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1

Tables of crystallographic properties of magnetic space groups.  

PubMed

Tables of crystallographic properties of the reduced magnetic superfamilies of space groups, i.e. the 7 one-dimensional, 80 two-dimensional and 1651 three-dimensional group types, commonly referred to as magnetic space groups, are presented. The content and format are similar to that of non-magnetic space groups and subperiodic groups given in International Tables for Crystallography. Additional content for each representative group of each magnetic space-group type includes a diagram of general positions with corresponding general magnetic moments, Seitz notation used as a second notation for symmetry operations, and general and special positions listed with the components of the corresponding magnetic moments allowed by symmetry. PMID:18421131

Litvin, D B

2008-04-18

2

Crystallographic Groups, Groupoids, and Orbifolds  

SciTech Connect

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.

Johnson, C.K.

2000-09-11

3

Tabulation of irreducible representations of the crystallographic space groups and their superspace extensions.  

PubMed

New tables of irreducible representations (IRs) are introduced for the 230 crystallographic space groups (SGs) in three-dimensional space, at both special and non-special k vectors, and for their extensions to (3 + d)-dimensional superspace (`superspace-extended SGs' or SSESGs). Neither a tabulation of SG IR matrices for non-special k vectors nor a tabulation of SSESG IR matrices for d > 1 have been previously published. These tabulations are made possible by a new form in which the IR matrices of SGs are separated as a product of a translation part T and a point-operation part P, and where the IR matrices of SSESGs are separated as a product of a phase-shift part Q and a point-operation part P(s). Both T and Q have a simple prescribed form that does not need to be tabulated. Also, the new IR matrices are in a convenient block form which allows one to see by inspection which parts of the matrices and the associated order parameters belong to which arm of the star of k. In addition to complex IR matrices, real physically irreducible representation (PIR) matrices are tabulated. The new IR and PIR tables are available on the ISO-IR website (http://stokes.byu.edu/iso/irtables.php) in both convenient human-readable and computer-readable forms. PMID:23778095

Stokes, Harold T; Campbell, Branton J; Cordes, Ryan

2013-05-08

4

On subgroups of crystallographic Coxeter groups.  

PubMed

A framework is presented based on color symmetry theory that will facilitate the determination of the subgroup structure of a crystallographic Coxeter group. It is shown that the method may be extended to characterize torsion-free subgroups. The approach is to treat these groups as groups of symmetries of tessellations in space by fundamental polyhedra. PMID:23778102

Provido, Eden Delight B; De Las Peñas, Ma Louise Antonette N; Felix, Rene P

2013-06-18

5

Structure solution of network materials by solid-state NMR without knowledge of the crystallographic space group.  

PubMed

An algorithm is presented for solving the structures of silicate network materials such as zeolites or layered silicates from solid-state (29)Si double-quantum NMR data for situations in which the crystallographic space group is not known. The algorithm is explained and illustrated in detail using a hypothetical two-dimensional network structure as a working example. The algorithm involves an atom-by-atom structure building process in which candidate partial structures are evaluated according to their agreement with Si-O-Si connectivity information, symmetry restraints, and fits to (29)Si double quantum NMR curves followed by minimization of a cost function that incorporates connectivity, symmetry, and quality of fit to the double quantum curves. The two-dimensional network material is successfully reconstructed from hypothetical NMR data that can be reasonably expected to be obtained for real samples. This advance in "NMR crystallography" is expected to be important for structure determination of partially ordered silicate materials for which diffraction provides very limited structural information. PMID:23415450

Brouwer, Darren H

2013-01-30

6

Physical applications of crystallographic color groups: Landau theory of phase transitions  

NASA Astrophysics Data System (ADS)

The simplest crystallographic color groups are the permutational color groups. Elements of these groups combine two types of transformations: One is a rotation and/or translation of physical space and the other is a permutation. The groups considered here are subgroups of direct products and abstractly isomorphic to crystallographic groups, hence their relative simplicity. Despite this simplicity, there is a richness of information contained in each such group. The group symbol GP?GH'H(A, A')n conveys the following: the isomorphic crystallographic group G, a subgroup H' of G, the largest normal subgroup H of G, contained in H', and a transitive group of permutations P?(A, A')n isomorphic to the factor group GH. We derive and tabulate here all classes of equivalent permutational color point groups using a definition of equivalence classes which we physically motivate. For applications we require and report here the permutation representation DH'G of G associated with each GP and we reduce DH'G into irreducible components. The major application given here is to the Landau theory of symmetry change in continuous phase transitions. A complete set of tables is presented for all allowed equitranslational ("Zellengleich" or k=0) phase transitions in crystals based on group-theoretical criteria, including a new "kernel-core" criterion. The tables may be used to determine all active representations for transitions between two specific groups or alternatively, all possible subgroups which can be obtained from a specific group and irreducible representation. We also relate two classifications schemes for phase transitions to the structure of permutational color groups.

Litvin, D. B.; Kotzev, J. N.; Birman, J. L.

1982-12-01

7

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.

8

Complete derivation of space groups of magnetic symmetry of crystals by numerical construction  

SciTech Connect

The solution is given to the problem regarding the derivation of the so-called space groups of magnetic symmetry with crystallographic angles of rotation of the spin vector, which was formulated as far back as the early 1970s. The crystallographic P-symmetries that should be used in the generalization with the three-dimensional space Fedorov groups G{sub 3} are revealed. The space groups G{sub 3} are generalized with each of these P-symmetries.

Palistrant, A. F. [State University of Moldova (Moldova, Republic of)], E-mail: mepalistrant@yandex.ru

2007-11-15

9

FUNDAMENTAL GROUPS AND COVERING SPACES  

Microsoft Academic Search

In this paper, I will briefly develop the theory of fundamental groups and covering spaces of topological spaces. Then I will point toward the manner in which covering spaces can be used prove some cool things in group theory. I presume a cursory knowledge of topological spaces—open and closed sets, continuous functions, and homeomorphisms should be enough background knowledge.

ETHAN JERZAK

10

Improved Monte Carlo sampling in a real space approach to the crystallographic phase problem  

NASA Astrophysics Data System (ADS)

A real space approach has been proposed to solve the x-ray phase problem formulated as a minimization problem. The cost function consists of two parts: one represents the usual crystallographical residual while the other enforces the probability distribution of the invariant phase triplets. Starting from a random real space structure, the atoms are moved one by one to gradually reduce the cost function (simulated annealing). In addition, the atoms are encouragd to preferentially sample the high density regions in space determined by an approximate density map which in turn is updated and modified by averaging and Fourier synthesis. Such a reduction of the configurational space has led to considerable improvement of the algorithm compared to an earlier version. Trial calculations for structures including hexadecaisoleucinomycin (HEXIL) and a collagenlike peptide (PPG) are presented.

Liu, Xiangan; Su, W. P.

2002-12-01

11

Hazy Spaces, Tangent Spaces, Manifolds and Groups.  

National Technical Information Service (NTIS)

The results on hazy spaces and the developments leading to hazy manifolds and groups are summarized. Proofs have appeared elsewhere so here examples are considered and some motivation for definitions and constructions in the theorems is analyzed. It is sh...

C. T. J. Dodson

1977-01-01

12

Affine extensions of non-crystallographic Coxeter groups induced by projection  

NASA Astrophysics Data System (ADS)

In this paper, we show that affine extensions of non-crystallographic Coxeter groups can be derived via Coxeter-Dynkin diagram foldings and projections of affine extended versions of the root systems E8, D6, and A4. We show that the induced affine extensions of the non-crystallographic groups H4, H3, and H2 correspond to a distinguished subset of those considered in [P.-P. Dechant, C. Bœhm, and R. Twarock, J. Phys. A: Math. Theor. 45, 285202 (2012)]. This class of extensions was motivated by physical applications in icosahedral systems in biology (viruses), physics (quasicrystals), and chemistry (fullerenes). By connecting these here to extensions of E8, D6, and A4, we place them into the broader context of crystallographic lattices such as E8, suggesting their potential for applications in high energy physics, integrable systems, and modular form theory. By inverting the projection, we make the case for admitting different number fields in the Cartan matrix, which could open up enticing possibilities in hyperbolic geometry and rational conformal field theory.

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

2013-09-01

13

Magnetic space-group types.  

PubMed

The interpretation of Opechowski-Guccione symbols for magnetic space-group types is based on coordinate triplets given in the now superceded International Tables for X-ray Crystallography [(1952), Vol. 1, edited by N. F. M. Henry & K. Lonsdale. Birmingham: Kynoch Press]. Changes to coordinate triplets in International Tables for Crystallography [(1983), Vol. A, edited by Th. Hahn. Dordrecht: Kluwer Academic Publishers] lead to misinterpretations of these symbols. A list is provided here of Opechowski-Guccione symbols for the 1651 magnetic space-group types with their original definitions given independent of International Tables. PMID:11679704

Litvin, D B

2001-10-26

14

Crystallographic topology and its applications  

SciTech Connect

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.

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

15

Space Interferometry Science Working Group  

NASA Astrophysics Data System (ADS)

Decisions taken by the astronomy and astrophysics survey committee and the interferometry panel which lead to the formation of the Space Interferometry Science Working Group (SISWG) are outlined. The SISWG was formed by the NASA astrophysics division to provide scientific and technical input from the community in planning for space interferometry and in support of an Astrometric Interferometry Mission (AIM). The AIM program hopes to measure the positions of astronomical objects with a precision of a few millionths of an arcsecond. The SISWG science and technical teams are described and the outcomes of its first meeting are given.

Ridgway, Stephen T.

1992-12-01

16

The space groups of icosahedral quasicrystals and cubic, orthorhombic, monoclinic, and triclinic crystals  

NASA Astrophysics Data System (ADS)

In 1962 Bienenstock and Ewald described a simple and systematic method for computing all the crystallographic space groups in Fourier space. Their approach is reformulated and further simplified, starting from the definition of the point group of a structure as the set of operations that take it into something indistinguishable and not merely identical to within a translation. The reformulation does not require periodicity, making it possible to define and compute on an equal footing the space groups for crystals, quasicrystals, and incommensurately modulated structures, without having to digress into the crystallography of unphysically many dimensions, and using only simple geometry and the most elementary properties of symmetry groups. The general scheme is illustrated by a unified computation of all the icosahedral, cubic, orthorhombic, monoclinic, and triclinic space groups. The remaining (axial) crystallographic and quasicrystallographic space groups have been discussed in a companion paper.

Mermin, N. David

1992-01-01

17

Automorphisms of Free Groups and Outer Space  

Microsoft Academic Search

This is a survey of recent results in the theory of automorphism groups of finitely-generated free groups, concentrating on results obtained by studying actions of these groups on Outer space and its variations.

Karen Vogtmann

2002-01-01

18

Quantum Symmetry Groups of Finite Spaces  

Microsoft Academic Search

We determine the quantum automorphism groups of finite spaces. These are compact matrix quantum groups in the sense of Woronowicz. Dedicated to Marc A. Rieffel on the occasion of his sixtieth birthday

Shuzhou Wang; Marc A. Rieffel

1998-01-01

19

Concept of a multimetrical space group  

NASA Astrophysics Data System (ADS)

A multimetrical space group G is the symmetry group of a pattern having lattice periodicity in an affine space made multimetrical by attaching to it a set of metrics of different signature. The Euclidean metric tensor is always supposed to be a member of the set. The point group K of G is generated by elements leaving the lattice invariant and transforming some of the metric tensors of the set into another one of the same set. When the pattern describes a crystal structure in the point-atom approximation, the Euclidean subgroup G0 of G is the space group of the crystal. When the pattern is defined in superspace, i.e., is obtained by the embedding of a quasicrystal structure (as in the cut-projection method), the subgroup GSR of G leaving the (lower-dimensional) physical space invariant is the scale-space group of the quasicrystal.

Janner, A.

1991-06-01

20

Space transformation for understanding group movement.  

PubMed

We suggest a methodology for analyzing movement behaviors of individuals moving in a group. Group movement is analyzed at two levels of granularity: the group as a whole and the individuals it comprises. For analyzing the relative positions and movements of the individuals with respect to the rest of the group, we apply space transformation, in which the trajectories of the individuals are converted from geographical space to an abstract 'group space'. The group space reference system is defined by both the position of the group center, which is taken as the coordinate origin, and the direction of the group's movement. Based on the individuals' positions mapped onto the group space, we can compare the behaviors of different individuals, determine their roles and/or ranks within the groups, and, possibly, understand how group movement is organized. The utility of the methodology has been evaluated by applying it to a set of real data concerning movements of wild social animals and discussing the results with experts in animal ethology. PMID:24051783

Andrienko, Natalia; Andrienko, Gennady; Barrett, Louise; Dostie, Marcus; Henzi, Peter

2013-12-01

21

Crystallographic oxide phase identification of char deposits obtained from space shuttle Columbia window debris  

NASA Astrophysics Data System (ADS)

Char deposits on recovered fragments of space shuttle Columbia windowpanes were analyzed to further understand the events that occurred during orbiter reentry and breakup. The TEM analysis demonstrated that 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, indicated that temperatures well above the Ti melt point were experienced. The stratified observations implied that additional exothermic reactions, expectedly metal combustion of a Ti-6Al-4V structure, had to occur for oxide formation. Results are significant for aerospace vehicles, where thermal protection system (TPS) breaches could cause material originally designed for substructural applications to be in direct path with reentry plasma.

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

2010-09-01

22

GroupSpace 0.2.0  

NSDL National Science Digital Library

The Internet can serve as a communal gathering place, where like-minded community members can come together to discuss various pressing issues, share documents, take polls, and engage in the decision-making process as well. A recent project, GroupSpace, started at Stanford University as part of a research partnership with a local community organization, allows groups of individuals to do all of the above. As their mission statement suggests, the creation of the program is Âto support the type of deliberation critical to the functioning of smaller, informal organizations in civil societyÂ. It should be noted that this version of GroupSpace is a beta version.

23

Quantum group gauge theory on quantum spaces  

Microsoft Academic Search

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.

Thomasz Brzezinski; Shahn Majid

1993-01-01

24

Symmetrized plane waves: 3. nonsymmorphic space groups  

NASA Astrophysics Data System (ADS)

A procedure for systematically constructing symmetrized plane waves, or more generally, arbitrary Bloch-functions, is extended to the case of nonsymmorphic space groups. The technical part to compute those transformations coefficients that are necessary to determine symmetrized plane waves or Bloch-functions, is transferred to a correspondingly tailored software package.

Dirl, R.; Payer, K.; Davies, B. L.

1996-10-01

25

Fourier-Space Crystallography as Group Cohomology  

NASA Astrophysics Data System (ADS)

David Mermin has argued persuasively that the theoretical significance of quasicrystals lies not so much in relaxing the requirement of periodicity as in replacing exact identity of a density function (e.g., electronic or mass) under symmetry operations with indistinguishability of correlation functions, as expressed in Fourier space.(N.D. Mermin, Phys. Stat. Sol. (a) 151), 275 (1995) and references. After reviewing the formalism of Fourier-space crystallography (phase functions and gauge transformations), we present a new formulation in the language of cohomology of groups. First we reexpress the classification of space groups in terms of a first cohomology group; we then show how recent work by König and Mermin(A. König and N.D. Mermin, Am. J. Phys. 68), 525 (2000). on band sticking in nonsymmorphic crystals derives naturally from a first homology group and discuss its connection to a second cohomology group. The new language lets us prove generally several theorems previously known only in special cases. Finally, we let the listener decide whether we're just ``speaking prose.''(N.D. Mermin, Rev. Mod. Phys. 64), 3 (1992).

Rabson, David; Fisher, Benji

2001-03-01

26

Conformational isomerism and effect of complexation on carboxylate group in two crystallographically independent coordination units of trans-di(4-chlorobenzoato- O)bis(1,3-diaminopropane- N, N?)cobalt(III) 4-chlorobenzoate dihydrate  

Microsoft Academic Search

The crystal and molecular structure of the title compound was determined by single crystal X-ray methods. The compound crystallises in the triclinic system, space group P1 (No. 2, a=10.477(3), b=12.309(2), c=13.420(3() A?, ?=85.40(2), ?=78.39(2), ?=71.46(2)°, Z=2, Dc=1.47, Dm-1.46(10 g cm?3. The final R value for 4415 reflections was 0.038 (Rw=0.033, 1\\/?2 weoghts). The structure consists of two crystallographically independent complex

Markku R. Sundberg; Rolf Uggla; Raikko Kivekäs

1995-01-01

27

Einstein Spaces with a Conformal Group  

Microsoft Academic Search

.  The pseudo-Riemannian Einstein spaces with a (local or global) conformal group of strictly positive dimension can be classified.\\u000a In this article we give a straightforward and systematic proof. As a common generalization, this includes the global theorem\\u000a of Yano and Nagano in the Riemannian case (1959, published in the Annals of Mathematics) and a pseudo-Riemannian analogue\\u000a proved by Kerckhove in

Wolfgang Kühnel; Hans-Bert Rademacher

2009-01-01

28

Report of a subcommittee on the nomenclature of n-dimensional crystallography. II. Symbols for arithmetic crystal classes, Bravais classes and space groups.  

PubMed

The Second Report of the Subcommittee on the Nomenclature of n-Dimensional Crystallography recommends specific symbols for R-irreducible groups in 4 and higher dimensions (nD), for centrings, for Bravais classes, for arithmetic crystal classes and for space groups (space-group types). The relation with higher-dimensional crystallographic groups used for the description of aperiodic crystals is briefly discussed. The Introduction discusses the general definitions used in the Report. PMID:12388880

Janssen, T; Birman, J L; Dénoyer, F; Koptsik, V A; Verger-Gaugry, J L; Weigel, D; Yamamoto, A; Abrahams, S C; Kopsky, V

2002-11-01

29

Cell Groups Reveal Structure of Stimulus Space  

PubMed Central

An important task of the brain is to represent the outside world. It is unclear how the brain may do this, however, as it can only rely on neural responses and has no independent access to external stimuli in order to “decode” what those responses mean. We investigate what can be learned about a space of stimuli using only the action potentials (spikes) of cells with stereotyped—but unknown—receptive fields. Using hippocampal place cells as a model system, we show that one can (1) extract global features of the environment and (2) construct an accurate representation of space, up to an overall scale factor, that can be used to track the animal's position. Unlike previous approaches to reconstructing position from place cell activity, this information is derived without knowing place fields or any other functions relating neural responses to position. We find that simply knowing which groups of cells fire together reveals a surprising amount of structure in the underlying stimulus space; this may enable the brain to construct its own internal representations.

2008-01-01

30

Actuator grouping optimization on flexible space reflectors  

NASA Astrophysics Data System (ADS)

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 accuracy, precision surface control is needed on these lightweight reflectors. While studies have shown that domain control of space reflectors via Polyvinylidene Fluoride (PVDF) actuators is promising, the challenge is to realistically control a large number of distributed actuators with limited number of power supplies. In this research, a new En Mass Elimination method is synthesized to determine the optimal grouping of actuators when the actuator number exceeds the number of power supplies available. An analytical model is developed and the methodology is demonstrated numerically through system simulation on the derived model.

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

2011-03-01

31

Space Station Group Activities Habitability Module Study.  

National Technical Information Service (NTIS)

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 Re...

D. Nixon

1986-01-01

32

Homothety groups in space-time  

NASA Astrophysics Data System (ADS)

This paper investigates space-times which admit anr-dimensional Lie algebra of homothetic vector fields at least one of which is proer homothetic. The situation is resolved completely ifr ? 6 and some general results are given whenr ? 5. Some applications to the study of affine vector fields in space-times are also given and the maximum dimension of this latter algebra is computed and corrects an earlier error.

Hall, G. S.; Steele, J. D.

1990-04-01

33

Actuator grouping optimization on flexible space reflectors  

Microsoft Academic Search

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 accuracy, precision surface control is needed on these lightweight reflectors. While studies have shown that domain control of space reflectors via Polyvinylidene Fluoride (PVDF) actuators is promising, the challenge is to realistically control

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

2011-01-01

34

Meeting of intercosmos space physics group  

Microsoft Academic Search

The 22nd meeting of scientists and specialists of Socialist countries in the Intercosmos program was held in April 1988, in Tbilisi. Taking part in the meeting were well-known Soviet scientists and major foreign specialists from Bulgaria, Hungary, GDR, Cuba, Mongolia, Poland, Rumania, and Czechoslovakia. The meeting focused on a plan for collaboration in space physics for the 1991 to 1995

N. A. Frolova

1989-01-01

35

Interactive 3D Space Group Visualization with CLUCalc and the Clifford Geometric Algebra Description of Space Groups  

Microsoft Academic Search

.  A new interactive software tool is described, that visualizes 3D space group symmetries. The software computes with Clifford\\u000a (geometric) algebra. The space group visualizer (SGV) originated as a script for the open source visual CLUCalc, which fully\\u000a supports geometric algebra computation.\\u000a \\u000a \\u000a Selected generators (Hestenes and Holt, JMP, 2007) form a multivector generator basis of each space group. The approach corresponds

Eckhard Hitzer; Christian Perwass

2010-01-01

36

Optimization of Drilled Shaft Group Spacing.  

National Technical Information Service (NTIS)

The report presents a summary of findings from an assessment of the technical literature, experience of engineers, and unpublished reports on lateral loads on pile groups. Specific interest is adopted in the design methods for drilled shafts, in particula...

B. Douthitt D. N. Frechette K. D. Walsh S. L. Houston W. N. Houston

1999-01-01

37

Moduli space of many BPS monopoles for arbitrary gauge groups  

Microsoft Academic Search

We study the moduli space for an arbitrary number of BPS monopoles in a gauge theory with an arbitrary gauge group that is maximally broken to U(1)k. From the low energy dynamics of well-separated dyons we infer the asymptotic form of the metric for the moduli space. For a pair of distinct fundamental monopoles, the space thus obtained is R3×(R1×M0)\\/Z,

Kimyeong Lee; Erick J. Weinberg; Piljin Yi

1996-01-01

38

Octonionic Hilbert spaces, the Poincare´ group and SU(3)  

Microsoft Academic Search

A formalism based on real octonions is developed in order to construct an octonionic Hilbert space for the description of colored quark states. The various possible forms of scalar products and related scalars are discussed. The choice of a direction in the space of octonion units leads naturally to a representation of the Poincare´ group in terms of complex scalar

1976-01-01

39

Octonionic Hilbert spaces, the Poincaré group and SU(3)  

Microsoft Academic Search

A formalism based on real octonions is developed in order to construct an octonionic Hilbert space for the description of colored quark states. The various possible forms of scalar products and related scalars are discussed. The choice of a direction in the space of octonion units leads naturally to a representation of the Poincaré group in terms of complex scalar

Murat Günaydin

1976-01-01

40

Isometric Group Actions on Hilbert Spaces: Growth of Cocycles  

Microsoft Academic Search

.  We study growth of 1-cocycles of locally compact groups, with values in unitary representations. Discussing the existence\\u000a of 1-cocycles with linear growth, we obtain the following alternative for a class of amenable groups G containing polycyclic groups and connected amenable Lie groups: either G has no quasi-isometric embedding into a Hilbert space, or G admits a proper cocompact action on

Yves de Cornulier; Romain Tessera; Alain Valette

2007-01-01

41

Radiological Protection in Space: Indication from the ICRP Task Group  

NASA Astrophysics Data System (ADS)

In 2007 the International Commission on Radiological Protection (ICRP) has established a Task Group (Radiation Protection in Space) dealing with the problems of radiation protection of astronauts in space missions. Its first task is a report on "Assessment of Radiation Exposure of Astronauts in Space". When the ICRP published its general recommendations for radiological protection in 2007 (ICRP Publication 103 following ICRP Publication 60 (1991)) it was obvious that these recommendations do not really consider the special situation of astronauts in space. The radiation field with its high content of charged particles of very high energies strongly differs from usual radiation fields on ground. For example, this has consequences for the assessment of doses in the body of astronauts. The ICRP Task Group has discussed this situation and the presentation will deal with some consequences for the concept of radiation dosimetry and radiological protection in space. This includes e. g. the assessment of organ doses and the application of the effective dose concept with its definition of radiation weighting factors. Radiation quality of high energy heavy ions may be defined different than usually performed on ground. An approach of using the quality factor concept in the definition of an "effective dose" is favored for application in space missions similar to the method proposed in NCRP Report 142. New data calculated on the basis of the reference anthropomorphic voxel phantoms recommended by ICRP support this procedure. Individual dosimetry is a further subject of discussion in the Task Group. While the operational dose equivalent quantities generally in use in radiation protection on ground are not helpful for applications in space, different procedures of the assessment of organ and effective doses are applied. The Task Group is dealing with this situation.

Dietze, Günther

42

Octonionic Hilbert spaces, the Poincare group and SU(3). [scalars, Poincare group, real octonions, colored states  

Microsoft Academic Search

A formalism based on real octonions is developed in order to construct an octonionic Hilbert space for the description of colored quark states. The various possible forms of scalar products and related scalars are discussed. The choice of a direction in the space of octonion units leads naturally to a representation of the Poincare group in terms of complex scalar

Gunaydin

1976-01-01

43

Group Action Recognition Using Space-Time Interest Points  

Microsoft Academic Search

Group action recognition is a challenging task in computer vision due to the large complexity induced by multiple motion patterns.\\u000a This paper aims at analyzing group actions in video clips containing several activities. We combine the probability summation\\u000a framework with the space-time (ST) interest points for this task. First, ST interest points are extracted from video clips\\u000a to form the

Qingdi Wei; Xiaoqin Zhang; Yu Kong; Weiming Hu; Haibin Ling

2009-01-01

44

Optical Fiber Assemblies for Space Flight from the NASA Goddard Space Flight Center, Photonics Group  

Microsoft Academic Search

The Photonics Group at NASA Goddard Space Flight Center in the Electrical Engineering Division of the Advanced Engineering and Technologies Directorate has been involved in the design, development, characterization, qualification, manufacturing, integration and anomaly analysis of optical fiber subsystems for over a decade. The group supports a variety of instrumentation across NASA and outside entities that build flight systems. Among

Melanie N. Ott; William Joe; Robert Switzer; Lance Day

45

Topological classification of crystalline insulators with space group symmetry  

SciTech Connect

We show that in crystalline insulators, space group symmetry alone gives rise to a topological classification based on the discretization of electric polarization. Using C3 rotational symmetry as an example, we first prove that the polarization is discretized into three distinct classes, i.e., it can only take three inequivalent values. We then prove that these classes are topologically distinct. Therefore, a Z3 topological classification exists, with polarization as a topological class index. A concrete tight-binding model is derived to demonstrate the Z3 topological phase transition. Using first-principles calculations, we identify graphene on a BN substrate as a possible candidate to realize these Z3 topological states. To complete our analysis, we extend the classification of band structures to all 17 two-dimensional space groups. This work will contribute to a complete theory of symmetry-conserved topological phases and also elucidate topological properties of graphenelike systems.

Jadaun, Priyamvada [University of Texas at Austin; Xiao, Di [Carnegie Mellon University (CMU); Niu, Q. [University of Texas at Austin; Banerjee, Sanjay K. [University of Texas at Austin

2013-01-01

46

Recommendations of the Space Interferometry Science Working Group  

NASA Astrophysics Data System (ADS)

The Space Interferometry Science Working Group (SISWG), soon to be disbanded, has spent four years helping with NASA's entry into space interferometry. The Working Group's initial charge was to help with the selection of the Astrometric Interferometry Mission (AIM) design and to advise on long term interferometry strategy. Events have overtaken the original goals. Programmatic concerns and the Future Mission Concepts reviews resulted in the focus landing on the Orbiting Stellar Interferometer (OSI) design. The rapidly developing roadmap for the detection and characterization of Earth-like planets has created a need for early technology development in interferometry. And the dramatic gains in the fields of adaptive optics and ground-based interferometry have shown that space is not the only location for high-spatial-resolution imaging and spectroscopy. Against this background, the science enabled by a 1000-fold improvement in wide angle positional accuracy (compared to Hipparchus) coupled with the major role in technology development, leaves the Space Interferometry Mission (SIM, an expanded OSI instrument) in a secure role. The narrowly focused, but electrifying science of the nulling IR interferometer/spectrometer designed for the planet search is correspondingly unique and secure. Funding of conceptual studies through the Future Missions Concepts program is allowing a close look at the potential of a mid-IR, 25m baseline, imaging interferometer (the Dilute Lens Imager) and of a widely Separated Spacecraft Interferometer (SSI) designed to test a highly dilute interferometer over baselines of up to 10 km. While not without complications, the birth of optical/IR interferometry in space seems well on schedule.

Peterson, D.

1995-12-01

47

Crystallographic properties of fertilizer compounds  

SciTech Connect

This bulletin is a compilation of crystallographic data collected at NFERC on 450 fertilizer-related compounds. In TVA's fertilizer R and D program, petrographic examination, XRD, and infrared spectroscopy are combined with conventional chemical analysis methods in identifying the individual compounds that occur in fertilizer materials. This handbook brings together the results of these characterization studies and supplemental crystallographic data from the literature. It is in one-compound-per-page, loose-leaf format, ordered alphabetically by IUPAC name. Indexes provided include IUPAC name, formula, group, alternate formula, synonyms, x-ray data, optical data. Tables are given for solids, compounds in commercial MAP and DAP, and matrix materials in phosphate rock.

Frazier, A.W.; Dillard, E.F.; Thrasher, R.D.; Waerstad, K.R.; Hunter, S.R.; Kohler, J.J.; Scheib, R.M.

1991-02-01

48

Groups acting on finite dimensional spaces with finite stabilizers  

Microsoft Academic Search

.   It is shown that every H\\u000a \\u000a -group G of type admits a finite dimensional G-CW-complex X with finite stabilizers and with the additional property that for each finite subgroup H, the fixed point subspace X\\u000a \\u000a \\u000a \\u000a H\\u000a \\u000a is contractible. This establishes conjecture (5.1.2) of [9]. The construction of X involves joining a family of spaces parametrized by the poset of

Peter H. Kropholler; Guido Mislin

1998-01-01

49

Crystallographic metrology and process control  

US Patent & Trademark Office Database

A system (70) for crystallography including a sample holder (74), an electron source (76) for generating an electron beam, and a scanning actuator (80) for controlling the relative movement between the electron beam and the crystalline sample, the scanning actuator being controllable for directing the electron beam at a series of spaced apart points within the sample area. The system also includes an image processor (84) for generating crystallographic data based upon electron diffraction from the crystalline sample and for determining whether sufficient data have been acquired to characterize the sample area. The system further includes a controller (86) for controlling the scanning actuator to space the points apart such that acquired data is representative of a different grains within the crystalline sample. IN other embodiments, the invention includes one or more ion beams (178, 188) for crystallography and a combination ion beam/electron beam (218, 228).

2008-03-11

50

Grouping Miller-Nicely by linear vector space rotations  

NASA Astrophysics Data System (ADS)

Human speech recognition has been studied using response to CV speech stimuli. Miller and Nicely (1955) studied such data in the form of confusion matrices to obtain insight into the psychological structure of the phone in noise. Here, the confusion matrices are modeled as phone coordinates in a high dimensional perceptual vector space. The model generalizes to an eigenvalue decomposition (EVD) [Allen (2004)]. This is followed by agglomerative hierarchical clustering of the transformed data, and an automated process is used to identify the main clusters. The resulting EVD clustering is very similar to other Miller-Nicely groupings, based on both production and MDS derived features, but is more model based. It was found that there is a gradual and highly consistent change in the clustering of sounds, independent of cluster size and configuration. By examining the change in similarity between various speech sounds, it is hoped that perceptual features may be uniquely identified.

Budhlakoti, Suvrat; Allen, Jont B.; Larsen, Erik

2001-05-01

51

LINE-TRANSITIVE AUTOMORPHISM GROUPS OF LINEAR SPACES  

Microsoft Academic Search

A linear space Sfisa. set & of points, together with a set if of distinguished subsets called lines, such that any two points lie on exactly one line. In this paper we shall be concerned with linear spaces in which every line has the same number of points, and we shall call such a system a regular linear space. Moreover,

ALAN R. CAMINA; CHERYL E. PRAEGER

2000-01-01

52

On position-space renormalization group approach to percolation  

NASA Astrophysics Data System (ADS)

In a position-space renormalization group (PSRG) approach to percolation one calculates the probability R(p,b) that a finite lattice of linear size b percolates, where p is the occupation probability of a site or bond. A sequence of percolation thresholds p c (b) is then estimated from R(p c , b)=p c (b) and extrapolated to the limit b?? to obtain p c = p c (?). Recently, it was shown that for a certain spanning rule and boundary condition, R(p c , ?)=R c is universal, and since p c is not universal, the validity of PSRG approaches was questioned. We suggest that the equation R(p c , b)=?, where ? is any number in (0,1), provides a sequence of p c (b)'s that always converges to p c as b??. Thus, there is an envelope from any point inside of which one can converge to p c . However, the convergence is optimal if ?= R c . By calculating the fractal dimension of the sample-spanning cluster at p c , we show that the same is true about any critical exponent of percolation that is calculated by a PSRG method. Thus PSRG methods are still a useful tool for investigating percolation properties of disordered systems.

Sahimi, Muhammad; Rassamdana, Hossein

1995-02-01

53

Structure of delta-Bi2O3 from density functional theory: A systematic crystallographic analysis  

Microsoft Academic Search

A systematic crystallographic analysis of the and vacancy-ordered structure of cubic delta-Bi2O3 obtained from electronic-structure calculations is presented. The ordering of vacancies leads to a doubling of the unit-cell that results in a 2×2×2 fluorite super-structure, with an associated reduction in its space group symmetry from Fm3¯m to Fm3¯. The Bi atoms present inside the vacancy-ordered oxygen sublattice have equal

Dilpuneet S. Aidhy; Susan B. Sinnott; Eric D. Wachsman; Simon R. Phillpot; Juan C. Nino

2009-01-01

54

Structure of ?-Bi 2O 3 from density functional theory: A systematic crystallographic analysis  

Microsoft Academic Search

A systematic crystallographic analysis of the ?110? and ?111? vacancy-ordered structure of cubic ?-Bi2O3 obtained from electronic-structure calculations is presented. The ordering of vacancies leads to a doubling of the unit-cell that results in a 2×2×2 fluorite super-structure, with an associated reduction in its space group symmetry from Fm3¯m to Fm3¯. The Bi atoms present inside the ?111? vacancy-ordered oxygen

Dilpuneet S. Aidhy; Susan B. Sinnott; Eric D. Wachsman; Simon R. Phillpot; Juan C. Nino

2009-01-01

55

Groups of hierarchomorphisms of trees and related Hilbert spaces  

Microsoft Academic Search

Consider an infinite tree. A hierarchomorphism (spheromorphism) is a\\u000ahomeomorphism of the absolute which can be extended to the tree except a finite\\u000asubtree. Examples of groups of hierarchomorphisms: groups of locally analitic\\u000adiffeomorphisms of $p$-adic line; also Richard Thompson groups. The groups of\\u000ahierarchomorphisms have some properties similar to the group of diffeomorphisms\\u000aof the circle. We discuss actions

Yurii A. Neretin

2003-01-01

56

Moving a Media Space into the Real World through Group Robot Interaction  

Microsoft Academic Search

New generation media spaces let group members see each other and share information. However, they are separate from the real world; participants cannot see beyond the video, and they cannot engage with people not attending to the computer. To solve this problem, we use a robot as a physical surrogate for a media space group, which allows this distance-separated group

Jim Young; Gregor McEwan; Saul Greenberg; Ehud Sharlin

2007-01-01

57

Study of liquid crystal space groups using controlled tilting with cryogenic transmission electron microscopy.  

PubMed

We developed a method that enables differentiation between liquid crystalline-phase particles corresponding to different space groups. It consists of controlled tilting of the specimen to observe different orientations of the same particle using cryogenic transmission electron microscopy. This leads to the visualization of lattice planes (or reflections) that are present for a given structure and absent for the other one(s) and that give information on liquid crystalline structures and their space groups. In particular, we show that we can unambiguously distinguish among particles having the inverted micellar cubic (space group Fd(3)m, 227), the inverted bicontinuous gyroid (space group Ia(3)d, 230), the inverted bicontinuous diamond (space group Pn(3)m, 224), and the inverted bicontinuous primitive cubic structure (space group Im(3)m, 229). PMID:17949111

Sagalowicz, Laurent; Acquistapace, Simone; Watzke, Heribert J; Michel, Martin

2007-10-20

58

Tall tales from de Sitter space I: Renormalization group flows  

Microsoft Academic Search

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

Frédéric Leblond; Robert C. Myers

2002-01-01

59

POLYIMIDES CONTAINING PENDENT PHOSPHINE OXIDE GROUPS FOR SPACE APPLICATIONS  

Microsoft Academic Search

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

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

60

On the Fourier transform for a symmetric group homogeneous space  

Microsoft Academic Search

By using properties of the Young orthogonal representation, this paper derives a simple form for the Fourier transform of permutations acting on the homogeneous space of $n$-dimensional vectors, and shows that the transform requires $2n-2$ multiplications and the same number of additions.

Ramakrishna Kakarala

2009-01-01

61

Exploration of Halley's comet from space: the Inter-Agency Consultative Group (IACG) and its associated working groups.  

NASA Astrophysics Data System (ADS)

After 76 years, Halley's comet is again approaching the inner solar system. A fleet of six spacecraft, from four space agencies, is being prepared to encounter the comet in March 1986. The four space agencies have agreed to coordinate informally all matters related to the space missions to Halley's comet and have formed the Inter-Agency Consultative Group (IACG) for this purpose. Since its formation in 1981 the IACG has demonstrated an evergrowing usefulness for the various flight projects as a focal point for exchange of information, discussion on common problems and mutual support to enhance the overall scientific return of the space missions to Halley's comet.

Reinhard, R.

62

Distributions on Minkowski space and their connection with analytic representations of the conformal group  

Microsoft Academic Search

Unitary analytic representations of the conformal group are relized on Hilbert spaces of holomoprhic or antiholomorphic functions over a tube domain in complex Minkowski space. The distributional boundary values of these functions are tempered distributions on real Minkowski space. The representations are characterized by an integral scale dimension labeln and two spin labelsj1 andj2. The connection between the dimensionn and

W. Rühl

1972-01-01

63

Space Weather Activities of IONOLAB Group: TEC Mapping  

NASA Astrophysics Data System (ADS)

Being a key player in Space Weather, ionospheric variability affects the performance of both communication and navigation systems. To improve the performance of these systems, ionosphere has to be monitored. Total Electron Content (TEC), line integral of the electron density along a ray path, is an important parameter to investigate the ionospheric variability. A cost-effective way of obtaining TEC is by using dual-frequency GPS receivers. Since these measurements are sparse in space, accurate and robust interpolation techniques are needed to interpolate (or map) the TEC distribution for a given region in space. However, the TEC data derived from GPS measurements contain measurement noise, model and computational errors. Thus, it is necessary to analyze the interpolation performance of the techniques on synthetic data sets that can represent various ionospheric states. By this way, interpolation performance of the techniques can be compared over many parameters that can be controlled to represent the desired ionospheric states. In this study, Multiquadrics, Inverse Distance Weighting (IDW), Cubic Splines, Ordinary and Universal Kriging, Random Field Priors (RFP), Multi-Layer Perceptron Neural Network (MLP-NN), and Radial Basis Function Neural Network (RBF-NN) are employed as the spatial interpolation algorithms. These mapping techniques are initially tried on synthetic TEC surfaces for parameter and coefficient optimization and determination of error bounds. Interpolation performance of these methods are compared on synthetic TEC surfaces over the parameters of sampling pattern, number of samples, the variability of the surface and the trend type in the TEC surfaces. By examining the performance of the interpolation methods, it is observed that both Kriging, RFP and NN have important advantages and possible disadvantages depending on the given constraints. It is also observed that the determining parameter in the error performance is the trend in the Ionosphere. Optimization of the algorithms in terms of their performance parameters (like the choice of the semivariogram function for Kriging algorithms and the hidden layer and neuron numbers for MLP-NN) mostly depend on the behavior of the ionosphere at that given time instant for the desired region. The sampling pattern and number of samples are the other important parameters that may contribute to the higher errors in reconstruction. For example, for all of the above listed algorithms, hexagonal regular sampling of the ionosphere provides the lowest reconstruction error and the performance significantly degrades as the samples in the region become sparse and clustered. The optimized models and coefficients are applied to regional GPS-TEC mapping using the IONOLAB-TEC data (www.ionolab.org). Both Kriging combined with Kalman Filter and dynamic modeling of NN are also implemented as first trials of TEC and space weather predictions.

Arikan, F.; Yilmaz, A.; Arikan, O.; Sayin, I.; Gurun, M.; Akdogan, K. E.; Yildirim, S. A.

2009-04-01

64

Group theoretical construction of mutually unbiased bases in Hilbert spaces of prime dimensions  

Microsoft Academic Search

Mutually unbiased bases in Hilbert spaces of finite dimensions are closely related to the quantal notion of complementarity. An alternative proof of existence of a maximal collection of (N +1 ) mutually unbiased bases in Hilbert spaces of prime dimension N is given by exploiting the finite Heisenberg group (also called the Pauli group) and the action of SL(2, ZN

65

Harmonic analysis and systems of covariance for phase space representation of the poincaré group  

Microsoft Academic Search

Continuing some earlier work on the Galilei group, the spectral resolution of phase space representations of the Poincaré group is achieved by deriving all possible decompositions into irreducible representations corresponding to reproducing, kernel Hilbert spaces. Systems of covariance related to quantum measurements performed with extended test particles are analyzed, and questions of global unitarity discussed.

S. Twareque Ali; Eduard Prugove?ki

1986-01-01

66

Invariant-theoretic method for calculating Clebsch-Gordan coefficients for space groups  

SciTech Connect

A new invariant-theoretic method to directly calculate Clebsch-Gordan coefficients for space and point groups representations is proposed. The method is exemplified with the space groups O{sub h}{sup 5} and D{sub 6h}{sup 1}. 34 refs.

Aizenberg, A.Ya.; Gufan, Yu.M. [North Caucasus Research Center, Rostov-na-Donu (Russian Federation)

1995-03-01

67

NATO RTO Space Science and Technology Advisory Group (SSTAG) Recommendations for Space Research Topics.  

National Technical Information Service (NTIS)

As NATO and Nations are facing increased global responsibilities for security and defence with smaller forces, the ability to meet objectives will increasingly depend on use of integral, force-enhancing support from space. In recognition of this trend for...

2007-01-01

68

The dynamics of group codes: State spaces, trellis diagrams, and canonical encoders  

Microsoft Academic Search

A group code C over a group G is a set of sequences of group elements that itself forms a group under a component-wise group operation. A group code has a well-defined state space ?k at each time k. Each code sequence passes through a well-defined state sequence. The set of all state sequences is also a group code, the

G. David Forney Jr.; Mitchell D. Trott

1993-01-01

69

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

PubMed

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

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

2011-01-22

70

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

PubMed Central

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.

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

2011-01-01

71

Exploration of the Chemical Space of Group 4 Polymer Dielectrics  

NASA Astrophysics Data System (ADS)

The current standards for capacitive energy storage applications are polypropylene (PP) and polyethylene (PE) which have large band gap and high breakdown strength, but a small dielectric constant. The envisaged next generation dielectric should provide high dielectric constant, while still preserving the insulating characteristics of PP and PE. To meet these growing needs, we use high throughput density functional theory (DFT) calculations in combination with machine learning (ML) methods to identify classes of polymers with large dielectric constant and band gap. In our work, we consider various possible local chemical modifications to polyethylene (PE). To be specific, we allow the -CH2- unit in the PE backbone segment to be replaced by -SiF2-, -SiCl2-, -GeF2-, -GeCl2-, -SnF2-, or -SnCl2- units in a systematic manner. High throughput methods were used first to accurately determine the dielectric constant and band gap of the chemically modified PE chains for a set of limited compositions and configurations. ML methods were then used to predict the properties of systems spanning a much larger part of the configurational and compositional space. A set of most promising PE modifications (with simultaneously large dielectric constant and band gap) is identified using this strategy.

Wang, Chenchen; Pilania, Ghanshyam; Ramprasad, Rampi

2013-03-01

72

CIF Crystallographic Information File: A Standard for Crystallographic Data Interchange.  

National Technical Information Service (NTIS)

The Crystallographic Information File (CIF) uses the self-defining STAR file structure. This requires the creation of a dictionary of data names and definitions. A basic dictionary of terms needed to describe the crystal structures of small molecules was ...

I. D. Brown

1996-01-01

73

Acanthamoeba polyphaga mimivirus NDK: preliminary crystallographic analysis of the first viral nucleoside diphosphate kinase.  

PubMed

The complete sequence of the largest known double-stranded DNA virus, Acanthamoeba polyphaga mimivirus, has recently been determined [Raoult et al. (2004), Science, 306, 1344-1350] and revealed numerous genes not expected to be found in a virus. A comprehensive structural and functional study of these gene products was initiated [Abergel et al. (2005), Acta Cryst. F61, 212-215] both to better understand their role in the virus physiology and to obtain some clues to the origin of DNA viruses. Here, the preliminary crystallographic analysis of the viral nucleoside diphosphate kinase protein is reported. The crystal belongs to the cubic space group P2(1)3, with unit-cell parameter 99.425 A. The self-rotation function confirms that there are two monomers per asymmetric unit related by a twofold non-crystallographic axis and that the unit cell thus contains four biological entities. PMID:16511098

Jeudy, Sandra; Coutard, Bruno; Lebrun, Régine; Abergel, Chantal

2005-06-01

74

Acanthamoeba polyphaga mimivirus NDK: preliminary crystallographic analysis of the first viral nucleoside diphosphate kinase  

PubMed Central

The complete sequence of the largest known double-stranded DNA virus, Acanthamoeba polyphaga mimivirus, has recently been determined [Raoult et al. (2004 ?), Science, 306, 1344–1350] and revealed numerous genes not expected to be found in a virus. A comprehensive structural and functional study of these gene products was initiated [Abergel et al. (2005 ?), Acta Cryst. F61, 212–215] both to better understand their role in the virus physiology and to obtain some clues to the origin of DNA viruses. Here, the preliminary crystallographic analysis of the viral nucleoside diphosphate kinase protein is reported. The crystal belongs to the cubic space group P213, with unit-cell parameter 99.425?Å. The self-rotation function confirms that there are two monomers per asymmetric unit related by a twofold non-crystallographic axis and that the unit cell thus contains four biological entities.

Jeudy, Sandra; Coutard, Bruno; Lebrun, Regine; Abergel, Chantal

2005-01-01

75

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

ERIC Educational Resources Information Center

|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…

Loomis, Thomas P.

1988-01-01

76

Extended weight semigroups of affine spherical homogeneous spaces of non-simple semisimple algebraic groups  

NASA Astrophysics Data System (ADS)

The extended weight semigroup of a homogeneous space G/H of a connected semisimple algebraic group G characterizes the spectra of the representations of G on spaces of regular sections of homogeneous line bundles over G/H, including the space of regular functions on G/H. We compute the extended weight semigroups for all strictly irreducible affine spherical homogeneous spaces G/H, where G is a simply connected non-simple semisimple complex algebraic group and H is a connected closed subgroup of G. In all cases we also find the highest-weight functions corresponding to the indecomposable elements of this semigroup. Among other things, our results complete the computation of the weight semigroups for all strictly irreducible simply connected affine spherical homogeneous spaces of semisimple complex algebraic groups.

Avdeev, Roman S.

2010-12-01

77

Schwinger representation for the symmetric group: Two explicit constructions for the carrier space  

NASA Astrophysics Data System (ADS)

We give two explicit constructions for the carrier space for the Schwinger representation of the group S. While the first relies on a class of functions consisting of monomials in antisymmetric variables, the second is based on the Fock space associated with the Greenberg algebra.

Chaturvedi, S.; Marmo, G.; Mukunda, N.; Simon, R.

2008-05-01

78

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

Microsoft Academic Search

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

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

2006-01-01

79

Unusual space-group pseudo symmetry in crystals of human phosphopantothenoylcysteine decarboxylase  

SciTech Connect

Phosphopantothenoylcysteine (PPC) decarboxylase is an essential enzyme in the biosynthesis of coenzyme A and catalyzes the decarboxylation of PPC to phosphopantetheine. Human PPC decarboxylase has been expressed in Escherichia coli, purified and crystallized. The Laue class of the diffraction data appears to be {bar 3}m, suggesting space group R32 with two monomers per asymmetric unit. However, the crystals belong to the space group R3 and the asymmetric unit contains four monomers. The structure has been solved using molecular replacement and refined to a current R factor of 29%. The crystal packing can be considered as two interlaced lattices, each consistent with space group R32 and with the corresponding twofold axes parallel to each other but separated along the threefold axis. Thus, the true space group is R3 with four monomers per asymmetric unit.

Manoj, N.; Ealick, S.E. (Cornell)

2010-12-01

80

Effects of group size and floor space allowance on grouped sows: Aggression, stress, skin injuries, and reproductive performance.  

PubMed

A total of 3,120 sows, in 4 time replicates, were used to determine the effects of group size and floor space on sow welfare using behavioral, physiological, health, and fitness variables. Within 1 to 7 d postinsemination, sows were assigned randomly to treatments of a 3 by 6 factorial arrangement, with 3 group sizes (10, 30, or 80 sows/pen) and 6 floor space allowances (1.4, 1.8, 2.0, 2.2, 2.4, or 3.0 m(2)/sow). Sows were housed on partially slatted concrete floors, and overhead feeders delivered 4 times/day to provide a total of 2.5 kg of feed/sow. As pen space increased from 1.4 to 3.0 m(2)/sow, aggression at feeding decreased from about 9 to 7 bouts/sow (linear, P = 0.029) and plasma cortisol concentrations decreased from about 28 to 21 ng/mL (linear, P = 0.0089) at 2 d. Although the results are in accord with a linear decline from 1.4 to 3 m(2)/sow, the results are also in accord with a decline in these measurements from 1.4 to 1.8 m(2)/sow and no further decline greater than 1.8 m(2)/sow. Farrowing rate (percentage of inseminated sows that farrowed) also increased from about 60 to 75% as space increased from 1.4 to 3.0 m(2)/sow (linear, P = 0.012). Group size was related to skin injuries on d 9 (P = 0.0017), 23 (P = 0.0046), and 51 (P = 0.0006), with groups of 10 consistently having the lowest number of total injuries over this period. Based on the aggression and cortisol results, it is credible to judge that, within the range of floor space allowances studied, sow welfare improves with increased space. However, from a sow welfare perspective, the experiment had insufficient precision to determine what is an adequate space allowance for sows. Thus, although the results definitely support a space allowance of 1.4 m(2)/sow being too small, it is not possible to give guidance on an actual space allowance at mixing that is adequate. PMID:23893983

Hemsworth, P H; Rice, M; Nash, J; Giri, K; Butler, K L; Tilbrook, A J; Morrison, R S

2013-07-26

81

Criteria for weak and strong continuity of representations of topological groups in Banach spaces  

SciTech Connect

Several necessary and sufficient conditions for weak and strong continuity of representations of topological groups in Banach spaces are obtained. In particular, it is shown that a representation S of a locally compact group G in a Banach space is continuous in the strong (or, equivalently, in the weak) operator topology if and only if for some real number q, 0{<=}q<1, and each unit vector {xi} in the representation space of S there exists a neighbourhood U=U({xi}) subset of G of the identity element e element of G such that ||S(g){xi}-{xi}||{<=}q for all g element of U. Versions of this criterion for other classes of groups (including not necessarily locally compact groups) and refinements for finite-dimensional representations are obtained; examples are discussed. Applications to the theory of quasirepresentations of topological groups are presented.

Shtern, A I [M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2002-10-31

82

OPERATOR K-THEORY FOR GROUPS WHICH ACT PROPERLY AND ISOMETRICALLY ON HILBERT SPACE  

Microsoft Academic Search

Let G be a countable discrete group which acts isometrically and metrically properly on an innite-dimensional Euclidean space. We calculate the K-theory groups of the C-algebras C max(G )a nd Cred(G). Our result is in accordance with the Baum-Connes conjecture.

NIGEL HIGSON; GENNADI KASPAROV

1997-01-01

83

Nonlinear wave and Schrödinger equations on compact Lie groups and homogeneous spaces  

Microsoft Academic Search

We develop linear and nonlinear harmonic analysis on compact Lie groups and homogeneous spaces relevant for the theory of evolutionary Hamiltonian PDEs. A basic tool is the theory of the highest weight for irreducible representations of compact Lie groups. This theory provides an accurate description of the eigenvalues of the Laplace-Beltrami operator as well as the multiplication rules of its

Massimiliano Berti; Michela Procesi

2011-01-01

84

Preliminary X-ray crystallographic analysis of the glycosyltransferase from a marine Streptomyces species  

PubMed Central

ElaGT is a glycosyltransferase from a marine Streptomyces species that is involved in the biosynthesis of elaiophylin. Here, the molecular cloning, protein expression and purification, preliminary crystallization and crystallographic characterization of ElaGT are reported. The rod-shaped crystals belonged to space group P2122, with unit-cell parameters a = 66.7, b = 131.7, c = 224.6?Å, ? = 90, ? = 90, ? = 90°. Data were collected to 2.9?Å resolution. A preliminary molecular-replacement solution implied the presence of two ElaGT molecules in the asymmetric unit.

Gong, Liping; Xiao, Yi; Liu, Qiang; Li, Sumei; Zhang, Changsheng; Liu, Jinsong

2011-01-01

85

A simple assay to study social behavior in Drosophila: measurement of social space within a group.  

PubMed

We have established a new simple behavioral paradigm in Drosophila melanogaster to determine how genes and the environment influence the behavior of flies within a social group. Specifically, we measure social space as the distance between two flies. The majority of Canton-s flies, regardless of their gender, are within two body lengths from each other. Their social experience affects this behavior, with social isolation reducing and mating enhancing social space respectively, in both males and females. Unlike several other social behaviors in the fly, including the formation of social groups themselves (a well-described behavior), social space does not require the perception of the previously identified aggregation pheromone cis-vaccenyl acetate. Conversely, performance of the assay in darkness or mutations in the eye pigmentation gene white increased social space. Our results establish a new assay for the genetic dissection of a fundamental mode of social interaction. PMID:22010812

Simon, A F; Chou, M-T; Salazar, E D; Nicholson, T; Saini, N; Metchev, S; Krantz, D E

2011-11-23

86

The extended loop group: An infinite dimensional manifold associated with the loop space  

NASA Astrophysics Data System (ADS)

A set of coordinates in the non-parametric loop-space is introduced. We show that these coordinates transform under infinite dimensional linear representations of the diffeomorphism group. An extension of the group of loops in terms of these objects is proposed. The enlarged group behaves locally as an infinite dimensional Lie group. Ordinary loops form a subgroup of this group. The algebraic properties of this new mathematical structure are analyzed in detail. Applications of the formalism to field theory, quantum gravity and knot theory are considered.

di Bartolo, Cayetano; Gambini, Rodolfo; Griego, Jorge

1993-11-01

87

Investigation of catalytic characterization of two-dimensional molecular space with regular ammonium and pyridine groups.  

PubMed

Novel two-dimensional molecular space with regular pyridine groups layered pyridine-4-amidepropylsilica (PAPS) and pyridine-4-amidephenylsilica (PAPhS) were successfully synthesized through grafting pyridine groups in the layer structure of two-dimensional molecular space with regular ammonium groups layered aminopropylsilica (ATMS-DS) and layered aminophenylsilica (APhTMS-DS). The two-dimensional structures were kept after grafting reaction of pyridine groups in PAPS and PAPhS. The catalytic potentials of two-dimensional molecular space with regular ammonium and pyridine groups were investigated. The catalytic capability of APhTMS-DS, PAPS, and PAPhS was confirmed through Knoevenagel condensation reactions. Knoevenagel condensation of aromatic aldehydes with malononitrile was not observed in the presence of ATMS-DS. Otherwise, the lower yield of Knoevenagel condensation of higher active 2-chlorobenzaldehyde with malononitrile in the presence of APhTMS-DS, PAPS, and PAPhS indicated the potential of the two-dimensional molecular space with regular catalyst molecules on influencing catalysis processes utilizing the chemical and geometrical limits. PMID:19296641

Chen, Jianming; Yao, Ken; Shangguan, Wenfeng; Yuan, Jian

2009-05-19

88

Overview of the Space Propulsion Synergy Group (SPSG) strategic planning support efforts for earth to orbit transportation  

Microsoft Academic Search

An essential requirement of a successful space program is the assurance of a safe affordable routine access to space. In view of this, a national organization known as the Space Propulsion Synergy Group (SPSG) has been directed for the past two years toward supporting strategic planning for earth-to-orbit space transportation and propulsion systems. This paper presents a short description of

Walter F. Dankhoff; William P. Hope Jr.

1993-01-01

89

An introduction to data reduction: space-group determination, scaling and intensity statistics.  

PubMed

This paper presents an overview of how to run the CCP4 programs for data reduction (SCALA, POINTLESS and CTRUNCATE) through the CCP4 graphical interface ccp4i and points out some issues that need to be considered, together with a few examples. It covers determination of the point-group symmetry of the diffraction data (the Laue group), which is required for the subsequent scaling step, examination of systematic absences, which in many cases will allow inference of the space group, putting multiple data sets on a common indexing system when there are alternatives, the scaling step itself, which produces a large set of data-quality indicators, estimation of |F| from intensity and finally examination of intensity statistics to detect crystal pathologies such as twinning. An appendix outlines the scoring schemes used by the program POINTLESS to assign probabilities to possible Laue and space groups. PMID:21460446

Evans, Philip R

2011-03-18

90

An introduction to data reduction: space-group determination, scaling and intensity statistics  

PubMed Central

This paper presents an overview of how to run the CCP4 programs for data reduction (SCALA, POINTLESS and CTRUNCATE) through the CCP4 graphical interface ccp4i and points out some issues that need to be considered, together with a few examples. It covers determination of the point-group symmetry of the diffraction data (the Laue group), which is required for the subsequent scaling step, examination of systematic absences, which in many cases will allow inference of the space group, putting multiple data sets on a common indexing system when there are alternatives, the scaling step itself, which produces a large set of data-quality indicators, estimation of |F| from intensity and finally examination of intensity statistics to detect crystal pathologies such as twinning. An appendix outlines the scoring schemes used by the program POINTLESS to assign probabilities to possible Laue and space groups.

Evans, Philip R.

2011-01-01

91

Space and time: an impact of spatial separation, apparent motion, and perceptual grouping on TOJ performance.  

PubMed

This study explored the effects of spacing and objecthood (ie grouping based on closure) on temporal order judgment (TOJ) with displays that either involved successive onset of the target stimuli, resulting in apparent motion (experiments 1 and 2), or included simultaneous onset but successive shortening of the stimuli, and therefore did not result in apparent motion (experiment 3). We found a robust effect of spatial separation whose nature depended on whether or not the display allowed the emergence of illusory motion. Specifically, with apparent motion TOJ was best with the smallest spacing, but without it TOJ was worst with the smallest spacing. Moreover, overall accuracy was better with, than without, apparent motion. A small effect of objecthood--poorer TOJ performance when the elements formed an object--emerged only when spacing was not manipulated. These findings suggest that different mechanisms mediate temporal processing when we have access to motion information than when we do not. PMID:23964380

Baruch, Orit; Yeshurun, Yaffa; Shore, David I

2013-01-01

92

Experiences of Young Bisexual Women in Lesbian\\/Bisexual Groups on MySpace  

Microsoft Academic Search

This exploratory study examined Topic threads in Lesbian\\/Bisexual Groups on MySpace to examine how young biwomen self-identify in online exchanges with other bisexuals and lesbians, as well as what attitudes and beliefs about bisexuality emerge from those exchanges. Four Topic threads from three Groups suggested that young biwomen use social networking sites to connect with others and create inclusive communities

M. Sue Crowley

2010-01-01

93

Real space renormalization group and totalitarian paradox of majority rule voting  

Microsoft Academic Search

The effect of majority rule voting in hierarchical structures is studied using the basic concepts from real space renormalization group. It shows in particular that a huge majority can be self-eliminated while climbing up the hierarchy levels. This majority democratic self-elimination articulates around the existence of fixed points in the voting flow. An unstable fixed point determines the critical threshold

Serge Galam

2000-01-01

94

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...

95

Group Decision Fiascoes Continue: Space Shuttle Challenger and a Revised Groupthink Framework  

Microsoft Academic Search

This paper reviews the decision situation surrounding the decision to launch the space shuttle Challenger in January 1986 in the light of the groupthink hypothesis. A revised framework is presented that proposes time and leadership style as moderators of the manner in which group characteristics lead to groupthink symptoms.

Gregory Moorhead; Richard Ference; Chris P. Neck

1991-01-01

96

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

Microsoft Academic Search

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

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

1993-01-01

97

Semisimple Banach algebras generated by compact groups of operators on a Banach space  

NASA Astrophysics Data System (ADS)

We prove that if [tau] is a strongly continuous representation of a compact group G on a Banach space X, then the weakly closed Banach algebra generated by the Fourier transforms with [mu][set membership, variant]M(G) is a semisimple Banach algebra.

Gale, Jose E.; Villena, Armando R.

2007-01-01

98

Unusual catalytic effect of the two-dimensional molecular space with regular triphenylphosphine groups.  

PubMed

A novel organic-inorganic hybrid 2D molecular space with regular triphenylphosphine groups (triphenylphosphineamidephenylsilica, PPh(3)APhS) was successfully synthesized through grafting triphenylphosphine groups in the 2D structure of layered aminophenylsilica dodecyl sulfate (APhTMS-DS), which was developed in our previous research, with regular ammonium groups. The 2D structures were kept after the grafting reaction of triphenylphosphine groups in PPh(3)APhS. The catalytic potentials of 2D molecular space with regular triphenylphosphine groups were investigated. An unusual catalytic effect was found in a carbon-phosphorus ylide reaction. The PPh(3)-catalyzed reaction of modified allylic compounds, including bromides and chlorides with tropone yielded a [3 + 6] annulation product. However, an unusual [8 + 3] cycloadduct was obtained in the reaction of modified allylic compounds, including bromides and chlorides with tropone catalyzed by PPh(3)APhS. Otherwise, the stable catalytic intermediate was successfully separated, and the reaction activity of the catalytic intermediate was confirmed in the reaction of modified allylic compounds with tropone catalyzed by PPh(3)APhS. This research is the first successful example of directly influencing catalytic reaction processes and product structures by utilizing the chemical and geometrical limits of 2D molecular spaces with regular catalyst molecules and affords a novel method for controlling catalytic reaction processes and catalyst design. PMID:21905651

Chen, Chen; Shao, Xue; Yao, Ken; Yuan, Jian; Shangguan, Wenfeng; Kawaguchi, Toshikazu; Shimazu, Katsuaki

2011-09-09

99

Space-time versus world-sheet renormalization group equation in string theory  

NASA Astrophysics Data System (ADS)

We discuss the relation between space-time renormalization group equation for closed string field theory and world-sheet renormalization group equation for first-quantized strings. Restricting our attention to massless states we argue that there is a one-to-one correspondence between the fixed point solutions of the two renormalization group equations. In particular, we show how to extract the Fischler-Susskind mechanism from the string field theory equation in the case of the bosonic string. Supported in part by the Danish Natural Science Research Council and the SARC Foundation.

Brustein, Ram; Roland, Kaj

1992-03-01

100

Bayesian probability theory applied to the space group problem in powder diffraction  

NASA Astrophysics Data System (ADS)

Crystal structure determination from powder diffraction data has become a viable option for molecules with less than 50 non-hydrogen atoms in the asymmetric unit and this includes the majority of compounds of pharmaceutical interest. The solution of crystal structures, including space group determination, is more challenging from powder diffraction data than from single crystal diffraction data. Here, it will be demonstrated how a Bayesian probability analysis of this problem has helped to provide a new algorithm for the determination of the space group symmetry of a crystal from powder diffraction data. Specifically, the relative probabilities of different extinction symbols are accessed within a particular crystal system. Examples will be presented to illustrate this approach.

Markvardsen, A. J.

2004-11-01

101

Realization of vector fields for quantum groups as pseudodifferential operators on quantum spaces  

SciTech Connect

The vector fields of the quantum Lie algebra are described for the quantum groups GL{sub q}(n), SL{sub q}(N) and SO{sub q}(N) as pseudodifferential operators on the linear quantum spaces covariant under the corresponding quantum group. Their expressions are simple and compact. It is pointed out that these vector fields satisfy certain characteristic polynomial identities. The real forms SU{sub q}(N) and SO{sub q}(N,R) are discussed in detail.

Chu, Chong-Sun; Zumino, B.

1995-01-24

102

Knowledge acquisition from crystallographic databases  

NASA Astrophysics Data System (ADS)

Four major crystallographic databases record bibliographic, 2D chemical and 3D structural data across the complete chemical spectrum. The largest of these databases, the Cambridge Structural Database, is described and software for search, retrieval, display and analysis of database contents is summarized. The CSD System is now used extensively as a basis for further research that is designed to acquire structural knowledge from the accumulated information. Statistical, numerical and graphical methods of data analysis are described and exemplified with special reference to studies of mean molecular dimensions, conformational preferences, reaction pathways and of intermolecular interactions and molecular recognition mechanisms.

Allen, Frank H.; Bird, Craig M.; Bruno, Ian J.; Johnson, Owen; Stewart, Neil S.

1995-04-01

103

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

Microsoft Academic Search

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

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

2010-01-01

104

Testing the accuracy of redshift-space group-finding algorithms  

NASA Astrophysics Data System (ADS)

Using simulated redshift surveys generated from a high-resolution N-body cosmological structure simulation, we study algorithms used to identify groups of galaxies in redshift space. Two algorithms are investigated; both are friends-of-friends schemes with variable linking lengths in the radial and transverse dimenisons. The chief difference between the algorithms is in the redshift linking length. The algorithm proposed by Huchra & Geller (1982) uses a generous linking length designed to find 'fingers of god,' while that of Nolthenius & White (1987) uses a smaller linking length to minimize contamination by projection. We find that neither of the algorithms studied is intrinsically superior to the other; rather, the ideal algorithm as well as the ideal algorithm parameters depends on the purpose for which groups are to be studied. The Huchra & Geller algorithm misses few real groups, at the cost of including some spurious groups and members, while the Nolthenius & White algorithm misses high velocity dispersion groups and members but is less likely to include interlopers in its group assignments. Adjusting the parameters of either algorithm results in a trade-off between group accuracy and completeness. In a companion paper we investigate the accuracy of virial mass estimates and clustering properties of groups identified using these algorithms.

Frederic, James J.

1995-04-01

105

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

PubMed Central

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.

Oyenarte, Iker; Majtan, Tomas; Ereno, June; Corral-Rodriguez, Maria Angeles; Kraus, Jan P.; Martinez-Cruz, Luis Alfonso

2012-01-01

106

IERS Working group on Combination of Space Geodetic Techniques at the Observation Level (COL)  

NASA Astrophysics Data System (ADS)

The different space geodetic techniques have different strengths and weaknesses for recovering geodetic parameters. This makes their combination useful. However they may have some systematic behaviour which can be detected and removed at the observation level. In order to review the interest in combining techniques at this level, a Working Group at the Combination Level (WG COL) was set up in the course of 2009 in the frame of the International Earth Rotation and Reference Systems Service (IERS). A major task of the WG COL is to study methods and advantages of combining space geodetic techniques (DORIS, GNSS, SLR, VLBI), searching for an optimal strategy to solve for geodetic parameters. The first action of the Working Group was to organize an inter-comparison benchmark campaign to serve as a test. The period chosen is from August 10 to August 30, 2008. It includes the intensive CONT08 VLBI period. The combination analyses are based on weekly or daily combined SINEX files which contain normal equations of station coordinates, Earth Orientation Parameters from all space geodetic techniques, tropospheric parameters for GNSS, DORIS and VLBI techniques and quasar coordinates for the VLBI technique. We will present the objectives and strategy of multi-technique combination, establishing conventions and some results already achieved.

Richard, J.-Y.; Biancale, R.; Bizouard, C.; Deleflie, F.; Gambis, G.; Koenig, R.; Loyer, S.; Sciaretta, C.; Seitz, M.; Spicakova, H.; Springer, T.; Thaller, D.

2012-04-01

107

Processor-Group Aware Runtime Support for Shared-and Global-Address Space Models  

SciTech Connect

Exploiting multilevel parallelism using processor groups is becoming increasingly important for programming on high-end systems. This paper describes a group-aware run-time support for shared-/global- address space programming models. The current effort has been undertaken in the context of the Aggregate Remote Memory Copy Interface (ARMCI) [5], a portable runtime system used as a communication layer for Global Arrays [6], Co-Array Fortran (CAF) [9], GPSHMEM [10], Co-Array Python [11], and also end-user applications. The paper describes the management of shared memory, integration of shared memory communication and RDMA on clusters with SMP nodes, and registration. These are all required for efficient multi- method and multi-protocol communication on modern systems. Focus is placed on techniques for supporting process groups while maximizing communication performance and efficiently managing global memory system-wide.

Krishnan, Manoj Kumar; Tipparaju, Vinod; Palmer, Bruce; Nieplocha, Jarek

2004-12-07

108

Opechowski-Guccione-like symbols labelling magnetic space groups independent of tabulated (0, 0, 0)+ sets.  

PubMed

For the magnetic space-group types with a black and white lattice two sets of symbols have been proposed: the BNS symbols [Belov et al. (1957). Sov. Phys. Crystallogr. 2, 311-322] and the OG symbols [Opechowski & Guccione (1965). Magnetism, edited by G. T. Rado & H. Suhl, Vol. II, Part A, pp. 105-165. New York: Academic Press]. Whereas generators of the group can be read off the BNS symbol, International Tables for X-ray Crystallography (1952) must be consulted to interpret the OG symbols. In the cases where the black and white lattice is centred, it is shown how the OG symbols can be modified so that generators of the group can be deduced directly from the symbol. PMID:20404436

Grimmer, Hans

2010-03-26

109

Crystallization and preliminary crystallographic studies of a cysteine protease inhibitor from the human nematode parasite Ascaris lumbricoides  

PubMed Central

The cysteine protease inhibitor from Ascaris lumbricoides, a roundworm that lives in the human intestine, may be involved in the suppression of human immune responses. Here, the molecular cloning, protein expression and purification, preliminary crystallization and crystallographic characterization of the cysteine protease inhibitor from A. lumbricoides are reported. The rod-shaped crystal belonged to space group C2, with unit-cell parameters a = 99.40, b = 37.52, c = 62.92?Å, ? = 118.26°. The crystal diffracted to 2.1?Å resolution and contained two molecules in the asymmetric unit.

Liu, Sanling; Dong, Jianmei; Mei, Guoqiang; Liu, Guiyun; Xu, Wei; Su, Zhong; Liu, Jinsong

2011-01-01

110

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

PubMed Central

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 F2?, 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 P21, 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.

Sugiyama, Shigeru; Tokuoka, Keiji; Uchiyama, Nahoko; Okamoto, Naoki; Okano, Yousuke; Matsumura, Hiroyoshi; Inaka, Koji; Urade, Yoshihiro; Inoue, Tsuyoshi

2007-01-01

111

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

SciTech Connect

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.

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

2011-03-31

112

Regularity properties and pathologies of position-space renormalization-group transformations  

NASA Astrophysics Data System (ADS)

We consider the conceptual foundations of the renormalization-group (RG) formalism. We show that the RG map, defined on a suitable space of interactions, 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 other hand, we prove in several cases that near a first-order phase transition the renormalized measure is not a Gibbs measure for any reasonable interaction. It follows that the conventional RG description of first-order transitions is not universally valid. Speaker at the conference.

van Enter, Aernout C. D.; Fernández, Roberto; Sokal, Alan D.

1991-05-01

113

Crystallization of the Focal Adhesion Kinase Targeting (FAT) Domain in a Primitive Orthorhombic Space Group  

SciTech Connect

X-ray diffraction data from the targeting (FAT) domain of focal adhesion kinase (FAK) were collected from a single crystal that diffracted to 1.99 Angstroms resolution and reduced to the primitive orthorhombic lattice. A single molecule was predicted to be present in the asymmetric unit based on the Matthews coefficient. The data were phased using molecular-replacement methods using an existing model of the FAK FAT domain. All structures of human focal adhesion kinase FAT domains solved to date have been solved in a C-centered orthorhombic space group.

Magis,A.; Bailey, K.; Kurenova, E.; Hernandez Prada, J.; Cance, W.; Ostrov, D.

2008-01-01

114

A Fun and Effective Exercise for Understanding Lattices and Space Groups  

NSDL National Science Digital Library

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.

Perkins, Dexter

115

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

PubMed

The system of Hermann-Mauguin symbols for space and subperiodic Euclidean groups in two and three dimensions is extended to groups with continuous and semicontinuous translation subgroups (lattices). An interpretation of these symbols is proposed in which each symbol defines a quite specific Euclidean group with reference to a crystallographic basis, including the location of the group in space. Symbols of subperiodic (layer and rod) groups are strongly correlated with symbols of decomposable space groups on the basis of the factorization theorem. Introduction of groups with continuous and semicontinuous lattices is connected with a proposal for several new terms that describe the properties of these groups and with a proposal to amend the meaning of space groups and of crystallographic groups. Charts of plane, layer and space groups describe variants of these groups with the same reducible point group but various types of lattices. Examples of such charts are given for plane, layer and space groups to illustrate the unification principle for groups with decomposable lattices. PMID:16489244

Kopský, Vojtech

2006-02-18

116

Crystallographic features of phase transformations in solids  

Microsoft Academic Search

The paper reviews the current knowledge and understanding of the crystallographic features of phase transformations in solid materials – metals, ceramics and alloys. It covers both of the broad classes of phase transformations in crystalline solids – martensitic or ‘displacive’ and ‘diffusional’ or ‘reconstructive’. The factors that govern the crystallographic features of these two classes of transformations are compared and

Ming-Xing Zhang; Patrick M. Kelly

2009-01-01

117

Crystallographic patterns in nature and Turkish art  

Microsoft Academic Search

In this paper, crystallographic aspects of ancient, medieval and modern Turkish ornaments are dealt with. Crystallographic patterns (CPs) are considerably different from other patterns. The following are characteristic of CPs: the edge of ornament elements draws the edge of the figure; maximal compactness of the ornament elements; lack of background or transformation of background to ornament elements; minimization of the

Hacali Necefoglu

2003-01-01

118

Electron precession microdiffraction as a useful tool for the identification of the space group.  

PubMed

The possible space groups of a crystal can be identified from a few zone axis microdiffraction patterns provided the position (and not the intensity) of the reflections on the patterns is taken into account. The method is based on the observation of the shifts and the 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). Electron precession microdiffraction patterns display more reflections in the ZOLZ and in the FOLZ than in the conventional microdiffraction patterns and this number increases with the precession angle. It is shown, from the TiAl example given in the present study, that this interesting feature brings a strong beneficial effect for the identification of the possible space groups since it becomes very easy to identify unambiguously the FOLZ/ZOLZ shifts and periodicity differences. In addition, the diffracted intensity on the precession patterns is the integrated intensity and this intensity can also be used to identify the Laue class. PMID:17845710

Morniroli, J-P; Redjaimia, A

2007-08-01

119

Space group symmetry applied to SCF calculations with periodic boundary conditions and Gaussian orbitals  

NASA Astrophysics Data System (ADS)

Space group symmetry is exploited and implemented in density functional calculations of extended systems with periodic boundary conditions. Our scheme for reducing the number of two-electron integrals employs the entire set of operations of the space group, including glide plains and screw axes. Speedups observed for the Fock matrix formation in simple 3D systems range from 2X to 9X for the near field Coulomb part and from 3X to 8X for the Hartree-Fock-type exchange, the slowest steps of the procedure, thus leading to a substantial reduction of the computational time. The relatively small speedup factors in special cases are attributed to the highly symmetric positions atoms occupy in crystals, including the ones tested here, as well as to the choice of the smallest possible unit cells. For quasi-1D systems with most atoms staying invariant only under identity, the speedup factors often exceed one order of magnitude reaching almost 70X (near-field Coulomb) and 57X (HFx) for the largest tested (16,7) single-walled nanotube with 278 symmetry operations.

Rusakov, Alexander A.; Frisch, Michael J.; Scuseria, Gustavo E.

2013-09-01

120

Space group symmetry applied to SCF calculations with periodic boundary conditions and Gaussian orbitals.  

PubMed

Space group symmetry is exploited and implemented in density functional calculations of extended systems with periodic boundary conditions. Our scheme for reducing the number of two-electron integrals employs the entire set of operations of the space group, including glide plains and screw axes. Speedups observed for the Fock matrix formation in simple 3D systems range from 2X to 9X for the near field Coulomb part and from 3X to 8X for the Hartree-Fock-type exchange, the slowest steps of the procedure, thus leading to a substantial reduction of the computational time. The relatively small speedup factors in special cases are attributed to the highly symmetric positions atoms occupy in crystals, including the ones tested here, as well as to the choice of the smallest possible unit cells. For quasi-1D systems with most atoms staying invariant only under identity, the speedup factors often exceed one order of magnitude reaching almost 70X (near-field Coulomb) and 57X (HFx) for the largest tested (16,7) single-walled nanotube with 278 symmetry operations. PMID:24070282

Rusakov, Alexander A; Frisch, Michael J; Scuseria, Gustavo E

2013-09-21

121

Finite-Dimensional Approximations of Operators in the Hilbert Spaces of Functions on Locally Compact Abelian Groups  

Microsoft Academic Search

A new approach to the approximation of operators in the Hilbert space of functions on a locally compact Abelian (LCA) group is developed. This approach is based on sampling the symbols of such operators. To choose the points for sampling, we use the approximations of LCA groups by finite groups, which were introduced and investigated by Gordon. In the case

S. Albeverio; E. I. Gordon; A. Yu. Khrennikov

2000-01-01

122

Public opinion and interest group positions on open-space issues in Albuquerque, New Mexico, USA: Implications for resource management  

NASA Astrophysics Data System (ADS)

The purpose of this research was to elicit and compare the open-space preferences of citizens and openspace experts in Albuquerque, New Mexico, USA. A randomly selected sample of 492 citizens and 35 open-space experts participated in a telephone survey during May 5 18, 1986. The following hypothesis was tested and used as a guideline for the study: HO1: There is no significant difference between respondents' status and preference for open space in Albuquerque, New Mexico. The hypothesis was rejected. Findings confirmed respondents' status affected preference for open space. Of the eight issues on which the citizen and expert groups were compared, five recorded significant differences in response profiles. The open-space expert group was significantly more supportive of using open space to accommodate offroad vehicle facilities, wildlife preserves, a citywide recreational trail, and a trail system along the arroyos and city ditches. The citizen sample was significantly more supportive of using open space to accommodate overnight camping facilities. Both groups equally supported using open space to accommodate an outdoor amphitheater, outdoor education facilities, and rafting, kayaking, and canoeing facilities. The finding indicated that expert preferences did not represent an aggregate of citizen preferences for managing open-space resources. Understanding both expert and citizen positions will facilitate decision-making processes and help resolve environmental disputes.

Tannery, Thomas Allan

1987-07-01

123

Crystallization and preliminary crystallographic analysis of eukaryotic transcription and mRNA export factor Iws1 from Encephalitozoon cuniculi  

PubMed Central

Transcription elongation by eukaryotic RNA polymerase II requires the coupling of mRNA synthesis and mRNA processing and export. The essential protein Iws1 is at the interface of these processes through its interaction with histone chaperone and elongation factor Spt6 as well as with complexes involved in mRNA processing and export. Upon crystallization of the evolutionarily conserved domain of Iws1 from Encephalitozoon cuniculi, four different crystal forms were obtained. Three of the crystal forms belonged to space group P21 and one belonged to space group P2221. Preliminary X-ray crystallo­graphic analysis of one of the crystal forms allowed the collection of data to 2.5?Å resolution.

Koch, Michael; Diebold, Marie-Laure; Cavarelli, Jean; Romier, Christophe

2010-01-01

124

Application of the renormalization group to the calculation of the vacuum decay rate in flat and curved space-time  

SciTech Connect

I show that an application of renormalization group arguments may lead to significant corrections to the vacuum decay rate for phase transitions in flat and curved space-time. It can also give some information regarding its dependence on the parameters of the theory, including the cosmological constant in the case of decay in curved space-time.

Metaxas, Dimitrios [Department of Physics, National Technical University of Athens, Zografou Campus, 15780 Athens (Greece)

2007-02-15

125

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

PubMed

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

Abrahams, S C

2006-01-17

126

Crystallographic Control in Ilmenite Reduction  

NASA Astrophysics Data System (ADS)

Scanning electron microscopy and transmission electron microscopy techniques were used to characterize the products from hydrogen reduction of polygranular synthetic ilmenite discs at temperatures in the range 823 to 1173 K and pressures in the range 1 to 13 atm. Reduction commences at grain boundaries and cracks and advances progressively to grain interiors. Within individual grains, the morphology of the reduction products was found to be crystallographically controlled. Near parallel bands of metallic iron (Fe m ) form within each grain, aligned with the basal plane of ilmenite (il) (0001) il . The separation between bands is of the order of 1 ?m and is relatively constant with change of pressure and temperature. In the interband region, conversion of ilmenite to rutile occurs preferentially parallel to \\{ 11ifmmodeexpandafterbarelseexpandafter\\=fi{2}0\\} _{{il}} ilmenite planes, generating platelets of rutile that grow normal to the Fe m bands. The intergrain duplex morphology of the reduction products closely resembles cellular precipitation in alloys. At reduction temperatures above ˜1000 K, the interband region comprises dense, nonporous oriented intergrowths of rutile platelets and residual ilmenite, whereas below ˜900 K, the interband region contains a fine, filamentary network of pores. In the intermediate temperature regime, a change from dense to porous interband region occurs with increasing pressure. The observations have been interpreted in terms of the relative rates of interfacial chemical reaction and solid-state diffusion, with the latter having a controlling influence at lower temperatures or higher pressures.

de Vries, M. L.; Grey, I. E.; Fitz Gerald, J. D.

2007-04-01

127

Exploring for 3D photonic bandgap structures in the 11 f.c.c. space groups  

NASA Astrophysics Data System (ADS)

The promise of photonic crystals and their potential applications has attracted considerable attention towards the establishment of periodic dielectric structures that in addition to possessing robust complete bandgaps, can be easily fabricated with current techniques. A number of theoretical structures have been proposed. To date, the best complete photonic bandgap structure is that of diamond networks having Fd3m symmetry (2-3 gap). The only other known complete bandgap in a face-centred-cubic (f.c.c.) lattice structure is that of air spheres in a dielectric matrix (8-9 gap; the so called 'inverse-opal' structure). Importantly, there is no systematic approach to discovering champion photonic crystal structures. Here we propose a level-set approach based on crystallography to systematically examine for photonic bandgap structures and illustrate this approach by applying it to the 11 f.c.c. groups. This approach gives us an insight into the effects of symmetry and connectivity. We classify the F-space groups into four fundamental geometries on the basis of the connectivity of high-symmetry Wyckoff sites. Three of the fundamental geometries studied display complete bandgaps-including two: the F-RD structure with Fm'3 m symmetry and a group 216 structure with F 4'3m symmetry that have not been reported previously. By using this systematic approach we were able to open gaps between the 2-3, 5-6 and 8-9 bands in the f.c.c. systems.

Maldovan, Martin; Ullal, Chaitanya K.; Carter, W. Craig; Thomas, Edwin L.

2003-10-01

128

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

NASA Astrophysics Data System (ADS)

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 of the Planets, an exhibition organized by the British Council, at Eugenides Foundation and The Planetarium, where I prepared some 15 posters). We are preparing an outreach site of Astrophysics with sections for the planets, the exploration of the solar system and solar terrestrial relations. I am preparing several posters for the planets. We organize with the Hellenic Physical Union a series of Astrophysics Lectures at the University of Athens. Together with the Hellenic Physical Union we are planning to produce a theatrical play and CD or DVD concerning the planets. We have excellent collaboration with the amateur astronomers allover Greece and Cyprus. We organize, together with Physics or mathematics teachers in high schools several events related to astronomical observations (e.g. Venus transit, solar eclipe, astronomy nights). 1 We also organize popular science programmes in TV channels. I brief we consider Astronomy and especially the planetary system as a "Great Attractor" of pupil and the general public to science and we use it on every occasion for the benefit of the pupil and science. 2

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

129

Purification, identification and preliminary crystallographic characterization of a novel seed protein from Vigna unguiculata.  

PubMed

A tropical legume, Vigna unguiculata, was explored in order to identify potential allergens among the abundant seed proteins and to attempt their crystallographic study. Salt fractionation of the seed extract followed by chromatographic separation led to the purification of a 25 kDa protein. Gel-filtration chromatography of the 80% ammonium sulfate precipitation fraction led to separation of this protein in pure form, which was subjected to N-terminal sequencing. The N-terminal sequences of internal fragments of this protein showed 85% homology to mung bean seed albumin. This family of proteins is known to be intrinsically allergenic. Rhombic shaped crystals were obtained that diffracted to about 2.1 A resolution. The crystals belong to space group C2 and have unit-cell parameters a = 124.9, b = 60.1, c = 67.5 A, beta = 111.1 degrees . PMID:15502340

Chanana, Veenu; Kaur, Kanwal J; Salunke, Dinakar M

2004-10-20

130

Crystallization and preliminary crystallographic investigation of methanol dehydrogenase from Methylobacterium extorquens AM1.  

PubMed

Single crystals of methanol dehydrogenase (MDH) from Methylobacterium extorquens AM1 have been grown by the vapour diffusion method. These crystals diffract to beyond 2 A resolution and are suitable for X-ray crystallography. They belong to the orthorhombic space group P2(1)2(1)2(1) and have the following unit cell parameters: a = 66.79 A, b = 108.9 A, c = 188.9 A. One asymmetric unit contains an alpha 2 beta 2 tetramer of MDH and the location of the non-crystallographic 2-fold symmetry axis of this tetramer is defined by the paired positions of the binding sites of heavy atoms in four MDH-derivatives. PMID:1447790

Ghosh, M; Harlos, K; Blake, C C; Richardson, I; Anthony, C

1992-11-01

131

Crystallization and preliminary crystallographic studies of GRASP65 GRASP domain from Rattus norvegicus.  

PubMed

GRASP65 and GRASP55 were classified as Golgi reassembly stacking proteins which play crucial and complementary roles in the stacking of Golgi cisternae. They also participate in vesicle tethering, mitotic progression, the disassembly and reassembly of the Golgi apparatus during mitosis and unconventional secretory pathway regulation. In this study, the expression, crystallization and preliminary crystallographic analysis of the GRASP65 GRASP domain from Rattus norvegicus are presented. The crystals diffracted to 2.0 Å resolution and belonged to space group P21212, with unit-cell parameters a = 44.99, b = 104.29, c = 37.93 Å, ? = ? = ? = 90°. Furthermore, molecular replacement was employed to determine the structure of the GRASP65 GRASP domain from R. norvegicus. PMID:23832210

Li, Xinxin; Feng, Yanbin; Liu, Xinqi

2013-06-28

132

Crystallographic, Ferroelectric and Electronic Properties of the Sr2ZrTiO6 Double Perovskite  

NASA Astrophysics Data System (ADS)

In this paper, we report structural analysis, ferroelectric behavior and electronic structure of Sr2ZrTiO6 double perovskite. Samples were produced by the solid state reaction recipe. Crystallographic analysis was performed by Rietveld refinement of experimental X-ray diffraction patterns. Results show that this material crystallizes in a tetragonal perovskite structure which corresponds to the space group I4/m. The curve of polarization as a function of applied voltage evidences a ferroelectric character with saturation polarization on the application of voltages up to 1800 V. Calculations of density of states and band structure for this manganite-like material were carried out by means of the density functional theory implemented into the Wien2k code. Results of total and partial density of states reveal the insulator character of this material with an energy gap of 2.66 eV.

Landínez Téllez, D. A.; Carrero Bermúdez, L. A.; Deluque Toro, C. E.; Cardona, R.; Roa-Rojas, J.

2013-08-01

133

Facilitated spin models in one dimension: A real-space renormalization group study  

NASA Astrophysics Data System (ADS)

We use a real-space renormalization group (RSRG) to study the low-temperature dynamics of kinetically constrained Ising chains (KCICs). We consider the cases of the Fredrickson-Andersen (FA) model, the East model, and the partially asymmetric KCIC. We show that the RSRG allows one to obtain in a unified manner the dynamical properties of these models near their zero-temperature critical points. These properties include the dynamic exponent, the growth of dynamical length scales, and the behavior of the excitation density near criticality. For the partially asymmetric chain, the RG predicts a crossover, on sufficiently large length and time scales, from East-like to FA-like behavior. Our results agree with the known results for KCICs obtained by other methods.

Whitelam, Stephen; Garrahan, Juan P.

2004-10-01

134

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

SciTech Connect

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.

Steinacker, H. [Univ. of California, Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (United States)

1997-05-23

135

Concealed cyclotrimeric polymorph of lithium 2,2,6,6-tetramethylpiperidide unconcealed: x-ray crystallographic and NMR spectroscopic studies.  

PubMed

Lithium 2,2,6,6-tetramethylpiperidide (LiTMP), one of the most important polar organometallic reagents both in its own right and as a key component of ate compositions, has long been known for its classic cyclotetrameric (LiTMP)4 solid-state structure. Made by a new approach through transmetalation of Zn(TMP)2 with tBuLi in n-hexane solution, a crystalline polymorph of LiTMP has been uncovered. X-ray crystallographic studies at 123(2)?K revealed this polymorph crystallises in the hexagonal space group P63 /m and exhibited a discrete cyclotrimeric (C3h ) structure with a strictly planar (LiN)3 ring containing three symmetrically equivalent TMP chair-shaped ligands. The molecular structure of (LiTMP)4 was redetermined at 123(2)?K, because its original crystallographic characterisation was done at ambient temperature. This improved redetermination confirmed a monoclinic C2/c space group with the planar (LiN)4 ring possessing pseudo (non-crystallographic) C4h symmetry. Investigation of both metalation and transmetalation routes to LiTMP under different conditions established that polymorph formation did not depend on the route employed but rather the temperature of crystallisation. Low-temperature (freezer at -35?°C) cooling of the reaction solution favoured (LiTMP)3 ; whereas high-temperature (bench) storage favoured (LiTMP)4 . Routine (1) H and (13) C?NMR spectroscopic studies in a variety of solvents showed that (LiTMP)3 and (LiTMP)4 exist in equilibrium, whereas (1) H?DOSY NMR studies gave diffusion coefficient results consistent with their relative sizes. PMID:24019109

Hevia, Eva; Kennedy, Alan R; Mulvey, Robert E; Ramsay, Donna L; Robertson, Stuart D

2013-09-09

136

Sex of preceding child and birth spacing among Nigerian ethnic groups.  

PubMed

In seeking for more effective ways of fertility control and improvement of maternal and child health through birth spacing in a predominantly patrilineal society like Nigeria, this study explores how the sex of a previous child affects birth interval among ethnic groups, controlling for demographic and socioeconomic variables. The study utilized birth history data from the 2008 Nigeria Demographic and Health Survey. The findings showed that the effect of sex of prior births on the birth interval is slightly significant among the Igbo and the Southern minorities, who tend to desire to have a male child sooner if preceding births were female. Among all the ethnic groups, women who are yet to meet their ideal sex preference have a shorter birth interval than those who have. Apart from the evident sex preferences, these results suggest that Nigerian parents also undertake sex balancing among their children. There is a consistent and strong relationship between the survival of a child and subsequent birth interval, which suggest that women have a short birth interval, and hence a large family size, because they are not certain that their children would survive. PMID:22590895

Fayehun, O A; Omololu, O O; Isiugo-Abanihe, U C

2011-06-01

137

Some algebraic properties of crystallographic sublattices.  

PubMed

In this article, a number of the results relevant to the concept of sublattices of a basic crystallographic lattice are reviewed, emphasizing particularly previously unpublished work on the algebraic aspects. A three-dimensional geometric lattice L can be considered as an infinite Abelian group under addition. A sublattice S of L, which is also three-dimensional, is a subgroup of L such that the finite quotient group, G approximately equals L/S, is an Abelian group of order the index of S in L. The sublattice itself in its standard form is represented by an upper triangular matrix. The index of the sublattice is given by the determinant of this matrix. It is first noted that a sublattice described by an arbitrary basis set in L may be converted to this standard form. Next the sublattice is expressed as the intersection of a set of sublattices of individual index a power of a distinct prime, i.e. S(n = p(a)(1)p(b)(2)...) = S(1)(p(a)(1)[cap]S(2)(p(b)(2)...[cap]... = [bigcap](i)S(i)(p(alpha(i)), where p(1), p(2) etc. are prime numbers and n = Pi(i)p(alpha)(i) is the Euclidean factorization of n. This decomposition is important because it corresponds to the Sylow decomposition of the corresponding quotient group G approximately equals (i)[sign: see text] A(p)(i). It is also useful to be able to carry out two commutative binary operations on sublattices of L; these are to find their common sublattice of lowest index in L, which is their intersection S(cap) = S(a)(m)[cap]S(b)(n) and their common superlattice of highest index in L, given by S(< >) = , where < > indicates the span of the sublattices. PMID:16489245

Rutherford, John S

2006-02-18

138

The crystallographic structure of Panicum Mosaic Virus (PMV).  

PubMed

The structure of Panicum Mosaic Virus (PMV) was determined by X-ray diffraction analysis to 2.9Å resolution. The crystals were of pseudo symmetry F23; the true crystallographic unit cell was of space group P2(1) with a=411.7Å, b=403.9Å and c=412.5Å, with ?=89.7°. The asymmetric unit was two entire T=3 virus particles, or 360 protein subunits. The structure was solved by conventional molecular replacement from two distant homologues, Cocksfoot Mottle Virus (CfMV) and Tobacco Necrosis Virus (TNV), of ?20% sequence identity followed by phase extension. The model was initially refined with exact icosahedral constraints and then with icosahedral restraints. The virus has Ca(++) ions octahedrally coordinated by six aspartic acid residues on quasi threefold axes, which is completely different than for either CfMV or TNV. Amino terminal residues 1-53, 1-49 and 1-21 of the A, B and C subunits, respectively, and the four C-terminal residues (239-242) are not visible in electron density maps. The additional ordered residues of the C chain form a prominent "arm" that intertwines with symmetry equivalent "arms" at icosahedral threefold axes, as was seen in both CfMV and TNV. A 17 nucleotide hairpin segment of genomic RNA is icosahedrally ordered and bound at 60 equivalent sites at quasi twofold A-B subunit interfaces at the interior surface of the capsid. This segment of RNA may serve as a conformational switch for coat protein subunits, as has been proposed for similar RNA segments in other viruses. PMID:23123270

Makino, Debora L; Larson, Steven B; McPherson, Alexander

2012-11-01

139

Lost in Transmission: Using Study Groups to Provide Space for Creativity and Reflexivity in an Instrumentalist University Environment  

ERIC Educational Resources Information Center

Since independent study groups can be important in providing spaces for students in creative disciplines to develop a critically reflexive approach to their creative practice, tutors in an Australian university introduced independent group learning to students studying in creative disciplines. However, student responses to the experience of…

Pearce, Jane; Crouch, Christopher

2010-01-01

140

On the space group of the double perovskite Ba{sub 2}PrIrO{sub 6}  

SciTech Connect

The structure of the double perovskite Ba{sub 2}PrIrO{sub 6} has been re-examined by profile analysis of X-ray diffraction data. It has been shown that neither the monoclinic P2{sub 1}/n nor the tetragonal P4/mnc space group correctly describes its structure. Ba{sub 2}PrIrO{sub 6} has cubic symmetry, space group Fm3-bar m, cell parameter a=8.40135(6)A. In agreement with earlier observations, Ba{sub 2}PrIrO{sub 6} is an ordered perovskite containing the valence pair Pr(IV)/Ir(IV)

Fu, W.T. [Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands)]. E-mail: w.fu@chem.leidenuniv.nl; IJdo, D.J.W. [Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands)

2005-04-15

141

On the perturbation of the group generalized inverse for a class of bounded operators in Banach spaces  

NASA Astrophysics Data System (ADS)

Given a bounded operator A on a Banach space X with Drazin inverse AD and index r, we study the class of group invertible bounded operators B such that I+AD(B-A) is invertible and . We show that they can be written with respect to the decomposition as a matrix operator, , where B1 and are invertible. Several characterizations of the perturbed operators are established, extending matrix results. We analyze the perturbation of the Drazin inverse and we provide explicit upper bounds of ||B#-AD|| and ||BB#-ADA||. We obtain a result on the continuity of the group inverse for operators on Banach spaces.

Castro-González, N.; Vélez-Cerrada, J. Y.

2008-05-01

142

Doubly special relativity in position space starting from the conformal group  

Microsoft Academic Search

We propose version of doubly special relativity theory starting from position space. The version is based on deformation of ordinary Lorentz transformations due to the special conformal transformation. There is unique deformation which does not modify rotations. In contrast to the Fock–Lorentz realization (as well as to recent position-space proposals), maximum signal velocity is position (and observer) independent scale in

A. A. Deriglazov

2004-01-01

143

Predicting stable stoichiometries of compounds via evolutionary global space-group optimization  

NASA Astrophysics Data System (ADS)

Whereas the Daltonian atom-to-atom ratios in ordinary molecules are well understood via the traditional theory of valence, the naturally occurring stoichiometries in intermetallic compounds ApBq , as revealed by phase-diagram compilations, are often surprising. Even equal-valence elements A and B give rise to unequal (p,q) stoichiometries, e.g., the 1:2, 2:1, and 3:1 ratios in AlpScq . Moreover, sometimes different stoichiometries are associated with different lattice types and hence rather different physical properties. Here, we extend the fixed-composition global space-group optimization (GSGO) approach used to predict, via density-functional calculations, fixed-composition lattice types [G. Trimarchi and A. Zunger, J. Phys.: Condens. Matter 20, 295212 (2008)] to identify simultaneously all the minimum-energy lattice types throughout the composition range. Starting from randomly selected lattice vectors, atomic positions and stoichiometries, we construct the T=0 “convex hull” of energy vs composition. Rather than repeat a set of GSGO searches over a fixed list of stoichiometries, we minimize the distance to the convex hull. This approach is far more efficient than the former one as a single evolutionary search sequence simultaneously identifies the lowest-energy structures at each composition and among these it selects those that are ground states. For Al-Sc we correctly identify the stable stoichiometries and relative structure types: AlSc2-B82 , AlSc-B2, and Al2Sc-C15 in the Nat=6 periodic cells, and Al2Sc6-D019 , AlSc-B2, and Al3Sc-L10 in the Nat=8 periodic cells. This extended evolutionary GSGO algorithm represents a step toward a fully ab initio materials synthesis, where compounds are predicted starting from sole knowledge of the chemical species of the constituents.

Trimarchi, Giancarlo; Freeman, Arthur J.; Zunger, Alex

2009-09-01

144

Real-space scaling methods applied to the one-dimensional extended Hubbard model. I. The real-space renormalization-group method  

Microsoft Academic Search

The real-space renormalization-group method is applied to the one-dimensional extended Hubbard model. It is shown that in the half-filled-band case, the phase diagram consists of two phases and that the transition from the spin-ordered phase to the charge-ordered phase is continuous, a result which differs from that obtained previously from the broken-symmetry Hartree-Fock approximation.

B. Fourcade; G. Spronken

1984-01-01

145

Purification, crystallization and preliminary X-ray crystallographic analysis of the C-terminal cytoplasmic domain of FlhB from Aquifex aeolicus  

PubMed Central

FlhB is a key protein in the regulation of protein export by the bacterial flagellar secretion system. It is composed of two domains: an N-terminal transmembrane domain and a C-terminal cytoplasmic domain (FlhBc). Here, the crystallization and preliminary crystallographic analysis of FlhBc from Aquifex aeolicus are reported. Purified protein was crystallized using the vapour-diffusion technique. The crystals diffracted to 2.3?Å resolution and belonged to space group C2, with unit-cell parameters a = 114.49, b = 33.89, c = 122.13?Å, ? = 107.53°.

Meshcheryakov, Vladimir A.; Yoon, Young-Ho; Samatey, Fadel A.

2011-01-01

146

Purification, crystallization and preliminary X-ray crystallographic analysis of the C-terminal cytoplasmic domain of FlhB from Aquifex aeolicus.  

PubMed

FlhB is a key protein in the regulation of protein export by the bacterial flagellar secretion system. It is composed of two domains: an N-terminal transmembrane domain and a C-terminal cytoplasmic domain (FlhBc). Here, the crystallization and preliminary crystallographic analysis of FlhBc from Aquifex aeolicus are reported. Purified protein was crystallized using the vapour-diffusion technique. The crystals diffracted to 2.3?Å resolution and belonged to space group C2, with unit-cell parameters a = 114.49, b = 33.89, c = 122.13?Å, ? = 107.53°. PMID:21301106

Meshcheryakov, Vladimir A; Yoon, Young-Ho; Samatey, Fadel A

2011-01-27

147

Group vector space method for estimating enthalpy of vaporization of organic compounds at the normal boiling point.  

PubMed

The specific position of a group in the molecule has been considered, and a group vector space method for estimating enthalpy of vaporization at the normal boiling point of organic compounds has been developed. Expression for enthalpy of vaporization Delta(vap)H(T(b)) has been established and numerical values of relative group parameters obtained. The average percent deviation of estimation of Delta(vap)H(T(b)) is 1.16, which show that the present method demonstrates significant improvement in applicability to predict the enthalpy of vaporization at the normal boiling point, compared the conventional group methods. PMID:15272851

Wenying, Wei; Jinyu, Han; Wen, Xu

148

Crystallographic orientation assessment by electron backscattered diffraction.  

PubMed

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

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

149

Group-Theoretical Approach to Extended Conformal Supersymmetry: Functional Space Realizations and Invariant Differential Operators.  

National Technical Information Service (NTIS)

We give function space realizations of all representations of the conformal superalgebra su(2,2/N) and of the corresponding supergroup induced from irreducible finite-dimensional Lorentz and SU(N) representations realized without spin and isospin indices....

V. K. Dobrev V. B. Petkova

1985-01-01

150

Conditions for the Nontriviality of the Hilbert Space of a Holomorphically Induced Representation of a Solvable Lie Group  

NASA Astrophysics Data System (ADS)

The notion of holomorphically induced representation is a generalization of the concept of representation induced by a representation of a subgroup. It permitted Kostant and Auslander to give a classification of irreducible unitary representations of solvable Lie groups. A holomorphically induced representation is constructed in a function space on the group, where the functions satisfy a number of algebraic conditions and lie in some L^2-space. It may happen that some nontrivial functions satisfy the algebraic conditions but none of them lie in L^2. In this paper a necessary and sufficient condition that this not occur when the Lie group under consideration is solvable is proved. The condition involves the Lie algebra and the parameters appearing in the definition of the representation. Bibliography: 10 titles.

Za?cev, A. A.

1981-04-01

151

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

NASA Astrophysics Data System (ADS)

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 understand its place in the universe. While nations can and do solve problems independently, it takes nations, working together, to accomplish great things. The formation of the JWG provided an opportunity for the opening of a series of productive relationships between the superpowers, the US and the Union of Soviet Socialist Republics (USSR); and served as a justification for continued relationship for medical assistance in spaceflight, and to showcase Earth benefits from space medicine research. This relationship has been played out on an international scale with the construction and operation of the International Space Station. The fundamental reason for this successful endeavor is a direct result of the spirit and perseverance of the men and women who have worked diligently side-by-side to promote science and move our understanding of space forward. This manuscript provides a historical perspective of the JWG; how it came about; its evolution; what it accomplished; and what impact it has had and continues to have in the 21st century with regard to human spaceflight and space life sciences research. It captures the spirit of this group, which has been in continuous existence for over 40 years, and provides a never before reported summary of its activities.

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

2010-10-01

152

Representations of locally compact groups on QSL p -spaces and a p-analog of the Fourier–Stieltjes algebra  

Microsoft Academic Search

For a locally compact group $G$ and $p \\\\in (1,\\\\infty)$, we define $B_p(G)$ to\\u000abe the space of all coefficient functions of isometric representations of $G$\\u000aon quotients of subspaces of $L_p$ spaces. For $p =2$, this is the usual\\u000aFourier--Stieltjes algebra. We show that $B_p(G)$ is a commutative Banach\\u000aalgebra that contractively (isometrically, if $G$ is amenable) contains the

Volker Runde

2005-01-01

153

On duality and negative dimensions in the theory of Lie groups and symmetric spaces  

NASA Astrophysics Data System (ADS)

We give one more interpretation of the symbolic formulas U( - N) = U(N) and Sp( - 2N) = SO(2N) and show that they can be extended to the classical symmetric spaces using Macdonald duality for Jack and Jacobi symmetric functions.

Mkrtchyan, Ruben L.; Veselov, Alexander P.

2011-08-01

154

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)

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.

Allner, M.; Rygalov, V.

2008-12-01

155

Clustering and group selection of multiple criteria alternatives with application to space-based networks.  

PubMed

In many real-world problems, the range of consequences of different alternatives are considerably different. In addition, sometimes, selection of a group of alternatives (instead of only one best alternative) is necessary. Traditional decision making approaches treat the set of alternatives with the same method of analysis and selection. In this paper, we propose clustering alternatives into different groups so that different methods of analysis, selection, and implementation for each group can be applied. As an example, consider the selection of a group of functions (or tasks) to be processed by a group of processors. The set of tasks can be grouped according to their similar criteria, and hence, each cluster of tasks to be processed by a processor. The selection of the best alternative for each clustered group can be performed using existing methods; however, the process of selecting groups is different than the process of selecting alternatives within a group. We develop theories and procedures for clustering discrete multiple criteria alternatives. We also demonstrate how the set of alternatives is clustered into mutually exclusive groups based on 1) similar features among alternatives; 2) ideal (or most representative) alternatives given by the decision maker; and 3) other preferential information of the decision maker. The clustering of multiple criteria alternatives also has the following advantages. 1) It decreases the set of alternatives to be considered by the decision maker (for example, different decision makers are assigned to different groups of alternatives). 2) It decreases the number of criteria. 3) It may provide a different approach for analyzing multiple decision makers problems. Each decision maker may cluster alternatives differently, and hence, clustering of alternatives may provide a basis for negotiation. The developed approach is applicable for solving a class of telecommunication networks problems where a set of objects (such as routers, processors, or intelligent autonomous vehicles) are to be clustered into similar groups. Objects are clustered based on several criteria and the decision maker's preferences. PMID:15369049

Malakooti, Behnam; Yang, Ziyong

2004-02-01

156

Distinctive Places, Suitable Spaces: Conceptualizing Mobile Group Occupational Duration and Landscape Use  

Microsoft Academic Search

While extreme mobility and ensconced sedentism can be easily distinguished in the archeological record, effective means are\\u000a lacking of discriminating between degrees of mobility that may range from seasonal shifts by farmers to recurrent moves across\\u000a the landscape as a way of life. Fortunately, site layout and the way space is used are related to expectations regarding length\\u000a of stay,

Deni J. Seymour

2009-01-01

157

Standard and Generalized Newtonian Gravities as ``Gauge'' Theories of the Extended Galilei Group - II: Dynamical Three-Space Theories  

Microsoft Academic Search

In a preceding paper we developed a reformulation of Newtonian gravitation as\\u000aa {\\\\it gauge} theory of the extended Galilei group. In the present one we\\u000aderive two true generalizations of Newton's theory (a {\\\\it ten-fields} and an\\u000a{\\\\it eleven-fields} theory), in terms of an explicit Lagrangian realization of\\u000athe {\\\\it absolute time} dynamics of a Riemannian three-space. They turn

R. De Pietri; L. Lusanna; M. Pauri

1994-01-01

158

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

PubMed Central

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 P212121, 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.

Mori, Tomoyuki; Kitano, Ken; Terawaki, Shin-ichi; Maesaki, Ryoko; Hakoshima, Toshio

2007-01-01

159

Preliminary X-ray crystallographic analysis of the d--xylulose 5-phosphate phospho-ketolase from Lactococcus lactis  

PubMed Central

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.

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

2010-01-01

160

The Effects of Status Space and Status Struggle on Group Decision Making.  

ERIC Educational Resources Information Center

Using Status Characteristic Theory as a theoretical framework, increasing status distinctions between professional group members were predicted to decrease the quantity of task related information and quality of decisions made in small problem-solving groups. Three experimental conditions were created: (1) occupational prestige manipulated, (2)…

Bloom, Joan R.

161

Purification, crystallization and preliminary crystallographic analysis of the 23S rRNA methyltransferase RlmM (Cm2498) from Escherichia coli.  

PubMed

RlmM is an AdoMet-dependent methyltransferase that is responsible for 2'-O-methylation of C2498 in the peptidyl-transferase loop of bacterial 23S rRNA. This modification occurs before assembly of the 50S ribosomal subunit, and lack of C2498 methylation can cause a slight reduction in bacterial fitness. Here, the purification and crystallization of RlmM from Escherichia coli as well as its preliminary crystallographic analysis are presented. Cocrystallization of RlmM with AdoMet was carried out and X-ray diffraction data were collected to a resolution of 2.30 Å on beamline BL17U at the SSRF. However, electron density for AdoMet cannot be observed by comprehensive crystallographic analysis, indicating that it is not bound by RlmM during the cocrystallization process. The structure was solved by molecular replacement and refinement is in progress. The crystal contained one molecule in the asymmetric unit and belonged to space group P2(1), with unit-cell parameters a = 56.07, b = 59.38, c = 54.35 Å, ? = 94.84°, which differs from the P3(1) or P3(1)21 space groups of previously reported RlmM structures (PDB entries 4auk, 4atn and 4b17). PMID:23722841

Guo, Hong Yue; Gao, Zeng Qiang; Zhang, Heng; Wei, Yong; Xu, Jian Hua; Wang, Wen Ya; Yan, Ai Xia; Dong, Yu Hui

2013-05-24

162

Crystal growth and first crystallographic characterization of mixed uranium(IV)-plutonium(III) oxalates.  

PubMed

The mixed-actinide uranium(IV)-plutonium(III) oxalate single crystals (NH4)0.5[Pu(III)0.5U(IV)0.5(C2O4)2·H2O]·nH2O (1) and (NH4)2.7Pu(III)0.7U(IV)1.3(C2O4)5·nH2O (2) have been prepared by the diffusion of different ions through membranes separating compartments of a triple cell. UV-vis, Raman, and thermal ionization mass spectrometry analyses demonstrate the presence of both uranium and plutonium metal cations with conservation of the initial oxidation state, U(IV) and Pu(III), and the formation of mixed-valence, mixed-actinide oxalate compounds. The structure of 1 and an average structure of 2 were determined by single-crystal X-ray diffraction and were solved by direct methods and Fourier difference techniques. Compounds 1 and 2 are the first mixed uranium(IV)-plutonium(III) compounds to be structurally characterized by single-crystal X-ray diffraction. The structure of 1, space group P4/n, a = 8.8558(3) Å, b = 7.8963(2) Å, Z = 2, consists of layers formed by four-membered rings of the two actinide metals occupying the same crystallographic site connected through oxalate ions. The actinide atoms are nine-coordinated by oxygen atoms from four bidentate oxalate ligands and one water molecule, which alternates up and down the layer. The single-charged cations and nonbonded water molecules are disordered in the same crystallographic site. For compound 2, an average structure has been determined in space group P6/mmm with a = 11.158(2) Å and c = 6.400(1) Å. The honeycomb-like framework [Pu(III)0.7U(IV)1.3(C2O4)5](2.7-) results from a three-dimensional arrangement of mixed (U0.65Pu0.35)O10 polyhedra connected by five bis-bidentate ?(2)-oxalate ions in a trigonal-bipyramidal configuration. PMID:23577593

Tamain, Christelle; Arab Chapelet, Bénédicte; Rivenet, Murielle; Abraham, Francis; Caraballo, Richard; Grandjean, Stéphane

2013-04-11

163

Two-Dimensional Space-Time Dependent Multi-group Diffusion Equation with SLOR Method  

NASA Astrophysics Data System (ADS)

The research of two-dimensional space-time diffusion equations with SLOR (Successive-Line Over Relaxation) has been done. SLOR method is chosen because this method is one of iterative methods that does not required to defined whole element matrix. The research is divided in two cases, homogeneous case and heterogeneous case. Homogeneous case has been inserted by step reactivity. Heterogeneous case has been inserted by step reactivity and ramp reactivity. In general, the results of simulations are agreement, even in some points there are differences.

Yulianti, Y.; Su'Ud, Z.; Waris, A.; Khotimah, S. N.

2010-06-01

164

Innovation in the teaching of astrophysics and space science - spacecraft design group study  

NASA Astrophysics Data System (ADS)

This paper describes how the design of a scientific satellite can be used to provide both a stimulating and effective subject for a physics based group study. The group study divides the satellite into distinct subsystems and small teams of two or three students carry out the detailed design of each subsystem. The aim is to produce a complete satellite system design along with the choice of launch vehicle, orbit and communications system so that all the mission requirements can be met. An important feature of the group study is that it is a student led activity with staff acting as mentors. The development of key skills and important learning outcomes from the group study is discussed along with the method for assessment, structuring and resourcing the study.

Castelli, C.

2003-03-01

165

Working Group 4 of international standardization organization Experience of developing the standards of space environment  

NASA Astrophysics Data System (ADS)

Over the past decade space environment international standards have been developed within the scope of ISO WG4 activities. This has been the first attempt to develop international standards of physical phenomena of natural environment such as galactic cosmic rays, solar energetic particles, the Earth’s magnetic field, the ionosphere, the plasmasphere, etc. The main difficulty faced when developing the international standards is the lack of common methods for characterizing many natural phenomena. However, if methods have been successfully developed, such standards can play an outstanding role in the engineering requirements for spacecraft designs. This report is a survey of the current status of the international standards under development within the scope of the WG4 activity plan.

Panasyuk, M. I.

2006-01-01

166

The Stafford Commission synthesis group evaluation of power for the space exploration initiative  

NASA Astrophysics Data System (ADS)

Power for life support systems, experiments, operation of computers and communications equipment, preparation of sites, surface transportation, and extraction and processing resources from planetary surface is an essential element of the space exploration initiative. The philosophies for meeting power system requirements include: use of multiple units and power system types to ensure high reliability and safety; modular units that can be launched as a unit; minimization/elimination of off-earth assembly; emergency backup power for manned operational product improvement rather than developing the ultimate in the first unit; and adequate power options to satisfy anticipated power demand growth. The assessment approach used was to first examine the needs in terms of power level, duration, specific power, reliability, and need dates. Then, an assessment was performed of candidate technologies. A decision matrix was used to assess the candidate technologies relative to the needs. From this, candidate power systems were selected. Finally, particular systems are recommended for flight development.

Buden, David; Bartine, David; Harrison, Steve; Foremen, Joe; Biringer, Kent

167

European Modelling Group Solar Space Heating and Domestic Hot Water Systems.  

National Technical Information Service (NTIS)

The co-operative work within the European Modelling Group for Solar Heating Systems and Domestic Hot Water is undertaken as part of the CEC's research and development program on Solar Applications for Dwellings. During the last two years of operation of t...

O. Balslev-Olesen

1985-01-01

168

Clustering and group selection of multiple criteria alternatives with application to space-based networks  

Microsoft Academic Search

In many real-world problems, the range of conse- quences of different alternatives are considerably different. In ad- dition, sometimes, selection of a group of alternatives (instead of only one best alternative) is necessary. Traditional decision making approaches treat the set of alternatives with the same method of analysis and selection. In this paper, we propose clustering alter- natives into different

Behnam Malakooti; Ziyong Yang

2004-01-01

169

A walk through energy, discrepancy, numerical integration and group invariant measures on measurable subsets of euclidean space  

NASA Astrophysics Data System (ADS)

(A) The celebrated Gaussian quadrature formula on finite intervals tells us that the Gauss nodes are the zeros of the unique solution of an extremal problem. We announce recent results of Damelin, Grabner, Levesley, Ragozin and Sun which derive quadrature estimates on compact, homogenous manifolds embedded in Euclidean spaces, via energy functionals associated with a class of group-invariant kernels which are generalizations of zonal kernels on the spheres or radial kernels in euclidean spaces. Our results apply, in particular, to weighted Riesz kernels defined on spheres and certain projective spaces. Our energy functionals describe both uniform and perturbed uniform distribution of quadrature point sets. (B) Given , some measurable subset of Euclidean space, one sometimes wants to construct, a design, a finite set of points, , with a small energy or discrepancy. We announce recent results of Damelin, Hickernell, Ragozin and Zeng which show that these two measures of quality are equivalent when they are defined via positive definite kernels . The error of approximating the integral by the sample average of f over has a tight upper bound in terms the energy or discrepancy of . The tightness of this error bound follows by requiring f to lie in the Hilbert space with reproducing kernel K. The theory presented here provides an interpretation of the best design for numerical integration as one with minimum energy, provided that the ? defining the integration problem is the equilibrium measure or charge distribution corresponding to the energy kernel, K. (C) Let be the orbit of a compact, possibly non Abelian group, , acting as measurable transformations of and the kernel K is invariant under the group action. We announce recent results of Damelin, Hickernell, Ragozin and Zeng which show that the equilibrium measure is the normalized measure on induced by Haar measure on . This allows us to calculate explicit representations of equilibrium measures. There is an extensive literature on the topics (A-C). We emphasize that this paper surveys recent work of Damelin, Grabner, Levesley, Hickernell, Ragozin, Sun and Zeng and does not mean to serve as a comprehensive survey of all recent work covered by the topics (A-C).

Damelin, S.

2008-07-01

170

Individual and grouping track pits etched in the exposed in a free space plastic track detectors  

NASA Astrophysics Data System (ADS)

New results concerned to the investigation of depth-dependent the pit-like surface-average and the grouping track-density distributions in the cosmic ray exposed column of CN-85 and CR-39 plastic solid state nuclear track detectors (SSNTD) are presented. Two main sources: solar cosmic ray protons and recoil nuclei for very short (length <3 ?m) track-pit formation are considered. Theoretical estimation of the total, uniform track-pit density indicates on failure of evidence of some additional radiation effects, partially, hypothetically conditioned with the Erzion theory. Some quantitative proofs of this hypothesis have been obtained in the measurements of the pit-groups. Totally, up to this time it was registered near of 30 pit groups with the surface pit-density in the interval of (1-15) × 106 cm2, that is two-three orders of magnitude higher than uniformly distributed track-pits on the same CR-39 plate surface. As a result of layer-by-layer investigation of the exposed CN-85 stock arrangement three pit swarms exactly correlated with the end point of high ionizing primary charge particle tracks were observed. Obtained data are considered in according to submission based on the probability of detection for the negative charged cosmic ray Erzion particles stopping events.

Kashkarov, L.; Bazhutov, Yu

2013-02-01

171

Building a research group of Space Physics at UAHuntsville -- the impact of an NSF career award  

NASA Astrophysics Data System (ADS)

G. Li (1,2) (1) Department of Physics, University of Alabama in Huntsville Huntsville, AL, 35899 (2) CSPAR, University of Alabama in Huntsville Huntsville, AL, 35899 The author joined the faculty of the department of Physics at University of Alabama in Huntsville in August 2008. He was awarded the NSF Career award ATM-0847719 in 2009. To date, the Career award has provided partial supports to one postdoc, two graduate students and three undergraduate students for a variety of periods. Three publications came out as a result of the award (one of which is first authored by one undergraduate). Another two publications are in preparation. The award also helped the PI to be further recognized by the field of space plasma physics and cosmic ray physics. For example, in July 2009, the PI was awarded the Young Scientist Medal by the International Union of Pure and Applied Physics (IUPAP); in April 2010, the PI won an Oak Ridge Associated Universities (ORAU) 2010 Ralph E. Powe Junior Faculty Enhancement Award. In short, the NSF CAREER has helped the PI to start his career at a level without which, will be impossible.

Li, G.

2011-12-01

172

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

PubMed

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

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

1996-01-01

173

LETTER TO THE EDITOR: Real space renormalization group analysis of the random field Ising model  

NASA Astrophysics Data System (ADS)

We present an analytic Migdal - Kadanoff renormalization group analysis of the random field Ising model. The renormalization flows to a zero-temperature critical point, from which we calculate independently three critical exponents in arbitrary dimension. In three dimensions the magnetization exponent 0305-4470/29/21/002/img1, and the Schwartz - Soffer inequality is almost satisfied as an equality. Expanding analytically in 0305-4470/29/21/002/img2 we find that 0305-4470/29/21/002/img3 and the distance from the upper bound of the equality go to zero exponentially with 0305-4470/29/21/002/img4.

Fortin, J.-Y.; Holdsworth, P. C. W.

1996-11-01

174

Behavioral and biological effects of autonomous versus scheduled mission management in simulated space-dwelling groups  

NASA Astrophysics Data System (ADS)

Logistical constraints during long-duration space expeditions will limit the ability of Earth-based mission control personnel to manage their astronaut crews and will thus increase the prevalence of autonomous operations. Despite this inevitability, little research exists regarding crew performance and psychosocial adaptation under such autonomous conditions. To this end, a newly-initiated study on crew management systems was conducted to assess crew performance effectiveness under rigid schedule-based management of crew activities by Mission Control versus more flexible, autonomous management of activities by the crews themselves. Nine volunteers formed three long-term crews and were extensively trained in a simulated planetary geological exploration task over the course of several months. Each crew then embarked on two separate 3-4 h missions in a counterbalanced sequence: Scheduled, in which the crews were directed by Mission Control according to a strict topographic and temporal region-searching sequence, and Autonomous, in which the well-trained crews received equivalent baseline support from Mission Control but were free to explore the planetary surface as they saw fit. Under the autonomous missions, performance in all three crews improved (more high-valued geologic samples were retrieved), subjective self-reports of negative emotional states decreased, unstructured debriefing logs contained fewer references to negative emotions and greater use of socially-referent language, and salivary cortisol output across the missions was attenuated. The present study provides evidence that crew autonomy may improve performance and help sustain if not enhance psychosocial adaptation and biobehavioral health. These controlled experimental data contribute to an emerging empirical database on crew autonomy which the international astronautics community may build upon for future research and ultimately draw upon when designing and managing missions.

Roma, Peter G.; Hursh, Steven R.; Hienz, Robert D.; Emurian, Henry H.; Gasior, Eric D.; Brinson, Zabecca S.; Brady, Joseph V.

2011-05-01

175

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

PubMed Central

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.

Oyenarte, Iker; Majtan, Tomas; Ereno, June; Corral-Rodriguez, Maria Angeles; Klaudiny, Jaroslav; Majtan, Juraj; Kraus, Jan P.; Martinez-Cruz, Luis Alfonso

2012-01-01

176

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

PubMed

Succinic semialdehyde reductase (SSAR) is an important enzyme involved in ?-aminobutyrate (GABA) metabolism. By converting succinic semialdehyde (SSA) to ?-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(+), and the resulting crystals diffracted to 1.89 Å (GsSSAR) and 2.25 Å (GmSSAR) resolution. The GsSSAR and GmSSAR crystals belong to the space groups P2(1)22(1) (a= 99.61 Å, b= 147.49 Å, c= 182.47 Å) and P1 (a= 75.97 Å, b= 79.14 Å, c= 95.47 Å, ? = 82.15°, ? = 88.80°, ? = 87.66°), respectively. Preliminary crystallographic data analysis suggests the presence of eight protein monomers in the asymmetric units for both GsSSAR and GmSSAR. PMID:22037946

Zhang, Yanfeng; Gao, Xiaoli; Zheng, Yi; Garavito, R Michael

2011-10-27

177

Expression, crystallization and preliminary crystallographic study of GluB from Corynebacterium glutamicum.  

PubMed

GluB is a substrate-binding protein (SBP) which participates in the uptake of glutamic acid in Corynebacterium glutamicum, a Gram-positive bacterium. It is part of an ATP-binding cassette (ABC) transporter system. Together with the transmembrane proteins GluC and GluD and the cytoplasmic protein GluA, which couples the hydrolysis of ATP to the translocation of glutamate, they form a highly active glutamate-uptake system. As part of efforts to study the amino-acid metabolism, especially the metabolism of glutamic acid by C. glutamicum, a bacterium that is widely used in the industrial production of glutamic acid, the GluB protein was expressed, purified and crystallized, an X-ray diffraction data set was collected to a resolution of 1.9 Å and preliminary crystallographic analysis was performed. The crystal belonged to space group P3(1)21 or P3(2)21, with unit-cell parameters a = b = 82.50, c = 72.69 Å. PMID:23722846

Liu, Qingbo; Li, Defeng; Hu, Yonglin; Wang, Da Cheng

2013-05-25

178

GROUP  

Microsoft Academic Search

In this paper we continue the study ofalg 1 (S) for minimal surfaces of general type S satisfying K2 S < 3?(S). We show that, if K 2 S = 3?(S) 1 and |?alg 1 (S)| = 8, then S is a Campedelli surface. In view of the results of (MP1) and (MP2), this implies that the fundamental group of

CIRO CILIBERTO; MARGARIDA MENDES LOPES; RITA PARDINI

179

Crystallization and preliminary X-ray crystallographic studies of an exo-?-d-glucosaminidase from Trichoderma reesei  

PubMed Central

Chitosan is degraded to glucosamine (GlcN) by chitosanase and exo-?-d-glucosaminidase (GlcNase). GlcNase from Trichoderma reesei (Gls93) is a 93?kDa extracellular protein composed of 892 amino acids. The enzyme liberates GlcN from the nonreducing end of the chitosan chain in an exo-type manner and belongs to glycoside hydrolase family 2. For crystallographic investigations, Gls93 was overexpressed in Pichia pastoris cells. The recombinant Gls93 had two molecular forms of ?105?kDa (Gls93-F1) and ?100?kDa (Gls93-F2), with the difference between them being caused by N-glycosylation. Both forms were crystallized by the hanging-drop vapour-diffusion method. Crystals of Gls93-F1 belonged to the orthorhombic space group P212121, with unit-cell parameters a = 98.27, b = 98.42, c = 108.28?Å, and diffracted to 1.8?Å resolution. Crystals of Gls93-F2 belonged to the ortho­rhombic space group P212121, with unit-cell parameters a = 67.84, b = 81.62, c = 183.14?Å, and diffracted to 2.4?Å resolution. Both crystal forms were suitable for X-ray structure analysis at high resolution.

Sakamoto, Yasumitsu; Ike, Masakazu; Tanaka, Nobutada; Suzuki, Yoshiyuki; Ogasawara, Wataru; Okada, Hirofumi; Nonaka, Takamasa; Morikawa, Yasushi; Nakamura, Kazuo T.

2010-01-01

180

Structure of delta-Bi{sub 2}O{sub 3} from density functional theory: A systematic crystallographic analysis  

SciTech Connect

A systematic crystallographic analysis of the <110> and <111> vacancy-ordered structure of cubic delta-Bi{sub 2}O{sub 3} obtained from electronic-structure calculations is presented. The ordering of vacancies leads to a doubling of the unit-cell that results in a 2x2x2 fluorite super-structure, with an associated reduction in its space group symmetry from Fm3-barm to Fm3-bar. The Bi atoms present inside the <111> vacancy-ordered oxygen sublattice have equal Bi-O bond lengths, whereas, those present inside the <110> vacancy-ordered oxygen sublattice have three different pairs of Bi-O bond lengths. The specific ionic displacements and electronic charge configurations also depend on the nature of vacancy ordering in the oxygen sub-lattice. - Graphical abstract: 1/8 of a 2x2x2 delta-Bi{sub 2}O{sub 3} superstructure having Fm3-bar space group. Every oxygen (black) has three possible positions, only one of which is filled either by O1 (red) or O{sub 2} (blue).

Aidhy, Dilpuneet S.; Sinnott, Susan B.; Wachsman, Eric D.; Phillpot, Simon R. [Department of Materials Science and Engineering, Rhines Hall, Gainesville, FL 32611 (United States); Nino, Juan C., E-mail: jnino@mse.ufl.ed [Department of Materials Science and Engineering, Rhines Hall, Gainesville, FL 32611 (United States)

2009-05-15

181

Crystallization and preliminary crystallographic analysis of endo-1,4-beta-xyalanase I from Aspergillus niger.  

PubMed

A family G xylanase from Aspergillus niger has been crystallized using the vapor-diffusion method. Several crystal forms could be obtained using various sodium salts as precipitants. Three of the crystal forms belong to space groups P21, P2(1)2(1)2(1) and P4(3) and have cell parameters of approximately a = b = 85.1, c = 113.6 A and alpha = beta = gamma = 90 degrees. These crystal forms can be converted into one another by flash freezing or macroseeding. A fourth crystal form is cubic (space group P2(1)3) with unit-cell axes of a = b = c = 112.3 A. Data sets for three of the four crystal forms have been collected, extending to a maximum resolution of 2.4 A. The structures of the monoclinic and orthorhombic crystals have been solved by molecular replacement by combining the crystallographic information of the different crystal forms. Refinement of the orthorhombic crystal form is now in progress. PMID:15299682

Krengel, U; Rozeboom, H J; Kalk, K H; Dijkstra, B W

1996-05-01

182

Crystal families and systems in higher dimensions, and geometrical symbols of their point groups. II. Cubic families in five- and n-dimensional spaces  

NASA Astrophysics Data System (ADS)

The definition, properties and symbols of the iso cubic groups are given. The mono cubic crystal families of space E^n are defined and listed for n = 3 to n = 7. As an application, four crystal families of space E^5 are studied in detail.

Weigel, D.; Phan, T.; Veysseyre, R.

2008-11-01

183

XTAL system of crystallographic programs: programmer's manual  

SciTech Connect

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.

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

1980-02-01

184

Saturated Kochen-Specker-type configuration of 120 projective lines in eight-dimensional space and its group of symmetry  

SciTech Connect

There exists an example of a set of 40 projective lines in eight-dimensional Hilbert space producing a Kochen-Specker-type contradiction. This set corresponds to a known no-hidden variables argument due to Mermin. In the present paper it is proved that this set admits a finite saturation, i.e., an extension up to a finite set with the following property: every subset of pairwise orthogonal projective lines has a completion, i.e., is contained in at least one subset of eight pairwise orthogonal projective lines. An explicit description of such an extension consisting of 120 projective lines is given. The idea to saturate the set of projective lines related to Mermin's example together with the possibility to have a finite saturation allow to find the corresponding group of symmetry. This group is described explicitely and is shown to be generated by reflections. The natural action of the mentioned group on the set of all subsets of pairwise orthogonal projective lines of the mentioned extension is investigated. In particular, the restriction of this action to complete subsets is shown to have only four orbits, which have a natural characterization in terms of the construction of the saturation.

Ruuge, Artur E.; Oystaeyen, Freddy van [Department of Quantum Statistics and Field Theory, Faculty of Physics, Moscow State University , Vorobyovy Gory, 119899 Moscow (Russian Federation); Department of Mathematics and Computer Science, University of Antwerp, Middelheim Campus, Building G, Meddelheimlaan 1, B-2020 Antwerp (Belgium); Department of Mathematics and Computer Science, University of Antwerp, Middelheim Campus, Building G, Meddelheimlaan 1, B-2020 Antwerp (Belgium)

2005-05-01

185

Critical Dynamics of the Xy-Model on the One-Dimensional Superlattice by Position Space Renormalization Group  

NASA Astrophysics Data System (ADS)

The critical dynamics of the isotropic XY-model on the one-dimensional superlattice is considered in the framework of the position space renormalization group theory. The decimation transformation is introduced by considering the equations of motion of the operators associated to the excitations of the system, and it corresponds to an extension of the procedure introduced by Stinchcombe and dos Santos (J. Phys. A18, L597 (1985)) for the homogeneous lattice. The dispersion relation is obtained exactly and the static and dynamic scaling forms are explicitly determined. The dynamic critical exponent is also obtained and it is shown that it is identical to the one of the XY-model on the homogeneous chain.

Lima, J. P. De; Gonçalves, L. L.

186

Crystallographic features of lath martensite in low-carbon steel  

Microsoft Academic Search

Electron backscattering diffraction with field-emission scanning electron microscopy was used to analyze crystallographically the lath martensite structure in a 0.20% carbon steel. The crystallographic features of the lath martensite structure, of the order of the prior austenite grain size or larger, were clarified. Although the orientations of the martensite crystals were scattered around the ideal variant orientations, the martensite in

Hiromoto Kitahara; Rintaro Ueji; Nobuhiro Tsuji; Yoritoshi Minamino

2006-01-01

187

Teaching Biochemists and Pharmacologists How to Use Crystallographic Data.  

ERIC Educational Resources Information Center

|Describes a one-semester course designed to teach first year graduate students how to extract, interpret, evaluate, and use the information provided by an X-ray crystallographic crystal structure determination. Presents a course outline and discusses the treatment of crystal composition, crystallographic parameters, molecular geometry and…

Duax, William L.

1988-01-01

188

Requirements for space-based observations in fire management: a report by the Wildland Fire Hazard Team, Committee on Earth Observation Satellites (CEOS) Disaster Management Support Group (DMSG)  

Microsoft Academic Search

The Wildland Fire Hazard Team reviewed potential requirements for space-based observations in fire management. The team produced a report, developed under the auspices of the Disaster Management Support Group (DMSG) of the G-7 Committee on Earth Observation Satellites (CEOS). The document was prepared by an international working group, with experience in the field of remote sensing as applied to wildland

T. J. Lynham; C. W. Dull; A. Singh

2002-01-01

189

Crystallographic and hydriding properties of the system La1-xCexY2Ni9 (xCe=0, 0.5 and 1)  

NASA Astrophysics Data System (ADS)

The structural properties of the system La1-xCexY2Ni9 with xCe=0, 0.5 and 1 have been investigated by electron probe microanalysis, powder X-ray diffraction and absorption spectroscopy. The compound LaY2Ni9 adopts a rhombohedral structure of PuNi3-type (R-3m space group, /Z=3). It can be described as an intergrowth between RM5 (Haücke phase) and RM2 (Laves phase) type structures. Among the two available crystallographic sites for R atoms, lanthanum occupies preferentially the site 3a leading to a partially ordered ternary compound. Substitution by cerium involves anisotropic variations of the cell parameter with a decrease of a and an increase of c leading to an overall cell volume reduction. Increasing cerium content does not induce any symmetry change but leads to a statistical distribution of the rare earths over the two sites 3a and 6c involving an evolution toward a pseudo-binary compound. This behavior is related to the intermediate valence state of cerium observed by X-ray absorption spectroscopy. The hydriding properties of the two compounds LaY2Ni9 and CeY2Ni9 are described in relation with their crystallographic structure.

Latroche, M.; Baddour-Hadjean, R.; Percheron-Guégan, A.

2003-06-01

190

Magnetic and crystallographic properties of synthetic titanomaghemite  

NASA Astrophysics Data System (ADS)

Systematic magnetic and crystallographic studies were made on 57 titanomaghemite samples produced from sintered titanomagnetites with x values of 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0. Curie temperature and lattice parameter values are often significantly different from results of previous studies (Ozima and Sakamoto, 1971; Readman and O'Reilly, 1972; Nishitani, 1979), particularly for x values of 0.4 and 0.6. Other important results are: (1) Oxidation of titanomagnetite is mainly a function of temperature. Atmosphere and Ti content have little influence. (2) Progressive oxidation of homogeneous titanomaghemites can take place in the presence of a rhombohedral phase. The amount of rhombohedral phase produced during oxidation increases with increasing temperature and (less conclusively) with decreasing Ti content. (3) Saturation magnetization measurements at low temperatures show both P- and Q-type ferrimagnetic behavior in titanomaghemites, and also show the Verwey (?) transition in titanomaghemites with composition x=0.0. (4) The temperature of spinel inversion increases with degree of oxidation. Slightly oxidized samples invert near 300°C; for samples with z > 0.8 the inversion temperature is above 450°C. This last result, although neither expected nor understood, is supported by results of thermomagnetic studies on some oceanic basalts.

Keefer, C. M.; Shive, P. N.

1982-12-01

191

Crystallization and preliminary X-ray crystallographic studies of the outer membrane cytochrome OmcA from Shewanella oneidensis MR-1.  

PubMed

The outer membrane cytochrome OmcA functions as a terminal metal reductase in the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. The ten-heme centers shuttle electrons from the transmembrane donor complex to extracellular electron acceptors. Here, the crystallization and preliminary crystallographic analysis of OmcA are reported. Crystals of OmcA were grown by the sitting-drop vapor-diffusion method using PEG 20,000 as a precipitant. The OmcA crystals belonged to space group P2(1), with unit-cell parameters a = 93.0, b = 246.0, c = 136.6 Å, ? = 90, ? = 97.8, ? = 90°. X-ray diffraction data were collected to a maximum resolution of 3.25 Å. PMID:22232171

Tomanicek, S J; Johs, A; Sawhney, M S; Shi, L; Liang, L

2011-12-24

192

Crystallization and preliminary X-ray crystallographic studies of the outer membrane cytochrome OmcA from Shewanella oneidensis MR-1  

SciTech Connect

The outer membrane cytochrome OmcA functions as a terminal metal reductase in the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. The ten-heme centers shuttle electrons from the transmembrane donor complex to extracellular electron acceptors. Here, the crystallization and preliminary crystallographic analysis of OmcA are reported. Crystals of OmcA were grown by the sitting-drop vapor-diffusion method using PEG 20 000 as a precipitant. The OmcA crystals belonged to space group P21, with unit-cell parameters a = 93.0, b = 246.0, c = 136.6 A ° , * = 90, * = 97.8, * = 90*. X-ray diffraction data were collected to a maximum resolution of 3.25 A ° .

Tomanicek, S. J.; Johs, Alexander; Sawhney, M. S.; Shi, Liang; Liang, L.

2012-01-01

193

Crystallization and preliminary X-ray crystallographic studies of the outer membrane cytochrome OmcA from Shewanella oneidensis MR-1  

SciTech Connect

The outer membrane cytochrome OmcA functions as a terminal metal reductase in the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. The ten-heme centers shuttle electrons from the transmembrane donor complex to extracellular electron acceptors. Here, the crystallization and preliminary crystallographic analysis of OmcA are reported. Crystals of OmcA were grown by the sitting-drop vapor-diffusion method using PEG 20 000 as a precipitant. The OmcA crystals belonged to space group P2{sub 1}, with unit-cell parameters a = 93.0, b = 246.0, c = 136.6 {angstrom}, = 90, {beta} = 97.8, {gamma} = 90{sup o}. X-ray diffraction data were collected to a maximum resolution of 3.25 {angstrom}.

Tomanicek, S.J.; Johs, A.; Sawhney, M.S.; Shi, L.; Liang, L. (PNNL); (ORNL)

2012-05-24

194

Purification, crystallization and preliminary X-ray crystallographic analysis of the transport unit of the monomeric autotransporter AIDA-I from Escherichia coli.  

PubMed

The adhesin involved in diffuse adherence (AIDA-I) from Escherichia coli belongs to the group of autotransporters, specifically the type Va secretion system (T5aSS). All autotransporter systems contain a C-terminal ?-domain, which forms a barrel-like structure in the outer membrane with a hydrophilic pore allowing passenger translocation across the outer membrane. The passenger domain harbours the biological activity in the extracellular space and functions, for example, as an adhesin, an enzyme and a toxin. The exact transport mechanism of passenger translocation across the outer membrane is not clear at present. Thus, structure determination of the transport unit of AIDA-I could provide new insights into the transport mechanism. Here, the purification, crystallization and preliminary X-ray crystallographic studies of the transport unit of AIDA-I are reported. PMID:24100572

Gawarzewski, Iris; Tschapek, Britta; Hoeppner, Astrid; Jose, Joachim; Smits, Sander H J; Schmitt, Lutz

2013-09-28

195

Crystallization and preliminary crystallographic studies of AAL-2, a novel lectin from Agrocybe aegerita that binds nonreducing terminal N-acetylglucosamine.  

PubMed

AAL-2 is a recently discovered lectin from the mushroom Agrocybe aegerita that specifically recognizes nonreducing terminal acetylglucosamine (GlcNAc) and that could be used as a probe in studies of protein O-linked ?-N-acetylglucosamination (O-GlyNAcylation). In order to illustrate the mechanism of how this protein specifically recognizes nonreducing terminal GlcNAc and to evaluate the efficacy of AAL-2 as a macromolecular probe in O-GlyNAcylation studies, expression and crystallization studies of AAL-2 were performed and a diffraction data set was collected to 2.0 Å resolution. Preliminary crystallographic studies revealed that the AAL-2 crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 52.60, b = 111.70, c = 135.97 Å. PMID:23722844

Ren, Xiaoming; Jiang, Shuai; Li, Defeng; Sun, Hui; Wang, Dacheng

2013-05-24

196

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

SciTech Connect

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.

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

2011-12-31

197

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

SciTech Connect

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.

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

2010-12-01

198

Representations of locally compact groups on QSL_p-spaces and a p-analog of the Fourier-Stieltjes algebra  

Microsoft Academic Search

For a locally compact group $G$ and $p \\\\in (1,\\\\infty)$, we define $B_p(G)$ to be the space of all coefficient functions of isometric representations of $G$ on quotients of subspaces of $L_p$ spaces. For $p =2$, this is the usual Fourier--Stieltjes algebra. We show that $B_p(G)$ is a commutative Banach algebra that contractively (isometrically, if $G$ is amenable) contains the

Volker Runde

2004-01-01

199

Occlusion in the primary dentition. Part 1: A preliminary report on comparison of antero-posterior relationships and spacing among children of the major Nigerian ethnic groups.  

PubMed

This paper compares the antero-posterior occlusal pattern and arch spacing in the primary dentition of Nigerian children from the 3 major ethnic groups in the country Ibo, Yoruba and Hausa tribes. This is a cross-sectional epidemiological study involving eight randomly selected pre-primary schools and day-care centers in Ibadan and Lagos cities of Nigeria. Two hundred and sixty-nine 3-5-year-old children consisting of 125 (46.5%) males and 144 (53.6%) females were examined. A two-stage sampling method was adopted. The occlusions of the children were assessed according to the criteria by Foster and Hamilton, under natural illumination in their schools premises. Chi-square statistic was used to analyse the data. No statistically significant differences were observed in the molar and canine relationships among the ethnic groups (p > 0.05). Highly statistically significant differences were noted in relation to spacing of the arches (p = 0.001) in both the anterior and posterior segments. Also, statistically significant differences were found in relation to post canine spaces (p < 0.05) but not with pre-canine spaces. Spacing was found most in the Ibo ethnic group children. Although no statistically significant ethnic differences were found in the molar relationships of the study sample, very statistically significant differences were revealed in the spacing of the arches in both incisor and molar regions. PMID:16910111

Onyeaso, C O

2006-06-01

200

Themed Space  

ERIC Educational Resources Information Center

|This article presents a classroom activity that introduces students to the concept of themed space. Students learn to think critically about the spaces they encounter on a regular basis by analyzing existing spaces and by working in groups to create their own themed space. This exercise gives students the chance to see the relevance of critical…

Lynch, Christopher O.

2010-01-01

201

LETTER TO THE EDITOR: Space-group symmetry for the perovskite Ca0.3Sr0.7TiO3  

NASA Astrophysics Data System (ADS)

It is shown, using synchrotron x-ray powder diffraction at room temperature and above, by invoking geometrical and symmetry arguments, and most directly by electron diffraction, that the perovskite Ca0.3Sr0.7TiO3 at room temperature is tetragonal with space-group symmetry I4/mcm. This is in accord with the common view (Ball et al 1998 J. Solid State Chem. 139 238-47). The proposition that the compound adopts a metrically tetragonal orthorhombic structure in space group Imma (Ranjan and Pandey 1999 J. Phys.: Condens. Matter 11 2247-58) cannot be sustained.

Howard, C. J.; Withers, R. L.; Zhang, Z.; Osaka, K.; Kato, K.; Takata, M.

2005-11-01

202

Correlated crystallographic etching of graphene and nanoribbon formation  

NASA Astrophysics Data System (ADS)

Catalytic etching is a promising method for constructing crystallographically defined graphene structures such as nanoribbons. Catalytic etching experiments are performed and shown to contain significant correlation yielding crystallographic graphene nanoribbons. This correlation is investigated as a function of etching conditions and compared to simulations with possible sources discussed. Supported in part by NSF Award No. DMR-0805136, the Kentucky NSF EPSCoR program, the University of Kentucky Center for Advanced Materials, and the University of Kentucky Center for Nanoscale Science and Engineering.

Johnson, Stephen; Hunley, D. Patrick; Stieha, Joseph; Sundararajan, Abhishek; Kar, Arunita; Johnson, A. T. Charlie; Strachan, Douglas

2011-03-01

203

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

Microsoft Academic Search

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

M. Allner; V. Rygalov

2008-01-01

204

“Here is the knowledge-where should I put it?” Findings from a study of how knowledge spaces are used within a support group  

Microsoft Academic Search

In order to design useful knowledge media spaces for knowledge workers it is essential that we understand the nature of the work conducted and the knowledge applied in real settings. The paper reports from a study of how a group of quality assurance specialists in the pharmaceutical industry gather, structure and distribute information and knowledge. Based on the findings, a

P. H. Carstensen; U. Snis

1999-01-01

205

Public opinion and interest group positions on open-space issues in Albuquerque, New Mexico, USA: Implications for resource management  

Microsoft Academic Search

The purpose of this research was to elicit and compare the open-space preferences of citizens and openspace experts in Albuquerque, New Mexico, USA. A randomly selected sample of 492 citizens and 35 open-space experts participated in a telephone survey during May 5 18, 1986. The following hypothesis was tested and used as a guideline for the study: HO1: There is

Thomas Allan Tannery

1987-01-01

206

Overexpression, crystallization and preliminary X--ray crystallographic analysis of d-ribose-5-phosphate isomerase from Clostridium thermocellum  

PubMed Central

Rare sugars are used for many industrial and medical purposes and are produced by the interconversion between aldoses and ketoses catalyzed by sugar and sugar-phosphate isomerases. Recently, Clostridium thermocellum d-­ribose-5-phosphate isomerase (CTRPI), an aldose–ketose isomerase, was cloned in order to synthesize d-allose and its substrate specificity was further characterized for industrial usage. CTRPI has a novel substrate specificity that differs from those of other isomerases, which have broad substrate specificities. CTRPI prefers aldose substrates such as l-talose, d-ribose and d-allose. CTRPI was purified and crystallized in order to determine its three-dimensional structure and thus to elucidate its enzymatic reaction mechanism and understand its substrate specificity. The crystal belonged to the trigonal space group P3221, with unit-cell parameters a = b = 69.5, c = 154.4?Å, and diffracted to 1.9?Å resolution. According to Matthews coefficient calculations, the crystallo­graphic structure consists of a dimer in the asymmetric unit, with a V M of 3.2?Å3?Da?1 and a solvent content of 61.7%.

Jung, Junho; Yeom, Soo-Jin; Kim, Jisun; Kim, Jin-Kwang; Natarajan, Sampath; Ahn, Yeh-Jin; Lim, Sang Boem; Oh, Deok-Kun; Kang, Lin-Woo

2009-01-01

207

Expression, purification and preliminary X-ray crystallographic studies of the human immunodeficiency virus 1 subtype C protease  

PubMed Central

Crystals of the human immunodeficiency virus 1 (HIV-1) subtype C protease (PR) complexed with the clinically used inhibitors indinavir (IDV) and nelfinavir (NFV) have been grown in the monoclinic space group P21, with mean unit-cell parameters a = 46.7 (±0.1), b = 59.8 (±0.3), c = 87.0 (±0.4) Å, ? = 95.2 (±0.5)°. The crystals of both complexes have been shown to diffract X-rays to 2.3?Å resolution. The diffraction data for the subtype C PR complexes with IDV and NFV were subsequently processed and reduced, with overall R sym values of 8.4 and 11.4%, respectively. Based on the unit-cell volumes, molecular-replacement results and packing considerations, there are two protease homodimers per crystallographic asymmetric unit in each of the complexes. The data were initially phased using a model based on the crystal structure of HIV-1 subtype B PR; the structures have been determined and further refinement and analysis are in progress. These structures and subsequent studies with other inhibitors will greatly aid in correlating the amino-acid variation between the different HIV PRs and understanding their differential sensitivity and resistance to current drug therapy.

Coman, Roxana M.; Robbins, Arthur; Goodenow, Maureen M.; McKenna, Robert; Dunn, Ben M.

2007-01-01

208

Crystallization and preliminary X-ray crystallographic analysis of full-length yeast tropomyosin 2 from Saccharomyces cerevisiae.  

PubMed

Tropomyosin is a highly conserved actin-binding protein that is found in most eukaryotic cells. It is critical for actin-filament stabilization and for cooperative regulation of many actin functions. Detailed structural information on tropomyosin is very important in order to understand the mechanisms of its action. Whereas structures of isolated tropomyosin fragments have been obtained at high resolution, the atomic structure of the entire tropomyosin molecule is still unknown. Here, the crystallization and preliminary crystallographic analysis of full-length yeast tropomyosin 2 (yTm2) from Saccharomyces cerevisiae are reported. Recombinant yTm2 expressed in Escherichia coli was crystallized using the hanging-drop vapour-diffusion method. The crystals belonged to space group C2, with unit-cell parameters a = 154.8, b = 49.9, c = 104.0 A, alpha = gamma = 90.0, beta = 124.0 degrees and two molecules in the asymmetric unit. A complete native X-ray diffraction data set was collected to 3.5 A resolution using synchrotron radiation. PMID:18540067

Meshcheryakov, Vladimir; Nitanai, Yasushi; Maytum, Robin; Geeves, Michael A; Maeda, Yuichiro

2008-05-23

209

Crystallization and preliminary X-ray crystallographic analysis of full-length yeast tropomyosin 2 from Saccharomyces cerevisiae  

PubMed Central

Tropomyosin is a highly conserved actin-binding protein that is found in most eukaryotic cells. It is critical for actin-filament stabilization and for cooperative regulation of many actin functions. Detailed structural information on tropo­myosin is very important in order to understand the mechanisms of its action. Whereas structures of isolated tropomyosin fragments have been obtained at high resolution, the atomic structure of the entire tropomyosin molecule is still unknown. Here, the crystallization and preliminary crystallo­graphic analysis of full-length yeast tropomyosin 2 (yTm2) from Saccharomyces cerevisiae are reported. Recombinant yTm2 expressed in Escherichia coli was crystallized using the hanging-drop vapour-diffusion method. The crystals belonged to space group C2, with unit-cell parameters a = 154.8, b = 49.9, c = 104.0?Å, ? = ? = 90.0, ? = 124.0° and two molecules in the asymmetric unit. A complete native X-ray diffraction data set was collected to 3.5?Å resolution using synchrotron radiation.

Meshcheryakov, Vladimir; Nitanai, Yasushi; Maytum, Robin; Geeves, Michael A.; Maeda, Yuichiro

2008-01-01

210

Crystallization and preliminary X-ray crystallographic studies of 3-deoxy-manno-octulosonate cytidylyltransferase from Haemophilus influenzae.  

PubMed

The enzyme 3-deoxy-manno-octulosonate cytidylyltransferase (CMP-KDO synthetase; CKS) catalyzes the activation of 3-deoxy-manno-octulosonate (KDO) by forming CMP-KDO. It is essential for the biosynthesis of lipopolysaccharides in Gram-negative bacteria and is a potential target for the discovery of antibacterial agents. L-CKS from Haemophilus influenzae was overexpressed with a C-terminal hexahistidine tag in Escherichia coli and crystallized in the presence of the substrate KDO at 297 K using PEG 4000 as a precipitant and ethylene glycol as an additive. The diffraction limit and spot shape of the native crystal could be improved significantly by dehydration/annealing. X-ray diffraction data were collected to 2.5 A resolution from a native crystal. The crystals are orthorhombic, belonging to the space group P2(1)2(1)2(1), with unit-cell parameters a = 48.6, b = 83.1, c = 117.3 A. The presence of two monomers of recombinant L-CKS in the crystallographic asymmetric unit gives a reasonable V(M) of 2.05 A(3) Da(-1), with a solvent content of 40.0%. PMID:12499564

Ku, Min-Je; Yoon, Hye-Jin; Ahn, Hyung Jun; Kim, Hyung-Wook; Baek, Seung-Hun; Suh, Se Won

2002-12-19

211

Overexpression, crystallization and preliminary X--ray crystallographic analysis of the C-terminal cytosolic domain of mouse anoctamin 1  

PubMed Central

Transmembrane protein 16A (TMEM16A, also known as anoctamin 1; ANO1) is a bona fide Ca2+-activated chloride channel that is activated by intracellular Ca2+- and Ca2+-mobilizing stimuli and plays important roles in a variety of physiological functions. To elucidate the structural features of ANO1, structural analysis of the C-terminal cytosolic domain of mouse ANO1 (mANO1-CTD) was initiated. mANO1-CTD was overexpressed in Escherichia coli and was crystallized at 297?K using a reservoir solution consisting of 0.2?M sodium acetate trihydrate, 0.1?M Tris–HCl pH 8.5 and 30%(w/v) PEG 4000. X-­ray diffraction data were collected to 2.3?Å resolution. The crystals belonged to the orthorhombic space group P212121, with unit-cell parameters a = 73.96, b = 103.73, c = 114.71?Å. If it is assumed that eight copies of a monomer molecule are present in the crystallographic asymmetric unit, the crystal volume per protein mass (V M) is 2.38?Å3 Da?1 and the solvent content is 48.38%. Attempts to solve the structure of mANO1-CTD by the MAD method using seleno­methionine-labelled mANO1-CTD or heavy-atom-derivatized crystals are in progress.

Park, Sang Ho; Chung, Ho Kyung; Kim, Do Jin; Han, Mi Ra; Park, Mi Seul; Oh, Uhtaek; Kim, Hyun-Jung; Han, Byung Woo

2011-01-01

212

Crystallographic and morphological textures in laser surface modified alumina ceramic  

NASA Astrophysics Data System (ADS)

Laser surface modification is an advanced technique for improving the surface performance of alumina ceramics in refractory and abrasive machining applications. Surface performance is expected to be greatly influenced by the crystallographic and morphological textures of surface grains generated during rapid solidification associated with laser processing. In this study, an investigation of the evolution of crystallographic and morphological textures during laser surface modifications of alumina ceramic was carried out using a 4 kW Nd:YAG laser with fluences in the range of 458-726 J/cm2. In these regimes of laser surface processing, the formation of equilibrium ?-alumina was found to be assisted by catalytic sites provided by the substrate. Microstructure evolution was explored in terms of the development of crystallographic and morphological (size and shape) textures of surface grains as a function of laser processing parameters. The interdependence of crystallographic and morphological textures of the surface grains is discussed within the framework of faceted growth model suggesting that the formation of crystal shapes is governed by the relative velocities of certain crystallographic facets. Also, the effect of thermal aspects of laser processing on the morphology of the surface grains is discussed from the viewpoint of existing solidification theories.

Harimkar, Sandip P.; Dahotre, Narendra B.

2006-07-01

213

Talk in Blended-Space Speech Communities: An Exploration of Discursive Practices of a Professional Development Group  

ERIC Educational Resources Information Center

This study is an exploration of alternative teacher professional development. While using symbolic interactionism for a research lens, it characterizes the discursive practices commonly found in formal, informal, and blended-space speech communities based on the talk within a leadership-development program comprised of five female, church-based…

Garvin, Tabitha Ann

2011-01-01

214

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

National Technical Information Service (NTIS)

NASA's mission is 'to understand and protect our home planet, to explore the universe and search for life, and to inspire the next generation of explorers' The Systems Management Office at Johnson Space Center (JSC) is searching for methods to effectively...

M. Tavana

2005-01-01

215

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

ERIC Educational Resources Information Center

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…

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

2009-01-01

216

Crystallization and preliminary X-ray crystallographic studies of the [NiFe] hydrogenase maturation proteins HypC and HypD.  

PubMed

HypC and HypD proteins are required for the insertion of the Fe atom with diatomic ligands into the large subunit of [NiFe] hydrogenases, an important step in the maturation process of this type of hydrogenase. The crystallization and preliminary crystallographic analysis of HypC and HypD from Thermococcus kodakaraensis KOD1 are reported. Crystals of HypC grew in two different forms. Monoclinic crystals of HypC in space group C2 with unit-cell parameters a = 78.2, b = 59.1, c = 54.0 A, beta = 109.0 degrees were obtained using PEG 4000 and ammonium sulfate or sodium bromide as precipitants. They diffracted X-rays to 1.8 A resolution and were suitable for structure determination. Crystals of HypD were also obtained in two different forms. The monoclinic crystals obtained using PEG 4000 and magnesium chloride diffracted X-rays to beyond 2.1 A resolution, despite growing as clusters. They belong to space group P2(1), with unit-cell parameters a = 42.3, b = 118.4, c = 81.2 A, beta = 100.9 degrees , and are suitable for data collection. PMID:17554182

Watanabe, Satoshi; Matsumi, Rie; Atomi, Haruyuki; Imanaka, Tadayuki; Miki, Kunio

2007-05-31

217

Crystallization and preliminary X-ray crystallographic studies of the oxidative-stress sensor SoxR and its complex with DNA  

PubMed Central

SoxR, a member of the MerR family of transcriptional activators, functions as a sensor of oxidative stress. The redox states of the 2Fe–2S cluster of SoxR regulate the activity of SoxR. Here, the crystallization and preliminary crystallographic analysis of SoxR and its complex with DNA are reported. Crystals of SoxR were obtained using PEG 10?000 and glycerol as precipitants. The crystals of SoxR belong to space group P62 or P64, with unit-cell parameters a = b = 80.0, c = 88.1?Å. Crystals of the SoxR–DNA complex were obtained using a 20?bp DNA fragment from a condition containing PEG 10?000 and sodium/potassium tartrate. The crystals of the SoxR–DNA complex belong to space group P6122 or P6522, with unit-cell parameters a = b = 53.5, c = 355.6?Å. Diffraction data were collected to a maximum resolution of 3.2 and 2.7?Å for SoxR and the SoxR–DNA complex, respectively.

Watanabe, Satoshi; Kita, Akiko; Kobayashi, Kazuo; Takahashi, Yasuhiro; Miki, Kunio

2006-01-01

218

Activity budget, diet, and use of space by two groups of squirrel monkeys (Saimiri sciureus) in eastern Amazonia.  

PubMed

Squirrel monkeys (Saimiri spp.) are widely distributed in the Amazon basin. This study describes the ecological and behavioral patterns of two social groups of S. sciureus in forests adjacent to the Tucuruí hydroelectric reservoir in eastern Amazonia, including range size, activity budgets, and composition of the diet. The groups were monitored at Base 4 (group B4) and Germoplasma Island (group GI). Quantitative behavioral data were collected using instantaneous scan sampling to record behavior, substrate use, and height. Home ranges were delimited using a GPS to determine group position after each 50 m of movement. Home ranges were 75.0 ha for group B4 (39 members) and 77.5 ha for group GI (32 members). The use of vertical strata was well defined, with a marked preference for the middle and lower levels of the canopy. The activity budgets of both groups were typical of those of other squirrel monkeys and were dominated by foraging (B4 = 48.7 %; GI = 49.6 %), moving (both groups 28.9 %), and feeding (B4 = 14.6 %; GI = 12.4 %). Resting was rare (B4 = 3.5 %; GI = 2.6 %) and less common than social behavior (B4 = 4.3 %; GI = 6.4 %). The diet of both groups was dominated by plant material (B4 = 70.7 % of feeding records; GI = 71.4 %), which is in contrast with the more insectivorous diets recorded for Saimiri at other sites. Group GI spent more time foraging during the dry season, whereas group B4 spent more time in the rainy season when the consumption of fruit increased (significantly, in the case of group GI). The less insectivorous diet of these groups may be due to a number of factors, including the unique habitat configuration at the site and reduced hydrological stress due to the proximity of the reservoir. PMID:23546826

Pinheiro, Tatyana; Ferrari, Stephen F; Lopes, Maria Aparecida

2013-04-02

219

Exceptional and non-crystallographic root systems and the Kochen Specker theorem  

NASA Astrophysics Data System (ADS)

The Kochen-Specker theorem states that a 3-dimensional complex Euclidean space admits a finite configuration of projective lines such that the corresponding quantum observables (the orthogonal projectors) cannot be assigned with 0 and 1 values in a classically consistent way. This paper shows that the irreducible root systems of exceptional and of non-crystallographic types are useful in constructing such configurations in other dimensions. The cases E6 and E7 lead to new examples, while F4, E8 and H4 yield a new interpretation of the known ones. The described configurations have an additional property: they are saturated, i.e. the tuples of mutually orthogonal lines, being partially ordered by inclusion, yield a poset with all maximal elements having the same cardinality (the dimension of space).

Ruuge, Artur E.

2007-03-01

220

Crystallographic variant selection in {alpha}-{beta} brass  

SciTech Connect

The transformation texture of {alpha}/{beta} brass with a diffusional Widmanstaetten {alpha} growth morphology has been investigated. Electron micrographs and electron backscattered diffraction was used to determine that the orientation relationship between the {beta} phase and the {alpha} associated with nucleation at {beta} grain boundaries was 44.3 deg <1 1 6>. Crystallographic variant selection was observed across those prior {beta}/{beta} grain boundaries, but this has little effect on the transformation texture due to the crystal symmetry. The effect of the crystallographic variant selection on texture is further weakened by nucleation of diffusional transformed {alpha} in the grain interior.

Stanford, N. [Manchester Materials Science Centre, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom); Bate, P.S. [Manchester Materials Science Centre, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom)]. E-mail: pete.bate@man.ac.uk

2005-02-01

221

A normalized family of representations of the group of motions of a Euclidean space and the inverse problem of the representation theory of this group  

SciTech Connect

There exists a well-known holomorphic family T{sup {lambda}} of representations of the isometry group of R such that T{sup -{lambda}}{approx}T{sup {lambda}} for {lambda}{ne}0. This paper presents a holomorphic family V{sub R}{sup {lambda}}, |{lambda}|

Ismagilov, R S [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Sultanov, Sh Sh [Nizhnevartovsk State Pedagogical University, Nizhnevartovsk (Russian Federation)

2004-12-31

222

Collective surface diffusion of repulsively interacting particles on a triangular lattice: Comparison of real-space renormalization group and Monte Carlo approaches  

Microsoft Academic Search

A two-dimensional lattice-gas model with triangular symmetry is investigated by using the real-space renormalization group (RSRG) approach with blocks of different size and symmetries. It has been shown that the precision of this method depends strongly not only on the number of sites in the block but also on its symmetry. In general, the accuracy of the method increases with

A. A. Tarasenko; F. Nieto; L. Jastrabík; C. Uebing

2001-01-01

223

Scaling and Renormalization Group in Replica-Symmetry-Breaking Space: Evidence for a Simple Analytical Solution of the Sherrington-Kirkpatrick Model at Zero Temperature  

Microsoft Academic Search

Using numerical self-consistent solutions of a sequence of finite replica symmetry breakings (RSB) and Wilson's renormalization group but with the number of RSB steps playing a role of decimation scales, we report evidence for a nontrivial T-->0 limit of the Parisi order function q(x) for the Sherrington-Kirkpatrick spin glass. Supported by scaling in RSB space, the fixed point order function

R. Oppermann; D. Sherrington

2005-01-01

224

Color Grouping in Space and Time: Evidence From Negative Color-Based Carryover Effects in Preview Search  

Microsoft Academic Search

Five experiments addressed the role of color grouping in preview search (D. G. Watson & G. W. Humphreys, 1997). Experiment 1 used opposite color ratios of distractors in preview and second search displays, creating equal numbers of distractors in each color group in the final display. There was selective slowing for new targets carrying the majority color of the old

Jason J. Braithwaite; Glyn W. Humphreys; John Hodsoll

2003-01-01

225

Slow-cooling protocols for crystallographic refinement by simulated annealing  

Microsoft Academic Search

An improved protocol for crystallographic refinement by simulated annealing is presented. It consists of slow cooling starting at high temperatures. Tests of refinements of aspartate aminotransferase and porcin pepsin show that the slow-cooling protocol produces lower R factors and better geometry than other pro- tocols previously published. The influence of the tem- perature-control method, weighting, cooling rate and duration of

AXEL T. BRUNGER; ANTON KRUKOWSKI; JOHN W. ERICKSON

1990-01-01

226

Calcium Oxalate: Crystallographic Analysis in Solid Aggregates in Urinary Sediments  

Microsoft Academic Search

A relationship between crystallographic structure and morphological form of calcium oxalates in urinary sediments is established. The common tetragonal bipyramids have been confirmed as weddellite from their electron diffraction patterns. Other solid forms, such as needles, biconcave disks, and dumbbell forms, that can appear in hyperoxalurias, of both metabolic and alimentary origin, have been identified as whewellite. Micrographs reveal fibrous

Fernando Catalina; Luis Cifuentes

1970-01-01

227

Crystallographic Shear in Niobium Oxyfluoride (NbO2F).  

National Technical Information Service (NTIS)

Crystallographic shear planes were observed to nucleate and grow in NbO2F crystals on beam heating in the electron microscope. At low concentrations and relatively low temperatures the shear planes grew by expansion of partial dislocation loops on (100) p...

L. A. Bursill B. G. Hyde

1969-01-01

228

On the identification of fossil tracks of Galactic space nuclei from the Th-U group in olivine crystals from meteorites  

NASA Astrophysics Data System (ADS)

This paper considers the origin of the group of space nuclei tracks of lengths between 190 and 220 microns in the meteorites Maryalakhti and Eagle Station. Several hundred 1- to 5-micron-size microscopic-size olivine crystals from these meteorites (obtained by cracking larger monocrystals) were irradiated by U-238 nuclei (in the energy range 30-70 MeV/nucleon), and the etching length spectra of accelerated U-238 nuclei were compared with fossil tracks in these crystals. The crystals containing tracks of U-238 were annealed under conditions identical to those used for the examination of fossil tracks in olivine crystals from these meteorites (Lhagvasuren et al., 1980). The comparison showed that the group of fossil tracks observed in Galactic space nuclei of length 200-210 microns is defined by the nuclei of the Th-U group. Tracks of the length of 350 microns (i.e., close in length to the group of fossil tracks of 340-360 microns) were also observed in the U-238 spectrum.

Perelygin, V. V. P.; Stetsenko, S. G.; Kashukeev, N. T.; Petrova, R. I.

229

Auditing Consistency and Usefulness of LOINC Use among Three Large Institutions - Using Version Spaces for Grouping LOINC Codes  

PubMed Central

Objectives We wanted to develop a method for evaluating the consistency and usefulness of LOINC code use across different institutions, and to evaluate the degree of interoperability that can be attained when using LOINC codes for laboratory data exchange. Our specific goals were to: 1) Determine if any contradictory knowledge exists in LOINC. 2) Determine how many LOINC codes were used in a truly interoperable fashion between systems. 3) Provide suggestions for improving the semantic interoperability of LOINC. Methods We collected Extensional Definitions (EDs) of LOINC usage from three institutions. The version space approach was used to divide LOINC codes into small sets, which made auditing of LOINC use across the institutions feasible. We then compared pairings of LOINC codes from the three institutions for consistency and usefulness. Results The number of LOINC codes evaluated were 1,917, 1,267 and 1,693 as obtained from ARUP, Intermountain and Regenstrief respectively. There were 2,022, 2,030, and 2,301 version spaces among ARUP & Intermountain, Intermountain & Regenstrief and ARUP & Regenstrief respectively. Using the EDs as the gold standard, there were 104, 109 and 112 pairs containing contradictory knowledge and there were 1,165, 765 and 1,121 semantically interoperable pairs. The interoperable pairs were classified into three levels: 1) Level I – No loss of meaning, complete information was exchanged by identical codes. 2) Level II – No loss of meaning, but processing of data was needed to make the data completely comparable. 3) Level III – Some loss of meaning. For example, tests with a specific ‘method’ could be rolled-up with tests that were ‘methodless’. Conclusions There are variations in the way LOINC is used for data exchange that result in some data not being truly interoperable across different enterprises. To improve its semantic interoperability, we need to detect and correct any contradictory knowledge within LOINC and add computable relationships that can be used for making reliable inferences about the data. The LOINC committee should also provide detailed guidance on best practices for mapping from local codes to LOINC codes and for using LOINC codes in data exchange.

Lin, M.C.; Vreeman, D.J.; Huff, S.M.

2012-01-01

230

Direct solution of renormalization group equations of QCD in x-space: NLO implementations at leading twist  

NASA Astrophysics Data System (ADS)

We illustrate the implementation of a method based on the use of recursion relations in (Bjorken) x-space for the solution of the evolution equations of QCD for all the leading twist distributions. The algorithm has the advantage of being very fast. The implementation that we release is written in C and is performed to next-to-leading order in ?s. Program summary Title of program: evolution.c Catalogue identifier: ADUB Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADUB Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer: Athlon 1800 plus Operating system under which the program has been tested: Linux Programming language used: C Peripherals used: Laser printer No. of bytes in distributed program, including test data, etc.: 4559 No. of lines in distributed program, including test data, etc.: 1048 Distribution format: gzip file Nature of physical problem: The program provided here solves the DGLAP evolution equations to next-to-leading order ?s, for unpolarized, longitudinally polarized and transversely polarized parton distributions. Method of solution: We use a recursive method based on an expansion of the solution in powers of log(?s(Q)/?s(Q0)). Typical running time: About 1 minute and 30 seconds for the unpolarized and longitudinally polarized cases and 1 minute for the transversely polarized case. Permanent address.

Cafarella, Alessandro; Corianò, Claudio

2004-07-01

231

H-bonded supramolecular assembly via proton transfer: Isolation, X-ray crystallographic characterization and SOD mimic activity of [Cu(dipic)2]2[PA-H]4·5H2O  

NASA Astrophysics Data System (ADS)

The title proton transfer complex was isolated from the reaction of CuCl2·2H2O with pyridine-2,6-dicarboxylic acid (dipic-H2) in presence of 3-amino-1-propanol (PA) under reflux condition. It was thoroughly characterized by FAB-mass, FT-IR, electronic (ligand field), EPR spectroscopic and X-ray crystallographic techniques. The complex crystallizes in the space group C1c1 of the monoclinic system. The unit cell parameters are, a = 17.247(5), b = 20.058(5) Å, c = 15.320(4) Å and ? = 109.235(5)°. Extensive H-bonding between the complex anion [Cu(dipic)2]2- and the surrounding cations [PA-H]+ results in a 3D network, supported with additional ?-? interactions of the ligand (dipic)2- neighboring units. The SOD mimic activity of the present complex was also examined using NBT assay.

Siddiqi, Zafar A.; Khalid, Mohd; Shahid, M.; Kumar, Sarvendra; Sharma, Prashant K.; Siddique, Armeen; Anjuli

2013-02-01

232

Consequences of crystallographic equivalence between bct and fct indium  

SciTech Connect

The force-constant relations involving the elastic constants and the phonon dispersion relations for bct indium, deduced on the basis of a general tensor force (GTF) model, are compared with those for fct indium to resolve some conflicting consequences of their crystallographic equivalence. It is shown that the numerical values of the force constants of this model differ from bct indium to fct indium, whereas those of other lattice-dynamical models are invariant, but the same transformation equation relates the phonon frequencies of the former with those of the latter in all cases. Further, the relations between the GTF constants of bct indium and those of fct indium, obtained by making use of their relations with other invariant force constants reveal their correct dependence on coordinate axes. The basic differences between GTF and other models, the transformation properties of these force constants, and their link with the various manifestations of the crystallographic equivalence are discussed.

Ramamurthy, V.

1986-11-15

233

Crystallographic reorganization of the calcitic prismatic layer of oysters  

Microsoft Academic Search

The calcitic columnar prisms of pteriomorphian bivalves have the crystallographic c-axis oriented perpendicular to the shell surface and the a-axes rotated without any preferential orientation. In oysters, SEM, XRD and EBSD analyses show that individual prisms initially have their a-axes randomly oriented but are able to progressively orient them parallel to those of their neighbors. This ability is apparently confined

Antonio G. Checa; Francisco J. Esteban-Delgado; Joaquín Ramírez-Rico; Alejandro B. Rodríguez-Navarro

2009-01-01

234

A 3D balanced-SSFP Dixon technique with group-encoded k-space segmentation for breath-held non-contrast-enhanced MR angiography.  

PubMed

A three-dimensional balanced steady-state free precession (b-SSFP)-Dixon technique with a novel group-encoded k-space segmentation scheme called GUINNESS (Group-encoded Ungated Inversion Nulling for Non-contrast Enhancement in the Steady State) was developed. GUINNESS was evaluated for breath-held non-contrast-enhanced MR angiography of the renal arteries on 18 subjects (6 healthy volunteers, 12 patients) at 3.0 T. The method provided high signal-to-noise and contrast renal angiograms with homogeneous fat and background suppression in short breath-holds on the order of 20 s with high spatial resolution and coverage. GUINNESS has potential as a short breath-hold alternative to conventional respiratory-gated methods, which are often suboptimal in pediatric subjects and patients with significant diaphragmatic drift/sleep apnea. PMID:22055852

Saranathan, Manojkumar; Bayram, Ersin; Worters, Pauline W; Glockner, James F

2011-11-03

235

Observation of phycoerythrin-containing cyanobacteria and other phytoplankton groups from space using Differential Optical Absorption Spectroscopy on SCIAMACHY data  

NASA Astrophysics Data System (ADS)

In order to understand the marine phytoplankton's role in the global marine ecosystem and biogeochemical cycles it is necessary to derive global information on the distribution of major functional phytoplankton types (PFT) in the world oceans. In our study we use instead of the common ocean color sensors such as CZCS, SeaWiFS, MODIS, MERIS, with rather low spectral resolution, the Differential Optical Absorption Spectroscopy (DOAS) to study the retrieval of phytoplankton distribution and absorption with the satellite sensor Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). SCIAMACHY measures back scattered solar radiation in the UV-Vis-NIR spectral region with a high spectral resolution (0.2 to 1.5 nm). We used in-situ measured phytoplankton absorption spectra from two different RV Polarstern expeditions where different phytoplankton groups were representing or dominating the phytoplankton composition in order to identify these characteristic absorption spectra in SCIAMACHY data in the range of 430 to 500 nm and also to identify absorption from cyanobacterial photosynthetic pigment phycoerythrin. Our results show clearly these absorptions in the SCIAMACHY data. The conversion of these differential absorptions by including the information of the light penetration depth (according to Vountas et al., Ocean Science, 2007) globally distributed pigment concentrations for these characteristic phytoplankton groups for two monthly periods (Feb-March 2004, Oct-Nov 2005 and Oct-Nov 2007) are derived. The satellite retrieved information on cyanobacteria (Synechococcus sp. and Prochlorococcus sp.) and diatoms distribution matches well with the concentration measured from collocated water samples with HPLC technique and also to global model analysis with the NASA Ocean Biogeochemical Model (NOBM from http://reason.gsfc.nasa.gov/OPS/Giovanni/) according to Gregg and Casey 2006 and Gregg 2006. Results are of great importance for global modelling of marine ecosystem and climate change studies regarding changes in the ocean.

Bracher, Astrid; Dinter, Tilman; Burrows, John P.; Vountas, Marco; Röttgers, Rüdiger; Peeken, Ilka

236

Crystallization and preliminary crystallographic analysis of GanB, a GH42 intracellular ?-galactosidase from Geobacillus stearothermophilus.  

PubMed

Geobacillus stearothermophilus T-6 is a Gram-positive thermophilic soil bacterium that contains a multi-enzyme system for the utilization of plant cell-wall polysaccharides, including xylan, arabinan and galactan. The bacterium uses a number of endo-acting extracellular enzymes that break down the high-molecular-weight polysaccharides into decorated oligosaccharides. These oligosaccharides enter the cell and are further hydrolyzed into sugar monomers by a set of intracellular glycoside hydrolases. One of these intracellular degrading enzymes is GanB, a glycoside hydrolase family 42 ?-galactosidase capable of hydrolyzing short ?-1,4-galactosaccharides to galactose. GanB and related enzymes therefore play an important part in the hemicellulolytic utilization system of many microorganisms which use plant biomass for growth. The interest in the biochemical characterization and structural analysis of these enzymes stems from their potential biotechnological applications. GanB 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 belong to the primitive orthorhombic space group P212121, with average crystallographic unit-cell parameters of a = 71.84, b = 181.35, c = 196.57?Å. Full diffraction data sets to 2.45 and 2.50?Å resolution have been collected for both the wild-type enzyme and its E323A nucleophile catalytic mutant, respectively, as measured from flash-cooled crystals at 100?K using synchrotron radiation. These data are currently being used for the full three-dimensional crystal structure determination of GanB. PMID:24100561

Solomon, Hodaya V; Tabachnikov, Orly; Feinberg, Hadar; Govada, Lata; Chayen, Naomi E; Shoham, Yuval; Shoham, Gil

2013-09-28

237

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

SciTech Connect

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.

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

2007-01-01

238

Reaction temperature variations on the crystallographic state of spinel cobalt aluminate.  

PubMed

In this study, we report a rapid and simple technique for obtaining cobalt aluminate having a spinel structure. The products were prepared from a hydroxide precursor synthesized by coprecipitation of cobalt (Co(2+)) and aluminum (Al(3+)) nitrates with an alkaline solution. The chosen precursor enabled low temperature fabrication of cobalt aluminate with a spinel structure by sintering it for 2 hours at low temperatures (>400 °C). Crystallographic and thermal analyses suggest that the low-temperature-sintered products contain Co(3+) ions stabilized by chemisorbed water and/or hydroxide groups, which was not observed for products sintered at temperatures higher than 1000 °C. The color of the products turned from clear blue (Thenard's blue) to dark green when sintering temperatures were below 1000 °C. Magnetic quantities, Curie constants, and Weiss temperatures show a strong dependence on the sintering temperature. These findings suggest that there are mixed valent states, i.e. Co(2+) and Co(3+), and unique cation distributions at the different crystallographic sites in the spinel structure, especially in the products sintered at lower temperatures. PMID:23525097

Taguchi, Minori; Nakane, Takayuki; Hashi, Kenjiro; Ohki, Shinobu; Shimizu, Tadashi; Sakka, Yoshio; Matsushita, Akiyuki; Abe, Hiroya; Funazukuri, Toshitaka; Naka, Takashi

2013-05-21

239

High resolution neutron crystallographic studies of the hydration of coenzyme cob(II)alamin  

SciTech Connect

The hydration of coenzyme cob(II)alamin has been studied using high resolution monochromatic neutron crystallographic data collected at room temperature to a resolution of surrounded by flexible side chains with terminal functional groups may be significant for 0.92 on the original diffractometer D19 with a prototype 4o x 64o detector at the high-flux reactor neutron source run by the Institute Laue Langevin. The resulting structure provides H bonding parameters for the hydration of biomacromolecules to unprecedented accuracy. These experimental parameters will be used to define more accurate force-fields for biomacromolecular structure refinement. The presence of a hydrophobic bowl motif efficient scavenging of ligands. The feasibility of extending the resolution of this structure to ultra high resolution was investigated by collecting time-of-flight neutron crystallographic data on diffractometer TOPAZ with a prototype array of 14 modular 21o x 21o detectors at the Spallation Neutron Source run by Oak Ridge National Laboratory.

Jogl, Gerwald [Brown University; Wang, Xiaoping [ORNL; Mason, Sax [Institut Laue-Langevin (ILL); Kovalevsky, Andrey [Los Alamos National Laboratory (LANL); Mustyakimov, Marat [Los Alamos National Laboratory (LANL); Fisher, Zoe [Los Alamos National Laboratory (LANL); Hoffmann, Christina [ORNL; Kratky, Christoph [Institute of Biosciences, University of Graz; Langan, Paul [ORNL

2011-01-01

240

Analysis of Martensite Pole Figure from Crystallographic View Point  

NASA Astrophysics Data System (ADS)

Martensite pole figures from three different steels have been studied using electron backscatter diffraction (EBSD) and mathematical models to show that the two stage transformation theory is not necessary for correct prediction of pole figure and popular orientation relationships, like Kurdjumov-Sachs. These theories can give misleading prediction. It has been proved that the use of correct crystallographic data can lead to a better texture prediction. The typical features of a pole figure in a {2 5 2} ? habit system have been studied in detail.

Chintha, Appa Rao; Sharma, Vikram; Kundu, Saurabh

2013-08-01

241

Crystallographic phase retrieval through image processing under constraints  

NASA Astrophysics Data System (ADS)

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.

Zhang, Kam Y.

1993-11-01

242

Analysis of Martensite Pole Figure from Crystallographic View Point  

NASA Astrophysics Data System (ADS)

Martensite pole figures from three different steels have been studied using electron backscatter diffraction (EBSD) and mathematical models to show that the two stage transformation theory is not necessary for correct prediction of pole figure and popular orientation relationships, like Kurdjumov-Sachs. These theories can give misleading prediction. It has been proved that the use of correct crystallographic data can lead to a better texture prediction. The typical features of a pole figure in a {2 5 2} ? habit system have been studied in detail.

Chintha, Appa Rao; Sharma, Vikram; Kundu, Saurabh

2013-11-01

243

Crystallographic phases in heavy rare earth metals under megabar pressures  

NASA Astrophysics Data System (ADS)

Experiments aimed at understanding the crystallographic phases of heavy rare earth metals were carried out in a diamond anvil cell at the Advanced Photon Source, Argonne National Laboratory. Heavy rare earth metals dysprosium (Dy), holmium (Ho), erbium (Er) and thulium (Tm) were compressed to multi-megabar pressures. The rare earth crystal sequence hcp?Sm-type?dhcp?distorted-fcc (dfcc) is observed in all four elements. Upon further compression, a structural transformation to a monoclinic C2/m phase has been observed. We summarize the results from these experiments and present Rietveld structural refinements on high pressure phases for the specific case of dysprosium.

Samudrala, G. K.; Vohra, Y. K.

2012-07-01

244

Statistical density modification with non-crystallographic symmetry.  

PubMed

Statistical density modification is a technique for phase improvement through a calculation of the posterior probability of the phases, given experimental phase information and expectations about features of the electron-density map. The technique can take advantage of both estimates of electron density in the map and uncertainties or probability distributions for those estimates. For crystals with non-crystallographic symmetry (NCS), this allows the use of the expected similarity of electron density at NCS-related points without requiring an implicit assumption that these regions are identical. PMID:12454468

Terwilliger, Thomas C

2002-11-23

245

Crystallographic and Magnetic Properties of KFeO  

Microsoft Academic Search

The crystallographic and magnetic properties of KFeO2 powder prepared by ball-mill method, have been studied by X-ray diffraction (XRD), Mossbauer spectroscopy, and vibrating sample magnetometer (VSM) measurements. The crystal structure of KFeO2 powder at room temperature is determined to be an orthorhombic structure of Pbca with its lattice constants a0=5.594,b0 =11.247, and c0=15.863 Aring by Reitveld refinement. The M-H curves

Seung Je Moon; In-Bo Shim; Chul Sung Kim

2006-01-01

246

Synthesis, capillary crystallization and preliminary joint X-ray and neutron crystallographic study of Z--DNA without polyamine at low pH  

PubMed Central

In order to crystallographically study the hydration of the major groove (convex surface) of Z-DNA, the oligonucleotide d(CGCGCG) has been synthesized. Single crystals were grown by vapor diffusion using the hanging-drop and sitting-drop methods for X-ray studies and by batch crystallization and evaporation within silicon tubes for neutron studies. Hexagonal crystals were obtained without the use of duplex-stabilizing polyamines and at an acid pH. X-­ray data collected at room temperature (1.5?Å resolution; unit-cell parameters a = 17.90, b = 30.59, c = 44.61?Å) and at 100?K (1?Å resolution; a = 17.99, b = 30.98, c = 44.07?Å) and neutron data collected at room temperature (1.6?Å resolution; a = 18.00, b = 31.16, c = 44.88?Å) indicate that the DNA is in the Z-form packing in space group P212121.

Langan, Paul; Li, Xinmin; Hanson, B. Leif; Coates, Leighton; Mustyakimov, Marat

2006-01-01

247

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

SciTech Connect

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.

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

2010-12-01

248

Crystallization and preliminary crystallographic analysis of porcine acylaminoacyl peptidase  

PubMed Central

Acylaminoacyl peptidase (also known as acylamino-acid-releasing enzyme or acylpeptide hydrolase; EC 3.4.19.1) is an unusual member of the prolyl oligopeptidase family catalysing the hydrolysis of an N-acylated peptide to an acylamino acid and a peptide with a free N-terminus. Acylaminoacyl peptidase purified from porcine liver has been crystallized in mother liquor containing 0.1?M Tris–HCl pH 7.0, 10%(w/v) polyethylene glycol 8000, 50?mM MgCl2 and 1%(w/v) CHAPS using the hanging-drop vapour-diffusion technique. A full data set to 3.4?Å resolution was collected at ESRF beamline ID14-4 and space group C222 was assigned, with unit-cell parameters a = 84.8, b = 421.1, c = 212.0?Å and four molecules in the asymmetric unit.

Wright, Helena; Kiss, Andras L.; Szeltner, Zoltan; Polgar, Laszlo; Fulop, Vilmos

2005-01-01

249

Crystallographic data collection using a 0.22% bandwidth multilayer.  

PubMed

To bridge the gap between traditional multilayer and crystal optics a high-resolution multilayer monochromator with a bandwidth of 0.22% has been designed and installed on a bending-magnet beamline (F3) at the Cornell High Energy Synchrotron Source (CHESS) to provide an unfocused monochromatic X-ray beam for protein crystallography experiments. Crystallographic data of excellent quality from a medium-sized protein, Concanavalin A, were collected and processed using standard crystallographic programs. The data were successfully used for a structure solution and refinement. The flux from the multilayer monochromator is enhanced, relative to that from a flat Si(111) monochromator, by a factor of 5; consequently, data collection is faster and/or smaller samples may be used. At the same time, the bandwidth is narrow enough to avoid streaked spots. This experiment suggests that multilayer optics may play a valuable role in satisfying the demands of the structural biology community for rapid X-ray data collection, particularly at under-utilized bending-magnet beamlines. PMID:15840920

Englich, Ulrich; Kazimirov, Alexander; Shen, Qun; Bilderback, Don H; Gruner, Sol M; Hao, Quan

2005-04-14

250

Crystallographic alignment of high-density gallium nitride nanowire arrays.  

PubMed

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

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

2004-07-25

251

Crystallographic preferred orientations and deformation mechanisms in mantle shear zones  

NASA Astrophysics Data System (ADS)

In this contribution we will review our research on deformation mechanisms and olivine crystallographic preferred orientation (CPO) development in naturally deformed peridotites from mantle shear zones. In naturally deformed exhumed upper mantle rocks a strong olivine crystallographic preferred orientation (CPO) is generally developed in coarse grained rocks. Fine grained peridotites (grain size less than 15 microns) tend to have random to weak olivine CPO and this weak CPO is usually interpreted in terms of dominant grain size sensitive deformation mechanisms. Recently examples have been found of modest CPO development in pyroxene rich olivine rocks with ultra-fine grain size and microstructures consistent with dominant grain boundary sliding and diffusion creep. Several mechanisms can explain CPO development and preservation during grain size sensitive creep, indicating that the magnitude of seismic anisotropy in mantle shear zones may not be simply related to deformation mechanisms. The studies on mantle rocks indicate that grain size sensitive creep is often important in exhumed mantle shear zones, although, in many cases deformation involves a combination of dislocation creep and grain size sensitive mechanisms. We will discuss the significance of observations made on exhumed mantle rocks to shear zones in the lithosphere and asthenosphere.

Drury, Martyn; Pennock, Gill; Palasse, Laurie; Ave Lallemant, Hans; Vissers, Reinoud

2013-04-01

252

Rigid protein motion as a model for crystallographic temperature factors  

SciTech Connect

The extent to which the librations of rigid molecules can model the crystallographic temperature factor profiles of proteins has been examined. For all proteins considered, including influenza virus hemagglutinin, glutathione reductase, myohemerythrin, myoglobin, and streptavidin, a simple 10-parameter model is found to reproduce qualitatively the patterns of maxima and minima in the isotropic backbone mean-square displacements. Large deviations between the rigid molecule and individual atomic temperature factors are found to be correlated with a region in hemagglutinin for which the refined structural model is unsatisfactory and with errors in the structure in a partially incorrect model of myohemerythrin. For the high-resolution glutathione reductase structure, better results are obtained on treating each of the compact domains in the structure as independent rigid bodies. The method allows for the refinement of reliable temperature factors with the introduction of minimal parameters and may prove useful for the evaluation of models in the early stages of x-ray structure refinement. While these results by themselves do not establish the nature of the underlying displacements, the success of the rigid protein model in reproducing qualitative features of temperature factor profiles suggests that rigid body refinement results should be considered in any interpretation of crystallographic thermal parameters.

Kuriyan, J. (Rockefeller Univ., New York, NY (United States)); Weis, W.I. (Columbia Univ., New York, NY (United States))

1991-04-01

253

High-resolution structure prediction and the crystallographic phase problem.  

PubMed

The energy-based refinement of low-resolution protein structure models to atomic-level accuracy is a major challenge for computational structural biology. Here we describe a new approach to refining protein structure models that focuses sampling in regions most likely to contain errors while allowing the whole structure to relax in a physically realistic all-atom force field. In applications to models produced using nuclear magnetic resonance data and to comparative models based on distant structural homologues, the method can significantly improve the accuracy of the structures in terms of both the backbone conformations and the placement of core side chains. Furthermore, the resulting models satisfy a particularly stringent test: they provide significantly better solutions to the X-ray crystallographic phase problem in molecular replacement trials. Finally, we show that all-atom refinement can produce de novo protein structure predictions that reach the high accuracy required for molecular replacement without any experimental phase information and in the absence of templates suitable for molecular replacement from the Protein Data Bank. These results suggest that the combination of high-resolution structure prediction with state-of-the-art phasing tools may be unexpectedly powerful in phasing crystallographic data for which molecular replacement is hindered by the absence of sufficiently accurate previous models. PMID:17934447

Qian, Bin; Raman, Srivatsan; Das, Rhiju; Bradley, Philip; McCoy, Airlie J; Read, Randy J; Baker, David

2007-10-14

254

International summer school on macromolecular crystallographic computing. Final report  

SciTech Connect

The School was the seventh in a series of International Union of Crystallography (IUCr) Crystallographic Symposia. The format of the School was formal lectures in the morning, tutorials in the afternoon, and software demonstrations and more lectures in the evening. The full program which left both the organizers and attendees exhausted, reflects the current state of excitement in the field of macromolecular structure determination using the technique of X-ray crystallography. The new and improved technologies and techniques described in these Proceedings are contributing to that growth and at the same time, as pointed out in the paper given by Sussman, creating challenges for the Protein Data Bank (PDB). As the School progressed, the authors were struck by the similarities to events which took place in small molecule crystallography beginning some 20 to 25 years ago. Growth then was fueled by the advent of new algorithms, affordable computer hardware, and good software. So it is today for macromolecular crystallography, but with the added bonus of the Internet which is changing how scientist conduct their research. Flack presented this view as part of his on-going contribution to how crystallographers use the Internet. After presentations discussing structures en masse they returned to the more traditional mode of presentation which parallels the determination of a single macromolecular structure: data collection -- phasing -- model building and visualization -- refinement.

NONE

1998-08-01

255

XAFS and crystallographic studies of Ni(II) porphyrins in single crystals and in solution  

SciTech Connect

Abstract. Nickel porphyrins serve as models for the active sites of several biological processes. Crystallographic and EXAFS results for a Ni meso-tetrapropyl porphyrin (NiTPrP) yield different Ni-N distances in solution and in the solid state. The Ni-N distances determined by single crystal polarized XAS and X-ray diffraction agree well. Polarized XANES experiments further establish that the pre-edge feature observed in square planar Ni(II) complexes is a ls-4pz transition. The single crystal and solution EXAFS results demonstrate that conformational variations of the porphyrin macrocycle can readily be imposed by environmental and/or packing forces and can thereby modulate the chemical and physical properties of porphyrinic chromophores and prosthetic groups.

Renner, M.W.; Furenlid, L.R.; Barkigia, K.M.; Fajer, J.

1996-09-01

256

Polarized red and blue light emission from silicon-based nanostructures correlated with crystallographic axes  

NASA Astrophysics Data System (ADS)

Energy-selective photoluminescence spectroscopy of porous silicon has been used to study the morphology of porous silicon layers prepared from (110) silicon wafers. We demonstrate that the electric field vector of the red emission band is aligned along the principal crystallographic axes of bulk silicon. From these observations, we conclude that large and small silicon nanocrystals assembling the layers have different preferential crystallographic orientations. Oxidized porous silicon layers exhibit a blue emission band which is strongly polarized along the <100> crystallographic axes. This indicates that chain-like silicon clusters, preferentially aligned along the same crystallographic directions, are responsible for the blue emission.

Goller, B.; Kovalev, D.

2011-06-01

257

Crystallographic variant selection in Ti-6Al-4V  

SciTech Connect

Transformation textures in the two-phase alloy Ti-6Al-4V have been studied. Samples were heated into the fully {beta} phase condition and then slow cooled to allow diffusional transformation to {alpha}. This produced a microstructure of grain boundary {alpha} encircling colonies of Widmanstaetten {alpha}. Electron backscattered diffraction (EBSD) texture measurements showed that the {alpha} texture was markedly sharper than that calculated on a basis of equal variant probability, indicating that significant variant selection was occurring during diffusional transformation. Investigation of the {alpha} variants produced across prior {beta} grain boundaries has shown that the selection of variants during transformation is highly dependant on the crystallography of those boundaries. The effect of this crystallographic variant selection on the transformation texture has been modelled.

Stanford, N. [Manchester Materials Science Centre, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom); Bate, P.S. [Manchester Materials Science Centre, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom)]. E-mail: pete.bate@man.ac.uk

2004-10-04

258

Crystallographic texture in cubic boron nitride thin films  

SciTech Connect

We examine the crystallographic texture exhibited by cubic boron nitride (cBN) in thin films grown by ion-assisted deposition. Our analysis indicates that the cBN is preferentially oriented such that individual crystallites have at least one [111] direction lying in the plane of the film but are otherwise randomly oriented about (1) the substrate normal and (2) the in-plane cBN [111] axis. This preferential orientation is consistent with an alignment between the cBN {l_brace}111{r_brace} planes and the basal planes of the layer of highly oriented graphitic boron nitride that forms in the initial stages of film growth. {copyright}{ital 1996 American Institute of Physics.}

Medlin, D.L.; Friedmann, T.A.; Mirkarimi, P.B.; Cardinale, G.F.; McCarty, K.F. [Sandia National Laboratories, Livermore, California 94551 (United States)

1996-04-01

259

Preliminary crystallographic characterization of an RNA helicase from Kunjin virus.  

PubMed

Kunjin virus is a member of the Flavivirus genus and is an Australian variant of West Nile virus. The C-terminal domain of the Kunjin virus NS3 protein displays helicase activity. The protein is thought to separate daughter and template RNA strands, assisting the initiation of replication by unwinding RNA secondary structure in the 3' nontranslated region. Expression, purification and preliminary crystallographic characterization of the NS3 helicase domain are reported. It is shown that Kunjin virus helicase may adopt a dimeric assembly in absence of nucleic acids, oligomerization being a means to provide the helicases with multiple nucleic acid-binding capability, facilitating translocation along the RNA strands. Kunjin virus NS3 helicase domain is an attractive model for studying the molecular mechanisms of flavivirus replication, while simultaneously providing a new basis for the rational development of anti-flaviviral compounds. PMID:16946468

Mastrangelo, Eloise; Bollati, Michela; Milani, Mario; Brisbarre, Nadège; de Lamballerie, Xavier; Coutard, Bruno; Canard, Bruno; Khromykh, Alexander; Bolognesi, Martino

2006-08-11

260

Preliminary crystallographic characterization of an RNA helicase from Kunjin virus  

PubMed Central

Kunjin virus is a member of the Flavivirus genus and is an Australian variant of West Nile virus. The C-terminal domain of the Kunjin virus NS3 protein displays helicase activity. The protein is thought to separate daughter and template RNA strands, assisting the initiation of replication by unwinding RNA secondary structure in the 3? nontranslated region. Expression, purification and preliminary crystallographic characterization of the NS3 helicase domain are reported. It is shown that Kunjin virus helicase may adopt a dimeric assembly in absence of nucleic acids, oligomerization being a means to provide the helicases with multiple nucleic acid-binding capability, facilitating translocation along the RNA strands. Kunjin virus NS3 helicase domain is an attractive model for studying the molecular mechanisms of flavivirus replication, while simultaneously providing a new basis for the rational development of anti-flaviviral compounds.

Mastrangelo, Eloise; Bollati, Michela; Milani, Mario; Brisbarre, Nadege; de Lamballerie, Xavier; Coutard, Bruno; Canard, Bruno; Khromykh, Alexander; Bolognesi, Martino

2006-01-01

261

Advanced temperature compensation for piezoresistive sensors based on crystallographic orientation.  

PubMed

We describe a highly effective method of reducing thermal sensitivity in piezoresistive sensors, in particular silicon cantilevers, by taking advantage of the dependence of the piezoresistive coefficient of silicon on crystallographic orientation. Two similar strain-sensing elements are used, positioned at 45 degrees to each other: One is set along a crystalline axis associated with a maximum piezoresistive coefficient to produce the displacement signal, while the other is set along an axis of the vanishing coefficient to produce the reference signal. Unlike other approaches, both sensing elements are coupled to the same cantilever body, maximizing thermal equilibration. Measurements show at least one order of magnitude improvement in thermal disturbance rejection over conventional approaches using uncoupled resistors. PMID:17477669

Chui, B W; Aeschimann, L; Akiyama, T; Staufer, U; de Rooij, N F; Lee, J; Goericke, F; King, W P; Vettiger, P

2007-04-01

262

Sharing electronic structure and crystallographic data with ETSF_IO  

NASA Astrophysics Data System (ADS)

We present a library of routines whose main goal is to read and write exchangeable files (NetCDF file format) storing electronic structure and crystallographic information. It is based on the specification agreed inside the European Theoretical Spectroscopy Facility (ETSF). Accordingly, this library is nicknamed ETSF_IO. The purpose of this article is to give both an overview of the ETSF_IO library and a closer look at its usage. ETSF_IO is designed to be robust and easy to use, close to Fortran read and write routines. To facilitate its adoption, a complete documentation of the input and output arguments of the routines is available in the package, as well as six tutorials explaining in detail various possible uses of the library routines. Catalogue identifier: AEBG_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBG_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Gnu Lesser General Public License No. of lines in distributed program, including test data, etc.: 63?156 No. of bytes in distributed program, including test data, etc.: 363?390 Distribution format: tar.gz Programming language: Fortran 95 Computer: All systems with a Fortran95 compiler Operating system: All systems with a Fortran95 compiler Classification: 7.3, 8 External routines: NetCDF, http://www.unidata.ucar.edu/software/netcdf Nature of problem: Store and exchange electronic structure data and crystallographic data independently of the computational platform, language and generating software Solution method: Implement a library based both on NetCDF file format and an open specification (http://etsf.eu/index.php?page=standardization)

Caliste, D.; Pouillon, Y.; Verstraete, M. J.; Olevano, V.; Gonze, X.

2008-11-01

263

Al-Si crystallographic-orientation transition in Al-Si/TiN layered structures and electromigration performance as interconnects  

NASA Astrophysics Data System (ADS)

Formation of aluminum-silicon (Al-Si) alloy/titanium nitride (TiN) layered structures and their electromigration (EM) performance have been investigated. The crystallographic structure of the TiN film changes with the sputter-deposition conditions. A large negative substrate bias in reactive sputtering induces a structural transition in the TiN film. The crystal orientation normal to the film surface is easily controlled from the zone axis group 111 to the zone axis group 200 direction. The crystallographic orientation of the Al-Si alloy film has been successfully controlled by the film deposition on an orientation controlled barrier TiN film. The Al-Si alloy film grows epitaxially on TiN at the initial stage of deposition and this causes the Al-Si alloy's preferred orientation to the underlying TiN film. These layered structures with different levels of Al-Si alloy preferred orientation have been subjected to EM tests, and the Al-Si alloy film with stronger zone axis group 111 orientation was found to have a longer EM lifetime. The best EM resistance has been obtained on Al-Si alloy film with the strongest zone axis group 111 orientation, which is achieved on a TiN film formed by the nitridation of a titanium (Ti) film. Thus, highly reliable interconnects can be obtained by improving the preferred orientation of Al-Si alloy film using texture improved TiN film.

Onoda, Hiroshi; Kageyama, Makiko; Hashimoto, Keiichi

1995-01-01

264

The nature of halogen...halide synthons: theoretical and crystallographic studies.  

PubMed

Two types of halogen...halide synthons are investigated on the basis of theoretical and crystallographic studies; the simple halogen...halide synthons and the charge assisted halogen...halide synthons. The former interactions were investigated theoretically (ab initio) by studying the energy of interaction of a halide anion with a halocarbon species as a function of Y...X- separation distance and the C-Y...X- angle in a series of complexes (R-Y...X-, R=methyl, phenyl, acetyl or pyridyl; Y=F, Cl, Br, or I; X-=F-, Cl-, Br-, or I-). The theoretical study of the latter interaction type was investigated in only one system, the [(4BP)Cl]2 dimer, (4BP=4-bromopyrdinium cation). Crystal structure determinations, to complement the latter theoretical calculations, were performed on 13 n-chloropyridinium and n-bromopyridinium halide salts (n=2-4). The theoretical and crystallographic studies indicate that these interactions are controlled by electrostatics and are characterized by linear C-Y...X- angles and separation distances less than the sum of van der Waals radius (rvdW) of the halogen atom and the ionic radii of the halide anion. The strength of these contacts from calculations varies from weak or absent, e.g., H3C-Cl...I-, to very strong, e.g., HCC-I...F- (energy of interaction ca. -153 kJ/mol). The strengths of these contacts are influenced by four factors: (a) the type of the halide anion; (b) the type of the halogen atom; (c) the hybridization of the ipso carbon; (d) the nature of the functional groups. The calculations also show that charge assisted halogen...halide synthons have a comparable strength to simple halogen...halide synthons. The nature of these contacts is explained on the basis of an electrostatic model. PMID:17388325

Awwadi, Firas F; Willett, Roger D; Peterson, Kirk A; Twamley, Brendan

2007-03-08

265

A Practical Method of Solving Cutoff Coulomb Problems in Momentum Space --- Application to the Lippmann-Schwinger Resonating-Group Method and the pd Elastic Scattering ---  

NASA Astrophysics Data System (ADS)

A practical method of solving cutoff Coulomb problems of two-cluster systems in momentum space is given. When a sharply cut-off Coulomb force with a cutoff radius ? is introduced at the level of constituent particles, the two-cluster direct potential of the Coulomb force becomes in general a local screened Coulomb potential. The asymptotic Hamiltonian yields two types of asymptotic waves; one is an approximate Coulomb wave with ? in the middle-range region, and the other a free (no-Coulomb) wave in the longest-range region. The constant Wronskians of this Hamiltonian can be calculated in either region. We can evaluate the Coulomb-modified nuclear phase shifts for the screened Coulomb problem using the matching condition proposed by Vincent and Phatak for the sharply cut-off Coulomb problem. We apply this method first to an exactly solvable model of the ? ? scattering with the Ali-Bodmer potential and confirm that a complete solution is obtained with a finite ?. The stability of nuclear phase shifts with respect to the change in ? within some appropriate range is demonstrated in the ? ? resonating-group method (RGM) calculation using the Minnesota three-range force. An application to the pd elastic scattering is also discussed.

Fujiwara, Y.; Fukukawa, K.

2012-08-01

266

Mineralogical, crystallographic and morphological characteristics of natural kaolins from the Ivory Coast (West Africa)  

Microsoft Academic Search

Thirteen clay samples from four deposits in the Ivory Coast (West Africa) were studied using X-ray diffraction, thermogravimetric analysis and chemical analysis. Mineralogical, crystallographic and morphological characteristics of these samples are given. Kaolinite is the principal mineral but other minerals are present in small quantities: illite, quartz, anatase and iron oxides (oxides and oxyhydroxides). The crystallographic, morphological and surface characteristics

J. Sei; F. Morato; G. Kra; S. Staunton; H. Quiquampoix; J. C. Jumas; J. Olivier-Fourcade

2006-01-01

267

Orbit trap rendering methods for generating artistic images with crystallographic symmetries  

Microsoft Academic Search

Building upon work that has illustrated families of chaotic functions with crystallographic symmetries, we explore combining these functions with orbit trap rendering methods in the rectangular coordinates plane. Visually fascinating images with crystallographic symmetries can be created in this way, and some of them exhibit an intricate 3-D appearance.

Jian Lu; Zhongxing Ye; Yuru Zou; Ruisong Ye

2005-01-01

268

The crystallographic fabric and texture of siderite in concretions: implications for siderite nucleation and growth processes  

Microsoft Academic Search

The crystallographic fabric of siderite in siderite concretions has been determined for upper Carboniferous (Westphalian-A) non-marine concretions and lower Jurassic (Pliensbachian) marine concretions. Compositional zoning indicates that individual siderite crystals grew over a period of changing pore water chemistry, consistent with the concretions being initially a diffuse patch of cement, which grew progressively. The siderite crystallographic fabric was analysed using

MARK W. H OUNSLOW

2001-01-01

269

Lie Groups  

Microsoft Academic Search

\\u000a This chapter discusses problems on Lie groups, Lie algebras and homogeneous spaces. After considering some specific examples\\u000a of Lie groups and Lie algebras and some questions on them, we consider homomorphisms, Lie subgroups and Lie subalgebras, integration\\u000a on Lie groups, the exponential map exp and its differential map exp*, the adjoint representation Ad and its differential map ad, and Lie

P. M. Gadea; J. Muñoz Masqué

270

Crystallographic and bioinformatic studies on restriction endonucleases: inference of evolutionary relationships in the "midnight zone" of homology.  

PubMed

Type II restriction endonucleases (ENases) cleave DNA with remarkable sequence specificity. Their discovery in 1970 and studies on molecular genetics and biochemistry carried out over the past four decades laid foundations for recombinant DNA techniques. Today, restriction enzymes are indispensable tools in molecular biology and molecular medicine and a paradigm for proteins that specifically interact with DNA as well as a challenging target for protein engineering. The sequence-structure-function relationships for these proteins are therefore of central interest in biotechnology. However, among numerous ENase sequences, only a few exhibit statistically significant similarity in pairwise comparisons, which was initially interpreted as evidence for the lack of common origin. Nevertheless, X-ray crystallographic studies of seemingly dissimilar type II ENases demonstrated that they share a common structural core and metal-binding/catalytic site, arguing for extreme divergence rather than independent evolution. A similar nuclease domain has been also identified in various enzymes implicated in DNA repair and recombination. Ironically, following the series of crystallographic studies suggesting homology of all type II ENases, bioinformatic studies provided evidence that some restriction enzymes are in fact diverged members of unrelated nuclease superfamilies: Nuc, HNH and GIY-YIG. Hence, the restriction enzymes as a whole, represent a group of functionally similar proteins, which evolved on multiple occasions and subsequently diverged into the "midnight zone" of homology, where common origins within particular groups can be inferred only from structure-guided comparisons. The structure-guided approaches used for this purpose include: identification of functionally important residues using superposition of atomic coordinates, alignment of sequence profiles enhanced by secondary structures, fold recognition, and homology modeling. This review covers recent results of comparative analyses of restriction enzymes from the four currently known superfamilies of nucleases with distinct folds, using crystallographic and bioinformatic methods, with the emphasis on theoretical predictions and their experimental validation by site-directed mutagenesis and biochemical analyses of the mutants. PMID:14529527

Bujnicki, Janusz M

2003-10-01

271

A Hubble Space Telescope Treasury Study of Star-forming Regions in the Local Group. II. Young Stellar Populations in M31  

NASA Astrophysics Data System (ADS)

We studied the young stellar populations of 22 star-forming regions in the Andromeda galaxy (M31), with Hubble Space Telescope (HST) multi-band imaging from far-UV to I. The regions were selected from Galaxy Evolution Explorer (GALEX) wide-field far-UV imaging; they sample different environments and galactocentric distances from 6 to 22 kpc. They were imaged with 30 HST fields (360 distinct images, in six bandpasses), with a pixel scale of 0.38 pc projected on the sky, at the distance of M31. This study is part of HST treasury survey program HST-GO-11079, which includes star-forming regions in eight Local Group galaxies. We provide a merged catalog of six-band stellar photometry in the 30 M31 fields, containing 118,036 sources brighter than V and B ~ 23 mag. Each HST field covers about 0.3 kpc2 in M31, and contains up to ~7000 stars, of which the number varies by a factor of >7 among the target regions; a large fraction of the sample are hot massive stars, due to our choice of filters and exposures. We derived stellar physical parameters and interstellar extinction for individual sources by spectral energy distribution analysis with model-atmosphere colors, and used the results to infer ages, massive stars content, and extinction of the star-forming regions. Reddening is up to E(B - V) <~ 0.6 mag in some OB associations, and lowest in the outermost regions (average of lsim0.12 mag in OB184 at 21.9 kpc). We examined the spatial distribution (clustering) of the hot massive stars, and defined OB associations on various spatial scales from compact to wider, more spread out ones. A hierarchical structuring is observed, with small compact groups arranged within large complexes. Their areas vary from less than 10 to 105 pc2, and masses are up to ?105 M ?, in the scales sampled by our analysis. Their cumulative mass distribution follows a power law, at least in part of the sampled regime. Hot-star counts in the young regions compare very well with integrated measurements of UV flux from GALEX.

Bianchi, Luciana; Efremova, Boryana; Hodge, Paul; Kang, Yongbeom

2012-11-01

272

Pulsed neutron spectroscopic imaging for crystallographic texture and microstructure  

NASA Astrophysics Data System (ADS)

A time-of-flight (TOF) spectroscopic neutron imaging at a pulsed neutron source is expected to be a new material analysis tool because this method can non-destructively investigate the spatial dependence of the crystallographic and metallographic information in a bulk material. For quantitative evaluation of such information, a spectral analysis code for the transmission data is necessary. Therefore, we have developed a Rietveld-like analysis code, RITS. Furthermore, we have applied the RITS code to evaluation of the position dependence of the crystal orientation anisotropy, the preferred orientation and the crystallite size of a welded ?-iron plate, and we successfully obtained the information on the texture and the microstructure. However, the reliability of the values given by the RITS code has not been evaluated yet in detail. For this reason, we compared the parameters provided by the RITS code with the parameters obtained by the neutron TOF powder diffractometry and its Rietveld analysis. Both the RITS code and the Rietveld analysis software indicated values close to each other, but there were systematic differences on the preferred orientation and the crystallite size.

Sato, Hirotaka; Kamiyama, Takashi; Iwase, Kenji; Ishigaki, Toru; Kiyanagi, Yoshiaki

2011-09-01

273

Determination of crystallographic polarity of ZnO layers  

SciTech Connect

The crystallographic polarity of ZnO epilayers was determined by x-ray diffraction (XRD) using anomalous dispersion near the Zn K edge. The method is not destructive and is straightforward to carry out using a typical XRD measurement system. The polarity difference between the Zn (0001) and O (0001) surfaces could be easily determined using a {l_brace}0002{r_brace} diffraction peak and the Bremstrahlung radiation from a Cu rotating anode source. By using the normalized pre- and post-Zn K-edge diffraction intensity ratios of the (0002) diffraction peak, Zn polar and O polar ZnO layers could always be distinguished but, the absolute value of the ratio was found to change with layer thickness. The absolute value of the ratio with layer thickness was found to have a linear dependence on layer thickness allowing determination of the polarity of (0001) ZnO epilayers with a single x-ray measurement and the known layer thickness in conjunction with standard data. Acid etching results confirmed the veracity of the polarity determination of the XRD measurement. To test the technique, Zn and O polar ZnO layers were grown by radical source molecular beam epitaxy (RS MBE) on MgO buffer layers on c-sapphire substrate and O polar ZnO layers were grown on a-plane substrates and measured using the x-ray technique with excellent agreement.

Tampo, H.; Fons, P.; Yamada, A.; Kim, K.-K.; Shibata, H.; Matsubara, K.; Niki, S.; Yoshikawa, H.; Kanie, H. [National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)

2005-10-03

274

Crystallographic Snapshot of Glycosylasparaginase Precursor Poised for Autoprocessing  

SciTech Connect

Glycosylasparaginase belongs to a family of N-terminal nucleophile hydrolases that autoproteolytically generate their mature enzymes from single-chain protein precursors. Previously, based on a precursor structure paused at pre-autoproteolysis stage by a reversible inhibitor (glycine), we proposed a mechanism of intramolecular autoproteolysis. A key structural feature, a highly strained conformation at the scissile peptide bond, had been identified and was hypothesized to be critical for driving autoproteolysis through an N-O acyl shift. To examine this 'twist-and-break' hypothesis, we report here a 1.9-{angstrom}-resolution structure of an autoproteolysis-active precursor (a T152C mutant) that is free of inhibitor or ligand and is poised to undergo autoproteolysis. The current crystallographic study has provided direct evidence for the natural conformation of the glycosylasparaginase autocatalytic site without influence from any inhibitor or ligand. This finding has confirmed our previous proposal that conformational strain is an intrinsic feature of an active precursor.

Wang, Y.; Guo, H

2010-01-01

275

Combining electron microscopic with x-ray crystallographic structures.  

PubMed

Analgorithm has been developed for placing three-dimensional atomic structures into appropriately scaled cryoelectron microscopy maps. The first stage in this process is to conduct a three-dimensional angular search in which the center of gravity of an X-ray crystallographically determined structure is placed on a selected position in the cryoelectron microscopy map. The quality of the fit is measured by the sum of the density at each atomic position. The second stage is to refine the three angles and three translational parameters for the best (usually 25 to 100) fits. Useful criteria for this refinement include the sum of densities at atomic sites, the lack of atoms in negative or low density, the absence of atomic clashes between symmetry-related positions of the atomic structure, and the distances between identifiable features in the map and their positions on the fitted atomic structure. These refinements generally lead to a convergence of the originally chosen, top scoring fits to just a few (about 3 to 8) acceptable possibilities. Usually, the best remaining fit is clearly superior to any of the others. PMID:12051899

Rossmann, M G; Bernal, R; Pletnev, S V

2001-12-01

276

Crystallographic studies of the Anthrax lethal toxin. Annual report  

SciTech Connect

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.

Frederick, C.A.

1996-07-01

277

Regulation of enamel hardness by its crystallographic dimensions.  

PubMed

Enamel is a composite biomaterial comprising a minor organic matrix (~2%) and a hierarchically organized inorganic ultrastructure (~96-98%). Surprisingly, to date there is no available information in the literature regarding the possible role of the enamel ultrastructure on the nanoscale level in tooth macroscopic properties. Understanding this relationship is of special interest for restorative purposes in dentistry. Accordingly, this study was designed to investigate how enamel nanocrystals regulate its hardness. We performed microindentation analysis on 100 extracted human teeth. The tooth enamel hardness was quantified and correlated with changes in enamel chemical composition and crystallographic dimensions obtained from Fourier transform infrared spectroscopy and X-ray diffraction, respectively. Enamel hardness was not related to the variability in organic content, but was associated with the size of apatite crystals along the c-axis. This association followed the Hall-Petch model for polycrystalline materials, indicating that the optimal size of apatite nanocrystals (larger than the critical size) provides enamel with the greatest hardness, which enables teeth to survive the heavy wear over a human lifetime. PMID:22684114

Eimar, Hazem; Ghadimi, Elnaz; Marelli, Benedetto; Vali, Hojatollah; Nazhat, Showan N; Amin, Wala M; Torres, Jesus; Ciobanu, Ovidiu; Albuquerque Junior, Rubens F; Tamimi, Faleh

2012-06-08

278

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

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.

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

279

Oast Space Theme Workshop. Volume 3: Working Group Summary. 1: Navigation, Guidance, Control (E-1) A. Statement. B. Technology Needs (Form 1). C. Priority Assessment (Form 2).  

National Technical Information Service (NTIS)

The six themes identified by the Workshop have many common navigation guidance and control needs. All the earth orbit themes have a strong requirement for attitude, figure and stabilization control of large space structures, a requirement not currently be...

1976-01-01

280

Measurement Results of the Crystallographic Orientation of the SC Cut Round Plates.  

National Technical Information Service (NTIS)

Investigations and analysis of the main measurement errors of crystallographic orientation of doubly rotated cuts are reported. On the basis of the results, a procedure to measure the crystal orientation of rectangular and round plates using the standard ...

K. Weiss

1992-01-01

281

Crystallographic study of fatigue cracking in Ni{sub 3}Al(CrB) single crystal  

SciTech Connect

The effect of crystallographic orientation on the fatigue-crack initiation and propagation in Ni{sub 3}Al(CrB) single crystal was studied using a compact-tension specimen. Stage I crystallographic cracking and cleavage fracture were observed. Crystallographic cracking can occur on two or more {l_brace}111{r_brace} slip planes simultaneously. It was shown that the threshold stress intensity for crack initiation from the notch root exhibits a dependence on crystallographic orientation. In addition, an effect of orientation on microcracking behavior was also shown. The number of {l_brace}111{r_brace} planes intersecting with each other determines the different microscopic features on the cleavage fracture surface.

Zhang, G.P.; Wang, Z.G.; Li, G.Y.; Wu, S.D. [Academia Sinica, Shenyang (China). State Key Lab. for Fatigue and Fracture of Materials

1997-03-01

282

Determination of Lower Bound Crystallographic Yield Loci of Zircaloy-4 Tubes.  

National Technical Information Service (NTIS)

The use of zircaloy-4 tubing in fuel elements of water cooled reactors is discussed with respect to its mechanisms of deformation and also its resulting anisotropic plastic behaviour. A method for obtaining lower bound crystallographic yield loci of alpha...

C. S. Costa Viana H. Brito Costa

1980-01-01

283

Experimental Studies on the Crystallographic and Plastic Anisotropies of Zircaloy-4 Tubes.  

National Technical Information Service (NTIS)

The crystallographic and plastic anisotropies of a zircaloy-4 tubing using direct pole figures and experimental yield loci are analyzed. Tensile and plane-strain compression tests were used to assess the mecahnical behaviour. The results are discussed wit...

C. S. da Costa Viana H. de Brito Costa

1982-01-01

284

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

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.

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

2009-05-21

285

Crystallographically Anisotropic Shape of Forsterite: New Probe for Evaluating Dust Formation History from Infrared Spectroscopy  

NASA Astrophysics Data System (ADS)

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 ?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 ?m and 15-20 ?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 (~25%) of forsterite dust may have experienced high-temperature evaporation (>1600 K).

Takigawa, Aki; Tachibana, Shogo

2012-05-01

286

Crystallization and preliminary X-ray crystallographic analysis of tyrosinase from the mushroom Agaricus bisporus.  

PubMed

Tyrosinase catalyzes the conversion of tyrosine to dihydroxyphenylalanine quinone, which is the main precursor for the biosynthesis of melanin. The enzyme from Agaricus bisporus, the common button mushroom, was purified and crystallized in two different space groups. Crystals belonging to space group P2(1) (unit-cell parameters a = 104.2, b = 105.0, c = 119.1 Å, ? = 110.6°, four molecules per asymmetric unit) diffracted to 3.0 Å resolution. Crystals belonging to space group P2(1)2(1)2 (unit-cell parameters a = 104.0, b = 104.5, c = 108.4 Å, two molecules per asymmetric unit) diffracted to 2.6 Å resolution. It was essential to include 5 mM HoCl(3) in all crystallization conditions in order to obtain well diffracting crystals. PMID:21543865

Ismaya, Wangsa T; Rozeboom, Henriëtte J; Schurink, Marloes; Boeriu, Carmen G; Wichers, Harry; Dijkstra, Bauke W

2011-04-27

287

Crystallization and preliminary crystallographic studies of CorC, a magnesium-ion transporter  

PubMed Central

CorC is a magnesium transporter that is involved in the Mg2+-efflux function of the CorA transporter system, an Mg2+ channel, from Shigella flexneri. Native CorC was purified and crystallized in the native form and in a ligand-free form and diffraction data sets were collected to 2.9 and 3.4?Å resolution, respectively. The native CorC crystals belonged to space group P212121, with unit-cell parameters a = 64.31, b = 74.44, c = 132.78?Å. The ligand-free CorC crystals belonged to space group P3121/P3221, with unit-cell parameters a = b = 71.89, c = 125.96?Å. The CorC–ATP complex has also been crystallized and the crystals belonged to space group P2 or P21.

Zhang, Ning; Ren, Xiaoming; Zhu, Deyu; Li, Defeng; Wang, Dacheng

2010-01-01

288

Soviet space  

NASA Astrophysics Data System (ADS)

A profusely illustrated history of the Soviet space program is presented. The topics addressed include: early Soviet rockets, satellites and planetary probes, cosmonauts in space, space stations, international cooperation in space, and the Soviet space program today and tomorrow.

Miller, Jay

289

Purification, crystallisation and preliminary crystallographic studies of succinate:ubiquinone oxidoreductase from Escherichia coli  

Microsoft Academic Search

A membrane protein complex, succinate dehydrogenase (SQR) from Escherichia coli has been purified and crystallised. This enzyme is composed of four subunits containing FAD, three iron–sulphur clusters and one haem b as prosthetic groups. The obtained crystals belong to the hexagonal space group P63 with the unit-cell dimensions of a=b=123.8 Å and c=214.6 Å. An asymmetric unit of the crystals

Susanna Törnroth; Victoria Yankovskaya; Gary Cecchini; So Iwata

2002-01-01

290

Crystallization and preliminary crystallographic analysis of molybdenum-cofactor biosynthesis protein C from Thermus thermophilus  

PubMed Central

The Gram-negative aerobic eubacterium Thermus thermophilus is an extremely important thermophilic microorganism that was originally isolated from a thermal vent environment in Japan. The molybdenum cofactor in this organism is considered to be an essential component required by enzymes that catalyze diverse key reactions in the global metabolism of carbon, nitrogen and sulfur. The molybdenum-cofactor biosynthesis protein C derived from T. thermophilus was crystallized in two different space groups. Crystals obtained using the first crystallization condition belong to the monoclinic space group P21, with unit-cell parameters a = 64.81, b = 109.84, c = 115.19?Å, ? = 104.9°; the crystal diffracted to a resolution of 1.9?Å. The other crystal form belonged to space group R32, with unit-cell parameters a = b = 106.57, c = 59.25?Å, and diffracted to 1.75?Å resolution. Preliminary calculations reveal that the asymmetric unit contains 12 monomers and one monomer for the crystals belonging to space group P21 and R32, respectively.

Kanaujia, Shankar Prasad; Ranjani, Chellamuthu Vasuki; Jeyakanthan, Jeyaraman; Baba, Seiki; Chen, Lirong; Liu, Zhi-Jie; Wang, Bi-Cheng; Nishida, Masami; Ebihara, Akio; Shinkai, Akeo; Kuramitsu, Seiki; Shiro, Yoshitsugu; Sekar, Kanagaraj; Yokoyama, Shigeyuki

2007-01-01

291

Space group and hydrogen positions of single crystal delta-AlOOH, (Al0.84Mg0.07Si0.09)H0.98O2 and its relation to stishovite and brucite  

NASA Astrophysics Data System (ADS)

A single crystal of ?-AlOOH synthesized by Suzuki et al. (2000) at conditions of 1000^oC and 21 GPa was used in this study. A set of X-ray diffraction intensities up to sin?/?=0.80 Å-1 were measured with a single crystal of 83×35×24 ?m using MoK? radiation (50 kV, 40 mA). Al:Mg:Si ratio 0.84:0.07:0.09 measured by EDS with the same crystal used in the X-ray diffraction intensity measurement yielded the chemical formula (Al0.84Mg0.07Si0.09)H0.98O_2. Suzuki et al. (2000) reported the space group P2_1nm from powder X-ray data but the systematic absence of reflections observed in this study indicated another space group Pnn2. The systematic absence of reflections observed in the present work were h+l odd for h0l and k+l odd for 0kl, indicating possible space group Pnn2 or Pnnm. The N(Z) test for a center of symmetry indicated an acentric space group. The non-centrosymmetric space group Pnn2 was therefore employed and was confirmed by the structural refinement. The agreement factors for 109 independent reflections (Io>= 3.0? Io) were R=3.6% with anisotropic temperature factors. The difference Fourier synthesis was calculated and two significant Fourier peaks H1 and H2 for the possible hydrogen sites were found. The H1 site locates around two-fold rotation axis with H1-H1 distance of 0.55 Å. The H1 site is considered to be for symmetrical statistical distribution of hydrogen atoms. The H2-H2 are separated with H2-H2 distance 2.12 Å which is larger than the sum of van der Waals radii of hydrogen atoms. The partial occupancy of Mg and Si atoms at Al site suggests the possibility of limited solid solution among ?-AlOOH, stishovite SiO_2 and hypothetical rutile-structured Mg(OH)_2. The H1 site is considered to be for AlOOH and the H_2 site for Mg(OH)_2.

Kudoh, Y.; Kuribayashi, T.; Suzuki, A.; Ohtani, E.; Kamada, T.

2003-04-01

292

Working group 4 of International Standardization Organization -experience of developing the standards of space environment: status of 2010 and roadmap for the future  

NASA Astrophysics Data System (ADS)

Since the beginning of 90's space environment international standards have been developed within the scope of ISO WG4 activities. This has been the first attempt to develop interna-tional standards of physical phenomena of natural environment such as galactic cosmic rays (GCR), solar energetic particles (SEP), the Earth's magnetic field, the ionosphere, the plasma-sphere, etc. The main difficulty faced when developing the international standards is the lack of common methods for characterizing many natural phenomena. However, if methods have been successfully developed, such standards can play an outstanding role in the engineering requirements for spacecraft designs. This report is a survey of the current status of the inter-national standards under development within the scope of the WG4 activity plan and roadmap for the future.

Panasyuk, Mikhail; Tobiska, W. Kent

293

The effect of silicon crystallographic orientation on the formation of silicon nanoclusters during anodic electrochemical etching  

SciTech Connect

Possible ways for increasing the photoluminescence quantum yield of porous silicon layers have been investigated. The effect of the anodization parameters on the photoluminescence properties for porous silicon layers formed on silicon substrates with different crystallographic orientations was studied. The average diameters for silicon nanoclusters are calculated from the photoluminescence spectra of porous silicon. The influence of the substrate crystallographic orientation on the photoluminescence quantum yield of porous silicon is revealed. A model explaining the effect of the substrate orientation on the photoluminescence properties for the porous silicon layers formed by anode electrochemical etching is proposed.

Timokhov, D. F. [National Polytechnical University of Odessa (Ukraine)], E-mail: Timokhov_D_F_UA@rambler.ru; Timokhov, F. P. [Mechnikov National University of Odessa (Ukraine)

2009-01-15

294

Identification of some crystallographic features of martensite in steels by microdiffraction  

SciTech Connect

Considerable attention should be paid to the interpretation of electron diffraction, such as the understanding of the extra reflections and other effects in an SAD pattern obtained from lath martensite by making allowances for spatial resolution limitations in the SAD patterns. These difficulties can be overcome by utilizing the convergent beam electron diffraction (CBED) method which permits the use of different probe sizes to obtain crystallographic information from very small regions. Some crystallographic features of lath martensite in low and medium C steels have been identified and some others verified by using CBED.

Sarikaya, M.; Rao, B.V.N.; Thomas, G.

1980-03-01

295

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

SciTech Connect

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.

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

2008-12-18

296

Crystallographic analysis of counterion effects on subtilisin enzymatic action in acetonitrile.  

PubMed

When enzymes are in low dielectric nonaqueous media, it would be expected that their charged groups would be more closely associated with counterions. There is evidence that these counterions may then affect enzymatic activity. Published crystal structures of proteins in organic solvents do not show increased numbers of associated counterions, and this might reflect the difficulty of distinguishing cations like Na(+) from water molecules. In this paper, the placement of several Cs(+) and Cl(-) ions in crystals of the serine protease subtilisin Carlsberg is presented. Ions are more readily identified crystallographically through their anomalous diffraction using softer X-rays. The protein conformation is very similar to that of the enzyme without CsCl in acetonitrile, both for the previously reported ( 1SCB ) and our own newly determined model. No fewer than 11 defined sites for Cs(+) cations and 8 Cl(-) anions are identified around the protein molecule, although most of these have partial occupancy and may represent nonspecific binding sites. Two Cs(+) and two Cl(-) ions are close to the mouth of the active site cleft, where they may affect catalysis. In fact, cross-linked CsCl-treated subtilisin crystals transferred to acetonitrile show catalytic activity several fold higher than the reference crystals containing Na(+). Presoaking with another large cation, choline, also increases the enzyme activity. The active site appears only minimally sterically perturbed by the ion presence around it, so alternative activation mechanisms can be suggested: an electrostatic redistribution and/or a larger hydration sphere that enhances the protein domain. PMID:20099851

Cianci, Michele; Tomaszewski, Bartlomiej; Helliwell, John R; Halling, Peter J

2010-02-24

297

Strategies, Programs and Projects 2008 of the Astrophysical Group "SPACE-Universidad Nacional Mayor De San Marcos, Peru" - Preparing for the IYA2009  

NASA Astrophysics Data System (ADS)

We present a review of our efforts to introduce astronomy as scientific career in Peru, showing how our astronomy outreach programs have been one of the most important keys to reach our national astronomical scientific goals, remarking the crucial role that the celebration of the IYA2009 must play, in order to promote PhD programmes in astronomy in developing countries. We show the importance of the creation of the Seminario Permanente de Astronomía y Ciencias Espaciales (SPACE) in the Universidad Nacional Mayor de San Marcos, as an academic scientific and cultural center in Peru, to support our 26 years-old "Astronomical Fridays” which are addressed to wide range of public, from schoolchildren to scientists. We also show how important was to rediscover our ancient astronomical cultural past of Incas in order to promote the construction of a Astronomical Center located near Cusco city over 4000 meters above sea level, which includes a tourist-educational observatory, a scientific optical observatory and a solar radio observatory.

Vera, Victor; Aguilar, M.; Huisacayna, J.

2008-05-01

298

Space Discovery.  

ERIC Educational Resources Information Center

|Describes one teacher's experience taking Space Discovery courses that were sponsored by the United States Space Foundation (USSF). These courses examine the history of space science, theory of orbits and rocketry, the effects of living in outer space on humans, and space weather. (DDR)|

Blackman, Joan

1998-01-01

299

Sterically Hindered Chiral Organometallic Complexes: AN X-Ray Crystallographic, NMR Spectroscopic and Ehmo Study.  

NASA Astrophysics Data System (ADS)

Sterically crowded organometallic complexes present fascinating problems of structure and molecular dynamics. Tetrahedral clusters such as (RCequivCR ^')rm(C_5H_5)_2M _2(CO)_4, where M = Mo or W, crystallize in conformations possessing three terminal carbonyls while the fourth is semi-bridging. However, these ligands undergo a rapid exchange process which can be followed by variable -temperature NMR spectroscopy. When the R substituent is derived from a chiral natural product, the low temperature NMR spectra reveal the presence of diastereomers which are interconvertible via rotations of the organometallic vertices. The fluxional behaviour of tetrahedral clusters containing such vertices as Co(CO)_3, Fe(CO)_3 or rm(C_5H _5)Mo(CO)_2 can be rationalized by means of molecular orbital calculations at the extended Huckel level of approximation. These studies show that the barriers to vertex rotation can usually be traced to one principal orbital interaction in each case. However, in rm(C_5H_5)_2Mo_2(CO) _4(R-CequivC-R) clusters, the barriers are primarily steric in character. The ability of transition metal clusters to delocalize electronic charge is well known and, in principle, could be used to stabilize intermediates of biochemical significance. Treatment of 2-methylcyclopentanone with an alkyne anion was carried out in order to generate 1-alkynyl-2-methylcyclopentanols in which the methyl and alkynyl groups are trans diaxial; the aim was to mimic the "D"-ring of the steroidal contraceptive mestranol. In fact, the major epimer was the one in which the methyl and alkynyl substituents were disposed in a cis manner. The conformation of 2-methyl-1-phenylethynylcyclopentanol 47 was elucidated by two-dimensional NMR techniques. Moreover, the structure of 47 and also of its rm Co _2(CO)_6 derivative have been determined crystallographically. Protonation of the dicobalt or dimolybdenum complexes of 47 lead to stable cations; treatment of these cations with nucleophiles results in elimination of water to yield 2-methylcyclopentene derivatives of which the dimolybdenum cluster has been characterized by x-ray crystallography. The sterically crowded complexes rm(C _6H_5)_3SiOH[ Cr(CO)_3 ]_{n}, where n = 1,2,3, have also been characterized X-ray crystallographically and all three have propellor-type geometries. The question of whether the phenyl ring rotations are correlated has been studied by variable-temperature NMR spectroscopy. These systems do not yield stable silicenium cations, but the analogous Cr(CO)_3 complex of triphenylcarbinol not only shows fluxional behaviour but also yields a metal -stabilized cation. The pathway for phenyl rotations in such systems can be followed via a Dunitz-type trajectory approach in which a number of x-ray structures were analyzed.

Malisza, Krisztina Laura

300

Spatial and temporal variability of the dimethylsulfide to chlorophyll ratio in the surface ocean: an assessment based on phytoplankton group dominance determined from space  

NASA Astrophysics Data System (ADS)

Dimethylsulfoniopropionate (DMSP) is produced in surface seawater by phytoplankton. Phytoplankton culture experiments have shown that nanoeucaryotes (NANO) display much higher mean DMSP-to-Carbon or DMSP-to-Chlorophyll (Chl) ratios than Prochlorococcus (PRO), Synechococcus (SYN) or diatoms (DIAT). Moreover, the DMSP-lyase activity of algae which cleaves DMSP into dimethylsulfide (DMS) is even more group specific than DMSP itself. Ship-based observations have shown at limited spatial scales, that sea surface DMS-to-Chl ratios (DMS:Chl) are dependent on the composition of phytoplankton groups. Here we use satellite remote sensing of Chl (from SeaWiFS) and of Phytoplankton Group Dominance (PGD from PHYSAT) with ship-based sea surface DMS concentrations (8 cruises in total) to assess this dependence on an unprecedented spatial scale. PHYSAT provides PGD (either NANO, PRO, SYN, DIAT, Phaeocystis (PHAEO) or coccolithophores (COC)) in each satellite pixel (1/4° horizontal resolution). While there are identification errors in the PHYSAT method, it is important to note that these errors are lowest for NANO PGD which we typify by high DMSP:Chl. In summer, in the Indian sector of the Southern Ocean, we find that mean DMS:Chl associated with NANO + PHAEO and PRO + SYN + DIAT are 13.6±8.4 mmol g-1 (n=34) and 7.3±4.8 mmol g-1 (n=24), respectively. That is a statistically significant difference (P<0.001) that is consistent with NANO and PHAEO being relatively high DMSP producers. However, in the western North Atlantic between 40° N and 60° N, we find no significant difference between the same PGD. This is most likely because coccolithophores account for the non-dominant part of the summer phytoplankton assemblages. Meridional distributions at 22° W in the Atlantic, and 95° W and 110° W in the Pacific, both show a marked drop in DMS:Chl near the equator, down to few mmol g-1, yet the basins exhibit different PGD (NANO in the Atlantic, PRO and SYN in the Pacific). In tropical and subtropical Atlantic and Pacific waters away from the equatorial and coastal upwelling, mean DMS:Chl associated with high and low DMSP producers are statistically significantly different, but the difference is opposite of that expected from culture experiments. Hence, in a majority of cases PGD is not of primary importance in controlling DMS:Chl variations. We therefore conclude that water-leaving radiance spectra obtained simultaneously from ocean color sensor measurements of Chl concentrations and dominant phytoplankton groups can not be used to predict global fields of DMS.

Masotti, I.; Belviso, S.; Alvain, S.; Johnson, J. E.; Bates, T. S.; Tortell, P. D.; Kasamatsu, N.; Mongin, M.; Marandino, C. A.; Saltzman, E. S.; Moulin, C.

2010-10-01

301

Combined effects of crystallographic orientation, stacking fault energy and grain size on deformation twinning in fcc crystals  

Microsoft Academic Search

The combined effects of crystallographic orientation, stacking fault energy (SFE) and grain size on deformation twinning behavior in several face-centred cubic (fcc) crystals were investigated experimentally and analytically. Three types of fcc crystals, Al single crystals, Cu single crystals and polycrystalline Cu–3% Si alloy with different SFEs and special crystallographic orientations, were selected. The orientations of the Al and Cu

W. Z. Han; Z. F. Zhang; S. D. Wu; S. X. Li

2008-01-01

302

Initial crystallographic studies of a small heat-shock protein from Xylella fastidiosa.  

PubMed

The ORF XF2234 in the Xylella fastidiosa genome was identified as encoding a small heat-shock protein of 17.9?kDa (HSP17.9). HSP17.9 was found as one of the proteins that are induced during X. fastidiosa proliferation and infection in citrus culture. Recombinant HSP17.9 was crystallized and surface atomic force microscopy experiments were conducted with the aim of better characterizing the HSP17.9 crystals. X-ray diffraction data were collected at 2.7?Å resolution. The crystal belonged to space group P4(3)22, with unit-cell parameters a = 68.90, b = 68.90, c = 72.51 Å, and is the first small heat-shock protein to crystallize in this space group. PMID:22691782

Tada, Susely F S; Saraiva, Antonio Marcos; Lorite, Gabriela S; Rosselli-Murai, Luciana K; Pelloso, Alexandre César; dos Santos, Marcelo Leite; Trivella, Daniela B B; Cotta, Mônica A; de Souza, Anete Pereira; Aparicio, Ricardo

2012-04-20

303

Refolding, crystallization and preliminary X-ray crystallographic study of the whole extracellular regions of nectins  

PubMed Central

The nectin family of Ca2+-independent immunoglobulin-like cell–cell adhesion molecules contains four members. Nectins, which have three Ig-like domains in their extracellular region, form cell–cell adherens junctions cooperatively with cadherins. The whole extracellular regions of nectin-1 (nectin-1-EC) and nectin-­2 (nectin-2-EC) were expressed in Escherichia coli as inclusion bodies, solubilized in 8?M urea and then refolded by rapid dilution into refolding solution. The refolded proteins were subsequently purified by three chromatographic steps and crystallized using the hanging-drop vapour-diffusion method. The nectin-1-EC crystals belonged to space group P213 and the nectin-2-EC crystals belonged to space group P6122 or P6522.

Narita, Hirotaka; Nakagawa, Atsushi; Yamamoto, Yasunori; Sakisaka, Toshiaki; Takai, Yoshimi; Suzuki, Mamoru

2011-01-01

304

Purification, crystallization and preliminary crystallographic analysis of a 6-pyruvoyltetrahydropterin synthase homologue from Esherichia coli  

PubMed Central

6-Pyruvoyltetrahydropterin synthase from E. coli (ePTPS) has been crystallized using the hanging-drop vapour-diffusion method. Hexagonal- and rectangular-shaped crystals were obtained. Diffraction data were collected from the hexagonal and rectangular crystals to 3.0 and 2.3?Å resolution, respectively. The hexagonal plate-shaped crystals belonged to space group P321, with unit-cell parameters a = b = 112.59, c = 68.82?Å, and contained two molecules in the asymmetric unit. The rectangular crystals belonged to space group I222, with unit-cell parameters a = 112.76, b = 117.66, c = 153.57?Å, and contained six molecules in the asymmetric unit. The structure of ePTPS in both crystal forms has been determined by molecular replacement.

Seo, Kyung Hye; Supangat; Kim, Hye Lim; Park, Young Shik; Jeon, Che Ok; Lee, Kon Ho

2008-01-01

305

Crystallization and preliminary X-ray crystallographic analysis of cycloisomaltooligosaccharide glucanotransferase from Bacillus circulans T-3040.  

PubMed

Bacillus circulans T-3040 cycloisomaltooligosaccharide glucanotransferase (BcCITase) catalyses an intramolecular transglucosylation reaction and produces cycloisomaltooligosaccharides from dextran. BcCITase was overexpressed in Escherichia coli in two different forms and crystallized by the sitting-drop vapour-diffusion method. The crystal of BcCITase bearing an N-terminal His? tag diffracted to a resolution of 2.3 Å and belonged to space group P3?21, containing a single molecule in the asymmetric unit. The crystal of BcCITase bearing a C-terminal His6 tag diffracted to a resolution of 1.9 Å and belonged to space group P2?2?2?, containing two molecules in the asymmetric unit. PMID:23908050

Suzuki, Nobuhiro; Kim, Young Min; Momma, Mitsuru; Fujimoto, Zui; Kobayashi, Mikihiko; Kimura, Atsuo; Funane, Kazumi

2013-07-27

306

Purification, crystallization and preliminary crystallographic analysis of WsaF, an essential rhamnosyltransferase from Geobacillus stearothermophilus  

PubMed Central

The ?1,2-rhamnosyltransferase WsaF is involved in the biosynthesis of a polyrhamnan chain which is attached to the surface-layer protein from Geobacillus stearothermophilus NRS 2004/3a. The enzyme belongs to the large retaining GT4 family. To date, no structure of a rhamnosyltransferase has been published. Recombinant purified native WsaF has been crystallized, resulting in crystals that belonged to space group P212121 with unit-cell parameters a = 50.5, b = 56.1, c = 276.8?Å and diffracted to 3.0?Å resolution. Selenomethionine-variant WsaF crystallized in space group P21 with unit-cell parameters a = 75.9, b = 75.5, c = 78.1?Å and diffracted to 2.3?Å resolution.

Steiner, Kerstin; Wojciechowska, Anna; Schaffer, Christina; Naismith, James H.

2008-01-01

307

Crystallographic study of restricted rotation in o -formanilides  

Microsoft Academic Search

The crystal structures ofcis- andtrans-o-methylformanilide, of itscis-thio analogue, and oftrans-o-phenylformanilide have been studied with a view to clarifying the anomalously high barrier to rotation of the carbonyl group. The pair of resolved geometrical isomers is shown to be stabilized in the solid state primarily by hydrogen bonding. The increased barrier to rotation is inferred not to arise from mesomeric involvement

Jan C. A. Boeyens; Louis Denner; Deborah G. Evans

1988-01-01

308

Effects of microwave and heating treatments on the crystallographic properties of a potassium acetate powder  

Microsoft Academic Search

The crystallographic properties of a commercial potassium acetate powder have been analysed before and after various heat treatments. From X-ray diffraction patterns and scanning electron microscopy it is shown that the initial material is constituted by two chemical compounds which are characterized by tetragonal structures. After heating either by means of a microwave monomode, or under a poor vacuum at

M. Gasgnier; A. Petit

1994-01-01

309

Effect of electrochemical deposition conditions on the crystallographic texture of bismuth telluride alloys  

Microsoft Academic Search

Bismuth telluride electrodeposition was carried out to investigate the effect of electroplating factors on the crystal orientation. It was found that the layers have a fibre crystallographic texture. The applied potential and current density have a strong effect on the chemical composition and therefore on the orientation of the electrodeposited films. According to the amount of tellurium in the deposits

S. Michel; S. Diliberto; C. Boulanger; B. Bolle

2006-01-01

310

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

PubMed

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

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

2011-07-12

311

Crystallographic texture optimisation in polycrystalline ferroelectric films for Random Access Memory applications  

Microsoft Academic Search

The present paper analyses the effect of crystallographic texture on the electromechanical interactions of polycrystalline PZT films. These interactions are responsible for inducing local enhancements of the remnant polarisation. Built-in stresses and electric fields are responsible for asymmetries in the local shape of the hysteretic loop that are as large as 25% in the coercive field and 10% in the

Heather A. Murdoch; R. Edwin Garcia

2009-01-01

312

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

Microsoft Academic Search

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

Gary Sheu

2005-01-01

313

Oscillatory kinetics of anodic oxidation of silicon – influence of the crystallographic orientation  

Microsoft Academic Search

This work describes the oscillatory kinetics of the anodic oxide growth on silicon with crystallographic orientations (111) and (100). Although the oscillations are observed for two orientations if the experimental variables are properly chosen, their shape, amplitude and period are essentially different. It is shown that the oscillations are caused by a continuous growth of thin oxide layers at the

V Parkhutik; F. Costa Gómez; L. Moya Tarazona; R. Fenollosa Esteve

2000-01-01

314

Crystallographic-magnetic correlations in single-crystal haemo-ilmenite: new evidence for lamellar magnetism  

Microsoft Academic Search

17 single crystals were identified by electron backscatter diffraction (EBSD) and isolated from coarse massive haemo-ilmenite ore from South Rogaland, Norway. These were studied using the EBSD results, natural remanent magnetization (NRM), and anisotropy of magnetic susceptibility (AMS), to gain a better understanding of angular relationships between crystallographic axes and magnetic properties of haemo-ilmenite in relation to lamellar magnetism. Electron

P. Robinson; F. Heidelbach; A. M. Hirt; S. A. McEnroe; L. L. Brown

2006-01-01

315

Preliminary X-ray crystallographic studies of ribonuclease I from Escherichia coli.  

PubMed

Single crystals of ribonuclease I from Escherichia coli have been obtained by the vapor diffusion method. The crystals belong to the tetragonal space group P4(1)2(1)2 or its enantiomer P4(3)2(1)2 and have cell parameters a = b = 119.01 A and c = 34.40 A. There is one 27,000 dalton monomer in the asymmetric unit. The crystals diffract to beyond 3.0 A resolution. PMID:8230230

Lim, L W; Mathur, S; Cannistraro, V J; Kennell, D

1993-11-20

316

Some errors from the crystallographic literature, some amplifications and a questionable result.  

PubMed

The space groups of [[Mo(2)(O(2)CCH(3))(4)('linker')](n)] are corrected from P1 to C2/m for 'linker' = pyrazine and 1,4-diazabicyclo[2.2.2]octane (dabco) and from P1 to C2/c for 'linker' = 4,4'-bipyridine. Also, [[tris-(2-pyridylmethyl)amine]BrV(mu-O)VBr[tris-(2-pyridylmethyl)amine

Herbstein, Frank H; Hu, Shengzhi; Kapon, Moshe

2002-09-24

317

Preliminary X-ray crystallographic study of glucose dehydrogenase from Thermus thermophilus HB8  

PubMed Central

Thermus thermophilus is an aerobic chemoorganotroph that has been found to grow anaerobically in the presence of nitrate. Crystals of glucose dehydrogenase (GDH) from T. thermophilus HB8 belong to space group P21, with unit-cell parameters a = 36.90, b = 132.96, c = 60.78?Å, ? = 97.2°. Preliminary studies and molecular-replacement calculations reveal that the asymmetric unit contains two monomers.

Kanaujia, Shankar Prasad; Ranjani, Chellamuthu Vasuki; Jeyakanthan, Jeyaraman; Nishida, Masami; Kitamura, Yoshiaki; Baba, Seiki; Ebihara, Akio; Shimizu, Nobutaka; Nakagawa, Noriko; Shinkai, Akeo; Yamamoto, Masaki; Kuramitsu, Seiki; Shiro, Yoshitsugu; Sekar, Kanagaraj; Yokoyama, Shigeyuki

2007-01-01

318

Crystallographic and magnetic structure of the novel compound ErGe 1.83  

Microsoft Academic Search

The crystal structure and the magnetic ordering of the novel orthorhombic compound ErGe2?x has been studied by neutron powder diffraction and magnetic measurements. The crystal structure belongs to the DyGe1.85-type (space group Cmc21)·ErGe2?x (x = 0.17 (2)) orders antiferromagnetically below TN = 6 K and displays a metamagnetic behaviour. The magnetic cell has the same size as the chemical unit

O. Oleksyn; P. Schobinger-Papamantellos; C. Ritter; C. H. de Groot; K. H. J. Buschow

1997-01-01

319

Expression, purification, crystallization and preliminary crystallographic analysis of spermidine acetyltransferase from Escherichia coli.  

PubMed

The spermidine acetyltransferase (SAT) from Escherichia coli catalyses the transfer of acetyl groups from acetyl-CoA to spermidine. SAT has been expressed and purified from E. coli. SAT was crystallized by the sitting-drop vapour-diffusion method to obtain a more detailed insight into the molecular mechanism. Preliminary X-ray diffraction studies revealed that the crystals diffracted to 2.5 Å resolution and belonged to the cubic space group P23, with unit-cell parameters a = b = c = 148.7 Å. They contained four molecules per asymmetric unit. PMID:23908034

Niiyama, Mayumi; Sugiyama, Shigeru; Hirose, Mika; Ishikawa, Sae; Tomitori, Hideyuki; Higashi, Kyohei; Yamashita, Tomoko; Adachi, Hiroaki; Takano, Kazufumi; Murakami, Satoshi; Murata, Michio; Inoue, Tsuyoshi; Mori, Yusuke; Kashiwagi, Keiko; Matsumura, Hiroyoshi; Igarashi, Kazuei

2013-07-27

320

A knowledge-driven approach for crystallographic protein model completion  

PubMed Central

One of the most cumbersome and time-demanding tasks in completing a protein model is building short missing regions or ‘loops’. A method is presented that uses structural and electron-density information to build the most likely conformations of such loops. Using the distribution of angles and dihedral angles in pentapeptides as the driving parameters, a set of possible conformations for the C? backbone of loops was generated. The most likely candidate is then selected in a hierarchical manner: new and stronger restraints are added while the loop is built. The weight of the electron-density correlation relative to geometrical considerations is gradually increased until the most likely loop is selected on map correlation alone. To conclude, the loop is refined against the electron density in real space. This is started by using structural information to trace a set of models for the C? backbone of the loop. Only in later steps of the algorithm is the electron-density correlation used as a criterion to select the loop(s). Thus, this method is more robust in low-density regions than an approach using density as a primary criterion. The algorithm is implemented in a loop-building program, Loopy, which can be used either alone or as part of an automatic building cycle. Loopy can build loops of up to 14 residues in length within a couple of minutes. The average root-mean-square deviation of the C? atoms in the loops built during validation was less than 0.4?Å. When implemented in the context of automated model building in ARP/wARP, Loopy can increase the completeness of the built models.

Joosten, Krista; Cohen, Serge X.; Emsley, Paul; Mooij, Wijnand; Lamzin, Victor S.; Perrakis, Anastassis

2008-01-01

321

Graph-theoretical characterization of periodicity in crystallographic nets and other infinite graphs.  

PubMed

Local automorphisms in infinite graphs are defined as those automorphisms for which the distance (in the graph-theoretical sense) between any vertex and its image possesses an upper bound. Abelian subgroups of direction-preserving local automorphisms without fixed point, so-called shift groups, are used to determine the quotient graph of infinite graphs. It is shown that the shift group, the closest topological analogue to a translation group in crystal structures, is isomorphic to the quotient group C/C(0) of the cycle space C of the quotient graph by some subgroup C(0), its kernel. As a main consequence, the isomorphism class of nets can be determined directly from their labeled quotient graph, without having recourse to any embedding. A general method is formulated and illustrated in the case of cristobalite and moganite structures. Application to carbon and other kinds of nanotubes is also described. PMID:16110198

Eon, Jean-Guillaume

2005-08-19

322

Axes in Outer Space  

Microsoft Academic Search

We develop a notion of axis in the Culler--Vogtmann outer space X_r of a finite rank free group F_r, with respect to the action of a nongeometric, fully irreducible outer automorphism phi. Unlike the situation of a loxodromic isometry acting on hyperbolic space, or a pseudo-Anosov mapping class acting on Teichmuller space, X_r has no natural metric, and phi seems

Michael Handel; Lee Mosher

2006-01-01

323

Austrian Space Agency  

NSDL National Science Digital Library

"The Austrian Space Agency, ASA, established by the Federal authorities in Vienna in 1972, serves as a focal point for the co-ordination of space activities in Austria and is the Austrian link to international space activities." The website offers summaries of the organization's past and present research activities with the ESA Space Science Programme and the International Mars Exploration Working Group (IMEWG). Users can find inspiring biographies of nine Austrian space pioneers as well as information on the latest news and events. While the English version of the organization's work in nanotechnology and aeronautics is not yet available, the Space link provides materials on many educational opportunities including details of the Alpbach Summer School and information on courses in space law.

324

Large-scale parallel configuration interaction. II. Two- and four-component double-group general active space implementation with application to BiH  

NASA Astrophysics Data System (ADS)

We present a parallel implementation of a large-scale relativistic double-group configuration interaction (CI) program. It is applicable with a large variety of two- and four-component Hamiltonians. The parallel algorithm is based on a distributed data model in combination with a static load balancing scheme. The excellent scalability of our parallelization scheme is demonstrated in large-scale four-component multireference CI (MRCI) benchmark tests on two of the most common computer architectures, and we also discuss hardware-dependent aspects with respect to possible speedup limitations. With the new code we have been able to calculate accurate spectroscopic properties for the ground state and the first excited state of the BiH molecule using extensive basis sets. We focused, in particular, on an accurate description of the splitting of these two states which is caused by spin-orbit coupling. Our largest parallel MRCI calculation thereby comprised an expansion length of 2.7×109 Slater determinants.

Knecht, Stefan; Jensen, Hans Jørgen Aa.; Fleig, Timo

2010-01-01

325

Large-scale parallel configuration interaction. II. Two- and four-component double-group general active space implementation with application to BiH.  

PubMed

We present a parallel implementation of a large-scale relativistic double-group configuration interaction (CI) program. It is applicable with a large variety of two- and four-component Hamiltonians. The parallel algorithm is based on a distributed data model in combination with a static load balancing scheme. The excellent scalability of our parallelization scheme is demonstrated in large-scale four-component multireference CI (MRCI) benchmark tests on two of the most common computer architectures, and we also discuss hardware-dependent aspects with respect to possible speedup limitations. With the new code we have been able to calculate accurate spectroscopic properties for the ground state and the first excited state of the BiH molecule using extensive basis sets. We focused, in particular, on an accurate description of the splitting of these two states which is caused by spin-orbit coupling. Our largest parallel MRCI calculation thereby comprised an expansion length of 2.7x10(9) Slater determinants. PMID:20078150

Knecht, Stefan; Jensen, Hans Jørgen Aa; Fleig, Timo

2010-01-01

326

STM and LEED observations of the surface structure of TiO2(110) following crystallographic shear plane formation  

NASA Astrophysics Data System (ADS)

Extended vacuum annealing of rutile TiO2(110) produces macroscopic and nanoscopic changes in the surface morphology. These result from the ordering of oxygen vacancies/Tin+ interstitials in bulk TiO2 into crystallographic shear (CS) planes. We have employed low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) to identify the surface termination of CS planes produced in the bulk. The directions of the planar defects along the surface indicate the \\{132\\} series of shear planes dominate the STM images, which is also supported by the LEED results. The spacing between planes gradually varies across the surface suggesting that a series of Magnéli phases are formed. LEED patterns confirm the coexistence of both relatively large areas of a single phase and a continuum of separations between planes. Formation of CS planes also leads to extensive facetting of the crystal, which is visible to the naked eye as a rippled surface finish. Some Ca segregation is observed during CS plane formation; however, when removed the CS planes remain, indicating they are not significantly stabilized by the Ca.

Bennett, R. A.; Poulston, S.; Stone, P.; Bowker, M.

1999-04-01

327

Space Day  

NSDL National Science Digital Library

Space Day '98, to be held on May 21, 1998, celebrates and honors the people who have made space exploration possible. The highlight of the Space Day homepage, maintained by Lockheed Martin Corporation, will be a live interactive webcast all day on May 21. Features of the webcast include experts in the fields of space discussing issues ranging from global collaboration to mysteries that remain. In addition to the webcast, the Space Day '98 home page provides resources for teachers and the curious alike. Mission: Fun allows visitors to test their space knowledge through interactive Shockwave games and quizzes while Teachers' Space provides educators with downloadable lesson plans (Adobe Acrobat [.pdf] format).

328

Space Stuff  

NSDL National Science Digital Library

Students are introduced to general space science with information about astronauts, space probes, space travel, the Hubble Space Telescope, space suits, and the Columbia Shuttle accident. Biographies of important scientists and astronauts are included, and vocabulary crossword puzzles, maps, logic riddles, and coloring pages extend learning. Each page offers links to a glossary of important terms. A link to content for more advanced students is included.

329

SpaceTech—Postgraduate space education  

NASA Astrophysics Data System (ADS)

SpaceTech is a postgraduate program geared primarily for mid-career space professionals seeking to gain or improve their expertise in space systems engineering and in business engineering. SpaceTech provides a lifelong impact on its participants by broadening their capabilities, encouraging systematic "end-to-end" thinking and preparing them for any technical or business-related engineering challenges they may encounter. This flexible 1-year program offers high competency gain and increased business skills. It is held in attractive locations in a flexible, multi-cultural environment. SpaceTech is a highly effective master's program certified by the esteemed Technical University of Delft (TUD), Netherlands. SpaceTech provides expert instructors who place no barriers between themselves and participants. The program combines innovative and flexible new approaches with time-tested methods to give participants the skills required for future missions and new business, while allowing participants to meet their work commitments at the same time as they study for their master's degree. The SpaceTech program is conducted in separate sessions, generally each of 2-week duration, separated by periods of some 6-8 weeks, during which time participants may return to their normal jobs. It also includes introductory online course material that the participants can study at their leisure. The first session is held at the TUD, with subsequent sessions held at strategic space agency locations. By participating at two or more of these sessions, attendees can earn certificates of satisfactory completion from TU Delft. By participating in all of the sessions, as well as taking part in the companion Central Case Project (CCP), participants earn an accredited and highly respected master's degree in Space Systems Engineering from the TUD. Seven distinct SpaceTech modules are provided during these sessions: Space Mission Analysis and Design, Systems Engineering, Business Engineering, Interpersonal Skills, Telecommunications, Earth Observation and Navigation. A group CCP, a major asset of this unique program, is a focused project, aimed at the formation of a credible virtual commercial space-related business. Participants exercise space systems engineering fundamentals as well as marketing and business engineering tools, with the goal of creating a financially viable business opportunity. They then present the result, in the form of an unsolicited proposal to potential investors, as well as a varied group of engineers, managers and executives from the space community. During the CCP, participants learn the ties between mission and system design and the potential return to investors. They develop an instinct for the technical concepts and which of the parameters to adjust to make their newly conceived business more effective and profitable.

de Bruijn, Ferdi J.; Ashford, Edward W.; Larson, Wiley J.

2008-07-01

330

Magnetic subperiodic groups.  

PubMed

The magnetic subperiodic groups, the 31 magnetic frieze-group types, the 394 magnetic rod-group types and the 528 magnetic layer-group types, are derived and given symbols based on the symbols for the nonmagnetic subperiodic groups in Volume E of International Tables for Crystallography. The symbols are constructed in analogy to the Opechowski-Guccione symbols for magnetic space groups. Tables are given that list one group from each type. Each group is specified not only by its symbol but also by explicitly listing the coset representatives of the coset decomposition of the group with respect to its translational subgroup. PMID:10927306

Litvin

1999-09-01

331

Esrange Space Center, a Gate to Space  

NASA Astrophysics Data System (ADS)

Swedish Space Corporation (SSC) is operating the Esrange Space Center in northern Sweden. Space operations have been performed for more than 40 years. We have a unique combination of maintaining balloon and rocket launch operations, and building payloads, providing space vehicles and service systems. Sub-orbital rocket flights with land recovery and short to long duration balloon flights up to weeks are offered. The geographical location, land recovery area and the long term experience makes Swedish Space Corporation and Esrange to an ideal gate for space activities. Stratospheric balloons are primarily used in supporting atmospheric research, validation of satellites and testing of space systems. Balloon operations have been carried out at Esrange since 1974. A large number of balloon flights are yearly launched in cooperation with CNES, France. Since 2005 NASA/CSBF and Esrange provide long duration balloon flights to North America. Flight durations up to 5 days with giant balloons (1.2 Million cubic metres) carrying heavy payload (up to 2500kg) with astronomical instruments has been performed. Balloons are also used as a crane for lifting space vehicles or parachute systems to be dropped and tested from high altitude. Many scientific groups both in US, Europe and Japan have indicated a great need of long duration balloon flights. Esrange will perform a technical polar circum balloon flight during the summer 2008 testing balloon systems and flight technique. We are also working on a permission giving us the opportunity on a circular stratospheric balloon flight around the North Pole.

Widell, Ola

332

The influence of preferred crystallographic orientation on blister size distribution in helium implanted surfaces  

SciTech Connect

Blister formation by ion implantation has been recently attributed to the near surface gas concentration and the mechanical properties of the metal. At a critical level of near surface concentration blisters are created with a typical range of diameter size for the specific material and specific implantation ion energy. Single crystal implantation with high near surface He concentration has shown different typical blister sizes due to the crystallographic directions. In the present work the authors report studies of blister formation in rolled and annealed aluminum and a Cu-Be alloy. It was observed that, as a consequence of the reflective stopping powers, there is a correlation between crystallographic orientation and resultant blister size distribution.

Zalkind, S.; Moreno, D. (Nuclear Research Center-Negev, Beer Sheva (Israel)); Lempert, G.D. (Soreq Nuclear Research Center, Yavne (Israel))

1994-07-15

333

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

PubMed Central

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.

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

2013-01-01

334

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

USGS Publications Warehouse

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 (101??0). A match to the observed preferred orientation using the viscoplastic self-consistent theory was obtained only when (101??0) [0001] was taken as the predominant slip system in ice II.

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

1997-01-01

335

Mineralogical, crystallographic and morphological characteristics of natural kaolins from the Ivory Coast (West Africa)  

NASA Astrophysics Data System (ADS)

Thirteen clay samples from four deposits in the Ivory Coast (West Africa) were studied using X-ray diffraction, thermogravimetric analysis and chemical analysis. Mineralogical, crystallographic and morphological characteristics of these samples are given. Kaolinite is the principal mineral but other minerals are present in small quantities: illite, quartz, anatase and iron oxides (oxides and oxyhydroxides). The crystallographic, morphological and surface characteristics are influenced by the presence of these impurities. In particular, the presence of iron oxides was associated with reduced structural ordering and thermal stability of kaolinite and increased specific surface area. These clays could be used in the ceramics industry to make tiles and bricks, and also in agronomy as supports for chemical fertilizers or for environmental protection by immobilising potentially toxic waste products.

Sei, J.; Morato, F.; Kra, G.; Staunton, S.; Quiquampoix, H.; Jumas, J. C.; Olivier-Fourcade, J.

2006-10-01

336

Developments in crystallographic phase analysis in the SEM: Backscattered electron Kikuchi patterns  

NASA Astrophysics Data System (ADS)

The recent development of a charge coupled device (CCD)-based detector for the acquisition of backscattered electron Kikuchi patterns has enabled on-line crystallographic phase identification studies to be conducted in the scanning electron microscope. High quality patterns have been obtained from a wide variety of materials with relatively little specimen preparation compared to electron diffraction in the transmission electron microscope (TEM). Crystallographic phase identification through a combination of BEKP and energy dispersive x-ray spectrometry is demonstrated by the identification of precipitates in a high temperature Ni-based alloy containing Cr and W. The precipitates that formed in this alloy were identified as M6C or M23C6.

Michael, J. R.; Goehner, R. P.; Hills, C. R.

337

A preliminary neutron crystallographic study of proteinase K at pD 6.5  

SciTech Connect

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.

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

2009-01-01

338

Far-ir Spectroscopy Of Various Mineral Groups: Providing Laboratory Data For Herschel  

NASA Astrophysics Data System (ADS)

To aid in interpreting data from Herschel Space Observatory Photodetector Array Camera and Spectrometer (PACS), we have collected mass absorption coefficient spectra in the wavelength range 15 to 250 micron of micron-sized powders for more than 140 mineral species representing various mineral groups. Mineral groups investigated included nesosilicates (olivines, garnets, phenakite), inosilicates (pyroxenes, pyroxenoids, amphiboles), sorosilicates, cyclosilicates, tectosilicates (silicas, feldspars), phyllosilicates, carbonates, sulfides, and oxides. The mineral samples were selected from AMNH mineral collection, chemical and crystallographic identity of all minerals was confirmed by means of electron microprobe and grain and powder XRD. Samples were ground to micron dimensions and the micron size distribution was ensured by Stokes settling, verified by scanning electron microscopy. Milligram quantities of mineral sample were dispersed in polyethylene powder and melted into pellets. Spectra were collected using a Fourier spectrometer with globar source, mylar beamsplitter, and a 4 K bolometer. Temperature dependence of the spectra down to 15 K revealed sharpening and blue-shifts of the characteristic absorption lines, and in some cases, resolution of additional features not seen at room temperature. Mineral spectra in the far-IR region are highly characteristic of mineral group, crystal structure and chemical composition. The spectral data obtained in this study, together with the accompanying mineral characterization data, will be added to Planetary Data System database to be used for mineral identification in cosmic dust populations, based on far-IR emission spectra of collected by Herschel and similar space IR missions.

Brusentsova, Tatyana; Peale, R.; Maukonen, D.; Figueiredo, P.; Harlow, G.; Ebel, D.; Lisse, C.

2011-01-01

339

Equally Spaced?  

NSDL National Science Digital Library

Urbanologists and other types have been interested in the interactions between different groups of people in cities for hundreds of years. There is quite a broad literature on studying different types of communities and public spaces, and this recent paper from the Demos group in the United Kingdom adds to that body of work. This 40-page report was first published in July 2007, and it was authored by Hannah Lownsbrough and Joost Beunderman. As the report's subtitle suggests, it is primarily concerned with presenting a dynamic look at how public places can effectively encourage interaction between diverse communities in urban areas. For this work, the researchers looked at three separate locations in Britain, and this report presents some of their findings on what works well (and not so well) in terms of creating and maintaining high-quality public places. The report is both thoughtful and thorough, and persons with an interest in urban planning, sociology, and related fields will find it quite compelling.

Lownsbrough, Hannah; Beunderman, Joost

2007-07-01

340

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

Microsoft Academic Search

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

L. Benziada; J. Ravez

1995-01-01

341

Influence of carbon content on the crystallographic structure of boron carbide films  

Microsoft Academic Search

Boron carbide thin films were synthesised by laser-assisted chemical vapour deposition (LCVD), using a CO2 laser beam and boron trichloride and methane as precursors. Boron and carbon contents were measured by electron probe microanalysis (EPMA). Microstructural analysis was carried out by Raman microspectroscopy and glancing-incidence X-ray diffraction (GIXRD) was used to study the crystallographic structure and to determine the lattice

O. Conde; A. J. Silvestre; J. C. Oliveira

2000-01-01

342

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

Microsoft Academic Search

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

Tao Liu; Dierk Raabe; Wei-Min Mao

2010-01-01

343

The role of crystallinity in the crystallographic texture evolution of polyethylenes during tensile deformation  

Microsoft Academic Search

The crystallographic texture evolution of rapidly crystallized high-density polyethylene (HDPE) and ethylene-1-octene copolymer prepared with a Ziegler–Natta (LLDPE) catalyst, was studied during tensile deformation using wide-angle X-ray diffraction WAXD. The popLA software suite, a methodology based on spherical harmonics for texture analysis, was utilized to produce recalculated pole figures and orientation distribution function plots from the raw data. An important

D. S. Li; H. Garmestani; R. G. Alamo; S. R. Kalidindi

2003-01-01

344

Crystallographic and metallurgical characterization of radiation detector grade cadmium telluride materials  

SciTech Connect

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.

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

345

Crystallographic and metallurgical characterization of radiation detector grade cadmium telluride materials  

SciTech Connect

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.

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

346

Invariants of the crystallographic system E 8, algebraic polytopes, and 3D ordered structures  

NASA Astrophysics Data System (ADS)

It is shown that constructions of algebraic geometry select peculiar subsystems of vectors of the first coordination sphere of the 8D crystallographic lattice E 8. A correspondence between such subsystems and pairs of 4D systems of vectors specifying vertices of "algebraic" polytopes on a 3D sphere is established. A 136-vertex algebraic polytope, whose symmetry determines the structure of a number of ordered diamond-like structures, is considered as an example.

Samo?lovich, M. I.; Talis, A. L.

2008-03-01

347

Crystallographically based model for transformation-induced plasticity in multiphase carbon steels  

Microsoft Academic Search

The microstructure of multiphase steels assisted by transformation-induced plasticity consists of grains of retained austenite embedded in a ferrite-based matrix. Upon mechanical loading, retained austenite may transform into martensite, as a result of which plastic deformations are induced in the surrounding phases, i.e., the ferrite-based matrix and the untransformed austenite. In the present work, a crystallographically based model is developed

D. D. Tjahjanto; S. Turteltaub; A. S. J. Suiker

2007-01-01

348

Crystallographically based model for transformation-induced plasticity in multiphase carbon steels  

Microsoft Academic Search

The microstructure of multiphase steels assisted by transformation-induced plasticity consists of grains of retained austenite\\u000a embedded in a ferrite-based matrix. Upon mechanical loading, retained austenite may transform into martensite, as a result\\u000a of which plastic deformations are induced in the surrounding phases, i.e., the ferrite-based matrix and the untransformed\\u000a austenite. In the present work, a crystallographically based model is developed

D. D. Tjahjanto; S. Turteltaub; A. S. J. Suiker

2008-01-01

349

Crystallographic and magnetic structures of Pr6Fe13Ge studied by powder neutron diffraction  

Microsoft Academic Search

Crystallographic and magnetic structures of Pr6Fe13Ge have been investigated by high-resolution powder neutron diffraction in the temperature range of 10-300 K. The magnetic structure consists of ferromagnetic Pr6Fe13 slabs that alternate antiferromagnetically, along c, with the next Pr6Fe13 slab separated by a non-magnetic Ge layer. The magnetic moments lie within the ab-planes. The propagation vector of this structure is k=(001)

Fang-Wei Wang; Pan-Lin Zhang; Bao-Gen Shen; Qi-Wei Yan

2004-01-01

350

A reciprocal space approach for locating symmetry elements in Patterson superposition maps  

SciTech Connect

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.

Hendrixson, T.

1990-09-21

351

Space Shuttle.  

ERIC Educational Resources Information Center

The plans for utilizing reusable space shuttles which could replace almost all present expendable launch vehicles are briefly described. Many illustrations are included showing the artists' concepts of various configurations proposed for space shuttles. (PR)

National Aeronautics and Space Administration, Washington, DC.

352

Space Industry.  

National Technical Information Service (NTIS)

The U.S. space industry is a product of Government necessity born of national security imperatives. From its inception, space has provided competitive advantages to the United States in terms of national security, national pride, and technological superio...

J. D. Estridge K. D. Biddlecombe M. Bailey P. F. Frakes R. Campos

2006-01-01

353

Space basic  

NASA Astrophysics Data System (ADS)

In this education video series, 'Liftoff to Learning', astronauts (Bruce Melnick, Thomas Akers, William Shepherd, Robert Cabana, and Richard Richards) describe the historical beginnings of space exploration from the time of Robert H. Goddard (considered the Father of Rocketry), who, in 1929, invented the first propellant rocket, the prototype of modern liquid propellant rockets, up to the modern Space Shuttles. The questions - where is space, what is space, and how do astronauts get to, stay in, and come back from space are answered through historical footage, computer graphics, and animation. The space environment effects, temperature effects, and gravitational effects on the launching, orbiting, and descent of the Shuttles are discussed. Included is historical still photos and film footage of past space programs and space vehicles.

Herbert, Dexter

1991-01-01

354

Crystallization and preliminary crystallographic characterization of endo-polygalacturonase II from Aspergillus niger.  

PubMed

The endo-polygalacturonase II from Aspergillus niger has been crystallized from an ammonium sulfate solution by the hanging drop method. The crystals belong to the monoclinic space group P2(1), with cell dimensions a = 69.6 A, b = 152.6 A, c = 74.0 A and beta = 91.2 degrees with four molecules per asymmetric unit. The crystals diffract to at least 2.8 A resolution and are suitable for X-ray analysis. PMID:7932761

Schröter, K H; Arkema, A; Kester, H C; Visser, J; Dijkstra, B W

1994-10-21

355

Crystallographic characterization of the passenger domain of the Bordetella autotransporter BrkA.  

PubMed

Autotransporters (ATs) are proteins that deliver effectors (the passenger domain) to the surface of Gram-negative bacteria by the type V secretion pathway. The passenger domain of BrkA, a Bordetella pertussis autotransporter mediating serum resistance and adherence, was cloned in a pET expression system and overexpressed in Escherichia coli. The gene product was correctly refolded, purified to homogeneity and crystallized. The crystals diffracted to 2.8 A resolution. The space group was assumed to be P4(1)2(1)2, with unit-cell parameters a = b = 108.19, c = 115.35 A. PMID:19478443

Zhao, Li; Nguyen, Nham T; Fernandez, Rachel C; Murphy, Michael E P

2009-05-22

356

Crystallization and preliminary crystallographic studies of human indoleamine 2,3-dioxygenase  

PubMed Central

Indoleamine 2,3-dioxygenase (IDO) is a haem-containing dioxygenase that catalyzes the oxidative cleavage of the pyrrole ring of indoleamines by the insertion of molecular oxygen. This reaction is the first and the rate-limiting step in the kynurenine pathway, the major Trp catabolic pathway in mammals. Recombinant human IDO was crystallized by the vapour-diffusion technique. The addition of 4-phenylimidazole as a haem ligand was essential for crystallization. The crystals belong to space group P212121, with unit-cell parameters a = 86.1, b = 98.0, c = 131.0?Å. Diffraction data were collected to 2.3?Å resolution.

Oda, Shun-ichiro; Sugimoto, Hiroshi; Yoshida, Tadashi; Shiro, Yoshitsugu

2006-01-01

357

Purification, identification and preliminary crystallographic studies of an allergenic protein from Lathyrus sativus  

PubMed Central

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.

Qureshi, Insaf A.; Sethi, Dhruv K.; Salunke, Dinakar M.

2006-01-01

358

Expression, purification, crystallization and preliminary crystallographic analysis of a putative Clostridium difficile surface protein Cwp19  

PubMed Central

Cwp19 is a putatively surface-located protein from Clostridium difficile. A recombinant N-terminal protein (residues 27–401) lacking the signal peptide and the C-terminal cell-wall-binding repeats (PFam04122) was crystallized using the sitting-drop vapour-diffusion method and diffracted to 2?Å resolution. The crystal appeared to belong to the primitive monoclinic space group P21, with unit-cell parameters a = 109.1, b = 61.2, c = 109.2?Å, ? = 111.85°, and is estimated to contain two molecules of Cwp19 per asymmetric unit.

Kirby, Jonathan M.; Thiyagarajan, Nethaji; Roberts, April K.; Shone, Clifford C.; Acharya, K. Ravi

2011-01-01

359

Crystallization and preliminary crystallographic analysis of recombinant hyaluronate lyase from Streptococcus suis.  

PubMed

Hyaluronate lyase is an important surface enzyme of many streptococcal species. The enzyme degrades several biologically important connective tissue components, which facilitates the spreading of the bacteria throughout the host tissues and presumably provides energy and a carbon source for bacterial cells. Recombinant hyaluronate lyase was expressed in Escherichia coli and was crystallized using the hanging-drop vapour-diffusion method. The crystals belonged to space group P222(1), with unit-cell parameters a = 58.08, b = 101.32, c = 103.47 Å and one molecule in the asymmetric unit. Diffraction data were collected to 2.50 Å resolution. PMID:23722851

Khan, Abdul Hamid; Mohamed Omar, Youssef Mohamed; Kakar, Mohammad Azam; Bangulzai, Nasrullah

2013-05-25

360

Crystallization and preliminary crystallographic investigations of the soluble glucose dehydrogenase from Acinetobacter calcoaceticus.  

PubMed

Single crystals of the soluble glucose dehydrogenase (GDH) from Acinetobacter calcoaceticus have been grown by the vapour diffusion method. These crystals diffract to beyond 2.1 A and are suitable for X-ray crystallography. The space group was determined to be P2(1) with unit cell parameters a = 55.5 A, b = 104.5 A, c = 86.5 A and beta = 99.8 degrees. One asymmetric unit contains a dimer of the GDH molecule. PMID:8411180

Schlunegger, M P; Grütter, M G; Streiff, M B; Olsthoorn, A J; Duine, J A

1993-10-20

361

Crystallization and preliminary X-ray crystallographic studies on 4-alpha-glucanotransferase from Thermotoga maritima.  

PubMed

Thermotoga maritima 4-alpha-glucanotransferase (GTase), a 52 kDa molecular-weight amylolytic enzyme, has been crystallized by the hanging-drop vapour-diffusion method using PEG monomethylether 5000 as a precipitating agent. A complete data set has been collected to 2.6 A resolution using cryocooling conditions and synchrotron radiation. The crystals belong to space group I222 or I2(1)2(1)2(1), with unit-cell parameters a = 92.6, b = 180.3, c = 199.2 A. PMID:11418778

Roujeinikova, A; Raasch, C; Sedelnikova, S; Liebl, W; Rice, D W

2001-06-21

362

Crystallization and preliminary crystallographic study of cathepsin D inhibitor from potatoes.  

PubMed

Single crystals of the glycosylated inhibitor of cathepsin D and trypsin isolated from potato tubers were obtained using the hanging drop vapor diffusion method and ammonium nitrate as precipitant. The crystals exhibit strong F222 pseudo symmetry but belong to the orthorhombic space group C222 or C222(1), with cell parameters a = 73.8 A, b = 119.9 A and c = 133.2 A with two molecules per asymmetric unit. The crystals diffract to a resolution of 2.4 A. PMID:2002505

Baudys, M; Ghosh, M; Harlos, K; Mares, M; Fusek, M; Kostka, V; Blake, C C

1991-03-01

363

Crystallization and preliminary X-ray crystallographic study of disproportionating enzyme from potato.  

PubMed

Disproportionating enzyme (D-enzyme; EC 2.4.1.25) is a 59 kDa protein that belongs to the alpha-amylase family. D-enzyme catalyses intramolecular and intermolecular transglycosylation reactions of alpha-1,4 glucan. A crystal of the D-enzyme from potato was obtained by the hanging-drop vapour-diffusion method. Preliminary X-ray data showed that the crystal diffracts to 2.0 A resolution and belongs to space group C222(1), with unit-cell parameters a = 69.7, b = 120.3, c = 174.2 A. PMID:16508106

Imamura, Kayo; Matsuura, Takanori; Ye, Zhengmao; Takaha, Takeshi; Fujii, Kazutoshi; Kusunoki, Masami; Nitta, Yasunori

2004-12-24

364

Crystallization and preliminary crystallographic analysis of poly-?-glutamate hydrolase from bacteriophage ?NIT1  

PubMed Central

Particular Bacillus subtilis strains produce a capsular polypeptide poly-?-­glutamate (?-PGA) that functions as a physical barrier against bacteriophage infection. Bacteriophage ?NIT1 can infect B. subtilis and produces a novel ?-­PGA hydrolase PghP. PghP was overexpressed, purified and crystallized by the sitting-drop vapour-diffusion method. The crystals diffracted to a resolution of 2.4?Å using a synchrotron X-ray source and were found to belong to space group P3121 or P3221.

Fujimoto, Zui; Shiga, Isao; Itoh, Yoshifumi; Kimura, Keitarou

2009-01-01

365

Groups on transformations in Finslerian spaces.  

National Technical Information Service (NTIS)

The article first appeared in the Internal Reports of the ICTP in 1981. Since then the topic has attracted a large number of authors and several contributions have been made thereafter. Thus, a previous work of the author is revised and up-dated here incl...

R. B. Misra

1993-01-01

366

A Group Exercise in Personal Space.  

ERIC Educational Resources Information Center

|Describes the development of a proxemics exercise from workshops conducted with school teachers and counselors (N=69). Concludes that territoriality involving human beings may be a far broader concept than has been previously thought. (LLL)|

Balgooyen, Theodore J.

1984-01-01

367

Real Space Refinement of Actomyosin Structures from Sectioned Muscle  

Microsoft Academic Search

We have adapted a real space refinement protocol originally developed for high-resolution crystallographic analysis for use in fitting atomic models of actin filaments and myosin subfragment 1 (S1) to 3-D images of thin-sectioned, plastic-embedded whole muscle. The rationale for this effort is to obtain a refinement protocol that will optimize the fit of the model to the density obtained by

Li Fan Chen; Eric Blanc; Michael S. Chapman; Kenneth A. Taylor

2001-01-01

368

Multipurpose Spaces  

ERIC Educational Resources Information Center

|The concept of multipurpose spaces in schools is certainly not new. Especially in elementary schools, the combination of cafeteria and auditorium (and sometimes indoor physical activity space as well) is a well-established approach to maximizing the use of school space and a school district's budget. Nonetheless, there continue to be refinements…

Gordon, Douglas

2010-01-01

369

Space Froggy  

NSDL National Science Digital Library

Help Captain Space Froggy and his family escape from a top secret lab located on the Space Station "Fluffy" above the Earth. To escape they must first cross the busy docking ramp and then traverse deep space landing on one of the transporter pads.

2010-01-01

370

Space Suit.  

National Technical Information Service (NTIS)

A pressure suit for high altitude flights, particularly space missions is reported. The suit is designed for astronauts in the Apollo space program and may be worn both inside and outside a space vehicle, as well as on the lunar surface. It comprises an i...

A. J. Kenneway G. P. Durney L. F. Shepard M. C. Case R. C. Wise

1973-01-01

371

Loop spaces and homotopy operations  

Microsoft Academic Search

The question of whether a given H-space X is, up to homotopy, a loop space has been studied from a variety of viewpoints. Here we address this question from the aspect of homotopy operations, in the classical sense of operations on homotopy groups. First, we show how an H-space structure on X can be used to define the action of

David Blanc

1998-01-01

372

Albite crystallographic preferred orientation and grain misorientation distribution in a low-grade mylonite: implications for granular flow  

Microsoft Academic Search

Crystallographic orientation data from pure albite domains in a low-grade sheared metagabbro from the Combin Zone of the western Italian Alps were measured by electron backscatter diffraction. Crystallographic preferred orientations (CPOs) in four high-strain domains are non-random and have a triclinic symmetry. The clusters of [100], [010] and [001] show an angular relationship that corresponds to that of the albite

Zhenting Jiang; David J Prior; John Wheeler

2000-01-01

373

Electron back-scattering patterns—A new technique for obtaining crystallographic information in the scanning electron microscope  

Microsoft Academic Search

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

J. A. Venables; C. J. Harland

1973-01-01

374

Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): I. Quartz textures in monomineral rocks  

SciTech Connect

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).

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

375

Transmission electron microscopy analysis of crystallographic transition from fcc to fct on PtMn spin valves  

Microsoft Academic Search

The structural changes during the crystallographic transition from fcc to fct of antiferromagnetic PtMn layers with postdeposition annealing, in spin-valve multilayers constructed by Ta\\/PtMn\\/CoFe\\/Cu\\/CoFe\\/NiFe\\/Ta\\/Si, were investigated using transmission electron microscopy and energy dispersive x-ray spectroscopy. We determined that the crystallographic orientation of the PtMn layers after postdeposition annealing depends on the initial size of the columnar grains in as-deposited spin

Akihiro Maesaka; Satoru Ishii; Akihiiko Okabe

2000-01-01

376

Controlling the crystallographic orientation in ultrathin L10 FePt(111) films on MgO(111) underlayer  

Microsoft Academic Search

Controlling the crystallographic orientation in ultrathin FePt longitudinal media for ultrahigh recording density is discussed with introducing sputtered MgO(111) underlayers selected as a template for inducing (111) texture in the FePt films. The MgO(111) underlayers significantly enhanced the crystallographic texture of FePt(111) for films as thin as 10 nm or less. Full width at half maximum (FWHM) of FePt(111) reflection

Jae-Yoon Jeong; Jung-Gi Kim; Seung-Young Bae; Kyung-Ho Shin

2001-01-01

377

Influence of anisotropy (crystallographic and microstructural) on spallation in Zr, Ta, HY-100 steel, and 1080 eutectoid steel  

Microsoft Academic Search

The purpose of this study is to quantify the influence of textural and microstructural anisotropy on spallation. This includes\\u000a the influence of anisotropically-oriented MnS inclusion stringers in the HY-100 and 1080 steels on spallation, within two\\u000a crystallographically-isotropic steels, and the influence of strong, anisotropic crystallographic texture in high-purity polycrystalline\\u000a Ta and Zr materials to assess the role of texture on

G. T. Gray; N. K. Bourne; K. S. Vecchio; J. C. F. Millett

2010-01-01

378

Bisubstrate analogue inhibitors of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase: synthesis and biochemical and crystallographic studies.  

PubMed

6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) catalyzes the transfer of pyrophosphate from ATP to 6-hydroxymethyl-7,8-dihydropterin (HP), leading to the biosynthesis of folate cofactors. Like other enzymes in the folate pathway, HPPK is an ideal target for the development of antimicrobial agents because the enzyme is essential for microorganisms but is absent from human and animals. Three bisubstrate analogues have been synthesized for HPPK and characterized by biochemical and X-ray crystallographic analyses. All three bisubstrate analogues consist of a pterin, an adenosine moiety, and a link composed of 2-4 phosphoryl groups. P(1)-(6-Hydroxymethylpterin)-P(2)-(5'-adenosyl)diphosphate (HP(2)A, 5) shows little affinity and inhibitory activity for E. coli HPPK. P(1)-(6-Hydroxymethylpterin)-P(3)-(5'-adenosyl)triphosphate (HP(3)A, 6) shows moderate affinity and inhibitory activity with K(d) = 4.25 microM in the presence of Mg(2+) and IC(50) = 1.27 microM. P(1)-(6-Hydroxymethylpterin)-P(4)-(5'-adenosyl)tetraphosphate (HP(4)A, 7) shows the highest affinity and inhibitory activity with K(d) = 0.47 microM in the presence of Mg(2+) and IC(50) = 0.44 microM. The affinity of MgHP(4)A for HPPK is approximately 116 and 76 times higher than that of MgADP and 6-hydroxymethylpterin, respectively. The crystal structure of HPPK in complex with 7 (HPPK.MgHP(4)A) has been determined at 1.85 A resolution with a crystallographic R factor of 0.185. The crystal structure shows that 7 occupies both HP- and ATP-binding sites and induces significant conformational changes in HPPK. The biochemical and structural studies of the bisubstrate analogues indicate that the bisubstrate analogue approach can produce more potent inhibitors for HPPK and the minimum length of the link for a bisubstrate analogue is approximately 7 A. PMID:11311059

Shi, G; Blaszczyk, J; Ji, X; Yan, H

2001-04-26

379

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)

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.

Khlebnikova, Yu. V.

2010-01-01

380

Recombinant bovine uteroglobin at 1.6 ? resolution: a preliminary X-ray crystallographic analysis  

PubMed Central

Uteroglobin (UG) is a conserved protein which is induced by progesterone and secreted by the epithelia of various mammalian reproductive and respiratory organs. Recombinant bovine uteroglobin (recbUG), consisting of 80 amino acids with a C-terminal His6 tag, was overexpressed in Escherichia coli and purified. The protein was crystallized in two geometric forms, rhomboid and cuneate (wedge-shaped), by the hanging-drop vapour-diffusion method at 295?K. The rhomboid crystals diffracted to a maximum resolution of 1.6?Å using synchrotron radiation. These crystals belong to space group P21212, with unit-cell parameters a = 81.42, b = 82.82, c = 45.26?Å, and contain four monomers per asymmetric unit. The cuneate crystals diffracted to 2.35?Å resolution using a rotating-anode generator. These crystals belong to space group C2221, with unit-cell parameters a = 43.39, b = 93.94, c = 77.30?Å, and contain two molecules per asymmetric unit.

von der Decken, Victoria; Delbruck, Heinrich; Herrler, Andreas; Beier, Henning M.; Fischer, Rainer; Hoffmann, Kurt M. V.

2005-01-01

381

Recombinant bovine uteroglobin at 1.6 A resolution: a preliminary X-ray crystallographic analysis.  

PubMed

Uteroglobin (UG) is a conserved protein which is induced by progesterone and secreted by the epithelia of various mammalian reproductive and respiratory organs. Recombinant bovine uteroglobin (recbUG), consisting of 80 amino acids with a C-terminal His6 tag, was overexpressed in Escherichia coli and purified. The protein was crystallized in two geometric forms, rhomboid and cuneate (wedge-shaped), by the hanging-drop vapour-diffusion method at 295 K. The rhomboid crystals diffracted to a maximum resolution of 1.6 A using synchrotron radiation. These crystals belong to space group P2(1)2(1)2, with unit-cell parameters a = 81.42, b = 82.82, c = 45.26 A, and contain four monomers per asymmetric unit. The cuneate crystals diffracted to 2.35 A resolution using a rotating-anode generator. These crystals belong to space group C222(1), with unit-cell parameters a = 43.39, b = 93.94, c = 77.30 A, and contain two molecules per asymmetric unit. PMID:16511079

von der Decken, Victoria; Delbrück, Heinrich; Herrler, Andreas; Beier, Henning M; Fischer, Rainer; Hoffmann, Kurt M V

2005-04-22

382

Expression, purification, crystallization and preliminary crystallographic analysis of phosphoserine aminotransferase from Bacillus alcalophilus.  

PubMed

Phosphoserine aminotransferase (PSAT; EC 2.6.1.52) from Bacillus alcalophilus, an obligatory alkalophile with optimum growth at pH 10.6, was overexpressed in Escherichia coli, purified and crystallized under two different conditions using the hanging-drop vapour-diffusion method. Crystals were obtained using trisodium citrate dihydrate or PEG 400 as a precipitating agent. Crystals grown in the presence of trisodium citrate belong to the orthorhombic space group C222(1), with unit-cell parameters a = 105.6, b = 136.6, c = 152.0 A, and those grown in the presence of PEG 400 belong to the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 143.7, b = 84.3, c = 67.4 A. Complete data sets were collected to 1.7 and 1.6 A resolution, respectively, at 100 K using synchrotron radiation. Analysis of the structure of B. alcalophilus PSAT may reveal structural features that contribute to enzyme adaptability at high pH values. PMID:14646107

Dubnovitsky, Anatoly P; Kapetaniou, Evangelia G; Papageorgiou, Anastassios C

2003-11-27

383

Crystallographic phases and transport properties in the superconducting Tm-Ba-Cu-O compound system  

SciTech Connect

The Tm-Ba-Cu-O compound system becomes a superconductor at critical temperature T/sub c/ measured at the midpoint of the resistive transition, of 92 K. From x-ray diffraction techniques, the material seems to be composed of two phases. The dominating (opaque) phase (approx. >94% in weight) is the superconducting TmBa/sub 2/Cu/sub 3/O/sub 6+//sub x/ oxide (isostructural with superconducting oxygen-deficient YBa/sub 2/Cu/sub 3/O/sub 6+//sub x/), which crystallizes in the orthorhombic Pmmm space group with a = 3.819(2), b = 3.889(2), c = 11.669(7)A, and D/sub c/ = 7.12(1) g cm/sup -3/. The other (green) phase is the semiconducting Tm/sub 2/BaCuO/sub 5/ oxide (space group Pbnm or Pbn2/sub 1/; a = 7.079(8), b = 12.09(1), c = 5.633(2)A, and D/sub c/ = 8.53(2)g cm/sup -3/) isostructural with the series of L/sub 2/BaCuO/sub 5/ (L = Y, Sm, Eu, Gd, Dy, Ho, Er, Yb) oxides.

Andreeta, J.P.; Basso, H.C.; Castellano, E.E.; Gallo, J.N.H.; Martin, A.A.; Piro, O.E.

1987-10-01

384

Crystallographic analysis of the structure of livingstonite HgSb{sub 4}S{sub 8} from refined data  

SciTech Connect

An X-ray diffraction study of mineral livingstonite (HgSb{sub 4}S{sub 8}) from Khaydarkan (Kyrgyzstan) has been performed on a Bruker Nonius X8Apex diffractometer with a 4K CCD detector (R = 0.031). The unit-cell parameters were found to be a = 30.1543(10) A, b = 3.9953(2) A, c = 21.4262(13) A, {beta} = 104.265(1){sup o}, V = 2501.7(2) A{sup 3}, Z = 8, d{sub calcd} = 5.013 g/cm{sup 3}, and sp. gr. A2/a. It was confirmed that livingstonite belongs to rod-layers structures. In one type of layer, two double Sb{sub 2}S{sub 4} chains are bound by disulfide groups [S{sub 2}]{sup 2-} (S-S 2.078(2) A); in the other type, these chains are bound via Hg{sup 2+} cations. A crystallographic analysis confirmed the existence of independent pseudotranslational ordering in the cation and anion matrices, which is characteristic of the lozenge-like structures of sulfides and sulfosalts.

Borisov, S. V., E-mail: borisov@che.nsk.su; Pervukhina, N. V.; Magarill, S. A.; Kuratieva, N. V. [Russian Academy of Sciences, Nikolaev Institute of Inorganic Chemistry, Siberian Branch (Russian Federation); Vasil'ev, V. I., E-mail: itret@uiggm.nsc.ru [Russian Academy of Sciences, Institute of Geology and Mineralogy, Siberian Branch (Russian Federation)

2010-03-15

385

Space Communication  

NASA Astrophysics Data System (ADS)

As the space era approaches, the importance of including space science in the general curriculum and communicating space science to the general public is becoming extremely important. The paper, points out that the inclusion of more space education in the school curriculum and to the general public will increase awareness and interest in the new developments of space exploration. The paper covers some of the many science communication projects under taken by students in the UK. One such success was the contribution to National Science Week by the University of Leicester in conjunction with UK Students for the Exploration and Development of Space (UKSEDS - a national body of students promoting space education). Children between the ages of 9-12 were taught about the solar system using enjoyable experiments. The paper will also cover other UKSEDS activities and projects. On a more worldwide scale `Under African Skies' is a fairly new and immensely exciting project (part of Cosmos Education): the participants last year including UKSEDS members travelled from school to school in Africa helping teachers and taking part in classes, including many in astronomy and physics. The paper also explains the benefits of the National Space Centre in the UK, the involvement of the University of Leicester in SSETI (Student Space Exploration and Technology Initiative) and Space School.

Patel, Bhavini

2002-01-01

386

Space Resources Roundtable 2  

NASA Astrophysics Data System (ADS)

Contents include following: Developing Technologies for Space Resource Utilization - Concept for a Planetary Engineering Research Institute. Results of a Conceptual Systems Analysis of Systems for 200 m Deep Sampling of the Martian Subsurface. The Role of Near-Earth Asteroids in Long-Term Platinum Supply. Core Drilling for Extra-Terrestrial Mining. Recommendations by the "LSP and Manufacturing" Group to the NSF-NASA Workshop on Autonomous Construction and Manufacturing for Space Electrical Power Systems. Plasma Processing of Lunar and Planetary Materials. Percussive Force Magnitude in Permafrost. Summary of the Issues Regarding the Martian Subsurface Explorer. A Costing Strategy for Manufacturing in Orbit Using Extraterrestrial Resources. Mine Planning for Asteroid Orebodies. Organic-based Dissolution of Silicates: A New Approach to Element Extraction from LunarRegohth. Historic Frontier Processes Active in Future Space-based Mineral Extraction. The Near-Earth Space Surveillance (NIESS) Mission: Discovery, Tracking, and Characterization of Asteroids, Comets, and Artificial Satellites with a microsatellite. Privatized Space Resource Property Ownership. The Fabrication of Silicon Solar Cells on the Moon Using In-Situ Resources. A New Strategy for Exploration Technology Development: The Human Exploration and Development of Space (HEDS) Exploratiori/Commercialization Technology Initiative. Space Resources for Space Tourism. Recovery of Volatiles from the Moon and Associated Issues. Preliminary Analysis of a Small Robot for Martian Regolith Excavation. The Registration of Space-based Property. Continuous Processing with Mars Gases. Drilling and Logging in Space; An Oil-Well Perspective. LORPEX for Power Surges: Drilling, Rock Crushing. An End-To-End Near-Earth Asteroid Resource Exploitation Plan. An Engineering and Cost Model for Human Space Settlement Architectures: Focus on Space Hotels and Moon/Mars Exploration. The Development and Realization of a Silicon-60-based Economy in CisLunar Space. Our Lunar Destiny: Creating a Lunar Economy. Cost-Effective Approaches to Lunar Passenger Transportation. Lunar Mineral Resources: Extraction and Application. Space Resources Development - The Link Between Human Exploration and the Long-term Commercialization of Space. Toward a More Comprehensive Evaluation of Space Information. Development of Metal Casting Molds by Sol-Gel Technology Using Planetary Resources. A New Concept in Planetary Exploration: ISRU with Power Bursts. Bold Space Ventures Require Fervent Public Support. Hot-pressed Iron from Lunar Soil. The Lunar Dust Problem: A Possible Remedy. Considerations on Use of Lunar Regolith in Lunar Constructions. Experimental Study on Water Production by Hydrogen Reduction of Lunar Soil Simulant in a Fixed Bed Reactor.

Ignatiev, A.

2000-01-01

387

Space extreme design  

Microsoft Academic Search

This paper is an introduction to the following five articles, that have been conceived together as one chapter on habitability\\u000a consideration for outer space habitations. Those contributions are made from authors in different fields, cultures and countries\\u000a working with the Extreme-Design.eu research group. Projects, theories and requirements are referred to the context of outer\\u000a space habitats, where for the love

Irene Lia Schlacht

2011-01-01

388

Normal Biconformal Spaces  

Microsoft Academic Search

A new 8-dimensional conformal gauging avoids the unphysical size change,\\u000athird order gravitational field equations, and auxiliary fields that prevent\\u000ataking the conformal group as a fundamental symmetry. We give the structure\\u000aequations, gauge transformations and intrinsic metric structure for the new\\u000abiconformal spaces. We prove that a torsion-free biconformal space with exact\\u000aWeyl form, closed dilational curvature and trace-free

James T. Wheeler

1997-01-01

389

Learning Spaces  

NSDL National Science Digital Library

This website from EDUCAUSE includes the full text of the book Learning Spaces, edited by Diana G. Oblinger. Space, whether physical or virtual, can have a significant impact on learning. Learning Spaces focuses on how learner expectations influence such spaces, the principles and activities that facilitate learning, and the role of technology from the perspective of those who create learning environments: faculty, learning technologists, librarians, and administrators. Information technology has brought unique capabilities to learning spaces, whether stimulating greater interaction through the use of collaborative tools, videoconferencing with international experts, or opening virtual worlds for exploration. This e-book represents an ongoing exploration as we bring together space, technology, and pedagogy to ensure learner success.

Oblinger, Diana

2010-07-12

390

Spaced Out  

NSDL National Science Digital Library

Students are introduced to the space environment, learning about the major differences between the environment on Earth and that of outer space (atmosphere, radiation, microgravity) â and the engineering challenges that arise because of these differences. To prepare students for the upcoming lessons on the human body, they are challenged to think about how their bodies would change and adapt in the unique environment of space.

Integrated Teaching And Learning Program

391

Conceptual Spaces  

Microsoft Academic Search

Spaces exist in the mind as well as on land and sea. They cannot be seen, or traversed by ship or on foot, not even with seven-league\\u000a boots. For they are abstract spaces, or styles of thinking. But although the geographer's methods of dealing with terrestrial\\u000a space do not reliably apply to the conceptual realm, there are other methods with

Margaret A. Boden

392

Noncommutative Spaces  

Microsoft Academic Search

In this chapter we present some of the basic concepts needed to describe noncommutative spaces and their topological and geometrical\\u000a features. We therefore complement the previous chapters where noncommutative spaces have been described by the commutation\\u000a relations of their coordinates. The full algebraic description of ordinary (commutative) spaces requires the completion of\\u000a the algebra of coordinates into a \\u000a C*<\\/font\\u000a>C^\\\\star

Fedele Lizzi

2009-01-01

393

Phonon softening and crystallographic orientation of strained graphene studied by Raman spectroscopy  

PubMed Central

We present a systematic study of the Raman spectra of optical phonons in graphene monolayers under tunable uniaxial tensile stress. Both the G and 2D bands exhibit significant red shifts. The G band splits into 2 distinct subbands (G+, G?) because of the strain-induced symmetry breaking. Raman scattering from the G+ and G? bands shows a distinctive polarization dependence that reflects the angle between the axis of the stress and the underlying graphene crystal axes. Polarized Raman spectroscopy therefore constitutes a purely optical method for the determination of the crystallographic orientation of graphene.

Huang, Mingyuan; Yan, Hugen; Chen, Changyao; Song, Daohua; Heinz, Tony F.; Hone, James

2009-01-01

394

Application of combined EBSD and 3D-SEM technique on crystallographic facet analysis of steel at low temperature.  

PubMed

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

Mohseni, P; Solberg, J K; Karlsen, M; Akselsen, O M; Ostby, E

2013-05-20

395

Chapter: Reflection groups  

Microsoft Academic Search

This chapter is concerned with the theory of finite reflection groups, that is, finite groups generated by reflections in a real or complex vector space. This is a rich theory, both for intrinsic reasons and as far as applications in other mathematical areas or mathematical physics are concerned. The origin of the theory can be traced back to the ancient

MEINOLF GECK; GUNTER MALLE

396

Group Creativity and Technology.  

ERIC Educational Resources Information Center

This paper first reviews the theory of group creativity and then examines characteristics of electronic brainstorming that make it more effective than verbal brainstorming. The success of electronic brainstorming suggests it might be the key to overcoming the space and time constraints commonly faced by a creativity group. (Author/DB)

Siau, Keng L.

1995-01-01

397

Crystallization and Preliminary Crystallographic Study of Stonustoxin, a Protein Lethal Factor Isolated from the Stonefish ( Synanceja horrida) Venom  

Microsoft Academic Search

Crystals of stonustoxin have been obtained and diffract to 3.4 Å 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 Å, c = 245.7 Å. A native stonustoxin molecule has two subunits, designated ? and

Wen Shan Yew; Prasanna R. Kolatkar; Peter Kuhn; Hoon Eng Khoo

1999-01-01

398

Collaborative Spaces  

ERIC Educational Resources Information Center

|When architects discuss the educational facilities of the next century and beyond, the conversation turns to collaborative spaces. They envision flexible and fluid spaces that will encourage creative and critical thinking, and free students to communicate clearly about the task at hand. While these are admirable ideals, there are some fundamental…

Lippman, Peter C.

2013-01-01

399

Space Handbook.  

National Technical Information Service (NTIS)

The responsibilities of the Air Force in space include a large and growing number of functions that contribute to the defense of the United States. Space operations are important elements of a credible deterrent to armed conflict. In the near-term, should...

C. D. Cochran D. M. Gorman J. D. Dumoulin

1985-01-01

400

Space Telescope.  

ERIC Educational Resources Information Center

This pamphlet describes the Space Telescope, an unmanned multi-purpose telescope observatory planned for launch into orbit by the Space Shuttle in the 1980s. The unique capabilities of this telescope are detailed, the major elements of the telescope are described, and its proposed mission operations are outlined. (CS)

National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

401

Space Debris  

NSDL National Science Digital Library

This Wikipedia article provides information about space debris, the objects in orbit around Earth left over from earlier space missions. The article introduces the history of orbital debris production as well as the growing concern about collisions between this debris and functional satellites. Links provide further information.

2008-02-26

402

Space Review.  

National Technical Information Service (NTIS)

Human space flight in the US and other space-faring countries is faced with a twin challenge that is likely to persist for many years: flat or declining budgets along with an expectation of continuing, significant achievements. A partial solution may invo...

D. Lester H. Thronson S. Hatfield

2011-01-01

403

Space flight  

NASA Astrophysics Data System (ADS)

Wayne Littles will take over the job of Associate Administrator for Space Flight at NASA from Maj.Gen. Jeremiah W. Pearson, who has resigned from the post. Littles, now NASA's Chief Engineer, was formerly deputy director of the Marshall Space Flight Center in Huntsville, Ala.

404

Space Weather  

NASA Astrophysics Data System (ADS)

This volume provides a comprehensive overview of our current observational knowledge, theoretical understanding, and numerical capability with regard to the phenomena known as space weather. Space weather refers to conditions on the Sun and in the solar wind, magnetosphere, ionosphere, and thermosphere that can influence the performance and reliability of space-borne and ground-based technological systems, and can endanger human life or health. The rapid advance in these technologies has provided us with unprecedented capability and convenience, and we have come to rely on them more and more. Technology has reduced society's risk to many kinds of natural disasters, but through its own vulnerability, it has actually increased society's risk to space weather. Adverse conditions in the space environment can cause disruption of satellite operations, communications, navigation, and electric power distribution grids, leading to a variety of socioeconomic losses.

Song, Paul; Singer, Howard J.; Siscoe, George L.

405

Space Weather  

NASA Astrophysics Data System (ADS)

Following James Van Allen's discovery of Earth's radiation belts (1958), it was immediately recognized that the space environment would be hostile to the communications satellites that had been envision by Arthur Clark (1945) and John Pierce (1955). Van Allen's discovery set off a burst of "space weather" research and engineering that continues to today, paralleling "space weather" research that had, prior to 1958, been directed toward understanding environment effects on cable and early wireless communications, electric power distribution, and pipelines. Van Allen's discovery also meant that the flight of humans above the sensible atmosphere would be fraught with more peril than mere weightlessness. This Van Allen lecture will discuss the space weather considerations that arose from Van Allen's discovery as well as space weather effects that occur from numerous other physical processes in the complex sun-heliosphere-magnetosphere environmental system.

Lanzerotti, L. J.

2005-05-01

406

Synthesis, Spectroscopic, Spectrophotometric and Crystallographic Investigations of 4-{[(1E)-(3,4-dimethoxyphenyl)methylene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one and 4-{[(1E)-(2-hydroxy-5-methoxyphenyl)methylene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one.  

PubMed

Two new Schiff base ligands 4-[(1E)-(3,4-dimethoxyphenyl)methylene]amino-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (1) and 4-[(1E)-(2-hydroxy-5-methoxyphenyl)methylene]amino-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (2) have been prepared and characterized using elemental analysis, UV-vis, FT-IR, 1H and 13C NMR spectroscopy, and X-ray crystallographic technique. Tautomeric equilibria (phenol-imine, O-H...N and keto-amine, O...H-N forms) have been studied by using UV-vis absorption spectra for the compound 2 in some solutions. Crystal structure analyses showed that the title molecules 1 and 2 crystallize in the monoclinic space group P21/c and P21 with the unit cell parameters: a = 12.5665(3) Å and 5.6666(2) Å; b = 10.4791(2) Å and 12.2444(5) Å; c = 14.6240(3) Å and 12.1556(4) Å; V =1820.65(7) Å3 and 826.84(5) Å3; Dx = 1.282 g.cm-3 and 1.355 g.cm-3; and Z = 4 and 2, respectively. PMID:24061812

Hayvali, Zeliha; Unver, Hüseyin; Svoboda, Ingrid

2010-09-01

407

Crystallization and preliminary crystallographic data for fructose-1,6-bisphosphate aldolase from Drosophila melanogaster.  

PubMed

Fructose-1,6-bisphosphate aldolase from Drosophila melanogaster has been crystallized from polyethylene glycol 6000 by vapor diffusion technique against buffered polyethylene glycol solutions at 2-4 degrees C. The insect enzyme crystallizes in the orthorhombic system, heretofore unknown for aldolases. The crystals have the space group P212121 (a = 86.3 A, b = 115.7 A, and c = 151.4 A) and contain four tetrameric aldolase molecules, each with Mr = 158,000/unit cell, i.e. one tetramer/asymmetric unit. The crystals are quite stable to x-ray deterioration. This stability may be related to the unusually low cysteine and histidine content of Drosophila aldolase. PMID:6811586

Brenner-Holzach, O; Smit, J D

1982-10-10

408

Expression, crystallization and preliminary crystallographic study of octaprenyl pyrophosphate synthase from Helicobacter pylori  

PubMed Central

Octaprenyl pyrophosphate synthase (OPPs) is involved in the synthesis of the side chains of ubiquinone and menaquinone and catalyzes consecutive con­densation reactions of farnesyl pyrophosphate with isopentenyl pyrophos­phate to generate polyprenyl pyrophosphate and pyrophosphate. In order to investigate the roles played by OPPs in the metabolism of ubiquinone and menaquinone and the enzymatic mechanisms of these enzymes, analysis of the structure–function relationship of OPPs from Helicobacter pylori was initiated. The gene for OPPs was cloned, the protein was expressed, purified and crystallized and a diffraction data set was collected to 2.00?Å resolution. The crystals belonged to space group P41212 or P43212, with unit-cell parameters a = b = 109.33, c = 103.41?Å.

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

2011-01-01

409

Expression, crystallization and preliminary crystallographic study of octaprenyl pyrophosphate synthase from Helicobacter pylori.  

PubMed

Octaprenyl pyrophosphate synthase (OPPs) is involved in the synthesis of the side chains of ubiquinone and menaquinone and catalyzes consecutive condensation reactions of farnesyl pyrophosphate with isopentenyl pyrophosphate to generate polyprenyl pyrophosphate and pyrophosphate. In order to investigate the roles played by OPPs in the metabolism of ubiquinone and menaquinone and the enzymatic mechanisms of these enzymes, analysis of the structure-function relationship of OPPs from Helicobacter pylori was initiated. The gene for OPPs was cloned, the protein was expressed, purified and crystallized and a diffraction data set was collected to 2.00?Å resolution. The crystals belonged to space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell parameters a = b = 109.33, c = 103.41?Å. PMID:21301101

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

2011-01-22

410

Crystallization and preliminary crystallographic analysis of the NAD(H)-binding domain of Escherichia coli transhydrogenase.  

PubMed

Transhydrogenase is a proton-pumping membrane protein that is required for the cellular regeneration of NADPH. The NAD(H)-binding domain (domain I) of transhydrogenase from Escherichia coli was crystallized using the hanging-drop vapour-diffusion technique at room temperature. The crystals, which were grown from PEG 4000 and ammonium acetate in citrate buffer, belong to the triclinic space group P1, with unit-cell parameters a = 38.8, b = 66.8, c = 76.4 A, alpha = 67.5, beta = 80.8, gamma = 81.5 degrees. X-ray diffraction data were collected to 1.9 A resolution using synchrotron radiation. The crystals contain one dimer of transhydrogenase domain I per asymmetric unit. PMID:15039572

Oswald, Christine; Johansson, Tomas; Törnroth, Susanna; Okvist, Mats; Krengel, Ute

2004-03-23

411

Purification, crystallization and preliminary X-ray crystallographic analysis of Lmo0540 from Listeria monocytogenes  

PubMed Central

Penicillin-binding proteins catalyze the biosynthesis of the peptidoglycan chains of the bacterial cell wall, which protects cells from osmotic pressure. Although Lmo0540 has been identified as a putative penicillin-binding protein that contributes to the virulence of Listeria monocytogenes, the biochemical role of Lmo0540 remains unclear. To provide insights into its biochemical function, Lmo0540 was overexpressed, purified and crystallized by the sitting-drop vapour-diffusion method. Diffraction data were collected to 1.5?Å resolution using synchrotron radiation. The crystal belonged to the C-­centred monoclinic space group C2, with unit-cell parameters a = 82.5, b = 75.7, c = 75.9?Å, ? = ? = 90, ? = 121.8°. A full structural determination is under way in order to elucidate the structure–function relationship of this protein.

Jeong, Jae-Hee; Kim, Yeon-Gil

2011-01-01

412

Preliminary crystallographic study of an acidic phospholipase A2 from Ophiophagus hannah (king cobra).  

PubMed

An acidic phospholipase A(2) (OH APLA(2)-II) with an isoelectric point (pI) of 4.0 was recently isolated from Ophiophagus hannah (king cobra) from Guangxi province, China. Comparison of this enzyme to a previously reported homologous phospholipase A(2) from the same venom shows that it lacks toxicity and exhibits a greater phospholipase activity. OH APLA(2)-II has been crystallized by the hanging-drop vapour-diffusion method using 1,6-hexanediol and magnesium chloride as precipitants. The crystal belongs to space group P6(3), with unit-cell parameters a = b = 98.06, c = 132.39 A. The diffraction data were collected under cryoconditions (100 K) and reduced to 2.1 A resolution. A molecular-replacement solution has been determined and shows that there are six molecules in one asymmetric unit. PMID:12351830

Xu, Sujuan; Gu, Lichuan; Wang, Qiuyan; Shu, Yuyan; Lin, Zhengjiong

2002-09-28

413

Expression, crystallization and preliminary X-ray crystallographic analysis of aldehyde dehydrogenase (ALDH) from Bacillus cereus.  

PubMed

Aldehyde dehydrogenase (ALDH) catalyses the oxidation of aldehydes using NAD(P)(+) as a cofactor. Most aldehydes are toxic at low levels. ALDHs are used to regulate metabolic intermediate aldehydes. The aldh gene from Bacillus cereus was cloned and the ALDH protein was expressed, purified and crystallized. A crystal of the ALDH protein diffracted to 2.6?Å resolution and belonged to the monoclinic space group P21, with unit-cell parameters a = 83.5, b = 93.3, c = 145.5?Å, ? = 98.05°. Four protomers were present in the asymmetric unit, with a corresponding VM of 2.55?Å(3)?Da(-1) and a solvent content of 51.8%. PMID:23695569

Ngo, Ho Phuong Thuy; Hong, Seung Hye; Oh, Deok Kun; Kang, Lin Woo

2013-04-30

414

1,5,9,13-Tetraselena[13]ferrocenophane: synthesis, complexation, crystallographic and electrochemical study.  

PubMed

A novel macrocyclic ferrocenophane, 1,5,9,13-tetraselena[13]ferrocenophane (L), was synthesized. Reaction of L with [M(NCMe)(4)](PF(6))(2) (M = Pd and Pt) or [Cu(NCMe)(4)](PF(6)) led to complexes [ML](PF(6))(2) (M = Pd and Pt) or [CuL](PF(6)). The Ag(i) cation induced the formation of a one-dimensional polymer {[AgL](PF(6))}(n) due to its large ionic radius. The structures of L and its four complexes have been determined by X-ray crystallography. Electrochemical studies showed that, in [ML](PF(6))(2) (M = Pd and Pt), the half-wave potential of the 1,1'-ferrocenediyl group shifts to much more positive potentials due to the strong through-space interaction between the two metals (M...Fe). PMID:20737065

Jing, Su; Morley, Christopher P; Gu, Cheng-Yun; Di Vaira, Massimo

2010-08-24

415

Purification, identification and preliminary crystallographic studies of Pru du amandin, an allergenic protein from Prunus dulcis  

PubMed Central

Food allergies appear to be one of the foremost causes of hypersensitivity reactions. Nut allergies account for most food allergies and are often permanent. The 360?kDa hexameric protein Pru du amandin, a known allergen, was purified from almonds (Prunus dulcis) by ammonium sulfate fractionation and ion-exchange chromatography. The protein was identified by a BLAST homology search against the nonredundant sequence database. Pru du amandin belongs to the 11S legumin family of seed storage proteins characterized by the presence of a cupin motif. Crystals were obtained by the hanging-drop vapour-diffusion method. The crystals belong to space group P41 (or P43), with unit-cell parameters a = b = 150.7, c = 164.9?Å.

Gaur, Vineet; Sethi, Dhruv K.; Salunke, Dinakar M.

2008-01-01

416

Purification, identification and preliminary crystallographic studies of a 2S albumin seed protein from Lens culinaris  

PubMed Central

Lens culinaris (lentil) is a widely consumed high-protein-content leguminous crop. A 2S albumin protein (26.5?kDa) has been identified using NH2-terminal sequencing from a 90% ammonium sulfate saturation fraction of total L. culinaris seed protein extract. The NH2-terminal sequence shows very high homology to PA2, an allergy-related protein from Pisum sativum. The 2S albumin protein was purified using a combination of size-exclusion and ion-exchange chromatography. Crystals of the 2S seed albumin obtained using the hanging-drop vapour-diffusion method diffracted to 2.5?Å resolution and were indexed in space group P41 (or P43), with unit-cell parameters a = b = 78.6, c = 135.2?Å.

Gupta, Pankaj; Gaur, Vineet; Salunke, Dinakar M.

2008-01-01

417

Expression, purification and preliminary crystallographic analysis of sucrose phosphate synthase (SPS) from Halothermothrix orenii  

PubMed Central

This is the first report of the crystallization of a sucrose phosphate synthase (SPS; EC 2.4.1.14). It also constitutes the first study of a sucrose phosphate synthase from a non-photosynthetic thermohalophilic anaerobic bacterium, Halothermothrix orenii. The purified recombinant spsA protein has been crystallized in the monoclinic space group C2, with unit-cell parameters a = 154.2, b = 47.9, c = 72.3?Å, ? = 103.16°, using the hanging-drop vapour-diffusion method. The crystal diffracts X-rays to a resolution limit of 3.01?Å. Heavy-metal and halide-soaking trials are currently in progress to solve the structure.

Huynh, Frederick; Tan, Tien-Chye; Swaminathan, Kunchithapadam; Patel, Bharat K. C.

2005-01-01

418

Purification, crystallization and preliminary X-ray crystallographic analysis of diaminopimelate epimerase from Acinetobacter baumannii.  

PubMed

The meso isomer of diaminopimelate (meso-DAP) is a biosynthetic precursor of L-lysine in bacteria and plants, and is a key component of the peptidoglycan layer in the cell walls of Gram-negative and some Gram-positive bacteria. Diaminopimelate epimerase (DapF) is a pyridoxal-5'-phosphate-independent racemase which catalyses the interconversion of (6S,2S)-2,6-diaminopimelic acid (LL-DAP) and meso-DAP. In this study, DapF from Acinetobacter baumannii was overexpressed in Escherichia coli strain SoluBL21, purified and crystallized using a vapour-diffusion method. A native crystal diffracted to a resolution of 1.9?Å and belonged to space group P3(1) or P3(2), with unit-cell parameters a = b = 74.91, c = 113.35?Å, ? = ? = 90, ? = 120°. There were two molecules in the asymmetric unit. PMID:23295484

Park, Jeong Soon; Lee, Woo Cheol; Song, Jung Hyun; Kim, Seung Il; Lee, Je Chul; Cheong, Chaejoon; Kim, Hye Yeon

2012-12-20

419

Crystallization and preliminary X-ray crystallographic studies of the PYD domain of human NALP3.  

PubMed

The NALP3 inflammasome is a macromolecular complex that is responsible for the innate immune response against infection by bacterial and viral pathogens. The NALP3 inflammasome is composed of three protein components: NALP3, ASC and caspase 1. Interaction between NALP3 and ASC via PYD domains is critical for the assembly of the NALP3 inflammasome. In this study, human NALP3 PYD, corresponding to amino acids 3-110, was overexpressed in Escherichia coli using engineered C-terminal His tags. NALP3 PYD was then purified to homogeneity and crystallized at 293 K. Finally, X-ray diffraction data were collected to a resolution of 1.7 Å from a crystal belonging to the primitive monoclinic space group P2(1), with unit-cell parameters a = 42.03, b = 60.14, c = 51.61 Å, ? = 107.40°. PMID:22102247

Bae, Ju Young; Park, Hyun Ho

2011-10-27

420

Purification, crystallization and preliminary crystallographic analysis of mouse myo-inositol oxygenase.  

PubMed

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

Brown, Peter M; Caradoc-Davies, Tom T; Dickson, James M; Cooper, Garth J S; Loomes, Kerry M; Baker, Edward N

2006-07-25

421

Crystallization and preliminary X-ray crystallographic analysis of phosphoribulokinase from Rhodobacter sphaeroides.  

PubMed

A recombinant form of Rhodobacter sphaeroides phosphoribulokinase (PRK), expressed in Escherichia coli and isolated by affinity chromatography, was crystallized by the sitting drop vapor diffusion technique using NH4H2PO4 (pH 5.6) as the precipitating agent. PRK crystallizes in the cubic space group P432, with unit cell parameters a = b = c = 129.55 A. Based on the assumption of one 32-kDa monomer per asymmetric unit, the Vm value is 2.83 A3/Da. The octameric molecular symmetry is consistent with two planar tetramers stacked in a nearly eclipsed arrangement. A native data set has been collected to 2.6 A resolution. PMID:8563645

Roberts, D L; Runquist, J A; Miziorko, H M; Kim, J J

1995-11-01

422

Purification, crystallization and preliminary X-ray crystallographic analysis of xylose reductase from Candida tropicalis  

PubMed Central

Xylose reductase (XR), which requires NADPH as a co-substrate, catalyzes the reduction of d-xylose to xylitol, which is the first step in the metabolism of d-­xylose. The detailed three-dimensional structure of XR will provide a better understanding of the biological significance of XR in the efficient production of xylitol from biomass. XR of molecular mass 36.6?kDa from Candida tropicalis was crystallized using the hanging-drop vapour-diffusion method. According to X-ray diffraction data from C. tropicalis XR crystals at 2.91?Å resolution, the unit cell belongs to space group P31 or P32. Preliminary analysis indicated the presence of four XR molecules in the asymmetric unit, with 68.0% solvent content.

Chen, Li-Chun; Huang, Sheng-Cih; Chuankhayan, Phimonphan; Chen, Chung-Der; Huang, Yen-Chieh; Jeyakanthan, Jeyaraman; Pang, Hsiao-Fang; Men, Lee-Chung; Chen, Yu-Ching; Wang, Yu-Kuo; Liu, Ming-Yih; Wu, Tung-Kung; Chen, Chun-Jung

2009-01-01

423

Expression, crystallization and preliminary crystallographic data analysis of filamin A repeats 14-16.  

PubMed

Human filamin A is a 280 kDa protein involved in actin-filament cross-linking. It is structurally divided into an actin-binding headpiece (ABD) and a rod domain containing 24 immunoglobulin-like (Ig) repeats. A fragment of human filamin A (Ig repeats 14-16) was cloned and expressed in Escherichia coli and the purified protein was crystallized in 1.6 M ammonium sulfate, 2% PEG 1000 and 100 mM HEPES pH 7.5. The crystals diffracted to 1.95 A and belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 50.63, b = 52.10, c = 98.46 A, alpha = beta = gamma = 90 degrees. PMID:17401197

Aguda, Adeleke Halilu; Sakwe, Amos Malle; Rask, Lars; Robinson, Robert Charles

2007-03-12

424

Crystallization and preliminary X-ray crystallographic studies on maltosyltransferase from Thermotoga maritima.  

PubMed

Thermotoga maritima maltosyltransferase (MTase) is a 73.7 kDa molecular weight amylolytic enzyme which catalyzes the transfer of maltosyl units from maltodextrins or starch to suitable acceptors. Crystals of recombinant MTase have been obtained by the hanging-drop vapour-diffusion method using ammonium phosphate as a precipitating agent. The crystals belong to space group P4(1)22 or its enantiomorph P4(3)22, with unit-cell parameters a = b = 148.7, c = 106.7 A. The asymmetric unit appears to contain one subunit, corresponding to a very low packing density of 4.0 A(3) Da(-1). The crystals diffract X-rays to at least 2.4 A resolution on a synchrotron-radiation source. PMID:10944350

Burke, J; Roujeinikova, A; Baker, P J; Sedelnikova, S; Raasch, C; Liebl, W; Rice, D W

2000-08-01

425

Crystallization and preliminary X-ray crystallographic analysis of human PACSIN 1 protein  

PubMed Central

PACSIN 1, which is mainly detected in brain tissue, is one of the PACSIN-family proteins involved in endocytosis and recruitment of synaptic vesicles. It binds to dynamin, synaptojanin 1 and N-WASP, and functions in vesicle formation and transport. However, the mechanisms of action of PACSIN 1 in these processes are largely unknown. Here, full-length and five C-terminal truncation constructs of human PACSIN 1 have been successfully expressed and purified in Escherichia coli. PACSIN 1 (1–344) was crystallized and diffracted to a resolution of 3.0?Å. The crystal belonged to space group C2, with unit-cell parameters a = 158.65, b = 87.38, c = 91.76?Å, ? = 90.00, ? = 113.61, ? = 90.00°. There were two molecules in the asymmetric unit and the solvent content was estimated to be about 70.47%.

Bai, Xiaoyun; Meng, Geng; Li, Guoming; Luo, Ming; Zheng, Xiaofeng

2010-01-01

426

Crystallization and preliminary crystallographic analysis of the global nitrogen regulator AmtR from Corynebacterium glutamicum  

PubMed Central

AmtR, a member of the TetR family of transcription regulators, is a global regulator of nitrogen control in Corynebacterium glutamicum. Unlike other TetR-family members, which are regulated by small-molecule effectors, AmtR is regulated by a protein called GlnK. It has been shown that a GlnK trimer has to become adenylylated prior to formation of a complex with AmtR. The physiological function of AmtR has been very well studied, but structural characterization of the mechanistic aspects of AmtR-regulated transcription has yet to be accomplished. AmtR has successfully been crystallized in space group P21212, with six molecules in the asymmetric unit and unit-cell parameters a = 153.34, b = 163.10, c = 51.93?Å. Preliminary phases were obtained using Se-­SAD.

Hasselt, Kristin; Sevvana, Madhumati; Burkovski, Andreas; Muller, Yves A.

2009-01-01

427

Crystallization and preliminary crystallographic analysis of human LR11 Vps10p domain  

PubMed Central

Low-density lipoprotein receptor (LDLR) relative with 11 binding repeats (LR11; also known as sorLA) is genetically associated with late-onset Alzheimer’s disease and is thought to be involved in neurodegenerative processes. LR11 contains a vacuolar protein-sorting 10 protein (Vps10p) domain. As this domain has been implicated in protein–protein interaction in other receptors, its structure and function are of great biological interest. Human LR11 Vps10p domain was expressed in mammalian cells and the purified protein was crystallized using the hanging-drop vapour-diffusion method. Enzymatic deglycosylation of the sample was critical to obtaining diffraction-quality crystals. Deglycosylated LR11 Vps10p-domain crystals belonged to the hexagonal space group P6122. A diffraction data set was collected to 2.4?Å resolution and a clear molecular-replacement solution was obtained.

Nakata, Zenzaburo; Nagae, Masamichi; Yasui, Norihisa; Bujo, Hideaki; Nogi, Terukazu; Takagi, Junichi

2011-01-01

428

Nucleation and growth of single crystals with uniform crystallographic orientation inside alumina nanopores  

NASA Astrophysics Data System (ADS)

Single crystal rods, having nanometer-size diameter, were grown with uniform crystallographic orientation inside a matrix of alumina nanopores. The fabrication process of this nanocomposite structure consists of several stages. First, a highly dense array of alumina pores (about 1011 cm-2 and an average diameter of about 35 nm) is prepared by an electrochemical anodization process of pure Al substrate. Then, the pores are filled with a liquid solution aided by the pores' capillary forces. Finally, the temperature of the liquid solution is slightly decreased to a supersaturated state where precipitation starts only at the pore bottom. The nucleation preference at the pore bottom is explained thermodynamically based on the contact angle, geometrical parameters of the nucleus, surface curvature, and pore diameter. In each pore the nucleus is grown to a single crystal that completely fills its volume. The crystallographic orientation of the single crystals inside the pores can be controlled by temperature and composition during growth. The nucleation and growth processes in the alumina nanopores are demonstrated with Rochelle salt (NaKC4H4O6.4H2O) and potassium nitrate (KNO3).

Yadlovker, D.; Berger, S.

2007-02-01

429

Protein crystallographic data acquisition and preliminary analysis using kodak storage phosphor plates  

NASA Astrophysics Data System (ADS)

X-ray diffraction data from single crystals of typical proteins are very weak, numerous, and subject to systematic errors arising from radiation damage at long exposure times. Compared with films, the Kodak storage phosphor technology described in the accompanying paper [1] offers the prospect of greatly improved signal-to-noise, increased sensitivity particularly at shorter wavelengths, and wide dynamic range, though with more modest spatial resolution. To assess the suitability of this technology for protein crystallographic data collection, we have collected both monochromatic oscillation and wide bandpass Laue data at CHESS on crystals ranging in unit cell size from ~ 50 Å (lysozyme) to ~ 300 Å (viruses). A direct comparison of the Kodak storage phosphor with conventional Kodak Direct Exposure Film (DEF-5) was obtained by making immediately sequential exposures on the same crystal with the two detector systems. Even with an exposure time one order of magnitude less than with the corresponding film, the storage phosphor yielded data with improved signal-to-noise. Thus, storage phosphors enable more data to be acquired per crystal, with less radiation damage, and with better precision. Such detectors appear extremely well suited to protein crystallographic applications, both static and time-resolved, with both monochromatic and polychromatic X-ray sources.

Bilderback, Donald; Moffat, Keith; Owen, James; Rubin, Byron; Schildkamp, Wilfried; Szebenyi, Doletha; Smith Temple, Brenda; Volz, Karl; Whiting, Bruce

1988-04-01

430

Crystallographic snapshots of an entire reaction cycle for a retaining xylanase from Streptomyces olivaceoviridis E-86.  

PubMed

Retaining glycosyl hydrolases, which catalyse both glycosylation and deglycosylation in a concerted manner, are the most abundant hydrolases. To date, their visualization has tended to be focused on glycosylation because glycosylation reactions can be visualized by inactivating deglycosylation step and/or using substrate analogues to isolate covalent intermediates. Furthermore, during structural analyses of glycosyl hydrolases with hydrolytic reaction products by the conventional soaking method, mutarotation of an anomeric carbon in the reaction products promptly and certainly occurs. This undesirable structural alteration hinders visualization of the second step in the reaction. Here, we investigated X-ray crystallographic visualization as a possible method for visualizing the conformational itinerary of a retaining xylanase from Streptomyces olivaceoviridis E-86. To clearly define the stereochemistry at the anomeric carbon during the deglycosylation step, extraneous nucleophiles, such as azide, were adopted to substitute for the missing base catalyst in an appropriate mutant. The X-ray crystallographic visualization provided snapshots of the components of the entire reaction, including the E*S complex, the covalent intermediate, breakdown of the intermediate and the enzyme-product (E*P)complex. PMID:19279191

Suzuki, Ryuichiro; Fujimoto, Zui; Ito, Shigeyasu; Kawahara, Shun-Ichi; Kaneko, Satoshi; Taira, Kazunari; Hasegawa, Tsunemi; Kuno, Atsushi

2009-03-11

431

Protein Crystallization in Agarose Gel with High Strength: Developing an Automated System for Protein Crystallographic Processes  

NASA Astrophysics Data System (ADS)

Agarose gel media reduce convection and prevent crystal sedimentation, resulting in the production of high-quality protein crystals. However, crystallographers have only tested agarose gel at concentrations between 0.0 and 0.6% (w/v), where it exhibits low gel strength. The effect of agarose gel on protein structures remains to be elucidated, because only a few structural studies have been performed using gel-grown protein crystals. Here, we crystallize thaumatin and elastase using a variety of crystallization methods in 2.0% (w/v) agarose gels, which are completely gellified and have sufficiently high-strength. This new crystallization approach using semi-solid agarose gels is compatible with several conventional crystallization techniques. A comparison of structures crystallized in non-gelled solution and those crystallized in 2.0% (w/v) agarose gels indicates that the crystal structures were not affected by the high-concentration agarose gels. This technique offers the practical advantages of efficient protection by the semi-solid gel media surrounding the protein crystals, allowing them to be handled and transported without affecting any later crystallographic analysis, and thereby providing an automated system for crystal capturing and mounting.

Sugiyama, Shigeru; Tanabe, Kana; Hirose, Mika; Kitatani, Tomoya; Hasenaka, Hitoshi; Takahashi, Yoshinori; Adachi, Hiroaki; Takano, Kazufumi; Murakami, Satoshi; Mori, Yusuke; Inoue, Tsuyoshi; Matsumura, Hiroyoshi

2009-07-01

432

Human ornithine transcarbamylase: crystallographic insights into substrate recognition and conformational changes.  

PubMed Central

Two crystal structures of human ornithine transcarbamylase (OTCase) complexed with the substrate carbamoyl phosphate (CP) have been solved. One structure, whose crystals were prepared by substituting N-phosphonacetyl-L-ornithine (PALO) liganded crystals with CP, has been refined at 2.4 A (1 A=0.1 nm) resolution to a crystallographic R factor of 18.4%. The second structure, whose crystals were prepared by co-crystallization with CP, has been refined at 2.6 A resolution to a crystallographic R factor of 20.2%. These structures provide important new insights into substrate recognition and ligand-induced conformational changes. Comparison of these structures with the structures of OTCase complexed with the bisubstrate analogue PALO or CP and L-norvaline reveals that binding of the first substrate, CP, induces a global conformational change involving relative domain movement, whereas the binding of the second substrate brings the flexible SMG loop, which is equivalent to the 240s loop in aspartate transcarbamylase, into the active site. The model reveals structural features that define the substrate specificity of the enzyme and that regulate the order of binding and release of products.

Shi, D; Morizono, H; Yu, X; Tong, L; Allewell, N M; Tuchman, M

2001-01-01

433

Crystallographic Structure Determination: An Experiment for Organic Analysis and Other Nontraditional Venues  

NASA Astrophysics Data System (ADS)

Single crystal diffraction analysis is a technique being increasingly utilized by non-specialists. To give students an introductory experience in this method, a one to two hour lecture and a three hour lab are described for use in courses such as organic analysis, biophysical chemistry, and instrumental methods. This class emphasizes the practical aspects of diffraction analysis, especially how routine structures are solved, how the results are prepared for publication as graphics and tables, and how reliable these results are. The student employ x-ray diffraction analysis software (i.e. SHELXTL) to solve the structures of compounds from supplied crystallographic data sets. Three data sets appropriate for this experiment are provided (i.e. for PhCH2-NH-CHPh-P(O)(OH)(OEt), (h6-1,4-C6H4(NH2)(NMe2))Cr(CO)3, and Pd(Ph2PCH2CH2PPh2)(S2C2(CN)2)) as is a link to a Youngstown State University Structure Center WEB page (i.e. http://www.as.ysu.edu/~adhunter/YSUSC/XRAYDPST/index.html) where additional properly formatted crystallographic data files may be downloaded.

Hunter, Allen D.

1998-10-01

434

X-ray crystallographic structures as a source of ligand alignment in 3D-QSAR.  

PubMed

Three-dimensional quantitative structure-activity relationships (3D-QSAR) analyses are methods correlating a pharmacological property with a mathematical representation of a molecular property distribution around three-dimensional molecular models for a set of congeners. 3D-QSAR methods are known to be highly sensitive to ligand conformation and alignment method. The current study collects 32 unique positions of congeneric ligands co-crystallized with the binding domain of AMPA receptors and aligns them using protein coordinates. Thus, it allows for a unique opportunity to consider a ligands' orientation aligned by their mode of binding in a native molecular target. Comparative molecular field analysis (CoMFA) models were generated for this alignment and compared with the results of analogous modeling using standard structure-based alignment or obtained in docking simulations of the ligands' molecules. In comparison with classically derived models, the model based on X-ray crystallographic studies showed much better performance and statistical significance. Although the 3D-QSAR methods are mainly employed when crystallographic information is limited, the current study underscores the importance that the selection of inappropriate molecular conformations and alignment methods can lead to generation of erroneous models and false conclusions. PMID:23705769

Urnia?, Rafa? D; Jó?wiak, Krzysztof

2013-06-05

435

A Three-Dimensional Cellular Automata Model for Dendrite Growth with Various Crystallographic Orientations During Solidification  

NASA Astrophysics Data System (ADS)

A three-dimensional (3-D) cellular automata (CA) model coupled with the finite-element (FE) method has been proposed to simulate dendrite growth with various crystallographic orientations during solidification. The model introduces a new tracking neighborhood method to resolve the mesh dependency caused by the cubic lattice in the CA model for simulating 3-D dendrite growth. The migration of the solid-liquid (SL) interface is associated with the dendritic preferential orientation and the driving force for the phase transition. The latter is obtained from a thermodynamics database. The local curvature and anisotropy of the surface energy are also incorporated to describe the growth kinetics of the SL interface. The solute transfer is calculated using the FE method. A numerical simulation has been performed on a Fe-1.5 wt pct C alloy. The grain morphologies with various crystallographic orientations and the solute distribution during isothermal solidification are studied and discussed. The simulation results are compared with analytical solutions and experimental results, which are in good agreement.

Zhao, Yan; Chen, Dengfu; Long, Mujun; Arif, Tansel T.; Qin, Rongshan

2013-10-01

436

The Structural Biology Center 19ID undulator beamline: facility specifications and protein crystallographic results.  

PubMed

The 19ID undulator beamline of the Structure Biology Center has been designed and built to take full advantage of the high flux, brilliance and quality of X-ray beams delivered by the Advanced Photon Source. The beamline optics are capable of delivering monochromatic X-rays with photon energies from 3.5 to 20 keV (3.5-0.6 A wavelength) with fluxes up to 8-18 x 10(12) photons s(-1) (depending on photon energy) onto cryogenically cooled crystal samples. The size of the beam (full width at half-maximum) at the sample position can be varied from 2.2 mm x 1.0 mm (horizontal x vertical, unfocused) to 0.083 mm x 0.020 mm in its fully focused configuration. Specimen-to-detector distances of between 100 mm and 1500 mm can be used. The high flexibility, inherent in the design of the optics, coupled with a kappa-geometry goniometer and beamline control software allows optimal strategies to be adopted in protein crystallographic experiments, thus maximizing the chances of their success. A large-area mosaic 3 x 3 CCD detector allows high-quality diffraction data to be measured rapidly to the crystal diffraction limits. The beamline layout and the X-ray optical and endstation components are described in detail, and the results of representative crystallographic experiments are presented. PMID:16371706

Rosenbaum, Gerd; Alkire, Randy W; Evans, Gwyndaf; Rotella, Frank J; Lazarski, Krzystof; Zhang, Rong Guang; Ginell, Stephan L; Duke, Norma; Naday, Istvan; Lazarz, Jack; Molitsky, Michael J; Keefe, Lisa; Gonczy, John; Rock, Larry; Sanishvili, Ruslan; Walsh, Martin A; Westbrook, Edwin; Joachimiak, Andrzej

2005-12-22

437

Crystallographic superstructure in R2PdSi3 (R = heavy rare earth) compounds  

SciTech Connect

The R2PdSi3 intermetallic compounds have been reported to crystallize in a hexagonal AlB2- derived structure, with the rare earth atoms on the Al sites and Pd and Si atoms randomly distributed on the B sites. However, the intricate magnetic properties observed in the series of compounds have always suggested complications to the assumed structure. To clarify the situation, x-ray and neutron diffraction measurements were performed on the heavy rare earth compounds with R = Gd, Tb, Dy, Ho, Er, Tm, which revealed the existence of a crystallographic superstructure. The superstructure features a doubled unit cell in the hexagonal basal plane and an octuplication along the perpendicular c direction with respect to the primitive cell. No structural transition was observed between 300 K and 1.5 K. Extended x-ray absorption fine structure (EXAFS) analysis as well as density functional theory (DFT) calculations were utilized to investigate the local environments of the respective atoms. In this article the various experimental results will be presented and it will be shown that the superstructure is mainly due to the Pd-Si order on the B sites. A structure model will be proposed to fully describe the superstructure of Pd-Si order in R2PdSi3. The connection between the crystallographic superstructure and the magnetic properties will be discussed in the framework of the presented model.

Tang, Fei [TU Dresden; Frontzek, Matthias D [ORNL; Dshemuchadse, Julia [ETH Zurich, Switzerland; Leisegang, Tilmann [Technische Universitat Dresden; Zschornak, Matthias [Technische Universitat Dresden; Mietrach, Robert [Technische Universitat Dresden; Hoffman, Jens-Uwe [Helmholtz-Zentrum Berlin; Loeser, W [IFW Dresden; Gemming, Sibylle [Forschungszentrum Rossendorf, Dresden, Germany; Meyer, Dirk [Technische Universitat Dresden; Loewenhaupt, Michael [TU Dresden

2011-01-01

438

The Structural Biology Center 19ID undulator beamline: facility specifications and protein crystallographic results  

PubMed Central

The 19ID undulator beamline of the Structure Biology Center has been designed and built to take full advantage of the high flux, brilliance and quality of X-ray beams delivered by the Advanced Photon Source. The beamline optics are capable of delivering monochromatic X-rays with photon energies from 3.5 to 20 keV (3.5–0.6 Å wavelength) with fluxes up to 8–18 × 1012 photons s?1 (depending on photon energy) onto cryogenically cooled crystal samples. The size of the beam (full width at half-maximum) at the sample position can be varied from 2.2 mm × 1.0 mm (horizontal × vertical, unfocused) to 0.083 mm × 0.020 mm in its fully focused configuration. Specimen-to-detector distances of between 100 mm and 1500 mm can be used. The high flexibility, inherent in the design of the optics, coupled with a ?-geometry goniometer and beamline control software allows optimal strategies to be adopted in protein crystallographic experiments, thus maximizing the chances of their success. A large-area mosaic 3 × 3 CCD detector allows high-quality diffraction data to be measured rapidly to the crystal diffraction limits. The beamline layout and the X-ray optical and endstation components are described in detail, and the results of representative crystallographic experiments are presented.

Rosenbaum, Gerd; Alkire, Randy W.; Evans, Gwyndaf; Rotella, Frank J.; Lazarski, Krzystof; Zhang, Rong-Guang; Ginell, Stephan L.; Duke, Norma; Naday, Istvan; Lazarz, Jack; Molitsky, Michael J.; Keefe, Lisa; Gonczy, John; Rock, Larry; Sanishvili, Ruslan; Walsh, Martin A.; Westbrook, Edwin; Joachimiak, Andrzej

2008-01-01

439

Comparative X-Ray crystallographic studies of systemic fungicides hexaconazole and tricyclazole  

NASA Astrophysics Data System (ADS)

Chemical structure of a chemical is useful for the synthesis of new compounds with more specific actions and fewer adverse reactions, to increase/decrease the duration of action of the original drug or to get a more potent compound, to restrict the action to a specific system of the body and to reduce the adverse reactions, toxicity and other disadvantages associated. Recently it has been observed that some of the fungicides are loosing their effects. So analogous compounds can be designed as substitute, if their structures are known. A rational approach to test these fungicides is to know the three dimensional structure of these compounds and macromolecular receptor sites as well as their molecular complex. The structures of these compounds can be obtained by X-ray diffraction method in crystalline form and they will invariably be similar to their structure in solutions. The composition of crystal (RS)-2-(2,4-dichlorophenyl)-1-(1H-1, 2,4-trizole-1-y1) hexane-2-ol or hexaconazole and Tricyclazole are confirmed by comparing the infra-red spectra of two components. The unit cell parameters of Hexaconozole are a=10. 9068(7) Å, b=10.9895(7) Å c=13.6124(8) Å, ?=90o, ?=106.554(2)o, ?=90.000(5)o. The Crystal system is Monoclinic, and space group P21/c . The unit cell parameters of Tricyclazole are a=14.896(5) Å, b=7.410(5)Å, c=7.556(5) Å, ?=90(5)o, ?=90.000(5)o, ?=90.000(5)o.The Crystal system is Orthorhombic and space group is Pca21.

Chauhan, Jyotsna; Sharma, Ashish Kumar; Bhattacharya, Gargi

2012-05-01

440

Magnetic and crystallographic properties of NdMn6-xFexSn6 intermetallics  

NASA Astrophysics Data System (ADS)

Intermetallic compounds of NdMn6-xFexSn6 (0 \\le x \\le 2.0 ) were studied by means of x-ray and neutron diffraction techniques and SQUID magnetic measurements in the temperature range of 30-400 K. The substitution of iron for manganese leads to a phase transition whereby NdMn6Sn6 with the HoFe6Sn6 structure (space group Immm) changes to TbFe6Sn6 (space group Cmcm) for NdMn6-xFexSn6 with x \\ge 0.5 . The iron atoms prefer to occupy the 8g sites at iron content x<2.0 due to the longest Mn/Fe-Sn bond distance. The Curie temperature (TC) increases from x = 0 to 1.5 and then decreases for the larger iron content. The magnetic moment of the iron sublattice couples ferromagnetically with the manganese and neodymium moments for the x<2.0 samples. Spin reorientation is observed in samples with iron content up to 1.5, and the spin reorientation temperature (Ts) increases with increasing iron content. Except for NdMn4Fe2Sn6, the easy direction of magnetization for all samples is parallel and perpendicular to the (bc) plane of the unit cell at 300 and 30 K, respectively. The easy direction of magnetization for NdMn4Fe2Sn6 is parallel to the a-axis in the entire temperature range mentioned above, as a result of the anisotropic contraction of the unit cell along the (bc) plane.

Han, J.; Marasinghe, G. K.; Yang, J. B.; James, W. J.; Chen, M.; Yelon, W. B.; l'Héritier, Ph; Dubenko, I.; Ali, N.

2004-08-01

441

Classical dynamics and Lie groups  

Microsoft Academic Search

The phase space time evolution operator for a dynamical system is derived directly from Newton's equation of motion. This operator is used to show, in an elementary way, how a Lie group enters into the description in phase space of the path of a one-dimensional damped, driven, harmonic oscillator. Concepts from Lie group theory are thus illustrated in a nontrivial

J. D. Louck

1986-01-01

442

Space making  

NASA Astrophysics Data System (ADS)

With discoveries from Mars, the Hubble Deep Field, and Ganymede reawakening Washington's interest in space, the U.S. federal government has started fine-tuning its stance on space flight and exploration. The attention comes as prelude to a proposed November meeting to discuss astronomical and planetary discoveries, and to a rumored space summit in December between Vice President Al Gore and congressional leaders.On September 17, the House of Representatives passed by voice vote H.R. 3936, the Space Commercialization Promotion Act. A measure with strong bipartisan support, the bill officially encourages private companies to participate in the space industry and requires NASA to find more ways to work with the private sector. Updating and amending several existing U.S. policies about commerce in space, H.R. 3936 gives the Department of Transportation the authority to provide and administer licenses for commercial spacecraft to reenter American airspace from orbit and outer space. It also prods NASA to purchase scientific data about the Earth and the solar system from the private sector, whenever possible.

Carlowicz, Michael

443

Braid Groups are Linear  

Microsoft Academic Search

The braid groups B_n can be defined as the mapping class group of the\\u000an-punctured disc. The Lawrence-Krammer representation of the braid group B_n is\\u000athe induced action on a certain twisted second homology of the space of\\u000aunordered pairs of points in the n-punctured disc. Recently, Daan Krammer\\u000ashowed that this is a faithful representation in the case n=4.

Stephen J. Bigelow

2000-01-01

444

Crystallographic analysis of plate martensite in Fe-28.5 at.% Ni by FE-SEM/EBSD  

SciTech Connect

Crystallographic analysis of plate martensite in an Fe-28.5 at.% Ni alloy was studied by electron backscattering diffraction (EBSD) in a scanning electron microscope equipped with a field emission gun (FE-SEM). It was shown that sound orientation mapping was possible even for the martensite having a high density of lattice defects and the FE-SEM/EBSD could be a strong tool for crystallographic/microstructural analysis of martensite in steels. It was confirmed that the martensite in this alloy held the Nishiyama-Wassermann (N-W) orientation relationship. Variant analysis of every martensite crystal was successfully done from orientation mapping data. It was clarified that a certain rule of variant selection operated within local areas. The procedures of crystallographic analysis of N-W martensite were explained in detail.

Kitahara, Hiromoto [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan)]. E-mail: kitahara@im.ams.eng.osaka-u.ac.jp; Ueji, Rintaro [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu 761-0396 (Japan); Ueda, Masato [Department of Materials Science and Processing, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Tsuji, Nobuhiro [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Minamino, Yoritoshi [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan)

2005-05-15

445

Space Sense  

NSDL National Science Digital Library

Another great resource from the University of Michigan's Windows to the Universe Web site is the new Space Science activity. This interactive space trivia game tests your knowledge of space trivia with the goal to boost your rocket ship out of the atmosphere with correct answers. As with other Windows to the Universe resources, users get to choose the difficulty level they'd like to play and even between an adult and kids version of the game. Every question accompanies three answers from which to choose; when a correct answer is chosen, the rocket ship on the screen ascends towards outer space. Perhaps the most useful part of the activity is the "learn more" link that accompanies each answer, providing kids with a wealth of additional information and encouraging them to explore the subject further.

1995-01-01

446

Space Rescue.  

National Technical Information Service (NTIS)

Space Rescue has been a topic of speculation for a wide community of people for decades. Astronauts, aerospace engineers, diplomats, medical and rescue professionals, inventors and science fiction writers have all speculated on this problem. Martin Caidin...

J. F. Muratore

2007-01-01

447

Space design  

Microsoft Academic Search

Space stations, Moon bases and Mars bases are artificial habitats intended to support human life in extreme conditions. Their\\u000a purpose is to pursue human progress and to gain knowledge and experience of the environment surrounding our planet. This research\\u000a focuses on visual investigation in order to improve interface design in space habitat interiors. The subject of this article\\u000a is why

Irene Lia Schlacht; Henrik Birke

2011-01-01

448

Space education  

NASA Astrophysics Data System (ADS)

An essential pre-requisite to a successful space technology applications programme is the building of various indigenous capacities, particularly human resources. Efforts to accomplish such a capacity-building must be devoted, at the local level, to the development of necessary high-level knowledge and expertise in space science and technology fields. Such a programme must also focus on long-term in-depth education and research opportunities in the developing countries, where the beneficiaries would gain an in-depth understanding and appreciation of not only the application potentials of a given technology but also an insight into why and how the technology works the way it does. In recognition of such a pre-requisite, it is universally acknowledged that if effective assimilation of space science and appropriate application of space technology are to succeed in the developing countries, and particularly if such a discipline as satellite remote sensing is to transcend its current image of being a technology-driven tool into a user-driven one, efforts must be devoted, at the local level, to the development of necessary high-level knowledge and expertise in requisite space science and technology fields. The justification for such an in-depth education is not far-fetched particularly as one reflects on the myriad of space science and technology activities that are both in progress and are planned. Aspects of these are reflected in this paper.

Abiodun, Adigun Ade

449

Large N reduction on coset spaces  

NASA Astrophysics Data System (ADS)

As an extension of our previous work concerning the large N reduction on group manifolds, we study the large N reduction on coset spaces. We show that large N field theories on coset spaces are described by certain corresponding matrix models. We also construct Chern-Simons-like theories on group manifolds and coset spaces, and give their reduced models.

Kawai, Hikaru; Shimasaki, Shinji; Tsuchiya, Asato

2010-04-01

450

Space Debris  

NSDL National Science Digital Library

This Topic in Depth begins with a Web site maintained by Dr. Richard B. Gomez of George Mason University called Space Debris (1). The site is offered as a slide presentation, which explains what space debris is, where it comes from, if it's dangerous, what is known about it, and what can be done about it. The very interesting site is perfect for non-experts because of its simple descriptions and abundance of graphics. The second site from Space.com is an article written by Robert Roy Britt entitled Space Junk: The Stuff Left Behind (2). Visitors can read about the number of objects being tracked (at the time the article was written), what the total weight of these objects is, view a table of the number of various pieces of space junk by country, and even find out it if there is a risk of getting hit in the head by these objects. The next site, Nature's Tiniest Space Junk (3), is offered by NASA's news portal Science@NASA Web site. The page describes how scientists are monitoring tiny dust sized meteoroids that are constantly flying around our planet that have the potential to be quite dangerous. For those really interested, the site lets people listen to audio files of the meteor radar in action. The fourth site on space junk, maintained by the Texas Advanced Computing Center, is a Simulation of Orbital Debris Shielding Performance at High Impact Velocities (4). The page highlights the work of Dr. Eric Fahrenthold, who is simulating orbital debris shielding performance at high impact velocities. A basic description of the work is offered along with the simulation itself, which shows a piece of space debris striking a surface. Next, from NASA's Hazards Assessment Web site, comes the Hypervelocity Impact Test Facility: Orbital Debris and Micrometeoroids (5) page. Readers can find out more on the problem of space junk, why NASA feels its so important to study simulating particle impacts on spacecraft, the lightweight shields that are in place on the International Space Station, and more. The sixth site is an article that appeared in the Bulletin of the Atomic Scientists by Joel Primack called Pelted by Paint, Downed by Debris (6). Although there's not a large amount of content on the site, it does give some interesting information on a different aspect of the subject. The author describes how any missile defense program could be detrimentally affected by space debris and suggests the need for space agencies to take active steps to prevent its buildup. The National Academies Press offers the next site, which is actually an online book on Protecting the Space Station from Meteoroids and Orbital Debris (7). Contents include risk management strategies for the space station, debris modeling, shielding the station, collision warning and avoidance, and more. The last site is from the Aerospace Corporation and its Center for Orbital and Reentry Debris Studies (8). Visitors will find an introduction to the Center, the basics of space debris, what happens during satellite reentry, re-entry data and predictions, additional links, and more.

Brieske, Joel A.

2003-01-01

451

Effect of crystallographic orientation on hillock formation in thermally cycled large grain tin films  

NASA Astrophysics Data System (ADS)

Tin whiskers and hillocks grow spontaneously from the surfaces of polycrystalline Sn films at room temperature. Whiskers can grow long enough to cause short circuits in electronic devices. We hypothesized that the anisotropies of the crystal structure lead to locally high strain energies that are relieved by the growth of whiskers and hillocks. This research studies hillock formations on large grain Sn-alloy films relative to the crystallographic orientations of the adjacent grains. Large grain films were produced by solidifying 96.5wt% Sn - 3wt% Ag - 0.5wt% Cu solder alloy on a Cu substrate. These surface defects (hillocks) grew predominately at grain boundaries during thermal cycling. The formation of the surface defects between two grains created a pseudo-bi-crystal sample geometry, making it ideal for studying surface defects relative to the local crystallographic orientations and the grains' corresponding anisotropic properties. The crystallographic orientations of the grains were studied with Electron Backscatter Diffraction (EBSD) and Laue micro-diffraction at the Lawrence Berkeley National Laboratory Advanced Light Source. Local orientation studies of the surface defects and the surrounding grains indicated that the surface defects nucleated and grew with low dislocation densities. In addition, the linear surface defect densities along the grain boundaries were measured and observed to change as a function of orientation. The change in linear defect density with respect to orientation was due, in part, to the anisotropy of the coefficient of thermal expansion of ?-Sn. In addition, it was important to account for elastic anisotropies. The elastic stresses, strains, and strain energy densities of the microstructures were determined with Object Oriented Finite element analysis. The simulations indicated that during thermal cycling the local stresses exceeded the yield strength. As a result, the highest linear defect densities did not occur at orientations with the highest local strain energies. Instead, the highest local strain energies were accommodated by other plastic deformation mechanisms, indicating that surface defect formation is not only affected by local strain energy densities but also the local dominant deformation mechanism. Therefore, the propensity of specific grain orientations to form surface defects will change as a function of the thermal cycling process.

Koppes, John Patrick

452

Structure, magnetic and crystallographic fabrics of columnar lava flows from the French Massif Central (France)  

NASA Astrophysics Data System (ADS)

We studied the structures and associated microstructures of two basalt flows from the French Massif Central that both display columnar jointing: La Palisse (LP - 75,000 yrs) and Saint-Arcons-d’Allier (SAA - 600,000 yrs). The La Palisse flow consists of three distinct levels (colonnade at the base, entablature and pseudo-colonnade to the top), with well-known emission centre and flow direction. Both flows are sufficiently fresh to be suitable for a magnetic fabric and crystallographic study at the flow scale. The SAA lava flow presents well-developed columns allowing a more precise study at the scale of the prism section. The anisotropy of magnetic susceptibility (AMS) measurements were performed to characterize the flow structure at various scales, from the whole flow to the grain. The AMS data were coupled with crystallographic preferred orientation measurements of magnetite, plagioclase and clinopyroxene using Electron Backscattered Diffraction (EBSD) and image analyses from perpendicular thin sections. The magnetic mineralogy studies of the LP flow, in particular the thermomagnetic curves, indicate that the main carrier of AMS is high-Ti titanomagnetite (100°C?Tc? 200°C, xulv ? 0.70-0.57. The AMS measurements of about a hundred samples show a higher degree of anisotropy (P' parameter) in the middle level compared to the base. Inversely, the bulk magnetic susceptibility (Km) is higher at the flow base compared to the other levels. These observations suggest that the magnetic parameters could be distinctive parameters for the different levels of the flow. Moreover, the comparison between AMS and EBSD data indicates that the magnetic susceptibility carried by the magnetic grains is controlled by the crystallographic orientation of plagioclase and then related to the direction of the lava flow. In addition, the AMS study carried out on a prism section of LP shows that Km and P'