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1

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

2

Crystallographic Groups, Groupoids, and Orbifolds  

SciTech Connect

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

Johnson, C.K.

2000-09-11

3

Symmetry and Space Groups Space groups arranged in order of frequency in the Cambridge Crystallographic Data Base.  

E-print Network

) = I(k, -h, l) Unique Intensity Data Set : 1/8 hemisphere 0 h ; 0 k; 0 l Class Space Groups 4 P41 P43 P4 P42 I41 I4 -4 P -4 I -4 2/m P42/n P4/n P42/m P4/m I4/m I41/a Laue Group : 4/mmm Tetragonal Cell

Meagher, Mary

4

Chevalley's theorem for the complex crystallographic groups  

Microsoft Academic Search

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

Joseph Bernstein; Ossip Schwarzman

2006-01-01

5

Simple crystal forms as the orbits of crystallographic symmetry groups  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

6

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

E-print Network

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

Motiejus Valiunas; Emilio Zappa; Briony Thomas; Reidun Twarock

2015-01-27

7

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).

8

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

E-print Network

Motivated by recent results in mathematical virology, we present novel asymmetric Z[tau]-integer-valued affine extensions of the non-crystallographic Coxeter groups H_2, H_3 and H_4 derived in a Kac-Moody-type formalism. In particular, we show that the affine reflection planes which extend the Coxeter group H_3 generate (twist) translations along 2-, 3- and 5-fold axes of icosahedral symmetry, and we classify these translations in terms of the Fibonacci recursion relation applied to different start values. We thus provide an explanation of previous results concerning affine extensions of icosahedral symmetry in a Coxeter group context, and extend this analysis to the case of the non-crystallographic Coxeter groups H_2 and H_4. These results will enable new applications of group theory in physics (quasicrystals), biology (viruses) and chemistry (fullerenes).

Pierre-Philippe Dechant; Celine Boehm; Reidun Twarock

2012-06-01

9

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

10

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

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

Torsional random walk statistics on lattices using convolution on crystallographic motion groups.  

PubMed Central

This paper presents a new algorithm for generating the conformational statistics of lattice polymer models. The inputs to the algorithm are the distributions of poses (positions and orientations) of reference frames attached to sequentially proximal bonds in the chain as it undergoes all possible torsional motions in the lattice. If z denotes the number of discrete torsional motions allowable around each of the n bonds, our method generates the probability distribution in end-to-end pose corresponding to all of the zn independent lattice conformations in O(nD+1) arithmetic operations for lattices in D-dimensional space. This is achieved by dividing the chain into short segments and performing multiple generalized convolutions of the pose distribution functions for each segment. The convolution is performed with respect to the crystallographic space group for the lattice on which the chain is defined. The formulation is modified to include the effects of obstacles (excluded volumes), and to calculate the frequency of the occurrence of each conformation when the effects of pairwise conformational energy are included. In the latter case (which is for 3 dimensional lattices only) the computational cost is O(z4n4). This polynomial complexity is a vast improvement over the O(zn) exponential complexity associated with the brute force enumeration of all conformations. The distribution of end-to-end distances and average radius of gyration are calculated easily once the pose distribution for the full chain is found. The method is demonstrated with square, hexagonal, cubic and tetrahedral lattices. PMID:17898862

Skliros, Aris; Chirikjian, Gregory S.

2007-01-01

13

Affine extensions of non-crystallographic Coxeter groups induced by projection  

E-print Network

In this paper, we show that affine extensions of non-crystallographic Coxeter groups can be derived via Coxeter-Dynkin diagram foldings and projections of affine extended versions of the root systems E_8, D_6 and A_4. We show that the induced affine extensions of the non-crystallographic groups H_4, H_3 and H_2 correspond to a distinguished subset of the Kac-Moody-type extensions considered in Dechant et al. This class of extensions was motivated by physical applications in icosahedral systems in biology (viruses), physics (quasicrystals) and chemistry (fullerenes). By connecting these here to extensions of E_8, D_6 and A_4, we place them into the broader context of crystallographic lattices such as E_8, suggesting their potential for applications in high energy physics, integrable systems and modular form theory. By inverting the projection, we make the case for admitting different number fields in the Cartan matrix, which could open up enticing possibilities in hyperbolic geometry and rational conformal field theory.

Pierre-Philippe Dechant; Celine Boehm; Reidun Twarock

2012-06-19

14

Crystallographic topology and its applications  

SciTech Connect

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

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

1996-10-01

15

International Space Exploration Coordination Group  

E-print Network

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

16

INTERNATIONAL SPACE EXPLORATION COORDINATION GROUP  

E-print Network

1 INTERNATIONAL SPACE EXPLORATION COORDINATION GROUP WORKPLAN Update following 3rd ISECG Meeting space exploration infrastructure standards facilitating interoperability through an international architecture working group. · Continue development of the INTERnational Space Exploration Coordination Tool

17

International Space Exploration Coordination Group  

E-print Network

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

18

International Space Exploration Coordination Group  

E-print Network

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

Rathbun, Julie A.

19

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

20

Space group Cc: an update.  

PubMed

A recent survey of the Cambridge Structural Database, CSD [Allen (2002). Acta Cryst. B58, 380-388], shows that the percentage of incorrect assignments of the space group Cc has remained at about 10% since the last survey in 1997. PMID:15017100

Marsh, Richard E

2004-04-01

21

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

22

Position and Orientation Distributions for Non-Reversal Random Walks using Space-Group Fourier Transforms  

PubMed Central

This paper presents an efficient group-theoretic approach for computing the statistics of non-reversal random walks (NRRW) on lattices. These framed walks evolve on proper crystallographic space groups. In a previous paper we introduced a convolution method for computing the statistics of NRRWs in which the convolution product is defined relative to the space-group operation. Here we use the corresponding concept of the fast Fourier transform for functions on crystallographic space groups together with a non-Abelian version of the convolution theorem. We develop the theory behind this technique and present numerical results for two-dimensional and three-dimensional lattices (square, cubic and diamond). In order to verify our results, the statistics of the end-to-end distance and the probability of ring closure are calculated and compared with results obtained in the literature for the random walks for which closed-form expressions exist. PMID:21037950

Skliros, Aris; Park, Wooram; Chirikjian, Gregory S.

2010-01-01

23

Renormalization group in internal space  

SciTech Connect

Renormalization group in the internal space consists of the gradual change of the coupling constants. Functional evolution equations corresponding to the change of the mass or the coupling constant are presented in the framework of a scalar model. The evolution in the mass which yields the functional generalization of the Callan-Symanzik equation for the one-particle irreducible effective action is given in its renormalized, cutoff-independent form. The evolution of the coupling constant generates an evolution equation for the two-particle irreducible effective action.

Polonyi, J. [Institute for Theoretical Physics, Louis Pasteur University, Strasbourg (France); Department of Atomic Physics, Lorand Eoetvoes University, Budapest (Hungary); Sailer, K. [Department for Theoretical Physics, University of Debrecen, Debrecen (Hungary)

2005-01-15

24

On Hawaiian Groups of Some Topological Spaces  

E-print Network

The paper is devoted to study the structure of Hawaiian groups of some topological spaces. We present some behaviors of Hawaiian groups with respect to product spaces, weak join spaces, cone spaces, covering spaces and locally trivial bundles. In particular, we determine the structure of the $n$-dimensional Hawaiian group of the $m$-dimensional Hawaiian earring space, for all $1\\leq m\\leq n$.

Babaee, Ameneh; Mirebrahimi, Hanieh

2011-01-01

25

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP  

E-print Network

Analyser Langmuir probe/ E-field booms Magnetometer LEIA #12;UCL DEPARTMENT OF SPACE & CLIMATE PHYSICSUCL 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

Anand, Mahesh

26

Filling three-dimensional space with tetrahedra: A geometric and crystallographic problem  

NASA Astrophysics Data System (ADS)

Exact, nonperiodic, close-packed structures with randomness that can fill three-dimensional space are found. We find many solutions for distances between atoms that satisfy the necessary conditions of filling three-dimensional space with tetrahedra formed with two kinds of atoms. Only three solutions that also satisfy the sufficient condition of filling three-dimensional space are discussed. They all involve periodic as well as nonperiodic structures resulting from the random stacking of layers. One solution corresponds to the NaCl structure. Another solution exhibits both tetragonal and hexagonal symmetry, which violates crystallography. A third solution has a unit cell whose surface exhibits distorted pentagonal symmetry and whose elementary unit is a 44-face polyhedron. Suggestions for a possible growth model in three dimensions with tetrahedra are discussed.

Szeto, K. Y.; Villain, J.

1987-09-01

27

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

28

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

29

On spaces of Kleinian groups  

Microsoft Academic Search

tinuity f2 of G, modulo the ideal boundary of D. The quasiconformal deformation space T(G) is the set of equivalence classes of M(G), and the strong quasiconformal deformation space T(G) is the set of strong equivalence classes. We shall prove that T(G) is a complex analytic manifold (a result previously obtained by Maskit [17], and under some restrictive assumptions by

Irwin Kra

1972-01-01

30

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

31

The International Space Life Sciences Working Group.  

PubMed

The International Space Life Sciences Working Group (ISLSWG) is made up of representatives from five space agencies: the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), the Canadian Space Agency (CSA), the Centre National d'Etudes Spatiale (CNES), the Deutsches Zentrum fur Luft- und Raumfahrt (DLR, formerly the Deutsche Agentur fur Raumfahrtangelegenheiten or DARA), and the National Space Development Agency of Japan (NASDA). The group met for the first time in 1989, and since that time has developed a Strategic Plan and has taken concrete steps to implement this plan. The result is a closely coordinated international program of Space Life Sciences which will enable optimal utilization of space flight opportunities. PMID:11542345

Vernikos, J; Ahlf, P R

1998-07-01

32

Crystallographic analysis of ground and space thermostable T1 lipase crystal obtained via counter diffusion method approach.  

PubMed

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; Mohamad Ali, Mohd Shukuri; Basri, Mahiran; Salleh, Abu Bakar; Raja Abd Rahman, Raja Noor Zaliha

2014-01-01

33

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

34

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

35

Quantum group gauge theory on quantum spaces  

Microsoft Academic Search

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

Thomasz Brzezinski; Shahn Majid

1993-01-01

36

UK Space Exploration Working Group Report of the  

E-print Network

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

Crowther, Paul

37

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

38

DYNAMICS OF PLANETCROSSING ASTEROIDS Space Mechanics Group,  

E-print Network

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

Milani, Andrea

39

NASA's Internal Space Weather Working Group  

NASA Technical Reports Server (NTRS)

Measurements from many of NASA's scientific spacecraft are used routinely by space weather forecasters, both in the U.S. and internationally. ACE, SOHO (an ESA/NASA collaboration), STEREO, and SDO provide images and in situ measurements that are assimilated into models and cited in alerts and warnings. A number of years ago, the Space Weather laboratory was established at NASA-Goddard, along with the Community Coordinated Modeling Center. Within that organization, a space weather service center has begun issuing alerts for NASA's operational users. NASA's operational user community includes flight operations for human and robotic explorers; atmospheric drag concerns for low-Earth orbit; interplanetary navigation and communication; and the fleet of unmanned aerial vehicles, high altitude aircraft, and launch vehicles. Over the past three years we have identified internal stakeholders within NASA and formed a Working Group to better coordinate their expertise and their needs. In this presentation we will describe this activity and some of the challenges in forming a diverse working group.

St. Cyr, O. C.; Guhathakurta, M.; Bell, H.; Niemeyer, L.; Allen, J.

2011-01-01

40

Cell Groups Reveal Structure of Stimulus Space  

PubMed Central

An important task of the brain is to represent the outside world. It is unclear how the brain may do this, however, as it can only rely on neural responses and has no independent access to external stimuli in order to “decode” what those responses mean. We investigate what can be learned about a space of stimuli using only the action potentials (spikes) of cells with stereotyped—but unknown—receptive fields. Using hippocampal place cells as a model system, we show that one can (1) extract global features of the environment and (2) construct an accurate representation of space, up to an overall scale factor, that can be used to track the animal's position. Unlike previous approaches to reconstructing position from place cell activity, this information is derived without knowing place fields or any other functions relating neural responses to position. We find that simply knowing which groups of cells fire together reveals a surprising amount of structure in the underlying stimulus space; this may enable the brain to construct its own internal representations. PMID:18974826

2008-01-01

41

TOPOLOGICAL SPACES AND THE FUNDAMENTAL GROUP MAXWELL XIONG  

E-print Network

TOPOLOGICAL SPACES AND THE FUNDAMENTAL GROUP MAXWELL XIONG Abstract. This paper provides a basic as a topological space, and what open 1 #12;2 MAXWELL XIONG and closed sets look like within those spaces. We

May, J. Peter

42

A new verification of Kovalev's tables of irreducible representations of the space groups  

NASA Astrophysics Data System (ADS)

In the application of representation theory to physical and crystallographic problems, Kovalev's tables provide a uniquely reliable and complete source for the required irreducible representations of the space groups. A number of programs based on these tables, designed to automate the lengthy calculations involved, generate non-physical or incorrect solutions to some problems, raising questions over the validity of Kovalev's work. In this work the tables are verified to the point of homomorphism with the groups and subgroups that they represent through the use of the digitized versions of the tables used in SARAh. The results support the correctness of Kovalev's definitions, highlighting difficulties in interpreting the tables themselves and some general failings of the programs used in the application of representation theory to physical problems.

Davies, Z. L.; Wills, A. S.

2008-03-01

43

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

44

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

45

International Space Station Earth Observations Working Group  

NASA Technical Reports Server (NTRS)

The multilateral Earth Observations Working Group (EOWG) was chartered in May 2012 in order to improve coordination and collaboration of Earth observing payloads, research, and applications on the International Space Station (ISS). The EOWG derives its authority from the ISS Program Science Forum, and a NASA representative serves as a permanent co-chair. A rotating co-chair position can be occupied by any of the international partners, following concurrence by the other partners; a JAXA representative is the current co-chair. Primary functions of the EOWG include, 1) the exchange of information on plans for payloads, from science and application objectives to instrument development, data collection, distribution and research; 2) recognition and facilitation of opportunities for international collaboration in order to optimize benefits from different instruments; and 3) provide a formal ISS Program interface for collection and application of remotely sensed data collected in response to natural disasters through the International Charter, Space and Major Disasters. Recent examples of EOWG activities include coordination of bilateral data sharing protocols between NASA and TsNIIMash for use of crew time and instruments in support of ATV5 reentry imaging activities; discussion of continued use and support of the Nightpod camera mount system by NASA and ESA; and review and revision of international partner contributions on Earth observations to the ISS Program Benefits to Humanity publication.

Stefanov, William L.; Oikawa, Koki

2015-01-01

46

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

47

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

PubMed

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

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

2015-03-01

48

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

49

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

50

Structure of human salivary ?-amylase crystallized in a C-centered monoclinic space group  

PubMed Central

Human salivary ?-amylase (HSA) is a major secretory protein component of saliva and has important biological functions, including the initial digestion of starch. HSA acts as a monomer and mediates the hydrolysis of ?-1,4-glucosidic linkages in oligosaccharides. To date, all published crystal structures of HSA have been crystallized as monomers in space group P212121. Here, the serendipitous purification, crystallization and ultimate structure determination of a HSA non-crystallographic symmetry (NCS) dimer, while attempting to purify human carbonic anhydrase VI (HCA VI) from saliva using an affinity resin for ?-class carbonic anhydrases, is presented. On further investigation, it was shown that HSA could only be copurified using the affinity resin in the presence of HCA VI which is glycosylated and not the non-glycosylated HCA II. The identification of the HSA crystals was carried out by peptide mapping and mass spectrometry. HSA was shown to have crystallized as an NCS dimer in space group C2, with unit-cell parameters a = 150.9, b = 72.3, c = 91.3?Å, ? = 102.8°. The NCS dimer crystal structure is reported to 3.0?Å resolution, with a refined R cryst of 0.228. The structure is compared with the previously reported P212121 monomer structures and the crystal packing and dimer interface are discussed. PMID:16511271

Fisher, S. Zoë; Govindasamy, Lakshmanan; Tu, Chingkuang; Agbandje-McKenna, Mavis; Silverman, David N.; Rajaniemi, Hannu J.; McKenna, Robert

2006-01-01

51

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

52

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

53

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

54

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

55

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

56

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

57

Crystallization and preliminary crystallographic analysis of acetophenone reductase from Geotrichum candidum NBRC 4597.  

PubMed

Acetophenone reductase (APRD) from Geotrichum candidium NBRC 4597 was crystallized by the hanging-drop vapour-diffusion method using PEG 3350 as a precipitant. The crystal belonged to space group P6522, with unit-cell parameters a = b = 104.5, c = 273.7?Å, and diffracted to 2.6?Å resolution. Phasing using the single-wavelength anomalous diffraction method was successful. Model building and crystallographic refinement are in progress. PMID:25760708

Sugiyama, Yosuke; Senda, Miki; Senda, Toshiya; Matsuda, Tomoko

2015-03-01

58

The space shuttle payload planning working groups. Volume 2: Atmospheric and space physics  

NASA Technical Reports Server (NTRS)

The findings of the Atmospheric and Space Physics working group of the space shuttle mission planning activity are presented. The principal objectives defined by the group are: (1) to investigate the detailed mechanisms which control the near-space environment of the earth, (2) to perform plasma physics investigations not feasible in ground-based laboratories, and (3) to conduct investigations which are important in understanding planetary and cometary phenomena. The core instrumentation and laboratory configurations for conducting the investigations are defined.

1973-01-01

59

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

60

Small-Bias Spaces for Group Products and David Zuckerman  

E-print Network

Small-Bias Spaces for Group Products Raghu Meka and David Zuckerman Department of Computer Science for width w ROPBPs are equivalent to functions P : {0, 1}r {0, 1}n that fool products of group elements and g P(y)1 1 g P(y)2 2 . . . g P(y)n n with y u {0, 1}r are -close in variation distance (for a multi

Zuckerman, David

61

Entanglement renormalization in free bosonic systems: real-space versus momentum-space renormalization group transforms  

E-print Network

The ability of entanglement renormalization (ER) to generate a proper real-space renormalization group (RG) flow in extended quantum systems is analysed in the setting of harmonic lattice systems in D=1 and D=2 spatial dimensions. A conceptual overview of the steps involved in momentum-space RG is provided and contrasted against the equivalent steps in the real-space setting. The real-space RG flow, as generated by ER, is compared against the exact results from momentum-space RG, including an investigation of a critical fixed point and the effect of relevant and irrelevant perturbations.

G. Evenbly; G. Vidal

2010-03-05

62

The Logic of Rotations Lie Groups and Homogeneous Spaces  

E-print Network

The Logic of Rotations Lie Groups and Homogeneous Spaces Jean Gallier CIS Department University(e.~ke, I OJ¥' q cat Figure: Dog Logic Jean Gallier (Upenn) The Logic of Rotations December 3, 2013 2 / 31 #12;Jean Gallier (Upenn) The Logic of Rotations December 3, 2013 3 / 31 #12;Jean Gallier (Upenn

Gallier, Jean

63

CONFIGURATION SPACES AND BRAID GROUPS ON GRAPHS IN ROBOTICS  

E-print Network

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

Ghrist, Robert W.

64

Improved low-resolution crystallographic refinement with Phenix and Rosetta  

PubMed Central

Refinement of macromolecular structures against low-resolution crystallographic data is limited by the ability of current methods to converge on a structure with realistic geometry. We developed a low-resolution crystallographic refinement method that combines the Rosetta sampling methodology and energy function with reciprocal-space X-ray refinement in Phenix. On a set of difficult low-resolution cases, the method yielded improved model geometry and lower free R factors than alternate refinement methods. PMID:24076763

DiMaio, Frank; Echols, Nathaniel; Headd, Jeffrey J; Terwilliger, Thomas C; Adams, Paul D; Baker, David

2014-01-01

65

On Topological Homotopy Groups of $n$-Hawaiian like spaces  

E-print Network

By an $n$-Hawaiian like space $X$ we mean the natural inverse limit, $\\displaystyle{\\varprojlim (Y_i^{(n)},y_i^*)}$, where $(Y_i^{(n)},y_i^*)=\\bigvee_{j\\leq i}(X_j^{(n)},x_j^*)$ is the wedge of $X_j^{(n)}$'s in which $X_j^{(n)}$'s are $(n-1)$-connected, locally $(n-1)$-connected, $n$-semilocally simply connected and compact CW spaces. In this paper, first we show that the natural homomorphism $\\displaystyle{\\beta_n:\\pi_n(X,*)\\rightarrow \\varprojlim \\pi_n(Y_i^{(n)},y_i^*)}$ is bijection. Second, using this fact we prove that the topological $n$-homotopy group of an $n$-Hawaiian like space, $\\pi_n^{top}(X,x^*)$, is a topological group for all $n\\geq 2$ which is a partial answer to the open question whether $\\pi_n^{top}(X,x^*)$ is a topological group for any space $X$ and $n\\geq 1$. Moreover, we show that $\\pi_n^{top}(X,x^*)$ is metrizable.

Ghane, Fateme Helen; Mashayekhy, Behrooz; Mirebrahimi, Hanieh

2010-01-01

66

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

67

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

68

A Computational Model for Periodic Pattern Perception Based on Frieze and Wallpaper Groups  

Microsoft Academic Search

We present a computational model for periodic pattern perception based on the mathematical theory of crystallographic groups. In each N-dimensional Euclidean space, a finite number of symmetry groups can characterize the structures of an infinite variety of periodic patterns. In 2D space, there are seven frieze groups describing monochrome patterns that repeat along one direction and 17 wallpaper groups for

Yanxi Liu; Robert T. Collins; Yanghai Tsin

2003-01-01

69

The Lorentzian oscillator group as a geodesic orbit space  

SciTech Connect

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

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

2012-10-15

70

National facilities study. Volume 4: Space operations facilities task group  

NASA Technical Reports Server (NTRS)

The principal objectives of the National Facilities Study (NFS) were to: (1) determine where U.S. facilities do not meet national aerospace needs; (2) define new facilities required to make U.S. capabilities 'world class' where such improvements are in the national interest; (3) define where consolidation and phase-out of existing facilities is appropriate; and (4) develop a long-term national plan for world-class facility acquisition and shared usage. The Space Operations Facilities Task Group defined discrete tasks to accomplish the above objectives within the scope of the study. An assessment of national space operations facilities was conducted to determine the nation's capability to meet the requirements of space operations during the next 30 years. The mission model used in the study to define facility requirements is described in Volume 3. Based on this model, the major focus of the Task Group was to identify any substantive overlap or underutilization of space operations facilities and to identify any facility shortfalls that would necessitate facility upgrades or new facilities. The focus of this initial study was directed toward facility recommendations related to consolidations, closures, enhancements, and upgrades considered necessary to efficiently and effectively support the baseline requirements model. Activities related to identifying facility needs or recommendations for enhancing U.S. international competitiveness and achieving world-class capability, where appropriate, were deferred to a subsequent study phase.

1994-01-01

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

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

PubMed

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

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

2011-02-01

73

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

PubMed Central

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

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

2011-01-01

74

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

75

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.

76

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

E-print Network

) 1. No. of Employee Spaces 2. No. of Visitor Spaces SIGNATURE (DIVISION HEAD) 3. No. of OfficialREQUEST FOR LEASED SPACE 1. DATE 2. TO: 3. FROM: (REQUESTING DIVISION) 4. FOR: (USER GROUP) CONTACT. SPACE REQUIREMENTS INITIAL EXPANSION REPLACEMENT TYPE OF SPACE NO. OF PERSONNEL SQ. FT. PER PERSON SQ

77

Space Weather Activities of IONOLAB Group: IONOLAB-TEC  

NASA Astrophysics Data System (ADS)

Space Weather (SW) is the concept of changing environmental conditions in outer space and affect Earth and its technological systems. SW is a consequence of the solar activities and the coupling of solar energy on Earth's atmosphere due to the Earth's magnetic field. The monitoring and prediction of SW has utmost importance for HF communication, Satellite communication, navigation and guidance systems, Low Earth Orbit (LEO) satellite systems, Space Craft exit and entry into the atmosphere. Ionosphere is the plasma layer of the atmosphere that is ionized by solar radiation and it is a key player of SW. Ionosphere is a temporally and spatially varying, dispersive, anisotropic and inhomogeneous medium that is characterized primarily by its electron density distribution. IONOLAB is a group of researchers of various disciplines, getting together to handle challenges of the Earth's ionosphere. The team has researchers from Hacettepe University and Bilkent University, Department of Electrical and Electronics Engineering and General Command of Mapping of Turkish Army. One of the most important contributions of IONOLAB group is the automated web-based computation service for Total Electron Content (TEC). TEC corresponds to the line integral of electron density distribution on a given path. TEC can also be expressed as the amount of free electrons within 1 m2 cross-sectional area of the cylinder on the ray path. Global Position System (GPS) provides a cost-effective medium for monitoring of ionosphere using the signals recorded by stationary GPS receivers in estimating TEC. IONOLAB group has developed IONOLAB-TEC for reliable and robust estimates for all latitudes and both calm and disturbed days by using RINEX, IONEX and satellite ephemeris data provided from the IGS centers. IONOLAB-TEC consists of a regularized signal estimation algorithm which combines signals from all GPS satellites for a given instant and a given receiver, for a desired time period or for 24 hours, with 30 s time resolution. IONOLAB-TEC values also include the receiver differential code bias (DCB) for each GPS station estimated uniquely by the IONOLAB-BIAS algorithm. The web based computation program is written in JAVA and it is provided both in Turkish and English at www.ionolab.org. The IONOLAB-TEC computation requires no installation or licensing on the client side. The application has a layered design. Developed components are modular that allows possible changes regarding the estimation method can be easily adapted. Same flexibility is also provided for the data access. Also, presentation of estimation data is architected to support different client types. Currently, the user can login to the IONOLAB-TEC web site and choose the desired location and dates on-line for TEC estimation. The carrier phase leveled TEC estimates of IONOLAB-TEC are provided for the chosen station/s and for the chosen day/s along with two-hourly GIM-TEC estimates of IGS centers. The output is provided in the user designated form either in graphs or an excel data sheet. The IONOLAB-TEC provides robust, reliable, and high resolution TEC estimates and provides a medium for comparison of the GIM-TEC values from the IGS centers.

Arikan, F.; Sezen, U.; Arikan, O.; Ugurlu, O.; Nayir, H.

2009-04-01

78

Preliminary crystallographic analysis of the bacteriophage P22 portal protein.  

PubMed

Portal proteins are components of large oligomeric dsDNA pumps connecting the icosahedral capsid of tailed bacteriophages to the tail. Prior to the tail attachment, dsDNA is actively pumped through a central cavity formed by the subunits. We have studied the portal protein of bacteriophage P22, which is the largest connector characterized among the tailed bacteriophages. The molecular weight of the monomer is 82.7 kDa, and it spontaneously assembles into an oligomeric structure of approximately 1.0 MDa. Here we present a preliminary biochemical and crystallographic characterization of this large macromolecular complex. The main difficulties related to the crystallization of P22 portal protein lay in the intrinsic dynamic nature of the portal oligomer. Recombinant connectors assembled from portal monomers expressed in Escherichia coli form rings of different stoichiometry in solution, which cannot be separated on the basis of their size. To overcome this intrinsic heterogeneity we devised a biochemical purification that separates different ring populations on the basis of their charge. Small ordered crystals were grown from drops containing a high concentration of the kosmotropic agent tert-butanol and used for data collection. A preliminary crystallographic analysis to 7.0-A resolution revealed that the P22 portal protein crystallized in space group I4 with unit cell dimensions a=b=409.4A, c=260.4A. This unit cell contains a total of eight connectors. Analysis of the noncrystallographic symmetry by the self-rotation function unambiguously confirmed that bacteriophage P22 portal protein is a dodecamer with a periodicity of 30 degrees. The cryo-EM reconstruction of the dodecahedral bacteriophage T3 portal protein will be used as a model to initiate phase extension and structure determination. PMID:12372319

Cingolani, Gino; Moore, Sean D; Prevelige, Peter E; Johnson, John E

2002-07-01

79

Urban space as a large-scale group playground Tech Report kmi-04-24  

E-print Network

behaviour and playful group interaction in public spaces through the use of mobile technologies. I discussTag' project is focused on social experiences and group play in public spaces, based on the awareness of other to encourage emergent social behaviours in an urban context. City space is used as a playground and passers

80

The birth of an infant decreases group spacing in a zoo-housed lowland gorilla group (Gorilla gorilla gorilla).  

PubMed

Changes in group composition can alter the behavior of social animals such as gorillas. Although gorilla births are presumed to affect group spacing patterns, there is relatively little data about how these events affect gorilla group cohesion. We investigated how members of a western lowland gorilla group (n?=?6) at Lincoln Park Zoo (Chicago, IL, USA) spaced themselves prior to and after the birth of an infant, to investigate changes in group cohesion. Gorillas were housed in an indoor-outdoor enclosure in which access to the outdoors was permitted when temperatures exceeded 5°C. We recorded spatial locations of each group member using 30-min group scans on tablet computers with an electronic map interface, as well as noting their access to outdoor areas. Data from the 4 months following the birth was compared to a control period corresponding to early pregnancy. We measured distances between all possible group dyads for each scan and subsequently calculated a mean distance between all group members. An ANOVA revealed that access to the outdoors had no effect on group spacing (F(1,56)?=?0.066, P?=?0.799). However, the presence of an infant resulted in a significant reduction in inter-individual distance (F(1,56)?=?23.988, P?=?0.000), decreasing inter-individual spacing by 12.5%. This information helps characterize the behavioral impact of a new birth on captive gorilla social structure and could potentially inform future management of breeding gorilla groups. PMID:25130595

Kurtycz, Laura M; Shender, Marisa A; Ross, Stephen R

2014-01-01

81

ISECG ToR 6 November 2007 INTERNATIONAL SPACE EXPLORATION COORDINATION GROUP  

E-print Network

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

82

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

83

Differential geometry of the space of orbits of a Coxeter group  

E-print Network

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

Boris Dubrovin

1993-03-27

84

Differential geometry of the space of orbits of a Coxeter group  

Microsoft Academic Search

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

Boris Dubrovin

1993-01-01

85

Towards a European vision for space exploration: Recommendations of the Space Advisory Group of the European Commission  

Microsoft Academic Search

As a result of increasing public and political interest in ‘space’ (i.e. solar system) exploration at the global scale, the Space Advisory Group of the European Commission has evaluated the situation in Europe with regard to its potential to participate in this ambitious global enterprise. Aspects of science, technology, environment and safety, society, spin-offs and international cooperation were all considered.

Gerda Horneck; Angioletta Coradini; Gerhard Haerendel; May-Britt Kallenrode; Paul Kamoun; Jean Pierre Swings; Alberto Tobias; Jean-Jacques Tortora

2010-01-01

86

A crystallographic study of haem binding to ferritin.  

PubMed

Ferritin, the iron-storage protein, binds porphyrins, metalloporphyrins and the fluorescent dyes ANS (8-anilino-1-naphthalenesulfonic acid) and TNS (2-p-toluidinyl-6-naphthalenesulfonic acid), similarly to apo-myoglobin. Octahedral crystals of horse-spleen apo-ferritin (HSF; 174 amino acids) complexes prepared by the addition of haem, hematoporphyrin or Sn-protoporphyrin IX to a solution of apo-ferritin crystallize in space group F432 with cell parameter a = 184.0 A. X-ray crystallographic analysis of single crystals prepared from a mixture containing haem or Sn-protoporphyrin IX shows that the haem-binding sites in these crystals are occupied by protoporphyrin IX, which is free of metal, rather than by the original metalloporphyrin. The present paper describes the structure of horse-spleen apo-ferritin cocrystallized with Sn-protoporphyrin IX. The 6797 reflections up to 2.6 A resolution used in the refinement were obtained from a data set recorded on a Nicolet/Xentronics area detector with Cu Kalpha radiation from a Rigaku RU 200 rotating anode. The final structure comprises 1613 non-H atoms, two Cd atoms and 170 solvent molecules. Four residues are described as disordered. The root-mean-square deviations from ideal bond lengths and angles are 0.013 A and 2.88 degrees, respectively. Protoporphyrins are observed in special positions on the twofold axes of the ferritin molecule with a stoichiometry of 0.4 per subunit. PMID:15299370

Précigoux, G; Yariv, J; Gallois, B; Dautant, A; Courseille, C; d'Estaintot, B L

1994-09-01

87

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

PubMed

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

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

2012-11-01

88

THE WEYL QUANTIZATION AND THE QUANTUM GROUP QUANTIZATION OF THE MODULI SPACE OF  

E-print Network

56, 81T45, 57M25. Key words and phrases. Weyl quantization, quantum groups, topological quantum #12THE WEYL QUANTIZATION AND THE QUANTUM GROUP QUANTIZATION OF THE MODULI SPACE OF FLAT SU(2, for the moduli space of at SU(2)-connections on the 2-dimensional torus, the Weyl quantization

Uribe, Alejandro

89

The NASA EEE parts assurance group (NEPAG) - An evolving approach to maximizing space parts assurance resources  

Microsoft Academic Search

This paper describes the activities of the National Aeronautics and Space Administration's (NASA's) Electrical, Electronic and Electromechanical (EEE) Parts Assurance Group (NEPAG) in its role as a resource sharing and coordinating force in EEE Parts assurance for space flight missions. NEPAG is a new organization, barely two years old. The EEE parts world for space applications faces a number of

M. J. Sampson

2002-01-01

90

Space Weather Activities of IONOLAB Group: TEC Mapping  

Microsoft Academic Search

Being a key player in Space Weather, ionospheric variability affects the performance of both communication and navigation systems. To improve the performance of these systems, ionosphere has to be monitored. Total Electron Content (TEC), line integral of the electron density along a ray path, is an important parameter to investigate the ionospheric variability. A cost-effective way of obtaining TEC is

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

2009-01-01

91

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

Microsoft Academic Search

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

Michael Heusener; Blaise Pascal

2003-01-01

92

The Picard group of the loop space of the Riemann sphere  

E-print Network

The loop space of the Riemann sphere consisting of all C^k or Sobolev W^{k,p} maps from the circle S^1 to the sphere is an infinite dimensional complex manifold. We compute the Picard group of holomorphic line bundles on this loop space as an infinite dimensional complex Lie group with Lie algebra the first Dolbeault group. The group of Mobius transformations G and its loop group LG act on this loop space. We prove that an element of the Picard group is LG-fixed if it is G-fixed; thus completely answer the question by Millson and Zombro about G-equivariant projective embedding of the loop space of the Riemann sphere.

Ning Zhang

2014-07-12

93

'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

94

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

95

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

96

Polyimides Containing Pendent Phosphine Oxide Groups for Space Applications  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

97

Recombinant production, crystallization and X-ray crystallographic structure determination of the peptidyl-tRNA hydrolase of Pseudomonas aeruginosa.  

PubMed

The peptidyl-tRNA hydrolase enzyme from the pathogenic bacterium Pseudomonas aeruginosa (Pth; EC 3.1.1.29) has been cloned, expressed in Escherichia coli and crystallized for X-ray structural analysis. Suitable crystals were grown using the sitting-drop vapour-diffusion method after one week of incubation against a reservoir solution consisting of 20% polyethylene glycol 4000, 100?mM Tris pH 7.5, 10%(v/v) isopropyl alcohol. The crystals were used to obtain the three-dimensional structure of the native protein at 1.77?Å resolution. The structure was determined by molecular replacement of the crystallographic data processed in space group P6(1)22 with unit-cell parameters a=b=63.62, c=155.20?Å, ?=?=90, ?=120°. The asymmetric unit of the crystallographic lattice was composed of a single copy of the enzyme molecule with a 43% solvent fraction, corresponding to a Matthews coefficient of 2.43?Å3?Da(-1). The crystallographic structure reported here will serve as the foundation for future structure-guided efforts towards the development of novel small-molecule inhibitors specific to bacterial Pths. PMID:23192026

Hughes, Ronny C; McFeeters, Hana; Coates, Leighton; McFeeters, Robert L

2012-12-01

98

Quantum group (CO)actions onG-spaces and quantum modules  

NASA Astrophysics Data System (ADS)

A generalized transformation theory is introduced by using quantum (non-commutative) spaces transformed by quantum Lie groups (Hopf algebras). In our method dual pairs of -quantum groups-comodule algebra. We use the quantized groupSU q (2) as a show case, and we determine its action on modules such as theq-oscillator and the quantum sphere. We also apply our method for the quantized Euclidean groupF q (E(2)) acting on a quantum homogeneous space. For the sphere case the construction leads to an analytic pseudodifferential vector field realization of the deformed algebra su q (2) on the quantum projective plane for north and south pole.

Arvanitoyeorgos, Andreas; Ellinas, Demosthenes

1996-12-01

99

Managing space for managed care: the challenge for a multispecialty group practice.  

PubMed

A project that began as an architectural study to determine space requirements and remedy space deficiencies for an academic medical center's faculty multispecialty group practice led to development of an analytical methodology for assessing real space needs and viable options for solutions in the context of the group's operational policies, physician practice patterns, and business goals. Major facility investments for new or renovated construction demand significant capital expenditure, which can severely affect a group's ability to complete as a financially viable player in a marketplace environment of increasingly competitive managed care delivery systems. The methodology created during this project helped the group practice to understand how they could optimize the use of existing space, minimize capital costs, and provide flexibility for future developments. PMID:10158956

Berkoff, M J; Burns, L A

1996-07-01

100

A corrected space group for Sulfolobus sulfataricus 5'-deoxy-5'-methylthioadenosine phosphorylase II.  

PubMed

5'-deoxy-5'-methylthioadenosine phosphorylase (MTAP) catalyzes the phosphorolytic cleavage of 5'-deoxy-5'-methylthioadenosine (MTA), a byproduct of polyamine biosynthesis. The Sulfolobus sulfataricus genome encodes two MTAPs. SsMTAP I has broad substrate specifity, accepting guanosine, inosine, adenosine and MTA, while SsMTAP II is specific for MTA. SsMTAP I forms a donut-shaped hexamer, while SsMTAP II is a hexamer formed from trimers packed face to face. The structure of SsMTAP II was originally determined in space group P1 (PDB entry 2a8y) and showed R32 pseudosymmetry. Post-analysis using phenix.xtriage showed that the correct space group is C2. Here, the structure refined in space group C2 is reported and the factors that initially led to the incorrect space-group assignment are discussed. PMID:22349226

Zhang, Yang; Zwart, Peter H; Ealick, Steven E

2012-03-01

101

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

SciTech Connect

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

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

2010-12-01

102

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.

103

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

104

Crystallographic and magnetic structure of UCu{sub 1.5}Sn{sub 2}  

SciTech Connect

We report on the crystallographic and magnetic structures of the antiferromagnet UCu{sub 1.5}Sn{sub 2}, as determined by x-ray and neutron powder diffraction. It forms in the tetragonal CaBe{sub 2}Ge{sub 2} structure type, with space group P/4nmm, and we find no site disorder between two different Sn 2c sites, in contrast with a previous report. UCu{sub 1.5}Sn{sub 2} orders antiferromagnetically with a Neel temperature of about 110 K. This is unusually high amongst uranium intermetallics. The uranium moments align along the c-axis in a collinear arrangement but alternating along the c-axis. The low-temperature uranium moment is 1.95{mu}{sub B}.

Purwanto, A.; Robinson, R.A.; Nakotte, H. [Los Alamos National Lab., NM (United States); Swainson, I. [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada). Chalk River Lab.; Torikachvili, M. [San Diego State Univ., CA (United States). Dept. of Physics

1995-09-01

105

Production, Purification and Preliminary X-ray Crystallographic Studies of Adeno-Associated Virus Serotype 9  

SciTech Connect

Adeno-associated virus (AAV) serotype 9, which is under development for gene-delivery applications, shows significantly enhanced capsid-associated transduction efficiency in muscle compared with other AAV serotypes. With the aim of characterizing the structural determinants of this property, the purification, crystallization and preliminary X-ray crystallographic analyses of the AAV9 viral capsid are reported. The crystals diffracted X-rays to 2.8 A resolution using synchrotron radiation and belonged to the trigonal space group P32, with unit-cell parameters a = b = 251.0, c = 640.0 A. There are three complete viral capsids in the crystal unit cell. The orientation and position of the asymmetric unit capsid have been determined by molecular-replacement methods and structure determination is in progress.

Mitchell, M.; Nam, H; Carter, A; McCall, A; Rence, C; Bennett, A; Gurda, B; McKenna, R; Porter, M; et. al.

2009-01-01

106

The Crystallographic Structure of Panicum Mosaic Virus (PMV)  

PubMed Central

The structure of Panicum Mosaic Virus (PMV) was determined by X-ray diffraction analysis to 2.9 Å resolution. The crystals were of pseudo symmetry F23; the true crystallographic unit cell was of space group P21 with a=411.7 Å, b=403.9 Å and c=412.5 Å, with ?=89.7°. The asymmetric unit was two entire T=3 virus particles, or 360 protein subunits. The structure was solved by conventional molecular replacement from two distant homologues, Cocksfoot Mottle Virus (CfMV) and Tobacco Necrosis Virus (TNV), of ~20% sequence identity followed by phase extension. The model was initially refined with exact icosahedral constraints and then with icosahedral restraints. The virus has Ca++ ions octahedrally coordinated by six aspartic acid residues on quasi threefold axes, which is completely different than for either CfMV or TNV. Amino terminal residues 1–53, 1–49 and 1-21 of the A, B and C subunits, respectively, and the four C-terminal residues (239-242) are not visible in electron density maps. The additional ordered residues of the C chain form a prominent “arm” that intertwines with symmetry equivalent “arms” at icosahedral threefold axes, as was seen in both CfMV and TNV. A 17 nucleotide hairpin segment of genomic RNA is icosahedrally ordered and bound at 60 equivalent sites at quasi twofold A–B subunit interfaces at the interior surface of the capsid. This segment of RNA may serve as a conformational switch for coat protein subunits, as has been proposed for similar RNA segments in other viruses. PMID:23123270

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

2012-01-01

107

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

108

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

109

The space shuttle payload planning working groups. Volume 3: High energy astrophysics  

NASA Technical Reports Server (NTRS)

The findings of the High Energy Astrophysics working group of the space shuttle payload planning activity are presented. The objectives to be accomplished during space shuttle missions are defined as: (1) X-ray astronomy, (2) hard X-ray and gamma ray astronomy, and (3) cosmic ray astronomy. The instruments and test equipment required to accomplish the mission are identified. Recommendations for managing the installation of the equipment and conducting the missions are included.

1973-01-01

110

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

111

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

NASA Astrophysics Data System (ADS)

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

Janda, Ji?í; Paseka, Jan

2015-02-01

112

Confessions of an icosahedral virus crystallographer  

PubMed Central

This is a personal history of my structural studies of icosahedral viruses that evolved from crystallographic studies, to hybrid methods with electron cryo-microscopy and image reconstruction (cryoEM) and then developed further by incorporating a variety of physical methods to augment the high resolution crystallographic studies. It is not meant to be comprehensive, even for my own work, but hopefully provides some perspective on the growth of our understanding of these remarkable biologic assemblies. The goal is to provide a historical perspective for those new to the field and to emphasize the limitations of any one method, even those that provide atomic resolution information about viruses. PMID:23291268

Johnson, John E.

2013-01-01

113

Crystallographic orientation assessment by electron backscattered diffraction.  

PubMed

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

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

1999-01-01

114

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

115

Combinatorial R-trees as generalized Cayley graphs for fundamental groups of one-dimensional spaces  

E-print Network

In their study of fundamental groups of one-dimensional path-connected compact metric spaces, Cannon and Conner have asked: Is there a tree-like object that might be considered the topological Cayley graph? We answer this question in the positive and provide a combinatorial description of such an object.

Fischer, Hanspeter

2011-01-01

116

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

EPA Science Inventory

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

117

School Mathematics Study Group, Unit Number One. Chapter 1 - Structuring Space. Chapter 2 - Functions.  

ERIC Educational Resources Information Center

This is the first unit of a 15-unit School Mathematics Study Group (SMSG) mathematics text for high school students. Topics presented in the first chapter (Structuring Space) include: lines and points; planes; intersections; intersections of lines and planes; betweenness and segments; separation; angles; locating positions and points; coordinates;…

Stanford Univ., CA. School Mathematics Study Group.

118

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

119

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 formalise this kind of encounter using the ubiquitous form of the two player single round Prisoner's Dilemma

Hales, David

120

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

NASA Technical Reports Server (NTRS)

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

Kolecki, Joseph C.; Hillard, G. Barry

1991-01-01

121

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

122

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

NASA Technical Reports Server (NTRS)

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

Radtke, Robert; Woolley, Charles; Arnold, Lana

1993-01-01

123

Graphically oriented method for obtaining atomic displacement fields in crystals from irreducible representations of space groups  

NASA Astrophysics Data System (ADS)

A method for obtaining distortion fields in a crystal from a given irreducible representation of the underlying space group is described. The method, based on projection operators of group theory, is graphically oriented and therefore calculation-free. For an example (space group P4¯21m), complete sets of representation matrices are analytically calculated for all irreducible representations which correspond to all wave vectors of the form k=(q,q,0). All 96 linear independent atomic displacement modes in the (3×3×1) supercell, which are induced by the two irreducible representations with k=(13,13,0), are explicitly determined: the obtained atomic displacement fields are plane waves with wave vector k.

Gutmann, Jürgen K.; Böhm, Horst

2000-06-01

124

Crystallographic texture of stress-affected bainite  

Microsoft Academic Search

1. Abstract A method is presented for calculating both the macroscopic strains and crystallographic bias which develop when a polycrystalline sample of austenitic steel is transformed into bainite or martensite under the inuence of an applied stress or a system of stresses. Any texture present in the austenite prior to transformation is taken into account, as is the detailed crystallography

Saurabh Kundu; Kazukuni Hase; H. K. D. H. Bhadeshia

2007-01-01

125

Phase-space shapes of clusters and rich groups of galaxies  

NASA Astrophysics Data System (ADS)

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

Wojtak, Rados?aw

2013-11-01

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

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

PubMed

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

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

1996-04-01

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

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

130

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

131

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

132

Cohomologies of Configuration Spaces and Higher-Dimensional Polylogarithms in Renormalization Group Problems  

SciTech Connect

The deviation from commutativity of the renormalization and the action of all linear partial differential operators is the main source of the anomalies in quantum field theory, including the renormalization group action. This deviation is characterized by certain 'renormalization cocycles' that are related to cohomologies of the so called (ordered) configuration spaces. Cohomological differential equations that determine the renormalization cocycles up to the renormalization freedom are obtained. The solution of these equations requires introducing transcendental extensions related to higher-dimensional polylogarithms.

Nikolov, Nikolay M. [Institute for Nuclear Research and Nuclear Energy, Tsarigradsko Chaussee 72, BG-1784 Sofia (Bulgaria)

2010-06-17

133

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

134

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

E-print Network

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

Sirianni, Marco

135

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

PubMed

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

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

2012-10-01

136

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

137

Preparation and Crystallographic Analysis of Gliclazide Polymorphs  

PubMed Central

Since the introduction of gliclazide in the pharmaceutical industry, a large number of research groups have been engaged in various investigations aiming to enhance its biomedical application. But, very limited efforts have been made to study polymorphism of gliclazide. Therefore, this study focuses on solvent-induced polymorphism of gliclazide and its characterization by thermal methods. Three polymorphs namely, Form-I, II and III and an amorphous powder were produced from different solvents and solvent mixtures. Crystals were analyzed using infrared spectroscopy, differential scanning calorimetry, X-ray powder diffraction and single crystal x-ray diffraction. Polymorph Form-I is found to exist in centro-symmetric triclinic P-1 space group and has endothermic peak at 162.93°. Form-II has endothermic peak from 171.2° to 172.35° and exists in centro-symmetric monoclinic P21/a space group while Form-III has endothermic peak from 168.93° to 169.86° and exists in centro-symmetric monoclinic P21/n space group. The equilibrium solubility values of Form-I, II, III and the amorphous form were 0.4825±0.025, 0.2341±0.042, 0.2581±0.038 and 0.5213±0.072 mg/ml, respectively. The Form-I has relatively higher solubility and similar to that of amorphous gliclazide. Form-II and Form-III are relatively most stable and least soluble. However, there was no remarkable difference in their aqueous solubility under the conditions in which study was conducted.

Rajamma, A. J.; Sateesha, S. B.; Narode, M. K.; Prashanth, V. R. S. S.; Karthik, A. M.

2015-01-01

138

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

139

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

140

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

141

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

142

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

143

Outstanding Student Paper Awards: Atmospheric and Space Electricity Focus Group; Volcanology, Geochemistry, and Petrology  

NASA Astrophysics Data System (ADS)

The following members received Outstanding Student Paper Awards at the 2004 Fall Meeting in San Francisco, California. (Winners in other sections and focus groups will be announced in subsequent issues of Eos).Atmospheric and Space ElectricityToru Adachi, Tohoku University, Spatial and temporal structures of sprites observed with the array photometer on board of the ROCSAT-2 satellite.Robert Marshall, Stanford University, High time resolution telescopic imaging of fine structure in sprites.Robert Olsen, University of Florida, Leader/return-stroke-like processes in the initial stage of rocket-triggered lightning.

2005-02-01

144

Group-galaxy correlations in redshift space as a probe of the growth of structure  

E-print Network

We investigate the use of the cross-correlation between galaxies and galaxy groups to measure redshift-space distortions (RSD) and thus probe the growth rate of cosmological structure. This is compared to the classical approach based on using galaxy auto-correlation. We make use of realistic simulated galaxy catalogues that have been constructed by populating simulated dark matter haloes with galaxies through halo occupation prescriptions. We adapt the classical RSD dispersion model to the case of the group-galaxy cross-correlation function and estimate the RSD parameter {\\beta} by fitting both the full anisotropic correlation function {\\xi}(rp, {\\pi}) and its multipole moments. In addition, we define a modified version of the latter statistics by truncating the multipole moments to exclude strongly non-linear distortions at small transverse scales. We fit these three observable quantities in our set of simulated galaxy catalogues and estimate statistical and systematic errors on {\\beta} for the case of galax...

Mohammad, Faizan G; Bianchi, Davide; Guzzo, Luigi; Peacock, John A

2015-01-01

145

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

146

A Minuet of Galaxies: Hickson Compact Group 87 as Viewed by the Hubble Space Telescope  

NASA Astrophysics Data System (ADS)

HCG 87 was selected from 3 visually, and scientifically, intriguing compact groups for HST WFPC2 imaging by members of the public who visited the Hubble Heritage website (http://heritage.stsci.edu) and registered their votes. The HST exposures in four filters (F450W, F555W, F675W and F814W) of the winning target were used to create a color image, released in September 1999 as part of the Hubble Heritage Team's program to provide images for public outreach and education. Along with these data and image, we present a preliminary determination of colors and brightness profiles for the large galaxies in this group. The pair of apparently interacting galaxies each harbour AGN. One is a ``boxy'' spiral with a prominent dust lane and the other a lenticular galaxy. Another group member is a smaller starbursting spiral galaxy. Our goal is to study their stellar populations and examine the influence of active nuclei on star formation histories. In addition, a similar analysis is being performed on all faint, extended objects distributed throughout the group. For those determined to be tidal dwarf galaxies, we plan to appraise the role gravitational instabilities play during their formation. Support for this work was provided by NASA through grant number GO-07632.01-96A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under the NASA contract NAS5-26555.

English, J.; Hunsberger, S.; Charlton, J.; Hamilton, F.; Bond, H. E.; Christian, C. A.; Frattare, L.; Levay, Z.; Noll, K.

2000-05-01

147

The Lorentz Group, Noncommutative Space-Time, and Nonlinear Electrodynamics in Majorana-Oppenheimer Formalism  

E-print Network

Non-linear electrodynamics arising in the frames of field theories in non-commutative space-time is examined on the base of the Riemann-Silberstein-Majorana-Oppenheimer formalism. The problem of form-invariance of the non-linear constitutive relations governed by six non-commutative parameters \\theta_{kl} \\sim {\\bf K} = {\\bf n} + i {\\bf m} is explored in detail on the base of the complex orthogonal group theory SO(3.C). Two Abelian 2-parametric small groups, isomorphic to each other in abstract sense, and leaving unchangeable the extended constitutive relations at arbitrary six parameters \\theta_{kl} of effective media have been found, their realization depends explicitly on invariant length {\\bf K}^{2}. In the case of non-vanishing length a special reference frame in which the small group has the structure SO(2) \\otimes SO(1,1) has been found. In isotropic case no such reference frame exists. The way to interpret both Abelian small groups in physical terms consists in factorizing corresponding Lorentz transformations into Euclidean rotations and boosts. In the context of general study of various dual symmetries in non-commutative field theory, it is demonstrated explicitly that the non-linear constitutive equations in non-commutative electrodynamics are not invariant under continuous dual rotations, instead only invariance under discrete dual transformation exists.

V. Red'kov; E. Tolkachev

2011-09-09

148

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

149

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

150

R. Bantges, C. Belotti, H. Brindley, J. Harries and D. Jabry Space and Atmospheric Physics Group, Imperial College London, UK.  

E-print Network

R. Bantges, C. Belotti, H. Brindley, J. Harries and D. Jabry Space and Atmospheric Physics Group. The mission concept represents a new phase in space based monitoring of climate, being specifically designed and monitoring of the critical climate processes that control the radiative balance of the Earth, including

151

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

152

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

153

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

PubMed

Cystathionine ?-synthase (CBS) is a pyridoxal-5'-phosphate-dependent enzyme that catalyzes the first step of the transsulfuration pathway, namely the condensation of serine with homocysteine to form cystathionine. Mutations in the CBS gene are the single most common cause of hereditary homocystinuria, a multisystemic disease affecting to various extents the vasculature, connective tissues and central nervous system. At present, the crystal structure of CBS from Drosophila melanogaster is the only available structure of the full-length enzyme. Here we describe a cloning, overexpression, purification and preliminary crystallographic analysis of a full-length CBS from Apis mellifera (AmCBS) which maintains 51 and 46% sequence identity with its Drosophila and human homologs, respectively. The AmCBS yielded crystals belonging to space group P2(1)2(1)2(1), with unit-cell parameters a=85.90, b=95.87, c=180.33?Å. Diffraction data were collected to a resolution of 3.0?Å. The crystal structure contained two molecules in the asymmetric unit which presumably correspond to the dimeric species observed in solution. PMID:23143241

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

2012-11-01

154

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

NASA Astrophysics Data System (ADS)

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

Whitelam, Stephen; Garrahan, Juan P.

2004-10-01

155

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

156

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

SciTech Connect

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

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

1997-05-23

157

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

158

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

159

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

NASA Astrophysics Data System (ADS)

We have a long tradition in Space and Solar System outreach at the University of Athens (Space Group). We have contributed with many popular science articles in encyclopaedias (a total of some 200000 words), magazines and newspapers, public lectures around Greece and radio and TV programmes. We contribute in exhibitions for the public on many occasions (e.g. The British Exploration of the Planets, an exhibition organized by the British Council, at Eugenides Foundation and The Planetarium, where I prepared some 15 posters). We are preparing an outreach site of Astrophysics with sections for the planets, the exploration of the solar system and solar terrestrial relations. I am preparing several posters for the planets. We organize with the Hellenic Physical Union a series of Astrophysics Lectures at the University of Athens. Together with the Hellenic Physical Union we are planning to produce a theatrical play and CD or DVD concerning the planets. We have excellent collaboration with the amateur astronomers allover Greece and Cyprus. We organize, together with Physics or mathematics teachers in high schools several events related to astronomical observations (e.g. Venus transit, solar eclipe, astronomy nights). 1 We also organize popular science programmes in TV channels. I brief we consider Astronomy and especially the planetary system as a "Great Attractor" of pupil and the general public to science and we use it on every occasion for the benefit of the pupil and science. 2

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

160

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

161

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

162

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

Microsoft Academic Search

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 group-based framework. The group-based model enables model predictions concerning the group as

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

2009-01-01

163

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

NASA Astrophysics Data System (ADS)

Single stars in ancient globular clusters (GCs) are believed incapable of producing planetary nebulae (PNs), because their post-asymptotic-giant-branch evolutionary timescales are slower than the dissipation timescales for PNs. Nevertheless, four PNs 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 PNs in bright Local Group GCs outside the Milky Way. I used a filter covering the 5007 Å 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 Å to 75, whose total luminosity slightly exceeds that of the entire Galactic GC system. I found no convincing PNs in these clusters, aside from one PN in a young M31 cluster misclassified as a GC, and two PNs at such large angular separations from an M31 GC that membership is doubtful. In a ground-based spectroscopic survey of 274 old GCs in M31, Jacoby et al. found three candidate PNs. My HST images of one of them suggest that the [O iii] emission actually arises from ambient interstellar medium rather than a PN; for the other two candidates, there are broadband archival UV HST images that show bright, blue point sources that are probably the PNs. In a literature search, I also identified five further PN candidates lying near old GCs in M31, for which follow-up observations are necessary to confirm their membership. The rates of incidence of PNs are similar, and small but nonzero, throughout the GCs of the Local Group. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, and from the data archive at STScI, which are operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Bond, Howard E.

2015-04-01

164

Biochemical and crystallographic analyses of a portal mutant of the adipocyte lipid-binding protein.  

PubMed

A number of crystallographic studies of the adipocyte lipid-binding protein have established that the fatty acid-binding site is within an internalized water-filled cavity. The same studies have also suggested the existence of a region physically distinct from the fatty acid-binding site which connects the cavity of the protein with the external solvent, hereafter referred to as the portal. In an effort to examine the portal region, we have used site-directed mutagenesis to introduce the mutations V32D/F57H into the murine ALBP cDNA. Mutant protein has been isolated, crystallized, and its stability and binding properties studied by biochemical methods. As assessed by guanidine-HCl denaturation, the mutant form exhibited a slight overall destabilization relative to the wild-type protein under both acid and alkaline conditions. Accessibility to the cavity in both the mutant and wild-type proteins was observed by stopped-flow analysis of the modification of a cavity residue, Cys117, by the sulfhydryl reactive agent 5, 5'-dithiobis(2-nitrobenzoic acid) at pH 8.5. Cys117 of V32D/F57H ALBP was modified 7-fold faster than the wild-type protein. The ligand binding properties of both the V32D/F57H mutant and wild-type proteins were analyzed using a fluorescent probe at pH 6.0 and 8.0. The apparent dissociation constants for 1-anilinonaphthalene-8-sulfonic acid were approximately 9-10-fold greater than the wild-type protein, independent of pH. In addition, there is a 6-fold increase in the Kd for oleic acid for the portal mutant relative to the wild-type at pH 8.0. To study the effect of pH on the double mutant, it was crystallized and analyzed in two distinct space groups at pH 4.5 and 6.4. While in general the differences in the overall main chain conformations are negligible, changes were observed in the crystallographic structures near the site of the mutations. At both pH values, the mutant side chains are positioned somewhat differently than in wild-type protein. To ensure that the mutations had not altered ionic conditions near the binding site, the crystallographic coordinates were used to monitor the electrostatic potentials from the head group site to the positions near the portal region. The differences in the electrostatic potentials were small in all regions, and did not explain the differences in ligand affinity. We present these results within the context of fatty acid binding and suggest lipid association is more complex than that described within a single equilibrium event. PMID:9092513

Ory, J; Kane, C D; Simpson, M A; Banaszak, L J; Bernlohr, D A

1997-04-11

165

Imaging crystallographic phases using time-of-flight neutron diffraction  

Microsoft Academic Search

Identification and imaging of crystallographic phases inside an object can be achieved by time-of-flight neutron diffraction, based on a correction formula that is usually used to account for a sample offset on a powder diffractometer. The procedure allows the distribution of crystallographic phases along the incident beam path through the thickness of the material to be reconstructed. Phase reconstruction is

Matthias Gutmann; Winfried Kockelmann; Laurent Chapon; Paolo G. Radaelli

2006-01-01

166

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

167

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

168

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

169

Detection vs. grouping thresholds for elements differing in spacing, size and luminance. An alternative approach towards the psychophysics of Gestalten.  

PubMed

Three experiments were performed to compare thresholds for the detection of non-uniformity in spacing, size and luminance with thresholds for grouping. In the first experiment a row of 12 black equi-spaced dots was used and the spacing after the 3rd, 6th, and 9th dot increased in random steps to determine the threshold at which the observer detected an irregularity in the size of the gaps. Thereafter, spacing in the same locations was increased further to find the threshold at which the observer perceived four groups of three dots each (triplets). In the second experiment, empty circles were used instead of dots and the diameter of the circles in the first and second triplet increased until the difference in size gave rise either to a detection or grouping response. In the third experiment, the dots in the second and fourth triplet were increased in luminance. The aim again was to compare the difference in brightness required for detection or grouping, respectively. Results demonstrate that the threshold for perceiving stimuli as irregularly spaced or dissimilar in size or brightness is much smaller than the threshold for grouping. In order to perceive stimuli as grouped, stimulus differences had to be 5.2 times (for dot spacing), 7.4 times (for size) and 6.6 times (for luminance) larger than for detection. Two control experiments demonstrated that the difference between the two kinds of thresholds persisted even when only two gaps were used instead of three and when gap position was randomized. PMID:20363241

Gori, Simone; Spillmann, Lothar

2010-06-11

170

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.

171

Crystallographic and magnetic structure of the perovskite-type compound BaFeO2.5: unrivaled complexity in oxygen vacancy ordering.  

PubMed

We report here on the characterization of the vacancy-ordered perovskite-type structure of BaFeO2.5 by means of combined Rietveld analysis of powder X-ray and neutron diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c [a = 6.9753(1) Å, b = 11.7281(2) Å, c = 23.4507(4) Å, ? = 98.813(1)°, and Z = 28] containing seven crystallographically different iron atoms. The coordination scheme is determined to be Ba7(FeO4/2)1(FeO3/2O1/1)3(FeO5/2)2(FeO6/2)1 = Ba7Fe([6])1Fe([5])2Fe([4])4O17.5 and is in agreement with the (57)Fe Mössbauer spectra and density functional theory based calculations. To our knowledge, the structure of BaFeO2.5 is the most complicated perovskite-type superstructure reported so far (largest primitive cell, number of ABX2.5 units per unit cell, and number of different crystallographic sites). The magnetic structure was determined from the powder neutron diffraction data and can be understood in terms of "G-type" antiferromagnetic ordering between connected iron-containing polyhedra, in agreement with field-sweep and zero-field-cooled/field-cooled measurements. PMID:24901981

Clemens, Oliver; Gröting, Melanie; Witte, Ralf; Perez-Mato, J Manuel; Loho, Christoph; Berry, Frank J; Kruk, Robert; Knight, Kevin S; Wright, Adrian J; Hahn, Horst; Slater, Peter R

2014-06-16

172

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

173

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

174

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

NASA Astrophysics Data System (ADS)

An essential requirement of a successful space program is the assurance of a safe affordable routine access to space. In view of this, a national organization known as the Space Propulsion Synergy Group (SPSG) has been directed for the past two years toward supporting strategic planning for earth-to-orbit space transportation and propulsion systems. This paper presents a short description of the approach the SPSG followed in their space transportation and propulsion systems strategic planning support activities. The SPSG study emphasized the identification of the transportation systems users/customers and the characteristics of attributes most valued by them in earth-to-LEO payload transportation services. The study initiated the process known as Quality Function Deployment to ensure that the customer/user real requirements and needs are properly addressed and that the transportation system concepts advocated had the greatest probability of satisfying the custosmer's requirements and desired attributes.

Dankhoff, Walter F.; Hope, William P., Jr.

1993-06-01

175

Rigidity of automorphism groups of invariant domains in homogeneous Stein spaces  

NASA Astrophysics Data System (ADS)

For a large class of Stein manifolds which are homogeneous under a complex reductive Lie group, we prove a rigidity property of the automorphism groups of domains invariant with respect to a compact form of this complex group.

Deng, F.; Zhou, X. Yu

2014-02-01

176

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

177

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

178

Global space-group optimization problem: Finding the stablest crystal structure without constraints  

NASA Astrophysics Data System (ADS)

Finding the most stable structure of a solid is one of the central problems in condensed matter physics. This entails finding both the lattice type (e.g., fcc, bcc, and orthorhombic) and (for compounds) the decoration of the lattice sites by atoms of types A , B , etc. (“configuration”). Most approaches to this problem either assumed that both lattice type and configuration are known, optimizing instead the cell volume and performing local relaxation. Other approaches assumed that the lattice type is known, searching for the minimum-energy decoration. We present here an approach to the global space-group optimization (GSGO) problem, i.e., the problem of predicting both the lattice structure and the atomic configuration of a crystalline solid. This search method is based on an evolutionary algorithm within which a population of crystal structures is evolved through mating and mutation operations, improving the population by substituting the highest total-energy structures with new ones. The crystal structures are not represented by bit strings as in conventional genetic algorithms. Instead, the evolutionary search is performed directly on the atomic positions and the unit-cell vectors after a similarity transformation is applied to bring structures of different unit-cell shapes to a common basis. Following this transformation, we can define a crossover operation that treats, on the same footing, structures with different unit-cell shapes. Once a new structure has been generated by mating or mutation, it is fully relaxed to the closest local total-energy minimum. We applied our procedure for the GSGO in the context of pseudopotential total-energy calculations to the semiconductor systems Si, SiC, and GaAs and to the metallic alloy AuPd with composition Au8Pd4 . Starting from random unit-cell vectors and random atomic positions, the present search procedure found for all semiconductor systems studied the correct lattice structure and configuration. In the case of Au8Pd4 , the search retrieved the correct underlying fcc lattice, but energetically closely spaced (˜2meV/at.) alloy configurations were not resolved. This approach to GSGO opens the way to predicting unsuspected structures by direct optimization using, in the cases noted above, an order of 100 total-energy ab initio calculations.

Trimarchi, Giancarlo; Zunger, Alex

2007-03-01

179

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

180

Production, crystallization and preliminary crystallographic analysis of Allochromatium vinosum thiosulfate dehydrogenase TsdA, an unusual acidophilic c-type cytochrome.  

PubMed

The ability to perform the very simple oxidation of two molecules of thiosulfate to tetrathionate is widespread among prokaryotes. Despite the prevalent occurrence of tetrathionate formation and its well documented significance within the sulfur cycle, little is known about the enzymes that catalyze the oxidative condensation of two thiosulfate anions. To fill this gap, the thiosulfate dehydrogenase (TsdA) enzyme from the purple sulfur bacterium Allochromatium vinosum was recombinantly expressed in Escherichia coli, purified and crystallized, and a crystallographic data set was collected. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 79.2, b = 69.9, c = 57.9?Å, ? = 129.3°, contained one monomer per asymmetric unit and diffracted to a resolution of 1.98?Å. PMID:25286955

Brito, José A; Gutierres, André; Denkmann, Kevin; Dahl, Christiane; Archer, Margarida

2014-10-01

181

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

182

Generalized X-ray and neutron crystallographic analysis: more accurate and complete structures for biological macromolecules  

PubMed Central

X-ray and neutron crystallographic techniques provide complementary information on the structure and function of biological macromolecules. X-ray and neutron (XN) crystallo­graphic data have been combined in a joint structure-refinement procedure that has been developed using recent advances in modern computational methodologies, including cross-validated maximum-likelihood target functions with gradient-based optimization and simulated annealing. The XN approach for complete (including hydrogen) macromolecular structure analysis provides more accurate and complete structures, as demonstrated for diisopropyl fluorophosphatase, photoactive yellow protein and human aldose reductase. Furthermore, this method has several practical advantages, including the easier determination of the orientation of water molecules, hydroxyl groups and some amino-acid side chains. PMID:19465771

Adams, Paul D.; Mustyakimov, Marat; Afonine, Pavel V.; Langan, Paul

2009-01-01

183

The orthogonal projections with respect to a periodic continuous unitary representation of the group (R,+) on a complex Hilbert space  

NASA Astrophysics Data System (ADS)

In this work, a family {Pn?}n?Z of orthogonal projections on a complex Hilbert space H is defined by means of a periodic continuous unitary representation ? of the topological group (R,+) on H, and some properties of this family are given.

Öztürk, Seda

2014-08-01

184

The meteor year of the Meteor Research Group of the European Space Agency's Research and Scientific Support Department  

Microsoft Academic Search

A lot of activities took place in 2007 at the Meteor Research Group (MRG) of the European Space Agency's (ESA) Research and Scientific Support Department (RSSD). Both special observing campaigns as well as continuous observations were performed, mainly with intensified video cameras, but also with still CCD cameras. Over 1400 meteors were observed; about 150 meteors were observed from more

D. V. Koschny; J. McAuliffe; G. Barentsen; F. C. M. Bettonvil; J. P. Hatton; F. Lowiessen; J. J. Zender

2008-01-01

185

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

186

Synchrotron Light on Ribosomes: The Development of Crystallographic Studies  

E-print Network

and B. Stearothermophilus Our first microcrystals were of Bacillus stearothermophilus 50S subunits 9)and. Stearothermophilus . . . . . . . . . . . . . . . . . 58 2.2 Halobacterium Marismortui . . . . . . . . . . . . . . . . . . . . 63 3 Crystallographic Data Collection -- Recent Developments . . . . . . . . . 64 3.1 Bacillus

Yonath, Ada E.

187

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

188

Grouping  

NSDL National Science Digital Library

This interactive Flash applet models the measurement interpretation of division. A child or teacher chooses a total number of objects and a divisor representing the size of equal groups. The applet allows the user to move the objects into equal groups and links the process to jumps on a number line. The applet can be used to introduce children to remainders and to reinforce the language and notation of division. It works well on an interactive white board or projector. A teacher's guide to this collection of applets is cataloged separately.

2006-01-01

189

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

190

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

191

Metric entropy of homogeneous spaces and Finsler geometry of classical Lie groups  

Microsoft Academic Search

For a (compact) subset $K$ of a metric space and $\\\\varepsilon > 0$, the {\\\\em\\u000acovering number} $N(K , \\\\varepsilon )$ is defined as the smallest number of\\u000aballs of radius $\\\\varepsilon$ whose union covers $K$. Knowledge of the {\\\\em\\u000ametric entropy}, i.e., the asymptotic behaviour of covering numbers for\\u000a(families of) metric spaces is important in many areas of

Stanislaw J. Szarek

1997-01-01

192

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

193

Variations in Reactivity on Different Crystallographic Orientations of Cerium Oxide  

SciTech Connect

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

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

2013-01-01

194

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

E-print Network

) Summary Loud calls can be expected to play an important role in the lives of howler monkeys, given-group encounters and extreme weather events triggered calling. Roars were given throughout the home range range of the study group, simulating invasions, or in border areas. In response to simulated invasions

195

SELECTION RULES FOR THE DOUBLE SPACE GROUP O1h H. KUNERT, J. POPENDA  

E-print Network

, is represented by several ionic crystals, including CsCI, CsBr, CsI, RbCI, TICI, TIBr, several compounds, is the structure of numerous ternary compounds where the molecules contain a transition metal and three oxygen de représentations irréductibles du groupe double O1h (groupe de symétrie de la structure cubique

Paris-Sud XI, Université de

196

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

197

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

198

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

PubMed

Rare sugars are used for many industrial and medical purposes and are produced by the interconversion between aldoses and ketoses catalyzed by sugar and sugar-phosphate isomerases. Recently, Clostridium thermocellum d-ribose-5-phosphate isomerase (CTRPI), an aldose-ketose isomerase, was cloned in order to synthesize d-allose and its substrate specificity was further characterized for industrial usage. CTRPI has a novel substrate specificity that differs from those of other isomerases, which have broad substrate specificities. CTRPI prefers aldose substrates such as l-talose, d-ribose and d-allose. CTRPI was purified and crystallized in order to determine its three-dimensional structure and thus to elucidate its enzymatic reaction mechanism and understand its substrate specificity. The crystal belonged to the trigonal space group P3(2)21, with unit-cell parameters a = b = 69.5, c = 154.4 angstrom, and diffracted to 1.9 angstrom resolution. According to Matthews coefficient calculations, the crystallographic structure consists of a dimer in the asymmetric unit, with a V(M) of 3.2 angstrom(3) Da(-1) and a solvent content of 61.7%. PMID:19923736

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

2009-11-01

199

Expression, purification and preliminary crystallographic analysis of the cryptic polo-box domain of Caenorhabditis elegans ZYG-1  

PubMed Central

ZYG-1 is a polo-like kinase essential for centriole assembly in Caenorhabditis elegans. The targeting of ZYG-1 to nascent centrioles is via its central cryptic polo-box (CPB) domain. To shed light on the molecular basis of ZYG-1 recruitment, it is necessary to obtain structural knowledge of the ZYG-1 CPB. Here, the expression, purification and preliminary crystallographic analysis of the ZYG-1 CPB are reported. The protein was overexpressed in Escherichia coli strain BL21 (DE3), purified by multi-step chromatography and crystallized using the vapour-diffusion method. Crystals of the wild-type protein exhibited an order–disorder pathology, which was solved by reductive lysine methylation. A complete anomalous data set was collected to 2.54 Å resolution at the Se K edge (? = 0.9792 Å). The crystal belonged to space group P2, with unit-cell parameters a = 53.3, b = 60.09, c = 87.51 Å, ? = 93.31°. There were two molecules in the asymmetric unit. PMID:25286937

Shimanovskaya, Ekaterina; Dong, Gang

2015-01-01

200

Expression, purification and preliminary crystallographic analysis of the N-terminal domain of Trypanosoma brucei BILBO1.  

PubMed

Trypanosoma brucei is a unicellular parasite that causes sleeping sickness in sub-Saharan Africa. It has a unique flagellar pocket (FP) at the base of the single flagellum. The FP is the sole site for endocytosis and exocytosis activity and plays crucial roles in the defence of the cell against the host immune response. In the neck region of the FP is an electron-dense material termed the flagellar pocket collar (FPC). T. brucei BILBO1 (TbBILBO1) was the first cytoskeletal protein to be characterized in the FPC. This protein is highly conserved among trypanosomatids and is essential for FP biogenesis. Structural information is needed to better understand the molecular mechanism of TbBILBO1 function in the cell. Here, the expression, purification and preliminary crystallographic analysis of the N-terminal domain of TbBILBO1 are reported. The protein was overexpressed in Escherichia coli strain BL21 (DE3), purified by multi-step chromatography and crystallized using the vapour-diffusion method. The crystal diffracted to 1.69 Å resolution and belonged to space group P21, with unit-cell parameters a = 29.69, b = 50.80, c = 37.22 Å, ? = 94.61°. There was one molecule in the asymmetric unit. PMID:24817725

Vidilaseris, Keni; Dong, Gang

2014-05-01

201

Expression, purification and preliminary crystallographic analysis of the N-terminal domain of Trypanosoma brucei BILBO1  

PubMed Central

Trypanosoma brucei is a unicellular parasite that causes sleeping sickness in sub-Saharan Africa. It has a unique flagellar pocket (FP) at the base of the single flagellum. The FP is the sole site for endocytosis and exocytosis activity and plays crucial roles in the defence of the cell against the host immune response. In the neck region of the FP is an electron-dense material termed the flagellar pocket collar (FPC). T. brucei BILBO1 (TbBILBO1) was the first cytoskeletal protein to be characterized in the FPC. This protein is highly conserved among trypanosomatids and is essential for FP biogenesis. Structural information is needed to better understand the molecular mechanism of TbBILBO1 function in the cell. Here, the expression, purification and preliminary crystallographic analysis of the N-terminal domain of TbBILBO1 are reported. The protein was overexpressed in Escherichia coli strain BL21 (DE3), purified by multi-step chromatography and crystallized using the vapour-diffusion method. The crystal diffracted to 1.69 Å resolution and belonged to space group P21, with unit-cell parameters a = 29.69, b = 50.80, c = 37.22 Å, ? = 94.61°. There was one molecule in the asymmetric unit. PMID:24817725

Vidilaseris, Keni; Dong, Gang

2015-01-01

202

SPALENDAR: Visualizing a Group's Calendar Events over a Geographic Space on a Public Display  

E-print Network

Science, University of Calgary 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada xiangchen's calendar events as spatiotemporal activities occurring over a geographic space animated over time, all animates people's past, present and forthcoming movements between event locations as well as their static

Greenberg, Saul

203

SPALENDAR: Visualizing a Group's Calendar Events over a Geographic Space on a Public Display  

E-print Network

at a small size, or even completely hidden. Event details may not even be visible until one opens or drills Science, University of Calgary 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada xiangchen's calendar events as spatiotemporal activities occurring over a geographic space animated over time, all

Greenberg, Saul

204

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

205

Structural studies in columnar basalts from crystallographic and magnetic fabrics  

NASA Astrophysics Data System (ADS)

The purpose of this study is to better characterize the columnar and the associated microstructure development in basalt flows. The thermal contraction (O'Reilly, 1879) is the main hypothesis to explain the columnar formation. However, neither the structures which appear in basalt flow constituted of three levels (Tomkeieff, 1940) nor circular and radial structures within the prisms (for which weathering nor fracturing can account for) can be explained by the thermal contraction theory alone. An early structuring process during solidification (Guy and Le Coze, 1990) could play for a part that must be discussed (Guy, 2010). We studied two recent basalt flows (75 000 years) from the French Massif Central, in which the three flow levels are clearly observed. In the first basalt flow (La Palisse, Ardèche), the emission centre and the flow direction are known. In the second one (Saint Arcons d'Allier, Haute Loire), the prismatic columns are particularly well developed. In order to characterize the flow structure at different scales, from the flow to the grain scale, anisotropy of magnetic susceptibility (AMS) measurements were performed. The AMS data were coupled with crystallographic preferred orientation measurements of magnetite, plagioclase and clinopyroxene using Electron Backscattered Diffraction (EBSD) and image analyses from perpendicular thin sections. Magnetic mineralogy studies of the La Palisse basalts, in particular the thermomagnetic curves, indicate that the main carrier of AMS is high-Ti titanomagnetite (Tc?130°C). AMS measurements of about a hundred samples show a higher degree of AMS (P parameter) in the middle level in comparison to the base. Inversely, the bulk magnetic susceptibility (Km) is higher at the flow base. Distinctive parameters for the different levels of the basaltic flows could be then provided by AMS measurements.. Moreover, the comparison between AMS and EBSD data indicate that the magnetic susceptibility carried by the magnetic grains is controlled by the crystallographic orientation of plagioclase and then related to the direction lava flow. In addition, an AMS study carried out on a prism section shows that Km and P magnetic parameters increase from the core to the rim of the prism. The analysis of hysteresis parameters on the same samples indicates that the magnetic grains are larger in size in the core than on the rim. This suggests processes inducing a magnetic grain size arrangement before the prism formation. References O'Reilly J.P (1879)Explanatory notes and discussion on the nature of the prismatic forms of a group of columnar basalts, Giant's Causeway. Trans. Roy. Irish Acad. Tomkeieff S.I, (1940)The basalt lavas of the Giant's Causeway district of the Northern Ireland. Bull. Volc vol 2, pp 89-146. Guy B. and Le Coze J. (1990) Reflections about columnar jointing in basalts: the instability of the planar solidification front, C.R.Acad.Sc. Paris, 311, II, 943-949. Guy B (2010) Basalt columns: Large scale constitutional supercooling? Comments on the paper by John Gilman (JVGR, 2009) and presentation of some new data, JVG to appear.

Tiphaine, Boiron; Jérôme, Bascou; Pierre, Camps; Eric, Ferre; Claire, Maurice; Bernard, Guy; Marie-Christine, Gerbe

2010-05-01

206

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

ERIC Educational Resources Information Center

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

Hunt, Clive

2012-01-01

207

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

208

Time and space optimization for processing groups of multi-dimensional scientific queries  

Microsoft Academic Search

Data analysis applications in areas as diverse as remote sensing and telepathology require operating on and processing very large datasets. For such applications to execute efficiently, careful attention must be paid to the storage, retrieval, and manipulation of the datasets. This paper addresses the optimizations performed by a high performance database system that processes groups of data analysis requests for

Suresh Aryangat; Henrique Andrade; Alan Sussman

2004-01-01

209

Deep neck space abscesses of dental origin: the impact of Streptococcus group Milleri.  

PubMed

In recent years, there has been rising interest in Streptococcus group Milleri (SM) because high mortality rates have been related to it. In case of deep neck infections (DNI), whatever the origin, mortality rates as high as 26% were reported. But there are no data available for DNI with SM of purely dental origin. The aim of our article was to describe and analyse DNI of purely dental origin involving on one hand SM and on the other hand infections without presence of SM. We compared these two groups and statistically investigated if there were differences in clinical presentation (age, mouth opening, length of hospital stay, laboratory parameters) or clinical behaviour (re-operation, re-hospitalisation, secondary osteomyelitis, stay at intensive care, length of antibiotic treatment, presence of resistances against antibiotics, incapacity to work). For this, we retrospectively searched medical records of our institution for all purulent DNI treated from 2004 till 2012. We found 81 patients meeting all inclusion criteria. Thirty-four patients had involvement of SM, 47 did not. The only statistically significant difference between the SM group and the non-SM group was the length of incapacity to work. All other parameters were non-significant. Furthermore, there were no fatalities. In conclusion, the clinical importance of this article is that patients with deep neck abscesses of purely dental origin involving SM do not need more or different care when compared to all other DNI of dental origin. PMID:24241360

Terzic, Andrej; Scolozzi, Paolo

2014-10-01

210

Plant population and row spacing effects on maturity group III soybean  

Technology Transfer Automated Retrieval System (TEKTRAN)

Maturity group IV and V soybean produced in the upper mid-southern states of Kentucky, Tennessee, eastern Mississippi, and northern Alabama are primarily nonirrigated due to rolling uplands, highly erodible soils, and small fields common to the region. Sole reliance on rainfall and the coinciding o...

211

An HI survey of the Centaurus and Sculptor Groups - Constraints on the space density of low mass galaxies  

E-print Network

We present results of two 21-cm HI surveys performed with the Australia Telescope Compact Array in the nearby Centaurus A and Sculptor galaxy groups. These surveys are sensitive to compact HI clouds and galaxies with HI masses as low as 3E+06 Msun, and are therefore among the most sensitive extragalactic HI surveys to date. The surveys consist of sparsely spaced pointings that sample approximately 2% of the groups' area on the sky. We detected previously known group members, but we found no new HI clouds or galaxies down to the sensitivity limit of the surveys. If the HI mass function had a faint end slope of alpha = 1.5 below M_{HI} = 10^{7.5} Msun in these groups, we would have expected ~3 new objects. Cold dark matter theories of galaxy formation predict the existence of a large number low mass DM sub-halos that might appear as tiny satellites in galaxy groups. Our results support and extend similar conclusions derived from previous HI surveys that a HI rich population of these satellites does not exist.

W. J. G. de Blok; M. A. Zwaan; M. Dijkstra; F. H. Briggs; K. C. Freeman

2001-11-13

212

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

213

Crystallographic analysis of metal-ion binding to human ubiquitin.  

PubMed

The metal-binding ability of human ubiquitin (hUb) towards a selection of biologically relevant metal ions and complexes has been probed. Different techniques have been used to obtain crystals suitable for crystallographic analysis. In the first type of experiments, crystals of hUb have been soaked in solutions containing copper(II) acetate and two metallodrugs, Zeise salt (K[PtCl(3)(?(2)-C(2)H(4))]·H(2)O) and cisplatin (cis-[PtCl(2)(NH(3))(2)]). The Zeise salt is used in a test for hepatitis, whereas cisplatin is one of the most powerful anticancer drugs in clinical use. The Zeise salt readily reacts with hUb crystals to afford an adduct with three platinum residues per protein molecule, Pt(3)-hUb. In contrast, copper(II) acetate and cisplatin were found to be unreactive for contact times up to one hour and to cause degradation of the hUb crystals for longer times. In the second type of experiments, hUb was cocrystallized with a solution of copper(II) or zinc(II) acetate or cisplatin. Zinc(II) acetate gives, at low metal-to-protein molar ratios (8:1), crystals containing one metal ion per three molecules of protein, Zn-hUb(3) (already reported in previous work), whereas at high metal-to-protein ratios (70:1) gives crystals containing three Zn(II) ions per protein molecule, Zn(3)-hUb. In contrast, once again, copper(II) acetate and cisplatin, even at low metal-to-protein ratios, do not give crystalline material. In the soaking experiment, the Zeise anion leads to simultaneous platination of His68, Met1, and Lys6. Present and previous results of cocrystallization experiments performed with Zn(II) and other Group 12 metal ions allow a comprehensive understanding of the metal-ion binding properties of hUb with His68 as the main anchoring site, followed by Met1 and carboxylic groups of Glu16, Glu18, Glu64, Asp21, and Asp32, to be reached. In the case of platinum, Lys6 can also be a binding site. The amount of bound metal ion, with respect to that of the protein, appears to be a relevant parameter influencing crystal packing. PMID:21268159

Arnesano, Fabio; Belviso, Benny Danilo; Caliandro, Rocco; Falini, Giuseppe; Fermani, Simona; Natile, Giovanni; Siliqi, Dritan

2011-02-01

214

X-ray Crystallographic Structure of the Norwalk Virus  

E-print Network

X-ray Crystallographic Structure of the Norwalk Virus Capsid B. V. Venkataram Prasad,1 * Michele E-ray structure of a calicivirus capsid, which consists of 180 copies of a single protein, has been determined by phase extension from a low-resolution electron microscopy structure. The capsid protein has a protruding

Rossmann, Michael G.

215

X-ray Crystallographic Computations Using a Programmable Calculator.  

ERIC Educational Resources Information Center

Describes six crystallographic programs which have been developed to illustrate the range of usefulness of programmable calculators in providing computational assistance in chemical analysis. These programs are suitable for the analysis of x-ray diffraction data in the laboratory by students. (HM)

Attard, Alfred E.; Lee, Henry C.

1979-01-01

216

Slow-cooling protocols for crystallographic refinement by simulated annealing  

Microsoft Academic Search

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

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

1990-01-01

217

PHENIX: Developing new software for automated crystallographic structure determination  

Microsoft Academic Search

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

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

2002-01-01

218

Crystallographic Texture in Pulsed Laser Deposited Hydroxyapatite Bioceramic Coatings  

E-print Network

of bulk and thin film ceramics as these systems have gained greater technological importance over the past decade [8-14]. Evaluation of the effect of crystallographic texture in complex ceramics with tetragonal hydroxyapatite [Ca10(PO4)6(OH)2] which constitutes the inorganic matrix of bone and tooth tissue. Naturally

Rohrer, Gregory S.

219

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

220

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

221

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

222

Anisotropies in the redshift-space correlations of galaxy groups and clusters - I. Simulated catalogues  

NASA Astrophysics Data System (ADS)

We analyse the correlation function of mock galaxy clusters in redshift space. We have constructed several mock catalogues designed to mimic the selection biases inherent in a variety of observational surveys. We explore different effects that contribute to the distortion of the clustering pattern: the pairwise velocity distribution of galaxy systems, coherent bulk motions, redshift errors and systematic effects in cluster identification. Our tests show that the redshift-space clustering pattern of galaxy systems is highly influenced by effects associated with the identification procedure from two-dimensional surveys. These systems show a spuriously large correlation amplitude, an effect that is present and even stronger in a subsample where the angular positions coincide with three-dimensional identified clusters. The effect of a small number of redshift measurements is also that of increasing the correlation amplitude. In a similar fashion, the bias parameter inferred from cluster samples is subject to these observational problems, which induce variations of up to a factor of 2 in such determinations. Also, we find that the estimated mean pairwise velocity dispersion can be up to an order of magnitude larger than the actual value. Errors in the estimated cluster redshift, originating from the use of too few redshift measurements per cluster, have a smaller impact on the measured correlation function. We show that an angular incompleteness in redshift surveys, such as that present in the 2dF Galaxy Redshift Survey 100 k public release, has no significant effect on the results. We suggest that the nature of projection effects arises mainly from structures along the line of sight in the filamentary large-scale clustering pattern. Thus, spectroscopic surveys are the only means of providing unbiased cluster samples. High-resolution plots and information are available at http://star-www.dur.ac.uk/~nelsonp/anisotropies.

Padilla, N. D.; Lambas, D. G.

2003-06-01

223

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.

2014-09-18

224

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

225

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 Central

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 (V M) of 2.31?Å3?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

2013-01-01

226

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

227

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

228

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

229

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

230

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

231

Crystallographic study on natural gas hydrates recovered from the eastern Nankai Trough  

NASA Astrophysics Data System (ADS)

Natural gas hydrates are crystalline clathrate compounds, which encage a large amount of natural gas. The crystallographic structure of natural gas hydrates depends on the encaged natural gas components. In addition, the amount of hydrate-bound natural gas is attributed to the crystallographic structure. Massive and pore-space natural gas hydrates were obtained from the eastern Nankai Trough area during Japan's Methane Hydrate R&D Program conducted by the Ministry of Economy, Trade and Industry (METI) of Japan, aboard the RV JOIDES Resolution. In this study, hydrate-bound gas, crystal structure, and cage occupancies, and hydration number of the natural gas hydrates were characterized. The pore-space natural gas hydrates recovered from the eastern Nankai Trough area existed in pore-spaces of sandy sediments with median diameters of approximately 80-180 ?m. The PXRD profiles of the massive and pore-space natural gas hydrates revealed that the crystallographic structures of the all natural gas hydrates studied were structure I. The lattice constants of the pore-space natural gas hydrates were ranging from 1.183-1.207 nm, depending on the content of fine sediment particles less than 40 ?m in the sandy samples. All samples contained CH4 as a main hydrocarbon component, indicating that the natural gas in marine sediment at the study areas is mainly CH4. The hydrocarbon compositions agreed well with those reported for microbial (CO2 reduction) natural gas in gas hydrate-bearing sediments recovered previously from the eastern Nankai Trough area. In this study, on the other hand, although almost all samples contained small amounts of C2H6 (less than 200 ppm), C3H8 (less than 50 ppm), and i-C4H10 (less than 20 ppm), large concentrations of heavier hydrocarbons such as C3H8 or i-C4H10 were found in three of 15 samples. 13C NMR and Raman spectroscopic techniques were used to obtain molecular information on the encaged hydrocarbon molecules. The 13C NMR chemical shifts and Raman shifts of guest molecules showed that the primary component of guest molecule is CH4 and their crystallographic structure is structure I, supporting the PXRD data. The occupancies of small and large cages were evaluated from the 13C NMR and Raman spectra, which the pore-space gas hydrates had 0.83 small cage occupancy of CH4 and 0.97 large cage occupancy of CH4, indicating the large cages were almost fully occupied by CH4 molecules. The hydration number estimated from the obtained cage occupancies was 6.1-6.2, which resembled those of the massive NGHs studied. The obtained cage occupancies and hydration numbers are important parameters for estimation of amount of hydrocarbons in hydrate-bound natural gases in the eastern Nankai Trough area. This work was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by METI.

Kida, Masato; Suzuki, Hiroyuki; Suzuki, Kiyofumi; Nagao, Jiro; Narita, Hideo

2010-05-01

232

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

233

Cation Distribution And Crystallographic Properties Of The Quaternary Spinel Compound Zn0.4Cu0.6AlxFe2-xO4 (0.0?x?1.0)  

NASA Astrophysics Data System (ADS)

The spinel system Zn0.4Cu0.6AlxFe2-xO4 with x = 0.0, 0.25, 0.50, 0.75 & 1.0 were obtained by solid state reactions in air at 1373 K. X-ray and neutron powder diffraction measurements were performed at room temperature (RT) to characterize the materials. Rietveld refinement of neutron diffraction data showed cubic symmetry corresponding to the space group Fd3m. The distribution of cations over the two sublattices and other crystallographic parameters were determined precisely. The cell parameter decreases and oxygen parameter increases with increasing Al. Sublattices and net magnetic moments at RT were also deduced from the analysis of neutron data. The magnetic structure at RT was found to be ferrimagnetic for x?0.75.

Zakaria, A. K. M.; Asgar, M. A.; Eriksson, S.-G.; Ahmed, F. U.; Yunus, S. M.; Hakim, M. A.

2008-04-01

234

Throughout this paper we denote the crystal axes in accord-ance with Ref. [8], i.e. the longest edge of the crystallographic  

E-print Network

edge of the crystallographic unit cell is the b axis. *Corresponding author. Tel.: #49 spectra of the referred compounds were detected, we achieved a satisfactory assignment of most of the high gray. (b) The P O group consist of two PO tetraeder connected by an apical oxygen atom building

Nabben, Reinhard

235

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

236

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

237

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

SciTech Connect

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 [Theoretical Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2014-03-21

238

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

239

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

240

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

241

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

PubMed Central

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

2011-01-01

242

Anisotropies in the redshift-space correlations of galaxy groups and clusters II: Analysis of observational cluster samples  

E-print Network

We study the redshift space correlation function of galaxy clusters for observational samples constructed in different surveys. We explore correlation amplitudes, pairwise velocity distributions and bias factors. Systematics in cluster identification procedures are the main source of biased estimates of the correlation amplitude and inferred velocity dispersions. By comparing our results with those of numerical simulations we explore the strong influence on the clustering distortion pattern in redshift space from effects associated with the cluster identification procedure from two dimensional surveys as is the case of Abell and APM clusters. The identification of clusters in X-ray surveys improves this situation, although there are still systematic effects which are probably due to identification of optical sources in the determination of cluster redshifts. These systematics are particularly strong for the most luminous X-ray selected clusters in the Extended Bright Cluster Survey, which exhibits very large anisotropies, comparable to those present in the Abell catalogue. Our results demonstrate that forthcoming large redshift surveys will be extremely important for the construction of new samples of groups and clusters as well as improving the determination of optical and X-ray selected cluster distances, essential for reliable analyses of the large scale structure.

N. D. Padilla; D. G. Lambas

2003-02-16

243

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

PubMed

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

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

2015-05-01

244

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

SciTech Connect

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

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

2007-01-01

245

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

PubMed

Geobacillus stearothermophilus T-6 is a Gram-positive thermophilic soil bacterium that contains a multi-enzyme system for the utilization of plant cell-wall polysaccharides, including xylan, arabinan and galactan. The bacterium uses a number of endo-acting extracellular enzymes that break down the high-molecular-weight polysaccharides into decorated oligosaccharides. These oligosaccharides enter the cell and are further hydrolyzed into sugar monomers by a set of intracellular glycoside hydrolases. One of these intracellular degrading enzymes is GanB, a glycoside hydrolase family 42 ?-galactosidase capable of hydrolyzing short ?-1,4-galactosaccharides to galactose. GanB and related enzymes therefore play an important part in the hemicellulolytic utilization system of many microorganisms which use plant biomass for growth. The interest in the biochemical characterization and structural analysis of these enzymes stems from their potential biotechnological applications. GanB from G. stearothermophilus T-6 has recently been cloned, overexpressed, purified, biochemically characterized and crystallized in our laboratory as part of its complete structure-function study. The best crystals obtained for this enzyme belong to the primitive orthorhombic space group P2?2?2?, with average crystallographic unit-cell parameters of a=71.84, b=181.35, c=196.57?Å. Full diffraction data sets to 2.45 and 2.50?Å resolution have been collected for both the wild-type enzyme and its E323A nucleophile catalytic mutant, respectively, as measured from flash-cooled crystals at 100?K using synchrotron radiation. These data are currently being used for the full three-dimensional crystal structure determination of GanB. PMID:24100561

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

2013-10-01

246

The use of Fourier reverse transforms in crystallographic phase refinement  

SciTech Connect

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

Ringrose, S.

1997-10-08

247

Crystallographic phases in heavy rare earth metals under megabar pressures  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

248

Substructures of the (252) ferrous martensite and their crystallographic significance  

SciTech Connect

Many ferrous martensites have been found to possess a macroscopically invariant habit plane close to (252){sub f} and to exhibit complex and variable substructures that cannot be not only satisfactorily explained but also fully characterized so far. The present work attempts to examine the mechanism of occurrence of the complex substructures and their correlation to other crystallographic properties, esp. to the shape strain, on the basis of a new theory. The theory describes the atomic movements in the lattice change represented with the Bain distortion in the past.

Wang Shidao [Lanzhou Railway Inst. (China). Dept. of Mechanical Engineering] [Lanzhou Railway Inst. (China). Dept. of Mechanical Engineering; [Chinese Academy of Sciences, Shenyang (China). Lab. of Atomic Imaging of Solids; Hei Zukun [Dalian Maritime Univ. (China). Research Inst. of Materials Technology] [Dalian Maritime Univ. (China). Research Inst. of Materials Technology

1999-04-23

249

Crystallographic Evidence for Noncoplanar Catalytic Aspartic Acids in plasmepsin II Resides in the Protein Data Bank  

SciTech Connect

The carboxylate atoms of the two catalytic aspartic acid residues in aspartic proteases are nearly coplanar and in the uncomplexed form share an in-plane nucleophilic water molecule that is central to the mechanism of these enzymes. This note reports that while reviewing the electron-density maps derived from the deposited data for uncomplexed plasmepsin II from Plasmodium falciparum (Asojo et al. (2003), J. Mol. Biol. 327, 173-181; PDB code 1lf4), it was discovered that the aspartic acid residues in this structure should in fact be distinctly noncoplanar. The crystallographic model from the deposited coordinates has been re-refined against the 1.9 {angstrom} resolution published diffraction data to an R{sub cryst} of 21.2% and an R{sub free} of 22.2%. The catalytic water molecule is present, but the plane of the carboxylate group of Asp214 is rotated by 66 degrees from its original position.

Robbins, A.; Dunn, B; Agbandje-McKenna, M; McKenna, R

2009-01-01

250

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

SciTech Connect

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

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

1996-09-01

251

Mechanistic, crystallographic, and computational studies on the catalytic, enantioselective sulfenofunctionalization of alkenes  

NASA Astrophysics Data System (ADS)

The stereocontrolled introduction of vicinal heteroatomic substituents into organic molecules is one of the most powerful ways of adding value and function. Although many methods exist for the introduction of oxygen- and nitrogen-containing substituents, the number of stereocontrolled methods for the introduction of sulfur-containing substituents pales by comparison. Previous reports from our laboratories have described sulfenofunctionalizations of alkenes that construct carbon–sulfur bonds vicinal to carbon–oxygen, carbon–nitrogen or carbon–carbon bonds with high levels of diastereospecificity and enantioselectivity. This process is enabled by the concept of Lewis-base activation of Lewis acids, which provides activation of Group 16 electrophiles. To provide a foundation for the expansion of substrate scope and improved selectivities, we have undertaken a comprehensive study of the catalytically active species. Insights gleaned from kinetic, crystallographic and computational methods have led to the introduction of a new family of sulfenylating agents that provide significantly enhanced selectivities.

Denmark, Scott E.; Hartmann, Eduard; Kornfilt, David J. P.; Wang, Hao

2014-12-01

252

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

PubMed Central

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

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

2010-01-01

253

"I am a waste of breath, of space, of time": metaphors of self in a pro-anorexia group.  

PubMed

According to recent research on eating disorders, heavy users of pro-anorexia (pro-ana) sites show higher levels of disordered eating and more severe impairment of quality of life than non-heavy users. A better understanding of how pro-ana members self-present in the virtual world could shed some light on these offline behaviors. Through discourse analysis, I examined the metaphors the members of a pro-ana group invoked in their personal profiles on a popular social networking site, to talk about the self. I applied the Metaphor Identification Procedure to 757 text profiles. I identified four key metaphorical constructions in pro-ana members' self-descriptions: self as space, self as weight, perfecting the self, and the social self. These four main metaphors represented discourse strategies, both to create a collective pro-ana identity and to enact an individual identity as pro-ana. In this article, I discuss the implications of these findings for the treatment of eating disorders. PMID:25225049

Bates, Carolina Figueras

2015-02-01

254

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

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

255

International summer school on macromolecular crystallographic computing. Final report  

SciTech Connect

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

NONE

1998-08-01

256

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

257

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

PubMed Central

In order to crystallographically study the hydration of the major groove (convex surface) of Z-DNA, the oligonucleotide d(CGCGCG) has been synthesized. Single crystals were grown by vapor diffusion using the hanging-drop and sitting-drop methods for X-ray studies and by batch crystallization and evaporation within silicon tubes for neutron studies. Hexagonal crystals were obtained without the use of duplex-stabilizing polyamines and at an acid pH. X-­ray data collected at room temperature (1.5?Å resolution; unit-cell parameters a = 17.90, b = 30.59, c = 44.61?Å) and at 100?K (1?Å resolution; a = 17.99, b = 30.98, c = 44.07?Å) and neutron data collected at room temperature (1.6?Å resolution; a = 18.00, b = 31.16, c = 44.88?Å) indicate that the DNA is in the Z-form packing in space group P212121. PMID:16682774

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

2006-01-01

258

X-ray crystallographic and tungsten-183 nuclear magnetic resonance structural studies of the [M4(H2O)2(XW9O34) 2]10- heteropolyanions (M = COII or Zn, X = P or As)  

USGS Publications Warehouse

The crystal structures of K10[Co4(H2O)2(PW9O 34)2]??22H2O (1) and isomorphous K10[Zn4(H2O)2(AsW9O 34)2]??23H2O (2) have been determined {Mo-K?? radiation, space group P21/n, Z = 2; (1) a = 15.794(2), b = 21.360(2), c = 12.312(1) A??, ?? = 91.96??, R = 0.084 for 3 242 observed reflections [I ??? 3??(I)]; (2) a = 15.842(4), b = 21.327(5), c = 12.308(4) A??, ?? = 92.42(4)??, R = 0.066 for 4 675 observed reflections [F ??? 3??(F)]}. The anions have crystallographic symmetry 1 and non-crystallographic symmetry very close to 2/m (C2h). Each consists of two [XW9O34]9- moieties [??-B isomers; X = P (1) or As (2)] linked via four CoIIO6 or ZnO6 groups. Two Co or Zn atoms each carry a water ligand. The 183W n.m.r. spectra of the anions [Zn4(H2O)2(XW9O34) 2]10- (X = P or As) confirm that the anions retain 2/m symmetry in aqueous solution. Homonuclear coupling constants between 183W atoms are 5.8-9.0 Hz for adjacent WO6 octahedra sharing edges, and 19.6-25.0 Hz for octahedra sharing corners.

Evans, H.T.; Tourne, C.M.; Tourne, G.F.; Weakley, T.J.R.

1986-01-01

259

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

260

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

261

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

262

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

263

Crystallographic fatigue crack growth in incompatible aluminum bicrystals: Its dependence on secondary slip  

NASA Astrophysics Data System (ADS)

The secondary slip behavior ahead of crystallographic fatigue cracks and its effect on the crack growth near the grain boundaries (GBs) in[12bar 1] tilt nonsymmetrical aluminum bicrystals under constant cyclic stress amplitude have been systematically examined. The displacement field ahead of short crack tips near the interfaces in two specimens has been measured by using a microfiducial grid technique. It has been observed that the critical persistent slip band (PSB) ahead of a short crack tip near the GB in a middle misoriented bicrystal was able to develop as long as the primary one and resulted in a temporary stage II growth. As a longer crystal- lographic crack grew into the grain boundary affected zone (GBAZ), activation of the critical slip ahead of the crack front and crack branching along the critical PSB occurred in all groups of the aluminum bicrystals, which reveals a crucial role of the critical slip in increasing the crack opening and triggering the slip in the adjacent grain. On the other hand, cross slip became the dominant slip mode ahead of the crystallographic crack front near the GB in a bicrystal of larger misfit angles and drove the crack along the cross PSB, a steep path with a remarkably high growth rate, until it propagated into the GBAZ. The resultant stress on the secondary slip system ahead of a crack front near the interface contributed by the internal stress due to both intergranular and intragranular incompatible strain, as well as the enhanced crack tip stress, has been evaluated and rationalizes the activation of the secondary slip systems.

Li, Chingshen

1992-12-01

264

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

265

Twinning-like lattice reorientation without a crystallographic twinning plane  

PubMed Central

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. PMID:24522756

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

2014-01-01

266

A prototype chopper for synchrotron time-resolved crystallographic measurements  

SciTech Connect

A mechanical x-ray chopper has been designed to perform microsecond time-resolved crystallographic studies at the DIAMOND synchrotron I19 beamline. It consists of two asymmetric absorbers rotating synchronously at frequencies from 0 to 50 Hz in the same direction around a rotation axis that is parallel to the x-ray beam. The duration of the x-ray pulses produced by the chopper is determined by the relative phase between the two blades, which can be adjusted. The chopper system presented in this paper offers a time resolution suitable for conducting in situ experiments that afford the crystal structure of materials while in their transient (>10 {mu}s) photoactivated excited states.

Husheer, S. L. G. [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Synchrotron Radiation Source, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Cole, J. M. [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Department of Physics, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Department of Chemistry, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick E3B 5A3 (Canada); Department of Physics, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick E3B 5A3 (Canada); D'Almeida, T. [Department of Physics, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Teat, S. J. [Synchrotron Radiation Source, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom)

2010-04-15

267

Automated identification of crystallographic ligands using sparse-density representations  

PubMed Central

A novel procedure for the automatic identification of ligands in macromolecular crystallographic electron-density maps is introduced. It is based on the sparse parameterization of density clusters and the matching of the pseudo-atomic grids thus created to conformationally variant ligands using mathematical descriptors of molecular shape, size and topology. In large-scale tests on experimental data derived from the Protein Data Bank, the procedure could quickly identify the deposited ligand within the top-ranked compounds from a database of candidates. This indicates the suitability of the method for the identification of binding entities in fragment-based drug screening and in model completion in macromolecular structure determination. PMID:25004962

Carolan, C. G.; Lamzin, V. S.

2014-01-01

268

Solid tryptophan as a pseudoracemate: physicochemical and crystallographic characterization.  

PubMed

The crystalline nature of solid tryptophan has been characterized by X-ray single crystal and powder diffraction analyses, differential scanning calorimetry, as well as measurement of solid-liquid equilibrium in water/isopropanol solution. Both the thermodynamic and crystallographic investigations have demonstrated unambiguously that solid tryptophan crystallizes in the form of a pseudoracemate (i.e., solid solution) with maximum melting over the entire enantiomeric composition range. Comparative single-crystal X-ray studies show that the crystal structures of racemic and enantiomeric tryptophan give very similar solid-state packing geometries dictated by hydrogen bonding interactions. Our results indicate that the insignificant difference between homochiral and heterochiral interactions accounts for the formation of a pseudoracemate for this system. PMID:25354341

Li, Yan; Zhao, Yuming; Zhang, Yan

2015-01-01

269

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

270

Effects of crystallographic texture on internal stress superplasticity induced by anisotropic thermal expansion  

SciTech Connect

Polycrystalline materials having crystallographic anisotropy show internal stress superplasticity under thermal cycling conditions. The deformation mechanism is analyzed using a theoretical model based on continuum micromechanics including the effects of crystallographic texture. The model is experimentally verified through the thermal cycling creep tests using polycrystalline zinc having two kinds of fiber-texture, and agrees well with the experimental results.

Kitazono, K.; Hirasaka, R.; Sato, E.; Kuribayashi, K.; Motegi, T.

2000-07-01

271

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, Ã?. E.thibaux@arcelormittal.com, dhkdb@cam.ac.uk Keywords: crystallographic texture; pipeline steel; induction welding; induction heat the welding process is immediately followed by induction heat treatment. The intention of the latter

Cambridge, University of

272

Crystallographic texture evolution in high-density polyethylene during uniaxial tension  

E-print Network

Crystallographic texture evolution in high-density polyethylene during uniaxial tension D. Lia , H experimental measurements of crystallographic texture evolution in high-density polyethylene subjected to very straining of high-density polyethylene to large strains. There are at least three distinct preferred

Garmestani, Hamid

273

Determination of the crystallographic orientation of a single crystal using resonant ultrasound spectroscopy  

Microsoft Academic Search

Using resonant ultrasound spectroscopy (RUS) we have determined the crystallographic orientation of a tantalum single crystal from a measurement of its mechanical resonance spectrum. This accomplishment is significant not only because it reduces the sample requirements for RUS but also because it is the simplest method for simultaneous determination of a crystal's elastic constants and microscopic crystallographic orientation.

J. L. Sarrao; S. R. Chen; W. M. Visscher; Ming Lei; U. F. Kocks; A. Migliori

1994-01-01

274

Determination of the crystallographic orientation of a single crystal using resonant ultrasound spectroscopy  

Microsoft Academic Search

Using resonant ultrasound spectroscopy (RUS) we have determined the crystallographic orientation of a tantalum single crystal from a measurement of its mechanical resonance spectrum. This accomplishment is significant not only because it reduces the sample requirements for RUS but also because it is the simplest method for simultaneous determination of a crystal’s elastic constants and microscopic crystallographic orientation.

J. L. Sarrao; S. R. Chen; W. M. Visscher; Ming Lei; U. F. Kocks; A. Migliori

1994-01-01

275

Determination of the crystallographic orientation of a single crystal using resonant ultrasound spectroscopy  

SciTech Connect

Using resonant ultrasound spectroscopy (RUS) we have determined the crystallographic orientation of a tantalum single crystal from a measurement of its mechanical resonance spectrum. This accomplishment is significant not only because it reduces the sample requirements for RUS but also because it is the simplest method for simultaneous determination of a crystal's elastic constants and microscopic crystallographic orientation.

Sarrao, J.L.; Chen, S.R.; Visscher, W.M.; Lei, M.; Kocks, U.F.; Migliori, A. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

1994-06-01

276

The moduli space and monodromies of the N=2 supersymmetric Yang-Mills theory with any Lie gauge groups  

E-print Network

We propose a unified scheme for finding the hyperelliptic curve of N=2 SUSY YM theory with any Lie gauge groups. Our general scheme gives the well known results for classical gauge groups and exceptional G_2 group. In particular, we present the curve for the exceptional gauge groups F_4, E_{6,7,8} and check consistency condition for them. The exact monodromies and the dyon spectrum of these theories are determined. We note that for any Lie gauge groups, the exact monodromies could be obtained only from the Cartan matrix.

Abolhasani, M R; Ghezelbash, A M; Abolhasani, Mohammad Reza; Alishahiha, Mohsen; Ghezelbash, Amir Masoud

1996-01-01

277

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

E-print Network

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

Cai, Long

278

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

SciTech Connect

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

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

2008-09-15

279

Efficient photocurrent generation by self-assembled monolayers composed of 3 10-helical peptides carrying linearly spaced naphthyl groups at the side chains.  

PubMed

Self-assembled monolayers (SAMs) were prepared on a gold substrate from a 310-helical peptide carrying three naphthyl groups at the side chain (SSN3B) or from the reference peptides carrying no or one naphthyl group. The 310-helical conformation of SSN3B in solution was confirmed by 1H NMR spectroscopy and geometry optimization. Cyclic voltammetry and infrared absorption-reflection spectroscopy showed vertical molecular orientation and a well-packed structure in the SSN3B SAM. Anodic photocurrent was successfully generated by the SSN3B SAM in the presence of triethanolamine, and the current intensity was found to be much larger than those by the other SAMs from peptides carrying one naphthyl group. It was therefore concluded that the linearly spaced naphthyl groups along the helical axis act as photosensitizer and electron-hopping site to promote photocurrent generation remarkably. PMID:15469265

Yanagisawa, Kazuyuki; Morita, Tomoyuki; Kimura, Shunsaku

2004-10-13

280

Preliminary crystallographic analysis of avian infectious bronchitis virus main protease  

PubMed Central

Infectious bronchitis virus (IBV) is the prototype of the genus Coronavirus. It causes a highly contagious disease which affects the respiratory, reproductive, neurological and renal systems of chickens, resulting great economic losses in the poultry industry worldwide. The coronavirus (CoV) main protease (Mpro), which plays a pivotal role in viral gene expression and replication through a highly complex cascade involving the proteolytic processing of replicase polyproteins, is an attractive target for antiviral drug design. In this study, IBV Mpro was overexpressed in Escherichia coli. Crystals suitable for X-ray crystallography have been obtained using microseeding techniques and belong to space group P6122. X-ray diffraction data were collected in-house to 2.7?Å resolution from a single crystal. The unit-cell parameters were a = b = 119.1, c = 270.7?Å, ? = ? = 90, ? = 120°. Three molecules were predicted to be present in the asymmetric unit from a calculated self-rotation function. PMID:17183167

Li, Jun; Shen, Wei; Liao, Ming; Bartlam, Mark

2007-01-01

281

Themed Space  

ERIC Educational Resources Information Center

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

Lynch, Christopher O.

2010-01-01

282

Report from the MPP Working Group to the NASA Associate Administrator for Space Science and Applications. Technical memorandum report, 1 October 1985-30 September 1986  

SciTech Connect

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

Fischer, J.R.; Grosch, C.; Mcanulty, M.; Odonnell, J.; Storey, O.

1987-11-01

283

A preliminary neutron crystallographic study of an A-DNA crystal  

PubMed Central

The LADI-III diffractometer at the Institut Laue–Langevin has been used to carry out a preliminary neutron crystallographic study of the self-complementary DNA oligonucleotide d(AGGGGCCCCT)2 in the A conformation. The results demonstrate the viability of a full neutron crystallographic analysis with the aim of providing enhanced information on the ion–water networks that are known to be important in stabilizing A-DNA. This is the first account of a single-crystal neutron diffraction study of A-DNA. The study was carried out with the smallest crystal used to date for a neutron crystallographic study of a biological macromolecule. PMID:19255472

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

2009-01-01

284

Nanocrystalline materials: recent advances in crystallographic characterization techniques  

PubMed Central

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

2014-01-01

285

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

286

Crystallographic studies of the Anthrax lethal toxin. Annual report  

SciTech Connect

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

Frederick, C.A.

1996-07-01

287

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

288

Group-theoretical approach to the construction of bases in 2{sup n}-dimensional Hilbert space  

SciTech Connect

We propose a systematic procedure to construct all the possible bases with definite factorization structure in 2{sup n}-dimensional Hilbert space and discuss an algorithm for the determination of basis separability. The results are applied for classification of bases for an n-qubit system.

Garcia, A.; Romero, J. L.; Klimov, A. B., E-mail: klimov@cencar.udg.mx [Universidad de Guadalajara, Departamento de Fisica (Mexico)

2011-06-15

289

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

E-print Network

to decrease. This purpose of this study is determine the best planting strategies in regards to row spacing varieties (REV 48R22 and AG 5632) used in the study were glyphosate-resistant and were selected based were determined. All harvested #12;plots were collected in bags to determine seed mass. Results

Balasundaram, Balabhaskar "Baski"

290

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

291

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

292

Ranging pattern and use of space in a group of red howler monkeys (Alouatta seniculus) in a southeastern Colombian rainforest.  

PubMed

We studied a group of red howler monkeys (Alouatta seniculus) bordering a lake in an eastern Colombian Amazon rainforest for 10 months. The group used an area of 182 ha located mainly on Pleistocene terrace forest and had no overlap with other howler home ranges. Home range use varied through the year as a consequence of fruit and leaf abundance. For example, during the fruit scarcity season the group used an area of flooded forest nearly exclusively, indicating that at least for a portion of the year they are habitat specialists. Two areas intensively used by the group were identified, representing 17.6 % of the home range, and within which 56.9 % of the feeding trees were located. Overall density of feeding trees within the group's home range was very low (1.12 trees/ha). Home range size, as well as mean length of daily ranges (1,150 m), is the largest reported for this species to date, and it is likely a consequence of the diminished productivity of the plant communities on poor soil. Our results give an interesting example of the ranging behavior of this primate, which clearly differs from previous descriptions of red howlers. PMID:11748695

Palacios, E; Rodriguez, A

2001-12-01

293

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

294

Effects of crystallographic orientation on plastic deformation and SCC initiation of zirconium alloys  

NASA Astrophysics Data System (ADS)

In order to investigate the effects of crystallographic orientation on deformation and crack initiation in iodine-induced SCC of zirconium alloys, uniaxial tensile tests of zirconium and Zircaloy-2 plates were conducted in an iodine atmosphere. The crystallographic orientation of individual grains was determined by an etch-pit technique prior to testing. After testing, the etch-pit technique showed that prismatic slip was predominant in the plastic deformation and that cleavage cracks extended along basal planes. The plastic deformation of individual grains was significantly influenced by their crystallographic orientations, which varied from one grain to another. Accordingly, inhomogeneous plastic deformation occurred between grains. The crack initiation took place preferentially at grain boundaries where differences of crystallographic orientations were large between adjacent grains. This indicated that crack initiations was caused by stress concentration due to strain incompatibility at those grain boundaries.

Kubo, T.; Wakashima, Y.; Amano, K.; Nagai, M.

1985-05-01

295

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

296

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

297

Crystallographic control on the substructure of nacre tablets.  

PubMed

Nacre tablets of mollusks develop two kinds of features when either the calcium carbonate or the organic portions are removed: (1) parallel lineations (vermiculations) formed by elongated carbonate rods, and (2) hourglass patterns, which appear in high relief when etched or in low relief if bleached. In untreated tablets, SEM and AFM data show that vermiculations correspond to aligned and fused aragonite nanogloblules, which are partly surrounded by thin organic pellicles. EBSD mapping of the surfaces of tablets indicates that the vermiculations are invariably parallel to the crystallographic a-axis of aragonite and that the triangles are aligned with the b-axis and correspond to the advance of the {010} faces during the growth of the tablet. According to our interpretation, the vermiculations appear because organic molecules during growth are expelled from the a-axis, where the Ca-CO3 bonds are the shortest. In this way, the subunits forming nacre merge uninterruptedly, forming chains parallel to the a-axis, whereas the organic molecules are expelled to the sides of these chains. Hourglass patterns would be produced by preferential adsorption of organic molecules along the {010}, as compared to the {100} faces. A model is presented for the nanostructure of nacre tablets. SEM and EBSD data also show the existence within the tablets of nanocrystalline units, which are twinned on {110} with the rest of the tablet. Our study shows that the growth dynamics of nacre tablets (and bioaragonite in general) results from the interaction at two different and mutually related levels: tablets and nanogranules. PMID:23933391

Checa, Antonio G; Mutvei, Harry; Osuna-Mascaró, Antonio J; Bonarski, Jan T; Faryna, Marek; Berent, Katarzyna; Pina, Carlos M; Rousseau, Marthe; Macías-Sánchez, Elena

2013-09-01

298

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

299

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

PubMed

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

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

2014-09-01

300

Human 17?-hydroxysteroid dehydrogenase-ligand complexes: crystals of different space groups with various cations and combined seeding and co-crystallization  

NASA Astrophysics Data System (ADS)

Human estrogenic 17?-hydroxysteroid dehydrogenase (17?-HSD1) is responsible for the synthesis of active estrogens that stimulate the proliferation of breast cancer cells. The enzyme has been crystallized using a Mg 2+/PEG (3500)/?-octyl glucoside system [Zhu et al., J. Mol. Biol. 234 (1993) 242]. The space group of these crystals is C2. Here we report that cations can affect 17?-HSD1 crystallization significantly. In the presence of Mn 2+ instead of Mg 2+, crystals have been obtained in the same space group with similar unit cell dimensions. In the presence of Li + and Na + instead of Mg 2+, the space group has been changed to P2 12 12 1. A whole data set for a crystal of 17ß-HSD1 complex with progesterone grown in the presence of Li + has been collected to 1.95 Å resolution with a synchrotron source. The cell dimensions are a=41.91 Å, b=108.21 Å, c=117.00 Å. The structure has been preliminarily determined by molecular replacement, yielding important information on crystal packing in the presence of different cations. In order to further understand the structure-function relationship of 17?-HSD1, enzyme complexes with several ligands have been crystallized. As the steroids have very low aqueous solubility, we used a combined method of seeding and co-crystallization to obtain crystals of 17?-HSD1 complexed with various ligands. This method provides ideal conditions for growing complex crystals, with ligands such as 20?-hydroxysteroid progesterone, testosterone and 17?-methyl-estradiol-NADP +. Several complex structures have been determined with reliable electronic density of the bound ligands.

Zhu, D.-W.; Han, Q.; Qiu, W.; Campbell, R. L.; Xie, B.-X.; Azzi, A.; Lin, S.-X.

1999-01-01

301

Exact hairy black brane solutions in 5D anti-de Sitter space and holographic renormalization group flows  

NASA Astrophysics Data System (ADS)

We construct a general class of exact regular black hole solutions with toroidal horizon topology in five-dimensional anti-de Sitter gravity with a self-interacting scalar field. With these boundary conditions and due to the nontrivial backreaction of the scalar field, the no-hair theorems can be evaded so that an event horizon can be formed. The scalar field is regular everywhere outside the curvature singularity and it vanishes at the boundary where the potential is finite. We study the properties of these black holes in the context of AdS/CFT duality and comment on the dual operators, which saturate the unitarity bound. We present exact expressions for the beta function and construct a c-function that characterizes the renormalization-group flow.

Aceña, Andrés; Anabalón, Andrés; Astefanesei, Dumitru

2013-06-01

302

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION BRITISH NATIONAL SPACE CENTRE  

E-print Network

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION­ BRITISH NATIONAL SPACE CENTRE JOINT WORKING GROUP ................................................................................................................ 14 6. UK PPP for NASA Commercial Development

Crowther, Paul

303

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

304

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

305

Electric-field induced changes in the band structure of trilayer graphene: The effect of crystallographic stacking order  

Microsoft Academic Search

We have studied by means of infrared spectroscopy the influence of a strong perpendicular electric-field on the band structure of graphene trilayers with two different types of crystallographic stacking: ABA (Bernal) and ABC (rhombohedral) stacking. The symmetries of the two crystallographic structures are different, the former having mirror symmetry and the latter inversion symmetry. Distinct infrared response was observed when

Zhiqiang Li; Chun Hung Lui; Kin Fai Mak; Emmanuele Cappelluti; Tony F. Heinz

2011-01-01

306

Crystallographic Preferred Orientations and Seismic Properties of Gabbroic Rocks Benot ILDEFONSE, David MAINPRICE & Cristina Maria GUSMO de BURGOS  

E-print Network

Crystallographic Preferred Orientations and Seismic Properties of Gabbroic Rocks Benoît ILDEFONSE rocks are a key component of our understanding of the physical properties (rheology, seismic velocities of crystallographic fabrics in gabbroic rocks from the Oman ophiolite and from the lower crust at the South

Demouchy, Sylvie

307

Development of new hardening evolution equation based on crystallographic misorientation theory for multi-scale finite element analysis  

Microsoft Academic Search

In this study, we try to reveal the relationship between the plastic deformation and the microscopic crystallographic misorientation evolution by using our multi-scale finite element (FE) code by using a crystallographic misorientation theory. We employed two-scale structure, such as a microscopic polycrystal structure and a macroscopic elastic plastic continuum. Our analysis code predicts the deformation behavior of polycrystal metal in

Yuki IKEYA; H. Kuramae; H. Morimoto; Hidetoshi SAKAMOTO; Tsutao KATAYAMA; Eiji NAKAMACHI

2010-01-01

308

An International Strategy for Human Exploration of the Moon: The International Space Exploration Coordination Group (ISECG) Reference Architecture for Human Lunar Exploration  

NASA Technical Reports Server (NTRS)

The International Space Exploration Coordination Group (ISECG) was established in response to The Global Exploration Strategy: The Framework for Coordination developed by fourteen space agencies and released in May 2007. Several ISECG participating space agencies have been studying concepts for human exploration of the moon that allow individual and collective goals and objectives to be met. This 18 month study activity culminated with the development of the ISECG Reference Architecture for Human Lunar Exploration. The reference architecture is a series of elements delivered over time in a flexible and evolvable campaign. This paper will describe the reference architecture and how it will inform near-term and long-term programmatic planning within interested agencies. The reference architecture is intended to serve as a global point of departure conceptual architecture that enables individual agency investments in technology development and demonstration, International Space Station research and technology demonstration, terrestrial analog studies, and robotic precursor missions to contribute towards the eventual implementation of a human lunar exploration scenario which reflects the concepts and priorities established to date. It also serves to create opportunities for partnerships that will support evolution of this concept and its eventual realization. The ISECG Reference Architecture for Human Lunar Exploration (commonly referred to as the lunar gPoD) reflects the agency commitments to finding an effective balance between conducting important scientific investigations of and from the moon, as well as demonstrating and mastering the technologies and capabilities to send humans farther into the Solar System. The lunar gPoD begins with a robust robotic precursor phase that demonstrates technologies and capabilities considered important for the success of the campaign. Robotic missions will inform the human missions and buy down risks. Human exploration will start with a thorough scientific investigation of the polar region while allowing the ability to demonstrate and validate the systems needed to take humans on more ambitious lunar exploration excursions. The ISECG Reference Architecture for Human Lunar Exploration serves as a model for future cooperation and is documented in a summary report and a comprehensive document that also describes the collaborative international process that led to its development. ISECG plans to continue with architecture studies such as this to examine an open transportation architecture and other destinations, with expanded participation from ISECG agencies, as it works to inform international partnerships and advance the Global Exploration Strategy.

Laurini, Kathleen C.; Hufenbach, Bernhard; Junichiro, Kawaguchi; Piedboeuf, Jean-Claude; Schade, Britta; Lorenzoni, Andrea; Curtis, Jeremy; Hae-Dong, Kim

2010-01-01

309

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

310

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

311

Analysis of experimental time-resolved crystallographic data by singular value decomposition.  

PubMed

Singular value decomposition (SVD) separates time-dependent crystallographic data into time-independent and time-dependent components. Procedures for the effective application of SVD to time-resolved macromolecular crystallographic data have yet to be explored systematically. Here, the applicability of SVD to experimental crystallographic data is tested by analyzing 30 time-resolved Laue data sets spanning a time range of nanoseconds to milliseconds through the photocycle of the E46Q mutant of photoactive yellow protein. The data contain random and substantial systematic errors, the latter largely arising from crystal-to-crystal variation. The signal-to-noise ratio of weighted difference electron-density maps is significantly improved by the SVD flattening procedure. Application of SVD to these flattened maps spreads the signal across many of the 30 singular vectors, but a rotation of the vectors partitions the large majority of the signal into only five singular vectors. Fitting the time-dependent vectors to a sum of simple exponentials suggests that a chemical kinetic mechanism can describe the time-dependent structural data. Procedures for the effective SVD analysis of experimental time-resolved crystallographic data have been established and emphasize the necessity for minimizing systematic errors by modification of the data-collection protocol. PMID:15103131

Rajagopal, Sudarshan; Schmidt, Marius; Anderson, Spencer; Ihee, Hyotcherl; Moffat, Keith

2004-05-01

312

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 using induction heating to produce pipelines is found to have lower toughness at the weld junction than, Crystallography Introduction High frequency induction heating is often used for brazing difficult alloys of iron1

Cambridge, University of

313

Crystallographic texture for tube and plate of the superelastic/shape-memory alloy Nitinol used for  

E-print Network

Crystallographic texture for tube and plate of the superelastic/shape-memory alloy Nitinol used of endovascular stents. As such stents are invariably laser-machined from Nitinol tubes or sheets rolled play a key role in influ- encing the mechanical properties of Nitinol. In this article, we present

Ritchie, Robert

314

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

315

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

316

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 polymer films (fig. 1). It is essentially dedicated to polyethylene, espe- cially for packaging in polyethylene blown films J.-M. Haudin, J.-M. André, G. Bellet, B. Monasse, P. Navard École des Mines de Paris

Paris-Sud XI, Université de

317

Short sequence-paper Cloning, characterization and preliminary crystallographic analysis of  

E-print Network

Short sequence-paper Cloning, characterization and preliminary crystallographic analysis~ocarlense 400, 13566-590, Sa~o Carlos--SP, Brazil b Howard Hughes Medical Institute, MacDonald Building, 90095 for antiparasitic drug design. The hgprt gene was cloned from a Leishmania tarentolae genomic library

Simpson, Larry

318

OFFICESOFFICES GROUP STUDY  

E-print Network

, PUBLIC PRINTER PUBLIC COMPUTERS & SCANNER STUDY SPACE STUDY SPACE 5 REFERENCE BRO W SERY NEWBOOKS STUDY SOUTH GROUP STUDY SPACES MEDIA ROOM MICROFICHE/ MICROFILM ATHENA COMPUTERS & ADA STATION SCANNER, COPIER SPACE 6 SOUTH EAST WEST NORTH Q335-QA76.7 ATHENA COMPUTERS A-Q335 THESES TA1-TA499 QA805-TA1 QA76.7-QA

319

Crystallographic and mechanistic aspects of growth by shear and by diffusional processes  

NASA Astrophysics Data System (ADS)

Growth by shear and by diffusional processes, both taking place predominantly by means of ledge mechanisms, are reviewed for the purpose of distinguishing critically between them at the atomic, microscopic, and macroscopic levels. At the atomic level, diffusional growth is described as individual, poorly coordinated, thermally activated jumps occurring in the manner of biased random walk, whereas growth by shear is taken to be tightly coordinated “glide” of atoms to sites in the product phase which are “predestined” to within the radius of a shuffle. Obedience to the invariant plane strain (IPS) surface relief effect and the transformation crystallography prescribed by the phenomenological theory of martensite is shown to be an unsatisfactory means of distinguishing between these two fundamentally different atomic growth mechanisms. In substitutional alloys, continuous differences in composition and in long-range order (LRO) from the earliest stages of growth onward are concluded to be the most useful phenomenological approach to achieving differentiation. At a more fundamental level, however, the details of interphase boundary structure are the primary determinant of the operative mechanism (when the driving force for growth is sufficient to permit either to occur). In the presence of a stacking sequence change across the boundary, terraces of ledges are immobile irrespective of their structural details during diffusional growth. Kinks on the risers of superledges are probably the primary sites for diffusional transfer of atoms across interphase boundaries. In martensitic transformations, on the other hand, terraces containing edge dislocations in glide orientation or pure screw dislocations are mobile and accomplish the lattice invariant deformation (LID), though probably only after being overrun by a transformation dislocation. Risers associated with transformation dislocations are also mobile and cause the crystal structure change during growth by shear. The successes achieved by the invariant line (IL) component of the phenomenological theory of martensite in predicting precipitate needle growth directions and precipitate plate habit planes (Dahmen and co-workers) are here ascribed to the rate of ledge formation usually being a minimum at an interface containing an IL, primarily because nuclei formed sympathetically at this boundary orientation are likely to have the highest edge energies. Since martensite plate broad faces also contain the IL, the ability of the phenomenological theory to predict the habit plane and the orientation relationships of both precipitate and martensite plates is no longer surprising. The IPS relief effect at a free surface can be generated by precipitate plates when growth ledges are generated predominantly on only one broad face and only one of several crystallographically equivalent Burgers vectors of growth ledges is operative. Both pReferences probably result from larger reductions in transformation strain energy for the particular geometry with which a given plate intercepts the free surface. Precipitate morphology often differs significantly from that of martensite even if precipitates are plate-shaped and can readily differ very greatly. Whereas martensite morphology is determined by the need to minimize shear strain energy, that of precipitates derives from the more flexible base of the interphase boundary orientation-dependence of the reciprocal of the average intergrowth ledge spacing, as modified by both the orientation-dependence of interkink spacing on growth ledge risers and the spacing/ height ratio dependence of diffusion field overlap upon growth kinetics.

Aaronson, H. I.; Furuhara, T.; Rigsbee, J. M.; Reynolds, W. T.; Howe, J. M.

1990-09-01

320

Crystallization and preliminary crystallographic analysis of two eukaryotic fructosyl peptide oxidases  

PubMed Central

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 P41212, with unit-cell parameters a = b = 110.09, c = 220.48?Å, and that of EFP-T5M belonged to the monoclinic space group P21, 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

2013-01-01

321

Synthesis, growth, spectral, thermal and crystallographic studies of 5?,6?-epoxycholestane single crystals  

NASA Astrophysics Data System (ADS)

?-Selective epoxidation of 3?-chlorocholest-5-ene and 3?-acetoxycholest-5-ene has been performed with m-CPBA to synthesize 3?-chloro-5?,6?-epoxycholestane (1) and 3?-acetoxy-5?,6?-epoxycholestane (2). We provided an analysis of these compounds by means of FT-IR, FT-Raman, 1H NMR, 13C NMR, 2D cosy, NOESY, UV-visible and X-ray crystallography. The compound 1 crystallizes in the orthorhombic space group P212121 while compound 2 crystallizes in the monoclinic space group P21. We compared the conformations of both compounds in solid state and in solution by calculation of dihedral angles and coupling constant values. The powder X-ray diffraction (PXRD) of the compound was recorded to ascertain the purity of the grown crystals. Thermogravimetric analysis showed stability of the compounds up to 250 °C. Moreover, the ICH rule has been applied to test the stability of two crystals, which showed significant stability.

Shamsuzzaman; Khanam, Hena; Mashrai, Ashraf; Ahmad, Musheer; Mabkhot, Yahia Nasser; Frey, Wolfgang; Siddiqui, Nazish

2013-12-01

322

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

PubMed

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

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

2012-05-01

323

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

PubMed

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

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

2002-10-01

324

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

Microsoft Academic Search

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

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

2005-01-01

325

Crystallization and X-ray crystallographic analysis of human STAT1.  

PubMed

Unphosphorylated human STAT1 (1-683) has been crystallized in the presence of a phosphopeptide derived from the alpha-chain of human interferon gamma (IFNgamma) receptor. A complete data set has been collected from a KAu(CN)2-derivatized and dehydrated crystal. The crystal belonged to space group P6(1)22, with unit-cell parameters a = b = 102.6, c = 646.5 A, alpha = beta = 90, gamma = 120 degrees. PMID:16511123

Mao, Xiang; Chen, Xiaomin

2005-07-01

326

Purification, crystallization and preliminary X-ray crystallographic studies of Rv3705c from Mycobacterium tuberculosis  

PubMed Central

The conserved protein Rv3705c from Mycobacterium tuberculosis has been cloned, expressed, purified and crystallized by the sitting-drop vapour-diffusion method using PEG 3350 as a precipitant. The Rv3705c crystals exhibited space group P6122 or P6522, with unit-cell parameters a = b = 198.0, c = 364.1?Å, ? = ? = 90, ? = 120°, and diffracted to a resolution of 3.3?Å. PMID:25084389

Lu, Feifei; Gao, Feng; Li, Honglin; Gong, Weimin; Zhou, Lin; Bi, Lijun

2014-01-01

327

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

328

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

329

A knowledge-driven approach for crystallographic protein model completion  

PubMed Central

One of the most cumbersome and time-demanding tasks in completing a protein model is building short missing regions or ‘loops’. A method is presented that uses structural and electron-density information to build the most likely conformations of such loops. Using the distribution of angles and dihedral angles in pentapeptides as the driving parameters, a set of possible conformations for the C? backbone of loops was generated. The most likely candidate is then selected in a hierarchical manner: new and stronger restraints are added while the loop is built. The weight of the electron-density correlation relative to geometrical considerations is gradually increased until the most likely loop is selected on map correlation alone. To conclude, the loop is refined against the electron density in real space. This is started by using structural information to trace a set of models for the C? backbone of the loop. Only in later steps of the algorithm is the electron-density correlation used as a criterion to select the loop(s). Thus, this method is more robust in low-density regions than an approach using density as a primary criterion. The algorithm is implemented in a loop-building program, Loopy, which can be used either alone or as part of an automatic building cycle. Loopy can build loops of up to 14 residues in length within a couple of minutes. The average root-mean-square deviation of the C? atoms in the loops built during validation was less than 0.4?Å. When implemented in the context of automated model building in ARP/wARP, Loopy can increase the completeness of the built models. PMID:18391408

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

2008-01-01

330

Real-space finite-difference approach for multi-body systems: path-integral renormalization group method and direct energy minimization method.  

PubMed

The path-integral renormalization group and direct energy minimization method of practical first-principles electronic structure calculations for multi-body systems within the framework of the real-space finite-difference scheme are introduced. These two methods can handle higher dimensional systems with consideration of the correlation effect. Furthermore, they can be easily extended to the multicomponent quantum systems which contain more than two kinds of quantum particles. The key to the present methods is employing linear combinations of nonorthogonal Slater determinants (SDs) as multi-body wavefunctions. As one of the noticeable results, the same accuracy as the variational Monte Carlo method is achieved with a few SDs. This enables us to study the entire ground state consisting of electrons and nuclei without the need to use the Born-Oppenheimer approximation. Recent activities on methodological developments aiming towards practical calculations such as the implementation of auxiliary field for Coulombic interaction, the treatment of the kinetic operator in imaginary-time evolutions, the time-saving double-grid technique for bare-Coulomb atomic potentials and the optimization scheme for minimizing the total-energy functional are also introduced. As test examples, the total energy of the hydrogen molecule, the atomic configuration of the methylene and the electronic structures of two-dimensional quantum dots are calculated, and the accuracy, availability and possibility of the present methods are demonstrated. PMID:21998159

Sasaki, Akira; Kojo, Masashi; Hirose, Kikuji; Goto, Hidekazu

2011-11-01

331

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

332

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

NASA Astrophysics Data System (ADS)

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

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

1999-04-01

333

Application of electron backscatter diffraction for crystallographic characterization of tin whiskers.  

PubMed

Understanding the growth of whiskers or high aspect ratio features on substrates can be aided when the crystallography of the feature is known. This study has evaluated three methods that utilize electron backscatter diffraction (EBSD) for the determination of the crystallographic growth direction of an individual whisker. EBSD has traditionally been a technique applied to planar, polished samples, and thus the use of EBSD for out-of-surface features is somewhat more difficult and requires additional steps. One of the methods requires the whiskers to be removed from the substrate resulting in the loss of valuable physical growth relationships between the whisker and the substrate. The other two techniques do not suffer this disadvantage and provide the physical growth information as well as the crystallographic growth directions. The final choice of method depends on the information required. The accuracy and the advantages and disadvantages of each method are discussed. PMID:22832083

Michael, Joseph R; McKenzie, Bonnie B; Susan, Donald F

2012-08-01

334

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

PubMed Central

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

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

2013-01-01

335

Effect of crystallographic texture on the bulk magnetic properties of non-oriented electrical steels  

NASA Astrophysics Data System (ADS)

Quantitative physical models for non-oriented electrical steels require precise knowledge of chemical and microstructural parameters for the material, with crystallographic texture being one of the most important. Describing the structure-property relationships in these materials is made difficult in that all of the parameters have an effect on magnetic properties. In the present study, a set of non-oriented electrical steel specimens are examined, where chemistry and grain size are kept similar from sample to sample, but texture is varied. A new texture parameter called Magnetic Texture Factor is introduced which is defined as the ratio of the volume fractions of <100> direction to <111> direction along magnetization vector. It was found that this Magnetic Texture Factor was a better parameter for identifying trends of magnetic properties with crystallographic texture than the often used Texture Factor, which is described as the ratio of the volume fractions of {100} planes to {111} planes.

Ghosh, Pampa; Chromik, Richard R.; Vaseghi, Babak; Knight, Andrew M.

2014-09-01

336

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

337

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

338

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

339

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

340

Crystallographic orientation-dependent pattern replication in direct imprint of aluminum nanostructures  

NASA Astrophysics Data System (ADS)

In the present work, we perform molecular dynamics simulations corroborated by experimental validations to elucidate the underlying deformation mechanisms of single-crystalline aluminum under direct imprint using a rigid silicon master. We investigate the influence of crystallographic orientation on the microscopic deformation behavior of the substrate materials and its correlation with the macroscopic pattern replications. Furthermore, the surface mechanical properties of the patterned structures are qualitatively characterized by nanoindentation tests. Our results reveal that dislocation slip and deformation twinning are two primary plastic deformation modes of single-crystalline aluminum under the direct imprint. However, both the competition between the individual deformation mechanisms and the geometry between activated dislocation slip systems and imprinted surface vary with surface orientation, which in turn leads to a strong crystallographic orientation dependence of the pattern replications. It is found that the (010) orientation leads to a better quality of pattern replication of single-crystalline aluminum than the (111) orientation.

Yuan, Ying; Zhang, Junjie; Sun, Tao; Liu, Cong; Geng, Yanquan; Yan, Yongda; Jin, Peng

2015-02-01

341

On the subgroup structure of the hyperoctahedral group in six dimensions  

PubMed Central

The subgroup structure of the hyperoctahedral group in six dimensions is investigated. In particular, the subgroups isomorphic to the icosahedral group are studied. The orthogonal crystallographic representations of the icosahedral group are classified and their intersections and subgroups analysed, using results from graph theory and their spectra. PMID:25176990

Zappa, Emilio; Dykeman, Eric C.; Twarock, Reidun

2014-01-01

342

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

343

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

344

Crystallographically oriented Zn nanocrystals formed in ZnO by Mn{sup +}-implantation  

SciTech Connect

The nanostructural characteristics of ZnO implanted with Mn{sup +} to doses ranging from 1x10{sup 15} to 1x10{sup 17} cm{sup -2} are systematically studied for both as-implanted and postannealed cases. The detailed structural characterizations confirmed that the Mn{sup +} implantation and postannealing result in (1) the formation of crystallographically orientated Zn nanocrystals in the ZnO matrix and (2) Mn atoms occupy the Zn sites in ZnO.

Li, Y. J.; Zhang, B.; Lu, W. [National Lab for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China); Wang, Y.; Zou, J. [School of Engineering and Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Queensland 4072 (Australia)

2008-09-29

345

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], 1, 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 1 is the result of an electron transfer/C-H activation process. PMID:25483257

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

2015-01-25

346

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

347

Crystallographic Study of a Cleaved, Non\\/activatable Form of Porcine Zymogen E  

Microsoft Academic Search

The crystal structure of a cleaved form of porcine zymogen E has been solved by molecular replacement using the bovine procarboxypeptidase A-S6 subunit III structure as search model. Crystallographic refinement using simulated annealing and energy minimization techniques resulted in a finalR-factor of 0.189 for all data between 8 and 2.3 Å resolution. The zymogen E three-dimensional model is very close

David Pignol; Simone Granon; Catherine Chapus; Juan Carlos Fontecilla-Camps

1995-01-01

348

Ensemble MD simulations restrained via crystallographic data: Accurate structure leads to accurate dynamics  

PubMed Central

Currently, the best existing molecular dynamics (MD) force fields cannot accurately reproduce the global free-energy minimum which realizes the experimental protein structure. As a result, long MD trajectories tend to drift away from the starting coordinates (e.g., crystallographic structures). To address this problem, we have devised a new simulation strategy aimed at protein crystals. An MD simulation of protein crystal is essentially an ensemble simulation involving multiple protein molecules in a crystal unit cell (or a block of unit cells). To ensure that average protein coordinates remain correct during the simulation, we introduced crystallography-based restraints into the MD protocol. Because these restraints are aimed at the ensemble-average structure, they have only minimal impact on conformational dynamics of the individual protein molecules. So long as the average structure remains reasonable, the proteins move in a native-like fashion as dictated by the original force field. To validate this approach, we have used the data from solid-state NMR spectroscopy, which is the orthogonal experimental technique uniquely sensitive to protein local dynamics. The new method has been tested on the well-established model protein, ubiquitin. The ensemble-restrained MD simulations produced lower crystallographic R factors than conventional simulations; they also led to more accurate predictions for crystallographic temperature factors, solid-state chemical shifts, and backbone order parameters. The predictions for 15N R1 relaxation rates are at least as accurate as those obtained from conventional simulations. Taken together, these results suggest that the presented trajectories may be among the most realistic protein MD simulations ever reported. In this context, the ensemble restraints based on high-resolution crystallographic data can be viewed as protein-specific empirical corrections to the standard force fields. PMID:24452989

Xue, Yi; Skrynnikov, Nikolai R

2014-01-01

349

The ferroelastic metal insulator transition in VO2: An electronically triggered crystallographic phase transition  

Microsoft Academic Search

We present a microscopic model of the first order phase transition of VO2, which incorporates both electron-electron and electron-lattice interactions. At a given temperature, the free energy is a function of two variational parameters: the static amplitude of a zone boundary normal mode, which is the crystallographic order parameter, and the mean amplitude of local magnetic moments, which describes electron-electron

D. Paquet; P. Leroux-Hugon

1980-01-01

350

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

Microsoft Academic Search

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

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

2008-01-01

351

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

352

Crystallographic preferred orientation of akimotoite and seismic anisotropy of Tonga slab.  

PubMed

The mineral akimotoite, ilmenite-structured MgSiO(3), exists at the bottom of the Earth's mantle transition zone and within the uppermost lower mantle, especially under low-temperature conditions. Akimotoite is thought to be a major constituent of the harzburgite layer of subducting slabs, and the most anisotropic mineral in the mantle transition zone. It has been predicted that if akimotoite crystals are preferentially oriented by plastic deformation, a cold subducted slab would be extremely anisotropic. However, there have been no studies of crystallographic preferred orientations and very few reports of plastic deformation experiments for MgSiO(3) ilmenite. Here we present plastic deformation experiments on polycrystalline akimotoite, which were conducted at confining pressures of 20-22 GPa and temperatures of 1,000-1,300 degrees C. We found a change in crystallographic preferred orientation pattern of akimotoite with temperature, where the c-axis maximum parallel to the compression direction develops at high temperature, whereas the c axes are preferentially oriented parallel to the shear direction or perpendicular to the compression direction at lower temperature. The previously reported difference in compressional-wave seismic anisotropy between the northern and southern segments of the Tonga slab at depths of the mantle transition zone can conceivably be attributed to the difference in the crystallographic preferred orientation pattern of akimotoite at varying temperature within the slab. PMID:18833278

Shiraishi, Rei; Ohtani, Eiji; Kanagawa, Kyuichi; Shimojuku, Akira; Zhao, Dapeng

2008-10-01

353

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

354

OAST Space Theme Workshop. Volume 3: Working group summary. 6: Power (P-2). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2)  

NASA Technical Reports Server (NTRS)

Power requirements for the multipurpose space power platform, for space industrialization, SETI, the solar system exploration facility, and for global services are assessed for various launch dates. Priorities and initiatives for the development of elements of space power systems are described for systems using light power input (solar energy source) or thermal power input, (solar, chemical, nuclear, radioisotopes, reactors). Systems for power conversion, power processing, distribution and control are likewise examined.

1976-01-01

355

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

SciTech Connect

Quartz crystallographic textures in different rocks have been investigated by neutron diffraction. Various types of crystallographic textures of quartz-bearing mineral associations in monomineral and multiphase rocks from a representative collection of samples have been revealed and classified. Experimental investigations have been performed on special neutron texture diffractometers designed at the Frank Laboratory of Neutron Physics and mounted in the seventh channel of the IBR-2 reactor at the Joint Institute for Nuclear Research (Dubna).

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

2008-09-15

356

Rearrangement of crystallographic domains driven by magnetic field in ferromagnetic Ni2MnGa and antiferromagnetic CoO  

Microsoft Academic Search

We have investigated the rearrangement of crystallographic domains (martensite variants) in Ni2MnGa ferromagnetic shape memory alloy and CoO antiferromagnetic oxide by applying magnetic field up to 8.0 MA\\/m. From the result of optical microscope observation of Ni2MnGa single crystal, when a magnetic field is applied along [001]p (p represents a parent phase), the rearrangement of crystallographic domains occurs and the

Tomoyuki Terai; Motoyoshi Yasui; Masataka Yamamoto; Tomoyuki Kakeshita

2009-01-01

357

Transgressive loop group extensions  

E-print Network

A central extension of the loop group of a Lie group is called transgressive, if it corresponds under transgression to a degree four class in the cohomology of the classifying space of the Lie group. Transgressive loop group extensions are those that can be explored by finite-dimensional, higher-categorical geometry over the Lie group. We show how transgressive central extensions can be characterized in a loop-group theoretical way, in terms of loop fusion and thin homotopy equivariance.

Konrad Waldorf

2015-02-17

358

Finite group symmetry breaking  

E-print Network

Finite group symmetry is commonplace in Physics, in particular through crystallographic groups occurring in condensed matter physics -- but also through the inversions (C,P,T and their combinations) occurring in high energy physics and field theory. The breaking of finite groups symmetry has thus been thoroughly studied, and general approaches exist to investigate it. In Landau theory, the state of a system is described by a finite dimensional variable (the {\\it order parameter}), and physical states correspond to minima of a potential, invariant under a group. In this article we describe the basics of symmetry breaking analysis for systems described by a symmetric polynomial; in particular we discuss generic symmetry breakings, i.e. those determined by the symmetry properties themselves and independent on the details of the polynomial describing a concrete system. We also discuss how the plethora of invariant polynomials can be to some extent reduced by means of changes of coordinates, i.e. how one can reduce to consider certain types of polynomials with no loss of generality. Finally, we will give some indications on extension of this theory, i.e. on how one deals with symmetry breakings for more general groups and/or more general physical systems.

G. Gaeta

2005-10-02

359

OFFICESOFFICES GROUP STUDY  

E-print Network

SOUTH GROUP STUDY SPACES MEDIA ROOM MICROFICHE/ MICROFILM CURRENT JOURNALS REFERENCE COLLECTION & GOVERNMENT DOCUMENTS ATHENA COMPUTERS & ADA STATION SCANNER, COPIER, PUBLIC PRINTER PUBLIC COMPUTERS & SCANNER STUDY SPACE STUDY SPACE 5 DVD/VHS BRO W SERY NEWBOOKS 6 SOUTH EAST WEST Q335-QA76.7 ATHENA

360

Purification, crystallization and preliminary crystallographic analysis of peroxidase from the palm tree Chamaerops excelsa  

PubMed Central

Plant peroxidases are presently used extensively in a wide range of bio­technological applications owing to their high environmental and thermal stability. As part of efforts towards the discovery of appealing new biotechnological enzymes, the peroxidase from leaves of the palm tree Chamaerops excelsa (CEP) was extracted, purified and crystallized in its native form. An X-­ray diffraction data set was collected at a synchrotron source and data analysis showed that the CEP crystals belonged to the orthorhombic space group P212121, with unit-cell parameters a = 70.2, b = 100.7, c = 132.3?Å. PMID:22139187

Textor, Larissa C.; Santos, Jademilson C.; Hidalgo Cuadrado, Nazaret; Roig, Manuel G.; Zhadan, Galina G.; Shnyrov, Valery L.; Polikarpov, Igor

2011-01-01

361

Purification, Crystallization, and Preliminary Crystallographic Analysis of Deoxyuridine Triphosphate Nucleotidohydrolase from Arabidopsis Thaliana  

SciTech Connect

The deoxyuridine triphosphate nucleotidohydrolase gene from Arabidopsis thaliana was expressed and the gene product was purified. Crystallization was performed by the hanging-drop vapour-diffusion method at 298 K using 2 M ammonium sulfate as the precipitant. X-ray diffraction data were collected to 2.2 Angstroms resolution using Cu K{alpha} radiation. The crystal belongs to the orthorhombic space group P212121, with unit-cell parameters a = 69.90, b = 70.86 Angstroms, c = 75.55 Angstroms . Assuming the presence of a trimer in the asymmetric unit, the solvent content was 30%, with a VM of 1.8 Angstroms 3 Da-1.

Bajaj,M.; Moriyama, H.

2007-01-01

362

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

363

Crystallization and preliminary crystallographic analysis of the chimeric protein LKB1-14-3-3?.  

PubMed

LKB1, a tumour suppressor, plays key roles in cell polarity, cell growth and energy metabolism. 14-3-3 proteins bind to LKB1 and suppress its functions. A chimera containing 14-3-3? and its binding region in LKB1 was constructed and the chimeric protein LKB1-14-4-3? was purified and crystallized. The crystal of LKB1-14-4-3? diffracted to 2.9 Å resolution and belonged to space group R32, with unit-cell parameters a = b = 130.262, c = 264.960 Å. Structure determination and refinement are in progress. PMID:24316833

Ding, Sheng; Zhou, Ruiqing; Zhu, Yaqin

2013-12-01

364

Purification, crystallization and preliminary X-ray crystallographic analysis of nucleoside diphosphate kinase from rice.  

PubMed

Nucleoside diphosphate kinase (NDK) catalyses the transfer of the gamma-phosphoryl group from a nucleoside triphosphate (NTP) to a nucleoside diphosphate (NDP). NDK is involved in and required for coleoptile elongation in rice. The level of the enzyme changes during seed germination and the early stages of seedling growth. Recombinant rice NDK (rNDK) has been crystallized using the hanging-drop vapour-diffusion method. rNDK crystals diffracted to a resolution of 2.50 A and belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 70.98, b = 182.26, c = 188.30 A. Preliminary analysis indicates there to be 12 rNDK molecules in each asymmetric unit, with a solvent content of 47.2%. PMID:12925801

Huang, Jen-Yen; Chang, Chia-Yu; Chang, Tschining; Chen, Chun-Jung

2003-09-01

365

Space Resources and Space Settlements  

NASA Technical Reports Server (NTRS)

The technical papers from the five tasks groups that took part in the 1977 Ames Summer Study on Space Settlements and Industrialization Using Nonterrestrial Materials are presented. The papers are presented under the following general topics: (1) research needs for regenerative life-support systems; (2) habitat design; (3) dynamics and design of electromagnetic mass drivers; (4) asteroids as resources for space manufacturing; and (5) processing of nonterrestrial materials.

Billingham, J. (editor); Gilbreath, W. P. (editor); Oleary, B. (editor); Gosset, B. (editor)

1979-01-01

366

Crystallization and preliminary X-ray crystallographic studies of a lectin from the mushroom Marasmius oreades.  

PubMed

The Marasmius oreades agglutinin (MOA) recognizes blood group B oligosaccharides. This mushroom lectin belongs to the ricin superfamily and is currently the only lectin known with exclusive specificity for Galalpha1,3Gal-structures, as occur in the subterminally fucosylated blood group B epitope Galalpha1,3(Fucalpha1,2)Galbeta1,4GlcNAc (MOA's preferred ligand) or without fucosylation in the xenotransplantation epitope. MOA has been co-crystallized with the linear blood group B trisaccharide Galalpha1,3Galbeta1,4GlcNAc using the hanging-drop vapour-diffusion technique at room temperature. MOA crystals were grown in the presence of ammonium formate and HEPES buffer. A 3.0 A data set has been collected. Preliminary analysis of the X-ray data is consistent with space group P3(1) or P3(2) and unit-cell parameters a = b = 105, c = 113 A, with two dimers per asymmetric unit. PMID:15502320

Grahn, Elin; Holmner, Asa; Cronet, Cecilia; Tateno, Hiroaki; Winter, Harry C; Goldstein, Irwin J; Krengel, Ute

2004-11-01

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, 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

368

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

369

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

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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

... 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...

2012-07-01

371

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

372

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

373

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

374

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

... 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...

2014-07-01

375

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

376

Application of combined EBSD and 3D-SEM technique on crystallographic facet analysis of steel at low temperature.  

PubMed

Electron backscatter diffraction has been increasingly used to identify the crystallographic planes and orientation of cleavage facets with respect to the rolling direction in fracture surfaces. The crystallographic indices of cleavage planes can be determined either directly from the fracture surface or indirectly from metallographic sections perpendicular to the plane of the fracture surface. A combination of electron backscatter diffraction and 3D scanning electron microscopy imaging technique has been modified to determine crystallographic facet orientations. The main purpose of this work has been to identify the macroscopic crystallographic orientations of cleavage facets in the fracture surfaces of weld heat affected zones in a well-known steel fractured at low temperatures. The material used for the work was an American Petroleum Institute (API) X80 grade steel developed for applications at low temperatures, and typical heat affected zone microstructures were obtained by carrying out weld thermal simulation. The fracture toughness was measured at different temperatures (0°C, -30°C, -60°C and -90°C) by using Crack Tip Opening Displacement testing. Fracture surfaces and changes in microstructure were analyzed by scanning electron microscopy and light microscopy. Crystallographic orientations were identified by electron backscatter diffraction, indirectly from a polished section perpendicular to the major fracture surface of the samples. Computer assisted 3D imaging was used to measure the angles between the cleavage facets and the adjacent polished surface, and then these angles were combined with electron backscatter diffraction measurements to determine the macroscopic crystallographic planes of the facets. The crystallographic indices of the macroscopic cleavage facet planes were identified to be {100}, {110}, {211} and {310} at all temperatures. PMID:23692572

Mohseni, P; Solberg, J K; Karlsen, M; Akselsen, O M; Ostby, E

2013-07-01

377

Crystallization and preliminary crystallographic studies of dihydrofolate reductase-thymidylate synthase from Trypanosoma cruzi, the Chagas disease pathogen  

PubMed Central

Trypanosoma cruzi dihydrofolate reductase-thymidylate synthase (TcDHFR-TS) was crystallized in complexes with the dihydrotriazine-based or quinazoline-based antifolates C-448, cycloguanil (CYC) and Q-8 in order to gain insight into the interactions of this DHFR enzyme with classical and novel inhibitors. The TcDHFR-TS–C-448–NDP–dUMP crystal belonged to space group C2221 with two molecules per asymmetric unit and diffracted to 2.37?Å resolution. The TcDHFR-TS–CYC, TcDHFR-TS–CYC–NDP and TcDHFR-TS–Q-8–NDP crystals belonged to space group P21 with four molecules per asymmetric unit and diffracted to 2.1, 2.6 and 2.8?Å resolution, respectively. Crystals belonging to the two different space groups were suitable for structure determination. PMID:19923744

Chitnumsub, Penchit; Yuvaniyama, Jirundon; Chahomchuen, Thippayarat; Vilaivan, Tirayut; Yuthavong, Yongyuth

2009-01-01

378

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

379

Facet and in-plane crystallographic orientations of GaN nanowires grown on Si(111).  

PubMed

We have determined the in-plane orientation of GaN nanowires relative to the Si (111) substrate on which they were grown. We used x-ray diffraction pole figure measurements to evidence two types of crystallographic orientation, all the nanowires having [Formula: see text] lateral facets. The proportion of these two orientations was determined and shown to be influenced by the pre-deposition of Al(Ga)N intermediate layers. In the main orientation, the GaN basal [Formula: see text] directions are aligned with the [Formula: see text] directions. This orientation corresponds to an in-plane coincidence of GaN and Si lattices. PMID:21825628

Largeau, L; Dheeraj, D L; Tchernycheva, M; Cirlin, G E; Harmand, J C

2008-04-16

380

``Crystallographic'' holes: new insights for a beneficial structural feature for photocatalytic applications  

NASA Astrophysics Data System (ADS)

One of the most fundamental aspects of the heterogeneous catalysis field is the manipulation of the catalysts' activity. In photocatalysis this is carried out by maximizing the right crystal plane of a semiconductor oxide. Until now, most of the papers have achieved this by a combination of different oxides, with noble metals and sometimes with carbon nanomaterials. In this work MWCNTs (multiwalled carbon nanotubes) were applied as ``crystallization promoters'' in a very simple, safe, one-step hydrothermal method. By this method TiO2 nano/micro crystals with exposed {001} facets were obtained in the first step. The next episode in the crystal manipulation ``saga'' was the modification of the (001) crystallographic plane's structure by creating ordered/own faceted ``crystallographic holes''. These elements are capable of further enhancing the obtained activity of titania microcrystals to a higher extent, as shown by the UV driven photocatalytic phenol degradation experiments. The appearance of the holes was ``provoked'' by simple calcination and their presence and influence were demonstrated by XPS and HRTEM.One of the most fundamental aspects of the heterogeneous catalysis field is the manipulation of the catalysts' activity. In photocatalysis this is carried out by maximizing the right crystal plane of a semiconductor oxide. Until now, most of the papers have achieved this by a combination of different oxides, with noble metals and sometimes with carbon nanomaterials. In this work MWCNTs (multiwalled carbon nanotubes) were applied as ``crystallization promoters'' in a very simple, safe, one-step hydrothermal method. By this method TiO2 nano/micro crystals with exposed {001} facets were obtained in the first step. The next episode in the crystal manipulation ``saga'' was the modification of the (001) crystallographic plane's structure by creating ordered/own faceted ``crystallographic holes''. These elements are capable of further enhancing the obtained activity of titania microcrystals to a higher extent, as shown by the UV driven photocatalytic phenol degradation experiments. The appearance of the holes was ``provoked'' by simple calcination and their presence and influence were demonstrated by XPS and HRTEM. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07157c

Vajda, Krisztina; Kása, Zsolt; Dombi, András; Németh, Zoltán; Kovács, Gábor; Danciu, Virginia; Radu, Teodora; Ghica, Corneliu; Baia, Lucian; Hernádi, Klára; Pap, Zsolt

2015-03-01

381

Expression, purification, crystallization and preliminary crystallographic analysis of the PAB0955 gene product  

PubMed Central

PAB0955 from Pyrococcus abyssi is a prototype of a new Walker-type ATPase/GTPase conserved in archaea and eukaryota but not found in bacteria. PAB0955 has been expressed, purified and crystallized, and it has been shown that this thermostable protein is dimeric in reductive conditions. Crystals have been obtained either without nucleotide or in the presence of GDP or GTP?S. Preliminary X-ray crystallographic data up to 2.08?Å resolution have been collected from these crystals. PMID:16510996

Gras, Stéphanie; Fernandez, Bernard; Chaumont, Valérie; Carpentier, Philippe; Armengaud, Jean; Housset, Dominique

2005-01-01

382

Replacement of the axial histidine heme ligand with cysteine in nitrophorin 1: spectroscopic and crystallographic characterization  

Microsoft Academic Search

To evaluate the potential of using heme-containing lipocalin nitrophorin 1 (NP1) as a template for protein engineering, we\\u000a have replaced the native axial heme-coordinating histidine residue with glycine, alanine, and cysteine. We report here the\\u000a characterization of the cysteine mutant H60C_NP1 by spectroscopic and crystallographic methods. The UV\\/vis, resonance Raman,\\u000a and magnetic circular dichroism spectra suggest weak thiolate coordination of

Stefan W. Vetter; Andrew C. Terentis; Robert L. Osborne; John H. Dawson; David B. Goodin

2009-01-01

383

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

384

Synthesis and Crystallographic Study of N ?-(1-benzylpiperidin-4-yl)acetohydrazide  

Microsoft Academic Search

\\u000a Abstract  As part of a study into new Fentanyl-derived opioid compounds with potent analgesic activity and reduced side effects the\\u000a starting material title compound, C14H21N3O (1), was synthesized and characterized by NMR spectroscopy and single-crystal X-ray diffraction. The crystal structure is monoclinic\\u000a Cc with unit cell parameters a = 14.1480(3) Å, b = 14.1720(4) Å, c = 27.6701(7) Å, ? = 96.956(1)°, ? = ? = 90°. The compound has crystallized with four crystallographically unique molecules

Gary S. Nichol; Ruben Vardanyan; Victor J. Hruby

2010-01-01

385

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

386

OAST Space Theme Workshop. Volume 3: Working group summary. 2: Data handling, communications (E-2). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2)  

NASA Technical Reports Server (NTRS)

Technologies required to support the stated OAST thrust to increase information return by X1000, while reducing costs by a factor of 10 are identified. The most significant driver is the need for an overall end-to-end data system management technology. Maximum use of LSI component technology and trade-offs between hardware and software are manifest in most all considerations of technology needs. By far, the greatest need for data handling technology was identified for the space Exploration and Global Services themes. Major advances are needed in NASA's ability to provide cost effective mass reduction of space data, and automated assessment of earth looking imagery, with a concomitant reduction in cost per useful bit. A combined approach embodying end-to-end system analysis, with onboard data set selection, onboard data processing, highly parallel image processing (both ground and space), low cost, high capacity memories, and low cost user data distribution systems would be necessary.

1976-01-01

387

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

388

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

389

OAST Space Theme Workshop. Volume 3: Working group summary. 9: Aerothermodynamics (M-3). A: Statement. B: Technology needs (form 1). C. Priority assessment (form 2). D. Additional assessments  

NASA Technical Reports Server (NTRS)

Twelve aerothermodynamic space technology needs were identified to reduce the design uncertainties in aerodynamic heating and forces experienced by heavy lift launch vehicles, orbit transfer vehicles, and advanced single stage to orbit vehicles for the space transportation system, and for probes, planetary surface landers, and sample return vehicles for solar system exploration vehicles. Research and technology needs identified include: (1) increasing the fluid dynamics capability by at least two orders of magnitude by developing an advanced computer processor for the solution of fluid dynamic problems with improved software; (2) predicting multi-engine base flow fields for launch vehicles; and (3) developing methods to conserve energy in aerothermodynamic ground test facilities.

1976-01-01

390

First Principles Study of Crystallographic Structure and Elastic Properties of Chromium Nitride  

NASA Astrophysics Data System (ADS)

Chromium nitride (CrN) has extreme hardness and corrosion resistance. That is why it is used as thin surface coatings on different details. For the characterization of the properties of the deposited films the elastic constants of the CrN are required. At room temperature CrN is paramagnetic and crystallizes in face cantered cubic crystal structure of NaCl type, however below the Neel temperature the structure undergoes orthorhombic distortion and becomes antiferromagnet with fourth type of magnetic ordering. The first principles calculations, based on density functional theory with ultra-soft pseudo potentials were performed to investigate the crystallographic structure and elastic properties of chromium nitride. Simulations were performed using generalized gradient approximation exchange-correlation functional. Assumed were non-magnetic, ferromagnetic and antiferromagnetic AFM1[110] and AFM2[110] orderings. For the nonmagnetic and ferromagnetic cases the crystallographic structure of CrN remains cubic. For the experimentally observed AFM[110] structure orthorhombic distortion is evident, while for the AFM1[110] there is a tendency for a small tetragonal distortion of the cubic structure. The calculated crystal and magnetic structures, lattice parameters, atomic postitions and elastic constants were compared with the available experimental and theoretical results. The most stable structure is the experimentally observed at low temperatures AFM2[110], however the results for the elastic constants of AFM1[110] are the most suitable for the high temperature structure.

Antonov, V.; Iordanova, I.

2010-01-01

391

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

392

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

393

Crystallographic structure of Ni-Co coating on the affinity adsorption of histidine-tagged protein.  

PubMed

The principle of immobilized metal affinity chromatography (IMAC) has been recently implemented for protein microarrays for the study of protein abundance and function. Ni-Co film fabricated by electrodeposition is a novel microarray surface in an alloy type for immobilizing histidine-tagged proteins based on IMAC. In this paper, the effects of crystallographic structures and surface properties of Ni-Co coatings, with and without the annealing process, on the immobilization of histidine-tagged proteins were systematically investigated. The experimental results reveal that the stronger hcp texture, due to a higher Co content, results in better affinity adsorption for histidine-tagged biotin. Nevertheless, the allotropic phase transformation from hcp to fcc, due to the annealing process, leads to the decrease of affinity adsorption. The wettability property and the surface roughness of Ni-Co coating are, however, not important factors. Obviously, the crystallographic structure of Ni-Co coating is the dominant factor for the specific affinity adsorption of histidine-tagged protein. PMID:25731093

Chang, Yaw-Jen; Chen, Sheng-Zheng; Ho, Ching-Yuan

2015-04-01

394

"Crystallographic" holes: new insights for a beneficial structural feature for photocatalytic applications.  

PubMed

One of the most fundamental aspects of the heterogeneous catalysis field is the manipulation of the catalysts' activity. In photocatalysis this is carried out by maximizing the right crystal plane of a semiconductor oxide. Until now, most of the papers have achieved this by a combination of different oxides, with noble metals and sometimes with carbon nanomaterials. In this work MWCNTs (multiwalled carbon nanotubes) were applied as "crystallization promoters" in a very simple, safe, one-step hydrothermal method. By this method TiO2 nano/micro crystals with exposed {001} facets were obtained in the first step. The next episode in the crystal manipulation "saga" was the modification of the (001) crystallographic plane's structure by creating ordered/own faceted "crystallographic holes". These elements are capable of further enhancing the obtained activity of titania microcrystals to a higher extent, as shown by the UV driven photocatalytic phenol degradation experiments. The appearance of the holes was "provoked" by simple calcination and their presence and influence were demonstrated by XPS and HRTEM. PMID:25757557

Vajda, Krisztina; Kása, Zsolt; Dombi, András; Németh, Zoltán; Kovács, Gábor; Danciu, Virginia; Radu, Teodora; Ghica, Corneliu; Baia, Lucian; Hernádi, Klára; Pap, Zsolt

2015-03-19

395

Crystallographic superstructure in R2PdSi3 (R = heavy rare earth) compounds  

SciTech Connect

The R2PdSi3 intermetallic compounds have been reported to crystallize in a hexagonal AlB2- derived structure, with the rare earth atoms on the Al sites and Pd and Si atoms randomly distributed on the B sites. However, the intricate magnetic properties observed in the series of compounds have always suggested complications to the assumed structure. To clarify the situation, x-ray and neutron diffraction measurements were performed on the heavy rare earth compounds with R = Gd, Tb, Dy, Ho, Er, Tm, which revealed the existence of a crystallographic superstructure. The superstructure features a doubled unit cell in the hexagonal basal plane and an octuplication along the perpendicular c direction with respect to the primitive cell. No structural transition was observed between 300 K and 1.5 K. Extended x-ray absorption fine structure (EXAFS) analysis as well as density functional theory (DFT) calculations were utilized to investigate the local environments of the respective atoms. In this article the various experimental results will be presented and it will be shown that the superstructure is mainly due to the Pd-Si order on the B sites. A structure model will be proposed to fully describe the superstructure of Pd-Si order in R2PdSi3. The connection between the crystallographic superstructure and the magnetic properties will be discussed in the framework of the presented model.

Tang, Fei [TU Dresden; Frontzek, Matthias D [ORNL; Dshemuchadse, Julia [ETH Zurich, Switzerland; Leisegang, Tilmann [Technische Universitat Dresden; Zschornak, Matthias [Technische Universitat Dresden; Mietrach, Robert [Technische Universitat Dresden; Hoffman, Jens-Uwe [Helmholtz-Zentrum Berlin; Loeser, W [IFW Dresden; Gemming, Sibylle [Forschungszentrum Rossendorf, Dresden, Germany; Meyer, Dirk [Technische Universitat Dresden; Loewenhaupt, Michael [TU Dresden

2011-01-01

396

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

397

Molecular dynamics analysis of HIV-1 matrix protein: clarifying differences between crystallographic and solution structures.  

PubMed

One of the main structural features of the mature HIV-1 virion is the matrix protein (p17). This partially globular protein presents four helixes centrally organized and a fifth one, H5, projecting away from the packed bundle of helixes. Comparison between solution and crystallographic data of p17 indicates a 6 A displacement of a short 3(10) helix and a partial unfolding of H5 in solution related to crystal. While the behavior of the 3(10) helix has been previously addressed to virion assembly, the relevance and origin of H5 partial unfolding is possibly related to the contacts between p17 and other viral elements, such as p24. In this context, we present a 40 ns conformational sampling of monomeric p17 using molecular dynamics simulations. The performed simulations presented a progressive conversion of the p17 crystallographic structure to the NMR conformation, suggesting that the biological form of this protein may have its C-terminal portion partially unfolded. PMID:17067836

Verli, Hugo; Calazans, Alexandre; Brindeiro, Rodrigo; Tanuri, Amilcar; Guimarães, Jorge A

2007-07-01

398

Purpose and Features of Web-Based Open-Access Crystallographic Databases  

NASA Astrophysics Data System (ADS)

Roughly 5,000 new crystal structures are added to the (approximately 104,000 entry) Inorganic Crystal Structure Database each year (see http://icsdweb.fiz-karlsruhe.de/index.php for an approximately 4,000 entry demonstration version). Other commercial crystallographic databases specialize in organics, metals and alloys, and ``non-organics'' including minerals. This presentation gives an overview over these databases and evaluates the potential of open-access databases such as the (approximately 68,000 entry) Crystallography Open Database (http://crystallography.net/) and Portland State University's (PSU's) Wiki Crystallography Database, Crystal Morphology Database, and Nano-Crystallography Database (http://nanocrystallography.research.pdx.edu/CIF-searchable). Key features of open-access crystallographic databases are: a universal data exchange format, unrestricted internet access to the actual data (including downloads), search capabilities, and crystal structure identification functionalities. Interactive three-dimensional structure or morphology visualizations are also available at PSU's site. Most recently, we implemented at PSU community-based, Wikipedia-inspired data upload and database content management provisions. A selection of all of these features will be demonstrated (online) during the presentation.

Sondergeld, Peter; Moeck, Peter; Dusek, Boris; Hanke, Hynek

2008-05-01

399

Crystallographic Structure Determination: An Experiment for Organic Analysis and Other Nontraditional Venues  

NASA Astrophysics Data System (ADS)

Single crystal diffraction analysis is a technique being increasingly utilized by non-specialists. To give students an introductory experience in this method, a one to two hour lecture and a three hour lab are described for use in courses such as organic analysis, biophysical chemistry, and instrumental methods. This class emphasizes the practical aspects of diffraction analysis, especially how routine structures are solved, how the results are prepared for publication as graphics and tables, and how reliable these results are. The student employ x-ray diffraction analysis software (i.e. SHELXTL) to solve the structures of compounds from supplied crystallographic data sets. Three data sets appropriate for this experiment are provided (i.e. for PhCH2-NH-CHPh-P(O)(OH)(OEt), (h6-1,4-C6H4(NH2)(NMe2))Cr(CO)3, and Pd(Ph2PCH2CH2PPh2)(S2C2(CN)2)) as is a link to a Youngstown State University Structure Center WEB page (i.e. http://www.as.ysu.edu/~adhunter/YSUSC/XRAYDPST/index.html) where additional properly formatted crystallographic data files may be downloaded.

Hunter, Allen D.

1998-10-01

400

Multi Scale Finite Element Analyses By Using SEM-EBSD Crystallographic Modeling and Parallel Computing  

SciTech Connect

A crystallographic homogenization procedure is introduced to the conventional static-explicit and dynamic-explicit finite element formulation to develop a multi scale - double scale - analysis code to predict the plastic strain induced texture evolution, yield loci and formability of sheet metal. The double-scale structure consists of a crystal aggregation - micro-structure - and a macroscopic elastic plastic continuum. At first, we measure crystal morphologies by using SEM-EBSD apparatus, and define a unit cell of micro structure, which satisfy the periodicity condition in the real scale of polycrystal. Next, this crystallographic homogenization FE code is applied to 3N pure-iron and 'Benchmark' aluminum A6022 polycrystal sheets. It reveals that the initial crystal orientation distribution - the texture - affects very much to a plastic strain induced texture and anisotropic hardening evolutions and sheet deformation. Since, the multi-scale finite element analysis requires a large computation time, a parallel computing technique by using PC cluster is developed for a quick calculation. In this parallelization scheme, a dynamic workload balancing technique is introduced for quick and efficient calculations.

Nakamachi, Eiji [Department of Mechanical Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka, Osaka 535-8585 (Japan)

2005-08-05

401

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

402

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

403

Identifying gaps in the use of urban green space for BEM (Black and Ethnic Minority) groups in London Borough of Hounslow, West London using GIS approach  

Microsoft Academic Search

The role of high quality green spaces has won a significant place in the London sustainable development agenda as to ensure all Londoners are within the walking distance of a quality nature. To achieve the goal of sustainable living via urban regeneration , each and every part of the society needs to be aware about their role, rights and responsibilities

Rekha Kharel-Bastola

404

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

405

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

406

First Principles Study of Electronic and Crystallographic Structure and Elastic Properties of RbNiF3  

NASA Astrophysics Data System (ADS)

First principles calculations, based on density functional theory (DFT) with ultra-soft pseudo potentials were performed to simulate the electronic, magnetic and crystallographic structure and elastic properties of RbNiF3, a candidate for magneto optical applications. The transparent magnetodielectric RbNiF3 is of interest because in contrast to the majority of other ABF3 compounds, which are orthorhombic perovskites, it is a representative of a much smaller group of chalcogenides with hexagonal crystal symmetry. In fact, this is the structural phase at normal pressure and it is isomorphous with the hexagonal modification of BaTiO3. The compound becomes ferrimagnetically ordered below a Néel temperature reported as 135 K. Synthesis at elevated temperature and pressure yields another phase that is a cubic perovskite (a0 = 4.077 ?), reported as antiferromagnetic. Computer simulations were performed using the generalized gradient approximation exchange-correlation functional with included Hubbard correction term; (GGA+U) approach. The relative stabilities of the hexagonal and cubic phases versus applied pressure were investigated. The stability of different magnetic structures available from theoretical calculations and experimental results has been studied. The elastic constants have been evaluated via the Birch-Murnaghan equation of state. According to the DFT calculations RbNiF3 is an insulator in both phase structures. The present results for calculated electronic band structure, magnetic structures, lattice parameters, atomic positions and elastic constants can reproduce reasonably well the available own and literature data. For the cubic phase G type antiferromagnetic ordering with magnetization collinear to axis <111> was predicted.

Antonov, V.; Krezhov, K.; Trendafilova, N.

2010-01-01

407

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

408

On the Hydration State of Amino Acids and Their Derivatives at Different Ionization States: A Comparative Multinuclear NMR and Crystallographic Investigation  

PubMed Central

2D, 13C, 14N, and 17O NMR and crystallographic data from the literature were critically evaluated in order to provide a coherent hydration model of amino acids and selected derivatives at different ionization states. 17O shielding variations, longitudinal relaxation times (T1) of 2D and 13C and line widths (??1/2) of 14N and 17O, may be interpreted with the hypothesis that the cationic form of amino acids is more hydrated by 1 to 3 molecules of water than the zwitterionic form. Similar behaviour was also observed for N-acetylated derivatives of amino acids. An exhaustive search in crystal structure databases demonstrates the importance of six-membered hydrogen-bonded conjugated rings of both oxygens of the ?-carboxylate group with a molecule of water in the vicinity. This type of hydrogen bond mode is absent in the case of the carboxylic groups. Moreover, a considerable number of structures was identified with the propensity to form intramolecular hydrogen bond both in the carboxylic acid (NH?O=C) and in the carboxylate (NH ? O?) ionization state. In the presence of bound molecules of water this interaction is significantly reduced in the case of the carboxylate group whereas it is statistically negligible in the carboxylic group. PMID:22675607

Pappas, Charalampos G.; Tzakos, Andreas G.; Gerothanassis, Ioannis P.

2012-01-01

409

Irreversible effects in the paramagnetic-state of DyVO4 in the crystallographic distorted phase  

E-print Network

by a great mobility of the domain-walls. J. Physique 45 (1984) 169-175 , JANVIER 1984, Classification Physics monodomaine. La grande mobilité des parois de domaine joue un rôle important dans cette transformation is lowered to orthorhombic with space group D2h [2]. In addition, DyV04 becomes antiferromagnetic below TN

Paris-Sud XI, Université de

410

Crystallization and preliminary crystallographic analysis of defective pollen wall (DPW) protein from Oryza sativa.  

PubMed

The defective pollen wall (dpw) gene of Oryza sativa encodes a fatty acid reductase (DPW) which plays important roles in primary fatty alcohol synthesis. DPW catalyzes the synthesis of 1-hexadecanol. The enzyme shows a higher specificity for palmitoyl-ACP than for palmitoyl-CoA as the substrate, and can only use NADPH as the cofactor. To gain an understanding of the molecular mechanism underlying the reaction catalyzed by DPW, the gene encoding DPW without the N-terminal 80 amino acids (DPW?80) was cloned into pET-28a vector and was overexpressed in Escherichia coli. DPW?80 was purified to homogeneity and screened for crystallization. DPW?80 in complex with NADPH produced crystals that diffracted X-rays to a resolution of 3.4?Å. The crystals belonged to space group P6? or P6?, with unit-cell parameters a=b=222.8, c=114.0?Å, ?=?=90, ?=120°. PMID:24915087

Wang, Wei; Ma, Yuanyuan; Suo, Yang; Yan, Liming; Zhang, Dabing; Miao, Chen

2014-06-01

411

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

412

Expression, crystallization and preliminary X-ray crystallographic studies of SCP3 coiled-coil domain.  

PubMed

The synaptonemal complex protein SCP3 is one of the components of the lateral element of the synaptonemal complex, which is a meiosis-specific complex structure formed at the synapse of homologous chromosomes. In this study, a C-terminal coiled-coil domain, SCP3, was overexpressed in Escherichia coli with an engineered C-terminal His tag. The coiled-coil domain of SCP3 was then purified to homogeneity and crystallized at 293?K. X-ray diffraction data were collected to a resolution of 3.2?Å from a crystal belonging to space group C2, with unit-cell parameters a = 121.29, b = 43.08, c = 57.42?Å, ? = 100.71°. The asymmetric unit was estimated to contain three molecules. PMID:24192369

Seo, Eun Kyoung; Kim, Tae Woo; Park, Hyun Ho

2013-11-01

413

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

414

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

415

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

416

Purification, identification and preliminary crystallographic studies of Pru du amandin, an allergenic protein from Prunus dulcis.  

PubMed

Food allergies appear to be one of the foremost causes of hypersensitivity reactions. Nut allergies account for most food allergies and are often permanent. The 360 kDa hexameric protein Pru du amandin, a known allergen, was purified from almonds (Prunus dulcis) by ammonium sulfate fractionation and ion-exchange chromatography. The protein was identified by a BLAST homology search against the nonredundant sequence database. Pru du amandin belongs to the 11S legumin family of seed storage proteins characterized by the presence of a cupin motif. Crystals were obtained by the hanging-drop vapour-diffusion method. The crystals belong to space group P4(1) (or P4(3)), with unit-cell parameters a = b = 150.7, c = 164.9 A. PMID:18097098

Gaur, Vineet; Sethi, Dhruv K; Salunke, Dinakar M

2008-01-01

417

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

418

Preliminary X-ray crystallographic analysis of a novel maltogenic amylase from Bacillus stearothermophilus ET1.  

PubMed

A novel maltogenic amylase from Bacillus stearothermophilus ET1, which has a dual activity of alpha-1,4- and alpha-1,6-glycosidic bond cleavages and alpha-1,6-glycosidic bond formation, was crystallized by using the hanging-drop vapor-diffusion method. The best crystals were obtained by employing a high concentration of protein (56 mg ml-1) and a precipitant containing 22% glycerol, 1.6 M ammonium sulfate in 0.1 M Tris-HCl (pH 8.5). Native diffraction data to 2.66 A resolution have been obtained from crystals flash-frozen at 110 K. The crystals belong to the space group P212121 with unit-cell dimensions of a = 77.62, b = 121.23, c = 244. 29 A, and contain three or four protomers per asymmetric unit. Structure determination by multiple isomorphous replacement is in progress. PMID:9761914

Cho, M J; Cha, S S; Park, J H; Cha, H J; Lee, H S; Park, K H; Oh, B H

1998-05-01

419

Crystallization and preliminary crystallographic analysis of recombinant VSP1 from Arabidopsis thaliana  

PubMed Central

VSP1 is a defence protein in Arabidopsis thaliana that may also be involved in control of plant development. The recombinant protein has been overexpressed in Escherichia coli, purified and crystallized using the sitting-drop vapour-diffusion method. The crystal diffracted to 1.9?Å resolution and a complete X-­ray data set was collected at 100?K using Cu?K? radiation from a rotating-anode X-ray source. The crystals belonged to space group C2. As there are no related structures that could be used as a search model for molecular replacement, work is in progress on experimental phasing using heavy-atom derivatives and selenomethionine derivatives. PMID:20124723

Shi, Zhu-Bing; Ge, Hong-Hua; Zhao, Ping; Zhang, Min

2010-01-01

420

Purification, crystallization and preliminary X-ray crystallographic studies of Rv3899c from Mycobacterium tuberculosis.  

PubMed

Rv3899c, a hypothetical protein from Mycobacterium tuberculosis that is conserved within the mycobacteria, is predicted to be secreted and has been found in culture filtrates. Here, Rv3899c has been cloned, expressed in Escherichia coli and purified using standard chromatographic techniques. The hanging-drop vapour-diffusion method with PEG 3350 as a precipitant was used to crystallize the protein. N-terminal sequencing results showed that the amino-acid sequence of the crystallized protein began with GATAG, indicating that it is a fragment containing residues 184-410 of Rv3899c. Rv3899c184-410 crystals exhibited the symmetry of space group P2(1)2(1)2(1), with unit-cell parameters a=49.88, b=54.72, c=75.52?Å, ?=?=?=90°, and diffracted to a resolution of 1.90?Å. PMID:25615980

Song, Yingjia; Liu, Jianghui; Li, De-Feng; Li, Honglin; Wang, Shihua; Wang, Da-Cheng; Zhou, Jie; Bi, Lijun

2015-01-01

421

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

PubMed Central

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 P61 or P65, with unit-cell parameters a = b = 89.1, c = 94.2?Å. The predicted Matthews coefficient (V M) value is 3.0?Å3?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?Å using synchrotron radiation. PMID:16511009

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

2005-01-01

422

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

423

Crystallization and preliminary X-ray crystallographic analysis of the human CKIP-1 pleckstrin homology domain.  

PubMed

The casein kinase 2 interacting protein-1 (CKIP-1) is involved in many cellular functions, including apoptosis, signalling pathways, cell growth, cytoskeleton and bone formation. Its N-terminal pleckstrin homology (PH) domain is thought to play an important role in membrane localization and controls shuttling of CKIP-1 between the plasma membrane and nucleus. In this study, the human CKIP-1 PH domain was purified but problems were encountered with nucleic acid contamination. An S84D/S86D/S88D triple mutant designed to abolish nucleic acid binding was purified and successfully crystallized. Single crystals diffracted to 1.7?Å resolution and belonged to space group P4?2?2 with unit-cell parameters a=53.0, b=53.0, c=113.8?Å, ?=?=?=90.0°. PMID:23519814

Li, Ping; Xu, Yuli; Li, Xin; Bartlam, Mark

2013-03-01

424

Expression, purification, crystallization and preliminary crystallographic studies of Rhagium inquisitor antifreeze protein.  

PubMed

Antifreeze proteins (AFPs) are a specialized evolutionary adaptation of a variety of bacteria, fish, arthropods and other organisms to inhibit ice-crystal growth for survival in harsh subzero environments. The recently reported novel hyperactive AFP from Rhagium inquisitor (RiAFP) is the second distinct type of AFP in beetles and its structure could reveal important molecular insights into the evolution of AFPs. For this purpose, RiAFP was overexpressed in Escherichia coli, purified and crystallized at 293?K using a combination of 23% PEG 3350 and 0.2?M ammonium sulfate as a precipitant. X-ray diffraction data were collected to 1.3?Å resolution using a synchrotron-radiation source. The crystals belonged to the trigonal space group P3(1)21 (or P3(2)21), with unit-cell parameters a = b = 46.46, c = 193.21?Å. PMID:22691785

Hakim, Aaron; Thakral, Durga; Zhu, Darren F; Nguyen, Jennifer B

2012-05-01

425

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

426

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

427

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.

428

Effect of crystallographic orientation on hillock formation in thermally cycled large grain tin films  

NASA Astrophysics Data System (ADS)

Tin whiskers and hillocks grow spontaneously from the surfaces of polycrystalline Sn films at room temperature. Whiskers can grow long enough to cause short circuits in electronic devices. We hypothesized that the anisotropies of the crystal structure lead to locally high strain energies that are relieved by the growth of whiskers and hillocks. This research studies hillock formations on large grain Sn-alloy films relative to the crystallographic orientations of the adjacent grains. Large grain films were produced by solidifying 96.5wt% Sn - 3wt% Ag - 0.5wt% Cu solder alloy on a Cu substrate. These surface defects (hillocks) grew predominately at grain boundaries during thermal cycling. The formation of the surface defects between two grains created a pseudo-bi-crystal sample geometry, making it ideal for studying surface defects relative to the local crystallographic orientations and the grains' corresponding anisotropic properties. The crystallographic orientations of the grains were studied with Electron Backscatter Diffraction (EBSD) and Laue micro-diffraction at the Lawrence Berkeley National Laboratory Advanced Light Source. Local orientation studies of the surface defects and the surrounding grains indicated that the surface defects nucleated and grew with low dislocation densities. In addition, the linear surface defect densities along the grain boundaries were measured and observed to change as a function of orientation. The change in linear defect density with respect to orientation was due, in part, to the anisotropy of the coefficient of thermal expansion of ?-Sn. In addition, it was important to account for elastic anisotropies. The elastic stresses, strains, and strain energy densities of the microstructures were determined with Object Oriented Finite element analysis. The simulations indicated that during thermal cycling the local stresses exceeded the yield strength. As a result, the highest linear defect densities did not occur at orientations with the highest local strain energies. Instead, the highest local strain energies were accommodated by other plastic deformation mechanisms, indicating that surface defect formation is not only affected by local strain energy densities but also the local dominant deformation mechanism. Therefore, the propensity of specific grain orientations to form surface defects will change as a function of the thermal cycling process.

Koppes, John Patrick

429

Making Space for Space.  

ERIC Educational Resources Information Center

Introduces some ideas for using space in classrooms. Provides a rationale for using space as part of the curriculum and focuses on the concept of a space mission as a vehicle for learning. Includes a list of some space-related web sites. (DDR)

Flanagan, Sue

2001-01-01

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

OPEN COMPUTING FACILITY Group Account Application Form 1. Pick an account name. It must consist of between three and eight lowercase letters (no spaces, numbers, underscores,  

E-print Network

of other users, re- spect the integrity of the systems and related physical resources, and observe all to protect the integrity of computer systems. For exam- ple, system administrators may access or examineOPEN COMPUTING FACILITY Group Account Application Form 1. Pick an account name. It must consist

Walker, Matthew P.

432

Quantification of thin film crystallographic orientation using X-ray diffraction with an area detector.  

PubMed

As thin films become increasingly popular (for solar cells, LEDs, microelectronics, batteries), quantitative morphological and crystallographic information is needed to predict and optimize the film's electrical, optical, and mechanical properties. This quantification can be obtained quickly and easily with X-ray diffraction using an area detector in two sample geometries. In this paper, we describe a methodology for constructing complete pole figures for thin films with fiber texture (isotropic in-plane orientation). We demonstrate this technique on semicrystalline polymer films, self-assembled nanoparticle semiconductor films, and randomly packed metallic nanoparticle films. This method can be immediately implemented to help understand the relationship between film processing and microstructure, enabling the development of better and less expensive electronic and optoelectronic devices. PMID:20361783

Baker, Jessy L; Jimison, Leslie H; Mannsfeld, Stefan; Volkman, Steven; Yin, Shong; Subramanian, Vivek; Salleo, Alberto; Alivisatos, A Paul; Toney, Michael F

2010-06-01

433

Crystallographically-dependent ripple formation on Sn surface irradiated with focused ion beam  

NASA Astrophysics Data System (ADS)

The metallographically polished polycrystalline Sn surface was sputtered by 30 kV focused Ga + ions at room temperature. The experiment was carried out using various FIB incidence angles (0°, 15°, 30°, and 45°) over a wide range of doses (10 16-10 18 ions/cm 2). The surface morphology was carefully characterized under the optical microscope, scanning electron microscope (SEM) and atomic force microscope (AFM). Ripples were observed on the irradiated areas even at the normal FIB incidence angle, which is not consistent with the Bradley-Harper (BH) rippling model. The orientation of ripples relies on crystallographic orientation rather than projected ion beam direction as predicted by BH model. The ripple wavelength is independent of ion dose, while ripple amplitude increases with ion dose. It is found that the ripples are formed by self-organization due to anisotropic surface diffusion in the low melting point metal.

Qian, H. X.; Zhou, W.; Fu, Y. Q.; Ngoi, B. K. A.; Lim, G. C.

2005-02-01

434

Crystallographic Orientation of the ? ? ?' Martensitic (Athermal) Transformation in a FeMnAlSi Steel  

NASA Astrophysics Data System (ADS)

The presence of athermal ?- and ?-martensite ( ?') in the as-cast structure of a Fe-0.08C-1.95Si-15.1Mn-1.4Al-0.017N alloy has been revealed by electron backscattered diffraction analysis. The alloy exhibited two athermal martensitic transformations described by ? ? ?' and ? ? ? ? ?'. The Shoji-Nishiyama orientation relationship was observed between ?-austenite and ?-martensite, while ?-martensite nucleated from ?-austenite exhibited a Kurdjumov-Sachs orientation relationship. Six crystallographic variants of ?-martensite consisting of three twin-related variant pairs were observed in ?-bands. A planar parallelism of {0001} ? || {110} ?' and a directional relation of lying within 1 deg of existed for these variants.

Pisarik, S. T.; Van Aken, D. C.

2014-07-01

435

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

436

Bacteriological and crystallographical analysis of urinary calculi: aid to patient management.  

PubMed Central

In an analysis, by both crystallographic and microbiological methods, of 50 urinary calculi recently removed by surgical operation, 33 proved to be of metabolic origin (mostly calcium oxalate and some uric acid or urate) and 17 of 'infective' origin (struvite, apatite or a mixture of the two). Metabolic stones were usually bacteriologically sterile or contained only small numbers (less than 10(3)/g of stone) of bacteria which did not produce urease, while infective stones always contained urease-producing organisms, usually Proteus mirabilis, in large numbers (greater than 10(5)/g). The combined approach of stone analysis by crystallography and microbiological culture yields more information than conventional techniques on which to base the treatment of urinary calculi and the prevention of their recurrence. Images Figure 1. PMID:6737406

Rosenstein, I; Osborn, R S; Hopewell, J P; Hamilton-Miller, J M; Brumfitt, W

1984-01-01

437

Reintroducing Electrostatics into Macromolecular Crystallographic Refinement: Application to Neutron Crystallography and DNA Hydration  

PubMed Central

Summary Most current crystallographic structure refinements augment the diffraction data with a priori information consisting of bond, angle, dihedral, planarity restraints and atomic repulsion based on the Pauli exclusion principle. Yet, electrostatics and van der Waals attraction are physical forces that provide additional a priori information. Here we assess the inclusion of electrostatics for the force field used for all-atom (including hydrogen) joint neutron/X-ray refinement. Two DNA and a protein crystal structure were refined against joint neutron/X-ray diffraction data sets using force fields without electrostatics or with electrostatics. Hydrogen bond orientation/geometry favors the inclusion of electrostatics. Refinement of Z-DNA with electrostatics leads to a hypothesis for the entropic stabilization of Z-DNA that may partly explain the thermodynamics of converting the B form of DNA to its Z form. Thus, inclusion of electrostatics assists joint neutron/X-ray refinements, especially for placing and orienting hydrogen atoms. PMID:21481775

Fenn, Timothy D.; Schnieders, Michael J.; Mustyakimov, Marat; Wu, Chuanjie; Langan, Paul; Pande, Vijay S.; Brunger, Axel T.

2011-01-01

438

Relationship between magnetic domain configuration and crystallographic orientation in a colossal magnetoresistive material.  

PubMed

We investigated the relationship between the magnetic domain (MD) configuration and crystallographic orientation in a colossal magnetoresistive (CMR) material La(0.69)Ca(0.31)MnO(3) in which anisotropic magnetoresistance (AMR) was observed as well. It was observed that the MD structure with a micrometre scale in the (001) plane collapses when a modulated structure with a nanometre scale emerges near the Curie temperature (T(c)). On the other hand, twin boundaries were observed to develop in the (110) plate, and they pin the MD walls. Like the pinning effect on MD walls, the emergence of vortex-like tadpole closure MDs upon the application of external magnetic field may be an origin of the AMR in La(0.69)Ca(0.31)MnO(3). PMID:20548105

Yu, Xiuzhen; Li, Run-Wei; Asaka, Toru; Ishizuka, Kazuo; Kimoto, Koji; Matsui, Yoshio

2010-08-01

439

Water-assisted highly enhanced crystallographic etching of graphene by iron catalysts  

NASA Astrophysics Data System (ADS)

We report the assisted role of water vapor in crystallographic cutting of graphene via iron catalysts in reduced atmosphere. Without water, graphene can be tailored with smooth trenches composed of straight lines with angles of 60° or 120° between two adjacent trenches. After the addition of water, new chacteristics are found: such as almost no iron particles can be detected along the trenches; each trench becomes longer and lots of graphene nanoribbons can be generated. The underlying mechanism is proposed and discussed, which is attributed to stimulating and lengthening of the catalytic activity of iron particles by water vapor. Project supported by the National Natural Science Foundation of China (Grant No. 10774032) and the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. Y2010031).

Xue, Lei-Jiang; Yu, Fang; Zhou, Hai-Qing; Sun, Lian-Feng

2015-03-01

440

Morphological and Crystallographic Properties of Rare Earth Oxides Coatings Deposited by Double Dual Beam-Pld  

NASA Astrophysics Data System (ADS)

Various rare earth oxide nanostructures were synthesized for the first time by dual-double pulsed gas feeding/pulsed laser deposition. The optically transparent and insulating nanostructures do not exhibit the standard columnar configuration of rare earth oxide thin films but rather dense structures and a significant chemical stoichiometry. More precisely, they exhibit single crystallographic low temperature phases with preferential textures, generally similar to that of the bulk used powder targets. For the cubic fluorine type CeO2 and Ho2O3 films, an epitaxial growth is observed with a special feature noticed in the case of the Eu2O3 nanostructure. For this latter, localized and very large oriented crystallites embedded in disordered packed pyramidal crystallites are observed.

Khamlich, S.; Ngom, B. D.; Kotsedi, C. K.; Bouziane, K.; Manikandan, E.; Maaza, M.

2014-11-01

441

Dianthraceno[a,e]pentalenes: synthesis, crystallographic structures and applications in organic field-effect transistors.  

PubMed

Two soluble and stable dianthraceno[a,e]pentalenes with two (DAP1) and six (DAP2) phenyl substituents were synthesized. Both compounds possess a small energy band gap and show amphoteric redox behaviour due to intramolecular donor-accepter interactions. X-ray crystallographic analysis revealed that DAP2 has a closely packed structure with multi-dimensional [C-H···?] interactions although there are no ?-? interactions between the dianthraceno[a,e]pentalene cores. As a result, solution-processed field effect transistors based on DAP2 exhibited an average hole mobility of 0.65 cm(2) V(-1) s(-1). Under similar conditions, DAP1 showed an average field effect hole mobility of 0.001 cm(2) V(-1) s(-1). PMID:25406768

Dai, Gaole; Chang, Jingjing; Zhang, Wenhua; Bai, Shiqiang; Huang, Kuo-Wei; Xu, Jianwei; Chi, Chunyan

2015-01-11

442

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

443

Determination of Crystallographic Texture in Steel Plates Using Laser-Generated Surface Waves  

NASA Astrophysics Data System (ADS)

A laser-ultrasonic approach based on the propagation of surface skimming longitudinal wave (P-wave) and Rayleigh wave (SAW) is investigated for the measurement of crystallographic texture in moderately thick steel plates. The angular dependence of the P-wave and SAW velocities presents different patterns, both of amplitude of a few % attributed to texture. Results obtained from fitting the angular profiles using relevant expressions for P-wave and SAW confirm that texture coefficients may accurately be measured by this approach. Moreover, the difference of the P-wave and SAW profiles is shown to be very robust against small path length changes or other detrimental effects such as surface roughness. For actual measurements on large plates, a solution based on the rotation of a generation line using an axicon lens is tested. Texture variations across the width of steel plates and the influence of residual stress are discussed.

Lévesque, D.; Lim, C. S.; Padioleau, C.; Blouin, A.

2011-06-01

444

Direct Measurement of the Crystallographically Sensitive Atomic Termination of Nanophase Cerium Dioxide  

NASA Astrophysics Data System (ADS)

Aberration-corrected high-resolution transmission electron microscopy (HRTEM) was used to study the surface termination of nanophase cerium dioxide particles. Application of computational exit-wave restoration and comparison with simulations confirmed the {111} surfaces to have an oxygen termination, and while structurally unstable at room temperature the {100} facets exhibited a metal terminating plane. This crystallographically sensitive atomic termination was found to be maintained under the reducing conditions of the electron beam. During electron beam irradiation, Electron Energy Loss Spectroscopy (EELS) analysis revealed that a change from Ce4+ to Ce3+ originates at the particle surface, and gradually extends into the particle as reduction continues. The results aid understanding of the oxygen buffering mechanism in cerium dioxide, and provide valuable insight into the use of CeO2 nanoparticles in catalysis.

Young, N. P.; Haigh, S. J.; Sawada, H.; Takayanagi, K.; Kirkland, A. I.

2012-07-01

445

Conformational analysis of environmental agents: use of X-ray crystallographic data to determine molecular reactivity.  

PubMed Central

This paper explores the use of crystallographic techniques as an aid in understanding the molecular reactivities of a number of agents that are of concern to pharmacologists and toxicologists. The selected examples demonstrate the role of structural data in the determination of absolute configuration, configurational flexibility and active-site topology for a reactive species. For example, the role of absolute stereochemistry in understanding synthetic pyrethroid structure-activity relationships is shown from analysis of their crystal structures; conformational flexibility among DDT analogues, and the importance of conformational and electronic properties in phenylalkanoic acid herbicides are shown from systematic analysis of their crystal structures; and interpretation of active-site stereochemistry is made by study of computer modeling of enzyme inhibitors in the active sites of related protein crystal structures. Thus, the observed patterns in conformational flexibility and their resultant effects on substrate pharmacological profile can be interpreted in understanding the molecular level events that influence biological reactivity. PMID:3905372

Cody, V

1985-01-01

446

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

447

Crystallographic structure and superconductive properties of Nb-Ti films with an artificially layered structure  

SciTech Connect

Artificially layered niobium-titanium (Nb-Ti) films with various thickness ratios (3/1--1/3) and periodicities (2--100 A) are made in an argon or in a mixed argon/nitrogen atmosphere by a dc magnetron sputtering method. Films with small periodicities (less than 30 A) have an artificial superlattice structure (ASL) with crystallographic coherence between constituent layers, where Nb and Ti grow epitaxially on the closest planes. The crystallographic structures of films are bcc with the (110) plane parallel to the film for films with the same or a thicker Nb layer than a Ti layer, and hcp with the (001) plane parallel to the film for films with a thinner Nb layer than a Ti layer. Films with large periodicities have an artificial superstructure (ASS) with only periodic stacking of constituent layers. Films deposited in the Ar/N atmosphere also have the artificially layered structures of ASL or ASS. The artificially layered structure is thermally stable at temperatures up to 500 {degree}C. The superconducting properties of the films depend strongly on the periodicity and thickness ratio of Nb and Ti layers. The dependence of the transition temperature on the periodicity and thickness ratio is qualitatively explained by a proximity effect with a three-region model. Films with periodicities less than 20 A, composed of the same or a thicker Nb layer than a Ti layer, show high transition temperatures (above 9.3 K). The highest {ital T}{sub {ital c}} of about 13.6 K is obtained in the film composed of monatomic layers of constituents deposited in an Ar atmosphere including 30 vol % N.

Sato, N. (SONY Corporation, Research Center, 7-35 Kitashinagawa-6, Shinagawa-ku, Tokyo 141, Japan (JP))

1990-06-15