The enzyme NahF (salicylaldehyde dehydrogenase) catalyzes the last reaction in this pathway. The nahF gene was subcloned into the pET28a(TEV) vector and the recombinant protein was overexpressed in Escherichia coli Arctic Express at 285?K. The soluble protein was purified by affinity chromatography followed by gel filtration. Crystals of recombinant NahF (6×His-NahF) were obtained at 291?K and diffracted to 2.42?Å resolution. They belonged to the hexagonal space group P6422, with unit-cell parameters a = b = 169.47, c = 157.94?Å. The asymmetric unit contained a monomer and a crystallographic twofold axis generated the dimeric biological unit. PMID:22232182

  9. High-level expression, purification, crystallization and preliminary X-ray crystallographic studies of the receptor binding domain of botulinum neurotoxin serotype D

    SciTech Connect

    Zhang, Yanfeng; Gao, Xiaoli; Qin, Lin; Buchko, Garry W.; Robinson, Howard; Varnum, Susan M.

    2010-12-01

    Botulinum neurotoxins (BoNTs) are highly toxic proteins for humans and can cause neuroparalytic disease botulism. Due to the limitations of production and manipulation of holoenzymes, expressing non-toxic heavy chain receptor binding domains (HCR) has become a common strategy for vaccine and antibody development. Meanwhile, large quantities and highly purified soluble proteins are required for research areas such as antibody maturation and structural biology. We present high level expression and purification of the BoNT serotype D HCR in E. coli using a codon-optimized cDNA. By varying expression conditions, especially at low temperature, the protein was expressed at a high level with high solubility. About 150-200 mg protein was purified to >90% purity from 1 L cell culture. The recombinant D_HCR was crystallized and the crystals diffracted to 1.65 Å resolution. The crystals belong to space group P212121 with unit cell dimensions a = 60.8 Å, b = 89.7 Å, c = 93.9 Å. Preliminary crystallographic data analysis revealed one molecule in asymmetric unit.

  10. Expression, purification, crystallization and preliminary X-ray crystallographic studies of the trehalulose synthase MutB from Pseudomonas mesoacidophila MX-45

    PubMed Central

    Ravaud, Stéphanie; Watzlawick, Hildegard; Haser, Richard; Mattes, Ralf; Aghajari, Nushin

    2005-01-01

    The trehalulose synthase (MutB) from Pseudomonas mesoacidophila MX-45, belonging to glycoside hydrolase family 13, catalyses the isomerization of sucrose to trehalulose (?-d-glucosylpyranosyl-1,1-d-fructofuranose) and isomaltulose (?-­d-glucosylpyranosyl-1,6-d-fructofuranose) as main products and glucose and fructose in residual amounts from the hydrolytic reaction. To date, a three-dimensional structure of a sucrose isomerase that produces mainly trehalulose, as is the case for MutB, has been lacking. Crystallographic studies of this 64?kDa enzyme have therefore been initiated in order to contribute to the understanding of the molecular basis of sucrose decomposition, isomerization and of the selectivity of this enzyme that leads to the formation of different products. The MutB protein has been overexpressed, purified and crystallized using the hanging-drop vapour-diffusion method. Two different crystal forms have been obtained: one diffracts X-rays to 1.6?Å resolution using synchrotron radiation and belongs to space group P1, with unit-cell parameters a = 63.8, b = 72.0, c = 82.2?Å, ? = 67.5, ? = 73.1, ? = 70.8°, while the other form diffracts to 1.8?Å resolution using synchrotron radiation and belongs to space group P21, with unit-cell parameters a = 63.7, b = 85.9, c = 119.7?Å, ? = 97.7°. A molecular-replacement solution has been found using the structure of the isomaltulose synthase (PalI) from Klebsiella sp. LX3 as a search model. PMID:16508103

  11. Expression, purification, crystallization and preliminary X-ray crystallographic studies of the trehalulose synthase MutB from Pseudomonas mesoacidophila MX-45.

    PubMed

    Ravaud, Stéphanie; Watzlawick, Hildegard; Haser, Richard; Mattes, Ralf; Aghajari, Nushin

    2005-01-01

    The trehalulose synthase (MutB) from Pseudomonas mesoacidophila MX-45, belonging to glycoside hydrolase family 13, catalyses the isomerization of sucrose to trehalulose (alpha-D-glucosylpyranosyl-1,1-D-fructofuranose) and isomaltulose (alpha-D-glucosylpyranosyl-1,6-D-fructofuranose) as main products and glucose and fructose in residual amounts from the hydrolytic reaction. To date, a three-dimensional structure of a sucrose isomerase that produces mainly trehalulose, as is the case for MutB, has been lacking. Crystallographic studies of this 64 kDa enzyme have therefore been initiated in order to contribute to the understanding of the molecular basis of sucrose decomposition, isomerization and of the selectivity of this enzyme that leads to the formation of different products. The MutB protein has been overexpressed, purified and crystallized using the hanging-drop vapour-diffusion method. Two different crystal forms have been obtained: one diffracts X-rays to 1.6 A resolution using synchrotron radiation and belongs to space group P1, with unit-cell parameters a = 63.8, b = 72.0, c = 82.2 A, alpha = 67.5, beta = 73.1, gamma = 70.8 degrees, while the other form diffracts to 1.8 A resolution using synchrotron radiation and belongs to space group P2(1), with unit-cell parameters a = 63.7, b = 85.9, c = 119.7 A, beta = 97.7 degrees. A molecular-replacement solution has been found using the structure of the isomaltulose synthase (PalI) from Klebsiella sp. LX3 as a search model. PMID:16508103

  12. Crystallographic Study of the LUMI Intermediate of Squid Rhodopsin

    PubMed Central

    Murakami, Midori; Kouyama, Tsutomu

    2015-01-01

    Upon absorption of light, the retinal chromophore in rhodopsin isomerizes from the 11-cis to the trans configuration, initiating a photoreaction cycle. The primary photoreaction state, bathorhodopsin (BATHO), relaxes thermally through lumirhodopsin (LUMI) into a photoactive state, metarhodopsin (META), which stimulates the conjugated G-protein. Previous crystallographic studies of squid and bovine rhodopsins have shown that the structural change in the primary photoreaction of squid rhodopsin is considerably different from that observed in bovine rhodopsin. It would be expected that there is a fundamental difference in the subsequent thermal relaxation process between vertebrate and invertebrate rhodopsins. In this work, we performed crystallographic analyses of the LUMI state of squid rhodopsin using the P62 crystal. When the crystal was illuminated at 100 K with blue light, a half fraction of the protein was converted into BATHO. This reaction state relaxed into LUMI when the illuminated crystal was warmed in the dark to 170 K. It was found that, whereas trans retinal is largely twisted in BATHO, it takes on a more planar configuration in LUMI. This relaxation of retinal is accompanied by reorientation of the Schiff base NH bond, the hydrogen-bonding partner of which is switched to Asn185 in LUMI. Unlike bovine rhodopsin, the BATHO-to-LUMI transition in squid rhodopsin was accompanied by no significant change in the position/orientation of the beta-ionone ring of retinal. PMID:26024518

  13. Crystallographic alignment of high-density gallium nitride nanowire arrays.

    PubMed

    Kuykendall, Tevye; Pauzauskie, Peter J; Zhang, Yanfeng; Goldberger, Joshua; Sirbuly, Donald; Denlinger, Jonathan; Yang, Peidong

    2004-08-01

    Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is extremely desirable, in that anisotropic parameters such as thermal and electrical conductivity, index of refraction, piezoelectric polarization, and bandgap may be used to tune the physical properties of nanowires made from a given material. Here we demonstrate the use of metal-organic chemical vapour deposition (MOCVD) and appropriate substrate selection to control the crystallographic growth directions of high-density arrays of gallium nitride nanowires with distinct geometric and physical properties. Epitaxial growth of wurtzite gallium nitride on (100) gamma-LiAlO(2) and (111) MgO single-crystal substrates resulted in the selective growth of nanowires in the orthogonal [1\\[Evec]0] and [001] directions, exhibiting triangular and hexagonal cross-sections and drastically different optical emission. The MOCVD process is entirely compatible with the current GaN thin-film technology, which would lead to easy scale-up and device integration. PMID:15273744

  14. Crystallographic site swapping of La3+ ion in BaA'LaTeO6 (A' = Na, K, Rb) double perovskite type compounds: diffraction and photoluminescence evidence for the site swapping.

    PubMed

    Phatak, R; Gupta, S K; Krishnan, K; Sali, S K; Godbole, S V; Das, A

    2014-02-28

    Double perovskite type compounds of the formula BaA'LaTeO6 (A' = Na, K, Rb) were synthesized by solid state route and their crystal structures were determined by Rietveld analysis using powder X-ray diffraction and neutron diffraction data. Na compound crystallizes in the monoclinic system with P2?/n space group whereas, K and Rb compounds crystallize in Fm3m space group. All the three compounds show rock salt type ordering at B site. Crystal structure analysis shows that La ion occupies A site in Na compound whereas, it occupies B site in K and Rb compounds according to the general formula of AA'BB'O6 for a double perovskite type compound. Effect of this crystallographic site swapping of the La ion was also observed in the photoluminescence study by doping Eu(3+) in La(3+) site. The large decrease in the intensity of the electric dipole ((5)D0-(7)F2) transition in the Rb compound compared to the Na compound indicates that Eu(3+) ion resides in the centrosymmetric octahedral environment in the Rb compound. PMID:24363108

  15. Preliminary crystallographic examination of a novel fungal lysozyme from Chalaropsis

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C.; He, Xiao-Min; Lyne, James E.; Stubbs, Gerald; Hash, John H.

    1990-01-01

    The lysozyme from the fungus of the Chalaropsis species has been crystallized. This lysozyme displays no sequence homology with avian, phage, or mammalian lysozymes, however, preliminary studies indicate significant sequence homology with the bacterial lysozyme from Streptomyces. Both enzymes are unusual in possessing beta-1,4-N-acetylmuramidase and beta-1,4-N,6-O-diacetylmuramidase activity. The crystals grow from solutions of ammonium sulfate during growth periods from several months to a year. The space group is P2(1)2(1)2(1) with a = 34.0 A, b = 42.6 A, c = 122.1 A. Preliminary data indicate that there is 1 molecule/asymmetric unit.

  16. Crystallization and preliminary crystallographic studies of Helicobacter pylori arginase

    PubMed Central

    Zhang, Jinyong; Zhang, Xiaoli; Mao, Xuhu; Zou, Quanming; Li, Defeng

    2011-01-01

    Helicobacter pylori arginase is an important factor in evasion of the host’s immune system and contributes to persistent infection by this bacterium. It is unique in many aspects compared with other arginases: for example, it has optimal activity with Co2+ as a cofactor rather than Mn2+ and has strongest activity at acidic pH instead of alkaline pH. In this study, H. pylori arginase was purified and crystallized in complex with Mn2+ and a diffraction data set was collected to 2.2?Å resolution. The crystals belonged to space group P212121, with unit-cell parameters a = 94.69, b = 102.24, c = 148.61?Å. PMID:21636918

  17. Crystallographic Texture of Induction-welded and Heat-treated Pipeline Steel

    E-print Network

    Cambridge, University of

    Crystallographic Texture of Induction-welded and Heat-treated Pipeline Steel P. Yan1,a, Ö. E.thibaux@arcelormittal.com, dhkdb@cam.ac.uk Keywords: crystallographic texture; pipeline steel; induction welding; induction heat°. Microstructural Characterisation Pipelines steels are normally hot­rolled at elevated temperatures

  18. A crystallographer keen on showing off the revealing properties of neutrons

    E-print Network

    - 1 - A crystallographer keen on showing off the revealing properties of neutrons February 27, 2014 At Los Alamos's Lujan Neutron Scattering Center, crystallographer Olivier Gourdon shows visiting for HIPPO, the High-Pressure-Preferred Orientation Neutron Diffractometer.Since the 1914 Nobel Prize

  19. Crystallographic preferred orientation (CPO) of gypsum measured by electron backscatter diffraction (EBSD).

    PubMed

    Hildyard, R C; Prior, D J; Mariani, E; Faulkner, D R

    2009-12-01

    An investigation by electron backscatter diffraction on gypsum shows that this technique can be used to study the microstructures and crystallographic preferred orientation of gypsum. Presented here are the methods, verification tests and data obtained from a naturally deformed sample of gypsum-rich rock. The electron backscatter diffraction data show the sample has a strong crystallographic preferred orientation. PMID:19941555

  20. Electron crystallographic methods for investigating gap junction structure.

    PubMed

    Sosinsky, G E; Perkins, G A

    2000-02-01

    Gap junctions are clusters of closely packed intercellular membrane channels embedded in the plasma membranes of two adjoining cells. The central pore of the membrane channels serves as a conduit between cell cytoplasms for molecules less than 1000 Da in size. Advances in the purification of gap junctions and electron cryocrystallography and computer reconstruction techniques have produced new insights into the intercellular channel structure. Methods are described here for the purification of gap junction membranes, biochemical treatments to produce hemichannel layers ("split junctions"), assessment of the purity of gap junction preparations, electron cryomicroscopy, image processing and reconstruction, three-dimensional visualization, and interpretation. The critical step in electron crystallographic structure determination remains the isolation of crystalline material in sufficient and pure quantities for recording of electron microscope images. Along with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting, the quality of gap junction purification is assessed using electron microscopy of negatively stained preparations. Electron microscopy is also used to assess the crystallinity of the purified gap junctions and split junctions. Electron cryocrystallography is a powerful technique for high-resolution structural characterization. Image processing is used to combine and enhance two-dimensional images. Electron crystallographic analysis is used to generate a three-dimensional structure from a set of electron micrographs. This three-dimensional information is extracted from a set of images recorded after tilting the specimen in the electron microscope stage and recombined using Fourier analysis techniques analogous to those used in X-ray crystallography. Computer modeling of the three-dimensional gap junction structures is a useful tool for analyzing hemichannel docking. PMID:10671308

  1. Spaced seed design on profile HMMs for precise HTS read-mapping e cient sliding window product on the matrix semi-group

    E-print Network

    Noé, Laurent

    product on the matrix semi-group Laurent No´e August 27, 2013 Abstract We propose a new method and itsDRAFT Spaced seed design on profile HMMs for precise HTS read-mapping e cient sliding window with a matrix product problem. Interestingly, it brings to light an interval product problem considered more

  2. Spaces of Kleinian Groups Cambridge University Press Lond. Math. Soc. Lec. Notes 329, 301336 Y. Minsky, M. Sakuma & C. Series (Eds.)

    E-print Network

    Wright, David J.

    . Minsky, M. Sakuma & C. Series (Eds.) © D. Wright, 2005 Searching for the cusp David J. Wright¡ Abstract-¢¡ Mullen's theorem [McM91] that the maximal cusp groups are dense in the boundary¢¢ #12;302 David J. Wright will explain how maximal cusps on the ¢ boundary of the Schottky space of genus g may be described

  3. Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): III. Relation of quartz texture types with means and conditions of texture formation

    SciTech Connect

    Nikitin, A. N., E-mail: nikitin@nf.jinr.ru; Ivankina, T. I. [Joint Institute for Nuclear Research (Russian Federation); Ullemeyer, K. [Universitaet Kiel, Institut fuer Geowissenschaften (Germany); Vasin, R. N. [Joint Institute for Nuclear Research (Russian Federation)

    2008-09-15

    Examples of different rocks collected in different regions of the continental earth's crust are presented. Groups of quartz crystallographic textures of the same type are selected for these rocks. The relationship between the types of textures and the physical means and conditions of their formation is analyzed. The effect of the {alpha}-{beta} phase transition in quartz on the texture transformations in rocks is considered.

  4. D-Side: A Facility and Workforce Planning Group Multi-criteria Decision Support System for Johnson Space Center

    NASA Technical Reports Server (NTRS)

    Tavana, Madjid

    2005-01-01

    "To understand and protect our home planet, to explore the universe and search for life, and to inspire the next generation of explorers" is NASA's mission. The Systems Management Office at Johnson Space Center (JSC) is searching for methods to effectively manage the Center's resources to meet NASA's mission. D-Side is a group multi-criteria decision support system (GMDSS) developed to support facility decisions at JSC. D-Side uses a series of sequential and structured processes to plot facilities in a three-dimensional (3-D) graph on the basis of each facility alignment with NASA's mission and goals, the extent to which other facilities are dependent on the facility, and the dollar value of capital investments that have been postponed at the facility relative to the facility replacement value. A similarity factor rank orders facilities based on their Euclidean distance from Ideal and Nadir points. These similarity factors are then used to allocate capital improvement resources across facilities. We also present a parallel model that can be used to support decisions concerning allocation of human resources investments across workforce units. Finally, we present results from a pilot study where 12 experienced facility managers from NASA used D-Side and the organization's current approach to rank order and allocate funds for capital improvement across 20 facilities. Users evaluated D-Side favorably in terms of ease of use, the quality of the decision-making process, decision quality, and overall value-added. Their evaluations of D-Side were significantly more favorable than their evaluations of the current approach. Keywords: NASA, Multi-Criteria Decision Making, Decision Support System, AHP, Euclidean Distance, 3-D Modeling, Facility Planning, Workforce Planning.

  5. The shape of things Advances in crystallographic methods, the rise of nuclear magnetic resonance, and the blossoming of global

    E-print Network

    Cai, Long

    The shape of things Advances in crystallographic methods, the rise of nuclear magnetic resonance approach protein crystallization. "Many X-ray crystallographers aren't inter- ested in`why'; they just want

  6. Group dynamics in a long-term blind endeavor on Earth: An analog for space missions (Lewis & Clark Expedition group dynamic analysis)

    Microsoft Academic Search

    M. Allner; V. Rygalov

    2008-01-01

    In 1803, President Thomas Jefferson set fourth a military expedition led by Captains M. Lewis and W. Clark (Lewis and Clark Expedition) on an exploration that would become an everlasting part of US national history and pride. Looking back at the events of this exploration, there are many similarities to the experiences future human space explorers will face as we

  7. Structural similarities in tetraaryltins described by virtual non-crystallographic rotations or translations: Kitaigorodskii's morphotropism is revisited.

    PubMed

    Kálmán, Alajos; Fábián, László

    2007-06-01

    Recently Kálmán [(2005), Acta Cryst. B61, 536-547] revealed that semirigid molecules or their patterns held together e.g. by hydrogen bonds may perform non-crystallographic rotations (through 180, 90 degrees etc.) around themselves whenever a substitution, ring enlargement or isomerization destroys the existing close packing, i.e. the novel substituent or the enlarged ring can no longer fit in the hollows formed between the molecules. In other words, the old and new arrangements of such chemically similar molecules can be converted into each other by virtual rotations. However, when a semirigid molecule without substitution, but under the influence of solvents, temperature etc., is fully or partly rearranged in the solid state, the corresponding non-crystallographic rotation (hereinafter ncr) is real and gives rise to polymorphism. Such polymorphs are hallmarked by full or partial isostructurality and show that ncrs always occur together with isostructurality. First Kitaigorodskii [(1961), Organic Chemical Crystallography, New York: Consultants Bureau] reported on the structural similarity of three tetraaryltins, (p-RC(6)H(4))(4)Sn, R = H, CH(3), CH(3)O, which is terminated by the larger C(2)H(5)O group. A revisit to these structures revealed that the tetragonal --> monoclinic conversion termed by Kitaigorodskii as a ;morphotropic step' is also performed by an ncr. Similarly, other tetraaryltins in the literature are related by ncrs or the nc translation of the semirigid tetrahedra, or they remain isostructural. Since one of the definitions of morphotropism, a word of Greek origin, is 'turn of form', the ncrs of semirigid molecules can be denoted--following Kitaigorodskii--by this word, whereas its alternative definition in the morphological crystallography of ;unidirectional changes' [applied by Groth (1870). Ber. Chem. Ges. 3, 449-457] covers the non-crystallographic translations described first in this work. PMID:17507754

  8. X-ray crystallographic analysis of inhibition of endothiapepsin by cyclohexyl renin inhibitors.

    PubMed

    Cooper, J; Quail, W; Frazao, C; Foundling, S I; Blundell, T L; Humblet, C; Lunney, E A; Lowther, W T; Dunn, B M

    1992-09-01

    The crystal structures of endothiapepsin, a fungal aspartic proteinase (EC 3.4.23.6), cocrystallized with two oligopeptide renin inhibitors, PD125967 and PD125754, have been determined at 2.0-A resolution and refined to R-factors of 0.143 and 0.153, respectively. These inhibitors, which are of the hydroxyethylene and statine types, respectively, possess a cyclohexylalanine side chain at P1 and have interesting functionalities at the P3 position which, until now, have not been subjected to crystallographic analysis. PD125967 has a bis(1-naphthylmethyl)acetyl residue at P3, and PD125754 possesses a hydroxyethylene analogue of the P3-P2 peptide bond for proteolytic stability. The structures reveal that the S3 pocket accommodates one naphthyl ring with conformational changes of the Asp 77 and Asp 114 side chains, the other naphthyl group residing in the S4 region. The P3-P2 hydroxyethylene analogue of PD125754 forms a hydrogen bond with the NH of Thr 219, thereby making the same interaction with the enzyme as the equivalent peptide groups of all inhibitors studied so far. The absence of side chains at the P2 and P1' positions of this inhibitor allows water molecules to occupy the respective pockets in the complex. The relative potencies of PD125967 and PD125754 for endothiapepsin are consistent with the changes in solvent-accessible area which take place on inhibitor binding. PMID:1525155

  9. Preliminary crystallographic studies on glutamine synthetase from Mycobacterium tuberculosis.

    PubMed

    Gill, H S; Pfluegl, G M; Eisenberg, D

    1999-04-01

    The etiologic agent of tuberculosis, Mycobacterium tuberculosis, has been shown to secrete the enzyme glutamine synthetase (TB-GS) which is apparently essential for infection. Four crystal forms of a recombinant TB-GS were grown. The one chosen for synchrotron X--ray data collection belongs to space group P212121 with unit-cell dimensions 208 x 258 x 274 A, yielding 2.4 A resolution data. A Matthews number of 2.89 A3 Da-1 is found, corresponding to 24 subunits of molecular mass 1300 kDa in the asymmetric unit. From earlier work, the structure of Salmonella typhimurium GS, which is 51% identical in sequence to TB-GS, is known to be dodecameric with 622 symmetry. Self-rotation calculations on the TB-GS X-ray data reveal only one set of sixfold and twofold axes of symmetry. A Patterson map calculated from the native X-ray data confirms that there are two dodecamers in the asymmetric unit, having both their sixfold and twofold axes parallel to one another. PMID:10089318

  10. Finding Galaxy Groups In Photometric Redshift Space: the Probability Friends-of-Friends (pFoF) Algorithm

    E-print Network

    I-hui Li; Howard K. C. Yee

    2008-01-16

    We present a structure finding algorithm designed to identify galaxy groups in photometric redshift data sets: the probability friends-of-friends (pFoF) algorithm. This algorithm is derived by combining the friends-of-friends algorithm in the transverse direction and the photometric redshift probability densities in the radial dimension. The innovative characteristic of our group-finding algorithm is the improvement of redshift estimation via the constraints given by the transversely connected galaxies in a group, based on the assumption that all galaxies in a group have the same redshift. Tests using the Virgo Consortium Millennium Simulation mock catalogs allow us to show that the recovery rate of the pFoF algorithm is larger than 80% for mock groups of at least $2\\times10^{13}M_{\\sun}$, while the false detection rate is about 10% for pFoF groups containing at least $\\sim8$ net members. Applying the algorithm to the CNOC2 group catalogs gives results which are consistent with the mock catalog tests. From all these results, we conclude that our group-finding algorithm offers an effective yet simple way to identify galaxy groups in photometric redshift catalogs.

  11. Integration of Nanotubes, Etch Tracks, and Nanoribbons in Crystallographic Alignment

    NASA Astrophysics Data System (ADS)

    Boland, Mathias J.; Hunley, D. Patrick; Sundrarajan, Abhishek; Nasseri, Mohsen; Strachan, Douglas R.

    2015-03-01

    Three nanomaterial components, carbon nanotubes (CNTs), few-layer graphene (FLG), and etch tracks exposing insulating SiO2 regions, are integrated to form crystallographically-aligned nanoscale systems. These integrated systems consist of CNTs grown across nanogap etch tracks and nanoribbons formed within the FLG films as a result of chemical vapor deposition (CVD) processing. Each nanoscale component is aligned along the underlying graphene lattice, resulting in their orientations being locked into precise values, with CNTs maintaining alignment even after crossing etch tracks. The growth of aligned CNTs across nanogap etch tracks and nanoribbons suggests that integrated formations can be achieved by growing CNTs directly over nanogap etch tracks and nanoribbons. This is supported by calculations of the vibrational energy of CNTs indicating that they should be capable of maintaining atomic registry with an underlying graphene lattice as they grow across a typical etch track, in agreement with our experimental results. Thus, this work is relevant to the integration of semiconducting, conducting, and insulating nano-materials all together into precise nano-electronic systems.

  12. Crystallographic studies of the Anthrax lethal toxin. Annual report

    SciTech Connect

    Frederick, C.A.

    1996-07-01

    The lethal form of Anthrax results from the inhalation of anthrax spores. Death is primarily due to the effects of the lethal toxin (Protective Antigen (PA) + Lethal Factor) from the causative agent, Bacillus anthracis. All the Anthrax vaccines currently in use or under development contain or produce PA, the major antigenic component of anthrax toxin, and there is a clear need for an improved vaccine for human use. In the previous report we described the first atomic resolution structure of PA, revealing that the molecule is composed largely of beta-sheets organized into four domains. This information can be used in the design. of recombinant PA vaccines. In this report we describe additional features of the full-length PA molecule derived from further crystallographic refinement and careful examination of the structure. We compare two crystal forms of PA grown at different pH values and discuss the functional implications. A complete definition of the function of each domain must await the crystal structure of the PA63 heptamer. We have grown crystals of the heptamer under both detergent and detergent-free conditions, and made substantial progress towards the crystal structure. The mechanism of anthrax intoxication in the light of our results is reviewed.

  13. A crystallographic model for nickel base single crystal alloys

    NASA Technical Reports Server (NTRS)

    Dame, L. T.; Stouffer, D. C.

    1988-01-01

    The purpose of this research is to develop a tool for the mechanical analysis of nickel-base single-crystal superalloys, specifically Rene N4, used in gas turbine engine components. This objective is achieved by developing a rate-dependent anisotropic constitutive model and implementing it in a nonlinear three-dimensional finite-element code. The constitutive model is developed from metallurgical concepts utilizing a crystallographic approach. An extension of Schmid's law is combined with the Bodner-Partom equations to model the inelastic tension/compression asymmetry and orientation-dependence in octahedral slip. Schmid's law is used to approximate the inelastic response of the material in cube slip. The constitutive equations model the tensile behavior, creep response and strain-rate sensitivity of the single-crystal superalloys. Methods for deriving the material constants from standard tests are also discussed. The model is implemented in a finite-element code, and the computed and experimental results are compared for several orientations and loading conditions.

  14. A Position-Space Renormalization-Group Approach for Driven Diffusive Systems Applied to the One-Dimensional Driven Asymmetric Chain

    Microsoft Academic Search

    Ivan T. Georgiev; Susan R. McKay

    2001-01-01

    We present a position-space renormalization-group method for nonequilibrium systems, and illustrate its application using the one-dimensional driven asymmetric chain. The dynamics in this case are characterized by three parameters: the probability alpha that a particle will enter the chain from the left boundary, the probability beta that a particle will exit the chain at the right boundary, and the probability

  15. CRYSTALLOGRAPHICALLY ANISOTROPIC SHAPE OF FORSTERITE: NEW PROBE FOR EVALUATING DUST FORMATION HISTORY FROM INFRARED SPECTROSCOPY

    SciTech Connect

    Takigawa, Aki; Tachibana, Shogo, E-mail: takigawa@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo Tokyo 113-0033 (Japan)

    2012-05-10

    Crystalline dust has been observed by infrared spectroscopy around dust-enshrouded asymptotic giant branch stars, in protoplanetary disks, and from some comets. Crystalline materials often have a specific shape related to a specific crystallographic orientation (crystallographically anisotropic shape), which reflects the anisotropic nature of crystals, and their infrared spectral features depend on crystallographically anisotropic shapes. The crystallographically anisotropic shape is thus a potentially powerful probe to evaluate circumstellar dust-forming conditions quantitatively. In order to assess the possibility to determine the crystallographically anisotropic shape from infrared spectra, we calculated mass absorption coefficients for ellipsoidal forsterite particles, the most abundant circumstellar crystalline silicate, elongated and flattened along the crystallographic a-, b-, and c-axes with various aspect ratios in the wavelength range of 9-70 {mu}m. It was found that differences in infrared features caused by various crystallographicaly anisotropic shapes are distinguishable from each other irrespective of the effects of temperature, size, chemical composition, and grain edges of forsterite in the range of 9-12 {mu}m and 15-20 {mu}m. We thus concluded that the crystallographically anisotropic shape of forsterite can be deduced from peak features in infrared spectra. We also showed that the crystallographically anisotropic shapes formed by evaporation and condensation of forsterite can be distinguished from each other and the temperature condition for evaporation can be evaluated from the peak features. We applied the present results to the infrared spectrum of a protoplanetary disk HD100546 and found that a certain fraction ({approx}25%) of forsterite dust may have experienced high-temperature evaporation (>1600 K).

  16. Crystallization, preliminary X-ray crystallographic and cryo-electron microscopy analysis of a bifunctional enzyme fucokinase/L-fucose-1-P-guanylyltransferase from Bacteroides fragilis.

    PubMed

    Cheng, Chongyun; Gu, Jianhua; Su, Jing; Ding, Wei; Yin, Jie; Liang, Wenguang; Yu, Xiaoxia; Ma, Jun; Wang, Peng George; Xiao, Zhicheng; Liu, Zhi-Jie

    2014-09-01

    Fucokinase/L-fucose-1-P-guanylyltransferase (FKP) is a bifunctional enzyme which converts L-fucose to Fuc-1-P and thence to GDP-L-fucose through a salvage pathway. The molecular weights of full-length FKP (F-FKP) and C-terminally truncated FKP (C-FKP, residues 300-949) are 105.7 and 71.7?kDa, respectively. In this study, both recombinant F-FKP and C-FKP were expressed and purified. Size-exclusion chromatography experiments and analytical ultracentrifugation results showed that both F-FKP and C-FKP are trimers. Native F-FKP protein was crystallized by the vapour-diffusion method and the crystals belonged to space group P212121 and diffracted synchrotron X-rays to 3.7?Å resolution. The crystal unit-cell parameters are a = 91.36, b = 172.03, c = 358.86?Å, ? = ? = ? = 90.00°. The three-dimensional features of the F-FKP molecule were observed by cryo-EM (cryo-electron microscopy). The preliminary cryo-EM experiments showed the F-FKP molecules as two parallel disc-shaped objects stacking together. Combining all results together, it is assumed that there are six FKP molecules in one asymmetric unit, which corresponds to a calculated Matthews coefficient of 2.19?Å(3)?Da(-1) with 43.83% solvent content. These preliminary crystallographic and cryo-EM microscopy analyses provide basic structural information on FKP. PMID:25195892

  17. Synthesis and study of the crystallographic and magnetic structure of DyFeMnO{sub 5}: A new ferrimagnetic oxide

    SciTech Connect

    Martinez-Lope, M.J.; Retuerto, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain)], E-mail: ja.alonso@icmm.csic.es; Pomjakushin, V. [Laboratory for Neutron Scattering, ETHZ and PSI, CH-5232 Villigen PSI (Switzerland)

    2008-09-15

    The title oxide has been obtained by replacing Mn{sup 3+} by Fe{sup 3+} in the parent oxide DyMn{sub 2}O{sub 5}. The crystallographic and magnetic structures have been analysed from neutron powder diffraction (NPD) data, in complement with susceptibility and magnetic measurements. DyFeMnO{sub 5} is orthorhombic, belonging to the Pbam space group as the parent compound. The crystal structure contains infinite chains of edge-sharing Mn{sup 4+}O{sub 6} octahedra, interconnected by dimer units of Fe{sup 3+}O{sub 5} square pyramids. There is a certain antisite disorder in the crystal structure, with 8.0% of the Mn{sup 4+} sites occupied by Fe cations, and 8.2% of the Fe{sup 3+} positions occupied by Mn{sup 3+} cations. The magnetization measurements show that DyFeMnO{sub 5} presents magnetic order below T{sub C}{approx}178 K; a study of the magnetic structure from the low-temperature NPD patterns indicates an antiferromagnetic coupling of the Mn{sup 4+} and Fe{sup 3+} spins, with the polarization of the Dy{sup 3+} magnetic moments parallel to the those of the Fe sublattice. - Graphical abstract: DyFeMnO{sub 5} is orthorhombic (Pbam) as the parent DyMn{sub 2}O{sub 5} oxide. The crystal structure contains infinite chains of edge-sharing Mn{sup 4+}O{sub 6} octahedra, interconnected by dimer units of Fe{sup 3+}O{sub 5} square pyramids. It is ferrimagnetic below T{sub C}{approx}178 K; a NPD study indicated an antiferromagnetic coupling of the Mn{sup 4+} and Fe{sup 3+} spins, with Dy{sup 3+} magnetic moments parallel to those of Fe.

  18. An EXAFS Spectroscopic, Large-Angle X-Ray Scattering, And Crystallographic Study of Hexahydrated, Dimethyl Sulfoxide And Pyridine 1-Oxide Hexasolvated Mercury(II) Ions

    SciTech Connect

    Persson, I.; Eriksson, L.; Lindqvist-Reis, P.; Persson, P.; Sandstrom, M.

    2009-05-21

    The structure of the solvated mercury(II) ion in water and dimethyl sulfoxide has been studied by means of large-angle X-ray scattering (LAXS) and extended X-ray absorption fine structure (EXAFS) techniques. The distribution of the Hg-O distances is unusually wide and asymmetric in both solvents. In aqueous solution, hexahydrated [Hg(OH{sub 2}){sub 6}]{sup 2+} ions in a distorted octahedral configuration, with the centroid of the HgO distance at 2.38(1) {angstrom}, are surrounded by a diffuse second hydration sphere with HgOII distances of 4.20(2) {angstrom}. In dimethyl sulfoxide, the six HgO and HgS distances of the hexasolvated [Hg{l_brace}OS(CH{sub 3}){sub 2}{r_brace}{sub 6}]{sup 2+} complex are centered around 2.38(1) and 3.45(2) {angstrom}, respectively. The crystal structure of hexakis(pyridine 1-oxide)mercury(II) perchlorate has been redetermined. The space group R implies six equal HgO distances of 2.3416(7) {angstrom} for the [Hg(ONC{sub 5}H{sub 5}){sub 6}]{sup 2+} complex at 100 K. However, EXAFS studies of this compound, and of the solids hexaaquamercury(II) perchlorate and hexakis(dimethyl sulfoxide)mercury(II) trifluoromethanesulfonate, also with six equidistant HgO bonds according to crystallographic results, reveal in all cases strongly asymmetric HgO distance distributions. Vibronic coupling of valence states in a so-called pseudo-Jahn-Teller effect probably induces the distorted configurations.

  19. Using Innovative Outliers to Detect Discrete Shifts in Dynamics in Group-Based State-Space Models

    ERIC Educational Resources Information Center

    Chow, Sy-Miin; Hamaker, Ellen L.; Allaire, Jason C.

    2009-01-01

    Outliers are typically regarded as data anomalies that should be discarded. However, dynamic or "innovative" outliers can be appropriately utilized to capture unusual but substantively meaningful shifts in a system's dynamics. We extend De Jong and Penzer's 1998 approach for representing outliers in single-subject state-space models to a…

  20. A study of space station needs, attributes and architectural options. Final briefing: Cost working group discussion session

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The economic factors involved in the design and utilization of the space station are investigated. Topics include the economic benefits associated with research and production, the orbit transfer vehicle, and satellite servicing. Program costs and design options are examined. The possibilities of financing from the private sector are discussed.

  1. A scientific program for infrared, submillimeter and radio astronomy from space: A report by the Management Operations Working Group

    NASA Technical Reports Server (NTRS)

    1989-01-01

    Important and fundamental scientific progress can be attained through space observations in the wavelengths longward of 1 micron. The formation of galaxies, stars, and planets, the origin of quasars and the nature of active galactic nuclei, the large scale structure of the Universe, and the problem of the missing mass, are among the major scientific issues that can be addressed by these observations. Significant advances in many areas of astrophysics can be made over the next 20 years by implementing the outlined program. This program combines large observatories with smaller projects to create an overall scheme that emphasized complementarity and synergy, advanced technology, community support and development, and the training of the next generation of scientists. Key aspects of the program include: the Space Infrared Telescope Facility; the Stratospheric Observatory for Infrared Astronomy; a robust program of small missions; and the creation of the technology base for future major observatories.

  2. On algebras and groups of formal series over a groupoïd and application to some spaces of cobordism

    E-print Network

    Jean-Pierre Magnot

    2015-07-03

    We develop here a concept of deformed algebras and their related groups through two examples. Deformed algebras are obtained from a fixed algebra by deformation along a family of indexes, through formal series. We show how the example of deformed algebra used in \\cite{Ma2013} is only an example among others, and how they often give rise to regular Fr\\"olicher Lie groups, and sometimes to Fr\\'echet Lie groups, that are regular. The first example, indexed by $\\N,$ is obtained by deformations of the gourp of bounded classical pseudo-differential operators $Cl^{0,*}$ by algebras of (maybe unbounded) classical pseudo-differential operators. In the second one, the set of indexes is a $\\N-$graded groupo\\"id, which is made of manifolds with boundary that are understood as morphisms of cobordisms. Here again, we get regular Lie groups, and we show how this setting applies to a class of examples that are derived of so-called stochastic cosurfaces.

  3. Summary Report of the NASA Management Study Group: Recommendations to the Administrator, National Aeronautics and Space Administration

    NASA Technical Reports Server (NTRS)

    Phillips, Samuel C.

    1986-01-01

    The NASA Management Study Group (NMSG) was established under the auspices of the National Acedamy of Public Administration at the request of the Administrator of NASA to assess NASA's management practices and to evaluate the effectiveness of the NASA organization. This report summarizes the conclusions and recommendations of the NMSG on the overall management and organization of NASA.

  4. Invariant conformal vectors in space-times admitting a group of G/sub 3/ of motions acting on spacelike orbits S/sub 2/

    SciTech Connect

    Bona, C.

    1988-11-01

    The paper deals with four-dimensional space-times admitting locally a three-dimensional group of motions G/sub 3/ acting on two-dimensional spacelike orbits S/sub 2/. The local existence problem for conformal vectors invariant under G/sub 3/ is shown to be equivalent to the local existence problem for Killing vectors of a given two-dimensional pseudo-Riemannian metric g. This problem is explicitly solved in terms of the Gaussian curvature R of g and two of its scalar differential concomitants. The results are applied to the case of dust-filled space-times, where an exhaustive list of metrics has been obtained by using the algebraic computing language Sm-smcapsp-smcaps.-smcaps The metrics are either homogeneous, self-similar, or Friedmann models.

  5. Crystallographic Image Processing with Unambiguous 2D Bravais Lattice Identification on the Basis of a Geometric Akaike Information Criterion

    NASA Astrophysics Data System (ADS)

    Bilyeu, Taylor Thomas

    Crystallographic image processing (CIP) is a technique first used to aid in the structure determination of periodic organic complexes imaged with a high-resolution transmission electron microscope (TEM). The technique has subsequently been utilized for TEM images of inorganic crystals, scanning TEM images, and even scanning probe microscope (SPM) images of two-dimensional periodic arrays. We have written software specialized for use on such SPM images. A key step in the CIP process requires that an experimental image be classified as one of only 17 possible mathematical plane symmetry groups. The current methods used for making this symmetry determination are not entirely objective, and there is no generally accepted method for measuring or quantifying deviations from ideal symmetry. Here, we discuss the crystallographic symmetries present in real images and the general techniques of CIP, with emphasis on the current methods for symmetry determination in an experimental 2D periodic image. The geometric Akaike information criterion (AIC) is introduced as a viable statistical criterion for both quantifying deviations from ideal symmetry and determining which 2D Bravais lattice best fits the experimental data from an image being processed with CIP. By objectively determining the statistically favored 2D Bravais lattice, the determination of plane symmetry in the CIP procedure can be greatly improved. As examples, we examine scanning tunneling microscope images of 2D molecular arrays of the following compounds: cobalt phthalocyanine on Au (111) substrate; nominal cobalt phthalocyanine on Ag (111); tetraphenoxyphthalocyanine on highly oriented pyrolitic graphite; hexaazatriphenylene-hexacarbonitrile on Ag (111). We show that the geometric AIC procedure can unambiguously determine which 2D Bravais lattice fits the experimental data for a variety of different lattice types. In some cases, the geometric AIC procedure can be used to determine which plane symmetry group best fits the experimental data, when traditional CIP methods fail to do so.

  6. Crystals with sublattices and their symmetry in multidimensional crystal spaces

    SciTech Connect

    Poplavnoi, A. S. [Kemerovo State University (Russian Federation)], E-mail: popl@kemsu.ru

    2007-07-15

    The symmetry of complex crystals composed of sublattices belonging to different Bravais typeshas been investigated. It is shown that description of this symmetry necessitates introduction of a multidimensional crystal space R{sup 3k} decomposing into the direct sum of k 3D orthogonal subspaces (S = 1, 2, ?, k), where k is the number of sublattices. The symmetry of the subspaces R{sub S}{sup 3} of the sublattices is a set of their crystallographic groups. The bases of subspaces R{sub S}{sup 3} are related by the transformation of translation compatibility, at which the scale changes. A method for studying the origin of the spectra of elementary excitations in crystals is presented that is based on the analysis of the sublattice symmetry. Complex lattices composed of cubic sublattices are considered as an illustration.

  7. Real-space renormalization-group study of the two-dimensional Blume-Capel model with a random crystal field

    NASA Astrophysics Data System (ADS)

    Branco, N. S.; Boechat, Beatriz M.

    1997-11-01

    The phase diagram of the two-dimensional Blume-Capel model with a random crystal field is investigated within the framework of a real-space renormalization-group approximation. Our results suggest that, for any amount of randomness, the model exhibits a line of Ising-like continuous transitions, as in the pure model, but no first-order transition. At zero temperature the transition is also continuous, but not in the same universality class as the Ising model. In this limit, the attractor (in the renormalization-group sense) is the percolation fixed point of the site diluted spin-1/2 Ising model. The results we found are in qualitative agreement with general predictions made by Berker and Hui on the critical behavior of random models.

  8. Crystallization and preliminary X-ray crystallographic analysis of the cysteine protease inhibitor clitocypin

    PubMed Central

    Galeša, Katja; Brzin, Jože; Saboti?, Jerica; Turk, Dušan

    2006-01-01

    Clitocypin is a cysteine protease inhibitor from the mushroom Clitocybe nebularis. The protein has been purified from natural sources and crystallized in a variety of non-isomorphous forms belonging to monoclinic and triclinic space groups. A diffraction data set to 1.55?Å resolution was obtained from a crystal belonging to space group P2, with unit-cell parameters a = 38.326, b = 33.597, c = 55.568?Å, ? = 104°. An inability to achieve isomorphism forced the use of MAD and SAD phasing methods. Phasing is in progress. PMID:16511249

  9. Determination of the crystal system and space group of BaBiO3 by convergent-beam electron diffraction and x-ray diffraction using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Hashimoto, Takuya; Tsuda, Kenji; Shiono, Junichiro; Mizusaki, Junichiro; Tanaka, Michiyoshi

    2001-12-01

    The crystal system and space group of BaBiO3 with a distorted perovskite structure were investigated by convergent-beam electron diffraction (CBED), selected area electron diffraction, and x-ray diffraction using synchrotron radiation. Since all the observed CBED patterns showed a symmetry of 1, and the +/-G dark-field disk of CBED patterns indicated the absence of an inversion center in BaBiO3, the crystal symmetry of BaBiO3 was concluded to be triclinic with a space group of P1 (No. 1). The diffraction angles of the x-ray-diffraction peaks of BaBiO3, obtained using synchrotron radiation, could apparently be explained by assuming a monoclinic symmetry. However, a larger full width at half maximum (FWHM) of the 440 peak, indexed assuming a monoclinic symmetry other than that of each peak of 008, 404¯, 404, and 044 could not be explained. The large FWHM of the 440 peak could be attributed to an overlapping of the 4¯40 and 440 peaks of triclinic symmetry, showing agreement with the result of CBED.

  10. Experimental and Theoretical Investigation of Crystallographic Orientation Dependence of Nanoscratching of Single Crystalline Copper

    PubMed Central

    Geng, Yanquan; Zhang, Junjie; Yan, Yongda; Yu, Bowen; Geng, Lin; Sun, Tao

    2015-01-01

    In the present work, we perform experiments and molecular dynamics simulations to elucidate the underlying deformation mechanisms of single crystalline copper under the load-controlled multi-passes nanoscratching using a triangular pyramidal probe. The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed. Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined. Our simulation results indicate that the plastic deformation of single crystalline Cu under the nanoscratching is exclusively governed by dislocation mechanisms. However, there is no glissile dislocation structure formed due to the probe oscillation under the load-controlled mode. Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations. PMID:26147506

  11. Phosphate tungsten bronze series: crystallographic and structural properties of low-dimensional conductors.

    PubMed

    Roussel, P; Pérez, O; Labbé, P

    2001-10-01

    Phosphate tungsten bronzes have been shown to be conductors of low dimensionality. A review of the crystallographic and structural properties of this huge series of compounds is given here, corresponding to the present knowledge of the different X-ray studies and electron microscopy investigations. Three main families are described, monophosphate tungsten bronzes, Ax(PO2)4(WO3)2m, either with pentagonal tunnels (MPTBp) or with hexagonal tunnels (MPTBh), and diphosphate tungsten bronzes, Ax(P2O4)2(WO3)2m, mainly with hexagonal tunnels (DPTBh). The general aspect of these crystal structures may be described as a building of polyhedra sharing oxygen corners made of regular stacking of WO3-type slabs with a thickness function of m, joined by slices of tetrahedral PO4 phosphate or P2O7 diphosphate groups. The relations of the different slabs with respect to the basic perovskite structure are mentioned. The structural description is focused on the tilt phenomenon of the WO6 octahedra inside a slab of WO3-type. In this respect, a comparison with the different phases of the WO3 crystal structures is established. The various modes of tilting and the different possible connections between two adjacent WO3-type slabs involve a great variety of structures with different symmetries, as well as the existence of numerous twins in MPTBp's. Several phase transitions, with the appearance of diffuse scattering and modulation phenomena, were analysed by X-ray scattering measurements and through the temperature dependence of various physical properties for the MPTBp's. The role of the W displacements within the WO3-type slabs, in two modulated structures (m = 4 and m = 10), already solved, is discussed. Finally, the complexity of the structural aspects of DPTBh's is explained on the basis of the average structures which are the only ones solved. PMID:11574717

  12. The redshift-space cluster-galaxy cross-correlation function - I. Modelling galaxy infall on to Millennium simulation clusters and SDSS groups

    NASA Astrophysics Data System (ADS)

    Zu, Ying; Weinberg, David H.

    2013-06-01

    The large-scale infall of galaxies around massive clusters provides a potentially powerful diagnostic of structure growth, dark energy and cosmological deviations from General Relativity. We develop and test a method to recover galaxy infall kinematics (GIK) from measurements of the redshift-space cluster-galaxy cross-correlation function ? s_cg(r_p,r_? ). Using galaxy and halo samples from the Millennium simulation, we calibrate an analytic model of the galaxy kinematic profiles comprising a virialized component with an isotropic Gaussian velocity distribution and an infall component described by a skewed 2D t-distribution with a characteristic infall velocity vr, c and separate radial and tangential dispersions. We show that convolving the real-space cross-correlation function with this velocity distribution accurately predicts the redshift-space ? s_cg, and we show that measurements of ? s_cg can be inverted to recover the four distinct elements of the GIK profiles. These in turn provide diagnostics of cluster mass profiles, and we expect the characteristic infall velocity vr, c(r) in particular to be insensitive to galaxy formation physics that can affect velocity dispersions within haloes. As a proof of concept we measure ? s_cg for rich galaxy groups in the Sloan Digital Sky Survey and recover GIK profiles for groups in two bins of central galaxy stellar mass. The higher mass bin has a vr, c(r) curve very similar to that of 1014 h-1 M? haloes in the Millennium simulation, and the recovered kinematics follow the expected trends with mass. GIK modelling of cluster-galaxy cross-correlations can be a valuable complement to stacked weak lensing analyses, allowing novel tests of modified gravity theories that seek to explain cosmic acceleration.

  13. Ongoing Analysis of Rocket Based Combined Cycle Engines by the Applied Fluid Dynamics Analysis Group at Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Ruf, Joseph; Holt, James B.; Canabal, Francisco

    1999-01-01

    This paper presents the status of analyses on three Rocket Based Combined Cycle configurations underway in the Applied Fluid Dynamics Analysis Group (TD64). TD64 is performing computational fluid dynamics analysis on a Penn State RBCC test rig, the proposed Draco axisymmetric RBCC engine and the Trailblazer engine. The intent of the analysis on the Penn State test rig is to benchmark the Finite Difference Navier Stokes code for ejector mode fluid dynamics. The Draco engine analysis is a trade study to determine the ejector mode performance as a function of three engine design variables. The Trailblazer analysis is to evaluate the nozzle performance in scramjet mode. Results to date of each analysis are presented.

  14. Ongoing Analyses of Rocket Based Combined Cycle Engines by the Applied Fluid Dynamics Analysis Group at Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Ruf, Joseph H.; Holt, James B.; Canabal, Francisco

    2001-01-01

    This paper presents the status of analyses on three Rocket Based Combined Cycle (RBCC) configurations underway in the Applied Fluid Dynamics Analysis Group (TD64). TD64 is performing computational fluid dynamics (CFD) analysis on a Penn State RBCC test rig, the proposed Draco axisymmetric RBCC engine and the Trailblazer engine. The intent of the analysis on the Penn State test rig is to benchmark the Finite Difference Navier Stokes (FDNS) code for ejector mode fluid dynamics. The Draco analysis was a trade study to determine the ejector mode performance as a function of three engine design variables. The Trailblazer analysis is to evaluate the nozzle performance in scramjet mode. Results to date of each analysis are presented.

  15. Modeling Thermal Effects in Fully-Depleted SOI Devices with Arbitrary Crystallographic Orientation

    Microsoft Academic Search

    K. Raleva; Dragica Vasileska; Stephen Marshall Goodnick

    2010-01-01

    \\u000a In this work we continue our investigation on the heating effects in nano-scale FD-SOI devices using an in-house thermal particle-based\\u000a device simulator. We focus on the current variations for FD-SOI devices with arbitrary crystallographic orientation and examine\\u000a which crystallographic orientation gives better results from electrical and thermal point of view. Our simulation results\\u000a demonstrate that one can obtain the lowest

  16. Correlation between Crystallographic and Magnetic Domains at Co/NiO(001) Interfaces

    SciTech Connect

    Ohldag, H.; van der Laan, G.; Arenholz, E.

    2008-12-18

    Using soft x-ray spectromicroscopy we show that NiO(001) exhibits a crystallographic and magnetic domain structure near the surface identical to that of the bulk. Upon Co deposition a perpendicular coupling between the Ni and Co moments is observed that persists even after formation of uncompensated Ni spins at the interface through annealing. The chemical composition at the interface alters its crystallographic structure and leads to a reorientation of the Ni moments from the <112> to the <110> direction. We show that this reorientation is driven by changes in the magnetocrystalline anisotropy rather than exchange coupling mediated by residual uncompensated spins.

  17. Magnetic versus crystallographic fabrics in a basaltic lava flow Jero^me BascouT, Pierre Camps, Jean Marie Dautria

    E-print Network

    Bascou, Jérôme

    Magnetic versus crystallographic fabrics in a basaltic lava flow Je´ro^me BascouT, Pierre Camps) and crystallographic studies were performed within a quaternary lava flow, for which we have a thorough knowledge in agreements with the known flow direction. In the lower part of the lava flow, the tight correlation between

  18. The Hubble Space Telescope Extragalactic Distance Scale Key Project. VII. The Discovery of Cepheids in the Leo I Group Galaxy NGC 3351

    NASA Astrophysics Data System (ADS)

    Graham, John A.; Phelps, Randy L.; Freedman, Wendy L.; Saha, Abhijit; Ferrarese, Laura; Stetson, Peter B.; Madore, Barry F.; Silbermann, N. A.; Sakai, Shoko; Kennicutt, Robert C.; Harding, Paul; Bresolin, Fabio; Turner, Anne; Mould, Jeremy R.; Rawson, Daya M.; Ford, Holland C.; Hoessel, John G.; Han, Mingsheng; Huchra, John P.; Macri, Lucas M.; Hughes, Shaun M.; Illingworth, Garth D.; Kelson, Daniel D.

    1997-03-01

    We report of the discovery and properties of Cepheid variable stars in the barred spiral galaxy NGC 3351 which is a member of the Leo I group of galaxies. NGC 3351 is one of 18 galaxies being observed as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale which aims to determine the Hubble constant to 10% accuracy. Our analysis is based on observations made with the Wide Field Planetary Camera 2 during 1994 and early 1995. The Leo I group contains several bright galaxies of diverse types and is very suitable for linking together a number of secondary calibrators which can be employed at much greater distances than the Cepheid variables. We identify 49 probable Cepheids within NGC 3351 in the period range 10-43 days which have been observed at 12 epochs with the F555W filter and 4 epochs using the F814W filter. The HST F555W and F814W data have been transformed to the Johnson V and Cousins I magnitude systems, respectively. Photometry has principally been carried out using the DAOPHOT/ALLFRAME package. Reference is made to parallel measurements being made with the DoPHOT package. Apparent period-luminosity functions for V and I have been constructed assuming values of ?0 = 18.50 +/- 0.10 mag and E(B - V) = 0.10 mag for the distance modulus and reddening of the Large Magellanic Cloud. A true distance modulus of 30.01 +/- 0.19 mag is derived corresponding to a distance of 10.05 +/- 0.88 Mpc with a reddening E(V - I) = 0.15 mag. A comparison is made with distances estimated for other galaxies in the Leo I group using various distance indicators. There is good agreement with the surface brightness fluctuation and planetary nebula luminosity function methods as calibrated by the Cepheids in M31. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, operated by AURA, Inc. under NASA contract No. NAS5-26555.

  19. Crystallographic preferred orientation and deformation of deep Earth minerals

    NASA Astrophysics Data System (ADS)

    Kaercher, Pamela Michelle

    This thesis aims to provide further insight into crystallographic preferred orientation (CPO) and deformation mechanisms active at high pressure. Preferred orientation of iron-rich magnesiowustite (Mg,Fe)O, a major mantle mineral phase, stishovite (SiO2), the high pressure polymorph of quartz that is likely present in the lower crust and mantle, and in NaMgF3 + NaCl, an analog system to lower mantle minerals MgSiO3 + MgO, have been examined with synchrotron X-ray diffraction while at high pressure in either a diamond anvil cell or a multianvil press. Magnesiowustite, (Mg0.08Fe0.88)O, and wustite, Fe0.94O, were compressed up to 37 GPa at ambient temperature in diamond anvil cells (DAC) at the Advanced Light Source (ALS). X-ray diffraction patterns were taken in situ in radial geometry in order to study the evolution of CPO through the cubic-to-rhombohedral phase transition. Under uniaxial stress in the DAC, cubic texture developed (i.e. {100} c planes aligned perpendicular to the compression direction). Variant selection of preferred orientation was observed immediately following the transition to the rhombohedral phase. Upon decompression in the DAC, FeO reverted back to cubic symmetry and the cubic texture reappeared, demonstrating that the transition is reversible and has texture memory. The crystal structure of the high pressure SiO2 polymorph stishovite has been studied in detail, but little is known about texture development during deformation, which provides information for understanding subduction of quartz-bearing crustal rocks into the mantle. Radial DAC experiments were done at the ALS and the Advanced Photon Source (APS) while collecting X-ray diffraction patterns in radial geometry to examine in situ development of CPO. Starting pressure in the sample chamber was still in the quartz stability field, and compression of quartz produced a weak texture, likely due to Dauphine twinning. Following compression of quartz into the stishovite stability field, near 13-16 GPa, the sample was laser heated to activate kinetics and transition to stishovite. Stishovite nucleated with (001) planes preferentially aligned perpendicular to compression. Increased preferred orientation during further compression up to 38 GPa is attributed to slip. Slip systems responsible were inferred from visco-plastic self-consistent modeling and are most likely basal and pyramidal slip at experimental conditions. Geodynamic models predict large strains due to convection in the mantle, and polycrystal plasticity simulations suggest strong preferred orientation. However, these models ignore interaction among phases, which is important for the lower mantle, estimated to be composed of ˜25% soft magnesiowustite (Mg,Fe)O and ˜70% harder Mg-perovskite (MgSiO3). How much preferred orientation develops as a result of large strains in the lower mantle depends on the volume percent ratios and arrangement of the two phases. If grains of the softer phase, MgO, become interconnected, they may act as a lubricant between grains of the harder phase, thereby absorbing most of the deformation. Alternatively, the soft phase may sit in pockets in between harder MgSiO 3 grains, and thus not be interconnected, leaving MgSiO3 to bear the load. In the former case, MgO will control the deformation, and in the later, MgSiO3, and the development of CPO in these two cases may greatly differ. To study CPO development in a two-phase system, deformation experiments were performed in the deformation-DIA (D-DIA, DIA being shortening of "diamond") at the APS while collecting X-ray diffraction patterns in situ. While the D-DIA offers more control over deformation conditions and temperature and can deform larger samples, resulting in better counting statistics than for DAC samples, it cannot reach pressures beyond 12 GPa or temperatures higher than 2000 K. Thus neighborite (NaMgF3) and halite (NaCl), which have the same structures and relative strengths as mantle minerals silicate-magnesium pervoskite (MgSiO3) and periclase (MgO) but deform more easily, were chosen a

  20. The generalization of the exterior square of a Bieberbach group

    NASA Astrophysics Data System (ADS)

    Masri, Rohaidah; Hassim, Hazzirah Izzati Mat; Sarmin, Nor Haniza; Ali, Nor Muhainiah Mohd; Idrus, Nor'ashiqin Mohd

    2014-06-01

    The exterior square of a group is one of the homological functors which were originated in the homotopy theory. Meanwhile, a Bieberbach group is a torsion free crystallographic group. A Bieberbach group with cyclic point group of order two, C2, of dimension n can be defined as the direct product of that group of the smallest dimension with a free abelian group. Using the group presentation and commutator generating sequence, the exterior square of a Bieberbach group with point group C2 of dimension n is computed.

  1. ANALYSIS OF INTERACTION BETWEEN A CRYSTALLOGRAPHICALLY UNIAXIAL FERRITE RESONATOR AND A HALL-EFFECT TRANSDUCER

    Microsoft Academic Search

    Marina Y. Koledintseva; Alexander A. Kitaitsev

    2007-01-01

    In this paper, a number of physical phenomena taking place at the interaction of a crystallographically uniaxial ferrite resonator (UFR) with a semiconductor element, such as a Hall-effect transducer (HET), are analyzed. The UFR in this study is in a direct contact with an unpackaged HET. The interaction is studied in the vicinity of the ferromagnetic resonance in the UFR.

  2. Room-and Low-Temperature Crystallographic Study of the Ambient Pressure Organic Superconductor

    E-print Network

    Coppens, Philip

    Room- and Low-Temperature Crystallographic Study of the Ambient Pressure Organic Superconductor) is an ambient pressure low-temperature superconductor (Tc ) 4.3K) with an incommensurate two. The monoclinic modification has been described as an ambient pressure superconductor, with a midpoint

  3. Crystallographically aligned carbon nanotubes grown on few-layer graphene films.

    PubMed

    Hunley, D Patrick; Johnson, Stephen L; Stieha, Joseph K; Sundararajan, Abhishek; Meacham, Aaron T; Ivanov, Ilia N; Strachan, Douglas R

    2011-08-23

    Carbon nanotubes are grown on few-layer graphene films using chemical vapor deposition without a carbon feedstock gas. We find that the nanotubes show a striking alignment to specific crystal orientations of the few-layer graphene films. The nanotubes are oriented predominantly at 60 degree intervals and are offset 30 degrees from crystallographically oriented etch tracks, indicating alignment to the armchair axes of the few-layer graphene films. Nanotubes grown on various thicknesses of few-layer graphene under identical process conditions show that the thinnest films, in the sub-6 atomic layer regime, demonstrate significantly improved crystallographic alignment. Intricate crystallographic patterns are also observed having sharp kinks with bending radii less than the ?10 nm lateral resolution of the electron and atomic force microscopy used to image them. Some of these kinks occur independently without interactions between nanotubes while others result when two nanotubes intersect. These intersections can trap nanotubes between two parallel nanotubes resulting in crystallographic back and forth zigzag geometries. These interactions suggest a tip-growth mechanism such that the catalyst particles remain within several nanometers of the few-layer graphene surface as they move leaving a nanotube in their wake. PMID:21749089

  4. Induction welding and heat treatment of steel pipes: evolution of crystallographic texture

    E-print Network

    Cambridge, University of

    Induction welding and heat treatment of steel pipes: evolution of crystallographic texture detrimental to toughness P. Yan*1 , O¨. E. Gu¨ngo¨r2 , P. Thibaux2 and H. K. D. H. Bhadeshia1 Steel welding using induction heating to produce pipelines is found to have lower toughness at the weld junction than

  5. Magnetic-field-induced crystallographic texture enhancement in cold-deformed FePt nanostructured magnets

    E-print Network

    Garmestani, Hamid

    Magnetic-field-induced crystallographic texture enhancement in cold-deformed FePt nanostructured magnets B. Z. Cuia and K. Han National High Magnetic Field Laboratory, Florida State University Grenoble, France H. J. Schneider-Muntau National High Magnetic Field Laboratory, Florida State University

  6. Crystallographic and EXAFS studies of conformationally designed nonplanar nickel(II) porphyrins

    Microsoft Academic Search

    Kathleen M. Barkigia; Mark W. Renner; Lars R. Furenlid; J. Fajer; C. J. Medforth; K. M. Smith

    1993-01-01

    A series of Ni(II) tetraphenylporphyrins with varying [beta] substituents was examined by X-ray crystallography and EXAFS to assess peripheral steric effects on the conformations of the macrocycles. Crystallographic results establish that ethyl, propyl, and cyclohexenyl substitutions lead to saddle conformations of the macrocycle skeletons that minimize steric interactions between the [beta] and meso substituents. We have also taken advantage of

  7. Effects of substrate crystallographic orientations on crystal growth and microstructure development in laser

    E-print Network

    DuPont, John N.

    Effects of substrate crystallographic orientations on crystal growth and microstructure development in laser surface-melted superalloy single crystals. Mathematical modeling of single-crystal growth that the substrate orientation has a predominant effect on crystal growth pattern, and simultaneously influences

  8. Crystallographic orientation analysis of magnetite thin films by means of electron backscatter diffraction (EBSD)

    Microsoft Academic Search

    A. D. Koblischka-Veneva; M. R. Koblischka; F. Muecklich; S. Murphy; Y. Zhou; I. V. Shvets

    2006-01-01

    Fe3O4[001] thin films is grown on MgO[001] substrates using oxygen-plasma-assisted molecular beam epitaxy and annealed in air at 250 degC. Automated EBSD scans is performed twice to study the crystallographic orientation by means of recording of Kikuchi patterns.

  9. Control of crystallographic orientation in diamond synthesis through laser resonant vibrational excitation of precursor molecules.

    PubMed

    Xie, Zhi Qiang; Bai, Jaeil; Zhou, Yun Shen; Gao, Yi; Park, Jongbok; Guillemet, Thomas; Jiang, Lan; Zeng, Xiao Cheng; Lu, Yong Feng

    2014-01-01

    Crystallographic orientations determine the optical, electrical, mechanical, and thermal properties of crystals. Control of crystallographic orientations has been studied by changing the growth parameters, including temperature, pressure, proportion of precursors, and surface conditions. However, molecular dynamic mechanisms underlying these controls remain largely unknown. Here we achieved control of crystallographic orientations in diamond growth through a joint experimental and theoretical study of laser resonant vibrational excitation of precursor molecules (ethylene). Resonant vibrational excitation of the ethylene molecules using a wavelength-tunable CO2 laser steers the chemical reactions and promotes proportion of intermediate oxide species, which results in preferential growth of {100}-oriented diamond films and diamond single crystals in open air. Quantum molecular dynamic simulations and calculations of chemisorption energies of radicals detected from our mass-spectroscopy experiment provide an in-depth understanding of molecular reaction mechanisms in the steering of chemical reactions and control of crystallographic orientations. This finding opens up a new avenue for controlled chemical vapor deposition of crystals through resonant vibrational excitations to steer surface chemistry. PMID:24694918

  10. Control of crystallographic orientation in diamond synthesis through laser resonant vibrational excitation of precursor molecules

    PubMed Central

    Xie, Zhi Qiang; Bai, Jaeil; Zhou, Yun Shen; Gao, Yi; Park, Jongbok; Guillemet, Thomas; Jiang, Lan; Zeng, Xiao Cheng; Lu, Yong Feng

    2014-01-01

    Crystallographic orientations determine the optical, electrical, mechanical, and thermal properties of crystals. Control of crystallographic orientations has been studied by changing the growth parameters, including temperature, pressure, proportion of precursors, and surface conditions. However, molecular dynamic mechanisms underlying these controls remain largely unknown. Here we achieved control of crystallographic orientations in diamond growth through a joint experimental and theoretical study of laser resonant vibrational excitation of precursor molecules (ethylene). Resonant vibrational excitation of the ethylene molecules using a wavelength-tunable CO2 laser steers the chemical reactions and promotes proportion of intermediate oxide species, which results in preferential growth of {100}-oriented diamond films and diamond single crystals in open air. Quantum molecular dynamic simulations and calculations of chemisorption energies of radicals detected from our mass-spectroscopy experiment provide an in-depth understanding of molecular reaction mechanisms in the steering of chemical reactions and control of crystallographic orientations. This finding opens up a new avenue for controlled chemical vapor deposition of crystals through resonant vibrational excitations to steer surface chemistry. PMID:24694918

  11. NMR, Molecular Modeling, and Crystallographic Studies of Lentil Lectin-Sucrose Interaction*

    E-print Network

    Hamelryck, Thomas

    NMR, Molecular Modeling, and Crystallographic Studies of Lentil Lectin-Sucrose Interaction- ing site of lentil lectin have been characterized through elucidation of a crystalline complex at 1, and molecular modeling. In the crys- tal, the lentil lectin dimer binds one sucrose molecule per monomer

  12. Decoupling of UPb dates from chemical and crystallographic domains in granulite facies zircon

    E-print Network

    Decoupling of U­Pb dates from chemical and crystallographic domains in granulite facies zircon form 2 November 2009 Accepted 3 November 2009 Editor: R.L. Rudnick Keywords: U­Pb Zircon Geochronology spots per crystal) U­Pb ion probe data were acquired for zircon crystals from a mafic granulite

  13. Local dynamics of proteins and DNA evaluated from crystallographic B factors

    SciTech Connect

    Schneider, Bohdan, E-mail: bohdan.schneider@gmail.com [Institute of Biotechnology AS CR, Videnska 1083, 142 20 Prague (Czech Republic); Gelly, Jean-Christophe; Brevern, Alexandre G. de [INSERM, U1134, DSIMB, 75739 Paris (France); Université Paris Diderot, Sorbonne Paris Cité, UMR-S 1134, 75739 Paris (France); Institut National de la Transfusion Sanguine (INTS), 75739 Paris (France); Laboratoire d’Excellence GR-Ex, 75739 Paris (France); ?erný, Ji?í [Institute of Biotechnology AS CR, Videnska 1083, 142 20 Prague (Czech Republic)

    2014-09-01

    Distributions of scaled B factors from 704 protein–DNA complexes reflect primarily the neighbourhood of amino-acid and nucleotide residues: their flexibility grows from the protein core to protein–protein and protein–DNA interfaces, to solvent-exposed residues. Some of the findings clearly observed at higher resolution structures can no longer be observed for structures at low resolution indicating problems in refinement protocols. The dynamics of protein and nucleic acid structures is as important as their average static picture. The local molecular dynamics concealed in diffraction images is expressed as so-called B factors. To find out how the crystal-derived B factors represent the dynamic behaviour of atoms and residues of proteins and DNA in their complexes, the distributions of scaled B factors from a carefully curated data set of over 700 protein–DNA crystal structures were analyzed [Schneider et al. (2014 ?), Nucleic Acids Res.42, 3381–3394]. Amino acids and nucleotides were categorized based on their molecular neighbourhood as solvent-accessible, solvent-inaccessible (i.e. forming the protein core) or lying at protein–protein or protein–DNA interfaces; the backbone and side-chain atoms were analyzed separately. The B factors of two types of crystal-ordered water molecules were also analyzed. The analysis confirmed several expected features of protein and DNA dynamics, but also revealed surprising facts. Solvent-accessible amino acids have B factors that are larger than those of residues at the biomolecular interfaces, and core-forming amino acids are the most restricted in their movement. A unique feature of the latter group is that their side-chain and backbone atoms are restricted in their movement to the same extent; in all other amino-acid groups the side chains are more floppy than the backbone. The low values of the B factors of water molecules bridging proteins with DNA and the very large fluctuations of DNA phosphates are surprising. The features discriminating different types of residues are less pronounced in structures with lower crystallographic resolution. Some of the observed trends are likely to be the consequence of improper refinement protocols that may need to be rectified.

  14. Petrographic and crystallographic study of silicate minerals in lunar rocks

    NASA Technical Reports Server (NTRS)

    Carmichael, I. S. E.; Turner, F. J.; Wenk, H. R.

    1974-01-01

    Optical U-stage measurements, chemical microprobe data, and X-ray procession photographs of a bytownite twin group from rock 12032,44 are compared. Sharp but weak b and no c-reflections were observed for this An89 bytownite indicating a partly disordered structure. Euler angles, used to characterize the orientation of the optical indicatrix, compare better with values for plutonic than for volcanic plagioclase. This indicates that structural and optical properties cannot be directly correlated.

  15. Crystallographic Texture and Orientation Variants in Al2O3-Y3Al5O12 Directionally Solidified Eutectic Crystals

    NASA Technical Reports Server (NTRS)

    Frazer, Colleen S.; Dickey, Elizabeth C.; Sayir, Ali; Farmer, Serene (Technical Monitor)

    2001-01-01

    Eutectic rods of Al2O3 and Y3Al5O12 were grown by a laser-heated float zone method, and their microstructure and crystallographic texture were studied by scanning electron microscopy, electron backscattered diffraction and x-ray diffraction. The composites were found to be highly textured with two twin-related crystallographic orientation relationships between the phases. Electron backscattered diffraction was employed to determine the spatial distribution of the orientational variants within the samples and to define the crystallographic orientation of various microstructural features.

  16. Crystallization and preliminary X-ray crystallographic analysis of extracellular giant hemoglobin from pogonophoran Oligobrachia mashikoi

    Microsoft Academic Search

    Nobutaka Numoto; Taro Nakagawa; Akiko Kita; Yuichi Sasayama; Yoshihiro Fukumori; Kunio Miki

    2005-01-01

    An extracellular giant hemoglobin of Oligobrachia mashikoi, composed of 24 globins with the molecular mass of ?400 kDa was crystallized in its intact form. Two crystal forms were obtained by the vapor-diffusion method. Form I crystals obtained using sodium acetate as a precipitant belong to the space group P6122 or P6522, with unit-cell parameters a=112.41, c=621.25 Å, and diffracted X-rays

  17. Crystallization and Preliminary X-ray Crystallographic Studies of the Alkanesulfonate FMN Reductase from Escherichia coli

    Microsoft Academic Search

    Benlian Gao; Adam Bertrand; William H. Boles; Holly R. Ellis; T. Conn Mallett

    2005-01-01

    The alkanesulfonate FMN reductase (SsuE) from Escherichia coli catalyzes the reduction of FMN by NADPH to provide reduced flavin for the monooxygenase (SsuD) enzyme. The vapor-diffusion technique yielded single crystals that grow as hexagonal rods and diffract to 2.9 Angstrom resolution using synchrotron X-ray radiation. The protein crystallizes in the primitive hexagonal space group P622. The SsuE protein lacks any

  18. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

    E-print Network

    NATIONAL AERONAUTICS AND SPACE ADMINISTRATION Earth Science Data Systems Working Group Standards-identified practices. #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION The Standards Process Group (SPG) · History #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION Insights (why the SPG?) · Interoperability does

  19. An evaluation of adhesive sample holders for advanced crystallographic experiments

    SciTech Connect

    Mazzorana, Marco; Sanchez-Weatherby, Juan, E-mail: juan.sanchez-weatherby@diamond.ac.uk; Sandy, James; Lobley, Carina M. C.; Sorensen, Thomas [Diamond Light Source, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Research Complex at Harwell (RCaH), Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA (United Kingdom)

    2014-09-01

    Commercially available adhesives have been evaluated for crystal mounting when undertaking complex macromolecular crystallography experiments. Here, their use as tools for advanced sample mounting and cryoprotection is assessed and their suitability for room-temperature data-collection and humidity-controlled studies is investigated. The hydration state of macromolecular crystals often affects their overall order and, ultimately, the quality of the X-ray diffraction pattern that they produce. Post-crystallization techniques that alter the solvent content of a crystal may induce rearrangement within the three-dimensional array making up the crystal, possibly resulting in more ordered packing. The hydration state of a crystal can be manipulated by exposing it to a stream of air at controlled relative humidity in which the crystal can equilibrate. This approach provides a way of exploring crystal hydration space to assess the diffraction capabilities of existing crystals. A key requirement of these experiments is to expose the crystal directly to the dehydrating environment by having the minimum amount of residual mother liquor around it. This is usually achieved by placing the crystal on a flat porous support (Kapton mesh) and removing excess liquid by wicking. Here, an alternative approach is considered whereby crystals are harvested using adhesives that capture naked crystals directly from their crystallization drop, reducing the process to a one-step procedure. The impact of using adhesives to ease the harvesting of different types of crystals is presented together with their contribution to background scattering and their usefulness in dehydration experiments. It is concluded that adhesive supports represent a valuable tool for mounting macromolecular crystals to be used in humidity-controlled experiments and to improve signal-to-noise ratios in diffraction experiments, and how they can protect crystals from modifications in the sample environment is discussed.

  20. A clue towards improving the European Society of Medical Oncology risk group classification in apparent early stage endometrial cancer? Impact of lymphovascular space invasion

    PubMed Central

    Bendifallah, S; Canlorbe, G; Raimond, E; Hudry, D; Coutant, C; Graesslin, O; Touboul, C; Huguet, F; Cortez, A; Daraï, E; Ballester, M

    2014-01-01

    Background: Lymphovascular space invasion (LVSI) is one of the most important predictors of nodal involvement and recurrence in early stage endometrial cancer (EC). Despite its demonstrated prognostic value, LVSI has not been incorporated into the European Society of Medical Oncology (ESMO) classification. The aim of this prospective multicentre database study is to investigate whether it may improve the accuracy of the ESMO classification in predicting the recurrence risk. Methods: Data of 496 patients with apparent early-stage EC who received primary surgical treatment between January 2001 and December 2012 were abstracted from prospective multicentre database. A modified ESMO classification including six risk groups was created after inclusion of the LVSI status in the ESMO classification. The primary end point was the recurrence accuracy comparison between the ESMO and the modified ESMO classifications with respect to the area under the receiver operating characteristic curve (AUC). Results: The recurrence rate in the whole population was 16.1%. The median follow-up and recurrence time were 31 (range: 1–152) and 27 (range: 1–134) months, respectively. Considering the ESMO modified classification, the recurrence rates were 8.2% (8 out of 98), 23.1% (15 out of 65), 25.9% (15 out of 58), and 45.1% (28 out of 62) for intermediate risk/LVSI?, intermediate risk/LVSI+, high risk/LVSI?, and high risk/LVSI+, respectively (P<0.001). In the low risk group, LVSI status was not discriminant as only 7.0% (14 out of 213) had LVSI+. The staging accuracy according to AUC criteria for ESMO and ESMO modified classifications were of 0.71 (95% CI: 0.68–0.74) and 0.74 (95% CI: 0.71–0.77), respectively. Conclusions: The current modified classification could be helpful to better define indications for nodal staging and adjuvant therapy, especially for patients with intermediate risk EC. PMID:24809776

  1. Microscopic, crystallographic and adherence properties of plasma-sprayed calcium phosphate coatings on Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Tufekci, Eser

    Recently, plasma-spayed titanium implants have become very popular in the dentistry because of their biocompatibility and ability of providing osseointegration with the surrounding bone. Although there are numerous published studies on these materials, information and standards are still lacking. This study investigated the miscrostructural, crystallographic and adherence properties of plasma-sprayed hydroxyapatite coatings on Ti-6Al-4V substrates. The microstructures of the coatings and the elemental interdiffusion near the coating/substrate interface were investigated using a scanning electron microscope (SEM) equipped with x-ray energy-dispersive spectroscopy (EDS). X-ray diffraction analyses performed on Ti-6Al-4V coupons prepared with different percent crystallinities have provided structural information such as degree of crystallinity, phases present, average crystallite size, as well as the residual stresses within the coating. For evaluation of the adherence of the coatings to the substrates, experimental rods were subjected to torsion. The fracture surfaces were analyzed using SEM/EDS to develop a new methodology to determine the percent adherence of the coatings. SEM studies indicated that the surface microstructures of commercial dental implants were consistent with the plasma-spraying. In cross-section, coatings exhibited minimal porosity and limited interdiffusion of titanium and calcium at the coating/substrate interface. X-ray diffraction analyses indicated that the highest crystallinity coatings consisted of almost entirely HA and an amorphous calcium phosphate phase. As the coating crystallinity decreased, increasing amounts of alpha- and beta-tricalcium phosphate and tetracalcium phosphate were detected. The mean percent crystallinity for the three sets of coatings ranged from 50-60%. The mean HA crystallite size for the three sets of coatings ranged from about 0.02-0.04 mum. Differences in mean interplanar spacings for three selected crystallographic planes of HA, compared with the pure ICDD (International Center for Diffraction Data) powder standards, implied that coatings had a nonuniform state of tensile stresses (0-130 MPa). The EDS analyses of the fractured coating surfaces indicated that the percent coating adherence was approximately 20%, which appeared to be comparable to that observed in SEM photomicrographs.

  2. Preferred crystallographic orientation in the ice I ? II transformation and the flow of ice II

    USGS Publications Warehouse

    Bennett, K.; Wenk, H.-R.; Durham, W.B.; Stern, L.A.; Kirby, S.H.

    1997-01-01

    The preferred crystallographic orientation developed during the ice I ? II transformation and during the plastic flow of ice II was measured in polycrystalline deuterium oxide (D2O) specimens using low-temperature neutron diffraction. Samples partially transformed from ice I to II under a non-hydrostatic stress developed a preferred crystallographic orientation in the ice II. Samples of pure ice II transformed from ice I under a hydrostatic stress and then when compressed axially, developed a strong preferred orientation of compression axes parallel to (1010). A match to the observed preferred orientation using the viscoplastic self-consistent theory was obtained only when (1010) [0001] was taken as the predominant slip system in ice II.

  3. A preliminary neutron crystallographic study of proteinase K at pD 6.5

    SciTech Connect

    Gardberg, Anna S [ORNL; Blakeley, Matthew P. [Institut Laue-Langevin (ILL); Myles, Dean A A [ORNL

    2009-01-01

    AbstractA preliminary neutron crystallographic study of the proteolytic enzyme proteinase K is presented. Large hydrogenated crystals were prepared in deuterated crystallization buffer using the vapour-diffusion method. Data were collected to a resolution of 2.3 on the LADI-III diffractometer at the Institut Laue Langevin (ILL) in 2.5 days. The results demonstrate the feasibility of a full neutron crystallographic analysis of this structure aimed at providing relevant information on the location of H atoms, particularly at the active site. This information will contribute to further understanding of the molecular mechanisms underlying proteinase K's catalytic activity and to an enriched understanding of the subtilisin clan of serine proteases.

  4. Exchange bias in epitaxial CoO/Co bilayers with different crystallographic symmetries

    NASA Astrophysics Data System (ADS)

    Blachowicz, Tomasz; Tillmanns, Andrea; Fraune, Michael; Ghadimi, Reza; Beschoten, Bernd; Güntherodt, Gernot

    2007-02-01

    The magnetic anisotropies of epitaxially grown exchange bias CoO/Co bilayers with (111), (110), and (100) crystallographic orientations have been investigated by Brillouin light scattering (BLS) by means of spin waves. Experiments were carried out at 293 and 140K , i.e., above and below, respectively, the Néel temperature of CoO. The unidirectional, twofold, and fourfold anisotropy constants, bulk and surface, were obtained by fitting the angular dependence of the spin wave frequencies. For all samples, we observed an isotropic up-shift of the spin wave frequencies. We conclude that all observed magnetic anisotropies are related to the crystallographic symmetry of the ferromagnetic and antiferromagnetic layers, depending on the lattice mismatch between layers, the sequence of layers upon deposition, and the quality of the ferromagnetic/antiferromagnetic interface.

  5. Crystallographic anisotropy of the resistivity size effect in single crystal tungsten nanowires.

    PubMed

    Choi, Dooho; Moneck, Matthew; Liu, Xuan; Oh, Soong Ju; Kagan, Cherie R; Coffey, Kevin R; Barmak, Katayun

    2013-01-01

    This work demonstrates an anisotropic increase in resistivity with decreasing width in single crystal tungsten (W) nanowires having a height of 21 nm. Nanowire-widths were in the range of 15-451 nm, with the anisotropy observed for widths below 50 nm. The longitudinal directions of the nanowires coincided with the <100>, <110> and <111> orientations of the body centered cubic phase of W. The resistivity increase was observed to be minimized for the <111>-oriented single crystal nanowires, exhibiting a factor of two lower increase in resistivity at a width of ~15 nm, relative to the thin film resistivity (i.e., an infinitely wide wire). The observed anisotropy is attributed to crystallographic anisotropy of the Fermi velocity and the resultant anisotropy of the electron mean free path in W, and underscores the critical role of crystallographic orientation in nanoscale metallic conduction. PMID:24005230

  6. The X-ray system of crystallographic programs for any computer having a PIDGIN FORTRAN compiler

    NASA Technical Reports Server (NTRS)

    Stewart, J. M.; Kruger, G. J.; Ammon, H. L.; Dickinson, C.; Hall, S. R.

    1972-01-01

    A manual is presented for the use of a library of crystallographic programs. This library, called the X-ray system, is designed to carry out the calculations required to solve the structure of crystals by diffraction techniques. It has been implemented at the University of Maryland on the Univac 1108. It has, however, been developed and run on a variety of machines under various operating systems. It is considered to be an essentially machine independent library of applications programs. The report includes definition of crystallographic computing terms, program descriptions, with some text to show their application to specific crystal problems, detailed card input descriptions, mass storage file structure and some example run streams.

  7. Growth and crystallographic feature-dependent characterization of spinel zinc ferrite thin films by RF sputtering

    PubMed Central

    2013-01-01

    ZnFe2O4 (ZFO) thin films exhibiting varying crystallographic features ((222)-epitaxially, (400)-epitaxially, and randomly oriented films) were grown on various substrates by radio-frequency magnetron sputtering. The type of substrate used profoundly affected the surface topography of the resulting ZFO films. The surface of the ZFO (222) epilayer was dense and exhibited small rectangular surface grains; however, the ZFO (400) epilayer exhibited small grooves. The surface of the randomly oriented ZFO thin film exhibited distinct three-dimensional island-like grains that demonstrated considerable surface roughness. Magnetization-temperature curves revealed that the ZFO thin films exhibited a spin-glass transition temperature of approximately 40 K. The crystallographic orientation of the ZFO thin films strongly affected magnetic anisotropy. The ZFO (222) epitaxy exhibited the strongest magnetic anisotropy, whereas the randomly oriented ZFO thin film exhibited no clear magnetic anisotropy. PMID:24354428

  8. Crystallographic and metallurgical characterization of radiation detector grade cadmium telluride materials

    SciTech Connect

    Johnson, C.J.; Eissler, E.E.; Cameron, S.E. (II-VI, Inc., Saxonburg, PA (United States). eV Products Div.); Kong, Y.; Fan, S.; Jovanovic, S.; Lynn, K.G. (Brookhaven National Lab., Upton, NY (United States))

    1993-01-01

    Radiation detector grade CdTe crystals are characterized by several crystallographic and metallurgical techniques including infrared microscopy, dislocation etch pitting and X-ray diffraction. Results are presented for a set of 50 detectors fabricated from an ingot produced by the High Pressure Bridgman method. Data on the temperature dependence of leakage current and pulse height analysis are presented, along with measurements of room temperature charge transport properties. Attempts to relate crystal structure to detector performance discussed.

  9. Crystallographic and metallurgical characterization of radiation detector grade cadmium telluride materials

    SciTech Connect

    Johnson, C.J.; Eissler, E.E.; Cameron, S.E. [II-VI, Inc., Saxonburg, PA (United States). eV Products Div.; Kong, Y.; Fan, S.; Jovanovic, S.; Lynn, K.G. [Brookhaven National Lab., Upton, NY (United States)

    1993-06-01

    Radiation detector grade CdTe crystals are characterized by several crystallographic and metallurgical techniques including infrared microscopy, dislocation etch pitting and X-ray diffraction. Results are presented for a set of 50 detectors fabricated from an ingot produced by the High Pressure Bridgman method. Data on the temperature dependence of leakage current and pulse height analysis are presented, along with measurements of room temperature charge transport properties. Attempts to relate crystal structure to detector performance discussed.

  10. Microstructure and crystallographic orientation relationship in directionally solidified Mg–Mg 17Al 12eutectic

    Microsoft Academic Search

    Sigrid Guldberg; Nils Ryum

    2000-01-01

    The microstructure and crystallographic orientation relationship of the Mg- and the Mg17Al12-phase in a directionally solidified Mg–Al-eutectic have been study in the light microscope and in the scanning electron microscope equipped with an electron back scattering facility. The effects of the addition of small amounts of Sr on the microstructure were also studied. The Mg–Al-eutectic solidified with a lamellar morphology

  11. Crystallographic finite element modeling for dislocation generation in semiconductor crystals grown by VGF process

    NASA Astrophysics Data System (ADS)

    Sheu, Gary

    The generation and multiplication of dislocations in Gallium Arsenide (GaAs) and Indium Phosphide (InP) single crystals grown by the Vertical Gradient Freeze (VGF) process is predicted using a transient crystallographic finite element model. This transient model is developed by coupling microscopic dislocation motion and multiplication to macroscopic plastic deformation in the slip system of the grown crystals during their growth process. During the growth of InP and GaAs crystals, dislocations are generated in plastically deformed crystal as a result of crystallographic glide caused by excessive thermal stresses. The temperature fields are determined by solving the partial differential equation of heat conduction in a VGF crystal growth system. The effects of growth orientations and growth parameters (i.e., imposed temperature gradients, crystal radius and growth rate) on dislocation generation and multiplication in GaAs and InP crystals are investigated using the developed transient crystallographic finite element model. Dislocation density patterns on the cross section of GaAs and InP crystals are numerically calculated and compared with experimental observations. For crystals grown along [001] and [111] orientations, the results show that more dislocations are generated as the temperature gradient, the crystal growth rate and the crystal radius increase. For the same growth process, it shows that the crystal grown along [111] orientation is a favorable growth direction to grow lower dislocation density crystals. All the results show a famous "W" shape and four fold symmetry dislocation density pattern in GaAs and InP crystals grown from both orientations regardless of crystal growth parameters, which agree well with the patterns observed in actual grown crystals. Therefore, this developed crystallographic model can be employed by crystal grower to design an optimal growth parameters and orientations for growing low dislocation density in advanced semiconductor and optical crystals.

  12. Correlation of crystallographic and magnetic domains at Co\\/NiO(001) interfaces

    Microsoft Academic Search

    H. Ohldag; G. van der Laan; E. Arenholz

    2009-01-01

    Using soft x-ray spectromicroscopy we show that NiO(001) exhibits a crystallographic and magnetic domain structure near the surface identical to that of the bulk. Upon Co deposition a perpendicular coupling between the Ni and Co moments is observed that persists even after formation of uncompensated Ni spins at the interface through annealing. The chemical composition at the interface alters its

  13. Spins and Twins: Correlation between Crystallographic and Magnetic Domains at Co\\/NiO(001) Interfaces

    Microsoft Academic Search

    Hendrik Ohldag; Elke Arenholz; Gerrit van der Laan

    2009-01-01

    Using soft x-ray spectromicroscopy we show that NiO(001) exhibits a crystallographic and magnetic domain structure near the surface identical to that of the bulk. Upon Co deposition a perpendicular coupling between the Ni and Co moments is observed that persists even after formation of uncompensated Ni spins at the interface through annealing. The chemical composition at the interface alters its

  14. Correlation between Crystallographic and Magnetic Domains at Co\\/NiO(001) Interfaces

    Microsoft Academic Search

    H. Ohldag; G. van der Laan; E. Arenholz

    2008-01-01

    Using soft x-ray spectromicroscopy we show that NiO(001) exhibits a crystallographic and magnetic domain structure near the surface identical to that of the bulk. Upon Co deposition a perpendicular coupling between the Ni and Co moments is observed that persists even after formation of uncompensated Ni spins at the interface through annealing. The chemical composition at the interface alters its

  15. 3D mapping of crystallographic phase distribution using energy-selective neutron tomography.

    PubMed

    Woracek, Robin; Penumadu, Dayakar; Kardjilov, Nikolay; Hilger, Andre; Boin, Mirko; Banhart, John; Manke, Ingo

    2014-06-25

    Nondestructive 3D mapping of crystallographic phases is introduced providing distribution of phase fractions within the bulk (centimeter range) of samples with micrometer-scale resolution. The novel neutron tomography based technique overcomes critical limitations of existing techniques and offers a wide range of potential applications. It is demonstrated for steel samples exhibiting phase transformation after being subjected to tensile and torsional deformation. PMID:24692200

  16. A review of crystallographic textures in chemical vapor-deposited diamond films

    Microsoft Academic Search

    Tao Liu; Dierk Raabe; Wei-Min Mao

    2010-01-01

    Diamond is one of the most important functional materials for film applications due to its extreme physical and mechanical\\u000a properties, many of which depend on the crystallographic texture. The influence of various deposition parameters matters to\\u000a the texture formation and evolution during chemical vapor deposition (CVD) of diamond films. In this overview, the texture\\u000a evolutions are presented in terms of

  17. Crystallographic and Electronic Structure of HfNi under High Pressure

    Microsoft Academic Search

    I. Halevy; S. Salhov; A. Yue; J. Hu; I. Yaar

    2005-01-01

    The crystallographic structure and electronic properties of HfNi were studied as a function of pressure by combining X-ray diffraction results with the full potential linearized augmented plane wave (LAPW) calculations. No phase transition was observed up to a pressure of 35.3 GPa, with a total volume contraction of V\\/V 0 = 0.85, a bulk modulus value of B 0 =

  18. High Pressure Study of HfNi Crystallographic and Electronic Structure

    Microsoft Academic Search

    I. Halevy; S. Salhov; A. F. Yue; J. Hu; I. Yaar

    2004-01-01

    The crystallographic structure and electronic properties of HfNi were studied as a function of pressure by combining X-ray\\u000a diffraction results with the full potential linearized augmented plane wave (LAPW) calculations. No phase transition was observed\\u000a up to a pressure of 35.3 GPa, with a total volume contraction of V\\/V\\u000a 0 = 0.85, a bulk modulus value of B\\u000a 0 = 52

  19. Crystallographic and dielectrich properties of (1 - x)batio3-xpbf2-xlif ceramics

    Microsoft Academic Search

    L. Benziada; J. Ravez

    1995-01-01

    Crystallographic and dielectric properties of ceramics with a (1 - x)BaTiO3 + xPbF2 + xLiF composition have been investigated. Mixing, grinding and heating are performed in air atmosphere. Solubility limit of PbF2 and LiF into BaTiO3 was found near of 20 moles % (PbF2 + LiF) at 1203 K for a sintering time of 2 hours. The composition dependence of

  20. Microstructure, crystallographic texture and mechanical properties of friction stir welded AA2017A

    SciTech Connect

    Ahmed, M.M.Z., E-mail: mohamed_ahmed4@s-petrol.suez.edu.eg [Institute for Microstructural and Mechanical Processing Engineering, University of Sheffield (IMMPETUS), Mappin Street, Sheffield S1 3JD (United Kingdom); Department of Metallurgical and Materials Engineering, Suez Canal University, Suez 43721 (Egypt); Wynne, B.P.; Rainforth, W.M. [Institute for Microstructural and Mechanical Processing Engineering, University of Sheffield (IMMPETUS), Mappin Street, Sheffield S1 3JD (United Kingdom); Threadgill, P.L. [TWI LTD, Granta Park, Great Abington, Cambridge CB21 6AL (United Kingdom)

    2012-02-15

    In this study a thick section (20 mm) friction stir welded AA2017A-T451 has been characterized in terms of microstructure, crystallographic texture and mechanical properties. For microstructural analysis both optical and scanning electron microscopes have been used. A detailed crystallographic texture analysis has been carried out using the electron back scattering diffraction technique. Crystallographic texture has been examined in both shoulder and probe affected regions of the weld NG. An entirely weak texture is observed at the shoulder affected region which is mainly explained by the effect of the sequential multi pass deformation experienced by both tool probe and tool shoulder. The texture in the probe dominated region at the AS side of the weld is relatively weak but still assembles the simple shear texture of FCC metals with B/B{sup Macron} and C components existing across the whole map. However, the texture is stronger at the RS than at the AS of the weld, mainly dominated byB/B{sup Macron} components and with C component almost absent across the map. An alternating bands between (B) components and (B{sup Macron }) component are observed only at the AS side of the weld. - Highlights: Black-Right-Pointing-Pointer Detailed investigation of microstructure and crystallographic texture. Black-Right-Pointing-Pointer The grain size is varied from the top to the bottom of the NG. Black-Right-Pointing-Pointer An entirely weak texture is observed at the shoulder affected region. Black-Right-Pointing-Pointer The texture in the probe affected region is dominated by simple shear texture.

  1. Crystallographic Orientation Analyses of Magnetite Thin Films Using Electron Backscatter Diffraction (EBSD)

    Microsoft Academic Search

    A. Koblischka-Veneva; M. R. Koblischka; F. Mucklich; S. Murphy; Y. Zhou; I. V. Shvets

    2006-01-01

    The crystallographic orientation of magnetite (Fe3O4) thin films was measured using electron backscatter diffraction (EBSD). Misorientation boundaries appear in maps of angular misorientation data. The distribution of misorientation angles changes after annealing the samples in air at 250degC. Most small-angle misorientations (<5deg) are removed after one minute of annealing, whereas larger misorientations (as high as 60deg) continue to persist

  2. Crystallographic laws governing the formation of the structure of pseudo-single crystals of some 3 d metals and related alloys

    NASA Astrophysics Data System (ADS)

    Khlebnikova, Yu. V.

    2010-01-01

    Methods of metallography, X-ray diffraction, transmission electron microscopy, and dilatometry have been used to study the formation of the structure of pseudo-single crystals of nitrogen-bearing steel Kh18AG20 upon the ? ? ? (bcc ? fcc) transformation, in pseudo-single crystals of pure cobalt and binary alloy Co-29.7% Ni upon the ? ? ? (fcc ? hcp) transformation, and in pseudo-single crystals of zirconium upon the ? ? ? (bcc ? hcp) transformation. It has been established that the precipitation of austenite from ferrite during the ? ? ? transformation in a single crystal of the Kh18AG20 steel occurs via a crystallographically ordered mechanism with the fulfillment of orientation relationships close to the Kurdjumov-Sachs orientation relationships. In the volume of the pseudo-single crystal there were realized six orientations of austenite with the retention at room temperature of a significant fraction of residual ? (?) ferrite. It has been shown that in the process of cooling of the ? single crystals of cobalt, Co-29.7% Ni alloy, and zirconium to below the temperature of the ? ? ? transition there formed several crystallographic orientations of the ? phase that are grouped into packets. In each packet, there exist crystals of the ? phase of one orientation. In accordance with the Wassermann orientation relationships, in the pseudo-single crystals of cobalt and Co-29.7% Ni alloy there are realized packets of four variants. In the pseudo-single crystal of zirconium, six variants of packets based on the Burgers orientation relationships are realized.

  3. A New Position-Space Renormalization-Group Approach for Non-Equilibrium Systems and its Application to the Three-State Driven Lattice Gas

    NASA Astrophysics Data System (ADS)

    Georgiev, Ivan T.; McKay, Susan R.

    2004-03-01

    We have introduced a general position-space renormalization-group approach for non-equilibrium systems developed from the microscopic master equation. The method is based upon a closed form representation of the parameters of the system in terms of the steady state probability distribution of small clusters. From the master equation in terms of these small clusters, we build recursion relations linking parameters affecting transition rates on various length scales and determine the flow topology. Results for the three-state driven lattice gas show many of the expected features associated with the phase diagrams previously reported for this system, (G. Korniss, B. Schmittmann, and R.K.P. Zia, Non-Equilibrium Phase Transitions in a Simple Three-State Lattice Gas, J. Stat. Phys. 86, 721 (1997).)in excellent agreement with simulations. The flow diagrams also exhibit added complexities, suggesting multiple regions within the ordered phase for some values of parameters and the presence of an extra "source" fixed point. (I.T. Georgiev, U. of Maine Ph.D. Thesis (2003); I.T. Georgiev and S.R. McKay, in preparation.)

  4. Validation of crystallographic models containing TLS or other descriptions of anisotropy

    PubMed Central

    Zucker, Frank; Champ, P. Christoph; Merritt, Ethan A.

    2010-01-01

    The use of TLS (translation/libration/screw) models to describe anisotropic displacement of atoms within a protein crystal structure has become increasingly common. These models may be used purely as an improved methodology for crystallographic refinement or as the basis for analyzing inter-domain and other large-scale motions implied by the crystal structure. In either case it is desirable to validate that the crystallographic model, including the TLS description of anisotropy, conforms to our best understanding of protein structures and their modes of flexibility. A set of validation tests has been implemented that can be integrated into ongoing crystallographic refinement or run afterwards to evaluate a previously refined structure. In either case validation can serve to increase confidence that the model is correct, to highlight aspects of the model that may be improved or to strengthen the evidence supporting specific modes of flexibility inferred from the refined TLS model. Automated validation checks have been added to the PARVATI and TLSMD web servers and incorporated into the CCP4i user interface. PMID:20693688

  5. Crystallographic preferred orientation of akimotoite and seismic anisotropy of Tonga slab.

    PubMed

    Shiraishi, Rei; Ohtani, Eiji; Kanagawa, Kyuichi; Shimojuku, Akira; Zhao, Dapeng

    2008-10-01

    The mineral akimotoite, ilmenite-structured MgSiO(3), exists at the bottom of the Earth's mantle transition zone and within the uppermost lower mantle, especially under low-temperature conditions. Akimotoite is thought to be a major constituent of the harzburgite layer of subducting slabs, and the most anisotropic mineral in the mantle transition zone. It has been predicted that if akimotoite crystals are preferentially oriented by plastic deformation, a cold subducted slab would be extremely anisotropic. However, there have been no studies of crystallographic preferred orientations and very few reports of plastic deformation experiments for MgSiO(3) ilmenite. Here we present plastic deformation experiments on polycrystalline akimotoite, which were conducted at confining pressures of 20-22 GPa and temperatures of 1,000-1,300 degrees C. We found a change in crystallographic preferred orientation pattern of akimotoite with temperature, where the c-axis maximum parallel to the compression direction develops at high temperature, whereas the c axes are preferentially oriented parallel to the shear direction or perpendicular to the compression direction at lower temperature. The previously reported difference in compressional-wave seismic anisotropy between the northern and southern segments of the Tonga slab at depths of the mantle transition zone can conceivably be attributed to the difference in the crystallographic preferred orientation pattern of akimotoite at varying temperature within the slab. PMID:18833278

  6. Crystallinity and Crystallographic Texture in Isotactic Polypropylene during Deformation and Heating

    E-print Network

    J. Jia; D. Raabe

    2008-11-14

    The development of the crystallinity and of the crystallographic orientation of isotactic polypropylene (iPP) during rolling deformation and subsequent heat treatment is studied. The experiments are conducted by using X-ray diffraction with an area detector. The evolution of crystallographic orientation is tracked by calculating the pole figures and by applying a quantitative 3D texture component fit method. The rolling orientation after a true strain of -1.5 mainly consists of the (010)[001], (130)[001], and [001]//RD fiber components (RD: rolling direction). The results reveal that the crystallinity drastically decreases during rolling. We suggest that decrystallization (disaggregation) is a deformation mechanism which takes place as a microscopic alternative to crystallographic intralamellar shear depending on the orientation of the lamellae relative to the imposed deformation tensor. Heat treatment after rolling leads to the recrystallization of amorphous material and to a strong enhancement of the fiber orientation component. The recrystallization orientation is explained in terms of an oriented nucleation mechanism where amorphous material aligns along existing crystalline lamellae blocks which prevailed during the preceding deformation.

  7. Crystallographic Preferred Orientations and Seismic Properties of Gabbroic Rocks Benot ILDEFONSE, David MAINPRICE & Cristina Maria GUSMO de BURGOS

    E-print Network

    Demouchy, Sylvie

    of crystallographic fabrics in gabbroic rocks from the Oman ophiolite and from the lower crust at the South: 1781- 1802. · Lamoureux, G., 1999. Structure des gabbros de l'ophiolite d'Oman : caractérisation

  8. Electron-crystallographic refinement of the structure of bacteriorhodopsin.

    PubMed

    Grigorieff, N; Ceska, T A; Downing, K H; Baldwin, J M; Henderson, R

    1996-06-14

    Using electron diffraction data corrected for diffuse scattering together with additional phase information from 30 new images of tilted specimens, an improved experimental density map has been calculated for bacteriorhodopsin. The atomic model has then been rebuilt into this new map with particular attention to the surface loops. All the residues from 7 to 227 as well as ten lipid molecules are now included, although a few amino acid residues in three of the six surface loops, about half of the lipid hydrophobic chains and all of the lipid head groups are disordered. The model has then been refined against the experimental diffraction amplitudes to an R-factor of 28% at 3.5 angstrom resolution with strict geometry (0.005 angstrom) bond length deviation) using the improvement of the "free" phase residual between calculated and experimental phases from images as an objective criterion of accuracy. For the refinement some new programs were developed to restrain the number of parameters, to be compatible with the limited resolution of our data. In the final refined model of the protein (2BRD), compared with earlier co-ordinates (1BRD), helix D has been moved towards the cytoplasm by almost 4 angstrom, and the overall accuracy of the co-ordinates of residues in the other six helices has been improved. As a result the positions of nearly all the important residues in bacteriorhodopsin are now well determined. In particular, the buried, protonated Asp115 is 7 angstrom from, and so not in contact with, the retinal and Met118 forms a cap on the pocket occupied by the beta-ionone ring. No clear density exists for the side-chain of Arg82, which forms a central part of the extracellular half-channel. The only arginine side-chain built into good density is that of Arg134 at the extracellular end of helix E, the others being disordered near one of the two surfaces. The interpretation of the end of helix F on the extracellular surface is now clearer; an extra loose helical turn has been built bringing the side-chain of Glu194 close to Arg134 to form a probable salt bridge. The model provides an improved framework for understanding the mechanism of the light-driven proton pumping. A number of cavities that could contain water molecules were found by searching the refined model, most of them above or below the Schiff base in the half-channels leading to the two surfaces. The ordered and disordered regions of the structure are described by the temperature factor distribution. PMID:8676377

  9. Electron back-scattering patterns—A new technique for obtaining crystallographic information in the scanning electron microscope

    Microsoft Academic Search

    J. A. Venables; C. J. Harland

    1973-01-01

    It is shown that the angular distribution of back-scattered electrons can be observed in a scanning electron microscope, and that the patterns observed can be used to obtain crystallographic information about the specimen. The patterns are termed electron back-scattering patterns (E.B.S.P.). The use of these patterns as a crystallographic techniques is shown to have several significant advantages over two other

  10. Crystallographic texture and orientation variants in Al 2O 3–Y 3Al 5O 12 directionally solidified eutectic crystals

    Microsoft Academic Search

    Colleen S. Frazer; Elizabeth C. Dickey; Ali Sayir

    2001-01-01

    Eutectic rods of Al2O3 and Y3Al5O12 were grown by a laser-heated float zone method, and their microstructure and crystallographic texture were studied by scanning electron microscopy, electron-backscattered diffraction and X-ray diffraction. The composites were found to be highly textured with two twin-related crystallographic orientation relationships between the phases. Electron-backscattered diffraction was employed to determine the spatial distribution of the orientational

  11. Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): I. Quartz textures in monomineral rocks

    SciTech Connect

    Nikitin, A. N., E-mail: nikitin@nf.jinr.ru; Ivankina, T. I. [Joint Institute for Nuclear Research (Russian Federation); Ullemeyer, K. [Universitaet Kiel, Institut fuer Geowissenschaften (Germany); Vasin, R. N. [Joint Institute for Nuclear Research (Russian Federation)

    2008-09-15

    Quartz crystallographic textures in different rocks have been investigated by neutron diffraction. Various types of crystallographic textures of quartz-bearing mineral associations in monomineral and multiphase rocks from a representative collection of samples have been revealed and classified. Experimental investigations have been performed on special neutron texture diffractometers designed at the Frank Laboratory of Neutron Physics and mounted in the seventh channel of the IBR-2 reactor at the Joint Institute for Nuclear Research (Dubna).

  12. Effect of the substrate bias voltage on the crystallographic orientation of reactively sputtered AlN thin films

    Microsoft Academic Search

    Hwan-Chul Lee; Jai-Young Lee; Hyo-Jun Ahn

    1994-01-01

    Aluminum nitride (AlN) films have been deposited on negatively biased Si(100) wafers by reactive r.f. magnetron sputtering in a mixed Ar-N2 discharge. It is important to control the crystallographic orientation and the physical properties of the films with deposition parameters for the surface acoustic wave device application. The change in crystallographic orientation with the negative bias voltage has been evaluated

  13. Finite group symmetry breaking

    E-print Network

    G. Gaeta

    2005-10-02

    Finite group symmetry is commonplace in Physics, in particular through crystallographic groups occurring in condensed matter physics -- but also through the inversions (C,P,T and their combinations) occurring in high energy physics and field theory. The breaking of finite groups symmetry has thus been thoroughly studied, and general approaches exist to investigate it. In Landau theory, the state of a system is described by a finite dimensional variable (the {\\it order parameter}), and physical states correspond to minima of a potential, invariant under a group. In this article we describe the basics of symmetry breaking analysis for systems described by a symmetric polynomial; in particular we discuss generic symmetry breakings, i.e. those determined by the symmetry properties themselves and independent on the details of the polynomial describing a concrete system. We also discuss how the plethora of invariant polynomials can be to some extent reduced by means of changes of coordinates, i.e. how one can reduce to consider certain types of polynomials with no loss of generality. Finally, we will give some indications on extension of this theory, i.e. on how one deals with symmetry breakings for more general groups and/or more general physical systems.

  14. The effect of a proline residue on the rate of growth and the space group of alpha-spectrin SH3-domain crystals.

    PubMed

    Cámara-Artigas, Ana; Andújar-Sánchez, Monserrat; Ortiz-Salmerón, Emilia; Cuadri, Celia; Casares, Salvador

    2009-12-01

    alpha-Spectrin SH3-domain (Spc-SH3) crystallization is characterized by very fast growth of the crystals in the presence of ammonium sulfate as a precipitant agent. The origin of this behaviour can be attributed to the presence of a proline residue that participates in a crystal contact mimicking the binding of proline-rich sequences to SH3 domains. This residue, Pro20, is located in the RT loop and is the main contact in one of the interfaces present in the orthorhombic Spc-SH3 crystal structures. In order to understand the molecular interactions that are responsible for the very fast crystal growth of the wild-type (WT) Spc-SH3 crystals, the crystal structure of a triple mutant in which the residues Ser19-Pro20-Arg21 in the RT loop have been replaced by Gly19-Asp20-Ser21 (GDS Spc-SH3 mutant) has been solved. The removal of the critical proline residue results in slower nucleation of the Spc-SH3 crystals and a different arrangement of the protein molecules in the unit cell, leading to a crystal that belongs to the tetragonal space group P4(1)2(1)2, with unit-cell parameters a = b = 42.231, c = 93.655 A, and that diffracts to 1.45 A resolution. For both WT Spc-SH3 and the GDS mutant, light-scattering experiments showed that a dimer was formed in solution within a few minutes of the addition of 2 M ammonium sulfate at pH 6.5 and allowed the proposal of a mechanism for the nucleation and crystal growth of Spc-SH3 in which the Pro20 residue plays a key role in the rate of crystal growth. PMID:19966410

  15. Crystallization and preliminary crystallographic analysis of the major acid phosphatase from Legionella pneumophila.

    PubMed

    Zhou, Dan; Pan, Yang; Chen, Xiaofang; Zhang, Nannan; Ge, Honghua

    2015-06-01

    The major acid phosphatase from Legionella pneumophila (LpMAP) belongs to the histidine acid phosphatase superfamily. It contains the characteristic histidine acid phosphatase (HAP) sequence motif RHGXRXP responsible for the hydrolysis of a phosphoryl group from phosphate monoesters under acidic conditions. Here, the crystallization and preliminary X-ray analysis of crystals of LpMAP in the apo form and in complex with L-(+)-tartrate are described. By using the hanging-drop vapour-diffusion method, apo LpMAP and LpMAP-tartrate were crystallized in space group P21, with unit-cell parameters a = 91.50, b = 56.48, c = 146.35?Å, ? = 110.01°, and in space group P1, with unit-cell parameters a = 55.51, b = 73.51?, c = 98.78?Å, ? = 78.82, ? = 77.65, ? = 67.73°, respectively. Diffraction data were collected at 100?K and the phases were determined using the molecular-replacement method. PMID:26057812

  16. OAST Space Theme Workshop. Volume 3: Working group summary. 6: Power (P-2). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2)

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Power requirements for the multipurpose space power platform, for space industrialization, SETI, the solar system exploration facility, and for global services are assessed for various launch dates. Priorities and initiatives for the development of elements of space power systems are described for systems using light power input (solar energy source) or thermal power input, (solar, chemical, nuclear, radioisotopes, reactors). Systems for power conversion, power processing, distribution and control are likewise examined.

  17. Combustion Group Group members

    E-print Network

    Wang, Wei

    Combustion Group Group members: Thierry Poinsot, Emilien Courtine, Luc Vervisch, Benjamin Farcy 2014 #12;Combustion Group Combustion Physics and Modeling Pollutants, Emissions, and Soot Formation Thermoacoustics and Combustion Dynamics Research focus § Examine mechanisms responsible for flame stabilization

  18. Expression, purification and preliminary crystallographic analysis of O-acetylhomoserine sulfhydrylase from Mycobacterium tuberculosis

    PubMed Central

    Yin, Jiang; Garen, Craig R.; Bateman, Katherine; Yu, Minmin; Alipio Lyon, Emily Z.; Habel, Jeff; Kim, Heungbok; Hung, Li-wei; Kim, Chang-Yub; James, Michael N. G.

    2011-01-01

    The gene product of the open reading frame Rv3340 from Mycobacterium tuberculosis is annotated as encoding a probable O-acetylhomoserine (OAH) sulfhydrylase (MetC), an enzyme that catalyzes the last step in the biosynthesis of methionine, which is an essential amino acid in bacteria and plants. Following overexpression in Escherichia coli, the M. tuberculosis MetC enzyme was purified and crystallized using the hanging-drop vapor-diffusion method. Native diffraction data were collected from crystals belonging to space group P21 and were processed to a resolution of 2.1?Å. PMID:21821905

  19. Expression, purification and preliminary crystallographic analysis of O-acetylhomoserine sulfhydrylase from Mycobacterium tuberculosis.

    PubMed

    Yin, Jiang; Garen, Craig R; Bateman, Katherine; Yu, Minmin; Lyon, Emily Z Alipio; Habel, Jeff; Kim, Heungbok; Hung, Li-wei; Kim, Chang-Yub; James, Michael N G

    2011-08-01

    The gene product of the open reading frame Rv3340 from Mycobacterium tuberculosis is annotated as encoding a probable O-acetylhomoserine (OAH) sulfhydrylase (MetC), an enzyme that catalyzes the last step in the biosynthesis of methionine, which is an essential amino acid in bacteria and plants. Following overexpression in Escherichia coli, the M. tuberculosis MetC enzyme was purified and crystallized using the hanging-drop vapor-diffusion method. Native diffraction data were collected from crystals belonging to space group P2(1) and were processed to a resolution of 2.1?Å. PMID:21821905

  20. Purification, identification and preliminary crystallographic studies of an allergenic protein from Lathyrus sativus

    PubMed Central

    Qureshi, Insaf A.; Sethi, Dhruv K.; Salunke, Dinakar M.

    2006-01-01

    A 24?kDa protein was purified from the seeds of Lathyrus sativus by ammonium sulfate fractionation and ion-exchange chromatography. The N-terminal amino-acid sequence showed significant homology with the 2S albumin class of seed storage proteins. The protein showed 85% sequence homology with the seed albumin of Pisum sativum within the 40 N-terminal residues. Crystals were obtained by the hanging-drop vapour-diffusion method. The crystals belonged to space group P212121, with unit-cell parameters a = 43.5, b = 82.7, c = 153.4?Å. PMID:16946466

  1. Crystallization and preliminary crystallographic analysis of D-aspartate oxidase from porcine kidney.

    PubMed

    Senda, Miki; Yamamoto, Atsushi; Tanaka, Hiroyuki; Ishida, Tetsuo; Horiike, Kihachiro; Senda, Toshiya

    2012-06-01

    D-Aspartate oxidase (DDO) from porcine kidney was crystallized by the sitting-drop vapour-diffusion method using PEG 8000 as a precipitant. The crystal belonged to space group P2(1), with unit-cell parameters a = 79.38, b = 144.0, c = 80.46 Å, ? = 101.1°, and diffracted to 1.80 Å resolution. Molecular-replacement trials using the structure of human D-amino-acid oxidase, which is 42% identical in sequence to DDO, as a search model provided a satisfactory solution. PMID:22684060

  2. Application of combined EBSD and 3D-SEM technique on crystallographic facet analysis of steel at low temperature.

    PubMed

    Mohseni, P; Solberg, J K; Karlsen, M; Akselsen, O M; Ostby, E

    2013-07-01

    Electron backscatter diffraction has been increasingly used to identify the crystallographic planes and orientation of cleavage facets with respect to the rolling direction in fracture surfaces. The crystallographic indices of cleavage planes can be determined either directly from the fracture surface or indirectly from metallographic sections perpendicular to the plane of the fracture surface. A combination of electron backscatter diffraction and 3D scanning electron microscopy imaging technique has been modified to determine crystallographic facet orientations. The main purpose of this work has been to identify the macroscopic crystallographic orientations of cleavage facets in the fracture surfaces of weld heat affected zones in a well-known steel fractured at low temperatures. The material used for the work was an American Petroleum Institute (API) X80 grade steel developed for applications at low temperatures, and typical heat affected zone microstructures were obtained by carrying out weld thermal simulation. The fracture toughness was measured at different temperatures (0°C, -30°C, -60°C and -90°C) by using Crack Tip Opening Displacement testing. Fracture surfaces and changes in microstructure were analyzed by scanning electron microscopy and light microscopy. Crystallographic orientations were identified by electron backscatter diffraction, indirectly from a polished section perpendicular to the major fracture surface of the samples. Computer assisted 3D imaging was used to measure the angles between the cleavage facets and the adjacent polished surface, and then these angles were combined with electron backscatter diffraction measurements to determine the macroscopic crystallographic planes of the facets. The crystallographic indices of the macroscopic cleavage facet planes were identified to be {100}, {110}, {211} and {310} at all temperatures. PMID:23692572

  3. Photovoltaic properties of (Pb,La)(Zr,Ti)O3 films with different crystallographic orientations

    NASA Astrophysics Data System (ADS)

    Ichiki, M.; Furue, H.; Kobayashi, T.; Maeda, R.; Morikawa, Y.; Nakada, T.; Nonaka, K.

    2005-11-01

    Photovoltaic (Pb,La)(Zr,Ti)O3 films in a layered structure of different crystallographic orientations are fabricated by an optimized metalorganic deposition method. Such films of (001) orientation exhibit a photovoltaic electrical power of approximately 20 times higher than that of random films. The anisotropic optical properties of the oriented films, including dark conductivity, photoconductivity, and photovoltaic tensor surfaces, are obtained quantitatively. These results show that the photovoltaic output current and power of the oriented films are highly improved to be equal to those of semiconductors and suitable for application in the optical sensor of microelectromechanical systems.

  4. Crystallographic dependence of photocatalytic activity of WO3 thin films prepared by molecular beam epitaxy.

    PubMed

    Li, Guoqiang; Varga, Tamas; Yan, Pengfei; Wang, Zhiguo; Wang, Chongmin; Chambers, Scott A; Du, Yingge

    2015-06-01

    We investigated the impact of crystallographic orientation on the photocatalytic activity of single crystalline WO3 thin films prepared by molecular beam epitaxy on the photodegradation of rhodamine B (RhB). A clear effect is observed, with (111) being the most reactive surface, followed by (110) and (001). Photoreactivity is directly correlated with the surface free energy determined by density functional theory calculations. The RhB photodegradation mechanism is found to involve hydroxyl radicals in solution formed from photo-generated holes and differs from previous studies performed on nanoparticles and composites. PMID:25989882

  5. Anisotropic constitutive modeling for nickel base single crystal superalloys using a crystallographic approach

    NASA Technical Reports Server (NTRS)

    Stouffer, D. C.; Sheh, M. Y.

    1988-01-01

    A micromechanical model based on crystallographic slip theory was formulated for nickel-base single crystal superalloys. The current equations include both drag stress and back stress state variables to model the local inelastic flow. Specially designed experiments have been conducted to evaluate the effect of back stress in single crystals. The results showed that (1) the back stress is orientation dependent; and (2) the back stress state variable in the inelastic flow equation is necessary for predicting anelastic behavior of the material. The model also demonstrated improved fatigue predictive capability. Model predictions and experimental data are presented for single crystal superalloy Rene N4 at 982 C.

  6. Blocks and residual stresses in sapphire rods of different crystallographic orientations grown by the Stepanov method

    NASA Astrophysics Data System (ADS)

    Krymov, V. M.; Nosov, Yu. G.; Bakholdin, S. I.; Maslov, V. N.; Shul'pina, I. L.

    2015-05-01

    The formation of blocks in shaped sapphire rods of two crystallographic orientations has been investigated. It is shown that, when growth occurs in the direction of the optical c axis, blocks are formed with a higher probability than in the case of growth in the a direction. A model of formation of blocks in rods of different orientations is proposed. The distribution of residual stresses over sapphire rod cross sections is measured by conoscopy. It is found that stresses increase from the middle of a rod to its periphery and reach 20 MPa.

  7. Ab Initio Phasing by Dual-Space Direct Methods

    Microsoft Academic Search

    George M. Sheldrick; Russ Miller; Isabel Usón; Herbert A. Hauptman

    Shake-and-Bake is an ab initio direct method for solving the crystallographic phase problem. Its most distinctive feature is the repeated alternation of reciprocal-space phase refinement with a complementary real-space process that seeks to improve phases by applying constraints. The Shake-and-Bake philosophy has been implemented in two independent computer programs, SnB and SHELXD. These programs have proven capable of solving complete

  8. Preliminary crystallographic analysis of ADP-glucose pyrophosphorylase from Agrobacterium tumefaciens

    PubMed Central

    Cupp-Vickery, Jill R.; Igarashi, Robert Y.; Meyer, Christopher R.

    2005-01-01

    ADP-glucose pyrophosphorylase catalyzes the conversion of glucose-1-phosphate and ATP to ADP-glucose and pyrophosphate, a key regulated step in both bacterial glycogen and plant starch biosynthesis. Crystals of ADP-glucose pyrophosphorylase from Agrobacterium tumefaciens (420 amino acids, 47?kDa) have been obtained by the sitting-drop vapor-diffusion method using lithium sulfate as a precipitant. A complete native X-ray diffraction data set was collected to a resolution of 2.0?Å from a single crystal at 100?K. The crystals belong to space group I222, with unit-cell parameters a = 92.03, b = 141.251, c = 423.64?Å. To solve the phase problem, a complete anomalous data set was collected from a selenomethionyl derivative. These crystals display one-fifth of the unit-cell volume of the wild-type crystals, with unit-cell parameters a = 85.38, b = 93.79, c = 140.29?Å and space group I222. PMID:16511013

  9. Local Group(s)

    E-print Network

    Eva K. Grebel

    2006-05-22

    The properties of the galaxies of the Local Group are reviewed, followed by a brief discussion of nearby groups. The galaxy groups in our vicinity - the M81 group, the Cen A group, and the IC 342/Maffei group - are in many respects Local Group analogs: Their luminosity functions, galaxy content, fractional galaxy type distribution, crossing times, masses, and zero-velocity surface radii are similar to those of the Local Group. Also, the nearby groups usually consist of two subgroups, some of which approach each other and may ultimately merge to form a fossil group. These poor groups contrast with the less evolved, loose and extended galaxy ``clouds'' such as the Scl group and the CVn I cloud. These are characterized by long crossing times, are dominated by gas-rich, late-type galaxies, and lack gas-deficient, low luminosity early-type dwarfs. These clouds may be groups still in formation. The local Hubble flow derived from the clouds and groups is very cold.

  10. 36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... false What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

  11. 36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... false What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

  12. 36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... false What space in the National Archives at College Park is available for use...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives at College Park, Md § 1280.85...

  13. 36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... false What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

  14. 36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... false What space in the National Archives at College Park is available for use...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives at College Park, Md § 1280.85...

  15. 36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... false What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

  16. 36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... false What space in the National Archives at College Park is available for use...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives at College Park, Md § 1280.85...

  17. 36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... false What space in the National Archives at College Park is available for use...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives at College Park, Md § 1280.85...

  18. 36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... true What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

  19. Enhancing nanoscale SEM image segmentation and reconstruction with crystallographic orientation data and machine learning

    SciTech Connect

    Converse, Matthew I., E-mail: mconverse85@yahoo.com; Fullwood, David T.

    2013-09-15

    Current methods of image segmentation and reconstructions from scanning electron micrographs can be inadequate for resolving nanoscale gaps in composite materials (1–20 nm). Such information is critical to both accurate material characterizations and models of piezoresistive response. The current work proposes the use of crystallographic orientation data and machine learning for enhancing this process. It is first shown how a machine learning algorithm can be used to predict the connectivity of nanoscale grains in a Nickel nanostrand/epoxy composite. This results in 71.9% accuracy for a 2D algorithm and 62.4% accuracy in 3D. Finally, it is demonstrated how these algorithms can be used to predict the location of gaps between distinct nanostrands — gaps which would otherwise not be detected with the sole use of a scanning electron microscope. - Highlights: • A method is proposed for enhancing the segmentation/reconstruction of SEM images. • 3D crystallographic orientation data from a nickel nanocomposite is collected. • A machine learning algorithm is used to detect trends in adjacent grains. • This algorithm is then applied to predict likely regions of nanoscale gaps. • These gaps would otherwise be unresolved with the sole use of an SEM.

  20. Characterization of strain and crystallographic defects in HgI2 single crystals

    NASA Astrophysics Data System (ADS)

    Alexander, W. Brock; Sandoval, John; van den Berg, Lodewijk

    2004-10-01

    We investigated bulk-grown HgI2 crystals to better understand the nature of crystallographic defects and strain/stress in different growth regions of the crystal and their affect on the performance of HgI2-based radiation detectors. Double-axis and triple-axis high-resolution x-ray diffraction were used to characterize the mosaic structure and strain in HgI2. Rocking curves revealed significant mosaic spreading in <110> growth regions exhibiting X-defects versus X-defect-free <100> growth regions. Both <110> and <100> growth regions exhibited little strain (~0.01%). We report the narrowest rocking curves (~ 9 arcsec) to date on HgI2 as a result of the resolution of the instrument (~ 6 arcsec). Raman spectroscopy was used collaboratively to confirm little residual stress in the crystals. We developed a growth rate ratio (chi) and show this geometric model used to describe crystal shape and regions of <100> and <110> growth. Optical characterization of X-defects are presented and discussed. Further the influence of crystallographic defects and strain on radiation detector performance are discussed.

  1. Integration of first-principles methods and crystallographic database searches for new ferroelectrics: Strategies and explorations

    SciTech Connect

    Bennett, Joseph W. [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States)] [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States); Rabe, Karin M., E-mail: rabe@physics.rutgers.edu [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States)

    2012-11-15

    In this concept paper, the development of strategies for the integration of first-principles methods with crystallographic database mining for the discovery and design of novel ferroelectric materials is discussed, drawing on the results and experience derived from exploratory investigations on three different systems: (1) the double perovskite Sr(Sb{sub 1/2}Mn{sub 1/2})O{sub 3} as a candidate semiconducting ferroelectric; (2) polar derivatives of schafarzikite MSb{sub 2}O{sub 4}; and (3) ferroelectric semiconductors with formula M{sub 2}P{sub 2}(S,Se){sub 6}. A variety of avenues for further research and investigation are suggested, including automated structure type classification, low-symmetry improper ferroelectrics, and high-throughput first-principles searches for additional representatives of structural families with desirable functional properties. - Graphical abstract: Integration of first-principles methods with crystallographic database mining, for the discovery and design of novel ferroelectric materials, could potentially lead to new classes of multifunctional materials. Highlights: Black-Right-Pointing-Pointer Integration of first-principles methods and database mining. Black-Right-Pointing-Pointer Minor structural families with desirable functional properties. Black-Right-Pointing-Pointer Survey of polar entries in the Inorganic Crystal Structural Database.

  2. Combustion Group Group members

    E-print Network

    Wang, Wei

    Combustion Group Group members: Thierry Poinsot, Emilien Courtine, Luc Vervisch, Benjamin Farcy § New combustion and energy-conversion concepts #12;Introduction Combustion research thrusts Combustion Dynamics and Flame-Stabilization Research objectives § Obtain fundamental understanding of combustion

  3. Listen to Me: Four Web-Based CSCL Students' Perspectives and Experiences in Group Collaboration and Knowledge Construction in Cyber Space.

    ERIC Educational Resources Information Center

    Wang, C. Y. Janey

    The main purpose of this Naturalistic inquiry study is to explore four ethically diverse Web-based Computer Supported Collaborative Learning (CSCL) students' perceptions of and experiences in knowledge construction and group collaboration. Findings suggest that individual and group successes are interconnected and rely on successful negotiation…

  4. Design, synthesis, and X-ray crystallographic analysis of a novel class of HIV-1 protease inhibitors.

    PubMed

    Ganguly, Ashit K; Alluri, Sesha S; Caroccia, Danielle; Biswas, Dipshikha; Wang, Chih-Hung; Kang, Eunhee; Zhang, Yong; McPhail, Andrew T; Carroll, Steven S; Burlein, Christine; Munshi, Vandna; Orth, Peter; Strickland, Corey

    2011-10-27

    In the present paper, design, synthesis, X-ray crystallographic analysis, and HIV-1 protease inhibitory activities of a novel class of compounds are disclosed. Compounds 28-30, 32, 35, and 40 were synthesized and found to be inhibitors of the HIV-1 protease. The crucial step in their synthesis involved an unusual endo radical cyclization process. Absolute stereochemistry of the three asymmetric centers in the above compounds have been established to be (4S,2'R,3'S) for optimal potency. X-ray crystallographic analysis has been used to determine the binding mode of the inhibitors to the HIV-1 protease. PMID:21916489

  5. OAST Space Theme Workshop. Volume 3: Working group summary. 2: Data handling, communications (E-2). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2)

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Technologies required to support the stated OAST thrust to increase information return by X1000, while reducing costs by a factor of 10 are identified. The most significant driver is the need for an overall end-to-end data system management technology. Maximum use of LSI component technology and trade-offs between hardware and software are manifest in most all considerations of technology needs. By far, the greatest need for data handling technology was identified for the space Exploration and Global Services themes. Major advances are needed in NASA's ability to provide cost effective mass reduction of space data, and automated assessment of earth looking imagery, with a concomitant reduction in cost per useful bit. A combined approach embodying end-to-end system analysis, with onboard data set selection, onboard data processing, highly parallel image processing (both ground and space), low cost, high capacity memories, and low cost user data distribution systems would be necessary.

  6. Benefits Stemming from Space Exploration

    E-print Network

    Waliser, Duane E.

    Benefits Stemming from Space Exploration September 2013 International Space Exploration Coordination Group #12; This page is intentionally left blank #12;ISECG ­ Benefits Stemming from Space Exploration Table of Content Executive Summary

  7. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

    E-print Network

    Christian, Eric

    NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 1 NASA Earth Science Data Systems Software Reuse #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION ESDS Reuse Working Group 2 Award Background: http://www.esdswg.com/softwarereuse/Resources/awards/ #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

  8. Space smarts

    NASA Astrophysics Data System (ADS)

    Colucci, Frank

    1991-02-01

    A review is presented of design and development work in space data processors at the Honeywell Space Systems Group in Florida. Space computers, some hardened for the first time against radiation from both man-made nuclear events and the natural space environment, are described. A specific illustration of this is the Space Shuttle main engine control which monitors some 120 engine parameters 50 times per second and operates the actuators that control the liquid-fueled engine through its eight minute burn. It is further pointed out that Space Station processors will be tied together by three different data buses, each with its own protocol, while the backbone of the data management system will be an optical fiber distributed data interface handling up to 100 Mbits/sec. Radiation hardening without heavy shielding can be accomplished in several ways, i.e., at the materials level, by insulating substrates which can limit the photo-currents generated by a nuclear event, and at the topological level, by spacing transistors so that photocurrents cannot concentrate at any particular node.

  9. Abelian groups 

    E-print Network

    Bolen, James Cordell

    1956-01-01

    groups. In order to d. o this, we will need the aid. of some vector space theorys D~ef ~tp 4s10 A vector ~sac 7 over the field. P is an abelian group which admits mult1plicatlon by elements of t' he field. such that, for a, b e P and. x, y s V& (l) a(x... (antisymmetry), (c) x & y, y & z implies that x & z (transitivity). Let S be a partially ordered set and T a subset. Defin1tion 4s2 The element x is an ~u er bound. of T if x & y for every y in T. The element x may or may not be in T. Definition 4...

  10. OAST Space Theme Workshop. Volume 3: Working group summary. 9: Aerothermodynamics (M-3). A: Statement. B: Technology needs (form 1). C. Priority assessment (form 2). D. Additional assessments

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Twelve aerothermodynamic space technology needs were identified to reduce the design uncertainties in aerodynamic heating and forces experienced by heavy lift launch vehicles, orbit transfer vehicles, and advanced single stage to orbit vehicles for the space transportation system, and for probes, planetary surface landers, and sample return vehicles for solar system exploration vehicles. Research and technology needs identified include: (1) increasing the fluid dynamics capability by at least two orders of magnitude by developing an advanced computer processor for the solution of fluid dynamic problems with improved software; (2) predicting multi-engine base flow fields for launch vehicles; and (3) developing methods to conserve energy in aerothermodynamic ground test facilities.

  11. OAST Space Theme Workshop. Volume 3: Working group summary. 7: Material (M-1). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2)

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The approach of matching technology areas with various themes needs was not effective for the materials and thermal control discipline because of the diversity of requirements for each. Top priorities were evolved from the advanced space transportation system and the space power platform because these are essential building blocks in fulfilling some of the other themes. Important needs identified include life long-life cryogenic cooling systems for sensors, masers, and other devices and the needs for lightweight nuclear shielding materials for nuclear electric propulsion.

  12. Crystallographic characterization of some intermetallic compounds in the Al-Cr system

    NASA Astrophysics Data System (ADS)

    Bendersky, L. A.; Roth, R. S.; Ramon, J. T.; Shechtman, D.

    1991-01-01

    Two Al-Cr compounds, known in the literature as the ? and ? phases, were studied by precession camera single crystal X-ray diffraction and transmission electron microscopy (TEM). The results are different from those reported in the literature. The ? Al4Cr phase was found to be hexagonal P63/mmc with lattice parameters a=2.01 nm and c=2.48 nm, and we suggest that it is isomorphous to the Al4Mn ? phase. The ? Al11Cr2 phase has a monoclinic (pseudo-orthorhombic) C-centered Bravais lattice with a 3?1.76 nm, b 3?3.05 nm, c 3?1.76 nm, and ??90 deg and a possible C2/c space group. Single crystals of the ? phase are usually twinned.

  13. Purification, crystallization and preliminary crystallographic analysis of mouse myo-inositol oxygenase.

    PubMed

    Brown, Peter M; Caradoc-Davies, Tom T; Dickson, James M; Cooper, Garth J S; Loomes, Kerry M; Baker, Edward N

    2006-08-01

    Myo-inositol oxygenase (MIOX) catalyzes the novel oxidative cleavage of myo-inositol (MI) and its epimer D-chiro inositol (DCI) to D-glucuronate. MIOX utilizes an Fe(II)/Fe(III) binuclear iron centre for the dioxygen-dependent cleavage of the C1-C6 bond in MI. Despite its key role in inositol metabolism, the structural basis of its unique four-electron oxidation mechanism and its substrate specificity remain unknown. In order to answer these questions and to facilitate the use of this key enzyme for the development of new therapeutic strategies for diabetes, the mouse enzyme has been cloned, expressed in Escherichia coli, purified and crystallized from 4.4 M sodium formate. The crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 44.87, b = 77.26, c = 84.84 angstroms, and diffract to 2.8 angstroms resolution. PMID:16880565

  14. Crystallization and preliminary crystallographic studies of a flavin-dependent thymidylate synthase from Helicobacter pylori

    PubMed Central

    Zhang, Xiaoli; Zhang, Jinyong; Mao, Xuhu; Zou, Quanming; Hu, Yonglin; Wang, Da-Cheng

    2010-01-01

    The ThyX enzymes that have recently been identified in various bacteria, including some important human pathogens such as Helicobacter pylori and Mycobacterium tuberculosis, are flavin-dependent thymidylate synthases that function in the place of classic thymidylate synthase enzymes in the biosynthesis of dTMP, which is one of the building blocks of DNA. They are promising targets for the development of novel antibiotics because they utilize catalytic mechanisms that are distinct from those of the classic thymidylate synthases found in most organisms, including humans. In this study, H. pylori ThyX was purified and crystallized in complex with flavin adenine dinucleotide (FAD) and a diffraction data set was collected to 2.5?Å resolution. The crystals belonged to space group C2, with unit-cell parameters a = 221.92, b = 49.43, c = 143.02?Å, ? = 98.84°. PMID:20445247

  15. Preliminary X-ray crystallographic studies of UDP-glucose-4-epimerase from Aspergillus nidulans.

    PubMed

    Dalrymple, Sean A; Sheoran, Inder; Kaminskyj, Susan G W; Sanders, David A R

    2011-08-01

    UDP-glucose-4-epimerase (GALE) from Aspergillus nidulans was overexpressed in Escherichia coli, purified via His-tag affinity chromatography and cocrystallized with UDP-galactose using the microbatch method. The crystals diffracted to 2.4?Å resolution using synchrotron radiation on the Canadian Light Source 08ID-1 beamline. Examination of the data with d*TREK revealed nonmerohedral twinning, from which a single lattice was ultimately extracted for processing. The final space group was found to be C2, with unit-cell parameters a = 66.13, b = 119.15, c = 161.42?Å, ? = 98.48°. An initial structure solution has been obtained via molecular replacement employing human GALE (PDB entry 1hzj) as a template model. PMID:21821886

  16. Crystallization and preliminary crystallographic analysis of ?-l-arabinopyranosidase from Streptomyces avermitilis NBRC14893

    PubMed Central

    Fujimoto, Zui; Ichinose, Hitomi; Harazono, Koichi; Honda, Mariko; Uzura, Atsuko; Kaneko, Satoshi

    2009-01-01

    ?-l-Arabinopyranosidase from Streptomyces avermitilis NBRC14893 is a monomeric protein consisting of a catalytic domain belonging to glycosyl hydrolase family 27, an unknown domain and a substrate-binding domain belonging to carbohydrate-binding module family 13. The complete enzyme (residues 45–658) has successfully been cloned and homologously expressed in the Streptomyces expression system. ?-l-Arabinopyranosidase was crystallized by the sitting-drop vapour-diffusion method. The crystals diffracted to 1.6?Å resolution and belonged to space group P212121, with unit-cell parameters a = 68.2, b = 98.9, c = 181.3?Å. The Matthews coefficient was calculated to be 2.38?Å3?Da?1. PMID:19478450

  17. Purification, crystallization and preliminary crystallographic analysis of the marine ?-amylase AmyP.

    PubMed

    Yu, Jigang; Wang, Chengliang; Hu, Yanjin; Dong, Yuanqiu; Wang, Ying; Tu, Xiaoming; Peng, Hui; Zhang, Xuecheng

    2013-03-01

    AmyP is a raw-starch-degrading ?-amylase newly identified from a marine metagenome library. It shares low sequence similarity with characterized glycoside hydrolases and was classified into a new subfamily of GH13. In particular, it showed preferential degradation to raw rice starch. Full-length AmyP was cloned and overexpressed in Escherichia coli, then purified and crystallized in the presence of its substrate analogue ?-cyclodextrin. X-ray diffraction data were collected to a resolution of 2.1?Å. The crystal belonged to space group P2?2?2, with unit-cell parameters a=129.824, b=215.534, c=79.699?Å, ?=?=?=90°, and was estimated to contain two molecules in one asymmetric unit. PMID:23519800

  18. Overexpression, purification, crystallization and preliminary X-ray crystallographic analysis of SF173 from Shigella flexneri.

    PubMed

    Kim, Ha-Neul; An, Jeong-Gi; Lee, Yoo-Sup; Seok, Seung-Hyeon; Yoo, Hee-Seop; Seo, Min-Duk

    2015-01-01

    Shigella flexneri is a Gram-negative, anaerobic bacterium in the genus Shigella that can cause diarrhoea in humans. SF173, a hypothetical protein from S. flexneri 5a strain M90T, has been cloned, overexpressed, purified and crystallized as a part of laboratory-scale structural genomics project. The SF173 protein was crystallized using the sitting-drop vapour-diffusion method in the presence of 0.8?M succinic acid pH 7.0 at 293?K. Preliminary X-ray diffraction analysis revealed that the crystal diffracted to 1.47?Å resolution and belonged to space group I432, with unit-cell parameters a=b=c=110.245?Å. PMID:25615969

  19. Crystallization and preliminary crystallographic analysis of a C2 protein from Arabidopsis thaliana.

    PubMed

    Diaz, Maira; Rodriguez, Lesia; Gonzalez-Guzman, Miguel; Martínez-Ripoll, Martín; Albert, Armando

    2011-12-01

    An uncharacterized protein from Arabidopsis thaliana consisting of a single C2 domain (At3g17980) was cloned into the pETM11 vector and expressed in Escherichia coli, allowing purification to homogeneity in a single chromatographic step. Good-quality diffracting crystals were obtained using vapour-diffusion techniques. The crystals diffracted to 2.2 Å resolution and belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 35.3, b = 88.9, c = 110.6 Å. A promising molecular-replacement solution has been found using the structure of the C2 domain of Munc13-C2b (PDB entry 3kwt) as the search model. PMID:22139170

  20. Conformal Carroll groups

    E-print Network

    C. Duval; G. W. Gibbons; P. A. Horvathy

    2014-07-02

    Conformal extensions of Levy-Leblond's Carroll group, based on geometric properties analogous to those of Newton-Cartan space-time are proposed. The extensions are labelled by an integer $k$. This framework includes and extends our recent study of the Bondi-Metzner-Sachs (BMS) and Newman-Unti (NU) groups. The relation to Conformal Galilei groups is clarified. Conformal Carroll symmetry is illustrated by "Carrollian photons". Motion both in the Newton-Cartan and Carroll spaces may be related to that of strings in the Bargmann space.

  1. Conformal Carroll groups

    NASA Astrophysics Data System (ADS)

    Duval, C.; Gibbons, G. W.; Horvathy, P. A.

    2014-08-01

    Conformal extensions of Lévy-Leblond's Carroll group, based on geometric properties analogous to those of Newton-Cartan space-time are proposed. The extensions are labeled by an integer k. This framework includes and extends our recent study of the Bondi-Metzner-Sachs (BMS) and Newman-Unti (NU) groups. The relation to conformal Galilei groups is clarified. Conformal Carroll symmetry is illustrated by ‘Carrollian photons’. Motion both in the Newton-Cartan and Carroll spaces may be related to that of strings in the Bargmann space.

  2. 36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2012-07-01 true What space in the National Archives at College Park is available for use...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives at College Park, Md § 1280.85...

  3. Expression, purification and preliminary crystallographic studies of human glutamate oxaloacetate transaminase 1 (GOT1).

    PubMed

    Jiang, Xiuping; Chang, Haiyang; Zhou, Yong

    2015-09-01

    Glutamate oxaloacetate transaminase (GOT) catalyzes the reversible reaction of l-aspartate and ?-ketoglutarate into oxaloacetate and l-glutamate and plays a key role in carbon and nitrogen metabolism in all organisms. In human tissues, GOTs are pyridoxal 5'-phosphate-dependent (PLP) enzymes which exist in cytoplasm and mitochondrial forms, GOT1 and GOT2, respectively. GOT1 expression correlates with the growth of several tumors because cancer cells can utilize the amino acid glutamine to fuel anabolic processes, and therefore, GOT1 represents a new therapeutic target in cancer. In this work, human GOT1 was expressed in Escherichia coli periplasmic space, and purified by a combination of His-tag immobilized metal-ion affinity chromatography and anion exchange chromatography. Optimal activity of the enzyme occurred at a temperature of 37°C and a pH of 7.5. Cations such as Na(+), K(+) and Mg(2+) slightly inhibited the activity of recombinant human GOT1, while Zn(2+), Mn(2+), Cu(2+), Ni(2+), Co(2+) and Ca(2+) had stronger inhibitory effects. Crystals of human GOT1 were grown using the hanging-drop vapor diffusion method at 4°C with 0.1M Bis-Tris pH 6.0% and 21% (w/v) PEG 3350. The crystals diffracted to 2.99Å resolution and belonged to space group P43212 with the unit cell parameters a=b=93.4, c=107.4Å, ?=?=?=90°. PMID:26003525

  4. Crystallographic and kinetic origins of acicular and banded microstructures in U-Nb alloys

    NASA Astrophysics Data System (ADS)

    Field, R. D.; Thoma, D. J.

    2013-05-01

    The transition from the acicular to banded structure in dilute U-Nb alloys (˜5 at.%Nb) has been investigated. The acicular morphology consists of large, single orientation laths with high densities of dislocations and deformation twins, while the banded morphology is comprised of fine transformation twins, often with complex, multiple twin orientation relationships. Detailed Transmission Electron Microscopy (TEM) studies of the crystallographic relationships and deformation structures of these two microstructures are presented. In addition, controlled thermal histories and Continuous Cooling Transformation (CCT) curves have been evaluated to characterize the transformation pathways associated with the change in morphology. While the change from acicular to banded morphology is associated with increasing Nb concentrations, the competition between a temperature invariant reaction (at higher cooling rates) and a thermally activated transformation is investigated.

  5. Nanoscale crystal imperfection-induced characterization changes of manganite nanolayers with various crystallographic textures

    PubMed Central

    2013-01-01

    (La,Sr)MnO3 (LSMO) nanolayers with various crystallographic textures were grown on the sapphire substrate with and without In2O3 epitaxial buffering. The LSMO nanolayer with In2O3 epitaxial buffering has a (110) preferred orientation. However, the nanolayer without buffering shows a highly (100)-oriented texture. Detailed microstructure analyses show that the LSMO nanolayer with In2O3 epitaxial buffering has a high degree of nanoscale disordered regions (such as subgrain boundaries and incoherent heterointerfaces) in the film. These structural inhomogeneities caused a low degree of ferromagnetic ordering in LSMO with In2O3 epitaxial buffering, which leads to a lower saturation magnetization value and Curie temperature, and higher coercivity and resistivity. PMID:23919442

  6. Crystallographic features of the ?-to- ? transformation in a Nb-added transformation-induced plasticity steel

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

    A Nb-bearing transformation-induced plasticity (TRIP) steel was control rolled and a certain amount of austenite was retained through appropriate heat treatment. Electron backscatter diffraction (EBSD) measurements were conducted on specimens deformed to various reductions, and the orientations of the ? grains formed within individual prior-austenite grains were compared to those expected from the common correspondence relationships. While most of the bainite orientations cluster around the Bain circles formed by these relations, the polygonal (allotriomorphic) ferrite formed at the austenite grain boundaries does not obey any of these relations with respect to the neighboring austenite orientations. Grain-scale variant selection was observed in both the deformed and undeformed austenite grains. The crystallographic features of the deformation-induced ferrite transformation are also discussed.

  7. Expression, purification and preliminary crystallographic characterization of FlhF from Bacillus subtilis

    PubMed Central

    Bange, Gert; Petzold, Georg; Wild, Klemens; Sinning, Irmgard

    2007-01-01

    The Gram-positive bacterium Bacillus subtilis contains three proteins belonging to the signal recognition particle (SRP) type GTPase family. The well characterized signal sequence-binding protein SRP54 and the SRP receptor protein FtsY are universally conserved components of the SRP system of protein transport. The third member, FlhF, has been implicated in the placement and assembly of polar flagella. This article describes the overexpression and preliminary X-ray crystallographic analysis of an FlhF fragment that corresponds to the well characterized GTPase domains in SRP54 and FtsY. Three crystal forms are reported with either GDP or GMPPNP and diffract to a resolution of about 3?Å. PMID:17565194

  8. Expression, purification and preliminary crystallographic characterization of FlhF from Bacillus subtilis.

    PubMed

    Bange, Gert; Petzold, Georg; Wild, Klemens; Sinning, Irmgard

    2007-05-01

    The gram-positive bacterium Bacillus subtilis contains three proteins belonging to the signal recognition particle (SRP) type GTPase family. The well characterized signal sequence-binding protein SRP54 and the SRP receptor protein FtsY are universally conserved components of the SRP system of protein transport. The third member, FlhF, has been implicated in the placement and assembly of polar flagella. This article describes the overexpression and preliminary X-ray crystallographic analysis of an FlhF fragment that corresponds to the well characterized GTPase domains in SRP54 and FtsY. Three crystal forms are reported with either GDP or GMPPNP and diffract to a resolution of about 3 A. PMID:17565194

  9. The effect of the cracking plane crystallographic orientation on the stress corrosion cracking process

    NASA Astrophysics Data System (ADS)

    Ciocan, Eugenia; Ignat, Margareta; Gheorghiu, Elena

    1998-05-01

    We have chosen from the literature a model which describes the SCC evolution considering three stages of the crack propagation: intergranular, transgranular and ductile rupture. We have verified the applicability of this model to describe the SCC failure of the CANDU type nuclear fuel and adapted it by considering the particular mechanical properties of the cladding, the actual value of the area of interest for SCC and by calculating the local concentration using the values of the iodine activities in the gap as predicted by an adequate fuel element computer code. We improved this overall model expressing the transgranular cracking threshold stress in terms of surface energy, crystallographic orientation of the fracture plane and of the fractional coverage with ZrI 4. The results of the calculations performed using this improved model confirmed the applicability of the model to describe the SCC failure of the CANDU type nuclear fuel.

  10. Direct Measurement of the Crystallographically Sensitive Atomic Termination of Nanophase Cerium Dioxide

    NASA Astrophysics Data System (ADS)

    Young, N. P.; Haigh, S. J.; Sawada, H.; Takayanagi, K.; Kirkland, A. I.

    2012-07-01

    Aberration-corrected high-resolution transmission electron microscopy (HRTEM) was used to study the surface termination of nanophase cerium dioxide particles. Application of computational exit-wave restoration and comparison with simulations confirmed the {111} surfaces to have an oxygen termination, and while structurally unstable at room temperature the {100} facets exhibited a metal terminating plane. This crystallographically sensitive atomic termination was found to be maintained under the reducing conditions of the electron beam. During electron beam irradiation, Electron Energy Loss Spectroscopy (EELS) analysis revealed that a change from Ce4+ to Ce3+ originates at the particle surface, and gradually extends into the particle as reduction continues. The results aid understanding of the oxygen buffering mechanism in cerium dioxide, and provide valuable insight into the use of CeO2 nanoparticles in catalysis.

  11. EBSD study on crystallographic texture and microstructure development of cold-rolled FePd alloy

    SciTech Connect

    Lin, Hung-Pin; Ng, Tin-San [Department of Materials Science and Engineering, National Cheng-Kung University, No. 1, University Road, Tainan 701, Taiwan (China); Kuo, Jui-Chao, E-mail: jckuo@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng-Kung University, No. 1, University Road, Tainan 701, Taiwan (China); Chen, Yen-Chun [Department of Materials Science and Engineering, National Cheng-Kung University, No. 1, University Road, Tainan 701, Taiwan (China); Chen, Chun-Liang [Department of Materials Science and Engineering, I-Shou University, No. 1 Sec. 1 Syuecheng Road, Kaohsiung 840, Taiwan (China); Ding, Shi-Xuan [Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, No. 70, Lienhai Road, Kaohsiung 804, Taiwan (China); Research Center for Physical Properties and Microstructure of Metals, National Sun Yat-Sen University, No. 70, Lienhai Road, Kaohsiung 804, Taiwan (China)

    2014-07-01

    The crystallographic texture and microstructure of FePd alloy after cold-rolling deformation were investigated using electron backscatter diffraction. The major orientations of twin copper and copper after 50% thickness reduction were observed in face-centered cubic-disordered FePd alloy, whereas the main orientation was obtained from brass type after 90% cold rolling. Increase in cold rolling resulted in the change of preferred orientation from copper to brass. Decrease in orientation intensity of copper also increased that of Goss and brass. - Highlights: • The evolution of texture and microstructure in FePd alloy was investigated after cold rolling using EBSD. • Increasing in reduction leads to the change of texture from Copper-type to Brass-type. • The reduction of Copper orientation results in increasing in Goss and Brass orientations.

  12. Dianthraceno[a,e]pentalenes: synthesis, crystallographic structures and applications in organic field-effect transistors.

    PubMed

    Dai, Gaole; Chang, Jingjing; Zhang, Wenhua; Bai, Shiqiang; Huang, Kuo-Wei; Xu, Jianwei; Chi, Chunyan

    2015-01-11

    Two soluble and stable dianthraceno[a,e]pentalenes with two (DAP1) and six (DAP2) phenyl substituents were synthesized. Both compounds possess a small energy band gap and show amphoteric redox behaviour due to intramolecular donor-accepter interactions. X-ray crystallographic analysis revealed that DAP2 has a closely packed structure with multi-dimensional [C-H···?] interactions although there are no ?-? interactions between the dianthraceno[a,e]pentalene cores. As a result, solution-processed field effect transistors based on DAP2 exhibited an average hole mobility of 0.65 cm(2) V(-1) s(-1). Under similar conditions, DAP1 showed an average field effect hole mobility of 0.001 cm(2) V(-1) s(-1). PMID:25406768

  13. Bacteriological and crystallographical analysis of urinary calculi: aid to patient management.

    PubMed Central

    Rosenstein, I; Osborn, R S; Hopewell, J P; Hamilton-Miller, J M; Brumfitt, W

    1984-01-01

    In an analysis, by both crystallographic and microbiological methods, of 50 urinary calculi recently removed by surgical operation, 33 proved to be of metabolic origin (mostly calcium oxalate and some uric acid or urate) and 17 of 'infective' origin (struvite, apatite or a mixture of the two). Metabolic stones were usually bacteriologically sterile or contained only small numbers (less than 10(3)/g of stone) of bacteria which did not produce urease, while infective stones always contained urease-producing organisms, usually Proteus mirabilis, in large numbers (greater than 10(5)/g). The combined approach of stone analysis by crystallography and microbiological culture yields more information than conventional techniques on which to base the treatment of urinary calculi and the prevention of their recurrence. Images Figure 1. PMID:6737406

  14. Investigation of rail wheel steel crystallographic texture changes due to modification and thermomechanical treatment

    NASA Astrophysics Data System (ADS)

    Lychagina, T.; Nikolayev, D.; Sanin, A.; Tatarko, J.; Ullemeyer, K.

    2015-04-01

    In this work crystallographic texture for a set of rail wheel steel samples with different regimes of thermo-mechanical treatment and with and without modification by system Al-Mg-Si- Fe-C-Ca-Ti-Ce was measured by neutron diffraction. The texture measurements were carried out by using time-of-flight technique at SKAT diffractometer situated at IBR-2 reactor (Dubna, JINR, Russia). The three complete pole figures (110), (200), (211) of ?-Fe phase in 5°×5°grid were extracted from a set of 1368 spectra measured for each sample. The samples were cut from rail wheel rim and from transitional zone (between rail wheel hub and wheel disk). It was concluded that the steel modification and some changes in the heat treatment modes of the rail wheels from the experimental (modified) and the conventional (non-modified) steel lead to reorientation of texture component.

  15. Reintroducing Electrostatics into Macromolecular Crystallographic Refinement: Application to Neutron Crystallography and DNA Hydration

    PubMed Central

    Fenn, Timothy D.; Schnieders, Michael J.; Mustyakimov, Marat; Wu, Chuanjie; Langan, Paul; Pande, Vijay S.; Brunger, Axel T.

    2011-01-01

    Summary Most current crystallographic structure refinements augment the diffraction data with a priori information consisting of bond, angle, dihedral, planarity restraints and atomic repulsion based on the Pauli exclusion principle. Yet, electrostatics and van der Waals attraction are physical forces that provide additional a priori information. Here we assess the inclusion of electrostatics for the force field used for all-atom (including hydrogen) joint neutron/X-ray refinement. Two DNA and a protein crystal structure were refined against joint neutron/X-ray diffraction data sets using force fields without electrostatics or with electrostatics. Hydrogen bond orientation/geometry favors the inclusion of electrostatics. Refinement of Z-DNA with electrostatics leads to a hypothesis for the entropic stabilization of Z-DNA that may partly explain the thermodynamics of converting the B form of DNA to its Z form. Thus, inclusion of electrostatics assists joint neutron/X-ray refinements, especially for placing and orienting hydrogen atoms. PMID:21481775

  16. Using a conformation-dependent stereochemical library improves crystallographic refinement of proteins

    SciTech Connect

    Tronrud, Dale E.; Berkholz, Donald S.; Karplus, P. Andrew (Oregon State U.)

    2010-07-02

    The major macromolecular crystallographic refinement packages restrain models to ideal geometry targets defined as single values that are independent of molecular conformation. However, ultrahigh-resolution X-ray models of proteins are not consistent with this concept of ideality and have been used to develop a library of ideal main-chain bond lengths and angles that are parameterized by the {phi}/{psi} angle of the residue [Berkholz et al. (2009), Structure, 17, 1316-1325]. Here, it is first shown that the new conformation-dependent library does not suffer from poor agreement with ultrahigh-resolution structures, whereas current libraries have this problem. Using the TNT refinement package, it is then shown that protein structure refinement using this conformation-dependent library results in models that have much better agreement with library values of bond angles with little change in the R values. These tests support the value of revising refinement software to account for this new paradigm.

  17. Effects of microstructure and crystallographic texture on yield behavior of aluminum-copper-lithium 2195 plate

    NASA Astrophysics Data System (ADS)

    Crosby, Karen Elizabeth

    2000-10-01

    The focus of this research is to study the effects of deformation and aging on the yield behavior of precipitation-hardened Al-Cu-Li alloys, specifically AI-Cu-Li 2195 plate. Al-Cu-Li 2195 is a relatively new and exceptionally strong, yet lightweight aluminum alloy. Experimental methods applicable to mechanical/structural engineering and materials science problems provide the means for understanding the interrelation of deformation, microstructure, and crystal orientation (texture) as they affect the mechanical properties of crystalline materials. Yield strength is a vital mechanical property in that it defines the boundary of stress that may be applied to a part before a permanent, in some cases, detrimental shape change occurs. The values of yield strength often have directional characteristics, such that the values assessed depend on the direction of measurement. The major elements affecting yield and anisotropic nature of Al-Cu-Li materials are induced crystallographic texture from prior deformation such as rolling, elongated grain structure, and the presence of microscopic precipitates. In order to complete the understanding of how these aspects relate, it is intended to characterize the material and model the yield behavior of the material using theoretical techniques based on polycrystal plasticity. Numerous phenomenological yield expressions exist that describe 2- or 3-dimensional yield behavior (i.e., yield surface or yield locus) and recent advances in computational methods and computer resources have enabled the application of polycrystal yield definitions. Meanwhile, whereas the cumulative effects of precipitate state and crystallographic texture on mechanical behavior have been acknowledged, they have not been widely studied in a quantitative manner. Therefore the intent of this research is to determine the influence of the combination of microstructural effects such as texture (arising from prior deformation) and precipitates (formed during the process of aging) on anisotropy and yield strength of Al-Cu-Li 2195. Finally, the results will be used to discuss the microstructural relationship between characteristics of the alloy and their cumulative effects on material properties.

  18. X-ray Crystallographic Structures of Oligomers of Peptides Derived from ?2-Microglobulin.

    PubMed

    Spencer, Ryan K; Kreutzer, Adam G; Salveson, Patrick J; Li, Hao; Nowick, James S

    2015-05-20

    Amyloid diseases such as Alzheimer's disease, Parkinson's disease, and type II diabetes share common features of toxic soluble protein oligomers. There are no structures at atomic resolution of oligomers formed by full-length amyloidogenic peptides and proteins, and only a few structures of oligomers formed by peptide fragments. The paucity of structural information provides a fundamental roadblock to understanding the pathology of amyloid diseases and developing preventions or therapies. Here, we present the X-ray crystallographic structures of three families of oligomers formed by macrocyclic peptides containing a heptapeptide sequence derived from the amyloidogenic E chain of ?2-microglobulin (?2m). Each macrocyclic peptide contains the heptapeptide sequence ?2m63-69 and a second heptapeptide sequence containing an N-methyl amino acid. These peptides form ?-sheets that further associate into hexamers, octamers, and dodecamers: the hexamers are trimers of dimers; the octamers are tetramers of dimers; and the dodecamers contain two trimer subunits surrounded by three pairs of ?-sheets. These structures illustrate a common theme in which dimer and trimer subunits further associate to form a hydrophobic core. The seven X-ray crystallographic structures not only illustrate a range of oligomers that a single amyloidogenic peptide sequence can form, but also how mutation can alter the size and topology of the oligomers. A cocrystallization experiment in which a dodecamer-forming peptide recruits a hexamer-forming peptide to form mixed dodecamers demonstrates that one species can dictate the oligomerization of another. These findings should also be relevant to the formation of oligomers of full-length peptides and proteins in amyloid diseases. PMID:25915729

  19. Palladium(II) complexes of 2-pyridylmethylamine and 8-aminoquinoline: A crystallographic and DFT study

    NASA Astrophysics Data System (ADS)

    Akerman, Kate J.; Venter, Chané; Hunter, Leigh A.; Akerman, Matthew P.

    2015-07-01

    Two nominally square planar palladium(II) chelates: dichloro-(2-aminomethylpyridine-N,N?)-palladium(II) ([Pd(L1)Cl2]) and dichloro-(8-aminoquinoline)-palladium(II) ([Pd(L2)Cl2]) have been synthesised and studied by X-ray crystallography and DFT methods. [Pd(L1)Cl2] crystallised in the monoclinic space group C2/c. In the solid state this compound exists as a one-dimensional supramolecular structure supported by Nsbnd H⋯Cl hydrogen bonds and metallophilic Pd⋯Pd interactions. The same hydrogen bonding motif leads to a two-dimensional supramolecular structure in the case of [Pd(L2)Cl2]; this structure is devoid of metallophilic interactions. DFT simulations show that the planar geometry of [Pd(L1)Cl2] in the solid state is not the lowest energy conformation. An out-of-plane distortion of the methylene group leads to a structure ca. 11 kJ mol-1 lower in energy. The NBO partial charges provide insight into the stability of the hydrogen bonding motif. TD-DFT calculations were used to delineate the experimental UV-visible spectra.

  20. Initiating a crystallographic analysis of recombinant (S)-2-hydroxypropylphosphonic acid epoxidase from Streptomyces wedmorensis

    SciTech Connect

    Cameron, Scott; McLuskey, Karen; Chamberlayne, Rachel; Hallyburton, Irene; Hunter, William N., E-mail: w.n.hunter@dundee.ac.uk [Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH,Scotland (United Kingdom)

    2005-05-01

    The gene encoding the unusual metal-ion-dependent epoxidase involved in fosfomycin biosynthesis, S. wedmorensis (S)-2-hydroxypropylphosphonic acid epoxidase, has been cloned and the protein expressed, purified and crystallized. Two crystal forms have been obtained, one of which diffracts to high resolution. The oxirane (1R,2S)-1,2-epoxypropylphosphonic acid (fosfomycin) is a natural product antibiotic produced in Streptomyces wedmorensis by the metal-ion-dependent (S)-2-hydroxypropylphosphonic acid epoxidase. This epoxidase is highly unusual since it has no requirement for a haem prosthetic group. The gene encoding the enzyme, fom4, has been cloned and a highly efficient recombinant source of the enzyme established. Two different crystal forms, tetragonal and hexagonal, have been obtained. The hexagonal form displays symmetry consistent with space group P6{sub 1/5}22 and unit-cell parameters a = 86.44, c = 221.56 Å, ? = 120°. The Matthews coefficient, V{sub M}, of 2.7 Å{sup 3} Da{sup ?1} corresponds to two subunits, each of approximate weight 21.4 kDa, in the asymmetric unit with 55% solvent content. These crystals diffract to high resolution and experimental phases are being sought to determine the structure.

  1. Effect of post-CVD thermal treatments on crystallographic orientation, microstructure, mechanical and optical properties of ZnS ceramics

    Microsoft Academic Search

    P. Biswas; R. Senthil Kumar; P. Ramavath; V. Mahendar; G. V. N. Rao; R. Johnson

    2010-01-01

    Chemical vapor deposited (CVD) zinc sulphide samples were subjected to hot isostatic pressing (HIP) and heat treatment under pressureless (HT) sintering conditions in argon. The effects of temperature and pressure on the crystallographic orientation, microstructure, optical and mechanical properties were studied. The removal of Zn–H absorption band present in CVD ZnS can be effected by temperature increase alone as observed

  2. Step bunching-induced vertical lattice mismatch and crystallographic tilt in vicinal BiFeO3,,001... films

    E-print Network

    Eom, Chang Beom

    in BiFeO3 BFO because of its room-temperature multiferroic properties and potential device applicationsStep bunching-induced vertical lattice mismatch and crystallographic tilt in vicinal BiFeO3 January 2011 Epitaxial 001 BiFeO3 thin films grown on vicinal SrTiO3 substrates are under large

  3. Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): II. Quartz textures in monophase rocks

    SciTech Connect

    Nikitin, A. N., E-mail: nikitin@nf.jinr.ru; Ivankina, T. I. [Joint Institute for Nuclear Research (Russian Federation); Ullemeyer, K. [Universitaet Kiel, Institut fuer Geowissenschaften (Germany); Vasin, R. N. [Joint Institute for Nuclear Research (Russian Federation)

    2008-09-15

    The types of quartz textures found in a large collection of multiphase rocks from different regions of the earth are analyzed. Crystallographic textures of granulite, amphibolite, slate, and gneiss samples are measured, classified, and compared with the similar textures of monomineral rocks.

  4. Effect of seed layers in improving the crystallographic texture of CoCrPt perpendicular recording media

    E-print Network

    Laughlin, David E.

    Effect of seed layers in improving the crystallographic texture of CoCrPt perpendicular recording, Pennsylvania 15213-3890 In this work, we have systematically investigated the effect of Ti and Ta seed layers. Both Ti and Ta improve the texture of CoCrPt perpendicular magnetic media depending on the seed layer

  5. Macrocyclic Inhibitors of Penicillopepsin. 2. X-ray Crystallographic Analyses of Penicillopepsin Complexed with a P3-P1 Macrocyclic

    E-print Network

    Macrocyclic Inhibitors of Penicillopepsin. 2. X-ray Crystallographic Analyses of Penicillopepsin Complexed with a P3-P1 Macrocyclic Peptidyl Inhibitor and with Its Two Acyclic Analogues Jinhui Ding, Marie, Berkeley, California 94720-1460 ReceiVed October 27, 1997 Abstract: Macrocyclic inhibitor 1 {methyl [cyclo

  6. Asymmetric cold/warm rolling simulation by crystal plasticity multi-scale finite element analysis based on crystallographic homogenization

    SciTech Connect

    Onishi, Koshiro; Sakamoto, Hidetoshi [Kumamoto University, 2-39-1 Kurokami, 860-8555 Kumamoto (Japan); Kuramae, Hiroyuki [Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, 535-8585 Osaka (Japan); Morimoto, Hideo [The Furukawa Electric Co. Ltd., 2-4-3 Okano, Nishi-ku, 220-0073 Yokohama (Japan); Nakamachi, Eiji [Doshisha University, 1-3 Tatara-Miyakodani, Kyotanabe, 610-0394 Kyoto (Japan)

    2010-06-15

    The purpose of this study is forming a high formability aluminum alloy sheet metal by controlling the microcrystal structure and the texture. So asymmetric rolling is applied to the material process. Analysis method is crystal plasticity multi-scale finite element analysis based on crystallographic homogenization.

  7. A reciprocal space approach for locating symmetry elements in Patterson superposition maps

    SciTech Connect

    Hendrixson, T.

    1990-09-21

    A method for determining the location and possible existence of symmetry elements in Patterson superposition maps has been developed. A comparison of the original superposition map and a superposition map operated on by the symmetry element gives possible translations to the location of the symmetry element. A reciprocal space approach using structure factor-like quantities obtained from the Fourier transform of the superposition function is then used to determine the best'' location of the symmetry element. Constraints based upon the space group requirements are also used as a check on the locations. The locations of the symmetry elements are used to modify the Fourier transform coefficients of the superposition function to give an approximation of the structure factors, which are then refined using the EG relation. The analysis of several compounds using this method is presented. Reciprocal space techniques for locating multiple images in the superposition function are also presented, along with methods to remove the effect of multiple images in the Fourier transform coefficients of the superposition map. In addition, crystallographic studies of the extended chain structure of (NHC{sub 5}H{sub 5})SbI{sub 4} and of the twinning method of the orthorhombic form of the high-{Tc} superconductor YBa{sub 2}Cu{sub 3}O{sub 7-x} are presented. 54 refs.

  8. Group Dynamics in Long -term blind endeavors on Earth as an analog for Remote Space Missions (Lewis & Clark Expedition, 1803 - 1806, Dynamic Analysis)

    NASA Astrophysics Data System (ADS)

    Allner, M.; Rygalov, V.; Reilly, J.

    In 1803 President Thomas Jefferson set fourth a military expedition led by Captains newline M Lewis and W Clark L C Expedition on an exploration to learn more about the large territory of land the U S had just purchased from France Cavan 1991 Their mission was to find a direct water route to the Pacific Ocean for the purpose of commerce and further industrial development Edwards 1999 Looking back at the events of this exploration there are many similarities to the experiences future human space explorers will face as we look to colonize the Moon and travel to Mars and beyond NASA Vision for Space Exploration 2004 - The L C Expedition lasted almost three years and involved a crew of 43 men traveling up the Missouri River to explore the unknown lands and a possible water route to the Pacific Ocean newline - The expedition took place far away from customary comfortable environments known to European settlers in early 18th century newline - The expedition involved a remotely confined high-perceived risk environment with high levels of uncertainty providing stresses and every day challenges for the crew newline - Supplies brought on the mission were limited mainly a mass weight issue rather than cost therefore the discovery and use of environmental resources In-Situ Resource Utilization approach including info-resources to mitigate uncertainty was necessary for crew survival The environments astronauts will encounter in space and on the Moon and Mars due to high risk and uncertainty will be in many aspects similar

  9. GROUP ACTIONS AND HOMOGENEOUS

    E-print Network

    Korbas, Julius

    ;Zostavili/Edited by: J´ulius Korbas, Masaharu Morimoto, Krzysztof Pawalowski N´azov/Title: Group Actions and Homogeneous Spaces Podn´azov/Subtitle: Proceedings of the International Conference Bratislava Topology

  10. OPEN COMPUTING FACILITY Group Account Application Form 1. Pick an account name. It must consist of between three and eight lowercase letters (no spaces, numbers, underscores,

    E-print Network

    Walker, Matthew P.

    of other users, re- spect the integrity of the systems and related physical resources, and observe all to protect the integrity of computer systems. For exam- ple, system administrators may access or examineOPEN COMPUTING FACILITY Group Account Application Form 1. Pick an account name. It must consist

  11. -Search-Register Submit News Blogs Protocols Forum Groups Shop All Health Bioscience Physical Science Environment Space Tech Life Origins Misc

    E-print Network

    Espinosa, Horacio D.

    -Search- Register Submit News Blogs Protocols Forum Groups Shop All Health Bioscience Physical Blog articles Vladimir R BaruchChani Ahmed Michal Labspaces.net on Facebook 1,238 people like Labspaces.net. Like Facebook social plugin Email Forgot password? Not a member?News Blogs Featured Blogs 3-dimensional

  12. Crystallization and preliminary crystallographic analysis of latent, active and recombinantly expressed aurone synthase, a polyphenol oxidase, from Coreopsis grandiflora.

    PubMed

    Molitor, Christian; Mauracher, Stephan Gerhard; Rompel, Annette

    2015-06-01

    Aurone synthase (AUS), a member of a novel group of plant polyphenol oxidases (PPOs), catalyzes the oxidative conversion of chalcones to aurones. Two active cgAUS1 (41.6?kDa) forms that differed in the level of phosphorylation or sulfation as well as the latent precursor form (58.9?kDa) were purified from the petals of Coreopsis grandiflora. The differing active cgAUS1 forms and the latent cgAUS1 as well as recombinantly expressed latent cgAUS1 were crystallized, resulting in six different crystal forms. The active forms crystallized in space groups P212121 and P1211 and diffracted to ?1.65?Å resolution. Co-crystallization of active cgAUS1 with 1,4-resorcinol led to crystals belonging to space group P3121. The crystals of latent cgAUS1 belonged to space group P1211 and diffracted to 2.50?Å resolution. Co-crystallization of recombinantly expressed pro-AUS with the hexatungstotellurate(VI) salt Na6[TeW6O24] within the liquid-liquid phase separation zone significantly improved the quality of the crystals compared with crystals obtained without hexatungstotellurate(VI). PMID:26057806

  13. Crystallization and preliminary crystallographic analysis of latent, active and recombinantly expressed aurone synthase, a polyphenol oxidase, from Coreopsis grandiflora

    PubMed Central

    Molitor, Christian; Mauracher, Stephan Gerhard; Rompel, Annette

    2015-01-01

    Aurone synthase (AUS), a member of a novel group of plant polyphenol oxidases (PPOs), catalyzes the oxidative conversion of chalcones to aurones. Two active cgAUS1 (41.6?kDa) forms that differed in the level of phosphorylation or sulfation as well as the latent precursor form (58.9?kDa) were purified from the petals of Coreopsis grandiflora. The differing active cgAUS1 forms and the latent cgAUS1 as well as recombinantly expressed latent cgAUS1 were crystallized, resulting in six different crystal forms. The active forms crystallized in space groups P212121 and P1211 and diffracted to ?1.65?Å resolution. Co-crystallization of active cgAUS1 with 1,4-resorcinol led to crystals belonging to space group P3121. The crystals of latent cgAUS1 belonged to space group P1211 and diffracted to 2.50?Å resolution. Co-crystallization of recombinantly expressed pro-AUS with the hexatungstotellurate(VI) salt Na6[TeW6O24] within the liquid–liquid phase separation zone significantly improved the quality of the crystals compared with crystals obtained without hexatungstotellurate(VI). PMID:26057806

  14. Space Weather Now

    NSDL National Science Digital Library

    Space Environment Center

    The Space Weather Now page is intended to give the non-technical user a "plain language" look at space weather. It includes information about relevant events and announcements, data from and about different instruments and satellites watching various aspects of space weather, alerts and advisories, daily themes of products and services, and links appropriate for the various groups of users.

  15. Studies of social group dynamics under isolated conditions. Objective summary of the literature as it relates to potential problems of long duration space flight

    NASA Technical Reports Server (NTRS)

    Vinograd, S. P.

    1974-01-01

    Scientific literature which deals with the study of human behavior and crew interaction in situations simulating long term space flight is summarized and organized. A bibliography of all the pertinent U.S. literature available is included, along with definitions of the behavioral characteristics terms employed. The summarized studies are analyzed according to behavioral factors and environmental conditions. The analysis consist of two matrices. (1) The matrix of factors studied correlates each research study area and individual study with the behavioral factors that were investigated in the study. (2) The matrix of conclusions identifies those studies whose investigators appeared to draw specific conclusions concerning questions of importance to NASA.

  16. PHYSICAL REVIEW B 86, 115112 (2012) Bulk topological invariants in noninteracting point group symmetric insulators

    E-print Network

    Gilbert, Matthew

    2012-01-01

    symmetric insulators Chen Fang,1 Matthew J. Gilbert,2,3 and B. Andrei Bernevig1 1 Department of Physics in two- and three-dimensional topological band insulators invariant under translational symmetry and crystallographic point group symmetries (PGS). In two-dimensional insulators, we show that (i) the Chern number

  17. Abundance of Jackfruit ( Artocarpus heterophyllus) Affects Group Characteristics and Use of Space by Golden-Headed Lion Tamarins ( Leontopithecus chrysomelas) in Cabruca Agroforest

    NASA Astrophysics Data System (ADS)

    Oliveira, Leonardo C.; Neves, Leonardo G.; Raboy, Becky E.; Dietz, James M.

    2011-08-01

    Cabruca is an agroforest of cacao trees shaded by native forest trees. It is the predominant vegetation type throughout eastern part of the range of the golden-headed lion tamarins, Leontopithecus chrysomelas, an endangered primate endemic to Atlantic Forest. Understanding how lion tamarins use this agroforest is a conservation priority. To address this question, we documented the diet, home range size, group sizes and composition, density, number of litters and body condition of lion tamarins living in cabruca, and other habitats. Jackfruit, Artocarpus heterophyllus, was the most used species used by lion tamarins in cabruca and was widely available and used throughout the year. In cabruca, home range size was the smallest (22-28 ha) and density of lion tamarins was the highest (1.7 ind/ha) reported for the species. Group size averaged 7.4 individuals and was not significantly different among the vegetation types. In cabruca, groups produced one or two litters a year, and all litters were twins. Adult males in cabruca were significantly heavier than males in primary forest. Our study is the first to demonstrate that breeding groups of golden-headed lion tamarins can survive and reproduce entirely within cabruca agroforest. Jackfruit proved to be a keystone resource for lion tamarins in cabruca, and bromeliads were important as an animal prey foraging microhabitat. In cases where cabruca contains concentrated resources, such as jackfruit and bromeliads, lion tamarins may not only survive and reproduce but may fare better than in other forest types, at least for body condition and reproduction.

  18. The structures of marialite (Me[subscript 6]) and meionite (Me[subscript 93]) in space groups P4[subscript 2]\\/n and I4\\/m, and the absence of phase transitions in the scapolite series

    Microsoft Academic Search

    Sytle M. Antao; Ishmael Hassan

    2011-01-01

    The crystal structures of marialite (Me) from Badakhshan, Afghanistan and meionite (Me) from Mt. Vesuvius, Italy were obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. Their structures were refined in space groups I4\\/m and P42\\/n, and similar results were obtained. The Me sample has a formula Ca{sub 0.24}Na{sub 3.37}K{sub 0.24}[Al{sub 3.16}Si{sub 8.84}O]Cl{sub 0.84}(CO){sub 0.15}, and

  19. X-ray crystallographic studies of alanine-65 variants of carbonic anhydrase II reveal the structural basis of compromised proton transfer in catalysis.

    PubMed

    Scolnick, L R; Christianson, D W

    1996-12-24

    The three-dimensional structures of A65F, A65L, A65H, A65T, A65S, and A65G human carbonic anhydrase II (CAII) variants have been solved by X-ray crystallographic methods to probe the importance of residue 65 and the structural implications of its evolutionary drift in the greater family of carbonic anhydrase isozymes. Structure-activity relationships in this series of CAII variants are correlated with those established for other carbonic anhydrase isozymes. We conclude that a bulky side chain at position 65 hinders the formation of an effective solvent bridge between zinc-bound water and H64 and thereby hinders solvent-mediated proton transfer between these two groups [Jackman, J. E., Merz, K. M., Jr., & Fierke, C. A. (1996) Biochemistry 35, 16421-16428]. Despite the introduction of a polar hydroxyl group at this position, smaller side chains such as serine or threonine substituted for A65 do not perturb the formation of a solvent bridge between H64 and zinc-bound solvent. Thus, the evolution of residue 65 size is one factor affecting the trajectory of catalytic proton transfer. PMID:8987974

  20. Nanoindentation, High-Temperature Behavior, and Crystallographic/Spectroscopic Characterization of the High-Refractive-Index Materials TiTa2O7 and TiNb2O7.

    PubMed

    Perfler, Lukas; Kahlenberg, Volker; Wikete, Christoph; Schmidmair, Daniela; Tribus, Martina; Kaindl, Reinhard

    2015-07-20

    Colorless single crystals, as well as polycrystalline samples of TiTa2O7 and TiNb2O7, were grown directly from the melt and prepared by solid-state reactions, respectively, at various temperatures between 1598 K and 1983 K. The chemical composition of the crystals was confirmed by wavelength-dispersive X-ray spectroscopy, and the crystal structures were determined using single-crystal X-ray diffraction. Structural investigations of the isostructural compounds resulted in the following basic crystallographic data: monoclinic symmetry, space group I2/m (No. 12), a = 17.6624(12) Å, b = 3.8012(3) Å, c = 11.8290(9) Å, ? = 95.135(7)°, V = 790.99(10) Å(3) for TiTa2O7 and a = 17.6719(13) Å, b = 3.8006(2) Å, c = 11.8924(9) Å, ? = 95.295(7)°, V = 795.33(10) Å(3), respectively, for TiNb2O7, Z = 6. Rietveld refinement analyses of the powder X-ray diffraction patterns and Raman spectroscopy were carried out to complement the structural investigations. In addition, in situ high-temperature powder X-ray diffraction experiments over the temperature range of 323-1323 K enabled the study of the thermal expansion tensors of TiTa2O7 and TiNb2O7. To determine the hardness (H), and elastic moduli (E) of the chemical compounds, nanoindentation experiments have been performed with a Berkovich diamond indenter tip. Analyses of the load-displacement curves resulted in a hardness of H = 9.0 ± 0.5 GPa and a reduced elastic modulus of Er = 170 ± 7 GPa for TiTa2O7. TiNb2O7 showed a slightly lower hardness of H = 8.7 ± 0.3 GPa and a reduced elastic modulus of Er = 159 ± 4 GPa. Spectroscopic ellipsometry of the polished specimens was employed for the determination of the optical constants n and k. TiNb2O7 as well as TiTa2O7 exhibit a very high average refractive index of nD = 2.37 and nD = 2.29, respectively, at ? = 589 nm, similar to that of diamond (nD = 2.42). PMID:26132138

  1. Crystallization and preliminary crystallographic analysis of a PHD domain of human JARID1B.

    PubMed

    Guo, Xue; Xu, Youwei; Wang, Ping; Li, Ze; Xu, Yanhui; Yang, Huirong

    2011-08-01

    Histone lysine methylation can be removed by proteins containing JmjC domains in a sequence- and methylation state-specific manner. JARID1B, a protein containing PHD and JmjC domains, is a histone demethylase specific for H3K4me2 and H3K4me3 which requires Fe(II) and ?-ketoglutarate (?-KG) as cofactors to remove the methyl group. JARID1B has also been shown to play a critical role in the development of breast cancer. JARID1B contains JmjN, Arid and JmjC domains, a C5HC2 zinc-finger domain and three PHD domains. The first PHD domain (PHD1(JARID1B); residues 306-360) is located at the N-terminus and is important for both histone demethylase activity and histone-tail recognition of JARID1B. Here, the expression, purification and crystallization of PHD1(JARID1B) is reported. A PHD1(JARID1B) crystal was grown by the hanging-drop vapour-diffusion method in reservoir solution consisting of 0.1?M HEPES pH 7.0, 2.2?M ammonium sulfate at 277?K. A zinc SAD data set was collected from a PHD1(JARID1B) crystal. The diffraction pattern of the PHD1(JARID1B) crystal extended to 1.65?Å resolution using synchrotron radiation. The crystal belonged to space group P4(3), with unit-cell parameters a = 51.7, b = 51.7, c = 36.2?Å. PMID:21821892

  2. A crystallographic, spectroscopic, thermal, and DFT investigation of mixed ligand Cu(II) complexes of 2-benzoylbenzoate

    Microsoft Academic Search

    Sema Caglar; Serkan Demir

    2012-01-01

    Two mixed ligand complexes of copper(II)-2-benzoylbenzoate (bba) with pyridazine and 4-picoline, namely bis(2-benzoylbenzoate)di(pyridazine)copper(II) 1 and bis(2-benzoylbenzoate)bis(4-picoline)copper(II) 2, have been synthesized and characterized by X-ray crystallography. Complex 1 and 2 crystallize in the monoclinic P21\\/c space groups. The calculated frequency shifts have shown that the participation of carboxylate groups in coordination to the metal centers in monodentate fashion (?(OCO) > 200 cm).

  3. Space Resources

    NASA Technical Reports Server (NTRS)

    McKay, Mary Fae (Editor); McKay, David S. (Editor); Duke, Michael S. (Editor)

    1992-01-01

    Space resources must be used to support life on the Moon and exploration of Mars. Just as the pioneers applied the tools they brought with them to resources they found along the way rather than trying to haul all their needs over a long supply line, so too must space travelers apply their high technology tools to local resources. The pioneers refilled their water barrels at each river they forded; moonbase inhabitants may use chemical reactors to combine hydrogen brought from Earth with oxygen found in lunar soil to make their water. The pioneers sought temporary shelter under trees or in the lee of a cliff and built sod houses as their first homes on the new land; settlers of the Moon may seek out lava tubes for their shelter or cover space station modules with lunar regolith for radiation protection. The pioneers moved further west from their first settlements, using wagons they had built from local wood and pack animals they had raised; space explorers may use propellant made at a lunar base to take them on to Mars. The concept for this report was developed at a NASA-sponsored summer study in 1984. The program was held on the Scripps campus of the University of California at San Diego (UCSD), under the auspices of the American Society for Engineering Education (ASEE). It was jointly managed under the California Space Inst. and the NASA Johnson Space Center, under the direction of the Office of Aeronautics and Space Technology (OAST) at NASA Headquarters. The study participants (listed in the addendum) included a group of 18 university teachers and researchers (faculty fellows) who were present for the entire 10-week period and a larger group of attendees from universities, Government, and industry who came for a series of four 1-week workshops. The organization of this report follows that of the summer study. Space Resources consists of a brief overview and four detailed technical volumes: (1) Scenarios; (2) Energy, Power, and Transport; (3) Materials; (4) Social Concerns. Although many of the included papers got their impetus from workshop discussions, most have been written since then, thus allowing the authors to base new applications on established information and tested technology. All these papers have been updated to include the authors' current work. This overview, drafted by faculty fellow Jim Burke, describes the findings of the summer study, as participants explored the use of space resources in the development of future space activities and defined the necessary research and development that must precede the practical utilization of these resources. Space resources considered included lunar soil, oxygen derived from lunar soil, material retrieved from near-Earth asteroids, abundant sunlight, low gravity, and high vacuum. The study participants analyzed the direct use of these resources, the potential demand for products from them, the techniques for retrieving and processing space resources, the necessary infrastructure, and the economic tradeoffs. This is certainly not the first report to urge the utilization of space resources in the development of space activities. In fact, Space Resources may be seen as the third of a trilogy of NASA Special Publications reporting such ideas arising from similar studies. It has been preceded by Space Settlements: A Design Study (NASA SP-413) and Space Resources and Space Settlements (NASA SP-428). And other, contemporaneous reports have responded to the same themes. The National Commission on Space, led by Thomas Paine, in Pioneering the Space Frontier, and the NASA task force led by astronaut Sally Ride, in Leadership and America's Future in Space, also emphasize expansion of the space Infrastructure; more detailed exploration of the Moon, Mars, and asteroids; an early start on the development of the technology necessary for using space resources; and systematic development of the skills necessary for long-term human presence in space. Our report does not represent any Government-authorized view or official NASA policy. NASA's official response to these challenging op

  4. Distinct Spacing Between Anionic Groups: An Essential Chemical Determinant for Achieving Thiophene-Based Ligands to Distinguish ?-Amyloid or Tau Polymorphic Aggregates.

    PubMed

    Klingstedt, Therése; Shirani, Hamid; Mahler, Jasmin; Wegenast-Braun, Bettina M; Nyström, Sofie; Goedert, Michel; Jucker, Mathias; Nilsson, K Peter R

    2015-06-15

    The accumulation of protein aggregates is associated with many devastating neurodegenerative diseases and the existence of distinct aggregated morphotypes has been suggested to explain the heterogeneous phenotype reported for these diseases. Thus, the development of molecular probes able to distinguish such morphotypes is essential. We report an anionic tetrameric oligothiophene compound that can be utilized for spectral assignment of different morphotypes of ?-amyloid or tau aggregates present in transgenic mice at distinct ages. The ability of the ligand to spectrally distinguish between the aggregated morphotypes was reduced when the spacing between the anionic substituents along the conjugated thiophene backbone was altered, which verified that specific molecular interactions between the ligand and the protein aggregate are necessary to detect aggregate polymorphism. Our findings provide the structural and functional basis for the development of new fluorescent ligands that can distinguish between different morphotypes of protein aggregates. PMID:26013403

  5. Ice in Space

    NSDL National Science Digital Library

    This is a detailed lesson about space and how Earth fits in it. Learners will consider the essential question, "What is space?" Activities include small group miming, speaking, drawing, and/or writing about space and the evidence for ice in space. Included are detailed games and dialogue. Native stories are shared. This is lesson 9 of 12 in the unit, Exploring Ice in the Solar System.

  6. Synthesis and X-ray Crystallographic Studies of ethyl 3-methyl5-(methylthio)-1H-pyrazole-4-carboxylate

    NASA Astrophysics Data System (ADS)

    Prasad, T. N. Mahadeva; Lakshminarayana, B. N.; Musad, Ebraheem Abdu; Sridhar, M. A.; Rai, K. M. Lokanath; Prasad, J. Shashidhara

    2011-07-01

    The title compound, C8H12N2O2S was synthesized and the structure was investigated by X-ray methods. The compound crystallizes in monoclinic crystal class in the space group P21/c with cell parameters a = 5.3900(6)Å, b = 11.7950(8)Å, c = 15.8320(17)Å, ? = 90.590(3)° and Z = 4.

  7. Crystallization and preliminary crystallographic study of stonustoxin, a protein lethal factor isolated from the stonefish (Synanceja horrida) venom.

    PubMed

    Yew, W S; Kolatkar, P R; Kuhn, P; Khoo, H E

    1999-12-15

    Crystals of stonustoxin have been obtained and diffract to 3.4 A resolution. Stonustoxin is a protein lethal factor isolated from the venom of the stonefish, Synanceja horrida. The crystals belong to the tetragonal space group P422, with unit cell constants a = b = 109.0 A, c = 245.7 A. A native stonustoxin molecule has two subunits, designated alpha and beta, respectively, and there is one stonustoxin molecule per asymmetric unit. PMID:10600575

  8. Crystallization and preliminary crystallographic analysis of the phosphotriesterase-like lactonase from Geobacillus kaustophilus

    PubMed Central

    Zheng, Baisong; Yu, Shanshan; Zhang, Yu; Feng, Yan; Lou, Zhiyong

    2011-01-01

    GK1506 from the thermophilic bacterium Geobacillus kaustophilus is a member of the phosphotriesterase-like lactonases, which can catalyze the hydrolysis of a broad range of compounds with different chemical properties. It is of particular interest because of its high thermostability and its dual activity towards organophosphate compounds and some lactones. These properties make GK1506 an attractive target for future enzyme engineering and use in practical applications. In order to resolve the crystal structure of GK1506 and to gain a better understanding of its biological function, recombinant GK1506 was expressed, purified and crystallized using 0.1?M HEPES pH 7.6, 12%(w/v) PEG 8000, 8%(v/v) ethylene glycol at 291?K. A 2.6?Å resolution native data set was collected from a single flash-cooled crystal (100?K) using 10%(v/v) glycerol as a cryoprotectant. These crystals belonged to space group P21, with unit-cell parameters a = 51.444, b = 80.453, c = 92.615?Å, ? = 99.29°. Two molecules were assumed to be present per asymmetric unit, which gives a Matthews coefficient of 2.7?Å3?Da?1. PMID:21795796

  9. Crystallization and preliminary crystallographic analysis of Abp, a GH27 ?-l-arabinopyranosidase from Geobacillus stearothermophilus

    PubMed Central

    Lansky, Shifra; Salama, Rachel; Solomon, Vered H.; Belrhali, Hassan; Shoham, Yuval; Shoham, Gil

    2013-01-01

    Geobacillus stearothermophilus T-6 is a thermophilic soil bacterium that possesses an extensive system for the utilization of hemicellulose. The bacterium produces a small number of endo-acting extracellular enzymes that cleave high-molecular-weight hemicellulolytic polymers into short decorated oligosaccharides, which are further hydrolysed into the respective sugar monomers by a battery of intracellular glycoside hydrolases. One of these intracellular processing enzymes is ?-l-arabinopyranosidase (Abp), which is capable of removing ?-l-arabinopyranose residues from naturally occurring arabino-polysaccharides. As arabino-polymers constitute a significant part of the hemicellulolytic content of plant biomass, their efficient enzymatic degradation presents an important challenge for many potential biotechnological applications. This aspect has led to an increasing interest in the biochemical characterization and structural analysis of this and related hemicellulases. Abp from G. stearothermophilus T-6 has recently been cloned, overexpressed, purified, biochemically characterized and crystallized in our laboratory, as part of its complete structure–function study. The best crystals obtained for this enzyme belonged to the primitive orthorhombic space group P212121, with average unit-cell parameters a = 107.7, b = 202.2, c = 287.3?Å. Full diffraction data sets to 2.3?Å resolution have been collected for both the wild-type enzyme and its D197A catalytic mutant from flash-cooled crystals at 100?K, using synchrotron radiation. These data are currently being used for a high-resolution three-dimensional structure determination of Abp. PMID:23722857

  10. Complex assembly, crystallization and preliminary X-ray crystallographic studies of duck MHC class I molecule

    PubMed Central

    Zhang, Jianhua; Chen, Yong; Gao, Feng; Chen, Weihong; Qi, Jianxun; Xia, Chun

    2010-01-01

    In order to understand the biological properties of the immune systems of waterfowl and to establish a system for structural studies of duck class I major histocompatibility complex (DuMHC I), a complex of DuMHC I with duck ?2-­microglobulin (Du?2m) and the peptide AEIEDLIF (AF8) derived from H5N1 NP residues 251–258 was assembled. The complex was crystallized; the crystals belonged to space group C2221, with unit-cell parameters a = 54.7, b = 72.4, c = 102.2?Å, and diffracted to 2.3?Å resolution. Matthews coefficient calculation and initial structure determination by molecular replacement showed that the crystals did not contain the whole DuMHC I complex, but instead contained the DuMHC I ?3 domain and a Du?2m molecule (DuMHC I ?3+?2m). Another complex of DuMHC I with the peptide IDWFDGKE derived from a chicken fusion protein also generated the same results. The stable structure of DuMHC I ?3+?2m may reflect some unique characteristics of DuMHC I and pave the way for novel MHC structure-related studies in the future. PMID:20057082

  11. Bacterial expression and preliminary crystallographic studies of a 149-residue fragment of human Caprin-1.

    PubMed

    Wu, Yuhong; Zhu, Jiang; Huang, Xiaolan; Du, Zhihua

    2015-03-01

    Caprin-1 is an RNA-binding protein which plays critical roles in several important biological processes, including cellular proliferation, the interferon-mediated antiviral innate immune response, the maintenance of synaptic plasticity and the formation of RNA stress granules. Caprin-1 has been implicated in the pathogenesis of several human diseases, including osteosarcoma, breast cancer, viral infections, hearing loss and neurodegenerative disorders. Despite the emerging biological and physiopathological significance of Caprin-1, no structural information is available for this protein. Moreover, Caprin-1 does not have sequence similarity to any other protein with a known structure. It is therefore expected that structural studies will play a particularly crucial role in revealing the functional mechanisms of Caprin-1. Here, a protein fragment of human Caprin-1 consisting of residues 112-260 was expressed, purified and crystallized. Native and Se-SAD data sets were collected to resolutions to 2.05 and 2.65?Å, respectively, in different space groups. PMID:25760709

  12. Crystallographic analysis of a novel aldo-keto reductase from Thermotoga maritima in complex with NADP(.).

    PubMed

    Hou, Hai; Li, Ruiying; Wang, Xiaoyan; Yuan, Zhen; Liu, Xuemeng; Chen, Zhenmin; Xu, Xiaoling

    2015-07-01

    Aldo-keto reductases (AKRs) are a superfamily of NAD(P)H-dependent oxidoreductases that catalyse the asymmetric reduction of aldehydes and ketones to chiral alcohols in various organisms. The novel aldo-keto reductase Tm1743 from Thermotoga maritima was identified to have a broad substrate specificity and high thermostability, serving as an important enzyme in biocatalysis and fine-chemical synthesis. In this study, Tm1743 was overexpressed in Escherichia coli BL21(DE3) cells with an N-terminal His6 tag and was purified by Ni(2+)-chelating affinity and size-exclusion chromatography. Purified recombinant enzyme was incubated with its cofactor NADP(+) and its substrate ethyl 2-oxo-4-phenylbutyrate (EOPB) for crystallization. Two X-ray diffraction data sets were collected at 2.0 and 1.7?Å resolution from dodecahedral crystals grown from samples containing Tm1743-NADP(+)-EOPB and Tm1743-NADP(+), respectively. Both crystals belonged to space group P3121, with similar unit-cell parameters. However, in the refined structure model only NADP(+) was observed in the active site of the full-length Tm1743 enzyme. Degradation of the N-terminal vector-derived amino acids during crystallization was confirmed by Western blot and mass-spectrometric analyses. PMID:26144229

  13. Expression, purification, crystallization and crystallographic study of Lutzomyia longipalpis LJL143.

    PubMed

    Kelleher, Alan; Liu, Zhuyun; Seid, Christopher A; Zhan, Bin; Asojo, Oluwatoyin A

    2015-07-01

    Leishmaniasis is a neglected vector-borne disease with a global prevalence of over 12 million cases and 59?000 annual deaths. Transmission of the parasite requires salivary proteins, including LJL143 from the New World sandfly Lutzomyia longipalpis. LJL143 is a known marker of sandfly exposure in zoonotic hosts. LJL143 was crystallized from soluble protein expressed using Pichia pastoris. X-ray data were collected to 2.6?Å resolution from orthorhombic crystals belonging to space group P212121, with average unit-cell parameters a = 57.39, b = 70.24, c = 79.58?Å. The crystals are predicted to have a monomer in the asymmetric unit, with an estimated solvent content of 48.5%. LJL143 has negligible homology to any reported structures, so the phases could not be determined by molecular replacement. All attempts at S-SAD failed and future studies include experimental phase determination using heavy-atom derivatives. PMID:26144240

  14. Crystallization and Preliminary X-ray Crystallographic Studies of the Alkanesulfonate FMN Reductase from Escherichia coli

    SciTech Connect

    Gao,B.; Bertrand, A.; Boles, W.; Ellis, H.; Mallett, T.

    2005-01-01

    The alkanesulfonate FMN reductase (SsuE) from Escherichia coli catalyzes the reduction of FMN by NADPH to provide reduced flavin for the monooxygenase (SsuD) enzyme. The vapor-diffusion technique yielded single crystals that grow as hexagonal rods and diffract to 2.9 Angstrom resolution using synchrotron X-ray radiation. The protein crystallizes in the primitive hexagonal space group P622. The SsuE protein lacks any cysteine or methionine residues owing to the role of the SsuE enzyme in the acquisition of sulfur during sulfate starvation. Therefore, substitution of two leucine residues (Leu114 and Leu165) to methionine was performed to obtain selenomethionine-containing SsuE for MAD phasing. The selenomethionine derivative of SsuE has been expressed and purified and crystals of the protein have been obtained with and without bound FMN. These preliminary studies should lead to the structure solution of SsuE. It is anticipated that this new protein structure will provide detailed structural information on specific active-site regions of the protein and insight into the mechanism of flavin reduction and transfer of reduced flavin.

  15. Crystallographic structure of the turbine C-ring from spinach chloroplast F-ATP synthase

    PubMed Central

    Balakrishna, Asha Manikkoth; Seelert, Holger; Marx, Sven-Hendric; Dencher, Norbert A.; Grüber, Gerhard

    2014-01-01

    In eukaryotic and prokaryotic cells, F-ATP synthases provide energy through the synthesis of ATP. The chloroplast F-ATP synthase (CF1FO-ATP synthase) of plants is integrated into the thylakoid membrane via its FO-domain subunits a, b, b’ and c. Subunit c with a stoichiometry of 14 and subunit a form the gate for H+-pumping, enabling the coupling of electrochemical energy with ATP synthesis in the F1 sector. Here we report the crystallization and structure determination of the c14-ring of subunit c of the CF1FO-ATP synthase from spinach chloroplasts. The crystals belonged to space group C2, with unit-cell parameters a=144.420, b=99.295, c=123.51 Å, and ?=104.34° and diffracted to 4.5 Å resolution. Each c-ring contains 14 monomers in the asymmetric unit. The length of the c-ring is 60.32 Å, with an outer ring diameter 52.30 Å and an inner ring width of 40 Å. PMID:24521269

  16. Crystallization and preliminary X-ray crystallographic analysis of Salmonella Typhimurium CueP.

    PubMed

    Yun, Bo-Young; Piao, Shunfu; Kim, Yeon-Gil; Moon, Hyung Ryong; Choi, Eun Joo; Kim, Young-Ok; Nam, Bo-Hye; Lee, Sang-Jun; Ha, Nam-Chul

    2011-06-01

    Salmonella enterica serovar Typhimurium (S. Typhimurium) can survive in the phagosome of macrophages, causing serious medical and veterinary problems. CueP is uniquely found in S. Typhimurium and has been characterized as a major periplasmic copper-binding protein. Although cueP has been identified as being responsible for the copper resistance of the bacterium in vivo, the biochemical role and three-dimensional structure of CueP remain unknown. In this study, CueP from S. Typhimurium was overexpressed and the recombinant protein was purified using Ni-NTA affinity, anion-exchange and gel-filtration chromatographies. The purified CueP protein was crystallized using the vapour-diffusion method. A diffraction data set was collected to 2.5?Å resolution at 100?K. The crystal belonged to space group P2(1)2(1)2(1). To obtain initial phases, selenomethionyl-substituted protein was overproduced and purified. Optimization of crystallization conditions for the selenomethionyl-substituted protein is in progress. PMID:21636909

  17. Crystallographic structure of the turbine c-ring from spinach chloroplast F-ATP synthase.

    PubMed

    Balakrishna, Asha Manikkoth; Seelert, Holger; Marx, Sven-Hendric; Dencher, Norbert A; Grüber, Gerhard

    2014-02-13

    In eukaryotic- and prokaryotic cells F-ATP synthases provide energy through the synthesis of adenosine triphosphate (ATP). The chloroplast F-ATP synthase (CF1FO-ATP synthase) of plants is integrated into the thylakoid membrane via its FO-domain subunits a, b, b' and c. Subunit c with a stoichiometry of 14 and subunit a form the gate for H+-pumping, enabling the coupling of electrochemical energy with ATP synthesis in the F1 sector. Here we report the crystallization and structure determination of the c14-ring of subunit c of the CF1FO-ATP synthase from spinach chloroplasts. The crystals belonged to space group C2, with unit-cell parameters a = 144.420, b = 99.295, c = 123.51 Å, and ? = 104.34º and diffracted to 4.5 Å resolution. Each c-ring contains fourteen monomers in the asymmetric unit. The length of the c-ring is 60.32 Å, with an outer ring diameter 52.30 Å, and an inner ring width of 40 Å. PMID:24521269

  18. Purification, crystallization and preliminary crystallographic analysis of a Thermostable Endonuclease IV from Thermotoga maritima

    SciTech Connect

    Coates, Leighton [ORNL; Tomanicek, Stephen J [ORNL; Hughes, Ronny C [ORNL; NG, Joseph D [ORNL; Demarse, Neil A [ORNL

    2009-01-01

    The DNA repair enzyme Endonuclease IV from the thermophilic bacterium Thermotoga Maritima MSB8 (reference sequence: NC_000853) has been expressed in Escherichia coli and crystallized for X ray analysis. Thermotoga maritima Endonuclease IV is a 287 amino acid protein with 32% sequence identity to the Escherichia coli Endonuclease IV. The protein was purified to homogeneity and was crystallized using the sitting drop vapor diffusion method. The protein crystallized in the space group P61, with a composition of one biological molecule in the asymmetric unit corresponding to a Mathew s coefficient of 2.39 and a 47% solvent fraction. The unit cell parameters for the crystals are a = 123.23 , b = 123.23 , c = 35.34 , = = 90 , = 120 . Microseeding and further optimization yielded crystals with an X ray diffraction limit of 2.4 . A single 70 data set was collected and processed resulting in an overall Rmerge and completeness of 9.5% and 99.3% respectively.

  19. Crystallization and preliminary crystallographic analysis of the phosphotriesterase-like lactonase from Geobacillus kaustophilus.

    PubMed

    Zheng, Baisong; Yu, Shanshan; Zhang, Yu; Feng, Yan; Lou, Zhiyong

    2011-07-01

    GK1506 from the thermophilic bacterium Geobacillus kaustophilus is a member of the phosphotriesterase-like lactonases, which can catalyze the hydrolysis of a broad range of compounds with different chemical properties. It is of particular interest because of its high thermostability and its dual activity towards organophosphate compounds and some lactones. These properties make GK1506 an attractive target for future enzyme engineering and use in practical applications. In order to resolve the crystal structure of GK1506 and to gain a better understanding of its biological function, recombinant GK1506 was expressed, purified and crystallized using 0.1?M HEPES pH 7.6, 12%(w/v) PEG 8000, 8%(v/v) ethylene glycol at 291?K. A 2.6?Å resolution native data set was collected from a single flash-cooled crystal (100?K) using 10%(v/v) glycerol as a cryoprotectant. These crystals belonged to space group P2(1), with unit-cell parameters a=51.444, b=80.453, c=92.615?Å, ?=99.29°. Two molecules were assumed to be present per asymmetric unit, which gives a Matthews coefficient of 2.7?Å3?Da(-1). PMID:21795796

  20. Expression, purification and preliminary crystallographic analysis of oligopeptidase B from Trypanosoma brucei

    PubMed Central

    Rea, Dean; Hazell, Carole; Andrews, Norma W.; Morty, Rory E.; Fülöp, Vilmos

    2006-01-01

    African sleeping sickness, also called trypanosomiasis, is a significant cause of morbidity and mortality in sub-Saharan Africa. Peptidases from Trypanosoma brucei, the causative agent, include the serine peptidase oligopeptidase B, a documented virulence factor and therapeutic target. Determination of the three-dimensional structure of oligopeptidase B is desirable to facilitate the development of novel inhibitors. Oligopeptidase B was overexpressed in Escherichia coli as an N-terminally hexahistidine-tagged fusion protein, purified using metal-affinity chromatography and crystallized using the hanging-drop vapour-diffusion technique in 7%(w/v) polyethylene glycol 6000, 1?M LiCl, 0.1?M bis-tris propane pH 7.5. Diffraction data to 2.7?Å resolution were collected using synchrotron radiation. The crystals belong to space group P3121 or P3221, with unit-cell parameters a = b = 124.5, c = 249.9?Å. A complete data set to 2.7?Å was collected using synchrotron radiation. PMID:16880564

  1. Purification and preliminary crystallographic studies of penicillin G acylase from Providencia rettgeri.

    PubMed Central

    Klei, H. E.; Daumy, G. O.; Kelly, J. A.

    1995-01-01

    Two isoforms of the heterodimeric enzyme penicillin G acylase (EC 3.5.1.11) from Providencia rettgeri ATCC 31052 (strain Bro1) were purified to near homogeneity. The isoforms exhibited comparable enzymatic activities but differed slightly in the molecular weight and pI of their respective alpha-subunit. The origin of this difference was traced to the partial conversion of the N-terminal Gln of the alpha-subunit to pyrrolidonecarboxylic acid (pyro-Glu). The boundaries of the mature enzyme within the translated DNA sequence of the wild-type propeptide (GenBank M86533) were determined. The results conclusively identified the length of the signal peptide and the position of the spacer cleaved from the propeptide to form the active heterodimer. The molecular weights of the alpha- and beta-subunits, based on these termini, were 23.7 and 62.2 kDa, respectively. Both isoforms were crystallized independently as hexagonal bipyramids up to 0.60 mm in diameter in either space group P6(1)22 or P6(5)22 (a = b = 140.5 A and c = 209.5 A) from ammonium sulfate solutions buffered by 50 mM potassium phosphate at pH 7.5. The presence of glycerol, although not required, facilitated crystal growth. Native and heavy atom derivative data were collected to 3.0 A resolution, and the calculation of isomorphous replacement phases is under way. PMID:7795527

  2. Cloning, purification and preliminary crystallographic analysis of the Bacillus subtilis GTPase YphC-GDP complex.

    PubMed

    Xu, Ling; Muench, Stephen P; Roujeinikova, Anna; Sedelnikova, Svetlana E; Rice, David W

    2006-05-01

    The Bacillus subtilis YphC gene encodes an essential GTPase thought to be involved in ribosome binding and whose protein product may represent a target for the development of a novel antibacterial agent. Sequence analysis reveals that YphC belongs to the EngA family of GTPases, which uniquely contain two adjacent GTP-binding domains. Crystals of a selenomethionine-incorporated YphC-GDP complex have been grown using the hanging-drop vapour-diffusion method and polyethylene glycol as a precipitating agent. The crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 62.71, b = 65.05, c = 110.61 angstroms, and have one molecule in the asymmetric unit. Data sets at three different wavelengths were collected on a single crystal to 2.5 angstroms resolution at the Daresbury SRS in order to solve the structure by MAD. Ultimately, analysis of YphC in complex with GDP may allow a greater understanding of the EngA family of essential GTPases. PMID:16682769

  3. Purification, crystallization and preliminary crystallographic analysis of Arabidopsis thaliana imidazoleglycerol-phosphate dehydratase

    SciTech Connect

    Glynn, Steven E.; Baker, Patrick J.; Sedelnikova, Svetlana E.; Levy, Colin W.; Rodgers, H. Fiona [Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN (United Kingdom); Blank, Jutta; Hawkes, Timothy R. [Syngenta, Jealott’s Hill International Research Station, Bracknell, Berkshire RG42 6EY (United Kingdom); Rice, David W., E-mail: d.rice@sheffield.ac.uk [Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN (United Kingdom)

    2005-08-01

    Imidazoleglycerol-phosphate dehydratase from A. thaliana has been overexpressed, purified and crystallized and data have been collected to 3 Å resolution. Imidazoleglycerol-phosphate dehydratase catalyses the sixth step of the histidine-biosynthesis pathway in plants and microorganisms and has been identified as a possible target for the development of novel herbicides. Arabidopsis thaliana IGPD has been cloned and overexpressed in Escherichia coli, purified and subsequently crystallized in the presence of manganese. Under these conditions, the inactive trimeric form of the metal-free enzyme is assembled into a fully active species consisting of a 24-mer exhibiting 432 symmetry. X-ray diffraction data have been collected to 3.0 Å resolution from a single crystal at 293 K. The crystal belongs to space group R3, with approximate unit-cell parameters a = b = 157.9, c = 480.0 Å, ? = ? = 90, ? = 120° and with either 16 or 24 subunits in the asymmetric unit. A full structure determination is under way in order to provide insights into the mode of subunit assembly and to initiate a programme of rational herbicide design.

  4. Protein crystallography for aspiring crystallographers or how to avoid pitfalls and traps in macromolecular structure determination

    PubMed Central

    Wlodawer, Alexander; Minor, Wladek; Dauter, Zbigniew; Jaskolski, Mariusz

    2014-01-01

    The number of macromolecular structures deposited in the Protein Data Bank now approaches 100 000, with the vast majority of them determined by crystallographic methods. Thousands of papers describing such structures have been published in the scientific literature, and 20 Nobel Prizes in chemistry or medicine have been awarded for discoveries based on macromolecular crystallography. New hardware and software tools have made crystallography appear to be an almost routine (but still far from being analytical) technique and many structures are now being determined by scientists with very limited experience in the practical aspects of the field. However, this apparent ease is sometimes illusory and proper procedures need to be followed to maintain high standards of structure quality. In addition, many noncrystallographers may have problems with the critical evaluation and interpretation of structural results published in the scientific literature. The present review provides an outline of the technical aspects of crystallography for less experienced practitioners, as well as information that might be useful for users of macromolecular structures, aiming to show them how to interpret (but not overinterpret) the information present in the coordinate files and in their description. A discussion of the extent of information that can be gleaned from the atomic coordinates of structures solved at different resolution is provided, as well as problems and pitfalls encountered in structure determination and interpretation. PMID:24034303

  5. Crystallographic and Computational Analyses of AUUCU Repeating RNA That Causes Spinocerebellar Ataxia Type 10 (SCA10).

    PubMed

    Park, HaJeung; González, Àlex L; Yildirim, Ilyas; Tran, Tuan; Lohman, Jeremy R; Fang, Pengfei; Guo, Min; Disney, Matthew D

    2015-06-23

    Spinocerebellar ataxia type 10 (SCA10) is caused by a pentanucleotide repeat expansion of r(AUUCU) within intron 9 of the ATXN10 pre-mRNA. The RNA causes disease by a gain-of-function mechanism in which it inactivates proteins involved in RNA biogenesis. Spectroscopic studies showed that r(AUUCU) repeats form a hairpin structure; however, there were no high-resolution structural models prior to this work. Herein, we report the first crystal structure of model r(AUUCU) repeats refined to 2.8 Å and analysis of the structure via molecular dynamics simulations. The r(AUUCU) tracts adopt an overall A-form geometry in which 3 × 3 nucleotide (5')UCU(3')/(3')UCU(5') internal loops are closed by AU pairs. Helical parameters of the refined structure as well as the corresponding electron density map on the crystallographic model reflect dynamic features of the internal loop. The computational analyses captured dynamic motion of the loop closing pairs, which can form single-stranded conformations with relatively low energies. Overall, the results presented here suggest the possibility for r(AUUCU) repeats to form metastable A-from structures, which can rearrange into single-stranded conformations and attract proteins such as heterogeneous nuclear ribonucleoprotein K (hnRNP K). The information presented here may aid in the rational design of therapeutics targeting this RNA. PMID:26039897

  6. Crystallographic structure of xanthorhodopsin, the light-driven proton pump with a dual chromophore.

    PubMed

    Luecke, Hartmut; Schobert, Brigitte; Stagno, Jason; Imasheva, Eleonora S; Wang, Jennifer M; Balashov, Sergei P; Lanyi, Janos K

    2008-10-28

    Homologous to bacteriorhodopsin and even more to proteorhodopsin, xanthorhodopsin is a light-driven proton pump that, in addition to retinal, contains a noncovalently bound carotenoid with a function of a light-harvesting antenna. We determined the structure of this eubacterial membrane protein-carotenoid complex by X-ray diffraction, to 1.9-A resolution. Although it contains 7 transmembrane helices like bacteriorhodopsin and archaerhodopsin, the structure of xanthorhodopsin is considerably different from the 2 archaeal proteins. The crystallographic model for this rhodopsin introduces structural motifs for proton transfer during the reaction cycle, particularly for proton release, that are dramatically different from those in other retinal-based transmembrane pumps. Further, it contains a histidine-aspartate complex for regulating the pK(a) of the primary proton acceptor not present in archaeal pumps but apparently conserved in eubacterial pumps. In addition to aiding elucidation of a more general proton transfer mechanism for light-driven energy transducers, the structure defines also the geometry of the carotenoid and the retinal. The close approach of the 2 polyenes at their ring ends explains why the efficiency of the excited-state energy transfer is as high as approximately 45%, and the 46 degrees angle between them suggests that the chromophore location is a compromise between optimal capture of light of all polarization angles and excited-state energy transfer. PMID:18922772

  7. Crystallographic structure of xanthorhodopsin, the light-driven proton pump with a dual chromophore

    PubMed Central

    Luecke, Hartmut; Schobert, Brigitte; Stagno, Jason; Imasheva, Eleonora S.; Wang, Jennifer M.; Balashov, Sergei P.; Lanyi, Janos K.

    2008-01-01

    Homologous to bacteriorhodopsin and even more to proteorhodopsin, xanthorhodopsin is a light-driven proton pump that, in addition to retinal, contains a noncovalently bound carotenoid with a function of a light-harvesting antenna. We determined the structure of this eubacterial membrane protein–carotenoid complex by X-ray diffraction, to 1.9-? resolution. Although it contains 7 transmembrane helices like bacteriorhodopsin and archaerhodopsin, the structure of xanthorhodopsin is considerably different from the 2 archaeal proteins. The crystallographic model for this rhodopsin introduces structural motifs for proton transfer during the reaction cycle, particularly for proton release, that are dramatically different from those in other retinal-based transmembrane pumps. Further, it contains a histidine–aspartate complex for regulating the pKa of the primary proton acceptor not present in archaeal pumps but apparently conserved in eubacterial pumps. In addition to aiding elucidation of a more general proton transfer mechanism for light-driven energy transducers, the structure defines also the geometry of the carotenoid and the retinal. The close approach of the 2 polyenes at their ring ends explains why the efficiency of the excited-state energy transfer is as high as ?45%, and the 46° angle between them suggests that the chromophore location is a compromise between optimal capture of light of all polarization angles and excited-state energy transfer. PMID:18922772

  8. Crystallographic Structure of Xanthorhodopsin, the Light-Driven Proton Pump With a Dual Chromophore

    SciTech Connect

    Luecke, H.; Schobert, B.; Stagno, J.; Imasheva, E.S.; Wang, J.M.; Balashov, S.P.; Lanyi, J.K.

    2009-05-19

    Homologous to bacteriorhodopsin and even more to proteorhodopsin, xanthorhodopsin is a light-driven proton pump that, in addition to retinal, contains a noncovalently bound carotenoid with a function of a light-harvesting antenna. We determined the structure of this eubacterial membrane protein-carotenoid complex by X-ray diffraction, to 1.9-{angstrom} resolution. Although it contains 7 transmembrane helices like bacteriorhodopsin and archaerhodopsin, the structure of xanthorhodopsin is considerably different from the 2 archaeal proteins. The crystallographic model for this rhodopsin introduces structural motifs for proton transfer during the reaction cycle, particularly for proton release, that are dramatically different from those in other retinal-based transmembrane pumps. Further, it contains a histidine-aspartate complex for regulating the pK{sub a} of the primary proton acceptor not present in archaeal pumps but apparently conserved in eubacterial pumps. In addition to aiding elucidation of a more general proton transfer mechanism for light-driven energy transducers, the structure defines also the geometry of the carotenoid and the retinal. The close approach of the 2 polyenes at their ring ends explains why the efficiency of the excited-state energy transfer is as high as {approx}45%, and the 46{sup o} angle between them suggests that the chromophore location is a compromise between optimal capture of light of all polarization angles and excited-state energy transfer.

  9. Total energies and bonding for crystallographic structures in titanium-carbon and tungsten-carbon systems

    SciTech Connect

    Price, D.L.; Cooper, B.R.

    1989-03-15

    A full-potential linearized muffin-tin orbital calculation is presented of titanium-carbon systems in a variety of crystallographic forms. The calculated electronic structure, total energies, and equilibrium lattice constants are determined for the ground-state NaCl structure of TiC and for prototype superlattice structures, and these results are discussed in terms of the nature of bonding found in TiC. Similar calculations are also given for WC in two of these crystalline forms, and the differing ground-state structure and equilibrium lattice constants in these two carbide materials are related to the behavior of those metallic d states which are occupied in WC and unoccupied in TiC. The behavior of these one-electron states, which stabilize WC in a simple hexagonal form, is similar to the calculated behavior of associated states in the prototype superlattice Ti-C structures, and these states are found to play a similar role in determining the structural characteristics in these systems. Some of the properties and probable stability of the various crystalline forms are also discussed in terms of our results.

  10. Performance of MnO2 Crystallographic Phases in Rechargeable Lithium-Air Oxygen Cathode

    NASA Astrophysics Data System (ADS)

    Oloniyo, Olubukun; Kumar, Senthil; Scott, Keith

    2012-05-01

    Manganese dioxide (MnO2) has been shown to be effective for improving the efficiency of cathodes in lithium-air cells. Different crystallographic phases including ?-, ?-, and ?-MnO2 nanowires, ?-MnO2 nanospheres, and ?-MnO2 nanowires on carbon ( ?-MnO2/C) were synthesized using the hydrothermal method. Their physical properties were examined using x-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurements, and scanning electron microscopy (SEM) and found to be in agreement with the literature. Electrochemical properties of the synthesized catalyst particles were investigated by fabricating cathodes and testing them in a lithium-air cell with lithium hexafluorophosphate in propylene carbonate (LiPF6/PC) and tetra(ethylene glycol)dimethyl ether (LiTFSi/TEGDME) electrolytes. ?-MnO2 had the highest discharge capacity in the LiTFSi/TEGDME electrolyte (2500 mAh/g), whilst ?-MnO2/C in LiPF6/PC showed a significantly higher discharge capacity of 11,000 mAh/g based on total mass of the catalytic cathode. However, the latter showed poor capacity retention compared with ?-MnO2 nanowires, which was stable for up to 30 cycles. The reported discharge capacity is higher than recorded in previous studies on lithium-air cells.

  11. Application of known X-ray phases in the crystallographic study of a small protein.

    PubMed

    Mo, F; Mathiesen, R H; Hauback, B C; Adman, E T

    1996-09-01

    Phase information, assumed known from three-beam diffraction experiments, has been used successfully as input to direct methods to re-determine the crystal structure of rubredoxin. With data at 1.54 A resolution, starting sets containing 26 single phases, or alternatively 45 triplet phases, in both cases known with a mean error of +/-22.5 degrees, were sufficient to initiate solution of the structure. Conventional figures of merit were employed in the early stages to reject the majority of the incorrect phase models. The presence of a FeS(4) cluster in the structure was used in the interpretation of the initial maps. Phase sets including 2500 E's with a mean single phase error approximately 70 degrees or a mean triplet phase error approximately 80 degrees, both relative to the model from the crystallographic refinement, could be refined and expanded by Fourier recycling using the SAYTAN formalism. Several parameters have been varied to study their influence on phase expansion and refinement. PMID:15299596

  12. Sr3Bi(PO4)3:Eu2+ Luminescence, Concentration Quenching and Crystallographic Sites

    NASA Astrophysics Data System (ADS)

    Gao, Shao-Jie; Li, Ting; Zhang, Zi-Cai; Li, Pan-Lai; Wang, Zhi-Jun; Yang, Zhi-Ping

    2014-07-01

    A blue emitting phosphor Sr3Bi(PO4)3:Eu2+ is synthesized by a high-temperature solid state method, and its luminescent property is investigated. Sr3Bi(PO4)3:Eu2+ can create blue emission under the 332 radiation excitation, and the prominent luminescence in blue (423 nm) due to the 4f 5d1 ?4 f7 transition of the Eu2+ ion. The crystallographic sites of the Eu2+ ion in Sr3Bi(PO4)3 are analyzed, and the 420 and 440 nm emission peaks of the Eu2+ ion are assigned to the nine-coordination and eight-coordination, respectively. The emission intensity of Sr3Bi(PO4)3:Eu2+ is influenced by the Eu2+ doping content, and the concentration quenching effect is observed. The quenching mechanism is the dipole-dipole interaction, and the critical distance of energy transfer is calculated by the concentration quenching method to be approximately 1.72 nm.

  13. Surface energy-mediated construction of anisotropic semiconductor wires with selective crystallographic polarity

    NASA Astrophysics Data System (ADS)

    Sohn, Jung Inn; Hong, Woong-Ki; Lee, Sunghoon; Lee, Sanghyo; Ku, Jiyeon; Park, Young Jun; Hong, Jinpyo; Hwang, Sungwoo; Park, Kyung Ho; Warner, Jamie H.; Cha, Seungnam; Kim, Jong Min

    2014-07-01

    ZnO is a wide band-gap semiconductor with piezoelectric properties suitable for opto-electronics, sensors, and as an electrode material. Controlling the shape and crystallography of any semiconducting nanomaterial is a key step towards extending their use in applications. Whilst anisotropic ZnO wires have been routinely fabricated, precise control over the specific surface facets and tailoring of polar and non-polar growth directions still requires significant refinement. Manipulating the surface energy of crystal facets is a generic approach for the rational design and growth of one-dimensional (1D) building blocks. Although the surface energy is one basic factor for governing crystal nucleation and growth of anisotropic 1D structures, structural control based on surface energy minimization has not been yet demonstrated. Here, we report an electronic configuration scheme to rationally modulate surface electrostatic energies for crystallographic-selective growth of ZnO wires. The facets and orientations of ZnO wires are transformed between hexagonal and rectangular/diamond cross-sections with polar and non-polar growth directions, exhibiting different optical and piezoelectrical properties. Our novel synthetic route for ZnO wire fabrication provides new opportunities for future opto-electronics, piezoelectronics, and electronics, with new topological properties.

  14. Effects of thermal treatment of nanostructured trititanates on their crystallographic and textural properties

    SciTech Connect

    Morgado, Edisson [PETROBRAS S.A./CENPES, Research and Development Centre, Cidade Universitaria, Quadra 7, 21949-900 Rio de Janeiro-RJ (Brazil) and Department of Chemistry, University of Rio Grande do Norte, CP 1662, 59078-970 Natal-RN (Brazil)]. E-mail: emorgado@petrobras.com.br; Abreu, Marco A.S. de [PETROBRAS S.A./CENPES, Research and Development Centre, Cidade Universitaria, Quadra 7, 21949-900 Rio de Janeiro-RJ (Brazil); Moure, Gustavo T. [PETROBRAS S.A./CENPES, Research and Development Centre, Cidade Universitaria, Quadra 7, 21949-900 Rio de Janeiro-RJ (Brazil); Marinkovic, Bojan A. [Department of Materials Science and Metallurgy, Pontifical Catholic University, CP 38008, 22453-900 Rio de Janeiro-RJ (Brazil); Jardim, Paula M. [Department of Materials Science and Metallurgy, Pontifical Catholic University, CP 38008, 22453-900 Rio de Janeiro-RJ (Brazil); Araujo, Antonio S. [Department of Chemistry, University of Rio Grande do Norte, CP 1662, 59078-970 Natal-RN (Brazil)

    2007-09-04

    Nanostructured titanates (TTNT) with general formula Na {sub x}H{sub 2-x}Ti{sub 3}O{sub 7}.nH{sub 2}O were synthesized by hydrothermally reacting different TiO{sub 2} anatase (distinct crystal sizes) with NaOH at 120 deg. C followed by washing with water or diluted acid and drying of the precipitate. The resulting powders with different sodium contents were submitted to various calcination temperatures up to 800 deg. C and each calcined product was characterized as for its phase structure, composition, crystallite size and textural properties, namely BET surface area, mesopore volume and pore size distribution. Thermal transformations of TTNT samples were investigated by monitoring the modifications on crystallographic (X-ray diffraction) and textural (N{sub 2} desorption isotherms) properties, revealing the influence of the type of starting anatase and sodium content over the stability of TTNT. Moreover, a detailed study on the reduction of the interlayer distance in TTNT samples upon thermal treatment allowed corroborating the formation of an intermediate nanostructured hexatitanate, just before phase transformation into the corresponding TiO{sub 2} polymorphs and/or titanate crystals, depending on the sodium content and calcination temperature.

  15. Surface energy-mediated construction of anisotropic semiconductor wires with selective crystallographic polarity

    PubMed Central

    Sohn, Jung Inn; Hong, Woong-Ki; Lee, Sunghoon; Lee, Sanghyo; Ku, JiYeon; Park, Young Jun; Hong, Jinpyo; Hwang, Sungwoo; Park, Kyung Ho; Warner, Jamie H.; Cha, SeungNam; Kim, Jong Min

    2014-01-01

    ZnO is a wide band-gap semiconductor with piezoelectric properties suitable for opto-electronics, sensors, and as an electrode material. Controlling the shape and crystallography of any semiconducting nanomaterial is a key step towards extending their use in applications. Whilst anisotropic ZnO wires have been routinely fabricated, precise control over the specific surface facets and tailoring of polar and non-polar growth directions still requires significant refinement. Manipulating the surface energy of crystal facets is a generic approach for the rational design and growth of one-dimensional (1D) building blocks1234. Although the surface energy is one basic factor for governing crystal nucleation and growth of anisotropic 1D structures, structural control based on surface energy minimization has not been yet demonstrated56789. Here, we report an electronic configuration scheme to rationally modulate surface electrostatic energies for crystallographic-selective growth of ZnO wires. The facets and orientations of ZnO wires are transformed between hexagonal and rectangular/diamond cross-sections with polar and non-polar growth directions, exhibiting different optical and piezoelectrical properties. Our novel synthetic route for ZnO wire fabrication provides new opportunities for future opto-electronics, piezoelectronics, and electronics, with new topological properties. PMID:25017476

  16. Study on crystallographically inequivalent protons in RbH2AsO4 using static NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Lee, Kwang-Sei

    2015-02-01

    Two inequivalent protons from 1H NMR spectra of RbH2AsO4 in the paraelectric phase were distinguished using static NMR and MAS NMR. From the 1H spin-lattice relaxation times in the laboratory frame, T1, and rotating frame, T1?, of the two crystallographically inequivalent hydrogen sites, i.e., H(1) and H(2), the temperature dependences of T1 and T1? for H(1) were related to the reorientational motion. The shorter H(1) bonds give rise to stronger H-bonds, and protons involved in stronger H-bonds have long relaxation times. Consequently, the RbH2AsO4 structure has two crystallographically inequivalent sites with two different hydrogen-bond lengths.

  17. Development of <100> crystallographic texture in magnetostrictive Fe-Ga microwires produced by in-rotating water spinning method

    NASA Astrophysics Data System (ADS)

    Lupu, N.; Lostun, M.; Corodeanu, S.; Chiriac, H.

    2011-04-01

    Fe-22.5 at.% Ga microwires with diameters ranging from 150 to 350 ?m were produced by the in-rotating water spinning (INROWASP) method. All microwires were found to be polycrystalline and developed <100> crystallographic textures along the wire symmetry axis. The microwires are magnetically soft with very little coercivity and reach saturation magnetization values of 1.5 T. The largest magnetostriction value, of 185 ppm, is obtained for microwires with a diameter of 260 ?m, in the absence of prestress and stress-annealing treatments. The increase/decrease of the microwires' diameter above/below 260 ?m results in smaller magnetostriction values, with the minimum of 130 ppm being reached for microwires of 150 ?m. The unique properties of microwires made by the INROWASP method make them attractive for further production of Fe-Ga long, continuous microwires with a specific crystallographic texture.

  18. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

    E-print Network

    Christian, Eric

    NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 1 Reuse Working Group Co-chairs: Robert Wolfe, NASA, PA October 21­23, 2008 #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION ESDS Reuse Working Group 2 on the Mailing List #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 4 Background #12;NATIONAL AERONAUTICS

  19. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

    E-print Network

    Christian, Eric

    NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 1 Reuse Working Group ­ Report Back Co-chairs: Robert Philadelphia, PA October 21­23, 2008 #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION ESDS Reuse Working Group system ­ Future reuse (persistent use) is important #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

  20. Low-temperature cooling behavior of single-domain magnetite: Forcing of the crystallographic axes and interactions

    Microsoft Academic Search

    Adrian R. Muxworthy; Wyn Williams

    2006-01-01

    Low-temperature cycling (LTC) of magnetic remanences carried by rocks has become a standard technique in paleomagnetism, rock magnetism, and environmental magnetism as a means of identifying mineralogy and grain size. LTC usually involves measuring low-temperature thermomagnetic curves on cooling through crystallographic transitions, such as magnetite's Verwey transition. Historically, it has been assumed that remanence carried by single-domain (SD) magnetite grains

  1. Automatic crystallographic characterization in a transmission electron microscope: applications to twinning induced plasticity steels and Al thin films.

    PubMed

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

    2013-06-01

    A new automated crystallographic orientation mapping tool in a transmission electron microscope technique, which is based on pattern matching between every acquired electron diffraction pattern and precalculated templates, has been used for the microstructural characterization of nondeformed and deformed aluminum thin films and twinning-induced plasticity steels. The increased spatial resolution and the use of electron diffraction patterns rather than Kikuchi lines make this tool very appropriate to characterize fine grained and deformed microstructures. PMID:23642730

  2. Complete miscibility between different crystallographic structures: Monte Carlo simulations of Cu-Ag deposited on Cu(001)

    Microsoft Academic Search

    I. Braems; F. Berthier; J. Creuze; R. Tétot; B. Legrand

    2006-01-01

    Monte Carlo simulations of an AgcCu1-c monolayer deposited onto Cu(001) show that complete miscibility of two elements adopting different crystallographic structures can be observed in the surface, while experimental bulk phase diagrams preclude a similar phenomenon in the bulk. While the deposited pure Ag monolayer is pseudohexagonal and the pure Cu monolayer is square and pseudomorphic, for intermediate concentrations at

  3. Space Station Human Factors Research Review. Volume 3: Space Station Habitability and Function: Architectural Research

    NASA Technical Reports Server (NTRS)

    Cohen, Marc M. (editor); Eichold, Alice (editor); Heers, Susan (editor)

    1987-01-01

    Articles are presented on a space station architectural elements model study, space station group activities habitability module study, full-scale architectural simulation techniques for space stations, and social factors in space station interiors.

  4. In situ high-temperature crystallographic evolution of a nonstoichiometric Li2O·2SiO2 glass.

    PubMed

    Huang, Saifang; Huang, Zhaohui; Gao, Wei; Cao, Peng

    2013-12-16

    In this work, the high-temperature crystallographic evolution of crystalline phases in a complex lithium disilicate glass was investigated using synchrotron X-ray powder diffraction. The lattice parameters and unit cell volume of Li2SiO3 (LS), Li2Si2O5 (LS2), Li3PO4 (LP), and ZrO2 as a function of temperature were determined upon heating. It is found that the lattice parameter c of LS2 shows a "V"-shaped trend during heating. The crystallographic evolution of the LS2 phase has a close correlation with the LS phase, indicating the mutual interaction between LS and LS2 phases along the c axis during the nucleation/crystallization process. The phase evolution processes were different upon heating and cooling, and the unit cell volume of both LS and LP phases demonstrated different change rates. In this glass system, no LS2 was detected during cooling and the main phases formed during cooling process were LP, LS, ?-cristobalite, and ?-quartz. Interestingly, there were two forms of ?-quartz with slightly different lattice constants, and the silica phases showed a near-zero expansion behavior. The crystallographic evolution mechanism is discussed. PMID:24266416

  5. Protein crystallography for non-crystallographers, or how to get the best (but not more) from published macromolecular structures

    PubMed Central

    Wlodawer, Alexander; Minor, Wladek; Dauter, Zbigniew; Jaskolski, Mariusz

    2015-01-01

    The number of macromolecular structures deposited in the Protein Data Bank now exceeds 45 000, with the vast majority determined using crystallographic methods. Thousands of studies describing such structures have been published in the scientific literature, and 14 Nobel prizes in chemistry or medicine have been awarded to protein crystallographers. As important as these structures are for understanding the processes that take place in living organisms and also for practical applications such as drug design, many non-crystallographers still have problems with critical evaluation of the structural literature data. This review attempts to provide a brief outline of technical aspects of crystallography and to explain the meaning of some parameters that should be evaluated by users of macromolecular structures in order to interpret, but not over-interpret, the information present in the coordinate files and in their description. A discussion of the extent of the information that can be gleaned from the coordinates of structures solved at different resolution, as well as problems and pitfalls encountered in structure determination and interpretation are also covered. PMID:18034855

  6. Effect of the substrate bias voltage on the crystallographic orientation of reactively sputtered AlN thin films

    NASA Astrophysics Data System (ADS)

    Lee, Hwan-Chul; Lee, Jai-Young; Ahn, Hyo-Jun

    1994-11-01

    Aluminum nitride (AlN) films have been deposited on negatively biased Si(100) wafers by reactive r.f. magnetron sputtering in a mixed Ar-N2 discharge. It is important to control the crystallographic orientation and the physical properties of the films with deposition parameters for the surface acoustic wave device application. The change in crystallographic orientation with the negative bias voltage has been evaluated from the calculation of the texture coefficient (TC) based on X-ray diffraction patterns. It is found that the TC of the (0002) plane is increased with increase in the bias voltage. With increase in the bias voltage, the compressive stress in the films is gradually relaxed and the column diameter in the films is slowly increased. A possible explanation for the above results is that, as the bias voltage increases, the adatom mobility at growing film surface is enhanced owing to the increase in the kinetic energy and the flux of bombarding positive ions. From the analysis of the plasma, the dominant positive ions in plasma are N2(+) ions responsible for the change in the crystallographic orientation of the films with the bias voltage.

  7. 78 FR 14401 - Commercial Space Transportation Advisory Committee; Public Teleconference

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-05

    ...Federal Aviation Administration Commercial Space Transportation Advisory Committee...DOT. ACTION: Notice of Commercial Space Transportation Advisory Committee...Systems Working Group of the Commercial Space Transportation Advisory...

  8. Bacillus anthracis-Like Bacteria and Other B. cereus Group Members in a Microbial Community Within the International Space Station: A Challenge for Rapid and Easy Molecular Detection of Virulent B. anthracis

    PubMed Central

    van Tongeren, Sandra P.; Roest, Hendrik I. J.; Degener, John E.; Harmsen, Hermie J. M.

    2014-01-01

    For some microbial species, such as Bacillus anthracis, the etiologic agent of the disease anthrax, correct detection and identification by molecular methods can be problematic. The detection of virulent B. anthracis is challenging due to multiple virulence markers that need to be present in order for B. anthracis to be virulent and its close relationship to Bacillus cereus and other members of the B. cereus group. This is especially the case in environments where build-up of Bacillus spores can occur and several representatives of the B. cereus group may be present, which increases the chance for false-positives. In this study we show the presence of B. anthracis-like bacteria and other members of the B. cereus group in a microbial community within the human environment of the International Space Station and their preliminary identification by using conventional culturing as well as molecular techniques including 16S rDNA sequencing, PCR and real-time PCR. Our study shows that when monitoring the microbial hygiene in a given human environment, health risk assessment is troublesome in the case of virulent B. anthracis, especially if this should be done with rapid, easy to apply and on-site molecular methods. PMID:24945323

  9. Bacillus anthracis-like bacteria and other B. cereus group members in a microbial community within the International Space Station: a challenge for rapid and easy molecular detection of virulent B. anthracis.

    PubMed

    van Tongeren, Sandra P; Roest, Hendrik I J; Degener, John E; Harmsen, Hermie J M

    2014-01-01

    For some microbial species, such as Bacillus anthracis, the etiologic agent of the disease anthrax, correct detection and identification by molecular methods can be problematic. The detection of virulent B. anthracis is challenging due to multiple virulence markers that need to be present in order for B. anthracis to be virulent and its close relationship to Bacillus cereus and other members of the B. cereus group. This is especially the case in environments where build-up of Bacillus spores can occur and several representatives of the B. cereus group may be present, which increases the chance for false-positives. In this study we show the presence of B. anthracis-like bacteria and other members of the B. cereus group in a microbial community within the human environment of the International Space Station and their preliminary identification by using conventional culturing as well as molecular techniques including 16S rDNA sequencing, PCR and real-time PCR. Our study shows that when monitoring the microbial hygiene in a given human environment, health risk assessment is troublesome in the case of virulent B. anthracis, especially if this should be done with rapid, easy to apply and on-site molecular methods. PMID:24945323

  10. Strong pinning effect and magnetic nanodomain formation by coupling between magnetic and crystallographic domains in the ordered double perovskite Ba2FeMoO6

    Microsoft Academic Search

    T. Asaka; X. Z. Yu; Y. Tomioka; Y. Kaneko; T. Nagai; K. Kimoto; K. Ishizuka; Y. Tokura; Y. Matsui

    2007-01-01

    We investigated relations between magnetic and crystallographic domains in a single crystal of an ordered double perovskite, Ba2FeMoO6 , by means of transmission electron microscopy. By direct observation of the magnetic domain and antiphase domain structures, we demonstrated that magnetic domain walls perfectly coincide with crystallographic antiphase domain boundaries. In addition, we observed a change of magnetic domain structures by

  11. Effect of orientation on crystallographic cracking in notched nickel-base superalloy single crystal subjected to far-field cyclic compression

    Microsoft Academic Search

    P. B. Aswath

    1994-01-01

    The effects of crystallographic orientation on the fatigue crack initiation and growth under far-field cyclic compression\\u000a are discussed in single crystals of nickel-base superalloy MAR-M200. Results indicate that cracking occurs primarily due to\\u000a planar slip on the {111}-type planes. Crystallographic cracking can occur on two or more slip planes simultaneously, but through-thickness\\u000a cracks are not observed. In addition, it has

  12. Control of phosphorylase b conformation by a modified cofactor: crystallographic studies on R-state glycogen phosphorylase reconstituted with pyridoxal 5'-diphosphate.

    PubMed Central

    Leonidas, D. D.; Oikonomakos, N. G.; Papageorgiou, A. C.; Acharya, K. R.; Barford, D.; Johnson, L. N.

    1992-01-01

    Previous crystallographic studies on glycogen phosphorylase have described the different conformational states of the protein (T and R) that represent the allosteric transition and have shown how the properties of the 5'-phosphate group of the cofactor pyridoxal phosphate are influenced by these conformational states. The present work reports a study on glycogen phosphorylase b (GPb) complexed with a modified cofactor, pyridoxal 5'-diphosphate (PLPP), in place of the natural cofactor. Solution studies (Withers, S.G., Madsen, N.B., & Sykes, B.D., 1982, Biochemistry 21, 6716-6722) have shown that PLPP promotes R-state properties of the enzyme indicating that the cofactor can influence the conformational state of the protein. GPb complexed with pyridoxal 5'-diphosphate (PLPP) has been crystallized in the presence of IMP and ammonium sulfate in the monoclinic R-state crystal form and the structure refined from X-ray data to 2.8 A resolution to a crystallographic R value of 0.21. The global tertiary and quaternary structure in the vicinity of the Ser 14 and the IMP sites are nearly identical to those observed for the R-state GPb-AMP complex. At the catalytic site the second phosphate of PLPP is accommodated with essentially no change in structure from the R-state structure and is involved in interactions with the side chains of two lysine residues (Lys 568 and Lys 574) and the main chain nitrogen of Arg 569. Superposition of the T-state structure shows that were the PLPP to be incorporated into the T-state structure there would be a close contact with the 280s loop (residues 282-285) that would encourage the T to R allosteric transition. The second phosphate of the PLPP occupies a site that is distinct from other dianionic binding sites that have been observed for glucose-1-phosphate and sulfate (in the R state) and for heptulose-2-phosphate (in the T state). The results indicate mobility in the dianion recognition site, and the precise position is dependent on other linkages to the dianion. In the modified cofactor the second phosphate site is constrained by the covalent link to the first phosphate of PLPP. The observed position in the crystal suggests that it is too far from the substrate site to represent a site for catalysis. PMID:1304390

  13. Glucopyranosylidene-spiro-iminothiazolidinone, a new bicyclic ring system: synthesis, derivatization, and evaluation for inhibition of glycogen phosphorylase by enzyme kinetic and crystallographic methods.

    PubMed

    Czifrák, Katalin; Páhi, András; Deák, Szabina; Kiss-Szikszai, Attila; Kövér, Katalin E; Docsa, Tibor; Gergely, Pál; Alexacou, Kyra-Melinda; Papakonstantinou, Maria; Leonidas, Demetres D; Zographos, Spyros E; Chrysina, Evangelia D; Somsák, László

    2014-08-01

    The reaction of thiourea with O-perbenzoylated C-(1-bromo-1-deoxy-?-D-glucopyranosyl)formamide gave the new anomeric spirocycle 1R-1,5-anhydro-D-glucitol-spiro-[1,5]-2-imino-1,3-thiazolidin-4-one. Acylation and sulfonylation with the corresponding acyl chlorides (RCOCl or RSO?Cl where R=tBu, Ph, 4-Me-C?H?, 1- and 2-naphthyl) produced the corresponding 2-acylimino- and 2-sulfonylimino-thiazolidinones, respectively. Alkylation by MeI, allyl-bromide and BnBr produced mixtures of the respective N-alkylimino- and N,N'-dialkyl-imino-thiazolidinones, while reactions with 1,2-dibromoethane and 1,3-dibromopropane furnished spirocyclic 5,6-dihydro-imidazo[2,1-b]thiazolidin-3-one and 6,7-dihydro-5H-thiazolidino[3,2-a]pyrimidin-3-one, respectively. Removal of the O-benzoyl protecting groups by the Zemplén protocol led to test compounds most of which proved micromolar inhibitors of rabbit muscle glycogen phosphorylase b (RMGPb). Best inhibitors were the 2-benzoylimino- (Ki=9?M) and the 2-naphthoylimino-thiazolidinones (Ki=10 ?M). Crystallographic studies of the unsubstituted spiro-thiazolidinone and the above most efficient inhibitors in complex with RMGPb confirmed the preference and inhibitory effect that aromatic (and especially 2-naphthyl) derivatives show for the catalytic site promoting the inactive conformation of the enzyme. PMID:25009003

  14. Topographic and crystallographic characterization of a grazing-ion-bombarded GaAs(110) surface by time-of-flight ion-scattering spectrometry

    SciTech Connect

    Gayone, J.E.; Pregliasco, R.G.; Gomez, G.R.; Sanchez, E.A.; Grizzi, O. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica and Consejo Nacional de Investigaciones Cientificas y Tecnicas, 8400 San Carlos de Bariloche, Rio Negro (Argentina)] [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica and Consejo Nacional de Investigaciones Cientificas y Tecnicas, 8400 San Carlos de Bariloche, Rio Negro (Argentina)

    1997-08-01

    We studied the topography and the atomic structure of a clean GaAs(110) surface by time-of-flight ion-scattering spectrometry (TOF-ISS). In a first series of measurements the surface was cleaned by standard cycles of ion bombardment and annealing (500 eV Ar{sup +}, 500{degree}C). This method was very efficient to remove surface contaminants but not to smooth out the damage produced in TOF-ISS experiments. A cleaning method consisting of grazing bombardment with 20 keV Ar{sup +} combined with annealing at 500{degree}C resulted in a clear improvement of the surface flatness. This was confirmed by measurements of electron energy distributions recorded under grazing proton bombardment and by a topographical analysis with an atomic force microscope. The crystallographic structure of the grazing ion bombarded surface was then studied by TOF-ISS. The quasisingle backscattered intensity measured for 5 keV Ne{sup +} presented strong variations with the incident and azimuthal angles which are consistent with the generally accepted relaxed GaAs(110) surface. From the comparison of critical angles measured and focusing regions calculated with a code recently developed we have obtained an As-Ga first interlayer spacing {Delta}Z=(0.66{plus_minus}0.08){Angstrom}, and the spacings between the first and second As layers {Delta}Z{sub 1,2}{sup As}=(2.25{plus_minus}0.08) {Angstrom} and between the first and second Ga layers {Delta}Z{sub 1,2}{sup Ga}=(1.57{plus_minus}0.1) {Angstrom}. {copyright} {ital 1997} {ital The American Physical Society}

  15. Purification, crystallization and preliminary crystallographic analysis of soybean mature glycinin A1bB2

    PubMed Central

    Prak, Krisna; Mikami, Bunzo; Itoh, Takafumi; Fukuda, Takako; Maruyama, Nobuyuki; Utsumi, Shigeru

    2013-01-01

    Glycinin is one of the most abundant storage-protein molecules in soybean seeds and is composed of five subunits (A1aB1b, A1bB2, A2B1a, A3B4 and A5A4B3). A1bB2 was purified from a mutant soybean cultivar containing glycinin composed of only A5A4B3 and A1bB2. At 281?K the protein formed hexagonal, rectangular and rod-shaped crystals in the first [0.1?M imidazole pH 8.0, 0.2?M MgCl2, 35%(v/v) MPD], second [0.1?M sodium citrate pH 5.6, 0.2?M ammonium acetate, 30%(v/v) MPD] and third (0.1?M phosphate–citrate pH 4.2, 2.0?M ammonium sulfate) crystallization conditions, respectively. X-ray diffraction data were collected to resolutions of 1.85, 1.85 and 2.5?Å from crystals of the three different shapes. The crystals belonged to space groups P6322, P21 and P1, with unit-cell parameters a = b = 143.60, c = 84.54?Å, a = 114.54, b = 105.82, c = 116.67?Å, ? = 94.99° and a = 94.45, b = 94.96, c = 100.66?Å, ? = 107.02, ? = 108.44, ? = 110.71°, respectively. One, six and six subunits of A1bB2 were estimated to be present in the respective asymmetric units. The three-dimensional structure of the A1bB2 hexamer is currently being determined. PMID:23908048

  16. Crystallographic analysis of the Arabidopsis thaliana BAG5-calmodulin protein complex.

    PubMed

    Cui, Boyang; Fang, Shasha; Xing, Yangfei; Shen, Yuequan; Yang, Xue

    2015-07-01

    Arabidopsis thaliana BAG5 (AtBAG5) belongs to the plant BAG (Bcl-2-associated athanogene) family that performs diverse functions ranging from growth and development to abiotic stress and senescence. BAG family members can act as nucleotide-exchange factors for heat-shock protein 70 (Hsp70) through binding of their evolutionarily conserved BAG domains to the Hsp70 ATPase domain, and thus may be involved in the regulation of chaperone-mediated protein folding in plants. AtBAG5 is distinguished from other family members by the presence of a unique IQ motif adjacent to the BAG domain; this motif is specific for calmodulin (CaM) binding, indicating a potential role in the plant calcium signalling pathway. To provide a better understanding of the IQ motif-mediated interaction between AtBAG5 and CaM, the two proteins were expressed and purified separately and then co-crystallized together. Diffraction-quality crystals of the complex were grown using the sitting-drop vapour-diffusion technique from a condition consisting of 0.1?M Tris-HCl pH 8.5, 2.5?M ammonium sulfate. The crystals belonged to space group P212121, with unit-cell parameters a = 64.56, b = 74.89, c = 117.09?Å. X-ray diffraction data were recorded to a resolution of 2.5?Å from a single crystal using synchrotron radiation. Assuming the presence of two molecules in the asymmetric unit, a Matthews coefficient of 2.44?Å(3)?Da(-1) was calculated, corresponding to a solvent content of approximately 50%. PMID:26144232

  17. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

    E-print Network

    Christian, Eric

    NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 1 Reuse Working Group Breakout #4 ­ Reuse Readiness;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 2 Overview of RRLs #12;NATIONAL AERONAUTICS AND SPACE in a laboratory; for example, an application tested with simulated inputs. #12;NATIONAL AERONAUTICS AND SPACE

  18. Biochemical and Crystallographic Analysis of Substrate Binding and Conformational Changes in Acetyl-CoA Synthetase

    SciTech Connect

    Reger,A.; Carney, J.; Gulick, A.

    2007-01-01

    The adenylate-forming enzymes, including acyl-CoA synthetases, the adenylation domains of non-ribosomal peptide synthetases (NRPS), and firefly luciferase, perform two half-reactions in a ping-pong mechanism. We have proposed a domain alternation mechanism for these enzymes whereby, upon completion of the initial adenylation reaction, the C-terminal domain of these enzymes undergoes a 140{sup o} rotation to perform the second thioester-forming half-reaction. Structural and kinetic data of mutant enzymes support this hypothesis. We present here mutations to Salmonella enterica acetyl-CoA synthetase (Acs) and test the ability of the enzymes to catalyze the complete reaction and the adenylation half-reaction. Substitution of Lys609 with alanine results in an enzyme that is unable to catalyze the adenylate reaction, while the Gly524 to leucine substitution is unable to catalyze the complete reaction yet catalyzes the adenylation half-reaction with activity comparable to the wild-type enzyme. The positions of these two residues, which are located on the mobile C-terminal domain, strongly support the domain alternation hypothesis. We also present steady-state kinetic data of putative substrate-binding residues and demonstrate that no single residue plays a dominant role in dictating CoA binding. We have also created two mutations in the active site to alter the acyl substrate specificity. Finally, the crystallographic structures of wild-type Acs and mutants R194A, R584A, R584E, K609A, and V386A are presented to support the biochemical analysis.

  19. Tricalcium aluminate hydration in additivated systems. A crystallographic study by SR-XRPD

    SciTech Connect

    Merlini, Marco [Dipartimento di Scienze della Terra 'Ardito Desio', Universita degli Studi di Milano, via Botticelli, 23, I-20133 Milan (Italy)], E-mail: marco.merlini@unimi.it; Artioli, Gilberto [Dipartimento di Scienze della Terra 'Ardito Desio', Universita degli Studi di Milano, via Botticelli, 23, I-20133 Milan (Italy); Cerulli, Tiziano; Cella, Fiorenza; Bravo, Anna [Mapei S.p.A, Lab. Ricerca e sviluppo, Via Cafiero 22, I-20158 Milan (Italy)

    2008-04-15

    Synchrotron radiation X-ray powder diffraction has been used to monitor the evolution of ettringite in C3A-gypsum synthetic mixture and in commercial cement systems during the first hours of the hydration process. The hydration of the paste was achieved using a remote controlled system, in order to collect data as soon as water is added to the system. The use of full-profile Rietveld method during the analysis of the diffractograms collected allowed us to monitor the evolution of phases weight fraction. The rigorous measurement of the lattice parameters and of the diffraction peak shape proved to be very useful to obtain information on the structural evolution of ettringite and on the mean grain size of the crystal phases. Depending on the admixture added to the system, the precipitation of well crystalline ettringite takes some hours. During this 'induction' period we observe a significant variation of a and c lattice parameter values for ettringite. In particular a increases from 11.8 A to 11.24 A, the value for pure ettringite. The c parameter decreases from 22 A to 21.48 A. The lattice parameter variation could be related to small crystallite size effect, but the large variation more likely reflects also crystallographic changes, such as defect re-organization during the nucleation and growth process or also changes in the SO{sub 3} and H{sub 2}O content in the ettringite channel. Not surprisingly the amount and the grain dimensions of crystalline ettringite are affected by the chemistry of the system. We observed the same evolution trend during ettringite formation also in shrinkage-compensating commercial cements (composed by mixture of Ca-Al cements, Portland cement and bassanite), in which ettringite is the main hydrous phase present.

  20. Crystallographic, Kinetic, and Spectroscopic Study of the First Ligninolytic Peroxidase Presenting a Catalytic Tyrosine*

    PubMed Central

    Miki, Yuta; Calviño, Fabiola R.; Pogni, Rebecca; Giansanti, Stefania; Ruiz-Dueñas, Francisco J.; Martínez, María Jesús; Basosi, Riccardo; Romero, Antonio; Martínez, Angel T.

    2011-01-01

    Trametes cervina lignin peroxidase (LiP) is a unique enzyme lacking the catalytic tryptophan strictly conserved in all other LiPs and versatile peroxidases (more than 30 sequences available). Recombinant T. cervina LiP and site-directed variants were investigated by crystallographic, kinetic, and spectroscopic techniques. The crystal structure shows three substrate oxidation site candidates involving His-170, Asp-146, and Tyr-181. Steady-state kinetics for oxidation of veratryl alcohol (the typical LiP substrate) by variants at the above three residues reveals a crucial role of Tyr-181 in LiP activity. Moreover, assays with ferrocytochrome c show that its ability to oxidize large molecules (a requisite property for oxidation of the lignin polymer) originates in Tyr-181. This residue is also involved in the oxidation of 1,4-dimethoxybenzene, a reaction initiated by the one-electron abstraction with formation of substrate cation radical, as described for the well known Phanerochaete chrysosporium LiP. Detailed spectroscopic and kinetic investigations, including low temperature EPR, show that the porphyrin radical in the two-electron activated T. cervina LiP is unstable and rapidly receives one electron from Tyr-181, forming a catalytic protein radical, which is identified as an H-bonded neutral tyrosyl radical. The crystal structure reveals a partially exposed location of Tyr-181, compatible with its catalytic role, and several neighbor residues probably contributing to catalysis: (i) by enabling substrate recognition by aromatic interactions; (ii) by acting as proton acceptor/donor from Tyr-181 or H-bonding the radical form; and (iii) by providing the acidic environment that would facilitate oxidation. This is the first structure-function study of the only ligninolytic peroxidase described to date that has a catalytic tyrosine. PMID:21367853