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1

Bilbao Crystallographic Server. II. Representations of crystallographic point groups and space groups.  

PubMed

The Bilbao Crystallographic Server is a web site with crystallographic programs and databases freely available on-line (http://www.cryst.ehu.es). The server gives access to general information related to crystallographic symmetry groups (generators, general and special positions, maximal subgroups, Brillouin zones etc.). Apart from the simple tools for retrieving the stored data, there are programs for the analysis of group-subgroup relations between space groups (subgroups and supergroups, Wyckoff-position splitting schemes etc.). There are also software packages studying specific problems of solid-state physics, structural chemistry and crystallography. This article reports on the programs treating representations of point and space groups. There are tools for the construction of irreducible representations, for the study of the correlations between representations of group-subgroup pairs of space groups and for the decompositions of Kronecker products of representations. PMID:16489249

Aroyo, Mois I; Kirov, Asen; Capillas, Cesar; Perez-Mato, J M; Wondratschek, Hans

2006-03-01

2

CRYSTALLOGRAPHIC POINT AND SPACE  

E-print Network

CRYSTALLOGRAPHIC POINT AND SPACE GROUPS Andy Elvin June 10, 2013 #12;Contents Point and Space no reflection axes #12;Cube and Octahedron are dual Symmetries under Oh #12;Space Groups Subgroups of E(3) Point Group + Translation { R | 0 }{ E | t }a = { R | t }a = Ra + t 230 Space Groups 73 symmorphic space

California at Santa Cruz, University of

3

Alternative Decompositions of the Regular Representations of Crystallographic Space Groups Into Band Representations  

NASA Astrophysics Data System (ADS)

We discuss the decomposition of the regular representation of crystallographic space groups into elementary band representations. This decomposition is in general not unique. These decompositions can be divided in two groups. On the one hand there are so-called generic ones, which exist for any space groups, involving only band representations corresponding to one Wyckoff position. On the other hand additional decompositions may exist under certain circumstances. Various kinds of these so-called alternative decompositions are discussed in terms of typical examples and some general conditions for their existence are presented.

Zeiner, P.; Dirl, R.; Davies, B. L.

2001-04-01

4

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

SciTech Connect

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

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

2001-10-05

5

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

PubMed

Algorithms for the treatment of special positions in three-dimensional crystallographic space groups are presented. These include an algorithm for the determination of the site-symmetry group given the coordinates of a point, an algorithm for the determination of the exact location of the nearest special position, an algorithm for the assignment of a Wyckoff letter given the site-symmetry group, and an alternative algorithm for the assignment of a Wyckoff letter given the coordinates of a point directly. All algorithms are implemented in ISO C++ and are integrated into the Computational Crystallography Toolbox. The source code is freely available. PMID:11752765

Grosse-Kunstleve, R W; Adams, P D

2002-01-01

6

Interactive 3D Space Group Visualization with CLUCalc and Crystallographic Subperiodic Groups in Geometric Algebra  

NASA Astrophysics Data System (ADS)

The Space Group Visualizer (SGV) for all 230 3D space groups is a standalone PC application based on the visualization software CLUCalc. We first explain the unique geometric algebra structure behind the SGV. In the second part we review the main features of the SGV: The GUI, group and symmetry selection, mouse pointer interactivity, and visualization options. We further introduce the joint use with Hahn (Space-group Symmetry, 5th edn., International Tables of Crystallography, vol. A, Springer, Dordrecht, 2005). In the third part we explain how to represent the 162 so-called subperiodic groups of crystallography in geometric algebra. We construct a new compact geometric algebra group representation symbol, which allows us to read off the complete set of geometric algebra generators. For clarity, we moreover state explicitly which generators are chosen. The group symbols are based on the representation of point groups in geometric algebra by versors.

Hitzer, Eckhard M. S.; Perwass, Christian; Ichikawa, Daisuke

7

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

PubMed

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

Mörschel, Philipp; Schmidt, Martin U

2015-01-01

8

Group actions on geodesic Ptolemy spaces  

E-print Network

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

Foertsch, Thomas

2008-01-01

9

Bilbao Crystallographic Server  

NSDL National Science Digital Library

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

10

From direct-space discrepancy functions to crystallographic least squares.  

PubMed

Crystallographic least squares are a fundamental tool for crystal structure analysis. In this paper their properties are derived from functions estimating the degree of similarity between two electron-density maps. The new approach leads also to modifications of the standard least-squares procedures, potentially able to improve their efficiency. The role of the scaling factor between observed and model amplitudes is analysed: the concept of unlocated model is discussed and its scattering contribution is combined with that arising from the located model. Also, the possible use of an ancillary parameter, to be associated with the classical weight related to the variance of the observed amplitudes, is studied. The crystallographic discrepancy factors, basic tools often combined with least-squares procedures in phasing approaches, are analysed. The mathematical approach here described includes, as a special case, the so-called vector refinement, used when accurate estimates of the target phases are available. PMID:25537387

Giacovazzo, Carmelo

2015-01-01

11

The Space Science Group  

NSDL National Science Digital Library

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

1997-01-01

12

The analysis of crystallographic symmetry types in finite groups  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

13

International Space Exploration Coordination Group  

E-print Network

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

Rathbun, Julie A.

14

Spaces Homotopy Classification Problem Homotopy Groups Homotopy Groups  

E-print Network

Spaces Homotopy Classification Problem Homotopy Groups Homotopy Groups Jie Wu Department of Mathematics National University of Singapore May 25, 2006 #12;Spaces Homotopy Classification Problem Homotopy Groups Homotopy Groups Topological Spaces Homotopy Classification Problem Homotopy Groups #12;Spaces

Wu, Jie

15

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP  

E-print Network

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP 18th September 2012 STFC 2012 #12;UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP 18th September 2012 STFC · Conclusion #12;UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP 18th September 2012 STFC

16

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

17

Platinum Group Thiophenoxyimine Complexes: Syntheses,Crystallographic and Computational Studies of Structural Properties  

SciTech Connect

Monomeric thiosalicylaldiminate complexes of rhodium(I) and iridium(I) were prepared by ligand transfer from the homoleptic zinc(II) species. In the presence of strongly donating ligands, the iridium complexes undergo insertion of the metal into the imine carbon-hydrogen bond. Thiophenoxyketimines were prepared by non-templated reaction of o-mercaptoacetophenone with anilines, and were complexed with rhodium(I), iridium(I), nickel(II) and platinum(II). X-ray crystallographic studies showed that while the thiosalicylaldiminate complexes display planar ligand conformations, those of the thiophenoxyketiminates are strongly distorted. Results of a computational study were consistent with a steric-strain interpretation of the difference in preferred ligand geometries.

Krinsky, Jamin L.; Arnold, John; Bergman, Robert G.

2006-10-03

18

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP  

E-print Network

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP ESA Lunar Lander ­ L-DEPP C.J. Owen and D.O. Kataria UCL/MSSL #12;UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP PLASMA PHYSICS GROUP What is L-DEPP? · L-DEPP = Lunar Dust Environment and Plasma Package; · Investigate

Anand, Mahesh

19

Band representations and duals of the nonsymmorphic crystallographic plane groups pg and p4gm  

NASA Astrophysics Data System (ADS)

Duals of the groups pg and p4gm are constructed. (1) The group pg has only one band representation (an elementary one) equivalent to the regular representation. There exists a quasiband representation close to it, of multiplicity two, which separates the branches of the band. Finite groups which approximate pg are discussed. (2) Two elementary band representations associated with the Wyckoff position b of the group p4gm are shown to be nonequivalent although they have the same decomposition in unirreps.

Bacry, Henri

1993-09-01

20

Crystallographic evidence of sulfate evaporites in the Kromberg Formation, Onverwacht Group, South Africa  

SciTech Connect

The 3.5 Ga Kromberg Formation of the Onverwacht Group, Barberton Greenstone Belt, South Africa, includes a basal silicified shallow-water evaporite sequence deposited in a series of small fault-bounded basins. Other early Archean replaced and recrystallized evaporites have been interpreted to have included both primary gypsum and aragonite based on general crystal morphology and the overall similarity of these units to Phanerozoic evaporites. Crystal interfacial angle measurements, however, have not been widely reported to support interpretations of primary mineralogy. Although the primary evaporite minerals in the Kromberg Formation have been replaced by chert and druzy megaquartz, interfacial angles of silicified pseudohexagonal, prismatic to bladed crystals can be measured with a contact goniometer. Measurement of angles between the six prism faces display a biomodal distribution about 55/sup 0/ and 69/sup 0/. Within individual crystals, these angles show a general arrangement of two at 69/sup 0/ separated by sets of two angles at 55/sup 0/. These relationships closely resemble those of gypsum which has four angles of (010) (120)=55.75/sup 0/ and two of (120) (120)-68.50/sup 0/. No evidence has been found for the existence of aragonite which has six angles of (110) (110)=60/sup 0/. Textural and geometric crystal comparisons of these silicified crystals with Messinian algal-related selenite and modern gypsum support the proposal of a gypsum precursor. The common presence of gypsum in this and other greenstone belts suggests that the early Archean ocean may have been at or near saturation with respect to sulfate.

Fisher, G.L.; Lowe, D.R.

1985-01-01

21

Point Groups and Space Groups in Geometric Algebra  

Microsoft Academic Search

Abstract. Geometric algebra provides the essential foundation for a new approach to symmetry,groups. Each of the 32 lattice point groups and 230 space groups in three dimensions is generated from a set of three symmetry vectors. This greatly facilitates representation, analysis and application of the groups to molecular modeling and crystal- lography.

David Hestenes

22

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

23

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

24

Noncommutative Phase Spaces on Aristotle group  

E-print Network

We realize noncommutative phase spaces as coadjoint orbits of extensions of the Aristotle group in a two-dimensional space. Through these constructions the momenta of the phase spaces do not commute due to the presence of a naturally introduced magnetic field. These cases correspond to the minimal coupling of the momentum with a magnetic potential.

Ancille Ngendakumana; Joachim Nzotungicimpaye; Leonard Todjihounde

2013-07-26

25

Crystallographic autostereograms.  

PubMed

Perspective drawings of crystal structures can be presented as autostereograms (or single-image stereograms), and their performance for in-depth perception is similar or even more advantageous than of stereopairs. The autostereograms offer a convenient means for realistic insight into crystal structures without excessive size reduction of their drawings, as required when preparing stereopairs; thus structures either as simple as elements or as complex as proteins can be illustrated in enhanced resolution. The mathematical background and guidelines for preparing crystallographic autostereograms are described. PMID:11449576

Katrusiak, A

2001-01-01

26

Distribution of mica polytypes among space groups.  

NASA Technical Reports Server (NTRS)

All the possible space groups for mica polytypes are deduced by making use of the characteristics of the mica unit layer and stacking mode. The algebraic properties of the vector-stacking symbol of Ross et al. (1966) are examined, and a simple algorithm for deducing the space group from this symbol is presented. A method considered for enumerating all possible stacking sequences of mica polytypes makes use of a computer.

Takeda, H.

1971-01-01

27

Scanning of two-dimensional space groups.  

PubMed

Tables of the scanning of two-dimensional space groups are presented to determine the frieze-group symmetry of lines that transect two-dimensional crystals. It is shown how these tables can be used to predict the (001) projection symmetries of migration-related segments of coincidence site lattice tilt boundaries with [001] tilt axis. PMID:25537394

Litvin, Daniel B

2015-01-01

28

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 â??to 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.

29

Crystallographic Topology 2: Overview and Work in Progress  

SciTech Connect

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

Johnson, C.K.

1999-08-01

30

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

PubMed Central

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

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

2014-01-01

31

The Geroch group in Einstein spaces  

NASA Astrophysics Data System (ADS)

Geroch's solution-generating method is extended to the case of Einstein spaces, which possess a Killing vector and are thus asymptotically (locally) (anti) de Sitter. This includes the reduction to a three-dimensional coset space, the description of the dynamics in terms of a sigma-model and its transformation properties under the SL(2,{R}) group, and the reconstruction of new four-dimensional Einstein spaces. The detailed analysis of the space of solutions is performed using the Hamilton-Jacobi method in the instance where the three-dimensional coset space is conformal to {R}× {{S}2}. The cosmological constant appears in this framework as a constant of motion and transforms under SL(2,{R}).

Leigh, Robert G.; Petkou, Anastasios C.; Marios Petropoulos, P.; Tripathy, Prasanta K.

2014-11-01

32

Guide to Space groups There are only 230 ways (space groups) to describe how identical objects can be  

E-print Network

Guide to Space groups There are only 230 ways (space groups) to describe how identical objects can but it gets better than that! If your structure contains a chrial center then any space group that has a mirror or an inversion operation can be rejected. Of the 230 space groups only 74 space groups

Meagher, Mary

33

Optimal space-time constellations from groups  

Microsoft Academic Search

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

Brian L. Hughes

2003-01-01

34

Schrodinger group on Zhidkov spaces Clement Gallo  

E-print Network

Schr¨odinger group on Zhidkov spaces Cl´ement Gallo UMR de Math´ematiques, Bat. 425 Universit ), and are pertinent to many physical contexts. In nonlinear optics, the so-called dark soliton (see [KLD 2 x 2 + i v 2 (2) The Gross-Pitaevskii equation (see [BeS1], [BeS2] and references therein) iut

Gallo, Clément

35

X-ray Crystallographic Studies Reveal That the Incorporation of Spacer Groups in Carbonic Anhydrase Inhibitors Causes Alternate Binding Modes  

SciTech Connect

Human carbonic anhydrases (CAs) are well studied targets for the development of inhibitors for pharmaceutical applications. The crystal structure of human CA II has been determined in complex with two CA inhibitors (CAIs) containing conventional sulfonamide and thiadiazole moieties separated by a -CF{sub 2}- or -CHNH{sub 2}- spacer group. The structures presented here reveal that these spacer groups allow novel binding modes for the thiadiazole moiety compared with conventional CAIs.

Fisher,S.; Govindasamy, L.; Boyle, N.; Agbandje-McKenna, M.; Silverman, D.; Blackburn, G.; McKenna, R.

2006-01-01

36

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

37

UCLA IGPP Space Plasma Simulation Group  

NASA Technical Reports Server (NTRS)

During the past 10 years the UCLA IGPP Space Plasma Simulation Group has pursued its theoretical effort to develop a Mission Oriented Theory (MOT) for the International Solar Terrestrial Physics (ISTP) program. This effort has been based on a combination of approaches: analytical theory, large scale kinetic (LSK) calculations, global magnetohydrodynamic (MHD) simulations and self-consistent plasma kinetic (SCK) simulations. These models have been used to formulate a global interpretation of local measurements made by the ISTP spacecraft. The regions of applications of the MOT cover most of the magnetosphere: the solar wind, the low- and high-latitude magnetospheric boundary, the near-Earth and distant magnetotail, and the auroral region. Most recent investigations include: plasma processes in the electron foreshock, response of the magnetospheric cusp, particle entry in the magnetosphere, sources of observed distribution functions in the magnetotail, transport of oxygen ions, self-consistent evolution of the magnetotail, substorm studies, effects of explosive reconnection, and auroral acceleration simulations.

1998-01-01

38

Universal quantum groups acting on classical and quantum spaces  

E-print Network

Universal quantum groups acting on classical and quantum spaces Lecture 2 - Quantum symmetry groups) Quantum symmetry groups Leeds, 25 May 2010 1 / 24 #12;1 Quantum permutation groups 2 Quantum symmetry groups of finite C-algebras 3 Quantum symmetry groups of AF-algebras 4 Free products of quantum groups

Haase, Markus

39

Space 2: My Body. Space Orientation Group 1.  

ERIC Educational Resources Information Center

Space orientation is a major area of development for preschool and early primary school children. Knowledge about one's own body and about body movements in space is a necessary condition for space orientation. Starting from their own bodies, children learn to focus on the space in which they move. They then learn to take a non-body perspective…

van Kuyk, Jef J.

40

The space shuttle payload planning working groups: Executive summaries  

NASA Technical Reports Server (NTRS)

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

1973-01-01

41

UNIVERSAL QUANTUM GROUPS ACTING ON QUANTUM AND CLASSICAL SPACES  

E-print Network

UNIVERSAL QUANTUM GROUPS ACTING ON QUANTUM AND CLASSICAL SPACES ADAM SKALSKI Abstract. Groups first, be it a finite set, a polygon, a metric space or a manifold. Original definitions of quantum groups (also in the topological context) had rather algebraic character. In these lectures we describe several examples of quantum

Haase, Markus

42

World Database of Crystallographers  

NSDL National Science Digital Library

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

43

Space station group activities habitability module study  

NASA Technical Reports Server (NTRS)

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

Nixon, David

1986-01-01

44

The CPT Group in the de Sitter Space  

E-print Network

$P$-, $T$-, $C$-transformations of the Dirac field in the de Sitter space are studied in the framework of an automorphism set of Clifford algebras. Finite group structure of the discrete transformations is elucidated. It is shown that $CPT$ groups of the Dirac field in Minkowski and de Sitter spaces are isomorphic.

V. V. Varlamov

2005-08-18

45

TRANSLATION NUMBERS OF GROUPS ACTING ON QUASICONVEX SPACES  

E-print Network

TRANSLATION NUMBERS OF GROUPS ACTING ON QUASICONVEX SPACES GREGORY R. CONNER Abstract. We define a group to be translation discrete if it carries a metric in which the translation numbers of the non discontinuously cocompactly on a proper quasiconvex metric space is translation discrete if and only if it does

Conner, Gregory R.

46

The International Space Life Sciences Strategic Planning Working Group  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

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

Exceptional groups, symmetric spaces and applications  

SciTech Connect

In this article we provide a detailed description of a technique to obtain a simple parameterization for different exceptional Lie groups, such as G{sub 2}, F{sub 4} and E{sub 6}, based on their fibration structure. For the compact case, we construct a realization which is a generalization of the Euler angles for SU(2), while for the non compact version of G{sub 2(2)}/SO(4) we compute the Iwasawa decomposition. This allows us to obtain not only an explicit expression for the Haar measure on the group manifold, but also for the cosets G{sub 2}/SO(4), G{sub 2}/SU(3), F{sub 4}/Spin(9), E{sub 6}/F{sub 4} and G{sub 2(2)}/SO(4) that we used to find the concrete realization of the general element of the group. Moreover, as a by-product, in the simplest case of G{sub 2}/SO(4), we have been able to compute an Einstein metric and the vielbein. The relevance of these results in physics is discussed.

Cerchiai, Bianca L.; Cacciatori, Sergio L.

2009-03-31

49

Isometric group actions on Hilbert spaces: structure of orbits  

E-print Network

Isometric group actions on Hilbert spaces: structure of orbits Yves de Cornulier, Romain Tessera actions, nilpotent groups. 1 Introduction The study of isometric actions of groups on affine Hilbert is a sequel to [CTV], but can be read independently. In [CTV], we focused, given an an isometric action

Tessera, Romain

50

Meeting of intercosmos space physics group  

NASA Astrophysics Data System (ADS)

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 period and up to the year 2000. The Mars-94 project, which is a component part of the program, Mars-2000, proposed by Soviet scientists, is discussed along with other proposed planetary projects. In the area of high energy astrophysics, a project involving a large orbital observatory (Spektr-Rentgen-Gamma) is being prepared for solving problems associated with cosmology, extragalactic astronomy, and stellar astronomy. It will be carried out through international cooperation with significant developments effected by socialist countries. Two other projects discussed include Radioastron which involves radiointerferometry, and Relikt-2 which will continue research that was begun aboard the unmanned Prognoz-9 station. In the area of solar terrestrial physics, instruments are being designed for the study of X-ray active formations in the solar atmosphere and processes that take place in solar plasma (the Koronas-1, F project, and the Neytron project). The study of cosmic plasma is called for in the Interbol project. Also, the Czech furnace Kristallizator-ChSk-1 is in operation aboard the Mir orbital station and the launch of another unit is expected. All 10 Intercosmos countries are taking part in the preparation of experiments involving space-based materials science.

Frolova, N. A.

1989-06-01

51

Actuator Grouping Optimization on Flexible Space Reflectors  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

52

Group theoretical construction of planar noncommutative phase spaces  

SciTech Connect

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

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

2014-01-15

53

Group theoretical construction of planar noncommutative phase spaces  

NASA Astrophysics Data System (ADS)

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

Ngendakumana, Ancille; Nzotungicimpaye, Joachim; Todjihoundé, Leonard

2014-01-01

54

Classifying spaces with virtually cyclic stabilizers for linear groups.  

E-print Network

We show that every discrete subgroup of $\\mathrm{GL}(n,\\mathbb{R})$ admits a finite dimensional classifying space with virtually cyclic stabilizers. Applying our methods to $\\mathrm{SL}(3,\\mathbb{Z})$, we obtain a four dimensional classifying space with virtually cyclic stabilizers and a decomposition of the algebraic $K$-theory of its group ring.

Dieter Degrijse; Ralf Köhl; Nansen Petrosyan.

55

SHELXT – Integrated space-group and crystal-structure determination  

PubMed Central

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

Sheldrick, George M.

2015-01-01

56

Space group and phonon symmetry of (RE1Ba 2 Cu 3 O 7) m (RE2Ba 2 Cu 3 O 7) n superlattices  

NASA Astrophysics Data System (ADS)

It is shown by group theory methods that the symmetry of (RE1Ba 2 Cu 3 O 7) m (RE2Ba 2 Cu 3 O 7) n superlattices grown along [1 0 0], [0 1 0] and [0 0 1] crystallographic directions is described by the same space group Pmmm ( D2 h1) as that of the initial bulk crystalline structure. The arrangement of atoms over Wyckoff positions in multiplied primitive cells of the superlattices is obtained for each of growth directions and all ( m, n) combinations. Symmetry classification of phonons at k = 0 is also carried out. Some features of phonon spectra of ultrathin superlattices are briefly discussed.

Mirovitskii, V. Yu.

1992-09-01

57

Metrics for comparison of crystallographic maps  

PubMed Central

Numerical comparison of crystallographic contour maps is used extensively in structure solution and model refinement, analysis and validation. However, traditional metrics such as the map correlation coefficient (map CC, real-space CC or RSCC) sometimes contradict the results of visual assessment of the corresponding maps. This article explains such apparent contradictions and suggests new metrics and tools to compare crystallographic contour maps. The key to the new methods is rank scaling of the Fourier syntheses. The new metrics are complementary to the usual map CC and can be more helpful in map comparison, in particular when only some of their aspects, such as regions of high density, are of interest. PMID:25286844

Urzhumtsev, Alexandre; Afonine, Pavel V.; Lunin, Vladimir Y.; Terwilliger, Thomas C.; Adams, Paul D.

2014-01-01

58

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

NASA Technical Reports Server (NTRS)

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

1973-01-01

59

Expression, purification and X-ray crystallographic analysis of the Helicobacter pylori blood group antigen-binding adhesin BabA.  

PubMed

Helicobacter pylori is a human pathogen that colonizes about 50% of the world's population, causing chronic gastritis, duodenal ulcers and even gastric cancer. A steady emergence of multiple antibiotic resistant strains poses an important public health threat and there is an urgent requirement for alternative therapeutics. The blood group antigen-binding adhesin BabA mediates the intimate attachment to the host mucosa and forms a major candidate for novel vaccine and drug development. Here, the recombinant expression and crystallization of a soluble BabA truncation (BabA(25-460)) corresponding to the predicted extracellular adhesin domain of the protein are reported. X-ray diffraction data for nanobody-stabilized BabA(25-460) were collected to 2.25?Å resolution from a crystal that belonged to space group P21, with unit-cell parameters a = 50.96, b = 131.41, c = 123.40?Å, ? = 90.0, ? = 94.8, ? = 90.0°, and which was predicted to contain two BabA(25-460)-nanobody complexes per asymmetric unit. PMID:25484214

Subedi, Suresh; Moonens, Kristof; Romão, Ema; Lo, Alvin; Vandenbussche, Guy; Bugaytsova, Jeanna; Muyldermans, Serge; Borén, Thomas; Remaut, Han

2014-12-01

60

1,3,5-Triisopropyl-2-nitrobenzene: Space group correction  

Microsoft Academic Search

The crystal structure of 1,3,5-triisopropyl-2-nitrobenzene, C15H23NO2, has been described and refined in space group Ia [De Ridder, Schenk and Döpp (1993). Acta Cryst. C49, 1970–1971]. Re-refinement in space group C2\\/c [a = 11.969(2), b = 14.057(2), c = 10.851(2) Å, ß = 120.59(1)°, Dx = 1.054 g cm-3, V = 1571.6(5) Å3, Z = 4] was carried out in which

Dirk J. A. De Ridder; Kees Goubitz; Henk Schenk

2000-01-01

61

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

62

Nielsen methods and groups acting on hyperbolic spaces  

Microsoft Academic Search

We show that for any positive integer $n$ there exists a constant $C(n)>0$ such that any $n$-generated group $G$, which acts by isometries on a $\\\\delta$-hyperbolic space (with $\\\\delta>0$), is either free or has a nontrivial element with translation length at most $\\\\delta C(n)$.

Ilya Kapovich; Richard Weidmann

2002-01-01

63

Preliminary crystallographic study of D(-)-mandelate dehydrogenase from Rhodotorula graminis.  

PubMed

NAD+ dependent D(-)-mandelate dehydrogenase from the yeast Rhodotorula graminis strain KGX 39 has been crystallized in three different forms using the hanging drop vapour diffusion method at 15 to 20 degrees C. Type I crystals belong to space group P222(1), P22(1)2(1) or P2(1)2(1)2(1) with a = 100.3 A, b = 117.4 A, c = 80.4 A and are likely to contain a dimer in the crystallographic asymmetric unit. They diffract to dmin = 3.0 A. Type II crystals belong to space group P22(1)2(1) or P2(1)2(1)2(1) with a = 187.8 A, b = 122.9 A, c = 72.1 A and contain probably two dimers in the crystallographic asymmetric unit. They diffract to dmin = 1.8 A. Type III crystals belong to space group P2(1)2(1)2(1) with a = 109.6, b = 52.0 A, c = 145.7 A, and are likely to contain a dimer in the crystallographic asymmetric unit. They diffract at least to dmin = 2.5 A. PMID:8411179

Basak, A K; Baker, D P; Fewson, C A; Stuart, D I

1993-10-20

64

The space shuttle payload planning working groups: Volume 9: Materials processing and space manufacturing  

NASA Technical Reports Server (NTRS)

The findings and recommendations of the Materials Processing and Space Manufacturing group of the space shuttle payload planning activity are presented. The effects of weightlessness on the levitation processes, mixture stability, and control over heat and mass transport in fluids are considered for investigation. The research and development projects include: (1) metallurgical processes, (2) electronic materials, (3) biological applications, and (4)nonmetallic materials and processes. Additional recommendations are provided concerning the allocation of payload space, acceptance of experiments for flight, flight qualification, and private use of the space shuttle.

1973-01-01

65

Gaussian distributions, Jacobi group, and Siegel-Jacobi space  

NASA Astrophysics Data System (ADS)

Let N be the space of Gaussian distribution functions over ?, regarded as a 2-dimensional statistical manifold parameterized by the mean ? and the deviation ?. In this paper, we show that the tangent bundle of N , endowed with its natural Kähler structure, is the Siegel-Jacobi space appearing in the context of Number Theory and Jacobi forms. Geometrical aspects of the Siegel-Jacobi space are discussed in detail (completeness, curvature, group of holomorphic isometries, space of Kähler functions, and relationship to the Jacobi group), and are related to the quantum formalism in its geometrical form, i.e., based on the Kähler structure of the complex projective space. This paper is a continuation of our previous work [M. Molitor, "Remarks on the statistical origin of the geometrical formulation of quantum mechanics," Int. J. Geom. Methods Mod. Phys. 9(3), 1220001, 9 (2012); M. Molitor, "Information geometry and the hydrodynamical formulation of quantum mechanics," e-print arXiv (2012); M. Molitor, "Exponential families, Kähler geometry and quantum mechanics," J. Geom. Phys. 70, 54-80 (2013)], where we studied the quantum formalism from a geometric and information-theoretical point of view.

Molitor, Mathieu

2014-12-01

66

Topological classification of crystalline insulators with space group symmetry  

NASA Astrophysics Data System (ADS)

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; Xiao, Di; Niu, Qian; Banerjee, Sanjay K.

2013-08-01

67

System theory on group manifolds and coset spaces.  

NASA Technical Reports Server (NTRS)

The purpose of this paper is to study questions regarding controllability, observability, and realization theory for a particular class of systems for which the state space is a differentiable manifold which is simultaneously a group or, more generally, a coset space. We show that it is possible to give rather explicit expressions for the reachable set and the set of indistinguishable states in the case of autonomous systems. We also establish a type of state space isomorphism theorem. Our objective is to reduce all questions about the system to questions about Lie algebras generated from the coefficient matrices entering in the description of the system and in that way arrive at conditions which are easily visualized and tested.

Brockett, R. W.

1972-01-01

68

A Geometric Renormalisation Group in Discrete Quantum Space-Time  

Microsoft Academic Search

We model quantum space-time on the Planck scale as dynamical networks of\\u000aelementary relations or time dependent random graphs, the time dependence being\\u000aan effect of the underlying dynamical network laws. We formulate a kind of\\u000ageometric renormalisation group on these (random) networks leading to a\\u000ahierarchy of increasingly coarse-grained networks of overlapping lumps. We\\u000aprovide arguments that this process

Manfred Requardt; Gottingen Bunsenstrasse

2001-01-01

69

The stratified spaces of a symplectic lie group action  

NASA Astrophysics Data System (ADS)

In this paper we show that the classical symplectic stratification theorem of the reduced spaces of a canonical group action in a symplectic manifold can be obtained even in the absence of a momentum map by replacing this object by its natural generalization, the cylinder valued momentum map introduced by Condevaux, Dazord, and Molino. In the process of proving this result we will provide a normal form for the cylinder valued momentum map.

Ortega, Juan-Pablo; Ratiu, Tudor S.

2006-08-01

70

Space station group activities habitability module study: A synopsis  

NASA Technical Reports Server (NTRS)

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

Nixon, David; Glassman, Terry

1987-01-01

71

Phaser crystallographic software  

PubMed Central

Phaser is a program for phasing macromolecular crystal structures by both molecular replacement and experimental phasing methods. The novel phasing algorithms implemented in Phaser have been developed using maximum likelihood and multivariate statistics. For molecular replacement, the new algorithms have proved to be significantly better than traditional methods in discriminating correct solutions from noise, and for single-wavelength anomalous dispersion experimental phasing, the new algorithms, which account for correlations between F + and F ?, give better phases (lower mean phase error with respect to the phases given by the refined structure) than those that use mean F and anomalous differences ?F. One of the design concepts of Phaser was that it be capable of a high degree of automation. To this end, Phaser (written in C++) can be called directly from Python, although it can also be called using traditional CCP4 keyword-style input. Phaser is a platform for future development of improved phasing methods and their release, including source code, to the crystallographic community. PMID:19461840

McCoy, Airlie J.; Grosse-Kunstleve, Ralf W.; Adams, Paul D.; Winn, Martyn D.; Storoni, Laurent C.; Read, Randy J.

2007-01-01

72

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

NASA Astrophysics Data System (ADS)

Supergene jarosite-group minerals are widespread in weathering profiles overlying Pb-Zn sulfide ores at Xitieshan, northern Tibetan Plateau, China. They consist predominantly of K-deficient natrojarosite, with lesser amounts of K-rich natrojarosite and plumbojarosite. Electron microprobe (EMP) analyses, scanning electron microcopy (SEM) investigation, and X-ray mapping reveal that the jarosite-group minerals are characterized by spectacular oscillatory zoning composed of alternating growth bands of K-deficient and K-bearing natrojarosite (K2O >1 wt.%). Plumbojarosite, whenever present, occurs as an overgrowth in the outermost bands, and its composition can be best represented by K0.29Na0.19Pb0.31Fe2.66Al0.22(SO4)1.65(PO4)0.31(AsO4)0.04(OH)7.37. The substitution of monovalent for divalent cations at the A site of plumbojarosite is charge balanced by the substitution of five-valent for six-valent anions in XO4 at the X site. Thermogravimetric analysis (TGA) of representative samples reveal mass losses of 11.46 wt.% at 446.6 °C and 21.42 wt.% at 683.4 °C due to dehydroxylation and desulfidation, respectively. TGA data also indicate that the natrojarosite structure collapses at 446.6 °C, resulting in the formation of NaFe(SO4)2 and minor hematite. The decomposition products of NaFe(SO4)2 are hematite and Na2SO4. Powder X-ray diffraction (XRD) analyses show that the jarosite-group minerals have mean unit-cell parameters of a = 7.315 Å and c = 016.598 Å. XRD and EMP data support the view that substitutions of Na for K in the A site and full Fe occupancy in the B site can considerably decrease the unit-cell parameter c, but only slightly increase a. The results from this study suggest that the observed oscillatory zoning of jarosite-group minerals at Xitieshan resulted mainly from substitutions of K for Na at the A site and P for S at the X site.

Chen, Lei; Li, Jian-Wei; Rye, R. O.; Benzel, W. M.; Lowers, H. A.; He, Ming-Zhong

2013-08-01

73

Report of the Working Group on Space/Lunar Tradeoffs  

NASA Technical Reports Server (NTRS)

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

1992-01-01

74

Quantum Circuit Synthesis using Group Decomposition and Hilbert Spaces  

NASA Astrophysics Data System (ADS)

The exponential nature of Moore's law has inadvertently created huge data storage complexes that are scattered around the world. Data elements are continuously being searched, processed, erased, combined and transferred to other storage units without much regard to power consumption. The need for faster searches and power efficient data processing is becoming a fundamental requirement. Quantum computing may offer an elegant solution to speed and power through the utilization of the natural laws of quantum mechanics. Therefore, minimal cost quantum circuit implementation methodologies are greatly desired. This thesis explores the decomposition of group functions and the Walsh spectrum for implementing quantum canonical cascades with minimal cost. Three different methodologies, using group decomposition, are presented and generalized to take advantage of different quantum computing hardware, such as ion traps and quantum dots. Quantum square root of swap gates and fixed angle rotation gates comprise the first two methodologies. The third and final methodology provides further quantum cost reduction by more efficiently utilizing Hilbert spaces through variable angle rotation gates. The thesis then extends the methodology to realize a robust quantum circuit synthesis tool for single and multi-output quantum logic functions.

Saraivanov, Michael S.

75

The space shuttle payload planning working groups. Volume 1: Astronomy  

NASA Technical Reports Server (NTRS)

The space astronomy missions to be accomplished by the space shuttle are discussed. The principal instrument is the Large Space Telescope optimized for the ultraviolet and visible regions of the spectrum, but usable also in the infrared. Two infrared telescopes are also proposed and their characteristics are described. Other instruments considered for the astronomical observations are: (1) a very wide angle ultraviolet camera, (2) a grazing incidence telescope, (3) Explorer-class free flyers to measure the cosmic microwave background, and (4) rocket-class instruments which can fly frequently on a variety of missions. The stability requirements of the space shuttle for accomplishing the astronomy mission are defined.

1973-01-01

76

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

E-print Network

-robot interaction. 1. INTRODUCTION Unplanned casual interaction is critical to how small groups work together [5Moving a Media Space into the Real World through Group- Robot Interaction Jim Young, Gregor Mc}@cpsc.ucalgary.ca ABSTRACT New generation media spaces let group members see each other and share information. However

Greenberg, Saul

77

Groups quasi-isometric to symmetric spaces Bruce Kleiner and Bernhard Leebz  

E-print Network

Groups quasi-isometric to symmetric spaces Bruce Kleiner and Bernhard Leebz November 10, 1998 Abstract We determine the structure of nitelygenerated groups whichare quasi-isometric to symmetric spaces with no Euclidean de Rham fac- tor, and is a nitely generated group quasi-isometric to the product Ek X

Kleiner, Bruce

78

The group approach to AdS space propagators  

E-print Network

We show that AdS two-point functions can be obtained by connecting two points in the interior of AdS space with one point on its boundary by a dual pair of Dobrev's boundary-to-bulk intertwiners and integrating over the boundary point.

Thorsten Leonhardt; Ruben Manvelyan; Werner Ruehl

2003-05-27

79

The group approach to AdS space propagators  

Microsoft Academic Search

We show that AdS two-point functions can be obtained by connecting two points in the interior of AdS space with one point on its boundary by a dual pair of Dobrev's boundary-to-bulk intertwiners and integrating over the boundary point.

Thorsten Leonhardt; Ruben Manvelyan; Werner Rühl

2003-01-01

80

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

81

Supporting Group Information Manipulation in Real Public Space by Functional Web and Web Boards  

Microsoft Academic Search

The opportunities to manipulate Web contents by group of people have been increasing, such as group meetings (brain stroming and presentation) and information presentations in real-world public spaces (advertize- ments and guidance etc.). In order to support such information manipulation and communication among people in real-world public space, we introduce the notions of the \\

Tomoyuki UCHIYAMA; Hiroya TANAKA; Katsumi TANAKA

2004-01-01

82

Metricization of thermodynamic-state space and the renormalization group  

Microsoft Academic Search

We suggest a new geometrical interpretation of the renormalization-group transformation near the critical point. Using the Weinhold-Ruppeiner metricization, conformal Killing symmetry is assumed and scaling laws are verified.

L. Diósi; G. Forgács; B. Lukács; H. L. Frisch

1984-01-01

83

Group Momentum Space and Hopf Algebra Symmetries of Point Particles Coupled to 2+1 Gravity  

NASA Astrophysics Data System (ADS)

We present an in-depth investigation of the SL(2,R) momentum space describing point particles coupled to Einstein gravity in three space-time dimensions. We introduce different sets of coordinates on the group manifold and discuss their properties under Lorentz transformations. In particular we show how a certain set of coordinates exhibits an upper bound on the energy under deformed Lorentz boosts which saturate at the Planck energy. We discuss how this deformed symmetry framework is generally described by a quantum deformation of the Poincaré group: the quantum double of SL(2,R). We then illustrate how the space of functions on the group manifold momentum space has a dual representation on a non-commutative space of coordinates via a (quantum) group Fourier transform. In this context we explore the connection between Weyl maps and different notions of (quantum) group Fourier transform appeared in the literature in the past years and establish relations between them.

Arzano, Michele; Latini, Danilo; Lotito, Matteo

2014-07-01

84

Group calls for space policies to transcend politics  

NASA Astrophysics Data System (ADS)

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

Showstack, Randy

2012-06-01

85

The space shuttle payload planning working groups. Volume 6: Communications and navigation  

NASA Technical Reports Server (NTRS)

The findings of the Communications and Navigation working group of the space shuttle payload planning activity are presented. The basic goals to be accomplished are to increase the use of space systems and to develop new space capabilities for providing communication and navigation services to the user community in the 1980 time period. Specific experiments to be conducted for improving space communication and navigation capabilities are defined. The characteristics of the experimental equipment required to accomplish the mission are discussed.

1973-01-01

86

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

87

Fixed point spaces in actions of classical algebraic groups  

Microsoft Academic Search

Let G be a simple classical algebraic group over an algebraically closed field K of characteristic pd 0, and let H be a maximal closed non-subspace subgroup of G. Given such a pair ðG; HÞ, we obtain a close to best possible upper bound for the ratio dimðx G V HÞ=dim x G, where x A G is a semisimple

Timothy C. Burness

2004-01-01

88

Kondo Lattice: Real-Space Renormalization-Group Approach  

Microsoft Academic Search

A one-dimensional analog of the Kondo lattice is studied by a renormalization-group technique. Previous mean-field results are shown to be reasonable: The system under-goes a second-order crossover transition from an antiferromagnetic state to a Kondo-like state at zero temperature as the spin-conduction-electron coupling is increased. Estimates are given for critical exponents and the behavior of correlation functions near the transition.

R. Jullien; J. Fields; S. Doniach

1977-01-01

89

'Seeing' atoms: the crystallographic revolution.  

PubMed

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

Schwarzenbach, Dieter

2014-01-01

90

Quantum group symmetric Bargmann-Fock space: Integral kernels, Green functions, driving forces  

Microsoft Academic Search

Raising and lowering operators that transform under the SUq(n)-quantum group get deformed commutation relations. They are represented as adjoint operators on a Hilbert space of noncommutative holomorphic functions. Through the algebraically defined integral on this function space, every operator on the Fock space can also be represented as an integral kernel. The Green function for free harmonic oscillators and spin-1\\/2’s

Achim Kempf

1993-01-01

91

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

92

Root filtration spaces from Lie algebras and abstract root groups 1  

E-print Network

Root filtration spaces from Lie algebras and abstract root groups 1 Arjeh M. Cohen a, G Academy of Sciences, Kende u. 13-17, 1111 Budapest, Hungary Abstract Both Timmesfeld's abstract root subgroups and simple Lie algebras generated by extremal elements lead to root filtration spaces

Cohen, Arjeh M.

93

Unitary Space-Time Constellations Based on Finite Reflection Group Codes  

E-print Network

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

Nevins, Monica

94

Weak and strong continuity of representations of topologically pseudocomplete groups in locally convex spaces  

NASA Astrophysics Data System (ADS)

Weak and strong continuity conditions for representations of topological groups in locally convex spaces are considered. In particular, weak continuity conditions of reducible locally equicontinuous representations of a topological group in a locally convex space that define weakly continuous representations in an invariant subspace and in the quotient space by this invariant subspace are investigated. These conditions help one to prove the weak continuity of averages and approximations related to weakly continuous locally equicontinuous quasirepresentations of amenable topological groups. Strong continuity conditions for a representation approximating a quasirepresentation of this kind are related to conditions of automatic strong continuity of weakly continuous representations, and fail to hold for some groups, spaces, and representations. In this connection, strong continuity conditions for weakly continuous representations in quasicomplete barrelled locally convex spaces are indicated for a broad class of topologically pseudocomplete groups (which includes the ?ech complete groups and the locally pseudocompact groups). Several examples are discussed, in particular, ones relating to the construction of \\Sigma-products with distinguished subgroups.

Shtern, A. I.

2006-04-01

95

Crystallization and preliminary crystallographic analysis of human aquaporin 1 at a resolution of 3.28?Å.  

PubMed

Aquaporin water channels (AQPs) are found in almost every organism from humans to bacteria. In humans, 13 classes of AQPs control water and glycerol homeostasis. Knockout studies have suggested that modulating the activity of AQPs could be beneficial for the treatment of several pathologies. In particular, aquaporin 1 is a key factor in cell migration and angiogenesis, and constitutes a possible target for anticancer compounds and also for the treatment of glaucoma. Here, a preliminary crystallographic analysis at 3.28?Å resolution of crystals of human aquaporin 1 (hAQP1) obtained from protein expressed in Sf9 insect cells is reported. The crystals belonged to the tetragonal space group I422, with unit-cell parameters a = b = 89.28, c = 174.9?Å, and contained one monomer per asymmetric unit. The hAQP1 biological tetramer is generated via the crystallographic fourfold axis. This work extends previous electron crystallographic studies that used material extracted from human red blood cells, in which the resolution was limited to approximately 3.8?Å. It will inform efforts to improve lattice contacts and the diffraction limit for the future structure-based discovery of specific hAQP1 inhibitors. PMID:25484221

Ruiz Carrillo, David; To Yiu Ying, Janet; Darwis, Dina; Soon, Cin Huang; Cornvik, Tobias; Torres, Jaume; Lescar, Julien

2014-12-01

96

Isometric group of $(?,?)$-type Finsler space and the symmetry of Very Special Relativity  

E-print Network

The Killing equation for a general Finsler space is set up. It is showed that the Killing equation of $(\\alpha,\\beta)$ space can be divided into two parts. One is the same with Killing equation of a Riemannian metric, another equation can be regarded as a constraint. The solutions of Killing equations present explicitly the isometric symmetry of Finsler space. We find that the isometric group of a special case of $(\\alpha,\\beta)$ space is the same with the symmetry of Very Special Relativity (VSR). The Killing vectors of Finsler-Funk space are given. Unlike Riemannian constant curvature space, the 4 dimensional Funk space with constant curvature just have 6 independent Killing vectors.

Xin Li; Zhe Chang; Xiaohuan Mo

2010-01-15

97

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

98

Isometric group actions on Banach spaces and representations vanishing at infinity  

E-print Network

Isometric group actions on Banach spaces and representations vanishing at infinity Yves de group G = Sp(n, 1) acts properly isometrically on Lp(G) if p > 4n + 2. To prove this, we introduce isometric action of G on V , such that the linear part is a C0-representation of G, either has a fixed point

Tessera, Romain

99

Connection between Group Based Quantum Tomography and Wavelet Transform in Banach Spaces  

Microsoft Academic Search

The intimate connection between the Banach space wavelet reconstruction method for each unitary representation of a given\\u000a group and some of well known quantum tomographies, such as: tomography of rotation group, Spinor tomography and tomography\\u000a of Unitary group, is established. Also both the atomic decomposition and Banach frame nature of these quantum tomographic\\u000a examples is revealed in details.

M. Mirzaee; M. Rezaei; M. A. Jafarizadeh

2007-01-01

100

The almost periodic rigidity of crystallographic bar-joint frameworks  

E-print Network

A crystallographic bar-joint framework C is shown to be almost periodically infinitesimally rigid if and only if it is strictly periodically infinitesimally rigid and the rigid unit mode (RUM) spectrum is a singleton. Moreover the almost periodic infinitesimal flexes of C are characterised in terms of a matrix-valued function on the d-torus determined by a full rank translation symmetry group and an associated motif of joints and bars.

G. Badri; D. Kitson; S. C. Power

2014-02-25

101

Challenges in Teaching Space Physics to Different Target Groups From Space Weather Forecasters to Heavy-weight Theorists  

NASA Astrophysics Data System (ADS)

Plasma physics as the backbone of space physics is difficult and thus the space physics students need to have strong foundations in general physics, in particular in classical electrodynamics and thermodynamics, and master the basic mathematical tools for physicists. In many universities the number of students specializing in space physics at Master's and Doctoral levels is rather small and the students may have quite different preferences ranging from experimental approach to hard-core space plasma theory. This poses challenges in building up a study program that has both the variety and depth needed to motivate the best students to choose this field. At the University of Helsinki we require all beginning space physics students, regardless whether they enter the field as Master's or Doctoral degree students, to take a one-semester package consisting of plasma physics and its space applications. However, some compromises are necessary. For example, it is not at all clear, how thoroughly Landau damping should be taught at the first run or how deeply should the intricacies of collisionless reconnection be discussed. In both cases we have left the details to an optional course in advanced space physics, even with the risk that the student's appreciation of, e.g., reconnection may remain at the level of a magic wand. For learning experimental work, data analysis or computer simulations we have actively pursued arrangements for the Master's degree students to get a summer employments in active research groups, which usually lead to the Master's theses. All doctoral students are members of research groups and participate in experimental work, data analysis, simulation studies or theory development, or any combination of these. We emphasize strongly "learning by doing" all the way from the weekly home exercises during the lecture courses to the PhD theses which in Finland consist typically of 4-6 peer-reviewed articles with a comprehensive introductory part.

Koskinen, H. E.

2008-12-01

102

National facilities study. Volume 5: Space research and development facilities task group  

NASA Technical Reports Server (NTRS)

With the beginnings of the U.S. space program, there was a pressing need to develop facilities that could support the technology research and development, testing, and operations of evolving space systems. Redundancy in facilities that was once and advantage in providing flexibility and schedule accommodation is instead fast becoming a burden on scarce resources. As a result, there is a clear perception in many sectors that the U.S. has many space R&D facilities that are under-utilized and which are no longer cost-effective to maintain. At the same time, it is clear that the U.S. continues to possess many space R&D facilities which are the best -- or among the best -- in the world. In order to remain world class in key areas, careful assessment of current capabilities and planning for new facilities is needed. The National Facility Study (NFS) was initiated in 1992 to develop a comprehensive and integrated long-term plan for future aerospace facilities that meets current and projected government and commercial needs. In order to assess the nation's capability to support space research and development (R&D), a Space R&D Task Group was formed. The Task Group was co-chaired by NASA and DOD. The Task Group formed four major, technologically- and functionally- oriented working groups: Human and Machine Operations; Information and Communications; Propulsion and Power; and Materials, Structures, and Flight Dynamics. In addition to these groups, three supporting working groups were formed: Systems Engineering and Requirements; Strategy and Policy; and Costing Analysis. The Space R&D Task Group examined several hundred facilities against the template of a baseline mission and requirements model (developed in common with the Space Operations Task Group) and a set of excursions from the baseline. The model and excursions are described in Volume 3 of the NFS final report. In addition, as a part of the effort, the group examined key strategic issues associated with space R&D facilities planning for the U.S., and these are discussed in Section 4 of this volume.

1994-01-01

103

Group Momentum Space and Hopf Algebra Symmetries of Point Particles Coupled to 2+1 Gravity  

E-print Network

We present an in-depth investigation of the ${\\rm SL}(2,\\mathbb{R})$ momentum space describing point particles coupled to Einstein gravity in three space-time dimensions. We introduce different sets of coordinates on the group manifold and discuss their properties under Lorentz transformations. In particular we show how a certain set of coordinates exhibits an upper bound on the energy under deformed Lorentz boosts which saturate at the Planck energy. We discuss how this deformed symmetry framework is generally described by a quantum deformation of the Poincar\\'e group: the quantum double of ${\\rm SL}(2,\\mathbb{R})$. We then illustrate how the space of functions on the group manifold momentum space has a dual representation on a non-commutative space of coordinates via a (quantum) group Fourier transform. In this context we explore the connection between Weyl maps and different notions of (quantum) group Fourier transform appeared in the literature in the past years and establish relations between them.

Michele Arzano; Danilo Latini; Matteo Lotito

2014-03-12

104

Preliminary X-ray crystallographic analysis of sulfide:quinone oxidoreductase from Acidithiobacillus ferrooxidans.  

PubMed

The gene product of open reading frame AFE_1293 from Acidithiobacillus ferrooxidans ATCC 23270 is annotated as encoding a sulfide:quinone oxidoreductase, an enzyme that catalyses electron transfer from sulfide to quinone. Following overexpression in Escherichia coli, the enzyme was purified and crystallized using the hanging-drop vapour-diffusion method. The native crystals belonged to the tetragonal space group P4(2)2(1)2, with unit-cell parameters a = b = 131.7, c = 208.8 A, and diffracted to 2.3 A resolution. Preliminary crystallographic analysis indicated the presence of a dimer in the asymmetric unit, with an extreme value of the Matthews coefficient (V(M)) of 4.53 A(3) Da(-1) and a solvent content of 72.9%. PMID:19652354

Zhang, Yanfei; Cherney, Maia M; Solomonson, Matthew; Liu, Jianshe; James, Michael N G; Weiner, Joel H

2009-08-01

105

Preliminary X-ray crystallographic analysis of glutathione transferase zeta 1 (GSTZ1a-1a)  

PubMed Central

Glutathione transferase zeta 1 (GSTZ1-1) is a homodimeric enzyme found in the cytosol and mitochondrial matrix of the liver and other tissues. It catalyzes the glutathione-dependent isomerization of maleylacetoacetate to fumaryl­acetoacetate in the tyrosine catabolic pathway and can metabolize small halogenated carboxylic acids. GSTZ1a-1a crystals diffracted to a resolution of 3.1?Å and belonged to space group P1, with unit-cell parameters a = 42.0, b = 49.6, c = 54.6?Å, ? = 82.9, ? = 69.9, ? = 73.4°, with a calculated Matthews coefficient of 2.1?Å3?Da?1 assuming a dimer in the crystallographic asymmetric unit. Refinement of the structure is currently in progress. PMID:24637752

Boone, Christopher D.; Zhong, Guo; Smeltz, Marci; James, Margaret O.; McKenna, Robert

2014-01-01

106

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

107

Crystallization and preliminary X-ray crystallographic analysis of human autotaxin.  

PubMed

Autotaxin (ATX), which is also known as ectonucleotide pyrophosphatase/phosphodiesterase 2 (NPP2 or ENPP2) or phosphodiesterase I? (PD-I?), is an extracellular lysophospholipase D which generates lysophosphatidic acid (LPA) from lysophosphatidylcholine (LPC). ATX stimulates tumour-cell migration, angiogenesis and metastasis and is an attractive target for cancer therapy. For crystallographic studies, the ? isoform of human ATX was overproduced in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. X-ray diffraction data were collected to 3.0?Å resolution from a monoclinic crystal form belonging to space group C2, with unit-cell parameters a = 311.4, b = 147.9, c = 176.9?Å, ? = 122.6°. PMID:21505238

Inoue, Keigo; Tanaka, Nobutada; Haga, Arayo; Yamasaki, Kyohei; Umeda, Tomonobu; Kusakabe, Yoshio; Sakamoto, Yasumitsu; Nonaka, Takamasa; Deyashiki, Yoshihiro; Nakamura, Kazuo T

2011-04-01

108

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

2013-10-11

109

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

2006-03-01

110

Crystallization and preliminary X-ray crystallographic analysis of two dimeric hyperthermostable thioredoxins isolated from Sulfolobus solfataricus  

PubMed Central

The thioredoxin system of the archaeon Sulfolobus solfataricus involves a number of different proteins: two thioredoxin reductases (SsTrxRB2 and SsTrxRB3), two distinct thioredoxins (SsTrxA1 and SsTrxA2) and a disulfide oxidoreductase (SsPDO). Here, the crystallization and preliminary crystallo­graphic analyses of SsTrxA1 and SsTrxA2, two dimeric proteins endowed with extraordinary thermal stability, are reported. In addition to the functional thioredoxin domain, both SsTrxA1 and SsTrxA2 present an extra N-terminal fragment of approximately 30 residues. Although crystallization trials have been conducted on both forms of the proteins, crystals that were suitable for X-ray crystallographic analyses have only been obtained for their truncated variants. The crystals of SsTrxA2 belonged to space group P2, with unit-cell parameters a = 28.27, b = 27.88, c = 62.06?Å, ? = 92.34°, and diffracted to 1.83?Å resolution, whereas the crystals of SsTrxA1 belonged to space group P21, with unit-cell parameters a = 51.76, b = 75.09, c = 55.35?Å, ? = 112.64°, and diffracted to 1.90?Å resolution. The structures of the two proteins have been solved by molecular replacement. PMID:19478442

Ruggiero, Alessia; Lanzotti, Maria Angela; Ruocco, Maria Rosaria; Grimaldi, Pasquale; Marasco, Daniela; Arcari, Paolo; Masullo, Mariorosario; Zagari, Adriana; Vitagliano, Luigi

2009-01-01

111

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

112

Elementary Energy Bands in Crystalline Solids:. Space Groups with 3-DIMENSIONAL Strata Only  

NASA Astrophysics Data System (ADS)

Elementary energy bands in solids are defined generalizing the notion of simple and composite energy bands. All energy branches of elementary energy bands are connected. Following the connectivity of the energy branches in elementary energy bands, a new notion of unavoidable degeneracy is established, for which the crossings can be moved but not removed. This degeneracy does not depend on the particular shape of the potential and is present in all crystals of some given space group symmetry. A review of unavoidable degeneracy is given for all 13 space groups of special kind in 3-dimensions whose only Wyckoff position (symmetry center in the crystal) is of trivial symmetry.

Michel, L.; Zak, J.

2001-04-01

113

Information theory and crystallographic phase determination  

E-print Network

INFORMATION THEORY AND CRYSTALLOGRAPHIC PHASE DETERMINATION A Thesis by PATRICIA LOUISE BRITTEN Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE August... 1981 Major Subject: Chemistry INFORMATION THEORY AND CRYSTALLOGRAPHIC PHASE DETERMINAT ION A Thesis by PATRICIA LOUISE BRITTEN Approved as to style and content by: (Chairman of Committee) (Member ) (Member) (Head of Depar ent) August 1981...

Britten, Patricia Louise

2012-06-07

114

Homotopy colimits of classifying spaces of abelian subgroups of a finite group.  

E-print Network

The classifying space BG of a topological group $G$ can be filtered by a sequence of subspaces $B(q,G)$, using the descending central series of free groups. If $G$ is finite, describing them as homotopy colimits is convenient when applying homotopy theoretic methods. In this paper we introduce natural subspaces $B(q,G)_p$ of $B(q,G)$ defined for a fixed prime $p$. We show that $B(q,G)$ is stably homotopy equivalent to a wedge of $B(q,G)_p$ as $p$ runs over the primes dividing the order of $G$. Colimits of abelian groups play an important role in understanding the homotopy type of these spaces. Extraspecial $2$-groups are key examples, for which these colimits turn out to be finite. We prove that for extraspecial 2-groups, $B(2,G)$ does not have the homotopy type of a $K(\\pi,1)$ space. For a finite group $G$, we compute the complex K-theory of $B(2,G)$ modulo torsion.

Cihan Okay.

115

Space group selection for crystal structure prediction of solvates{ Aurora J. Cruz Cabeza,a  

E-print Network

Space group selection for crystal structure prediction of solvates{ Aurora J. Cruz Cabeza,a Elna with common solvents are presented to assist crystal structure prediction calculations on these complex systems. Introduction Many programs for the computer generation of crystal structures (e.g. UPACK,1

de Gispert, Adrià

116

Cooperation Without Memory or Space: Tags, Groups and the Prisoner's Dilemma  

E-print Network

Cooperation Without Memory or Space: Tags, Groups and the Prisoner's Dilemma David Hales Department] model demonstrated that image scoring produces high cooperation between strangers in the Prisoner] reproduction of strategies is population wide. Contrary to previous tag models [15] cooperation is demonstrated

Hales, David

117

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

118

On the Construction of Space-time Hamiltonian Constellations from Group Codes  

E-print Network

On the Construction of Space-time Hamiltonian Constellations from Group Codes Terasan Niyomsataya, Canada K1N 6N5 mnevins@uottawa.ca Abstract-- Full diversity signal constellations for any numbers in this paper. The diversity product of a 2Ã?2 Hamiltonian constellation equals one half of the Euclidean

Nevins, Monica

119

On The K-Ring of the Classifying Space of the Symmetric Group on Four Letters.  

E-print Network

We describe $K(BS_4)$ and make a connection of the order of the bundle induced from the standart representation over the four dimensional skeleton of $BS_4$ with the stable homotopy group $\\pi_3^s=Z_{24}$ explaining the reasons of this connection by pulling this bundle over lens spaces.

Mehmet Kirdar

120

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

E-print Network

REQUEST FOR LEASED SPACE 1. DATE 2. TO: 3. FROM: (REQUESTING DIVISION) 4. FOR: (USER GROUP) CONTACT LEASING ACTION Advertise Solicitation For Lease 18. REAL ESTATE Other (See attached)Initiate Short Form Lease Initiate Sole Source DATE APPROVED DATE19. DEPARTMENT OF ENERGY PRINT NAME AND TITLEAPPROVAL

121

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

122

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

NASA Technical Reports Server (NTRS)

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

Thronson, Harley; Lester, Dan

2013-01-01

123

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

124

Communication: Active space decomposition with multiple sites: Density matrix renormalization group algorithm  

NASA Astrophysics Data System (ADS)

We extend the active space decomposition method, recently developed by us, to more than two active sites using the density matrix renormalization group algorithm. The fragment wave functions are described by complete or restricted active-space wave functions. Numerical results are shown on a benzene pentamer and a perylene diimide trimer. It is found that the truncation errors in our method decrease almost exponentially with respect to the number of renormalization states M, allowing for numerically exact calculations (to a few ?Eh or less) with M = 128 in both cases. This rapid convergence is because the renormalization steps are used only for the interfragment electron correlation.

Parker, Shane M.; Shiozaki, Toru

2014-12-01

125

The space shuttle payload planning working groups. Volume 7: Earth observations  

NASA Technical Reports Server (NTRS)

The findings of the Earth Observations working group of the space shuttle payload planning activity are presented. The objectives of the Earth Observation experiments are: (1) establishment of quantitative relationships between observable parameters and geophysical variables, (2) development, test, calibration, and evaluation of eventual flight instruments in experimental space flight missions, (3) demonstration of the operational utility of specific observation concepts or techniques as information inputs needed for taking actions, and (4) deployment of prototype and follow-on operational Earth Observation systems. The basic payload capability, mission duration, launch sites, inclinations, and payload limitations are defined.

1973-01-01

126

The space shuttle payload planning working groups. Volume 8: Earth and ocean physics  

NASA Technical Reports Server (NTRS)

The findings and recommendations of the Earth and Ocean Physics working group of the space shuttle payload planning activity are presented. The requirements for the space shuttle mission are defined as: (1) precision measurement for earth and ocean physics experiments, (2) development and demonstration of new and improved sensors and analytical techniques, (3) acquisition of surface truth data for evaluation of new measurement techniques, (4) conduct of critical experiments to validate geophysical phenomena and instrumental results, and (5) development and validation of analytical/experimental models for global ocean dynamics and solid earth dynamics/earthquake prediction. Tables of data are presented to show the flight schedule estimated costs, and the mission model.

1973-01-01

127

Crystallographic evidence for dual coordination around zinc in the T3R3 human insulin hexamer.  

PubMed

The T3R3 human insulin hexamer (T and R referring to extended and alpha-helical conformations, respectively, of the first eight residues of the B-chain), complexed to two zinc ions, crystallizes in space group R3 with hexagonal cell constants a = 80.64 and c = 37.78 A. The structure has been refined to a residual of 0.172 using 9225 independent data to 1.6-A resolution. The asymmetric unit consists of a TR dimer, and the insulin hexamer is generated by the action of the crystallographic 3-fold axis. The conformation of one insulin trimer is nearly identical to that of the T6 hexamer, while the other trimer approximates that of the R6 hexamer, except for the three N-terminal B-chain residues that adopt an extended rather than an alpha-helical conformation. Each of the two zinc ions, which lie on the crystallographic 3-fold axis and exhibit two different, disordered coordination geometries, is coordinated by the imidazole groups of three symmetry-related B10 histidine residues. The coordination sphere of the zinc in the T3 trimer is either tetrahedral, with the fourth site filled by a chloride ion, or octahedral, completed by three water molecules. The coordination of the zinc in the 12-A narrow channel in the R3 trimer is tetrahedral, with either a second chloride ion or a water molecule completing the coordination sphere. The putative off-axial zinc binding sites that result from the T-->R transition of monomer II do not contain zinc ion, but instead are filled with clusters of ordered water molecules.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8312271

Ciszak, E; Smith, G D

1994-02-15

128

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

SciTech Connect

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

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

2011-05-31

129

Real space renormalization group for twisted lattice =4 super Yang-Mills  

NASA Astrophysics Data System (ADS)

A necessary ingredient for our previous results on the form of the long distance effective action of the twisted lattice =4 super Yang-Mills theory is the existence of a real space renormalization group which preserves the lattice structure, both the symmetries and the geometric interpretation of the fields. In this brief article we provide an explicit example of such a blocking scheme and illustrate its practicality in the context of a small scale Monte Carlo renormalization group calculation. We also discuss the implications of this result, and the possible ways in which to use it in order to obtain further information about the long distance theory.

Catterall, Simon; Giedt, Joel

2014-11-01

130

Science Requirements Working Group (SRWG) in float zone materials processing in space: A review  

NASA Technical Reports Server (NTRS)

A summary and history of the Float Zone Working Group was presented. The functions of this working group are to: provide an informal forum of scientific investigators for the exchange of information and ideas in the approach of the solution of common problems in float zone processing, help plan the research and development necessary to place the float zone process on a firm base of scientific understanding and advanced technological development, establish the science requirements for the AFZES for Spacelab, and seek ways to maximize the advantages of the space environment in the pursuit of these goals.

Fowle, A. A.

1980-01-01

131

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

NASA Technical Reports Server (NTRS)

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

Roberts, Barry C.

2004-01-01

132

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

SciTech Connect

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

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

2009-03-16

133

Constructive Axiomatic Approach to the Determination of the Orbit Spaces of Coregular Compact Linear Groups  

Microsoft Academic Search

We review the proposal of a constructive axiomatic approach to the determination of the orbit spaces of all the real compact linear groups, obtained through the computation of a metric matrix \\u000a\\u000a\\u000a, which is defined only in terms of the scalar products between the gradients ?p1(x),.?.?.,?pq(x) of the elements of a minimal integrity basis (MIB) for the ring R[Rn]G of

G. Sartori; G. Valente

2005-01-01

134

One dimensional zone center phonons in $O_{h}$ space group  

E-print Network

Motivated by experiments, we performed a systematic study on the one dimensional zone center phonons in $O_{h}$ space groups. All the one dimensional phonon modes for different Wyckoff positions are tabulated. We show that at least four (inequivalent) atoms (in one set of Wyckoff positions) are needed to carry a single one dimensional phonon. A general restriction rule on the number of atoms and the number of one dimensional phonons is obtained. The same restriction applies to phonons of all cubic crystal systems ($T$, $T_{h}$, $T_{d}$, $O$, $O_{h}$) and to magnons for crystals whose unitary symmetry elements are in ($T$, $T_{h}$, $T_{d}$, $O$, $O_{h}$). Crystals with $A15$ structure are found to satisfy experimental requirements (to have a $\\Gamma_{2}^{+}$ phonon) while most crystals of $O_{h}$ space groups do not. $A15$ is also used to demonstrate the rules we found regarding the phonon structure in $O_{h}$ space groups.

Jian Li; Jiufeng J. Tu; Joseph L. Birman

2014-03-04

135

Crystallization and preliminary X-ray crystallographic analysis of the plant defensin NaD1.  

PubMed

Plant defensins are small (~5 kDa) basic cysteine-rich proteins that are being explored in important agricultural crops for their ability to confer enhanced disease resistance against fungal pathogens. NaD1, isolated from the flowers of the ornamental tobacco (Nicotiana alata), is a particularly well characterized antifungal defensin. Here, the crystallization and preliminary X-ray crystallographic analysis of NaD1 is reported. Crystals of NaD1 were crystallized using the sitting-drop vapour-diffusion method at 291 K. Data were collected from two crystal forms to 1.4 and 1.6 Å resolution, respectively. The crystals of form A belonged to the monoclinic space group P2(1), with unit-cell parameters a = 32.697, b = 32.685, c = 41.977 Å, ? = 90, ? = 100.828, ? = 90°, whereas crystals of form B belonged to the trigonal space group P3(2)21, with unit-cell parameters a = b = 33.091, c = 128.77 Å, ? = ? = 90, ? = 120°. PMID:22232180

Lay, Fung T; Mills, Grant D; Hulett, Mark D; Kvansakul, Marc

2012-01-01

136

The redshift-space neighborhoods of 36 loose groups of galaxies. 1: The data  

NASA Technical Reports Server (NTRS)

We have selected 36 loose groups of galaxies (RGH89) with at least five members, and with mean redshift average value of CZ is greater than 3200 km/s. These groups all lie within the first two slices of the CfA redshift survey 8(sup h) less than or equal to alpha less than or equal to 17(sup h) and 26.5 deg less than or equal to delta less than or equal to 38.5 deg). For each of these groups, we define the redshift-space neighborhood as a region centered on the group coordinates and delimited by a circle of projected radius R(sub cir) = 1.5/h Mpc on the sky, and by a velocity interval delta (sub cz) = 3000 km/s. Here we give the redshifts of 334 galaxies in these redshift-space neighborhoods. For completeness, we also give the redshifts of the 232 original members. These data include 199 new redshifts. We demonstrate that these samples of fainter galaxies significantly increase the number of members.

Ramella, Massimo; Geller, Margaret J.; Hurchra, John P.; Thorstensen, John R.

1995-01-01

137

Topological entropy and renormalization group flow in 3-dimensional spherical spaces  

NASA Astrophysics Data System (ADS)

We analyze the renormalization group (RG) flow of the temperature independent term of the entropy in the high temperature limit ?/a ? 1 of a massive field theory in 3-dimensional spherical spaces, M 3, with constant curvature 6 /a 2. For masses lower than , this term can be identified with the free energy of the same theory on M 3 considered as a 3-dimensional Euclidean space-time. The non-extensive part of this free energy, S hol, is generated by the holonomy of the spatial metric connection. We show that for homogeneous spherical spaces the holonomy entropy S hol decreases monotonically when the RG scale flows to the infrared. At the conformal fixed points the values of the holonomy entropy do coincide with the genuine topological entropies recently introduced. The monotonic behavior of the RG flow leads to an inequality between the topological entropies of the conformal field theories connected by such flow, i.e. S {top/ UV } > S {top/ IR }. From a 3-dimensional viewpoint the same term arises in the 3-dimensional Euclidean effective action and has the same monotonic behavior under the RG group flow. We conjecture that such monotonic behavior is generic, which would give rise to a 3-dimensional generalization of the c-theorem, along the lines of the 2-dimensional c-theorem and the 4-dimensional a-theorem. The conjecture is related to recent formulations of the F -theorem. In particular, the holonomy entropy on lens spaces is directly related to the topological Rényi entanglement entropy on disks of 2-dimensional flat spaces.

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

2015-01-01

138

A Perceptual Phonetic Similarity Space for Languages: Evidence from Five Native Language Listener Groups1  

PubMed Central

The goal of the present study was to devise a means of representing languages in a perceptual similarity space based on their overall phonetic similarity. In Experiment 1, native English listeners performed a free classification task in which they grouped 17 diverse languages based on their perceived phonetic similarity. A similarity matrix of the grouping patterns was then submitted to clustering and multidimensional scaling analyses. In Experiment 2, an independent group of native English listeners sorted the group of 17 languages in terms of their distance from English. Experiment 3 repeated Experiment 2 with four groups of non-native English listeners: Dutch, Mandarin, Turkish and Korean listeners. Taken together, the results of these three experiments represent a step towards establishing an approach to assessing the overall phonetic similarity of languages. This approach could potentially provide the basis for developing predictions regarding foreign-accented speech intelligibility for various listener groups, and regarding speech perception accuracy in the context of background noise in various languages. PMID:21179563

Bradlow, Ann; Clopper, Cynthia; Smiljanic, Rajka; Walter, Mary Ann

2010-01-01

139

Nanopatterning of graphene with crystallographic orientation control  

Microsoft Academic Search

The recent papers on the nanopatterning of graphene and cutting of graphene nanoribbons were reviewed. It was found that until now the simultaneous control of crystallographic orientation and of the ribbon width in the range of nanometers was possible only by scanning tunneling lithography. The cutting process by local anodic oxidation under the AFM tip is a similar process, but

László P. Biró; Philippe Lambin

2010-01-01

140

The Community-based Organizations Working Group of the Space Science Education Support Network  

NASA Astrophysics Data System (ADS)

The NASA Space Science Support Network Community-based Organizations Working Group (CBOWG) has been working for the past two years on issues surrounding afterschool programs and programs for youth (e.g., Girl Scouts, Boy Scouts, Boys and Girls Clubs, 4-H, summer camps, afterschool and weekend programs for various ages, programs with emphases on minority youth). In this session the co-leaders of the CBOWG will discuss the challenges of working with community-based organizations on a regional or national level. We will highlight some ties that we have forged with the National Institute for Out of School Time (NIOST) and the National Afterschool Association (NAA). We will also talk about efforts to coordinate how various entities within NASA cooperate with community-based organizations to serve the best interests of these groups. We will give a couple of examples of how NASA space science organizations have partnered with community-based organizations. The session will include some handouts of information and resources that the CBOWG has found useful in developing an understanding of this segment of informal education groups. We would like to thank NASA for providing resources to support the work of the CBOWG.

Lutz, J. H.; Lowes, L. L.; Asplund, S.

2004-12-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

142

Purification, crystallization and preliminary crystallographic analysis of the CBS-domain pair of cyclin M2 (CNNM2)  

PubMed Central

This work describes the purification and preliminary crystallographic analysis of the CBS-domain pair of the murine CNNM2 magnesium transporter (formerly known as ancient domain protein 2; ACDP2), which consists of a pair of cystathionine ?-synthase (CBS) motifs and has 100% sequence identity to its human homologue. CNNM proteins represent the least-studied members of the eight different types of magnesium transporters identified to date in mammals. In humans, the CNNM family is encoded by four genes: CNNM1–4. CNNM1 acts as a cytosolic copper chaperone, whereas CNNM2 and CNNM4 have been associated with magnesium handling. Interestingly, mutations in the CNNM2 gene cause familial dominant hypomagnesaemia (MIM:607803), a rare human disorder characterized by renal and intestinal magnesium (Mg2+) wasting, which may lead to symptoms of Mg2+ depletion such as tetany, seizures and cardiac arrhythmias. This manuscript describes the preliminary crystallographic analysis of two different crystal habits of a truncated form of the protein containing its regulatory CBS-domain pair, which has been reported to host the pathological mutation T568I in humans. The crystals belonged to space groups P21212 and I222 (or I212121) and diffracted X-­rays to 2.0 and 3.6?Å resolution, respectively, using synchrotron radiation. PMID:23027747

Gómez-García, Inmaculada; Stuiver, Marchel; Ereño, June; Oyenarte, Iker; Corral-Rodríguez, María Angeles; Müller, Dominik; Martínez-Cruz, Luis Alfonso

2012-01-01

143

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

PubMed

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

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

2014-07-01

144

The space shuttle payload planning working groups. Volume 5: Solar physics  

NASA Technical Reports Server (NTRS)

The findings of the Solar Physics working group of the space shuttle payload planning activity are presented. The areas to be investigated by the solar physics experiments are: (1) the production of mechanical energy in the subphotospheric layers and its transport and dissipation in the upper layers of the atmosphere, (2) the mass flux from the subphotospheric layers into the chromosphere and corona and beyond the solar wind, (3) solar activity and its relationship to magnetic fields, and (4) the production of solar flares. The approach to be followed in conducting the experiments and the equipment required are defined.

1973-01-01

145

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.

Dexter Perkins

146

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

NASA Technical Reports Server (NTRS)

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

1973-01-01

147

Taut foliations and the actions of fundamental groups on leaf spaces and universal circles  

E-print Network

Let $F$ be a leafwise hyperbolic taut foliation of a closed 3-manifold $M$ and let $L$ be the leaf space of the pullback of $F$ to the universal cover of $M$. We show that if $F$ has branching, then the natural action of $\\pi_1(M)$ on $L$ is faithful. We also show that if $F$ has a finite branch locus $B$ whose stabilizer acts on $B$ nontrivially, then the stabilizer is an infinite cyclic group generated by an indivisible element of $\\pi_1(M)$.

Kano, Yosuke

2012-01-01

148

Benzyltripropylammonium bromide: a structure in polar space group P4(2)bc.  

PubMed

Crystals of the title compound, C(16)H(28)N(+).Br(-), were grown from solution in a mixture of acetone and propan-2-ol by slow evaporation. The structure was solved in the polar space group P4(2)bc with five moieties in the asymmetric unit, namely two benzyltripropylammonium cations in general positions, and two Br(-) anions in special Wyckoff positions (4a2. and 4b2.) and one in a general position. The structure consists of two kinds of molecular columns parallel to c, built of cations connected through C-H.pi hydrogen bonds and stabilized by weak C-H.Br interactions. PMID:14532666

Hodorowicz, Maciej A; Czapkiewicz, Jan; Stadnicka, Katarzyna

2003-10-01

149

Hubble Space Telescope Images of Stephan's Quintet: Star Cluster Formation in a Compact Group Environment  

E-print Network

Analysis of Hubble Space Telescope/Wide Field Planetary Camera 2 images of Stephan's Quintet, Hickson Compact Group 92, yielded 115 candidate star clusters (with V-I < 1.5). Unlike in merger remants, the cluster candidates in Stephan's Quintet are not clustered in the inner regions of the galaxies; they are spread over the debris and surrounding area. Specifically, these sources are located in the long sweeping tail and spiral arms of NGC 7319, in the tidal debris of NGC 7318B/A, and in the intragroup starburst region north of these galaxies. Analysis of the colors of the clusters indicates several distinct epochs of star formation that appear to trace the complex history of dynamical interactions in this compact group.

S. C. Gallagher; J. C. Charlton; S. D. Hunsberger; D. Zaritsky; B. C. Whitmore

2001-03-31

150

Analysis of the structural continuity in twinned crystals in terms of pseudo-eigensymmetry of crystallographic orbits  

PubMed Central

The reticular theory of twinning gives the necessary conditions on the lattice level for the formation of twins. The latter are based on the continuation, more or less approximate, of a substructure through the composition surface. The analysis of this structural continuity can be performed in terms of the eigensymmetry of the crystallographic orbits corresponding to occupied Wyckoff positions in the structure. If is the space group of the individual and a space group which fixes the twin lattice obtained as an intersection of the space groups of the individuals in their respective orientations, then a structural continuity is obtained if (1) the eigensymmetry of an orbit under contains the twin operation; (2) the eigensymmetry of a union of orbits under contains the twin operation; (3) the eigensymmetry of a split orbit under contains the twin operation; or (4) the eigensymmetry of a union of split orbits under contains the twin operation. The case of the twins in melilite is analysed: the (approximate) restoration of some of the orbits explains the formation of these twins. PMID:25075318

Marzouki, Mohamed Amine; Souvignier, Bernd; Nespolo, Massimo

2014-01-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

152

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

PubMed Central

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

Maher, Christine R.; Burger, Joseph Robert

2012-01-01

153

The mimivirus R355 gene product: preliminary crystallographic analysis of a putative ubiquitin-like protein-specific protease.  

PubMed

The complete genome sequence of the largest known double-stranded DNA virus, mimivirus, reveals the presence of a gene (denoted R355) that potentially encodes a cysteine protease that is expressed late (after 6?h) in the infectious cycle of the virus. In order to verify a sequence-based functional prediction and understand its role during the infectious process, the R355 protein was produced to assay its proteolytic activity and solve its three-dimensional structure. Here, the preliminary crystallographic analysis of the recombinant viral protein is reported. The crystals belonged to the orthorhombic space group P2(1)2(1)2(1), with a monomer in the asymmetric unit. A MAD data set was used for preliminary phasing using the selenium signal from a selenomethionine-substituted protein crystal. PMID:21206054

Jeudy, Sandra; Lartigue, Audrey; Mansuelle, Pascal; Ogata, Yuki; Abergel, Chantal

2011-01-01

154

Expression, purification and preliminary crystallographic analysis of a haem-utilizing protein, HutX, from Vibrio cholerae.  

PubMed

Vibrio cholerae, the causative agent of cholera, has developed a variety of mechanisms to obtain the limited-availability iron from human hosts. One important method for iron acquisition is through haem-uptake systems. Although the transport of haem has been widely studied, the fate of haem once it enters the cytoplasm remains an open question. Here, preliminary X-ray crystallographic analysis was performed on HutX, a member of the conserved haem-utilization operon from V. cholerae strain N16961. The crystals of HutX were found to belong to the orthorhombic space group C2221, with unit-cell parameters a = 50.1, b = 169.0, c = 81.8?Å. There are two protein molecules in the asymmetric unit, with a corresponding Matthews coefficient VM of 2.06?Å(3)?Da(-1) and a solvent content of 40.28%. PMID:25664785

Su, Tiantian; Chi, Kaikai; Wang, Kang; Guo, Liming; Huang, Yan

2015-02-01

155

Purification, crystallization and preliminary crystallographic studies of a Kunitz-type proteinase inhibitor from tamarind (Tamarindus indica) seeds  

PubMed Central

A Kunitz-type proteinase inhibitor has been purified from tamarind (Tamarindus indica) seeds. SDS–PAGE analysis of a purified sample showed a homogeneous band corresponding to a molecular weight of 21?kDa. The protein was identified as a Kunitz-type proteinase inhibitor based on N-terminal amino-acid sequence analysis. It was crystallized by the vapour-diffusion method using PEG 6000. The crystals belonged to the orthorhombic space group C2221, with unit-cell parameters a = 37.2, b = 77.1, c = 129.1?Å. Diffraction data were collected to a resolution of 2.7?Å. Preliminary crystallographic analysis indicated the presence of one proteinase inhibitor molecule in the asymmetric unit, with a solvent content of 44%. PMID:19574654

Patil, Dipak N.; Preeti; Chaudhry, Anshul; Sharma, Ashwani K.; Tomar, ­Shailly; Kumar, Pravindra

2009-01-01

156

Quantization of the optical phase space in terms of the group  

NASA Astrophysics Data System (ADS)

The problem of quantizing properly the canonical pair angle and action variables, and I, is almost as old as quantum mechanics itself and since decades an intensively debated but still unresolved issue in quantum optics. The present paper proposes a new approach to the problem, namely quantization in terms of the group SO(1,2): The crucial point is that the phase space %200%5C%7D%24%5Cend%7Bdocument%7D"> has the global structure (a simple cone) and cannot be quantized in the conventional manner. As the group SO(1,2) acts transitively, effectively and Hamilton-like on that space its irreducible unitary representations of the positive discrete series provide the appropriate quantum theoretical framework. The phase space has the conic structure of an orbifold . That structure is closely related to a Z2 gauge symmetry which corresponds to the center of a 2-fold covering of SO(1,2), the symplectic group . The basic variables on the phase space are the functions h0 = I , h1 = I cos and h2 = -I sin the Poisson brackets of which obey the Lie algebra . In the quantum theory they are represented by the self-adjoint Lie algebra generators K0, K1, and K2 of a unitary representation, where K0 has the spectrum {k + n, n = 0, 1, ...; k > 0}. A crucial prediction is that the classical Pythagorean relation h12 + h22 = h02 can be violated in the quantum theory. For each representation one can define three different types of coherent states the complex phases of which may be measured by means of the operators K1 and K2 alone without introducing any new phase operators! The SO(1,2) structure of optical squeezing and interference properties as well as that of the harmonic oscillator are analyzed in detail. The additional coherent states can be used for the introduction of (Husimi type) Q distributions and (Sudarshan-Glauber type) P representations of the density operator. The three operators K0, K1, and K2 are fundamental in the sense that one can construct composite position and momentum operators out of them! The new framework poses quite a number of fascinating experimental and theoretical challenges.

Kastrup, H. A.

2003-10-01

157

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

E-print Network

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

Hao Song; Michael Hermele

2015-02-05

158

Crystallographic studies of gas sorption in metal–organic frameworks  

PubMed Central

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

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

2014-01-01

159

Crystallographic studies on sterically affected chemical species  

Microsoft Academic Search

The crystal and molecular structure of 2-carboxy-2'-methoxybiphenyl has been determined to R=0.035. Crystals are tetragonal, of space group I41cd, witha=b=15.181(2)c=19.874(2) Å. Mean esd values for bond lengths and bond angles are 0.005 Å and 0.3°, respectively. The angle between phenyl rings is 54.5(1)°. The C(1) (carboxy) and O (methoxy) distance is 3.02 Å. Dimers of the title compound are hydrogen

T. M. Krygowski; R. Anulewicz; T. Daniluk; T. Drapa?a

1990-01-01

160

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

PubMed

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. PMID:15600482

Whitelam, Stephen; Garrahan, Juan P

2004-10-01

161

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

162

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

163

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

164

On the reflection type decomposition of the adjoint reduced phase space of a compact semisimple Lie group  

NASA Astrophysics Data System (ADS)

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

Hofmann, M.; Rudolph, G.; Schmidt, M.

2013-08-01

165

On the reflection type decomposition of the adjoint reduced phase space of a compact semisimple Lie group  

SciTech Connect

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

Hofmann, M. [Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Str. 3, 57068 Siegen (Germany)] [Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Str. 3, 57068 Siegen (Germany); Rudolph, G.; Schmidt, M. [Institut für Theoretische Physik, Universität Leipzig, Augustusplatz 10/11, 04109 Leipzig (Germany)] [Institut für Theoretische Physik, Universität Leipzig, Augustusplatz 10/11, 04109 Leipzig (Germany)

2013-08-15

166

[HOWTODO: INDEX & FIND SPACE GROUP FOR CITRIC ACID] February 23, 2010 o Down load CRYSFIRE, PowderCell and Citric zip files.  

E-print Network

[HOWTODO: INDEX & FIND SPACE GROUP FOR CITRIC ACID] February 23, 2010 o Down load CRYSFIRE the cd command) to the citric folder o #12;[HOWTODO: INDEX & FIND SPACE GROUP FOR CITRIC ACID & FIND SPACE GROUP FOR CITRIC ACID] February 23, 2010 o o Use the defaults for the next 7 queries

Meagher, Mary

167

Tangent spaces to motivic cohomology groups-on $CH^{\\bullet}(X,1)$ and $CH^{\\bullet}(X,2)$.  

E-print Network

Using higher K-theory and tensor triangular geometry, we propose K-theoretic higher Chow groups, at position 1 and 2, of derived categories of noetherian schemes and their Milnoe variants for regular schemes and infinitesimal thickenings. We discuss fuctoriality ans show that these new higher Chow groups agree with the classical ones for regular schemes. As an application, we define tangent spaces to these new higher Chow groups as usually and identify them with cohomology groups of absolute differentials. Moreover, combing our results with Green-Griffiths' work on tangent spaces to algebraic cycles, we put a geometric meaning to the tangent space to $CH^{2}(X,1)$, where X is a smooth projective surface over a field k, chark=0.

Sen Yang

168

Target selection and comparison of mission design for space debris removal by DLR's advanced study group  

NASA Astrophysics Data System (ADS)

Space debris is a growing problem. Models show that the Kessler syndrome, the exponential growth of debris due to collisions, has become unavoidable unless an active debris removal program is initiated. The debris population in LEO with inclination between 60° and 95° is considered as the most critical zone. In order to stabilize the debris population in orbit, especially in LEO, 5 to 10 objects will need to be removed every year. The unique circumstances of such a mission could require that several objects are removed with a single launch. This will require a mission to rendezvous with a multitude of objects orbiting on different altitudes, inclinations and planes. Removal models have assumed that the top priority targets will be removed first. However this will lead to a suboptimal mission design and increase the ?V-budget. Since there is a multitude of targets to choose from, the targets can be selected for an optimal mission design. In order to select a group of targets for a removal mission the orbital parameters and political constraints should also be taken into account. Within this paper a number of the target selection criteria are presented. The possible mission targets and their order of retrieval is dependent on the mission architecture. A comparison between several global mission architectures is given. Under consideration are 3 global missions of which a number of parameters are varied. The first mission launches multiple separate deorbit kits. The second launches a mother craft with deorbit kits. The third launches an orbital tug which pulls the debris in a lower orbit, after which a deorbit kit performs the final deorbit burn. A RoM mass and cost comparison is presented. The research described in this paper has been conducted as part of an active debris removal study by the Advanced Study Group (ASG). The ASG is an interdisciplinary student group working at the DLR, analyzing existing technologies and developing new ideas into preliminary concepts.

van der Pas, Niels; Lousada, Joao; Terhes, Claudia; Bernabeu, Marc; Bauer, Waldemar

2014-09-01

169

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

NASA Technical Reports Server (NTRS)

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

1983-01-01

170

Isolation and preliminary crystallographic studies of two new phospholipases A2 from Vipera nikolskii venom  

PubMed Central

Snake-venom phospholipases A2 (PLA2s) represent a good model for studies of structure–function relationships, mainly because of their small size and diverse pharmacological and toxicological activities. To obtain new members of the abundant PLA2 family, the venom of the viper Vipera nikolskii was fractionated for the first time and two new proteins, VN5-3 and VN4-3, were isolated. Both proteins show phospholipase A2 activity and may possess neurotoxic activity. Based on the determined partial amino-acid sequences, the new proteins can be classified as basic Asp49 phospholipases A2. They were crystallized using the hanging-drop vapour-diffusion method and crystals of both proteins belong to space group R32, with similar unit-cell parameters: a = b = 76.29, c = 303.35?Å for protein VN5-3 and a = b = 76.28, c = 304.39?Å for protein VN4-3. Diffraction data sets to 3.0 and 2.2?Å resolution were collected and processed for the VN5-3 and VN4-3 crystals, respectively. Preliminary analysis indicates that there are two molecules in the asymmetric unit for both crystals. Further crystallographic studies will help in understanding the structural basis for the multiple functions of snake-venom PLA2s. PMID:16510990

Gao, Wei; Starkov, Vladislav G.; Tsetlin, Victor I.; Utkin, Yuri N.; Lin, Zheng-jiong; Bi, Ru-chang

2005-01-01

171

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

PubMed

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

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

2014-03-01

172

Purification, crystallization and preliminary X-ray crystallographic analysis of TssL from Vibrio cholerae.  

PubMed

The type VI secretion system (T6SS) is a macromolecular complex that is conserved in Gram-negative bacteria. The T6SS secretes effector proteins into recipient cells in a contact-dependent manner in order to accomplish cooperative and competitive interactions with the cells. Although the composition and mechanism of the T6SS have been intensively investigated across many Gram-negative bacteria, to date structural information on T6SS components from the important pathogen Vibrio cholerae has been rare. Here, the cloning, purification, crystallization and preliminary X-ray crystallographic analysis of the cytoplasmic domain of TssL, an inner membrane protein of the T6SS, from V. cholerae are reported. Diffraction data were collected to 1.5?Å resolution using synchrotron radiation. The crystal belonged to the hexagonal space group P61, with unit-cell parameters a = 78.4, b = 78.4, c = 49.5?Å. The successful structural characterization of TssL from V. cholerae will contribute to understanding the role of the membrane-associated subunits of the T6SS in more detail. PMID:25195905

Jeong, Jae-Hee; Chang, Jeong Ho; Kim, Yeon Gil

2014-09-01

173

Purification, crystallization and preliminary crystallographic investigation of FrnE, a disulfide oxidoreductase from Deinococcus radiodurans.  

PubMed

In prokaryotes, Dsb proteins catalyze the formation of native disulfide bonds through an oxidative folding pathway and are part of the cell machinery that protects proteins from oxidative stress. Deinococcus radiodurans is an extremophile which shows unparalleled resistance to ionizing radiation and oxidative stress. It has a strong mechanism to protect its proteome from oxidative damage. The genome of Deinococcus shows the presence of FrnE, a Dsb protein homologue that potentially provides the bacterium with oxidative stress tolerance. Here, crystallization and preliminary X-ray crystallographic analysis of FrnE from D. radiodurans are reported. Diffraction-quality single crystals were obtained using the hanging-drop vapour-diffusion method with reservoir solution consisting of 100?mM sodium acetate pH 5.0, 10% PEG 8000, 15-20% glycerol. Diffraction data were collected on an Agilent SuperNova system using a microfocus sealed-tube X-ray source. The crystal diffracted to 1.8?Å resolution at 100?K. The space group of the crystal was found to be P2?22?, with unit-cell parameters a=47.91, b=62.94, c=86.75?Å, ?=?=?=90°. Based on Matthews coefficient analysis, one monomer per asymmetric unit is present in the crystal, with a solvent content of approximately 45%. PMID:25372826

Panicker, Lata; Misra, Hari Sharan; Bihani, Subhash Chandra

2014-11-01

174

Collaborative annotation of 3D crystallographic models.  

PubMed

This paper describes the AnnoCryst system-a tool that was designed to enable authenticated collaborators to share online discussions about 3D crystallographic structures through the asynchronous attachment, storage, and retrieval of annotations. Annotations are personal comments, interpretations, questions, assessments, or references that can be attached to files, data, digital objects, or Web pages. The AnnoCryst system enables annotations to be attached to 3D crystallographic models retrieved from either private local repositories (e.g., Fedora) or public online databases (e.g., Protein Data Bank or Inorganic Crystal Structure Database) via a Web browser. The system uses the Jmol plugin for viewing and manipulating the 3D crystal structures but extends Jmol by providing an additional interface through which annotations can be created, attached, stored, searched, browsed, and retrieved. The annotations are stored on a standardized Web annotation server (Annotea), which has been extended to support 3D macromolecular structures. Finally, the system is embedded within a security framework that is capable of authenticating users and restricting access only to trusted colleagues. PMID:17900174

Hunter, J; Henderson, M; Khan, I

2007-01-01

175

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

NASA Technical Reports Server (NTRS)

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

James, John T.; Zalesak, Selina M.

2011-01-01

176

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

177

Hubble Space Telescope Snapshot Search for Planetary Nebulae in Globular Clusters of the Local Group  

E-print Network

Single stars in ancient globular clusters (GCs) are believed incapable of producing planetary nebulae (PNe), because their post-asymptotic-giant-branch evolutionary timescales are slower than the dissipation timescales for PNe. Nevertheless, four PNe are known in Galactic GCs. Their existence likely requires more exotic evolutionary channels, including stellar mergers and common-envelope binary interactions. I carried out a snapshot imaging search with the Hubble Space Telescope (HST) for PNe in bright Local Group GCs outside the Milky Way. I used a filter covering the 5007 A nebular emission line of [O III], and another one in the nearby continuum, to image 66 GCs. Inclusion of archival HST frames brought the total number of extragalactic GCs imaged at 5007 A to 75, whose total luminosity slightly exceeds that of the entire Galactic GC system. I found no convincing PNe in these clusters, aside from one PN in a young M31 cluster misclassified as a GC, and two PNe at such large angular separations from an M31 ...

Bond, Howard E

2015-01-01

178

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

NASA Astrophysics Data System (ADS)

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

Nelson, Mark; Allen, John P.

179

Conformal group and fundamental theorem for a class of symmetric * *spaces 1  

E-print Network

such spaces, called symmetric spaces with twist, are equi* *valent to Jordan triple systems (JTS), and we canonically associate* * a chart, called Jordan coordinates, such that Ep is represented by the usual

Bertram, Wolfgang - Institut de Mathématiques �lie Cartan, Université Henri Poincaré

180

The q-analog of the boson algebra, its representation on the Fock space, and applications to the quantum group  

NASA Astrophysics Data System (ADS)

In this paper, a realization of the q-deformed boson operators on the Fock space from a generally algebraic point of view is given. The representations of the quantum group (Cn)q are thereby constructed in terms of this realization. Some infinite- and finite-dimensional representations of the q-analog of the Heisenberg-Weyl algebra are obtained on certain quotient spaces. Finally, the q-deformed differential realization of quantum group given by Alvarez-Gaume, Gomez, and Sierra (Preprint CERN-Th 5369/89) is derived from the boson realization.

Sun, Chang-Pu; Ge, Mo-Lin

1991-03-01

181

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

Microsoft Academic Search

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

C. Campbell; M. Skovdal; A. Gibbs

2011-01-01

182

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

183

Preliminary neutron crystallographic study of human transthyretin  

PubMed Central

Preliminary studies of perdeuterated crystals of human transthyretin (TTR) have been carried out using the LADI-III and D19 diffractometers at the Institut Laue–Langevin in Grenoble. The results demonstrate the feasibility of a full crystallographic analysis to a resolution of 2.0?Å using Laue diffraction and also illustrate the potential of using monochromatic instruments such as D19 for higher resolution studies where larger crystals having smaller unit cells are available. This study will yield important information on hydrogen bonding, amino-acid protonation states and hydration in the protein. Such information will be of general interest for an understanding of the factors that stabilize/destabilize TTR and for the design of ligands that may be used to counter TTR amyloid fibrillogenesis. PMID:22102249

Haupt, Melina; Blakeley, Matthew P.; Teixeira, Susana C. M.; Mason, Sax A.; Mitchell, Edward P.; Cooper, Jonathan B.; Forsyth, V. Trevor

2011-01-01

184

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

185

Group space allowance has little effect on sow health, productivity, or welfare in a free-access stall system.  

PubMed

Free-access stalls allow sows to choose the protection of a stall or use of a shared group space. This study investigated the effect of group space width, 0.91 (SS), 2.13 (IS), and 3.05 (LS) m, on the health, production, behavior, and welfare of gestating sows. Nine replications of 21 (N = 189) gestating sows were used. At gestational d 35.4 ± 2.3, the pregnant sows were distributed into 3 pens of 7 sows, where they remained until 104.6 ± 3.5 d. Each treatment pen had 7 free-access stalls and a group space that together provided 1.93 (SS), 2.68 (IS), or 3.24 (LS) m(2)/sow. Baseline measurements were obtained before mixing. Back fat depth, BW, BCS, and lameness were measured monthly, and skin lesions were scored weekly. Blood was collected monthly for hematological, immunological, and cortisol analyses. Sow behavior was video recorded continuously during the initial 4 d of treatment and 24 h every other week thereafter. Behavior was analyzed for location, posture, pen investigation, social contact, and aggression. Skin response to the mitogen concanavalin A (Con A) was tested at mean gestational d 106. Litter characteristics including size and weight were collected at birth and weaning. The data were analyzed using a mixed model. Multiple comparisons were adjusted with the Tukey-Kramer and Bejamini-Hochberg methods. Group space allowance had no effect on any measure of sow health, physiology, or production (P ? 0.10). Sows in the SS, IS, and LS pens spent 77.88% ± 3.88%, 66.02% ± 3.87%, and 63.64% ± 3.91%, respectively, of their time in the free-access stalls (P = 0.12). However, SS sows used the group space less than IS and LS sows (P = 0.01). Overall, pen investigatory behavior was not affected by group space allowance (P = 0.91). Sows in the LS pens spent more time in a social group than SS sows (P = 0.02), whereas sows in IS pens were intermediate to, but not different from, the other treatments (P ? 0.10). The size of the social groups was also affected by the group space allowance (P = 0.03), with SS sows forming smaller groups than LS sows; again, IS sows were intermediate to, but not different from, the other treatments. Although the group space allowance had no measurable impact on the health, physiology, or productivity of the sows, the lower group space use and social contact of the SS sows reduced the behavioral diversity benefits of group housing and may indicate an avoidance of social stressors or a lack of physical comfort in the smallest pens. PMID:24668955

Mack, L A; Lay, D C; Eicher, S D; Johnson, A K; Richert, B T; Pajor, E A

2014-06-01

186

Ultraviolet-Optical Space Astronomy Beyond HST Conference (Origins Conference and UV-Optical Working Group Support)  

NASA Technical Reports Server (NTRS)

This grant supported three major activities, from 1997-2001. (1) Origins Conference. The funds from this grant were used, initially, to support a Conference on "Origins", held May 19-23, 1997 at Estes Park, CO and attended by a wide range of astronomers, planetary scientists, and astrobiologists. The scientific proceedings of this meeting were published in 1998 by the Astronomical Society of the Pacific: "Origins" (1998) "Proceedings of the International Origins Conference". (2) UV-Optical Space Astronomy. Conference Additional funds provided by the NASA Office of Space Science were used to support a meeting held August 5-7, 1998 at Boulder, CO and attended by ultraviolet and optical astronomers and instrumentalists interested in a UV-O successor to the Hubble Space Telescope. The scientific proceedings of this meeting were published in 1999: "Ultraviolet-Optical Space Astronomy Beyond the Hubble Space Telescope" (1999), NASA provided funds and commissioned the UVOWG (Ultraviolet-Optical Working Group), charged with recommending a set of fundamental scientific problems and new space missions in the UV/Optical wavelength bands. The working group was chaired by J. M. Shull, and included ten other astrophysicists. Their report was published as a "White Paper" (Nov. 1999) entitled "The Emergence of the Modern Universe: Tracing the Cosmic Web" available. The results of this report were used in the NASA Strategic Planning ("Roadmap") exercise and by the NRC Astronomy/Astrophysics Decade Committee.

Shull, J. Michael; Morse, Jon

2001-01-01

187

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

NASA Technical Reports Server (NTRS)

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

1972-01-01

188

INTRINSIC FINE-SCALE STRUCTURE IN COMPLEX MATERIALS: BEYOND GLOBAL CRYSTALLOGRAPHIC ANALYSIS  

SciTech Connect

Many important classes of materials owe their interesting properties to structures and patterns produced by local atomic deviations from ideal crystallographic positions. The pattern scale may vary from a few atomic spacings to many microns. In a macroscopic sample these deviations may still average to an ideal lattice while retaining the intrinsic fine-scale structures, or a phase transition may create a pattern of variants of a new crystallographic structure. We have carried out experiments on the formation of fine-scale structures in a range of materials, particularly those produced by phase transitions. We have used Resonant Ultrasound Spectroscopy for elastic properties and dissipation, neutron pair-distribution function, and electronic transport measurements to characterize samples. We have carried out extensive dynamical modeling based on Ginzberg-Landau formalisms to simulate the development and appearance of the structures. Our results highlight the importance of long-range strain fields and the intrinsic unstable equilibrium features of the materials studied.

A. MIGLIORI; ET AL

2000-12-01

189

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

190

Crystallization and preliminary crystallographic studies of PotA, a membrane-associated ATPase of the spermidine-preferential uptake system in Thermotoga maritima.  

PubMed

A membrane-associated ATPase, PotA, is a component of the spermidine-preferential uptake system in prokaryotes that plays an important role in normal cell growth by regulating the cellular polyamine concentration. No three-dimensional structures of membrane-associated ATPases in polyamine-uptake systems have been determined to date. Here, the crystallization and preliminary X-ray diffraction analysis of PotA from Thermotoga maritima are reported. Diffraction data were collected and processed to 2.7?Å resolution from both native and selenomethionine-labelled crystals. Preliminary crystallographic analysis revealed that the crystals belonged to the hexagonal space group P3?12 (or P3?12), with unit-cell parameters a=b=88.9, c=221.2?Å, ?=90, ?=90, ?=120°, indicating that a dimer was present in the asymmetric unit. PMID:24915082

Sugiyama, Shigeru; Kashiwagi, Keiko; Kakinouchi, Keisuke; Tomitori, Hideyuki; Kanai, Ken; Murata, Michio; Adachi, Hiroaki; Matsumura, Hiroyoshi; Takano, Kazufumi; Murakami, Satoshi; Inoue, Tsuyoshi; Mori, Yusuke; Igarashi, Kazuei

2014-06-01

191

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

192

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

193

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

2013-10-01

194

Spectroscopic, crystallographic, and docking studies of 3,4-dimethyl- N-((thiophen-2-yl)methylene)isoxazol-5-amine Schiff base  

NASA Astrophysics Data System (ADS)

A novel 3,4-dimethyl- N-((thiophen-2-yl)methylene)isoxazol-5-amine ( DMTMIA) Schiff base has been synthesized by condensation of 3,4-dimethyl-5-amine isoxazole with thiophene-2-carboxaldehyde and characterized by using elemental analysis, 1H NMR, 13C NMR, Mass, IR and UV-Visible spectroscopic techniques. The structure of DMTMIA has also been determined crystallographically. It crystallizes in the orthorhombic crystal system with Pbca space group. The unit cell dimensions of the Schiff base are a = 11.326(4), b = 12.198(4), c = 14.954(5) Å. The Schiff base was designed and energy minimization was carried out with the help of HyperChem software and subsequently structure activity study was employed to investigate the ability to stabilize DNA-Topoisomerase I. Docking results revealed that the Schiff base involved in van der Waals interactions.

Kumar, Ch. Vijay; Kumar, M. Pradeep; Tejaswi, S.; Shivaraj

2014-12-01

195

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

196

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

197

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

2012-01-01

198

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

2013-06-01

199

Determination of crystallographic intensities from sparse data  

PubMed Central

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

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

2015-01-01

200

Determination of crystallographic intensities from sparse data.  

PubMed

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

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

2015-01-01

201

Improved Crystallographic Structures using Extensive Combinatorial Refinement  

PubMed Central

Summary Identifying errors and alternate conformers, and modeling multiple main-chain conformers in poorly ordered regions are overarching problems in crystallographic structure determination that have limited automation efforts and structure quality. Here, we show that implementation of a full factorial designed set of standard refinement approaches, which we call ExCoR (Extensive Combinatorial Refinement), significantly improves structural models compared to the traditional linear tree approach, in which individual algorithms are tested linearly, and only incorporated if the model improves. ExCoR markedly improved maps and models, and reveals building errors and alternate conformations that were masked by traditional refinement approaches. Surprisingly, an individual algorithm that renders a model worse in isolation could still be necessary to produce the best overall model, suggesting that model distortion allows escape from local minima of optimization target function, here shown to be a hallmark limitation of the traditional approach. ExCoR thus provides a simple approach to improving structure determination. PMID:24076406

Nwachukwu, Jerome C.; Southern, Mark R.; Kiefer, James R.; Afonine, Pavel V.; Adams, Paul D.; Terwilliger, Thomas C.; Nettles, Kendall W.

2013-01-01

202

Preliminary crystallographic study of turkey gizzard vinculin.  

PubMed

Vinculin is a 117 kDa microfilament-associated protein located at the cytoplasmic aspects of focal contacts and cell-cell adherens type junctions. In both sites, vinculin participates in the formation of a submembrane 'plaque' structure which is responsible for the attachment of actin filaments to the plasma membrane. Vinculin consists of 1066 amino acids, which form a large 90 kDa globular head domain and a rod-like 29 kDa tail domain. The two domains are separated by several stretches of proline residues where the major proteolytic cleavage sites are located. The experimental procedure for isolation and purification of vinculin from smooth muscle has been developed and crystals of native vinculin suitable for X-ray analysis have been obtained. The homogeneity of the vinculin solution was analyzed prior to crystallization using dynamic light scattering. Crystals of vinculin have been obtained in buffer containing 2 mg ml(-1) protein, 0.9 M ammonium sulfate, 0.1 M MES pH 6.5 using both the hanging-drop and sitting-drop vapour-diffusion methods. The crystals have the form of rhombic plates and grow to maximal dimensions of 0.3 x 0.3 x 0.05 mm in two weeks. Preliminary X-ray data show that the crystals diffract to 3.5 A resolution at the X11 beamline of DESY and belong to the monoclinic space group P2(1). Crystal unit-cell parameters are estimated to be a = 57, b = 351, c = 70 A, alpha = 90, beta = 113, gamma = 90 degrees. PMID:10944352

Kogan, O; Yarden, A; Gimona, M; Geiger, B; Safro, M

2000-08-01

203

Crystallization and preliminary X-ray crystallographic analysis of ?-glucosidase HaG from Halomonas sp. strain H11.  

PubMed

The ?-glucosidase HaG from the halophilic bacterium Halomonas sp. strain H11 catalyzes the hydrolysis of the glucosidic linkage at the nonreducing end of ?-glucosides, such as maltose and sucrose, to release ?-glucose. Based on its amino-acid sequence, this enzyme is classified as a member of glycoside hydrolase family 13. HaG has three unique characteristics: (i) a very narrow substrate specificity, almost exclusively hydrolyzing disaccharides; (ii) activation by monovalent cations, such as K(+), Rb(+), Cs(+) and NH4(+); and (iii) high transfer activity of the glucose moiety to the OH group of low-molecular-weight compounds, including glycerol and 6-gingerol. Crystallographic studies have been performed in order to understand these special features. An expression vector was constructed and recombinant HaG protein was overexpressed, purified and crystallized. A data set to 2.15?Å resolution was collected and processed. The crystal belonged to space group P212121, with unit-cell parameters a = 60.2, b = 119.2, c = 177.2?Å. The structure has been determined by molecular replacement using the isomaltulose synthase PalI as the search model (PDB entry 1m53). PMID:24699739

Shen, Xing; Saburi, Wataru; Gai, Zuo-Qi; Komoda, Keisuke; Yu, Jian; Ojima-Kato, Teruyo; Kido, Yusuke; Matsui, Hirokazu; Mori, Haruhide; Yao, Min

2014-04-01

204

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

205

Iterative Spatial Sequence Estimator for Multi-Group Space Time Trellis Coded Systems  

E-print Network

-Ghadhban, Maruf Mohammad, and B. Woerner Mobile and Portable Radio Research Group Virginia Tech E-Mail: {maruf with soft-input soft- output (SISO) maximum a posteriori (MAP) algorithm as the detection stage in the multi-group receiver. It will iterate and share soft information with the soft decoding stage. The remainder

Al-Ghadhban, Samir

206

REVIEW ARTICLE From SARS to MERS: crystallographic studies on  

E-print Network

REVIEW ARTICLE From SARS to MERS: crystallographic studies on coronaviral proteases enable antiviral drug design Rolf Hilgenfeld Institute of Biochemistry, Center for Structural and Cell Biology design Correspondence R. Hilgenfeld, Institute of Biochemistry, Center for Structural and Cell Biology

Groppe, Sven

207

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

NASA Technical Reports Server (NTRS)

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

1983-01-01

208

Crystallization and preliminary X-ray analysis of thiaminase I from Bacillus thiaminolyticus: space group change upon freezing of crystals.  

PubMed

Thiaminase I (Mr = 42 100) from B. thiaminolyticus, expressed in E. coli, has been crystallized by the vapor-diffusion method. Three crystal forms, two of which grew from 0.1 M sodium acetate (pH = 4.6), 0.2 M ammonium sulfate and 30%(w/v) PEG 2000, have been examined by X-ray analysis. One crystal form diffracted to 2.5 A at room temperature, was orthorhombic, and had unit-cell edges of a = 87.7, b = 120.5 and c = 76.7 A with space group P212121. A self-Patterson map showed a strong peak indicating noncrystallographic translational pseudosymmetry with (u, v, w) = (0.03, 0.0, 0.5). When these crystals were frozen at liquid-nitrogen temperatures, a second crystal form was observed which had unit-cell dimensions a = 85.5, b = 117.5 and c = 36.6 A with space group P21212. A third crystal form grew from 0.1 M Tris (pH = 8.5), 0.2 M sodium acetate trihydrate and 28%(w/v) PEG 6000 to produce orthorhombic crystals of space group P212121 with cell edges of a = 114.4, b = 123.1 and c = 92.5 A. PMID:9761925

Campobasso, N; Begun, J; Costello, C A; Begley, T P; Ealick, S E

1998-05-01

209

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

PubMed Central

An expanding body of literature explores the role of African church groups in facilitating or hindering the support of people living with AIDS and challenging or contributing to HIV/AIDS-related stigma. Treating church groups as social spaces in which HIV/AIDS-related stigma may potentially be challenged, we systematically review this literature, identifying five themes that highlight the complex and contradictory role of the church as a potential agent of health-enhancing social change. In many ways the church perpetuates HIV/AIDS-related stigma through (i) moralistic attitudes and (ii) its reinforcement of conservative gender ideologies. However some churches have managed move towards action that makes a more positive contribution to HIV/AIDS management through (iii) promoting various forms of social control for HIV prevention, (iv) contributing to the care and support of the AIDS-affected and (v) providing social spaces for challenging stigmatising ideas and practices. We conclude that church groups, including church leadership, can play a key role in facilitating or hindering the creation of supportive social spaces to challenge stigma. Much work remains to be done in developing deeper understandings of the multi-layered factors that enable some churches, but not others, to respond effectively to HIV/AIDS. PMID:20668927

Skovdal, M.; Gibbs, A.

2012-01-01

210

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

SciTech Connect

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

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

2012-04-30

211

Evaluating a Safe Space Training for School Counselors and Trainees Using a Randomized Control Group Design  

ERIC Educational Resources Information Center

School counselors need to advocate and act as an ally for all students. Safe Space, a training designed to facilitate competency for working with and serving LGBTQ youth (i.e., LGBTQ competency), has received increased attention in the field of school counseling. However, limited empirical support exists for training interventions such as Safe…

Byrd, Rebekah; Hays, Danica G.

2014-01-01

212

Determination of the orbit spaces of non-coregular compact linear groups with one relation among the basic polynomial invariants in the $\\\\hat P$-matrix approach  

Microsoft Academic Search

Invariant functions under the transformations of a compact linear group $G$ acting in $\\\\real^n$ can be expressed in terms of functions defined in the orbit space of $G$. We develop a method to determine the isotropy classes of the orbit spaces of all the real linear groups whose integrity bases (IB) satisfy only one independent relation. The method is tested

G. Sartori; G. Valente

2000-01-01

213

Unsteady Reynolds averaged Navier-Stokes simulation of the post-critical flow around a closely spaced group of silos  

NASA Astrophysics Data System (ADS)

During a storm in October 2002, wind induced ovalling vibrations were observed on several empty silos of a closely spaced group (pitch-to-diameter ratio of 1.05) consisting of 8 by 5 silos in the port of Antwerp (Belgium). Numerical simulations of the turbulent wind flow are performed to clarify the occurrence of the observed ovalling vibrations near the lee side corner of the group by studying the dynamic wind pressures on the silo surfaces and linking to the dynamic properties of the silo structures. As the orientation of the group largely affects the pressure distribution around the cylinders of the group, the influence of the angle of incidence of the wind flow on these ovalling vibrations is examined while other parameters, such as spacing ratio and Reynolds number are unchanged. To achieve results within a reasonable computation time, 2D unsteady Reynolds averaged Navier-Stokes (URANS) equations using Menter's shear stress transport turbulence model were performed. In order to elucidate the influence of the applied turbulence model and to qualitatively validate the spatial and temporal discretization of the 2D highly turbulent post-critical (Re=1.24×107) flow simulations for the silo group, single cylinder simulations were used. The geometric resemblance of the group arrangement with rectangular cylinders on the one hand and of the interstitial spaces with tube arrays (e.g. heat exchangers) on the other hand is used to qualitatively compare the observed flow phenomena. The simulations show that the silo group can be treated neither as a tube array nor as a solid bluff body. Subsequent linking of dynamic wind pressures to dynamic properties of the silo structures reveals strong narrow band frequency peaks in the turbulent pressure coefficient spectra of the silos near the lee side corners of the group that match the structural natural frequencies of the third and fourth ovalling mode shape of the silos. This match indicates a forced, resonant response which corresponds with the observed pattern of ovalling vibrations with three and four circumferential wavelengths. While the precise physical excitation mechanism is not yet fully understood, the simulations exclude discrete vortex shedding and since fluidelastic instability could not be considered, only turbulent buffeting remains which could very well give rise to the narrow band wake phenomena causing the ovalling silo wall vibrations.

Hillewaere, J.; Dooms, D.; Van Quekelberghe, B.; Degroote, J.; Vierendeels, J.; De Roeck, G.; Lombaert, G.; Degrande, G.

2012-04-01

214

Decomposable representations and Lagrangian submanifolds of moduli spaces associated to surface groups  

Microsoft Academic Search

The importance of explicit examples of Lagrangian submanifolds of moduli spaces is revealed by papers such as Dostoglou and\\u000a Salamon (Ann. of Math (2), 139(3), 581–640, 1994) and Salamon (Proceedings of the international congress of mathematicians,\\u000a vol.1, 2 (Zürich, 1994), pp. 526–536. Birkhäuser, Basel, 1995): given a 3-manifold M with boundary ?M = ?, Dostoglou and Salamon use such examples to

Florent Schaffhauser

2008-01-01

215

The group approach to AdS space propagators: a fast algorithm  

Microsoft Academic Search

In this paper we show how the method of [4] for the calculation of two-point functions in (d + 1)-dimensional AdS space can be simplified. This results in an algorithm for the evaluation of the two-point functions as linear combinations of Legendre functions of the second kind. This algorithm can be easily implemented on a computer. For the sake of

Thorsten Leonhardt; Werner Rühl; Ruben Manvelyan

2004-01-01

216

The redshift-space neighborhoods of 36 loose groups. 2: Analysis  

NASA Technical Reports Server (NTRS)

We explore the kinematics of 36 rich RGH89 groups identified from the first two complete slices of the CfA redshift survey. These groups have more than five members identified by a friends-of-friends algorithm at a number density contrast delta rho/rho greater than or equal to 80. To examine the stability of the determination of the velocity dispersion for these systems, we compare results for the original 232 members with results for a larger redshift sample, including 334 fainter members in the redshift neighborhoods. On average, we double the number of group members in each system. The observed distribution of velocity dispersions is stable. In fact, the velocity dispersion based on the original members identified in the CfA redshift survey is a reliable predictor of the value for the enlarged sample in an individual group. The velocity dispersion is thus a stable physical parameter for discrimination among systems galaxies. A larger sample of groups, particularly one selected from a distance limited catalog, should provide an interesting constraint on models for the formation of large-scale structure. We take H(sub 0) = km/s/Mpc.

Ramella, Massimo; Geller, Margaret J.; Hurchra, John P.; Thorstensen, John R.

1995-01-01

217

Job Scheduling with Lookahead Group Matchmaking for Time/Space Sharing on Multi-core Parallel Machines  

NASA Astrophysics Data System (ADS)

Multi-core nodes of parallel machines may only provide gradual performance improvement per application due to competition on resources like the cache. As shown in our earlier work, spreading out applications over as many nodes as possible or letting different applications with potentially complementary characteristics (semi time) share each node by allocating different cores to them may provide better performance. In the latter case, groups of jobs may be necessary to obtain balanced resource utilization due to different sizes of jobs. We present a scheduler G-LOMARC-TS which can match groups of jobs and consider both space- and time-sharing allocation. Since matchmaking may select jobs further down in the waiting queue, fairness in regards to possible delays of the other jobs is watched and delays are kept within certain bounds. This results in a large number of possible combinations. A number of heuristics to select the most promising combinations make it possible to deal with the NP-completeness of the problem. We show that our scheduler improves utilization of high-load phases by about 27% and subsequently average response times by about 36% (and 53% for long jobs) compared to space sharing scheduling for normal workloads. Additionally the scheduler can handle much higher workloads than a space-sharing scheduler.

Zeng, Xijie; Sodan, Angela C.

218

Creating Spaces for Critical Transformative Dialogues: Legitimising Discussion Groups as Professional Practice  

ERIC Educational Resources Information Center

Focussed dialogue (as lived and living practices) can have a powerful role in renewing professional practice, advancing its sustainability and development as administrative and political systems colonise the practices of teachers and teacher educators. However, participating in discussion groups for many teachers, including those in academia, is…

Edwards-Groves, Christine J.

2013-01-01

219

The Uncertainty Principle: Group Theoretic Approach, Possible Minimizers and Scale-Space Properties  

Microsoft Academic Search

The uncertainty principle is a fundamental concept in the context of signal and image processing, just as much as it has been in the framework of physics and more recently in harmonic analysis. Uncertainty principles can be derived by using a group theoretic approach. This approach yields also a formalism for finding functions which are the minimizers of the uncertainty

Chen Sagiv; Nir A. Sochen; Yehoshua Y. Zeevi

2006-01-01

220

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

SciTech Connect

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. [Physics Department, University of Lampung (UNILA), Jl. Sumantri Brojonegoro No. 1 Bandar Lampung (Indonesia); Su'ud, Z.; Waris, A.; Khotimah, S. N. [Physics Department, Bandung Institute of Technology (ITB), Jl. Ganesha 10 Bandung (Indonesia)

2010-06-22

221

The group approach to AdS space propagators: A fast algorithm  

E-print Network

In this letter we show how the method of [4] for the calculation of two-point functions in d+1-dimensional AdS space can be simplified. This results in an algorithm for the evaluation of the two-point functions as linear combinations of Legendre functions of the second kind. This algorithm can be easily implemented on a computer. For the sake of illustration, we displayed the results for the case of symmetric traceless tensor fields with rank up to l=4.

Thorsten Leonhardt; Ruben Manvelyan; Werner Ruhl

2003-10-07

222

Space  

NSDL National Science Digital Library

This unit begins by introducing students to the historical motivation for space exploration. They learn about the International Space Station, including current and futuristic ideas that engineers are designing to propel space research. Then they learn about the physical properties of the Moon, and think about what types of products engineers would need to design in order for humans to live on the Moon. Lastly, students learn some descriptive facts about asteroids, such as their sizes and how that relates to the potential danger of an asteroid colliding with the Earth.

Integrated Teaching And Learning Program

223

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

224

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

225

Between-group behaviour in health care: gaps, edges, boundaries, disconnections, weak ties, spaces and holes. A systematic review  

PubMed Central

Background Gaps are typically regarded as a problem to be solved. People are stimulated to close or plug them. Researchers are moved to fill deficits in the literature in order to realise a more complete knowledge base, health authorities want to bridge policy-practice disconnections, managers to secure resources to remedy shortfalls between poor and idealised care, and clinicians to provide services to patients across the divides of organisational silos. Despite practical and policy work in many health systems to bridge gaps, it is valuable to study research examining them for the insights provided. Structural holes, spaces between social clusters and weak or absent ties represent fissures in networks, located in less densely populated parts of otherwise closely connected social structures. Such gaps are useful as they illustrate how communication potentially breaks down or interactivity fails. This paper discusses empirical and theoretical work on this phenomenon with the aim of analysing a specific exemplar, the structures of silos within health care organisations. Methods The research literature on social spaces, holes, gaps, boundaries and edges was searched systematically, and separated into health [n = 13] and non-health [n = 55] samples. The health literature was reviewed and synthesised in order to understand the circumstances between stakeholders and stakeholder groups that both provide threats to networked interactions and opportunities to strengthen the fabric of organisational and institutional inter-relationships. Results The research examples illuminate various network structure characteristics and group interactions. They explicate a range of opportunities for improved social and professional relations that understanding structural holes, social spaces and absent ties affords. A principal finding is that these kinds of gaps illustrate the conditions under which connections are strained or have been severed, where the limits of integration between groups occurs, the circumstances in which social spaces are or need to be negotiated and the way divides are bridged. The study's limitations are that it is bounded by the focus of attention and the search terms used and there is yet to be developed a probabilistic, predictive model for gaps and how to connect them. Conclusions Gaps offer insights into social structures, and how real world behaviours of participants in workplaces, organisations and institutions are fragile. The paper highlights the circumstances in which network disjunctures and group divides manifest. Knowledge of these phenomenon provides opportunities for working out ways to improve health sector organisational communications, knowledge transmission and relationships. PMID:21134295

2010-01-01

226

Purification, crystallization and preliminary crystallographic analysis of the 16S rRNA methyltransferase RsmI from Escherichia coli.  

PubMed

RsmI and RsmH are AdoMet-dependent methyltransferases that are responsible for the 2'-O-methylation and N(4)-methylation of C1402 of Escherichia coli 16S rRNA, respectively. Modification of this site has been found to play a role in fine-tuning the shape and function of the P-site to increase the decoding fidelity. It is interesting to study the mechanism by which C1402 can be methylated by both RsmI and RsmH. The crystal structure of RsmH in complex with AdoMet and cytidine has recently been determined and provided some implications for N(4)-methylation of this site. Here, the purification and crystallization of RsmI as well as its preliminary crystallographic analysis are reported. Co-crystallization of RsmI with AdoMet was carried out by the sitting-drop vapour-diffusion method and X-ray diffraction data were collected to 2.60?Å resolution on beamline 1W2B at BSRF. The crystal contained three molecules per asymmetric unit and belonged to space group C2, with unit-cell parameters a = 121.9, b = 152.5, c = 54.2?Å, ? = 93.4°. PMID:25195904

Zhao, Mohan; Wang, Li; Zhang, Heng; Dong, Yuhui; Gong, Yong; Zhang, Linbo; Wang, Jian

2014-09-01

227

Purification, crystallization and preliminary crystallographic analysis of KatB, a manganese catalase from Anabaena PCC 7120.  

PubMed

Catalases are enzymes that play an important role in the detoxification of hydrogen peroxide (H2O2) in aerobic organisms. Among catalases, haem-containing catalases are ubiquitously distributed and their enzymatic mechanism is very well understood. On the other hand, manganese catalases that contain a bimanganese core in the active site have been less well characterized and their mode of action is not fully understood. The genome of Anabaena PCC 7120 does not show the presence of a haem catalase-like gene; instead, two ORFs encoding manganese catalases (Mn-catalases) are present. Here, the crystallization and preliminary X-ray crystallographic analysis of KatB, one of the two Mn-catalases from Anabaena, are reported. KatB was crystallized using the hanging-drop vapour-diffusion method with PEG 400 as a precipitant and calcium acetate as an additive. Diffraction data were collected in-house on an Agilent SuperNova system using a microfocus sealed-tube X-ray source. The crystal diffracted to 2.2?Å resolution at 100?K. The tetragonal crystal belonged to space group P4(1)2(1)2 (or enantiomer), with unit-cell parameters a = b = 101.87, c = 138.86?Å. Preliminary X-ray diffraction analysis using the Matthews coefficient and self-rotation function suggests the presence of a trimer in the asymmetric unit. PMID:24192374

Bihani, Subhash Chandra; Chakravarty, Dhiman; Ballal, Anand

2013-11-01

228

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

229

The effect of spacing transverse to the wave direction on the Morison force coefficients in two cylinder groups  

SciTech Connect

This paper provides some results from an experimental study currently being carried out in the Michell laboratory at the University of Melbourne. The principal purpose of the study is to investigate the Morison in-line hydrodynamic force characteristics of slender surface-piercing multi-cylinder structures. The test program has been tailored to provide more detailed observations within the close-spaced region (Separation/Diameter ratio, s/D < 2) of the group interference effect in such multi-cylinder structures over the Keulegan Carpenter range 0 < KC < 20 which encompasses the inertia force dominant Morison regime (KC < 5), as well as the so-called troublesome region (5 < KC < 15) where both drag and inertia force components are significant. Results currently in hand for the side-by-side two-cylinder group configuration are presented which clearly depict the characteristics of this interference effect.

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

1995-12-31

230

Evolution equations invariant under two-dimensional space-time Schrödinger group  

NASA Astrophysics Data System (ADS)

The most general second order evolution equation ?t+F(x,t,??*,?x,?x*,?xx, ?xx*)=0, invariant under the Galilei, Galilei-similitude, and Schrödinger groups in two dimensions, is constructed. A preliminary step is a classification of all possible realizations of the corresponding Lie algebras of vector fields in R2×C parametrized by x, t, ?, and ?*. Applications of this study include the investigation of nonlinear alternatives to quantum mechanics and nonrelativistic classical field theories. Among the Schrödinger invariant equations, in particular, are found integrable equations, linearizable by contact transformations.

Rideau, G.; Winternitz, P.

1993-02-01

231

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

232

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

PubMed

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

Morton, Alison; Forsey, Philippa

2013-05-01

233

Localization properties of random-mass Dirac fermions from real-space renormalization group.  

PubMed

Localization properties of random-mass Dirac fermions for a realization of mass disorder, commonly referred to as the Cho-Fisher model, are studied on the D-class chiral network. We show that a simple renormalization group (RG) description captures accurately a rich phase diagram: thermal metal and two insulators with quantized ?(xy), as well as transitions (including critical exponents) between them. Our main finding is that, even with small transmission of nodes, the RG block exhibits a sizable portion of perfect resonances. Delocalization occurs by proliferation of these resonances to larger scales. Evolution of the thermal conductance distribution towards a metallic fixed point is synchronized with evolution of signs of transmission coefficients, so that delocalization is accompanied with sign percolation. PMID:21770661

Mkhitaryan, V V; Raikh, M E

2011-06-24

234

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

235

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

NASA Astrophysics Data System (ADS)

We study square lattice space-group symmetry fractionalization in a family of exactly solvable models with Z2 topological order in two dimensions. In particular, we have obtained a complete understanding of which distinct types of symmetry fractionalization (symmetry classes) can be realized within this class of models, which are generalizations of Kitaev's Z2 toric code to arbitrary lattices. This question is motivated by earlier work of Essin and one of us (M. H.) [Phys. Rev. B 87, 104406 (2013), 10.1103/PhysRevB.87.104406], where the idea of symmetry classification was laid out, and which, for square lattice symmetry, produces 2080 symmetry classes consistent with the fusion rules of Z2 topological order. This approach does not produce a physical model for each symmetry class, and indeed there are reasons to believe that some symmetry classes may not be realizable in strictly two-dimensional systems, thus raising the question of which classes are in fact possible. While our understanding is limited to a restricted class of models, it is complete in the sense that for each of the 2080 possible symmetry classes, we either prove rigorously that the class cannot be realized in our family of models, or we give an explicit model realizing the class. We thus find that exactly 487 symmetry classes are realized in the family of models considered. With a more restrictive type of symmetry action, where space-group operations act trivially in the internal Hilbert space of each spin degree of freedom, we find that exactly 82 symmetry classes are realized. In addition, we present a single model that realizes all 26=64 types of symmetry fractionalization allowed for a single anyon species (Z2 charge excitation), as the parameters in the Hamiltonian are varied. The paper concludes with a summary and a discussion of two results pertaining to more general bosonic models.

Song, Hao; Hermele, Michael

2015-01-01

236

Inter-Agency Consultative Group for Space Science (IACG): Handbook of Missions and Payloads  

NASA Technical Reports Server (NTRS)

The ACE spacecraft design is based on the Charge Composition Explorer (CCE) built by Johns Hopkins University (JHU) and the Applied Physics Lab (APL) for the AMPTE program. ACE is designed as a spinning spacecraft with its spin axis aligned to the Earth-Sun axis. The ACE launch weight will be approx. 633 kg, including 105 kg of scientific instruments and 184 kg of propellant. Using a Delta-class expendable launch vehicle, ACE will be launched into an L1 libration point (240 R(sub e)) orbit. Telemetry will be 6.7 kbps average, using tape recorder storage with daily readout to DSN. The experiment power requirement is approximately 76 W nominal and 96 W peak. The prime objective of the ACE mission is: (1) to determine accurate elemental and isotropic abundances including solar matter, local interstellar matter and local galactic matter; (2) to study the origin of elements and evolutionary processing in galactic nucleosynthesis, galactic evolution, origin and evolution of the solar system; (3) to study coronal formation and solar-wind acceleration processes; and (4) to study particle acceleration and transport, including coronal shock acceleration, stochastic flare acceleration, interplanetary shock acceleration, and interstellar acceleration and propagation. To accomplish this objective, ACE will perform comprehensive and coordinated determinations of the elemental and isotopic composition of energetic nuclei accelerated on the Sun, in interplanetary space, and from galactic sources. These observations will span five decades in energy, from solar wind to galactic cosmic ray energies, and will cover the element range from H-1 to Zr-40. Comparison of these samples of matter will be used to study the origin and subsequent evolution of both solar system and galactic material by isolating the effects of fundamental processes that include nucleosynthesis, charged and neutral particle separation, bulk plasma acceleration, and the acceleration of suprathermal and high-energy particles.

1994-01-01

237

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

238

Detailed insights from microarray and crystallographic studies into carbohydrate  

E-print Network

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

Davis, Ben G.

239

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

PubMed

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

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

2014-02-17

240

Investigation of Some Potent Medicinal Plants of N.E.INDIA with Respect to Thermophysical, Chromatographic and Crystallographic Properties  

NASA Astrophysics Data System (ADS)

North East India is readily available of various kinds of medicinal plants. A lot of studies on thermophysical properties of plant leaves, fluids, stems and roots had already been made[3,4,8]. In the present studies of thermophysical properties, chromatographic and crystallographic properties of specific medicinal plant leaves (Azadirechta indica)A, (Vinca rosea)B, (Clerodrendrum colebrookianum)C, (Osimum sanctum)D and fruits (Chisocheton paniculatus) E, and (Cudrania javanensis) F have been made plant based drugs for curing for different chronic diseases. The thermophysical properties of these leaves and fruits have been studies with XRD, XRF, TG, DTG, DTA, and DSC thermograms. From weight loss(%), time and temperature variations, the Activation Energies of these medicinal plant samples have been computed. The thermal stability is found more for the fruits samples than that of the leave samples. Thermal behaviours of all six samples have shown hygroscopic behaviour. The results TG, DTG and DTA thermograms confirmed that all samples show similar dehydration and decomposition reactions and hydrophilic nature. Both chromatographic techniques thin layer (TLC) and Column chromatography have been used for separation of components of the mixtures of samples. From these methods of the fruit sample E a pure crystalline white solids have been identified and confirm them as (MK 01) ?-isomer. Our interest to study the molecular and crystal structure of the sample E. The single crystal of (MK 01) is found to be orthorhombic cell with lattice parameters a = 10?699(3)Å b = 15?5100(4)Å c = 16?626(4)Å ? = 90° ? = 90° ? = 90° with space group P212121 Again from fruit sample F a light yellow solid is isolated and on crystallization give crystalline solid MN-01 and MN-02 and it is confirmed that these two compounds are unsaturated isoflavonoids. The single crystal of MN-01 has been found monoclinic with lattice parameters a = 6.2374(11)Å, b = 8.4243(11)Å, c = 21.181(4)Å, ? = 96.083(13)°, ? = 95.602(10)° and ? = 107.419(7)° with Space group P-1. Again single crystal MN-02 has been found monoclinic with lattice parameters being a = 25.2732 Å, b = 7.4414 Å, c = 22.3113 Å, ? = 90°, ? = 93.063°, ? = 90°, with space group C2/c.

Bora, M. N.; Kalita, Mahendra

2010-06-01

241

Calculating field emission current in nanodiodes—A multi-group formalism with space charge and exchange-correlation effects  

NASA Astrophysics Data System (ADS)

Inclusion of electron-electron interaction is essential in nano-diodes to understand the underlying physical phenomenon and tailor devices accordingly. However, both space charge and exchange-correlation interaction involve electrons at different energies and hence a self-consistent multi-energy-group solution of the Schrödinger-Poisson system is required. It is shown here that the existence of a limiting density-dependent potential at low applied voltages allows calculation of the field emission current. Despite additional interactions, a Fowler-Nordheim behaviour is observed. It is also found that the exchange-correlation potential dominates at these voltages in nanogaps and possibly leads to a higher turn-on voltage.

Biswas, Debabrata; Kumar, Raghwendra

2014-03-01

242

Recovery of Crystallographic Texture in Remineralized Dental Enamel  

PubMed Central

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

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

2014-01-01

243

Recovery of crystallographic texture in remineralized dental enamel.  

PubMed

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

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

2014-01-01

244

Inorganic structures in space group P3m1; coordinate analysis and systematic prediction of new ferroelectrics.  

PubMed

ICSD Release 2007/1 contains 47 families of inorganic crystal structures, some single-member only, within the 311 entries listed under the polar space group P3m1. Coordinate analysis reveals 12 such families to be candidate ferroelectrics, over a range of confidence levels. Selection is based on the detection of an approach to nonpolar supergroup symmetry, within specified limits, by the atomic arrangement as reported in a confirmed polar space group. The primary source of uncertainty in such predictions is the reliability of the underlying structural determination. The candidates include In(2)ZnS(4), TlSn(2)F(5), Cu(7)Te(4), NaMnSe(2), Na(2)In(2)(Mo(3)O(8))(MoO(4))(2), Nb(3)Br(7)S, Nb(3)TeI(7), fencooperite, Bi(HCOO)(3), Li(NpO(2))(CO(3))(H(2)O)(2), LiPtD(0.66) and Ag(3)(MoO(3)F(3))(Ag(3)(MoO(4))Cl). A total of 20 structures examined are likely to be nonpolar, a further 20 have reduced predictive properties and three others are more likely to retain P3m1 symmetry over a wide thermal range. Substantial uncertainties associated with many of the listed 163 CdI(2), 69 ZnS and 10 SiC polytype structures, together with their low potential for use as possible ferroelectrics, led to their exclusion from fuller analysis. PMID:18641444

Abrahams, S C

2008-08-01

245

Expression, purification, crystallization and X-ray crystallographic studies of different redox states of the active site of thioredoxin 1 from the whiteleg shrimp Litopenaeus vannamei.  

PubMed

Thioredoxin (Trx) is a 12?kDa cellular redox protein that belongs to a family of small redox proteins which undergo reversible oxidation to produce a cystine disulfide bond through the transfer of reducing equivalents from the catalytic site cysteine residues (Cys32 and Cys35) to a disulfide substrate. In this study, crystals of thioredoxin 1 from the Pacific whiteleg shrimp Litopenaeus vannamei (LvTrx) were successfully obtained. One data set was collected from each of four crystals at 100?K and the three-dimensional structures of the catalytic cysteines in different redox states were determined: reduced and oxidized forms at 2.00?Å resolution using data collected at a synchrotron-radiation source and two partially reduced structures at 1.54 and 1.88?Å resolution using data collected using an in-house source. All of the crystals belonged to space group P3212, with unit-cell parameters a = 57.5?(4), b = 57.5?(4), c = 118.1?(8)?Å. The asymmetric unit contains two subunits of LvTrx, with a Matthews coefficient (VM) of 2.31?Å(3)?Da(-1) and a solvent content of 46%. Initial phases were determined by molecular replacement using the crystallographic model of Trx from Drosophila melanogaster as a template. In the present work, LvTrx was overexpressed in Escherichia coli, purified and crystallized. Structural analysis of the different redox states at the Trx active site highlights its reactivity and corroborates the existence of a dimer in the crystal. In the crystallographic structures the dimer is stabilized by several interactions, including a disulfide bridge between Cys73 of each LvTrx monomer, a hydrogen bond between the side chain of Asp60 of each monomer and several hydrophobic interactions, with a noncrystallographic twofold axis. PMID:23695560

Campos-Acevedo, Adam A; Garcia-Orozco, Karina D; Sotelo-Mundo, Rogerio R; Rudiño-Piñera, Enrique

2013-05-01

246

A Commutative Model of a Representation of the Group O ( n , 1) X and a Generalized Lebesgue Measure in the Space of Distributions  

Microsoft Academic Search

For an irreducible unitary representation of an O(n, 1) current group, we consider a commutative model obtained by diagonalization with respect to a maximal unipotent subgroup. This model leads to a new measure on the space of distributions. The measure is invariant with respect to an infinite-dimensional linear symmetry group.

M. I. Graev; A. M. Vershik

2005-01-01

247

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

NASA Technical Reports Server (NTRS)

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

Wu, S. T.

1989-01-01

248

Crystallization and preliminary crystallographic analysis of the Clostridium perfringens enterotoxin.  

PubMed

Clostridium perfringens is a Gram-positive anaerobic species of bacterium that is notable for its ability to produce a plethora of toxins, including membrane-active toxins (alpha-toxins), pore-forming toxins (-toxins) and binary toxins (iota-toxins). Here, the crystallization of the full-length wild-type C. perfringens enterotoxin is reported, which is the causative agent of the second most prevalent food-borne illness in the United States and has been implicated in many other gastrointestinal pathologies. Several crystal forms were obtained. However, only two of these optimized crystal forms (I and II) were useable for X-ray diffraction data collection. The form I crystals diffracted to d(min) = 2.7 A and belonged to space group C2, while the form II crystals diffracted to d(min) = 4 A and belonged to space group P2(1)3. PMID:20606275

Briggs, David C; Smedley, James G; McClane, Bruce A; Basak, Ajit K

2010-07-01

249

A database survey of molecular and crystallographic symmetry.  

PubMed

The point of contact between molecular and crystallographic symmetries is that of the Wyckoff position, the position at which a molecule resides in a crystal structure. These Wyckoff positions may have the same symmetry as the molecules, some symmetry in common with the molecules or no symmetry at all. Using CSDSymmetry [Yao et al. (2002). Acta Cryst. B58, 640-646], a relational database containing information pertaining to the symmetry of molecules and the crystal structures that play host to them, the distribution of molecules over Wyckoff positions and the occupancy of Wyckoff positions in crystal structures is presented. Analysis of these data has led to the characterization of some relationships between molecular and crystallographic symmetry. PMID:14586084

Pidcock, Elna; Motherwell, W D Samuel; Cole, Jason C

2003-10-01

250

Finite part of operator K-theory for groups finitely embeddable into Hilbert space and the degree of non-rigidity of manifolds.  

E-print Network

In this paper, we study lower bounds on the K-theory of the maximal $C^*$-algebra of a discrete group based on the amount of torsion it contains. We call this the finite part of the operator K-theory and give a lower bound that is valid for a large class of groups, called the "finitely embeddable groups". The class of finitely embeddable groups includes all residually finite groups, amenable groups, Gromov's monster groups, virtually torsion free groups (e.g. $Out(F_n)$), and any group of analytic diffeomorphisms of an analytic connected manifold fixing a given point. It is an open question if every countable group is finitely embeddable. We apply this result to measure the degree of non-rigidity for any compact oriented manifold $M$ with dimension $4k-1$ $(k>1)$. We derive a lower bound on the rank of the structure group $S(M)$ in this case. For a compact Riemannian manifold $M$ with dimension greater than or equal to 5 and positive scalar curvature metric, there is an abelian group $P(M)$ that measures the size of the space of all positive scalar curvature metrics on $M$. We obtain a lower bound on the rank of the abelian group $P(M)$ when the compact smooth spin manifold $M$ has dimension $2k-1$ $(k>2)$ and the fundamental group of $M$ is finitely embeddable.

Shmuel Weinberger; Guoliang Yu

251

Combining Electron Microscopic with X-Ray Crystallographic Structures  

Microsoft Academic Search

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

Michael G. Rossmann; Ricardo Bernal; Sergei V. Pletnev

2001-01-01

252

Crystallographic alignment of high-density gallium nitride nanowire arrays  

Microsoft Academic Search

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

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

2004-01-01

253

Atoms.inp Archive: Crystallographic Data from GSECARS  

DOE Data Explorer

The Atoms.inp Archive is a collection of crystallographic data for use in XAFS analysis. The crystallographic data is stored as atoms.inp files, which contain all the information necessary to describe the crystal, and can be used by the program ATOMS to generate feff.inp files. These files can then be used by the FEFF program [See http://leonardo.phys.washington.edu/feff/] to calculate a theoretical XAFS spectrum for the crystal. This archive exists because it can take a considerable amount of time to locate a suitable reference for a model structure to use for making theoretical XAFS standards. Even then, references sometimes give non-standard or incomplete crystallographic notation that ATOMS has difficulty interpreting. All of this means that getting a reliable atoms.inp file can take quite a bit of effort. It is hoped that this collection of well-documented and well-tested atoms.inp files will eliminate much of the work in creating theoretical XAFS standards from FEFF. [Taken from http://cars9.uchicago.edu/~newville/adb/]. The collection currently has more than 200 crystal structures, 2748 data files, and it continues to expand. The collection is related to the UWXAFS Project [http://depts.washington.edu/uwxafs/] and to the work of the Consortium for Advanced Radiation Sources (CARS). After searching the Archive, a user may also choose to run the web version of ATOMS software.

Newville, Matthew

254

Asymmetrical quartz crystallographic fabrics formed during constrictional deformation  

NASA Astrophysics Data System (ADS)

Numerical simulations predict unique quartz crystallographic fabric patterns for plane strain, flattening, and constriction. Multiple studies support the predictions for plane strain and flattening. To test predictions for constriction, this paper analyzes five examples of quartz crystallographic fabrics from a 1-km-wide domain of L tectonites in the Pigeon Point high-strain zone, Klamath Mountains, California, U.S.A. These samples were deformed under greenschist- to amphibolite-facies conditions. Quartz c-axis fabrics are similar to the predicted double-girdle fabrics except that amphibolite-facies samples exhibit c-axis maxima and are distinctly asymmetrical about the elongation lineations. Activation of different slip systems combined with small deviations from pure constriction account for the c-axis maxima, and noncoaxial flow accounts for the fabric asymmetry. The simple-shear component is randomly oriented in geographic coordinates throughout the domain of L tectonites. These data confirm that numerical simulations predict the quartz c-axis fabric geometry developed during constriction for some deformation conditions, and they confirm the quartz a-axis patterns predicted for constriction for the first time. These data also demonstrate that the relationship between quartz crystallographic fabrics and strain geometry is not straightforward, and they indicate that a-axis fabrics may be more useful indicators of strain geometry variations.

Sullivan, W. A.; Beane, R. J.

2010-10-01

255

Crystallographically uniform arrays of ordered (In)GaN nanocolumns  

NASA Astrophysics Data System (ADS)

In this work, through a comparative study of self-assembled (SA) and selective area grown (SAG) (In)GaN nanocolumn (NC) ensembles, we first give a detailed insight into improved crystallographic uniformity (homogeneity of crystallographic tilts and twists) of the latter ones. The study, performed making use of: reflective high energy electron diffraction, X-ray diffraction and scanning electron microscopy, reveals that unlike their SA counterparts, the ensembles of SAG NCs show single epitaxial relationship to both sapphire(0001) and Si(111) underlying substrates. In the second part of the article, making use of X-ray diffraction, we directly show that the selective area growth leads to improved compositional uniformity of InGaN NC ensembles. This further leads to improved spectral purity of their luminescence, as confirmed by comparative macro-photoluminescence measurements performed on SA and SAG InGaN NC ensembles. An improved crystallographic uniformity of NC ensembles facilitates their integration into optoelectronic devices, whereas their improved compositional uniformity allows for their employment in single-color optoelectronic applications.

Ga?evi?, Ž.; Bengoechea-Encabo, A.; Albert, S.; Torres-Pardo, A.; González-Calbet, J. M.; Calleja, E.

2015-01-01

256

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

PubMed

The hydration of the coenzyme cob(II)alamin has been studied using high-resolution monochromatic neutron crystallographic data collected at room temperature to a resolution of 0.92 Å on the original D19 diffractometer with a prototype 4° × 64° detector at the high-flux reactor neutron source run by the Institute Laue-Langevin. The resulting structure provides hydrogen-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 surrounded by flexible side chains with terminal functional groups may be significant for the efficient scavenging of ligands. The feasibility of extending the resolution of this structure to ultrahigh resolution was investigated by collecting time-of-flight neutron crystallographic data during commissioning of the TOPAZ diffractometer with a prototype array of 14 modular 2° × 21° detectors at the Spallation Neutron Source run by Oak Ridge National Laboratory. PMID:21636899

Jogl, Gerwald; Wang, Xiaoping; Mason, Sax A; Kovalevsky, Andrey; Mustyakimov, Marat; Fisher, Zöe; Hoffman, Christina; Kratky, Christoph; Langan, Paul

2011-06-01

257

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

258

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

E-print Network

We present uniformly measured star formation histories (SFHs) of 40 Local Group dwarf galaxies based on color-magnitude diagram (CMD) analysis from archival Hubble Space Telescope imaging. We demonstrate that accurate SFHs can be recovered from CMDs that do not reach the oldest main sequence turn-off (MSTO), but emphasize that the oldest MSTO is critical for precisely constraining the earliest epochs of star formation. We find that: (1) the average lifetime SFHs of dwarf spheroidals (dSphs) can be approximated by an exponentially declining SFH with $\\tau$ $\\sim$ 5 Gyr; (2) lower luminosity dSphs are less likely to have extended SFHs than more luminous dSphs; (3) the average SFHs of dwarf irregulars (dIrrs), transition dwarfs (dTrans), and dwarf ellipticals (dEs) can be approximated by the combination of an exponentially declining SFH ($\\tau$ $\\sim$ 3-4 Gyr) for lookback ages $>$ 10-12 Gyr ago and a constant SFH thereafter; (4) the observed fraction of stellar mass formed prior to z=2 ranges considerably (80\\%...

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

2014-01-01

259

The behavioural and physiological reactions of farmed red deer to transport: effects of sex, group size, space allowance and vehicular motion  

Microsoft Academic Search

Sixty yearling red deer (30 males, 30 females), comprising eight single-sex groups of either 5 or 10 animals, were loaded onto a livestock transporter for 3 h, during which they were either transported or remained stationary, at one of two space allowances (males: 0.5 m2 or 1 m2\\/deer, females: 0.4 m2 or 0.8 m2\\/deer). One group was tested each day,

P. N Grigor; P. J Goddard; C. A Littlewood

1998-01-01

260

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

261

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

NASA Technical Reports Server (NTRS)

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

Tavana, Madjid

2005-01-01

262

CASE STUDY -- LEAN 94-02: A Case Study of Self-Directed Work Teams at Boeing Defense and Space Group - Corinth  

E-print Network

Boeing Defense & Space Group - Corinth (BD&SG-C) is a self-directed team based unionized facility in the defense and commercial aircraft industry. The plant was a greenfield start-up in 1987. Due to the nature of the defense ...

Klein, Janice

1994-02-24

263

Crystallographic Polarity and Etching Behavior of ZnSe  

Microsoft Academic Search

The crystallographic polarity of ZnSe has been identified uniquely by employing X-ray diffraction techniques. The X-ray identification has been correlated with the etch-pit figures formed on the (111)Zn and (\\\\bar{1}\\\\bar{1}\\\\bar{1}) Se surfaces. When etched with the K2Cr2O7-H2SO4 solution, the (111) surface is highly polished, while the (\\\\bar{1}\\\\bar{1}\\\\bar{1}) surface forms triangular pyramidal shaped pits with positive orientation. Subsequently etched with the

Atsuko Ebina; Kiyomitsu Asano; Tadashi Takahashi

1977-01-01

264

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

PubMed Central

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

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

2005-01-01

265

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

PubMed

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

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

2005-01-01

266

Crystallization and preliminary X-ray crystallographic analysis of UDP-N-acetylglucosamine enolpyruvyl transferase from Haemophilus influenzae in complex with UDP-N-acetylglucosamine and fosfomycin.  

PubMed

The bacterial enzyme UDP-N-acetylglucosamine enolpyruvyl transferase catalyzes the first committed step of peptidoglycan biosynthesis, i.e., transfer of enolpyruvate from phosphoenolpyruvate to UDP-N-acetyl-glucosamine. We have overexpressed the enzyme from Haemophilus influenzae in Escherichia coli and crystallized it in the apo-form, as well as in a complex with UDP-N-acetylglucosamine and fosfomycin using ammonium sulfate as the precipitant. X-ray diffraction data from a crystal of the apo-form were collected to 2.8 A resolution at 293 K. The crystal quality was improved by co-crystallization with UDP-N-acetylglucosamine and fosfomycin. X-ray data to 2.2 A have been collected at 100 K from a flash-frozen crystal of the complex. The complex crystals belong to the orthorhombic space group I222 (or I212121) with unit-cell parameters of a = 63.7, b = 124.5, and c = 126.3 A. Assuming a monomer of the recombinant enzyme in the crystallographic asymmetric unit, the calculated Matthews parameter (VM) is 2.71 A3 Da-1 and solvent content is 54.6%. PMID:15995357

Yoon, Hye-Jin; Ku, Min-Je; Ahn, Hyung Jun; Lee, Byung Il; Mikami, Bunzo; Suh, Se Won

2005-06-30

267

Purification, crystallization and preliminary crystallographic analysis of Gan1D, a GH1 6-phospho-?-galactosidase from Geobacillus stearothermophilus T1.  

PubMed

Geobacillus stearothermophilus T1 is a Gram-positive thermophilic soil bacterium that contains an extensive system for the utilization of plant cell-wall polysaccharides, including xylan, arabinan and galactan. The bacterium uses a number of extracellular enzymes that break down the high-molecular-weight polysaccharides into short oligosaccharides, which enter the cell and are further hydrolyzed into sugar monomers by dedicated intracellular glycoside hydrolases. The interest in the biochemical characterization and structural analysis of these proteins originates mainly from the wide range of their potential biotechnological applications. Studying the different hemicellulolytic utilization systems in G. stearothermophilus T1, a new galactan-utilization gene cluster was recently identified, which encodes a number of proteins, one of which is a GH1 putative 6-phospho-?-galactosidase (Gan1D). Gan1D has recently been cloned, overexpressed, purified and crystallized as part of its comprehensive structure-function study. The best crystals obtained for this enzyme belonged to the triclinic space group P1, with average crystallographic unit-cell parameters of a = 67.0, b = 78.1, c = 92.1 Å, ? = 102.4, ? = 93.5, ? = 91.7°. A full diffraction data set to 1.33 Å resolution has been collected for the wild-type enzyme, as measured from flash-cooled crystals at 100 K, using synchrotron radiation. These data are currently being used for the detailed three-dimensional crystal structure analysis of Gan1D. PMID:24637762

Lansky, Shifra; Zehavi, Arie; Dann, Roie; Dvir, Hay; Belrhali, Hassan; Shoham, Yuval; Shoham, Gil

2014-02-01

268

Prospects for the direct electron crystallographic determination of zeolite structures.  

PubMed

Recently two successful zeolite structures based on experimental electron crystallographic data have been published. Diffraction and image data based on the silicate portion of the zeolite, mordenite, which are perturbed by dynamical (as well as secondary) scattering, have been simulated by a multiple-beam dynamical scattering program. Structure analyses with these data show that the above claims are not unreasonable, given a high enough accelerating voltage for the electron beam. If, for example, 2.9 A resolution micrographs are taken from a 120 A thick crystal in a 200 or 400 kV electron microscope, the crystallographic phases found by image analysis (Fourier filtration) are accurate enough to be extended by the Sayre equation to the (atomic) resolution limit of the electron diffraction pattern (for example from a 105 A thick crystal illuminated by a 1,200 kV electron source). The resultant potential map can be interpreted to find most of the atomic positions and the remaining ones will appear during the progress of a Fourier refinement. PMID:9080411

Dorset, D L; McCourt, M P

1997-02-01

269

Controlling the Synthesis of New Polyoxometalates and Removing Their Crystallographic Disorder.  

E-print Network

??Abstract Crystallographic disorder encompasses a wide range of frequently-encountered problems in many areas of chemistry. These problems include, but are not limited to, positional disorder,… (more)

O'Halloran, Kevin Patrick

2011-01-01

270

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

E-print Network

of the soybean acreage is double cropped after winter wheat harvest in June. This results in a soybean planting (Great Plains Mfg., Salina, KS) with 7 rows spaced at 7.5 inches. Inoculants, soil #12;fertility

Balasundaram, Balabhaskar "Baski"

271

Crystallization and preliminary crystallographic analysis of ?-mannanase from Bacillus licheniformis  

PubMed Central

The mannan endo-1,4-?-mannosidase (ManB) from Bacillus licheniformis strain DSM13 was overexpressed in Escherichia coli. Purification of the thermostable and alkali-stable recombinant mannanase yielded approximately 50?mg enzyme per litre of culture. Crystals were grown by hanging-drop vapour diffusion using a precipitant solution consisting of 12%(w/v) PEG 8000, 0.2?M magnesium acetate tetrahydrate and 0.1?M MES pH 6.5. The protein crystallized in the monoclinic space group P21, with two molecules per asymmetric unit and unit-cell parameters a = 48.58, b = 91.75, c = 89.55?Å, ? = 98.29°, and showed diffraction to 2.3?Å resolution. PMID:21301089

Songsiriritthigul, Chomphunuch; Lapboonrueng, Sasithorn; Roytrakul, Sittiruk; Haltrich, Dietmar; Yamabhai, Montarop

2011-01-01

272

Preliminary X-ray crystallographic study of staphylococcal ?-haemolysin monomer.  

PubMed

Staphylococcal ?-haemolysin is a ?-barrel pore-forming toxin expressed by Staphylococcus aureus. ?-Haemolysin is secreted as a water-soluble monomeric protein which binds to target membranes and forms membrane-inserted heptameric pores. Although the crystal structures of the heptameric pore and monomer bound to an antibody have been determined, that of monomeric ?-haemolysin without binder has yet to be elucidated. Previous mutation studies showed that mutants of His35 retain the monomeric structure but are unable to assemble into heptamers. Here, ?-haemolysin H35A mutants were expressed, purified and crystallized. Diffraction data were collected to 2.90 Å resolution. The crystals belonged to space group P6?, with unit-cell parameters a = b = 151.3, c = 145.0 Å. Molecular replacement found four molecules in an asymmetric unit. The relative orientation among molecules was distinct from that of the pore, indicating that the crystal contained monomeric ?-haemolysin. PMID:23908030

Sugawara, Takaki; Yamashita, Daichi; Tanaka, Yoshikazu; Kaneko, Jun; Kamio, Yoshiyuki; Tanaka, Isao; Yao, Min

2013-08-01

273

Preliminary crystallographic examination of a novel fungal lysozyme from Chalaropsis  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

274

Crystallization and preliminary crystallographic analysis of dextranase from Streptococcus mutans  

PubMed Central

Streptococcus mutans dextranase hydrolyzes the internal ?-1,6-linkages of dextran and belongs to glycoside hydrolase family 66. An N- and C-terminal deletion mutant of S. mutans dextranase was crystallized by the sitting-drop vapour-diffusion method. The crystals diffracted to a resolution of 1.6?Å and belonged to space group P21, with unit-cell parameters a = 53.2, b = 89.7, c = 63.3?Å, ? = 102.3°. Assuming that the asymmetric unit of the crystal contained one molecule, the Matthews coefficient was calculated to be 4.07?Å3?Da?1; assuming the presence of two molecules in the asymmetric unit it was calculated to be 2.03?Å3?Da?1. PMID:22139161

Suzuki, Nobuhiro; Kim, Young-Min; Fujimoto, Zui; Momma, Mitsuru; Kang, Hee-Kwon; Funane, Kazumi; Okuyama, Masayuki; Mori, Haruhide; Kimura, Atsuo

2011-01-01

275

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

PubMed

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

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

2014-02-28

276

OAST Space Theme Workshop. Volume 3: Working Group Summary. 5: Propulsion (P-1). A. Summary Statement. B. Technology Needs (Form 1). C. Priority Assessments (Form 2)  

NASA Technical Reports Server (NTRS)

All themes require some form of advanced propulsion capabilities to achieve their stated objectives. Requirements cover a broad spectrum ranging from a new generation of heavy lift launch vehicles to low thrust, long lift system for on-orbit operations. The commonality extant between propulsive technologies was established and group technologies were grouped into vehicle classes by functional capability. The five classes of launch vehicles identified by the space transportation theme were augmented with a sixth class, encompassing planetary and on-orbit operations. Propulsion technologies in each class were then ranked, and assigned priority numbers. Prioritized technologies were matched to theme requirements.

1976-01-01

277

A 2.2?Å resolution structure of the USP7 catalytic domain in a new space group elaborates upon structural rearrangements resulting from ubiquitin binding.  

PubMed

A sparse-matrix screen for new crystallization conditions for the USP7 catalytic domain (USP7CD) led to the identification of a condition in which crystals grow reproducibly in 24-48?h. Variation of the halide metal, growth temperature and seed-stock concentration resulted in a shift in space group from P21 with two molecules in the asymmetric unit to C2 with one molecule in the asymmetric unit. Representative structures from each space group were determined to 2.2?Å resolution and these structures support previous findings that the catalytic triad and switching loop are likely to be in unproductive conformations in the absence of ubiquitin (Ub). Importantly, the new structures reveal previously unobserved electron density for blocking loop 1 (BL1) residues 410-419. The new structures indicate a distinct rearrangement of the USP7 BL1 compared with its position in the presence of bound Ub. PMID:24598911

Molland, Katrina; Zhou, Qing; Mesecar, Andrew D

2014-03-01

278

Infrared Space Observatory Observations of the 53W002 Group at 6.7 Microns: In Search of the Oldest Stellar Populations at z = 2.4  

Microsoft Academic Search

We present a deep Infrared Space Observatory (ISO) observation at 6.7 mum of the 53W002 group of galaxies and active galactic nuclei (AGNs) at z=2.4. This approximately samples the emitted K band. Faint, blue star-forming objects are not detected, as expected from their very blue color across the emitted optical and UV spectrum. However, 53W002 itself is detected at the

William C. Keel; Wentao Wu; Paul P. van der Werf; Rogier A. Windhorst; James S. Dunlop; Stephen A. Eales; Ian Waddington; Martha Holmes

2004-01-01

279

Twinning-like lattice reorientation without a crystallographic twinning plane  

NASA Astrophysics Data System (ADS)

Twinning on the plane is a common mode of plastic deformation for hexagonal-close-packed metals. Here we report, by monitoring the deformation of submicron-sized single-crystal magnesium compressed normal to its prismatic plane with transmission electron microscopy, the reorientation of the parent lattice to a ‘twin’ lattice, producing an orientational relationship akin to that of the conventional twinning, but without a crystallographic mirror plane, and giving plastic strain that is not simple shear. Aberration-corrected transmission electron microscopy observations reveal that the boundary between the parent lattice and the ‘twin’ lattice is composed predominantly of semicoherent basal/prismatic interfaces instead of the twinning plane. The migration of this boundary is dominated by the movement of these interfaces undergoing basal/prismatic transformation via local rearrangements of atoms. This newly discovered deformation mode by boundary motion mimics conventional deformation twinning but is distinct from the latter and, as such, broadens the known mechanisms of plasticity.

Liu, Bo-Yu; Wang, Jian; Li, Bin; Lu, Lu; Zhang, Xi-Yan; Shan, Zhi-Wei; Li, Ju; Jia, Chun-Lin; Sun, Jun; Ma, Evan

2014-02-01

280

Crystallographic data processing for free-electron laser sources  

PubMed Central

A processing pipeline for diffraction data acquired using the ‘serial crystallography’ methodology with a free-electron laser source is described with reference to the crystallographic analysis suite CrystFEL and the pre-processing program Cheetah. A detailed analysis of the nature and impact of indexing ambiguities is presented. Simulations of the Monte Carlo integration scheme, which accounts for the partially recorded nature of the diffraction intensities, are presented and show that the integration of partial reflections could be made to converge more quickly if the bandwidth of the X-rays were to be increased by a small amount or if a slight convergence angle were introduced into the incident beam. PMID:23793149

White, Thomas A.; Barty, Anton; Stellato, Francesco; Holton, James M.; Kirian, Richard A.; Zatsepin, Nadia A.; Chapman, Henry N.

2013-01-01

281

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

E-print Network

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

Cambridge, University of

282

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

283

Ocean acidification reduces the crystallographic control in juvenile mussel shells.  

PubMed

Global climate change threatens the oceans as anthropogenic carbon dioxide causes ocean acidification and reduced carbonate saturation. Future projections indicate under saturation of aragonite, and potentially calcite, in the oceans by 2100. Calcifying organisms are those most at risk from such ocean acidification, as carbonate is vital in the biomineralisation of their calcium carbonate protective shells. This study highlights the importance of multi-generational studies to investigate how marine organisms can potentially adapt to future projected global climate change. Mytilus edulis is an economically important marine calcifier vulnerable to decreasing carbonate saturation as their shells comprise two calcium carbonate polymorphs: aragonite and calcite. M. edulis specimens were cultured under current and projected pCO2 (380, 550, 750 and 1000?atm), following 6months of experimental culture, adults produced second generation juvenile mussels. Juvenile mussel shells were examined for structural and crystallographic orientation of aragonite and calcite. At 1000?atm pCO2, juvenile mussels spawned and grown under this high pCO2 do not produce aragonite which is more vulnerable to carbonate under-saturation than calcite. Calcite and aragonite were produced at 380, 550 and 750?atm pCO2. Electron back scatter diffraction analyses reveal less constraint in crystallographic orientation with increased pCO2. Shell formation is maintained, although the nacre crystals appear corroded and crystals are not so closely layered together. The differences in ultrastructure and crystallography in shells formed by juveniles spawned from adults in high pCO2 conditions may prove instrumental in their ability to survive ocean acidification. PMID:25180664

Fitzer, Susan C; Cusack, Maggie; Phoenix, Vernon R; Kamenos, Nicholas A

2014-10-01

284

Temperature dependent crystallographic transformations in chalcedony, SiO2, assessed in mid infrared spectroscopy.  

PubMed

Chalcedony consists of hydroxylated 50-100 nanometre measuring ?-quartz (SiO(2)) crystallites that lose their surface silanole groups (Si-OH) upon heating between 350°C and 600°C. The loss of the chalcedony's ?1% of silanole groups allows for the healing of water related defects in the crystallites. We investigated these crystallographic transformations using Fourier Transform mid Infrared Spectroscopy in direct transmission, Attenuated Total Reflection (ATR) and the reflectivity. We found that an absorption band that is specific for chalcedony at 555 cm(-1) disappears gradually upon heating between 350°C and 600°C. The reduction of the band is correlated to the loss of surface silanoles. This result leads to the assignment of the band to free Si-O vibrations in non bridging Si-OH groups that have a lower natural frequency than Si-O vibrations in bridging Si-O-Si. The recognition of a silanole signal in the mid infrared allows for an easy, cheap and rapid recognition of hydroxyl in chalcedony. PMID:21333586

Schmidt, Patrick; Fröhlich, François

2011-05-01

285

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

286

Space, time and the pattern of individual associations in a group-living species: Sanderlings have no friends  

Microsoft Academic Search

The persistence of flock membership through time and space was examined for wintering sanderlings Calidris alba at Bodega Bay, California from October 1978 to March 1981. Observed patterns of association were then compared with those expected from a null model: that the set of birds within a given flock represent a random sample from the local population.

J. P. Myers

1983-01-01

287

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

288

Layered perovskite-like Pb2Fe2O5 structure as a parent matrix for the nucleation and growth of crystallographic shear planes.  

PubMed

The Pb(2)Fe(2)O(5) compound with a layered intergrowth structure has been prepared by a solid-state reaction at 700 °C. The incommensurate compound crystallizes in a tetragonal system with a = 3.9037(2) Å, c = 3.9996(4) Å, and q = 0.1186(4)c*, or when treated as a commensurate approximant, a = 3.9047(2) Å, c = 36.000(3) Å, space group I4/mmm. The crystal structure of Pb(2)Fe(2)O(5) was resolved from transmission electron microscopy data. Atomic coordinates and occupancies of the cation positions were estimated from high-angle annular dark-field scanning transmission electron microscopy data. Direct visualization of the positions of the oxygen atoms was possible using annular bright-field scanning transmission electron microscopy. The structure can be represented as an intergrowth of perovskite blocks and partially disordered blocks with a structure similar to that of the Bi(2)O(2) blocks in Aurivillius-type phases. The A-cation positions at the border of the perovskite block and the cation positions in the Aurivillius-type blocks are jointly occupied by Pb(2+) and Fe(3+) cations, resulting in a layer sequence along the c axis: -PbO-FeO(2)-PbO-FeO(2)-Pb(7/8)Fe(1/8)-O(1-x)-Fe(5/8)Pb(3/8)-O(2)-Fe(5/8)Pb(3/8)-. Upon heating, the layered Pb(2)Fe(2)O(5) structure transforms into an anion-deficient perovskite modulated by periodically spaced crystallographic shear (CS) planes. Considering the layered Pb(2)Fe(2)O(5) structure as a parent matrix for the nucleation and growth of CS planes allows an explanation of the specific microstructure observed for the CS structures in the Pb-Fe-O system. PMID:21528885

Batuk, Dmitry; Hadermann, Joke; Abakumov, Artem; Vranken, Thomas; Hardy, An; Van Bael, Marlies; Van Tendeloo, Gustaaf

2011-06-01

289

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

NASA Technical Reports Server (NTRS)

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

1989-01-01

290

Compact operators and algebraic $K$-theory for groups which act properly and isometrically on Hilbert space.  

E-print Network

We prove the $K$-theoretic Farrell-Jones conjecture for groups as in the title with coefficient rings and $C^*$-algebras which are stable with respect to compact operators. We use this and Higson-Kasparov's result that the Baum-Connes conjecture with coefficients holds for such groups, to show that if $G$ is as in the title then the algebraic and the $C^*$-crossed products of $G$ with a stable $C^*$-algebra have the same $K$-theory.

Guillermo Cortiñas; Gisela Tartaglia

291

Determination of the orbit spaces of non-coregular compact linear groups with one relation among the basic polynomial invariants in the $\\hat P$-matrix approach  

E-print Network

Invariant functions under the transformations of a compact linear group $G$ acting in $\\real^n$ can be expressed in terms of functions defined in the orbit space of $G$. We develop a method to determine the isotropy classes of the orbit spaces of all the real linear groups whose integrity bases (IB) satisfy only one independent relation. The method is tested for IB's formed by 3 (independent) basic invariants. The result is obtained through a metric matrix $\\hat P(p)$, defined only from the scalar products between the gradients of a minimal IB. We determine the matrices $\\wP(p)$ from a universal differential equation, which satisfy new convenient additional conditions, which fit for the non-coregular case. Our results may be relevant in physical contexts where the study of covariant or invariant functions is important, like in the determination of patterns of spontaneous symmetry breaking in quantum field theory, in the analysis of phase spaces and structural phase transitions (Landau's theory), in covariant bifurcation theory, in crystal field theory and so on.

G. Sartori; G. Valente

2000-08-02

292

Microfocus/Polycapillary-Optic Crystallographic X-Ray System  

NASA Technical Reports Server (NTRS)

A system that generates an intense, nearly collimated, nearly monochromatic, small-diameter x-ray beam has been developed for use in macromolecular crystallography. A conventional x-ray system for macromolecular crystallography includes a rotating-anode x-ray source, which is massive (.500 kg), large (approximately 2 by 2 by 1 m), and power-hungry (between 2 and 18 kW). In contrast, the present system generates a beam of the required brightness from a microfocus source, which is small and light enough to be mounted on a laboratory bench, and operates at a power level of only tens of watts. The figure schematically depicts the system as configured for observing x-ray diffraction from a macromolecular crystal. In addition to the microfocus x-ray source, the system includes a polycapillary optic . a monolithic block (typically a bundle of fused glass tubes) that contains thousands of straight or gently curved capillary channels, along which x-rays propagate with multiple reflections. This particular polycapillary optic is configured to act as a collimator; the x-ray beam that emerges from its output face consists of quasi-parallel subbeams with a small angular divergence and a diameter comparable to the size of a crystal to be studied. The gap between the microfocus x-ray source and the input face of the polycapillary optic is chosen consistently with the focal length of the polycapillary optic and the need to maximize the solid angle subtended by the optic in order to maximize the collimated x-ray flux. The spectrum from the source contains a significant component of Cu K (photon energy is 8.08 keV) radiation. The beam is monochromatized (for Cu K ) by a nickel filter 10 m thick. In a test, this system was operated at a power of 40 W (current of 897 A at an accelerating potential of 45 kV), with an anode x-ray spot size of 41+/-2 microns. Also tested, in order to provide a standard for comparison, was a commercial rotating-anode x-ray crystallographic system with a pyrolytic graphite monochromator and a 250-micron pinhole collimator, operating at a power of 3.15 kW (current of 70 mA at an accelerating potential of 45 kV). The flux of collimated Cu K radiation in this system was found to be approximately 16 times that in the rotatinganode system. Data on x-ray diffraction from crystals of tetragonal form of lysozyme (protein) in this system were found to be of high quality and to be reducible by use of standard crystallographic software.

Joy, Marshall; Gubarev, Mikhail; Ciszak, Ewa

2005-01-01

293

Zero-temperature real-space renormalization-group method for a Kondo-lattice model Hamiltonian  

Microsoft Academic Search

Details are given of work on a one-dimensional analog of the Kondo-lattice problem, in which a conduction band interacts with a spin in each cell of a lattice. Results of a renormalization-group calculation (generalized from Wilson's approach to the single-site Kondo problem) published earlier in letter form, showed that the system undergoes a second-order crossover transition from an antiferromagnetic state

R. Jullien; J. N. Fields; S. Doniach

1977-01-01

294

Nanocrystalline materials: recent advances in crystallographic characterization techniques.  

PubMed

Most properties of nanocrystalline materials are shape-dependent, providing their exquisite tunability in optical, mechanical, electronic and catalytic properties. An example of the former is localized surface plasmon resonance (LSPR), the coherent oscillation of conduction electrons in metals that can be excited by the electric field of light; this resonance frequency is highly dependent on both the size and shape of a nanocrystal. An example of the latter is the marked difference in catalytic activity observed for different Pd nanoparticles. Such examples highlight the importance of particle shape in nanocrystalline materials and their practical applications. However, one may ask 'how are nanoshapes created?', 'how does the shape relate to the atomic packing and crystallography of the material?', 'how can we control and characterize the external shape and crystal structure of such small nanocrystals?'. This feature article aims to give the reader an overview of important techniques, concepts and recent advances related to these questions. Nucleation, growth and how seed crystallography influences the final synthesis product are discussed, followed by shape prediction models based on seed crystallography and thermodynamic or kinetic parameters. The crystallographic implications of epitaxy and orientation in multilayered, core-shell nanoparticles are overviewed, and, finally, the development and implications of novel, spatially resolved analysis tools are discussed. PMID:25485133

Ringe, Emilie

2014-11-01

295

Crystallographic tilting during heteroepitaxial growth of rubidium iodide on mica  

NASA Astrophysics Data System (ADS)

Heteroepitaxial deposits of RbI on mica were prepared by the evaporation of aqueous solutions under controlled conditions. Using four-circle x-ray diffractometer measurements to determine the orientation of the alkali halide lattice relative to the mica substrate, we find that the RbI [111] axis is often tilted relative to the substrate normal, along specific in-plane azimuths. Crystallographic tilting is a well-known phenomenon during heteroepitaxial growth of semiconductors and metals, but our results are somewhat unusual, since they involve the growth of an ionic crystal on mica. It is generally acknowledged that tilting is driven by epitaxial misfit accommodation, and for a net tilt to occur the interfacial system requires a symmetry-breaking component. In the vast majority of previous studies the broken symmetry is due to substrate miscut, but miscut is entirely absent in the case of cleaved mica substrates. In order to explain our results, we show that the tilting of RbI on mica is made possible by the inherent threefold symmetry of the [111] axis in fcc crystals, and we also show that the observed tilt angles are consistent with the lattice parameters of RbI and mica.

Lamelas, F. J.; Xiong, May; Sloane, C. V.

2000-09-01

296

Crystallographic Orientation of Cuttlebone Shield Determined by Electron Backscatter Diffraction  

NASA Astrophysics Data System (ADS)

In common with many cephalopod mollusks, cuttlefish produce an internal biomineral buoyancy device. This cuttlebone is analogous to a surf board in shape and structure, providing rigidity and a means of controlling buoyancy. The cuttlebone is composed of calcium carbonate in the form of aragonite and comprises an upper dorsal shield and a lower lamellar matrix. The lamellar matrix comprises layers of chambers with highly corrugated walls. The dorsal shield comprises bundles of aragonite needles stacked on top of each other. Electron backscatter diffraction analyses of the dorsal shield reveal that the c-axis of aragonite is parallel with the long axis of the needles in the bundles such that any spread in crystallographic orientation is consistent with the spread in orientation of the fibers as they radiate to form the overall structure of the dorsal shield. This arrangement of c-axis coincident with the long axis of the biomineral structure is similar to the arrangement in corals and in contrast to the situation in the molluskan aragonite nacre of brachiopod calcite where the c-axis is perpendicular to the aragonite tablet or calcite fiber, respectively.

Cusack, Maggie; Chung, Peter

2014-01-01

297

Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite  

PubMed Central

The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy–electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic units are single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occur mainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface and do not show preferential tilting along any of the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, in which the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is a matter of future research. PMID:23804442

Checa, Antonio G.; Bonarski, Jan T.; Willinger, Marc G.; Faryna, Marek; Berent, Katarzyna; Kania, Bogusz; González-Segura, Alicia; Pina, Carlos M.; Pospiech, Jan; Morawiec, Adam

2013-01-01

298

Thickness dependent crystallographic transition in Fe/Ni multilayers  

NASA Astrophysics Data System (ADS)

The crystallographic transition between bcc- and fcc-structures has been studied in Fe/Ni multilayers with Mössbauer spectroscopy and X-ray diffraction. Layered structures have been confirmed and the structures depends both on individual layer thickness and the ratio of the constituents. Two sets of samples are made: the Fe layer thickness kept constant to 12 monolayer (ML) and 24ML, while the Ni layer thicknesses varied from 3 to 12ML. When the Ni layer is thin, the Fe/Ni multilayers have the bcc phase. When the thickness of Ni layer reaches 6ML and larger, a gradual transition to the fcc phase occurs. Mössbauer spectroscopy studies confirm the existence of a magnetic Fe bcc phase with in-plane magnetization in all samples, two magnetic fcc phases with fields of 28 T and 10 T and small amounts of nonmagnetic fcc phases in the thicker films. The observed behaviour can be attributed to the existence of two types of interfaces which are not necessary overlapping each other: An elemental interface between Fe and Ni and a structural interface between fcc and bcc phases.

Häggström, Lennart; Soroka, Inna; Kamali, Saeed

2010-03-01

299

K-theory for the Leaf Spaces of the Orbit Foliations of the co-adjoint Action of some 5-dimensional Solvable Lie groups.  

E-print Network

In this paper, combining Kirillov's method of orbits with Connes' method in Differential Geometry, we study the so-called MD(5,3C)-foliations, i.e. the orbit foliations of the co-adjoint action of MD(5,3C)-groups. First, we classify topologically MD(5,3C)-foliations based on the classification of all MD(5,3C)-algebras in [22] and the picture of co-adjoint orbits (K-orbits) of all MD(5,3C)-groups in [23]. Finally, we study K-theory for leaf space of MD(5,3C)-foliations and describe analytically or characterize Connes' C*-algebras of the considered foliations by KK-functors.

Le Anh Vu; Nguyen Anh Tuan; Duong Quang Hoa

300

M8, Abstracts of the American CrystallographicAssociation Meeting,New Orleans, La., 1970.  

E-print Network

8087 M8, Abstracts of the American CrystallographicAssociation Meeting,New Orleans, La., 1970. (10 the Department of Chemistry, University of Colorado, Boulder, Colorado 80309. Received January 19, 1976 Abstract

Showalter, Kenneth

301

CRYSTALLOGRAPHIC PROPERTIES AND MECHANICAL BEHAVIOR OF TITANIUM HYDRIDE LAYERS GROWN ON TITANIUM IMPLANTS  

E-print Network

CRYSTALLOGRAPHIC PROPERTIES AND MECHANICAL BEHAVIOR OF TITANIUM HYDRIDE LAYERS GROWN ON TITANIUM, Switzerland Keywords: SLA treated titanium - bone-anchored dental implants - transmission and scanning electron microscopy - titanium hydride sub-surface layer - epitaxy Abstract Commercially pure titanium

Paris-Sud XI, Université de

302

Calcium Phosphate Bioceramics with Tailored Crystallographic Texture for Controlling Cell Adhesion  

E-print Network

Calcium Phosphate Bioceramics with Tailored Crystallographic Texture for Controlling Cell Adhesion at Birmingham, Birmingham, AL, 35294 ABSTRACT The orientation distribution of crystalline grains in calcium. INTRODUCTION The excellent biocompatibility and bioactivity of calcium phosphate nanostructured surfaces offer

Rohrer, Gregory S.

303

Crystallographic flat origami with three flat foldability types of the generating unit  

NASA Astrophysics Data System (ADS)

In this paper, we determine crystallographic flat origami from a crease pattern having three flat foldability types of its generating unit. In particular, we consider crease patterns arising from Archimedean tilings via the hinged tiling method.

Taganap, Eduard C.; De Las Peñas, Ma. Louise Antonette N.; Rapanut, Teofina A.

2014-06-01

304

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

305

A crystallographic texture perspective formability investigation of aluminium 5052 alloy sheets at various annealing temperatures  

Microsoft Academic Search

Formability, an important mechanical property of the sheet metal is strongly reliant on the crystallographic texture. Consequently deep drawability is also influenced. This paper deals with the perspective of crystallographic texture and its relevance with the formability of AA 5052 aluminium alloy sheet of 2mm thickness annealed at four different temperatures namely 200°C, 250°C, 300°C and 350°C. Forming limit diagrams

R. Narayanasamy; R. Ravindran; K. Manonmani; J. Satheesh

2009-01-01

306

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

SciTech Connect

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

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

2012-05-10

307

Chemical and crystallographic events in the caries process.  

PubMed

The chemical and crystallographic events associated with the caries process can be described based on the results from the following studies: (a) effects of carbonate, magnesium, fluoride, and strontium on the physico-chemical properties--lattice parameters, crystallinity (crystal size and strain); dissolution properties of synthetic apatites; (b) factors influencing the in vitro formation and transformation of DCPD, OCP, AP (Ca-deficient apatites), FAP, beta-TCMP (Mg-substituted), and CaF2; and (c) studies on properties (crystallinity, composition, chemical, and thermal stabilities) of enamel, dentin, and bone. The dissolution of CO3-rich/Mg-rich/F-poor dental apatite crystals and re-precipitation of CO3-poor/Mg-poor/F-rich apatite in the presence of F- ions in solution contribute to a more acid-resistant surface layer of the caries lesion. Fluoride promotes the formation of less Ca-deficient and more stable apatite crystals. The presence of Ca, P, and F in solution inhibits dissolution of apatite more than does the presence of F alone. Low levels of F in solution promote the formation of (F, OH)-apatite, even under very acid conditions; an increase in F levels causes the formation of CaF2 at the expense of DCPD or apatite, especially in acid conditions. F in apatite and/or in solution suppresses extensive dissolution of dental apatite and enhances the formation of (F, OH)-apatite crystals which are more resistant against acid-dissolution than are F-free apatite crystals. PMID:2179315

LeGeros, R Z

1990-02-01

308

An EXAFS spectroscopic, large-angle X-ray scattering, and crystallographic study of hexahydrated, dimethyl sulfoxide and pyridine 1-oxide hexasolvated mercury(II) ions.  

PubMed

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(2))(6)](2+) ions in a distorted octahedral configuration, with the centroid of the Hg-O distance at 2.38(1) A, are surrounded by a diffuse second hydration sphere with HgO(II) distances of 4.20(2) A. In dimethyl sulfoxide, the six Hg-O and HgS distances of the hexasolvated [Hg{OS(CH(3))(2)}(6)](2+) complex are centered around 2.38(1) and 3.45(2) A, respectively. The crystal structure of hexakis(pyridine 1-oxide)mercury(II) perchlorate has been redetermined. The space group R(-)3 implies six equal Hg-O distances of 2.3416(7) A for the [Hg(ONC(5)H(5))(6)](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 Hg-O bonds according to crystallographic results, reveal in all cases strongly asymmetric Hg-O distance distributions. Vibronic coupling of valence states in a so-called pseudo-Jahn-Teller effect probably induces the distorted configurations. PMID:18563768

Persson, Ingmar; Eriksson, Lars; Lindqvist-Reis, Patric; Persson, Per; Sandström, Magnus

2008-01-01

309

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

310

Improved crystallographic models through iterated local density-guided model deformation and reciprocal-space refinement  

PubMed Central

An approach is presented for addressing the challenge of model rebuilding after molecular replacement in cases where the placed template is very different from the structure to be determined. The approach takes advantage of the observation that a template and target structure may have local structures that can be superimposed much more closely than can their complete structures. A density-guided procedure for deformation of a properly placed template is introduced. A shift in the coordinates of each residue in the structure is calculated based on optimizing the match of model density within a 6?Å radius of the center of that residue with a prime-and-switch electron-density map. The shifts are smoothed and applied to the atoms in each residue, leading to local deformation of the template that improves the match of map and model. The model is then refined to improve the geometry and the fit of model to the structure-factor data. A new map is then calculated and the process is repeated until convergence. The procedure can extend the routine applicability of automated molecular replacement, model building and refinement to search models with over 2?Å r.m.s.d. representing 65–100% of the structure. PMID:22751672

Terwilliger, Thomas C.; Read, Randy J.; Adams, Paul D.; Brunger, Axel T.; Afonine, Pavel V.; Grosse-Kunstleve, Ralf W.; Hung, Li-Wei

2012-01-01

311

Braid groups of imprimitive reflection groups  

E-print Network

6/5/2012 1 Braid groups of imprimitive reflection groups Ruth Corran Cap Hornu May 30, 2012 Finite complex reflection groups V a vector space over C with dim(V) = r. A complex reflection s is a non) is the reflection hyperplane for the reflection s A (finite) complex reflection group W is a (finite) group

Digne, François

312

Laboratory and space experiments for the exploration of the interplanetary dust. Memories of the activities of the dust group of the MPI for Nuclear Physics during the years 1964 through 1994  

NASA Astrophysics Data System (ADS)

The dust group in the Max-Planck-Institut für Kernphysik during its 30 years from 1964 through 1994 largely contributed to the cosmic dust research by the study of microcraters on lunar rocks and of the dust population in the inner solar system with experiments on the 2nd high eccentric orbiting Earth satellite and on the German-American space probe HELIOS. In the 1980s the group has flown successful experiments on the European space agency mission GIOTTO as well as on the soviet space probes Venus Galley to comet Halley. Finally, it was engaged in the laboratory analysis of collected interplanetary dust particles.

Fechtig, Hugo

2001-05-01

313

K-theory for the Leaf Space of Foliations Formed by the Generic K-orbits of a class of Solvable Real Lie Groups.  

E-print Network

The paper is a continuation of the works [17] of Vu and Shum, [18] and [19] of Vu and Hoa. In [17], Vu and Shum classified all the MD5-algebras having commutative derived ideals. In [18], Vu and Hoa considered foliations formed by the maximal dimensional K-orbits (for short, MD5-foliations) of connected MD5-groups such that their Lie algebras have 4-dimensional commutative derived ideals and gave a topological classification of the considered foliations. In [19], Vu and Hoa characterized the Connes' C*-algebras of some MD5-foliations considered in \\cite{VU-HO09} by the method of K-functors. In this paper, we study K-theory for the leaf space of all MD5-foliations which are classified in [18] and characterize the Connes' C*-algebras of them by the method of K-functors.

Anh Vu Le; Quang Hoa Duong; Anh Tuan Nguyen

314

Effects of Dissolution-Precipitation Creep on the Crystallographic Preferred Orientation of Quartz Within the Purgatory Conglomerate, RI.  

E-print Network

??Crystallographic Preferred Orientations (CPO) are common in deformed rocks, and usually result from crystal plastic deformation by dislocation creep. Whether deformation mechanisms that occur at… (more)

McPherren, Eric

2010-01-01

315

Preliminary joint neutron and X-ray crystallographic study of human carbonic anhydrase II  

PubMed Central

Carbonic anhydrases catalyze the interconversion of CO2 to HCO3 ?, with a subsequent proton-transfer (PT) step. PT proceeds via a proposed hydrogen-bonded water network in the active-site cavity that is stabilized by several hydrophilic residues. A joint X-ray and neutron crystallographic study has been initiated to determine the specific water network and the protonation states of the hydrophilic residues that coordinate it in human carbonic anhydrase II. Time-of-flight neutron crystallographic data have been collected from a large (?1.2?mm3) hydrogen/deuterium-exchanged crystal to 2.4?Å resolution and X-­ray crystallographic data have been collected from a similar but smaller crystal to 1.5?Å resolution. Obtaining good-quality neutron data will contribute to the understanding of the catalytic mechanisms that utilize water networks for PT in protein environments. PMID:19407386

Fisher, S. Z.; Kovalevsky, A. Y.; Domsic, J. F.; Mustyakimov, M.; Silverman, D. N.; McKenna, R.; Langan, Paul

2009-01-01

316

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

317

Hydrogen-bond interactions of nicotine and acetylcholine salts: a combined crystallographic, spectroscopic, thermodynamic and theoretical study.  

PubMed

The hydrogen-bond (HB) interactions of the monocharged active forms of nicotine and acetylcholine (ACh) have been compared theoretically by using density functional theory (DFT) calculations and experimentally on the basis of crystallographic observations and the measurement of equilibrium constants in solution. The 2,4,6-trinitrophenolate (picrate) counterion was used to determine the experimental HB basicity of the cations despite its potential multisite HB acceptor properties. The preferred HB interaction site of the ammonium picrate salts was determined from a survey of crystallographic data found in the Cambridge Structural Database (CSD) and is supported by theoretical calculations. Two distinct classes of ammonium groups were characterised depending on the absence (quaternary ammonium) or presence (tertiary, secondary and primary ammoniums) of an N(+)HO hydrogen bond linking the two ions. The crystal structure of nicotinium picrate was determined and compared with that of ACh. This analysis revealed the peculiar behaviour of the ammonium moiety of nicotinic acetylcholine receptor (nAChR) ligands towards the picrate anion. Dedicated methods have been developed to separate the individual contributions of the anion and cation accepting sites to the overall HB basicity of the ion pairs measured in solution. The HB basicities of the picrate anions associated with the two different ammonium classes were determined in dichloromethane solution by using several model ion pairs with non-basic ammonium cations. The experimental and theoretical studies performed on the nicotine and ACh cations consistently show the significant HB ability of the acceptor site of nAChR agonists in their charged form. Both the greater HB basicity of the pyridinic nitrogen over the carbonyl oxygen and the greater HB acidity of the N(+)H unit relative to N(+)CH could contribute to the higher affinity for nAChRs of nicotine-like ligands relative to ACh-like ligands. PMID:17103466

Arnaud, Virginie; Berthelot, Michel; Evain, Michel; Graton, Jérôme; Le Questel, Jean-Yves

2007-01-01

318

Crystallographic preferred orientation and deformation of deep Earth minerals  

NASA Astrophysics Data System (ADS)

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

Kaercher, Pamela Michelle

319

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

320

Combined use of physicochemical data and small-molecule crystallographic contact propensities to predict interactions in protein binding sites.  

PubMed

Knowledge-based methods are a good alternative to force-field-based methods for the analysis of sites of interaction in protein binding cavities. Both the Protein Data Bank (PDB) and the Cambridge Structural Database (CSD) offer a good amount of data on non-covalent interactions. Although different from protein-derived data, small-molecule crystal data from the CSD are worth looking at as they provide a much more abundant and diverse set of intermolecular contacts. CSD data, when properly corrected by use of octanol-water pi values, can be used to predict the type of ligand chemical group most likely to occupy a given position within a protein binding site. Comparison with observed positions of ligand groups shows that the success rates of these predictions vary from 23% to 84%. Often, the group predicted to be most preferred at a given position is similar but not identical to the observed ligand group; if these are considered successes, prediction success rates range from 71% to 94%. Using PDB data, the corresponding rates are 16% to 79%, and 61% to 96%. Specificity of prediction of NH groups is somewhat better when using PDB interaction data, but results of prediction of hydrophobic groups seem worse than those obtained with CSD data. We have analysed the importance of data selection by applying different filters to eliminate unwanted interactions from our knowledge-base. The presence of certain types of interactions can be undesirable if they are unrepresentative of biological situations (contact to solvent molecules in small-molecule crystal structures, secondary crystallographic contacts) or if they are likely to add noise to the data without conveying much new information (long-distance contacts, sparsely-populated data sets). The elimination of solvent contacts was found to have no effect on the prediction of ligand groups in our test set. Both secondary-contact filtering and noise filtering were found to have a clear beneficial effect on predictive ability. PMID:15534701

Nissink, J Willem M; Taylor, Robin

2004-11-21

321

Estimation of the crystallographic strain limit during the reversible ? ? ?? martensitic transformation in titanium shape memory alloys  

NASA Astrophysics Data System (ADS)

Three methods are described to calculate the crystallographic strain limit that is determined by the maximum deformation of the crystal lattice in the reversible ?bcc ? ??orth martensitic transformation and ensures pseudoelastic deformation accumulation and shape recovery in Ti-Nb-Ta alloys.

Zhukova, Yu. S.; Petrzhik, M. I.; Prokoshkin, S. D.

2010-11-01

322

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

PubMed Central

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

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

2014-01-01

323

Electronic Supporting Information NMR Crystallography of L-Arginine: Disentangling Crystallographic  

E-print Network

Electronic Supporting Information NMR Crystallography of L-Arginine: Disentangling Crystallographic Inequivalence and Polymorphism by One- and Two-Dimensional Solid- State NMR Spectroscopy Jose-Enrique Herbert, France Figure S1. Expansions of the 13 C CP/MAS spectrum of L-arginine (sample 1). The resonance lines

324

Crystallographic Dependence of CO Activation on Cobalt Catalysts: HCP versus FCC  

E-print Network

Crystallographic Dependence of CO Activation on Cobalt Catalysts: HCP versus FCC Jin-Xun Liu, Hai-packed (HCP) Co not only has much higher intrinsic activity than that of face centered-cubic (FCC) Co but also on the FCC Co. The origin is identified from the formation of various denser yet favorable active sites

Li, Weixue

325

Contribution to crystallographic slip assessment by means of topographic measurements achieved with atomic force microscopy  

SciTech Connect

In this paper, atomic force microscopy (AFM) is used to quantitatively characterize the plastic glide occurring during tensile deformation of a duplex 2205 stainless steel sample. We demonstrate that an appropriate treatment of the topographic image issued from AFM measurements allows precise and quantitative information about the characteristics of plastic deformation and especially the amount of crystallographic slip.

Kahloun, C. [LPMTM - CNRS, Universite Paris 13, 99 av. J.B. Clement, 93430 Villetaneuse (France); Badji, R. [LPMTM - CNRS, Universite Paris 13, 99 av. J.B. Clement, 93430 Villetaneuse (France); Welding and NDT Research Centre, B. P. 64, Cheraga (Algeria); Bacroix, B., E-mail: bacroix@lpmtm.univ-paris13.fr [LPMTM - CNRS, Universite Paris 13, 99 av. J.B. Clement, 93430 Villetaneuse (France); Bouabdallah, M. [E.N.P, 10 av. Hassan Badi, 16200 El Harrah Alger (Algeria)

2010-09-15

326

Y O N A T H E T AL.. Crystallographic Studies of Protein Denaturation and Renaturation.  

E-print Network

Y O N A T H E T AL.. Crystallographic Studies of Protein Denaturation and Renaturation. 2. Sodium Honig,* Anita Sielecki, and Wolfie Traub ABSTRACT: Cross-linked triclinic lysozyme was denatured with sodium dodecyl sulfate. Removal of the denaturant re- sulted in a refolding of the protein

Yonath, Ada E.

327

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

E-print Network

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

Garmestani, Hamid

328

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

329

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

E-print Network

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

Hamelryck, Thomas

330

Acta Cryst. (1962). 15, 24 The Detection of Sub-Units Within the Crystallographic Asymmetric Unit  

E-print Network

24 Acta Cryst. (1962). 15, 24 The Detection of Sub-Units Within the Crystallographic Asymmetric polypeptide chains, four times the molecular weight and exactly four times the iron content of the related how we have detected the existence of this partial, approximate symmetry from a knowledge

Rossmann, Michael G.

331

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

Microsoft Academic Search

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

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

2006-01-01

332

Protein structure prediction provides comparable performance to crystallographic structures in docking-based virtual screening  

E-print Network

Ligand docking Protein structure prediction a b s t r a c t Structure based virtual screening has largely-based docking and advanced protein structure modeling methods should be a valuable approach to the largeProtein structure prediction provides comparable performance to crystallographic structures

Zhang, Yang

333

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

E-print Network

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

Cambridge, University of

334

INFLUENCE OF CRYSTALLOGRAPHIC ORIENTATION AND LAYER THICKNESS ON FRACTURE BEHAVIOR OF Ni/Ni3Al  

E-print Network

INFLUENCE OF CRYSTALLOGRAPHIC ORIENTATION AND LAYER THICKNESS ON FRACTURE BEHAVIOR OF Ni/Ni3Al (Received October 25, 2000) (Accepted in revised form February 7, 2001) Abstract--Ni / Ni3Al multilayers. Two interfacial orientations were achieved: {001} Ni // {001} Ni3Al, 100 Ni // 100 Ni3Al and {111} Ni

Anderson, Peter M.

335

Crystallographic structural organization of human rhinovirus serotype 16, 14, 3, 2 and 1A  

NASA Astrophysics Data System (ADS)

The capsid of the icosahedral virion is encapsulated between two polyhedra scaled according to the golden mean, each being composed of an icosahedron and a dodecahedron. Structural units of the coat proteins are enclosed into forms whose projections along the icosahedral symmetry axes obey the crystallographic law of rational indices.

Janner, A.

2006-07-01

336

The crystallographic texture of a great number of polyethylene films manufactured by the film  

E-print Network

The crystallographic texture of a great number of polyethylene films manufactured by the film blowing process has been investigated by X-ray diffraction. Some films present a classical texture (c an original texture (c-axis in the film thickness) and no satisfactory morphological model has been proposed

Paris-Sud XI, Université de

337

Petrographic and crystallographic study of silicate minerals in lunar rocks  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

338

Real-time renormalization group in frequency space: A two-loop analysis of the nonequilibrium anisotropic Kondo model at finite magnetic field  

NASA Astrophysics Data System (ADS)

We apply a recently developed nonequilibrium real-time renormalization group (RG) method in frequency space to describe nonlinear quantum transport through a small fermionic quantum system coupled weakly to several reservoirs via spin and/or orbital fluctuations. Within a weak-coupling two-loop analysis, we derive analytic formulas for the nonlinear conductance and the kernel determining the time evolution of the reduced density matrix. A consistent formalism is presented how the RG flow is cut off by relaxation and dephasing rates. We apply the general formalism to the nonequilibrium anisotropic Kondo model at finite magnetic field. We consider the weak-coupling regime, where the maximum of voltage and bare magnetic field is larger than the Kondo temperature. In this regime, we calculate the nonlinear conductance, the magnetic susceptibility, the renormalized spin relaxation and dephasing rates, and the renormalized g factor. All quantities are considered up to the first logarithmic correction beyond leading order at resonance. Up to a redefinition of the Kondo temperature, we confirm previous results for the conductance and the magnetic susceptibility in the isotropic case. In addition, we present a consistent calculation of the resonant line shapes, including the determination whether the spin relaxation or dephasing rate cuts off the logarithmic divergence. Furthermore, we calculate quantities characterizing the exponential decay of the time evolution of the magnetization. In contrast to the conductance, we find that the derivative of the spin relaxation (dephasing) rate with respect to the magnetic field is logarithmically enhanced (suppressed) for voltages smaller (larger) than the renormalized magnetic field, and that the logarithmic divergence is cut off by the opposite rate. The renormalized g factor is predicted to show a symmetric logarithmic suppression at resonance, which is cut off by the spin relaxation rate. We propose a three-terminal setup to measure the suppression at resonance. For all quantities, we analyze also the anisotropic case and find additional nonequilibrium effects at resonance.

Schoeller, Herbert; Reininghaus, Frank

2009-07-01

339

Relationship between Thin-Film Transistor Characteristics and Crystallographic Orientation in Excimer-Laser-Processed Pseudo-Single-Crystal-Silicon Films  

NASA Astrophysics Data System (ADS)

The characteristics of thin-film transistors (TFTs) fabricated on pseudo-single-crystal (PSX)-Si thin films were examined. The variations of mobility were more than the theoretical values derived from the crystallographic orientation dependence of a bulk Si metal-oxide-semiconductor (MOS) transistor. To clarify the origin of this discrepancy, the relationships between the TFT characteristics and the crystallographic orientation of Si films in the channel region were investigated by using an electron backscattering pattern (EBSP) method. It was found that the surface orientation dependence for the PSX-Si TFT was different from that for a bulk Si MOS transistor, especially for the p-channel mode. A group of TFTs having a nearly {100}-oriented nucleus had a mobility close to those of simultaneously processed silicon-on-insulator (SOI) devices in the p-channel mode as well as in the n-channel mode. In contrast, a group of TFTs having a nearly {110}-oriented nucleus had a low and widely scattered mobility. The reason for these results is that twin boundaries with dislocations are easily generated in a grain grown from a {110}-oriented nucleus in order to compensate for the difference of the growth rates in different directions.

Mitani, Masahiro; Endo, Takahiko; Tsuboi, Shinzo; Okada, Takashi; Kawachi, Genshiro; Matsumura, Masakiyo

2010-12-01

340

Three 1-phenylindolin-2-one derivatives displaying different molecular dipole moments and different crystallographic symmetries.  

PubMed

Three 1-phenylindolin-2-one derivatives, namely 1-phenylindolin-2-one, C14H11NO, (I), 5-bromo-1-phenylindolin-2-one, C14H10BrNO, (II), and 5-iodo-1-phenylindolin-2-one, C14H10INO, (III), have been synthesized and their structures determined. Compounds (I) and (II) crystallized in the centrosymmetric space groups Pbca and P21/c, respectively, while compound (III) crystallized in the polar space group Aea2. Density functional theory (DFT) calculations show that the molecular dipole moment gradually decreases in the order (I) > (II) > (III). The relatively smaller dipole moment of (III) and the larger non-electrostatic intermolecular interactions may be the main reasons for the noncentrosymmetric and polar structure of (III). PMID:25567579

Wang, Lei; Zhang, Man; Jin, Ying Ying; Lu, Qing; Fang, Qi

2015-01-01

341

Magnetic and Crystallographic Properties of LnCrO 4 ( Ln=Nd, Sm, and Dy)  

NASA Astrophysics Data System (ADS)

Zircon-type compounds LnCrO4 (Ln=Nd, Sm, and Dy) were prepared. Their precise crystal structures at room temperature were determined from X-ray diffraction measurements. These compounds have a tetragonal system with space group I41/amd. Magnetic susceptibility and specific heat measurements have been performed for all the compounds in the temperature range between 1.8 and 300 K. For NdCrO4, an antiferromagnetic transition was found at 25.2 K. SmCrO4 and DyCrO4 show magnetic transitions at 15.0 and 22.8 K, respectively. In addition, structural phase transitions were observed at 58.5 and 31.2 K, respectively. For DyCrO4, the crystal structure below the transition temperature was determined by low-temperature powder X-ray diffraction measurements to be orthorhombic with space group Imma.

Tezuka, Keitaro; Hinatsu, Yukio

2001-09-01

342

Crystallographic texture in pulsed laser deposited hydroxyapatite bioceramic coatings  

PubMed Central

The orientation texture of pulsed laser deposited hydroxyapatite coatings was studied by X-ray diffraction techniques. Increasing the laser energy density of the KrF excimer laser used in the deposition process from 5 to 7 J/cm2 increases the tendency for the c-axes of the hydroxyapatite grains to be aligned perpendicular to the substrate. This preferred orientation is most pronounced when the incidence direction of the plume is normal to the substrate. Orientation texture of the hydroxyapatite grains in the coatings is associated with the highly directional and energetic nature of the ablation plume. Anisotropic stresses, transport of hydroxyl groups and dehydroxylation effects during deposition all seem to play important roles in the texture development. PMID:18563207

Kim, Hyunbin; Camata, Renato P.; Lee, Sukbin; Rohrer, Gregory S.; Rollett, Anthony D.; Vohra, Yogesh K.

2008-01-01

343

An NMR crystallographic approach to monitoring cation substitution in the aluminophosphate STA-2.  

PubMed

The substitution of the divalent cations Mg(2+) and Zn(2+) into the aluminophosphate (AlPO) framework of STA-2 has been studied using an "NMR crystallographic" approach, combining multinuclear solid-state NMR spectroscopy, X-ray diffraction and first-principles calculations. Although the AlPO framework itself is inherently neutral, the positive charge of the organocation template in an as-made material is usually balanced either by the coordination to the framework of anions from the synthesis solution, such as OH(-) or F(-), and/or by the substitution of aliovalent cations. However, the exact position and distribution of the substituted cations can be difficult to determine, but can have a significant impact upon the catalytic properties a material exhibits once calcined. For as-made Mg substituted STA-2, the positive charge of the organocation template is balanced by the substitution of Mg(2+) for Al(3+) and, where required, by hydroxide anions coordinated to the framework [27] Al MAS NMR spectra show that Al is present in both tetrahedral and five-fold coordination, with the latter dependent on the amount of substituted cations, and confirms the bridging nature of the hydroxyl groups, while high-resolution MQMAS spectra are able to show that Mg appears to preferentially substitute on the Al1 site. This conclusion is also supported by first-principles calculations. The calculations also show that (31)P chemical shifts depend not only on the topologically-distinct site in the SAT framework, but also on the number of next-nearest-neighbour Mg species, and the exact nature of the coordinated hydroxyls (whether the P atom forms part of a six-membered ring, P(OAl)2OH, where OH bridges between two Al atoms). The calculations demonstrate a strong correlation between the (31)P isotropic chemical shift and the average ?P-O-M? bond angle. In contrast, for Zn substituted STA-2, both X-ray diffraction and NMR spectroscopy show less preference for substitution onto Al1 or Al2, with both appearing to be present, although that into Al1 appears slightly more favoured. PMID:25465483

Seymour, Valerie R; Eschenroeder, Eike C V; Wright, Paul A; Ashbrook, Sharon E

2014-11-01

344

An evaluation of adhesive sample holders for advanced crystallographic experiments.  

PubMed

The hydration state of macromolecular crystals often affects their overall order and, ultimately, the quality of the X-ray diffraction pattern that they produce. Post-crystallization techniques that alter the solvent content of a crystal may induce rearrangement within the three-dimensional array making up the crystal, possibly resulting in more ordered packing. The hydration state of a crystal can be manipulated by exposing it to a stream of air at controlled relative humidity in which the crystal can equilibrate. This approach provides a way of exploring crystal hydration space to assess the diffraction capabilities of existing crystals. A key requirement of these experiments is to expose the crystal directly to the dehydrating environment by having the minimum amount of residual mother liquor around it. This is usually achieved by placing the crystal on a flat porous support (Kapton mesh) and removing excess liquid by wicking. Here, an alternative approach is considered whereby crystals are harvested using adhesives that capture naked crystals directly from their crystallization drop, reducing the process to a one-step procedure. The impact of using adhesives to ease the harvesting of different types of crystals is presented together with their contribution to background scattering and their usefulness in dehydration experiments. It is concluded that adhesive supports represent a valuable tool for mounting macromolecular crystals to be used in humidity-controlled experiments and to improve signal-to-noise ratios in diffraction experiments, and how they can protect crystals from modifications in the sample environment is discussed. PMID:25195752

Mazzorana, Marco; Sanchez-Weatherby, Juan; Sandy, James; Lobley, Carina M C; Sorensen, Thomas

2014-09-01

345

An evaluation of adhesive sample holders for advanced crystallographic experiments  

PubMed Central

The hydration state of macromolecular crystals often affects their overall order and, ultimately, the quality of the X-ray diffraction pattern that they produce. Post-crystallization techniques that alter the solvent content of a crystal may induce rearrangement within the three-dimensional array making up the crystal, possibly resulting in more ordered packing. The hydration state of a crystal can be manipulated by exposing it to a stream of air at controlled relative humidity in which the crystal can equilibrate. This approach provides a way of exploring crystal hydration space to assess the diffraction capabilities of existing crystals. A key requirement of these experiments is to expose the crystal directly to the dehydrating environment by having the minimum amount of residual mother liquor around it. This is usually achieved by placing the crystal on a flat porous support (Kapton mesh) and removing excess liquid by wicking. Here, an alternative approach is considered whereby crystals are harvested using adhesives that capture naked crystals directly from their crystallization drop, reducing the process to a one-step procedure. The impact of using adhesives to ease the harvesting of different types of crystals is presented together with their contribution to background scattering and their usefulness in dehydration experiments. It is concluded that adhesive supports represent a valuable tool for mounting macromolecular crystals to be used in humidity-controlled experiments and to improve signal-to-noise ratios in diffraction experiments, and how they can protect crystals from modifications in the sample environment is discussed. PMID:25195752

Mazzorana, Marco; Sanchez-Weatherby, Juan; Sandy, James; Lobley, Carina M. C.; Sorensen, Thomas

2014-01-01

346

36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false What space in the National Archives at College...NARA FACILITIES USE OF NARA FACILITIES What Rules Apply to Use NARA Public Areas in...Archives at College Park, Md § 1280.85 What space in the National Archives at...

2012-07-01

347

36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...  

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false What space in the National Archives at College...NARA FACILITIES USE OF NARA FACILITIES What Rules Apply to Use NARA Public Areas in...Archives at College Park, Md § 1280.85 What space in the National Archives at...

2014-07-01

348

Surface acidity of quartz: understanding the crystallographic control.  

PubMed

We report a first principles molecular dynamics (FPMD) study of surface acid chemistry of the two growth surfaces of quartz, (101[combining macron]0) (including Alpha and Beta terminations) and (101[combining macron]1) facets. The interfacial hydration structures are characterized in detail and the intrinsic pKas of surface silanols are evaluated using the FPMD based vertical energy gap method. The calculated acidity constants reveal that every surface termination shows a bimodal acid-base behavior. It is found that all doubly-protonated forms (i.e. SiOH2) on the three terminations have pKas lower than -2.5, implying that the silanols hardly get protonated in a common pH range. The pKas of surface silanols can be divided into 3 groups. The most acidic silanol is the donor SiOH on the (101[combining macron]0)-beta surface (pKa = 4.8), the medium includes the germinal silanol on (101[combining macron]0)-alpha and the outer silanol on (101[combining macron]1) (pKa = 8.5-9.3) and the least acidic are inner silanols on the (101[combining macron]1)-facet, acceptor SiOH on (101[combining macron]0)-beta, and the secondly-deprotonated OH (i.e. Si(O-)(OH)) on (101[combining macron]0)-alpha (pKa > 11.0). With the pKa values, we discuss the implication for understanding metal cations complexing on quartz surfaces. PMID:25376935

Liu, Xiandong; Cheng, Jun; Lu, Xiancai; Wang, Rucheng

2014-11-19

349

Crystallographic characterisation of benzoyl azides. A comparative study  

NASA Astrophysics Data System (ADS)

The crystal structures of five benzoyl azides XC 6H 4C(O)N 3 (X=2-nitro, 4-nitro, 4-cyano, 4-methoxy, 4-dimethylamino) are reported together with the low temperature structure determinations of XC 6H 4SO 2N 3 (X=2-nitro) and XC 6H 4SO 2Cl (X=2-nitro, 4-nitro). The extensive ? delocalisation in benzoyl azides keeps the C(O)N 3 moiety in the plane of the phenyl ring and this overall planar conformation is retained by distorting bond angles when steric effects become significant. Strong electron-releasing substituents that also lie in the plane of the phenyl ring result in chinoidally disturbed aromatic systems. The crystal packing of benzoyl azides is mainly affected by short C-H⋯A interactions and ? interactions of stacked aromatic rings. The low temperature reinvestigation of 2-nitrobenzenesulfonyl azide confirmed the existence of dipole-dipole interaction between the nitro, sulfonyl, and azide groups.

Párkányi, László; Besenyei, Gábor

2004-03-01

350

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

351

Molecular squares with paramagnetic diruthenium corners: synthetic and crystallographic challenges.  

PubMed

The reaction of Ru(2)(mu-O(2)CMe)(4)Cl with approximately 2.5 equiv of HDAniF (HDAniF = N,N'-di(p-anisyl)formamidine) in refluxing THF resulted in the synthesis of cis-Ru(2)(mu-DAniF)(2)(mu-O(2)CMe)(2)Cl (1). This Ru(2)(5+)complex, which has two labile acetate groups occupying two equatorial cisoid positions, was used for the construction of discrete paramagnetic supramolecular arrays. Subsequent reactions of 1 with HO(2)C-CO(2)H (oxalic acid) and 1,4-HO(2)C-C(6)H(4)-CO(2)H (terephthalic acid) followed by recrystallization from 1,2-C(2)H(4)Cl(2)/hexanes solutions containing wet MeCN or 4-Bu(t)py (4-tert-butylpyridine) gave crystals of [[is-Ru(2)(mu-DAniF)(2)Cl(H(2)O)]mu-oxalate)](4).MeCN.2(C(6)H(14)).12(H(2)O) (2) and [[is-Ru(2)(mu-DAniF)(2)Cl(0.646)(4-Bu(t)py)(1.354)]mu-terephthlate)](4)Cl(1.414).17(1,2-C(2)H(4)Cl(2)).C(6)H(14) (3), respectively. These are the first polygonal supramolecular assemblies consisting of paramagnetic M(2) units at each apex, where M(2) = Ru(2)(5+). Compounds 2 and 3 have been structurally characterized, and their electrochemistry and magnetic properties have been studied. These studies have confirmed that oxalate linkers are better than the terephthalate linkers in effecting electronic and magnetic coupling. PMID:12926957

Angaridis, Panagiotis; Berry, John F; Cotton, F Albert; Murillo, Carlos A; Wang, Xiaoping

2003-08-27

352

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

353

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

354

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

PubMed Central

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

2013-01-01

355

Controlled crystallinity and crystallographic orientation of Cu nanowires fabricated in ion-track templates.  

PubMed

The hallmark of materials science is the ability to tailor the structures of a given material to provide a desired response. In this work, the structures involving crystallinity and crystallographic orientation of Cu nanowires electrochemically fabricated in ion-track templates have been investigated as a function of fabrication condition. Both single crystalline and polycrystalline nanowires were obtained by adjusting applied voltages and temperatures of electrochemical deposition. The anti-Hall-Petch effect was experimentally evidenced in the polycrystalline nanowires. The dominant crystallographic orientations of wires along [111], [100], or [110] directions were obtained by selecting electrochemical deposition conditions, i.e., H(2)SO(4) concentration in electrolyte, applied voltage, and electrodeposition temperature. PMID:20705973

Duan, Jinglai; Liu, Jie; Mo, Dan; Yao, Huijun; Maaz, Khan; Chen, Yonghui; Sun, Youmei; Hou, Mingdong; Qu, Xiaohua; Zhang, Ling; Chen, Yanfeng

2010-09-10

356

A crystallographically characterized salt of self-generated N-protonated tetraethylurea.  

PubMed

The reaction of 1,1,3,3-tetraethylurea (teu) with WCl6 in dichloromethane afforded [teuH][WCl6], , in 50-60% yield. The X-ray structure determined for includes the first example of crystallographic characterization of a N-protonated urea. According to spectroscopic and DFT outcomes, the formation of is the result of an electron transfer/C-H activation process. PMID:25483257

Bortoluzzi, Marco; Marchetti, Fabio; Pampaloni, Guido; Zacchini, Stefano

2014-12-23

357

Integrated nanotubes, etch tracks, and nanoribbons in crystallographic alignment to a graphene lattice.  

PubMed

Carbon nanotubes, few-layer graphene, and etch tracks exposing insulating SiO2 regions are integrated into nanoscale systems with precise crystallographic orientations. These integrated systems consist of nanotubes grown across nanogap etch tracks and nanoribbons formed within the few-layer graphene films. This work is relevant to the integration of semiconducting, conducting, and insulating nanomaterials together into precise intricate systems. PMID:25522261

Hunley, D Patrick; Boland, Mathias J; Strachan, Douglas R

2015-02-01

358

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

PubMed

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

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

2014-06-25

359

Crystallographically-oriented single-crystalline copper nanowire arrays electrochemically grown into nanoporous anodic alumina templates  

Microsoft Academic Search

Highly crystallographically-oriented single-crystalline copper nanowire arrays were electrochemically deposited into nanoporous commercial alumina templates. A gold\\/copper backward contact was needed in the template, while the nanowires were grown from a 0.5 M CuSO4·5H2O solution adjusted to pH=1. The kinetics of the growing process is studied by means of current vs. time curves. The pore filling is between 80 to 90%. The

G. Riveros; H. Gómez; A. Cortes; R. E. Marotti; E. A. Dalchiele

2005-01-01

360

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

Microsoft Academic Search

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

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

2006-01-01

361

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

SciTech Connect

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

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

2012-02-15

362

36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...  

Code of Federal Regulations, 2010 CFR

... false What space in the National Archives at College Park is available for use...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives at College Park, Md § 1280.85...

2010-07-01

363

36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...  

Code of Federal Regulations, 2010 CFR

... false What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

2010-07-01

364

36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...  

Code of Federal Regulations, 2014 CFR

... false What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

2014-07-01

365

36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...  

Code of Federal Regulations, 2012 CFR

... false What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

2012-07-01

366

36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...  

Code of Federal Regulations, 2013 CFR

... true What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

2013-07-01

367

36 CFR 1280.74 - What spaces in the National Archives Building are available for use by non-NARA groups and...  

Code of Federal Regulations, 2011 CFR

... false What spaces in the National Archives Building are available for use by non-NARA...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives Building, Washington, Dc §...

2011-07-01

368

36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...  

Code of Federal Regulations, 2011 CFR

... false What space in the National Archives at College Park is available for use...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives at College Park, Md § 1280.85...

2011-07-01

369

Magnetic-crystallographic phase diagram of the superconducting parent compound Fe1+xTe  

NASA Astrophysics Data System (ADS)

Through neutron diffraction experiments, including spin-polarized measurements, we find a collinear incommensurate spin-density wave with propagation vector k= [0.4481(4)0(1)/(2)] at base temperature in the superconducting parent compound Fe1+xTe. This critical concentration of interstitial iron corresponds to x?12% and leads to crystallographic phase separation at base temperature. The spin-density wave is short-range ordered with a correlation length of 22(3) Å, and as the ordering temperature is approached its propagation vector decreases linearly in the H direction and becomes long-range ordered. Upon further populating the interstitial iron site, the spin-density wave gives way to an incommensurate helical ordering with propagation vector k= [0.3855(2)0(1)/(2)] at base temperature. For a sample with x?9(1)%, we also find an incommensurate spin-density wave that competes with the bicollinear commensurate ordering close to the Néel point. The shifting of spectral weight between competing magnetic orderings observed in several samples is supporting evidence for the phase separation being electronic in nature, and hence leads to crystallographic phase separation around the critical interstitial iron concentration of 12%. With results from both powder and single crystal samples, we construct a magnetic-crystallographic phase diagram of Fe1+xTe for 5%

Rodriguez, E. E.; Stock, C.; Zajdel, P.; Krycka, K. L.; Majkrzak, C. F.; Zavalij, P.; Green, M. A.

2011-08-01

370

On the importance of crystallographic texture in the biocompatibility of titanium based substrate.  

PubMed

The role of grain size and crystallographic orientation on the biocompatibility of commercially pure titanium was investigated. Samples, with significant differences in crystallographic texture and average grain size (from 0.4 to 40 µm) were produced by equal channel angular pressing (ECAP) and post deformation annealing. X-ray diffraction and electron back scattered diffraction (EBSD) were used to evaluate differences in texture and microstructural characteristics. The titanium oxide film present on the surface of the samples was analyzed to determine the oxidation state of titanium and the chemical bonds between oxygen and titanium using X-ray photoelectron spectroscopy (XPS). Biocompatibility experiments were conducted using MC3T3 preosteoblast cells. Cell attachment was found to be texture-sensitive, where the number of attached cells was higher on the samples with higher number of (0002) planes exposed to the surface, regardless of the grain size. A relationship was also found between the titanium oxide species formed on the surface and the crystallographic texture underneath. The surface texture consisting of more densely packed basal planes promote the formation of Ti-OH on the surface, which in turn, enhances the cell-substrate interactions. These surface characteristics are deemed responsible for the observed difference in cell attachment behaviour of surfaces with different textures. Finally, it is inferred that texture, rather than the grain size, plays the major role in controlling the surface biocompatibility of biomedical devices fabricated from pure metallic titanium. PMID:24254817

Hoseini, Majid; Bocher, Philippe; Shahryari, Arash; Azari, Fereshteh; Szpunar, Jerzy A; Vali, Hojatollah

2014-10-01

371

The control and characterization of the crystallographic texture of longitudinal thin film recording media  

SciTech Connect

In this overview the authors summarize their methods of changing important microstructural features such as grain size and crystallographic texture, in magnetic thin films for longitudinal recording. The methods the authors have used to better control the grain size and texture of the magnetic films include the use of different underlayers (NiAl and FeAl), the use of seed layers underneath the underlayers and the use of intermediate layers between the underlayer and the magnetic thin film. Examples of the structure and magnetic properties of such films will be presented and discussed. They also present the newly developed method of quantitatively characterizing the crystallographic textures of the thin films used in the multilayered structures. The method relies on the examination of the intensity weighted reciprocal lattice by means of tilted electron beam diffraction patterns. These patterns contain arcs, the number and location of which can be correlated with specific thin film textures. They will present an overview of the technique from the point of view of the reciprocal lattice and include an example which shows how the crystallographic texture of thin films can be examined and characterized.

Laughlin, D.E.; Lee, L.L.; Tang, L.; Lambeth, D.N. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Date Storage Systems Center] [Carnegie Mellon Univ., Pittsburgh, PA (United States). Date Storage Systems Center

1996-09-01

372

Space languages  

NASA Technical Reports Server (NTRS)

Applications of linguistic principles to potential problems of human and machine communication in space settings are discussed. Variations in language among speakers of different backgrounds and change in language forms resulting from new experiences or reduced contact with other groups need to be considered in the design of intelligent machine systems.

Hays, Dan

1987-01-01

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

Confirmation of the Structures of Synthetic Derivatives of Migrastatin in the Light of Recently Disclosed Crystallographically Based Claims.  

PubMed

In the light of recently disclosed crystallographic studies on migrastatin ketone 2 complex with fascin, the structures of migrastatin ketone 2 and migrastatin ether 4 have been re-evaluated by NMR and X-Ray crystallographic techniques. The results of these studies established the correctness of the previously reported structural assignment and confirm that the "small molecule" co-crystallized in complex with fascin is not the migrastatin ketone, which was provided for the infusion experiment, but rather its stereoisomer. PMID:20676392

Nagorny, Pavel; Krauss, Isaac; Njardarson, Jón T; Perez, Lucy; Gaul, Christoph; Yang, Guangli; Ouerfelli, Ouathek; Danishefsky, Samuel J

2010-07-28

375

Confirmation of the Structures of Synthetic Derivatives of Migrastatin in the Light of Recently Disclosed Crystallographically Based Claims  

PubMed Central

In the light of recently disclosed crystallographic studies on migrastatin ketone 2 complex with fascin, the structures of migrastatin ketone 2 and migrastatin ether 4 have been re-evaluated by NMR and X-Ray crystallographic techniques. The results of these studies established the correctness of the previously reported structural assignment and confirm that the “small molecule” co-crystallized in complex with fascin is not the migrastatin ketone, which was provided for the infusion experiment, but rather its stereoisomer. PMID:20676392

Nagorny, Pavel; Krauss, Isaac; Njardarson, Jón T.; Perez, Lucy; Gaul, Christoph; Yang, Guangli; Ouerfelli, Ouathek; Danishefsky, Samuel J.

2010-01-01

376

Biological control of crystallographic architecture: hierarchy and co-alignment parameters.  

PubMed

Mytilus edulis prismatic calcite and nacre layers exhibit a crystallographic structural hierarchy which differs substantially from the morphological hierarchy. This makes these biomaterials fundamentally different from classical crystalline materials. Morphological building units are defined by their surrounding organic matrix membranes, e.g. calcite fibers or nacre tablets. The crystallographic building units are defined by crystallographic co-orientation. Electron backscatter diffraction quantitatively shows how crystallographic co-orientation propagates across matrix membranes to form highly co-oriented low-mosaic composite-crystal grains, i.e. calcite fiber bundles with an internal mosaic spread of 0.5° full width at half maximum (FWHM) or nacre towergrains with an internal mosaic spread of 2° FWHM. These low-mosaic composite crystals form much larger composite-crystal supergrains, which exhibit a high mosaicity due to misorientations of their constituting calcite fiber bundles or nacre towergrains. For the aragonite layer these supergrains nucleate in one of three aragonite {110} twin orientations; as a consequence the nacre layer exhibits a twin-domain structure, i.e. the boundaries of adjacent supergrains exhibit a high probability for misorientations around the aragonite c-axis with an angle near 63.8°. Within the supergrains, the constituting towergrains exhibit a high probability for misorientations around the aragonite a-axis with a geometric mean misorientation angle of 10.6°. The calcite layer is composed of a single composite-crystal supergrain on at least the submillimeter length scale. Mutual misorientations of adjacent fiber bundles within the calcite supergrain are mainly around the calcite c-axis with a geometric mean misorientation angle of 9.4°. The c-axis is not parallel to the long axis of the fibers but rather to the (107) plane normal. The frequency distribution for the occurrence of misorientation angles within supergrains reflects the ability of the organism to maintain homoepitaxial crystallization over a certain length scale. This probability density is distributed log-normally which can be described by a geometric mean and a multiplicative standard deviation. Hence, those parameters are suggested to be a numerical measure for the biological control over crystallographic texture. PMID:24590164

Maier, B J; Griesshaber, E; Alexa, P; Ziegler, A; Ubhi, H S; Schmahl, W W

2014-09-01

377

Inhibition of Class A ?-Lactamases by Carbapenems: Crystallographic Observation of Two Conformations of Meropenem in SHV-1  

PubMed Central

Carbapenem antibiotics are often the “last resort” in the treatment of infections caused by bacteria resistant to penicillins and cephalosporins. To understand why meropenem is resistant to hydrolysis by the SHV-1 class A ?-lactamase, the atomic structure of meropenem inactivated SHV-1 was solved to 1.05 Å resolution. Two conformations of the Ser70 acylated intermediate are observed in the SHV-1-meropenem complex; the meropenem carbonyl oxygen atom of the acyl-enzyme is in the oxyanion hole in one conformation, while in the other conformation it is not. Although the structures of the SHV-1 apoenzyme and the SHV-1-meropenem complex are very similar (0.29 Å rmsd for C? atoms), the orientation of the conserved Ser130 is different. Notably, the Ser130-OH group of the SHV-1-meropenem complex is directed toward Lys234Nz, while the Ser130-OH of the apo enzyme is oriented toward the Lys73 amino group. This altered position may affect proton transfer via Ser130 and the rate of hydrolysis. A most intriguing finding is the crystallographic detection of protonation of the Glu166 known to be involved in the deacylation mechanism. The critical deacylation water molecule has an additional hydrogen-bonding interaction with the OH group of meropenem’s 6?-1R-hydroxyethyl substituent. This interaction may weaken the nucleophilicity and/or change the direction of the lone pair of electrons of the water molecule and result in poor turnover of meropenem by the SHV-1 ?-lactamase. Using timed mass spectrometry, we further show that meropenem is covalently attached to SHV-1 ?-lactamase for at least 60 min. These observations explain key properties of meropenem’s ability to resist hydrolysis by SHV-1 and lead to important insights regarding future carbapenem and ?-lactamase inhibitor design. PMID:18761444

Nukaga, Michiyosi; Bethel, Christopher R.; Thomson, Jodi M.; Hujer, Andrea M.; Distler, Anne; Anderson, Vernon E.; Knox, James R.; Bonomo, Robert A.

2014-01-01

378

Crystal planes and reciprocal space in Clifford geometric algebra  

E-print Network

This paper discusses the geometry of $k$D crystal cells given by $(k+1)$ points in a projective space $\\R^{n+1}$. We show how the concepts of barycentric and fractional (crystallographic) coordinates, reciprocal vectors and dual representation are related (and geometrically interpreted) in the projective geometric algebra $Cl(\\R^{n+1})$ (see Grassmann H., edited by Engel F., Die Ausdehnungslehre von 1844 und die Geom. Anal., vol. 1, part 1, Teubner: Leipzig, 1894.) and in the conformal algebra $Cl(\\R^{n+1,1})$. The crystallographic notions of $d$-spacing, phase angle, structure factors, conditions for Bragg reflections, and the interfacial angles of crystal planes are obtained in the same context. Keywords: Clifford geometric algebra, crystallography, reciprocal space, $d$-spacing, phase angle, structure factors, Bragg reflections, interfacial angles

Hitzer, Eckhard

2013-01-01

379

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)  

NASA Technical Reports Server (NTRS)

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 being supported. All but the space transportation theme have need for precision pointing of spacecraft and instruments. In addition all the themes have requirements for increasing autonomous operations for such activities as spacecraft and experiment operations, onboard mission modification, rendezvous and docking, spacecraft assembly and maintenance, navigation and guidance, and self-checkout, test and repair. Major new efforts are required to conceptualize new approaches to large space antennas and arrays that are lightweight, readily deployable, and capable of precise attitude and figure control. Conventional approaches offer little hope of meeting these requirements. Functions that can benefit from increasing automation or autonomous operations are listed.

1976-01-01

380

Design of a back-illuminated, crystallographically etched, silicon-on-sapphire avalanche photodiode with monolithically integrated microlens, for dual-mode passive & active imaging arrays  

NASA Astrophysics Data System (ADS)

There is a growing need in space and environmental research applications for dual-mode, passive and active 2D and 3D ladar imaging methods. To fill this need, an advanced back-illuminated avalanche photodiode (APD) design is presented based on crystallographically etched (100) epitaxial silicon on R-plane sapphire (SOS), enabling single photon sensitive, solid-state focal plane arrays (FPAs) with wide dynamic range, supporting passive and active imaging capability in a single FPA. When (100) silicon is properly etched with KOH:IPA:H2O solution through a thermally grown oxide mask, square based pyramidal frustum or mesa arrays result with the four mesa sidewalls of the APD formed by (111) silicon planes that intersect the (100) planes at a crystallographic angle, ?c = 54.7°. The APD device is fabricated in the mesa using conventional silicon processing technology. Detectors are back-illuminated through light focusing microlenses fabricated in the thinned, AR-coated sapphire substrate. The APDs share a common, front-side anode contact, made locally at the base of each device mesa. A low resistance (Al) or (Cu) metal anode grid fills the space between pixels and also inhibits optical cross-talk. SOS-APD arrays are indium bump-bonded to CMOS readout ICs to produce hybrid FPAs. The quantum efficiency for the square 27 µm pixels exceeds 50% for 250 nm < ? < 400 nm and exceeds 80% for 400 nm < ? < 700 nm. The sapphire microlenses compensate detector quantum efficiency loss resulting from the mesa geometry and yield 100% sensitive-area-fill-factor arrays, limited in size only by the wafer diameter.

Stern, Alvin G.; Cole, Daniel C.

2008-12-01

381

OAST Space Theme Workshop. Volume 3: Working group summary. 7: Material (M-1). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2)  

NASA Technical Reports Server (NTRS)

The approach of matching technology areas with various themes needs was not effective for the materials and thermal control discipline because of the diversity of requirements for each. Top priorities were evolved from the advanced space transportation system and the space power platform because these are essential building blocks in fulfilling some of the other themes. Important needs identified include life long-life cryogenic cooling systems for sensors, masers, and other devices and the needs for lightweight nuclear shielding materials for nuclear electric propulsion.

1976-01-01

382

Crystallization and preliminary X-ray crystallographic analysis of Sulfolobus solfataricus thioredoxin reductase  

PubMed Central

A thermostable thioredoxin reductase isolated from Sulfolobus solfataricus (SsTrxR) has been successfully crystallized in the absence and in the presence of NADP. Two different crystal forms have been obtained. Crystals of the form that yields higher resolution data (1.8?Å) belong to space group P212121, with unit-cell parameters a = 76.77, b = 120.68, c = 126.85?Å. The structure of the enzyme has been solved by MAD methods using the anomalous signal from the Se atoms of selenomethionine-labelled SsTrxR. PMID:16511192

Ruggiero, Alessia; Ruocco, Maria Rosaria; Grimaldi, Pasquale; Arcari, Paolo; Masullo, Mariorosario; Zagari, Adriana; Vitagliano, Luigi

2005-01-01

383

Crystallization and preliminary crystallographic analysis of bifunctional ?-glutamylcysteine synthetase–glutatione synthetase from Streptococcus agalactiae  

PubMed Central

?-Glutamylcysteine synthetase–glutathione synthetase (?GCS-GS) is a bifunctional enzyme that catalyzes two consecutive steps of ATP-dependent peptide formation in glutathione biosynthesis. Streptococcus agalactiae ?GCS-GS is a target for the development of potential therapeutic agents. ?GCS-GS was crystallized using the sitting-drop vapour-diffusion method. The crystals grew to dimensions of 0.3 × 0.2 × 0.2?mm under reducing conditions with 5?mM TCEP. X-ray data were collected to 2.8?Å resolution from a tetragonal crystal that belonged to space group I41. PMID:19574637

Nakashima, Yasunori; Nii, Hiroshi; Janowiak, Blythe E.; Griffith, Owen W.; Hibi, Takao

2009-01-01

384

Isolation, purification, crystallization and preliminary crystallographic studies of a chitinase from Crocus vernus.  

PubMed

A chitinase has been isolated and purified from Crocus vernus corms. N-terminal amino-acid sequence analysis of the approximately 30?kDa protein showed 33% identity to narbonin, a seed protein from Vicia narbonensis L. The C. vernus chitinase was crystallized by the hanging-drop vapour-diffusion method using PEG 8000 as the main precipitant. The crystal belonged to the monoclinic space group C2, with unit-cell parameters a=172.3, b=37.1, c=126.4?Å, ?=127° and two molecules per asymmetric unit. Diffraction data were collected to a resolution of 2.1?Å. PMID:21393839

Akrem, Ahmed; Iqbal, Sadaf; Buck, Friedrich; Meyer, Arne; Perbandt, Markus; Voelter, Wolfgang; Betzel, Christian

2011-03-01

385

Isolation, purification, crystallization and preliminary crystallographic studies of chitinase from tamarind (Tamarindus indica) seeds  

PubMed Central

A protein with chitinase activity has been isolated and purified from tamarind (Tamarindus indica) seeds. N-terminal amino-acid sequence analysis of this protein confirmed it to be an ?34?kDa endochitinase which belongs to the acidic class III chitinase family. The protein was crystallized by the vapour-diffusion method using PEG 4000. The crystals belonged to the tetragonal space group P41, with two molecules per asymmetric unit. Diffraction data were collected to a resolution of 2.6?Å. PMID:19342775

Patil, Dipak N.; Datta, Manali; Chaudhary, Anshul; Tomar, Shailly; Kumar Sharma, Ashwani; Kumar, Pravindra

2009-01-01

386

Isolation, purification, crystallization and preliminary crystallographic studies of a chitinase from Crocus vernus  

PubMed Central

A chitinase has been isolated and purified from Crocus vernus corms. N-­terminal amino-acid sequence analysis of the approximately 30?kDa protein showed 33% identity to narbonin, a seed protein from Vicia narbonensis L. The C. vernus chitinase was crystallized by the hanging-drop vapour-diffusion method using PEG 8000 as the main precipitant. The crystal belonged to the monoclinic space group C2, with unit-cell parameters a = 172.3, b = 37.1, c = 126.4?Å, ? = 127° and two molecules per asymmetric unit. Diffraction data were collected to a resolution of 2.1?Å. PMID:21393839

Akrem, Ahmed; Iqbal, Sadaf; Buck, Friedrich; Meyer, Arne; Perbandt, Markus; Voelter, Wolfgang; Betzel, Christian

2011-01-01

387

Narbonin, a 2 S globulin from Vicia narbonensis L. Crystallization and preliminary crystallographic data.  

PubMed

A seed globulin from Vicia narbonensis L. has been crystallized by vapour diffusion induced pH-shift. Crystals are suitable for high-resolution X-ray structural analysis and diffract to better than 1.5 A. Narbonin crystallizes in the monoclinic space group P21 with alpha = 46.9 A, b = 75.5 A, c = 50.9 A, alpha = gamma = 90 degrees, beta = 120.5 degrees. The protein consists of one polypeptide chain that does not coincide with the subunits of legumin or vicilin after SDS/polyacrylamide gel electrophoresis and has a relative molecular mass of about 33,000. PMID:2231708

Hennig, M; Schlesier, B; Pfeffer, S; Höhne, W E

1990-10-01

388

36 CFR 1280.85 - What space in the National Archives at College Park is available for use by non-NARA groups and...  

Code of Federal Regulations, 2013 CFR

...2012-07-01 true What space in the National Archives at College Park is available for use...Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION NARA FACILITIES...the Washington, DC, Area? National Archives at College Park, Md § 1280.85...

2013-07-01

389

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION  

E-print Network

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 1 NASA Earth Science Data Systems Software Reuse #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION ESDS Reuse Working Group 2 Award Background: http://www.esdswg.com/softwarereuse/Resources/awards/ #12;NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

Christian, Eric

390

Cloning, expression, purification and preliminary X-ray crystallographic analysis of mouse protein arginine methyltransferase 7.  

PubMed

Protein arginine methyltransferase 7 (PRMT7) is a unique but less characterized member of the family of protein arginine methyltransferases (PRMTs) that plays a role in male germline gene imprinting. PRMT7 is the only known PRMT member that catalyzes the monomethylation but not the dimethylation of the target arginine residues and harbours two catalytic domains in tandem. PRMT7 genes from five different species were cloned and expressed in Escherichia coli and Sf21 insect cells. Four gave soluble proteins from Sf21 cells, of which two were homogeneous and one gave crystals. The mouse PRMT7 structure was solved by the single anomalous dispersion method using a crystal soaked with thimerosal that diffracted to beyond 2.1?Å resolution. The crystal belonged to space group P4(3)2(1)2, with unit-cell parameters a = b = 97.4, c = 168.1?Å and one PRMT7 monomer in the asymmetric unit. The structure of another crystal form belonging to space group I222 was solved by molecular replacement. PMID:24419624

Cura, Vincent; Troffer-Charlier, Nathalie; Lambert, Marie-Annick; Bonnefond, Luc; Cavarelli, Jean

2014-01-01

391

Expression, crystallization and preliminary X-ray crystallographic studies of Arthrobacter globiformis inulin fructotransferase.  

PubMed

A recombinant form of Arthrobacter globiformis inulin fructotransferase (DFAIII-producing) has been overexpressed in Escherichia coli and purified to homogeneity. Crystals were obtained at 293 K by the hanging-drop vapour-diffusion technique using 0.1 M Na HEPES pH 7.5 buffer containing 1.5 M lithium sulfate as a precipitant. Crystals of the recombinant wild-type enzyme diffracted to better than 1.5 A at 100 K using a synchrotron-radiation source at the Photon Factory. The crystal belonged to space group R32, with unit-cell parameters a = b = 92.02, c = 229.82 A in the hexagonal axes. Assuming the presence of one molecule in the asymmetric unit, the V(M) value for the crystal was 2.15 A(3) Da(-1), indicating a solvent content of 42.8%. Selenomethionine-derivative crystals belonged to a different space group, C2, with unit-cell parameters a = 159.32, b = 91.92, c = 92.58 A, beta = 125.06. Matthews coefficient calculations suggested that the C2 selenomethionine-derivative crystal contained three molecules per asymmetric unit. PMID:14646096

Momma, Mitsuru; Fujimoto, Zui; Maita, Nobuo; Haraguchi, Kazutomo; Mizuno, Hiroshi

2003-12-01

392

Recombinant bovine uteroglobin at 1.6?Å 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. PMID:16511079

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

2005-01-01

393

Crystallization and preliminary crystallographic analysis of two eukaryotic fructosyl peptide oxidases.  

PubMed

Fructosyl peptide oxidase (FPOX) catalyses the oxidation of ?-glycated dipeptides such as N(?)-(1-deoxy-D-fructos-1-yl)-L-valyl-L-histidine (Fru-ValHis) and is used in the diagnosis of diabetes mellitus. Here, two thermostable mutants of FPOX, CFP-T7 and EFP-T5M, were crystallized by the sitting-drop vapour-diffusion method. The crystal of CFP-T7 belonged to the tetragonal space group P4(1)2(1)2, with unit-cell parameters a = b = 110.09, c = 220.48 Å, and that of EFP-T5M belonged to the monoclinic space group P2(1), with unit-cell parameters a = 43.00, b = 230.05, c = 47.27 Å, ? = 116.99°. The crystals of CFP-T7 and EFP-T5M diffracted to 1.8 and 1.6 Å resolution, respectively. PMID:23385752

Ichiyanagi, Atsushi; Hirokawa, Kozo; Gomi, Keiko; Nakatsu, Toru; Kato, Hiroaki; Kajiyama, Naoki

2013-02-01

394

OAST Space Theme Workshop. Volume 3: Working group summary. 3: Sensors (E-3). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2). D. Additional assessment  

NASA Technical Reports Server (NTRS)

Developments required to support the space power, SETI, solar system exploration and global services programs are identified. Instrumentation and calibration sensors (rather than scientific) are needed for the space power system. Highly sophisticated receivers for narrowband detection of microwave sensors and sensors for automated stellar cataloging to provide a mapping data base for SETI are needed. Various phases of solar system exploration require large area solid state imaging arrays from UV to IR; a long focal plane telescope; high energy particle detectors; advanced spectrometers; a gravitometer; and atmospheric distanalyzer; sensors for penetrometers; in-situ sensors for surface chemical analysis, life detection, spectroscopic and microscopic analyses of surface soils, and for meteorological measurements. Active and passive multiapplication sensors, advanced multispectral scanners with improved resolution in the UV and IR ranges, and laser techniques for advanced probing and oceanographic characterization will enhance for global services.

1976-01-01

395

Conformal Carroll groups  

NASA Astrophysics Data System (ADS)

Conformal extensions of Lévy-Leblond's Carroll group, based on geometric properties analogous to those of Newton-Cartan space-time are proposed. The extensions are labeled by an integer k. This framework includes and extends our recent study of the Bondi-Metzner-Sachs (BMS) and Newman-Unti (NU) groups. The relation to conformal Galilei groups is clarified. Conformal Carroll symmetry is illustrated by ‘Carrollian photons’. Motion both in the Newton-Cartan and Carroll spaces may be related to that of strings in the Bargmann space.

Duval, C.; Gibbons, G. W.; Horvathy, P. A.

2014-08-01

396

Group Dynamics in Long -term blind endeavors on Earth as an analog for Remote Space Missions (Lewis & Clark Expedition, 1803 - 1806, Dynamic Analysis)  

NASA Astrophysics Data System (ADS)

In 1803 President Thomas Jefferson set fourth a military expedition led by Captains newline M Lewis and W Clark L C Expedition on an exploration to learn more about the large territory of land the U S had just purchased from France Cavan 1991 Their mission was to find a direct water route to the Pacific Ocean for the purpose of commerce and further industrial development Edwards 1999 Looking back at the events of this exploration there are many similarities to the experiences future human space explorers will face as we look to colonize the Moon and travel to Mars and beyond NASA Vision for Space Exploration 2004 - The L C Expedition lasted almost three years and involved a crew of 43 men traveling up the Missouri River to explore the unknown lands and a possible water route to the Pacific Ocean newline - The expedition took place far away from customary comfortable environments known to European settlers in early 18th century newline - The expedition involved a remotely confined high-perceived risk environment with high levels of uncertainty providing stresses and every day challenges for the crew newline - Supplies brought on the mission were limited mainly a mass weight issue rather than cost therefore the discovery and use of environmental resources In-Situ Resource Utilization approach including info-resources to mitigate uncertainty was necessary for crew survival The environments astronauts will encounter in space and on the Moon and Mars due to high risk and uncertainty will be in many aspects similar

Allner, M.; Rygalov, V.; Reilly, J.

397

Crystallographic, luminescence and photoconductive characteristics of chemically tailored ZnO nanorods  

SciTech Connect

The optoelectronic properties of zinc oxide (ZnO) nanorods synthesized using two different chemical methods have been explored in the light of microstructural features. The presence/absence of band edge emission in the luminescence spectra of the nanorods is found to be governed by the crystallographic properties. Moreover, we observed a pronounced effect of variation in crystallite size on the UV photoconductivity of the nanorods. Understanding the influence of microstructural aspects on the optical and electronic properties of the nanostructures may help in the fabrication of prototype, miniaturized optoelectronic devices.

Bayan, Sayan, E-mail: sayan.bayan@gmail.com; Chakraborty, Purushottam [Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata- 700 064 (India); Mohanta, Dambarudhar [Department of Physics, Tezpur University, Napaam, Tezpur -784028, Assam (India)

2014-04-24

398

Substituent effects in nitro derivatives of carbazoles investigated by comparison of low-temperature crystallographic studies with density functional theory (DFT) calculations.  

PubMed

The crystal structure of 9H-carbazole, C12H9N, (I), has been redetermined at low temperature for use as a reference structure in a comparative study with the structures of 1-nitro-9H-carbazole, C12H8N2O2, (II), and 9-nitrocarbazole, C12H8N2O2, (III). The molecule of (I) has crystallographically imposed mirror symmetry (Z' = 0.5). All three solid-state structures are slightly nonplanar, the dihedral angles between the planes of the arene and pyrrole rings ranging from 0.40?(7)° in (III) to 1.82?(18)° in (II). Nevertheless, a density functional theory (DFT) study predicts completely planar conformations for the isolated molecules. To estimate the influence of nitro-group substitution on aromaticity, the HOMA (harmonic oscillator model of aromaticity) descriptor of ?-electron delocalization has been calculated in each case. The HOMA indices for the isolated and solid-state molecules are relatively consistent and decrease in value for aromatic rings that are substituted with a ?-electron-withdrawing nitro group. Substitution of the arene ring influences the ?-electron delocalization in the ring only weakly, showing strong resistance to a perturbation of its geometry, contrary to what is observed for nitro substitution of the five-membered heterocyclic pyrrole ring. In (II), the molecules are arranged in near-planar dimers connected to each other by strong N-H···O hydrogen bonds that stack parallel to the crystallographic b axis. A similar stacking arrangement is observed in (III), although here the stacked structure is formed by stand-alone molecules. PMID:25279602

Gajda, Katarzyna; Zarychta, Bartosz; Kopka, Katarzyna; Daszkiewicz, Zdzis?aw; Ejsmont, Krzysztof

2014-10-15

399

The study of space communications spread spectrum systems. Part 1: Saw-based joint group demodulation of frequency shift keyed and differential phase shift keyed signals  

Microsoft Academic Search

A surface acoustic wave (SAW) device based processor, capable of the joint group demodulation of frequency shift keying (FSK) and differential phase shift keying (DPSK) signals, and intended for use in the Canadian extremely high frequency (EHF) Satcom system is proposed. The processor is based on the ability of SAW filters to implement wideband, real time, Fourier transforms with an

Peter T. Traynor; Peter J. McLane

1990-01-01

400

Enhancing nanoscale SEM image segmentation and reconstruction with crystallographic orientation data and machine learning  

SciTech Connect

Current methods of image segmentation and reconstructions from scanning electron micrographs can be inadequate for resolving nanoscale gaps in composite materials (1–20 nm). Such information is critical to both accurate material characterizations and models of piezoresistive response. The current work proposes the use of crystallographic orientation data and machine learning for enhancing this process. It is first shown how a machine learning algorithm can be used to predict the connectivity of nanoscale grains in a Nickel nanostrand/epoxy composite. This results in 71.9% accuracy for a 2D algorithm and 62.4% accuracy in 3D. Finally, it is demonstrated how these algorithms can be used to predict the location of gaps between distinct nanostrands — gaps which would otherwise not be detected with the sole use of a scanning electron microscope. - Highlights: • A method is proposed for enhancing the segmentation/reconstruction of SEM images. • 3D crystallographic orientation data from a nickel nanocomposite is collected. • A machine learning algorithm is used to detect trends in adjacent grains. • This algorithm is then applied to predict likely regions of nanoscale gaps. • These gaps would otherwise be unresolved with the sole use of an SEM.

Converse, Matthew I., E-mail: mconverse85@yahoo.com; Fullwood, David T.

2013-09-15

401

Integration of first-principles methods and crystallographic database searches for new ferroelectrics: Strategies and explorations  

SciTech Connect

In this concept paper, the development of strategies for the integration of first-principles methods with crystallographic database mining for the discovery and design of novel ferroelectric materials is discussed, drawing on the results and experience derived from exploratory investigations on three different systems: (1) the double perovskite Sr(Sb{sub 1/2}Mn{sub 1/2})O{sub 3} as a candidate semiconducting ferroelectric; (2) polar derivatives of schafarzikite MSb{sub 2}O{sub 4}; and (3) ferroelectric semiconductors with formula M{sub 2}P{sub 2}(S,Se){sub 6}. A variety of avenues for further research and investigation are suggested, including automated structure type classification, low-symmetry improper ferroelectrics, and high-throughput first-principles searches for additional representatives of structural families with desirable functional properties. - Graphical abstract: Integration of first-principles methods with crystallographic database mining, for the discovery and design of novel ferroelectric materials, could potentially lead to new classes of multifunctional materials. Highlights: Black-Right-Pointing-Pointer Integration of first-principles methods and database mining. Black-Right-Pointing-Pointer Minor structural families with desirable functional properties. Black-Right-Pointing-Pointer Survey of polar entries in the Inorganic Crystal Structural Database.

Bennett, Joseph W. [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States)] [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States); Rabe, Karin M., E-mail: rabe@physics.rutgers.edu [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States)

2012-11-15

402

Differential Stability of the Crystallographic Interfaces of Mu- and Kappa-Opioid Receptors  

PubMed Central

The recent mu-opioid receptor (MOPr) and kappa-opioid receptor (KOPr) crystal structures have inspired hypotheses of physiologically relevant dimerization contacts, specifically: a closely packed interface involving transmembrane (TM) helices TM5 and TM6, and a less compact interface, involving TM1, TM2, and helix 8 (H8). While the former was only found in MOPr crystals, similar arrangements of the latter were identified for both KOPr and MOPr. The relevance of these interfaces outside of a crystal lattice is called into question by the possibility that they might be influenced by the specific crystallization conditions. In this study, we have employed umbrella sampling molecular dynamics simulations of coarse-grained representations of the interacting MOPr or KOPr crystallographic structures, in the absence of the T4 lysozyme, and in an explicit lipid-water environment, to determine the strength of receptor dimerization at the different crystallographic interfaces. We note that the shape of the interface plays a dominant role in the strength of the interaction, and the pattern of contacting residues defines the shape of the potential of mean force. This information can be used to guide experiments aimed at exploring the role of dimerization in opioid receptor function. PMID:24651466

Johnston, Jennifer M.; Filizola, Marta

2014-01-01

403

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

2009-07-01

404

Crystallographic study of grain refinement in aluminum alloys using the edge-to-edge matching model  

SciTech Connect

The edge-to-edge matching model for describing the interfacial crystallographic characteristics between two phases that are related by reproducible orientation relationships has been applied to the typical grain refiners in aluminum alloys. Excellent atomic matching between Al{sub 3}Ti nucleating substrates, known to be effective nucleation sites for primary Al, and the Al matrix in both close packed directions and close packed planes containing these directions have been identified. The crystallographic features of the grain refiner and the Al matrix are very consistent with the edge-to-edge matching model. For three other typical grain refiners for Al alloys, TiC (when a = 0.4328 nm), TiB{sub 2} and AlB{sub 2}, the matching only occurs between the close packed directions in both phases and between the second close packed plane of the Al matrix and the second close packed plane of the refiners. According to the model, it is predicted that Al{sub 3}Ti is a more powerful nucleating substrate for Al alloy than TiC, TiB{sub 2} and AlB{sub 2}. This agrees with the previous experimental results. The present work shows that the edge-to-edge matching model has the potential to be a powerful tool in discovering new and more powerful grain refiners for Al alloys.

Zhang, M.-X. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia)]. E-mail: m.zhang@minmet.uq.edu.au; Kelly, P.M. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia); Easton, M.A. [School of Physics and Materials Engineering, Monash University, Clayton, VIC 3800 (Australia); Taylor, J.A. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia)

2005-03-01

405

Effect of tungsten crystallographic orientation on He-ion-induced surface morphology changes  

SciTech Connect

In order to study the early stages of nanofuzz growth in fusion-plasma-facing tungsten, mirror-polished high-purity tungsten was exposed to 80 eV helium at 1130 C to a fluence of 4 1024 He/m2. The previously smooth surface shows morphology changes, and grains form one of four qualitatively different morphologies: smooth, wavy, pyramidal, or terraced/wide waves. Combining high-resolution scanning electron microscopy (SEM) observations to determine the morphology of each grain with quantitative measurement of the grain's orientation via electron backscatter diffraction (EBSD) in SEM shows that the normal-direction crystallographic orientation of the underlying grain controls the growth morphology. Specifically, near-<001> || normal direction (ND) grains formed pyramids, near-<114> to <112> || ND grains formed wavy and stepped structures, and near-<103> || ND grains remained smooth. Comparisons to control specimens indicate no changes to underlying bulk crystallographic texture, and the effects are attributed to surface energy anisotropy, although, surprisingly, the expected {101} low-energy planes were not the most stable. Future developments to control tungsten texture via thermomechanical processing, ideally obtaining a sharp near- <103> || ND processing texture, may delay the formation of nanofuzz.

Parish, Chad M [ORNL; Hijazi, Hussein Dib [ORNL; Meyer III, Harry M [ORNL; Meyer, Fred W [ORNL

2014-01-01

406

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. 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

2008-01-01

407

Scatter in nonlinear ultrasonic measurements due to crystallographic orientation change induced anisotropy in harmonics generation  

NASA Astrophysics Data System (ADS)

Present study endeavors to establish the physical basis of an unprecedented trend in scatter, observed in nonlinear ultrasonic (NLU) parameter, associated with varying degree of crystallographic orientation change across crystallites in a polycrystalline material. It is shown that this scatter arises due to anisotropy in harmonics generation as a result of orientation change of slip systems in polycrystals with respect to the wave propagation direction. A near ? titanium alloy has been taken as a model alloy to demonstrate this effect of crystallographic orientation change vis-à-vis change in the orientation of slip systems. Scale of crystal orientation change is shown to have a strong correlation with the degree of scatter in NLU measurements. Further, the study establishes the dominating effect of the scale of crystalline orientation change on harmonics generation as compared to variation in other microstructural parameters such as dislocation density, interface structure etc. Frequency distribution analysis of the scatter indicates that the distribution depends on the colony size which exhibits a linear correlation with standard deviation value. The dislocation string vibration model has been extended for harmonics generation in polycrystalline aggregates to explain the trend in the scatter during measurement of NLU parameter in the material.

Mukhopadhyay, Amretendu; Sarkar, Rajdeep; Punnose, Sony; Valluri, Jitendra; Nandy, T. K.; Balasubramaniam, Krishnan

2012-03-01

408

Crystallographically controlled crystal-plastic deformation of zircon in shear zones  

NASA Astrophysics Data System (ADS)

Plastically-deformed zircons from various types of strained natural metamorphic rocks have been investigated in-situ by electron backscatter diffraction analysis (EBSD), allowing crystallographic orientation mapping at high spatial resolution. Plastic deformation often forms under the control of grain-internal heterogeneities. At the crystal structure scale deformation is controlled by the physical anisotropy of the lattice. Three most common slip systems in zircon are [100]{010}, [010]{001} and [001]{010} (Leroux et. al., 1999; Reddy et. al., 2007). They are genetically connected with the main zircon crystallographic directions: [001] (c-axis), [100] and [010] (a and b axes). Atomic models show weak planes normal to these directions that preferably evolve to glide planes in the deforming crystal. The visualization of seismic (elastic) properties of zircon with the MATLAB toolbox MTEX shows a similar pattern. The slowest S-wave velocities are observed in directions parallel to [100], [010] and [001] crystallographic directions. The highest Young's modulus values lie in the same directions. In natural zircon grains, the common slip systems are preferably activated when zircon is hosted by rheologically comparatively weaker phases or a fine-grained matrix. In these cases zircon behaves as a rigid clast. During progressive deformation high deviatoric stresses together with high strain rates concentrate at crystal tips, as shown by numerical modeling. Softer host phases allow more degrees of freedom for zircon to be deformed according to its crystallographic and internal properties. These conclusions are supported by the misorientation axes density distribution maps, derived with MTEX. Deformed zircon hosted by a relatively soft phase (mostly biotite) develops a crystallographic preferred orientation (CPO), which has not been documented for zircon before. At the same time deformation of zircon hosted by a rheologically stronger matrix causes the activation of less common slip systems, screw dislocations or the development of brittle deformation. In this case the internal deformation is mainly controlled by the host phase microstructural arrangement. Crystal lattice distortions of zircon such as plastic deformation features may facilitate intragranular material transport. Enhanced mobility of trace elements or radiogenic isotopes influences isotopic systems used for geochronology. In-situ microstructural study of plastically deformed accessory zircon grains allows linking different stages of high-grade regional metamorphism and deformation. Understanding of zircon deformation mechanisms and their effects on the distribution of trace elements and isotopic systems is important for deriving the age of deformation events. References: Leroux, H., Reimold, W.U., Koeberl, C., Hornemann, U., Doukhan, J.C., 1999. Experimental shock deformation in zircon: a transmission electron microscopic study. Earth and Planetary Science Letters, 169, 291-301. Reddy, S.M., Timms, N.E., Pantleon, W., Trimby, T., 2007. Quantitative characterization of plastic deformation of zircon and geological implications. Contributions to Mineralogy and Petrology 153, 625-645.

Kovaleva, Elizaveta; Klötzli, Urs

2014-05-01

409

Space transportation alternatives for large space programs - The International Space University summer session - 1992  

Microsoft Academic Search

The issues discussed in this paper are the result of a 10-week study by the Space Solar Power Program design project members and the Space Transportation Group at the International Space University (ISU) summer session of 1992 to investigate new paradigms in space propulsion and how those paradigms might reduce the costs for large space programs. The program plan was

Bryan Palaszewski

1993-01-01

410

The nonabelian tensor square of Bieberbach group of dimension five with dihedral point group of order eight  

NASA Astrophysics Data System (ADS)

The nonabelian tensor product was originated in homotopy theory as well as in algebraic K-theory. The nonabelian tensor square is a special case of the nonabelian tensor product where the product is defined if the two groups act on each other in a compatible way and their action are taken to be conjugation. In this paper, the computation of nonabelian tensor square of a Bieberbach group, which is a torsion free crystallographic group, of dimension five with dihedral point group of order eight is determined. Groups, Algorithms and Programming (GAP) software has been used to assist and verify the results.

Fauzi, Wan Nor Farhana Wan Mohd; Idrus, Nor'ashiqin Mohd; Masri, Rohaidah; Sarmin, Nor Haniza

2014-07-01

411

Crystallization and preliminary crystallographic studies of the hypothetical protein BPSL1038 from Burkholderia pseudomallei.  

PubMed

Melioidosis is an infectious disease caused by the pathogenic bacterium Burkholderia pseudomallei. Whole-genome sequencing revealed that the B. pseudomallei genome includes 5855 coding DNA sequences (CDSs), of which ?25% encode hypothetical proteins. A pathogen-associated hypothetical protein, BPSL1038, was overexpressed in Escherichia coli, purified and crystallized using vapour-diffusion methods. A BPSL1038 protein crystal that grew using sodium formate as precipitant diffracted to 1.55?Å resolution. It belonged to space group C2221, with unit-cell parameters a = 85.36, b = 115.63, c = 46.73?Å. The calculated Matthews coefficient (VM) suggests that there are two molecules per asymmetric unit, with a solvent content of 48.8%. PMID:25484229

Shaibullah, Sofiyah; Mohd-Sharif, Nurhikmah; Ho, Kok Lian; Firdaus-Raih, Mohd; Nathan, Sheila; Mohamed, Rahmah; Ng, Chyan Leong

2014-12-01

412

Crystallization and preliminary crystallographic analysis of the cellulose biosynthesis-related protein CMCax from Acetobacter xylinum.  

PubMed

The cellulose biosynthesis-related protein CMCax from Acetobacter xylinum was overexpressed in Escherichia coli, purified and crystallized. Single crystals of selenomethionine (SeMet) substituted CMCax were obtained by the hanging-drop vapour-diffusion method at 293 K, primarily using polyethylene glycol 4000 as a precipitant. The crystals belong to the primitive hexagonal space group P6(1) or P6(5), with unit-cell parameters a = b = 89.1, c = 94.2 A. The predicted Matthews coefficient (VM) value is 3.0 A3 Da(-1) for one CMCax monomer in the asymmetric unit. A single-wavelength anomalous dispersion (SAD) data set was collected to a resolution of 2.3 A using synchrotron radiation. PMID:16511009

Kawano, Shin; Yasutake, Yoshiaki; Tajima, Kenji; Satoh, Yasuharu; Yao, Min; Tanaka, Isao; Munekata, Masanobu

2005-02-01

413

Preliminary crystallographic analysis of a cruciferin protein from seeds of Moringa oleifera.  

PubMed

A 55 kDa cruciferin protein has been purified and characterized from seeds of Moringa oleifera plant. Protein blast of N-terminal amino-acid sequence showed 60 % sequence similarity with cruciferin from Brassica napus. The M. oleifera protein has been crystallized applying the sitting drop method using 5 % polyethylene glycol 8,000, 38.5 % 3-methyl-1,5-pentanediol and 0.1 M sodium cacodylate pH 6.5. The crystals belonged to the P6322 hexagonal space group with cell dimensions, a = b = 98.4, c = 274.3 Å. Initial diffraction data have been collected to a resolution of 6 Å. PMID:24705831

Akrem, Ahmed; Yousef, Nasser; Begum, Afshan; Negm, Amr; Meyer, Arne; Perbandt, Markus; Buck, Friedrich; Betzel, Christian

2014-06-01

414

X-ray crystallographic studies of recombinant inorganic pyrophosphatase from Escherichia coli.  

PubMed

An E. coli inorganic pyrophosphatase overproducer and a method for a large-scale production of the homogeneous enzyme are described. The inorganic pyrophosphatase was crystallized in the form containing one subunit of a homohexameric molecule per asymmetric unit: space group R32, a = 110.4 A, c = 76.8 A. The electron density map to 2.5 A resolution phased with Eu- and Hg-derivatives (figure of merit, = 0.51) was improved by the solvent flattening procedure ( = 0.77). The course of the polypeptide chain and the secondary structure elements, intersubunit contacts and positions of the active sites were characterized. Homology with S. cerevisiae inorganic pyrophosphatase structure was found. PMID:8034059

Oganessyan VYu; Kurilova, S A; Vorobyeva, N N; Nazarova, T I; Popov, A N; Lebedev, A A; Avaeva, S M; Harutyunyan, E H

1994-07-18

415

Cloning, purification, crystallization and X-ray crystallographic analysis of Ignicoccus hospitalis neelaredoxin.  

PubMed

Superoxide reductases (SORs) are metalloproteins which constitute the most recently identified oxygen-detoxification system in anaerobic and microaerobic bacteria and archaea. SORs are involved in scavenging superoxide radicals from the cell by catalyzing the reduction of superoxide ({\\rm O}_{2};{\\bullet -}) to hydrogen peroxide and are characterized by a catalytic nonhaem iron centre coordinated by four histidine ligands and one cysteine ligand. Ignicoccus hospitalis, a hyperthermophilic crenarchaeon, is known to have a neelaredoxin-type SOR that keeps toxic oxygen species levels under control. Blue crystals of recombinant I. hospitalis oxidized neelaredoxin (14.1 kDa, 124 residues) were obtained. These crystals diffracted to 2.4 A resolution in-house at room temperature and belonged to the hexagonal space group P6(2)22 or P6(4)22, with unit-cell parameters a = b = 108, c = 64 A. Cell-content analysis indicated the presence of one monomer in the asymmetric unit. PMID:20445270

Pinho, Filipa G; Romão, Célia V; Pinto, Ana F; Saraiva, Lígia M; Huber, Harald; Matias, Pedro M; Teixeira, Miguel; Bandeiras, Tiago M

2010-05-01

416

Crystallization and preliminary crystallographic analysis of a surface antigen glycoprotein, SAG19, from Eimeria tenella.  

PubMed

Coccidiosis in chickens is caused by the apicomplexan parasite Eimeria tenella and is thought to involve a role for a superfamily of more than 20 cysteine-rich surface antigen glycoproteins (SAGs) in host-parasite interactions. A representative member of the family, SAG19, has been overexpressed in Escherichia coli, purified and crystallized by the hanging-drop method of vapour diffusion using ammonium sulfate as the precipitant. Crystals of SAG19 diffracted to beyond 1.50 Å resolution and belonged to space group I4, with unit-cell parameters a = b = 108.2, c = 37.5 Å. Calculation of possible values of VM suggests that there is a single molecule in the asymmetric unit. PMID:24316835

Ramly, Nur Zazarina; Rouzheinikov, Sergey N; Sedelnikova, Svetlana E; Baker, Patrick J; Chow, Yock Ping; Wan, Kiew Lian; Nathan, Sheila; Rice, David W

2013-12-01

417

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

2002-10-01

418

Crystallization and Preliminary X-Ray Crystallographic Analysis of Human Plasma Platelet Activating Factor Acetylhydrolase  

SciTech Connect

The plasma form of the human enzyme platelet activating factor acetylhydrolase (PAF-AH) has been crystallized, and X-ray diffraction data were collected at a synchrotron source to a resolution of 1.47 {angstrom}. The crystals belong to space group C2, with unit cell parameters of a = 116.18, b = 83.06, c = 96.71 {angstrom}, and {beta} = 115.09 and two molecules in the asymmetric unit. PAF-AH functions as a general anti-inflammatory scavenger by reducing the levels of the signaling molecule PAF. Additionally, the LDL bound enzyme has been linked to atherosclerosis due to its hydrolytic activities of pro-inflammatory agents, such as sn-2 oxidatively fragmented phospholipids.

Samanta, U.; Wilder, C; Bahnson, B

2009-01-01

419

Crystallization and preliminary crystallographic analysis of endo-1,3-?-glucanase from Arthrobacter sp.  

PubMed Central

Endo-1,3-?-glucanases hydrolyze internal 1,3-?-glucosyl linkages. The endo-1,3-?-glucanase from Arthrobacter sp. was crystallized by the hanging-drop vapour-diffusion method. The crystals belonged to space group P41, with unit-cell parameters a = 71.31, c = 60.07?Å, and contained one molecule per asymmetric unit. The Matthews coefficient (V M) and the solvent content were 2.35?Å3?Da?1 and 47.63%, respectively. Diffraction data were collected to a resolution of 1.66?Å at SPring-8 using a MAR CCD area detector and gave a data set with an overall R merge of 5.4% and a completeness of 99.4%. PMID:16508094

Pang, Zhongcun; Kang, You-Na; Ban, Mizuho; Oda, Masayuki; Kobayashi, Ryo; Ohnishi, Masatake; Mikami, Bunzo

2005-01-01

420

Expression, purification, crystallization and preliminary X-ray crystallographic analysis of tomato ?-galactosidase 4.  

PubMed

Plant ?-galactosidases play important roles in carbohydrate-reserve mobilization, cell-wall expansion and degradation, and turnover of signalling molecules during ripening. Tomato ?-galactosidase 4 (TBG4) not only has ?-galactosidase activity but also has exo-?-(1,4)-galactanase activity, and prefers ?-(1,4)-galactans longer than pentamers as its substrates; most other ?-galactosidases only have the former activity. Recombinant TBG4 protein expressed in the yeast Pichia pastoris was crystallized by the sitting-drop vapour-diffusion method using PEG 10?000 as a precipitant. The crystals belonged to the orthorhombic space group P212121, with unit-parameters a = 92.82, b = 96.30, c = 159.26?Å, and diffracted to 1.65?Å resolution. Calculation of the Matthews coefficient suggested the presence of two monomers per asymmetric unit (VM = 2.2?Å(3)?Da(-1)), with a solvent content of 45%. PMID:25664788

Eda, Masahiro; Ishimaru, Megumi; Tada, Toshiji

2015-02-01

421

Purification, identification and preliminary crystallographic studies of an allergenic protein from Solanum melongena.  

PubMed

Solanum melongena (eggplant), a member of the Solanaceae family, is a widely cultivated vegetable crop and is commonly used as a food throughout the world. Allergic reactions caused by members of this family are well known. However, mechanistic analyses to understand their molecular basis have not been adequately explored. In order to address this issue, the 7S vicilin protein (SM80.1) of size 45?kDa was purified from seeds of S. melongena by ammonium sulfate fractionation and size-exclusion chromatography. Significant homology of SM80.1 to an allergy-related protein from S. lycopersicum was identified through a BLAST search. Crystallization attempts with purified protein using the hanging-drop vapour-diffusion method led to hexagonal-shaped crystals. The crystals diffracted to 2.21?Å resolution and belonged to space group P6322, with unit-cell parameters a = 117.9, c = 123.5?Å. PMID:25664800

Jain, Abha; Salunke, Dinakar Masanu

2015-02-01

422

Expression, purification, crystallization and preliminary X-ray crystallographic analysis of Enpp1  

PubMed Central

Enpp1 is an extracellular membrane-bound glycoprotein that regulates bone mineralization by hydrolyzing ATP to generate pyrophosphate. The extracellular region of mouse Enpp1 was expressed in HEK293S GnT1? cells, purified using the TARGET tag/P20.1-Sepharose system and crystallized. An X-­ray diffraction data set was collected to 3.0?Å resolution. The crystal belonged to space group P31, with unit-cell parameters a = b = 105.3, c = 173.7?Å. A single-wavelength anomalous dispersion (SAD) data set was also collected to 2.7?Å resolution using a selenomethionine-labelled crystal. The experimental phases determined by the SAD method produced an interpretable electron-density map. PMID:22750863

Kato, Kazuki; Nishimasu, Hiroshi; Mihara, Emiko; Ishitani, Ryuichiro; Takagi, Junichi; Aoki, Junken; Nureki, Osamu

2012-01-01

423

Purification, crystallization and preliminary crystallographic analysis of the adhesion domain of Epf from Streptococcus pyogenes  

PubMed Central

The extracellular protein Epf from Streptococcus pyogenes is important for streptococcal adhesion to human epithelial cells. However, Epf has no sequence identity to any protein of known structure or function. Thus, several predicted domains of the 205?kDa protein Epf were cloned separately and expressed in Escherichia coli. The N-terminal domain of Epf was crystallized in space groups P21 and P212121 in the presence of the protease chymotrypsin. Mass spectrometry showed that the species crystallized corresponded to a fragment comprising residues 52–357 of Epf. Complete data sets were collected to 2.0 and 1.6?Å resolution, respectively, at the Australian Synchrotron. PMID:22750867

Linke, Christian; Siemens, Nikolai; Middleditch, Martin J.; Kreikemeyer, Bernd; Baker, Edward N.

2012-01-01

424

Crystallization and preliminary crystallographic studies of the recombinant antitumour lectin from the edible mushroom Agrocybe aegerita.  

PubMed

The antitumour lectin from Agrocybe aegerita, named AAL, shows strong inhibition effects on human and mouse tumour cells via apoptosis induction activity. Recombinant AAL (rAAL) has been expressed and purified. Both rAAL and rAAL-lactose complex have been crystallized and their X-ray diffraction data were collected to resolutions of 1.9 A and 1.6 A, respectively. Both crystals belong to space group P2(1) with unit cell parameters a = 53.20 A, b = 66.01 A, c = 57.86 A, beta = 109.38 and a = 53.38 A, b = 66.29 A, c = 58.02 A, beta = 109.03, respectively. PMID:15996911

Yang, Na; Tong, Xin; Xiang, Ye; Zhang, Ying; Sun, Hui; Wang, Da-Cheng

2005-08-10

425

Crystallization and preliminary crystallographic studies of an antitumour lectin from the edible mushroom Agrocybe aegerita.  

PubMed

An antitumour lectin named AAL has been purified from the fruiting body of edible mushroom Agrocybe aegerita. In addition to having a distinct bioactivity, AAL shows strong inhibition effects on human and mouse tumour cells. It has been shown that AAL exerts its antitumour effects via apoptosis-induction. AAL and AAL-lactose complex have been crystallized and their diffraction data were collected with resolution of 2.6 A and 3.0 A, respectively. Both crystals belong to space group P 6122 with unit cell parameters a = 123.98 A, b = 123.98 A, c = 56.86 A, alpha= beta=90 degrees, gamma = 120 degrees and a = 123.69 A, b = 123.69 A, c = 56.64 A, alpha = beta = 90 degrees, gamma = 120 degrees, respectively. PMID:16522188

Yang, Na; Liang, Yi; Xiang, Ye; Zhang, Ying; Sun, Hui; Wang, Da-Cheng

2005-10-01

426

Preliminary crystallographic study of the phenylalanyl-tRNA synthetase from Thermus thermophilus HB8.  

PubMed

Phenylalanyl-tRNA synthetase (EC 6.1.1.20) from the extreme thermophile Thermus thermophilus HB8 has been isolated and crystallized. The enzyme was found to consist of two types of subunits with molecular masses 38 X 10(3) (alpha) and 94 X 10(3) (beta) and is likely to be a tetrameric protein with a molecular mass of about 260 X 10(3) (alpha 2 beta 2). Crystals of phenylalanyl-tRNA synthetase were grown by the hanging-drop technique at 4 degrees C in the presence of ammonium sulfate. Trigonal crystals, space group P3(1)21, with cell dimensions a = b = 176 A and c = 142 A (1 A = 0.1 nm), are suitable for medium-resolution X-ray analysis. PMID:3430620

Chernaya, M M; Korolev, S V; Reshetnikova, L S; Safro, M G

1987-12-01

427

Overexpression, crystallization and preliminary X-ray crystallographic analysis of the phosphotriesterase from Mycobacterium tuberculosis  

PubMed Central

Organophosphates (OPs) are extremely toxic compounds that are used as insecticides or even as chemical warfare agents. Phosphotriesterases (PHPs) are responsible for the detoxification of OPs by catalysing their degradation. Almost 100 PHP structures have been solved to date, yet the crystal structure of the phosphotriesterase from Mycobacterium tuberculosis (mPHP) remains unavailable. This study reports the first crystallization of mPHP. The crystal belonged to space group C2221, with unit-cell parameters a = 68.03, b = 149.60, c = 74.23?Å, ? = ? = ? = 90°. An analytical ultracentrifugation experiment suggested that mPHP exists as a dimer in solution, even though one molecule is calculated to be present in the asymmetric unit according to the structural data. PMID:23295488

Zhang, Liang; Chen, Ruyi; Dong, Zhe; Li, Xin

2013-01-01

428

Caffeic acid phenethyl ester (CAPE): synthesis and X-ray crystallographic analysis.  

PubMed

The structure of caffeic acid phenethyl ester [2-propenoic acid, 3-(3,4-dihydroxyphenyl)-, 2-phenethyl ester] (I), C17H16O4 x 1/2C6H6, synthesized by base-catalyzed alkylation of caffeic acid salt with beta-bromoethylbenzene in HMPA (hexamethylphosphoramide) and recrystallized from benzene, was confirmed by single crystal X-ray diffraction. The crystals are triclinic, space group P1, Z=2, unit cell dimension a=5.8129 (9) A, b=11.122 (2) A, c=13.226 (2) A, alpha=97.080 (3) degrees, beta=101.467 (3) degrees, gamma=95.405 (3) degrees , V=825.4 (2) A3, Dcalc=1.301 g/cm3, F(000)=342. The packing of the molecule is stabilized by intermolecular O1H...O4 (2.69 A) and O1...HO2 (2.82 A) hydrogen bonds. PMID:11217116

Son, S; Lobkowsky, E B; Lewis, B A

2001-02-01

429

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

430

Nanowire-templated lateral epitaxial growth of non-polar group III nitrides  

DOEpatents

A method for growing high quality, nonpolar Group III nitrides using lateral growth from Group III nitride nanowires. The method of nanowire-templated lateral epitaxial growth (NTLEG) employs crystallographically aligned, substantially vertical Group III nitride nanowire arrays grown by metal-catalyzed metal-organic chemical vapor deposition (MOCVD) as templates for the lateral growth and coalescence of virtually crack-free Group III nitride films. This method requires no patterning or separate nitride growth step.

Wang, George T. (Albuquerque, NM); Li, Qiming (Albuquerque, NM); Creighton, J. Randall (Albuquerque, NM)

2010-03-02

431

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

432

Crystallographic and Spectroscopic Studies of Solid Methylene Bromide, Methylene Iodide and 1,1-DICHLOROETHENE  

NASA Astrophysics Data System (ADS)

The crystal structures of the three solid phases of methylene iodide and the stable phase of deuterated methylene bromide have been determined using the neutron powder profile structure refinement technique. For CH _2I_2, both phase I at 50 K and phase III at 16 K, and for CD _2Br_2, the stable phase at 15 K, have eight molecules per unit cell on general sites of the space group C2/c. The structure of CH _2I_2, phase II, has been determined at 16 K, 30 K, 50 K and 255 K. This phase is face centred orthorhombic, space group Fmm2, with four molecules per unit cell on sites with C_ {rm 2V} symmetry. Molecular bond lengths and angles, corrected for thermal motions, are given for all structures. The lattice energy of each structure has been calculated using an empirical potential. The most stable phase of CH_2I _2 is phase II, but the energy differences between all three phases are small. Neutron powder diffraction profiles of 1,1-dichloroethene -d_2 (CD_2CC l_2) at 12 K and 120 K have been recorded. The diffraction peaks are indexed on the basis of a non-primitive hexagonal unit cell containing 32 molecules. The molecular positions are not refined. The far infrared spectra of crystalline CH _2CCl_2 and CD_2CCl_2 have been recorded from 30 cm^{ -1} to 400 cm^{-1} at 20 K and 80 K. The corresponding Raman spectra have been recorded from 20 cm^{-1} to 3200 cm^{-1} at the same temperatures. The lattice spectra contain 29 Raman and 15 infrared active modes. A centrosymmetric crystal structure is indicated by these spectra. The lattice modes are assigned on the basis of their isotopic frequency shifts. Crystal field and isotopic splittings are observed in the internal mode spectra at 20 K.

Prystupa, David Allan

433

Comparison of three calcium phosphate bone graft substitutes from biomechanical, histological, and crystallographic perspectives using a rat posterolateral lumbar fusion model.  

PubMed

This study evaluated the effectiveness of three calcium phosphate bone graft substitutes with different chemical compositions on spinal fusion using a rat posterolateral lumbar fusion model. Specifically, two recently developed non-dispersive tetracalcium phosphate/dicalcium phosphate anhydrous-based calcium phosphate cements (CPCs), namely a CPC consisting of equimolar amounts of the two compounds (nd-CPC) and a CPC consisting of a two-fold greater amount of dicalcium phosphate anhydrous (DCP-rich CPC), were compared with a commercial calcium phosphate bone graft (c-CPG) consisting of hydroxyapatite (60%) and ?-tricalcium phosphate (40%). Single-level posterolateral lumbar fusion was performed at the L4-L5 vertebrae in fifteen adult rats (n=5 for each group). Spinal fusion was evaluated with radiographs, manual palpation, mechanical testing, micro-CT, and histology 8 weeks post-surgery. In particular, the crystallographic phases in the three substitutes were identified before and 8 weeks after their implantation. Manual palpation revealed stable constructs in nearly all of the spine specimens. The stiffness and bending load of fused spines in the two CPC groups were comparable to those in the c-CPG group. The radiographs specifically revealed implant resorption and bone remodeling in the DCP-rich CPC group. Analysis of 3D micro-CT images revealed that the bone volume ratio in the DCP-rich CPC group was significantly greater than those in the nd-CPC and c-CPG groups. Histology showed that the DCP-rich CPC group exhibited the highest degree of bone regeneration and osseointegration. Notably, DCP-rich CPC led to a pronounced phase transformation, generating the greatest amount of poorly crystalline apatite among the three groups, which together with adequate resorption may explain the aforementioned positive findings. We therefore conclude that of the bone graft substitutes considered, DCP-rich CPC has the greatest potential to be used in spinal fusion. PMID:25491804

Hu, Ming-Hsien; Lee, Pei-Yuan; Chen, Wen-Cheng; Hu, Jin-Jia

2014-12-01

434

Ecosystem Analysis from Space: Diagnosis of Phytoplankton Functional Groups from Satellite Data and Skill Assessment for Coupled Hydrodynamic-Ecosystem Models  

NASA Astrophysics Data System (ADS)

A suite of empirical and semi-analytic ocean color algorithms were applied to three years of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data from the Gulf of Mexico. Examination of the interdependencies between various ocean color products and their relationships to satellite-retrieved physical variables (sea surface temperature, sea surface height) provided a means to diagnose potential changes in the taxonomic composition and size-structure of the surface phytoplankton community and attendant changes in the upper- ocean thermal structure. The principal method used to discern dominant phytoplankton functional groups was via examination of the satellite-estimated phytoplankton absorption efficiency: the ratio of phytoplankton absorption (443 nm) product to the surface pigment concentration product. The results were used to analyze a model of phytoplankton functional group dynamics for the surface mixed layer. Statistical plots summarizing the root-mean-square-errors and correlation coefficients between the model's results and the satellite-estimated chlorophyll fractionation were used to implement a model skill assessment for a range of potential model parameter settings.

Jolliff, J. K.; Penta, B.; Kindle, J.

2006-12-01

435

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

436

Integration of first-principles methods and crystallographic database searches for new ferroelectrics: Strategies and explorations  

NASA Astrophysics Data System (ADS)

In this concept paper, the development of strategies for the integration of first-principles methods with crystallographic database mining for the discovery and design of novel ferroelectric materials is discussed, drawing on the results and experience derived from exploratory investigations on three different systems: (1) the double perovskite Sr(Sb1/2Mn1/2)O3 as a candidate semiconducting ferroelectric; (2) polar derivatives of schafarzikite MSb2O4; and (3) ferroelectric semiconductors with formula M2P2(S,Se)6. A variety of avenues for further research and investigation are suggested, including automated structure type classification, low-symmetry improper ferroelectrics, and high-throughput first-principles searches for additional representatives of structural families with desirable functional properties.

Bennett, Joseph W.; Rabe, Karin M.

2012-11-01

437

Intrinsic Compressibility of Sperm Whale Myoglobin Determined from High-Pressure Crystallographic Structures  

NASA Astrophysics Data System (ADS)

Myoglobin, considered a paradigm for biocomplexity, may serve as a model system for studying the role of cavities and volume fluctuations in proteins. Volume fluctuations are directly probed by pressure via the compressibility. While the physico-chemical basis for pressure effects is well established, effects in structurally complex systems have yet to be fully explored. Biocomplexity can lead to significant effects at moderate, kilo-atmosphere pressures, and is the reason detailed structural information under pressure is needed to understand pressure effects in proteins and other biological systems. Structural determination of proteins at kilo-atmosphere pressures using x-ray crystallography is a powerful method for investigating the effects of pressure on structure. Here we present results quantifying the spatial distribution of intrinsic compressibility in sperm whale myoglobin calculated from crystallographic structures solved at ambient and at 1500 atm pressures.

Clark, Jeremy

2005-04-01

438

Ge/SrTiO{sub 3}(001): Correlation between interface chemistry and crystallographic orientation  

SciTech Connect

In this work, the desorption of a submonolayer deposit of Ge on SrTiO{sub 3}(001) is studied by reflection high energy electron diffraction. The results are compared to those of a previous experiment done using soft x-ray photoelectron spectroscopy. Combining these techniques allows for correlating interface chemistry and crystal orientation, and for bringing clarifying elements concerning the competition between (111) and (001) crystal orientation typical for the semiconductor/perovskite epitaxial systems. Despite poor interface matching, (111)-oriented islands are stabilized at the expense of (001)-oriented islands due to the relatively low energy of their free facets. Such 'surface energy driven' crystallographic orientation of the deposit is enhanced by the low adhesion energy characteristic of the Ge/SrTiO{sub 3} system.

Gobaut, B.; Penuelas, J.; Grenet, G.; Ferrah, D.; Benamrouche, A.; Chettaoui, A.; Robach, Y.; Botella, C.; Saint-Girons, G. [Universite de Lyon, Institut des Nanotechnologies de Lyon, Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69134 Ecully (France); El Kazzi, M.; Silly, M. G.; Sirotti, F. [Synchrotron SOLEIL (TEMPO beamline), l'Orme des Merisiers, Saint-Aubin, 91192 Gif-sur-Yvette (France)

2012-11-01

439

Nanoscale crystal imperfection-induced characterization changes of manganite nanolayers with various crystallographic textures  

PubMed Central

(La,Sr)MnO3 (LSMO) nanolayers with various crystallographic textures were grown on the sapphire substrate with and without In2O3 epitaxial buffering. The LSMO nanolayer with In2O3 epitaxial buffering has a (110) preferred orientation. However, the nanolayer without buffering shows a highly (100)-oriented texture. Detailed microstructure analyses show that the LSMO nanolayer with In2O3 epitaxial buffering has a high degree of nanoscale disordered regions (such as subgrain boundaries and incoherent heterointerfaces) in the film. These structural inhomogeneities caused a low degree of ferromagnetic ordering in LSMO with In2O3 epitaxial buffering, which leads to a lower saturation magnetization value and Curie temperature, and higher coercivity and resistivity. PMID:23919442

2013-01-01

440

Influence of crystallographic texture on Young's modulus of various Alloy 82H welds.  

PubMed

Electron backscatter diffraction (EBSD) was employed to analyze the microstructure and texture of four different Alloy 82H gas tungsten arc welds that previously underwent static and dynamic modulus testing. The Young's moduli were shown to differ among the various welds, but also within each weld, dependent upon the direction measured. These differences were attributed to anisotropy of the crystallographic textures, which were described using inverse pole figures with respect to each of the weld's three orthogonal axes. The Young's modulus demonstrated a strong correlation with the texture, consistent with single crystal experiments. Sample directions containing a large population of {100} orientations had the lowest Young's modulus, while those with {111} grains possessed the highest. Microstructures with {110} textures were closer to the average modulus value of 207 GPa (30.0 Msi). X-ray diffraction texture measurements on four samples were used to verify the EBSD results. PMID:21473809

Claves, Steven R; Mills, William J

2011-06-01

441

Using a conformation-dependent stereochemical library improves crystallographic refinement of proteins  

SciTech Connect

The major macromolecular crystallographic refinement packages restrain models to ideal geometry targets defined as single values that are independent of molecular conformation. However, ultrahigh-resolution X-ray models of proteins are not consistent with this concept of ideality and have been used to develop a library of ideal main-chain bond lengths and angles that are parameterized by the {phi}/{psi} angle of the residue [Berkholz et al. (2009), Structure, 17, 1316-1325]. Here, it is first shown that the new conformation-dependent library does not suffer from poor agreement with ultrahigh-resolution structures, whereas current libraries have this problem. Using the TNT refinement package, it is then shown that protein structure refinement using this conformation-dependent library results in models that have much better agreement with library values of bond angles with little change in the R values. These tests support the value of revising refinement software to account for this new paradigm.

Tronrud, Dale E.; Berkholz, Donald S.; Karplus, P. Andrew (Oregon State U.)

2010-07-02

442

Catalyst-Directed Crystallographic Orientation Control of GaN Nanowire Growth.  

PubMed

In this work, we demonstrate that catalyst composition can be used to direct the crystallographic growth axis of GaN nanowires. By adjusting the ratio of gold to nickel in a bimetallic catalyst, we achieved selective growth of dense, uniform nanowire arrays along two nonpolar directions. A gold-rich catalyst resulted in single-crystalline nanowire growth along the ?11?00? or m axis, whereas a nickel-rich catalyst resulted in nanowire growth along the ?112?0? or a axis. The same growth control was demonstrated on two different epitaxial substrates. Using proper conditions, many of the nanowires were observed to switch direction midgrowth, resulting in monolithic single-crystal structures with segments of two distinct orientations. Cathodoluminescence spectra revealed significant differences in the optical properties of these nanowire segments, which we attribute to the electronic structures of their semipolar {112?2} or {11?01} sidewalls. PMID:25390285

Kuykendall, Tevye R; Altoe, M Virginia P; Ogletree, D Frank; Aloni, Shaul

2014-12-10

443

Expression, purification and preliminary crystallographic characterization of FlhF from Bacillus subtilis  

PubMed Central

The Gram-positive bacterium Bacillus subtilis contains three proteins belonging to the signal recognition particle (SRP) type GTPase family. The well characterized signal sequence-binding protein SRP54 and the SRP receptor protein FtsY are universally conserved components of the SRP system of protein transport. The third member, FlhF, has been implicated in the placement and assembly of polar flagella. This article describes the overexpression and preliminary X-ray crystallographic analysis of an FlhF fragment that corresponds to the well characterized GTPase domains in SRP54 and FtsY. Three crystal forms are reported with either GDP or GMPPNP and diffract to a resolution of about 3?Å. PMID:17565194

Bange, Gert; Petzold, Georg; Wild, Klemens; Sinning, Irmgard

2007-01-01

444

Role of substrate crystallographic characteristics on structure and properties of rutile TiO2 epilayers  

NASA Astrophysics Data System (ADS)

To investigate heterostructures of interest for catalytic applications, we integrated rutile TiO2 epitaxial thin films with Al2O3(0001), Al2O3(101¯0), and Al2O3(011¯2) substrates and studied structure and properties of the epilayers as a function of the crystallographic characteristics of the substrate. The epitaxial relationship across the film/substrate interfaces was established as (100)rutile?(0001)c-sapphire and [001]rutile?[101¯0]c-sapphire, (001)rutile?[101¯0)m-sapphire, and [100]rutile?[0001]m-sapphire, (101)rutile?(011¯2)r-sapphire and [010]rutile?(011¯2)r-sapphire. The origin and the relaxation mechanism of stress and strain for each heterostructure were studied in detail. It was revealed that large lattice misfit strains relax easily even if the primary slip system is not active due to the epitaxial alignment between the film and substrate and orientation of the in-plane stresses. We also showed that even small misfit strains can relax provided that the primary slip system is active. The origin of the residual strains in the epilayers was found to be primarily due to thermal misfit and defect/impurity strains. In addition, the decomposition rate of 4-chlorophenol by the rutile/sapphire heterostructures under ultraviolet illumination was measured. The (001)-plane was found to be the most photoactive face of rutile TiO2, while the (100)-plane showed the lowest photocatalytic activity. The difference in the photochemical characteristics was attributed to the atomic arrangement on different crystallographic surface planes.

Bayati, M. R.; Molaei, R.; Budai, J. D.; Narayan, R. J.; Narayan, J.

2013-07-01

445

EULER-POINCARÉ Flows on the Loop Bott-Virasoro Group and Space of Tensor Densities and (2 + 1)-DIMENSIONAL Integrable Systems  

NASA Astrophysics Data System (ADS)

Following the work of Ovsienko and Roger ([54]), we study loop Virasoro algebra. Using this algebra, we formulate the Euler-Poincaré flows on the coadjoint orbit of loop Virasoro algebra. We show that the Calogero-Bogoyavlenskii-Schiff equation and various other (2 + 1)-dimensional Korteweg-deVries (KdV) type systems follow from this construction. Using the right invariant H1 inner product on the Lie algebra of loop Bott-Virasoro group, we formulate the Euler-Poincaré framework of the (2 + 1)-dimensional of the Camassa-Holm equation. This equation appears to be the Camassa-Holm analogue of the Calogero-Bogoyavlenskii-Schiff type (2 + 1)-dimensional KdV equation. We also derive the (2 + 1)-dimensional generalization of the Hunter-Saxton equation. Finally, we give an Euler-Poincaré formulation of one-parameter family of (1 + 1)-dimensional partial differential equations, known as the b-field equations. Later, we extend our construction to algebra of loop tensor densities to study the Euler-Poincaré framework of the (2 + 1)-dimensional extension of b-field equations.

Guha, Partha

446

ON THE INFLUENCE OF 3d4 IONS ON THE MAGNETIC AND CRYSTALLOGRAPHIC PROPERTIES OF MAGNETIC OXIDES (1)  

E-print Network

155 ON THE INFLUENCE OF 3d4 IONS ON THE MAGNETIC AND CRYSTALLOGRAPHIC PROPERTIES OF MAGNETIC OXIDES properties of several Mn3+-containing, perovskite-type oxides can be interpreted as due to this peculiar ferrimagnétisme dans les réseaux perovskites contenant des cations Mn3+, Abstract. 2014 After a brief reference

Boyer, Edmond

447

Effective nonlinearity coefficients for three-wave interactions in biaxial crystal of mm2 point group symmetry  

Microsoft Academic Search

The effective nonlinearity coefficients for three-wave interactions in the orthorhombic biaxial crystal of mm2 point group symmetry for six different assignments between the crystallophysical (optical) and crystallographic (piezoelectric) coordinate systems have been obtained. In the former coordinate system the dielectric permeability tensor is the diagonal one, in the latter the square nonlinearity tensor is defined. The point group mm2 includes

V. G. Dmitriev; D. N. Nikogosyan

1993-01-01

448

Crystal planes and reciprocal space in Clifford geometric algebra  

NASA Astrophysics Data System (ADS)

This contribution discusses the geometry of $k$D crystal cells given by $(k+1)$ points in a projective space $\\R^{n+1}$. We show how the concepts of barycentric and fractional (crystallographic) coordinates, reciprocal vectors and dual representati on are related (and geometrically interpreted) in the projective geometric algebra $\\R_{n+1}$ (see H. Grassmann, edited by F. Engel, Sie Ausdehnungslehre von 1844 und die Geom. Anal., vol. 1, part 1, Teubner, Leipzig, 1894.) and in the conformal algebra $\\R_{n+1,1}$. The crystallographic notions of $d$-spacing, phase angle (in structure factors), extinction of Bragg reflections, and the interfacial angles of crystal planes are obtained in the same context.

Hitzer, E.

2011-08-01

449

Bacillus anthracis-like bacteria and other B. cereus group members in a microbial community within the International Space Station: a challenge for rapid and easy molecular detection of virulent B. anthracis.  

PubMed

For some microbial species, such as Bacillus anthracis, the etiologic agent of the disease anthrax, correct detection and identification by molecular methods can be problematic. The detection of virulent B. anthracis is challenging due to multiple virulence markers that need to be present in order for B. anthracis to be virulent and its close relationship to Bacillus cereus and other members of the B. cereus group. This is especially the case in environments where build-up of Bacillus spores can occur and several representatives of the B. cereus group may be present, which increases the chance for false-positives. In this study we show the presence of B. anthracis-like bacteria and other members of the B. cereus group in a microbial community within the human environment of the International Space Station and their preliminary identification by using conventional culturing as well as molecular techniques including 16S rDNA sequencing, PCR and real-time PCR. Our study shows that when monitoring the microbial hygiene in a given human environment, health risk assessment is troublesome in the case of virulent B. anthracis, especially if this should be done with rapid, easy to apply and on-site molecular methods. PMID:24945323

van Tongeren, Sandra P; Roest, Hendrik I J; Degener, John E; Harmsen, Hermie J M

2014-01-01

450

Space Station Human Factors Research Review. Volume 3: Space Station Habitability and Function: Architectural Research  

NASA Technical Reports Server (NTRS)

Articles are presented on a space station architectural elements model study, space station group activities habitability module study, full-scale architectural simulation techniques for space stations, and social factors in space station interiors.

Cohen, Marc M. (editor); Eichold, Alice (editor); Heers, Susan (editor)

1987-01-01

451

Communication spaces  

PubMed Central

Background and objective Annotations to physical workspaces such as signs and notes are ubiquitous. When densely annotated, work areas become communication spaces. This study aims to characterize the types and purpose of such annotations. Methods A qualitative observational study was undertaken in two wards and the radiology department of a 440-bed metropolitan teaching hospital. Images were purposefully sampled; 39 were analyzed after excluding inferior images. Results Annotation functions included signaling identity, location, capability, status, availability, and operation. They encoded data, rules or procedural descriptions. Most aggregated into groups that either created a workflow by referencing each other, supported a common workflow without reference to each other, or were heterogeneous, referring to many workflows. Higher-level assemblies of such groupings were also observed. Discussion Annotations make visible the gap between work done and the capability of a space to support work. Annotations are repairs of an environment, improving fitness for purpose, fixing inadequacy in design, or meeting emergent needs. Annotations thus record the missing information needed to undertake tasks, typically added post-implemented. Measuring annotation levels post-implementation could help assess the fit of technology to task. Physical and digital spaces could meet broader user needs by formally supporting user customization, ‘programming through annotation’. Augmented reality systems could also directly support annotation, addressing existing information gaps, and enhancing work with context sensitive annotation. Conclusions Communication spaces offer a model of how work unfolds. Annotations make visible local adaptation that makes technology fit for purpose post-implementation and suggest an important role for annotatable information systems and digital augmentation of the physical environment. PMID:24005797

Coiera, Enrico

2014-01-01

452

Superoxide reductase from Nanoarchaeum equitans: expression, purification, crystallization and preliminary X-ray crystallographic analysis.  

PubMed

Superoxide reductases (SORs) are the most recent oxygen-detoxification system to be identified in anaerobic and microaerobic bacteria and archaea. SORs are metalloproteins