Science.gov

Sample records for materials crystal structure

  1. Materials research at Stanford University. [composite materials, crystal structure, acoustics

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Research activity related to the science of materials is described. The following areas are included: elastic and thermal properties of composite materials, acoustic waves and devices, amorphous materials, crystal structure, synthesis of metal-metal bonds, interactions of solids with solutions, electrochemistry, fatigue damage, superconductivity and molecular physics and phase transition kinetics.

  2. Solar cell structure incorporating a novel single crystal silicon material

    DOEpatents

    Pankove, Jacques I.; Wu, Chung P.

    1983-01-01

    A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

  3. Materials for Alternative Energies: Computational Materials Discovery and Crystal Structure Prediction

    NASA Astrophysics Data System (ADS)

    Wolverton, Chris

    2013-03-01

    Many of the key technological problems associated with alternative energies may be traced back to the lack of suitable materials. The materials discovery process may be greatly aided by the use of computational methods, particular those atomistic methods based on density functional theory. In this talk, we present an overview of recent work on energy-related materials from density-functional based approaches. We have developed novel computational tools which enable accurate prediction of crystal structures for new materials (using both Monte Carlo and Genetic Algorithm based approaches), materials discovery via high-throughput, data mining techniques, and automated phase diagram calculations. We highlight applications in the area of Li battery materials and hydrogen storage materials.

  4. Crystal networks in silk fibrous materials: from hierarchical structure to ultra performance.

    PubMed

    Nguyen, Anh Tuan; Huang, Qiao-Ling; Yang, Zhen; Lin, Naibo; Xu, Gangqin; Liu, Xiang Yang

    2015-03-01

    This review provides a comprehensive survey of the structural characteristics of crystal networks of silk soft fibrous materials in correlation with the macroscopic properties/performance and the network formation mechanisms. The correlation between the hierarchical mesoscopic structures and the mechanical properties of silk soft fibrous materials including silk fibroin hydrogels and naturally spun silk fibers are addressed based on the hierarchical crystal network models. Namely, two types of hierarchical networks are identified: the weak nanofibril-nanofibril interaction case (i.e., silk fibroin hydrogels), and the strong nanofibril-nanofibril interaction case (i.e., silk fibers). The macroscopic properties, i.e., the rheological/mechanical properties, can be controlled in terms of tuning different levels of hierarchical network structures by ultrasonication-induced gelation, introducing the initial nucleation centers, etc. Such controls take effect by different mesoscale assembly pathways, which are found to occur via different routes of the nucleation and growth processes. Furthermore, the hierarchical network model of soft fibrous materials can be applied to explain the superior mechanical properties and the unique strain-hardening behaviors of spider silk fibers within the framework of hierarchical breaking mechanism. Obviously, a knowledge of crystal networks will allow the prediction of the performance and engineering strategy of silk fibrous materials in generals. PMID:25510895

  5. Theoretical Studies on the Electronic Structures and Properties of Complex Ceramic Crystals and Novel Materials

    SciTech Connect

    Ching, Wai-Yim

    2012-01-14

    This project is a continuation of a long program supported by the Office of Basic Energy Science in the Office of Science of DOE for many years. The final three-year continuation started on November 1, 2005 with additional 1 year extension to October 30, 2009. The project was then granted a two-year No Cost Extension which officially ended on October 30, 2011. This report covers the activities within this six year period with emphasis on the work completed within the last 3 years. A total of 44 papers with acknowledgement to this grant were published or submitted. The overall objectives of this project are as follows. These objectives have been evolved over the six year period: (1) To use the state-of-the-art computational methods to investigate the electronic structures of complex ceramics and other novel crystals. (2) To further investigate the defects, surfaces/interfaces and microstructures in complex materials using large scale modeling. (3) To extend the study on ceramic materials to more complex bioceramic crystals. (4) To initiate the study on soft condensed matters including water and biomolecules. (5) To focus on the spectroscopic studies of different materials especially on the ELNES and XANES spectral calculations and their applications related to experimental techniques. (6) To develop and refine computational methods to be effectively executed on DOE supercomputers. (7) To evaluate mechanical properties of different crystals and those containing defects and relate them to the fundamental electronic structures. (8) To promote and publicize the first-principles OLCAO method developed by the PI (under DOE support for many years) for applications to large complex material systems. (9) To train a new generation of graduate students and postdoctoral fellows in modern computational materials science and condensed matter physics. (10) To establish effective international and domestic collaborations with both experimentalists and theorists in materials research. Because of the large amount of work accomplished, a diverse class of materials covered and the desire for an easier reporting process, this report will list six categories (A to F) of major accomplishments and findings under the following headings with references to the published papers under DOE support. These six categories obviously have heavy overlaps. A complete list of published papers follows the brief description on each category. Each paper also indicates to which of the six categories the main accomplishment it belongs to. A. Electronic structure of complex and novel crystals B. Impurities, surfaces, interfaces and microstructures in ceramics C. Structures and properties of complex bioceramics D. Soft condensed matters E. Spectroscopic characterizations, XANES and ELNES spectroscopy F. Large-scale simulations

  6. Advanced thermoelectric materials with enhanced crystal lattice structure and methods of preparation

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

    1998-01-01

    New skutterudite phases including Ru.sub.0.5 Pd.sub.0.5 Sb.sub.3, RuSb.sub.2 Te, and FeSb.sub.2 Te, have been prepared having desirable thermoelectric properties. In addition, a novel thermoelectric device has been prepared using skutterudite phase Fe.sub.0.5 Ni.sub.0.5 Sb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor compounds and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor materials having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using powder metallurgy techniques. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities and good Seebeck coefficients. These materials have low thermal conductivity and relatively low electrical resistivity, and are good candidates for low temperature thermoelectric applications.

  7. Prediction and Design of Materials from Crystal Structures to Nanocrystal Morphology and Assembly

    NASA Astrophysics Data System (ADS)

    Hennig, Richard

    2012-02-01

    Predictions of structure formation by computational methods have the potential to accelerate materials discovery and design. Here we present two computational approaches for the prediction of crystal structures and the morphology of nanoparticles. Many materials properties are controlled by composition and crystal structure. We show that evolutionary algorithms coupled to ab-initio relaxations can accurately predict the crystal structure and composition of compounds without any prior information about the system. We will discuss results for various systems including the prediction of unexpected quasi-1D and 2D electronic structures in Li-Be compounds under pressure [1] and of the crystal structure of the superconducting high-pressure phase of Eu [2]. The self-assembly of nanocrystals into mesoscale superlattices provides a path to the design of materials with tunable electronic, physical and chemical properties for various applications. The self-assembly is controlled by the nanocrystal shape and by ligand-mediated interactions between them. To understand this, it is necessary to know the effect of the ligands on the surface energies (which tune the nanocrystal shape), as well as the relative coverage of the different facets (which control the interactions). Density functional calculations for the binding energy of oleic acid-based ligands on PbSe nanocrystals determine the surface energies as a function of ligand coverage. The Wulff construction predicts the thermodynamic equilibrium shape of the PbSe nanocrystals as a function of the ligand coverage. We show that the different ligand binding energies on the 100 and 111 facets results in different ligand coverages on the facets and predict a transition in the equilibrium shape from octahedral to cubic when increasing the ligand concentration during synthesis. Our results furthermore suggest that the experimentally observed transformation of the nanocrystal superlattice structure from fcc to bcc is caused by the preferential detachment of ligands from particular facets, leading to anisotropic ligand coverage [3]. [4pt] [1] J. Feng, R. G. Hennig, N. W. Ashcroft and Roald Hoffmann. Nature 451, 445 (2008). [0pt] [2] W. Bi, Y. Meng, R. S. Kumar, A. L. Cornelius, W. W. Tipton, R. G. Hennig, Y. Zhang, C. Chen, and J. S. Schilling. Phys. Rev. B 83, 104106 (2011). [0pt] [3] J. J. Choi, C. R. Bealing, K. Bian, K. J. Hughes, W. Zhang, D.-M. Smilgies, R. G. Hennig, James R. Engstrom, and Tobias Hanrath. J. Am. Chem. Soc. 133, 3131 (2011).

  8. Correlation between hierarchical structure of crystal networks and macroscopic performance of mesoscopic soft materials and engineering principles.

    PubMed

    Lin, Naibo; Liu, Xiang Yang

    2015-11-01

    This review examines how the concepts and ideas of crystallization can be extended further and applied to the field of mesoscopic soft materials. It concerns the structural characteristics vs. the macroscopic performance, and the formation mechanism of crystal networks. Although this subject can be discussed in a broad sense across the area of mesoscopic soft materials, our main focus is on supramolecular materials, spider and silkworm silks, and biominerals. First, the occurrence of a hierarchical structure, i.e. crystal network and domain network structures, will facilitate the formation kinetics of mesoscopic phases and boost up the macroscopic performance of materials in some cases (i.e. spider silk fibres). Second, the structure and performance of materials can be correlated in some way by the four factors: topology, correlation length, symmetry/ordering, and strength of association of crystal networks. Moreover, four different kinetic paths of crystal network formation are identified, namely, one-step process of assembly, two-step process of assembly, mixed mode of assembly and foreign molecule mediated assembly. Based on the basic mechanisms of crystal nucleation and growth, the formation of crystal networks, such as crystallographic mismatch (or noncrystallographic) branching (tip branching and fibre side branching) and fibre/polymeric side merging, are reviewed. This facilitates the rational design and construction of crystal networks in supramolecular materials. In this context, the (re-)construction of a hierarchical crystal network structure can be implemented by thermal, precipitate, chemical, and sonication stimuli. As another important class of soft materials, the unusual mechanical performance of spider and silkworm silk fibres are reviewed in comparison with the regenerated silk protein derivatives. It follows that the considerably larger breaking stress and unusual breaking strain of spider silk fibres vs. silkworm silk fibres can be interpreted according to the synergistically correlated hierarchical structures of the domain and crystal networks, which can be quantified by the hierarchical structural correlation and the four structural parameters. Based on the concept of crystal networks, the new understanding acquired will transfer the research and engineering of mesoscopic materials, particularly, soft functional materials, to a new phase. PMID:26214062

  9. Elastico-mechanoluminescence and crystal-structure relationships in persistent luminescent materials and II-VI semiconductor phosphors

    NASA Astrophysics Data System (ADS)

    Chandra, B. P.; Chandra, V. K.; Jha, Piyush

    2015-04-01

    Elastico-mechanoluminescence (EML) has recently attracted the attention of a large number of researchers because of its potential in different types of mechano-optical devices. For understanding the mechanism of EML the relationships between elastico-mechanoluminescence (EML) and crystal-structure of a large number of persistent luminescent materials and II-VI semiconductor phosphors known to date are investigated. It is found that, although most of the non-centrosymmetric crystals exhibit EML, certain non-centrosymmetric crystals do not show EML. Whereas, many centrosymmetric crystals do not exhibit EML, certain centrosymmetric crystals exhibit EML. Piezoelectric ZnS:Cu,Cl single crystals do not show EML, but piezoelectric ZnS:Cu,Cl microcrystalline phosphors show very intense EML. Piezoelectric single crystals of undoped ZnS do not show EML. It seems that EML is related to local piezoelectrification near the impurities in crystals where piezoelectric constant is high. Suitable piezoelectric field near the local piezoelectric region and stable charge carriers in traps are required for appearance of EML. The EML of persistent luminescent materials and II-VI semiconductor phosphors can be understood on the basis of piezoelectrically-induced trap-depth reduction model of EML. Using suitable dopants both in non-centrosymmetric and centrosymmetric crystals intense elastico-mechanoluminescent materials emitting desired colours can be tailored, which may find applications in several mechano-optical devices.

  10. The influence of material properties on the elastic band structures of one-dimensional functionally graded phononic crystals

    NASA Astrophysics Data System (ADS)

    Su, Xing-liang; Gao, Yuan-wen; Zhou, You-he

    2012-12-01

    We study the influence of material parameters on elastic band gaps of one-dimensional functionally graded phononic crystals (FGPCs). By using plane-wave expansion, we calculate the first four band structures of FGPCs consisting of functionally graded materials (FGMs). These structures vary exponentially. We systematically study the influence of material parameters for four different FGPC models. Compared with traditional phononic crystals (PCs), the FGPC band gaps are clearly changed by FGMs. We also consider the influence of material composition, material properties and geometrical parameters on band gaps. Results show that different FGM properties can change the band structures remarkably. Our work can facilitate the design of vibration filters and noise insulators and provide more design freedom in engineering.

  11. Crystal Structure Prediction and its Application in Earth and Materials Sciences

    NASA Astrophysics Data System (ADS)

    Zhu, Qiang

    First of all, we describe how to predict crystal structure by evolutionary approach, and extend this method to study the packing of organic molecules, by our specially designed constrained evolutionary algorithm. The main feature of this new approach is that each unit or molecule is treated as a whole body, which drastically reduces the search space and improves the efficiency. The improved method is possibly to be applied in the fields of (1) high pressure phase of simple molecules (H2O, NH3, CH4, etc); (2) pharmaceutical molecules (glycine, aspirin, etc); (3) complex inorganic crystals containing cluster or molecular unit, (Mg(BH4)2, Ca(BH4)2, etc). One application of the constrained evolutionary algorithm is given by the study of (Mg(BH4)2, which is a promising materials for hydrogen storage. Our prediction does not only reproduce the previous work on Mg(BH4)2 at ambient condition, but also yields two new tetragonal structures at high pressure, with space groups P4 and I41/acd are predicted to be lower in enthalpy, by 15.4 kJ/mol and 21.2 kJ/mol, respectively, than the earlier proposed P42nm phase. We have simulated X-ray diffraction spectra, lattice dynamics, and equations of state of these phases. The density, volume contraction, bulk modulus, and the simulated XRD patterns of P4 and I41/acd structures are in excellent agreement with the experimental results. Two kinds of oxides (Xe-O and Mg-O) have been studied under megabar pressures. For XeO, we predict the existence of thermodynamically stable Xe-O compounds at high pressures (XeO, XeO2 and XeO3 become stable at pressures of 83, 102 and 114 GPa, respectively). For Mg-O, our calculations find that two extraordinary compounds MgO2 and Mg3O 2 become thermodynamically stable at 116 GPa and 500 GPa, respectively. Our calculations indicate large charge transfer in these oxides for both systems, suggesting that large electronegativity difference and pressure are the key factors favouring their formations. We also discuss if these oxides might exist at earth and planetary conditions. If the target properties are set as the global fitness functions while structure relaxations are energy/enthalpy minimization, such hybrid optimization technique could effectively explore the landscape of properties for the given systems. Here we illustrate this function by the case of searching for superdense carbon allotropes. We find three structures (hP3, tI12, and tP12) that have significantly greater density. Furthermore, we find a collection of other superdense structures based on different ways of packing carbon tetrahedral. Superdense carbon allotropes are predicted to have remarkably high refractive indices and strong dispersion of light. Apart from evolutionary approach, there also exist some other methods for structural prediction. One can also combine the features from different methods. We develop a novel method for crystal structure prediction, based on metadynamics and evolutionary algorithms. This technique can be used to produce efficiently both the ground state and metastable states easily reachable from a reasonable initial structure. We use the cell shape as collective variable and evolutionary variation operators developed in the context of the USPEX method to equilibrate the system as a function of the collective variables. We illustrate how this approach helps one to find stable and metastable states for Al2SiO5, SiO2, MgSiO3. Apart from predicting crystal structures, the new method can also provide insight into mechanisms of phase transitions. This method is especially powerful in sampling the metastable structures from a given configuration. Experiments on cold compression indicated the existence of a new superhard carbon allotrope. Numerous metastable candidate structures featuring different topologies have been proposed for this allotrope. We use evolutionary metadynamics to systematically search for possible candidates which could be accessible from graphite. (Abstract shortened by UMI.)

  12. Nondestructive optical testing of the materials surface structure based on liquid crystals

    NASA Astrophysics Data System (ADS)

    Tomilin, M. G.; Stafeev, S. K.

    2011-08-01

    Thin layers of nematic liquid crystals (NLCs) may be used as recording media for visualizing structural and microrelief defects, distribution of low power physical fields and modifications of the surface. NLCs are more sensitive in comparison with cholesteric and smectic LCs having super molecular structures. The detecting properties of NLCs are based on local layers deformation, induced by surface fields and observed in polarizing microscope. The structural surface defects or physical field's distribution are dramatically change the distribution of surface tension. Surface defects recording becomes possible if NLC deformed structure is illuminated in transparent or reflective modes and observed in optical polarizing microscope and appearing image is compared with background structure. In this case one observes not the real defect but the local deformation in NLCs. The theory was developed to find out the real size of defects. The resolution of NLC layer is more than 2000 lines/mm. The fields of NLC application are solid crystals symmetry, minerals, metals, semiconductors, polymers and glasses structure inhomogeneities and optical coatings defects detecting. The efficiency of NLC method in biophotonics is illustrated by objective detecting cancer tissues character and visualizing the interaction traces of grippe viruses with antibodies. NLCs may detect solvent components structure in tea, wine and perfume giving unique information of their structure. It presents diagnostic information alternative to dyes and fluorescence methods. For the first time the structures of some juices and beverages are visualized to illustrate the unique possibilities of NLCs.

  13. Material-binding peptide application--ZnO crystal structure control by means of a ZnO-binding peptide.

    PubMed

    Togashi, Takanari; Yokoo, Nozomi; Umetsu, Mitsuo; Ohara, Satoshi; Naka, Takashi; Takami, Seiichi; Abe, Hiroya; Kumagai, Izumi; Adschiri, Tadafumi

    2011-02-01

    Recently, a zinc oxide (ZnO)-binding peptide (ZnOBP) has been identified and has been used to assist the synthesis of unique crystalline ZnO particles. We analyzed the influence of ZnOBP on the crystal growth of ZnO structures formed from zinc hydroxide. The addition of ZnOBP in the hydrothermal synthesis of ZnO suppressed [0001] crystal growth in the ZnO particles, indicating that the specificity of the material-binding peptide for specific inorganic crystal faces controlled the crystal growth. Furthermore, the dipeptides with a partial sequence of ZnO-binding "hot spot" in ZnOBP were used to synthesize ZnO particles, and we found that the presence of these dipeptides more strictly suppressed (0001) growth in ZnO crystals than did the complete ZnOBP sequence. These results demonstrate the applicability of dipeptides selected from material-binding peptides to control inorganic crystal growth. PMID:20947422

  14. Thermoelectric material including a multiple transition metal-doped type I clathrate crystal structure

    DOEpatents

    Yang, Jihui; Shi, Xun; Bai, Shengqiang; Zhang, Wenqing; Chen, Lidong; Yang, Jiong

    2012-01-17

    A thermoelectric material includes a multiple transition metal-doped type I clathrate crystal structure having the formula A.sub.8TM.sub.y.sub.1.sup.1TM.sub.y.sub.2.sup.2 . . . TM.sub.y.sub.n.sup.nM.sub.zX.sub.46-y.sub.1.sub.-y.sub.2.sub.- . . . -y.sub.n.sub.-z. In the formula, A is selected from the group consisting of barium, strontium, and europium; X is selected from the group consisting of silicon, germanium, and tin; M is selected from the group consisting of aluminum, gallium, and indium; TM.sup.1, TM.sup.2, and TM.sup.n are independently selected from the group consisting of 3d, 4d, and 5d transition metals; and y.sub.1, y.sub.2, y.sub.n and Z are actual compositions of TM.sup.1, TM.sup.2, TM.sup.n, and M, respectively. The actual compositions are based upon nominal compositions derived from the following equation: z=8q.sub.A-|.DELTA.q.sub.1|y.sub.1-|.DELTA.q.sub.2|y.sub.2- . . . -|.DELTA.q.sub.n|y.sub.n, wherein q.sub.A is a charge state of A, and wherein .DELTA.q.sub.1, .DELTA.q.sub.2, .DELTA.q.sub.n are, respectively, the nominal charge state of the first, second, and n-th TM.

  15. Photonic Crystal Laser Accelerator Structures

    SciTech Connect

    Cowan, Benjamin M

    2003-05-21

    Photonic crystals have great potential for use as laser-driven accelerator structures. A photonic crystal is a dielectric structure arranged in a periodic geometry. Like a crystalline solid with its electronic band structure, the modes of a photonic crystal lie in a set of allowed photonic bands. Similarly, it is possible for a photonic crystal to exhibit one or more photonic band gaps, with frequencies in the gap unable to propagate in the crystal. Thus photonic crystals can confine an optical mode in an all-dielectric structure, eliminating the need for metals and their characteristic losses at optical frequencies. We discuss several geometries of photonic crystal accelerator structures. Photonic crystal fibers (PCFs) are optical fibers which can confine a speed-of-light optical mode in vacuum. Planar structures, both two- and three-dimensional, can also confine such a mode, and have the additional advantage that they can be manufactured using common microfabrication techniques such as those used for integrated circuits. This allows for a variety of possible materials, so that dielectrics with desirable optical and radiation-hardness properties can be chosen. We discuss examples of simulated photonic crystal structures to demonstrate the scaling laws and trade-offs involved, and touch on potential fabrication processes.

  16. Soap Froths and Crystal Structures

    NASA Astrophysics Data System (ADS)

    Ziherl, P.; Kamien, Randall D.

    2000-10-01

    We propose a physical mechanism to explain the crystal symmetries found in macromolecular and supramolecular micellar materials. We argue that the packing entropy of the hard micellar cores is frustrated by the entropic interaction of their brushlike coronas. The latter interaction is treated as a surface effect between neighboring Voronoi cells. The observed crystal structures correspond to the Kelvin and Weaire-Phelan minimal foams. We show that these structures are stable for reasonable areal entropy densities.

  17. Soap froths and crystal structures

    NASA Astrophysics Data System (ADS)

    Ziherl, P.; Kamien, Randall D.

    2001-03-01

    We propose a physical mechanism to explain the crystal symmetries found in macromolecular and supramolecular micellar materials. We argue that the packing entropy of the hard micellar cores is frustrated by the entropic interaction of their brush-like coronas. The latter interaction is treated as a surface effect between neighboring Voronoi cells. The observed crystal structures correspond to the Kelvin and Weaire-Phelan minimal foams. We show that these structures are stable for reasonable areal entropy densities.

  18. Crystal structure and mechanical properties of spark plasma sintered Cu2Se: An efficient photovoltaic and thermoelectric material

    NASA Astrophysics Data System (ADS)

    Tyagi, Kriti; Gahtori, Bhasker; Bathula, Sivaiah; Jayasimhadri, M.; Sharma, Sakshi; Singh, Niraj Kumar; Haranath, D.; Srivastava, A. K.; Dhar, Ajay

    2015-04-01

    Copper selenide (Cu2Se) based materials are currently being investigated globally for efficient photovoltaic and thermoelectric (TE) device applications. Despite having enormous device potential its crystal structure and mechanical properties are still not fully explored owing to its complex behavior. Stereographic projection is one of such useful tools to estimate the crystallography of the material conclusively. In the current study, the crystal structure of α and β-phases of Cu2Se was determined by its stereographic projections in reciprocal space. Further, mechanical properties of Cu2Se are highly important to avoid catastrophic failure and ensure longevity of the TE devices made out of these materials. Cu2Se exhibited the compressive strength of ~45 MPa with ~3% of plastic strain and a fracture toughness value of ~2±0.02 MPa√m, the latter being significantly higher than that of the other known TE materials. Finally, thermal shock resistance, which is one of the crucial parameters for the stability and longevity of the device applications, was calculated to be ~281±12 W m-1. Superior mechanical properties coupled with highly reported thermoelectric behavior makes Cu2Se as a potential candidate for green energy generation.

  19. Two inorganic-organic hybrid materials based on polyoxometalate anions and methylene blue: Preparations, crystal structures and properties

    SciTech Connect

    Nie Shanshan; Zhang Yaobin; Liu Bin; Li Zuoxi; Hu Huaiming; Xue Ganglin; Fu Feng; Wang Jiwu

    2010-12-15

    Two novel inorganic-organic hybrid materials based on an organic dye cation methylene blue (MB) and Lindqvist-type POM polyanions, [C{sub 22}H{sub 18}N{sub 3}S]{sub 2}Mo{sub 6}O{sub 19} 2DMF (1) and [C{sub 22}H{sub 18}N{sub 3}S]{sub 2}W{sub 6}O{sub 19} 2DMF (2) were synthesized under ambient conditions and characterized by CV, IR spectroscopy, solid diffuse reflectance spectrum, UV-vis spectra in DMF solution, luminescent spectrum and single crystal X-ray diffraction. Crystallographic data reveal that compounds 1 and 2 are isostructural and both crystallize in the triclinic space group P1-bar . Their crystal structures present that the layers of organic molecules and inorganic anions array alternatively, and there exist strong {pi}...{pi} stacking interactions between dimeric MB cations and near distance interactions among organic dye cations, Lindqvist-type POM polyanions and DMF molecules. The solid diffuse reflectance spectra and UV-vis spectra in DMF solution appear new absorption bands ascribed to the charge-transfer transition between the cationic MB donor and the POM acceptors. Studies of the photoluminescent properties show that the formation of 1 and 2 lead to the fluorescence quenching of starting materials. -- Graphical abstract: Their crystal structures present that the layers of organic molecules and inorganic anions array alternatively, and there exist strong {pi}...{pi} stacking interactions between dimeric MB cations. Display Omitted

  20. Na 4Nb(PO 4) 3, a material with a reversible crystal-glass transformation: Structural and optical comparison

    NASA Astrophysics Data System (ADS)

    El Jazouli, A.; Parent, C.; Dance, J. M.; Le Flem, G.; Hagenmuller, P.; Viala, J. C.

    1988-06-01

    The phosphate Na 4Nb(PO 4) 3 exhibits a reversible crystal-glass phase change. Raman and optical investigations give evidence of the similarity between the covalent skeleton of the Nasicon-like crystalline phosphate and the network of the glass. Both types of materials contain octahedral NbO 6 groups with various Nb sbnd O lengths. It is shown for the neodymium-doped glasses that these structural features induce a strong self concentration quenching of the Nd 3+ emission.

  1. Crystal Structure of New Carbon-Nitride-Related Material C2N2(CH2)

    NASA Astrophysics Data System (ADS)

    Sougawa, Masaya; Sumiya, Takahiro; Takarabe, Kenichi; Mori, Yoshihisa; Okada, Taku; Gotou, Hirotada; Yagi, Takehiko; Yamazaki, Daisuke; Tomioka, Naotaka; Katsura, Tomoo; Kariyazaki, Hiroaki; Sueoka, Koji; Kunitsugu, Shinsuke

    2011-09-01

    A new carbon-nitride-related C2N2(CH2) nanoplatelet was synthesized by subjecting a precursor C3N4HxOy nanoparticle in a laser-heating diamond anvil cell to the pressure of 40 GPa and temperature of 1200-2000 K. The C and N composition of the quenched sample was determined to be C3N2 by using an energy dispersive X-ray spectroscope attached to a transmission electron microscope. The crystal structure and atomic positions of this C3N2 were obtained through Rietveld analysis of the X-ray diffraction pattern measured using synchrotron radiation. The hydrogen composition was difficult to determine experimentally because of the several-hundred-nanometer dimensions of the sample. First-principles calculation was alternatively used to discover the hydrogen composition. The synthesized C2N2(CH2) was accordingly found to be an orthorhombic unit cell of the space group Cmc21 with lattice constants a = 7.625 Å, b = 4.490 Å, and c = 4.047 Å. If the CH2 atomic unit is replaced with the CN2 atomic unit and the bonding rearranged, the C2N2(CH2) becomes the expected superhard C3N4.

  2. Crystal growth, structure and characterizations of a new semiorganic nonlinear optical material-{beta}-Alanine zinc chloride

    SciTech Connect

    Anbuchezhiyan, M.; Ponnusamy, S.; Muthamizhchelvan, C.; Sivakumar, K.

    2010-08-15

    The title compound, {beta}-alanine zinc chloride-a new semiorganic nonlinear optical crystal was grown by slow evaporation technique. Single crystals of {beta}-alanine zinc chloride have been subjected to X-ray diffraction analysis to determine the crystal structure. The powder X-ray diffractogram of the crystal has also been recorded. The amount of carbon, nitrogen and hydrogen in the crystals was also estimated. Fourier Transform Infrared and Raman spectral measurements have been carried out on the grown crystals in order to identify the functional groups. The presence of hydrogen and carbon in the {beta}-alanine zinc chloride was confirmed by using proton and carbon nuclear magnetic resonance spectral analyses. The percentage of zinc in the crystal was determined by atomic absorption spectroscopy. Optical behavior such as ultraviolet-vis-near infrared transmittance spectrum and second harmonic generation has been investigated. The mechanical strength and thermal behavior of the grown crystal have been analyzed.

  3. Multiscale Modeling of Structurally-Graded Materials Using Discrete Dislocation Plasticity Models and Continuum Crystal Plasticity Models

    NASA Technical Reports Server (NTRS)

    Saether, Erik; Hochhalter, Jacob D.; Glaessgen, Edward H.

    2012-01-01

    A multiscale modeling methodology that combines the predictive capability of discrete dislocation plasticity and the computational efficiency of continuum crystal plasticity is developed. Single crystal configurations of different grain sizes modeled with periodic boundary conditions are analyzed using discrete dislocation plasticity (DD) to obtain grain size-dependent stress-strain predictions. These relationships are mapped into crystal plasticity parameters to develop a multiscale DD/CP model for continuum level simulations. A polycrystal model of a structurally-graded microstructure is developed, analyzed and used as a benchmark for comparison between the multiscale DD/CP model and the DD predictions. The multiscale DD/CP model follows the DD predictions closely up to an initial peak stress and then follows a strain hardening path that is parallel but somewhat offset from the DD predictions. The difference is believed to be from a combination of the strain rate in the DD simulation and the inability of the DD/CP model to represent non-monotonic material response.

  4. Four-material one dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Scotognella, Francesco

    2012-07-01

    Photonic crystals made with more than two materials have been attracting increasing attention due to their peculiar optical properties. In this work, we present a theoretical analysis, by using the transfer matrix method, of one dimensional photonic crystals made of four different materials. A new photonic band gap is observed with respect to conventional one dimensional photonic crystals. Furthermore, we discuss the strong influence that the material permutations plays on the intensity and the shape of the photonic band gaps of the proposed structure.

  5. Materials and structures

    NASA Technical Reports Server (NTRS)

    Saito, Theodore T.; Langenbeck, Sharon L.; Al-Jamily, Ghanim; Arnold, Joe; Barbee, Troy; Coulter, Dan; Dolgin, Ben; Fichter, Buck; George, Patricia; Gorenstein, Paul

    1992-01-01

    Materials and structures technology covers a wide range of technical areas. Some of the most pertinent issues for the Astrotech 21 missions include dimensionally stable structural materials, advanced composites, dielectric coatings, optical metallic coatings for low scattered light applications, low scattered light surfaces, deployable and inflatable structures (including optical), support structures in 0-g and 1-g environments, cryogenic optics, optical blacks, contamination hardened surfaces, radiation hardened glasses and crystals, mono-metallic telescopes and instruments, and materials characterization. Some specific examples include low coefficients of thermal expansion (CTE) structures (0.01 ppm/K), lightweight thermally stable mirror materials, thermally stable optical assemblies, high reliability/accuracy (1 micron) deployable structures, and characterization of nanometer level behavior of materials/structures for interferometry concepts. Large filled-aperture concepts will require materials with CTE's of 10(exp 9) at 80 K, anti-contamination coatings, deployable and erectable structures, composite materials with CTE's less than 0.01 ppm/K and thermal hysteresis, 0.001 ppm/K. Gravitational detection systems such as LAGOS will require rigid/deployable structures, dimensionally stable components, lightweight materials with low conductivity, and high stability optics. The Materials and Structures panel addressed these issues and the relevance of the Astrotech 21 mission requirements by dividing materials and structures technology into five categories. These categories, the necessary development, and applicable mission/program development phasing are summarized. For each of these areas, technology assessments were made and development plans were defined.

  6. Crystal structure of the high-energy-density material guanylurea dipicryl­amide

    PubMed Central

    Deblitz, Raik; Hrib, Cristian G.; Hilfert, Liane; Edelmann, Frank T.

    2014-01-01

    The title compound, 1-carbamoylguanidinium bis­(2,4,6-tri­nitro­phen­yl)amide [H2NC(=O)NHC(NH2)2]+[N{C6H2(NO2)3-2,4,6}2]− (= guanylurea dipicryl­amide), was prepared as dark-red block-like crystals in 70% yield by salt-metathesis reaction between guanylurea sulfate and sodium dipicryl­amide. In the solid state, the new compound builds up an array of mutually linked guanylurea cations and dipicryl­amide anions. The crystal packing is dominated by an extensive network of N—H⋯O hydrogen bonds, resulting in a high density of 1.795 Mg m−3, which makes the title compound a potential secondary explosive. PMID:25249869

  7. Structure, crystal growth, optical and mechanical studies of poly bis (thiourea) silver (I) nitrate single crystal: A new semi organic NLO material

    NASA Astrophysics Data System (ADS)

    Sivakumar, N.; Kanagathara, N.; Varghese, B.; Bhagavannarayana, G.; Gunasekaran, S.; Anbalagan, G.

    2014-01-01

    A new semi organic non linear optical polymeric crystal, bis (thiourea) silver (I) nitrate (TuAgN) with dimension 8 × 7 × 1.5 mm3 has been successfully grown from aqueous solution by slow evaporation solution technique. Single crystal X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non centrosymmetric space group C2221. The crystalline perfection of the crystal was analyzed by high resolution X-ray diffraction (HRXRD) rocking curve measurements. Functional groups present in the crystal were analyzed qualitatively by infrared and Confocal Raman spectral analysis. Effects due to coordination of thiourea with metal ions were also discussed. Optical absorption study on TuAgN crystal shows the minimum absorption in the entire UV-Vis region and the lower cut off wavelength of TuAgN is found to be 318 nm. Thermal analysis shows that the material is thermally stable up to 180 °C. The mechanical strength and its parameters of the grown crystal were estimated by Vicker's microhardness test. The second harmonic generation (SHG) efficiency of the crystal was measured by Kurtz's powder technique infers that the crystal has nonlinear optical (NLO) efficiency 0.85 times that of KDP.

  8. Synthesis, growth, structural, spectral, thermal, chemical etching, linear and nonlinear optical and mechanical studies of an organic single crystal 4-chloro 4-nitrostilbene (CONS): a potential NLO material.

    PubMed

    Dinakaran, Paul M; Kalainathan, S

    2013-07-01

    4-Chloro 4-nitrostilbene (CONS) a new organic nonlinear optical material has been synthesized. Employing slow evaporation method, good optical quality single crystals (dimensions up to 6×2×3 mm(3)) have been grown using ethyl methyl ketone (EMK) as a solvent. The grown crystals have been subjected to various characterizations such as single crystal X-ray diffraction, powder XRD, Fourier Transform Infrared spectroscopy (FTIR), proton NMR, solid UV absorption, SHG studies. Single crystal X-ray diffraction reveals that the crystal system belongs to monoclinic with noncentrosymmetric space group P21. The UV-Vis absorption spectrum has been recorded and found that the cut off wavelength is 380 nm. Functional groups and the structure of the title compound have been confirmed by FTIR and (1)H NMR spectroscopic analyses respectively. Molecular mass of the CONS confirmed by the high resolution mass spectral analysis .The thermal behavior of the grown crystal has been studied by TG/DTA analysis and it shows the melting point is at 188.66 °C. Dislocations and growth pattern present in the grown crystal revealed by the etching study. The mechanical strength of the CONS crystal has been studied by Vicker's hardness measurement. The SHG efficiency of the grown crystal has been determined by Kurtz and Perry powder test which revealed that the CONS crystal (327 mV) has 15 times greater efficiency than that of KDP (21.7 mV). PMID:23624038

  9. The loss function of complex materials: Interplay between localized orbitals and crystal structure (*)

    NASA Astrophysics Data System (ADS)

    Eguiluz, A. G.; Restrepo, O. D.

    2004-03-01

    The loss function (imaginary part of the dynamical density response function) of a large class of materials is shown to feature sharp electronic collective modes whose existence is determined by a novel interplay between the availability of localized states and the periodic environment in which the excitations are realized. A new energy scale determines the location of the collective mode; the same corresponds, approximately, to the upper edge of the "upper Hubbard band complex". We introduce an "effective dielectric function," whose role is similar to that of its scalar counterpart in the case of simple materials; this "observable" allows a visualization of the physics of the collective mode. We present results for some transition metal oxides, cobaltates, and also MgB_2. (*) Supported by NSF-DMR 0219332 (**) Managed by UT-Battelle for the U.S. DOE under contract DE-AC05-00OR22725.

  10. Crystal and electronic structures of nitridophosphate compounds as cathode materials for Na-ion batteries

    NASA Astrophysics Data System (ADS)

    Debbichi, M.; Lebègue, S.

    2015-08-01

    Using density-functional theory, we have studied the electronic and magnetic properties of two promising compounds that can be used as cathode materials, namely, Na2Fe2P3O9N and Na3TiP3O9N . When Na is extracted, we found the volume change to be quite small, with values of ˜-0.6 % for Na3TiP3O9N and -5 % for Na2Fe2P3O9N . Our calculated voltages with the Hubbard-type correction (GGA+U) approximation are 2.93 V for Na3TiP3O9N /Na2TiP3O9N and 2.68 V for Na2Fe2P3O9N /NaFe2P3O9N , in good agreement with the experimental data. Our results confirm that these compounds are very promising for rechargeable Na-ion batteries.

  11. A 3.90 V iron-based fluorosulphate material for lithium-ion batteries crystallizing in the triplite structure

    SciTech Connect

    Barpanda, P.; Ati, M.; Melot, B.C.; Rousse, G.; Chotard, J-N.; Doublet, M-L.; Sougrati, M.T.; Corr, S.A.; Jumas, J-C.; Tarascon, J-M.

    2011-11-17

    Li-ion batteries have empowered consumer electronics and are now seen as the best choice to propel forward the development of eco-friendly (hybrid) electric vehicles. To enhance the energy density, an intensive search has been made for new polyanionic compounds that have a higher potential for the Fe{sup 2+}/Fe{sup 3+} redox couple. Herein we push this potential to 3.90 V in a new polyanionic material that crystallizes in the triplite structure by substituting as little as 5 atomic per cent of Mn for Fe in Li(Fe{sub 1-{delta}}Mn{delta})SO{sub 4}F. Not only is this the highest voltage reported so far for the Fe{sup 2+}/Fe{sup 3+} redox couple, exceeding that of LiFePO{sub 4} by 450 mV, but this new triplite phase is capable of reversibly releasing and reinserting 0.7-0.8 Li ions with a volume change of 0.6% (compared with 7 and 10% for LiFePO{sub 4} and LiFeSO{sub 4}F respectively), to give a capacity of {approx}125 mA h g{sup -1}.

  12. Materials discovery through crystal growth

    NASA Astrophysics Data System (ADS)

    zur Loye, Hans-Conrad

    2016-04-01

    The discovery of new materials and associated desirable properties has been a driving force behind chemical innovation for centuries. When we look at some of the many recent technological advances, and how widespread and significant their impact has been, we appreciate how much they have relied on new materials. The increase in hard drive storage capacity due to new giant magneto-resistive materials, the ever-shrinking cell phone due to improved microwave dielectric materials, the enhancement in lithium battery storage capacity due to new intercalation materials, or the improved capacitor due to new ferroelectric materials are all excellent examples. How were these materials discovered? While there is no single answer, in all cases there was a First-Material, the archetype in which the phenomenon was first observed, the one that led to further investigations and the subsequent preparation of improved 2nd or 3rd generation materials. It is this First-Material, the archetype, that was discovered - often via crystal growth.

  13. Characterization of pore and crystal structure of synthesized LiBOB with varying quality of raw materials as electrolyte for lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Lestariningsih, Titik; Ratri, Christin Rina; Wigayati, Etty Marty; Sabrina, Qolby

    2016-02-01

    Characterization of pore structure and crystal structure of the LiB(C2O4)2H2O or LIBOB compound has been performed in this study. These recent years, research regarding LiBOB electrolyte salt have been performed using analytical-grade raw materials, therefore this research was aimed to synthesized LiBOB electrolyte salt using the cheaper and abundant technical-grade raw materials. Lithium hydroxide (LiOH), oxalic acid dihydrate (H2C2O4.2H2O), and boric acid (H3BO3) both in technical-grade and analytical-grade quality were used as raw materials for the synthesis of LiBOB. Crystal structure characterization results of synthesized LiBOB from both technical-grade and analytical-grade raw materials have shown the existence of LiBOB and LiBOB hydrate phase with orthorombic structure. These results were also confirmed by FT-IR analysis, which showed the functional groups of LiBOB compounds. SEM analysis results showed that synthesized LiBOB has spherical structure, while commercial LiBOB has cylindrical structure. Synthesized LiBOB has a similar pore size of commercial LiBOB, i.e. 19 nm (mesoporous material). Surface area of synthesized LiBOB from analytical-grade raw materials and technical-grade materials as well as commercial LIBOB were 88.556 m2/g, 41.524 m2/g, and 108.776 m2/g, respectively. EIS analysis results showed that synthesized LiBOB from technical-grade raw materials has lower conductivity than synthesized LiBOB from analytical-grade raw materials.

  14. Crystal growth of drug materials by spherical crystallization

    NASA Astrophysics Data System (ADS)

    Szabó-Révész, P.; Hasznos-Nezdei, M.; Farkas, B.; Göcző, H.; Pintye-Hódi, K.; Erős, I.

    2002-04-01

    One of the crystal growth processes is the production of crystal agglomerates by spherical crystallization. Agglomerates of drug materials were developed by means of non-typical (magnesium aspartate) and typical (acetylsalicylic acid) spherical crystallization techniques. The growth of particle size and the spherical form of the agglomerates resulted in formation of products with good bulk density, flow, compactibility and cohesivity properties. The crystal agglomerates were developed for direct capsule-filling and tablet-making.

  15. Inorganic Crystal Structure Database (ICSD)

    National Institute of Standards and Technology Data Gateway

    SRD 84 FIZ/NIST Inorganic Crystal Structure Database (ICSD) (PC database for purchase)   The Inorganic Crystal Structure Database (ICSD) is produced cooperatively by the Fachinformationszentrum Karlsruhe(FIZ) and the National Institute of Standards and Technology (NIST). The ICSD is a comprehensive collection of crystal structure data of inorganic compounds containing more than 140,000 entries and covering the literature from 1915 to the present.

  16. Ionic Liquid Crystals: Versatile Materials.

    PubMed

    Goossens, Karel; Lava, Kathleen; Bielawski, Christopher W; Binnemans, Koen

    2016-04-27

    This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions. PMID:27088310

  17. Crystal Structures of Phosphoketolase

    PubMed Central

    Suzuki, Ryuichiro; Katayama, Takane; Kim, Byung-Jun; Wakagi, Takayoshi; Shoun, Hirofumi; Ashida, Hisashi; Yamamoto, Kenji; Fushinobu, Shinya

    2010-01-01

    Thiamine diphosphate (ThDP)-dependent enzymes are ubiquitously present in all organisms and catalyze essential reactions in various metabolic pathways. ThDP-dependent phosphoketolase plays key roles in the central metabolism of heterofermentative bacteria and in the pentose catabolism of various microbes. In particular, bifidobacteria, representatives of beneficial commensal bacteria, have an effective glycolytic pathway called bifid shunt in which 2.5 mol of ATP are produced per glucose. Phosphoketolase catalyzes two steps in the bifid shunt because of its dual-substrate specificity; they are phosphorolytic cleavage of fructose 6-phosphate or xylulose 5-phosphate to produce aldose phosphate, acetyl phosphate, and H2O. The phosphoketolase reaction is different from other well studied ThDP-dependent enzymes because it involves a dehydration step. Although phosphoketolase was discovered more than 50 years ago, its three-dimensional structure remains unclear. In this study we report the crystal structures of xylulose 5-phosphate/fructose 6-phosphate phosphoketolase from Bifidobacterium breve. The structures of the two intermediates before and after dehydration (α,β-dihydroxyethyl ThDP and 2-acetyl-ThDP) and complex with inorganic phosphate give an insight into the mechanism of each step of the enzymatic reaction. PMID:20739284

  18. PSSP, a Computer Program for the Crystal Structure Solution of Molecular Materials from X-ray Powder Diffraction Data

    SciTech Connect

    Pagola, S.; Stephens, P

    2010-01-01

    This work describes the computer program PSSP (powder structure solution program) for the crystal structure solution of molecular solids from X-ray powder diffraction data. This direct-space structure solution program uses the simulated annealing global optimization algorithm to minimize the difference between integrated intensities calculated from trial models and those extracted in a Le Bail fit of the experimental pattern, using a cost function for dealing with peak overlap through defined intensity correlation coefficients, computationally faster to calculate than R{sub wp}. The methodology outlined is applicable to organic solids composed of moderately complex rigid and flexible molecules, using diffraction data up to relatively low resolution. PSSP performance tests using 11 molecular solids with six to 20 degrees of freedom are analyzed.

  19. Structures beyond crystals

    NASA Astrophysics Data System (ADS)

    Hargittai, István

    2010-07-01

    Dan Shechtman made a seminal observation of the appearance on "non-crystallographic" symmetry in an alloy at the US National Bureau of Standards on April 8, 1982. This day has become known as the date of the discovery of quasicrystals. It was not easy to gain recognition for this discovery and the first printed report about it appeared two and a half years after the observation, which then was followed by an avalanche of publications. This was as if theoreticians and other experimentalists had only been waiting for a pioneer to come out with this revolutionary experiment. The discovery of quasicrystals just as the discovery of the structure of biological macromolecules was part of the development in which the framework of classical crystallography was crumbling and generalized crystallography—the science of structures—has emerged that had long been advanced by J. Desmond Bernal and his pupils. The discovery of quasicrystals offers some lessons about the nature of scientific discovery. This contribution presents selected aspects of the recognition of the importance of structures beyond crystals and is by far not a complete history of the areas involved.

  20. Temperature Dependence of Crystal Structure and THz Absorption Spectra of Organic Nonlinear Optical Stilbazolium Material for High-Output THz-Wave Generation

    NASA Astrophysics Data System (ADS)

    Matsukawa, Takeshi; Hoshina, Hiromichi; Hoshikawa, Akinori; Otani, Chiko; Ishigaki, Toru

    2016-02-01

    A stilbazolium material comprising 4-dimethylamino-N'-methyl-4'-stilbazolium tosylate (DAST), which has a large nonlinear optical susceptibility, was studied for application in terahertz (THz)-wave generation. The temperature-dependent structure of the DAST crystal was measured by using powder X-ray diffraction from -100 to 200 °C, indicating a volume expansion of 4.6 %. The lattice constants show anisotropic thermal expansion. Also, the temperature dependence of THz absorption spectra was measured by terahertz time-domain spectroscopy (THz-TDS) in the temperature range varying from -80 to 88.1 °C. A strong absorption peak was found at around 1 THz, shifting slightly toward a lower frequency with increasing temperature. The temperature dependence of the THz spectra was compared with that of X-ray diffraction. The shifting of THz-vibrational frequencies of the DAST crystal suggests that the change in its lattice structure is temperature dependent.

  1. Semiorganic nonlinear optical material: Crystal growth, structure and optical properties of NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2}

    SciTech Connect

    Huang, Hongwei; Yao, Wenjiao; He, Ying; Tian, Na; Chen, Chuangtian; Zhang, Yihe

    2013-09-01

    Graphical abstract: - Highlights: • Semiorganic NLO material NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has been grown with sizes up to 8 × 5 × 2 mm{sup 3}. • It crystallizes in the noncentrosymmetric Monoclinic space group P2. • Thermal analysis demonstrated NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} are thermally stable up to 280. • NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has an absorption edge about 220 nm in the UV region. • It exhibits a NLO efficiency of about two times that of KDP (KH{sub 2}PO{sub 4}) standard. - Abstract: Single crystal of the semiorganic NLO material NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has been grown with sizes up to 8 × 5 × 2 mm{sup 3} by the slow evaporation method. The crystal structure of this compound was determined by single crystal X-ray diffraction. It crystallizes in the Monoclinic space group P2 with lattice parameters a = 5.4045(11) Å, b = 11.692(2) Å, c = 9.4773(19) Å and Z = 2. Thermal analysis demonstrated NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} are thermally stable up to 280 °C. NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} exhibits an absorption edge about 220 nm in the UV region. The powder second-harmonic generation (SHG) measurement performed on the ground crystal indicates that it has a NLO efficiency of about 2 times that of KDP (KH{sub 2}PO{sub 4}) standard. In addition, the origin of stronger SHG effect was discussed.

  2. Crystal structure of ZnWO(4) scintillator material in the range of 3-1423 K.

    PubMed

    Trots, D M; Senyshyn, A; Vasylechko, L; Niewa, R; Vad, T; Mikhailik, V B; Kraus, H

    2009-08-12

    The behaviour of the crystal structure of ZnWO(4) was investigated by means of synchrotron and neutron powder diffraction in the range of 3-300 K. Thermal analysis showed the sample's melting around 1486 K upon heating and subsequent solidification at 1442 K upon cooling. Therefore, the structure was also investigated at 1423 K by means of neutron diffraction. It is found that the compound adopts the wolframite structure type over the whole temperature range investigated. The lattice parameters and volume of ZnWO(4) at low temperatures were parametrized on the basis of the first order Grüneisen approximation and a Debye model for an internal energy. The expansivities along the a- and b-axes adopt similar values and saturate close to 8 × 10(-6) K(-1), whereas the expansion along the c-axis is much smaller and shows no saturation up to 300 K. The minimum expansivity corresponds to the direction close to the c-axis where edge-sharing linkages of octahedra occur. PMID:21693966

  3. Crystal structure of ZnWO4 scintillator material in the range of 3-1423 K

    NASA Astrophysics Data System (ADS)

    Trots, D. M.; Senyshyn, A.; Vasylechko, L.; Niewa, R.; Vad, T.; Mikhailik, V. B.; Kraus, H.

    2009-08-01

    The behaviour of the crystal structure of ZnWO4 was investigated by means of synchrotron and neutron powder diffraction in the range of 3-300 K. Thermal analysis showed the sample's melting around 1486 K upon heating and subsequent solidification at 1442 K upon cooling. Therefore, the structure was also investigated at 1423 K by means of neutron diffraction. It is found that the compound adopts the wolframite structure type over the whole temperature range investigated. The lattice parameters and volume of ZnWO4 at low temperatures were parametrized on the basis of the first order Grüneisen approximation and a Debye model for an internal energy. The expansivities along the a- and b-axes adopt similar values and saturate close to 8 × 10-6 K-1, whereas the expansion along the c-axis is much smaller and shows no saturation up to 300 K. The minimum expansivity corresponds to the direction close to the c-axis where edge-sharing linkages of octahedra occur.

  4. Crystal structure determination of Efavirenz

    NASA Astrophysics Data System (ADS)

    Popeneciu, Horea; Tripon, Carmen; Borodi, Gheorghe; Pop, Mihaela Maria; Dumitru, Ristoiu

    2015-12-01

    Needle-shaped single crystals of the title compound, C14H9ClF3NO2, were obtained from a co-crystallization experiment of Efavirenz with maleic acid in a (1:1) ratio, using methanol as solvent. Crystal structure determination at room temperature revealed a significant anisotropy of the lattice expansion compared to the previously reported low-temperature structure. In both low- and room temperature structures the cyclopropylethynyl fragment in one of the asymmetric unit molecules is disordered. While at low-temperature only one C atom exhibits positional disorder, at room temperature the disorder is present for two C atoms of the cyclopropane ring.

  5. Design of tunable transmission filter using one-dimensional defective photonic crystal structure containing electro-optic material

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Rajorshi; Chakraborty, Rajib

    2015-11-01

    A narrowband tunable transmission filter suitable for wavelength division multiplexing is designed. The basic structure is a one-dimensional Fabry-Perot structure formed by layers of dielectric magnesium fluoride and electro-optic lithium niobate, which act as low and high refractive index material layers, respectively. A narrowband phase shifted transmission peak occurs within the stopband of the reflectance spectra of the structure by introducing the defect of a low-index material at a suitable position in the structure. The bandwidth of the peak depends on the number of bilayers and also on the operating wavelength. The phase shift of the transmission peak is linearly related to the wavelength under consideration. By adjusting the defect layer width, this shift of the transmission peak from the operating wavelength can be avoided. The device dimensions are so chosen that such a structure can be fabricated and used with presently available technology. A linear transmission peak tunability of 4 nm/10 V is achieved for this device by varying the refractive index of the electro-optic lithium niobate layer with externally applied voltage along its z axis. All the simulations have been carried out using the finite difference time domain method in a MATLAB® environment.

  6. Crystal growth of organic energetic materials: pentaerythritol tetranitrate

    NASA Astrophysics Data System (ADS)

    Zhang, Gengxin; Weeks, Brandon; Zhang, Xin

    2012-09-01

    The energy output performance and thermal stability of organic energetic materials have a strong dependence on the porosity, particle morphology, and micro-scale crystal structure. This paper reviews the growth habit of pure pentaerythritol tetranitrate (PETN) crystals and the effect of metal impurities on microcrystal morphology of PETN films. The pure crystal growth shows that PETN molecules diffuse on the surface and nucleate in a two-dimensional layer-by-layer fashion; the final structure is controlled by the deposition flux. Also, the effect of metal cation impurities has a strong impact on the thermal stability and crystal structure, and is dependent on the doping level.

  7. Na/sub 4/Nb(PO/sub 4/)/sub 3/, a material with a reversible crystal-glass transformation: structural and optical comparison

    SciTech Connect

    El Jazouli, A.; Parent, C.; Dance, J.M.; Le Flem, G.; Hagenmuller, P.; Viala, J.C.

    1988-06-01

    The phosphate Na/sub 4/Nb(PO/sub 4/)/sub 3/ exhibits a reversible crystal-phase change. Raman and optical investigations give evidence of the similarity between the covalent skeleton of the Nasicon-like crystalline phosphate and the network of the glass. Both types of materials contain octahedral NbO/sub 6/ groups with various Nb-O lengths. It is shown for the neodymium-doped glasses that these structural features induce a strong self concentration quenching of the Nd/sup 3 +/ emission.

  8. Automating the application of smart materials for protein crystallization

    PubMed Central

    Khurshid, Sahir; Govada, Lata; EL-Sharif, Hazim F.; Reddy, Subrayal M.; Chayen, Naomi E.

    2015-01-01

    The fabrication and validation of the first semi-liquid nonprotein nucleating agent to be administered automatically to crystallization trials is reported. This research builds upon prior demonstration of the suitability of molecularly imprinted polymers (MIPs; known as ‘smart materials’) for inducing protein crystal growth. Modified MIPs of altered texture suitable for high-throughput trials are demonstrated to improve crystal quality and to increase the probability of success when screening for suitable crystallization conditions. The application of these materials is simple, time-efficient and will provide a potent tool for structural biologists embarking on crystallization trials. PMID:25760603

  9. Crystallization and functionality of inorganic materials

    SciTech Connect

    Xue, Dongfeng; School of Chemical Engineering, Dalian University of Technology, Dalian 116024 ; Li, Keyan; Liu, Jun; Sun, Congting; Chen, Kunfeng; School of Chemical Engineering, Dalian University of Technology, Dalian 116024

    2012-10-15

    In this article, we briefly summarized our recent work on the studies of crystallization and functionality of inorganic materials. On the basis of the chemical bonding theory of single crystal growth, we can quantitatively simulate Cu{sub 2}O crystallization processes in solution system. We also kinetically controlled Cu{sub 2}O crystallization process in the reduction solution route. Lithium ion battery and supercapacitor performances of some oxides such as Co{sub 3}O{sub 4} and MnO{sub 2} were shown to elucidate the important effect of crystallization on functionality of inorganic materials. This work encourages us to create novel functionalities through the study of crystallization of inorganic materials, which warrants more chances in the field of functional materials.

  10. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons and methods for making such materials. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  11. Data mining chemistry and crystal structure

    NASA Astrophysics Data System (ADS)

    Yang, Lusann W.

    The availability of large amounts of data generated by high-throughput computing and experimentation has generated interest in the application of machine learning techniques to materials science. Machine learning of materials behavior requires the use of feature vectors that capture compositional or structural information influence a target property. We present methods for assessing the similarity of compositions, substructures, and crystal structures. Similarity measures are important for the classification and clustering of data points, allowing for the organization of data and the prediction of materials properties. The similarity functions between ions, compositions, substructures and crystal structure are based upon a data-mined probability with which two ions will substitute for each other within the same structure prototype. The composition similarity is validated via the prediction of crystal structure prototypes for oxides from the Inorganic Crystal Structure Database. It performs particularly well on the quaternary oxides, predicting the correct prototype within 5 guesses 90% of the time. The sustructural similarity is validated via the prediction of Li insertion sites in the oxides; it finds all of the Li sites with less than 8 incorrect guesses 90% of the time.

  12. Crystal structure of oryzalin

    PubMed Central

    Kang, Gihaeng; Kim, Jineun; Jeon, Youngeun; Kim, Tae Ho

    2015-01-01

    The title compound, C12H18N4O6S (systematic name: 4-di­propyl­amino-3,5-di­nitro­benzene­sulfonamide), is a sulfonamide with herbicidal properties marketed as oryzalin. The dihedral angles between the benzene ring and the mean planes of the nitro groups are 26.15 (11) and 54.80 (9)°. The propyl arms of the di­propyl­amino substituent lie on opposite sides of this ring plane. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds generate a three-dimensional network. PMID:26090208

  13. Phototropic liquid crystal materials containing naphthopyran dopants

    NASA Astrophysics Data System (ADS)

    Rumi, Mariacristina; Cazzell, Seth; Kosa, Tamas; Sukhomlinova, Ludmila; Taheri, Bahman; Bunning, Timothy; White, Timothy

    2015-03-01

    Dopant molecules dispersed in a liquid crystalline material usually affects the order of the system and the transition temperature between various phases. If the dopants undergo photoisomerization between conformers with different shapes, the interactions with the liquid crystal molecules can be different for the material in the dark and during exposure to light of appropriate wavelength. This can be used to achieve isothermal photoinduced phase transitions (phototropism). With proper selection of materials components, both order-to-disorder and disorder-to-order photoinduced transition have been demonstrated. Isothermal order-increasing transitions have been observed recently using naphthopyran derivatives as dopants. We are investigating the changes in order parameter and transition temperature of liquid crystal mixtures containing naphthopyrans and how they are related to exposure conditions and to the concentration and molecular structure of the dopants. We are also studying the nature of the photoinduced phase transitions, and comparing the behavior with that of azobenzene-doped mixtures, in which exposure to light leads to a decrease, instead of an increase, in the order of the system.

  14. CuLi2Sn and Cu2LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries

    PubMed Central

    Fürtauer, Siegfried; Effenberger, Herta S.; Flandorfer, Hans

    2014-01-01

    The stannides CuLi2Sn (CSD-427095) and Cu2LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu2Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi2Sn, the space group F-43m. was verified (structure type CuHg2Ti; a=6.295(2) Å; wR2(F²)=0.0355 for 78 unique reflections). The 4(c) and 4(d) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu2LiSn, the space group P63/mmc was confirmed (structure type InPt2Gd; a=4.3022(15) Å, c=7.618(3) Å; wR2(F²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2(a), 2(b) and 4(e). Both phases seem to be interesting in terms of application of Cu–Sn alloys as anode materials for Li-ion batteries. PMID:25473128

  15. CuLi2Sn and Cu2LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries.

    PubMed

    Fürtauer, Siegfried; Effenberger, Herta S; Flandorfer, Hans

    2014-12-01

    The stannides CuLi2Sn (CSD-427095) and Cu2LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu2Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi2Sn, the space group F-43m. was verified (structure type CuHg2Ti; a=6.295(2) Å; wR 2(F²)=0.0355 for 78 unique reflections). The 4(c) and 4(d) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu2LiSn, the space group P63/mmc was confirmed (structure type InPt2Gd; a=4.3022(15) Å, c=7.618(3) Å; wR 2(F²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2(a), 2(b) and 4(e). Both phases seem to be interesting in terms of application of Cu-Sn alloys as anode materials for Li-ion batteries. PMID:25473128

  16. CuLi2Sn and Cu2LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Fürtauer, Siegfried; Effenberger, Herta S.; Flandorfer, Hans

    2014-12-01

    The stannides CuLi2Sn (CSD-427095) and Cu2LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu2Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi2Sn, the space group F-43m. was verified (structure type CuHg2Ti; a=6.295(2) Å; wR2(F²)=0.0355 for 78 unique reflections). The 4(c) and 4(d) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu2LiSn, the space group P63/mmc was confirmed (structure type InPt2Gd; a=4.3022(15) Å, c=7.618(3) Å; wR2(F²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2(a), 2(b) and 4(e). Both phases seem to be interesting in terms of application of Cu-Sn alloys as anode materials for Li-ion batteries.

  17. Materials and structures

    NASA Technical Reports Server (NTRS)

    Venneri, Samuel L.

    1988-01-01

    Information on materials and structures for use in space is given in viewgraph form. Information is given on the Materials and Structures Division of NASA's Office of Aeronautics and Space Technology. The Division's space research and development budget is given. Further information is given on space materials and structures, space environmental effects, radiation effects, high temperature materials research, metal matrix composites, SiC fiber reinforced titanium alloys, structural dynamics, and control of flexible structures.

  18. Crystal structure of cyproconazole

    PubMed Central

    Kang, Gihaeng; Kim, Jineun; Kwon, Eunjin; Kim, Tae Ho

    2015-01-01

    The title compound [systematic name: 2-(4-chlorophenyl)-3-cyclopropyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol], C15H18ClN3O, is a conazole fungicide. The asymmetric unit comprises two enantiomeric pairs (molecules A and B) in which the dihedral angles between the chlorophenyl and triazole rings are 46.54?(9) (molecule A) and 67.03?(8) (molecule B). In the crystal, CH?O, OH?N and CH?Cl hydrogen bonds and weak CH?? interactions [3.473?(2)?] link adjacent molecules, forming columns along the a axis. PMID:26870467

  19. Crystal structure refinement with SHELXL.

    PubMed

    Sheldrick, George M

    2015-01-01

    The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as `a CIF') containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors. PMID:25567568

  20. Crystal structure refinement with SHELXL

    PubMed Central

    Sheldrick, George M.

    2015-01-01

    The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as ‘a CIF’) containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors. PMID:25567568

  1. Crystal structure refinement with SHELXL

    SciTech Connect

    Sheldrick, George M.

    2015-01-01

    New features added to the refinement program SHELXL since 2008 are described and explained. The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as ‘a CIF’) containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.

  2. Automating the application of smart materials for protein crystallization

    SciTech Connect

    Khurshid, Sahir; Govada, Lata; EL-Sharif, Hazim F.; Reddy, Subrayal M.; Chayen, Naomi E.

    2015-03-01

    The first semi-liquid, non-protein nucleating agent for automated protein crystallization trials is described. This ‘smart material’ is demonstrated to induce crystal growth and will provide a simple, cost-effective tool for scientists in academia and industry. The fabrication and validation of the first semi-liquid nonprotein nucleating agent to be administered automatically to crystallization trials is reported. This research builds upon prior demonstration of the suitability of molecularly imprinted polymers (MIPs; known as ‘smart materials’) for inducing protein crystal growth. Modified MIPs of altered texture suitable for high-throughput trials are demonstrated to improve crystal quality and to increase the probability of success when screening for suitable crystallization conditions. The application of these materials is simple, time-efficient and will provide a potent tool for structural biologists embarking on crystallization trials.

  3. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1983-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  4. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  5. Crystal structure of pyrazoxyfen.

    PubMed

    Kwon, Eunjin; Kim, Jineun; Kang, Gihaeng; Kim, Tae Ho

    2015-12-01

    The title compound, C20H16Cl2N2O3 (systematic name: 2-{[4-(2,4-di-chloro-benzo-yl)-1,3-di-methyl-pyrazol-5-yl}-oxy}-1-phenyl-ethan-1-one), is the benzoyl-pyrazole herbicide pyrazoxyfen. The asymmetric unit comprises two independent mol-ecules, A and B, in which the pyrazole ring makes dihedral angles of 80.29?(10) and 61.70?(10) and 87.60?(10) and 63.92?(8), respectively, with the di-chloro-phenyl and phenyl rings. In the crystal, C-H?O and C-H?N hydrogen bonds, and C-H?? and ?-? [3.646?(2)?] inter-actions link adjacent mol-ecules, forming a two-dimensional network parellel to (011). In addition, the networks are linked by weak inter-molecular C-Cl?? [3.356?(2), 3.950?(2), 3.250?(2) and 3.575?(2)?] inter-actions, resulting in a three-dimensional architecture. PMID:26870483

  6. Crystal structure of pyrazoxyfen

    PubMed Central

    Kwon, Eunjin; Kim, Jineun; Kang, Gihaeng; Kim, Tae Ho

    2015-01-01

    The title compound, C20H16Cl2N2O3 (systematic name: 2-{[4-(2,4-di­chloro­benzo­yl)-1,3-di­methyl­pyrazol-5-yl}­oxy}-1-phenyl­ethan-1-one), is the benzoyl­pyrazole herbicide pyrazoxyfen. The asymmetric unit comprises two independent mol­ecules, A and B, in which the pyrazole ring makes dihedral angles of 80.29 (10) and 61.70 (10)° and 87.60 (10) and 63.92 (8)°, respectively, with the di­chloro­phenyl and phenyl rings. In the crystal, C—H⋯O and C—H⋯N hydrogen bonds, and C—H⋯π and π–π [3.646 (2) Å] inter­actions link adjacent mol­ecules, forming a two-dimensional network parellel to (011). In addition, the networks are linked by weak inter­molecular C—Cl⋯π [3.356 (2), 3.950 (2), 3.250 (2) and 3.575 (2) Å] inter­actions, resulting in a three-dimensional architecture. PMID:26870483

  7. Gallium Nitride Crystals: Novel Supercapacitor Electrode Materials.

    PubMed

    Wang, Shouzhi; Zhang, Lei; Sun, Changlong; Shao, Yongliang; Wu, Yongzhong; Lv, Jiaxin; Hao, Xiaopeng

    2016-05-01

    A type of single-crystal gallium nitride mesoporous membrane is fabricated and its supercapacitor properties are demonstrated for the first time. The supercapacitors exhibit high-rate capability, stable cycling life at high rates, and ultrahigh power density. This study may expand the range of crystals as high-performance electrode materials in the field of energy storage. PMID:27007502

  8. Interpreting intensities from white beam single-crystal Laue diffraction: A tool for structural characterization of Earth materials at extreme conditions.

    NASA Astrophysics Data System (ADS)

    Kunz, M.; Tamura, N.; Dejoie, C.; Baerlocher, C.; McCusker, L.

    2012-12-01

    Monochromatic X-ray powder diffraction is the traditional method of choice for structural characterization of Earth material at extreme conditions of pressure and temperature. This method is intrinsically limited for such conditions due to the requirement for small sample volumes in order to attain very high pressure on the one hand and recrystallization at high temperature on the other hand, both of which are detrimental to powder statistics. The use of well established monochromatic single crystal diffraction as an alternative in such cases is often hampered by the lack of mobility and/or access of crystals within pressure devices. White beam Laue diffraction on static samples may offer a solution to this problem. This technique has already been exploited by the protein community mostly for time resolved measurements. It's application to small unit-cell inorganic materials is however complicated by the lack of data redundancy. The combination of white beam Laue diffraction with a micro-focused beam allows selectively probing individual crystallites within a diamond anvil cell (DAC) without the need to move the sample in the beam. However, to make this method a valid tool, a number of specific problems inherent to Laue diffraction have to be addressed. 1) Experimental geometry: Due to the nature of Laue diffraction, reciprocal space is covered mostly at high diffraction angles. This requires either a DAC with very wide opening or a set-up involving X-ray transparent gaskets. 2) energy specific absorption and Lorentz corrections: These can be done analytically and do not pose any serious problems. 3) harmonic overlap: Independent of symmetry and unit cell size, a significant fraction of observed reflections consist of two or more harmonic reflections, whose intensities need to be deconvoluted. This can be in principle solved using a lower energy threshold as offered by the Pilatus detector. Alternatives are deconvolution during refinement starting from non overlapped peaks, analogous to the Rietveld method in powder diffraction or - in the future - fully energy discriminating area detectors. A third alternative currently explored on the high-pressure beamline of the Advanced Light Source is step-scanning the monochromator across the available energy spectrum. 4) incident spectrum normalization: This is not straight forward since it is usually convoluted with detector response and cannot be easily measured. We found that comparing the measured intensities of a structurally well characterized crystal (e.g. calcite) with the calculated structure factor allows to establish a very satisfactory correction curve that includes both the variation in the flux and in the detector response. We will present details of procedures developed, together with examples of first structure solutions and refinements.

  9. Materials science: How crystals get an edge

    NASA Astrophysics Data System (ADS)

    Fontcuberta I Morral, Anna

    2016-03-01

    Microscopy reveals how nanowires of a widely used semiconductor grow during preparation. The findings will allow the crystal phases of such nanowires to be engineered -- a crucial advance for materials science. See Article p.317

  10. Synthetic thermoelectric materials comprising phononic crystals

    DOEpatents

    El-Kady, Ihab F; Olsson, Roy H; Hopkins, Patrick; Reinke, Charles; Kim, Bongsang

    2013-08-13

    Synthetic thermoelectric materials comprising phononic crystals can simultaneously have a large Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Such synthetic thermoelectric materials can enable improved thermoelectric devices, such as thermoelectric generators and coolers, with improved performance. Such synthetic thermoelectric materials and devices can be fabricated using techniques that are compatible with standard microelectronics.

  11. Crystal structure of guggulsterone Z

    SciTech Connect

    Gupta, V. K. Bandhoria, P.; Gupta, B. D.; Gupta, K. K.

    2006-03-15

    The crystal structure of the title compound (4,17(20)-trans-pregnadiene-3,16-dione, C{sub 21}H{sub 28}O{sub 2}) has been determined by direct methods using single-crystal X-ray diffraction data. The compound crystallizes into the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1} with the unit cell parameters a = 7.908(2) A, b = 13.611(3) A, c = 16.309(4) A, and Z = 4. The structure has been refined to R = 0.058 for 3667 observed reflections. The bond distances and angles are in good agreement with guggulsterone E and other related steroid molecules. Ring A exists in the distorted sofa conformation, while rings B and C adopt the distorted chair conformation. Five-membered ring D is intermediate between the half-chair and envelope conformations. The A/B ring junction is quasi-trans, while ring systems B/C and C/D are trans fused about the C(8)-C(9) and C(13)-C(14) bonds, respectively. The steroid nucleus has a small twist, as shown by the C(19)-C(10)...C(13)-C(18) pseudo-torsion angle of 7.2{sup o}. The crystal structure is stabilized by intra-and intermolecular C-H...O hydrogen bonds.

  12. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, Benjamin M.

    2007-08-22

    Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques.

  13. Diamond-structured photonic crystals.

    PubMed

    Maldovan, Martin; Thomas, Edwin L

    2004-09-01

    Certain periodic dielectric structures can prohibit the propagation of light for all directions within a frequency range. These 'photonic crystals' allow researchers to modify the interaction between electromagnetic fields and dielectric media from radio to optical wavelengths. Their technological potential, such as the inhibition of spontaneous emission, enhancement of semiconductor lasers, and integration and miniaturization of optical components, makes the search for an easy-to-craft photonic crystal with a large bandgap a major field of study. This progress article surveys a collection of robust complete three-dimensional dielectric photonic-bandgap structures for the visible and near-infrared regimes based on the diamond morphology together with their specific fabrication techniques. The basic origin of the complete photonic bandgap for the 'champion' diamond morphology is described in terms of dielectric modulations along principal directions. Progress in three-dimensional interference lithography for fabrication of near-champion diamond-based structures is also discussed. PMID:15343291

  14. An Example of Body-Centered Cubic Crystal Structure: The Atomium in Brussels as an Educative Tool for Introductory Materials Chemistry

    ERIC Educational Resources Information Center

    Pinto, Gabriel

    2012-01-01

    When students are introduced to the ways in which atoms are arranged in crystal structures, transposing the textbook illustrations into three-dimensional structures is difficult for some of them. To facilitate this transition, this article describes an approach to the study of the structure of solids through a well-known monument, the Atomium in…

  15. An Example of Body-Centered Cubic Crystal Structure: The Atomium in Brussels as an Educative Tool for Introductory Materials Chemistry

    ERIC Educational Resources Information Center

    Pinto, Gabriel

    2012-01-01

    When students are introduced to the ways in which atoms are arranged in crystal structures, transposing the textbook illustrations into three-dimensional structures is difficult for some of them. To facilitate this transition, this article describes an approach to the study of the structure of solids through a well-known monument, the Atomium in

  16. Fundamental Studies of Crystal Growth of Microporous Materials

    NASA Technical Reports Server (NTRS)

    Singh, Ramsharan; Doolittle, John, Jr.; Payra, Pramatha; Dutta, Prabir K.; George, Michael A.; Ramachandran, Narayanan; Schoeman, Brian J.

    2003-01-01

    Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (a) Nature of the molecular units responsible for the crystal nuclei formation; (b) Nature of the nuclei and nucleation process; (c) Growth process of the nuclei into crystal; (d) Morphological control and size of the resulting crystal; (e) Surface structure of the resulting crystals; and (f) Transformation of frameworks into other frameworks or condensed structures.

  17. Crystal Structure of the Ba

    SciTech Connect

    Mironov, A. V.; Istomin, S. Ya.; D'yachenko, O. G.; Antipov, E. V.

    2001-02-15

    The structure of the cation-deficient Ba{sub 4}CeNb{sub 10}O{sub 30} barium cerium reduced niobate with a tetragonal tungsten bronze (TTB) type structure was refined from X-ray single crystal data (tetragonal, a=12.508(2) {angstrom}, c=3.9328(4) {angstrom}, S. G. P4/mbm, Z=1, R=0.019, R{sub w}=0.023). It was found that rare earth substitution for Ba is accompanied by formation of vacancies in A sites. Vacancies were preferably formed in the A (1) cavities in the structure.

  18. Design and realization of one-dimensional double hetero-structure photonic crystals for infrared-radar stealth-compatible materials applications

    NASA Astrophysics Data System (ADS)

    Wang, Zhixun; Cheng, Yongzhi; Nie, Yan; Wang, Xian; Gong, Rongzhou

    2014-08-01

    In this paper, a new type one-dimensional (1D) double hetero-structure composite photonic crystal (CPC) for infrared-radar stealth-compatible materials applications was proposed and studied numerically and experimentally. First, based on transfer matrix method of thin-film optical theory, the propagation characteristics of the proposed structure comprising a stack of different alternating micrometer-thick layers of germanium and zinc sulfide were investigated numerically. Calculation results exhibit that this 1D single hetero-structure PC could achieve a flat high reflectivity gradually with increasing the number of the alternating media layers in a single broadband range. Then, based on principles of distributed Bragg reflector micro-cavity, a 1D double hetero-structure CPC comprising four PCs with thickness of 0.797 μm, 0.592 μm, 1.480 μm, and 2.114 μm, respectively, was proposed. Calculation results exhibit that this CPC could achieve a high reflectance of greater than 0.99 in the wavelength ranges of 3-5 μm and 8-14 μm and agreed well with experiment. Further experiments exhibit that the infrared emissivity of the proposed CPC is as low as 0.073 and 0.042 in the wavelength ranges of 3-5 μm and 8-12 μm, respectively. In addition, the proposed CPC can be used to construct infrared-radar stealth-compatible materials due to its high transmittance in radar wave band.

  19. Design and realization of one-dimensional double hetero-structure photonic crystals for infrared-radar stealth-compatible materials applications

    SciTech Connect

    Wang, Zhixun; Cheng, Yongzhi Nie, Yan; Wang, Xian; Gong, Rongzhou

    2014-08-07

    In this paper, a new type one-dimensional (1D) double hetero-structure composite photonic crystal (CPC) for infrared-radar stealth-compatible materials applications was proposed and studied numerically and experimentally. First, based on transfer matrix method of thin-film optical theory, the propagation characteristics of the proposed structure comprising a stack of different alternating micrometer-thick layers of germanium and zinc sulfide were investigated numerically. Calculation results exhibit that this 1D single hetero-structure PC could achieve a flat high reflectivity gradually with increasing the number of the alternating media layers in a single broadband range. Then, based on principles of distributed Bragg reflector micro-cavity, a 1D double hetero-structure CPC comprising four PCs with thickness of 0.797 μm, 0.592 μm, 1.480 μm, and 2.114 μm, respectively, was proposed. Calculation results exhibit that this CPC could achieve a high reflectance of greater than 0.99 in the wavelength ranges of 3–5 μm and 8–14 μm and agreed well with experiment. Further experiments exhibit that the infrared emissivity of the proposed CPC is as low as 0.073 and 0.042 in the wavelength ranges of 3–5 μm and 8–12 μm, respectively. In addition, the proposed CPC can be used to construct infrared-radar stealth-compatible materials due to its high transmittance in radar wave band.

  20. The Surface Structure of Ground Metal Crystals

    NASA Technical Reports Server (NTRS)

    Boas, W.; Schmid, E.

    1944-01-01

    The changes produced on metallic surfaces as a result of grinding and polishing are not as yet fully understood. Undoubtedly there is some more or less marked change in the crystal structure, at least, in the top layer. Hereby a diffusion of separated crystal particles may be involved, or, on plastic material, the formation of a layer in greatly deformed state, with possible recrystallization in certain conditions. Czochralski verified the existence of such a layer on tin micro-sections by successive observations of the texture after repeated etching; while Thomassen established, roentgenographically by means of the Debye-Scherrer method, the existence of diffused crystal fractions on the surface of ground and polished tin bars, which he had already observed after turning (on the lathe). (Thickness of this layer - 0.07 mm). Whether this layer borders direct on the undamaged base material or whether deformed intermediate layers form the transition, nothing is known. One observation ty Sachs and Shoji simply states that after the turning of an alpha-brass crystal the disturbance starting from the surface, penetrates fairly deep (approx. 1 mm) into the crystal (proof by recrystallization at 750 C).

  1. Crystal structure and chemistry of a complex indium phosphate framework material, (ethylenediammonium)In{sub 3}P{sub 3}O{sub 12}(OH){sub 2}

    SciTech Connect

    Broach, Robert W.; Bedard, Robert L.; King, Lisa M.; Pluth, Joseph J.; Smith, Joseph V.; Kirchner, Richard M.

    2012-12-15

    The chemistry and structure of a novel indium phosphate material (RIPS-4), (H{sub 3}NCH{sub 2}CH{sub 2}NH{sub 3})In{sub 3}-P{sub 3}O{sub 12}(OH){sub 2}, are described. RIPS-4 was synthesized using ethylene diamine as a structure-directing organic agent. The X-ray crystal structure was determined from a 12 Multiplication-Sign 12 Multiplication-Sign 42 {mu}m{sup 3} crystal in space group C2/m with a=18.662(4) A, b=6.600(2) A, c=12.573(3) A and {beta}=120.92(1) Degree-Sign . The structure consists of a complex edge- and vertex-shared open framework of InO{sub 6} octahedra and PO{sub 4} tetrahedra enclosing cavities occupied by ethylenediamonium ions. One set of octahedra share opposing edges to form chains along the b-axis matching the structural unit in rutile (TiO{sub 2}). This rutile edge-shared chain has its projecting oxygen atoms shared with the vertexes of either a PO{sub 4} tetrahedron or a second type of InO{sub 6} octahedron. The O atoms are 2-connected, each to one In and one P, except for two protonated O atoms (hydroxyl groups) that connect to two and three In atoms, giving three- and four-coordinate O atoms, respectively. - Graphical abstract: The unique topology contains an unusual 4-connected oxygen atom (O{sub 1}) in a complex edge- and vertex-shared open framework of InO{sub 6} octahedra (blue) and PO{sub 4} tetrahedra (yellow) that encloses cavities occupied by ethylenediammonium ions. Highlights: Black-Right-Pointing-Pointer The structure has a unique open-framework topology. Black-Right-Pointing-Pointer The framework contains an unusual 4-connected oxygen atom. Black-Right-Pointing-Pointer Hydrogen bonds hold the ethylenediammonium ions in the cavities.

  2. Modeling Polymorphic Molecular Crystals with Electronic Structure Theory.

    PubMed

    Beran, Gregory J O

    2016-05-11

    Interest in molecular crystals has grown thanks to their relevance to pharmaceuticals, organic semiconductor materials, foods, and many other applications. Electronic structure methods have become an increasingly important tool for modeling molecular crystals and polymorphism. This article reviews electronic structure techniques used to model molecular crystals, including periodic density functional theory, periodic second-order Møller-Plesset perturbation theory, fragment-based electronic structure methods, and diffusion Monte Carlo. It also discusses the use of these models for predicting a variety of crystal properties that are relevant to the study of polymorphism, including lattice energies, structures, crystal structure prediction, polymorphism, phase diagrams, vibrational spectroscopies, and nuclear magnetic resonance spectroscopy. Finally, tools for analyzing crystal structures and intermolecular interactions are briefly discussed. PMID:27008426

  3. High-resolution 3D structural and optical analyses of hybrid or composite materials by means of scanning probe microscopy combined with the ultramicrotome technique: an example of application to engineering of liquid crystals doped with fluorescent quantum dots

    NASA Astrophysics Data System (ADS)

    Mochalov, Konstantin E.; Efimov, Anton E.; Bobrovsky, Alexey Yu.; Agapov, Igor I.; Chistyakov, Anton A.; Oleinikov, Vladimir A.; Nabiev, Igor

    2013-05-01

    Combination of nanometer-scale 3D structural analysis with optical characterization of the same material is a challenging task. Its results may be important for nanophotonics, materials science, and quality control. We have developed a new technique for complementary high-resolution structural and optical characterization followed by optical spectroscopic and microscopic measurements accompanied by reconstruction of the 3D structure in the same area of the sample. The 3D structure is reconstructed by combination of ultramicrotomic and SPM techniques allowing the study of the 3D distribution of implanted nanoparticles and their effect on the matrix structure. The combination of scanning probe nanotomography (SPN) and optical microspectroscopy makes it possible to direct estimate how the 3D structural characteristics of materials affect their macroscopic optical properties. The technique developed has been applied to the engineering of materials made from cholesteric liquid crystals and fluorescent quantum dots (QDs). These materials permit photochemical patterning and image recording through the changes in the dissymmetry factor of circular polarization of QD emission. The differences in the polarisation images and morphological characteristics of the liquid crystal matrix have proved to be correlated with the arrangement of the areas of homogeneous distribution and nonhomogeneous clustering of QDs. The reconstruction of the 3D structure of the liquid crystal matrix in the areas of homogeneous QD distribution has shown that QDs embedded into cholesteric liquid crystal matrices do not perturb their periodic planar texture. The combined optical/SPM/ultramicrotome technique will be indispensable for evaluating the effects of inorganic nanoparticles on the organisation of organic and liquid crystal matrices, biomedical materials, cells, and tissues.

  4. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R. G.; Wiberley, S. E.

    1985-01-01

    Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

  5. The effects of Co doping on the crystal structure and electrochemical performance of Mg(Mn2 - xCox)O4 negative materials for lithium ion battery

    NASA Astrophysics Data System (ADS)

    Zhao, Hu; Liu, Lei; Xiao, Xiaoling; Hu, Zhongbo; Han, Songbai; Liu, Yuntao; Chen, Dongfeng; Liu, Xiangfeng

    2015-01-01

    MgMn2O4 and Co doped Mg(Mn2 - xCox)O4 (x = 0.5, 1.0 and 2.0) compounds have been successfully synthesized and studied as negative materials for lithium ion battery for the first time. Co doping induced a phase transition of MgMn2O4 from a tetragonal spinel-structure with a space group of I41/amd to a cubic spinel structure with a space group of Fd-3m. Electrochemical measurements indicate that the reversible capacity and cyclability of Mg(Mn2 - xCox)O4 first increases and then decreases with increasing Co content indicating that Co content has a significant effect on the electrochemical performance. MgMn1.5Co0.5O4 shows the best electrochemical performance compared to the other three samples. This might be largely attributed to the phase transition and anti-sites defects of spinel crystal cell resulting from the Co substitution for Mn, which was further confirmed by Rietveld refinement of neutron diffraction.

  6. Structural, optical, thermal, photoconductivity, laser damage threshold and fluorescence analysis of an organic material: β-P-amino benzoic acid single crystal

    NASA Astrophysics Data System (ADS)

    Chandran, SenthilKumar; Paulraj, Rajesh; Ramasamy, P.

    2016-02-01

    β-P-amino benzoic acid, an organic single crystal was grown by slow evaporation technique. Single crystal X-ray diffraction studies show that the grown crystal has β-polymorph of P-amino benzoic acid [β-PABA] form and the lattice parameters are a = 6.30 Å, b = 8.61 Å, c = 12.43 Å α = γ = 90° and β = 100.20°. FTIR analysis confirms that bands at 1588 cm-1, 1415 cm-1 are assigned to ring skeletal vibrations of title compound. The molecular structure of the grown crystal has been identified by Nuclear Magnetic Resonance spectral study. The optical absorbance spectrum from 200 to 1100 nm shows that there is an edge absorbance in UV region. Optical band gap of the crystal has been assessed from the absorbance spectrum. The thermal properties of crystals were evaluated from TG-DTA analysis, it exhibits that there is no weight loss up to 187 °C. Laser damage threshold indicates that the grown crystal has no surface damage up to 35 mJ. Photoconductivity and fluorescence spectral experiments are also carried out and the results are discussed.

  7. Composite structural materials. [aircraft structures

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1980-01-01

    The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

  8. Iodobismuthates Containing One-Dimensional BiI4(-) Anions as Prospective Light-Harvesting Materials: Synthesis, Crystal and Electronic Structure, and Optical Properties.

    PubMed

    Yelovik, Natalie A; Mironov, Andrei V; Bykov, Mikhail A; Kuznetsov, Alexey N; Grigorieva, Anastasia V; Wei, Zheng; Dikarev, Evgeny V; Shevelkov, Andrei V

    2016-05-01

    Four iodobismuthates, LiBiI4·5H2O (1), MgBi2I8·8H2O (2), MnBi2I8·8H2O (3), and KBiI4·H2O (4), were prepared by a facile solution route and revealed thermal stability in air up to 120 °C. Crystal structures of compounds 1-4 were solved by a single crystal X-ray diffraction method. 1: space group C2/c, a = 12.535(2), b = 16.0294(18), c = 7.6214(9) Å, β = 107.189(11)°, Z = 4, R = 0.029. 2: space group P21/c, a = 7.559(2), b = 13.1225(15), c = 13.927(4) Å, β = 97.14(3)°, Z = 2, R = 0.031. 3: space group P21/c, a = 7.606(3), b = 13.137(3), c = 14.026(5) Å, β = 97.14(3)°, Z = 2, R = 0.056. 4: space group P21/n, a = 7.9050(16), b = 7.7718(16), c = 18.233(4) Å, β = 97.45(3)°, Z = 4, R = 0.043. All solid state structures feature one-dimensional (BiI4)(-) anionic chains built of [BiI6] octahedra that share two opposite edges in such a fashion that two iodine atoms in cis-positions remain terminal. The calculated electronic structures and observed optical properties confirmed that compounds 1-4 are semiconductors with direct band gaps of 1.70-1.76 eV, which correspond to their intense red color. It was shown that the cations do not affect the optical properties, and the optical absorption is primarily associated with the charge transfer from the I 5p orbitals at the top of the valence band to the Bi 6p orbitals at the bottom of the conduction band. Based on their properties and facile synthesis, the title compounds are proposed as promising light-harvesting materials for all-solid solar cells. PMID:27074093

  9. Three-Dimensional Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, B.; /SLAC

    2006-09-07

    We discuss simulated photonic crystal structure designs for laser-driven particle acceleration, focusing on three-dimensional planar structures based on the so-called ''woodpile'' lattice. We describe guiding of a speed-of-light accelerating mode by a defect in the photonic crystal lattice and discuss the properties of this mode, including particle beam dynamics and potential coupling methods for the structure. We also discuss possible materials and power sources for this structure and their effects on performance parameters, as well as possible manufacturing techniques and the required tolerances. In addition we describe the computational technique and possible improvements in numerical modeling that would aid development of photonic crystal structures.

  10. Crystal structure of lignin peroxidase

    SciTech Connect

    Edwards, S.L. National Institutes of Health, Bethesda, MD ); Raag, R. ); Wariishi, Hiroyuki; Gold, M.H. ); Poulos, T.L. Univ. of California, Irvine )

    1993-01-15

    The crystal structure of lignin peroxidase (LiP) from the basidiomycete Phanerochaete chrysosporium has been determined to 2.6 [Angstrom] resolution by using multiple isomorphous replacement methods and simulated annealing refinement. Of the 343 residues, residues 3-335 have been accounted for in the electron density map, including four disulfide bonds. The overall three-dimensional structure is very similar to the only other peroxidase in this group for which a high-resolution crystal structure is available, cytochrome c peroxidase, despite the fact that the sequence identity is only [approx]20%, LiP has four disulfide bonds, while cytochrome c peroxidase has none, and Lip is larger (343 vs. 294 residues). The basic helical fold and connectivity defined by 11 helical segments with the heme sandwiched between the distal and proximal helices found in cytochrome c peroxidase is maintained in LiP. Both enzymes have a histidine as a proximal heme ligand, which is hydrogen bonded to a buried aspartic acid side chain. The distal or peroxide binding pocket also is similar, including the distal arginine and histidine. The most striking difference is that, whereas cytochrome c peroxidase has tryptophans contacting the distal and proximal heme surfaces, LiP has phenylalanines. This in part explains why, in the reaction with peroxides, cytochrome c peroxidase forms an amino acid-centered free radical, whereas LiP forms a porphyrin [pi] cation radical. 42 refs., 4 figs., 2 tabs.

  11. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R.; Wiberley, S. E.

    1986-01-01

    Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

  12. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Wiberley, S. E.

    1978-01-01

    The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

  13. Preparation of porous polymer materials for bulky liquid crystal devices

    NASA Astrophysics Data System (ADS)

    Nose, T.; Ito, T.; Watanabe, T.; Ito, K.; Yanagihara, S.; Ito, R.; Honma, M.

    2012-03-01

    Polymer dispersed liquid crystal (PDLC) type of liquid crystal (LC) cell structure is investigated to attain extremely large size LC layer for the millimeter waves (MMW) and/or terahertz (THz) LC device applications. It is known that the porous PMMA material (PMMA monolith) is easy to fabricate from the PMMA ethanol/water solution, and we try to use the monolith as a polymer matrix of the PDLC type LC devices. It may be possible to make arbitrary bulky structure by using suitable container for the initial solution such as Fresnel zone shape, grating shape and so on, where the thickness of the LC layer can be several millimeters.

  14. Spectroscopic, thermal and structural studies on manganous malate crystals

    SciTech Connect

    Thomas, J. Lincy, A. Mahalakshmi, V.; Saban, K. V.

    2013-01-15

    Prismatic crystals of manganous malate have been prepared by controlled ionic diffusion in hydrosilica gel. The structure was elucidated using single crystal X-ray diffraction. The crystals are orthorhombic with space group Pbca. Vibrations of the functional groups were identified by the FTIR spectrum. Thermogravimetric and differential thermal analyses (TG-DTA) were carried out to explore the thermal decomposition pattern of the material. Structural information derived from FTIR and TG-DTA studies is in conformity with the single crystal XRD data.

  15. Predicting polymeric crystal structures by evolutionary algorithms

    NASA Astrophysics Data System (ADS)

    Zhu, Qiang; Sharma, Vinit; Oganov, Artem R.; Ramprasad, Ramamurthy

    2014-10-01

    The recently developed evolutionary algorithm USPEX proved to be a tool that enables accurate and reliable prediction of structures. Here we extend this method to predict the crystal structure of polymers by constrained evolutionary search, where each monomeric unit is treated as a building block with fixed connectivity. This greatly reduces the search space and allows the initial structure generation with different sequences and packings of these blocks. The new constrained evolutionary algorithm is successfully tested and validated on a diverse range of experimentally known polymers, namely, polyethylene, polyacetylene, poly(glycolic acid), poly(vinyl chloride), poly(oxymethylene), poly(phenylene oxide), and poly (p-phenylene sulfide). By fixing the orientation of polymeric chains, this method can be further extended to predict the structures of complex linear polymers, such as all polymorphs of poly(vinylidene fluoride), nylon-6 and cellulose. The excellent agreement between predicted crystal structures and experimentally known structures assures a major role of this approach in the efficient design of the future polymeric materials.

  16. Bone as a Structural Material.

    PubMed

    Zimmermann, Elizabeth A; Ritchie, Robert O

    2015-06-24

    As one of the most important natural materials, cortical bone is a composite material comprising assemblies of tropocollagen molecules and nanoscale hydroxyapatite mineral crystals, forming an extremely tough, yet lightweight, adaptive and multi-functional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are vital physiologically. Like many mineralized tissues, bone can resist deformation and fracture from the nature of its hierarchical structure, which spans molecular to macroscopic length-scales. In fact, bone derives its fracture resistance with a multitude of deformation and toughening mechanisms that are active at most of these dimensions. It is shown that bone's strength and ductility originate primarily at the scale of the nano to submicrometer structure of its mineralized collagen fibrils and fibers, whereas bone toughness is additionally generated at much larger, micro- to near-millimeter, scales from crack-tip shielding associated with interactions between the crack path and the microstructure. It is further shown how the effectiveness with which bone's structural features can resist fracture at small to large length-scales can become degraded by biological factors such as aging and disease, which affect such features as the collagen cross-linking environment, the homogeneity of mineralization, and the density of the osteonal structures. PMID:25865873

  17. Structural Materials: 95. Concrete

    SciTech Connect

    Naus, Dan J

    2012-01-01

    Nuclear power plant concrete structures and their materials of construction are described, and their operating experience noted. Aging and environmental factors that can affect the durability of the concrete structures are identified. Basic components of a program to manage aging of these structures are identified and described. Application of structural reliability theory to devise uniform risk-based criteria by which existing facilities can be evaluated to achieve a desired performance level when subjected to uncertain demands and to quantify the effects of degradation is outlined. Finally, several areas are identified where additional research is desired.

  18. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1984-01-01

    Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

  19. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been achieved since the initial developments in the mid 1960's. Rather limited applications to primary aircraft structure have been made, however, mainly in a material-substitution mode on military aircraft, except for a few experiments currently underway on large passenger airplanes in commercial operation. To fulfill the promise of composite materials completely requires a strong technology base. NASA and AFOSR recognize the present state of the art to be such that to fully exploit composites in sophisticated aerospace structures, the technology base must be improved. This, in turn, calls for expanding fundamental knowledge and the means by which it can be successfully applied in design and manufacture.

  20. Optimization of photonic crystal structures.

    PubMed

    Smajic, Jasmin; Hafner, Christian; Erni, Daniel

    2004-11-01

    We report on the numerical structural optimization of two-dimensional photonic crystal (PhC) power dividers by using two different classes of optimization algorithms, namely, a modified truncated Newton (TN) gradient search as deterministic local optimization scheme and an evolutionary optimization representing the probabilistic global search strategies. Because of the severe accuracy requirements during optimization, the proper PhC device has been simulated by using the multiple-multipole program that is contained in the MaX-1 software package. With both optimizer classes, we found reliable and promising solutions that provide vanishing power reflection and perfect power balance at any specified frequency within the photonic bandgap. This outcome is astonishing in light of the discrete nature inherent in the underlying PhC structure, especially when the optimizer is allowed to intervene only within a very small volume of the device. Even under such limiting constraints structural optimization is not only feasible but has proven to be highly successful. PMID:15535381

  1. Uranocircite: luminescence and crystal structure

    SciTech Connect

    Matkovskiy, A.O.; Sidorenko, G.A.; Tarashchan, A.N.

    1981-01-01

    A study on the determination of the complex structure of the electron-vibration spectra and the elucidation of their relation to crystallochemical factors in uranocircite is presented. The work was performed on samples from zones of a single crystal of the same natural meta-uranocircite, differing in color, and also on other specimens from various Soviet and foreign deposits. Of the 15 meta-uranocircite specimens investigated, in 14 cases the luminescence spectra were homoypic and were a series of equidistant groups of lines of the fine structure; the spectral position of which was practically constant for all the specimens. The degree of hydration was found to have practically no influence on the luminescence of the meta-uranocircite. The investigation supports the supposition that there are marked differences in the structures of minerals of the uran-mica group, although in the authors' opinion, the mechanism itself of multi-center radiation is universal and manifested for all secondary uranium minerals. (JMT)

  2. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1979-01-01

    A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

  3. Composite Structural Materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

    1984-01-01

    The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

  4. Novel Microstructures for Polymer-Liquid Crystal Composite Materials

    NASA Technical Reports Server (NTRS)

    Magda, Jules J.

    2004-01-01

    There are a number of interface-dominated composite materials that contain a liquid crystalline (LC) phase in intimate contact with an isotropic phase. For example, polymer- dispersed liquid crystals, used in the fabrication of windows with switchable transparency, consist of micron size LC droplets dispersed in an isotropic polymer matrix. Many other types of liquid crystal composite materials can be envisioned that might have outstanding optical properties that could be exploited in novel chemical sensors, optical switches, and computer displays. This research project was based on the premise that many of these potentially useful LC composite materials can only be fabricated under microgravity conditions where gravity driven flows are absent. In the ground-based research described below, we have focused on a new class of LC composites that we call thermotropic- lyotropic liquid crystal systems (TLLCs). TLLCs consist of nanosize droplets of water dispersed in an LC matrix, with surfactants at the interface that stabilize the structure. By varying the type of surfactant one can access almost an infinite variety of unusual LC composite microstructures. Due to the importance of the interface in these types of systems, we have also developed molecular simulation models for liquid crystals at interfaces, and made some of the first measurements of the interfacial tension between liquid crystals and water.

  5. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

  6. Materials and structures technology

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Glasgow, T. K.; Halford, G. R.; Levine, S. R.

    1979-01-01

    Materials and structures performance limitations, particularly for the hot section of the engine in which these limitations limit the life of components, are considered. Failure modes for components such as blades, vanes, and combustors and how they are affected by the environment for such components are discussed. Methods used to improve the materials used for such components are: (1) application of directional structures to turbine components for high strength at high temperatures; (2) improved coatings to increase oxidation and corrosion resistance; (3) increase strength and stiffness with reduced weight by applying higher specific properties of composite materials; and (4) cost effective processing such as near net shape powder methods applied to disks. Life prediction techniques developed to predict component life accurately in advance of service and progress in improving the intermediate and cold section components of turbine engines are covered.

  7. Crystal structure analysis of intermetallic compounds

    NASA Technical Reports Server (NTRS)

    Conner, R. A., Jr.; Downey, J. W.; Dwight, A. E.

    1968-01-01

    Study concerns crystal structures and lattice parameters for a number of new intermetallic compounds. Crystal structure data have been collected on equiatomic compounds, formed between an element of the Sc, Ti, V, or Cr group and an element of the Co or Ni group. The data, obtained by conventional methods, are presented in an easily usable tabular form.

  8. Synthesis, crystal structure, physico-chemical characterization and dielectric properties of a new hybrid material, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate

    NASA Astrophysics Data System (ADS)

    Dhieb, A. C.; Valkonen, A.; Rzaigui, M.; Smirani, W.

    2015-12-01

    A new organic-inorganic hybrid metal complex, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate was synthesized and the structure is determined by single crystal X-Ray diffraction analyses. The title compound crystallizes in the orthorhombic system with space group Pbca. The unit cell parameters are a = 11.5129 (2) Å, b = 9.7801 (2) Å, c = 23.8599 (4) Å with Z = 8 and V = 2686.56 (8) Å3. The examination of the structure shows that Cd(II) is coordinated by 4 chlorine atoms and adopt a tetrahedral geometry. Three-dimensional frameworks of the title compound are produced by N-H⋯Cl and C-H⋯Cl hydrogen bonding. IR, Raman and UV-Visible spectroscopies were also used to characterize this complex. Moreover, the fluorescent properties of the compound have been investigated in the solid state at room temperature. Solid state 13C MAS NMR spectroscopy results are in agreement with the X-ray structure. Differential scanning calorimetry (DSC) has revealed a structural phase transition of the order-disorder type around 373 K, and dielectric measurements were performed to discuss the mechanism of this phase transition. The evolution of dielectric constant as a function of temperature of the sample has been investigated in order to determine some related parameters.

  9. Predicting Crystal Structures with Data Mining of Quantum Calculations

    NASA Astrophysics Data System (ADS)

    Curtarolo, Stefano; Morgan, Dane; Persson, Kristin; Rodgers, John; Ceder, Gerbrand

    2003-09-01

    Predicting and characterizing the crystal structure of materials is a key problem in materials research and development. It is typically addressed with highly accurate quantum mechanical computations on a small set of candidate structures, or with empirical rules that have been extracted from a large amount of experimental information, but have limited predictive power. In this Letter, we transfer the concept of heuristic rule extraction to a large library of abinitio calculated information, and we demonstrate that this can be developed into a tool for crystal structure prediction.

  10. Crystal structure of benzimidazolium salicylate.

    PubMed

    Amudha, M; Kumar, P Praveen; Chakkaravarthi, G

    2015-10-01

    In the anion of the title mol-ecular salt, C7H7N2 (+)·C7H5O3 (-) (systematic name: 1H-benzimidazol-3-ium 2-hy-droxy-ben-zo-ate), there is an intra-molecular O-H⋯O hydrogen bond that generates an S(6) ring motif. The CO2 group makes a dihedral angle of 5.33 (15)° with its attached ring. In the crystal, the dihedral angle between the benzimidazolium ring and the anion benzene ring is 75.88 (5)°. Two cations bridge two anions via two pairs of N-H⋯O hydrogen bonds, enclosing an R (4) 4(16) ring motif, forming a four-membered centrosymmetric arrangement. These units are linked via C-H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by C-H⋯π and π-π inter-actions [inter-centroid distances = 3.4156 (7) and 3.8196 (8) Å], forming a three-dimensional structure. PMID:26594483

  11. Crystal structure of benzimidazolium salicylate

    PubMed Central

    Amudha, M.; Kumar, P. Praveen; Chakkaravarthi, G.

    2015-01-01

    In the anion of the title mol­ecular salt, C7H7N2 +·C7H5O3 − (systematic name: 1H-benzimidazol-3-ium 2-hy­droxy­ben­zo­ate), there is an intra­molecular O—H⋯O hydrogen bond that generates an S(6) ring motif. The CO2 group makes a dihedral angle of 5.33 (15)° with its attached ring. In the crystal, the dihedral angle between the benzimidazolium ring and the anion benzene ring is 75.88 (5)°. Two cations bridge two anions via two pairs of N—H⋯O hydrogen bonds, enclosing an R 4 4(16) ring motif, forming a four-membered centrosymmetric arrangement. These units are linked via C—H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by C—H⋯π and π–π inter­actions [inter-centroid distances = 3.4156 (7) and 3.8196 (8) Å], forming a three-dimensional structure. PMID:26594483

  12. Materials/structures testing

    NASA Astrophysics Data System (ADS)

    Matthews, R. K.

    An overview of the materials/structures test methodology used in the development of hypersonic vehicle components is presented. Focus is on aerothermal methodology and weather/erosion testing. For the latter, testing techniques which evaluate particle impact effects on vehicles operating at supersonic through hypersonic speeds in particle laden environments are described. Such facilities for increasing velocities are: wind tunnels/sleds; arc facilities; aeroballistic ranges. It is noted that it is of particular importance to demonstrate that flight components such as leading edges, cowl lips, and structural panels will survive the aerothermal flight environment. Specific components can experience very high heating rates and surface temperatures from 1100 to 1950 C.

  13. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, B.; Javanmard, M.; Wu, N.

    2004-12-07

    We discuss simulated photonic crystal structure designs for laser-driven particle acceleration. We focus on three-dimensional planar structures based on the so-called 'woodpile' lattice, demonstrating guiding of a speed-of-light accelerating mode by a defect in the photonic crystal lattice. We introduce a candidate geometry and discuss the properties of the accelerating mode. We also discuss the linear beam dynamics in the structure present a novel method for focusing the beam. In addition we describe ongoing investigations of photonic crystal fiber-based structures.

  14. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, B

    2004-08-06

    The authors discuss simulated photonic crystal structure designs for laser-driven particle acceleration. They focus on three-dimensional planar structures based on the so-called ''woodpile'' lattice, demonstrating guiding of a speed-of-light accelerating mode by a defect in the photonic crystal lattice. They introduce a candidate geometry and discuss the properties of the accelerating mode. They also discuss the linear beam dynamics in the structure present a novelmethod for focusing the beam. In addition they describe ongoing investigations of photonic crystal fiber-based structures.

  15. Liquid-crystal materials find a new order in biomedical applications

    NASA Astrophysics Data System (ADS)

    Woltman, Scott J.; Jay, Gregory D.; Crawford, Gregory P.

    2007-12-01

    With the maturation of the information display field, liquid-crystal materials research is undergoing a modern-day renaissance. Devices and configurations based on liquid-crystal materials are being developed for spectroscopy, imaging and microscopy, leading to new techniques for optically probing biological systems. Biosensors fabricated with liquid-crystal materials can allow label-free observations of biological phenomena. Liquid-crystal polymers are starting to be used in biomimicking colour-producing structures, lenses and muscle-like actuators. New areas of application in the realms of biology and medicine are stimulating innovation in basic and applied research into these materials.

  16. Beyond crystals: the dialectic of materials and information.

    PubMed

    Cartwright, Julyan H E; Mackay, Alan L

    2012-06-28

    We argue for a convergence of crystallography, materials science and biology, that will come about through asking materials questions about biology and biological questions about materials, illuminated by considerations of information. The complex structures now being studied in biology and produced in nanotechnology have outstripped the framework of classical crystallography, and a variety of organizing concepts are now taking shape into a more modern and dynamic science of structure, form and function. Absolute stability and equilibrium are replaced by metastable structures existing in a flux of energy-carrying information and moving within an energy landscape of complex topology. Structures give place to processes and processes to systems. The fundamental level is that of atoms. As smaller and smaller groups of atoms are used for their physical properties, quantum effects become important; already we see quantum computation taking shape. Concepts move towards those in life with the emergence of specifically informational structures. We now see the possibility of the artificial construction of a synthetic living system, different from biological life, but having many or all of the same properties. Interactions are essentially nonlinear and collective. Structures begin to have an evolutionary history with episodes of symbiosis. Underlying all the structures are constraints of time and space. Through hierarchization, a more general principle than the periodicity of crystals, structures may be found within structures on different scales. We must integrate unifying concepts from dynamical systems and information theory to form a coherent language and science of shape and structure beyond crystals. To this end, we discuss the idea of categorizing structures based on information according to the algorithmic complexity of their assembly. PMID:22615461

  17. Beyond crystals: the dialectic of materials and information

    PubMed Central

    Cartwright, Julyan H. E.; Mackay, Alan L.

    2012-01-01

    We argue for a convergence of crystallography, materials science and biology, that will come about through asking materials questions about biology and biological questions about materials, illuminated by considerations of information. The complex structures now being studied in biology and produced in nanotechnology have outstripped the framework of classical crystallography, and a variety of organizing concepts are now taking shape into a more modern and dynamic science of structure, form and function. Absolute stability and equilibrium are replaced by metastable structures existing in a flux of energy-carrying information and moving within an energy landscape of complex topology. Structures give place to processes and processes to systems. The fundamental level is that of atoms. As smaller and smaller groups of atoms are used for their physical properties, quantum effects become important; already we see quantum computation taking shape. Concepts move towards those in life with the emergence of specifically informational structures. We now see the possibility of the artificial construction of a synthetic living system, different from biological life, but having many or all of the same properties. Interactions are essentially nonlinear and collective. Structures begin to have an evolutionary history with episodes of symbiosis. Underlying all the structures are constraints of time and space. Through hierarchization, a more general principle than the periodicity of crystals, structures may be found within structures on different scales. We must integrate unifying concepts from dynamical systems and information theory to form a coherent language and science of shape and structure beyond crystals. To this end, we discuss the idea of categorizing structures based on information according to the algorithmic complexity of their assembly. PMID:22615461

  18. Synthesis, crystal structure and optical properties of a novel organic-inorganic hybrid materials (C 9H 14N) 2PbCl 4

    NASA Astrophysics Data System (ADS)

    Liu, Yao; Yang, Peipei; Meng, Jian

    2011-05-01

    A novel organic-inorganic hybrid compound (C 9H 14N) 2PbCl 4 was grown via a solution-cooling process by employing the organic cation-2,4,6-trimethylaniline to control the hybrid compound and the structure was determined by single-crystal X-ray diffraction to be monoclinic, P2(1)/c with a = 24.350(0) , b = 25.167(0) , c = 7.694(0) , ? = 95.77(9), and Z = 8. The compound adopted an unprecedented structure, which was built with the staircase-like 1-D chains of PbCl 4 octahedra sandwiched with the square pyramids of PbCl 5. Raman and infrared spectra were used to gain more information of the title compound. The hybrid compound showed the photoluminescence emission at 424 nm.

  19. Concrete Materials and Structures

    SciTech Connect

    Wilby, C.B.

    1991-12-31

    Concrete Materials and Structures provides one of the most comprehensive treatments on the topic of concrete engineering. The author covers a gamut of concrete subjects ranging from concrete mix design, basic reinforced concrete theory, prestressed concrete, shell roofs, and two-way slabs-including a through presentation of Hillerborg`s strip method. Prior to Wilby`s book, the scope of these topics would require at least four separate books to cover. With this new book he has succeeded, quite remarkably, in condensing a fairly complete knowledge of concrete engineering into one single easy-to-carry volume.

  20. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1987-01-01

    The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

  1. Crystal growth, structure analysis and characterisation of 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid single crystal

    SciTech Connect

    Sankari, R. Siva; Perumal, Rajesh Narayana

    2014-04-24

    Single crystal of dielectric material 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid has been grown by slow evaporation solution growth method. The grown crystal was harvested in 25 days. The crystal structure was analyzed by Single crystal X - ray diffraction. UV-vis-NIR analysis was performed to examine the optical property of the grown crystal. The thermal property of the grown crystal was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The dielectric measurements were carried out and the dielectric constant was calculated and plotted at all frequencies.

  2. Laser fabrication and crystallization of nano materials

    NASA Astrophysics Data System (ADS)

    Sugiyama, Teruki; Asahi, Tsuyoshi; Yuyama, Kenichi; Takeuchi, Hiroki; Jeon, Hyeon-Gu; Hosokawa, Yoichiroh; Masuhara, Hiroshi

    2008-02-01

    We have prepared nanoparticles of five organic dye molecules by laser ablation of their microcrystals in poor solvents using the third harmonics of nanosecond Nd 3+:YAG laser as an excitation light source. Their colloidal solutions were stable for longer than 1 week without any surfactants. The mean size was almost common to all the dyes (about 50 nm) and its distribution was narrow, which was confirmed by SEM observation. By applying electrophoretic deposition, the homogeneous thin film of quinacridone nanoparticles was fabricated on an indium-tin-oxide electrode. It was demonstrated that the films with different grain size and crystalline phase can be fabricated arbitrarily by using different nanoparticles. Laser ablation is also useful for crystallization of organic molecules, which was demonstrated for a representative organic nonlinear optical material.

  3. Evolution of molecular crystal optical phonons near structural phase transitions

    NASA Astrophysics Data System (ADS)

    Michki, Nigel; Niessen, Katherine; Xu, Mengyang; Markelz, Andrea

    Molecular crystals are increasingly important photonic and electronic materials. For example organic semiconductors are lightweight compared to inorganic semiconductors and have inexpensive scale up processing with roll to roll printing. However their implementation is limited by their environmental sensitivity, in part arising from the weak intermolecular interactions of the crystal. These weak interactions result in optical phonons in the terahertz frequency range. We examine the evolution of intermolecular interactions near structural phase transitions by measuring the optical phonons as a function of temperature and crystal orientation using terahertz time-domain spectroscopy. The measured orientation dependence of the resonances provides an additional constraint for comparison of the observed spectra with the density functional calculations, enabling us to follow specific phonon modes. We observe crystal reorganization near 350 K for oxalic acid as it transforms from dihydrate to anhydrous form. We also report the first THz spectra for the molecular crystal fructose through its melting point.

  4. Structures of cyano-biphenyl liquid crystals

    NASA Technical Reports Server (NTRS)

    Chu, Yuan-Chao; Tsang, Tung; Rahimzadeh, E.; Yin, L.

    1989-01-01

    The structures of p-alkyl- p'-cyano- bicyclohexanes, C(n)H(2n+1) (C6H10)(C6H10) CN (n-CCH), and p-alkyl- p'-cyano- biphenyls, C(n)H(2n+1) (C6H4)(C6H4) CN (n-CBP), were studied. It is convenient to use an x ray image intensification device to search for symmetric x ray diffraction patterns. Despite the similarities in molecular structures of these compounds, very different crystal structures were found. For the smectic phase of 2CCH, the structure is close to rhombohedral with threefold symmetry. In contrast, the structure is close to hexagonal close-packed with two molecules per unit cell for 4CCH. Since intermolecular forces may be quite weak for these liquid crystals systems, it appears that crystal structures change considerably when the alkyl chain length is slightly altered. Different structures were also found in the crystalline phase of n-CBP for n = 6 to 9. For n = 7 to 9, the structures are close to monclinic. The structures are reminiscent of the smectic-A liquid crystal structures with the linear molecules slightly tilted away from the c-axis. In contrast, the structure is quite different for n = 6 with the molecules nearly perpendicular to the c-axis.

  5. Polymer Stabilized Liquid Crystals: Materials, Physics and Applications

    NASA Astrophysics Data System (ADS)

    Kumar, Rishi; Raina, K. K.

    2011-12-01

    Polymer dispersed liquid crystal (PDLC) are a novel class of optical composite materials. They offer varied range of applications in optical devices as device materials. The polymer stabilized liquid crystals (PSLC), have improved upon some of the device characteristics. The presence of a polymer network formed at low polymer concentrations provides similar advantages in enhancing the stability of the structure, aiding the re-orientation of liquid crystal director to the desired stable configuration, reducing the switching time, and improving the optical contrast in the devices. Electro-optic switching behavior with variation in voltage and temperature is studied for application in switchable display devices. The color response (RGB) of textures is calibrated against temperature by suitable polynomial fitting. The variation in R, G and B intensities of PSLC film with temperature is used to determine hue, saturation and intensity corresponds to HSI model. We shall present interesting results on these materials and discuss how performance of devices can be improved by tailoring some functional groups in polymer networks to control some physical parameters.

  6. CuLi{sub 2}Sn and Cu{sub 2}LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries

    SciTech Connect

    Fürtauer, Siegfried; Effenberger, Herta S.; Flandorfer, Hans

    2014-12-15

    The stannides CuLi{sub 2}Sn (CSD-427095) and Cu{sub 2}LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu{sub 2}Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi{sub 2}Sn, the space group F-43m. was verified (structure type CuHg{sub 2}Ti; a=6.295(2) Å; wR{sub 2}(F²)=0.0355 for 78 unique reflections). The 4(c) and 4(d) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu{sub 2}LiSn, the space group P6{sub 3}/mmc was confirmed (structure type InPt{sub 2}Gd; a=4.3022(15) Å, c=7.618(3) Å; wR{sub 2}(F²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2(a), 2(b) and 4(e). Both phases seem to be interesting in terms of application of Cu–Sn alloys as anode materials for Li-ion batteries. - Highlights: • First single crystal investigation of CuLi{sub 2}Sn and Cu{sub 2}LiSn clarifies contradictions from literature. • Lithium atoms are ordered in channels, which is interesting for application as anode materials for lithium ion batteries. • Structural relationships to binary Cu–Sn-phases are shown. • Close structural relationship between both ternary phases exists.

  7. Molecular-Level Understanding of Structural Changes of Organic Crystals Induced by Macroscopic Mechanical Stimulation.

    PubMed

    Seki, Tomohiro; Ito, Hajime

    2016-03-18

    Structural changes to molecular crystals upon mechanical stimulation have attracted attention for sensing, recording, and microactuation. Comprehensive structure information is required to understand relationships between the mechanical force applied, the crystal structure, and the bulk property changes in order to develop general design concepts for mechanoresponsive compounds. Unfortunately, mechanical stimulation of organic crystals typically deteriorates their integrity, preventing detailed structure analyses by single-crystal X-ray diffraction (XRD) methods. However, in the past three years, several interesting studies have been reported in which molecular crystals retain their integrity even after a mechanically induced crystalline structure change. These materials have allowed us to investigate how macroscopic mechanical forces affect the microscopic structures of molecular crystals by single-crystal XRD analyses. This Minireview summarizes current knowledge of mechanically induced structure changes in molecular crystals, which will facilitate research in this field. PMID:26748640

  8. Pholcodine monohydrate: Crystal structure and polymorphism

    NASA Astrophysics Data System (ADS)

    Petruševski, Gjorgji; Zbačnik, Marija; Kajdžanoska, Marina; Ugarkovic, Sonja; Trimčeski, Vase; Kaitner, Branko; Jovanovski, Gligor; Makreski, Petre

    2013-07-01

    The first crystal structure elucidation of pholcodine monohydrate, an important antitussive active pharmaceutical ingredient is reported herein. The studied compound crystallizes in the orthorhombic system in the space group P212121. Each H2O molecule is shared by two pholcodine molecules via three strong hydrogen bonds. The detailed crystallization screening from several different organic solvents afforded single crystals with various quality, all exhibiting prism-to-needlelike micro morphology. The investigation of the obtained single crystals by means of several physico-chemical, solid-state instrumental techniques (FT-IR, DSC, TG/DTG and XRPD) proved that pholcodine monohydrate exists in a single crystalline modification, identical to the commercial form of the compound.

  9. Discrete structures in continuum descriptions of defective crystals.

    PubMed

    Parry, G P

    2016-04-28

    I discuss various mathematical constructions that combine together to provide a natural setting for discrete and continuum geometric models of defective crystals. In particular, I provide a quite general list of 'plastic strain variables', which quantifies inelastic behaviour, and exhibit rigorous connections between discrete and continuous mathematical structures associated with crystalline materials that have a correspondingly general constitutive specification. PMID:27002070

  10. Crystal structure and characterization of a novel organic optical crystal: 2-Aminopyridinium trichloroacetate

    SciTech Connect

    Dhanaraj, P.V.; Rajesh, N.P.; Vinitha, G.; Bhagavannarayana, G.

    2011-05-15

    Research highlights: {yields} Good quality crystals of 2-aminopyridinium trichloroacetate were grown for first time. {yields} 2-Aminopyridinium trichloroacetate crystal belongs to monoclinic crystal system with space group P21/c. {yields} 2-Aminopyridinium trichloroacetate crystal exhibits third order nonlinear optical properties. {yields} 2-Aminopyridinium trichloroacetate is a low dielectric constant material. -- Abstract: 2-Aminopyridinium trichloroacetate, a novel organic optical material has been synthesized and crystals were grown from aqueous solution employing the technique of controlled evaporation. 2-Aminopyridinium trichloroacetate crystallizes in monoclinic system with space group P2{sub 1}/c and the lattice parameters are a = 8.598(5) A, b = 11.336(2) A, c = 11.023(2) A, {beta} = 102.83(1){sup o} and volume = 1047.5(3) A{sup 3}. High-resolution X-ray diffraction measurements were performed to analyze the structural perfection of the grown crystals. Thermal analysis shows a sharp endothermic peak at 124 {sup o}C due to melting reaction of 2-aminopyridinium trichloroacetate. UV-vis-NIR studies reveal that 2-aminopyridinium trichloroacetate has UV cutoff wavelength at 354 nm. Dielectric studies show that dielectric constant and dielectric loss decreases with increasing frequency and finally it becomes almost a constant at higher frequencies for all temperatures. The negative nonlinear optical parameters of 2-aminopyridinium trichloroacetate were derived by the Z-scan technique.

  11. Crystallization and Structure Analysis of Membrane Proteins

    NASA Astrophysics Data System (ADS)

    Newman, Richard

    In recent years, there has been great progress in the determination of high-resolution three-dimensional (3D) structures of membrane proteins. The first major breakthrough came with the crystallization (1) and X-ray crystallography (2,3) of the bacterial photosynthetic reaction center (see refs. 4 and 5 for reviews). The structure of another, entirely different membrane protein, the bacterial outer membrane porin from Rhodobacter capsulatus, has now been determined by X-ray crystallography (6). Recent results by electron crystallography of two-dimensional (2D) crystals have been most encouraging. The high-resolution 3D structure of bacteriorhodopsin (7) plant light-harvesting complex (8) and projection maps of several other membrane proteins at similar resolutions (9-11) have been obtained by this technique. Electron crystallography seems particularly appropriate for membrane proteins that are prone to form 2D crystals, and it is hoped that many more structures will be determined in this way.

  12. Structural complexity and configurational entropy of crystals.

    PubMed

    Krivovichev, Sergey V

    2016-04-01

    Using a statistical approach, it is demonstrated that the complexity of a crystal structure measured as the Shannon information per atom [Krivovichev (2012). Acta Cryst. A68, 393-398] represents a negative contribution to the configurational entropy of a crystalline solid. This conclusion is in full accordance with the general agreement that information and entropy are reciprocal variables. It also agrees well with the understanding that complex structures possess lower entropies relative to their simpler counterparts. The obtained equation is consistent with the Landauer principle and points out that the information encoded in a crystal structure has a physical nature. PMID:27048729

  13. Method of making macrocrystalline or single crystal semiconductor material

    NASA Technical Reports Server (NTRS)

    Shlichta, P. J. (Inventor); Holliday, R. J. (Inventor)

    1986-01-01

    A macrocrystalline or single crystal semiconductive material is formed from a primary substrate including a single crystal or several very large crystals of a relatively low melting material. This primary substrate is deposited on a base such as steel or ceramic, and it may be formed from such metals as zinc, cadmium, germanium, aluminum, tin, lead, copper, brass, magnesium silicide, or magnesium stannide. These materials generally have a melting point below about 1000 C and form on the base crystals the size of fingernails or greater. The primary substrate has an epitaxial relationship with a subsequently applied layer of material, and because of this epitaxial relationship, the material deposited on the primary substrate will have essentially the same crystal size as the crystals in the primary substrate. If required, successive layers are formed, each of a material which has an epitaxial relationship with the previously deposited layer, until a layer is formed which has an epitaxial relationship with the semiconductive material. This layer is referred to as the epitaxial substrate, and its crystals serve as sites for the growth of large crystals of semiconductive material. The primary substrate is passivated to remove or otherwise convert it into a stable or nonreactive state prior to deposition of the seconductive material.

  14. Microscopic characterization of defect structure in RDX crystals.

    PubMed

    Bouma, R H B; Duvalois, W; Van der Heijden, A E D M

    2013-12-01

    Three batches of the commercial energetic material RDX, as received from various production locations and differing in sensitivity towards shock initiation, have been characterized with different microscopic techniques in order to visualize the defect content in these crystals. The RDX crystals are embedded in an epoxy matrix and cross-sectioned. By a treatment of grinding and polishing of the crystals, the internal defect structure of a multitude of energetic crystals can be visualized using optical microscopy, scanning electron microscopy and confocal scanning laser microscopy. Earlier optical micrographs of the same crystals immersed in a refractive index matched liquid could visualize internal defects, only not in the required detail. The combination of different microscopic techniques allows for a better characterization of the internal defects, down to inclusions of approximately 0.5 μm in size. The defect structure can be correlated to the sensitivity towards a high-amplitude shock wave of the RDX crystals embedded in a polymer bonded explosive. The obtained experimental results comprise details on the size, type and quantity of the defects. These details should provide modellers with relevant and realistic information for modelling defects in energetic materials and their effect on the initiation and propagation of shock waves in PBX formulations. PMID:24117989

  15. Crystal structure of 9-methacryloylanthracene

    PubMed Central

    Agrahari, Aditya; Wagers, Patrick O.; Schildcrout, Steven M.; Masnovi, John; Youngs, Wiley J.

    2015-01-01

    In the title compound, C18H14O, with systematic name 1-(anthracen-9-yl)-2-methyl­prop-2-en-1-one, the ketonic C atom lies 0.2030 (16) Å out of the anthryl-ring-system plane. The dihedral angle between the planes of the anthryl and methacryloyl moieties is 88.30 (3)° and the stereochemistry about the Csp 2—Csp 2 bond in the side chain is transoid. In the crystal, the end rings of the anthryl units in adjacent mol­ecules associate in parallel–planar orientations [shortest centroid–centroid distance = 3.6320 (7) Å]. A weak hydrogen bond is observed between an aromatic H atom and the O atom of a mol­ecule displaced by translation in the a-axis direction, forming sheets of parallel-planar anthryl groups packing in this direction. PMID:26029389

  16. Smart materials and structures

    NASA Technical Reports Server (NTRS)

    Rogowski, Robert S.; Heyman, Joseph S.

    1993-01-01

    Embedded optical fibers allow not only the cure-monitoring and in-service lifetime measurements of composite materials, but the NDE of material damage and degradation with aging. The capabilities of such damage-detection systems have been extended to allow the quantitative determination of 2D strain in materials by several different methods, including the interferometric and the numerical. It remains to be seen, what effect the embedded fibers have on the strength of the 'smart' materials created through their incorporation.

  17. Intelligent materials and structures revisited

    NASA Astrophysics Data System (ADS)

    Shahinpoor, Mohsen

    1996-02-01

    Presented are new definitions and interpretations for smartness and intelligence associated with materials, structures, and material systems (MS & MS). These newly proposed definitions complement and augment the present notion of smart and/or intelligent materials, structures and material systems, as accepted by our scientific community. These new definitions numerically quantify the concepts of smartness and intelligence for materials, structures and material systems. In this context amino acid sequences and structures such as proteins are proposed to be the smartest material family and are given an MSQ of 1000. Correspondingly, ribonucleic acid sequences such as RNA and DNA macromolecular assemblies and structures are proposed to be the most intelligent material family and are given an MIQ of 1000. In the same category the proteins are given an MIQ of about 700. Ionic polymeric gels, shape memory alloys, electromagnetic (electrostrictive, piezoelectric, ferroelectric, ferromagnetic) materials, electrorheological fluids and magnetorheological fluids are then categorized under this hierarchy of smart/intelligent materials with MSQs and MIQs of smaller values. A similar classification is also applied to smart/intelligent structures with reference to simple cells such as bacteria and viruses such as T4 Bacteriophages. A number of examples are presented and the corresponding MSQs and MIQs are estimated to show that materials, structure and material systems can truly be numerically categorized in connection with their smartness and intelligence and thus be compared with biological and botanical structures and material systems.

  18. Band electronic structures and crystal packing forces

    NASA Astrophysics Data System (ADS)

    Whangbo, M. H.

    1988-02-01

    Progress has been made in several aspects of our research on organic conducting salts, high temperature inorganic superconductors, and other low-dimensional materials. Band electronic structure study on the new ambient-pressure superconductor (BEDT-TTF)2Cu(NCS)2 (T(sub c) = 10.4 K) revealed that this salt is a two-dimensional metal. The (BPDT-TTF)3(INI4)2 salt consists of BPDT-TTF molecules in two different oxidation states. Band electronic structure calculations on (2,5-DM-DCNQI)2Cu revealed that its metallic character must arise from the presence of copper atom mixed-valence (i.e., Cu(+) and Cu(2+). Band electronic structure calculations were performed to examine the difference between the orthorhombic and tetragonal phases of YBa2Cu3O(7-y). We developed empirical atom-atom potentials that reproduce the crystal structure of binary oxides BaO, CuO, La2O3, and Y2O3. On the basis of our band electronic and empirical atom-atom potential studies, we proposed that linear electron-hole-electron pairing in Cu(2+)-O-Cu(3+)-O-Cu(2+) units via concerted breathing-mode vibration is essential for the high-temperature superconductivity in La(2-x)M(x)CuO4 and YBa2Cu3O(7-y). We also found that our empirical atom-atom potentials provide a reasonable set of IR and Raman frequencies for La(2-x)M(x)CuO4.

  19. Free-Standing Photonic Crystal Films with Gradient Structural Colors.

    PubMed

    Ding, Haibo; Liu, Cihui; Ye, Baofen; Fu, Fanfan; Wang, Huan; Zhao, Yuanjin; Gu, Zhongze

    2016-03-23

    Hydrogel colloidal crystal composite materials have a demonstrated value in responsive photonic crystals (PhCs) via controllable stimuli. Although they have been successfully exploited to generate a gradient of color distribution, the soft hydrogels have limitations in terms of stability and storage caused by dependence on environment. Here, we present a practical strategy to fabricate free-standing PhC films with a stable gradient of structural colors using binary polymer networks. A colloidal crystal hydrogel film was prepared for this purpose, with continuously varying photonic band gaps corresponding to the gradient of the press. Then, a second polymer network was used to lock the inside non-close-packed PhC structures and color distribution of the hydrogel film. It was demonstrated that our strategy could bring about a solution to the angle-dependent structural colors of the PhC films by coating the surface with special microstructures. PMID:26962967

  20. Synthesis and crystal structure of maleopimaric acid.

    PubMed

    Rao, Xiaoping; Song, Zhanqian; Yao, Xujie; Han, Chunrui; Shang, Shibin

    2008-01-01

    The title compound maleopimaric acid was synthesized by a Diels-Alder reaction between maleic anhydride and Pinus elliottii engelm oleoresin at room temperature and it was characterized by single crystal X-ray diffraction. The white crystals crystallized in the orthorhombic system, space group P2(12121) with cell dimensions: a = 7.6960 (15) A, b = 11.851 (2) A, c = 24.577 (5) A, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, V = 2241.6(8) A(3), and R(1) = 0.0716, wR(2) = 0.1975. The two fused and unbridged cyclohexane rings form a trans ring junction with chair conformation with two methyl groups in axis positions, the anhydride ring is planar. Crystal water existed in the molecular and stabilized the structure through intermolecular hydrogen bonds. PMID:18626819

  1. Crystal structure of potassium sodium tartrate trihydrate

    SciTech Connect

    Egorova, A. E. Ivanov, V. A.; Somov, N. V.; Portnov, V. N.; Chuprunov, E. V.

    2011-11-15

    Crystals of potassium sodium tartrate trihydrate (dl-KNaC{sub 4}H{sub 4}O{sub 6} {center_dot} 3H{sub 2}O) were obtained from an aqueous solution. The crystal shape was described. The atomic structure of the compound was determined and compared with the known structures of dl-KNaC{sub 4}H{sub 4}O{sub 6} {center_dot} 4H{sub 2}O and l-KNaC{sub 4}H{sub 4}O{sub 6} {center_dot} 4H{sub 2}O.

  2. A terminally protected dipeptide: from crystal structure and self-assembly, through co-assembly with carbon-based materials, to a ternary catalyst for reduction chemistry in water.

    PubMed

    Mazzier, Daniela; Carraro, Francesco; Crisma, Marco; Rancan, Marzio; Toniolo, Claudio; Moretto, Alessandro

    2016-01-01

    A terminally protected, hydrophobic dipeptide Boc-L-Cys(Me)-L-Leu-OMe (1) was synthesized and its 3D-structure was determined by single crystal X-ray diffraction analysis. This peptide is able to hierarchically self-assemble in a variety of superstructures, including hollow rods, ranging from the nano- to the macroscale, and organogels. In addition, 1 is able to drive fullerene (C60) or multiwalled carbon nanotubes (MWCNTs) in an organogel by co-assembling with them. A hybrid 1-C60–MWCNT organogel was prepared and converted (through a high vacuum-drying process) into a robust, high-volume, water insoluble, solid material where C60 is well dispersed over the entire superstructure. This ternary material was successfully tested as a catalyst for: (i) the reduction reaction of water-soluble azo compounds mediated by NaBH4 and UV-light with an overall performance remarkably better than that provided by C60 alone, and (ii) the NaBH4-mediated reduction of benzoic acid to benzyl alcohol. Our results suggest that the self-assembly properties of 1 might be related to the occurrence in its single crystal structure of a sixfold screw axis, a feature shared by most of the linear peptides known so far to give rise to nanotubes. PMID:26463728

  3. Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors

    PubMed Central

    Wang, Hui; Zhang, Ke-Qin

    2013-01-01

    Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

  4. Computing stoichiometric molecular composition from crystal structures

    PubMed Central

    Gražulis, Saulius; Merkys, Andrius; Vaitkus, Antanas; Okulič-Kazarinas, Mykolas

    2015-01-01

    Crystallographic investigations deliver high-accuracy information about positions of atoms in crystal unit cells. For chemists, however, the structure of a molecule is most often of interest. The structure must thus be reconstructed from crystallographic files using symmetry information and chemical properties of atoms. Most existing algorithms faithfully reconstruct separate molecules but not the overall stoichiometry of the complex present in a crystal. Here, an algorithm that can reconstruct stoichiometrically correct multimolecular ensembles is described. This algorithm uses only the crystal symmetry information for determining molecule numbers and their stoichiometric ratios. The algorithm can be used by chemists and crystallographers as a standalone implementation for investigating above-molecular ensembles or as a function implemented in graphical crystal analysis software. The greatest envisaged benefit of the algorithm, however, is for the users of large crystallographic and chemical databases, since it will permit database maintainers to generate stoichiometrically correct chemical representations of crystal structures automatically and to match them against chemical databases, enabling multidisciplinary searches across multiple databases. PMID:26089747

  5. Structure-property evolution during polymer crystallization

    NASA Astrophysics Data System (ADS)

    Arora, Deepak

    The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We ) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We>1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEW(TM) based code (LabVIEW(TM) 7.1) in real time. The SALS apparatus was custom built for ExxonMobil Research in Clinton NJ.

  6. Automated protein crystal structure determination using ELVES.

    PubMed

    Holton, James; Alber, Tom

    2004-02-10

    Efficient determination of protein crystal structures requires automated x-ray data analysis. Here, we describe the expert system ELVES and its use to determine automatically the structure of a 12-kDa protein. Multiwavelength anomalous diffraction analysis of a selenomethionyl derivative was used to image the Asn-16-Ala variant of the GCN4 leucine zipper. In contrast to the parallel, dimeric coiled coil formed by the WT sequence, the mutant unexpectedly formed an antiparallel trimer. This structural switch reveals how avoidance of core cavities at a single site can select the native fold of a protein. All structure calculations, including indexing, data processing, locating heavy atoms, phasing by multiwavelength anomalous diffraction, model building, and refinement, were completed without human intervention. The results demonstrate the feasibility of automated methods for determining high-resolution, x-ray crystal structures of proteins. PMID:14752198

  7. Phase-Field Crystal Modeling of Polycrystalline Materials

    NASA Astrophysics Data System (ADS)

    Adland, Ari Joel

    In this thesis, we use and further develop the phase-field crystal (PFC) method derived from classical density functional theory to investigate polycyrstalline materials. The PFC method resolves atomistic scale processes by tracking the evolution of the local time averaged crystal density field, thereby naturally describing dislocations and grian boundaries (GBs), but with a phenomenological incorporation of vacancy diffusion that accesses long diffusive time scales beyond the reach of MD simulations. We use the PFC method to investigate two technologically important classes of polycrystalline materials whose properties are strongly influenced by GB equilibrium and non-equilibrium properties. The first are structural polycyrstalline materials such as nickel based superalloys used for turbine blades. Those alloys can develop large defects known as "hot tears'' due to the lack of complete crystal cohesion and strain localization during the late stages of solidification. We investigate the equilibrium structure of symmetric tilt GBs at high homologous temperatures and identify a wide range of misorientation that leads to the formation of nanometer-thick intergranular films with liquid like properties. The phase transition character of this "GB premelting'' phenomenon is investigated through the quantitative computation of a disjoining thermodynamic potential in both pure materials and alloys, using body-centered-cubic Fe as a model system. The analysis of this potential sheds light on the physical origin of attractive and repulsive forces that promote and suppress crystal cohesion, respectively, and are found to be strongly affected by solute addition. Our equilibrium studies also reveal the existence of novel structural transitions of low angle GBs driven by the pairing of dislocations with both screw and edge character. Non-equilibrium PFC simulations in turn characterize the response of GBs to an applied shear stress, showing that intergranular liquid-like films promote GB sliding and strain localization underlying hot tearing. The second class of polycrystalline materials investigated are nanocrystalline materials with a grain size less than a few hundred nanometers. Those materials exhibit desirable properties that include high strength and corrosion resistance. In order to understand basic mechanisms that control the thermal and mechanical stability of nanocrystalline materials, we investigate the stress-driven motion of GBs over a complete range of GB bicrystallography, which includes asymmetrical tilt boundaries with non-vanishing misorientation and inclination angles. We show that asymmetrical GBs exhibit coupled motion to a shear stress parallel to the GB plane and identify a wealth of different dislocation mechanisms mediated by glide, climb, and dislocation reactions, which underlie this coupled motion. We also show that asymmetrical GBs exhibit sliding due to the existence of discontinuous transitions between different coupling modes. Importantly, unlike sliding of symmetrical GBs promoted by GB premelting, sliding of asymmetrical GBs can exist at low temperature, thereby providing an important mechanism for the stress-driven evolution of nanocrystalline structures. In addition to the above studies of polycrystalline materials, we also use the PFC method as a theoretical framework for investigating the grain coarsening dynamics of polycrystalline structures in a broad class of systems that form crystal lattices through self-organization or self-assembly, including driven non-equilibrium systems, modulated phases of macromolecular systems such as diblock copolymers, and colloidal crystals. Our studies reveal that grain growth in those systems is governed by an entirely different dissipation mechanism than in polycrystalline materials. While the rate of curvature-driven grain growth in polycrystalline materials is well-known to be limited by interface dissipation, we find that bulk dissipation associated with lattice translation dramatically slows down grain coarsening in self- organized or assembled lattice forming systems. We also show that bulk dissipation is reduced by thermal noise so that those systems exhibit faster coarsening behavior dominated by interface dissipation for high Peierls barrier and high noise. Those results provide a unified theoretical framework for understanding and modeling polycrystalline pattern evolution in diverse systems over a broad range of length and time scales. They also provide the basis for extending the PFC methodology to model more quantitatively and faithfully the dynamics of polycrystalline materials. This extension forms an important part of PFC model development in this thesis together with the development of free-energy functionals for different crystal structures. (Abstract shortened by UMI.)

  8. Structural engineering of three-dimensional phononic crystals

    NASA Astrophysics Data System (ADS)

    Delpero, Tommaso; Schoenwald, Stefan; Zemp, Armin; Bergamini, Andrea

    2016-02-01

    Artificially-structured materials are attracting the research interest of a growing community of scientists for the possibility to develop novel materials with advantageous properties that arise from the ability to tailor the propagation of elastic waves, and thus energy, through them. In this work, we propose a three-dimensional phononic crystal whose unit cell has been engineered to obtain a strong wave-attenuation band in the middle of the acoustic frequency range. The combination of its acoustic properties with the dimensions of the unit cell and its static mechanical properties makes it an interesting material for possibly several applications in civil and mechanical engineering, for instance as the core of an acoustically insulating sandwich panel. A sample of this crystal has been manufactured and experimentally tested with respect to its acoustic transmissibility. The performance of the phononic crystal core is remarkable both in terms of amplitude reduction in the transmissibility and width of the attenuation band. A parametric study has been finally conducted on selected geometrical parameters of the unit cell and on their effect on the macroscopic properties of the crystal. This work represents an application-oriented example of how the macroscopic properties of an artificially-structured material can be designed, according to specific needs, by a conventional engineering of its unit cell.

  9. Structural and optical properties of a new chalcone single crystal

    NASA Astrophysics Data System (ADS)

    Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Poojary, Boja

    2012-09-01

    A new nonlinear optical material 1-(4-methylthiophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one with molecular formula C17H16O2S was synthesized by using the Claisen-Schmidt condensation reaction method. The Various functional groups present in the compound were identified using recorded FT-IR spectrum. The crystal growth parameters have been studied using solubility test and acetone is found to be a very good solvent for the crystal growth at an ambient temperature. The transparent high quality single crystals up to a size of 26×2×2 mm3 were grown using the slow evaporation solution growth technique. UV-visible study was carried out and the spectrum reveals that the crystal is transparent in the entire visible region and absorptive in the UV region. The refractive index is determined using Brewster's angle method. The optical energy band gap of the material is measured using Tauc's plot and the direct method. The single crystal XRD of MMPP crystal shows the following cell parameters: a=5.9626(2) Å, b=15.3022(6) Å, c=16.0385(7) Å, α=β=γ=90°, volume=1463.37(10) Å3 with a space group of Pna21. The compound MMPP exhibits optical nonlinearity (NLO) and its second order NLO efficiency is 3.15 times to that of urea. The effect of functional groups OCH3 and SCH3 on the non-linearity as well as the structural property of the compound has been discussed. The crystal is thermally stable. High NLO efficiency, good thermal stability, good transparency and ability to grow as a high quality single crystal make this material very attractive for opto-electronic applications.

  10. Microstructure and Crystal Structure in TAGS Compositions

    SciTech Connect

    Thompson, A. J.; Sharp, J; Rawn, Claudia J

    2009-01-01

    GeTe, a small bandgap semiconductor that has native p-type defects due to Ge vacancies, is an important constituent in the thermoelectric material known as TAGS. TAGS is an acronym for alloys of GeTe with AgSbTe{sub 2}, and compositions are normally designated as TAGS-x, where x is the fraction of GeTe. TAGS-85 is the most important with regard to applications, and there is also commercial interest in TAGS-80. The crystal structure of GeTe{sub 1+{delta}} has a composition-dependent phase transformation at a temperature ranging from 430 C ({delta} = 0) to {approx}400 C ({delta} = 0.02). The high-temperature form is cubic. The low-temperature form is rhombohedral for {delta} < 0.01, as is the case for good thermoelectric performance. Addition of AgSbTe{sub 2} shifts the phase transformation to lower temperatures, and one of the goals of this work is a systematic study of the dependence of transformation temperature on the parameter x. We present results on phase transformations and associated instabilities in TAGS compositions in the range of 70 at.% to 85 at.% GeTe.

  11. Shear induced structures in crystallizing cocoa butter

    NASA Astrophysics Data System (ADS)

    Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

    2004-03-01

    Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

  12. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1979-01-01

    Technology utilization of fiber reinforced composite materials is discussed in the areas of physical properties, and life prediction. Programs related to the Composite Aircraft Program are described in detail.

  13. Crystal structure of monobasic sodium tartrate monohydrate

    SciTech Connect

    Titaeva, E. K. Somov, N. V.; Portnov, V. N.; Titaev, D. N.

    2015-01-15

    Crystals of a new polymorphic modification of monobasic sodium tartrate monohydrate NaHC{sub 4}H{sub 4}O{sub 6} · H{sub 2}O have been grown in a metasilicate gel. Their atomic structure is solved by X-ray diffraction.

  14. Structure analysis on synthetic emerald crystals

    NASA Astrophysics Data System (ADS)

    Lee, Pei-Lun; Lee, Jiann-Shing; Huang, Eugene; Liao, Ju-Hsiou

    2013-05-01

    Single crystals of emerald synthesized by means of the flux method were adopted for crystallographic analyses. Emerald crystals with a wide range of Cr3+-doping content up to 3.16 wt% Cr2O3 were examined by X-ray single crystal diffraction refinement method. The crystal structures of the emerald crystals were refined to R 1 (all data) of 0.019-0.024 and w R 2 (all data) of 0.061-0.073. When Cr3+ substitutes for Al3+, the main adjustment takes place in the Al-octahedron and Be-tetrahedron. The effect of substitution of Cr3+ for Al3+ in the beryl structure results in progressively lengthening of the Al-O distance, while the length of the other bonds remains nearly unchanged. The substitution of Cr3+ for Al3+ may have caused the expansion of a axis, while keeping the c axis unchanged in the emerald lattice. As a consequence, the Al-O-Si and Al-O-Be bonding angles are found to decrease, while the angle of Si-O-Be increases as the Al-O distance increases during the Cr replacement.

  15. Crystal structure of a plectonemic RNA supercoil

    SciTech Connect

    Stagno, Jason R.; Ma, Buyong; Li, Jess; Altieri, Amanda S.; Byrd, R. Andrew; Ji, Xinhua

    2012-12-14

    Genome packaging is an essential housekeeping process in virtually all organisms for proper storage and maintenance of genetic information. Although the extent and mechanisms of packaging vary, the process involves the formation of nucleic-acid superstructures. Crystal structures of DNA coiled coils indicate that their geometries can vary according to sequence and/or the presence of stabilizers such as proteins or small molecules. However, such superstructures have not been revealed for RNA. Here we report the crystal structure of an RNA supercoil, which displays one level higher molecular organization than previously reported structures of DNA coiled coils. In the presence of an RNA-binding protein, two interlocking RNA coiled coils of double-stranded RNA, a 'coil of coiled coils', form a plectonemic supercoil. Molecular dynamics simulations suggest that protein-RNA interaction is required for the stability of the supercoiled RNA. This study provides structural insight into higher order packaging mechanisms of nucleic acids.

  16. Preparation, structural, and calorimetric characterization of bicomponent metallic photonic crystals

    NASA Astrophysics Data System (ADS)

    Kozlov, M. E.; Murthy, N. S.; Udod, I.; Khayrullin, I. I.; Baughman, R. H.; Zakhidov, A. A.

    2007-03-01

    We report preparation and characterization of novel bicomponent metal-based photonic crystals having submicron three-dimensional (3D) periodicity. Fabricated photonic crystals include SiO2 sphere lattices infiltrated interstitially with metals, carbon inverse lattices filled with metal or metal alloy spheres, Sb inverse lattices, and Sb inverse lattices filled with Bi spheres. Starting from a face centered SiO2 lattice template, these materials were obtained by sequences of either templating and template extraction or templating, template extraction, and retemplating. Surprising high fidelity was obtained for all templating and template extraction steps. Scanning electron microscopy (SEM), small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to characterize the structure and the effects of the structure on calorimetric properties. To the best of our knowledge, SAXS data on metallic photonic crystals were collected for first time.

  17. Dynamic Theory for Polydomain Structures in Liquid-Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Duzgun, Ayhan; Selinger, Jonathan

    2015-03-01

    Liquid-crystal elastomers are remarkable materials that combine the elastic properties of cross-linked polymer networks with the anisotropy of liquid crystals. Any distortion of the polymer network affects the nematic order of the liquid crystal, and, likewise, any change in the magnitude or direction of the nematic order influences the shape of the elastomer. When elastomers are prepared without any alignment, they develop disordered polydomain structures as they are cooled into the nematic phase. To model these polydomain structures, we develop a dynamic theory for the isotropic-nematic transition in elastomers. In this theory, the local nematic order is coupled to the strain tensor, which satisfies the constraint of elastic compatibility. If the system is rapidly cooled into the nematic phase, a polydomain state with a characteristic length scale can emerge. This polydomain state may eventually become uniform, or it may be locked in by quenched impurities. This work was supported by NSF Grant DMR-1409658.

  18. Crystal Structure of Human Enterovirus 71

    SciTech Connect

    Plevka, Pavel; Perera, Rushika; Cardosa, Jane; Kuhn, Richard J.; Rossmann, Michael G.

    2013-04-08

    Enterovirus 71 is a picornavirus associated with fatal neurological illness in infants and young children. Here, we report the crystal structure of enterovirus 71 and show that, unlike in other enteroviruses, the 'pocket factor,' a small molecule that stabilizes the virus, is partly exposed on the floor of the 'canyon.' Thus, the structure of antiviral compounds may require a hydrophilic head group designed to interact with residues at the entrance of the pocket.

  19. Crystal structure of zwitterionic bisimidazolium sulfonates

    NASA Astrophysics Data System (ADS)

    Kohmoto, Shigeo; Okuyama, Shinpei; Yokota, Nobuyuki; Takahashi, Masahiro; Kishikawa, Keiki; Masu, Hyuma; Azumaya, Isao

    2012-05-01

    Crystal structures of three zwitterionic bisimidazolium salts 1-3 in which imidazolium sulfonate moieties were connected with aromatic linkers, p-xylylene, 4,4'-dimethylenebiphenyl, and phenylene, respectively, were examined. The latter two were obtained as hydrates. An S-shaped molecular structure in which the sulfonate moiety was placed on the imidazolium ring was observed for 1. A helical array of hydrated water molecules was obtained for 2 while a linear array of hydrated water molecules was observed for 3.

  20. Structural, magnetic and optical properties of two concomitant molecular crystals

    NASA Astrophysics Data System (ADS)

    Silva, Manuela Ramos; Milne, Bruce; Coutinho, Joana T.; Pereira, Laura C. J.; Martín-Ramos, Pablo; Pereira da Silva, Pedro S.; Martín-Gil, Jesús

    2016-03-01

    A new 1D complex has been prepared and characterized. X-ray single crystal structure confirms that the Cu(II) ions assemble in alternating chains with Cu … Cu distances of 2.5685(4) and 3.1760(4) Å. The temperature dependence of the magnetic susceptibility reveals an antiferromagnetic interaction between the paddle-wheel copper centers with an exchange of -300 cm-1. The exchange integral was also determined by quantum chemical ab-initio calculations, using polarised and unpolarised basis sets reproducing well the experimental value. The second harmonic generation efficiency of a concomitantly crystallized material was evaluated and was found to be comparable to urea.

  1. Study on a Photonic Crystal Hydrogel Material for Chemical Sensing

    NASA Astrophysics Data System (ADS)

    Xu, Jia-Yu; Yan, Chun-Xiao; Hu, Xiao-Chun; Liu, Chao; Tang, Hua-Min; Zhou, Chao-Hua; Xue, Fei

    2014-01-01

    There is intense interest in the applications of photonic crystal hydrogel materials for the detection of glucose, metal ions, organophosphates and so on. In this paper, monodisperse polystyrene spheres with diameters between 100 440 nm were synthesized by emulsion polymerization. Highly charged polystyrene spheres readily self-assembled into crystalline colloidal array because of electrostatic interactions. Photonic crystal hydrogel materials were formed by polymerization of acrylamide hydrogel around the crystalline colloidal arrays of polystyrene spheres. After chemical modification of hydrogel backbone with carboxyl groups, our photonic crystals hydrogel materials are demonstrated to be excellent in response to pH and ionic strength changes.

  2. Methods of using structures including catalytic materials disposed within porous zeolite materials to synthesize hydrocarbons

    DOEpatents

    Rollins, Harry W.; Petkovic, Lucia M.; Ginosar, Daniel M.

    2011-02-01

    Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

  3. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1983-01-01

    Transverse properties of fiber constituents in composites, fatigue in composite materials, matrix dominated properties of high performance composites, numerical investigation of moisture effects, numerical investigation of the micromechanics of composite fracture, advanced analysis methods, compact lug design, and the RP-1 and RP-2 sailplanes projects are discussed.

  4. Crystal structure prediction: a novel approach based on minima hopping

    NASA Astrophysics Data System (ADS)

    Amsler, Maximilian; Goedecker, Stefan

    2012-02-01

    With increasing computational resources the prediction of crystal structures from first principle calculations has become feasible, but still remains a demanding task. A reliable method to perform an efficient, systematic search for the ground state structure based solely on the system's composition is essential. Motivated by the promising results of the minima hopping method obtained on isolated systems, we have generalized the algorithm for crystal structure prediction. Optimized moves in the configurational space spanned by both atomic coordinates and simulation cell variables are performed to escape from local enthalpy minima, and revisiting known minima is avoided, thus allowing a fast exploration of the enthalpy surface. The predictive power of the novel method has been shown in several applications, of which the following will be presented. Superconducting phases in hydrogen rich materials were investigated, leading to the discovery of novel ground state structures. For the longstanding question of the crystal structure of cold compressed graphite a new candidate phase could be identified to perfectly match experimental results. And at last, new low energy structures for materials with possible applications in hydrogen storage are presented.

  5. Crystal structure of riboflavin synthase

    SciTech Connect

    Liao, D.-I.; Wawrzak, Z.; Calabrese, J.C.; Viitanen, P.V.; Jordan, D.B.

    2010-03-05

    Riboflavin synthase catalyzes the dismutation of two molecules of 6,7-dimethyl-8-(1'-D-ribityl)-lumazine to yield riboflavin and 4-ribitylamino-5-amino-2,6-dihydroxypyrimidine. The homotrimer of 23 kDa subunits has no cofactor requirements for catalysis. The enzyme is nonexistent in humans and is an attractive target for antimicrobial agents of organisms whose pathogenicity depends on their ability to biosynthesize riboflavin. The first three-dimensional structure of the enzyme was determined at 2.0 {angstrom} resolution using the multiwavelength anomalous diffraction (MAD) method on the Escherichia coli protein containing selenomethionine residues. The homotrimer consists of an asymmetric assembly of monomers, each of which comprises two similar {beta} barrels and a C-terminal {alpha} helix. The similar {beta} barrels within the monomer confirm a prediction of pseudo two-fold symmetry that is inferred from the sequence similarity between the two halves of the protein. The {beta} barrels closely resemble folds found in phthalate dioxygenase reductase and other flavoproteins. The three active sites of the trimer are proposed to lie between pairs of monomers in which residues conserved among species reside, including two Asp-His-Ser triads and dyads of Cys-Ser and His-Thr. The proposed active sites are located where FMN (an analog of riboflavin) is modeled from an overlay of the {beta} barrels of phthalate dioxygenase reductase and riboflavin synthase. In the trimer, one active site is formed, and the other two active sites are wide open and exposed to solvent. The nature of the trimer configuration suggests that only one active site can be formed and be catalytically competent at a time.

  6. Absorption enhancement in graphene photonic crystal structures.

    PubMed

    Khaleque, Abdul; Hattori, Haroldo T

    2016-04-10

    Graphene, a single layer of carbon atoms arranged in a honeycomb lattice, is attracting significant interest because of its potential applications in electronic and optoelectronic devices. Although graphene exhibits almost uniform absorption within a large wavelength range, its interaction with light is weak. In this paper, the enhancement of the optical absorption in graphene photonic crystal structures is studied: the structure is modified by introducing scatterers and mirrors. It is shown that the absorption of the graphene photonic crystal structure can be enhanced about four times (nearly 40%) with respect to initial reference absorption of 9.8%. The study can be a useful tool for investigating graphene physics in different optical settings. PMID:27139857

  7. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1981-01-01

    The composite aircraft program component (CAPCOMP) is a graduate level project conducted in parallel with a composite structures program. The composite aircraft program glider (CAPGLIDE) is an undergraduate demonstration project which has as its objectives the design, fabrication, and testing of a foot launched ultralight glider using composite structures. The objective of the computer aided design (COMPAD) portion of the composites project is to provide computer tools for the analysis and design of composite structures. The major thrust of COMPAD is in the finite element area with effort directed at implementing finite element analysis capabilities and developing interactive graphics preprocessing and postprocessing capabilities. The criteria for selecting research projects to be conducted under the innovative and supporting research (INSURE) program are described.

  8. Thermoelectric Materials With the Skutterudite Structure: New Results

    NASA Technical Reports Server (NTRS)

    Fleurial, J. -P.; Caillat, T.; Borshchevsky, A.

    1995-01-01

    New experimental findings on semiconductors with the relatively complex 32 atom unit cell skutterudite crystal structure show that these materials possess attractive transport properties and have a good potential for achieving ZT values larger than for state-of- the-art thermoelectric materials. An overview of recent results is provided, and current approaches to experimentally achieving high ZT in skutterudite materials are discussed.

  9. Can antimonide-based nanowires form wurtzite crystal structure?

    NASA Astrophysics Data System (ADS)

    Gorji Ghalamestani, Sepideh; Lehmann, Sebastian; Dick, Kimberly A.

    2016-01-01

    The epitaxial growth of antimonide-based nanowires has become an attractive subject due to their interesting properties required for various applications such as long-wavelength IR detectors. The studies conducted on antimonide-based nanowires indicate that they preferentially crystallize in the zinc blende (ZB) crystal structure rather than wurtzite (WZ), which is common in other III-V nanowire materials. Also, with the addition of small amounts of antimony to arsenide- and phosphide-based nanowires grown under conditions otherwise leading to WZ structure, the crystal structure of the resulting ternary nanowires favors the ZB phase. Therefore, the formation of antimonide-based nanowires with the WZ phase presents fundamental challenges and is yet to be explored, but is particularly interesting for understanding the nanowire crystal phase in general. In this study, we examine the formation of Au-seeded InSb and GaSb nanowires under various growth conditions using metalorganic vapor phase epitaxy. We address the possibility of forming other phases than ZB such as WZ and 4H in binary nanowires and demonstrate the controlled formation of WZ InSb nanowires. We further discuss the fundamental aspects of WZ growth in Au-seeded antimonide-based nanowires.The epitaxial growth of antimonide-based nanowires has become an attractive subject due to their interesting properties required for various applications such as long-wavelength IR detectors. The studies conducted on antimonide-based nanowires indicate that they preferentially crystallize in the zinc blende (ZB) crystal structure rather than wurtzite (WZ), which is common in other III-V nanowire materials. Also, with the addition of small amounts of antimony to arsenide- and phosphide-based nanowires grown under conditions otherwise leading to WZ structure, the crystal structure of the resulting ternary nanowires favors the ZB phase. Therefore, the formation of antimonide-based nanowires with the WZ phase presents fundamental challenges and is yet to be explored, but is particularly interesting for understanding the nanowire crystal phase in general. In this study, we examine the formation of Au-seeded InSb and GaSb nanowires under various growth conditions using metalorganic vapor phase epitaxy. We address the possibility of forming other phases than ZB such as WZ and 4H in binary nanowires and demonstrate the controlled formation of WZ InSb nanowires. We further discuss the fundamental aspects of WZ growth in Au-seeded antimonide-based nanowires. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07362f

  10. The Incorporation of C in the Crystal Lattice of Metals; Its Role on the Structure and Properties of these New Materials Called Covetics

    NASA Astrophysics Data System (ADS)

    Salamanca-Riba, Lourdes; Isaacs, Romaine; Forrest, David; Mansour, Azzam; Herzing, Andrew; Lemieux, Melburne; Shugart, Jason

    2013-03-01

    Nanocarbon has been successfully incorporated in molten metals and metal alloys using a new method of manufacturing in which the molten metal (or metal alloy) acts as ionizing medium causing nanocarbon structures to form in-situ. C in concentrations up to ~10% weight was incorporated in Ag, Al and Cu. The bonding between the carbon and the metal is very strong and persists after re-melting and resolidification. These materials, called ``covetics,'' show improved properties over those of the host metal. For example, the thermal conductivity of Cu covetic is higher than pure Cu. The electrical conductivity of Al covetic is higher than for pure Al. The yield strength of Al and Cu covetics is higher than the pure metals. We have used X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy to investigate the incorporation of C in the metal. Scanning and transmission electron microscopy (TEM) were also employed along with energy dispersive X-ray spectroscopy and electron energy loss spectroscopy (EELS). The nanocarbons in the covetics are in the form of, graphene nanoribbons, and amorphous nanocarbon, and all are bonded to the metal. The C-K edge in the EELS, and the Raman spectra from these samples show signals characteristic of graphitic sp2 bonding. Supported in part by NSF MRSEC DMR 0520471 and ONR Code 332 # N0001410WX20992.

  11. Visible stealth materials based on photonic crystals

    NASA Astrophysics Data System (ADS)

    Yao, Guozheng; Liu, Ying

    2014-08-01

    Optical thin film can be used for invisible cloak. As a kind of low-dimension photonic crystal, it is a candidate for metamaterial with designed Σ and μ. As a coating, it is convenient to be stacked to mimic continuous changing of electromagnetic media. Anti-reflection film is suitable for matching coating between layers of media.

  12. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1983-01-01

    Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

  13. Synthesis and Crystal Structure of Gold Nanobelts

    PubMed Central

    2015-01-01

    Gold nanobelts were synthesized by the reduction of tetrachloroauric acid with ascorbic acid in the presence of the surfactants cetyltrimethylammonium bromide and sodium dodecylsulfate. The resulting structures have rectangular cross sectional dimensions that are tens of nanometers and lengths that are tens to hundreds of micrometers. We find that the nanobelt yield and resulting structures are very sensitive to temperature which is likely due to the transition of the surfactant solution from wormlike micelles to spherical micelles. The nanobelt crystal structure contains a mixture of face centered cubic and hexagonally close packed lattice phases that can be isolated and examined individually due to the unique nanobelt size and shape. PMID:24803725

  14. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1988-01-01

    A decade long program to develop critical advanced composite technology in the areas of physical properties, structural concept and analysis, manufacturing, reliability, and life predictions is reviewed. Specific goals are discussed. The status of the chemical vapor deposition effects on carbon fiber properties; inelastic deformation of metal matrix laminates; fatigue damage in fibrous MMC laminates; delamination fracture toughness in thermoplastic matrix composites; and numerical analysis of composite micromechanical behavior are presented.

  15. Studies on synthesis, growth, structural, optical properties of organic 8-hydroxyquinolinium succinate single crystals

    SciTech Connect

    Thirumurugan, R. Anitha, K.

    2014-04-24

    8-hydroxyquinolinium succinate (8HQSU), an organic material has been synthesized and single crystals were grown by employing the technique of slow evaporation. The structure of the grown crystal was elucidated by using single crystal X-ray diffraction analysis. 8HQSU crystal belongs to the monoclinic crystallographic system with non-centro symmetric space group of P2{sub 1}. FT-IR spectral investigation has been carried out to identify the various functional groups present in the grown crystal. UV–vis spectral studies reveal that 8HQSU crystals are transparent in the entire visible region and the cut-off wavelength has been found to be 220nm.

  16. Method and apparatus for nucleating the crystallization of undercooled materials

    DOEpatents

    Benson, David K.; Barret, Peter F.

    1989-01-01

    A method of storing and controlling a release of latent heat of transition of a phase-change material is disclosed. The method comprises trapping a crystallite of the material between two solid objects and retaining it there under high pressure by applying a force to press the two solid objects tightly together. A crystallite of the material is exposed to a quantity of the material that is in a supercooled condition to nucleate the crystallization of the supercooled material.

  17. Coagulation factor XII protease domain crystal structure

    PubMed Central

    Pathak, M; Wilmann, P; Awford, J; Li, C; Hamad, BK; Fischer, PM; Dreveny, I; Dekker, LV; Emsley, J

    2015-01-01

    Background Coagulation factor XII is a serine protease that is important for kinin generation and blood coagulation, cleaving the substrates plasma kallikrein and FXI. Objective To investigate FXII zymogen activation and substrate recognition by determining the crystal structure of the FXII protease domain. Methods and results A series of recombinant FXII protease constructs were characterized by measurement of cleavage of chromogenic peptide and plasma kallikrein protein substrates. This revealed that the FXII protease construct spanning the light chain has unexpectedly weak proteolytic activity compared to β-FXIIa, which has an additional nine amino acid remnant of the heavy chain present. Consistent with these data, the crystal structure of the light chain protease reveals a zymogen conformation for active site residues Gly193 and Ser195, where the oxyanion hole is absent. The Asp194 side chain salt bridge to Arg73 constitutes an atypical conformation of the 70-loop. In one crystal form, the S1 pocket loops are partially flexible, which is typical of a zymogen. In a second crystal form of the deglycosylated light chain, the S1 pocket loops are ordered, and a short α-helix in the 180-loop of the structure results in an enlarged and distorted S1 pocket with a buried conformation of Asp189, which is critical for P1 Arg substrate recognition. The FXII structures define patches of negative charge surrounding the active site cleft that may be critical for interactions with inhibitors and substrates. Conclusions These data provide the first structural basis for understanding FXII substrate recognition and zymogen activation. PMID:25604127

  18. Elastic constants and material properties of novel shaped liquid crystals

    NASA Astrophysics Data System (ADS)

    Schmitthenner, M.; Challa, P. K.; Gleeson, J. T.; Garg, S.

    2013-03-01

    We report the Frank elastic constants along with other material properties of the newly synthesized liquid crystals RB01115 and RB01189. These materials are being investigated due to their Y and H-shaped structures respectively and possible biaxial nature of the latter. At T* = (T / TNI) = 0.94, we found the extraordinary refractive index of RB01189 to be 1.548 while the ordinary index was 1.469. We applied magnetic fields to induce Freedericksz transitions in order to find the elastic constants and determined their values to be: K11 = 0.12 × 10-12 N, K22 = 5.6 × 10-12 N, and K33 = 4.6 × 10-12 N. For the Y-shaped RB0115 at T*=0.98, we found K11 = 2.8 × 10-12 N, K22 = 2.5 × 10-12 N, and K33 = 4.5 × 10-12 N. These constants are similar to values found for other materials with non-rod shaped or bent-core structure. This work was supported by NSF DMR 0964765.

  19. Some quality characteristics of profiled sapphire crystals produced from different starting materials and their new applications

    NASA Astrophysics Data System (ADS)

    Zatulovskii, L. M.; Pelts, B. B.; Berezina, I. E.; Kravetskii, D. Ia.; Averianov, V. V.

    1985-12-01

    Results of an experimental study of the properties of sapphire crystals grown by the Stepanov method from 11 different grades of Al2O3 are reported. The starting materials used are classified into four groups on the basis of the quality of the resulting sapphire crystals, and each group is briefly characterized. Methods for purifying the starting material are examined, and some current applications of profiled sapphire crystals are discussed, including high-pressure sodium lamps, laser pumping lamps, and structural elements of solid-state lasers.

  20. Structural phase transitions in layered perovskitelike crystals

    SciTech Connect

    Aleksandrov, K.S.

    1995-03-01

    Possible symmetry changes due to small tilts of octahedra are considered for layered perovskite-like crystals containing slabs of several ({ell}) layers of comer-sharing octahedra. In the crystals with {ell} > 1, four types of distortions are possible; as a rule, these distortions correspond to the librational modes of the parent lattice. Condensation of these soft modes is the reason for structural phase transitions or sequences of phase transitions. The results obtained are compared with the known experimental data for a number of layered ferroelectric and ferroelastic perovskite-like compounds. An application of the results to the initial stage of determining unknown structures is discussed with particular attention paid to high-temperature superconductors. 76 refs., 9 figs., 7 tabs.

  1. Confined Crystals of the Smallest Phase-Change Material

    PubMed Central

    2013-01-01

    The demand for high-density memory in tandem with limitations imposed by the minimum feature size of current storage devices has created a need for new materials that can store information in smaller volumes than currently possible. Successfully employed in commercial optical data storage products, phase-change materials, that can reversibly and rapidly change from an amorphous phase to a crystalline phase when subject to heating or cooling have been identified for the development of the next generation electronic memories. There are limitations to the miniaturization of these devices due to current synthesis and theoretical considerations that place a lower limit of 2 nm on the minimum bit size, below which the material does not transform in the structural phase. We show here that by using carbon nanotubes of less than 2 nm diameter as templates phase-change nanowires confined to their smallest conceivable scale are obtained. Contrary to previous experimental evidence and theoretical expectations, the nanowires are found to crystallize at this scale and display amorphous-to-crystalline phase changes, fulfilling an important prerequisite of a memory element. We show evidence for the smallest phase-change material, extending thus the size limit to explore phase-change memory devices at extreme scales. PMID:23984706

  2. Crystal Structures of New Ammonium 5-Aminotetrazolates

    PubMed Central

    Lampl, Martin; Salchner, Robert; Laus, Gerhard; Braun, Doris E.; Kahlenberg, Volker; Wurst, Klaus; Fuhrmann, Gerda; Schottenberger, Herwig; Huppertz, Hubert

    2015-01-01

    The crystal structures of three salts of anionic 5-aminotetrazole are described. The tetramethylammonium salt (P1‒) forms hydrogen-bonded ribbons of anions which accept weak C–H⋯N contacts from the cations. The cystamine salt (C2/c) shows wave-shaped ribbons of anions linked by hydrogen bonds to screw-shaped dications. The tetramethylguanidine salt (P21/c) exhibits layers of anions hydrogen-bonded to the cations. PMID:26753100

  3. Observations on the crystal structures of lueshite

    NASA Astrophysics Data System (ADS)

    Mitchell, Roger H.; Burns, Peter C.; Knight, Kevin S.; Howard, Christopher J.; Chakhmouradian, Anton R.

    2014-06-01

    Laboratory powder XRD patterns of the perovskite-group mineral lueshite from the type locality (Lueshe, Kivu, DRC) and pure NaNbO3 demonstrate that lueshite does not adopt the same space group ( Pbma; #57) as the synthetic compound. The crystal structures of lueshite (2 samples) from Lueshe, Mont Saint-Hilaire (Quebec, Canada) and Sallanlatvi (Kola, Russia) have been determined by single-crystal CCD X-ray diffraction. These room temperature X-ray data for all single-crystal samples can be satisfactorily refined in the orthorhombic space group Pbnm (#62). Cell dimensions, atomic coordinates of the atoms, bond lengths and octahedron tilt angles are given for four crystals. Conventional neutron diffraction patterns for Lueshe lueshite recorded over the temperature range 11-1,000 K confirm that lueshite does not adopt space group Pbma within these temperatures. Neutron diffraction indicates no phase changes on cooling from room temperature to 11 K. None of these neutron diffraction data give satisfactorily refinements but suggest that this is the space group Pbnm. Time-of-flight neutron diffraction patterns for Lueshe lueshite recorded from room temperature to 700 °C demonstrate phase transitions above 550 °C from Cmcm through P4 /mbm to above 650 °C. Cell dimensions and atomic coordinates of the atoms are given for the three high-temperature phases. The room temperature to 400 °C structures cannot be satisfactorily resolved, and it is suggested that the lueshite at room temperature consists of domains of pinned metastable phases with orthorhombic and/or monoclinic structures. However, the sequence of high-temperature phase transitions observed is similar to those determined for synthetic NaTaO3, suggesting that the equilibrated room temperature structure of lueshite is orthorhombic Pbnm.

  4. Synthesis, crystal growth and characterization of an organic material: 2-Aminopyridinium succinate succinic acid single crystal.

    PubMed

    Magesh, M; Bhagavannarayana, G; Ramasamy, P

    2015-11-01

    The 2-aminopyridinium succinate succinic acid (2APS) single crystal was synthesized and grown by slow evaporation method. The crystal structure has been confirmed by powder X-ray diffraction as well as single crystal X-ray diffraction analysis. The crystal perfection has been evaluated by high resolution X-ray diffraction (HRXRD). The grown crystal is transparent in the visible and near infrared region. The optical absorption edge was found to be 348 nm. The fluorescence study was carried out by spectrofluorophotometer. The thermal stability of grown crystal was analyzed by thermal gravimetric and differential thermal gravimetric (TG-DTA) analysis. Vicker's hardness study carried out at room temperature shows increased hardness while increasing the load. Laser damage threshold value was determined by Nd:YAG laser operating at 1064 nm. The grown 2APS crystal was characterized by etching studies using water as etchant. PMID:26099828

  5. Focusing concave lens using photonic crystals with magnetic materials.

    PubMed

    Yang, Shieh-Yueh; Hong, Chin-Yih; Yang, Hong-Chang

    2006-04-01

    The guided modes lying in the upper gap-edge band in the photonic band structure of photonic crystals have negative values of refractive index. This feature generates many interesting optical phenomena, and some spectacular photonic devices such as focusing slabs have been developed. We report the design of a photonic-crystal, planoconcave lens for focusing incident parallel light, and theoretically analyze the chromatic aberrations for TM and TE modes. In addition to dielectric photonic crystals, the chromatic aberration of a magnetic photonic-crystal planoconcave lens was investigated because the magnetic permeability may also contribute to the periodic index contrast in photonic crystals, especially at long wavelengths. A significant difference was found in the chromatic aberration for a TM mode propagating in a dielectric than in a magnetic photonic-crystal planoconcave lens. PMID:16604781

  6. Structural materials for fusion reactors

    NASA Astrophysics Data System (ADS)

    Victoria, M.; Baluc, N.; Sptig, P.

    2001-08-01

    In order to preserve the conditions for an environmentally safe machine, at present the selection of materials for the structural components of fusion reactors is made not only on the basis of adequate mechanical properties, behaviour under irradiation, and compatibility with other materials and cooling media, but also on their radiological properties, i.e. radioactivity, decay heat and radiotoxicity. These conditions strongly limit the number of suitable materials to a few families of alloys, generically known as low activation materials. The criteria for making decisions about such materials, the alloys resulting from the application of these ideas and the main issues and problems with their use in a fusion environment are discussed.

  7. Synthesis, crystal structure, vibrational spectroscopy, optical properties and theoretical studies of a new organic-inorganic hybrid material: [((CH3)2NH2)(+)]6·[(BiBr6)(3-)]2.

    PubMed

    Ben Ahmed, A; Feki, H; Abid, Y

    2014-12-10

    A new organic-inorganic hybrid material, [((CH3)2NH2)(+)]6·[(BiBr6)(3-)]2, has been synthesized and characterized by X-ray diffraction, FT-IR, Raman spectroscopy and UV-Visible absorption. The studied compound crystallizes in the triclinic system, space group P1¯ with the following parameters: a=8.4749(6)(Å), b=17.1392(12)(Å), c=17.1392(12)(Å), α=117.339(0)°, β=99.487(0)°, γ=99.487(0)° and Z=2. The crystal lattice is composed of a two discrete (BiBr6)(3-) anions surrounded by six ((CH3)2NH2)(+) cations. Complex hydrogen bonding interactions between (BiBr6)(3-) and organic cations from a three-dimensional network. Theoretical calculations were performed using density functional theory (DFT) for studying the molecular structure, vibrational spectra and optical properties of the investigated molecule in the ground state. The full geometry optimization of designed system is performed using DFT method at B3LYP/LanL2DZ level of theory using the Gaussian03. The optimized geometrical parameters obtained by DFT calculations are in good agreement with single crystal XRD data. The vibrational spectral data obtained from FT-IR and Raman spectra are assigned based on the results of the theoretical calculations. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complements with the experimental findings. The simulated spectra satisfactorily coincide with the experimental UV-Visible spectrum. The results show good consistent with the experiment and confirm the contribution of metal orbital to the HOMO-LUMO boundary. PMID:24967541

  8. Crystal structure and DFT calculations of andrographiside

    NASA Astrophysics Data System (ADS)

    Seth, Saikat Kumar; Banerjee, Sukdeb; Kar, Tanusree

    2010-02-01

    Crystal and molecular structure of a labdane diterpenoid glucoside, andrographiside ( 1) is determined from 2D-NMR and X-ray diffraction data. The 2D-NMR study indicates that the carbohydrate moiety is in β-linkage and the sugar moiety is linked to C-19 of the aglycon. These observations are further confirmed from the X-ray diffraction studies. Both the six-membered rings are in chair conformation whereas the glucose ring adopts a twist-boat conformation. The molecular geometries and electronic structure of ( 1) were calculated at the DFT level using the hybrid exchange-correlation functional, BLYP, PW91 and PBE.

  9. ORTEP2. Crystal Structure Illustration Plots

    SciTech Connect

    Johnson, C.K.

    1982-02-17

    ORTEP2 draws crystal structure illustrations using a CalComp plotter. Ball and stick type illustrations of publication quality are produced with either spheres or thermal motion probability ellipsoids on the atomic sites. The program can produce stereoscopic pairs of illustrations which aid in the visualization of complex packing arrangements of atoms and thermal motion patterns. Interatomic distances, bond angles, and principal axes of thermal motion are calculated also as part of the structural study. ORTEP2 includes a hidden line algorithm to eliminate those portions of atoms or bonds behind other atoms or bonds.

  10. Manganese oxide minerals: crystal structures and economic and environmental significance.

    PubMed

    Post, J E

    1999-03-30

    Manganese oxide minerals have been used for thousands of years-by the ancients for pigments and to clarify glass, and today as ores of Mn metal, catalysts, and battery material. More than 30 Mn oxide minerals occur in a wide variety of geological settings. They are major components of Mn nodules that pave huge areas of the ocean floor and bottoms of many fresh-water lakes. Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Their typical occurrence as fine-grained mixtures makes it difficult to study their atomic structures and crystal chemistries. In recent years, however, investigations using transmission electron microscopy and powder x-ray and neutron diffraction methods have provided important new insights into the structures and properties of these materials. The crystal structures for todorokite and birnessite, two of the more common Mn oxide minerals in terrestrial deposits and ocean nodules, were determined by using powder x-ray diffraction data and the Rietveld refinement method. Because of the large tunnels in todorokite and related structures there is considerable interest in the use of these materials and synthetic analogues as catalysts and cation exchange agents. Birnessite-group minerals have layer structures and readily undergo oxidation reduction and cation-exchange reactions and play a major role in controlling groundwater chemistry. PMID:10097056

  11. Manganese oxide minerals: Crystal structures and economic and environmental significance

    PubMed Central

    Post, Jeffrey E.

    1999-01-01

    Manganese oxide minerals have been used for thousands of yearsby the ancients for pigments and to clarify glass, and today as ores of Mn metal, catalysts, and battery material. More than 30 Mn oxide minerals occur in a wide variety of geological settings. They are major components of Mn nodules that pave huge areas of the ocean floor and bottoms of many fresh-water lakes. Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Their typical occurrence as fine-grained mixtures makes it difficult to study their atomic structures and crystal chemistries. In recent years, however, investigations using transmission electron microscopy and powder x-ray and neutron diffraction methods have provided important new insights into the structures and properties of these materials. The crystal structures for todorokite and birnessite, two of the more common Mn oxide minerals in terrestrial deposits and ocean nodules, were determined by using powder x-ray diffraction data and the Rietveld refinement method. Because of the large tunnels in todorokite and related structures there is considerable interest in the use of these materials and synthetic analogues as catalysts and cation exchange agents. Birnessite-group minerals have layer structures and readily undergo oxidation reduction and cation-exchange reactions and play a major role in controlling groundwater chemistry. PMID:10097056

  12. Single Crystal Structure Determination of Alumina to 1 Mbar

    NASA Astrophysics Data System (ADS)

    Dong, H.; Zhang, L.; Prakapenka, V.; Mao, H.

    2014-12-01

    Aluminum oxide (Al2O3) is an important ceramic material and a major oxide in the earth. Additionally, alumina is a widely used pressure standard in static high-pressure experiments (Cr3+-bearing corundum, ruby). The changes of its crystal structure with pressure (P) and temperature (T) are important for its applications and understanding its physical properties in the deep Earth. There have been numerous reports on the high P-T polymorphs of alumina. Previous theoretical calculations and experiments suggest that the crystal structure of Al2O3 evolves greatly at high P-T. In this study, we used the newly developed multigrain crystallography method combined with single-crystal x-ray diffraction analysis technique for the structure determination of alumina at high P-T to provide single-crystal structure refinement for high-pressure phases of Al2O3. Alumina powder was mixed with ~10% Pt and Ne was used as both pressure transmitting media and thermal insulating layers during laser-heating. Coarse-grained aggregates of Al2O3 were synthesized in a laser-heated diamond anvil cell. The structure change of Al2O3 was monitored by in situ x-ray diffraction at ~1 Mbar and 2700 K. The results allow us to distinguish the structural differences between the Rh2O3 (II) structure (space group Pbcn) and perovskite structure (space group Pbnm) for the first high-pressure phase of Al2O3. More detailed results will be discussed in the later work.

  13. Crystal structure of natural phaeosphaeride A.

    PubMed

    Abzianidze, Victoria V; Poluektova, Ekaterina V; Bolshakova, Ksenia P; Panikorovskii, Taras L; Bogachenkov, Alexander S; Berestetskiy, Alexander O

    2015-08-01

    The asymmetric unit of the title compound, C15H23NO5, contains two independent mol-ecules. Phaeosphaeride A contains two primary sections, an alkyl chain consisting of five C atoms and a cyclic system consisting of fused five- and six-membered rings with attached substituents. In the crystal, the mol-ecules form layered structures. Nearly planar sheets, parallel to the (001) plane, form bilayers of two-dimensional hydrogen-bonded networks with the hy-droxy groups located on the inter-ior of the bilayer sheets. The network is constructed primarily of four O-H⋯O hydrogen bonds, which form a zigzag pattern in the (001) plane. The butyl chains inter-digitate with the butyl chains on adjacent sheets. The crystal was twinned by a twofold rotation about the c axis, with refined major-minor occupancy fractions of 0.718 (6):0.282 (6). PMID:26396831

  14. Crystal structures and freezing of dipolar fluids.

    PubMed

    Groh, B; Dietrich, S

    2001-02-01

    We investigate the crystal structure of classical systems of spherical particles with an embedded point dipole at T=0. The ferroelectric ground state energy is calculated using generalizations of the Ewald summation technique. Due to the reduced symmetry compared to the nonpolar case the crystals are never strictly cubic. For the Stockmayer (i.e., Lennard-Jones plus dipolar) interaction three phases are found upon increasing the dipole moment: hexagonal, body-centered orthorhombic, and body-centered tetragonal. An even richer phase diagram arises for dipolar soft spheres with a purely repulsive inverse power law potential approximately r(-n). A crossover between qualitatively different sequences of phases occurs near the exponent n=12. The results are applicable to electro- and magnetorheological fluids. In addition to the exact ground state analysis we study freezing of the Stockmayer fluid by density-functional theory. PMID:11308482

  15. Crystal Structure of Cryptosporidium parvum Pyruvate Kinase

    PubMed Central

    Cook, William J.; Senkovich, Olga; Aleem, Khadijah; Chattopadhyay, Debasish

    2012-01-01

    Pyruvate kinase plays a critical role in cellular metabolism of glucose by serving as a major regulator of glycolysis. This tetrameric enzyme is allosterically regulated by different effector molecules, mainly phosphosugars. In response to binding of effector molecules and substrates, significant structural changes have been identified in various pyruvate kinase structures. Pyruvate kinase of Cryptosporidium parvum is exceptional among known enzymes of protozoan origin in that it exhibits no allosteric property in the presence of commonly known effector molecules. The crystal structure of pyruvate kinase from C. parvum has been solved by molecular replacement techniques and refined to 2.5 Å resolution. In the active site a glycerol molecule is located near the γ-phosphate site of ATP, and the protein structure displays a partially closed active site. However, unlike other structures where the active site is closed, the α6' helix in C. parvum pyruvate kinase unwinds and assumes an extended conformation. In the crystal structure a sulfate ion is found at a site that is occupied by a phosphate of the effector molecule in many pyruvate kinase structures. A new feature of the C. parvum pyruvate kinase structure is the presence of a disulfide bond cross-linking the two monomers in the asymmetric unit. The disulfide bond is formed between cysteine residue 26 in the short N-helix of one monomer with cysteine residue 312 in a long helix (residues 303–320) of the second monomer at the interface of these monomers. Both cysteine residues are unique to C. parvum, and the disulfide bond remained intact in a reduced environment. However, the significance of this bond, if any, remains unknown at this time. PMID:23056503

  16. Crystal structures of carbonates up to Mbar pressures determined by single crystal synchrotron radiation diffraction

    NASA Astrophysics Data System (ADS)

    Merlini, M.

    2013-12-01

    The recent improvements at synchrotron beamlines, currently allow single crystal diffraction experiments at extreme pressures and temperatures [1,2] on very small single crystal domains. We successfully applied such technique to determine the crystal structure adopted by carbonates at mantle pressures. The knowledge of carbon-bearing phases is in fact fundamental for any quantitative modelling of global carbon cycle. The major technical difficulty arises after first order transitions or decomposition reactions, since original crystal (apx. 10x10x5 μm3) is transformed in much smaller crystalline domains often with random orientation. The use of 3D reciprocal space visualization software and the improved resolution of new generation flat panel detectors, however, allow both identification and integration of each single crystal domain, with suitable accuracy for ab-initio structure solution, performed with direct and charge-flipping methods and successive structure refinements. The results obtained on carbonates, indicate two major crystal-chemistry trends established at high pressures. The CO32- units, planar and parallel in ambient pressure calcite and dolomite structures, becomes non parallel in calcite- and dolomite-II and III phases, allowing more flexibility in the structures with possibility to accommodate strain arising from different cation sizes (Ca and Mg in particular). Dolomite-III is therefore also observed to be thermodynamically stable at lower mantle pressures and temperatures, differently from dolomite, which undergoes decomposition into pure end-members in upper mantle. At higher pressure, towards Mbar (lowermost mantle and D'' region) in agreement with theoretical calculations [3,4] and other experimental results [5], carbon coordination transform into 4-fold CO4 units, with different polymerisation in the structure depending on carbonate composition. The second important crystal chemistry feature detected is related to Fe2+ in Fe-bearing magnesite, which spontaneously oxidises at HP/HT, forming Fe3+ carbonates, Fe3+ oxides and reduced carbon (diamonds). Single crystal diffraction approach allowed full structure determination of these phases, yielding to the discovery of few unpredicted structures, such as Mg2Fe2C4O13 and Fe13O19, which can be well reproduced in different experiments. Mg2Fe2C4O13 carbonate present truncated chain C4O13 groups, and Fe13O19 oxide, whose stoichiometry is intermediate between magnetite and hematite, is a one-layer structure, with features encountered in superconducting materials. The results fully support the ideas of unexpected complexities in the mineralogy of the lowermost mantle, and single crystal technique, once properly optimized in ad-hoc synchrotron beamlines, is fundamental for extracting accurate structural information, otherwise rarely accessible with other experimental techniques. References: [1] Merlini M., Hanfland M. (2013). Single crystal diffraction at Mbar conditions by synchrotron radiation. High Pressure Research, in press. [2] Dubrovinsky et al., (2010). High Pressure Research, 30, 620-633. [3] Arapan et al. (1997). Phys. Rev. Lett., 98, 268501. [4] Oganov et al. (2008) EPSL, 273, 38-47. [5] Boulard et al. (2011) PNAS, 108, 5184-5187.

  17. Crystal structure of MboIIA methyltransferase.

    SciTech Connect

    Osipiuk, J.; Walsh, M. A.; Joachimiak, A.; Biosciences Division; Univ. of Gdansk; Medical Research Council France

    2003-09-15

    DNA methyltransferases (MTases) are sequence-specific enzymes which transfer a methyl group from S-adenosyl-L-methionine (AdoMet) to the amino group of either cytosine or adenine within a recognized DNA sequence. Methylation of a base in a specific DNA sequence protects DNA from nucleolytic cleavage by restriction enzymes recognizing the same DNA sequence. We have determined at 1.74 {angstrom} resolution the crystal structure of a {beta}-class DNA MTase MboIIA (M {center_dot} MboIIA) from the bacterium Moraxella bovis, the smallest DNA MTase determined to date. M {center_dot} MboIIA methylates the 3' adenine of the pentanucleotide sequence 5'-GAAGA-3'. The protein crystallizes with two molecules in the asymmetric unit which we propose to resemble the dimer when M {center_dot} MboIIA is not bound to DNA. The overall structure of the enzyme closely resembles that of M {center_dot} RsrI. However, the cofactor-binding pocket in M {center_dot} MboIIA forms a closed structure which is in contrast to the open-form structures of other known MTases.

  18. Crystal Structure of the Human Primase*

    PubMed Central

    Baranovskiy, Andrey G.; Zhang, Yinbo; Suwa, Yoshiaki; Babayeva, Nigar D.; Gu, Jianyou; Pavlov, Youri I.; Tahirov, Tahir H.

    2015-01-01

    DNA replication in bacteria and eukaryotes requires the activity of DNA primase, a DNA-dependent RNA polymerase that lays short RNA primers for DNA polymerases. Eukaryotic and archaeal primases are heterodimers consisting of small catalytic and large accessory subunits, both of which are necessary for RNA primer synthesis. Understanding of RNA synthesis priming in eukaryotes is currently limited due to the lack of crystal structures of the full-length primase and its complexes with substrates in initiation and elongation states. Here we report the crystal structure of the full-length human primase, revealing the precise overall organization of the enzyme, the relative positions of its functional domains, and the mode of its interaction with modeled DNA and RNA. The structure indicates that the dramatic conformational changes in primase are necessary to accomplish the initiation and then elongation of RNA synthesis. The presence of a long linker between the N- and C-terminal domains of p58 provides the structural basis for the bulk of enzyme's conformational flexibility. Deletion of most of this linker affected the initiation and elongation steps of the primer synthesis. PMID:25550159

  19. Critical parameters of superconducting materials and structures

    SciTech Connect

    Fluss, M.J.; Howell, R.H.; Sterne, P.A.; Dykes, J.W.; Mosley, W.D.; Chaiken, A.; Ralls, K.; Radousky, H.

    1995-02-01

    We report here the completion of a one year project to investigate the synthesis, electronic structure, defect structure, and physical transport properties of high temperature superconducting oxide materials. During the course of this project we produced some of the finest samples of single crystal detwinned YBa{sub 2}Cu{sub 3}O{sub 7}, and stoichiometrically perfect (Ba,K)BiO{sub 3}. We deduced the Fermi surface of YBa{sub 2}Cu{sub 3}O{sub 7}, (La,Sr){sub 2}CuO{sub 4}, and (Ba,K)BiO{sub 3} through the recording of the electron momentum density in these materials as measured by positron annihilation spectroscopy and angle resolved photoemission. We also performed extensive studies on Pr substituted (Y,Pr)Ba{sub 2}Cu{sub 3}O{sub 7} so as to further understand the origin of the electron pairing leading to superconductivity.

  20. [Band electronic structures and crystal packing forces

    SciTech Connect

    Not Available

    1993-01-01

    We investigated the electronic and structural properties of low-dimensional materials and explored the structure-property correlations governing their physical properties. Progress was made on how to interpret the scanning tunneling microscopy and atomic force microscopy images of layered materials and on how to account for charge density wave instabilities in 2-D metals. Materials studied included transition metal chalcogenides, transition metal halides, organic conducting salts, Mo bronzes, A[sub 2]PdH[sub 2], fullerenes, squarate tetrahydrate polymers Fe, Cu(C[sub 4]O[sub 4])4[center dot]H[sub 2]O, BEDT salts, etc.

  1. Microscopic Mechanism of Doping-Induced Kinetically Constrained Crystallization in Phase-Change Materials.

    PubMed

    Lee, Tae Hoon; Loke, Desmond; Elliott, Stephen R

    2015-10-01

    A comprehensive microscopic mechanism of doping-induced kinetically constrained crystallization in phase-change materials is provided by investigating structural and dynamical dopant characteristics via ab initio molecular dynamics simulations. The information gained from this study may provide a basis for a fast screening of dopant species for electronic memory devices, or for understanding the general physics involved in the crystallization of doped glasses. PMID:26426723

  2. The crystal structure of ice under mesospheric conditions

    NASA Astrophysics Data System (ADS)

    Murray, Benjamin J.; Malkin, Tamsin L.; Salzmann, Christoph G.

    2015-05-01

    Ice clouds form in the summer high latitude mesopause region, which is the coldest part of the Earth's atmosphere. At these very low temperatures (<150 K) ice can exist in metastable forms, but the nature of these ices remains poorly understood. In this paper we show that ice which is grown at mesospherically relevant temperatures does not have a structure corresponding to the well-known hexagonal form or the metastable cubic form. Instead, the ice which forms under mesospheric conditions is a material in which cubic and hexagonal sequences of ice are randomly arranged to produce stacking disordered ice (ice Isd). The structure of this ice is in the trigonal crystal system, rather than the cubic or hexagonal systems, and is expected to produce crystals with aspect ratios consistent with lidar observations.

  3. Liquid crystal photoalignment material based on chloromethylated polyimide

    SciTech Connect

    Zhong Zhenxin; Li Xiangdan; Lee, Seung Hee; Lee, Myong-Hoon

    2004-09-27

    We report a liquid crystal photoalignment material with high photosensitivity and excellent thermal stability. The chloromethylated aromatic polyimide exhibited defect-free homogeneous alignment of liquid crystals upon irradiation of polarized deep ultraviolet (UV) for 50 s. The aligning ability of the film was retained up to 210 deg. C, and the cell containing liquid crystals could be stored at 85 deg. C for more than 14 days without any deterioration. FT-IR and UV-vis spectra confirmed that the alignment was induced by photodecomposition of polyimide, drastically accelerated by the introduction of chloromethyl side group.

  4. A dynamic beam splitter using polymer dispersed liquid crystal materials

    NASA Astrophysics Data System (ADS)

    Riquelme, Marina; Ortuo, Manuel; Mrquez, Andrs.; Gallego, Sergi; Pascual, Inmaculada; Belndez, Augusto

    2012-10-01

    We build a dynamic beam splitter with a holographic optical element (HOE). The laser light goes through the HOE and a fraction of intensity diffracted and transmitted could be tuned by an electric signal. We use holographic polymer dispersed liquid crystals materials. It is made by holographic recording in which the liquid crystal molecules diffuse to dark zones in the diffraction grating and they can be oriented by means of an electric field. The orientation of the liquid crystal produces a refraction index variation which changes the diffraction efficiency and therefore the grating has a dynamic behavior.

  5. Crystal Structure of the 30S Ribosomal Subunit from Thermus Thermophilus. Purification, Crystallization and Structure Determination

    SciTech Connect

    Clemons, William M.; Brodersen, Ditlev E.; McCutcheonn, John P.; May, Joanna L.C.; Carter, Andrew P.; Morgan-Warren, Robert J.; Wimberly, Brian T.; Ramakrishnan, Venki

    2009-10-07

    We describe the crystallization and structure determination of the 30 S ribosomal subunit from Thermus thermophilus. Previous reports of crystals that diffracted to 10 {angstrom} resolution were used as a starting point to improve the quality of the diffraction. Eventually, ideas such as the addition of substrates or factors to eliminate conformational heterogeneity proved less important than attention to detail in yielding crystals that diffracted beyond 3 {angstrom} resolution. Despite improvements in technology and methodology in the last decade, the structure determination of the 30 S subunit presented some very challenging technical problems because of the size of the asymmetric unit, crystal variability and sensitivity to radiation damage. Some steps that were useful for determination of the atomic structure were: the use of anomalous scattering from the LIII edges of osmium and lutetium to obtain the necessary phasing signal; the use of tunable, third-generation synchrotron sources to obtain data of reasonable quality at high resolution; collection of derivative data precisely about a mirror plane to preserve small anomalous differences between Bijvoet mates despite extensive radiation damage and multi-crystal scaling; the pre-screening of crystals to ensure quality, isomorphism and the efficient use of scarce third-generation synchrotron time; pre-incubation of crystals in cobalt hexaammine to ensure isomorphism with other derivatives; and finally, the placement of proteins whose structures had been previously solved in isolation, in conjunction with biochemical data on protein-RNA interactions, to map out the architecture of the 30 S subunit prior to the construction of a detailed atomic-resolution model.

  6. Crystal Structure of Human β-Galactosidase

    PubMed Central

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

    2012-01-01

    GM1 gangliosidosis and Morquio B are autosomal recessive lysosomal storage diseases associated with a neurodegenerative disorder or dwarfism and skeletal abnormalities, respectively. These diseases are caused by deficiencies in the lysosomal enzyme β-d-galactosidase (β-Gal), which lead to accumulations of the β-Gal substrates, GM1 ganglioside, and keratan sulfate. β-Gal is an exoglycosidase that catalyzes the hydrolysis of terminal β-linked galactose residues. This study shows the crystal structures of human β-Gal in complex with its catalytic product galactose or with its inhibitor 1-deoxygalactonojirimycin. Human β-Gal is composed of a catalytic TIM barrel domain followed by β-domain 1 and β-domain 2. To gain structural insight into the molecular defects of β-Gal in the above diseases, the disease-causing mutations were mapped onto the three-dimensional structure. Finally, the possible causes of the diseases are discussed. PMID:22128166

  7. Crystal structure of plant photosystem I

    NASA Astrophysics Data System (ADS)

    Ben-Shem, Adam; Frolow, Felix; Nelson, Nathan

    2003-12-01

    Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on Earth. The conversion of sunlight into chemical energy is driven by two multisubunit membrane protein complexes named photosystem I and II. We determined the crystal structure of the complete photosystem I (PSI) from a higher plant (Pisum sativum var. alaska) to 4.4Å resolution. Its intricate structure shows 12 core subunits, 4 different light-harvesting membrane proteins (LHCI) assembled in a half-moon shape on one side of the core, 45 transmembrane helices, 167 chlorophylls, 3 Fe-S clusters and 2 phylloquinones. About 20 chlorophylls are positioned in strategic locations in the cleft between LHCI and the core. This structure provides a framework for exploration not only of energy and electron transfer but also of the evolutionary forces that shaped the photosynthetic apparatus of terrestrial plants after the divergence of chloroplasts from marine cyanobacteria one billion years ago.

  8. Crystal structure prediction from first principles: The crystal structures of glycine

    NASA Astrophysics Data System (ADS)

    Lund, Albert M.; Pagola, Gabriel I.; Orendt, Anita M.; Ferraro, Marta B.; Facelli, Julio C.

    2015-04-01

    Here we present the results of our unbiased searches of glycine polymorphs obtained using the genetic algorithms search implemented in MGAC, modified genetic algorithm for crystals, coupled with the local optimization and energy evaluation provided by Quantum Espresso. We demonstrate that it is possible to predict the crystal structures of a biomedical molecule using solely first principles calculations. We were able to find all the ambient pressure stable glycine polymorphs, which are found in the same energetic ordering as observed experimentally and the agreement between the experimental and predicted structures is of such accuracy that the two are visually almost indistinguishable.

  9. Crystal Structure Prediction from First Principles: The Crystal Structures of Glycine

    PubMed Central

    Lund, Albert M.; Pagola, Gabriel I.; Orendt, Anita M.; Ferraro, Marta B.; Facelli, Julio C.

    2015-01-01

    Here we present the results of our unbiased searches of glycine polymorphs obtained using the Genetic Algorithms search implemented in Modified Genetic Algorithm for Crystals coupled with the local optimization and energy evaluation provided by Quantum Espresso. We demonstrate that it is possible to predict the crystal structures of a biomedical molecule using solely first principles calculations. We were able to find all the ambient pressure stable glycine polymorphs, which are found in the same energetic ordering as observed experimentally and the agreement between the experimental and predicted structures is of such accuracy that the two are visually almost indistinguishable. PMID:25843964

  10. Crystal structure of a DNA catalyst.

    PubMed

    Ponce-Salvatierra, Almudena; Wawrzyniak-Turek, Katarzyna; Steuerwald, Ulrich; Höbartner, Claudia; Pena, Vladimir

    2016-01-14

    Catalysis in biology is restricted to RNA (ribozymes) and protein enzymes, but synthetic biomolecular catalysts can also be made of DNA (deoxyribozymes) or synthetic genetic polymers. In vitro selection from synthetic random DNA libraries identified DNA catalysts for various chemical reactions beyond RNA backbone cleavage. DNA-catalysed reactions include RNA and DNA ligation in various topologies, hydrolytic cleavage and photorepair of DNA, as well as reactions of peptides and small molecules. In spite of comprehensive biochemical studies of DNA catalysts for two decades, fundamental mechanistic understanding of their function is lacking in the absence of three-dimensional models at atomic resolution. Early attempts to solve the crystal structure of an RNA-cleaving deoxyribozyme resulted in a catalytically irrelevant nucleic acid fold. Here we report the crystal structure of the RNA-ligating deoxyribozyme 9DB1 (ref. 14) at 2.8 Å resolution. The structure captures the ligation reaction in the post-catalytic state, revealing a compact folding unit stabilized by numerous tertiary interactions, and an unanticipated organization of the catalytic centre. Structure-guided mutagenesis provided insights into the basis for regioselectivity of the ligation reaction and allowed remarkable manipulation of substrate recognition and reaction rate. Moreover, the structure highlights how the specific properties of deoxyribose are reflected in the backbone conformation of the DNA catalyst, in support of its intricate three-dimensional organization. The structural principles underlying the catalytic ability of DNA elucidate differences and similarities in DNA versus RNA catalysts, which is relevant for comprehending the privileged position of folded RNA in the prebiotic world and in current organisms. PMID:26735012

  11. Elasticity of some mantle crystal structures. II.

    NASA Technical Reports Server (NTRS)

    Wang, H.; Simmons, G.

    1973-01-01

    The single-crystal elastic constants are determined as a function of pressure and temperature for rutile structure germanium dioxide (GeO2). The data are qualitatively similar to those of rutile TiO2 measured by Manghnani (1969). The compressibility in the c direction is less than one-half that in the a direction, the pressure derivative of the shear constant is negative, and the pressure derivative of the bulk modulus has a relatively high value of about 6.2. According to an elastic strain energy theory, the negative shear modulus derivative implies that the kinetic barrier to diffusion decreases with increasing pressure.

  12. Temperature dependent spin structures in Hexaferrite crystal

    NASA Astrophysics Data System (ADS)

    Chao, Y. C.; Lin, J. G.; Chun, S. H.; Kim, K. H.

    2016-01-01

    In this work, the Hexaferrite Ba0.5Sr1.5Zn2Fe12O22 (BSZFO) is studied due to its interesting characteristics of long-wavelength spin structure. Ferromagnetic resonance (FMR) is used to probe the magnetic states of BSZFO single crystal and its temperature dependence behavior is analyzed by decomposing the multiple lines of FMR spectra into various phases. Distinguished phase transition is observed at 110 K for one line, which is assigned to the ferro(ferri)-magnetic transition from non-collinear to collinear spin state.

  13. Bio-Inspired Approaches to Crystals with Composite Structures

    NASA Astrophysics Data System (ADS)

    Meldrum, Fiona

    2013-03-01

    Advances in technology demand an ever-increasing degree of control over material structure, properties and function. As the properties of monolithic materials are necessary limited, one route to extending them is to create a composite by combining contrasting materials. The potential of this approach is beautifully illustrated by the formation of biominerals where organic macromolecules are combined with brittle minerals such as calcite to create crystals with considerable fracture toughness. This talk will discuss how bio-inspired approaches can be used to generate single crystals with composite crystals through a simple one-pot method. By precipitating calcite crystals in the presence of ``occlusion species'' ranging from latex particles, to organic and inorganic nanoparticles and finally small molecules we demonstrate that high amounts of foreign species can be incorporated through control over the additive surface chemistry, and that this can lead to an enhancement of the mechanical properties of the calcite. Occlusion of 20 nm anionic diblock copolymer micelles was achieved at levels of over 13 wt%, and the properties of the resuktant composite calcite crystals were measured using a range of techniques including IR spectroscopy, high resolution powder XRD and high resolution TEM. Incorporation of these macromolecules leads to crystals with structures and mechanical properties similar to those of biominerals. With sizes in the range of some intracrystalline proteins, the micelles act as ``pseudo-proteins'', thereby providing an excellent model system for investigation of the mechanism of macromolecule insertion within biominerals. Extension of these studies to the incorporation of small molecules (amino acids) again demonstrated high levels of incorporation without any change in the crystal morphology. Further, occlusion of these small molecules within the calcite lattice again resulted in a significant increase in the hardness of the calcite, a result which appears to derive from an increase in lattice strain on molecular occlusion. Finally, the generality of this strategy is demonstrated by its extension to the incorporation of inorganic particles such as magnetite and gold within calcite, leading to the formation of inorganic-inorganic composites. I would like to acknowledge the EPSRC for funding under grants EP/G00868X/1, EP/E037364/1 and EP/K006304/1

  14. Synthesis and crystal structure of the new ternary halide series Ba{sub 2}MCl{sub 7} (M = Gd-Yb, Y) containing the highly efficient up-conversion material Ba{sub 2}ErCl{sub 7}

    SciTech Connect

    Wickleder, M.S.; Egger, P.; Riedener, T.

    1996-12-01

    Single crystals of Ba{sub 2}MCl{sub 7} (M = Gd-Yb, Y) were prepared. The crystal structure of Ba{sub 2}ErCl{sub 7} and Ba{sub 2}GdCl{sub 7} were determined by X-ray diffraction. Lattice parameters were determined for the series. IR and UV/vis spectroscopy for the erbium analogue were presented.

  15. Monoolein lipid phases as incorporation and enrichment materials for membrane protein crystallization.

    SciTech Connect

    Wallace, E.; Dranow, D.; Laible, P. D.; Christensen, J.; Nollert, P.

    2011-01-01

    The crystallization of membrane proteins in amphiphile-rich materials such as lipidic cubic phases is an established methodology in many structural biology laboratories. The standard procedure employed with this methodology requires the generation of a highly viscous lipidic material by mixing lipid, for instance monoolein, with a solution of the detergent solubilized membrane protein. This preparation is often carried out with specialized mixing tools that allow handling of the highly viscous materials while minimizing dead volume to save precious membrane protein sample. The processes that occur during the initial mixing of the lipid with the membrane protein are not well understood. Here we show that the formation of the lipidic phases and the incorporation of the membrane protein into such materials can be separated experimentally. Specifically, we have investigated the effect of different initial monoolein-based lipid phase states on the crystallization behavior of the colored photosynthetic reaction center from Rhodobacter sphaeroides. We find that the detergent solubilized photosynthetic reaction center spontaneously inserts into and concentrates in the lipid matrix without any mixing, and that the initial lipid material phase state is irrelevant for productive crystallization. A substantial in-situ enrichment of the membrane protein to concentration levels that are otherwise unobtainable occurs in a thin layer on the surface of the lipidic material. These results have important practical applications and hence we suggest a simplified protocol for membrane protein crystallization within amphiphile rich materials, eliminating any specialized mixing tools to prepare crystallization experiments within lipidic cubic phases. Furthermore, by virtue of sampling a membrane protein concentration gradient within a single crystallization experiment, this crystallization technique is more robust and increases the efficiency of identifying productive crystallization parameters. Finally, we provide a model that explains the incorporation of the membrane protein from solution into the lipid phase via a portal lamellar phase.

  16. Growth of bulk single crystals of organic materials for nonlinear optical devices - An overview

    NASA Technical Reports Server (NTRS)

    Penn, Benjamin G.; Cardelino, Beatriz H.; Moore, Craig E.; Shields, Angela W.; Frazier, D. O.

    1991-01-01

    Highly perfect single crystals of nonlinear optical organic materials are required for use in optical devices. An overview of the bulk crystal growth of these materials by melt, vapor, and solution processes is presented. Additionally, methods that may be used to purify starting materials, detect impurities at low levels, screen materials for crystal growth, and process grown crystals are discussed.

  17. Glass Formation of a Coordination Polymer Crystal for Enhanced Proton Conductivity and Material Flexibility.

    PubMed

    Chen, Wenqian; Horike, Satoshi; Umeyama, Daiki; Ogiwara, Naoki; Itakura, Tomoya; Tassel, Cédric; Goto, Yoshihiro; Kageyama, Hiroshi; Kitagawa, Susumu

    2016-04-18

    The glassy state of a two-dimensional (2D) Cd(2+) coordination polymer crystal was prepared by a solvent-free mechanical milling process. The glassy state retains the 2D structure of the crystalline material, albeit with significant distortion, as characterized by synchrotron X-ray analyses and solid-state multinuclear NMR spectroscopy. It transforms to its original crystal structure upon heating. Thus, reversible crystal-to-glass transformation is possible using our new processes. The glass state displays superior properties compared to the crystalline state; specifically, it shows anhydrous proton conductivity and a dielectric constant two orders of magnitude greater than the crystalline material. It also shows material flexibility and transparency. PMID:26990042

  18. Crystal growth and third order NLO properties of a photonic material

    NASA Astrophysics Data System (ADS)

    Rajesh Kumar, P. C.; Janardhana, K.; Crasta, Vincent

    2014-02-01

    Organic compound 1-(4-bromophenyl)-3-(4-N, N dimethylaminophenyl) prop-2-en-1-one [BDPP] was synthesized using Claisen-Schmidt condensation reaction method. Single crystals were grown using slow evaporation solution growth technique. The FTIR study was carried out for structural confirmation. The UV-Visible spectrum reveals that the crystal is transparent in the entire visible region and absorption takes place in the UV-region. Third order non-linearity has been explored using Z-scan technique. The material exhibits non-linear absorption which can be attributed to reverse saturable absorption. This study also exploits the optical limiting behavior of the material. The theoretical study using Mopac confirms the non-linearity of the compound at the molecular level. The structural parameters were determined by using single crystal XRD. The thermal study confirms the good thermal stability of the material.

  19. Nanoscale Imaging of Mineral Crystals inside Biological Composite Materials Using X-Ray Diffraction Microscopy

    NASA Astrophysics Data System (ADS)

    Jiang, Huaidong; Ramunno-Johnson, Damien; Song, Changyong; Amirbekian, Bagrat; Kohmura, Yoshiki; Nishino, Yoshinori; Takahashi, Yukio; Ishikawa, Tetsuya; Miao, Jianwei

    2008-01-01

    We for the first time applied x-ray diffraction microscopy to the imaging of mineral crystals inside biological composite materials—intramuscular fish bone—at the nanometer scale resolution. We identified mineral crystals in collagen fibrils at different stages of mineralization. Based on the experimental results and biomineralization analyses, we suggested a dynamic model to account for the nucleation and growth of mineral crystals in the collagen matrix. The results obtained from this study not only further our understanding of the complex structure of bone, but also demonstrate that x-ray diffraction microscopy will become an important tool to study biological materials.

  20. Lead pyrovanadate single crystal as a new SRS material

    SciTech Connect

    Basiev, Tasoltan T; Voronko, Yu K; Maslov, Vladislav A; Sobol, A A; Shukshin, V E

    2011-02-28

    Lead pyrovanadate Pb{sub 2}V{sub 2}O{sub 7} single crystals of optical quality suitable for laser experiments are obtained. Vibrational modes are identified based on the analysis of the polarised Raman spectra of the single crystals. The main parameters (width at half maximum, peak and integral intensities) of the spectral lines most promising for SRS conversion in this material are estimated. These parameters are compared with the corresponding parameters of the most frequently used lines of known Raman materials: yttrium and gadolinium vanadates, potassium and lead tungstates, and lead molybdate. (active media)

  1. Crystal structure of yeast Sco1

    SciTech Connect

    Abajian, Carnie; Rosenzweig, Amy C.

    2010-03-05

    The Sco family of proteins are involved in the assembly of the dinuclear CuA site in cytochrome c oxidase (COX), the terminal enzyme in aerobic respiration. These proteins, which are found in both eukaryotes and prokaryotes, are characterized by a conserved CXXXC sequence motif that binds copper ions and that has also been proposed to perform a thiol:disulfide oxidoreductase function. The crystal structures of Saccharomyces cerevisiae apo Sco1 (apo-ySco1) and Sco1 in the presence of copper ions (Cu-ySco1) were determined to 1.8- and 2.3-{angstrom} resolutions, respectively. Yeast Sco1 exhibits a thioredoxin-like fold, similar to that observed for human Sco1 and a homolog from Bacillus subtilis. The Cu-ySco1 structure, obtained by soaking apo-ySco1 crystals in copper ions, reveals an unexpected copper-binding site involving Cys181 and Cys216, cysteine residues present in ySco1 but not in other homologs. The conserved CXXXC cysteines, Cys148 and Cys152, can undergo redox chemistry in the crystal. An essential histidine residue, His239, is located on a highly flexible loop, denoted the Sco loop, and can adopt positions proximal to both pairs of cysteines. Interactions between ySco1 and its partner proteins yeast Cox17 and yeast COX2 are likely to occur via complementary electrostatic surfaces. This high-resolution model of a eukaryotic Sco protein provides new insight into Sco copper binding and function.

  2. Crystal structure and electrochemical properties of rare earth non-stoichiometric AB5-type alloy as negative electrode material in Ni-MH battery

    NASA Astrophysics Data System (ADS)

    Zhang, Xinbo; Chai, Yujun; Yin, Wenya; Zhao, Minshou

    2004-07-01

    The La 0.85Mg xNi 4.5Co 0.35Al 0.15 (0.05⩽ x⩽0.35) system compounds have been prepared by arc melting method under Ar atmosphere. X-ray diffraction (XRD) analysis reveals that the as-prepared alloys have different lattice parameters and cell volumes. The electrochemical properties of these alloys have been studied through the charge-discharge recycle testing at different temperatures and discharge currents. It is found that the La 0.85Mg 0.25Ni 4.5Co 0.35Al 0.15 alloy electrode is capable of performing high-rate discharge. Moreover, it has very excellent electrochemical properties as negative electrode materials in Ni-MH battery at low temperature, even at -40°C.

  3. Crystal structure of human nicotinamide riboside kinase.

    PubMed

    Khan, Javed A; Xiang, Song; Tong, Liang

    2007-08-01

    Nicotinamide riboside kinase (NRK) has an important role in the biosynthesis of NAD(+) as well as the activation of tiazofurin and other NR analogs for anticancer therapy. NRK belongs to the deoxynucleoside kinase and nucleoside monophosphate (NMP) kinase superfamily, although the degree of sequence conservation is very low. We report here the crystal structures of human NRK1 in a binary complex with the reaction product nicotinamide mononucleotide (NMN) at 1.5 A resolution and in a ternary complex with ADP and tiazofurin at 2.7 A resolution. The active site is located in a groove between the central parallel beta sheet core and the LID and NMP-binding domains. The hydroxyl groups on the ribose of NR are recognized by Asp56 and Arg129, and Asp36 is the general base of the enzyme. Mutation of residues in the active site can abolish the catalytic activity of the enzyme, confirming the structural observations. PMID:17698003

  4. Crystal Structure of Human Nicotinamide Riboside Kinase

    SciTech Connect

    Khan,J.; Xiang, S.; Tong, L.

    2007-01-01

    Nicotinamide riboside kinase (NRK) has an important role in the biosynthesis of NAD{sup +} as well as the activation of tiazofurin and other NR analogs for anticancer therapy. NRK belongs to the deoxynucleoside kinase and nucleoside monophosphate (NMP) kinase superfamily, although the degree of sequence conservation is very low. We report here the crystal structures of human NRK1 in a binary complex with the reaction product nicotinamide mononucleotide (NMN) at 1.5 {angstrom} resolution and in a ternary complex with ADP and tiazofurin at 2.7 {angstrom} resolution. The active site is located in a groove between the central parallel {beta} sheet core and the LID and NMP-binding domains. The hydroxyl groups on the ribose of NR are recognized by Asp56 and Arg129, and Asp36 is the general base of the enzyme. Mutation of residues in the active site can abolish the catalytic activity of the enzyme, confirming the structural observations.

  5. Structure, thermodynamics, and crystallization of amorphous hafnia

    NASA Astrophysics Data System (ADS)

    Luo, Xuhui; Demkov, Alexander A.

    2015-09-01

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO2. The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia.

  6. The Crystal Structure of Human Argonaute2

    SciTech Connect

    Schirle, Nicole T.; MacRae, Ian J.

    2012-07-18

    Argonaute proteins form the functional core of the RNA-induced silencing complexes that mediate RNA silencing in eukaryotes. The 2.3 angstrom resolution crystal structure of human Argonaute2 (Ago2) reveals a bilobed molecule with a central cleft for binding guide and target RNAs. Nucleotides 2 to 6 of a heterogeneous mixture of guide RNAs are positioned in an A-form conformation for base pairing with target messenger RNAs. Between nucleotides 6 and 7, there is a kink that may function in microRNA target recognition or release of sliced RNA products. Tandem tryptophan-binding pockets in the PIWI domain define a likely interaction surface for recruitment of glycine-tryptophan-182 (GW182) or other tryptophan-rich cofactors. These results will enable structure-based approaches for harnessing the untapped therapeutic potential of RNA silencing in humans.

  7. Crystallization of Stretched Polyimides: A Structure-Property Study

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Dezern, James F.

    2002-01-01

    A simple rotational isomeric state model was used to detect the degree to which polyimide repeat units might align to give an extended crystal. It was found experimentally that the hallmarks of stretch-crystallization were more likely to occur in materials whose molecules could readily give extended, aligned conformations. A proposed screening criterion was 84% accurate in selecting crystallizing molecules.

  8. Structural contribution to the roughness of supersmooth crystal surface

    SciTech Connect

    Butashin, A. V.; Muslimov, A. E. Kanevsky, V. M.; Deryabin, A. N.; Pavlov, V. A.; Asadchikov, V. E.

    2013-05-15

    Technological advances in processing crystals (Si, sapphire {alpha}-Al{sub 2}O{sub 3}, SiC, GaN, LiNbO{sub 3}, SrTiO{sub 3}, etc.) of substrate materials and X-ray optics elements make it possible to obtain supersmooth surfaces with a periodicity characteristic of the crystal structure. These periodic structures are formed by atomically smooth terraces and steps of nano- and subnanometer sizes, respectively. A model surface with such nanostructures is proposed, and the relations between its roughness parameters and the height of atomic steps are determined. The roughness parameters calculated from these relations almost coincide with the experimental atomic force microscopy (AFM) data obtained from 1 Multiplication-Sign 1 and 10 Multiplication-Sign 10 {mu}m areas on the surface of sapphire plates with steps. The minimum roughness parameters for vicinal crystal surfaces, which are due to the structural contribution, are calculated based on the approach proposed. A comparative analysis of the relief and roughness parameters of sapphire plate surfaces with different degrees of polishing is performed. A size effect is established: the relief height distribution changes from stochastic to regular with a decrease in the surface roughness.

  9. Prediction of binary hard-sphere crystal structures

    NASA Astrophysics Data System (ADS)

    Filion, Laura; Dijkstra, Marjolein

    2009-04-01

    We present a method based on a combination of a genetic algorithm and Monte Carlo simulations to predict close-packed crystal structures in hard-core systems. We employ this method to predict the binary crystal structures in a mixture of large and small hard spheres with various stoichiometries and diameter ratios between 0.4 and 0.84. In addition to known binary hard-sphere crystal structures similar to NaCl and AlB2 , we predict additional crystal structures with the symmetry of CrB, γCuTi , αIrV , HgBr2 , AuTe2 , Ag2Se , and various structures for which an atomic analog was not found. In order to determine the crystal structures at infinite pressures, we calculate the maximum packing density as a function of size ratio for the crystal structures predicted by our GA using a simulated annealing approach.

  10. How evolutionary crystal structure prediction works--and why.

    PubMed

    Oganov, Artem R; Lyakhov, Andriy O; Valle, Mario

    2011-03-15

    Once the crystal structure of a chemical substance is known, many properties can be predicted reliably and routinely. Therefore if researchers could predict the crystal structure of a material before it is synthesized, they could significantly accelerate the discovery of new materials. In addition, the ability to predict crystal structures at arbitrary conditions of pressure and temperature is invaluable for the study of matter at extreme conditions, where experiments are difficult. Crystal structure prediction (CSP), the problem of finding the most stable arrangement of atoms given only the chemical composition, has long remained a major unsolved scientific problem. Two problems are entangled here: search, the efficient exploration of the multidimensional energy landscape, and ranking, the correct calculation of relative energies. For organic crystals, which contain a few molecules in the unit cell, search can be quite simple as long as a researcher does not need to include many possible isomers or conformations of the molecules; therefore ranking becomes the main challenge. For inorganic crystals, quantum mechanical methods often provide correct relative energies, making search the most critical problem. Recent developments provide useful practical methods for solving the search problem to a considerable extent. One can use simulated annealing, metadynamics, random sampling, basin hopping, minima hopping, and data mining. Genetic algorithms have been applied to crystals since 1995, but with limited success, which necessitated the development of a very different evolutionary algorithm. This Account reviews CSP using one of the major techniques, the hybrid evolutionary algorithm USPEX (Universal Structure Predictor: Evolutionary Xtallography). Using recent developments in the theory of energy landscapes, we unravel the reasons evolutionary techniques work for CSP and point out their limitations. We demonstrate that the energy landscapes of chemical systems have an overall shape and explore their intrinsic dimensionalities. Because of the inverse relationships between order and energy and between the dimensionality and diversity of an ensemble of crystal structures, the chances that a random search will find the ground state decrease exponentially with increasing system size. A well-designed evolutionary algorithm allows for much greater computational efficiency. We illustrate the power of evolutionary CSP through applications that examine matter at high pressure, where new, unexpected phenomena take place. Evolutionary CSP has allowed researchers to make unexpected discoveries such as a transparent phase of sodium, a partially ionic form of boron, complex superconducting forms of calcium, a novel superhard allotrope of carbon, polymeric modifications of nitrogen, and a new class of compounds, perhydrides. These methods have also led to the discovery of novel hydride superconductors including the "impossible" LiH(n) (n=2, 6, 8) compounds, and CaLi(2). We discuss extensions of the method to molecular crystals, systems of variable composition, and the targeted optimization of specific physical properties. PMID:21361336

  11. Crystal Structure of Staphylococcus aureus Cas9.

    PubMed

    Nishimasu, Hiroshi; Cong, Le; Yan, Winston X; Ran, F Ann; Zetsche, Bernd; Li, Yinqing; Kurabayashi, Arisa; Ishitani, Ryuichiro; Zhang, Feng; Nureki, Osamu

    2015-08-27

    The RNA-guided DNA endonuclease Cas9 cleaves double-stranded DNA targets with a protospacer adjacent motif (PAM) and complementarity to the guide RNA. Recently, we harnessed Staphylococcus aureus Cas9 (SaCas9), which is significantly smaller than Streptococcus pyogenes Cas9 (SpCas9), to facilitate efficient in vivo genome editing. Here, we report the crystal structures of SaCas9 in complex with a single guide RNA (sgRNA) and its double-stranded DNA targets, containing the 5'-TTGAAT-3' PAM and the 5'-TTGGGT-3' PAM, at 2.6 and 2.7 Å resolutions, respectively. The structures revealed the mechanism of the relaxed recognition of the 5'-NNGRRT-3' PAM by SaCas9. A structural comparison of SaCas9 with SpCas9 highlighted both structural conservation and divergence, explaining their distinct PAM specificities and orthologous sgRNA recognition. Finally, we applied the structural information about this minimal Cas9 to rationally design compact transcriptional activators and inducible nucleases, to further expand the CRISPR-Cas9 genome editing toolbox. PMID:26317473

  12. Crystal structure of bacterioferritin from Rhodobacter sphaeroides

    SciTech Connect

    Nam, Ki Hyun; Xu, Yongbin; Piao, Shunfu; Priyadarshi, Amit; Lee, Eun Hye; Kim, Hye-Yeon; Jeon, Young Ho; Ha, Nam-Chul; Hwang, Kwang Yeon

    2010-01-01

    Iron is essential for the survival of organisms, but either excess or deficient levels of iron induce oxidative stress, thereby causing cell damage. As a result, iron regulation is essential for proper cell growth and proliferation in most organisms. Bacterioferritin is a ferritin-like family protein that contains a heme molecule and a ferroxidase site at the di-iron center. This protein plays a primary role in intracellular iron storage for iron homeostasis, as well as in the maintenance of iron in a soluble and non-toxic form. Although several bacterioferritin structures have been determined, no structural studies have successfully elucidated the molecular function of the heme molecule and the ferroxidase center. Here, we report the crystal structure of bacterioferritin from Rhodobacter sphaeroides. This protein exists in a roughly spherical configuration via the assembly of 24 subunits. We describe the oligomeric arrangement, ferroxidase center and heme-binding site based on this structure. The protein contains a single iron-binding configuration in the ferroxidase center, which allows for the release of iron by His130 when the protein is in the intermediate state. The heme molecule in RsBfr is stabilized by shifting of the van der Waals interaction center between the porphyrin of the heme and Trp26. We anticipate that further structural analysis will provide a more complete understanding of the molecular mechanisms of members of the ferritin-like family.

  13. Composite structural materials. [aircraft applications

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1981-01-01

    The development of composite materials for aircraft applications is addressed with specific consideration of physical properties, structural concepts and analysis, manufacturing, reliability, and life prediction. The design and flight testing of composite ultralight gliders is documented. Advances in computer aided design and methods for nondestructive testing are also discussed.

  14. Magnetic and Crystal Structure of α-RuCl3

    NASA Astrophysics Data System (ADS)

    Sears, Jennifer

    The layered honeycomb material α-RuCl3 has been proposed as a candidate material to show significant bond-dependent Kitaev type interactions. This has prompted several recent studies of magnetism in this material that have found evidence for multiple magnetic transitions in the temperature range of 8-14 K. We will present elastic neutron scattering measurements collected using a co-aligned array of α-RuCl3 crystals, identifying zigzag magnetic order within the honeycomb planes with an ordering temperature of ~8 K. It has been reported that the ordering temperature depends on the c axis periodicity of the layered structure, with ordering temperatures of 8 and 14 K for three and two-layer periodicity respectively. While the in-plane magnetic order has been identified, it is clear that a complete understanding of magnetic ordering and interactions will depend on the three dimensional structure of the crystal. Evidence of a structural transition at ~150 K has been reported and questions remain about the structural details, in particular the stacking of the honeycomb layers. We will present x-ray diffraction measurements investigating the low and high temperature structures and stacking disorder in α-RuCl3. Finally, we will present inelastic neutron scattering measurements of magnetic excitations in this material. Work done in collaboration with K. W. Plumb (Johns Hopkins University), J. P. Clancy, Young-June Kim (University of Toronto), J. Britten (McMaster University), Yu-Sheng Chen (Argonne National Laboratory), Y. Qiu, Y. Zhao, D. Parshall, and J. W. Lynn (NCNR).

  15. Revealing Structural Transformations during Crystallization of DNA-Nanoparticle Assemblies

    NASA Astrophysics Data System (ADS)

    Zhang, Yugang; Lu, Fang; van der Lelie, Daniel; Gang, Oleg

    2013-03-01

    Nanoparticle assembly via sequence-specific DNA recognition emerges as a powerful strategy for the fabrication of nanoparticle (NP)-based crystalline materials. Generally, a delicate thermal annealing is essential for the crystallization of NPs from kinetically trapped disordered states. Due to the complex coupling between interactions, entropic and chain effects in these systems, the crystallization pathway remains an intricate and open question. Herein, we present an experimental study of the crystallization process for DNA-directed nanoparticle assembly systems using synchrotron-based small angle x-ray scattering (SAXS). We demonstrated the effects of two crystallization-dominant factors, namely, temperature and volume fraction, on the structural transformation and order development. By combining a single component and binary systems we uncovered the evolution of global and local particle arrangements, such as correlation length, compositional disorder and coordination number, during the phase transformation. Research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

  16. High temperature structural insulating material

    DOEpatents

    Chen, W.Y.

    1984-07-27

    A high temperature structural insulating material useful as a liner for cylinders of high temperature engines through the favorable combination of high service temperature (above about 800/sup 0/C), low thermal conductivity (below about 0.2 W/m/sup 0/C), and high compressive strength (above about 250 psi). The insulating material is produced by selecting hollow ceramic beads with a softening temperature above about 800/sup 0/C, a diameter within the range of 20-200 ..mu..m, and a wall thickness in the range of about 2 to 4 ..mu..m; compacting the beads and a compatible silicate binder composition under pressure and sintering conditions to provide the desired structural form with the structure having a closed-cell, compact array of bonded beads.

  17. High temperature structural insulating material

    DOEpatents

    Chen, Wayne Y.

    1987-01-01

    A high temperature structural insulating material useful as a liner for cylinders of high temperature engines through the favorable combination of high service temperature (above about 800.degree. C.), low thermal conductivity (below about 0.2 W/m.degree. C.), and high compressive strength (above about 250 psi). The insulating material is produced by selecting hollow ceramic beads with a softening temperature above about 800.degree. C., a diameter within the range of 20-200 .mu.m, and a wall thickness in the range of about 2-4 .mu.m; compacting the beads and a compatible silicate binder composition under pressure and sintering conditions to provide the desired structural form with the structure having a closed-cell, compact array of bonded beads.

  18. Crystal structures of five 6-mercaptopurine derivatives.

    PubMed

    Gomes, Lígia R; Low, John Nicolson; Magalhães E Silva, Diogo; Cagide, Fernando; Borges, Fernanda

    2016-03-01

    The crystal structures of five 6-mercaptopurine derivatives, viz. 2-[(9-acetyl-9H-purin-6-yl)sulfan-yl]-1-(3-meth-oxy-phen-yl)ethan-1-one (1), C16H14N4O3S, 2-[(9-acetyl-9H-purin-6-yl)sulfan-yl]-1-(4-meth-oxy-phen-yl)ethan-1-one (2), C16H14N4O3S, 2-[(9-acetyl-9H-purin-6-yl)sulfan-yl]-1-(4-chloro-phen-yl)ethan-1-one (3), C15H11ClN4O2S, 2-[(9-acetyl-9H-purin-6-yl)sulfan-yl]-1-(4-bromo-phen-yl)ethan-1-one (4), C15H11BrN4O2S, and 1-(3-meth-oxy-phen-yl)-2-[(9H-purin-6-yl)sulfan-yl]ethan-1-one (5), C14H12N4O2S. Compounds (2), (3) and (4) are isomorphous and accordingly their mol-ecular and supra-molecular structures are similar. An analysis of the dihedral angles between the purine and exocyclic phenyl rings show that the mol-ecules of (1) and (5) are essentially planar but that in the case of the three isomorphous compounds (2), (3) and (4), these rings are twisted by a dihedral angle of approximately 38°. With the exception of (1) all mol-ecules are linked by weak C-H⋯O hydrogen bonds in their crystals. There is π-π stacking in all compounds. A Cambridge Structural Database search revealed the existence of 11 deposited compounds containing the 1-phenyl-2-sulfanyl-ethanone scaffold; of these, only eight have a cyclic ring as substituent, the majority of these being heterocycles. PMID:27006794

  19. Crystal structure of strontium dinickel iron orthophosphate

    PubMed Central

    Ouaatta, Said; Assani, Abderrazzak; Saadi, Mohamed; El Ammari, Lahcen

    2015-01-01

    The title compound, SrNi2Fe(PO4)3, synthesized by solid-state reaction, crystallizes in an ordered variant of the α-CrPO4 structure. In the asymmetric unit, two O atoms are in general positions, whereas all others atoms are in special positions of the space group Imma: the Sr cation and one P atom occupy the Wyckoff position 4e (mm2), Fe is on 4b (2/m), Ni and the other P atom are on 8g (2), one O atom is on 8h (m) and the other on 8i (m). The three-dimensional framework of the crystal structure is built up by [PO4] tetra­hedra, [FeO6] octa­hedra and [Ni2O10] dimers of edge-sharing octa­hedra, linked through common corners or edges. This structure comprises two types of layers stacked alternately along the [100] direction. The first layer is formed by edge-sharing octa­hedra ([Ni2O10] dimer) linked to [PO4] tetra­hedra via common edges while the second layer is built up from a strontium row followed by infinite chains of alternating [PO4] tetra­hedra and FeO6 octa­hedra sharing apices. The layers are held together through vertices of [PO4] tetra­hedra and [FeO6] octa­hedra, leading to the appearance of two types of tunnels parallel to the a- and b-axis directions in which the Sr cations are located. Each Sr cation is surrounded by eight O atoms. PMID:26594419

  20. Acoustic wave velocities in two-dimensional composite structures based on acousto-optical crystals

    NASA Astrophysics Data System (ADS)

    Mal'neva, P. V.; Trushin, A. S.

    2015-04-01

    Sound velocities in two-dimensional composite structures based on isotropic and anisotropic acousto-optical crystals have been determined by numerical simulations. The isotropic materials are represented by fused quartz (SiO2) and flint glass, while anisotropic materials include tetragonal crystals of paratellurite (TeO2) and rutile (TiO2) and a trigonal crystal of tellurium (Te). It is established that the acoustic anisotropy of periodic composite structures strongly depends on both the chemical composition and geometric parameters of components.

  1. Crystal structures of the human adiponectin receptors.

    PubMed

    Tanabe, Hiroaki; Fujii, Yoshifumi; Okada-Iwabu, Miki; Iwabu, Masato; Nakamura, Yoshihiro; Hosaka, Toshiaki; Motoyama, Kanna; Ikeda, Mariko; Wakiyama, Motoaki; Terada, Takaho; Ohsawa, Noboru; Hato, Masakatsu; Ogasawara, Satoshi; Hino, Tomoya; Murata, Takeshi; Iwata, So; Hirata, Kunio; Kawano, Yoshiaki; Yamamoto, Masaki; Kimura-Someya, Tomomi; Shirouzu, Mikako; Yamauchi, Toshimasa; Kadowaki, Takashi; Yokoyama, Shigeyuki

    2015-04-16

    Adiponectin stimulation of its receptors, AdipoR1 and AdipoR2, increases the activities of 5'AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor (PPAR), respectively, thereby contributing to healthy longevity as key anti-diabetic molecules. AdipoR1 and AdipoR2 were predicted to contain seven transmembrane helices with the opposite topology to G-protein-coupled receptors. Here we report the crystal structures of human AdipoR1 and AdipoR2 at 2.9 and 2.4 resolution, respectively, which represent a novel class of receptor structure. The seven-transmembrane helices, conformationally distinct from those of G-protein-coupled receptors, enclose a large cavity where three conserved histidine residues coordinate a zinc ion. The zinc-binding structure may have a role in the adiponectin-stimulated AMPK phosphorylation and UCP2 upregulation. Adiponectin may broadly interact with the extracellular face, rather thanthe carboxy-terminal tail, of the receptors. The present information will facilitate the understanding of novel structure-function relationships and the development and optimization of AdipoR agonists for the treatment of obesity-related diseases, such as type 2 diabetes. PMID:25855295

  2. Crystal structures of respiratory pathogen neuraminidases

    PubMed Central

    Hsiao, Yu-Shan; Parker, Dane; Ratner, Adam J.; Prince, Alice; Tong, Liang

    2013-01-01

    Currently there is pressing need to develop novel therapeutic agents for the treatment of infections by the human respiratory pathogens Pseudomonas aeruginosa and Streptococcus pneumoniae. The neuraminidases of these pathogens are important for host colonization in animal models of infection and are attractive targets for drug discovery. To aid in the development of inhibitors against these neuraminidases, we have determined the crystal structures of the P. aeruginosa enzyme NanPs and S. pneumoniae enzyme NanA at 1.6 and 1.7 Å resolution, respectively. In situ proteolysis with trypsin was essential for the crystallization of our recombinant NanA. The active site regions of the two enzymes are strikingly different. NanA contains a deep pocket that is similar to that in canonical neuraminidases, while the NanPs active site is much more open. The comparative studies suggest that NanPs may not be a classical neuraminidase, and may have distinct natural substrates and physiological functions. This work represents an important step in the development of drugs to prevent respiratory tract colonization by these two pathogens. PMID:19284989

  3. Crystal Structures of Respiratory Pathogen Neuraminidases

    SciTech Connect

    Hsiao, Y.; Parker, D; Ratner, A; Prince, A; Tong, L

    2009-01-01

    Currently there is pressing need to develop novel therapeutic agents for the treatment of infections by the human respiratory pathogens Pseudomonas aeruginosa and Streptococcus pneumoniae. The neuraminidases of these pathogens are important for host colonization in animal models of infection and are attractive targets for drug discovery. To aid in the development of inhibitors against these neuraminidases, we have determined the crystal structures of the P. aeruginosa enzyme NanPs and S. pneumoniae enzyme NanA at 1.6 and 1.7 {angstrom} resolution, respectively. In situ proteolysis with trypsin was essential for the crystallization of our recombinant NanA. The active site regions of the two enzymes are strikingly different. NanA contains a deep pocket that is similar to that in canonical neuraminidases, while the NanPs active site is much more open. The comparative studies suggest that NanPs may not be a classical neuraminidase, and may have distinct natural substrates and physiological functions. This work represents an important step in the development of drugs to prevent respiratory tract colonization by these two pathogens.

  4. Crystal structure of natural phaeosphaeride A

    PubMed Central

    Abzianidze, Victoria V.; Poluektova, Ekaterina V.; Bolshakova, Ksenia P.; Panikorovskii, Taras L.; Bogachenkov, Alexander S.; Berestetskiy, Alexander O.

    2015-01-01

    The asymmetric unit of the title compound, C15H23NO5, contains two independent mol­ecules. Phaeosphaeride A contains two primary sections, an alkyl chain consisting of five C atoms and a cyclic system consisting of fused five- and six-membered rings with attached substituents. In the crystal, the mol­ecules form layered structures. Nearly planar sheets, parallel to the (001) plane, form bilayers of two-dimensional hydrogen-bonded networks with the hy­droxy groups located on the inter­ior of the bilayer sheets. The network is constructed primarily of four O—H⋯O hydrogen bonds, which form a zigzag pattern in the (001) plane. The butyl chains inter­digitate with the butyl chains on adjacent sheets. The crystal was twinned by a twofold rotation about the c axis, with refined major–minor occupancy fractions of 0.718 (6):0.282 (6). PMID:26396831

  5. Growth and structure of a new photonic crystal: Chlorine substituted chalcone

    NASA Astrophysics Data System (ADS)

    Sarveshwara, H. P.; Raghavendra, S.; A, Jayarama; Menezes, Anthoni Praveen; Dharmaprakash, S. M.

    2015-06-01

    A new organic photonic material 3-(2, 4-dichlorophenyl)-1-(2,5-dimethylthiophen-3-yl)propan-1-one(DMTP) has been synthesized and crystallised in acetone solution. The functional groups present in the new material were identified by FTIR spectroscopy. The material is optically transparent in the wavelength range of 400-1100 nm. The crystal structure of DMTP was determined by single crystal X-ray diffraction. The title compound crystallizes in monoclinic system with a centrosymmetric space group P21/c. The Z-scan study revealed that the optical limiting property exhibited by the DMTP molecule is based on the reverse saturable absorption phenomena.

  6. Crystal Structure of Uronate Dehydrogenase from Agrobacterium tumefaciens*

    PubMed Central

    Parkkinen, Tarja; Boer, Harry; Jänis, Janne; Andberg, Martina; Penttilä, Merja; Koivula, Anu; Rouvinen, Juha

    2011-01-01

    Uronate dehydrogenase from Agrobacterium tumefaciens (AtUdh) belongs to the short-chain dehydrogenase/reductase superfamily and catalyzes the oxidation of d-galacturonic acid and d-glucuronic acid with NAD+ as a cofactor. We have determined the crystal structures of an apo-form of AtUdh, a ternary form in complex with NADH and product (substrate-soaked structure), and an inactive Y136A mutant in complex with NAD+. The crystal structures suggest AtUdh to be a homohexamer, which has also been observed to be the major form in solution. The monomer contains a Rossmann fold, essential for nucleotide binding and a common feature of the short-chain dehydrogenase/reductase family enzymes. The ternary complex structure reveals a product, d-galactaro-1,5-lactone, which is bound above the nicotinamide ring. This product rearranges in solution to d-galactaro-1,4-lactone as verified by mass spectrometry analysis, which agrees with our previous NMR study. The crystal structure of the mutant with the catalytic residue Tyr-136 substituted with alanine shows changes in the position of Ile-74 and Ser-75. This probably altered the binding of the nicotinamide end of NAD+, which was not visible in the electron density map. The structures presented provide novel insights into cofactor and substrate binding and the reaction mechanism of AtUdh. This information can be applied to the design of efficient microbial conversion of d-galacturonic acid-based waste materials. PMID:21676870

  7. Crystal structure of a snake venom cardiotoxin

    SciTech Connect

    Rees, B.; Samama, J.P.; Thierry, J.C.; Gilibert, M.; Fischer, J.; Schweitz, H.; Lazdunski, M.; Moras, D.

    1987-05-01

    Cardiotoxin V/sup II/4 from Naja mossambica crystallizes in space group P6/sub 1/ (a = b = 73.9 A; c = 59.0 A) with two molecules of toxin (molecular mass = 6715 Da) in the asymmetric unit. The structure was solved by using a combination of multiple isomorphous replacement and density modification methods. Model building and least-squares refinement led to an agreement factor of 27% for a data set to 3-A resolution prior to any inclusion of solvent molecules. The topology of the molecule is similar to that found in short and long snake neurotoxins, which block the nicotinic acetylcholine receptor. Major differences occur in the conformation of the central loop, resulting in a change in the concavity of the molecule. Hydrophobic residues are clustered in two distinct areas. The existence of stable dimeric entities in the crystalline state, with the formation of a six-stranded antiparallel ..beta.. sheet, may be functionally relevant.

  8. Exploring structural phase transitions of ion crystals

    NASA Astrophysics Data System (ADS)

    Yan, L. L.; Wan, W.; Chen, L.; Zhou, F.; Gong, S. J.; Tong, X.; Feng, M.

    2016-02-01

    Phase transitions have been a research focus in many-body physics over past decades. Cold ions, under strong Coulomb repulsion, provide a repealing paradigm of exploring phase transitions in stable confinement by electromagnetic field. We demonstrate various conformations of up to sixteen laser-cooled 40Ca+ ion crystals in a home-built surface-electrode trap, where besides the usually mentioned structural phase transition from the linear to the zigzag, two additional phase transitions to more complicated two-dimensional configurations are identified. The experimental observation agrees well with the numerical simulation. Heating due to micromotion of the ions is analysed by comparison of the numerical simulation with the experimental observation. Our investigation implies very rich and complicated many-body behaviour in the trapped-ion systems and provides effective mechanism for further exploring quantum phase transitions and quantum information processing with ultracold trapped ions.

  9. Exploring structural phase transitions of ion crystals

    PubMed Central

    Yan, L. L.; Wan, W.; Chen, L.; Zhou, F.; Gong, S. J.; Tong, X.; Feng, M.

    2016-01-01

    Phase transitions have been a research focus in many-body physics over past decades. Cold ions, under strong Coulomb repulsion, provide a repealing paradigm of exploring phase transitions in stable confinement by electromagnetic field. We demonstrate various conformations of up to sixteen laser-cooled 40Ca+ ion crystals in a home-built surface-electrode trap, where besides the usually mentioned structural phase transition from the linear to the zigzag, two additional phase transitions to more complicated two-dimensional configurations are identified. The experimental observation agrees well with the numerical simulation. Heating due to micromotion of the ions is analysed by comparison of the numerical simulation with the experimental observation. Our investigation implies very rich and complicated many-body behaviour in the trapped-ion systems and provides effective mechanism for further exploring quantum phase transitions and quantum information processing with ultracold trapped ions. PMID:26865229

  10. Exploring structural phase transitions of ion crystals.

    PubMed

    Yan, L L; Wan, W; Chen, L; Zhou, F; Gong, S J; Tong, X; Feng, M

    2016-01-01

    Phase transitions have been a research focus in many-body physics over past decades. Cold ions, under strong Coulomb repulsion, provide a repealing paradigm of exploring phase transitions in stable confinement by electromagnetic field. We demonstrate various conformations of up to sixteen laser-cooled (40)Ca(+) ion crystals in a home-built surface-electrode trap, where besides the usually mentioned structural phase transition from the linear to the zigzag, two additional phase transitions to more complicated two-dimensional configurations are identified. The experimental observation agrees well with the numerical simulation. Heating due to micromotion of the ions is analysed by comparison of the numerical simulation with the experimental observation. Our investigation implies very rich and complicated many-body behaviour in the trapped-ion systems and provides effective mechanism for further exploring quantum phase transitions and quantum information processing with ultracold trapped ions. PMID:26865229

  11. Crystal structure of oligoacenes under high pressure

    SciTech Connect

    Oehzelt, M.; Aichholzer, A.; Resel, R.; Heimel, G.; Venuti, E.; Della Valle, R. G.

    2006-09-01

    We report crystal structures of anthracene, tetracene, and pentacene under pressure. Energy dispersive x-ray diffraction experiments up to 9 GPa were performed. Quasiharmonic lattice dynamics calculations are compared to the experimental results and show excellent agreement. The results are discussed with particular emphasis on the pressure dependence of the unit cell dimensions and the rearrangement of the molecules. The high pressure data also allow an analysis of the equation of state of these substances as a function of molecular length. We report the bulk modulus of tetracene and pentacene (B{sub 0}=9.0 and 9.6 GPa, respectively) and its pressure derivative (B{sub 0}{sup '}=7.9 and 6.4, respectively). We find that the unit-cell volume and bulk modulus at ambient pressure follow a linear relationship with the molecular length.

  12. Crystal structure of betulinic acid methanol monosolvate.

    PubMed

    Tang, Wei; Chen, Neng-Hua; Li, Guo-Qiang; Wang, Guo-Cai; Li, Yao-Lan

    2014-12-01

    The title compound [systematic name: 3β-hy-droxy-lup-20(29)-en-28-oic acid methanol monosolvate], C30H48O3·CH3OH, is a solvent pseudopolymorph of a naturally occurring plant-derived lupane-type penta-cyclic triterpenoid, which was isolated from the traditional Chinese medicinal plant Syzygium jambos (L.) Alston. The dihedral angle between the planes of the carb-oxy-lic acid group and the olefinic group is 12.17 (18)°. The A/B, B/C, C/D and D/E ring junctions are all trans-fused. In the crystal, O-H⋯O hydrogen bonds involving the hy-droxy and carb-oxy-lic acid groups and the methanol solvent mol-ecule give rise to a two-dimensional network structure lying parallel to (001). PMID:25553022

  13. Crystal Structure of the VS ribozyme

    PubMed Central

    Suslov, Nikolai B.; DasGupta, Saurja; Huang, Hao; Fuller, James R.; Lilley, David M.J.; Rice, Phoebe A.; Piccirilli, Joseph A.

    2015-01-01

    Varkud Satellite (VS) ribozyme mediates rolling circle replication of a plasmid found in the Neurospora mitochondria. We report crystal structures of this ribozyme at 3.1Å resolution, revealing an intertwined dimer formed by an exchange of substrate helices. Within each protomer, an arrangement of three-way helical junctions organizes seven helices into a global fold that creates a docking site for the substrate helix of the other protomer, resulting in the formation of two active sites in trans. This mode of RNA-RNA association resembles the process of domain swapping in proteins and has implications for RNA regulation and evolution. Within each active site, adenine and guanine nucleobases abut the scissile phosphate, poised to serve direct roles in catalysis. Similarities to the active sites of the hairpin and hammerhead ribozymes highlight the functional significance of active site features, underscore the ability of RNA to access functional architectures from distant regions of sequence space, and suggest convergent evolution. PMID:26414446

  14. Some Lower Valence Vanadium Fluorides: Their Crystal Distortions, Domain Structures, Modulated Structures, Ferrimagnetism, and Composition Dependence.

    ERIC Educational Resources Information Center

    Hong, Y. S.; And Others

    1980-01-01

    Describes some contemporary concepts unique to the structure of advanced solids, i.e., their crystal distortions, domain structures, modulated structures, ferrimagnetism, and composition dependence. (Author/CS)

  15. Nucleational Energy Traps and Their Role in Crystal Structure Formation.

    NASA Astrophysics Data System (ADS)

    Loeffler, T. D.; Galatas, A. C.; Chen, B.

    2014-12-01

    Crystallization has been one of the most important topics in a wide array of fields because of its importance to biology, atmospheric science, material science, etc. Unlike vapor-liquid nucleation, crystallization has an added level of complexity because the nucleation process can form anything from a perfectly ordered single crystal to an amorphous solid. When a nucleating cluster consists of a few dozen molecules, a large majority of the particles are exposed on the surface of the cluster unlike in the bulk phase where the majority of the particles are contained within the interior. As a consequence a cluster must attempt to minimize the surface area while simultaneously maximizing the intermolecular interactions within the cluster in order to maintain stability. The ideal bulk phase configuration is often less stable due to these factors and will not form directly from the gas/liquid phase. Instead the clusters can adopt many non-crystalline structures due to their incredibly high stability at these small cluster sizes. Once these non-crystalline clusters aggregate enough molecules they can attempt to transition from the non-crystalline structure into an ordered crystalline structure; however, if there is a sizable free energy barrier for this crystalline transition the cluster can become trapped in these states and subsequently the formation of an ordered crystal will be unfeasible. This of course can yield physical properties that are significantly different from that of the bulk.This talk will discuss the simulational study of the underlying nucleation mechanics and their role in the formation of atmospheric ice. The focus will be on the formation of energy traps at small cluster sizes and how these traps are avoided by reducing the conformational degrees of freedom.

  16. The crystal structure of a nonstoichiometric nasicon

    SciTech Connect

    Rudolf, F.; Clearfield, A.; Jorgensen, J.D.; Subramanian, M.A.

    1985-06-01

    The crystal structure of a nonstoichiometric NASICON prepared from a hydrothermally synthesized precursor phase was solved by means of Xray powder and neutron powder diffraction methods. The NASICON phase is monoclinic with unit cell parameters, from Rietveld refinement of the neutron data, of a = 15.6209(8), b = 9.0326(5), c = 9.2172(5)A, ..beta.. = 123.67(1)A, V = 1082.5A/sup 3/. The space group is C2/c with Z = 4. The structure is essentially that proposed earlier by Hong, but the nonstoichiometry results from replacement of part of the Zr/sup 4 +/ by Na/sup +/. Refinement of site occupancies coupled with the requirement of overall charge balance yields the formula Na /sub 2.88/ (Na /sub 0.32/ Zr /sub 1.68/ )Si /sub 1.84/ P /sub 1.16/ O /sub 11.54/ which also agrees well with analytical data. Only 20% of the Na1 sites are occupied, but 80% of the Na3 sites are filled. This structure provides a framework from which to rationalize the many reports in the literature that NASICON can only be prepared with difficulty by high temperature solid state reactions.

  17. Crystal structure of human GDF11.

    PubMed

    Padyana, Anil K; Vaidialingam, Bhamini; Hayes, David B; Gupta, Priyanka; Franti, Michael; Farrow, Neil A

    2016-03-01

    Members of the TGF-β family of proteins are believed to play critical roles in cellular signaling processes such as those involved in muscle differentiation. The extent to which individual family members have been characterized and linked to biological function varies greatly. The role of myostatin, also known as growth differentiation factor 8 (GDF8), as an inhibitor of muscle differentiation is well understood through genetic linkages. In contrast, the role of growth differentiation factor 11 (GDF11) is much less well understood. In humans, the mature forms of GDF11 and myostatin are over 94% identical. In order to understand the role that the small differences in sequence may play in the differential signaling of these molecules, the crystal structure of GDF11 was determined to a resolution of 1.50 Å. A comparison of the GDF11 structure with those of other family members reveals that the canonical TGF-β domain fold is conserved. A detailed structural comparison of GDF11 and myostatin shows that several of the differences between these proteins are likely to be localized at interfaces that are critical for the interaction with downstream receptors and inhibitors. PMID:26919518

  18. Crystal Structure of Human Spermine Synthase

    PubMed Central

    Wu, Hong; Min, Jinrong; Zeng, Hong; McCloskey, Diane E.; Ikeguchi, Yoshihiko; Loppnau, Peter; Michael, Anthony J.; Pegg, Anthony E.; Plotnikov, Alexander N.

    2008-01-01

    The crystal structures of two ternary complexes of human spermine synthase (EC 2.5.1.22), one with 5′-methylthioadenosine and spermidine and the other with 5′-methylthioadenosine and spermine, have been solved. They show that the enzyme is a dimer of two identical subunits. Each monomer has three domains: a C-terminal domain, which contains the active site and is similar in structure to spermidine synthase; a central domain made up of four β-strands; and an N-terminal domain with remarkable structural similarity to S-adenosylmethionine decarboxylase, the enzyme that forms the aminopropyl donor substrate. Dimerization occurs mainly through interactions between the N-terminal domains. Deletion of the N-terminal domain led to a complete loss of spermine synthase activity, suggesting that dimerization may be required for activity. The structures provide an outline of the active site and a plausible model for catalysis. The active site is similar to those of spermidine synthases but has a larger substrate-binding pocket able to accommodate longer substrates. Two residues (Asp201 and Asp276) that are conserved in aminopropyltransferases appear to play a key part in the catalytic mechanism, and this role was supported by the results of site-directed mutagenesis. The spermine synthase·5′-methylthioadenosine structure provides a plausible explanation for the potent inhibition of the reaction by this product and the stronger inhibition of spermine synthase compared with spermidine synthase. An analysis to trace possible evolutionary origins of spermine synthase is also described. PMID:18367445

  19. Crystal structure of human nicotinic acid phosphoribosyltransferase

    PubMed Central

    Marletta, Ada Serena; Massarotti, Alberto; Orsomando, Giuseppe; Magni, Giulio; Rizzi, Menico; Garavaglia, Silvia

    2015-01-01

    Nicotinic acid phosphoribosyltransferase (EC 2.4.2.11) (NaPRTase) is the rate-limiting enzyme in the three-step Preiss–Handler pathway for the biosynthesis of NAD. The enzyme catalyzes the conversion of nicotinic acid (Na) and 5-phosphoribosyl-1-pyrophosphate (PRPP) to nicotinic acid mononucleotide (NaMN) and pyrophosphate (PPi). Several studies have underlined the importance of NaPRTase for NAD homeostasis in mammals, but no crystallographic data are available for this enzyme from higher eukaryotes. Here, we report the crystal structure of human NaPRTase that was solved by molecular replacement at a resolution of 2.9 Å in its ligand-free form. Our structural data allow the assignment of human NaPRTase to the type II phosphoribosyltransferase subfamily and reveal that the enzyme consists of two domains and functions as a dimer with the active site located at the interface of the monomers. The substrate-binding mode was analyzed by molecular docking simulation and provides hints into the catalytic mechanism. Moreover, structural comparison of human NaPRTase with the other two human type II phosphoribosyltransferases involved in NAD biosynthesis, quinolinate phosphoribosyltransferase and nicotinamide phosphoribosyltransferase, reveals that while the three enzymes share a conserved overall structure, a few distinctive structural traits can be identified. In particular, we show that NaPRTase lacks a tunnel that, in nicotinamide phosphoribosiltransferase, represents the binding site of its potent and selective inhibitor FK866, currently used in clinical trials as an antitumoral agent. PMID:26042198

  20. Crystal structure of human nicotinic acid phosphoribosyltransferase.

    PubMed

    Marletta, Ada Serena; Massarotti, Alberto; Orsomando, Giuseppe; Magni, Giulio; Rizzi, Menico; Garavaglia, Silvia

    2015-01-01

    Nicotinic acid phosphoribosyltransferase (EC 2.4.2.11) (NaPRTase) is the rate-limiting enzyme in the three-step Preiss-Handler pathway for the biosynthesis of NAD. The enzyme catalyzes the conversion of nicotinic acid (Na) and 5-phosphoribosyl-1-pyrophosphate (PRPP) to nicotinic acid mononucleotide (NaMN) and pyrophosphate (PPi). Several studies have underlined the importance of NaPRTase for NAD homeostasis in mammals, but no crystallographic data are available for this enzyme from higher eukaryotes. Here, we report the crystal structure of human NaPRTase that was solved by molecular replacement at a resolution of 2.9 Å in its ligand-free form. Our structural data allow the assignment of human NaPRTase to the type II phosphoribosyltransferase subfamily and reveal that the enzyme consists of two domains and functions as a dimer with the active site located at the interface of the monomers. The substrate-binding mode was analyzed by molecular docking simulation and provides hints into the catalytic mechanism. Moreover, structural comparison of human NaPRTase with the other two human type II phosphoribosyltransferases involved in NAD biosynthesis, quinolinate phosphoribosyltransferase and nicotinamide phosphoribosyltransferase, reveals that while the three enzymes share a conserved overall structure, a few distinctive structural traits can be identified. In particular, we show that NaPRTase lacks a tunnel that, in nicotinamide phosphoribosiltransferase, represents the binding site of its potent and selective inhibitor FK866, currently used in clinical trials as an antitumoral agent. PMID:26042198

  1. Invited review liquid crystal models of biological materials and silk spinning.

    PubMed

    Rey, Alejandro D; Herrera-Valencia, Edtson E

    2012-06-01

    A review of thermodynamic, materials science, and rheological liquid crystal models is presented and applied to a wide range of biological liquid crystals, including helicoidal plywoods, biopolymer solutions, and in vivo liquid crystals. The distinguishing characteristics of liquid crystals (self-assembly, packing, defects, functionalities, processability) are discussed in relation to biological materials and the strong correspondence between different synthetic and biological materials is established. Biological polymer processing based on liquid crystalline precursors includes viscoelastic flow to form and shape fibers. Viscoelastic models for nematic and chiral nematics are reviewed and discussed in terms of key parameters that facilitate understanding and quantitative information from optical textures and rheometers. It is shown that viscoelastic modeling the silk spinning process using liquid crystal theories sheds light on textural transitions in the duct of spiders and silk worms as well as on tactoidal drops and interfacial structures. The range and consistency of the predictions demonstrates that the use of mesoscopic liquid crystal models is another tool to develop the science and biomimetic applications of mesogenic biological soft matter. PMID:21994072

  2. Crystal morphology variation in inkjet-printed organic materials

    NASA Astrophysics Data System (ADS)

    Ihnen, Andrew C.; Petrock, Anne M.; Chou, Tsengming; Samuels, Phillip J.; Fuchs, Brian E.; Lee, Woo Y.

    2011-11-01

    The recent commercialization of piezoelectric-based drop-on-demand inkjet printers provides an additive processing platform for producing and micropatterning organic crystal structures. We report an inkjet printing approach where macro- and nano-scale energetic composites composed of cyclotrimethylenetrinitramine (RDX) crystals dispersed in a cellulose acetate butyrate (CAB) matrix are produced by direct phase transformation from organic solvent-based all-liquid inks. The characterization of printed composites illustrates distinct morphological changes dependent on ink deposition parameters. When 10 pL ink droplets rapidly formed a liquid pool, a coffee ring structure containing dendritic RDX crystals was produced. By increasing the substrate temperature, and consequently the evaporation rate of the pooled ink, the coffee ring structure was mitigated and shorter dendrites from up to ∼1 to 0.2 mm with closer arm spacing from ∼15 to 1 μm were produced. When the nucleation and growth of RDX and CAB were confined within the evaporating droplets, a granular structure containing nanoscale RDX crystals was produced. The results suggest that evaporation rate and microfluidic droplet confinement can effectively be used to tailor the morphology of inkjet-printed energetic composites.

  3. Scanning probe acoustic microscopy of extruded starch materials: direct visual evidence of starch crystal.

    PubMed

    Liu, Zhongdong; Liu, Boxiang; Li, Mengxing; Wei, Min; Li, Hua; Liu, Peng; Wan, Tuo

    2013-10-15

    Scanning probe acoustic microscopy (SPAM) has been successfully used to study inorganic and keratin biomaterials. However, few studies have attempted to apply SPAM to structural study of non-keratin organic materials such as starch based materials. This study investigated hardness and surface finish to establish sample preparation method suitable for SPAM imaging and acquired clear acoustic images of extruded starch materials. Acquired acoustic images directly exhibited certain structure of starch materials and provided visual evidence of starch material components and aggregates. In addition, through correlating acoustic images with X-ray diffraction data, crystal-structural information in nano-scale was obtained and acoustic image contrast showed a linear relationship with starch amylose content in extruded starch materials. PMID:23987357

  4. Synthesis, structure, crystal growth and characterization of a novel semiorganic nonlinear optical l-proline lithium bromide monohydrate single crystal.

    PubMed

    Sathiskumar, S; Balakrishnan, T; Ramamurthi, K; Thamotharan, S

    2015-03-01

    l-Proline lithium bromide monohydrate (LPLBM), a promising semiorganic nonlinear optical material, was synthesized and single crystals of LPLBM were grown from solution by slow evaporation technique. Single crystal X-ray structure solution reveals that the grown crystal belongs to monoclinic system with space group P21. Presence of various functional groups was identified by FT-IR and FT-Raman spectral analyses. UV-Vis-NIR spectroscopic study shows that the LPLBM crystal possesses 90% of transmittance in the range of 250-1100nm. Vickers microhardness values, the dielectric constant and dielectric loss of the LPLBM crystal were reported. Elemental analysis by energy dispersive X-ray analysis shows the presence of carbon, nitrogen, oxygen and bromine. The surface morphology of the crystal was investigated using scanning electron microscopic study. The thermal stability of the LPLBM crystal was studied from TGA and DSC analysis. Second harmonic generation efficiency of the LPLBM crystal measured by Kurtz and Perry powder technique using Nd:YAG laser is about 0.3 times that of urea. PMID:25498813

  5. Crystal and electronic structure of copper sulfides

    NASA Astrophysics Data System (ADS)

    Lukashev, Pavel

    Copper sulfides with different copper concentration exist in mineral form ranging from CuS to Cu2S. Among these, chalcosite Cu 2S, and digenite Cu1.8S were the subject of extensive research for decades mainly because of their use as the absorber in photovoltaic cells. Yet; their electronic structure is poorly understood because their crystal structure is complex. Most of the results published so far report the semiconducting nature of these compounds with the energy band gap being in the range of 0.84 to 1.9 eV. The crystal structure consists of a close-packed lattice of S with mobile Cu occupying various types of interstitial sites with a statistical distribution depending on temperature. In this thesis we present the first computational study of their electronic band structure. Initially, we investigated the simpler antifluorite structure. Both local density approximation (LDA) and self-consistent quasiparticle GW calculations with the full-potential linearized muffin-tin orbital method give a semimetallic band structure. Inspection of the nature of the bands shows that the lowest conduction band is mainly Cu-s-like except right near the center of the Brillouin zone where a Cu-s-like state lies about 1 eV below the valence band maximum. Significantly, in GW calculations, this state shifts up by several 0.1 eV but not sufficiently to open a gap. A random distortion of the Cu atoms from the perfect antifluorite positions is found to break the degeneracy of the d state at the Gamma-point and thus opens up a small gap of about 0.1 eV in LDA. As our next step we constructed supercell models for the cubic and hexagonal phases with the Cu positions determined by a weighted random number generator. The low temperature monoclinic phase was also studied. The computed total energies of these structures follow the same order as the reported phases with increasing temperatures. All these models gave similar small band gaps of order 0.1-0.2 eV. However, their conduction band is now mainly s-like and addition of an expected Cu-s level shift opens the gap to about 0.5 eV. Some simpler hexagonal model structures gave slightly larger band gap but were found to be unrealistic. The optical absorption data all show a strong intraband absorption with a minimum in absorption at about 1 eV. Our calculations suggest a significantly lower gap of order 0.5 eV with low absorption cross section, the true nature of which is masked by the free carrier absorption. As part of our study of the related Cu-compounds, we analyzed the quasiparticle effects beyond LDA obtained from a GW calculation on the effective masses and Kohn-Luttinger hamiltonian parameters for CuBr.

  6. Crystal structures of five 6-mercaptopurine derivatives

    PubMed Central

    Gomes, Lígia R.; Low, John Nicolson; Magalhães e Silva, Diogo; Cagide, Fernando; Borges, Fernanda

    2016-01-01

    The crystal structures of five 6-mercaptopurine derivatives, viz. 2-[(9-acetyl-9H-purin-6-yl)sulfan­yl]-1-(3-meth­oxy­phen­yl)ethan-1-one (1), C16H14N4O3S, 2-[(9-acetyl-9H-purin-6-yl)sulfan­yl]-1-(4-meth­oxy­phen­yl)ethan-1-one (2), C16H14N4O3S, 2-[(9-acetyl-9H-purin-6-yl)sulfan­yl]-1-(4-chloro­phen­yl)ethan-1-one (3), C15H11ClN4O2S, 2-[(9-acetyl-9H-purin-6-yl)sulfan­yl]-1-(4-bromo­phen­yl)ethan-1-one (4), C15H11BrN4O2S, and 1-(3-meth­oxy­phen­yl)-2-[(9H-purin-6-yl)sulfan­yl]ethan-1-one (5), C14H12N4O2S. Compounds (2), (3) and (4) are isomorphous and accordingly their mol­ecular and supra­molecular structures are similar. An analysis of the dihedral angles between the purine and exocyclic phenyl rings show that the mol­ecules of (1) and (5) are essentially planar but that in the case of the three isomorphous compounds (2), (3) and (4), these rings are twisted by a dihedral angle of approximately 38°. With the exception of (1) all mol­ecules are linked by weak C—H⋯O hydrogen bonds in their crystals. There is π–π stacking in all compounds. A Cambridge Structural Database search revealed the existence of 11 deposited compounds containing the 1-phenyl-2-sulfanyl­ethanone scaffold; of these, only eight have a cyclic ring as substituent, the majority of these being heterocycles. PMID:27006794

  7. Biomolecular crystals for material applications and a mechanistic study of an iron oxide nanoparticle synthesis

    NASA Astrophysics Data System (ADS)

    Falkner, Joshua Charles

    The three projects within this work address the difficulties of controlling biomolecular crystal formats (i.e. size and shape), producing 3-D ordered composite materials from biomolecular crystal templates, and understanding the mechanism of a practical iron oxide synthesis. The unifying thread consistent throughout these three topics is the development of methods to manipulate nanomaterials using a bottom-up approach. Biomolecular crystals are nanometer to millimeter sized crystals that have well ordered mesoporous solvent channels. The overall physical dimensions of these crystals are highly dependent on crystallization conditions. The controlled growth of micro- and nanoprotein crystals was studied to provide new pathways for creating smaller crystalline protein materials. This method produced tetragonal hen egg-white lysozyme crystals (250--100,000 nm) with near monodisperse size distributions (<15%). With this degree of control, existing protein crystal applications such as drug delivery and analytical sensors can reach their full potential. Applications for larger crystals with inherently ubiquitous pore structures could extend to materials used for membranes or templates. In this work, the porous structure of larger cowpea mosaic virus crystals was used to template metal nanoparticle growth within the body centered cubic crystalline network. The final composite material was found to have long range ordering of palladium and platinum nonocrystal aggregates (10nm) with symmetry consistent to the virus template. Nanoparticle synthesis itself is an immense field of study with an array of diverse applications. The final piece of this work investigates the mechanism behind a previously developed iron oxide synthesis to gain more understanding and direction to future synthesis strategies. The particle growth mechanism was found to proceed by the formation of a solvated iron(III)oleate complex followed by a reduction of iron (III) to iron (II). This unstable iron(II) nucleates to form a wustite (FeO) core which serves as an epitaxial surface for the magnetite (Fe3O4) shell growth. This method produces spherical particles (6-60nm) with relative size distributions of less than 15%.

  8. Reactive liquid crystal materials for optically anisotropic patterned retarders

    NASA Astrophysics Data System (ADS)

    Harding, Richard; Gardiner, Iain; Yoon, Hyun-Jin; Perrett, Tara; Parri, Owain; Skjonnemand, Karl

    2008-11-01

    Merck has developed a range of reactive liquid crystal materials (Reactive Mesogens) that are designed to form thin, birefringent, coatable films for optical applications. Reactive Mesogen (RM) films are typically coated from solution and polymerized in-situ to form thin, optics-grade coatings. Merck RM materials are customized formulations including reactive liquid crystals, surfactants, photoinitiators and other proprietary additives. Merck have optimized the materials to achieve the optimum physical performance in each application. In this paper we focus on the optimization of RM materials to achieve the finest patterning resolution and defined feature shape whilst maintaining good physical properties of the films. Several conventional trade-offs are investigated and circumvented using novel material concepts. Different methods of patterning RM materials are discussed and the merits of each considered. Thermal annealing of non-polymerized regions can create isotropic islands within the polymerized anisotropic matrix. Alternatively, the non polymerized material can be re-dissolved in the coating solvent and rinsed away. Each of these techniques has benefits depending on the processing conditions and these are discussed in depth.

  9. Crystal Structure of Human Kynurenine Aminotransferase ll*

    SciTech Connect

    Han,Q.; Robinson, H.; Li, J.

    2008-01-01

    Human kynurenine aminotransferase II (hKAT-II) efficiently catalyzes the transamination of knunrenine to kynurenic acid (KYNA). KYNA is the only known endogenous antagonist of N-methyl-d-aspartate (NMDA) receptors and is also an antagonist of 7-nicotinic acetylcholine receptors. Abnormal concentrations of brain KYNA have been implicated in the pathogenesis and development of several neurological and psychiatric diseases in humans. Consequently, enzymes involved in the production of brain KYNA have been considered potential regulatory targets. In this article, we report a 2.16 Angstroms crystal structure of hKAT-II and a 1.95 Angstroms structure of its complex with kynurenine. The protein architecture of hKAT-II reveals that it belongs to the fold-type I pyridoxal 5-phosphate (PLP)-dependent enzymes. In comparison with all subclasses of fold-type I-PLP-dependent enzymes, we propose that hKAT-II represents a novel subclass in the fold-type I enzymes because of the unique folding of its first 65 N-terminal residues. This study provides a molecular basis for future effort in maintaining physiological concentrations of KYNA through molecular and biochemical regulation of hKAT-II.

  10. Crystal structure of a Trypanosoma brucei metacaspase

    PubMed Central

    McLuskey, Karen; Rudolf, Jana; Proto, William R.; Isaacs, Neil W.; Coombs, Graham H.; Moss, Catherine X.; Mottram, Jeremy C.

    2012-01-01

    Metacaspases are distantly related caspase-family cysteine peptidases implicated in programmed cell death in plants and lower eukaryotes. They differ significantly from caspases because they are calcium-activated, arginine-specific peptidases that do not require processing or dimerization for activity. To elucidate the basis of these differences and to determine the impact they might have on the control of cell death pathways in lower eukaryotes, the previously undescribed crystal structure of a metacaspase, an inactive mutant of metacaspase 2 (MCA2) from Trypanosoma brucei, has been determined to a resolution of 1.4 Å. The structure comprises a core caspase fold, but with an unusual eight-stranded β-sheet that stabilizes the protein as a monomer. Essential aspartic acid residues, in the predicted S1 binding pocket, delineate the arginine-specific substrate specificity. In addition, MCA2 possesses an unusual N terminus, which encircles the protein and traverses the catalytic dyad, with Y31 acting as a gatekeeper residue. The calcium-binding site is defined by samarium coordinated by four aspartic acid residues, whereas calcium binding itself induces an allosteric conformational change that could stabilize the active site in a fashion analogous to subunit processing in caspases. Collectively, these data give insights into the mechanistic basis of substrate specificity and mode of activation of MCA2 and provide a detailed framework for understanding the role of metacaspases in cell death pathways of lower eukaryotes. PMID:22529389

  11. Crystal structure and characterization of a novel organic crystal: 4-Dimethylaminobenzophenone

    SciTech Connect

    Anandha babu, G.; Ramasamy, P.; Ravikumar, K.; Sridhar, B.

    2009-06-03

    Single crystals of a novel organic material, dimethylaminobenzophenone were grown from aqueous solution employing the technique of controlled evaporation. Dimethylaminobenzophenone belongs to the monoclinic system, with a = 12.5755(7) A, b = 7.9749(4) A, c = 13.0946(7) A, {alpha} = 90{sup o}, {beta} = 111.6380(10){sup o} and {gamma} = 90{sup o}. Fourier transform infrared study has been performed to identify the functional groups. The transmittance of dimethylaminobenzophenone has been used to calculate the refractive index n; the extinction coefficient K and both the real {epsilon}{sub r} and imaginary {epsilon}{sub i} components of the dielectric constant as functions of photon energy. The optical band gap of dimethylaminobenzophenone is 2.9 eV. The structural prefection of the grown crystals has been analyzed by high-resolution X-ray diffraction rocking curve measurements. Thermo gravimetric analysis and differential thermal analysis have also been carried out, and the thermal behavior of dimethylaminobenzophenone crystal has been studied. The dielectric properties and mechanical properties have been investigated.

  12. Selective crystallization with preferred lithium-ion storage capability of inorganic materials

    PubMed Central

    2012-01-01

    Lithium-ion batteries are supposed to be a key method to make a more efficient use of energy. In the past decade, nanostructured electrode materials have been extensively studied and have presented the opportunity to achieve superior performance for the next-generation batteries which require higher energy and power densities and longer cycle life. In this article, we reviewed recent research activities on selective crystallization of inorganic materials into nanostructured electrodes for lithium-ion batteries and discuss how selective crystallization can improve the electrode performance of materials; for example, selective exposure of surfaces normal to the ionic diffusion paths can greatly enhance the ion conductivity of insertion-type materials; crystallization of alloying-type materials into nanowire arrays has proven to be a good solution to the electrode pulverization problem; and constructing conversion-type materials into hollow structures is an effective approach to buffer the volume variation during cycling. The major goal of this review is to demonstrate the importance of crystallization in energy storage applications. PMID:22353373

  13. Selective crystallization with preferred lithium-ion storage capability of inorganic materials

    NASA Astrophysics Data System (ADS)

    Liu, Fei; Song, Shuyan; Xue, Dongfeng; Zhang, Hongjie

    2012-02-01

    Lithium-ion batteries are supposed to be a key method to make a more efficient use of energy. In the past decade, nanostructured electrode materials have been extensively studied and have presented the opportunity to achieve superior performance for the next-generation batteries which require higher energy and power densities and longer cycle life. In this article, we reviewed recent research activities on selective crystallization of inorganic materials into nanostructured electrodes for lithium-ion batteries and discuss how selective crystallization can improve the electrode performance of materials; for example, selective exposure of surfaces normal to the ionic diffusion paths can greatly enhance the ion conductivity of insertion-type materials; crystallization of alloying-type materials into nanowire arrays has proven to be a good solution to the electrode pulverization problem; and constructing conversion-type materials into hollow structures is an effective approach to buffer the volume variation during cycling. The major goal of this review is to demonstrate the importance of crystallization in energy storage applications.

  14. Selective crystallization with preferred lithium-ion storage capability of inorganic materials.

    PubMed

    Liu, Fei; Song, Shuyan; Xue, Dongfeng; Zhang, Hongjie

    2012-01-01

    Lithium-ion batteries are supposed to be a key method to make a more efficient use of energy. In the past decade, nanostructured electrode materials have been extensively studied and have presented the opportunity to achieve superior performance for the next-generation batteries which require higher energy and power densities and longer cycle life. In this article, we reviewed recent research activities on selective crystallization of inorganic materials into nanostructured electrodes for lithium-ion batteries and discuss how selective crystallization can improve the electrode performance of materials; for example, selective exposure of surfaces normal to the ionic diffusion paths can greatly enhance the ion conductivity of insertion-type materials; crystallization of alloying-type materials into nanowire arrays has proven to be a good solution to the electrode pulverization problem; and constructing conversion-type materials into hollow structures is an effective approach to buffer the volume variation during cycling. The major goal of this review is to demonstrate the importance of crystallization in energy storage applications. PMID:22353373

  15. Crystallization and Characterization of Galdieria sulphuraria RUBISCO in Two Crystal Forms: Structural Phase Transition Observed in P21 Crystal Form

    PubMed Central

    Baranowski, Michael; Stec, Boguslaw

    2007-01-01

    We have isolated ribulose-1,5-bisphosphate-carboxylase/oxygenase (RUBISCO) from the red algae Galdieria Sulphuraria. The protein crystallized in two different crystal forms, the I422 crystal form being obtained from high salt and the P21 crystal form being obtained from lower concentration of salt and PEG. We report here the crystallization, preliminary stages of structure determination and the detection of the structural phase transition in the P21 crystal form of G. sulphuraria RUBISCO. This red algae enzyme belongs to the hexadecameric class (L8S8) with an approximate molecular weight 0.6MDa. The phase transition in G. sulphuraria RUBISCO leads from two hexadecamers to a single hexadecamer per asymmetric unit. The preservation of diffraction power in a phase transition for such a large macromolecule is rare.

  16. Crystal phase transition to green emission wurtzite AlInP by crystal structure transfer

    NASA Astrophysics Data System (ADS)

    Hiraya, Yoshihiro; Ishizaka, Fumiya; Tomioka, Katsuhiro; Fukui, Takashi

    2016-03-01

    We grew AlInP on two types of GaN substrate in order to transfer the wurtzite (WZ) structure to grown layers. An AlInP epitaxial layer grown on GaN(10\\bar{1}0) with high-density stacking faults was obtained. X-ray diffraction and Raman scattering analyses indicate that the dominant crystal structure of the AlInP layer grown on GaN(10\\bar{1}0) was WZ. Cathode luminescence measurements at 35 K revealed strong green emissions from the WZ AlInP layer, suggesting an energy band gap change from indirect to direct. These results demonstrate the potential of WZ AlInP as a new candidate for high-efficiency green emission material.

  17. Undergraduates Improve upon Published Crystal Structure in Class Assignment

    ERIC Educational Resources Information Center

    Horowitz, Scott; Koldewey, Philipp; Bardwell, James C.

    2014-01-01

    Recently, 57 undergraduate students at the University of Michigan were assigned the task of solving a crystal structure, given only the electron density map of a 1.3 Å crystal structure from the electron density server, and the position of the N-terminal amino acid. To test their knowledge of amino acid chemistry, the students were not given the…

  18. Undergraduates Improve upon Published Crystal Structure in Class Assignment

    ERIC Educational Resources Information Center

    Horowitz, Scott; Koldewey, Philipp; Bardwell, James C.

    2014-01-01

    Recently, 57 undergraduate students at the University of Michigan were assigned the task of solving a crystal structure, given only the electron density map of a 1.3 crystal structure from the electron density server, and the position of the N-terminal amino acid. To test their knowledge of amino acid chemistry, the students were not given the

  19. Tunable structural color in organisms and photonic materials for design of bioinspired materials

    NASA Astrophysics Data System (ADS)

    Fudouzi, Hiroshi

    2011-12-01

    In this paper, the key topics of tunable structural color in biology and material science are overviewed. Color in biology is considered for selected groups of tropical fish, octopus, squid and beetle. It is caused by nanoplates in iridophores and varies with their spacing, tilting angle and refractive index. These examples may provide valuable hints for the bioinspired design of photonic materials. 1D multilayer films and 3D colloidal crystals with tunable structural color are overviewed from the viewpoint of advanced materials. The tunability of structural color by swelling and strain is demonstrated on an example of opal composites.

  20. Structural materials for space applications

    NASA Technical Reports Server (NTRS)

    Tenney, Darrel R.

    1989-01-01

    The long-term performance of structural materials in the space environment is a key research activity within NASA. The primary concerns for materials in low Earth orbit (LEO) are atomic oxygen erosion and space debris impact. Atomic oxygen studies have included both laboratory exposures in atomic oxygen facilities and flight exposures using the Shuttle. Characterization of atomic oxygen interaction with materials has included surface recession rates, residual mechanical properties, optical property measurements, and surface analyses to establish chemical changes. The Long Duration Exposure Facility (LDEF) is scheduled to be retrieved in 1989 and is expected to provide a wealth of data on atomic oxygen erosion in space. Hypervelocity impact studies have been conducted to establish damage mechanisms and changes in mechanical properties. Samples from LDEF will be analyzed to determine the severity of space debris impact on coatings, films, and composites. Spacecraft placed in geosynchronous Earth orbit (GEO) will be subjected to high doses of ionizing radiation which for long term exposures will exceed the damage threshold of many polymeric materials. Radiation interaction with polymers can result in chain scission and/or cross-linking. The formation of low molecular weight products in the epoxy plasticize the matrix at elevated temperatures and embrittle the matrix at low temperatures. This affects both the matrix-dominated mechanical properties and the dimensional stability of the composite. Embrittlement of the matrix at low temperatures results in enhanced matrix microcracking during thermal cycling. Matrix microcracking changes the coefficient of thermal expansion (CTE) of composite laminates and produces permanent length changes. Residual stress calculations were performed to estimate the conditions necessary for microcrack development in unirradiated and irradiated composites. The effects of UV and electron exposure on the optical properties of transparent polymer films were also examined to establish the optimum chemical structure for good radiation resistance. Thoughts on approaches to establishing accelerated testing procedures are discussed.

  1. Generation of spectral holes by inserting central structurally chiral layer defects in periodic structurally chiral materials

    NASA Astrophysics Data System (ADS)

    Lakhtakia, Akhlesh

    2007-07-01

    The insertion of a structurally chiral layer defect between two identical chiral mirrors, made of periodic structurally chiral materials such as chiral liquid crystals and chiral sculptured thin films, generates two different types of spectral holes, depending on the thicknesses of the chiral mirrors and the central layer defect.

  2. Method of binding structural material

    DOEpatents

    Wagh, Arun S.; Antink, Allison L.

    2007-12-25

    A structural material of a polystyrene base and the reaction product of the polystyrene base and a solid phosphate ceramic. The ceramic is applied as a slurry which includes one or more of a metal oxide or a metal hydroxide with a source of phosphate to produce a phosphate ceramic and a poly (acrylic acid or acrylate) or combinations or salts thereof and polystyrene or MgO applied to the polystyrene base and allowed to cure so that the dried aqueous slurry chemically bonds to the polystyrene base. A method is also disclosed of applying the slurry to the polystyrene base.

  3. Explosive scabbling of structural materials

    DOEpatents

    Bickes, Jr., Robert W.; Bonzon, Lloyd L.

    2002-01-01

    A new approach to scabbling of surfaces of structural materials is disclosed. A layer of mildly energetic explosive composition is applied to the surface to be scabbled. The explosive composition is then detonated, rubbleizing the surface. Explosive compositions used must sustain a detonation front along the surface to which it is applied and conform closely to the surface being scabbled. Suitable explosive compositions exist which are stable under handling, easy to apply, easy to transport, have limited toxicity, and can be reliably detonated using conventional techniques.

  4. The synergic effects of Na and K co-doping on the crystal structure and electrochemical properties of Li4Ti5O12 as anode material for lithium ion battery

    NASA Astrophysics Data System (ADS)

    Liu, Zhongxiao; Sun, Limei; Yang, Wenyun; Yang, Jinbo; Han, Songbai; Chen, Dongfeng; Liu, Yuntao; Liu, Xiangfeng

    2015-06-01

    The effects of Na and K co-doping on the crystal structure and electrochemical properties of Li4Ti5O12 have been comprehensively investigated by means of X-ray diffraction (XRD), neutron diffraction (ND), scanning electron microscope (SEM) and galvanostatic charge-discharge tests. Rietveld refinements of XRD and ND data indicate that the lattice parameters increase with the doping of Na and K, and Na or K prefers to take 8a site (tetrahedral site) in Li3.98K0.01Na0.01Ti5O12. The lattice parameter and unit cell volume of Li3.98Na0.01K0.01Ti5O12 are even larger than that of Li3.98Na0.02Ti5O12 and Li3.98K0.02Ti5O12 indicating a cooperative effect of Na and K co-doping on the enlargement of lattice parameters and unit cell volume. The electrochemical property results demonstrate that Na and K co-doped Li3.98Na0.01K0.01Ti5O12 has a larger reversible capacity and rate capability as anode material for lithium ion battery compared to un-doped Li4Ti5O12, Na-doped Li3.98Na0.02Ti5O12 or K-doped Li3.98Ka0.02Ti5O12, which indicates the significant synergic effect of Na and K co-doping on the improvement of the electrochemical performances of Li4Ti5O12.

  5. Crystal structure of morpholin-4-ium cinnamate

    PubMed Central

    Smith, Graham

    2015-01-01

    In the anhydrous salt formed from the reaction of morpholine with cinnamic acid, C4H10NO+·C9H7O2 −, the acid side chain in the trans-cinnamate anion is significantly rotated out of the benzene plane [C—C—C— C torsion angle = 158.54 (17)°]. In the crystal, one of the the aminium H atoms is involved in an asymmetric three-centre cation–anion N—H⋯(O,O′) R 1 2(4) hydrogen-bonding inter­action with the two carboxyl­ate O-atom acceptors of the anion. The second aminium-H atom forms an inter-species N—H⋯Ocarboxyl­ate hydrogen bond. The result of the hydrogen bonding is the formation of a chain structure extending along [100]. Chains are linked by C—H⋯O inter­actions, forming a supra­molecular layer parallel to (01-1). PMID:26594560

  6. Crystal structure of the Varkud satellite ribozyme.

    PubMed

    Suslov, Nikolai B; DasGupta, Saurja; Huang, Hao; Fuller, James R; Lilley, David M J; Rice, Phoebe A; Piccirilli, Joseph A

    2015-11-01

    The Varkud satellite (VS) ribozyme mediates rolling-circle replication of a plasmid found in the Neurospora mitochondrion. We report crystal structures of this ribozyme from Neurospora intermedia at 3.1 Å resolution, which revealed an intertwined dimer formed by an exchange of substrate helices. In each protomer, an arrangement of three-way helical junctions organizes seven helices into a global fold that creates a docking site for the substrate helix of the other protomer, resulting in the formation of two active sites in trans. This mode of RNA-RNA association resembles the process of domain swapping in proteins and has implications for RNA regulation and evolution. Within each active site, adenine and guanine nucleobases abut the scissile phosphate, poised to serve direct roles in catalysis. Similarities to the active sites of the hairpin and hammerhead ribozymes highlight the functional importance of active-site features, underscore the ability of RNA to access functional architectures from distant regions of sequence space, and suggest convergent evolution. PMID:26414446

  7. Lasing properties of a cholesteric liquid crystal containing aggregation-induced-emission material.

    PubMed

    Wang, Nan; Evans, Julian S; Mei, Ju; Zhang, Jianhao; Khoo, Iam-Choon; He, Sailing

    2015-12-28

    We demonstrate band edge lasing action from a cholesteric liquid crystal (CLC) containing an aggregation-induced-emission (AIE) dye as gain material. AIE materials do not suffer aggregation-caused quenching, have strong resistance to photobleaching, and can show large Stokes shift. The amplified spontaneous emission (ASE) and lasing emission of the dye-doped CLC cell have been characterized, the lasing threshold has been estimated, and its resistance to photobleaching has been measured. AIE materials with their unique properties are especially suitable for acting as gain materials in liquid crystal lasers where defect structures lower the threshold for nanoscale aggregation effects. Our studies have shown that such AIE-dye-doped CLC is capable of lasing action with unusually large Stokes shift at moderate threshold with strong resistance to photobleaching. PMID:26832052

  8. Preparation of iridescent colloidal crystal coatings with variable structural colors.

    PubMed

    Cong, Hailin; Yu, Bing; Wang, Shaopeng; Qi, Limin; Wang, Jilei; Ma, Yurong

    2013-07-29

    Iridescent colloidal crystal coatings with variable structural colors were fabricated by incorporating carbon black nanoparticles (CB-NPs) into the voids of polystyrene (PS) colloidal crystals. The structural color of the colloid crystal coatings was not only greatly enhanced after the composition but also varied with observation angles. By changing the diameter of monodisperse PS colloids in the composites, colloidal crystal coatings with three primary colors for additive or subtractive combination were obtained. After incorporation of the PS/CB-NPs hybrid coatings into polydimethylsiloxane (PDMS) matrix, manmade opal jewelry with variable iridescent colors was made facilely. PMID:23938656

  9. The rheology of structured materials

    NASA Astrophysics Data System (ADS)

    Sun, Ning

    2000-10-01

    In this work, the rheological properties of structured materials are studied via both theoretical (continuum mechanics and molecular theory) and experimental approaches. Through continuum mechanics, a structural model, involving shear-induced structural breakdown and buildup, is extended to model biofluids. In particular, we study the cases of steady shear flow, hysteresis, yield stress, small amplitude oscillatory flow as well as non-linear viscoelasticity. Model predictions are successfully compared with experimental data on complex materials such as blood and a penicillin suspension. Next, modifications are introduced into the network model. A new formulation involving non-affine motion is proposed and its applications are presented. The major improvement is that a finite elongational viscosity is predicted for finite elongational rate, contrary to infinite elongational viscosities existing at some elongational rates predicted by most previous network models. Comparisons with experimental data on shear viscosity, primary normal stress coefficient and elongational viscosity are given, in terms of the same set of model parameters. Model predictions for the stress growth are also shown. The model is successfully tested with data on a polyisobutylene solution (S1), on a polystyrene solution and on a poly-alpha-methylstyrene solution. A further extension of the network model is related to the prediction of the stress jump phenomenon which is defined as the instantaneous gain or loss of stress on startup or cessation of a deformation. It is not predicted by most existing models. In this work, the internal viscosity idea used in the dumbbell model is incorporated into the transient network model. Via appropriate approximations, a closed form constitutive equation, which predicts a stress jump, is obtained. Successful comparisons with the available stress jump measurements are given. In addition, the model yields good quantitative predictions of the standard steady, transient and dynamic material functions, for xanthan solutions and for polyacrylamide solutions. The experimental part on the rheology of structured systems involves yield stress measurement of aqueous TiO2 pigment suspensions (40, 50, 60 and 70 wt.%), using (i) extrapolations, (ii) vane creep testing and stress ramp measurements and (iii) a modified plate technique. The data obtained via the techniques mentioned earlier are critically evaluated. It is established that the perforated plate technique removes the wall slip effect at the plate surface and provides a fast and easy way to evaluate yield stress.

  10. Crystal Growth and Other Materials Physical Researches in Space Environment

    NASA Astrophysics Data System (ADS)

    Pan, Mingxiang

    Material science researches in space environment are based on reducing the effects of buoyancy driven transport, the effects of atomic oxygen, radiation, extremes of heat and cold and the ultrahigh vacuum, so as to unveil the underlying fundamental phenomena, lead maybe to new potential materials or new industrial processes and develop space techniques. Currently, research program on materials sciences in Chinese Manned Space Engineering (CMSE) is going on. More than ten projects related to crystal growth and materials processes are selected as candidates to be executed in Shenzhou spacecraft, Tiangong Space Laboratory and Chinese Space Station. In this talk, we will present some examples of the projects, which are being prepared and executed in the near future flight tasks. They are both basic and applied research, from discovery to technology.

  11. Long-range Periodic Structure in Porous High Density Polyethylene Crystallized from the Gel State

    NASA Astrophysics Data System (ADS)

    Chen, Shujun; Nandi, Souvik

    2005-03-01

    Porous polymeric materials have a variety of applications from filtration membranes, low k dielectric materials to artificial organs. Characterization of such porous materials, however, has been limited to surface techniques such as SEM and adsorption isotherms. Little work has been done on the internal structure characterization of porous materials due to the difficulty in obtaining suitable samples without disrupting the structure. In this research, a comprehensive structural characterization was performed on porous HDPE material using SEM, TEM, electron diffraction and AFM. The porous HDPE material was obtained through crystallization from swollen crosslinked gels (CSX process) in supercritical propane. SEM showed micron-size open porous structure in the CSX processed HDPE. TEM revealed long-range periodic structure in its pore walls, much different from structures found in typical HDPE material. Electron diffraction and AFM results confirmed the presence of long-range lamella stacking.

  12. Advanced Structural Materials and Cladding

    SciTech Connect

    Allen, Todd R.; Burlet, H.; Nanstad, Randy K; SAMARAS, M.; Ukai, S.

    2009-01-01

    Advanced nuclear energy systems, both fission- and fusion-based, aim to operate at higher temperatures and greater radiation exposure levels than experienced in current light water reactors. Additionally, they are envisioned to operate in coolants such as helium and sodium that allow for higher operating temperatures. Because of these unique environments, different requirements and challenges are presented for both structural materials and fuel cladding. For core and cladding applications in intermediate-temperature reactors (400-650 C), the primary candidates are 9-12Cr ferritic-martensitic steels (where the numbers represent the weight percentage of Cr in the material, i.e., 9-12 wt%) and advanced austenitic steels, adapted to maximize high temperature strength without compromising lower temperature toughness. For very high temperature reactors (>650 C), strength and oxidation resistance are more critical. In such conditions, high-temperature metals as well as ceramics and ceramic composites are candidates. For all advanced systems operating at high pressures, performance of the pressure boundary materials (i.e., those components responsible for containing the high-pressure liquids or gases that cool the reactor) is critical to reactor safety. For some reactors, pressure vessels are anticipated to be significantly larger and thicker than those used in light water reactors. The properties through the entire thickness of these components, including the effects of radiation damage as a function of damage rate, are important. For all of these advanced systems, optimizing the microstructures of candidate materials will allow for improved radiation and high-temperature performance in nuclear applications, and advanced modeling tools provide a basis for developing optimized microstructures.

  13. Structural and photoluminescence studies of Eu3+ doped L-Tartaric single crystal through evaporation technique

    NASA Astrophysics Data System (ADS)

    Prasad, P. V.; Visweswara Rao, T. K.; Satya Kamal, Ch.; Rajya Lakshmi, S.; Ramachandra, R. K.; Sudarsan, V.; Rao, M. C.; SubbaRao, P. S. V.

    2015-04-01

    Europium doped L-Tartaric acid; a non-linear optical single crystal was grown by slow evaporation solution growth method. The grown crystal was characterized by XRD for phase analysis, HRXRD for crystalline perfection, functional group by FTIR spectroscopy and powder SHG measurement for getting an estimate of NLO efficiency. The emission spectrum of Eu3+ doped L-Tartaric acid obtained after excitation at 394 nm and corresponding excitation spectrum by monitoring at 615 nm emissions. The decay curve is recorded corresponding to the 5D0 level of Eu3+ from tartaric acid doped with europium ions. The transparency of the crystal shows >90%, thermal analysis shows that the crystal to be thermally stable up to 189 °C and estimated atomic elemental composition in grown crystal with EDAX. L-Tartaric acid with chiral structure acts as a good host material for probing Eu3+ ions in synthesis of luminescent materials.

  14. Crystal structures at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Caldwell, Wendel Alexander

    2000-10-01

    The diamond anvil cell (DAC) is a unique instrument that can generate pressures equivalent to those inside planetary interiors (pressures on the order of 1 million atmospheres) under sustained conditions. When combined with a bright source of collimated x-rays, the DAC can be used to probe the structure of materials in-situ at ultra-high pressures. An understanding of the high-pressure structure of materials is important in determining what types of processes may take place in the Earth at great depths. Motivated by previous studies showing that xenon becomes metallic at pressures above ˜1 megabar (100 GPa), we examined the stable structures and reactivity of xenon at pressures approaching that of the core-mantle boundary in the Earth. Our findings indicate the transformation of xenon from face-centered cubic (fcc) to hexagonal close-packed (hcp) structures is kinetically hindered at room temperature, with the equilibrium fcc--hcp phase boundary at 21 (+/-3) gigapascals, a pressure lower than was previously thought. Additionally, we find no tendency on the part of xenon to form a metal alloy with iron or platinum to at least 100 to 150 gigapascals, making it unlikely that the Earth's core serves as a reservoir for primordial xenon. Measurements of the compressibility of natural (Mg.75,Fe .25)2SiO4 gamma-spinel at pressures of the Earth's transition zone yield a pressure derivative of the bulk modulus K0 ' = 6.3 (+/-0.3). As gamma-spinel is considered to be a dominant mineral phase of the transition-zone of the Earth's mantle (400--670 km depth), the relatively high value of K0' for gamma-spinel may help explain the rapid increase with depth of seismic velocities through the transition zone. The thermodynamics, mechanisms and kinetics of pressure-induced amorphization are not well understood. We report here new studies indicating little or no entropy difference between the crystalline and glassy states of Ca(OH) 2 (portlandite). Additional work on the pressure-induced amorphization of AlPO4 (berlinite) shows that this material, which is a close analog to quartz, shows a rich behavior that is dependent upon the pressure, temperature, stress-state and time-scales of the experimental conditions.

  15. Novel photonic crystal cavities and related structures.

    SciTech Connect

    Luk, Ting Shan

    2007-11-01

    The key accomplishment of this project is to achieve a much more in-depth understanding of the thermal emission physics of metallic photonic crystal through theoretical modeling and experimental measurements. An improved transfer matrix technique was developed to enable incorporation of complex dielectric function. Together with microscopic theory describing emitter radiative and non-radiative relaxation dynamics, a non-equilibrium thermal emission model is developed. Finally, experimental methodology was developed to measure absolute emissivity of photonic crystal at high temperatures with accuracy of +/-2%. Accurate emissivity measurements allow us to validate the procedure to treat the effect of the photonic crystal substrate.

  16. NASA Sponsored Research Involving Crystallization of Biological Materials

    NASA Technical Reports Server (NTRS)

    Downey, James Patton

    2000-01-01

    An overview of NASA's plans for the performing experiments involving the crystallization of biological materials on the International Space Station (ISS) is presented. In addition, a brief overview of past work is provided as background. Descriptions of flight hardware currently available for use on the ISS are given and projections of future developments are discussed. In addition, experiment selection and funding is described. As of the flight of STS-95, these crystallization projects have proven to be some of the most successful in the history of microgravity research. The NASA Microgravity Research Division alone has flown 185 different proteins, nucleic acids, viruses, and complexes on 43 different missions. 37 of the 185 have resulted, in, diffraction patterns with higher resolution than was obtained in all previous ground based experiments. This occurred despite the fact that an average of only 41 samples per protein were flown. A number of other samples have shown improved signal to noise characteristics, i.e. relative Wilson plots, when compared to the best ground experiments. In addition, a number of experiments investigating the effects of microgravity conditions on the crystallization of biological material have been conducted.

  17. A Dominant Factor for Structural Classification of Protein Crystals.

    PubMed

    Qi, Fei; Fudo, Satoshi; Neya, Saburo; Hoshino, Tyuji

    2015-08-24

    With the increasing number of solved protein crystal structures, much information on protein shape and atom geometry has become available. It is of great interest to know the structural diversity for a single kind of protein. Our preliminary study suggested that multiple crystal structures of a single kind of protein can be classified into several groups from the viewpoint of structural similarity. In order to broadly examine this finding, cluster analysis was applied to the crystal structures of hemoglobin (Hb), myoglobin (Mb), human serum albumin (HSA), hen egg-white lysozyme (HEWL), and human immunodeficiency virus type 1 protease (HIV-1 PR), downloaded from the Protein Data Bank (PDB). As a result of classification by cluster analysis, 146 crystal structures of Hb were separated into five groups. The crystal structures of Mb (n = 284), HEWL (n = 336), HSA (n = 63), and HIV-1 PR (n = 488) were separated into six, five, three, and six groups, respectively. It was found that a major factor causing these structural separations is the space group of crystals and that crystallizing agents have an influence on the crystal structures. Amino acid mutation is a minor factor for the separation because no obvious point mutation making a specific cluster group was observed for the five kinds of proteins. In the classification of Hb and Mb, the species of protein source such as humans, rabbits, and mice is another significant factor. When the difference in amino sequence is large among species, the species of protein source is the primary factor causing cluster separation in the classification of crystal structures. PMID:26230289

  18. Structural and Thermoelectric Properties of Tungsten Diselenide Crystals

    NASA Astrophysics Data System (ADS)

    Patel, K. K.; Patel, K. D.; Patel, Mayur; Patel, C. A.; Pathak, V. M.; Srivastava, R.

    2011-12-01

    Crystals of Tungsten diselenide (WSe2) have been grown by direct vapour transport (DVT) technique using micro processor controlled dual zone horizontal furnace. The chemical composition and structure of grown crystals were confirmed using energy dispersive analysis of X-ray (EDAX) and X-ray diffraction (XRD). In the present investigation thermoelectric power measurements (TEP) have been carried out on the grown crystals. Different electrical transport parameters of semiconductors have been determined and discussed in the paper.

  19. Synthesis, crystal structure and thermal analysis of a new stilbazolium salt crystal

    NASA Astrophysics Data System (ADS)

    Teng, Bing; Kong, Weijin; Feng, Ke; You, Fei; Cao, Lifeng; Zhong, Degao; Hao, Lun; Sun, Qing; van Smaalen, Sander; Gong, Wenhui

    2015-04-01

    A new organic crystal of 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium benzene sulfonate (DASBS) was synthesized and characterized for the first time. It is a derivative of 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST) with the benzene sulfonate replacing p-toluenesulfonate. Single crystal XRD demonstrated that the crystal structure of DASBSH2O was triclinic. The thermal analysis of this new crystal was also conducted, and the melting point was obtained to be 232C.

  20. Photostimulated structural changes of liquid crystal physical gels

    NASA Astrophysics Data System (ADS)

    Moriyama, Masaya; Mizoshita, Norihiro; Kato, Takashi

    2004-10-01

    Photoresponsive liquid crystal physical gels are formed from a hydrogen-bonded gelator containing photochromic azobenzene moieties and nematic or discotic liquid crystals. The bistable gel structures based on the trans-azobenzene gelator could be achieved by combining the trans-cis photoisomerization of the azobenzene moieties and thermal treat-ment. Upon UV irradiation, the trans-cis photoisomerization causes the transition from the initial gel states to the liquid crystal sol states. The cis-trans back-isomerization causes reaggregation of the trans-gelator in the liquid crystals. This leads to the formation of the second gel states which have the structures reflecting the liquid crystal order. The initial gel states can be reversibly changed to the reformed gel states by photoirradiation and thermal treatments. The photo-induced reversible structural changes of the anisotropic physical gels are applied to rewritable information recordings.

  1. [Validation of the crystal structure of medicinal realgar in China].

    PubMed

    Zhang, Zhi-Jie; Zhou, Qun; Wei, Jing-Zhi; Zhang, Yan-Ling; Sun, Su-Qin; Huang, Lu-Qi; Yuan, Si-Tong

    2011-02-01

    The crystal structure of medicated realgar in China was validated as alpha-As4 S4 by X-ray diffraction and Raman spectroscopy in the present paper. Ten batches of medicinal realgar were analyzed including realgar ore, medicinal realgar powder, and prepared Chinese medicine. Identification of two As4 S4 polymorphs confirmed that the crystal structure of medicated realgar in China is alpha-As4 S4. Studies on 18 batches of preparative realgar powder showed that processing of realgar can not change the crystal structure of realgar. PMID:21510367

  2. Method and structure for passivating semiconductor material

    SciTech Connect

    Pankove, Jacques I.

    1981-01-01

    A structure for passivating semiconductor material comprises a substrate of crystalline semiconductor material, a relatively thin film of carbon disposed on a surface of the crystalline material, and a layer of hydrogenated amorphous silicon deposited on the carbon film.

  3. Design of a confined environment using protein cages and crystals for the development of biohybrid materials.

    PubMed

    Abe, Satoshi; Maity, Basudev; Ueno, Takafumi

    2016-05-01

    There is growing interest in the design of protein assemblies for use in materials science and bionanotechnology. Protein assemblies, such as cages and crystalline protein structures, provide confined chemical environments that allow immobilization of metal complexes, nanomaterials, and proteins by metal coordination, assembly/disassembly reactions, genetic manipulation and crystallization methods. Protein assembly composites can be used to prepare hybrid materials with catalytic, magnetic and optical properties for cellular applications due to their high stability, solubility and biocompatibility. In this feature article, we focus on the recent development of ferritin as the most promising molecular template protein cage and in vivo and in vitro engineering of protein crystals as solid protein materials with functional properties. PMID:27032539

  4. Isomorph invariance of the structure and dynamics of classical crystals

    NASA Astrophysics Data System (ADS)

    Albrechtsen, Dan E.; Olsen, Andreas E.; Pedersen, Ulf R.; Schrøder, Thomas B.; Dyre, Jeppe C.

    2014-09-01

    This paper shows by computer simulations that some crystalline systems have curves in their thermodynamic phase diagrams, so-called isomorphs, along which structure and dynamics in reduced units are invariant to a good approximation. The crystals are studied in a classical-mechanical framework, which is generally a good description except significantly below melting. The existence of isomorphs for crystals is validated by simulations of particles interacting via the Lennard-Jones pair potential arranged into a face-centered cubic (fcc) crystalline structure; the slow vacancy-jump dynamics of a defective fcc crystal is also shown to be isomorph invariant. In contrast, a NaCl crystal model does not exhibit isomorph invariances. Other systems simulated, though in less detail, are the Wahnström binary Lennard-Jones crystal with the MgZn2 Laves crystal structure, monatomic fcc crystals of particles interacting via the Buckingham pair potential and via a purely repulsive pair potential diverging at a finite separation, an ortho-terphenyl molecular model crystal, and SPC/E hexagonal ice. Except for NaCl and ice, the crystals simulated all have isomorphs. Based on previous simulations of liquid models, we conjecture that crystalline solids with isomorphs include most or all formed by atoms or molecules interacting via metallic or van der Waals forces, whereas covalently bonded or hydrogen-bonded crystals are not expected to have isomorphs; crystals of ions or dipolar molecules constitute a limiting case for which isomorphs are only expected when the Coulomb interactions are relatively weak. We briefly discuss the consequences of the findings for theories of melting and crystallization.

  5. Effect of melt composition on the electrical properties and structure of undoped gallium arsenide single crystals

    SciTech Connect

    Koval'chuk, I.A.; Markov, A.V.; Mil'vidskii, M.G.

    1988-07-01

    We present results on the electrical properties and structure of single crystal GaAs, 40 mm in diameter, obtained by a combined synthesis process and grown by the Czochralski method in an inert gas at high pressure. For crystals of each group the composition of the starting melt was varied during growing between 46-54 at. % As. The intrinsic resistivity of the material was obtained by measuring the Hall effect at room temperature.

  6. Study on the Reflection Spectra of One Dimensional Plasma Photonic Crystals Having Exponentially Graded Materials

    NASA Astrophysics Data System (ADS)

    Prasad, S.; Vivek, Singh; K. Singh, A.

    2013-05-01

    The transfer matrix method is used to study the effect of the permittivity profile on the reflectivity of a one dimensional plasma photonic crystal having exponentially graded material. The analysis shows that the proposed structure works as a perfect mirror within a certain frequency range. These frequency ranges can be completely controlled by the permittivity profile of a graded dielectric layer. As expected we observed that these frequency ranges are also controlled by plasma parameters.

  7. Hydroflux synthesis and crystal structure of new lanthanide tungstate oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Latshaw, Allison M.; Smith, Mark D.; Chance, W. Michael; zur Loye, Hans-Conrad

    2015-04-01

    Single crystals of Na5Ln(OH)6WO4 where Ln = Er, Tm, and Yb were grown out of a NaOH hydroflux. The crystals were characterized by single crystal X-ray diffraction and were found to crystallize in the monoclinic space group I2/a. The lattice parameter ranges for the three structures are a = 11.2024(7) Å-11.2412(6) Å, b = 16.1850(10) Å-16.2220(10) Å, and c = 11.9913(7) Å-12.0323(7) Å while the β angle range is 101.999(2)°-102.025(2)°.

  8. Electro- and nonlinear optics of liquid crystals with nano-dopants and nano-structures

    NASA Astrophysics Data System (ADS)

    Williams, Yana Zhang

    Nano materials are useful materials with interesting optical and electronic properties. When combined with liquid crystals, they can improve the optical performance of liquid crystals. On the other hand, liquid crystals are very versatile materials which can be easily incorporated with nanoscale materials, or encapsulated inside nanoscale structures. Combining nano materials with liquid crystals, and studying the optical properties of these composites for the purpose of discovering new materials for low optical power, high resolution, and fast response, is the driving force behind our research. The motivation of this work is presented in Chapter 1 and a brief introduction of liquid crystals and nano materials is presented in Chapter 2. In Chapter 3, we blended photosensitive cadmium selenide (CdSe) nanorods (7nm in diameter, 40nm in length) inside a nematic liquid crystal system. The effective intensity dependent refractive index coefficients are on the order of 10-2 (cm2/ Watt). This is at least 10 times larger than that of undoped liquid crystals. Most importantly, it is a transient process. We also observed one of the lowest electro-optical (E-O) switching threshold voltages from this doped system Vth = 0.78 ( Volts). It is postulated that the photosensitive CdSe nanorods improved the charge generation and charge transportation, as well as permittivity and conductivity anisotropy, of the liquid crystal system. In Chapter 4, a unique 4-beam holographic method in an umbrella configuration is used to successfully fabricate three dimensional photonic structures within polymer dispersed liquid crystals. The resultant 3D structures exhibit multicolor reflection, and are optically characterized by taking transmission spectrum, as well as Bragg diffraction. An electro-optical switching time of tens of milliseconds is obtained from the structures. This tuning ability is achieved by the encapsulated liquid crystal droplets at the nodes of the structures. The fabrication is a fast, clean process over a large sample area. It is very useful for tunable photonics applications. In addition to providing further detail on these works, I will briefly mention a few future research plans in Chapter 5.

  9. Materials processing threshold report. 1: Semiconductor crystals for infrared detectors

    NASA Technical Reports Server (NTRS)

    Sager, E. V.; Thompson, T. R.; Nagler, R. G.

    1980-01-01

    An extensive search was performed of the open literature pertaining to infrared detectors to determine what constitutes a good detector and in what way performance is limited by specific material properties. Interviews were conducted with a number of experts in the field to assess their perceptions of the state of the art and of the utility of zero-gravity processing. Based on this information base and on a review of NASA programs in crystal growth and infrared sensors, NASA program goals were reassessed and suggestions are presented as to possible joint and divergent efforts between NASA and DOD.

  10. Noise control by sonic crystal barriers made of recycled materials.

    PubMed

    Snchez-Dehesa, Jos; Garcia-Chocano, Victor M; Torrent, Daniel; Cervera, Francisco; Cabrera, Suitberto; Simon, Francisco

    2011-03-01

    A systematic study of noise barriers based on sonic crystals made of cylinders that use recycled materials like absorbing component is reported here. The barriers consist of only three rows of perforated metal shells filled with rubber crumb. Measurements of reflectance and transmittance by these barriers are reported. Their attenuation properties result from a combination of sound absorption by the rubber crumb and reflection by the periodic distribution of scatterers. It is concluded that the porous cylinders can be used as building blocks whose physical parameters can be optimized in order to design efficient barriers adapted to different noisy environments. PMID:21428481

  11. Activating efficient phosphorescence from purely organic materials by crystal design.

    PubMed

    Bolton, Onas; Lee, Kangwon; Kim, Hyong-Jun; Lin, Kevin Y; Kim, Jinsang

    2011-03-01

    Phosphorescence is among the many functional features that, in practice, divide pure organic compounds from organometallics and inorganics. Considered to be practically non-phosphorescent, purely organic compounds (metal-free) are very rarely explored as emitters in phosphor applications, despite the emerging demand in this field. To defy this paradigm, we describe novel design principles to create purely organic materials demonstrating phosphorescence that can be turned on by incorporating halogen bonding into their crystals. By designing chromophores to contain triplet-producing aromatic aldehydes and triplet-promoting bromine, crystal-state halogen bonding can be made to direct the heavy atom effect to produce surprisingly efficient solid-state phosphorescence. When this chromophore is diluted into the crystal of a bi-halogenated, non-carbonyl analogue, ambient phosphorescent quantum yields reach 55%. Here, using this design, a series of pure organic phosphors are colour-tuned to emit blue, green, yellow and orange. From this initial discovery, a directed heavy atom design principle is demonstrated that will allow for the development of bright and practical purely organic phosphors. PMID:21336325

  12. Structure of cleaved (001) USb2 single crystal

    SciTech Connect

    Chen, Shao-ping; Hawley, Marilyn; Bauer, Eric D; Stockum, Phil B; Manoharan, Hari C

    2009-01-01

    We have achieved what we believe to be the first atomic resolution STM images for a uranium compound taken at room temperature. The a, b, and c lattice parameters in the images confirm that the USb{sub 2} crystals cleave on the (001) basal plane as expected. The a and b dimensions were equal, with the atoms arranged in a cubic pattern. Our calculations indicate a symmetric cut between Sb planes to be the most favorable cleavage plane and U atoms to be responsible for most of the DOS measured by STM. Some strange features observed in the STM will be discussed in conjunction with ab initio calculations. The purpose of this work is to demonstrate the power of scanning tunneling microscopy (STM) techniques combined with a theoretical underpinning to determine the surface atomic structure and properties of actinide materials, such as the quasi 2-dimensional uranium dipnictide USb{sub 2} single crystal, thereby contributing to the understanding of their surface structural and electronic properties. The members of this interesting UX{sub 2} (X=P, As, Sb, Bi) series of compounds display dual localized and itinerant 5f electron behavior within the same compound due to the hybridization of the 5f orbitals with the conduction band. With the exception of UO{sub 2}, which has to be studied at elevated temperature to generate enough carriers for STM imaging, STM techniques have not been applied successfully to the characterization of the surface atomic structure of any other single crystal actinide compound, to the best of our knowledge. However, STM has been used to a limited extent for the study of some cerium compounds. STM probes electronic properties at the atomic level and can directly provide information about the local density of filled and empty states (LDOS) states simultaneously. A STM topograph provides the local atomic arrangement and spacing of the atoms on the surface, local defect structures (e.g. steps, vacancies, and kink sites) and the presence of contaminants, all of which are averaged over when probed in photoemission studies. The quasi two-dimensional USb{sub 2} has a layered tetragonal structure that is easily cleaved and has been extensively studied by a number of different techniques, such as resistivity, Hall effect measurements, photoemission and angle-resolved photoemission spectroscopy, de Haas-van Alphen, neutron diffraction, nuclear magnetic resonance, and U{sup 238} Mossbauer spectroscopy techniques. Here, we provide local information about the surfaces of this interesting compound, which we find to contain a high density of defects.

  13. A co-crystal between benzene and ethane: a potential evaporite material for Saturn's moon Titan.

    PubMed

    Maynard-Casely, Helen E; Hodyss, Robert; Cable, Morgan L; Vu, Tuan Hoang; Rahm, Martin

    2016-05-01

    Using synchrotron X-ray powder diffraction, the structure of a co-crystal between benzene and ethane formed in situ at cryogenic conditions has been determined, and validated using dispersion-corrected density functional theory calculations. The structure comprises a lattice of benzene molecules hosting ethane molecules within channels. Similarity between the intermolecular interactions found in the co-crystal and in pure benzene indicate that the C-H⋯π network of benzene is maintained in the co-crystal, however, this expands to accommodate the guest ethane molecules. The co-crystal has a 3:1 benzene:ethane stoichiometry and is described in the space group [Formula: see text] with a = 15.977 (1) Å and c = 5.581 (1) Å at 90 K, with a density of 1.067 g cm(-3). The conditions under which this co-crystal forms identify it is a potential that forms from evaporation of Saturn's moon Titan's lakes, an evaporite material. PMID:27158505

  14. A comparative study on the crystal structure of bicycle analogues to the natural phytotoxin helminthosporins

    NASA Astrophysics Data System (ADS)

    Barbosa, Luiz Cláudio de Almeida; Teixeira, Robson Ricardo; Nogueira, Leonardo Brandão; Maltha, Celia Regina Alvares; Doriguetto, Antônio Carlos; Martins, Felipe Terra

    2016-02-01

    Herein we described structural insights of a series of analogues to helminthosporin phytotoxins. The key reaction used to prepare the compounds corresponded to the [3 + 4] cycloaddition between the oxyallyl cation generated from 2,4-dibromopentan-3-one and different furans. Their structures were confirmed upon IR, NMR and X-ray diffraction analyses. While bicycles 7, 8 and 9 crystallize in the centrosymmetric monoclinic space group P21/c, compound 10 was solved in the noncentrosymmetric orthorhombic space group P212121. The solid materials obtained were shown to be racemic crystals (7, 8, 9) or racemic conglomerate (10). In all compounds, there is formation of a bicycle featured by fused tetrahydropyranone and 2,5-dihydrofuran rings. They adopt chair and envelope conformations, respectively. Crystal packing of all compounds is stabilized through C-H•••O contacts. Conformational aspects as well as similarities and differences among the crystal structures of the synthesized analogues are discussed.

  15. Electric field generation of Skyrmion-like structures in a nematic liquid crystal.

    PubMed

    Cattaneo, Laura; Kos, Žiga; Savoini, Matteo; Kouwer, Paul; Rowan, Alan; Ravnik, Miha; Muševič, Igor; Rasing, Theo

    2016-01-21

    Skyrmions are particle-like topological objects that are increasingly drawing attention in condensed matter physics, where they are connected to inversion symmetry breaking and chirality. Here we report the generation of stable Skyrmion-like structures in a thin nematic liquid crystal film on chemically patterned patchy surfaces. Using the interplay of material elasticity and surface boundary conditions, we use a strong electric field to quench the nematic liquid crystal from a fully aligned phase to vortex-like nematic liquid crystal structures, centered on patterned patches, which carry two different sorts of topological defects. Numerical calculations reveal that these are Skyrmion-like structures, seeded from the surface boojum topological defects and swirling towards the second confining surface. These observations, supported by numerical methods, demonstrate the possibility to generate, manipulate and study Skyrmion-like objects in nematic liquid crystals on patterned surfaces. PMID:26549212

  16. Standard Reference Material (SRM 1990) for Single Crystal Diffractometer Alignment

    USGS Publications Warehouse

    Wong-Ng, W.; Siegrist, T.; DeTitta, G.T.; Finger, L.W.; Evans, H.T., Jr.; Gabe, E.J.; Enright, G.D.; Armstrong, J.T.; Levenson, M.; Cook, L.P.; Hubbard, C.R.

    2001-01-01

    An international project was successfully completed which involved two major undertakings: (1) a round-robin to demonstrate the viability of the selected standard and (2) the certification of the lattice parameters of the SRM 1990, a Standard Reference Material?? for single crystal diffractometer alignment. This SRM is a set of ???3500 units of Cr-doped Al2O3, or ruby spheres [(0 420.011 mole fraction % Cr (expanded uncertainty)]. The round-robin consisted of determination of lattice parameters of a pair of crystals' the ruby sphere as a standard, and a zeolite reference to serve as an unknown. Fifty pairs of crystals were dispatched from Hauptman-Woodward Medical Research Institute to volunteers in x-ray laboratories world-wide. A total of 45 sets of data was received from 32 laboratories. The mean unit cell parameters of the ruby spheres was found to be a=4.7608 A?? ?? 0.0062 A??, and c=12.9979 A?? ?? 0.020 A?? (95 % intervals of the laboratory means). The source of errors of outlier data was identified. The SRM project involved the certification of lattice parameters using four well-aligned single crystal diffractometers at (Bell Laboratories) Lucent Technologies and at NRC of Canada (39 ruby spheres), the quantification of the Cr content using a combined microprobe and SEM/EDS technique, and the evaluation of the mosaicity of the ruby spheres using a double-crystal spectrometry method. A confirmation of the lattice parameters was also conducted using a Guinier-Ha??gg camera. Systematic corrections of thermal expansion and refraction corrections were applied. These rubies_ are rhombohedral, with space group R3c. The certified mean unit cell parameters are a=4.76080 ?? 0.00029 A??, and c=12 99568 A?? ?? 0.00087 A?? (expanded uncertainty). These certified lattice parameters fall well within the results of those obtained from the international round-robin study. The Guinier-Ha??gg transmission measurements on five samples of powdered rubies (a=4.7610 A?? ?? 0.0013 A??, and c=12.9954 A?? ?? 0.0034 A??) agreed well with the values obtained from the single crystal spheres.

  17. Graphene liquid crystal retarded percolation for new high-k materials

    NASA Astrophysics Data System (ADS)

    Yuan, Jinkai; Luna, Alan; Neri, Wilfrid; Zakri, Cécile; Schilling, Tanja; Colin, Annie; Poulin, Philippe

    2015-11-01

    Graphene flakes with giant shape anisotropy are extensively used to establish connectedness electrical percolation in various heterogeneous systems. However, the percolation behaviour of graphene flakes has been recently predicted to be far more complicated than generally anticipated on the basis of excluded volume arguments. Here we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals below the onset of percolation. The competition of percolation and liquid crystal transition provides a new route towards high-k materials. Indeed, near-percolated liquid-crystalline graphene-based composites display unprecedented dielectric properties with a dielectric constant improved by 260-fold increase as compared with the polymer matrix, while maintaining the loss tangent as low as 0.4. This performance is shown to depend on the structure of monodomains of graphene liquid-crystalline phases. Insights into how the liquid crystal phase transition interferes with percolation transition and thus alters the dielectric constant are discussed.

  18. Graphene liquid crystal retarded percolation for new high-k materials

    PubMed Central

    Yuan, Jinkai; Luna, Alan; Neri, Wilfrid; Zakri, Cécile; Schilling, Tanja; Colin, Annie; Poulin, Philippe

    2015-01-01

    Graphene flakes with giant shape anisotropy are extensively used to establish connectedness electrical percolation in various heterogeneous systems. However, the percolation behaviour of graphene flakes has been recently predicted to be far more complicated than generally anticipated on the basis of excluded volume arguments. Here we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals below the onset of percolation. The competition of percolation and liquid crystal transition provides a new route towards high-k materials. Indeed, near-percolated liquid-crystalline graphene-based composites display unprecedented dielectric properties with a dielectric constant improved by 260-fold increase as compared with the polymer matrix, while maintaining the loss tangent as low as 0.4. This performance is shown to depend on the structure of monodomains of graphene liquid-crystalline phases. Insights into how the liquid crystal phase transition interferes with percolation transition and thus alters the dielectric constant are discussed. PMID:26567720

  19. Graphene liquid crystal retarded percolation for new high-k materials.

    PubMed

    Yuan, Jinkai; Luna, Alan; Neri, Wilfrid; Zakri, Cécile; Schilling, Tanja; Colin, Annie; Poulin, Philippe

    2015-01-01

    Graphene flakes with giant shape anisotropy are extensively used to establish connectedness electrical percolation in various heterogeneous systems. However, the percolation behaviour of graphene flakes has been recently predicted to be far more complicated than generally anticipated on the basis of excluded volume arguments. Here we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals below the onset of percolation. The competition of percolation and liquid crystal transition provides a new route towards high-k materials. Indeed, near-percolated liquid-crystalline graphene-based composites display unprecedented dielectric properties with a dielectric constant improved by 260-fold increase as compared with the polymer matrix, while maintaining the loss tangent as low as 0.4. This performance is shown to depend on the structure of monodomains of graphene liquid-crystalline phases. Insights into how the liquid crystal phase transition interferes with percolation transition and thus alters the dielectric constant are discussed. PMID:26567720

  20. Growth of mesoporous materials within colloidal crystal films by spin-coating.

    PubMed

    Villaescusa, Luis A; Mihi, Agustín; Rodríguez, Isabel; García-Bennett, Alfonso E; Míguez, Hernan

    2005-10-27

    A combination of colloidal crystal planarization, stabilization, and novel infiltration techniques is used to build a bimodal porous silica film showing order at both the micron and the nanometer length scale. An infiltration method based on the spin-coating of the mesophase precursor onto a three-dimensional polystyrene colloidal crystal film allows a nanometer control tuning of the filling fraction of the mesoporous phase while preserving the optical quality of the template. These materials combine a high specific surface arising from the nanopores with increased mass transport and photonic crystal properties provided by the order of the macropores. Optical Bragg diffraction from these type of hierarchically ordered oxides is observed, allowing performing of optical monitoring of the different processes involved in the formation of the bimodal silica structure. PMID:16853540

  1. Errors in Crystal structure of HINT from Helicobacter pylori

    PubMed Central

    Maize, Kimberly M.

    2016-01-01

    Inaccuracies in the article, Crystal structure of HINT from Helicobacter pylori by Tarique et al. [(2016) Acta Cryst. F72, 42–48] are presented, and a brief history of HINT nomenclature is discussed. PMID:27050269

  2. Errors in Crystal structure of HINT from Helicobacter pylori.

    PubMed

    Maize, Kimberly M

    2016-04-01

    Inaccuracies in the article, Crystal structure of HINT from Helicobacter pylori by Tarique et al. [(2016) Acta Cryst. F72, 42-48] are presented, and a brief history of HINT nomenclature is discussed. PMID:27050269

  3. Determination of channeling perspectives for complex crystal structures

    SciTech Connect

    Allen, W.R.

    1993-03-01

    Specification of the atomic arrangement for axes and planes of high symmetry is essential for crystal alignment using Rutherford backscattering and for studies of the lattice location of impurities in single crystals. By rotation of an inscribed orthogonal coordinate system, a visual image for a given perspective of a crystal structure can be specified. Knowledge of the atomic arrangement permits qualitative channeling perspectives to be visualized and calculation of continuum potentials for channeling. Channeling angular-yield profiles can then be analytically modeled and, subsequently, shadowing by host atoms of positions within the unit cell predicted. Software to calculate transformed atom positions for a channeling perspective in a single crystal are described and illustrated for the spinel crystal structure.

  4. Crystal structure of a methimazole-based ionic liquid.

    PubMed

    Gaitor, Jamie C; Zayas, Manuel Sanchez; Myrthil, Darrel J; White, Frankie; Hendrich, Jeffrey M; Sykora, Richard E; O'Brien, Richard A; Reilly, John T; Mirjafari, Arsalan

    2015-12-01

    The structure of 1-methyl-2-(prop-2-en-1-ylsulfan-yl)-1H-imidazol-3-ium bromide, C7H11N2S(+)·Br(-), has monoclinic (P21/c) symmetry. In the crystal, the components are linked by N-H⋯Br and C-H⋯Br hydrogen bonds. The crystal structure of the title compound undeniably proves that methimazole reacts through the thione tautomer, rather than the thiol tautomer in this system. PMID:26870468

  5. Crystal structure of a methimazole-based ionic liquid

    PubMed Central

    Gaitor, Jamie C.; Zayas, Manuel Sanchez; Myrthil, Darrel J.; White, Frankie; Hendrich, Jeffrey M.; Sykora, Richard E.; O’Brien, Richard A.; Reilly, John T.; Mirjafari, Arsalan

    2015-01-01

    The structure of 1-methyl-2-(prop-2-en-1-ylsulfan­yl)-1H-imidazol-3-ium bromide, C7H11N2S+·Br−, has monoclinic (P21/c) symmetry. In the crystal, the components are linked by N—H⋯Br and C—H⋯Br hydrogen bonds. The crystal structure of the title compound undeniably proves that methimazole reacts through the thione tautomer, rather than the thiol tautomer in this system. PMID:26870468

  6. Tuning the magnetic anisotropy in single-layer crystal structures

    NASA Astrophysics Data System (ADS)

    Torun, E.; Sahin, H.; Bacaksiz, C.; Senger, R. T.; Peeters, F. M.

    2015-09-01

    The effect of an applied electric field and the effect of charging are investigated on the magnetic anisotropy (MA) of various stable two-dimensional (2D) crystals such as graphene, FeCl2, graphone, fluorographene, and MoTe2 using first-principles calculations. We found that the magnetocrystalline anisotropy energy of Co-on-graphene and Os-doped-MoTe2 systems change linearly with electric field, opening the possibility of electric field tuning MA of these compounds. In addition, charging can rotate the easy-axis direction of Co-on-graphene and Os-doped-MoTe2 systems from the out-of-plane (in-plane) to in-plane (out-of-plane) direction. The tunable MA of the studied materials is crucial for nanoscale electronic technologies such as data storage and spintronics devices. Our results show that controlling the MA of the mentioned 2D crystal structures can be realized in various ways, and this can lead to the emergence of a wide range of potential applications where the tuning and switching of magnetic functionalities are important.

  7. The Crystal and Molecular Structure of Dianhydrogossypol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dianhydrogossypol (4,4'-dihydroxy-5,5'-diisopropyl-7,7'-dimethyl-bis(3H-naphtho[1,8-bc]furan-3-one)) was made by refluxing gossypol in m-xylene. Proton NMR confirmed that complete conversion was achieved over several hours. Single crystals were obtained by slow evaporation of the product from dichl...

  8. Allophycocyanin and phycocyanin crystal structures reveal facets of phycobilisome assembly.

    PubMed

    Marx, Ailie; Adir, Noam

    2013-03-01

    X-ray crystal structures of the isolated phycobiliprotein components of the phycobilisome have provided high resolution details to the description of this light harvesting complex at different levels of complexity and detail. The linker-independent assembly of trimers into hexamers in crystal lattices of previously determined structures has been observed in almost all of the phycocyanin (PC) and allophycocyanin (APC) structures available in the Protein Data Bank. In this paper we describe the X-ray crystal structures of PC and APC from Synechococcus elongatus sp. PCC 7942, PC from Synechocystis sp. PCC 6803 and PC from Thermosynechococcus vulcanus crystallized in the presence of urea. All five structures are highly similar to other PC and APC structures on the levels of subunits, monomers and trimers. The Synechococcus APC forms a unique loose hexamer that may show the structural requirements for core assembly and rod attachment. While the Synechococcus PC assembles into the canonical hexamer, it does not further assemble into rods. Unlike most PC structures, the Synechocystis PC fails to form hexamers. Addition of low concentrations of urea to T. vulcanus PC inhibits this proteins propensity to form hexamers, resulting in a crystal lattice composed of trimers. The molecular source of these differences in assembly and their relevance to the phycobilisome structure is discussed. PMID:23201474

  9. Millimeter-wave Bragg diffraction of microfabricated crystal structures

    NASA Astrophysics Data System (ADS)

    Yuan, C. P.; Lin, S. Y.; Chang, T. H.; Shew, B. Y.

    2011-06-01

    A compact diffraction apparatus is developed with millimeter-wave propagation between two parallel plates. Two types of microfabricated model crystals are individually mounted on a rotatable structure. In contrast to previous work, the experimental results agree well with Bragg's predictions because multiple scattering is minimized in this configuration. Factors that affect the resolution and signal strength, such as the number of scatterers, cylinder radius, and the distance between the detector and the model crystal, are analyzed. The apparatus offers a visually accessible way to teach students about crystal structure as well as scattering and diffraction.

  10. Radiation effects on structural materials

    SciTech Connect

    Ghoniem, N.M.

    1991-06-28

    This report discusses the following topics on the effect radiation has on thermonuclear reactor materials: Atomic Displacements; Microstructure Evolution; Materials Engineering, Mechanics, and Design; Research on Low-Activation Steels; and Research Motivated by Grant Support.

  11. Microscopic structure of molecularly thin confined liquid-crystal films

    NASA Astrophysics Data System (ADS)

    Gruhn, Thomas; Schoen, Martin

    1997-03-01

    The microscopic structure of a molecularly thin liquid-crystal film confined between two plane parallel surfaces (i.e., walls) composed of rigidly fixed atoms is investigated in grand canonical ensemble Monte Carlo simulations in which the temperature T, the chemical potential μ, and the wall separation sz are the relevant thermodynamic state variables. These conditions correspond to those encountered in related experiments employing the surface forces apparatus (SFA). Wall atoms are distributed according to the (100) configuration of a face-centered cubic (fcc) lattice. Film molecules interact with each other via the Gay-Berne potential which may be viewed as a Lennard-Jones (12,6) potential modified to account for the anisotropy of the interaction between two ellipsoidal film molecules. Parameters governing the film-wall interaction are chosen such that molecules tend to arrange their symmetry axes parallel with the plane of a wall (i.e., the x-y plane). The thermodynamic state of a bulk phase in equilibrium with the confined film pertains to the isotropic phase of the Gay-Berne fluid, so that preferred orientations in the film are unambiguously ascribed to confinement (i.e., to the presence of the walls). In general, film structure is characterized by stratification, that is, the tendency of film molecules to arrange their centers of mass in individual strata parallel with the walls. The strata are more diffuse than in films composed of ``simple'' molecules without rotational degrees of freedom due to a larger geometric incompatibility between film and wall structure and to orientability of film molecules in the present model. As sz is increased at fixed T and μ, molecularly thin liquid-crystal films undergo complex structural changes resulting from a competition between wall-induced orientation and lack of space. These effects are analyzed in depth by density-alignment histograms and correlated with variations of the normal stress Tzz exerted by the film on the walls. The normal stress, which is in principle accessible in SFA experiments, depends strongly on sz even in rather thick films, indicating the importance of cooperative wall-induced phenomena for materials properties of confined liquid-crystal films.

  12. Research on the large band gaps in multilayer radial phononic crystal structure

    NASA Astrophysics Data System (ADS)

    Gao, Nansha; Wu, Jiu Hui; Guan, Dong

    2016-04-01

    In this paper, we study the band gaps (BGs) of new proposed radial phononic crystal (RPC) structure composed of multilayer sections. The band structure, transmission spectra and eigenmode displacement fields of the multilayer RPC are calculated by using finite element method (FEM). Due to the vibration coupling effects between thin circular plate and intermediate mass, the RPC structure can exhibit large BGs, which can be effectively shifted by changing the different geometry values. This study shows that multilayer RPC can unfold larger and lower BGs than traditional phononic crystals (PCs) and RPC can be composed of single material.

  13. Crystal structure of a actinide metals at high compression

    SciTech Connect

    Fast, L.; Soederlind, P.

    1996-05-01

    The crystal structures of some light actinide metals are studied theoretically as a function of applied pressure. The first principles electronic structure theory is formulated in the framework of density functional theory, with the gradient corrected local density approximation of the exchange-correlation functional. The light actinide metals are shown to be well described as itinerant (metallic) f-electron metals and generally, they display a crystal structure which have, in agreement with previous theoretical suggestions, increasing degree of symmetry and closed-packing upon compression. The theoretical calculations agree well with available experimental data. At very high compression, the theory predicts closed-packed structures such as the fcc or the hcp structures or the nearly closed-packed bcc structure for the light actinide metals. A simple canonical band picture is presented to explain in which particular closed-packed form these metals will crystallize at ultra-high pressure. {copyright} {ital 1996 American Institute of Physics.}

  14. Membrane protein structures without crystals, by single particle electron cryomicroscopy

    PubMed Central

    Vinothkumar, Kutti R

    2015-01-01

    It is an exciting period in membrane protein structural biology with a number of medically important protein structures determined at a rapid pace. However, two major hurdles still remain in the structural biology of membrane proteins. One is the inability to obtain large amounts of protein for crystallization and the other is the failure to get well-diffracting crystals. With single particle electron cryomicroscopy, both these problems can be overcome and high-resolution structures of membrane proteins and other labile protein complexes can be obtained with very little protein and without the need for crystals. In this review, I highlight recent advances in electron microscopy, detectors and software, which have allowed determination of medium to high-resolution structures of membrane proteins and complexes that have been difficult to study by other structural biological techniques. PMID:26435463

  15. High-throughput screening for thermoelectric sulphides by using crystal structure features as descriptors

    NASA Astrophysics Data System (ADS)

    Zhang, Ruizhi; Du, Baoli; Chen, Kan; Reece, Mike; Materials Research Insititute Team

    With the increasing computational power and reliable databases, high-throughput screening is playing a more and more important role in the search of new thermoelectric materials. Rather than the well established density functional theory (DFT) calculation based methods, we propose an alternative approach to screen for new TE materials: using crystal structural features as 'descriptors'. We show that a non-distorted transition metal sulphide polyhedral network can be a good descriptor for high power factor according to crystal filed theory. By using Cu/S containing compounds as an example, 1600+ Cu/S containing entries in the Inorganic Crystal Structure Database (ICSD) were screened, and of those 84 phases are identified as promising thermoelectric materials. The screening results are validated by both electronic structure calculations and experimental results from the literature. We also fabricated some new compounds to test our screening results. Another advantage of using crystal structure features as descriptors is that we can easily establish structural relationships between the identified phases. Based on this, two material design approaches are discussed: 1) High-pressure synthesis of metastable phase; 2) In-situ 2-phase composites with coherent interface. This work was supported by a Marie Curie International Incoming Fellowship of the European Community Human Potential Program.

  16. Gallium arsenide single crystal solar cell structure and method of making

    NASA Technical Reports Server (NTRS)

    Stirn, Richard J. (Inventor)

    1983-01-01

    A production method and structure for a thin-film GaAs crystal for a solar cell on a single-crystal silicon substrate (10) comprising the steps of growing a single-crystal interlayer (12) of material having a closer match in lattice and thermal expansion with single-crystal GaAs than the single-crystal silicon of the substrate, and epitaxially growing a single-crystal film (14) on the interlayer. The material of the interlayer may be germanium or graded germanium-silicon alloy, with low germanium content at the silicon substrate interface, and high germanium content at the upper surface. The surface of the interface layer (12) is annealed for recrystallization by a pulsed beam of energy (laser or electron) prior to growing the interlayer. The solar cell structure may be grown as a single-crystal n.sup.+ /p shallow homojunction film or as a p/n or n/p junction film. A Ga(Al)AS heteroface film may be grown over the GaAs film.

  17. Synthesis, growth, structural, thermal and optical studies of pyrrolidinium-2-carboxylate-4-nitrophenol single crystals.

    PubMed

    Swarna Sowmya, N; Sampathkrishnan, S; Vidyalakshmi, Y; Sudhahar, S; Mohan Kumar, R

    2015-06-15

    Organic nonlinear optical material, pyrrolidinium-2-carboxylate-4-nitrophenol (PCN) was synthesized and single crystals were grown by slow evaporation solution growth method. Single crystal X-ray diffraction analysis confirmed the structure and lattice parameters of PCN crystals. Infrared, Raman and NMR spectral analyses were used to elucidate the functional groups present in the compound. The thermal behavior of synthesized compound was studied by thermogravimetric and differential scanning calorimetry (TG-DSC) analyses. The photoluminescence property was studied by exciting the crystal at 360 nm. The relative second harmonic generation (SHG) efficiency of grown crystal was estimated by using Nd:YAG laser with fundamental wavelength of 1,064 nm. PMID:25795607

  18. Synthesis, growth, structure determination and optical properties of chalcone derivative single crystal

    NASA Astrophysics Data System (ADS)

    Karthi, S.; Girija, E. K.

    2014-04-01

    Acquiring large nonlinear optical (NLO) efficient organic material is essential for the development of optoelectronics and photonic devices. Chalcone is the donor - Π - acceptor - Π - donor (D-Π-A-Π-D) type conjugated molecule with appreciable hyperpolarizability of potential interest in NLO applications. The addition of vinyl and electron donor groups in the chalcone molecule may enhance the second harmonic generation (SHG) efficiency. Here we report the synthesis, crystal growth and characterization of a chalcone derivative 1-(4-methylphenyl)-5-(4-methoxyphenyl)-penta-2,4-dien-1-one (MPMPP). The MPMPP crystal was grown by slow evaporation solution growth technique from acetone. The grown crystal structure was studied by single crystal X-ray diffraction. The SHG efficiency of the grown crystal was determined by Kurtz and Perry method.

  19. Synthesis, growth, structure determination and optical properties of chalcone derivative single crystal

    SciTech Connect

    Karthi, S. Girija, E. K.

    2014-04-24

    Acquiring large nonlinear optical (NLO) efficient organic material is essential for the development of optoelectronics and photonic devices. Chalcone is the donor - Π - acceptor - Π - donor (D-Π-A-Π-D) type conjugated molecule with appreciable hyperpolarizability of potential interest in NLO applications. The addition of vinyl and electron donor groups in the chalcone molecule may enhance the second harmonic generation (SHG) efficiency. Here we report the synthesis, crystal growth and characterization of a chalcone derivative 1-(4-methylphenyl)-5-(4-methoxyphenyl)-penta-2,4-dien-1-one (MPMPP). The MPMPP crystal was grown by slow evaporation solution growth technique from acetone. The grown crystal structure was studied by single crystal X-ray diffraction. The SHG efficiency of the grown crystal was determined by Kurtz and Perry method.

  20. Structure of orthorhombic crystals of beef liver catalase.

    PubMed

    Ko, T P; Day, J; Malkin, A J; McPherson, A

    1999-08-01

    The growth mechanisms and physical properties of the orthorhombic crystal form of beef liver catalase were investigated using in situ atomic force microscopy (AFM). It was observed that the crystals grow in the <001> direction by an unusual progression of sequential two-dimensional nuclei of half unit-cell layers corresponding to the 'bottoms' and 'tops' of unit cells. These were easily discriminated by their alternating asymmetric shapes and their strong growth-rate anisotropy. This pattern has not previously been observed with other macromolecular crystals. Orthorhombic beef liver catalase crystals exhibit an extremely high defect density and incorporate great numbers of misoriented microcrystals, revealed intact by etching experiments, which may explain their marginal diffraction properties. To facilitate interpretation of AFM results in terms of intermolecular interactions, the structure of the orthorhombic crystals, having an entire tetramer of the enzyme as the asymmetric unit, was solved by molecular replacement using a model derived from a trigonal crystal form. It was subsequently refined by conventional techniques. Although the packing of molecules in the two unit cells was substantially different, with very few exceptions no significant differences in the molecular structures were observed. In addition, no statistically significant deviation from ideal 222 molecular symmetry appeared within the tetramer. The packing of molecules in the crystal revealed by X-ray analysis explained in a satisfying way the process of crystal growth revealed by AFM. PMID:10417406

  1. Investigation of the La2O3-Nb2O5-WO3 ternary phase diagram: Isolation and crystal structure determination of the original La3NbWO10 material

    NASA Astrophysics Data System (ADS)

    Vu, T. D.; Barre, M.; Adil, K.; Jouanneaux, A.; Suard, E.; Goutenoire, F.

    2015-09-01

    In the course of the exploration of the La2O3-WO3-Nb2O5 ternary phase diagram, a new compound with the formula La3NbWO10 was discovered. Its structure was determined from a combination of powder X-ray and neutron diffraction data. It crystallizes in the tetragonal space group P42/nmc (no. 137) with the lattice parameters: a=10.0807(1) Å; c=12.5540(1) Å. The structure is built up from infinite ribbons of octahedra (W/Nb)O5 which are perpendicular to each other, lanthanum ions being distributed around these ribbons. The electrical properties of this compound were investigated on sintered pellets by means of complex impedance spectroscopy.

  2. Homodiselenacalix[4]arenes: Molecules with Unique Channelled Crystal Structures.

    PubMed

    Thomas, Joice; Dobrza?ska, Liliana; Van Meervelt, Luc; Quevedo, Mario Alfredo; Wo?niak, Krzysztof; Stachowicz, Marcin; Smet, Mario; Maes, Wouter; Dehaen, Wim

    2016-01-01

    A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert-butyl ester groups. Single-crystal X-ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level. In both crystal structures, solvent channels are present and differ in both shape and capacity. Furthermore, the methoxy-substituted macrocycle undergoes a single-crystal-to-single-crystal transformation during which the molecular structure changes its conformation from 1,3-alternate (loaded with THF/water) to 1,2-alternate (apohost form). Molecular modelling techniques were applied to explore the conformational and energetic behaviour of the macrocycles. PMID:26639087

  3. Effective second-order susceptibility in photonic crystals mode of centrosymmetric materials

    NASA Astrophysics Data System (ADS)

    Feigel, A.; Kotler, Z.; Sfez, B.

    2002-02-01

    A technique for obtaining efficient bulk second-order susceptibility in noncentrosymmetric photonic crystals (PC) made of centrosymmetric materials is discussed. The effect is based on the electric quadrupole effect, strong electromagnetic mode deformation, and nonhomogeneous contribution to volume polarization from different parts of the PC. The required symmetry breaking is introduced on the macroscale of the PC unit cell. The obtained structural χ(2)str is comparable with the second-order susceptibility of ordinary nonlinear materials. Phase matching can be achieved by introducing symmetry modulation (quasi-phase-matching) during fabrication of the PC.

  4. Theoretical exploration of various lithium peroxide crystal structures in a Li-air battery

    DOE PAGESBeta

    Lau, Kah; Qiu, Dantong; Luo, Xiangyi; Greeley, Jeffrey; Curtiss, Larry; Lu, Jun; Amine, Khalil

    2015-01-14

    We describe a series of metastable Li₂O₂ crystal structures involving different orientations and displacements of the O₂²⁻ peroxy ions based on the known Li₂O₂ crystal structure. Within the vicinity of the chemical potential ΔG ~ 0.20 eV/Li from the thermodynamic ground state of the Li₂O₂ crystal structure (i.e., Föppl structure), all of these newly found metastable Li₂O₂ crystal structures are found to be insulating and high-k materials, and they have a common unique signature of an O₂²⁻ O-O vibration mode (ω ~ 799–865 cm⁻¹), which is in the range of that commonly observed in Li-air battery experiments, regardless of themore » random O₂²⁻ orientations and the symmetry in the crystal lattice. From XRD patterns analysis, the commercially available Li₂O₂ powder is confirmed to be the thermodynamic ground state Föppl-like structure. However, for Li₂O₂ compounds that are grown electrochemically under the environment of Li-O₂ cells, we found that the XRD patterns alone are not sufficient for structural identification of these metastable Li₂O₂ crystalline phases due to the poor crystallinity of the sample. In addition, the commonly known Raman signal of O₂²⁻ vibration mode is also found to be insufficient to validate the possible existence of these newly predicted Li₂O₂ crystal structures, as all of them similarly share the similar O₂²⁻ vibration mode. However considering that the discharge voltage in most Li-O₂ cells are typically several tenths of an eV below the thermodynamic equilibrium for the formation of ground state Föppl structure, the formation of these metastable Li₂O₂ crystal structures appears to be thermodynamically feasible.« less

  5. Theoretical exploration of various lithium peroxide crystal structures in a Li-air battery

    SciTech Connect

    Lau, Kah; Qiu, Dantong; Luo, Xiangyi; Greeley, Jeffrey; Curtiss, Larry; Lu, Jun; Amine, Khalil

    2015-01-14

    We describe a series of metastable Li₂O₂ crystal structures involving different orientations and displacements of the O₂²⁻ peroxy ions based on the known Li₂O₂ crystal structure. Within the vicinity of the chemical potential ΔG ~ 0.20 eV/Li from the thermodynamic ground state of the Li₂O₂ crystal structure (i.e., Föppl structure), all of these newly found metastable Li₂O₂ crystal structures are found to be insulating and high-k materials, and they have a common unique signature of an O₂²⁻ O-O vibration mode (ω ~ 799–865 cm⁻¹), which is in the range of that commonly observed in Li-air battery experiments, regardless of the random O₂²⁻ orientations and the symmetry in the crystal lattice. From XRD patterns analysis, the commercially available Li₂O₂ powder is confirmed to be the thermodynamic ground state Föppl-like structure. However, for Li₂O₂ compounds that are grown electrochemically under the environment of Li-O₂ cells, we found that the XRD patterns alone are not sufficient for structural identification of these metastable Li₂O₂ crystalline phases due to the poor crystallinity of the sample. In addition, the commonly known Raman signal of O₂²⁻ vibration mode is also found to be insufficient to validate the possible existence of these newly predicted Li₂O₂ crystal structures, as all of them similarly share the similar O₂²⁻ vibration mode. However considering that the discharge voltage in most Li-O₂ cells are typically several tenths of an eV below the thermodynamic equilibrium for the formation of ground state Föppl structure, the formation of these metastable Li₂O₂ crystal structures appears to be thermodynamically feasible.

  6. Photonic crystals based on opals and inverse opals: synthesis and structural features

    NASA Astrophysics Data System (ADS)

    Klimonsky, S. O.; Abramova, Vera V.; Sinitskii, Alexander S.; Tretyakov, Yuri D.

    2011-12-01

    Methods of synthesis of photonic crystals based on opals and inverse opals are considered. Their structural features are discussed. Data on different types of structural defects and their influence on the optical properties of opaline materials are systematized. The possibilities of investigation of structural defects by optical spectroscopy, electron microscopy, microradian X-ray diffraction, laser diffraction and using an analysis of Kossel ring patterns are described. The bibliography includes 253 references.

  7. Material Flows in an Active Nematic Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Decamp, Stephen; Redner, Gabriel; Baskaran, Aparna; Hagan, Michael; Dogic, Zvonimir

    Active matter systems are composed of energy consuming constituent components which drive far-from-equilibrium dynamics. As such, active materials exhibit energetic states which would be unfavorable in passive, equilibrium materials. We study one such material; an active nematic liquid crystal which exists in a dynamical steady state where +/-1/2 defects are continuously generated and annihilated at a constant rate. The active nematic is composed of micron-sized microtubule filaments which are highly concentrated into a quasi-2D film that resides on an oil-water interface. Kinesin motor proteins drive inter-filament sliding which results in net extensile motion of the microtubule film. Notably, we find a mesophase in which motile +1/2 defects, acquire system-spanning orientational order. Currently, we are tracking material flows generated by the active stresses in the system to measure length scales at which energy is dissipated, and to measure the relation between internally generated flows and bend in the nematic field.

  8. Crystal growth and materials research in photovoltaics: progress and challenges

    NASA Astrophysics Data System (ADS)

    Surek, Thomas

    2005-02-01

    Photovoltaics (PV) is solar electric power—a semiconductor-based technology that converts sunlight to electricity. Three decades of research has led to the discovery of new materials and devices and new processing techniques for low-cost manufacturing. This has resulted in improved sunlight-to-electricity conversion efficiencies, improved outdoor reliability, and lower module and system costs. The manufacture and sale of PV has grown into a $5 billion industry worldwide, with more than 740 megawatts of PV modules shipped in 2003. This paper reviews the significant progress that has occurred in PV materials and devices research over the past 30 years, focusing on the advances in crystal growth and materials research, and examines the challenges to reaching the ultimate potential of current-generation (crystalline silicon), next-generation (thin films and concentrators), and future-generation PV technologies. The latter includes innovative materials and device concepts that hold the promise of significantly higher conversion efficiencies and/or much lower costs.

  9. Crystal structure of Bacillus anthracis transpeptidase enzyme CapD.

    SciTech Connect

    Wu, R.; Richter, S.; Zhang, R.; Anderson, V. J.; Missiakas, D.; Joachimiak, A.; Biosciences Division; Univ. of Chicago

    2009-09-04

    Bacillus anthracis elaborates a poly-{gamma}-d-glutamic acid capsule that protects bacilli from phagocytic killing during infection. The enzyme CapD generates amide bonds with peptidoglycan cross-bridges to anchor capsular material within the cell wall envelope of B. anthracis. The capsular biosynthetic pathway is essential for virulence during anthrax infections and can be targeted for anti-infective inhibition with small molecules. Here, we present the crystal structures of the {gamma}-glutamyltranspeptidase CapD with and without {alpha}-l-Glu-l-Glu dipeptide, a non-hydrolyzable analog of poly-{gamma}-d-glutamic acid, in the active site. Purified CapD displays transpeptidation activity in vitro, and its structure reveals an active site broadly accessible for poly-{gamma}-glutamate binding and processing. Using structural and biochemical information, we derive a mechanistic model for CapD catalysis whereby Pro{sup 427}, Gly{sup 428}, and Gly{sup 429} activate the catalytic residue of the enzyme, Thr{sup 352}, and stabilize an oxyanion hole via main chain amide hydrogen bonds.

  10. Structural phase field crystal approach for modeling graphene and other two-dimensional structures

    NASA Astrophysics Data System (ADS)

    Seymour, Matthew; Provatas, Nikolas

    2016-01-01

    This paper introduces a new structural phase field crystal (PFC) type model that expands the PFC methodology to a wider class of structurally complex crystal structures than previously possible. Specifically, our approach allows for stabilization of graphene, as well as its coexistence with a disordered phase. It also preserves the ability to model the usual triangular and square lattices previously reported in two-dimensional (2D) PFC studies. Our approach is guided by the formalism of classical field theory, wherein the free-energy functional is expanded to third order in PFC density correlations. It differs from previous PFC approaches in two main features. First, it utilizes a hard-sphere repulsion to describe two-point correlations. Second, and more important, is that it uses a rotationally invariant three-point correlation function that provides a unified way to control the formation of crystalline structures that can be described by a specific bond angle, such as graphene, triangular, or square symmetries. Our approach retains much of the computational simplicity of previous PFC models and allows for efficient simulation of nucleation and growth of polycrystalline 2D materials. In preparation for future applications, this paper details the mathematical derivation of the model and its equilibrium properties and uses dynamical simulations to demonstrate defect structures produced by the model.

  11. Crystal structure of the co-crystal butyl­paraben–isonicotinamide (1/1)

    PubMed Central

    Bhardwaj, Rajni M.; Yang, Huaiyu; Florence, Alastair J.

    2016-01-01

    The title 1:1 co-crystal, C11H14O3·C6H6N2O [systematic name: butyl 4-hy­droxy­benzoate–isonicotinamide (1/1)], crystallizes with one mol­ecule of butyl­paraben (BPN) and one mol­ecule of isonicotinamide (ISN) in the asymmetric unit. In the crystal, BPN and ISN mol­ecules form hydrogen-bonded (O—H⋯N and N—H⋯O) dimers of paired BPN and ISN mol­ecules. These dimers are further connected to each other via N—H⋯O=C hydrogen bonds, creating ribbons in [011] which further stack along the a axis to form a layered structure with short C⋯C contacts of 3.285 (3) Å. Packing inter­actions within the crystal structure were assessed using PIXEL calculations. PMID:26870584

  12. Growth, characterization, and crystal structure of a new chalcone derivative single crystal

    NASA Astrophysics Data System (ADS)

    Shettigar, Venkataraya; Dharmaprakash, S. M.

    2006-09-01

    A new organic nonlinear optical (NLO) chalcone derivative viz.1- ( 4- methoxyphenyl )-3- (3,4 - dimethoxy phenyl ) - 2 - propene-1-one, has been synthesized by Claisen-Schmidt condensation method. The synthesized compound was purified by repeated recrystallization process. To confirm the identity of the synthesized compound, FTIR spectra was recorded and various functional groups present were identified. NMR spectra were recorded for structural identity and purity confirmation of the synthesized compound. Good quality single crystals were grown by solvent evaporation and slow cooling technique using acetone as solvent. The grown crystals were characterized by UV-Visible , differential thermal analysis and linear refractive index measurement. The hardness of the crystal was determined using Vicker's indentation method. The single crystal structure analysis of the crystal was performed and it is found that the crystal belongs to monoclinic system with space group P2 I. The powder second harmonic generation(SHG)frequency conversion efficiency of the crystal was determined using Nd: YAG laser(λ = 1064nm)and it is 15 times that of Urea.

  13. Three-Dimensional Visualization of Ice Crystals in Frozen Materials by Near-Infrared Imaging Spectroscopy

    NASA Astrophysics Data System (ADS)

    Do, Gab-Soo; Ueno, Shigeaki; Sagara, Yasuyuki; Tsuta, Mizuki; Sugiyama, Junichi

    Micro Slicer Spectral Imaging System (MSSIS) has been applied to observe the three-dimensional(3-D) structure and distribution of ice crystals formed in biological materials. MSSIS is composed of a micro-slicer, near-infrared (NIR) illuminator and spectral imaging system. NIR Spectroscopic analysis using MSSIS confirmed that there are a water absorption band around 965 nm and an ice absorption band around 1025 nm. Spectroscopic images of a frozen agar gel and a piece of raw beef at 1,025 nm were obtained by the MSSIS. These images showed the ice crystals could be clearly distinguished from the other components by the different absorbance. The average area of ice crystals was 6,253 μm2, and the average distances of major and minor axis were 111μm and 62μm respectively. In addition, the 3-D re-constructed image of the ice crystal morphology revealed that they were formed along with the direction of heat transfer. The proposed method provided a novel tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals.

  14. Crystal structure and thermal behaviour of pyridinium styphnate

    PubMed Central

    Muthulakshmi, Selvarasu; Kalaivani, Doraisamyraja

    2015-01-01

    In the crystal structure of the title mol­ecular salt, C5H6N+·C6H2N3O8 − (systematic name: pyridinium 3-hy­droxy-2,4,6-tri­nitro­phenolate), the pyridin­ium cation and the 3-hy­droxy-2,4,6-tri­nitro­phenolate anion are linked through bifurcated N—H⋯(O,O) hydrogen bonds, forming an R 1 2(6) ring motif. The nitro group para with respect to phenolate ion forms an intra­molecular hydrogen bond with the adjacent phenolic –OH group, which results in an S(6) ring motif. The nitro group flanked by the phenolate ion and the phenolic –OH group deviates noticeably from the benzene ring, subtending a dihedral angle of 89.2 (4)°. The other two nitro groups deviate only slightly from the plane of the benzene ring, making dihedral angles of 2.8 (4) and 3.4 (3)°. In the crystal, the 3-hy­droxy-2,4,6-tri­nitro­phenolate anions are linked through O—H⋯O hydrogen bonds, forming chains along [100]. These anionic chains, to which the cations are attached, are linked via C—H⋯O hydrogen bonds, forming a three-dimensional structure. Impact friction sensitivity tests and TGA/DTA studies on the title mol­ecular salt imply that it is an insensitive high-energy-density material. PMID:25878796

  15. On the Use of Dynamical Diffraction Theory To Refine Crystal Structure from Electron Diffraction Data: Application to KLa5O5(VO4)2, a Material with Promising Luminescent Properties.

    PubMed

    Colmont, Marie; Palatinus, Lukas; Huvé, Marielle; Kabbour, Houria; Saitzek, Sébastien; Djelal, Nora; Roussel, Pascal

    2016-03-01

    A new lanthanum oxide, KLa5O5(VO4)2, was synthesized using a flux growth technique that involved solid-state reaction under an air atmosphere at 900 °C. The crystal structure was solved and refined using an innovative approach recently established and based on three-dimensional (3D) electron diffraction data, using precession of the electron beam and then validated against Rietveld refinement and denisty functional theory (DFT) calculations. It crystallizes in a monoclinic unit cell with space group C2/m and has unit cell parameters of a = 20.2282(14) Å, b = 5.8639(4) Å, c = 12.6060(9) Å, and β = 117.64(1)°. Its structure is built on Cresnel-like two-dimensional (2D) units (La5O5) of 4*3 (OLa4) tetrahedra, which run parallel to (001) plane, being surrounded by isolated VO4 tetrahedra. Four isolated vanadate groups create channels that host K(+) ions. Substitution of K(+) cations by another alkali metal is possible, going from lithium to rubidium. Li substitution led to a similar phase with a primitive monoclinic unit cell. A complementary selected area electron diffraction (SAED) study highlighted diffuse streaks associated with stacking faults observed on high-resolution electron microscopy (HREM) images of the lithium compound. Finally, preliminary catalytic tests for ethanol oxidation are reported, as well as luminescence evidence. This paper also describes how solid-state chemists can take advantages of recent progresses in electron crystallography, assisted by DFT calculations and powder X-ray diffraction (PXRD) refinements, to propose new structural types with potential applications to the physicist community. PMID:26901292

  16. Oxide Thermoelectric Materials: A Structure-Property Relationship

    NASA Astrophysics Data System (ADS)

    Nag, Abanti; Shubha, V.

    2014-04-01

    Recent demand for thermoelectric materials for power harvesting from automobile and industrial waste heat requires oxide materials because of their potential advantages over intermetallic alloys in terms of chemical and thermal stability at high temperatures. Achievement of thermoelectric figure of merit equivalent to unity ( ZT ≈ 1) for transition-metal oxides necessitates a second look at the fundamental theory on the basis of the structure-property relationship giving rise to electron correlation accompanied by spin fluctuation. Promising transition-metal oxides based on wide-bandgap semiconductors, perovskite and layered oxides have been studied as potential candidate n- and p-type materials. This paper reviews the correlation between the crystal structure and thermoelectric properties of transition-metal oxides. The crystal-site-dependent electronic configuration and spin degeneracy to control the thermopower and electron-phonon interaction leading to polaron hopping to control electrical conductivity is discussed. Crystal structure tailoring leading to phonon scattering at interfaces and nanograin domains to achieve low thermal conductivity is also highlighted.

  17. Crystal structure of benzobi­cyclon

    PubMed Central

    Kang, Gihaeng; Kim, Jineun; Lim, Hansu; Kim, Tae Ho

    2015-01-01

    In the title compound, C22H19ClO4S2 [systematic name: 3-(2-chloro-4-mesylbenzo­yl)-4-(phenyl­sulfan­yl)bi­cyclo­[3.2.1]oct-3-en-2-one], which is an unclassified herbicide, the dihedral angle between the plane of the phenyl and chloro­benzene rings is 19.9 (2)°. In the crystal, C—H⋯O hydrogen bonds link adjacent mol­ecules, generating two-dimensional networks extending parellel to (011). PMID:26870484

  18. Mechanisms of crystal formation in gout-a structural approach.

    PubMed

    Pascual, Eliseo; Addadi, Lia; Andrés, Mariano; Sivera, Francisca

    2015-12-01

    The mechanisms and sites of monosodium urate monohydrate (MSU) crystal deposition in gout have received little attention from the scientific community to date. Formalin fixation of tissues leads to the dissolution of MSU crystals, resulting in their absence from routinely processed pathological samples and hence neglect. However, modern imaging techniques-especially ultrasonography but also conventional CT and dual-energy CT-reveal that MSU crystals form at the cartilage surface as well as inside tendons and ligaments, often at insertion sites. Tophi comprise round white formations of different sizes surrounded by inflammatory tissue. Studies of fibres recovered from gouty synovial fluid indicate that these fibres are likely to be a primary site of crystal formation by templated nucleation, with crystals deposited parallel to the fibres forming transverse bands. In tophi, two areas can be distinguished: one where crystals are formed on cellular tissues and another consisting predominantly of crystals, where secondary nucleation seems to take place; this organization could explain how tophi can grow rapidly. From these observations based on a crystallographic approach, it seems that initial templated nucleation on structural fibres-probably collagen-followed at some sites by secondary nucleation could explain MSU crystal deposition in gout. PMID:26369610

  19. Optical and structural properties of chalcone NLO single crystals

    NASA Astrophysics Data System (ADS)

    Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Manjunath, H. R.; Karegouda, Prakash; Crasta, Vincent; Sridhar, M. A.

    2011-11-01

    Organic compound (E)-1-(4-methoxyphenyl)-3-(2,3,5-trichlorophenyl)prop-2-en-1-one [MPTCPP] with molecular formula C 16H 11Cl 3O 2 was synthesized using Claisen-Schmidt condensation reaction method. 1H NMR spectra was recorded to identify the various functional groups present in the compound and confirm the chemical structure. The single crystals were grown using slow evaporation solution growth technique. The UV-Visible spectrum study reveals that the crystal is transparent in the entire visible region and the absorption is observed at 364 nm. The Kurtz powder second harmonic generation (SHG) test shows that the MPTCPP is NLO active and its SHG efficiency is three times that of urea. Single crystal XRD study shows that the compound crystallizes in the monoclinic system with a space group Cc. The corresponding lattice parameters of the crystal are a = 28.215(5) Å, b = 3.9740(4) Å, c = 16.178(3) Å and V = 1503.0(4) Å 3. The micro hardness test was carried out and the work hardening coefficient value ( n) of the crystal was found to be 1.48. This indicates that the crystal is hard and is suitable for device application. The thermal study reveals that the thermal stability of the crystal is good.

  20. Material Selection for Cryogenic Support Structures

    NASA Astrophysics Data System (ADS)

    Kramer, Erik; Kellaris, Nicholas; Daal, Miguel; Sadoulet, Bernard; Golwala, Sunil; Hollister, Matthew

    2014-09-01

    Design specifications for the support structures of low temperature instrumentation often call for low thermal conductivity between temperature stages, high stiffness, and specific load bearing capabilities. While overall geometric design plays an important role in both overall stiffness and heat conduction between stages, material selection can affect a structure's properties significantly. In this contribution, we suggest and compare several alternative materials to the current standard materials for building cryogenic support structures.

  1. Fabrication of three-dimensional photonic crystal structures containing an active nonlinear optical chromophore

    NASA Astrophysics Data System (ADS)

    Farsari, M.; Ovsianikov, A.; Vamvakaki, M.; Sakellari, I.; Gray, D.; Chichkov, B. N.; Fotakis, C.

    2008-10-01

    Direct laser writing by two-photon polymerization of photosensitive materials has emerged as a very promising technique for rapid and flexible fabrication of photonic crystals. In this work, a photosensitive silica sol-gel containing the nonlinear optical chromophore Disperse Red 1 is synthesized, and the two-photon polymerization technique is employed to fabricate three-dimensional photonic crystals with stop-gaps in the near-infrared. The composite material exhibits minimal shrinkage during photopolymerization, eliminating the need for shrinkage compensation or the fabrication of support structures.

  2. Salt transport and crystallization in porous building materials.

    PubMed

    Pel, L; Huinink, H; Kopinga, K

    2003-01-01

    Salt weathering is a major cause of deterioration of porous building materials. To obtain information about the mechanisms underlying these damage processes we have studied the moisture and ion transport. We measured the time evolution of NaCl saturated samples of fired-clay brick during one-sided drying using Nuclear Magnetic Resonance. The moisture content and amount of dissolved Na ions could be measured quantitatively as a function of position. The NaCl concentration profiles obtained from these data reflect the competition between advection to the surface and redistribution by diffusion. By representing the measured moisture and NaCl profiles in an efflorescence pathway diagram (EPD) also the crystallization can be taken into account. PMID:12850725

  3. The different conformations and crystal structures of dihydroergocristine

    NASA Astrophysics Data System (ADS)

    Mönch, B.; Kraus, W.; Köppen, R.; Emmerling, F.

    2016-02-01

    The identification of different forms of dihydroergocristine (DHEC) was carried out by crystallization from different organic solvents. DHEC was identified as potential template for molecularly imprinted polymers (MIPs) for the epimeric specific analysis of ergot alkaloids (EAs) in food. DHEC was crystallized from different solvents in order to mimic the typical MIP synthesis conditions. Four new solvatomorphs of DHEC were obtained. All solvatomorphs contain a water molecule in the crystal structure, whereas three compounds contain an additional solvent molecule. Based on the conformation of DHEC a comparison with typical EA molecules was possible. The analysis showed that DHEC is a suitable template for MIPs for EAs.

  4. Elastic octopoles and colloidal structures in nematic liquid crystals.

    PubMed

    Chernyshuk, S B; Tovkach, O M; Lev, B I

    2014-03-01

    We propose a simple theoretical model which explains the formation of dipolar two- (2D) and three-dimensional (3D) colloidal structures in nematic liquid crystals. The colloidal particles are treated as effective hard spheres interacting via their elastic dipole, quadrupole, and octopole moments. It is shown that the octopole moment plays an important role in the formation of 2D and 3D nematic colloidal crystals. We generalize this assumption to the case of an external electric field and theoretically explain a giant electrostriction effect in 3D crystals observed recently. PMID:24730862

  5. Broadband single-polarization single-mode photonic crystal fibers with three different background materials.

    PubMed

    Li, Hui; Li, Shu-guang; Li, Jian-She; Zhang, Wan; An, Guo-Wen

    2015-04-01

    A modified structure of single-polarization single-mode (SPSM) photonic crystal fiber (PCF) with different background materials is presented and analyzed by using the full-vector finite-element method. Simulation results confirmed that the proposed PCF can realize low-loss SPSM on three wavebands with the same structure and different background materials. The wavebands are 1.46-1.60 μm for silica-based fiber, 1.97-2.3 μm for lead silicate glass fiber, and 3.16-3.58 μm for chalcogenide glass fiber. For three PCFs with different background materials, only the slow-axis mode exists and the confinement loss is less than 100 dB/m in the SPSM wavebands. PMID:25967199

  6. Crystal structure of a theta-class glutathione transferase.

    PubMed Central

    Wilce, M C; Board, P G; Feil, S C; Parker, M W

    1995-01-01

    Glutathione S-transferases (GSTs) are a family of enzymes involved in the cellular detoxification of xenotoxins. Cytosolic GSTs have been grouped into four evolutionary classes for which there are representative crystal structures of three of them. Here we report the first crystal structure of a theta-class GST. So far, all available GST crystal structures suggest that a strictly conserved tyrosine near the N-terminus plays a critical role in the reaction mechanism and such a role has been convincingly demonstrated by site-directed mutagenesis. Surprisingly, the equivalent residue in the theta-class structure is not in the active site, but its role appears to have been replaced by either a nearby serine or by another tyrosine residue located in the C-terminal domain of the enzyme. Images PMID:7774571

  7. Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals

    DOEpatents

    Todt, Volker; Miller, Dean J.; Shi, Donglu; Sengupta, Suvankar

    1998-01-01

    A method of fabricating bulk YBa.sub.2 Cu.sub.3 O.sub.x where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa.sub.2 Cu.sub.3 O.sub.x are heated in the presence of a Nd.sub.1+x Ba.sub.2-x Cu.sub.3 O.sub.y seed crystal to a temperature sufficient to form a liquid phase in the YBa.sub.2 Cu.sub.3 O.sub.x while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa.sub.2 Cu.sub.3 O.sub.x material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material.

  8. Bulk Crystal Growth of Nonlinear Optical Organic Materials Using Inverted Vertical Gradient Freeze Method

    NASA Technical Reports Server (NTRS)

    Choi, J.; Cruz, Magda; Metzl, R.; Wang, W. S.; Aggarwal, M. D.; Penn, Benjamin G.; Frazier, Donald O.

    1998-01-01

    A new process for producing large bulk single crystals of benzil (C6H5COCOC6H5) is reported in this paper. Good quality crystals have been successfully grown using this approach to crystal growth. This method seems to be very promising for other thermally stable NLO organic materials also. The entire contents vycor crucible 1.5 inch in diameter and 2 inch deep was converted to single crystal. Purity of the starting growth material is also an important factor in the final quality of the grown crystals. The entire crystal can be very easily taken out of the crucible by simple maneuvering. Initial characterization of the grown crystals indicated that the crystals are as good as other crystals grown by conventional Bridgman Stockbarger technique.

  9. Structure of ice crystallized from supercooled water

    PubMed Central

    Malkin, Tamsin L.; Murray, Benjamin J.; Brukhno, Andrey V.; Anwar, Jamshed; Salzmann, Christoph G.

    2012-01-01

    The freezing of water to ice is fundamentally important to fields as diverse as cloud formation to cryopreservation. At ambient conditions, ice is considered to exist in two crystalline forms: stable hexagonal ice and metastable cubic ice. Using X-ray diffraction data and Monte Carlo simulations, we show that ice that crystallizes homogeneously from supercooled water is neither of these phases. The resulting ice is disordered in one dimension and therefore possesses neither cubic nor hexagonal symmetry and is instead composed of randomly stacked layers of cubic and hexagonal sequences. We refer to this ice as stacking-disordered ice I. Stacking disorder and stacking faults have been reported earlier for metastable ice I, but only for ice crystallizing in mesopores and in samples recrystallized from high-pressure ice phases rather than in water droplets. Review of the literature reveals that almost all ice that has been identified as cubic ice in previous diffraction studies and generated in a variety of ways was most likely stacking-disordered ice I with varying degrees of stacking disorder. These findings highlight the need to reevaluate the physical and thermodynamic properties of this metastable ice as a function of the nature and extent of stacking disorder using well-characterized samples. PMID:22232652

  10. Boron-oxygen polyanion in the crystal structure of tunellite

    USGS Publications Warehouse

    Clark, J.R.

    1963-01-01

    The crystal structure of tunellite, SrO??3B2O 3??4H2O, with infinite sheets of composition n[B6O9(OH)2]2-, has cations and water molecules in the spaces within the sheets. Adjacent sheets are held together by hydrogen bonding through the water molecules. The boron-oxygen polyanions provide the first example in hydrated borate crystals of one oxygen linked to three borons.

  11. Growth and structure of a new photonic crystal: Chlorine substituted chalcone

    SciTech Connect

    Sarveshwara, H. P. Menezes, Anthoni Praveen; Raghavendra, S.; Dharmaprakash, S. M.; A, Jayarama

    2015-06-24

    A new organic photonic material 3-(2, 4-dichlorophenyl)-1-(2,5-dimethylthiophen-3-yl)propan-1-one(DMTP) has been synthesized and crystallised in acetone solution. The functional groups present in the new material were identified by FTIR spectroscopy. The material is optically transparent in the wavelength range of 400–1100 nm. The crystal structure of DMTP was determined by single crystal X-ray diffraction. The title compound crystallizes in monoclinic system with a centrosymmetric space group P2{sub 1}/c. The Z-scan study revealed that the optical limiting property exhibited by the DMTP molecule is based on the reverse saturable absorption phenomena.

  12. Structure and local structure of perovskite based materials

    NASA Astrophysics Data System (ADS)

    Rossell Abrodos, Marta Dacil

    Perovskites, with general formula ABX3, where A and B are cations and X is an anion, form a very important class of inorganic crystals whose physical properties are extensively used in many technological applications. The basic, so-called aristotype structure, consists of an infinite array of corner-linked anion octahedra, with the A cations in the spaces between the octahedra and a B cation at the center of each octahedron. Interesting physical properties are often related to the flexibility of the perovskite structure to deform or to form non-stoichiometric compositions. In this thesis, four perovskite-related systems are studied. Transmission electron microscopy (TEM) is of prime interest to analyze the influence of the structure and microstructure on the physical properties of these systems. (1) The anion-deficient Sr4Fe6O12+delta (delta < 1) derivatives. These materials are mixed conducting oxides with high oxygen and electronic conductivity. A complete characterization of the structure of these anion-deficient compounds is deduced from electron diffraction and high-resolution TEM. The presence of anion vacancies in the Sr4Fe6O12+delta (delta < 1) structure is suggested to have an influence on the transport properties. (2) The CaRMnSnO6 (R = La, Pr, Nd, Sm-Dy) double perovskites. A random distribution of the Ca and R cations over the A positions and Mn and Sn cations over the B positions is found. Due to a random distribution of the Mn 3+ and Sn4+ cations, a spin glass behavior was found for CaLaMnSnO6. (3) The K3AlF6 elpasolite-type (or ordered double perovskite) structure. This compound is of high technological importance since it is a basic component of the melts for low temperature electrolysis in aluminum smelting. A sequence of phase transitions at different temperatures in K3AlF6 along with the data on unit cell dimensions and space symmetry of three major polymorphs is reported. (4) Ca 2Fe2O5 brownmillerite-type thin films deposited on three different perovskite-type substrates. TEM allows to demonstrate that minor variations in the lattice mismatch of the Ca2Fe2O 5 film and the three different substrates strongly determine the growth direction of the films. Thus, misfit stress clearly influences the structure and the microstructure of epitaxial films.

  13. Structural and electronic properties of Diisopropylammonium bromide molecular ferroelectric crystal

    NASA Astrophysics Data System (ADS)

    Alsaad, A.; Qattan, I. A.; Ahmad, A. A.; Al-Aqtash, N.; Sabirianov, R. F.

    2015-10-01

    We report the results of ab-initio calculations based on Generalized Gradient Approximation (GGA) and hybrid functional (HSE06) of electronic band structure, density of states and partial density of states to get a deep insight into structural and electronic properties of P21 ferroelectric phase of Diisopropylammonium Bromide molecular crystal (DIPAB). We found that the optical band gap of the polar phase of DIPAB is ∼ 5 eV confirming it as a good dielectric. Examination of the density of states and partial density of states reveal that the valence band maximum is mainly composed of bromine 4p orbitals and the conduction band minimum is dominated by carbon 2p, carbon 2s, and nitrogen 2s orbitals. A unique aspect of P21 ferroelectric phase is the permanent dipole within the material. We found that P21 DIPAB has a spontaneous polarization of 22.64 consistent with recent findings which make it good candidate for the creation of ferroelectric tunneling junctions (FTJs) which have the potential to be used as memory devices.

  14. Modulated structures in electroconvection in nematic liquid crystals.

    PubMed

    Komineas, S; Zhao, H; Kramer, L

    2003-03-01

    Motivated by experiments in electroconvection in nematic liquid crystals with homeotropic alignment we study the coupled amplitude equations describing the formation of a stationary roll pattern in the presence of a weakly damped mode that breaks isotropy. The equations can be generalized to describe the planarly aligned case if the orienting effect of the boundaries is small, which can be achieved by a destabilizing magnetic field. The slow mode represents the in-plane director at the center of the cell. The simplest uniform states are normal rolls, which may undergo a pitchfork bifurcation to abnormal rolls with a misaligned in-plane director. We present a new class of defect-free solutions with spatial modulations perpendicular to the rolls. In a parameter range where the zigzag instability is not relevant these solutions are stable attractors, as observed in experiments. We also present two-dimensionally modulated states with and without defects which result from the destabilization of the one-dimensionally modulated structures. Finally, for no (or very small) damping, and away from the rotationally symmetric case, we find static chevrons made up of a periodic arrangement of defect chains (or bands of defects) separating homogeneous regions of oblique rolls with very small amplitude. These states may provide a model for a class of poorly understood stationary structures observed in various highly conducting materials ("prechevrons" or "broad domains"). PMID:12689082

  15. Isolation, crystallization and crystal structure determination of bovine kidney Na(+),K(+)-ATPase.

    PubMed

    Gregersen, Jonas Lindholt; Mattle, Daniel; Fedosova, Natalya U; Nissen, Poul; Reinhard, Linda

    2016-04-01

    Na(+),K(+)-ATPase is responsible for the transport of Na(+) and K(+) across the plasma membrane in animal cells, thereby sustaining vital electrochemical gradients that energize channels and secondary transporters. The crystal structure of Na(+),K(+)-ATPase has previously been elucidated using the enzyme from native sources such as porcine kidney and shark rectal gland. Here, the isolation, crystallization and first structure determination of bovine kidney Na(+),K(+)-ATPase in a high-affinity E2-BeF3(-)-ouabain complex with bound magnesium are described. Crystals belonging to the orthorhombic space group C2221 with one molecule in the asymmetric unit exhibited anisotropic diffraction to a resolution of 3.7 Å with full completeness to a resolution of 4.2 Å. The structure was determined by molecular replacement, revealing unbiased electron-density features for bound BeF3(-), ouabain and Mg(2+) ions. PMID:27050261

  16. Crystal structure of ammonia dihydrate II

    NASA Astrophysics Data System (ADS)

    Griffiths, Gareth I. G.; Fortes, A. Dominic; Pickard, Chris J.; Needs, R. J.

    2012-05-01

    We have used density-functional-theory (DFT) methods together with a structure searching algorithm to make an experimentally constrained prediction of the structure of ammonia dihydrate II (ADH-II). The DFT structure is in good agreement with neutron diffraction data and verifies the prediction. The structure consists of the same basic structural elements as ADH-I, with a modest alteration to the packing, but a considerable reduction in volume. The phase diagram of the known ADH and ammonia monohydrate + water-ice structures is calculated with the Perdew-Burke-Ernzerhof density functional, and the effects of a semi-empirical dispersion corrected functional are investigated. The results of our DFT calculations of the finite-pressure elastic constants of ADH-II are compared with the available experimental data for the elastic strain coefficients.

  17. Crystal Structures and Band Structures of Acene Chalcogenides: Their Application for OFET.

    NASA Astrophysics Data System (ADS)

    Ugawa, A.

    2005-03-01

    We have systematically studied acene chalcogenides as active channel materials for Organic Field Effect Transistor (OFET). The molecules have a common structural feature which is of great advantage for carrier channel: chalcogen atoms are located at outside of molecule so that larger orbitals of chalcogen atoms would intensify intermolecular interactions not only for the molecular stacking direction but also for the inter-stacking directions. We then expect that the conduction channels would become more isotropic and the effective mass of the carriers would become lighter compared to the case of aromatic hydrocarbons. The materials we have surveyed are as follows: Hexathiopentacene (HTP), Tetrathiotetracene (TTT), Hexathioanthracene (HTA), Tetrathioanthracene (TTA), Benzo[1,2-c;3,4-c';5,6-c'']tris[1,2]dithiole-1,4,7-trithione (abbreviated as C9S9, which is its chemical formula), and some selenium analogues. The first-principle band structure calculations based on the crystal structures determined by x-ray analysis reveal that the materials have an anisotropic 2-D HOMO band with an effective mass of 1.1me for TSeA, 1.3me for HTA, 1.4me for TTT, respectively. HTP is proved to have a 1-D HOMO band with m*=2.5me in spite of 2-D structural feature. It is interesting that C9S9 has an isotropic 3-D HOMO band with m*=0.68me, properties which are suitable for OFET channel.

  18. Combined crystal structure prediction and high-pressure crystallization in rational pharmaceutical polymorph screening

    NASA Astrophysics Data System (ADS)

    Neumann, M. A.; van de Streek, J.; Fabbiani, F. P. A.; Hidber, P.; Grassmann, O.

    2015-07-01

    Organic molecules, such as pharmaceuticals, agro-chemicals and pigments, frequently form several crystal polymorphs with different physicochemical properties. Finding polymorphs has long been a purely experimental game of trial-and-error. Here we utilize in silico polymorph screening in combination with rationally planned crystallization experiments to study the polymorphism of the pharmaceutical compound Dalcetrapib, with 10 torsional degrees of freedom one of the most flexible molecules ever studied computationally. The experimental crystal polymorphs are found at the bottom of the calculated lattice energy landscape, and two predicted structures are identified as candidates for a missing, thermodynamically more stable polymorph. Pressure-dependent stability calculations suggested high pressure as a means to bring these polymorphs into existence. Subsequently, one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib.

  19. Ytterbium- and neodymium-doped vanadate laser hose crystals having the apatite crystal structure

    DOEpatents

    Payne, S.A.; Kway, W.L.; DeLoach, L.D.; Krupke, W.F.; Chai, B.H.T.

    1994-08-23

    Yb[sup 3+] and Nd[sup 3+] doped Sr[sub 5](VO[sub 4])[sub 3]F crystals serve as useful infrared laser media that exhibit low thresholds of oscillation and high slope efficiencies, and can be grown with high optical quality. These laser media possess unusually high absorption and emission cross sections, which provide the crystals with the ability to generate greater gain for a given amount of pump power. Many related crystals such as Sr[sub 5](VO[sub 4])[sub 3]F crystals doped with other rare earths, transition metals, or actinides, as well as the many structural analogs of Sr[sub 5](VO[sub 4])[sub 3]F, where the Sr[sup 2+] and F[sup [minus

  20. Ytterbium- and neodymium-doped vanadate laser hose crystals having the apatite crystal structure

    DOEpatents

    Payne, Stephen A.; Kway, Wayne L.; DeLoach, Laura D.; Krupke, William F.; Chai, Bruce H. T.

    1994-01-01

    Yb.sup.3+ and Nd.sup.3+ doped Sr.sub.5 (VO.sub.4).sub.3 F crystals serve as useful infrared laser media that exhibit low thresholds of oscillation and high slope efficiencies, and can be grown with high optical quality. These laser media possess unusually high absorption and emission cross sections, which provide the crystals with the ability to generate greater gain for a given amount of pump power. Many related crystals such as Sr.sub.5 (VO.sub.4).sub.3 F crystals doped with other rare earths, transition metals, or actinides, as well as the many structural analogs of Sr.sub.5 (VO.sub.4).sub.3 F, where the Sr.sup.2+ and F.sup.- ions are replaced by related chemical species, have similar properties.

  1. How to predict very large and complex crystal structures

    NASA Astrophysics Data System (ADS)

    Lyakhov, Andriy O.; Oganov, Artem R.; Valle, Mario

    2010-09-01

    Evolutionary crystal structure prediction proved to be a powerful approach in discovering new materials. Certain limitations are encountered for systems with a large number of degrees of freedom ("large systems") and complex energy landscapes ("complex systems"). We explore the nature of these limitations and address them with a number of newly developed tools. For large systems a major problem is the lack of diversity: any randomly produced population consists predominantly of high-energy disordered structures, offering virtually no routes toward the ordered ground state. We offer two solutions: first, modified variation operators that favor atoms with higher local order (a function we introduce here), and, second, construction of the first generation non-randomly, using pseudo-subcells with, in general, fractional atomic occupancies. This enhances order and diversity and improves energies of the structures. We introduce an additional variation operator, coordinate mutation, which applies preferentially to low-order ("badly placed") atoms. Biasing other variation operators by local order is also found to produce improved results. One promising version of coordinate mutation, explored here, displaces atoms along the eigenvector of the lowest-frequency vibrational mode. For complex energy landscapes, the key problem is the possible existence of several energy funnels - in this situation it is possible to get trapped in one funnel (not necessarily containing the ground state). To address this problem, we develop an algorithm incorporating the ideas of abstract "distance" between structures. These new ingredients improve the performance of the evolutionary algorithm USPEX, in terms of efficiency and reliability, for large and complex systems.

  2. Study of structural and optical properties of YAG and Nd:YAG single crystals

    SciTech Connect

    Kostić, S.; Lazarević, Z.Ž.; Radojević, V.; Milutinović, A.; Romčević, M.; Romčević, N.Ž.; Valčić, A.

    2015-03-15

    Highlights: • Transparent YAG and pale pink Nd:YAG single crystals were produced by the Czochralski technique. • Growth mechanisms and shape of the liquid/solid interface and incorporation of Nd{sup 3+} were studied. • The structure of the crystals was investigated by X-ray diffraction, Raman and IR spectroscopy. • The 15 Raman and 17 IR modes were observed. • The obtained YAG and Nd:YAG single crystals were without core and of good optical quality. - Abstract: Yttrium aluminum garnet (YAG, Y{sub 3}Al{sub 5}O{sub 12}) and yttrium aluminum garnet doped with neodymium (Nd:YAG) single crystals were grown by the Czochralski technique. The critical diameter and the critical rate of rotation were calculated. Suitable polishing and etching solutions were determined. As a result of our experiments, the transparent YAG and pale pink Nd:YAG single crystals were produced. The obtained crystals were studied by X-ray diffraction, Raman and IR spectroscopy. The crystal structure was confirmed by XRD. The 15 Raman and 17 IR modes were observed. The Raman and IR spectroscopy results are in accordance with X-ray diffraction analysis. The obtained YAG and Nd:YAG single crystals were without core and of good optical quality. The absence of a core was confirmed by viewing polished crystal slices. Also, it is important to emphasize that the obtained Nd:YAG single crystal has a concentration of 0.8 wt.% Nd{sup 3+} that is characteristic for laser materials.

  3. Materials and structures/ACEE

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Light weight composites made from graphite fibers, glass, or man made materials held in an epoxy matrix, and their application to airframe design are reviewed. The Aircraft Energy Efficiency program is discussed. Characteristics of composites, acceptable risks, building parts and confidence, and aeroelastic tailoring are considered.

  4. Crystal structures of gold, silver, and sodium chalcogenides: Sphenoidal interpretation

    SciTech Connect

    Bakakin, V. V.

    2011-11-15

    The crystal structures of 13 chalcogenides of Na, Au(I), and Ag(I) in the Na{sub 2-n}(Au,Ag){sub n}(S,Se,Te) series, where 0 {<=} n {<=} 2, are interpreted from unified positions based on the sphenoidal representation. Its essence is in the consideration of the entire crystal space (with packing X atoms in the framework of close-packing, body-centered, or hybrid schemes) as a set of elementary space units (sphenoids). Unified one-dimensional associates of sphenoids, the so-called basic rods, with sets of possible atomic positions in them are selected for all structures. The mutual effect of the dimensional and stoichiometric ratios of all components on the features of filling rod positions is analyzed. New possibilities in the crystallochemical and crystal-geometry analysis of inorganic compounds whose structures are characterized by a relatively uniform distribution of atoms are demonstrated by the example of chalcogenides.

  5. Compact Couplers for Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, Benjamin; Lin, M.C.; Schwartz, Brian; Byer, Robert; McGuinness, Christopher; Colby, Eric; England, Robert; Noble, Robert; Spencer, James; /SLAC

    2012-07-02

    Photonic crystal waveguides are promising candidates for laser-driven accelerator structures because of their ability to confine a speed-of-light mode in an all-dielectric structure. Because of the difference between the group velocity of the waveguide mode and the particle bunch velocity, fields must be coupled into the accelerating waveguide at frequent intervals. Therefore efficient, compact couplers are critical to overall accelerator efficiency. We present designs and simulations of high-efficiency coupling to the accelerating mode in a three-dimensional photonic crystal waveguide from a waveguide adjoining it at 90{sup o}. We discuss details of the computation and the resulting transmission. We include some background on the accelerator structure and photonic crystal-based optical acceleration in general.

  6. Development of Measurement System for Three-Dimensional Structure of Ice Crystals in Raw Beef Samples

    NASA Astrophysics Data System (ADS)

    Do, Gab-Soo; Sagara, Yasuyuki; Tabata, Mizuho; Kudoh, Ken-Ichi; Higuchi, Toshiro

    Micro-Slicer Image Processing System (MSIPS) has been developed for measuring the three-dimensional(3-D) structure and distribution of ice crystals formed in biological materials. The system has functions to reconstruct the 3-D image based on the image data of exposed cross sections obtained by multi-slicing of a frozen sample with the minimum thickness of 1?m and to display the internal structure as well as an arbitrary cross section of the sample choosing observation angles. The effects of freezing conditions on the morphology and distribl1tion of ice crystals were demonstrated quantitatively from the observations of raw beef stained by fluorescent indicator. The 3-D image of the sample demonstrated that the growth of ice columns was restricted by the intrinsic structure of muscle fibers. The proposed method provided a new tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals.

  7. Crystal structure of simple metals at high pressures

    SciTech Connect

    Degtyareva, Olga

    2010-10-22

    The effects of pressure on the crystal structure of simple (or sp-) elements are analysed in terms of changes in coordination number, packing density, and interatomic distances, and general rules are established. In the polyvalent elements from groups 14-17, the covalently bonded structures tend to transform to metallic phases with a gradual increase in coordination number and packing density, a behaviour normally expected under pressure. Group 1 and 2 metallic elements, however, show a reverse trend towards structures with low packing density due to intricate changes in their electronic structure. Complex crystal structures such as host-guest and incommensurately modulated structures found in these elements are given special attention in this review in an attempt to determine their role in the observed phase-transition sequences.

  8. Crystal/defect structures and phase stability in Ba hexaaluminates

    SciTech Connect

    Park, J.G.; Cormack, A.N.

    1996-02-01

    Computer atomistic simulation techniques have been used to investigate the crystal chemistry, defect structures, and phase relationships in Ba hexaaluminates. Equilibrated lattice energies for several structural models, proposed to explain the nonstoichiometries of Ba hexaaluminates, have been calculated and suggest that Ba hexaaluminate in the magnetoplumbite structure is unstable compared to nonstoichiometric {beta}-alumina type structures. The lack of superstructure in phase is explained by the very small difference in lattice energies between the structures in which the defect complex of this phase is differently arranged. The author`s calculations also suggest that the most appropriate structural model for phase II is one which includes both triple Reidinger defects and barium interstitials inside the spinel blocks from the viewpoints of both energy and crystal symmetry.

  9. Crystal/Defect Structures and Phase Stability in Ba Hexaaluminates

    NASA Astrophysics Data System (ADS)

    Park, Jae-Gwan; Cormack, A. N.

    1996-02-01

    Computer atomistic simulation techniques have been used to investigate the crystal chemistry, defect structures, and phase relationships in Ba hexaaluminates. Equilibrated lattice energies for several structural models, proposed to explain the nonstoichiometries of Ba hexaaluminates, have been calculated and suggest that Ba hexaaluminate in the magnetoplumbite structure is unstable compared to nonstoichiometric β-alumina type structures. The lack of superstructure in phase I is explained by the very small difference in lattice energies between the structures in which the defect complex of this phase is differently arranged. Our calculations also suggest that the most appropriate structural model for phase II is one which includes both triple Reidinger defects and barium interstitials inside the spinel blocks from the viewpoint of both energy and crystal symmetry.

  10. Managing Training Materials with Structured Text Design.

    ERIC Educational Resources Information Center

    Streit, Les D.; And Others

    1986-01-01

    Describes characteristics of structured text design; benefits of its use in training; benefits for developers of training materials and steps in preparing training materials. A case study illustrating how the structured text design process solved the sales training needs of the Mercedes-Benz Truck Company is presented. (MBR)

  11. Prediction of incommensurate crystal structure in Ca at high pressure.

    PubMed

    Arapan, Sergiu; Mao, Ho-Kwang; Ahuja, Rajeev

    2008-12-30

    Ca shows an interesting high-pressure phase transformation sequence, but, despite similar physical properties at high pressure and affinity in the electronic structure with its neighbors in the periodic table, no complex phase has been identified for Ca so far. We predict an incommensurate high-pressure phase of Ca from first principle calculations and describe a procedure of estimating incommensurate structure parameters by means of electronic structure calculations for periodic crystals. Thus, by using the ab initio technique for periodic structures, one can get not only reliable information about the electronic structure and structural parameters of an incommensurate phase, but also identify and predict such phases in new elements. PMID:19104037

  12. The crystal structure of GXGD membrane protease FlaK

    SciTech Connect

    Hu, Jian; Xue, Yi; Lee, Sangwon; Ha, Ya

    2011-09-20

    The GXGD proteases are polytopic membrane proteins with catalytic activities against membrane-spanning substrates that require a pair of aspartyl residues. Representative members of the family include preflagellin peptidase, type 4 prepilin peptidase, presenilin and signal peptide peptidase. Many GXGD proteases are important in medicine. For example, type 4 prepilin peptidase may contribute to bacterial pathogenesis, and mutations in presenilin are associated with Alzheimer's disease. As yet, there is no atomic-resolution structure in this protease family. Here we report the crystal structure of FlaK, a preflagellin peptidase from Methanococcus maripaludis, solved at 3.6 {angstrom} resolution. The structure contains six transmembrane helices. The GXGD motif and a short transmembrane helix, helix 4, are positioned at the centre, surrounded by other transmembrane helices. The crystal structure indicates that the protease must undergo conformational changes to bring the GXGD motif and a second essential aspartyl residue from transmembrane helix 1 into close proximity for catalysis. A comparison of the crystal structure with models of presenilin derived from biochemical analysis reveals three common transmembrane segments that are similarly arranged around the active site. This observation reinforces the idea that the prokaryotic and human proteases are evolutionarily related. The crystal structure presented here provides a framework for understanding the mechanism of the GXGD proteases, and may facilitate the rational design of inhibitors that target specific members of the family.

  13. The Crystal Structure of GXGD Membrane Protease FlaK

    SciTech Connect

    J Hu; Y Xue; S Lee; Y Ha

    2011-12-31

    The GXGD proteases are polytopic membrane proteins with catalytic activities against membrane-spanning substrates that require a pair of aspartyl residues. Representative members of the family include preflagellin peptidase, type 4 prepilin peptidase, presenilin and signal peptide peptidase. Many GXGD proteases are important in medicine. For example, type 4 prepilin peptidase may contribute to bacterial pathogenesis, and mutations in presenilin are associated with Alzheimer's disease. As yet, there is no atomic-resolution structure in this protease family. Here we report the crystal structure of FlaK, a preflagellin peptidase from Methanococcus maripaludis, solved at 3.6 {angstrom} resolution. The structure contains six transmembrane helices. The GXGD motif and a short transmembrane helix, helix 4, are positioned at the centre, surrounded by other transmembrane helices. The crystal structure indicates that the protease must undergo conformational changes to bring the GXGD motif and a second essential aspartyl residue from transmembrane helix 1 into close proximity for catalysis. A comparison of the crystal structure with models of presenilin derived from biochemical analysis reveals three common transmembrane segments that are similarly arranged around the active site. This observation reinforces the idea that the prokaryotic and human proteases are evolutionarily related. The crystal structure presented here provides a framework for understanding the mechanism of the GXGD proteases, and may facilitate the rational design of inhibitors that target specific members of the family.

  14. Utilization of Protein Crystal Structures in Industry

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kohki

    In industry, protein crystallography is used in mainly two technologies. One is structure-based drug design, and the other is structure-based enzyme engineering. Some successful cases together with recent advances are presented in this article. The cases include the development of an anti-influenza drug, and the introduction of engineered acid phosphatase to the manufacturing process of nucleotides used as umami seasoning.

  15. Fabrication of large binary colloidal crystals with a NaCl structure

    PubMed Central

    Vermolen, E. C. M.; Kuijk, A.; Filion, L. C.; Hermes, M.; Thijssen, J. H. J.; Dijkstra, M.; van Blaaderen, A.

    2009-01-01

    Binary colloidal crystals offer great potential for tuning material properties for applications in, for example, photonics, semiconductors and spintronics, because they allow the positioning of particles with quite different characteristics on one lattice. For micrometer-sized colloids, it is believed that gravity and slow crystallization rates hinder the formation of high-quality binary crystals. Here, we present methods for growing binary colloidal crystals with a NaCl structure from relatively heavy, hard-sphere-like, micrometer-sized silica particles by exploring the following external fields: electric, gravitational, and dielectrophoretic fields and a structured surface (colloidal epitaxy). Our simulations show that the free-energy difference between the NaCl and NiAs structures, which differ in their stacking of the hexagonal planes of the larger spheres, is very small (≈0.002 kBT). However, we demonstrate that the fcc stacking of the large spheres, which is crucial for obtaining the pure NaCl structure, can be favored by using a combination of the above-mentioned external fields. In this way, we have successfully fabricated large, 3D, oriented single crystals having a NaCl structure without stacking disorder. PMID:19805259

  16. New crystal structural families of lanthanide chloride alcohol/water complexes

    SciTech Connect

    Chakoumakos, Bryan C; Custelcean, Radu; Ramey, Joanne Oxendine; Boatner, Lynn A

    2012-01-01

    The exploration of lanthanide chloride compounds as possible scintillation materials for gamma ray and neutron detection has led to the discovery of several new families of crystal structures with the general formula LnCl3(CH3OH)x(H2O)y. The specific crystal structure depends on the water/methanol content and lanthanide ion. The coordination of the light (large) lanthanides is the typical value of 8 and reduces to 7 for the heavier (small) lanthanides. The binding energy of water versus alcohol ligands is comparable, so that if water is present in the system, it is typically incorporated as a ligand in the crystal. In these crystals, the molecular adducts occur as monomers, dimers, and dichloro-bridged chains. These, in turn, form 3-D frameworks through H-bonds to the Cl atoms. Other distinct crystal structures are predicted, given the volume changes due to the lanthanide contraction, the water content of the crystal growth solutions, and the specific halide.

  17. Structures and materials technology for hypersonic aerospacecraft

    NASA Technical Reports Server (NTRS)

    Mccomb, Harvey G., Jr.; Murrow, Harold N.; Card, Michael F.

    1990-01-01

    Major considerations in structural design of a transatmospheric aerospacecraft are discussed. The general direction of progress in structures and materials technology is indicated, and technical areas in structures and materials where further research and development is necessary are indicated. Various structural concepts under study and materials which appear to be most applicable are discussed. Structural design criteria are discussed with particular attention to the factor-of-safety approach and the probabilistic approach. Structural certification requirements for the aerospacecraft are discussed. The kinds of analyses and tests which would be required to certify the structural integrity, safety, and durability of the aerospacecraft are discussed, and the type of test facility needed to perform structural certification tests is identified.

  18. Crystal chemistry and structure refinement of five hydrated calcium borates

    USGS Publications Warehouse

    Clark, J.R.; Appleman, D.E.; Christ, C.L.

    1964-01-01

    The crystal structures of the five known members of the series Ca2B6O11??xH2O (x = 1, 5, 5, 7, 9, and 13) have been refined by full-matrix least-squares techniques, yielding bond distances and angles with standard errors of less than 0??01 A?? and 0??5??, respectively. The results illustrate the crystal chemical principles that govern the structures of hydrated borate compounds. The importance of hydrogen bonding in the ferroelectric transition of colemanite is confirmed by more accurate proton assignments. ?? 1964.

  19. Rhombohedral cubic semiconductor materials on trigonal substrate with single crystal properties and devices based on such materials

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

    2012-01-01

    Growth conditions are developed, based on a temperature-dependent alignment model, to enable formation of cubic group IV, group II-V and group II-VI crystals in the [111] orientation on the basal (0001) plane of trigonal crystal substrates, controlled such that the volume percentage of primary twin crystal is reduced from about 40% to about 0.3%, compared to the majority single crystal. The control of stacking faults in this and other embodiments can yield single crystalline semiconductors based on these materials that are substantially without defects, or improved thermoelectric materials with twinned crystals for phonon scattering while maintaining electrical integrity. These methods can selectively yield a cubic-on-trigonal epitaxial semiconductor material in which the cubic layer is substantially either directly aligned, or 60 degrees-rotated from, the underlying trigonal material.

  20. Structure-mechanical property correlations in mechanochromic luminescent crystals of boron difluoride dibenzoylmethane derivatives.

    PubMed

    Krishna, Gamidi Rama; Devarapalli, Ramesh; Prusty, Rajesh; Liu, Tiandong; Fraser, Cassandra L; Ramamurty, Upadrasta; Reddy, Chilla Malla

    2015-11-01

    The structure and mechanical properties of crystalline materials of three boron difluoride dibenzoylmethane (BF2dbm) derivatives were investigated to examine the correlation, if any, among mechanochromic luminescence (ML) behaviour, solid-state structure, and the mechanical behaviour of single crystals. Qualitative mechanical deformation tests show that the crystals of BF2dbm( (t) Bu)2 can be bent permanently, whereas those of BF2dbm(OMe)2 exhibit an inhomogeneous shearing mode of deformation, and finally BF2dbmOMe crystals are brittle. Quantitative mechanical analysis by nano-indentation on the major facets of the crystals shows that BF2dbm( (t) Bu)2 is soft and compliant with low values of elastic modulus, E, and hardness, H, confirming its superior suceptibility for plastic deformation, which is attributed to the presence of a multitude of slip systems in the crystal structure. In contrast, both BF2dbm(OMe)2 and BF2dbmOMe are considerably stiffer and harder with comparable E and H, which are rationalized through analysis of the structural attributes such as the intermolecular interactions, slip systems and their relative orientation with respect to the indentation direction. As expected from the qualitative mechanical behaviour, prominent ML was observed in BF2dbm( (t) Bu)2, whereas BF2dbm(OMe)2 exhibits only a moderate ML and BF2dbmOMe shows no detectable ML, all examined under identical conditions. These results confirm that the extent of ML in crystalline organic solid-state fluorophore materials can be correlated positively with the extent of plasticity (low recovery). In turn, they offer opportunities to design new and improved efficient ML materials using crystal engineering principles. PMID:26594368

  1. Conical photonic crystals for enhancing light extraction efficiency from high refractive index materials.

    PubMed

    Kim, Jeong-Gil; Hsieh, Chih-Hung; Choi, Hyungryul J; Gardener, Jules; Singh, Bipin; Knapitsch, Arno; Lecoq, Paul; Barbastathis, George

    2015-08-24

    We propose, analyze and optimize a two-dimensional conical photonic crystal geometry to enhance light extraction from a high refractive index material, such as an inorganic scintillator. The conical geometry suppresses Fresnel reflections at an optical interface due to adiabatic impedance matching from a gradient index effect. The periodic array of cone structures with a pitch larger than the wavelength of light diffracts light into higher-order modes with different propagating angles, enabling certain photons to overcome total internal reflection (TIR). The numerical simulation shows simultaneous light yield gains relative to a flat surface both below and above the critical angle and how key parameters affect the light extraction efficiency. Our optimized design provides a 46% gain in light yield when the conical photonic crystals are coated on an LSO (cerium-doped lutetium oxyorthosilicate) scintillator. PMID:26368241

  2. Crystal Structures of Monomeric Actin Bound to Cytochalasin D

    PubMed Central

    Nair, Usha B.; Joel, Peteranne B.; Wan, Qun; Lowey, Susan; Rould, Mark A.; Trybus, Kathleen M.

    2008-01-01

    The fungal toxin cytochalasin D (CD) interferes with the normal dynamics of the actin cytoskeleton by binding to the barbed end of actin filaments. Despite its widespread use as a tool for studying actin-mediated processes, the exact location and nature of its binding to actin has not been previously determined. Here we describe two crystal structures of an expressed monomeric actin in complex with CD, one obtained by soaking preformed actin crystals with CD, and the other by co-crystallization. The binding site for CD, in the hydrophobic cleft between actin subdomains 1 and 3, is the same in the two structures. Polar and hydrophobic contacts play an equally important role in CD binding, and six hydrogen bonds stabilize the actin-CD complex. Many unrelated actin-binding proteins and marine toxins target this cleft, and the hydrophobic pocket at the front end of the cleft (viewing actin with subdomain 2 in the upper right corner). CD differs in that it binds to the back half of the cleft. The ability of CD to induce actin dimer formation and actin-catalyzed ATP hydrolysis may be related to its unique binding site, and the necessity to fit its bulky macrocycle into this cleft. Contacts with residues lining this cleft appear to be crucial to capping and/or severing. The co-crystallized actin-CD structure also revealed changes in actin conformation. A rotation of ~6° of the smaller actin domain (subdomains 1 and 2) with respect to the larger domain (subdomains 3 and 4) results in small changes in crystal packing that allow the D-loop to adopt an extended loop structure, instead of being disordered as it is in most crystal structures of actin. We speculate that these changes represent a potential conformation that the actin monomer can adopt on the pathway to polymerization or in the filament. PMID:18938176

  3. Effect of crystallization time on the physico-chemical and catalytic properties of the hierarchical porous materials

    SciTech Connect

    Xu, Ling; College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities, Tongliao 028000 ; Ma, Yuanyuan; Ding, Wenli; Guan, Jingqi; Wu, Shujie; Kan, Qiubin

    2010-09-15

    A series of hierarchical porous materials were prepared by a dual template method. The effect of different crystallization time on the channel architecture, morphology, acid performance of the hierarchical porous materials was investigated. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption and {sup 27}Al nuclear magnetic resonance were performed to obtain information on the physico-chemical properties of the materials. It was shown that the change in crystallization time could influence the structure/texture and surface acid properties of the hierarchical porous materials. In addition, alkylation of phenol with tert-butanol reaction was carried out to investigate the catalytic performance of the hierarchical porous materials. The results showed that the catalytic activity of the hierarchical porous materials and the selectivity to the bulkly product 2,4-di-tert-butyl-phenol decreased with processing time.

  4. Crystal structure of rat liver dihydropteridine reductase.

    PubMed Central

    Varughese, K I; Skinner, M M; Whiteley, J M; Matthews, D A; Xuong, N H

    1992-01-01

    The structure of a binary complex of dihydropteridine reductase [DHPR; NAD(P)H:6,7-dihydropteridine oxidoreductase, EC 1.6.99.7] with its cofactor, NADH, has been solved and refined to a final R factor of 15.4% by using 2.3 A diffraction data. DHPR is an alpha/beta protein with a Rossmann-type dinucleotide fold for NADH binding. Insertion of an extra threonine residue in the human enzyme is associated with severe symptoms of a variant form of phenylketonuria and maps to a tightly linked sequence of secondary-structural elements near the dimer interface. Dimerization is mediated by a four-helix bundle motif (two helices from each protomer) having an unusual right-handed twist. DHPR is structurally and mechanistically distinct from dihydrofolate reductase, appearing to more closely resemble certain nicotinamide dinucleotide-requiring flavin-dependent enzymes, such as glutathione reductase. Images PMID:1631094

  5. Crystal structure of a human GABAA receptor

    PubMed Central

    Miller, Paul S.; Aricescu, A. Radu

    2014-01-01

    Summary Type-A γ-aminobutyric acid receptors (GABAARs) are the principal mediators of rapid inhibitory synaptic transmission in the human brain. A decline in GABAAR signalling triggers hyperactive neurological disorders such as insomnia, anxiety and epilepsy. Here we present the first three-dimensional structure of a GABAAR, the human β3 homopentamer, at 3 Å resolution. This structure reveals architectural elements unique to eukaryotic Cys-loop receptors, explains the mechanistic consequences of multiple human disease mutations and shows a surprising structural role for a conserved N-linked glycan. The receptor was crystallised bound to a previously unknown agonist, benzamidine, opening a new avenue for the rational design of GABAAR modulators. The channel region forms a closed gate at the base of the pore, representative of a desensitised state. These results offer new insights into the signalling mechanisms of pentameric ligand-gated ion channels and enhance current understanding of GABAergic neurotransmission. PMID:24909990

  6. Structure of self - assembled two-dimensional spherical crystals

    NASA Astrophysics Data System (ADS)

    Bausch, Andreas R.

    2004-03-01

    Dense spherical particles on a flat surface usually pack into a simple triangular lattice, similar to billiard balls at the start of a game. The minimum energy configuration for interacting particles on the curved surface of a sphere, however, presents special difficulties, as recognized already by J.J. Thomson. We describe experimental investigations of the structure of two-dimensional spherical crystals. The crystals, formed by beads self-assembled on water droplets in oil, serve as model systems for exploring very general theories about the minimum energy configurations of particles with arbitrary repulsive interactions on curved surfaces. Above a critical system size we find that crystals develop distinctive high-angle grain boundaries or "scars" not found in planar crystals. The number of excess defects in a scar is shown to grow linearly with the dimensionless system size. First experiments where the melting of the crystal structure was observable will be discussed. Dynamic triangulation methods allow the analysis of the dynamics of the defects. Possible modifications towards mechanically stabilized self assembly structures result in so called Colloidosomes, which are promising for many different encapsulation purposes.

  7. Formation of the structure of gold nanoclusters during crystallization

    SciTech Connect

    Gafner, Yu. Ya. Goloven'ko, Zh. V.; Gafner, S. L.

    2013-02-15

    The structure formation in gold nanoparticles 1.6-5.0 nm in diameter is studied by molecular dynamics simulation using a tight-binding potential. The simulation shows that the initial fcc phase in small Au clusters transforms into other structural modifications as temperature changes. As the cluster size increases, the transition temperature shifts toward the melting temperature of the cluster. The effect of various crystallization conditions on the formation of the internal structure of gold nanoclusters is studied in terms of microcanonical and canonical ensembles. The stability boundaries of various crystalline isomers are analyzed. The obtained dependences are compared with the corresponding data obtained for copper and nickel nanoparticles. The structure formation during crystallization is found to be characterized by a clear effect of the particle size on the stability of a certain isomer modification. Nickel and copper clusters are shown to exhibit common features in the formation of their structural properties, whereas gold clusters demonstrate much more complex behavior.

  8. Recent global trends in structural materials research

    NASA Astrophysics Data System (ADS)

    Murakami, Hideyuki; Ohmura, Takahito; Nishimura, Toshiyuki

    2013-02-01

    Structural materials support the basis of global society, such as infrastructure and transportation facilities, and are therefore essential for everyday life. The optimization of such materials allows people to overcome environmental, energy and resource depletion issues on a global scale. The creation and manufacture of structural materials make a large contribution to economies around the world every year. The use of strong, resistant materials can also have profound social effects, providing a better quality of life at both local and national levels. The Great East Japan Earthquake of 11 March 2011 caused significant structural damage in the Tohoku and Kanto regions of Japan. On a global scale, accidents caused by the ageing and failure of structural materials occur on a daily basis. Therefore, the provision and inspection of structural reliability, safety of nuclear power facilities and construction of a secure and safe society hold primary importance for researchers and engineers across the world. Clearly, structural materials need to evolve further to address both existing problems and prepare for new challenges that may be faced in the future. With this in mind, the National Institute for Materials Science (NIMS) organized the 'NIMS Conference 2012' to host an extensive discussion on a variety of global issues related to the future development of structural materials. Ranging from reconstruction following natural disasters, verification of structural reliability, energy-saving materials to fundamental problems accompanying the development of materials for high safety standards, the conference covered many key issues in the materials industry today. All the above topics are reflected in this focus issue of STAM, which introduces recent global trends in structural materials research with contributions from world-leading researchers in this field. This issue covers the development of novel alloys, current methodologies in the characterization of structural materials and fundamental research on structure-property relationships. We are grateful to the authors who contributed to cover these issues, and sincerely hope that our readers will expand their knowledge of emerging international research within the field of structural materials.

  9. CRYSTAL STRUCTURE ANALYSIS OF A PUTATIVE OXIDOREDUCTASE FROM KLEBSIELLA PNEUMONIAE

    SciTech Connect

    Baig, M.; Brown, A.; Eswaramoorthy, S.; Swaminathan, S.

    2009-01-01

    Klebsiella pneumoniae, a gram-negative enteric bacterium, is found in nosocomial infections which are acquired during hospital stays for about 10% of hospital patients in the United States. The crystal structure of a putative oxidoreductase from K. pneumoniae has been determined. The structural information of this K. pneumoniae protein was used to understand its function. Crystals of the putative oxidoreductase enzyme were obtained by the sitting drop vapor diffusion method using Polyethylene glycol (PEG) 3350, Bis-Tris buffer, pH 5.5 as precipitant. These crystals were used to collect X-ray data at beam line X12C of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). The crystal structure was determined using the SHELX program and refi ned with CNS 1.1. This protein, which is involved in the catalysis of an oxidation-reduction (redox) reaction, has an alpha/beta structure. It utilizes nicotinamide adenine dinucleotide phosphate (NADP) or nicotine adenine dinucleotide (NAD) to perform its function. This structure could be used to determine the active and co-factor binding sites of the protein, information that could help pharmaceutical companies in drug design and in determining the protein’s relationship to disease treatment such as that for pneumonia and other related pathologies.

  10. The crystal structure of aluminum doped β-rhombohedral boron

    NASA Astrophysics Data System (ADS)

    Bykova, Elena; Parakhonskiy, Gleb; Dubrovinskaia, Natalia; Chernyshov, Dmitry; Dubrovinsky, Leonid

    2012-10-01

    A crystal structure of aluminum doped β-rhombohedral boron was studied by single-crystal X-ray diffraction at 80 K. The crystals were synthesized using high-pressure high temperature technique at 3 GPa and 2100 K. The structure is based on three-dimensional framework made of B12 icosahedra with voids occupied by the B28-B-B28 units, it has the R-3m space group with a=10.9014(3), c=23.7225(7) Å lattice dimensions in hexagonal setting. Aluminum atoms are located in A1 and D special positions of the β-B structure with occupancies of 82.7(6)% and 11.3(4)%, respectively. Additional boron atoms are located near the D-site. Their possible distribution is discussed. Finally we have found two appropriate structural models whose refinement suggests two possible chemical compositions, AlB44.8(5) and AlB37.8(5), which are in a good agreement with the chemical analysis data obtained from EDX. The crystal structure of AlB44.8(5) is described in detail.

  11. HSCT materials and structures: An MDC perspective

    NASA Technical Reports Server (NTRS)

    Sutton, Jay O.

    1992-01-01

    The key High Speed Civil Transport (HSCT) features which control the materials selection are discussed. Materials are selected based on weight and production economics. The top-down and bottoms-up approaches to material selection are compared for the Mach 2.4 study baseline aircraft. The key materials and structures related tasks which remain to be accomplished prior to proceeding with the building of the HSCT aircraft are examined.

  12. Crystal structure of hexagonal MnAl4

    PubMed Central

    Pauling, Linus

    1987-01-01

    A structure is proposed for the hexagonal form of MnAl4, with aH = 28.4 Å and cH = 12.43 Å, on the basis of a high-resolution electron micrograph and comparison with crystals of known structures. The proposed structure involves seven 104-atom complexes of 20 Friauf polyhedra, sharing some atoms with one another. It is closely related to the 23.36-Å cubic structure of MnAl4 and to the 14.19-Å cubic structure of Mg32(Al,Zn)49. Images PMID:16593837

  13. Crystal structure of N'-(furan-2-ylmethylene)-4-hydroxybenzohydrazide

    NASA Astrophysics Data System (ADS)

    Dilek, N.; Güneş, B.; Gokce, C.; Gup, R.

    2014-12-01

    We report the molecular and crystal structures of the title compound. The structure of title compound in crystal was determined by the X-ray diffraction method. The molecule exists in a trans-configuration with respect to the C=N bond. The dihedral angle between two rings is 47.7(1)°. This compound crystallizes in the orthorhombic, Pna21 space group with unit cell parameter a = 9.6014(6) Å, b = 11.1849(8) Å, c = 10.3574(7) Å. The N-H⋯O and O-H⋯N interactions stabilize the molecules in the lattice. A weak C-H⋯π interactions are also present.

  14. Ultrafast characterization of phase-change material crystallization properties in the melt-quenched amorphous phase.

    PubMed

    Jeyasingh, Rakesh; Fong, Scott W; Lee, Jaeho; Li, Zijian; Chang, Kuo-Wei; Mantegazza, Davide; Asheghi, Mehdi; Goodson, Kenneth E; Wong, H-S Philip

    2014-06-11

    Phase change materials are widely considered for application in nonvolatile memories because of their ability to achieve phase transformation in the nanosecond time scale. However, the knowledge of fast crystallization dynamics in these materials is limited because of the lack of fast and accurate temperature control methods. In this work, we have developed an experimental methodology that enables ultrafast characterization of phase-change dynamics on a more technologically relevant melt-quenched amorphous phase using practical device structures. We have extracted the crystallization growth velocity (U) in a functional capped phase change memory (PCM) device over 8 orders of magnitude (10(-10) < U < 10(-1) m/s) spanning a wide temperature range (415 < T < 580 K). We also observed direct evidence of non-Arrhenius crystallization behavior in programmed PCM devices at very high heating rates (>10(8) K/s), which reveals the extreme fragility of Ge2Sb2Te5 in its supercooled liquid phase. Furthermore, these crystallization properties were studied as a function of device programming cycles, and the results show degradation in the cell retention properties due to elemental segregation. The above experiments are enabled by the use of an on-chip fast heater and thermometer called as microthermal stage (MTS) integrated with a vertical phase change memory (PCM) cell. The temperature at the PCM layer can be controlled up to 600 K using MTS and with a thermal time constant of 800 ns, leading to heating rates ∼10(8) K/s that are close to the typical device operating conditions during PCM programming. The MTS allows us to independently control the electrical and thermal aspects of phase transformation (inseparable in a conventional PCM cell) and extract the temperature dependence of key material properties in real PCM devices. PMID:24798660

  15. Effects of the Coordinates Planes Crystal Orientation on the Structural Strength of Single-Crystal Turbine Vanes and Blades

    NASA Astrophysics Data System (ADS)

    Chen, Jinxiang; Hashimoto, Ryosaku; Fukuyama, Yoshitaka; Matsushita, Masahiro; Ogawa, Akinori; Osawa, Makoto; Yokokawa, Tadaharu; Harada, Hiroshi

    The effects of crystal orientation (θ) on the structural strength of single crystal turbine vanes and blades calculated with the finite element method (FEM) are discussed in this paper. TMS-75, a 3rd generation single-crystal Ni-base superalloy, is chosen as the model material for turbine vanes and blades. It became clear that, (1) the elastic constant matrix changes were equivalence for each of three coordinate due to the orientation variation (0° < θ < 90°), and the strength of the turbine vane and blade were strongly related to θ, and also depended on the load and model shape. (2) The strength dependence of the turbine vane on the crystal orientation was depended on coordinate plane: there are lower Mises stress in XY plane and maximum Mises stress in near the θ=45° at both YZ and ZX Planes. (3) In the case of a blade, the influence is similar to the vane on blade tip, but the converse holds for the blade root. It is clear that the creep rupture time can be extended, when the <100> crystallographic axes is the Y or X axis of the blade under higher rotation speed.

  16. Radiation Effects on Spacecraft Structural Materials

    SciTech Connect

    Wang, Jy-An J.; Ellis, Ronald J.; Hunter, Hamilton T.; Singleterry, Robert C. Jr.

    2002-07-01

    Research is being conducted to develop an integrated technology for the prediction of aging behavior for space structural materials during service. This research will utilize state-of-the-art radiation experimental apparatus and analysis, updated codes and databases, and integrated mechanical and radiation testing techniques to investigate the suitability of numerous current and potential spacecraft structural materials. Also included are the effects on structural materials in surface modules and planetary landing craft, with or without fission power supplies. Spacecraft structural materials would also be in hostile radiation environments on the surface of the moon and planets without appreciable atmospheres and moons around planets with large intense magnetic and radiation fields (such as the Jovian moons). The effects of extreme temperature cycles in such locations compounds the effects of radiation on structural materials. This paper describes the integrated methodology in detail and shows that it will provide a significant technological advance for designing advanced spacecraft. This methodology will also allow for the development of advanced spacecraft materials through the understanding of the underlying mechanisms of material degradation in the space radiation environment. Thus, this technology holds a promise for revolutionary advances in material damage prediction and protection of space structural components as, for example, in the development of guidelines for managing surveillance programs regarding the integrity of spacecraft components, and the safety of the aging spacecraft. (authors)

  17. In situ studies of a platform for metastable inorganic crystal growth and materials discovery

    PubMed Central

    Shoemaker, Daniel P.; Hu, Yung-Jin; Chung, Duck Young; Halder, Gregory J.; Chupas, Peter J.; Soderholm, L.; Mitchell, J. F.; Kanatzidis, Mercouri G.

    2014-01-01

    Rapid shifts in the energy, technological, and environmental demands of materials science call for focused and efficient expansion of the library of functional inorganic compounds. To achieve the requisite efficiency, we need a materials discovery and optimization paradigm that can rapidly reveal all possible compounds for a given reaction and composition space. Here we provide such a paradigm via in situ X-ray diffraction measurements spanning solid, liquid flux, and recrystallization processes. We identify four new ternary sulfides from reactive salt fluxes in a matter of hours, simultaneously revealing routes for ex situ synthesis and crystal growth. Changing the flux chemistry, here accomplished by increasing sulfur content, permits comparison of the allowable crystalline building blocks in each reaction space. The speed and structural information inherent to this method of in situ synthesis provide an experimental complement to computational efforts to predict new compounds and uncover routes to targeted materials by design. PMID:25024201

  18. Structural diversity in hybrid organic-inorganic lead iodide materials.

    PubMed

    Weber, Oliver J; Marshall, Kayleigh L; Dyson, Lewis M; Weller, Mark T

    2015-12-01

    The structural chemistry of hybrid organic-inorganic lead iodide materials has become of increasing significance for energy applications since the discovery and development of perovskite solar cells based on methylammonium lead iodide. Seven new hybrid lead iodide compounds have been synthesized and structurally characterized using single-crystal X-ray diffraction. The lead iodide units in materials templated with bipyridyl, 1,2-bis(4-pyridyl)ethane, 1,2-di(4-pyridyl)ethylene and imidazole adopt one-dimensional chain structures, while crystallization from solutions containing piperazinium cations generates a salt containing isolated [PbI6](4-) octahedral anions. Templating with 4-chlorobenzylammonium lead iodide adopts the well known two-dimensional layered perovskite structure with vertex shared sheets of composition [PbI4](2-) separated by double layers of organic cations. The relationships between the various structures determined, their compositions, stability and hydrogen bonding between the protonated amine and the iodide ions of the PbI6 octahedra are described. PMID:26634723

  19. Crystal structure of fully oxidized human thioredoxin.

    PubMed

    Hwang, Jungwon; Nguyen, Loi T; Jeon, Young Ho; Lee, Chan Yong; Kim, Myung Hee

    2015-11-13

    In addition to the active cysteines located at positions 32 and 35 in humans, mammalian cytosolic thioredoxin (TRX) possesses additional conserved cysteine residues at positions 62, 69, and 73. These non-canonical cysteine residues, that are distinct from prokaryotic TRX and also not found in mammalian mitochondrial TRX, have been implicated in biological functions regulating signal transduction pathways via their post-translational modifications. Here, we describe for the first time the structure of a fully oxidized TRX. The structure shows a non-active Cys62-Cys69 disulfide bond in addition to the active Cys32-Cys35 disulfide. The non-active disulfide switches the ?3-helix of TRX, composed of residues Cys62 to Glu70, to a bulging loop and dramatically changes the environment of the TRX residues involved in the interaction with its reductase and other cellular substrates. This structural modification may have implications for a number of potential functions of TRX including the regulation of redox-dependent signaling pathways. PMID:26453009

  20. Space structures concepts and materials

    NASA Technical Reports Server (NTRS)

    Nowitzky, A. M.; Supan, E. C.

    1988-01-01

    An extension is preseted of the evaluation of graphite/aluminum metal matrix composites (MMC) for space structures application. A tubular DWG graphite/aluminum truss assembly was fabricated having the structural integrity and thermal stability needed for space application. DWG is a proprietary thin ply continuous graphite reinforced aluminum composite. The truss end fittings were constructed using the discontinuous ceramic particulate reinforced MMC DWAl 20 (trademark). Thermal stability was incorporated in the truss by utilizing high stiffness, negative coefficient of thermal expansion (CTE) P100 graphite fibers in a 6061 aluminum matrix, crossplied to provide minimized CTE in the assembled truss. Tube CTE was designed to be slightly negative to offset the effects of the end fitting and sleeve, CTE values of which are approx. 1/2 that of aluminum. In the design of the truss configuration, the CTE contribution of each component was evaluated to establish the component dimension and layup configuration required to provide a net zero CTE in the subassemblies which would then translate to a zero CTE for the entire truss bay produced.

  1. The effect of pressure on the crystal structure of bianthrone.

    PubMed

    Johnstone, Russell D L; Allan, David; Lennie, Alistair; Pidcock, Elna; Valiente, Rafael; Rodríguez, Fernando; Gonzalez, Jesús; Warren, John; Parsons, Simon

    2011-06-01

    Bianthrone [10(10-oxoanthracen-9-ylidene)anthracen-9-one] consists of two tricyclic anthraceneone units connected by a carbon-carbon double bond. Crystals of the form obtained under ambient conditions are yellow and contain folded centrosymmetric conformers in which the central ring of the anthraceneone unit is non-planar. When hydrostatic pressure is applied the crystals assume a red colouration which gradually deepens as pressures increases. The colour change is limited in extent to the surface of the crystals, the bulk remaining yellow. Comparison of high-pressure, single-crystal UV-vis spectra and powder diffraction data demonstrate that the colour change is associated with the formation of a polymorph containing a conformer in which the tricyclic fragments are planar and the molecule is twisted about the central C-C bond. Single-crystal diffraction data collected as a function of pressure up to 6.5 GPa reveal the effect of compression on the yellow form, which consists of layers of molecules which stack along the [010] direction. The structure remains in a compressed form of the ambient-pressure phase when subjected to hydrostatic pressure up to 6.5 GPa, and the most prominent effect of pressure is to push the layers closer together. PIXEL calculations show that considerable strain builds up in the crystal as pressure is increased with a number of intermolecular contacts being pushed into destabilizing regions of their potentials. PMID:21586830

  2. Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

    NASA Astrophysics Data System (ADS)

    Caskey, Christopher M.; Holder, Aaron; Shulda, Sarah; Christensen, Steven T.; Diercks, David; Schwartz, Craig P.; Biagioni, David; Nordlund, Dennis; Kukliansky, Alon; Natan, Amir; Prendergast, David; Orvananos, Bernardo; Sun, Wenhao; Zhang, Xiuwen; Ceder, Gerbrand; Ginley, David S.; Tumas, William; Perkins, John D.; Stevanovic, Vladan; Pylypenko, Svitlana; Lany, Stephan; Richards, Ryan M.; Zakutayev, Andriy

    2016-04-01

    Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non-ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here, we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin film experiments indicate that this novel material is N-deficient SnN with tin in the mixed ii/iv valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn3N4 spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of metastable materials. In addition to reporting on the discovery of the simple binary SnN compound, this paper illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials.

  3. Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures.

    PubMed

    Caskey, Christopher M; Holder, Aaron; Shulda, Sarah; Christensen, Steven T; Diercks, David; Schwartz, Craig P; Biagioni, David; Nordlund, Dennis; Kukliansky, Alon; Natan, Amir; Prendergast, David; Orvananos, Bernardo; Sun, Wenhao; Zhang, Xiuwen; Ceder, Gerbrand; Ginley, David S; Tumas, William; Perkins, John D; Stevanovic, Vladan; Pylypenko, Svitlana; Lany, Stephan; Richards, Ryan M; Zakutayev, Andriy

    2016-04-14

    Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non-ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here, we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin film experiments indicate that this novel material is N-deficient SnN with tin in the mixed ii/iv valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn3N4 spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of metastable materials. In addition to reporting on the discovery of the simple binary SnN compound, this paper illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials. PMID:27083713

  4. Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

    DOE PAGESBeta

    Caskey, Christopher M.; Holder, Aaron; Shulda, Sarah; Christensen, Steven T.; Diercks, David; Schwartz, Craig P.; Biagioni, David; Nordlund, Dennis; Kukliansky, Alon; Natan, Amir; et al

    2016-04-12

    Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin filmmore » experiments indicate that this novel material is N-deficient SnN with tin in the mixed II/IV valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn3N4 spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of the metastable material. In addition to reporting on the discovery of the simple binary SnN compound, this study illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials.« less

  5. The diammoniate of diborane: Crystal structure and hydrogen release

    SciTech Connect

    Bowden, Mark E.; Heldebrant, David J.; Karkamkar, Abhijeet J.; Proffen, Thomas E.; Schenter, Gregory K.; Autrey, Thomas

    2010-10-12

    [(NH3)2BH2]+[BH4]- is formed from the room temperature decomposition of NH4+BH4-, via a NH3BH3 intermediate. Its crystal structure has been determined and contains disordered BH4- ions in 2 distinct sites. Hydrogen release is similar to that from NH3BH3 but with faster kinetics.

  6. Unusual Features of Crystal Structures of Some Simple Copper Compounds

    ERIC Educational Resources Information Center

    Douglas, Bodie

    2009-01-01

    Some simple copper compounds have unusual crystal structures. Cu[subscript 3]N is cubic with N atoms at centers of octahedra formed by 6 Cu atoms. Cu[subscript 2]O (cuprite) is also cubic; O atoms are in tetrahedra formed by 4 Cu atoms. These tetrahedra are linked by sharing vertices forming two independent networks without linkages between them.…

  7. Unusual Features of Crystal Structures of Some Simple Copper Compounds

    ERIC Educational Resources Information Center

    Douglas, Bodie

    2009-01-01

    Some simple copper compounds have unusual crystal structures. Cu[subscript 3]N is cubic with N atoms at centers of octahedra formed by 6 Cu atoms. Cu[subscript 2]O (cuprite) is also cubic; O atoms are in tetrahedra formed by 4 Cu atoms. These tetrahedra are linked by sharing vertices forming two independent networks without linkages between them.

  8. Crystal structures of fusion proteins with large-affinity tags.

    PubMed

    Smyth, Douglas R; Mrozkiewicz, Marek K; McGrath, William J; Listwan, Pawel; Kobe, Bostjan

    2003-07-01

    The fusion of a protein of interest to a large-affinity tag, such as the maltose-binding protein (MBP), thioredoxin (TRX), or glutathione-S-transferase (GST), can be advantageous in terms of increased expression, enhanced solubility, protection from proteolysis, improved folding, and protein purification via affinity chromatography. Unfortunately, crystal growth is hindered by the conformational heterogeneity induced by the fusion tag, requiring that the tag is removed by a potentially problematic cleavage step. The first three crystal structures of fusion proteins with large-affinity tags have been reported recently. All three structures used a novel strategy to rigidly fuse the protein of interest to MBP via a short three- to five-amino acid spacer. This strategy has the potential to aid structure determination of proteins that present particular experimental challenges and are not conducive to more conventional crystallization strategies (e.g., membrane proteins). Structural genomics initiatives may also benefit from this approach as a way to crystallize problematic proteins of significant interest. PMID:12824478

  9. Crystal structures and morphologies of fractionated milk fat in nanoemulsions.

    PubMed

    Truong, Tuyen; Morgan, Garry P; Bansal, Nidhi; Palmer, Martin; Bhandari, Bhesh

    2015-03-15

    The triacylglycerol (TAG) crystal structures and morphologies of fractionated milk lipids in nanoemulsions were investigated at 4°C. Droplet size (0.17 versus 1.20 μm), lipid composition (stearin versus olein) and cooling rate (1 versus 10°C min(-1)) had an influence on the structural properties. Five crystal polymorphs (α, β'1, β'2, β1, and β2) were formed with either triple and/or double chain length structures in the solid phases of the emulsified systems. X-ray scattering peak intensities were reduced with the nanoemulsion particles. The internal structure of TAG exhibited stacking of individual lamellar layers (3.8-4.2 nm). Various anisometric shapes of fat nanoparticles were formed due to a highly sharp curvature of the nano-size droplets. The shape of olein nanoparticles was more polyhedral compared to the stearin. TAG crystals arranged in a planar-layered organisation at the slower cooling rate. These differences imply that the nanometric confinement of oil droplets modifies the fat crystal habit. PMID:25308656

  10. Photonic guiding structures in lithium niobate crystals produced by energetic ion beams

    NASA Astrophysics Data System (ADS)

    Chen, Feng

    2009-10-01

    A range of ion beam techniques have been used to fabricate a variety of photonic guiding structures in the well-known lithium niobate (LiNbO3 or LN) crystals that are of great importance in integrated photonics/optics. This paper reviews the up-to-date research progress of ion-beam-processed LiNbO3 photonic structures and reports on their fabrication, characterization, and applications. Ion beams are being used with this material in a wide range of techniques, as exemplified by the following examples. Ion beam milling/etching can remove the selected surface regions of LiNbO3 crystals via the sputtering effects. Ion implantation and swift ion irradiation can form optical waveguide structures by modifying the surface refractive indices of the LiNbO3 wafers. Crystal ion slicing has been used to obtain bulk-quality LiNbO3 single-crystalline thin films or membranes by exfoliating the implanted layer from the original substrate. Focused ion beams can either generate small structures of micron or submicron dimensions, to realize photonic bandgap crystals in LiNbO3, or directly write surface waveguides or other guiding devices in the crystal. Ion beam-enhanced etching has been extensively applied for micro- or nanostructuring of LiNbO3 surfaces. Methods developed to fabricate a range of photonic guiding structures in LiNbO3 are introduced. Modifications of LiNbO3 through the use of various energetic ion beams, including changes in refractive index and properties related to the photonic guiding structures as well as to the materials (i.e., electro-optic, nonlinear optic, luminescent, and photorefractive features), are overviewed in detail. The application of these LiNbO3 photonic guiding structures in both micro- and nanophotonics are briefly summarized.

  11. Constrained evolutionary algorithm for structure prediction of molecular crystals: methodology and applications.

    PubMed

    Zhu, Qiang; Oganov, Artem R; Glass, Colin W; Stokes, Harold T

    2012-06-01

    Evolutionary crystal structure prediction proved to be a powerful approach for studying a wide range of materials. Here we present a specifically designed algorithm for the prediction of the structure of complex crystals consisting of well defined molecular units. The main feature of this new approach is that each unit is treated as a whole body, which drastically reduces the search space and improves the efficiency, but necessitates the introduction of new variation operators described here. To increase the diversity of the population of structures, the initial population and part (~20%) of the new generations are produced using space-group symmetry combined with random cell parameters, and random positions and orientations of molecular units. We illustrate the efficiency and reliability of this approach by a number of tests (ice, ammonia, carbon dioxide, methane, benzene, glycine and butane-1,4-diammonium dibromide). This approach easily predicts the crystal structure of methane A containing 21 methane molecules (105 atoms) per unit cell. We demonstrate that this new approach also has a high potential for the study of complex inorganic crystals as shown on examples of a complex hydrogen storage material Mg(BH(4))(2) and elemental boron. PMID:22610672

  12. Co-crystal formation based on structural matching.

    PubMed

    Zhou, Liping; Dodd, Stephanie; Capacci-Daniel, Christina; Garad, Sudhakar; Panicucci, Riccardo; Sethuraman, Vijay

    2016-06-10

    A co-crystal is defined as a single crystalline structure composed of two or more components with no proton transfer which are solid at room temperature. Our group has come up with the following rationale selection of co-formers for initial co-crystal screening: 1) selection of co-formers with the highest potential for hydrogen bonding with the API and 2) selection of co-formers with diversity of secondary structural characteristics. We demonstrate the feasibility of this technique with a Novartis drug candidate A. In the first tier, 20 co-formers were screened and two hits were identified. By examining the two co-formers, which worked from the first round, a second round of screening was undertaken with more focused chemical matter. Nineteen co-crystal formers closely related to the two hits in the first screen were screened in the second tier. From this screen five hits were identified. All the hits were compared for their physical and chemical stability and dissolution profile. Based on the comparison 4-aminobenzoic co-crystal was chosen for in-vivo comparison with the free form. The co-crystal had 12 times higher exposure than the free form thus overcoming the solubility limited exposure. PMID:26948852

  13. Effect of local structures on structural evolution during crystallization in undercooled metallic glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Wu, Z. W.; Li, M. Z.; Wang, W. H.; Song, W. J.; Liu, K. X.

    2013-02-01

    The effect of local structures on structural evolution during the crystallization of undercooled ZrCu metallic glass-forming liquid was studied via molecular dynamics simulations. It is found that body-centered-cubic (bcc)-like clusters play a key role in structural evolution during crystallization. In contrast to previous speculations, the number of bcc-like crystal nuclei does not change much before the onset of crystallization. Instead, the development of a bcc-like critical nucleus during annealing leads to a strong spatial correlation with other nuclei in its surroundings, forming a crystalline structure template. It is also found that the size distribution of bcc-like nuclei follows a power-law form with an exponential cutoff in the early stage of annealing, but changes to a pure power-law behavior just before the onset of crystallization. This implies that the crystalline structure template has fractal feature and the undercooled liquids evolve to a self-organized critical state before the onset of crystallization, which might trigger the subsequent rapid crystallization. According to the graph theory analysis, it is also found that the observed large scatter of the onset time of crystallization in different liquid samples results from the connectivity of the bcc-like clusters.

  14. Pericentriolar material structure and dynamics

    PubMed Central

    Woodruff, Jeffrey B.; Wueseke, Oliver; Hyman, Anthony A.

    2014-01-01

    A centrosome consists of two barrel-shaped centrioles embedded in a matrix of proteins known as the pericentriolar material (PCM). The PCM serves as a platform for protein complexes that regulate organelle trafficking, protein degradation and spindle assembly. Perhaps most important for cell division, the PCM concentrates tubulin and serves as the primary organizing centre for microtubules in metazoan somatic cells. Thus, similar to other well-described organelles, such as the nucleus and mitochondria, the cell has compartmentalized a multitude of vital biochemical reactions in the PCM. However, unlike these other organelles, the PCM is not membrane bound, but rather a dynamic collection of protein complexes and nucleic acids that constitute the organelle's interior and determine its boundary. How is the complex biochemical machinery necessary for the myriad centrosome functions concentrated and maintained in the PCM? Recent advances in proteomics and RNAi screening have unveiled most of the key PCM components and hinted at their molecular interactions ( table 1). Now we must understand how the interactions between these molecules contribute to the mesoscale organization and the assembly of the centrosome. Among outstanding questions are the intrinsic mechanisms that determine PCM shape and size, and how it functions as a biochemical reaction hub. PMID:25047613

  15. Crystal Structure of the Bacillus subtilis Superoxide Dismutase

    SciTech Connect

    Liu, Ping; Ewis, H.E.; Huang, Y.-J; Lu, C.-D.; Tai, P.C.; Weber, Irene T.

    2008-06-01

    The sodA gene of Bacillus subtilis was expressed in Escherichia coli, purified and crystallized. The crystal structure of MnSOD was solved by molecular replacement with four dimers per asymmetric unit and refined to an R factor of 21.1% at 1.8 {angstrom} resolution. The dimer structure is very similar to that of the related enzyme from B. anthracis. Larger structural differences were observed with the human MnSOD, which has one less helix in the helical domain and a longer loop between two -strands and also showed differences in three amino acids at the intersubunit interface in the dimer compared with the two bacterial MnSODs. These structural differences can be exploited in the design of drugs that selectively target the Bacillus enzymes.

  16. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    PubMed Central

    Parshin, Alexander M.; Gunyakov, Vladimir A.; Zyryanov, Victor Y.; Shabanov, Vasily F.

    2013-01-01

    Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface. PMID:23965955

  17. VO{sub 2} (A): Reinvestigation of crystal structure, phase transition and crystal growth mechanisms

    SciTech Connect

    Rao Popuri, Srinivasa; Artemenko, Alla; Labrugere, Christine; Miclau, Marinela; Villesuzanne, Antoine; Pollet, Michaël

    2014-05-01

    Well crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal reaction in the presence of V{sub 2}O{sub 5} and oxalic acid. With the advantage of high crystalline samples, we propose P4/ncc as an appropriate space group at room temperature. From morphological studies, we found that the oriented attachment and layer by layer growth mechanisms are responsible for the formation of VO{sub 2} (A) micro rods. The structural and electronic transitions in VO{sub 2} (A) are strongly first order in nature, and a marked difference between the structural transition temperatures and electronic transitions temperature was evidenced. The reversible intra- (LTP-A to HTP-A) and irreversible inter- (HTP-A to VO{sub 2} (M1)) structural phase transformations were studied by in-situ powder X-ray diffraction. Attempts to increase the size of the VO{sub 2} (A) microrods are presented and the possible formation steps for the flower-like morphologies of VO{sub 2} (M1) are described. - Graphical abstract: Using a single step and template free hydrothermal synthesis, well crystallized VO{sub 2} (A) microrods were prepared and the P4/ncc space group was assigned to the room temperature crystal structure. Reversible and irreversible phase transitions among different VO{sub 2} polymorphs were identified and their progressive nature was highlighted. Attempts to increase the microrods size, involving layer by layer formation mechanisms, are presented. - Highlights: • Highly crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal process. • The P4/ncc space group was determined for VO{sub 2} (A) at room temperature. • The electronic structure and progressive nature of the structural phase transition were investigated. • A weak coupling between structural and electronic phase transitions was identified. • Different crystallite morphologies were discussed in relation with growth mechanisms.

  18. Microstructure of Li(Mn{sub 1/3}Ni{sub 1/3}Co{sub 1/3})O{sub 2} cathode material for lithium ion battery: Dependence of crystal structure on calcination and heat-treatment temperature

    SciTech Connect

    Kabi, S.; Ghosh, A.

    2013-09-01

    Graphical abstract: TEM micrograph of Li(Mn{sub 1/3}Ni{sub 1/3}Co{sub 1/3})O{sub 2} compound calcined at 900 °C. - Highlights: • Synthesis condition of Li(Mn{sub 1/3}Ni{sub 1/3}Co{sub 1/3})O{sub 2} compound was optimized. • Effect of calcination and heat treatment on the structure was investigated. • Controlled heat-treatment reduced cation mixing and improved structural ordering. • Calcination and heat-treatment condition affected distribution of particle size. - Abstract: Cathode compounds of composition Li(Mn{sub 1/3}Ni{sub 1/3}Co{sub 1/3})O{sub 2} have been prepared by calcination of the precursor materials at 700, 800, 900 and 1000 °C for 24 h and by subsequent heat-treatments at 1100 °C for 4–6 h. It has been observed that the structural ordering and particle size increase with increasing calcination temperature. The compounds calcined at 700 °C and 800 °C are not well-crystallized, but the distribution of particles is uniform. However, the compounds calcined at 900 °C and 1000 °C are well-crystallized with a non-uniform distribution of particles. The compounds calcined at 900 °C are well-crystallized with a well-ordered hexagonal structure. The samples calcined at 800 °C and heat treated at 1100 °C for 4 h also show same structure. They have smooth surface morphology with uniform distribution of particles in the sub-micron (0.15–0.40 μm) range and less amount of cation mixing.

  19. Crystal structure of new AsS2 compound

    NASA Astrophysics Data System (ADS)

    Bolotina, N. B.; Brazhkin, V. V.; Dyuzheva, T. I.; Lityagina, L. M.; Kulikova, L. F.; Nikolaev, N. A.; Verin, I. A.

    2013-01-01

    AsS2 single crystals have been obtained for the first time from an As2S3 melt at pressures above 6 GPa and temperatures above 800 K in the As2S3 → AsS + AsS2 reaction. The monoclinic structure of the new high-pressure phase is solved by X-ray diffraction analysis and compared to the structure of high-pressure AsS phase, which was studied previously.

  20. Crystal Structure of Sphingosine Kinase 1 with PF-543

    PubMed Central

    2014-01-01

    The most potent inhibitor of Sphingosine Kinase 1 (SPHK1) so far identified is PF-543. The crystal structure of SPHK1 in complex with inhibitor PF-543 to 1.8 Å resolution reveals the inhibitor bound in a bent conformation analogous to that expected of a bound sphingosine substrate but with a rotated head group. The structural data presented will aid in the design of SPHK1 and SPHK2 inhibitors with improved properties. PMID:25516793

  1. Structural evolution in the crystallization of rapid cooling silver melt

    SciTech Connect

    Tian, Z.A.; Dong, K.J.; Yu, A.B.

    2015-03-15

    The structural evolution in a rapid cooling process of silver melt has been investigated at different scales by adopting several analysis methods. The results testify Ostwald’s rule of stages and Frank conjecture upon icosahedron with many specific details. In particular, the cluster-scale analysis by a recent developed method called LSCA (the Largest Standard Cluster Analysis) clarified the complex structural evolution occurred in crystallization: different kinds of local clusters (such as ico-like (ico is the abbreviation of icosahedron), ico-bcc like (bcc, body-centred cubic), bcc, bcc-like structures) in turn have their maximal numbers as temperature decreases. And in a rather wide temperature range the icosahedral short-range order (ISRO) demonstrates a saturated stage (where the amount of ico-like structures keeps stable) that breeds metastable bcc clusters. As the precursor of crystallization, after reaching the maximal number bcc clusters finally decrease, resulting in the final solid being a mixture mainly composed of fcc/hcp (face-centred cubic and hexagonal-closed packed) clusters and to a less degree, bcc clusters. This detailed geometric picture for crystallization of liquid metal is believed to be useful to improve the fundamental understanding of liquid–solid phase transition. - Highlights: • A comprehensive structural analysis is conducted focusing on crystallization. • The involved atoms in our analysis are more than 90% for all samples concerned. • A series of distinct intermediate states are found in crystallization of silver melt. • A novelty icosahedron-saturated state breeds the metastable bcc state.

  2. Crystal growth, spectral, structural and optical studies of ?-conjugated stilbazolium crystal: 4-bromobenzaldehyde-4'-N'-methylstilbazolium tosylate.

    PubMed

    Krishna Kumar, M; Sudhahar, S; Bhagavannarayana, G; Mohan Kumar, R

    2014-05-01

    Nonlinear optical (NLO) organic compound, 4-bromobenzaldehyde-4'-N'-methylstilbazolium tosylate was synthesized by reflux method. The formation of molecular complex was confirmed from (1)H NMR, FT-IR and FT-Raman spectral analyses. The single crystals were grown by slow evaporation solution growth method and the crystal structure and atomic packing of grown crystal was identified. The morphology and growth axis of grown crystal were determined. The crystal perfection was analyzed using high resolution X-ray diffraction study on (001) plane. Thermal stability, decomposition stages and melting point of the grown crystal were analyzed. The optical absorption coefficient (?) and energy band gap (E(g)) of the crystal were determined using UV-visible absorption studies. Second harmonic generation efficiency of the grown crystal was examined by Kurtz powder method with different particle size using 1064 nm laser. Laser induced damage threshold study was carried out for the grown crystal using Nd:YAG laser. PMID:24531108

  3. Crystal growth, spectral, structural and optical studies of ?-conjugated stilbazolium crystal: 4-Bromobenzaldehyde-4?-N?-methylstilbazolium tosylate

    NASA Astrophysics Data System (ADS)

    Krishna Kumar, M.; Sudhahar, S.; Bhagavannarayana, G.; Mohan Kumar, R.

    Nonlinear optical (NLO) organic compound, 4-bromobenzaldehyde-4?-N?-methylstilbazolium tosylate was synthesized by reflux method. The formation of molecular complex was confirmed from 1H NMR, FT-IR and FT-Raman spectral analyses. The single crystals were grown by slow evaporation solution growth method and the crystal structure and atomic packing of grown crystal was identified. The morphology and growth axis of grown crystal were determined. The crystal perfection was analyzed using high resolution X-ray diffraction study on (0 0 1) plane. Thermal stability, decomposition stages and melting point of the grown crystal were analyzed. The optical absorption coefficient (?) and energy band gap (Eg) of the crystal were determined using UV-visible absorption studies. Second harmonic generation efficiency of the grown crystal was examined by Kurtz powder method with different particle size using 1064 nm laser. Laser induced damage threshold study was carried out for the grown crystal using Nd:YAG laser.

  4. Solvent-controlled assembly of crystal structures: From centrosymmetric structure to noncentrosymmetric structure

    NASA Astrophysics Data System (ADS)

    Zhang, Le; Dang, Lilong; Luo, Feng; Feng, Xuefeng

    2016-02-01

    Reported here are two isomeric organic crystals and two HgI2-based coordination compounds by solvo(hydro)thermal method: [(TPTA)·H2O]n (1, Cc), [(TPTA)·H2O]n (2, Pbca), [Hg1.5I3(TPTA)0.5(CH3CN)·(H2O)0.5]n (3, P21) and [HgI2(TPTA)·H2O]n (4, P21/c) (TPTA = N,N‧,N″-tris(3-pyridyl)trimesic amide). Single crystal X-ray diffraction show that they afford noncentrosymmetric and centrosymmetric structures, respectively. Note that this kind of formations can be precisely controlled by changing the reaction solvent, thus indicating a facile method towards generating noncentrosymmetric structure.

  5. Growth, optical and structural reports on new glycine D-tartaric acid complex crystal

    NASA Astrophysics Data System (ADS)

    Inbaseelan, C. Ranjith Dev; Saravanan, S.

    2013-06-01

    A new organic complex crystal of glycine D-tartaric acid (GDT) has been grown from combination of amino acid glycine and D-tartaric acid by slow evaporation method under ambient temperature. The Solubility, Optical parameters, and structural studies were carried out. The solubility of the material was measured at various temperatures in de-ionized water. The UV-vis spectrum of GDT crystal shows less optical absorption and good transparency above 96% in the entire visible region enabling its use in optical application and the band gap was calculated as 3.08 eV.

  6. Crystal structures of Ziegler-Natta catalyst supports.

    PubMed

    Malizia, Federica; Fait, Anna; Cruciani, Giuseppe

    2011-12-01

    The crystal structures of three MgCl(2)·nEtOH complexes with n=1.5, 2.8, and 3.3 have been fully determined. Such complexes are the fundamental precursors for Ziegler-Natta polymerization catalysts used to produce polyolefins on a multimillion-ton scale worldwide. The ab initio structure solution showed that the structure of MgCl(2)·nEtOH complexes with n=1.5 and 2.8 are based on ribbons of metal-centered octahedra, whereas for n=3.3 this chainlike arrangement breaks into a threadlike structure of isolated octahedra linked by hydrogen bonds. A clear correlation between catalyst performance and the crystal structure of precursors has been found, and reveals the fundamental role of the latter in determining catalyst properties. The direct knowledge of building blocks in the precursor structures will help to develop more accurate models for activated catalysts. These models will not require the arbitrary and oversimplified assumption of locating the catalyst active sites on selected cut surfaces of the α-MgCl(2) crystal lattice. PMID:22052708

  7. Crystal Structure of Triosephosphate Isomerase from Trypanosoma cruzi in Hexane

    NASA Astrophysics Data System (ADS)

    Gao, Xiu-Gong; Maldonado, Ernesto; Perez-Montfort, Ruy; Garza-Ramos, Georgina; Tuena de Gomez-Puyou, Marietta; Gomez-Puyou, Armando; Rodriguez-Romero, Adela

    1999-08-01

    To gain insight into the mechanisms of enzyme catalysis in organic solvents, the x-ray structure of some monomeric enzymes in organic solvents was determined. However, it remained to be explored whether the structure of oligomeric proteins is also amenable to such analysis. The field acquired new perspectives when it was proposed that the x-ray structure of enzymes in nonaqueous media could reveal binding sites for organic solvents that in principle could represent the starting point for drug design. Here, a crystal of the dimeric enzyme triosephosphate isomerase from the pathogenic parasite Trypanosoma cruzi was soaked and diffracted in hexane and its structure solved at 2- angstrom resolution. Its overall structure and the dimer interface were not altered by hexane. However, there were differences in the orientation of the side chains of several amino acids, including that of the catalytic Glu-168 in one of the monomers. No hexane molecules were detected in the active site or in the dimer interface. However, three hexane molecules were identified on the surface of the protein at sites, which in the native crystal did not have water molecules. The number of water molecules in the hexane structure was higher than in the native crystal. Two hexanes localized at <4 angstrom from residues that form the dimer interface; they were in close proximity to a site that has been considered a potential target for drug design.

  8. Revolutionary opportunities for materials and structures study

    NASA Technical Reports Server (NTRS)

    Schweiger, F. A.

    1987-01-01

    The revolutionary opportunities for materials and structures study was performed to provide Government and Industry focus for advanced materials technology. Both subsonic and supersonic engine studies and aircraft fuel burn and DOC evaluation are examined. Year 2010 goal materials were used in the advanced engine studies. These goal materials and improved component aero yielded subsonic fuel burn and DOC improvements of 13.4 percent and 5 percent, respectively and supersonic fuel burn and DOC improvements of 21.5 percent and 18 percent, respectively. Conclusions are that the supersonic study engine yielded fuel burn and DOC improvements well beyond the program goals; therefore, it is appropriate that advanced material programs be considered.

  9. Crystal structure and optical properties of polymorphic octasilacubane

    NASA Astrophysics Data System (ADS)

    Tachibana, Hiroaki; Goto, Midori; Matsumoto, Mutsuyoshi; Kishida, Hideo; Tokura, Yoshinori

    1994-05-01

    Single crystal x-ray crystallographic analysis of tert-butyloctasilacubane showed that a new polymorphic form (β form) exists with a slightly modified shape of the Si cage as compared with the previously reported form (α form) [K. Furukawa, M. Fujino, and N. Matsumoto, Appl. Phys. Lett. 60, 2744 (1991)]. Spectroscopic investigations of the single crystal indicate that the electronic band gap and luminescence band position differ by ˜0.4 eV between the polymorphs, signaling the sensitivity of the electronic structure to the distortion of the octasilacubane framework.

  10. Crystal structure of alpha poly-p-xylylene.

    NASA Technical Reports Server (NTRS)

    Kubo, S.; Wunderlich, B.

    1971-01-01

    A crystal structure of alpha poly-p-xylylene is proposed with the help of data of oriented crystals grown during polymerization. The unit cell is monoclinic with the parameters a = 8.57 A, b = 10.62 A, c = 6.54 A (chain axis), and beta = 101.3 deg. Four repeating units per cell lead to a calculated density of 1.185 g/cu cm and a packing density of 0.71. The probable space group is P2 sub 1/m.

  11. Structural analysis of three-dimenstionl photonic crystals in nature

    NASA Astrophysics Data System (ADS)

    Yoon, Beom-Jin; Park, Jung Ok; Srinivasarao, Mohan

    2012-02-01

    We studied the structural origin of the color and photonic band structure in exoskeletons of Eupholus weevils and dorsal wings of lycaenids butterflies. The internal structures of the insects were systematically investigated using focused ion beam (FIB) milling, and the optical response of the insects was observed by optical microscopy and a microspectrophotometer. A series of sequential SEM images were obtained during the FIB milling process and 3D structures were reconstructed by image processing. The correlation of the structures and the optical responses were studied by theoretical modeling. Diamond-based 3D photonic crystal lattice existed in Eupholus weevils, while gyroid structure was in lycaenids butterflies. The calculated photonic band structures matched the measured optical response. Aluminum oxide and titanium oxide were deposited on the weevils and the butterflies in order to study the effect of refractive index contrast to the photonic band structure and the optical response.

  12. A preliminary review of organic materials single crystal growth by the Czochralski technique

    NASA Technical Reports Server (NTRS)

    Penn, B. G.; Shields, A. W.; Frazier, D. O.

    1988-01-01

    The growth of single crystals of organic compounds by the Czochralski method is reviewed. From the literature it is found that single crystals of benzil, a nonlinear optical material with a d sub 11 value of 11.2 + or - 1.5 x d sub 11 value of alpha quartz, has fewer dislocations than generally contained in Bridgman crystals. More perfect crystals were grown by repeated Czochralski growth. This consists of etching away the defect-containing portion of a Czochralski grown crystal and using it as a seed for further growth. Other compounds used to grow single crystals are benzophenone, 12-tricosanone (laurone), and salol. The physical properties, growth apparatus, and processing conditions presented in the literature are discussed. Moreover, some of the possible advantages of growing single crystals of organic compounds in microgravity to obtain more perfect crystals than on Earth are reviewed.

  13. Transport of nanoparticulate material in self-assembled block copolymer micelle solutions and crystals.

    PubMed

    Cheng, Vicki A; Walker, Lynn M

    2016-04-12

    Water soluble poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) [PEO-PPO-PEO] triblock copolymers self-assemble into thermoreversible micellar crystals comprised of periodically spaced micelles. The micelles have PPO cores surrounded by hydrated PEO coronas and the dimensions of the unit cell of the organized micelles is on the order of several to tens of nanometers. Fluorescence recovery after photobleaching (FRAP) is used to quantify nanoparticle transport in these nanostructured polymer micelle systems. Diffusivity of bovine serum albumin (BSA, Dh ∼ 7 nm) is quantified across a wide range of polymer, or micelle, concentrations covering both the disordered fluid as well as the structured micellar crystal to understand the effects of nanoscale structure on particle transport. Measured particle diffusivity in these micellar systems is reduced by as much as four orders of magnitude when compared to diffusivity in free solution. Diffusivity in the disordered micellar fluid is best understood in terms of diffusion through a polymeric solution, while transport in the structured micellar phase is possibly due to hopping between interstitial sites. These results not only show that the nanoscale structures of the micelles have a measureable impact on particle diffusivity, but also demonstrate the ability to tune nanoscale transport in self-assembled materials. PMID:26796632

  14. Plastics as structural materials for aircraft

    NASA Technical Reports Server (NTRS)

    Kline, G M

    1937-01-01

    The purpose here is to consider the mechanical characteristics of reinforced phenol-formaldehyde resin as related to its use as structural material for aircraft. Data and graphs that have appeared in the literature are reproduced to illustrate the comparative behavior of plastics and materials commonly used in aircraft construction. Materials are characterized as to density, static strength, modulus of elasticity, resistance to long-time loading, strength under repeated impact, energy absorption, corrosion resistance, and ease of fabrication.

  15. Anisole at 100 K: the first crystal structure determination.

    PubMed

    Seidel, Rüdiger W; Goddard, Richard

    2015-08-01

    The simplest alkyl aryl ether, anisole (methoxybenzene), C7H8O, is a feedstock chemical and is widely used in the pharmaceutical industry. The structure of anisole at 100 K, as determined by single-crystal X-ray analysis, is reported. A crystal (m.p. 236 K) suitable for X-ray diffraction was obtained from the melt. The title compound crystallizes in the centrosymmetric space group P2(1)/c with two molecules in the asymmetric unit (Z' = 2). Both crystallographically distinct molecules adopt a virtually flat (Cs-symmetric) conformation. The arrangement of the molecules in the solid state appears to be governed by close packing. No face-to-face π-π stacking of the molecules is observed, but rather edge-to-face interactions result in a herringbone packing motif. PMID:26243411

  16. Crystal structure and mechanistic investigation of the twister ribozyme.

    PubMed

    Liu, Yijin; Wilson, Timothy J; McPhee, Scott A; Lilley, David M J

    2014-09-01

    We present a crystal structure at 2.3- resolution of the recently described nucleolytic ribozyme twister. The RNA adopts a previously uncharacterized compact fold based on a double-pseudoknot structure, with the active site at its center. Eight highly conserved nucleobases stabilize the core of the ribozyme through the formation of one Watson-Crick and three noncanonical base pairs, and the highly conserved adenine 3' of the scissile phosphate is bound in the major groove of an adjacent pseudoknot. A strongly conserved guanine nucleobase directs its Watson-Crick edge toward the scissile phosphate in the crystal structure, and mechanistic evidence supports a role for this guanine as either a general base or acid in a concerted, general acid-base-catalyzed cleavage reaction. PMID:25038788

  17. GPCR crystal structures: Medicinal chemistry in the pocket.

    PubMed

    Shonberg, Jeremy; Kling, Ralf C; Gmeiner, Peter; Löber, Stefan

    2015-07-15

    Recent breakthroughs in GPCR structural biology have significantly increased our understanding of drug action at these therapeutically relevant receptors, and this will undoubtedly lead to the design of better therapeutics. In recent years, crystal structures of GPCRs from classes A, B, C and F have been solved, unveiling a precise snapshot of ligand-receptor interactions. Furthermore, some receptors have been crystallized in different functional states in complex with antagonists, partial agonists, full agonists, biased agonists and allosteric modulators, providing further insight into the mechanisms of ligand-induced GPCR activation. It is now obvious that there is enormous diversity in the size, shape and position of the ligand binding pockets in GPCRs. In this review, we summarise the current state of solved GPCR structures, with a particular focus on ligand-receptor interactions in the binding pocket, and how this can contribute to the design of GPCR ligands with better affinity, subtype selectivity or efficacy. PMID:25638496

  18. Smart materials and structures: what are they?

    NASA Astrophysics Data System (ADS)

    Spillman, W. B., Jr.; Sirkis, J. S.; Gardiner, P. T.

    1996-06-01

    There has been considerable discussion in the technical community on a number of questions concerned with smart materials and structures, such as what they are, whether smart materials can be considered a subset of smart structures, whether a smart structure and an intelligent structure are the same thing, etc. This discussion is both fueled and confused by the technical community due to the truly multidisciplinary nature of this new field. Smart materials and structures research involves so many technically diverse fields that it is quite common for one field to completely misunderstand the terminology and start of the art in other fields. In order to ascertain whether a consensus is emerging on a number of questions, the technical community was surveyed in a variety of ways including via the internet and by direct contact. The purpose of this survey was to better define the smart materials and structures field, its current status and its potential benefits. Results of the survey are presented and discussed. Finally, a formal definition of the field of smart materials and structures is proposed.

  19. Spontaneous Formation of Eutectic Crystal Structures in Binary and Ternary Charged Colloids due to Depletion Attraction.

    PubMed

    Toyotama, Akiko; Okuzono, Tohru; Yamanaka, Junpei

    2016-01-01

    Crystallization of colloids has extensively been studied for past few decades as models to study phase transition in general. Recently, complex crystal structures in multi-component colloids, including alloy and eutectic structures, have attracted considerable attention. However, the fabrication of 2D area-filling colloidal eutectics has not been reported till date. Here, we report formation of eutectic structures in binary and ternary aqueous colloids due to depletion attraction. We used charged particles + linear polyelectrolyte systems, in which the interparticle interaction could be represented as a sum of the electrostatic, depletion, and van der Waals forces. The interaction was tunable at a lengthscale accessible to direct observation by optical microscopy. The eutectic structures were formed because of interplay of crystallization of constituent components and accompanying fractionation. An observed binary phase diagram, defined by a mixing ratio and inverse area fraction of the particles, was analogous to that for atomic and molecular eutectic systems. This new method also allows the adjustment of both the number and wavelengths of Bragg diffraction peaks. Furthermore, these eutectic structures could be immobilized in polymer gel to produce self-standing materials. The present findings will be useful in the design of the optical properties of colloidal crystals. PMID:26984298

  20. Spontaneous Formation of Eutectic Crystal Structures in Binary and Ternary Charged Colloids due to Depletion Attraction

    NASA Astrophysics Data System (ADS)

    Toyotama, Akiko; Okuzono, Tohru; Yamanaka, Junpei

    2016-03-01

    Crystallization of colloids has extensively been studied for past few decades as models to study phase transition in general. Recently, complex crystal structures in multi-component colloids, including alloy and eutectic structures, have attracted considerable attention. However, the fabrication of 2D area-filling colloidal eutectics has not been reported till date. Here, we report formation of eutectic structures in binary and ternary aqueous colloids due to depletion attraction. We used charged particles + linear polyelectrolyte systems, in which the interparticle interaction could be represented as a sum of the electrostatic, depletion, and van der Waals forces. The interaction was tunable at a lengthscale accessible to direct observation by optical microscopy. The eutectic structures were formed because of interplay of crystallization of constituent components and accompanying fractionation. An observed binary phase diagram, defined by a mixing ratio and inverse area fraction of the particles, was analogous to that for atomic and molecular eutectic systems. This new method also allows the adjustment of both the number and wavelengths of Bragg diffraction peaks. Furthermore, these eutectic structures could be immobilized in polymer gel to produce self-standing materials. The present findings will be useful in the design of the optical properties of colloidal crystals.

  1. Spontaneous Formation of Eutectic Crystal Structures in Binary and Ternary Charged Colloids due to Depletion Attraction

    PubMed Central

    Toyotama, Akiko; Okuzono, Tohru; Yamanaka, Junpei

    2016-01-01

    Crystallization of colloids has extensively been studied for past few decades as models to study phase transition in general. Recently, complex crystal structures in multi-component colloids, including alloy and eutectic structures, have attracted considerable attention. However, the fabrication of 2D area-filling colloidal eutectics has not been reported till date. Here, we report formation of eutectic structures in binary and ternary aqueous colloids due to depletion attraction. We used charged particles + linear polyelectrolyte systems, in which the interparticle interaction could be represented as a sum of the electrostatic, depletion, and van der Waals forces. The interaction was tunable at a lengthscale accessible to direct observation by optical microscopy. The eutectic structures were formed because of interplay of crystallization of constituent components and accompanying fractionation. An observed binary phase diagram, defined by a mixing ratio and inverse area fraction of the particles, was analogous to that for atomic and molecular eutectic systems. This new method also allows the adjustment of both the number and wavelengths of Bragg diffraction peaks. Furthermore, these eutectic structures could be immobilized in polymer gel to produce self-standing materials. The present findings will be useful in the design of the optical properties of colloidal crystals. PMID:26984298

  2. The use of biophysical methods increases success in obtaining liganded crystal structures

    SciTech Connect

    Chung, Chun-wa

    2007-01-01

    This paper highlights some of the problems that can arise when attempting to obtain crystal structures of small molecule–protein complexes and how biophysical methods can be used to define and overcome these problems. Many of the techniques mentioned are also applicable to the study of protein–protein complexes and mode-of-action analysis. In attempts to determine the crystal structure of small molecule–protein complexes, a common frustration is the absence of ligand binding once the protein structure has been solved. While the first structure, even with no ligand bound (apo), can be a cause for celebration, the solution of dozens of apo structures can give an unwanted sense of déjà vu. Much time and material is wasted on unsuccessful experiments, which can have a serious impact on productivity and morale. There are many reasons for the lack of observed binding in crystals and this paper highlights some of these. Biophysical methods may be used to confirm and optimize solution conditions to increase the success rate of crystallizing protein–ligand complexes. As there are an overwhelming number of biophysical methods available, some of the factors that need to be considered when choosing the most appropriate technique for a given system are discussed. Finally, a few illustrative examples where biophysical methods have proven helpful in real systems are given.

  3. Crystallization and preliminary structural results of catalase from human erythrocytes.

    PubMed

    Maté, M J; Ortiz-Lombardía, M; Marina, A; Fita, I

    1999-05-01

    Catalase (hydrogen peroxide:hydrogen peroxide oxidoreductase, E.C. 1. 11.1.6) is present in most aerobic prokaryotic and eukaryotic cells. Despite a large number of studies on catalases, the only mammalian catalase structure available is that from beef liver, in which about 50% of the haem groups are degraded to bile pigments. Three different crystal forms of human erythrocyte catalase were obtained by the hanging-drop vapour-diffusion technique using PEG as precipitant. Monoclinic crystals, with space group P21 and unit-cell parameters a = 102.9, b = 140.0, c = 173.6 A and beta = 103.2 degrees, require NADP(H) in the crystallization solution. Two types of hexagonal packing, with unit-cell parameters of either a = b = 86. 9, c = 255.5 A or a = b = 90.0, c = 521.2 A, were obtained under identical crystallization conditions in the absence of NADP(H). Only one diffraction data set could be collected: this was obtained from the hexagonal crystals with the smaller c axis using synchrotron radiation, with resolution to 2.65 A. A molecular-replacement solution, determined using a modified beef-liver catalase model as a search structure, corresponds to space group P6422 and contains a single subunit in the asymmetric unit, with an estimated solvent volume of about 50%. The packing determined suggests how minor rearrangements might allow the transition between both hexagonal crystal forms and provides an explanation for the anisotropic character of the corresponding diffractions. PMID:10216308

  4. Crystal and molecular structure of N-methylpiperidine betaine hydrochloride

    NASA Astrophysics Data System (ADS)

    Dega-Szafran, Z.; Szafran, M.; Dulewicz, E.; Addlagatta, A.; Jaskólski, M.

    2003-06-01

    A 1:1 complex between N-methylpiperidine betaine and hydrochloric acid, MPBH·Cl, has been characterized by single crystal X-ray analysis, FTIR spectroscopy, and DFT calculations. The crystals are monoclinic, space group P2 1/ n, with a=6.0644(3), b=13.0220(6), c=12.7653(7) Å, β=101.925(5)°. The piperidine ring adopts a chair conformation with the -CH 2COOH group in an axial and the-CH 3 group in an equatorial position. In the crystal, the Cl -anion is engaged in a medium-strong hydrogen bond with the COOH group (O-H⋯Cl -=2.9503(7) Å), in several C-H⋯Cl - contacts and, additionally, in three N +⋯Cl -intermolecular interactions. Four conformations (axial and equatorial, both protonated and unprotonated) of MPBHCl were examined by the B3LYP/6-31G(d,p) method. The calculated structure of MPBH·Cl(ax) is very similar to that in the crystal, except the N(1)-C(8)-C(9)-O(1) and N(1)-C(8)-C(9)-O(2) units, which are planar in the crystal but nonplanar in the isolated molecule. Powder FTIR spectra of MPBH·Cl and its deuterated analogue (MPBD·Cl) were measured and assignments of the observed bands to vibrations of the hydrogen bond and to internal vibrations are proposed.

  5. The Influence of Reduced Gravity on the Crystal Growth of Electronic Materials

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Gillies, D. C.; Szofran, F. R.; Watring, D. A.; Lehoczky, S. L.

    1996-01-01

    The imperfections in the grown crystals of electronic materials, such as compositional nonuniformity, dopant segregation and crystalline structural defects, are detrimental to the performance of the opto-electronic devices. Some of these imperfections can be attributed to effects caused by Earth gravity during crystal growth process and four areas have been identified as the uniqueness of material processing in reduced gravity environment. The significant results of early flight experiments, i.e. prior to space shuttle era, are briefly reviewed followed by an elaborated review on the recent flight experiments conducted on shuttle missions. The results are presented for two major growth methods of electronic materials: melt and vapor growth. The use of an applied magnetic field in the melt growth of electrically conductive melts on Earth to simulate the conditions of reduced gravity has been investigated and it is believed that the superimposed effect of moderate magnetic fields and the reduced gravity environment of space can result in reduction of convective intensities to the extent unreachable by the exclusive use of magnet on Earth or space processing. In the Discussions section each of the significant results of the flight experiments is attributed to one of the four effects of reduced gravity and the unresolved problems on the measured mass fluxes in some of the vapor transport flight experiments are discussed.

  6. Graphene as a protein crystal mounting material to reduce background scatter

    PubMed Central

    Wierman, Jennifer L.; Alden, Jonathan S.; Kim, Chae Un; McEuen, Paul L.; Gruner, Sol M.

    2013-01-01

    The overall signal-to-noise ratio per unit dose for X-ray diffraction data from protein crystals can be improved by reducing the mass and density of all material surrounding the crystals. This article demonstrates a path towards the practical ultimate in background reduction by use of atomically thin graphene sheets as a crystal mounting platform for protein crystals. The results show the potential for graphene in protein crystallography and other cases where X-ray scatter from the mounting material must be reduced and specimen dehydration prevented, such as in coherent X-ray diffraction imaging of microscopic objects. PMID:24068843

  7. Composite material characterization for large space structures.

    NASA Technical Reports Server (NTRS)

    Macneill, C. E.

    1972-01-01

    A program phase to characterize advanced composite materials for a large reflector support truss on the ATS F & G spacecraft is described. The selection of a Hercules Incorporated, 2002M graphite fiber reinforced epoxy material was based on criteria of spacecraft system requirements and the potential of this material to meet these requirements. The objective of this phase was to develop materials data required for development, design, fabrication, test, and flight of a graphite-fiber, reinforced-plastic spacecraft structure. Testing within a temperature range from -300 F to +200 F covered the generation of data for physical, mechanical, thermophysical, and space environmental properties for the selected material. Additional testing covered adhesive bonded joint materials within the temperature ranges of the spacecraft environment. Descriptions of the spacecraft, reflector support truss, design, requirements, materials, tests, and developed data are presented.

  8. Synthesis of Two-Photon Materials and Two-Photon Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Subramaniam, Girija

    2001-01-01

    The duration of the grant was interrupted by two major accidents that the PI met with-- an auto accident in Pasadena, CA during her second summer at JPL which took almost eight months for recovery and a second accident during Fall 2000 that left her in crutches for the entire semester. Further, the time released agreed by the University was not given in a timely fashion. The candidate has been given post-grant expire time off. In spite of all these problems, the PI synthesized a number of new two-photon materials and studied the structure-activity correlation to arrive at the best-optimized structure. The PI's design proved to be one of the best in the sense that these materials has a hitherto unreported two-photon absorption cross section. Many materials based on PI's design was later made by the NASA colleague. This is Phase 1. Phase II of this grant is to orate liquid crystalline nature into this potentially useful materials and is currently in progress. Recent observations of nano- and pico-second response time of homeotropically aligned liquid crystals suggest their inherent potentials to act as laser hardening materials, i.e., as protective devices against short laser pulses. The objective of the current project is to exploit this potential by the synthesis of liquid crystals with high optical nonlinearity and optimizing their performance. The PI is trying structural variations to bring in liquid crystalline nature without losing the high two-photon cross section. Both Phase I and Phase II led to many invited presentations and publications in reputed journals like 'Science' and 'Molecular Crystals'. The list of presentations and reprints are enclosed. Another important and satisfying outcome of this grant is the opportunity that this grant offered to the budding undergraduate scientists to get involved in a visible research of international importance. All the students had a chance to learn a lot during research, had the opportunity to present their work at the National level conferences. They continue to retain their interest in their research and went on to accomplish further laurels.

  9. Optical Spectroscopy of Nano Materials and Structures

    NASA Astrophysics Data System (ADS)

    Guo, Wenhao

    In this thesis, nanostructures and nanomaterials ranging from 3D to OD will be studied compresively, by using optical methods. Firstly, for 3D and 2D nanomaterials, nanoporous zeolite crystals, such as AFI and AEL are introduced as host materials to accommodate diatomic iodine molecules. Polarized Raman spectroscopy is utilized to identify the two configurations of iodine molecules to stay in the channels of AEL: the lying mode (the bond of the two atoms is parallel to the direction of the channels) and the standing mode (the bond is perpendicular to the direction of the channels). The lying mode and standing mode are switchable and can be well controlled by the amount of water molecules inside the crystal, revealed by both molecule dynamics simulation and experiment observation. With more water molecules inside, iodine molecules choose to stay in the standing mode, while with less water molecules, iodine molecules prefer to lie along the channel. Therefore, the configurations of molecules could be precisely controlled, globally by the surrounding pressure and temperature, and locally by the laser light. Ii is believed that this easy and reversible control of single molecule will be valuable in nanostructured devices, such as molecular sieving or molecular detection. Secondly, for 1D case, the PL spectrum of ZnO nanowire under uniaxial strain is studied. When a ZnO nanowire is bent, besides the lattice constant induced bandgap change on the tensile and compressive sides, there is a piezoelectric field generated along the cross section. This piezoelectric potential, together with the bandgap changes induced by the deformation, will redistribute the electrons excited by incident photons from valence band to conduction band. As a result, the electrons occupying the states at the tensile side will largely outnumbered the ones at the compressive side. Therefore, the PL spectrum we collected at the whole cross section will manifest a redshift, other than the peak broadening which is caused by the bandgap change. The experimental results confirm our speculation. When we make the nanowire straight again, the redshift disappears. It is believed that this piezoelectric effect is very important to the application of nanowires, and it would benefit the actual design and fabrication for the electronic devices for the next generation. Lastly, as for the OD case, the charge transfer mechanism occurring at the interface between graphene and ZnO QDs is investigated. We fabricate a hybrid structure by placing ZnO QDs on top of graphene. With UV light illumination on this device, it will generate electron-hole pairs inside QDs. Before they recombine, the holes will be separated and trapped into the surface states, and discharge the oxygen ions adsorbed on the surface of QDs. The unpaired electrons are then transferred to the graphene layer with a relative long lifetime. After the UV light is switched off, the oxygen molecules will re-adsorb to the QDs surface, capture electrons and recover the graphene's transport properties. Therefore, this hybrid device shows an ultrasensitive response to on-off of the UV laser, with a photoconductive gain as high as 10 7, which can be utilized for practical graphene-based UV sensors and detectors with very high responsivity. This gain can be further enhanced by another 2-3 orders by increasing source-drain voltage, shortening the sample's length, etc. It is believed that optical spectroscopy provides a convenient, efficient and useful method to study the nanomaterials and nanostructures. It is easy to set up, has no harm or degradation to the sample, and could go beyond the diffraction limit. With appropriate design and creative ideas, optical spectroscopy can be further explored, and will boost the development of nanoscience and technology. (Abstract shortened by UMI.).

  10. Crystal structure of inactive form of Rab3B

    SciTech Connect

    Zhang, Wei; Shen, Yang; Jiao, Ronghong; Liu, Yanli; Deng, Lingfu; Qi, Chao

    2012-06-28

    Rab proteins are the largest family of ras-related GTPases in eukaryotic cells. They act as directional molecular switches at membrane trafficking, including vesicle budding, cargo sorting, transport, tethering, and fusion. Here, we generated and crystallized the Rab3B:GDP complex. The structure of the complex was solved to 1.9 {angstrom} resolution and the structural base comparison with other Rab3 members provides a structural basis for the GDP/GTP switch in controlling the activity of small GTPase. The comparison of charge distribution among the members of Rab3 also indicates their different roles in vesicular trafficking.

  11. The Rapid Crystallization Strategy for Structure-Based Inhibitor Design

    NASA Astrophysics Data System (ADS)

    Bergfors, Terese

    RAPID (Rapid Approaches to Pathogen Inhibitor Discovery) is an integrated center for structural biology, computational chemistry, and medicinal chemistry at Uppsala University, Sweden. The main target of the structural biology section is Mycobacterium tuberculosis. Key concepts in the crystallization strategy include minimal screening and buffer optimization. Examples are presented showing how these concepts have been successful in RAPID projects. Three screening methods are used: vapor-diffusion, micro-batch, and microfluidics. Our experiences may be relevant for other small, academic laboratories involved in structure-based inhibitor design.

  12. Crystal structure of four-stranded Oxytricha telomeric DNA

    NASA Technical Reports Server (NTRS)

    Kang, C.; Zhang, X.; Ratliff, R.; Moyzis, R.; Rich, A.

    1992-01-01

    The sequence d(GGGGTTTTGGGG) from the 3' overhang of the Oxytricha telomere has been crystallized and its three-dimensional structure solved to 2.5 A resolution. The oligonucleotide forms hairpins, two of which join to make a four-stranded helical structure with the loops containing four thymine residues at either end. The guanine residues are held together by cyclic hydrogen bonding and an ion is located in the centre. The four guanine residues in each segment have a glycosyl conformation that alternates between anti and syn. There are two four-stranded molecules in the asymmetric unit showing that the structure has some intrinsic flexibility.

  13. Integrated design of structures, controls, and materials

    NASA Technical Reports Server (NTRS)

    Blankenship, G. L.

    1994-01-01

    In this talk we shall discuss algorithms and CAD tools for the design and analysis of structures for high performance applications using advanced composite materials. An extensive mathematical theory for optimal structural (e.g., shape) design was developed over the past thirty years. Aspects of this theory have been used in the design of components for hypersonic vehicles and thermal diffusion systems based on homogeneous materials. Enhancement of the design methods to include optimization of the microstructure of the component is a significant innovation which can lead to major enhancements in component performance. Our work is focused on the adaptation of existing theories of optimal structural design (e.g., optimal shape design) to treat the design of structures using advanced composite materials (e.g., fiber reinforced, resin matrix materials). In this talk we shall discuss models and algorithms for the design of simple structures from composite materials, focussing on a problem in thermal management. We shall also discuss methods for the integration of active structural controls into the design process.

  14. Computational chemistry modeling and design of photoswitchable alignment materials for optically addressable liquid crystal devices

    NASA Astrophysics Data System (ADS)

    Marshall, K. L.; Sekera, E. R.; Xiao, K.

    2015-09-01

    Photoalignment technology based on optically switchable "command surfaces" has been receiving increasing interest for liquid crystal optics and photonics device applications. Azobenzene compounds in the form of low-molar-mass, watersoluble salts deposited either directly on the substrate surface or after dispersion in a polymer binder have been almost exclusively employed for these applications, and ongoing research in the area follows a largely empirical materials design and development approach. Recent computational chemistry advances now afford unprecedented opportunities to develop predictive capabilities that will lead to new photoswitchable alignment layer materials with low switching energies, enhanced bistability, write/erase fatigue resistance, and high laser-damage thresholds. In the work described here, computational methods based on the density functional theory and time-dependent density functional theory were employed to study the impact of molecular structure on optical switching properties in photoswitchable methacrylate and acrylamide polymers functionalized with azobenzene and spiropyran pendants.

  15. Predicting different losses of photonic crystal fibers in material and hetero-core domain

    NASA Astrophysics Data System (ADS)

    Paul, Dimpi; Biswas, Rajib; Bhattacharyya, N. S.

    2015-10-01

    In order to develop the effective transmission in photonic crystal fiber (PCF), the (realizable fiber i.e.,) losses arising from bending as well as splicing are very vital issues. We report here macrobending loss of PCFs in different material composites. Further, we make comprehensive numerical analysis related to splice loss issues arising from joining PCF with PCF and single mode fiber as well. We additionally investigate dependence of all these losses with respect to structural parameters of PCF. Hetero core systems are found to yield lower losses as compared to their identical counterpart. The numerical estimates reported here will provide a base for engineering effective communication guides in the context of material and hybrid core domain.

  16. Structural evolution in the crystallization of rapid cooling silver melt

    NASA Astrophysics Data System (ADS)

    Tian, Z. A.; Dong, K. J.; Yu, A. B.

    2015-03-01

    The structural evolution in a rapid cooling process of silver melt has been investigated at different scales by adopting several analysis methods. The results testify Ostwald's rule of stages and Frank conjecture upon icosahedron with many specific details. In particular, the cluster-scale analysis by a recent developed method called LSCA (the Largest Standard Cluster Analysis) clarified the complex structural evolution occurred in crystallization: different kinds of local clusters (such as ico-like (ico is the abbreviation of icosahedron), ico-bcc like (bcc, body-centred cubic), bcc, bcc-like structures) in turn have their maximal numbers as temperature decreases. And in a rather wide temperature range the icosahedral short-range order (ISRO) demonstrates a saturated stage (where the amount of ico-like structures keeps stable) that breeds metastable bcc clusters. As the precursor of crystallization, after reaching the maximal number bcc clusters finally decrease, resulting in the final solid being a mixture mainly composed of fcc/hcp (face-centred cubic and hexagonal-closed packed) clusters and to a less degree, bcc clusters. This detailed geometric picture for crystallization of liquid metal is believed to be useful to improve the fundamental understanding of liquid-solid phase transition.

  17. Crystal structure optimisation using an auxiliary equation of state.

    PubMed

    Jackson, Adam J; Skelton, Jonathan M; Hendon, Christopher H; Butler, Keith T; Walsh, Aron

    2015-11-14

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy-volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other "beyond" density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu2ZnSnS4 and the magnetic metal-organic framework HKUST-1. PMID:26567640

  18. Liquid phase crystallized silicon on glass: Technology, material quality and back contacted heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Haschke, Jan; Amkreutz, Daniel; Rech, Bernd

    2016-04-01

    Liquid phase crystallization has emerged as a novel approach to grow large grained polycrystalline silicon films on glass with high electronic quality. In recent years a lot of effort was conducted by different groups to determine and optimize suitable interlayer materials, enhance the crystallographic quality or to improve post crystallization treatments. In this paper, we give an overview on liquid phase crystallization and describe the necessary process steps and discuss their influence on the absorber properties. Available line sources are compared and different interlayer configurations are presented. Furthermore, we present one-dimensional numerical simulations of a rear junction device, considering silicon absorber thicknesses between 1 and 500 µm. We vary the front surface recombination velocity as well as doping density and minority carrier lifetime in the absorber. The simulations suggest that a higher absorber doping density is beneficial for layer thicknesses below 20 µm or when the minority carrier lifetime is short. Finally, we discuss possible routes for device optimization and propose a hybride cell structure to circumvent current limitations in device design.

  19. Dielectric relaxations in structurally disordered materials

    NASA Astrophysics Data System (ADS)

    Laredo, E.; Hernandez, M. C.; Bello, A.; Grimau, M.; Balsamo, V.; Muller, A. J.

    2003-01-01

    Chain mobility in multiphase polymeric materials is studied by thermally stimulated depolarization currents and dielectric spectroscopy in poly(styrene)-b-poly(butadiene)-b-poly(c-caprolactone) triblock copolymers and poly(carbonate)/poly(epsilon-caprolactone) blends. The variation in the relaxation time distribution of the dielectrically active components and in the number of orientable dipoles in the amorphous phases of these materials is interpreted as the result of the existence of a rigid amorphous phase constrained by the crystalline regions or in the case of the blends by a phase segregation which takes place when the crystallization process of the blend components advances. The mean relaxation times for the secondary and segmental motions are not affected when the phases are segregated.

  20. EVO—Evolutionary algorithm for crystal structure prediction

    NASA Astrophysics Data System (ADS)

    Bahmann, Silvia; Kortus, Jens

    2013-06-01

    We present EVO—an evolution strategy designed for crystal structure search and prediction. The concept and main features of biological evolution such as creation of diversity and survival of the fittest have been transferred to crystal structure prediction. EVO successfully demonstrates its applicability to find crystal structures of the elements of the 3rd main group with their different spacegroups. For this we used the number of atoms in the conventional cell and multiples of it. Running EVO with different numbers of carbon atoms per unit cell yields graphite as the lowest energy structure as well as a diamond-like structure, both in one run. Our implementation also supports the search for 2D structures and was able to find a boron sheet with structural features so far not considered in literature. Program summaryProgram title: EVO Catalogue identifier: AEOZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOZ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 23488 No. of bytes in distributed program, including test data, etc.: 1830122 Distribution format: tar.gz Programming language: Python. Computer: No limitations known. Operating system: Linux. RAM: Negligible compared to the requirements of the electronic structure programs used Classification: 7.8. External routines: Quantum ESPRESSO (http://www.quantum-espresso.org/), GULP (https://projects.ivec.org/gulp/) Nature of problem: Crystal structure search is a global optimisation problem in 3N+3 dimensions where N is the number of atoms in the unit cell. The high dimensional search space is accompanied by an unknown energy landscape. Solution method: Evolutionary algorithms transfer the main features of biological evolution to use them in global searches. The combination of the "survival of the fittest" (deterministic) and the randomised choice of the parents and normally distributed mutation steps (non-deterministic) provides a thorough search. Restrictions: The algorithm is in principle only restricted by a huge search space and simultaneously increasing calculation time (memory, etc.), which is not a problem for our piece of code but for the used electronic structure programs. Running time: The simplest provided case runs serially and takes 30 minutes to one hour. All other calculations run for significantly longer time depending on the parameters like the number and sort of atoms and the electronic structure program in use as well as the level of parallelism included.

  1. Electronic and crystal structure of NiTi martensite

    SciTech Connect

    Sanati, M.; Albers, R.C.; Pinski, F.J.

    1998-11-01

    All of the first-principles electronic-structure calculations for the martensitic structure of NiTi have used the experimental atomic parameters reported by Michal and Sinclair [Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. {bold B37}, 1803 (1981)]. We have used first-principles, full-potential, linear muffin-tin orbital calculations to examine the total energy of all the experimental martensitic structures reported in the literature. We find that another crystal structure, that of Kudoh {ital et al.} [Acta Metall. Mater. {bold 33}, 2049 (1985)], has the lowest total energy at zero temperature. Ground-state and formation energies were calculated for all of the experimental structures. Total and local densities of states were calculated and compared with each other for the structures of both Kudoh {ital et al.} and Michal and Sinclair thinsp {copyright} {ital 1998} {ital The American Physical Society}

  2. Structural investigation of cooperite (PtS) crystals

    NASA Astrophysics Data System (ADS)

    Rozhdestvina, V. I.; Udovenko, A. A.; Rubanov, S. V.; Mudrovskaya, N. V.

    2016-03-01

    The single-crystal structure of cooperite, a natural platinum sulfide PtS, is studied by X-ray diffraction supported by high-resolution scanning transmission electron microscopy and X-ray spectrum microanalysis. It is found that, in addition to the main reflections corresponding to the known tetragonal cell ( a = 3.47 and c = 6.11 Å; space group P42/ mmc), many weak reflections with intensities I ≤ 60 σ( I) are clearly observed. These reflections fit the tetragonal cell (space group I4/ mmm) with doubled parameters. In structures with small ( P42/ mmc) and large ( I4/ mmm) cells, the S atoms occupy statistically two special positions. It is shown that the chemical composition of the cooperite crystals deviates from the stoichiometric composition: sulfur-deficient specimens predominate.

  3. Crystal structures and properties of nylon polymers from theory

    SciTech Connect

    Dasgupta, S.; Goddard, W.A. III; Hammond, W.B.

    1996-12-11

    A complete force field (MSXX) for simulation of all nylon polymers is derived from ab initio quantum calculations. Special emphasis is given to the accuracy of the hydrogen bond potential for the amide unit and the torsional potential between the peptide and alkane fragments. The MSXX force field was used to predict the structures, moduli, and detailed geometries of all nine nylons for which there are experimental crystal data plus one other. For nylon-(2n) with 2n = 6, the {alpha} crystal structure (with all-trans CH{sub 2} chains nearly coplanar with the hydrogen bonding plane) is more stable, while for 2n > 6, {gamma} (with the alkane plane twisted by 70{degree}) is more stable. This change results from the increased importance of methylene packing interactions over H bonds for larger 2n. We find the highest Young`s modulus for nylon-7. 51 refs., 6 figs., 7 tabs.

  4. Crystal structure of tris-(hydroxyl-ammonium) orthophosphate.

    PubMed

    Leinemann, Malte; Jess, Inke; Boeckmann, Jan; Näther, Christian

    2015-11-01

    The crystal structure of the title salt, ([H3NOH](+))3·[PO4](3-), consists of discrete hydroxyl-ammonium cations and ortho-phos-phate anions. The atoms of the cation occupy general positions, whereas the anion is located on a threefold rotation axis that runs through the phospho-rus atom and one of the phosphate O atoms. In the crystal structure, cations and anions are linked by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds into a three-dimensional network. Altogether, one very strong O-H⋯O, two N-H⋯O hydrogen bonds of medium strength and two weaker bifurcated N-H⋯O inter-actions are observed. PMID:26594525

  5. Crystal structure of tris­(hydroxyl­ammonium) orthophosphate

    PubMed Central

    Leinemann, Malte; Jess, Inke; Boeckmann, Jan; Näther, Christian

    2015-01-01

    The crystal structure of the title salt, ([H3NOH]+)3·[PO4]3−, consists of discrete hydroxyl­ammonium cations and ortho­phos­phate anions. The atoms of the cation occupy general positions, whereas the anion is located on a threefold rotation axis that runs through the phospho­rus atom and one of the phosphate O atoms. In the crystal structure, cations and anions are linked by inter­molecular O—H⋯O and N—H⋯O hydrogen bonds into a three-dimensional network. Altogether, one very strong O—H⋯O, two N—H⋯O hydrogen bonds of medium strength and two weaker bifurcated N—H⋯O inter­actions are observed. PMID:26594525

  6. Crystal structure of the human mitochondrial chaperonin symmetrical football complex

    PubMed Central

    Nisemblat, Shahar; Yaniv, Oren; Parnas, Avital; Frolow, Felix; Azem, Abdussalam

    2015-01-01

    Human mitochondria harbor a single type I chaperonin system that is generally thought to function via a unique single-ring intermediate. To date, no crystal structure has been published for any mammalian type I chaperonin complex. In this study, we describe the crystal structure of a football-shaped, double-ring human mitochondrial chaperonin complex at 3.15 Å, which is a novel intermediate, likely representing the complex in an early stage of dissociation. Interestingly, the mitochondrial chaperonin was captured in a state that exhibits subunit asymmetry within the rings and nucleotide symmetry between the rings. Moreover, the chaperonin tetradecamers show a different interring subunit arrangement when compared to GroEL. Our findings suggest that the mitochondrial chaperonins use a mechanism that is distinct from the mechanism of the well-studied Escherichia coli system. PMID:25918392

  7. Crystal structure of naturally occurring mercury(II) amidonitrate

    NASA Astrophysics Data System (ADS)

    Randall, Charles J.; Peacor, Donald R.; Rouse, Roland C.; Dunn, Pete J.

    1982-05-01

    A naturally-occurring mercuroammonium compound from Pitkin County, Colorado, is shown to be the natural analog of synthetic HgNH 2NO 3. The crystals are isometric, P4 132 or P4 332, with a = 10.254(1) and twelve formula weights per cell. Using 437 symmetry-independent reflections, the crystal structure was partially determined and refined to a residual of 0.090. The positions of the Hg atoms and the N and O atoms of the nitrate group were determined, but the amide ion could not be located, probably due to positional disorder. The structure contains mercury atoms arranged in equilateral triangles 3.421(1) on a side. These triangles are linked through shared vertices into helical chains wound around the fourfold screw axes. Similar triangular units occur in other inorganic Hg(II) compounds. The distortion of the nitrate ion from trigonal planar symmetry is also discussed.

  8. Surface modes and reconstruction of diamond structure crystals

    NASA Astrophysics Data System (ADS)

    Goldammer, W.; Ludwig, W.; Zierau, W.

    1986-08-01

    Applying our recently proposed Green function method we calculate the surface phonon spectra for the (111) surfaces of the diamond structure crystals C, Si, Ge and α-Sn on the basis of a phenomenological force constant model. Allowing for changes in the surface force constants we investigate the possibility of a surface phonon softening. Relating these soft modes to surface reconstructions we find evidence for a Si (7 × 7), Ge (8 × 8) and α-Sn (3 × 3) reconstruction, while diamond does not exhibit a soft mode behavior at all. We can thus explain the occurrence of different surface structures in these geometrically identical crystals as being determined to a great extent already by bulk properties. Finally, we derive models of the reconstructed surfaces and discuss our model for the Si (7 × 7) surface with respect to experimental TED patterns.

  9. Crystal Structure of the Product of Mg 2+Insertion into V 2O 5Single Crystals

    NASA Astrophysics Data System (ADS)

    Shklover, V.; Haibach, T.; Ried, F.; Nesper, R.; Novák, P.

    1996-05-01

    Chemical (by interaction with a dibutylmagnesium solution) and electrochemical (in acetonitrile solution of magnesium perchlorate) insertion of Mg 2+into the single crystals of V 2O 5was performed. The morphology change of V 2O 5crystals as a result of the Mg 2+insertion was studied by scanning electron microscopy. The wavelength dispersive electron probe microanalysis clearly showed the presence of Mg (at least) at the surface of intercalated V 2O 5. Based on the single crystal X-ray diffraction study of intercalated V 2O 5(orthorhombic, Pmn2 1, a= 11.544(6), b= 4.383(3), c= 3.574(2) Å, Z= 4) the location of a small amount of Mg (˜1%) in the bulk V 2O 5may be suggested, with [6 + 4] oxygen atoms surrounding Mg. The resulting Mg-O separations essentially exceed the accepted values for the Mg-O distances in crystals with hexacoordinated Mg atoms, which may be correlated with the structural and electrochemical properties of Mg 2+-inserted V 2O 5.

  10. Combined crystal structure prediction and high-pressure crystallization in rational pharmaceutical polymorph screening

    PubMed Central

    Neumann, M. A.; van de Streek, J.; Fabbiani, F. P. A.; Hidber, P.; Grassmann, O.

    2015-01-01

    Organic molecules, such as pharmaceuticals, agro-chemicals and pigments, frequently form several crystal polymorphs with different physicochemical properties. Finding polymorphs has long been a purely experimental game of trial-and-error. Here we utilize in silico polymorph screening in combination with rationally planned crystallization experiments to study the polymorphism of the pharmaceutical compound Dalcetrapib, with 10 torsional degrees of freedom one of the most flexible molecules ever studied computationally. The experimental crystal polymorphs are found at the bottom of the calculated lattice energy landscape, and two predicted structures are identified as candidates for a missing, thermodynamically more stable polymorph. Pressure-dependent stability calculations suggested high pressure as a means to bring these polymorphs into existence. Subsequently, one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib. PMID:26198974

  11. Enhanced absorption in two-dimensional materials via Fano-resonant photonic crystals

    SciTech Connect

    Wang, Wenyi; Klots, Andrey; Bolotin, Kirill I.; Yang, Yuanmu; Li, Wei; Valentine, Jason; Kravchenko, Ivan I.; Briggs, Dayrl P.

    2015-05-04

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and near-infrared regimes monolayer MoS{sub 2} and graphene absorb only ∼10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ∼0.2 μm adjacent to the graphene/electrode interface.

  12. Internal strain monitoring in composite materials with embedded photonic crystal fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Geernaert, Thomas; Sulejmani, Sanne; Sonnenfeld, Camille; Chah, Karima; Luyckx, Geert; Lammens, Nicolas; Voet, Eli; Becker, Martin; Thienpont, Hugo; Berghmans, Francis

    2014-09-01

    The possibility of embedding optical fiber sensors inside carbon fiber reinforced polymer (CFRP) for structural health monitoring purposes has already been demonstrated previously. So far however, these sensors only allowed axial strain measurements because of their low sensitivity for strain in the direction perpendicular to the optical fiber's axis. The design flexibility provided by novel photonic crystal fiber (PCF) technology now allows developing dedicated fibers with substantially enhanced sensitivity to such transverse loads. We exploited that flexibility and we developed a PCF that, when equipped with a fiber Bragg grating (FBG), leads to a sensor that allows measuring transverse strains in reinforced composite materials, with an order of magnitude increase of the sensitivity over the state-of-the-art. In addition it allows shear strain sensing in adhesive bonds, which are used in composite repair patches. This is confirmed both with experiments and finite element simulations on such fibers embedded in CFRP coupons and adhesive bonds. Our sensor brings the achievable transverse strain measurement resolution close to a target value of 1 μstrain and could therefore play an important role for multi-dimensional strain sensing, not only in the domain of structural health monitoring, but also in the field of composite material production monitoring. Our results thereby illustrate the added value that PCFs have to offer for internal strain measurements inside composite materials and structures.

  13. Crystal Structures of Aedes Aegypt Alanine Glyoxylate Aminotransferase

    SciTech Connect

    Han,Q.; Robinson, H.; Gao, Y.; Vogelaar, N.; Wilson, S.; Rizzi, M.; Li, J.

    2006-01-01

    Mosquitoes are unique in having evolved two alanine glyoxylate aminotransferases (AGTs). One is 3-hydroxykynurenine transaminase (HKT), which is primarily responsible for catalyzing the transamination of 3-hydroxykynurenine (3-HK) to xanthurenic acid (XA). Interestingly, XA is used by malaria parasites as a chemical trigger for their development within the mosquito. This 3-HK to XA conversion is considered the major mechanism mosquitoes use to detoxify the chemically reactive and potentially toxic 3-HK. The other AGT is a typical dipteran insect AGT and is specific for converting glyoxylic acid to glycine. Here we report the 1.75{angstrom} high-resolution three-dimensional crystal structure of AGT from the mosquito Aedes aegypti (AeAGT) and structures of its complexes with reactants glyoxylic acid and alanine at 1.75 and 2.1{angstrom} resolution, respectively. This is the first time that the three-dimensional crystal structures of an AGT with its amino acceptor, glyoxylic acid, and amino donor, alanine, have been determined. The protein is dimeric and adopts the type I-fold of pyridoxal 5-phosphate (PLP)-dependent aminotransferases. The PLP co-factor is covalently bound to the active site in the crystal structure, and its binding site is similar to those of other AGTs. The comparison of the AeAGT-glyoxylic acid structure with other AGT structures revealed that these glyoxylic acid binding residues are conserved in most AGTs. Comparison of the AeAGT-alanine structure with that of the Anopheles HKT-inhibitor complex suggests that a Ser-Asn-Phe motif in the latter may be responsible for the substrate specificity of HKT enzymes for 3-HK.

  14. Crystal Structures of Cisplatin Bound to a Human Copper Chaperone

    SciTech Connect

    Boal, Amie K.; Rosenzweig, Amy C.

    2010-08-16

    Copper trafficking proteins, including the chaperone Atox1 and the P{sub 1B}-type ATPase ATP7B, have been implicated in cellular resistance to the anticancer drug cisplatin. We have determined two crystal structures of cisplatin-Atox1 adducts that reveal platinum coordination by the conserved CXXC copper-binding motif. Direct interaction of cisplatin with this functionally relevant site has significant implications for understanding the molecular basis for resistance mediated by copper transport pathways.

  15. The Crystal and Molecular Structure of Acetatochlorobis(4-methylpyridine)oxovanadium (IV)

    NASA Technical Reports Server (NTRS)

    Schupp, John D.; Hepp, Aloysius F.; Duraj, Stan A.; Richman, Robert M.; Fanwick, Phillip E.; Hakimzadeh, Roshanak (Technical Monitor)

    2001-01-01

    The crystal and molecular structure of the title compound, VOCl(O2CCH3)(4-CH3C5H4N)2, has been determined by single-crystal x-ray diffraction. The material crystallizes in the space group P 1(bar) (#2) with a = 7.822(2), b = 8.023(l), c = 14.841(2) Angstroms, alpha = 99.73(l), beta = 91.41(l), and gamma = 117.13(l). The coordination geometry around the vanadium is a highly distorted octahedron. The molecule is remarkable for being a monomeric oxovanadium (IV) carboxylate. A generalized synthetic strategy is proposed for the preparation of oxovanadium (IV) monomers.

  16. Structural considerations on acridine/acridinium derivatives: Synthesis, crystal structure, Hirshfeld surface analysis and computational studies

    NASA Astrophysics Data System (ADS)

    Wera, Michał; Storoniak, Piotr; Serdiuk, Illia E.; Zadykowicz, Beata

    2016-02-01

    This article describes a detailed study of the molecular packing and intermolecular interactions in crystals of four derivatives of acridine, i.e. 9-methyl-, 9-ethyl, 9-bromomethyl- and 9-piperidineacridine (1, 2, 3 and 4, respectively) and three 10-methylacridinium salts containing the trifluoromethanesulphonate anion and 9-vinyl-, 9-bromomethyl, and 9-phenyl-10-methylacridinium cations (5, 6 and 7, respectively). The crystal structures of all of the compounds are stabilized by long-range electrostatic interactions, as well as by a network of short-range C-HṡṡṡO (in hydrates and salts 3 and 5-7, respectively), C-Hṡṡṡπ, π-π, C-Fṡṡṡπ and S-Oṡṡṡπ (in salts 5-7) interactions. Hirshfeld surface analysis shows that various intermolecular contacts play an important role in the crystal packing, graphically exhibiting the differences in spatial arrangements of the acridine/acridinium derivatives under scrutiny here. Additionally, computational methods have been used to compare the intermolecular interactions in the crystal structures of the investigated compounds. Computations have confirmed the great contribution of dispersive interactions for crystal lattice stability in the case of 9-substituted acridine and electrostatic interactions for the crystal lattice stability in the case of 9-substituted 10-methylacridinium trifluoromethanesulphonates. The value of crystal lattice energy and the electrostatic contribution in the crystal lattice energy of monohydrated acridine derivatives have confirmed that these compounds have behave as acridinium derivatives.

  17. Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals

    DOEpatents

    Todt, V.; Miller, D.J.; Shi, D.; Sengupta, S.

    1998-07-07

    A method of fabricating bulk YBa{sub 2}Cu{sub 3}O{sub x} where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa{sub 2}Cu{sub 3}O{sub x} are heated in the presence of a Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y} seed crystal to a temperature sufficient to form a liquid phase in the YBa{sub 2}Cu{sub 3}O{sub x} while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa{sub 2}Cu{sub 3}O{sub x} material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material. 7 figs.

  18. The influence of recycled material on the crystallization kinetics of semi-crystalline thermoplastic polymers

    SciTech Connect

    Janoschek, J.; Kaisersbergen, E.; Knappe, S.; Opfermann, J.

    1993-12-31

    The injection moulding of semi-crystalline thermoplastic polymers requires an exact knowledge of the thermodynamic data and of the crystallization kinetics. The behavior of the polymer melt during rapid cooling in the mould determines, to a great extent, the quality and usability of a final product. Technical raw materials are often equipped with nucleating agents in order to obtained crystallization within the desired temperature range at the required rate. The use of recycled material (regranulate) shows an analogous effect such as the addition of nucleating agents, i.e. crystallization begins at a higher temperature and a higher crystallization rate is detected compared to materials without added regranulate. Heat flux DSC was used to study the crystallization of polyamides, polyolefins and polyoxymethylene during cooling at various cooling rates. Although the temperature gradient and pressures which occur in the processing machine cannot be realized in DSC tests, the DSC results reproduce the direction of influence of the regranulate additive very clearly.

  19. Crystal Structures of the β2-Adrenergic Receptor

    NASA Astrophysics Data System (ADS)

    Weis, William I.; Rosenbaum, Daniel M.; Rasmussen, Søren G. F.; Choi, Hee-Jung; Thian, Foon Sun; Kobilka, Tong Sun; Yao, Xiao-Jie; Day, Peter W.; Parnot, Charles; Fung, Juan J.; Ratnala, Venkata R. P.; Kobilka, Brian K.; Cherezov, Vadim; Hanson, Michael A.; Kuhn, Peter; Stevens, Raymond C.; Edwards, Patricia C.; Schertler, Gebhard F. X.; Burghammer, Manfred; Sanishvili, Ruslan; Fischetti, Robert F.; Masood, Asna; Rohrer, Daniel K.

    G protein coupled receptors (GPCRs) constitute the largest family of membrane proteins in the human genome, and are responsible for the majority of signal transduction events involving hormones and neuro-transmitters across the cell membrane. GPCRs that bind to diffusible ligands have low natural abundance, are relatively unstable in detergents, and display basal G protein activation even in the absence of ligands. To overcome these problems two approaches were taken to obtain crystal structures of the β2-adrenergic receptor (β2AR), a well-characterized GPCR that binds cate-cholamine hormones. The receptor was bound to the partial inverse agonist carazolol and co-crystallized with a Fab made to a three-dimensional epitope formed by the third intracellular loop (ICL3), or by replacement of ICL3 with T4 lysozyme. Small crystals were obtained in lipid bicelles (β2AR-Fab) or lipidic cubic phase (β2AR-T4 lysozyme), and diffraction data were obtained using microfocus technology. The structures provide insights into the basal activity of the receptor, the structural features that enable binding of diffusible ligands, and the coupling between ligand binding and G-protein activation.

  20. Nanoconfinement-Induced Structures in Chiral Liquid Crystals

    PubMed Central

    Melle, Michael; Theile, Madlona; Hall, Carol K.; Schoen, Martin

    2013-01-01

    We employ Monte Carlo simulations in a specialized isothermal-isobaric and in the grand canonical ensemble to study structure formation in chiral liquid crystals as a function of molecular chirality. Our model potential consists of a simple Lennard-Jones potential, where the attractive contribution has been modified to represent the orientation dependence of the interaction between a pair of chiral liquid-crystal molecules. The liquid crystal is confined between a pair of planar and atomically smooth substrates onto which molecules are anchored in a hybrid fashion. Hybrid anchoring allows for the formation of helical structures in the direction perpendicular to the substrate plane without exposing the helix to spurious strains. At low chirality, we observe a cholesteric phase, which is transformed into a blue phase at higher chirality. More specifically, by studying the unit cell and the spatial arrangement of disclination lines, this blue phase can be established as blue phase II. If the distance between the confining substrates and molecular chirality are chosen properly, we see a third structure, which may be thought of as a hybrid, exhibiting mixed features of a cholesteric and a blue phase. PMID:23989605