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Sample records for surface structure determinations

  1. Advances on surface structural determination by LEED

    International Nuclear Information System (INIS)

    Soares, Edmar A; De Carvalho, Vagner E; De Castilho, Caio M C

    2011-01-01

    In the last 40 years, low energy electron diffraction (LEED) has proved to be the most reliable quantitative technique for surface structural determination. In this review, recent developments related to the theory that gives support to LEED structural determination are discussed under a critical analysis of the main theoretical approximation-the muffin-tin calculation. The search methodologies aimed at identifying the best matches between theoretical and experimental intensity versus voltage curves are also considered, with the most recent procedures being reviewed in detail. (topical review)

  2. Structure determination by photoelectron diffraction of small molecules on surfaces

    International Nuclear Information System (INIS)

    Booth, N.A.

    1998-05-01

    The synchrotron radiation based technique of Photoelectron Diffraction (PhD) has been applied to three adsorption systems. Structure determinations, are presented for each system which involve the adsorption of small molecules on the low index {110} plane of single crystal Cu and Ni substrates. For the NH 3 -Cu(110) system PhD was successful in determining a N-Cu bondlength of 2.05 ± 0.03 A as well as values for the anisotropic vibrational amplitudes of the N and an expansion of the 1st to 2nd Cu substrate layer spacing from the bulk value of 0.08 ± 0.08 A. The most significant and surprising structural parameter determined for this system was that the N atom occupies an asymmetric adsorption site. Rather than being situated in the expected high symmetry atop site the N atom was found to be offset parallel to the surface by 0.37 ± 0.12 A in the [001] azimuth. In studying the glycine-Cu(110) system the adsorption structure of an amino-acid has been quantified. The local adsorption geometries of all the atoms involved in the molecule to surface bond have been determined. The glycine molecule is found to be bonded to the surface via both its amino and carboxylate functional groups. The molecule straddles two [11-bar0] rows of the Cu substrate. The two O atoms are found to be in identical sites both approximately atop Cu atoms on the [11-bar0] rows offset parallel to the surface by 0.80 ± 0.05 A in the [001] azimuth, the O-Cu bondlength was found to be 2.03 ± 0.05 A. The N atom was also found to adsorb in an approximately atop geometry but offset parallel to the surface by 0.24 ± 0.10A in the [11-bar0] direction, the N-Cu bondlength was found to be 2.05± 0.05 A. PhD was unsuccessful in determining the positions of the two C atoms that form a bridge between the two functional groups bonded to the surface due to difficulties in separating the two inequivalent contributions to the final intensity modulation function. For the CN-Ni(110) system both PhD and Near Edge

  3. Simple surface structure determination from Fourier transforms of angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Y. [Pennsylvania State Univ., University Park, PA (United States)]|[Lawrence Berkeley Lab., CA (United States); Shirley, D.A. [Pennsylvania State Univ., University Park, PA (United States)

    1995-02-01

    The authors show by Fourier analyses of experimental data, with no further treatment, that the positions of all the strong peaks in Fourier transforms of angle-resolved photoemission extended fine structure (ARPEFS) from adsorbed surfaces can be explicitly predicted from a trial structure with an accuracy of about {+-} 0.3 {angstrom} based on a single-scattering cluster model together with the concept of a strong backscattering cone, and without any additional analysis. This characteristic of ARPEFS Fourier transforms can be developed as a simple method for determining the structures of adsorbed surfaces to an accuracy of about {+-} 0.1 {angstrom}.

  4. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  5. Low-energy electron diffraction experiment, theory and surface structure determination

    CERN Document Server

    Hove, Michel A; Chan, Chi-Ming

    1986-01-01

    Surface crystallography plays the same fundamental role in surface science which bulk crystallography has played so successfully in solid-state physics and chemistry. The atomic-scale structure is one of the most important aspects in the understanding of the behavior of surfaces in such widely diverse fields as heterogeneous catalysis, microelectronics, adhesion, lubrication, cor­ rosion, coatings, and solid-solid and solid-liquid interfaces. Low-Energy Electron Diffraction or LEED has become the prime tech­ nique used to determine atomic locations at surfaces. On one hand, LEED has yielded the most numerous and complete structural results to date (almost 200 structures), while on the other, LEED has been regarded as the "technique to beat" by a variety of other surface crystallographic methods, such as photoemission, SEXAFS, ion scattering and atomic diffraction. Although these other approaches have had impressive successes, LEED has remained the most productive technique and has shown the most versatility...

  6. Surface buckling of black phosphorus: Determination, origin, and influence on electronic structure

    Science.gov (United States)

    Dai, Zhongwei; Jin, Wencan; Yu, Jie-Xiang; Grady, Maxwell; Sadowski, Jerzy T.; Kim, Young Duck; Hone, James; Dadap, Jerry I.; Zang, Jiadong; Osgood, Richard M.; Pohl, Karsten

    2017-12-01

    The surface structure of black phosphorus materials is determined using surface-sensitive dynamical microspot low energy electron diffraction (μ LEED ) analysis using a high spatial resolution low energy electron microscopy (LEEM) system. Samples of (i) crystalline cleaved black phosphorus (BP) at 300 K and (ii) exfoliated few-layer phosphorene (FLP) of about 10 nm thickness which were annealed at 573 K in vacuum were studied. In both samples, a significant surface buckling of 0.22 Å and 0.30 Å, respectively, is measured, which is one order of magnitude larger than previously reported. As direct evidence for large buckling, we observe a set of (for the flat surface forbidden) diffraction spots. Using first-principles calculations, we find that the presence of surface vacancies is responsible for the surface buckling in both BP and FLP, and is related to the intrinsic hole doping of phosphoresce materials previously reported.

  7. Structural determinants for protein adsorption/non-adsorption to silica surface

    International Nuclear Information System (INIS)

    Mathe, Christelle; Devineau, Stephanie; Aude, Jean-Christophe; Lagniel, Gilles; Chedin, Stephane; Legros, Veronique; Mathon, Marie-Helene; Renault, Jean-Philippe; Pin, Serge; Boulard, Yves; Labarre, Jean

    2013-01-01

    The understanding of the mechanisms involved in the interaction of proteins with inorganic surfaces is of major interest in both fundamental research and applications such as nano-technology. However, despite intense research, the mechanisms and the structural determinants of protein/surface interactions are still unclear. We developed a strategy consisting in identifying, in a mixture of hundreds of soluble proteins, those proteins that are adsorbed on the surface and those that are not. If the two protein subsets are large enough, their statistical comparative analysis must reveal the physicochemical determinants relevant for adsorption versus non-adsorption. This methodology was tested with silica nanoparticles. We found that the adsorbed proteins contain a higher number of charged amino acids, particularly arginine, which is consistent with involvement of this basic amino acid in electrostatic interactions with silica. The analysis also identified a marked bias toward low aromatic amino acid content (phenylalanine, tryptophan, tyrosine and histidine) in adsorbed proteins. Structural analyses and molecular dynamics simulations of proteins from the two groups indicate that non-adsorbed proteins have twice as many p-p interactions and higher structural rigidity. The data are consistent with the notion that adsorption is correlated with the flexibility of the protein and with its ability to spread on the surface. Our findings led us to propose a refined model of protein adsorption. (authors)

  8. Structural determinants for protein adsorption/non-adsorption to silica surface.

    Directory of Open Access Journals (Sweden)

    Christelle Mathé

    Full Text Available The understanding of the mechanisms involved in the interaction of proteins with inorganic surfaces is of major interest in both fundamental research and applications such as nanotechnology. However, despite intense research, the mechanisms and the structural determinants of protein/surface interactions are still unclear. We developed a strategy consisting in identifying, in a mixture of hundreds of soluble proteins, those proteins that are adsorbed on the surface and those that are not. If the two protein subsets are large enough, their statistical comparative analysis must reveal the physicochemical determinants relevant for adsorption versus non-adsorption. This methodology was tested with silica nanoparticles. We found that the adsorbed proteins contain a higher number of charged amino acids, particularly arginine, which is consistent with involvement of this basic amino acid in electrostatic interactions with silica. The analysis also identified a marked bias toward low aromatic amino acid content (phenylalanine, tryptophan, tyrosine and histidine in adsorbed proteins. Structural analyses and molecular dynamics simulations of proteins from the two groups indicate that non-adsorbed proteins have twice as many π-π interactions and higher structural rigidity. The data are consistent with the notion that adsorption is correlated with the flexibility of the protein and with its ability to spread on the surface. Our findings led us to propose a refined model of protein adsorption.

  9. Determination of the object surface function by structured light: application to the study of spinal deformities

    International Nuclear Information System (INIS)

    Buendia, M.; Salvador, R.; Cibrian, R.; Sotoca, J.M.; Laguia, M.

    1999-01-01

    The projection of structured light is a technique frequently used to determine the surface shape of an object. In this paper, a new procedure is described that efficiently resolves the correspondence between the knots of the projected grid and those obtained on the object when the projection is made. The method is based on the use of three images of the projected grid. In two of them the grid is projected over a flat surface placed, respectively, before and behind the object; both images are used for calibration. In the third image the grid is projected over the object. It is not reliant on accurate determination of the camera and projector pair relative to the grid and object. Once the method is calibrated, we can obtain the surface function by just analysing the projected grid on the object. The procedure is especially suitable for the study of objects without discontinuities or large depth gradients. It can be employed for determining, in a non-invasive way, the patient's back surface function. Symmetry differences permit a quantitative diagnosis of spinal deformities such as scoliosis. (author)

  10. Beyond Cassie equation: Local structure of heterogeneous surfaces determines the contact angles of microdroplets

    Science.gov (United States)

    Zhang, Bo; Wang, Jianjun; Liu, Zhiping; Zhang, Xianren

    2014-01-01

    The application of Cassie equation to microscopic droplets is recently under intense debate because the microdroplet dimension is often of the same order of magnitude as the characteristic size of substrate heterogeneities, and the mechanism to describe the contact angle of microdroplets is not clear. By representing real surfaces statistically as an ensemble of patterned surfaces with randomly or regularly distributed heterogeneities (patches), lattice Boltzmann simulations here show that the contact angle of microdroplets has a wide distribution, either continuous or discrete, depending on the patch size. The origin of multiple contact angles observed is ascribed to the contact line pinning effect induced by substrate heterogeneities. We demonstrate that the local feature of substrate structure near the contact line determines the range of contact angles that can be stabilized, while the certain contact angle observed is closely related to the contact line width. PMID:25059292

  11. Surface structural determination of UO2(111) using MeV ions

    International Nuclear Information System (INIS)

    Thompson, K.A.; Ellis, W.P.; Taylor, T.N.; Valone, S.M.; Maggiore, C.J.

    1983-01-01

    The UO 2 (111) surface was studied using MeV ions incident along the and directions. In addition, this surface was well characterized by LEED and Auger analysis. A resonance at 3.05 MeV for 4 He elastic scattering from 16 O made it possible to study the surface peaks for uranium and oxygen simultaneously. By combining previous surface studies with detailed analysis of the surface peaks and rocking curves for this compound material, an outward relaxation of 0.19 A +- 0.01 A was determined for uranium

  12. The use of angle resolved electron and photon stimulated desorption for the determination of molecular structure at surfaces

    International Nuclear Information System (INIS)

    Madey, T.E.; Stockbauer, R.

    1983-01-01

    A brief review of recent data related to the use of angle-resolved electron stimulated desorption and photon stimulated desorption in determining the structures of molecules at surfaces is made. Examples include a variety of structural assignments based on ESIAD (electron stimulated desorption ion angular distributions), the observation of short-range local ordering effects induced in adsorbed molecules by surface impurities, and the application of photon stimulated desorption to both ionic and covalent adsorbate systems. (Author) [pt

  13. The power of joint application of LEED and DFT in quantitative surface structure determination

    International Nuclear Information System (INIS)

    Heinz, K; Hammer, L; Mueller, S

    2008-01-01

    It is demonstrated for several cases that the joint application of low-energy electron diffraction (LEED) and structural calculations using density functional theory (DFT) can retrieve the correct surface structure even though single application of both methods fails. On the experimental side (LEED) the failure can be due to the simultaneous presence of weak and very strong scatterers or to an insufficient data base leaving different structures with the same quality of fit between experimental data and calculated model intensities. On the theory side (DFT) it can be difficult to predict the coverage of an adsorbate or two different structures may own almost the same total energy, but only one of the structures is assumed in experiment due to formation kinetics. It is demonstrated how in the different cases the joint application of both methods-which yield about the same structural precision-offers a way out of the dilemma

  14. Comparison of segmentation techniques to determine the geometric parameters of structured surfaces

    International Nuclear Information System (INIS)

    MacAulay, Gavin D; Giusca, Claudiu L; Leach, Richard K; Senin, Nicola

    2014-01-01

    Structured surfaces, defined as surfaces characterized by topography features whose shape is defined by design specifications, are increasingly being used in industry for a variety of applications, including improving the tribological properties of surfaces. However, characterization of such surfaces still remains an issue. Techniques have been recently proposed, based on identifying and extracting the relevant features from a structured surface so they can be verified individually, using methods derived from those commonly applied to standard-sized parts. Such emerging approaches show promise but are generally complex and characterized by multiple data processing steps making performance difficult to assess. This paper focuses on the segmentation step, i.e. partitioning the topography so that the relevant features can be separated from the background. Segmentation is key for defining the geometric boundaries of the individual feature, which in turn affects any computation of feature size, shape and localization. This paper investigates the effect of varying the segmentation algorithm and its controlling parameters by considering a test case: a structured surface for bearing applications, the relevant features being micro-dimples designed for friction reduction. In particular, the mechanisms through which segmentation leads to identification of the dimple boundary and influences dimensional properties, such as dimple diameter and depth, are illustrated. It is shown that, by using different methods and control parameters, a significant range of measurement results can be achieved, which may not necessarily agree. Indications on how to investigate the influence of each specific choice are given; in particular, stability of the algorithms with respect to control parameters is analyzed as a means to investigate ease of calibration and flexibility to adapt to specific, application-dependent characterization requirements. (paper)

  15. Template-controlled mineralization: Determining film granularity and structure by surface functionality patterns

    Directory of Open Access Journals (Sweden)

    Nina J. Blumenstein

    2015-08-01

    Full Text Available We present a promising first example towards controlling the properties of a self-assembling mineral film by means of the functionality and polarity of a substrate template. In the presented case, a zinc oxide film is deposited by chemical bath deposition on a nearly topography-free template structure composed of a pattern of two self-assembled monolayers with different chemical functionality. We demonstrate the template-modulated morphological properties of the growing film, as the surface functionality dictates the granularity of the growing film. This, in turn, is a key property influencing other film properties such as conductivity, piezoelectric activity and the mechanical properties. A very pronounced contrast is observed between areas with an underlying fluorinated, low energy template surface, showing a much more (almost two orders of magnitude coarse-grained film with a typical agglomerate size of around 75 nm. In contrast, amino-functionalized surface areas induce the growth of a very smooth, fine-grained surface with a roughness of around 1 nm. The observed influence of the template on the resulting clear contrast in morphology of the growing film could be explained by a contrast in surface adhesion energies and surface diffusion rates of the nanoparticles, which nucleate in solution and subsequently deposit on the functionalized substrate.

  16. Fibrillar Structure and Charge Determine the Interaction of Polyglutamine Protein Aggregates with the Cell Surface*

    Science.gov (United States)

    Trevino, R. Sean; Lauckner, Jane E.; Sourigues, Yannick; Pearce, Margaret M.; Bousset, Luc; Melki, Ronald; Kopito, Ron R.

    2012-01-01

    The pathogenesis of most neurodegenerative diseases, including transmissible diseases like prion encephalopathy, inherited disorders like Huntington disease, and sporadic diseases like Alzheimer and Parkinson diseases, is intimately linked to the formation of fibrillar protein aggregates. It is becoming increasingly appreciated that prion-like intercellular transmission of protein aggregates can contribute to the stereotypical spread of disease pathology within the brain, but the mechanisms underlying the binding and uptake of protein aggregates by mammalian cells are largely uninvestigated. We have investigated the properties of polyglutamine (polyQ) aggregates that endow them with the ability to bind to mammalian cells in culture and the properties of the cell surface that facilitate such uptake. Binding and internalization of polyQ aggregates are common features of mammalian cells and depend upon both trypsin-sensitive and trypsin-resistant saturable sites on the cell surface, suggesting the involvement of cell surface proteins in this process. polyQ aggregate binding depends upon the presence of a fibrillar amyloid-like structure and does not depend upon electrostatic interaction of fibrils with the cell surface. Sequences in the huntingtin protein that flank the amyloid-forming polyQ tract also influence the extent to which aggregates are able to bind to cell surfaces. PMID:22753412

  17. Surface structure of VN0.89(100) determined by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Gauthier, Y.; Joly, Y.; Rundgren, J.; Johansson, L.I.; Wincott, P.

    1990-01-01

    The structure of the (100) surface of substoichiometric vanadium nitride was studied by low-energy electron diffraction on a VN 0.89 (100) sample. A simple 1x1 (100) diffractogram was observed. To describe the electron scattering in substoichiometric VN we apply the averaged t-matrix approximation to the nitrogen atoms. We find that the best structural model is one having no nitrogen vacancies in the surface region. It turns out that the first layer is rippled with the N atoms displaced 0.17 A above the subplane of V atoms, that the spacing between this subplane and the second layer is 1.92 A, and that the spacing between the second and the third layer is 2.08 A. In relation to the (100) spacing of the bulk, 2.06 A, these spacings are 6.8% contracted and 1% expanded, respectively. The Debye temperature of VN is found to be 660 K in good agreement with a prediction from entropy data and from neutron diffraction and helium-ion channeling experiments

  18. Normal emission photoelectron diffraction: a new technique for determining surface structure

    International Nuclear Information System (INIS)

    Kevan, S.D.

    1980-05-01

    One technique, photoelectron diffraction (PhD) is characterized. It has some promise in surmounting some of the problems of LEED. In PhD, the differential (angle-resolved) photoemission cross-section of a core level localized on an adsorbate atom is measured as a function of some final state parameter. The photoemission final state consists of two components, one of which propagates directly to the detector and another which scatters off the surface and then propagates to the detector. These are added coherently, and interference between the two manifests itself as cross-section oscillations which are sensitive to the local structure around the absorbing atom. We have shown that PhD deals effectively with two- and probably also three-dimensionally disordered systems. Its non-damaging and localized, atom-specific nature gives PhD a good deal of promise in dealing with molecular overlayer systems. It is concluded that while PhD will never replace LEED, it may provide useful, complementary and possibly also more accurate surface structural information

  19. Determination of Surface Potential and Electrical Double-Layer Structure at the Aqueous Electrolyte-Nanoparticle Interface

    Directory of Open Access Journals (Sweden)

    Matthew A. Brown

    2016-01-01

    Full Text Available The structure of the electrical double layer has been debated for well over a century, since it mediates colloidal interactions, regulates surface structure, controls reactivity, sets capacitance, and represents the central element of electrochemical supercapacitors. The surface potential of such surfaces generally exceeds the electrokinetic potential, often substantially. Traditionally, a Stern layer of nonspecifically adsorbed ions has been invoked to rationalize the difference between these two potentials; however, the inability to directly measure the surface potential of dispersed systems has rendered quantitative measurements of the Stern layer potential, and other quantities associated with the outer Helmholtz plane, impossible. Here, we use x-ray photoelectron spectroscopy from a liquid microjet to measure the absolute surface potentials of silica nanoparticles dispersed in aqueous electrolytes. We quantitatively determine the impact of specific cations (Li^{+}, Na^{+}, K^{+}, and Cs^{+} in chloride electrolytes on the surface potential, the location of the shear plane, and the capacitance of the Stern layer. We find that the magnitude of the surface potential increases linearly with the hydrated-cation radius. Interpreting our data using the simplest assumptions and most straightforward understanding of Gouy-Chapman-Stern theory reveals a Stern layer whose thickness corresponds to a single layer of water molecules hydrating the silica surface, plus the radius of the hydrated cation. These results subject electrical double-layer theories to direct and falsifiable tests to reveal a physically intuitive and quantitatively verified picture of the Stern layer that is consistent across multiple electrolytes and solution conditions.

  20. Determination of Surface Potential and Electrical Double-Layer Structure at the Aqueous Electrolyte-Nanoparticle Interface

    Science.gov (United States)

    Brown, Matthew A.; Abbas, Zareen; Kleibert, Armin; Green, Richard G.; Goel, Alok; May, Sylvio; Squires, Todd M.

    2016-01-01

    The structure of the electrical double layer has been debated for well over a century, since it mediates colloidal interactions, regulates surface structure, controls reactivity, sets capacitance, and represents the central element of electrochemical supercapacitors. The surface potential of such surfaces generally exceeds the electrokinetic potential, often substantially. Traditionally, a Stern layer of nonspecifically adsorbed ions has been invoked to rationalize the difference between these two potentials; however, the inability to directly measure the surface potential of dispersed systems has rendered quantitative measurements of the Stern layer potential, and other quantities associated with the outer Helmholtz plane, impossible. Here, we use x-ray photoelectron spectroscopy from a liquid microjet to measure the absolute surface potentials of silica nanoparticles dispersed in aqueous electrolytes. We quantitatively determine the impact of specific cations (Li+ , Na+ , K+ , and Cs+ ) in chloride electrolytes on the surface potential, the location of the shear plane, and the capacitance of the Stern layer. We find that the magnitude of the surface potential increases linearly with the hydrated-cation radius. Interpreting our data using the simplest assumptions and most straightforward understanding of Gouy-Chapman-Stern theory reveals a Stern layer whose thickness corresponds to a single layer of water molecules hydrating the silica surface, plus the radius of the hydrated cation. These results subject electrical double-layer theories to direct and falsifiable tests to reveal a physically intuitive and quantitatively verified picture of the Stern layer that is consistent across multiple electrolytes and solution conditions.

  1. Surface structure of Bi2Se3(111) determined by low-energy electron diffraction and surface x-ray diffraction

    DEFF Research Database (Denmark)

    dos Reis, Diogo Duarte; Barreto, Lucas; Bianchi, Marco

    2013-01-01

    The surface structure of the prototypical topological insulator Bi2Se3 is determined by low-energy electron diffraction and surface x-ray diffraction at room temperature. Both approaches show that the crystal is terminated by an intact quintuple layer. Specifically, an alternative termination by ...... by a bismuth bilayer is ruled out. Surface relaxations obtained by both techniques are in good agreement with each other and found to be small. This includes the relaxation of the van der Waals gap between the first two quintuple layers....

  2. Ultrathin Pt films on Ni(111): Structure determined by surface x-ray diffraction

    International Nuclear Information System (INIS)

    Robach, O.; Isern, H.; Quiros, C.; Ferrer, S.; Steadman, P.; Peters, K. F.

    2003-01-01

    The growth of platinum on a nickel (111) single crystal under ultrahigh vacuum conditions was studied using surface x-ray diffraction on the ID03 beamline of the ESRF. Film thickness ranged from one to eight monoatomic layers (ML). Specular reflectivity was used to determine the growth mode and vertical lattice parameter of the Pt film. A two-dimensional (2D) growth up to 1 ML followed by more 3D growth was found. A small expansion of the Pt vertical lattice parameter was found. The Pt in-plane lattice parameter was measured. Its relaxation was found to be very slow, with a residual contraction of 2.3% in an 8-ML-thick film (with respect to bulk Pt). A Ni crystal truncation rod measured before and after growing 1 ML of Pt revealed the presence of a small amount of pseudomorphic Pt, adsorbed on both fcc and hcp sites. The stacking of the (111) Pt planes was investigated by measuring stacking-sensitive Pt diffraction rods. A strong tendency to stacking reversal was found at room temperature, with an amount of 'reversed' Pt about ten times higher than the amount of Pt with the same stacking as the Ni. An eight-layer Ni film on Pt(111) was also studied for comparison

  3. Determination of line profiles on nano-structured surfaces using EUV and x-ray scattering

    Science.gov (United States)

    Soltwisch, Victor; Wernecke, Jan; Haase, Anton; Probst, Jürgen; Schoengen, Max; Krumrey, Michael; Scholze, Frank; Pomplun, Jan; Burger, Sven

    2014-09-01

    Non-imaging techniques like X-ray scattering are supposed to play an important role in the further development of CD metrology for the semiconductor industry. Grazing Incidence Small Angle X-ray Scattering (GISAXS) provides directly assessable information on structure roughness and long-range periodic perturbations. The disadvantage of the method is the large footprint of the X-ray beam on the sample due to the extremely shallow angle of incidence. This can be overcome by using wavelengths in the extreme ultraviolet (EUV) spectral range, EUV small angle scattering (EUVSAS), which allows for much steeper angles of incidence but preserves the range of momentum transfer that can be observed. Generally, the potentially higher momentum transfer at shorter wavelengths is counterbalanced by decreasing diffraction efficiency. This results in a practical limit of about 10 nm pitch for which it is possible to observe at least the +/- 1st diffraction orders with reasonable efficiency. At the Physikalisch-Technische Bundesanstalt (PTB), the available photon energy range extends from 50 eV up to 10 keV at two adjacent beamlines. PTB commissioned a new versatile Ellipso-Scatterometer which is capable of measuring 6" square substrates in a clean, hydrocarbon-free environment with full flexibility regarding the direction of the incident light polarization. The reconstruction of line profiles using a geometrical model with six free parameters, based on a finite element method (FEM) Maxwell solver and a particle swarm based least-squares optimization yielded consistent results for EUV-SAS and GISAXS. In this contribution we present scatterometry data for line gratings and consistent reconstruction results of the line geometry for EUV-SAS and GISAXS.

  4. Conformational analysis of an acyclic tetrapeptide: ab-initio structure determination from X-ray powder diffraction, Hirshfeld surface analysis and electronic structure.

    Science.gov (United States)

    Das, Uday; Naskar, Jishu; Mukherjee, Alok Kumar

    2015-12-01

    A terminally protected acyclic tetrapeptide has been synthesized, and the crystal structure of its hydrated form, Boc-Tyr-Aib-Tyr-Ile-OMe·2H2O (1), has been determined directly from powder X-ray diffraction data. The backbone conformation of tetrapeptide (1) exhibiting two consecutive β-turns is stabilized by two 4 → 1 intramolecular N-H · · · O hydrogen bonds. In the crystalline state, the tetrapeptide molecules are assembled through water-mediated O-H · · · O hydrogen bonds to form two-dimensional molecular sheets, which are further linked by intermolecular C-H · · · O hydrogen bonds into a three-dimensional supramolecular framework. The molecular electrostatic potential (MEP) surface of (1) has been used to supplement the crystallographic observations. The nature of intermolecular interactions in (1) has been analyzed quantitatively through the Hirshfeld surface and two-dimensional fingerprint plot. The DFT optimized molecular geometry of (1) agrees closely with that obtained from the X-ray structure analysis. The present structure analysis of Boc-Tyr-Aib-Tyr-Ile-OMe·2H2 O (1) represents a case where ab-initio crystal structure of an acyclic tetrapeptide with considerable molecular flexibility has been accomplished from laboratory X-ray powder diffraction data. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.

  5. Surface structure determination of group 11 metals adsorbed on a rhenium(10 anti 10) surface by low-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Messahel, Lyria

    2012-11-12

    This thesis deals with the computational surface determination of various long-range ordered phases formed by thin films of copper, silver, and gold adsorbed on the rhenium- (10 anti 10) surface. It is based upon LEED-I,V curves for these phases that were recorded in the course of detailed experimental investigations of the respective films carried out in our group (using techniques such as LEED, MEED, and TPD). In order to solve the intricate puzzle of surface structural analysis, the electron elastic scattering behaviour of the investigated coinage metal phases was calculated using the Erlangen TensErLEED program package. Thereby first a set of theoretical LEED-I,V curves is derived for a guessed reference structure. Subsequently its structural input parameters are varied in a trial-and-error procedure until optimal agreement between experiment and theory is attained. The (1 x 1) phases formed by the deposited metals were tackled first to establish an absolute coverage calibration and to elucidate the respective growth modes on the Re(10 anti 10) surface. In all three cases the (1 x 1) structure is developed best at a coverage {Theta}{sub Cu,Ag,Au}=2 ML=1 BL. Extension of the investigation to experimental I,V curves for higher Cu coverages revealed that this element continues to grow bilayerwise, thereby retaining the Re hcp morphology. Ag, in contrast to Cu and Au, happens not to grow as homogeneously, and the TPD data suggest that Ag films exhibit the so-called simultaneous-multilayer (SM) growth mode. The following analysis of the sub-bilayer coverage range shows that the three systems exhibit considerable differences. While Cu, having a negative lattice misfit compared to Re, shows no long-range ordered superstructures, Ag and Au with a similar positive misfit form a couple of such phases. Ag features both a (1 x 4) phase, stable at ambient temperatures, that upon heating transforms into a c(2 x 2) phase that only exists at elevated temperatures. The

  6. Surface structure determination of group 11 metals adsorbed on a rhenium(10 anti 10) surface by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Messahel, Lyria

    2012-01-01

    This thesis deals with the computational surface determination of various long-range ordered phases formed by thin films of copper, silver, and gold adsorbed on the rhenium- (10 anti 10) surface. It is based upon LEED-I,V curves for these phases that were recorded in the course of detailed experimental investigations of the respective films carried out in our group (using techniques such as LEED, MEED, and TPD). In order to solve the intricate puzzle of surface structural analysis, the electron elastic scattering behaviour of the investigated coinage metal phases was calculated using the Erlangen TensErLEED program package. Thereby first a set of theoretical LEED-I,V curves is derived for a guessed reference structure. Subsequently its structural input parameters are varied in a trial-and-error procedure until optimal agreement between experiment and theory is attained. The (1 x 1) phases formed by the deposited metals were tackled first to establish an absolute coverage calibration and to elucidate the respective growth modes on the Re(10 anti 10) surface. In all three cases the (1 x 1) structure is developed best at a coverage Θ Cu,Ag,Au =2 ML=1 BL. Extension of the investigation to experimental I,V curves for higher Cu coverages revealed that this element continues to grow bilayerwise, thereby retaining the Re hcp morphology. Ag, in contrast to Cu and Au, happens not to grow as homogeneously, and the TPD data suggest that Ag films exhibit the so-called simultaneous-multilayer (SM) growth mode. The following analysis of the sub-bilayer coverage range shows that the three systems exhibit considerable differences. While Cu, having a negative lattice misfit compared to Re, shows no long-range ordered superstructures, Ag and Au with a similar positive misfit form a couple of such phases. Ag features both a (1 x 4) phase, stable at ambient temperatures, that upon heating transforms into a c(2 x 2) phase that only exists at elevated temperatures. The structure

  7. Determination of retinal surface area.

    Science.gov (United States)

    Nagra, Manbir; Gilmartin, Bernard; Thai, Ngoc Jade; Logan, Nicola S

    2017-09-01

    Previous attempts at determining retinal surface area and surface area of the whole eye have been based upon mathematical calculations derived from retinal photographs, schematic eyes and retinal biopsies of donor eyes. 3-dimensional (3-D) ocular magnetic resonance imaging (MRI) allows a more direct measurement, it can be used to image the eye in vivo, and there is no risk of tissue shrinkage. The primary purpose of this study is to compare, using T2-weighted 3D MRI, retinal surface areas for superior-temporal (ST), inferior-temporal (IT), superior-nasal (SN) and inferior-nasal (IN) retinal quadrants. An ancillary aim is to examine whether inter-quadrant variations in area are concordant with reported inter-quadrant patterns of susceptibility to retinal breaks associated with posterior vitreous detachment (PVD). Seventy-three adult participants presenting without retinal pathology (mean age 26.25 ± 6.06 years) were scanned using a Siemens 3-Tesla MRI scanner to provide T2-weighted MR images that demarcate fluid-filled internal structures for the whole eye and provide high-contrast delineation of the vitreous-retina interface. Integrated MRI software generated total internal ocular surface area (TSA). The second nodal point was used to demarcate the origin of the peripheral retina in order to calculate total retinal surface area (RSA) and quadrant retinal surface areas (QRSA) for ST, IT, SN, and IN quadrants. Mean spherical error (MSE) was -2.50 ± 4.03D and mean axial length (AL) 24.51 ± 1.57 mm. Mean TSA and RSA for the RE were 2058 ± 189 and 1363 ± 160 mm 2 , respectively. Repeated measures anova for QRSA data indicated a significant difference within-quadrants (P area/mm increase in AL. Although the differences between QRSAs are relatively small, there was evidence of concordance with reported inter-quadrant patterns of susceptibility to retinal breaks associated with PVD. The data allow AL to be converted to QRSAs, which will assist further

  8. Surface structure of AU3Cu(001)

    DEFF Research Database (Denmark)

    Eckstein, G.A.; Maupai, S.; Dakkouri, A.S.

    1999-01-01

    The surface morphology, composition, and structure of Au3Cu(001) as determined by scanning tunneling microscopy and surface x-ray diffraction are presented. Atomic resolution STM images reveal distinctive geometric features. The analysis of the surface x-ray diffraction data provides clear evidence...... for the surface structure. [S0163-1829(99)04535-X]....

  9. The structure of stepped surfaces

    International Nuclear Information System (INIS)

    Algra, A.J.

    1981-01-01

    The state-of-the-art of Low Energy Ion Scattering (LEIS) as far as multiple scattering effects are concerned, is discussed. The ion fractions of lithium, sodium and potassium scattered from a copper (100) surface have been measured as a function of several experimental parameters. The ratio of the intensities of the single and double scattering peaks observed in ion scattering spectroscopy has been determined and ion scattering spectroscopy applied in the multiple scattering mode is used to determine the structure of a stepped Cu(410) surface. The average relaxation of the (100) terraces of this surface appears to be very small. The adsorption of oxygen on this surface has been studied with LEIS and it is indicated that oxygen absorbs dissociatively. (C.F.)

  10. A system for the determination of surface strain in the measurement of residual stress in structural elements in mechanical engineering

    International Nuclear Information System (INIS)

    Boehm, W.; Stuecker, E.; Wolf, H.

    1975-01-01

    The device is made up of an integrated module which can be glued to the measuring point. It consists of a strain gauge rosette system to determine surface strains which is installed on a baseplate. Each of the strain gauges of the system has two connection wires. One of these connection wires each is led to a common connection point, whilst the others lead to separate connection points. The layer of strain gauges is covered with a cover plate equipped with openings which leave open the connection points. The connection wires leading from the connection points are soldered into these openings, the solder in addition arresting the baseplate and the cover plate relative to each other. In addition, the solder constitutes soldered support points for the feeder lines. The cover plate may be transparent or have a coordinate system to indicate the locations of the strain gauges. (DG/RF) [de

  11. Structure of the moon's surface

    CERN Document Server

    Fielder, Gilbert

    1961-01-01

    Structure of the Moon's Surface aims to assemble and marshal relevant matter, and to produce a largely unprejudiced text which brings lunar studies up to date and stresses the importance of certain features of the Moon which have frequently been disregarded in the past, largely because of lack of knowledge about them. The book contains 14 chapters organized into two parts. Part I reviews and summarizes important physical problems. These include the liberations of the moon; height determinations of points of the moon's surface; the figure of the moon; and the moon's temperature and atmosphere.

  12. Structure determination of the Si(001)-(2 x 1)-H reconstruction by surface X-ray diffraction: Weakening of the dimer bond by the addition of hydrogen

    DEFF Research Database (Denmark)

    Lauridsen, E.M.; Baker, J.; Nielsen, M.

    2000-01-01

    The atomic structure of the monohydride Si(001)-(2 x 1)-H reconstruction has been investigated by surface X-ray diffraction. Atomic relaxations down to the eighth layer have been determined. The bond length of the hydrogenated silicon dimers was found to be 2.47 +/- 0.02 Angstrom. which is longer...... than the dimer bond of the clean (2 x 1)-reconstructed Si(001) surface and also 5% longer than the bulk bond length of 2.35 Angstrom. The differences to the (2 x 1) structure of the clean surface are discussed in terms of the elimination of the weak pi-bond character of the dimer bond by the addition...

  13. Structure determination of the ordered (2 × 1) phase of NiSi surface alloy on Ni(111) using low-energy electron diffraction

    Science.gov (United States)

    Sazzadur Rahman, Md.; Amirul Islam, Md.; Saha, Bidyut Baran; Nakagawa, Takeshi; Mizuno, Seigi

    2015-12-01

    The (2 × 1) structure of the two-dimensional nickel silicide surface alloy on Ni(111) was investigated using quantitative low-energy electron diffraction analysis. The unit cell of the determined silicide structure contains one Si and one Ni atom, corresponding to a chemical formula of NiSi. The Si atoms adopt substitutional face-centered cubic hollow sites on the Ni(111) substrate. The Ni-Si bond lengths were determined to be 2.37 and 2.34 Å. Both the alloy surface and the underlying first layers of Ni atoms exhibit slight corrugation. The Ni-Si interlayer distance is smaller than the Ni-Ni interlayer distance, which indicates that Si atoms and underlying Ni atoms strongly interact.

  14. Using Spatial Structure Analysis of Hyperspectral Imaging Data and Fourier Transformed Infrared Analysis to Determine Bioactivity of Surface Pesticide Treatment

    Directory of Open Access Journals (Sweden)

    Christian Nansen

    2010-03-01

    Full Text Available Many food products are subjected to quality control analyses for detection of surface residue/contaminants, and there is a trend of requiring more and more documentation and reporting by farmers regarding their use of pesticides. Recent outbreaks of food borne illnesses have been a major contributor to this trend. With a growing need for food safety measures and “smart applications” of insecticides, it is important to develop methods for rapid and accurate assessments of surface residues on food and feed items. As a model system, we investigated detection of a miticide applied to maize leaves and its miticidal bioactivity over time, and we compared two types of reflectance data: fourier transformed infrared (FTIR data and hyperspectral imaging (HI data. The miticide (bifenazate was applied at a commercial field rate to maize leaves in the field, with or without application of a surfactant, and with or without application of a simulated “rain event”. In addition, we collected FTIR and HI from untreated control leaves (total of five treatments. Maize leaf data were collected at seven time intervals from 0 to 48 hours after application. FTIR data were analyzed using conventional analysis of variance of miticide-specific vibration peaks. Two unique FTIR vibration peaks were associated with miticide application (1,700 cm−1 and 763 cm−1. The integrated intensities of these two peaks, miticide application, surfactant, rain event, time between miticide application, and rain event were used as explanatory variables in a linear multi-regression fit to spider mite mortality. The same linear multi-regression approach was applied to variogram parameters derived from HI data in five selected spectral bands (664, 683, 706, 740, and 747 nm. For each spectral band, we conducted a spatial structure analysis, and the three standard variogram parameters (“sill”, “range”, and “nugget” were examined as possible “indicators” of miticide

  15. Determinants of capital structure.

    Science.gov (United States)

    McCue, M J; Ozcan, Y A

    1992-01-01

    This study analyzes the determinants of hospital capital structure in a new market setting that are created by the financial pressures of prospective payment and the intense price competition among hospitals. Using California data, the study found hospital system affiliation, bed size, growth rate in revenues, operating risk, and asset structure affected both short- and long-term debt borrowings. In addition, percentage of uncompensated care, profitability, and payer mix influenced short-term borrowings while market conditions and ownership affected long-term borrowings. Most significant of all is the finding that smaller hospitals tend to borrow more, possibly because they cannot generate funds internally.

  16. Simultaneous Determination of Structure and Event Location Using Body and Surface Wave Measurements at a Single Station: Preparation for Mars Data from the InSight Mission

    Science.gov (United States)

    Panning, M. P.; Banerdt, W. B.; Beucler, E.; Blanchette-Guertin, J. F.; Boese, M.; Clinton, J. F.; Drilleau, M.; James, S. R.; Kawamura, T.; Khan, A.; Lognonne, P. H.; Mocquet, A.; van Driel, M.

    2015-12-01

    An important challenge for the upcoming InSight mission to Mars, which will deliver a broadband seismic station to Mars along with other geophysical instruments in 2016, is to accurately determine event locations with the use of a single station. Locations are critical for the primary objective of the mission, determining the internal structure of Mars, as well as a secondary objective of measuring the activity of distribution of seismic events. As part of the mission planning process, a variety of techniques have been explored for location of marsquakes and inversion of structure, and preliminary procedures and software are already under development as part of the InSight Mars Quake and Mars Structure Services. One proposed method, involving the use of recordings of multiple-orbit surface waves, has already been tested with synthetic data and Earth recordings. This method has the strength of not requiring an a priori velocity model of Mars for quake location, but will only be practical for larger events. For smaller events where only first orbit surface waves and body waves are observable, other methods are required. In this study, we implement a transdimensional Bayesian inversion approach to simultaneously invert for basic velocity structure and location parameters (epicentral distance and origin time) using only measurements of body wave arrival times and dispersion of first orbit surface waves. The method is tested with synthetic data with expected Mars noise and Earth data for single events and groups of events and evaluated for errors in both location and structural determination, as well as tradeoffs between resolvable parameters and the effect of 3D crustal variations.

  17. Surface magnetic structures in amorphous ferromagnetic microwires

    Energy Technology Data Exchange (ETDEWEB)

    Usov, N.A., E-mail: usov@obninsk.ru [National University of Science and Technology «MISIS», 119049 Moscow (Russian Federation); Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, IZMIRAN, 108840 Troitsk, Moscow (Russian Federation); Serebryakova, O.N.; Gudoshnikov, S.A. [National University of Science and Technology «MISIS», 119049 Moscow (Russian Federation); Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, IZMIRAN, 108840 Troitsk, Moscow (Russian Federation); Tarasov, V.P. [National University of Science and Technology «MISIS», 119049 Moscow (Russian Federation)

    2017-05-01

    The spatial period of magnetization perturbations that occur near the surface of magnetic nanotube or nanowire under the influence of surface magnetic anisotropy is determined by means of numerical simulation as a function of the sample geometry and material parameters. The surface magnetization distribution obtained is then used to estimate the period of the surface magnetic texture in amorphous microwire of several micrometers in diameter by means of appropriate variational procedure. The period of the surface magnetic texture in amorphous microwire is found to be significantly smaller than the wire diameter. - Highlights: • Magnetic structure may arise near the magnetic nanotube surface under the influence of surface magnetic anisotropy. • The period of the surface magnetization pattern is calculated as a function of the sample geometry. • Similar magnetic structure may exist in amorphous microwire of several micrometers in diameter. • The period of the surface magnetic structure in amorphous wire is found to be significantly smaller than the wire diameter.

  18. Potential of Future Hurricane Imaging Radiometer (HIRAD) Ocean Surface Wind Observations for Determining Tropical Storm Vortex Intensity and Structure

    Science.gov (United States)

    Atlas, Robert; Bailey, M. C.; Black, Peter; James, Mark; Johnson, James; Jones, Linwood; Miller, Timothy; Ruf, Christopher; Uhlhorn, Eric

    2008-01-01

    The Hurricane Imaging Radiometer (HIRAD) is an innovative technology development, which offers the potential of new and unique remotely sensed observations of both extreme oceanic wind events and strong precipitation from either UAS or satellite platforms. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR), which is a proven aircraft remote sensing technique for observing tropical cyclone ocean surface wind speeds and rain rates, including those of major hurricane intensity. The proposed HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer technology. This sensor will operate over 4-7 GHz (C-band frequencies) where the required tropical cyclone remote sensing physics has been validated by both SFMR and WindSat radiometers. HIRAD incorporates a unique, technologically advanced array antenna and several other technologies successfully demonstrated by the NASA's Instrument Incubator Program. A brassboard version of the instrument is complete and has been successfully tested in an anechoic chamber, and development of the aircraft instrument is well underway. HIRAD will be a compact, lightweight, low-power instrument with no moving parts that will produce wide-swath imagery of ocean vector winds and rain during hurricane conditions when existing microwave sensors (radiometers or scatterometers) are hindered. Preliminary studies show that HIRAD will have a significant positive impact on analyses as either a new aircraft or satellite sensor.

  19. Atomic and electronic structures of novel silicon surface structures

    Energy Technology Data Exchange (ETDEWEB)

    Terry, J.H. Jr.

    1997-03-01

    The modification of silicon surfaces is presently of great interest to the semiconductor device community. Three distinct areas are the subject of inquiry: first, modification of the silicon electronic structure; second, passivation of the silicon surface; and third, functionalization of the silicon surface. It is believed that surface modification of these types will lead to useful electronic devices by pairing these modified surfaces with traditional silicon device technology. Therefore, silicon wafers with modified electronic structure (light-emitting porous silicon), passivated surfaces (H-Si(111), Cl-Si(111), Alkyl-Si(111)), and functionalized surfaces (Alkyl-Si(111)) have been studied in order to determine the fundamental properties of surface geometry and electronic structure using synchrotron radiation-based techniques.

  20. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    International Nuclear Information System (INIS)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2√3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (√3 x √3) reconstruction on the (111) face of the α-CuAl alloy has been determined

  1. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2..sqrt..3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (..sqrt..3 x ..sqrt..3) reconstruction on the (111) face of the ..cap alpha..-CuAl alloy has been determined.

  2. Unoccupied surface electronic structure of Gd(0001)

    International Nuclear Information System (INIS)

    Li, D.; Dowben, P.A.; Ortega, J.E.; Himpsel, F.J.

    1994-01-01

    The unoccupied surface electronic structure of Gd(0001) was investigated with high-resolution inverse-photoemission spectroscopy. An empty surface state near E F is observed at bar Γ. Two other surface-sensitive features are also revealed at 1.2 and 3.1 eV above the Fermi level. Hydrogen adsorption on Gd surfaces was used to distinguish the surface-sensitive features from the bulk features. The unoccupied bulk-band critical points are determined to be Γ 3 + at 1.9 eV and A 1 at 0.8 eV

  3. DETERMINATION OF RADIATOR COOLING SURFACE

    Directory of Open Access Journals (Sweden)

    A. I. Yakubovich

    2009-01-01

    Full Text Available The paper proposes a methodology for calculation of a radiator cooling surface with due account of heat transfer non-uniformity on depth of its core. Calculation of radiator cooling surfaces of «Belarus-1221» and «Belarus-3022» tractors has been carried out in the paper. The paper also advances standard size series of radiators for powerful «Belarus» tractor type.

  4. In-Plane Structure of Underpotentially Deposited Copper on Gold (111) Determined by Surface EXAFS (Extended X-Ray Absorption Fine Structure).

    Science.gov (United States)

    1988-01-28

    EXAFS is the inverse transform of the two peaks in the RSF using a filtering a12 function to isolate the range between I and 4A. Both the frequency...backscattering of different neighbors. This inverse transform contains only one frequency and its envelope of intensity is the backscattering amplitude function...and the inverse transform of the RSF using a fourier filter between 1 and 4A (Solid line). Insert: Radial Structure Function (RSF) analyzed between

  5. Determination of three-dimensional interfacial strain - A novel method of probing interface structure with X-ray Bragg-surface diffraction

    International Nuclear Information System (INIS)

    Sun, W.-C.; Chu, C.-H.; Chang, H.-C.; Wu, B.-K.; Chen, Y.-R.; Cheng, C.-W.; Chiu, M.-S.; Shen, Y.-C.; Wu, H.-H.; Hung, Y.-S.; Chang, S.-L.; Hong, M.-H.; Tang, M.-T.; Stetsko, Yu.P.

    2007-01-01

    A new X-ray diffraction technique is developed to probe structural variations at the interfaces between epitaxy thin films and single-crystal substrates. The technique utilizes three-wave Bragg-surface diffraction, where a symmetric Bragg reflection and an asymmetric surface reflection are involved. The propagation of the latter along the interfaces conveys structural information about the interfacial region between the substrate and epi-layers. The sample systems of Au/GaAs(001) are subject to the three-wave diffraction investigation using synchrotron radiation. The GaAs three-wave Bragg-surface diffractions (006)/(11-bar3) and (006)/(1-bar1-bar3), are employed. The images of the surface diffracted waves are recorded with an image plate. The obtained images show relative positions of diffraction spots near the image of the interfacial boundary, which give the variation of lattice constant along the surface normal and in-plane directions. With the aid of grazing-incidence diffraction, three-dimensional mapping of strain field at the interfaces is possible. Details about this diffraction technique and the analysis procedures are discussed

  6. Structure determination of disordered organic molecules on surfaces from the Bragg spots of low-energy electron diffraction and total energy calculations

    International Nuclear Information System (INIS)

    Poon, H.C.; Weinert, M.; Saldin, D.K.; Stacchiola, D.; Zheng, T.; Tysoe, W.T.

    2004-01-01

    We show that an analysis of the intensity versus energy variation of Bragg spots due to low-energy electron diffraction from a disordered overlayer of molecules on a crystal surface allows a much more convenient method of determining the local adsorption geometries of such molecules than previously analyzed weak diffuse diffraction patterns. For the case of methanol on Pd(111), we show that the geometry determined by this means from experimental diffraction data is in excellent agreement with the predictions of density functional total energy calculations

  7. Surface band structures on Nb(001)

    International Nuclear Information System (INIS)

    Fang, B.; Lo, W.; Chien, T.; Leung, T.C.; Lue, C.Y.; Chan, C.T.; Ho, K.M.

    1994-01-01

    We report the joint studies of experimental and theoretical surface band structures of Nb(001). Angle-resolved photoelectron spectroscopy was used to determine surface-state dispersions along three high-symmetry axes bar Γ bar M, bar Γ bar X, and bar M bar X in the surface Brillouin zone. Ten surface bands have been identified. The experimental data are compared to self-consistent pseudopotential calculations for the 11-layer Nb(001) slabs that are either bulk terminated or fully relaxed (with a 12% contraction for the first interlayer spacing). The band calculations for a 12% surface-contracted slab are in better agreement with the experimental results than those for a bulk-terminated slab, except for a surface resonance near the Fermi level, which is related to the spin-orbit interaction. The charge profiles for all surface states or resonances have been calculated. Surface contraction effects on the charge-density distribution and the energy position of surface states and resonances will also be discussed

  8. Crystal structure determination of Efavirenz

    International Nuclear Information System (INIS)

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

    2015-01-01

    Needle-shaped single crystals of the title compound, C 14 H 9 ClF 3 NO 2 , were obtained from a co-crystallization experiment of Efavirenz with maleic acid in a (1:1) ratio, using methanol as solvent. Crystal structure determination at room temperature revealed a significant anisotropy of the lattice expansion compared to the previously reported low-temperature structure. In both low- and room temperature structures the cyclopropylethynyl fragment in one of the asymmetric unit molecules is disordered. While at low-temperature only one C atom exhibits positional disorder, at room temperature the disorder is present for two C atoms of the cyclopropane ring

  9. Structural determination of organic compounds

    International Nuclear Information System (INIS)

    Kintzinger, J.P.

    1991-01-01

    This paper reports that the current methods available in high-field NMR spectroscopy are such that the tridimensional structure determination of any rigid molecule containing only carbon and hydrogen atoms may be achieved. The connectivities between carbon-carbon, carbon-hydrogen, and hydrogen-hydrogen atoms are determined by multipulse and two-dimensional (2D) experiments. These connectivity patterns or maps allow a step-by-step reconstruction of the molecular structures. From the carbon-carbon connectivity map, the carbon framework of the molecule is obtained, whereas the carbon-hydrogen pattern allows determination of the positions of the hydrogen atoms on their corresponding carbon atoms. High-field spectrometers are then necessary to remove fortuitous degeneracy and to reduce the proton spectra to a nearly first-order one, allowing an easy measurement of the chemical shifts and the coupling constants

  10. Determination of scattering character and structural parameters of a surface layer according to X-ray data for a film with variable deformation gradient

    International Nuclear Information System (INIS)

    Dyshekov, A.A.; Khapachev, Yu.P.

    1997-01-01

    The problem of the dynamic X-ray diffraction for a crystal with the exponential variation of the deformation is considered. The qualitative criteria of the deformation is considered. The qualitative criteria of the degree of the solvability of the problem of determination of the deformation amplitude and the deformed range thickness on X-ray diffraction results are established. The unambiguous solvability of this problem, is connected with two alternative cases: the slowness condition for the ratio of the surface crystal deformation to the deformed layer thickness or, vice versa, the high value of this ratio. The estimation expressions for the deformed surface layer thickness and the deformation amplitude on the data of angular shifts of the main diffraction maximum and oscillations are obtained for two limit cases [ru

  11. Structure determination of enterovirus 71

    Energy Technology Data Exchange (ETDEWEB)

    Plevka, Pavel; Perera, Rushika; Cardosa, Jane; Kuhn, Richard J.; Rossmann, Michael G. (Purdue); (Sentinext)

    2013-02-20

    Enterovirus 71 is a picornavirus that causes hand, foot and mouth disease but may induce fatal neurological illness in infants and young children. Enterovirus 71 crystallized in a body-centered orthorhombic space group with two particles in general orientations in the crystallographic asymmetric unit. Determination of the particle orientations required that the locked rotation function excluded the twofold symmetry axes from the set of icosahedral symmetry operators. This avoided the occurrence of misleading high rotation-function values produced by the alignment of icosahedral and crystallographic twofold axes. Once the orientations and positions of the particles had been established, the structure was solved by molecular replacement and phase extension.

  12. On real structures on rigid surfaces

    International Nuclear Information System (INIS)

    Kulikov, Vik S; Kharlamov, V M

    2002-01-01

    We construct examples of rigid surfaces (that is, surfaces whose deformation class consists of a unique surface) with a particular behaviour with respect to real structures. In one example the surface has no real structure. In another it has a unique real structure, which is not maximal with respect to the Smith-Thom inequality. These examples give negative answers to the following problems: the existence of real surfaces in each deformation class of complex surfaces, and the existence of maximal real surfaces in every complex deformation class that contains real surfaces. Moreover, we prove that there are no real surfaces among surfaces of general type with p g =q=0 and K 2 =9. These surfaces also provide new counterexamples to the 'Dif = Def' problem

  13. On real structures on rigid surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kulikov, Vik S [Steklov Mathematical Institute, Russian Academy of Sciences (Russian Federation); Kharlamov, V M [Institut de Recherche Matematique Avanee Universite Louis Pasteur et CNRS 7 rue Rene Descartes (France)

    2002-02-28

    We construct examples of rigid surfaces (that is, surfaces whose deformation class consists of a unique surface) with a particular behaviour with respect to real structures. In one example the surface has no real structure. In another it has a unique real structure, which is not maximal with respect to the Smith-Thom inequality. These examples give negative answers to the following problems: the existence of real surfaces in each deformation class of complex surfaces, and the existence of maximal real surfaces in every complex deformation class that contains real surfaces. Moreover, we prove that there are no real surfaces among surfaces of general type with p{sub g}=q=0 and K{sup 2}=9. These surfaces also provide new counterexamples to the 'Dif = Def' problem.

  14. Determinants of Glycosaminoglycan (GAG Structure

    Directory of Open Access Journals (Sweden)

    Kristian Prydz

    2015-08-01

    Full Text Available Proteoglycans (PGs are glycosylated proteins of biological importance at cell surfaces, in the extracellular matrix, and in the circulation. PGs are produced and modified by glycosaminoglycan (GAG chains in the secretory pathway of animal cells. The most common GAG attachment site is a serine residue followed by a glycine (-ser-gly-, from which a linker tetrasaccharide extends and may continue as a heparan sulfate, a heparin, a chondroitin sulfate, or a dermatan sulfate GAG chain. Which type of GAG chain becomes attached to the linker tetrasaccharide is influenced by the structure of the protein core, modifications occurring to the linker tetrasaccharide itself, and the biochemical environment of the Golgi apparatus, where GAG polymerization and modification by sulfation and epimerization take place. The same cell type may produce different GAG chains that vary, depending on the extent of epimerization and sulfation. However, it is not known to what extent these differences are caused by compartmental segregation of protein cores en route through the secretory pathway or by differential recruitment of modifying enzymes during synthesis of different PGs. The topic of this review is how different aspects of protein structure, cellular biochemistry, and compartmentalization may influence GAG synthesis.

  15. Smears for determinations surface unfixed tritium contamination

    International Nuclear Information System (INIS)

    Postolache, Cristian; Matei, Lidia

    2003-01-01

    The present paper describes a method of obtaining expanded polystyrene with hydrophilized surface smears by radioinduced grafting of acrylic acid. The grafting was carried out by using a 60 Co γ radiation source. The variation of grafting rates as a function of dose range and absorbed dose was established. Grafting radiochemical rates were determined by radiometric methods using acrylic acid labeled with tritium as a grafting agent. The sampling coefficients and the reproducibility were analyzed as a function of the nature of the contaminated surface. (authors)

  16. MR imaging of brain surface structures: Surface anatomy scanning

    International Nuclear Information System (INIS)

    Katada, K.; Koga, S.; Asahina, M.; Kanno, T.; Asahina, K.

    1987-01-01

    Preoperative evaluation of brain surface anatomy, including cortical sulci and veins, relative to cerebral and cerebellar lesions is an important subject for surgeons. Until now, no imaging modality existed that allowed direct visualization of brain surface anatomy. A new MR imaging technique (surface anatomy scanning) was developed to visualize brain surface structures. The technique uses a spin-echo pulse sequence with long repetition and echo times, thick sections and a surface coil. Cortical sulci, fissures, veins, and intracranial lesions were clearly identified with this technique. Initial clinical results indicate that surface anatomy scanning is useful for lesion localization and for detailed evaluation of cortical and subcortical lesions

  17. Biofilm Surface Density Determines Biocide Effectiveness

    Directory of Open Access Journals (Sweden)

    Sara Bas

    2017-12-01

    Full Text Available High resistance of biofilms for chemical challenges is a serious industrial and medical problem. In this work a gradient of surface covered with biofilm has been produced and correlated to the effectiveness of different commercially available oxidative biocides. The results for thin Escherichia coli biofilms grown in rich media supplemented with glucose or lactose on glass or poly methyl methacrylate surfaces indicate that the effectiveness of hydrogen peroxide or chlorine dioxide and quaternary ammonium compounds is inversely proportional to the fraction of the surface covered with the biofilm. In areas where biofilm covered more than 90% of the available surface the biocide treatment was inefficient after 60 min of incubation. The combined effect of oxidant and surfactant increased the effectiveness of the biocide. On the other hand, the increased biofilm viscoelasticity reduced biocide effectiveness. The results emphasize differential biocide effectiveness depending on the fraction of the attached bacterial cells. The results suggest that biofilm biocide resistance is an acquired property that increases with biofilm maturation. The more dense sessile structures present lower log reductions compared to less dense ones.

  18. Cluster structures influenced by interaction with a surface.

    Science.gov (United States)

    Witt, Christopher; Dieterich, Johannes M; Hartke, Bernd

    2018-05-30

    Clusters on surfaces are vitally important for nanotechnological applications. Clearly, cluster-surface interactions heavily influence the preferred cluster structures, compared to clusters in vacuum. Nevertheless, systematic explorations and an in-depth understanding of these interactions and how they determine the cluster structures are still lacking. Here we present an extension of our well-established non-deterministic global optimization package OGOLEM from isolated clusters to clusters on surfaces. Applying this approach to intentionally simple Lennard-Jones test systems, we produce a first systematic exploration that relates changes in cluster-surface interactions to resulting changes in adsorbed cluster structures.

  19. Contact area measurements on structured surfaces

    DEFF Research Database (Denmark)

    Kücükyildiz, Ömer Can; Jensen, Sebastian Hoppe Nesgaard; De Chiffre, Leonardo

    In connection with the use of brass specimens featuring structured surfaces in a tribology test, an algorithm was developed for automatic measurement of the contact area by optical means.......In connection with the use of brass specimens featuring structured surfaces in a tribology test, an algorithm was developed for automatic measurement of the contact area by optical means....

  20. Photoelectric effect in surface-barrier structures

    International Nuclear Information System (INIS)

    Kononenko, V.K.; Tupenevich, P.A.

    1985-08-01

    Deviations from the Fowler law were observed when investigating photoelectric emission in p-type ZnTe surface-barrier structures. The revealed peculiarities of the structure photosensitivity spectrum are explained by the electron transitions involving surface states at the metal-semiconductor interface. (author)

  1. Impact damage reduction by structured surface geometry

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Fedorov, Vladimir; McGugan, Malcolm

    2018-01-01

    performance was observed for polyurethane-coated fibre composites with structured geometries at the back surfaces. Repeated impacts by rubber balls on the coated side caused damage and delamination of the coating. The laminates with structured back surfaces showed longer durability than those with a flat back...

  2. Moulding of Sub-micrometer Surface Structures

    DEFF Research Database (Denmark)

    Pranov, Henrik; Rasmussen, Henrik K.; Larsen, Niels Bent

    2006-01-01

    The experiments strongly suggest that the possibility to injection mould sub-micrometer surface structures in polymers mainly relates to the forces originating from the adhesive energy between polymer and shim.......The experiments strongly suggest that the possibility to injection mould sub-micrometer surface structures in polymers mainly relates to the forces originating from the adhesive energy between polymer and shim....

  3. The influence of the surface atomic structure on surface diffusion

    International Nuclear Information System (INIS)

    Ghaleb, Dominique

    1984-03-01

    This work represents the first quantitative study of the influence of the surface atomic structure on surface diffusion (in the range: 0.2 Tf up 0.5 Tf; Tf: melting temperature of the substrate). The analysis of our results on a microscopic scale shows low formation and migration energies for adatoms; we can describe the diffusion on surfaces with a very simple model. On (110) surfaces at low temperature the diffusion is controlled by the exchange mechanism; at higher temperature direct jumps of adatoms along the channels contribute also to the diffusion process. (author) [fr

  4. Structure of stable degeneration of K3 surfaces into pairs of rational elliptic surfaces

    Science.gov (United States)

    Kimura, Yusuke

    2018-03-01

    F-theory/heterotic duality is formulated in the stable degeneration limit of a K3 fibration on the F-theory side. In this note, we analyze the structure of the stable degeneration limit. We discuss whether stable degeneration exists for pairs of rational elliptic surfaces. We demonstrate that, when two rational elliptic surfaces have an identical complex structure, stable degeneration always exists. We provide an equation that systematically describes the stable degeneration of a K3 surface into a pair of isomorphic rational elliptic surfaces. When two rational elliptic surfaces have different complex structures, whether their sum glued along a smooth fiber admits deformation to a K3 surface can be determined by studying the structure of the K3 lattice. We investigate the lattice theoretic condition to determine whether a deformation to a K3 surface exists for pairs of extremal rational elliptic surfaces. In addition, we discuss the configurations of singular fibers under stable degeneration. The sum of two isomorphic rational elliptic surfaces glued together admits a deformation to a K3 surface, the singular fibers of which are twice that of the rational elliptic surface. For special situations, singular fibers of the resulting K3 surface collide and they are enhanced to a fiber of another type. Some K3 surfaces become attractive in these situations. We determine the complex structures and the Weierstrass forms of these attractive K3 surfaces. We also deduce the gauge groups in F-theory compactifications on these attractive K3 surfaces times a K3. E 6, E 7, E 8, SU(5), and SO(10) gauge groups arise in these compactifications.

  5. Solution NMR structure determination of proteins revisited

    International Nuclear Information System (INIS)

    Billeter, Martin; Wagner, Gerhard; Wuethrich, Kurt

    2008-01-01

    This 'Perspective' bears on the present state of protein structure determination by NMR in solution. The focus is on a comparison of the infrastructure available for NMR structure determination when compared to protein crystal structure determination by X-ray diffraction. The main conclusion emerges that the unique potential of NMR to generate high resolution data also on dynamics, interactions and conformational equilibria has contributed to a lack of standard procedures for structure determination which would be readily amenable to improved efficiency by automation. To spark renewed discussion on the topic of NMR structure determination of proteins, procedural steps with high potential for improvement are identified

  6. Diamond surface: atomic and electronic structure

    International Nuclear Information System (INIS)

    Pate, B.B.

    1984-01-01

    Experimental studies of the diamond surface (with primary emphasis on the (111) surface) are presented. Aspects of the diamond surface which are addressed include (1) the electronic structure, (2) the atomic structure, and (3) the effect of termination of the lattice by foreign atoms. Limited studies of graphite are discussed for comparison with the diamond results. Experimental results from valence band and core level photoemission spectroscopy (PES), Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and carbon 1s near edge x-ray absorption fine structure (NEXAFS) spectroscopy (both the total electron yield (TEY) and Auger electron yield (AEY) techniques) are used to study and characterize both the clean and hydrogenated surface. In addition, the interaction of hydrogen with the diamond surface is examined using results from vibrational high resolution low energy electron loss spectroscopy (in collaboration with Waclawski, Pierce, Swanson, and Celotta at the National Bureau of Standards) and photon stimulated ion desorption (PSID) yield at photon energies near the carbon k-edge (hv greater than or equal to 280 eV). Both EELS and PSID verify that the mechanically polished 1 x 1 surface is hydrogen terminated and also that the reconstructed surface is hydrogen free. The (111) 2 x 2/2 x 1 reconstructed surface is obtained from the hydrogenated (111) 1 x 1:H surface by annealing to approx. = 1000 0 C. We observe occupied intrinsic surface states and a surface chemical shift (0.95 +- 0.1 eV) to lower binding energy of the carbon 1s level on the hydrogen-free reconstructed surface. Atomic hydrogen is found to be reactive with the reconstructed surface, while molecular hydrogen is relatively inert. Exposure of the reconstructed surface to atomic hydrogen results in chemisorption of hydrogen and removal of the intrinsic surface state emission in and near the band gap region

  7. Spectroscopic determination of optimal hydration time of zircon surface

    Energy Technology Data Exchange (ETDEWEB)

    Ordonez R, E. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Garcia R, G. [Instituto Tecnologico de Toluca, Division de Estudios del Posgrado, Av. Tecnologico s/n, Ex-Rancho La Virgen, 52140 Metepec, Estado de Mexico (Mexico); Garcia G, N., E-mail: eduardo.ordonez@inin.gob.m [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Av. Colon y Av. Tollocan, 50180 Toluca, Estado de Mexico (Mexico)

    2010-07-01

    When a mineral surface is immersed in an aqueous solution, it develops and electric charge produced by the amphoteric dissociation of hydroxyl groups created by the hydration of the solid surface. This is one influential surface property. The complete hydration process takes a time which is specific for each mineral species. The knowledge of the aqueous solution contact time for complete surface hydration is mandatory for further surface phenomena studies. This study deals with the optimal hydration time of the raw zircon (ZrSiO{sub 4}) surface comparing the classical potentiometric titrations with a fluorescence spectroscopy technique. The latter is easy and rea liable as it demands only one sample batch to determine the optimal time to ensure a total hydration of the zircon surface. The analytical results of neutron activation analysis showed the presence of trace quantities of Dy{sup 3+}, Eu{sup 3+} and Er{sup 3} in the bulk of zircon. The Dy{sup 3+} is structured in the zircon crystalline lattice and undergoes the same chemical reactions as zircon. Furthermore, the Dy{sup 3+} has a good fluorescent response whose intensity is enhanced by hydration molecules. The results show that, according to the potentiometric analysis, the hydration process for each batch (at least 8 sample batches) takes around 2 h, while the spectrometric method indicates only 5 minutes from only one batch. Both methods showed that the zircon surface have a 16 h optimal hydration time. (Author)

  8. Spectroscopic determination of optimal hydration time of zircon surface

    International Nuclear Information System (INIS)

    Ordonez R, E.; Garcia R, G.; Garcia G, N.

    2010-01-01

    When a mineral surface is immersed in an aqueous solution, it develops and electric charge produced by the amphoteric dissociation of hydroxyl groups created by the hydration of the solid surface. This is one influential surface property. The complete hydration process takes a time which is specific for each mineral species. The knowledge of the aqueous solution contact time for complete surface hydration is mandatory for further surface phenomena studies. This study deals with the optimal hydration time of the raw zircon (ZrSiO 4 ) surface comparing the classical potentiometric titrations with a fluorescence spectroscopy technique. The latter is easy and rea liable as it demands only one sample batch to determine the optimal time to ensure a total hydration of the zircon surface. The analytical results of neutron activation analysis showed the presence of trace quantities of Dy 3+ , Eu 3+ and Er 3 in the bulk of zircon. The Dy 3+ is structured in the zircon crystalline lattice and undergoes the same chemical reactions as zircon. Furthermore, the Dy 3+ has a good fluorescent response whose intensity is enhanced by hydration molecules. The results show that, according to the potentiometric analysis, the hydration process for each batch (at least 8 sample batches) takes around 2 h, while the spectrometric method indicates only 5 minutes from only one batch. Both methods showed that the zircon surface have a 16 h optimal hydration time. (Author)

  9. Surface Chloride Levels in Colorado Structural Concrete

    Science.gov (United States)

    2018-01-01

    This project focused on the chloride-induced corrosion of reinforcing steel in structural concrete. The primary goal of this project is to analyze the surface chloride concentration level of the concrete bridge decks throughout Colorado. The study in...

  10. Architectural Surfaces and Structures from Circular Arcs

    KAUST Repository

    Shi, Ling

    2013-01-01

    the most attention from geometry researchers. In this thesis, we aim to realize this process with simple geometric primitives, circular arcs. We investigate architectural surfaces and structures consisting of circular arcs. Our focus is lying on how

  11. Designing visual appearance using a structured surface

    DEFF Research Database (Denmark)

    Johansen, Villads Egede; Thamdrup, Lasse Højlund; Smitrup, Christian

    2015-01-01

    followed by numerical and experimental verification. The approach comprises verifying all design and fabrication steps required to produce a desired appearance. We expect that the procedure in the future will yield structurally colored surfaces with appealing prescribed visual appearances.......We present an approach for designing nanostructured surfaces with prescribed visual appearances, starting at design analysis and ending with a fabricated sample. The method is applied to a silicon wafer structured using deep ultraviolet lithography and dry etching and includes preliminary design...

  12. Protein-mediated surface structuring in biomembranes

    Directory of Open Access Journals (Sweden)

    Maggio B.

    2005-01-01

    Full Text Available The lipids and proteins of biomembranes exhibit highly dissimilar conformations, geometrical shapes, amphipathicity, and thermodynamic properties which constrain their two-dimensional molecular packing, electrostatics, and interaction preferences. This causes inevitable development of large local tensions that frequently relax into phase or compositional immiscibility along lateral and transverse planes of the membrane. On the other hand, these effects constitute the very codes that mediate molecular and structural changes determining and controlling the possibilities for enzymatic activity, apposition and recombination in biomembranes. The presence of proteins constitutes a major perturbing factor for the membrane sculpturing both in terms of its surface topography and dynamics. We will focus on some results from our group within this context and summarize some recent evidence for the active involvement of extrinsic (myelin basic protein, integral (Folch-Lees proteolipid protein and amphitropic (c-Fos and c-Jun proteins, as well as a membrane-active amphitropic phosphohydrolytic enzyme (neutral sphingomyelinase, in the process of lateral segregation and dynamics of phase domains, sculpturing of the surface topography, and the bi-directional modulation of the membrane biochemical reactivity.

  13. Synthesis of α-MoC1-x Nanoparticles with a Surface-Modified SBA-15 Hard Template: Determination of Structure-Function Relationships in Acetic Acid Deoxygenation.

    Science.gov (United States)

    Baddour, Frederick G; Nash, Connor P; Schaidle, Joshua A; Ruddy, Daniel A

    2016-07-25

    Surface modification of mesoporous SBA-15 silica generated a hydrophobic environment for a molybdenum diamine (Mo-diamine) precursor solution, enabling direct growth of isolated 1.9±0.4 nm α-MoC1-x nanoparticles (NPs) inside the pores of the support. The resulting NP catalysts are bifunctional, and compared to bulk α-MoC1-x and β-Mo2 C, the NPs exhibit a greater acid-site:H-site ratio and a fraction of stronger acid sites. The greater acid-site:H-site ratio results in higher decarbonylation (DCO) selectivity during acetic acid hydrodeoxygenation (HDO) reactions, and the stronger acid sites lead to higher activity and ketonization (KET) selectivity at high temperatures. The hard-templating synthetic method could be a versatile route toward carbide NPs of varying size, composition, and phase, on a range of mesoporous oxide supports. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. The structure of reconstructed chalcopyrite surfaces

    Science.gov (United States)

    Thinius, Sascha; Islam, Mazharul M.; Bredow, Thomas

    2018-03-01

    Chalcopyrite (CuFeS2) surfaces are of major interest for copper exploitation in aqueous solution, called leaching. Since leaching is a surface process knowledge of the surface structure, bonding pattern and oxidation states is important for improving the efficiency. At present such information is not available from experimental studies. Therefore a detailed computational study of chalcopyrite surfaces is performed. The structures of low-index stoichiometric chalcopyrite surfaces {hkl} h, k, l ∈ {0, 1, 2} have been studied with density functional theory (DFT) and global optimization strategies. We have applied ab initio molecular dynamics (MD) in combination with simulated annealing (SA) in order to explore possible reconstructions via a minima hopping (MH) algorithm. In almost all cases reconstruction involving substantial rearrangement has occurred accompanied by reduction of the surface energy. The analysis of the change in the coordination sphere and migration during reconstruction reveals that S-S dimers are formed on the surface. Further it was observed that metal atoms near the surface move toward the bulk forming metal alloys passivated by sulfur. The obtained surface energies of reconstructed surfaces are in the range of 0.53-0.95 J/m2.

  15. 30 CFR 75.1708-1 - Surface structures; fireproof construction.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Surface structures; fireproof construction. 75... Surface structures; fireproof construction. Structures of fireproof construction is interpreted to mean structures with fireproof exterior surfaces. ...

  16. Sub-µm structured lotus surfaces manufacturing

    DEFF Research Database (Denmark)

    Worgull, Matthias; Heckele, Mathias; Mappes, Timo

    2009-01-01

    . Unlike to stochastic methods, patterning with a LIGA-mold insert it is possible to structure surfaces very uniformly or even with controlled variations (e.g., with gradients). In this paper we present the process chain to realize polymer sub-lm structures with minimum lateral feature size of 400 nm...

  17. Sub-µ structured Lotus Surfaces Manufacturing

    DEFF Research Database (Denmark)

    Worgull, Matthias; Heckele, Mathias; Mappes, Timo

    2008-01-01

    . Unlike to stochastic methods, patternin¬g with a LIGA-mold insert it is possible to structure surfaces very uniformly or even with controlled variations (e.g. with gradients). In this paper we present the process chain to realize polymer sub-micro structures with minimum lateral feature size of 400 nm...

  18. MR imaging of brain surface structures

    International Nuclear Information System (INIS)

    Katada, Kazuhiro; Anno, Hirofumi; Takesita, Gen; Koga, Sukehiko; Kanno, Tetuo; Sakakibara, Tatuo; Yamada, Kazuhiro; Suzuki, Hirokazu; Saito, Sigeki.

    1989-01-01

    An imaging technique that permits direct and non-invasive visualization of brain surface structures was proposed. This technique (Surface anatomy scanning, SAS) consists of long TE-long TR spin echo sequence, thick slice and surface coil. Initial clinical trials in 31 patients with various cerebral pathology showed excellent visualization of sulci, gyri and major cortical veins on the lateral surface of the brain together with cortical and subcortical lesions. Our preliminary results indicate that the SAS is an effective method for the diagnosis and localization of cortical and subcortical pathology, and the possible application of SAS to the surgical and the radiation therapy planning is sugessted. (author)

  19. Surface structure investigations using noncontact atomic force microscopy

    International Nuclear Information System (INIS)

    Kolodziej, J.J.; Such, B.; Goryl, M.; Krok, F.; Piatkowski, P.; Szymonski, M.

    2006-01-01

    Surfaces of several A III B V compound semiconductors (InSb, GaAs, InP, InAs) of the (0 0 1) orientation have been studied with noncontact atomic force microscopy (NC-AFM). Obtained atomically resolved patterns have been compared with structural models available in the literature. It is shown that NC-AFM is an efficient tool for imaging complex surface structures in real space. It is also demonstrated that the recent structural models of III-V compound surfaces provide a sound base for interpretation of majority of features present in recorded patterns. However, there are also many new findings revealed by the NC-AFM method that is still new experimental technique in the context of surface structure determination

  20. Surface structure of polymer Gels and emerging functions

    CERN Document Server

    Kobiki, Y

    1999-01-01

    We report the surface structure of polymer gels on a submicrometer scale during the volume phase transition. Sponge-like domains with a mesoscopic scale were directly observed in water by using at atomic force microscope (AFM). The surface structure characterized by the domains is discussed in terms of the root-mean-square roughness and the auto-correlation function, which were calculated from the AFM images. In order to demonstrate the role of surface structure in determining the macroscopic properties of film-like poly (N-isopropylacrylamide: NIPA) gels. It was found that the temperature dependence, as well as the absolute values of the static contact angle, were strongly dependent on the bulk network inhomogeneities. The relation between the mesoscopic structure and the macroscopic properties is qualitatively discussed in terms of not only the changes in the chemical, but also in the physical, surface properties of the NIPA gels in response to a temperature change.

  1. Electronic structure of disordered alloys, surfaces and interfaces

    CERN Document Server

    Turek, Ilja; Kudrnovský, Josef; Šob, Mojmír; Weinberger, Peter

    1997-01-01

    At present, there is an increasing interest in the prediction of properties of classical and new materials such as substitutional alloys, their surfaces, and metallic or semiconductor multilayers. A detailed understanding based on a thus of the utmost importance for fu­ microscopic, parameter-free approach is ture developments in solid state physics and materials science. The interrela­ tion between electronic and structural properties at surfaces plays a key role for a microscopic understanding of phenomena as diverse as catalysis, corrosion, chemisorption and crystal growth. Remarkable progress has been made in the past 10-15 years in the understand­ ing of behavior of ideal crystals and their surfaces by relating their properties to the underlying electronic structure as determined from the first principles. Similar studies of complex systems like imperfect surfaces, interfaces, and mul­ tilayered structures seem to be accessible by now. Conventional band-structure methods, however, are of limited use ...

  2. Solving complex and disordered surface structures with electron diffraction

    International Nuclear Information System (INIS)

    Van Hove, M.A.

    1987-10-01

    The past of surface structure determination with low-energy electron diffraction (LEED) will be briefly reviewed, setting the stage for a discussion of recent and future developments. The aim of these developments is to solve complex and disordered surface structures. Some efficient solutions to the theoretical and experimental problems will be presented. Since the theoretical problems dominate, the emphasis will be on theoretical approaches to the calculation of the multiple scattering of electrons through complex and disordered surfaces. 49 refs., 13 figs., 1 tab

  3. Monte Carlo determination of heteroepitaxial misfit structures

    DEFF Research Database (Denmark)

    Baker, J.; Lindgård, Per-Anker

    1996-01-01

    We use Monte Carlo simulations to determine the structure of KBr overlayers on a NaCl(001) substrate, a system with large (17%) heteroepitaxial misfit. The equilibrium relaxation structure is determined for films of 2-6 ML, for which extensive helium-atom scattering data exist for comparison...

  4. Projective and superconformal structures on surfaces

    International Nuclear Information System (INIS)

    Harvey, W.J.

    1990-01-01

    Much attention has recently been given to the study of super Riemann surfaces. Detailed accounts of these objects and their infinitesimal deformation theory are referenced where they are fitted into the framework of complex supermanifolds, superconformal structures and graded sheaves. One difficulty, which seems even more of a barrier than in the case of classical deformations of Riemann surface structure, is the lack of a good global description of super-moduli spaces. In this note, we outline an approach which places the theory in the classical setting of projective structures on variable Riemann surfaces. We explain how to construct a distribution (family of vector subspaces) inside the holomorphic cotangent space to the moduli space M g of Riemann surfaces with genus g and furnished with a level-4 homology structure, such that the corresponding rank-(2g-2) complex vector bundle models the soul deformations of a family of super-Riemann surfaces. The keystone in this construction is the existence of holomorphic sections for the space of non-singular odd theta characteristics on C g the universal curve over M g . (author)

  5. Thermodynamics and structure of liquid surfaces investigated directly with surface analytical tools

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Gunther [Flinders Univ., Adelaide, SA (Australia). Centre for NanoScale Science and Technology; Morgner, Harald [Leipzig Univ. (Germany). Wilhelm Ostwald Inst. for Physical and Theoretical Chemistry

    2017-06-15

    Measuring directly the composition, the distribution of constituents as function of the depth and the orientation of molecules at liquid surfaces is essential for determining physicochemical properties of liquid surfaces. While the experimental tools that have been developed for analyzing solid surfaces can in principal be applied to liquid surfaces, it turned out that they had to be adjusted to the particular challenges imposed by liquid samples, e.g. by the unavoidable vapor pressure and by the mobility of the constituting atoms/molecules. In the present work it is shown, how electron spectroscopy and ion scattering spectroscopy have been used for analyzing liquid surfaces. The emphasis of this review is on using the structural information gained for determining the physicochemical properties of liquid surfaces. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. ‘Action’ on structured freeform surfaces

    Science.gov (United States)

    Whitehouse, David J.

    2018-06-01

    Surfaces are becoming more complex partly due to the more complicated function required of them and partly due to the introduction of different manufacturing processes. These have thrown into relief the need to consider new ways of measuring and characterizing such surfaces and more importantly to make such characterization more relevant by tying together the geometry and the function more closely. The surfaces which have freeform and structure have been chosen to be a carrier for this investigation because so far there has been little work carried out in this neglected but potentially important area. This necessitates the development of a strategy for their characterization. In this article, some ways have been found of identifying possible strategies for tackling this characterization problem but also linking this characterization to performance and manufacture, based in part on the principles of least action and on the way that nature has evolved to solve the marriage of flexible freeform geometry, structure and function. Recommendations are made for the most suitable surface parameter to use which satisfies the requirement for characterizing structured freeform surfaces as well as utilizing ‘Action’ to predict functionality.

  7. Surface and mineral structure of ferrihydrite

    NARCIS (Netherlands)

    Hiemstra, T.

    2013-01-01

    Ferrihydrite (Fh) is an yet enigmatic nano Fe(III)-oxide material, omnipresent in nature that can bind ions in large quantities, regulating bioavailability and ion mobility. Although extensively studied, to date no proper view exists on the surface structure and composition, while it is of vital

  8. Multiresolution Computation of Conformal Structures of Surfaces

    Directory of Open Access Journals (Sweden)

    Xianfeng Gu

    2003-10-01

    Full Text Available An efficient multiresolution method to compute global conformal structures of nonzero genus triangle meshes is introduced. The homology, cohomology groups of meshes are computed explicitly, then a basis of harmonic one forms and a basis of holomorphic one forms are constructed. A progressive mesh is generated to represent the original surface at different resolutions. The conformal structure is computed for the coarse level first, then used as the estimation for that of the finer level, by using conjugate gradient method it can be refined to the conformal structure of the finer level.

  9. Craterlike structures on the laser cut surface

    Science.gov (United States)

    Shulyatyev, V. B.; Orishich, A. M.

    2017-10-01

    Analysis of the laser cut surface morphology remain topical. It is related with the fact that the surface roughness is the main index of the cut quality. The present paper deals with the experimental study of the relatively unstudied type of defects on the laser cut surface, dimples, or craters. According to the measurement results, amount of craters per unit of the laser cut surface area rises as the sheet thickness rises. The crater diameter rises together with the sheet thickness and distance from the upper sheet edge. The obtained data permit concluding that the defects like craters are observed predominantly in the case of thick sheets. The results agree with the hypothesis of crater formation as impact structures resulting from the melt drops getting on the cut channel walls upon separation from the cut front by the gas flow.

  10. DETERMINATION OF SURFACE CHARGE DENSITY OF α ...

    African Journals Online (AJOL)

    a

    The whole set up was interfaced with a computer for easy data acquisition. It was observed that ... parameters. KEY WORDS: Alumina, Surface charge density, Acid-base titration, Point of zero charge ... For instance, Al2(SO4)3 is used in water ...

  11. Basic reactions of osteoblasts on structured material surfaces

    Directory of Open Access Journals (Sweden)

    U. Meyer

    2005-04-01

    Full Text Available In order to assess how bone substitute materials determine bone formation in vivo it is useful to understand the mechanisms of the material surface/tissue interaction on a cellular level. Artificial materials are used in two applications, as biomaterials alone or as a scaffold for osteoblasts in a tissue engineering approach. Recently, many efforts have been undertaken to improve bone regeneration by the use of structured material surfaces. In vitro studies of bone cell responses to artificial materials are the basic tool to determine these interactions. Surface properties of materials surfaces as well as biophysical constraints at the biomaterial surface are of major importance since these features will direct the cell responses. Studies on osteoblast-like cell reactivity towards materials will have to focus on the different steps of protein and cell reactions towards defined surface properties. The introduction of new techniques allows nowadays the fabrication of materials with ordered surface structures. This paper gives a review of present knowledge on the various stages of osteoblast reactions on material surfaces, focused on basic cell events under in vitro conditions. Special emphasis is given to cellular reactions towards ordered nano-sized topographies.

  12. Structural determinants of students' employability: Influence of ...

    African Journals Online (AJOL)

    Structural determinants of students' employability: Influence of career ... greatest influence on students' employability, followed by decision-making skills, and ... efforts in developing app-ropriate strategies so as to engage undergraduates with ...

  13. Protein Structure Determination Using Chemical Shifts

    DEFF Research Database (Denmark)

    Christensen, Anders Steen

    is determined using only chemical shifts recorded and assigned through automated processes. The CARMSD to the experimental X-ray for this structure is 1.1. Å. Additionally, the method is combined with very sparse NOE-restraints and evolutionary distance restraints and tested on several protein structures >100...

  14. Structural determination and gynecological tumor diagnosis using ...

    African Journals Online (AJOL)

    covalent bonding patterns and branched structures. Studies have shown that changes in protein glycosylation at the cell surface during tumorigenesis are closely related to the occurrence and development of some cancers, including pancreatic cancer, mammary cancer, prostatic cancer, colon cancer, and gastric cancer [1].

  15. Rapid and reliable protein structure determination via chemical shift threading.

    Science.gov (United States)

    Hafsa, Noor E; Berjanskii, Mark V; Arndt, David; Wishart, David S

    2018-01-01

    Protein structure determination using nuclear magnetic resonance (NMR) spectroscopy can be both time-consuming and labor intensive. Here we demonstrate how chemical shift threading can permit rapid, robust, and accurate protein structure determination using only chemical shift data. Threading is a relatively old bioinformatics technique that uses a combination of sequence information and predicted (or experimentally acquired) low-resolution structural data to generate high-resolution 3D protein structures. The key motivations behind using NMR chemical shifts for protein threading lie in the fact that they are easy to measure, they are available prior to 3D structure determination, and they contain vital structural information. The method we have developed uses not only sequence and chemical shift similarity but also chemical shift-derived secondary structure, shift-derived super-secondary structure, and shift-derived accessible surface area to generate a high quality protein structure regardless of the sequence similarity (or lack thereof) to a known structure already in the PDB. The method (called E-Thrifty) was found to be very fast (often chemical shift refinement, these results suggest that protein structure determination, using only NMR chemical shifts, is becoming increasingly practical and reliable. E-Thrifty is available as a web server at http://ethrifty.ca .

  16. Coal surface structure and thermodynamics. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, J.W.; Wernett, P.C.; Glass, A.S.; Quay, D.; Roberts, J.

    1994-05-01

    Coals surfaces were studied using static surface adsorption measurements, low angle x-ray scattering (LAXS), inverse gas chromatography (IGC) and a new {sup 13}C NMR relaxation technique. A comparison of surface areas determined by hydrocarbon gas adsorption and LAXS led to the twin conclusions that the hydrocarbons had to diffuse through the solid to reach isolated pores and that the coal pores do not form interconnected networks, but are largely isolated. This conclusion was confirmed when IGC data for small hydrocarbons showed no discontinuities in their size dependence as usually observed with porous solids. IGC is capable of providing adsorption thermodynamics of gases on coal surfaces. The interactions of non-polar molecules and coal surfaces are directly proportioned to the gas molecular polarizability. For bases, the adsorption enthalpy is equal to the polarizability interaction plus the heat of hydrogen bond formation with phenol. Amphoteric molecules have more complex interactions. Mineral matter can have highly specific effects on surface interactions, but with most of the molecules studied is not an important factor.

  17. Understanding surface structure and chemistry of single crystal lanthanum aluminate

    KAUST Repository

    Pramana, Stevin S.

    2017-03-02

    The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600 °C) and chamber pressure of 10−10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10−6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

  18. Determination of the surface drag coefficient

    DEFF Research Database (Denmark)

    Mahrt, L.; Vickers, D.; Sun, J.L.

    2001-01-01

    This study examines the dependence of the surface drag coefficient on stability, wind speed, mesoscale modulation of the turbulent flux and method of calculation of the drag coefficient. Data sets over grassland, sparse grass, heather and two forest sites are analyzed. For significantly unstable...... conditions, the drag coefficient does not depend systematically on z/L but decreases with wind speed for fixed intervals of z/L, where L is the Obukhov length. Even though the drag coefficient for weak wind conditions is sensitive to the exact method of calculation and choice of averaging time, the decrease...... of the drag coefficient with wind speed occurs for all of the calculation methods. A classification of flux calculation methods is constructed, which unifies the most common previous approaches. The roughness length corresponding to the usual Monin-Obukhov stability functions decreases with increasing wind...

  19. Global structural optimizations of surface systems with a genetic algorithm

    International Nuclear Information System (INIS)

    Chuang, Feng-Chuan

    2005-01-01

    Global structural optimizations with a genetic algorithm were performed for atomic cluster and surface systems including aluminum atomic clusters, Si magic clusters on the Si(111) 7 x 7 surface, silicon high-index surfaces, and Ag-induced Si(111) reconstructions. First, the global structural optimizations of neutral aluminum clusters Al n (n up to 23) were performed using a genetic algorithm coupled with a tight-binding potential. Second, a genetic algorithm in combination with tight-binding and first-principles calculations were performed to study the structures of magic clusters on the Si(111) 7 x 7 surface. Extensive calculations show that the magic cluster observed in scanning tunneling microscopy (STM) experiments consist of eight Si atoms. Simulated STM images of the Si magic cluster exhibit a ring-like feature similar to STM experiments. Third, a genetic algorithm coupled with a highly optimized empirical potential were used to determine the lowest energy structure of high-index semiconductor surfaces. The lowest energy structures of Si(105) and Si(114) were determined successfully. The results of Si(105) and Si(114) are reported within the framework of highly optimized empirical potential and first-principles calculations. Finally, a genetic algorithm coupled with Si and Ag tight-binding potentials were used to search for Ag-induced Si(111) reconstructions at various Ag and Si coverages. The optimized structural models of √3 x √3, 3 x 1, and 5 x 2 phases were reported using first-principles calculations. A novel model is found to have lower surface energy than the proposed double-honeycomb chained (DHC) model both for Au/Si(111) 5 x 2 and Ag/Si(111) 5 x 2 systems

  20. Capital Structure Determinants and Governance Structure Variety in Franchising

    NARCIS (Netherlands)

    T. Jiang (Tao)

    2009-01-01

    textabstractThis thesis investigates two questions: the determinants of capital structure in franchising and its subsequent impact on the franchise financing decisions; and the efficient governance structure choice in franchising. We posit that firms franchise in order to benefit from the reduced

  1. The determination of the surface potential for the CdxHg1-xTe crystals and the V-CdxHg1-xTe and Ni-V-CdxMg1-xTe structures

    International Nuclear Information System (INIS)

    Veliyulin, Eh.I.; Ragimova, R.A.; Mamedov, A.A.

    1996-01-01

    Surface potential of semiconductor crystals n-Cd x Hg 1-x Te (unannealed and annealed in mercury vapors) and of the structures V-Cd x Hg 1-x Te, Ni-V-Cd x Hg 1-x Te has been defined using spectroscopy of weak-field electric reflection. It is shown that a deep penetration of vanadium atoms in near the surface region of the crystal occurs in the structures on the basis of unannealed Cd x Hg 1-x Te. 1 ref.; 4 figs

  2. Nanoscale surface topographies for structural colors

    DEFF Research Database (Denmark)

    Clausen, Jeppe Sandvik

    The thesis describes and demonstrates the possibilities for utilization of structural colors in mass fabricated plastic products as replacement for or in combination with pigments and inks. The motivation is the possible advantages related to re-cycling and re-use of plastic by limiting the number......-polymer interface is suppressed. This improves the ability to see through a clear plastic in the presence of specular reflection. The tapered nanostructures are also utilized to enhance the chroma of pigmented polymers. Larger tapered structures fabricated in a similar manor are shown to work as color filters....... Through an experimental study is the color of the transmitted light linked directly to the random topography of the surface by use of diffraction theory. The color effects from periodic structures and how these might be employed to create bright colors are investigated. This is done both for opaque...

  3. Structure and optical properties of water covered Cu(110) surfaces

    International Nuclear Information System (INIS)

    Baghbanpourasl, A.

    2014-01-01

    (110) surface due to surface relaxation is studied using elastooptic theory. The RAS of the most thermodynamically stable structures are calculated. The calculated spectra can be used as a reference for RAS experiments for determining the adsorbed structure. Calculations show that for all of these structures, RA spectra are sensitive to the water structures considered. In other words different adsorbed water structures have different RA spectra, which makes the structures distinguishable from each other. The origins of the peaks are studied in the band structure and it is observed that surface states are not quenched when water adsorbs in intact form. (author) [de

  4. Architectural Surfaces and Structures from Circular Arcs

    KAUST Repository

    Shi, Ling

    2013-12-01

    In recent decades, the popularity of freeform shapes in contemporary architecture poses new challenges to digital design. One of them is the process of rationalization, i.e. to make freeform skins or structures affordable to manufacture, which draws the most attention from geometry researchers. In this thesis, we aim to realize this process with simple geometric primitives, circular arcs. We investigate architectural surfaces and structures consisting of circular arcs. Our focus is lying on how to employ them nicely and repetitively in architectural design, in order to decrease the cost in manufacturing. Firstly, we study Darboux cyclides, which are algebraic surfaces of order ≤ 4. We provide a computational tool to identify all families of circles on a given cyclide based on the spherical model of M ̈obius geometry. Practical ways to design cyclide patches that pass through certain inputs are presented. In particular, certain triples of circle families on Darboux cyclides may be suitably arranged as 3-webs. We provide a complete classification of all possible 3-webs of circles on Darboux cyclides. We then investigate the circular arc snakes, which are smooth sequences of circu- lar arcs. We evolve the snakes such that their curvature, as a function of arc length, remains unchanged. The evolution of snakes is utilized to approximate given surfaces by circular arcs or to generated freeform shapes, and it is realized by a 2-step pro- cess. More interestingly, certain 6-arc snake with boundary constraints can produce a smooth self motion, which can be employed to build flexible structures. Another challenging topic is approximating smooth freeform skins with simple panels. We contribute to this problem area by approximating a negatively-curved 5 surface with a smooth union of rational bilinear patches. We provide a proof for vertex consistency of hyperbolic nets using the CAGD approach of the rational B ́ezier form. Moreover, we use Darboux transformations for the

  5. Neisserial surface lipoproteins: structure, function and biogenesis.

    Science.gov (United States)

    Hooda, Yogesh; Shin, Hyejin E; Bateman, Thomas J; Moraes, Trevor F

    2017-03-01

    The surface of many Gram-negative bacteria contains lipidated protein molecules referred to as surface lipoproteins or SLPs. SLPs play critical roles in host immune evasion, nutrient acquisition and regulation of the bacterial stress response. The focus of this review is on the SLPs present in Neisseria, a genus of bacteria that colonise the mucosal surfaces of animals. Neisseria contains two pathogens of medical interest, namely Neisseria meningitidis and N. gonorrhoeae. Several SLPs have been identified in Neisseria and their study has elucidated key strategies used by these pathogens to survive inside the human body. Herein, we focus on the identification, structure and function of SLPs that have been identified in Neisseria. We also survey the translocation pathways used by these SLPs to reach the cell surface. Specifically, we elaborate on the strategies used by neisserial SLPs to translocate across the outer membrane with an emphasis on Slam, a novel outer membrane protein that has been implicated in SLP biogenesis. Taken together, the study of SLPs in Neisseria illustrates the widespread roles played by this family of proteins in Gram-negative bacteria. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  6. Using photoelectron diffraction to determine complex molecular adsorption structures

    International Nuclear Information System (INIS)

    Woodruff, D P

    2010-01-01

    Backscattering photoelectron diffraction, particularly in the energy-scan mode, is now an established technique for determining in a quantitative fashion the local structure of adsorbates on surfaces, and has been used successfully for ∼100 adsorbate phases. The elemental and chemical-state specificity afforded by the characteristic core level photoelectron binding energies means that it has particular advantages for molecular adsorbates, as the local geometry of inequivalent atoms in the molecule can be determined in a largely independent fashion. On the other hand, polyatomic molecules present a general problem for all methods of surface structure determination in that a mismatch of intramolecular distances with interatomic distances on the substrate surface means that the atoms in the adsorbed molecule are generally in low-symmetry sites. The quantities measured experimentally then represent an incoherent sum of the properties of each structural domain that is inequivalent with respect to the substrate point group symmetry. This typically leads to greater ambiguity or precision in the structural solutions. The basic principles of the method are described and illustrated with a simple example involving molecule/substrate bonding through only one constituent atom (TiO 2 -(110)/H 2 O). This example demonstrates the importance of obtaining quantitative local structural information. Further examples illustrate both the successes and the problems of this approach when applied to somewhat more complex molecular adsorbates.

  7. The surface electronic structure of Y(0001)

    International Nuclear Information System (INIS)

    Searle, C.

    1998-12-01

    Yttrium has been grown epitaxially on W(110). The growth was monitored by using photoemission spectroscopy with a synchrotron radiation source. The film thickness has been gauged by the attenuation of the W 4f 7/2 bulk component. The films have been grown reproducibly and show a prominent surface state which is indicative of good order and low contamination. Angle-Resolved Ultra-Violet Photoemission Spectroscopy has been used to examine the valence band of these ultra-thin films. The films show a very different structure to the valence band of a bulk crystal of yttrium. The differences have been investigated by a series of model calculations using the LMASA-46 tight-binding LMTO program. The calculations suggest that the ultra-thin film surface state may be hybridised with a tungsten orbital having (x 2 - y 2 ) character. (author)

  8. Structured thermal surface for radiative camouflage.

    Science.gov (United States)

    Li, Ying; Bai, Xue; Yang, Tianzhi; Luo, Hailu; Qiu, Cheng-Wei

    2018-01-18

    Thermal camouflage has been successful in the conductive regime, where thermal metamaterials embedded in a conductive system can manipulate heat conduction inside the bulk. Most reported approaches are background-dependent and not applicable to radiative heat emitted from the surface of the system. A coating with engineered emissivity is one option for radiative camouflage, but only when the background has uniform temperature. Here, we propose a strategy for radiative camouflage of external objects on a given background using a structured thermal surface. The device is non-invasive and restores arbitrary background temperature distributions on its top. For many practical candidates of the background material with similar emissivity as the device, the object can thereby be radiatively concealed without a priori knowledge of the host conductivity and temperature. We expect this strategy to meet the demands of anti-detection and thermal radiation manipulation in complex unknown environments and to inspire developments in phononic and photonic thermotronics.

  9. Frequency Selective Surface for Structural Health Monitoring

    Science.gov (United States)

    Norlyana Azemi, Saidatul; Mustaffa, Farzana Hazira Wan; Faizal Jamlos, Mohd; Abdullah Al-Hadi, Azremi; Soh, Ping Jack

    2018-03-01

    Structural health monitoring (SHM) technologies have attained attention to monitor civil structures. SHM sensor systems have been used in various civil structures such as bridges, buildings, tunnels and so on. However the previous sensor for SHM is wired and encounter with problem to cover large areas. Therefore, wireless sensor was introduced for SHM to reduce network connecting problem. Wireless sensors for Structural Health monitoring are new technology and have many advantages to overcome the drawback of conventional and wired sensor. This project proposed passive wireless SHM sensor using frequency selective surface (FSS) as an alternative to conventional sensors. The electromagnetic wave characteristic of FSS will change by geometrical changes of FSS due to mechanical strain or structural failure. The changes feature is used as a sensing function without any connecting wires. Two type of design which are circular ring and square loop along with the transmission and reflection characteristics of SHM using FSS were discussed in this project. A simulation process has shown that incident angle characteristics can be use as a data for SHM application.

  10. Global search in photoelectron diffraction structure determination using genetic algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Viana, M L [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil); Muino, R Diez [Donostia International Physics Center DIPC, Paseo Manuel de Lardizabal 4, 20018 San Sebastian (Spain); Soares, E A [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil); Hove, M A Van [Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China); Carvalho, V E de [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil)

    2007-11-07

    Photoelectron diffraction (PED) is an experimental technique widely used to perform structural determinations of solid surfaces. Similarly to low-energy electron diffraction (LEED), structural determination by PED requires a fitting procedure between the experimental intensities and theoretical results obtained through simulations. Multiple scattering has been shown to be an effective approach for making such simulations. The quality of the fit can be quantified through the so-called R-factor. Therefore, the fitting procedure is, indeed, an R-factor minimization problem. However, the topography of the R-factor as a function of the structural and non-structural surface parameters to be determined is complex, and the task of finding the global minimum becomes tough, particularly for complex structures in which many parameters have to be adjusted. In this work we investigate the applicability of the genetic algorithm (GA) global optimization method to this problem. The GA is based on the evolution of species, and makes use of concepts such as crossover, elitism and mutation to perform the search. We show results of its application in the structural determination of three different systems: the Cu(111) surface through the use of energy-scanned experimental curves; the Ag(110)-c(2 x 2)-Sb system, in which a theory-theory fit was performed; and the Ag(111) surface for which angle-scanned experimental curves were used. We conclude that the GA is a highly efficient method to search for global minima in the optimization of the parameters that best fit the experimental photoelectron diffraction intensities to the theoretical ones.

  11. Representing Personal Determinants in Causal Structures.

    Science.gov (United States)

    Bandura, Albert

    1984-01-01

    Responds to Staddon's critique of the author's earlier article and addresses issues raised by Staddon's (1984) alternative models of causality. The author argues that it is not the formalizability of causal processes that is the issue but whether cognitive determinants of behavior are reducible to past stimulus inputs in causal structures.…

  12. Nanosecond Surface Microdischarges in Multilayer Structures

    Science.gov (United States)

    Dubinov, A. E.; Lyubimtseva, V. A.

    2018-05-01

    Multilayer structures in which nanosecond surface microdischarges are generated have been developed, fabricated, and investigated. In these structures, layers are made in the form of thin transparent films, and a plasma discharge channel is formed in thin spacings between the layers. Passage of the discharge channel from one layer into the neighboring layer is implemented via pre-fabricated microholes. Images of microdischarges were obtained which confirmed that their plasma channels are formed according to the route assigned by the holes. The route may follow a fairly complex scheme and have self-intersection points and portions in which the electrons are bound to move in opposition to the electric field. In studying the shape of channels in multilayer strictures, the authors have found a new physical effect which lies in the azimuthal self-orientation of the discharge channel as it passes from one microhole to another.

  13. Complementary structure for designer localized surface plasmons

    Science.gov (United States)

    Gao, Zhen; Gao, Fei; Zhang, Youming; Zhang, Baile

    2015-11-01

    Magnetic localized surface plasmons (LSPs) supported on metallic structures corrugated by very long and curved grooves have been recently proposed and demonstrated on an extremely thin metallic spiral structure (MSS) in the microwave regime. However, the mode profile for the magnetic LSPs was demonstrated by measuring only the electric field, not the magnetic field. Here, based on Babinet's principle, we propose a Babinet-inverted, or complementary MSS whose electric/magnetic mode profiles match the magnetic/electric mode profiles of MSS. This complementarity of mode profiles allows mapping the magnetic field distribution of magnetic LSP mode profile on MSS by measuring the electric field distribution of the corresponding mode on complementary MSS. Experiment at microwave frequencies also demonstrate the use of complementary MSS in sensing refractive-index change in the environment.

  14. Capital Structure Determinants and Governance Structure Variety in Franchising

    OpenAIRE

    Jiang, Tao

    2009-01-01

    textabstractThis thesis investigates two questions: the determinants of capital structure in franchising and its subsequent impact on the franchise financing decisions; and the efficient governance structure choice in franchising. We posit that firms franchise in order to benefit from the reduced franchisees’ operational risks by limiting the debt level, such that the franchisor can bear more debt and gain tax-deduction benefits. Specific hypotheses are based on various theories like resource...

  15. Thermocapillary droplet actuation on structured solid surfaces

    Science.gov (United States)

    Karapetsas, George; Chamakos, Nikolaos T.; Papathanasiou, Athanasios G.

    2017-11-01

    The present work investigates, through 2D and 3D finite element simulations, the thermocapillary-driven flow inside a droplet which resides on a non-uniformly heated patterned surface. We employ a recently proposed sharp-interface scheme capable of efficiently modelling the flow over complicate surfaces and consider a wide range of substrate wettabilities, i.e. from hydrophilic to super-hydrophobic surfaces. Our simulations indicate that due to the presence of the solid structures and the induced effect of contact angle hysteresis, inherently predicted by our model, a critical thermal gradient arises beyond which droplet migration is possible, in line with previous experimental observations. The migration velocity as well as the direction of motion depends on the combined action of the net mechanical force along the contact line and the thermocapillary induced flow at the liquid-air interface. We also show that through a proper control and design of the substrate wettability, the contact angle hysteresis and the induced flow field it is possible to manipulate the droplet dynamics, e.g. controlling its motion along a predefined track or entrapping by a wetting defect a droplet based on its size as well as providing appropriate conditions for enhanced mixing inside the droplet. Funding from the European Research Council under the Europeans Community's Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement no. [240710] is acknowledged.

  16. Learning surface molecular structures via machine vision

    Science.gov (United States)

    Ziatdinov, Maxim; Maksov, Artem; Kalinin, Sergei V.

    2017-08-01

    Recent advances in high resolution scanning transmission electron and scanning probe microscopies have allowed researchers to perform measurements of materials structural parameters and functional properties in real space with a picometre precision. In many technologically relevant atomic and/or molecular systems, however, the information of interest is distributed spatially in a non-uniform manner and may have a complex multi-dimensional nature. One of the critical issues, therefore, lies in being able to accurately identify (`read out') all the individual building blocks in different atomic/molecular architectures, as well as more complex patterns that these blocks may form, on a scale of hundreds and thousands of individual atomic/molecular units. Here we employ machine vision to read and recognize complex molecular assemblies on surfaces. Specifically, we combine Markov random field model and convolutional neural networks to classify structural and rotational states of all individual building blocks in molecular assembly on the metallic surface visualized in high-resolution scanning tunneling microscopy measurements. We show how the obtained full decoding of the system allows us to directly construct a pair density function—a centerpiece in analysis of disorder-property relationship paradigm—as well as to analyze spatial correlations between multiple order parameters at the nanoscale, and elucidate reaction pathway involving molecular conformation changes. The method represents a significant shift in our way of analyzing atomic and/or molecular resolved microscopic images and can be applied to variety of other microscopic measurements of structural, electronic, and magnetic orders in different condensed matter systems.

  17. Determination of Surface Fluxes Using a Bowen Ratio System

    African Journals Online (AJOL)

    USER

    Components of the surface fluxes of the energy balance equation were determined ... and vapour pressure in combination with point measurements of net .... approaches zero, then almost all the energy available is used in evapotranspiration.

  18. Simultaneous determination of protein structure and dynamics

    DEFF Research Database (Denmark)

    Lindorff-Larsen, Kresten; Best, Robert B.; DePristo, M. A.

    2005-01-01

    at the atomic level about the structural and dynamical features of proteins-with the ability of molecular dynamics simulations to explore a wide range of protein conformations. We illustrate the method for human ubiquitin in solution and find that there is considerable conformational heterogeneity throughout......We present a protocol for the experimental determination of ensembles of protein conformations that represent simultaneously the native structure and its associated dynamics. The procedure combines the strengths of nuclear magnetic resonance spectroscopy-for obtaining experimental information...... the protein structure. The interior atoms of the protein are tightly packed in each individual conformation that contributes to the ensemble but their overall behaviour can be described as having a significant degree of liquid-like character. The protocol is completely general and should lead to significant...

  19. The Dynamics and Structures of Adsorbed Surfaces

    DEFF Research Database (Denmark)

    Nielsen, M; Ellenson, W. D.; McTague, J. P.

    1978-01-01

    . Elastic neutron diffraction measurements, determining the two-dimensional structural ordering of the adsorbed films, have been performed on layers of N2, Ar, H2, D2, O2, Kr, and He. Measurements on layers of larger molecules such as CD4 and ND3 have also been reported. Inelastic neutron scattering...... measurements, studying the dynamics of the adsorbed films are only possible in a few especially favourable cases such as 36Ar and D2 films, where the coherent phonon scattering cross-sections are very large. In other cases incoherent scattering from hydrogen can give information about e.g. the mobility...

  20. THERMAL TOMOGRAPHY OF ASTEROID SURFACE STRUCTURE

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Alan W.; Drube, Line, E-mail: alan.harris@dlr.de [German Aerospace Center (DLR) Institute of Planetary Research, Rutherfordstrasse 2, D-12489 Berlin (Germany)

    2016-12-01

    Knowledge of the surface thermal inertia of an asteroid can provide insight into its surface structure: porous material has a lower thermal inertia than rock. We develop a means to estimate thermal inertia values of asteroids and use it to show that thermal inertia appears to increase with spin period in the case of main-belt asteroids (MBAs). Similar behavior is found on the basis of thermophysical modeling for near-Earth objects (NEOs). We interpret our results in terms of rapidly increasing material density and thermal conductivity with depth, and provide evidence that thermal inertia increases by factors of 10 (MBAs) to 20 (NEOs) within a depth of just 10 cm. Our results are consistent with a very general picture of rapidly changing material properties in the topmost regolith layers of asteroids and have important implications for calculations of the Yarkovsky effect, including its perturbation of the orbits of potentially hazardous objects and those of asteroid family members after the break-up event. Evidence of a rapid increase of thermal inertia with depth is also an important result for studies of the ejecta-enhanced momentum transfer of impacting vehicles (“kinetic impactors”) in planetary defense.

  1. Effect of surface structure on catalytic reactions: A sum frequency generation surface vibrational spectroscopy study

    International Nuclear Information System (INIS)

    McCrea, Keith R.

    2001-01-01

    In the results discussed above, it is clear that Sum Frequency Generation (SFG) is a unique tool that allows the detection of vibrational spectra of adsorbed molecules present on single crystal surfaces under catalytic reaction conditions. Not only is it possible to detect active surface intermediates, it is also possible to detect spectator species which are not responsible for the measured turnover rates. By correlating high-pressure SFG spectra under reaction conditions and gas chromatography (GC) kinetic data, it is possible to determine which species are important under reaction intermediates. Because of the flexibility of this technique for studying surface intermediates, it is possible to determine how the structures of single crystal surfaces affect the observed rates of catalytic reactions. As an example of a structure insensitive reaction, ethylene hydrogenation was explored on both Pt(111) and Pt(100). The rates were determined to be essentially the same. It was observed that both ethylidyne and di-(sigma) bonded ethylene were present on the surface under reaction conditions on both crystals, although in different concentrations. This result shows that these two species are not responsible for the measured turnover rate, as it would be expected that one of the two crystals would be more active than the other, since the concentration of the surface intermediate would be different on the two crystals. The most likely active intermediates are weakly adsorbed molecules such as(pi)-bonded ethylene and ethyl. These species are not easily detected because their concentration lies at the detection limit of SFG. The SFG spectra and GC data essentially show that ethylene hydrogenation is structure insensitive for Pt(111) and Pt(100). SFG has proven to be a unique and excellent technique for studying adsorbed species on single crystal surfaces under high-pressure catalytic reactions. Coupled with kinetic data obtained from gas chromatography measurements, it can

  2. Photoelectron spectroscopy bulk and surface electronic structures

    CERN Document Server

    Suga, Shigemasa

    2014-01-01

    Photoelectron spectroscopy is now becoming more and more required to investigate electronic structures of various solid materials in the bulk, on surfaces as well as at buried interfaces. The energy resolution was much improved in the last decade down to 1 meV in the low photon energy region. Now this technique is available from a few eV up to 10 keV by use of lasers, electron cyclotron resonance lamps in addition to synchrotron radiation and X-ray tubes. High resolution angle resolved photoelectron spectroscopy (ARPES) is now widely applied to band mapping of materials. It attracts a wide attention from both fundamental science and material engineering. Studies of the dynamics of excited states are feasible by time of flight spectroscopy with fully utilizing the pulse structures of synchrotron radiation as well as lasers including the free electron lasers (FEL). Spin resolved studies also made dramatic progress by using higher efficiency spin detectors and two dimensional spin detectors. Polarization depend...

  3. Surface and interface electronic structure: Three year activity report

    International Nuclear Information System (INIS)

    Kevan, S.D.

    1992-01-01

    The 3-year activity report covers surface structure and phonon anomalies (surface reconstruction on W(001) and Mo(001), adsorbate lateral ordering, surface Fermi contours and phonon anomalies on Pt(111) and Pd(001)), adsorbate vibrational damping, charge transfer in momentum space: W(011)-K, surface states and resonances (relativistic effects ampersand computations, surface resonances)

  4. High Resolution Powder Diffraction and Structure Determination

    International Nuclear Information System (INIS)

    Cox, D. E.

    1999-01-01

    It is clear that high-resolution synchrotrons X-ray powder diffraction is a very powerful and convenient tool for material characterization and structure determination. Most investigations to date have been carried out under ambient conditions and have focused on structure solution and refinement. The application of high-resolution techniques to increasingly complex structures will certainly represent an important part of future studies, and it has been seen how ab initio solution of structures with perhaps 100 atoms in the asymmetric unit is within the realms of possibility. However, the ease with which temperature-dependence measurements can be made combined with improvements in the technology of position-sensitive detectors will undoubtedly stimulate precise in situ structural studies of phase transitions and related phenomena. One challenge in this area will be to develop high-resolution techniques for ultra-high pressure investigations in diamond anvil cells. This will require highly focused beams and very precise collimation in front of the cell down to dimensions of 50 (micro)m or less. Anomalous scattering offers many interesting possibilities as well. As a means of enhancing scattering contrast it has applications not only to the determination of cation distribution in mixed systems such as the superconducting oxides discussed in Section 9.5.3, but also to the location of specific cations in partially occupied sites, such as the extra-framework positions in zeolites, for example. Another possible application is to provide phasing information for ab initio structure solution. Finally, the precise determination of f as a function of energy through an absorption edge can provide useful information about cation oxidation states, particularly in conjunction with XANES data. In contrast to many experiments at a synchrotron facility, powder diffraction is a relatively simple and user-friendly technique, and most of the procedures and software for data analysis

  5. 30 CFR 75.1708 - Surface structures, fireproofing.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Surface structures, fireproofing. 75.1708... structures, fireproofing. [Statutory Provisions] After March 30, 1970, all structures erected on the surface within 100 feet of any mine opening shall be of fireproof construction. Unless structures existing on or...

  6. Orientation determination of interfacial beta-sheet structures in situ.

    Science.gov (United States)

    Nguyen, Khoi Tan; King, John Thomas; Chen, Zhan

    2010-07-01

    Structural information such as orientations of interfacial proteins and peptides is important for understanding properties and functions of such biological molecules, which play crucial roles in biological applications and processes such as antimicrobial selectivity, membrane protein activity, biocompatibility, and biosensing performance. The alpha-helical and beta-sheet structures are the most widely encountered secondary structures in peptides and proteins. In this paper, for the first time, a method to quantify the orientation of the interfacial beta-sheet structure using a combined attenuated total reflectance Fourier transformation infrared spectroscopic (ATR-FTIR) and sum frequency generation (SFG) vibrational spectroscopic study was developed. As an illustration of the methodology, the orientation of tachyplesin I, a 17 amino acid peptide with an antiparallel beta-sheet, adsorbed to polymer surfaces as well as associated with a lipid bilayer was determined using the regular and chiral SFG spectra, together with polarized ATR-FTIR amide I signals. Both the tilt angle (theta) and the twist angle (psi) of the beta-sheet at interfaces are determined. The developed method in this paper can be used to obtain in situ structural information of beta-sheet components in complex molecules. The combination of this method and the existing methodology that is currently used to investigate alpha-helical structures will greatly broaden the application of optical spectroscopy in physical chemistry, biochemistry, biophysics, and structural biology.

  7. Structure of solid surfaces and of adsorbates by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Somorjai, G.A.

    1977-01-01

    LEED theory has developed to the point where the diffraction beam intensities can be computed using the locations of the surface atoms as the only adjustable parameters. The position of atoms in many clean monatomic solid surfaces and the surface structures of ordered monolayers of adsorbed atoms have been determined this way. Surface crystallography studies are now extended to small hydrocarbon molecules that are adsorbed on metal surfaces. These studies are reviewed

  8. Elementary structural building blocks encountered in silicon surface reconstructions

    International Nuclear Information System (INIS)

    Battaglia, Corsin; Monney, Claude; Didiot, Clement; Schwier, Eike Fabian; Garnier, Michael Gunnar; Aebi, Philipp; Gaal-Nagy, Katalin; Onida, Giovanni

    2009-01-01

    Driven by the reduction of dangling bonds and the minimization of surface stress, reconstruction of silicon surfaces leads to a striking diversity of outcomes. Despite this variety even very elaborate structures are generally comprised of a small number of structural building blocks. We here identify important elementary building blocks and discuss their integration into the structural models as well as their impact on the electronic structure of the surface. (topical review)

  9. Atomic probes of surface structure and dynamics

    International Nuclear Information System (INIS)

    Heller, E.J.; Jonsson, H.

    1992-01-01

    The following were studied: New semiclassical method for scattering calculations, He atom scattering from defective Pt surfaces, He atom scattering from Xe overlayers, thermal dissociation of H 2 on Cu(110), spin flip scattering of atoms from surfaces, and Car-Parrinello simulations of surface processes

  10. DETERMINING REFLECTANCE SPECTRA OF SURFACES AND CLOUDS ON EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Cowan, Nicolas B.; Strait, Talia E., E-mail: n-cowan@northwestern.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 2131 Tech Dr., IL 60208 (United States)

    2013-03-01

    Planned missions will spatially resolve temperate terrestrial planets from their host star. Although reflected light from such a planet encodes information about its surface, it has not been shown how to establish surface characteristics of a planet without assuming known surfaces to begin with. We present a reanalysis of disk-integrated, time-resolved, multiband photometry of Earth obtained by the Deep Impact spacecraft as part of the EPOXI Mission of Opportunity. We extract reflectance spectra of clouds, ocean, and land without a priori knowledge of the numbers or colors of these surfaces. We show that the inverse problem of extracting surface spectra from such data is a novel and extreme instance of spectral unmixing, a well-studied problem in remote sensing. Principal component analysis is used to determine an appropriate number of model surfaces with which to interpret the data. Shrink-wrapping a simplex to the color excursions of the planet yields a conservative estimate of the planet's endmember spectra. The resulting surface maps are unphysical, however, requiring negative or larger-than-unity surface coverage at certain locations. Our ''rotational unmixing'' supersedes the endmember analysis by simultaneously solving for the surface spectra and their geographical distributions on the planet, under the assumption of diffuse reflection and known viewing geometry. We use a Markov Chain Monte Carlo to determine best-fit parameters and their uncertainties. The resulting albedo spectra are similar to clouds, ocean, and land seen through a Rayleigh-scattering atmosphere. This study suggests that future direct-imaging efforts could identify and map unknown surfaces and clouds on exoplanets.

  11. Determining Surface Infiltration Rate of Permeable Pavements with Digital Imaging

    Directory of Open Access Journals (Sweden)

    Caterina Valeo

    2018-01-01

    Full Text Available Cell phone images of pervious pavement surfaces were used to explore relationships between surface infiltration rates (SIR measured using the ASTM C1701 standard test and using a simple falling head test. A fiber-reinforced porous asphalt surface and a highly permeable material comprised of stone, rubber and a polymer binder (Porous Pave were tested. Images taken with a high-resolution cellphone camera were acquired as JPEG files and converted to gray scale images in Matlab® for analysis. The distribution of gray levels was compared to the surface infiltration rates obtained for both pavements with attention given to the mean of the distribution. Investigation into the relationships between mean SIR and parameters determined from the gray level distribution produced in the image analysis revealed that mean SIR measured in both pavements were proportional to the inverse of the mean of the distribution. The relationships produced a coefficient of determination over 85% using both the ASTM and the falling head test in the porous asphalt surface. SIR measurements determined with the ASTM method were highly correlated with the inverse mean of the distribution of gray levels in the Porous Pave material as well, producing coefficients of determination of over 90% and Kendall’s tau-b of roughly 70% for nonparametric data.

  12. Structures and Functions of Pestivirus Glycoproteins: Not Simply Surface Matters

    Directory of Open Access Journals (Sweden)

    Fun-In Wang

    2015-06-01

    Full Text Available Pestiviruses, which include economically important animal pathogens such as bovine viral diarrhea virus and classical swine fever virus, possess three envelope glycoproteins, namely Erns, E1, and E2. This article discusses the structures and functions of these glycoproteins and their effects on viral pathogenicity in cells in culture and in animal hosts. E2 is the most important structural protein as it interacts with cell surface receptors that determine cell tropism and induces neutralizing antibody and cytotoxic T-lymphocyte responses. All three glycoproteins are involved in virus attachment and entry into target cells. E1-E2 heterodimers are essential for viral entry and infectivity. Erns is unique because it possesses intrinsic ribonuclease (RNase activity that can inhibit the production of type I interferons and assist in the development of persistent infections. These glycoproteins are localized to the virion surface; however, variations in amino acids and antigenic structures, disulfide bond formation, glycosylation, and RNase activity can ultimately affect the virulence of pestiviruses in animals. Along with mutations that are driven by selection pressure, antigenic differences in glycoproteins influence the efficacy of vaccines and determine the appropriateness of the vaccines that are currently being used in the field.

  13. Structures and Functions of Pestivirus Glycoproteins: Not Simply Surface Matters.

    Science.gov (United States)

    Wang, Fun-In; Deng, Ming-Chung; Huang, Yu-Liang; Chang, Chia-Yi

    2015-06-29

    Pestiviruses, which include economically important animal pathogens such as bovine viral diarrhea virus and classical swine fever virus, possess three envelope glycoproteins, namely Erns, E1, and E2. This article discusses the structures and functions of these glycoproteins and their effects on viral pathogenicity in cells in culture and in animal hosts. E2 is the most important structural protein as it interacts with cell surface receptors that determine cell tropism and induces neutralizing antibody and cytotoxic T-lymphocyte responses. All three glycoproteins are involved in virus attachment and entry into target cells. E1-E2 heterodimers are essential for viral entry and infectivity. Erns is unique because it possesses intrinsic ribonuclease (RNase) activity that can inhibit the production of type I interferons and assist in the development of persistent infections. These glycoproteins are localized to the virion surface; however, variations in amino acids and antigenic structures, disulfide bond formation, glycosylation, and RNase activity can ultimately affect the virulence of pestiviruses in animals. Along with mutations that are driven by selection pressure, antigenic differences in glycoproteins influence the efficacy of vaccines and determine the appropriateness of the vaccines that are currently being used in the field.

  14. Electronic structure of epitaxial chalcopyrite surfaces and interfaces for photovoltaics

    International Nuclear Information System (INIS)

    Hofmann, Andreas

    2012-01-01

    This thesis constitutes a comprehensive study of the surface physics of epitaxial CuInSe 2 films. It comprises analyses of the surface morphology and reconstruction, electronic band structure as well as hetero-junctions relevant to photovoltaic applications. Therefore, especially the aspect of stoichiometry variation from the CuInSe 2 to the copper-deficient defect phases was considered. Preparation and analysis was completely performed under ultra-high vacuum conditions in order to ensure the investigation of well-defined samples free of contaminants. For some of the analysis techniques, single-crystalline samples are indispensable: They allow for the determination of surface periodicity by low-energy electron diffraction (LEED). In combination with concentration depth profiling by angle-resolved x-ray photoemission, to types of surface reconstructions could be distinguished for the near-stoichiometric CuInSe 2 (112) surface. In the copper-rich case, it is stabilized by Cu In anti-site defects and on the indium-rich side by 2 V Cu defects, as predicted by surface total energy calculations by Jaffe and Zunger. Both configurations correspond to a c(4 x 2) reconstruction of the zinc blende type (111) surface. For the defect compound CuIn 3 Se 5 , a sphalerite order of the surface was found, which points at a weakening or absence of the chalcopyrite order in the bulk of the material. The unusual stability of the (112) surface could also be proven by comparison with the reconstruction and surface order of (001) and (220) surfaces. The results from surface analysis were used to measure the valence band structure of the epitaxial samples by synchrotron-based angle-resolved photoelectron spectroscopy. The CuInSe 2 (001) surface gives access to the high symmetry directions Γ-T and Γ-N of momentum space. By contrasting the data obtained for the stoichiometric surface with the copper-poor defect compound, a reduction of the valence band dispersion and a broadening of

  15. Surface temperature and surface heat flux determination of the inverse heat conduction problem for a slab

    International Nuclear Information System (INIS)

    Kuroyanagi, Toshiyuki

    1983-07-01

    Based on an idea that surface conditions should be a reflection of interior temperature and interior heat flux variation as inverse as interior conditions has been determined completely by the surface temperature and/on surface heat flux as boundary conditions, a method is presented for determining the surface temperature and the surface heat flux of a solid when the temperature and heat flux at an interior point are a prescribed function of time. The method is developed by the integration of Duhumels' integral which has unknown temperature or unknown heat flux in its integrand. Specific forms of surface condition determination are developed for a sample inverse problem: slab. Ducussing the effect of a degree of avairable informations at an interior point due to damped system and the effect of variation of surface conditions on those formulations, it is shown that those formulations are capable of representing the unknown surface conditions except for small time interval followed by discontinuous change of surface conditions. The small un-resolved time interval is demonstrated by a numerical example. An evaluation method of heat flux at an interior point, which is requested by those formulations, is discussed. (author)

  16. Atomic probes of surface structure and dynamics

    International Nuclear Information System (INIS)

    Heller, E.J.; Jonsson, H.

    1992-01-01

    Progress for the period Sept. 15, 1992 to Sept. 14, 1993 is discussed. Semiclassical methods that will allow much faster and more accurate three-dimensional atom--surface scattering calculations, both elastic and inelastic, are being developed. The scattering of He atoms from buckyballs is being investigated as a test problem. Somewhat more detail is given on studies of He atom scattering from defective Pt surfaces. Molecular dynamics simulations of He + and Ar + ion sputtering of Pt surfaces are also being done. He atom scattering from Xe overlayers on metal surfaces and the thermalized dissociation of H 2 on Cu(110) are being studied. (R.W.R.) 64 refs

  17. Structure determination by X-ray crystallography

    CERN Document Server

    Ladd, M F C

    1977-01-01

    Crystallography may be described as the science of the structure of materi­ als, using this word in its widest sense, and its ramifications are apparent over a broad front of current scientific endeavor. It is not surprising, therefore, to find that most universities offer some aspects of crystallography in their undergraduate courses in the physical sciences. It is the principal aim of this book to present an introduction to structure determination by X-ray crystal­ lography that is appropriate mainly to both final-year undergraduate studies in crystallography, chemistry, and chemical physics, and introductory post­ graduate work in this area of crystallography. We believe that the book will be of interest in other disciplines, such as physics, metallurgy, biochemistry, and geology, where crystallography has an important part to play. In the space of one book, it is not possible either to cover all aspects of crystallography or to treat all the subject matter completely rigorously. In particular, certain ...

  18. Tensioned Fabric Structures with Surface in the Form of Chen-Gackstatter

    Directory of Open Access Journals (Sweden)

    Yee Hooi Min

    2016-01-01

    Full Text Available Form-finding has to be carried out for tensioned fabric structure in order to determine the initial equilibrium shape under prescribed support condition and prestress pattern. Tensioned fabric structures are normally designed to be in the form of equal tensioned surface. Tensioned fabric structure is highly suited to be used for realizing surfaces of complex or new forms. However, research study on a new form as a tensioned fabric structure has not attracted much attention. Another source of inspiration minimal surface which could be adopted as form for tensioned fabric structure is very crucial. The aim of this study is to propose initial equilibrium shape of tensioned fabric structures in the form of Chen-Gackstatter. Computational form-finding using nonlinear analysis method is used to determine the Chen-Gackstatter form of uniformly stressed surfaces. A tensioned fabric structure must curve equally in opposite directions to give the resulting surface a three dimensional stability. In an anticlastic doubly curved surface, the sum of all positive and all negative curvatures is zero. This study provides an alternative choice for structural designer to consider the Chen-Gackstatter applied in tensioned fabric structures. The results on factors affecting initial equilibrium shape can serve as a reference for proper selection of surface parameter for achieving a structurally viable surface.

  19. Quantative determination of surface temperatures using an infrared camera

    International Nuclear Information System (INIS)

    Hsieh, C.K.; Ellingson, W.A.

    1977-01-01

    A method is presented to determine the surface-temperature distribution at each point in an infrared picture. To handle the surface reflection problem, three cases are considered that include the use of black coatings, radiation shields, and band-pass filters. For uniform irradiation on the test surface, the irradiation can be measured by using a cooled, convex mirror. Equations are derived to show that this surrounding irradiation effect can be subtracted out from the scanned radiation; thus the net radiation is related to only emission from the surface. To provide for temperature measurements over a large field, the image-processing technique is used to digitize the infrared data. The paper spells out procedures that involve the use of a computer for making point-by-point temperature calculations. Finally, a sample case is given to illustrate applications of the method. 6 figures, 1 table

  20. The structure of surface texture knowledge

    International Nuclear Information System (INIS)

    Yan Wang; Scott, Paul J; Jiang Xiangqian

    2005-01-01

    This research aims to create an intelligent knowledge-based system for engineering and bio-medical engineering surface texture, which will provide expert knowledge of surface texture to link surface function, specification of micro- and nano-geometry through manufacture, and verification. The intelligent knowledge base should be capable of incorporating knowledge from multiple sources (standards, books, experts, etc), adding new knowledge from these sources and still remain a coherent reliable system. A new data model based on category theory will be adopted to construct this system

  1. Importance of surface structure on dissolution of fluorite

    DEFF Research Database (Denmark)

    Godinho, Jose; Piazolo, Sandra; Balic Zunic, Tonci

    2014-01-01

    forming the initial surface and its inclination to the closest stable planes, which are specific for each surface orientation. During an initial dissolution regime dissolution rates decrease significantly, even though the total surface area increases. During a second dissolution regime, some surfaces...... by the relative stability of the planes and type of edges that constitute a surface needs to be considered. Significant differences between dissolution rates calculated based on surface area alone, and based on surface reactivity are expected for materials with the fluorite structure....

  2. Hydroxyl migration disorders the surface structure of hydroxyapatite nanoparticles

    Science.gov (United States)

    Cheng, Xiajie; Wu, Hong; Zhang, Li; Ma, Xingtao; Zhang, Xingdong; Yang, Mingli

    2017-09-01

    The surface structure of nano-hydroxyapatite (HAP) was investigated using a combined simulated annealing and molecular dynamics method. The stationary structures of nano-HAP with 4-7 nm in diameter and annealed under different temperatures were analyzed in terms of pair distribution function, structural factor, mean square displacement and atomic coordination number. The particles possess different structures from bulk crystal. A clear radial change in their atomic arrangements was noted. From core to surface the structures change from ordered to disordered. A three-shell model was proposed to describe the structure evolution of nano-HAP. Atoms in the core zone keep their arrangements as in crystal, while atoms in the surface shell are in short-range order and long-range disorder, adopting a typically amorphous structure. Atoms in the middle shell have small displacements and/or deflections but basically retain their original locations as in crystal. The disordered shell is about 1 nm in thickness, in agreement with experimental observations. The disordering mainly stems from hydroxyl migration during which hydroxyls move to the surface and bond with the exposed Ca ions, and their left vacancies bring about a rearrangement of nearby atoms. The disordering is to some extent different for particles unannealed under different temperatures, resulting from fewer number of migrated hydroxyls at lower temperatures. Particles with different sizes have similar surface structures, and their surface energy decreases with increasing size. Moreover, the surface energy is reduced by hydroxyl migration because the exposed Ca ions on the surface are ionically bonded with the migrated hydroxyls. Our calculations proposed a new structure model for nano-HAP, which indicates a surface structure with activities different from those without surface reorganization. This is particularly interesting because most bioactivities of biomaterials are dominated by their surface activity.

  3. Determination of forest road surface roughness by Kinect depth imaging

    Directory of Open Access Journals (Sweden)

    Francesco Marinello

    2017-12-01

    Full Text Available Roughness is a dynamic property of the gravel road surface that affects safety, ride comfort as well as vehicle tyre life and maintenance costs. A rapid survey of gravel road condition is fundamental for an effective maintenance planning and definition of the intervention priorities.Different non-contact techniques such as laser scanning, ultrasonic sensors and photogrammetry have recently been proposed to reconstruct three-dimensional topography of road surface and allow extraction of roughness metrics. The application of Microsoft Kinect™ depth camera is proposed and discussed here for collection of 3D data sets from gravel roads, to be implemented in order to allow quantification of surface roughness.The objectives are to: i verify the applicability of the Kinect sensor for characterization of different forest roads, ii identify the appropriateness and potential of different roughness parameters and iii analyse the correlation with vibrations recoded by 3-axis accelerometers installed on different vehicles. The test took advantage of the implementation of the Kinect depth camera for surface roughness determination of 4 different forest gravel roads and one well-maintained asphalt road as reference. Different vehicles (mountain bike, off-road motorcycle, ATV vehicle, 4WD car and compact crossover were included in the experiment in order to verify the vibration intensity when travelling on different road surface conditions. Correlations between the extracted roughness parameters and vibration levels of the tested vehicles were then verified. Coefficients of determination of between 0.76 and 0.97 were detected between average surface roughness and standard deviation of relative accelerations, with higher values in the case of lighter vehicles.

  4. Compression and Injection Moulding of Nano-Structured Polymer Surfaces

    DEFF Research Database (Denmark)

    Pranov, Henrik; Rasmussen, Henrik Koblitz

    2006-01-01

    In our research we investigate the non-isothermal replication of complex nano and micro surface structures in injection and compression moulding.......In our research we investigate the non-isothermal replication of complex nano and micro surface structures in injection and compression moulding....

  5. Surface modification method for reactor incore structural component

    International Nuclear Information System (INIS)

    Obata, Minoru; Sudo, Akira.

    1996-01-01

    A large number of metal or ceramic small spheres accelerated by pressurized air are collided against a surface of a reactor incore structures or a welded surface of the structural components, and then finishing is applied by polishing to form compression stresses on the surface. This can change residual stresses into compressive stress without increasing the strength of the surface. Accordingly, stress corrosion crackings of the incore structural components or welded portions thereof can be prevented thereby enabling to extend the working life of equipments. (T.M.)

  6. Characterization of technical surfaces by structure function analysis

    Science.gov (United States)

    Kalms, Michael; Kreis, Thomas; Bergmann, Ralf B.

    2018-03-01

    The structure function is a tool for characterizing technical surfaces that exhibits a number of advantages over Fourierbased analysis methods. So it is optimally suited for analyzing the height distributions of surfaces measured by full-field non-contacting methods. The structure function is thus a useful method to extract global or local criteria like e. g. periodicities, waviness, lay, or roughness to analyze and evaluate technical surfaces. After the definition of line- and area-structure function and offering effective procedures for their calculation this paper presents examples using simulated and measured data of technical surfaces including aircraft parts.

  7. Fragmentation pathways of nanofractal structures on surfaces

    DEFF Research Database (Denmark)

    Dick, Veronika V.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2011-01-01

    We present a theoretical analysis of the post-growth processes occurring in nanofractals grown on a surface. For this study we have developed a method that accounts for the internal dynamics of particles in a fractal. We demonstrate that the detachment of particles from the fractal and their diff...

  8. Determination of 3D Equilibria from Flux Surface Knowledge Only

    International Nuclear Information System (INIS)

    Mynick, H.E.; Pomphrey, N.

    2001-01-01

    We show that the method of Christiansen and Taylor, from which complete tokamak equilibria can be determined given only knowledge of the shape of the flux surfaces, can be extended to 3-dimensional equilibria, such as those of stellarators. As for the tokamak case, the given geometric knowledge has a high degree of redundancy, so that the full equilibrium can be obtained using only a small portion of that information

  9. Host Proteins Determine MRSA Biofilm Structure and Integrity

    DEFF Research Database (Denmark)

    Dreier, Cindy; Nielsen, Astrid; Jørgensen, Nis Pedersen

    Human extracellular matrix (hECM) proteins aids the initial attachment and initiation of an infection, by specific binding to bacterial cell surface proteins. However, the importance of hECM proteins in structure, integrity and antibiotic resilience of a biofilm is unknown. This study aims...... to determine how specific hECM proteins affect S. aureus USA300 JE2 biofilms. Biofilms were grown in the presence of synovial fluid from rheumatoid arteritis patients to mimic in vivo conditions, where bacteria incorporate hECM proteins into the biofilm matrix. Difference in biofilm structure, with and without...... addition of hECM to growth media, was visualized by confocal laser scanning microscopy. Two enzymatic degradation experiments were used to study biofilm matrix composition and importance of hECM proteins: enzymatic removal of specific hECM proteins from growth media, before biofilm formation, and enzymatic...

  10. Urban Surface Radiative Energy Budgets Determined Using Aircraft Scanner Data

    Science.gov (United States)

    Luvall, Jeffrey C.; Quattrochi, Dale A.; Rickman, Doug L.; Estes, Maury G.; Arnold, James E. (Technical Monitor)

    2002-01-01

    It is estimated that by the year 2025, 80% of the world's population will live in cities. The extent of these urban areas across the world can be seen in an image of city lights from the Defense Meteorological Satellite Program. In many areas of North America and Europe, it is difficult to separate individual cities because of the dramatic growth and sprawl of urbanized areas. This conversion of the natural landscape vegetation into man-made urban structures such as roads and buildings drastically alter the regional surface energy budgets, hydrology, precipitation patterns, and meteorology. One of the earliest recognized and measured phenomena of urbanization is the urban heat island (UHI) which was reported as early as 1833 for London and 1862 for Paris. The urban heat island results from the energy that is absorbed by man-made materials during the day and is released at night resulting in the heating of the air within the urban area. The magnitude of the air temperature difference between the urban and surrounding countryside is highly dependent on the structure of the urban area, amount of solar immolation received during the day, and atmospheric conditions during the night. These night time air temperature differences can be in the range of 2 to 5 C. or greater. Although day time air temperature differences between urban areas and the countryside exists during the day, atmospheric mixing and stability reduce the magnitude. This phenomena is not limited to large urban areas, but also occurs in smaller metropolitan areas. The UHI has significant impacts on the urban air quality, meteorology, energy use, and human health. The UPI can be mitigated through increasing the amount of vegetation and modification of urban surfaces using high albedo materials for roofs and paved surfaces. To understand why the urban heat island phenomenon exists it is useful to define the surface in terms of the surface energy budget. Surface temperature and albedo is a major component of

  11. Electronic structure of incident carbon ions on a graphite surface

    International Nuclear Information System (INIS)

    Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.

    1997-01-01

    The electronic structure of an incident carbon ion on a graphite surface is discussed on the basis of ab initio molecular orbital calculations. A carbon cation forms a covalent bond with the graphite, and a carbon nonion is attracted to the graphite surface through van der Waals interaction. A carbon anion has no stable state on a graphite surface. The charge effects of incident ions become clear upon detailed examination of the electronic structure. (author)

  12. Facile fabrication of superhydrophobic surfaces with hierarchical structures.

    Science.gov (United States)

    Lee, Eunyoung; Lee, Kun-Hong

    2018-03-06

    Hierarchical structures were fabricated on the surfaces of SUS304 plates using a one-step process of direct microwave irradiation under a carbon dioxide atmosphere. The surface nanostructures were composed of chrome-doped hematite single crystals. Superhydrophobic surfaces with a water contact angle up to 169° were obtained by chemical modification of the hierarchical structures. The samples maintained superhydrophobicity under NaCl solution up to 2 weeks.

  13. Modulation of photonic structures by surface acoustic waves

    International Nuclear Information System (INIS)

    Mauricio M de Lima Jr; Santos, Paulo V

    2005-01-01

    This paper reviews the interaction between coherently stimulated acoustic phonons in the form of surface acoustic waves with light beams in semiconductor based photonic structures. We address the generation of surface acoustic wave modes in these structures as well as the technological aspects related to control of the propagation and spatial distribution of the acoustic fields. The microscopic mechanisms responsible for the interaction between light and surface acoustic modes in different structures are then reviewed. Particular emphasis is given to the acousto-optical interaction in semiconductor microcavities and its application in photon control. These structures exhibit high optical modulation levels under acoustic excitation and are compatible with integrated light sources and detectors

  14. Shallow lunar structure determined from the passive seismic experiment

    International Nuclear Information System (INIS)

    Nakamura, Y.; Dorman, J.; Duennebier, F.; Lammlein, D.; Latham, G.

    1975-01-01

    Data relevant to the shallow structure of the Moon obtained at the Apollo seismic stations are compared with previously published results of the active seismic experiments. It is concluded that the lunar surface is covered by a layer of low seismic velocity (Vsub(p) approximately equal to 100 ms -1 ), which appears to be equivalent to the lunar regolith defined previously by geological observations. This layer is underlain by a zone of distinctly higher seismic velocity at all of the Apollo landing sites. The regolith thicknesses at the Apollo 11, 12, and 15 sites are estimated from the shear-wave resonance to be 4.4, 3.7, and 4.4m, respectively. These thicknesses and those determined at the other Apollo sites by the active seismic experiments appear to be correlated with the age determinations and the abundances of extra-lunar components at the sites. (Auth.)

  15. LASER SURFACE CLADDING FOR STRUCTURAL REPAIR

    OpenAIRE

    SANTANU PAUL

    2018-01-01

    Laser cladding is a powder deposition technique, which is used to deposit layers of clad material on a substrate to improve its surface properties. It has widespread application in the repair of dies and molds used in the automobile industry. These molds and dies are subjected to cyclic thermo-mechanical loading and therefore undergo localized damage and wear. The final clad quality and integrity is influenced by various physical phenomena, namely, melt pool morphology, microst...

  16. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    Science.gov (United States)

    2014-10-27

    Diamond. Phys. Rev. Lett. 2000, 84, 5160−5163. (31) Ownby, P. D.; Yang, X.; Liu, J. Calculated X-Ray-Diffraction Data for Diamond Polytypes. J. Am. Ceram...Surfaces from Ab-Initio Calculations . Phys. Rev. B 1995, 51, 14669−14685. (39) Ferrari, A. C.; Robertson, J. Raman Spectroscopy of Amorphous, Nanostructured...Y.; Takami, S.; Kubo , M.; Belosludov, R. V.; Miyamoto, A.; Imamura, A.; Gamo, M. N.; Ando, T. First-Principle Study on Reactions of Diamond (100

  17. Structural and electronic properties of hydrosilylated silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Baumer, A.

    2005-11-15

    The structural and electronic properties of alkyl-terminated Si surfaces prepared by thermallyinduced hydrosilylation have been studied in detail in the preceding chapters. Various surfaces have been used for the functionalization ranging from crystalline Si over amorphous hydrogenated Si to nanoscaled materials such as Si nanowires and nanoparticles. In each case, the alkyl-terminated surfaces have been compared to the native oxidized and H-terminated surfaces. (orig.)

  18. Surface topographical and structural analysis of Ag+-implanted polymethylmethacrylate

    International Nuclear Information System (INIS)

    Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Naab, Fabian; Toader, Ovidiu; Sagheer, Riffat; Bashir, Shazia; Zia, Rehana; Siraj, Khurram; Iqbal, Saman

    2016-01-01

    Specimens of polymethylmethacrylate (PMMA) were implanted with 400-keV Ag + ions at different ion fluences ranging from 1 × 10 14 to 5 × 10 15 ions/cm 2 using a 400-kV NEC ion implanter. The surface topographical features of the implanted PMMA were investigated by a confocal microscope. Modifications in the structural properties of the implanted specimens were analyzed in comparison with pristine PMMA by X-ray diffraction (XRD) and Raman spectroscopy. UV–Visible spectroscopy was applied to determine the effects of ion implantation on optical transmittance of the implanted PMMA. The confocal microscopic images revealed the formation of hillock-like microstructures along the ion track on the implanted PMMA surface. The increase in ion fluence led to more nucleation of hillocks. The XRD pattern confirmed the amorphous nature of pristine and implanted PMMA, while the Raman studies justified the transformation of Ag + -implanted PMMA into amorphous carbon at the ion fluence of ⩾5 × 10 14 ions/cm 2 . Moreover, the decrease in optical transmittance of PMMA is associated with the formation of hillocks and ion-induced structural modifications after implantation.

  19. Surface, structural and tensile properties of proton beam irradiated zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Rafique, Mohsin; Chae, San; Kim, Yong-Soo, E-mail: yongskim@hanyang.ac.kr

    2016-02-01

    This paper reports the surface, structural and tensile properties of proton beam irradiated pure zirconium (99.8%). The Zr samples were irradiated by 3.5 MeV protons using MC-50 cyclotron accelerator at different doses ranging from 1 × 10{sup 13} to 1 × 10{sup 16} protons/cm{sup 2}. Both un-irradiated and irradiated samples were characterized using Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD) and Universal Testing Machine (UTM). The average surface roughness of the specimens was determined by using Nanotech WSxM 5.0 develop 7.0 software. The FESEM results revealed the formation of bubbles, cracks and black spots on the samples’ surface at different doses whereas the XRD results indicated the presence of residual stresses in the irradiated specimens. Williamson–Hall analysis of the diffraction peaks was carried out to investigate changes in crystallite size and lattice strain in the irradiated specimens. The tensile properties such as the yield stress, ultimate tensile stress and percentage elongation exhibited a decreasing trend after irradiation in general, however, an inconsistent behavior was observed in their dependence on proton dose. The changes in tensile properties of Zr were associated with the production of radiation-induced defects including bubbles, cracks, precipitates and simultaneous recovery by the thermal energy generated with the increase of irradiation dose.

  20. Surface, structural and tensile properties of proton beam irradiated zirconium

    Science.gov (United States)

    Rafique, Mohsin; Chae, San; Kim, Yong-Soo

    2016-02-01

    This paper reports the surface, structural and tensile properties of proton beam irradiated pure zirconium (99.8%). The Zr samples were irradiated by 3.5 MeV protons using MC-50 cyclotron accelerator at different doses ranging from 1 × 1013 to 1 × 1016 protons/cm2. Both un-irradiated and irradiated samples were characterized using Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD) and Universal Testing Machine (UTM). The average surface roughness of the specimens was determined by using Nanotech WSxM 5.0 develop 7.0 software. The FESEM results revealed the formation of bubbles, cracks and black spots on the samples' surface at different doses whereas the XRD results indicated the presence of residual stresses in the irradiated specimens. Williamson-Hall analysis of the diffraction peaks was carried out to investigate changes in crystallite size and lattice strain in the irradiated specimens. The tensile properties such as the yield stress, ultimate tensile stress and percentage elongation exhibited a decreasing trend after irradiation in general, however, an inconsistent behavior was observed in their dependence on proton dose. The changes in tensile properties of Zr were associated with the production of radiation-induced defects including bubbles, cracks, precipitates and simultaneous recovery by the thermal energy generated with the increase of irradiation dose.

  1. Compact complex surfaces with geometric structures related to split quaternions

    International Nuclear Information System (INIS)

    Davidov, Johann; Grantcharov, Gueo; Mushkarov, Oleg; Yotov, Miroslav

    2012-01-01

    We study the problem of existence of geometric structures on compact complex surfaces that are related to split quaternions. These structures, called para-hypercomplex, para-hyperhermitian and para-hyperkähler, are analogs of the hypercomplex, hyperhermitian and hyperkähler structures in the definite case. We show that a compact 4-manifold carries a para-hyperkähler structure iff it has a metric of split signature together with two parallel, null, orthogonal, pointwise linearly independent vector fields. Every compact complex surface admitting a para-hyperhermitian structure has vanishing first Chern class and we show that, unlike the definite case, many of these surfaces carry infinite-dimensional families of such structures. We provide also compact examples of complex surfaces with para-hyperhermitian structures which are not locally conformally para-hyperkähler. Finally, we discuss the problem of non-existence of para-hyperhermitian structures on Inoue surfaces of type S 0 and provide a list of compact complex surfaces which could carry para-hypercomplex structures.

  2. Experimental determinations of the performances of heat transfer surfaces

    International Nuclear Information System (INIS)

    Pirovano, Alain; Viannay, Stephane; Mazeas, C.Y.

    1974-01-01

    With the help of flow schemes and of assumptions on the heat transfer, it is possible, in some cases, to predict the thermal and aerodynamical performances of a new heat transfer surface with moderate accuracy. These estimates, valid for an approximate classification of a new surface among known surfaces, are not accurate enough to be taken as a basis for the design of heat exchangers. In the present state of knowledge, the performances of a new heat transfer surface can only be determined accurately with experimental measurements. Bertin and Co have at their disposal two air test rigs especially designed for this purpose. The first one, more directly concerned with the measurements on tube bundles with fluid flow perpendicular to the generatrices of the tubes, is a semi-closed loop equipped with a high-efficiency ejector which amplifies the air flow rate supplied by an external source and thus allows high values of Reynolds number to be reached. The second one is adapted to other types of surfaces: tubes with external flow parallel to the generatrices, tubes with sophisticated cross section and with internal flow, compact surfaces with finned plates, etc. Both test rigs, the relevant equipment, the methods of data acquisition and of test results analysis are described in this paper. During the 5 past years, 60 configurations were tested. It was possible to compare some of the test results with the results of measurements performed later, on entire heat exchangers working with numbers of tubes, fluids, and temperature levels different from those prevailing during the tests on the small scale mock-up; the agreement is quite good [fr

  3. Synthesis, structural and surface morphological characterizations of ...

    African Journals Online (AJOL)

    Sulfated zirconia (SZ) nanoparticles (NPs) were successfully synthesized and deposited via chemical route called sol-gel technique. The structural, morphological, and optical properties the samples were investigated by X-ray diffraction (XRD), Energy Dispersive X-ray Spectrometry (EDX), Scanning Electron Microscopy ...

  4. The determination of specific surface of sodium polyuranates

    International Nuclear Information System (INIS)

    Bilgin, B.; Atun, G.

    2002-01-01

    Three different sodium polyuranates were prepared by titration of uranyl nitrate with a sodium hydroxide solution labeled with 22 Na as the radiotracer. Polyuranates whose composition was *Na 2 O.7,5UO 3 .11H 2 O (sample A), *Na 2 O.4,3 UO 3 .4,7H 2 O (sample B), and *Na 2 O.2UO 3 .4H 2 O (sample C) were precipitated at pH 5.6, 8.5 and 11.2, respectively. The specific surface areas of these samples were determined by the BET method using methylene blue (MB) as the adsorbate. The sodium polyuranate surfaces were saturated by sequential adsorption of MB. The adsorption data gave an S-shaped isotherm and were fitted to the BET equation. The specific surface areas calculated from the BET isotherm decreased in order A > B > C. The isotope and ion exchange reactions between the sodium polyuranates and Li + , Na + , K + , Rb + , Cs + , Ca 2+ , Sr 2+ , and Ba 2+ ions were compared before and after MB coverage. The results showed that the isotope and ion exchange fractions decrease on the covered surfaces indicating particle diffusion mechanism dominated exchange reactions

  5. Overcoming barriers to membrane protein structure determination.

    Science.gov (United States)

    Bill, Roslyn M; Henderson, Peter J F; Iwata, So; Kunji, Edmund R S; Michel, Hartmut; Neutze, Richard; Newstead, Simon; Poolman, Bert; Tate, Christopher G; Vogel, Horst

    2011-04-01

    After decades of slow progress, the pace of research on membrane protein structures is beginning to quicken thanks to various improvements in technology, including protein engineering and microfocus X-ray diffraction. Here we review these developments and, where possible, highlight generic new approaches to solving membrane protein structures based on recent technological advances. Rational approaches to overcoming the bottlenecks in the field are urgently required as membrane proteins, which typically comprise ~30% of the proteomes of organisms, are dramatically under-represented in the structural database of the Protein Data Bank.

  6. Surfaces of Microparticles in Colloids: Structure and Molecular Adsorption Kinetics

    Science.gov (United States)

    Dai, Hai-Lung

    2002-03-01

    Surfaces of micron and sub-micron size particles in liquid solution are probed by second harmonic generation (SHG) facilitated with femtosecond laser pulses. The particles probed include inorganic objects such as carbon black and color pigments, polymeric species like polystyrene beads, and biological systems such as blood cells and ecoli. In the experiments, dye molecules are first adsorbed onto the particle surface to allow generation of second harmonics upon light irradiation. Competition for adsorption between these surface dye molecules and the molecules of interest in the solution is then monitored by the SHG signal to reveal the molecular adsorption kinetics and surface structure. Specifically, surfactant adsorption on polymer surfaces, the structure of carbon black surface, and protein adsorption on biological surfaces, monitored by this technique, will be discussed.

  7. Structures of adsorbed CO on atomically smooth and on stepped sngle crystal surfaces

    International Nuclear Information System (INIS)

    Madey, T.E.; Houston, J.E.

    1980-01-01

    The structures of molecular CO adsorbed on atomically smooth surfaces and on surfaces containing monatomic steps have been studied using the electron stimulated desorption ion angular distribution (ESDIAD) method. For CO adsorbed on the close packed Ru(001) and W(110) surfaces, the dominant bonding mode is via the carbon atom, with the CO molecular axis perpendicular to the plane of the surface. For CO on atomicaly rough Pd(210), and for CO adsorbed at step sites on four different surfaces vicinal to W(110), the axis of the molecule is tilted or inclined away from the normal to the surface. The ESDIAD method, in which ion desorption angles are related to surface bond angles, provides a direct determination of the structures of adsorbed molecules and molecular complexes on surfaces

  8. determination of verticality of reservoir engineering structure

    African Journals Online (AJOL)

    user

    applications is 3D survey and management of oil and gas facilities and other engineering structures. This recent .... also affect ground water contamination. 2. VERTICALITY ...... The soil, water and concrete in a Reservoir at the foundation bed ...

  9. DETERMINANTS OF FINANCIAL STRUCTURE OF GREEK COMPANIES

    Directory of Open Access Journals (Sweden)

    Gargalis PANAGIOTIS

    2016-06-01

    Full Text Available Capital structure is essential for the survival, growth and performance of a firm. There has been a growing interest worldwide in identifying the factors associated with debt leverage. This article aims to investigate the factors affecting the capital structure of companies listed on the Athens Stock Exchange (ASE. The data set used is composed of indicators reflecting the financial position and performance of 40 firms listed on the ASE in 2014. Using a regression model we estimate in what extent the financial structure of companies is affected by performance indicators and other specific factors like the field of activity or the size of the firms. The results obtained show an important influence of share of tangible assets in total assets of the company on the financial leverage, as main variable selected in order to reflect the capital structure of Greek companies.

  10. Structure of stable degeneration of K3 surfaces into pairs of rational elliptic surfaces

    OpenAIRE

    Kimura, Yusuke

    2018-01-01

    F-theory/heterotic duality is formulated in the stable degeneration limit of a K3 fibration on the F-theory side. In this note, we analyze the structure of the stable degeneration limit. We discuss whether stable degeneration exists for pairs of rational elliptic surfaces. We demonstrate that, when two rational elliptic surfaces have an identical complex structure, stable degeneration always exists. We provide an equation that systematically describes the stable degeneration of a K3 surface i...

  11. Characterization of polymer surface structure and surface mechanical behaviour by sum frequency generation surface vibrational spectroscopy and atomic force microscopy

    International Nuclear Information System (INIS)

    Opdahl, Aric; Koffas, Telly S; Amitay-Sadovsky, Ella; Kim, Joonyeong; Somorjai, Gabor A

    2004-01-01

    Sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM) have been used to study polymer surface structure and surface mechanical behaviour, specifically to study the relationships between the surface properties of polymers and their bulk compositions and the environment to which the polymer is exposed. The combination of SFG surface vibrational spectroscopy and AFM has been used to study surface segregation behaviour of polyolefin blends at the polymer/air and polymer/solid interfaces. SFG surface vibrational spectroscopy and AFM experiments have also been performed to characterize the properties of polymer/liquid and polymer/polymer interfaces, focusing on hydrogel materials. A method was developed to study the surface properties of hydrogel contact lens materials at various hydration conditions. Finally, the effect of mechanical stretching on the surface composition and surface mechanical behaviour of phase-separated polyurethanes, used in biomedical implant devices, has been studied by both SFG surface vibrational spectroscopy and AFM. (topical review)

  12. In-situ determination of amine/epoxy and carboxylic/epoxy exothermic heat of reaction on surface of modified carbon nanotubes and structural verification of covalent bond formation

    Science.gov (United States)

    Neves, Juliana C.; de Castro, Vinícius G.; Assis, Ana L. S.; Veiga, Amanda G.; Rocco, Maria Luiza M.; Silva, Glaura G.

    2018-04-01

    An effective nanofiller-matrix interaction is considered crucial to produce enhanced nanocomposites. Nevertheless, there is lack of experiments focused in the direct measurement of possible filler-matrix covalent linkage, which was the main goal of this work for a carbon nanotube (CNT)/epoxy system. CNT were functionalized with oxygenated (ox) functions and further with triethylenetetramine (TETA). An in-situ determination methodology of epoxy-CNTs heat of reaction was developed by Differential Scanning Calorimetry (DSC). Values of -(8.7 ± 0.4) and -(6.0 ± 0.6) J/g were observed for epoxy with CNT-ox and CNT-TETA, respectively. These results confirm the occurrence of covalent bonds for both functionalized CNTs, a very important information due to the literature generally disregard this possibility for oxygenated functions. The higher value obtained for CNT-ox can be attributed to a not complete amidation and to steric impediments in the CNT-TETA structure. The modified CNTs produced by DSC experiments were then characterized by X-Ray Photoelectron Spectroscopy, Transmission Electron Microscopy and Thermogravimetry, which confirmed the covalent linkage. This characterization methodology can be used to verify the occurrence of covalent bonds in various nanocomposites with a quantitative evaluation, providing data for better understanding of the role of CNT functional groups and for tailoring its interface with polymers.

  13. The surface and deep structure of the waterfall illusion.

    Science.gov (United States)

    Wade, Nicholas J; Ziefle, Martina

    2008-11-01

    The surface structure of the waterfall illusion or motion aftereffect (MAE) is its phenomenal visibility. Its deep structure will be examined in the context of a model of space and motion perception. The MAE can be observed following protracted observation of a pattern that is translating, rotating, or expanding/contracting, a static pattern appears to move in the opposite direction. The phenomenon has long been known, and it continues to present novel properties. One of the novel features of MAEs is that they can provide an ideal visual assay for distinguishing local from global processes. Motion during adaptation can be induced in a static central grating by moving surround gratings; the MAE is observed in the static central grating but not in static surrounds. The adaptation phase is local and the test phase is global. That is, localised adaptation can be expressed in different ways depending on the structure of the test display. These aspects of MAEs can be exploited to determine a variety of local/global interactions. Six experiments on MAEs are reported. The results indicated that relational motion is required to induce an MAE; the region adapted extends beyond that stimulated; storage can be complete when the MAE is not seen during the storage period; interocular transfer (IOT) is around 30% of monocular MAEs with phase alternation; large field spiral patterns yield MAEs with characteristic monocular and binocular interactions.

  14. Science achievement determinants: factorial structure of family ...

    African Journals Online (AJOL)

    The family plays an important role in determining the academic achievement ... parents' assistance, expectation, and encouragement in their children's mathematics ... suggested that cultural upbringing is a strong factor contributing to the.

  15. Surface structure analysis by means of Rutherford scattering: methods to study surface relaxation

    International Nuclear Information System (INIS)

    Turkenburg, W.C.; Soszka, W.; Saris, F.W.; Kersten, H.H.; Colenbrander, B.G.

    1976-01-01

    The use of Rutherford backscattering for structural analysis of single crystal surfaces is reviewed, and a new method is introduced. With this method, which makes use of the channeling and blocking phenomenon of light ions of medium energy, surface atoms can be located with a precision of 0.02 A. This is demonstrated in a measurement of surface relaxation for the Cu(110) surface. (Auth.)

  16. Structure sensitivity of CO dissociation on Rh surfaces

    DEFF Research Database (Denmark)

    Mavrikakis, Manos; Baumer, M.; Freund, H.J.

    2002-01-01

    than the flat surface, but the effect is considerably weaker than the effect of surface structure on the dissociation barrier. Our findings are compared with available experimental data, and the consequences for CO activation in methanation and Fischer-Tropsch reactions are discussed.......Using periodic self-consistent density functional calculations it is shown that the barrier for CO dissociation is similar to120 kJ/mol lower on the stepped Rh(211) surface than on the close-packed Rh(111) surface. The stepped surface binds molecular CO and the dissociation products more strongly...

  17. Structure determination by X-ray crystallography

    CERN Document Server

    Ladd, M F C

    1995-01-01

    X-ray crystallography provides us with the most accurate picture we can get of atomic and molecular structures in crystals. It provides a hard bedrock of structural results in chemistry and in mineralogy. In biology, where the structures are not fully crystalline, it can still provide valuable results and, indeed, the impact here has been revolutionary. It is still an immense field for young workers, and no doubt will provide yet more striking develop­ ments of a major character. It does, however, require a wide range of intellectual application, and a considerable ability in many fields. This book will provide much help. It is a very straightforward and thorough guide to every aspect of the subject. The authors are experienced both as research workers themselves and as teachers of standing, and this is shown in their clarity of exposition. There are plenty of iliustrations and worked examples to aid the student to obtain a real grasp of the subject.

  18. Structural determinants in the bulk heterojunction.

    Science.gov (United States)

    Acocella, Angela; Höfinger, Siegfried; Haunschmid, Ernst; Pop, Sergiu C; Narumi, Tetsu; Yasuoka, Kenji; Yasui, Masato; Zerbetto, Francesco

    2018-02-21

    Photovoltaics is one of the key areas in renewable energy research with remarkable progress made every year. Here we consider the case of a photoactive material and study its structural composition and the resulting consequences for the fundamental processes driving solar energy conversion. A multiscale approach is used to characterize essential molecular properties of the light-absorbing layer. A selection of bulk-representative pairs of donor/acceptor molecules is extracted from the molecular dynamics simulation of the bulk heterojunction and analyzed at increasing levels of detail. Significantly increased ground state energies together with an array of additional structural characteristics are identified that all point towards an auxiliary role of the material's structural organization in mediating charge-transfer and -separation. Mechanistic studies of the type presented here can provide important insights into fundamental principles governing solar energy conversion in next-generation photovoltaic devices.

  19. Some structural determinants of melody recall.

    Science.gov (United States)

    Boltz, M

    1991-05-01

    Sophisticated musicians were asked to recall, using musical notation, a set of unfamiliar folk tunes that varied in rhythmic structure and referents of tonality. The results showed that memory was facilitated by tonic triad members marking phrase endings, but only when their presence was highlighted by a corresponding pattern of temporal accents. Conversely, recall significantly declined when tonal information was either absent or obscured by rhythmic structure. Error analyses further revealed that the retention of overall pitch contour and information at phrase ending points varied as a function of these manipulations. The results are discussed in terms of a framework that links the acts of perceiving and remembering to a common attentional scheme.

  20. Overcoming barriers to membrane protein structure determination

    NARCIS (Netherlands)

    Bill, Roslyn M.; Henderson, Peter J. F.; Iwata, So; Kunji, Edmund R. S.; Michel, Hartmut; Neutze, Richard; Newstead, Simon; Poolman, Bert; Tate, Christopher G.; Vogel, Horst

    After decades of slow progress, the pace of research on membrane protein structures is beginning to quicken thanks to various improvements in technology, including protein engineering and microfocus X-ray diffraction. Here we review these developments and, where possible, highlight generic new

  1. DETERMINATION OF IMPORTANCE EVALUATION FOR THE SURFACE EXPLORATORY STUDIES FACILITY

    International Nuclear Information System (INIS)

    C.J. Byrne

    2000-01-01

    This DIE applies to the surface facilities component of the Yucca Mountain Site Characterization Project (W) ESF. The ESF complex-including surface and subsurface accommodations--encompasses an area that is approximately six miles wide and nine miles long (approximately 30,000 acres total) (United States Department of Energy [DOE] 1997, p. 9.04). It is located on federally withdrawn lands, near the southwest border of the Nevada Test Site (NTS) in southern Nevada (DOE 1997, p. 9.04). Site characterization activities are conducted within the subsurface ESF to obtain the information necessary to determine whether the Yucca Mountain Site is suitable as a geologic repository for spent nuclear fuel and high-level radioactive waste. Most ESF surface facilities are located within the Conceptual Controlled Area Boundary (CCAB) (DOE 1997, p. 9.04), with the exception of the southeastern most portions of the H-Road and the Water Supply System. Various SBT activities are also conducted throughout the Yucca Mountain region as a part of the overall site-characterization effort. In general, the DIE for SBT Activities (Civilian Radioactive Waste Management System [CRWMS] Management and Operating Contractor [M andO] 1998a) evaluates activities associated with SBT. Potential test-to-test interference and waste isolation impacts associated with SBT activities are also evaluated in CRWMS M andO (1998a)

  2. DETERMINATION OF IMPORTANCE EVALUATION FOR THE SURFACE EXPLORATORY STUDIES FACILITY

    Energy Technology Data Exchange (ETDEWEB)

    C.J. Byrne

    2000-07-25

    This DIE applies to the surface facilities component of the Yucca Mountain Site Characterization Project (W) ESF. The ESF complex-including surface and subsurface accommodations--encompasses an area that is approximately six miles wide and nine miles long (approximately 30,000 acres total) (United States Department of Energy [DOE] 1997, p. 9.04). It is located on federally withdrawn lands, near the southwest border of the Nevada Test Site (NTS) in southern Nevada (DOE 1997, p. 9.04). Site characterization activities are conducted within the subsurface ESF to obtain the information necessary to determine whether the Yucca Mountain Site is suitable as a geologic repository for spent nuclear fuel and high-level radioactive waste. Most ESF surface facilities are located within the Conceptual Controlled Area Boundary (CCAB) (DOE 1997, p. 9.04), with the exception of the southeastern most portions of the H-Road and the Water Supply System. Various SBT activities are also conducted throughout the Yucca Mountain region as a part of the overall site-characterization effort. In general, the DIE for SBT Activities (Civilian Radioactive Waste Management System [CRWMS] Management and Operating Contractor [M&O] 1998a) evaluates activities associated with SBT. Potential test-to-test interference and waste isolation impacts associated with SBT activities are also evaluated in CRWMS M&O (1998a).

  3. Determining the surface roughness coefficient by 3D Scanner

    Directory of Open Access Journals (Sweden)

    Karmen Fifer Bizjak

    2010-12-01

    Full Text Available Currently, several test methods can be used in the laboratory to determine the roughness of rock joint surfaces.However, true roughness can be distorted and underestimated by the differences in the sampling interval of themeasurement methods. Thus, these measurement methods produce a dead zone and distorted roughness profiles.In this paper a new rock joint surface roughness measurement method is presented, with the use of a camera-typethree-dimensional (3D scanner as an alternative to current methods. For this study, the surfaces of ten samples oftuff were digitized by means of a 3D scanner, and the results were compared with the corresponding Rock JointCoefficient (JRC values. Up until now such 3D scanner have been mostly used in the automotive industry, whereastheir use for comparison with obtained JRC coefficient values in rock mechanics is presented here for the first time.The proposed new method is a faster, more precise and more accurate than other existing test methods, and is apromising technique for use in this area of study in the future.

  4. Determining the structure of Carbon-60

    International Nuclear Information System (INIS)

    Wif, D.

    1994-01-01

    Carbon-60 is the most stable and best known of the carbon cage structures known collectively as the fullerenes. It is a remarkable molecule that forms a fascinating solid. Although the molecular shape of C sub 6 sub 0 is familiar - it is simply the shape of a soccer ball with 12 pentagons and 20 hexagons - the manner in which it forms a crystal structure is by no means obvious. This talk will focus on the insights which neutron scattering at ISIS has brought to our understanding of solid C sub6 sub 0. At room temperature, the structure may be regarded as forming as essentially ideal cubic-close packed molecular b ubble-raft : each molecule is reorienting so rapidly that a time-averaged picture, over as little as a nanosecond, reveals a closely spherical shell of atomic density. At 260 K, a rather unusual structural transition occurs. The molecules order but still retain cubic symmetry. Although this may not appear to be a rather dramatic change, detailed considerations show that a profound transition has occurred that bears close similarities to a solid-liquid phase transition but in two dimensions. Below 260 K, reorientation still occurs but at a dramatically reduced rate as the temperature is lowered. Indeed at around 90 K, The reorientation is so slow that thermodynamic equilibrium cannot be achieved in a reasonable timescale an orientational glass transition occurs. Although the behaviour of solid C sub 6 sub 0 undergoes dramatic changes as a function of temperature, a coherent description has evolved in which neutron scattering plays a central role. Close analogies are to be found in the study of systems as diverse as solid H sub 2 and human-rhinovirus structures. These analogies and the central role played by neutron scattering at ISIS will be emphasised in this paper. 5 figs., 10 refs. (author)

  5. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    Directory of Open Access Journals (Sweden)

    Vasily F. Shabanov

    2013-08-01

    Full Text Available Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.

  6. Ion track membranes providing heat pipe surfaces with capillary structures

    International Nuclear Information System (INIS)

    Akapiev, G.N.; Dmitriev, S.N.; Erler, B.; Shirkova, V.V.; Schulz, A.; Pietsch, H.

    2003-01-01

    The microgalvanic method for metal filling of etched ion tracks in organic foils is of particular interest for the fabrication of microsized structures. Microstructures like copper whiskers with a high aspect ratio produced in ion track membranes are suitable for the generation of high-performance heat transfer surfaces. A surface with good heat transfer characteristics is defined as a surface on which a small temperature difference causes a large heat transfer from the surface material to the liquid. It is well-known that a porous surface layer transfers to an evaporating liquid a given quantity of heat at a smaller temperature difference than does a usual smooth surface. Copper whiskers with high aspect ratio and a density 10 5 per cm 2 form such a porous structure, which produces strong capillary forces and therefore a maximum of heat transfer coefficients

  7. A Surface Modeling Paradigm for Electromagnetic Applications in Aerospace Structures

    OpenAIRE

    Jha, RM; Bokhari, SA; Sudhakar, V; Mahapatra, PR

    1989-01-01

    A systematic approach has been developed to model the surfaces encountered in aerospace engineering for EM applications. The basis of this modeling is the quadric canonical shapes which are the coordinate surfaces of the Eisenhart Coordinate systems. The building blocks are visualized as sections of quadric cylinders and surfaces of revolution. These truncated quadrics can successfully model realistic aerospace structures which are termed a s hybrid quadrics, of which the satellite launch veh...

  8. Vascular structure determines pulmonary blood flow distribution

    Science.gov (United States)

    Hlastala, M. P.; Glenny, R. W.

    1999-01-01

    Scientific knowledge develops through the evolution of new concepts. This process is usually driven by new methodologies that provide observations not previously available. Understanding of pulmonary blood flow determinants advanced significantly in the 1960s and is now changing rapidly again, because of increased spatial resolution of regional pulmonary blood flow measurements.

  9. Facile method for preparing superoleophobic surfaces with hierarchical microcubic/nanowire structures

    Science.gov (United States)

    Kwak, Wonshik; Hwang, Woonbong

    2016-02-01

    To facilitate the fabrication of superoleophobic surfaces having hierarchical microcubic/nanowire structures (HMNS), even for low surface tension liquids including octane (surface tension = 21.1 mN m-1), and to understand the influences of surface structures on the oleophobicity, we developed a convenient method to achieve superoleophobic surfaces on aluminum substrates using chemical acid etching, anodization and fluorination treatment. The liquid repellency of the structured surface was validated through observable experimental results the contact and sliding angle measurements. The etching condition required to ensure high surface roughness was established, and an optimal anodizing condition was determined, as a critical parameter in building the superoleophobicity. The microcubic structures formed by acid etching are essential for achieving the formation of the hierarchical structure, and therefore, the nanowire structures formed by anodization lead to an enhancement of the superoleophobicity for low surface tension liquids. Under optimized morphology by microcubic/nanowire structures with fluorination treatment, the contact angle over 150° and the sliding angle less than 10° are achieved even for octane.

  10. Surface electron structure of short-period semiconductor superlattice

    International Nuclear Information System (INIS)

    Bartos, I.; Czech Academy Science, Prague,; Strasser, T.; Schattke, W.

    2004-01-01

    Full text: Semiconductor superlattices represent man-made crystals with unique physical properties. By means of the directed layer-by-layer molecular epitaxy growth their electric properties can be tailored (band structure engineering). Longer translational periodicity in the growth direction is responsible for opening of new electron energy gaps (minigaps) with surface states and resonances localized at superlattice surfaces. Similarly as for the electron structure of the bulk, a procedure enabling to modify the surface electron structure of superlattices is desirable. Short-period superlattice (GaAs) 2 (AlAs) 2 with unreconstructed (100) surface is investigated in detail. Theoretical description in terms of full eigenfunctions of individual components has to be used. The changes of electron surface state energies governed by the termination of a periodic crystalline potential, predicted on simple models, are confirmed for this system. Large surface state shifts are found in the lowest minigap of the superlattice when this is terminated in four different topmost layer configurations. The changes should be observable in angle resolved photoelectron spectroscopy as demonstrated in calculations based on the one step model of photoemission. Surface state in the center of the two dimensional Brillouin zone moves from the bottom of the minigap (for the superlattice terminated by two bilayers of GaAs) to its top (for the superlattice terminated by two bilayers of AlAs) where it becomes a resonance. No surface state/resonance is found for a termination with one bilayer of AlAs. The surface state bands behave similarly in the corresponding gaps of the k-resolved section of the electron band structure. The molecular beam epitaxy, which enables to terminate the superlattice growth with atomic layer precision, provides a way of tuning the superlattice surface electron structure by purely geometrical means. The work was supported by the Grant Agency of the Academy of Sciences

  11. Bionic Duplication of Fresh Navodon septentrionalis Fish Surface Structures

    Directory of Open Access Journals (Sweden)

    Bing Qu

    2011-01-01

    Full Text Available Biomimetic superhydrophobic surface was fabricated by replicating topography of the fresh fish skin surface of Navodon septentrionalis with polydimethylsiloxane (PDMS elastomer. A two-step replicating method was developed to make the surface structure of the fresh fish skin be replicated with high fidelity. After duplication, it was found that the static contact angle of the replica was as large as 173°. Theoretic analysis based on Young's and Cassie-Baxter (C-B model was performed to explain the relationship between structure and hydrophobicity.

  12. Three-Dimensional Structure Determination of Botulinum Toxin

    National Research Council Canada - National Science Library

    Stevens, Ray

    1997-01-01

    ...) Based on the structure of the neurotoxin, understand the toxins mechanism of action. We have accomplished the first goal of determining the three-dimensional structure of the 150 kD botulinum neurotoxin serotype...

  13. Three-Dimensional Structure Determination of Botulinum Toxin

    National Research Council Canada - National Science Library

    Stevens, Ray

    1998-01-01

    ...) Based on the structure of the neurotoxin, understand the toxins mechanism of action. We have accomplished the first goal of determining the three-dimensional structure of the 150 kD botulinum neurotoxin serotype...

  14. Influence of the atomic structure of crystal surfaces on the surface diffusion in medium temperature range

    International Nuclear Information System (INIS)

    Cousty, J.P.

    1981-12-01

    In this work, we have studied the influence of atomic structure of crystal surface on surface self-diffusion in the medium temperature range. Two ways are followed. First, we have measured, using a radiotracer method, the self-diffusion coefficient at 820 K (0.6 T melting) on copper surfaces both the structure and the cleanliness of which were stable during the experiment. We have shown that the interaction between mobile surface defects and steps can be studied through measurements of the anisotropy of surface self diffusion. Second, the behavior of an adatom and a surface vacancy is simulated via a molecular dynamics method, on several surfaces of a Lennard Jones crystal. An inventory of possible migration mechanisms of these surface defects has been drawn between 0.35 and 0.45 Tsub(m). The results obtained with both the methods point out the influence of the surface atomic structure in surface self-diffusion in the medium temperature range [fr

  15. Color effects from scattering on random surface structures in dielectrics

    DEFF Research Database (Denmark)

    Clausen, Jeppe; Christiansen, Alexander B; Garnæs, Jørgen

    2012-01-01

    We show that cheap large area color filters, based on surface scattering, can be fabricated in dielectric materials by replication of random structures in silicon. The specular transmittance of three different types of structures, corresponding to three different colors, have been characterized...

  16. Surface morphology and electronic structure of Ni/Ag(100)

    International Nuclear Information System (INIS)

    Hite, D. A.; Kizilkaya, O.; Sprunger, P. T.; Howard, M. M.; Ventrice, C. A. Jr.; Geisler, H.; Zehner, D. M.

    2000-01-01

    The growth morphology and electronic structure of Ni on Ag(100) has been studied with scanning tunneling microscopy (STM) and synchrotron based angle resolved photoemission spectroscopy. At deposition temperatures at or below 300 K, STM reveals Ni cluster growth on the surface along with some subsurface growth. Upon annealing to 420 K, virtually all Ni segregates into the subsurface region forming embedded nanoclusters. The electronic structure of Ni d bands in the unannealed surface shows dispersion only perpendicular to the surface whereas the annealed surface has Ni d bands that exhibit a three-dimensional-like structure. This is a result of the increased Ni d-Ag sp hybridization bonding and increased coordination of the embedded Ni nanoclusters. (c) 2000 American Vacuum Society

  17. Surface forces between rough and topographically structured interfaces

    DEFF Research Database (Denmark)

    Thormann, Esben

    2017-01-01

    Within colloidal science, direct or indirect measurements of surface forces represent an important tool for developing a fundamental understanding of colloidal systems, as well as for predictions of the stability of colloidal suspensions. While the general understanding of colloidal interactions...... and manufactured materials, which possess topographical variations. Further, with technological advances in nanotechnology, fabrication of nano- or micro-structured surfaces has become increasingly important for many applications, which calls for a better understanding of the effect of surface topography...... on the interaction between interfaces. This paper presents a review of the current state of understanding of the effect of surface roughness on DLVO forces, as well as on the interactions between topographically structured hydrophobic surfaces in water. While the first case is a natural choice because it represents...

  18. Structure of adsorbed monolayers. The surface chemical bond

    International Nuclear Information System (INIS)

    Somorjai, G.A.; Bent, B.E.

    1984-06-01

    This paper attempts to provide a summary of what has been learned about the structure of adsorbed monolayers and about the surface chemical bond from molecular surface science. While the surface chemical bond is less well understood than bonding of molecules in the gas phase or in the solid state, our knowledge of its properties is rapidly accumulating. The information obtained also has great impact on many surface science based technologies, including heterogeneous catalysis and electronic devices. It is hoped that much of the information obtained from studies at solid-gas interfaces can be correlated with molecular behavior at solid-liquid interfaces. 31 references, 42 figures, 1 table

  19. The determinants of capital structure: evidence from Dutch panel data

    OpenAIRE

    Chen, Linda H.; Lensink, Robert; Sterken, Elmer

    1999-01-01

    This paper studies the determinants of capital structure choice of Dutch firms. Our main objective is to investigate whether and to what extent the main capital structure theories can explain capital structure choice of Dutch firms. A better understanding of the capital structure determinants in a rela-tively small yet open industrialized economy is essential not only for enrich-ing empirical studies in this field, but also for the purpose of cross country asset evaluation. By estimating a pa...

  20. How structure determines correlations in neuronal networks.

    Directory of Open Access Journals (Sweden)

    Volker Pernice

    2011-05-01

    Full Text Available Networks are becoming a ubiquitous metaphor for the understanding of complex biological systems, spanning the range between molecular signalling pathways, neural networks in the brain, and interacting species in a food web. In many models, we face an intricate interplay between the topology of the network and the dynamics of the system, which is generally very hard to disentangle. A dynamical feature that has been subject of intense research in various fields are correlations between the noisy activity of nodes in a network. We consider a class of systems, where discrete signals are sent along the links of the network. Such systems are of particular relevance in neuroscience, because they provide models for networks of neurons that use action potentials for communication. We study correlations in dynamic networks with arbitrary topology, assuming linear pulse coupling. With our novel approach, we are able to understand in detail how specific structural motifs affect pairwise correlations. Based on a power series decomposition of the covariance matrix, we describe the conditions under which very indirect interactions will have a pronounced effect on correlations and population dynamics. In random networks, we find that indirect interactions may lead to a broad distribution of activation levels with low average but highly variable correlations. This phenomenon is even more pronounced in networks with distance dependent connectivity. In contrast, networks with highly connected hubs or patchy connections often exhibit strong average correlations. Our results are particularly relevant in view of new experimental techniques that enable the parallel recording of spiking activity from a large number of neurons, an appropriate interpretation of which is hampered by the currently limited understanding of structure-dynamics relations in complex networks.

  1. Application of nitrogen plasma immersion ion implantation to titanium nasal implants with nanonetwork surface structure

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Ying-Sui; Yang, Wei-En [Department of Dentistry, National Yang-Ming University, Taipei 112, Taiwan (China); Zhang, Lan [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Zhu, Hongqin [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Lan, Ming-Ying [Division of Rhinology, Department of Otolaryngology Head and Neck Surgery, Taipei Veterans General Hospital, Taipei 112, Taiwan and School of Medicine, National Yang-Ming University, Taipei 112, Taiwan (China); Lee, Sheng-Wei [Institute of Materials Science and Engineering, National Central University, Taoyuan 320, Taiwan (China); Huang, Her-Hsiung, E-mail: hhhuang@ym.edu.tw [Department of Dentistry, National Yang-Ming University, Taipei 112, Taiwan (China); Institute of Oral Biology, National Yang-Ming University, Taipei 112, Taiwan (China); Graduate Institute of Basic Medical Science, China Medical University, Taichung 404, Taiwan (China); Department of Medical Research, China Medical University Hospital, Taichung 407, Taiwan (China); Department of Bioinformatics and Medical Engineering, Asia University, Taichung 413, Taiwan (China); Department of Stomatology, Taipei Veterans General Hospital, Taipei 112, Taiwan (China)

    2016-07-15

    In nasal reconstruction, the response of cells to titanium (Ti) implants is mainly determined by surface features of the implant. In a pilot study, the authors applied electrochemical anodization to Ti surfaces in an alkaline solution to create a network of nanoscale surface structures. This nanonetwork was intended to enhance the responses of primary human nasal epithelial cell (HNEpC) to the Ti surface. In this study, the authors then treated the anodized, nanonetwork-structured Ti surface using nitrogen plasma immersion ion implantation (NPIII) in order to further improve the HNEpC response to the Ti surface. Subsequently, surface characterization was performed to elucidate morphology, roughness, wettability, and chemistry of specimens. Cytotoxicity, blood, and HNEpC responses were also evaluated. Our results demonstrate that NPIII treatment led to the formation of a noncytotoxic TiN-containing thin film (thickness <100 nm) on the electrochemically anodized Ti surface with a nanonetwork-structure. NPIII treatment was shown to improve blood clotting and the adhesion of platelets to the anodized Ti surface as well as the adhesion and proliferation of hNEpC. This research spreads our understanding of the fact that a TiN-containing thin film, produced using NPIII treatment, could be used to improve blood and HNEpC responses to anodized, nanonetwork-structured Ti surfaces in nasal implant applications.

  2. Sliding surface searching method for slopes containing a potential weak structural surface

    Directory of Open Access Journals (Sweden)

    Aijun Yao

    2014-06-01

    Full Text Available Weak structural surface is one of the key factors controlling the stability of slopes. The stability of rock slopes is in general concerned with set of discontinuities. However, in soft rocks, failure can occur along surfaces approaching to a circular failure surface. To better understand the position of potential sliding surface, a new method called simplex-finite stochastic tracking method is proposed. This method basically divides sliding surface into two parts: one is described by smooth curve obtained by random searching, the other one is polyline formed by the weak structural surface. Single or multiple sliding surfaces can be considered, and consequently several types of combined sliding surfaces can be simulated. The paper will adopt the arc-polyline to simulate potential sliding surface and analyze the searching process of sliding surface. Accordingly, software for slope stability analysis using this method was developed and applied in real cases. The results show that, using simplex-finite stochastic tracking method, it is possible to locate the position of a potential sliding surface in the slope.

  3. Scale-adaptive surface modeling of vascular structures

    Directory of Open Access Journals (Sweden)

    Ma Xin

    2010-11-01

    Full Text Available Abstract Background The effective geometric modeling of vascular structures is crucial for diagnosis, therapy planning and medical education. These applications require good balance with respect to surface smoothness, surface accuracy, triangle quality and surface size. Methods Our method first extracts the vascular boundary voxels from the segmentation result, and utilizes these voxels to build a three-dimensional (3D point cloud whose normal vectors are estimated via covariance analysis. Then a 3D implicit indicator function is computed from the oriented 3D point cloud by solving a Poisson equation. Finally the vessel surface is generated by a proposed adaptive polygonization algorithm for explicit 3D visualization. Results Experiments carried out on several typical vascular structures demonstrate that the presented method yields both a smooth morphologically correct and a topologically preserved two-manifold surface, which is scale-adaptive to the local curvature of the surface. Furthermore, the presented method produces fewer and better-shaped triangles with satisfactory surface quality and accuracy. Conclusions Compared to other state-of-the-art approaches, our method reaches good balance in terms of smoothness, accuracy, triangle quality and surface size. The vessel surfaces produced by our method are suitable for applications such as computational fluid dynamics simulations and real-time virtual interventional surgery.

  4. Determining surface areas of marine alga cells by acid-base titration method.

    Science.gov (United States)

    Wang, X; Ma, Y; Su, Y

    1997-09-01

    A new method for determining the surface area of living marine alga cells was described. The method uses acid-base titration to measure the surface acid/base amount on the surface of alga cells and uses the BET (Brunauer, Emmett, and Teller) equation to estimate the maximum surface acid/base amount, assuming that hydrous cell walls have carbohydrates or other structural compounds which can behave like surface Brönsted acid-base sites due to coordination of environmental H2O molecules. The method was applied to 18 diverse alga species (including 7 diatoms, 2 flagellates, 8 green algae and 1 red alga) maintained in seawater cultures. For the species examined, the surface areas of individual cells ranged from 2.8 x 10(-8) m2 for Nannochloropsis oculata to 690 x 10(-8) m2 for Dunaliella viridis, specific surface areas from 1,030 m2.g-1 for Dunaliella salina to 28,900 m2.g-1 for Pyramidomonas sp. Measurement accuracy was 15.2%. Preliminary studies show that the method may be more promising and accurate than light/electron microscopic measurements for coarse estimation of the surface area of living algae.

  5. Atomic structure of the SbCu surface alloy: A surface X-ray diffraction study

    DEFF Research Database (Denmark)

    Meunier, I.; Gay, J.M.; Lapena, L.

    1999-01-01

    The dissolution at 400 degrees C of an antimony layer deposited at room temperature on a Cu(111) substrate leads to a surface alloy with a p(root 3x root 3)R 30 degrees x 30 degrees superstructure and a Sb composition of 1/3.We present here a structural study of this Sb-Cu compound by surface X...

  6. Determining building interior structures using compressive sensing

    Science.gov (United States)

    Lagunas, Eva; Amin, Moeness G.; Ahmad, Fauzia; Nájar, Montse

    2013-04-01

    We consider imaging of the building interior structures using compressive sensing (CS) with applications to through-the-wall imaging and urban sensing. We consider a monostatic synthetic aperture radar imaging system employing stepped frequency waveform. The proposed approach exploits prior information of building construction practices to form an appropriate sparse representation of the building interior layout. We devise a dictionary of possible wall locations, which is consistent with the fact that interior walls are typically parallel or perpendicular to the front wall. The dictionary accounts for the dominant normal angle reflections from exterior and interior walls for the monostatic imaging system. CS is applied to a reduced set of observations to recover the true positions of the walls. Additional information about interior walls can be obtained using a dictionary of possible corner reflectors, which is the response of the junction of two walls. Supporting results based on simulation and laboratory experiments are provided. It is shown that the proposed sparsifying basis outperforms the conventional through-the-wall CS model, the wavelet sparsifying basis, and the block sparse model for building interior layout detection.

  7. Language structure is partly determined by social structure.

    Directory of Open Access Journals (Sweden)

    Gary Lupyan

    Full Text Available BACKGROUND: Languages differ greatly both in their syntactic and morphological systems and in the social environments in which they exist. We challenge the view that language grammars are unrelated to social environments in which they are learned and used. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a statistical analysis of >2,000 languages using a combination of demographic sources and the World Atlas of Language Structures--a database of structural language properties. We found strong relationships between linguistic factors related to morphological complexity, and demographic/socio-historical factors such as the number of language users, geographic spread, and degree of language contact. The analyses suggest that languages spoken by large groups have simpler inflectional morphology than languages spoken by smaller groups as measured on a variety of factors such as case systems and complexity of conjugations. Additionally, languages spoken by large groups are much more likely to use lexical strategies in place of inflectional morphology to encode evidentiality, negation, aspect, and possession. Our findings indicate that just as biological organisms are shaped by ecological niches, language structures appear to adapt to the environment (niche in which they are being learned and used. As adults learn a language, features that are difficult for them to acquire, are less likely to be passed on to subsequent learners. Languages used for communication in large groups that include adult learners appear to have been subjected to such selection. Conversely, the morphological complexity common to languages used in small groups increases redundancy which may facilitate language learning by infants. CONCLUSIONS/SIGNIFICANCE: We hypothesize that language structures are subjected to different evolutionary pressures in different social environments. Just as biological organisms are shaped by ecological niches, language structures appear to adapt to the

  8. Superhydrophobicity of biological and technical surfaces under moisture condensation: stability in relation to surface structure.

    Science.gov (United States)

    Mockenhaupt, Bernd; Ensikat, Hans-Jürgen; Spaeth, Manuel; Barthlott, Wilhelm

    2008-12-02

    The stability of superhydrophobic properties of eight plants and four technical surfaces in respect to water condensation has been compared. Contact and sliding angles were measured after application of water drops of ambient temperature (20 degrees C) onto cooled surfaces. Water evaporating from the drops condensed, due to the temperature difference between the drops and the surface, on the cooled samples, forming "satellite droplets" in the vicinity of the drops. Surface cooling to 15, 10, and 5 degrees C showed a gradual decrease of superhydrophobicity. The decrease was dependent on the specific surface architecture of the sample. The least decrease was found on hierarchically structured surfaces with a combination of a coarse microstructure and submicrometer-sized structures, similar to that of the Lotus leaf. Control experiments with glycerol droplets, which show no evaporation, and thus no condensation, were carried out to verify that the effects with water were caused by condensation from the drop (secondary condensation). Furthermore, the superhydrophobic properties after condensation on cooled surfaces from a humid environment for 10 min were examined. After this period, the surfaces were covered with spherical water droplets, but most samples retained their superhydrophobicity. Again, the best stability of the water-repellent properties was found on hierarchically structured surfaces similar to that of the Lotus leaf.

  9. SurfCut: Surfaces of Minimal Paths From Topological Structures

    KAUST Repository

    Algarni, Marei Saeed Mohammed

    2018-03-05

    We present SurfCut, an algorithm for extracting a smooth, simple surface with an unknown 3D curve boundary from a noisy image and a seed point. Our method is built on the novel observation that certain ridge curves of a function defined on a front propagated using the Fast Marching algorithm lie on the surface. Our method extracts and cuts these ridges to form the surface boundary. Our surface extraction algorithm is built on the novel observation that the surface lies in a valley of the distance from Fast Marching. We show that the resulting surface is a collection of minimal paths. Using the framework of cubical complexes and Morse theory, we design algorithms to extract these critical structures robustly. Experiments on three 3D datasets show the robustness of our method, and that it achieves higher accuracy with lower computational cost than state-of-the-art.

  10. SurfCut: Surfaces of Minimal Paths From Topological Structures

    KAUST Repository

    Algarni, Marei Saeed Mohammed

    2017-04-30

    We present SurfCut, an algorithm for extracting a smooth, simple surface with an unknown 3D curve boundary from a noisy 3D image and a seed point. Our method is built on the novel observation that certain ridge curves of a function defined on a front propagated using the Fast Marching algorithm lie on the surface. Our method extracts and cuts these ridges to form the surface boundary. Our surface extraction algorithm is built on the novel observation that the surface lies in a valley of the distance from Fast Marching. We show that the resulting surface is a collection of minimal paths. Using the framework of cubical complexes and Morse theory, we design algorithms to extract these critical structures robustly. Experiments on three 3D datasets show the robustness of our method, and that it achieves higher accuracy with lower computational cost than state-of-the-art.

  11. SurfCut: Surfaces of Minimal Paths From Topological Structures

    KAUST Repository

    Algarni, Marei Saeed Mohammed; Sundaramoorthi, Ganesh

    2018-01-01

    We present SurfCut, an algorithm for extracting a smooth, simple surface with an unknown 3D curve boundary from a noisy image and a seed point. Our method is built on the novel observation that certain ridge curves of a function defined on a front propagated using the Fast Marching algorithm lie on the surface. Our method extracts and cuts these ridges to form the surface boundary. Our surface extraction algorithm is built on the novel observation that the surface lies in a valley of the distance from Fast Marching. We show that the resulting surface is a collection of minimal paths. Using the framework of cubical complexes and Morse theory, we design algorithms to extract these critical structures robustly. Experiments on three 3D datasets show the robustness of our method, and that it achieves higher accuracy with lower computational cost than state-of-the-art.

  12. Microwave Determination of the Structure of Pyridine

    Energy Technology Data Exchange (ETDEWEB)

    Bak, B.; Hansen, L.; Rastrup-Andersen, J. [Chemical Laboratory of the University of Copenhagen, Copenhagen (Denmark)

    1954-12-15

    2‐, 3‐, and 4‐mono‐deutero‐pyridine have been prepared and the microwave spectra recorded. For each of the isotopic species 11—12 transitions (Q‐ and R‐branch lines) were localized, a number of which could be identified by their Stark effect. For all three species rotational constants of high precision were calculated. The material so provided in connection with known rotational constants for ordinary pyridine is insufficient for a complete determination of the ten geometrical parameters of the molecule. Seven models with a choice of C – H distances close to the correct value (1.075‐1.085 A) were considered one of which was shown to be consistent with electron‐diffraction work and current valence theory. In this model d(N – C(2)) = 1.340±0.005; d(C(2) – C(3)) = 1.390±0.005; d(C(3) – C(4)) = 1.400±0.005 A. The valence angles in the aromatic ring (starting with the C(6) – N – C(2) angle) are: 116° 42′; 124° 00′; 118° 36′; 118° 06′.

  13. Fatigue behaviour of 304L steel welded structures: influence of residual stresses and surface mechanical finishing

    International Nuclear Information System (INIS)

    Magnier-Monin, L.

    2007-12-01

    This study focuses on the influence of residual stresses and surface mechanical finishing on lifetime of stainless steel 304L welded structures. Residual stresses are determined on specific specimens of three types: base-metal, as-welded and ground-welded specimens. Each type is submitted to fatigue tests in order to assess the influence of these parameters on the lifetime, and to determine their evolution. The experiments show that an important surface stress concentration is located in the weld root of as-welded structures, which has a negative effect on the fatigue life. The grinding operation generates high-level surface residual stresses but the lifetime is higher thanks to the reduction of the notch effect. The fatigue test results are compared to the nuclear industry best-fit S-N curves. This enables the determination of correction factors related to fatigue test results of polished specimens, and to assess the lifetime of structures. (author)

  14. Condensation and Wetting Dynamics on Micro/Nano-Structured Surfaces

    Science.gov (United States)

    Olceroglu, Emre

    Because of their adjustable wetting characteristics, micro/nanostructured surfaces are attractive for the enhancement of phase-change heat transfer where liquid-solid-vapor interactions are important. Condensation, evaporation, and boiling processes are traditionally used in a variety of applications including water harvesting, desalination, industrial power generation, HVAC, and thermal management systems. Although they have been studied by numerous researchers, there is currently a lack of understanding of the underlying mechanisms by which structured surfaces improve heat transfer during phase-change. This PhD dissertation focuses on condensation onto engineered surfaces including fabrication aspect, the physics of phase-change, and the operational limitations of engineered surfaces. While superhydrophobic condensation has been shown to produce high heat transfer rates, several critical issues remain in the field. These include surface manufacturability, heat transfer coefficient measurement limitations at low heat fluxes, failure due to surface flooding at high supersaturations, insufficient modeling of droplet growth rates, and the inherent issues associated with maintenance of non-wetted surface structures. Each of these issues is investigated in this thesis, leading to several contributions to the field of condensation on engineered surfaces. A variety of engineered surfaces have been fabricated and characterized, including nanostructured and hierarchically-structured superhydrophobic surfaces. The Tobacco mosaic virus (TMV) is used here as a biological template for the fabrication of nickel nanostructures, which are subsequently functionalized to achieve superhydrophobicity. This technique is simple and sustainable, and requires no applied heat or external power, thus making it easily extendable to a variety of common heat transfer materials and complex geometries. To measure heat transfer rates during superhydrophobic condensation in the presence of non

  15. Structural and vibrational studies of clean and chemisorbed metal surfaces

    International Nuclear Information System (INIS)

    Jiang, Qing-Tang.

    1992-01-01

    Using Medium Energy Ion Scattering, we have studied the structural and vibrational properties of a number of clean and chemisorbed metal surfaces. The work presented in this thesis is mainly of a fundamental nature. However, it is believed that an atomistic understanding of the forces that affect surface structural and vibrational properties can have a beneficial impact on a large number of areas of applied nature. We find that the surface structure of Cu(001) follows the common trend for metal surfaces, where a small oscillatory relaxation exists beginning with a slight contraction in the top layer. In addition, the surface vibrational amplitude is enhanced (as s usually the case) by ∼80%. A detailed analysis of our data shows an unexpected anisotropy of the vibrational amplitude, such that the out-of-plane vibrational amplitude is 30% smaller than the in-plane vibrational amplitude. The unexpected results may imply a large tensile stress on Cu(001). Upon adsorption of 1/4 of a monolayer of S, a p(2 x 2)-S/Cu(001) surface is created. This submonolayer amount of S atoms makes the surface bulk-like, in which the anisotropy of the surface vibrations is removed and the first interlayer contraction is lifted. By comparing our model to earlier contradictory results on this controversial system. We find excellent agreement with a recent LEED study. The presence of 0.1 monolayer of Ca atoms on the Au(113) surface induces a drastic atomic rearrangements, in which half of the top layer Au atoms are missing and a (1 x 2) symmetry results. In addition, the first interlayer spacing of Au(113) is significantly reduced. Our results are discussed in terms of the energy balance between competing surface electronic charge densities

  16. Surface and Core Electronic Structure of Oxidized Silicon Nanocrystals

    Directory of Open Access Journals (Sweden)

    Noor A. Nama

    2010-01-01

    Full Text Available Ab initio restricted Hartree-Fock method within the framework of large unit cell formalism is used to simulate silicon nanocrystals between 216 and 1000 atoms (1.6–2.65 nm in diameter that include Bravais and primitive cell multiples. The investigated properties include core and oxidized surface properties. Results revealed that electronic properties converge to some limit as the size of the nanocrystal increases. Increasing the size of the core of a nanocrystal resulted in an increase of the energy gap, valence band width, and cohesive energy. The lattice constant of the core and oxidized surface parts shows a decreasing trend as the nanocrystal increases in a size that converges to 5.28 Ǻ in a good agreement with the experiment. Surface and core convergence to the same lattice constant reflects good adherence of oxide layer at the surface. The core density of states shows highly degenerate states that split at the oxygenated (001-(1×1 surface due to symmetry breaking. The nanocrystal surface shows smaller gap and higher valence and conduction bands when compared to the core part, due to oxygen surface atoms and reduced structural symmetry. The smaller surface energy gap shows that energy gap of the nanocrystal is controlled by the surface part. Unlike the core part, the surface part shows a descending energy gap that proves its obedience to quantum confinement effects. Nanocrystal geometry proved to have some influence on all electronic properties including the energy gap.

  17. Crystallography and surface structure an introduction for surface scientists and nanoscientists

    CERN Document Server

    Hermann, Klaus

    2017-01-01

    A valuable learning tool as well as a reference, this book provides students and researchers in surface science and nanoscience with the theoretical crystallographic foundations, which are necessary to understand local structure and symmetry of bulk crystals, including ideal and real single crystal surfaces. The author deals with the subject at an introductory level, providing numerous graphic examples to illustrate the mathematical formalism. The book brings together and logically connects many seemingly disparate structural issues and notations used frequently by surface scientists and nanoscientists. Numerous exercises of varying difficulty, ranging from simple questions to small research projects, are included to stimulate discussions about the different subjects.

  18. TED analysis of the Si(113) surface structure

    Science.gov (United States)

    Suzuki, T.; Minoda, H.; Tanishiro, Y.; Yagi, K.

    1999-09-01

    We carried out a TED (transmission electron diffraction) analysis of the Si(113) surface structure. The TED patterns taken at room temperature showed reflections due to the 3×2 reconstructed structure. The TED pattern indicated that a glide plane parallel to the direction suggested in some models is excluded. We calculated the R-factors (reliability factors) for six surface structure models proposed previously. All structure models with energy-optimized atomic positions have large R-factors. After revision of the atomic positions, the R-factors of all the structure models decreased below 0.3, and the revised version of Dabrowski's 3×2 model has the smallest R-factor of 0.17.

  19. Determination of atomic cluster structure with cluster fusion algorithm

    DEFF Research Database (Denmark)

    Obolensky, Oleg I.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2005-01-01

    We report an efficient scheme of global optimization, called cluster fusion algorithm, which has proved its reliability and high efficiency in determination of the structure of various atomic clusters.......We report an efficient scheme of global optimization, called cluster fusion algorithm, which has proved its reliability and high efficiency in determination of the structure of various atomic clusters....

  20. Multi-Dimensional Damage Detection for Surfaces and Structures

    Science.gov (United States)

    Williams, Martha; Lewis, Mark; Roberson, Luke; Medelius, Pedro; Gibson, Tracy; Parks, Steen; Snyder, Sarah

    2013-01-01

    Current designs for inflatable or semi-rigidized structures for habitats and space applications use a multiple-layer construction, alternating thin layers with thicker, stronger layers, which produces a layered composite structure that is much better at resisting damage. Even though such composite structures or layered systems are robust, they can still be susceptible to penetration damage. The ability to detect damage to surfaces of inflatable or semi-rigid habitat structures is of great interest to NASA. Damage caused by impacts of foreign objects such as micrometeorites can rupture the shell of these structures, causing loss of critical hardware and/or the life of the crew. While not all impacts will have a catastrophic result, it will be very important to identify and locate areas of the exterior shell that have been damaged by impacts so that repairs (or other provisions) can be made to reduce the probability of shell wall rupture. This disclosure describes a system that will provide real-time data regarding the health of the inflatable shell or rigidized structures, and information related to the location and depth of impact damage. The innovation described here is a method of determining the size, location, and direction of damage in a multilayered structure. In the multi-dimensional damage detection system, layers of two-dimensional thin film detection layers are used to form a layered composite, with non-detection layers separating the detection layers. The non-detection layers may be either thicker or thinner than the detection layers. The thin-film damage detection layers are thin films of materials with a conductive grid or striped pattern. The conductive pattern may be applied by several methods, including printing, plating, sputtering, photolithography, and etching, and can include as many detection layers that are necessary for the structure construction or to afford the detection detail level required. The damage is detected using a detector or

  1. Sulfur-induced structural motifs on copper and gold surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Walen, Holly [Iowa State Univ., Ames, IA (United States)

    2016-01-01

    The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. The experimental observations presented here—made under identical conditions—together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence of metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.

  2. Electron backscatter diffraction characterization of laser-induced periodic surface structures on nickel surface

    Energy Technology Data Exchange (ETDEWEB)

    Sedao, Xxx, E-mail: sedao.xxx@gmail.com [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France); Maurice, Claire [Laboratoire Georges Friedel, Ecole Nationale Supérieure des Mines, 42023 St-Etienne (France); Garrelie, Florence; Colombier, Jean-Philippe; Reynaud, Stéphanie [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France); Quey, Romain; Blanc, Gilles [Laboratoire Georges Friedel, Ecole Nationale Supérieure des Mines, 42023 St-Etienne (France); Pigeon, Florent [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France)

    2014-05-01

    Graphical abstract: -- Highlight: •Lattice rotation and its distribution in laser-induced periodic surface structures (LIPSS) and the subsurface region on a nickel substrate are revealed using electron backscatter diffraction (EBSD). -- Abstract: We report on the structural investigation of laser-induced periodic surface structures (LIPSS) generated in polycrystalline nickel target after multi-shot irradiation by femtosecond laser pulses. Electron backscatter diffraction (EBSD) is used to reveal lattice rotation caused by dislocation storage during LIPSS formation. Localized crystallographic damages in the LIPSS are detected from both surface and cross-sectional EBSD studies. A surface region (up to 200 nm) with 1–3° grain disorientation is observed in localized areas from the cross-section of the LIPSS. The distribution of the local disorientation is inhomogeneous across the LIPSS and the subsurface region.

  3. Compact surface structures for the efficient excitation of surface plasmon-polaritons

    Energy Technology Data Exchange (ETDEWEB)

    De la Cruz, S.; Mendez, E.R. [Division de Fisica Applicada, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Carretera Ensenada-Tijuana No. 3918, Ensenada 22860, BC (Mexico); Macias, D.; Salas-Montiel, R.; Adam, P.M. [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP-2060, 10010 Troyes Cedex (France)

    2012-06-15

    We present calculations of the efficiency of excitation of surface plasmon-polaritons (SPPs) with surface structures illuminated by focussed beams. First, it is shown that the low reflectivity observed with broad highly directional beams and periodic gratings does not necessarily imply an efficient coupling to SPPs. We then consider the coupling through surface features like steps, grooves and angled steps, and calculate efficiency maps for these structures as functions of the parameters that define them. Finally, we explore the possibilities of improving the coupling efficiency using periodic structures consisting of a small number of rectangular grooves. We find that a surface section with a length of about four wavelengths can couple as much as 45% of the incident light into a directional SPP. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Robust biomimetic-structural superhydrophobic surface on aluminum alloy.

    Science.gov (United States)

    Li, Lingjie; Huang, Tao; Lei, Jinglei; He, Jianxin; Qu, Linfeng; Huang, Peiling; Zhou, Wei; Li, Nianbing; Pan, Fusheng

    2015-01-28

    The following facile approach has been developed to prepare a biomimetic-structural superhydrophobic surface with high stabilities and strong resistances on 2024 Al alloy that are robust to harsh environments. First, a simple hydrothermal treatment in a La(NO3)3 aqueous solution was used to fabricate ginkgo-leaf like nanostructures, resulting in a superhydrophilic surface on 2024 Al. Then a low-surface-energy compound, dodecafluoroheptyl-propyl-trimethoxylsilane (Actyflon-G502), was used to modify the superhydrophilic 2024 Al, changing the surface character from superhydrophilicity to superhydrophobicity. The water contact angle (WCA) of such a superhydrophobic surface reaches up to 160°, demonstrating excellent superhydrophobicity. Moreover, the as-prepared superhydrophobic surface shows high stabilities in air-storage, chemical and thermal environments, and has strong resistances to UV irradiation, corrosion, and abrasion. The WCAs of such a surface almost remain unchanged (160°) after storage in air for 80 days, exposure in 250 °C atmosphere for 24 h, and being exposed under UV irradiation for 24 h, are more than 144° whether in acidic or alkali medium, and are more than 150° after 48 h corrosion and after abrasion under 0.98 kPa for 1000 mm length. The remarkable durability of the as-prepared superhydrophobic surface can be attributed to its stable structure and composition, which are due to the existence of lanthanum (hydr)oxides in surface layer. The robustness of the as-prepared superhydrophobic surface to harsh environments will open their much wider applications. The fabricating approach for such robust superhydrophobic surface can be easily extended to other metals and alloys.

  5. Structure of catalase determined by MicroED

    Science.gov (United States)

    Nannenga, Brent L; Shi, Dan; Hattne, Johan; Reyes, Francis E; Gonen, Tamir

    2014-01-01

    MicroED is a recently developed method that uses electron diffraction for structure determination from very small three-dimensional crystals of biological material. Previously we used a series of still diffraction patterns to determine the structure of lysozyme at 2.9 Å resolution with MicroED (Shi et al., 2013). Here we present the structure of bovine liver catalase determined from a single crystal at 3.2 Å resolution by MicroED. The data were collected by continuous rotation of the sample under constant exposure and were processed and refined using standard programs for X-ray crystallography. The ability of MicroED to determine the structure of bovine liver catalase, a protein that has long resisted atomic analysis by traditional electron crystallography, demonstrates the potential of this method for structure determination. DOI: http://dx.doi.org/10.7554/eLife.03600.001 PMID:25303172

  6. Structure and properties of GMA surfaced armour plates

    OpenAIRE

    A. Klimpel; K. Luksa; M. Burda

    2010-01-01

    Purpose: In the combat vehicles many materials can be used for the armour. Application of the monolithic armour plates in light combat vehicles is limited by the high armour weigh. Introduction of the layered armour plates is a way to limit the vehicle weight. In the paper test results of graded and nanostructural GMA surfaced armour plates are presented.Design/methodology/approach: Metallographic structure, chemical composition and hardness of surfaced layers were investigated in order to ex...

  7. Surface layer determination for the Si spheres of the Avogadro project

    Science.gov (United States)

    Busch, I.; Azuma, Y.; Bettin, H.; Cibik, L.; Fuchs, P.; Fujii, K.; Krumrey, M.; Kuetgens, U.; Kuramoto, N.; Mizushima, S.

    2011-04-01

    For the accurate determination of the Avogadro constant, two 28Si spheres were produced, whose macroscopic density, in addition to other values, must be determined. To make a contribution to the new definition of the kilogram, a relative standard uncertainty of less than 2 × 10-8 has to be achieved. Each silicon surface is covered by a surface layer (SL). Consequently, correction parameters for the SL are determined to be applied to the mass and volume determination of the enriched spheres. With the use of a large set of surface analysing techniques, the structure of the SL is investigated. An unexpected metallic contamination existing on the sphere surface enlarges the uncertainty contribution of the correction parameters above the originally targeted value of 1 × 10-8. In the framework of this investigation this new obstacle is resolved in two ways. A new combination of analytical methods is applied to measure the SL mass mSL and the thickness dSL, including this new contamination, with an uncertainty of u(mSL) = 14.5 µg and 14.4 µg, respectively, and u(dSL) = 0.33 nm and 0.32 nm for the 28Si spheres AVO28-S5 and AVO28-S8, respectively. In the second part of the work, the chemical composition of these metallic contaminations is found to be Cu, Ni and Zn silicide compounds. For the removal of this contamination, a special procedure is developed, tested and applied to the spheres to produce the originally expected surface structure on the spheres. After the application of this new procedure the use of x-ray reflectometry directly at the spheres will be possible. It is expected to reduce the uncertainty contribution due to the SL down to 1 × 10-8.

  8. Surface plasmon polariton amplification in semiconductor-graphene-dielectric structure

    Energy Technology Data Exchange (ETDEWEB)

    Dadoenkova, Yuliya S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Novgorod State University, Veliky Novgorod (Russian Federation); Donetsk Institute for Physics and Technology, Donetsk (Ukraine); Moiseev, Sergey G. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Ulyanovsk (Russian Federation); Abramov, Aleksei S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kadochkin, Aleksei S.; Zolotovskii, Igor O. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Institute of Nanotechnologies of Microelectronics of the Russian Academy of Sciences, 32A Leninskiy Prosp., 119991, Moscow (Russian Federation); Fotiadi, Andrei A. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Universite de Mons (Belgium)

    2017-05-15

    A mechanism of amplification of surface plasmon polaritons due to the transfer of electromagnetic energy from a drift current wave into a far-infrared surface wave propagating along a semiconductor-dielectric boundary in waveguide geometry is proposed. A necessary condition of the interaction of these waves is phase matching condition, i. e., when the phase velocity of the surface wave approaches the drift velocity of charge carriers. It is shown that in the spectral region of the surface plasmon polariton slowing-down its amplification coefficient can reach values substantially exceeding the ohmic loss coefficient of the surface wave in the structure. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Soil Structure - A Neglected Component of Land-Surface Models

    Science.gov (United States)

    Fatichi, S.; Or, D.; Walko, R. L.; Vereecken, H.; Kollet, S. J.; Young, M.; Ghezzehei, T. A.; Hengl, T.; Agam, N.; Avissar, R.

    2017-12-01

    Soil structure is largely absent in most standard sampling and measurements and in the subsequent parameterization of soil hydraulic properties deduced from soil maps and used in Earth System Models. The apparent omission propagates into the pedotransfer functions that deduce parameters of soil hydraulic properties primarily from soil textural information. Such simple parameterization is an essential ingredient in the practical application of any land surface model. Despite the critical role of soil structure (biopores formed by decaying roots, aggregates, etc.) in defining soil hydraulic functions, only a few studies have attempted to incorporate soil structure into models. They mostly looked at the effects on preferential flow and solute transport pathways at the soil profile scale; yet, the role of soil structure in mediating large-scale fluxes remains understudied. Here, we focus on rectifying this gap and demonstrating potential impacts on surface and subsurface fluxes and system wide eco-hydrologic responses. The study proposes a systematic way for correcting the soil water retention and hydraulic conductivity functions—accounting for soil-structure—with major implications for near saturated hydraulic conductivity. Modification to the basic soil hydraulic parameterization is assumed as a function of biological activity summarized by Gross Primary Production. A land-surface model with dynamic vegetation is used to carry out numerical simulations with and without the role of soil-structure for 20 locations characterized by different climates and biomes across the globe. Including soil structure affects considerably the partition between infiltration and runoff and consequently leakage at the base of the soil profile (recharge). In several locations characterized by wet climates, a few hundreds of mm per year of surface runoff become deep-recharge accounting for soil-structure. Changes in energy fluxes, total evapotranspiration and vegetation productivity

  10. Fermi Surface with Dirac Fermions in CaFeAsF Determined via Quantum Oscillation Measurements

    Science.gov (United States)

    Terashima, Taichi; Hirose, Hishiro T.; Graf, David; Ma, Yonghui; Mu, Gang; Hu, Tao; Suzuki, Katsuhiro; Uji, Shinya; Ikeda, Hiroaki

    2018-02-01

    Despite the fact that 1111-type iron arsenides hold the record transition temperature of iron-based superconductors, their electronic structures have not been studied much because of the lack of high-quality single crystals. In this study, we comprehensively determine the Fermi surface in the antiferromagnetic state of CaFeAsF, a 1111 iron-arsenide parent compound, by performing quantum oscillation measurements and band-structure calculations. The determined Fermi surface consists of a symmetry-related pair of Dirac electron cylinders and a normal hole cylinder. From analyses of quantum-oscillation phases, we demonstrate that the electron cylinders carry a nontrivial Berry phase π . The carrier density is of the order of 10-3 per Fe. This unusual metallic state with the extremely small carrier density is a consequence of the previously discussed topological feature of the band structure which prevents the antiferromagnetic gap from being a full gap. We also report a nearly linear-in-B magnetoresistance and an anomalous resistivity increase above about 30 T for B ∥c , the latter of which is likely related to the quantum limit of the electron orbit. Intriguingly, the electrical resistivity exhibits a nonmetallic temperature dependence in the paramagnetic tetragonal phase (T >118 K ), which may suggest an incoherent state. Our study provides a detailed knowledge of the Fermi surface in the antiferromagnetic state of 1111 parent compounds and moreover opens up a new possibility to explore Dirac-fermion physics in those compounds.

  11. Studies on electronic structure of GaN(0001) surface

    CERN Document Server

    Xie Chang Kun; Xu Fa Qiang; Deng Rui; Liu Feng; Yibulaxin, K

    2002-01-01

    An electronic structure investigation on GaN(0001) is reported. The authors employ a full-potential linearized augmented plane-wave (FPLAPW) approach to calculate the partial density of state, which is in agreement with previous experimental results. The effects of the Ga3d semi-core levels on the electronic structure of GaN are discussed. The valence-electronic structure of the wurtzite GaN(0001) surface is investigated using synchrotron radiation excited angle-resolved photoemission spectroscopy. The bulk bands dispersion along GAMMA A direction in the Brillouin zones is measured using normal-emission spectra by changing photon-energy. The band structure derived from authors' experimental data is compared well with the results of authors' FPLAPW calculation. Furthermore, off-normal emission spectra are also measured along the GAMMA K and GAMMA M directions. Two surface states are identified, and their dispersions are characterized

  12. An Allergen Portrait Gallery: Representative Structures and an Overview of IgE Binding Surfaces

    Directory of Open Access Journals (Sweden)

    Ovidiu Ivanciuc

    2010-10-01

    Full Text Available Recent progress in the biochemical classification and structural determination of allergens and allergen–antibody complexes has enhanced our understanding of the molecular determinants of allergenicity. Databases of allergens and their epitopes have facilitated the clustering of allergens according to their sequences and, more recently, their structures. Groups of similar sequences are identified for allergenic proteins from diverse sources, and all allergens are classified into a limited number of protein structural families. A gallery of experimental structures selected from the protein classes with the largest number of allergens demonstrate the structural diversity of the allergen universe. Further comparison of these structures and identification of areas that are different from innocuous proteins within the same protein family can be used to identify features specific to known allergens. Experimental and computational results related to the determination of IgE binding surfaces and methods to define allergen-specific motifs are highlighted.

  13. Moduli spaces of convex projective structures on surfaces

    DEFF Research Database (Denmark)

    Fock, V. V.; Goncharov, A. B.

    2007-01-01

    We introduce explicit parametrisations of the moduli space of convex projective structures on surfaces, and show that the latter moduli space is identified with the higher Teichmüller space for defined in [V.V. Fock, A.B. Goncharov, Moduli spaces of local systems and higher Teichmüller theory, math.......AG/0311149]. We investigate the cluster structure of this moduli space, and define its quantum version....

  14. Structural and electronic properties of low-index stoichiometric BiOI surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Wen-Wu; Zhao, Zong-Yan, E-mail: zzy@kmust.edu.cn

    2017-06-01

    As promising photocatalyst driven by visible-light, BiOI has attracted more and more attention in the past years. However, the surface structure and properties of BiOI that is the most important place for the photocatalytic have not been investigated in details. To this end, density functional theory was performed to calculate the structural and electronic properties of four low-index stoichiometric surfaces of BiOI. It is found that the relaxation of the low-index BiOI surfaces are relatively small, especially the (001) surface. Thus, the surface energies of BiOI are very relatively small. Moreover, there are a few surface states below the bottom of conduction band in the first layer except the (001) surface, which maybe capture the photo-excited carriers. In all of the most stable terminated planes, all the dangling bonds are cleaved from the broken Bi-O bonds. In the case of (001) surface, the dangling bond density of Bi atoms for the (001) surface is zero per square nano. Therefore, the (001) surface is thermodynamically lowest-energy surface of BiOI, and it is the predominant surface (51.4%). As a final remark, the dangling bonds density of bismuth atoms determines not only the surface energy, but also the surface relaxation. Finally, the equilibrium morphology of BiOI was also proposed and provided, which is determined through the Wulff construction. These results will help us to better understand the underlying photocatalytic mechanism that is related to BiOI surfaces, and provide theoretical support for some experimental studies about BiOI-based photocatalyst in future. - Highlights: • Four low-index BiOI surfaces have been calculated by DFT method. • The relaxations of the low-index BiOI surfaces are relatively small. • There are a few surface states below the bottom of conduction band in the first layer. • The dangling bonds density of bismuth atoms determines not only the surface energy, but also the surface relaxation. • The thermodynamic

  15. Structure and dynamics at the liquid surface of benzyl alcohol

    International Nuclear Information System (INIS)

    Dietter, J.; Morgner, H.

    1999-01-01

    A molecular dynamics simulation of a liquid layer of benzyl alcohol has been performed in order to compare the results with those obtained in experimental studies of our group. The main result of the experimental work was a strong orientational ordering of the benzyl alcohol molecules in the surface as well as an exceptionally large surface potential of ca. 0.6 V. According to the experiments the surface molecules orientate in such a way that the benzene ring points toward the vapor phase while the CH 2 group and the OH group are directed towards the bulk of the liquid. The simulation confirms this orientation of the surface molecules. The surface potential resulting from the simulation is 350 mV. The simulation reveals that the rather large surface potential can be understood as a consequence of the mean orientation of the molecular dipole moment in the surface region. The mean orientation of the molecules themselves in the surface is due to the tendency of the system to maintain the hydrogen bonding structure of the bulk in the surface region as well. The preferential orientation of the surface molecules causes a change of the dynamics of the individual components of the molecules when switching from bulk to surface which depends on the separation of these components from the polar group. This becomes most obvious in case of the reorientation dynamics of the molecular axes, e.g. the reorientation of the benzene ring is faster than the reorientation of the OH group. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  16. Structured surface reflector design for oblique incidence beam splitter at 610 GHz

    OpenAIRE

    Defrance , Fabien; Casaletti , Massimiliano; Sarrazin , Julien; Wiedner , Martina; Gibson , Hugh; Gay , Gregory; Lefevre , Roland; Delorme , Yan

    2016-01-01

    International audience; An iterative alternate projection-based algorithm is developed to design structured surface reflectors to operate as beam splitters at GHz and THz frequencies. To validate the method, a surface profile is determined to achieve a reflector at 610 GHz that generates four equal-intensity beams towards desired directions of ±12.6° with respect to the specular reflection axis. A prototype is fabricated and the beam splitter behavior is experimentally demonstrated. Measureme...

  17. Refining femtosecond laser induced periodical surface structures with liquid assist

    International Nuclear Information System (INIS)

    Jiao, L.S.; Ng, E.Y.K.; Zheng, H.Y.

    2013-01-01

    Highlights: ► LIPSS on silicon wafer was made in air and in ethanol environment. ► Ethanol environment produce cleaner surface ripples. ► Ethanol environment decrease spatial wavelength of the LIPSS by 30%. ► More number of pulses produce smaller spatial wavelength in air. ► Number of pulses do not influence spatial wavelength in ethanol environment. - Abstract: Laser induced periodic surface structures were generated on silicon wafer using femtosecond laser. The medium used in this study is both air and ethanol. The laser process parameters such as wavelength, number of pulse, laser fluence were kept constant for both the mediums. The focus of the study is to analyze spatial wavelength. When generating surface structures with air as a medium and same process parameter of the laser, spatial wavelength results showed a 30% increase compared to ethanol. The cleanliness of the surface generated using ethanol showed considerably less debris than in air. The results observed from the above investigation showed that the medium plays a predominant role in the generation of surface structures.

  18. Microphase separated structure and surface properties of fluorinated polyurethane resin

    International Nuclear Information System (INIS)

    Sudaryanto; Nishino, T.; Hori, Y.; Nakamae, K.

    2000-01-01

    The effect of fluorination on microphase separation and surface properties of segmented polyurethane (PU) resin were investigated. A series of fluorinated polyurethane resin (FPU) was synthesized by reacting a fluorinated diol with aromatic diisocyanate. The microphase separated structure of FPU was studied by thermal analysis, and small angle X-ray scattering (SAXS) as well as wide angle X-ray diffraction (WAXD). The surface structure and properties were characterized by X-ray photoelectron spectroscopy (XPS) and dynamic contact angle measurement. The incorporation of fluorine into hard segment brings the FPU to have a higher hard domain cohesion and increase the phase separation, however localization of fluorine on the surface could not be observed. On the other hands, localization of fluorine on the surface could be achieved for soft segment fluorinated PU without any significant change in microphase separated structure. The result from this study give an important basic information for designing PU coating material with a low surface energy and strong adhesion as well as for development of release film on pressure sensitive adhesive tape. (author)

  19. Determination of Surface Properties of Liquid Transition Metals

    International Nuclear Information System (INIS)

    Korkmaz, S. D.

    2008-01-01

    Certain surface properties of liquid simple metals are reported. Using the expression derived by Gosh and coworkers we investigated the surface entropy of liquid transition metals namely Fe, Co and Ni. We have also computed surface tensions of the metals concerned. The pair distribution functions are calculated from the solution of Ornstein-Zernike integral equation with Rogers-Young closure using the individual version of the electron-ion potential proposed by Fioalhais and coworkers which was originally developed for solid state. The predicted values of surface tension and surface entropy are in very good agreement with available experimental data. The present study results show that the expression derived by Gosh and coworkers is very useful for the surface entropy by using Fioalhais pseudopotential and Rogers-Young closure

  20. Mercury's Surface Magnetic Field Determined from Proton-Reflection Magnetometry

    Science.gov (United States)

    Winslow, Reka M.; Johnson, Catherine L.; Anderson, Brian J.; Gershman, Daniel J.; Raines, Jim M.; Lillis, Robert J.; Korth, Haje; Slavin, James A.; Solomon, Sean C.; Zurbuchen, Thomas H.; hide

    2014-01-01

    Solar wind protons observed by the MESSENGER spacecraft in orbit about Mercury exhibit signatures of precipitation loss to Mercury's surface. We apply proton-reflection magnetometry to sense Mercury's surface magnetic field intensity in the planet's northern and southern hemispheres. The results are consistent with a dipole field offset to the north and show that the technique may be used to resolve regional-scale fields at the surface. The proton loss cones indicate persistent ion precipitation to the surface in the northern magnetospheric cusp region and in the southern hemisphere at low nightside latitudes. The latter observation implies that most of the surface in Mercury's southern hemisphere is continuously bombarded by plasma, in contrast with the premise that the global magnetic field largely protects the planetary surface from the solar wind.

  1. Towards friction control using laser-induced periodic surface structures

    NARCIS (Netherlands)

    Eichstädt, J.; Römer, Gerardus Richardus, Bernardus, Engelina; Huis in 't Veld, Bert; Schmidt, M.; Zaeh, M.

    2011-01-01

    This paper aims at contributing to the study of laser-induced periodic surface structures (LIPSS) and the description of their tribological properties in order to facilitate the knowledge for contact mechanical applications. To obtain laser parameters for LIPSS formation, we propose to execute two

  2. Fracture Resistance, Surface Defects and Structural Strength of Glass

    NARCIS (Netherlands)

    Rodichev, Y.M.; Veer, F.A.

    2010-01-01

    This paper poses the theory that the fracture resistance of basic float glass is dependent on it physicochemical properties and the surface defects fonned under the float glass production, glass processing and handling at the service conditions compose the aggregate basis for structural glass

  3. Surface Structures of Binary Mixture of Ionic Liquids.

    Czech Academy of Sciences Publication Activity Database

    Nakajima, K.; Nakanishi, S.; Lísal, Martin; Kimura, K.

    2017-01-01

    Roč. 230, MARCH (2017), s. 542-549 ISSN 0167-7322 R&D Projects: GA ČR(CZ) GA16-12291S Institutional support: RVO:67985858 Keywords : ionic liquids * mixture * surface structure Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 3.648, year: 2016

  4. Anomalous sea surface structures as an object of statistical topography

    Science.gov (United States)

    Klyatskin, V. I.; Koshel, K. V.

    2015-06-01

    By exploiting ideas of statistical topography, we analyze the stochastic boundary problem of emergence of anomalous high structures on the sea surface. The kinematic boundary condition on the sea surface is assumed to be a closed stochastic quasilinear equation. Applying the stochastic Liouville equation, and presuming the stochastic nature of a given hydrodynamic velocity field within the diffusion approximation, we derive an equation for a spatially single-point, simultaneous joint probability density of the surface elevation field and its gradient. An important feature of the model is that it accounts for stochastic bottom irregularities as one, but not a single, perturbation. Hence, we address the assumption of the infinitely deep ocean to obtain statistic features of the surface elevation field and the squared elevation gradient field. According to the calculations, we show that clustering in the absolute surface elevation gradient field happens with the unit probability. It results in the emergence of rare events such as anomalous high structures and deep gaps on the sea surface almost in every realization of a stochastic velocity field.

  5. Surface structure evolution in a homologous series of ionic liquids.

    Science.gov (United States)

    Haddad, Julia; Pontoni, Diego; Murphy, Bridget M; Festersen, Sven; Runge, Benjamin; Magnussen, Olaf M; Steinrück, Hans-Georg; Reichert, Harald; Ocko, Benjamin M; Deutsch, Moshe

    2018-02-06

    Interfaces of room temperature ionic liquids (RTILs) are important for both applications and basic science and are therefore intensely studied. However, the evolution of their interface structure with the cation's alkyl chain length [Formula: see text] from Coulomb to van der Waals interaction domination has not yet been studied for even a single broad homologous RTIL series. We present here such a study of the liquid-air interface for [Formula: see text], using angstrom-resolution X-ray methods. For [Formula: see text], a typical "simple liquid" monotonic surface-normal electron density profile [Formula: see text] is obtained, like those of water and organic solvents. For [Formula: see text], increasingly more pronounced nanoscale self-segregation of the molecules' charged moieties and apolar chains yields surface layering with alternating regions of headgroups and chains. The layering decays into the bulk over a few, to a few tens, of nanometers. The layering periods and decay lengths, their linear [Formula: see text] dependence, and slopes are discussed within two models, one with partial-chain interdigitation and the other with liquid-like chains. No surface-parallel long-range order is found within the surface layer. For [Formula: see text], a different surface phase is observed above melting. Our results also impact general liquid-phase issues like supramolecular self-aggregation and bulk-surface structure relations.

  6. De novo protein structure determination using sparse NMR data

    International Nuclear Information System (INIS)

    Bowers, Peter M.; Strauss, Charlie E.M.; Baker, David

    2000-01-01

    We describe a method for generating moderate to high-resolution protein structures using limited NMR data combined with the ab initio protein structure prediction method Rosetta. Peptide fragments are selected from proteins of known structure based on sequence similarity and consistency with chemical shift and NOE data. Models are built from these fragments by minimizing an energy function that favors hydrophobic burial, strand pairing, and satisfaction of NOE constraints. Models generated using this procedure with ∼1 NOE constraint per residue are in some cases closer to the corresponding X-ray structures than the published NMR solution structures. The method requires only the sparse constraints available during initial stages of NMR structure determination, and thus holds promise for increasing the speed with which protein solution structures can be determined

  7. Nanofluidic structures with complex three-dimensional surfaces

    International Nuclear Information System (INIS)

    Stavis, Samuel M; Gaitan, Michael; Strychalski, Elizabeth A

    2009-01-01

    Nanofluidic devices have typically explored a design space of patterns limited by a single nanoscale structure depth. A method is presented here for fabricating nanofluidic structures with complex three-dimensional (3D) surfaces, utilizing a single layer of grayscale photolithography and standard integrated circuit manufacturing tools. This method is applied to construct nanofluidic devices with numerous (30) structure depths controlled from ∼10 to ∼620 nm with an average standard deviation of 1 cm. A prototype 3D nanofluidic device is demonstrated that implements size exclusion of rigid nanoparticles and variable nanoscale confinement and deformation of biomolecules.

  8. Cryo-EM Structure Determination Using Segmented Helical Image Reconstruction.

    Science.gov (United States)

    Fromm, S A; Sachse, C

    2016-01-01

    Treating helices as single-particle-like segments followed by helical image reconstruction has become the method of choice for high-resolution structure determination of well-ordered helical viruses as well as flexible filaments. In this review, we will illustrate how the combination of latest hardware developments with optimized image processing routines have led to a series of near-atomic resolution structures of helical assemblies. Originally, the treatment of helices as a sequence of segments followed by Fourier-Bessel reconstruction revealed the potential to determine near-atomic resolution structures from helical specimens. In the meantime, real-space image processing of helices in a stack of single particles was developed and enabled the structure determination of specimens that resisted classical Fourier helical reconstruction and also facilitated high-resolution structure determination. Despite the progress in real-space analysis, the combination of Fourier and real-space processing is still commonly used to better estimate the symmetry parameters as the imposition of the correct helical symmetry is essential for high-resolution structure determination. Recent hardware advancement by the introduction of direct electron detectors has significantly enhanced the image quality and together with improved image processing procedures has made segmented helical reconstruction a very productive cryo-EM structure determination method. © 2016 Elsevier Inc. All rights reserved.

  9. Flow Structure and Surface Topology on a UCAV Planform

    Science.gov (United States)

    Elkhoury, Michel; Yavuz, Metin; Rockwell, Donald

    2003-11-01

    Flow past a X-45 UCAV planform involves the complex generation and interaction of vortices, their breakdown and occurrence of surface separation and stall. A cinema technique of high-image-density particle image velocimetry, in conjunction with dye visualization, allows characterization of the time-averaged and instantaneous states of the flow, in terms of critical points of the near-surface streamlines. These features are related to patterns of surface normal vorticity and velocity fluctuation. Spectral analysis of the naturally occurring unsteadiness of the flow allows definition of the most effective frequencies for small-amplitude perturbation of the wing, which leads to substantial alterations of the aforementioned patterns of flow structure and topology adjacent to the surface.

  10. Bio-Inspired Functional Surfaces Based on Laser-Induced Periodic Surface Structures.

    Science.gov (United States)

    Müller, Frank A; Kunz, Clemens; Gräf, Stephan

    2016-06-15

    Nature developed numerous solutions to solve various technical problems related to material surfaces by combining the physico-chemical properties of a material with periodically aligned micro/nanostructures in a sophisticated manner. The utilization of ultra-short pulsed lasers allows mimicking numerous of these features by generating laser-induced periodic surface structures (LIPSS). In this review paper, we describe the physical background of LIPSS generation as well as the physical principles of surface related phenomena like wettability, reflectivity, and friction. Then we introduce several biological examples including e.g., lotus leafs, springtails, dessert beetles, moth eyes, butterfly wings, weevils, sharks, pangolins, and snakes to illustrate how nature solves technical problems, and we give a comprehensive overview of recent achievements related to the utilization of LIPSS to generate superhydrophobic, anti-reflective, colored, and drag resistant surfaces. Finally, we conclude with some future developments and perspectives related to forthcoming applications of LIPSS-based surfaces.

  11. Bio-Inspired Functional Surfaces Based on Laser-Induced Periodic Surface Structures

    Directory of Open Access Journals (Sweden)

    Frank A. Müller

    2016-06-01

    Full Text Available Nature developed numerous solutions to solve various technical problems related to material surfaces by combining the physico-chemical properties of a material with periodically aligned micro/nanostructures in a sophisticated manner. The utilization of ultra-short pulsed lasers allows mimicking numerous of these features by generating laser-induced periodic surface structures (LIPSS. In this review paper, we describe the physical background of LIPSS generation as well as the physical principles of surface related phenomena like wettability, reflectivity, and friction. Then we introduce several biological examples including e.g., lotus leafs, springtails, dessert beetles, moth eyes, butterfly wings, weevils, sharks, pangolins, and snakes to illustrate how nature solves technical problems, and we give a comprehensive overview of recent achievements related to the utilization of LIPSS to generate superhydrophobic, anti-reflective, colored, and drag resistant surfaces. Finally, we conclude with some future developments and perspectives related to forthcoming applications of LIPSS-based surfaces.

  12. Local structural ordering in surface-confined liquid crystals

    Science.gov (United States)

    Śliwa, I.; Jeżewski, W.; Zakharov, A. V.

    2017-06-01

    The effect of the interplay between attractive nonlocal surface interactions and attractive pair long-range intermolecular couplings on molecular structures of liquid crystals confined in thin cells with flat solid surfaces has been studied. Extending the McMillan mean field theory to include finite systems, it has been shown that confining surfaces can induce complex orientational and translational ordering of molecules. Typically, local smectic A, nematic, and isotropic phases have been shown to coexist in certain temperature ranges, provided that confining cells are sufficiently thick, albeit finite. Due to the nonlocality of surface interactions, the spatial arrangement of these local phases can display, in general, an unexpected complexity along the surface normal direction. In particular, molecules located in the vicinity of surfaces can still be organized in smectic layers, even though nematic and/or isotropic order can simultaneously appear in the interior of cells. The resulting surface freezing of smectic layers has been confirmed to occur even for rather weak surface interactions. The surface interactions cannot, however, prevent smectic layers from melting relatively close to system boundaries, even when molecules are still arranged in layers within the central region of the system. The internal interfaces, separating individual liquid-crystal phases, are demonstrated here to form fronts of local finite-size transitions that move across cells under temperature changes. Although the complex molecular ordering in surface confined liquid-crystal systems can essentially be controlled by temperature variations, specific thermal properties of these systems, especially the nature of the local transitions, are argued to be strongly conditioned to the degree of molecular packing.

  13. Electronic structure of graphene on Ni surfaces with different orientation

    International Nuclear Information System (INIS)

    Pudikov, D.A.; Zhizhin, E.V.; Rybkin, A.G.; Rybkina, A.A.; Zhukov, Y.M.; Vilkov, O. Yu.; Shikin, A.M.

    2016-01-01

    An experimental study of the graphene, synthesized by propylene cracking on Ni surfaces with different orientation: (100) and (111), using angle-resolved photoemission, has been performed. It has been shown that graphene on Ni(111) had a perfect lateral structure due to consistency of their lattices, whereas graphene/Ni(100) consisted of a lot of domains. For both systems electronic structure was quite similar and demonstrated a strong bonding of graphene to the underlying Ni surface. After Au intercalation the electronic structure of graphene in both systems was shifted to the Fermi level and became linear in the vicinity of the K point of the Brillouin zone. - Highlights: • Graphene on Ni(111) is well-ordered, whereas on Ni(100) – multi-domain. • Graphene on Ni(111) and Ni(100) is strongly bonded with substrate. • Intercalation of Au atoms restores the linearity in dispersion and makes graphene quasi-free on both Ni(100) and Ni(111).

  14. Structural features of the adsorption layer of pentacene on the graphite surface and the PMMA/graphite hybrid surface

    Science.gov (United States)

    Fadeeva, A. I.; Gorbunov, V. A.; Litunenko, T. A.

    2017-08-01

    Using the molecular dynamics and the Monte Carlo methods, we have studied the structural features and growth mechanism of the pentacene film on graphite and polymethylmethacrylate /graphite surfaces. Monolayer capacity and molecular area, optimal angles between the pentacene molecules and graphite and PMMA/graphite surfaces as well as the characteristic angles between the neighboring pentacene molecules in the adsorption layer were estimated. It is shown that the orientation of the pentacene molecules in the film is determined by a number of factors, including the surface concentration of the molecules, relief of the surface, presence or absence of the polymer layer and its thickness. The pentacene molecules adsorbed on the graphite surface keep a horizontal position relative to the long axis at any surface coverage/thickness of the film. In the presence of the PMMA layer on the graphite, the increase of the number of pentacene molecules as well as the thickness of the PMMA layer induce the change of molecular orientation from predominantly horizontal to vertical one. The reason for such behavior is supposed to be the roughness of the PMMA surface.

  15. Nanoscale array structures suitable for surface enhanced raman scattering and methods related thereto

    Science.gov (United States)

    Bond, Tiziana C.; Miles, Robin; Davidson, James C.; Liu, Gang Logan

    2014-07-22

    Methods for fabricating nanoscale array structures suitable for surface enhanced Raman scattering, structures thus obtained, and methods to characterize the nanoscale array structures suitable for surface enhanced Raman scattering. Nanoscale array structures may comprise nanotrees, nanorecesses and tapered nanopillars.

  16. Nanoscale array structures suitable for surface enhanced raman scattering and methods related thereto

    Science.gov (United States)

    Bond, Tiziana C; Miles, Robin; Davidson, James; Liu, Gang Logan

    2015-11-03

    Methods for fabricating nanoscale array structures suitable for surface enhanced Raman scattering, structures thus obtained, and methods to characterize the nanoscale array structures suitable for surface enhanced Raman scattering. Nanoscale array structures may comprise nanotrees, nanorecesses and tapered nanopillars.

  17. Nanoscale array structures suitable for surface enhanced raman scattering and methods related thereto

    Science.gov (United States)

    Bond, Tiziana C.; Miles, Robin; Davidson, James C.; Liu, Gang Logan

    2015-07-14

    Methods for fabricating nanoscale array structures suitable for surface enhanced Raman scattering, structures thus obtained, and methods to characterize the nanoscale array structures suitable for surface enhanced Raman scattering. Nanoscale array structures may comprise nanotrees, nanorecesses and tapered nanopillars.

  18. Structural coloration of metallic surfaces with micro/nano-structures induced by elliptical vibration texturing

    Science.gov (United States)

    Yang, Yang; Pan, Yayue; Guo, Ping

    2017-04-01

    Creating orderly periodic micro/nano-structures on metallic surfaces, or structural coloration, for control of surface apparent color and optical reflectivity has been an exciting research topic over the years. The direct applications of structural coloration include color marking, display devices, and invisibility cloak. This paper presents an efficient method to colorize metallic surfaces with periodic micro/nano-gratings using elliptical vibration texturing. When the tool vibration is coupled with a constant cutting velocity, controlled periodic ripples can be generated due to the overlapping tool trajectory. These periodic ripples with a wavelength near visible spectrum can act as micro-gratings to introduce iridescent colors. The proposed technique also provides a flexible method for color marking of metallic surfaces with arbitrary patterns and images by precise control of the spacing distance and orientation of induced micro/nano-ripples. Theoretical analysis and experimental results are given to demonstrate structural coloration of metals by a direct mechanical machining technique.

  19. Determinants of capital structure and financial crisis impact: evidence

    OpenAIRE

    Proença, Pedro Miguel Correia

    2012-01-01

    Mestrado em contabilidade The objectives of this empirical work are to investigate the determinants of Portuguese SMEs capital structure, evaluate whether and how the impacts of those determinants affect the debt ratios and examine the effects of financial crisis and industry on Portuguese SMEs capital structure. The sample used considers the period 2007-2010, resulting in 12.857 Portugues e SMEs per year observations. R...

  20. Structural rearrangements in the C/W(001) surface system

    International Nuclear Information System (INIS)

    Lyman, P.F.; Mullins, D.R.

    1995-01-01

    We have investigated the surface structure of the C/W(001) surface system at submonolayer C coverages using Auger-electron spectroscopy and high-resolution core-level photoelectron spectroscopy. Core-level spectroscopy is a sensitive probe of an atom's local electronic environment; by examining the core levels of the W atoms in the selvedge region, we monitored the response of the substrate to C adsorption. The average shift of the 4f core-level binding energy provided evidence for a heretofore unknown surface reconstruction that occurs upon submonolayer C adsorption. We also performed line-shape analysis on these core-level spectra, and have thereby elucidated the mechanism by which the low-coverage (√2 x √2 )R45 degree structure evolves to a c(3 √2 x √2 )R45 degree arrangement upon further C adsorption. The line-shape analysis also provides corroborating evidence for a proposed model of the saturated C/W(001)-(5x1) surface structure, and suggests that the first two or three atomic W layers are perturbed by the C adsorption and attendant reconstruction

  1. Supramolecular structures on silica surfaces and their adsorptive properties.

    Science.gov (United States)

    Belyakov, Vladimir N; Belyakova, Lyudmila A; Varvarin, Anatoly M; Khora, Olexandra V; Vasilyuk, Sergei L; Kazdobin, Konstantin A; Maltseva, Tetyana V; Kotvitskyy, Alexey G; Danil de Namor, Angela F

    2005-05-01

    The study of adsorptive and chemical immobilization of beta-cyclodextrin on a surface of hydroxylated silicas with various porous structure is described. Using IR spectroscopy, thermal gravimetrical analysis with a programmed heating, and chemical analysis of the silica surface, it is shown that the process of adsorption-desorption of beta-cyclodextrin depends on the porous structure of the silica. The reaction of esterification was used for chemical grafting of beta-cyclodextrin on the surface of hydroxylated silicas. Hydrolytic stability of silicas chemically modified by beta-cyclodextrin apparently is explained by simultaneous formation of chemical and hydrogen bonds between surface silanol groups and hydroxyl groups of beta-cyclodextrin. The uptake of the cations Cu(II), Cd(II), and Pb(II) and the anions Cr(VI) and As(V) by silicas modified with beta-cyclodextrin is investigated as a function of equilibrium ion concentrations. The increase of ion uptake and selectivity of ion extraction in comparison with starting silicas is established. It is due to the formation of surface inclusion complexes of the "host-guest" type in which one molecule of beta-cyclodextrin interacts simultaneously with several ions.

  2. Voltammetric determination of metal impurities on semiconductor surface

    International Nuclear Information System (INIS)

    Knyazeva, E.P.; Mokrousov, G.M.; Volkova, V.N.

    1995-01-01

    A modification of voltamperometric method used for analysis of semiconductor surfaces which make it possible to exclude a contact between surface and background solution. This technique is based on solubility of elemental metal forms in low melting electroconductor systems (e.g., in mercury. The voltampere characteristics of amalgams formed are then studied. The suggested method is simple, rapid, and makes it possible to perform a nondestructive qualitative analysis of the sample surface area measuring about 10 -3 cm -2 and more. 4 refs.; 2 figs

  3. Determination of surface dose rate for cloisonne using thermoluminescent dosimeters

    Energy Technology Data Exchange (ETDEWEB)

    Hengyuan, Zhao; Yulian, Zhang

    1985-07-01

    In this paper, the measuring method and results of surface dose rate of cloisonne using CaSO/sub 4/ Dy-Teflon foil dosimeter are described. The surface dose rate of all products are below 0.015 mrad/h. These products contain 42 sorts of jewelery and 20 sets of wares (such as vases, plates, ash-trays, etc.). Most of the data fall within the range of natural background. For comparison, some jewelery from Taiwan and 3 vases from Japan are measured. The highest surface dose rate of 0.78 mrad/h is due to the necklace jewelery from Taiwan.

  4. Transaction cost determinants of credit governance structures of ...

    African Journals Online (AJOL)

    This paper explores transaction cost determinants of credit governance structures (CGS) of commercial banks in Tanzania. Descriptive statistics, linear regression model, binary and multinomial logistic regression models were employed for analysis. Findings revealed four modes of credit governance structures that are ...

  5. Language learners privilege structured meaning over surface frequency

    Science.gov (United States)

    Culbertson, Jennifer; Adger, David

    2014-01-01

    Although it is widely agreed that learning the syntax of natural languages involves acquiring structure-dependent rules, recent work on acquisition has nevertheless attempted to characterize the outcome of learning primarily in terms of statistical generalizations about surface distributional information. In this paper we investigate whether surface statistical knowledge or structural knowledge of English is used to infer properties of a novel language under conditions of impoverished input. We expose learners to artificial-language patterns that are equally consistent with two possible underlying grammars—one more similar to English in terms of the linear ordering of words, the other more similar on abstract structural grounds. We show that learners’ grammatical inferences overwhelmingly favor structural similarity over preservation of superficial order. Importantly, the relevant shared structure can be characterized in terms of a universal preference for isomorphism in the mapping from meanings to utterances. Whereas previous empirical support for this universal has been based entirely on data from cross-linguistic language samples, our results suggest it may reflect a deep property of the human cognitive system—a property that, together with other structure-sensitive principles, constrains the acquisition of linguistic knowledge. PMID:24706789

  6. On the interaction of Rayleigh surface waves with structures

    International Nuclear Information System (INIS)

    Simpson, I.C.

    1976-12-01

    A two-dimensional soil-structure interaction analysis is carried out for transient Rayleigh surface waves that are incident on a structure. The structure is modelled by a three-degree of freedom rigid basemat to which is attached a flexible superstructure, modelled by a single mass-spring system. The structural responses to a given Rayleigh wave train are compared with those that would have been obtained if the free-field acceleration-time history had been applied as a normally incident body wave. The results clearly exhibit the 'frequency filtering' effects of the rigid basemat on the incident Rayleigh waves. It is shown that, if seismic excitation of a structure is, in fact, due to Rayleigh surface waves, then an analysis assuming normally incident body waves can considerably over-estimate structural response, both at basemat level for horizontal and vertical oscillations of the superstructure. However, in the examples considered here, relatively large rocking effects were induced by the Rayleigh waves, thus giving maximum horizontal accelerations in the superstructure that were of comparable magnitude for Rayleigh and normally incident body waves. (author)

  7. Biomimetic surface structuring using cylindrical vector femtosecond laser beams

    Science.gov (United States)

    Skoulas, Evangelos; Manousaki, Alexandra; Fotakis, Costas; Stratakis, Emmanuel

    2017-03-01

    We report on a new, single-step and scalable method to fabricate highly ordered, multi-directional and complex surface structures that mimic the unique morphological features of certain species found in nature. Biomimetic surface structuring was realized by exploiting the unique and versatile angular profile and the electric field symmetry of cylindrical vector (CV) femtosecond (fs) laser beams. It is shown that, highly controllable, periodic structures exhibiting sizes at nano-, micro- and dual- micro/nano scales can be directly written on Ni upon line and large area scanning with radial and azimuthal polarization beams. Depending on the irradiation conditions, new complex multi-directional nanostructures, inspired by the Shark’s skin morphology, as well as superhydrophobic dual-scale structures mimicking the Lotus’ leaf water repellent properties can be attained. It is concluded that the versatility and features variations of structures formed is by far superior to those obtained via laser processing with linearly polarized beams. More important, by exploiting the capabilities offered by fs CV fields, the present technique can be further extended to fabricate even more complex and unconventional structures. We believe that our approach provides a new concept in laser materials processing, which can be further exploited for expanding the breadth and novelty of applications.

  8. The Determinants of Capital Structure: Some Evidence from Banks

    OpenAIRE

    Heider, Florian; Gropp, Reint

    2008-01-01

    This paper documents that standard cross-sectional determinants of firm leverage also apply to the capital structure of large banks in the United States and Europe. We find a remarkable consistency in sign, significance and economic magnitude. Like non-financial firms, banks appear to have stable capital structures at levels that are specific to each individual bank. The results suggest that capital requirements may only be of second-order importance for banks’ capital structures and confirm ...

  9. Atomic structures of Cd Te and Cd Se (110) surfaces

    International Nuclear Information System (INIS)

    Watari, K.; Ferraz, A.C.

    1996-01-01

    Results are reported based on the self-consistent density-functional theory, within the local-density approximation using ab-initio pseudopotentials of clean Cd Te and Cd Se (110) surfaces. We analyzed the trends for the equilibrium atomic structures, and the variations of the bond angles at the II-VI (110). The calculations are sensitive to the ionicity of the materials and the results are in agreement with the arguments which predict that the relaxed zinc-blend (110) surfaces should depend on ionicity. (author). 17 refs., 1 figs., 3 tabs

  10. Improved protein surface comparison and application to low-resolution protein structure data

    Directory of Open Access Journals (Sweden)

    Kihara Daisuke

    2010-12-01

    Full Text Available Abstract Background Recent advancements of experimental techniques for determining protein tertiary structures raise significant challenges for protein bioinformatics. With the number of known structures of unknown function expanding at a rapid pace, an urgent task is to provide reliable clues to their biological function on a large scale. Conventional approaches for structure comparison are not suitable for a real-time database search due to their slow speed. Moreover, a new challenge has arisen from recent techniques such as electron microscopy (EM, which provide low-resolution structure data. Previously, we have introduced a method for protein surface shape representation using the 3D Zernike descriptors (3DZDs. The 3DZD enables fast structure database searches, taking advantage of its rotation invariance and compact representation. The search results of protein surface represented with the 3DZD has showngood agreement with the existing structure classifications, but some discrepancies were also observed. Results The three new surface representations of backbone atoms, originally devised all-atom-surface representation, and the combination of all-atom surface with the backbone representation are examined. All representations are encoded with the 3DZD. Also, we have investigated the applicability of the 3DZD for searching protein EM density maps of varying resolutions. The surface representations are evaluated on structure retrieval using two existing classifications, SCOP and the CE-based classification. Conclusions Overall, the 3DZDs representing backbone atoms show better retrieval performance than the original all-atom surface representation. The performance further improved when the two representations are combined. Moreover, we observed that the 3DZD is also powerful in comparing low-resolution structures obtained by electron microscopy.

  11. Improved protein surface comparison and application to low-resolution protein structure data.

    Science.gov (United States)

    Sael, Lee; Kihara, Daisuke

    2010-12-14

    Recent advancements of experimental techniques for determining protein tertiary structures raise significant challenges for protein bioinformatics. With the number of known structures of unknown function expanding at a rapid pace, an urgent task is to provide reliable clues to their biological function on a large scale. Conventional approaches for structure comparison are not suitable for a real-time database search due to their slow speed. Moreover, a new challenge has arisen from recent techniques such as electron microscopy (EM), which provide low-resolution structure data. Previously, we have introduced a method for protein surface shape representation using the 3D Zernike descriptors (3DZDs). The 3DZD enables fast structure database searches, taking advantage of its rotation invariance and compact representation. The search results of protein surface represented with the 3DZD has showngood agreement with the existing structure classifications, but some discrepancies were also observed. The three new surface representations of backbone atoms, originally devised all-atom-surface representation, and the combination of all-atom surface with the backbone representation are examined. All representations are encoded with the 3DZD. Also, we have investigated the applicability of the 3DZD for searching protein EM density maps of varying resolutions. The surface representations are evaluated on structure retrieval using two existing classifications, SCOP and the CE-based classification. Overall, the 3DZDs representing backbone atoms show better retrieval performance than the original all-atom surface representation. The performance further improved when the two representations are combined. Moreover, we observed that the 3DZD is also powerful in comparing low-resolution structures obtained by electron microscopy.

  12. Determination of the thickness of chemically removed thin layers on GaAs VPE structures

    Energy Technology Data Exchange (ETDEWEB)

    Somogyi, K.; Nemeth-Sallay, M.; Nemcsics, A. (Research Inst. for Technical Physics, Hungarian Academy of Sciences, Budapest (Hungary))

    1991-01-01

    Thinning of epitaxial GaAs layers was studied during the surface etching, with a special attention to submicron epitaxial structures, like MESFET or varactor-type structures. Each chemical treatment influences the crystal surface during the device preparation processes, though the possible thinning of the active layer is small. Therefore a method allowing determination of thicknesses as small as at about 20 nm of the layer removed by chemical etching from GaAs VPE structures was applied. Using special multilayered structures and a continuous electrochemical carrier concentration depth profiling, the influence of the layer thickness inhomogeneity and of some measurement errors can be minimized. Some frequently used etchants and the influence of different - so called - non-etching processes were compared in different combinations. It was shown that besides the direct etching a change of the surface conditions occurs, which influences the etch rate in the succeeding etching procedure. (orig.).

  13. Labor Market Structure and Salary Determination among Professional Basketball Players.

    Science.gov (United States)

    Wallace, Michael

    1988-01-01

    The author investigates the labor market structure and determinants of salaries for professional basketball players. An expanded version of the resource perspective is used. A three-tiered model of labor market segmentation is revealed for professional basketball players, but other variables also are important in salary determination. (Author/CH)

  14. Denotational, Causal, and Operational Determinism in Event Structures

    NARCIS (Netherlands)

    Rensink, Arend; Kirchner, H.

    1996-01-01

    Determinism of labelled transition systems and trees is a concept of theoretical and practical importance. We study its generalisation to event structures. It turns out that the result depends on what characterising property of tree determinism one sets out to generalise. We present three distinct

  15. Denotational, Causal, and Operational Determinism in Event Structures

    NARCIS (Netherlands)

    Rensink, Arend

    Determinism is a theoretically and practically important concept in labelled transition systems and trees. We study its generalisation to event structures. It turns out that the result depends on what characterising property of tree determinism one sets out to generalise. We present three distinct

  16. Electrostatic cloaking of surface structure for dynamic wetting

    Science.gov (United States)

    Shiomi, Junichiro; Nita, Satoshi; Do-Quang, Minh; Wang, Jiayu; Chen, Yu-Chung; Suzuki, Yuji; Amberg, Gustav

    2017-11-01

    Dynamic wetting problems are fundamental to the understanding of the interaction between liquids and solids. Even in a superficially simple experimental situation, such as a droplet spreading over a dry surface, the result may depend not only on the liquid properties but also strongly on the substrate-surface properties; even for macroscopically smooth surfaces, the microscopic geometrical roughness can be important. In addition, as surfaces may often be naturally charged, or electric fields are used to manipulate fluids, electric effects are crucial components that influence wetting phenomena. Here we investigate the interplay between electric forces and surface structures in dynamic wetting. While surface microstructures can significantly hinder the spreading, we find that the electrostatics can ``cloak'' the microstructures, i.e. deactivate the hindering. We identify the physics in terms of reduction in contact-line friction, which makes the dynamic wetting inertial force dominant and insensitive to the substrate properties. This work was financially supported in part by, the Japan Society for the Promotion of Science, Swedish Governmental Agency for Innovation Systems, and the Japan Science and Technology Agency.

  17. Structure of the Streptococcus pneumoniae Surface Protein and Adhesin PfbA

    OpenAIRE

    Suits, Michael D.; Boraston, Alisdair B.

    2013-01-01

    PfbA (plasmin- and fibronectin-binding protein A) is an extracellular Streptococcus pneumoniae cell-wall attached surface protein that binds to fibronectin, plasmin, and plasminogen. Here we present a structural analysis of the surface exposed domains of PfbA using a combined approach of X-ray crystallography and small-angle X-ray scattering (SAXS). The crystal structure of the PfbA core domain, here called PfbAβ, determined to 2.28 Å resolution revealed an elongated 12-stranded parallel β-he...

  18. Integral membrane protein structure determination using pseudocontact shifts

    Energy Technology Data Exchange (ETDEWEB)

    Crick, Duncan J.; Wang, Jue X. [University of Cambridge, Department of Biochemistry (United Kingdom); Graham, Bim; Swarbrick, James D. [Monash University, Monash Institute of Pharmaceutical Sciences (Australia); Mott, Helen R.; Nietlispach, Daniel, E-mail: dn206@cam.ac.uk [University of Cambridge, Department of Biochemistry (United Kingdom)

    2015-04-15

    Obtaining enough experimental restraints can be a limiting factor in the NMR structure determination of larger proteins. This is particularly the case for large assemblies such as membrane proteins that have been solubilized in a membrane-mimicking environment. Whilst in such cases extensive deuteration strategies are regularly utilised with the aim to improve the spectral quality, these schemes often limit the number of NOEs obtainable, making complementary strategies highly beneficial for successful structure elucidation. Recently, lanthanide-induced pseudocontact shifts (PCSs) have been established as a structural tool for globular proteins. Here, we demonstrate that a PCS-based approach can be successfully applied for the structure determination of integral membrane proteins. Using the 7TM α-helical microbial receptor pSRII, we show that PCS-derived restraints from lanthanide binding tags attached to four different positions of the protein facilitate the backbone structure determination when combined with a limited set of NOEs. In contrast, the same set of NOEs fails to determine the correct 3D fold. The latter situation is frequently encountered in polytopical α-helical membrane proteins and a PCS approach is thus suitable even for this particularly challenging class of membrane proteins. The ease of measuring PCSs makes this an attractive route for structure determination of large membrane proteins in general.

  19. Structural determination of intact proteins using mass spectrometry

    Science.gov (United States)

    Kruppa, Gary [San Francisco, CA; Schoeniger, Joseph S [Oakland, CA; Young, Malin M [Livermore, CA

    2008-05-06

    The present invention relates to novel methods of determining the sequence and structure of proteins. Specifically, the present invention allows for the analysis of intact proteins within a mass spectrometer. Therefore, preparatory separations need not be performed prior to introducing a protein sample into the mass spectrometer. Also disclosed herein are new instrumental developments for enhancing the signal from the desired modified proteins, methods for producing controlled protein fragments in the mass spectrometer, eliminating complex microseparations, and protein preparatory chemical steps necessary for cross-linking based protein structure determination.Additionally, the preferred method of the present invention involves the determination of protein structures utilizing a top-down analysis of protein structures to search for covalent modifications. In the preferred method, intact proteins are ionized and fragmented within the mass spectrometer.

  20. BIRTHDAY CAKE ACTIVITY STRUCTURED ARRANGEMENT FOR HELPING CHILDREN DETERMINING QUANTITIES

    Directory of Open Access Journals (Sweden)

    Neni Mariana

    2010-07-01

    Full Text Available Few researches have been concerned about relation between children’s spatialthinking and number sense. Narrowing for this small research, we focused onone component of spatial thinking, that is structuring objects, and onecomponent of number senses, that is cardinality by determining quantities. Thisstudy focused on a design research that was conducted in Indonesia in which weinvestigated pre-school children’s (between 2 and 3.5 years old ability inmaking structured arrangement and their ability to determine the quantities bylooking at the arrangements. The result shows us that some of the children wereable to make such arrangement. However, the children found difficulties eitherto determine quantities from those arrangements or to compare some structuresto easily recognize number of objects.Keywords: structures, structured arrangement, cardinality DOI: http://dx.doi.org/10.22342/jme.1.1.790.53-70

  1. Energy group structure determination using particle swarm optimization

    International Nuclear Information System (INIS)

    Yi, Ce; Sjoden, Glenn

    2013-01-01

    Highlights: ► Particle swarm optimization is applied to determine broad group structure. ► A graph representation of the broad group structure problem is introduced. ► The approach is tested on a fuel-pin model. - Abstract: Multi-group theory is widely applied for the energy domain discretization when solving the Linear Boltzmann Equation. To reduce the computational cost, fine group cross libraries are often down-sampled into broad group cross section libraries. Cross section data collapsing generally involves two steps: Firstly, the broad group structure has to be determined; secondly, a weighting scheme is used to evaluate the broad cross section library based on the fine group cross section data and the broad group structure. A common scheme is to average the fine group cross section weighted by the fine group flux. Cross section collapsing techniques have been intensively researched. However, most studies use a pre-determined group structure, open based on experience, to divide the neutron energy spectrum into thermal, epi-thermal, fast, etc. energy range. In this paper, a swarm intelligence algorithm, particle swarm optimization (PSO), is applied to optimize the broad group structure. A graph representation of the broad group structure determination problem is introduced. And the swarm intelligence algorithm is used to solve the graph model. The effectiveness of the approach is demonstrated using a fuel-pin model

  2. Determination of Vertical Thermal Structure from Sea Surface Temperature

    National Research Council Canada - National Science Library

    Chu, Peter C; Fan, Chenwu; Liu, W. T

    2000-01-01

    ...), and deep layer stratification (DLS). These parameters vary on different timescales: SST and MLD on scales of minutes to hours, TBD and TTG on months to seasons, and DLS on an even longer timescale...

  3. Atomic and electronic structure of surfaces theoretical foundations

    CERN Document Server

    Lannoo, Michel

    1991-01-01

    Surfaces and interfaces play an increasingly important role in today's solid state devices. In this book the reader is introduced, in a didactic manner, to the essential theoretical aspects of the atomic and electronic structure of surfaces and interfaces. The book does not pretend to give a complete overview of contemporary problems and methods. Instead, the authors strive to provide simple but qualitatively useful arguments that apply to a wide variety of cases. The emphasis of the book is on semiconductor surfaces and interfaces but it also includes a thorough treatment of transition metals, a general discussion of phonon dispersion curves, and examples of large computational calculations. The exercises accompanying every chapter will be of great benefit to the student.

  4. Wetting on micro-structured surfaces: modelling and optimization

    DEFF Research Database (Denmark)

    Cavalli, Andrea

    -patterns, and suggests that there is a balance between optimal wetting properties and mechanical robustness of the microposts. We subsequently analyse liquid spreading on surfaces patterned with slanted microposts. Such a geometry induces unidirectional liquid spreading, as observed in several recent experiments. Our...... liquid spreading and spontaneous drop removal on superhydrophobic surfaces. We do this by applying different numerical techniques, suited for the specific topic. We first consider superhydrophobicity, a condition of extreme water repellency associated with very large static contact angles and low roll......The present thesis deals with the wetting of micro-structured surfaces by various fluids, and its goal is to elucidate different aspects of this complex interaction. In this work we address some of the most relevant topics in this field such as superhydrophobicity, oleophobicity, unidirectional...

  5. Nonlinear surface waves at ferrite-metamaterial waveguide structure

    Science.gov (United States)

    Hissi, Nour El Houda; Mokhtari, Bouchra; Eddeqaqi, Noureddine Cherkaoui; Shabat, Mohammed Musa; Atangana, Jacques

    2016-09-01

    A new ferrite slab made of a metamaterial (MTM), surrounded by a nonlinear cover cladding and a ferrite substrate, was shown to support unusual types of electromagnetic surface waves. We impose the boundary conditions to derive the dispersion relation and others necessary to formulate the proposed structure. We analyse the dispersion properties of the nonlinear surface waves and we calculate the associated propagation index and the film-cover interface nonlinearity. In the calculation, several sets of the permeability of the MTM are considered. Results show that the waves behaviour depends on the values of the permeability of the MTM, the thickness of the waveguide and the film-cover interface nonlinearity. It is also shown that the use of the singular solutions to the electric field equation allows to identify several new properties of surface waves which do not exist in conventional waveguide.

  6. Gradient limitation in accelerating structures imposed by surface melting

    International Nuclear Information System (INIS)

    Wilson, Perry B

    2003-01-01

    A rough picture is beginning to emerge of the physics behind the maximum gradient that can be sustained in an accelerating structure without producing surface damage at a level sufficient to cause a measurable change in the rf properties of the structure. Field emission sites are known to trigger the formation of so-called plasma spots in regions of high dc or rf surface electric fields. A single plasma spot has a finite lifetime (∼ 20-50ns) and leaves behind a single crater. In the rf case, some fraction of the electrons emitted from the spot pick up energy from the rf field and back-bombard the area around the spot. Depending on the gradient, pulse length and available rf energy, multiple spots can form in close proximity. The combined back-bombardment power density from such a spot cluster can be sufficient to raise the surface temperature to the melting point in tens of nanoseconds over an area on the order of 100 microns in diameter. This molten area can now support a plasma capable of emitting several kiloamperes of electrons with an average energy of 50-100kV. This is sufficient beam power to collapse the field in a travelling structure in 30 ns or so. The plasma also exerts a tremendous pressure on the molten surface, sufficient to cause a macroscopic amount of material to migrate toward a region of lower surface field. Over time, this process can modify the profile of the iris tip and produce an unacceptable change in the phase shift per cell

  7. Development of XAFS Into a Structure Determination Technique

    Science.gov (United States)

    Stern, E. A.

    After the detection of diffraction of x-rays by M. Laue in 1912, the technique was soon applied to structure determination by Bragg within a year. On the other hand, although the edge steps in X-Ray absorption were discovered even earlier by Barkla and both the near edge (XANES) and extended X-Ray fine structure (EXAFS) past the edge were detected by 1929, it still took over 40 years to realize the structure information contained in this X-Ray absorption fine structure (XAFS). To understand this delay a brief historical review of the development of the scientific ideas that transformed XAFS into the premiere technique for local structure determination is given. The development includes both advances in theoretical understanding and calculational capabilities, and in experimental facilities, especially synchrotron radiation sources. The present state of the XAFS technique and its capabilities are summarized.

  8. Fracture Resistance, Surface Defects and Structural Strength of Glass

    OpenAIRE

    Rodichev, Y.M.; Veer, F.A.

    2010-01-01

    This paper poses the theory that the fracture resistance of basic float glass is dependent on it physicochemical properties and the surface defects fonned under the float glass production, glass processing and handling at the service conditions compose the aggregate basis for structural glass strength assessment. The effect of loading conditions, constructional and technological factors on the engineering strength of glass can be evaluated in certain cases using fracture mechanics with inform...

  9. An Algorithm for Investigating the Structure of Material Surfaces

    Directory of Open Access Journals (Sweden)

    M. Toman

    2003-01-01

    Full Text Available The aim of this paper is to summarize the algorithm and the experience that have been achieved in the investigation of grain structure of surfaces of certain materials, particularly from samples of gold. The main parts of the algorithm to be discussed are:1. acquisition of input data,2. localization of grain region,3. representation of grain size,4. representation of outputs (postprocessing.

  10. Intelligent sampling for the measurement of structured surfaces

    International Nuclear Information System (INIS)

    Wang, J; Jiang, X; Blunt, L A; Scott, P J; Leach, R K

    2012-01-01

    Uniform sampling in metrology has known drawbacks such as coherent spectral aliasing and a lack of efficiency in terms of measuring time and data storage. The requirement for intelligent sampling strategies has been outlined over recent years, particularly where the measurement of structured surfaces is concerned. Most of the present research on intelligent sampling has focused on dimensional metrology using coordinate-measuring machines with little reported on the area of surface metrology. In the research reported here, potential intelligent sampling strategies for surface topography measurement of structured surfaces are investigated by using numerical simulation and experimental verification. The methods include the jittered uniform method, low-discrepancy pattern sampling and several adaptive methods which originate from computer graphics, coordinate metrology and previous research by the authors. By combining the use of advanced reconstruction methods and feature-based characterization techniques, the measurement performance of the sampling methods is studied using case studies. The advantages, stability and feasibility of these techniques for practical measurements are discussed. (paper)

  11. Electronic structures near surfaces of perovskite type oxides

    International Nuclear Information System (INIS)

    Hara, Toru

    2005-01-01

    This work is intended to draw attention to the origin of the electronic structures near surfaces of perovskite type oxides. Deep states were observed by ultraviolet photoelectron spectroscopic measurements. The film thickness dependent electronic structures near surfaces of (Ba 0.5 Sr 0.5 )TiO 3 thin films were observed. As for the 117-308 nm thick (Ba 0.5 Sr 0.5 )TiO 3 films, deep states were lying at 0.20, 0.55, and 0.85 eV below the quasi-fermi level, respectively. However, as for the 40 nm thick (Ba 0.5 Sr 0.5 )TiO 3 film, the states were overlapped. The A-site doping affected electronic structures near surfaces of SrTiO 3 single crystals. No evolution of deep states in non-doped SrTiO 3 single crystal was observed. However, the evolution of deep states in La-doped SrTiO 3 single crystal was observed

  12. Application of response surfaces for reliability analysis of marine structures

    International Nuclear Information System (INIS)

    Leira, Bernt J.; Holmas, Tore; Herfjord, Kjell

    2005-01-01

    Marine structures subjected to multiple environmental loads (i.e. waves, current, wind) are considered. These loads are characterized by a set of corresponding parameters. The structural fatigue damage and long-term response are expressed in terms of these environmental parameters based on application of polynomial response surfaces. For both types of analysis, an integration across the range of variation for all the environmental parameters is required. The location of the intervals which give rise to the dominant contribution for these integrals depends on the relative magnitude of the coefficients defining the polynomials. The required degree of numerical subdivision in order to obtain accurate results is also of interest. These issues are studied on a non-dimensional form. The loss of accuracy which results when applying response surfaces of too low order is also investigated. Response surfaces with cut-off limits at specific lower-bound values for the environmental parameters are further investigated. Having obtained general expressions on non-dimensional form, examples which correspond to specific response quantities for marine structures are considered. Typical values for the polynomial coefficients, and for the statistical distributions representing the environmental parameters, are applied. Convergence studies are subsequently performed for the particular example response quantities in order to make comparison with the general formulation. For the extreme response, the application of 'extreme contours' obtained from the statistical distributions of the environmental parameters is explored

  13. Determining eyeball surface area directly exposed to the effects of external factors.

    Science.gov (United States)

    Juliszewski, Tadeusz; Kadłuczka, Filip; Kiełbasa, Paweł

    2016-01-01

    This article discusses determining the surface area of eyeballs of men and women exposed to the direct effects of external factors in the working environment. For one eye, the mean surface is 172-182 mm(2). The determined surface area can be used in formulas for calculating the exposure of eyeballs to harmful chemical substances in workplace air.

  14. SPREADING OF A FLUID JET ON THE CORRUGATED SURFACE OF THE STRUCTURED PACKING OF WET SCRUBBERS

    Directory of Open Access Journals (Sweden)

    Gorodilov A.A.

    2014-08-01

    Full Text Available The new packing for wet scrubbers for cooling exhaust gases of furnaces is presented. Spreading features of the fluid jet on the corrugated surface of the proposed packing have been studied. Flow rate of the liquid flowing through slits to the opposite side of the packing element was determined. Several regimes of a fluid flow on the surface of the proposed structured packing were determined. An optimal range of rational flow rates for more intense cooling of exhaust gases is proposed. It was discovered that the range of optimum flow rates may be extended if the surface of the packing element is pre-wetted. The way of increasing the rate of effective interfacial surface area for gas-liquid contact per unit volume of the packing of the scrubber is presented.

  15. Capital Structure Determinants of Small and Medium Enterprises in Croatia

    Directory of Open Access Journals (Sweden)

    Nataša Šarlija

    2016-09-01

    Full Text Available Most of the research about capital structure is focused towards two theories: trade off theory (TOT and pecking order theory (POT. The idea is to explore which theory works better in certain conditions and identify the key determinants that affect the capital structure of the company. However, in different countries different determinants with opposite relation to the leverage are found to be significant. Besides, most of the previous researches are oriented on listed companies. The aim of this paper is to analyse the capital structure of small and medium enterprises in Croatia through the analysis of the fundamental determinants of the capital structure. The research was conducted on a data sample of 500 SMEs in Croatia in the period of 2005–2011. On the unbalanced panel data set a linear regression is applied. Influence of determinants on leverage is estimated by a static panel model with random effect and with fixed effect estimation. Four capital structure determinants are analysed: growth, size, profitability and tangible assets. The results of this research support the pecking order theory confirming that SMEs in Croatia are primarily financed frominternally generated funds that affect profitability, growth, tangible assets and enterprise size.

  16. Surface versus Edge-Based Determinants of Visual Recognition.

    Science.gov (United States)

    Biederman, Irving; Ju, Ginny

    1988-01-01

    The latency at which objects could be identified by 126 subjects was compared through line drawings (edge-based) or color photography (surface depiction). The line drawing was identified about as quickly as the photograph; primal access to a mental representation of an object can be modeled from an edge-based description. (SLD)

  17. Surface determinants of low density lipoprotein uptake by endothelial cells

    International Nuclear Information System (INIS)

    Goeroeg, P.; Pearson, J.D.

    1984-01-01

    The surface sialic acid content of aortic endothelial cells in vitro was substantially lower in sparse cultures than at confluence. Binding of LDL to endothelial cells did not change at different culture densities and was unaffected by brief pretreatment with neuraminidase to partially remove surface sialic acid residues. In contrast, internalisation of LDL declined by a factor of 3 between low density cell cultures and confluent monolayers; neuraminidase pretreatment increased LDL uptake and the effect was most marked (>10-fold) at confluence. Pretreatment with cationised ferritin, which removed most of the surface sialic acid residues as well as glycosaminoglycans, increased LDL internalisation by up to 20-fold, again with most effect on confluent monolayers. Thus LDL uptake is inversely correlated with sialic acid content. We conclude that changes in the surface density of sialic acid (and possibly other charged) residues significantly modulate endothelial LDL uptake, and suggest that focal increases in LDL accumulation during atherogenesis may be related to alterations in endothelial endocytic properties at sites of increased cell turnover or damage. (author)

  18. Determining the energetics of vicinal perovskite oxide surfaces

    NARCIS (Netherlands)

    Wessels, W.A.; Bollmann, Tjeerd Rogier Johannes; Koster, Gertjan; Zandvliet, Henricus J.W.; Rijnders, Augustinus J.H.M.

    2017-01-01

    The energetics of vicinal SrTiO3(001) and DyScO3(110), prototypical perovskite vicinal surfaces, has been studied using topographic atomic force microscopy imaging. The kink formation and strain relaxation energies are extracted from a statistical analysis of the step meandering. Both perovskite

  19. Universal binding energy relation for cleaved and structurally relaxed surfaces

    International Nuclear Information System (INIS)

    Srirangarajan, Aarti; Datta, Aditi; Gandi, Appala Naidu; Ramamurty, U; Waghmare, U V

    2014-01-01

    The universal binding energy relation (UBER), derived earlier to describe the cohesion between two rigid atomic planes, does not accurately capture the cohesive properties when the cleaved surfaces are allowed to relax. We suggest a modified functional form of UBER that is analytical and at the same time accurately models the properties of surfaces relaxed during cleavage. We demonstrate the generality as well as the validity of this modified UBER through first-principles density functional theory calculations of cleavage in a number of crystal systems. Our results show that the total energies of all the relaxed surfaces lie on a single (universal) energy surface, that is given by the proposed functional form which contains an additional length-scale associated with structural relaxation. This functional form could be used in modelling the cohesive zones in crack growth simulation studies. We find that the cohesive law (stress–displacement relation) differs significantly in the case where cracked surfaces are allowed to relax, with lower peak stresses occurring at higher displacements. (paper)

  20. Universal binding energy relation for cleaved and structurally relaxed surfaces.

    Science.gov (United States)

    Srirangarajan, Aarti; Datta, Aditi; Gandi, Appala Naidu; Ramamurty, U; Waghmare, U V

    2014-02-05

    The universal binding energy relation (UBER), derived earlier to describe the cohesion between two rigid atomic planes, does not accurately capture the cohesive properties when the cleaved surfaces are allowed to relax. We suggest a modified functional form of UBER that is analytical and at the same time accurately models the properties of surfaces relaxed during cleavage. We demonstrate the generality as well as the validity of this modified UBER through first-principles density functional theory calculations of cleavage in a number of crystal systems. Our results show that the total energies of all the relaxed surfaces lie on a single (universal) energy surface, that is given by the proposed functional form which contains an additional length-scale associated with structural relaxation. This functional form could be used in modelling the cohesive zones in crack growth simulation studies. We find that the cohesive law (stress-displacement relation) differs significantly in the case where cracked surfaces are allowed to relax, with lower peak stresses occurring at higher displacements.

  1. Atomistic modeling determination of placeholder binding energy of Ti, C, and N atoms on a-Fe (100) surfaces

    International Nuclear Information System (INIS)

    Wei, X J; Liu, Y P; Han, S P

    2015-01-01

    A Fe(100) surface containing Ti, C, and N was constructed and optimized to study the placeholder binding energy of the Ti, C, and N surface atoms; this was achieved by searching the transition state with the LST (linear synchronous transit) method of the CASTEP (Cambridge Serial Total Energy Package) module. Also, the authors analyzed electron structures to determine how Ti, C, and N atoms strengthen the Fe(100) surface. The results show that when Ti, C, or N atoms take placeholder alone, or simultaneously at the Fe(100) surface, the structure stability is at its best. When including Ti, C, and N as solid solutions on the Fe(100) surface, orbital electrons of Fe3d, Ti3d, C2p, and N2p hybridize near the Fermi level; the number of electronic bonding peaks increase and bonding capacity enhances. Also, a large amount of covalent bonds formed. Covalent bonds and metallic bond coexisted. (paper)

  2. Electronic structure, molecular bonding and potential energy surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ruedenberg, K. [Ames Laboratory, IA (United States)

    1993-12-01

    By virtue of the universal validity of the generalized Born-Oppenheimer separation, potential energy surfaces (PES`) represent the central conceptual as well as quantitative entities of chemical physics and provide the basis for the understanding of most physicochemical phenomena in many diverse fields. The research in this group deals with the elucidation of general properties of PES` as well as with the quantitative determination of PES` for concrete systems, in particular pertaining to reactions involving carbon, oxygen, nitrogen and hydrogen molecules.

  3. Fermi Surface with Dirac Fermions in CaFeAsF Determined via Quantum Oscillation Measurements

    Directory of Open Access Journals (Sweden)

    Taichi Terashima

    2018-02-01

    Full Text Available Despite the fact that 1111-type iron arsenides hold the record transition temperature of iron-based superconductors, their electronic structures have not been studied much because of the lack of high-quality single crystals. In this study, we comprehensively determine the Fermi surface in the antiferromagnetic state of CaFeAsF, a 1111 iron-arsenide parent compound, by performing quantum oscillation measurements and band-structure calculations. The determined Fermi surface consists of a symmetry-related pair of Dirac electron cylinders and a normal hole cylinder. From analyses of quantum-oscillation phases, we demonstrate that the electron cylinders carry a nontrivial Berry phase π. The carrier density is of the order of 10^{-3} per Fe. This unusual metallic state with the extremely small carrier density is a consequence of the previously discussed topological feature of the band structure which prevents the antiferromagnetic gap from being a full gap. We also report a nearly linear-in-B magnetoresistance and an anomalous resistivity increase above about 30 T for B∥c, the latter of which is likely related to the quantum limit of the electron orbit. Intriguingly, the electrical resistivity exhibits a nonmetallic temperature dependence in the paramagnetic tetragonal phase (T>118  K, which may suggest an incoherent state. Our study provides a detailed knowledge of the Fermi surface in the antiferromagnetic state of 1111 parent compounds and moreover opens up a new possibility to explore Dirac-fermion physics in those compounds.

  4. Surface science study of selective ethylene epoxidation catalyzed by the Ag(110) surface: Structural sensitivity

    International Nuclear Information System (INIS)

    Campbell, C.T.

    1984-01-01

    The selective oxidation of ethylene to ethylene epoxide (C 2 H 4 +1/2O 2 →C 2 H 4 O) over Ag is the simplest example of kinetically controlled, selective heterogeneous catalysis. We have studied the steady-state kinetics and selectivity of this reaction for the first time on a clean, well-characterized Ag(110) surface by using a special apparatus which allows rapid (approx.20 s) transfer between a high-pressure catalytic microreactor and an ultrahigh vacuum surface analysis (AES, XPS, LEED, TDS) chamber. The effects of temperature and reactant pressures upon the rate and selectivity are virtually identical on Ag(110) and supported, high surface area Ag catalysts. The absolute specific rate (per Ag surface atom) is, however, some 100-fold higher for Ag(110) than for high surface area catalysts. This is related to the well-known structural sensitivity of this reaction. It is postulated that a small percentage of (110) planes (or [110]-like sites) are responsible for most of the catalytic activity of high surface area catalysts. The high activity of the (110) plane is attributed to its high sticking probability for dissociative oxygen adsorption, since the rate of ethylene epoxidation is shown in a related work [Ref. 1: C. T. Campbell and M. T. Paffett, Surf. Sci. (in press)] to be proportional to the coverage of atomically adsorbed oxygen at constant temperature and ethylene pressure

  5. In cellulo structure determination of a novel cypovirus polyhedrin

    International Nuclear Information System (INIS)

    Axford, Danny; Ji, Xiaoyun; Stuart, David I.; Sutton, Geoff

    2014-01-01

    The crystal structure of a previously unsolved type of cypovirus polyhedrin has been determined from data collected directly from frozen live insect cells. This work demonstrates that with the use of a microfocus synchrotron beam the structure of a novel viral polyhedrin could be successfully determined from microcrystals within cells, removing the preparatory step of sample isolation and maintaining a favourable biological environment. The data obtained are of high quality, comparable to that obtained from isolated crystals, and enabled a facile structure determination. A small but significant difference is observed between the unit-cell parameters and the mosaic spread of in cellulo and isolated crystals, suggesting that even these robust crystals are adversely affected by removal from the cell

  6. Birthday Cake Activity Structured Arrangement for Helping Children Determining Quantities

    Directory of Open Access Journals (Sweden)

    Neni Mariana

    2010-07-01

    Full Text Available Few researches have been concerned about relation between children’s spatial thinking and number sense. Narrowing for this small research, we focused on one component of spatial thinking, that is structuring objects, and one component of number senses, that is cardinality by determining quantities. This study focused on a design research that was conducted in Indonesia in which we investigated pre-school children’s (between 2 and 3.5 years old ability in making structured arrangement and their ability to determine the quantities by looking at the arrangements. The result shows us that some of the children were able to make such arrangement. However, the children found difficulties either to determine quantities from those arrangements or to compare some structures to easily recognize number of objects.

  7. Nucleic acid helix structure determination from NMR proton chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Werf, Ramon M. van der; Tessari, Marco; Wijmenga, Sybren S., E-mail: S.Wijmenga@science.ru.nl [Radboud University Nijmegen, Department of Biophysical Chemistry, Institute of Molecules and Materials (Netherlands)

    2013-06-15

    We present a method for de novo derivation of the three-dimensional helix structure of nucleic acids using non-exchangeable proton chemical shifts as sole source of experimental restraints. The method is called chemical shift de novo structure derivation protocol employing singular value decomposition (CHEOPS) and uses iterative singular value decomposition to optimize the structure in helix parameter space. The correct performance of CHEOPS and its range of application are established via an extensive set of structure derivations using either simulated or experimental chemical shifts as input. The simulated input data are used to assess in a defined manner the effect of errors or limitations in the input data on the derived structures. We find that the RNA helix parameters can be determined with high accuracy. We finally demonstrate via three deposited RNA structures that experimental proton chemical shifts suffice to derive RNA helix structures with high precision and accuracy. CHEOPS provides, subject to further development, new directions for high-resolution NMR structure determination of nucleic acids.

  8. Topography measurements for determining the decay factors in surface replication

    International Nuclear Information System (INIS)

    Song, J; Zheng, A; Vorburger, T V; Rubert, P

    2008-01-01

    The electro-forming technique is used at National Institute of Standards and Technology (NIST) for the production of standard reference material (SRM) 2461 standard casings to support nationwide ballistics measurement traceability and measurement quality control in the US. In order to ensure that the SRM casings are produced with virtually the same surface topography, it is necessary to test the decay factors of the replication process. Twenty-six replica casings are replicated from the same master casing for the decay factor tests. The NIST topography measurement system is used for measurements and correlations of surface topography. The topography decays are quantified by the cross-correlation function maximum CCF max . Based on the test, it is expected that 256 SRM casings can be replicated from the same master with CCF max values higher than 95%

  9. Electronegativity determination of individual surface atoms by atomic force microscopy

    Czech Academy of Sciences Publication Activity Database

    Onoda, J.; Ondráček, Martin; Jelínek, Pavel; Sugimoto, Y.

    2017-01-01

    Roč. 8, Apr (2017), 1-6, č. článku 15155. ISSN 2041-1723 R&D Projects: GA ČR(CZ) GC14-16963J Institutional support: RVO:68378271 Keywords : AFM * DFT * electronegativity * surface science Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 12.124, year: 2016

  10. Structure of Ge(100) surfaces for high-efficiency photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Olson, J.M.; McMahon, W.E. [National Renewable Energy Lab., Golden, CO (United States)

    1998-09-01

    While much is known about the Ge(100) surface in a UHV/MBE environment, little has been published about this surface in an MOCVD environment. The main objective of this study is to determine the structure of the surface of Ge substrates in the typical MOCVD reactor immediately prior to and following the heteronucleation of GaAs and other lattice-matched III-V alloys, and to determine the conditions necessary for the growth of device-quality epilayers. In this paper the authors present the first STM images of the MOCVD-prepared Ge surfaces. Although many of the observed features are very similar to UHV- or MBE-prepared surfaces, there are distinct and important differences. For example, while the As-terminated surfaces for MBE-Ge and MOCVD-Ge are virtually identical, the AsH{sub 3}-treated surfaces in an MOCVD reactor are quite different. The terrace reconstruction is rotated by {pi}/2, and significant step bunching or faceting is also observed. Time-dependent RD kinetic studies also reveal, for the first time, several interesting features: the transition rate from an As-terminated (1 x 2) terrace reconstruction to a stable AsH{sub 3}-annealed surface is a function of the substrate temperature, substrate miscut from (100) and AsH{sub 3} partial pressure, and, for typical prenucleation conditions, is relatively slow. These results explain many of the empirically derived nucleation conditions that have been devised by numerous groups.

  11. Application of Volta potential mapping to determine metal surface defects

    International Nuclear Information System (INIS)

    Nazarov, A.; Thierry, D.

    2007-01-01

    As a rule, stress or fatigue cracks originate from various surface imperfections, such as pits, inclusions or locations showing a residual stress. It would be very helpful for material selection to be able to predict the likelihood of environment-assisted cracking or pitting corrosion. By using Scanning Kelvin Probe (the vibrating capacitor with a spatial resolution of 80 μm) the profiling of metal electron work function (Volta potential) in air is applied to the metal surfaces showing residual stress, MnS inclusions and wearing. The Volta potential is influenced by the energy of electrons at the Fermi level and drops generally across the metal/oxide/air interfaces. Inclusions (e.g. MnS) impair continuity of the passive film that locally decreases Volta potential. The stress applied gives rise to dislocations, microcracks and vacancies in the metal and the surface oxide. The defects decrease Volta and corrosion potentials; reduce the overvoltage for processes of passivity breakdown and anodic metal dissolution. These 'anodic' defects can be visualized in potential mapping that can help us to predict locations with higher risk of pitting corrosion or cracking

  12. Determinants of Capital Structure in Non-Financial Companies

    OpenAIRE

    Kühnhausen, Fabian; Stieber, Harald W.

    2014-01-01

    In this paper, we evaluate firm-, industry- and country-specific factors determining a firm's capital structure. The empirical validity of several capital structure theories has been ambiguous so far. We shed light on the main drivers of leverage and depict differences in industry and country characteristics. Using a short panel data set with a large cross-section, we are able to show that firm size, industry leverage, industry growth and tax shield positively affect leverage ratios, while pr...

  13. A study on determinants of capital structure in India

    Directory of Open Access Journals (Sweden)

    Anshu Handoo

    2014-09-01

    Full Text Available The paper identifies the most important determinants of capital structure of 870 listed Indian firms comprising both private sector companies and government companies for the period 2001–2010. Ten independent variables and three dependent variables have been tested using regression analysis. It has been concluded that factors such as profitability, growth, asset tangibility, size, cost of debt, tax rate, and debt serving capacity have significant impact on the leverage structure chosen by firms in the Indian context.

  14. Sulfated oligosaccharide structures, as determined by NMR techniques

    International Nuclear Information System (INIS)

    Noseda, M.D.; Duarte, M.E.R.; Tischer, C.A.; Gorin, P.A.J.; Cerezo, A.S.

    1997-01-01

    Carrageenans are sulfated polysaccharides, produced by red seaweeds (Rhodophyta), that have important biological and physico-chemical properties. Using partial autohydrolysis, we obtained sulfated oligosaccharides from a λ-carrageenan (Noseda and Cerezo, 1993). These oligosaccharides are valuable not only for the study of the structures of the parent carrageenans but also for their possible biological activities. In this work we determined the chemical structure of one of the sulfated oligosaccharides using 1D and 2D NMR techniques. (author)

  15. Determinants of Market Structure and the Airline Industry

    Science.gov (United States)

    Raduchel, W.

    1972-01-01

    The general economic determinants of market structure are outlined with special reference to the airline industry. Included are the following facets: absolute size of firms; distributions of firms by size; concentration; entry barriers; product and service differentiation; diversification; degrees of competition; vertical integration; market boundaries; and economies of scale. Also examined are the static and dynamic properties of market structure in terms of mergers, government policies, and economic growth conditions.

  16. Generative probabilistic models extend the scope of inferential structure determination

    DEFF Research Database (Denmark)

    Olsson, Simon; Boomsma, Wouter; Frellsen, Jes

    2011-01-01

    demonstrate that the use of generative probabilistic models instead of physical forcefields in the Bayesian formalism is not only conceptually attractive, but also improves precision and efficiency. Our results open new vistas for the use of sophisticated probabilistic models of biomolecular structure......Conventional methods for protein structure determination from NMR data rely on the ad hoc combination of physical forcefields and experimental data, along with heuristic determination of free parameters such as weight of experimental data relative to a physical forcefield. Recently, a theoretically...

  17. Rotational characterization of methyl methacrylate: Internal dynamics and structure determination

    Science.gov (United States)

    Herbers, Sven; Wachsmuth, Dennis; Obenchain, Daniel A.; Grabow, Jens-Uwe

    2018-01-01

    Rotational constants, Watson's S centrifugal distortion coefficients, and internal rotation parameters of the two most stable conformers of methyl methacrylate were retrieved from the microwave spectrum. Splittings of rotational energy levels were caused by two non equivalent methyl tops. Constraining the centrifugal distortion coefficients and internal rotation parameters to the values of the main isotopologues, the rotational constants of all single substituted 13C and 18O isotopologues were determined. From these rotational constants the substitution structures and semi-empirical zero point structures of both conformers were precisely determined.

  18. Organizational Structure as a Determinant of Job Burnout.

    Science.gov (United States)

    Bilal, Atif; Ahmed, Hafiz Mushtaq

    2017-03-01

    This exploratory study determined the impact of organizational structure, particularly participation in decision making, instrumental communication, formalization, integration, and promotional opportunity, on burnout among Pakistani pediatric nurses. Data were collected from pediatric nurses working for Punjab's largest state-run hospital. The findings revealed that participation in decision making, instrumental communication, and promotional opportunity prevented burnout. Formalization contributed to burnout but integration was not related to burnout. Quite interestingly, except for supervisory status, most control variables for this study were not significantly related to emotional burnout. Hence, the hypothesis that organizational structure is a determinant of job burnout was accepted.

  19. Fouling of Structured Surfaces during Pool Boiling of Aqueous Solutions

    International Nuclear Information System (INIS)

    Esawy, M.

    2011-01-01

    Bubble characteristics in terms of density, size, frequency and motion are key factors that contribute to the superiority of nucleate pool boiling over the other modes of heat transfer. Nevertheless, if heat transfer occurs in an environment which is prone to fouling, the very same parameters may lead to accelerated deposit formation due to concentration effects beneath the growing bubbles. This has led heat exchanger designers frequently to maintain the surface temperature below the boiling point if fouling occurs, e.g. in thermal seawater desalination plants. The present study investigates the crystallization fouling of various structured surfaces during nucleate pool boiling of CaSO 4 solutions to shed light into their fouling behaviour compared with that of plain surfaces for the same operating conditions. As for the experimental part, a comprehensive set of clean and fouling experiments was performed rigorously. The structured tubes included low finned tubes of different fin densities, heights and materials and re-entrant cavity Turbo-B tube types.The fouling experiments were carried out at atmospheric pressure for different heat fluxes ranging from 100 to 300 k W/m 2 and CaSO 4 concentrations of 1.2 and 1.6 g/L. For the sake of comparison, similar runs were performed on plain stainless steel and copper tubes.Overall for the finned tubes, the experimental results showed a significant reduction of fouling resistances of up to 95% compared to those of the stainless steel and copper plain tubes. In addition, the scale formation that occurred on finned tubes was primarily a scattered and thin crystalline layer which differs significantly from those of plain tubes which suffered from a thick and homogenous layer of deposit with strong adhesion. Higher fin densities and lower fin heights always led to better antifouling performance for all investigated finned tubes. It was also shown that the surface material strongly affects the scale formation of finned tubes i

  20. Rupture of thin liquid films on structured surfaces.

    Science.gov (United States)

    Ajaev, Vladimir S; Gatapova, Elizaveta Ya; Kabov, Oleg A

    2011-10-01

    We investigate stability and breakup of a thin liquid film on a solid surface under the action of disjoining pressure. The solid surface is structured by parallel grooves. Air is trapped in the grooves under the liquid film. Our mathematical model takes into account the effect of slip due to the presence of menisci separating the liquid film from the air inside the grooves, the deformation of these menisci due to local variations of pressure in the liquid film, and nonuniformities of the Hamaker constant which measures the strength of disjoining pressure. Both linear stability and strongly nonlinear evolution of the film are analyzed. Surface structuring results in decrease of the fastest growing instability wavelength and the rupture time. It is shown that a simplified description of film dynamics based on the standard formula for effective slip leads to significant deviations from the behavior seen in our simulations. Self-similar decay over several orders of magnitude of the film thickness near the rupture point is observed. We also show that the presence of the grooves can lead to instability in otherwise stable films if the relative groove width is above a critical value, found as a function of disjoining pressure parameters.

  1. Surface structure and tribology of legless squamate reptiles.

    Science.gov (United States)

    Abdel-Aal, Hisham A

    2018-03-01

    Squamate reptiles (around 10,000 species of snakes and lizards) comprise a myriad of distinct terrestrial vertebrates. The diversity within this biological group offers a great opportunity for customized bio-inspired solutions that address a variety of current technological problems especially within the realm of surface engineering and tribology. One subgroup within squamata is of interest in that context, namely the legless reptiles (mainly snakes and few lizards). The promise of that group lies within their functional adaptation as manifested in optimized surface designs and locomotion that is distinguished by economy of effort even when functioning within hostile tribological environments. Legless reptiles are spread over a wide range in the planet, this geographical diversity demands customized response to local habitats. Customization, in turn, is facilitated through specialized surface design features. In legless reptiles, micro elements of texture, their geometry and topological layout advance mitigation of frictional effects both in locomotion and in general function. Lately, the synergy between functional traits and intrinsic surface features has emerged as focus of research across disciplines. Many investigations have sought to characterize the structural as well as the tribological response of legless species from an engineering point of view. Despite the sizable amount of data that have accumulated in the literature over the past two decades or so, no effort to review the available information, whence this review. This manuscript, therefore, endeavors to assess available data on surface metrology and tribological behavior of legless reptiles and to define aspects of that performance necessary to formulate an advanced paradigm for bio-inspired surface engineering. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Simultaneous measurements of top surface and its underlying film surfaces in multilayer film structure.

    Science.gov (United States)

    Ghim, Young-Sik; Rhee, Hyug-Gyo; Davies, Angela

    2017-09-19

    With the growth of 3D packaging technology and the development of flexible, transparent electrodes, the use of multilayer thin-films is steadily increasing throughout high-tech industries including semiconductor, flat panel display, and solar photovoltaic industries. Also, this in turn leads to an increase in industrial demands for inspection of internal analysis. However, there still remain many technical limitations to overcome for measurement of the internal structure of the specimen without damage. In this paper, we propose an innovative optical inspection technique for simultaneous measurements of the surface and film thickness corresponding to each layer of multilayer film structures by computing the phase and reflectance over a wide range of wavelengths. For verification of our proposed method, the sample specimen of multilayer films was fabricated via photolithography process, and the surface profile and film thickness of each layer were measured by two different techniques of a stylus profilometer and an ellipsometer, respectively. Comparison results shows that our proposed technique enables simultaneous measurements of the top surface and its underlying film surfaces with high precision, which could not be measured by conventional non-destructive methods.

  3. Determination of lunar surface ages from crater frequency–size ...

    Indian Academy of Sciences (India)

    and the images from Apollo missions have been calibrated from the lunar soil samples from Apollo and Luna landing sites (Head 1976; Neukum et al. 1975). ... Table 1 shows the ages as derived for the craters with errors. Mare Humorum is believed to be made up of six ring structures of 210, 340, 425, 570 and 1195km.

  4. Laser-based structural sensing and surface damage detection

    Science.gov (United States)

    Guldur, Burcu

    Damage due to age or accumulated damage from hazards on existing structures poses a worldwide problem. In order to evaluate the current status of aging, deteriorating and damaged structures, it is vital to accurately assess the present conditions. It is possible to capture the in situ condition of structures by using laser scanners that create dense three-dimensional point clouds. This research investigates the use of high resolution three-dimensional terrestrial laser scanners with image capturing abilities as tools to capture geometric range data of complex scenes for structural engineering applications. Laser scanning technology is continuously improving, with commonly available scanners now capturing over 1,000,000 texture-mapped points per second with an accuracy of ~2 mm. However, automatically extracting meaningful information from point clouds remains a challenge, and the current state-of-the-art requires significant user interaction. The first objective of this research is to use widely accepted point cloud processing steps such as registration, feature extraction, segmentation, surface fitting and object detection to divide laser scanner data into meaningful object clusters and then apply several damage detection methods to these clusters. This required establishing a process for extracting important information from raw laser-scanned data sets such as the location, orientation and size of objects in a scanned region, and location of damaged regions on a structure. For this purpose, first a methodology for processing range data to identify objects in a scene is presented and then, once the objects from model library are correctly detected and fitted into the captured point cloud, these fitted objects are compared with the as-is point cloud of the investigated object to locate defects on the structure. The algorithms are demonstrated on synthetic scenes and validated on range data collected from test specimens and test-bed bridges. The second objective of

  5. Full surface inspection methods regarding reinforcement corrosion of concrete structures

    International Nuclear Information System (INIS)

    Reichling, K.; Raupach, M.; Broomfield, J.; Gulikers, J.; L'Hostis, Valerie

    2013-01-01

    For reinforced concrete structures a localisation of all significant critical areas can only be done by a full surface inspection. The economic advantages are obvious: uncritical areas have not to be repaired expensively.The first step of the assessment should always be a visual inspection. The range of deterioration causes can be limited and the degree of deterioration may be estimated roughly. The inspection program can be adjusted to the requirements. By means of a full surface potential mapping areas with a high risk for chloride induced reinforcement corrosion can be localised, although no deteriorations are visually detectable at the concrete surface. In combination with concrete cover depth and resistivity measurements areas with corrosion promoting exposure conditions can be localised even if the reinforcement is not yet de-passivated. The following publication gives an overview about the essential full surface investigation methods to localise critical areas regarding corrosion of steel in concrete. The selection of methods is based on the inspection procedure given in reference 2. (authors)

  6. High-throughput determination of RNA structure by proximity ligation.

    Science.gov (United States)

    Ramani, Vijay; Qiu, Ruolan; Shendure, Jay

    2015-09-01

    We present an unbiased method to globally resolve RNA structures through pairwise contact measurements between interacting regions. RNA proximity ligation (RPL) uses proximity ligation of native RNA followed by deep sequencing to yield chimeric reads with ligation junctions in the vicinity of structurally proximate bases. We apply RPL in both baker's yeast (Saccharomyces cerevisiae) and human cells and generate contact probability maps for ribosomal and other abundant RNAs, including yeast snoRNAs, the RNA subunit of the signal recognition particle and the yeast U2 spliceosomal RNA homolog. RPL measurements correlate with established secondary structures for these RNA molecules, including stem-loop structures and long-range pseudoknots. We anticipate that RPL will complement the current repertoire of computational and experimental approaches in enabling the high-throughput determination of secondary and tertiary RNA structures.

  7. Determination of near surface in-situ stresses

    International Nuclear Information System (INIS)

    Garritty, P.; Irvin, R.

    1983-06-01

    One of the major unknowns affecting aspects of underground construction and the geohydrology of rock masses is the magnitude and direction of the geostatic principal stresses in the earth's crust. This is particularly the case in near surface rocks where there are indications that high horizontal stresses may exist. The techniques, experiences and results of a preliminary rock stress measurement programme conducted at shallow depth in the Carnmenellis Granite, Cornwall, using C.S.I.R.O. triaxial hollow inclusion cells are described. (author)

  8. Homogenization models for thin rigid structured surfaces and films.

    Science.gov (United States)

    Marigo, Jean-Jacques; Maurel, Agnès

    2016-07-01

    A homogenization method for thin microstructured surfaces and films is presented. In both cases, sound hard materials are considered, associated with Neumann boundary conditions and the wave equation in the time domain is examined. For a structured surface, a boundary condition is obtained on an equivalent flat wall, which links the acoustic velocity to its normal and tangential derivatives (of the Myers type). For a structured film, jump conditions are obtained for the acoustic pressure and the normal velocity across an equivalent interface (of the Ventcels type). This interface homogenization is based on a matched asymptotic expansion technique, and differs slightly from the classical homogenization, which is known to fail for small structuration thicknesses. In order to get insight into what causes this failure, a two-step homogenization is proposed, mixing classical homogenization and matched asymptotic expansion. Results of the two homogenizations are analyzed in light of the associated elementary problems, which correspond to problems of fluid mechanics, namely, potential flows around rigid obstacles.

  9. Submerged Fixed Floating Structure under the Action of Surface Current

    Directory of Open Access Journals (Sweden)

    Zhen Cui

    2018-01-01

    Full Text Available The implementation of floating structures has increased with the construction of new sluices for flood control. The overturning moment of floating structure and its influencing factors are the important parameters that determine the structural safety. It is essential to understand the overturning characteristics of these structures in currents. Based on hydrodynamic theory and equilibrium analysis, the hydraulic characteristics of a floating structure are discussed by means of theoretical analysis and experiments. A formula for the overturning moment is developed in terms of the time-averaged pressure on the structure. The corresponding parametric study aims to assess the effects of flow velocities, vertical positions, shape ratios and water levels on the overturning moment. The experimental results show that hydrodynamic factors have a significant influence on the overturning of the structure. Furthermore, a relationship is obtained between the overturning moment and the contributing parameters according to dimensional analysis and the linear fitting method of multidimensional ordinary least squares (OLS. The results predicted by the formula agree with the experimental results, demonstrating the potential for general applicability.

  10. Response surface reconciliation method of bolted joints structure

    Directory of Open Access Journals (Sweden)

    Yunus Mohd Azmi

    2017-01-01

    Full Text Available Structural joining methods such as bolted joints are commonly used for the assembly of structural components due to their simplicity and easy maintenance. Understandably, the dynamic characteristic of bolted joined structure is mainly influenced by the properties of their joints such as preload on the bolts and joints stiffness which alter the measured dynamics response of the structure. Therefore, the need to include the local effect of the bolted joints into the numerical model of the bolted joined structure is vitally important in order to represent the model accurately. In this paper, a few types of connector elements that can be used to represent the bolted joints such as CBAR, CBEAM and CELAS have been investigated numerically and experimentally. The initial numerical results of these element connectors are compared with the experimental results in term of natural frequencies and mode shapes. The comparative evaluation of numerical and the experimental data are performed in order to provide some insights of inaccuracies in the numerical model due to invalid assumption in the numerical modelling such as geometry, material properties, and boundary conditions. The discrepancies between both results (numerical and experimental data are then corrected using the response surface reconciliation method (RSRM through which the finite element model is altered in order to provide closer agreement with the measured data so that it can be used for subsequence analysis.

  11. A structural model for composite rotor blades and lifting surfaces

    Science.gov (United States)

    Rehfield, Lawrence W.; Atilgan, Ali R.

    1987-01-01

    Composite material systems are currently candidates for aerospace structures, primarily for the design flexibiity they offer i.e., it is possible to tailor the material and manufacturing approach to the application. Two notable examples are the wing of the Grumman/USAF/DARPA X-29 and rotor blades under development by the U.S.A. Aerostructures Directorate (AVSCOM), Langley Research Center. A working definition of elastic or structural tailoring is the use of structural concept, fiber orientation, ply stacking sequence, and a blend of materials to achieve specific performance goals. In the design process, choices of materials and dimensions are made which produce specific response characteristics which permit the selected goals to be achieved. Common choices for tailoring goals are preventing instabilities or vibration resonances or enhancing damage tolerance. An essential, enabling factor in the design of tailored composite structures is structural modeling that accurately, but simply, characterizes response. The objective of this paper is to improve the single-cell beam model for composite rotor blades or lifting surfaces and to demonstrate its usefullness in applications.

  12. Utilization threshold of surface water and groundwater based on the system optimization of crop planting structure

    Directory of Open Access Journals (Sweden)

    Qiang FU,Jiahong LI,Tianxiao LI,Dong LIU,Song CUI

    2016-09-01

    Full Text Available Based on the diversity of the agricultural system, this research calculates the planting structures of rice, maize and soybean considering the optimal economic-social-ecological aspects. Then, based on the uncertainty and randomness of the water resources system, the interval two-stage stochastic programming method, which introduces the uncertainty of the interval number, is used to calculate the groundwater exploitation and the use efficiency of surface water. The method considers the minimum cost of water as the objective of the uncertainty model for surface water and groundwater joint scheduling optimization for different planting structures. Finally, by calculating harmonious entropy, the optimal exploitation utilization interval of surface water and groundwater is determined for optimal cultivation in the Sanjiang Plain. The optimal matching of the planting structure under the economic system is suitable when the mining ratio of the surface is in 44.13%—45.45% and the exploitation utilization of groundwater is in 54.82%—66.86%, the optimal planting structure under the social system is suitable when surface water mining ratio is in 47.84%—48.04% and the groundwater exploitation threshold is in 67.07%—72.00%. This article optimizes the economic-social-ecological-water system, which is important for the development of a water- and food-conserving society and providing a more accurate management environment.

  13. Induction Thermography for Surface Crack Detection and Depth Determination

    Directory of Open Access Journals (Sweden)

    Beate Oswald-Tranta

    2018-02-01

    Full Text Available In the last few years, induction thermography has been established as a non-destructive testing method for localizing surface cracks in metals. The sample to be inspected is heated with a short induced electrical current pulse, and the infrared camera records—during and after the heating pulse—the temperature distribution at the surface. Transforming the temporal temperature development for each pixel to phase information makes not only highly reliable detection of the cracks possible but also allows an estimation of its depth. Finite element simulations were carried out to investigate how the phase contrast depends on parameters such as excitation frequency, pulse duration, material parameters, crack depth, and inclination angle of the crack. From these results, generalized functions for the dependency of the phase difference on all these parameters were derived. These functions can be used as an excellent guideline as to how measurement parameters should be optimized for a given material to be able to detect cracks and estimate their depth. Several experiments on different samples were also carried out, and the results compared with the simulations showed very good agreement.

  14. Quantitative characterization of the atomic-scale structure of oxyhydroxides in rusts formed on steel surfaces

    International Nuclear Information System (INIS)

    Saito, M.; Suzuki, S.; Kimura, M.; Suzuki, T.; Kihira, H.; Waseda, Y.

    2005-01-01

    Quantitative X-ray structural analysis coupled with anomalous X-ray scattering has been used for characterizing the atomic-scale structure of rust formed on steel surfaces. Samples were prepared from rust layers formed on the surfaces of two commercial steels. X-ray scattered intensity profiles of the two samples showed that the rusts consisted mainly of two types of ferric oxyhydroxide, α-FeOOH and γ-FeOOH. The amounts of these rust components and the realistic atomic arrangements in the components were estimated by fitting both the ordinary and the environmental interference functions with a model structure calculated using the reverse Monte Carlo simulation technique. The two rust components were found to be the network structure formed by FeO 6 octahedral units, the network structure itself deviating from the ideal case. The present results also suggest that the structural analysis method using anomalous X-ray scattering and the reverse Monte Carlo technique is very successful in determining the atomic-scale structure of rusts formed on the steel surfaces

  15. Direct electron crystallographic determination of zeolite zonal structures

    International Nuclear Information System (INIS)

    Dorset, Douglas L.; Gilmore, Christopher J.; Jorda, Jose Luis; Nicolopoulos, Stavros

    2007-01-01

    The prospect for improving the success of ab initio zeolite structure investigations with electron diffraction data is evaluated. First of all, the quality of intensities obtained by precession electron diffraction at small hollow cone illumination angles is evaluated for seven representative materials: ITQ-1, ITQ-7, ITQ-29, ZSM-5, ZSM-10, mordenite, and MCM-68. It is clear that, for most examples, an appreciable fraction of a secondary scattering perturbation is removed by precession at small angles. In one case, ZSM-10, it can also be argued that precession diffraction produces a dramatically improved 'kinematical' data set. There seems to no real support for application of a Lorentz correction to these data and there is no reason to expect for any of these samples that a two-beam dynamical scattering relationship between structure factor amplitude and observed intensity should be valid. Removal of secondary scattering by the precession mode appears to facilitate ab initio structure analysis. Most zeolite structures investigated could be solved by maximum entropy and likelihood phasing via error-correcting codes when precession data were used. Examples include the projected structure of mordenite that could not be determined from selected area data alone. One anomaly is the case of ZSM-5, where the best structure determination in projection is made from selected area diffraction data. In a control study, the zonal structure of SSZ-48 could be determined from selected area diffraction data by either maximum entropy and likelihood or traditional direct methods. While the maximum entropy and likelihood approach enjoys some advantages over traditional direct methods (non-dependence on predicted phase invariant sums), some effort must be made to improve the figures of merit used to identify potential structure solutions

  16. Structure and energetics of bimetallic surface confined alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bergbreiter, Andreas; Roetter, Ralf T.; Engstfeld, Albert K.; Hoster, Harry E.; Behm, R. Juergen [Institute of Surface Chemistry and Catalysis, Ulm University (Germany); Gross, Axel [Institute for Theoretical Chemistry, Ulm University (Germany)

    2009-07-01

    The atomic distribution in a number of A{sub x}B{sub 1-x}/B type surface alloys was determined by STM imaging with chemical contrast and statistically evaluated. Whereas in the systems Au{sub x}Pt{sub 1-x}/Pt(111), Ag{sub x}Pt{sub 1-x}/Pt(111), and Pd{sub x}Ru{sub 1-x}/Ru(0001) we find preferences for larger homoatomic aggregates, the atom distribution in Pt{sub x}Ru{sub 1-x}/Ru(0001) and Ag{sub x}Pd{sub 1-x}/Pd(111) is very close to a random one[1]. In Ag{sub x}Pd{sub 1-x}/Pd(111), our data show a small tendency towards clustering for x{sub Ag}<0.5, whereas at x{sub Ag}>0.5 this is reversed to a slight preference for heteroatomic neighborhoods. Based on these experimental results, we have derived effective cluster interaction energies for all surface alloys. These allow us to calculate phase diagrams for the surface alloys that we compare to predictions from theoretical work and to the behaviour of the corresponding bulk systems. We also discuss in how far the different atom distributions affect chemical and catalytic properties of the surface alloys.

  17. Document boundary determination using structural and lexical analysis

    Science.gov (United States)

    Taghva, Kazem; Cartright, Marc-Allen

    2009-01-01

    The document boundary determination problem is the process of identifying individual documents in a stack of papers. In this paper, we report on a classification system for automation of this process. The system employs features based on document structure and lexical content. We also report on experimental results to support the effectiveness of this system.

  18. New method to determine structures in thermonuclear plasmas

    International Nuclear Information System (INIS)

    Tanzi, C.P.

    1998-01-01

    The information from tomographic methods is not always sufficient to determine fast changing structures, e.g. very hot plasmas. A new method has been developed by means of which, among other things, physical mechanisms of plasma instability can be disentangled. 4 refs

  19. Dynamic Capital Structure: Dynamics, Determinants and Speed of Adjustment

    NARCIS (Netherlands)

    Tamirat, A.S.; Trujillo Barrera, A.A.; Pennings, J.M.E.

    2017-01-01

    The corporate finance literature has focused on explaining the determinants of firms target capital structure and speed of adjustment using the well-established theories such as pecking order, signaling and trade-off theories. However, less attention has been paid to understanding the financing

  20. Farm Target Capital Structure: Dynamics, Determinants and Speed of Adjustment

    NARCIS (Netherlands)

    Tamirat, A.S.; Trujillo Barrera, A.A.; Pennings, J.M.E.

    2017-01-01

    The corporate finance literature has focused on explaining the determinants of firms target capital structure and speed of adjustment using the well-established theories such as pecking order, signaling and trade-off theories. However, less attention has been paid to understanding the financing

  1. A Laboratory Exercise in the Determination of Carbohydrate Structures.

    Science.gov (United States)

    White, Bernard J.; Robyt, John F.

    1988-01-01

    Describes an experiment in which students are given a naturally occurring oligosaccharide as an unknown and are asked to determine both its monosaccharide composition and its structure. Discusses methods and experimental techniques including thin layer chromatography and the use of enzymes. (CW)

  2. Determining modulus of elasticity of ancient structural timber

    Science.gov (United States)

    Houjiang Zhang; Lei Zhu; Yanliang Sun; Xiping Wang; Haicheng Yan

    2011-01-01

    During maintenance of ancient timber architectures, it is important to determine mechanical properties of the wood component materials non-destructively and effectively, so that degraded members may be replaced or repaired to avoid structural failure. Experimental materials are four larch (Larix principis-rupprechtii Mayr.) components, which were taken down from the...

  3. Birthday Cake Activity Structured Arrangement for Helping Children Determining Quantities

    Science.gov (United States)

    Mariana, Neni

    2010-01-01

    Few researches have been concerned about relation between children's spatial thinking and number sense. Narrowing for this small research, we focused on one component of spatial thinking, that is structuring objects, and one component of number senses, that is cardinality by determining quantities. This study focused on a design research that was…

  4. Macromolecular structure determination in the post-genome era

    International Nuclear Information System (INIS)

    Kuhn, P.; Soltis, S.M.

    2001-01-01

    Recent advances in genetics, molecular biology and crystallographic instrumentation and methodology have led to a revolution in the field of Structural Molecular Biology (SMB). These combined advances have paved the way to a more complete and detailed understanding of the biological macromolecules that make up an organism, both in terms of their individual functions and also the interactions between them. In this paper we describe a large-scale, genomic approach to the three-dimensional structure determination of macromolecules and their complexes, using high-throughput methodology to streamline all aspects of the process. This task requires the development of automated high-intensity synchrotron beam lines for X-ray diffraction data collection from single crystal samples. Furthermore, these beam lines must be operated within a sophisticated software and hardware environment, which is capable of delivering a completely automated structure determination pipeline. The SMB resource at SSRL is developing a system for the structure determination steps of this process, starting with the initial characterization of the frozen sample, followed by data collection, data reduction, phase determination, and model building. This paper focuses on the data collection elements of this high-throughput system

  5. From bacterial to human dihydrouridine synthase: automated structure determination

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, Fiona, E-mail: fiona.whelan@york.ac.uk; Jenkins, Huw T., E-mail: fiona.whelan@york.ac.uk [The University of York, Heslington, York YO10 5DD (United Kingdom); Griffiths, Samuel C. [University of Oxford, Headington, Oxford OX3 7BN (United Kingdom); Byrne, Robert T. [Ludwig-Maximilians-University Munich, Feodor-Lynen-Strasse 25, 81377 Munich (Germany); Dodson, Eleanor J.; Antson, Alfred A., E-mail: fiona.whelan@york.ac.uk [The University of York, Heslington, York YO10 5DD (United Kingdom)

    2015-06-30

    The crystal structure of a human dihydrouridine synthase, an enzyme associated with lung cancer, with 18% sequence identity to a T. maritima enzyme, has been determined at 1.9 Å resolution by molecular replacement after extensive molecular remodelling of the template. The reduction of uridine to dihydrouridine at specific positions in tRNA is catalysed by dihydrouridine synthase (Dus) enzymes. Increased expression of human dihydrouridine synthase 2 (hDus2) has been linked to pulmonary carcinogenesis, while its knockdown decreased cancer cell line viability, suggesting that it may serve as a valuable target for therapeutic intervention. Here, the X-ray crystal structure of a construct of hDus2 encompassing the catalytic and tRNA-recognition domains (residues 1–340) determined at 1.9 Å resolution is presented. It is shown that the structure can be determined automatically by phenix.mr-rosetta starting from a bacterial Dus enzyme with only 18% sequence identity and a significantly divergent structure. The overall fold of the human Dus2 is similar to that of bacterial enzymes, but has a larger recognition domain and a unique three-stranded antiparallel β-sheet insertion into the catalytic domain that packs next to the recognition domain, contributing to domain–domain interactions. The structure may inform the development of novel therapeutic approaches in the fight against lung cancer.

  6. From bacterial to human dihydrouridine synthase: automated structure determination

    International Nuclear Information System (INIS)

    Whelan, Fiona; Jenkins, Huw T.; Griffiths, Samuel C.; Byrne, Robert T.; Dodson, Eleanor J.; Antson, Alfred A.

    2015-01-01

    The crystal structure of a human dihydrouridine synthase, an enzyme associated with lung cancer, with 18% sequence identity to a T. maritima enzyme, has been determined at 1.9 Å resolution by molecular replacement after extensive molecular remodelling of the template. The reduction of uridine to dihydrouridine at specific positions in tRNA is catalysed by dihydrouridine synthase (Dus) enzymes. Increased expression of human dihydrouridine synthase 2 (hDus2) has been linked to pulmonary carcinogenesis, while its knockdown decreased cancer cell line viability, suggesting that it may serve as a valuable target for therapeutic intervention. Here, the X-ray crystal structure of a construct of hDus2 encompassing the catalytic and tRNA-recognition domains (residues 1–340) determined at 1.9 Å resolution is presented. It is shown that the structure can be determined automatically by phenix.mr-rosetta starting from a bacterial Dus enzyme with only 18% sequence identity and a significantly divergent structure. The overall fold of the human Dus2 is similar to that of bacterial enzymes, but has a larger recognition domain and a unique three-stranded antiparallel β-sheet insertion into the catalytic domain that packs next to the recognition domain, contributing to domain–domain interactions. The structure may inform the development of novel therapeutic approaches in the fight against lung cancer

  7. Enhanced surface structuring by ultrafast XUV/NIR dual action

    Czech Academy of Sciences Publication Activity Database

    Jakubczak, Krzysztof; Mocek, Tomáš; Chalupský, Jaromír; Lee, G.H.; Kim, T.K.; Park, S.B.; Nam, Ch. H.; Hájková, Věra; Toufarová, Martina; Juha, Libor; Rus, Bedřich

    2011-01-01

    Roč. 13, č. 5 (2011), s. 1-12 ISSN 1367-2630 R&D Projects: GA AV ČR KAN300100702; GA MŠk(CZ) LC528; GA MŠk LA08024; GA ČR GC202/07/J008 Grant - others:AV ČR(CZ) M100100911 Institutional research plan: CEZ:AV0Z10100523 Keywords : XUV beam * ultrafast NIR laser pulses * high-order harmonics * laser-induced periodic surface structures Subject RIV: BH - Optics, Masers, Lasers Impact factor: 4.177, year: 2011 http://iopscience.iop.org/1367-2630/13/5/053049

  8. Macromolecular structure determination in the post-genome era

    CERN Document Server

    Kuhn, P

    2001-01-01

    Recent advances in genetics, molecular biology and crystallographic instrumentation and methodology have led to a revolution in the field of Structural Molecular Biology (SMB). These combined advances have paved the way to a more complete and detailed understanding of the biological macromolecules that make up an organism, both in terms of their individual functions and also the interactions between them. In this paper we describe a large-scale, genomic approach to the three-dimensional structure determination of macromolecules and their complexes, using high-throughput methodology to streamline all aspects of the process. This task requires the development of automated high-intensity synchrotron beam lines for X-ray diffraction data collection from single crystal samples. Furthermore, these beam lines must be operated within a sophisticated software and hardware environment, which is capable of delivering a completely automated structure determination pipeline. The SMB resource at SSRL is developing a system...

  9. Strengthening of the RAFMS RUSFER-EK181 through nano structuring surface layers

    Energy Technology Data Exchange (ETDEWEB)

    Panin, A.; Melnikova, E.A. [Tomsk State Univ., lnstitute of Strength Physics and Materials Science, SB, RAS (Russian Federation); Chernov, V.M. [Bochvar Institute of Inorganic Materials, Moscow (Russian Federation); Leontieva-Smirnova, M.V. [A.A. Bochvar Research Institute of Inorganic Materials, Moscow (Russian Federation)

    2007-07-01

    Full text of publication follows: Surface nano-structuring increases yield point and strength of the reduced activation ferritic-martensitic steel (RAFMS ) RUSREF - EK181. Ultrasonic impact treatment was used to produce a nano-structure within the surface layers of the specimens. Using scanning tunnelling microscope reveals a new mechanism of mesoscale-level plastic deformation of nano-structured surface layers of the RAFMS RUSREF - EK181 as doubled spirals of localised-plastic deformation meso-bands. A linear dependence of their sizes on thickness of strengthened layer was obtained. The effect of localised deformation meso-bands on macro-mechanical properties of a material was demonstrated. A certain combination of thermal and mechanical treatment as well as optimum proportion of nano-structured surface layer thickness to thickness of a whole specimen are necessary to achieve maximum strength values. Tests performed at high temperatures in the range from 20 to 700 deg. C shows efficiency of the surface hardening of the RAFMS RUSREF - EK181. The effect of nano-structured surface layer on the character of plastic deformation and mechanical properties of the RAFMS RUSREF - EK181 was considered in the framework of a multilevel model in which loss of shear stability and generation of structural defects occur self-consistently at various scale levels such as nano-, micro-, meso-, and macro-Chessboard like distribution of stresses and misfit deformations was theoretical and experimentally shown to appear at the 'nano-structured surface layer - bulk of material' interface. Zones of compressive normal stresses alternates with zones of tensile normal stresses as on a chessboard. Plastic shear can generate only within local zones of tensile normal stresses. Critical meso-volume of non-equilibrium states required for local structure-phase transformation can be formed within these zones. Whereas within the zones of compressive normal stresses acting from both

  10. Direct experimental determination of the atomic structure at internal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Browning, N.D. [Oak Ridge National Lab., TN (United States)]|[Illinois Univ., Chicago, IL (United States); Pennycook, S.J. [Oak Ridge National Lab., TN (United States)

    1995-07-01

    A crucial first step in understanding the effect that internal interfaces have on the properties of materials is the ability to determine the atomic structure at the interface. As interfaces can contain atomic disorder, dislocations, segregated impurities and interphases, sensitivity to all of these features is essential for complete experimental characterization. By combining Z-contrast imaging and electron energy loss spectroscopy (EELS) in a dedicated scanning transmission electron microscope (STEM), the ability to probe the structure, bonding and composition at interfaces with the necessary atomic resolution has been obtained. Experimental conditions can be controlled to provide, simultaneously, both incoherent imaging and spectroscopy. This enables interface structures observed in the image to be interpreted intuitively and the bonding in a specified atomic column to be probed directly by EELS. The bonding and structure information can then be correlated using bond-valence sum analysis to produce structural models. This technique is demonstrated for 25{degrees}, 36{degrees} and 67{degrees} symmetric and 45{degrees} and 25{degrees} asymmetric [001] tilt grain boundaries in SrTiO{sub 3} The structures of both types of boundary were found to contain partially occupied columns in the boundary plane. From these experimental results, a series of structural units were identified which could be combined, using continuity of gain boundary structure principles, to construct all [001] tilt boundaries in SrTiO{sub 3}. Using these models, the ability of this technique to address the issues of vacancies and dopant segregation at grain boundaries in electroceramics is discussed.

  11. Evolution of atomic-scale surface structures during ion bombardment: A fractal simulation

    International Nuclear Information System (INIS)

    Shaheen, M.A.; Ruzic, D.N.

    1993-01-01

    Surfaces of interest in microelectronics have been shown to exhibit fractal topographies on the atomic scale. A model utilizing self-similar fractals to simulate surface roughness has been added to the ion bombardment code TRIM. The model has successfully predicted experimental sputtering yields of low energy (less then 1000 eV) Ar on Si and D on C using experimentally determined fractal dimensions. Under ion bombardment the fractal surface structures evolve as the atoms in the collision cascade are displaced or sputtered. These atoms have been tracked and the evolution of the surface in steps of one monolayer of flux has been determined. The Ar--Si system has been studied for incidence energies of 100 and 500 eV, and incidence angles of 0 degree, 30 degree, and 60 degree. As expected, normally incident ion bombardment tends to reduce the roughness of the surface, whereas large angle ion bombardment increases the degree of surface roughness. Of particular interest though, the surfaces are still locally self-similar fractals after ion bombardment and a steady state fractal dimension is reached, except at large angles of incidence

  12. CAPITAL STRUCTURE DETERMINANTS: EVIDENCE FROM PALESTINE AND EGYPT STOCK EXCHANGES

    Directory of Open Access Journals (Sweden)

    Abdul Razak Abdul Hadi

    2017-04-01

    Full Text Available Abstract -This study is driven by the motivation to examine the capital structure determinants for Palestine Stock Exchange (PEX and Egypt Stock Exchange (EGX. Within the framework of capital structure theories, this study uses Generalized Method of Moments (GMM,1982 as an estimation model employing quarterly panel data analysis during the observed period from 2008 till 2012. The test results from GMM indicate that all the examined determinants have significant relationship with leverage. It has a negative value with liquidity, non-debt tax shield, profitability, size and growth. The Egyptian firms have some uniqueness in its trend. Current assets, debt ratio and liquidity behave positively with leverage except for growth. The other tested determinants in Egyptian companies are found to be not significant.

  13. Adsorption effectiveness of β-lactoglobulin onto gold surface determined by quartz crystal microbalance.

    Science.gov (United States)

    Jachimska, B; Świątek, S; Loch, J I; Lewiński, K; Luxbacher, T

    2018-06-01

    Bovine β-lactoglobulin (LGB) is a transport protein that can bind to its structure hydrophobic bioactive molecules. Due to the lack of toxicity, high stability and pH-dependent molecular binding mechanism, lactoglobulin can be used as a carrier of sparingly soluble drugs. Dynamic light scattering has confirmed LGB's tendency to create oligomeric forms. The hydrodynamic diameter of LGB molecules varies from 4 nm to 6 nm in the pH range of 2-10 and ionic strength I = 0.001-0.15 M, which corresponds to the presence of mono or dimeric LGB forms. The LGB zeta potential varies from 26.5 mV to -33.3 mV for I = 0.01 M and from 13.3 mV to -16 mV for I = 0.15 M in the pH range of 2-10. The isoelectric point is at pH 4.8. As a result of strong surface charge compensation, the maximum effective ionization degree of the LGB molecule is 35% for ionic strength I = 0.01 M and 22% for I = 0.15 M. The effectiveness of adsorption is linked with the properties of the protein, as well as those of the adsorption surface. The functionalization of gold surfaces with β-lactoglobulin (LGB) was studied using a quartz crystal microbalance with energy dissipation monitoring (QCM-D). The effectiveness of LGB adsorption correlates strongly with a charge of gold surface and the zeta potential of the molecule. The greatest value of the adsorbed mass was observed in the pH range in which LGB has a positive zeta potential values, below pH 4.8. This observation shows that electrostatic interactions play a dominant role in LGB adsorption on gold surfaces. Based on the adsorbed mass, protein orientation on gold surfaces was determined. The preferential side-on orientation of LGB molecules observed in the adsorption layer is consistent with the direction of the molecule dipole momentum determined by molecular dynamics simulations of the protein (MD). The use of the QCM-D method also allowed us to determine the effectiveness of adsorption of LGB on gold

  14. Laser-induced oxidation of titanium substrate: Analysis of the physicochemical structure of the surface and sub-surface layers

    Energy Technology Data Exchange (ETDEWEB)

    Antończak, Arkadiusz J., E-mail: arkadiusz.antonczak@pwr.edu.pl [Laser and Fiber Electronics Group, Faculty of Electrical Engineering, Wroclaw University of Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw (Poland); Skowroński, Łukasz; Trzcinski, Marek [Institute of Mathematics and Physics, University of Technology and Life Sciences, Kaliskiego 7, 85-789 Bydgoszcz (Poland); Kinzhybalo, Vasyl V. [Wroclaw Research Centre EIT+, Stabłowicka 147, 54-066 Wrocław (Poland); Institute of Low Temperature and Structure Research, Okólna 2, 50-422 Wrocław (Poland); Łazarek, Łukasz K.; Abramski, Krzysztof M. [Laser and Fiber Electronics Group, Faculty of Electrical Engineering, Wroclaw University of Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw (Poland)

    2015-01-15

    Highlights: • Chemical structure of the films induced by laser on titanium surface was analyzed. • It was shown that outer layer of this films consist of oxides doped with nitrogen. • The optical properties of the laser-induced oxynitride films were characterized. • We found that the films demonstrated significant absorption in the band of 300–580 nm. • The morphology of the layers as a function of the laser fluence was investigated. - Abstract: This paper presents the results of the analysis of the complex chemical structure of the layers made on titanium in the process of the heating of its surfaces in an atmospheric environment, by irradiating samples with a nanosecond-pulsed laser. The study was carried out for electroplated, high purity, polycrystalline titanium substrates using a Yb:glass fiber laser. All measurements were made for samples irradiated in a broad range of accumulated fluence, below the ablation threshold. It has been determined how the complex index of refraction of both the oxynitride layers and the substrate vary as a function of accumulated laser fluence. It was also shown that the top layer of the film produced on titanium, which is transparent, is not a pure TiO{sub 2} as had been supposed before. The XPS and XRD analyses confirmed the presence of nitrogen compounds and the existence of nonstoichiometric compounds. By sputtering of the sample's surface using an Ar{sup +} ion gun, the changes in the concentration of individual elements as a function of the layer's cross-section were determined. Lastly, an analysis of the surface morphology has also been carried out, explaining why the layers crack and exfoliate from their substrate.

  15. Detection for flatness of large surface based on structured light

    Science.gov (United States)

    He, Wenyan; Cao, Xuedong; Long, Kuang; Peng, Zhang

    2016-09-01

    In order to get flatness of a large plane, this paper set up a measurement system, composed by Line Structured Light, imaging system, CCD, etc. Line Structured Light transmits parallel fringes at a proper angle onto the plane which is measured; the imaging system and CCD locate above the plane to catch the fringes. When the plane is perfect, CCD will catch straight fringes; however, the real plane is not perfect; according to the theory of projection, the fringes caught by CCD will be distorted by convex and concave. Extract the center of line fringes to obtain the distortion of the fringe, according to the functional relationship between the distortion of fringes and the height which is measured, then we will get flatness of the entire surface. Data from experiment approached the analysis of theory. In the simulation, the vertical resolution is 0.0075 mm per pixel when measuring a plane of 400mm×400mm, choosing the size of CCD 4096×4096, at the angle 85°. Helped by sub-pixel, the precision will get the level of submicron. There are two obvious advantages: method of surface sampling can increase the efficiency for auto-repairing of machines; considering the center of fringe is required mainly in this system, as a consequence, there is no serious demand for back light.

  16. The use of radar and visual observations to characterize the surface structure of the planet Mercury

    Science.gov (United States)

    Clark, P. E.; Kobrick, M.; Jurgens, R. F.

    1985-01-01

    An analysis is conducted of available topographic profiles and scattering parameters derived from earth-based S- and X-band radar observations of Mercury, in order to determine the nature and origin of regional surface variations and structures that are typical of the planet. Attention is given to the proposal that intercrater plains on Mercury formed from extensive volcanic flooding during bombardment, so that most craters were formed on a partially molten surface and were thus obliterated, together with previously formed tectonic features.

  17. X-ray structure determination and deuteration of nattokinase

    International Nuclear Information System (INIS)

    Yanagisawa, Yasuhide; Chatake, Toshiyuki; Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki; Kawaguchi, Akio; Chiba-Kamosida, Kaori; Ogawa, Megumi; Adachi, Tatsumi; Morimoto, Yukio

    2013-01-01

    X-ray structure determination and deuteration of nattokinase were performed to facilitate neutron crystallographic analysis. Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D 2 O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D 2 O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis

  18. X-ray structure determination and deuteration of nattokinase

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Yasuhide [Chiba Institute of Science, 15-8 Shiomi-cho, Cho-shi, Chiba 288-025 (Japan); Chatake, Toshiyuki [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan); Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki [Kurashiki University of Science and the Arts, 2640 Nishinoura, Tsurajima-cho, Kurashiki, Okayama 712-8505 (Japan); Kawaguchi, Akio [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan); Chiba-Kamosida, Kaori [Nippon Advanced Technology Co. Ltd, J-PARC, 2-4 Shirane Shirakata, Tokai, Ibaraki 319-1195 (Japan); Ogawa, Megumi; Adachi, Tatsumi [Chiba Institute of Science, 15-8 Shiomi-cho, Cho-shi, Chiba 288-025 (Japan); Morimoto, Yukio [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan)

    2013-11-01

    X-ray structure determination and deuteration of nattokinase were performed to facilitate neutron crystallographic analysis. Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D{sub 2}O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D{sub 2}O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis.

  19. Overconfidence, Managerial Optimism, and the Determinants of Capital Structure

    Directory of Open Access Journals (Sweden)

    Alexandre di Miceli da Silveira

    2008-12-01

    Full Text Available This research examines the determinants of the capital structure of firms introducing a behavioral perspective that has received little attention in corporate finance literature. The following central hypothesis emerges from a set of recently developed theories: firms managed by optimistic and/or overconfident people will choose more levered financing structures than others, ceteris paribus. We propose different proxies for optimism/overconfidence, based on the manager’s status as an entrepreneur or non-entrepreneur, an idea that is supported by theories and solid empirical evidence, as well as on the pattern of ownership of the firm’s shares by its manager. The study also includes potential determinants of capital structure used in earlier research. We use a sample of Brazilian firms listed in the Sao Paulo Stock Exchange (Bovespa in the years 1998 to 2003. The empirical analysis suggests that the proxies for the referred cognitive biases are important determinants of capital structure. We also found as relevant explanatory variables: profitability, size, dividend payment and tangibility, as well as some indicators that capture the firms’ corporate governance standards. These results suggest that behavioral approaches based on human psychology research can offer relevant contributions to the understanding of corporate decision making.

  20. The New Horizons Radio Science Experiment: Performance and Measurements of Pluto's Atmospheric Structure, Surface Pressure, and Surface Temperature

    Science.gov (United States)

    Linscott, I.; Hinson, D. P.; Bird, M. K.; Stern, A.; Weaver, H. A., Jr.; Olkin, C.; Young, L. A.; Ennico Smith, K.

    2015-12-01

    The New Horizons (NH) spacecraft payload contained the Radio Science Experiment (REX) for determining key characteristics of Pluto and Charon during the July 14, 2015, flyby of the Pluto/Charon system. The REX flight equipment augments the NH X-band radio transceiver by providing a high precision, narrow band recording of high power uplink transmissions from Earth stations, as well as a record of broadband radiometric power. This presentation will review the performance and initial results of two high- priority observations. First, REX received two pair of 20-kW signals, one pair per polarization, transmitted from the DSN at 4.2-cm wavelength during a diametric radio occultation by Pluto. REX recorded these uplink signals and determined precise measurement of the surface pressure, the temperature structure of the lower atmosphere, and the surface radius of Pluto. The ingress portion of one polarization was played back from the spacecraft in July and processed to obtain the pressure and temperature structure of Pluto's atmosphere. Second, REX measured the thermal emission from Pluto at 4.2- cm wavelength during two linear scans across the disk at close range when both the dayside and the night side are visible. Both scans extend from limb to limb with a resolution of one-tenth Pluto's disk and temperature resolution of 0.1 K. Occultation and radiometric temperature results presented here will encompass additional data scheduled for playback in September.

  1. Surface molecular aggregation structure and surface physicochemical properties of poly(fluoroalkyl acrylate) thin films

    International Nuclear Information System (INIS)

    Honda, K; Yamaguchi, H; Takahara, A; Kobayashi, M; Morita, M

    2008-01-01

    Effect of side chain length on the molecular aggregation states and surface properties of poly(fluoroalkyl acrylate)s [PFA-C y , where y is fluoromethylene number in R f group] thin films were systematically investigated. Spin-coated PFA-C y thin films were characterized by static and dynamic contact angle measurements, X-ray photoelectron spectroscopy (XPS), and grazing- incidence X-ray diffraction (GIXD). The receding contact angles showed small values for PFA-C y with short side chain (y≤6) and increased above y≥8. GIXD revealed that fluoroalkyl side chain of PFA-C y with y≥8 was crystallized and formed ordered structures at the surface region as well as bulk one. These results suggest that water repellent mechanism of PFA-C y can be attributed to the presence of highly ordered fluoroalkyl side chains at the outermost surfaces. The results of XPS in the dry and hydrated states and contact angle measurement in water support the mechanism of lowering contact angle for water by exposure of carbonyl group to the water interface through reorientation of short fluoroalkyl chains. The surface nanotextured PFA-C 8 through imprinting of anodic aluminum oxide mold showed extremely high hydrophobicity as well as high oleophobicity

  2. Preparation, Surface and Pore Structure of High Surface Area Activated Carbon Fibers from Bamboo by Steam Activation

    Directory of Open Access Journals (Sweden)

    Xiaojun Ma

    2014-06-01

    Full Text Available High surface area activated carbon fibers (ACF have been prepared from bamboo by steam activation after liquefaction and curing. The influences of activation temperature on the microstructure, surface area and porosity were investigated. The results showed that ACF from bamboo at 850 °C have the maximum iodine and methylene blue adsorption values. Aside from the graphitic carbon, phenolic and carbonyl groups were the predominant functions on the surface of activated carbon fiber from bamboo. The prepared ACF from bamboo were found to be mainly type I of isotherm, but the mesoporosity presented an increasing trend after 700 °C. The surface area and micropore volume of samples, which were determined by application of the Brunauer-Emmett-Teller (BET and t-plot methods, were as high as 2024 m2/g and 0.569 cm3/g, respectively. It was also found that the higher activation temperature produced the more ordered microcrystalline structure of ACF from bamboo.

  3. Surfaces of Minimal Paths from Topological Structures and Applications to 3D Object Segmentation

    KAUST Repository

    Algarni, Marei

    2017-10-24

    Extracting surfaces, representing boundaries of objects of interest, from volumetric images, has important applications in various scientific domains, from medicine to geology. In this thesis, I introduce novel mathematical, computational, and algorithmic machinery for extraction of sheet-like surfaces (with boundary), whose boundary is unknown a-priori, a particularly important case in applications that has no convenient methods. This case of a surface with boundaries has applications in extracting faults (among other geological structures) from seismic images in geological applications. Another application domain is in the extraction of structures in the lung from computed tomography (CT) images. Although many methods have been developed in computer vision for extraction of surfaces, including level sets, convex optimization approaches, and graph cut methods, none of these methods appear to be applicable to the case of surfaces with boundary. The novel methods for surface extraction, derived in this thesis, are built on the theory of Minimal Paths, which has been used primarily to extract curves in noisy or corrupted images and have had wide applicability in 2D computer vision. This thesis extends such methods to surfaces, and it is based on novel observations that surfaces can be determined by extracting topological structures from the solution of the eikonal partial differential equation (PDE), which is the basis of Minimal Path theory. Although topological structures are known to be difficult to extract from images, which are both noisy and discrete, this thesis builds robust methods based on Morse theory and computational topology to address such issues. The algorithms have run-time complexity O(NlogN), less complex than existing approaches. The thesis details the algorithms, theory, and shows an extensive experimental evaluation on seismic images and medical images. Experiments show out-performance in accuracy, computational speed, and user convenience

  4. Experimental determination of the structure of H3+

    International Nuclear Information System (INIS)

    Gaillard, M.J.; Gemmell, D.S.; Goldring, G.; Levine, I.; Pietsch, W.J.; Poizat, J.C.; Ratkowski, A.J.; Remillieux, J.; Vager, Z.; Zabransky, B.J.

    1978-01-01

    Three different measurements on the structure of the H 3 + molecular ion are reported. The measurements all make use of a new technique: the foil-induced dissociation of a fast molecular-ion beam. It is shown that the structure is equilaterally triangular in shape. The most probable length of side of the triangle is determined by the three measurements to be 0.97 +- 0.03 A, 0.95 +- 0.06 A, and 1.2 +- 0.2 A, respectively

  5. Sulfated oligosaccharide structures, as determined by NMR techniques

    Energy Technology Data Exchange (ETDEWEB)

    Noseda, M.D.; Duarte, M.E.R.; Tischer, C.A.; Gorin, P.A.J. [Parana Univ., Curitiba, PR (Brazil). Dept. De Bioquimica; Cerezo, A.S. [Buenos Aires Univ. Nacional (Argentina). Dept. de Quimica Organica

    1997-12-31

    Carrageenans are sulfated polysaccharides, produced by red seaweeds (Rhodophyta), that have important biological and physico-chemical properties. Using partial autohydrolysis, we obtained sulfated oligosaccharides from a {lambda}-carrageenan (Noseda and Cerezo, 1993). These oligosaccharides are valuable not only for the study of the structures of the parent carrageenans but also for their possible biological activities. In this work we determined the chemical structure of one of the sulfated oligosaccharides using 1D and 2D NMR techniques. (author) 4 refs., 8 figs., 1 tabs.

  6. Taking MAD to the extreme: ultrafast protein structure determination

    International Nuclear Information System (INIS)

    Walsh, M.A.; Dementieva, I.; Evans, G.; Sanishvili, R.; Joachimiak, A.

    1999-01-01

    Multiwavelength anomalous diffraction data were measured in 23 min from a 16 kDa selenomethionyl-substituted protein, producing experimental phases to 2.25 (angstrom) resolution. The data were collected on a mosaic 3 x 3 charge-coupled device using undulator radiation from the Structural Biology Center 19ID beamline at the Argonne National Laboratory's Advanced Photon Source. The phases were independently obtained semiautomatically by two crystallographic program suites, CCP4 and CNS. The quality and speed of this data acquisition exemplify the opportunities at third-generation synchrotron sources for high-throughput protein crystal structure determination

  7. Implantation measurements to determine tritium permeation in first wall structures

    International Nuclear Information System (INIS)

    Holland, D.F.; Causey, R.A.

    1983-01-01

    A principal safety concern for a D-T burning fusion reactor is release of tritium during routine operation. Tritium implantation into first wall structures, and subsequent permeation into coolants, is potentially an important source of tritium loss. This paper reports on an experiment in which an ion accelerator was used to implant deuterium atoms in a stainless steel disk to simulate tritium implantation in first wall structures. The permeation rate was measured under various operating conditions. These results were used in the TMAP computer code to determine potential tritium loss rates for fusion reactors

  8. DETERMINANT FACTORS OF THE CAPITAL STRUCTURE OF BRAZILIAN TECHNOLOGY COMPANIES

    Directory of Open Access Journals (Sweden)

    Camila Freitas Sant´Ana

    2015-12-01

    Full Text Available The purpose of this study is to identify determinant factors of the capital structure of Brazilian technology companies. The research was characterized as descriptive, document and quantitative, consisting of 21 companies in the communications, telecommunications and digital industry, according to the Exame magazine ranking. The analysis was established from 2009 to 2013 using panel data regression. The results indicate that the growth rate of capital and control type have a positive relationship with the general and long-term debt. However, it was found that company size, profitability and type of capital point to a negative relationship with the capital structure.

  9. Superhydrophilic nanopillar-structured quartz surfaces for the prevention of biofilm formation in optical devices

    Science.gov (United States)

    Han, Soo; Ji, Seungmuk; Abdullah, Abdullah; Kim, Duckil; Lim, Hyuneui; Lee, Donghyun

    2018-01-01

    Bacterial biofilm formation on optical devices such as contact lenses, optical glasses, endoscopic devices, and microscopic slides and lenses are major concerns in the field of medicine and biomedical engineering. To solve these problems, here we present the first report of superhydrophilic transparent nanopillar-structured surfaces with bactericidal properties. To construct bactericidal surfaces, we imitated a topological mechanism found in nature in which nanopillar-structured surfaces cause a mechanical disruption of the outer cell membranes of bacteria, resulting in bacterial cell death. We used nanosphere lithography to fabricate nanopillars with various sharpnesses and heights on a quartz substrate. Water contact angle and light reflectance measurements revealed superhydrophilic, antifogging and antireflective properties, which are important for use in optical devices. To determine bactericidal efficiency, the fabricated surfaces were incubated and tested against two Gram-negative bacteria associated with biofilm formation and various diseases in humans, Pseudomonas aeruginosa and Escherichia coli. The highest bactericidal activity was achieved with nanopillars that measured 300 nm in height and 10 nm in apex diameter. Quartz substrates patterned with such nanopillars killed ∼38,000 P. aeruginosa and ∼27,000 E. coli cells cm-2 min-1, respectively. Thus, the newly designed nanopillar-structured bactericidal surfaces are suitable for use in the development of superhydrophilic and transparent optical devices.

  10. Effect of volume and surface charges on discharge structure of glow dielectric barrier discharge

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Shao-Wei; He, Feng; Wang, Yu; Li, Lulu; Ouyang, Ji-Ting [School of Physics, Beijing Institute of Technology, Beijing 100081 (China)

    2013-08-15

    The effect of volume and surface charges on the structure of glow dielectric barrier discharge (DBD) has been investigated numerically by using two-dimensional (2D) fluid modeling. The local increase of volume or surface charges induces a kind of activation-inhibition effect, which enhances the local volume discharge and inhibits the discharge in neighborhoods, resulting in non-uniform discharge. The activation-inhibition effect due to the non-uniform volume and/or surface charges depends on the non-uniformity itself and the applied voltage. The activation-inhibition of non-uniform charges has different effects on the volume charges and the accumulated surface charges. The distribution of remaining free charges (seed electrons) in volume at the beginning of voltage pulse plays a key role for the glow DBD structure, resulting in a patterned DBD, when the seed electrons are non-uniform at higher frequency and moderate voltage or uniform DBD, when the seed electrons are uniform at lower frequency or high voltage. The distribution of surface charges is not the determining factor but a result of the formed DBD structure.

  11. Microwave effective surface impedance of structures including a high-Tc superconducting film

    International Nuclear Information System (INIS)

    Hartemann, P.

    1992-01-01

    The microwave effective surface impedances of different stacks made of high-temperature superconducting films, dielectric materials and bulk normal metals were computed. The calculations were based on the two-fluid model of superconductors and the conventional transmission line theory. These effective impedances are compared to the calculated intrinsic surface impedances of the stacked superconducting films. The considered superconducting material has been the oxide YBa 2 Cu 3 O 7 epitaxially grown on crystalline substrates (MgO, LaAlO 3 , SrTiO 3 ), the film thickness ranging from a few nm to 1μm. Discrepancies between the effective surface resistances or reactances and the corresponding intrinsic values were determined at 10 GHz for non resonant or resonant structures. At resonance the surface resistance discrepancy exhibits a sharp peak which reaches 10 4 or more in relative value according to the geometry and the used materials. Obviously the effective surface reactance shows also huge variations about the resonance and may be negative. Moreover geometries allowing to obtain an effective resistance smaller than the film intrinsic value have been found. The effects of the resonance phenomenon on the electromagnetic wave reflectivity and reflection phase shift are investigated. Therefore the reported theoretical results demonstrate that the effective surface impedance of YBCO films with a thickness smaller than 500 nm can be very different from the intrinsic film impedance according to the structures. (Author). 3 refs., 10 figs., 2 tabs

  12. Patterns of motor recruitment can be determined using surface EMG.

    Science.gov (United States)

    Wakeling, James M

    2009-04-01

    Previous studies have reported how different populations of motor units (MUs) can be recruited during dynamic and locomotor tasks. It was hypothesised that the higher-threshold units would contribute higher-frequency components to the sEMG spectra due to their faster conduction velocities, and thus recruitment patterns that increase the proportion of high-threshold units active would lead to higher-frequency elements in the sEMG spectra. This idea was tested by using a model of varying recruitment coupled to a three-layer volume conductor model to generate a series of sEMG signals. The recruitment varied from (A) orderly recruitment where the lowest-threshold MUs were initially activated and higher-threshold MUs were sequentially recruited as the contraction progressed, (B) a recurrent inhibition model that started with orderly recruitment, but as the higher-threshold units were activated they inhibited the lower-threshold MUs (C) nine models with intermediate properties that were graded between these two extremes. The sEMG was processed using wavelet analysis and the spectral properties quantified by their mean frequency, and an angle theta that was determined from the principal components of the spectra. Recruitment strategies that resulted in a greater proportion of faster MUs being active had a significantly lower theta and higher mean frequency.

  13. The structure of organic langmuir films on liquid metal surfaces

    International Nuclear Information System (INIS)

    Kraack, H.; Deutsch, M.; Ocko, B.M.; Pershan, P.S.

    2003-01-01

    Langmuir films (LFs) on water have long been studied for their interest for basic science and their numerous applications in chemistry, physics, materials science and biology. We present here A-resolution synchrotron X-ray studies of the structure of stearic acid LFs on a liquid mercury surface. At low coverage, ≥110 A 2 /mol, a 2D gas phase of flat-lying molecules is observed. At high coverage, ≤23 A 2 /mol, two different hexatic phases of standing-up molecules are observed. At intermediate coverage, 52≤A≤110 A 2 /mol, novel single- and double-layered phases of flat-lying molecular dimers are found, exhibiting a 1D in-layer order. Such flat-lying phases were not hitherto observed in any LF. Measurements on LFs of fatty acids of other chain lengths indicate that this structure is generic to chain molecules on mercury, although the existence of some of the flat-lying phases, and the observed phase sequence, depend on the chain length. Organic LFs on Hg, and in particular the new flat-lying phases, should provide a broader nano-structural tunability range for molecular electronic device construction than most solid-supported self-assembled monolayers used at present

  14. Calculation of surface acoustic waves in a multilayered piezoelectric structure

    International Nuclear Information System (INIS)

    Zhang Zuwei; Wen Zhiyu; Hu Jing

    2013-01-01

    The propagation properties of the surface acoustic waves (SAWs) in a ZnO—SiO 2 —Si multilayered piezoelectric structure are calculated by using the recursive asymptotic method. The phase velocities and the electromechanical coupling coefficients for the Rayleigh wave and the Love wave in the different ZnO—SiO 2 —Si structures are calculated and analyzed. The Love mode wave is found to be predominantly generated since the c-axis of the ZnO film is generally perpendicular to the substrate. In order to prove the calculated results, a Love mode SAW device based on the ZnO—SiO 2 —Si multilayered structure is fabricated by micromachining, and its frequency responses are detected. The experimental results are found to be mainly consistent with the calculated ones, except for the slightly larger velocities induced by the residual stresses produced in the fabrication process of the films. The deviation of the experimental results from the calculated ones is reduced by thermal annealing. (semiconductor physics)

  15. The potential for biological structure determination with pulsed neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, C.C. [CLRC Rutherford Appleton Laboratory, Chilton Didcot Oxon (United Kingdom)

    1994-12-31

    The potential of pulsed neutron diffraction in structural determination of biological materials is discussed. The problems and potential solutions in this area are outlined, with reference to both current and future sources and instrumentation. The importance of developing instrumentation on pulsed sources in emphasized, with reference to the likelihood of future expansion in this area. The possibilities and limitations of single crystal, fiber and powder diffraction in this area are assessed.

  16. The potential for biological structure determination with pulsed neutrons

    International Nuclear Information System (INIS)

    Wilson, C.C.

    1994-01-01

    The potential of pulsed neutron diffraction in structural determination of biological materials is discussed. The problems and potential solutions in this area are outlined, with reference to both current and future sources and instrumentation. The importance of developing instrumentation on pulsed sources in emphasized, with reference to the likelihood of future expansion in this area. The possibilities and limitations of single crystal, fiber and powder diffraction in this area are assessed

  17. Determining the helicity structure of third generation resonances

    International Nuclear Information System (INIS)

    Papaefstathiou, Andreas

    2011-11-01

    We examine methods that have been proposed for determining the helicity structure of decays of new resonances to third generation quarks and/or leptons. We present analytical and semi-analytical predictions and assess the applicability of the relevant variables in realistic reconstruction scenarios using Monte Carlo-generated events, including the effects of QCD radiation and multiple parton interactions, combinatoric ambiguities and fast detector simulation. (orig.)

  18. Determination of the Basin Structure Beneath European Side of Istanbul

    Science.gov (United States)

    Karabulut, Savas; Cengiz Cinku, Mulla; Thomas, Michael; Lamontagne, Maurice

    2016-04-01

    Istanbul (near North Anatolian Fault Zone:NAFZ, Turkey) is located in northern part of Sea of Marmara, an area that has been influenced by possible Marmara Earthquakes. The general geology of Istanbul divided into two stratigraphic unit such as sedimentary (from Oligocene to Quaternary Deposits) and bedrock (Paleozoic and Eocene). The bedrock units consists of sand stone, clay stone to Paleozoic age and limestone to Eocene age and sedimentary unit consist of sand, clay, mil and gravel from Oligocene to Quaternary age. Earthquake disaster mitigation studies divided into two important phases, too. Firstly, earthquake, soil and engineering structure problems identify for investigation area, later on strategic emergency plan can prepare for these problems. Soil amplification play important role the disaster mitigation and the site effect analysis and basin structure is also a key parameter for determining of site effect. Some geophysical, geological and geotechnical measurements are requeired to defined this relationship. Istanbul Megacity has been waiting possible Marmara Earthquake and their related results. In order to defined to possible damage potential related to site effect, gravity measurements carried out for determining to geological structure, basin geometry and faults in Istanbul. Gravity data were collected at 640 sites by using a Scientrex CG-5 Autogravity meter Standard corrections applied to the gravity data include those for instrumental drift, Earth tides and latitude, and the free-air and Bouguer corrections. The corrected gravity data were imported into a Geosoft database to create a grid and map of the Bouguer gravity anomaly (grid cell size of 200 m). As a previously results, we determined some lineminants, faults and basins beneath Istanbul City. Especially, orientation of faults were NW-SE direction and some basin structures determined on between Buyukcekmece and Kucukcekmece Lake.

  19. TGP, an extremely stable, non-aggregating fluorescent protein created by structure-guided surface engineering

    OpenAIRE

    Close, Devin W.; Don Paul, Craig; Langan, Patricia S.; Wilce, Matthew C.J.; Traore, Daouda A.K.; Halfmann, Randal; Rocha, Reginaldo C.; Waldo, Geoffery S.; Payne, Riley J.; Rucker, Joseph B.; Prescott, Mark; Bradbury, Andrew R.M.

    2015-01-01

    In this paper we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP....

  20. MOTIVATION INTERNALIZATION AND SIMPLEX STRUCTURE IN SELF-DETERMINATION THEORY.

    Science.gov (United States)

    Ünlü, Ali; Dettweiler, Ulrich

    2015-12-01

    Self-determination theory, as proposed by Deci and Ryan, postulated different types of motivation regulation. As to the introjected and identified regulation of extrinsic motivation, their internalizations were described as "somewhat external" and "somewhat internal" and remained undetermined in the theory. This paper introduces a constrained regression analysis that allows these vaguely expressed motivations to be estimated in an "optimal" manner, in any given empirical context. The approach was even generalized and applied for simplex structure analysis in self-determination theory. The technique was exemplified with an empirical study comparing science teaching in a classical school class versus an expeditionary outdoor program. Based on a sample of 84 German pupils (43 girls, 41 boys, 10 to 12 years old), data were collected using the German version of the Academic Self-Regulation Questionnaire. The science-teaching format was seen to not influence the pupils' internalization of identified regulation. The internalization of introjected regulation differed and shifted more toward the external pole in the outdoor teaching format. The quantification approach supported the simplex structure of self-determination theory, whereas correlations may disconfirm the simplex structure.

  1. Determinants of capital structure: evidence from the Czech automotive industry

    Directory of Open Access Journals (Sweden)

    Pavlína Pinková

    2012-01-01

    Full Text Available The objective of the paper is to identify the determinants influencing the capital structure of large and medium-sized enterprises of the automotive industry in the Czech Republic. The sample consists of 100 companies belonging to NACE division 29. The data come from financial statements of selected companies and cover a period from 2006 to 2010. For the purpose of the paper quantitative research is used. The selection of appropriate dependent and independent is realized on the basis of secondary research on studies of capital structure. The analysis of variance, correlation and regression analyses have been performed to see the nature of relationship between variables. Size, tangibility, profitability and liquidity appear to be relevant determinants of capital structure. Growth is not a statistically significant determinant of leverage. It has been observed that the maturity of debt has to be considered, since the investigation of total debt only does not provide precious results. The findings do not unequivocally support either the static trade-off theory or the pecking order theory.

  2. Local magnetic structure determination using polarized neutron holography

    International Nuclear Information System (INIS)

    Szakál, Alex; Markó, Márton; Cser, László

    2015-01-01

    A unique and important property of the neutron is that it possesses magnetic moment. This property is widely used for determination of magnetic structure of crystalline samples observing the magnetic components of the diffraction peaks. Investigations of diffraction patterns give information only about the averaged structure of a crystal but for discovering of local spin arrangement around a specific (e.g., impurity) nucleus remains still a challenging problem. Neutron holography is a useful tool to investigate the local structure around a specific nucleus embedded in a crystal lattice. The method has been successfully applied experimentally in several cases using non-magnetic short range interaction of the neutron and the nucleus. A mathematical model of the hologram using interaction between magnetic moment of the atom and the neutron spin for polarized neutron holography is provided. Validity of a polarized neutron holographic experiment is demonstrated by applying the proposed method on model systems

  3. Surface and interface electronic structure: Third year progress report, December 1, 1988--November 30, 1989

    International Nuclear Information System (INIS)

    Kevan, S.D.

    1989-01-01

    This paper discusses the following topics: linewidths of surface states and resonances; surface bonds and fermi surface of Pd(001); state-resonance transition of Ta(011); and electronic structure of W(010)-2H. 5 figs

  4. DNA nanotubes for NMR structure determination of membrane proteins.

    Science.gov (United States)

    Bellot, Gaëtan; McClintock, Mark A; Chou, James J; Shih, William M

    2013-04-01

    Finding a way to determine the structures of integral membrane proteins using solution nuclear magnetic resonance (NMR) spectroscopy has proved to be challenging. A residual-dipolar-coupling-based refinement approach can be used to resolve the structure of membrane proteins up to 40 kDa in size, but to do this you need a weak-alignment medium that is detergent-resistant and it has thus far been difficult to obtain such a medium suitable for weak alignment of membrane proteins. We describe here a protocol for robust, large-scale synthesis of detergent-resistant DNA nanotubes that can be assembled into dilute liquid crystals for application as weak-alignment media in solution NMR structure determination of membrane proteins in detergent micelles. The DNA nanotubes are heterodimers of 400-nm-long six-helix bundles, each self-assembled from a M13-based p7308 scaffold strand and >170 short oligonucleotide staple strands. Compatibility with proteins bearing considerable positive charge as well as modulation of molecular alignment, toward collection of linearly independent restraints, can be introduced by reducing the negative charge of DNA nanotubes using counter ions and small DNA-binding molecules. This detergent-resistant liquid-crystal medium offers a number of properties conducive for membrane protein alignment, including high-yield production, thermal stability, buffer compatibility and structural programmability. Production of sufficient nanotubes for four or five NMR experiments can be completed in 1 week by a single individual.

  5. Structural determinants and mechanism of HIV-1 genome packaging.

    Science.gov (United States)

    Lu, Kun; Heng, Xiao; Summers, Michael F

    2011-07-22

    Like all retroviruses, the human immunodeficiency virus selectively packages two copies of its unspliced RNA genome, both of which are utilized for strand-transfer-mediated recombination during reverse transcription-a process that enables rapid evolution under environmental and chemotherapeutic pressures. The viral RNA appears to be selected for packaging as a dimer, and there is evidence that dimerization and packaging are mechanistically coupled. Both processes are mediated by interactions between the nucleocapsid domains of a small number of assembling viral Gag polyproteins and RNA elements within the 5'-untranslated region of the genome. A number of secondary structures have been predicted for regions of the genome that are responsible for packaging, and high-resolution structures have been determined for a few small RNA fragments and protein-RNA complexes. However, major questions regarding the RNA structures (and potentially the structural changes) that are responsible for dimeric genome selection remain unanswered. Here, we review efforts that have been made to identify the molecular determinants and mechanism of human immunodeficiency virus type 1 genome packaging. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Improving energy conversion efficiency for triboelectric nanogenerator with capacitor structure by maximizing surface charge density.

    Science.gov (United States)

    He, Xianming; Guo, Hengyu; Yue, Xule; Gao, Jun; Xi, Yi; Hu, Chenguo

    2015-02-07

    Nanogenerators with capacitor structures based on piezoelectricity, pyroelectricity, triboelectricity and electrostatic induction have been extensively investigated. Although the electron flow on electrodes is well understood, the maximum efficiency-dependent structure design is not clearly known. In this paper, a clear understanding of triboelectric generators with capacitor structures is presented by the investigation of polydimethylsiloxane-based composite film nanogenerators, indicating that the generator, in fact, acts as both an energy storage and output device. Maximum energy storage and output depend on the maximum charge density on the dielectric polymer surface, which is determined by the capacitance of the device. The effective thickness of polydimethylsiloxane can be greatly reduced by mixing a suitable amount of conductive nanoparticles into the polymer, through which the charge density on the polymer surface can be greatly increased. This finding can be applied to all the triboelectric nanogenerators with capacitor structures, and it provides an important guide to the structural design for nanogenerators. It is demonstrated that graphite particles with sizes of 20-40 nm and 3.0% mass mixed into the polydimethylsiloxane can reduce 34.68% of the effective thickness of the dielectric film and increase the surface charges by 111.27% on the dielectric film. The output power density of the triboelectric nanogenerator with the composite polydimethylsiloxane film is 3.7 W m(-2), which is 2.6 times as much as that of the pure polydimethylsiloxane film.

  7. Electronic structure of benzene adsorbed on Ni and Cu surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Weinelt, M.; Nilsson, A.; Wassdahl, N. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    Benzene has for a long time served as a prototype adsorption system of large molecules. It adsorbs with the molecular plane parallel to the surface. The bonding of benzene to a transition metal is typically viewed to involve the {pi} system. Benzene adsorbs weakly on Cu and strongly on Ni. It is interesting to study how the adsorption strength is reflected in the electronic structure of the adsorbate-substrate complex. The authors have used X-ray Emission (XE) and X-ray Absorption (XA) spectroscopies to selectively study the electronic states localized on the adsorbed benzene molecule. Using XES the occupied states can be studies and with XAS the unoccupied states. The authors have used beamline 8.0 and the Swedish endstation equipped with a grazing incidence x-ray spectrometer and a partial yield absorption detector. The resolution in the XES and XAS were 0.5 eV and 0.05 eV, respectively.

  8. Crystallographic Orientation Determination of Hexagonal Structure Crystals by Laser Ultrasonic Technique

    International Nuclear Information System (INIS)

    Li, W; Coulson, J; Marrow, P; Smith, R J; Clark, M; Sharples, S D; Lainé, S J

    2016-01-01

    Spatially resolved acoustic spectroscopy (SRAS) is a laser ultrasonic technique that shows qualitative contrast between grains of different orientation, illustrating the sensitivity of acoustic waves to the material structure. The technique has been improved significantly on determining the full orientation of multigrain cubic metals, by comparing the measured surface acoustic wave (SAW) velocity to a pre-calculated model. In this paper we demonstrate the ability of this technique to determine the orientation of hexagonal structure crystals, such as magnesium and titanium based alloys. Because of the isotropy of the SAW velocity on the basal plane (0001) of hexagonal crystals, the slowness surface is shown as a circle. As the plane moves from (0001) towards (112-bar0) or towards (101-bar0), the slowness surface gradually turns into an oval. These acoustic properties increase the difficulty in orientation determination. The orientation results of a grade 1 commercially pure titanium by SRAS is presented, with comparison with electron backscattered diffraction (EBSD) results. Due to the nature of SAWs on hexagonal structure crystals, only the results of Euler angles 1 and 2 are discussed. The error between SRAS and EBSD is also investigated. (paper)

  9. Femtosecond laser surface structuring of molybdenum thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Mthunzi, P. [Council for Scientific and Industrial Research (CSIR), Biophotonics Lab: National Laser Centre Pretoria, 0001 (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Itala (Italy); Sechoghela, P.; Mongwaketsi, N. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Ramponi, R. [Institute for Photonics and Nanotechnologies (IFN)–CNR, Piazza Leanardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa)

    2015-10-30

    Highlights: • Color change of the molybdenum thin film from shinny to violet–yellowish color after laser irradiation at various laser powers. • Formation of the molybdenum dioxide coating after laser exposure, as confirmed by the X-ray diffraction spectrometry. • Selective solar absorbing nature of the laser exposed films. • Study of the binding energies is presented in this contribution using the XPS spectrometry. - Abstract: This contribution reports on the femtosecond surface structuring of molybdenum thin coatings deposited by electron beam evaporation onto Corning glass substrates. The 1-D type periodic grating lines created by such an ablation showed that the widths of the shallow grooves followed a logarithmic dependence with the laser energy incident on the molybdenum film. The electronic valence “x” of the created oxide surface layer MoO{sub x} was found to be incident laser power dependent via Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction investigations. Such a photo-induced MoO{sub x}–Mo nanocomposite exhibited effective selective solar absorption in the UV–vis–IR spectral range.

  10. Andrew Liehr and the structure of Jahn-Teller surfaces

    International Nuclear Information System (INIS)

    Chibotaru, Liviu F.; Iwahara, Naoya

    2017-01-01

    The present article is an attempt to draw attention to a seminal work by Andrew Liehr “Topological aspects of conformational stability problem” [1, 2] issued more than half century ago. The importance of this work stems from two aspects of static Jahn-Teller and pseudo-Jahn-Teller problems fully developed by the author. First, the work of Liehr offers an almost complete overview of adiabatic potential energy surfaces for most known Jahn-Teller problems including linear, quadratic and higher-order vibronic couplings. Second, and most importantly, it identifies the factors defining the structure of Jahn-Teller surfaces. Among them, one should specially mention the minimax principle stating that the distorted Jahn-Teller systems tend to preserve the highest symmetry consistent with the loss of their orbital degeneracy. We believe that the present short reminiscence not only will introduce a key Jahn-Teller scientist to the young members of the community but also will serve as a vivid example of how a complete understanding of a complex problem, which the Jahn-Teller effect certainly was in the beginning of 1960s, can be achieved. (paper)

  11. Micropatterned Azopolymer Surfaces Modulate Cell Mechanics and Cytoskeleton Structure.

    Science.gov (United States)

    Rianna, Carmela; Ventre, Maurizio; Cavalli, Silvia; Radmacher, Manfred; Netti, Paolo A

    2015-09-30

    Physical and chemical characteristics of materials are important regulators of cell behavior. In particular, cell elasticity is a fundamental parameter that reflects the state of a cell. Surface topography finely modulates cell fate and function via adhesion mediated signaling and cytoskeleton generated forces. However, how topographies alter cell mechanics is still unclear. In this work we have analyzed the mechanical properties of peripheral and nuclear regions of NIH-3T3 cells on azopolymer substrates with different topographic patterns. Micrometer scale patterns in the form of parallel ridges or square lattices of surface elevations were encoded on light responsive azopolymer films by means of contactless optical methods. Cell mechanics was investigated by atomic force microscopy (AFM). Cells and consequently the cell cytoskeleton were oriented along the linear patterns affecting cytoskeletal structures, e.g., formation of actin stress fibers. Our data demonstrate that topographic substrate patterns are recognized by cells and mechanical information is transferred by the cytoskeleton. Furthermore, cytoskeleton generated forces deform the nucleus, changing its morphology that appears to be related to different mechanical properties in the nuclear region.

  12. Structural properties of oligonucleotide monolayers on gold surfaces probed by fluorescence investigations.

    Science.gov (United States)

    Rant, Ulrich; Arinaga, Kenji; Fujita, Shozo; Yokoyama, Naoki; Abstreiter, Gerhard; Tornow, Marc

    2004-11-09

    We present optical investigations on the conformation of oligonucleotide layers on Au surfaces. Our studies concentrate on the effect of varying surface coverage densities on the structural properties of layers of 12- and 24mer single-stranded DNA, tethered to the Au surface at one end while being labeled with a fluorescent marker at the opposing end. The distance-dependent energy transfer from the marker dye to the metal surface, which causes quenching of the observed fluorescence, is used to provide information on the orientation of the DNA strands relative to the surface. Variations in the oligonucleotide coverage density, as determined from electrochemical quantification, over 2 orders of magnitude are achieved by employing different preparation conditions. The observed enhancement in fluorescence intensity with increasing DNA coverage can be related to a model involving mutual steric interactions of oligonucleotides on the surface, as well as fluorescence quenching theory. Finally, the applicability of the presented concepts for investigations of heterogeneous monolayers is demonstrated by means of studying the coadsorption of mercaptohexanol onto DNA-modified Au surfaces.

  13. 30 CFR 57.4530 - Exits for surface buildings and structures.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Exits for surface buildings and structures. 57... Fire Prevention and Control Installation/construction/maintenance § 57.4530 Exits for surface buildings and structures. Surface buildings or structures in which persons work shall have a sufficient number...

  14. Reversible structural modulation of Fe-Pt bimetallic surfaces and its effect on reactivity.

    Science.gov (United States)

    Ma, Teng; Fu, Qiang; Su, Hai-Yan; Liu, Hong-Yang; Cui, Yi; Wang, Zhen; Mu, Ren-Tao; Li, Wei-Xue; Bao, Xin-He

    2009-05-11

    Tunable surface: The surface structure of the Fe-Pt bimetallic catalyst can be reversibly modulated between the iron-oxide-rich Pt surface and the Pt-skin structure with subsurface Fe via alternating reduction and oxidation treatments (see figure). The regenerated active Pt-skin structure is active in reactions involving CO and/or O.

  15. Defining an essence of structure determining residue contacts in proteins.

    Science.gov (United States)

    Sathyapriya, R; Duarte, Jose M; Stehr, Henning; Filippis, Ioannis; Lappe, Michael

    2009-12-01

    The network of native non-covalent residue contacts determines the three-dimensional structure of a protein. However, not all contacts are of equal structural significance, and little knowledge exists about a minimal, yet sufficient, subset required to define the global features of a protein. Characterisation of this "structural essence" has remained elusive so far: no algorithmic strategy has been devised to-date that could outperform a random selection in terms of 3D reconstruction accuracy (measured as the Ca RMSD). It is not only of theoretical interest (i.e., for design of advanced statistical potentials) to identify the number and nature of essential native contacts-such a subset of spatial constraints is very useful in a number of novel experimental methods (like EPR) which rely heavily on constraint-based protein modelling. To derive accurate three-dimensional models from distance constraints, we implemented a reconstruction pipeline using distance geometry. We selected a test-set of 12 protein structures from the four major SCOP fold classes and performed our reconstruction analysis. As a reference set, series of random subsets (ranging from 10% to 90% of native contacts) are generated for each protein, and the reconstruction accuracy is computed for each subset. We have developed a rational strategy, termed "cone-peeling" that combines sequence features and network descriptors to select minimal subsets that outperform the reference sets. We present, for the first time, a rational strategy to derive a structural essence of residue contacts and provide an estimate of the size of this minimal subset. Our algorithm computes sparse subsets capable of determining the tertiary structure at approximately 4.8 A Ca RMSD with as little as 8% of the native contacts (Ca-Ca and Cb-Cb). At the same time, a randomly chosen subset of native contacts needs about twice as many contacts to reach the same level of accuracy. This "structural essence" opens new avenues in the

  16. Effects of self-assembled monolayer structural order, surface homogeneity and surface energy on pentacene morphology and thin film transistor device performance.

    Science.gov (United States)

    Hutchins, Daniel Orrin; Weidner, Tobias; Baio, Joe; Polishak, Brent; Acton, Orb; Cernetic, Nathan; Ma, Hong; Jen, Alex K-Y

    2013-01-04

    A systematic study of six phosphonic acid (PA) self-assembled monolayers (SAMs) with tailored molecular structures is performed to evaluate their effectiveness as dielectric modifying layers in organic field-effect transistors (OFETs) and determine the relationship between SAM structural order, surface homogeneity, and surface energy in dictating device performance. SAM structures and surface properties are examined by near edge X-ray absorption fine structure (NEXAFS) spectroscopy, contact angle goniometry, and atomic force microscopy (AFM). Top-contact pentacene OFET devices are fabricated on SAM modified Si with a thermally grown oxide layer as a dielectric. For less ordered methyl- and phenyl-terminated alkyl ~(CH 2 ) 12 PA SAMs of varying surface energies, pentacene OFETs show high charge carrier mobilities up to 4.1 cm 2 V -1 s -1 . It is hypothesized that for these SAMs, mitigation of molecular scale roughness and subsequent control of surface homogeneity allow for large pentacene grain growth leading to high performance pentacene OFET devices. PA SAMs that contain bulky terminal groups or are highly crystalline in nature do not allow for a homogenous surface at a molecular level and result in charge carrier mobilities of 1.3 cm 2 V -1 s -1 or less. For all molecules used in this study, no causal relationship between SAM surface energy and charge carrier mobility in pentacene FET devices is observed.

  17. Structure of the c(2x2) Mn/Ni(001) surface alloy by quantitative photoelectron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, S.; Denlinger, J.; Chen, X. [Univ. of Wisconsin, Milwaukee, WI (United States)] [and others

    1997-04-01

    Surface alloys are two-dimensional metallic systems that can have structures that are unique to the surface, and have no counterpart in the bulk binary phase diagram. A very unusual structure was reported for the Mn-Ni system, based on a quantitative LEED structure determination, which showed that the Mn atoms were displaced out of the surface by a substantial amount. This displacement was attributed to a large magnetic moment on the Mn atoms. The structure of the Mn-Ni surface alloy was proposed to be based on a bulk termination model. Magnetic measurements on the Mn-Ni surface alloys, however, showed conclusively that the magnetic structure of these surface alloys is completely different from the bulk alloy analogs. For example, bulk MnNi is an antiferromagnet, whereas the surface alloy is ferromagnetic. This suggests that the proposed structure based on bulk termination, may not be correct. X-ray Photoelectron Diffraction (XPD) techniques were used to investigate this structure, using both a comparison to multiple scattering calculations and photoelectron holography. In this article the authors present some of the results from the quantitative analysis of individual diffraction patterns by comparison to theory.

  18. The interior structure of Ceres as revealed by surface topography

    Science.gov (United States)

    Fu, Roger R.; Ermakov, Anton; Marchi, Simone; Castillo-Rogez, Julie C.; Raymond, Carol A.; Hager, Bradford; Zuber, Maria; King, Scott D.; Bland, Michael T.; De Sanctis, Maria Cristina; Preusker, Frank; Park, Ryan S.; Russell, Christopher T.

    2017-01-01

    Ceres, the largest body in the asteroid belt (940 km diameter), provides a unique opportunity to study the interior structure of a volatile-rich dwarf planet. Variations in a planetary body's subsurface rheology and density affect the rate of topographic relaxation. Preferential attenuation of long wavelength topography (≥150 km) on Ceres suggests that the viscosity of its crust decreases with increasing depth. We present finite element (FE) geodynamical simulations of Ceres to identify the internal structures and compositions that best reproduce its topography as observed by the NASA Dawn mission. We infer that Ceres has a mechanically strong crust with maximum effective viscosity ∼1025 Pa s. Combined with density constraints, this rheology suggests a crustal composition of carbonates or phyllosilicates, water ice, and at least 30 volume percent (vol.%) low-density, high-strength phases most consistent with salt and/or clathrate hydrates. The inference of these crustal materials supports the past existence of a global ocean, consistent with the observed surface composition. Meanwhile, we infer that the uppermost ≥60 km of the silicate-rich mantle is mechanically weak with viscosity <1021 Pa s, suggesting the presence of liquid pore fluids in this region and a low temperature history that avoided igneous differentiation due to late accretion or efficient heat loss through hydrothermal processes.

  19. Effect of nanoscale flows on the surface structure of nanoporous catalysts.

    Science.gov (United States)

    Montemore, Matthew M; Montessori, Andrea; Succi, Sauro; Barroo, Cédric; Falcucci, Giacomo; Bell, David C; Kaxiras, Efthimios

    2017-06-07

    The surface structure and composition of a multi-component catalyst are critical factors in determining its catalytic performance. The surface composition can depend on the local pressure of the reacting species, leading to the possibility that the flow through a nanoporous catalyst can affect its structure and reactivity. Here, we explore this possibility for oxidation reactions on nanoporous gold, an AgAu bimetallic catalyst. We use microscopy and digital reconstruction to obtain the morphology of a two-dimensional slice of a nanoporous gold sample. Using lattice Boltzmann fluid dynamics simulations along with thermodynamic models based on first-principles total-energy calculations, we show that some sections of this sample have low local O 2 partial pressures when exposed to reaction conditions, which leads to a pure Au surface in these regions, instead of the active bimetallic AgAu phase. We also explore the effect of temperature on the surface structure and find that moderate temperatures (≈300-450 K) should result in the highest intrinsic catalytic performance, in apparent agreement with experimental results.

  20. Study on mechanics of driving drum with superelastic convexity surface covering-layer structure

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, L.J.; Sui, X.H.; Miao, D.J. [Shandong University of Science & Technology, Qingdao (China)

    2008-09-15

    Belt conveyor is one of the main transport equipment in coal mine and the driving drum is its key part. With the method of bionic design, the mushroom morphological structure is applied to the design of covering-layer structure of driving drum surface of belt conveyor. Superelastic rubber with large deformation is adopted as the covering-layer material. Nonlinear constitutive model of rubber, which is of superelasticity and large deformation, is established. The stress states and deformation principles of driving drums including both bionic covering-layer and common covering-layer are obtained by static intensity analysis with Finite Element Analysis (FEA) software ANSYS. The values of the stress and strain on the driving drum surface are gotten and the dangerous area is determined. FEA results show that the superelastic convexity surface structure can enlarge the contact area between the driving drum and viscoelastic belt. The results also show that in comparison with common driving drum, the bionic surface driving drum can not only increase the friction coefficient between drum and belt but also prolong its service life.

  1. Synthesis and Structural Determination of Temocapril Sulfoxide Hydrochlorides

    International Nuclear Information System (INIS)

    Seong, Seok Bong; Moon, Jong Taik; Kim, Jung Ahn; Choo, Dong Joon; Lee, Jae Yeol

    2012-01-01

    Impurity (or related substance) control in pharmaceutical products is a primary goal of drug development. Stringent international regulatory requirements have been in place for several years as outlined in the International Conference on Harmonization (ICH) Guidelines Q3A (R), Q3B (R) and Q3C. According to ICH guidelines, impurities associated with the manufacture of a drug substance, also known as an active pharmaceutical ingredient (API), are classified into the following categories: (1) organic impurities (process and drug-related); (2) inorganic impurities (3) residual solvents. Many potential impurities result from the API manufacturing process including starting materials, isomers, intermediates, reagents, solvents, catalysts and reaction by-products. These potential impurities should be investigated to determine process control mechanisms for their removal and the need for specification controls at appropriate points in the process. The suggested structures of the impurities can be synthesized and will provide the final evidence for their structures, previously determined by spectroscopic methods. Therefore it is essential to know the structure of these impurities in the bulk drug in order to alter the reaction condition and to reduce the quantity of impurity to an acceptable level. Isolation, identification and quantification of impurities help the pharmaceutical company to obtain a pure substance with less toxicity and safety in drug therapy

  2. Assessment of carotid plaque vulnerability using structural and geometrical determinants

    International Nuclear Information System (INIS)

    Li, Z.Y.; Tang, T.; U-King-Im, J.; Graves, M.; Gillard, J.H.; Sutcliffe, M.

    2008-01-01

    Because many acute cerebral ischemic events are caused by rupture of vulnerable carotid atheroma and subsequent thrombosis, the present study used both idealized and patient-specific carotid atheromatous plaque models to evaluate the effect of structural determinants on stress distributions within plaque. Using a finite element method, structural analysis was performed using models derived from in vivo high-resolution magnetic resonance imaging (MRI) of carotid atheroma in 40 non-consecutive patients (20 symptomatic, 20 asymptomatic). Plaque components were modeled as hyper-elastic materials. The effects of varying fibrous cap thickness, lipid core size and lumen curvature on plaque stress distributions were examined. Lumen curvature and fibrous cap thickness were found to be major determinants of plaque stress. The size of the lipid core did not alter plaque stress significantly when the fibrous cap was relatively thick. The correlation between plaque stress and lumen curvature was significant for both symptomatic (p=0.01; correlation coefficient: 0.689) and asymptomatic patients (p=0.01; correlation coefficient: 0.862). Lumen curvature in plaques of symptomatic patients was significantly larger than those of asymptomatic patients (1.50±1.0 mm -1 vs 1.25±0.75 mm -1 ; p=0.01). Specific plaque morphology (large lumen curvature and thin fibrous cap) is closely related to plaque vulnerability. Structural analysis using high-resolution MRI of carotid atheroma may help in detecting vulnerable atheromatous plaque and aid the risk stratification of patients with carotid disease. (author)

  3. X-ray structure determination and deuteration of nattokinase.

    Science.gov (United States)

    Yanagisawa, Yasuhide; Chatake, Toshiyuki; Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki; Kawaguchi, Akio; Chiba-Kamosida, Kaori; Ogawa, Megumi; Adachi, Tatsumi; Morimoto, Yukio

    2013-11-01

    Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D2O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D2O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis.

  4. Trajectory resolved analysis of LEIS energy spectra: Neutralization and surface structure

    International Nuclear Information System (INIS)

    Beikler, Robert; Taglauer, Edmund

    2001-01-01

    For a quantitative evaluation of low-energy ion scattering (LEIS) data with respect to surface composition and structure a detailed analysis of the energy spectra is required. This includes the identification of multiple scattering processes and the determination of ion survival probabilities. We analyzed scattered ion energy spectra by using the computer code MARLOWE for which we developed a new analysis routine that allows to record energy distributions in dependence of the number of projectile-target atom collisions, in dependence of the distance of closest approach, or in dependence of the scattering crystalline layer. This procedure also permits the determination of ion survival probabilities by applying simple collision-dependent neutralization models. Experimental energy spectra for various projectile (He + , Ne + , Na + ) and target (transition metals, oxides) combinations are well reproduced and quantitative results for ion survival probabilities are obtained. These are largely in agreement with results obtained for bimetallic crystal surfaces obtained in a different way. Such MARLOWE calculations are also useful for the identification of structure relevant processes. This is shown exemplarily for the reconstructed Au(1 1 0) surface including a possibility to determine the (1x2)→(1x1) transition temperature

  5. Gaussian process based intelligent sampling for measuring nano-structure surfaces

    Science.gov (United States)

    Sun, L. J.; Ren, M. J.; Yin, Y. H.

    2016-09-01

    Nanotechnology is the science and engineering that manipulate matters at nano scale, which can be used to create many new materials and devices with a vast range of applications. As the nanotech product increasingly enters the commercial marketplace, nanometrology becomes a stringent and enabling technology for the manipulation and the quality control of the nanotechnology. However, many measuring instruments, for instance scanning probe microscopy, are limited to relatively small area of hundreds of micrometers with very low efficiency. Therefore some intelligent sampling strategies should be required to improve the scanning efficiency for measuring large area. This paper presents a Gaussian process based intelligent sampling method to address this problem. The method makes use of Gaussian process based Bayesian regression as a mathematical foundation to represent the surface geometry, and the posterior estimation of Gaussian process is computed by combining the prior probability distribution with the maximum likelihood function. Then each sampling point is adaptively selected by determining the position which is the most likely outside of the required tolerance zone among the candidates and then inserted to update the model iteratively. Both simulationson the nominal surface and manufactured surface have been conducted on nano-structure surfaces to verify the validity of the proposed method. The results imply that the proposed method significantly improves the measurement efficiency in measuring large area structured surfaces.

  6. Atomic Resolution Structures of Human Bufaviruses Determined by Cryo-Electron Microscopy

    Directory of Open Access Journals (Sweden)

    Maria Ilyas

    2018-01-01

    Full Text Available Bufavirus strain 1 (BuV1, a member of the Protoparvovirus genus of the Parvoviridae, was first isolated from fecal samples of children with acute diarrhea in Burkina Faso. Since this initial discovery, BuVs have been isolated in several countries, including Finland, the Netherlands, and Bhutan, in pediatric patients exhibiting similar symptoms. Towards their characterization, the structures of virus-like particles of BuV1, BuV2, and BuV3, the current known genotypes, have been determined by cryo-electron microscopy and image reconstruction to 2.84, 3.79, and 3.25 Å, respectively. The BuVs, 65–73% identical in amino acid sequence, conserve the major viral protein, VP2, structure and general capsid surface features of parvoviruses. These include a core β-barrel (βB-βI, α-helix A, and large surface loops inserted between these elements in VP2. The capsid contains depressions at the icosahedral 2-fold and around the 5-fold axes, and has three separated protrusions surrounding the 3-fold axes. Structure comparison among the BuVs and to available parvovirus structures revealed capsid surface variations and capsid 3-fold protrusions that depart from the single pinwheel arrangement of the animal protoparvoviruses. These structures provide a platform to begin the molecular characterization of these potentially pathogenic viruses.

  7. Superhydrophobic hierarchically structured surfaces in biology: evolution, structural principles and biomimetic applications.

    Science.gov (United States)

    Barthlott, W; Mail, M; Neinhuis, C

    2016-08-06

    A comprehensive survey of the construction principles and occurrences of superhydrophobic surfaces in plants, animals and other organisms is provided and is based on our own scanning electron microscopic examinations of almost 20 000 different species and the existing literature. Properties such as self-cleaning (lotus effect), fluid drag reduction (Salvinia effect) and the introduction of new functions (air layers as sensory systems) are described and biomimetic applications are discussed: self-cleaning is established, drag reduction becomes increasingly important, and novel air-retaining grid technology is introduced. Surprisingly, no evidence for lasting superhydrophobicity in non-biological surfaces exists (except technical materials). Phylogenetic trees indicate that superhydrophobicity evolved as a consequence of the conquest of land about 450 million years ago and may be a key innovation in the evolution of terrestrial life. The approximate 10 million extant species exhibit a stunning diversity of materials and structures, many of which are formed by self-assembly, and are solely based on a limited number of molecules. A short historical survey shows that bionics (today often called biomimetics) dates back more than 100 years. Statistical data illustrate that the interest in biomimetic surfaces is much younger still. Superhydrophobicity caught the attention of scientists only after the extreme superhydrophobicity of lotus leaves was published in 1997. Regrettably, parabionic products play an increasing role in marketing.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'. © 2016 The Author(s).

  8. Superhydrophobic hierarchically structured surfaces in biology: evolution, structural principles and biomimetic applications

    Science.gov (United States)

    Mail, M.; Neinhuis, C.

    2016-01-01

    A comprehensive survey of the construction principles and occurrences of superhydrophobic surfaces in plants, animals and other organisms is provided and is based on our own scanning electron microscopic examinations of almost 20 000 different species and the existing literature. Properties such as self-cleaning (lotus effect), fluid drag reduction (Salvinia effect) and the introduction of new functions (air layers as sensory systems) are described and biomimetic applications are discussed: self-cleaning is established, drag reduction becomes increasingly important, and novel air-retaining grid technology is introduced. Surprisingly, no evidence for lasting superhydrophobicity in non-biological surfaces exists (except technical materials). Phylogenetic trees indicate that superhydrophobicity evolved as a consequence of the conquest of land about 450 million years ago and may be a key innovation in the evolution of terrestrial life. The approximate 10 million extant species exhibit a stunning diversity of materials and structures, many of which are formed by self-assembly, and are solely based on a limited number of molecules. A short historical survey shows that bionics (today often called biomimetics) dates back more than 100 years. Statistical data illustrate that the interest in biomimetic surfaces is much younger still. Superhydrophobicity caught the attention of scientists only after the extreme superhydrophobicity of lotus leaves was published in 1997. Regrettably, parabionic products play an increasing role in marketing. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’. PMID:27354736

  9. Atomic structure of diamond {111} surfaces etched in oxygen water vapor

    International Nuclear Information System (INIS)

    Theije, F.K. de; Reedijk, M.F.; Arsic, J.; Enckevort, W.J.P. van; Vlieg, E.

    2001-01-01

    The atomic structure of the {111} diamond face after oxygen-water-vapor etching is determined using x-ray scattering. We find that a single dangling bond diamond {111} surface model, terminated by a full monolayer of -OH fits our data best. To explain the measurements it is necessary to add an ordered water layer on top of the -OH terminated surface. The vertical contraction of the surface cell and the distance between the oxygen atoms are generally in agreement with model calculations and results on similar systems. The OH termination is likely to be present during etching as well. This model experimentally confirms the atomic-scale mechanism we proposed previously for this etching system

  10. Self-assembly of InAs and Si/Ge quantum dots on structured surfaces

    International Nuclear Information System (INIS)

    Patella, F; Sgarlata, A; Arciprete, F; Nufris, S; Szkutnik, P D; Placidi, E; Fanfoni, M; Motta, N; Balzarotti, A

    2004-01-01

    We discuss the self-aggregation process of InAs and Si-Ge quantum dots (QDs) on natural and patterned GaAs(001) and Si(001) and Si(111) surfaces, with reference to our recent studies with scanning tunnelling and atomic force microscopy and current experimental and theoretical works. Various methods for obtaining naturally structured surfaces are briefly surveyed, as the patterning formed by the surface instability and by the strain in mismatched heteroepitaxy, and the latest methods of pre-patterning and growth at selected sites are discussed. Basic topics are also addressed that determine the final morphology of QDs, such as the wetting layer formation, the elastic strain field and the two-dimensional to three-dimensional phase transition

  11. Determination of Optimum Viewing Angles for the Angular Normalization of Land Surface Temperature over Vegetated Surface

    Directory of Open Access Journals (Sweden)

    Huazhong Ren

    2015-03-01

    Full Text Available Multi-angular observation of land surface thermal radiation is considered to be a promising method of performing the angular normalization of land surface temperature (LST retrieved from remote sensing data. This paper focuses on an investigation of the minimum requirements of viewing angles to perform such normalizations on LST. The normally kernel-driven bi-directional reflectance distribution function (BRDF is first extended to the thermal infrared (TIR domain as TIR-BRDF model, and its uncertainty is shown to be less than 0.3 K when used to fit the hemispheric directional thermal radiation. A local optimum three-angle combination is found and verified using the TIR-BRDF model based on two patterns: the single-point pattern and the linear-array pattern. The TIR-BRDF is applied to an airborne multi-angular dataset to retrieve LST at nadir (Te-nadir from different viewing directions, and the results show that this model can obtain reliable Te-nadir from 3 to 4 directional observations with large angle intervals, thus corresponding to large temperature angular variations. The Te-nadir is generally larger than temperature of the slant direction, with a difference of approximately 0.5~2.0 K for vegetated pixels and up to several Kelvins for non-vegetated pixels. The findings of this paper will facilitate the future development of multi-angular thermal infrared sensors.

  12. Leveraging structure determination with fragment screening for infectious disease drug targets: MECP synthase from Burkholderia pseudomallei

    Energy Technology Data Exchange (ETDEWEB)

    Begley, Darren W.; Hartley, Robert C.; Davies, Douglas R.; Edwards, Thomas E.; Leonard, Jess T.; Abendroth, Jan; Burris, Courtney A.; Bhandari, Janhavi; Myler, Peter J.; Staker, Bart L.; Stewart, Lance J. (UWASH); (Emerald)

    2011-09-28

    As part of the Seattle Structural Genomics Center for Infectious Disease, we seek to enhance structural genomics with ligand-bound structure data which can serve as a blueprint for structure-based drug design. We have adapted fragment-based screening methods to our structural genomics pipeline to generate multiple ligand-bound structures of high priority drug targets from pathogenic organisms. In this study, we report fragment screening methods and structure determination results for 2C-methyl-D-erythritol-2,4-cyclo-diphosphate (MECP) synthase from Burkholderia pseudomallei, the gram-negative bacterium which causes melioidosis. Screening by nuclear magnetic resonance spectroscopy as well as crystal soaking followed by X-ray diffraction led to the identification of several small molecules which bind this enzyme in a critical metabolic pathway. A series of complex structures obtained with screening hits reveal distinct binding pockets and a range of small molecules which form complexes with the target. Additional soaks with these compounds further demonstrate a subset of fragments to only bind the protein when present in specific combinations. This ensemble of fragment-bound complexes illuminates several characteristics of MECP synthase, including a previously unknown binding surface external to the catalytic active site. These ligand-bound structures now serve to guide medicinal chemists and structural biologists in rational design of novel inhibitors for this enzyme.

  13. Examination of the effect of blowing on the near-surface flow structure over a dimpled surface

    Science.gov (United States)

    Borchetta, C. G.; Martin, A.; Bailey, S. C. C.

    2018-03-01

    The near surface flow over a dimpled surface with flow injection through it was documented using time-resolved particle image velocimetry. The instantaneous flow structure, time-averaged statistics, and results from snapshot proper orthogonal decomposition were used to examine the coherent structures forming near the dimpled surface. In particular, the modifications made to the flow structures by the addition of flow injection through the surface were studied. It was observed that without flow injection, inclined flow structures with alternating vorticity from neighboring dimples are generated by the dimples and advect downstream. This behavior is coupled with fluid becoming entrained inside the dimples, recirculating and ejecting away from the surface. When flow injection was introduced through the surface, the flow structures became more disorganized, but some of the features of the semi-periodic structures observed without flow injection were preserved. The structures with flow injection appear in multiple wall-normal layers, formed from vortical structures shed from upstream dimples, with a corresponding increase in the size of the advecting structures. As a result of the more complex flow field observed with flow injection, there was an increase in turbulent kinetic energy and Reynolds shear stress, with the Reynolds shear stress representing an increase in vertical transport of momentum by sweeping and ejecting motions that were not present without flow injection.

  14. A use of Ramachandran potentials in protein solution structure determinations

    International Nuclear Information System (INIS)

    Bertini, Ivano; Cavallaro, Gabriele; Luchinat, Claudio; Poli, Irene

    2003-01-01

    A strategy is developed to use database-derived φ-ψ constraints during simulated annealing procedures for protein solution structure determination in order to improve the Ramachandran plot statistics, while maintaining the agreement with the experimental constraints as the sole criterion for the selection of the family. The procedure, fully automated, consists of two consecutive simulated annealing runs. In the first run, the database-derived φ-ψ constraints are enforced for all aminoacids (but prolines and glycines). A family of structures is then selected on the ground of the lowest violations of the experimental constraints only, and the φ-ψ values for each residue are examined. In the second and final run, the database-derived φ-ψ constraints are enforced only for those residues which in the first run have ended in one and the same favored φ-ψ region. For residues which are either spread over different favored regions or concentrated in disallowed regions, the constraints are not enforced. The final family is then selected, after the second run, again only based on the agreement with the experimental constraints. This automated approach was implemented in DYANA and was tested on as many as 12 proteins, including some containing paramagnetic metals, whose structures had been previously solved in our laboratory. The quality of the structures, and of Ramachandran plot statistics in particular, was notably improved while preserving the agreement with the experimental constraints

  15. Overview on the Surface Functionalization Mechanism and Determination of Surface Functional Groups of Plasma Treated Carbon Nanotubes.

    Science.gov (United States)

    Saka, Cafer

    2018-01-02

    The use of carbon materials for many applications is due to the unique diversity of structures and properties ranging from chemical bonds between the carbon atoms of the materials to nanostructures, crystallite alignment, and microstructures. Carbon nanotubes and other nanoscale carbonaceous materials draw much attention due to their physical and chemical properties, such as high strength, high resistance to corrosion, electrical and thermal conductivity, stability and a qualified adsorbent. Carbon-based nanomaterials, which have a relatively large specific area and layered structure, can be used as an adsorbent for efficient removal of organic and inorganic contaminants. However, one of the biggest obstacles to the development of carbon-based nanomaterials adsorbents is insolubility and the lack of functional groups on the surface. There are several approaches to introduce functional groups on carbon nanotubes. One of these approaches, plasma applications, now has an important place in the creation of surface functional groups as a flexible, fast, and environmentally friendly method. This review focuses on recent information concerning the surface functionalization and modification of plasma treated carbon nanotube. This review considers the surface properties, advantages, and disadvantages of plasma-applied carbon nanotubes. It also examines the reaction mechanisms involved in the functional groups on the surface.

  16. What determines the structures of native folds of proteins?

    International Nuclear Information System (INIS)

    Trovato, Antonio; Hoang, Trinh X; Banavar, Jayanth R; Maritan, Amos; Seno, Flavio

    2005-01-01

    We review a simple physical model (Hoang et al 2004 Proc. Natl Acad. Sci. USA 101 7960, Banavar et al 2004 Phys. Rev. E at press) which captures the essential physico-chemical ingredients that determine protein structure, such as the inherent anisotropy of a chain molecule, the geometrical and energetic constraints placed by hydrogen bonds, sterics, and hydrophobicity. Within this framework, marginally compact conformations resembling the native state folds of proteins emerge as competing minima in the free energy landscape. Here we demonstrate that a hydrophobic-polar (HP) sequence composed of regularly repeated patterns has as its ground state a β-helical structure remarkably similar to a known architecture in the Protein Data Bank

  17. Generalized molybdenum oxide surface chemical state XPS determination via informed amorphous sample model

    Energy Technology Data Exchange (ETDEWEB)

    Baltrusaitis, Jonas, E-mail: job314@lehigh.edu [Department of Chemical Engineering, Lehigh University, B336 Iacocca Hall, 111 Research Drive, Bethlehem, PA 18015 (United States); PhotoCatalytic Synthesis group, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Meander 229, P.O. Box 217, 7500 AE Enschede (Netherlands); Mendoza-Sanchez, Beatriz [CRANN, Chemistry School, Trinity College Dublin, Dublin (Ireland); Fernandez, Vincent [Institut des Matériaux Jean Rouxel, 2 rue de la Houssinière, BP 32229, F-44322 Nantes Cedex 3 (France); Veenstra, Rick [PhotoCatalytic Synthesis group, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Meander 229, P.O. Box 217, 7500 AE Enschede (Netherlands); Dukstiene, Nijole [Department of Physical and Inorganic Chemistry, Kaunas University of Technology, Radvilenu pl. 19, LT-50254 Kaunas (Lithuania); Roberts, Adam [Kratos Analytical Ltd, Trafford Wharf Road, Wharfside, Manchester, M17 1GP (United Kingdom); Fairley, Neal [Casa Software Ltd, Bay House, 5 Grosvenor Terrace, Teignmouth, Devon TQ14 8NE (United Kingdom)

    2015-01-30

    Highlights: • We analyzed and modeled spectral envelopes of complex molybdenum oxides. • Molybdenum oxide films of varying valence and crystallinity were synthesized. • MoO{sub 3} and MoO{sub 2} line shapes from experimental data were created. • Informed amorphous sample model (IASM) developed. • Amorphous molybdenum oxide XPS envelopes were interpreted. - Abstract: Accurate elemental oxidation state determination for the outer surface of a complex material is of crucial importance in many science and engineering disciplines, including chemistry, fundamental and applied surface science, catalysis, semiconductors and many others. X-ray photoelectron spectroscopy (XPS) is the primary tool used for this purpose. The spectral data obtained, however, is often very complex and can be subject to incorrect interpretation. Unlike traditional XPS spectra fitting procedures using purely synthetic spectral components, here we develop and present an XPS data processing method based on vector analysis that allows creating XPS spectral components by incorporating key information, obtained experimentally. XPS spectral data, obtained from series of molybdenum oxide samples with varying oxidation states and degree of crystallinity, were processed using this method and the corresponding oxidation states present, as well as their relative distribution was elucidated. It was shown that monitoring the evolution of the chemistry and crystal structure of a molybdenum oxide sample due to an invasive X-ray probe could be used to infer solutions to complex spectral envelopes.

  18. Purification and primary structure determination of human lysosomal dipeptidase.

    Science.gov (United States)

    Dolenc, Iztok; Mihelic, Marko

    2003-02-01

    The lysosomal metallopeptidase is an enzyme that acts preferentially on dipeptides with unsubstituted N- and C-termini. Its activity is highest in slightly acidic pH. Here we describe the isolation and characterization of lysosomal dipeptidase from human kidney. The isolated enzyme has the amino-terminal sequence DVAKAIINLAVY and is a homodimer with a molecular mass of 100 kDa. So far no amino acid sequence has been determined for this metallopeptidase. The complete primary structure as deduced from the nucleotide sequence revealed that the isolated dipeptidase is similar to blood plasma glutamate carboxypeptidase.

  19. Structure determination of spider silk from X-ray images

    Energy Technology Data Exchange (ETDEWEB)

    Ulrich, Stephan; Zippelius, Annette [Universitaet Goettingen, Institut fuer Theoretische Physik (Germany); Meling, Martin [Max-Planck-Institut fuer biophysikalische Chemie, Goettingen (Germany); Glisovic, Anja; Salditt, Tim [Universitaet Goettingen, Institut fuer Roentgenphysik (Germany)

    2008-07-01

    Spider silk consists of interconnected crystallites, which are typically aligned along the fiber axis. We present a method to systematically determine the structure of these crystallites. Hereby we introduce a model that calculates the scattering function G(q) which is fitted to the measured X-ray image (silk from nephila clavipes). With it, the crystallites' size, the constitution and dimensions of their unit cell, as well as their tilt with respect to the fiber axis is identified, and furthermore the effect of coherent scattering from different crystallites is investigated. The shown methods and the presented model can easily be generalized to a wide class of composite materials.

  20. Upper Mantle Structure beneath Afar: inferences from surface waves.

    Science.gov (United States)

    Sicilia, D.; Montagner, J.; Debayle, E.; Lepine, J.; Leveque, J.; Cara, M.; Ataley, A.; Sholan, J.

    2001-12-01

    The Afar hotspot is related to one of the most important plume from a geodynamic point of view. It has been advocated to be the surface expression of the South-West African Superswell. Below the lithosphere, the Afar plume might feed other hotspots in central Africa (Hadiouche et al., 1989; Ebinger & Sleep, 1998). The processes of interaction between crust, lithosphere and plume are not well understood. In order to gain insight into the scientific issue, we have performed a surface-wave tomography covering the Horn of Africa. A data set of 1404 paths for Rayleigh waves and 473 paths for Love waves was selected in the period range 45-200s. They were collected from the permanent IRIS and GEOSCOPE networks and from the PASSCAL experiment, in Tanzania and Saudi Arabia. Other data come from the broadband stations deployed in Ethiopia and Yemen in the framework of the French INSU program ``Horn of Africa''. The results presented here come from a path average phase velocities obtained with a method based on a least-squares minimization (Beucler et al., 2000). The local phase velocity distribution and the azimuthal anisotropy were simultaneously retrieved by using the tomographic technique of Montagner (1986). A correction of the data is applied according to the crustal structure of the 3SMAC model (Nataf & Ricard, 1996). We find low velocities down to 200 km depth beneath the Red Sea, the Gulf of Aden, Afars, the Ethiopian Plateau and southern Arabia. High velocities are present in the eastern Arabia and the Tanzania Craton. The anisotropy beneath Afar seems to be complex, but enables to map the flow pattern at the interface lithosphere-asthenosphere. The results presented here are complementary to those obtained by Debayle et al. (2001) at upper-mantle transition zone depths using waveform inversion of higher Rayle igh modes.

  1. Computer-aided study of key factors determining high mechanical properties of nanostructured surface layers in metal-ceramic composites

    Science.gov (United States)

    Konovalenko, Igor S.; Shilko, Evgeny V.; Ovcharenko, Vladimir E.; Psakhie, Sergey G.

    2017-12-01

    The paper presents the movable cellular automaton method. It is based on numerical models of surface layers of the metal-ceramic composite NiCr-TiC modified under electron beam irradiation in inert gas plasmas. The models take into account different geometric, concentration and mechanical parameters of ceramic and metallic components. The authors study the contributions of key structural factors in mechanical properties of surface layers and determine the ranges of their variations by providing the optimum balance of strength, strain hardening and fracture toughness.

  2. Surface modification induced by UV nanosecond Nd:YVO4 laser structuring on biometals

    Science.gov (United States)

    Fiorucci, M. Paula; López, Ana J.; Ramil, Alberto

    2014-08-01

    Laser surface texturing is a promising tool for improving metallic biomaterials performance in dental and orthopedic bone-replacing applications. Laser ablation modifies the topography of bulk material and might alter surface properties that govern the interactions with the surrounding tissue. This paper presents a preliminary evaluation of surface modifications in two biometals, stainless steel 316L and titanium alloy Ti6Al4V by UV nanosecond Nd:YVO4. Scanning electron microscopy of the surface textured by parallel micro-grooves reveals a thin layer of remelted material along the grooves topography. Furthermore, X-ray diffraction allowed us to appreciate a grain refinement of original crystal structure and consequently induced residual strain. Changes in the surface chemistry were determined by means of X-ray photoelectron spectroscopy; in this sense, generalized surface oxidation was observed and characterization of the oxides and other compounds such hydroxyl groups was reported. In case of titanium alloy, oxide layer mainly composed by TiO2 which is a highly biocompatible compound was identified. Furthermore, laser treatment produces an increase in oxide thickness that could improve the corrosion behavior of the metal. Otherwise, laser treatment led to the formation of secondary phases which might be detrimental to physical and biocompatibility properties of the material.

  3. Evaluation of the surface structure of composite restorations in light of own pilot research

    Directory of Open Access Journals (Sweden)

    Chalas Renata

    2016-09-01

    Full Text Available Research on the dental restorative materials employed in remedying dental cavities has been conducted on many levels and areas, both with application of clinical and laboratory methods. One of the elements that determines whether the restoration may be degraded is the condition of its surface. The aim of the study was to assess the texture surface of composite restorations using a non-contact method of teeth models scanning. In this work, ten medium size cavities on the occlusal surfaces of molars in adult patients were prepared and restored with resin composite. Before undertaking the procedure and after the finishing and polishing of the restorations, impressions were taken and sent into the laboratory so as to prepare plaster casts. Every cast was then scanned utilizing the non-contact 3D surface measurement instrument so as to assess the texture surface of the restoration. The resulting three dimensional analyses of post-restoration models showed the correct marginal adaptation of resin composite dental material to the hard tooth structures and its smooth filling occlusal surface. Additional comparison of scans done before and after restoring the cavities allowed the calculating of differences in volume, mean and maximum heights. The applied method of analysis is thought to be helpful in the detailed evaluation of restoration dental material texture. Moreover, the enabled possibility of continuous observation is expedient for assessing the usefulness of the method in standard dental practice.

  4. Determination of an Optimal Control Strategy for a Generic Surface Vehicle

    Science.gov (United States)

    2014-06-18

    TERMS Autonomous Vehicles Boundary Value Problem Dynamic Programming Surface Vehicles Optimal Control Path Planning 16...to follow prescribed motion trajectories. In particular, for autonomous vehicles , this motion trajectory is given by the determination of the

  5. Quantifying watershed surface depression storage: determination and application in a hydrologic model

    Science.gov (United States)

    Joseph K. O. Amoah; Devendra M. Amatya; Soronnadi. Nnaji

    2012-01-01

    Hydrologic models often require correct estimates of surface macro-depressional storage to accurately simulate rainfall–runoff processes. Traditionally, depression storage is determined through model calibration or lumped with soil storage components or on an ad hoc basis. This paper investigates a holistic approach for estimating surface depressional storage capacity...

  6. Determination of optimum "multi-channel surface wave method" field parameters.

    Science.gov (United States)

    2012-12-01

    Multi-channel surface wave methods (especially the multi-channel analyses of surface wave method; MASW) are routinely used to : determine the shear-wave velocity of the subsurface to depths of 100 feet for site classification purposes. Users are awar...

  7. Whole genome expression profiling using DNA microarray for determining biocompatibility of polymeric surfaces

    DEFF Research Database (Denmark)

    Stangegaard, Michael; Wang, Zhenyu; Kutter, Jörg Peter

    2006-01-01

    There is an ever increasing need to find surfaces that are biocompatible for applications like medical implants and microfluidics-based cell culture systems. The biocompatibility of five different surfaces with different hydrophobicity was determined using gene expression profiling as well as more...

  8. Structural re-alignment in an immunologic surface region of ricin A chain

    Energy Technology Data Exchange (ETDEWEB)

    Zemla, A T; Zhou, C E

    2007-07-24

    We compared structure alignments generated by several protein structure comparison programs to determine whether existing methods would satisfactorily align residues at a highly conserved position within an immunogenic loop in ribosome inactivating proteins (RIPs). Using default settings, structure alignments generated by several programs (CE, DaliLite, FATCAT, LGA, MAMMOTH, MATRAS, SHEBA, SSM) failed to align the respective conserved residues, although LGA reported correct residue-residue (R-R) correspondences when the beta-carbon (Cb) position was used as the point of reference in the alignment calculations. Further tests using variable points of reference indicated that points distal from the beta carbon along a vector connecting the alpha and beta carbons yielded rigid structural alignments in which residues known to be highly conserved in RIPs were reported as corresponding residues in structural comparisons between ricin A chain, abrin-A, and other RIPs. Results suggest that approaches to structure alignment employing alternate point representations corresponding to side chain position may yield structure alignments that are more consistent with observed conservation of functional surface residues than do standard alignment programs, which apply uniform criteria for alignment (i.e., alpha carbon (Ca) as point of reference) along the entirety of the peptide chain. We present the results of tests that suggest the utility of allowing user-specified points of reference in generating alternate structural alignments, and we present a web server for automatically generating such alignments.

  9. Structural and molecular insights into novel surface-exposed mucus adhesins from Lactobacillus reuteri human strains.

    Science.gov (United States)

    Etzold, Sabrina; MacKenzie, Donald A; Jeffers, Faye; Walshaw, John; Roos, Stefan; Hemmings, Andrew M; Juge, Nathalie

    2014-05-01

    The mucus layer covering the gastrointestinal tract is the first point of contact of the intestinal microbiota with the host. Cell surface macromolecules are critical for adherence of commensal bacteria to mucus but structural information is scarce. Here we report the first molecular and structural characterization of a novel cell-surface protein, Lar_0958 from Lactobacillus reuteri JCM 1112(T) , mediating adhesion of L. reuteri human strains to mucus. Lar_0958 is a modular protein of 133 kDa containing six repeat domains, an N-terminal signal sequence and a C-terminal anchoring motif (LPXTG). Lar_0958 homologues are expressed on the cell-surface of L. reuteri human strains, as shown by flow-cytometry and immunogold microscopy. Adhesion of human L. reuteri strains to mucus in vitro was significantly reduced in the presence of an anti-Lar_0958 antibody and Lar_0958 contribution to adhesion was further confirmed using a L. reuteri ATCC PTA 6475 lar_0958 KO mutant (6475-KO). The X-ray crystal structure of a single Lar_0958 repeat, determined at 1.5 Å resolution, revealed a divergent immunoglobulin (Ig)-like β-sandwich fold, sharing structural homology with the Ig-like inter-repeat domain of internalins of the food borne pathogen Listeria monocytogenes. These findings provide unique structural insights into cell-surface protein repeats involved in adhesion of Gram-positive bacteria to the intestine. © 2014 John Wiley & Sons Ltd.

  10. Osteoblast growth behavior on porous-structure titanium surface

    International Nuclear Information System (INIS)

    Tian Yuan; Ding Siyang; Peng Hui; Lu Shanming; Wang Guoping; Xia Lu; Wang Peizhi

    2012-01-01

    Highlights: ► Micro-arc oxidation technology formed a porous feature on titanium surface. ► This porous surface accelerated adhesion, proliferation and differentiation compared with smooth surface. ► Osteogenesis-related proteins and genes were up regulated by this porous surface. ► It is anticipated that micro-arc oxidation surface could enhance osteoblastic activity and bone regeneration. - Abstract: A bioavailable surface generated by nano-technology could accelerate implant osteointegration, reduce healing time and enable implants to bear early loading. In this study, a nano-porous surface of titanium wafers was modified using micro-arc oxidation technique; surface of smooth titanium was used as control group. Surface characteristic was evaluated by investigating morphology, roughness and hydrophilicity of titanium wafers. In vitro studies, osteoblastic adhesion, proliferation and ALP activity, as well as gene and protein expressions relative to mineralization were assayed. Our results showed that a crater-liked nano-porous surface with greater roughness and better hydrophilicity were fabricated by micro-arc oxidation. It was further indicated that nano-porous surface could enhance adhesion, proliferation and ALP activity of osteoblasts compared with smooth surfaces. In addition, gene and protein expression of collagen-I, osteocalcin and osteopontin were also obviously increased. In summary, micro-arc oxidized techniques could form an irregular nano-porous morphology on implant surface which is favorable to improve osteoblastic function and prospected to be a potent modification of dental implant.

  11. The New Horizons Radio Science Experiment: Expected Performance in Measurements of Pluto's Atmospheric Structure, Surface Pressure, and Surface Temperature

    Science.gov (United States)

    Hinson, D. P.; Linscott, I.; Woods, W. W.; Tyler, G. L.; Bird, M. K.; Paetzold, M.; Strobel, D. F.

    2014-12-01

    The New Horizons (NH) payload includes a Radio Science Experiment (REX) for investigating key characteristics of Pluto and Charon during the upcoming flyby in July 2015. REX flight equipment augments the NH radio transceiver used for spacecraft communications and tracking. The REX hardware implementation requires 1.6 W and 160 g. This presentation will focus on the final design and the predicted performance of two high-priority observations. First, REX will receive signals from a pair of 70-m antennas on Earth - each transmitting 20 kW at 4.2-cm wavelength - during a diametric radio occultation by Pluto. The data recorded by REX will reveal the surface pressure, the temperature structure of the lower atmosphere, and the surface radius. Second, REX will measure the thermal emission from Pluto at 4.2-cm wavelength during two linear scans across the disk at close range when both the dayside and the nightside are visible, allowing the surface temperature and its spatial variations to be determined. Both scans extend from limb to limb with a resolution of about 10 pixels; one bisects Pluto whereas the second crosses the winter pole. We will illustrate the capabilities of REX by reviewing the method of analysis and the precision achieved in a lunar occultation observed by New Horizons in May 2011. Re-analysis of radio occultation measurements by Voyager 2 at Triton is also under way. More generally, REX objectives include a radio occultation search for Pluto's ionosphere; examination of Charon through both radio occultation and radiometry; a search for a radar echo from Pluto's surface; and improved knowledge of the Pluto system mass and the Pluto-Charon mass ratio from a combination of two-way and one-way Doppler frequency measurements.

  12. Study of the Adsorption of Atoms and Molecules on Silicon Surfaces: Crystallographics and Electronic Structure

    International Nuclear Information System (INIS)

    Bengio, Silvina

    2003-01-01

    This thesis work has been concerned with adsorption properties of silicon surfaces.The atomic and electronic structure of molecules and atoms adsorbed on Si has been investigated by means of photoemission experiments combined with synchrotron radiation.The quantitative atomic structure determination was held applying the photoelectron diffraction technique.This technique is sensible to the local structure of a reference atomic specie and has elemental and chemical-state specificity.This approach has been applied to three quite different systems with different degrees of complexity, Sb/Si(111) √3x √3R30 0 , H 2 O/Si(100)2x1 and NH 3 /Si(111)7x7.Our results show that Sb which forms a ( √3√3)R30 0 phase produces a bulklike-terminated Si(111)1x1 substrate free of stacking faults.Regarding the atomic structure of its interface, this study strongly favours the T4-site milkstool model over the H3 one.An important aspect regarding the H 2 O/Si(100)(2x1) system was establishing the limits of precision with which one can determine not only the location of the adsorbed hydroxyl (OH) species, but also the extent to which this adsorption modifes the asymmetric dimers of the clean surface to which it is bonded.On the Si(111)(7x7) surface the problem is particularly complex because there are several different potentially active sites for NH3 adsorption and fragmentation.The application of the PhD method, however, has shown that the majority of the N atoms are on so-called 'rest atom' sites when deposited at RT.This is consistent with the N in the NH2 chemical state.This investigation represents the first quantitative structural study of any molecular adsorbate on the complex Si(111)(7x7) surface.This atomic structures determination shows the PhD is a powerful tool for the atomic structure determination.The molecular systems interacting with the active sites of the substrate fragments producing a short-range order surface.This long-range disorder is produced by the

  13. Determining the near-surface current profile from measurements of the wave dispersion relation

    Science.gov (United States)

    Smeltzer, Benjamin; Maxwell, Peter; Aesøy, Eirik; Ellingsen, Simen

    2017-11-01

    The current-induced Doppler shifts of waves can yield information about the background mean flow, providing an attractive method of inferring the current profile in the upper layer of the ocean. We present measurements of waves propagating on shear currents in a laboratory water channel, as well as theoretical investigations of inversion techniques for determining the vertical current structure. Spatial and temporal measurements of the free surface profile obtained using a synthetic Schlieren method are analyzed to determine the wave dispersion relation and Doppler shifts as a function of wavelength. The vertical current profile can then be inferred from the Doppler shifts using an inversion algorithm. Most existing algorithms rely on a priori assumptions of the shape of the current profile, and developing a method that uses less stringent assumptions is a focus of this study, allowing for measurement of more general current profiles. The accuracy of current inversion algorithms are evaluated by comparison to measurements of the mean flow profile from particle image velocimetry (PIV), and a discussion of the sensitivity to errors in the Doppler shifts is presented.

  14. Electronic structure of the chromium dioxide (001) surface

    NARCIS (Netherlands)

    Leuken, H. van; Groot, R.A. de

    1995-01-01

    Local-density calculations on the CrO2 (001) surface are reported. The half-metallic character of the bulk is found to be maintained at the surface. Surface states of oxygen p character at the top of the valence band for the semiconducting spin direction are discussed.

  15. Atomic structure of the SnO2 (110) surface

    International Nuclear Information System (INIS)

    Godin, T.J.; LaFemina, J.P.

    1991-12-01

    Using a tight-binding, total-energy model, we examine atomic relaxations of the ideal stoichiometric and reduced tin oxide (11) surfaces. In both cases we find a nearly bond-length conserving rumple of the top layer, and a smaller counter-relaxation of the second layer. These calculations show no evidence of surface states in the band gap for either surface

  16. Electronic structure at metal-smiconductor surfaces and interfaces: effects of disorder

    International Nuclear Information System (INIS)

    Rodrigues, D.E.

    1988-01-01

    The main concern of this work is the study of the electronic structure at metal and semiconductor surfaces or interfaces, with special emphasis in the effects of disorder and local microstructure upon them. Various factors which determine this structure are presented and those of central importance are identified. A model that allows the efficient and exact calculation of the local density of states at disordered interfaces is described. This model is based on a tight-binding hamiltonian that has enough flexibility so as to allow an adequate description of real solids. The disorder is taken into account by including stochastic perturbations in the diagonal elements of the hamiltonian in a site orbital basis. These perturbations are taken at each layer from a lorentzian probability distribution. An exact expression for the calculation of the local density of states is derived and applied to a model surface built up from a type orbitals arranged in a simple cubic lattice. The effects of disorder on the local densities of states and on the existence of surface Tamm states are studied. The properties of the electronic states with this kind of model of disorder are considered. The self-consistent calculation of the electronic structure of the Si(111) - (1x1) surface is presented. The effects of disorder on the electronic properties such as the work function or the position of surface states within the gap are evaluated. The surface of the metallic compound NiSi 2 is also treated. The first self-consistent calculation of the electronic structure of its (111) surface is presented. The electronic structure of the Si/NiSi 2 (111) interfaces is calculated for the two types of junctions that can be grown experimentally. The origin of the difference between the Schottky barrier heights at both interfaces is discussed. The results are compared with available experimental data. The implications of this calculation on existing theories about the microscopic mechanism that causes

  17. Determination of surface tension coefficient of liquids by diffraction of light on capillary waves

    International Nuclear Information System (INIS)

    Nikolić, D; Nešić, Lj

    2012-01-01

    This paper describes a simple technique for determining the coefficient of the surface tension of liquids, based on laser light diffraction on capillary waves. Capillary waves of given frequency are created by an exciter needle acting on the surface of liquid and represent a reflective diffraction grating, the constant of which (the wavelength of capillary waves) can be determined based on a known incidence angle of light (grazing angle). We obtain the coefficient of the surface tension of liquids by applying the dispersion relation for capillary waves and analyze the difficulties that arise when setting up and conducting the experiment in detail. (paper)

  18. Comparison of 3 methods on fabricating micro- /nano- structured surface on 3D mold cavity

    DEFF Research Database (Denmark)

    Zhang, Yang; Hansen, Hans Nørgaard; Bissacco, Giuliano

    2015-01-01

    The methods to manufacture micro- or nano- structures on surfaces have been an area of intense investigation. Demands are shown for technologies for surface structuring on real 3D parts in many fields. However, most technologies for the fabrication of micro-structured functional surfaces are still...... limited to flat or simple shaped geometries. In this paper, 3 approaches for fabricating micro and nano- structured surfaces on a mold cavity for injection moulding are investigated and compared. The first approach is to use pre-fabricated plate with micro-structured surface as an insert for the mold......, in this way micro holes (Ø4 μm) was obtained. The second approach is to produce the cavity part using anodizing process chain, and in this way sub-micro structures can be obtained all over the cavity surface. The third approach is to machine the surface inside the cavity directly by femtosecond laser combined...

  19. TECHNIQUE FOR DETERMINATION OF SURFACE FRACTAL DIMENSION AND MORPHOLOGY OF MESOPOROUS TITANIA USING DYNAMIC FLOW ADSORPTION AND ITS CHARACTERIZATION

    Directory of Open Access Journals (Sweden)

    Silvester Tursiloadi

    2010-06-01

    Full Text Available A technique to determine the surface fractal dimension of mesoporous TiO­2 using a dynamic flow adsorption instrument is described. Fractal dimension is an additional technique to characterize surface morphology. Surface fractal dimension, a quantitative measurement of surface ruggedness, can be determined by adsorbing a homologous series of adsorbates onto an adsorbent sample of mesoporous TiO­2. Titania wet gel prepared by hydrolysis of Ti-alkoxide was immersed in the flow of supercritical CO2 at 60 °C and the solvent was extracted.  Mesoporous TiO­2 consists of anatase nano-particles, about 5nm in diameter, have been obtained. After calcination at 600 °C, the average pore size of the extracted gel, about 20nm in diameter, and the pore volume, about 0.35cm3g-1, and the specific surface area, about 58 m2g-1. Using the N2 adsorption isotherm, the surface fractal dimension, DS, has been estimated according to the Frenkel-Halsey-Hill (FHH theory. The N2 adsorption isotherm for the as-extracted aerogel indicates the mesoporous structure. Two linear regions are found for the FHH plot of the as-extracted aerogel. The estimated surface fractal dimensions are about 2.49 and 2.68. Both of the DS  values indicate rather complex surface morphology. The TEM observation shows that there are amorphous and crystalline particles. Two values of DS may be attributed to these two kinds of particles. The two regions are in near length scales, and the smaller DS, DS =2.49, for the smaller region. This result indicates that there are two kinds of particles, probably amorphous and anatase particles as shown by the TEM observation.     Keywords: surface fractal dimensions, CO2 supercritically extraction, sol-gel, aerogel, titania

  20. Structure, biomimetics, and fluid dynamics of fish skin surfaces*

    Science.gov (United States)

    Lauder, George V.; Wainwright, Dylan K.; Domel, August G.; Weaver, James C.; Wen, Li; Bertoldi, Katia

    2016-10-01

    The interface between the fluid environment and the surface of the body in swimming fishes is critical for both physiological and hydrodynamic functions. The skin surface in most species of fishes is covered with bony scales or toothlike denticles (in sharks). Despite the apparent importance of fish surfaces for understanding aquatic locomotion and near-surface boundary layer flows, relatively little attention has been paid to either the nature of surface textures in fishes or possible hydrodynamic effects of variation in roughness around the body surface within an individual and among species. Fish surfaces are remarkably diverse and in many bony fishes scales can have an intricate surface texture with projections, ridges, and comblike extensions. Shark denticles (or scales) are toothlike and project out of the skin to form a complexly textured surface that interacts with free-stream flow. Manufacturing biomimetic foils with fishlike surfaces allows hydrodynamic testing and we emphasize here the importance of dynamic test conditions where the effect of surface textures is assessed under conditions of self-propulsion. We show that simple two-dimensional foils with patterned cuts do not perform as well as a smooth control surface, but that biomimetic shark skin foils can swim at higher self-propelled speeds than smooth controls. When the arrangement of denticles on the foil surface is altered, we find that a staggered-overlapped pattern outperforms other arrangements. Flexible foils made of real shark skin outperform sanded controls when foils are moved with a biologically realistic motion program. We suggest that focus on the mechanisms of drag reduction by fish surfaces has been too limiting and an additional role of fish surface textures may be to alter leading edge vortices and flow patterns on moving surfaces in a way that enhances thrust. Analysis of water flow over an artificial shark skin foil under both static and dynamic conditions shows that a shear layer

  1. Investigation of surface porosity measurements and compaction pressure as means to ensure consistent contact angle determinations

    DEFF Research Database (Denmark)

    Holm, René; Borkenfelt, Simon; Allesø, Morten

    2016-01-01

    for a compound is determined by its contact angle to a liquid, which in the present study was measured using the sessile drop method applied to a disc compact of the compound. Precise determination of the contact angle is important should it be used to either rank compounds or selected excipients to e.......g. increase the wetting from a solid dosage form. Since surface roughness of the compact has been suggested to influence the measurement this study investigated if the surface quality, in terms of surface porosity, had an influence on the measured contact angle. A correlation to surface porosity was observed......, however for six out of seven compounds similar results were obtained by applying a standard pressure (866MPa) to the discs in their preparation. The data presented in the present work therefore suggest that a constant high pressure should be sufficient for most compounds when determining the contact angle...

  2. Effective Method for Determining Environmental Loads on Supporting Structures for Offshore Wind Turbines

    Directory of Open Access Journals (Sweden)

    Dymarski Paweł

    2016-01-01

    Full Text Available This paper presents a description of an effective method for determining loads due to waves and current acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates pyramids of polygon with a large number of sides (8 or more. The presented computational method is based on the Morison equation, which was originally developed only for cylindrically shaped structures. The new algorithm shown here uses the coefficients of inertia and drag forces that were calculated for non-cylindrical shapes. The analysed structure consists of segments which are truncated pyramids on the basis of a hex decagon. The inertia coefficients, CM, and drag coefficients, CD, were determined using RANSE-CFD calculations. The CFD simulations were performed for a specific range of variation of the period, and for a certain range of amplitudes of the velocity. In addition, the analysis of influence of the surface roughness on the inertia and drag coefficients was performed. In the next step, the computations of sea wave, current and wind load on supporting structure for the fifty-year storm were carried out. The simulations were performed in the time domain and as a result the function of forces distribution along the construction elements was obtained. The most unfavourable distribution of forces will be used, to analyse the strength of the structure, as the design load.

  3. Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface

    NARCIS (Netherlands)

    Wolthers, M.; Di Tommaso, D.; Du, Z.; de Leeuw, N.H.

    2012-01-01

    Calcite–water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity.

  4. The role of (sub)-surface oxygen on the surface electronic structure of hydrogen terminated (100) CVD diamond

    NARCIS (Netherlands)

    Deferme, W.; Tanasa, G.; Amir, J.; Haenen, K.; Nesladek, M.; Flipse, C.F.J.

    2006-01-01

    In this work, scanning tunnelling microscopy (STM) and scanning tunnelling spectroscopy (STS) were applied to investigate the surface morphol. and the surface electronic structure of plasma-treated (100)-oriented CVD diamond films. These films were hydrogenated using a conventional MWPE-CVD

  5. Surface characteristics determining the cell compatibility of ionically cross-linked alginate gels

    International Nuclear Information System (INIS)

    Machida-Sano, Ikuko; Hirakawa, Makoto; Matsumoto, Hiroki; Kamada, Mitsuki; Ogawa, Sakito; Satoh, Nao; Namiki, Hideo

    2014-01-01

    In this study we investigated differences in the characteristics determining the suitability of five types of ion (Fe 3+ , Al 3+ , Ca 2+ , Ba 2+ and Sr 2+ )-cross-linked alginate films as culture substrates for cells. Human dermal fibroblasts were cultured on each alginate film to examine the cell affinity of the alginates. Since cell behavior on the surface of a material is dependent on the proteins adsorbed to it, we investigated the protein adsorption ability and surface features (wettability, morphology and charge) related to the protein adsorption abilities of alginate films. We observed that ferric, aluminum and barium ion-cross-linked alginate films supported better cell growth and adsorbed higher amounts of serum proteins than other types. Surface wettability analysis demonstrated that ferric and aluminum ion-cross-linked alginates had moderate hydrophilic surfaces, while other types showed highly hydrophilic surfaces. The roughness was exhibited only on barium ion-cross-linked alginate surface. Surface charge measurements revealed that alginate films had negatively charged surfaces, and showed little difference among the five types of gel. These results indicate that the critical factors of ionically cross-linked alginate films determining the protein adsorption ability required for their cell compatibility may be surface wettability and morphology. (paper)

  6. Propagation of liquid surface waves over finite graphene structured arrays of cylinders

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Based on the multiple scattering method,this paper investigates a benchmark problem of the propagation of liquid surface waves over finite graphene (or honeycomb) structured arrays of cylinders.Comparing the graphene structured array with the square structured and with triangle structured arrays,it finds that the finite graphene structure can produce more complete band gaps than the other finite structures,and the finite graphene structure has less localized ability than the other finite structures.

  7. Osteoblast growth behavior on porous-structure titanium surface

    Energy Technology Data Exchange (ETDEWEB)

    Tian Yuan; Ding Siyang; Peng Hui; Lu Shanming; Wang Guoping [Research Institute of Stomatology, Nanjing Medical University, Nanjing 210029 (China); Xia Lu, E-mail: shelueia@yahoo.com.cn [Research Institute of Stomatology, Nanjing Medical University, Nanjing 210029 (China); Wang Peizhi, E-mail: wangpzi@sina.com [Research Institute of Stomatology, Nanjing Medical University, Nanjing 210029 (China)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Micro-arc oxidation technology formed a porous feature on titanium surface. Black-Right-Pointing-Pointer This porous surface accelerated adhesion, proliferation and differentiation compared with smooth surface. Black-Right-Pointing-Pointer Osteogenesis-related proteins and genes were up regulated by this porous surface. Black-Right-Pointing-Pointer It is anticipated that micro-arc oxidation surface could enhance osteoblastic activity and bone regeneration. - Abstract: A bioavailable surface generated by nano-technology could accelerate implant osteointegration, reduce healing time and enable implants to bear early loading. In this study, a nano-porous surface of titanium wafers was modified using micro-arc oxidation technique; surface of smooth titanium was used as control group. Surface characteristic was evaluated by investigating morphology, roughness and hydrophilicity of titanium wafers. In vitro studies, osteoblastic adhesion, proliferation and ALP activity, as well as gene and protein expressions relative to mineralization were assayed. Our results showed that a crater-liked nano-porous surface with greater roughness and better hydrophilicity were fabricated by micro-arc oxidation. It was further indicated that nano-porous surface could enhance adhesion, proliferation and ALP activity of osteoblasts compared with smooth surfaces. In addition, gene and protein expression of collagen-I, osteocalcin and osteopontin were also obviously increased. In summary, micro-arc oxidized techniques could form an irregular nano-porous morphology on implant surface which is favorable to improve osteoblastic function and prospected to be a potent modification of dental implant.

  8. Production, purification, crystallization and structure determination of H-1 Parvovirus

    International Nuclear Information System (INIS)

    Halder, Sujata; Nam, Hyun-Joo; Govindasamy, Lakshmanan; Vogel, Michèle; Dinsart, Christiane; Salomé, Nathalie; McKenna, Robert; Agbandje-McKenna, Mavis

    2012-01-01

    The production, purification, crystallization and crystallographic analysis of H-1 Parvovirus, a gene-therapy vector, are reported. Crystals of H-1 Parvovirus (H-1PV), an antitumor gene-delivery vector, were obtained for DNA-containing capsids and diffracted X-rays to 2.7 Å resolution using synchrotron radiation. The crystals belonged to the monoclinic space group P2 1 , with unit-cell parameters a = 255.4, b = 350.4, c = 271.6 Å, β = 90.34°. The unit cell contained two capsids, with one capsid per crystallographic asymmetric unit. The H-1PV structure has been determined by molecular replacement and is currently being refined

  9. Structure of HIV-1 protease determined by neutron crystallography

    International Nuclear Information System (INIS)

    Adachi, Motoyasu; Kuroki, Ryota

    2009-01-01

    HIV-1 protease is an aspartic protease, and plays an essential role in replication of HIV. To develop HIV-1 protease inhibitors through structure-based drug design, it is necessary to understand the catalytic mechanism and inhibitor recognition of HIV-1 protease. We have determined the crystal structure of HIV-1 protease in complex with KNI-272 to 1.9 A resolution by neutron crystallography in combination with 1.4 A resolution X-ray diffraction data. The results show that the carbonyl group of hydroxymethylcarbonyl (HMC) in KNI-272 forms a hydrogen bonding interaction with protonated Asp 25 and the hydrogen atom from the hydroxyl group of HMC forms a hydrogen bonding interaction with the deprotonated Asp125. This is the first neutron report for HIV-1/inhibitor complex and shows directly the locations of key hydrogen atoms in catalysis and in the binding of a transition-state analog. The results confirm key aspect of the presumed catalytic mechanism of HIV-1 protease and will aid in the further development of protease inhibitors. (author)

  10. Determination of subsurface geological structure with borehole gravimetry

    International Nuclear Information System (INIS)

    Clark, S.R.; Hearst, J.R.

    1983-07-01

    Conventional gamma-gamma and gravimetric density measurements are routinely gathered for most holes used for underground nuclear tests. The logs serve to determine the subsurface structural geology near the borehole. The gamma-gamma density log measures density of the rock within about 15 cm of the borehole wall. The difference in gravity measured at two depths in a borehole can be interpreted in terms of the density of an infinite, homogeneous, horizontal bed between those depths. When the gravimetric density matches the gamma-gamma density over a given interval it is assumed that the bed actualy exists, and that rocks far from the hole must be the same as those encountered adjacent to the borehole. Conversely, when the gravimetric density differs from the gamma-gamma density it is apparent that the gravimeter is being influenced by a rock mass of different density than that at the hole wall. This mismatch can be a powerful tool to deduce the local structural geology. The geology deduced from gravity mesurements in emplacement hole, U4al, and the associated exploratory hole, UE4al, is an excellent example of the power of the method

  11. Determination of scattering structures from spatial coherence measurements.

    Science.gov (United States)

    Zarubin, A M

    1996-03-01

    A new method of structure determination and microscopic imaging with short-wavelength radiations (charged particles, X-rays, neutrons), based on measurements of the modulus and the phase of the degree of spatial coherence of the scattered radiation, is developed. The underlying principle of the method--transfer of structural information about the scattering potential via spatial coherence of the secondary (scattering) source of radiation formed by this potential--is expressed by the generalization of the van Cittert-Zernike theorem to wave and particle scattering [A.M. Zarubin, Opt. Commun. 100 (1993) 491; Opt. Commun. 102 (1993) 543]. Shearing interferometric techniques are proposed for implementing the above measurements; the limits of spatial resolution attainable by reconstruction of the absolute square of a 3D scattering potential and its 2D projections from the measurements are analyzed. It is shown theoretically that 3D imaging with atomic resolution can be realized in a "synthetic aperture" electron or ion microscope and that a 3D resolution of about 6 nm can be obtained with a "synthetic aperture" X-ray microscope. A proof-of-principle optical experiment is presented.

  12. Synergistic cytotoxic effects of antibodies directed against different cell surface determinants

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, E V; Pindar, A; Stevenson, F K; Stevenson, G T [Southampton General Hospital (UK). Tenovus Research Lab.

    1978-03-01

    Three antibody populations were raised in rabbits against surface antigens on guinea-pig L/sub 2/C leukaemic lymphocytes: against idiotypic determinants on the lambda chain of the surface immunoglobulin, against C region determinants on the lambda chain, and against the surface antigens recognised by conventional anti-lymphocyte sera. Complement and K-cell cytotoxicities effected by the antibodies on L/sub 2/C cells were studied in vitro. In both cytotoxic systems mixtures of the antibodies revealed synergy, in that the titres of the mixtures exceeded predicted additive titres of their components. The synergy was greater when the mixed antibodies were directed to determinants on the same molecule rather than to determinants on different molecules.

  13. A Determination of the Neutron Spin Structure Function

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Emlyn W

    2003-08-18

    The authors report the results of the experiment E142 which measured the spin dependent structure function of the neutron, g{sub 1}{sup n}(x, Q{sup 2}). The experiment was carried out at the Stanford Linear Accelerator Center by measuring an asymmetry in the deep inelastic scattering of polarized electrons from a polarized {sup 3}He target, at electron energies from 19 to 26 GeV. The structure function was determined over the kinematic range 0.03 < BJorken x < 0.6 and 1.0 < Q{sup 2} < 5.5 (GeV/c){sup 2}. An evaluation of the integral {integral}{sub 0}{sup 1} g{sub 1}{sup n}(x,Q{sup 2})dx at fixed Q{sup 2} = 2 (GeV/c){sup 2} yields the final result {Lambda}{sub 1}{sup n} = -0.032 {+-} 0.006 (stat.) {+-} 0.009 (syst.). This result, when combined with the integral of the proton spin structure function measured in other experiments, confirms the fundamental Bjorken sum rule with O({alpha}{sub s}{sup 3}) corrections to within one standard deviation. This is a major success for perturbative Quantum Chromodynamics. Some ancillary results include the findings that the Ellis-Jaffe sum rule for the neutron is violated at the 2 {sigma} level, and that the total contribution of the quarks to the helicity of the nucleon is 0.36 {+-} 0.10. The strange sea polarization is estimated to be small and negative, {Delta}s = -0.07 {+-} 0.04.

  14. Modification on surface oxide layer structure and surface morphology of niobium by gas cluster ion beam treatments

    International Nuclear Information System (INIS)

    Wu, A.T.; Swenson, D.R.; Insepov, Z.

    2010-01-01

    Recently, it was demonstrated that significant reductions in field emission on Nb surfaces could be achieved by means of a new surface treatment technique called gas cluster ion beam (GCIB). Further study as shown in this paper revealed that GCIB treatments could modify surface irregularities and remove surface asperities leading to a smoother surface finish as demonstrated through measurements using a 3D profilometer, an atomic force microscope, and a scanning electron microscope. These experimental observations were supported by computer simulation via atomistic molecular dynamics and a phenomenological surface dynamics. Measurements employing a secondary ion mass spectrometry found that GCIB could also alter Nb surface oxide layer structure. Possible implications of the experimental results on the performance of Nb superconducting radio frequency cavities treated by GCIB will be discussed. First experimental results on Nb single cell superconducting radio frequency cavities treated by GCIB will be reported.

  15. Fabrication of Hierarchically Micro- and Nano-structured Mold Surfaces Using Laser Ablation for Mass Production of Superhydrophobic Surfaces

    Science.gov (United States)

    Noh, Jiwhan; Lee, Jae-Hoon; Na, Suckjoo; Lim, Hyuneui; Jung, Dae-Hwan

    2010-10-01

    Many studies have examined the formation of surfaces with mixed patterns of micro- and nano-sized lotus leaves that have hydrophobic properties. In this study, micro- and nano-shapes such as lotus leaves were fabricated on a metal mold surface using laser ablation and ripple formation. A microstructure on the mold surface was replicated onto poly(dimethylsiloxane) (PDMS) using the polymer casting method to manufacture low-cost hydrophobic surfaces. A PDMS surface with micro- and nano-structures that were the inverse image of a lotus leaf showed hydrophobic characteristics (water contact angle: 157°). From these results, we deduced that portions of the microstructures were wet and that air gaps existed between the microstructures and the water drops. In this paper we suggest the possibility of the mass production of hydrophobic plastic surfaces and the development of a methodology for the hydrophobic texturing of various polymer surfaces, using the polymer casting method with laser-processed molds.

  16. Comprehensive study of rheological and surface properties of the selected slag system in the context of its internal structure

    Directory of Open Access Journals (Sweden)

    L. Řeháčková

    2016-10-01

    Full Text Available Rheological (dynamic viscosity, flow curves and surface properties (surface tension of real slag system were experimentally investigated. Measurements of dynamic viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1 600. The method of sessile drop was used for measurement of surface tension. Surface tension and dynamic viscosity were measured in the temperature interval from 1 200 to 1 600 °C. The structural characteristics of the selected samples were determined by X-ray diffraction (XRD. The samples for given analysis were prepared by quench cooling. Experimentally determined values of dynamic viscosity and surface tension were compared with the results of X-ray diffraction phase analysis.

  17. Localized surface plasmon enhanced cellular imaging using random metallic structures

    Science.gov (United States)

    Son, Taehwang; Lee, Wonju; Kim, Donghyun

    2017-02-01

    We have studied fluorescence cellular imaging with randomly distributed localized near-field induced by silver nano-islands. For the fabrication of nano-islands, a 10-nm silver thin film evaporated on a BK7 glass substrate with an adhesion layer of 2-nm thick chromium. Micrometer sized silver square pattern was defined using e-beam lithography and then the film was annealed at 200°C. Raw images were restored using electric field distribution produced on the surface of random nano-islands. Nano-islands were modeled from SEM images. 488-nm p-polarized light source was set to be incident at 60°. Simulation results show that localized electric fields were created among nano-islands and that their average size was found to be 135 nm. The feasibility was tested using conventional total internal reflection fluorescence microscopy while the angle of incidence was adjusted to maximize field enhancement. Mouse microphage cells were cultured on nano-islands, and actin filaments were selectively stained with FITC-conjugated phalloidin. Acquired images were deconvolved based on linear imaging theory, in which molecular distribution was sampled by randomly distributed localized near-field and blurred by point spread function of far-field optics. The optimum fluorophore distribution was probabilistically estimated by repetitively matching a raw image. The deconvolved images are estimated to have a resolution in the range of 100-150 nm largely determined by the size of localized near-fields. We also discuss and compare the results with images acquired with periodic nano-aperture arrays in various optical configurations to excite localized plasmonic fields and to produce super-resolved molecular images.

  18. Reinforcement Toolbox, a Parametric Reinforcement Modelling Tool for Curved Surface Structures

    NARCIS (Netherlands)

    Lauppe, J.; Rolvink, A.; Coenders, J.L.

    2013-01-01

    This paper presents a computational strategy and parametric modelling toolbox which aim at enhancing the design- and production process of reinforcement in freeform curved surface structures. The computational strategy encompasses the necessary steps of raising an architectural curved surface model

  19. Scanning moiré and spatial-offset phase-stepping for surface inspection of structures

    Science.gov (United States)

    Yoneyama, S.; Morimoto, Y.; Fujigaki, M.; Ikeda, Y.

    2005-06-01

    In order to develop a high-speed and accurate surface inspection system of structures such as tunnels, a new surface profile measurement method using linear array sensors is studied. The sinusoidal grating is projected on a structure surface. Then, the deformed grating is scanned by linear array sensors that move together with the grating projector. The phase of the grating is analyzed by a spatial offset phase-stepping method to perform accurate measurement. The surface profile measurements of the wall with bricks and the concrete surface of a structure are demonstrated using the proposed method. The change of geometry or fabric of structures and the defects on structure surfaces can be detected by the proposed method. It is expected that the surface profile inspection system of tunnels measuring from a running train can be constructed based on the proposed method.

  20. The elastic-plastic failure assessment diagram of surface cracked structure

    International Nuclear Information System (INIS)

    Ning, J.; Gao, Q.

    1987-01-01

    The simplified NLSM is able to calculate the EPFM parameters and failure assessment curve for the surface cracked structure correctly and conveniently. The elastic-plastic failure assessment curve of surface crack is relevant to crack geometry, loading form and material deformation behaviour. It is necessary to construct the EPFM failure assessment curve of the surface crack for the failure assessment of surface cracked structure. (orig./HP)

  1. Water infiltration and surface soil structural properties as influenced by animal traffic in the Southern Piedmont USA

    Science.gov (United States)

    Surface-soil structural condition in long-term perennial pastures is expected to be modified by how forage is (a) harvested through haying or grazing and (b) stimulated through source of nutrient application. We determined the effects of harvest management and nutrient source on macropore filling, ...

  2. The Structure of a Hypersonic Air Flow near a Plane Surface at Various Intensities of Magnetogasdynamic Interaction

    Science.gov (United States)

    Fomichev, V. P.; Yadrenkin, M. A.

    2017-12-01

    This Letter presents a systematization of the effects observed in experiments on the magnetogasdynamic interaction near the surface of a plate in a high-speed gas flow. Ranges of the hydromagnetic-interaction parameter determining various levels of influence on the shock-wave structure of the flow are established.

  3. Imprinted and injection-molded nano-structured optical surfaces

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun; Højlund-Nielsen, Emil; Clausen, Jeppe Sandvik

    2013-01-01

    . In this paper, nanostructured polymer surfaces suitable for up-scalable polymer replication methods, such as imprinting/embossing and injection-molding, are discussed. The limiting case of injection-moulding compatible designs is investigated. Anti-reflective polymer surfaces are realized by replication...

  4. Assessment of Wind Turbine Structural Integrity using Response Surface Methodology

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Svenningsen, Lasse; Moser, Wolfgang

    2016-01-01

    Highlights •A new approach to assessment of site specific wind turbine loads is proposed. •The approach can be applied in both fatigue and ultimate limit state. •Two different response surface methodologies have been investigated. •The model uncertainty introduced by the response surfaces...

  5. Surface and interface electronic structure: Sixth year activity report

    International Nuclear Information System (INIS)

    Kevan, S.D.

    1992-01-01

    Several productive runs were made on beamline U4A at NSLS. An upgrade of angle-resolved photoemission spectrometer was largely completed on the beamline. Progress was made on studies of surface states and reconstruction on Mo(001) and W(001), and of surface states and resonances on Pt(111)

  6. Droplet impact on superheated micro-structured surfaces

    NARCIS (Netherlands)

    Tran, Tuan; Staat, Erik-Jan; Susarrey Arce, A.; Foertsch, T.C.; van Houselt, Arie; Gardeniers, Johannes G.E.; Prosperetti, Andrea; Lohse, Detlef; Sun, Chao

    2013-01-01

    When a droplet impacts upon a surface heated above the liquid's boiling point, the droplet either comes into contact with the surface and boils immediately (contact boiling), or is supported by a developing vapor layer and bounces back (film boiling, or Leidenfrost state). We study the transition

  7. Structured surface reflector design for oblique incidence beam splitter at 610 GHz.

    Science.gov (United States)

    Defrance, F; Casaletti, M; Sarrazin, J; Wiedner, M C; Gibson, H; Gay, G; Lefèvre, R; Delorme, Y

    2016-09-05

    An iterative alternate projection-based algorithm is developed to design structured surface reflectors to operate as beam splitters at GHz and THz frequencies. To validate the method, a surface profile is determined to achieve a reflector at 610 GHz that generates four equal-intensity beams towards desired directions of ±12.6° with respect to the specular reflection axis. A prototype is fabricated and the beam splitter behavior is experimentally demonstrated. Measurements confirm a good agreement (within 1%) with computer simulations using Feko, validating the method. The beam splitter at 610 GHz has a measured efficiency of 78% under oblique incidence illumination that ensures a similar intensity between the four reflected beams (variation of about 1%).

  8. Surface, dynamic and structural properties of liquid Al-Ti alloys

    International Nuclear Information System (INIS)

    Novakovic, R.; Giuranno, D.; Ricci, E.; Tuissi, A.; Wunderlich, R.; Fecht, H.-J.; Egry, I.

    2012-01-01

    The systems containing highly reactive element such as Ti are the most difficult to be determined experimentally and therefore, it is often necessary to estimate the missing values by theoretical models. The thermodynamic data of the Al-Ti system are scarce, its phase diagram is still incomplete and there are very few data on the thermophysical properties of Al-Ti melts. The study on surface, dynamic and static structural properties of liquid Al-Ti alloys has been carried out within the framework of the Compound Formation Model. In spite of the experimental difficulties, the surface tension of liquid Al-2 at.%Ti alloy has been measured over a temperature range by the pinned drop method.

  9. 3D silicon breast surface mapping via structured light profilometry

    Science.gov (United States)

    Vairavan, R.; Ong, N. R.; Sauli, Z.; Kirtsaeng, S.; Sakuntasathien, S.; Shahimin, M. M.; Alcain, J. B.; Lai, S. L.; Paitong, P.; Retnasamy, V.

    2017-09-01

    Digital fringe projection technique is one of the promising optical methods for 3D surface imaging as it demonstrates non contact and non invasive characteristics. The potential of this technique matches the requirement for human body evaluation, as it is vital for disease diagnosis and for treatment option selection. Thus, the digital fringe projection has addressed this requirement with its wide clinical related application and studies. However, the application of this technique for 3D surface mapping of the breast is very minimal. Hence, in this work, the application of digital fringe projection for 3D breast surface mapping is reported. Phase shift fringe projection technique was utilized to perform the 3D breast surface mapping. Maiden results have confirmed the feasibility of using the digital fringe projection method for 3D surface mapping of the breast and it can be extended for breast cancer detection.

  10. Metrology of sub-micron structured polymer surfaces

    DEFF Research Database (Denmark)

    Quagliotti, Danilo; Tosello, Guido; Salaga, J.

    metal masters with different types of finish has been carried out.Four types of surface finish were considered: a) Diamond buff polishing. b) Grit paper polishing. c) Stone polishing. d) Dry blast polishing (see Fig. 1). Both master and replicated surfaces were measured using a laser scanning confocal...... of about 70 %. The worst amplitude replication was achieved for both diamond buff and grit paper polished surfaces with a replication fidelity around 50 %.The tendency is almost the same for slope replication but the replication fidelity values are lower: 70 % for stone polished surfaces. 50 % for dry...... evaluated according to ISO 15530-3:2011, adapted to optical measure-ments, and propagated to the replication fidelity.A good amplitude replication was achieved for stone polished surfaces with a replication fidelity larger than 90 %. The dry blast ones were evaluated with an amplitude replication fidelity...

  11. Improving the chances of successful protein structure determination with a random forest classifier

    Energy Technology Data Exchange (ETDEWEB)

    Jahandideh, Samad [Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92307 (United States); Joint Center for Structural Genomics, (United States); Jaroszewski, Lukasz; Godzik, Adam, E-mail: adam@burnham.org [Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92307 (United States); Joint Center for Structural Genomics, (United States); University of California, San Diego, La Jolla, California (United States)

    2014-03-01

    Using an extended set of protein features calculated separately for protein surface and interior, a new version of XtalPred based on a random forest classifier achieves a significant improvement in predicting the success of structure determination from the primary amino-acid sequence. Obtaining diffraction quality crystals remains one of the major bottlenecks in structural biology. The ability to predict the chances of crystallization from the amino-acid sequence of the protein can, at least partly, address this problem by allowing a crystallographer to select homologs that are more likely to succeed and/or to modify the sequence of the target to avoid features that are detrimental to successful crystallization. In 2007, the now widely used XtalPred algorithm [Slabinski et al. (2007 ▶), Protein Sci.16, 2472–2482] was developed. XtalPred classifies proteins into five ‘crystallization classes’ based on a simple statistical analysis of the physicochemical features of a protein. Here, towards the same goal, advanced machine-learning methods are applied and, in addition, the predictive potential of additional protein features such as predicted surface ruggedness, hydrophobicity, side-chain entropy of surface residues and amino-acid composition of the predicted protein surface are tested. The new XtalPred-RF (random forest) achieves significant improvement of the prediction of crystallization success over the original XtalPred. To illustrate this, XtalPred-RF was tested by revisiting target selection from 271 Pfam families targeted by the Joint Center for Structural Genomics (JCSG) in PSI-2, and it was estimated that the number of targets entered into the protein-production and crystallization pipeline could have been reduced by 30% without lowering the number of families for which the first structures were solved. The prediction improvement depends on the subset of targets used as a testing set and reaches 100% (i.e. twofold) for the top class of predicted

  12. Fabrication and condensation characteristics of metallic superhydrophobic surface with hierarchical micro-nano structures

    Science.gov (United States)

    Chu, Fuqiang; Wu, Xiaomin

    2016-05-01

    Metallic superhydrophobic surfaces have various applications in aerospace, refrigeration and other engineering fields due to their excellent water repellent characteristics. This study considers a simple but widely applicable fabrication method using a two simultaneous chemical reactions method to prepare the acid-salt mixed solutions to process the metal surfaces with surface deposition and surface etching to construct hierarchical micro-nano structures on the surface and then modify the surface with low surface-energy materials. Al-based and Cu-based superhydrophobic surfaces were fabricated using this method. The Al-based superhydrophobic surface had a water contact angle of 164° with hierarchical micro-nano structures similar to the lotus leaves. The Cu-based surface had a water contact angle of 157° with moss-like hierarchical micro-nano structures. Droplet condensation experiments were also performed on these two superhydrophobic surfaces to investigate their condensation characteristics. The results show that the Al-based superhydrophobic surface has lower droplet density, higher droplet jumping probability, slower droplet growth rate and lower surface coverage due to the more structured hierarchical structures.

  13. Self-consistent electronic structure of the contracted tungsten (001) surface

    International Nuclear Information System (INIS)

    Posternak, M.; Krakauer, H.; Freeman, A.J.

    1982-01-01

    Self-consistent linearized-augmented-plane-wave energy-band studies using the warped muffin-tin approximation for a seven-layer W(001) single slab with the surface-layer separation contracted by 6% of the bulk interlayer spacing are reported. Surface electronic structure, local densities of states, generalized susceptibility for the surface, work function, and core-level shifts are found to have insignificant differences with corresponding results for the unrelaxed surface. Several differences in surface states between theory and recent angle-resolved photoemission experiments are discussed in the light of new proposed models of the actual unreconstructed surface structure at high temperatures

  14. Investigations of the Electronic Properties and Surface Structures of Aluminium-Rich Quasicrystalline Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Barrow, Jason A. [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    The work presented in this dissertation has investigated three distinct areas of interest in the field of quasicrystals: bulk structure, transport properties, and electronic structure. First, they have described the results of a study which explored the fundamental interactions between the atomic species of the icosahedral Al-Pd-Mn quasicrystal. The goal of this work was to determine whether the pseudo-MacKay or Bergman type clusters have a special stability or are merely a geometric coincidence. This was carried out by using laser vaporization to produce gas-phase metal clusters, which were analyzed using time-of-flight mass spectrometry. Both the kinetic and thermodynamic stabilities of the clusters were probed. The data indicated no special stability for either pseudo-MacKay or Bergman type clusters as isolated units. This, however, is not proof that these clusters are simply a geometric coincidence. It is possible that such clusters only have stability in the framework of the bulk matrix and do not exist as isolated units. Next, they have reported their investigations of the bulk thermal transport properties of a decagonal Al-Ni-Co two dimensional quasicrystal in the temperature range 373K-873K. The properties of a sample oriented along the periodic axis and another oriented along the aperiodic axis were measured. A high degree of anisotropy was observed between the aperiodic and periodic directions. Additionally, the properties were measured for a sample miscut to an orientation 45° off-axis. The properties of the miscut sample were shown to have good agreement with a theoretical model used to describe thermal transport in metallic single crystals. This model only considers thermal transport by a free-electron gas; therefore, agreement with experimental data suggests the validity of the Drude free-electron model for the decagonal Al-Ni-Co at these temperatures. Consequently, the observed anisotropy may be adequately described using classical transport

  15. Structure investigation of organic molecules on Au(111) surfaces; Strukturuntersuchung organischer Molekuele auf Au(111)-Oberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Kazempoor, Michel

    2009-02-02

    The present work covers two topics namely the coadsorption of formic acid and water on Au(111) and the structure of biphenylalkanthiole SAMs on Au(111) surfaces. The coadsorption of formic acid and water on Au(111) surfaces has been investigated by means of vibrational and photoelectron spectroscopy (HREELS, XPS). Formic acid adsorbs at 90 K molecularly with vibrational modes characteristic for flat lying zig-zag chains in the mono- and multilayer regime, like in solid formic acid. The structure of the flat lying formic acid chains was determined by low energy electron diffraction (LEED) as a (2r3 x r19) unit cell. Annealing results in a complete desorption at 190 K. Sequential adsorption of formic acid and water at 90 K shows no significant chemical interaction. Upon annealing the coadsorbed layer to 140 K a hydrogenbonded cyclic complex of formic acid with one water molecule could be identified using isotopically labelled adsorbates. Upon further annealing this complex decomposes leaving molecularly adsorbed formic acid on the surface at 160 K, accompanied by a proton exchange between formic acid and water. The influence of the alkane spacer chain length on the structure of biphenylalkanethiols on Au(111) surfaces was investigated as well. A systematic study was done on BPn-SAMs deposited from the gas phase. For every chain length a structure was found by LEED. Furthermore the influence of temperature on the structure was investigated in the range from room temperature up to about 400 K. To obviate influences from different preparation methods BP3 and BP4 was deposited from gas phase and from solution. No LEED spots were observed on BP4 SAMs deposited from solution. For BP3 an influence of the preparation could be excluded. For all BPn-SAMs a good agreement between LEED and STM data's was found. Nevertheless different unit cells were determined by LEED and STM consistent structures could be suggested considering the unit cell size given by LEED and the

  16. Surface sites on carbon-supported Ru, Co and Ni nanoparticles as determined by microcalorimetry of CO adsorption

    International Nuclear Information System (INIS)

    Cerro-Alarcon, M.; Maroto-Valiente, A.; Rodriguez-Ramos, I.; Guerrero-Ruiz, A.

    2005-01-01

    The adsorption of CO on carbon-supported metal (Ru, Co and Ni) catalysts was studied by microcalorimetry. A correlation of the results thus obtained with those reported for monocrystals or with other studies available in the scientific literature for supported metal catalysts, including infrared spectroscopy data, enables the determination of the type of exposed crystalline planes and/or of the different types of CO adsorbed species. The results obtained suggest that the energetic distribution of the surface sites depends on the carbon support material and on the applied reduction treatment. In this way, the use of a high surface area graphite (clean of surface oxygen groups) leads to an electron density enrichment on the small metal particles (Ru) and, in general, to a higher heterogeneity of the active surface sites. The elimination of surface oxygen functional groups (with the reduction treatment at the higher temperature) of the carbon molecular sieve support leads to changes in the surface structure of the metal particles and, consequently, to higher CO adsorption heats, particularly for Ru and Co

  17. Structural colours and applications to anodised aluminium surfaces

    DEFF Research Database (Denmark)

    Johansen, Villads Egede

    to solve the problem. The problem is investigated by first reviewing existing work within colouration and visual appearance. This includes a study on how colours are perceived by humans and an investigation of the characteristics with which a surface appearance is properly described. Subsequently......, nanostructures and surface profiles are investigated using optimisation and topology optimisation in order to understand the limitations and design freedom of colour engineering. This is then followed by a study of the effect of disorder on a nanoscale level in order to tailor surface reflections for a smooth...

  18. Design of structurally colored surfaces based on scalar diffraction theory

    DEFF Research Database (Denmark)

    Johansen, Villads Egede; Andkjær, Jacob Anders; Sigmund, Ole

    2014-01-01

    In this paper we investigate the possibility of controlling the color and appearance of surfaces simply by modifying the height profile of the surface on a nanoscale level. The applications for such methods are numerous: new design possibilities for high-end products, color engraving on any highly...... reflective surface, paint-free text and coloration, UV-resistant coloring, etc. In this initial study, the main focus is on finding a systematic way to obtain these results. For now the simulation and optimization is based on a simple scalar diffraction theory model. From the results, several design issues...

  19. TGP, an extremely stable, non-aggregating fluorescent protein created by structure-guided surface engineering

    Science.gov (United States)

    Close, Devin W.; Don Paul, Craig; Langan, Patricia S.; Wilce, Matthew C.J.; Traore, Daouda A.K.; Halfmann, Randal; Rocha, Reginaldo C.; Waldo, Geoffery S.; Payne, Riley J.; Rucker, Joseph B.; Prescott, Mark; Bradbury, Andrew R.M.

    2014-01-01

    In this paper we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP. The approach involved simultaneously eliminating crystal lattice contacts while increasing the overall negative charge of the protein. Despite intentional disruption of lattice contacts and introduction of high entropy glutamate side chains, TGP crystallized readily in a number of different conditions and the X-ray crystal structure of TGP was determined to 1.9 Å resolution. The structural reasons for the enhanced stability of TGP and eCGP123 are discussed. We demonstrate the utility of using TGP as a fusion partner in various assays and significantly, in amyloid assays in which the standard fluorescent protein, EGFP, is undesirable because of aberrant oligomerization. PMID:25287913

  20. Thermal green protein, an extremely stable, nonaggregating fluorescent protein created by structure-guided surface engineering.

    Science.gov (United States)

    Close, Devin W; Paul, Craig Don; Langan, Patricia S; Wilce, Matthew C J; Traore, Daouda A K; Halfmann, Randal; Rocha, Reginaldo C; Waldo, Geoffery S; Payne, Riley J; Rucker, Joseph B; Prescott, Mark; Bradbury, Andrew R M

    2015-07-01

    In this article, we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP. The approach involved simultaneously eliminating crystal lattice contacts while increasing the overall negative charge of the protein. Despite intentional disruption of lattice contacts and introduction of high entropy glutamate side chains, TGP crystallized readily in a number of different conditions and the X-ray crystal structure of TGP was determined to 1.9 Å resolution. The structural reasons for the enhanced stability of TGP and eCGP123 are discussed. We demonstrate the utility of using TGP as a fusion partner in various assays and significantly, in amyloid assays in which the standard fluorescent protein, EGFP, is undesirable because of aberrant oligomerization. © 2014 Wiley Periodicals, Inc.

  1. Elucidation of Peptide-Directed Palladium Surface Structure for Biologically Tunable Nanocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Bedford, Nicholas M.; Ramezani-Dakhel, Hadi; Slocik, Joseph M.; Briggs, Beverly D.; Ren, Yang; Frenkel, Anatoly I.; Petkov, Valeri; Heinz, Hendrik; Naik, Rajesh R.; Knecht, Mark R.

    2015-05-01

    Peptide-enabled synthesis of inorganic nanostructures represents an avenue to access catalytic materials with tunable and optimized properties. This is achieved via peptide complexity and programmability that is missing in traditional ligands for catalytic nanomaterials. Unfortunately, there is limited information available to correlate peptide sequence to particle structure and catalytic activity to date. As such, the application of peptide-enabled nanocatalysts remains limited to trial and error approaches. In this paper, a hybrid experimental and computational approach is introduced to systematically elucidate biomolecule-dependent structure/function relationships for peptide-capped Pd nanocatalysts. Synchrotron X-ray techniques were used to uncover substantial particle surface structural disorder, which was dependent upon the amino acid sequence of the peptide capping ligand. Nanocatalyst configurations were then determined directly from experimental data using reverse Monte Carlo methods and further refined using molecular dynamics simulation, obtaining thermodynamically stable peptide-Pd nanoparticle configurations. Sequence-dependent catalytic property differences for C-C coupling and olefin hydrogenation were then eluddated by identification of the catalytic active sites at the atomic level and quantitative prediction of relative reaction rates. This hybrid methodology provides a clear route to determine peptide-dependent structure/function relationships, enabling the generation of guidelines for catalyst design through rational tailoring of peptide sequences

  2. Use of abrupt strain path change for determining subsequent yield surface

    DEFF Research Database (Denmark)

    Kuroda, Mitsutoshi; Tvergaard, Viggo

    1999-01-01

    is prescribed, which makes the stress point move quickly along the yield surface. It is assumed that a closed-loop testing machine is used for the experiment, so that the strain path can be prescribed according to strain gauge measurements. Relative to the standard method of determining yield surface shapes...... by probing in many different stress directions from the elastic region, using some chosen plastic strain offset, the main advantage of the proposed method is that elastic unloading is not needed prior to tracing the yield surface. The method is illustrated here by a few analyses, first for the simplest how...

  3. Surface morphology, structural and electrical properties of RF ...

    Indian Academy of Sciences (India)

    5

    electrical properties of RF sputtered ITO thin films deposited onto Si(100). .... scanning electron microscopy (SEM) surface images are shown along with the cross- ..... annealing effect”, J. of Alloys and Compounds 509, (2011) 6072-6076.

  4. Facile fabrication of dendritic silver structures and their surface ...

    Indian Academy of Sciences (India)

    have high sensitivity to surface enhanced Raman spectroscopy response. ... of interfaces and molecularly thin-films. SERS is a ... face plasmon polaritons, while the second is attributed ... 2.2 Fabrication and characterization of dendritic.

  5. Investigation of surface porosity measurements and compaction pressure as means to ensure consistent contact angle determinations.

    Science.gov (United States)

    Holm, René; Borkenfelt, Simon; Allesø, Morten; Andersen, Jens Enevold Thaulov; Beato, Stefania; Holm, Per

    2016-02-10

    Compounds wettability is critical for a number of central processes including disintegration, dispersion, solubilisation and dissolution. It is therefore an important optimisation parameter both in drug discovery but also as guidance for formulation selection and optimisation. Wettability for a compound is determined by its contact angle to a liquid, which in the present study was measured using the sessile drop method applied to a disc compact of the compound. Precise determination of the contact angle is important should it be used to either rank compounds or selected excipients to e.g. increase the wetting from a solid dosage form. Since surface roughness of the compact has been suggested to influence the measurement this study investigated if the surface quality, in terms of surface porosity, had an influence on the measured contact angle. A correlation to surface porosity was observed, however for six out of seven compounds similar results were obtained by applying a standard pressure (866 MPa) to the discs in their preparation. The data presented in the present work therefore suggest that a constant high pressure should be sufficient for most compounds when determining the contact angle. Only for special cases where compounds have poor compressibility would there be a need for a surface-quality-control step before the contact angle determination. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Microwave emission measurements of sea surface roughness, soil moisture, and sea ice structure

    Science.gov (United States)

    Gloersen, P.; Wilheit, T. T.; Schmugge, T. J.

    1972-01-01

    In order to demonstrate the feasibility of the microwave radiometers to be carried aboard the Nimbus 5 and 6 satellites and proposed for one of the earth observatory satellites, remote measurements of microwave radiation at wavelengths ranging from 0.8 to 21 cm have been made of a variety of the earth's surfaces from the NASA CV-990 A/C. Brightness temperatures of sea water surfaces of varying roughness, of terrain with varying soil moisture, and of sea ice of varying structure were observed. In each case, around truth information was available for correlation with the microwave brightness temperature. The utility of passive microwave radiometry in determining ocean surface wind speeds, at least for values higher than 7 meters/second has been demonstrated. In addition, it was shown that radiometric signatures can be used to determine soil moisture in unvegetated terrain to within five percentage points by weight. Finally, it was demonstrated that first year thick, multi-year, and first year thin sea ice can be distinguished by observing their differing microwave emissivities at various wavelengths.

  7. Synthesis, Structure and Hirshfeld surface analysis, vibrational and ...

    Indian Academy of Sciences (India)

    3

    expression for dnorm, where two Hirshfeld surfaces touch, both will display a red spot identical in color intensity as well ... surface by using a red-blue-white color scheme: where red regions correspond to closer contacts and ..... A, Piskorz P, Komaromi I, Martin R L, Fox D J, Keith T, Al-Laham M A, Peng C Y,. 1. 2. 3. 4. 5. 6. 7.

  8. Ionic liquids at the surface of graphite: Wettability and structure

    Science.gov (United States)

    Bordes, Emilie; Douce, Laurent; Quitevis, Edward L.; Pádua, Agílio A. H.; Costa Gomes, Margarida

    2018-05-01

    The aim of this work is to provide a better understanding of the interface between graphite and different molecular and ionic liquids. Experimental measurements of the liquid surface tension and of the graphite-liquid contact angle for sixteen ionic liquids and three molecular liquids are reported. These experimental values allowed the calculation of the solid/liquid interfacial energy that varies, for the ionic liquids studied, between 14.5 mN m-1 for 1-ethyl-3-methylimidazolium dicyanamide and 37.8 mN m-1 for 3-dodecyl-1-(naphthalen-1-yl)-1H-imidazol-3-ium tetrafluoroborate. Imidazolium-based ionic liquids with large alkyl side-chains or functionalized with benzyl groups seem to interact more favourably with freshly peeled graphite surfaces. Even if the interfacial energy seems a good descriptor to assess the affinity of a liquid for a carbon-based solid material, we conclude that both the surface tension of the liquid and the contact angle between the liquid and the solid can be significant. Molecular dynamics simulations were used to investigate the ordering of the ions near the graphite surface. We conclude that the presence of large alkyl side-chains in the cations increases the ordering of ions at the graphite surface. Benzyl functional groups in the cations lead to a large affinity towards the graphite surface.

  9. Modeling of Surface Geometric Structure State After Integratedformed Milling and Finish Burnishing

    Science.gov (United States)

    Berczyński, Stefan; Grochała, Daniel; Grządziel, Zenon

    2017-06-01

    The article deals with computer-based modeling of burnishing a surface previously milled with a spherical cutter. This method of milling leaves traces, mainly asperities caused by the cutting crossfeed and cutter diameter. The burnishing process - surface plastic treatment - is accompanied by phenomena that take place right in the burnishing ball-milled surface contact zone. The authors present the method for preparing a finite element model and the methodology of tests for the assessment of height parameters of a surface geometrical structure (SGS). In the physical model the workpieces had a cuboidal shape and these dimensions: (width × height × length) 2×1×4.5 mm. As in the process of burnishing a cuboidal workpiece is affected by plastic deformations, the nonlinearities of the milled item were taken into account. The physical model of the process assumed that the burnishing ball would be rolled perpendicularly to milling cutter linear traces. The model tests included the application of three different burnishing forces: 250 N, 500 N and 1000 N. The process modeling featured the contact and pressing of a ball into the workpiece surface till the desired force was attained, then the burnishing ball was rolled along the surface section of 2 mm, and the burnishing force was gradually reduced till the ball left the contact zone. While rolling, the burnishing ball turned by a 23° angle. The cumulative diagrams depict plastic deformations of the modeled surfaces after milling and burnishing with defined force values. The roughness of idealized milled surface was calculated for the physical model under consideration, i.e. in an elementary section between profile peaks spaced at intervals of crossfeed passes, where the milling feed fwm = 0.5 mm. Also, asperities after burnishing were calculated for the same section. The differences of the obtained values fall below 20% of mean values recorded during empirical experiments. The adopted simplification in after

  10. Influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures and lattice defects accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Sedao, Xxx; Garrelie, Florence, E-mail: florence.garrelie@univ-st-etienne.fr; Colombier, Jean-Philippe; Reynaud, Stéphanie; Pigeon, Florent [Université de Lyon, CNRS, UMR5516, Laboratoire Hubert Curien, Université de Saint Etienne, Jean Monnet, F-42023 Saint-Etienne (France); Maurice, Claire; Quey, Romain [Ecole Nationale Supérieure des Mines de Saint-Etienne, CNRS, UMR5307, Laboratoire Georges Friedel, F-42023 Saint-Etienne (France)

    2014-04-28

    The influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures (LIPSS) has been investigated on a polycrystalline nickel sample. Electron Backscatter Diffraction characterization has been exploited to provide structural information within the laser spot on irradiated samples to determine the dependence of LIPSS formation and lattice defects (stacking faults, twins, dislocations) upon the crystal orientation. Significant differences are observed at low-to-medium number of laser pulses, outstandingly for (111)-oriented surface which favors lattice defects formation rather than LIPSS formation.

  11. Structural Determinants of Autoproteolysis of the Haemophilus influenzae Hap Autotransporter▿

    Science.gov (United States)

    Kenjale, Roma; Meng, Guoyu; Fink, Doran L.; Juehne, Twyla; Ohashi, Tomoo; Erickson, Harold P.; Waksman, Gabriel; St. Geme, Joseph W.

    2009-01-01

    Haemophilus influenzae is a gram-negative bacterium that initiates infection by colonizing the upper respiratory tract. The H. influenzae Hap autotransporter protein mediates adherence, invasion, and microcolony formation in assays with respiratory epithelial cells and presumably facilitates colonization. The serine protease activity of Hap is associated with autoproteolytic cleavage and extracellular release of the HapS passenger domain, leaving the Hapβ C-terminal domain embedded in the outer membrane. Cleavage occurs most efficiently at the LN1036-37 peptide bond and to a lesser extent at three other sites. In this study, we utilized site-directed mutagenesis, homology modeling, and assays with a peptide library to characterize the structural determinants of Hap proteolytic activity and cleavage specificity. In addition, we used homology modeling to predict the S1, S2, and S4 subsite residues of the Hap substrate groove. Our results indicate that the P1 and P2 positions at the Hap cleavage sites are critical for cleavage, with leucine preferred over larger hydrophobic residues or other amino acids in these positions. The substrate groove is formed by L263 and N274 at the S1 subsite, R264 at the S2 subsite, and E265 at the S4 subsite. This information may facilitate design of approaches to block Hap activity and interfere with H. influenzae colonization. PMID:19687208

  12. Comparative study on two different seal surface structure for reactor pressure vessel sealing behavior

    International Nuclear Information System (INIS)

    Chen Jun; Xiong Guangming; Deng Xiaoyun

    2014-01-01

    The seal surface structure is very important to reactor pressure vessel (RPV) sealing behavior. In this paper, two 3-D RPV sealing analysis finite models have been established with different seal surface structures, in order to study the influence of two structures. The separation of RPV upper and lower flanges, bolt loads and etc. are obtained, which are used to evaluate the sealing behavior of the RPV. Meanwhile, the comparative analysis of safety margin of two seal surface structural had been done, which provides the theoretical basis for RPV seal structure design optimization. (authors)

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

    International Nuclear Information System (INIS)

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

    2001-01-01

    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.

  14. Cell surface appearance of unexpected host MHC determinants on thymocytes from radiation bone marrow chimeras

    International Nuclear Information System (INIS)

    Sharrow, S.O.; Mathieson, B.J.; Singer, A.

    1981-01-01

    The phenotypic appearance of cell surface antigens on murine thymocytes from long-term radiation bone marrow chimeras was analyzed using indirect immunofluorescence and flow microfluorometry. Cells maturing in the thymi of these mice were typed for MHC (Kk, I-Ak, H-2b, Kb, and Ib) and non-MHC (Lty 1, Ly 9, and TL) determinants. All cells were of donor origin as determined by non-MHC (Ly) phenotype in P1 leads to P2, P1 x P2 leads to P1, and P1 leads to P2 radiation chimeras. In contrast, the MHC phenotypes of these thymocytes were markedly affected by the host environment. Specifically, H-2 and I-A determinants of both parental phenotypes were detected on thymocytes from P1 leads to P1 x P2 chimeras; I-A determinants of host phenotype were present, whereas I-A determinants of donor phenotype were reduced on thymocytes from P1 x P2 leads to P1 chimeras; and thymocytes from P1 leads to P2 chimeras possessed H-2 and I-A determinants of host phenotype but showed reduction of donor I-A phenotype determinants. The appearance of host cell surface H-2 and I-A determinants on thymocytes from chimeras closely parallels the functional recognition of MHC determinants by T cells from chimeric mice and thus may be significantly related to the development of the self-recognition repertoire by maturing T cells

  15. Superhydrophobic Natural and Artificial Surfaces-A Structural Approach.

    Science.gov (United States)

    Avrămescu, Roxana-Elena; Ghica, Mihaela Violeta; Dinu-Pîrvu, Cristina; Prisada, Răzvan; Popa, Lăcrămioara

    2018-05-22

    Since ancient times humans observed animal and plants features and tried to adapt them according to their own needs. Biomimetics represents the foundation of many inventions from various fields: From transportation devices (helicopter, airplane, submarine) and flying techniques, to sports' wear industry (swimming suits, scuba diving gear, Velcro closure system), bullet proof vests made from Kevlar etc. It is true that nature provides numerous noteworthy models (shark skin, spider web, lotus leaves), referring both to the plant and animal kingdom. This review paper summarizes a few of "nature's interventions" in human evolution, regarding understanding of surface wettability and development of innovative special surfaces. Empirical models are described in order to reveal the science behind special wettable surfaces (superhydrophobic /superhydrophilic). Materials and methods used in order to artificially obtain special wettable surfaces are described in correlation with plants' and animals' unique features. Emphasis is placed on joining superhydrophobic and superhydrophilic surfaces, with important applications in cell culturing, microorganism isolation/separation and molecule screening techniques. Bio-inspired wettability is presented as a constitutive part of traditional devices/systems, intended to improve their characteristics and extend performances.

  16. A molecular surface science study of the structure of adsorbates on surfaces: Importance to lubrication

    International Nuclear Information System (INIS)

    Mate, C.M.

    1986-09-01

    The interaction and bonding of atoms and molecules on metal surfaces is explored under ultra-high vacuum conditions using a variety of surface science techniques: high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES), work function measurements, and second harmonic generation (SHG). 164 refs., 51 figs., 3 tabs

  17. CCDC 1416891: Experimental Crystal Structure Determination : Methyl-triphenyl-germanium

    KAUST Repository

    Bernatowicz, Piotr; Shkurenko, Aleksander; Osior, Agnieszka; Kamieński, Bohdan; Szymański, Sławomir

    2015-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from

  18. Use of structured surfaces for friction and wear control on bearing surfaces

    International Nuclear Information System (INIS)

    Wang, Ling

    2014-01-01

    Surface texturing with purposely made regular micropatterns on flat or curved surfaces, as opposed to random roughness inherited from machining processes, has attracted significant attention in recent years. At the 2013 World Tribology Congress in Turin alone there were over 40 presentations related to surface texturing for tribological applications, from magnetic hard discs and hydrodynamic bearings to artificial joints. Although surface texturing has been reported being successfully applied in industrial applications such as seals, pistons, and thrust pad bearings, the demand for robust design is still high. Etsion has recently reviewed the modeling research mainly conducted by his group Etsion I (2013 Friction 1 195–209). This paper aims to review the state-of-the-art development of surface texturing made by a wider range of researchers. (topical review)

  19. Plasmonic nanopillar structures for surface-enhanced raman scattering applications

    DEFF Research Database (Denmark)

    Rindzevicius, Tomas; Schmidt, Michael Stenbæk; Wu, Kaiyu

    2016-01-01

    have been utilized in surfaceenhanced Raman spectroscopy (SERS) for biological and chemical sensing. We present Au nanopillar (NP) SERS structures that are excellent for molecular detection. The NP structures can be fabricated using a simple two-step process. We analyze NP optical properties...

  20. Proposal for Certifying Expandable Planetary Surface Habitation Structures

    Science.gov (United States)

    Dorsey, John T.

    2011-01-01

    A factor-of-safety (FS) of 4.0 is currently used to design habitation structures made from structural soft goods. This approach is inconsistent with using a FS of 2.0 for metallic and polymeric composite pressure vessels as well as soft good structures such as space suits and parachutes. This inconsistency arises by using the FS to improperly account for the unknown effects of a variety of environmental and loading uncertainties. Using a 4.0 FS not only results in additional structural mass, it also makes it difficult to gain insight into the limitations of the material and/or product form and thus, it becomes difficult to make improvements. In order to bring consistency to the design and certification of expandable habitat structures, the approach used by the Federal Aviation Administration (FAA) to certify polymeric composite aircraft structures is used as a model and point of departure. A draft certification plan for Expandable Habitat Structures is developed in this paper and offered as an option for placing habitats made from soft goods on an equal footing with other structural implementations.