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1

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

NASA Technical Reports Server (NTRS)

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.

1975-01-01

2

Solar cell structure incorporating a novel single crystal silicon material  

DOEpatents

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.

Pankove, Jacques I. (Princeton, NJ); Wu, Chung P. (Trenton, NJ)

1983-01-01

3

Hierarchical structuring of liquid crystal polymer-Laponite hybrid materials.  

PubMed

Biomimetic organic-inorganic composite materials were fabricated via one-step self-organization on three hierarchical levels. The organic component was a polyoxazoline with pendent cholesteryl and carboxyl (N-Boc-protected amino acid) side chains that was able to form a chiral nematic lyotropic phase and bind to positively charged inorganic faces of Laponite. The Laponite particles formed a mesocrystalline arrangement within the liquid-crystal (LC) polymer phase upon shearing a viscous dispersion of Laponite nanoparticles and LC polymer in DMF. Complementary analytical and mechanical characterization techniques (AUC, POM, TEM, SEM, SAXS, ?CT, and nanoindentation) covering the millimeter, micrometer, and nanometer length scales reveal the hierarchical structures and properties of the composite materials consisting of different ratios of Laponite nanoparticles and liquid-crystalline polymer. PMID:23790152

Tritschler, Ulrich; Zlotnikov, Igor; Zaslansky, Paul; Aichmayer, Barbara; Fratzl, Peter; Schlaad, Helmut; Cölfen, Helmut

2013-09-01

4

Single crystal silicon as a low-temperature structural material  

NASA Astrophysics Data System (ADS)

In neutron scattering applications, it is frequently desirable to construct a sample container from a material that is strong but has very little neutron absorption of scattering. Single crystal silicon is very good by these criteria but it is difficult to work with because of its brittleness. A technique for gluing silicon was developed that yields high strength joints at low temperatures and allows very compact designs for sample containers.

Roach, P. R.

1984-07-01

5

Synthesis, crystal growth, structural, optical, thermal and mechanical properties of novel organic NLO material: Ammonium malate  

Microsoft Academic Search

Ammonium malate (AM), an organic nonlinear optical material, has been synthesized and single crystals, with dimensions up to 38×35×27mm3, have been grown from aqueous solution. The crystal structure of AM has been determined, and it belongs to the non-centro symmetric space group Cc. The structural perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD) rocking curve

G. Anandha babu; G. Bhagavannarayana; P. Ramasamy

2008-01-01

6

Exploring Materials: Liquid Crystals  

NSDL National Science Digital Library

In this activity, learners discover that the way a material behaves on the macroscale is affected by its structure on the nanoscale. Learners investigate the properties of a heat sensitive liquid crystal and make their own liquid crystal sensor to take home. This is a fun and engaging activity, especially since liquid crystals are used in many consumer products, including cell phone displays, laptop computer screens, strip thermometers, and even "mood" rings! SAFETY: learners must be supervised when doing this activity. They must wear safety glasses to protect their eyes. Before doing this activity, read through the Material Safety Data Sheets.

Nanoscale Informal Science Education Network

2010-01-01

7

Silks: crystal networks in silk fibrous materials: from hierarchical structure to ultra performance (small 9-10/2015).  

PubMed

Crystal networks bridge the hard and the soft worlds of materials, as described by X. Y. Liu and co-workers on page 1039. For many functional materials of complex structures, the functionality that is critical to macroscopic behavior begins to manifest itself at the mesoscale. While crystals have been hard functional materials for centuries, crystal networks are found to be one type of mesoscopic structure, and they play a key role in the macroscopic performance of various soft materials. PMID:25737353

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

2015-03-01

8

Single crystal silicon as a macro-world structural material : application to compact, lightweight high pressure vessels  

E-print Network

Single crystal silicon has promising inherent structural properties which are attractive for weight sensitive applications. Single crystal silicon, however, is a brittle material which makes the usable strength that can ...

Garza, Tanya Cruz

2011-01-01

9

Active materials in photonic crystals  

E-print Network

I analyze new phenomena arising from embedding active materials inside of photonic crystal structures. These structures strongly modify the photonic local density of states (LDOS), leading to quantitative and qualitative ...

Bermel, Peter (Peter A.)

2007-01-01

10

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

PubMed

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

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

2015-03-01

11

Colloidal crystals as templates for porous materials  

Microsoft Academic Search

Close-packed colloidal crystals are promising precursors for novel materials, but only after appropriate methods are developed to fix their structure. A wide range of advanced materials has recently been synthesized by replicating the structure of colloidal crystals into durable solid matrices. Such materials with structured pores have promise as photonic crystals, catalysts, and membranes, and in a variety of other

Orlin D. Velev; Abraham M. Lenhoff

2000-01-01

12

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

13

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

NASA Astrophysics Data System (ADS)

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).

Hennig, Richard

2012-02-01

14

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

NASA Astrophysics Data System (ADS)

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.

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

2015-04-01

15

Single crystal Ce doped scintillator material with garnet structure sensitive to gamma ray and neutron radiation  

NASA Astrophysics Data System (ADS)

A mixed garnet scintillator host material is obtained from the melt—Yttrium Gadolinium Gallium Aluminum Garnet (YGGAG). In addition to the high thermal and chemical stability and radiation hardness found in garnet crystals, it offers sensitivity to neutrons due to the presence of Gd atoms, has lower melting temperature than yttrium aluminum garnet, and similar crystallization behavior suitable for growth of large volume crystals. Crystals of YGGAG doped with Ce of 10×10×10 mm3 have already demonstrated energy resolution of 10% at 662 keV.

Solodovnikov, D.; Weber, M. H.; Haven, D. T.; Lynn, K. G.

2012-08-01

16

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

17

The thermal, magnetic, and structural characterization of the crystallization kinetics of amorphous soft magnetic materials  

Microsoft Academic Search

Summary form only given. The characterization of the crystallization kinetics of amorphous soft magnetic materials, namely NANOPERM™, an Fe88Zr7B4Cu1 amorphous soft magnetic alloy, and its derivatives, is presented. Crystallization kinetics are observed isothermally and non-isothermally by differential scanning calorimetry (DSC), synchrotron x-ray diffraction (XRD) and vibrating sample magnetometry (VSM). Vibrating sample magnetometry and x-ray diffractometry, used concurrently with differential scanning

A. C. Hsiao

2002-01-01

18

Crystal Structure Prediction and its Application in Earth and Materials Sciences  

NASA Astrophysics Data System (ADS)

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.)

Zhu, Qiang

19

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

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

20

Crystal structure of MCM-70: A microporous material with high framework density.  

PubMed

The crystal structure of the borosilicate MCM-70 (siliceous framework formula Si12O24) was determined from synchrotron powder diffraction data with the program FOCUS. The framework crystallizes in space group Pmn2(1), where a = 13.663, b = 4.779, c = 8.723 A, and forms 1D ellipsoidal 10-ring channels with the following dimensions: 5.0 x 3.1 A. Rietveld refinement of the model against synchrotron powder data from solvated material gives Rwp = 0.15, R(F2) = 0.11. In addition to the four tetrahedral sites and seven framework oxygens, one potassium position is found during this refinement. Because of the unreasonable geometry of five putative extraframework oxygen sites, another synchrotron pattern was obtained from a dehydrated specimen. A refinement in space group P1n1 (removing the mirror operation of Pmn2(1)), where a = 13.670, b = 4.781, c = 8.687 A, and beta = 90.24 degrees , verified that the previous framework geometry is preserved as well as the potassium position. One extraframework oxygen was located that would yield a reasonable K-O distance. The existence of potassium is verified by electron energy dispersive spectroscopic measurements as well as quantitative elemental analysis. (There are approximately 2.35 K sites per 12 Si in the unit cell.) It is likely that the constricted channels occlude KOH. 11B and 29Si MAS NMR measurements indicate a framework SiO2/B2O3 of approximately 40:1, which is consistent with a wavelength dispersive spectroscopic measurement. The silicate framework density is 2.10 gm/cm3. The resulting framework density for T sites, 21.1, is unusually high for a zeolite, just below the value for paracelsian (21.4) or scapolite (21.8), each of which also has a smallest four-ring loop. The 1H --> 29Si CP MAS measurements suggest sample heterogeneity, that is, a portion of the sample that is strongly coupled to hydrogen and efficiently cross polarizes and another portion that does not. PMID:16852743

Dorset, Douglas L; Kennedy, Gordon J

2005-07-28

21

Crystal structure and prediction.  

PubMed

The notion of structure is central to the subject of chemistry. This review traces the development of the idea of crystal structure since the time when a crystal structure could be determined from a three-dimensional diffraction pattern and assesses the feasibility of computationally predicting an unknown crystal structure of a given molecule. Crystal structure prediction is of considerable fundamental and applied importance, and its successful execution is by no means a solved problem. The ease of crystal structure determination today has resulted in the availability of large numbers of crystal structures of higher-energy polymorphs and pseudopolymorphs. These structural libraries lead to the concept of a crystal structure landscape. A crystal structure of a compound may accordingly be taken as a data point in such a landscape. PMID:25422850

Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R

2015-04-01

22

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

DOEpatents

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.

Yang, Jihui (Lakeshore, CA); Shi, Xun (Troy, MI); Bai, Shengqiang (Shanghai, CN); Zhang, Wenqing (Shanghai, CN); Chen, Lidong (Shanghai, CN); Yang, Jiong (Shanghai, CN)

2012-01-17

23

Band structure of photonic crystal with dispersive and lossy materials using Dirichlet-to-Neumann wave vector eigen equation method  

NASA Astrophysics Data System (ADS)

We present the Dirichlet-to-Neumann wave vector eigen equation (DtN-WVEE) method to calculate the band structure of photonic crystal (PhC) with dispersive and lossy materials, and then use finite-difference time-domain method to verify the validity of the results of the DtN-WVEE method. Since the material is lossy with a non-zero imaginary part of epsilon, the wave vector of PhC band structure also has a non-zero imaginary part which results in the reduction of the intensity of the mode. We further present the band structure which gives the relationship among the normalized frequency, the real part of the wave vector, and the imaginary part of the wave vector. To our knowledge, the band structure of lossy PhC has not been well studied yet, and our results can be useful in designing the devices using surface plasmon polariton effect.

Jiang, Bin; Zhang, Yejin; Wang, Yufei; Zheng, Wanhua

2012-08-01

24

Computerized crystal-chemical classification of silicates and related materials with CRYSTANA and formula notation for classified structures  

SciTech Connect

The computer program CRYSTANA is described which implements a method for the crystal-chemical classification of silicates and related materials. This method is mainly based upon the topological structure of the connected units of a compound and can be applied when the units are built from tetrahedra as coordination polyhedra. The classification parameters and the rules which have to be applied for their determination are summarized and a formalization of the method is provided based upon a finite graph representation of the units. A description of how CRYSTANA can be used and which kind of output it produces is included. From this output crystal-chemical formulas can be derived, which differ slightly from an existing notation in order to meet recommendations of the International Union of Crystallography. - The computer program CRYSTANA is described which implements a method for the crystal-chemical classification of silicates and related materials. The implementation is based upon a graph-theoretical formalization of the classification method. An extended notation of crystal-chemical formulas is introduced. The formulas can be derived from the output of the program.

Klein, Hans-Joachim [Institut fuer Informatik, Universitaet Kiel, D-24098 Kiel (Germany)], E-mail: hjk@is.informatik.uni-kiel.de; Liebau, Friedrich [Institut fuer Geowissenschaften, Universitaet Kiel, D-24098 Kiel (Germany)], E-mail: liebau@min.uni-kiel.de

2008-09-15

25

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

NASA Astrophysics Data System (ADS)

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 ? and ?-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.

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

2015-04-01

26

Liquid Crystal Materials and Liquid Crystal Displays  

Microsoft Academic Search

Since the early 1970s, three major prerequisites have brought the success of the liquid crystal display (LCD) technology to its key role of today. Namely, the discovery of electro-optical field-effects on which the displays are based, the successful search for liquid crystals (LCs) with material properties that meet the complex requirements of electro-optical effects and render the effects applicable in

Martin Schadt

1997-01-01

27

Soap Froths and Crystal Structures  

E-print Network

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.

Primoz Ziherl; Randall D. Kamien

2000-07-14

28

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

SciTech Connect

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

Nie Shanshan; Zhang Yaobin; Liu Bin; Li Zuoxi; Hu Huaiming [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry, Northwest University, Xi'an 710069 (China); Xue Ganglin, E-mail: xglin707@163.co [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry, Northwest University, Xi'an 710069 (China); Fu Feng; Wang Jiwu [Department of Chemistry, Yanan University, Yan'an 716000 (China)

2010-12-15

29

Photoemission spectroscopy of single crystal HTSC materials: A Fermi liquid electronic structure  

SciTech Connect

Photoemission spectra from HTSC materials (primarily 123-type), cleaved and measured at 20K, reveal a rich DOS structure which compares favorably with a calculated band structure, except for a residual 0.5 eV shift which may reflect some correlation effects. Band dispersion is observed throughout the valence bands, with clear evidence for a 0.2 eV wide band dispersing through E/sub F/. The orbital character at E/sub F/ is a mix of Cu-3d and O-2p. There is unambiguous evidence for a large BCS-like gap (2..delta.. greater than or equal to 4kT/sub c/). 25 refs., 5 figs.

Arko, A.J.; List, R.S.; Bartlett, R.J.; Cheong, S.W.; Olson, C.G.; Yang, A.B.; Liu, R.; Gu, C.; Veal, B.W.; Liu, J.Z.

1989-01-01

30

Materials and structures  

NASA Technical Reports Server (NTRS)

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.

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

31

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

32

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

SciTech Connect

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.

Anbuchezhiyan, M. [Department of Physics, Valliammai Engineering College, S.R.M. Nagar, Kattankulathur, Chennai 603203 (India)] [Department of Physics, Valliammai Engineering College, S.R.M. Nagar, Kattankulathur, Chennai 603203 (India); Ponnusamy, S., E-mail: suruponnus@gmail.com [Centre for Material Science and Nano Devices, Department of Physics, SRM University, Kattankulathur, Kanchipuram, Chennai 603203 (India); Muthamizhchelvan, C. [Centre for Material Science and Nano Devices, Department of Physics, SRM University, Kattankulathur, Kanchipuram, Chennai 603203 (India)] [Centre for Material Science and Nano Devices, Department of Physics, SRM University, Kattankulathur, Kanchipuram, Chennai 603203 (India); Sivakumar, K. [Department of Physics, Anna University, Chennai 600 025 (India)] [Department of Physics, Anna University, Chennai 600 025 (India)

2010-08-15

33

Crystal Structure of Ovalene  

Microsoft Academic Search

THE synthesis of the hydrocarbon ovalene, or octabenzonaphthalene (Fig. 1) has recently been described by E. Clar1. We have now examined the crystal structure of this compound and find it to be remarkably similar to that of the analogous hydrocarbon coronene2,3. We are indebted to Dr. Clar for some very beautiful crystal specimens of ovalene, which made this work possible.

D. M. Donaldson; J. Monteath Robertson

1949-01-01

34

Crystal growth, structural, optical, dielectric and thermal studies of an amino acid based organic NLO material: L-phenylalanine L-phenylalaninium malonate.  

PubMed

Good transparent single crystals of L-phenylalanine L-phenylalaninium malonate (LPPMA) have been grown successfully by slow evaporation technique from aqueous solution. Single crystal X-ray diffractometer was utilized to measure unit cell parameter and to confirm the crystal structure. The chemical structure of compound was established by FT-NMR technique. The vibrational modes of the molecules of elucidated from FTIR spectra. Its optical behaviour has been examined by UV-vis spectral analysis, which shows the absence of absorbance in the visible region. Thermal properties of the LPPMA crystal were carried out by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques, which indicate that the material does not decompose before melting. The melting point of grown crystal was observed as 180°C by melting point apparatus. The NLO property was confirmed by the powder technique of Kurtz and Perry. The dielectric behaviour of the sample was also studied for the first time. PMID:21943710

Prakash, M; Geetha, D; Caroline, M Lydia; Ramesh, P S

2011-12-01

35

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)

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.

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

2014-01-01

36

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

PubMed Central

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

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

2014-01-01

37

Simulations of Photonic Crystal and Dielectric Structures  

SciTech Connect

Dielectric materials and photonic crystal structures have electromagnetic properties that could potentially offer great benefits for accelerators. Computer simulation plays a critical role in designing, understanding, and optimizing these structures, especially the non-intuitive photonic crystal structures for which there is no relevant zeroth-order analytic model.

Werner, G. R. [Center for Integrated Plasma Studies, University of Colorado, Boulder, CO 80309 (United States)

2010-11-04

38

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

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

Dinakaran, Paul M; Kalainathan, S

2013-07-01

39

Breaking symmetries in ordered materials : spin polarized light transport in magnetized noncentrosymmetric 1D photonic crystals, and photonic gaps and fabrication of quasiperiodic structured materials from interference lithography  

E-print Network

Effects of breaking various symmetries on optical properties in ordered materials have been studied. Photonic crystals lacking space-inversion and time-reversal symmetries were shown to display nonreciprocal dispersion ...

Bita, Ion

2006-01-01

40

Molecular arrangement for twisted nematic liquid crystal displays having liquid crystalline materials with opposite chiral structures (reverse twisted nematic liquid crystal displays)  

Microsoft Academic Search

It was found that in twisted nematic liquid crystal displays (TN-LCDs) in which the chiral direction of the liquid crystalline (LC) material is opposite to the twist direction determined by the rubbing directions, which are referred to as a reverse twisted nematic LCDs, LC molecules tilt largely without the application of an electric field. Reducing the pitch length of LC

Kohki Takatoh; Mitsuhiro Akimoto; Hiroomi Kaneko; Koji Kawashima; Shunsuke Kobayashi

2009-01-01

41

Optical properties of gyroid structured materials: from photonic crystals to metamaterials  

E-print Network

. Saranathan et al. in 2010 investigated the reflectivity of the wing scales of five papilionid and lycaenid butterflies with unit cell sizes ranging from 250 to 330 nm and chitin filling fractions from 25% to 34% [14]. Curiously, the wavelength... expression of chitin). Figure 11. Reflectivity spectra of a biological gyroid. a) Optical micrograph of Callophrys rubi wing scales and b) their reflectivity spectra. The arrows label the high symmetry points of the structure and correspond to the approximate...

Dolan, James A.; Wilts, Bodo D.; Vignolini, Silvia; Baumberg, Jeremy J.; Steiner, Ullrich; Wilkinson, Timothy D.

2014-11-29

42

Optical properties of gyroid structured materials: from photonic crystals to metamaterials  

E-print Network

. Saranathan et al. in 2010 investigated the reflectivity of the wing scales of five papilionid and lycaenid butterflies with unit cell sizes ranging from 250 to 330 nm and chitin filling fractions from 25% to 34% [14]. Curiously, the wavelength... expression of chitin). Figure 11. Reflectivity spectra of a biological gyroid. a) Optical micrograph of Callophrys rubi wing scales and b) their reflectivity spectra. The arrows label the high symmetry points of the structure and correspond to the approximate...

Dolan, James A.; Wilts, Bodo D.; Vignolini, Silvia; Baumberg, Jeremy J.; Steiner, Ullrich; Wilkinson, Timothy D.

2014-01-01

43

Crystal structure, optical and thermal studies of a new organic nonlinear optical material: L-Histidinium maleate 1.5-hydrate  

SciTech Connect

Highlights: ? L-Histidinium maleate 1.5-hydrate, a new organic crystal has been grown for the first time. ? The crystal structure is reported for the first time (CCDC 845975). ? The crystal belongs to monoclinic system with space group P2{sub 1}, Z = 4, a = 11.4656(7) ?, b = 8.0530(5) ?, c = 14.9705(9) ? and ? = 101.657(2)°. ? The optical absorption study substantiates the complete transparency of the crystal. ? Kurtz powder SHG test confirms the nonlinear property of the crystal. -- Abstract: A new organic nonlinear optical material L-histidinium maleate 1.5-hydrate (LHM) with the molecular formula C{sub 10}H{sub 16}N{sub 3}O{sub 7.5} has been successfully synthesized from aqueous solution by slow solvent evaporation method. The structural characterization of the grown crystal was carried out by single crystal X-ray diffraction at 293(2) K. In the crystal, molecules are linked through inter and intramolecular N-H?O and O-H?O hydrogen bonds, generate edge fused ring motif. The hydrogen bonded motifs are linked to each other to form a three dimensional network. The FT-IR spectroscopy was used to identify the functional groups of the synthesized compound. The optical behavior of the grown crystal was examined by UV–visible spectral analysis, which shows that the optical absorption is almost negligible in the wavelength range 280–1300 nm. The nonlinear optical property was confirmed by the powder technique of Kurtz and Perry. The thermal behavior of the grown crystal was analyzed by thermogravimetric analysis.

Gonsago, C. Alosious [Department of Physics, A. J. College of Engineering, Chennai 603103 (India)] [Department of Physics, A. J. College of Engineering, Chennai 603103 (India); Albert, Helen Merina [Department of Physics, Sathyabama University, Chennai 600119 (India)] [Department of Physics, Sathyabama University, Chennai 600119 (India); Karthikeyan, J. [Department of Chemistry, Sathyabama University, Chennai 600119 (India)] [Department of Chemistry, Sathyabama University, Chennai 600119 (India); Sagayaraj, P. [Department of Physics, Loyola College, Chennai 600034 (India)] [Department of Physics, Loyola College, Chennai 600034 (India); Pragasam, A. Joseph Arul, E-mail: drjosephsu@gmail.com [Department of Physics, Sathyabama University, Chennai 600119 (India)] [Department of Physics, Sathyabama University, Chennai 600119 (India)

2012-07-15

44

Syntheses, crystal structures, thermal stabilities and luminescence of six M(II)-hydroxyphosphonoacetate materials  

NASA Astrophysics Data System (ADS)

Hydrothermal reactions of Zn II, Ba II or Co II ion with 2-hydroxyphosphonoacetic acid (H 3L) afforded six metal phosphonates, namely, [Zn 5(O 3PCH(OH)CO 2) 4(C 6H 9N 2) 2] ( 1), [(C 4H 12N 2)Zn 5(O 3PCH(OH)CO 2) 4(H 2O) 2] ( 2), [(C 3H 12N 2) 0.5Zn 5(HO 3PCH(OH)CO 2)(O 3PCH(OH)CO 2) 3(H 2O) 2]·0.75H 2O ( 3), [BaZn 2(O 3P CH(OH)CO 2) 2] ( 4), [Ba(HO 3PCH(OH)CO 2)] ( 5) and [(NH 4) 2Co 7(HO 3PCH(OH) CO 2) 6(HPO 4) 2(H 2O) 6]·4H 2O ( 6). In 1, zinc tetrahedra ([ZnO 4]) and octahedra ([ZnO 5N], [ZnO 6]) are bridged by 2-hydroxyphosphonoacetate with penta- and hexadendate modes into a hybrid layer, which is further pillared by the 3-picolylamines to form a 3D structure through Zn-N bonds and hydrogen bondings. Both 2 and 3 are 3D framework encapsulating piperazine and 1,2-propanediamine cations, respectively. In solids 4- 6, the cross-linkages of [ZnO 4], [BaO 10] and [CoO 6] polyhedral with 2-hydroxyphosphonoacetate form 3D frameworks. Solids 3 and 4 behave thermally stable up to 250 and 300 °C under air atmosphere, respectively. It is interesting that the peak emission of solid 3 displays a 10 nm red-shift after simple heat-treatment.

Fu, Ruibiao; Hu, Shengmin; Wu, Xintao

2011-04-01

45

Prototype electrostatic ground state approach to predicting crystal structures of ionic compounds: Application to hydrogen storage materials  

Microsoft Academic Search

We have developed a procedure for crystal structure generation and prediction for ionic compounds consisting of a collection of cations and rigid complex anions. Our approach is based on global optimization of an energy functional consisting of the electrostatic and soft-sphere repulsive energies using Metropolis Monte Carlo (MMC) simulated annealing in conjunction with smoothing of the potential energy landscape via

E. H. Majzoub; V. Ozolins

2008-01-01

46

Crystal growth, structural, optical, spectral and thermal studies of tris( L-phenylalanine) L-phenylalaninium nitrate: A new organic nonlinear optical material  

NASA Astrophysics Data System (ADS)

Tris( L-phenylalanine) L-phenylalaninium nitrate, C 9H 12NO 2+·NO 3-·3C 9H 11NO 2 (TPLPN), a new organic nonlinear optical material was grown from aqueous solution by slow evaporation solution growth at room temperature. The grown crystals were subjected to powder X-ray diffraction and single crystal X-ray diffraction studies to confirm the crystalline nature and crystal structure. The modes of vibration of different molecular groups present in TPLPN have been identified by FTIR spectral analysis. The presence of hydrogen and carbon in the grown crystal were confirmed by using proton and carbon nuclear magnetic resonance (NMR) spectral analyses. The optical transmission spectral study establishes good transmitting ability of the crystal in the entire visible region. The thermogravimetric (TG) and differential thermal analyses (DTA) were carried out to understand the thermal stability of the sample. The nonlinear optical property of the compound observed using Kurtz powder second harmonic generation test assets the suitability of the grown material for the frequency conversion of laser radiation of Nd:YAG.

Prakash, M.; Geetha, D.; Lydia Caroline, M.

2011-10-01

47

Automating the application of smart materials for protein crystallization.  

PubMed

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

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

2015-03-01

48

Automating the application of smart materials for protein crystallization  

PubMed Central

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

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

2015-01-01

49

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.

50

Directed Discovery of Crystal Structures  

NSDL National Science Digital Library

This contribution is modified from a published exercise "Directed Discovery of Crystal Structures Using Ball-and-Stick Models" [Mogk, 1997] . While the published exercise is based on student exploration of traditional ball-and-stick models of crystal structures, this modified version uses a similar "discovery-based" approach and the latest online crystallographic information and visualization software to teach the spatial relationships and crystal-chemical rules that govern the crystal structures of common minerals and crystalline solids. A few changes in the content have been made from the published exercise, mainly to accommodate the new digital media.

Dave Mogk

51

Making Crystals from Crystals: A Solid-State Route to the Engineering of Crystalline Materials, Polymorphs, Solvates and Co-Crystals; Considerations on the Future of Crystal Engineering  

NASA Astrophysics Data System (ADS)

Making crystals by design is the paradigm of crystal engineering. The main goal is that of obtaining and controlling the collective properties of a crystalline material from the convolution of the physical and chemical properties of the individual building blocks (whether molecules, ions, or metal atoms and ligands) with crystal periodicity and symmetry. Crystal engineering encompasses nowadays all traditional sectors of chemistry from organic to inorganic, organometallic, biological and pharmaceutical chemistry and nanotechnology. The investigation and characterization of the products of a crystal engineering experiment require the utilization of solid state techniques, including theoretical and advanced crystallography methods. Moreover, reactions between crystalline solids and/or between a crystalline solid and a vapour can be used to obtain crystalline materials, including new crystal forms, solvates and co-crystals. Indeed, crystal polymorphism, resulting from different packing arrangements of the same molecular or supramolecular entity in the crystal structure, represents a challenge to crystal makers.

Braga, Dario; Curzi, Marco; Dichiarante, Elena; Giaffreda, Stefano Luca; Grepioni, Fabrizia; Maini, Lucia; Palladino, Giuseppe; Pettersen, Anna; Polito, Marco

52

Structural materials and components  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

53

TOPICAL REVIEW: First-principles approaches to intrinsic strength and deformation of materials: perfect crystals, nano-structures, surfaces and interfaces  

NASA Astrophysics Data System (ADS)

First-principles studies on the intrinsic mechanical properties of various materials and systems through ab initio tensile and shear testing simulations based on density-functional theory are reviewed. For various materials, ideal tensile and shear strength and features of the deformation of bulk crystals without any defects have been examined, and the relation with the bonding nature has been analyzed. The surfaces or low-dimensional nano-structures reveal peculiar strength and deformation behavior due to local different bonding nature. For grain boundaries and metal/ceramic interfaces, tensile and shear behaviors depend on the interface bonding, which impacts on the research of real engineering materials. Remaining problems and future directions in this research field are discussed.

Ogata, Shigenobu; Umeno, Yoshitaka; Kohyama, Masanori

2009-01-01

54

Materials and structures  

NASA Technical Reports Server (NTRS)

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.

Venneri, Samuel L.

1988-01-01

55

Modification of porous protein crystals in development of biohybrid materials.  

PubMed

Protein assemblies have attracted increasing attention for construction of biohybrid materials. Protein crystals can also be regarded as solid protein assemblies. The present work demonstrates that protein crystals can be employed as porous biomaterials by site-specific modifications of the crystals of recombinant sperm whale myoglobin mutants. The myoglobin crystals of space group P6 provide hexagonal pores consisting of the building blocks of six Mb molecules, which form a pore with a diameter of 40 A. On the basis of the lattice structure of the Mb crystals, we have selected appropriate residues located on the surface of the pores for replacement with cysteine. This enables modification of the pore surface via coupling with maleimide derivatives. We have succeeded in crystallizing the modified Mb mutants, retaining the P6 lattice, and consistently aligning nanosized functional molecules such as fluorescein, eosin, and Ru(bpy)(3) into the hexagonal pores of the Mb crystals. Our strategy for site-specific modification of protein crystal pores is applicable to various protein crystals with porous structures. We believe that modified porous protein crystals will provide attractive candidates for novel solid materials in nanotechnology applications. PMID:20099839

Koshiyama, Tomomi; Kawaba, Naomi; Hikage, Tatsuo; Shirai, Masanobu; Miura, Yuki; Huang, Cheng-Yuan; Tanaka, Koichiro; Watanabe, Yoshihito; Ueno, Takafumi

2010-02-17

56

Structural materials and components  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

57

Structural materials and components  

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

58

Data mining chemistry and crystal structure  

NASA Astrophysics Data System (ADS)

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.

Yang, Lusann W.

59

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

60

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

PubMed Central

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

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

2014-01-01

61

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

PubMed

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

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

2014-12-01

62

Fundamental Studies of Crystal Growth of Microporous Materials  

NASA Technical Reports Server (NTRS)

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: (1) Nature of the molecular units responsible for the crystal nuclei formation; (2) Nature of the nuclei and nucleation process; (3) Growth process of the nuclei into crystal; (4) Morphological control and size of the resulting crystal; (5) Surface structure of the resulting crystals; (6) Transformation of frameworks into other frameworks or condensed structures. The NASA-funded research described in this report focuses to varying degrees on all of the above issues and has been described in several publications. Following is the presentation of the highlights of our current research program. The report is divided into five sections: (1) Fundamental aspects of the crystal growth process; (2) Morphological and Surface properties of crystals; (3) Crystal dissolution and transformations; (4) Modeling of Crystal Growth; (5) Relevant Microgravity Experiments.

Dutta, P.; George, M.; Ramachandran, N.; Schoeman, B.; Curreri, Peter A. (Technical Monitor)

2002-01-01

63

Synthetic thermoelectric materials comprising phononic crystals  

DOEpatents

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.

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

2013-08-13

64

Crystal growth and characterization of new laser materials  

NASA Astrophysics Data System (ADS)

Two new laser materials are described. The first one belongs to the magnetoplumbite structural type and the second one belongs to the gehlenite type. Crystal growth, optical properties and laser efficiency are determined. These materials exhibit two main advantages: broad tunability ranges and ability to be diode-pumped.

Collongues, R.; Lejus, A. M.; Théry, J.; Vivien, D.

1993-03-01

65

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

SciTech Connect

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??m, 0.592??m, 1.480??m, and 2.114??m, 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??m and 8–14??m 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??m and 8–12??m, 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.

Wang, Zhixun; Cheng, Yongzhi, E-mail: cyz0715@126.com; Nie, Yan; Wang, Xian; Gong, Rongzhou, E-mail: rzhgong@mail.hust.edu.cn [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

2014-08-07

66

Materials with structural hierarchy  

NASA Technical Reports Server (NTRS)

The role of structural hierarchy in determining bulk material properties is examined. Dense hierarchical materials are discussed, including composites and polycrystals, polymers, and biological materials. Hierarchical cellular materials are considered, including cellular solids and the prediction of strength and stiffness in hierarchical cellular materials.

Lakes, Roderic

1993-01-01

67

An insight into crystal, electronic, and local structures of lithium iron silicate (Li2FeSiO4) materials upon lithium extraction  

NASA Astrophysics Data System (ADS)

Recently, orthosilicate, Li2MSiO4 (where M=transition metal) materials have been attracting considerable attention for potential use as a new generation cathode for Li-ion batteries due to their safety, low toxicity, and low cost characteristics. In addition, the presence of two Li+ ions in the molecule offers a multiple electron-charge transfer (M2+/M3+ and M3+/M4+ redox couples), thus allowing a high achievable capacity of more than 320 mA h/g per M unit. Good electrochemical properties of Li2FeSiO4 have been reported through several approaches such as downsizing of the particles, carbon-coating, etc. However, in addition to electrochemical performance, fundamental understanding regarding crystal, electronic and local structure changes during charge/discharge processes is also important and needs more rigorous investigation. In this work, lithium iron silicates (Li2FeSiO4/C) in space group of Pnma: a=10.6671(3) Å, b=6.2689(2) Å, and c=5.0042(2) Å have been prepared by solid-state reaction. The synthesized as well as chemical delithiated samples have been characterized by XRD, HRTEM, AAS and XAS techniques. We will show the results focusing on Fe K-edge XANES, EXAFS, HRTEM and XRD of the Li2-xFeSiO4 samples and discuss how the crystal, electronic, and local structure changes upon Li+ de-intercalation.

Kamon-in, O.; Klysubun, W.; Limphirat, W.; Srilomsak, S.; Meethong, N.

2013-05-01

68

Layered exfoliable crystalline materials based on Sm-, Eu- and Eu/Gd-2-phenylsuccinate frameworks. Crystal structure, topology and luminescence properties.  

PubMed

Three new layered metal-organic frameworks (MOFs) based on 2-phenylsuccinic acid (H2psa) and lanthanide ions with the formula [Ln2(C10H8O4)3(H2O)] (Ln = Eu, Sm and Eu-Gd) have been synthesized under solvothermal conditions and fully characterized by single-crystal X-ray diffraction, thermal and vibrational analyses. The compounds are isostructural featuring 2D frameworks that consist of infinite zigzag chains composed of [LnO8] and [LnO8(H2O)] edge-sharing polyhedra linked by psa ligands leading to layers further connected by weak ?-? interactions in an edge orientation. Moreover, a topological study was carried out to obtain the simplified net for better comparison with structurally related compounds. The crystals were exfoliated into nanolayers after miniaturization by addition of sodium acetate as a capping agent in the reaction medium. Scanning electron microscopy was applied to characterize the miniaturized samples whereas the exfoliated hybrid nanosheets were studied by atomic force microscopy. The photoluminescence (PL) properties of the bulk compounds as well as the miniaturized and exfoliated materials were investigated and compared with other related ones. An exhaustive study of the Eu(iii)-based MOFs was performed on the basis of the obtained PL parameters (excitation and emission spectra, kr, knr, intrinsic quantum yields and lifetimes) to explore the underlying structure-property relationships. PMID:25599977

Gomez, G E; Bernini, M C; Brusau, E V; Narda, G E; Vega, D; Kaczmarek, A M; Van Deun, R; Nazzarro, M

2015-02-21

69

Fundamental Studies of Crystal Growth of Microporous Materials  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

70

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)

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.

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

2012-12-01

71

Growth, structural, optical and mechanical studies on acid mixed glycine metal salt (GABN) crystal as potential NLO material  

NASA Astrophysics Data System (ADS)

Transparent crystals of ?-glycine with ammonium nitrate and barium nitrate (GABN) have been grown from aqueous solution by slow evaporation technique at room temperature. Crystals of size 11 × 7 × 4 mm 3 have been obtained in about 3-4 weeks time. The solubility of GABN has been determined in water. The grown crystal belongs to orthorhombic system with cell parameters a = 7.317 A.U, b = 12.154 A.U and c = 5.468 A.U with a unit cell volume 486.35 (A.U) 3. The presence of chemical components/groups has been identified by CHN, EDAX and NMR analysis. Comparative IR and Raman studies indicate a molecule with a lack of centre of symmetry. A wide transparency window useful for optoelectronic applications is indicated by the UV Studies. Using a Nd-YAG laser (1064 nm), the optical second harmonic generation (SHG) conversion efficiency of GABN is found to be 1.406 times of that of standard KDP. On exposure to light the GABN crystals are found to exhibit negative photoconductivity. I-V characteristics, SEM studies, dielectrics studies, and Vickers micro hardness measurement have been carried out.

Khandpekar, Mahendra M.; Dongare, Shailesh S.; Patil, Shirish B.; Pati, Shankar P.

2012-03-01

72

Invited Lecture. Material properties, structural relations with molecular ensembles and electro-optical performance of new bicyclohexane liquid crystals in field-effect liquid crystal displays  

Microsoft Academic Search

Several new classes of polar and non-polar bicyclohexane liquid crystals comprising alkenyl side chains are presented. The compounds exhibit low optical anisotropies, ?n, < 0.1 and rotational viscosities, ?1, as low as 35 cP at 22°C. This leads, in combination with large elastic expressions k = k1 + (k3 - 2k2)\\/4 > 12 × 10 N, to low viscoelastic ratios

Martin Schadt; Richard Buchecker; Klaus Müller

1989-01-01

73

Crystal structure refinement with SHELXL.  

PubMed

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

Sheldrick, George M

2015-01-01

74

Crystal structure refinement with SHELXL  

PubMed Central

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

Sheldrick, George M.

2015-01-01

75

Materials for freeform fabrication of GHz tunable dielectric photonic crystals.  

SciTech Connect

Photonic crystals are of interest for GHz transmission applications, including rapid switching, GHz filters, and phased-array technology. 3D fabrication by Robocasting enables moldless printing of high solid loading slurries into structures such as the ''woodpile'' structures used to fabricate dielectric photonic band gap crystals. In this work, tunable dielectric materials were developed and printed into woodpile structures via solid freeform fabrication (SFF) toward demonstration of tunable photonic crystals. Barium strontium titanate ceramics possess interesting electrical properties including high permittivity, low loss, and high tunability. This paper discusses the processing route and dielectric characterization of (BaxSr1-XTiO3):MgO ceramic composites, toward fabrication of tunable dielectric photonic band gap crystals.

Niehaus, Michael Keith; Lewis, Jennifer A. (University of Illinois, Urbana, IL); Smay, James Earl; Clem, Paul Gilbert; Lin, Shawn-Yu; Cesarano, Joseph, III (,; ); Carroll, James F.

2003-01-01

76

Analytical method for band structure calculation of photonic crystal fibers filled with liquid crystal.  

PubMed

An analytical method for band structure calculations of photonic crystal fibers with liquid crystal infiltrations is presented. The scalar eigenvalue equation is extended to treat both isotropic and anisotropic materials by introducing a coefficient to describe the index contrast between the extraordinary and ordinary refractive index of the liquid crystal. The simple model provides a fast insight into bandgap formation in photonic crystal fibers filled with anisotropic material such as liquid crystal, which would be useful to aid the design based on such fibers. PMID:18545370

Hu, Juan Juan; Ren, Guobin; Shum, Ping; Yu, Xia; Wang, Guanghui; Lu, Chao

2008-04-28

77

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

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…

Pinto, Gabriel

2012-01-01

78

Crystal structure of fenpropathrin  

PubMed Central

In the title compound [systematic name: cyano­(3-phen­oxy­phen­yl)methyl 2,2,3,3-tetra­methyl­cyclo­propane­carboxyl­ate], C22H23NO3, which is the pyrethroid insecticide fenpropathrin, the dihedral angle between the cyclo­propane ring plane and the carboxyl­ate group plane is 88.25?(11)°. The dihedral angle between the benzene and phenyl rings in the phen­oxy­benzyl group is 82.99?(4)°. In the crystal, C—H?N hydrogen bonds and weak C—H?? inter­actions link adjacent mol­ecules, forming loop chains along the b-axis direction. PMID:25553036

Kang, Gihaeng; Jeon, Youngeun; Lee, Sangjin; Kim, Tae Ho

2014-01-01

79

Making Matter: The Atomic Structure of Materials  

NSDL National Science Digital Library

The Institut Laue Langevin provides the Making Matter: The Atomic Structure of Materials Website. This site offers information as well as 3D structures of inorganic materials (such as salt) in the Inorganic Crystal Structure Database. Sections included at the site are Close Packing, Compounds, Bonding, and Gems & Minerals, among others. This site provides spectacular 3D images (.gif and VRML format) of inorganic materials and is well worth the visit.

80

Photonic Crystal Laser-Driven Accelerator Structures  

SciTech Connect

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.

Cowan, Benjamin M.

2007-08-22

81

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

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.

Broach, Robert W., E-mail: robert.broach@uop.com [UOP, a Honeywell Co., 50 E. Algonquin Rd., Des Plaines, IL 60017 (United States); Bedard, Robert L. [UOP, a Honeywell Co., 50 E. Algonquin Rd., Des Plaines, IL 60017 (United States)] [UOP, a Honeywell Co., 50 E. Algonquin Rd., Des Plaines, IL 60017 (United States); King, Lisa M., E-mail: lisa.king@uop.com [UOP, a Honeywell Co., 50 E. Algonquin Rd., Des Plaines, IL 60017 (United States); Pluth, Joseph J., E-mail: pluth@cars.uchicago.edu [The University of Chicago, Department of the Geophysical Sciences, Consortium for Advanced Radiation Sources, Chicago, IL 60637 (United States); The University of Chicago, The Materials Research Science and Engineering Center, Chicago, IL 60637 (United States); Smith, Joseph V. [The University of Chicago, Department of the Geophysical Sciences, Consortium for Advanced Radiation Sources, Chicago, IL 60637 (United States)] [The University of Chicago, Department of the Geophysical Sciences, Consortium for Advanced Radiation Sources, Chicago, IL 60637 (United States); Kirchner, Richard M., E-mail: richard.kirchner@manhattan.edu [Manhattan College, Chemistry Department, Bronx, NY 10471 (United States)

2012-12-15

82

Bulk Crystal Growth - Methods and Materials  

NASA Astrophysics Data System (ADS)

This chapter covers the field of bulk single crystals of materials used in electronics and optoelectronics. These crystals are used in both active and passive modes (to produce devices directly in/on bulk-grown slices of material, or as substrates in epitaxial growth, respectively). Single-crystal material usually provides superior properties to polycrystalline or amorphous equivalents. The various bulk growth techniques are outlined, together with specific critical features, and examples are given of the types of materials (and their current typical sizes) grown by these techniques. Materials covered range from Group IV (Si, Ge, SiGe, diamond, SiC), Group III-V (such as GaAs, InP, nitrides) Group II-IV (including CdTe, ZnSe, MCT) through to a wide range of oxide/halide/phosphate/borate materials. This chapter is to be treated as a snapshot only; the interested reader is referred to the remainder of the chapters in this Handbook for more specific growth and characterization details on the various materials outlined in this chapter. This chapter also does not cover the more fundamental aspects of the growth of the particular materials covered; for these, the reader is again referred to relevant chapters within the Handbook, or to other sources of information in the general literature.

Capper, Peter

83

Crystal structure of chlorfluazuron.  

PubMed

The title compound (systematic name: 1-{3,5-di-chloro-4-[3-chloro-5-(tri-fluoro-meth-yl)pyridin-2-yl-oxy]phen-yl}-3-(2,6-difluoro-benzo-yl)urea), C20H9Cl3F5N3O3, is a benzoyl-phenyl-urea insecticide. The dihedral angles between the planes of the central di-chloro-phenyl and the terminal di-fluoro-phenyl and chloro-pyridyl rings are 79.51?(6) and 78.84 6)°, respectively. In the crystal, pairs of N-H?O hydrogen bonds link adjacent mol-ecules, forming R 2 (2)(8) inversion dimers. In addition, the dimers are linked by short F?Cl [3.1060?(16)?Å] and Cl?Cl [3.2837?(7)?Å] contacts, as well as weak inter-molecular ?-? inter-actions [ring centroid separation = 3.6100?(11) and 3.7764?(13)?Å], resulting in a two-dimensional architecture parallel to (111). PMID:25705506

Cho, Seonghwa; Kim, Jineun; Lee, Sangjin; Kim, Tae Ho

2015-01-01

84

Crystal structure of chlorfluazuron  

PubMed Central

The title compound (systematic name: 1-{3,5-di­chloro-4-[3-chloro-5-(tri­fluoro­meth­yl)pyridin-2-yl­oxy]phen­yl}-3-(2,6-difluoro­benzo­yl)urea), C20H9Cl3F5N3O3, is a benzoyl­phenyl­urea insecticide. The dihedral angles between the planes of the central di­chloro­phenyl and the terminal di­fluoro­phenyl and chloro­pyridyl rings are 79.51?(6) and 78.84 6)°, respectively. In the crystal, pairs of N—H?O hydrogen bonds link adjacent mol­ecules, forming R 2 2(8) inversion dimers. In addition, the dimers are linked by short F?Cl [3.1060?(16)?Å] and Cl?Cl [3.2837?(7)?Å] contacts, as well as weak inter­molecular ?–? inter­actions [ring centroid separation = 3.6100?(11) and 3.7764?(13)?Å], resulting in a two-dimensional architecture parallel to (111). PMID:25705506

Cho, Seonghwa; Kim, Jineun; Lee, Sangjin; Kim, Tae Ho

2015-01-01

85

Crystal structure of difenoconazole  

PubMed Central

In the title compound difenoconazole [systematic name: 1-({2-[2-chloro-4-(4-chloro­phen­oxy)phen­yl]-4-methyl-1,3-dioxolan-2-yl}meth­yl)-1H-1,2,4-triazole], C19H17Cl2N3O3, the dihedral angle between the planes of the 4-chloro­phenyl and 2-chloro­phenyl rings is 79.34?(9)°, while the dihedral angle between the planes of the triazole ring and the dioxolanyl group is 59.45?(19)°. In the crystal, pairs of C—H?N hydrogen bonds link adjacent mol­ecules, forming dimers with R 2 2(6) loops. In addition, the dimers are linked by C—H?O hydrogen bonds, resulting in a three-dimensional architecture. Disorder was modeled for one C atom of the dioxolanyl group over two sets of sites with an occupancy ratio of 0.566?(17):0.434?(17). PMID:25484812

Cho, Seonghwa; Kang, Gihaeng; Lee, Sangjin; Kim, Tae Ho

2014-01-01

86

Bioinspired structural materials.  

PubMed

Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts. PMID:25344782

Wegst, Ulrike G K; Bai, Hao; Saiz, Eduardo; Tomsia, Antoni P; Ritchie, Robert O

2015-01-01

87

Bioinspired structural materials  

NASA Astrophysics Data System (ADS)

Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts.

Wegst, Ulrike G. K.; Bai, Hao; Saiz, Eduardo; Tomsia, Antoni P.; Ritchie, Robert O.

2015-01-01

88

Crystal structures and growth mechanism for ultrathin films of ionic compound materials: FeO(111) on Pt(111)  

Microsoft Academic Search

The growth and atomic structures of epitaxial iron-oxide films on Pt(111) were studied with scanning tunneling microscopy and high-resolution low-energy electron diffraction. During the initial layer-by-layer growth of FeO(111) four different structures are formed as the coverage increases to 2.5 monolayers, then a three-dimensional growth of Fe3O4(111) islands begins. The structural transformations demonstrate that the relaxations within the FeO(111) films

W. Ranke; M. Ritter; W. Weiss

1999-01-01

89

Optical and physical properties of ceramic crystal laser materials  

Microsoft Academic Search

Historically ceramic crystal laser material has had disadvantages compared to single crystal laser material. However, progress has been made in the last decade and a half to overcome the disadvantages associated with ceramic crystal. Today, because of the promise of ceramic crystal as a high power laser material, investigation into its properties, both physical and optical, is warranted and important.

Jed A. Simmons

2007-01-01

90

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

Loewy, R.; Wiberley, S. E.

1986-01-01

91

Composite structural materials. [aircraft structures  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

92

A machine learning approach to crystal structure prediction  

E-print Network

This thesis develops a machine learning framework for predicting crystal structure and applies it to binary metallic alloys. As computational materials science turns a promising eye towards design, routine encounters with ...

Fischer, Christopher Carl

2007-01-01

93

Predicting Polymeric Crystal Structures by Evolutionary Algorithms  

E-print Network

The recently developed evolutionary algorithm USPEX proved to be a tool that enables accurate and reliable prediction of structures for a given chemical composition. Here we extend this method to predict the crystal structure of polymers by performing constrained evolutionary search, where each monomeric unit is treated as one or several building blocks with fixed connectivity. This greatly reduces the search space and allows the initial structure generation with different sequences and packings using these blocks. The new constrained evolutionary algorithm is successfully tested and validated on a diverse range of experimentally known polymers, namely polyethylene (PE), polyacetylene (PA), poly(glycolic acid) (PGA), poly(vinyl chloride) (PVC), poly(oxymethylene) (POM), poly(phenylene oxide) (PPO), and poly (p-phenylene sulfide) (PPS). By fixing the orientation of polymeric chains, this method can be further extended to predict all polymorphs of poly(vinylidene fluoride) (PVDF), and the complex linear polymer crystals, such as 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.

Qiang Zhu; Vinit Sharma; Artem R Oganov; Rampi Ramprasad

2014-06-05

94

CALYPSO: A method for crystal structure prediction  

NASA Astrophysics Data System (ADS)

We have developed a software package CALYPSO (Crystal structure AnaLYsis by Particle Swarm Optimization) to predict the energetically stable/metastable crystal structures of materials at given chemical compositions and external conditions (e.g., pressure). The CALYPSO method is based on several major techniques (e.g. particle-swarm optimization algorithm, symmetry constraints on structural generation, bond characterization matrix on elimination of similar structures, partial random structures per generation on enhancing structural diversity, and penalty function, etc.) for global structural minimization from scratch. All of these techniques have been demonstrated to be critical to the prediction of global stable structure. We have implemented these techniques into the CALYPSO code. Testing of the code on many known and unknown systems shows high efficiency and the highly successful rate of this CALYPSO method [Y. Wang, J. Lv, L. Zhu, Y. Ma, Phys. Rev. B 82 (2010) 094116] [29]. In this paper, we focus on descriptions of the implementation of CALYPSO code and why it works.

Wang, Yanchao; Lv, Jian; Zhu, Li; Ma, Yanming

2012-10-01

95

Light propagation in liquid crystals and liquid crystalline structures  

Microsoft Academic Search

Liquid crystals are optically complex materials, characterized in general by anisotropy, loss and chirality. Understanding light propagation both in uniform samples, and in stratified structures consisting of layers of such materials is of considerable interest for fundamental reasons. It is also essential for the effective use of these materials in technology. Light propagation in matter can be understood classically in

Haijun Yuan

2000-01-01

96

Novel Microstructures for Polymer-Liquid Crystal Composite Materials  

NASA Technical Reports Server (NTRS)

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.

Magda, Jules J.

2004-01-01

97

The crystal structure of katayamalite  

Microsoft Academic Search

The crystal structure of katayamalite has been determined by Patterson method and refined by the least-squares method using single crystal diffractometer data, giving R = 0.057 for 5785 reflections. Formula: (K,Na)Li.Ca,(Ti,Fe'+,Mn)2(Si60'8).(OH,F)2' Cell dimensions: a 9.721(2), b 16.923(3), c 19.942(3)A, a 91.43(10t, iJ 104.15(11t, 'Y 89.94(10t, space group Cl, Z = 4; or a 9.763(2), b 9.721(2), c 19.942(3)A, a 104.15(11t,

Toshio KATO; Nobuhide MURAKAMI

1985-01-01

98

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

99

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

100

Structural Materials: 95. Concrete  

SciTech Connect

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.

Naus, Dan J [ORNL

2012-01-01

101

Actuating materials. Voxelated liquid crystal elastomers.  

PubMed

Dynamic control of shape can bring multifunctionality to devices. Soft materials capable of programmable shape change require localized control of the magnitude and directionality of a mechanical response. We report the preparation of soft, ordered materials referred to as liquid crystal elastomers. The direction of molecular order, known as the director, is written within local volume elements (voxels) as small as 0.0005 cubic millimeters. Locally, the director controls the inherent mechanical response (55% strain) within the material. In monoliths with spatially patterned director, thermal or chemical stimuli transform flat sheets into three-dimensional objects through controlled bending and stretching. The programmable mechanical response of these materials could yield monolithic multifunctional devices or serve as reconfigurable substrates for flexible devices in aerospace, medicine, or consumer goods. PMID:25722408

Ware, Taylor H; McConney, Michael E; Wie, Jeong Jae; Tondiglia, Vincent P; White, Timothy J

2015-02-27

102

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

103

Composite Structural Materials  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

104

Crystal structures of tungsten disulfide and diselenide  

NASA Astrophysics Data System (ADS)

The crystal structures of the 2 H- and 3 R-forms of WS 2 have been refined from single-crystal data. The results are summarized and the interatomic distances are compared with those in related compounds.

Schutte, W. J.; De Boer, J. L.; Jellinek, F.

1987-10-01

105

Crystal structures of tungsten disulfide and diselenide  

Microsoft Academic Search

The crystal structures of the 2H- and 3R-forms of WS2 have been refined from single-crystal data. The results are summarized and the interatomic distances are compared with those in related compounds.

W. J. Schutte; J. L. de Boer; F. Jellinek

1987-01-01

106

Crystal structure of lignin peroxidase  

SciTech Connect

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.

Edwards, S.L. (Center for Advanced Research in Biotechnology, Rockville, MD (United States) National Institutes of Health, Bethesda, MD (United States)); Raag, R. (Center for Advanced Research in Biotechnology, Rockville, MD (United States)); Wariishi, Hiroyuki; Gold, M.H. (Oregon Graduate Institute of Science and Technology, Beaverton (United States)); Poulos, T.L. (Center for Advanced Reseaarch in Biotechnology, Rockville, MD (United States) Univ. of California, Irvine (United States))

1993-01-15

107

Predicting polymeric crystal structures by evolutionary algorithms  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

108

Liquid crystal materials and tunable devices for optical communications  

Microsoft Academic Search

In this dissertation, liquid crystal materials and devices are investigated in meeting the challenges for photonics and communications applications. The first part deals with polymer-stabilized liquid crystal (PSLC) materials and devices. Three polymer-stabilized liquid crystal systems are developed for optical communications. The second part reports the experimental investigation of a novel liquid-crystal-infiltrated photonic crystal fiber (PCF) and explores its applications

Fang Du

2005-01-01

109

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

110

Liquid impact erosion of single-crystal and coated material  

NASA Astrophysics Data System (ADS)

Lithium fluoride in its single-crystal form is an interesting material for investigating the development of fracture by multiple liquid impact owing to its well-characterized crystal structure. The development of fracture during liquid impact is attributed to the extension of short circumferential cracks produced around the loaded area by the passing Rayleigh stress wave after the impact event. The damage threshold of single-crystal lithium fluoride is developed using the multiple-impact jet apparatus (MIJA) as a result of identifying the characteristic fracture annulus associated with liquid impact during a controlled experimental procedure. The observation of damage produced in solids by liquid impact has practical significance in the problems associated with supersonic aircraft flying through rain and in the erosion of turbine blades. The addition of coatings to the surface provides a form of protection at higher speeds but may not completely inhibit damage.

Jackson, M. J.; Telling, R. H.; Field, J. E.

2006-04-01

111

Synthesis and crystal structure of two tin fluoride materials: NaSnF 3 (BING12) and Sn 3F 3PO 4  

Microsoft Academic Search

A new compound, sodium tin trifluoride (NaSnF3, which we denote BING-12 for SUNY at Binghamton, Structure No. 12), was synthesized solvothermally from a pyridine–water solvent system. The new compound crystallized in the monoclinic space group C2\\/c (No. 15), with a=11.7429(12)Å, b=17.0104(18)Å, c=6.8528(7)Å, ?=100.6969(2)°, V=1345.1(2)Å3 and Z=16. The layered structure consists of outer pyramidal SnF3 units, where the fluorides surround a

Tolulope O Salami; Peter Y Zavalij; Scott R. J Oliver

2004-01-01

112

Synthesis and crystal structure of two tin fluoride materials: NaSnF3 (BING12) and Sn3F3PO4  

Microsoft Academic Search

A new compound, sodium tin trifluoride (NaSnF3, which we denote BING-12 for SUNY at Binghamton, Structure No. 12), was synthesized solvothermally from a pyridine-water solvent system. The new compound crystallized in the monoclinic space group C2\\/c (No. 15), with a=11.7429(12)Å, b=17.0104(18)Å, c=6.8528(7)Å, beta=100.6969(2)°, V=1345.1(2)Å3 and Z=16. The layered structure consists of outer pyramidal SnF3 units, where the fluorides surround a

Tolulope O. Salami; Peter Y. Zavalij; Scott R. J. Oliver

2004-01-01

113

Beyond crystals: the dialectic of materials and information  

PubMed Central

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

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

2012-01-01

114

Beyond crystals: the dialectic of materials and information.  

PubMed

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

Cartwright, Julyan H E; Mackay, Alan L

2012-06-28

115

New crystal structure maps for intermetallic compounds  

NASA Astrophysics Data System (ADS)

New crystal structure maps have been proposed on the basis of the 0953-8984/9/38/008/img6 molecular orbital calculations of electronic structures. Two electronic parameters have been introduced and employed as new parameters for the classification of crystal structures. One is the bond order and the other is the d-orbital energy level of elements. Both of them change following the position of elements in the periodic table. With these parameters crystal structure maps have been constructed for aluminides, silicides, and some transition-metal-based compounds. There is a clear separation of the crystal structures on the maps. These maps are found to be applicable to the prediction of crystal structures not only for binary compounds but also for ternary compounds. The possibilities of structural modification of 0953-8984/9/38/008/img7 and 0953-8984/9/38/008/img8 by alloying are also discussed with the aid of these maps.

Harada, Yoshihisa; Morinaga, Masahiko; Saito, Jun-ichi; Takagi, Yasuharu

1997-09-01

116

Phase-Field Crystal Modeling of Polycrystalline Materials  

NASA Astrophysics Data System (ADS)

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 la

Adland, Ari Joel

117

Effect of microgravity on the crystallization of a self-assembling layered material  

Microsoft Academic Search

In microgravity, crystals of semiconductors and proteins can be grown with improved crystallinity, offering the prospect of improved structural analyses (for proteins) and better electronic properties (for semiconductors). Here we study the effect of a microgravity environment on the crystallization of a class of materials-layered microporous tin(IV) sulphides-whose crystal structure is determined by weak interlayer interactions (electrostatic, hydrogen-bonding and van

Homayoun Ahari; Robert L. Bedard; Carol L. Bowes; Neil Coombs; Omer Dag; Tong Jiang; Geoffrey A. Ozin; Srebri Petrov; Igor Sokolov; Atul Verma; Gregory Vovk; David Young

1997-01-01

118

Structural, optical and electrical characteristics of a new NLO crystal  

NASA Astrophysics Data System (ADS)

A new nonlinear optical (NLO) organic crystal 1-[4-({(E)-[4-(methylsulfanyl)phenyl]methylidene}amino)phenyl]ethanone (MMP) has been grown by slow evaporation technique at ambient temperature. The crystal structure of MMP was determined by single crystal X-ray diffraction. MMP crystallizes in non-centrosymmetric monoclinic system with space group P21. The FT-IR spectrum recorded for new crystal confirmed the presence of various functional groups in the material. MMP was found to be thermally stable up to 300 °C. The grown crystal was optically transparent in the wavelength range of 400-1100 nm. The second harmonic generation (SHG) efficiency of the crystal was measured by the classical powder technique using Nd:YAG laser and was found to be 4.13 times more efficient than reference material, urea. Third order nonlinear parameters were measured by employing the Z-scan technique. The laser damage threshold for MMP crystal was determined to be 4.26 GW/cm2. The Brewster angle technique was employed to measure the refractive index of the crystal and the values for green and red wavelengths were found to be 1.35 and 1.33, respectively. The dielectric and electrical measurements were carried out to study the different polarization mechanisms and conductivity of the crystal.

D'silva, E. D.; Krishna Podagatlapalli, G.; Venugopal Rao, S.; Dharmaprakash, S. M.

2012-09-01

119

4.1 Photonic Crystals Photonic crystals are materials that interact very strongly with light. These crystals can  

E-print Network

Chapter 4 Results 4.1 Photonic Crystals Photonic crystals are materials that interact very strongly beforehand what the best filling is. The class of known photonic crystals containing a full bandgap can cubic (sc) or face centered cubic (fcc), etc. Some photonic crystals can be created by mak

120

Crystal morphology characteristics of the domain structure and superconducting properties of 123 single crystals  

Microsoft Academic Search

The characteristics of the domain structure of YBa(2-x)Sr(x)Cu3O(7-delta) single crystals are investigated for x = 0, 0.2, 0.4. and 0.5. A domain structure analysis is also carried out for TmBa(1.5)Sr(0.5)Cu3O(7-delta) single crystals. Various types of domain structure in these materials are identified, and a relationship is established between the domain structure type and the characteristics of the superconducting transition.

A. I. Otko; A. A. Nosenko; O. P. Bal'Va; M. B. Kosmyna; S. F. Prokopovich; A. S. Chernyi

1991-01-01

121

Crystal Structure of the Carboxyltransferase Domain of  

E-print Network

Crystal Structure of the Carboxyltransferase Domain of Acetyl­Coenzyme A Carboxylase Hailong Zhang, Zhiru Yang,* Yang Shen,* Liang Tong Acetyl­coenzyme A carboxylases (ACCs) are required determined the crystal structure of the free enzyme and the coenzyme A complex of yeast CT at 2.7 angstrom

Tong, Liang

122

Crystal structure analysis of intermetallic compounds  

NASA Technical Reports Server (NTRS)

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.

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

1968-01-01

123

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

Loewy, Robert G.; Wiberley, Stephen E.

1987-01-01

124

Artificially structured magnetic materials  

SciTech Connect

This document reports the progress made during the first six months of the current three-year DOE grant on Artificially Structured Magnetic Materials.'' However, because some of the results of our previous three-year DOE grant on Artificially Structured Superconductors'' continue to emerge, both topics are addressed in this Progress Report. This report describes progress with DOE funding during the current calendar year; description of the research to be conducted during the remaining six months of the current grant year; a description of the status of the graduate students working on this research; lists of the invited talks, seminars and colloquia, of other recognition of our research, and of the publications crediting DOE sponsorship; and a summary of current and pending federal support. Since the research proposed to be conducted during the next 2 1/2 years is described in detail in our DOE proposal, it is only briefly reviewed here.

Falco, C.M.

1990-09-28

125

Polymer Stabilized Liquid Crystals: Materials, Physics and Applications  

NASA Astrophysics Data System (ADS)

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.

Kumar, Rishi; Raina, K. K.

2011-12-01

126

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

NASA Astrophysics Data System (ADS)

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) Å, b = 25.167(0) Å, c = 7.694(0) Å, ? = 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.

Liu, Yao; Yang, Peipei; Meng, Jian

2011-05-01

127

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

NASA Astrophysics Data System (ADS)

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.

Sankari, R. Siva; Perumal, Rajesh Narayana

2014-04-01

128

Synthesis of single crystal nanoreactor materials with multiple catalytic functions by incipient wetness impregnation and ion exchange.  

PubMed

ZSM-5 hollow crystals are functionalized with multiple catalytic sites, the structure of which resembles a cell-like structure on the nanometer scale. The crystal size of the nanoreactor is below 100 nm. The material is functionalized with metal oxide particles within the hollow or on the external crystal surface. Additionally, Brønsted acid sites are present in the zeolite channels. PMID:25645289

Fodor, Daniel; Ishikawa, Takashi; Krumeich, Frank; van Bokhoven, Jeroen A

2015-03-01

129

Method of making macrocrystalline or single crystal semiconductor material  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

130

Introduction to Crystal Structure: Bond Strength  

NSDL National Science Digital Library

This exercise is designed to familiarize students with some basic crystal structures The exercise helps students fully understand the nature and significance of ionic bonds and Pauling's second rule It also builds a bit on Pauling's first rule (radius ratio principle) It is one of several related activities, all of which are intended to help students understand the nature of ionic crystals

Dexter Perkins

131

Novel electromagnetic materials from functionalized structures  

NASA Astrophysics Data System (ADS)

Materials, exhibiting the novel electromagnetic responses those may not be found in nature, have the potential to manipulate the electromagnetic field passing through them. Consequently, these materials promise a number of applications, such as highly sensitive sensor, superlenses, high-gain antennas and electromagnetic wave cloaking. In the literature we would investigate various electromagnetic materials composed from functionalized structures (components). The novel electromagnetic materials can be photonic crystals, which are composed of the periodic dielectric or metallic structures. The propagation of the electromagnetic wave in photonic crystals is affected in the same way as the electrons propagating in the periodic potential in solid. We demonstrated that the photonic crystals can be used as a tool to tune the birefringence of the electromagnetic field. Metamaterials, which are composed of the artificial structures exhibiting strong local resonances, are also a kind of novel electromagnetic materials. The strong local resonance can squeeze the wavelength of the incoming electromagnetic field to the subwavelength region (i.e. superlenses) and revise the effective electromagnetic response of the materials (i.e. the negative indexes). For metamaterials we focus on the Plasmonic metamaterials in the thesis: we would show that these materials could be used to guide electromagnetic wave or introduce various kinds of extraordinary transmissions, both of which, of course, are achieved at subwavelength region. Moreover, the novel electromagnetic materials can be even the topological insulators, whose non-trivial electronic surface states can have extraordinary responses under the electromagnetic field. These non-trivial quantum hall surface states can introduce the mode conversion between different electromagnetic modes on the surfaces of the topological insulators and thus modify the propagation properties of the electromagnetic field through them. We would demonstrate that the non-trivial surface states of the topological insulators could modify the coherence of the thermal radiation from them.

Xiao, Xiao

132

The Twisted Nematic Effect: Liquid Crystal Displays and Liquid Crystal Materials  

Microsoft Academic Search

The rapid progress of the young liquid crystal display (LCD) technology is due to the synergisms resulting from combining research on electro-optical effects, liquid crystal materials and display technology. The design and production of liquid crystal molecules with specific physical properties and their application in displays based on the twisted nematic effect has led within only seventeen years from simple

M. Schadt

1988-01-01

133

ICSD Web: the Inorganic Crystal Structure Database  

NSDL National Science Digital Library

This site contains a free demonstration version of the Inorganic Crystal Structure Database. This database contains a 3325 structure subset of the 76,480 inorganic structures as of 2004. The demo version can be queried and accessed by a web-interface which allows multiple methods of searching, and the resulting crystal structures can then be viewed online (with the CHIME plug-in) or downloaded for viewing with other visualization software. Also included on the site are updates of bug fixes, conditions of use and prices, tips for displaying the structures, a gallery of images, a flash movie, and instructions for installing a ICSD server.

Hewat Alan

134

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

DOEpatents

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.

Rollins, Harry W. (Idaho Falls, ID); Petkovic, Lucia M. (Idaho Falls, ID); Ginosar, Daniel M. (Idaho Falls, ID)

2011-02-01

135

Active materials and adaptive structures  

NASA Astrophysics Data System (ADS)

The paper discusses the objectives, issues and research directions of the ONR program on active materials and adaptive structures. It addresses the mechanics tools necessary for the design of this new class of structures. The paper reviews the research in the mechanics of materials of high strain active materials and engineering active materials, hybrid active materials, constitutive modeling, failure of ferroelectric ceramics, and active material interaction with host material. Understanding failure mechanisms in active materials was recognized early in the program to be of great importance to reliable design of high performance actuators and their acceptance by the design community. New concept of engineering active materials, and developments of hybrid active materials are introduced, as means to achieve high performance actuation. The paper covers different design approaches for high strain/high frequency actuators and new actuator concepts and the mechanics of embedding of actuators in composite structures.

Barsoum, Roshdy G. S.

1996-05-01

136

Crystal growth, characterization and structure refinement of neodymium[sup 3+] doped gehlenite, a new laser material (Ca[sub 2]Al[sub 2]SiO[sub 7])  

SciTech Connect

In order to find new Nd[sup 3+] laser materials pumpable by laser diode, gehlenite (Ca[sub 2]Al[sub 2]SiO[sub 7]) was chosen as a host matrix for neodymium ions. Large single crystals of Ca[sub 2[minus]x] Nd[sub x] Al[sub 2+x] Si[sub 1[minus]x] O[sub 7] (0 < x < 0.3) were obtained by Czochralski and floating zone methods. The main characteristics of these crystals (crystal perfection, thermal and mechanical behavior, optical properties...) were determined. The structure refinement revealed a structural disorder, occurring both on position and distribution of ions around Nd[sup 3+] and resulting in a broadening of the absorption bands. This means that less effort is required for diode laser pumping, and the laser effect has been observed. Therefore, Nd[sup 3+] doped Ca[sub 2]Al[sub 2]SiO[sub 7] appears as a good candidate as diode pumped laser.

Lejus, A.M.; Kahn-Harari, A.; Benitez, J.M.; Viana, B. (CNRS-URA1466, Paris (France). Lab. de Chimie Appliquee de l'Etat Solide)

1994-07-01

137

Crystal Growth and Properties of Nonlinear Optical Materials  

NASA Astrophysics Data System (ADS)

Nonlinear optical (NLO) crystals are a critical, enabling technology in the development of solid state laser sources, allowing the output from the most mature laser source operating a few discrete wavelengths to be shifted almost anywhere in the electromagnetic spectrum spanning from the ultraviolet to the far-infrared. For efficient frequency conversion, a nonlinear crystal must simultaneously satisfy a long list of material requirements, some of which are intrinsic, while others are extrinsic and must be controlled through careful processing. A wide range of materials and growth techniques are required to in order to produce crystals which operate in the various wavelength regimes of interest. The basic principles of NLO frequency conversion are introduced and used to derive the material property requirements. The crystal growth, properties, and performance of state-of-the-art nonlinear optical crystals are surveyed, and future directions in the development of new and improved NLO materials are identified.

Schunemann, Peter G.

2007-06-01

138

Pholcodine monohydrate: Crystal structure and polymorphism  

NASA Astrophysics Data System (ADS)

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.

Petruševski, Gjorgji; Zba?nik, Marija; Kajdžanoska, Marina; Ugarkovic, Sonja; Trim?eski, Vase; Kaitner, Branko; Jovanovski, Gligor; Makreski, Petre

2013-07-01

139

Amphidynamic Crystals: Structural Blueprints for Molecular Machines  

Microsoft Academic Search

By considering the relation between molecular structure, molecular dynamics, and phase order,\\u000a we suggest that certain structures should be able to make up supramolecular assemblies with structurally\\u000a programmed molecular dynamics. Given that the simplest members of these structures should have the\\u000a elements required to form a rigid lattice with moving parts, we propose the term amphidynamic\\u000a crystals to describe them. We

Steven D. Karlen; Miguel A. Garcia-Garibay

140

Natural photonic crystals: formation, structure, function  

NASA Astrophysics Data System (ADS)

The structure and properties of natural photonic crystals are discussed using the colored scales of the beetle Lamprocyphus augustus as an example. While the exact mechanism behind the formation of these biopolymeric photonic structures has yet to be fully explored, similarities of these structures to intracellular cubic membrane architectures are introduced. Some crucial parameters behind the formation of cubic membranes are discussed. Using these insights, intracellular cubic membrane structures are transformed into an extracellular environment.

Bartl, Michael H.; Dahlby, Michael R.; Barrows, Frank P.; Richens, Zachary J.; Terooatea, Tommy; Jorgensen, Matthew R.

2012-03-01

141

Chromonic liquid crystals: properties and applications as functional materials.  

PubMed

Chromonic liquid crystals (or chromonics) are formed by the self-organization of aromatic compounds with ionic or hydrophilic groups in aqueous solutions. This review summarizes the research on chromonic liquid crystals in the last two decades. The research embraced the studies of commercially available chromonic dyes and drugs, the syntheses and investigations of molecularly designed mesogens, the invention of novel processes for aligning chromonic liquid crystals, and the development of new applications as functional materials and biosensors. PMID:18536789

Tam-Chang, Suk-Wah; Huang, Liming

2008-05-01

142

Optics of magnetic photonic crystals with mu-negative materials  

NASA Astrophysics Data System (ADS)

In this paper, we have made an analysis of the optics of magnetic photonic crystals having mu-negative materials. We consider the magnetic photonic crystal with different values of the magnetic permeability of the materials (PIM). Such materials will be affected by the applied magnetic field and can also exhibit the properties of superconducting materials. We infer that PhC with MNM and PIM materials can be used as tunable devices by choosing proper thickness, damping factor, and mu-value of the PIM.

Kumar, N.; Thapa, K. B.; Janma, Ram; Pandey, G. N.; Reena

2013-06-01

143

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

144

Crystal structure of plant photosystem I  

Microsoft Academic Search

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

Adam Ben-Shem; Felix Frolow; Nathan Nelson

2003-01-01

145

Novel nonreciprocal materials based on magnetic photonic crystals  

Microsoft Academic Search

Magnetic photonic crystals are spatially periodic dielectric composites with at least one of the constitutive components being a magnetically polarized material. Magnetic polarization, either spontaneous or induced, is always associated with nonreciprocal circular birefringence (Faraday rotation), which can bring qualitatively new features to the electrodynamics of photonic crystals. If the geometry of the periodic array meets certain symmetry criterion, the

A. Figotin; I. Vitebskiy

2005-01-01

146

Epitaxial Crystal Growth: Methods and Materials  

NASA Astrophysics Data System (ADS)

The epitaxial growth of thin films of material for a wide range of applications in electronics and optoelectronics is a critical activity in many industries. The original growth technique used, in most instances, was liquid-phase epitaxy (LPE), as this was the simplest and often the cheapest route to producing device-quality layers. These days, while some production processes are still based on LPE, most research into and (increasingly) much of the production of electronic and optoelectronic devices now centers on metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). These techniques are more versatile than LPE (although the equipment is more expensive), and they can readily produce multilayer structures with atomic-layer control, which has become more and more important in the type of nanoscale engineering used to produce device structures in as-grown multilayers. This chapter covers these three basic techniques, including some of their more common variants, and outlines the relative advantages and disadvantages of each. Some examples of growth in various important systems are also outlined for each of the three techniques.

Capper, Peter; Irvine, Stuart; Joyce, Tim

147

Method and apparatus for nucleating the crystallization of undercooled materials  

DOEpatents

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.

Benson, David K. (Golden, CO); Barret, Peter F. (Peterbourgh, CA)

1989-01-01

148

Structural, thermal and optical characterization of a Schiff base as a new organic material for nonlinear optical crystals and films with reversible noncentrosymmetry  

NASA Astrophysics Data System (ADS)

Macroscopic single crystals of (E)-5-(diethylamino)-2-((3,5-dinitrophenylimino)methyl)phenol ( DNP) were obtained from slow cooling of chloroform or dichlorometane saturated solutions at controlled temperature. X-ray diffraction analysis showed that this compound crystallizes in a noncentrosymmetric space group ( P212121). Thermal analysis was performed and indicated that the crystals are stable until 260 °C. Second-order nonlinear optical properties of DNP were experimentally investigated in solution through EFISH technique and in solid state through the Kurtz-Perry powder technique. Crystals of compound DNP exhibited a second-harmonic signals 39 times larger than of the technologically useful potassium dihydrogenphosphate (KDP) under excitation at infrared wavelengths. In addition, the second-order nonlinear optical properties of DNP were also studied at visible wavelengths through the photorefractive effect and applied to demonstrate dynamic holographic reconstruction.

Rodríguez, Mario; Ramos-Ortíz, Gabriel; Maldonado, José Luis; Herrera-Ambriz, Víctor M.; Domínguez, Oscar; Santillan, Rosa; Farfán, Norberto; Nakatani, Keitaro

2011-09-01

149

Nanoscale imaging of mineral crystals inside biological composite materials using X-ray diffraction microscopy.  

PubMed

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. PMID:18233041

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

2008-01-25

150

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

NASA Astrophysics Data System (ADS)

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.

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

2008-01-01

151

Building Crystal Structure Ball Models Using Pre-Drilled Templates: Sheet Structures, Tridymite, and Cristobalite  

NSDL National Science Digital Library

This activity involves building crystal structure ball models in order to strengthen students' understanding of crystalline order, relative atomic size, atomic coordination, crystal chemistry, and crystal symmetry.

Kurt Hollocher

152

Elastic constants and material properties of novel shaped liquid crystals  

NASA Astrophysics Data System (ADS)

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 x 10-12 N, K22 = 5.6 x 10-12 N, and K33 = 4.6 x 10-12 N. For the Y-shaped RB0115 at T*=0.98, we found K11 = 2.8 x 10-12 N, K22 = 2.5 x 10-12 N, and K33 = 4.5 x 10-12 N. These constants are similar to values found for other materials with non-rod shaped or bent-core structure.

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

2013-03-01

153

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

154

Confined Crystals of the Smallest Phase-Change Material  

PubMed Central

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

2013-01-01

155

Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors  

PubMed Central

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

Wang, Hui; Zhang, Ke-Qin

2013-01-01

156

Solvothermal synthesis, crystal structure, and second-order nonlinear optical properties of a new noncentrosymmetric gallium-organic framework material, [N(C3H7)4]3Ga3[C6H3(CO2)3]4  

NASA Astrophysics Data System (ADS)

A novel noncentrosymmetric (NCS) gallium-organic framework material, [N(C3H7)4]3Ga3[C6H3(CO2)3]4 (CAUMOF-11) has been synthesized by a solvothermal reaction using Ga(NO3)3·xH2O, 1,3,5-C6H3(CO2H)3, N(C3H7)4Cl, HNO3, and HCON(CH3)2 at 180 °C. The structure of the reported material has been determined by single-crystal X-ray diffraction. CAUMOF-11 has an anionic three-dimensional framework with aligned four-coordinate GaO4 tetrahedra and 1,3,5-benzenetricarboxylate groups. Tetrapropylammonim cations reside within the channel and maintain the charge balance. Detailed structural analyses with full characterization including infrared spectroscopy, thermogravimetric analysis, elemental analysis, ion-exchange reactions, topotactic decomposition, and gas adsorption experiments are reported. Powder second-harmonic generating (SHG) measurements on CAUMOF-11, using 1064 nm radiation, exhibit SHG efficiency of 15 times that of ?-SiO2 and the material is phase-matchable (type-1).

Lee, Dong Woo; Jo, Vinna; Ok, Kang Min

2012-10-01

157

Crystal structure and chirality of natural floridoside.  

PubMed

The crystal structure and absolute configuration of natural floridoside (2-O-alpha-D-galactopyranosylglycerol) were determined by single-crystal X-ray diffraction analysis. The space group is orthorhombic P2(1)2(1)2(1) with Z=4, a=4.885(1), b=9.734(1), c=23.886(2) A at 296 +/- 2 K. The structure was solved by a direct method and refined to R=0.0351 from 1914 reflections of Cu Kalpha radiation. PMID:14572727

Simon-Colin, Christelle; Michaud, François; Léger, Jean-Michel; Deslandes, Eric

2003-10-31

158

Visible stealth materials based on photonic crystals  

NASA Astrophysics Data System (ADS)

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 ? and ?. 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.

Yao, Guozheng; Liu, Ying

2014-08-01

159

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

160

Growth and characterization of organic material 4-dimethylaminobenzaldehyde single crystal  

NASA Astrophysics Data System (ADS)

The organic material 4-dimethylaminobenzaldehyde single crystals were grown by slow evaporation technique. The grown crystal was confirmed by the single crystal and powder X-ray diffraction analyses. The functional groups of the crystal have been identified from the Fourier Transform Infrared (FTIR) and FT-Raman studies. The optical property of the grown crystal was analyzed by UV-Vis-NIR and photoluminescence (PL) spectral measurements. The thermal behavior of the grown crystal was analyzed by thermogravimetric (TG) and differential thermal analyses (DTA). Dielectric measurements were carried out with different frequencies by using parallel plate capacitor method. The third order nonlinear optical properties of 4-dimethylaminobenzaldehyde was measured by the Z-scan technique using 532 nm diode pumped continuous wave (CW) Nd:YAG laser.

Jebin, R. P.; Suthan, T.; Rajesh, N. P.; Vinitha, G.; Madhusoodhanan, U.

2015-01-01

161

Crystal Structure Representations for Machine Learning Models of Formation Energies  

E-print Network

We introduce and evaluate a set of feature vector representations of crystal structures for machine learning (ML) models of formation energies of solids. ML models of atomization energies of organic molecules have been successful using a Coulomb matrix representation of the molecule. We consider three ways to generalize such representations to periodic systems: (i) a matrix where each element is related to the Ewald sum of the electrostatic interaction between two different atoms in the unit cell repeated over the lattice; (ii) an extended Coulomb-like matrix that takes into account a number of neighboring unit cells; and (iii) an Ansatz that mimics the periodicity and the basic features of the elements in the Ewald sum matrix by using a sine function of the crystal coordinates of the atoms. The representations are compared for a Laplacian kernel with Manhattan norm, trained to reproduce formation energies using a data set of 3938 crystal structures obtained from the Materials Project. For training sets consi...

Faber, Felix; von Lilienfeld, O Anatole; Armiento, Rickard

2015-01-01

162

Synthesis, crystal growth, structural, thermal, optical and mechanical properties of solution grown 4-methylpyridinium 4-hydroxybenzoate single crystal.  

PubMed

Organic nonlinear optical material, 4-methylpyridinium 4-hydroxybenzoate (4MPHB) was synthesized and single crystal was grown by slow evaporation solution growth method. Single crystal and powder X-ray diffraction analyses confirm the structure and crystalline perfection of 4MPHB crystal. Infrared, Raman and NMR spectroscopy techniques were used to elucidate the functional groups present in the compound. TG-DTA analysis was carried out in nitrogen atmosphere to study the decomposition stages, endothermic and exothermic reactions. UV-visible and Photoluminescence spectra were recorded for the grown crystal to estimate the transmittance and band gap energy respectively. Linear refractive index, birefringence, and SHG efficiency of the grown crystal were studied. Laser induced surface damage threshold and mechanical properties of grown crystal were studied to assess the suitability of the grown crystals for device applications. PMID:24184578

Sudhahar, S; Krishna Kumar, M; Sornamurthy, B M; Mohan Kumar, R

2014-01-24

163

Synthesis, crystal growth, structural, thermal, optical and mechanical properties of solution grown 4-methylpyridinium 4-hydroxybenzoate single crystal  

NASA Astrophysics Data System (ADS)

Organic nonlinear optical material, 4-methylpyridinium 4-hydroxybenzoate (4MPHB) was synthesized and single crystal was grown by slow evaporation solution growth method. Single crystal and powder X-ray diffraction analyses confirm the structure and crystalline perfection of 4MPHB crystal. Infrared, Raman and NMR spectroscopy techniques were used to elucidate the functional groups present in the compound. TG-DTA analysis was carried out in nitrogen atmosphere to study the decomposition stages, endothermic and exothermic reactions. UV-visible and Photoluminescence spectra were recorded for the grown crystal to estimate the transmittance and band gap energy respectively. Linear refractive index, birefringence, and SHG efficiency of the grown crystal were studied. Laser induced surface damage threshold and mechanical properties of grown crystal were studied to assess the suitability of the grown crystals for device applications.

Sudhahar, S.; Krishna Kumar, M.; Sornamurthy, B. M.; Mohan Kumar, R.

2014-01-01

164

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

165

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

Loewy, Robert G.; Wiberley, Stephen E.

1988-01-01

166

Requirements for structure determination of aperiodic crystals  

NASA Astrophysics Data System (ADS)

Using computer simulation, we compared the Patterson functions of one-dimensional (1D) randomly packed and quasiperiodic Fibonacci lattices with or without disorder, and a 2D Penrose lattice and random packing of pentagons (icosahedral glass model). Based on these comparisons, we derived some empirical guidelines for distinguishing ideal quasicrystals from aperiodic crystals with disorder using diffraction data. In contrast to periodic crystals, it is essential to include the background to obtain correct Patterson functions of the average structure since the background contains unresolved peaks. In particular, a Bragg peak scattering measurement cannot, in general, determine the structure of aperiodic crystals. Instead, a diffuse scattering measurement is required, which determines the absolute value of the diffraction background, in addition to the Bragg peaks. We further estimate that, dependent upon the disorder present, it is necessary to include up to 75% of the total diffracted intensity in any analysis.

Li, Xiao-Ou; Stern, Edward A.; Ma, Yanjun

1991-01-01

167

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

SciTech Connect

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.

Thirumurugan, R., E-mail: singlecrystalxrd@gmail.com; Anitha, K., E-mail: singlecrystalxrd@gmail.com [School of Physics, Madurai Kamaraj University, Madurai-625021 (India)

2014-04-24

168

Focusing concave lens using photonic crystals with magnetic materials.  

PubMed

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

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

2006-04-01

169

Shear induced structures in crystallizing cocoa butter  

NASA Astrophysics Data System (ADS)

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.

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

2004-03-01

170

Crystal structure of the anthrax lethal factor  

Microsoft Academic Search

Lethal factor (LF) is a protein (relative molecular mass 90,000) that is critical in the pathogenesis of anthrax. It is a highly specific protease that cleaves members of the mitogen-activated protein kinase kinase (MAPKK) family near to their amino termini, leading to the inhibition of one or more signalling pathways. Here we describe the crystal structure of LF and its

Andrew D. Pannifer; Thiang Yian Wong; Robert Schwarzenbacher; Martin Renatus; Carlo Petosa; Jadwiga Bienkowska; D. Borden Lacy; R. John Collier; Stephen H. Leppla; Philip Hanna; Robert C. Liddington

2001-01-01

171

Crystal structure of a plectonemic RNA supercoil  

SciTech Connect

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.

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

2012-12-14

172

A hierarchical structure for apatite crystals  

Microsoft Academic Search

Based on the experimental results taken from the references, a reasonable hierarchical structure of apatite (both fluorapatite and hydroxyapatite) crystals has been proposed for the first time. The structure consists of four levels of the hierarchy: the smallest level is made of single unit-cells and\\/or Posner's clusters with the linear dimensions slightly below 1 nm, the second level comprises X-ray

Sergey V. Dorozhkin

2007-01-01

173

STRUCTURAL ENGINEERING, MECHANICS AND MATERIALS  

E-print Network

Buildings · Masonry Structures · Nano/Microstructure of Cement-based Materials · Polymeric Composite stability tests of reinforced and prestressed concrete beams. Fiber optic laser interferometer. Use of fiber reinforced polymer deck panels for rapid repair of bridge structures. `Smart' wireless

Wang, Yuhang

174

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

NASA Astrophysics Data System (ADS)

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 P1bar with the following parameters: a=8.4749(6)(Å), b=17.1392(12)(Å), c=17.1392(12)(Å), ? = 117.339(0)°, ? = 99.487(0)°, ? = 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.

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

2014-12-01

175

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

PubMed

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)(?), b=17.1392(12)(?), c=17.1392(12)(?), ?=117.339(0)°, ?=99.487(0)°, ?=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

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

2014-12-10

176

Crystal growth and third order NLO properties of a photonic material  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

177

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

SciTech Connect

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.

Wallace, E.; Dranow, D.; Laible, P. D.; Christensen, J.; Nollert, P. (Biosciences Division); (Emerald BioStructures)

2011-01-01

178

Crystal structure and magnetic structure of TbOOH  

Microsoft Academic Search

The monoclinic modification of terbium oxide hydroxide, TbOOH, was prepared using hydrothermal technique. The crystal structure was investigated by three-dimensional single-crystal X-ray analysis and was refined to a conventional R-value of 8.1%. The space group is P21\\/m, No. 11, with a = 6.04 Å, b = 3.69 Å, c = 4.33 Å, and beta = 109.0°. The terbium atom is

A. Nørlund Christensen; S. Quézel

1974-01-01

179

5.841 Crystal Structure Refinement, Fall 2006  

E-print Network

This course in crystal structure refinement examines the practical aspects of crystal structure determination from data collection strategies to data reduction and basic and advanced refinement problems of organic and ...

Mueller, Peter

180

5.067 Crystal Structure Refinement, Fall 2007  

E-print Network

This course in crystal structure refinement examines the practical aspects of crystal structure determination from data collection strategies to data reduction and basic and advanced refinement problems of organic and ...

Mueller, Peter

181

Manganese oxide minerals: Crystal structures and economic and environmental significance  

PubMed Central

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

Post, Jeffrey E.

1999-01-01

182

Crystal structure of riboflavin synthase  

SciTech Connect

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.

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

2010-03-05

183

Fourier Analysis and Structure Determination--Part III: X-ray Crystal Structure Analysis.  

ERIC Educational Resources Information Center

Discussed is single crystal X-ray crystal structure analysis. A common link between the NMR imaging and the traditional X-ray crystal structure analysis is reported. Claims that comparisons aid in the understanding of both techniques. (MVL)

Chesick, John P.

1989-01-01

184

Crystal morphology variation in inkjet-printed organic materials  

Microsoft Academic Search

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

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

2011-01-01

185

Exploring Crystal Structures with XtalDraw  

NSDL National Science Digital Library

At the end of this exercise students will be able to use computer-based software to draw crystal structures and visualize symmetries present in minerals. By varying the way in which atoms or groups of atoms are displayed, they will begin to see how atoms link through bonds. Students will also begin to investigate the effects of variable composition on bonding on unit cell parameters.

Wendy Panero

186

Crystal Structures of the ?2-Adrenergic Receptor  

NASA Astrophysics Data System (ADS)

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 ?2-adrenergic receptor (?2AR), 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 (?2AR-Fab) or lipidic cubic phase (?2AR-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.

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.

187

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

NASA Astrophysics Data System (ADS)

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 ?m3) 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.

Merlini, M.

2013-12-01

188

A Solid-State NMR Method for Solution of Zeolite Crystal Structures  

Microsoft Academic Search

Since zeolites are notoriously difficult to prepare as large single crystals, structure determination usually relies on powder X-ray diffraction (XRD). However, structure solution (i.e., deriving an initial structural model) directly from powder XRD data is often very difficult due to the diffraction phase problem and the high degree of overlap between the individual reflections, particularly for materials with the structural

Darren H. Brouwer; Richard J. Darton; Russell E. Morris; Malcolm H. Levitt

2005-01-01

189

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

PubMed

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 360nm. The relative second harmonic generation (SHG) efficiency of grown crystal was estimated by using Nd:YAG laser with fundamental wavelength of 1064nm. PMID:25795607

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

2015-06-15

190

Thermally Triggered Solid-State Single-Crystal-to-Single-Crystal Structural Transformation Accompanies Property Changes.  

PubMed

The 1D complex [(CuL0.5 H2 O)?H2 O]n (1) (H4 L=2,2'-bipyridine-3,3',6,6'-tetracarboxylic acid) undergoes an irreversible thermally triggered single-crystal-to-single-crystal (SCSC) transformation to produce the 3D anhydrous complex [CuL0.5 ]n (2). This SCSC structural transformation was confirmed by single-crystal X-ray diffraction analysis, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD) patterns, variable-temperature powder X-ray diffraction (VT-PXRD) patterns, and IR spectroscopy. Structural analyses reveal that in complex 2, though the initial 1D chain is still retained as in complex 1, accompanied with the Cu-bound H2 O removed and new O(carboxyl)?Cu bond forming, the coordination geometries around the Cu(II) ions vary from a distorted trigonal bipyramid to a distorted square pyramid. With the drastic structural transition, significant property changes are observed. Magnetic analyses show prominent changes from antiferromagnetism to weak ferromagnetism due to the new formed Cu1-O-C-O-Cu4 bridge. The catalytic results demonstrate that, even though both solid-state materials present high catalytic activity for the synthesis of 2-imidazolines derivatives and can be reused, the activation temperature of complex 1 is higher than that of complex 2. In addition, a possible pathway for the SCSC structural transformations is proposed. PMID:25663637

Li, Quan-Quan; Ren, Chun-Yan; Huang, Yang-Yang; Li, Jian-Li; Liu, Ping; Liu, Bin; Liu, Yang; Wang, Yao-Yu

2015-03-16

191

A hierarchical structure for apatite crystals.  

PubMed

Based on the experimental results taken from the references, a reasonable hierarchical structure of apatite (both fluorapatite and hydroxyapatite) crystals has been proposed for the first time. The structure consists of four levels of the hierarchy: the smallest level is made of single unit-cells and/or Posner's clusters with the linear dimensions slightly below 1 nm, the second level comprises X-ray coherent scattering blocks of 50-80 nm in size, the third level is represented by dislocation blocks of 0.3-2.0 microm in size and, finally, there are macroblocks of 35-50 microm in size. PMID:17323170

Dorozhkin, Sergey V

2007-02-01

192

Geometry of crystal structure with defects. I. Euclidean picture  

SciTech Connect

Continuously distributed defects of crystal structure are considered. The starting point is the Euclidean geometry of the ideal crystal lattice and the topological description of the distortion of the crystal structure. It is shown how the non-Euclidean geometry of distorted crystal structure, as well as the basic assumptions of the phenomenological plasticity theory concerning the deformation of a continuum, are related to those theories. A form for an affine connection describing continuously distributed dislocations is proposed.

Trzesowski, A.

1987-04-01

193

STRUCTURES AND MATERIALS TEST LABORATORY  

E-print Network

STRUCTURES AND MATERIALS TEST LABORATORY CIVIL ENGINEERING COLLEGE OF ENGINEERING UNIVERSITY and Environmental Engineering University of Wisconsin Madison, Wisconsin January 2008 #12;ii Abstract Shrinkage concrete highway bridge girders. A normal concrete mix from Spancrete was used as a basic reference

Russell, Jeffrey S.

194

Crystal Structure of A-amylose: a Revisit from Synchrotron Microdiffraction Analysis of Single Crystals  

E-print Network

1 Crystal Structure of A-amylose: a Revisit from Synchrotron Microdiffraction Analysis of Single;2 Abstract The three-dimensional structure of A-amylose crystals, as a model of the crystal domains of A the resolution of important new fine details. These include a distortion of the amylose double helices resulting

Paris-Sud XI, Université de

195

A general approach to increasing the radiation hardness of complex structure oxide scintillation crystals  

Microsoft Academic Search

An approach to increasing the radiation hardness of scintillation materials based on complex structure oxide single crystals is proposed. It is shown that damage of the scintillation mechanism and radiation-induced optical absorption are strongly suppressed when a crystal is doped by a specific impurity. The necessary impurity properties are formulated. The proposed approach is illustrated by radiation hardness improvement of

M. V. Korzhik

2003-01-01

196

The nature of crystal disorder in milled pharmaceutical materials  

Microsoft Academic Search

The purpose of this study was to study the nature of disorder in milled crystalline materials. Specifically to elucidate if the induced disorder represents crystal defects or amorphous regions. Felodipine and griseofulvin were chosen as model drugs and subjected to milling. Cryomilling was chosen in order to mitigate the influence of heat generated by the process. Amorphous drug samples were

Sai Prasanth Chamarthy; Rodolfo Pinal

2008-01-01

197

Microstructural characterization of sputtered garnet materials and all-garnet magnetic heterostructures: establishing the technology for magnetic photonic crystal fabrication  

Microsoft Academic Search

We have established a set of technologies for the deposition and annealing of magneto-optic ferrite and paramagnetic garnets, as well as multilayer nanostructures which are based on these materials, for use in magnetic photonic crystals. Transmission electron microscope analysis has been performed to investigate the structure of both amorphous and crystallized garnet layers, nanocrystallites and layer interfaces within all-garnet heterostructures.

Mikhail Vasiliev; P. C. Wo; Kamal Alameh; Paul Munroe; Zonghan Xie; V. A. Kotov; V. I. Burkov

2009-01-01

198

Microstructural characterization of sputtered garnet materials and all-garnet magnetic heterostructures: establishing the technology for magnetic photonic crystal fabrication  

NASA Astrophysics Data System (ADS)

We have established a set of technologies for the deposition and annealing of magneto-optic ferrite and paramagnetic garnets, as well as multilayer nanostructures which are based on these materials, for use in magnetic photonic crystals. Transmission electron microscope analysis has been performed to investigate the structure of both amorphous and crystallized garnet layers, nanocrystallites and layer interfaces within all-garnet heterostructures.

Vasiliev, M.; Wo, P. C.; Alameh, K.; Munroe, P.; Xie, Z.; Kotov, V. A.; Burkov, V. I.

2009-07-01

199

[Band electronic structures and crystal packing forces  

SciTech Connect

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.

Not Available

1993-01-01

200

High temperature structural insulating material  

DOEpatents

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.

Chen, W.Y.

1984-07-27

201

Revisiting the crystal structure of rhombohedral lead metaniobate.  

PubMed

Lead metaniobate (PbNb2O6) can exist both as a stable rhombohedral and a metastable orthorhombic tungsten-bronze-type polymorph. Although the orthorhombic is a well-known ferroelectric material, the rhombohedral polymorph has been far less studied. The crystal structure and energetic stability of the stable rhombohedral polymorph of lead metaniobate is re-examined by powder X-ray diffraction and powder neutron diffraction in combination with ab initio calculations. We show that this structure is described by the polar space group R3, in contradiction to the previously reported space group R3m. The crystal structure is unusual, consisting of edge-sharing dimers of NbO(6/2) octahedra forming layers with 6- and 3-fold rings of octahedra and lead ions in channels formed by these rings. The layers are connected by corner-sharing between octahedra. Finally, the crystal structure is discussed in relation to other AB2O6 compounds with B = Nb, Ta. PMID:25167129

Olsen, Gerhard Henning; Sørby, Magnus Helgerud; Hauback, Bjørn Christian; Selbach, Sverre Magnus; Grande, Tor

2014-09-15

202

Variable temperature study of the crystal and magnetic structures of the giant magnetoresistant materials LMnAsO(L = La, Nd)  

Microsoft Academic Search

A variable temperature neutron and synchrotron diffraction study has been performed on the giant magnetoresistant oxypnictides LMnAsO (L = La, Nd). The low-temperature magnetic structures have been studied, and results show a spin reorientation of the Mn2+ spins below TN (Nd) for NdMnAsO. The Mn2+ spins rotate from alignment along c to alignment into the basal plane, and the Mn2+

N. Emery; E. J. Wildman; J. M. S. Skakle; A. C. McLaughlin; R. I. Smith; A. N. Fitch

2011-01-01

203

PROTEIN STRUCTURE REPORT Crystal structure of the Yersinia type III  

E-print Network

, 2005; FINAL REVISION July 15, 2005; ACCEPTED July 27, 2005) Abstract The plague-causing bacterium of oligomerization is discussed. Keywords: Yersinia pestis; plague; type III secretion; YscE; crystal structure Yersinia pestis, the causative agent of plague, utilizes a type III secretion system (T3SS) to inject

204

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

SciTech Connect

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.

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 (MRC); (Utah); (MRC)

2009-10-07

205

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

PubMed

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

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

2012-01-01

206

Synthesis, growth, crystal structure and characterization of a new organic NLO crystal: L-Lysine 4-nitrophenolate monohydrate (LLPNP)  

NASA Astrophysics Data System (ADS)

L-Lysine 4-nitrophenolate monohydrate (LLPNP) has been synthesized and grown by solution growth method at room temperature using deionised water as a solvent. The crystal structure of the materials was solved by single crystal X-ray diffraction analysis and it was found that the material has orthorhombic system. The crystallinity of the grown crystals was studied by the powder X-ray diffraction analysis. Molecular structure of the grown crystal was investigated by 1H NMR spectroscopy. The various functional groups of the sample were identified by Fourier transform infrared and Fourier transform-Raman spectroscopic analyses. Thermal stability of the grown crystal has been studied by Thermogravimetric and Differential thermal (TG&DTA) analysis. The optical absorption of the grown crystals has been ascertained by UV-Vis-NIR absorption studies. Second harmonic generation (SHG) efficiency of the material has been determined by Kurtz and Perry technique and the efficiency was found to be 4.45 and 1.4 times greater than that of standard KDP and urea samples, respectively.

Mahadevan, M.; Magesh, M.; Ramachandran, K.; Anandan, P.; Arivanandhan, M.; Hayakawa, Y.

2014-09-01

207

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

NASA Astrophysics Data System (ADS)

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%.

Falkner, Joshua Charles

208

Crystal structure of the Golgi casein kinase  

PubMed Central

The family with sequence similarity 20 (Fam20) kinases phosphorylate extracellular substrates and play important roles in biomineralization. Fam20C is the Golgi casein kinase that phosphorylates secretory pathway proteins within Ser-x-Glu/pSer motifs. Mutations in Fam20C cause Raine syndrome, an osteosclerotic bone dysplasia. Here we report the crystal structure of the Fam20C ortholog from Caenorhabditis elegans. The nucleotide-free and Mn/ADP-bound structures unveil an atypical protein kinase-like fold and highlight residues critical for activity. The position of the regulatory ?C helix and the lack of an activation loop indicate an architecture primed for efficient catalysis. Furthermore, several distinct elements, including the presence of disulfide bonds, suggest that the Fam20 family diverged early in the evolution of the protein kinase superfamily. Our results reinforce the structural diversity of protein kinases and have important implications for patients with disorders of biomineralization. PMID:23754375

Xiao, Junyu; Tagliabracci, Vincent S.; Wen, Jianzhong; Kim, Soo-A; Dixon, Jack E.

2013-01-01

209

Crystal structure of plant photosystem I  

NASA Astrophysics Data System (ADS)

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.

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

2003-12-01

210

Structural contribution to the roughness of supersmooth crystal surface  

SciTech Connect

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.

Butashin, A. V.; Muslimov, A. E., E-mail: amuslimov@mail.ru; Kanevsky, V. M.; Deryabin, A. N.; Pavlov, V. A.; Asadchikov, V. E. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2013-05-15

211

Crystal growth, characterization and structure refinement of neodymium[sup 3+] doped gehlenite, a new laser material (Ca[sub 2]Al[sub 2]SiO[sub 7])  

Microsoft Academic Search

In order to find new Nd[sup 3+] laser materials pumpable by laser diode, gehlenite (Ca[sub 2]Al[sub 2]SiO[sub 7]) was chosen as a host matrix for neodymium ions. Large single crystals of Ca[sub 2[minus]x] Nd[sub x] Al[sub 2+x] Si[sub 1[minus]x] O[sub 7] (0 < x < 0.3) were obtained by Czochralski and floating zone methods. The main characteristics of these crystals

A. M. Lejus; A. Kahn-Harari; J. M. Benitez; B. Viana

1994-01-01

212

Synthesis and structural characterization of new microporous framework materials  

Microsoft Academic Search

Porous solids have attracted a great amount of attention in the last few years because of not only their interesting crystal structures but also their potential applications in catalysis, ion-exchange and sorption. In this dissertation research, the exploratory synthesis of novel crystalline microporous materials was studied in detail. The types of open frameworks of interest include organically templated metal phosphates

Hyunsoo Park

2007-01-01

213

How evolutionary crystal structure prediction works--and why.  

PubMed

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

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

2011-03-15

214

Characterisation of zeolitic materials with a HEU-type structure modified by transition metal elements: definition of acid sites in nickel-loaded crystals in the light of experimental and quantum-chemical results.  

PubMed

Nickel-loaded HEU-type zeolite crystals have been obtained by well-known synthetic procedures and characterised by X-ray fluorescence (XRF), scanning-electron microscopy/ energy-dispersive spectroscopy (SEM-EDS), FT-IR, diffuse reflectance UV/ Vis spectroscopy (DR(UV/Vis)S) and X-ray photoelectron spectroscopy (XPS) measurements as non-homoionic and non-stoichiometric substances containing exchangeable hydrated Ni2+ ions in the micropores and nickel hydroxide phases supported on the surface. Thermogravimetric analysis/differential gravimetry (TGA/DTG) and differential thermal analysis (DTA) demonstrated that full dehydration below approximately 400 degrees C follows a clearly endothermic process, whereas at higher temperatures the zeolite is amorphised and finally partially recrystallised to Ni(Al,Si) oxides, detected by powder X-ray powder diffraction (XRD). The solid acidity of NiHEU, initially determined by temperature-programmed desorption (TPD) of ammonia to be 8.93 mgg(-1) NH3, is attributed to the weak acid sites (fundamentally Lewis sites) resolved at approximately 183 degrees C, and to the strong acid sites (essentially Brønsted sites) resolved at approximately 461 degrees C in the TPD pattern. A more sophisticated study based on in situ/ex situ FT-IR with in situ/ex situ 27Al MAS NMR and pyridine (Py) as a probe molecule, revealed that the Lewis acid sites can be attributed primarily to Ni2+ ions, whereas the Brønsted ones can probably be associated with the surface-supported nickel hydroxide phases. The spectroscopic measurements in conjunction with powder XRD and 29Si MAS NMR data strongly suggest that distorted Al tetrahedra are formed during the dehydration process and Py chemisorption/complexation (NiHEU-Py), whereas the crystal structure is remarkably well preserved in the rehydrated material (NiHEU-Py/R). The structural, electronic, energetic and spectroscopic properties of all possible nickel(II) aqua and dihydroxy complexes absorbed in the zeolite micropores or supported on the zeolite surface were studied theoretically by density functional theory (DFT). The computed proton affinity, found to be in the range 182.0-210.0 kcalmol(-1), increases with increasing coordination number of the aqua and dihydroxy nickel(II) complexes. PMID:11575771

Godelitsas, A; Charistos, D; Tsipis, A; Tsipis, C; Filippidis, A; Triantafyllidis, C; Manos, G; Siapkas, D

2001-09-01

215

Morphology, crystal structure and hydration of calcined and modified anhydrite  

NASA Astrophysics Data System (ADS)

The effects of calcination and modification on the morphology (shapes and textures) and crystal structure of anhydrite powders were studied. The results show that, calcination at 100°C causes anhydrite to disintegrate into smaller crystals, accompanied by a slight increase in d-spacing. Without calcination and modification, the solidification time and curing time of anhydrite are 15 and 77 h, respectively. After the treatment, however, the solidification time and curing time are shortened significantly to 9.5 and 14 min, respectively. The compressive and flexural strengths of hydration products made from the treated anhydrite reach 10.2 and 2.0 MPa, respectively. The much shorter solidification and curing time make it possible to use anhydrite as a building and construction material.

Niu, Xiao-qing; Chen, Ji-chun

2014-10-01

216

Microwave Material Properties of Nanoparticle-Doped Nematic Liquid Crystals  

NASA Astrophysics Data System (ADS)

This letter presents the material properties of nanoparticle-doped liquid crystal (LC) mixtures at microwave frequencies. A host (undoped) nematic LC material is doped with several concentrations of ferroelectric, gold and silver nanoparticles. The measurements are conducted at 30 GHz by using a cavity perturbation method. Based on these measurements, relative permittivity and dielectric losses are extracted, then the resultant material tunability and figure-of-merit are calculated. Compared to the host LC, some changes in the electrical parameters of the doped samples are observed, reducing the tunability and material figure-of-merit of all samples. Nevertheless, depending on the shape of the nanoparticles, their impact on the material figure-of-merit is more significant than on the tunability, reducing the figure-of-merit drastically once the tunability changed slightly only.

Karabey, O. H.

2015-03-01

217

Crystal structure of yeast Sco1  

SciTech Connect

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.

Abajian, Carnie; Rosenzweig, Amy C. (NWU)

2010-03-05

218

Dense packing crystal structures of physical tetrahedra  

E-print Network

We present a method for discovering dense packings of general convex hard particles and apply it to study the dense packing behavior of a one-parameter family of particles with tetrahedral symmetry representing a deformation of the ideal mathematical tetrahedron into a less ideal, physical, tetrahedron and all the way to the sphere. Thus, we also connect the two well studied problems of sphere packing and tetrahedron packing on a single axis. Our numerical results uncover a rich optimal-packing behavior, compared to that of other continuous families of particles previously studied. We present four structures as candidates for the optimal packing at different values of the parameter, providing an atlas of crystal structures which might be observed in systems of nano-particles with tetrahedral symmetry.

Yoav Kallus; Veit Elser

2010-11-17

219

Dense packing crystal structures of physical tetrahedra  

E-print Network

We present a method for discovering dense packings of general convex hard particles and apply it to study the dense packing behavior of a one-parameter family of particles with tetrahedral symmetry representing a deformation of the ideal mathematical tetrahedron into a less ideal, physical, tetrahedron and all the way to the sphere. Thus, we also connect the two well studied problems of sphere packing and tetrahedron packing on a single axis. Our numerical results uncover a rich optimal-packing behavior, compared to that of other continuous families of particles previously studied. We present four structures as candidates for the optimal packing at different values of the parameter, providing an atlas of crystal structures which might be observed in systems of nano-particles with tetrahedral symmetry.

Kallus, Yoav

2010-01-01

220

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

ERIC Educational Resources Information Center

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)

Hong, Y. S.; And Others

1980-01-01

221

Structural materials for space applications  

NASA Technical Reports Server (NTRS)

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.

Tenney, Darrel R.

1989-01-01

222

Short Article The Crystal Structure of the Intact E. coli  

E-print Network

the crystal structure of the intact Escherichia coli RelB2E2 complex at 2.8 A° resolution, comprising both The Escherichia coli relBE locus encodes a bacterial type II toxin- antitoxin (TA) complex consisting of a toxinStructure Short Article The Crystal Structure of the Intact E. coli RelBE Toxin-Antitoxin Complex

Passmore, Lori A.

223

Ab initio molecular crystal structures, spectra, and phase diagrams.  

PubMed

Conspectus Molecular crystals are chemists' solids in the sense that their structures and properties can be understood in terms of those of the constituent molecules merely perturbed by a crystalline environment. They form a large and important class of solids including ices of atmospheric species, drugs, explosives, and even some organic optoelectronic materials and supramolecular assemblies. Recently, surprisingly simple yet extremely efficient, versatile, easily implemented, and systematically accurate electronic structure methods for molecular crystals have been developed. The methods, collectively referred to as the embedded-fragment scheme, divide a crystal into monomers and overlapping dimers and apply modern molecular electronic structure methods and software to these fragments of the crystal that are embedded in a self-consistently determined crystalline electrostatic field. They enable facile applications of accurate but otherwise prohibitively expensive ab initio molecular orbital theories such as Møller-Plesset perturbation and coupled-cluster theories to a broad range of properties of solids such as internal energies, enthalpies, structures, equation of state, phonon dispersion curves and density of states, infrared and Raman spectra (including band intensities and sometimes anharmonic effects), inelastic neutron scattering spectra, heat capacities, Gibbs energies, and phase diagrams, while accounting for many-body electrostatic (namely, induction or polarization) effects as well as two-body exchange and dispersion interactions from first principles. They can fundamentally alter the role of computing in the studies of molecular crystals in the same way ab initio molecular orbital theories have transformed research practices in gas-phase physical chemistry and synthetic chemistry in the last half century. In this Account, after a brief summary of formalisms and algorithms, we discuss applications of these methods performed in our group as compelling illustrations of their unprecedented power in addressing some of the outstanding problems of solid-state chemistry, high-pressure chemistry, or geochemistry. They are the structure and spectra of ice Ih, in particular, the origin of two peaks in the hydrogen-bond-stretching region of its inelastic neutron scattering spectra, a solid-solid phase transition from CO2-I to elusive, metastable CO2-III, pressure tuning of Fermi resonance in solid CO2, and the structure and spectra of solid formic acid, all at the level of second-order Møller-Plesset perturbation theory or higher. PMID:24754304

Hirata, So; Gilliard, Kandis; He, Xiao; Li, Jinjin; Sode, Olaseni

2014-09-16

224

Aggregate Structure and Free Energy Changes in Chromonic Liquid Crystals  

E-print Network

Aggregate Structure and Free Energy Changes in Chromonic Liquid Crystals Alexandra J. Dickinson, Swarthmore College, Swarthmore, PA, USA Past and recent x-ray and absorption data on chromonic liquid crystal phase forms at higher concentrations. Keywords: aggregation; chromonic; liquid crystals

Collings, Peter

225

Method of binding structural material  

DOEpatents

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.

Wagh, Arun S. (Orland Park, IL); Antink, Allison L. (Bolingbrook, IL)

2007-12-25

226

Crystal Growth, Structure, and Properties of New Nonlinear Optical Materials: K 2Ln(NO 3) 5·2H 2O ( Ln=La, Ce, Pr, Nd, Sm)  

NASA Astrophysics Data System (ADS)

Single crystals of K2Ln(NO3)5·2H2O (Ln=La, Ce, Pr, Nd, Sm) (KLnN) were grown by evaporation in aqueous solution under constant temperature conditions. The structure of KPrN was determined from the single-crystal X-ray diffraction data. The KPrN crystallizes in the orthorhombic space group Fdd2 with parameters a=21.411(3) Å, b=11.2210(10) Å, c=12.208(2) Å, Z=6, V=2933.0(7) Å3, R=0.0240, Rw=0.0603. The powder second harmonic generation (SHG) intensities of KLnN (Ln=La, Ce, Pr, Nd, Sm) are also studied. The results demonstrate that their SHG intensities are 4-9 times larger than that of KDP, in which the KPrN shows the highest SHG coefficient.

Dong, Wenting; Zhang, Hongjie; Su, Qiang; Lin, Yonghua; Wang, Shumei; Zhu, Congshan

1999-12-01

227

Fabrication of Quasi-Phase-Matching Structure during Paraelectric Borate Crystal Growth  

NASA Astrophysics Data System (ADS)

We report an unconventional approach to produce a periodically twinned crystal of a non-ferroelectric material that can function as a quasi-phase matching (QPM) device. A twin boundary control method was developed based on the twin boundary formation mechanism during crystallization, and a periodically twinned QPM structure was realized in a non-ferroelectric lithium tetraborate (Li2B4O7; LB4) crystal. It was demonstrated that the periodically twinned LB4 crystal can function as a QPM device, and the second-harmonic generation (SHG) light of a Nd:YAG laser was observed.

Maeda, Kensaku; Uda, Satoshi; Fujiwara, Kozo; Nozawa, Jun; Koizumi, Haruhiko; Sato, Shun-ichi; Kozawa, Yuichi; Nakamura, Takahiro

2013-01-01

228

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

PubMed

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

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

2015-03-01

229

Modification of phonon processes in nano-structured rare-earth-ion-doped crystals  

E-print Network

Nano-structuring impurity-doped crystals affects the phonon density of states and thereby modifies the atomic dynamics induced by interaction with phonons. We propose the use of nano-structured materials in the form of powders or phononic bandgap crystals to enable, or improve, persistent spectral hole-burning and optical coherence for inhomogeneously broadened absorption lines in rare-earth-ion-doped crystals. This is crucial for applications such as ultra-precise radio-frequency spectrum analyzers and certain approaches to optical quantum memories. We specifically discuss how phonon engineering can enable spectral hole burning in erbium-doped materials operating in the telecommunication band, and present simulations for density of states of nano-sized powders and phononic crystals for the case of Y$_2$SiO$_5$, a widely-used material in current quantum memory research.

Thomas Lutz; Lucile Veissier; Charles W. Thiel; Rufus L. Cone; Paul E. Barclay; Wolfgang Tittel

2015-04-09

230

Modification of phonon processes in nano-structured rare-earth-ion-doped crystals  

E-print Network

Nano-structuring impurity-doped crystals affects the phonon density of states and thereby modifies the atomic dynamics induced by interaction with phonons. We propose the use of nano-structured materials in the form of powders or phononic bandgap crystals to enable, or improve, persistent spectral hole-burning and optical coherence for inhomogeneously broadened absorption lines in rare-earth-ion-doped crystals. This is crucial for applications such as ultra-precise radio-frequency spectrum analyzers and certain approaches to optical quantum memories. We specifically discuss how phonon engineering can enable spectral hole burning in erbium-doped materials operating in the telecommunication band, and present simulations for density of states of nano-sized powders and phononic crystals for the case of Y$_2$SiO$_5$, a widely-used material in current quantum memory research.

Lutz, Thomas; Thiel, Charles W; Cone, Rufus L; Barclay, Paul E; Tittel, Wolfgang

2015-01-01

231

Crystal structure of Junin virus nucleoprotein.  

PubMed

Junin virus (JUNV) has been identified as the aetiological agent of Argentine haemorrhagic fever (AHF), which is a serious public health problem with approximately 5 million people at risk. It is treated as a potential bioterrorism agent because of its rapid transmission by aerosols. JUNV is a negative-sense ssRNA virus that belongs to the genus Arenavirus within the family Arenaviridae, and its genomic RNA contains two segments encoding four proteins. Among these, the nucleoprotein (NP) has essential roles in viral RNA synthesis and immune suppression, but the molecular mechanisms of its actions are only partially understood. Here, we determined a 2.2 Å crystal structure of the C-terminal domain of JUNV NP. This structure showed high similarity to the Lassa fever virus (LASV) NP C-terminal domain. However, both the structure and function of JUNV NP showed differences compared with LASV NP. This study extends our structural insight into the negative-sense ssRNA virus NPs. PMID:23884367

Zhang, Yinjie; Li, Le; Liu, Xiang; Dong, Shishang; Wang, Wenming; Huo, Tong; Guo, Yu; Rao, Zihe; Yang, Cheng

2013-10-01

232

Crystal structures of the human adiponectin receptors.  

PubMed

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 Å 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 than the 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

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

233

Magnetism and Crystal Structure of Zirconium Compound with Laves Structure  

Microsoft Academic Search

Magnetic studies were performed on intermetallic compounds with Laves-type structure, (Zr, Nb)Fe2, (Zr, Mo)Fe2, Zr(Fe, Mn)2, Zr(Fe, V)2, and Zr(Fe, Co)2. The crystal structure of all the compounds except Zr(Fe, Co)2 changes from the MgCu2 type to MgZn2 type with decreasing ZrFe2 content. The magnetism changes from ferromagnetism to paramagnetism with change from MgCu2 type to MgZn2 type, and it

K. Kanematsu

1968-01-01

234

Structural, Spectral And Optical Characterization Of Calcium Barium Tartrate Crystals  

NASA Astrophysics Data System (ADS)

Single crystals of Calcium Barium tartrate (CBT) were grown by controlled diffusion in silica gel at ambient temperature. The structural characterization of the grown crystals was carried out by Powder X-ray diffraction analysis. The functional groups present in the crystals were identified using Fourier Transform Infrared spectral analysis. The UV-Vis-NIR transmission spectrum was recorded to study the optical transparency of the grown crystals.

Freeda, M. Mary; Priya, R. Krishna; Freeda, T. H.; Delphine, S. Mary

2011-10-01

235

Crystal structure of human uroporphyrinogen decarboxylase.  

PubMed Central

Uroporphyrinogen decarboxylase (URO-D) catalyzes the fifth step in the heme biosynthetic pathway, converting uroporphyrinogen to coproporphyrinogen by decarboxylating the four acetate side chains of the substrate. This activity is essential in all organisms, and subnormal activity of URO-D leads to the most common form of porphyria in humans, porphyria cutanea tarda (PCT). We have determined the crystal structure of recombinant human URO-D at 1.60 A resolution. The 40.8 kDa protein is comprised of a single domain containing a (beta/alpha)8-barrel with a deep active site cleft formed by loops at the C-terminal ends of the barrel strands. Many conserved residues cluster at this cleft, including the invariant side chains of Arg37, Arg41 and His339, which probably function in substrate binding, and Asp86, Tyr164 and Ser219, which may function in either binding or catalysis. URO-D is a dimer in solution (Kd = 0.1 microM), and this dimer also appears to be formed in the crystal. Assembly of the dimer juxtaposes the active site clefts of the monomers, suggesting a functionally important interaction between the catalytic centers. PMID:9564029

Whitby, F G; Phillips, J D; Kushner, J P; Hill, C P

1998-01-01

236

Crystal Structures of Respiratory Pathogen Neuraminidases  

SciTech Connect

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.

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

2009-01-01

237

Emergence of Zeolite Analogs and other Microporous Crystals in an Atomic Lattice Model of Silica and Related Materials  

E-print Network

Emergence of Zeolite Analogs and other Microporous Crystals in an Atomic Lattice Model of Silica with a rich variety of structures including known chalcogenides, zeolite analogs, and layered materials. We and Nanostructures Nanoporous materials such as zeolites have been studied extensively for over 50 years because

Auerbach, Scott M.

238

Lightweight Materials & Structures - Duration: 3:57.  

NASA Video Gallery

The Lightweight Materials and Structures (LMS) project will mature high-payoff structures and materials technologies that have direct application to NASA’s future space exploration needs.One of the...

239

The rheology of structured materials  

NASA Astrophysics Data System (ADS)

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.

Sun, Ning

2000-10-01

240

Crystal structures of saposins A and C  

PubMed Central

Saposins A and C are sphingolipid activator proteins required for the lysosomal breakdown of galactosylceramide and glucosylceramide, respectively. The saposins interact with lipids, leading to an enhanced accessibility of the lipid headgroups to their cognate hydrolases. We have determined the crystal structures of human saposins A and C to 2.0 Å and 2.4 Å, respectively, and both reveal the compact, monomeric saposin fold. We confirmed that these two proteins were monomeric in solution at pH 7.0 by analytical centrifugation. However, at pH 4.8, in the presence of the detergent C8E5, saposin A assembled into dimers, while saposin C formed trimers. Saposin B was dimeric under all conditions tested. The self-association of the saposins is likely to be relevant to how these small proteins interact with lipids, membranes, and hydrolase enzymes. PMID:16823039

Ahn, Victoria E.; Leyko, Paul; Alattia, Jean-René; Chen, Lu; Privé, Gilbert G.

2006-01-01

241

Crystal structure of betulinic acid methanol monosolvate.  

PubMed

The title compound [systematic name: 3?-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

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

2014-12-01

242

Crystal structure of betulinic acid methanol monosolvate  

PubMed Central

The title compound [systematic name: 3?-hy­droxy­lup-20(29)-en-28-oic acid methanol monosolvate], C30H48O3·CH3OH, is a solvent pseudopolymorph of a naturally occurring plant-derived lupane-type penta­cyclic triterpenoid, which was isolated from the traditional Chinese medicinal plant Syzygium jambos (L.) Alston. The dihedral angle between the planes of the carb­oxy­lic 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 hy­droxy and carb­oxy­lic acid groups and the methanol solvent mol­ecule give rise to a two-dimensional network structure lying parallel to (001). PMID:25553022

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

2014-01-01

243

Crystal structure of a snake venom cardiotoxin  

SciTech Connect

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.

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

1987-05-01

244

Formation of structured nanophases in halide crystals.  

PubMed

When halide crystals KCl and NaCl are slightly doped by PbCl(2), (in orders of 10(-4)?mol/mol) the structurally stable nanophases ("quantum dots") are formed via nucleation within the bulks of their matrices. Using lattice modeling we have found in KCl-Pb system natural nucleation pathway from single impurity-vacancy complex to Suzuki phase, not demonstrated in previous analyses; further transition to PbCl(2) is difficult due to high stability of this phase. In the case of NaCl-Pb, no stable "end point" of aggregation was observed and our calculations suggest nucleation may readily proceed to large PbCl(2) clusters when initially formed platelike cluster reaches a certain critical thickness. These results coincide with our experimental data. PMID:21495761

Kulveit, J; Demo, P; Polák, K; Sveshnikov, A M; Kožíšek, Z

2011-04-14

245

Formation of structured nanophases in halide crystals  

NASA Astrophysics Data System (ADS)

When halide crystals KCl and NaCl are slightly doped by PbCl_2, (in orders of 10^{-4} mol/mol) the structurally stable nanophases ("quantum dots") are formed via nucleation within the bulks of their matrices. Using lattice modeling we have found in KCl-Pb system natural nucleation pathway from single impurity-vacancy complex to Suzuki phase, not demonstrated in previous analyses; further transition to PbCl_2 is difficult due to high stability of this phase. In the case of NaCl-Pb, no stable "end point" of aggregation was observed and our calculations suggest nucleation may readily proceed to large PbCl_2 clusters when initially formed platelike cluster reaches a certain critical thickness. These results coincide with our experimental data.

Kulveit, J.; Demo, P.; Polák, K.; Sveshnikov, A. M.; Kožíšek, Z.

2011-04-01

246

Method and structure for passivating semiconductor material  

DOEpatents

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.

Pankove, Jacques I. (Princeton, NJ)

1981-01-01

247

Preface to some crystal structure communications  

Microsoft Academic Search

Crystals are prepared and\\/or recrystallized [solvent] in one of the chemistry departments of our university. One crystal is selected [approximate size] and used on an Enraf-Nonius CAD4 single-crystal diffractometer, employing Cu Ker (X = 1.54184 ,&) or Mo Ka (~ = 0.71073 ,~) radiation with a graphite crystal monochromator. The unit-cell dimensions are determined from the angular settings of 25

J. M. M. Smits; H. Behm; W. P. Bosman; Paul T. Beurskens

1988-01-01

248

Superionics: crystal structures and conduction processes  

NASA Astrophysics Data System (ADS)

Superionic conductors are compounds that exhibit exceptionally high values of ionic conductivity within the solid state. Indeed, their conductivities often reach values of the order of 1 OHgr-1 cm-1, which are comparable to those observed in the molten state. Following Faraday's first observation of high ionic conductivity within the solids bgr-PbF2 and Ag2S in 1836, a fundamental understanding of the nature of the superionic state has provided one of the major challenges in the field of condensed matter science. However, experimental and theoretical approaches to their study are often made difficult by the extensive dynamic structural disorder which characterizes superionic conduction and the inapplicability of many of the commonly used approximations in solid state physics. Nevertheless, a clearer picture of the nature of the superionic state at the ionic level has emerged within the past few decades. Many different techniques have contributed to these advances, but the most significant insights have been provided by neutron scattering experiments and molecular dynamics simulations. This review will summarize the state of current knowledge concerning the crystal structures and conduction processes of superionic conductors, beginning with a comparison of the behaviour of two of the most widely studied binary compounds, AgI and bgr-PbF2. Each can be considered a parent of two larger families of highly conducting compounds which are related by either chemical or structural means. These include perovskite-structured oxides and Li+ containing spinel-structured compounds, which have important commercial applications in fuel cells and lightweight batteries, respectively. In parallel with these discussions, the relative importance of factors such as bonding character and the properties of the mobile and immobile ions (charge, size, polarizability, etc) in promoting the extensive lattice disorder which characterizes superionic behaviour will be assessed and the possibilities for predicting a priori which compounds will display high ionic conductivity discussed.

Hull, Stephen

2004-07-01

249

Undergraduates Improve upon Published Crystal Structure in Class Assignment  

ERIC Educational Resources Information Center

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…

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

2014-01-01

250

Neutron-diffraction studies of magnetic structures of crystals  

Microsoft Academic Search

The contemporary state of neutron diffraction of magnetic structures is analyzed from the standpoint of the theory of symmetry of crystals. It is shown that the varied and numerous structures determined in neutron-diffraction studies can be classified and described by the theory of representations of space groups of crystals. This approach is based on expanding the spin density of the

Yurii A Izyumov

1980-01-01

251

Crystal Structure of Adenosine 5-Phosphosulfate Kinase from Penicillium chrysogenum,  

E-print Network

Crystal Structure of Adenosine 5-Phosphosulfate Kinase from Penicillium chrysogenum, Ian J. Mac crystal structure of ligand-free APS kinase from the filamentous fungus, Penicillium chrysogenum focuses on APS kinase from the filamentous fungus, Penicillium chrysogenum, an enzyme possessing several

Fisher, Andrew J.

252

Growth and crystal structure of the BeAl 6O 10 single crystals  

NASA Astrophysics Data System (ADS)

Unlike earlier published works we have established incongruent melting for the compound BeAl 6O 10 (BHA). The conditions of growing crystals from their own melt with a superstoichiometric excess of BeO, using the Czochralski method, have been determined. The nature of inclusions in grown BHA crystals is described. On the basis of X-ray crystal structure analysis and data of spectroscopic studies the symmetry and space group of BHA crystal structure have been refined, as well as uncertainties arising in their interpretation are discussed.

Alimpiev, A. I.; Merkulov, A. A.; Solntsev, V. P.; Tsvetkov, E. G.; Matrosov, V. N.; Pestryakov, E. V.

2002-04-01

253

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

254

High-speed prediction of crystal structures for organic molecules  

NASA Astrophysics Data System (ADS)

We developed a master-worker type parallel algorithm for allocating tasks of crystal structure optimizations to distributed compute nodes, in order to improve a performance of simulations for crystal structure predictions. The performance experiments were demonstrated on TUT-ADSIM supercomputer system (HITACHI HA8000-tc/HT210). The experimental results show that our parallel algorithm could achieve speed-ups of 214 and 179 times using 256 processor cores on crystal structure optimizations in predictions of crystal structures for 3-aza-bicyclo(3.3.1)nonane-2,4-dione and 2-diazo-3,5-cyclohexadiene-1-one, respectively. We expect that this parallel algorithm is always possible to reduce computational costs of any crystal structure predictions.

Obata, Shigeaki; Goto, Hitoshi

2015-02-01

255

Crystal and magnetic structure of Mn3IrSi  

Microsoft Academic Search

A new ternary Ir-Mn-Si phase with stoichiometry Mn3IrSi has been synthesized and found to crystallize in the cubic AlAu4-type structure, space group P213 with Z=4, which is an ordered form of the beta-Mn structure. The unit cell dimension was determined by x-ray powder diffraction to a=6.4973(3) Å. In addition to the crystal structure, we have determined the magnetic structure and

T. Eriksson; R. Lizárraga; S. Felton; L. Bergqvist; Y. Andersson; P. Nordblad; O. Eriksson

2004-01-01

256

Electronic Structure of Rare-Earth Sesquisulfide Crystals  

Microsoft Academic Search

Single crystals of R2S3, R = Dy, Gd, Nd, and Y, have been grown by flame fusion in an argon plasma torch and by the Bridgman technique. The purification of R2O3 starting materials, synthesis and analysis of compound powders R2S3, crystal growth, analysis to determine if single crystals are produced, and measurement of electrical resistivity and thermoelectric power coefficient from

J. R. Henderson; M. Muramoto; E. Loh; John B. Gruber

1967-01-01

257

Poly(vinyl alcohol) Rehydratable Photonic Crystal Sensor Materials.  

PubMed

We developed a new photonic crystal hydrogel material based on the biocompatible polymer poly (vinyl alcohol) (PVA), which can be reversibly dehydrated and rehydrated, without the use of additional fillers, while retaining the diffraction and swelling properties of polymerized crystalline colloidal arrays (PCCA). This chemically modified PVA hydrogel photonic crystal efficiently diffracts light from the embedded crystalline colloidal array. This diffraction optically reports on volume changes occurring in the hydrogel by shifts in the wavelength of the diffracted light. We fabricated a pH sensor, which demonstrates a 350 nm wavelength shift between pH values of 3.3 and 8.5. We have also fabricated a Pb(+2) sensor, in which pendant crown ether groups bind lead ions. Immobilization of the ions within the hydrogel increases the osmotic pressure due to the formation of a Donnan potential, swelling the hydrogel and shifting the observed diffraction in proportion to the concentration of bound ions. The sensing responses of rehydrated PVA pH and Pb(+2) sensors were similar to that before drying. This reversibility of rehydration enables storage of these hydrogel photonic crystal sensors in the dry state, which makes them much more useful for commercial applications. PMID:21666875

Muscatello, Michelle M Ward; Asher, Sanford A

2008-04-25

258

Plastic deformation treated as material flow through adjustable crystal lattice  

NASA Astrophysics Data System (ADS)

Looking at severe plastic deformation experiments, it seems that crystalline materials at yield behave as a special kind of anisotropic, highly viscous fluids flowing through an adjustable crystal lattice space. High viscosity provides a possibility to describe the flow as a quasi-static process, where inertial and other body forces can be neglected. The flow through the lattice space is restricted to preferred crystallographic planes and directions causing anisotropy. In the deformation process the lattice is strained and rotated. The proposed model is based on the rate form of the decomposition rule: the velocity gradient consists of the lattice velocity gradient and the sum of the velocity gradients corresponding to the slip rates of individual slip systems. The proposed crystal plasticity model allowing for large deformations is treated as the flow-adjusted boundary value problem. As a test example we analyze a plastic flow of an single crystal compressed in a channel die. We propose three step algorithm of finite element discretization for a numerical solution in the Arbitrary Lagrangian Eulerian (ALE) configuration.

Minakowski, P.; Hron, J.; Kratochvíl, J.; Kružík, M.; Málek, J.

2014-08-01

259

The solution structure of liquid-crystal polymers with small liquid-crystal thermoset maleimides and nadimides  

SciTech Connect

The solution structure of the deuterated liquid-crystal polyamide polymer (LCP) poly(p-phenylene-2-nitroterephthalamide), alone and mixed with small, rodlike, amide, liquid-crystal molecules (LCT) in N-methyl-2-pyrrolidinone (NMP), is studied using small-angle neutron scattering. Measurements were made as a function of LCP concentration using different LCTs mixed at 20 and 40 wt% relative to LCP. Our motivation for studying this system comes from a need to connect solution structure with film morphology in processing these materials for high-performance molecular composites. Our analysis shows that LCP in NMP forms large domain-like structures. The presence of LCT breaks up the LCP domains into smaller structures, some of which are filamentous LCP-LCT aggregates. This result suggests that the simple entropic description of the solution behavior of mixtures of long and short rods is not adequate in describing systems of this type.

Hjelm, R.P.; Douglas, E.P.; Benicewicz, B.C. [Los Alamos National Lab., NM (United States)

1995-03-01

260

Stabilization of a new ?' polymorph in P-substituted Pb 2BiVO 6: Single crystal structure of Pb 2Bi(V 0.84P 0.16)O 6 and conduction properties of related materials  

NASA Astrophysics Data System (ADS)

The single crystal structure of a new polymorph ?'-PbBi(VP)O has been investigated; on heating, direct phase transitions ????? and ??? were identified in Pb 2Bi(V 1-xP x)O 6 solid solutions for x?0.10, thus avoiding the high-temperature form decomposition noted in the ( ?-PbBiVO) mother phase at 480 °C, to a mixture of PbBiVO 5 and Pb 4BiVO 8 before recomposition at 650 °C. Under a slow cooling process, the ?-Bi(VP)O high-temperature phase transforms into a closely related ?'-PbBi(VP)O new polymorph, preserved at room temperature. The structure of ?'-PbBi(VP)O has been solved from a single crystal data in the orthorhombic system, Pbca space group, with a=5.922(1) Å, b=18.395(5) Å, c=11.864(3) Å, Z=8, and compared to a previous description of ?-PbBiVO in Pmcn, with b lattice constant halved. Complementary structural investigations of ?'-PbBi(VP)O powder sample by the Rietveld method, and TEM diffraction studies, confirmed the lattice and space group settings. The structural relationship between the ?, ? and ?' forms is completed for Pb 2Bi(V 1-xP x)O 6, and ionic conductivity versus temperature has been measured in the new phase as well as in its related solid solutions.

Labidi, Olfa; Roussel, Pascal; Huve, Marielle; Drache, Michel; Conflant, Pierre; Wignacourt, Jean Pierre

2005-07-01

261

Recovery of valuable materials from waste liquid crystal display panel  

SciTech Connect

Associated with the rapid development of the information and electronic industry, liquid crystal displays (LCDs) have been increasingly sold as displays. However, during the discarding at their end-of-life stage, significant environmental hazards, impacts on health and a loss of resources may occur, if the scraps are not managed in an appropriate way. In order to improve the efficiency of the recovery of valuable materials from waste LCDs panel in an environmentally sound manner, this study presents a combined recycling technology process on the basis of manual dismantling and chemical treatment of LCDs. Three key processes of this technology have been studied, including the separation of LCD polarizing film by thermal shock method the removal of liquid crystals between the glass substrates by the ultrasonic cleaning, and the recovery of indium metal from glass by dissolution. The results show that valuable materials (e.g. indium) and harmful substances (e.g. liquid crystals) could be efficiently recovered or separated through above-mentioned combined technology. The optimal conditions are: (1) the peak temperature of thermal shock to separate polarizing film, ranges from 230 to 240 deg. C, where pyrolysis could be avoided; (2) the ultrasonic-assisted cleaning was most efficient at a frequency of 40 KHz (P = 40 W) and the exposure of the substrate to industrial detergents for 10 min; and (3) indium separation from glass in a mix of concentrated hydrochloric acid at 38% and nitric acid at 69% (HCl:HNO{sub 3}:H{sub 2}O = 45:5:50, volume ratio). The indium separation process was conducted with an exposure time of 30 min at a constant temperature of 60 deg. C.

Li Jinhui [Department of Environmental Science and Engineering, Tsinghua University (China); Sino-Italia Environmental Energy Building, Room 804, Haidian District, Beijing 100084 (China)], E-mail: jinhui@tsinghua.edu.cn; Gao Song; Duan Huabo; Liu Lili [Department of Environmental Science and Engineering, Tsinghua University (China)

2009-07-15

262

Crystal structure and thermal behaviour of pyridinium styphnate  

PubMed Central

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.

Muthulakshmi, Selvarasu; Kalaivani, Doraisamyraja

2015-01-01

263

Observations on structural features and characteristics of biological apatite crystals. 9. Observation on dissolution of carious enamel crystals.  

PubMed

In a series of studies to investigate the basic structural features and characteristics of the biological apatite crystals using a transmission electron microscope, we examined the ultrastructure of the human enamel, dentin, and bone crystals through the cross and longitudinal sections at near atomic resolution. Subsequently, using the same approach, we have been able to directly examine the images of the lattice imperfections in the crystal lattices of the human tooth and bone crystals, and the images of the fusion of the crystals. In this research, furthermore, using transmission and scanning electron microscopes, we examined the dissolution of the enamel crystals caused by the carious enamel from the same viewpoint. The material used for the observation of the dissolution of the enamel crystals was obtained from the region which corresponds to the middle layer of the enamel at the portion near the wall of a carious cavity caused by the fissure caries on the occlusal surface of the lower first molars. Small cubes of the materials used for the observation by transmission electron electron microscope were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with the HITACHI H-800H type transmission electron microscope operated at 200 kV. Each crystal was observed at an initial magnification of 300,000 times and at a final magnification of 10,000,000 times and over. The material used for the observation by the scanning electron microscope was the fractured surface obtained from the carious enamel. The fractured carious enamel surfaces were coated with carbon and gold and observed with the HITACHI HHS-2R type scanning electron microscope operated at 25 kV. The crystals were observed at a final magnification of 50,000 times. As a result, we have confirmed that the dissolution of the enamel crystals caused by a caries occurs in the units of "hexagonal cell". We sincerely believe that the electron micrographs shown in this report are the first to show the images of the dissolution of the enamel crystals caused by a caries at near atomic resolution. PMID:8137451

Ichijo, T; Yamashita, Y; Terashima, T

1994-03-01

264

Crystal structure of 2-pentyl­oxybenzamide  

PubMed Central

In the title mol­ecule, C12H17NO2, the amide NH2 group is oriented toward the pent­yloxy substituent and an intra­molecular N—H?O hydrogen bond is formed with the pent­yloxy O atom. The benzene ring forms dihedral angles of 2.93?(2) and 5.60?(2)° with the amide group and the pent­yloxy group mean planes, respectively. In the crystal, mol­ecules are linked by pairs of N—H?O hydrogen bonds, forming inversion dimers with their mol­ecular planes parallel, but at an offset of 0.45?(1)?Å to each other. These dimers are ordered into two types of symmetry-related columns extended along the a axis, with the mean plane of one set of dimers in a column approximately parallel to (121) and the other in a column approximately parallel to (1-21). The two planes form a dihedral angle of 85.31?(2)°, and are linked via C—H?O hydrogen bonds and C—H?? inter­actions, forming a three-dimensional framework structure. PMID:25484660

Bugenhagen, Bernhard; Al Jasem, Yosef; Thiemann, Thies

2014-01-01

265

Crystal structure of lithium beryllium hydride  

NASA Astrophysics Data System (ADS)

Analysis of powder diffraction data, published by Bell and Coates, reveals that LiBeH3 and Li2BeH4 both have an fcc translation group with lattice constants 5.09 and 5.14 Å, respectively. The cubic cell of each contains eight formula units; so the total atomic concentrations, 3.03×1023 and 4.12×1023 cm-3, exceed that of diamond by factors of 1.7 and 2.3. The computed densities are 1.91 and 2.63 g/cm3. Both crystals have a modified perovskite structure involving cubes with edges half the size of the lattice constant. The (otherwise) sc lattice is broken by a chemical superstructure in LiBeH3 and by an orientational superstructure in Li2BeH4. The ``conduction''-electron density of the latter is 4.71×1023 cm3; so the equivalent-sphere-radius parameter is rs=1.51 Bohr, a value in the range typically assumed for metallic hydrogen. Infrared absorption at 1600 cm-1 (~=2300 K) was reported. Consequently, these compounds, if metallic, may manifest the high-temperature superconductivity often envisioned for metallic hydrogen.

Overhauser, A. W.

1987-01-01

266

Photonic crystals for monitoring fatigue phenomena in steel structures  

NASA Astrophysics Data System (ADS)

This paper introduces the concept and development of a strain sensing system for structural application based on the properties of photonic crystals. Photonic crystals are artificially created periodic structures, usually produced in the thinfilm form, where optical properties are tailored by a periodicity in the refractive index. The idea of using the crystal as a sensor is based on the observation that a distortion in the crystal structure produces a change in the reflected bandwidth. When a photonic crystal is designed to operate in the visible part of the spectrum, a permanent distortion of the film results in a change in its apparent color. This property makes photonic crystals suitable for permanent monitoring of structural elements, as any critical changes in the strain field can be promptly and easily detected by visual inspection. A simple and low-cost example of photonic crystals consists of opals synthesized by vertical deposition. In this contribution we introduce a target application for the fatigue monitoring of wind turbines, and then provide the reader with some basic information concerning modeling of the crystal architecture and fabrication of these structures. Next we discuss their application to strain measurement, specifying how reflection and transmission properties of the opals have to be designed to satisfy the expected strain response of the sensor. Finally, we present the preliminary results of a laboratory validation carried out on thin films applied to a rubber support.

Zonta, Daniele; Chiappini, Andrea; Chiasera, Alessandro; Ferrari, Maurizio; Pozzi, Matteo; Battisti, Lorenzo; Benedetti, Matteo

2009-03-01

267

Evolutionary Crystal Structure Prediction and Novel High-Pressure Phases  

Microsoft Academic Search

\\u000a Prediction of stable crystal structures at given pressure-temperature conditions, based only on the knowledge of the chemical\\u000a composition, is a central problem of condensed matter physics. This extremely challenging problem is often termed “crystal\\u000a structure prediction problem”, and recently developed evolutionary algorithm USPEX (Universal Structure Predictor: Evolutionary\\u000a Xtallography) made an important progress in solving it, enabling efficient and reliable prediction

Artem R. Oganov; Yanming Ma; Andriy O. Lyakhov; Mario Valle; Carlo Gatti

2010-01-01

268

Single-crystal X-ray diffraction studies on structural transformations of porous coordination polymers.  

PubMed

X-Ray single-crystal diffraction has been the most straightforward and important technique in structural determination of crystalline materials for understanding their structure-property relationships. This powerful tool can be used to directly visualize the precise and detailed structural information of porous coordination polymers or metal-organic frameworks at different states, which are unique for their flexible host frameworks compared with conventional adsorbents. With a series of selected recent examples, this review gives a brief overview of single-crystal X-ray diffraction studies and single-crystal to single-crystal transformations of porous coordination polymers under various chemical and physical stimuli such as solvent and gas sorption/desorption/exchange, chemical reaction and temperature change. PMID:24971601

Zhang, Jie-Peng; Liao, Pei-Qin; Zhou, Hao-Long; Lin, Rui-Biao; Chen, Xiao-Ming

2014-08-21

269

In vivo protein crystallization opens new routes in structural biology  

PubMed Central

Protein crystallization in cells has been observed several times in nature. However, owing to their small size these crystals have not yet been used for X-ray crystallographic analysis. We prepared nano-sized in vivo–grown crystals of Trypanosoma brucei enzymes and applied the emerging method of free-electron laser-based serial femtosecond crystallography to record interpretable diffraction data. This combined approach will open new opportunities in structural systems biology. PMID:22286384

Koopmann, Rudolf; Cupelli, Karolina; Redecke, Lars; Nass, Karol; DePonte, Daniel P; White, Thomas A; Stellato, Francesco; Rehders, Dirk; Liang, Mengning; Andreasson, Jakob; Aquila, Andrew; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J; Bostedt, Christoph; Boutet, Sébastien; Bozek, John D; Caleman, Carl; Coppola, Nicola; Davidsson, Jan; Doak, R Bruce; Ekeberg, Tomas; Epp, Sascha W; Erk, Benjamin; Fleckenstein, Holger; Foucar, Lutz; Graafsma, Heinz; Gumprecht, Lars; Hajdu, Janos; Hampton, Christina Y; Hartmann, Andreas; Hartmann, Robert; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Hunter, Mark S; Kassemeyer, Stephan; Kirian, Richard A; Lomb, Lukas; Maia, Filipe R N C; Kimmel, Nils; Martin, Andrew V; Messerschmidt, Marc; Reich, Christian; Rolles, Daniel; Rudek, Benedikt; Rudenko, Artem; Schlichting, Ilme; Schulz, Joachim; Seibert, M Marvin; Shoeman, Robert L; Sierra, Raymond G; Soltau, Heike; Stern, Stephan; Strüder, Lothar; Timneanu, Nicusor; Ullrich, Joachim; Wang, Xiaoyu; Weidenspointner, Georg; Weierstall, Uwe; Williams, Garth J; Wunderer, Cornelia B; Fromme, Petra; Spence, John C H; Stehle, Thilo; Chapman, Henry N; Betzel, Christian; Duszenko, Michael

2012-01-01

270

Oxide Thermoelectric Materials: A Structure-Property Relationship  

NASA Astrophysics Data System (ADS)

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.

Nag, Abanti; Shubha, V.

2014-04-01

271

Crystal structure and characterization of pyrroloquinoline quinone disodium trihydrate  

PubMed Central

Background Pyrroloquinoline quinone (PQQ), a tricarboxylic acid, has attracted attention as a growth factor, and its application to supplements and cosmetics is underway. The product used for these purposes is a water-soluble salt of PQQ disodium. Although in the past, PQQ disodiumpentahydrates with a high water concentration were used, currently, low hydration crystals of PQQ disodiumpentahydrates are preferred. Results We prepared a crystal of PQQ disodium trihydrate in a solution of ethanol and water, studied its structure, and analyzed its properties. In the prepared crystal, the sodium atom interacted with the oxygen atom of two carboxylic acids as well as two quinones of the PQQ disodium trihydrate. In addition, the hydration water of the prepared crystal was less than that of the conventional PQQ disodium crystal. From the results of this study, it was found that the color and the near-infrared (NIR) spectrum of the prepared crystal changed depending on the water content in the dried samples. Conclusions The water content in the dried samples was restored to that in the trihydrate crystal by placing the samples in a humid environment. In addition, the results of X-ray diffraction (XRD) and X-ray diffraction-differential calorimetry (XRD-DSC) analyses show that the phase of the trihydrate crystal changed when the crystallization water was eliminated. The dried crystal has two crystalline forms that are restored to the original trihydrate crystals in 20% relative humidity (RH). This crystalline (PQQ disodium trihydrate) is stable under normal environment. PMID:22713213

2012-01-01

272

Synthesis, characterization, and crystal structures of novel single and mixed-metal framework materials assembled from 2-(4-pyridyl)thiazole-4-carboxylic acid with cobalt, cadmium, and vanadium oxide  

NASA Astrophysics Data System (ADS)

Three new coordination polymers containing 2-(4-pyridyl)thiazole-4-carboxylate (pytac) with cobalt, vanadium oxide, or cadmium iodide have been synthesized solvothermally, isolated, and characterized by single-crystal X-ray diffraction and powder X-ray diffraction. [Co 3(pytac) 6](H 2O) 8 ( 1), which crystallizes in the space group C2/ c ( a = 24.1418(8) Å, b = 17.5088(6) Å, and c = 14.4562(5) Å, ? = 96.0390(10)°), has 1D hexameric water channels that constitute a 14.4% of the unit cell volume. Co 3(pytac) 2(H 2O) 4V 4O 12 ( 2), which crystallizes in the space group P1¯ ( a = 8.6591(5) Å, b = 9.0044(5) Å, and c = 10.6495(6) Å, ? = 67.1160(10)°, ? = 82.6880(10)°, and ? = 83.9880(10)°), is an extension of the former in that it contains Co(H 2O) 4V 4O 12 in addition to the Co-only 2D layers. [CdI(pytac)(H 2O)]·H 2O ( 3), which also crystallizes in the space group P1¯ ( a = 8.2376(4) Å, b = 8.4859(4) Å, and c = 11.1261(5) Å, ? = 68.2020(10)°, ? = 77.5610(10)°, and ? = 69.1230(10)°), exhibits structural characteristics similar to 2, in that both contain 1D chains where the pytac ligand simultaneously engages in three different coordination modes: chelating, single bond coordination, and ?-2 bridging between two metal centers via carboxylate oxygen atoms.

Ellsworth, Joseph M.; Khaliq, Zeeshan M.; Smith, Mark D.; zur Loye, Hans-Conrad

2008-07-01

273

Novel photonic crystal cavities and related structures.  

SciTech Connect

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.

Luk, Ting Shan

2007-11-01

274

Crystal structure of ?-d,l-allose  

PubMed Central

The title compound, C6H12O6, a C-3 position epimer of glucose, was crystallized from an equimolar mixture of d- and l-allose. It was confirmed that d-allose (l-allose) formed ?-pyran­ose with a 4 C 1 (1 C 4) conformation in the crystal. In the crystal, molecules are linked by O—H?O hydrogen bond, forming a three-dimensional framework. The cell volume of the racemic ?-d,l-allose is 739.36?(3)?Å3, which is about 10?Å3 smaller than that of chiral ?-d-allose [V = 751.0?(2)?Å3].

Ishii, Tomohiko; Senoo, Tatsuya; Kozakai, Taro; Fukada, Kazuhiro; Sakane, Genta

2015-01-01

275

Band structure analysis of crystals with discontinuous metallic wires  

Microsoft Academic Search

The band structure for normal propagation of crystals with finite straight metallic wires is studied for different wire diameters and lengths. The crystal is considered as a set of parallel grids. Dispersion characteristics are obtained by using a transmission line model where the parameters are calculated from the reflection and transmission coefficients of the grids. These coefficients are computed rigorously

Halim Boutayeb; Tayeb A. Denidni; Abdel Razik Sebak; Larbi Talbi

2005-01-01

276

Isomorph invariance of the structure and dynamics of classical crystals  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

277

Biomineralized structural materials with functional optical properties  

E-print Network

Many biological structural materials exhibit "mechanical property amplification" through their intricate hierarchical composite designs. In the past several decades, significant progress has been achieved in elucidating ...

Li, Ling, Ph. D. Massachusetts Institute of Technology

2014-01-01

278

Structural materials for cryogenic applications  

Microsoft Academic Search

Characterization, mechanical and fracture mechanics property and magnetic property determinations, and metallurgical and fractographic evaluations on the FY76 materials, namely Pyromet 538 (21 Cr-6 Ni-9 Mn) and A286 stainless steels were completed. Fracture toughness values at 4K for GTA Weldments in Pyromet 538 with matching composition filler material were only about 50% of that of the unwelded material, whereas fracture

J. M. Wells; R. Kossowsky; W. A. Logsdon; R. Daniel

1976-01-01

279

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

280

Stability Enhanced Flexible Liquid Crystal Display Based on a MicroStructure  

Microsoft Academic Search

We demonstrate the stability-enhanced novel flexible liquid crystal display (LCD) mode by using the micro-structure of rigid columnar spacer array and a micro-contact printing (µCP) assembling method. Specially designed multi-column structure induces self-collected structure of adhesion material which resulted in the good adhesion properties of device to an external deformation as well as enhanced mechanical stability of electro-optic characteristics for

Se-Jin Jang; Jun-Hyung Kim; Ji-Hong Bae; Yoonseuk Choi; Hak-Rin Kim; Sang Il Kim; JunHyung Souk; Jae-Hoon Kim

2007-01-01

281

The crystal structure of kesterite type compounds: A neutron and X-ray diffraction study  

Microsoft Academic Search

The atomic structure of the potential photovoltaic materials Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) is discussed on the basis of a structural analysis of neutron powder diffraction data refined by the Rietveld analysis. Both compounds were found to crystallize in the kesterite type structure, but with a disorder within the Cu–Zn layers at z=1\\/4 and 3\\/4. The latter causes CuZn and

Susan Schorr

2011-01-01

282

Angle and Thickness-Dependent Photonic Band Structure in a Superconducting Photonic Crystal  

Microsoft Academic Search

The angle- and thickness-dependent photonic band structures in a one-dimensional superconducting photonic crystal are theoretically\\u000a investigated based on the transfer matrix method. The band structure is studied near and below the threshold frequency at\\u000a which the superconducting material has a zero permittivity. The gap structure is analyzed as a function of the thicknesses\\u000a of the two constituent superconducting and dielectric

Chien-Jang Wu; Zheng-Hui Wang; Tzong-Jer Yang

2010-01-01

283

Hydroflux synthesis and crystal structure of new lanthanide tungstate oxyhydroxides  

NASA Astrophysics Data System (ADS)

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 ? angle range is 101.999(2)°-102.025(2)°.

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

2015-04-01

284

The Crystal Structures of the Tryparedoxin-Tryparedoxin Peroxidase Couple Unveil the Structural Determinants of  

E-print Network

The Crystal Structures of the Tryparedoxin-Tryparedoxin Peroxidase Couple Unveil the Structural of electrons by the tryparedoxin/tryparedoxin peroxidase system (TXN/TXNPx) to reduce the hydroperoxides A (2012) The Crystal Structures of the Tryparedoxin-Tryparedoxin Peroxidase Couple Unveil the Structural

Paris-Sud XI, Université de

285

The influence of material parameters on the frozen modes of magnetic photonic crystals  

Microsoft Academic Search

Multilayered structures known as photonic crystals are object of many researches lately. Some special Photonic Crystals, containing magnetic layers and misaligned anisotropic dielectric layers, show an asymmetric dispersion relation. These structures are referred as magnetic photonic crystals (MPC). The asymmetric dispersion relation can be associated with the electromagnetic unidirectionality. A unidirectional medium \\

Gianni Portela; Victor Dmitriev; Licinius Alcantara

2007-01-01

286

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

DOEpatents

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.

Todt, Volker (Lemont, IL); Miller, Dean J. (Darien, IL); Shi, Donglu (Oak Park, OH); Sengupta, Suvankar (Columbus, OH)

1998-01-01

287

EPR diagnostics of laser materials based on ZnSe crystals doped with transition elements  

NASA Astrophysics Data System (ADS)

The electron paramagnetic resonance (EPR) spectra observed in laser materials based on zinc selenide (ZnSe) crystals doped with transition elements have been analyzed and identified. It has been shown that, in addition to working impurities (Cr2+, Co2+, or Fe2+), the diffusion layer exhibits EPR spectra of accompanying impurities due to the diffusion of transition elements (chromium, cobalt, or iron) used in the preparation of active materials for quantum electronics (lasers, switches) operating in the mid-infrared range. EPR diagnostics of these impurities can be used in the development of appropriate regimes for minimizing concentrations of accompanying impurities that adversely affect the performance characteristics of laser materials. It has been found that, during the diffusion of transition metals, ions of the accompanying impurity Mn2+, which is characterized by extremely informative EPR spectra, are embedded in the crystal lattice. It has been proposed to use these ions as ideal markers to control, on the electronic level, the crystal structure of the active diffusion layer.

Kramushchenko, D. D.; Ilyin, I. V.; Soltamov, V. A.; Baranov, P. G.; Kalinushkin, V. P.; Studenikin, M. I.; Danilov, V. P.; Il'ichev, N. N.; Shapkin, P. V.

2013-02-01

288

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

NASA Astrophysics Data System (ADS)

Acquiring large nonlinear optical (NLO) efficient organic material is essential for the development of optoelectronics and photonic devices. Chalcone is the donor - ? - acceptor - ? - donor (D-?-A-?-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.

Karthi, S.; Girija, E. K.

2014-04-01

289

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

SciTech Connect

Acquiring large nonlinear optical (NLO) efficient organic material is essential for the development of optoelectronics and photonic devices. Chalcone is the donor - ? - acceptor - ? - donor (D-?-A-?-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.

Karthi, S., E-mail: girijaeaswaradas@gmail.com; Girija, E. K., E-mail: girijaeaswaradas@gmail.com [Department of Physics, Periyar University, Salem - 636011 (India)

2014-04-24

290

Metal insulator semiconductor structure single crystal silicon liquid crystal light valve  

NASA Astrophysics Data System (ADS)

Detailed description of the structure, operation, fabrication, and performance of a fast-response metal- insulator-semiconductor structure single crystal silicon liquid crystal light valve (MIS-Si-LCLV) is given. A 45 degree(s) twisted nematic liquid crystal configuration has been utilized. A MIS-Si-LCLV is demonstrated with a limiting resolution of 40 lp/mm over a 45 mm aperture and contrast ratios of > 50:1, input light sensitivities at (lambda) equals 930 nm ((Delta) (lambda) equals 40 nm) of better than 30 (mu) W/cm2 and response times as fast as 20 ms have been measured.

Gao, JiaoBo; Ye, Ke-fei; Feng, Yue-you

1996-09-01

291

Structural material irradiations in FFTF  

SciTech Connect

Information is presented concerning the Materials Open Test Assembly (MOTA); instrumentation and control system; MOTA neutronic data; pressurized tube specimens; stress-rupture measurements for reactor materials; miniature specimen design; the Interim Examination and Maintenance (IEM) cell at the FFTF; support services; and general information concerning the FFTF.

Not Available

1985-01-01

292

The Effect of High Pressure on Crystal Structure Topology   

E-print Network

This thesis describes the effects of the application of high pressure to single crystals of small organic compounds. A range of different structural analysis techniques have been used with the emphasis on whole molecule interactions rather than atom...

Wood, Peter Andrew

2008-01-01

293

Photonic-band-gap structures and guide modes in two-dimensional magnetic photonic crystal heterostructures  

Microsoft Academic Search

We first investigate the band gap structures of two-dimensional magnetic photonic crystals (MPC) composed of rectangular (square) magnetic cylinders embedded in a host dielectric material in the rectangular (square) lattice, and we then study guide modes at interface of MPC heterostructures (MPCHs) by use of plane wave expansion method in combination with supercell technique. We find that both the mirror-symmetric

Yun-Song Zhou; Ben-Yuan Gu; Fu-He Wang

2003-01-01

294

Magnetic films with laminar domain structure as tunable 1D photonic crystal  

Microsoft Academic Search

Summary form only given. Photonic band gap (PBG) materials, or photonic crystals, which can be presented as one-, two-, or three dimensional superstructures, are the object of intensive theoretical and experimental research, because it are very promising for applications in opto-electronics In our contribution we investigate PBG effects in magnetic film with stripe domain structure of 180° magnetic domains. Because

I. L. Lyubchanskii; N. N. Dadoenkova; M. I. Lyubchanskii; E. A. Shapovalov; A. Lakhtakia; T. Rasing

2002-01-01

295

The crystal structure of faustite and its copper analogue turquoise  

Microsoft Academic Search

The crystal structure of faustite, ZnAI6(P04MOHhAH20, was determined using single-crystal data (Mo-KIX X-radiation, CCD area detector, 1624 unique reflections, RI = 4.91 %, wR2 = 9.23%), and compared with results of a reinvestigation of the structure of its copper analogue turquoise, CuAI6(P04MOH)gAH20 (2737 unique reflections, RI = 2.81%, wR2 = 6.90%). Both are isostructural and crystallize in space group PI,

U. Kolitsch; G. Giester

2000-01-01

296

Crystal structure of a actinide metals at high compression  

SciTech Connect

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.}

Fast, L. [Condensed Matter Theory Group, Physics Department, Uppsala University, Box 530 (Sweden); Soederlind, P. [Physics Department, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

1996-05-01

297

Tamm states at the interface between a conventional material and a one dimensional photonic crystal with metamaterials  

NASA Astrophysics Data System (ADS)

Using the Green's function formalism, Tamm states of localized modes are investigated at the interface separating auniform conventional material and a one-dimensional semi-infinite photonic crystal consisting of a series of alternating conventional materials and metamaterials. We investigate how the presence of such metamaterials influences the band structure of collective modes that appear in the photonic crystal, with special attention to the power spectrum of collective excitations and the dispersion relations. It is shown that there is one localized backward TE mode with frequencies below the resonance frequency of the metamaterial magnetic permeability and above such frequency there are one forward TM, and two backward TM and TE localized modes.

Becerra O, G.; Granada E, J. C.

2014-12-01

298

Sticking effect of liquid crystal on photosensitive aligning materials  

NASA Astrophysics Data System (ADS)

The sticking effect on photoaligning surfaces was investigated. We demonstrated that additional irradiation of photoaligning polymers with cinnamoil side groups with not-polarized UV-light strongly decreases their sticking parameter. We associate this effect with cross-linking of the flexible side-groups by UV light and, as a consequence, with light-induced strengthening of the photoaligning surface. Restriction of mobility of the flexible groups on the photoaligning surface (surface strengthening) resulted in depressing the sticking effect. The method of the decrease of the sticking effect by the light-induced strengthening is rather general, and it can be applied for any photoaligning materials undergoing a light-induced cross-linking of polymer fragments. For fluoro polyvinyl-cinnamate the light-induced strengthening allowed us to get the record value of the sticking parameter, S0 = 0.2%, which is better than traditional rubbed polyimide surfaces provide. Such a value of the sticking parameter along with other aligning characteristics allows considering fluoro polyvinyl-cinnamate as very prospective material for modern liquid crystal display technologies.

Gerus, I.; Glushchenko, Anatoliy V.; Kurioz, Yu.; Reznikov, Yu.; Tereshchenko, Olexander

2004-09-01

299

The Crystal and Molecular Structure of Dianhydrogossypol  

Microsoft Academic Search

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 spectroscopy was used to confirm that complete conversion was achieved over a time period of several hours.\\u000a Single crystals of the compound were obtained by slow evaporation from dichloromethane. Diffraction studies indicate that\\u000a this crystal form is tetragonal with a I41\\/a space group and with cell dimensions of a = b = 33.8265(4) Å,

Samat A. Talipov; Azimjon A. Mamadrakhimov; Zavkibek G. Tiljakov; Michael K. Dowd; Bakhtiyar T. Ibragimov; Muhabbat T. Xonkeldieva

2009-01-01

300

Crystal Structure of DL-Alanine Sulfate  

Microsoft Academic Search

Crystals of [(C3NO2H7)2·H2SO4] composition were analyzed by single-crystal X-ray diffraction (triclinic, P\\u000a$${\\\\bar 1}$$\\u000a, a = 7.431(3), b = 9.826(3), c = 10.081(3) Å, a = 120.07(5), ß = 104.73(5), ? = 94.24(5)°). The independent part of the unit cell contains two alanine molecules and one sulfate ion. The amino group is additionally protonated in both molecules. One of

Yu. I. Smolin; A. E. Lapshin; G. A. Pankova; Yu. N. Osipova

2004-01-01

301

Crystal structure of Bacillus anthracis transpeptidase enzyme CapD.  

SciTech Connect

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.

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

2009-09-04

302

Crystal and magnetic structures of hexagonal YMnO3.  

PubMed

The available data on the structural and magnetic transitions in multiferroic hexagonal YMnO3 have been reviewed, first making use of the computer programs from the group theoretical ISOTROPY software suite to list possible crystal and magnetic structures, then taking into account the capability of neutron diffraction and other physical methods to distinguish them. This leads to a clear view of the transformation sequence, as follows. Hexagonal YMnO3 is paraelectric in P63/mmc at elevated temperatures, and undergoes a single structural transition on cooling through 1250?K to a ferrielectric phase in P63cm that is retained through room temperature. At a much lower temperature, 70?K, there is a magnetic transition from paramagnetic to a triangular antiferromagnetic arrangement, most likely with symmetry P63'cm'. Comment is made on the unusual coupling of ferroelectric and magnetic domains reported to occur in this material, as well as on the so-called `giant magneto-elastic' effect. PMID:24253077

Howard, Christopher J; Campbell, Branton J; Stokes, Harold T; Carpenter, Michael A; Thomson, Richard I

2013-12-01

303

Structures and materials technology for hypersonic aerospacecraft  

NASA Technical Reports Server (NTRS)

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.

Mccomb, Harvey G., Jr.; Murrow, Harold N.; Card, Michael F.

1990-01-01

304

Doped iron garnet materials for magnetic photonic crystals  

Microsoft Academic Search

We have established a set of technologies for the deposition and annealing of magneto-optic garnets for use in photonic crystals. Devices for sensing magnetic fields and polarisation control using reconfigurable photonic crystals are being developed.

Mikhail Vasiliev; Kamal Alameh; Viatcheslav Kotov

2008-01-01

305

Cutting-edge techniques used for the structural investigation of single crystals.  

PubMed

X-ray crystallography has become the leading technique for studying the structure of matter at the atomic and molecular level. Today it underpins all sciences and is widely applied in industry. It is essential in the development of new materials. The technique is very powerful, and the range of materials that can be studied expands as new technologies evolve and are applied in innovative ways to structure solution. It is now possible to record vast amounts of diffraction data in seconds electronically, whereas it took days and months by photographic methods 30 to 40 years ago. Single crystals can be created in various ways; they can be produced from compounds that are liquids or gases at room temperature, and complete molecular structures can be presented within minutes. This short review presents recent developments that are appropriate to the single-crystal x-ray studies of chemical and materials sciences. PMID:24604193

Howard, Judith A K; Probert, Michael R

2014-03-01

306

In situ studies of a platform for metastable inorganic crystal growth and materials discovery.  

PubMed

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

Shoemaker, Daniel P; Hu, Yung-Jin; Chung, Duck Young; Halder, Gregory J; Chupas, Peter J; Soderholm, L; Mitchell, J F; Kanatzidis, Mercouri G

2014-07-29

307

In situ studies of a platform for metastable inorganic crystal growth and materials discovery  

PubMed Central

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

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

308

Ethylenediaminium di(2-nitrophenolate) single crystals as materials for optical second harmonic generation  

NASA Astrophysics Data System (ADS)

An organic second harmonic generation (SHG) active material, ethylenediaminium di(2-nitrophenolate) (EDA2NP) was synthesized through proton transfer reaction. Good quality single crystals of dimension 6×4×2 mm3 were grown by solvent evaporation method using ethanol as a solvent for the first time in literature. The lattice parameters of the grown crystals were determined by X-ray diffraction studies. Fourier Transform Infra Red (FT-IR) spectrum was recorded to identify the presence of various functional groups and the molecular structure was confirmed by nuclear magnetic resonance (NMR) spectrum. Thermal analyses of the grown crystal were carried out using thermo gravimetric-differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC) curves. Optical (UV-vis-NIR) analysis shows that the grown crystals were found to be transparent (450-2500 nm) in the entire visible region. The existence of second harmonic generation signals was observed by using Nd:YAG laser with fundamental wavelength of 1064 nm.

Thangaraj, M.; Ravi, G.; Sabari Girisun, T. C.

2014-09-01

309

Effect of crystal structure on magnetic-field-induced strain in Ni-Mn-Ga  

Microsoft Academic Search

Magnetic shape memory materials are expected to have a high potential in practical applications. Several ferromagnetic materials exhibiting the large magnetic-field-induced strain have been found in recent years. The largest field-induced strain is observed in Ni-Mn-Ga system. The most important experimental results on crystal structure, magnetic anisotropy and twinning stress of martensitic phases in Ni-Mn-Ga having tetragonal five-layered, orthorhombic seven-layered

Alexei Sozinov; Alexander A. Likhachev; Nataliya Lanska; Outi Söderberg; Kari Ullakko; Veikko K. Lindroos

2003-01-01

310

Fe II Spin crossover materials based on dissymmetrical N 4 Schiff bases including 2-pyridyl and 2R-imidazol-4-yl rings: Synthesis, crystal structure and magnetic and Mössbauer properties  

Microsoft Academic Search

The synthesis and characterization of new symmetrical FeII complexes, [FeLA(NCS)2] (1), and [FeLBx(NCS)2] (2–4), are reported (LA is the tetradentate Schiff base N,N?-bis(1-pyridin-2-ylethylidene)-2,2-dimethylpropane-1,3-diamine, and LBx stands for the family of tetradentate Schiff bases N,N?-bis[(2-R-1H-imidazol-4-yl)methylene]-2,2-dimethylpropane-1,3-diamine, with: R=H for LB1 in 2, R=Me for LB2 in 3, and R=Ph for LB3 in 4). Single-crystal X-ray structures have been determined for 1 (low-spin

Nicolas Bréfuel; Isabelle Vang; Sergiu Shova; Françoise Dahan; Jean-Pierre Costes; Jean-Pierre Tuchagues

2007-01-01

311

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...

312

Recent global trends in structural materials research  

NASA Astrophysics Data System (ADS)

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.

Murakami, Hideyuki; Ohmura, Takahito; Nishimura, Toshiyuki

2013-02-01

313

The local structure and crystallization of FeB nanoparticle  

NASA Astrophysics Data System (ADS)

Using molecular dynamics simulation, we have studied the structural evolution of FeB nanoparticle under annealing and the physical properties of its polymorphs such as crystalline, amorphous and mixed samples. The main focus of present work is the crystallization mechanism and the local structure of polymorphs of FeB nanoparticle. The simulation result shows that the amorphous sample undergoes the crystallization via the nucleation mechanism. During the crystallization, B atoms move out the places where the Fe crystal locates, and diffuse to the boundary region of Fe crystal. The crystal growth proceeds when this boundary region attains specific properties which are defined by the fraction of B atoms and the energies of AB-atoms and CB-atoms. Further our study indicates that unlike amorphous sample, the crystalline and mixed samples consist of three distinct parts including Fe crystalline and two FeB amorphous parts (B-poor and B-rich amorphous part). The different polymorphs of FeB nanoparticle differ in the local structure, size of Fe crystal and energies of different type atoms.

Kien, P. H.; Thao, N. T.; Hung, P. K.

2014-12-01

314

Ultrafast characterization of phase-change material crystallization properties in the melt-quenched amorphous phase.  

PubMed

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

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

315

Mechanics of Materials and Structures  

E-print Network

conditions. Investigations on piezoelectric materials in the presence of defects such as dislocations, cracks that these defects can adversely influence the performance of the piezoelectric devices. Recently He and Lim [2003 is confined to the quasistatic assumption, ignoring the inertial force in the piezoelectric inclusion

Pan, Ernie

316

Materials and structures/ACEE  

NASA Technical Reports Server (NTRS)

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.

1981-01-01

317

Biomimetic photonic materials with tunable structural colors.  

PubMed

Nature is a huge gallery of art involving nearly perfect structures and forms over the millions of years developing. Inspiration from natural structures exhibiting structural colors is first discussed. We give some examples of natural one-, two-, and three-dimensional photonic structures. This review article presents a brief summary of recent progress on bio-inspired photonic materials with variable structural colors, including the different facile and efficient routes to construct the nano-architectures, and the development of the artificial variable structural color photonic materials. Besides the superior optical properties, the excellent functions such as robust mechanical strength, good wettability are also mentioned, as well as the technical importance in various applications. This review will provide significant insight into the fabrication, design and application of the structural color materials. PMID:23816221

Xu, Jun; Guo, Zhiguang

2013-09-15

318

LTA structures and materials technology. [airships  

NASA Technical Reports Server (NTRS)

The state-of-the-art concerning structures and materials technology is reviewed. It is shown that many present materials developments resulting from balloon and aircraft research programs can be applied to new concepts in LTA vehicles. Both buoyant and semi-buoyant vehicles will utilize similar approaches to solving structural problems and could involve pressurized non-rigid and unpressurized rigid structures. System designs common to both and vital to structural integrity will include much of the past technology as well. Further research is needed in determination of structural loads, especially in future design concepts.

Mayer, N. J.

1975-01-01

319

Crystal structure and vibrational spectra of piperazinium bis(4-hydroxybenzenesulphonate) molecular-ionic crystal  

NASA Astrophysics Data System (ADS)

The piperazinium bis(4-hydroxybenzenesulphonate) crystallizes from water solution at room temperature in P2 1/ c space group of monoclinic system. The crystals are built up of doubly protonated piperazinium cations and ionized 4-hydroxybenzenesulphonate anions that interact through weak hydrogen bonds of O-H⋯O and N-H⋯O type. Mutual orientation of anions is determined by non-conventional hydrogen bonds of C-H⋯? type. Room temperature powder FT IR and FT Raman measurements were carried out. The vibrational spectra are in full agreement with the structure obtained from X-ray crystallography. The big single crystals of the title salt can be grown.

Marchewka, M. K.; Pietraszko, A.

2008-02-01

320

Single-crystal growth, crystal and electronic structure of NaCoO 2  

Microsoft Academic Search

Single crystals of NaCoO2 have been successfully synthesized for the first time by a flux method at 1323K. A single-crystal X-ray diffraction study confirmed the trigonal R3?m space group and the lattice parameters a=2.8897(15)A?, c=15.609(3)A?. The crystal structure has been refined to the conventional values R=1.9% and wR=2.1% for 309 independent observed reflections. The electron density distribution of NaCoO2 has

Yasuhiko Takahashi; Yoshito Gotoh; Junji Akimoto

2003-01-01

321

Crystal Structure and Interaction Dependence of the Crystal-Melt Interfacial Free Energy  

Microsoft Academic Search

We examine via molecular simulation the dependence of the crystal-melt interfacial free energy gamma on molecular interaction and crystal structure (fcc vs bcc) for systems interacting with inverse-power repulsive potentials, u(r)=?(sigma\\/r)n, 6<=n<=100. Both the magnitude and anisotropy of gamma are found to increase as the range of the potential increases. Also we find that gammabcc

Ruslan L. Davidchack; Brian B. Laird

2005-01-01

322

Electro-Optical and Morphological Characterization of Electron Beam Cured Liquid Crystal-Polymer Composite Materials  

Microsoft Academic Search

Polymer dispersed liquid crystals (PDLCs) are promising new materials for electro-optic applications such as switchable windows and flexible displays. Thin films were prepared via a polymerization induced phase separation process using electron beam radiation. The PDLC material was obtained from a blend of a eutectic nematic liquid crystal mixture E7 and a polyester acrylate based polymer as a precursor of

U. Maschke; J.-M. Gloaguen; J.-D. Turgis; X. Coqueret

1996-01-01

323

Datamining protein structure databanks for crystallization patterns of proteins.  

PubMed

A study of 345 protein structures selected among 1,500 structures determined by nuclear magnetic resonance (NMR) methods, revealed useful correlations between crystallization properties and several parameters for the studied proteins. NMR methods of structure determination do not require the growth of protein crystals, and hence allow comparison of properties of proteins that have or have not been the subject of crystallographic approaches. One- and two-dimensional statistical analyses of the data confirmed a hypothesized relation between the size of the molecule and its crystallization potential. Furthermore, two-dimensional Bayesian analysis revealed a significant relationship between relative ratio of different secondary structures and the likelihood of success for crystallization trials. The most immediate result is an apparent correlation of crystallization potential with protein size. Further analysis of the data revealed a relationship between the unstructured fraction of proteins and the success of its crystallization. Utilization of Bayesian analysis on the latter correlation resulted in a prediction performance of about 64%, whereas a two-dimensional Bayesian analysis succeeded with a performance of about 75%. PMID:12594078

Valafar, Homayoun; Prestegard, James H; Valafar, Faramarz

2002-12-01

324

[Material and structure of drainages].  

PubMed

The long history of surgical drainages stands in contradiction to available and reliable data. As of today, closed systems made of silicone are preferable. Taking possible complications into consideration and the good results of routine operations without drainages, indication for use should be critically evaluated. Interdisciplinary research,however, offers the chance of optimizing material and surface characteristics, biostability, biocompatibility, and flow rates. New drainages with improved performance and reduced side effects may counteract the current tendency to do without. PMID:12599024

Treutner, K-H; Bertram, P; Müller, S A; Schumpelick, V

2003-02-01

325

Energy absorption of composite material and structure  

NASA Technical Reports Server (NTRS)

Results are presented from a joint research program on helicopter crashworthiness conducted by the U.S. Army Aerostructures Directorate and NASA Langley. Through the ongoing research program an in-depth understanding has been developed on the cause/effect relationships between material and architectural variables and the energy-absorption capability of composite material and structure. Composite materials were found to be efficient energy absorbers. Graphite/epoxy subfloor structures were more efficient energy absorbers than comparable structures fabricated from Kevlar or aluminum. An accurate method of predicting the energy-absorption capability of beams was developed.

Farley, Gary L.

1987-01-01

326

Czochralski growth of NiAl single crystals:. effect of crucible support/insulation material  

NASA Astrophysics Data System (ADS)

Single crystals of NiAl were grown by Czochralski pulling. The crystals were grown in the [1 0 0] direction up to 3 cm in diameter from alumina crucibles of 99.8% purity in a vacuum induction furnace under argon purging. EPMA analysis of the crystals indicated uniformity in composition. It was observed during crystal growth that an ashy material grew inward from the crucible wall to reduce the space available for crystal growth. It was found that the amount of the ashy material is affected significantly by the material supporting and/or insulating the crucible, and that it decreases in the order of graphite, zirconia and alumina. The ashy material was identified as mainly Al 4O 4C in the case of graphite, and Al 2O 3 in the cases of zirconia and alumina. The formation of the ashy material was explained.

Fan, X.; Kou, S.

1999-07-01

327

Nano-Dispersed Liquid Crystalline Structures for Tunable Negative, Zero, and Positive Index Materials in the Optical-Terahertz Regimes  

Microsoft Academic Search

We describe here three approaches to realize tunable or reconfigurable negative-zero-positive index materials: (1) planar nano-structured frequency selective surfaces [FSS] with aligned nematic liquid crystal; (2) core-shell nano-size spheres randomly distributed in a bulk nematic liquid crystal matrix; (3) magneto-optics active cholesteric liquid crystal as 1-D photonic crystal. Such metamaterials can be designed for applications in the optical, terahertz and

I. C. Khoo; A. Diaz; J. Bossard; X. Liang; D. Werner

2006-01-01

328

Predicting crystal structure by merging data mining with quantum mechanics  

E-print Network

ARTICLES Predicting crystal structure by merging data mining with quantum mechanics CHRISTOPHER C@mit.edu Published online: 9 July 2006; doi:10.1038/nmat1691 Modern methods of quantum mechanics have proved with quantum mechanics if an algorithm to direct the search through the large space of possible structures

Ceder, Gerbrand

329

Structures of Four Crystal Forms of Decaplanin by Christopher Lehmanna  

E-print Network

birthday The glycopeptide antibiotic decaplanin (1; formerly known as MM 47761 and M86-1410) crystallizes facilitated the MAD structure solution. The structures contain the dimer units typical of antibiotics related threat presented by pathogens that have developed multiple resistance to antibiotics [1], in particular

330

Hexagonal structures for two-dimensional photonic crystals  

Microsoft Academic Search

Periodic dielectric structures have been recently proposed to inhibit spontaneous emission in semiconductors. From this suggestion, the new concepts of photonic band gap and photonic crystal have been developed. Zero-threshold lasers, waveguides, antenna substrates, filters and polarizers are promising applications. We propose a new class of two-dimensional periodic dielectric structures with hexagonal symmetry. We study the gap opening according to

D. Cassagne; C. Jouanin; D. Bertho

1996-01-01

331

Optimization of liquid crystal structures for real time holography applications.  

PubMed

In this paper we present results of experiments designed to increase our understanding of the photorefractive effect occurring during processes of dynamic hologram generation in Hybrid Photorefractive Liquid Crystal Structures (HPLCS). We also propose equivalent mathematical model which can be used to optimize those structures in order to obtain the highest diffraction efficiency in possibly shortest time. PMID:22109472

Sahraoui, B; Anczykowska, A; Bartkiewicz, S; Mysliwiec, J

2011-11-21

332

Boron-oxygen polyanion in the crystal structure of tunellite  

USGS Publications Warehouse

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.

Clark, J.R.

1963-01-01

333

Crystal Structure of L-Histidinium 2-Nitrobenzoate  

PubMed Central

A new nonlinear optical organic compound, namely, L-histidinium 2-nitrobenzoate (abbreviated as LH2NB (I); ([C6H10N3O2]+ [C7H4NO4]?)), was synthesized. The molecular structure of LH2NB (I) was elucidated using single crystal X-ray diffraction technique. The second harmonic generation (SHG) efficiency of this compound is about two times that of the standard potassium dihydrogen phosphate crystals. PMID:22536482

Natarajan, Subramanian; Moovendaran, Kalimuthu; Kalyana Sundar, Jeyaperumal; Ravikumar, Krishnan

2012-01-01

334

Crystal Structures of Two Putative Phosphoheptose  

SciTech Connect

Structural genomic centers use both NMR spectroscopic and X-ray crystallographic methods to determine three-dimensional structures of proteins on a genomic scale in a high-throughput mode and to deposit in the PDB. The main goal of structural genomics is to determine a large number of protein structures to complement the ever-expanding database of genome sequences. Another role of structural genomics is to delineate the correspondence between sequence and structure space; a number of protein structures from otherwise unrelated (i.e., 8-10% sequence identity) families often prove to have remarkably similar folds. This finding, in turn, allows better understanding of the structure-function relationships in those proteins for which either structures are not available or cannot be experimentally determined.

Seetharaman,J.; Rajashankar, K.; Solarzano, V.; Kniewel, R.; Lima, C.; Bonanno, J.; Burley, S.; Swaminathan, S.

2006-01-01

335

New crystal structural families of lanthanide chloride alcohol/water complexes  

SciTech Connect

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.

Chakoumakos, Bryan C [ORNL; Custelcean, Radu [ORNL; Ramey, Joanne Oxendine [ORNL; Boatner, Lynn A [ORNL

2012-01-01

336

Revolutionary opportunities for materials and structures study  

NASA Technical Reports Server (NTRS)

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.

Schweiger, F. A.

1987-01-01

337

BRIEF COMMUNICATION: Active materials and adaptive structures  

NASA Astrophysics Data System (ADS)

This paper gives a brief discussion of the ONR program on active materials and adaptive structures, and addresses its objectives and issues as they relate to naval applications. The main focus is on the mechanics tools necessary for the design of this new class of structures. A review of the research in the mechanics of high-strain active materials and engineering active materials, hybrid active materials, constitutive modeling, failure of ferroelectric ceramics, and active material interaction with host material is given. The majority of the effort is devoted to understanding failure mechanisms in active materials, which were recognized early in the program to be of great importance to reliable design of high-performance actuators and their acceptance by the design community. Some new concepts of engineering active materials, and developments of hybrid active materials, are introduced as a means to achieve high-performance actuation. The paper also covers various design approaches for high-strain - high-frequency actuators in addition to some new actuator concepts. The reliability issue of the host materials and the mechanics of embedding of actuators in composite structures are addressed.

Barsoum, Roshdy George S.

1997-02-01

338

Crystal engineering with thioureas: A structure-based inquiry  

NASA Astrophysics Data System (ADS)

Structural trends applicable to crystal engineering were studied in three classes of thiourea-based compounds. The aim of the study was to identify, predict, and ultimately design reliable single-molecule structural features, which could then be used to engineer crystals with desirable properties. In one class of compounds, this goal was achieved: N-alkyl and N-aryl derivatives of N,N'-bis(3-thioureidopropyl)piperazine adopted an identical conformation in the solid state, which resulted in near-identical crystal packing. A second class of closely related compounds, N-substituted tris(2-thioureidoethyl)amines, showed no such reliability in the solid state, likely because the parent structure lacked hydrogen-bonding functionalities sufficient to control intramolecular structure. In the third class of compounds that we studied, 1-benzoyl-3-(2-pyridyl)thioureas, substitution patterns were often predictive of molecular conformation; however, these intramolecular trends did not lead to recognizable crystal packing motifs. Nevertheless, certain physical properties observed in this last class of compounds---color, solubility, and often crystallinity---were conformer-specific, interestingly without any apparent relevance to crystal lattice structure. Solution-state and solid-state conformational trends in these 1-benzoyl-3-(2-pyridyl)thioureas have been documented, and speculations as to the source of color in one of the two observed conformations have been noted.

Paisner, Kathryn A.

2011-12-01

339

Optical and Crystal Structure Characterizations of Nanowires for Infrared Applications  

NASA Astrophysics Data System (ADS)

Semiconductor nanowires (NWs) are one dimensional materials and have size quantization effect when the diameter is sufficiently small. They can serve as optical wave guides along the length direction and contain optically active gain at the same time. Due to these unique properties, NWs are now very promising and extensively studied for nanoscale optoelectronic applications. A systematic and comprehensive optical and microstructural study of several important infrared semiconductor NWs is presented in this thesis, which includes InAs, PbS, InGaAs, erbium chloride silicate and erbium silicate. Micro-photoluminescence (PL) and transmission electron microscope (TEM) were utilized in conjunction to characterize the optical and microstructure of these wires. The focus of this thesis is on optical study of semiconductor NWs in the mid-infrared wavelengths. First, differently structured InAs NWs grown using various methods were characterized and compared. Three main PL peaks which are below, near and above InAs bandgap, respectively, were observed. The octadecylthiol self-assembled monolayer was employed to passivate the surface of InAs NWs to eliminate or reduce the effects of the surface states. The band-edge emission from wurtzite-structured NWs was completely recovered after passivation. The passivated NWs showed very good stability in air and under heat. In the second part, mid-infrared optical study was conducted on PbS wires of subwavelength diameter and lasing was demonstrated under optical pumping. The PbS wires were grown on Si substrate using chemical vapor deposition and have a rock-salt cubic structure. Single-mode lasing at the wavelength of ˜3000--4000 nm was obtained from single as-grown PbS wire up to the temperature of 115 K. PL characterization was also utilized to demonstrate the highest crystallinity of the vertical arrays of InP and InGaAs/InP composition-graded heterostructure NWs made by a top-down fabrication method. TEM-related measurements were performed to study the crystal structures and elemental compositions of the Er-compound core-shell NWs. The core-shell NWs consist of an orthorhombic-structured erbium chloride silicate shell and a cubic-structured silicon core. These NWs provide unique Si-compatible materials with emission at 1530 nm for optical communications and solid state lasers.

Sun, Minghua

340

Growth, structure, spectral and optical properties of semiorganic crystal: Pyridine-1-ium-2-carboxylatehydrogenbromide.  

PubMed

Pyridine-1-ium-2-carboxylatehydrogenbromide (PHBr) crystal was grown from aqueous solution by slow evaporation method. The calculated lattice parameters of single crystal X-ray diffraction have shown the triclinic crystal system with centrosymmetric space group of P?. The interaction of functional groups and their importance in their application was identified by FTIR spectral analysis. The material is optically transparent and the grown crystal is having lower cut off wavelength as 294nm, thereby confirming the enhancement of non-linear optical (NLO) property and optical band gap of the PHBr have been determined as 2.49eV by UV-Vis-NIR studies. The (1)H NMR spectrum confirms the molecular structure and the presence of different kinds of protons. PMID:25727296

Gowri, S; Devi, T Uma; Priya, S; Dilip, C Surendra; Selvanayagam, S; Lawrence, N

2015-05-15

341

Synthesis, crystal structure, and magnetic properties of the oxometallates KBaMnO4 and KBaAsO4  

NASA Astrophysics Data System (ADS)

Single crystals of KBaMnO4 and KBaAsO4 were grown using the hydroflux method and characterized by single crystal X-ray diffraction. Both compounds crystallize in the orthorhombic space group Pnma with a = 7.7795(4) Å, b = 5.8263(3) Å, and c = 10.2851(5) Å for the manganate and a = 7.7773(10) Å, b = 5.8891(8) Å, and c = 10.3104(13) Å for the arsenate. The materials exhibit a three-dimensional crystal structure consisting of isolated MnO43- or AsO43- tetrahedra, with the charge balance maintained by K+ and Ba2+. Each tetrahedron is surrounded by six K+ and five Ba2+, and shares its corner/edge with KO10 polyhedra and corner/edge/face with BaO9 polyhedra, respectively. The crystal growth, crystal structure and magnetic properties are discussed.

zur Loye, Karl D.; Chance, W. Michael; Yeon, Jeongho; zur Loye, Hans-Conrad

2014-11-01

342

A preliminary review of organic materials single crystal growth by the Czochralski technique  

NASA Technical Reports Server (NTRS)

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.

Penn, B. G.; Shields, A. W.; Frazier, D. O.

1988-01-01

343

Crystal structures of bile salts: Sodium taurocholate  

Microsoft Academic Search

Crystals of sodium taurocholate (NaC26H44NO7S · 2.5 H2O) belonging to the triclinic space groupP1 have unit cell parametersa = 12.731 (2),b = 16.104 (2),c = 7.628 (1) ?A, a =83.40 (1),ß = 101.20 (1), ? = 105.35 (1)°, and two molecules in the asymmetric unit. The refinement, carried out on 4424 observed reflections, gaveR = 0.059 andRw = 0.066. The

Anna Rita Campanelli; Sofia Candeloro De Sanctis; Angelo Antonio D'Archivio; Edoardo Giglio; Lucid Scaramuzza

1991-01-01

344

Plastics as structural materials for aircraft  

NASA Technical Reports Server (NTRS)

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.

Kline, G M

1937-01-01

345

Space structures concepts and materials  

NASA Technical Reports Server (NTRS)

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.

Nowitzky, A. M.; Supan, E. C.

1988-01-01

346

Ytterbium- and neodymium-doped vanadate laser hose crystals having the apatite crystal structure  

DOEpatents

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

Payne, S.A.; Kway, W.L.; DeLoach, L.D.; Krupke, W.F.; Chai, B.H.T.

1994-08-23

347

Ytterbium- and neodymium-doped vanadate laser hose crystals having the apatite crystal structure  

DOEpatents

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.

Payne, Stephen A. (Castro Valley, CA); Kway, Wayne L. (Fremont, CA); DeLoach, Laura D. (Manteca, CA); Krupke, William F. (Pleasanton, CA); Chai, Bruce H. T. (Oviedo, FL)

1994-01-01

348

Liquid crystal materials, devices, and applications; Proceedings of the Meeting, San Jose, CA, Feb. 11-13, 1992  

Microsoft Academic Search

Consideration is given to nematic dispersions, ferroelectric liquid crystals, novel anisotropic organic materials, and applications of liquid crystal devices. Particular attention is given to the light-scattering properties and mechanism in nematic dispersions, electrical properties of polymer-dispersed liquid crystal films, new fluorinated heterocyclic compounds for improved FLC mixtures, photopolymerization of oriented monomeric liquid crystals, photochemical image storage in polymer liquid crystals,

Paul S. Drzaic; Uzi Efron

1992-01-01

349

Pericentriolar material structure and dynamics.  

PubMed

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

Woodruff, Jeffrey B; Wueseke, Oliver; Hyman, Anthony A

2014-09-01

350

Pericentriolar material structure and dynamics  

PubMed Central

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

Woodruff, Jeffrey B.; Wueseke, Oliver; Hyman, Anthony A.

2014-01-01

351

Structure of ice crystallized from supercooled water  

PubMed Central

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

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

2012-01-01

352

Graphene as a protein crystal mounting material to reduce background scatter  

PubMed Central

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

Wierman, Jennifer L.; Alden, Jonathan S.; Kim, Chae Un; McEuen, Paul L.; Gruner, Sol M.

2013-01-01

353

Band-structure determination for finite 3-D photonic crystals  

NASA Astrophysics Data System (ADS)

The partial band structure from a finite photonic crystal is determined using a model based on light diffraction and the transfer-matrix formalism. The predictions from such a model are compared to an experimental measurement of the bands in the LU direction of a face centered cubic colloidal crystal. Then, both the theoretical predictions and the experimental measurements are compared with the usual band-structure calculation based on a plane-wave expansion with perfectly periodic boundary conditions. As in measurements performed in the past, discrepancies between the predictions of this later model and the experimentally determined bands are observed. On the contrary, using the model presented based on light propagation through a finite crystal, where no periodicity is imposed in the direction perpendicular to any of the set of planes considered to determine a specific branch of the band structure, we found a very good agreement between the experimentally determined and the predicted bandwidths.

Botey, M.; Maymó, M.; Martorell, J.

2005-07-01

354

Compact Couplers for Photonic Crystal Laser-Driven Accelerator Structures  

SciTech Connect

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.

Cowan, Benjamin; /Tech-X, Boulder; Lin, M.C.; /Tech-X, Boulder; Schwartz, Brian; /Tech-X, Boulder; Byer, Robert; /Stanford U., Phys. Dept.; McGuinness, Christopher; /Stanford U., Phys. Dept.; Colby, Eric; /SLAC; England, Robert; /SLAC; Noble, Robert; /SLAC; Spencer, James; /SLAC

2012-07-02

355

Crystal Growth and Properties of Nonlinear Optical Materials  

Microsoft Academic Search

Nonlinear optical (NLO) crystals are a critical, enabling technology in the development of solid state laser sources, allowing the output from the most mature laser source operating a few discrete wavelengths to be shifted almost anywhere in the electromagnetic spectrum spanning from the ultraviolet to the far-infrared. For efficient frequency conversion, a nonlinear crystal must simultaneously satisfy a long list

Peter G. Schunemann

2007-01-01

356

Relationship between Crystallization Behavior and Structure in Cocoa Butter  

Microsoft Academic Search

Cocoa butter was crystallized statically from the melt to various temperatures in the range of -20 to 26 °C and annealed for up to 45 days. During this period, the polymorphism of the solid state was monitored using differential scanning calorimetry and powder X-ray diffraction. Moreover, the microstructure of the materials was imaged using polarized light microscopy. Below -15 °C,

Alejandro G. Marangoni; Sara E. McGauley

2003-01-01

357

Crystal chemistry and structure refinement of five hydrated calcium borates  

USGS Publications Warehouse

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.

Clark, J.R.; Appleman, D.E.; Christ, C.L.

1964-01-01

358

Crystal Structure Effect on Electrical Properties of Ysz Ceramics  

NASA Astrophysics Data System (ADS)

YSZ samples were prepared by Plasma Spray (PS) and Electron Beam Physical Vapor Deposition (EB-PVD) respectively. Microstructure and morphology were observed by SEM and XRD. Grain size of PS-YSZ was non-uniform caused by the inclusion of nano particle by molten particle and column crystal structure was observed for EB-PVD-YSZ. The Arrhenius plots of two samples were graphed by analysis of the measurement results of AC impedance spectra. The conductive mechanisms for EB-PVD and PS YSZ were different due to the crystal structure.

Zhang, Chunxia; Gong, Shengkai; Zhou, Chungen; Xu, Huibin

359

Estimation of diffusion anisotropy in microporous crystalline materials and optimization of crystal orientation in membranes  

NASA Astrophysics Data System (ADS)

The complex nature of the porous networks in microporous materials is primarily responsible for a high degree of intracrystalline diffusion anisotropy. Although this is a well-understood phenomenon, little attention has been paid in the literature with regards to classifying such anisotropy and elucidating its effect on the performance of membrane-based separation systems. In this paper, we develop a novel methodology to estimate full diffusion tensors based on the detailed description of the porous network geometry through our recent advances for the characterization of such networks. The proposed approach explicitly accounts for the tortuosity and complex connectivity of the porous framework, as well as for the variety of diffusion regimes that may be experienced by a guest molecule while it travels through the different localities of the crystal. Results on the diffusion of light gases in silicalite demonstrate good agreement with results from experiments and other computational techniques that have been reported in the literature. A comprehensive computational study involving 183 zeolite frameworks classifies these structures in terms of a number of anisotropy metrics. Finally, we utilize the computed diffusion tensors in a membrane optimization model that determines optimal crystal orientations. Application of the model in the context of separating carbon dioxide from nitrogen demonstrates that optimizing crystal orientation can offer significant benefit to membrane-based separation processes.

Gounaris, Chrysanthos E.; First, Eric L.; Floudas, Christodoulos A.

2013-09-01

360

Internal strain monitoring in composite materials with embedded photonic crystal fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

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 ?strain 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.

Geernaert, Thomas; Sulejmani, Sanne; Sonnenfeld, Camille; Chah, Karima; Luyckx, Geert; Lammens, Nicolas; Voet, Eli; Becker, Martin; Thienpont, Hugo; Berghmans, Francis

2014-09-01

361

Crystal Structures of Monomeric Actin Bound to Cytochalasin D  

PubMed Central

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

Nair, Usha B.; Joel, Peteranne B.; Wan, Qun; Lowey, Susan; Rould, Mark A.; Trybus, Kathleen M.

2008-01-01

362

Solvothermal synthesis, crystal structure, and second-order nonlinear optical properties of a new noncentrosymmetric gallium-organic framework material, [N(C{sub 3}H{sub 7}){sub 4}]{sub 3}Ga{sub 3}[C{sub 6}H{sub 3}(CO{sub 2}){sub 3}]{sub 4}  

SciTech Connect

A novel noncentrosymmetric (NCS) gallium-organic framework material, [N(C{sub 3}H{sub 7}){sub 4}]{sub 3}Ga{sub 3}[C{sub 6}H{sub 3}(CO{sub 2}){sub 3}]{sub 4} (CAUMOF-11) has been synthesized by a solvothermal reaction using Ga(NO{sub 3}){sub 3}{center_dot}xH{sub 2}O, 1,3,5-C{sub 6}H{sub 3}(CO{sub 2}H){sub 3}, N(C{sub 3}H{sub 7}){sub 4}Cl, HNO{sub 3}, and HCON(CH{sub 3}){sub 2} at 180 Degree-Sign C. The structure of the reported material has been determined by single-crystal X-ray diffraction. CAUMOF-11 has an anionic three-dimensional framework with aligned four-coordinate GaO{sub 4} tetrahedra and 1,3,5-benzenetricarboxylate groups. Tetrapropylammonim cations reside within the channel and maintain the charge balance. Detailed structural analyses with full characterization including infrared spectroscopy, thermogravimetric analysis, elemental analysis, ion-exchange reactions, topotactic decomposition, and gas adsorption experiments are reported. Powder second-harmonic generating (SHG) measurements on CAUMOF-11, using 1064 nm radiation, exhibit SHG efficiency of 15 times that of {alpha}-SiO{sub 2} and the material is phase-matchable (type-1). - Graphical Abstract: Second-order nonlinear optical measurements on CAUMOF-11 reveal that the material is phase-matchable (type-1) with SHG efficiency of 15 times that of {alpha}-SiO{sub 2}. Highlights: Black-Right-Pointing-Pointer A new NCS Ga-organic framework was solvothermally synthesized. Black-Right-Pointing-Pointer CAUMOF-11 exhibits SHG efficiency of 15 times that of {alpha}-SiO{sub 2}. Black-Right-Pointing-Pointer Thermal decomposition of CAUMOF-11 crystal maintains the original morphology.

Lee, Dong Woo; Jo, Vinna [Department of Chemistry, Chung-Ang University, Seoul, 156-756 (Korea, Republic of)] [Department of Chemistry, Chung-Ang University, Seoul, 156-756 (Korea, Republic of); Ok, Kang Min, E-mail: kmok@cau.ac.kr [Department of Chemistry, Chung-Ang University, Seoul, 156-756 (Korea, Republic of)

2012-10-15

363

Crystal structure of the human spastin AAA domain  

PubMed Central

Hereditary spastic paraplegia (HSP) is a motor neuron disease caused by a progressive degeneration of the motor axons of the corticospinal tract. Point mutations or exon deletions in the microtubule-severing ATPase, spastin, are responsible for approximately 40% of cases of autosomal dominant HSP. Here, we report the 3.3 Å X-ray crystal structure of a hydrolysis- deficient mutant (E442Q) of the human spastin protein AAA domain. This structure is analyzed in the context of the existing Drosophila melanogaster spastin AAA domain structure and crystal structures of other closely related proteins in order to build a more unifying framework for understanding the structural features of this group of microtubule-severing ATPases. PMID:22446388

Taylor, Jennifer L.; White, Susan Roehl; Lauring, Brett; Kull, F. Jon

2012-01-01

364

Crystal structure of the human spastin AAA domain.  

PubMed

Hereditary spastic paraplegia (HSP) is a motor neuron disease caused by a progressive degeneration of the motor axons of the corticospinal tract. Point mutations or exon deletions in the microtubule-severing ATPase, spastin, are responsible for approximately 40% of cases of autosomal dominant HSP. Here, we report the 3.3 Å X-ray crystal structure of a hydrolysis-deficient mutant (E442Q) of the human spastin protein AAA domain. This structure is analyzed in the context of the existing Drosophila melanogaster spastin AAA domain structure and crystal structures of other closely related proteins in order to build a more unifying framework for understanding the structural features of this group of microtubule-severing ATPases. PMID:22446388

Taylor, Jennifer L; White, Susan Roehl; Lauring, Brett; Kull, F Jon

2012-08-01

365

Formation of the structure of gold nanoclusters during crystallization  

SciTech Connect

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.

Gafner, Yu. Ya., E-mail: ygafner@khsu.ru; Goloven'ko, Zh. V.; Gafner, S. L. [Khakassian State University (Russian Federation)] [Khakassian State University (Russian Federation)

2013-02-15

366

CRYSTAL STRUCTURE ANALYSIS OF A PUTATIVE OXIDOREDUCTASE FROM KLEBSIELLA PNEUMONIAE  

SciTech Connect

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.

Baig, M.; Brown, A.; Eswaramoorthy, S.; Swaminathan, S.

2009-01-01

367

Optical Spectroscopy of Nano Materials and Structures  

NASA Astrophysics Data System (ADS)

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.).

Guo, Wenhao

368

Influence law of structural characteristics on the surface roughness of a magnetorheological-finished KDP crystal.  

PubMed

A new nonaqueous and abrasive-free magnetorheological finishing (MRF) method is adopted for processing potassium dihydrogen phosphate (KDP) crystal due to its low hardness, high brittleness, temperature sensitivity, and water solubility. This paper researches the influence of structural characteristics on the surface roughness of MRF-finished KDP crystal. The material removal by dissolution is uniform layer by layer when the polishing parameters are stable. The angle between the direction of the polishing wheel's linear velocity and the initial turning lines will affect the surface roughness. If the direction is perpendicular to the initial turning lines, the polishing can remove the lines. If the direction is parallel to the initial turning lines, the polishing can achieve better surface roughness. The structural characteristic of KDP crystal is related to its internal chemical bonds due to its anisotropy. During the MRF finishing process, surface roughness will be improved if the structural characteristics of the KDP crystal are the same on both sides of the wheel. The processing results of (001) plane crystal show we can get the best surface roughness (RMS of 0.809 nm) if the directions of cutting and MRF polishing are along the (110) direction. PMID:25402879

Chen, Shaoshan; Li, Shengyi; Hu, Hao; Li, Qi; Tie, Guipeng

2014-11-01

369

Modeling for ultrasonic nondestructive evaluation or columnar structures in anisotropic materials. Progress report  

SciTech Connect

The levitation zone refiner facility has been upgraded with a new crystal pulley. This produces larger crystals with better control of the crystallographic orientation. Progress also has been made toward controlled bicrystal production. Ultrasonic measurements and calculations have been performed to determine elastic constants and study velocity and alternation along principal directions in single crystal Ni; study velocity, attenuation and mode conversion along nonprincipal directions in single crystal Ni; and measure attenuation through two crystals coupled together with different orientations. Finite element development of ultrasonic wave propagation has been extended into material having cubic symmetry. Mode conversion for waves along nonprincipal directions has been demonstrated and preliminary work has been done on the two-crystal problem. Progress has advanced our understanding on techniques for ultrasonic inspection of oriented structures such as weldments and castings.

Dewey, B.R.; Oliver, B.F.; Adler, L.

1981-12-15

370

Fibrous Thiosilicates And Their Crystal Chemical Analogs: Considerations As Infrared Materials  

NASA Astrophysics Data System (ADS)

Materials with high toughness often have fibrous microstructures or are made as fibrous composites. One possible route to new infrared-transmitting materials is through sulfide analogs of those silicates known to have fibrous structures. SiS2 itself occurs as fibrous crystals isostructural with the rare oxide polymorph, silica-W. However, it is extremely reactive with oxygen and water. An investigation is underway of compound formation in the systems CaS-SiS2, MgS-SiS2, and NaS-Al2S3-SiS2 to search for such fibrous silicate analogs as CaSiS3 (thiowollastonite), MgSiS3 (thioenstatite), CaMgSi2S6 (thiodiopside), and NaA1Si2S6 (thiojadeite). A second phase of the investigation is to construct crystal chemical analogs with less chemical reactivity: e.g. Ge for Si, rare earths for Al, and the larger alkaline earths (Ba, Sr) for the more reactive smaller ones (Ca, Mg).

White, William B.; Veni, George; Steele, Sarah; Knight, Diane S.

1986-12-01

371

Crystal structure of a human GABAA receptor  

PubMed Central

Summary Type-A ?-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 ?3 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

Miller, Paul S.; Aricescu, A. Radu

2014-01-01

372

Crystal structures of two engineered thiol trypsins.  

PubMed

We have determined the three-dimensional structures of engineered rat trypsins which mimic the active sites of two classes of cysteine proteases. The catalytic serine was replaced with cysteine (S195C) to test the ability of sulfur to function as a nucleophile in a serine protease environment. This variant mimics the cysteine trypsin class of thiol proteases. An additional mutation of the active site aspartate to an asparagine (D102N) created the catalytic triad of the papain-type cysteine proteases. Rat trypsins S195C and D102N,S195C were solved to 2.5 and 2.0 A, respectively. The refined structures were analyzed to determine the structural basis for the 10(6)-fold loss of activity of trypsin S195C and the 10(8)-fold loss of activity of trypsin D102N,S195C, relative to rat trypsin. The active site thiols were found in a reduced state in contrast to the oxidized thiols found in previous thiol protease structures. These are the first reported structures of serine proteases with the catalytic centers of sulfhydryl proteases. Structure analysis revealed only subtle global changes in enzyme conformation. The substrate binding pocket is unaltered, and active site amino acid 102 forms hydrogen bonds to H57 and S214 as well as to the backbone amides of A56 and H57. In trypsin S195C, D102 is a hydrogen-bond acceptor for H57 which allows the other imidazole nitrogen to function as a base during catalysis. In trypsin D102N,S195C, the asparagine at position 102 is a hydrogen-bond donor to H57 which places a proton on the imidazole nitrogen proximal to the nucleophile. This tautomer of H57 is unable to act as a base in catalysis.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2611228

McGrath, M E; Wilke, M E; Higaki, J N; Craik, C S; Fletterick, R J

1989-11-28

373

Effect of local structures on structural evolution during crystallization in undercooled metallic glass-forming liquids.  

PubMed

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. PMID:23445019

Wu, Z W; Li, M Z; Wang, W H; Song, W J; Liu, K X

2013-02-21

374

Effect of local structures on structural evolution during crystallization in undercooled metallic glass-forming liquids  

NASA Astrophysics Data System (ADS)

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.

Wu, Z. W.; Li, M. Z.; Wang, W. H.; Song, W. J.; Liu, K. X.

2013-02-01

375

Crystal growth, spectral, structural and optical studies of ?-conjugated stilbazolium crystal: 4-Bromobenzaldehyde-4?-N?-methylstilbazolium tosylate  

NASA Astrophysics Data System (ADS)

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.

Krishna Kumar, M.; Sudhahar, S.; Bhagavannarayana, G.; Mohan Kumar, R.

376

Crystal growth, spectral, structural and optical studies of ?-conjugated stilbazolium crystal: 4-bromobenzaldehyde-4'-N'-methylstilbazolium tosylate.  

PubMed

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

Krishna Kumar, M; Sudhahar, S; Bhagavannarayana, G; Mohan Kumar, R

2014-05-01

377

The Crystal Structure of the Human Hepatitis B Virus Capsid  

Microsoft Academic Search

Hepatitis B is a small enveloped DNA virus that poses a major hazard to human health. The crystal structure of the T = 4 capsid has been solved at 3.3 Å resolution, revealing a largely helical protein fold that is unusual for icosahedral viruses. The monomer fold is stabilized by a hydrophobic core that is highly conserved among human viral

S. A Wynne; R. A Crowther; A. G. W Leslie

1999-01-01

378

Crystal structure of S-glutathiolated carbonic anhydrase III  

Microsoft Academic Search

S-Glutathiolation of carbonic anhydrase III (CAIII) occurs rapidly in hepatocytes under oxidative stress. The crystal structure of the S-glutathiolated CAIII from rat liver reveals covalent adducts on cysteines 183 and 188. Electrostatic charge and steric contacts at each modification site inversely correlate with the relative rates of reactivity of these cysteines toward glutathione (GSH). Diffuse electron density associated with the

Robert J. Mallis; Bradley W. Poland; Tapan K. Chatterjee; Rory A. Fisher; Steven Darmawan; Richard B. Honzatko; James A. Thomas

2000-01-01

379

Crystal structure of the Anabaena sensory rhodopsin transducer  

PubMed Central

Presented in this paper are crystal structures of the Anabaena sensory rhodopsin transducer (ASRT), a soluble cytoplasmic protein that interacts with the first structurally characterized eubacterial retinylidene photoreceptor Anabaena sensory rhodopsin (ASR). Four crystal structures of ASRT from three different spacegroups were obtained, in all of which ASRT is present as a planar (C4) tetramer, consistent with our characterization of ASRT as a tetramer in solution. The ASRT tetramer is tightly packed with large interfaces where the well-structured ?-sandwich portion of the monomers provides the bulk of the tetramer-forming interactions and forms a flat, stable surface on one side of the tetramer (the “?-face”). Only one of our four different ASRT crystals reveals a C-terminal ?-helix in the otherwise all-? protein, together with a large loop from each monomer on the opposite face of the tetramer (the “?-face”), which is flexible and largely disordered in the other three crystal forms. Gel filtration demonstrates that ASRT forms stable tetramers in solution and isothermal microcalorimetry shows that the ASRT tetramer binds to ASR with a stoichiometry of one ASRT tetramer per one ASR photoreceptor with a Kd of 8 ?M. Possible mechanisms for the interaction of this transducer tetramer with the ASR photoreceptor via its flexible ?-face to mediate transduction of the light signal are discussed. PMID:17289074

Vogeley, Lutz; Trivedi, Vishwa D.; Sineshchekov, Oleg A.; Spudich, Elena N.; Spudich, John L.; Luecke, Hartmut

2007-01-01

380

COMMUNICATION Crystal Structure of Apaf-1 Caspase Recruitment  

E-print Network

a proteolytic cascade that leads to apoptotic cell death. We report the crystal structure of the Apaf-1 CARD). It triggers the proteolytic cascade by activating caspase-9 (Thornberry & Lazebnik, 1998) in response as molecules that bind to them like Apaf-1 and RAIDD. DEDs often occur as tandem repeats and are found

Joshua-Tor, Leemor

381

Unusual Features of Crystal Structures of Some Simple Copper Compounds  

ERIC Educational Resources Information Center

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.…

Douglas, Bodie

2009-01-01

382

Classification, representation and prediction of crystal structures of ionic compounds  

Microsoft Academic Search

The aim of this paper is to show that with the aid of a qualitative model of ionic bonding, including polarizability, many crystal structures, mainly of halides and chalcogenides, can be explained or even predicted. Polarization of O2- and F- ions may be neglected unless these ions have very small, or small and highly charged cation neighbours. The polarizability of

E. W. Gorter

1970-01-01

383

Crystal structures and morphologies of fractionated milk fat in nanoemulsions.  

PubMed

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 ?m), lipid composition (stearin versus olein) and cooling rate (1 versus 10°C min(-1)) had an influence on the structural properties. Five crystal polymorphs (?, ?'1, ?'2, ?1, and ?2) 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

Truong, Tuyen; Morgan, Garry P; Bansal, Nidhi; Palmer, Martin; Bhandari, Bhesh

2015-03-15

384

~ Animation of Crystal Structure Variations with Pressure, Temperature and Composition  

E-print Network

~ Animation of Crystal Structure Variations with Pressure, Temperature and Composition Robert T as a function of temperature, pressure and composition. Examples of these animations are found on the cover another is an effective way to make the computer animations. This paper presents an outline

Downs, Robert T.

385

Magnetic activity at infrared frequencies in structured metallic photonic crystals  

Microsoft Academic Search

We derive the effective permeability and permittivity of a nanostructured metallic photonic crystal by analysing the complex reflection and transmission coefficients for slabs of various thicknesses. These quantities were calculated using the transfer matrix method. Our results indicate that these structures could be used to realize a negative effective permeability, at least up to infrared frequencies. The origin of the

J B Pendry

2002-01-01

386

Exotic behavior and crystal structures of calcium under pressure  

E-print Network

Exotic behavior and crystal structures of calcium under pressure Artem R. Oganova,b,1 , Yanming Mac that calcium undergoes sev- eral counterintuitive transitions under pressure: fcc bcc simple cubic Ca-IV Ca-V, and becomes a good superconductor in the simple cubic and higher-pressure phases. Here, using ab initio

Oganov, Artem R.

387

Microporous and Mesoporous Materials 21( 1998)403-409 Combination of single crystal zeolites and microfabrication  

E-print Network

Microporous and Mesoporous Materials 21( 1998)403-409 Combination of single crystal zeolites and microfabrication: Two applications towards zeolite nanodevices L. Scandella a, G. Binder a, T. Mezzacasa a, J;accepted12January 1998 Abstract We present two novel approaches to using zeolite crystals for `nanodevices

Gimzewski, James

388

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

DOEpatents

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.

Todt, V.; Miller, D.J.; Shi, D.; Sengupta, S.

1998-07-07

389

National Launch System: Structures and materials  

NASA Technical Reports Server (NTRS)

The National Launch System provides an opportunity to realize the potential of Al-Li. Advanced structures can reduce weights by 5-40 percent as well as relax propulsion system performance specifications and reduce requirements for labor and materials. The effect on costs will be substantial. Advanced assembly and process control technologies also offer the potential for greatly reduced labor during the manufacturing and inspection processes. Current practices are very labor-intensive and, as a result, labor costs far outweigh material costs for operational space transportation systems. The technological readiness of new structural materials depends on their commercial availability, producibility and materials properties. Martin Marietta is vigorously pursuing the development of its Weldalite 049 Al-Li alloys in each of these areas. Martin Marietta is also preparing to test an automated work cell concept that it has developed using discrete event simulation.

Bunting, Jack O.

1993-01-01

390

Binary hard-sphere crystals with the cesium chloride structure  

NASA Astrophysics Data System (ADS)

The possibility of binary hard-sphere colloids crystallizing with the cesium chloride (CsCl) structure was examined experimentally using poly (methyl methacrylate) particles dispersed in organic solvents. Towards this end, two dispersions were prepared that contained particles with a radius ratio ?=RB/RA, where A refers to the large particles and B the small, of 0.736. This is close to the optimum ratio of 0.732 at which this structure is predicted to form as determined by space-filling calculations. The phases found within the binary mixture were examined using laser light crystallography and scanning electromicroscopy, and some were shown to have the CsCl structure. Over a period of time some of the CsCl crystals disappeared indicating that they were metastable and that this structure may not be the most enduring phase at this size ratio.

Schofield, A. B.

2001-11-01

391

Structure of the trigonal crystal form of bovine annexin IV.  

PubMed Central

The structure of a trigonal crystal form of N-terminally truncated [des-(1-9)] bovine annexin IV, an annexin variant that exhibits the distinctive property of binding both phospholipids and carbohydrates in a Ca2+-dependent manner, has been determined at 3 A (0.3 nm) resolution -space group: R3; cell parameters: a=b=118.560 (8) A and c=82.233 (6) A-. The overall structure of annexin IV, crystallized in the absence of Ca2+ ions, is highly homologous to that of the other known members of the annexin family. The trimeric assembly in the trigonal crystals of annexin IV is quite similar to that found previously in non-isomorphous crystals of human, chicken and rat annexin V and to the subunit arrangement in half of the hexamer of hydra annexin XII. Moreover, it resembles that found in two-dimensional crystals of human annexin V bound to phospholipid monolayers. The propensity of several annexins to generate similar trimeric arrays supports the hypothesis that trimeric complexes of such annexins, including annexin IV, may represent the functional units that interact with membranes. PMID:9405281

Zanotti, G; Malpeli, G; Gliubich, F; Folli, C; Stoppini, M; Olivi, L; Savoia, A; Berni, R

1998-01-01

392

Crystal structures of two engineered thiol trypsins  

Microsoft Academic Search

We have determined the three-dimensional structures of engineered rat trypsins which mimic the active sites of two classes of cysteine proteases. The catalytic serine was replaced with cysteine (S195C) to test the ability of sulfur to function as a nucleophile in a serine protease environment. This variant mimics the cysteine trypsin class of thiol proteases. An additional mutation of the

Mary E. McGrath; Marjorie E. Wilke; Jeffrey N. Higaki; Charles S. Craik; Robert J. Fletterick

1989-01-01

393

Crystal structure of new AsS2 compound  

NASA Astrophysics Data System (ADS)

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.

Bolotina, N. B.; Brazhkin, V. V.; Dyuzheva, T. I.; Lityagina, L. M.; Kulikova, L. F.; Nikolaev, N. A.; Verin, I. A.

2013-01-01

394

Photonic-band structure of magnetic photonic crystal slabs  

Microsoft Academic Search

In this paper, we introduce a rigorous computational method for the evaluation of the band structure of magnetic photonic crystal (MPC) slabs. With the help of this method, the full-wave analysis of the structure can be reduced to the analysis of an equivalent multi-conductor transmission line. In this work, we present a semi-analytical characteristic equation for the evaluation of the

Hasan Ajam; Mahmoud Shahabadi

2005-01-01

395

Crystal Structure of Mistletoe Lectin I from Viscum album  

Microsoft Academic Search

The crystal structure of the ribosome-inactivating protein (RIP) mistletoe lectin I (ML-I) fromViscum albumhas been solved by molecular replacement techniques. The structure has been refined to a crystallographic R-factor of 24.5% using X-ray diffraction data to 2.8 Å resolution. The heterodimeric 63-kDa protein consists of a toxic A subunit which exhibits RNA-glycosidase activity and a galactose-specific lectin B subunit. The

Ruth Krauspenhaar; Susanne Eschenburg; Markus Perbandt; Vjacheslav Kornilov; Nina Konareva; Inna Mikailova; Stanka Stoeva; Roland Wacker; Timm Maier; Tej Singh; Albert Mikhailov; Wolfgang Voelter; Christian Betzel

1999-01-01

396

Synthesis, crystal structure, and photoluminescence of a zinc metalloporphyrin  

NASA Astrophysics Data System (ADS)

A zinc metalloporphyrin, ZnTCPP(acetone) ( 1) (TCPP = meso-tetra(4-carboxyphenyl)porphyrin), has been prepared via a solvothermal reaction and structurally characterized by single-crystal X-ray diffraction. Compound 1 features an isolated structure with a planar macrocycle and an embedded zinc ion binded to four pyrrole nitrogen atoms and one acetone oxygen atom. Photoluminescent investigation reveals that compound 1 displays an intensive emission in the red region.

Chen, Wen-Tong; Yi, Xiu-Guang; Luo, Zhi-Gang; Fu, Hong-Ru; Liu, Juan

2014-07-01

397

Modeling liquid crystal bilayer structures with minimal surfaces J. D. Enlowa)  

E-print Network

.1063/1.1635811 I. INTRODUCTION The term ``liquid crystal'' is commonly associated with the simple polymer liquidModeling liquid crystal bilayer structures with minimal surfaces J. D. Enlowa) and R. L. Enlow crystal phase used in familiar liquid crystal displays, but the term also refers to structures with far

Gruner, Sol M.

398

Intermetallic crystal structures as foams. Beyond Frank-Kasper.  

PubMed

In many intermetallic structures, the atoms and bonds divide space into tilings by tetrahedra. The well-known Frank-Kasper phases are examples. The dual tilings divide space into a tiling by polyhedra that is topologically a foam. The number of faces of the dual polyhedron corresponds to the atom coordination number in the direct structure, and face sharing by adjacent polyhedra corresponds to bonds in the direct structure. A number of commonly occurring intermetallic crystal structures are shown as their duals. A major advantage of this alternative mode of depiction is that coordination of all of the atoms can be seen simultaneously. PMID:25247234

Bonneau, Charlotte; O'Keeffe, Michael

2015-02-01

399

Crystal structure and vibrational spectra of piperazinium bis(4-hydroxybenzenesulphonate) molecular-ionic crystal.  

PubMed

The piperazinium bis(4-hydroxybenzenesulphonate) crystallizes from water solution at room temperature in P2(1)/c space group of monoclinic system. The crystals are built up of doubly protonated piperazinium cations and ionized 4-hydroxybenzenesulphonate anions that interact through weak hydrogen bonds of O-H...O and N-H...O type. Mutual orientation of anions is determined by non-conventional hydrogen bonds of C-Hcdots, three dots, centeredpi type. Room temperature powder FT IR and FT Raman measurements were carried out. The vibrational spectra are in full agreement with the structure obtained from X-ray crystallography. The big single crystals of the title salt can be grown. PMID:17627870

Marchewka, M K; Pietraszko, A

2008-02-01

400

Crystal structure, spectral-luminescence properties, and stimulated radiation of gallium gehlenite  

SciTech Connect

The Czochralski method has been used to grow a complete concentration series of Ca/sub 2-x/Nd/sub x/Ga/sub 2+x/Si/sub 1-x/O/sub 7/ single crystals, an x-ray structure analysis has been made of Ca/sub 2/Ga/sub 2/-SiO/sub 7/, and the spectral-luminescence properties and stimulated radiation of this inorganic material with Nd/sup 3 +/ ions have been studied.

Kaminskii, A.A.; Belokoneva, E.L.; Mill', B.V.; Tamazyan, S.A.; Kurbanov, K.

1986-12-01

401

Crystal structure, spectral-luminescence properties, and stimulated radiation of gallium gehlenite  

Microsoft Academic Search

The Czochralski method has been used to grow a complete concentration series of Ca\\/sub 2-x\\/Nd\\/sub x\\/Ga\\/sub 2+x\\/Si\\/sub 1-x\\/Oâ single crystals, an x-ray structure analysis has been made of CaâGaâ-SiOâ, and the spectral-luminescence properties and stimulated radiation of this inorganic material with Nd\\/sup 3 +\\/ ions have been studied.

A. A. Kaminskii; E. L. Belokoneva; B. V. Mill; S. A. Tamazyan; K. Kurbanov

1986-01-01

402

Uraniumhydrogen interactions: synthesis and crystal structures of tris(N,N-dimethylaminodiboranato)uranium(III)w  

E-print Network

Uranium­hydrogen interactions: synthesis and crystal structures of tris(N,N-dimethylaminodiboranato)uranium919490h The reaction of UCl4 with Na(H3BNMe2BH3) in diethyl ether affords the uranium(III) product U(H3 in the two forms. Uranium hydride, UH3, has been proposed to be an ideal material for the generation of safe

Girolami, Gregory S.

403

Dynamic and structural control utilizing smart materials and structures  

NASA Technical Reports Server (NTRS)

An account is given of several novel 'smart material' structural control concepts that are currently under development. The thrust of these investigations is the evolution of intelligent materials and structures superceding the recently defined variable-geometry trusses and shape memory alloy-reinforced composites; the substances envisioned will be able to autonomously evaluate emergent environmental conditions and adapt to them, and even change their operational objectives. While until now the primary objective of the developmental efforts presently discussed has been materials that mimic biological functions, entirely novel concepts may be formulated in due course.

Rogers, C. A.; Robertshaw, H. H.

1989-01-01

404

Crystal structure prediction via particle-swarm optimization  

NASA Astrophysics Data System (ADS)

We have developed a method for crystal structure prediction from “scratch” through particle-swarm optimization (PSO) algorithm within the evolutionary scheme. PSO technique is different with the genetic algorithm and has apparently avoided the use of evolution operators (e.g., crossover and mutation). The approach is based on an efficient global minimization of free-energy surfaces merging total-energy calculations via PSO technique and requires only chemical compositions for a given compound to predict stable or metastable structures at given external conditions (e.g., pressure). A particularly devised geometrical structure parameter which allows the elimination of similar structures during structure evolution was implemented to enhance the structure search efficiency. The application of designed variable unit-cell size technique has greatly reduced the computational cost. Moreover, the symmetry constraint imposed in the structure generation enables the realization of diverse structures, leads to significantly reduced search space and optimization variables, and thus fastens the global structure convergence. The PSO algorithm has been successfully applied to the prediction of many known systems (e.g., elemental, binary, and ternary compounds) with various chemical-bonding environments (e.g., metallic, ionic, and covalent bonding). The high success rate demonstrates the reliability of this methodology and illustrates the promise of PSO as a major technique on crystal structure determination.

Wang, Yanchao; Lv, Jian; Zhu, Li; Ma, Yanming

2010-09-01

405

Structured materials for catalytic and sensing applications  

NASA Astrophysics Data System (ADS)

The optical and chemical properties of the materials used in catalytic and sensing applications directly determine the characteristics of the resultant catalyst or sensor. It is well known that a catalyst needs to have high activity, selectivity, and stability to be viable in an industrial setting. The hydrogenation activity of palladium catalysts is known to be excellent, but the industrial applications are limited by the cost of obtaining catalyst in amounts large enough to make their use economical. As a result, alloying palladium with a cheaper, more widely available metal while maintaining the high catalytic activity seen in monometallic catalysts is, therefore, an attractive option. Similarly, the optical properties of nanoscale materials used for sensing must be attuned to their application. By adjusting the shape and composition of nanoparticles used in such applications, very fine changes can be made to the frequency of light that they absorb most efficiently. The design, synthesis, and characterization of (i) size controlled monometallic palladium nanoparticles for catalytic applications, (ii) nickel-palladium bimetallic nanoparticles and (iii) silver-palladium nanoparticles with applications in drug detection and biosensing through surface plasmon resonance, respectively, will be discussed. The composition, size, and shape of the nanoparticles formed were controlled through the use of wet chemistry techniques. After synthesis, the nanoparticles were analyzed using physical and chemical characterization techniques such as X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Scanning Transmission Electron Microscopy- Energy-Dispersive Spectrometry (STEM-EDX). The Pd and Ni-Pd nanoparticles were then supported on silica for catalytic testing using mass spectrometry. The optical properties of the Ag-Pd nanoparticles in suspension were further investigated using ultraviolet-visible spectrometry (UV-Vis). Monometallic palladium particles have been synthesized and characterized to establish the effects of nanoparticle size on catalytic activity in methanol decomposition. The physicochemical properties of the synthesized palladium-nickel nanoparticles will be discussed, as a function of the synthesis parameters. The optical characteristics of the Ag and Pd nanoparticles will be determined, with a view toward tuning the response of the nanoparticles for incorporation in sensors. Analysis of the monometallic palladium particles revealed a dependence of syngas production on nanoparticle size. The peak and steady state TOFs increased roughly linearly with the average nanoparticle diameter. The amount of coke deposited on the particle surfaces was found to be independent on the size of the nanoparticles. Shape control of the nickel-palladium nanoparticles with a high selectivity for (100) and (110) facets (? 80%) has been demonstrated. The resulting alloy nanoparticles were found to have homogeneous composition throughout their volume and maintain FCC crystal structure. Substitution of Ni atoms in the Pd lattice at a 1:3 molar ratio was found to induce lattice strains of ~1%. The Ag nanocubes synthesized exhibited behavior very similar to literature values, when taken on their own, exhibiting a pair of distinct absorbance peaks at 350 nm and 455 nm. In physical mixtures with the Pd nanoparticles synthesized, their behavior showed that the peak position of the Ag nanocubes' absorbance in UV-Vis could be tuned based on the relative proportions of the Ag and Pd nanoparticles present in the suspension analysed. The Ag polyhedra synthesized for comparison showed a broad doublet peak throughout the majority of the visible range before testing as a component in a physical mixture with the Pd nanoparticles. The addition of Pd nanoparticles to form a physical mixture resulted in some damping of the doublet peak observed as well as a corresponding shift in the baseline absorbance proportional to the amount of Pd added to the mixture.

Hokenek, Selma

406

BE.442 Molecular Structure of Biological Materials, Fall 2002  

E-print Network

Basic molecular structural principles of biological materials. Molecular structures of various materials of biological origin, including collagen, silk, bone, protein adhesives, GFP, self-assembling peptides. Molecular ...

Zhang, Shuguang, Dr.

407

BE.442 Molecular Structure of Biological Materials, Fall 2005  

E-print Network

Basic molecular structural principles of biological materials. Molecular structures of various materials of biological origin, including collagen, silk, bone, protein adhesives, GFP, self-assembling peptides. Molecular ...

Zhang, Shuguang, Dr.

408

Crystal Chemistry and Ceramic Processing of Rare Earth Chalcogenide Optical and Electronic Materials  

NASA Astrophysics Data System (ADS)

The thesis is concerned with the development of new IR transmitting materials for the 8-14 micrometer atomspheric window. The strategy was to investigate, in detail, the synthesis, crystal chemistry, processing, optical, and electronic properties of the rare earth sulfide as candidate materials. The rare earths crystallize in five known structures. Study of their temperature stabilities during long reaction times showed that alpha (orthorhombic, Pnma) exists as the low temperature form, and gamma (cubic, I| 43d) exists as the high temperature form in the large rare earths. Delta (monoclinic, P2/m) exists in the smaller rare earths from Ho through Tm over all temperature ranges, and episilon (trigonal, R| 3c) forms from Yb and Lu. Beta (tetragonal, I4/acd), which is reported in literature as a mid temperature range, oxygen stabilized rare earth sulfide, appears to be an oxysulfide and is an intermediate step between the oxide and sulfide from La through Nd. Extremely fine-grained precursor oxides were synthesized by evaporative decomposition of solution. An ultrasonic dispersion of aqueous nitrate salts is misted into a hot walled furnace. The 2-5 micrometer resulting oxides were predominantly well-crystallized spherical particles. The sesquisulfides could be readily synthesized by direct reaction of the oxides with flowing H_2S in the presence of graphite. These reactive, fine-grained, EDS-derived sulfides could be sintered into ceramic compacts that achieved 92 -98 percent of theoretical density. Sintering temperatures from 1200^circ-1400 ^circC and time of 80-120 minutes in flowing H_2S produced the best ceramics. This method of preparation is superior to the method using stock 25-35 micrometer starting materials which only received 70-78 percent of theoretical density. The measurement of the electronic absorption edge yielded band gaps of 1.6-2.6 eV. The first-order transverse and longitudinal phonon frequencies obtained by specular reflectance FTIR spectroscopy occurred in the range of 200 cm^{-1} and 300 cm ^{-1}, respectively. The evaluation of the rare earth sesquisulfide shows, from the stability, processing electronic and optical properties, these materials have the characteristics required for IR window materials.

Vaughan, Cheryl Marie

1990-01-01

409

Crystal structure and mechanistic investigation of the twister ribozyme.  

PubMed

We present a crystal structure at 2.3-Å 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

Liu, Yijin; Wilson, Timothy J; McPhee, Scott A; Lilley, David M J

2014-09-01

410

Damage mechanisms of porous materials due to in-pore salt crystallization.  

PubMed

Pressure exerted by crystallization of salts within porous materials contributes to damage in historic and modern construction. By unequivocally identifying the precipitating phase(s) while simultaneously determining solution supersaturation and associated crystallization pressure in subsurface pores, we show that the formation of a thermodynamically metastable salt phase (heptahydrate; Na2SO4·7H2O) and the resulting transition to a less soluble stable phase (mirabilite; Na2SO4·10H2O) is largely responsible for the high supersaturation and crystallization pressure developed during evaporative crystallization of sodium sulfate, the most damaging salt known. These results help to explain why salts with various (stable and metastable) hydrated phases are the most damaging. We also show that damage associated with metastable-stable phase transitions can be suppressed by the use of crystallization promoters. These results open new ways for the prevention of salt damage to building materials. PMID:23368580

Schiro, Mara; Ruiz-Agudo, Encarnacion; Rodriguez-Navarro, Carlos

2012-12-28

411

A method for hierarchical comparative analysis of crystal structures.  

PubMed

A geometrical-topological description of crystal structure as a three-dimensional graph with coloured nodes, weighted and coloured edges is used to generate a hierarchical sequence of the structure representations. The solid angles of Voronoi-Dirichlet polyhedra of atoms are used as the edge weights and the nodes and edges are coloured according to chemical reasons. Two operations are defined to derive the representations: contracting an atom to other atoms keeping the local connectivity, and removing an atom together with all its bonds. The atoms of the crystal structure are called origin, removed, contracted or target according to their roles in the operations. Each structure representation is described as a labelled quotient graph and determined by (i) colours of the graph nodes and edges, (ii) some level for edge weights, and (iii) an arrangement of atoms according to their roles. The computer enumeration and topological comparative analysis of all representations for crystal structures of any composition and complexity are implemented into the TOPOS program package. The advantages of the method are shown by the analysis of typical inorganic compounds and a molecular packing. PMID:16926484

Blatov, Vladislav A

2006-09-01

412

The crystal structure and the phase transitions of pyridinium trifluoromethanesulfonate  

NASA Astrophysics Data System (ADS)

The calorimetric and optical studies and the structural properties of pyridinium trifluoromethanesulfonate (abbreviated as PyHOTf) are reported. A sequence of four fully reversible solid-solid phase transitions, at 223.0, 309.0, 359.9 and 394.3 K, has been discovered. The phase transition sequence was confirmed by x-ray diffraction data. The crystal structures of three phases (V, IV and III) have been determined from the single crystal x-ray diffraction data. Structural properties of the high temperature phases are characterized using powder x-ray diffraction data measured in the 290-425 K temperature range. The structural changes triggered by the temperature change are discussed in relation to the phase transitions. Two low temperature phases (V and IV) belong to the P43212 space group of the tetragonal system. The intermediate phases (III and II) are monoclinic and the prototype high temperature phase (I) is a pseudo-cubic (tetragonal) one. The low temperature phases (V and IV) are well ordered. The crystal structure of intermediate (III and II) and prototype (I) phases are characterized by high disorder of the pyridinium cations and triflate anions.

Jesariew, Dominik; Ilczyszyn, Maria M.; Pietraszko, Adam

2014-03-01

413

Structure and melting behavior of classical bilayer crystals of dipoles  

SciTech Connect

We study the structure and melting of a classical bilayer system of dipoles in a setup where the dipoles are oriented perpendicular to the planes of the layers and the density of dipoles is the same in each layer. Due to the anisotropic character of the dipole-dipole interactions, we find that the ground-state configuration is given by two hexagonal crystals positioned on top of each other, independent of the interlayer spacing and dipolar density. For large interlayer distances these crystals are independent, while in the opposite limit of small interlayer distances the system behaves as a two-dimensional crystal of paired dipoles. Within the harmonic approximation for the phonon excitations, the melting temperature of these crystalline configurations displays a nonmonotonic dependence on the interlayer distance, which is associated with a re-entrant melting behavior in the form of solid-liquid-solid-liquid transitions at fixed temperature.

Lu Xin; Wu Changqin; Micheli, Andrea; Pupillo, Guido [Surface Physics Laboratory (National Key Laboratory) and Department of Physics, Fudan University, Shanghai 200433 (China); Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria) and Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-6020 Innsbruck (Austria)

2008-07-01

414

Hierarchically structured materials for lithium batteries  

NASA Astrophysics Data System (ADS)

The lithium-ion battery (LIB) is one of the most promising power sources to be deployed in electric vehicles, including solely battery powered vehicles, plug-in hybrid electric vehicles, and hybrid electric vehicles. With the increasing demand for devices of high-energy densities (>500 Wh kg-1), new energy storage systems, such as lithium-oxygen (Li-O2) batteries and other emerging systems beyond the conventional LIB, have attracted worldwide interest for both transportation and grid energy storage applications in recent years. It is well known that the electrochemical performance of these energy storage systems depends not only on the composition of the materials, but also on the structure of the electrode materials used in the batteries. Although the desired performance characteristics of batteries often have conflicting requirements with the micro/nano-structure of electrodes, hierarchically designed electrodes can be tailored to satisfy these conflicting requirements. This work will review hierarchically structured materials that have been successfully used in LIB and Li-O2 batteries. Our goal is to elucidate (1) how to realize the full potential of energy materials through the manipulation of morphologies, and (2) how the hierarchical structure benefits the charge transport, promotes the interfacial properties and prolongs the electrode stability and battery lifetime.

Xiao, Jie; Zheng, Jianming; Li, Xiaolin; Shao, Yuyan; Zhang, Ji-Guang

2013-10-01

415

Self-healing structural composite materials  

Microsoft Academic Search

A self-healing fiber-reinforced structural polymer matrix composite material is demonstrated. In the composite, a microencapsulated healing agent and a solid chemical catalyst are dispersed within the polymer matrix phase. Healing is triggered by crack propagation through the microcapsules, which then release the healing agent into the crack plane. Subsequent exposure of the healing agent to the chemical catalyst initiates polymerization

M. R. Kessler; N. R. Sottos; S. R. White

2003-01-01

416

Hierarchically Structured Materials for Lithium Batteries  

SciTech Connect

Lithium-ion battery (LIB) is one of the most promising power sources to be deployed in electric vehicles (EV), including solely battery powered vehicles, plug-in hybrid electric vehicles, and hybrid electrical vehicles. With the increasing demand on devices of high energy densities (>500 Wh/kg) , new energy storage systems, such as lithium-oxygen (Li-O2) batteries and other emerging systems beyond the conventional LIB also attracted worldwide interest for both transportation and grid energy storage applications in recent years. It is well known that the electrochemical performances of these energy storage systems depend not only on the composition of the materials, but also on the structure of electrode materials used in the batteries. Although the desired performances characteristics of batteries often have conflict requirements on the micro/nano-structure of electrodes, hierarchically designed electrodes can be tailored to satisfy these conflict requirements. This work will review hierarchically structured materials that have been successfully used in LIB and Li-O2 batteries. Our goal is to elucidate 1) how to realize the full potential of energy materials through the manipulation of morphologies, and 2) how the hierarchical structure benefits the charge transport, promotes the interfacial properties, prolongs the electrode stability and battery lifetime.

Xiao, Jie; Zheng, Jianming; Li, Xiaolin; Shao, Yuyan; Zhang, Jiguang

2013-09-25

417

Hierarchically structured materials for lithium batteries.  

PubMed

The lithium-ion battery (LIB) is one of the most promising power sources to be deployed in electric vehicles, including solely battery powered vehicles, plug-in hybrid electric vehicles, and hybrid electric vehicles. With the increasing demand for devices of high-energy densities (>500 Wh kg(-1)), new energy storage systems, such as lithium-oxygen (Li-O2) batteries and other emerging systems beyond the conventional LIB, have attracted worldwide interest for both transportation and grid energy storage applications in recent years. It is well known that the electrochemical performance of these energy storage systems depends not only on the composition of the materials, but also on the structure of the electrode materials used in the batteries. Although the desired performance characteristics of batteries often have conflicting requirements with the micro/nano-structure of electrodes, hierarchically designed electrodes can be tailored to satisfy these conflicting requirements. This work will review hierarchically structured materials that have been successfully used in LIB and Li-O2 batteries. Our goal is to elucidate (1) how to realize the full potential of energy materials through the manipulation of morphologies, and (2) how the hierarchical structure benefits the charge transport, promotes the interfacial properties and prolongs the electrode stability and battery lifetime. PMID:24067410

Xiao, Jie; Zheng, Jianming; Li, Xiaolin; Shao, Yuyan; Zhang, Ji-Guang

2013-10-25

418

Liquid crystal materials with asymmetric switching for microdisplay applications  

NASA Astrophysics Data System (ADS)

Liquid crystals are customarily used in several kinds of flat panel displays. Besides usual nematic liquid crystals, smectic tristate antiferroelectric liquid crystals have shown analogue grayscale and full color video rate at high-end devices with passive multiplexing. These devices ultimately are intended to be applied to small size devices on microdisplay applications. When a symmetric driving signal is applied, the electrooptic response of the devices usually consists of two symmetric hysteresis lobes. An asymmetric hysteresis cycle can be developed by using dissimilar aligning layers onto the two glass plates of the cell. This kind of devices can lead to analogue optical multistability, i.e., devices whose optical transmission may be arbitrarily set and maintained reducing or eliminating the bias voltage. In this work, a study of the asymmetric behavior of cells filled with commercial antiferroelectric liquid crystal is presented. Optical hysteresis cycles have been obtained applying a low frequency triangular waveform to the devices. Analogue grayscales have been generated only at one lobe of the hysteresis cycle. Electrical characterization has been carried out measuring the switching current of the cells test. Multiplexed driving waveforms have been applied with and without bias voltage in order to evaluate the stability of the optical transmission for video rate working. Results demonstrating analogue optical multistability on asymmetric antiferroelectric cells have been obtained. Narrow dynamic ranges, compatible with standard electronics for dynamic grayscale in data columns have been found. Preliminary measurements of the frequency dependence of impedance have been obtained on the capacitive device.

Urruchi, V.; Perez, I.; Pena, J. M. S.; Torres, J. C.; Manzanares, R.; Quintana, X.; Oton, J. M.

2005-07-01

419

Recovery of valuable materials from waste liquid crystal display panel  

Microsoft Academic Search

Associated with the rapid development of the information and electronic industry, liquid crystal displays (LCDs) have been increasingly sold as displays. However, during the discarding at their end-of-life stage, significant environmental hazards, impacts on health and a loss of resources may occur, if the scraps are not managed in an appropriate way. In order to improve the efficiency of the

Jinhui Li; Song Gao; Huabo Duan; Lili Liu

2009-01-01

420

A Simple Inexpensive Bridgman-Stockbarger Crystal Growth System for Organic Materials  

NASA Technical Reports Server (NTRS)

Direct observation of solid-liquid interface is important for the directional solidification to determine the desired interface shape by controlling the growth parameters. To grow good quality single crystals of novel organic nonlinear optical materials, a simple inexpensive Bridgman-Stockbarger (BS) crystal growth system has been designed and fabricated. Two immiscible liquids have been utilized to create two zones for this crystal growth system. Bulk single crystals of benzil derivative and n-salicylidene-aniline have been successfully grown in this system. The optimum lowering rate has been found to be 0.1 mm/h for the flat interface. Results on the crystal growth and other parameters of the grown crystals are presented.

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

1996-01-01

421

Structural and chemical characterization of fluorinated amorphous carbon films (aC:F) as a liquid crystal alignment layer  

Microsoft Academic Search

a-C:F thin films with varying fluorine content were prepared by plasma CVD and the sputtering method as inorganic alignment layers for overcoming the disadvantages of conventional liquid crystal (LC) alignment layers. The material and structural properties were investigated by X-ray photoelectron spectroscopy, Fourier transform infrared absorption, and contact angle measurement. For elucidation of the liquid crystal alignment layers, LC cells

Han Jin Ahn; Jong Bok Kim; Byoung Har Hwang; Hong Koo Baik; Jin Seol Park; Daeseung Kang

2008-01-01

422

The Crystal and Molecular Structure of Acetatochlorobis(4-methylpyridine)oxovanadium (IV)  

NASA Technical Reports Server (NTRS)

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.

Schupp, John D.; Hepp, Aloysius F.; Duraj, Stan A.; Richman, Robert M.; Fanwick, Phillip E.; Hakimzadeh, Roshanak (Technical Monitor)

2001-01-01

423

Fabrication of photonic structures in crystals of the KTiOPO 4 family by ultrafast laser ablation  

NASA Astrophysics Data System (ADS)

We investigate the growth and fabrication of photonic structures by ultrafast laser ablation on nonlinear optical materials of the KTiOPO4 family. We studied how the ultrafast laser ablation process affected on the structure of the material by micro-Raman scattering and micro-X-ray diffraction. The modifications of the Raman frequencies and their intensities have been discussed and compared with those previously reported for unablated crystals.

Golconda, Raj Kumar; Carvajal, Joan Josep; Pujol, Maria Cinta; Mateos, Xavier; Aguiló, Magdalena; Diaz, Francesc; Vázquez de Aldana, Javier R.; Romero, Carolina; Méndez, Cruz; Moreno, Pablo; Roso, Luis

424

Simulation of crystallization in Ge2Sb2Te5: A memory effect in the canonical phase-change material  

NASA Astrophysics Data System (ADS)

Crystallization of amorphous Ge2Sb2Te5 (GST) has been studied using four extensive (460 atoms, up to 4 ns) density functional/molecular dynamics simulations at 600 K. This phase change material is a rare system where crystallization can be simulated without adjustable parameters over the physical time scale, and the results could provide insight into order-disorder processes in general. Crystallization is accompanied by an increase in the number of A B A B squares (A :Ge,Sb;B :Te), percolation, and the occurrence of low-frequency localized vibration modes. A sample with a history of order crystallizes completely in 1.2 ns, but ordering in others was less complete, even after 4 ns. The amorphous starting structures without memory display phases (>1 ns) with subcritical nuclei (10-50 atoms) ranging from nearly cubical blocks to stringlike configurations of A B A B squares and A B bonds extending across the cell. Percolation initiates the rapid phase of crystallization and is coupled to the directional p -type bonding in metastable GST. Cavities play a crucial role, and the final ordered structure is distorted rock salt with a face-centered cubic sublattice containing predominantly Te atoms. We comment on earlier models based on smaller and much shorter simulations.

Kalikka, J.; Akola, J.; Jones, R. O.

2014-11-01

425

Edinburgh Research Explorer Europium-IV: An Incommensurately Modulated Crystal Structure  

E-print Network

Edinburgh Research Explorer Europium-IV: An Incommensurately Modulated Crystal Structure 2012, 'Europium-IV: An Incommensurately Modulated Crystal Structure in the Lanthanides' Physical Review to the work immediately and investigate your claim. Download date: 27. Jun. 2014 #12;Europium

Millar, Andrew J.

426

Electrical test structures replicated in silicon-on-insulator material  

SciTech Connect

Measurements of the linewidths of submicrometer features made by different metrology techniques have frequently been characterized by differences of up to 90 nm. The purpose of the work reported here is to address the special difficulties that this phenomenon presents to the certification of reference materials for the calibration of linewidth-measurement instruments. Accordingly, a new test structure has been designed, fabricated, and undergone preliminary tests. Its distinguishing characteristics are assured cross-sectional profile geometries with known side-wall slopes, surface planarity, and compositional uniformity when it is formed in mono-crystalline material at selected orientations to the crystal lattice. To allow the extraction of electrical linewidth, the structure is replicated in a silicon film of uniform conductivity which is separated from the silicon substrate by a buried oxide layer. The utilization of a Silicon-On-Insulator (SKI) substrate further allows the selective removal of substrate material from local regions below the reference features, thus facilitating measurements by optical and electron-beam transmission microscopy. The combination of planar feature surfaces having known side-wall slopes is anticipated to eliminate factors which are believed to be responsible for methods divergence in linewidth measurements, a capability which is a prerequisite for reliable certification of the linewidths of features on reference materials.

Cresswell, M.W.; Ghoshtagore, R.N.; Allen, R.A.; Linholm, L.W.; Villarrubia, J.S. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Sniegowski, J.J. [Sandia National Labs., Albuquerque, NM (United States)

1996-02-27

427

Crystal and molecular structure of N-methylpiperidine betaine hydrochloride  

NASA Astrophysics Data System (ADS)

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, ?=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.

Dega-Szafran, Z.; Szafran, M.; Dulewicz, E.; Addlagatta, A.; Jaskólski, M.

2003-06-01

428

Two new bismuth thiourea bromides: crystal structure, growth, and characterization.  

PubMed

Crystals of two new bismuth thiourea bromides, bismuth trithiourea bromide (Bi[CS(NH2)2]3Br3, BTB) and bismuth protonated-hexathiourea bromide (Bi[CS(NH2)2H]6Br9, BHB), have been successfully grown from hydrobromic acid solution with different pH values by slow evaporation. Single crystal X-ray diffraction reveals that BTB is isostructural to its Cl-analog crystallizing in a monoclinic space group Cc with unit cell dimensions of a = 8.6238(7) Å, b = 12.2506(11) Å, c = 15.5040(13) Å, ? = 90.7810(10)° and Z = 4. In contrast, BHB crystallizes in a trigonal space group R3[combining macron]c with unit cell dimensions of a = b = 12.748(17) Å, c = 40.45(11) Å, and Z = 6. The protonation of the thiourea in BHB is confirmed by the structure solution, IR and Raman spectroscopy. The UV diffuse reflection spectra clearly indicate that both of the two crystals have good optical transparency in the range below 2000 nm. Both compounds decompose above 190 °C, and BHB melts at around 140 °C while BTB possesses a phase transition at 145 °C as indicated by thermogravimetric (TG) and differential thermal analysis (DTA). PMID:24316978

Li, Ming; Li, R K

2014-02-14

429

Crystal structure of a putative isochorismatase hydrolase from Oleispira antarctica.  

PubMed

Isochorismatase-like hydrolases (IHL) constitute a large family of enzymes divided into five structural families (by SCOP). IHLs are crucial for siderophore-mediated ferric iron acquisition by cells. Knowledge of the structural characteristics of these molecules will enhance the understanding of the molecular basis of iron transport, and perhaps resolve which of the mechanisms previously proposed in the literature is the correct one. We determined the crystal structure of the apo-form of a putative isochorismatase hydrolase OaIHL (PDB code: 3LQY) from the antarctic ?-proteobacterium Oleispira antarctica, and did comparative sequential and structural analysis of its closest homologs. The characteristic features of all analyzed structures were identified and discussed. We also docked isochorismate to the determined crystal structure by in silico methods, to highlight the interactions of the active center with the substrate. The putative isochorismate hydrolase OaIHL from O. antarctica possesses the typical catalytic triad for IHL proteins. Its active center resembles those IHLs with a D-K-C catalytic triad, rather than those variants with a D-K-X triad. OaIHL shares some structural and sequential features with other members of the IHL superfamily. In silico docking results showed that despite small differences in active site composition, isochorismate binds to in the structure of OaIHL in a similar mode to its binding in phenazine biosynthesis protein PhzD (PDB code 1NF8). PMID:22350524

Goral, Anna M; Tkaczuk, Karolina L; Chruszcz, Maksymilian; Kagan, Olga; Savchenko, Alexei; Minor, Wladek

2012-03-01

430

Crystal structure of a putative isochorismatase hydrolase from Oleispira antarctica  

PubMed Central

Isochorismatase-like hydrolases (IHL) constitute a large family of enzymes divided into five structural families (by SCOP). IHLs are crucial for siderophore-mediated ferric iron acquisition by cells. Knowledge of the structural characteristics of these molecules will enhance the understanding of the molecular basis of iron transport, and perhaps resolve which of the mechanisms previously proposed in the literature is the correct one. We determined the crystal structure of the apo-form of a putative isochorismatase hydrolase OaIHL (PDB code: 3LQY) from the antarctic ?-proteobacterium Oleispira antarctica, and did comparative sequential and structural analysis of its closest homologs. The characteristic features of all analyzed structures were identified and discussed. We also docked isochorismate to the solved crystal structure by in silico methods, to highlight the interactions of the active center with the substrate. The putative isochorismate hydrolase OaIHL from Oleispira antarctica possesses the typical catalytic triad for IHL proteins. Its active center resembles those IHLs with a D-K-C catalytic triad, rather than those variants with a D-K-X triad. OaIHL shares some structural and sequential features with other members of the IHL superfamily. In silico docking results showed that despite small differences in active site composition, isochorismate binds to in the structure of OaIHL in a similar mode to its binding in phenazine biosynthesis protein PhzD (PDB code 1NF8). PMID:22350524

Goral, Anna M.; Tkaczuk, Karolina L.; Chruszcz, Maksymilian; Kagan, Olga; Savchenko, Alexei; Minor, Wladek

2012-01-01

431

Microstrip Photonic Crystals and their Application for Measurement Parameters of Materials  

Microsoft Academic Search

The computer simulation and experimental investigation of frequency dependencies of the reflectance and the transmittance of photonic crystals based on the microstrip structures in the frequency band 0-20 GHz have been performed. The investigations were performed for the photonic crystal with irregularity introduced as changed geometry size of the stripline conductor or changed substrate permittivity of one of the sequence

Dmitry A. Usanov; Alexander V. Skripal; Anton V. Abramov; Anton S. Bogolubov; Maxim Y. Kulikov

2008-01-01

432

Crystal structure and microstructure of ?-Er 2S 3  

Microsoft Academic Search

The atomic structure of Er2S3 was refined by single-crystal X-ray diffraction methods. The compound is isostructural to the ?-Ho2S3 structure type, which has monoclinic symmetry and space group P21\\/m, a=10.072 (1) Å, b=3.976 (2) Å, c=17.389 (2) Å, ?=98.66(1)°, Z=6. Refinement proceeded to R=0.037 for 1745 observed reflections. Experimental high-resolution micrographs (structural images) were obtained along the [010] zone axis

A. R Landa-Cánovas; U Amador; L. C Otero-D??az

2001-01-01

433

Crystal structure of four-stranded Oxytricha telomeric DNA  

NASA Technical Reports Server (NTRS)

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.

Kang, C.; Zhang, X.; Ratliff, R.; Moyzis, R.; Rich, A.

1992-01-01

434

The Rapid Crystallization Strategy for Structure-Based Inhibitor Design  

NASA Astrophysics Data System (ADS)

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.

Bergfors, Terese

435

Effects of nematic polymer liquid crystal on crystallization and structure of PET\\/Vectra blends  

Microsoft Academic Search

We investigate the effects of a nematic liquid crystalline polymer, Vectra A, on the structure and properties of its blends with a semicrystalline polymer, poly(ethylene terephthalate),PET. PET\\/Vectra blend composition ranged from 100\\/0 to 60\\/40. Real-time, in situ studies ofisothermal and non-isothermal melt crystallizations of these blends were conducted usingsimultaneous wide and small angle X-ray scattering (WAXS and SAXS), differentialscanning calorimetry

G. Georgiev; P. Cebe; M. Capel

2005-01-01

436

838 nature structural biology volume 8 number 10 october 2001 Crystal structure of the  

E-print Network

functions. Here we determine the crystal structure of the BRCT domain of human BRCA1 at 2.5 Å resolution to DNA damage. The structure provides a basis to predict the structural consequences of uncharacter- ized suppressor function of BRCA1. We predict that a similar packing arrange- ment exists in other DNA repair

Glover, Mark

437

EVO—Evolutionary algorithm for crystal structure prediction  

NASA Astrophysics Data System (ADS)

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.

Bahmann, Silvia; Kortus, Jens

2013-06-01

438

Gold binary-structured arrays based on monolayer colloidal crystals and their optical properties.  

PubMed

A simple and flexible route is presented to fabricate a gold binary-structured ordered array by one step based on non-shadow deposition on a plasma etching-induced dualistic monolayer colloidal crystal. Such a Au binary-structure array is built of hexagonally arranged nanoshells and nanorings which stand between two adjacent nanoshells. Six gold nanorings surround each nanoshell. The obtained arrays exhibit both the controllable surface-plasmon-resonance (SPR) properties of Au nanoshells and the strong electromagnetic-field-enhancement effects of Au nanorings, with the high structural stability of ordered arrays, and show promising potential as the substrate of surface-enhanced Raman scattering (SERS)-based devices. The method could also be suitable for fabrication of other material binary-structured arrays. This study is important in designing and fabricating basal materials for the next generation of multifunctional nanostructured devices. PMID:24599634

Liu, Guangqiang; Li, Xinhua; Wang, Wenbo; Zhou, Fei; Duan, Guotao; Li, Yue; Xu, Zongke; Cai, Weiping

2014-06-25

439

Dipole Parallel Alignment in the Crystal Structure of a Polar Biphenyl: 4-Acetyl-4-Methoxybiphenyl (AMB)  

E-print Network

-aligned polar molecules bearing biphenyl spacers. We are aware of only two reports of crystal structuresDipole Parallel Alignment in the Crystal Structure of a Polar Biphenyl: 4-Acetyl-4-Methoxybiphenyl.4 D and affords about 53% of maximal polar alignment. The polar crystal structure of syn-AMB contrasts

Glaser, Rainer

440

Fabrication of three-dimensional photonic crystal structures by interferometric lithography and nanoparticle self-assembly  

E-print Network

Fabrication of three-dimensional photonic crystal structures by interferometric lithography 2008 We report a simple approach to fabrication of three-dimensional photonic crystal structures. One to fabricate three-dimensional photonic crystals with void channels in a woodpile structure. The optical

New Mexico, University of

441

Structural materials: understanding atomic scale microstructures  

SciTech Connect

With the ability to locate and identify atoms in three dimensions, atom-probe tomography (APT) has revolutionized our understanding of structure-property relationships in materials used for structural applications. The atomic-scale details of clusters, second phases, and microstructural defects that control alloy properties have been investigated, providing an unprecedented level of detail on the origins of aging behavior, strength, creep, fracture toughness, corrosion, and irradiation resistance. Moreover, atomic-scale microscopy combined with atomistic simulation and theoretical modeling of material behavior can guide new alloy design. In this article, selected examples highlight how APT has led to a deeper understanding of materials structures and therefore properties, starting with the phase transformations controlling the aging and strengthening behavior of complex Al-, Fe-, and Ni-based alloys systems. The chemistry of interfaces and structural defects that play a crucial role in high-temperature strengthening, fracture, and corrosion resistance are also discussed, with particular reference to Zr- and Al-alloys and FeAl intermetallics.

Marquis, E A [University of Oxford; Miller, Michael K [ORNL; Blavette, D [Universite de Rouen, France; Ringer, S. P. [University of Sydney, Australia; Sudbrack, C [Northwestern University, Evanston; Smith, G.D.W. [University of Oxford

2009-01-01

442

Indigo carmine: An organic crystal as a positive-electrode material for rechargeable sodium batteries  

PubMed Central

Using sodium, instead of lithium, in rechargeable batteries is a way to circumvent the lithium's resource problem. The challenge is to find an electrode material that can reversibly undergo redox reactions in a sodium-electrolyte at the desired electrochemical potential. We proved that indigo carmine (IC, 5,5?-indigodisulfonic acid sodium salt) can work as a positive-electrode material in not only a lithium-, but also a sodium-electrolyte. The discharge capacity of the IC-electrode was ~100?mAh g?1 with a good cycle stability in either the Na or Li electrolyte, in which the average voltage was 1.8?V vs. Na+/Na and 2.2?V vs. Li+/Li, respectively. Two Na ions per IC are stored in the electrode during the discharge, testifying to the two-electron redox reaction. An X-ray diffraction analysis revealed a layer structure for the IC powder and the DFT calculation suggested the formation of a band-like structure in the crystal. PMID:24413423

Yao, Masaru; Kuratani, Kentaro; Kojima, Toshikatsu; Takeichi, Nobuhiko; Senoh, Hiroshi; Kiyobayashi, Tetsu

2014-01-01

443

Surface transport and band gap structure of exfoliated 2H-MoTe2 crystals  

NASA Astrophysics Data System (ADS)

Semiconducting transition metal dichalcogenides (TMDs) have emerged as materials that can be used to realize two-dimensional (2D) crystals possessing rather unique transport and optical properties. Most research has so far focused on sulfur and selenium compounds, while tellurium-based materials have attracted little attention so far. As a first step in the investigation of T