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1

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

SciTech Connect

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

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

2001-10-05

2

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

3

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

4

Space Group Symmetry  

NSDL National Science Digital Library

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

5

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).

6

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

7

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

8

Affine extensions of non-crystallographic Coxeter groups induced by projection  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

9

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

10

Double antisymmetry and the rotation-reversal space groups.  

PubMed

Rotation-reversal symmetry was recently introduced to generalize the symmetry classification of rigid static rotations in crystals such as tilted octahedra in perovskite structures and tilted tetrahedra in silica structures. This operation has important implications for crystallographic group theory, namely that new symmetry groups are necessary to properly describe observations of rotation-reversal symmetry in crystals. When both rotation-reversal symmetry and time-reversal symmetry are considered in conjunction with space-group symmetry, it is found that there are 17,803 types of symmetry which a crystal structure can exhibit. These symmetry groups have the potential to advance understanding of polyhedral rotations in crystals, the magnetic structure of crystals and the coupling thereof. The full listing of the double antisymmetry space groups can be found in the supplementary materials of the present work and at http://sites.psu.edu/gopalan/research/symmetry/. PMID:24419168

VanLeeuwen, Brian K; Gopalan, Venkatraman; Litvin, Daniel B

2014-01-01

11

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

12

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.

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

2010-01-01

13

Crystallographic analysis of the NNA7 Fab and proposal for the mode of human blood-group recognition.  

PubMed

The NNA7 Fab antibody fragment recognizes the human N-type blood-group antigen comprised of the N-terminal glycopeptide of glycophorin A (GPA). A mutant form of this Fab fragment, NNA7-G91S, exhibits markedly reduced antigen binding. To provide insight into how these Fab fragments recognize this glycopeptide antigen, the crystal structures of NNA7 and NNA7-G91S were solved and refined to 1.83 and 1.97 A resolution, respectively. Both molecules are composed of the same heavy (H) chain Fd fragment, but each contains a slightly different light (L) chain owing to the G91S substitution. Specifically, the G91S mutation pushes the backbone of the neighboring H chain away from complementarity-determining region 3 (CDR3) of the L-chain variable region, allowing an additional glycerol cryoprotectant molecule to enter the antigen-combining site near the putative location of O-linked glycosylation. Each Fab fragment also possesses a well defined 2-(N-morpholino)ethanesulfonic acid (MES) molecule trapped in its antigen-combining site, as well as a crystallographic symmetry-related molecule comprising an amino-acid sequence that is virtually identical to the N-terminus of GPA. The MES molecule interacts with the H-chain CDR in a manner reminiscent of antibody-carbohydrate complexes. These results suggest a model for recognition of the glycopeptide antigen that accounts for the deleterious effect of the G91S substitution. PMID:16204891

Xie, Kefang; Song, Shuh Chyung; Spitalnik, Steven L; Wedekind, Joseph E

2005-10-01

14

Aeritalia Space Systems Group, Turin, Italy  

NASA Technical Reports Server (NTRS)

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

Donlan, Vincent

1989-01-01

15

Distribution of mica polytypes among space groups.  

NASA Technical Reports Server (NTRS)

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

Takeda, H.

1971-01-01

16

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

17

Fourier-Space Crystallography as Group Cohomology  

NASA Astrophysics Data System (ADS)

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

Rabson, David; Fisher, Benji

2001-03-01

18

Teaching Space Group Symmetry through Problems  

NASA Astrophysics Data System (ADS)

Symmetry in the solid state is often neglected in chemical education. Worked examples of high symmetry structures including NaCl, CaF2, K2SiF6, hexamethylenetetramine, and cubane help the student visualize space group symmetry. The student first determines the number of molecules or formula units per cell from the density and unit-cell dimensions. The numbers of atoms of each element are then compared with the numbers of equivalent general or special positions for the space group. Atoms are then placed in positions in the unit cell consistent with the geometry expected for the molecule or ion. References are then given to 11 other compounds suitable for this type of analysis.

Hardgrove, George L., Jr.

1997-07-01

19

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.

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

2014-01-01

20

Teaching Space Group Symmetry through Problems  

Microsoft Academic Search

Symmetry in the solid state is often neglected in chemical education. Worked examples of high symmetry structures including NaCl, CaF2, K2SiF6, hexamethylenetetramine, and cubane help the student visualize space group symmetry. The student first determines the number of molecules or formula units per cell from the density and unit-cell dimensions. The numbers of atoms of each element are then compared

George L. Hardgrove Jr.

1997-01-01

21

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

22

Crystallographic Topology 2: Overview and Work in Progress  

SciTech Connect

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

Johnson, C.K.

1999-08-01

23

The Space Shuttle Payload Planning Working Groups. Volume 2: Atmospheric and Space Physics.  

National Technical Information Service (NTIS)

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 enviro...

1973-01-01

24

The space shuttle payload planning working groups: Executive summaries  

NASA Technical Reports Server (NTRS)

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

1973-01-01

25

Crystallization of dienelactone hydrolase in two space groups: structural changes caused by crystal packing.  

PubMed

Dienelactone hydrolase (DLH) is a monomeric protein with a simple ?/?-hydrolase fold structure. It readily crystallizes in space group P212121 from either a phosphate or ammonium sulfate precipitation buffer. Here, the structure of DLH at 1.85?Å resolution crystallized in space group C2 with two molecules in the asymmetric unit is reported. When crystallized in space group P212121 DLH has either phosphates or sulfates bound to the protein in crucial locations, one of which is located in the active site, preventing substrate/inhibitor binding. Another is located on the surface of the enzyme coordinated by side chains from two different molecules. Crystallization in space group C2 from a sodium citrate buffer results in new crystallographic protein-protein interfaces. The protein backbone is highly similar, but new crystal contacts cause changes in side-chain orientations and in loop positioning. In regions not involved in crystal contacts, there is little change in backbone or side-chain configuration. The flexibility of surface loops and the adaptability of side chains are important factors enabling DLH to adapt and form different crystal lattices. PMID:25005082

Porter, Joanne L; Carr, Paul D; Collyer, Charles A; Ollis, David L

2014-07-01

26

Mappings of homogeneous groups and imbeddings of functional spaces  

Microsoft Academic Search

Varying the functional space ~, we obtain each time a new problem (see [2-7], where one has considered several characteristic cases of isotropic spaces of differentiab!e functions). In this paper we investigate a similar problem for functional spaces, defined on an arbitrary homogeneous group. Model examples are the fundamental anisotropic spaces of differentiable functions. The corresponding mappings have qualitative new

S. K. Vodop'yanov

1989-01-01

27

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

28

The Space Shuttle Payload Planning Working Groups. Volume 10: Space Technology.  

National Technical Information Service (NTIS)

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) phy...

1973-01-01

29

Computations in isometry groups of finite metric spaces  

Microsoft Academic Search

A meaningful analysis of the structure or properties of a finite metric space requires using its isometry group. This is the group of permutations on the set of points in the space that preserves the binary relations {open_quotes}the points x and y are at a given distance from one another.{close_quotes} The theory of isometry groups of finite metric spaces is

A. G. Ganyushkin; V. I. Sushchanskii; V. V. Tsvirkunov

1995-01-01

30

The Space Shuttle Payload Planning Working Groups: Executive Summaries.  

National Technical Information Service (NTIS)

The findings of a space shuttle payload planning group session are presented. The purpose of the workshop is: (1) to provide guidance for the design and development of the space shuttle and the spacelab and (2) to plan a space science and applications pro...

1973-01-01

31

The International Space Life Sciences Strategic Planning Working Group  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

32

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

33

The Space Shuttle Payload Planning Working Groups: Volume 9: Materials Processing and Space Manufacturing.  

National Technical Information Service (NTIS)

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 an...

1973-01-01

34

Group theoretical construction of planar noncommutative phase spaces  

NASA Astrophysics Data System (ADS)

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

Ngendakumana, Ancille; Nzotungicimpaye, Joachim; Todjihoundé, Leonard

2014-01-01

35

World Database of Crystallographers  

NSDL National Science Digital Library

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

36

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

PubMed

Human salivary alpha-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 alpha-1,4-glucosidic linkages in oligosaccharides. To date, all published crystal structures of HSA have been crystallized as monomers in space group P2(1)2(1)2(1). 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 alpha-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 A, beta = 102.8 degrees. The NCS dimer crystal structure is reported to 3.0 A resolution, with a refined Rcryst of 0.228. The structure is compared with the previously reported P2(1)2(1)2(1) 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

2006-02-01

37

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

38

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

39

Environmental interactions in space exploration: 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 heretofore unattempted 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 was established as part of the Robotic Missions Working Group. The working group is described, and its current activities are updated.

Kolecki, Joseph C.; Hillard, G. Barry

1992-01-01

40

The origin of space group violations in a lunar orthopyroxene  

NASA Astrophysics Data System (ADS)

The space group of an orthopyroxene (En86) from a deep crustal lunar rock (sample 76535) that was previously reported as having space group P21 ca has been re-examined on an automated X-ray diffractometer. In addition to diffractions violating the b-glide of the conventional space group, Pbca (0kl,k-odd) reported in the earlier study, diffractions violating the a-glide of Pbca are also present. Careful examination of both the a-glide- and b-glide-violations shows them to be sharp, with no evidence of diffuse streaks parallel to a *, and with consistent intensities at several rotations about ?. Diffractions violating the b-glide are in registry with the host, however, those violating the a-glide appear to be out of registry and result from a cell with a slightly longer a of about 18.4 Å, consistent with previous electron diffraction studies. The most reasonable explanation for the observed space group violations is that both the a- and b-glide violations result from ordering of Ca into (100) Guinier-Preston (G-P) zones that possess orthopyroxene topology, but have space group P21/c and a cell of a=18.4 Å, b=8.83 Å, c=5.18 Å, and ?=90.0°; whereas the Cadepleted host has space group Pbca and a cell of a= 18.230(6) Å, b = 8.828(2) Å, and c=5.1946(9) Å. In addition to the G-P zones which may compose 12% or more of the sample, the crystal contains (100) lamellae of pigeonite, and other samples from the same rock contain lamellae of augite.

Smyth, Joseph R.; Swope, R. Jeffrey

1990-12-01

41

Radiological Protection in Space: Indication from the ICRP Task Group  

NASA Astrophysics Data System (ADS)

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

Dietze, Günther

42

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

43

Real-space parallel density matrix renormalization group  

NASA Astrophysics Data System (ADS)

We demonstrate how to parallelize the density matrix renormalization group (DMRG) algorithm in real space through a straightforward modification of serial DMRG. This makes it possible to apply at least an order of magnitude more computational power to challenging simulations, greatly accelerating investigations of two-dimensional systems and large parameter spaces. We discuss details of the algorithm and present benchmark results including a study of valence-bond-solid order within the square-lattice Q2 model and Néel order within the triangular lattice Heisenberg model. The parallel DMRG algorithm also motivates an alternative canonical form for matrix product states.

Stoudenmire, E. M.; White, Steven R.

2013-04-01

44

System theory on group manifolds and coset spaces.  

NASA Technical Reports Server (NTRS)

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

Brockett, R. W.

1972-01-01

45

Dynamical real space renormalization group applied to sandpile models.  

PubMed

A general framework for the renormalization group analysis of self-organized critical sandpile models is formulated. The usual real space renormalization scheme for lattice models when applied to nonequilibrium dynamical models must be supplemented by feedback relations coming from the stationarity conditions. On the basis of these ideas the dynamically driven renormalization group is applied to describe the boundary and bulk critical behavior of sandpile models. A detailed description of the branching nature of sandpile avalanches is given in terms of the generating functions of the underlying branching process. PMID:11969882

Ivashkevich, E V; Povolotsky, A M; Vespignani, A; Zapperi, S

1999-08-01

46

Crystallographic CourseWare  

NASA Astrophysics Data System (ADS)

Literature Cited

  1. International Tables for Crystallography: Volume A: Space Group Symmetry; Hanh, T., Ed.; D. Reidel: Boston, 1983.
  2. International Tables for Crystallography, Brief Teaching Edition of Volume A, Space-Group Symmetry, 3rd ed.; Hanh, T., Ed.; Dordrecht: Boston, 1993.
  3. Kastner, M. E. J. Appl. Crystallogr. 1999, 32, 327-331.
  4. Macromedia Director, version 6.5; Macromedia, Inc., San Francisco, CA; 1998.
  5. QuickTime, version 3.0; Apple Computer: Cupertino, CA, 1998.
  6. ToolBook II, Instructor, version 6.0; Asymetrix: Bellevue, WA, 1998.
  7. HyperCard 2.3.5; Apple Computer: Cupertino, CA, 1998.

Kastner, Margaret E.; Vasbinder, Eric; Kowalcyzk, Deborah; Jackson, Sean; Giammalvo, Joseph; Braun, James; Dimarco, Keith

2000-09-01

47

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

SciTech Connect

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

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

2010-07-20

48

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

49

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

PubMed

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

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

2002-09-01

50

The Space Shuttle Payload Planning Working Groups. Volume 1: Astronomy.  

National Technical Information Service (NTIS)

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 tele...

1973-01-01

51

Report of the Working Group on Space/Lunar Tradeoffs  

NASA Technical Reports Server (NTRS)

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

1992-01-01

52

Various cross-reactivity of the grass pollen group 4 allergens: crystallographic study of the Bermuda grass isoallergen Cyn d 4.  

PubMed

The structure of Cyn d 4, the group 4 allergen from Bermuda grass, is reported at 2.15 Å resolution and is the first crystal structure of a naturally isolated pollen allergen. A conserved N-terminal segment that is only present in the large isoallergens forms extensive interactions with surrounding residues and hence greatly enhances the structural stability of the protein. Cyn d 4 contains an FAD cofactor that is covalently linked to His88 and Cys152. To date, all identified bicovalent flavoproteins are oxidases and their substrates are either sugars or secondary metabolites. A deep large hydrophobic substrate-binding cleft is present. Thus, Cyn d 4 may be an oxidase that is involved in the biosynthesis of a pollen-specific metabolite. Cyn d 4 shares ~70% sequence identity with the Pooideae group 4 allergens. Various cross-reactivities between grass pollen group 4 allergens have previously been demonstrated using sera from allergic patients. The protein surface displays an unusually large number of positively charged clusters, reflecting the high pI of ~10. 38 decapeptides that cover the solvent-accessible sequences did not show any significant IgE-binding activity using sera with high Cyn d 4 reactivity from four patients, suggesting that the IgE epitopes of Cyn d 4 are predominantly conformational in nature. Several group 4 structures were then modelled and their potential cross-reactive and species-specific IgE epitopes were proposed. PMID:22993084

Huang, Tse-Hao; Peng, Ho-Jen; Su, Song-Nan; Liaw, Shwu-Huey

2012-10-01

53

Improved low-resolution crystallographic refinement with Phenix and Rosetta.  

PubMed

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

2013-11-01

54

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.

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

2007-01-01

55

Metricization of Thermodynamic State Space and the Renormalization Group.  

National Technical Information Service (NTIS)

After introducing a suitable Riemannian metric in thermodynamic state space, with a simple statistical thermodynamic interpretation, the authors suggest that the existence of scaling must imply the existence of a conformal Killing vector field in the neig...

L. Diosi G. Forgacs B. Lukacs H. L. Frisch

1983-01-01

56

The Space Shuttle Payload Planning Working Groups. Volume 8: Earth and Ocean Physics.  

National Technical Information Service (NTIS)

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 physic...

1973-01-01

57

Working Group 2 Summary:. Space Charge Effects in Bending Systems  

NASA Astrophysics Data System (ADS)

Participants in Working Group 2 included: Y. Batygin, C. Bohn, B. Carlsten, J. Ellison, P. Emma, Z. Huang, A. Kabel, R. Kishek, R. Li, P. Musumeci, S. Nagaitsev, J. Qiang, M. Reiser, A. Ruggerio, R. Warnock, and M. Zeitlin.

Bohn, Courtlandt L.; Emma, Paul J.

2000-12-01

58

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

59

The Space Shuttle Payload Planning Working Groups. Volume 6: Communications and Navigation.  

National Technical Information Service (NTIS)

The findings of the Communications and Navigation working group of the space shuttle payload planning activity are presented. The basic goals to be accomplished are to increase the use of space systems and to develop new space capabilities for providing c...

1973-01-01

60

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

61

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

SciTech Connect

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

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

1995-03-01

62

Algebraic loop groups and moduli spaces of bundles  

Microsoft Academic Search

.   We study algebraic loop groups and affine Grassmannians in positive characteristic. The main results are normality of Schubert-varieties,\\u000a the construction of line-bundles on the affine Grassmannian, and the proof that they induce line-bundles on the moduli-stack\\u000a of torsors.

Gerd Faltings

2003-01-01

63

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

64

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

NASA Technical Reports Server (NTRS)

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

1973-01-01

65

Exploration of the Chemical Space of Group 4 Polymer Dielectrics  

NASA Astrophysics Data System (ADS)

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

Wang, Chenchen; Pilania, Ghanshyam; Ramprasad, Rampi

2013-03-01

66

MCMC-Particle-based group tracking of space objects within Bayesian framework  

NASA Astrophysics Data System (ADS)

With the intense increase in space objects, especially space debris, it is necessary to efficiently track and catalog the extensive dense clusters of space objects. As the main instrument for low earth orbit (LEO) space surveillance, ground-based radar system is usually limited by its resolution while tracking small space debris with high density. Thus, the obtained measurement information could have been seriously missed, which makes the traditional tracking method inefficient. To address this issue, we conceived the concept of group tracking. For group tracking, the overall tendency of the group objects is expected to be revealed, and the trajectories of individual objects are simultaneously reconstructed explicitly. According to model the interaction between the group center and individual trajectories using the Markov random field (MRF) within Bayesian framework, the objects' number and individual trajectory can be estimated more accurately in the condition of high miss alarm probability. The Markov chain Monte Carlo (MCMC)-Particle algorithm was utilized for solving the Bayesian integral problem. Furthermore, we introduced the mechanism for describing the behaviors of groups merging and splitting, which can expand the single group tracking algorithm to track variable multiple groups. Finally, simulation of the group tracking of space objects was carried out to validate the efficiency of the proposed method.

Huang, Jian; Hu, Weidong

2014-01-01

67

Concise tables of James numbers and some homotopy of classical Lie groups and associated homogeneous spaces  

Microsoft Academic Search

The following tables express the James numbers and homotopy groups of the homogeneous spaces involved in the Bott maps, with the exception of the Grassmann manifolds, in as concise a manner as we know, consistant with displaying the various periodicities involved. Throughout the tables of groups c~ has been used to represent the infinite cyclic group Z, and an integer

ALBERT T. LUNDELL

68

Group theoretical quantization and the example of a phase space S1×R+  

Microsoft Academic Search

The group theoretical quantization scheme is reconsidered by means of elementary systems. Already the quantization of a particle on a circle shows that the standard procedure has to be supplemented by an additional condition on the admissibility of group actions. A systematic strategy for finding admissible group actions for particular subbundles of cotangent spaces is developed, two-dimensional prototypes of which

Martin Bojowald; Thomas Strobl

2000-01-01

69

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

Microsoft Academic Search

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

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

2010-01-01

70

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

PubMed

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

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

2013-10-01

71

Space Group of Beta-Ga203, Its Morphology, and Unusual Twinning.  

National Technical Information Service (NTIS)

Evidence is presented that the space group of beta-Ga2O3 is P1, although, metrically, the lattice is strictly monoclinic. The morphology is described and examples of twinning are given, including several that are unusual. (Author)

A. B. Chase G. M. Wolten

1973-01-01

72

The Space Shuttle Payload Planning Working Groups. Volume 7: Earth Observations.  

National Technical Information Service (NTIS)

The findings of the Earth Observations working group of the space shuttle payload planning activity are presented. The objectives of the Earth Observation experiments are: (1) establishment of quantitative relationships between observable parameters and g...

1973-01-01

73

The Space Shuttle Payload Planning Working Groups. Volume 5: Solar Physics.  

National Technical Information Service (NTIS)

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 ...

1973-01-01

74

The Space Shuttle Payload Planning Working Groups. Volume 4: Life Sciences.  

National Technical Information Service (NTIS)

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 ...

1973-01-01

75

Interrelationship Between Anisotropy and Crystallographic Structure.  

National Technical Information Service (NTIS)

The variations in normal and planar anisotropy in rolled metal products are shown to be functions of crystallographic structure. Each type (cubic and hexagonal) of crystallographic structure exhibits a characteristic strain ratio versus orientation curve....

R. M. Colton G. J. Enyedy

1965-01-01

76

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

Microsoft Academic Search

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

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

2006-01-01

77

The Space Shuttle Payload Planning Working Groups. Volume 3: High Energy Astrophysics.  

National Technical Information Service (NTIS)

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 astr...

1973-01-01

78

Internet Based Open Access Crystallographic Databases  

Microsoft Academic Search

Two freely accessible crystallographic databases are discussed: the Crystallographic Open Database (COD, http:\\/\\/crystallography.net) which contains over 37,000 crystal structures, and the Nano-Crystallography Database (NCD, http:\\/\\/nanocrystallography.research.pdx.edu) which we recently started to support image-based nanocrystallography and (nano) materials science education. Both databases collect crystallographic relevant information in a standardized format; the Crystallographic Information File (CIF). CIF is the standard file format adopted

Girish Upreti; Bjoern Seipel; Morgan Harvey; Will Garrick; Peter Moeck

2006-01-01

79

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

Microsoft Academic Search

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

Massimiliano Berti; Michela Procesi

2011-01-01

80

Environmental complexity and group size: Immediate effects on use of space by domestic fowl  

Microsoft Academic Search

Current housing conditions for domestic fowl (Gallus gallus domesticus) offer little in the way of environmental features biologically relevant to the birds. More specifically there is a notable absence of protective cover, a fundamental element that influences how domestic fowl use space. The availability of cover could be more relevant to small, as opposed to larger groups, because large groups

Erin Hoerl Leone; Inma Estevez; Mary Catherine Christman

2007-01-01

81

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

National Technical Information Service (NTIS)

We discuss the relation between space-time renormalization group equation for closed string field theory and world-sheet renormalization group equation for first-quantized strings. Restricting our attention to massless states we argue that there is a one-...

R. Brustein K. Roland

1991-01-01

82

Fourier multiplier theorem for atomic Hardy spaces on unbounded Vilenkin groups  

Microsoft Academic Search

We characterize atomic Hardy spaces on unbounded locally compact Vilenkin groups by means of a modified maximal function. The obtained Fourier multiplier theorem is more general than the corresponding results due to Kitada, Onneweer and Quek, Daly and Phillips that were proved under the boundedness assumption on the underlying group.

M. Avdispahi?; N. Memi?

2010-01-01

83

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

84

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

NASA Technical Reports Server (NTRS)

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

Roberts, Barry C.; Batts, Wade

1997-01-01

85

Group Theoretical Quantization and the Example of a Phase Space S^1 x R^+  

Microsoft Academic Search

The group theoretical quantization scheme is reconsidered by means of\\u000aelementary systems. Already the quantization of a particle on a circle shows\\u000athat the standard procedure has to be supplemented by an additional condition\\u000aon the admissibility of group actions. A systematic strategy for finding\\u000aadmissible group actions for particular subbundles of cotangent spaces is\\u000adeveloped, two-dimensional prototypes of which

Martin Bojowald; Thomas Strobl

1999-01-01

86

An aluminophosphate molecular sieve with 36 crystallographically distinct tetrahedral sites.  

PubMed

The structure of the new medium-pore aluminophosphate molecular sieve PST-6 is determined by the combined use of rotation electron diffraction tomography, synchrotron X-ray powder diffraction, and computer modeling. PST-6 was prepared by calcination of another new aluminophosphate material with an unknown structure synthesized using diethylamine as a structure-directing agent, which is thought to contain bridging hydroxy groups. PST-6 has 36 crystallographically distinct tetrahedral sites in the asymmetric unit and is thus crystallographically the most complex zeolitic structure ever solved. PMID:24862164

Lee, Jun Kyu; Turrina, Alessandro; Zhu, Liangkui; Seo, Seungwan; Zhang, Daliang; Cox, Paul A; Wright, Paul A; Qiu, Shilun; Hong, Suk Bong

2014-07-14

87

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

88

On the space group of MgAl2O4 spinel  

Microsoft Academic Search

[001] electron diffraction patterns of MgAl2O4 spinel show (hk0) reflections with h + k = 4n + 2 ((200), (420), etc.) that violate the accepted Fd3m space group of this material. Since these ‘forbidden’ reflections cannot be attributed to double diffraction, non-zero Laue zones, or a second phase, this result is consistent with Grimes' recent suggestion that the correct space

L. Hwang; A. H. Heuer; T. E. Mitchell

1973-01-01

89

P-SPACE: A program for simulating spatial behavior in small groups  

Microsoft Academic Search

P-SPACE is a computer program that simulates spatial behavior in a small group of individuals. The program describes how interpersonal\\u000a distances change through time as a result of changes in microlevel features, such as the minimization of local dissatisfaction.\\u000a Agents are located in a two-dimensional lattice and can move some discrete space units at each discrete time unit within their

Vicenç Quera; Antoni Solanas; LLUíS SALAFRANCA; Francesc S. Beltran; Salvador Herrando

2000-01-01

90

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

PubMed

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

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

2009-05-19

91

'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

92

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

PubMed Central

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

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

2012-01-01

93

Space and Naval Warfare Systems Command Preparations for Year 2000 Battle Group Systems Integration Testing.  

National Technical Information Service (NTIS)

The overall audit objective was to evaluate whether the Space and Naval Warfare Systems Command effectively prepared for the U.S.S. Constellation Battle Group Systems Integration Testing for the year 2000 impact and to make recommendations for improving f...

1999-01-01

94

On the Space Group of MgAl2O4 Spinel.  

National Technical Information Service (NTIS)

(0001) electron diffraction patterns of MgAl2O4 spinel show (hk0) reflections with h + k = 4n + 2 ((200), (420), etc.) that violate the accepted Fd3m space group of this material. Since these 'forbidden' reflections cannot be attributed to double diffract...

L. Hwang A. H. Heuer T. E. Mitchell

1973-01-01

95

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

96

Real-space renormalisation group approach for linear and branched polymers  

Microsoft Academic Search

A real-space renormalisation group (RG) approach for polymers is presented and is used to calculate the exponent v for the radius of gyration of three types of molecules on a square lattice. In all three cases the excluded volume effect is taken into account. The three cases studied are linear polymers, randomly branched polymers without loops and randomly branched polymers

F. Family

1980-01-01

97

Vertically extended Frenkel-Kontorova model: A real space renormalization group study  

SciTech Connect

A modification of the Frenkel-Kontorova model is presented in which particles are allowed to move in the vertical direction. This model is used to study the formation of islands for a monolayer of 1D interfaces and the corresponding roughness transition. Both analytical and numerical approaches are employed, and the numerical algorithm is based upon real space renormalization group techniques.

Rodriguez-Laguna, Javier [Departamento Fisica Teorica, Universidad Complutense de Madrid, Madrid (Spain); Santalla, Silvia N. [Departamento de Fisica, Universidad Carlos III de Madrid, Leganes (Spain)

2005-09-15

98

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...

99

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

100

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

101

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

102

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

103

Crystallization and preliminary X-ray crystallographic studies of dipeptidyl aminopeptidase BII from Pseudoxanthomonas mexicana WO24.  

PubMed

Dipeptidyl aminopeptidase BII from Pseudoxanthomonas mexicana WO24 (DAP BII) is able to cleave a variety of dipeptides from the amino-terminus of substrate peptides. For crystallographic studies, DAP BII was overproduced in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. X-ray diffraction data to 2.3 Å resolution were collected using an orthorhombic crystal form belonging to space group P2(1)2(1)2(1), with unit-cell parameters a = 76.55, b = 130.86, c = 170.87 Å. Structural analysis by the multi-wavelength anomalous diffraction method is in progress. PMID:24637761

Sakamoto, Yasumitsu; Suzuki, Yoshiyuki; Iizuka, Ippei; Tateoka, Chika; Roppongi, Saori; Okada, Hirofumi; Nonaka, Takamasa; Morikawa, Yasushi; Nakamura, Kazuo T; Ogasawara, Wataru; Tanaka, Nobutada

2014-02-01

104

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

PubMed Central

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

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

2011-01-01

105

Purification, crystallization and preliminary crystallographic analysis of the CBS-domain protein MJ1004 from Methanocaldococcus jannaschii  

PubMed Central

The purification and preliminary crystallographic analysis of the archaeal CBS-domain protein MJ1004 from Methanocaldococcus jannaschii are described. The native protein was overexpressed, purified and crystallized in the monoclinic space group P21, with unit-cell parameters a = 54.4, b = 53.8, c = 82.6?Å, ? = 106.1°. The crystals diffracted X-rays to 2.7?Å resolution using synchrotron radiation. Matthews-volume calculations suggested the presence of two molecules in the asymmetric unit that are likely to correspond to a dimeric species, which is also observed in solution.

Oyenarte, Iker; Lucas, Maria; Gomez Garcia, Inmaculada; Martinez-Cruz, Luis Alfonso

2011-01-01

106

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

107

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

NASA Technical Reports Server (NTRS)

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

1973-01-01

108

Seitz symbols for crystallographic symmetry operations.  

PubMed

The aim of this report is to describe the Seitz notation for symmetry operations adopted by the Commission on Crystallographic Nomenclature as the standard convention for Seitz symbolism of the International Union of Crystallography. The established notation follows the existing crystallographic conventions in the descriptions of symmetry operations. PMID:24815978

Glazer, A Michael; Aroyo, Mois I; Authier, André

2014-05-01

109

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

110

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

PubMed Central

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 P6122 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.

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

2012-01-01

111

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

112

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

SciTech Connect

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

Chu, Chong-Sun; Zumino, B.

1995-01-24

113

Internet Based Open Access Crystallographic Databases  

NASA Astrophysics Data System (ADS)

Two freely accessible crystallographic databases are discussed: the Crystallographic Open Database (COD, http://crystallography.net) which contains over 37,000 crystal structures, and the Nano-Crystallography Database (NCD, http://nanocrystallography.research.pdx.edu) which we recently started to support image-based nanocrystallography and (nano) materials science education. Both databases collect crystallographic relevant information in a standardized format; the Crystallographic Information File (CIF). CIF is the standard file format adopted by the International Union of Crystallography (http://iucr.org) for the archiving and distribution of crystallographic information. A subset of the COD, the Predicted Crystallographic Online Database, allows for 3D structural displays of structural polyhedra and wireframes of approximately 2,600 entries. Since electron microscopist are interested in simple, yet technologically important materials, the crystallographic information for those materials will be included in our database. At our NCD site, entries in the COD and the NCD can be visualized in three dimensions (3D) along with (2D) lattice fringe fingerprints plots. The latter supports the identification of unknown nanocrystal phases from high-resolution transmission electron microscopy (HRTEM) images. Morphological crystal information from the database ``Bestimmungstabellen f"ur Kristalle/ ???????????? ??????????,'' (A.K. Boldyrew and W.W. Doliwo-Dobrowolsky, Zentrales Wissenschaftlichers Institute der Geologie und Sch"urfung, Leningrad/ Moscow, 1937/1939) will also be included in the NCD to support image-based nanocrystallography in 3D.

Upreti, Girish; Seipel, Bjoern; Harvey, Morgan; Garrick, Will; Moeck, Peter

2006-05-01

114

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

115

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

PubMed Central

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

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

2010-01-01

116

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.

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

2010-01-01

117

Expression, purification, crystallization and preliminary X-ray crystallographic analysis of human ?-galactosidase  

PubMed Central

?-d-Galactosidase (?-Gal) is an exoglycosidase that cleaves ?-galactosides from glycoproteins, sphingolipids and keratan sulfate. This study reports the expression, purification, crystallization and preliminary X-ray crystallographic analysis of human lysosomal ?-Gal. The sitting-drop vapour-diffusion method was used to crystallize ?-Gal in complexes with its product galactose and with the inhibitor 1-deoxygalactonojirimycin. The resulting crystals were isomorphous and belonged to space group P21. The crystals of the ?-Gal–galactose and the ?-Gal–inhibitor complexes had unit-cell parameters a = 94.8, b = 116.1, c = 140.3?Å, ? = 92.2° and a = 94.8, b = 116.0, c = 140.3?Å, ? = 92.2°, respectively. Diffraction data were collected to 1.8?Å resolution for both crystals.

Usui, Kimihito; Ohto, Umeharu; Ochi, Toshinari; Shimizu, Toshiyuki; Satow, Yoshinori

2012-01-01

118

Crystallization and preliminary X-ray crystallographic studies of DnaJ from Streptococcus pneumoniae.  

PubMed

DnaJ, cooperating with DnaK and GrpE, promotes the folding of unfolded hydrophobic polypeptides, dissociates protein complexes and translocates protein across membranes. Additionally, DnaJ from Streptococcus pneumoniae (SpDnaJ) is involved in the infectious disease process and is being developed as a potential vaccine to prevent bacterial infection. Here the expression, purification, crystallization and preliminary crystallographic analysis of SpDnaJ are reported. The crystals belong to space groups I222 or I2?2?2? and the diffraction resolution is 3.0?Å with unit-cell parameters a=47.68, b=104.45, c=234.57?Å. The crystal most likely contains one molecule in the asymmetric unit, with a VM value of 3.24?Å3?Da(-1) and a solvent content of 62.1%. PMID:23519801

Zhao, Shasha; Jin, Li; Niu, Siqiang; Yang, Wei; Zhang, Shaocheng; Guo, Zhen; Zhang, Hongpeng; Huang, Ailong; Yin, Yibing; Wang, Deqiang

2013-03-01

119

Crystallographic, Ferroelectric and Electronic Properties of the Sr2ZrTiO6 Double Perovskite  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

120

NIST Crystallographic Databases for Research and Analysis.  

National Technical Information Service (NTIS)

The NIST Crystal and Electron Diffraction Data Center builds a comprehensive database with evaluated chemical, physical, and crystallographic information on all types of well-characterized substances. The data are evaluated and standardized by specially d...

A. D. Mighell V. L. Karen

1996-01-01

121

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

SciTech Connect

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

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

2008-01-01

122

Finiteness of the number of arithmetic groups generated by reflections in Lobachevsky spaces  

NASA Astrophysics Data System (ADS)

After results of the author (1980, 1981) and Vinberg (1981), the finiteness of the number of maximal arithmetic groups generated by reflections in Lobachevsky spaces remained unknown in dimensions 2\\le n\\le 9 only. It was proved recently (2005) in dimension 2 by Long, Maclachlan and Reid and in dimension 3 by Agol. Here we use the results in dimensions 2 and 3 to prove the finiteness in all remaining dimensions 4\\le n\\le 9. The methods of the author (1980, 1981) are more than sufficient for this using a very short and very simple argument.

Nikulin, V. V.

2007-02-01

123

A Fun and Effective Exercise for Understanding Lattices and Space Groups  

NSDL National Science Digital Library

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

Perkins, Dexter

124

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

125

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

126

Local Group and Star Cluster Dynamics from HSTPROMO: The Hubble Space Telescope Proper Motion Collaboration  

NASA Astrophysics Data System (ADS)

The Hubble Space Telescope (HST) has proven to be uniquely suited for the measurement of proper motions (PMs) of stars and galaxies in the nearby Universe. Here we summarize the main results and ongoing studies of the HSTPROMO collaboration, which over the past decade has executed some two dozen observational and theoretical HST projects on this topic. This is continuing to revolutionize our dynamical understanding of many objects, including: globular clusters; young star clusters; stars and stellar streams in the Milky Way halo; Local Group galaxies, including dwarf satellite galaxies, the Magellanic Clouds, and the Andromeda galaxy; and AGN black hole Jets.

van der Marel, R. P.; Anderson, J.; Bellini, A.; Besla, G.; Bianchini, P.; Boylan-Kolchin, M.; Chaname, J.; Deason, A.; Do, T.; Guhathakurta, P.; Kallivayalil, N.; Lennon, D.; Massari, D.; Meyer, E.; Platais, I.; Sabbi, E.; Sohn, S. T.; Soto, M.; Trenti, M.; Watkins, L.

2014-03-01

127

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.

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

2012-01-01

128

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

PubMed

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

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

2013-09-21

129

Real-space renormalization group method for quantum 1/2 spins on the pyrochlore lattice.  

PubMed

A simple phenomenological real-space renormalization group method for quantum Heisenberg spins with nearest and next nearest neighbour interactions on a pyrochlore lattice is presented. Assuming a scaling law for the order parameter of two clusters of different sizes, a set of coupled equations that gives the fixed points of the renormalization group transformation and, thus, the critical temperatures and ordered phases of the system is found. The particular case of spins 1/2 is studied in detail. Furthermore, to simplify the mathematical details, from all the possible phases arising from the renormalization group transformation, only those phases in which the magnetic lattice is commensurate with a subdivision of the crystal lattice into four interlocked face-centred cubic sublattices are considered. These correspond to a quantum spin liquid, ferromagnetic order, or non-collinear order in which the total magnetic moment of a tetrahedral unit is zero. The corresponding phase diagram is constructed and the differences with respect to the classical model are analysed. It is found that this method reproduces fairly well the phase diagram of the pyrochlore lattice under the aforementioned constraints. PMID:24625859

Garcia-Adeva, Angel J

2014-04-01

130

Low orthopyroxene from a lunar deep crustal rock - A new pyroxene polymorph of space group P21ca  

NASA Technical Reports Server (NTRS)

Bronzite crystals (En86Fs11Wo3) from a slowly-cooled lunar troctolitic granulite, have space group P21ca, a postulated, but previously unreported space group. Diffractions violating the b-glide extinction conditions have been observed in long-exposure X-ray precession photographs from three of these crystals and on an automated X-ray diffractometer. P21ca is a subgroup of the common orthopyroxene space group Pbca, and its cell dimensions (a = 18.235 plus or minus 0.004 A, b = 8.831 plus or minus 0.002 A, c = 5.189 plus or minus 0.001 A) are similar to those of terrestrial bronzites. It is postulated that the lower symmetry space group has developed as a result of very slow cooling at pressures of one to two kilobars deep in the lunar crust.

Smyth, J. R.

1974-01-01

131

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

132

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

133

Fractal space-times under the microscope: a renormalization group view on Monte Carlo data  

NASA Astrophysics Data System (ADS)

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

Reuter, Martin; Saueressig, Frank

2011-12-01

134

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

SciTech Connect

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

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

1997-05-23

135

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.

Johnson, John E.

2013-01-01

136

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

NASA Technical Reports Server (NTRS)

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

1983-01-01

137

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

138

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

139

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

ERIC Educational Resources Information Center

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

Pearce, Jane; Crouch, Christopher

2010-01-01

140

Handling cell errors in crystallographic data  

Microsoft Academic Search

Recent developments in crystallographic error analysis are described. This report provides an introduction to more-formal work, originally published in Ref. (Haestier, J., J. Appl. Cryst. 2009, 42, 798). Prior to the main discussion, a brief overview of the normal distribution and error-propagation is provided, with some simplified examples to demonstrate the effects of covariance terms on error calculations. A new

James Haestier

2010-01-01

141

Graphene Nanoribbons with Crystallographically-Orientated Edges  

Microsoft Academic Search

When graphene is confined to a nanoribbon a transport gap is opened which allows for field effect transistor operation. Such graphene nanoribbon FETs have been demonstrated, but are thought to be dominated by edge disorder and hence operate far from the the intrinsic regime. We present graphene devices with nanoribbons defined by crystallographically-orientated edges. The devices are formed by Ni

Javier Sanchez-Yamagishi; Ken van Tilburg; Vitor Manfrinato; Leonardo Campos; Karl Bergerren; Pablo Jarillo-Herrero

2010-01-01

142

Crystallographic R Factor Refinement by Molecular Dynamics  

Microsoft Academic Search

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

Axel T. Brunger; John Kuriyan; Martin Karplus

1987-01-01

143

Gas and dust in the beta Pictoris moving group as seen by the Herschel Space Observatory  

NASA Astrophysics Data System (ADS)

Context. Debris discs are thought to be formed through the collisional grinding of planetesimals, and then can be considered as the outcome of planet formation. Understanding the properties of gas and dust in debris discs can help us comprehend the architecture of extrasolar planetary systems. Herschel Space Observatory far-infrared (IR) photometry and spectroscopy have provided a valuable dataset for the study of debris discs gas and dust composition. This paper is part of a series of papers devoted to the study of Herschel-PACS observations of young stellar associations. Aims: This work aims at studying the properties of discs in the beta Pictoris moving group (BPMG) through far-IR PACS observations of dust and gas. Methods: We obtained Herschel-PACS far-IR photometric observations at 70, 100, and 160 ?m of 19 BPMG members, together with spectroscopic observations for four of them. These observations were centred at 63.18 ?m and 157 ?m, aiming to detect [OI] and [CII] emission. We incorporated the new far-IR observations in the SED of BPMG members and fitted modified blackbody models to better characterise the dust content. Results: We have detected far-IR excess emission towards nine BPMG members, including the first detection of an IR excess towards HD 29391.The star HD 172555, shows [OI] emission, while HD 181296 shows [CII] emission, expanding the short list of debris discs with a gas detection. No debris disc in BPMG is detected in both [OI] and [CII]. The discs show dust temperatures in the range 55-264 K, with low dust masses (<6.6 × 10-5 M? to 0.2 M?) and radii from blackbody models in the range 3 to ~82 AU. All the objects with a gas detection are early spectral type stars with a hot dust component. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Riviere-Marichalar, P.; Barrado, D.; Montesinos, B.; Duchêne, G.; Bouy, H.; Pinte, C.; Menard, F.; Donaldson, J.; Eiroa, C.; Krivov, A. V.; Kamp, I.; Mendigutía, I.; Dent, W. R. F.; Lillo-Box, J.

2014-05-01

144

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

SciTech Connect

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

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

2009-03-16

145

X-ray crystallographic, scanning microprobe X-ray diffraction, and cross-polarized/magic angle spinning 13C NMR studies of the structure of cellulose III(II).  

PubMed

The X-ray crystallographic structure of cellulose III(II) is characterized by disorder; the unit cell (space group P2(1); a = 4.45 A, b = 7.64 A, c = 10.36 A, alpha = beta = 90 degrees, gamma = 106.96 degrees) is occupied by one chain that is the average of statistically disordered antiparallel chains. 13C CP/MAS NMR studies reveal the presence of three distinct molecular conformations that can be interpreted as a mixture of two different crystal forms, one equivalent to cellulose III(I), and another with two independent glucosyl conformations in the asymmetric unit. Both X-ray crystallographic and 13C NMR spectroscopic results are consistent with an aggregated microdomain structure for cellulose III(II). This structure can be generated from a new crystal form (space group P2(1); a = 4.45 A, b = 14.64 A, c = 10.36 A, alpha = beta = 90 degrees, gamma = 90.05 degrees; two crystallographically independent and antiparallel chains; gt hydroxymethyl groups) by multiple dislocation defects. These defects produce microdomains of the new crystal form and cellulose III(I) that scanning microprobe diffraction studies show are distributed consistently through the cellulose III(II) fiber. PMID:19199578

Wada, Masahisa; Heux, Laurent; Nishiyama, Yoshiharu; Langan, Paul

2009-02-01

146

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

147

Macromolecular Calculations in the XTAL System of Crystallographic Programs.  

National Technical Information Service (NTIS)

This project is concerned with the production of crystallographic computer codes for the solution and refinement of macromolecular crystal structures. The computer programs are being prepared within the context of an existing suite of crystallographic com...

J. M. Stewart

1988-01-01

148

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

149

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

150

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

151

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

PubMed Central

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

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

2014-01-01

152

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

153

Crystallographic texture determinations from inverse susceptibility measurements  

SciTech Connect

Determination of the quantitative relationship between crystallographic texture and magnetic properties in advanced permanent magnets may be hampered by complex microstructures, which complicate methods that rely on diffraction, or by interparticulate interactions, which adversely affect methods based on magnetic remanence measurements. To this end, new techniques in the determination of texture of bulk permanent magnets are being explored to overcome these inherent experimental difficulties. The analysis of inverse paramagnetic susceptibility measurements constitutes a new method to investigate crystallographic texture. Such measurements also provide Curie temperature data, which is sensitive to chemical changes that may have occurred in the magnetic phase during processing. The mathematical formalism underlying the analysis of inverse susceptibility measurements is outlined, and is used to evaluate magnetic measurements taken from a series of Nd{sub 2}Fe{sub 14}B magnets that have been processed by different means, and thus contain different degrees of texture. While this method does provide qualitative information concerning the relative crystallographic alignment of magnet samples, it needs calibration to obtain an explicit value for a texture order parameter.

Lewis, L.H.; Welch, D.O.

1996-10-01

154

Renormgruppa v statisticheskoj fizike - impul'snoe i real'noe prostranstva. (Renormalization group in statistical physics - momentum and real spaces).  

National Technical Information Service (NTIS)

Two variants of the renormalization group approach in statistical physics are considered, the renormalization group in the momentum and the renormalization group in the real spaces. Common properties of these methods and their differences are cleared up. ...

V. I. Yukalov

1988-01-01

155

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

PubMed Central

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

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

2010-01-01

156

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

PubMed

A Kunitz-type proteinase inhibitor has been purified from tamarind (Tamarindus indica) seeds. SDS-PAGE analysis of a purified sample showed a homogeneous band corresponding to a molecular weight of 21 kDa. The protein was identified as a Kunitz-type proteinase inhibitor based on N-terminal amino-acid sequence analysis. It was crystallized by the vapour-diffusion method using PEG 6000. The crystals belonged to the orthorhombic space group C222(1), with unit-cell parameters a = 37.2, b = 77.1, c = 129.1 A. Diffraction data were collected to a resolution of 2.7 A. Preliminary crystallographic analysis indicated the presence of one proteinase inhibitor molecule in the asymmetric unit, with a solvent content of 44%. PMID:19574654

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

2009-07-01

157

Expression, purification and preliminary crystallographic analysis of the T6SS effector protein Tse3 from Pseudomonas aeruginosa.  

PubMed

Pseudomonas aeruginosa uses the type VI secretion system (T6SS) to inject effector proteins into rival cells in niche competition. Tse3, one of the effectors of T6SS, is delivered into the periplasm of recipient cells. Tse3 functions as a muramidase that degrades the ?-1,4-linkage between N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) in peptidoglycan, thus leading to lysis of the recipient cells and providing a competitive advantage to the donor cells. Here, the preliminary crystallographic study of Tse3 is reported. A crystal of Tse3 diffracted to 1.5?Å resolution. It belonged to space group C121, with unit-cell parameters a = 166.99, b = 70.13, c = 41.94?Å, ? = 90.00, ? = 90.52, ?  = 90.00° and one molecule per asymmetric unit. PMID:23695568

Lu, Defen; Shang, Guijun; Yu, Qian; Zhang, Heqiao; Zhao, Yanyu; Cang, Huaixing; Gu, Lichuan; Xu, Sujuan; Huang, Yan

2013-05-01

158

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

PubMed

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

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

2014-06-01

159

Extreme value statistics from the real space renormalization group: Brownian motion, Bessel processes and continuous time random walks  

Microsoft Academic Search

We use the real space renormalization group (RSRG) method to study extreme value statistics for a variety of Brownian motions, free or constrained, such as the Brownian bridge, excursion, meander and reflected bridge, recovering some standard results, and extending others. We apply the same method to compute the distribution of extrema of Bessel processes. We briefly show how the continuous

Grégory Schehr; Pierre Le Doussal

2010-01-01

160

Talking ‘gender superiority’ in virtual spaces: web?based discourses of Hindu student groups in the US and UK  

Microsoft Academic Search

This study focuses on the public assertion of gendered ethno?religious identities on the websites of Hindu student groups (HSGs) in the South Asian Diaspora in the USA and UK. HSGs are a part of a larger phenomenon of individuals and organizations engaged in creating and promoting ethnicities in virtual spaces. In this paper we focus particularly on the HSGs deployment

Anjana Narayan; Bandana Purkayastha

2011-01-01

161

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

Microsoft Academic Search

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

ANTHONY P. CLEVENGER; MICHAEL R. PELTON

162

Crystallographic studies of gas sorption in metal-organic frameworks.  

PubMed

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

2014-06-01

163

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.

Carrington, Elliot J.; Vitorica-Yrezabal, Inigo J.; Brammer, Lee

2014-01-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

165

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

166

Holographic phase space: c-functions and black holes as renormalization group flows  

NASA Astrophysics Data System (ADS)

We construct a mathcal{N} -function for Lovelock theories of gravity, which yields a holographic c-function in domain-wall backgrounds, and seemingly generalizes the concept for black hole geometries. A flow equation equates the monotonicity properties of mathcal{N} with the gravitational field, which has opposite signs in the domain-wall and black hole backgrounds, due to the presence of negative/positive energy in the former/latter, and accordingly mathcal{N} monotonically decreases/increases from the UV to the IR. On AdS spaces the mathcal{N} -function is related to the Euler anomaly, and at a black hole horizon it is generically proportional to the entropy. For planar black holes, mathcal{N} diverges at the horizon, which we interpret as an order N 2 increase in the number of effective degrees of freedom. We show how mathcal{N} can be written as the ratio of the Wald entropy to an effective phase space volume, and using the flow equation relate this to Verlinde's notion of gravity as an entropic force. From the effective phase space we can obtain an expression for the dual field theory momentum cut-off, matching a previous proposal in the literature by Polchinski and Heemskerk. Finally, we propose that the area in Planck units counts states, not degrees of freedom, and identify it also as a phase space volume. Written in terms of the proper radial distance ?, it takes the suggestive form of a canonical partition function at inverse temperature ?, leading to a "mean energy" which is simply the extrinsic curvature of the surface. Using this we relate this definition of holographic phase space with the effective phase space appearing in the mathcal{N} -function.

Paulos, Miguel F.

2011-05-01

167

Renormalization-group analysis of grand unified theories in curved space-time  

Microsoft Academic Search

We consider a class of grand unified theories (GUT's) based on the Georgi-Glashow model in curved space-time. We are particularly concerned with the coupling constants involving the curvature. These include the cosmological and gravitational constants, as well as coupling constants appearing in terms quadratic in the curvature and in terms which link the Higgs bosons to the scalar curvature. For

L. Parker; D. J. Toms

1984-01-01

168

On Four-group ML Decodable Distributed Space Time Codes for Cooperative Communication  

Microsoft Academic Search

A construction of a new family of distributed space time codes (DSTCs) having full diversity and low Maximum Likelihood (ML) decoding complexity is provided for the two phase based cooperative diversity protocols of Jing-Hassibi and the recently proposed Generalized Non-orthogonal Amplify and Forward (GNAF) protocol of Rajan et al. The salient feature of the proposed DSTCs is that they satisfy

G. Susinder Rajan; Anshoo Tandon; B. Sundar Rajan

2007-01-01

169

Working group report on advanced high-voltage high-power and energy-storage space systems  

NASA Technical Reports Server (NTRS)

Space systems in the future will probably include high-voltage, high-power energy-storage and -production systems. Two such technologies are high-voltage ac and dc systems and high-power electrodynamic tethers. The working group identified several plasma interaction phenomena that will occur in the operation of these power systems. The working group felt that building an understanding of these critical interaction issues meant that several gaps in our knowledge had to be filled, and that certain aspects of dc power systems have become fairly well understood. Examples of these current collection are in quiescent plasmas and snap over effects. However, high-voltage dc and almost all ac phenomena are, at best, inadequately understood. In addition, there is major uncertainty in the knowledge of coupling between plasmas and large scale current flows in space plasmas. These gaps in the knowledge are addressed.

Cohen, H. A.; Cooke, D. L.; Evans, R. W.; Hastings, D.; Jongeward, G.; Laframboise, J. G.; Mahaffey, D.; Mcintyre, B.; Pfizer, K. A.; Purvis, C.

1986-01-01

170

Andrographolide: an X-ray crystallographic analysis  

Microsoft Academic Search

The structure of andrographolide, isolated fromAndrographis paniculata Nees, has been established by means of a single crystal X-ray analysis. The crystals have the space groupP21, witha=6.550(1),b=8.005(2),c=17.991(7) Å,ß=97.36(2)°, andZ=2. The structure was refined toR=7.3%. The molecular stereochemistry, bond distances, bond angles, and hydrogen bonding scheme have all been determined. The systematic name is 3-[2-[decahydro-6-hydroxy-5-(hydroxymethyl)-5,8a-dimethyl-2-methylene-1-naphthalenyl]ethylidine]dihydro-4-hydroxy-2(3H)-furanone.

Amos B. Smith; Bruce H. Toder; Patrick J. Carroll; Jerry Donohue

1982-01-01

171

Amplification of in-plane seismic ground motion by group cavities in layered half-space (I)  

NASA Astrophysics Data System (ADS)

Amplification of in-plane seismic ground motion by underground group cavities in layered half-space is studied both in frequency domain and time domain by using indirect boundary element method (IBEM), and the effect of cavity interval and spectrum of incident waves on the amplification are studied by numerical examples. It is shown that there may be large interaction between cavities, and group cavities with certain intervals may have significant amplification to seismic ground motion. The amplification of PGA (peak ground acceleration) and its PRS (peak response spectrum) can be increased up to 45.2% and 84.4%, for an example site in Tianjin, under the excitation of Taft wave and El Centro wave; and group cavities may also affect the spectra of the seismic ground motion. It is suggested that the effect of underground group cavities on design seismic ground motion should be considered.

Liang, Jianwen; Zhang, Ji; Ba, Zhenning

2012-08-01

172

Preliminary crystallographic analysis of a possible transcription factor encoded by the mimivirus L544 gene  

PubMed Central

Mimivirus is the prototype of a new family (the Mimiviridae) of nucleocytoplasmic large DNA viruses (NCLDVs), which already include the Poxviridae, Iridoviridae, Phycodnaviridae and Asfarviridae. Mimivirus specifically replicates in cells from the genus Acanthamoeba. Proteomic analysis of purified mimivirus particles revealed the presence of many subunits of the DNA-directed RNA polymerase II complex. A fully functional pre-transcriptional complex appears to be loaded in the virions, allowing mimivirus to initiate transcription within the host cytoplasm immediately upon infection independently of the host nuclear apparatus. To fully understand this process, a systematic study of mimivirus proteins that are predicted (by bioinformatics) or suspected (by proteomic analysis) to be involved in transcription was initiated by cloning and expressing them in Escherichia coli in order to determine their three-dimensional structures. Here, preliminary crystallographic analysis of the recombinant L544 protein is reported. The crystals belonged to the orthorhombic space group C2221 with one monomer per asymmetric unit. A MAD data set was used for preliminary phasing using the selenium signal present in a selenomethionine-substituted protein crystal.

Ciaccafava, Alexandre; Lartigue, Audrey; Mansuelle, Pascal; Jeudy, Sandra; Abergel, Chantal

2011-01-01

173

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

PubMed Central

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

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

2012-01-01

174

Crystallization and preliminary crystallographic analysis of the ADP-ribosyltransferase HopU1  

PubMed Central

Several Gram-negative pathogens of plants and animals and some eukaryotic associated bacteria use type III protein-secretion systems (T3SSs) to deliver bacterial virulence-associated ‘effector’ proteins directly into host cells. HopU1 is a type III effector protein from the plant pathogen Pseudomonas syringae, which causes plant bacterial speck disease. HopU1 quells host immunity through ADP-ribosylation of GRP7 as a substrate. HopU1 has been reported as the first ADP-ribosyltransferase virulence protein to be identified in a plant pathogen. Although several structures of ADP-ribosyltransferases have been determined to date, no structure of an ADP-ribosyltransferase from a plant pathogen has been determined. Here, the protein expression, purification, crystallization and preliminary crystallographic analysis of HopU1 are reported. Diffracting crystals were grown by hanging-drop vapour diffusion using polyethylene glycol 10?000 as a precipitant. Native and SAD data sets were collected using native and selenomethionine-derivative HopU1 crystals. The diffraction pattern of the crystal extended to 2.7?Å resolution using synchrotron radiation. The crystals belonged to space group P43, with unit-cell parameters a = 92.6, b = 92.6, c = 101.6?Å.

Lin, Yan; Wang, Ping; Yang, Huirong; Xu, Yanhui

2010-01-01

175

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

PubMed Central

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

Skovdal, M.; Gibbs, A.

2012-01-01

176

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

177

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

SciTech Connect

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

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

2010-06-22

178

Preliminary neutron crystallographic study of human transthyretin  

PubMed Central

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

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

2011-01-01

179

XTAL system of crystallographic programs: programmer's manual  

SciTech Connect

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

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

1980-02-01

180

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

National Technical Information Service (NTIS)

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

O. Balslev-Olesen

1985-01-01

181

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

182

Synthesis, physicochemical characterization and crystallographic twinning of Li{sub 2}ZnSnS{sub 4}  

SciTech Connect

Li{sub 2}ZnSnS{sub 4} is a new diamond-like semiconductor, which is of interest as a host structure for the creation of potentially interesting electronic, magnetic and photovoltaic materials. The compound was synthesized via traditional high-temperature solid-state methods and was predicted to adopt a wurtz-stannite structure with all atoms possessing tetrahedral environments. Initial analysis of single-crystal X-ray diffraction data indicated crystallographic disorder that upon closer examination violated basic chemical principles. The structure was subsequently re-evaluated and the apparent 'disorder' problem was found to be the result of pseudo-merohedral twinning. The crystal structure was finally solved in the monoclinic space group Pn, which resulted in a chemically reasonable model. The refinement converged with R1=1.68% (for all data). Additional characterization of the sample, including diffuse reflectance, thermal analysis and second harmonic generation measurements, was also performed. - Abstract: Li{sub 2}ZnSnS{sub 4} is a new diamond-like semiconductor synthesized via high-temperature solid-state methods. Analysis of single-crystal X-ray diffraction data indicated that the structure was a pseudo-merohedral twin crystallizing in space group Pn and related to the wurtz-stannite structure. Additional characterization of the sample is reported. Display Omitted.

Lekse, Jonathan W. [Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Mellon Hall 302, Pittsburgh, PA 15282 (United States); Leverett, Beth M.; Lake, Charles H. [Department of Chemistry, Indiana University of Pennsylvania, 975 Oakland Avenue, Indiana, PA 15705 (United States); Aitken, Jennifer A. [Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Mellon Hall 302, Pittsburgh, PA 15282 (United States)], E-mail: aitkenj@duq.edu

2008-12-15

183

Assessment of various natural orbitals as the basis of large active space density-matrix renormalization group calculations.  

PubMed

It is well-known that not only the orbital ordering but also the choice of the orbitals itself as the basis may significantly influence the computational efficiency of density-matrix renormalization group (DMRG) calculations. In this study, for assessing the efficiency of using various natural orbitals (NOs) as the DMRG basis, we performed benchmark DMRG calculations with different bases, which included the NOs obtained by various traditional electron correlation methods, as well as NOs acquired from preliminary moderate DMRG calculations (e.g., preserved states less than 500). The tested systems included N2, transition metal Cr2 systems, as well as 1D hydrogen polyradical chain systems under equilibrium and dissociation conditions and 2D hydrogen aggregates. The results indicate that a good compromise between the requirement for low computational costs of acquiring NOs and the demand for high efficiency of NOs as the basis of DMRG calculations may be very dependent on the studied systems' diverse electron correlation characteristics and the size of the active space. It is also shown that a DMRG-complete active space configuration interaction (DMRG-CASCI) calculation in a basis of carefully chosen NOs can provide a less expensive alternative to the standard DMRG-complete active space self-consistent field (DMRG-CASSCF) calculation and avoid the convergence difficulties of orbital optimization for large active spaces. The effect of different NO ordering schemes on DMRG-CASCI calculations is also discussed. PMID:23781781

Ma, Yingjin; Ma, Haibo

2013-06-14

184

Teaching Biochemists and Pharmacologists How to Use Crystallographic Data.  

ERIC Educational Resources Information Center

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

Duax, William L.

1988-01-01

185

Aggression and nest spacing in single and mixed species groups of seabirds  

Microsoft Academic Search

When heterospecific seabirds are part of a nesting colony, there may be less opportunity for conspecifics to come in direct\\u000a contact with each other, resulting in lower intraspecific aggressiveness. To determine if individuals spend less time in aggressive\\u000a behavior when nesting in conspecific rather than heterospecific groups, we compared the behavior of black skimmers (Rhynchops niger) nesting with gull-billed terns

Sandra M. Pius; Paul L. Leberg

1997-01-01

186

The effects of time, space and spectrum on auditory grouping in túngara frogs  

Microsoft Academic Search

Male túngara frogs (Physalaemus pustulosus) produce complex calls consisting of two components, a ~350 ms FM sweep called the “whine” followed by up to seven ~40 ms\\u000a harmonic bursts called “chucks”. In order to choose and locate a calling male, females attending to choruses must group call\\u000a components into auditory streams to correctly assign calls to their sources. Previously we showed that

H. E. Farris; A. Stanley Rand; Michael J. Ryan

2005-01-01

187

Space  

NSDL National Science Digital Library

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

Integrated Teaching And Learning Program

188

The influence of multiple diffraction on the space group determination of orthopyroxene, spodumene, low omphacite and pigeonite  

NASA Astrophysics Data System (ADS)

Forbidden reflections of some pyroxenes described as having a lower symmetry than Pbca or C2/ c have been examined, mainly using the detailed ?-scanning method of the four-circle automated diffractometer. All reflections violating the systematic absences of Pbca orthopyroxene, C2/ c spodumene, P2/ n omphacite and P21/ c pigeonite were found to be due to the Umweganregung process of multiple diffraction; the Umweganregung peaks observed for the ? azimuth were indexed in terms of a four-circle geometry. Thus, the space groups of orthopyroxene, ? spodumene, low omphacite and low pigeonite were confirmed to be Pbca, C2/ c, P2/ n and P21/ c, respectively.

Sasaki, Satoshi; Matsumoto, Takeo; Sawada, Chikako

1981-12-01

189

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.

2010-01-01

190

Sobolev metrics on diffeomorphism groups and the derived geometry of spaces of submanifolds  

NASA Astrophysics Data System (ADS)

Given a finite-dimensional manifold N, the group \\operatorname{Diff}_{ S}(N) of diffeomorphisms diffeomorphism of N which decrease suitably rapidly to the identity, acts on the manifold B(M,N) of submanifolds of N of diffeomorphism-type M, where M is a compact manifold with \\operatorname{dim} M<\\operatorname{dim} N. Given the right-invariant weak Riemannian metric on \\operatorname{Diff}_{ S}(N) induced by a quite general operator L\\colon \\mathfrak{X}_{ S}(N)\\to \\Gamma(T^*N\\otimes\\operatorname{vol}(N)), we consider the induced weak Riemannian metric on B(M,N) and compute its geodesics and sectional curvature. To do this, we derive a covariant formula for the curvature in finite and infinite dimensions, we show how it makes O'Neill's formula very transparent, and we finally use it to compute the sectional curvature on B(M,N).

Micheli, Mario; Michor, Peter W.; Mumford, David

2013-06-01

191

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

192

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

NASA Astrophysics Data System (ADS)

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.

2006-09-01

193

Preliminary crystallographic analysis of the NAC domain of ANAC, a member of the plant-specific NAC transcription factor family.  

PubMed

The NAC domain (residues 1-168) of ANAC, encoded by the abscisic acid-responsive NAC gene from Arabidopsis thaliana, was recombinantly produced in Escherichia coli and crystallized in hanging drops. Three morphologically different crystal forms were obtained within a relatively narrow range of conditions: 10-15% PEG 4000 and 0.1 M imidazole/malic acid buffer pH 7.0 in the reservoir, 3.2-7.7 mg ml(-1) protein stock and a 1:1 ratio of reservoir to protein solution in the hanging drop. One of the crystal forms, designated crystal form III, was found to be suitable for further X-ray analysis. Form III crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 62.0, b = 75.2, c = 80.8 A at 100 K. The unit-cell volume is consistent with two molecules in the asymmetric unit and a peak in the native Patterson map suggests the presence of a non-crystallographic twofold axis parallel to a crystallographic axis. Size-exclusion chromatography of the NAC domain showed that the dimeric state is also the preferred state in solution and probably represents the biologically active form. Data sets were collected from four potential heavy-atom derivatives of the form III crystals. The derivatized crystals are reasonably isomorphous with the non-derivatized crystals and the four data sets are being evaluated for use in structure determination by multiple isomorphous replacement. PMID:14684901

Olsen, Addie Nina; Ernst, Heidi Asschenfeldt; Lo Leggio, Leila; Johansson, Eva; Larsen, Sine; Skriver, Karen

2004-01-01

194

Magnetic versus crystallographic fabrics in a basaltic lava flow  

NASA Astrophysics Data System (ADS)

Combined anisotropy of magnetic susceptibility (AMS) and crystallographic studies were performed within a quaternary lava flow, for which we have a thorough knowledge of the flow direction. Microscope examinations, microprobe analyses and studies of rock magnetic properties show that AMS is carried by homogeneous multidomain Ti-rich titanomagnetite ( x?0.6). This mineral, forming either subhedral isolate individuals or grouped in various elongated aggregates, represents a late crystallized interstitial phase. AMS determined from samples collected in the lower, the middle and the upper part of the flow is characterized by a well-defined magnetic foliation whereas magnetic lineation is generally poorly grouped and therefore meaningless. The foliation plane of the lower and upper part of the flow show an obliquity, which is interpreted as an opposite imbrication indicating a westward flow in agreements with the known flow direction. In the lower part of the lava flow, the tight correlation between AMS and plagioclase lattice preferred orientation suggests that a silicate framework control the titanomagnetite crystallization and thus the orientation of the AMS ellipsoid.

Bascou, Jérôme; Camps, Pierre; Marie Dautria, Jean

2005-07-01

195

Crystallographic snapshot of a productive glycosylasparaginase-substrate complex  

PubMed Central

Summary Glycosylasparaginase (GA) plays an important role in asparagine-linked glycoprotein degradation. A deficiency in the activity of human GA leads to a lysosomal storage disease named aspartylglycosaminuria. GA belongs to a superfamily of N-terminal nucleophile hydrolases that autoproteolytically generate their mature enzymes from inactive single chain protein precursors. The side-chain of the newly exposed N-terminal residue then acts as a nucleophile during substrate hydrolysis. By taking advantage of mutant enzyme of F. meningosepticum GA with reduced enzymatic activity, we have obtained a crystallographic snapshot of a productive complex with its substrate (NAcGlc-Asn), at 2.0 ? resolution. This complex structure provided us an excellent model for the Michaelis complex to examine the specific contacts critical for substrate binding and catalysis. Substrate-binding induces a conformational change near the active site of GA. To initiate catalysis, the side-chain of the N-terminal Thr152 is polarized by the free ?-amino group on the same residue, mediated by the side-chain hydroxyl group of Thr170. Cleavage of the amide bond is then accomplished by a nucleophilic attack at the carbonyl carbon of the amide linkage in the substrate, leading to the formation of an acyl-enzyme intermediate through a negatively charged tetrahedral transition-state.

Wang, Yeming; Guo, Hwai-Chen

2007-01-01

196

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

197

Crystallographic phasing with NMR models: an envelope approach.  

PubMed

X-ray crystallography and NMR are complementary tools in structural biology. However, it is often difficult to use NMR structures as search models in molecular replacement (MR) to phase crystallographic data. In this study, a new approach is reported utilizing a molecular envelope of NMR structures for MR phasing with the program FSEARCH at low resolution (about 6?Å). Several targets with both crystallographic and NMR structures available have been tested. FSEARCH was able to find the correct translation and orientation of the search model in the crystallographic unit cell, while conventional MR procedures were unsuccessful. PMID:25004974

Zhang, Weizhe; Zhang, Tao; Zhang, Hongmin; Hao, Quan

2014-07-01

198

Coupling between Magnetic and Crystallographic Domains in Ordered Double Perovskite  

NASA Astrophysics Data System (ADS)

Correlations between magnetic and crystallographic domains in an ordered double perovskite, Ba2FeMoO6, were investigated by transmission electron microscopy. We found that magnetic domain walls perfectly coincide with crystallographic antiphase domain boundaries. This suggests a pinning effect on the magnetic domains at the antiphase boundaries. In addition, we observed a magnetic nanodomain structure derived from coupling between magnetic and structural ordering domains where Fe/Mo short-range ordering was developed. The magnetic domain structure in the ordered double perovskite is significantly affected by the crystallographic structures, i.e., the antiphase boundary and the short-range ordering, due to their strong mutual coupling.

Asaka, Toru; Yu, Xiuzhen; Kimoto, Koji; Matsui, Yoshio

199

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 P21/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

200

Space.  

ERIC Educational Resources Information Center

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

Web Feet K-8, 2001

2001-01-01

201

Butene oxidation by molybdenum crystallographic shear compounds  

SciTech Connect

The reduced molybdenum oxides Mo/sub 4/O/sub 11/-orh, Mo/sub 4/O/sub 11/-mon, Mo/sub 8/O/sub 23/, and Mo/sub 18/O/sub 52/ were synthesized. These compounds, as well as MoO/sub 3/, were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, Raman and FT-IR spectroscopies, and BET surface area measurements. The oxides were then studied in a pulsed reactor at 500/sup 0/C in the selective oxidation of butene and butadiene. The data suggested a process in which the surface site must become more oxidized in parallel with the oxidation of the adsorbed hydrocarbon. Evidence supporting this idea included the high selectivity to maleic anhydride observed over a completely oxidized surface and differences in the reactivity of butene and butadiende. In particular, oxygen insertion into butadiene to form furan occurred in the absence of gas phase O/sub 2/ over the reduced phases, while oxygen insertion into butene required the presence of molecular oxygen. Maleic anhydride formation required the presence of molecular oxygen except in the case of butadiene oxidation over MoO/sub 3/. The long range ordering of defects, known as crystallographic shear, was not shown to have any influence on the initial interaction of reactant and solid. However, the unusual coordination geometries and surface structures that are thought to be caused by the presence of shear planes may be related to the differences in catalytic selectivity observed for these oxides.

McCormick, R.L.

1984-06-01

202

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

SciTech Connect

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

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

2012-05-24

203

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

PubMed Central

Botulinum neurotoxins (BoNTs) are highly toxic proteins for humans and animals that are responsible for the deadly neuroparalytic disease botulism. Here, details of the expression and purification of the receptor-binding domain (HCR) of BoNT/D in Escherichia coli are presented. Using a codon-optimized cDNA, BoNT/D_HCR was expressed at a high level (150–200 mg per litre of culture) in the soluble fraction. Following a three-step purification protocol, very pure (>98%) BoNT/D_HCR was obtained. The recombinant BoNT/D_HCR was crystallized and the crystals diffracted to 1.65?Å resolution. The crystals belonged to space group P212121, with unit-cell parameters a = 60.8, b = 89.7, c = 93.9?Å. Preliminary crystallographic data analysis revealed the presence of one molecule in the asymmetric unit.

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

2010-01-01

204

Crystallization and preliminary X-ray crystallographic characterization of a cyclic nucleotide-binding homology domain from the mouse EAG potassium channel  

PubMed Central

The members of the family of voltage-gated KCNH potassium channels play important roles in cardiac and neuronal repolarization, tumour proliferation and hormone secretion. These channels have a C-terminal cytoplasmic domain which is homologous to cyclic nucleotide-binding domains (CNB-homology domains), but it has been demonstrated that channel function is not affected by cyclic nucleotides and that the domain does not bind nucleotides in vitro. Here, the crystallization and preliminary crystallographic analysis of a CNB-homology domain from a member of the KCNH family, the mouse EAG channel, is reported. X-ray diffraction data were collected to 2.2?Å resolution and the crystal belonged to the hexagonal space group P3121.

Marques-Carvalho, Maria Joao; Morais-Cabral, Joao Henrique

2012-01-01

205

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

PubMed

A membrane-associated ATPase, PotA, is a component of the spermidine-preferential uptake system in prokaryotes that plays an important role in normal cell growth by regulating the cellular polyamine concentration. No three-dimensional structures of membrane-associated ATPases in polyamine-uptake systems have been determined to date. Here, the crystallization and preliminary X-ray diffraction analysis of PotA from Thermotoga maritima are reported. Diffraction data were collected and processed to 2.7?Å resolution from both native and selenomethionine-labelled crystals. Preliminary crystallographic analysis revealed that the crystals belonged to the hexagonal space group P3112 (or P3212), with unit-cell parameters a = b = 88.9, c = 221.2?Å, ? = 90, ? = 90, ? = 120°, indicating that a dimer was present in the asymmetric unit. PMID:24915082

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

2014-06-01

206

Preliminary crystallographic analysis of the ankyrin-repeat domain of Arabidopsis thaliana AKT1: identification of the domain boundaries for protein crystallization.  

PubMed

The Arabidopsis thaliana K(+) transporter 1 (AKT1) participates in the maintenance of an adequate cell potassium (K(+)) concentration. The CBL-interacting protein kinase 23 (CIPK23) activates AKT1 for K(+) uptake under low-K(+) conditions. This process is mediated by the interaction between the cytosolic ankyrin-repeat (AR) domain of AKT1 and the kinase domain of CIPK23. However, the precise boundaries of the AR domain and the residues responsible for the interaction are still unknown. Here, the optimization procedure to obtain an AR domain construct suitable for crystallization and the preliminary crystallographic analysis of the obtained crystals are reported. The crystals belonged to space group P21212, with unit-cell parameters a = 34.83, b = 65.89, c = 85.44?Å, and diffracted to 1.98?Å resolution. PMID:24699751

Chaves-Sanjuán, Antonio; Sánchez-Barrena, María José; González-Rubio, Juana María; Albert, Armando

2014-04-01

207

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

208

Physical and Geometrical Principles of Crystallographic Shear in Rutile.  

National Technical Information Service (NTIS)

Recent studies by electron microscopy and diffraction have elucidated many of the structural patterns of formation of homologous series of oxides derived from the rutile structure by crystallographic shear. In this paper, the physical and geometrical prin...

B. G. Hyde L. A. Bursill M. O'Keeffe

1972-01-01

209

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

210

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

211

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

212

Iron-sulfur cluster in aconitase. Crystallographic evidence for a three-iron center.  

PubMed

Native x-ray diffraction data from single crystals of inactive aconitase from pig heart (Mr 80,000) have been collected on oscillation films to 2.7 A. Analysis shows that significant measurements of the anomalous scattering signal from the Fe-S cluster in the enzyme are available in the film data. The 5.0-A resolution anomalous difference Patterson function contains vectors for one Fe-S cluster (one aconitase molecule) per asymmetric unit in space group P2(1)2(1)2 with a = 173.6, b = 72.0, and c = 72.7 A. At 2.7-A resolution, the vector map is best interpreted by three Fe sites separated from each other by less than 3 A. The single-crystal diffraction data thus confirm the presence of a 3Fe center in the inactive form of aconitase. Furthermore, the data provide crystallographic evidence that 3Fe clusters exhibit structural heterogeneity. The Fe-Fe vectors cannot be interpreted in terms of 4-A distances as observed for the [3Fe-3S] cluster in Azotobacter ferrodoxin (Ghosh, D., O'Donnell, S., Furey, W., Robbins, A. H., and Stout, C. D. (1982) J. Mol. Biol. 158, 73-109). The results are therefore in agreement with a [3Fe-4S] cluster having 2.7-A Fe-Fe distances (Beinert, H., Emptage, M. H., Dreyer, J.-L., Scott, R. A., Hahn, J. E., Hodgson, K. O., and Thomson, A. J. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 393-396). However, the data do not unambiguously discriminate between this model and other 3Fe clusters having short Fe-Fe distances. PMID:3972791

Robbins, A H; Stout, C D

1985-02-25

213

Crystallographic Characterization: 3D Mapping of Crystallographic Phase Distribution using Energy-Selective Neutron Tomography (Adv. Mater. 24/2014).  

PubMed

On page 4069, D. Penumadu and co-workers describe studies involving non-destructive 3D mapping of crystallographic phases in stainlesssteel samples. The background of the image shows a digitally altered neutron-radiograph of the phase transformed tensile and torsion samples. Photographs of the specimen and the reconstructed neutron-tomography data, revealing the crystallographic phase fraction distribution, are also shown. PMID:24946996

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

2014-06-01

214

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

Microsoft Academic Search

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

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

2002-01-01

215

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

216

Antiferrodistortive phase transition in Pb(Ti0.48Zr0.52)O3: Space group of the lowest temperature monoclinic phase  

NASA Astrophysics Data System (ADS)

Ranjan et al. [Phys. Rev. B 65, 060102(R) (2002)] have recently presented results of a powder neutron-diffraction study of the high-temperature monoclinic (FHTM) to low-temperature monoclinic (FLTM) phase transition in Pb(Ti1-xZrx)O3 discovered by Ragini et al. [Phys. Rev. B 64, 054101 (2001)]. They attribute the presence of superlattice reflections in the diffraction data to tilting of oxygen octahedra and propose a monoclinic space group Pc for the FLTM phase. It is shown that for the model proposed by Ranjan et al., the correct space group of the FLTM phase should be Cc. This has also been corroborated by a group-theoretical approach to the problem. A different set of refined structural parameters for the Cc space group obtained from the Rietveld analysis of the powder neutron-diffraction data of Ranjan et al. is also presented.

Hatch, D. M.; Stokes, H. T.; Ranjan, Rajeev; Ragini; Mishra, S. K.; Pandey, Dhananjai; Kennedy, Brendan J.

2002-06-01

217

Regularity properties and pathologies of position-space renormalization-group transformations: Scope and limitations of Gibbsian theory  

NASA Astrophysics Data System (ADS)

We reconsider the conceptual foundations of the renormalization-group (RG) formalism, and prove some rigorous theorems on the regularity properties and possible pathologies of the RG map. Our main results apply to local (in position space) RG maps acting on systems of bounded spins (compact single-spin space). Regarding regularity, we show that the RG map, defined on a suitable space of interactions (=formal Hamiltonians), is always single-valued and Lipschitz continuous on its domain of definition. This rules out a recently proposed scenario for the RG description of first-order phase transitions. On the pathological side, we make rigorous some arguments of Griffiths, Pearce, and Israel, and prove in several cases that the renormalized measure is not a Gibbs measure for any reasonable interaction. This means that the RG map is ill-defined, and that the conventional RG description of first-order phase transitions is not universally valid. For decimation or Kadanoff transformations applied to the Ising model in dimension d?3, these pathologies occur in a full neighborhood { ?> ? 0, ¦h¦< ?( ?)} of the low-temperature part of the first-order phase-transition surface. For block-averaging transformations applied to the Ising model in dimension d?2, the pathologies occur at low temperatures for arbitrary magnetic field strength. Pathologies may also occur in the critical region for Ising models in dimension d?4. We discuss the heuristic and numerical evidence on RG pathologies in the light of our rigorous theorems. In addition, we discuss critically the concept of Gibbs measure, which is at the heart of present-day classical statistical mechanics. We provide a careful, and, we hope, pedagogical, overview of the theory of Gibbsian measures as well as (the less familiar) non-Gibbsian measures, emphasizing the distinction between these two objects and the possible occurrence of the latter in different physical situations. We give a rather complete catalogue of the known examples of such occurrences. The main message of this paper is that, despite a well-established tradition, Gibbsianness should not be taken for granted.

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

1993-09-01

218

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

PubMed

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

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

2004-05-17

219

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

PubMed

Phosphoketolases are thiamine diphosphate-dependent enzymes which play a central role in the pentose-phosphate pathway of heterofermentative lactic acid bacteria. They belong to the family of aldehyde-lyases and in the presence of phosphate ion cleave the carbon-carbon bond of the specific substrate D-xylulose 5-phosphate (or D-fructose 6-phosphate) to give acetyl phosphate and D-glyceraldehyde 3-phosphate (or D-erythrose 4-phosphate). Structural information about phosphoketolases is particularly important in order to fully understand their mechanism as well as the steric course of phosphoketolase-catalyzed reactions. Here, the purification, preliminary crystallization and crystallographic characterization of D-xylulose 5-phosphate phosphoketolase from Lactococcus lactis are reported. The presence of thiamine diphosphate during purification was essential for the enzymatic activity of the purified protein. The crystals belonged to the monoclinic space group P2(1). Diffraction data were obtained to a resolution of 2.2 A. PMID:20606278

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

2010-07-01

220

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

PubMed

Adenylosuccinate synthetase (AdSS) is a ubiquitous enzyme that catalyzes the first committed step in the conversion of inosine monophosphate (IMP) to adenosine monophosphate (AMP) in the purine-biosynthetic pathway. Although AdSS from the vast majority of organisms is 430-457 amino acids in length, AdSS sequences isolated from thermophilic archaea are 90-120 amino acids shorter. In this study, crystallographic studies of a short AdSS sequence from Pyrococcus horikoshii OT3 (PhAdSS) were performed in order to reveal the unusual structure of AdSS from thermophilic archaea. Crystals of PhAdSS were obtained by the microbatch-under-oil method and X-ray diffraction data were collected to 2.50 Å resolution. The crystal belonged to the trigonal space group P3(2)12, with unit-cell parameters a = b = 57.2, c = 107.9 Å. There was one molecule per asymmetric unit, giving a Matthews coefficient of 2.17 Å(3) Da(-1) and an approximate solvent content of 43%. In contrast, the results of native polyacrylamide gel electrophoresis and analytical ultracentrifugation showed that the recombinant PhAdSS formed a dimer in solution. PMID:22139164

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

2011-12-01

221

Protein expression, characterization, crystallization and preliminary X-ray crystallographic analysis of a Fic protein from Clostridium difficile.  

PubMed

Fic domains in proteins are found in abundance in nature from the simplest prokaryotes to animals. Interestingly, Fic domains found in two virulence factors of Gram-negative bacteria have recently been demonstrated to catalyse the transfer of the AMP moiety from ATP to small host GTPases. This post-translational modification has attracted considerable interest and a role for adenylylation in pathology and physiology is emerging. This work was aimed at the structural characterization of a newly identified Fic protein of the Gram-positive bacterium Clostridium difficile. A constitutively active inhibitory helix mutant of C. difficile Fic was overexpressed in Escherichia coli, purified and crystallized by the vapour-diffusion technique. Preliminary X-ray crystallographic analysis shows that the crystals diffract to at least 1.68?Å resolution at a synchrotron X-ray source. The crystals belonged to the orthorhombic space group P2?2?2?, with unit-cell parameters a=45.6, b=80.8, c=144.7?Å, ?=?=?=90°. Two molecules per asymmetric unit corresponds to a Matthews coefficient of 2.37?Å3?Da(-1) and a solvent content of 48%. PMID:24915103

Welner, Ditte; Dedic, Emil; van Leeuwen, Hans C; Kuijper, Ed; Bjerrum, Morten Jannik; Østergaard, Ole; Jørgensen, René

2014-06-01

222

Group theoretical quantization of a phase space S1×R+ and the mass spectrum of Schwarzschild black holes in D space-time dimensions  

Microsoft Academic Search

The symplectic reduction of pure spherically symmetric (Schwarzschild) classical gravity in D space-time dimensions yields a two-dimensional phase space of observables consisting of the mass M (>0) and a canonically conjugate (Killing) time variable T. Imposing (mass-dependent) periodic boundary conditions in time on the associated quantum-mechanical plane waves which represent the Schwarzschild system in the period just before or during

M. Bojowald; H. A. Kastrup; F. Schramm; T. Strobl

2000-01-01

223

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

224

The Contribution of Thin PFPE Lubricants to Slider-Disk Spacing. 2. Effect of Film Thickness and Lubricant End Groups  

Microsoft Academic Search

We have investigated the effect of film thickness of a perfluoropolyether lubricant, Zdol 4000, on slider-disk spacing, or clearance. The major conclusion of this work is that the Zdol lubricant impacts the slider-disk spacing. A decrease in the film thickness of Zdol 4000 by ~10Å results in an increase in the effective slider-disk spacing by ~1 nm. The effect of

R. J. Waltman; A. G. Khurshudov

2002-01-01

225

Cluster analysis of time-dependent crystallographic data: Direct identification of time-independent structural intermediates.  

PubMed

The initial output of a time-resolved macromolecular crystallography experiment is a time-dependent series of difference electron density maps that displays the time-dependent changes in underlying structure as a reaction progresses. The goal is to interpret such data in terms of a small number of crystallographically refinable, time-independent structures, each associated with a reaction intermediate; to establish the pathways and rate coefficients by which these intermediates interconvert; and thereby to elucidate a chemical kinetic mechanism. One strategy toward achieving this goal is to use cluster analysis, a statistical method that groups objects based on their similarity. If the difference electron density at a particular voxel in the time-dependent difference electron density (TDED) maps is sensitive to the presence of one and only one intermediate, then its temporal evolution will exactly parallel the concentration profile of that intermediate with time. The rationale is therefore to cluster voxels with respect to the shapes of their TDEDs, so that each group or cluster of voxels corresponds to one structural intermediate. Clusters of voxels whose TDEDs reflect the presence of two or more specific intermediates can also be identified. From such groupings one can then infer the number of intermediates, obtain their time-independent difference density characteristics, and refine the structure of each intermediate. We review the principles of cluster analysis and clustering algorithms in a crystallographic context, and describe the application of the method to simulated and experimental time-resolved crystallographic data for the photocycle of photoactive yellow protein. PMID:21244840

Kostov, Konstantin S; Moffat, Keith

2011-01-19

226

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

227

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

PubMed

SoxR, a member of the MerR family of transcriptional activators, functions as a sensor of oxidative stress. The redox states of the 2Fe-2S cluster of SoxR regulate the activity of SoxR. Here, the crystallization and preliminary crystallographic analysis of SoxR and its complex with DNA are reported. Crystals of SoxR were obtained using PEG 10,000 and glycerol as precipitants. The crystals of SoxR belong to space group P6(2) or P6(4), with unit-cell parameters a = b = 80.0, c = 88.1 A. Crystals of the SoxR-DNA complex were obtained using a 20 bp DNA fragment from a condition containing PEG 10,000 and sodium/potassium tartrate. The crystals of the SoxR-DNA complex belong to space group P6(1)22 or P6(5)22, with unit-cell parameters a = b = 53.5, c = 355.6 A. Diffraction data were collected to a maximum resolution of 3.2 and 2.7 A for SoxR and the SoxR-DNA complex, respectively. PMID:17142916

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

2006-12-01

228

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

229

Crystallographic texture effects in hydroforming of aluminum sheet  

Microsoft Academic Search

The success of hydroforming operations, as well as many other sheet forming processes, depends strongly on the initial condition of the stock material. The stock material may be in a variety of states as a consequence of its processing history. The crystallographic texture may range from a pronounced deformation texture imparted by rolling operations to a cube texture that could

P. R. Dawson; A. J. Beaudoin; K. K. Mathur; U. F. Kocks; D. A. Korzekwa

1992-01-01

230

Crystallographic Orientation of Fractured Plane about Fresh Snow Particles  

Microsoft Academic Search

It is necessary to understand sufficiently the structure of snowflakes fractured in the blizzard, in order to make a clear explanation for the electric charge on drifting snow. The author investigated the crystallographic orientations about the fractured planes of snowflakes and the cracks of single ice crystal created by the thermal shock, the impact and the scratch. As a result,

Hisashi SHIO

1979-01-01

231

Calcium Oxalate: Crystallographic Analysis in Solid Aggregates in Urinary Sediments  

Microsoft Academic Search

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

Fernando Catalina; Luis Cifuentes

1970-01-01

232

On the space group of garronite. [61. 10. Bp. 3; 61. 10. Bp. 6; 07. 85. Yy; 61. 66. Va. 5; 61. 66. Rm. 1  

SciTech Connect

The crystal structure of the natural zeolite garronite from Goble, Oregon has been refined using high resolution synchrotron X-ray powder diffraction data. Garronite has the same tetrahedral aluminosilicate framework as gismondine [GIS], and earlier structural models indicated a strong tetragonal pseudosymmetry. Proposed models in the literature were based on the I[bar 4]m2 and I4[sub 1]/a space groups, on account of symmetry lowering from the topological I4[sub 1]/amd space due to partial cation/water molecule order in the zeolitic cavities. Test structure analysis has been performed in all possible space subgroups including monoclinic space groups, and the refinement has been successfully carried out in space group I2/a (C2/c). The resulting monoclinic structure model is to be preferred over the tetragonal ones on the basis of: (1) lower agreement indices of the refinement; (2) a chemically sound framework geometry; and (3) a more satisfactory interpretation of the Ca atoms coordination in the extraframework cages. [copyright] [ital 1999 International Centre for Diffraction Data.

Artioli, G.; Marchi, M. (Dipartimento di Scienze della Terra, Universita di Milano, via Botticelli 23, I 20133 Milano (Italy))

1999-09-01

233

Crystallization and preliminary crystallographic analysis of the Clostridium perfringens enterotoxin  

PubMed Central

Clostridium perfringens is a Gram-positive anaerobic species of bacterium that is notable for its ability to produce a plethora of toxins, including membrane-active toxins (?-toxins), pore-forming toxins (?-toxins) and binary toxins (?-toxins). Here, the crystallization of the full-length wild-type C. perfringens enterotoxin is reported, which is the causative agent of the second most prevalent food-borne illness in the United States and has been implicated in many other gastrointestinal pathologies. Several crystal forms were obtained. However, only two of these optimized crystal forms (I and II) were useable for X-ray diffraction data collection. The form I crystals diffracted to d min = 2.7?Å and belonged to space group C2, while the form II crystals diffracted to d min = 4?Å and belonged to space group P213.

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

2010-01-01

234

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

PubMed

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

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

2014-02-17

235

Dynamical Groups SO S(3.2) and SO sub 0 (4.2) as Space-Time Groups of Elementary Particles.  

National Technical Information Service (NTIS)

Elementary particles are described by representations of SO sub 0 (4.2) and SO sub 0 (3.2). An S-matrix invariant under the corresponding group constrains the possible scattering channels. The simptest used representations have each one gauge freedom, the...

W. Heidenreich

1981-01-01

236

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)A? b = 15.5100(4)A? c = 16.626(4)A? ? = 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)A?, b = 8.4243(11)A?, c = 21.181(4)A?, ? = 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 A?, b = 7.4414 A?, c = 22.3113 A?, ? = 90°, ? = 93.063°, ? = 90°, with space group C2/c.

Bora, M. N.; Kalita, Mahendra

2010-06-01

237

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.

Campos-Acevedo, Adam A.; Garcia-Orozco, Karina D.; Sotelo-Mundo, Rogerio R.; Rudino-Pinera, Enrique

2013-01-01

238

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

PubMed

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

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

2013-07-01

239

Crystallographic Symmetry of Surface State Density in Thermally Oxidized Silicon  

Microsoft Academic Search

The detailed dependence of surface state density on crystallographic orientation was determined by measuring the ac metal-oxide-semiconductor conductance on the surface of a thermally oxidized single-crystal silicon hemisphere. It was found that the ?111? poles are located at maxima, the ?100? poles at minima, and the ?110? poles at saddle points in the surface state density distribution. The symmetry of

Emil Arnold; Joshua Ladell; Gerald Abowitz

1968-01-01

240

Crystallographic preferred orientation development by dissolution–precipitation creep  

Microsoft Academic Search

Crystallographic preferred orientations (CPOs) in deformed rocks are commonly interpreted as resulting from crystal plastic deformation mechanisms, where deformation is achieved by the movement of dislocations. In this paper we investigate the possibility of CPO-development by dissolution–precipitation creep or pressure solution. A numerical model is presented, which simulates the development of a grain aggregate that deforms by reaction-controlled dissolution–precipitation creep.

Paul D. Bons; Bas den Brok

2000-01-01

241

Crystallographic distortion in TbVO4 at 32°K  

Microsoft Academic Search

X-ray diffraction measurements on single crystals and powders of TbVO4 have shown that it undergoes a crystallographic transition from tetragonal to orthorhombic below 32°K. The orthorhombic cell is related to the original cell by having its a and b axes along the original directions. The fractional distortion between the a and b axes is 21.7 × 10-3 and the transition

G. Will; H. Gobel; C. F. Sampson; J. B. Forsyth

1972-01-01

242

Crystallographic alignment of high-density gallium nitride nanowire arrays  

Microsoft Academic Search

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

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

2004-01-01

243

Chemical and Crystallographic Events in the Caries Process  

Microsoft Academic Search

The chemical and crystallographic events associated with the caries process can be described based on the results from the following studies: (a) effects of carbonate, magnesium, fluoride, and strontium on the physico-chemical properties—lattice parameters, crystallinity (crystal size and strain); dissolution properties of synthetic apatites; (b) factors influencing the in vitro formation and transformation of DCPD, OCP, AP (Ca-deficient apatites), FAP,

R. Z. LeGeros

1990-01-01

244

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

245

Asymmetrical quartz crystallographic fabrics formed during constrictional deformation  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

246

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

247

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

Microsoft Academic Search

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

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

2003-01-01

248

The Space Density of Primordial Gas Clouds near Galaxies and Groups and their Relation to Galactic High-Velocity Clouds.  

PubMed

The Arecibo H i Strip Survey probed the halos of approximately 300 cataloged galaxies and the environments of approximately 14 groups with sensitivity to neutral hydrogen masses >/=107 M middle dot in circle. The survey detected no objects with properties resembling the high-velocity clouds (HVCs) associated with the Milky Way or Local Group. If the HVCs were typically MHi=107.5 M middle dot in circle objects distributed throughout groups and galaxy halos at distances of approximately 1 Mpc, the survey should have made approximately 70 HVC detections in groups and approximately 250 detections around galaxies. The null detection implies that HVCs are deployed at typical distances of group barycenters. If the clouds are in virial equilibrium, their average dark matter fraction must be 98% or higher. PMID:10655165

Zwaan; Briggs

2000-02-20

249

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

NASA Technical Reports Server (NTRS)

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

1976-01-01

250

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

251

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

252

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

253

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

254

Amplification of in-plane seismic ground motion by group cavities in layered half-space (II): with saturated poroelastic soil layers  

NASA Astrophysics Data System (ADS)

As the continuation study on amplification of in-plane seismic ground motion by underground group cavities in layered half-space, this study extends to the case of poroelastic half-space with dry poroelastic and saturated poroelastic soil layers. The influence of poroelastic layers on the amplification of seismic ground motion is studied both in frequency domain and time domain using indirect boundary element method (IBEM). It is shown that for the example of a saturated poroelastic site in Tianjin under the excitation of Taft wave and El Centro wave, the amplification of seismic ground motion in poroelastic case is slightly smaller than that in the elastic case, and the amplification of PGA (peak ground acceleration) and its PRS (peak response spectrum) can be increased up to 38.8% and 64.6%; the predominant period of response spectra in poroelastic case becomes shorter to some extent compared with that in the elastic case. It is suggested that the effect of underground group cavities in poroelastic half-space on design seismic ground motion should be considered.

Liang, Jianwen; Zhang, Ji; Ba, Zhenning

2012-08-01

255

Crystallographic phase retrieval through image processing under constraints  

NASA Astrophysics Data System (ADS)

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

Zhang, Kam Y.

1993-11-01

256

Analysis of Martensite Pole Figure from Crystallographic View Point  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

257

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.

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

2014-01-01

258

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

SciTech Connect

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

Bona, C.

1988-11-01

259

Crystallographic texture effects in hydroforming of aluminum sheet  

SciTech Connect

The success of hydroforming operations, as well as many other sheet forming processes, depends strongly on the initial condition of the stock material. The stock material may be in a variety of states as a consequence of its processing history. The crystallographic texture may range from a pronounced deformation texture imparted by rolling operations to a cube texture that could arise from recrystallization. Such variations in the texture impose significant differences on the plastic response of the material. To accurately predict the deformations during hydroforming, the effects of the crystallographic texture on the anisotropy of the plasticity must be included in the forming model. In this paper polycrystalline plasticity is used in conjunction with a three dimensional, transient, finite element formulation to simulate hydroforming. The procedure to initialize the starting state of the material in terms of aggregates of crystals is emphasized as it is an essential element in treating work hardened materials. Massively parallel algorithms are employed to interrogate aggregates for the purpose of evaluating mechanical properties and to update their states. Application to drawing of aluminum sheet using the hydroform process demonstrates the ability of the formulation to capture effects such as earing.

Dawson, P.R.; Beaudoin, A.J. [Cornell Univ., Ithaca, NY (United States). Sibley School of Mechanical and Aerospace Engineering; Mathur, K.K. [Thinking Machines Corp., Cambridge, MA (United States); Kocks, U.F.; Korzekwa, D.A. [Los Alamos National Lab., NM (United States)

1992-09-01

260

Crystallographic texture effects in hydroforming of aluminum sheet  

SciTech Connect

The success of hydroforming operations, as well as many other sheet forming processes, depends strongly on the initial condition of the stock material. The stock material may be in a variety of states as a consequence of its processing history. The crystallographic texture may range from a pronounced deformation texture imparted by rolling operations to a cube texture that could arise from recrystallization. Such variations in the texture impose significant differences on the plastic response of the material. To accurately predict the deformations during hydroforming, the effects of the crystallographic texture on the anisotropy of the plasticity must be included in the forming model. In this paper polycrystalline plasticity is used in conjunction with a three dimensional, transient, finite element formulation to simulate hydroforming. The procedure to initialize the starting state of the material in terms of aggregates of crystals is emphasized as it is an essential element in treating work hardened materials. Massively parallel algorithms are employed to interrogate aggregates for the purpose of evaluating mechanical properties and to update their states. Application to drawing of aluminum sheet using the hydroform process demonstrates the ability of the formulation to capture effects such as earing.

Dawson, P.R.; Beaudoin, A.J. (Cornell Univ., Ithaca, NY (United States). Sibley School of Mechanical and Aerospace Engineering); Mathur, K.K. (Thinking Machines Corp., Cambridge, MA (United States)); Kocks, U.F.; Korzekwa, D.A. (Los Alamos National Lab., NM (United States))

1992-01-01

261

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

PubMed

The mannan endo-1,4-?-mannosidase (ManB) from Bacillus licheniformis strain DSM13 was overexpressed in Escherichia coli. Purification of the thermostable and alkali-stable recombinant mannanase yielded approximately 50?mg enzyme per litre of culture. Crystals were grown by hanging-drop vapour diffusion using a precipitant solution consisting of 12%(w/v) PEG 8000, 0.2?M magnesium acetate tetrahydrate and 0.1?M MES pH 6.5. The protein crystallized in the monoclinic space group P2(1), with two molecules per asymmetric unit and unit-cell parameters a = 48.58, b = 91.75, c = 89.55?Å, ? = 98.29°, and showed diffraction to 2.3?Å resolution. PMID:21301089

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

2011-02-01

262

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

PubMed

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

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

2013-08-01

263

Crystallization and preliminary crystallographic analysis of dextranase from Streptococcus mutans  

PubMed Central

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

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

2011-01-01

264

Crystallization and preliminary crystallographic analysis of dextranase from Streptococcus mutans.  

PubMed

Streptococcus mutans dextranase hydrolyzes the internal ?-1,6-linkages of dextran and belongs to glycoside hydrolase family 66. An N- and C-terminal deletion mutant of S. mutans dextranase was crystallized by the sitting-drop vapour-diffusion method. The crystals diffracted to a resolution of 1.6 Å and belonged to space group P2(1), with unit-cell parameters a = 53.2, b = 89.7, c = 63.3 Å, ? = 102.3°. Assuming that the asymmetric unit of the crystal contained one molecule, the Matthews coefficient was calculated to be 4.07 Å(3) Da(-1); assuming the presence of two molecules in the asymmetric unit it was calculated to be 2.03 Å(3) Da(-1). PMID:22139161

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

2011-12-01

265

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.

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

2010-01-01

266

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

PubMed Central

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

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

2005-01-01

267

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

268

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

269

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

270

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

SciTech Connect

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

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

2010-12-01

271

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

PubMed Central

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

Coitinho, Juliana Barbosa; Costa, Debora Maria Abrantes; Guimaraes, Samuel Leite; de Goes, Alfredo Miranda; Nagem, Ronaldo Alves Pinto

2012-01-01

272

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

NASA Astrophysics Data System (ADS)

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

Zu, Ying; Weinberg, David H.

2013-06-01

273

Local Group Populations With the Hubble Space Telescope. I. The M31 Globular Cluster G1=Mayall II  

NASA Astrophysics Data System (ADS)

We present WFPC2 photometry of the M31 globular cluster G1 and its adjacent halo field population. The cluster is one of the most luminous in the Local Group (~10^6^ L_sun_) and is at a projected distance of 39.5 kpc from the nucleus near the major axis of M31. The color of the red giant branch is similar to that of 47 Tuc, confirming previous ground- based imaging of its brightest giants. G1 has a red horizontal branch at V = 25.32 +/- 0.05 mag (M_v_ = +0.82 mag) and a small number of blue horizontal branch stars at (V - I) = 0.0 mag. We find no evidence for an extended giant branch: a deep image at 1 micron finds no red, luminous AGB stars. We conclude that the properties of the color-magnitude diagram are most consistent with those of an old globular cluster with the metallicity of 47 Tuc. The surrounding halo field has a red horizontal branch at the same color and luminosity of the cluster. The luminosity function of the field in V and I is more steep (fewer bright stars) than that of G1. While G1 is well fit by published luminosity functions of 47 Tuc and M3, these templates fail for the field luminosity function. If this difference is real, then either the outer M31 halo largely consists of stars as metal rich as 47 Tuc, or the red horizontal branch and steep giant branch luminosity function may be the product of a field population younger than the oldest Galactic globular clusters. We present a surface brightness profile for G1. We find a high central surface brightness of V = 13.5 mag arcsec^-2^. The core radius of G1 is r_c_ = 0.54 pc and its tidal radius is r_t_ = 90.0 pc.

Rich, R. Michael; Mighell, Kenneth J.; Freedman, Wendy L.; Neill, James D.

1996-02-01

274

Using OLCI/Sentinel-3 and Sentinel-5-P data synergistically for retrieving different phytoplankton groups from space  

NASA Astrophysics Data System (ADS)

We are proposing the development of an algorithm, using the combination of data from OCLI (Sentinel-3) and Sentinel-5P sensors, which derives globally pyhtoplankton groups (phytoplankton functional types) biomass. The information of the total biomass will be achieved by standard processing of the Chlorophyll-a (chl-a) concentration using satellite data from multispectral imaging instruments (firstly SeaWiFS, MODIS and MERIS merged within the GlobColour data set, later OLCI data). The percentage of the main phytoplankton types on the total biomass will be retrieved by the analysis of characteristic absorption features in hyperspectral satellite measurements (firstly SCIAMACHY, later Sentinel-5-P) using the PhytoDOAS method by Bracher et al. (2009) and improved by Sadeghi et al. (2011). Thus, a synergistic product from information of multi- and hyperspectral satellite instruments which complements one another will be developed. The two instruments of the Sentinel mission will enable a data product of weekly to monthly temporal and 7 km by 7 km spatial resolution. On the the SCIAMACHY/Globcolour product (starting in 2002 until today) will be limited to a monthly and 0.5° degree resolution. The application of the algorithm is for assessing the spatial and temporal variability of specific phytoplankton types' biomass on longer time scale (10 to 20 and more years) with global coverage. This will engross the understanding of the role of different phytoplankton types in the world ocean's ecosystem and improve estimates on the contribution of different phytoplankton types to the global carbon cycle. The concept of the algorithm development, including its uncertainity determined via validaton with in-situ phytoplankton data and sensitivity studies using the coupled atmospheric-oceanic radiative transfer model SCIATRAN (Rozanov et al. 2002, Blum et al. in press) and examples for its application are given in the presentation.

Bracher, A.; Dinter, T.; Altenburg Soppa, M.; Taylor, B.; Rozanov, V.

2012-04-01

275

Advanced temperature compensation for piezoresistive sensors based on crystallographic orientation.  

PubMed

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

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

2007-04-01

276

Nanoscale lithography of graphene with crystallographic orientation control  

NASA Astrophysics Data System (ADS)

The two scanning probe microscope based methods for the production of graphene nanoarchitectures with crystallographically oriented edges: scanning tunneling lithography (STL) and carbothermal etching (CTE) are compared. STL offers higher freedom in choosing the orientation, it makes possible sophisticated manipulation of the etched nanoarchitectures and immediate atomic resolution of the etched structure, but it suffers from the need of a conductive substrate. CTE at present can produce only zigzag edges, but these edges by the very nature of the process producing them are more regular than the edges produced by STL. CTE has the clear advantage that the produced nanoarchitectures are on an insulating substrate, no further transfer steps are needed. To date STL can produce graphene nanoribbons (GNRs) of a few nanometers in width, while the width of the GNRs produced by CTE is in the range of 20 nm.

Dobrik, G.; Nemes-Incze, P.; Tapasztó, L.; Lambin, Ph.; Biró, L. P.

2012-03-01

277

Automated identification of crystallographic ligands using sparse-density representations.  

PubMed

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

2014-07-01

278

Growth of KDP single crystal blocks in defined crystallographic direction  

NASA Astrophysics Data System (ADS)

It has been shown that sectorial and zonary unhomogeneities of the crystal together with changing temperature conditions in the course of its growth are among the main causes of appearance of the structure defectiveness and property unhomogeneities in the volume of crystals grown. The method of rapid growing in the defined crystallographic direction [101] of the large-size KDP and DKDP single crystallites on the plain seed has been developed, which are applicable for production of wide aperture frequency multipliers of laser emission into the second/third harmonics (type II). Usage of such a method of growing allows to increase the coefficient of use of crystal material (KDP up to 40% and DKDP up to 70%) at production of nonlinear laser elements. High quality of the crystals grown has been confirmed by the results of investigation of structural perfection, optical homogeneity and bulk laser damage resistance threshold.

Salo, V. I.; Voronov, A. P.; Tkachenko, V. F.; Babenko, G. N.; Makoveev, A. V.

2011-12-01

279

Crystallographic data processing for free-electron laser sources  

PubMed Central

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

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

2013-01-01

280

Crystallographic data processing for free-electron laser sources.  

PubMed

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

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

2013-07-01

281

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

282

Microstructural and crystallographic surface changes after grinding zirconia-based dental ceramics.  

PubMed

The purpose of this study was to evaluate microstructural and crystallographic phase changes after grinding 3Y-TZP dental ceramics. Ceramic blanks were sintered according to manufacturer's recommendations and divided into four groups: (A) as-sintered control, (B) diamond-ground manually under water, (C) ground and polished, and (D) ground and annealed at 1000 degrees C for 1 h. Bulk specimens were analyzed by X-ray diffraction to characterize the crystalline phases. The microstructure was investigated by SEM. XRD analyses showed that the control group and the group that was ground and annealed contained only tetragonal zirconia. However, after grinding or after grinding followed by polishing, rhombohedral zirconia and strained tetragonal zirconia were present, without any detectable amount of monoclinic zirconia. Annealing led to the disappearance of both residual lattice strain and the rhombohedral phase. The microstructure of the ground and polished specimens was characterized by significant residual surface damage associated with grain pullout to a depth of about 20 microm. This type of damage could have an impact on the long-term fatigue behavior of 3Y-TZP. PMID:16184529

Denry, I L; Holloway, J A

2006-02-01

283

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

NASA Astrophysics Data System (ADS)

We present a position-space renormalization-group method for nonequilibrium systems, and illustrate its application using the one-dimensional driven asymmetric chain. The dynamics in this case are characterized by three parameters: the probability ? that a particle will enter the chain from the left boundary, the probability ? that a particle will exit the chain at the right boundary, and the probability p that a particle will jump to its right neighboring site if that site is empty. Rescaling trajectories flow in the space of these probabilities and the dynamics are implemented sequentially. The phase diagram for the steady states consists of three distinct regions, one with high current and two others distinguished by their average densities. This method yields a multicritical point at ?_c=?_c=0.5, in agreement with the exact solution.(B. Derrida, et al., J. Phys. A: Math. Gen. 26), 1493 (1993); G. Schutz and E. Domany, J. Stat. Phys. 72, 277 (1993). We find the exponent ? = 2.71 associated with this fixed point, as compared with the exact value of 2.00.

Georgiev, Ivan T.; McKay, Susan R.

2001-03-01

284

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

PubMed

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

Bujnicki, Janusz M

2003-10-01

285

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

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

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

2013-09-01

288

Crystallographic preferred orientation development by dissolution?precipitation creep  

NASA Astrophysics Data System (ADS)

Crystallographic preferred orientations (CPOs) in deformed rocks are commonly interpreted as resulting from crystal plastic deformation mechanisms, where deformation is achieved by the movement of dislocations. In this paper we investigate the possibility of CPO-development by dissolution-precipitation creep or pressure solution. A numerical model is presented, which simulates the development of a grain aggregate that deforms by reaction-controlled dissolution-precipitation creep. Grains are simulated as rectangular boxes that change their shape by growth, or dissolution of their surfaces, depending on the normal stresses acting on the individual surfaces. Grains can also rotate due to an applied vorticity (for non-coaxial deformation) and if they have a non-equidimensional shape. For each strain increment, stress that is applied to the grains is the same for all grains, while individual grains deform and rotate by different amounts. A variety of CPOs develop at moderate strains, depending on the reaction rates of the different crystal-surfaces and type of deformation (uni-axial shortening, plane strain pure shear and simple shear). The modelling results confirm that dissolution-precipitation creep may play a role in CPO-development in rocks.

Bons, Paul D.; den Brok, Bas

2000-11-01

289

Regulation of enamel hardness by its crystallographic dimensions.  

PubMed

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

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

2012-09-01

290

Pulsed neutron spectroscopic imaging for crystallographic texture and microstructure  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

291

Luminescence of high temperature materials for thermometry and crystallographic studies  

NASA Astrophysics Data System (ADS)

The use of luminescence decay lifetimes to measure temperature is in many ways an ideal solution to the challenges presented to thermometry by aggressive high temperature environments with chemically or mechanically dynamic environments. Additionally, many such systems in which knowledge of temperature is desired already incorporate oxides as surface layers for tribological or environmental protection, or thermal insulation. These oxides can in many cases be made luminescent by appropriate rare-earth doping. This work examines the lifetime decay behavior of numerous doped oxides pertinent to thermal barrier and environmental barrier systems. Towards application in jet turbines, one of the chief fields of interest in this technique, the creation and demonstration of discrete sensor layers in or on top of zirconia coatings is presented. Implementation of luminescence lifetime thermometry in thermal barrier and environmental barrier systems is discussed specifically, and application to other systems is discussed in general. Materials are presented showing temperature sensitivity up to at least 1450°C. Approaches to analysis of decay traces and luminescence spectra are described that yield greater precision of lifetime values (and thus temperature) and deeper understanding of the crystal chemistry from which the luminescent properties are derived. This later point is particularly important for the commercial thermal barrier, yttria-stabilized zirconia, which possesses rich crystallographic properties and exhibits luminescent properties which are dependent on composition and thermal history as is discussed at the conclusion of this work.

Chambers, Matthew David

292

Crystallographic Studies of Chemically Modified Nucleic Acids: A Backward Glance  

PubMed Central

Chemically modified nucleic acids (CNAs) are widely explored as antisense oligonucleotide or small interfering RNA (siRNA) candidates for therapeutic applications. CNAs are also of interest in diagnostics, high-throughput genomics and target validation, nanotechnology and as model systems in investigations directed at a better understanding of the etiology of nucleic acid structure as well as the physical-chemical and pairing properties of DNA and RNA and for probing protein-nucleic acid interactions. In this article we review research conducted by our laboratory over the past two decades with a focus on crystal structure analyses of CNAs and artificial pairing systems. We highlight key insights into issues ranging from conformational distortions as a consequence of modification to the modulation of pairing strength and RNA affinity by stereoelectronic effects and hydration. Although crystal structures have only been determined for a subset of the large number of modifications that were synthesized and analyzed in the oligonucleotide context to date, they have yielded guiding principles for the design of new analogs with tailormade properties, including pairing specificity, nuclease resistance and cellular uptake. And, perhaps less obviously, crystallographic studies of CNAs and synthetic pairing systems have shed light on fundamental aspects of DNA and RNA structure and function that would not have been disclosed by investigations solely focused on the natural nucleic acids.

Egli, Martin; Pallan, Pradeep S.

2010-01-01

293

Lattice mismatch and crystallographic tilt induced by high-dose ion-implantation into 4H-SiC  

NASA Astrophysics Data System (ADS)

Lattice parameters of high-dose ion-implanted 4H-SiC were investigated with reciprocal space mapping (RSM). N, P, Al, or (C+Si) ions were implanted into lightly doped epilayers to form a (330-520) nm-deep box profile with concentrations of 1019-1020atoms/cm3. After activation annealing at 1800 °C, RSM measurements were conducted. The RSM images for (0008) reflection revealed that high-dose ion implantation causes c-lattice expansion in implanted layers, irrespective of ion species. In addition, crystallographic tilt was observed after high-dose ion implantation. The tilt direction is the same for all the samples investigated; the c-axis of the implanted layers is inclined toward the ascending direction of the off-cut. The c-lattice mismatch and the tilt angle increased as the implantation dose increases, indicating that the implantation damage is responsible for the lattice parameter change. From these results and transmission electron microscopy observation, the authors conclude that the c-lattice mismatch and the crystallographic tilt are mainly caused by secondary defects formed after the ion-implantation and activation-annealing process.

Sasaki, S.; Suda, J.; Kimoto, T.

2012-05-01

294

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.  

National Technical Information Service (NTIS)

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 rece...

1976-01-01

295

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

PubMed

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

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

2014-05-27

296

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

297

Conventional and Eccentric Uses of Crystallographic Databases in Practical Materials Identification Problems.  

National Technical Information Service (NTIS)

The crystallographic database are powerfull and cost-effective tools for solving materials identification problems, both individually and in combination. Examples of the conventional and unconventional use of the databases in solving practical problems in...

J. A. Kaduk

1996-01-01

298

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

National Technical Information Service (NTIS)

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

C. S. Costa Viana H. Brito Costa

1980-01-01

299

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

National Technical Information Service (NTIS)

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

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

1982-01-01

300

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

301

Standards for the Publication of Powder Patterns: The American Crystallographic Association Subcommittee's Final Report.  

National Technical Information Service (NTIS)

A subcommittee of the American Crystallographic Association (ACA) was formed to recommend some guidelines that would improve the overall quality of published powder diffraction data. An analysis of the Powder Diffraction File shows that many of the well-k...

L. D. Calvert J. L. Flippen-Anderson C. R. Hubbard

1979-01-01

302

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

National Technical Information Service (NTIS)

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

K. Weiss

1992-01-01

303

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

SciTech Connect

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

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

2012-05-10

304

Crystallographic analysis of demineralized human enamel treated by laser-irradiation or remineralization  

Microsoft Academic Search

Crystallographic information on dental hard tissue is helpful in evaluating whether incipient caries that has received preventative treatments is resistant to subsequent attack. The aim here was to analyse crystallographically by means of high-resolution electron microscopy (HREM) demineralized human enamel that had been laser-irradiated or remineralized. Electron-microscopic observation identified a distinct layer at a depth of 100 nm in the demineralized

K Kawasaki; Y Tanaka; O Takagi

2000-01-01

305

A complement to the modern crystallographer's toolbox: caged gadolinium complexes with versatile binding modes.  

PubMed

A set of seven caged gadolinium complexes were used as vectors for introducing the chelated Gd(3+) ion into protein crystals in order to provide strong anomalous scattering for de novo phasing. The complexes contained multidentate ligand molecules with different functional groups to provide a panel of possible interactions with the protein. An exhaustive crystallographic analysis showed them to be nondisruptive to the diffraction quality of the prepared derivative crystals, and as many as 50% of the derivatives allowed the determination of accurate phases, leading to high-quality experimental electron-density maps. At least two successful derivatives were identified for all tested proteins. Structure refinement showed that the complexes bind to the protein surface or solvent-accessible cavities, involving hydrogen bonds, electrostatic and CH-? interactions, explaining their versatile binding modes. Their high phasing power, complementary binding modes and ease of use make them highly suitable as a heavy-atom screen for high-throughput de novo structure determination, in combination with the SAD method. They can also provide a reliable tool for the development of new methods such as serial femtosecond crystallography. PMID:24914962

Stelter, Meike; Molina, Rafael; Jeudy, Sandra; Kahn, Richard; Abergel, Chantal; Hermoso, Juan A

2014-06-01

306

NMR and crystallographic characterization of adventitious borate binding by trypsin.  

PubMed

Recent 11B NMR studies of the formation of ternary complexes of trypsin, borate, and S1-binding alcohols revealed evidence for an additional binding interaction external to the enzyme active site. We have explored this binding interaction as a prototypical interaction of borate and boronate ligands with residues on the protein surface. NMR studies of trypsin in which the active site is blocked with leupeptin or with the irreversible inhibitor 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) indicate the existence of a low-affinity borate binding site with an apparent dissociation constant of 97 mM, measured at pH 8.0. Observation of a field-dependent dynamic frequency shift of the (11)B resonance indicates that it corresponds to a complex for which omegatau > 1. The 0.12 ppm shift difference of the borate resonances measured at 11.75 and 7.05 T, corresponds to a quadrupole coupling constant of 260 kHz. A much larger 2.0 ppm shift is observed in the 11B NMR spectra of trypsin complexed with benzene boronic acid (BBA), leading to a calculated quadrupole coupling constant of 1.1 MHz for this complex. Crystallographic studies identify the second borate binding site as a serine-rich region on the surface of the molecule. Specifically, a complex obtained at pH 10.6 shows a borate ion covalently bonded to the hydroxyl oxygen atoms of Ser164 and Ser167, with additional stabilization coming from two hydrogen-bonding interactions. A similar structure, although with low occupancy (30%), is observed for a trypsin-BBA complex. In this case, the BBA is also observed in the active site, covalently bound in two different conformations to both His57 Nepsilon and Ser195 Ogamma. An analysis of pairwise hydroxyl oxygen distances was able to predict the secondary borate binding site in porcine trypsin, and this approach is potentially useful for prediction of borate binding sites on the surfaces of other proteins. However, the distances between the Ser164/Ser167 Ogamma atoms in all of the reported trypsin crystal structures is significantly greater than the Ogamma distances of 2.2 and 1.9 angstroms observed in the trypsin complexes with borate and BBA, respectively. Thus, the ability of the hydroxyl oxygens to adopt a sufficiently close orientation to allow bidentate ligation is a critical limit on the borate binding affinity of surface-accessible serine/threonine/tyrosine residues. PMID:16536459

Transue, Thomas R; Gabel, Scott A; London, Robert E

2006-01-01

307

Significance of Dauphiné twins in crystallographic fabrics of quartz tectonites  

NASA Astrophysics Data System (ADS)

Dauphine twins are commonly found in quartz tectonites, however their role in deformation processes are not completely understood. This study represents a new attempt to understand the interaction between slip systems and Dauphine twins in deforming quartz-rich rocks at different temperatures. There is no doubt that Dauphine twins are mobilized under stress as this has been shown by experiments for single crystals and in polycrystalline aggregates where distinct crystallographic fabrics develop in previously randomly oriented aggregates related to minimization of elastic energy (Tullis 1972). However in quartz tectonites the Dauphine twin process is a part of interplay between plastic deformation and recovery processes which depends on PT, strain-rate and fluid composition and availability. In quartz tectonites with Y-girdle C-axis (GBM-regime) fabrics Dauphiné twins are abundant, relating different parts of r- and z rhomb "comet" distributions. This is interpreted as completion between prism slip and Dauphiné twinning. Slip rotates grains such that CRSS is low on the prism planes, but then Dauphiné twin boundaries sweeps through the grain back to the orientation giving lower stored elastic energy. The faster recovery at higher temperatures gives subgrain walls slowing down twin movement across the mm-sized grain of the GBM regime. At lower temperatures in the SGR-regime grain-size is reduced and different rotations of the grains are happening due to the domination of rhomb and basal slip. Because recrystallization is effective relative to grain-size the grains are commonly free of internal strain and subgrain walls, allowing the favorably oriented Dauphiné twin member to sweep across the whole grain overwhelming the unfavorably oriented Dauphiné twin member. As a consequence high strain reduces the number of Dauphiné twins and quartz rhomb fabrics appear trigonal, missing the "comet" shape of the GBM regime rhomb fabrics. Since Dauphiné twinning is also efficient at low temperatures rocks deformed in the brittle regime may also display stress-induced movement of Dauphiné twins. Though still highly debated Dauphiné twins and quartz rhombs fabrics may evolve as critical tools for determining paleostress orientation. Tullis, J. and Tullis, T. E., 1972, Preferred orientation of quartz produced by mechanical Dauphine twinning: thermodynamics and axial experiments in H. Heard et al., eds., Flow and Fracture of Rocks, Am. Geophys. Union Monograph 16, 67-82.

Eske Sørensen, Bjørn

2014-05-01

308

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

PubMed Central

Tyrosinase catalyzes the conversion of tyrosine to dihydroxyphenylalanine quinone, which is the main precursor for the biosynthesis of melanin. The enzyme from Agaricus bisporus, the common button mushroom, was purified and crystallized in two different space groups. Crystals belonging to space group P21 (unit-cell parameters a = 104.2, b = 105.0, c = 119.1?Å, ? = 110.6°, four molecules per asymmetric unit) diffracted to 3.0?Å resolution. Crystals belonging to space group P21212 (unit-cell parameters a = 104.0, b = 104.5, c = 108.4?Å, two molecules per asymmetric unit) diffracted to 2.6?Å resolution. It was essential to include 5?mM HoCl3 in all crystallization conditions in order to obtain well diffracting crystals.

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

2011-01-01

309

Crystals with sublattices and their symmetry in multidimensional crystal spaces  

SciTech Connect

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

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

2007-07-15

310

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

311

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

312

DFT calculation of the electronic and optical properties of Ag2PdO2 from X-ray and neutron crystallographic data  

NASA Astrophysics Data System (ADS)

Electronic and optical properties of ternary silver palladium oxide (Ag2PdO2) are investigated using density functional theory. Two different possible approximations for the exchange correlation potentials were employed. The X-ray and neutron crystallographic data were optimized by minimization of the forces (1 mRy/a.u.) acting on the atoms. The electronic structure, electron space charge density, chemical bonding and optical dielectric were determined from the relaxed geometry seeking deep insight understanding of this material. Our calculated energy band gap (0.15 eV) shows a good agreement with the experimental value (0.18 eV).

Alahmed, Zeyad A.; Reshak, Ali H.

2013-08-01

313

Identifying unknown nanocrystals by fringe fingerprinting in two dimensions and free-access crystallographic databases  

NASA Astrophysics Data System (ADS)

New needs to determine the crystallography of nanocrystals arise with the advent of science and engineering on the nanometer scale. Direct space high-resolution phase-contrast transmission electron microscopy (HRTEM) and atomic resolution Z-contrast scanning TEM (Z-STEM), when combined with tools for image-based nanocrystallography possess the capacity to meet these needs. This paper introduces such a tool, i.e. fringe fingerprinting in two dimensions (2D), for the identification of unknown nanocrystal phases and compares this method briefly to qualitative standard powder X-ray diffractometry (i.e. spatial frequency fingerprinting). Free-access crystallographic databases are also discussed because the whole fingerprinting concept is only viable if there are comprehensive databases to support the identification of an unknown nanocrystal phase. This discussion provides the rationale for our ongoing development of a dedicated free-access Nano-Crystallography Database (NCD) that contains comprehensive information on both nanocrystal structures and morphologies. The current status of the NCD project and plans for its future developments are briefly outlined. Although feasible in contemporary HRTEMs and Z-STEMs, fringe fingerprinting in 2D (and image-based nanocrystallography in general) will become much more viable with the increased availability of aberration-corrected transmission electron microscopes. When the image acquisition and interpretation are, in addition, automated in such microscopes, fringe fingerprinting in 2D will be able to compete with powder X-ray diffraction for the identification of unknown nanocrystal phases on a routine basis. Since it possesses a range of advantages over powder X-ray diffractometry, e.g., fringe fingerprint plots contain much more information for the identification of an unknown crystal phase, fringe fingerprinting in 2D may then capture a significant part of the nanocrystal metrology market.

Moeck, Peter; ?ertik, Ond?ej; Seipel, Bjoern; Groebner, Rebecca; Noice, Lori; Upreti, Girish; Fraundorf, Philip; Erni, Rolf; Browning, Nigel D.; Kiesow, Andreas; Jolivet, Jean-Pierre

2005-12-01

314

Crystallographic Preferred Orientation of Amphibole Experimentally Deformed in Simple Shear  

NASA Astrophysics Data System (ADS)

Seismic anisotropy of the intermediate to lower crust can be attributed to the crystallographic preferred orientation (CPO) of deformed amphibole because of its high anisotropy and abundance in the deep crust. However, the lack of in-depth studies on simple-shear experiments of amphibole has obstructed the view of the CPO of amphibole to explain the intricate flow patterns in the crust. Therefore, we conducted simple-shear deformation experiments of amphibolite at the pressure of 1 GPa and at the temperatures of 500 - 700°C. Starting material is a fine-grained natural amphibolite which consists of hornblende (70 %), anorthite (30 %), and minor ilmenite and titanite (~2 %). Sample was deformed to large shear strain with a strain rate of 10-5 to 10-4 s-1 by using a modified griggs apparatus installed at Seoul National University (SNU). Microstructure of the deformed amphibolite was observed by scanning electron microscope, and the CPO of hornblende was analyzed by electron backscatter diffraction (EBSD) technique with Channel 5 software. Deformed amphibolites showed strong grain-size reduction by fracturing with strain localization, suggesting that the dominant deformation mechanism was cataclastic flow accompanied by mechanical rotation of grains. We found three types of CPOs of hornblende: type-I, type-II, and type-III. All fabric types showed (100) plane aligning nearly parallel to the shear plane. Type-I fabric represented that [001] axes are aligned subparallel to the shear direction. Type-II fabric represented that (010) poles are aligned subparallel to the shear direction. Type-III fabric represented that (010) poles and [001] axes form a girdle nearly parallel to the shear plane. Type-I fabric was produced at low temperatures (500 - 550°C), but type-II and type-III fabrics were developed at higher temperatures (600 - 700°C) in a dry and wet condition, respectively. Seismic velocities and anisotropies corresponding to each CPO type were calculated. The P-wave velocity of amphibole was up to 7.24 km/s, and the P- and S-wave anisotropies were up to 14.6 and 13.0 %, respectively, indicating that the CPO of amphibole can be a major contributor for strong seismic anisotropy in the intermediate to lower crust as previous studies of naturally deformed amphibole suggested. The P-wave anisotropy depends on the fabric type of amphibole. For vertically propagating S-wave, the fast S-wave anisotropy with a dipping angle of 45° depicts that its polarization direction is nearly normal to the flow direction with much higher anisotropy (up to ~9 %) than that (less than 1 %) in horizontal shear. This result suggests that trench-parallel seismic anisotropy at the subduction channel where amphibole is available can be attributed to the CPO of amphibole.

Ko, B.; Jung, H.

2013-12-01

315

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

SciTech Connect

The Gram-negative aerobic eubacterium Thermus thermophilus is an extremely important thermophilic microorganism that was originally isolated from a thermal vent environment in Japan. The molybdenum cofactor in this organism is considered to be an essential component required by enzymes that catalyze diverse key reactions in the global metabolism of carbon, nitrogen and sulfur. The molybdenum-cofactor biosynthesis protein C derived from T. thermophilus was crystallized in two different space groups. Crystals obtained using the first crystallization condition belong to the monoclinic space group P2{sub 1}, with unit-cell parameters a = 64.81, b = 109.84, c = 115.19 {angstrom}, {beta} = 104.9{sup o}; the crystal diffracted to a resolution of 1.9 {angstrom}. The other crystal form belonged to space group R32, with unit-cell parameters a = b = 106.57, c = 59.25 {angstrom}, and diffracted to 1.75 {angstrom} resolution. Preliminary calculations reveal that the asymmetric unit contains 12 monomers and one monomer for the crystals belonging to space group P2{sub 1} and R32, respectively.

Kanaujia, Shankar Prasad; Ranjani, Chellamuthu Vasuki; Jeyakanthan, Jeyaraman; Baba, Seiki; Chen, Lirong; Liu, Zhi-Jie; Wang, Bi-Cheng; Nishida, Masami; Ebihara, Akio; Shinkai, Akeo; Kuramitsu, Seiki; Shiro, Yoshitsugu; Sekar, Kanagaraj; Yokoyama, Shigeyuki (IIS); (SP8); (Georgia)

2010-12-03

316

The Extended Relativity Theory in Born-Clifford Phase Spaces with a Lower and Upper Length Scales and Clifford Group Geometric Unification  

Microsoft Academic Search

We construct the Extended Relativity Theory in Born-Clifford-Phase spaces with an upperR and lower length ? scales (infrared\\/ultraviolet cutoff). The invariance symmetry leads naturally to the real Clifford algebra Cl (2, 6, R) and complexified Clifford ClC (4) algebra related to Twistors. A unified theory of all Noncommutative branes in Clifford-spaces is developed based on the Moyal-Yang star product deformation

Carlos Castro

2005-01-01

317

Expression, purification, and preliminary X-ray crystallographic analysis of the complex of G(alphai3)-RGS5 from human with GDP/Mg2+)/AlF4-.  

PubMed

Regulator of G-protein signaling 5 (RGS5), an inhibitor of Gq and Gi activation, is a member of the small RGS protein subfamily. However, despite significant process in the investigation of RGS5, no structure is yet available. In order to elucidate the mechanism of the RGS5 in G protein signaling pathway, we have overexpressed the RGS5 and Galphai(3) from human in Escherichia coli and crystallized the complex of RGS5 and Galphai(3) proteins with GDP/Mg(2+)/AlF(4)(-) at 3.0 A resolution using a synchrotron radiation source. The complex crystals belong to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2, with unit cell parameters a=b=95.9 A, and c=138.8 A. Assuming one complex protein in the crystallographic asymmetric unit, the calculated Matthews parameter (V(M)) is 2.57 A(3)/Da and solvent content is 52.2 %. PMID:17100651

Rhee, Kyung-Hee; Nam, Ki-Hyun; Lee, Won-Ho; Ko, Young-Gyu; Kim, Eunice Eunkyeong; Hwang, Kwang Yeon

2006-01-01

318

Elasto-Plastic Behavior of High RRR Niobium: Effects of Crystallographic Texture, Microstructure and Hydrogen Concentration  

SciTech Connect

Conventional assessments of the mechanical properties of polycrystalline high RRR niobium via tensile testing have revealed unusually low apparent Young's moduli and yield strength in annealed samples. These observations motivated the current investigation of a variety of possible contributors: crystallographic texture, grain size, and impurity concentration. It is shown that the crystallographic textures of a single lot of niobium are essentially unchanged by post-recrystallization anneals at temperatures up to 800 C. Ultrasonic measurements reveal that the elastic response is not degraded by annealing. Rather, the material's extremely low yield point gives the impression of a low elastic modulus during tensile testing.

G.R. Myneni; S.R. Agnew

2002-11-01

319

Measurement of thermal diffusivity, elastic anisotropy and crystallographic orientation by interferometric photothermal microscopy  

NASA Astrophysics Data System (ADS)

This paper describes the use of interferometric photothermal microscopy for measuring the thermal diffusivity, crystallographic orientation and elastic anisotropy of a microscopic homogeneous volume of matter. This purely optical technique makes use of an intensity-modulated and focused laser beam to periodically heat the surface of the sample tested. An interferometer is used to detect the thermal expansion. After describing the experimental setup, we explain the inversion scheme allowing the determination of the local thermal diffusivity from the periodic sample surface displacement map, as well as the crystallographic orientation and elastic anisotropy in the case of cubic materials. These parameters are measured with a spatial resolution of a few cubic micrometres.

Jumel, Julien; Rochais, Denis

2007-07-01

320

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

321

X-Ray Crystallographic Studies of Electrostatic Effects in Cubic Insulin  

NASA Astrophysics Data System (ADS)

Cubic crystals of bovine insulin were obtained at pH 9 from sodium phosphate buffer. Pathway dependence of crystallization was analysed and crystallization using controlled nucleation was developed. Crystal stability and solubility were surveyed by dialysing the crystals against salt solutions varying in salt composition and ionic strength. Crystals dialysed in 0.1-0.2M Li, Na, K, Rb, NH(4) or Tl salt solutions at pH 9 diffracted to beyond 2.8A, while crystals dialysed in Cs, Mg, Ca or La rapidly lost lattice order. Change in the solvent anion did not affect crystal stability. Electron density maps calculated from X-ray data to 2.8A resolution showed two specific cation binding sites which may be occupied by monovalent cations with ionic radii <1.5A. One site lies between insulin dimers near crystallographic two-fold axis without the close involvement of protein charged groups. Cation binding at this site is important for crystal stability. The other site is alternatively occupied by B10 His in one of its two conformations. At pH 7, the Tl occupancy at both sites was decreased, at pH 9.5 the Tl occupancy of the site near B10 His was increased. The structure was refined using the refined model of cubic porcine insulin and the X-ray data collected to 2A resolution from a bovine insulin crystal at pH 9, to R = 16.1% for the data extending from 10A to 2A. High -resolution data from crystals at pH 7 and pH 10 were collected and analysed. The weights of the two B10 His conformers and the cation occupancy near B10 vary in the pH range from 7 to 10, indicating histidine titration. Shifts in the positions of B1-B4 at pH 7 suggest titration of the B-chain terminal amino groups. Co-operative conformational changes in the surface charged residues A1, A4, B21, B29, B30 at pH 10.2 suggest titration of the A-chain terminal amino groups. In several crystals treated with dichloroethane, the syn-dichloroethane was bound in the niche across the two-fold axis connecting insulin monomers. Dichloroethane binding does not perturb the site geometry and probably leads to cubic insulin preparations of increased stability.

Gursky, Olga

1992-09-01

322

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

323

Exploring structural variability in X-ray crystallographic models using protein local optimization by torsion-angle sampling  

PubMed Central

Modeling structural variability is critical for understanding protein function and for modeling reliable targets for in silico docking experiments. Because of the time-intensive nature of manual X-ray crystallographic refinement, automated refinement methods that thoroughly explore conformational space are essential for the systematic construction of structurally variable models. Using five proteins spanning resolutions of 1.0–2.8?Å, it is demonstrated how torsion-angle sampling of backbone and side-chain libraries with filtering against both the chemical energy, using a modern effective potential, and the electron density, coupled with minimization of a reciprocal-space X-ray target function, can generate multiple structurally variable models which fit the X-ray data well. Torsion-angle sampling as implemented in the Protein Local Optimization Program (PLOP) has been used in this work. Models with the lowest R free values are obtained when electrostatic and implicit solvation terms are included in the effective potential. HIV-1 protease, calmodulin and SUMO-conjugating enzyme illustrate how variability in the ensemble of structures captures structural variability that is observed across multiple crystal structures and is linked to functional flexibility at hinge regions and binding interfaces. An ensemble-refinement procedure is proposed to differentiate between variability that is a consequence of physical con­formational heterogeneity and that which reflects uncertainty in the atomic coordinates.

Knight, Jennifer L.; Zhou, Zhiyong; Gallicchio, Emilio; Himmel, Daniel M.; Friesner, Richard A.; Arnold, Eddy; Levy, Ronald M.

2008-01-01

324

Exploring structural variability in X-ray crystallographic models using protein local optimization by torsion-angle sampling.  

PubMed

Modeling structural variability is critical for understanding protein function and for modeling reliable targets for in silico docking experiments. Because of the time-intensive nature of manual X-ray crystallographic refinement, automated refinement methods that thoroughly explore conformational space are essential for the systematic construction of structurally variable models. Using five proteins spanning resolutions of 1.0-2.8 A, it is demonstrated how torsion-angle sampling of backbone and side-chain libraries with filtering against both the chemical energy, using a modern effective potential, and the electron density, coupled with minimization of a reciprocal-space X-ray target function, can generate multiple structurally variable models which fit the X-ray data well. Torsion-angle sampling as implemented in the Protein Local Optimization Program (PLOP) has been used in this work. Models with the lowest R(free) values are obtained when electrostatic and implicit solvation terms are included in the effective potential. HIV-1 protease, calmodulin and SUMO-conjugating enzyme illustrate how variability in the ensemble of structures captures structural variability that is observed across multiple crystal structures and is linked to functional flexibility at hinge regions and binding interfaces. An ensemble-refinement procedure is proposed to differentiate between variability that is a consequence of physical conformational heterogeneity and that which reflects uncertainty in the atomic coordinates. PMID:18391405

Knight, Jennifer L; Zhou, Zhiyong; Gallicchio, Emilio; Himmel, Daniel M; Friesner, Richard A; Arnold, Eddy; Levy, Ronald M

2008-04-01

325

Quaternionic representation of the Coxeter group W(H4) and the polyhedra  

NASA Astrophysics Data System (ADS)

The vertices of the four-dimensional polytope {3, 3, 5} and its dual {5, 3, 3} admitting the symmetry of the non-crystallographic Coxeter group W(H4) of order 14 400 are represented in terms of quaternions with unit norm where the polytope {3, 3, 5} is represented by the elements of the binaryicosahedral group of quaternions of order 120. We projected the polytopes to three-dimensional Euclidean space where the quaternionic vertices are the orbits of the Coxeter group W(H3), icosahedral group with inversion, where W(H3) × Z2 is one of the maximal subgroups of the Coxeter group W(H4). The orbits of the icosahedral group W(H3) in the polytope {3, 3, 5} are the conjugacy classes of the binary icosahedral group and represent a number of icosahedrons, dodecahedrons and one icosidodecahedron in three dimensions. The 15 orbits of the icosahedral group W(H3) in the polytope {5, 3, 3} represent the dodecahedrons, icosidodecahedrons, small rhombicosidodecahedrons and some convex solids possessing the icosahedral symmetry. One of the convex solids with 60 vertices is very similar to the truncated icosahedron (soccer ball) but with two different edge lengths which can be taken as a realistic model of the C60 molecule at extreme temperature and pressure.

Koca, Mehmet; Al-Ajmi, Mudhahir; Koç, Ramazan

2006-11-01

326

Wyartite: Crystallographic evidence for the first pentavalent-uranium mineral  

SciTech Connect

Determination of the structure of wyartite provides the first evidence for a pentavalent-U mineral. The structure of wyartite, CaU{sup 5+}(UO{sub 2}){sub 2}(CO{sub 3})O{sub 4}(OH)(H{sub 2}O), was solved by direct methods and refined to an agreement index (R) of 4.9% for 2309 unique reflections collected using MoK{alpha}X-radiation and a CCD-based detector. The structure contains three unique U positions; two contain U{sup 6+} and involve uranyl ions with typical pentagonal-bipyramidal coordination. Seven anions coordinate the other U position, but there is no uranyl ion present. The polyhedral geometry, the bond-valence sum incident at this U site, and electroneutrality requirements, all indicate that this site contains U{sup 5+}. The U{phi}{sub 7} ({phi}: O, OH, H{sub 2}O) polyhedra share edges and corners to form a unique sheet in which a CO{sub 3} group shares an edge with the U{sup 5+}{phi}{sub 7} polyhedron. The structure contains one Ca site coordinated by seven anions. The Ca atom and its associated H{sub 2}O groups occupy interlayer sites, along with two H{sub 2}O groups that are held in the structure by H bonds only. The Ca{phi}{sub 7} polyhedron is linked to one adjacent sheet by sharing an edge with the CO{sub 3} group and an O atom with a U{sup 6+}{phi}{sub 7} polyhedron. Structural units are linked together through hydrogen bonds only.

Burns, P.C. [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Finch, R.J. [Argonne National Lab., IL (United States). Chemical Technology Div.

1999-09-01

327

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

328

The generalization of the exterior square of a Bieberbach group  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

329

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

PubMed

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

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

2011-08-23

330

Computer programs for structural chemistry: STATUS. A FORTRAN program for statistical analysis of crystallographic quantities  

Microsoft Academic Search

A FORTRAN computer program was described for evaluation of: (1) the results of crystallographic least-squares refinements by examination of the residuals, (2) differences in sets of data collected by different methods from the same crystal, (3) differences in data sets collected by the same method from different crystals of the same material, and (4) the differences in parameters in different

L. W. Schroeder; B. Dickens

1976-01-01

331

EFFECT OF CRYSTALLOGRAPHIC ORIENTATION ON CUTTING FORCES AND SURFACE FINISH IN DUCTILE CUTTING OF KDP CRYSTALS  

Microsoft Academic Search

In order to investigate the influence of material anisotropy in ductile cutting of Potassium Dihydrogen Phosphate (KDP) crystals, experiments of face cutting of (001) plane of KDP crystals are carried out by using an ultra-precision lathe with a single point diamond tool. The cutting forces, surface finish, and surface roughness in all crystallographic orientations of the machined surface are measured,

Haofeng Chen; Yifan Dai; Ziwen Zheng; Hang Gao; Xiaoping Li

2011-01-01

332

3D Strain Geometry and Crystallographic Fabric in Experimental HT Deformation of Solnhofen Limestone  

Microsoft Academic Search

Under conditions where calcite deforms plastically, high temperature deformation tests on Solnhofen limestone have been run using different strain configurations: axi-symmetric shortening and extension, and direct shear. The aim of the work is to relate strain geometry and the development of crystallographic fabrics in different strain paths. We produced constrictional, flattening, and nearly plane strain deformations. In addition to this,

S. Llana-Funez; E. H. Rutter

2003-01-01

333

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

SciTech Connect

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

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

2010-09-15

334

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.

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

335

Development of a morphological texture in relation with the crystallographic texture during sintering of strontium hexaferrites  

Microsoft Academic Search

Quantitative analysis of grain size, grain shape, morphological and crystallographic texture has been performed in strontium hexaferrites materials, sintered from filter-pressed powders oriented or not with a magnetic field. The results provide evidence for anisotropic and abnormal grain growth at high temperature (T ? 1250°C). A morphological texture develops during heating for oriented samples, with plate-like grains preferentially aligned with

C. Genevois; J.-M. Missiaen; F. Robaut; F. Grillon; C. P. Carry

2005-01-01

336

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

337

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

338

ARGES (Atmospheric Revitalization Group Expert System): An Expert System for Fault Diagnosis within Space-Based ECLS (Environmental Control and Life Support) Systems.  

National Technical Information Service (NTIS)

ARGES (Atmospheric Revitalization Group Expert System) is a demonstration prototype expert system for fault management for the Solid Amine, Water Desorbed (SAWD) CO2 removal assembly, associated with the Environmental Control and Life Support (ECLS) Syste...

D. W. Pachura S. A. Suleiman A. P. Mendler

1988-01-01

339

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

340

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.

341

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

PubMed

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

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

2013-08-01

342

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

PubMed Central

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 P4322, 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.

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

2012-01-01

343

Crystallization and preliminary X-ray crystallographic study of the human MST2 SARAH domain  

PubMed Central

The SARAH domain at the C-terminus of human MST2 (residues 436–484) was overproduced and purified using an Escherichia coli expression system. The purified domain was crystallized using the hanging-drop vapour-diffusion technique. Two crystal forms were obtained. The crystals belonged to space group P2, with unit-cell parameters a = 62.0, b = 119.2, c = 62.0?Å, ? = 90.0, ? = 90.5, ? = 90.0°, or to space group P6122, with unit-cell parameters a = 54.5, b = 54.5, c = 303.1?Å. These crystals diffracted to 2.7 and 3.0?Å resolution, respectively.

Song, Jinsue; Hong, Hyerim; Choi, Saehae; Lee, Yong Hee; Yamashita, Eiki; Bae, Suk-Chul; Park, Il Yeong; Lee, Soo Jae

2011-01-01

344

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

PubMed Central

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

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

2008-01-01

345

Crystallographic characterization and molecular symmetry of edestin, a legumin from hemp.  

PubMed

Edestin, a legumin class reserve protein from hemp seeds having six identical subunits was crystallized from ammonium phosphate at pH 5 and subsequently characterized by X-ray diffraction. The crystals are of space group R32 with a = 127 A and gamma = 116 degrees having an equivalent triply centered hexagonal cell of a = b = 215 A, c = 80 A. There is one hexameric protein in the rhombohedral unit cell, hence the subunits of the Edestin molecule must be arranged with 32 point group symmetry. PMID:8289257

Patel, S; Cudney, R; McPherson, A

1994-01-01

346

Expression, purification, crystallization and preliminary crystallographic analysis of laminin-binding protein (Lmb) from Streptococcus agalactiae.  

PubMed

Laminin-binding protein (Lmb), a surface-exposed lipoprotein from Streptococcus agalactiae (group B streptococcus), mediates attachment to human laminin and plays a crucial role in the adhesion/invasion of eukaryotic host cells. However, the structural basis of laminin binding still remains unclear. In the context of detailed structural analysis, the lmb gene has been cloned, expressed in Escherichia coli, purified and crystallized. The crystals diffracted to a resolution of 2.5 A and belonged to the monoclinic space group P2(1), with unit-cell parameters a = 56.63, b = 70.60, c = 75.37 A, beta = 96.77 degrees . PMID:19407385

Ragunathan, Preethi; Spellerberg, Barbara; Ponnuraj, Karthe

2009-05-01

347

Crystallographic texture in pulsed laser deposited hydroxyapatite bioceramic coatings  

PubMed Central

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

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

2008-01-01

348

Studies of social group dynamics under isolated conditions. Objective summary of the literature as it relates to potential problems of long duration space flight  

NASA Technical Reports Server (NTRS)

Scientific literature which deals with the study of human behavior and crew interaction in situations simulating long term space flight is summarized and organized. A bibliography of all the pertinent U.S. literature available is included, along with definitions of the behavioral characteristics terms employed. The summarized studies are analyzed according to behavioral factors and environmental conditions. The analysis consist of two matrices. (1) The matrix of factors studied correlates each research study area and individual study with the behavioral factors that were investigated in the study. (2) The matrix of conclusions identifies those studies whose investigators appeared to draw specific conclusions concerning questions of importance to NASA.

Vinograd, S. P.

1974-01-01

349

Quasirepresentations of amenable groups: Unbounded tame quasirepresentations  

NASA Astrophysics Data System (ADS)

Continuing the study of representations of amenable groups, we discuss a model case in which a (not necessarily bounded) Banach space quasirepresentation of an amenable group is close to an ordinary representation of the group in the same space.

Shtern, A. I.

2013-07-01

350

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

Microsoft Academic Search

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

Peter T. Traynor; Peter J. McLane

1990-01-01

351

Abundance of jackfruit (Artocarpus heterophyllus) affects group characteristics and use of space by golden-headed lion tamarins (Leontopithecus chrysomelas) in Cabruca agroforest.  

PubMed

Cabruca is an agroforest of cacao trees shaded by native forest trees. It is the predominant vegetation type throughout eastern part of the range of the golden-headed lion tamarins, Leontopithecus chrysomelas, an endangered primate endemic to Atlantic Forest. Understanding how lion tamarins use this agroforest is a conservation priority. To address this question, we documented the diet, home range size, group sizes and composition, density, number of litters and body condition of lion tamarins living in cabruca, and other habitats. Jackfruit, Artocarpus heterophyllus, was the most used species used by lion tamarins in cabruca and was widely available and used throughout the year. In cabruca, home range size was the smallest (22-28 ha) and density of lion tamarins was the highest (1.7 ind/ha) reported for the species. Group size averaged 7.4 individuals and was not significantly different among the vegetation types. In cabruca, groups produced one or two litters a year, and all litters were twins. Adult males in cabruca were significantly heavier than males in primary forest. Our study is the first to demonstrate that breeding groups of golden-headed lion tamarins can survive and reproduce entirely within cabruca agroforest. Jackfruit proved to be a keystone resource for lion tamarins in cabruca, and bromeliads were important as an animal prey foraging microhabitat. In cases where cabruca contains concentrated resources, such as jackfruit and bromeliads, lion tamarins may not only survive and reproduce but may fare better than in other forest types, at least for body condition and reproduction. PMID:21079956

Oliveira, Leonardo C; Neves, Leonardo G; Raboy, Becky E; Dietz, James M

2011-08-01

352

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

353

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

NASA Astrophysics Data System (ADS)

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.

Liang, Yuan-Chang; Hsia, Hao-Yuan

2013-12-01

354

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

PubMed Central

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

2013-01-01

355

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

PubMed

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

Liang, Yuan-Chang; Hsia, Hao-Yuan

2013-01-01

356

Crystallographic analysis of demineralized human enamel treated by laser-irradiation or remineralization.  

PubMed

Crystallographic information on dental hard tissue is helpful in evaluating whether incipient caries that has received preventative treatments is resistant to subsequent attack. The aim here was to analyse crystallographically by means of high-resolution electron microscopy (HREM) demineralized human enamel that had been laser-irradiated or remineralized. Electron-microscopic observation identified a distinct layer at a depth of 100 nm in the demineralized and laser-irradiated enamel. The crystallinity in the shallower area was inferior to that in the deeper area. Comparison of the HREM findings from the deeper area with the data provided by the Joint Committee on Powdered Diffraction Standards revealed that the mineral in the demineralized and laser-irradiated enamel was either alpha- or beta-tricalcium phosphate, while that in the remineralized enamel was thought to be tetracalcium diphosphate monoxide. PMID:10869493

Kawasaki, K; Tanaka, Y; Takagi, O

2000-09-01

357

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

358

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

PubMed Central

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

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

2013-01-01

359

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

360

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

2014-06-01

361

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

Microsoft Academic Search

This paper reports a unique approach to the fabrication of magnetically anisotropic nanostructured FePt magnets: cyclic sheath cold rolling and subsequent magnetic annealing. High magnetic fields enhance both crystallographic texture and magnetic properties of cold-deformed FePt nanostructured magnets. Magnetic annealing increases (001) out-of-plane texture of the FePt hard phase by 50% and introduces magnetic anisotropy in the annealed samples. It

B. Z. Cui; K. Han; D. S. Li; H. Garmestani; J. P. Liu; N. M. Dempsey; H. J. Schneider-Muntau

2006-01-01

362

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

363

A 9 Å Resolution X-Ray Crystallographic Map of the Large Ribosomal Subunit  

Microsoft Academic Search

The 50S subunit of the ribosome catalyzes the peptidyl-transferase reaction of protein synthesis. We have generated X-ray crystallographic electron density maps of the large ribosomal subunit from Haloarcula marismortui at various resolutions up to 9 Å using data from crystals that diffract to 3 Å. Positioning a 20 Å resolution EM image of these particles in the crystal lattice produced

Nenad Ban; Betty Freeborn; Poul Nissen; Pawel Penczek; Robert A. Grassucci; Robert Sweet; Joachim Frank; Peter B. Moore; Thomas A. Steitz

1998-01-01

364

Viscosity enhancement In non-Newtonian flow of dilute polymer solutions through crystallographic porous media  

Microsoft Academic Search

We report results of the flow of dilute mono-disperse solutions of atactic poly(styrene) in di-octyl phthalate through regular crystallographic packed beds of spheres. Pressure drop measurements made as a function of flow rate across simple cubic and body centred cubic arrays of spheres have been used to estimate the specific viscosities of the polymer solutions as a function of the

Simon J. Haward; Jeffrey A. Odell

2003-01-01

365

Crystallographic studies on substituted m-terphenyls: identification of weak [CH3···I] interactions  

Microsoft Academic Search

Crystallographic studies of 2,6-bis(2,4,6-trimethylphenyl)-4-methyliodobenzene 1 and 2,6-diphenyl-4-methyliodobenzene 2 were performed and in both cases [CH3···I] interactions were identified. Theoretical calculation of the dipole moment of 1 and the partial charges of the iodine and methyl hydrogens were performed. These charges, although small, suggest that they are large enough to encourage the formation of weak dipole-dipole interactions in the absence of

Diane A. Dickie; Deepa Abeysekera; Iain D. McKenzie; Hilary A. Jenkins; Jason A. C. Clyburne

2003-01-01

366

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

367

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

368

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

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

369

Space Resources  

NASA Technical Reports Server (NTRS)

Space resources must be used to support life on the Moon and exploration of Mars. Just as the pioneers applied the tools they brought with them to resources they found along the way rather than trying to haul all their needs over a long supply line, so too must space travelers apply their high technology tools to local resources. The pioneers refilled their water barrels at each river they forded; moonbase inhabitants may use chemical reactors to combine hydrogen brought from Earth with oxygen found in lunar soil to make their water. The pioneers sought temporary shelter under trees or in the lee of a cliff and built sod houses as their first homes on the new land; settlers of the Moon may seek out lava tubes for their shelter or cover space station modules with lunar regolith for radiation protection. The pioneers moved further west from their first settlements, using wagons they had built from local wood and pack animals they had raised; space explorers may use propellant made at a lunar base to take them on to Mars. The concept for this report was developed at a NASA-sponsored summer study in 1984. The program was held on the Scripps campus of the University of California at San Diego (UCSD), under the auspices of the American Society for Engineering Education (ASEE). It was jointly managed under the California Space Inst. and the NASA Johnson Space Center, under the direction of the Office of Aeronautics and Space Technology (OAST) at NASA Headquarters. The study participants (listed in the addendum) included a group of 18 university teachers and researchers (faculty fellows) who were present for the entire 10-week period and a larger group of attendees from universities, Government, and industry who came for a series of four 1-week workshops. The organization of this report follows that of the summer study. Space Resources consists of a brief overview and four detailed technical volumes: (1) Scenarios; (2) Energy, Power, and Transport; (3) Materials; (4) Social Concerns. Although many of the included papers got their impetus from workshop discussions, most have been written since then, thus allowing the authors to base new applications on established information and tested technology. All these papers have been updated to include the authors' current work. This overview, drafted by faculty fellow Jim Burke, describes the findings of the summer study, as participants explored the use of space resources in the development of future space activities and defined the necessary research and development that must precede the practical utilization of these resources. Space resources considered included lunar soil, oxygen derived from lunar soil, material retrieved from near-Earth asteroids, abundant sunlight, low gravity, and high vacuum. The study participants analyzed the direct use of these resources, the potential demand for products from them, the techniques for retrieving and processing space resources, the necessary infrastructure, and the economic tradeoffs. This is certainly not the first report to urge the utilization of space resources in the development of space activities. In fact, Space Resources may be seen as the third of a trilogy of NASA Special Publications reporting such ideas arising from similar studies. It has been preceded by Space Settlements: A Design Study (NASA SP-413) and Space Resources and Space Settlements (NASA SP-428). And other, contemporaneous reports have responded to the same themes. The National Commission on Space, led by Thomas Paine, in Pioneering the Space Frontier, and the NASA task force led by astronaut Sally Ride, in Leadership and America's Future in Space, also emphasize expansion of the space Infrastructure; more detailed exploration of the Moon, Mars, and asteroids; an early start on the development of the technology necessary for using space resources; and systematic development of the skills necessary for long-term human presence in space. Our report does not represent any Government-authorized view or official NASA policy. NASA's official response to these challenging op

McKay, Mary Fae (Editor); McKay, David S. (Editor); Duke, Michael S. (Editor)

1992-01-01

370

Crystallization and preliminary X-ray crystallographic analysis of Lon from Thermococcus onnurineus NA1.  

PubMed

Lon is an oligomeric ATP-dependent protease that degrades defective or denatured proteins as well as some folded proteins for the control of cellular protein quality and metabolism. Lon from Thermococcus onnurineus NA1 was purified and crystallized at 295 K. A 2.0 A resolution data set was collected using synchrotron radiation. The crystals belonged to space group P6(3), with unit-cell parameters a = 121.45, b = 121.45, c = 195.24 A. Assuming the presence of two monomers in the asymmetric unit, the solvent content was estimated to be about 60.7%. PMID:20057071

An, Young Jun; Lee, Chang-Ro; Supangat, Supangat; Lee, Hyun Sook; Lee, Jung-Hyun; Kang, Sung Gyun; Cha, Sun-Shin

2010-01-01

371

Expression, purification, crystallization and preliminary crystallographic analysis of the phosphoglycerate kinase from Acinetobacter baumannii  

PubMed Central

Acinetobacter baumannii is a common multidrug-resistant clinical pathogen that is often found in hospitals. The A. baumannii phosphoglycerate kinase (AbPGK) is involved in the key energy-producing pathway of glycolysis and presents a potential target for antibiotic development. AbPGK has been expressed and purified; it was crystallized using lithium sulfate as the precipitant. The AbPGK crystals belonged to space group P2221. They diffracted to a resolution of 2.5?Å using synchrotron radiation at the Canadian Light Source.

Baretta, Kayla; Garen, Craig; Yin, Jiang; James, Michael N. G.

2012-01-01

372

Cloning, preparation and preliminary crystallographic studies of penicillin V acylase autoproteolytic processing mutants  

PubMed Central

The crystallization of three catalytically inactive mutants of penicillin V acylase (PVA) from Bacillus sphaericus in precursor and processed forms is reported. The mutant proteins crystallize in different primitive monoclinic space groups that are distinct from the crystal forms for the native enzyme. Directed mutants and clone constructs were designed to study the post-translational autoproteolytic processing of PVA. The catalytically inactive mutants will provide three-dimensional structures of precursor PVA forms, plus open a route to the study of enzyme–substrate complexes for this industrially important enzyme.

Chandra, P. Manish; Brannigan, James A.; Prabhune, Asmita; Pundle, Archana; Turkenburg, Johan P.; Dodson, G. Guy; Suresh, C. G.

2005-01-01

373

Anisotropic crystallographic properties, strain, and their effects on band structure of m-plane GaN on LiAlO2(100)  

NASA Astrophysics Data System (ADS)

The m-plane GaN films grown on LiAlO2(100) by metal-organic chemical vapor deposition exhibit anisotropic crystallographic properties. The Williamson-Hall plots point out they are due to the different tilts and lateral correlation lengths of mosaic blocks parallel and perpendicular to GaN[0001] in the growth plane. The symmetric and asymmetric reciprocal space maps reveal the strain of m-plane GaN to be biaxial in-plane compress ?xx=-0.79% and Vzz=-0.14% with an out-of-plane dilatation Vyy=0.38%. This anisotropic strain further separates the energy levels of top valence band at ? point. The energy splitting as 37 meV as well as in-plane polarization anisotropy for transitions are found by the polarized photoluminescence spectra at room temperature.

Liu, B.; Zhang, R.; Xie, Z. L.; Kong, J. Y.; Yao, J.; Liu, Q. J.; Zhang, Z.; Fu, D. Y.; Xiu, X. Q.; Chen, P.; Han, P.; Shi, Y.; Zheng, Y. D.; Zhou, S. M.; Edwards, G.

2008-06-01

374

Crystallographic analysis of the structure of livingstonite HgSb{sub 4}S{sub 8} from refined data  

SciTech Connect

An X-ray diffraction study of mineral livingstonite (HgSb{sub 4}S{sub 8}) from Khaydarkan (Kyrgyzstan) has been performed on a Bruker Nonius X8Apex diffractometer with a 4K CCD detector (R = 0.031). The unit-cell parameters were found to be a = 30.1543(10) A, b = 3.9953(2) A, c = 21.4262(13) A, {beta} = 104.265(1){sup o}, V = 2501.7(2) A{sup 3}, Z = 8, d{sub calcd} = 5.013 g/cm{sup 3}, and sp. gr. A2/a. It was confirmed that livingstonite belongs to rod-layers structures. In one type of layer, two double Sb{sub 2}S{sub 4} chains are bound by disulfide groups [S{sub 2}]{sup 2-} (S-S 2.078(2) A); in the other type, these chains are bound via Hg{sup 2+} cations. A crystallographic analysis confirmed the existence of independent pseudotranslational ordering in the cation and anion matrices, which is characteristic of the lozenge-like structures of sulfides and sulfosalts.

Borisov, S. V., E-mail: borisov@che.nsk.su; Pervukhina, N. V.; Magarill, S. A.; Kuratieva, N. V. [Russian Academy of Sciences, Nikolaev Institute of Inorganic Chemistry, Siberian Branch (Russian Federation); Vasil'ev, V. I., E-mail: itret@uiggm.nsc.ru [Russian Academy of Sciences, Institute of Geology and Mineralogy, Siberian Branch (Russian Federation)

2010-03-15

375

Expression, crystallization and preliminary X-ray crystallographic analysis of alcohol dehydrogenase (ADH) from Kangiella koreensis.  

PubMed

Alcohol dehydrogenases (ADHs) are a group of dehydrogenase enzymes that facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of NAD(+) to NADH. In bacteria, some alcohol dehydrogenases catalyze the opposite reaction as part of fermentation to ensure a constant supply of NAD(+). The adh gene from Kangiella koreensis was cloned and the protein (KkADH) was expressed, purified and crystallized. A KkADH crystal diffracted to 2.5?Å resolution and belonged to the monoclinic space group P2(1), with unit-cell parameters a = 94.1, b = 80.9, c = 115.6?Å, ? = 111.9°. Four monomers were present in the asymmetric unit, with a corresponding VM of 2.55?Å(3)?Da(-1) and a solvent content of 51.8%. PMID:23989158

Ngo, Ho-Phuong-Thuy; Hong, Seung-Hye; Hong, Myoung-Ki; Pham, Tan-Viet; Oh, Deok-Kun; Kang, Lin-Woo

2013-09-01

376

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

PubMed Central

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

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

2014-01-01

377

Hyperreflection groups  

Microsoft Academic Search

We introduce the concept of hyperreflection groups, which are a generalization of Coxeter groups. We prove the Deletion and Exchange Conditions for hyperreflection groups, and we discuss special subgroups and fundamental sectors of hyperreflection groups. In the second half of the paper, we prove that Coxeter groups and graph products of groups are examples of hyperreflection groups.

David G. Radcliffe

2010-01-01

378

HisB from Mycobacterium tuberculosis: cloning, overexpression in Mycobacterium smegmatis, purification, crystallization and preliminary X-ray crystallographic analysis  

PubMed Central

HisB, encoded by open reading frame Rv1601, possesses enzymatic activity as an imidazoleglycerol-phosphate dehydratase in the histidine-biosynthetic pathway of Mycobacterium tuberculosis. A recombinant form of HisB was crystallized in three crystal forms: crystals grown using 20% PEG 1500 as a precipitant belonged to either the cubic space group P432 or the tetragonal space group P4, while an orthorhombic crystal form belonging to space group P21212 was obtained using 15% PEG 5000 and 10?mM MnCl2 as precipitant. The structure of HisB in the orthorhombic crystal form was solved by the molecular-replacement method using the crystal structure of its Arabidopsis thaliana counterpart, which shares 47% sequence identity with Rv1601, as the search model.

Ahangar, Mohammad Syed; Khandokar, Yogesh; Nasir, Nazia; Vyas, Rajan; Biswal, Bichitra K.

2011-01-01

379

Exceptional Groups and Physics  

Microsoft Academic Search

Quarks and leptons charges and interactions are derived from gauge theories associated with symmetries. Their space-time labels come from representations of the non-compact algebra of Special Relativity. Common to these descriptions are the Lie groups stemming from their invariances. Does Nature use Exceptional Groups, the most distinctive among them? We examine the case for and against their use. They do

Pierre Ramond

2003-01-01

380

Preliminary crystallographic analysis of two hypothetical ribose-5-phosphate isomerases from Streptococcus mutans  

PubMed Central

Study of the enzymes from sugar metabolic pathways may provide a better understanding of the pathogenesis of the human oral pathogen Streptococcus mutans. Bioinformatics, biochemical and crystallization methods were used to characterize and understand the function of two putative ribose-5-phosphate isomerases: SMU1234 and SMU2142. The proteins were cloned and constructed with N-terminal His tags. Protein purification was performed by Ni2+-chelating and size-exclusion chromatography. The crystals of SUM1234 diffracted to 1.9?Å resolution and belonged to space group P212121, with unit-cell parameters a = 48.97, b = 98.27, c = 101.09?Å, ? = ? = ? = 90°. The optimized SMU2142 crystals diffracted to 2.7?Å resolution and belonged to space group P1, with unit-cell parameters a = 53.7, b = 54.1, c = 86.5?Å, ? = 74.2, ? = 73.5, ? = 83.7°. Initial phasing of both proteins was attempted by molecular replacement; the structure of SMU1234 could easily be solved, but no useful results were obtained for SMU2142. Therefore, SeMet-labelled SMU2142 will be prepared for phasing.

Wang, Chen; Fan, Xuexin; Cao, Xiaofang; Liu, Xiang; Li, Lanfen; Su, Xiaodong

2012-01-01

381

Expression, purification, crystallization and preliminary crystallographic analysis of phosphoserine aminotransferase from Bacillus alcalophilus.  

PubMed

Phosphoserine aminotransferase (PSAT; EC 2.6.1.52) from Bacillus alcalophilus, an obligatory alkalophile with optimum growth at pH 10.6, was overexpressed in Escherichia coli, purified and crystallized under two different conditions using the hanging-drop vapour-diffusion method. Crystals were obtained using trisodium citrate dihydrate or PEG 400 as a precipitating agent. Crystals grown in the presence of trisodium citrate belong to the orthorhombic space group C222(1), with unit-cell parameters a = 105.6, b = 136.6, c = 152.0 A, and those grown in the presence of PEG 400 belong to the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 143.7, b = 84.3, c = 67.4 A. Complete data sets were collected to 1.7 and 1.6 A resolution, respectively, at 100 K using synchrotron radiation. Analysis of the structure of B. alcalophilus PSAT may reveal structural features that contribute to enzyme adaptability at high pH values. PMID:14646107

Dubnovitsky, Anatoly P; Kapetaniou, Evangelia G; Papageorgiou, Anastassios C

2003-12-01

382

Crystallization and preliminary crystallographic studies of the HA3 subcomponent of the type B botulinum neurotoxin complex  

PubMed Central

The haemagglutinin subcomponent HA3 of the type B botulinum neurotoxin complex, which is important in toxin absorption from the gastrointestinal tract, has been expressed, purified and subsequently crystallized in two crystal forms at different pH values. Form I belonged to space group R32, with unit-cell parameters a = b = 357.4, c = 249.5?Å, ? = ? = 90, ? = 120°. Form II belonged to space group I4132, with unit-cell parameters a = b = c = 259.0?Å, ? = ? = ? = 90°. Diffraction data were collected from these crystals to a resolution of 3.0?Å for both form I and form II.

Nishimura, Kohsuke; Kitadokoro, Kengo; Takegahara, Yuki; Sugawara, Yo; Matsumura, Takuhiro; Karatani, Hajime; Fujinaga, Yukako

2011-01-01

383

Bacillus anthracis-Like Bacteria and Other B. cereus Group Members in a Microbial Community Within the International Space Station: A Challenge for Rapid and Easy Molecular Detection of Virulent B. anthracis  

PubMed Central

For some microbial species, such as Bacillus anthracis, the etiologic agent of the disease anthrax, correct detection and identification by molecular methods can be problematic. The detection of virulent B. anthracis is challenging due to multiple virulence markers that need to be present in order for B. anthracis to be virulent and its close relationship to Bacillus cereus and other members of the B. cereus group. This is especially the case in environments where build-up of Bacillus spores can occur and several representatives of the B. cereus group may be present, which increases the chance for false-positives. In this study we show the presence of B. anthracis-like bacteria and other members of the B. cereus group in a microbial community within the human environment of the International Space Station and their preliminary identification by using conventional culturing as well as molecular techniques including 16S rDNA sequencing, PCR and real-time PCR. Our study shows that when monitoring the microbial hygiene in a given human environment, health risk assessment is troublesome in the case of virulent B. anthracis, especially if this should be done with rapid, easy to apply and on-site molecular methods.

van Tongeren, Sandra P.; Roest, Hendrik I. J.; Degener, John E.; Harmsen, Hermie J. M.

2014-01-01

384

Phonon softening and crystallographic orientation of strained graphene studied by Raman spectroscopy  

PubMed Central

We present a systematic study of the Raman spectra of optical phonons in graphene monolayers under tunable uniaxial tensile stress. Both the G and 2D bands exhibit significant red shifts. The G band splits into 2 distinct subbands (G+, G?) because of the strain-induced symmetry breaking. Raman scattering from the G+ and G? bands shows a distinctive polarization dependence that reflects the angle between the axis of the stress and the underlying graphene crystal axes. Polarized Raman spectroscopy therefore constitutes a purely optical method for the determination of the crystallographic orientation of graphene.

Huang, Mingyuan; Yan, Hugen; Chen, Changyao; Song, Daohua; Heinz, Tony F.; Hone, James

2009-01-01

385

Crystallographic, luminescence and photoconductive characteristics of chemically tailored ZnO nanorods  

NASA Astrophysics Data System (ADS)

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; Mohanta, Dambarudhar; Chakraborty, Purushottam

2014-04-01

386

High-resolution transmission electron microscopy for crystallographic study of nanomaterials  

SciTech Connect

The potential of high-resolution transmission electron microscopy (including the quantitative computer processing of images and computer simulation) in a local analysis of nanomaterials is discussed. A number of examples of the application of fast Fourier transform and simulated high-resolution electronmicroscopy images in the identification of nanophases and the crystallographic study of nanocrystals and nanoparticles are considered. The role that B.K. Vainshtein played in the development of a unified approach for determination of the structure of materials using short-wave diffraction is indicated.

Imamov, R. M.; Klechkovskaya, V. V., E-mail: klechvv@ns.crys.ras.ru; Suvorova, E. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2011-07-15

387

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

388

Cavity growth and rupture of {beta}-treated zirconium: A crystallographic model  

SciTech Connect

This study aims to understand the damage mechanisms observed in {beta}-treated zirconium. Damage voids are characterized by a tubular morphology with hexagonal cross-section; their growth kinetics is determined experimentally. From these observations, a model based on the principle of creation of free surface by crystallographic slip permits one to explain the stability of the hexagonal shape and to predict a growth rate closer to the experimental value than traditional models. This improvement is due to the sensitivity of the free surface creation mechanism to the stress concentration factor k, which can not be accounted for in models based on continuum mechanics.

Crepin, J.; Bretheau, T.; Caldemaison, D. [Ecole Polytechnique, Palaiseau (France). Lab. de Mecanique des Solides] [Ecole Polytechnique, Palaiseau (France). Lab. de Mecanique des Solides

1996-12-01

389

Anisotropic constitutive modeling for nickel base single crystal superalloys using a crystallographic approach  

NASA Technical Reports Server (NTRS)

A micromechanical model based on crystallographic slip theory was formulated for nickel-base single crystal superalloys. The current equations include both drag stress and back stress state variables to model the local inelastic flow. Specially designed experiments have been conducted to evaluate the effect of back stress in single crystals. The results showed that (1) the back stress is orientation dependent; and (2) the back stress state variable in the inelastic flow equation is necessary for predicting anelastic behavior of the material. The model also demonstrated improved fatigue predictive capability. Model predictions and experimental data are presented for single crystal superalloy Rene N4 at 982 C.

Stouffer, D. C.; Sheh, M. Y.

1988-01-01

390

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

391

Communication spaces  

PubMed Central

Background and objective Annotations to physical workspaces such as signs and notes are ubiquitous. When densely annotated, work areas become communication spaces. This study aims to characterize the types and purpose of such annotations. Methods A qualitative observational study was undertaken in two wards and the radiology department of a 440-bed metropolitan teaching hospital. Images were purposefully sampled; 39 were analyzed after excluding inferior images. Results Annotation functions included signaling identity, location, capability, status, availability, and operation. They encoded data, rules or procedural descriptions. Most aggregated into groups that either created a workflow by referencing each other, supported a common workflow without reference to each other, or were heterogeneous, referring to many workflows. Higher-level assemblies of such groupings were also observed. Discussion Annotations make visible the gap between work done and the capability of a space to support work. Annotations are repairs of an environment, improving fitness for purpose, fixing inadequacy in design, or meeting emergent needs. Annotations thus record the missing information needed to undertake tasks, typically added post-implemented. Measuring annotation levels post-implementation could help assess the fit of technology to task. Physical and digital spaces could meet broader user needs by formally supporting user customization, ‘programming through annotation’. Augmented reality systems could also directly support annotation, addressing existing information gaps, and enhancing work with context sensitive annotation. Conclusions Communication spaces offer a model of how work unfolds. Annotations make visible local adaptation that makes technology fit for purpose post-implementation and suggest an important role for annotatable information systems and digital augmentation of the physical environment.

Coiera, Enrico

2014-01-01

392

Hyperreflection groups  

Microsoft Academic Search

We introduce the concept of hyperreflection groups, which are a\\u000ageneralization of Coxeter groups. We prove the Deletion and Exchange Conditions\\u000afor hyperreflection groups, and we discuss special subgroups and fundamental\\u000asectors of hyperreflection groups. In the second half of the paper, we prove\\u000athat Coxeter groups and graph products of groups are examples of\\u000ahyperreflection groups.

David G. Radcliffe

2010-01-01

393

An area detector data acquisition system for X-ray crystallographic studies of macromolecules and other X-ray diffraction experiments  

NASA Astrophysics Data System (ADS)

A data acquisition system, incorporating a flat multi-wire proportional chamber, is currently being developed at SSRL in collaboration with research groups at UCSD and LBL [1]. It will be primarily used to rapidly measure X-ray crystallographic data at multiple wavelengths for the investigation of anomalous scattering techniques in the field of protein crystallography. This system, which is in the final stages of development, is controlled by a PDP11/34 computer and incorporates the MWPC area detector, a Huber 5-circle single-crystal goniometer, an alignment carriage, an incident-beam intensity monitor and a fast television display system. An outline of the complete system and the proposed method of data collection will be presented.

Phizackerley, R. P.; Cork, C. W.; Merritt, E. A.; Hamlin, R. C.; Nielsen, C. P.; Vernon, W.; Xuong, Ng. H.; Perez-Mendez, V.

394

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

395

Conformation-changing aggregation in hydroxyacetone: a combined low-temperature FTIR, jet, and crystallographic study.  

PubMed

Aggregation in hydroxyacetone (HA) is studied using low-temperature FTIR, supersonic jet expansion, and X-ray crystallographic (in situ cryocrystallization) techniques. Along with quantum chemical methods (MP2 and DFT), the experiments unravel the conformational preferences of HA upon aggregation to dimers and oligomers. The O-H···O?C intramolecular hydrogen bond present in the gas-phase monomer partially opens upon aggregation in supersonic expansions, giving rise to intermolecular cooperatively enhanced O-H···O-H hydrogen bonds in competition with isolated O-H···O?C hydrogen bonds. On the other hand, low-temperature IR studies on the neat solid and X-ray crystallographic data reveal that HA undergoes profound conformational changes upon crystallization, with the HOCC dihedral angle changing from ~0° in the gas phase to ~180° in the crystalline phase, hence giving rise to a completely new conformation. These conclusions are supported by theoretical calculations performed on the geometry derived from the crystalline phase. PMID:21961479

Sharma, Archna; Reva, Igor; Fausto, Rui; Hesse, Susanne; Xue, Zhifeng; Suhm, Martin A; Nayak, Susanta K; Sathishkumar, Ranganthan; Pal, Rumpa; Row, Tayur N Guru

2011-12-21

396

Differential stability of the crystallographic interfaces of mu- and kappa-opioid receptors.  

PubMed

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

397

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

398

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

399

The Structural Biology Center 19ID undulator beamline: facility specifications and protein crystallographic results.  

PubMed

The 19ID undulator beamline of the Structure Biology Center has been designed and built to take full advantage of the high flux, brilliance and quality of X-ray beams delivered by the Advanced Photon Source. The beamline optics are capable of delivering monochromatic X-rays with photon energies from 3.5 to 20 keV (3.5-0.6 A wavelength) with fluxes up to 8-18 x 10(12) photons s(-1) (depending on photon energy) onto cryogenically cooled crystal samples. The size of the beam (full width at half-maximum) at the sample position can be varied from 2.2 mm x 1.0 mm (horizontal x vertical, unfocused) to 0.083 mm x 0.020 mm in its fully focused configuration. Specimen-to-detector distances of between 100 mm and 1500 mm can be used. The high flexibility, inherent in the design of the optics, coupled with a kappa-geometry goniometer and beamline control software allows optimal strategies to be adopted in protein crystallographic experiments, thus maximizing the chances of their success. A large-area mosaic 3 x 3 CCD detector allows high-quality diffraction data to be measured rapidly to the crystal diffraction limits. The beamline layout and the X-ray optical and endstation components are described in detail, and the results of representative crystallographic experiments are presented. PMID:16371706

Rosenbaum, Gerd; Alkire, Randy W; Evans, Gwyndaf; Rotella, Frank J; Lazarski, Krzystof; Zhang, Rong Guang; Ginell, Stephan L; Duke, Norma; Naday, Istvan; Lazarz, Jack; Molitsky, Michael J; Keefe, Lisa; Gonczy, John; Rock, Larry; Sanishvili, Ruslan; Walsh, Martin A; Westbrook, Edwin; Joachimiak, Andrzej

2006-01-01

400

A combined quantum chemical and crystallographic study on the oxidized binuclear center of cytochrome c oxidase.  

PubMed

Cytochrome c oxidase (CcO) is the terminal enzyme of the respiratory chain. By reducing oxygen to water, it generates a proton gradient across the mitochondrial or bacterial membrane. Recently, two independent X-ray crystallographic studies ((Aoyama et al. Proc. Natl. Acad. Sci. USA 106 (2009) 2165-2169) and (Koepke et al. Biochim. Biophys. Acta 1787 (2009) 635-645)), suggested that a peroxide dianion might be bound to the active site of oxidized CcO. We have investigated this hypothesis by combining quantum chemical calculations with a re-refinement of the X-ray crystallographic data and optical spectroscopic measurements. Our data suggest that dianionic peroxide, superoxide, and dioxygen all form a similar superoxide species when inserted into a fully oxidized ferric/cupric binuclear site (BNC). We argue that stable peroxides are unlikely to be confined within the oxidized BNC since that would be expected to lead to bond splitting and formation of the catalytic P intermediate. Somewhat surprisingly, we find that binding of dioxygen to the oxidized binuclear site is weakly exergonic, and hence, the observed structure might have resulted from dioxygen itself or from superoxide generated from O(2) by the X-ray beam. We show that the presence of O(2) is consistent with the X-ray data. We also discuss how other structures, such as a mixture of the aqueous species (H(2)O+OH(-) and H(2)O) and chloride fit the experimental data. PMID:21211513

Kaila, Ville R I; Oksanen, Esko; Goldman, Adrian; Bloch, Dmitry A; Verkhovsky, Michael I; Sundholm, Dage; Wikström, Mårten

2011-07-01

401

A Three-Dimensional Cellular Automata Model for Dendrite Growth with Various Crystallographic Orientations During Solidification  

NASA Astrophysics Data System (ADS)

A three-dimensional (3-D) cellular automata (CA) model coupled with the finite-element (FE) method has been proposed to simulate dendrite growth with various crystallographic orientations during solidification. The model introduces a new tracking neighborhood method to resolve the mesh dependency caused by the cubic lattice in the CA model for simulating 3-D dendrite growth. The migration of the solid-liquid (SL) interface is associated with the dendritic preferential orientation and the driving force for the phase transition. The latter is obtained from a thermodynamics database. The local curvature and anisotropy of the surface energy are also incorporated to describe the growth kinetics of the SL interface. The solute transfer is calculated using the FE method. A numerical simulation has been performed on a Fe-1.5 wt pct C alloy. The grain morphologies with various crystallographic orientations and the solute distribution during isothermal solidification are studied and discussed. The simulation results are compared with analytical solutions and experimental results, which are in good agreement.

Zhao, Yan; Chen, Dengfu; Long, Mujun; Arif, Tansel T.; Qin, Rongshan

2014-04-01

402

Thermoelectric properties and crystallographic shear structures in titanium oxides of the Magnèli phases  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of Magnèli phase titanium oxides TinO2n-1 (n=2,3,...) have been investigated, paying special attention to how the thermoelectric performance can be altered by changing the microstructure. Dense polycrystalline specimens with nominal composition of TiO2-x (x=0.05, 0.10, 0.15, and 0.20) prepared by conventional hot-pressing are all identified to be one of the Magnèli phases, in which crystallographic shear planes are regularly introduced according to the oxygen deficiency. Electrical conduction is n-type for all specimens and the carrier concentration increases with the increase in the oxygen deficiency. The values of lattice thermal conductivity, on the other hand, decrease with the increase in the oxygen deficiency, which can be attributed to phonon scattering at the crystallographic shear plane. The largest value of thermoelectric figure of merit Z, 1.6×10-4 K-1 was obtained at 773 K for the hot-pressed specimen of TiO1.90.

Harada, Shunta; Tanaka, Katsushi; Inui, Haruyuki

2010-10-01

403

Groups32  

NSDL National Science Digital Library

A group theory calculator. Groups32 computes information about groups of orders 1-32; has a permutation group package; and provides a search for groups with given generators and relations. Site includes documentation as well as course handouts in PDF format.

2007-11-08

404

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

405

Crystallization and Preliminary Crystallographic Study of Stonustoxin, a Protein Lethal Factor Isolated from the Stonefish ( Synanceja horrida) Venom  

Microsoft Academic Search

Crystals of stonustoxin have been obtained and diffract to 3.4 Å resolution. Stonustoxin is a protein lethal factor isolated from the venom of the stonefish, Synanceja horrida. The crystals belong to the tetragonal space group P422, with unit cell constants a = b = 109.0 Å, c = 245.7 Å. A native stonustoxin molecule has two subunits, designated ? and

Wen Shan Yew; Prasanna R. Kolatkar; Peter Kuhn; Hoon Eng Khoo

1999-01-01

406

Space Station Human Factors Research Review. Volume 3: Space Station Habitability and Function: Architectural Research  

NASA Technical Reports Server (NTRS)

Articles are presented on a space station architectural elements model study, space station group activities habitability module study, full-scale architectural simulation techniques for space stations, and social factors in space station interiors.

Cohen, Marc M. (editor); Eichold, Alice (editor); Heers, Susan (editor)

1987-01-01

407

Electronic structure, crystallographic, magnetic, and transport characterization of EuMn2 films  

NASA Astrophysics Data System (ADS)

We report the formation of EuMn2, in the form of a thin film, grown by the reaction of Eu/Mn multilayers in the solid state phase at 480 K. X-ray diffraction (XRD) studies revealed that the EuMn2 crystallizes in a hexagonal structure, with the P6/mmc space group, and lattice parameters a=0.72 nm and c=1.07 nm. X-ray photoelectron spectroscopy measurements showed divalent europium forming the compound. Transition to a magnetically ordered phase was observed at 15 K. The value of 4?Ms was estimated to be 1.5 kG at 2 K. An unusual behavior of the temperature dependence of resistivity was observed in the film, suggesting the presence of valence fluctuation systems.

Balin, K.; Szade, J.; Hutchison, A. J.; Nowak, A.; Gibaud, A.; Celinski, Z.

2010-05-01

408

Protein expression, crystallization and preliminary X-ray crystallographic analysis of chicken interferon-? receptor ? chain  

PubMed Central

The activity of interferon-? (IFN-?) relies on signal transduction, which is triggered by combination with the receptors interferon-? receptor ? chain (IFNGR1) and ? chain (IFNGR2). Native recombinant chicken IFNGR1 (chIFNGR1; residues 25–237) was overexpressed in Escherichia coli, purified by refolding and crystallized using the vapour-diffusion technique. The crystals belonged to space group P6522, with unit-cell parameters a = b = 64.1, c = 216.3?Å, ? = ? = 90, ? = 120°. The Matthews coefficient and solvent content were calculated as 2.67?Å3?Da?1 and 53.97%, respectively. X-ray diffraction data for chIFNGR1 were collected to 2.0?Å resolution at a synchrotron source.

Ping, Zhiguang; Shi, Yi; Sun, Yanling; Ma, Liping; Wang, Ming

2012-01-01

409

Crystallographic characterization of the DIX domain of the Wnt signalling positive regulator Ccd1  

PubMed Central

Coiled-coil DIX1 (Ccd1) is a positive regulator that activates the canonical Wnt signalling pathway by inhibiting the degradation of the key signal transducer ?-­catenin. The C-terminal DIX domain of Ccd1 plays an important role in the regulation of signal transduction through homo-oligomerization and protein complex formation with other DIX domain-containing proteins, i.e. axin and dishevelled proteins. Here, the expression, purification, crystallization and X-ray data collection of the Ccd1 DIX domain are reported. The crystals of the Ccd1 DIX domain belonged to space group P212121, with unit-cell parameters a = 72.9, b = 75.7, c = 125.6?Å. An X-ray diffraction data set was collected at 3.0?Å resolution.

Terawaki, Shin-ichi; Yano, Koumei; Katsutani, Takuya; Shiomi, Kensuke; Keino-Masu, Kazuko; Masu, Masayuki; Shomura, Yasuhito; Komori, Hirofumi; Shibata, Naoki; Higuchi, Yoshiki

2011-01-01

410

Purification, crystallization and preliminary crystallographic studies of a calmodulin-OLFp hybrid molecule  

PubMed Central

A hybrid molecule consisting of calmodulin (CaM) and the CaM-binding domain of olfactory nucleotide-gated ion-channel peptide (CaM-OLFp) was purified and crystallized by the hanging-drop vapour-diffusion method at 298?K. The crystals diffracted to a maximum resolution of 1.85?Å at cryogenic temperature (100?K) using X-rays from a rotating anode (Cu, wavelength 1.54?Å). The crystal belongs to the monoclinic space group C2, with unit-cell parameters a = 64.76, b = 36.23, c = 70.96?Å, ? = ? = 90, ? = 109.4°. Analysis of the packing density shows that the asymmetric unit contains one CaM-OLFp hybrid molecule with a solvent content of 36.42%.

Chyan, Chia-Lin; Huang, Po-Chung; Lin, Ta-Hsien; Huang, Jian-Wen; Lin, S. S.; Huang, Hsien-bin; Chen, Yi-Cheng

2005-01-01

411

Crystallization and preliminary crystallographic studies of a flavin-dependent thymidylate synthase from Helicobacter pylori  

PubMed Central

The ThyX enzymes that have recently been identified in various bacteria, including some important human pathogens such as Helicobacter pylori and Mycobacterium tuberculosis, are flavin-dependent thymidylate synthases that function in the place of classic thymidylate synthase enzymes in the biosynthesis of dTMP, which is one of the building blocks of DNA. They are promising targets for the development of novel antibiotics because they utilize catalytic mechanisms that are distinct from those of the classic thymidylate synthases found in most organisms, including humans. In this study, H. pylori ThyX was purified and crystallized in complex with flavin adenine dinucleotide (FAD) and a diffraction data set was collected to 2.5?Å resolution. The crystals belonged to space group C2, with unit-cell parameters a = 221.92, b = 49.43, c = 143.02?Å, ? = 98.84°.

Zhang, Xiaoli; Zhang, Jinyong; Mao, Xuhu; Zou, Quanming; Hu, Yonglin; Wang, Da-Cheng

2010-01-01

412

Crystallization and preliminary crystallographic studies of Schizolobium parahyba chymotrypsin inhibitor (SPCI) at 1.8 ? resolution  

PubMed Central

SPCI, a Kunitz-type chymotrypsin inhibitor, is a 180-amino-acid polypeptide isolated from Schizolobium parahyba seeds. This inhibitor has been characterized as a highly stable protein over a broad pH and temperature range. SPCI was crystallized using a solution containing 0.1?M sodium acetate trihydrate buffer pH 4.6, 33%(v/v) PEG 2000 and 0.2?M ammonium sulfate. Data were collected to 1.80?Å resolution from a single crystal of SPCI under cryogenic conditions. The protein crystallized in space group P21212, with unit-cell parameters a = 40.01, b = 71.58, c = 108.68?Å and an R merge of 0.052. The structure of SPCI has been solved by molecular replacement using the known structure of the Kunitz-type trypsin inhibitor from Delonix regia (PDB code 1r8n) as the search model.

Teles, Rozeni Chagas Lima; Esteves, Gisele Ferreira; Araujo, Marcus Aurelio Miranda; Bloch, Carlos; Barbosa, Joao Alexandre Ribeiro Goncalves; de Freitas, Sonia Maria

2007-01-01

413

Crystallization and preliminary X-ray crystallographic analysis of PBPD2 from Listeria monocytogenes.  

PubMed

Penicillin-binding proteins (PBPs), which mediate the peptidoglycan biosynthetic pathway in the bacterial cell wall, have been intensively investigated as a target for the design of antibiotics. In this study, PBPD2, a low-molecular-weight PBP encoded by lmo2812 from Listeria monocytogenes, was overexpressed in Escherichia coli, purified and crystallized at 295?K using the sitting-drop vapour-diffusion method. The crystal belonged to the primitive orthorhombic space group P212121, with unit-cell parameters a = 37.7, b = 74.7, c = 75.1?Å, and diffracted to 1.55?Å resolution. There was one molecule in the asymmetric unit. The preliminary structure was determined by the molecular-replacement method. PMID:24699757

Cha, Hyung Jin; Jeong, Jae Hee; Kim, Yeon Gil

2014-04-01

414

Crystallization and preliminary crystallographic analysis of a C2 protein from Arabidopsis thaliana.  

PubMed

An uncharacterized protein from Arabidopsis thaliana consisting of a single C2 domain (At3g17980) was cloned into the pETM11 vector and expressed in Escherichia coli, allowing purification to homogeneity in a single chromatographic step. Good-quality diffracting crystals were obtained using vapour-diffusion techniques. The crystals diffracted to 2.2 Å resolution and belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 35.3, b = 88.9, c = 110.6 Å. A promising molecular-replacement solution has been found using the structure of the C2 domain of Munc13-C2b (PDB entry 3kwt) as the search model. PMID:22139170

Diaz, Maira; Rodriguez, Lesia; Gonzalez-Guzman, Miguel; Martínez-Ripoll, Martín; Albert, Armando

2011-12-01

415

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

416

Expression, crystallization and preliminary X-ray crystallographic analysis of peptide deformylase from Campylobacter jejuni.  

PubMed

Campylobacter jejuni is one of the major foodborne pathogens causing human infection. Peptide deformylase, a metallohydrolase, catalyzes the deformylation of N-formylated methionine in newly synthesized polypeptides in prokaryotes and some eukaryotic organelles. The deformylation process is an essential step in protein synthesis and has attracted much attention as a potential target for the development of novel antibacterial agents. Here, the cloned codon-optimized def gene from C. jejuni was synthesized and the protein was expressed, purified and crystallized. C. jejuni peptide deformylase crystals obtained at pH 7.0 and pH 6.5 diffracted to 2.9?Å resolution and belonged to the trigonal space group R3, with unit-cell parameters a=b=105.7, c=58.0?Å. One monomer existed in the asymmetric unit, with a corresponding VM of 3.1?Å3?Da(-1) and a solvent content of 60.4%. PMID:24100562

Tran, Huyen Thi; Pham, Tan-Viet; Ngo, Ho-Phuong-Thuy; Hong, Myoung-ki; Ahn, Yeh-Jin; Kang, Lin-Woo

2013-10-01

417

Preliminary X-ray crystallographic studies of Bacillus subtilis SpeA protein  

PubMed Central

The speA gene in Bacillus subtilis encodes arginine decarboxylase, which catalyzes the conversion of arginine to agmatine. Arginine decarboxylase is an important enzyme in polyamine metabolism in B. subtilis. In order to further illustrate the catalytic mechanism of arginine decarboxylase by determining the three-dimensional structure of the enzyme, the speA gene was amplified from B. subtilis genomic DNA and cloned into the expression vector pET-28a(+). SpeA was expressed in Escherichia coli and purified to homogeneity by nickel-chelation chromatography followed by size-exclusion chromatography. High-quality crystals were obtained using the hanging-drop vapour-diffusion method at 289?K. The best crystal diffracted to 2.0?Å resolution and belonged to space group P21, with unit-cell parameters a = 86.4, b = 63.3 c = 103.3?Å, ? = 113.9°.

Liu, Xiao-Yan; Lei, Jian; Liu, Xiang; Su, Xiao-Dong; Li, Lanfen

2009-01-01

418

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

419

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 P61 or P65, 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

420

Crystallization and preliminary crystallographic analysis of ?-l-arabinopyranosidase from Streptomyces avermitilis NBRC14893  

PubMed Central

?-l-Arabinopyranosidase from Streptomyces avermitilis NBRC14893 is a monomeric protein consisting of a catalytic domain belonging to glycosyl hydrolase family 27, an unknown domain and a substrate-binding domain belonging to carbohydrate-binding module family 13. The complete enzyme (residues 45–658) has successfully been cloned and homologously expressed in the Streptomyces expression system. ?-l-Arabinopyranosidase was crystallized by the sitting-drop vapour-diffusion method. The crystals diffracted to 1.6?Å resolution and belonged to space group P212121, with unit-cell parameters a = 68.2, b = 98.9, c = 181.3?Å. The Matthews coefficient was calculated to be 2.38?Å3?Da?1.

Fujimoto, Zui; Ichinose, Hitomi; Harazono, Koichi; Honda, Mariko; Uzura, Atsuko; Kaneko, Satoshi

2009-01-01

421

Space Shuttle.  

National Technical Information Service (NTIS)

The space shuttle is discussed as a reusable space vehicle operated as a transportation system for space missions in low earth orbit. Space shuttle studies and operational capabilities are reported for potential missions indicating that about 38 percent a...

1974-01-01

422

Comparative X-Ray crystallographic studies of systemic fungicides hexaconazole and tricyclazole  

NASA Astrophysics Data System (ADS)

Chemical structure of a chemical is useful for the synthesis of new compounds with more specific actions and fewer adverse reactions, to increase/decrease the duration of action of the original drug or to get a more potent compound, to restrict the action to a specific system of the body and to reduce the adverse reactions, toxicity and other disadvantages associated. Recently it has been observed that some of the fungicides are loosing their effects. So analogous compounds can be designed as substitute, if their structures are known. A rational approach to test these fungicides is to know the three dimensional structure of these compounds and macromolecular receptor sites as well as their molecular complex. The structures of these compounds can be obtained by X-ray diffraction method in crystalline form and they will invariably be similar to their structure in solutions. The composition of crystal (RS)-2-(2,4-dichlorophenyl)-1-(1H-1, 2,4-trizole-1-y1) hexane-2-ol or hexaconazole and Tricyclazole are confirmed by comparing the infra-red spectra of two components. The unit cell parameters of Hexaconozole are a=10. 9068(7) Å, b=10.9895(7) Å c=13.6124(8) Å, ?=90o, ?=106.554(2)o, ?=90.000(5)o. The Crystal system is Monoclinic, and space group P21/c . The unit cell parameters of Tricyclazole are a=14.896(5) Å, b=7.410(5)Å, c=7.556(5) Å, ?=90(5)o, ?=90.000(5)o, ?=90.000(5)o.The Crystal system is Orthorhombic and space group is Pca21.

Chauhan, Jyotsna; Sharma, Ashish Kumar; Bhattacharya, Gargi

2012-05-01

423

Overview of International Space Standards  

NASA Technical Reports Server (NTRS)

This presentation reviews space standards as put forth by the International Organization for Standardization, additionally the organizational structure for both the international and US groups are presented. A new technical committee for space is proposed, areas of technical coverage are highlighted and models of space communications protocol and space link access service are presented.

Hooke, Adrian J.

2005-01-01

424

Crystallographic analysis of plate martensite in Fe-28.5 at.% Ni by FE-SEM/EBSD  

SciTech Connect

Crystallographic analysis of plate martensite in an Fe-28.5 at.% Ni alloy was studied by electron backscattering diffraction (EBSD) in a scanning electron microscope equipped with a field emission gun (FE-SEM). It was shown that sound orientation mapping was possible even for the martensite having a high density of lattice defects and the FE-SEM/EBSD could be a strong tool for crystallographic/microstructural analysis of martensite in steels. It was confirmed that the martensite in this alloy held the Nishiyama-Wassermann (N-W) orientation relationship. Variant analysis of every martensite crystal was successfully done from orientation mapping data. It was clarified that a certain rule of variant selection operated within local areas. The procedures of crystallographic analysis of N-W martensite were explained in detail.

Kitahara, Hiromoto [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan)]. E-mail: kitahara@im.ams.eng.osaka-u.ac.jp; Ueji, Rintaro [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu 761-0396 (Japan); Ueda, Masato [Department of Materials Science and Processing, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Tsuji, Nobuhiro [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Minamino, Yoritoshi [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan)

2005-05-15

425

Crystallographic Structure of Human ?-Hexosaminidase A: Interpretation of Tay-Sachs Mutations and Loss of GM2 Ganglioside Hydrolysis  

PubMed Central

Lysosomal ?-hexosaminidase A (Hex A) is essential for the degradation of GM2 gangliosides in the central and peripheral nervous system. Accumulation of GM2 leads to severely debilitating neurodegeneration associated with Tay-Sachs disease (TSD), Sandoff disease (SD) and AB variant. Here, we present the X-ray crystallographic structure of Hex A to 2.8 Å resolution and the structure of Hex A in complex with NAG-thiazoline, (NGT) to 3.25 Å resolution. NGT, a mechanism-based inhibitor, has been shown to act as a chemical chaperone that, to some extent, prevents misfolding of a Hex A mutant associated with adult onset Tay Sachs disease and, as a result, increases the residual activity of Hex A to a level above the critical threshold for disease. The crystal structure of Hex A reveals an ?? heterodimer, with each subunit having a functional active site. Only the ?-subunit active site can hydrolyze GM2 gangliosides due to a flexible loop structure that is removed post-translationally from ?, and to the presence of ?Asn423 and ?Arg424. The loop structure is involved in binding the GM2 activator protein, while ?Arg424 is critical for binding the carboxylate group of the N-acetyl-neuraminic acid residue of GM2. The ?-subunit lacks these key residues and has ?Asp452 and ?Leu453 in their place; the ?-subunit therefore cleaves only neutral substrates efficiently. Mutations in the ?-subunit, associated with TSD, and those in the ?-subunit, associated with SD are discussed. The effect of NGT binding in the active site of a mutant Hex A and its effect on protein function is discussed.

Lemieux, M. Joanne; Mark, Brian L.; Cherney, Maia M.; Withers, Stephen G.; Mahuran, Don J.; James, Michael N. G.

2010-01-01

426

Space Elevator: Path to Space  

NASA Astrophysics Data System (ADS)

The Space Elevator is the most promising Space Transportation system on the drawing boards today, combining scalability, qualify of ride, and safety to deliver truly commercial-grade space access-practically comparable to a train ride to space.

Kaushal, A. K.

2012-05-01

427

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

SciTech Connect

A method for determining the location and possible existence of symmetry elements in Patterson superposition maps has been developed. A comparison of the original superposition map and a superposition map operated on by the symmetry element gives possible translations to the location of the symmetry element. A reciprocal space approach using structure factor-like quantities obtained from the Fourier transform of the superposition function is then used to determine the best'' location of the symmetry element. Constraints based upon the space group requirements are also used as a check on the locations. The locations of the symmetry elements are used to modify the Fourier transform coefficients of the superposition function to give an approximation of the structure factors, which are then refined using the EG relation. The analysis of several compounds using this method is presented. Reciprocal space techniques for locating multiple images in the superposition function are also presented, along with methods to remove the effect of multiple images in the Fourier transform coefficients of the superposition map. In addition, crystallographic studies of the extended chain structure of (NHC{sub 5}H{sub 5})SbI{sub 4} and of the twinning method of the orthorhombic form of the high-{Tc} superconductor YBa{sub 2}Cu{sub 3}O{sub 7-x} are presented. 54 refs.

Hendrixson, T.

1990-09-21

428

Space Biology: A New Science.  

National Technical Information Service (NTIS)

The primary task of space biology is the study of three large groups of problems: (1) The influence of liminal (extreme) conditions, which are characteristic of space flight, on living terrestrial organisms; (2) The study and realization of the biological...

N. Hurduc

1964-01-01

429

Grouping Dinosaurs  

NSDL National Science Digital Library

In this classroom activity, young students are introduced to sets and subsets. The activity opens with background information for teachers about cladistics. After brainstorming different ways to group the class itself, students work in small groups to identify subsets of coins. The groups then complete a worksheet that challenges them to group dinosaurs into sets and subsets and share their results with the class.

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

Space Tug  

NASA Technical Reports Server (NTRS)

This Space Tug concept, proposed as a reusable multipurpose space vehicle to transport payloads to different orbital inclinations, was intended to serve as an important link between the Space Shuttle and the Space Station or any other orbital element requiring crew and/or cargo transportation. The Marshall Space Flight Center managed NASA's Space Tug activities. The Space Tug program was cancelled and did not become a reality.

2004-01-01

432

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.

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

2012-01-01

433

Military Space Station Implications.  

National Technical Information Service (NTIS)

Justifying the relevancy of a Manned Military Space Station (MMSS) and subsequently proposing its deployment to capitalize upon the United States' national security interests is the essence and purpose of this group study project. The MMSS is intended to ...

G. D. Bourne G. D. Skirvin G. R. Wilson

1987-01-01

434