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Sample records for diffraction resolution studies

  1. Synchrotron X-Ray Reciprocal Space Mapping, Topography and Diffraction Resolution Studies of Macromolecular Crystal Quality

    NASA Technical Reports Server (NTRS)

    Boggon, T. J.; Helliwell, J. R.; Judge, Russell A.; Siddons, D. P.; Snell, Edward H.; Stojanoff, V.

    2000-01-01

    A comprehensive study of microgravity and ground grown chicken egg white lysozyme crystals is presented using synchrotron X-ray reciprocal space mapping, topography techniques and diffraction resolution. Microgravity crystals displayed, on average, reduced intrinsic mosaicities but no differences in terms of stress over their earth grown counterparts. Topographic analysis revealed that in the microgravity case the majority of the crystal was contributing to the peak of the reflection at the appropriate Bragg angle. In the earth case at the diffraction peak only a small volume of the crystal contributed to the intensity. The techniques prove to be highly complementary with the reciprocal space mapping providing a quantitative measure of the crystal mosaicity and stress (or variation in lattice spacing) and topography providing a qualitative overall assessment of the crystal in terms of its X-ray diffraction properties. Structural data collection was also carried out both at the synchrotron and in the laboratory.

  2. Study of the spatial resolution of laser thermochemical technology for recording diffraction microstructures

    SciTech Connect

    Veiko, V P; Korol'kov, V I; Poleshchuk, A G; Sametov, A R; Shakhno, E A; Yarchuk, M V

    2011-07-31

    The thermochemical method for recording data, which is based on local laser oxidation of a thin metal film with subsequent etching of the unirradiated region, is an alternative to laser photolithography and direct laser removal of the film material. This recording technology is characterised by the absence of thermal and hydrodynamic image distortions, as in the case of laser ablation, and the number of necessary technological operations is much smaller as compared with the photomask preparation in classical photolithography. The main field of application of the thermochemical technology is the fabrication of diffraction optical elements (DOEs), which are widely used in printers, bar-code readers, CD and DVD laser players, etc. The purpose of this study is to increase the resolution of thermochemical data recording on thin chromium films. (interaction of laser radiation with matter)

  3. A multicrystal diffraction data-collection approach for studying structural dynamics with millisecond temporal resolution

    PubMed Central

    Schubert, Robin; Kapis, Svetlana; Gicquel, Yannig; Bourenkov, Gleb; Schneider, Thomas R.; Heymann, Michael; Betzel, Christian; Perbandt, Markus

    2016-01-01

    Many biochemical processes take place on timescales ranging from femto­seconds to seconds. Accordingly, any time-resolved experiment must be matched to the speed of the structural changes of interest. Therefore, the timescale of interest defines the requirements of the X-ray source, instrumentation and data-collection strategy. In this study, a minimalistic approach for in situ crystallization is presented that requires only a few microlitres of sample solution containing a few hundred crystals. It is demonstrated that complete diffraction data sets, merged from multiple crystals, can be recorded within only a few minutes of beamtime and allow high-resolution structural information of high quality to be obtained with a temporal resolution of 40 ms. Global and site-specific radiation damage can be avoided by limiting the maximal dose per crystal to 400 kGy. Moreover, analysis of the data collected at higher doses allows the time-resolved observation of site-specific radiation damage. Therefore, our approach is well suited to observe structural changes and possibly enzymatic reactions in the low-millisecond regime. PMID:27840678

  4. High-Resolution Infrared and Electron-Diffraction Studies of Trimethylenecyclopropane ([3]-Radialene)

    SciTech Connect

    Wright, Corey; Holmes, Joshua; Nibler, Joseph W.; Hedberg, Kenneth; White, James D.; Hedberg, Lise; Weber, Alfons; Blake, Thomas A.

    2013-05-16

    Combined high-resolution spectroscopic, electron-diffraction, and quantum theoretical methods are particularly advantageous for small molecules of high symmetry and can yield accurate structures that reveal subtle effects of electron delocalization on molecular bonds. The smallest of the radialene compounds, trimethylenecyclopropane, [3]-radialene, has been synthesized and examined in the gas phase by these methods. The first high-resolution infrared spectra have been obtained for this molecule of D3h symmetry, leading to an accurate B0 rotational constant value of 0.1378629(8) cm-1, within 0.5% of the value obtained from electronic structure calculations (density functional theory (DFT) B3LYP/cc-pVTZ). This result is employed in an analysis of electron-diffraction data to obtain the rz bond lengths (in Å): C-H = 1.072 (17), C-C = 1.437 (4), and C=C = 1.330 (4). The analysis does not lead to an accurate value of the HCH angle; however, from comparisons of theoretical and experimental angles for similar compounds, the theoretical prediction of 117.5° is believed to be reliable to within 2°. The effect of electron delocalization in radialene is to reduce the single C-C bond length by 0.07 Å compared to that in cyclopropane.

  5. Crystallography: Resolution beyond the diffraction limit

    NASA Astrophysics Data System (ADS)

    Shen, Jian-Ren

    2016-02-01

    A method has been devised that extends the resolution of X-ray crystal structures beyond the diffraction limit. This might help to improve the visualization of structures of proteins that form 'poorly diffracting' crystals. See Letter p.202

  6. High Resolution Low Energy Electron Diffraction Studies of Thermal Instabilities in Lead Surfaces

    NASA Astrophysics Data System (ADS)

    Yang, Hongning

    1991-02-01

    Thermal instability in a crystal surface is one of the most fascinating phenomena that occur in surfaces. Recent advances in many surface analytical tools allow researchers to examine surface instabilities on the atomic scale. One outstanding example is the observation of surface melting in a Pb(110) surface 100 K below the bulk melting temperature, T_{m} (bulk) = 600.7 K, using medium-energy ion channeling techniques. Using the high-resolution low-energy electron diffraction (HRLEED) technique, we have observed several novel surface instabilities that occur below the Pb(110) surface melting temperature. First of all we found that Pb(110) surface melting is preceded by a surface roughening transition which begins at ~415 K, about 185 K below T_{m}. The value of the roughening temperature agrees very well with the prediction of the molecular dynamic calculation that a (110) surface should start to rough at 0.7 T _{m} (~420 K for Pb). This roughening transition is of the Korsterlitz -Thouless type and is an infinite order transition in which the height-height correlation diverges. We observed a critical line which extends from the roughening temperature to the surface melting temperature. Below the surface roughening temperature (at around 380 K), we have observed an extremely interesting disordered flat (DOF) phase in which positionally disordered steps are confined to two levels and the surface remains flat on the average. This DOF phase (sometimes called the preroughened phase), as predicted by K. Rommelse and M. den Nijs recently, is stabilized by entropy as a result of step interactions beyond the nearest neighbors. The energetics of the DOF phase are intimately related to that of the surface reconstruction. In fact, a reconstruction phase has been considered as a "condensate" of the DOF phase. In contrast, the more tightly packed Pb(100) surface behaves very differently. There is a non-conventional liquid-like disordering which occurs at 570 K. This disordering

  7. High-resolution neutron diffraction study of CuNCN: New evidence of structure anomalies at low temperature

    SciTech Connect

    Jacobs, Philipp; Houben, Andreas; Dronskowski, Richard; Tchougréeff, Andrei L.

    2013-12-14

    Copper carbodiimide (CuNCN) is the nitrogen-containing analogue of cupric oxide. Based on high-resolution neutron-diffraction data, CuNCN's lattice parameters are derived as a function of the temperature. In accordance with a recent synchrotron study, a clear trend in the cell parameter a is observed accompanying the changing magnetic behavior. With decreasing temperature, a slowly decreases to a minimum at ∼100 K after which it rises again. The same trend—albeit more pronounced—is observed for the c lattice parameter at ∼35 K. The herein presented neutron powder-diffraction data also support the conjectured sequence of transitions from the high-temperature one-dimensional resonating valence-bond (RVB) state to a transient two-dimensional RVB state and eventually, at lowest temperatures, into another two-dimensional RVB state, presumably the ground state.

  8. High Resolution Powder Diffraction and Structure Determination

    SciTech Connect

    Cox, D. E.

    1999-04-23

    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

  9. Atomic resolution 3D electron diffraction microscopy

    SciTech Connect

    Miao, Jianwei; Ohsuna, Tetsu; Terasaki, Osamu; O'Keefe, Michael A.

    2002-03-01

    Electron lens aberration is the major barrier limiting the resolution of electron microscopy. Here we describe a novel form of electron microscopy to overcome electron lens aberration. By combining coherent electron diffraction with the oversampling phasing method, we show that the 3D structure of a 2 x 2 x 2 unit cell nano-crystal (framework of LTA [Al12Si12O48]8) can be ab initio determined at the resolution of 1 Angstrom from a series of simulated noisy diffraction pattern projections with rotation angles ranging from -70 degrees to +70 degrees in 5 degrees increments along a single rotation axis. This form of microscopy (which we call 3D electron diffraction microscopy) does not require any reference waves, and can image the 3D structure of nanocrystals, as well as non-crystalline biological and materials science samples, with the resolution limited only by the quality of sample diffraction.

  10. Stacking disorder in silicon carbide supported cobalt crystallites: an X-ray diffraction, electron diffraction and high resolution electron microscopy study.

    PubMed

    du Plessis, H E; de Villiers, J P R; Tuling, A; Olivier, E J

    2016-11-21

    Supported cobalt Fischer-Tropsch catalysts are characteristically nanoparticulate and the reduced SiC supported catalyst was found to contain both HCP and FCC polymorphs. This is reflected in the powder XRD patterns and generally there is a poor fit between the experimental and calculated diffractograms. This was ascribed to small crystallite sizes and the occurrence of disorder, manifested as peak broadening and peak shifts. Selected area electron diffraction data of suitably oriented cobalt catalyst grains on silicon carbide supports show non-periodic disorder in the zone axis orientations that contain the common (001) (HCP) and (111) (FCC) reciprocal lattice planes. Both FCC and HCP polymorphs are present in the same grains and these show disorder mainly in the HCP component. The disorder is further examined using high angle annular dark field (HAADF) scanning transmission electron microscopy at atomic resolution and the stacking sequences elucidated. Random sequences of mainly FCC are interrupted by HCP sequences and twin surfaces with reverse stacking sequences are also present. This study highlights the presence of significant disorder in cobalt catalyst grains confirmed by HAADF microscopy.

  11. High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt

    SciTech Connect

    Ueland, B. G.; Saunders, S. M.; Bud'ko, S. L.; Schmiedeshoff, G. M.; Canfield, P. C.; Kreyssig, A.; Goldman, A. I.

    2015-11-30

    In this study, YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below a temperature of T*=0.7K, fragile antiferromagnetic order below TN = 0.4K, a Kondo temperature of TK ≈ 1K, and crystalline-electric-field splitting on the order of E/kB = 1 – 10K. Whereas the compound has a face-centered-cubic lattice at ambient temperature, certain experimental data, particularly those from studies aimed at determining its crystalline-electric-field scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-resolution, high-energy x-ray diffraction experiments which show that, within our experimental resolution of ≈ 6 – 10 × 10–5 Å, no structural phase transition occurs between T = 1.5 and 50 K. In combination with results from dilatometry measurements, we further show that the compound's thermal expansion has a minimum at ≈ 18 K and a region of negative thermal expansion for 9 ≲ T ≲ 18 K. Despite diffraction patterns taken at 1.6 K which indicate that the lattice is face-centered cubic and that the Yb resides on a crystallographic site with cubic point symmetry, we demonstrate that the linear thermal expansion may be modeled using crystalline-electric-field level schemes appropriate for Yb3+ residing on a site with either cubic or less than cubic point symmetry.

  12. High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt

    DOE PAGES

    Ueland, B. G.; Saunders, S. M.; Bud'ko, S. L.; ...

    2015-11-30

    In this study, YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below a temperature of T*=0.7K, fragile antiferromagnetic order below TN = 0.4K, a Kondo temperature of TK ≈ 1K, and crystalline-electric-field splitting on the order of E/kB = 1 – 10K. Whereas the compound has a face-centered-cubic lattice at ambient temperature, certain experimental data, particularly those from studies aimed at determining its crystalline-electric-field scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-resolution, high-energy x-ray diffraction experiments which show that, within our experimental resolution of ≈ 6 – 10 × 10–5 Å,more » no structural phase transition occurs between T = 1.5 and 50 K. In combination with results from dilatometry measurements, we further show that the compound's thermal expansion has a minimum at ≈ 18 K and a region of negative thermal expansion for 9 ≲ T ≲ 18 K. Despite diffraction patterns taken at 1.6 K which indicate that the lattice is face-centered cubic and that the Yb resides on a crystallographic site with cubic point symmetry, we demonstrate that the linear thermal expansion may be modeled using crystalline-electric-field level schemes appropriate for Yb3+ residing on a site with either cubic or less than cubic point symmetry.« less

  13. Multi foci with diffraction limited resolution.

    PubMed

    Waller, Erik H; von Freymann, Georg

    2013-09-09

    The generation of multi foci is an established method for high-speed parallel direct laser writing, scanning microscopy and for optical tweezer arrays. However, the quality of multi foci reduces with increasing resolution due to interference effects. Here, we report on a spatial-light-modulator-based method that allows for highly uniform, close to Gaussian spots with diffraction limited resolution using a wavelength of 780 nm. We introduce modifications of a standard algorithm that calculates a field distribution on the entrance pupil of a high numerical aperture objective splitting the focal volume into a multitude of spots. Our modified algorithm compares favourably to a commonly used algorithm in full vectorial calculations as well as in point-spread-function measurements. The lateral and axial resolution limits of spots generated by the new algorithm are found to be close to the diffraction limit.

  14. Hard x-ray monochromator with milli-electron volt bandwidth for high-resolution diffraction studies of diamond crystals

    SciTech Connect

    Stoupin, Stanislav; Shvyd'ko, Yuri; Shu Deming; Khachatryan, Ruben; Xiao, Xianghui; DeCarlo, Francesco; Goetze, Kurt; Roberts, Timothy; Roehrig, Christian; Deriy, Alexey

    2012-02-15

    We report on design and performance of a high-resolution x-ray monochromator with a spectral bandwidth of {Delta}E{sub X}{approx_equal} 1.5 meV, which operates at x-ray energies in the vicinity of the backscattering (Bragg) energy E{sub H} = 13.903 keV of the (008) reflection in diamond. The monochromator is utilized for high-energy-resolution diffraction characterization of diamond crystals as elements of advanced x-ray crystal optics for synchrotrons and x-ray free-electron lasers. The monochromator and the related controls are made portable such that they can be installed and operated at any appropriate synchrotron beamline equipped with a pre-monochromator.

  15. Hard x-ray monochromator with milli-electron volt bandwidth for high-resolution diffraction studies of diamond crystals.

    PubMed

    Stoupin, Stanislav; Shvyd'ko, Yuri; Shu, Deming; Khachatryan, Ruben; Xiao, Xianghui; DeCarlo, Francesco; Goetze, Kurt; Roberts, Timothy; Roehrig, Christian; Deriy, Alexey

    2012-02-01

    We report on design and performance of a high-resolution x-ray monochromator with a spectral bandwidth of ΔE(X) ≃ 1.5 meV, which operates at x-ray energies in the vicinity of the backscattering (Bragg) energy E(H) = 13.903 keV of the (008) reflection in diamond. The monochromator is utilized for high-energy-resolution diffraction characterization of diamond crystals as elements of advanced x-ray crystal optics for synchrotrons and x-ray free-electron lasers. The monochromator and the related controls are made portable such that they can be installed and operated at any appropriate synchrotron beamline equipped with a pre-monochromator.

  16. Hard x-ray monochromator with milli-electron volt bandwidth for high-resolution diffraction studies of diamond crystals.

    SciTech Connect

    Stoupin, S.; Shvydko, Y.; Shu, D.; Khachatryan, R.; Xiao, X.

    2012-01-01

    We report on design and performance of a high-resolution x-ray monochromator with a spectral bandwidth of {Delta}E{sub x} {approx_equal} 1.5 meV, which operates at x-ray energies in the vicinity of the backscattering (Bragg) energy E{sub H} = 13.903 keV of the (008) reflection in diamond. The monochromator is utilized for high-energy-resolution diffraction characterization of diamond crystals as elements of advanced x-ray crystal optics for synchrotrons and x-ray free-electron lasers. The monochromator and the related controls are made portable such that they can be installed and operated at any appropriate synchrotron beamline equipped with a pre-monochromator.

  17. Atomic Resolution Coherent Diffractive Imaging and Ultrafast Science

    SciTech Connect

    Zuo, Jian-min

    2011-01-12

    A major scientific challenge is determining the 3-D atomic structure of small nanostructures, including single molecules. Coherent diffractive imaging (CDI) is a promising approach. Recent progress has demonstrated coherent diffraction patterns can be recorded from individual nanostructures and phased to reconstruct their structure. However, overcoming the dose limit imposed by radiation damage is a major obstacle toward the full potential of CDI. One approach is to use ultrafast x-ray or electron pulses. In electron diffraction, amplitudes recorded in a diffraction pattern are unperturbed by lens aberrations, defocus, and other microscope resolution-limiting factors. Sub-A signals are available beyond the information limit of direct imaging. Significant contrast improvement is obtained compared to high-resolution electron micrographs. progress has also been made in developing time-resolved electron diffraction and imaging for the study of ultrafast dynamic processes in materials. This talk will cover these crosscutting issues and the convergence of electron and x-ray diffraction techniques toward structure determination of single molecules.

  18. Optical diffraction tomography for high resolution live cell imaging.

    PubMed

    Sung, Yongjin; Choi, Wonshik; Fang-Yen, Christopher; Badizadegan, Kamran; Dasari, Ramachandra R; Feld, Michael S

    2009-01-05

    We report the experimental implementation of optical diffraction tomography for quantitative 3D mapping of refractive index in live biological cells. Using a heterodyne Mach-Zehnder interferometer, we record complex field images of light transmitted through a sample with varying directions of illumination. To quantitatively reconstruct the 3D map of complex refractive index in live cells, we apply optical diffraction tomography based on the Rytov approximation. In this way, the effect of diffraction is taken into account in the reconstruction process and diffraction-free high resolution 3D images are obtained throughout the entire sample volume. The quantitative refractive index map can potentially serve as an intrinsic assay to provide the molecular concentrations without the addition of exogenous agents and also to provide a method for studying the light scattering properties of single cells.

  19. Calcium binding in. alpha. -amylases: An X-ray diffraction study at 2. 1- angstrom resolution of two enzymes from Aspergillus

    SciTech Connect

    Boel, E.; Jensen, V.J.; Petersen, S.B.; Thim, L. Woldike, H.F. ); Brady, L.; Brzozowski, AM.; Derewenda, Z.; Dodson, G.G.; Swift, H. )

    1990-07-03

    X-ray diffraction analysis (at 2.1-{angstrom} resolution) of an acid alpha-amylase from Aspergillus niger allowed a detailed description of the stereochemistry of the calcium-binding sites. The primary site (which is essential in maintaining proper folding around the active site) contains a tightly bound Ca{sup 2+} with an unusually high number of eight ligands. A secondary binding site was identified at the bottom of the substrate binding cleft; it involves the residues presumed to play a catalytic role (Asp206 and Glu230). This explains the inhibitory effect of calcium observed at higher concentrations. Neutral Aspergillus oryzae (TAKA) {alpha}-amylase was also refined in a new crystal at 2.1-{angstrom} resolution. The structure of this homologous (over 80%) enzyme and addition kinetic studies support all the structural conclusions regarding both calcium-binding sites.

  20. Sub-diffraction limit resolution in microscopy

    NASA Technical Reports Server (NTRS)

    Cheng, Ming (Inventor); Chen, Weinong (Inventor)

    2007-01-01

    A method and apparatus for visualizing sub-micron size particles employs a polarizing microscope wherein a focused beam of polarized light is projected onto a target, and a portion of the illuminating light is blocked from reaching the specimen, whereby to produce a shadow region, and projecting diffracted light from the target onto the shadow region.

  1. The High Resolution Powder Diffraction Beam Line at ESRF

    PubMed Central

    Fitch, A. N.

    2004-01-01

    The optical design and performance of the high-resolution powder diffraction beam line BM16 at ESRF are discussed and illustrated. Some recent studies carried out on BM16 are described, including crystal structure solution and refinement, anomalous scattering, in situ measurements, residual strain in engineering components, investigation of microstructure, and grazing-incidence diffraction from surface layers. The beam line is built on a bending magnet, and operates in the energy range from 5 keV to 40 keV. After the move to an undulator source in 2002, it will benefit from an extented energy range up to 60 keV and increased flux and resolution. It is anticipated that enhancements to the data quality will be achieved, leading to the solution of larger crystal structures, and improvements in the accuracy of refined structures. The systematic exploitation of anisotropic thermal expansion will help reduce the effects of peak overlap in the analysis of powder diffraction data. PMID:27366602

  2. Room-temperature ultrahigh-resolution time-of-flight neutron and X-ray diffraction studies of H/D-exchanged crambin

    PubMed Central

    Chen, Julian C.-H.; Fisher, Zoë; Kovalevsky, Andrey Y.; Mustyakimov, Marat; Hanson, B. Leif; Zhurov, Vladimir V.; Langan, Paul

    2012-01-01

    The room-temperature (RT) X-ray structure of H/D-exchanged crambin is reported at 0.85 Å resolution. As one of the very few proteins refined with anisotropic atomic displacement parameters at two temperatures, the dynamics of atoms in the RT and 100 K structures are compared. Neutron diffraction data from an H/D-exchanged crambin crystal collected at the Protein Crystallo­graphy Station (PCS) showed diffraction beyond 1.1 Å resolution. This is the highest resolution neutron diffraction reported to date for a protein crystal and will reveal important details of the anisotropic motions of H and D atoms in protein structures. PMID:22297981

  3. High-resolution electron-energy-loss spectroscopy and photoelectron-diffraction studies of the geometric structure of adsorbates on single-crystal metal surfaces

    SciTech Connect

    Rosenblatt, D.H.

    1982-11-01

    Two techniques which have made important contributions to the understanding of surface phenomena are high resolution electron energy loss spectroscopy (EELS) and photoelectron diffraction (PD). EELS is capable of directly measuring the vibrational modes of clean and adsorbate covered metal surfaces. In this work, the design, construction, and performance of a new EELS spectrometer are described. These results are discussed in terms of possible structures of the O-Cu(001) system. Recommendations for improvements in this EELS spectrometer and guidelines for future spectrometers are given. PD experiments provide accurate quantitative information about the geometry of atoms and molecules adsorbed on metal surfaces. The technique has advantages when used to study disordered overlayers, molecular overlayers, multiple site systems, and adsorbates which are weak electron scatterers. Four experiments were carried out which exploit these advantages.

  4. Prospects of high-resolution resonant X-ray inelastic scattering studies on solid materials, liquids and gases at diffraction-limited storage rings

    PubMed Central

    Schmitt, Thorsten; de Groot, Frank M. F.; Rubensson, Jan-Erik

    2014-01-01

    The spectroscopic technique of resonant inelastic X-ray scattering (RIXS) will particularly profit from immensely improved brilliance of diffraction-limited storage rings (DLSRs). In RIXS one measures the intensities of excitations as a function of energy and momentum transfer. DLSRs will allow for pushing the achievable energy resolution, signal intensity and the sampled spot size to new limits. With RIXS one nowadays probes a broad range of electronic systems reaching from simple molecules to complex materials displaying phenomena like peculiar magnetism, two-dimensional electron gases, superconductivity, photovoltaic energy conversion and heterogeneous catalysis. In this article the types of improved RIXS studies that will become possible with X-ray beams from DLSRs are envisioned. PMID:25177995

  5. High-resolution diffraction grating interferometric transducer of linear displacements

    NASA Astrophysics Data System (ADS)

    Shang, Ping; Xia, Haojie; Fei, Yetai

    2016-01-01

    A high-resolution transducer of linear displacements is presented. The system is based on semiconductor laser illumination and a diffraction grating applied as a length master. The theory of the optical method is formulated using Doppler description. The relationship model among the interference strips, measurement errors, grating deflection around the X, Y and Z axes and translation along the Z axis is built. The grating interference strips' direction and space is not changed with movement along the X (direction of grating movement), Y (direction of grating line), Z axis, and the direction and space has a great effect when rotating around the X axis. Moreover the space is little affected by deflection around the Z axis however the direction is changed dramatically. In addition, the strips' position shifted rightward or downwards respectively for deflection around the X or Y axis. Because the emitted beams are separated on the grating plane, the tilt around the X axis error of the stage during motion will lead to the optical path difference of the two beams resulting in phase shift. This study investigates the influence of the tilt around the X axis error. Experiments show that after yaw error compensation, the high-resolution diffraction grating interferometric transducer readings can be significantly improved. The error can be reduced from +/-80 nm to +/-30 nm in maximum.

  6. X-ray high-resolution diffraction and reflectivity studies of defects related to the mechanical treatment of ? single crystals

    NASA Astrophysics Data System (ADS)

    Mazur, K.; Sass, J.; Eichhorn, F.

    1998-07-01

    Triple-crystal x-ray diffractometry and x-ray reflectometry have been used to determine defects in 0953-8984/10/27/007/img7 epi-ready wafers caused by mechanical treatment. Reciprocal space maps around the 400 lattice point were separately made for mechanically polished wafers before and after etching treatment. The lattice imperfections have been studied by measuring the diffusion scattering. The surface morphology has been controlled by means of x-ray reflectometry. It was shown that measurements of diffuse scattering could be made with good sensitivity in a reasonable time when there was a moderate difference between the d spacing of the sample and the monochromator.

  7. Study of optical Laue diffraction

    SciTech Connect

    Chakravarthy, Giridhar E-mail: aloksharan@email.com; Allam, Srinivasa Rao E-mail: aloksharan@email.com; Satyanarayana, S. V. M. E-mail: aloksharan@email.com; Sharan, Alok E-mail: aloksharan@email.com

    2014-10-15

    We present the study of the optical diffraction pattern of one and two-dimensional gratings with defects, designed using desktop pc and printed on OHP sheet using laser printer. Gratings so prepared, using novel low cost technique provides good visual aid in teaching. Diffraction pattern of the monochromatic light (632.8nm) from the grating so designed is similar to that of x-ray diffraction pattern of crystal lattice with point defects in one and two-dimensions. Here both optical and x-ray diffractions are Fraunhofer. The information about the crystalline lattice structure and the defect size can be known.

  8. Study of optical Laue diffraction

    NASA Astrophysics Data System (ADS)

    Chakravarthy, Giridhar; Allam, Srinivasa Rao; Satyanarayana, S. V. M.; Sharan, Alok

    2014-10-01

    We present the study of the optical diffraction pattern of one and two-dimensional gratings with defects, designed using desktop pc and printed on OHP sheet using laser printer. Gratings so prepared, using novel low cost technique provides good visual aid in teaching. Diffraction pattern of the monochromatic light (632.8nm) from the grating so designed is similar to that of x-ray diffraction pattern of crystal lattice with point defects in one and two-dimensions. Here both optical and x-ray diffractions are Fraunhofer. The information about the crystalline lattice structure and the defect size can be known.

  9. Purification, crystallization and preliminary X-ray diffraction studies to near-atomic resolution of dihydrodipicolinate synthase from methicillin-resistant Staphylococcus aureus

    SciTech Connect

    Burgess, Benjamin R.; Dobson, Renwick C. J. Dogovski, Con; Jameson, Geoffrey B.; Parker, Michael W.; Perugini, Matthew A.

    2008-07-01

    Dihydrodipicolinate synthase (DHDPS), an enzyme of the lysine-biosynthetic pathway, is a promising target for antibiotic development against pathogenic bacteria. Here, the expression, purification, crystallization and preliminary diffraction analysis to 1.45 Å resolution of DHDPS from methicillin-resistant S. aureus is reported. In recent years, dihydrodipicolinate synthase (DHDPS; EC 4.2.1.52) has received considerable attention from both mechanistic and structural viewpoints. DHDPS is part of the diaminopimelate pathway leading to lysine, coupling (S)-aspartate-β-semialdehyde with pyruvate via a Schiff base to a conserved active-site lysine. In this paper, the cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of DHDPS from methicillin-resistant Staphylococcus aureus, an important bacterial pathogen, are reported. The enzyme was crystallized in a number of forms, predominantly from PEG precipitants, with the best crystal diffracting to beyond 1.45 Å resolution. The space group was P1 and the unit-cell parameters were a = 65.4, b = 67.6, c = 78.0 Å, α = 90.1, β = 68.9, γ = 72.3°. The crystal volume per protein weight (V{sub M}) was 2.34 Å{sup 3} Da{sup −1}, with an estimated solvent content of 47% for four monomers per asymmetric unit. The structure of the enzyme will help to guide the design of novel therapeutics against the methicillin-resistant S. aureus pathogen.

  10. Enhancing resolution in coherent x-ray diffraction imaging

    NASA Astrophysics Data System (ADS)

    Noh, Do Young; Kim, Chan; Kim, Yoonhee; Song, Changyong

    2016-12-01

    Achieving a resolution near 1 nm is a critical issue in coherent x-ray diffraction imaging (CDI) for applications in materials and biology. Albeit with various advantages of CDI based on synchrotrons and newly developed x-ray free electron lasers, its applications would be limited without improving resolution well below 10 nm. Here, we review the issues and efforts in improving CDI resolution including various methods for resolution determination. Enhancing diffraction signal at large diffraction angles, with the aid of interference between neighboring strong scatterers or templates, is reviewed and discussed in terms of increasing signal-to-noise ratio. In addition, we discuss errors in image reconstruction algorithms—caused by the discreteness of the Fourier transformations involved—which degrade the spatial resolution, and suggest ways to correct them. We expect this review to be useful for applications of CDI in imaging weakly scattering soft matters using coherent x-ray sources including x-ray free electron lasers.

  11. Improving diffraction resolution using a new dehydration method.

    PubMed

    Huang, Qingqiu; Szebenyi, Doletha M E

    2016-02-01

    The production of high-quality crystals is one of the major obstacles in determining the three-dimensional structure of macromolecules by X-ray crystallography. It is fairly common that a visually well formed crystal diffracts poorly to a resolution that is too low to be suitable for structure determination. Dehydration has proven to be an effective post-crystallization treatment for improving crystal diffraction quality. Several dehydration methods have been developed, but no single one of them is suitable for all crystals. Here, a new convenient and effective dehydration method is reported that makes use of a dehydrating solution that will not dry out in air for several hours. Using this dehydration method, the resolution of Archaeoglobus fulgidus Cas5a crystals has been increased from 3.2 to 1.95 Å and the resolution of Escherichia coli LptA crystals has been increased from <5 to 3.4 Å.

  12. Super-resolution optical telescopes with local light diffraction shrinkage

    PubMed Central

    Wang, Changtao; Tang, Dongliang; Wang, Yanqin; Zhao, Zeyu; Wang, Jiong; Pu, Mingbo; Zhang, Yudong; Yan, Wei; Gao, Ping; Luo, Xiangang

    2015-01-01

    Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found that fine target features concealed in diffraction-limited optical images of a telescope could be observed in a small local field of view, benefiting from a relayed metasurface-based super-oscillatory imaging optics in which some local Fourier components beyond the cut-off frequency of telescope could be restored. As experimental examples, a minimal resolution to 0.55 of Rayleigh criterion is obtained, and imaging complex targets and large targets by superimposing multiple local fields of views are demonstrated as well. This investigation provides an access for real-time, incoherent and super-resolution telescopes without the manipulation of distant targets. More importantly, it gives counterintuitive evidence to the common knowledge that relayed optics could not deliver more imaging details than objective systems. PMID:26677820

  13. Super-resolution optical telescopes with local light diffraction shrinkage.

    PubMed

    Wang, Changtao; Tang, Dongliang; Wang, Yanqin; Zhao, Zeyu; Wang, Jiong; Pu, Mingbo; Zhang, Yudong; Yan, Wei; Gao, Ping; Luo, Xiangang

    2015-12-18

    Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found that fine target features concealed in diffraction-limited optical images of a telescope could be observed in a small local field of view, benefiting from a relayed metasurface-based super-oscillatory imaging optics in which some local Fourier components beyond the cut-off frequency of telescope could be restored. As experimental examples, a minimal resolution to 0.55 of Rayleigh criterion is obtained, and imaging complex targets and large targets by superimposing multiple local fields of views are demonstrated as well. This investigation provides an access for real-time, incoherent and super-resolution telescopes without the manipulation of distant targets. More importantly, it gives counterintuitive evidence to the common knowledge that relayed optics could not deliver more imaging details than objective systems.

  14. Super-resolution optical telescopes with local light diffraction shrinkage

    NASA Astrophysics Data System (ADS)

    Wang, Changtao; Tang, Dongliang; Wang, Yanqin; Zhao, Zeyu; Wang, Jiong; Pu, Mingbo; Zhang, Yudong; Yan, Wei; Gao, Ping; Luo, Xiangang

    2015-12-01

    Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found that fine target features concealed in diffraction-limited optical images of a telescope could be observed in a small local field of view, benefiting from a relayed metasurface-based super-oscillatory imaging optics in which some local Fourier components beyond the cut-off frequency of telescope could be restored. As experimental examples, a minimal resolution to 0.55 of Rayleigh criterion is obtained, and imaging complex targets and large targets by superimposing multiple local fields of views are demonstrated as well. This investigation provides an access for real-time, incoherent and super-resolution telescopes without the manipulation of distant targets. More importantly, it gives counterintuitive evidence to the common knowledge that relayed optics could not deliver more imaging details than objective systems.

  15. Structural studies of a non-stoichiometric channel hydrate using high resolution X-ray powder diffraction, solid-state nuclear magnetic resonance, and moisture sorption methods.

    PubMed

    Kiang, Y-H; Cheung, Eugene; Stephens, Peter W; Nagapudi, Karthik

    2014-09-01

    Structural investigations of a nonstoichiometric hydrate, AMG 222 tosylate, a DPP-IV inhibitor in clinical development for type II diabetes, were performed using a multitechnique approach. The moisture sorption isotherm is in good agreement with a simple Langmuir model, suggesting that the hydrate water is located in well-defined crystallographic sites, which become vacant during dehydration. Crystal structures of AMG 222 tosylate at ambient and dry conditions were determined from high-resolution X-ray diffraction using the direct space method. On the basis of these crystal structures, hydrated water is located in channels formed by the drug framework. Upon dehydration, an isostructural dehydrate is formed with the channels remaining void and accessible to water for rehydration. Kitaigorodskii packing coefficients of the solid between relative humidity of 0% and 90% indicate that the equilibrium form of AMG 222 tosylate is the fully hydrated monohydrate.

  16. High-resolution x-ray diffraction study of MnO nanostructured within a MCM-48 silica matrix with a gyroidal system of channels

    SciTech Connect

    Golosovsky, I. V.; Mirebeau, I.; Fauth, F.; Mazaj, M.; Kurdyukov, D. A.; Kumzerov, Yu. A.

    2006-10-15

    Antiferromagnetic MnO was synthesized within a mesoporous matrix MCM-48 with a gyroidal system of channels. Synchrotron radiation studies reveal that the embedded nanoparticles have a ribbonlike shape and a length of about 53(3) A . The peculiar diffraction line shape shows the loss of long-range atomic order. In spite of positional disorder, a transition from a cubic structure to a rhombohedral one, similar to the transition known for the bulk, is observed.

  17. Imaging outside the box: Resolution enhancement in X-ray coherent diffraction imaging by extrapolation of diffraction patterns

    SciTech Connect

    Latychevskaia, Tatiana Fink, Hans-Werner; Chushkin, Yuriy; Zontone, Federico

    2015-11-02

    Coherent diffraction imaging is a high-resolution imaging technique whose potential can be greatly enhanced by applying the extrapolation method presented here. We demonstrate the enhancement in resolution of a non-periodical object reconstructed from an experimental X-ray diffraction record which contains about 10% missing information, including the pixels in the center of the diffraction pattern. A diffraction pattern is extrapolated beyond the detector area and as a result, the object is reconstructed at an enhanced resolution and better agreement with experimental amplitudes is achieved. The optimal parameters for the iterative routine and the limits of the extrapolation procedure are discussed.

  18. Towards high-resolution ptychographic x-ray diffraction microscopy

    SciTech Connect

    Takahashi, Yukio; Suzuki, Akihiro; Yamauchi, Kazuto; Zettsu, Nobuyuki; Kohmura, Yoshiki; Ishikawa, Tetsuya; Senba, Yasunori; Ohashi, Haruhiko

    2011-06-01

    Ptychographic x-ray diffraction microscopy is a lensless imaging technique with a large field of view and high spatial resolution, which is also useful for characterizing the wavefront of an x-ray probe. The performance of this technique is degraded by positioning errors due to the drift between the sample and illumination optics. We propose an experimental approach for correcting the positioning errors and demonstrate success by two-dimensionally reconstructing both the wavefront of the focused x-ray beam and the complex transmissivity of the weakly scattering objects at the pixel resolution of better than 10 nm in the field of view larger than 5 {mu}m. This method is applicable to not only the observation of organelles inside cells or nano-mesoscale structures buried within bulk materials but also the characterization of probe for single-shot imaging with x-ray free electron lasers.

  19. The Influence of Surface Morphology and Diffraction Resolution of Canavalin Crystals

    NASA Technical Reports Server (NTRS)

    Plomp, M.; Thomas, B. R.; Day, J. S.; McPherson, A.; Chernov, A. A.; Malkin, A.

    2003-01-01

    Canavalin crystals grown from material purified and not purified by High Performance Liquid Chromatography were studied by atomic force microscopy and x-ray diffraction. After purification, resolution was improved from 2.55Angstroms to 2.22Angstroms and jagged isotropic spiral steps transformed into regular, well polygonized steps.

  20. Field studies in geophysical diffraction tomography

    SciTech Connect

    Witten, A.J.; Stevens, S.S. ); King, W.C. . Dept. of Geography and Environmental Engineering); Ursic, J.R. . Region V)

    1992-01-01

    Geophysical diffraction tomography (GDT) is a quantitative, high- resolution technique for subsurface imaging. This method has been used in a number of shallow applications to image buried waste, trenches, soil strata, tunnels, synthetic magma chambers, and the buried skeletal remains of seismosaurus, the longest dinosaur ever discovered. The theory associated with the GDT inversion and implementing software have been developed for acoustic and scalar electromagnetic waves for bistatic and monostatic measurements in cross-borehole, offset vertical seismic profiling and reflection geometries. This paper presents an overview of some signal processing algorithms, a description of the instrumentation used in field studies, and selected imaging results.

  1. Field studies in geophysical diffraction tomography

    SciTech Connect

    Witten, A.J.; Stevens, S.S.; King, W.C.; Ursic, J.R.

    1992-07-01

    Geophysical diffraction tomography (GDT) is a quantitative, high- resolution technique for subsurface imaging. This method has been used in a number of shallow applications to image buried waste, trenches, soil strata, tunnels, synthetic magma chambers, and the buried skeletal remains of seismosaurus, the longest dinosaur ever discovered. The theory associated with the GDT inversion and implementing software have been developed for acoustic and scalar electromagnetic waves for bistatic and monostatic measurements in cross-borehole, offset vertical seismic profiling and reflection geometries. This paper presents an overview of some signal processing algorithms, a description of the instrumentation used in field studies, and selected imaging results.

  2. High resolution x-ray scattering and diffraction

    SciTech Connect

    Moncton, D.

    1983-01-01

    In the general class of high resolution x-ray scattering studies experiments one analyzes the distribution of photon energies and wave vectors resulting from illumination of a sample with collimated monochromatic radiation. Applications abound in the field of structural physics, which may be described as the study of structures for their intrinsic physical interest. This includes studies of novel states of matter, phase transitions, and dynamics. As both the wave vector and the energy of scattered photons are of interest, one may conceptually divide high resolution experimental setups for this work into two classes: those with high Q-resolution (momemtum transfer analysis) and those with high E-resolution (energy transfer analysis). The former class is exemplified by the existing experimental station on SSRL wiggler experimental station VII-2 and the proposed high Q-resolution wiggler station for NSLS Phase II. The latter class is dependent on extremely high flux, as discussed more fully below, and the possibility of constructing a high E-resolution scattering station fed by an x-ray undulator is one of the exciting opportunities presented by the proposed construction of a 6 GeV storage ring.

  3. Novel optical super-resolution pattern with upright edges diffracted by a tiny thin aperture.

    PubMed

    Wu, Jiu Hui; Zhou, Kejiang

    2015-08-24

    In the past decade numerous efforts have been concentrated to achieve optical imaging resolution beyond the diffraction limit. In this letter a thin microcavity theory of near-field optics is proposed by using the power flow theorem firstly. According to this theory, the near-field optical diffraction from a tiny aperture whose diameter is less than one-tenth incident wavelength embedded in a thin conducting film is investigated by considering this tiny aperture as a thin nanocavity. It is very surprising that there exists a kind of novel super-resolution diffraction patterns showing resolution better than λ/80 (λ is the incident wavelength), which is revealed for the first time to our knowledge in this letter. The mechanism that has allowed the imaging with this kind of super-resolution patterns is due to the interaction between the incident wave and the thin nanocavity with a complex wavenumber. More precisely, these super-resolution patterns with discontinuous upright peaks are formed by one or three items of the integration series about the cylindrical waves according to our simulation results. This novel optical super-resolution with upright edges by using the thin microcavity theory presented in the study could have potential applications in the future semiconductor lithography process, nano-size laser-drilling technology, microscopy, optical storage, optical switch, and optical information processing.

  4. The fluence–resolution relationship in holographic and coherent diffractive imaging1

    PubMed Central

    Hagemann, Johannes; Salditt, Tim

    2017-01-01

    This work presents a numerical study of the fluence–resolution behaviour for two coherent lensless X-ray imaging techniques. To this end the fluence–resolution relationship of inline near-field holography and far-field coherent diffractive imaging are compared in numerical experiments. To achieve this, the phase reconstruction is carried out using iterative phase-retrieval algorithms on simulated noisy data. Using the incident photon fluence on the specimen as the control parameter, the achievable resolution for two example phantoms (cell and bitmap) is studied. The results indicate the superior performance of holography compared with coherent diffractive imaging, for the same fluence and phase-reconstruction procedure. PMID:28381977

  5. High-resolution neutron and X-ray diffraction room-temperature studies of an H-FABP-oleic acid complex: study of the internal water cluster and ligand binding by a transferred multipolar electron-density distribution.

    PubMed

    Howard, E I; Guillot, B; Blakeley, M P; Haertlein, M; Moulin, M; Mitschler, A; Cousido-Siah, A; Fadel, F; Valsecchi, W M; Tomizaki, Takashi; Petrova, T; Claudot, J; Podjarny, A

    2016-03-01

    Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader's quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H⋯H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface.

  6. Diffraction studies for microcellular applications

    NASA Astrophysics Data System (ADS)

    Levy, M. F.

    The introduction of Global System for Mobility (GSM) systems, with the use of microcells, has shifted the emphasis in mobile radio propagation modeling towards deterministic models. These models will become more and more relevant with the development of 3-dimensional building databases for most large cities. Ultimately 3-dimensional methods are needed in order to model combined diffraction effects around the sides and over the top of a building, and also to account for backscattering from nearby buildings. However an accurate 2-dimensional model can be very useful for assessment of multiple diffraction effects in a vertical plane. Renewed interest in accurate diffraction models has led to further developments of parabolic equation techniques. In this paper, we present 2-dimensional results obtained with a wide-angle PE code, and some examples of current 3D capabilities. The methods are immediately applicable to the planning of microcellular networks.

  7. A GUINIER CAMERA FOR SR POWDER DIFFRACTION: HIGH RESOLUTION AND HIGH THROUGHPUT.

    SciTech Connect

    SIDDONS,D.P.; HULBERT, S.L.; STEPHENS, P.W.

    2006-05-28

    The paper describe a new powder diffraction instrument for synchrotron radiation sources which combines the high throughput of a position-sensitive detector system with the high resolution normally only provided by a crystal analyzer. It uses the Guinier geometry which is traditionally used with an x-ray tube source. This geometry adapts well to the synchrotron source, provided proper beam conditioning is applied. The high brightness of the SR source allows a high resolution to be achieved. When combined with a photon-counting silicon microstrip detector array, the system becomes a powerful instrument for radiation-sensitive samples or time-dependent phase transition studies.

  8. Improved longitudinal resolution in tomographic diffractive microscopy with an ellipsoidal mirror.

    PubMed

    Ding, C; Tan, Z

    2016-04-01

    Tomographic diffractive microscopy is a technique, which is able to image transparent unstained samples with high resolution. The three-dimensional distribution of the complex refractive index can be reconstructed quantitatively from the measured scattered fields under various illumination and detection angles, according to the diffraction tomography theorem. We propose a tomographic diffractive microscopy setup with an ellipsoidal mirror as the light collector. We demonstrate analytically and with numerical simulation that this approach permits to obtain images with drastically improved resolution.

  9. High throughput screening of ligand binding to macromolecules using high resolution powder diffraction

    DOEpatents

    Von Dreele, Robert B.; D'Amico, Kevin

    2006-10-31

    A process is provided for the high throughput screening of binding of ligands to macromolecules using high resolution powder diffraction data including producing a first sample slurry of a selected polycrystalline macromolecule material and a solvent, producing a second sample slurry of a selected polycrystalline macromolecule material, one or more ligands and the solvent, obtaining a high resolution powder diffraction pattern on each of said first sample slurry and the second sample slurry, and, comparing the high resolution powder diffraction pattern of the first sample slurry and the high resolution powder diffraction pattern of the second sample slurry whereby a difference in the high resolution powder diffraction patterns of the first sample slurry and the second sample slurry provides a positive indication for the formation of a complex between the selected polycrystalline macromolecule material and at least one of the one or more ligands.

  10. High-resolution neutron and X-ray diffraction room-temperature studies of an H-FABP–oleic acid complex: study of the internal water cluster and ligand binding by a transferred multipolar electron-density distribution

    PubMed Central

    Howard, E. I.; Guillot, B.; Blakeley, M. P.; Haertlein, M.; Moulin, M.; Mitschler, A.; Cousido-Siah, A.; Fadel, F.; Valsecchi, W. M.; Tomizaki, Takashi; Petrova, T.; Claudot, J.; Podjarny, A.

    2016-01-01

    Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader’s quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H⋯H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface. PMID:27006775

  11. High Resolution Triple Axis X-Ray Diffraction Analysis of II-VI Semiconductor Crystals

    NASA Technical Reports Server (NTRS)

    Volz, H. M.; Matyi, R. J.

    1999-01-01

    The objective of this research program is to develop methods of structural analysis based on high resolution triple axis X-ray diffractometry (HRTXD) and to carry out detailed studies of defect distributions in crystals grown in both microgravity and ground-based environments. HRTXD represents a modification of the widely used double axis X-ray rocking curve method for the characterization of grown-in defects in nearly perfect crystals. In a double axis rocking curve experiment, the sample is illuminated by a monochromatic X-ray beam and the diffracted intensity is recorded by a fixed, wide-open detector. The intensity diffracted by the sample is then monitored as the sample is rotated through the Bragg reflection condition. The breadth of the peak, which is often reported as the full angular width at half the maximum intensity (FWHM), is used as an indicator of the amount of defects in the sample. This work has shown that high resolution triple axis X-ray diffraction is an effective tool for characterizing the defect structure in semiconductor crystals, particularly at high defect densities. Additionally, the technique is complimentary to X-ray topography for defect characterization in crystals.

  12. Conical diffraction illumination opens the way for low phototoxicity super-resolution imaging

    PubMed Central

    Caron, Julien; Fallet, Clément; Tinevez, Jean-Yves; Moisan, Lionel; Braitbart, L Philippe (Ori); Sirat, Gabriel Y; Shorte, Spencer L

    2014-01-01

    We present a new technology for super-resolution fluorescence imaging, based on conical diffraction. Conical diffraction is a linear, singular phenomenon, taking place when a laser beam is diffracted through a biaxial crystal. We use conical diffraction in a thin biaxial crystal to generate illumination patterns that are more compact than the classical Gaussian beam, and use them to generate a super-resolution imaging modality. While there already exist several super-resolution modalities, our technology (biaxial super-resolution: BSR) is distinguished by the unique combination of several performance features. Using BSR super-resolution data are achieved using low light illumination significantly less than required for classical confocal imaging, which makes BSR ideal for live-cell, long-term time-lapse super-resolution imaging. Furthermore, no specific sample preparation is required, and any fluorophore can be used. Perhaps most exciting, improved resolution BSR-imaging resolution enhancement can be achieved with any type of objective no matter the magnification, numerical aperture, working distance, or the absence or presence of immersion medium. In this article, we present the first implementation of BSR modality on a commercial confocal microscope. We acquire and analyze validation data, showing high quality super-resolved images of biological objects, and demonstrate the wide applicability of the technology. We report live-cell super-resolution imaging over a long period, and show that the light dose required for super-resolution imaging is far below the threshold likely to generate phototoxicity. PMID:25482642

  13. Conical diffraction illumination opens the way for low phototoxicity super-resolution imaging.

    PubMed

    Caron, Julien; Fallet, Clément; Tinevez, Jean-Yves; Moisan, Lionel; Braitbart, L Philippe Ori; Sirat, Gabriel Y; Shorte, Spencer L

    2014-01-01

    We present a new technology for super-resolution fluorescence imaging, based on conical diffraction. Conical diffraction is a linear, singular phenomenon, taking place when a laser beam is diffracted through a biaxial crystal. We use conical diffraction in a thin biaxial crystal to generate illumination patterns that are more compact than the classical Gaussian beam, and use them to generate a super-resolution imaging modality. While there already exist several super-resolution modalities, our technology (biaxial super-resolution: BSR) is distinguished by the unique combination of several performance features. Using BSR super-resolution data are achieved using low light illumination significantly less than required for classical confocal imaging, which makes BSR ideal for live-cell, long-term time-lapse super-resolution imaging. Furthermore, no specific sample preparation is required, and any fluorophore can be used. Perhaps most exciting, improved resolution BSR-imaging resolution enhancement can be achieved with any type of objective no matter the magnification, numerical aperture, working distance, or the absence or presence of immersion medium. In this article, we present the first implementation of BSR modality on a commercial confocal microscope. We acquire and analyze validation data, showing high quality super-resolved images of biological objects, and demonstrate the wide applicability of the technology. We report live-cell super-resolution imaging over a long period, and show that the light dose required for super-resolution imaging is far below the threshold likely to generate phototoxicity.

  14. High-resolution ab initio Three-dimensional X-ray Diffraction Microscopy

    SciTech Connect

    Chapman, H N; Barty, A; Marchesini, S; Noy, A; Cui, C; Howells, M R; Rosen, R; He, H; Spence, J H; Weierstall, U; Beetz, T; Jacobsen, C; Shapiro, D

    2005-08-19

    Coherent X-ray diffraction microscopy is a method of imaging non-periodic isolated objects at resolutions only limited, in principle, by the largest scattering angles recorded. We demonstrate X-ray diffraction imaging with high resolution in all three dimensions, as determined by a quantitative analysis of the reconstructed volume images. These images are retrieved from the 3D diffraction data using no a priori knowledge about the shape or composition of the object, which has never before been demonstrated on a non-periodic object. We also construct 2D images of thick objects with infinite depth of focus (without loss of transverse spatial resolution). These methods can be used to image biological and materials science samples at high resolution using X-ray undulator radiation, and establishes the techniques to be used in atomic-resolution ultrafast imaging at X-ray free-electron laser sources.

  15. High-resolution ab initio three-dimensional x-ray diffraction microscopy

    SciTech Connect

    Chapman, Henry N.; Barty, Anton; Marchesini, Stefano; Noy, Aleksandr; Hau-Riege, Stefan P.; Cui, Congwu; Howells, Malcolm R.; Rosen, Rachel; He, Haifeng; Spence, John C. H.; Weierstall, Uwe; Beetz, Tobias; Jacobsen, Chris; Shapiro, David

    2006-01-01

    Coherent x-ray diffraction microscopy is a method of imaging nonperiodic isolated objects at resolutions limited, in principle, by only the wavelength and largest scattering angles recorded. We demonstrate x-ray diffraction imaging with high resolution in all three dimensions, as determined by a quantitative analysis of the reconstructed volume images. These images are retrieved from the three-dimensional diffraction data using no a priori knowledge about the shape or composition of the object, which has never before been demonstrated on a nonperiodic object. We also construct two-dimensional images of thick objects with greatly increased depth of focus (without loss of transverse spatial resolution). These methods can be used to image biological and materials science samples at high resolution with x-ray undulator radiation and establishes the techniques to be used in atomic-resolution ultrafast imaging at x-ray free-electron laser sources.

  16. High-resolution ab initio three-dimensional x-ray diffraction microscopy

    DOE PAGES

    Chapman, Henry N.; Barty, Anton; Marchesini, Stefano; ...

    2006-01-01

    Coherent x-ray diffraction microscopy is a method of imaging nonperiodic isolated objects at resolutions limited, in principle, by only the wavelength and largest scattering angles recorded. We demonstrate x-ray diffraction imaging with high resolution in all three dimensions, as determined by a quantitative analysis of the reconstructed volume images. These images are retrieved from the three-dimensional diffraction data using no a priori knowledge about the shape or composition of the object, which has never before been demonstrated on a nonperiodic object. We also construct two-dimensional images of thick objects with greatly increased depth of focus (without loss of transverse spatialmore » resolution). These methods can be used to image biological and materials science samples at high resolution with x-ray undulator radiation and establishes the techniques to be used in atomic-resolution ultrafast imaging at x-ray free-electron laser sources.« less

  17. High Resolution X-Ray Diffraction of Macromolecules with Synchrotron Radiation

    NASA Technical Reports Server (NTRS)

    Stojanoff, Vivian; Boggon, Titus; Helliwell, John R.; Judge, Russell; Olczak, Alex; Snell, Edward H.; Siddons, D. Peter; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We recently combined synchrotron-based monochromatic X-ray diffraction topography methods with triple axis diffractometry and rocking curve measurements: high resolution X-ray diffraction imaging techniques, to better understand the quality of protein crystals. We discuss these methods in the light of results obtained on crystals grown under different conditions. These non destructive techniques are powerful tools in the characterization of the protein crystals and ultimately will allow to improve, develop, and understand protein crystal growth. High resolution X-ray diffraction imaging methods will be discussed in detail in light of recent results obtained on Hen Egg White Lysozyme crystals and other proteins.

  18. Numerical study of grating-assisted optical diffraction tomography

    SciTech Connect

    Chaumet, Patrick C.; Belkebir, Kamal; Sentenac, Anne

    2007-07-15

    We study the resolution of an optical diffraction tomography system in which the objects are either in an homogeneous background or deposited onto a glass prism, a prism surmounted by a thin metallic film or a prism surmounted by a metallic film covered by a periodically nanostructured dielectric layer. For all these configurations, we present an inversion procedure that yields the map of the relative permittivity of the objects from their diffracted far field. When multiple scattering can be neglected, we show that the homogeneous, prism, and metallic film configurations yield a resolution about {lambda}/4 while the grating substrate yields a resolution better than {lambda}/10. When Born approximation fails, we point out that it is possible to neglect the coupling between the object and the substrate and account solely for the multiple scattering within the objects to obtain a satisfactory reconstruction. Last, we present the robustness of our inversion procedure to noise.

  19. Resolution enhancement in coherent x-ray diffraction imaging by overcoming instrumental noise.

    PubMed

    Kim, Chan; Kim, Yoonhee; Song, Changyong; Kim, Sang Soo; Kim, Sunam; Kang, Hyon Chol; Hwu, Yeukuang; Tsuei, Ku-Ding; Liang, Keng San; Noh, Do Young

    2014-11-17

    We report that reference objects, strong scatterers neighboring weak phase objects, enhance the phase retrieval and spatial resolution in coherent x-ray diffraction imaging (CDI). A CDI experiment with Au nano-particles exhibited that the reference objects amplified the signal-to-noise ratio in the diffraction intensity at large diffraction angles, which significantly enhanced the image resolution. The interference between the diffracted x-ray from reference objects and a specimen also improved the retrieval of the phase of the diffraction signal. The enhancement was applied to image NiO nano-particles and a mitochondrion and confirmed in a simulation with a bacteria phantom. We expect that the proposed method will be of great help in imaging weakly scattering soft matters using coherent x-ray sources including x-ray free electron lasers.

  20. A Curved Image-Plate Detector System for High-Resolution Synchrotron X-ray Diffraction

    SciTech Connect

    Sarin, P.; Haggerty, R; Yoon, W; Knapp, M; Berghaeuser, A; Zschack, P; Karapetrova, E; Yang, N; Kriven, W

    2009-01-01

    The developed curved image plate (CIP) is a one-dimensional detector which simultaneously records high-resolution X-ray diffraction (XRD) patterns over a 38.7 2{theta} range. In addition, an on-site reader enables rapid extraction, transfer and storage of X-ray intensity information in {le}30 s, and further qualifies this detector to study kinetic processes in materials science. The CIP detector can detect and store X-ray intensity information linearly proportional to the incident photon flux over a dynamical range of about five orders of magnitude. The linearity and uniformity of the CIP detector response is not compromised in the unsaturated regions of the image plate, regardless of saturation in another region. The speed of XRD data acquisition together with excellent resolution afforded by the CIP detector is unique and opens up wide possibilities in materials research accessible through X-ray diffraction. This article presents details of the basic features, operation and performance of the CIP detector along with some examples of applications, including high-temperature XRD.

  1. Surface diffusion studies by optical diffraction techniques

    SciTech Connect

    Xiao, X.D.

    1992-11-01

    The newly developed optical techniques have been combined with either second harmonic (SH) diffraction or linear diffraction off a monolayer adsorbate grating for surface diffusion measurement. Anisotropy of surface diffusion of CO on Ni(l10) was used as a demonstration for the second harmonic dim reaction method. The linear diffraction method, which possesses a much higher sensitivity than the SH diffraction method, was employed to study the effect of adsorbate-adsorbate interaction on CO diffusion on Ni(l10) surface. Results showed that only the short range direct CO-CO orbital overlapping interaction influences CO diffusion but not the long range dipole-dipole and CO-NI-CO interactions. Effects of impurities and defects on surface diffusion were further explored by using linear diffraction method on CO/Ni(110) system. It was found that a few percent S impurity can alter the CO diffusion barrier height to a much higher value through changing the Ni(110) surface. The point defects of Ni(l10) surface seem to speed up CO diffusion significantly. A mechanism with long jumps over multiple lattice distance initiated by CO filled vacancy is proposed to explain the observed defect effect.

  2. Diffraction pattern study for cell type identification.

    PubMed

    Mihailescu, M; Costescu, J

    2012-01-16

    This paper presents our study regarding diffracted intensity distribution in Fresnel and Fraunhofer approximation from different cell types. Starting from experimental information obtained through digital holographic microscopy, we modeled the cell shapes as oblate spheroids and built their phase-only transmission functions. In Fresnel approximation, the experimental and numerical diffraction patterns from mature and immature red blood cells have complementary central intensity values at different distances. The Fraunhofer diffraction patterns of deformed red blood cells were processed in the reciprocal space where, the isoamplitude curves were formed independently for each degree of cell deformation present within every sample; the values on each separate isoamplitude curve are proportional with the percentage of the respective cell type within the sample.

  3. High-resolution x-ray diffraction microscopy of specifically labeled yeast cells

    DOE PAGES

    Nelson, Johanna; Huang, Xiaojing; Steinbrener, Jan; ...

    2010-04-20

    X-ray diffraction microscopy complements other x-ray microscopy methods by being free of lens-imposed radiation dose and resolution limits, and it allows for high-resolution imaging of biological specimens too thick to be viewed by electron microscopy. We report here the highest resolution (11-13 nm) x-ray diffraction micrograph of biological specimens, and a demonstration of molecular-specific gold labeling at different depths within cells via through-focus propagation of the reconstructed wavefield. The lectin concanavalin A conjugated to colloidal gold particles was used to label the α-mannan sugar in the cell wall of the yeast Saccharomyces cerevisiae. Cells were plunge-frozen in liquid ethane andmore » freeze-dried, after which they were imaged whole using x-ray diffraction microscopy at 750 eV photon energy.« less

  4. High-resolution x-ray diffraction microscopy of specifically labeled yeast cells

    SciTech Connect

    Nelson, Johanna; Huang, Xiaojing; Steinbrener, Jan; Shapiro, David; Kirz, Janos; Marchesini, Stephano; Neiman, Aaron M.; Turner, Joshua J.; Jacobsen, Chris

    2010-04-20

    X-ray diffraction microscopy complements other x-ray microscopy methods by being free of lens-imposed radiation dose and resolution limits, and it allows for high-resolution imaging of biological specimens too thick to be viewed by electron microscopy. We report here the highest resolution (11-13 nm) x-ray diffraction micrograph of biological specimens, and a demonstration of molecular-specific gold labeling at different depths within cells via through-focus propagation of the reconstructed wavefield. The lectin concanavalin A conjugated to colloidal gold particles was used to label the α-mannan sugar in the cell wall of the yeast Saccharomyces cerevisiae. Cells were plunge-frozen in liquid ethane and freeze-dried, after which they were imaged whole using x-ray diffraction microscopy at 750 eV photon energy.

  5. High-resolution x-ray diffraction of epitaxial bismuth chalcogenide topological insulator layers

    NASA Astrophysics Data System (ADS)

    Holý, V.; Kriegner, D.; Steiner, H.; Stangl, J.; Bauer, G.; Springholz, G.

    2017-03-01

    Stoichiometry and lattice structure of epitaxial layers of topological insulators Bi2Te3 and Bi2Se3 grown by molecular-beam epitaxy is studied by high-resolution x-ray diffraction. We show that the stoichiometry of Bi2X3 – δ (X  =  Te, Se) epitaxial layers depends on the additional flux of the chalcogens Te or Se during growth. If no excess flux is employed, the resulting structure is very close to Bi1X1 (δ  =  1), whereas with a high excess flux the stoichiometric Bi2X3 phase is obtained. From the x-ray data we determined the lattice parameters of the layers and their dependence on composition δ, as well as the degree of crystal quality of the layers. Invited talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8–12 November 2016, Ha Long City, Vietnam.

  6. Optimizing Crystal Volume for Neutron Diffraction Studies

    NASA Technical Reports Server (NTRS)

    Snell, E. H.

    2003-01-01

    For structural studies with neutron diffraction more intense neutron sources, improved sensitivity detector and larger volume crystals are all means by which the science is being advanced to enable studies on a wider range of samples. We have chosen a simplistic approach using a well understood crystallization method, with minimal amounts of sample and using design of experiment techniques to maximize the crystal volume all for minimum effort. Examples of the application are given.

  7. High spatial resolution X-ray and gamma ray imaging system using diffraction crystals

    DOEpatents

    Smither, Robert K.

    2011-05-17

    A method and a device for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation are provided. The device comprises a plurality of arrays, with each array comprising a plurality of elements comprising a first collimator, a diffracting crystal, a second collimator, and a detector.

  8. DNA hydration studied by neutron fiber diffraction

    SciTech Connect

    Fuller, W.; Forsyth, V.T.; Mahendrasingam, A.; Langan, P.; Pigram, W.J.

    1994-12-31

    The development of neutron high angle fiber diffraction to investigate the location of water around the deoxyribonucleic acid (DNA) double-helix is described. The power of the technique is illustrated by its application to the D and A conformations of DNA using the single crystal diffractometer, D19, at the Institute Laue-Langevin, Grenoble and the time of flight diffractometer, SXD, at the Rutherford Appleton ISIS Spallation Neutron Source. These studies show the existence of bound water closely associated with the DNA. The patterns of hydration in these two DNA conformations are quite distinct and are compared to those observed in X-ray single crystal studies of two-stranded oligodeoxynucleotides. Information on the location of water around the DNA double-helix from the neutron fiber diffraction studies is combined with that on the location of alkali metal cations from complementary X-ray high angle fiber diffraction studies at the Daresbury Laboratory SRS using synchrotron radiation. These analyses emphasize the importance of viewing DNA, water and ions as a single system with specific interactions between the three components and provide a basis for understanding the effect of changes in the concentration of water and ions in inducing conformations] transitions in the DNA double-helix.

  9. Diffraction studies of papaya mosaic virus.

    PubMed

    Tollin, P; Bancroft, J B; Richardson, J F; Payne, N C; Beveridge, T J

    1979-10-15

    X-ray and optical diffraction studies of the flexuous papaya mosaic virus are described. The virus is constructed so that there are 35 coat protein subunits in 4 turns of the helix. The virus contains about 1410 protein subunits and 6800 nucleotides and has a molecular weight of about 33 x 10(6). The structure of tubes assembled in vitro from coat protein both in the presence and absence of nucleic acid resembles that of the native virus.

  10. Very High Resolution Solar X-ray Imaging Using Diffractive Optics

    NASA Technical Reports Server (NTRS)

    Dennis, B. R.; Skinner, G. K.; Li, M. J.; Shih, A. Y.

    2012-01-01

    This paper describes the development of X-ray diffractive optics for imaging solar flares with better than 0.1 arcsec angular resolution. X-ray images with this resolution of the greater than or equal to 10 MK plasma in solar active regions and solar flares would allow the cross-sectional area of magnetic loops to be resolved and the coronal flare energy release region itself to be probed. The objective of this work is to obtain X-ray images in the iron-line complex at 6.7 keV observed during solar flares with an angular resolution as fine as 0.1 arcsec - over an order of magnitude finer than is now possible. This line emission is from highly ionized iron atoms, primarily Fe xxv, in the hottest flare plasma at temperatures in excess of approximately equal to 10 MK. It provides information on the flare morphology, the iron abundance, and the distribution of the hot plasma. Studying how this plasma is heated to such high temperatures in such short times during solar flares is of critical importance in understanding these powerful transient events, one of the major objectives of solar physics.We describe the design, fabrication, and testing of phase zone plate X-ray lenses with focal lengths of approximately equal to 100 m at these energies that would be capable of achieving these objectives. We show how such lenses could be included on a two-spacecraft formation-flying mission with the lenses on the spacecraft closest to the Sun and an X-ray imaging array on the second spacecraft in the focal plane approximately equal to 100 m away. High resolution X-ray images could be obtained when the two spacecraft are aligned with the region of interest on the Sun. Requirements and constraints for the control of the two spacecraft are discussed together with the overall feasibility of such a formation-flying mission.

  11. High resolution X-ray diffraction imaging of lead tin telluride

    NASA Technical Reports Server (NTRS)

    Steiner, Bruce; Dobbyn, Ronald C.; Black, David; Burdette, Harold; Kuriyama, Masao; Spal, Richard; Simchick, Richard; Fripp, Archibald

    1991-01-01

    High resolution X-ray diffraction images of two directly comparable crystals of lead tin telluride, one Bridgman-grown on Space Shuttle STS 61A and the other terrestrially Bridgman-grown under similar conditions from identical material, present different subgrain structure. In the terrestrial, sample 1 the appearance of an elaborate array of subgrains is closely associated with the intrusion of regions that are out of diffraction in all of the various images. The formation of this elaborate subgrain structure is inhibited by growth in microgravity.

  12. Beamline I11 at Diamond: a new instrument for high resolution powder diffraction.

    PubMed

    Thompson, S P; Parker, J E; Potter, J; Hill, T P; Birt, A; Cobb, T M; Yuan, F; Tang, C C

    2009-07-01

    The performance characteristics of a new synchrotron x-ray powder diffraction beamline (I11) at the Diamond Light Source are presented. Using an in-vacuum undulator for photon production and deploying simple x-ray optics centered around a double-crystal monochromator and a pair of harmonic rejection mirrors, a high brightness and low bandpass x-ray beam is delivered at the sample. To provide fast data collection, 45 Si(111) analyzing crystals and detectors are installed onto a large and high precision diffractometer. High resolution powder diffraction data from standard reference materials of Si, alpha-quartz, and LaB6 are used to characterize instrumental performance.

  13. Simple fiber-optic confocal microscopy with nanoscale depth resolution beyond the diffraction barrier.

    PubMed

    Ilev, Ilko; Waynant, Ronald; Gannot, Israel; Gandjbakhche, Amir

    2007-09-01

    A novel fiber-optic confocal approach for ultrahigh depth-resolution (diffraction barrier in the subwavelength nanometric range below 200 nm is presented. The key idea is based on a simple fiber-optic confocal microscope approach that is compatible with a differential confocal microscope technique. To improve the dynamic range of the resolving laser power and to achieve a high resolution in the nanometric range, we have designed a simple apertureless reflection confocal microscope with a highly sensitive single-mode-fiber confocal output. The fiber-optic design is an effective alternative to conventional pinhole-based confocal systems and offers a number of advantages in terms of spatial resolution, flexibility, miniaturization, and scanning potential. Furthermore, the design is compatible with the differential confocal pinhole microscope based on the use of the sharp diffraction-free slope of the axial confocal response curve rather than the area around the maximum of that curve. Combining the advantages of ultrahigh-resolution fiber-optic confocal microscopy, we can work beyond the diffraction barrier in the subwavelength (below 200 nm) nanometric range exploiting confocal nanobioimaging of single cell and intracellular analytes.

  14. Ultra-high aspect ratio high-resolution nanofabrication for hard X-ray diffractive optics.

    PubMed

    Chang, Chieh; Sakdinawat, Anne

    2014-06-27

    Although diffractive optics have played a major role in nanoscale soft X-ray imaging, high-resolution and high-efficiency diffractive optics have largely been unavailable for hard X-rays where many scientific, technological and biomedical applications exist. This is owing to the long-standing challenge of fabricating ultra-high aspect ratio high-resolution dense nanostructures. Here we report significant progress in ultra-high aspect ratio nanofabrication of high-resolution, dense silicon nanostructures using vertical directionality controlled metal-assisted chemical etching. The resulting structures have very smooth sidewalls and can be used to pattern arbitrary features, not limited to linear or circular. We focus on the application of X-ray zone plate fabrication for high-efficiency, high-resolution diffractive optics, and demonstrate the process with linear, circular, and spiral zone plates. X-ray measurements demonstrate high efficiency in the critical outer layers. This method has broad applications including patterning for thermoelectric materials, battery anodes and sensors among others.

  15. Pinhole diffraction holography for fabrication of high-resolution Fresnel zone plates.

    PubMed

    Sarkar, Sankha S; Solak, Harun H; David, Christian; van der Veen, J Friso

    2014-01-27

    Fresnel zone plates (FZPs) play an essential role in high spatial resolution x-ray imaging and analysis of materials in many fields. These diffractive lenses are commonly made by serial writing techniques such as electron beam or focused ion beam lithography. Here we show that pinhole diffraction holography has potential to generate FZP patterns that are free from aberrations and imperfections that may be present in alternative fabrication techniques. In this presented method, FZPs are fabricated by recording interference pattern of a spherical wave generated by diffraction through a pinhole, illuminated with coherent plane wave at extreme ultraviolet (EUV) wavelength. Fundamental and practical issues involved in formation and recording of the interference pattern are considered. It is found that resolution of the produced FZP is directly related to the diameter of the pinhole used and the pinhole size cannot be made arbitrarily small as the transmission of EUV or x-ray light through small pinholes diminishes due to poor refractive index contrast found between materials in these spectral ranges. We also find that the practical restrictions on exposure time due to the light intensity available from current sources directly imposes a limit on the number of zones that can be printed with this method. Therefore a trade-off between the resolution and the FZP diameter exists. Overall, we find that this method can be used to fabricate aberration free FZPs down to a resolution of about 10 nm.

  16. Electron Diffraction and High-Resolution Electron Microscopy of Mineral Structures

    NASA Astrophysics Data System (ADS)

    Nord, Gordon L., Jr.

    This book is a well-written English translation of the original 1981 Russian edition, Strukturnoye issledovaniye mineralov metodami mikrodifraktsii i elechtronnoi mikroskopii vysokogo razresheniya. The 1987 English version has been extensively updated and includes references up to 1986. The book is essentially a text on the theoretical and experimental aspects of transmission electron microscopy and has chapters on the reciprocal lattice, electron diffraction (both kinematic and dynamic), and high-resolution electron microscopy.Electron diffraction is emphasized, especially its use for structure analysis of poorly crystalline and fine-grained phases not readily determined by the more exact X ray diffraction method. Two methods of electron diffraction are discussed: selected area electron diffraction (SAED) and oblique-texture electron diffraction (OTED); the latter technique is rarely used in the west and is never discussed in western electron microscopy texts. A SAED pattern is formed by isolating a small micrometer-size area with an aperture and obtaining single-crystal patterns from the diffracted beams. By tilting the sample and obtaining many patterns, a complete picture of the reciprocal lattice can be taken. An OTED pattern is formed when the incident electron beam passes through an inclined preparation consisting of a great number of thin platy crystals lying normal to the texture axis (axis normal to the support grid). To form an OTED pattern, the plates must all lie on a common face, such as a basal plane in phyllosilicates. Upon tilting the plates, an elliptical powder diffraction pattern is formed. Intensities measured from these patterns are used for a structural analysis of the platy minerals.

  17. Coherent diffractive imaging of time-evolving samples with improved temporal resolution

    NASA Astrophysics Data System (ADS)

    Ulvestad, A.; Tripathi, A.; Hruszkewycz, S. O.; Cha, W.; Wild, S. M.; Stephenson, G. B.; Fuoss, P. H.

    2016-05-01

    Bragg coherent x-ray diffractive imaging is a powerful technique for investigating dynamic nanoscale processes in nanoparticles immersed in reactive, realistic environments. Its temporal resolution is limited, however, by the oversampling requirements of three-dimensional phase retrieval. Here, we show that incorporating the entire measurement time series, which is typically a continuous physical process, into phase retrieval allows the oversampling requirement at each time step to be reduced, leading to a subsequent improvement in the temporal resolution by a factor of 2-20 times. The increased time resolution will allow imaging of faster dynamics and of radiation-dose-sensitive samples. This approach, which we call "chrono CDI," may find use in improving the time resolution in other imaging techniques.

  18. Coherent diffractive imaging of time-evolving samples with improved temporal resolution

    SciTech Connect

    Ulvestad, A.; Tripathi, A.; Hruszkewycz, S. O.; Cha, W.; Wild, S. M.; Stephenson, G. B.; Fuoss, P. H.

    2016-05-19

    Bragg coherent x-ray diffractive imaging is a powerful technique for investigating dynamic nanoscale processes in nanoparticles immersed in reactive, realistic environments. Its temporal resolution is limited, however, by the oversampling requirements of three-dimensional phase retrieval. Here, we show that incorporating the entire measurement time series, which is typically a continuous physical process, into phase retrieval allows the oversampling requirement at each time step to be reduced, leading to a subsequent improvement in the temporal resolution by a factor of 2-20 times. The increased time resolution will allow imaging of faster dynamics and of radiation-dose-sensitive samples. This approach, which we call "chrono CDI," may find use in improving the time resolution in other imaging techniques.

  19. Super-accuracy and super-resolution getting around the diffraction limit.

    PubMed

    Toprak, Erdal; Kural, Comert; Selvin, Paul R

    2010-01-01

    In many research areas such as biology, biochemistry, and biophysics, measuring distances or identifying and counting objects can be of great importance. To do this, researchers often need complicated and expensive tools in order to have accurate measurements. In addition, these measurements are often done under nonphysiological settings. X-ray diffraction, for example, gets Angstrom-level structures, but it requires crystallizing a biological specimen. Electron microscopy (EM) has about 10A resolution, but often requires frozen (liquid nitrogen) samples. Optical microscopy, while coming closest to physiologically relevant conditions, has been limited by the minimum distances to be measured, typically about the diffraction limit, or approximately 200 nm. However, most biological molecules are <5-10nm in diameter, and getting molecular details requires imaging at this scale. In this chapter, we will describe some of the experimental approaches, from our lab and others, that push the limits of localization accuracy and optical resolution in fluorescence microscopy.

  20. High resolution x-ray and gamma ray imaging using diffraction lenses with mechanically bent crystals

    DOEpatents

    Smither, Robert K.

    2008-12-23

    A method for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation is provided. High quality mechanically bent diffracting crystals of 0.1 mm radial width are used for focusing the radiation and directing the radiation to an array of detectors which is used for analyzing their addition to collect data as to the location of the source of radiation. A computer is used for converting the data to an image. The invention also provides for the use of a multi-component high resolution detector array and for narrow source and detector apertures.

  1. Neutron diffraction studies of viral fusion peptides

    NASA Astrophysics Data System (ADS)

    Bradshaw, Jeremy P.; J. M. Darkes, Malcolm; Katsaras, John; Epand, Richard M.

    2000-03-01

    Membrane fusion plays a vital role in a large and diverse number of essential biological processes. Despite this fact, the precise molecular events that occur during fusion are still not known. We are currently engaged on a study of membrane fusion as mediated by viral fusion peptides. These peptides are the N-terminal regions of certain viral envelope proteins that mediate the process of fusion between the viral envelope and the membranes of the host cell during the infection process. As part of this study, we have carried out neutron diffraction measurements at the ILL, BeNSC and Chalk River, on a range of viral fusion peptides. The peptides, from simian immunodeficiency virus (SIV), influenza A and feline leukaemia virus (FeLV), were incorporated into stacked phospholipid bilayers. Some of the peptides had been specifically deuterated at key amino acids. Lamellar diffraction data were collected and analysed to yield information on the peptide conformation, location and orientation relative to the bilayer.

  2. Structural anomalies in undoped Gallium Arsenide observed in high resolution diffraction imaging with monochromatic synchrotron radiation

    NASA Technical Reports Server (NTRS)

    Steiner, B.; Kuriyama, M.; Dobbyn, R. C.; Laor, U.; Larson, D.; Brown, M.

    1988-01-01

    Novel, streak-like disruption features restricted to the plane of diffraction have recently been observed in images obtained by synchrotron radiation diffraction from undoped, semi-insulating gallium arsenide crystals. These features were identified as ensembles of very thin platelets or interfaces lying in (110) planes, and a structural model consisting of antiphase domain boundaries was proposed. We report here the other principal features observed in high resolution monochromatic synchrotron radiation diffraction images: (quasi) cellular structure; linear, very low-angle subgrain boundaries in (110) directions, and surface stripes in a (110) direction. In addition, we report systematic differences in the acceptance angle for images involving various diffraction vectors. When these observations are considered together, a unifying picture emerges. The presence of ensembles of thin (110) antiphase platelet regions or boundaries is generally consistent not only with the streak-like diffraction features but with the other features reported here as well. For the formation of such regions we propose two mechanisms, operating in parallel, that appear to be consistent with the various defect features observed by a variety of techniques.

  3. Time-resolved diffraction and interference: Young's interference with photons of different energy as revealed by time resolution.

    PubMed

    Garcia, N; Saveliev, I G; Sharonov, M

    2002-05-15

    We present time-resolved diffraction and two-slit interference experiments using a streak camera as a detector for femtosecond pulses of photons. These experiments show how the diffraction pattern is built by adding frames of a few photons to each frame. It is estimated that after 300 photons the diffraction pattern emerges. With time resolution we can check the speed of light and put an upper limit of 2 ps at our resolution to the time for wave function collapse in the quantum measurement process. We then produce interference experiments with photons of different energies impinging on the slits, i.e. we know which photon impinges on each slit. We show that for poor time resolution, no interference is observed, but for high time resolution, we have interference that is revealed as beats of 100 GHz frequency. The condition for interference is that the two pulses should overlap spatially at the detector, even if the pulses have different energies but are generated from the same pulse of the laser. The interference seems to be in agreement with classical theory at first sight. However, closer study and analysis of the data show deviations in the visibility of the interference fringes and of their phase. These experiments are discussed in connection with quantum mechanics and it may be concluded that the time resolution provides new data for understanding the longstanding and continuing arguments on wave-particle duality initiated by Newton, Young, Fresnel, Planck and others. A thought experiment is presented in the appendix to try to distinguish the photons at the detector by making it sensitive to colour.

  4. Small angle detectors for study diffractive processes with CMS

    NASA Astrophysics Data System (ADS)

    Albrow, M.; Bell, A. J.; Enterria, D. d.; Hall-Wilton, R.; Los, S.; Mokhov, N.; Murray, M.; Penzo, A.; Popescu, S.; Ronzhin, A.; Samoylenko, V. D.; Sobol, A.; Veres, G.

    2014-10-01

    The approach and detectors for diffractive physics based on two current projects—Forward Shower Counter (FSC) and Proton Precision Spectrometer (PPS) are presented. FSC system consists of six (3+3) Stations of scintillator counters, which surround closely the beam pipes along 59 m < |z| < 140 m from IP5 on both plus (+) and minus (-) sides. These will detect showers from very forward particles with rapidity 7.5 < |η| < 10 interacting in the beam pipe and surrounding material. FSC allow measurements of single diffraction: p+p → p+G+X (where G is rapidity gap) for lower masses and double diffraction p+p → X+G+X with a large central rapidity gap. The counters can also be used for beam real-time monitoring and will make an invaluable contribution to the understanding of the background environment and its topology. PPS is designed for study the central exclusive production pp → p+X+p, where the + signs denote the absence of hadronic activity (that is, the presence of a rapidity gap) between the outgoing protons and the decay products of the central system X. The precise measurement of the kinematical parameters of the outgoing protons enables to study the properties of the central state X. In PPS part we consider the detector for high precision timing of these protons—QUARTIC. It consists of L-shape bars with quartz or sapphire radiator. The time resolution of the QUARTIC prototypes achieved ≈ 10 ps.

  5. Experimental study of spatial coherence diffraction based on full-field coherence visualization.

    PubMed

    Zhao, Juan; Wang, Wei

    2014-10-01

    A novel optical geometry for direct visualization of the optical coherence function is proposed. The diffractions of partially coherent light by apertures with various forms are experimentally investigated, and the full-field spatial coherence functions have been observed by using the proposed interferometric system. Similar to the well-known Airy disk stemming from optical diffraction, we studied the spatial coherence function near the coherence focal plane on the analogy of the Fraunhofer and Fresnel diffraction integrals. Following the conventional definitions for the optical resolutions in the optical imaging system, the lateral and longitudinal resolutions for spatial coherence imaging have been proposed.

  6. Diffraction Ellipsometry Studies of Skeletal Muscle Structure

    NASA Astrophysics Data System (ADS)

    Kerr, William Lloyd

    Many of the techniques used to study the structure and contraction mechanism of muscle rely on the interaction of light or other electromagnetic radiation with the muscle. Some of the most important of these techniques are light and electron microscopy, x-ray diffraction, spectroscopy of muscle fibers "labelled" with spin or fluorescent probes, visible spectrum diffraction, and transmission birefringence. Chapter I of this dissertation reviews these techniques, focussing on what they have to tell us about muscle structure. In Chapter II, we discuss experiments in which the microstructural features of relaxed, skinned fibers compressed with polyvinylpyrollidone were examined by optical diffraction ellipsometry. The change in polarization state of light after interacting with the muscle is described by the differential field ratio (DFR) and birefringence (Deltan). Compression of single fibers with 0%-21% PVP caused an increase in up to 23% and 31% for DFR and Deltan, respectively. Theoretical modelling suggests that the average S-1 tilt angle may be reduced upon compression of the filament lattice. This is supported by experiments in which S-1 was cleaved with alpha-chymotrypsin. Experiments comparing fibers with intact membranes and skinned fibers compressed to an equivalent lattice spacing showed little difference in DFR or Deltan. Chapter III deals with experiments on contracting, intact fibers. The differential field ratio (DFR) was monitored for tetanically contracting muscle fibers subject to rapid (<0.4 msec) release or stretch. Upon stimulation, DFR decreases 14% from its resting value; the half-time for the decrease leads that of tension rise by 10 msecs. This suggests that the movement of cross -bridges precedes tension development and that the average cross-bridge angle is more perpendicular in the contracting state. Upon rapid release of 0.5% of the fiber length, DFR decreases 9.5% further simultaneous with the length step. Rapid and slow recovery phases

  7. Ultrafast electron diffraction optimized for studying structural dynamics in thin films and monolayers

    PubMed Central

    Badali, D. S.; Gengler, R. Y. N.; Miller, R. J. D.

    2016-01-01

    A compact electron source specifically designed for time-resolved diffraction studies of free-standing thin films and monolayers is presented here. The sensitivity to thin samples is achieved by extending the established technique of ultrafast electron diffraction to the “medium” energy regime (1–10 kV). An extremely compact design, in combination with low bunch charges, allows for high quality diffraction in a lensless geometry. The measured and simulated characteristics of the experimental system reveal sub-picosecond temporal resolution, while demonstrating the ability to produce high quality diffraction patterns from atomically thin samples. PMID:27226978

  8. Revisit of alpha-chitin crystal structure using high resolution X-ray diffraction data.

    PubMed

    Sikorski, Pawel; Hori, Ritsuko; Wada, Masahisa

    2009-05-11

    High resolution synchrotron X-ray fiber diffraction data recorded from crab tendon chitin have been used to describe the crystal structure of alpha-chitin. Crystal structures at 100 and 300 K have been solved using restrained crystallographic refinement against diffraction intensities measured from the fiber diffraction patterns. The unit cell contains two polymer chains in a 2(1) helix conformation and in the antiparallel orientation. The best agreement between predicated and observed X-ray diffraction intensities is obtained for a model that includes two distinctive conformations of C6-O6 hydroxymethl group. Those conformations are different from what is proposed in the generally accepted alpha-chitin crystal structure (J. Mol. Biol. 1978, 120, 167-181). Based on refined positions of the O6 atoms, a network of hydrogen bonds involving O6 is proposed. This network of hydrogen bonds can explain the main features of the polarized FTIR spectra of alpha-chitin and sheds some light on the origin of splitting of the amide I band observed on alpha-chitin IR spectra.

  9. Enhancement of image resolution beyond the diffraction limit by double dark resonances

    NASA Astrophysics Data System (ADS)

    Verma, Onkar N.; Dey, Tarak N.

    2014-03-01

    We show how quantum coherence effects can be used to improve the resolution and the contrast of diffraction-limited images imprinted onto a probe field. The narrow and sharp spectral features generated by double dark resonances (DDR) are exploited to control absorption, dispersion, and diffraction properties of the medium. The spatially modulated control field can produce inhomogeneous susceptibility of the medium that encodes the spatial feature of the control image to probe field in the presence of DDR. The transmission of a cloned image can be enhanced by the use of an incoherent pump field. We find that the feature size of the cloned image is four times smaller than the initial characteristic size of the control image even though the control image is completely distorted after propagation through a 3-cm-long Rb vapor cell. We further discuss how spatial optical switching is possible by using induced transparency and absorption of the medium.

  10. Fluvial suspended sediment characteristics by high-resolution, surrogate metrics of turbidity, laser-diffraction, acoustic backscatter, and acoustic attenuation

    NASA Astrophysics Data System (ADS)

    Landers, Mark Newton

    Sedimentation is a primary and growing environmental, engineering, and agricultural issue around the world. However, collection of the data needed to develop solutions to sedimentation issues has declined by about three-fourths since 1983. Suspended-sediment surrogates have the potential to obtain sediment data using methods that are more accurate, of higher spatial and temporal resolution, and with less manually intensive, costly, and hazardous methods. The improved quality of sediment data from high-resolution surrogates may inform improved understanding and solutions to sedimentation problems. The field experiments for this research include physical samples of suspended sediment collected concurrently with surrogate metrics from instruments including 1.2, 1.5, and 3.0 megahertz frequency acoustic doppler current profilers, a nephelometric turbidity sensor, and a laser-diffraction particle size analyzer. This comprehensive data set was collected over five storms in 2009 and 2010 at Yellow River near Atlanta, Georgia. Fluvial suspended sediment characteristics in this study can be determined by high-resolution surrogate parameters of turbidity, laser-diffraction and acoustics with model errors 33% to 49% lower than traditional methods using streamflow alone. Hysteresis in sediment-turbidity relations for single storm events was observed and quantitatively related to PSD changes of less than 10 microns in the fine silt to clay size range. Suspended sediment particle size detection (PSD) is significantly correlated with ratios of measured acoustic attenuation at different frequencies; however the data do not fit the theoretical relations. Using both relative acoustic backscatter (RB) and acoustic attenuation as explanatory variables results in a significantly improved model of suspended sediment compared with traditional sonar equations using only RB. High resolution PSD data from laser diffraction provide uniquely valuable information; however the size detection

  11. Semiconductor-based superlens for subwavelength resolution below the diffraction limit at extreme ultraviolet frequencies

    NASA Astrophysics Data System (ADS)

    Vincenti, M. A.; D'Orazio, A.; Cappeddu, M. G.; Akozbek, Neset; Bloemer, M. J.; Scalora, M.

    2009-05-01

    We theoretically demonstrate negative refraction and subwavelength resolution below the diffraction limit in the UV and extreme UV ranges using semiconductors. The metal-like response of typical semiconductors such as GaAs or GaP makes it possible to achieve negative refraction and superguiding in resonant semiconductor/dielectric multilayer stacks, similar to what has been demonstrated in metallodielectric photonic band gap structures. The exploitation of this basic property in semiconductors raises the possibility of yet-untapped applications in the UV and soft x-ray ranges.

  12. High resolution diffraction imaging of crystals grown in microgravity and closely related terrestrial crystals

    NASA Technical Reports Server (NTRS)

    Steiner, B.; Dobbyn, R.; Black, D.; Burdette, H.; Kuriyama, M.; Spal, R.; Vandenberg, L.; Fripp, A.; Simchick, R.; Lal, R.

    1991-01-01

    Irregularities found in three crystals grown in space, in four crystals grown entirely on the ground were examined and compared. Irregularities were observed in mercuric iodide, lead tin telluride, triglycine sulfate, and gallium arsenide by high resolution synchrotron x radiation diffraction imaging. Radiation detectors made from mercuric iodide crystals grown in microgravity were reported to perform far better than conventional detectors grown from the same material under full gravity. Effort is now underway to reproduce these 'space' crystals, optimize their properties, and extend comparable superiority to other types of materials.

  13. High-resolution X-ray diffraction in crystalline structures with quantum dots

    NASA Astrophysics Data System (ADS)

    Punegov, V. I.

    2015-05-01

    We review the current status of nondestructive high-resolution X-ray diffractometry research on semiconductor structures with quantum dots (QDs). The formalism of the statistical theory of diffraction is used to consider the coherent and diffuse X-ray scattering in crystalline systems with nanoinclusions. Effects of the shape, elastic strain, and lateral and vertical QD correlation on the diffuse scattering angular distribution near the reciprocal lattice nodes are considered. Using short-period and multicomponent superlattices as an example, we demonstrate the efficiency of data-assisted simulations in the quantitative analysis of nanostructured materials.

  14. Strain mapping at nanometer resolution using advanced nano-beam electron diffraction

    SciTech Connect

    Ozdol, V. B.; Ercius, P.; Ophus, C.; Ciston, J.; Gammer, C. E-mail: aminor@lbl.gov; Jin, X. G.; Minor, A. M. E-mail: aminor@lbl.gov

    2015-06-22

    We report on the development of a nanometer scale strain mapping technique by means of scanning nano-beam electron diffraction. Only recently possible due to fast acquisition with a direct electron detector, this technique allows for strain mapping with a high precision of 0.1% at a lateral resolution of 1 nm for a large field of view reaching up to 1 μm. We demonstrate its application to a technologically relevant strain-engineered GaAs/GaAsP hetero-structure and show that the method can even be applied to highly defected regions with substantial changes in local crystal orientation. Strain maps derived from atomically resolved scanning transmission electron microscopy images were used to validate the accuracy, precision and resolution of this versatile technique.

  15. The Effect of Ionic Liquids on Protein Crystallization and X-ray Diffraction Resolution

    SciTech Connect

    Judge, Russell A.; Takahashi, Sumiko; Longenecker, Kenton L.; Fry, Elizabeth H.; Abad-Zapatero, Cele; Chiu, Mark L.

    2009-09-08

    Ionic liquids exhibit a variety of properties that make them attractive solvents for biomaterials. Given the potential for productive interaction between ionic liquids and biological macromolecules, we investigated the use of ionic liquids as precipitating agents and additives for protein crystallization for six model proteins (lysozyme, catalase, myoglobin, trypsin, glucose isomerase, and xylanase). The ionic liquids produced changes in crystal morphology and mediated significant increases in crystal size in some cases. Crystals grown using ionic liquids as precipitating agents or as additives provided X-ray diffraction resolution similar to or better than that obtained without ionic liquids. Based upon the experiments performed with model proteins, the ionic liquids were used as additives for the crystallization of the poorly diffracting monoclonal antibody 106.3 Fab in complex with the B-type natriuretic peptide (5-13). The ionic liquids improved the crystallization behavior and provided improved diffraction resulting in the determination of the structure. Ionic liquids should be considered as useful additives for the crystallization of other proteins.

  16. Coherent X-ray beam metrology using 2D high-resolution Fresnel-diffraction analysis.

    PubMed

    Ruiz-Lopez, M; Faenov, A; Pikuz, T; Ozaki, N; Mitrofanov, A; Albertazzi, B; Hartley, N; Matsuoka, T; Ochante, Y; Tange, Y; Yabuuchi, T; Habara, T; Tanaka, K A; Inubushi, Y; Yabashi, M; Nishikino, M; Kawachi, T; Pikuz, S; Ishikawa, T; Kodama, R; Bleiner, D

    2017-01-01

    Direct metrology of coherent short-wavelength beamlines is important for obtaining operational beam characteristics at the experimental site. However, since beam-time limitation imposes fast metrology procedures, a multi-parametric metrology from as low as a single shot is desirable. Here a two-dimensional (2D) procedure based on high-resolution Fresnel diffraction analysis is discussed and applied, which allowed an efficient and detailed beamline characterization at the SACLA XFEL. So far, the potential of Fresnel diffraction for beamline metrology has not been fully exploited because its high-frequency fringes could be only partly resolved with ordinary pixel-limited detectors. Using the high-spatial-frequency imaging capability of an irradiated LiF crystal, 2D information of the coherence degree, beam divergence and beam quality factor M(2) were retrieved from simple diffraction patterns. The developed beam metrology was validated with a laboratory reference laser, and then successfully applied at a beamline facility, in agreement with the source specifications.

  17. Effect of microscope parameter and specimen thickness of spatial resolution of transmission electron backscatter diffraction.

    PubMed

    Wang, Y Z; Kong, M G; Liu, Z W; Lin, C C; Zeng, Y

    2016-10-01

    The spatial resolution of transmission electron backscatter diffraction (t-EBSD) with a standard conventional EBSD detector was evaluated quantitatively based on the calculation of the correlation coefficient of transmission patterns which were acquired across a twin boundary in the sample of austenitic steel. The results showed that the resolution of t-EBSD improved from tens of nanometres to below 10 nm with increasing accelerating voltage and thinning of specimen thickness. High voltage could enhance the penetration depth and reduce the scattering angle. And the thinning of specimen thickness would result in decreasing of the scattering events according to the theory of thermal diffuse scattering (TDS). In addition, the transmission patterns were found to be weak and noisy if the specimen was too thin, because of the decreasing intensity detected by the screen. Consequently, in this work, the best spatial resolution of 7 nm was achieved at 30 kV and 41 nm thickness. Moreover, the specimen thickness range was also discussed using Monte-Carlo simulation. This approach was helpful to account for the differences of measured spatial resolutions, by t-EBSD, of lamellas with different thickness.

  18. High resolution electron diffraction analysis of structural changes associated with the photocycle of bacteriorhodopsin

    SciTech Connect

    Han, B. -G.

    1994-04-01

    Changes in protein structure that occur during the formation of the M photointermediate of bacteriorhodopsin can be directly visualized by electron diffraction techniques. Samples containing a high percentage of the M intermediate were trapped by rapidly cooling the crystals with liquid nitrogen following illumination with filtered green light at 240K and 260K respectively. Difference Fourier projection maps for M minus bR at two temperatures and for M{sub 260K} minus M{sub 240K} are presented. While it is likely that a unique M-substate is trapped when illuminated at 260K produces a mixture of the M{sub 240K} substate and a second M-substate which may have a protein structure similar to the N-intermediate. The diffraction data clearly show that statistically significant structural changes occur upon formation of the M{sub 240K} specimen and then further upon formation of the second substate which is present in the mixture that is produced at 260K. A preliminary 3-D difference map, based on data collected with samples tilted up to 30{degree}, has been constructed at a resolution of 3.5{angstrom} parallel to the membrane plane and a resolution of 8.5{angstrom} perpendicular to the membrane. The data have been analyzed by a number of different criteria to ensure that the differences seen reflect real conformation changes at a level which is significantly above the noise in the map. Furthermore, a comparison of the positions of specific backbone and side-chain groups relative to significant difference peaks suggests that it will be necessary to further refine the atomic resolution model before it will be possible to interpret the changes in chemical structure that occur in the protein at this stage of the photocycle.

  19. Small angle detectors for study diffractive processes with CMS

    SciTech Connect

    Albrow, M.; Bell, A. J.; d'Enterria, D.; Hall-Wilton, R.; Los, S.; Mokhov, N.; Murray, M.; Penzo, A.; Popescu, S.; Ronzhin, A.; Samoylenko, V. D.; Sobol, A.; Veres, G.

    2014-10-22

    The approach and detectors for diffractive physics based on two current projects—Forward Shower Counter (FSC) and Proton Precision Spectrometer (PPS) are presented. FSC system consists of six (3+3) Stations of scintillator counters, which surround closely the beam pipes along 59 m < |z| < 140 m from IP5 on both plus (+) and minus (-) sides. These will detect showers from very forward particles with rapidity 7.5 < |η| < 10 interacting in the beam pipe and surrounding material. FSC allow measurements of single diffraction: p+p → p+G+X (where G is rapidity gap) for lower masses and double diffraction p+p → X+G+X with a large central rapidity gap. The counters can also be used for beam real-time monitoring and will make an invaluable contribution to the understanding of the background environment and its topology. PPS is designed for study the central exclusive production pp → p+X+p, where the + signs denote the absence of hadronic activity (that is, the presence of a rapidity gap) between the outgoing protons and the decay products of the central system X. The precise measurement of the kinematical parameters of the outgoing protons enables to study the properties of the central state X. In PPS part we consider the detector for high precision timing of these protons—QUARTIC. It consists of L-shape bars with quartz or sapphire radiator. The time resolution of the QUARTIC prototypes achieved ≈ 10 ps.

  20. An assessment of the resolution limitation due to radiation-damage in X-ray diffraction microscopy

    SciTech Connect

    Howells, M. R.; Beetz, T.; Chapman, H. N.; Cui, C.; Holton, J. M.; Jacobsen, C. J.; Kirz, J.; Lima, E.; Marchesini, S.; Miao, H.; Sayre, D.; Shapiro, D. A.; Spence, J. C.H.; Starodub, D.

    2008-11-17

    X-ray diffraction microscopy (XDM) is a new form of x-ray imaging that is being practiced at several third-generation synchrotron-radiation x-ray facilities. Nine years have elapsed since the technique was first introduced and it has made rapid progress in demonstrating high-resolution three-dimensional imaging and promises few-nm resolution with much larger samples than can be imaged in the transmission electron microscope. Both life- and materials-science applications of XDM are intended, and it is expected that the principal limitation to resolution will be radiation damage for life science and the coherent power of available x-ray sources for material science. In this paper we address the question of the role of radiation damage. We use a statistical analysis based on the so-called "dose fractionation theorem" of Hegerl and Hoppe to calculate the dose needed to make an image of a single life-science sample by XDM with a given resolution. We find that for simply-shaped objects the needed dose scales with the inverse fourth power of the resolution and present experimental evidence to support this finding. To determine the maximum tolerable dose we have assembled a number of data taken from the literature plus some measurements of our own which cover ranges of resolution that are not well covered otherwise. The conclusion of this study is that, based on the natural contrast between protein and water and "Rose-criterion" image quality, one should be able to image a frozen-hydrated biological sample using XDM at a resolution of about 10 nm.

  1. An assessment of the resolution limitation due to radiation-damage in X-ray diffraction microscopy

    DOE PAGES

    Howells, M. R.; Beetz, T.; Chapman, H. N.; ...

    2008-11-17

    X-ray diffraction microscopy (XDM) is a new form of x-ray imaging that is being practiced at several third-generation synchrotron-radiation x-ray facilities. Nine years have elapsed since the technique was first introduced and it has made rapid progress in demonstrating high-resolution three-dimensional imaging and promises few-nm resolution with much larger samples than can be imaged in the transmission electron microscope. Both life- and materials-science applications of XDM are intended, and it is expected that the principal limitation to resolution will be radiation damage for life science and the coherent power of available x-ray sources for material science. In this paper wemore » address the question of the role of radiation damage. We use a statistical analysis based on the so-called "dose fractionation theorem" of Hegerl and Hoppe to calculate the dose needed to make an image of a single life-science sample by XDM with a given resolution. We find that for simply-shaped objects the needed dose scales with the inverse fourth power of the resolution and present experimental evidence to support this finding. To determine the maximum tolerable dose we have assembled a number of data taken from the literature plus some measurements of our own which cover ranges of resolution that are not well covered otherwise. The conclusion of this study is that, based on the natural contrast between protein and water and "Rose-criterion" image quality, one should be able to image a frozen-hydrated biological sample using XDM at a resolution of about 10 nm.« less

  2. An assessment of the resolution limitation due to radiation-damage in x-ray diffraction microscopy

    PubMed Central

    Howells, M. R.; Beetz, T.; Chapman, H. N.; Cui, C.; Holton, J. M.; Jacobsen, C. J.; Kirz, J.; Lima, E.; Marchesini, S.; Miao, H.; Sayre, D.; Shapiro, D. A.; Spence, J. C. H.; Starodub, D.

    2010-01-01

    X-ray diffraction microscopy (XDM) is a new form of x-ray imaging that is being practiced at several third-generation synchrotron-radiation x-ray facilities. Nine years have elapsed since the technique was first introduced and it has made rapid progress in demonstrating high-resolution three-dimensional imaging and promises few-nm resolution with much larger samples than can be imaged in the transmission electron microscope. Both life- and materials-science applications of XDM are intended, and it is expected that the principal limitation to resolution will be radiation damage for life science and the coherent power of available x-ray sources for material science. In this paper we address the question of the role of radiation damage. We use a statistical analysis based on the so-called “dose fractionation theorem” of Hegerl and Hoppe to calculate the dose needed to make an image of a single life-science sample by XDM with a given resolution. We find that for simply-shaped objects the needed dose scales with the inverse fourth power of the resolution and present experimental evidence to support this finding. To determine the maximum tolerable dose we have assembled a number of data taken from the literature plus some measurements of our own which cover ranges of resolution that are not well covered otherwise. The conclusion of this study is that, based on the natural contrast between protein and water and “Rose-criterion” image quality, one should be able to image a frozen-hydrated biological sample using XDM at a resolution of about 10 nm. PMID:20463854

  3. Time of flight Laue fiber diffraction studies of perdeuterated DNA

    SciTech Connect

    Forsyth, V.T.; Whalley, M.A.; Mahendrasingam, A.; Fuller, W.

    1994-12-31

    The diffractometer SXD at the Rutherford Appleton Laboratory ISIS pulsed neutron source has been used to record high resolution time-of-flight Laue fiber diffraction data from DNA. These experiments, which are the first of their kind, were undertaken using fibers of DNA in the A conformation and prepared using deuterated DNA in order to minimis incoherent background scattering. These studies complement previous experiments on instrument D19 at the Institute Laue Langevin using monochromatic neutrons. Sample preparation involved drawing large numbers of these deuterated DNA fibers and mounting them in a parallel array. The strategy of data collection is discussed in terms of camera design, sample environment and data collection. The methods used to correct the recorded time-of-flight data and map it into the final reciprocal space fiber diffraction dataset are also discussed. Difference Fourier maps showing the distribution of water around A-DNA calculated on the basis of these data are compared with results obtained using data recorded from hydrogenated A-DNA on D19. Since the methods used for sample preparation, data collection and data processing are fundamentally different for the monochromatic and Laue techniques, the results of these experiments also afford a valuable opportunity to independently test the data reduction and analysis techniques used in the two methods.

  4. Powder diffraction studies using anomalous dispersion

    SciTech Connect

    Cox, D.E. ); Wilkinson, A.P. . Dept. of Materials)

    1993-01-01

    With the increasing availability and accessibility of high resolution powder diffractometers at many synchrotron radiation sources throughout the world, there is rapidly-growing interest in the exploitation of anomalous dispersion techniques for structural studies of polycrystalline materials. In conjunction with the Rietveld profile method for structure refinement, such studies are especially useful for the determination of the site distributions of two or more atoms which are near neighbors in the periodic table, or atoms which are distributed among partially occupied sites. Additionally, it is possible to (1) determine the mean-square displacements associated with different kinds of atoms distributed over a single set of sites, (2) distinguish between different oxidation states and coordination geometries of a particular atom in a compound and (3) to determine f' for a wide range of atomic species as a function of energy in the vicinity of an absorption edge. Experimental methods for making anomalous dispersion measurements are described in some detail, including data collection strategies, data analysis and correlation problems, possible systematic errors, and the accuracy of the results. Recent work in the field is reviewed, including cation site-distribution studies (e.g. doped high [Tc] superconductors, ternary alloys, FeCo[sub 2](PO[sub 4])[sub 3], FeNi[sub 2]BO[sub 5]), oxidation-state contrast (e.g. YBa[sub 2]Cu[sub 3]O[sub 6+x], Eu[sub 3]O[sub 4], GaCl[sub 2], Fe[sub 2]PO[sub 5]), and the effect of coordination geometry (e.g. Y[sub 3]Ga[sub 5]O[sub l2]).

  5. Powder diffraction studies using anomalous dispersion

    SciTech Connect

    Cox, D.E.; Wilkinson, A.P.

    1993-05-01

    With the increasing availability and accessibility of high resolution powder diffractometers at many synchrotron radiation sources throughout the world, there is rapidly-growing interest in the exploitation of anomalous dispersion techniques for structural studies of polycrystalline materials. In conjunction with the Rietveld profile method for structure refinement, such studies are especially useful for the determination of the site distributions of two or more atoms which are near neighbors in the periodic table, or atoms which are distributed among partially occupied sites. Additionally, it is possible to (1) determine the mean-square displacements associated with different kinds of atoms distributed over a single set of sites, (2) distinguish between different oxidation states and coordination geometries of a particular atom in a compound and (3) to determine f` for a wide range of atomic species as a function of energy in the vicinity of an absorption edge. Experimental methods for making anomalous dispersion measurements are described in some detail, including data collection strategies, data analysis and correlation problems, possible systematic errors, and the accuracy of the results. Recent work in the field is reviewed, including cation site-distribution studies (e.g. doped high {Tc} superconductors, ternary alloys, FeCo{sub 2}(PO{sub 4}){sub 3}, FeNi{sub 2}BO{sub 5}), oxidation-state contrast (e.g. YBa{sub 2}Cu{sub 3}O{sub 6+x}, Eu{sub 3}O{sub 4}, GaCl{sub 2}, Fe{sub 2}PO{sub 5}), and the effect of coordination geometry (e.g. Y{sub 3}Ga{sub 5}O{sub l2}).

  6. Multi-crystal Anomalous Diffraction for Low-resolution Macromolecular Phasing

    SciTech Connect

    Q Liu; Z Zhang; W Hendrickson

    2011-12-31

    Multiwavelength anomalous diffraction (MAD) and single-wavelength anomalous diffraction (SAD) are the two most commonly used methods for de novo determination of macromolecular structures. Both methods rely on the accurate extraction of anomalous signals; however, because of factors such as poor intrinsic order, radiation damage, inadequate anomalous scatterers, poor diffraction quality and other noise-causing factors, the anomalous signal from a single crystal is not always good enough for structure solution. In this study, procedures for extracting more accurate anomalous signals by merging data from multiple crystals are devised and tested. SAD phasing tests were made with a relatively large (1456 ordered residues) poorly diffracting (d{sub min} = 3.5 {angstrom}) selenomethionyl protein (20 Se). It is quantified that the anomalous signal, success in substructure determination and accuracy of phases and electron-density maps all improve with an increase in the number of crystals used in merging. Structure solutions are possible when no single crystal can support structural analysis. It is proposed that such multi-crystal strategies may be broadly useful when only weak anomalous signals are available.

  7. Metalenses at visible wavelengths: Diffraction-limited focusing and subwavelength resolution imaging.

    PubMed

    Khorasaninejad, Mohammadreza; Chen, Wei Ting; Devlin, Robert C; Oh, Jaewon; Zhu, Alexander Y; Capasso, Federico

    2016-06-03

    Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Metasurfaces allow the miniaturization of conventional refractive optics into planar structures. We show that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA = 0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405, 532, and 660 nm with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. Our results firmly establish that metalenses can have widespread applications in laser-based microscopy, imaging, and spectroscopy.

  8. NIST High Resolution X-Ray Diffraction Standard Reference Material: SRM 2000

    NASA Astrophysics Data System (ADS)

    Windover, Donald; Gil, David L.; Henins, Albert; Cline, James P.

    2009-09-01

    NIST recently released a standard reference material (SRM) for the calibration of high resolution X-ray diffraction (HRXRD) instruments. HRXRD is extensively used in the characterization of lattice distortion in thin single, epitaxial crystal layers on single-crystal wafer substrates. Currently, there is a great need for improved accuracy and transferability for the measurement of strain fields in these epitaxial thin films. This implies an essential need for the calibration of HRXRD instruments to allow measurement intercomparison for both research and manufacturing communities. This first HRXRD SRM release provides certified measurements of diffraction features for a silicon reference substrate, Si (220) in transmission and Si (004) in reflection, allowing for calibration of either monochromator wavelength or goniometer angles. The SRM also provides information on the surface-to-crystal-plane misalignment, which allows calibration of sample holders and sample alignment hardware. This calibration should reduce the uncertainties when comparing, for instance, reciprocal space maps. Here we present a detailed description of these measured values and provide methods for using these to calibrate HRXRD instrumentation. SRM 2000 provides the semiconductor and the larger nanoscience community with the first nanometer length-scale reference standard with femtometer accuracy; the Si (220) transmission-feature-derived silicon lattice spacing, dSRM, has a value of 0.1920161 nm with an expanded uncertainty, U (dSRM), of 0.87 fm.

  9. Compact high-resolution spectrographs for large and extremely large telescopes: using the diffraction limit

    NASA Astrophysics Data System (ADS)

    Robertson, J. Gordon; Bland-Hawthorn, Joss

    2012-09-01

    As telescopes get larger, the size of a seeing-limited spectrograph for a given resolving power becomes larger also, and for ELTs the size will be so great that high resolution instruments of simple design will be infeasible. Solutions include adaptive optics (but not providing full correction for short wavelengths) or image slicers (which give feasible but still large instruments). Here we develop the solution proposed by Bland-Hawthorn and Horton: the use of diffraction-limited spectrographs which are compact even for high resolving power. Their use is made possible by the photonic lantern, which splits a multi-mode optical fiber into a number of single-mode fibers. We describe preliminary designs for such spectrographs, at a resolving power of R ~ 50,000. While they are small and use relatively simple optics, the challenges are to accommodate the longest possible fiber slit (hence maximum number of single-mode fibers in one spectrograph) and to accept the beam from each fiber at a focal ratio considerably faster than for most spectrograph collimators, while maintaining diffraction-limited imaging quality. It is possible to obtain excellent performance despite these challenges. We also briefly consider the number of such spectrographs required, which can be reduced by full or partial adaptive optics correction, and/or moving towards longer wavelengths.

  10. Neutron diffraction studies of thin film multilayer structures

    SciTech Connect

    Majkrzak, C.F.

    1985-01-01

    The application of neutron diffraction methods to the study of the microscopic chemical and magnetic structures of thin film multilayers is reviewed. Multilayer diffraction phenomena are described in general and in particular for the case in which one of the materials of a bilayer is ferromagnetic and the neutron beam polarized. Recent neutron diffraction measurements performed on some interesting multilayer systems are discussed. 70 refs., 5 figs.

  11. Studies Related to Crystal Growth Using Synchrotron Radiation Diffraction.

    NASA Astrophysics Data System (ADS)

    Rule, Robert J.

    1990-01-01

    Available from UMI in association with The British Library. Small crystals of ammonium dihydrogenphosphate (ADP), sodium chlorate and sucrose, generated by secondary nucleation in aqueous solution, have been grown under constant conditions of supersaturation. A wide dispersion of growth rates was observed for each material using optical microscopy. A number of individual crystals of known growth rate were successfully retrieved from solution for each system. An assessment of the mosaic spread of each crystal was made using synchrotron radiation Laue diffraction on station 9.7 at Daresbury laboratory. All of the crystals produced diffraction patterns comprising small, sharp spots, indicative of low mosaic spread (<0.5 ^circ), contrary to published work. No correlation was found between growth rate and mosaic spread for these simple, small-molecule materials. An explanation of the previously reported discrepancies has been provided. The susceptibility of these compounds to radiation damage has been systematically investigated; ADP proved highly robust whilst sucrose and sodium chlorate showed significant sensitivity to irradiation. The role of mosaic spread in the growth of more complex systems is discussed with specific reference to two materials possessing channel structures: chenodeoxycholic acid and SAPO-5. In each case, the directions of slow growth have been related to high mosaic spread. An order of magnitude calculation of the rate of absorption of energy has been made for a variety of materials in the SRS white beam. The associated theoretical heating capability of the beam has also been estimated. A crystal melting experiment using crystals of 2 bromobenzophenone has indicated that the heating rate under standard experimental conditions is of the order of 1-2^circ C per sec., substantially less than anticipated. A pilot study of the combined use of SR Laue diffraction and high resolution powder diffraction for microcrystal structure determination has been

  12. Crystallization and preliminary X-ray diffraction study of porcine carboxypeptidase B

    SciTech Connect

    Akparov, V. Kh.; Timofeev, V. I. Kuranova, I. P.

    2015-05-15

    Crystals of porcine pancreatic carboxypeptidase B have been grown in microgravity by the capillary counter-diffusion method through a gel layer. The X-ray diffraction study showed that the crystals belong to sp. gr. P4{sub 1}2{sub 1}2 and have the following unit-cell parameters: a = b = 79.58 Å, c = 100.51 Å; α = β = γ = 90.00°. The X-ray diffraction data set suitable for the determination of the three-dimensional structure at atomic resolution was collected from one of the grown crystals at the SPring 8 synchrotron facility to 0.98 Å resolution.

  13. Neutron diffraction studies of natural glasses

    SciTech Connect

    Wright, A.C.; Erwin Desa, J.A.; Weeks, R.A.; Sinclair, R.N.; Bailey, D.K.

    1983-08-01

    A neutron diffraction investigation has been carried out of the structures of several naturally occurring glasses, viz. Libyan Desert glass, a Fulgurite, Wabar glass, Lechatelierite from Canon Diablo, a Tektite, Obsidian (3 samples), and Macusani glass. Libyan Desert sand has also been examined, together with crystalline ..cap alpha..-quartz and ..cap alpha..-cristobalite. A comparison of data for the natural glasses and synthetic vitreous silica (Spectrosil B) in both reciprocal and real space allows a categorisation into Silicas, which closely resemble synthetic vitreous silica, and Silicates, for which the resemblance to silica is consistently less striking. The data support the view that Libyan Desert glass and sand have a common origin, while the Tektite has a structure similar to that of volcanic glasses.

  14. Neutron and X-Ray Diffraction Studies of Advanced Materials

    SciTech Connect

    Barabash, Rozaliya; Tiley, Jaimie; Wang, Yandong; Liaw, Peter K

    2010-01-01

    The selection of articles in the special topic 'Neutron and X-Ray Studies of Advanced Materials' is based on the materials presented during the TMS 2009 annual meeting in San Francisco, CA, February 15-19, 2009. The development of ultrabrilliant third-generation synchrotron X-ray sources, together with advances in X-ray optics, has created intense X-ray microbeams, which provide the best opportunities for in-depth understanding of mechanical behavior in a broad spectrum of materials. Important applications include ultrasensitive elemental detection by X-ray fluorescence/absorption and microdiffraction to identify phase and strain with submicrometer spatial resolution. X-ray microdiffraction is a particularly exciting application compared with alternative probes of crystalline structure, orientation, and strain. X-ray microdiffraction is nondestructive with good strain resolution, competitive or superior spatial resolution in thick samples, and with the ability to probe below the sample surface. Moreover, the high-energy X-ray diffraction technique provides an effective tool for characterizing the mechanical and functional behavior in various environments (temperature, stress, and magnetic field). At the same time, some neutron diffraction instruments constructed mainly for the purpose of engineering applications can be found at nearly all neutron facilities. The first generation-dedicated instruments designed for studying in-situ mechanical behavior have been commissioned and used, and industrial standards for reliable and repeatable measurements have been developed. Furthermore, higher penetration of neutron beams into most engineering materials provides direct measurements on the distribution of various stresses (i.e., types I, II, and III) beneath the surface up to several millimeters, even tens of millimeters for important industrial components. With X-ray and neutron measurements, it is possible to characterize material behavior at different length scales. It

  15. Diffraction Ellipsometry Studies on Insect Flight Muscle

    NASA Astrophysics Data System (ADS)

    Shen, Sui

    Characterization of the orientation and distribution of myosin cross-bridge at rigor, relax, low ionic strength (36 mM) and activation (pCa 4.3) conditions are of great interest since these states have been proposed to be transient steps in the cyclical interaction of myosin heads with actin during contraction. Measurements sensitive to the cross-bridge orientation in chemically skinned single muscle fibers of the insect, Lethocerus collossicus have been performed under various physiological conditions using laser diffraction ellipsometry. Determination of both the total birefringence, Deltan, and the differential field ratio, rm DFR (defined as {E_parallel -E_|over E_parallel-E _|}),is necessary for complete characterization of the optical polarization state. For rigor insect fiber, the birefringence value was close to the value we obtained from chemically skinned frog muscle fibers. However, the differential field ratio, DFR, was a negative value for insect fiber, while we always measured a positive value from frog muscle fibers. Polarization states of light diffracted from fibers exhibited a dependence on configurations of structural proteins at different conditions: fluid index matching using o-toluidine, alpha -chymotrypsin cleavage, KCl myosin extraction, rigor state, relaxed state, exogenous S-1 binding on rigor fiber, low ionic strength state, activation state at resting or stretched length. Results of our data analysis suggested that: (1) the negative DFR value of the insect flight muscle was contributed by alpha-actinin arranged perpendicular to the fiber axis in the Z-line, (2) in rigor fiber, 70% of myosin heads are doubly bound (45^circ and 90^ circ) while the rest of 30% are in single head binding configuration (90^circ), (3) myosin heads are randomly oriented in relaxed fiber, (4) mean axial angle is about 62^ circ for exogenous myosin heads binding on rigor fiber, (5) at low ionic strength, 25% of the total myosin heads are weakly attached to actin

  16. PREFACE: XTOP 2004 -- 7th Biennial Conference on High Resolution X-Ray Diffraction and Imaging

    NASA Astrophysics Data System (ADS)

    Holý, Vaclav

    2005-05-01

    The 7th Biennial Conference on High Resolution X-Ray Diffraction and Imaging (XTOP 2004) was held in the Prague suburb of Pruhonice, Czech Republic, during 7-10 September 2004. It was organized by the Czech and Slovak Crystallographic Association in cooperation with the Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Masaryk University, Brno, and Charles University, Prague. XTOP 2004 took place just after EPDIC IX (European Powder Diffraction Conference) organised in Prague by the same Association during 2-5 September 2004. The Organizing Committee was supported by an International Programme Committee including about 20 prominent scientists from several European and overseas countries, whose helpful suggestions for speakers are acknowledged. The conference was sponsored by the International Union of Crystallography and by several industrial sponsors; this sponsorship allowed us to support about 20 students and young scientists. In total, 147 official delegates and 8 accompanying persons from 16 countries of three continents attended our conference. The scientific programme of the conference was divided into 11 half-day sessions and 2 poster sessions. The participants presented 147 accepted contributions; of these 9 were 45-minute long invited talks, 34 were 20-minute oral presentations and 104 were posters. All posters were displayed for the whole meeting to ensure maximum exposure and interaction between delegates. We followed the very good experience from the previous conference, XTOP 2002, and also organized pre-conference tutorial lectures presented by experts in the field: `Imaging with hard synchrotron radiation' (J Härtwig, Grenoble), `High-resolution x-ray diffractometry: determination of strain and composition' (J Stangl, Linz), `X-ray grazing-incidence scattering from surfaces and nanostructures' (U Pietsch, Potsdam) and `Hard x-ray optics' (J Hrdý, Prague). According to the recommendation of the International Program Committee

  17. Breaking the diffraction-limited resolution barrier in fiber-optical two-photon fluorescence endoscopy by an azimuthally-polarized beam.

    PubMed

    Gu, Min; Kang, Hong; Li, Xiangping

    2014-01-10

    Although fiber-optical two-photon endoscopy has been recognized as a potential high-resolution diagnostic and therapeutic procedure in vivo, its resolution is limited by the optical diffraction nature to a few micrometers due to the low numerical aperture of an endoscopic objective. On the other hand, stimulated emission depletion (STED) achieved by a circularly-polarized vortex beam has been used to break the diffraction-limited resolution barrier in a bulky microscope. It has been a challenge to apply the STED principle to a fiber-optical two-photon endoscope as a circular polarization state cannot be maintained due to the birefringence of a fiber. Here, we demonstrate the first fiber-optical STED two-photon endoscope using an azimuthally-polarized beam directly generated from a double-clad fiber. As such, the diffraction-limited resolution barrier of fiber-optical two-photon endoscopy can be broken by a factor of three. Our new accomplishment has paved a robust way for high-resolution in vivo biomedical studies.

  18. Breaking the diffraction-limited resolution barrier in fiber-optical two-photon fluorescence endoscopy by an azimuthally-polarized beam

    NASA Astrophysics Data System (ADS)

    Gu, Min; Kang, Hong; Li, Xiangping

    2014-01-01

    Although fiber-optical two-photon endoscopy has been recognized as a potential high-resolution diagnostic and therapeutic procedure in vivo, its resolution is limited by the optical diffraction nature to a few micrometers due to the low numerical aperture of an endoscopic objective. On the other hand, stimulated emission depletion (STED) achieved by a circularly-polarized vortex beam has been used to break the diffraction-limited resolution barrier in a bulky microscope. It has been a challenge to apply the STED principle to a fiber-optical two-photon endoscope as a circular polarization state cannot be maintained due to the birefringence of a fiber. Here, we demonstrate the first fiber-optical STED two-photon endoscope using an azimuthally-polarized beam directly generated from a double-clad fiber. As such, the diffraction-limited resolution barrier of fiber-optical two-photon endoscopy can be broken by a factor of three. Our new accomplishment has paved a robust way for high-resolution in vivo biomedical studies.

  19. A Numerical Study on X-Ray Diffraction Effects within Objects

    SciTech Connect

    Lehman, S K

    2005-09-29

    X-rays, being waves, always undergo the propagation effects of reflection, refraction, diffraction, geometric attenuation and absorption. In most circumstances the first four effects are considered negligible given the resolution sizes demanded of the measurement systems, x-ray energies involved, and physical properties of the materials under evaluation. We have reached the point, however, in some x-ray non-destructive evaluation (NDE) and imaging where we wish to resolve features of micrometer size in millimeter size objects to less than micrometer resolution. Given this resolution and the sizes of the measurement systems, diffraction effects within the object may become observable. We studied the extent to which diffraction is observable numerically using a two-dimensional paraxial approximation wave propagation code using a multislice method. We modeled realistic parts of interest at worst-case x-ray energies, comparing wave propagation and straight-ray simulated results. In two cases, we compare the numerical results to experimental measurements. The conclusion, based upon the results of the simulation code, is that diffraction effects on the measured data will be insignificant. However, we demonstrate by a single example, that in certain cases diffraction effects may be significant.

  20. Diffraction and Imaging Study of Imperfections of Protein Crystals with Coherent X-rays

    NASA Technical Reports Server (NTRS)

    Hu, Z. W.; Thomas, B. R.; Chernov, A. A.; Chu, Y. S.; Lai, B.

    2004-01-01

    High angular-resolution x-ray diffraction and phase contrast x-ray imaging were combined to study defects and perfection of protein crystals. Imperfections including line defects, inclusions and other microdefects were observed in the diffraction images of a uniformly grown lysozyme crystal. The observed line defects carry distinct dislocation features running approximately along the <110> growth front and have been found to originate mostly in a central growth area and occasionally in outer growth regions. Slow dehydration led to the broadening of a fairly symmetric 4 4 0 rocking curve by a factor of approximately 2.6, which was primarily attributed to the dehydration-induced microscopic effects that are clearly shown in diffraction images. X-ray imaging and diffraction characterization of the quality of apoferritin crystals will also be discussed in the presentation.

  1. Carbonado revisited: Insights from neutron diffraction, high resolution orientation mapping and numerical simulations

    NASA Astrophysics Data System (ADS)

    Piazolo, Sandra; Kaminsky, Felix V.; Trimby, Patrick; Evans, Lynn; Luzin, V.

    2016-11-01

    One of the most controversial diamond types is carbonado, as its origin and geological history are still under debate. Here, we investigate selected carbonado samples using neutron diffraction and high resolution orientation mapping in combination with numerical simulations. Neutron diffraction analyses show that fine grained carbonado samples exhibit a distinct lack of crystallographic preferred orientation. Quantitative crystallographic orientation analyses performed on transmission electron microscope (TEM) sections reveal that the 2-10 μm grains exhibit locally significant internal deformation. Such features are consistent with crystal plastic deformation of a grain aggregate that initially formed by rapid nucleation, characterized by a high number of nucleation sites and no crystallographic preferred orientation. Crystal plastic deformation resulted in high stress heterogeneities close to grain boundaries, even at low bulk strains, inducing a high degree of lattice distortion without significant grain size reduction and the development of a crystallographic preferred orientation. Observed differences in the character of the grain boundary network and internal deformation structures can be explained by significant post-deformation annealing occurring to variable degrees in the carbonado samples. Differences in intensity of crystal bending and subgrain boundary sharpness can be explained by dislocation annihilation and rearrangement, respectively. During annealing grain energy is reduced resulting in distinct changes to the grain boundary geometry. Grain scale numerical modelling shows that anisotropic grain growth, where grain boundary energy is determined by the orientation of a boundary segment relative to the crystallographic orientation of adjacent grains results in straight boundary segments with abrupt changes in orientation even if the boundary is occurring between two triple junctions forming a ;zigzag; pattern. In addition, in diamond anisotropic

  2. Development of an ultra-high resolution diffraction grating forsoft x-rays

    SciTech Connect

    Voronov, Dmitriy L.; Cambie, Rossana; Feshchenko, Ruslan M.; Gullikson, Eric M.; Padmore, Howard A.; Vinogradov, Alexander V.; Yashchuk, Valeriy V.

    2007-08-21

    Resonant Inelastic X-ray Scattering (RIXS) is the one of themost powerful methods for investigation of the electronic structure ofmaterials, specifically of excitations in correlated electron systems.However the potential of the RIXS technique has not been fully exploitedbecause conventional grating spectrometers have not been capable ofachieving the extreme resolving powers that RIXS can utilize. State ofthe art spectrometers in the soft x-ray energy range achieve ~;0.25 eVresolution, compared to the energy scales of soft excitations andsuperconducting gap openings down to a few meV. Development ofdiffraction gratings with super high resolving power is necessary tosolve this problem. In this paper we study the possibilities offabrication of gratings of resolving power of up to 106 for the 0.5 1.5KeV energy range. This energy range corresponds to all or most of theuseful dipole transitions for elements of interest in most correlatedelectronic systems, i.e., oxygen K-edge of relevance to all oxides, thetransition metal L2,3 edges, and the M4,5 edges of the rare earths.Various approaches based on different kinds of diffraction gratings suchas deep-etched multilayer gratings, and multilayer coated echelettes arediscussed. We also present simulations of diffraction efficiency for suchgratings, and investigate the necessary fabricationtolerances.

  3. Ultrafast Time Resolved X-ray Diffraction Studies of Laser Heated Metals and Semiconductors

    NASA Astrophysics Data System (ADS)

    Chen, Peilin; Tomov, I. V.; Rentzepis, P. M.

    1998-03-01

    Time resolved hard x-ray diffraction has been employed to study the dynamics of lattice structure deformation. When laser pulse energy is deposited in a material it generates a non uniform transient temperature distribution, which alters the lattice structure of the crystal. The deformed crystal lattice will change the angle of diffraction for a monochromatic x-ray beam. We report picosecond and nanosecond time resolved x-ray diffraction measurements of the lattice temperature distribution, transient structure and stress, in Pt (111) and GaAs (111) crystals, caused by pulsed UV laser irradiation. An ArF excimer laser operated at 300 Hz was used, both, to drive an x-ray diode with copper anode and heat the crystal. Bragg diffracted x-ray radiation was recorded by a direct imaging x-ray CCD. Changes in the diffraction patterns induced by a few millijouls pulse energy were observed at different time delays between the laser heating pulse and the x-ray probing pulse. A kinematical model for time resolved x-ray diffraction was used to analyze the experimental data. Good agreement between the measured and calculated scattered x-ray intensities profiles was achieved, indicating that detailed time resolved x-ray diffraction measurements can be made with nanosecond and picosecond resolution for small temperature changes. Our system can detect changes in the lattice spacing of about 10-3 A.

  4. Laser-Doppler velocity profile sensor with submicrometer spatial resolution that employs fiber optics and a diffractive lens.

    PubMed

    Büttner, Lars; Czarske, Jürgen; Knuppertz, Hans

    2005-04-20

    We report a novel laser-Doppler velocity profile sensor for microfluidic and nanofluidic applications and turbulence research. The sensors design is based on wavelength-division multiplexing. The high dispersion of a diffractive lens is used to generate a measurement volume with convergent and divergent interference fringes by means of two laser wavelengths. Evaluation of the scattered light from tracers allows velocity gradients to be measured in flows with submicrometer spatial resolution inside a measurement volume of 700-microm length. Using diffraction optics and fiber optics, we achieved a miniaturized and robust velocity profile sensor for highly resolved velocity measurements.

  5. A preliminary neutron diffraction study of rasburicase, a recombinant urate oxidase enzyme, complexed with 8-azaxanthin

    SciTech Connect

    Budayova-Spano, Monika; Bonneté, Françoise; Ferté, Natalie; El Hajji, Mohamed; Meilleur, Flora; Blakeley, Matthew Paul; Castro, Bertrand

    2006-03-01

    Neutron diffraction data of hydrogenated recombinant urate oxidase enzyme (Rasburicase), complexed with a purine-type inhibitor 8-azaxanthin, was collected to 2.1 Å resolution from a crystal grown in D{sub 2}O by careful control and optimization of crystallization conditions via knowledge of the phase diagram. Deuterium atoms were clearly seen in the neutron-scattering density map. Crystallization and preliminary neutron diffraction measurements of rasburicase, a recombinant urate oxidase enzyme expressed by a genetically modified Saccharomyces cerevisiae strain, complexed with a purine-type inhibitor (8-azaxanthin) are reported. Neutron Laue diffraction data were collected to 2.1 Å resolution using the LADI instrument from a crystal (grown in D{sub 2}O) with volume 1.8 mm{sup 3}. The aim of this neutron diffraction study is to determine the protonation states of the inhibitor and residues within the active site. This will lead to improved comprehension of the enzymatic mechanism of this important enzyme, which is used as a protein drug to reduce toxic uric acid accumulation during chemotherapy. This paper illustrates the high quality of the neutron diffraction data collected, which are suitable for high-resolution structural analysis. In comparison with other neutron protein crystallography studies to date in which a hydrogenated protein has been used, the volume of the crystal was relatively small and yet the data still extend to high resolution. Furthermore, urate oxidase has one of the largest primitive unit-cell volumes (space group I222, unit-cell parameters a = 80, b = 96, c = 106 Å) and molecular weights (135 kDa for the homotetramer) so far successfully studied with neutrons.

  6. Improved strain precision with high spatial resolution using nanobeam precession electron diffraction

    SciTech Connect

    Rouviere, Jean-Luc Martin, Yannick; Denneulin, Thibaud; Cooper, David

    2013-12-09

    NanoBeam Electron Diffraction is a simple and efficient technique to measure strain in nanostructures. Here, we show that improved results can be obtained by precessing the electron beam while maintaining a few nanometer probe size, i.e., by doing Nanobeam Precession Electron Diffraction (N-PED). The precession of the beam makes the diffraction spots more uniform and numerous, making N-PED more robust and precise. In N-PED, smaller probe size and better precision are achieved by having diffraction disks instead of diffraction dots. Precision in the strain measurement better than 2 × 10{sup −4} is obtained with a probe size approaching 1 nm in diameter.

  7. Crystal structure of human tooth enamel studied by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ouladdiaf, Bachir; Rodriguez-Carvajal, Juan; Goutaudier, Christelle; Ouladdiaf, Selma; Grosgogeat, Brigitte; Pradelle, Nelly; Colon, Pierre

    2015-02-01

    Crystal structure of human tooth enamel was investigated using high-resolution neutron powder diffraction. Excellent agreement between observed and refined patterns is obtained, using the hexagonal hydroxyapatite model for the tooth enamel, where a large hydroxyl deficiency ˜70% is found in the 4e site. Rietveld refinements method combined with the difference Fourier maps have revealed, however, that the hydroxyl ions are not only disordered along the c-axis but also within the basal plane. Additional H ions located at the 6h site and forming HPO42- anions were found.

  8. Measurement method for roll angular displacement with a high resolution by using diffraction gratings and a heterodyne interferometer

    SciTech Connect

    Tang, Shanzhi; Wang, Zhao; Gao, Jianmin; Guo, Junjie

    2014-04-15

    The roll angle measurement is difficult to be achieved directly using a typical commercial interferometer due to its low sensitivity in axial direction, where the axial direction is orthogonal to the plane of the roll angular displacement. A roll angle measurement method combined diffraction gratings with a laser heterodyne interferometer is discussed in this paper. The diffraction grating placed in the plane of a roll angular displacement and the interferometer arranged in the plane's orthogonal direction, constitute the measurement pattern for the roll angle with high resolution. The roll angular displacement, considered as the linear, can be tested precisely when the corresponding angle is very small. Using the proposed method, the angle roll measurement obtains the high resolution of 0.002{sup ″}. Experiment has proved its feasibility and practicability.

  9. An evaluation of the clinical potential of tissue diffraction studies

    NASA Astrophysics Data System (ADS)

    Speller, R.; Abuchi, S.; Zheng, Y.; Vassiljev, N.; Konstantinidis, A.; Griffiths, J.

    2015-09-01

    Medical imaging is a long established part of patient management in the treatment of disease. However, in most cases it only provides anatomical detail and does not provide any form of tissue characterisation. This is particularly true for X-ray imaging. Recent studies on tissue diffraction have shown that true molecular signatures can be derived for different tissue types. Breast cancer samples and liver tissue have been studied. It has been shown that diffraction profiles can be traced away from the primary tumour in excised breast tissue samples and that potentially 3mm fat nodules in liver tissue can be identified in patients at acceptable doses.

  10. Structural anomalies in undoped gallium arsenide observed in high-resolution diffraction imaging with monochromatic synchrotron radiation

    NASA Technical Reports Server (NTRS)

    Steiner, B.; Kuriyama, M.; Dobbyn, R. C.; Laor, U.; Larson, D.

    1989-01-01

    Novel, streak-like disruption features restricted to the plane of diffraction have recently been observed in images obtained by synchrotron radiation diffraction from undoped, semi-insulating gallium arsenide crystals. These features were identified as ensembles of very thin platelets or interfaces lying in (110) planes, and a structural model consisting of antiphase domain boundaries was proposed. We report here the other principal features observed in high resolution monochromatic synchrotron radiation diffraction images: (quasi) cellular structure; linear, very low-angle subgrain boundaries in (110) directions, and surface stripes in a (110) direction. In addition, we report systematic differences in the acceptance angle for images involving various diffraction vectors. When these observations are considered together, a unifying picture emerges. The presence of ensembles of thin (110) antiphase platelet regions or boundaries is generally consistent not only with the streak-like diffraction features but with the other features reported here as well. For the formation of such regions we propose two mechanisms, operating in parallel, that appear to be consistent with the various defect features observed by a variety of techniques.

  11. [Microdiffraction measurements of natural tooth by high resolution X-ray diffraction equipment].

    PubMed

    Xue, Jing; Li, Wei; Liao, Yunmao; Zhou, Jinglin; Song, Jukun

    2008-02-01

    The main mineral component of natural tooth was determined as calcium apatite many years ago; most of them exist in the form of hydroxyapatite with different crystallites. If a tooth decayed, the crystalline of hydroxyapatite would be changed and decomposed. In our experiment, a natural tooth with caries was measured by high resolution XRD equipment: X'pert Pro. Three spots which included normal enamel, normal dentin and caries tissue were analyzed. The results showed that tooth was a kind of biological mixed crystal composed of many crystal phases, the main crystal phase was hydroxyapatite. From normal enamel to normal dentin and to caries tissue, the length of the a-axis of hydroxyapatite crystallite increased, the length of the c-axis of hydroxyapatite crystallite remained unchanged. The crystal sizes were: normal enamel D002 = 27.600 nm; normal dentin D002 = 16.561 nm; caries tissue D002 = 13.163 nm. Crystallinity: normal enamel>normal dentin>caries tissue. According to our experiment, tooth could be conveniently studied by high resolution microdiffracion XRD equipment.

  12. Molecular Visualization of Methane - Carbon Dioxide Solid Solution in Gas Hydrates by High Resolution Neutron Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Everett, M.; Rawn, C.; Huq, A.; Chakoumakos, B. C.; Phelps, T. J.

    2012-12-01

    The exchange of CO2 for CH4 in natural gas hydrates could produce energy from untapped sources while at the same time sequestering CO2. In addition to the energy and environmental aspects the solid solution of (CH4)1-x(CO2)x 5.75H2O provides a framework inclusion structure that enables the scientific study of how two molecules that differ greatly in their bonding, shape, coordination and molecular weight can influence the structure and properties of the compound and interact with the framework that occludes the molecules. Samples synthesized by cooling liquid water pressurized with either pure CH4 or CO2 or mixtures of the two gases to temperatures where hydrate formation occurs have been studied using high-resolution neutron diffraction. Static images of the nuclear scattering density of the free moving gas molecules have been determined. Cage occupants and occupancies, the volume change of the unit cell and the individual cages based on composition have been determined.

  13. High Pressure X-Ray Diffraction Studies of Nanocrystalline Materials

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Stel'makh, S.; Grzanka, E.; Gierlotka, S.; Palosz, W.

    2004-01-01

    Experimental evidence obtained for a variety of nanocrystalline materials suggest that the crystallographic structure of a very small size particle deviates from that in the bulk crystals. In this paper we show the effect of the surface of nanocrystals on their structure by the analysis of generation and distribution of macro- and micro-strains at high pressures and their dependence on the grain size in nanocrystalline powders of Sic. We studied the structure of Sic nanocrystals by in-situ high-pressure powder diffraction technique using synchrotron and neutron sources and hydrostatic or isostatic pressure conditions. The diffraction measurements were done in HASYLAB at DESY using a Diamond Anvil Cell (DAC) in the energy dispersive geometry in the diffraction vector range up to 3.5 - 4/A and under pressures up to 50 GPa at room temperature. In-situ high pressure neutron diffraction measurements were done at LANSCE in Los Alamos National Laboratory using the HIPD and HIPPO diffractometers with the Paris-Edinburgh and TAP-98 cells, respectively, in the diffraction vector range up to 26 Examination of the response of the material to external stresses requires nonstandard methodology of the materials characterization and description. Although every diffraction pattern contains a complete information on macro- and micro-strains, a high pressure experiment can reveal only those factors which contribute to the characteristic diffraction patterns of the crystalline phases present in the sample. The elastic properties of powders with the grain size from several nm to micrometers were examined using three methodologies: (l), the analysis of positions and widths of individual Bragg reflections (used for calculating macro- and micro-strains generated during densification) [I], (2). the analysis of the dependence of the experimental apparent lattice parameter, alp, on the diffraction vector Q [2], and (3), the atomic Pair Distribution Function (PDF) technique [3]. The results

  14. Bunch evolution study in optimization of MeV ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Lu, Xian-Hai; Du, Ying-Chao; Huang, Wen-Hui; Tang, Chuan-Xiang

    2014-12-01

    Megaelectronvolt ultrafast electron diffraction (UED) is a promising detection tool for ultrafast processes. The quality of diffraction image is determined by the transverse evolution of the probe bunch. In this paper, we study the contributing terms of the emittance and space charge effects to the bunch evolution in the MeV UED scheme, employing a mean-field model with an ellipsoidal distribution as well as particle tracking simulation. The small transverse dimension of the drive laser is found to be critical to improve the reciprocal resolution, exploiting both smaller emittance and larger transverse bunch size before the solenoid. The degradation of the reciprocal spatial resolution caused by the space charge effects should be carefully controlled.

  15. Application of Transmitted Kikuchi Diffraction in Studying Nano-oxide and Ultrafine Metallic Grains.

    PubMed

    Abbasi, Majid; Kim, Dong-Ik; Guim, Hwan-Uk; Hosseini, Morteza; Danesh-Manesh, Habib; Abbasi, Mehrdad

    2015-11-24

    Transmitted Kikuchi diffraction (TKD) is an emerging SEM-based technique that enables investigation of highly refined grain structures. It offers higher spatial resolution by utilizing conventional electron backscattered diffraction equipment on electron-transparent samples. A successful attempt has been made to reveal nano-oxide grain structures as well as ultrafine severely deformed metallic grains. The effect of electron beam current was studied. Higher beam currents enhance pattern contrast and intensity. Lower detector exposure times could be employed to accelerate the acquisition time and minimize drift and carbon contamination. However, higher beam currents increase the electron interaction volume and compromise the spatial resolution. Lastly, TKD results were compared to orientation mapping results in TEM (ASTAR). Results indicate that a combination of TKD and EDS is a capable tool to characterize nano-oxide grains such as Al2O3 and Cr2O3 with similar crystal structures.

  16. Real-time, high-resolution x-ray diffraction measurements on shocked crystals at a synchrotron facility.

    PubMed

    Gupta, Y M; Turneaure, Stefan J; Perkins, K; Zimmerman, K; Arganbright, N; Shen, G; Chow, P

    2012-12-01

    The Advanced Photon Source (APS) at Argonne National Laboratory was used to obtain real-time, high-resolution x-ray diffraction measurements to determine the microscopic response of shock-compressed single crystals. Disk shaped samples were subjected to plane shock wave compression by impacting them with half-inch diameter, flat-faced projectiles. The projectiles were accelerated to velocities ranging between 300 and 1200 m/s using a compact powder gun designed specifically for use at a synchrotron facility. The experiments were designed to keep the sample probed volume under uniaxial strain and constant stress for a duration longer than the 153.4 ns spacing between x-ray bunches. X-rays from a single pulse (<100 ps duration) out of the periodic x-ray pulses emitted by the synchrotron were used for the diffraction measurements. A synchronization and x-ray detection technique was developed to ensure that the measured signal was obtained unambiguously from the desired x-ray pulse incident on the sample while the sample was in a constant uniaxial strain state. The synchronization and x-ray detection techniques described can be used for a variety of x-ray measurements on shock compressed solids and liquids at the APS. Detailed procedures for applying the Bragg-Brentano parafocusing approach to single crystals at the APS are presented. Analytic developments to determine the effects of crystal substructure and non-ideal geometry on the diffraction pattern position and shape are presented. Representative real-time x-ray diffraction data, indicating shock-induced microstructural changes, are presented for a shock-compressed Al(111) sample. The experimental developments presented here provided, in part, the impetus for the Dynamic Compression Sector (DCS) currently under development at the APS. Both the synchronization∕x-ray detection methods and the analysis equations for high-resolution single crystal x-ray diffraction can be used at the DCS.

  17. Real-time, high-resolution x-ray diffraction measurements on shocked crystals at a synchrotron facility

    NASA Astrophysics Data System (ADS)

    Gupta, Y. M.; Turneaure, Stefan J.; Perkins, K.; Zimmerman, K.; Arganbright, N.; Shen, G.; Chow, P.

    2012-12-01

    The Advanced Photon Source (APS) at Argonne National Laboratory was used to obtain real-time, high-resolution x-ray diffraction measurements to determine the microscopic response of shock-compressed single crystals. Disk shaped samples were subjected to plane shock wave compression by impacting them with half-inch diameter, flat-faced projectiles. The projectiles were accelerated to velocities ranging between 300 and 1200 m/s using a compact powder gun designed specifically for use at a synchrotron facility. The experiments were designed to keep the sample probed volume under uniaxial strain and constant stress for a duration longer than the 153.4 ns spacing between x-ray bunches. X-rays from a single pulse (<100 ps duration) out of the periodic x-ray pulses emitted by the synchrotron were used for the diffraction measurements. A synchronization and x-ray detection technique was developed to ensure that the measured signal was obtained unambiguously from the desired x-ray pulse incident on the sample while the sample was in a constant uniaxial strain state. The synchronization and x-ray detection techniques described can be used for a variety of x-ray measurements on shock compressed solids and liquids at the APS. Detailed procedures for applying the Bragg-Brentano parafocusing approach to single crystals at the APS are presented. Analytic developments to determine the effects of crystal substructure and non-ideal geometry on the diffraction pattern position and shape are presented. Representative real-time x-ray diffraction data, indicating shock-induced microstructural changes, are presented for a shock-compressed Al(111) sample. The experimental developments presented here provided, in part, the impetus for the Dynamic Compression Sector (DCS) currently under development at the APS. Both the synchronization/x-ray detection methods and the analysis equations for high-resolution single crystal x-ray diffraction can be used at the DCS.

  18. Beamline P02.1 at PETRA III for high-resolution and high-energy powder diffraction.

    PubMed

    Dippel, Ann-Christin; Liermann, Hanns-Peter; Delitz, Jan Torben; Walter, Peter; Schulte-Schrepping, Horst; Seeck, Oliver H; Franz, Hermann

    2015-05-01

    Powder X-ray diffraction techniques largely benefit from the superior beam quality provided by high-brilliance synchrotron light sources in terms of photon flux and angular resolution. The High Resolution Powder Diffraction Beamline P02.1 at the storage ring PETRA III (DESY, Hamburg, Germany) combines these strengths with the power of high-energy X-rays for materials research. The beamline is operated at a fixed photon energy of 60 keV (0.207 Å wavelength). A high-resolution monochromator generates the highly collimated X-ray beam of narrow energy bandwidth. Classic crystal structure determination in reciprocal space at standard and non-ambient conditions are an essential part of the scientific scope as well as total scattering analysis using the real space information of the pair distribution function. Both methods are complemented by in situ capabilities with time-resolution in the sub-second regime owing to the high beam intensity and the advanced detector technology for high-energy X-rays. P02.1's efficiency in solving chemical and crystallographic problems is illustrated by presenting key experiments that were carried out within these fields during the early stage of beamline operation.

  19. Beamline P02.1 at PETRA III for high-resolution and high-energy powder diffraction

    PubMed Central

    Dippel, Ann-Christin; Liermann, Hanns-Peter; Delitz, Jan Torben; Walter, Peter; Schulte-Schrepping, Horst; Seeck, Oliver H.; Franz, Hermann

    2015-01-01

    Powder X-ray diffraction techniques largely benefit from the superior beam quality provided by high-brilliance synchrotron light sources in terms of photon flux and angular resolution. The High Resolution Powder Diffraction Beamline P02.1 at the storage ring PETRA III (DESY, Hamburg, Germany) combines these strengths with the power of high-energy X-rays for materials research. The beamline is operated at a fixed photon energy of 60 keV (0.207 Å wavelength). A high-resolution monochromator generates the highly collimated X-ray beam of narrow energy bandwidth. Classic crystal structure determination in reciprocal space at standard and non-ambient conditions are an essential part of the scientific scope as well as total scattering analysis using the real space information of the pair distribution function. Both methods are complemented by in situ capabilities with time-resolution in the sub-second regime owing to the high beam intensity and the advanced detector technology for high-energy X-rays. P02.1’s efficiency in solving chemical and crystallographic problems is illustrated by presenting key experiments that were carried out within these fields during the early stage of beamline operation. PMID:25931084

  20. Expression, Purification and Preliminary Diffraction Studies of CmlS

    SciTech Connect

    Latimer, R.; Podzelinska, K; Soares, A; Bhattacharya, A; Vining, L; Jia, Z; Zechel, D

    2009-01-01

    CmlS, a flavin-dependent halogenase (FDH) present in the chloramphenicol-biosynthetic pathway in Streptomyces venezuelae, directs the dichlorination of an acetyl group. The reaction mechanism of CmlS is of considerable interest as it will help to explain how the FDH family can halogenate a wide range of substrates through a common mechanism. The protein has been recombinantly expressed in Escherichia coli and purified to homogeneity. The hanging-drop vapour-diffusion method was used to produce crystals that were suitable for X-ray diffraction. Data were collected to 2.0 Angstroms resolution. The crystal belonged to space group C2, with unit-cell parameters

  1. Synchrotron and laboratory studies utilizing a new powder diffraction technique

    SciTech Connect

    Knapp, G.S.; Beno, M.A.; Jennings, G.; Engbretson, M.; Ramanathan, M.

    1992-10-01

    We have developed a new type of powder diffractometer that is much more efficient than existing methods. The diffractometer has the potential of both high count rates and very high resolution when used at a synchrotron source. The laboratory based instrument has an order of magnitude improvement in count rate over existing methods. The method uses a focusing diffracted beam monochromator in combination with a multichannel detector. The incident x-rays fall on a flat plate or capillary sample and are intercepted by a bent focusing monochromator which has the focus of the bend at the sample surface. The powder diffraction lines emerging from the bent crystal monochromator are detected by a linear or 2-dimensional detector. This allows us to eliminate the background from fluorescence or other scattering and to take data over a range of 3[degrees] to 4[degrees] instead of one angle at a time thereby providing a large improvement over conventional diffractometers. Results are presented for fluorapatite Fe[sub 2]O[sub 3], and a high-TC superconductor.

  2. Synchrotron and laboratory studies utilizing a new powder diffraction technique

    SciTech Connect

    Knapp, G.S.; Beno, M.A.; Jennings, G.; Engbretson, M.; Ramanathan, M.

    1992-10-01

    We have developed a new type of powder diffractometer that is much more efficient than existing methods. The diffractometer has the potential of both high count rates and very high resolution when used at a synchrotron source. The laboratory based instrument has an order of magnitude improvement in count rate over existing methods. The method uses a focusing diffracted beam monochromator in combination with a multichannel detector. The incident x-rays fall on a flat plate or capillary sample and are intercepted by a bent focusing monochromator which has the focus of the bend at the sample surface. The powder diffraction lines emerging from the bent crystal monochromator are detected by a linear or 2-dimensional detector. This allows us to eliminate the background from fluorescence or other scattering and to take data over a range of 3{degrees} to 4{degrees} instead of one angle at a time thereby providing a large improvement over conventional diffractometers. Results are presented for fluorapatite Fe{sub 2}O{sub 3}, and a high-TC superconductor.

  3. A study of X-ray multiple diffraction by means of section topography.

    PubMed

    Kohn, V G; Smirnova, I A

    2015-09-01

    The results of theoretical and experimental study are presented for the question of how the X-ray multiple diffraction in a silicon single crystal influences the interference fringes of section topography for the 400 reflection in the Laue case. Two different cases of multiple diffraction are discovered for zero and very small values of the azimuthal angle for the sample in the form of a plate with the surface normal to the 001 direction. The cases are seen on the same topogram without rotation of the crystal. Accurate computer simulations of the section topogram for the case of X-ray multiple diffraction are performed for the first time. It is shown that the structure of interference fringes on the section topogram in the region of multiple diffraction becomes more complicated. It has a very sharp dependence on the azimuthal angle. The experiment is carried out using a laboratory source under conditions of low resolution over the azimuthal angle. Nevertheless, the characteristic inclination of the interference fringes on the tails of the multiple diffraction region is easily seen. This phenomenon corresponds completely to the computer simulations.

  4. High resolution synchrotron X-radiation diffraction imaging of crystals grown in microgravity and closely related terrestrial crystals

    NASA Technical Reports Server (NTRS)

    Steiner, Bruce; Dobbyn, Ronald C.; Black, David; Burdette, Harold; Kuriyama, Masao; Fripp, Archibald; Simchik, Richard

    1991-01-01

    Irregularities in three crystals grown in space and in four terrestrial crystals grown under otherwise comparable conditions have been observed in high resolution diffraction imaging. The images provide important new clues to the nature and origins of irregularities in each crystal. For two of the materials, mercuric iodide and lead tin telluride, more than one phase (an array of non-diffracting inclusions) was observed in terrestrial samples; but the formation of these multiple phases appears to have been suppressed in directly comparable crystals grown in microgravity. The terrestrial seed crystal of triglycine sulfate displayed an unexpected layered structure, which propagated during directly comparable space growth. Terrestrial Bridgman regrowth of gallium arsenide revealed a mesoscopic structure substantially different from that of the original Czochralski material. A directly comparable crystal is to be grown shortly in space.

  5. Contrast and resolution in direct Fresnel diffraction phase-contrast imaging with partially coherent x-ray source

    SciTech Connect

    Han Shensheng; Yu Hong; Cheng Jing; Gao Chen; Luo Zhenlin

    2004-10-01

    A general treatment of x-ray image formation by direct Fresnel diffraction with partially coherent hard x rays is presented. Contrast and resolution are the criteria used to specify the visibility of an image, which depend primarily on the spatial coherence of the illumination and the distance from object to the image, with chromatic coherence of lesser importance. The dependence of the quality of phase-contrast images on the parameters of in-line imaging configuration is described quantitatively. The influence of spatial coherence of hard x-ray source on the imaging quality is also discussed based on the partially coherent direct Fresnel diffraction phase-contrast imaging theory. Experimental results are also presented for phase-contrast x-ray images with partially coherent hard x rays.

  6. Structure-change-dependent transmittance of PtOx thin film in super-resolution near-field structure: Diffraction effect analysis

    NASA Astrophysics Data System (ADS)

    Qu, Qingling; Wang, Yang; Gan, Fuxi

    2007-08-01

    To study working mechanism of super-resolution near-field structure (super-RENS) optical disk from a far-field optics view is very necessary because of the actual far-field writing/readout process in the optical disk system. A Gaussian diffraction model based on Fresnel Kirchhoff diffraction theory of PtOx-type super-RENS has been set up in this Letter. The relationship between micro-structural deformation (change of bubble structure and refractive index profile) with far-field optical response of PtOx thin film has been studied with it in detail. The simulation results are in good agreement with the experimental results reported in literatures with a designed configuration. These results may provide more quantitative information for better understanding of the working mechanism of metal-oxide-type super-RENS.

  7. Diffraction-limited spatial resolution of circumstellar shells at 10 microns

    NASA Technical Reports Server (NTRS)

    Bloemhof, E. E.; Townes, C. H.; Vanderwyck, A. H. B.

    1983-01-01

    A new spatial array instrument provided diffraction-limited mid-infrared intensity profiles of the type-M supergiant stars alpha Orionis and alpha Scorpii, both of which are known to exhibit excess 10 microns radiation due to the presence of circumstellar dust shells. In the case of alpha Ori, there is a marked asymmetry in the dust distribution, with peak intensity of dust emission a distance of 0.9 inches from the star.

  8. A 3-D numerical study of pinhole diffraction to predict the accuracy of EUV point diffraction interferometry

    SciTech Connect

    Goldberg, K.A. |; Tejnil, E.; Bokor, J. |

    1995-12-01

    A 3-D electromagnetic field simulation is used to model the propagation of extreme ultraviolet (EUV), 13-nm, light through sub-1500 {Angstrom} dia pinholes in a highly absorptive medium. Deviations of the diffracted wavefront phase from an ideal sphere are studied within 0.1 numerical aperture, to predict the accuracy of EUV point diffraction interferometersused in at-wavelength testing of nearly diffraction-limited EUV optical systems. Aberration magnitudes are studied for various 3-D pinhole models, including cylindrical and conical pinhole bores.

  9. Combined X-ray and neutron fibre diffraction studies of biological and synthetic polymers.

    SciTech Connect

    Parrot, I. M.; Urban, Volker S; Gardner, K. H.; Forsyth, V. T.

    2005-04-01

    The fibrous state is a natural one for polymer molecules which tend to assume regular helical conformations rather than the globular structures characteristic of many proteins. Fibre diffraction therefore has broad application to the study of a wide range of biological and synthetic polymers. The purpose of this paper is to illustrate the general scope of the method and in particular to demonstrate the impact of a combined approach involving both X-ray and neutron diffraction methods. While the flux of modern X-ray synchrotron radiation sources allows high quality datasets to be recorded with good resolution within a very short space of time, neutron studies can provide unique information through the ability to locate hydrogen or deuterium atoms that are often difficult or impossible to locate using X-ray methods. Furthermore, neutron fibre diffraction methods can, through the ability to selectively label specific parts of a structure, be used to highlight novel aspects of polymer structure that can not be studied using X-rays. Two examples are given. The first describes X-ray and neutron diffraction studies of conformational transitions in DNA. The second describes structural studies of the synthetic high-performance polymer poly(p-phenylene terephthalamide) (PPTA), known commercially as Kevlar{reg_sign} or Twaron{reg_sign}.

  10. Signal enhancement and Patterson-search phasing for high-spatial-resolution coherent X-ray diffraction imaging of biological objects.

    PubMed

    Takayama, Yuki; Maki-Yonekura, Saori; Oroguchi, Tomotaka; Nakasako, Masayoshi; Yonekura, Koji

    2015-01-28

    In this decade coherent X-ray diffraction imaging has been demonstrated to reveal internal structures of whole biological cells and organelles. However, the spatial resolution is limited to several tens of nanometers due to the poor scattering power of biological samples. The challenge is to recover correct phase information from experimental diffraction patterns that have a low signal-to-noise ratio and unmeasurable lowest-resolution data. Here, we propose a method to extend spatial resolution by enhancing diffraction signals and by robust phasing. The weak diffraction signals from biological objects are enhanced by interference with strong waves from dispersed colloidal gold particles. The positions of the gold particles determined by Patterson analysis serve as the initial phase, and this dramatically improves reliability and convergence of image reconstruction by iterative phase retrieval. A set of calculations based on current experiments demonstrates that resolution is improved by a factor of two or more.

  11. X-RAY DIFFRACTION STUDIES ON FROG MUSCLES.

    PubMed

    Spiegel-Adolf, M; Henny, G C; Ashkenaz, E W

    1944-11-20

    1. X-ray diffraction studies of sartorius muscles of Rana pipiens were made in a new x-ray diffraction camera which permits exposures of 3 to 6 minutes. The object-film distance can be varied from 20 to 80 mm; the muscle inside the camera can be electrically stimulated while contracting isotonically or isometrically, and can be observed by a special device. After exposures up to 30 minutes (approximately 40,830 r) muscles are still alive and responsive. 2. Contrary to the x-ray diffraction pattern of powdered dry muscle, which pattern consists of two rings corresponding to spacings of 4.46 A.u. and 9.66 A.u., both moist and dried whole sartorius muscle show signs of orientation in both rings, consisting of two equatorial streaks (wet) or points (dry) and meridional sickles. The moist muscle shows in addition a diffuse water ring. The spacings corresponding to the orientation points and elliptical structure show only slight differences in moist and dried samples. Through statistical computations based on two different series consisting of thirteen moist and twenty-eight dried samples, and nine muscles before and after drying, it was shown that only the divergence in the smaller spacing has some real significance, which indicates that most water of the moist muscle is bound intermolecularly. Upon resoaking of dried muscle the x-ray diffraction pattern of the moist muscle is restored. 3. Stretching of muscle by weights below the breaking point produces an additional well defined diffraction line, corresponding to a spacing of 4.32 A.u. A similar diffraction line can be produced in frog tendon upon stretching. 4. The influence of heat on the x-ray diffraction pattern of muscle depends upon the maximum temperature and the length of action; 5 minutes at 50 degrees C. markedly reduces the orientation of the sample; 5 minutes' immersion in boiling Ringer's solution destroys the orientation and produces a ring corresponding to a spacing of 5.3 to 5.5 A.u. in the moist and

  12. X-ray diffraction studies of shocked lunar analogs

    NASA Technical Reports Server (NTRS)

    Hanss, R. E.

    1979-01-01

    The X-ray diffraction experiments on shocked rock and mineral analogs of particular significance to lunar geology are described. Materials naturally shocked by meteorite impact, nuclear-shocked, or artificially shocked in a flat plate accelerator were utilized. Four areas were outlined for investigation: powder diffractometer studies of shocked single crystal silicate minerals (quartz, orthoclase, oligoclase, pyroxene), powder diffractometer studies of shocked polycrystalline monomineralic samples (dunite), Debye-Scherrer studies of single grains of shocked granodiorite, and powder diffractometer studies of shocked whole rock samples. Quantitative interpretation of peak shock pressures experienced by materials found in lunar or terrestrial impact structures is presented.

  13. Rapid super-resolution imaging of sub-surface nanostructures beyond diffraction limit by high refractive index microsphere optical nanoscopy

    NASA Astrophysics Data System (ADS)

    Lee, Seoungjun; Li, Lin

    2015-01-01

    Sub-surface nanostructures cannot be observed by scanning electronic microscopy or standard scanning probe microscopy. They are also outside the resolution limit of standard optical microscopes. In this paper, we demonstrate super-resolution imaging of sub-surface nanostructures beyond the optical diffraction limit. Sub-surface Blu-ray recorded data structures (100-200 nm) have been observed directly with submerged microsphere optical nanoscopy (SMON) using TiO2-BaO-ZnO glass microspheres (refractive index=2.2) of 60 μm diameter immersed in water coupled with a standard optical microscope. Theoretical analysis of the imaging phenomena was carried out by the characteristics of electrical field Poynting vectors and photonic nanojets.

  14. Isomorphism and solid solution as shown by an accurate high-resolution diffraction experiment.

    PubMed

    Poulain, Agnieszka; Kubicki, Maciej; Lecomte, Claude

    2014-12-01

    High-resolution crystal structure determination and spherical and multipolar refinement enabled an organic solid solution of 1-(4'-chlorophenyl)-2-methyl-4-nitro-1H-imidazole-5-carbonitrile and 5-bromo-1-(4'-chlorophenyl)-2-methyl-4-nitro-1H-imidazole to be found, which would not normally be revealed using only standard resolution data (ca 0.8 Å), as the disordered part is only visible at high resolution. Therefore, this new structure would have been reported as just another polymorphic form, even more reasonably as isostructural with other derivatives. To the best of our knowledge this is the first example of organic solid solution modelled via charge density Hansen-Coppens formalism and analysed by means of quantum theory of atoms in molecules (QTAIM) theory.

  15. Preliminary time-of-flight neutron diffraction study on diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris

    SciTech Connect

    Blum, Marc-Michael; Koglin, Alexander; Rüterjans, Heinz; Schoenborn, Benno; Langan, Paul; Chen, Julian C.-H.

    2007-01-01

    Diisopropyl fluorophosphatase (DFPase) effectively hydrolyzes a number of organophosphorus nerve agents, including sarin, cyclohexylsarin, soman and tabun. Neutron diffraction data have been collected from DFPase crystals to 2.2 Å resolution in an effort to gain further insight into the mechanism of this enzyme. The enzyme diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris is capable of decontaminating a wide variety of toxic organophosphorus nerve agents. DFPase is structurally related to a number of enzymes, such as the medically important paraoxonase (PON). In order to investigate the reaction mechanism of this phosphotriesterase and to elucidate the protonation state of the active-site residues, large-sized crystals of DFPase have been prepared for neutron diffraction studies. Available H atoms have been exchanged through vapour diffusion against D{sub 2}O-containing mother liquor in the capillary. A neutron data set has been collected to 2.2 Å resolution on a relatively small (0.43 mm{sup 3}) crystal at the spallation source in Los Alamos. The sample size and asymmetric unit requirements for the feasibility of neutron diffraction studies are summarized.

  16. Research of the new optical diffractive super-resolution element of the two-photon microfabrication

    NASA Astrophysics Data System (ADS)

    Wei, Peng; Zhu, Yu; Duan, Guanghong

    2006-11-01

    The new optical diffractive superresolution element (DSE) is being applied to improve the microfabrication radial superresolution in the two-photon three-dimension (3D) microfabrication system, which appeared only a few years ago and can provide the ability to confine photochemical and physical reactions to the order of laser wavelength in three dimensions. The design method of the DSE is that minimizing M if the lowest limit S l of the S and the highest limit G u of the G is set, where Liu [1] explained the definition of the S, M and G. Simulation test result proved that the microfabrication radial superresolution can be improved by the new optical DSE. The phenomenon can only be interpreted as the intensity of high-order and side of the zero-order diffraction peaks have been clapped under the twophoton absorption (TPA) polymerization threshold. In a word the polymerized volume can be chosen because the S l and the G u is correspondingly adjustable, even if the laser wavelength, objective lens and the photosensitive resin is fixed for a given two-photon microfabrication system. That means the radial superresolution of the two-photon microfabrication can be chosen.

  17. Theoretical study of precision and accuracy of strain analysis by nano-beam electron diffraction.

    PubMed

    Mahr, Christoph; Müller-Caspary, Knut; Grieb, Tim; Schowalter, Marco; Mehrtens, Thorsten; Krause, Florian F; Zillmann, Dennis; Rosenauer, Andreas

    2015-11-01

    Measurement of lattice strain is important to characterize semiconductor nanostructures. As strain has large influence on the electronic band structure, methods for the measurement of strain with high precision, accuracy and spatial resolution in a large field of view are mandatory. In this paper we present a theoretical study of precision and accuracy of measurement of strain by convergent nano-beam electron diffraction. It is found that the accuracy of the evaluation suffers from halos in the diffraction pattern caused by a variation of strain within the area covered by the focussed electron beam. This effect, which is expected to be strong at sharp interfaces between materials with different lattice plane distances, will be discussed for convergent-beam electron diffraction patterns using a conventional probe and for patterns formed by a precessing electron beam. Furthermore, we discuss approaches to optimize the accuracy of strain measured at interfaces. The study is based on the evaluation of diffraction patterns simulated for different realistic structures that have been investigated experimentally in former publications. These simulations account for thermal diffuse scattering using the frozen-lattice approach and the modulation-transfer function of the image-recording system. The influence of Poisson noise is also investigated.

  18. High Resolution X-ray Diffraction Dataset for Bacillus licheniformis Gamma Glutamyl Transpeptidase-acivicin complex: SUMO-Tag Renders High Expression and Solubility.

    PubMed

    Kumari, Shobha; Pal, Ravi Kant; Gupta, Rani; Goel, Manisha

    2017-02-01

    Gamma glutamyl transpeptidase, (GGT) is a ubiquitous protein which plays a central role in glutathione metabolism and has myriad clinical implications. It has been shown to be a virulence factor for pathogenic bacteria, inhibition of which results in reduced colonization potential. However, existing inhibitors are effective but toxic and therefore search is on for novel inhibitors, which makes it imperative to understand the interactions of various inhibitors with the protein in substantial detail. High resolution structures of protein bound to different inhibitors can serve this purpose. Gamma glutamyl transpeptidase from Bacillus licheniformis is one of the model systems that have been used to understand the structure-function correlation of the protein. The structures of the native protein (PDB code 4OTT), of its complex with glutamate (PDB code 4OTU) and that of its precursor mimic (PDB code 4Y23) are available, although at moderate/low resolution. In the present study, we are reporting the preliminary analysis of, high resolution X-ray diffraction data collected for the co-crystals of B. licheniformis, Gamma glutamyl transpeptidase, with its inhibitor, Acivicin. Crystals belong to the orthorhombic space group P212121 and diffract X-ray to 1.45 Å resolution. This is the highest resolution data reported for all GGT structures available till now. The use of SUMO fused expression system enhanced yield of the target protein in the soluble fraction, facilitating recovery of protein with high purity. The preliminary analysis of this data set shows clear density for the inhibitor, acivicin, in the protein active site.

  19. A flow-through hydrothermal cell for in situ neutron diffraction studies of phase transformations

    NASA Astrophysics Data System (ADS)

    O'Neill, Brian; Tenailleau, Christophe; Nogthai, Yung; Studer, Andrew; Brugger, Joël; Pring, Allan

    2006-11-01

    A flow-through hydrothermal cell for the in situ neutron diffraction study of crystallisation and phase transitions has been developed. It can be used for kinetic studies on materials that exhibit structural transformations under hydrothermal conditions. It is specifically designed for use on the medium-resolution powder diffractometer (MRPD) at ANSTO, Lucas Heights, Sydney. But it is planned to adapt the design for the Polaris beamline at ISIS and the new high-intensity powder diffractometer (Wombat) at the new Australian reactor Opal. The cell will operate in a flow-through mode over the temperature range from 25-300 °C and up to pressures of 100 bar. The first results of a successful transformation of pentlandite (Fe,Ni) 9S 8 to violarite (Fe,Ni) 3S 4 under mild conditions (pH∼4) at 120 °C and 3 bar using in situ neutron diffraction measurements are presented.

  20. High-resolution triple-crystal x-ray-diffraction experiments performed at the Australian National Beamline Facility in Japan (abstract)

    NASA Astrophysics Data System (ADS)

    Nikulin, A. Yu.; Stevenson, A. W.; Hashizume, H.; Wilkins, S. W.; Cookson, D.; Foran, G.; Garrett, R. F.

    1995-02-01

    The x-ray-diffraction results reported here are from the first high-resolution triple-crystal experiments to be performed at the Australian National Beamline Facility at the Photon Factory. The heart of the facility is a multipurpose two-axis high-resolution vacuum diffractometer (BIGDIFF) Z. Barnea et al., Rev. Sci. Instrum. 63, 1069 (1992) capable of use for high-resolution powder diffraction (using both conventional scintillation detectors and imaging plates), protein crystallography, reflectometry, as well as single-crystal diffractometry. The present experiments were conducted on BIGDIFF in triple-crystal diffraction mode with a monolithic channel-cut Si monochromator (supplied by Professor M. Hart), a single-crystal Si sample, and a four-reflection monolithic channel-cut Si analyzer crystal. The Si(111) sample is a part of a wafer which had been implanted with 100 keV B+ ions (doses 1×1015 and 5×1015 cm-2) through a one-dimensional 0.5 μm thick oxide strip pattern with a 5.83 μm period and 4 μm open region. The triple-crystal data were collected in the form of two-dimensional intensity maps in the vicinity of the 111 Bragg peak, varying the sample rotation (ω) and the analyzer/scintillation detector rotation (2θ). The first results were collected in air both with the as-described sample and after the oxide layer had been removed. Certain slice scans (one-dimensional sections of the two-dimensional intensity maps) were also collected with a vacuum of 1 Torr and reveal considerable improvement in signal to background. The data will be compared with a recent similar study A. Yu. Nikulin et al., J. Appl. Cryst. 27, 338 (1994) performed on BL-14B at the Photon Factory. The new data collected in air indicate that lattice distortion may be mapped with a resolution of approximately 160 Å, to a depth of approximately 1.0 μm, providing valuable quantitative information on ion diffusion in such implanted materials. The slice scans collected in vacuum indicate

  1. An electron diffraction study of alkali chloride vapors

    NASA Technical Reports Server (NTRS)

    Mawhorter, R. J.; Fink, M.; Hartley, J. G.

    1985-01-01

    A study of monomers and dimers of the four alkali chlorides NaCl, KCl, RbCl, and CsCl in the vapor phase using the counting method of high energy electron diffraction is reported. Nozzle temperatures from 850-960 K were required to achieve the necessary vapor pressures of approximately 0.01 torr. Using harmonic calculations for the monomer and dimer 1 values, a consistent set of structures for all four molecules was obained. The corrected monomer distances reproduce the microwave values very well. The experiment yields information on the amount of dimer present in the vapor, and these results are compared with thermodynamic values.

  2. Diffractive telescope for protoplanetary disks study in UV

    NASA Astrophysics Data System (ADS)

    Roux, W.; Koechlin, L.

    2015-12-01

    The direct observation of exoplanetary systems and their environment remains a technological challenge: on the one hand, because of the weak luminosity of objects surrounding the central star, and on the other hand, because of their small size compared to the distance from Earth. The fresnel imager is a concept of space telescope based on focusing by diffraction, developed by our team in Institut de Recherche en Astrophysique et Planétologie (IRAP). Its high photometric dynamics and its low angular resolution make it a competitive candidate. Currently we propose a space mission on board the International Space Station (ISS), observing in the ultraviolet band, in order to validate its capabilities in space and so increase the Technological Readiness Level (TRL), anticipating a larger mission in the future. To reach this goal, we have to provide some evolutions, like improving the design of Fresnel arrays or conceive a new chromatism corrector. This paper presents the evolutions for the ISS prototype and its possible applications like protoplanetary disks imaging.

  3. Crystal regularity with high-resolution synchrotron x-radiation diffraction imaging

    SciTech Connect

    Steiner, B.; Dobbyn, R.C. )

    1991-06-01

    Large perfect crystals do not occur in nature, and crystal perfection is seldom approached naturally even on a mesoscopic scale. This paper reports that recently, however, the ability to realize macroscopic single crystals with a high degree of perfection and therefore with novel properties has stimulated a surge of interest in the perfection of crystals. This time, however, real crystals, not merely their abstraction, are the focus. One source of this new interest has been the new age of single-crystal devices based on silicon, which process information for a ubiquitous array of gadgets, instruments, vehicles, and systems. A substantial expansion of this capability through the incorporation of optics in sophisticated electrooptic devices for even faster and more complex information processing is now foreseen. Initial success is so promising that fully photonic information processing systems are being contemplated. Images formed by X-ray beams diffracting from single crystals have contributed to each of these strands of interest in crystal perfection, conceptual and practical.

  4. Ab initio simulation of diffractometer instrumental function for high-resolution X-ray diffraction.

    PubMed

    Mikhalychev, Alexander; Benediktovitch, Andrei; Ulyanenkova, Tatjana; Ulyanenkov, Alex

    2015-06-01

    Modeling of the X-ray diffractometer instrumental function for a given optics configuration is important both for planning experiments and for the analysis of measured data. A fast and universal method for instrumental function simulation, suitable for fully automated computer realization and describing both coplanar and noncoplanar measurement geometries for any combination of X-ray optical elements, is proposed. The method can be identified as semi-analytical backward ray tracing and is based on the calculation of a detected signal as an integral of X-ray intensities for all the rays reaching the detector. The high speed of calculation is provided by the expressions for analytical integration over the spatial coordinates that describe the detection point. Consideration of the three-dimensional propagation of rays without restriction to the diffraction plane provides the applicability of the method for noncoplanar geometry and the accuracy for characterization of the signal from a two-dimensional detector. The correctness of the simulation algorithm is checked in the following two ways: by verifying the consistency of the calculated data with the patterns expected for certain simple limiting cases and by comparing measured reciprocal-space maps with the corresponding maps simulated by the proposed method for the same diffractometer configurations. Both kinds of tests demonstrate the agreement of the simulated instrumental function shape with the measured data.

  5. Probing of protein localization and shuttling in mitochondrial microcompartments by FLIM with sub-diffraction resolution.

    PubMed

    Söhnel, Anna-Carina; Kohl, Wladislaw; Gregor, Ingo; Enderlein, Jörg; Rieger, Bettina; Busch, Karin B

    2016-08-01

    The cell is metabolically highly compartmentalized. Especially, mitochondria host many vital reactions in their different microcompartments. However, due to their small size, these microcompartments are not accessible by conventional microscopy. Here, we demonstrate that time-correlated single-photon counting (TCSPC) fluorescence lifetime-imaging microscopy (FLIM) classifies not only mitochondria, but different microcompartments inside mitochondria. Sensor proteins in the matrix had a different lifetime than probes at membrane proteins. Localization in the outer and inner mitochondrial membrane could be distinguished by significant differences in the lifetime. The method was sensitive enough to monitor shifts in protein location within mitochondrial microcompartments. Macromolecular crowding induced by changes in the protein content significantly affected the lifetime, while oxidizing conditions or physiological pH changes had only marginal effects. We suggest that FLIM is a versatile and completive method to monitor spatiotemporal events in mitochondria. The sensitivity in the time domain allows for gaining substantial information about sub-mitochondrial localization overcoming diffraction limitation. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.

  6. Synchrotron powder diffraction simplified: The high-resolution diffractometer at 11-BM at the Advanced Photon Source

    NASA Astrophysics Data System (ADS)

    Ribaud, Lynn; Suchomel, Matthew; von Dreele, Robert; Toby, Brian

    2013-03-01

    Synchrotrons have revolutionized powder diffraction through higher resolution and sensitivity and much faster data collection. Few scientists beyond the synchrotron community make use of these capabilities. To help address this, the high resolution powder diffractometer beamline 11-BM at the APS offers rapid and easy mail-in access with world-class quality data 1. This instrument offers the highest resolution available in the Americas and is a free service for non-proprietary users 2. The instrument can collect a superb pattern in an hour, has an automated sample changer, and features variable temperature sample environments. Users of the mail-in program often receive their data within two weeks of sample receipt. The instrument is also available for on-site experiments requiring other conditions. Our poster will describe this instrument, highlight its capabilities, explain the types of measurements available, and discuss plans to improve access and available sample environments and collection protocols. More information about the 11-BM instrument and our mail-in program can be found at: http://11bm.xray.aps.anl.gov.

  7. Apparatus and method to achieve high-resolution microscopy with non-diffracting or refracting radiation

    DOEpatents

    Tobin, Jr., Kenneth W.; Bingham, Philip R.; Hawari, Ayman I.

    2012-11-06

    An imaging system employing a coded aperture mask having multiple pinholes is provided. The coded aperture mask is placed at a radiation source to pass the radiation through. The radiation impinges on, and passes through an object, which alters the radiation by absorption and/or scattering. Upon passing through the object, the radiation is detected at a detector plane to form an encoded image, which includes information on the absorption and/or scattering caused by the material and structural attributes of the object. The encoded image is decoded to provide a reconstructed image of the object. Because the coded aperture mask includes multiple pinholes, the radiation intensity is greater than a comparable system employing a single pinhole, thereby enabling a higher resolution. Further, the decoding of the encoded image can be performed to generate multiple images of the object at different distances from the detector plane. Methods and programs for operating the imaging system are also disclosed.

  8. Crystal regularity with high-resolution synchrotron X-radiation diffraction imaging

    NASA Technical Reports Server (NTRS)

    Steiner, Bruce; Dobbyn, Ronald C.

    1991-01-01

    New, high-resolution sources of X-radiation such as monochromatic synchrotron radiation beams with subarcsec divergence allow observation of regularities in a range of crystals with sufficient clarity for comprehensive analyses, whose results can deepen understanding of the nature of various crystal irregularities, their sources, and their effects on device performance. An account is presented of the results thus achievable with irregularities encountered in lattice orientation and strain, grain and subgrain boundaries, dislocations, domain boundaries, additional phases, and surface scratches. Significant achievements to date encompass the observation of critical anomalies in lead tin telluride, the reconciliation of disparate observations of GaAs, the determination of the performance effects of irregularities in mercuric iodide, and the characterization of the origins of crystal growth in bismuth silicon oxide.

  9. Evaluation of dislocation densities in HgCdTe films by high-resolution x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Wang, Qingxue; Yang, Jianrong; Wei, Yanfeng; Fang, Weizheng; He, Li

    2005-01-01

    The dislocation densities in HgCdTe films grown on CdZnTe by Liquid Phase Epitaxy (LPE) are calculated based on their effects on the x-ray rocking curves. The dislocation densities derived from three kinds of methods, i.e. FWHM of X-ray double axis diffraction, Williamson-Hall plot and Pseudo-Voigt function, are approximately the same. It is found that the thickness of HgCdTe epilayers about 10 um is large enough so that effect of crystallize size on the rocking curves width can be ignored. Because the intrinsic FWHM of HgCdTe and the instrumental function of high resolution X-ray diffraction are neglected in Williamson-Hall plot and Pseudo-Voigt function, the dislocation densities obtained by these methods are a little larger than those derived from the first kind of method. Among three kinds of methods, Pseudo-Voigt function method is the easiest one to fit the rocking curves and calculate the dislocation densities.

  10. X-ray Diffraction Studies of Striated Muscles

    SciTech Connect

    Squire, J.M.; Knupp, C.; Roessle, M.; Al-Khayat, H.A.; Irving, T.C.; Eakins, F.; Mok, N.-S.; Harford, J.J.; Reedy, M.K.

    2006-04-24

    In this short review a number of recent X-ray diffraction results on the highly ordered striated muscles in insects and in bony fish have been briefly described. What is clear is that this technique applied to muscles which are amenable to rigorous analysis, taken together with related data from other sources (e.g. protein crystallography, biochemistry, mechanics, computer modelling) can provide not only the best descriptions yet available on the myosin head organisations on different myosin filaments in the relaxed state, but can also show the sequence of molecular events that occurs in the contractile cycle, and may also help to explain such phenomena as stretch-activation. X-ray diffraction is clearly an enormously powerful tool in studies of muscle. It has already provided a wealth of detail on muscle ultrastructure; it is providing ever more fascinating insights into molecular events in the 50-year old sliding filament mechanism, and there remains a great deal more potential that is as yet untapped.

  11. Determination of lattice parameters, strain state and composition in semipolar III-nitrides using high resolution X-ray diffraction

    SciTech Connect

    Frentrup, Martin Wernicke, Tim; Stellmach, Joachim; Kneissl, Michael; Hatui, Nirupam; Bhattacharya, Arnab

    2013-12-07

    In group-III-nitride heterostructures with semipolar or nonpolar crystal orientation, anisotropic lattice and thermal mismatch with the buffer or substrate lead to a complex distortion of the unit cells, e.g., by shearing of the lattice. This makes an accurate determination of lattice parameters, composition, and strain state under assumption of the hexagonal symmetry impossible. In this work, we present a procedure to accurately determine the lattice constants, strain state, and composition of semipolar heterostructures using high resolution X-ray diffraction. An analysis of the unit cell distortion shows that four independent lattice parameters are sufficient to describe this distortion. Assuming only small deviations from an ideal hexagonal structure, a linear expression for the interplanar distances d{sub hkl} is derived. It is used to determine the lattice parameters from high resolution X-ray diffraction 2ϑ-ω-scans of multiple on- and off-axis reflections via a weighted least-square fit. The strain and composition of ternary alloys are then evaluated by transforming the elastic parameters (using Hooke's law) from the natural crystal-fixed coordinate system to a layer-based system, given by the in-plane directions and the growth direction. We illustrate our procedure taking an example of (112{sup ¯}2) Al{sub κ}Ga{sub 1−κ}N epilayers with Al-contents over the entire composition range. We separately identify the in-plane and out-of-plane strains and discuss origins for the observed anisotropy.

  12. Anomalous X-ray Diffraction Studies for Photovoltaic Applications

    SciTech Connect

    Not Available

    2011-06-22

    Anomalous X-ray Diffraction (AXRD) has become a useful technique in characterizing bulk and nanomaterials as it provides specific information about the crystal structure of materials. In this project we present the results of AXRD applied to materials for photovoltaic applications: ZnO loaded with Ga and ZnCo{sub 2}O{sub 4} spinel. The X-ray diffraction data collected for various energies were plotted in Origin software. The peaks were fitted using different functions including Pseudo Voigt, Gaussian, and Lorentzian. This fitting provided the integrated intensity data (peaks area values), which when plotted as a function of X-ray energies determined the material structure. For the first analyzed sample, Ga was not incorporated into the ZnO crystal structure. For the ZnCo{sub 2}O{sub 4} spinel Co was found in one or both tetrahedral and octahedral sites. The use of anomalous X-ray diffraction (AXRD) provides element and site specific information for the crystal structure of a material. This technique lets us correlate the structure to the electronic properties of the materials as it allows us to probe precise locations of cations in the spinel structure. What makes it possible is that in AXRD the diffraction pattern is measured at a number of energies near an X-ray absorption edge of an element of interest. The atomic scattering strength of an element varies near its absorption edge and hence the total intensity of the diffraction peak changes by changing the X-ray energy. Thus AXRD provides element specific structural information. This method can be applied to both crystalline and liquid materials. One of the advantages of AXRD in crystallography experiments is its sensitivity to neighboring elements in the periodic tables. This method is also sensitive to specific crystallographic phases and to a specific site in a phase. The main use of AXRD in this study is for transparent conductors (TCs) analysis. TCs are considered to be important materials because of their

  13. Super-resolution photoacoustic microscopy using photonic nanojets: a simulation study.

    PubMed

    Upputuri, Paul Kumar; Wen, Zhuo-Bin; Wu, Zhe; Pramanik, Manojit

    2014-01-01

    Optical resolution photoacoustic microscopy (ORPAM) is important for various biomedical applications, such as the study of cellular structures, microcirculation systems, and tumor angiogenesis. However, the lateral resolution of a conventional ORPAM is limited by optical diffraction. In this work, we report a simulation study to achieve subdiffraction-limited super-resolution in ORPAM using microspheres. Laser radiation is focused through a microsphere to generate a photonic nanojet, which provides the possibility to break the diffraction limit in ORPAM by reducing the size of the excitation volume. In our simulations using microspheres, we observed improvement in the lateral resolution up to compared to conventional ORPAM. The method is simple, cost effective, and can provide far-field resolution. This approach may provide new opportunities for many biomedical imaging applications that require finer resolution.

  14. Super-resolution photoacoustic microscopy using photonic nanojets: a simulation study

    NASA Astrophysics Data System (ADS)

    Upputuri, Paul Kumar; Wen, Zhuo-Bin; Wu, Zhe; Pramanik, Manojit

    2014-11-01

    Optical resolution photoacoustic microscopy (ORPAM) is important for various biomedical applications, such as the study of cellular structures, microcirculation systems, and tumor angiogenesis. However, the lateral resolution of a conventional ORPAM is limited by optical diffraction. In this work, we report a simulation study to achieve subdiffraction-limited super-resolution in ORPAM using microspheres. Laser radiation is focused through a microsphere to generate a photonic nanojet, which provides the possibility to break the diffraction limit in ORPAM by reducing the size of the excitation volume. In our simulations using microspheres, we observed improvement in the lateral resolution up to ˜fourfold compared to conventional ORPAM. The method is simple, cost effective, and can provide far-field resolution. This approach may provide new opportunities for many biomedical imaging applications that require finer resolution.

  15. Transmission Electron Diffraction Studies of Xenon Adsorbed on Graphite.

    NASA Astrophysics Data System (ADS)

    Faisal, A. Q. D.

    1987-09-01

    Available from UMI in association with The British Library. Adsorption studies of xenon on graphite were performed using the Hitachi HU-11B Transmission Electron Microscope (TEM). It has been used as a Transmission High Energy Electron Diffraction (THEED) camera. This has been modified to include an Ultra High Vacuum (UHV) environmental chamber. This chamber was isolated from the microscope vacuum by two 400 μm diameter differentially pumped apertures. Pressures of {~}10 ^{-6} torr and {~ }10^{-9} torr were achieved inside the microscope column and the environmental chamber respectively. The chamber was fitted with a new sample holder designed with double "O" rings. The sample was cooled with liquid helium. Previous THEED experiments by Venables et al and Schabes-Retchkiman and Venables revealed the presence of a 2D-solid incommensurate (I)-commensurate (C) phase transition as the temperature is lowered. These results were confirmed and extended in the present work. Hong et al have recently interpreted their X-ray diffraction experiments as showing an incommensurate-striped domain phase transition at {~}65rm K. No evidence was found for the existence of a striped domain structure on any part of the xenon phase diagram studied. Experiments of xenon adsorbed on the basal plane (0001) of graphite were carried out at pressures from {~}1.5 times 10^{-5} torr to {~}1.8 times 10^{-8} torr over a temperature range from 55K^.90K. A set of lattice parameter (misfit) measurements were made as a function of temperature at constant pressure with an accuracy of +/-0.1% rather than +/-0.3% previously obtained. The misfit data was fitted to a power law formula, i.e. misfit m = B_{rm o} (rm T - rm T_{rm o})^{rm A} , where A is a constant and equal to 0.8. It was found that B_{rm o} and T_{rm o} are functions of log(P). The data fell into two groups corresponding to two phase transitions. The same power law was used for both sets of data. Two transitions were found, one is I-C and

  16. Recombination of photodissociated iodine: A time-resolved x-ray-diffraction study

    SciTech Connect

    Wulff, M.; Bratos, S.; Plech, A.; Vuilleumier, R.; Mirloup, F.; Lorenc, M.; Kong, Q.; Ihee, H.

    2006-01-21

    A time-resolved x-ray-diffraction experiment is presented that aims to study the recombination of laser-dissociated iodine molecules dissolved in CCl{sub 4}. This process is monitored over an extended time interval from pico- to microseconds. The variations of atom-atom distances are probed with a milliangstrom resolution. A recent theory of time-resolved x-ray diffraction is used to analyze the experimental data; it employs the correlation function approach of statistical mechanics. The most striking outcome of this study is the experimental determination of time-dependent I-I atom-atom distribution functions. The structure of the CCl{sub 4} solvent changes simultaneously; the solvent thus appears as a reaction partner rather than an inert medium hosting it. Thermal expansion of the system is nonuniform in time, an effect due to the presence of the acoustic horizon. One concludes that a time-resolved x-ray diffraction permits real-time visualization of solvent and solute motions during a chemical reaction.

  17. High-resolution computational ghost imaging and ghost diffraction through turbulence via a beam-shaping method

    NASA Astrophysics Data System (ADS)

    Luo, Chun-Ling; Zhuo, Ling-Qing

    2017-01-01

    Imaging through atmospheric turbulence is a topic with a long history and grand challenges still exist in the remote sensing and astro observation fields. In this letter, we try to propose a simple scheme to improve the resolution of imaging through turbulence based on the computational ghost imaging (CGI) and computational ghost diffraction (CGD) setup via the laser beam shaping techniques. A unified theory of CGI and CGD through turbulence with the multi-Gaussian shaped incoherent source is developed, and numerical examples are given to see clearly the effects of the system parameters to CGI and CGD. Our results show that the atmospheric effect to the CGI and CGD system is closely related to the propagation distance between the source and the object. In addition, by properly increasing the beam order of the multi-Gaussian source, we can improve the resolution of CGI and CGD through turbulence relative to the commonly used Gaussian source. Therefore our results may find applications in remote sensing and astro observation.

  18. Diffraction study of protein crystals grown in cryoloops and micromounts.

    PubMed

    Berger, Michael A; Decker, Johannes H; Mathews, Irimpan I

    2010-12-01

    Protein crystals are usually grown in hanging or sitting drops and generally get transferred to a loop or micromount for cryocooling and data collection. This paper describes a method for growing crystals on cryoloops for easier manipulation of the crystals for data collection. This study also investigates the steps for the automation of this process and describes the design of a new tray for the method. The diffraction patterns and the structures of three proteins grown by both the new method and the conventional hanging-drop method are compared. The new setup is optimized for the automation of the crystal mounting process. Researchers could prepare nanolitre drops under ordinary laboratory conditions by growing the crystals directly in loops or micromounts. As has been pointed out before, higher levels of supersaturation can be obtained in very small volumes, and the new method may help in the exploration of additional crystallization conditions.

  19. A neutron diffraction study of ancient Greek ceramics

    NASA Astrophysics Data System (ADS)

    Siouris, I. M.; Walter, J.

    2006-11-01

    Non-destructive neutron diffraction studies were performed on three 2nd-century BC archaeological pottery fragments from the excavation site of Neos Scopos, Serres, in North Greece. In all the 273 K diagrams quartz and feldspars phase fractions are dominant. Diopside and iron oxide phases were also identifiable. The diopside content is found to decrease with increasing quartz-feldspar compositions. Iron oxides containing minerals were found to be present and the phase compositions reflect upon the coloring of the samples. However, the different content compositions of the phases may suggest different regions of the original clay materials as well as different preparation techniques. The firing temperatures were determined to be in the range of 900-1000 °C.

  20. High resolution grazing-incidence in-plane x-ray diffraction for measuring the strain of a Si thin layer.

    PubMed

    Omote, Kazuhiko

    2010-12-01

    We have measured the strain of a thin Si layer deposited on a SiGe layer using a high resolution x-ray diffraction system. The Si layer was deposited on the SiGe layer in order to introduce a tensile strain to the Si layer. To measure the in-plane lattice constant accurately, we have employed so-called grazing-incidence in-plane diffraction. For this measurement, we have made a new five-axis x-ray goniometer which has four ordinal circles (ω, 2θ, χ, φ) plus a counter-χ-axis for selecting the exit angle of the diffracted x-rays. In grazing-incidence geometry, an incident x-ray is focused on the sample surface in order to obtain good diffraction intensity even though the layer thickness is less than 5 nm. Because diffracted x-rays are detected through analyzer crystals, the diffraction angle can be determined with an accuracy of ± 0.0003°. This indicates that the strain sensitivity is about 10( - 5) when we measure in-plane Si 220 diffraction. Use of x-ray diffraction could be the best standard metrology method for determining strain in thin layers. Furthermore, we have demonstrated that incident/exit angle selected in-plane diffraction is very useful for height/depth selective strain determination.

  1. Quantitative energy-dispersive x-ray diffraction for identification of counterfeit medicines: a preliminary study

    NASA Astrophysics Data System (ADS)

    Crews, Chiaki C. E.; O'Flynn, Daniel; Sidebottom, Aiden; Speller, Robert D.

    2015-06-01

    The prevalence of counterfeit and substandard medicines has been growing rapidly over the past decade, and fast, nondestructive techniques for their detection are urgently needed to counter this trend. In this study, energy-dispersive X-ray diffraction (EDXRD) combined with chemometrics was assessed for its effectiveness in quantitative analysis of compressed powder mixtures. Although EDXRD produces lower-resolution diffraction patterns than angular-dispersive X-ray diffraction (ADXRD), it is of interest for this application as it carries the advantage of allowing the analysis of tablets within their packaging, due to the higher energy X-rays used. A series of caffeine, paracetamol and microcrystalline cellulose mixtures were prepared with compositions between 0 - 100 weight% in 20 weight% steps (22 samples in total, including a centroid mixture), and were pressed into tablets. EDXRD spectra were collected in triplicate, and a principal component analysis (PCA) separated these into their correct positions in the ternary mixture design. A partial least-squares (PLS) regression model calibrated using this training set was validated using both segmented cross-validation, and with a test set of six samples (mixtures in 8:1:1 and 5⅓:2⅓:2⅓ ratios) - the latter giving a root-mean square error of prediction (RMSEP) of 1.30, 2.25 and 2.03 weight% for caffeine, paracetamol and cellulose respectively. These initial results are promising, with RMSEP values on a par with those reported in the ADXRD literature.

  2. A Quantitative Analysis of Room Temperature Recrystallization Kinetics in Electroplated Copper Films using High Resolution X-ray Diffraction

    SciTech Connect

    A Ying; K Witt; J Jordan-Sweet; R Rosenberg; I Noyan

    2011-12-31

    Time-resolved in situ x-ray diffraction measurements were used to study the room-temperature recrystallization kinetics of electroplated copper thin films with thicknesses between 400 and 1000 nm. The thinnest films exhibited limited recrystallization and subsequent growth of grains, while recrystallized grains in the thicker films grew until all as-plated microstructure was consumed. For all films, recrystallized grains that belonged to the majority texture component, <111>, started growing after the shortest incubation time. These grains exhibited volumetric growth until they achieved the film thickness. After this point the growth mode became planar, with the <111>-type grains growing in the plane of the film. Grains with the <111> direction normal to the film surface started growing after the <111>-type grains switched to planar growth. However, the planar growth of this texture component finished at the same time as the growth of the <111> grains. Profile fitting of the 111 peak permitted the separation of the diffraction signals from recrystallized and as-plated grain populations. The average strains in these two populations, calculated from the peak position of the corresponding {l_brace}111{r_brace} reflections, were different, indicating a heterogeneous stress state within this texture component. The increasing volume fraction of recrystallized <111> grains with time was monitored via the variation in the diffracted intensity. This variation could be represented by the Johnson-Mehl-Avrami-Kolmogorov model.

  3. Overexpression, purification, crystallization and preliminary diffraction studies of the Protaminobacter rubrum sucrose isomerase SmuA

    SciTech Connect

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

    2006-01-01

    The P. rubrum sucrose isomerase SmuA, a key enzyme in the industrial production of isomaltulose, was crystallized and diffraction data were collected to 1.95 Å resolution. Palatinose (isomaltulose, α-d-glucosylpyranosyl-1,6-d-fructofuranose), a nutritional and acariogenic reducing sugar, is industrially obtained from sucrose by using immobilized cells of Protaminobacter rubrum that produce the sucrose isomerase SmuA. The isomerization of sucrose catalyzed by this enzyme also results in the formation of trehalulose (α-d-glucosylpyranosyl-1,1-d-fructofuranose) in smaller amounts and glucose, fructose and eventually isomaltose as by-products, which lower the yield of the reaction and complicate the recovery of palatinose. The determination of the three-dimensional structure of SmuA will provide a basis for rational protein-engineering studies in order to optimize the industrial production of palatinose. A recombinant form of the 67.3 kDa SmuA enzyme has been crystallized in the native state by the vapour-diffusion method. Crystals belong to the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 61.6, b = 81.4, c = 135.6 Å, and diffract to 1.95 Å resolution on a synchrotron-radiation source.

  4. A computational technique to optimally design in-situ diffractive elements: applications to projection lithography at the resist resolution limit

    NASA Astrophysics Data System (ADS)

    Feijóo, Gonzalo R.; Tirapu-Azpiroz, Jaione; Rosenbluth, Alan E.; Oberai, Assad A.; Jagalur Mohan, Jayanth; Tian, Kehan; Melville, David; Gil, Dario; Lai, Kafai

    2009-03-01

    Near-field interference lithography is a promising variant of multiple patterning in semiconductor device fabrication that can potentially extend lithographic resolution beyond the current materials-based restrictions on the Rayleigh resolution of projection systems. With H2O as the immersion medium, non-evanescent propagation and optical design margins limit achievable pitch to approximately 0.53λ/nH2O = 0.37λ. Non-evanescent images are constrained only by the comparatively large resist indices (typically1.7) to a pitch resolution of 0.5/nresist (typically 0.29). Near-field patterning can potentially exploit evanescent waves and thus achieve higher spatial resolutions. Customized near-field images can be achieved through the modulation of an incoming wavefront by what is essentially an in-situ hologram that has been formed in an upper layer during an initial patterned exposure. Contrast Enhancement Layer (CEL) techniques and Talbot near-field interferometry can be considered special cases of this approach. Since the technique relies on near-field interference effects to produce the required pattern on the resist, the shape of the grating and the design of the film stack play a significant role on the outcome. As a result, it is necessary to resort to full diffraction computations to properly simulate and optimize this process. The next logical advance for this technology is to systematically design the hologram and the incident wavefront which is generated from a reduction mask. This task is naturally posed as an optimization problem, where the goal is to find the set of geometric and incident wavefront parameters that yields the closest fit to a desired pattern in the resist. As the pattern becomes more complex, the number of design parameters grows, and the computational problem becomes intractable (particularly in three-dimensions) without the use of advanced numerical techniques. To treat this problem effectively, specialized numerical methods have been

  5. An X-ray diffraction study of titanium oxidation

    NASA Technical Reports Server (NTRS)

    Wiedemann, K. E.; Unnam, J.

    1984-01-01

    Titanium specimens of commercial purity were exposed at 1100 to 1400 F to laboratory air for times up to 100 hours. The extent of substrate contamination by interstitial oxygen was was determined by a new X-ray diffraction analysis involving transformation of X-ray diffraction intensity bands. The oxygen solid-solubility at the oxide-metal interfaces and its variation with time at temperature were also determined. Diffusion coefficients are deduced from the oxygen depth profiles.

  6. Palladium deuteride formation in the cathode of an electrochemical cell: An in situ neutron diffraction study

    SciTech Connect

    Rotella, F.J.; Richardson, J.W. Jr.; Redey, L.; Felcher, G.P.; Hitterman, R.L.; Kleb, R.

    1991-12-31

    In this report, neutron diffraction of palladium cathodes is utilized to reveal palladium deuteride formation within the crystal structure of the metal. The experiment described in this report demonstrates the efficacy of neutron powder diffraction as a tool for structural studies of metal deuterides/hydrides and the feasibility of in situ diffraction measurements from a working electrochemical cell. (JL)

  7. Palladium deuteride formation in the cathode of an electrochemical cell: An in situ neutron diffraction study

    SciTech Connect

    Rotella, F.J.; Richardson, J.W. Jr.; Redey, L.; Felcher, G.P.; Hitterman, R.L.; Kleb, R.

    1991-01-01

    In this report, neutron diffraction of palladium cathodes is utilized to reveal palladium deuteride formation within the crystal structure of the metal. The experiment described in this report demonstrates the efficacy of neutron powder diffraction as a tool for structural studies of metal deuterides/hydrides and the feasibility of in situ diffraction measurements from a working electrochemical cell. (JL)

  8. A Study of Detonation Propagation and Diffraction with Compliant Confinement

    SciTech Connect

    Banks, J; Schwendeman, D; Kapila, A; Henshaw, W

    2007-08-13

    A previous computational study of diffracting detonations with the ignition-and-growth model demonstrated that contrary to experimental observations, the computed solution did not exhibit dead zones. For a rigidly confined explosive it was found that while diffraction past a sharp corner did lead to a temporary separation of the lead shock from the reaction zone, the detonation re-established itself in due course and no pockets of unreacted material were left behind. The present investigation continues to focus on the potential for detonation failure within the ignition-and-growth (IG) model, but now for a compliant confinement of the explosive. The aim of the present paper is two fold. First, in order to compute solutions of the governing equations for multi-material reactive flow, a numerical method of solution is developed and discussed. The method is a Godunov-type, fractional-step scheme which incorporates an energy correction to suppress numerical oscillations that would occur near the material interface separating the reactive material and the inert confiner for standard conservative schemes. The numerical method uses adaptive mesh refinement (AMR) on overlapping grids, and the accuracy of solutions is well tested using a two-dimensional rate-stick problem for both strong and weak inert confinements. The second aim of the paper is to extend the previous computational study of the IG model by considering two related problems. In the first problem, the corner-turning configuration is re-examined, and it is shown that in the matter of detonation failure, the absence of rigid confinement does not affect the outcome in a material way; sustained dead zones continue to elude the model. In the second problem, detonations propagating down a compliantly confined pencil-shaped configuration are computed for a variety of cone angles of the tapered section. It is found, in accord with experimental observation, that if the cone angle is small enough, the detonation fails

  9. X-ray Diffraction Study of Molybdenum to 900 GPa

    NASA Astrophysics Data System (ADS)

    Wang, J.; Coppari, F.; Smith, R.; Eggert, J.; Boehly, T.; Collins, G. W.; Duffy, T. S.

    2013-12-01

    Molybdenum (Mo) is a transition metal that is important as a high-pressure standard. Its equation of state, structure, and melting behavior have been explored extensively in both experimental and theoretical studies. Melting data up to the Mbar pressure region from static compression experiments in the diamond anvil cell [Errandonea et al. 2004] are inconsistent with shock wave sound velocity measurements [Hixson et al., 1989]. There are also conflicting reports as to whether body-centered cubic (BCC) Mo transforms to a face-centered cubic (FCC), hexagonal close packed (HCP) or double hexagonal close packed (DHCP) structure at either high pressure or high pressure and temperature conditions [Belonoshko et al. 2008, Mikhaylushkin et al., 2008 and Cazorla et al., 2008]. Recently, a phase transition from BCC to the DHCP phase at 660 GPa and 0 K was predicted using the particle swam optimization (PSO) method (Wang et al, 2013). Here we report an x-ray diffraction study of dynamically compressed molybdenum. Experiments were conducted using the Omega laser at the Laboratory for Laser Energetics at the University of Rochester. Mo targets were either ramp or shock compressed using a laser drive. In ramp loading, the sample is compressed sufficiently slowly that a shock wave does not form. This results in lower temperatures, keeping the sample in the solid state to higher pressures. X-ray diffraction measurements were performed using quasi-monochromatic x-rays from a highly ionized He-α Cu source and image plate detectors. Upon ramp compression, we found no evidence of phase transition in solid Mo up to 900 GPa. The observed peaks can be assigned to the (110) and (200) or (220) reflections of BCC Mo up to the highest pressure, indicating that Mo does not melt under ramp loading to maximum pressure reached. Under shock loading, we did not observe any evidence for the solid-solid phase transformation around 210 GPa as reported in previous work (Hixson et al, 1989). The BCC

  10. X-ray diffraction study of crystalline barium titanate ceramics

    SciTech Connect

    Zali, Nurazila Mat; Mahmood, Che Seman; Mohamad, Siti Mariam; Foo, Choo Thye; Murshidi, Julie Adrianny

    2014-02-12

    In this study, BaTiO{sub 3} ceramics have been prepared via solid-state reaction method. The powders were calcined for 2 hours at different temperatures ranging from 600°C to 1200°C. Using X-ray diffraction with a Rietveld analysis, the phase formation and crystal structure of the BaTiO{sub 3} powders were studied. Change in crystallite size and tetragonality as a function of calcination temperature were also discussed. It has been found that the formation of pure perovskite phase of BaTiO{sub 3} began at calcination condition of 1000 °C for 2 hours. The crystal structure of BaTiO{sub 3} formed is in the tetragonal structure. The second phases of BaCO{sub 3} and TiO{sub 2} existed with calcination temperature below 1000 °C. Purity, crystallite size and tetragonality of BaTiO{sub 3} powders were found to increase with increasing calcination temperature.

  11. 3-D Ultrasound Localization Microscopy for Identifying Microvascular Morphology Features of Tumor Angiogenesis at a Resolution Beyond the Diffraction Limit of Conventional Ultrasound

    PubMed Central

    Lin, Fanglue; Shelton, Sarah E.; Espíndola, David; Rojas, Juan D.; Pinton, Gianmarco; Dayton, Paul A.

    2017-01-01

    Angiogenesis has been known as a hallmark of solid tumor cancers for decades, yet ultrasound has been limited in its ability to detect the microvascular changes associated with malignancy. Here, we demonstrate the potential of 'ultrasound localization microscopy' applied volumetrically in combination with quantitative analysis of microvascular morphology, as an approach to overcome this limitation. This pilot study demonstrates our ability to image complex microvascular patterns associated with tumor angiogenesis in-vivo at a resolution of tens of microns - substantially better than the diffraction limit of traditional clinical ultrasound, yet using an 8 MHz clinical ultrasound probe. Furthermore, it is observed that data from healthy and tumor-bearing tissue exhibit significant differences in microvascular pattern and density. Results suggests that with continued development of these novel technologies, ultrasound has the potential to detect biomarkers of cancer based on the microvascular 'fingerprint' of malignant angiogenesis rather than through imaging of blood flow dynamics or the tumor mass itself. PMID:28042327

  12. Neutron irradiated uranium silicides studied by neutron diffraction and Rietveld analysis

    SciTech Connect

    Birtcher, R.C.; Mueller, M.H.; Richardson, J.W. Jr.

    1990-11-01

    The irradiation behavior of high-density uranium silicides has been a matter of interest to the nuclear industry for use in high power or low enrichment applications. Transmission electron microscopy studies have found that heavy ion bombardment renders U{sub 3}Si and U{sub 3}Si{sub 2} amorphous at temperatures below about 250 C and that U{sub 3}Si becomes mechanically unstable suffering rapid growth by plastic flow. In this present work, crystallographic changes preceding amorphization by fission fragment damage have been studied by high-resolution neutron diffraction as a function of damage produced by uranium fission at room temperature. Initially, both silicides had tetragonal crystal structures. Crystallographic and amorphous phases were studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier-filtering analysis of the non-crystalline scattering component. 13 refs., 5 figs.

  13. Accurate unrestrained DDM refinement of crystal structures from highly distorted and low-resolution powder diffraction data.

    PubMed

    Solovyov, Leonid A

    2016-10-01

    The structure of benzene:ethane co-crystal at 90 K is refined with anisotropic displacement parameters without geometric restraints from high-resolution synchrotron X-ray powder diffraction (XRPD) data using the derivative difference method (DDM) with properly chosen weighting schemes. The average C-C bond precision achieved is 0.005 Å and the H-atom positions in ethane are refined independently. A new DDM weighting scheme is introduced that compensates for big distortions of experimental data. The results are compared with density functional theory (DFT) calculations reported by Maynard-Casely et al. [(2016). IUCrJ, 3, 192-199] where a rigid-body Rietveld refinement was also applied to the same dataset due to severe distortions of the powder pattern attributable to experimental peculiarities. For the crystal structure of 2-aminopyridinium fumarate-fumaric acid formerly refined applying 77 geometric restraints by Dong et al. [(2013). Acta Cryst. C69, 896-900], an unrestrained DDM refinement using the same XRPD pattern surprisingly gave two times narrower dispersion of interatomic distances.

  14. Neutron diffraction studies for realtime leaching of catalytic Ni

    SciTech Connect

    Iles, Gail N. Reinhart, Guillaume; Devred, François; Henry, Paul F. Hansen, Thomas C.

    2014-07-21

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni{sub 2}Al{sub 3} and NiAl{sub 3} continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials.

  15. Neutron diffraction study of metal-matrix composite with fullerite

    NASA Astrophysics Data System (ADS)

    Borisova, P. A.; Blanter, M. S.; Brazhkin, VV; Somenkov, VA; Filonenko, V. P.

    2016-09-01

    Interaction of amorphous fullerite C60 with austenitic Fe-33.2 wt. % Ni alloy at pressures 0-8 GPa and temperatures 600-1100 °C was studied by neutron diffraction. The amorphous fullerite was obtained by ball milling and mixed with the powder of the crystalline alloy. The interaction at sintering led to the dissolution of carbon in fcc Fe-Ni solid solution and the formation of carbide (Fe, Ni)3C, but the Fe-Ni-C alloy did not undergo phase transformations and preserved the original fcc structure. As a result, the alloy hardened, we could also witness a clear barometric effect: at the pressure of 2 GPa the amount of the dissolved carbon and the microhardness turned out to be significantly higher than those at 8 GPa. During sintering amorphous fullerite is undergoing phase transitions and its microhardness is higher than the microhardness of the metal component. At high temperatures of interaction graphite appears. The presence of Fe-Ni alloy in the composite reduces the temperature of graphite formation in comparison with transformations in the pure amorphous fullerene.

  16. SPARTAN high resolution solar studies

    NASA Technical Reports Server (NTRS)

    Bruner, Marilyn E.

    1993-01-01

    This report summarizes the work performed on Contract NAS5-29739, a sub-orbital research program directed toward the study of the geometry of and physical conditions in matter found in the upper layers of the solar atmosphere. The report describes a new sounding rocket payload developed under the contract, presents a guide to the contents of semiannual reports submitted during the contract, discusses the results of the first flight of the payload and the progress on scientific analysis. A bibliography of papers and publications is included.

  17. Analytical study of diffraction effects in extremely large segmented telescopes.

    PubMed

    Yaitskova, Natalia; Dohlen, Kjetil; Dierickx, Philippe

    2003-08-01

    We present an analysis of the diffraction effects from a segmented aperture with a very large number of segments-prototype of the next generation of extremely large telescopes. This analysis is based on the point-spread-function analytical calculation for Keck-type hexagonal segmentation geometry. We concentrate on the effects that lead to the appearance of speckles and/or a regular pattern of diffraction peaks. These effects are related to random piston and tip-tilt errors on each segment, gaps between segments, and segment edge distortion. We deliver formulas and the typical numerical values for the Strehl ratio, the relative intensity of higher-order diffraction peaks, and the averaged intensity of speckles associated with each particular case of segmentation error.

  18. Crystal structure of Bi{sub 1-x}Tb{sub x}FeO{sub 3} from high-resolution neutron diffraction

    SciTech Connect

    Saxin, Stefan; Knee, Christopher S.

    2011-06-15

    Samples of Bi{sub 1-x}Tb{sub x}FeO{sub 3}, with x=0.05, 0.10, 0.15, 0.20 and 0.25, have been synthesised by solid state reaction. The crystal structures of the perovskite phases, characterised via Rietveld analysis of high resolution powder neutron diffraction data, reveal a structural transition from the R3c symmetry of the parent phase BiFeO{sub 3} to orthorhombic Pnma symmetry, which is complete for x=0.20. The x=0.10 and 0.15 samples are bi-phasic. The transition from a rhombohedral to orthorhombic unit cell is suggested to be driven by the dilution of the stereochemistry of the Bi{sup 3+} lone pair at the A-site. The G-type antiferromagnetic spin structure, the size of the ordered magnetic moment ({approx}3.8 {mu}{sub B}) and the T{sub N} ({approx}375 deg. C) are relatively insensitive to increasing Tb concentrations at the A-site. - Graphical abstract: High resolution neutron powder diffraction has been used to study the evolution of the RT crystal structure of Bi{sub 1-x}Tb{sub x}FeO{sub 3} (0.05{<=}x{<=}0.25) with terbium content. A transition from polar R3c to centrosymmetric Pnma symmetry is observed. The antiferromagnetic ordering temperature and size of the ordered magnetic moment are relatively insensitive to the change of crystal structure. Highlights: > Structural transition from polar R3c symmetry to non-polar Pnma symmetry occurs. > Behaviour is rationalised via dilution of the stereochemical nature of the Bi lone pair. > Magnetic properties are largely unaffected.

  19. Investigations in space-related molecular biology. [cryo-electron microscopic and diffraction studies on terrestrial and extraterrestrial specimens

    NASA Technical Reports Server (NTRS)

    Fernandez-Moran, H.; Pritzker, A. N.

    1974-01-01

    Improved instrumentation and preparation techniques for high resolution, high voltage cryo-electron microscopic and diffraction studies on terrestrial and extraterrestrial specimens are reported. Computer correlated ultrastructural and biochemical work on hydrated and dried cell membranes and related biological systems provided information on membrane organization, ice crystal formation and ordered water, RNA virus linked to cancer, lunar rock samples, and organometallic superconducting compounds. Apollo 11, 12, 14, and 15 specimens were analyzed

  20. The susceptibility of pure tubulin to high magnetic fields: a magnetic birefringence and x-ray fiber diffraction study.

    PubMed Central

    Bras, W; Diakun, G P; Díaz, J F; Maret, G; Kramer, H; Bordas, J; Medrano, F J

    1998-01-01

    The orientational behavior of microtubules assembled in strong magnetic fields has been studied. It is shown that when microtubules are assembled in a magnetic field, they align with their long axis parallel to the magnetic field. The effect of several parameters known to affect the microtubule assembly are investigated with respect to their effect on the final degree of alignment. Aligned samples of hydrated microtubules suitable for low-resolution x-ray fiber diffraction experiments have been produced, and the results obtained from the fiber diffraction experiments have been compared with the magnetic birefringence experiments. Comparisons with earlier fiber diffraction work and small-angle x-ray solution scattering experiments have been made. PMID:9512047

  1. Breaking the diffraction limit by saturation in stimulated-Raman-scattering microscopy: A theoretical study

    NASA Astrophysics Data System (ADS)

    Gong, Li; Wang, Haifeng

    2014-07-01

    We present a theoretical investigation on the saturation of stimulated Raman scattering (SRS) and propose an application of it to break the diffraction limit in SRS microscopy. In our proposed scheme, a donut-shaped Stokes beam is used to saturate SRS at the rim of a focused Gaussian pump beam; thus the addition of another Gaussian Stokes beam can only induce additional stimulated Raman loss to the pump beam in a small area inside the donut-shaped beam. Resembling stimulated-emission-depletion microscopy, this method can significantly improve the lateral imaging resolution. Compared with the diffraction-limited resolution, theoretical simulations show that it may be possible to double the spatial resolution with a few TW/cm2 of laser intensity. Such super-resolution could greatly enhance the advantage of SRS microscopy for potential applications.

  2. A Numerical Study of Diffraction in Reentrant Geologic Structure.

    DTIC Science & Technology

    1985-07-15

    Geophysics Lab ~rator,,’,, This first tech - im ln,,.Jd_ fault- sca- s and other block ;ons Approximatinc these regons of high curvature • by Perfect...SvReflected SV Incidente SV Diffrated SP RDiffracte P Reflected PV Figure 2-25. Diffractions for SV-wave incidence from below for different qcometri

  3. Diffraction-Enhanced Imaging for studying pattern recognition in cranial ontogeny of bats and marsupials

    NASA Astrophysics Data System (ADS)

    Rocha, H. S.; Lopes, R. T.; Pessôa, L. M.; Hönnicke, M. G.; Tirao, G.; Cusatis, C.; Mazzaro, I.; Giles, C.

    2005-08-01

    The key to understanding evolution lies in the elucidation of mechanisms responsible for the observed underlying patterns and in the observation of sequences that emerge from those evolutionary landmarks. The comparative development can be used to access the derivation of form and the homology versus the convergence of evolution features. Phylogenetic and biological homologies are necessary to discern the evolutionary origins of these features. This work examined the patterns of cranial formation in pre-born bat specimens as well as post-born opossum by means of microradiography and Diffraction-Enhanced Radiography (DER) techniques. A direct conversion CCD camera was used to provide micrometer spatial resolution in order to acquire highly detailed density images. This technique allows the observation of structures, in early stages of development, which were impossible to be observed with traditional techniques, such as clearing and staining. Some cranial features have been described for adults in the literature, but the detailed description of the appearance sequence of those features in these species is still unknown and obscure. Microradiography and diffraction-enhanced imaging can improve quality of morphological detail analysis and permit the identification of anatomical landmarks that are useful in comparative studies and are still unknown in both species. In this study, we access evolution features in cranial morphology of bats and marsupials using both X-ray techniques.

  4. High-resolution diffraction from crystals of a membrane-protein complex: bacterial outer membrane protein OmpC complexed with the antibacterial eukaryotic protein lactoferrin

    SciTech Connect

    Sundara Baalaji, N.; Acharya, K. Ravi; Singh, T. P.; Krishnaswamy, S. E-mail: mkukrishna@rediffmail.com

    2005-08-01

    Crystals of the complex formed between the bacterial membrane protein OmpC and the antibacterial protein lactoferrin suitable for high-resolution structure determination have been obtained. The crystals belong to the hexagonal space group P6, with unit-cell parameters a = b = 116.3, c = 152.4 Å. Crystals of the complex formed between the outer membrane protein OmpC from Escherichia coli and the eukaryotic antibacterial protein lactoferrin from Camelus dromedarius (camel) have been obtained using a detergent environment. Initial data processing suggests that the crystals belong to the hexagonal space group P6, with unit-cell parameters a = b = 116.3, c = 152.4 Å, α = β = 90, γ = 120°. This indicated a Matthews coefficient (V{sub M}) of 3.3 Å{sup 3} Da{sup −1}, corresponding to a possible molecular complex involving four molecules of lactoferrin and two porin trimers in the unit cell (4832 amino acids; 533.8 kDa) with 63% solvent content. A complete set of diffraction data was collected to 3 Å resolution at 100 K. Structure determination by molecular replacement is in progress. Structural study of this first surface-exposed membrane-protein complex with an antibacterial protein will provide insights into the mechanism of action of OmpC as well as lactoferrin.

  5. Photoelectron diffraction

    NASA Astrophysics Data System (ADS)

    Fadley, Charles S.

    1987-01-01

    The use of core-level photoelectron diffraction for structural studies of surfaces and epitaxial overlayers is discussed. Photoelectron diffraction is found to provide several direct and rather unique types of structural information, including the sites and positions of adsorbed atoms; the orientations of small molecules or fragments bound to surfaces; the orientations, layer thicknesses, vertical lattice constants, and degrees of short-range order of epitaxial or partially-epitaxial overlayers; and the presence of short-range spin order in magnetic materials. Specific systems considered are the reaction of oxygen with Ni(001), the growth of epitaxial Cu on Ni(001), the well-defined test case S on Ni(001), and short-range spin order in the antiferromagnet KMnF3. A rather straightforward single scattering cluster (SSC) model also proves capable of quantitatively describing such data, particularly for near-surface species and with corrections for spherical-wave scattering effects and correlated vibrational motion. Promising new directions in such studies also include measurements with high angular resolution and the expanded use of synchrotron radiation.

  6. High Pressure X-Ray Diffraction Studies on Nanocrystalline Materials

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Stelmakh, S.; Grzanka, E.; Gierlotka, S.; Pielaszek, R.; Bismayer, U.; Werner, S.; Palosz, W.

    2003-01-01

    Application of in situ high pressure powder diffraction technique for examination of specific structural properties of nanocrystals based on the experimental data of SiC nanocrystalline powders of 2 to 30 nrn diameter in diameter is presented. Limitations and capabilities of the experimental techniques themselves and methods of diffraction data elaboration applied to nanocrystals with very small dimensions (< 30 nm) are discussed. It is shown that due to the complex structure, constituting a two-phase, core/surface shell system, no unique lattice parameter value and, consequently, no unique compressibility coefficient can satisfactorily describe the behavior of nanocrystalline powders under pressure. We offer a tentative interpretation of the distribution of macro- and micro-strains in nanoparticles of different grain size.

  7. Fresnel diffractive imaging: Experimental study of coherence and curvature

    SciTech Connect

    Whitehead, L. W.; Williams, G. J.; Quiney, H. M.; Nugent, K. A.; Peele, A. G.; Paterson, D.; Jonge, M. D. de; McNulty, I.

    2008-03-01

    A Fresnel coherent diffractive imaging experiment is performed using a pinhole as a test object. The experimental parameters of the beam curvature and coherence length of the illuminating radiation are varied to investigate their effects on the reconstruction process. It is found that a sufficient amount of curvature across the sample strongly ameliorates the effects of low coherence, even when the sample size exceeds the coherence length.

  8. Neutron diffraction study of α-iron titanium cerium hydride

    NASA Astrophysics Data System (ADS)

    Lin, Hong; Niu, Shiwen; Gou, Cheng; Jin, Longhuan; Tao, Fang; Bao, Deyou; Su, Lanying

    1987-03-01

    The results of the neutron scattering method shows that the crystal structure of Fe0.94TiCe0.06H0.03 is the same as that of the FeTiH0.02. However, its diffraction peak intensities drop by 47-58%, the background increased markedly about 2 times and the lattice constant increase by 5%.

  9. Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

    PubMed Central

    Zhang, Tiantian; Britton, Ben; Shollock, Barbara; Dunne, Fionn

    2016-01-01

    A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270–1480 MPa. PMID:27279765

  10. Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Jiang, Jun; Britton, Ben; Shollock, Barbara; Dunne, Fionn

    2016-05-01

    A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270-1480 MPa.

  11. High Pressure X-ray Diffraction Study of Potassium Azide

    SciTech Connect

    C Ji; F Zhang; D Hong; H Zhu; J Wu; M Chyu; V Levitas; Y Ma

    2011-12-31

    Crystal structure and compressibility of potassium azide was investigated by in-situ synchrotron powder X-ray diffraction in a diamond anvil cell at room temperature up to 37.7 GPa. In the body-centered tetragonal (bct) phase, an anisotropic compressibility was observed with greater compressibility in the direction perpendicular to the plane containing N{sub 3}{sup -} ions than directions within that plane. The bulk modulus of the bct phase was determined to be 18.6(7) GPa. A pressure-induced phase transition may occur at 15.5 GPa.

  12. MOKE Diffraction Study of Magnetic Dot and Antidot Arrays.

    NASA Astrophysics Data System (ADS)

    Grimsditch, Marcos

    2003-03-01

    A beam of visible light, incident on a particle array with a submicron period, is diffracted. Extending conventional Magneto Optic Kerr Effect (MOKE) techniques to include the diffracted beams leads to a variety of 'hysteresis' loops. From these loops we show that it is possible to obtain information on the magnetic structure within a unit cell of the array. A brief review of the experimental technique, the theoretical interpretation of the results, and a brief summary of our earlier results on vortices in circular disks [1] and coherent domain formation in antidot arrays [2] will be given. The D-MOKE results from square Permalloy rings will then be presented and compared with micromagnetic simulations. Our results show that magnetization reversal in these ring structures, which is expected to be a jump between two onion states, actually occurs via intermediate, metastable states. For different directions of the applied field these intermediate states are a vortex state or a horseshoe state. A suitable field history allows these states to be quenched and observed using Magnetic Force Microscopy. Work at ANL supported by the US DOE BES Mater. Sci. under contract # W-31-109-ENG-38. [1] M. Grimsditch et al, Phys. Rev. B 65, 172419 (2002) [2] I. Guedes et al, Phys, Rev. B 66, 014434 (2002)

  13. Neutron diffraction studies of welds of aerospace aluminum alloys

    SciTech Connect

    Martukanitz, R.P.; Howell, P.R.; Payzant, E.A.; Spooner, S.; Hubbard, C.R.

    1996-10-01

    Neutron diffraction and electron microscopy were done on residual stress in various regions comprising variable polarity plasma arc welds of alloys 2219 (Al-6.3Cu) and 2195 (Al-4.0Cu-1.0Li-0.5Mg-0.5Ag). Results indicate that lattice parameter changes in the various weld regions may be attributed to residual stresses generated during welding, as well as local changes in microstructure. Distribution of longitudinal and transverse stress of welded panels shows peaks of tension and compression, respectively, within the HAZ and corroborate earlier theoretical results. Position of these peaks are related to position of minimum strength within the HAZ, and the magnitude of these peaks are a fraction of the local yield strength in this region. Weldments of alloy 2195-T8 exhibited higher peak residual stress than alloy 2219-T87. Comparison of neutron diffraction and microstructural analysis indicate decreased lattice parameters associated with the solid solution of the near HAZ; this results in decreased apparent tensile residual stress within this region and may significantly alter interpretation of residual stress measurements of these alloys. Considerable relaxation of residual stress occurs during removal of specimens from welded panels and was used to aid in differentiating changes in lattice parameters attributed to residual stress from welding and modifications in microstructure.

  14. Molecular origins of nonlinear optical activity in zinc tris(thiourea)sulfate revealed by high-resolution x-ray diffraction data and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Cole, Jacqueline M.; Hickstein, Daniel D.

    2013-11-01

    Structure-property relationships are established in the nonlinear optical (NLO) material, zinc tris(thiourea)sulfate (ZTS), via an experimental charge-density study, x-ray constrained wave-function refinement, and quantum-mechanical calculations. The molecular charge-transfer characteristics of ZTS, that are important for NLO activity, are topologically analyzed via a multipolar refinement of high-resolution x-ray diffraction data, which is supported by neutron diffraction measurements. The extent to which each chemical bond is ionic or covalent in nature is categorized by Laplacian-based bonding classifiers of the electron density; these include bond ellipticities, energy densities, and the local source function. Correspondingly, the NLO origins of ZTS are judged to best resemble those of organic NLO materials. The molecular dipole moment, μi, and (hyper)polarizability coefficients, αij and βijk, are calculated from the experimental diffraction data using the x-ray constrained wave-function method. Complementary gas-phase ab initio quantum-mechanical calculations of μi, αij, and βijk offer a supporting comparison. When taken alone, the experimental charge-density analysis does not fare well in deriving μi, αij, or βijk, which is not entirely surprising given that the associated calculations are only generally valid for organic molecules. However, by refining the x-ray data within the constrained wave-function method, the evaluations of μi, αij, and βijk are shown to agree very well with those from ab initio calculations and show remarkable normalization to experimental refractive index measurements. The small differences observed between ab initio and x-ray constrained wave-function refinement results can be related directly to gas- versus solid-state phase differences. μi is found to be 28.3 Debye (gas phase) and 29.7 Debye (solid state) while βijk coefficients are not only significant but are also markedly three dimensional in form. Accordingly

  15. High-speed classification of coherent X-ray diffraction patterns on the K computer for high-resolution single biomolecule imaging.

    PubMed

    Tokuhisa, Atsushi; Arai, Junya; Joti, Yasumasa; Ohno, Yoshiyuki; Kameyama, Toyohisa; Yamamoto, Keiji; Hatanaka, Masayuki; Gerofi, Balazs; Shimada, Akio; Kurokawa, Motoyoshi; Shoji, Fumiyoshi; Okada, Kensuke; Sugimoto, Takashi; Yamaga, Mitsuhiro; Tanaka, Ryotaro; Yokokawa, Mitsuo; Hori, Atsushi; Ishikawa, Yutaka; Hatsui, Takaki; Go, Nobuhiro

    2013-11-01

    Single-particle coherent X-ray diffraction imaging using an X-ray free-electron laser has the potential to reveal the three-dimensional structure of a biological supra-molecule at sub-nanometer resolution. In order to realise this method, it is necessary to analyze as many as 1 × 10(6) noisy X-ray diffraction patterns, each for an unknown random target orientation. To cope with the severe quantum noise, patterns need to be classified according to their similarities and average similar patterns to improve the signal-to-noise ratio. A high-speed scalable scheme has been developed to carry out classification on the K computer, a 10PFLOPS supercomputer at RIKEN Advanced Institute for Computational Science. It is designed to work on the real-time basis with the experimental diffraction pattern collection at the X-ray free-electron laser facility SACLA so that the result of classification can be feedback for optimizing experimental parameters during the experiment. The present status of our effort developing the system and also a result of application to a set of simulated diffraction patterns is reported. About 1 × 10(6) diffraction patterns were successfully classificatied by running 255 separate 1 h jobs in 385-node mode.

  16. Neutron diffraction studies of amphipathic helices in phospholipid bilayers

    SciTech Connect

    Bradshaw, J.P.; Gilchrist, P.J.; Duff, K.C.; Saxena, A.M.

    1994-12-31

    The structural feature which is thought to facilitate the interaction of many peptides with phospholipid bilayers is the ability to fold into an amphipathic helix. In most cases the exact location and orientation of this helix with respect to the membrane is not known, and may vary with factors such as pH and phospholipid content of the bilayer. The growing interest in this area is stimulated by indications that similar interactions can contribute to the binding of certain hormones to their cell-surface receptors. We have been using the techniques of neutron diffraction from stacked phospholipid bilayers in an attempt to investigate this phenomenon with a number of membrane-active peptides. Here we report some of our findings with three of these: the bee venom melittin; the hormone calcitonin; and a synthetic peptide representing the ion channel fragment of influenza A M2 protein.

  17. Powder neutron diffraction studies of a carbonate fluorapatite

    SciTech Connect

    Leventouri, Th.; Chakoumakos, B. C.; Moghaddam, H. Y.; Perdikatsis, V.

    2000-02-01

    Atomic positional disorder of a single-phase natural carbonate fluorapatite (francolite) is revealed from analysis of the atomic displacement parameters (ADPs) refined from neutron powder diffraction data as a function of temperature and carbonate content. The ADPs of the francolite show a strong disturbance at the P, O3, and F sites. When it is heat treated to partially or completely remove the carbonate, the ADPs as well as the other structural parameters resemble those of a fluorapatite (Harding pegmatite) that was measured under the same conditions. The various structural changes are consistent with a substitution mechanism whereby the planar carbonate group replaces a phosphate group and lies on the mirror plane of the apatite structure. (c) 2000 Materials Research Society.

  18. Structural Studies of Matrix Metalloproteinase by X-Ray Diffraction.

    PubMed

    Decaneto, Elena; Lubitz, Wolfgang; Ogata, Hideaki

    2017-01-01

    Matrix Metalloproteinases (MMPs) are a family of proteolytic enzymes whose endopeptidase activity is dependent on the presence of specific metal ions. MT1-MMP (or MMP-14), which has been implicated in tumor progression and cellular invasion, contains a membrane-spanning region located C-terminal to a hemopexin-like domain and an N-terminal catalytic domain. We recombinantly expressed the catalytic domain of human MT1-MMP in E. coli and purified it from inclusion bodies using a refolding protocol that yielded significant quantities of active protein. Crystals of MT1-MMP were obtained using the vapour diffusion method. Here, we describe the protocols used for crystallization and the data analysis together with the resulting diffraction pattern.

  19. Low Energy Electron Diffraction and Cyclic Voltammetry Studies of Flame-Annealed Platinum Single Crystals.

    DTIC Science & Technology

    Low energy electron diffraction (LEED) and cyclic voltammetry were used to examine the surface structure of flame-annealed platinum (I 00), (II 0...electron diffraction studies of platinum single crystal surfaces, Cyclic voltammetry of flamed-annealed platinum single crystal.

  20. Femtosecond electron diffraction and spectroscopic studies of a solid state organic chemical reaction

    NASA Astrophysics Data System (ADS)

    Jean-Ruel, Hubert

    Photochromic diarylethene molecules are excellent model systems for studying electrocyclic reactions, in addition to having important technological applications in optoelectronics. The photoinduced ring-closing reaction in a crystalline photochromic diarylethene derivative was fully resolved using the complementary techniques of transient absorption spectroscopy and femtosecond electron crystallography. These studies are detailed in this thesis, together with the associated technical developments which enabled them. Importantly, the time-resolved crystallographic investigation reported here represents a highly significant proof-of-principle experiment. It constitutes the first study directly probing the molecular structural changes associated with an organic chemical reaction with sub-picosecond temporal and atomic spatial resolution---to follow the primary motions directing chemistry. In terms of technological development, the most important advance reported is the implementation of a radio frequency rebunching system capable of producing femtosecond electron pulses of exceptional brightness. The temporal resolution of this newly developed electron source was fully characterized using laser ponderomotive scattering, confirming a 435 +/- 75 fs instrument response time with 0.20 pC bunches. The ultrafast spectroscopic and crystallographic measurements were both achieved by exploiting the photoreversibility of diarylethene. The transient absorption study was first performed, after developing a novel robust acquisition scheme for thermally irreversible reactions in the solid state. It revealed the formation of an open-ring excited state intermediate, following photoexcitation of the open-ring isomer with an ultraviolet laser pulse, with a time constant of approximately 200 fs. The actual ring closing was found to occur from this intermediate with a time constant of 5.3 +/- 0.3 ps. The femtosecond diffraction measurements were then performed using multiple crystal

  1. High Time Resolution Studies with the GBT

    NASA Astrophysics Data System (ADS)

    Lewandowska, Natalia; Lynch, Ryan S.

    2017-01-01

    The detection of neutron stars 49 years ago has created many new and independent branches of research. In 1967, fast rotating neutron stars, or pulsars, became the first objects of this kind to be discovered at radio wavelengths -- more than 30years after their theoretical prediction.In spite of numerous studies throughout the years, the mechanism of the observed radio emission of pulsars is still not understood. Recent technological developments allow observations of pulsars with time resolutions extending into the nanoseconds range, providing a unique insight into the momentary state of a pulsar.Radio giant pulses are known to occur non-periodically in certain phase ranges, exhibit much higher peak flux densities than regular pulses, and to have pulse widths ranging from the micro- to nanoseconds. Their characteristics make them suitable for high time resolution studies. We present the first high time resolution observations of the original millisecond pulsar PSR B1937+21 carried out with the Robert C. Byrd Green Bank Radio Telescope.

  2. High spatial resolution, high energy synchrotron x-ray diffraction characterization of residual strains and stresses in laser shock peened Inconel 718SPF alloy

    NASA Astrophysics Data System (ADS)

    Gill, Amrinder S.; Zhou, Zhong; Lienert, Ulrich; Almer, Jonathan; Lahrman, David F.; Mannava, S. R.; Qian, Dong; Vasudevan, Vijay K.

    2012-04-01

    Laser shock peening (LSP) is an advanced surface enhancement technique used to enhance the fatigue strength of metal parts by imparting deep compressive residual stresses. In the present study, LSP was performed on IN718 SPF alloy, a fine grained nickel-based superalloy, with three different power densities and depth resolved residual strain and stress characterization was conducted using high energy synchrotron x-ray diffraction in beam line 1-ID-C at the Advanced Photon Source at the Argonne National laboratory. A fine probe size and conical slits were used to non-destructively obtain data from specific gauge volumes in the samples, allowing for high-resolution strain measurements. The results show that LSP introduces deep compressive residual stresses and the magnitude and depth of these stresses depend on the energy density of the laser. The LSP induced residual stresses were also simulated using three-dimensional nonlinear finite element analysis, with employment of the Johnson-Cook model for describing the nonlinear materials constitutive behavior. Good agreement between the experimental and simulated data was obtained. These various results are presented and discussed.

  3. Diffraction studies applicable to 60-foot microwave research facilities

    NASA Technical Reports Server (NTRS)

    Schmidt, R. F.

    1973-01-01

    The principal features of this document are the analysis of a large dual-reflector antenna system by vector Kirchhoff theory, the evaluation of subreflector aperture-blocking, determination of the diffraction and blockage effects of a subreflector mounting structure, and an estimate of strut-blockage effects. Most of the computations are for a frequency of 15.3 GHz, and were carried out using the IBM 360/91 and 360/95 systems at Goddard Space Flight Center. The FORTRAN 4 computer program used to perform the computations is of a general and modular type so that various system parameters such as frequency, eccentricity, diameter, focal-length, etc. can be varied at will. The parameters of the 60-foot NRL Ku-band installation at Waldorf, Maryland, were entered into the program for purposes of this report. Similar calculations could be performed for the NELC installation at La Posta, California, the NASA Wallops Station facility in Virginia, and other antenna systems, by a simple change in IBM control cards. A comparison is made between secondary radiation patterns of the NRL antenna measured by DOD Satellite and those obtained by analytical/numerical methods at a frequency of 7.3 GHz.

  4. Density functional and neutron diffraction studies of lithium polymer electrolytes.

    SciTech Connect

    Baboul, A. G.

    1998-06-26

    The structure of PEO doped with lithium perchlorate has been determined using neutron diffraction on protonated and deuterated samples. The experiments were done in the liquid state. Preliminary analysis indicates the Li-O distance is about 2.0 {angstrom}. The geometries of a series of gas phase lithium salts [LiCF{sub 3}SO{sub 3}, Li(CF{sub 3}SO{sub 2}){sub 2}N, Li(CF{sub 3}SO{sub 2}){sub 2}CH, LiClO{sub 4}, LiPF{sub 6}, LiAsF{sub 6}] used in polymer electrolytes have been optimized at B3LYP/6-31G(d) density functional level of theory. All local minima have been identified. For the triflate, imide, methanide, and perchlorate anions, the lithium cation is coordinated to two oxygens and have binding energies of ca 141 kcal/mol at the B3LYP/6-311+G(3df,2p)/B3LYP/6-31G* level of theory. For the hexafluoroarsenate and hexafluorophosphate the lithium cation is coordinated to three oxygens and have binding energies of ca. 136 kcal/mol.

  5. Classifying and assembling two-dimensional X-ray laser diffraction patterns of a single particle to reconstruct the three-dimensional diffraction intensity function: resolution limit due to the quantum noise.

    PubMed

    Tokuhisa, Atsushi; Taka, Junichiro; Kono, Hidetoshi; Go, Nobuhiro

    2012-05-01

    A new two-step algorithm is developed for reconstructing the three-dimensional diffraction intensity of a globular biological macromolecule from many experimentally measured quantum-noise-limited two-dimensional X-ray laser diffraction patterns, each for an unknown orientation. The first step is classification of the two-dimensional patterns into groups according to the similarity of direction of the incident X-rays with respect to the molecule and an averaging within each group to reduce the noise. The second step is detection of common intersecting circles between the signal-enhanced two-dimensional patterns to identify their mutual location in the three-dimensional wavenumber space. The newly developed algorithm enables one to detect a signal for classification in noisy experimental photon-count data with as low as ~0.1 photons per effective pixel. The wavenumber of such a limiting pixel determines the attainable structural resolution. From this fact, the resolution limit due to the quantum noise attainable by this new method of analysis as well as two important experimental parameters, the number of two-dimensional patterns to be measured (the load for the detector) and the number of pairs of two-dimensional patterns to be analysed (the load for the computer), are derived as a function of the incident X-ray intensity and quantities characterizing the target molecule.

  6. Purification, crystallization and preliminary diffraction studies of an ectromelia virus glutaredoxin

    SciTech Connect

    Bacik, John-Paul; Brigley, Angela M.; Channon, Lisa D.; Audette, Gerald F.; Hazes, Bart

    2005-06-01

    Ectromelia virus glutaredoxin has been crystallized in the presence of the reducing agent DTT. A diffraction data set has been collected and processed to 1.8 Å resolution. Ectromelia, vaccinia, smallpox and other closely related viruses of the orthopoxvirus genus encode a glutaredoxin gene that is not present in poxviruses outside of this genus. The vaccinia glutaredoxin O2L has been implicated as the reducing agent for ribonucleotide reductase and may thus play an important role in viral deoxyribonucleotide synthesis. As part of an effort to understand nucleotide metabolism by poxviruses, EVM053, the O2L ortholog of the ectromelia virus, has been crystallized. EVM053 crystallizes in space group C222{sub 1}, with unit-cell parameters a = 61.98, b = 67.57, c = 108.55 Å. Diffraction data have been processed to 1.8 Å resolution and a self-rotation function indicates that there are two molecules per asymmetric unit.

  7. Fraunhofer diffraction of atomic matter waves: electron transfer studies with a laser cooled target.

    PubMed

    van der Poel, M; Nielsen, C V; Gearba, M A; Andersen, N

    2001-09-17

    We have constructed an apparatus combining the experimental techniques of cold target recoil ion momentum spectroscopy and a laser cooled target. We measure angle differential cross sections in Li(+)+Na-->Li+Na(+) electron transfer collisions in the keV energy regime with a momentum resolution of 0.12 a.u. yielding an order of magnitude better angular resolution than previous measurements. We resolve Fraunhofer-type diffraction patterns in the differential cross sections. Good agreement with predictions of the semiclassical impact parameter method is obtained.

  8. Purification, crystallization and preliminary X-ray diffraction studies of N-acetylglucosamine-phosphate mutase from Candida albicans

    SciTech Connect

    Nishitani, Yuichi; Maruyama, Daisuke; Nonaka, Tsuyoshi; Kita, Akiko; Fukami, Takaaki A.; Mio, Toshiyuki; Yamada-Okabe, Hisafumi; Yamada-Okabe, Toshiko; Miki, Kunio

    2006-04-01

    Preliminary X-ray diffraction studies on N-acetylglucosamine-phosphate mutase from C. albicans are reported. N-acetylglucosamine-phosphate mutase (AGM1) is an essential enzyme in the synthesis of UDP-N-acetylglucosamine (UDP-GlcNAc) in eukaryotes and belongs to the α-d-phosphohexomutase superfamily. AGM1 from Candida albicans (CaAGM1) was purified and crystallized by the sitting-drop vapour-diffusion method. The crystals obtained belong to the primitive monoclinic space group P2{sub 1}, with unit-cell parameters a = 60.2, b = 130.2, c = 78.0 Å, β = 106.7°. The crystals diffract X-rays to beyond 1.8 Å resolution using synchrotron radiation.

  9. Purification, crystallization and preliminary X-ray diffraction studies of the arsenic repressor ArsR from Corynebacterium glutamicum

    PubMed Central

    Santha, Sangilimadan; Pandaranayaka, Eswari P. J.; Rosen, Barry P.; Thiyagarajan, Saravanamuthu

    2011-01-01

    ArsR is a member of the SmtB/ArsR family of metalloregulatory proteins that regulate prokaryotic arsenic-resistance operons. Here, the crystallization and preliminary X-ray diffraction studies of a cysteine-free derivative of ArsR from Corynebacterium glutamicum (CgArsR-C15/16/55S) are reported. CgArsR-C15/16/55S was expressed, purified, crystallized and X-ray diffraction data were collected to 1.86 Å resolution. The protein crystallized in a tetragonal space group (P4), with unit-cell parameters a = b = 41.84, c = 99.47 Å. PMID:22139180

  10. X-ray diffraction study of highly purified human ceruloplasmin

    SciTech Connect

    Samygina, V. R.; Sokolov, A. V.; Pulina, M. O.; Bartunik, H. D.; Vasil'ev, V. B.

    2008-07-15

    The three-dimensional structure of ceruloplasmin (CP) with unoccupied labile metal-binding sites and the structure of CP containing Ni{sup 2+} in the labile sites were solved for the first time at 2.6 and 2.95 A resolution, respectively. Crystallization was performed with the use of storage-stable CP, which was prepared in the presence of proteinase inhibitors and purified from (pre)proteinases. Ceruloplasmin with Ni{sup 2+} crystallized in the orthorhombic space group, which had been earlier unknown for CP. Ceruloplasmin with the unoccupied labile sites crystallized in the trigonal crystal form. The differences in intermolecular contacts observed in the trigonal and orthorhombic crystal structures of CP are considered. The conformational changes attendant upon Ni{sup 2+} binding are described. It was suggested that the labile sites are multifunctional and can both bind metal ions potentially toxic to organisms and be involved in electron transfer from substrates to the active site.

  11. X-ray diffraction study of highly purified human ceruloplasmin

    NASA Astrophysics Data System (ADS)

    Samygina, V. R.; Sokolov, A. V.; Pulina, M. O.; Bartunik, H. D.; Vasil'Ev, V. B.

    2008-07-01

    The three-dimensional structure of ceruloplasmin (CP) with unoccupied labile metal-binding sites and the structure of CP containing Ni2+ in the labile sites were solved for the first time at 2.6 and 2.95 Å resolution, respectively. Crystallization was performed with the use of storage-stable CP, which was prepared in the presence of proteinase inhibitors and purified from (pre)proteinases. Ceruloplasmin with Ni2+ crystallized in the orthorhombic space group, which had been earlier unknown for CP. Ceruloplasmin with the unoccupied labile sites crystallized in the trigonal crystal form. The differences in intermolecular contacts observed in the trigonal and orthorhombic crystal structures of CP are considered. The conformational changes attendant upon Ni2+ binding are described. It was suggested that the labile sites are multifunctional and can both bind metal ions potentially toxic to organisms and be involved in electron transfer from substrates to the active site.

  12. Statistical analysis of multipole-model-derived structural parameters and charge-density properties from high-resolution X-ray diffraction experiments.

    PubMed

    Kamiński, Radosław; Domagała, Sławomir; Jarzembska, Katarzyna N; Hoser, Anna A; Sanjuan-Szklarz, W Fabiola; Gutmann, Matthias J; Makal, Anna; Malińska, Maura; Bąk, Joanna M; Woźniak, Krzysztof

    2014-01-01

    A comprehensive analysis of various properties derived from multiple high-resolution X-ray diffraction experiments is reported. A total of 13 charge-density-quality data sets of α-oxalic acid dihydrate (C2H2O4·2H2O) were subject to Hansen-Coppens-based modelling of electron density. The obtained parameters and properties were then statistically analysed yielding a clear picture of their variability across the different measurements. Additionally, a computational approach (CRYSTAL and PIXEL programs) was utilized to support and examine the experimental findings. The aim of the study was to show the real accuracy and interpretation limits of the charge-density-derived data. An investigation of raw intensities showed that most of the reflections (60-70%) fulfil the normality test and the lowest ratio is observed for weak reflections. It appeared that unit-cell parameters are determined to the order of 10(-3) Å (for cell edges) and 10(-2) ° (for angles), and compare well with the older studies of the same compound and with the new 100 K neutron diffraction data set. Fit discrepancy factors are determined within a 0.5% range, while the residual density extrema are about ±0.16 (3) e Å(-3). The geometry is very well reproducible between different data sets. Regarding the multipole model, the largest errors are present on the valence shell charge-transfer parameters. In addition, symmetry restrictions of multipolar parameters, with respect to local coordinate systems, are well preserved. Standard deviations for electron density are lowest at bond critical points, being especially small for the hydrogen-bonded contacts. The same is true for kinetic and potential energy densities. This is also the case for the electrostatic potential distribution, which is statistically most significant in the hydrogen-bonded regions. Standard deviations for the integrated atomic charges are equal to about 0.1 e. Dipole moments for the water molecule are comparable with

  13. Switching kinetics of the ferroelectric transition in K2SeO4 studied by stroboscopic γ-ray diffraction

    NASA Astrophysics Data System (ADS)

    Leist, J.; Gibhardt, H.; Eckold, G.

    2013-11-01

    The kinetics of the ferroelectric lock-in transition in potassium selenate (K2SeO4) was studied on a millisecond timescale using high-resolution γ-ray diffraction. A large change of the line width and wavevector of the first order satellite is observed during the switching process. This is attributed to a loss of long-range order under the influence of the electric field. In addition, the incommensurate phase is stabilized by the pulsed field and the transition to the pure commensurate phase is shifted to lower temperatures. Strains that may build up during the rapid switching process are supposed to be the reason for this behaviour.

  14. High-resolution three-dimensional imaging of red blood cells parasitized by Plasmodium falciparum and in situ hemozoin crystals using optical diffraction tomography

    NASA Astrophysics Data System (ADS)

    Kim, Kyoohyun; Yoon, HyeOk; Diez-Silva, Monica; Dao, Ming; Dasari, Ramachandra R.; Park, YongKeun

    2014-01-01

    We present high-resolution optical tomographic images of human red blood cells (RBC) parasitized by malaria-inducing Plasmodium falciparum (Pf)-RBCs. Three-dimensional (3-D) refractive index (RI) tomograms are reconstructed by recourse to a diffraction algorithm from multiple two-dimensional holograms with various angles of illumination. These 3-D RI tomograms of Pf-RBCs show cellular and subcellular structures of host RBCs and invaded parasites in fine detail. Full asexual intraerythrocytic stages of parasite maturation (ring to trophozoite to schizont stages) are then systematically investigated using optical diffraction tomography algorithms. These analyses provide quantitative information on the structural and chemical characteristics of individual host Pf-RBCs, parasitophorous vacuole, and cytoplasm. The in situ structural evolution and chemical characteristics of subcellular hemozoin crystals are also elucidated.

  15. High-resolution three-dimensional imaging of red blood cells parasitized by Plasmodium falciparum and in situ hemozoin crystals using optical diffraction tomography

    PubMed Central

    Kim, Kyoohyun; Yoon, HyeOk; Diez-Silva, Monica; Dao, Ming; Dasari, Ramachandra R.

    2013-01-01

    Abstract. We present high-resolution optical tomographic images of human red blood cells (RBC) parasitized by malaria-inducing Plasmodium falciparum (Pf)-RBCs. Three-dimensional (3-D) refractive index (RI) tomograms are reconstructed by recourse to a diffraction algorithm from multiple two-dimensional holograms with various angles of illumination. These 3-D RI tomograms of Pf-RBCs show cellular and subcellular structures of host RBCs and invaded parasites in fine detail. Full asexual intraerythrocytic stages of parasite maturation (ring to trophozoite to schizont stages) are then systematically investigated using optical diffraction tomography algorithms. These analyses provide quantitative information on the structural and chemical characteristics of individual host Pf-RBCs, parasitophorous vacuole, and cytoplasm. The in situ structural evolution and chemical characteristics of subcellular hemozoin crystals are also elucidated. PMID:23797986

  16. Neutron scattering and diffraction instrument for structural study on biology in Japan

    SciTech Connect

    Niimura, Nobuo

    1994-12-31

    Neutron scattering and diffraction instruments in Japan which can be used for structural studies in biology are briefly introduced. Main specifications and general layouts of the instruments are shown.

  17. Feasibility study of an avalanche photodiode readout for a high resolution PET with nsec time resolution

    SciTech Connect

    Schmelz, C.; Ziegler, S.; Bradbury, S.M.; Holl, I.; Lorenz, E.; Renker, D.

    1995-08-01

    A feasibility study for a high resolution positron emission tomograph, based on 9.5 x 4 x 4 mm{sup 3} LSO crystals viewed by 3 mm diameter avalanche photodiodes, has been carried out. Using a Na{sup 22} source the authors determined a spatial resolution of 2.3 {+-} 0.1 mm, an energy resolution around 15 % and a time resolution of 2.6 nsec. Possible configurations for larger scale tests and a tomograph are given.

  18. High-Resolution Scintimammography: A Pilot Study

    SciTech Connect

    Rachel F. Brem; Joelle M. Schoonjans; Douglas A. Kieper; Stan Majewski; Steven Goodman; Cahid Civelek

    2002-07-01

    This study evaluated a novel high-resolution breast-specific gamma camera (HRBGC) for the detection of suggestive breast lesions. Methods: Fifty patients (with 58 breast lesions) for whom a scintimammogram was clinically indicated were prospectively evaluated with a general-purpose gamma camera and a novel HRBGC prototype. The results of conventional and high-resolution nuclear studies were prospectively classified as negative (normal or benign) or positive (suggestive or malignant) by 2 radiologists who were unaware of the mammographic and histologic results. All of the included lesions were confirmed by pathology. Results: There were 30 benign and 28 malignant lesions. The sensitivity for detection of breast cancer was 64.3% (18/28) with the conventional camera and 78.6% (22/28) with the HRBGC. The specificity with both systems was 93.3% (28/30). For the 18 nonpalpable lesions, sensitivity was 55.5% (10/18) and 72.2% (13/18) with the general-purpose camera and the HRBGC, respectively. For lesions 1 cm, 7 of 15 were detected with the general-purpose camera and 10 of 15 with the HRBGC. Four lesions (median size, 8.5 mm) were detected only with the HRBGC and were missed by the conventional camera. Conclusion: Evaluation of indeterminate breast lesions with an HRBGC results in improved sensitivity for the detection of cancer, with greater improvement shown for nonpalpable and 1-cm lesions.

  19. Corrosion of an alloy studied in situ with synchrotron x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Renner, Frank; Lee, Tien-Lin; Kolb, Dieter M.; Stierle, Andreas; Dosch, Helmut; Zegenhagen, Jorg

    2004-03-01

    Corrosion processes are mostly electrochemical in nature. For the basic understanding of corrosion and similar technical processes, in-situ structural methods capable of atomic resolution, such as scanning probe microscopy or hard X-ray techniques are necessary. We used in-situ X-ray diffraction and in addition ex-situ AFM, to study Cu_3Au(111) single crystal surfaces in 0.1M H_2SO4 electrolyte as a function of electrode potential in the sub-critical regime. This binary metal alloys serves as model systems for more complicated technically utilized metal alloys. During the initial electrochemical corrosion, Cu atoms are dissolved and a passivating layer is formed. The experiments show the formation of an epitaxial and highly strained ultra-thin Cu_xAu_1-x(111) phase on the surface at a potential where Cu dissolution starts. At higher potentials, thicker epitaxial Au islands are growing on the surface. AFM images reveal a surface, densely packed with Au islands of a homogeneous size-distribution. On a prolonged timescale, a percolating, porous morphology of the surface evolves by ripening, even at an electrode potential well below the critical potential.

  20. Overexpression, purification, crystallization and preliminary diffraction studies of the Protaminobacter rubrum sucrose isomerase SmuA.

    PubMed

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

    2006-01-01

    Palatinose (isomaltulose, alpha-D-glucosylpyranosyl-1,6-D-fructofuranose), a nutritional and acariogenic reducing sugar, is industrially obtained from sucrose by using immobilized cells of Protaminobacter rubrum that produce the sucrose isomerase SmuA. The isomerization of sucrose catalyzed by this enzyme also results in the formation of trehalulose (alpha-D-glucosylpyranosyl-1,1-D-fructofuranose) in smaller amounts and glucose, fructose and eventually isomaltose as by-products, which lower the yield of the reaction and complicate the recovery of palatinose. The determination of the three-dimensional structure of SmuA will provide a basis for rational protein-engineering studies in order to optimize the industrial production of palatinose. A recombinant form of the 67.3 kDa SmuA enzyme has been crystallized in the native state by the vapour-diffusion method. Crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 61.6, b = 81.4, c = 135.6 A, and diffract to 1.95 A resolution on a synchrotron-radiation source.

  1. Trapping the M sub 1 and M sub 2 substrates of bacteriorhodopsin for electron diffraction studies

    SciTech Connect

    Perkins, G.A.

    1992-05-01

    Visible and Fourier transform infrared (FTIR) absorption spectroscopies are used to observe protein conformational changes occuring during the bacteriorhodopsin photocycle. Spectroscopic measurements which define the conditions under which bacteriorhodopsin can be isolated and trapped in two distinct substates of the m intermediate of the photocycle, M{sub 1}, and M{sub 2}, are described. A protocol that can be used for high-resolution electron diffraction studies is presented that will trap glucose-embedded purple membrane in the M{sub 1}and M{sub 2} substates at greater than 90% concentration. It was discovered that glucose alone does not provide a fully hydrated environment for bacteriorhodopsin. Equilibration of glucose-embedded samples at high humidity can result in a physical state that is demonstrably closer to the native, fully hydrated state. An extension of the C-T Model of bacteriorhodopsin functionality (Fodor et al., 1988; Mathies et al., 1991) is proposed based on FTIR results and guided by published spectra from resonance Raman and FTIR work. 105 refs.

  2. Crystallization and X-ray diffraction studies of crustacean proliferating cell nuclear antigen

    PubMed Central

    Carrasco-Miranda, Jesus S.; Cardona-Felix, Cesar S.; Lopez-Zavala, Alonso A.; de-la-Re-Vega, Enrique; De la Mora, Eugenio; Rudiño-Piñera, Enrique; Sotelo-Mundo, Rogerio R.; Brieba, Luis G.

    2012-01-01

    Proliferating cell nuclear antigen (PCNA), a member of the sliding clamp family of proteins, interacts specifically with DNA replication and repair proteins through a small peptide motif called the PCNA-interacting protein or PIP box. PCNA is recognized as one of the key proteins involved in DNA metabolism. In the present study, the recombinant PCNA from Litopenaeus vannamei (LvPCNA) was heterologously overexpressed and purified using metal ion-affinity chromatography. Crystals suitable for diffraction grew overnight using the hanging-drop vapour-diffusion method. LvPCNA crystals belong to space group C2 with unit-cell parameters a = 144.6, b = 83.4, c = 74.3 Å, β = 117.6°. One data set was processed to 3 Å resolution, with an overall R meas of 0.09 and a completeness of 93.3%. Initial phases were obtained by molecular replacement using a homology model of LvPCNA as the search model. Refinement and structural analysis are underway. This report is the first successful crystallographic analysis of a marine crustacean decapod shrimp (L. vannamei) proliferating cell nuclear antigen. PMID:23143251

  3. Crystallization and X-ray diffraction studies of crustacean proliferating cell nuclear antigen.

    PubMed

    Carrasco-Miranda, Jesus S; Cardona-Felix, Cesar S; Lopez-Zavala, Alonso A; de-la-Re-Vega, Enrique; De la Mora, Eugenio; Rudiño-Piñera, Enrique; Sotelo-Mundo, Rogerio R; Brieba, Luis G

    2012-11-01

    Proliferating cell nuclear antigen (PCNA), a member of the sliding clamp family of proteins, interacts specifically with DNA replication and repair proteins through a small peptide motif called the PCNA-interacting protein or PIP box. PCNA is recognized as one of the key proteins involved in DNA metabolism. In the present study, the recombinant PCNA from Litopenaeus vannamei (LvPCNA) was heterologously overexpressed and purified using metal ion-affinity chromatography. Crystals suitable for diffraction grew overnight using the hanging-drop vapour-diffusion method. LvPCNA crystals belong to space group C2 with unit-cell parameters a=144.6, b=83.4, c=74.3 Å, β=117.6°. One data set was processed to 3 Å resolution, with an overall Rmeas of 0.09 and a completeness of 93.3%. Initial phases were obtained by molecular replacement using a homology model of LvPCNA as the search model. Refinement and structural analysis are underway. This report is the first successful crystallographic analysis of a marine crustacean decapod shrimp (L. vannamei) proliferating cell nuclear antigen.

  4. High Resolution Chemical Study of ALH84001

    NASA Technical Reports Server (NTRS)

    Conrad, Pamela G.; Douglas, Susanne; Kuhlman, Kimberly R.

    2001-01-01

    We have studied the chemistry of a sample of the SNC meteorite ALH84001 using an environmental scanning electron microscope (ESEM) with an energy dispersive chemical analytical detector and a focused ion beam secondary ion mass spectrometer (FIB-SIMS). Here we present the chemical data, both spectra and images, from two techniques that do not require sample preparation with a conductive coating, thus eliminating the possibility of preparation-induced textural artifacts. The FIB-SIMS instrument includes a column optimized for SEM with a quadrupole type mass spectrometer. Its spatial and spectral resolution are 20 nm and 0.4 AMU, respectively. The spatial resolution of the ESEM for chemical analysis is about 100 nm. Limits of detection for both instruments are mass dependent. Both the ESEM and the FIB-SIMS instrument revealed contrasting surficial features; crumbled, weathered appearance of the matrix in some regions as well as a rather ubiquitous presence of euhedral halite crystals, often associated with cracks or holes in the surface of the rock. Other halogen elements present in the vicinity of the NaCl crystals include K and Br. In this report, elemental inventories are shown as mass spectra and as X-ray maps.

  5. Crystal structure of silica-ZSM-12 by the combined use of high-resolution solid-state MAS NMR spectroscopy and synchrotron x-ray powder diffraction

    SciTech Connect

    Fyfe, C.A.; Kokotailo, G.T. ); Gies, H.; Marler, B. ); Cox, D.E. )

    1990-05-03

    The crystal structure of the synthetic zeolite silica-ZSM-12, 56 SiO{sub 2}, has been solved by the combined use of high-resolution solid-state MAS NMR spectroscopy and high-resolution synchrotron X-ray powder diffraction ZSM-12 crystallizes in the monoclinic space group C2/c with a{sub 0} = 24.863 {angstrom}, b{sub 0} = 5.012 {angstrom}, c{sub 0} = 24.328 {angstrom}, and {beta} = 107.7{degree}. The zeolite host structure is built from corner-linked SiO{sub 4} tetrahedra to give a three-dimensional 4-connected net. The pores of the structure are one-dimensional channels that do not intersect, with 12-membered ring pore openings of approximately 5.6 {times} 7.7 {angstrom}. The structure of ZSM-12 is frequently twinned with (100) as the twin plane, which indicates a new zeolite structure type.

  6. High-resolution 2-D Bragg diffraction reveal heterogeneous domain transformation behavior in a bulk relaxor ferroelectric

    DOE PAGES

    Pramanick, Abhijit; Stoica, Alexandru D.; An, Ke

    2016-09-02

    In-situ measurement of fine-structure of neutron Bragg diffraction peaks from a relaxor single-crystal using a time-of-flight instrument reveals highly heterogeneous mesoscale domain transformation behavior under applied electric fields. We observed that only 25% of domains undergo reorienta- tion or phase transition contributing to large average strains, while at least 40% remain invariant and exhibit microstrains. Such insights could be central for designing new relaxor materials with better performance and longevity. The current experimental technique can also be applied to resolve com- plex mesoscale phenomena in other functional materials.

  7. Optically confined polarized resonance Raman studies in identifying crystalline orientation of sub-diffraction limited AlGaN nanostructure

    SciTech Connect

    Sivadasan, A. K. Patsha, Avinash; Dhara, Sandip

    2015-04-27

    An optical characterization tool of Raman spectroscopy with extremely weak scattering cross section tool is not popular to analyze scattered signal from a single nanostructure in the sub-diffraction regime. In this regard, plasmonic assisted characterization tools are only relevant in spectroscopic studies of nanoscale object in the sub-diffraction limit. We have reported polarized resonance Raman spectroscopic (RRS) studies with strong electron-phonon coupling to understand the crystalline orientation of a single AlGaN nanowire of diameter ∼100 nm. AlGaN nanowire is grown by chemical vapor deposition technique using the catalyst assisted vapor-liquid-solid process. The results are compared with the high resolution transmission electron microscopic analysis. As a matter of fact, optical confinement effect due to the dielectric contrast of nanowire with respect to that of surrounding media assisted with electron-phonon coupling of RRS is useful for the spectroscopic analysis in the sub-diffraction limit of 325 nm (λ/2N.A.) using an excitation wavelength (λ) of 325 nm and near ultraviolet 40× far field objective with a numerical aperture (N.A.) value of 0.50.

  8. Diffraction and imaging study of imperfections of crystallized lysozyme with coherent X-rays

    NASA Technical Reports Server (NTRS)

    Hu, Z. W.; Chu, Y. S.; Lai, B.; Thomas, B. R.; Chernov, A. A.

    2004-01-01

    Phase-contrast X-ray diffraction imaging and high-angular-resolution diffraction combined with phase-contrast radiographic imaging were employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme crystal in the symmetric Laue case. The full-width at half-maximum (FWHM) of a 4 4 0 rocking curve measured from the original crystal was approximately 16.7 arcsec and imperfections including line defects, inclusions and other microdefects were observed in the diffraction images of the crystal. The observed line defects carry distinct dislocation features running approximately along the <1 1 0> growth front and have been found to originate mostly in a central growth area and occasionally in outer growth regions. Inclusions of impurities or formations of foreign particles in the central growth region are resolved in the images with high sensitivity to defects. Slow dehydration led to the broadening of a fairly symmetric 4 4 0 rocking curve by a factor of approximately 2.6, which was primarily attributed to the dehydration-induced microscopic effects that are clearly shown in X-ray diffraction images. The details of the observed defects and the significant change in the revealed microstructures with drying provide insight into the nature of imperfections, nucleation and growth, and the properties of protein crystals.

  9. A multi-step strategy to obtain crystals of the dengue virus RNA-dependent RNA polymerase that diffract to high resolution

    SciTech Connect

    Yap, Thai Leong; Chen, Yen Liang; Xu, Ting; Wen, Daying; Vasudevan, Subhash G.; Lescar, Julien

    2007-02-01

    Crystals of the RNA-dependent RNA polymerase catalytic domain from the dengue virus NS5 protein have been obtained using a strategy that included expression screening of naturally occurring serotype variants of the protein, the addition of divalent metal ions and crystal dehydration. These crystals diffract to 1.85 Å resolution and are thus suitable for a structure-based drug-design program. Dengue virus, a member of the Flaviviridae genus, causes dengue fever, an important emerging disease with several million infections occurring annually for which no effective therapy exists. The viral RNA-dependent RNA polymerase NS5 plays an important role in virus replication and represents an interesting target for the development of specific antiviral compounds. Crystals that diffract to 1.85 Å resolution that are suitable for three-dimensional structure determination and thus for a structure-based drug-design program have been obtained using a strategy that included expression screening of naturally occurring serotype variants of the protein, the addition of divalent metal ions and crystal dehydration.

  10. Studies of electron diffusion in photo-excited Ni using time-resolved X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Persson, A. I. H.; Jarnac, A.; Wang, Xiaocui; Enquist, H.; Jurgilaitis, A.; Larsson, J.

    2016-11-01

    We show that the heat deposition profile in a laser-excited metal can be determined by time-resolved X-ray diffraction. In this study, we investigated the electron diffusion in a 150 nm thick nickel film deposited on an indium antimonide substrate. A strain wave that mimics the heat deposition profile is generated in the metal and propagates into the InSb, where it influences the temporal profile of X-rays diffracted from InSb. We found that the strain pulse significantly deviated from a simple exponential profile, and that the two-temperature model was needed to reproduce the measured heat deposition profile. Experimental results were compared to simulations based on the two-temperature model carried out using commercial finite-element software packages and on-line dynamical diffraction tools. To reproduce the experimental data, the electron-phonon coupling factor was lowered compared to previously measured values. The experiment was carried out at a third-generation synchrotron radiation source using a high-brightness beam and an ultrafast X-ray streak camera with a temporal resolution of 3 ps.

  11. Synchrotron x-ray multiple diffraction in the study of Fe+ ion implantation in Si(0 0 1)

    NASA Astrophysics Data System (ADS)

    dos Santos, A. O.; Lang, R.; de Menezes, A. S.; Meneses, E. A.; Amaral, L.; Reboh, S.; Cardoso, L. P.

    2009-10-01

    In this work, x-ray multiple diffraction has been used as a three-dimensional high-resolution probe to study the Fe+ ion implantation process in Si(0 0 1). The semiconducting β-FeSi2 crystallographic phase has been synthesized by Fe ion co-implantation in Si(0 0 1) followed by ion-beam-induced epitaxial crystallization (IBIEC) and thermal treatment. This phase was clearly detected by the conventional techniques, micro-Raman scattering spectroscopy, transmission electron microscopy (TEM) and grazing incidence x-ray diffraction. Synchrotron radiation rocking curves (ω-scans) and mapping of the Bragg surface diffraction (BSD) of the Si matrix, as-implanted, after the IBIEC process and thermally treated, have enabled the detection of co-implanted regions formation that present distinct lattices in comparison with the matrix one clearly observed by TEM. Also, the compressive strain of both regions in depth by rocking curve and in-plane has been determined by using BSD, which is one order of magnitude smaller.

  12. Quantitative locomotion study of freely swimming micro-organisms using laser diffraction.

    PubMed

    Magnes, Jenny; Susman, Kathleen; Eells, Rebecca

    2012-10-25

    Soil and aquatic microscopic organisms live and behave in a complex three-dimensional environment. Most studies of microscopic organism behavior, in contrast, have been conducted using microscope-based approaches, which limit the movement and behavior to a narrow, nearly two-dimensional focal field.(1) We present a novel analytical approach that provides real-time analysis of freely swimming C. elegans in a cuvette without dependence on microscope-based equipment. This approach consists of tracking the temporal periodicity of diffraction patterns generated by directing laser light through the cuvette. We measure oscillation frequencies for freely swimming nematodes. Analysis of the far-field diffraction patterns reveals clues about the waveforms of the nematodes. Diffraction is the process of light bending around an object. In this case light is diffracted by the organisms. The light waves interfere and can form a diffraction pattern. A far-field, or Fraunhofer, diffraction pattern is formed if the screen-to-object distance is much larger than the diffracting object. In this case, the diffraction pattern can be calculated (modeled) using a Fourier transform.(2) C. elegans are free-living soil-dwelling nematodes that navigate in three dimensions. They move both on a solid matrix like soil or agar in a sinusoidal locomotory pattern called crawling and in liquid in a different pattern called swimming.(3) The roles played by sensory information provided by mechanosensory, chemosensory, and thermosensory cells that govern plastic changes in locomotory patterns and switches in patterns are only beginning to be elucidated.(4) We describe an optical approach to measuring nematode locomotion in three dimensions that does not require a microscope and will enable us to begin to explore the complexities of nematode locomotion under different conditions.

  13. The structure study of thin semiconductor and dielectric films by diffraction of synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Yurjev, G. S.; Fainer, N. I.; Maximovskiy, E. A.; Kosinova, M. L.; Sheromov, M. A.; Rumyantsev, Yu. M.

    1998-02-01

    The structure of semiconductor and dielectric thin (100-300 nm) films was studied by diffraction of synchrotron radiation. The diffraction experiments were performed at both the station "Anomalous scattering" of the storage ring synchrotron facility VEPP-3 and DRON-4 diffractometer. The structure of CdS thin films grown on fused silica, single Si(100) and InP(100) substrates was investigated. The structure of Cu 2S thin films grown on fused silica, single Si(100) substrates and CdS/Si(100)-heterostructure was studied. The structure study was performed on Si 3N 4 films grown on GaAs(100) substrates. The structure of thin BN layers grown on single Si(100) substrates was studied. It was established that structural parameters of above-mentioned thin films coincide on the parameters of JCPDS International Centre for Diffraction Data.

  14. X-ray absorption and diffraction study of II VI dilute oxide semiconductor alloy epilayers

    NASA Astrophysics Data System (ADS)

    Boscherini, F.; Malvestuto, M.; Ciatto, G.; D'Acapito, F.; Bisognin, G.; DeSalvador, D.; Berti, M.; Felici, M.; Polimeni, A.; Nabetani, Y.

    2007-11-01

    Dilute oxide semiconductor alloys obtained by adding oxygen to a II-VI binary compound are of potential applicative interest for blue-light emitters in which the oxygen content could be used to tune the band gap. Moreover, their properties can be usefully compared to the more thoroughly studied dilute nitrides in order to gain insight into the common mechanisms which give rise to their highly non-linear physical properties. Recently, it has been possible to deposit ZnSeO and ZnSeOS epilayers on GaAs(001), which exhibit a red-shift of the band gap and giant optical bowing. In order to provide a structural basis for an understanding of their physical properties, we have performed a study of a set of ZnSeO and ZnSeOS epilayers on GaAs by high resolution x-ray diffraction and x-ray absorption fine structure. We have found that the strain goes from compressive to tensile with increasing O and S concentration and that, while all epilayers are never found to be pseudomorphic, the ternary ones exhibit a low relaxed fraction if compared to the ZnSe/GaAs sample. O K-edge x-ray absorption near edge spectra and corresponding simulations within the full multiple-scattering regime show that O is substitutionally incorporated in the host lattice. Zn and Se K-edge extended x-ray absorption fine structure detect the formation of Zn-O and Zn-S bonds; the analysis of these spectra within multiple-scattering theory has allowed us to measure the local structural parameters. The value of Zn-Se bond length is found to be in agreement with estimates based on models of local distortions in strained and relaxed epilayers; an increase of the mean-square relative displacement is detected at high O and S concentration and is related to both intrinsic and extrinsic factors.

  15. Purification, crystallization, and preliminary X-ray diffraction study of purine nucleoside phosphorylase from E. coli

    SciTech Connect

    Abramchik, Yu. A. Timofeev, V. I. Zhukhlistova, N. E.; Muravieva, T. I.; Esipov, R. S.; Kuranova, I. P.

    2015-07-15

    Crystals of E. coli purine nucleoside phosphorylase were grown in microgravity by the capillary counter-diffusion method through a gel layer. The X-ray diffraction data set suitable for the determination of the three-dimensional structure at atomic resolution was collected from one crystal at the Spring-8 synchrotron facility to 0.99 Å resolution. The crystals belong to sp. gr. P2{sub 1} and have the following unit-cell parameters: a = 74.1 Å, b = 110.2 Å, c = 88.2 Å, α = γ = 90°, β = 111.08°. The crystal contains six subunits of the enzyme comprising a hexamer per asymmetric unit. The hexamer is the biological active form of E. coli. purine nucleoside phosphorylase.

  16. Purification, crystallization, and preliminary X-ray diffraction study of purine nucleoside phosphorylase from E. coli

    NASA Astrophysics Data System (ADS)

    Abramchik, Yu. A.; Timofeev, V. I.; Zhukhlistova, N. E.; Muravieva, T. I.; Esipov, R. S.; Kuranova, I. P.

    2015-07-01

    Crystals of E. coli purine nucleoside phosphorylase were grown in microgravity by the capillary counter-diffusion method through a gel layer. The X-ray diffraction data set suitable for the determination of the three-dimensional structure at atomic resolution was collected from one crystal at the Spring-8 synchrotron facility to 0.99 Å resolution. The crystals belong to sp. gr. P21 and have the following unit-cell parameters: a = 74.1 Å, b = 110.2 Å, c = 88.2 Å, α = γ = 90°, β = 111.08°. The crystal contains six subunits of the enzyme comprising a hexamer per asymmetric unit. The hexamer is the biological active form of E. coli. purine nucleoside phosphorylase.

  17. Phase Sensitive X-Ray Diffraction Imaging Study of Protein Crystals

    NASA Technical Reports Server (NTRS)

    Hu, Z. W.

    2003-01-01

    The study of defects and growth of protein crystals is of importance in providing a fundamental understanding of this important category of systems and the rationale for crystallization of better ordered crystals for structural determination and drug design. Yet, as a result of the extremely weak scattering power of x-rays in protein and other biological macromolecular crystals, the extinction lengths for those crystals are extremely large and, roughly speaking, of the order of millimeters on average compared to the scale of micrometers for most small molecular crystals. This has significant implication for x-ray diffraction and imaging study of protein crystals, and presents an interesting challenge to currently available x-ray analytical techniques. We proposed that coherence-based phase sensitive x-ray diffraction imaging could provide a way to augment defect contrast in x-ray diffraction images of weakly diffracting biological macromolecular crystals. I shall examine the principles and ideas behind this approach and compare it to other available x-ray topography and diffraction methods. I shall then present some recent experimental results in two model protein systems-cubic apofemtin and tetragonal lysozyme crystals to demonstrate the capability of the coherence-based imaging method in mapping point defects, dislocations, and the degree of perfection of biological macromolecular crystals with extreme sensitivity. While further work is under way, it is intended to show that the observed new features have yielded important information on protein crystal perfection and nucleation and growth mechanism otherwise unobtainable.

  18. The study of diffractive lenses displayed in a phase-only liquid crystal spatial light modulator

    NASA Astrophysics Data System (ADS)

    Ma, Si-jin; Panezai, Spozmai; Wang, Da-yong; Wang, Yun-xin; Rong, Lu

    2013-08-01

    Phase-only spatial light modulator (SLM) based on liquid crystal on silicon (LCOS) is a kind of device based on electrically controlled birefringence effect to realize phase modulation. Due to its low cost, programmable, high resolution, fast response time, LCOS has been widely used in multi-channel imaging, adaptive optics, diffraction optical elements (DOEs), dynamic holographic, optical tweezers and other fields. It is necessary to numerically evaluate the modulation characterization of LCOS before application. Firstly, the phase modulation characterization of the LCOS (PLUTO HED6010XXX by Holoeye Company) was measured based on the Twyman-Green interferometer, and the curves of both phase shift and normalized intensity as grey level functions were obtained. Experimental results indicated that phase modulation of the LCOS could be achieved to 3.99π, and the root-mean-square value (RMS) of normalized intensity was less than 0.01, which demonstrated that LCOS could be regarded as a phase-only modulation device. This method is also suitable for the evaluation of modulation characterization of other LCOS devices. Secondly, a phase pattern of thin lens written onto LCOS was demonstrated. Because of the pixel structure of LCOS, the theory of discretization of lenses was studied. Both simulation and experimental results were obtained. The experimental results proved that the convergence character of the lens written onto LCOS was similar to optical lenses. In the experiment, the measured focal length was in a good agreement to the theoretical deduction, and the relative error (RE) of which was below 1%. Both simulation and experimental results showed that LCOS could be used as lens to converge the plane wave, and replace the optical lens successfully.

  19. A Mixed {alpha}/{beta} Superstructure in NASICON Ionic Conductors: Neutron Diffraction Study of Li

    SciTech Connect

    Catti, Michele

    2001-02-01

    The lithium conductors Li{sub 2}FeTi(PO{sub 4}){sub 3} and Li{sub 2}FeZr(PO{sub 4}){sub 3}, synthesized by solid-state reaction and characterized by X-ray powder diffractometry, were studied structurally at room temperature by neutron powder diffraction at high resolution (HRPD, ISIS Facility, U.K.). By trial-and-error and Rietveld refinements (R{sub p}=0.111, R(F{sup 2})=0.112), the first compound (orthorhombic Pbca, Z=8; a=8.5515(1), b=8.6229(1), c=23.9116(3) {angstrom}) was shown to have a complex superstructure sharing features of both the {alpha} and {beta} NASICON-type phases of LiZr{sub 2}(PO{sub 4}){sub 3}. Four (001) layers of PO{sub 4} and (Fe, Ti)O{sub 6} polyhedra are present per unit-cell, and they are related both by -1 inversion centers ({alpha} structure) and by a glide planes ({beta} structure). Ti{sup 4+} and Fe{sup 3+} order in the two interlayer regions, respectively. Owing to the structure complexity, only half of the lithium atoms could be refined in tetrahedral coordination with < Li-O > =1.99 {angstrom}. Li{sub 2}FeZr(PO{sub 4}){sub 3} (orthorhombic Pbna, Z=4; a=8.70559(8), b=8.78572(9), c=12.2202(1) {angstrom}) proved to be similar to {beta}-LiZr2(PO4)3; however, by Fourier synthesis and Rietveld refinement (R{sub p}=0.0618, R(F{sup 2})=0.0574) Li was located in a fully ordered tetrahedral configuration with < Li-O >=2.01 {angstrom}, instead of being disordered as in the phase of LiZr{sub 2}(PO{sub 4}){sub 3}.

  20. Crystallization and preliminary X-ray diffraction studies of cyanuric acid hydrolase from Azorhizobium caulinodans.

    PubMed

    Cho, Seunghee; Shi, Ke; Wackett, Lawrence P; Aihara, Hideki

    2013-08-01

    Cyanuric acid is synthesized industrially and forms during the microbial metabolism of s-triazine herbicides. Cyanuric acid is metabolized by some microorganisms via cyanuric acid hydrolase (CAH), which opens the s-triazine ring as a prelude to further metabolism. CAH is a member of the rare cyanuric acid hydrolase/barbiturase family. Here, the crystallization and preliminary X-ray diffraction analysis of CAH from Azorhizobium caulinodans are reported. CAH was cocrystallized with barbituric acid, a close analog of cyanuric acid that is a tight-binding competitive inhibitor. Crystals suitable for X-ray diffraction experiments were grown in conditions containing PEG 8K or magnesium sulfate as precipitants. An X-ray diffraction data set was collected from CAH-barbituric acid crystals to 2.7 Å resolution. The crystals were found to belong to space group I4₁22, with unit-cell parameters a = b = 237.9, c = 105.3 Å, α = β = γ = 90°.

  1. Firing of Clays Studied by X-ray Diffraction and Mössbauer Spectroscopy

    NASA Astrophysics Data System (ADS)

    Häusler, W.

    2004-06-01

    Three bentonites of varying purity were fired in air under controlled conditions up to 1300°C in an attempt to provide data for the assessment of firing techniques used in prehistoric pottery making. X-ray diffraction of samples heated at increasing temperatures allows to study the mineral transformations, the breakdown of the clay structure and the formation of new minerals in the high-temperature region. Mössbauer spectroscopy reveals the change of valence state and of the environment of the iron atoms on heating. Non iron-bearing minerals are only accessible by X-ray diffraction, while iron-containing oxidic and amorphous phases may be difficult to detect, due to poor crystallinity and small particle size. The combination of X-ray diffraction and Mössbauer spectroscopy therefore has a considerable potential in the study of the chemical and physical transformations occurring in pottery clays during firing.

  2. Bulk crystal growth, and high-resolution x-ray diffraction results of LiZnP semiconductor material

    NASA Astrophysics Data System (ADS)

    Montag, Benjamin W.; Reichenberger, Michael A.; Sunder, Madhana; Ugorowski, Philip B.; Nelson, Kyle A.; McGregor, Douglas S.

    2015-06-01

    Nowotny-Juza compounds continue to be explored as a candidate for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q-value of 4.78 MeV, larger than 10B, an energy easily identified above background radiations. Hence, devices fabricated from semiconducting compounds containing either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) may provide a semiconductor material for compact high efficiency neutron detectors. Starting material was synthesized by preparing equimolar portions of Li, Zn, and P sealed under vacuum (10-6 Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace [1]. The synthesized material showed signs of high impurity levels from material and electrical property characterizations. A static vacuum sublimation in quartz was performed to help purify the synthesized material [2]. Bulk crystalline samples were grown from the purified material. An ingot 9.6 mm in diameter and 4.0 mm in length was harvested. Individual samples were characterized for crystallinity on a Bruker AXS Inc. D2 CRYSO, energy dispersive x-ray diffractometer, and a Bruker AXS D8 DISCOVER, high-resolution x-ray diffractometer with a 0.004° beam divergence. The (220) orientation was characterized as the main orientation with the D2 CRYSO, and confirmed with the D8 DISCOVER. An out-of-plane high-resolution rocking curve yielded a 0.417° full width at half maximum (FWHM) for the (220) LiZnP. In-plane ordering was confirmed by observation of the (311) orientation, where a rocking curve was collected with a FWHM of 0.294°.

  3. Crystallization and preliminary X-ray diffraction study of phosphoribosyl pyrophosphate synthetase from E. Coli

    SciTech Connect

    Timofeev, V. I. Abramchik, Yu. A. Zhukhlistova, N. E. Kuranova, I. P.

    2015-09-15

    Enzymes of the phosphoribosyl pyrophosphate synthetase family (PRPPS, EC 2.7.6.1) catalyze the formation of 5-phosphoribosyl pyrophosphate (5-PRPP) from adenosine triphosphate and ribose 5-phosphate. 5-Phosphoribosyl pyrophosphate is an important intermediate in the synthesis of purine, pyrimidine, and pyridine nucleotides, as well as of the amino acids histidine and tryptophan. The crystallization conditions for E. coli PRPPS were found by the vapor-diffusion technique and were optimized to apply the capillary counter-diffusion technique. The X-ray diffraction data set was collected from the crystals grown by the counter-diffusion technique using a synchrotron radiation source to 3.1-Å resolution. The crystals of PRPPS belong to sp. gr. P6{sub 3}22 and have the following unit-cell parameters: a = b = 104.44 Å, c = 124.98 Å, α = β = 90°, γ = 120°. The collected X-ray diffraction data set is suitable for the solution of the three-dimensional structure of PRPPS at 3.1-Å resolution.

  4. Crystallization and preliminary X-ray diffraction study of phosphoribosyl pyrophosphate synthetase from E. Coli

    NASA Astrophysics Data System (ADS)

    Timofeev, V. I.; Abramchik, Yu. A.; Zhukhlistova, N. E.; Kuranova, I. P.

    2015-09-01

    Enzymes of the phosphoribosyl pyrophosphate synthetase family (PRPPS, EC 2.7.6.1) catalyze the formation of 5-phosphoribosyl pyrophosphate (5-PRPP) from adenosine triphosphate and ribose 5-phosphate. 5-Phosphoribosyl pyrophosphate is an important intermediate in the synthesis of purine, pyrimidine, and pyridine nucleotides, as well as of the amino acids histidine and tryptophan. The crystallization conditions for E. coli PRPPS were found by the vapor-diffusion technique and were optimized to apply the capillary counter-diffusion technique. The X-ray diffraction data set was collected from the crystals grown by the counter-diffusion technique using a synchrotron radiation source to 3.1-Å resolution. The crystals of PRPPS belong to sp. gr. P6322 and have the following unit-cell parameters: a = b = 104.44 Å, c = 124.98 Å, α = β = 90°, γ = 120°. The collected X-ray diffraction data set is suitable for the solution of the three-dimensional structure of PRPPS at 3.1-Å resolution.

  5. Crystallization and preliminary X-ray diffraction studies of the glutaminyl cyclase from Carica papaya latex

    SciTech Connect

    Azarkan, Mohamed; Clantin, Bernard; Bompard, Coralie; Belrhali, Hassan; Baeyens-Volant, Danielle; Looze, Yvan; Wintjens, René

    2005-01-01

    The glutaminyl cyclase isolated from C. papaya latex has been crystallized using the hanging-drop method. Diffraction data have been collected at ESRF beamline BM14 and processed to 1.7 Å resolution. In living systems, the intramolecular cyclization of N-terminal glutamine residues is accomplished by glutaminyl cyclase enzymes (EC 2.3.2.5). While in mammals these enzymes are involved in the synthesis of hormonal and neurotransmitter peptides, the physiological role played by the corresponding plant enzymes still remains to be unravelled. Papaya glutaminyl cyclase (PQC), a 33 kDa enzyme found in the latex of the tropical tree Carica papaya, displays an exceptional resistance to chemical and thermal denaturation as well as to proteolysis. In order to elucidate its enzymatic mechanism and to gain insights into the structural determinants underlying its remarkable stability, PQC was isolated from papaya latex, purified and crystallized by the hanging-drop vapour-diffusion method. The crystals belong to the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 62.82, b = 81.23, c = 108.17 Å and two molecules per asymmetric unit. Diffraction data have been collected at ESRF beamline BM14 and processed to a resolution of 1.7 Å.

  6. Crystallization and preliminary X-ray diffraction studies of Seneca Valley Virus-001, a new member of the Picornaviridae family

    SciTech Connect

    Venkataraman, Sangita; Reddy, Seshidhar P.; Loo, Jackie; Idamakanti, Neeraja; Hallenbeck, Paul L.; Reddy, Vijay S.

    2008-04-01

    Seneca Valley Virus-001 of the Picornavirdae family was crystallized in the space group R3 and X-ray diffraction data was collected to a resolution of 2.3 Å. Rotation-function studies suggested the presence of two distict sets of 20 protomers that belong to two different virus particles in the crystallographic asymmetric unit. Seneca Valley Virus-001 (SVV-001) is a newly found species in the Picornaviridae family. SVV-001 is the first naturally occurring nonpathogenic picorna@@virus observed to mediate selective cytotoxicity towards tumor cells with neuroendocrine cancer features. The nonsegmented (+)ssRNA genome of SVV-001 shares closest sequence similarity to the genomes of the members of the Cardiovirus genus. However, based on the distinct characteristics of the genome organization and other biochemical properties, it has been suggested that SVV-001 represents a new genus, namely ‘Senecavirus’, in the Picornaviridae family. In order to understand the oncolytic properties of SVV-001, the native virus was crystallized using the hanging-drop vapour-diffusion method. The crystals belonged to space group R3, with unit-cell parameters (in the hexagonal setting) a = b = 311.5, c = 1526.4 Å. Although the SVV crystals diffracted to better than 2.3 Å resolution, the data quality is acceptable [I/σ(I) > 2.0] to 2.6 Å resolution. The unit-cell volume and the locked rotation-function analysis suggest that six particles could be accommodated in the unit cell, with two distinct sets of one third of a particle, each containing 20 protomers, occupying the crystallographic asymmetric unit.

  7. An In-situ method for the study of strain broadening usingsynchrotronx-ray diffraction

    SciTech Connect

    Tang, Chiu C.; Lynch, Peter A.; Cheary, Robert W.; Clark, Simon M.

    2006-12-15

    A tensonometer for stretching metal foils has beenconstructed for the study of strain broadening in x-ray diffraction lineprofiles. This device, which is designed for use on the powderdiffractometer in Station 2.3 at Daresbury Laboratory, allows in-situmeasurements to be performed on samples under stress. It can be used fordata collection in either transmission or reflection modes using eithersymmetric or asymmetric diffraction geometries. As a test case,measurements were carried out on a 18mum thick copper foil experiencingstrain levels of up to 5 percent using both symmetric reflection andsymmetric transmission diffraction. All the diffraction profilesdisplayed peak broadening and asymmetry which increased with strain. Themeasured profiles were analysed by the fundamental parameters approachusing the TOPAS peak fitting software. All the observed broadenedprofiles were modelled by convoluting a refineable diffraction profile,representing the dislocation and crystallite size broadening, with afixed instrumental profile pre-determined usinghigh quality LaB6reference powder. The de-convolution process yielded "pure" sampleintegral breadths and asymmetry results which displayed a strongdependence on applied strain and increased almost linearly with appliedstrain. Assuming crystallite size broadening in combination withdislocation broadening arising from fcc a/2<110>111 dislocations,we have extracted the variation of mechanic al property with strain. Theobservation of both peak asymmetry and broadening has been interpreted asa manifestation of a cellular structure with cell walls and cellinteriors possessing high and low dislocation densities.

  8. Combining 2 nm Spatial Resolution and 0.02% Precision for Deformation Mapping of Semiconductor Specimens in a Transmission Electron Microscope by Precession Electron Diffraction.

    PubMed

    Cooper, David; Bernier, Nicolas; Rouvière, Jean-Luc

    2015-08-12

    Precession electron diffraction has been used to provide accurate deformation maps of a device structure showing that this technique can provide a spatial resolution of better than 2 nm and a precision of better than 0.02%. The deformation maps have been fitted to simulations that account for thin specimen relaxation. By combining the experimental deformation maps and simulations, we have been able to separate the effects of the stressor and recessed sources and drains and show that the Si3N4 stressor increases the in-plane deformation in the silicon channel from 0.92 to 1.52 ± 0.02%. In addition, the stress in the deposited Si3N4 film has been calculated from the simulations, which is an important parameter for device design.

  9. High-resolution x-ray diffraction investigation of relaxation and dislocations in SiGe layers grown on (001), (011), and (111) Si substrates

    SciTech Connect

    Zhylik, A.; Benediktovich, A.; Ulyanenkov, A.; Guerault, H.; Myronov, M.; Dobbie, A.; Leadley, D. R.; Ulyanenkova, T.

    2011-06-15

    This work presents a detailed characterization, using high-resolution x-ray diffraction, of multilayered Si{sub 1-x}Ge{sub x} heterostructures grown on (001), (011), and (111) Si substrates by reduced pressure chemical vapor deposition. Reciprocal space mapping has been used to determine both the strain and Ge concentration depth profiles within each layer of the heterostructures after initially determining the crystallographic tilt of all the layers. Both symmetric and asymmetric reciprocal space maps were measured on each sample, and the evaluation was performed simultaneously for the whole data set. The ratio of misfit to threading dislocation densities has been estimated for each individual layer based on an analysis of diffuse x-ray scattering from the defects.

  10. Structural properties of Pb{sub 3}Mn{sub 7}O{sub 15} determined from high-resolution synchrotron powder diffraction

    SciTech Connect

    Rasch, Julia C.E.; Sheptyakov, D.V.; Schefer, J.; Keller, L.; Boehm, M.; Gozzo, F.; Volkov, N.V.; Sablina, K.A.; Petrakovskii, G.A.; Grimmer, H.; Conder, K.; Loeffler, J.F.

    2009-05-15

    We report on the crystallographic structure of the layered compound Pb{sub 3}Mn{sub 7}O{sub 15}. Previous analysis based on laboratory X-ray data at room temperature gave contradictory results in terms of the description of the unit cell. Motivated by recent magnetic bulk measurements of this system [N.V. Volkov, K.A. Sablina, O.A. Bayukov, E.V. Eremin, G.A. Petrakovskii, D.A. Velikanov, A.D. Balaev, A.F. Bovina, P. Boni, E. Clementyev, J. Phys. Condens. Matter 20 (2008) 055217], we re-investigated the chemical structure with high-resolution synchrotron powder diffraction at temperatures between 15 and 295 K. Our results show that the crystal structure of stoichiometric Pb{sub 3}Mn{sub 7}O{sub 15} has a pronounced 2-dimensional character and can be described in the orthorhombic space group Pnma. - The crystal structure of Pb{sub 3}Mn{sub 7}O{sub 15} has been reinvestigated by synchrotron powder diffraction. The compound crystallizes in the orthorhombic space group Pnma and shows no structural transition between 15 and 295 K.

  11. Neutron diffraction studies of magnetic-shape memory Ni-Mn-Ga single crystal

    NASA Astrophysics Data System (ADS)

    Heczko, Oleg; Prokes, Karel; Hannula, Simo-Pekka

    2007-09-01

    Neutron diffraction of single crystal of the typical example of magnetic-shape memory (MSM) alloy Ni 49.7Mn 29.3Ga 21 was carried out with a 2D position sensitive detector. The quality and inhomogeneity of the single crystal and martensite variant distribution was studied using ω-scan of selected nuclear Bragg reflections. The neutron diffraction reveals split of the (2 0 0) reflection of major martensite variant and large structural inhomogeneities in martensite phase. Using measurement in reciprocal space, we recorded a set of reflections that appear due to structural modulation (5 M) of the martensite, however, the set seems to be incomplete with missing or very weak reflections of second order compared with X-ray diffraction. The line of the magnetic reflection arising from the supposed antiferromagnetic ordering of the excess Mn atoms was very weak and it is difficult to discern from the background.

  12. Nepheline: Structure of Three Samples from the Bancroft Area, Ontario, Obtained using Synchrotron High-Resolution Powder X-Ray Diffraction

    SciTech Connect

    Antao, Sytle M.; Hassan, Ishmael

    2010-05-25

    The crystal structure of three samples of nepheline (ideally, K{sub 2}Na{sub 6}[Al{sub 8}Si{sub 8}O{sub 32}]) from the Bancroft area of Ontario (1a, b: Egan Chute, 2: Nephton, and 3: Davis Hill), each with different types of superstructure reflections, has been studied using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinement. The samples have different origins. The structure was refined in space group P6{sub 3}. The R{sub F}{sup 2} index, number of unique observed reflections, pseudohexagonal subcell parameters, and site-occupancy factor (sof) for the K site are as follows: Sample 1b: R{sub F}{sup 2} = 0.0433, N{sub obs} = 1399, a = 9.99567(1), c = 8.37777(1) {angstrom}, V = 724.907(2) {angstrom}{sub 3}, and K (sof) = 0.716(1). Sample 2: R{sub F}{sup 2} = 0.0669, N{sub obs} = 1589, a = 10.00215(1), c = 8.38742(1) {angstrom}, V = 726.684(1) {angstrom}{sub 3}, and K (sof) = 0.920(1). Sample 3: R{sub F}{sup 2} = 0.0804, N{sub obs} = 1615, a = 9.99567(1), c = 8.37873(1) {angstrom}, V = 724.991(1) {angstrom}{sub 3}, and K (sof) = 0.778(2). Sample 2 has the largest sof for K and the largest volume. The satellite reflections in the three nepheline samples were observed in the HRPXRD traces and give rise to different incommensurate superstructures. The Al and Si atoms in the T{sub 3} and T{sub 4} sites are ordered differently in the three samples, which may indicate the presence of a domain structure based on Al-Si order. The positions for the Al and Si atoms were interchanged in two samples because of the resulting distances. The slight excess of Si over Al atoms, characteristically encountered in well-analyzed samples of nepheline, is reflected in the distances.

  13. An X-Ray Diffraction Study of Chromium-Gold Thin Films.

    DTIC Science & Technology

    The chromium-gold thin films system was studied using direct recording X-ray diffraction. Chromium and/or gold thin films were deposited, in vacuum...onto glass substrates at ambient and elevated temperatures. Those thin films deposited at ambient temperatures were later annealed. The resultant X-ray

  14. Effect of microfibril twisting in theoretical powder diffraction studies of cellulose Iß

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previous studies of calculated diffraction patterns for cellulose crystallites have suggested that the distortions arising once models have been subjected to MD simulation are likely the result of dimensional changes induced by the empirical force field, but have been unable to determine to what ext...

  15. X-Ray Diffraction Study of L2005 AG17 (IDPs) by Using SR

    NASA Technical Reports Server (NTRS)

    Ohsumi, K. O.; Hagiya, K. H.; Zolensky, M. E.

    2002-01-01

    X-ray diffraction study revealed the existence of magnetite and new type of pyrrhotite with the chemical formula of Fe0.56S in L2005 AG17. Considering the total chemical formula of Fe0.83S, residual iron in amorphous state might exist in this sample. Additional information is contained in the original extended abstract.

  16. Method for studying the phase function in tunable diffraction optical elements

    SciTech Connect

    Paranin, V D; Tukmakov, K N

    2014-04-28

    A method for studying the phase function in tunable diffraction optical elements is proposed, based on measurement of the transmission of interelectrode gaps. The mathematical description of the method, which is approved experimentally, is developed. The instrumental error effects are analysed. (laser applications and other topics in quantum electronics)

  17. Structure of porcine heart cytoplasmic malate dehydrogenase: combining x-ray diffraction and chemical sequence data in structural studies

    SciTech Connect

    Birktoft, J.J.; Bradshaw, R.A.; Banaszak, L.J.

    1987-05-19

    The amino acid sequence of cytoplasmic malate dehydrogenase (sMDH) has been determined by a combination of X-ray crystallographic and chemical sequencing methods. The initial molecular model incorporated an X-ray amino acid sequence that derived primarily from an evaluation of a multiple isomorphous replacement phased electron density map calculated at 2.5-A resolution. Following restrained least-squares crystallographic refinement, difference electron density maps were calculated from model phases, and attempts were made to upgrade the X-ray amino acid sequence. The method used to find the positions of peptides in the X-ray structure was similar to those used for studying protein homology and was shown to be successful for large fragments. For sMDH, X-ray methods by themselves were insufficient to derive a complete amino acid sequence, even with partial chemical sequence data. However, for this relatively large molecule at medium resolution, the electron density maps were of considerable help in determining the linear position of peptide fragments. The N-acetylated polypeptide chain of sMDH has 331 amino acids and has been crystallographically refined to an R factor of 19% for 2.5-A resolution diffraction data.

  18. Preliminary design of a zone plate based hard X-ray monochromatic diffraction nanoprobe for materials studies at APS

    NASA Astrophysics Data System (ADS)

    Cai, Zhonghou; Liu, Wenjun; Tischler, Jonathan Z.; Shu, Deming; Xu, Ruqing; Schmidt, Oliver

    2013-09-01

    Aiming at studies of the micro/nano-structures of a broad range materials and electronic devices, Advance Photon Source (APS) is developing a dedicated diffraction nanoprobe (DNP) beamline for the needs arising from a multidiscipline research community. As a part of the APS Upgrade Project, the planed facility, named Sub-micron 3-D Diffraction (S3DD) beamline1, integrates the K-B mirror based polychromatic Laue diffraction and the Fresnel zone-plate based monochromatic diffraction techniques that currently support 3D/2D microdiffraction programs at the 34-ID-E and 2-ID-D of the APS, respectively. Both diffraction nanoprobes are designed to have a 50-nm or better special resolution. The zone-plate based monochromatic DNP has been preliminarily designed and will be constructed at the sector 34-ID. It uses an APS-3.0-cm period or APS-3.3-cm period undulator, a liquid-nitrogen cooled mirror as its first optics, and a water cooled small gap silicon double-crystal monochromator with an energy range of 5-30 keV. A set of zone plates have been designed to optimize for focusing efficiency and the working distance based on the attainable beamline length and the beam coherence. To ensure the nanoprobe performance, high stiffness and high precision flexure stage systems have been designed or demonstrated for optics mounting and sample scanning, and high precision temperature control of the experimental station will be implemented to reduce thermal instability. Designed nanoprobe beamline has a good management on thermal power loading on optical components and allows high degree of the preservation of beam brilliance for high focal flux and coherence. Integrated with variety of X-ray techniques, planed facility provides nano-XRD capability with the maximum reciprocal space accessibility and allows micro/nano-spectroscopy studies with K-edge electron binding energies of most elements down to Vanadium in the periodic table. We will discuss the preliminary design of the zone

  19. Crystallization and preliminary X-ray diffraction studies of the (R)-selective amine transaminase from Aspergillus fumigatus.

    PubMed

    Thomsen, Maren; Skalden, Lilly; Palm, Gottfried J; Höhne, Matthias; Bornscheuer, Uwe T; Hinrichs, Winfried

    2013-12-01

    The (R)-selective amine transaminase from Aspergillus fumigatus was expressed in Escherichia coli and purified to homogeneity. Bright yellow crystals appeared while storing the concentrated solution in the refrigerator and belonged to space group C222(1). X-ray diffraction data were collected to 1.27 Å resolution, as well as an anomalous data set to 1.84 Å resolution that was suitable for S-SAD phasing.

  20. High resolution studies of complex solar active regions

    NASA Astrophysics Data System (ADS)

    Deng, Na

    Flares and Coronal Mass Ejections (CMEs) are energetic events, which can even impact the near-Earth environment and are the principal source of space weather. Most of them originate in solar active regions. The most violent events are produced in sunspots with a complex magnetic field topology. Studying their morphology and dynamics is helpful in understanding the energy accumulation and release mechanisms for flares and CMEs, which are intriguing problems in solar physics. The study of complex active regions is based on high-resolution observations from space missions and new instruments at the Big Bear Solar Observatory (BBSO). Adaptive optics (AO) in combination with image restoration techniques (speckle masking imaging) can achieve improved image quality and a spatial resolution (about 100 km on the solar surface) close to the diffraction limit of BBSO's 65 cm vacuum telescope. Dopplergrams obtained with a two-dimensional imaging spectrometer combined with horizontal flow maps derived with Local Correlation Tracking (LCT) provide precise measurements of the three-dimensional velocity field in sunspots. Magnetic field measurements from ground- and space-based instruments complement these data. At the outset of this study, the evolution and morphology of a typical round sunspot are described in some detail. The sunspot was followed from disk center to the limb, thus providing some insight into the geometry of the magnetic flux system. Having established a benchmark for a stable sunspot, the attention is turned to changes of the sunspot structure associated with flares and CMEs. Rapid penumbral decay and the strengthening of sunspot umbrae are manifestations of photospheric magnetic field changes after a flare. These sudden intensity changes are interpreted as a result of magnetic reconnection during the flare, which causes the magnetic field lines to be turned from more inclined to more vertical. Strong photospheric shear flows along the flaring magnetic

  1. Comparative study of the accuracy of the PSM and Kogelnik models of diffraction in reflection and transmission holographic gratings.

    PubMed

    Brotherton-Ratcliffe, David; Shi, Lishen; Osanlou, Ardie; Excell, Peter

    2014-12-29

    Calculated diffractive efficiencies in the visible spectral band from lossless planar holographic gratings are studied using the PSM and Kogelnik models of diffraction for the case of the σ-polarization. The results are numerically compared with rigorous coupled wave calculations over a wide parameter space covering both transmission and reflection geometries. For most reflection gratings, the PSM model is shown to consistently provide a marginally superior estimation of the diffractive efficiency. This is particularly evident in a clearly superior description of the diffractive sideband structure for most gratings, both in terms of angle and wavelength. For the transmission grating, the PSM model continues to provide a relatively good description of diffraction at low permittivity modulations and lower incidence angles with respect to the grating plane normal. However, overall Kogelnik's theory is shown to provide a somewhat superior estimation of diffractive efficiency and a clearly superior description of the diffractive side-band structure in the transmission case.

  2. Computer Simulations to Study Diffraction Effects of Stacking Faults in Beta-SiC: II. Experimental Verification. 2; Experimental Verification

    NASA Technical Reports Server (NTRS)

    Pujar, Vijay V.; Cawley, James D.; Levine, S. (Technical Monitor)

    2000-01-01

    Earlier results from computer simulation studies suggest a correlation between the spatial distribution of stacking errors in the Beta-SiC structure and features observed in X-ray diffraction patterns of the material. Reported here are experimental results obtained from two types of nominally Beta-SiC specimens, which yield distinct XRD data. These samples were analyzed using high resolution transmission electron microscopy (HRTEM) and the stacking error distribution was directly determined. The HRTEM results compare well to those deduced by matching the XRD data with simulated spectra, confirming the hypothesis that the XRD data is indicative not only of the presence and density of stacking errors, but also that it can yield information regarding their distribution. In addition, the stacking error population in both specimens is related to their synthesis conditions and it appears that it is similar to the relation developed by others to explain the formation of the corresponding polytypes.

  3. Purification, crystallization, preliminary X-ray diffraction and molecular-replacement studies of great cormorant (Phalacrocorax carbo) haemoglobin.

    PubMed

    Jagadeesan, G; Malathy, P; Gunasekaran, K; Harikrishna Etti, S; Aravindhan, S

    2014-11-01

    Haemoglobin is the iron-containing oxygen-transport metalloprotein that is present in the red blood cells of all vertebrates. In recent decades, there has been substantial interest in attempting to understand the structural basis and functional diversity of avian haemoglobins. Towards this end, purification, crystallization, preliminary X-ray diffraction and molecular-replacement studies have been carried out on cormorant (Phalacrocorax carbo) haemoglobin. Crystals were grown by the hanging-drop vapour-diffusion method using PEG 3350, NaCl and glycerol as precipitants. The crystals belonged to the trigonal system P3₁21, with unit-cell parameters a=b=55.64, c=153.38 Å, β=120.00°; a complete data set was collected to a resolution of 3.5 Å. Matthews coefficient analysis indicated that the crystals contained a half-tetramer in the asymmetric unit.

  4. Crystallization and X-ray diffraction studies of a complete bacterial fatty-acid synthase type I

    PubMed Central

    Enderle, Mathias; McCarthy, Andrew; Paithankar, Karthik Shivaji; Grininger, Martin

    2015-01-01

    While a deep understanding of the fungal and mammalian multi-enzyme type I fatty-acid synthases (FAS I) has been achieved in recent years, the bacterial FAS I family, which is narrowly distributed within the Actinomycetales genera Mycobacterium, Corynebacterium and Nocardia, is still poorly understood. This is of particular relevance for two reasons: (i) although homologous to fungal FAS I, cryo-electron microscopic studies have shown that bacterial FAS I has unique structural and functional properties, and (ii) M. tuberculosis FAS I is a drug target for the therapeutic treatment of tuberculosis (TB) and therefore is of extraordinary importance as a drug target. Crystals of FAS I from C. efficiens, a homologue of M. tuberculosis FAS I, were produced and diffracted X-rays to about 4.5 Å resolution. PMID:26527268

  5. Fresnel Coherent Diffractive Imaging

    SciTech Connect

    Williams, G. J.; Quiney, H. M.; Dhal, B. B.; Tran, C. Q.; Nugent, K. A.; Peele, A. G.; Paterson, D.; Jonge, M. D. de

    2006-07-14

    We present an x-ray coherent diffractive imaging experiment utilizing a nonplanar incident wave and demonstrate success by reconstructing a nonperiodic gold sample at 24 nm resolution. Favorable effects of the curved beam illumination are identified.

  6. Structural and magnetic properties of LaFe{sub 0.5}Cr{sub 0.5}O{sub 3} studied by neutron diffraction, electron diffraction and magnetometry

    SciTech Connect

    Azad, A.K. . E-mail: azad@studsvik.uu.se; Mellergard, A.; Eriksson, S.-G.; Ivanov, S.A.; Yunus, S.M.; Lindberg, F.; Svensson, G.; Mathieu, R.

    2005-10-06

    The structural and magnetic properties of the perovskite type compound LaFe{sub 0.5}Cr{sub 0.5}O{sub 3} have been studied by temperature dependent neutron powder diffraction and magnetization measurements. Rietveld refinement of the neutron diffraction data shows that the compound crystallizes in an orthorhombic perovskite structure with a random positioning of the Fe and Cr cations at the B sublattice. The magnetic structure at 10 K is a collinear antiferromagnetic one with the magnetic moment per site being equal to 2.79(4) {mu}{sub B}. Magnetisation measurements confirm the overall antiferromagnetic behaviour. Moreover, it indicates a weak uncompensated magnetic moment close to the transition temperature T {sub N} {approx} 265 K. This moment can be described by a magnetic cluster state, which remains up to 550 K. Electron diffraction patterns along with high-resolution transmission electron microscopy images reveal that the crystallites are composed by domains of different orientation, which share the same cubic perovskite sub-cell reflections.

  7. Re-refinement of 4g4a: room-temperature X-ray diffraction study of cisplatin and its binding to His15 of HEWL after 14 months chemical exposure in the presence of DMSO.

    PubMed

    Tanley, Simon W M; Schreurs, Antoine M M; Kroon-Batenburg, Loes M J; Helliwell, John R

    2016-03-01

    A re-refinement of 4g4a, the room-temperature X-ray diffraction study of cisplatin and its binding to His15 of HEWL after 14 months chemical exposure in the presence of DMSO is published as an addendum to Tanley et al. [(2012), Acta Cryst. F68, 1300-1306]. This example illustrates the benefits of sharing raw diffraction images, as well as structure factors and molecular coordinates, as the diffraction resolution of the study is now much improved at 1.70 Å.

  8. Ice Recrystallization in a Solution of a Cryoprotector and Its Inhibition by a Protein: Synchrotron X-Ray Diffraction Study.

    PubMed

    Zakharov, Boris; Fisyuk, Alexander; Fitch, Andy; Watier, Yves; Kostyuchenko, Anastasia; Varshney, Dushyant; Sztucki, Michael; Boldyreva, Elena; Shalaev, Evgenyi

    2016-07-01

    Ice formation and recrystallization is a key phenomenon in freezing and freeze-drying of pharmaceuticals and biopharmaceuticals. In this investigation, high-resolution synchrotron X-ray diffraction is used to quantify the extent of disorder of ice crystals in binary aqueous solutions of a cryoprotectant (sorbitol) and a protein, bovine serum albumin. Ice crystals in more dilute (10 wt%) solutions have lower level of microstrain and larger crystal domain size than these in more concentrated (40 wt%) solutions. Warming the sorbitol-water mixtures from 100 to 228 K resulted in partial ice melting, with simultaneous reduction in the microstrain and increase in crystallite size, that is, recrystallization. In contrast to sorbitol solutions, ice crystals in the BSA solutions preserved both the microstrain and smaller crystallite size on partial melting, demonstrating that BSA inhibits ice recrystallization. The results are consistent with BSA partitioning into quasi-liquid layer on ice crystals but not with a direct protein-ice interaction and protein sorption on ice surface. The study shows for the first time that a common (i.e., not-antifreeze) protein can have a major impact on ice recrystallization and also presents synchrotron X-ray diffraction as a unique tool for quantification of crystallinity and disorder in frozen aqueous systems.

  9. Crystallization and X-ray diffraction studies of a complete bacterial fatty-acid synthase type I

    SciTech Connect

    Enderle, Mathias; McCarthy, Andrew; Paithankar, Karthik Shivaji; Grininger, Martin

    2015-10-23

    Bacterial and fungal type I fatty-acid synthases (FAS I) are evolutionarily connected, as bacterial FAS I is considered to be the ancestor of fungal FAS I. In this work, the production, crystallization and X-ray diffraction data analysis of a bacterial FAS I are reported. While a deep understanding of the fungal and mammalian multi-enzyme type I fatty-acid synthases (FAS I) has been achieved in recent years, the bacterial FAS I family, which is narrowly distributed within the Actinomycetales genera Mycobacterium, Corynebacterium and Nocardia, is still poorly understood. This is of particular relevance for two reasons: (i) although homologous to fungal FAS I, cryo-electron microscopic studies have shown that bacterial FAS I has unique structural and functional properties, and (ii) M. tuberculosis FAS I is a drug target for the therapeutic treatment of tuberculosis (TB) and therefore is of extraordinary importance as a drug target. Crystals of FAS I from C. efficiens, a homologue of M. tuberculosis FAS I, were produced and diffracted X-rays to about 4.5 Å resolution.

  10. Crystallization and preliminary X-ray diffraction studies of FAD synthetase from Corynebacterium ammoniagenes

    PubMed Central

    Herguedas, Beatriz; Martínez-Júlvez, Marta; Frago, Susana; Medina, Milagros; Hermoso, Juan A.

    2009-01-01

    FAD synthetase from Corynebacterium ammoniagenes (CaFADS), a prokary­otic bifunctional enzyme that catalyses the phosphorylation of riboflavin as well as the adenylylation of FMN, has been crystallized using the hanging-drop vapour-diffusion method at 277 K. Diffraction-quality cubic crystals of native and selenomethionine-labelled (SeMet-CaFADS) protein belonged to the cubic space group P213, with unit-cell parameters a = b = c = 133.47 Å and a = b = c = 133.40 Å, respectively. Data sets for native and SeMet-containing crystals were collected to 1.95 and 2.42 Å resolution, respectively. PMID:20054130

  11. Crystallization and preliminary X-ray diffraction studies of human RANTES.

    PubMed

    Shaw, J P; Kryger, G; Cleasby, A; Wonacott, A; Power, C A; Proudfoot, A E; Wells, T N

    1994-09-30

    The chemotactic cytokine RANTES (Regulated on Activation, Normal T-cell Expressed and Secreted) is a potent chemoattractant and activator of a number of leukocytes, with a molecular mass of 8 kDa. Crystals of this protein have been grown from 100 mM sodium acetate buffer (pH 4.6) containing 200 mM magnesium acetate, with 20% (w/v) PEG 4000 and 6% (v/v) glycerol. The crystals grow as thick rods, which diffract to at least 1.8 A resolution on a rotating anode X-ray source. The crystals belong to space group p2(1)2(1)2(1) with unit cell dimensions a = 95.14 A, b = 57.58 A and c = 24.01 A with alpha = beta = gamma = 90 degrees. The asymmetric unit contains two molecules of the RANTES monomer, with a VM of 2.0 A(3)/Da.

  12. Crystallization and preliminary X-ray diffraction studies on recombinant isopenicillin N synthase from Aspergillus nidulans.

    PubMed Central

    Roach, P. L.; Schofield, C. J.; Baldwin, J. E.; Clifton, I. J.; Hajdu, J.

    1995-01-01

    Recombinant Aspergillus nidulans isopenicillin N synthase was purified from an Escherichia coli expression system. The apoenzyme in the presence of saturating concentrations of MnCl2 could be crystallized by either macro- or microseeding, using the hanging drop vapor diffusion technique with polyethylene glycol 8000 as precipitant. The crystals (0.5-1.0 mm overall dimensions) diffract X-rays to at least 2.0 A resolution at synchrotrons and belong to space group P212121 with unit cell dimensions of a = 59.2 A, b = 127.0 A, and c = 139.6 A. The asymmetric unit contains one dimer, and the solvent content of the crystals is 60%. The crystals are radiation sensitive. PMID:7663335

  13. Crystallization and preliminary X-ray diffraction studies of a catechol-O-methyltransferase/inhibitor complex

    SciTech Connect

    Rodrigues, M. L.; Bonifácio, M. J.; Soares-da-Silva, P.; Carrondo, M. A.; Archer, M.

    2005-01-01

    Catechol-O-methyltransferase has been co-crystallized with a novel inhibitor, which has potential therapeutic application in the Parkinson’s disease therapy. Inhibitors of the enzyme catechol-O-methyltransferase (COMT) are used as co-adjuvants in the therapy of Parkinson’s disease. A recombinant form of the soluble cytosolic COMT from rat has been co-crystallized with a new potent inhibitor, BIA 8-176 [(3,4-dihydroxy-2-nitrophenyl)phenylmethanone], by the vapour-diffusion method using PEG 6K as precipitant. Crystals diffract to 1.6 Å resolution on a synchrotron-radiation source and belong to the monoclinic space group P2{sub 1}, with unit-cell parameters a = 52.77, b = 79.63, c = 61.54 Å, β = 91.14°.

  14. Study of holographic diffraction gratings implemented in photopolymerizable glasses incorporating ionic liquid

    NASA Astrophysics Data System (ADS)

    Velasco, A. V.; Hernández-Garay, M. P.; Calvo, M. L.; Cheben, P.; del Monte, F.

    2011-05-01

    In this work we analyze the optical quality, performance, and recording mechanism of holographic diffraction gratings recorded in photopolymerizable sol-gel glasses. These classes of holographic photomaterials have various compositions, one of which incorporates a High Refractive Index Species (HRIS), already developed in our group GICO-UCM. The new types of photopolymerizable glasses under study incorporate ionic liquid (IL). We present a comparative study, showing distinctive behaviors for each photopolymerizable glass class, and determining particular features for various ranges of applications.

  15. In Situ Powder Diffraction Studies of Electrode Materials in Rechargeable Batteries.

    PubMed

    Sharma, Neeraj; Pang, Wei Kong; Guo, Zaiping; Peterson, Vanessa K

    2015-09-07

    The ability to directly track the charge carrier in a battery as it inserts/extracts from an electrode during charge/discharge provides unparalleled insight for researchers into the working mechanism of the device. This crystallographic-electrochemical information can be used to design new materials or modify electrochemical conditions to improve battery performance characteristics, such as lifetime. Critical to collecting operando data used to obtain such information in situ while a battery functions are X-ray and neutron diffractometers with sufficient spatial and temporal resolution to capture complex and subtle structural changes. The number of operando battery experiments has dramatically increased in recent years, particularly those involving neutron powder diffraction. Herein, the importance of structure-property relationships to understanding battery function, why in situ experimentation is critical to this, and the types of experiments and electrochemical cells required to obtain such information are described. For each battery type, selected research that showcases the power of in situ and operando diffraction experiments to understand battery function is highlighted and future opportunities for such experiments are discussed. The intention is to encourage researchers to use in situ and operando techniques and to provide a concise overview of this area of research.

  16. X-Ray Photoelectron Diffraction Studies of Structural and Magnetic Disordering Transitions Near Surfaces

    NASA Astrophysics Data System (ADS)

    Tran, Thuy Thu

    This thesis deals with order/disorder transitions near solid surfaces as studied by x-ray photoelectron diffraction and photoelectron holography. Transitions involving both atomic positional order and magnetic order have been studied. Further evidence for a reversible high-temperature surface-disordering phase transition on Ge(111) has been found using Ge 3p x-ray photoelectron diffraction (a short -range-order probe of surface structure) and photoelectron holography. Azimuthal diffraction data at takeoff angles with respect to the surface of theta = 19^circ and theta = 55^circ show abrupt drops in intensity of ~30%-40% over the temperature interval of 900-1200 K. Photoelectron holographic near-neighbor images at temperatures below and above the transition region furthermore indicate an identical near-neighbor structure for all atoms present in ordered sites. These combined diffraction and holography data show that by 1200 K, the Ge(111) surface is covered by a completely disordered overlayer of about 2 Ge monolayers in thickness. The rate of growth of this overlayer with increasing temperature is in excellent agreement with recent medium-energy ion scattering results, although the thickness we find for the overlayer is 1.5-2.0x larger than that derived from ion scattering. Based on these data, a disordering model for the Ge(111) surface phase transition occurring at 1050 K is discussed. Spin-polarized photoelectron diffraction is a recently developed and promising application of photoelectron diffraction to the study of the magnetic structure near surfaces. This technique is based on an internal source of spin-polarized electrons as produced in core-level multiplet splittings and it is thus sensitive to the short-range magnetic order around a given type of emitter in the crystal. In prior studies, it has been applied to two antiferromagnets, KMnF_3 and MnO, and the effects seen at temperatures well above the Neel (or long-range -order) temperature have been

  17. Study of the spatial resolution for binary readout detectors

    NASA Astrophysics Data System (ADS)

    Yonamine, R.; Maerschalk, T.; Lentdecker, G. De

    2016-07-01

    Often the binary readout is proposed for high granularity detectors to reduce the generated data volume to be readout at the price of a somewhat reduced spatial resolution compared to an analogue readout. We have been studying single hit resolutions obtained with a binary readout using simulations as well as analytical approaches. In this note we show that the detector geometry could be optimized to offer an equivalent spatial resolution than with an analogue readout.

  18. Simultaneous fluorescence and phase imaging with extensions toward sub-diffraction resolution via structured-illumination (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Chowdhury, Shwetadwip; Izatt, Joseph A.

    2016-03-01

    In the biological sciences, there is much emphasis on elucidating the functions of various biological components and processes. To do so, advances in general microscopy have yielded various imaging modalities to probe such processes under specific visualization and contrast requirements. Examples of modalities that are popularly integrated into conventional biological studies include fluorescent, dark-field, phase-contrast, and polarization-sensitive microscopies, with each modality offering unique insights into the biological function of the sample. Often times, however, a comprehensive understanding of biological phenomena requires the integration of the unique and separate visualizations of various modalities. Unfortunately, conventional microscopes typically support only one modality and rarely allow multiple modalities to be used in conjunction. Though high-end microscopes may support multimodal visualization, they often require either mechanical (and often manual) toggling, which obstruct real-time multimodal imaging, or simultaneous detection via multiple cameras, which dramatically increases the microscope's cost. Here, we present a one-shot technique that allows multiple imaging channels, of potentially different modalities, to be simultaneously detected by a single camera. We experimentally demonstrate this method on transparent cells that have been tagged for F-actin and nuclear fluorescence. Our multimodal system consists of 2-channel fluorescence and 1-channel quantitative-phase (QP) imaging, and clearly demonstrates ability for simultaneous fluorescent and QP visualization. Though we experimentally verify our framework using dual fluorescent/QP imaging, we emphasize that our framework for single-shot, simultaneous single-camera detection is applicable to an arbitrary number of widefield imaging modalities so long as they fulfill criteria for Fourier spectra separation, SNR, and detector dynamic range

  19. Auger electron diffraction study of the growth of Fe(001) films on ZnSe(001)

    NASA Astrophysics Data System (ADS)

    Jonker, B. T.; Prinz, G. A.

    1991-03-01

    The growth of Fe films on ZnSe(001) epilayers and bulk GaAs(001) substrates has been studied to determine the mode of film growth, the formation of the interface, and the structure of the overlayer at the 1-10 monolayer level. Auger electron diffraction (AED), x-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction data are obtained for incremental deposition of the Fe(001) overlayer. The coverage dependence of the AED forward scattering peaks reveals a predominantly layer-by-layer mode of film growth at 175 °C on ZnSe, while a more three-dimensional growth mode occurs on the oxide-desorbed GaAs(001) substrate. XPS studies of the semiconductor 3d levels indicate that the Fe/ZnSe interface is less reactive than the Fe/GaAs interface.

  20. In situ X-ray diffraction study on the growth kinetics of NiO nanoparticles.

    PubMed

    Meneses, C T; Almeida, J M A; Sasaki, J M

    2010-05-01

    The growth kinetics of NiO nanoparticles have been studied by in situ X-ray diffraction using two detection systems (conventional and imaging plate). NiO nanoparticles were formed by thermal decomposition after heating of an amorphous compound formed by the coprecipitation method. It was found that the detection method using an imaging plate is more efficient than the conventional detection mode for observing changes in the crystallite growth of nanocrystalline materials. Studies have been carried out to investigate the effects of the heating rates on the particles growth. The results suggest that the growth process of the particles is accelerated when the samples are treated at low heating rates. The evolution of particles size and the diffusion coefficient obtained from X-ray powder diffraction patterns are discussed in terms of the thermal conditions for the two types of detection.

  1. Theoretical study on the interference pattern of femtosecond pulses diffracted by a phase mask

    NASA Astrophysics Data System (ADS)

    Bueno, A.; Kinet, D.; Chah, K.; Mégret, P.; Caucheteur, C.

    2016-05-01

    In this paper, we describe a theoretical study on the interference created by a phase mask when a femtosecond laser is used. The limitations of the phase mask-to-fiber distance are discussed and the optimal inscription range is established. Femtosecond lasers have the unique feature of short coherence length and thus the diffraction orders do not interfere after a certain distance travelled from the phase mask even if the phase mask has a poor zero order suppression. The equation describing this behaviour is presented and simulations are included for validation. The intensity profile of the overlapping +/-1 diffraction orders after the phase mask is also studied for 1st order (1070 nm pitch) and for 2nd order (2140 nm pitch) phase masks.

  2. Possibilities and limitations of synchrotron X-ray powder diffraction with double crystal and double multilayer monochromators for microscopic speciation studies

    NASA Astrophysics Data System (ADS)

    De Nolf, Wout; Jaroszewicz, Jakub; Terzano, Roberto; Lind, Ole Christian; Salbu, Brit; Vekemans, Bart; Janssens, Koen; Falkenberg, Gerald

    2009-08-01

    The performance of a combined microbeam X-ray fluorescence/X-ray powder diffraction (XRF/XRPD) measurement station at Hamburger Synchrotronstrahlungslabor (HASYLAB) Beamline L is discussed in comparison to that at European Synchrotron Radiation Facility (ESRF) ID18F/ID22. The angular resolution in the X-ray diffractograms is documented when different combinations of X-ray source, optics and X-ray diffraction detectors are employed. Typical angular resolution values in the range 0.3-0.5° are obtained at the bending magnet source when a 'pink' beam form of excitation is employed. A similar setup at European Synchrotron Radiation Facility beamlines ID18F and ID22 allows to reach angular resolution values of 0.1-0.15°. In order to document the possibilities and limitations for speciation of metals in environmental materials by means of Hamburger Synchrotronstrahlungslabor Beamline L X-ray fluorescence/X-ray powder diffraction setup, two case studies are discussed, one involved in the identification of the crystal phases in which heavy metals such as chromium, iron, barium and lead are present in polluted soils of an industrial site (Val Basento, Italy) and another involved in the speciation of uranium in depleted uranium particles (Ceja Mountains, Kosovo). In the former case, the angular resolution is sufficient to allow identification of most crystalline phases present while in the latter case, it is necessary to dispose of an angular resolution of ca. 0.2° to distinguish between different forms of oxidized uranium.

  3. X-ray diffraction studies of phase transformations in heavy-metal fluoride glasses

    NASA Technical Reports Server (NTRS)

    Bansal, N. P.; Doremus, R. H.

    1985-01-01

    Powder X-ray diffraction and differential scanning calorimetry studies of the crystallization properties of five ZrF4-based glass compositions have indicated that the crystalline phase in Zr-Ba-La-Pb fluoride glass is beta-BaZrF6; no such identification of crystal phases was obtainable, however, for the other glasses. Reversible polymorphic phase transformations occur in Zr-Ba-La-Li and Zr-Ba-La-Na fluoride glasses, upon heating to higher temperatures.

  4. Component analyses of urinary nanocrystallites of uric acid stone formers by combination of high-resolution transmission electron microscopy, fast Fourier transformation, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy.

    PubMed

    Sun, Xin-Yuan; Xue, Jun-Fa; Xia, Zhi-Yue; Ouyang, Jian-Ming

    2015-06-01

    This study aimed to analyse the components of nanocrystallites in urines of patients with uric acid (UA) stones. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy (HRTEM), fast Fourier transformation (FFT) of HRTEM, and energy dispersive X-ray spectroscopy (EDS) were performed to analyse the components of these nanocrystallites. XRD and FFT showed that the main component of urinary nanocrystallites was UA, which contains a small amount of calcium oxalate monohydrate and phosphates. EDS showed the characteristic absorption peaks of C, O, Ca and P. The formation of UA stones was closely related to a large number of UA nanocrystallites in urine. A combination of HRTEM, FFT, EDS and XRD analyses could be performed accurately to analyse the components of urinary nanocrystallites.

  5. Study of low speed flow cytometry for diffraction imaging with different chamber and nozzle designs.

    PubMed

    Sa, Yu; Feng, Yuanming; Jacobs, Kenneth M; Yang, Jun; Pan, Ran; Gkigkitzis, Ioannis; Lu, Jun Q; Hu, Xin-Hua

    2013-11-01

    Achieving effective hydrodynamic focusing and flow stability at low speed presents a challenging design task in flow cytometry for studying phenomena such as cell adhesion and diffraction imaging of cells with low-cost cameras. We have developed different designs of flow chamber and sheath nozzle to accomplish the above goal. A 3D computational model of the chambers has been established to simulate the fluid dynamics in different chamber designs and measurements have been performed to determine the velocity and size distributions of the core fluid from the nozzle. Comparison of the simulation data with experimental results shows good agreement. With the computational model significant insights were gained for optimization of the chamber design and improvement of the cell positioning accuracy for study of slow moving cells. The benefit of low flow speed has been demonstrated also by reduced blurring in the diffraction images of single cells. Based on these results, we concluded that the new designs of chamber and sheath nozzle produce stable hydrodynamic focusing of the core fluid at low speed and allow detailed study of cellular morphology under various rheological conditions using the diffraction imaging method.

  6. Ultrafast lattice response of photoexcited thin films studied by X-ray diffraction

    PubMed Central

    Herzog, Marc; Bojahr, André; Leitenberger, Wolfram; Hertwig, Andreas; Bargheer, Matias

    2014-01-01

    Using ultrafast X-ray diffraction, we study the coherent picosecond lattice dynamics of photoexcited thin films in the two limiting cases, where the photoinduced stress profile decays on a length scale larger and smaller than the film thickness. We solve a unifying analytical model of the strain propagation for acoustic impedance-matched opaque films on a semi-infinite transparent substrate, showing that the lattice dynamics essentially depend on two parameters: One for the spatial profile and one for the amplitude of the strain. We illustrate the results by comparison with high-quality ultrafast X-ray diffraction data of SrRuO3 films on SrTiO3 substrates. PMID:26798784

  7. In-Situ Studies of Intercritically Austempered Ductile Iron Using Neutron Diffraction

    SciTech Connect

    Druschitz, Alan; Aristizabal, Ricardo; Druschitz, Edward; Hubbard, Camden R; Watkins, Thomas R; Walker, Larry R; Ostrander, M

    2012-01-01

    Intercritically austempered ductile irons hold promise for applications requiring fatigue durability, excellent castability, low production energy requirements, reduced greenhouse gas emissions and excellent machinability. In the present study, four different ductile iron alloys, containing manganese and nickel as the primary austenite-stabilizing elements, were heat treated to obtain different quantities of austenite in the final microstructure. This paper reports the microstructures and phases present in these alloys. Further, lattice strains and diffraction elastic constants in various crystallographic directions and the transformation characteristics of the austenite as a function of applied stress were determined using in-situ loading with neutron diffraction at the second generation Neutron Residual Stress Facility (NRSF2) at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL).

  8. Shedding new light on viruses: super-resolution microscopy for studying human immunodeficiency virus.

    PubMed

    Müller, Barbara; Heilemann, Mike

    2013-10-01

    For more than 70 years electron microscopy (EM) techniques have played an important role in investigating structures of enveloped viruses. By contrast, use of fluorescence microscopy (FM) methods for this purpose was limited by the fact that the size of virus particles is generally around or below the diffraction limit of light microscopy. Various super-resolution (SR) fluorescence imaging techniques developed over the past two decades bypass the diffraction limit of light microscopy, allowing visualization of subviral details and bridging the gap between conventional FM and EM methods. We summarize here findings on human immunodeficiency virus (HIV-1) obtained using SR-FM techniques. Although the number of published studies is currently limited and some of the pioneering analyses also covered methodological or descriptive aspects, recent publications clearly indicate the potential to approach open questions in HIV-1 replication from a new angle.

  9. Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

    DOE PAGES

    Wang, H.; Kirkham, M. J.; Watkins, T. R.; ...

    2016-02-17

    N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubicmore » symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. Ultimately, this knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.« less

  10. Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

    SciTech Connect

    Wang, H.; Kirkham, M. J.; Watkins, T. R.; Payzant, E. A.; Salvador, J. R.; Thompson, A. J.; Sharp, J.; Brown, D.; Miller, D.

    2016-02-17

    N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubic symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. Ultimately, this knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.

  11. In situ synchrotron radiation diffraction study of low carbon steel during ion nitriding

    NASA Astrophysics Data System (ADS)

    Feugeas, J. N.; Hermida, J. D.; Gomez, B. J.; Kellermann, G.; Craievich, A.

    1999-09-01

    The volume close to the surface of materials subjected to ion implantation or ion diffusion exhibits structural transformations that are usually studied by x-ray diffraction. In order to characterize the kinetic aspects of structural transformations in low carbon AISI 1010 steel during ion nitriding, an in situ synchrotron radiation diffraction study was performed. An experimental set-up, a specially designed reactor, was constructed for x-ray measurements in real time. The variation in the lattice parameter with time of the initial Fe-icons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/> phase was attributed to the heating effect produced by the action of an electric discharge during the first stages of the process. The analysis of the x-ray diffraction patterns indicates the formation of several iron nitrides. The Fe3N phase exhibits a progressive decrease in the interplanar distances, which is clearly a different behaviour with respect to the other observed phases, even considering a phase with nearly the same stoichiometry.

  12. Synchrotron Powder X-ray Diffraction Study of the Structure and Dehydration Behavior of Sepiolite

    NASA Astrophysics Data System (ADS)

    Post, J. E.; Bish, D. L.; Heaney, P. J.

    2006-05-01

    Sepiolite is a hydrous Mg-silicate clay mineral with fibrous morphology that typically occurs as fine-grained, poorly crystalline masses. It occurs in a wide variety of geological environments and has been mined for centuries because of its many uses, e.g. in the pharmaceutical, fertilizer, and pesticide industries. Its versatile functionality derives from the large surface area and microporosity that are characteristic of the material. In recent years, sepiolite has received considerable attention with regard to the adsorption of organics, for use as a support for catalysts, as a molecular sieve, and as an inorganic membrane for ultrafiltration. Because of its fine-grained and poorly crystalline nature, it has not been possible to study sepiolite's crystal structure using single-crystal X-ray diffraction methods, and consequently many details of the structure are still not well known. In this study, Rietveld refinements using synchrotron powder X-ray diffraction data were used to investigate the crystal structure and dehydration behavior of sepiolite from Durango, Mexico. The room- temperature (RT) sepiolite structure in air compares well with previous models but reveals an additional zeolitic water site. The RT structure under vacuum retained only ~1/8 of the zeolitic water and the volume decreased 1.3%. Real-time, temperature-resolved synchrotron powder X-ray diffraction data and Rietveld refinements were used to investigate the behavior of the sepiolite structure from 300 to 925 K. Rietveld refinements revealed that most of the zeolitic water is lost by ~390 K, accompanied by a decrease in the a and c unit-cell parameters. Above ~600 K the sepiolite structure folds as one-half of the crystallographically bound water is lost. Rietveld refinements of the "anhydrous" sepiolite structure reveal that, in general, unit-cell parameters a, b, â and volume steadily decrease with increasing temperature; there is an obvious change in slope at ~820 K suggesting a phase

  13. ELECTRON MICROSCOPE AND X-RAY DIFFRACTION STUDIES ON A HOMOLOGOUS SERIES OF SATURATED PHOSPHATIDYLCHOLINES.

    PubMed

    ELBERS, P F; VERVERGAERT, P H

    1965-05-01

    Three homologous saturated phosphatidylcholines were studied by electron microscopy after tricomplex fixation. The results are compared with those obtained by x-ray diffraction analysis of the same and some other homologous compounds, in the dry crystalline state and after tricomplex fixation. By electron microscopy alternating dark and light bands are observed which are likely to correspond to phosphatide double layers. X-Ray diffraction reveals the presence of lamellar structures of regular spacing. The layer spacings obtained by both methods are in good agreement. From the electron micrographs the width of the polar parts of the double layers can be derived directly. The width of the carboxylglycerylphosphorylcholine moiety of the layers is found by extrapolating the x-ray diffraction data to zero chain length of the fatty acids. When from this width the contribution of the carboxylglyceryl part of the molecules is subtracted, again we find good agreement with the electron microscope measurements. An attempt has been made to account for the different layer spacings measured in terms of orientation of the molecules within the double layers.

  14. Perfection of Apoferritin Crystals: An Advanced X-Ray Imaging and Diffraction Study

    NASA Technical Reports Server (NTRS)

    Hu, Z. W.; Thomas, B. R.; Chernov, A. A.; Chu, Y. S.

    2003-01-01

    Ferritin is a well-known iron-storage protein, and is a spherical shell that consists of 24 identical subunits packed in a 432 symmetry. The typically large protein size and its distinction from lysozyme as to chemical and physical characteristics make ferritin an attractive model protein for crystal growth and perfection investigation-as an alternative to the most widely studied lysozyme. In this contribution, the latest results obtained from coherence-based x-ray diffraction imaging and diffraction experiments will be presented on octahedral apoferritin (a demetalized form of ferritin) crystals grown from various growth conditions. Crystal specimens, which have the measured rocking-curve widths varying from a few arcseconds to several tens arcseconds (or more), are comparatively examined by intrinsically highly sensitive mapping of lattice perfection and defects. The richness of the observed defects and growth features offers insight into perfection and growth of protein crystals. Beautiful interference fringe patterns formed in diffraction images and fine oscillation structure of rocking curves observed will be discussed for understanding of physical origins and the underlying impact.

  15. Study on diffraction effect and microstructure profile fabricated by one-step backside lithography

    NASA Astrophysics Data System (ADS)

    Yang, Wen-Cheng; Huang, Yu-Sheng; Shew, Bor-Yuan; Fu, Chien-Chung

    2013-03-01

    Backside exposure lithography has been proven to be able to generate needle-like microstructures. The structure profile can be controlled by varying the aperture diameter on the photomask and the distance between the photomask and the photoresist. This distance is usually defined by the glass thickness of the glass in backside exposure lithography. However, in our experience, needle-like structures can be generated easily in some cases but not in others. In order to accurately predict the microstructure profile fabricated by backside exposure lithography, in this study, we built a complete three-dimensional Fresnel-Kirchhoff diffraction model and used a binary approach to simulate the curing threshold. We found that the microstructure profile is influenced by diffraction in both the near-field (Fresnel) and far-field regions (Fraunhofer). Diffraction depends on the design pattern on the photomask and the glass thickness. In many cases, it changes gradually from the near-field to the far-field. This is exactly the reason that our approach generates needle-like structures. Structures ranging from 50 to 450 µm in height were simulated by our model and had a high degree of consistency with the fabricated results. This research may provide potential guidelines for the prediction and the fabrication of needle-like structures for future applications.

  16. Higher Resolution for Water Resources Studies

    NASA Astrophysics Data System (ADS)

    Dumenil-Gates, L.

    2009-12-01

    The Earth system science community is providing an increasing range of science results for the benefit of achieving the Millennium Development Goals. In addressing questions such as reducing poverty and hunger, achieving sustainable global development, or by defining adaptation strategies for climate change, one of the key issues will be the quantitative description and understanding of the global water cycle, which will allow useful projections of available future water resources for several decades ahead. The quantities of global water cycle elements that we observe today - and deal with in hydrologic and atmospheric modeling - are already very different from the natural flows as human influence on the water cycle by storage, consumption and edifice has been going on for millennia, and climate change is expected to add more uncertainty. In this case Tony Blair’s comment that perhaps the most worrying problem is climate change does not cover the full story. We shall also have to quantify how the human demand for water resources and alterations of the various elements of the water cycle may proceed in the future: will there be enough of the precious water resource to sustain current and future demands by the various sectors involved? The topics that stakeholders and decision makers concerned with managing water resources are interested in cover a variety of human uses such as agriculture, energy production, ecological flow requirements to sustain biodiversity and ecosystem services, or human cultural aspects, recreation and human well-being - all typically most relevant at the regional or local scales, this being quite different from the relatively large-scale that the IPCC assessment addresses. Halfway through the Millennium process, the knowledge base of the global water cycle is still limited. The sustainability of regional water resources is best assessed through a research program that combines high-resolution climate and hydrologic models for expected

  17. Transmission electron microscopy and x-ray diffraction studies of the detonation soot of high explosives

    NASA Astrophysics Data System (ADS)

    Kashkarov, A. O.; Pruuel, E. R.; Ten, K. A.; Rubtsov, I. A.; Gerasimov, E. Yu; Zubkov, P. I.

    2016-11-01

    This paper presents the results of electron microscopy and x-ray diffraction studies of the recovered carbonaceous residue (soot) from the detonation of some high explosives: TNT, a mixture of TNT and RDX (50/50), benzotrifuroxane, and triaminotrinitrobenzene. The use of the same experimental setup allowed a qualitative and quantitative comparison of the detonation products formed under similar conditions. The results clearly show differences in the morphology of graphite-like and diamond inclusions and in the quantitative content of nanodiamonds for the explosives used in this study.

  18. Surface, morphology and X-ray diffraction studies of Co (II) complexes of pyrazole ligands

    NASA Astrophysics Data System (ADS)

    Mishra, A.; Jain, Garima; Ninama, S.

    2014-09-01

    Pyrazole based complexes of the cobalt (II) Bis-(diethyl 4-amino-1-(P-nitrophenyl) 1H-pyrazole-3,5dicarboxylate) [Co (D4A1(P-N)1HP35D)] and cobalt (II) Bis-(diethyl 4- amino-1-(3-chlorophenyl) 1H-pyrazole-3,5dicarboxylate) [Co (D4A1(3-Cl)1HP35D)] were synthesized by chemical root method and characterized by different method viz. X-ray diffraction, Fourier transform infrared spectroscopy and Transmission electron microscopy studies. All these studies were in good agreement with the synthesized complexes.

  19. Neutron diffraction study of multiferroic Mo-doped CoFe2O4

    NASA Astrophysics Data System (ADS)

    Das, A.; Dwivedi, G. D.; Kumari, Poonam; Shahi, P.; Yang, H. D.; Ghosh, A. K.; Chatterjee, Sandip

    2015-04-01

    Neutron diffraction measurements have been carried out to study the coexistence of magnetic ordering and ferroelectricity at room temperature in CoFe1.8Mo0.2O4. It is observed from this study that the Mo6+ preferentially occupies the octahedral site and it converts some of the Fe3+ ions into Fe2+ ions in the tetrahedral site. The conversion of Fe3+ ions into Fe2+ ions modulate the Fe-Fe distances which in effect induce the ferroelectricity in magnetically ordered CoFe1.8Mo0.2O4.

  20. A highly hydrated α-cyclodextrin/1-undecanol inclusion complex: crystal structure and hydrogen-bond network from high-resolution neutron diffraction at 20 K.

    PubMed

    Gallois-Montbrun, Delphine; Le Bas, Geneviève; Mason, Sax A; Prangé, Thierry; Lesieur, Sylviane

    2013-04-01

    The monoclinic C2 crystal structure of an α-cyclodextrin/1-undecanol host-guest inclusion complex was solved using single-crystal neutron diffraction. Large high-quality crystals were specially produced by optimizing temperature-controlled growth conditions. The hydrate crystallizes in a channel-type structure formed by head-to-head dimer units of α-cyclodextrin molecules stacked like coins in a roll. The alkyl chain of the guest lipid is entirely embedded inside the tubular cavity delimited by the α-cyclodextrin dimer and adopts an all-trans planar zigzag conformation, while the alcohol polar head group is outside close to the α-cyclodextrin primary hydroxyl groups. The cyclodextrin dimer forms columns, which adopt a quasi-square arrangement much less compact than the quasi-hexagonal close packing already observed in the less hydrated α-cyclodextrin channel-type structures usually found with similar linear guests. The lack of compactness of this crystal form is related to the high number of interstitial water molecules. The replacement of 1-undecanol by 1-decanol does not modify the overall crystal structure of the hydrate as shown by additional X-ray diffraction investigations comparing the two host-guest assemblies. This is the first study that analyses the entire hydrogen-bonding network involved in the formation of a cyclodextrin dimer surrounded by its shell of water molecules.

  1. A X-Ray Diffraction Study of the Structure of Fluid Argon.

    NASA Astrophysics Data System (ADS)

    Yan, Kam-Leung

    X-ray diffraction patterns of liquid argon were measured and analyzed at six thermodynamic states, all above the critical pressure. These states were on the isotherms T = 105.4K ((rho) = 1.43, 1.36, & 1.30 g/cm('3)) and T = 152.0K ((rho) = 1.30, 1.15, & 1.00 g/cm('3)), with pressures between 70 and 765 kg/cm('2). Samples of fluid argon confined in a beryllium cell were irradiated by monochromatized Mo x-radiation. The scattered intensities were detected with a NaI scintillation counter using step-scanning technique. A total resolution of 0.06(DEGREES) in the scattering plane allowed the scanning process to be performed in uniform step-increments of 0.125(DEGREES). Cooling of the Be cell was accomplished with a two-stage N(,2)-He cooling system. Static structure factors S(k) were obtained from the diffraction data. Refinement of these factors and determination of the radial distribution function g(r) were performed by iterative Fourier analysis. The efficacy of this method was exemplified by the overall improvement in the general form as well as the fine details of both functions. The principal features in S(k) and g(r) were located below k = 9 (ANGSTROM)('-1) and r = 16 (ANGSTROM), respectively. The first three maxima in S(k) were approximately at 1.98, 3.66, and 5.28 (ANGSTROM)('-1), respectively, and their respective averaged heights were 2.19, 1.23, and 1.07. In g(r), the positions of the first three coordinate shells were consistently at 3.37, 7.11, and 10.31 (ANGSTROM), respectively; their respective averaged magnitudes were 2.41, 1.20, and 1.07. Both functions were examined for their response to variations of (rho) and T. The main structures in both functions were found to be strongly dependent of the bulk density of the fluid, and relatively insensitive to temperature changes. g(r) for the state of (rho) = 1.43 g/cm('3) presently studied was compared with the results of computer simulation studies of Lennard-Jones fluids (Verlet 1968). The excellent overall

  2. Signature of dislocations and stacking faults of face-centred cubic nanocrystals in coherent X-ray diffraction patterns: a numerical study1

    PubMed Central

    Dupraz, Maxime; Beutier, Guillaume; Rodney, David; Mordehai, Dan; Verdier, Marc

    2015-01-01

    Crystal defects induce strong distortions in diffraction patterns. A single defect alone can yield strong and fine features that are observed in high-resolution diffraction experiments such as coherent X-ray diffraction. The case of face-centred cubic nanocrystals is studied numerically and the signatures of typical defects close to Bragg positions are identified. Crystals of a few tens of nanometres are modelled with realistic atomic potentials and ‘relaxed’ after introduction of well defined defects such as pure screw or edge dislocations, or Frank or prismatic loops. Diffraction patterns calculated in the kinematic approximation reveal various signatures of the defects depending on the Miller indices. They are strongly modified by the dissociation of the dislocations. Selection rules on the Miller indices are provided, to observe the maximum effect of given crystal defects in the initial and relaxed configurations. The effect of several physical and geometrical parameters such as stacking fault energy, crystal shape and defect position are discussed. The method is illustrated on a complex structure resulting from the simulated nanoindentation of a gold nanocrystal. PMID:26089755

  3. Crystallization and preliminary X-ray diffraction studies of maleylacetate reductase from Rhizobium sp. strain MTP-10005

    SciTech Connect

    Fujii, Tomomi; Goda, Yuko; Yoshida, Masahiro; Oikawa, Tadao; Hata, Yasuo

    2008-08-01

    Maleylacetate reductase from Rhizobium sp. strain MTP-10005 has been crystallized using the sitting-drop vapour-diffusion method and microseeding. The crystals contained one dimeric molecule per asymmetric unit and diffracted to 1.79 Å resolution. Maleylacetate reductase (EC 1.3.1.32), which catalyzes the reduction of maleylacetate to 3-oxoadipate, plays an important role in the aerobic microbial catabolism of resorcinol. The enzyme has been crystallized at 293 K by the sitting-drop vapour-diffusion method supplemented with a microseeding technique, using ammonium sulfate as the precipitating agent. The crystal belonged to the monoclinic space group C2, with unit-cell parameters a = 56.85, b = 121.13, c = 94.09 Å, β = 101.48°, and contained one dimeric molecule in the asymmetric unit. It diffracted to 1.79 Å resolution.

  4. Purification, crystallization and preliminary X-ray diffraction studies of d-tagatose 3-epimerase from Pseudomonas cichorii

    SciTech Connect

    Yoshida, Hiromi; Yamada, Mitsugu; Nishitani, Takeyori; Takada, Goro; Izumori, Ken; Kamitori, Shigehiro

    2007-02-01

    Recombinant d-tagatose 3-epimerase from P. cichorii was purified and crystallized. Diffraction data were collected to 2.5 Å resolution. d-Tagatose 3-epimerase (D-TE) from Pseudomonas cichorii catalyzes the epimerization of various ketohexoses at the C3 position. The epimerization of d-psicose has not been reported with epimerases other than P. cichorii D-TE and d-psicose 3-epimerase from Agrobacterium tumefaciens. Recombinant P. cichorii D-TE has been purified and crystallized. Crystals of P. cichorii D-TE were obtained by the sitting-drop method at room temperature. The crystal belongs to the monoclinic space group P2{sub 1}, with unit-cell parameters a = 76.80, b = 94.92, c = 91.73 Å, β = 102.82°. Diffraction data were collected to 2.5 Å resolution. The asymmetric unit is expected to contain four molecules.

  5. High Resolution Cloud Microphysics and Radiation Studies

    DTIC Science & Technology

    2011-06-16

    characteristics of mid level altocumulus clouds and upper level visible and subvisual cirrus clouds The MPL lidar provided information about the temporal...balloon, lidar, and radar study of cirrus and altocumulus clouds to further investigate the presence of multi- cloud and nearly cloud -free layers...data set of the clouds and thermodynanuc structure to build a mesoscale and LF.S test-bed for cirrus and altocumulus cloud layers. The project was

  6. Magnetic and crystal structure correlations in PrMn 1.5Co 0.5Ge 2: a synchrotron diffraction study

    NASA Astrophysics Data System (ADS)

    Ehrenberg, H.; Dincer, I.; Elmali, A.; Elerman, Y.; Fuess, H.

    2002-12-01

    Structure details of PrMn 2- xCo xGe 2, x=0.5, with the tetragonal ThCr 2Si 2-type structure have been studied by high-resolution synchrotron powder diffraction. Unit cell parameters a and c, unit cell volume V, c/ a, (∂ a/∂ x) T and (∂ c/∂ x) T were determined from Rietveld refinements in the temperature range 10-300 K. The average composition < x>=0.49(4) is determined based on a detailed diffraction profile analysis. Our measurements indicate three anomalies in the c/ a ratio, (∂ a/∂ x) T and (∂c/∂ x) T at a temperature of about 150 K, which is very close to the transition temperature from antiferromagnetic to ferromagnetic intralayer ordering.

  7. Mössbauer spectroscopy and neutron diffraction studies of neptunium antimonide NpSb

    NASA Astrophysics Data System (ADS)

    Sanchez, J. P.; Burlet, P.; Quézel, S.; Bonnisseau, D.; Rossat-Mignod, J.; Spirlet, J. C.; Rebizant, J.; Vogt, O.

    1988-09-01

    NpSb has been studied by Mössbauer spectroscopy ( 237Np and 121Sb resonances) and by neutron diffraction using single crystals. Np 3+ magnetic moments order antiferromagnetically below TN = 200 K in a triple- k type I structure. A strong mixing of 5 f electrons with anion p states can be deduced from results of 121Sb resonance. This mixing is certainty at the origin of the interaction mechanism responsible of the coupling between the Fourier components leading to the triple- k multiaxial magnetic structure.

  8. Mössbauer effect and X-ray diffraction studies of synthetic iron bearing trioctahedral micas

    NASA Astrophysics Data System (ADS)

    Ferrow, Embaie

    1987-03-01

    Mössbauer effect, (ME) and powder X-ray diffraction, (XRD) have been used to study the relationship between cationic size, tetrahedral layer rotation, octahedral layer flattening, stability, and Mössbauer quadrupole splitting, qs, of iron bearing trioctahedral micas. Tetrahedral layer rotation accounts for much of the lattice adjustment but biotites that require an angle of rotation higher than 21 degrees are not stable. Both experimental and computational data show that qs for Fe3+ (IV) increases with increasing degree of tetrahedral layer rotation. A systematic increase of qs for Fe2+ (VI) is also observed, but this could be due to factors other than tetrahedral layer rotation.

  9. X-ray powder diffraction study of poly/carbon monofluoride/, CF/1.12/

    NASA Technical Reports Server (NTRS)

    Mahajan, V. K.; Badachhape, R. B.; Margrave, J. L.

    1974-01-01

    Data from X-ray diffraction studies of the poly(carbon monofluoride) with empirical formula CF(1.09-1.15) are reported, and possible intercalation arrangements for the substance are discussed. The data do not conform to true hexagonal symmetry, indicating that the carbon atoms are not coplanar. Each bond angle of carbon is 118.8 deg, and the carbon-carbon distance is 1.47 A. The interlayer distance is 5.76 A. A total absence of (hkl) reflections in the X-ray pattern shows that the separate CF layers are not regularly arranged with respect to one another.

  10. [X-ray diffraction study of high hydrostatic pressure on crystalline structure of different type starches].

    PubMed

    Liu, Pei-Ling; Shen, Qun; Hu, Xiao-Song; Wu, Ji-Hong

    2012-09-01

    Crystalline changes of different type starches after high hydrostatic pressure treated under 300, 450, 600 MPa were studied by X-ray diffraction. Waxy maize (A type, 100% amylopectin), hylon VII (B type, 30% amylopectin) and tapioca starch (C type, 83% amylopectin) were chosen. The results indicated that for waxy maize starch, annealing effect was observed at 300 MPa, disappearance of crystalline structure happened at 450 MPa and retrogradation at 600 MPa. The results proved that the granule under high hydrostatic pressure processing experiences "three development stages" including annealling effect, disappearance of crystalline structure and recrystalline after granule disintegration.

  11. Re-entrant magneto-elastic transition in HoFe 4Ge 2 a neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Schobinger-Papamantellos, P.; Rodríguez-Carvajal, J.; André, G.; Ritter, C.; Buschow, K. H. J.

    2004-09-01

    The re-entrant magneto-elastic transition of the antiferromagnetic HoFe 4Ge 2 compound has been studied by neutron powder diffraction as a function of temperature. The magnetic phase diagram comprises the wave vectors: ( q1o, q2o, q1t) and three magnetic transitions, two of them occurring simultaneously with the structural changes at Tc, TN=52 and Tc', Tic1 =15 K, the third being purely magnetic at Tic2 =40 K. The first transition is of second order while the latter two of first order. The sequence of phases follows the path: P42/mnm (HT), Tc, TN=52 K→ Cmmm (IT): ( q1o=(0,1/2,0) , T i c2 =40 K ⇒ q2o=(0,q y,0)) , Tc', T i c1 =15 K⇒ P42/mnm (LT): q1t=(0,1/2,0) . The magnetic structures described by the wave vectors ( q1o, q2o and q1t), where the components are referred to the reciprocal basis of the conventional Cmmm cell, correspond to canted multi-axial arrangements. The q2o wave vector length of the amplitude modulated phase varies non-monotonously, decreasing fast just below Tic2 ,—slowly between 36 K— Tc', Tic1 and jumping to the q1t=(0,1/2,0) lock-in value at Tc', Tic1 simultaneously with the first order re-entrant transition to the (LT) tetragonal phase. In the coexisting meta-stable orthorhombic phase from Tc', Tic1 down to 1.5 K the length of the wave vector q2o continues to decrease. To solve the magnetic structures of all the phases appearing in this complex situation, arising from competing ordering mechanisms and anisotropies of the underlying sublattices, we have used the simulated annealing method of global optimisation on high-resolution neutron powder diffraction data.

  12. Studies of clays and clay minerals using x-ray powder diffraction and the Rietveld method

    SciTech Connect

    Bish, D.L.

    1993-09-01

    The Rietveld method was originally developed (Rietveld, 1967, 1969) to refine crystal structures using neutron powder diffraction data. Since then, the method has been increasingly used with X-ray powder diffraction data, and today it is safe to say that this is the most common application of the method. The method has been applied to numerous natural and synthetic materials, most of which do not usually form crystals large enough for study with single-crystal techniques. It is the ability to study the structures of materials for which sufficiently large single crystals do not exist that makes the method so powerful and popular. It would thus appear that the method is ideal for studying clays and clay minerals. In many cases this is true, but the assumptions implicit in the method and the disordered nature of many clay minerals can limit titsapplicability. This chapter will describe the Rietveld method, emphasizing the assumptions important for the study of disordered materials, and it will outline the potential applications of the method to these minerals. These applications include, in addition to the refinement of crystal structures, quantitative analysis of multicomponent mixtures, analysis of peak broadening, partial structure solution, and refinement of unit-cell parameters.

  13. Single crystal X-ray diffraction, spectroscopic and mass spectrometric studies of furanocoumarin peucedanin.

    PubMed

    Bartnik, Magdalena; Arczewska, Marta; Hoser, Anna A; Mroczek, Tomasz; Kamiński, Daniel M; Głowniak, Kazimierz; Gagoś, Mariusz; Woźniak, Krzysztof

    2014-01-01

    The structure of peucedanin, isolated from Peucedanum tauricum Bieb. (Apiaceae), has been established using single crystal X-ray diffraction. This furanocoumarin isolated from the light petroleum extract of P. tauricum fruits was characterized by high resolution EI-MS, sATR-FTIR and 2D NMR spectroscopic techniques. The EI-MS showed the typical fragmentation pattern of methoxyfuranocoumarins. Extensive 1D (1H and 13C) as well as 2D NMR data enabled complete assignment of the carbon atoms in the peucedanin molecule. The FTIR data confirms intermolecular hydrogen bonding between peucedanin molecules in polar solvents. Peucedanin crystallises in the R-3 space group from the trigonal system with one molecule in the asymmetric part of the unit cell. The crystal lattice of peucedanin consists of the molecules arranged in separate columns. They are related by two fold screw axes and centres of symmetry. Interestingly, peucedanin columns form two channels per unit cell with a diameter of 7.5angstrom going through the crystal lattice in the Z-direction. These channels are filled with disordered water molecules, which are surrounded by hydrophobic methyl groups and are located exactly at the centres of the channels. The peucedanin molecules are stacked in a single column with the opposite orientation of the neighbouring molecules. These results could be interesting in further application of this molecule, for example in biological tests of its activity.

  14. Anomalous thermal expansion in rare-earth gallium perovskites: a comprehensive powder diffraction study

    NASA Astrophysics Data System (ADS)

    Senyshyn, A.; Trots, D. M.; Engel, J. M.; Vasylechko, L.; Ehrenberg, H.; Hansen, T.; Berkowski, M.; Fuess, H.

    2009-04-01

    Crystal structures of rare-earth gallium perovskites LaGaO3, PrGaO3, NdGaO3 and Pr1-xNdxGaO3 (x = 0.25, 0.50, 0.75) solid solutions were investigated in the temperature range 12-300 K by high-resolution powder diffraction using synchrotron or neutron radiation. The previously reported negative thermal expansion in the b direction of the PrGaO3 lattice has been found to be persistent in Pr1-xNdxGaO3 solid solutions and its magnitude has been revealed as proportional to the amount of praseodymium. Evaluation of the obtained temperature evolution of cell dimensions indicated a weak anomalous behaviour of the b lattice parameter in NdGaO3, and its origin is supposed to be the same as in PrGaO3, i.e. a coupling of the crystal electric field levels with phonon excitations of about 23-25 meV energy. The performed bond length analysis revealed an anomalous behaviour of both LnO12 (Ln—rare-earth) and GaO6 coordination polyhedra, which can be a structural manifestation of anomalous thermal expansion in the considered compounds.

  15. High resolution studies of deep earth structure

    NASA Astrophysics Data System (ADS)

    Ding, Xiaoming

    1998-11-01

    Recent advances in seismic tomography has imaged major deep structure in the lower mantle. The ring of fast velocities originally derived from global long-period inversions has been resolved into interspersed sheet-like structure which appears to be old slabs. Beneath some of the structure, there are high velocity zones (HVZ) with variable thickness approaching the core mantle boundary (CMB). Seismic data recorded on TERRAscope and Berkeley Digital Seismic Network are used to study the HVZ beneath Central America. Modeling these waveforms (P, SV and SH) constitutes a major portion of this thesis. Two modeling strategies were employed in the thesis: (1) Assume a "Lay type" D ″ with a sharp velocity discontinuity; (2) Assume an upper transition zone approaching D″, and a lower transition zone approaching the CMB (old slabs). Our preferred model following strategy (1) (Chapter 2) has an S discontinuity 200 km above the CMB with 3% jump and a negative gradient in the D″ layer. In Chapter 4 the ULVZ beneath Iceland and Africa are addressed. The major phases used to study the ULVZ are SKS and SPdiffKS which travels along the CMB as P at both the core entry (SPdiffKS) and exit (SKPdiffS) locations. A major structure beneath Iceland (SKPdiffS) as identified from data recorded on stations in Northern Europe appears to be shaped like a dome, 80 km high, 200 km wide with a 10% drop in P and S velocities. The data for Africa is less complete but highly anomalous. Shear wave record sections across Africa and Europe containing the cross-over from S to SKS and extended core-phases (75° to 120°) are presented from deep South American events. By studying the various branches of the core phases PKP, it has become quite clear that North-South paths in the inner-core appear faster than East-West paths Moreover, the broadband seismograms associated with these paths are distinct. The reason for this difference is not known but suggests a lower (anisotropic) inner-core with an

  16. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  17. Crystallization and preliminary X-ray diffraction studies on the bicupin YwfC from Bacillus subtilis

    SciTech Connect

    Rajavel, M.; Gopal, B.

    2006-12-01

    The bicupin YwfC from B. subtilis was crystallized in two crystal forms and diffraction data were collected to 2.2 Å resolution. A central tenet of evolutionary biology is that proteins with diverse biochemical functions evolved from a single ancestral protein. A variation on this theme is that the functional repertoire of proteins in a living organism is enhanced by the evolution of single-chain multidomain polypeptides by gene-fusion or gene-duplication events. Proteins with a double-stranded β-helix (cupin) scaffold perform a diverse range of functions. Bicupins are proteins with two cupin domains. There are four bicupins in Bacillus subtilis, encoded by the genes yvrK, yoaN, yxaG and ywfC. The extensive phylogenetic information on these four proteins makes them a good model system to study the evolution of function. The proteins YvrK and YoaN are oxalate decarboxylases, whereas YxaG is a quercetin dioxygenase. In an effort to aid the functional annotation of YwfC as well as to obtain a complete structure–function data set of bicupins, it was proposed to determine the crystal structure of YwfC. The bicupin YwfC was crystallized in two crystal forms. Preliminary crystallographic studies were performed on the diamond-shaped crystals, which belonged to the tetragonal space group P422. These crystals were grown using the microbatch method at 298 K. Native X-ray diffraction data from these crystals were collected to 2.2 Å resolution on a home source. These crystals have unit-cell parameters a = b = 68.7, c = 211.5 Å. Assuming the presence of two molecules per asymmetric unit, the V{sub M} value was 2.3 Å{sup 3} Da{sup −1} and the solvent content was approximately 45%. Although the crystals appeared less frequently than the tetragonal form, YwfC also crystallizes in the monoclinic space group P2{sub 1}, with unit-cell parameters a = 46.7, b = 106.3, c = 48.7 Å, β = 92.7°.

  18. Crystallization and preliminary X-ray diffraction studies of polyketide synthase-1 (PKS-1) from Cannabis sativa

    SciTech Connect

    Taguchi, Chiho; Taura, Futoshi; Tamada, Taro; Shoyama, Yoshinari; Shoyama, Yukihiro; Tanaka, Hiroyuki; Kuroki, Ryota; Morimoto, Satoshi

    2008-03-01

    Polyketide synthase-1 from C. sativa has been crystallized. The crystal diffracted to 1.55 Å resolution with sufficient quality for further structure determination. Polyketide synthase-1 (PKS-1) is a novel type III polyketide synthase that catalyzes the biosynthesis of hexanoyl triacetic acid lactone in Cannabis sativa (Mexican strain). PKS-1 was overproduced in Escherichia coli, purified and finally crystallized in two different space groups. The crystal obtained in 0.1 M HEPES buffer pH 7.5 containing 0.2 M calcium acetate and 20%(w/v) polyethylene glycol 3350 diffracted to 1.65 Å resolution and belonged to space group P1, with unit-cell parameters a = 54.3, b = 59.3, c = 62.6 Å, α = 69, β = 81, γ = 80°. Another crystal obtained in 0.1 M HEPES buffer pH 7.5 containing 0.2 M sodium chloride and 20%(w/v) polyethylene glycol 3350 diffracted to 1.55 Å resolution and belonged to space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 54.3, b = 110, c = 130 Å. These data will enable us to determine the crystal structure of PKS-1.

  19. The chemical reactivity and structure of collagen studied by neutron diffraction

    SciTech Connect

    Wess, T.J.; Wess, L.; Miller, A.

    1994-12-31

    The chemical reactivity of collagen can be studied using neutron diffraction (a non-destructive technique), for certain reaction types. Collagen contains a number of lysine and hydroxylysine side chains that can react with aldehydes and ketones, or these side chains can themselves be converted to aldehydes by lysyl oxidase. The reactivity of these groups not only has an important role in the maintenance of mechanical strength in collagen fibrils, but can also manifest pathologically in the cases of aging, diabetes (reactivity with a variety of sugars) and alcoholism (reactivity with acetaldehyde). The reactivity of reducing groups with collagen can be studied by neutron diffraction, since the crosslink formed in the adduction process is initially of a Schiff base or keto-imine nature. The nature of this crosslink allows it to be deuterated, and the position of this relatively heavy scattering atom can be used in a process of phase determination by multiple isomorphous replacement. This process was used to study the following: the position of natural crosslinks in collagen; the position of adducts in tendon from diabetic rats in vivo and the in vitro position of acetaidehyde adducts in tendon.

  20. Neutron diffraction study of water freezing on aircraft engine combustor soot.

    PubMed

    Tishkova, V; Demirdjian, B; Ferry, D; Johnson, M

    2011-12-14

    The study of the formation of condensation trails and cirrus clouds on aircraft emitted soot particles is important because of its possible effects on climate. In the present work we studied the freezing of water on aircraft engine combustor (AEC) soot particles under conditions of pressure and temperature similar to the upper troposphere. The microstructure of the AEC soot was found to be heterogeneous containing both primary particles of soot and metallic impurities (Fe, Cu, and Al). We also observed various surface functional groups such as oxygen-containing groups, including sulfate ions, that can act as active sites for water adsorption. Here we studied the formation of ice on the AEC soot particles by using neutron diffraction. We found that for low amount of adsorbed water, cooling even up to 215 K did not lead to the formation of hexagonal ice. Whereas, larger amount of adsorbed water led to the coexistence of liquid water (or amorphous ice) and hexagonal ice (I(h)); 60% of the adsorbed water was in the form of ice I(h) at 255 K. Annealing of the system led to the improvement of the crystal quality of hexagonal ice crystals as demonstrated from neutron diffraction.

  1. High-resolution studies of protoplanetary disks

    NASA Astrophysics Data System (ADS)

    Schütz, Oliver

    2005-02-01

    This work presents a multiwavelength search (near-IR, mid-IR, mm) for previously unknown circumstellar disks and a study of those disk candidate objects which are not jet well characterised in the literature. 22 candidate stars, most of these constituting known exoplanet systems, were examined for circumstellar material using the Adaptive Optics instrument ADONIS at La Silla Observatory (Chile). With the new Adaptive Optics system NAOS-CONICA at Paranal (Chile) we tested the technique of Polarimetric Differential Imaging. Advances in mid-IR data reduction were achieved, e.g., a method was developed to correct the chromatic and airmass dependent extinction. We show new N-band photometry and spectra for eight pre-main sequence stars, six main sequence stars and one post-MS object using the TIMMI2 camera at La Silla, and model the emission spectra with a mixture of silicates consisting of different grain sizes and composition. The most important result thereof is the discovery of two previously unknown circumstellar disks around HD 72106 and HD 113766. Both objects are host to highly processed silicates, resembling those found in solar-system comets. We further present the first observational confirmation for an extended circumstellar dust disk around ɛ Eri obtained with the bolometer array SIMBA at the 15 m radio telescope SEST in La Silla and demonstrate that the previously claimed disk substructure may alternatively be explained by remnant noise effects.

  2. Nanoindentation and x-ray diffraction studies of pressure-induced amorphization in C-70 fullerene

    NASA Astrophysics Data System (ADS)

    Patterson, Jeremy R.; Catledge, Shane A.; Vohra, Yogesh K.

    2000-08-01

    We have carried out high-pressure studies on a C-70 fullerene sample in a diamond anvil cell to 46 GPa at room temperature. Synchrotron energy dispersive x-ray diffraction studies were carried out to monitor the irreversible amorphization transformation followed by nanoindentation studies of the pressure-quenched samples. Micro-Raman studies indicate broad bands at 1570 and 1422 cm-1 indicative of an amorphous phase with a mixture of sp2- and sp3-bonded carbon. Nanoindentation studies on the quenched amorphous phase shows an elastic loading behavior with a hardness of 18 GPa, which is 2-3 times that of the surrounding steel gasket. Our results conclusively establish that the hard carbon phases can be produced from C-70 fullerene by application of pressure at room temperature.

  3. Nanoindentation and x-ray diffraction studies of pressure-induced amorphization in C-70 fullerene

    SciTech Connect

    Patterson, Jeremy R.; Catledge, Shane A.; Vohra, Yogesh K.

    2000-08-07

    We have carried out high-pressure studies on a C-70 fullerene sample in a diamond anvil cell to 46 GPa at room temperature. Synchrotron energy dispersive x-ray diffraction studies were carried out to monitor the irreversible amorphization transformation followed by nanoindentation studies of the pressure-quenched samples. Micro-Raman studies indicate broad bands at 1570 and 1422 cm-1 indicative of an amorphous phase with a mixture of sp{sup 2}- and sp{sup 3}-bonded carbon. Nanoindentation studies on the quenched amorphous phase shows an elastic loading behavior with a hardness of 18 GPa, which is 2-3 times that of the surrounding steel gasket. Our results conclusively establish that the hard carbon phases can be produced from C-70 fullerene by application of pressure at room temperature. (c) 2000 American Institute of Physics.

  4. The beta-SiC(100) surface studied by low energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectra

    NASA Technical Reports Server (NTRS)

    Dayan, M.

    1986-01-01

    The beta-SiC(100) surface has been studied by low energy electron diffraction, Auger electron spectroscopy, high resolution electron energy loss spectra (HREELS), and core level excitation EELS. Two new Si-terminated phases have been discovered, one with (3 x 2) symmetry, and the other with (2 x 1) symmetry. Models are presented to describe these phases. New results, for the C-rich surface, are presented and discussed. In addition, core level excitation EELS results are given and compared with theory.

  5. Diffraction Studies from Minerals to Organics - Lessons Learned from Materials Analyses

    SciTech Connect

    Whitfield, Pamela S

    2014-01-01

    In many regards the study of materials and minerals by powder diffraction techniques are complimentary, with techniques honed in one field equally applicable to the other. As a long-time materials researcher many of the examples are of techniques developed for materials analysis applied to minerals. However in a couple of cases the study of new minerals was the initiation into techniques later used in materials-based studies. Hopefully they will show that the study of new minerals structures can provide opportunities to add new methodologies and approaches to future problems. In keeping with the AXAA many of the examples have an Australian connection, the materials ranging from organics to battery materials.

  6. A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations.

    PubMed

    Xia, Fang; Qian, Gujie; Brugger, Joël; Studer, Andrew; Olsen, Scott; Pring, Allan

    2010-10-01

    A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300 °C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite (KAlSi(2)O(6)) to analcime (NaAlSi(2)O(6)⋅H(2)O) at 210 °C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3±1.1 kJ  mol(-1). Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

  7. A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations

    NASA Astrophysics Data System (ADS)

    Xia, Fang; Qian, Gujie; Brugger, Joël; Studer, Andrew; Olsen, Scott; Pring, Allan

    2010-10-01

    A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300 °C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite (KAlSi2O6) to analcime (NaAlSi2O6ṡH2O) at 210 °C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3±1.1 kJ mol-1. Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

  8. In-situ high-pressure x-ray diffraction study of zinc ferrite nanoparticles

    DOE PAGES

    Ferrari, S.; Kumar, R. S.; Grinblat, F.; ...

    2016-04-23

    We have studied the high-pressure structural behavior of zinc ferrite (ZnFe2O4) nanoparticles by powder X-ray diffraction measurements up to 47 GPa. We found that the cubic spinel structure of ZnFe2O4 remains up to 33 GPa and a phase transition is induced beyond this pressure. The high-pressure phase is indexed to an orthorhombic CaMn2O4-type structure. Upon decompression the low- and high-pressure phases coexist. The compressibility of both structures was also investigated. We have observed that the lattice parameters of the high-pressure phase behave anisotropically upon compression. Further, we predict possible phase transition around 55 GPa. For comparison, we also studied themore » compression behavior of magnetite (Fe3O4) nanoparticles by X-ray diffraction up to 23 GPa. Spinel-type ZnFe2O4 and Fe3O4 nanoparticles have a bulk modulus of 172 (20) GPa and 152 (9) GPa, respectively. Lastly, this indicates that in both cases the nanoparticles do not undergo a Hall-Petch strengthening.« less

  9. Magnetic Structure of Goethite α-FeOOH: A Neutron Diffraction Study

    NASA Astrophysics Data System (ADS)

    Zepeda-Alarcon, E.; Nakotte, H.; Vogel, S. C.; Wenk, H.

    2013-12-01

    Goethite (α-FeOOH) is found in diverse natural ecosystems, it is by far the most common oxyhydroxide in terrestrial soils, sediments and clays and an important mineral in the biogeochemical cycle of iron at the Earth's surface. Neutron diffraction studies have found that the iron magnetic moments are collinear in a two sublattice antiferromagnetic structure, aligned parallel to the c axis in space group Pbnm (Forsyth et. al. 1968). However, goethite shows superparamagnetic behavior and also a weak ferromagnetic component that has been attributed to the presence of lattice distortions. It is thought that these changes in magnetic ordering could be due to a 13° canting of the magnetic moment with respect to the c-axis, which enables the flipping of the spins due to small perturbations in the lattice (Coey et. al. 1995). In this study we used neutron diffraction at HIPPO and NPDF beamlines at LANSCE of Los Alamos National Laboratory on a powder of natural goethite provided by A. Gualtieri. The nuclear and magnetic structures were determined by means of a Rietveld refinement with GSAS and it was found that the spins of the iron atoms are aligned parallel to the c-axis, with no evidence of spin canting. The net magnetic moment is lower than what has previously been found. These results provide further insight into the magnetic ordering of this mineral and can be important in understanding the physical processes responsible for goethite's intriguing magnetic behavior.

  10. High-pressure powder x-ray diffraction study of EuVO{sub 4}

    SciTech Connect

    Garg, Alka B.; Errandonea, D.

    2015-03-15

    The high-pressure structural behavior of europium orthovanadate has been studied using in-situ, synchrotron based, high-pressure x-ray powder diffraction technique. Angle-dispersive x-ray diffraction measurements were carried out at room temperature up to 34.7 GPa using a diamond-anvil cell, extending the pressure range reported in previous experiments. We confirmed the occurrence of zircon–scheelite phase transition at 6.8 GPa and the coexistence of low- and high-pressure phases up to 10.1 GPa. In addition, clear evidence of a scheelite–fregusonite transition is found at 23.4 GPa. The fergusonite structure remains stable up to 34.7 GPa, the highest pressure reached in the present measurements. A partial decomposition of EuVO{sub 4} was also observed from 8.1 to 12.8 GPa; however, this fact did not preclude the identification of the different crystal structures of EuVO{sub 4}. The crystal structures of the different phases have been Rietveld refined and their equations of state (EOS) have been determined. The results are compared with the previous experimental data and theoretical calculations. - Graphical abstract: The high-pressure structural sequence of EuVO{sub 4}. - Highlights: • EuVO{sub 4} is studied under pressure up to 35 GPa using synchrotron XRD. • The zircón–scheelite–fergusonite structural sequence is observed. • Crystal structures are refined and equations of state determined.

  11. In-situ high-pressure x-ray diffraction study of zinc ferrite nanoparticles

    SciTech Connect

    Ferrari, S.; Kumar, R. S.; Grinblat, F.; Aphesteguy, J. C.; Saccone, F. D.; Errandonea, D.

    2016-04-23

    We have studied the high-pressure structural behavior of zinc ferrite (ZnFe2O4) nanoparticles by powder X-ray diffraction measurements up to 47 GPa. We found that the cubic spinel structure of ZnFe2O4 remains up to 33 GPa and a phase transition is induced beyond this pressure. The high-pressure phase is indexed to an orthorhombic CaMn2O4-type structure. Upon decompression the low- and high-pressure phases coexist. The compressibility of both structures was also investigated. We have observed that the lattice parameters of the high-pressure phase behave anisotropically upon compression. Further, we predict possible phase transition around 55 GPa. For comparison, we also studied the compression behavior of magnetite (Fe3O4) nanoparticles by X-ray diffraction up to 23 GPa. Spinel-type ZnFe2O4 and Fe3O4 nanoparticles have a bulk modulus of 172 (20) GPa and 152 (9) GPa, respectively. Lastly, this indicates that in both cases the nanoparticles do not undergo a Hall-Petch strengthening.

  12. Crystal microstructure of annealed nanocrystalline Chromium studied by synchrotron radiation diffraction

    NASA Astrophysics Data System (ADS)

    Wardecki, D.; Przeniosło, R.; Fitch, A. N.; Bukowski, M.; Hempelmann, R.

    2011-03-01

    The microstructure of electrodeposited nanocrystalline chromium (n-Cr) was studied by using synchrotron radiation (SR) diffraction, SEM, TEM, and EDX techniques. The as-prepared n-Cr samples show the standard bcc crystal structure of Cr with volume-averaged column lengths varying from 25 to 30 nm. The grain growth kinetics and the oxidation kinetics were studied by time resolved SR diffraction measurements with n-Cr samples annealed at 400, 600, and 800 °C. The grain growth process is relatively fast and it occurs within the first 10 min of annealing. The final crystallite size depends only on the annealing temperature and not on the initial grain size or on the oxygen content. The final volume-averaged column lengths observed after 50 min annealing are 40(4), 80(1), and 120(2) nm for temperatures 400, 600, and 800 °C, respectively. It is shown that annealing ex situ of n-Cr at 800 °C both under vacuum and in air gives a grain growth process with the same final crystallite sizes. The formation of the Cr2O3 and CrH phases is observed during annealing.

  13. Neutron diffraction study of a non-strichiometric Ni-Mn-Ga MSM alloy

    SciTech Connect

    Ari-Gur, Pnina; Garlea, Vasile O

    2013-01-01

    The structure and chemical order of a Heusler alloy of non-stoichiometric composition Ni-Mn-Ga were studied using constant-wavelength (1.538 ) neutron diffraction at 363K and the diffraction pattern was refined using the FullProf software. At this temperature the structure is austenite (cubic) with Fm-3m space group and lattice constant of a = 5.83913(4) [ ]. The chemical order is of critical importance in these alloys, as Mn becomes antiferromagnetic when the atoms are closer than the radius of the 3d shell. In the studied alloy the refinement of the site occupancy showed that the 4b (Ga site) contained as much as 22% Mn; that significantly alters the distances between the Mn atoms in the crystal and, as a result, also the exchange energy between some of the Mn atoms. Based on the refinement, the composition was determined to be Ni1.91Mn1.29Ga0.8

  14. Aging behavior of lithium iron phosphate based 18650-type cells studied by in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Paul, Neelima; Wandt, Johannes; Seidlmayer, Stefan; Schebesta, Sebastian; Mühlbauer, Martin J.; Dolotko, Oleksandr; Gasteiger, Hubert A.; Gilles, Ralph

    2017-03-01

    The aging behavior of commercially produced 18650-type Li-ion cells consisting of a lithium iron phosphate (LFP) based cathode and a graphite anode based on either mesocarbon microbeads (MCMB) or needle coke (NC) is studied by in situ neutron diffraction and standard electrochemical techniques. While the MCMB cells showed an excellent cycle life with only 8% relative capacity loss (i.e., referenced to the capacity after formation) after 4750 cycles and showed no capacity loss on storage for two years, the needle coke cells suffered a 23% relative capacity loss after cycling and a 11% loss after storage. Based on a combination of neutron diffraction and electrochemical characterization, it is shown that the entire capacity loss for both cell types is dominated by the loss of active lithium; no other aging mechanisms like structural degradation of anode or cathode active materials or deactivation of active material could be found, highlighting the high structural stability of the active material and the excellent quality of the investigated cells.

  15. Auger electron diffraction study of the initial stage of Ge heteroepitaxy on Si(001)

    NASA Astrophysics Data System (ADS)

    Sasaki, M.; Abukawa, T.; Yeom, H. W.; Yamada, M.; Suzuki, S.; Sato, S.; Kono, S.

    1994-12-01

    The initial stage of pure and surfactant (Sb)-assisted Ge growth on a Si(001) surface has been studied by Auger electron diffraction (AED) and X-ray photoelectron diffraction (XPD). A single-domain Si(001)2 × 1 substrate was used to avoid the ambiguity arising from the usual double-domain substrate. For the pure Ge growth, 1 monolayer of Ge was deposited onto the room temperature substrate followed by annealing at 350°C-600°C, which appeared to have (1 × 2) periodicity by LEED. Ge LMM AED patterns were measured to find that a substantial amount of Ge atoms diffuse to the bulk Si positions up to the fourth layer at least. For the Sb-assisted Ge growth, a Sb(1 × 2)/Si(001) surface was first prepared and Sb 3d XPD patterns were measured to find that Sb forms dimers on the substrate. 1 ML of Ge was deposited onto the Sb(1 × 2)/Si(001) surface and then the surface was annealed at 600°C. Ge LMM AED and Sb 3d XPD patterns measured for this surface showed that surfactant Sb atoms are indeed present on the first layer forming dimers and that Ge atoms are present mainly on the second layer with a substantial amount of Ge diffused into the third and fourth layers.

  16. Cage occupancies in the high pressure structure H methane hydrate: A neutron diffraction study

    SciTech Connect

    Tulk, Christopher A; Klug, Dennis D; Moreira Dos Santos, Antonio F; Karotsis, Georgios; Guthrie, Malcolm; Molaison, Jamie J; Pradhan, Neelam

    2012-01-01

    A neutron diffraction study was performed on the CD{sub 4}: D{sub 2}O structure H clathrate hydrate to refine its CD{sub 4} fractional cage occupancies. Samples of ice VII and hexagonal (sH) methane hydrate were produced in a Paris-Edinburgh press and in situ neutron diffraction data collected. The data were analyzed with the Rietveld method and yielded average cage occupancies of 3.1 CD{sub 4} molecules in the large 20-hedron (5{sup 12}6{sup 8}) cages of the hydrate unit cell. Each of the pentagonal dodecahedron (5{sup 12}) and 12-hedron (4{sup 3}5{sup 6}6{sup 3}) cages in the sH unit cell are occupied with on average 0.89 and 0.90 CD{sub 4} molecules, respectively. This experiment avoided the co-formation of Ice VI and sH hydrate, this mixture is more difficult to analyze due to the proclivity of ice VI to form highly textured crystals, and overlapping Bragg peaks of the two phases. These results provide essential information for the refinement of intermolecular potential parameters for the water methane hydrophobic interaction in clathrate hydrates and related dense structures.

  17. Cage occupancies in the high pressure structure H methane hydrate: A neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Tulk, C. A.; Klug, D. D.; dos Santos, A. M.; Karotis, G.; Guthrie, M.; Molaison, J. J.; Pradhan, N.

    2012-02-01

    A neutron diffraction study was performed on the CD4 : D2O structure H clathrate hydrate to refine its CD4 fractional cage occupancies. Samples of ice VII and hexagonal (sH) methane hydrate were produced in a Paris-Edinburgh press and in situ neutron diffraction data collected. The data were analyzed with the Rietveld method and yielded average cage occupancies of 3.1 CD4 molecules in the large 20-hedron (51268) cages of the hydrate unit cell. Each of the pentagonal dodecahedron (512) and 12-hedron (435663) cages in the sH unit cell are occupied with on average 0.89 and 0.90 CD4 molecules, respectively. This experiment avoided the co-formation of Ice VI and sH hydrate, this mixture is more difficult to analyze due to the proclivity of ice VI to form highly textured crystals, and overlapping Bragg peaks of the two phases. These results provide essential information for the refinement of intermolecular potential parameters for the water-methane hydrophobic interaction in clathrate hydrates and related dense structures.

  18. A neutron diffraction study of chemisorbed methyl groups in the structure of Y zeolite

    NASA Astrophysics Data System (ADS)

    Vratislav, S.; Dlouhá, M.; Bosáček, V.

    A powder diffraction study of the structure of NaY zeolites with chemisorbed CD 3+ species created by a reaction of Na + cations with d-methyliodide show that chemisorbed methyl groups are preferentially located in alfa cages at O(1) oxygen sites. A complete set of the structural parameters in the frame of Fd3m space group for unperturbed NaY with NaY after the formation of surface methoxy groups were given and an influence of chemisorbed species on the distribution of Na + cations in the lattice was detected by neutron diffraction. Our results show that the population of cationic sites has been changed significantly after the chemisorption of methyl iodide. While the occupation of S II in NaY without adsorbate was 32 Na + per unit cell (i.e. 100%), after the chemisorption of CH 3I it was found to be 19.6 (61%) and in case of CD 3I 21.4 (67%). On the same samples also a significant decrease of population in S I‧ was detected accompanied by a slight increase of population in S I sites.

  19. High energy white beam x-ray diffraction studies of residual strains in engineering components

    NASA Astrophysics Data System (ADS)

    Zhang, S. Y.; Vorster, W.; Jun, T. S.; Song, X.; Golshan, M.; Laundy, D.; Walsh, M. J.; Korsunsky, A. M.

    2008-09-01

    In order to predict the durability of engineering components and improve performance, it is mandatory to understand residual stresses. The last decade has witnessed a significant increase of residual stress evaluation using diffraction of penetrating radiation, such as neutrons or high energy X-rays. They provide a powerful non-destructive method for determining the level of residual stresses in engineering components through precise characterisation of interplanar crystal lattice spacing. The unique non-destructive nature of these measurement techniques is particularly beneficial in the context of engineering design, since it allows the evaluation of a variety of structural and deformational parameters inside real components without material removal, or at worst with minimal interference. However, while most real engineering components have complex shape and are often large in size, leading to measurement and interpretation difficulties, since experimental facilities usually have limited space for mounting the sample, limited sample travel range, limited loading capacity of the sample positioning system, etc. Consequently, samples often have to be sectioned, requiring appropriate corrections on measured data; or facilities must be improved. Our research group has contributed to the development of engineering applications of high-energy X-ray diffraction methods for residual stress evaluation, both at synchrotron sources and in the lab setting, including multiple detector setup, large engineering component manipulation and measurement at the UK Synchrotron Radiation Source (SRS Daresbury), and in our lab at Oxford. A nickel base superalloy combustion casing and a large MIG welded Al alloy plate were successfully studied.

  20. Stress-induced martensite variant reorientation in magnetic shape memory Ni Mn Ga single crystal studied by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Molnar, P.; Sittner, P.; Lukas, P.; Hannula, S.-P.; Heczko, O.

    2008-06-01

    Stress-induced martensite variant reorientation in magnetic shape memory Ni-Mn-Ga single crystal was studied in situ by the neutron diffraction technique. Principles of determination of individual tetragonal martensitic variants in shape memory alloys are explained. Using neutron diffraction we show that the macroscopic strain originates solely from the martensite structure reorientation or variant redistribution. Neutron diffraction also reveals that the reorientation of martensite is not fully completed even at a stress value of 25 MPa, which is about 20 times larger than the mean stress needed for reorientation. Only one twinning system is active during the reorientation process.

  1. Intensity and phase fields behind Phase Shifting Masks studied with High Resolution Interference Microscopy

    NASA Astrophysics Data System (ADS)

    Puthankovilakam, Krishnaparvathy; Scharf, Toralf; Herzig, Hans Peter; Weichelt, Tina; Zeitner, Uwe; Vogler, Uwe; Voelkel, Reinhard

    2015-03-01

    The proximity printing industry is in real need of high resolution results and it can be done using Phase Shift Mask (PSM) or by applying Optical Proximity Correction (OPC). In our research we are trying to find out details of how light fields behind the structures of photo masks develop in order to determine the best conditions and designs for proximity printing. We focus here on parameters that are used in real situation with gaps up to 50 μm and structure sizes down to 2 μm. The light field evolution behind the structures is studied and delivers insight in to precisions and tolerances that need to be respected. It is the first time that an experimental analysis of light propagation through mask is presented in detail, which includes information on intensity and phase. The instrument we use is known as High Resolution Interference Microscopy (HRIM). HRIM is a Mach-Zehnder interferometer which is capable of recording three dimensional distributions of intensity and phase with diffraction limited resolution. Our characterization technique allows plotting the evolution of the desired light field and therefore printable structure till the desired proximity gap. In this paper we discuss in detail the evolution of intensity and phase fields of elbow or corner structure at different position behind a phase mask and interpret the main parameters. Of particular interest are tolerances against proximity gap variation and the resolution in printed structures.

  2. Evolution of titania nanotubes-supported WO{sub x} species by in situ thermo-Raman spectroscopy, X-ray diffraction and high resolution transmission electron microscopy

    SciTech Connect

    Cortes-Jacome, M.A.; Angeles-Chavez, C.; Morales, M.; Lopez-Salinas, E.; Toledo-Antonio, J.A.

    2007-10-15

    Structural evolution of WO{sub x} species on the surface of titania nanotubes was followed by in situ thermo-Raman spectroscopy. A total of 15 wt% of W atoms were loaded on the surface of a hydroxylated titania nanotubes by impregnation with ammonium metatungstate solution and then, the sample was thermally treated in a Linkam cell at different temperatures in nitrogen flow. The band characteristic of the W=O bond was observed at 962 cm{sup -1} in the dried sample, which vanished between 300 and 700 deg. C, and reappear again after annealing at 800 deg. C, along with a broad band centered at 935 cm{sup -1}, attributed to the v{sub 1} vibration of W=O in tetrahedral coordination. At 900 and 1000 deg. C, the broad band decomposed into four bands at 923, 934, 940 and 950 cm{sup -1}, corresponding to the symmetric and asymmetric vibration of W=O bonds in Na{sub 2}WO{sub 4} and Na{sub 2}W{sub 2}O{sub 7} phases as determined by X-ray diffraction and High resolution transmission electron microscopy (HRTEM). The structure of the nanotubular support was kept at temperatures below 450 deg. C, thereafter, it transformed into anatase being stabilized at temperatures as high as 900 deg. C. At 1000 deg. C, anatase phase partially converted into rutile. After annealing at 1000 deg. C, a core-shell model material was obtained, with a shell of ca. 5 nm thickness, composed of sodium tungstate nanoclusters, and a core composed mainly of rutile TiO{sub 2} phase. - Graphical abstract: Titania nanotubes loaded with 15 wt% W atoms were characterized from room temperature (rt) to 1000 deg. C by thermo-Raman spectroscopy in N{sub 2}. At 1000 deg. C, a core-shell model material was obtained, with a shell thickness of ca. 5 nm composed by nanoclusters of sodium tungstate, and a core composed mainly of rutile TiO{sub 2} phase.

  3. Crystallization and preliminary X-ray diffraction studies of Tyr167His mutant α-cyclodextrin glucanotransferase from Bacillus macerans.

    PubMed

    Yue, Yang; Liu, Shengquan; Li, Hongbin; Song, Binghong; Xie, Ting; Sun, Yan; Chao, Yapeng; Qian, Shijun

    2013-10-01

    Improving the specificity of α-cyclodextrin glucanotransferase is a significant issue in the field of α-cyclodextrin production. In this study, a constructed Y167H mutant α-cyclodextrin glucanotransferase with enhanced α-cyclodextrin specificity was successfully expressed and purified. Single crystals were grown using PEG 4000 as a precipitating agent by the hanging-drop vapour-diffusion method at 293 K. The crystals exhibited two kinds of morphology in different crystallization conditions. The crystals diffracted to at least 2.2 Å resolution (space group P2₁2₁2₁), with unit-cell parameters a=65.69, b=78.70, c=137.00 Å. Assuming the asymmetric cell to be occupied by a monomer of 75 kDa, the unit cell contains 43.77% solvent with a crystal volume per protein mass, VM, of 2.19 Å3 Da(-1).

  4. Purification, crystallization, preliminary X-ray diffraction and molecular-replacement studies of great cormorant (Phalacrocorax carbo) haemoglobin

    SciTech Connect

    Jagadeesan, G.; Malathy, P.; Gunasekaran, K.; Harikrishna Etti, S.; Aravindhan, S.

    2014-10-25

    The great cormorant hemoglobin has been isolated, purified and crystallized and the three dimensional structure is solved using molecular replacement technique. Haemoglobin is the iron-containing oxygen-transport metalloprotein that is present in the red blood cells of all vertebrates. In recent decades, there has been substantial interest in attempting to understand the structural basis and functional diversity of avian haemoglobins. Towards this end, purification, crystallization, preliminary X-ray diffraction and molecular-replacement studies have been carried out on cormorant (Phalacrocorax carbo) haemoglobin. Crystals were grown by the hanging-drop vapour-diffusion method using PEG 3350, NaCl and glycerol as precipitants. The crystals belonged to the trigonal system P3{sub 1}21, with unit-cell parameters a = b = 55.64, c = 153.38 Å, β = 120.00°; a complete data set was collected to a resolution of 3.5 Å. Matthews coefficient analysis indicated that the crystals contained a half-tetramer in the asymmetric unit.

  5. Trapping the M{sub 1} and M{sub 2} substrates of bacteriorhodopsin for electron diffraction studies

    SciTech Connect

    Perkins, G.A.

    1992-05-01

    Visible and Fourier transform infrared (FTIR) absorption spectroscopies are used to observe protein conformational changes occuring during the bacteriorhodopsin photocycle. Spectroscopic measurements which define the conditions under which bacteriorhodopsin can be isolated and trapped in two distinct substates of the m intermediate of the photocycle, M{sub 1}, and M{sub 2}, are described. A protocol that can be used for high-resolution electron diffraction studies is presented that will trap glucose-embedded purple membrane in the M{sub 1}and M{sub 2} substates at greater than 90% concentration. It was discovered that glucose alone does not provide a fully hydrated environment for bacteriorhodopsin. Equilibration of glucose-embedded samples at high humidity can result in a physical state that is demonstrably closer to the native, fully hydrated state. An extension of the C-T Model of bacteriorhodopsin functionality (Fodor et al., 1988; Mathies et al., 1991) is proposed based on FTIR results and guided by published spectra from resonance Raman and FTIR work. 105 refs.

  6. In-situ time resolved synchrotron powder diffraction studies of synthesis and chemical reactions

    SciTech Connect

    Norby, P.

    1995-09-01

    Equipment for time and temperature dependent powder diffraction has been developed, especially in order to be able to study hydrothermal syntheses of zeolites. The system is very versatile and has so far been used to study e.g. hydrothermal syntheses of zeolites and aluminophosphates, syntheses of layered phosphates, formation of Sorel cements, dehydration and phase transformations of zeolites, solid state synthesis of lanthanum manganites, ion exchange of zeolites using molten salt, and oxidation/reduction of lanthanum manganites at high temperatures. The sample is contained in quartz capillaries and is heated using a stream of hot air. External pressure can be applied allowing hydrothermal syntheses at temperatures up to 200 C to be performed. Controlled atmosphere is obtained by flowing gas or a mixture of gases through the capillary.

  7. A Mössbauer and X-ray powder diffraction study of some ferrous hematinics.

    PubMed

    Coe, E M; Bowen, L H; Bereman, R D

    1995-06-01

    Iron deficiency anemia is a relatively common illness that can arise from a number of different causes. Three ferrous salts are usually used in its treatment: ferrous fumarate, gluconate, and sulfate. They are administered orally and are relatively well tolerated. These hematinics have been studied by Mössbauer spectroscopy and X-ray powder diffraction, and can easily be distinguished by both techniques. It was found that the two ferrous sulfates studied (Eckerd and SmithKline Beckman Co.) most closely resemble the monohydrate by comparison of the X-ray powder pattern with those of the JCPDS. Both the ferrous fumarate (Femiron) and gluconate (Spring Valley) had approximately 10% ferric iron present. To the authors' knowledge, this is the first reported Mössbauer spectrum for ferrous fumarate.

  8. Orthorhombic boron oxide under pressure: In situ study by X-ray diffraction and Raman scattering

    NASA Astrophysics Data System (ADS)

    Cherednichenko, Kirill A.; Le Godec, Yann; Kalinko, Aleksandr; Mezouar, Mohamed; Solozhenko, Vladimir L.

    2016-11-01

    High-pressure phase of boron oxide, orthorhombic β-B2O3, has been studied in situ by synchrotron X-ray diffraction to 22 GPa and Raman scattering to 46 GPa at room temperature. The bulk modulus of β-B2O3 has been found to be 169(3) GPa that is in good agreement with our ab initio calculations. Raman and IR spectra of β-B2O3 have been measured at ambient pressure; all experimentally observed bands have been attributed to the theoretically calculated ones, and the mode assignment has been performed. Based on the data on Raman shift as a function of pressure, combined with equation-of-state data, the Grüneisen parameters of all experimentally observed Raman bands have been calculated. β-B2O3 enriched by 10B isotope has been synthesized, and the effect of boron isotopic substitution on Raman spectra has been studied.

  9. Study of cell classification with a diffraction imaging flow cytometer method

    NASA Astrophysics Data System (ADS)

    Dong, Ke; Jacobs, Kenneth M.; Sa, Yu; Feng, Yuanming; Lu, Jun Q.; Hu, Xin-Hua

    2011-02-01

    With a diffraction imaging flow cytometer, we have acquired and analyzed the diffraction imaging data from 5 types of cultured cells. A gray level co-occurrence matrix (GLCM) algorithm was applied to extract the interference fringe related textures from the diffraction image data. Six GLCM parameters were chosen and imported into a support vector machine algorithm for automated classification of about 20 cells for each of the 5 cell types. We found that the GLCM based algorithm has the capacity for rapid processing of diffraction images and yield feature parameters for subsequent cell classification except the T- and B-lymphocytes.

  10. A Study of Detonation Diffraction in the Ignition-and-Growth Model

    SciTech Connect

    Kapila, A K; Schwendeman, D W; Bdzil, J B; Henshaw, W D

    2006-04-14

    Heterogeneous high-energy explosives are morphologically, mechanically and chemically complex. As such, their ab-initio modeling, in which well-characterized phenomena at the scale of the microstructure lead to a rationally homogenized description at the scale of observation, is a subject of active research but not yet a reality. An alternative approach is to construct phenomenological models, in which forms of constitutive behavior are postulated with an eye on the perceived picture of the micro-scale phenomena, and which are strongly linked to experimental calibration. Most prominent among these is the ignition-and-growth model conceived by Lee and Tarver. The model treats the explosive as a homogeneous mixture of two distinct constituents, the unreacted explosive and the products of reaction. To each constituent is assigned an equation of state, and a single reaction-rate law is prescribed for the conversion of the explosive to products. It is assumed that the two constituents are always in pressure and temperature equilibrium. The purpose of this paper is to investigate in detail the behavior of the model in situations where a detonation turns a corner and undergoes diffraction. A set of parameters appropriate for the explosive LX-17 is selected. The model is first examined analytically for steady, planar, 1-D solutions and the reaction-zone structure of Chapman-Jouguet detonations is determined. A computational study of two classes of problems is then undertaken. The first class corresponds to planar, 1-D initiation by an impact, and the second to corner turning and diffraction in planar and axisymmetric geometries. The 1-D initiation, although interesting in its own right, is utilized here as a means for interpretation of the 2-D results. It is found that there are two generic ways in which 1-D detonations are initiated in the model, and that these scenarios play a part in the post-diffraction evolution as well. For the parameter set under study the model

  11. In Situ Grazing Incidence X-Ray Diffraction Study of Electrochemically Deposited Pb Monolayer on Ag(111),

    DTIC Science & Technology

    1987-05-12

    potential for the deposition of Pb2 on a Pb electrode and hence is termed underpotential deposition (UPD). 19 No additional lead is deposited until...K. 0 In Situ Grazing Incidence X-ray Diffraction Study Interim Technical Report of Electrochemically Deposited Pb rMbno layers on...nunoalayer adsorbed at a metal-liquid interface. Diffraction peaks were * ~. observed from a monoalayer of lead electrochemicially deposited onto a

  12. High-resolution seismic studies applied to injected geothermal fluids

    SciTech Connect

    Smith, A.T.; Kasameyer, P.

    1985-01-01

    The application of high-resolution microseismicity studies to the problem of monitoring injected fluids is one component of the Geothermal Injection Monitoring Project at LLNL. The evaluation of microseismicity includes the development of field techniques, and the acquisition and processing of events during the initial development of a geothermal field. To achieve a specific detection threshold and location precision, design criteria are presented for seismic networks. An analysis of a small swarm near Mammoth Lakes, California, demonstrates these relationships and the usefulness of high-resolution seismic studies. A small network is currently monitoring the Mammoth-Pacific geothermal power plant at Casa Diablo as it begins production.

  13. High-pressure X-ray diffraction studies of potassium chlorate

    SciTech Connect

    Pravica, Michael; Bai, Ligang; Bhattacharya, Neelanjan

    2012-03-15

    Two static high-pressure X-ray diffraction (XRD) studies of potassium chlorate have been performed at pressures of up to {approx}14.3 GPa in a diamond anvil cell at ambient temperature using the 16 ID-B undulator beamline at the Advanced Photon Source for the X-ray source. The first experiment was conducted to ascertain decomposition rates of potassium chlorate as a function of pressure. Below 2 GPa, the sample was observed to decompose rapidly in the presence of the X-ray beam and release oxygen. Above 2 GPa (near the phase I phase II transition), the decomposition rate dramatically slowed so that good quality XRD patterns could be acquired. This suggests a phase-dependent decomposition rate. In the second study, X-ray diffraction spectra were collected at pressures from 2 to 14.3 GPa by aligning virgin portions of the sample into the focused X-ray beam at each pressure. The results suggest the co-existence of mixed monoclinic (I) and rhombohedral (II) phases of potassium chlorate near 2 GPa. At pressures beyond 4 GPa, the XRD patterns show a very good fit to KClO{sub 3} in the rhombohedral phase with space group R3m, in agreement with earlier studies. No further phase transitions were observed with pressure. Decompression of the sample to ambient pressure indicated mixed phases I and II coupled with a small amount of synchrotron X-ray-induced decomposition product. The equation of state within this pressure regime has been determined.

  14. X-ray micro-diffraction studies on biological samples at the BioCAT Beamline 18-ID at the Advanced Photon Source.

    PubMed

    Barrea, R A; Antipova, O; Gore, D; Heurich, R; Vukonich, M; Kujala, N G; Irving, T C; Orgel, J P R O

    2014-09-01

    The small source sizes of third-generation synchrotron sources are ideal for the production of microbeams for diffraction studies of crystalline and non-crystalline materials. While several such facilities have been available around the world for some time now, few have been optimized for the handling of delicate soft-tissue specimens under cryogenic conditions. Here the development of a new X-ray micro-diffraction instrument at the Biophysics Collaborative Access Team beamline 18-ID at the Advanced Photon Source, and its use with newly developed cryo-diffraction techniques for soft-tissue studies, are described. The combination of the small beam sizes delivered by this instrument, the high delivered flux and successful cryo-freezing of rat-tail tendon has enabled us to record data to better than 4 Å resolution. The ability to quickly raster scan samples in the beam allows selection of ordered regions in fibrous samples for markedly improved data quality. Examples of results of experiments obtainable using this instrument are presented.

  15. X-ray micro-diffraction studies on biological samples at the BioCAT Beamline 18-ID at the Advanced Photon Source

    PubMed Central

    Barrea, R. A.; Antipova, O.; Gore, D.; Heurich, R.; Vukonich, M.; Kujala, N. G.; Irving, T. C.; Orgel, J. P. R. O.

    2014-01-01

    The small source sizes of third-generation synchrotron sources are ideal for the production of microbeams for diffraction studies of crystalline and non-crystalline materials. While several such facilities have been available around the world for some time now, few have been optimized for the handling of delicate soft-tissue specimens under cryogenic conditions. Here the development of a new X-ray micro-diffraction instrument at the Biophysics Collaborative Access Team beamline 18-ID at the Advanced Photon Source, and its use with newly developed cryo-diffraction techniques for soft-tissue studies, are described. The combination of the small beam sizes delivered by this instrument, the high delivered flux and successful cryo-freezing of rat-tail tendon has enabled us to record data to better than 4 Å resolution. The ability to quickly raster scan samples in the beam allows selection of ordered regions in fibrous samples for markedly improved data quality. Examples of results of experiments obtainable using this instrument are presented. PMID:25178013

  16. High-resolution, high-pressure NMR studies of proteins.

    PubMed Central

    Jonas, J; Ballard, L; Nash, D

    1998-01-01

    Advanced high-resolution NMR spectroscopy, including two-dimensional NMR techniques, combined with high pressure capability, represents a powerful new tool in the study of proteins. This contribution is organized in the following way. First, the specialized instrumentation needed for high-pressure NMR experiments is discussed, with specific emphasis on the design features and performance characteristics of a high-sensitivity, high-resolution, variable-temperature NMR probe operating at 500 MHz and at pressures of up to 500 MPa. An overview of several recent studies using 1D and 2D high-resolution, high-pressure NMR spectroscopy to investigate the pressure-induced reversible unfolding and pressure-assisted cold denaturation of lysozyme, ribonuclease A, and ubiquitin is presented. Specifically, the relationship between the residual secondary structure of pressure-assisted, cold-denatured states and the structure of early folding intermediates is discussed. PMID:9649405

  17. Bone mineral change during experimental calcination: an X-ray diffraction study.

    PubMed

    Galeano, Sergio; García-Lorenzo, Mari Luz

    2014-11-01

    The effects of calcination (400-1200°C) on pig bones have been studied using powder X-ray diffraction (XRD) and secondary modifications, such as color change and weight loss. The characterisation by powder XRD confirmed the presence of the crystalline phase of hydroxyapatite, and comparison of the results obtained at different temperatures suggested that at 650°C, all the organic components and carbonate substitutions were completely removed. Accordingly, these samples were white. In addition, the crystallinity degree and the crystallite size progressively increased with the calcination temperature until 650°C, remaining stable until 1200°C. Below 650°C, bone samples presented organic compounds, resulting in background noise in the diffractogram and gray or black color. In addition, impurities in the lattice correspond to low crystallite sizes.

  18. Kinetics of Methane Hydrate Decomposition Studied via in Situ Low Temperature X-ray Powder Diffraction

    SciTech Connect

    Everett, Susan M; Rawn, Claudia J; Keffer, David J.; Mull, Derek L; Payzant, E Andrew; Phelps, Tommy Joe

    2013-01-01

    Gas hydrates are known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice termed self-preservation or anomalous preservation. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Two regions of slowed decomposition for methane hydrate, 180 200 K and 230 260 K, were observed, and the kinetics were studied by in situ low temperature x-ray powder diffraction. The kinetic constants for ice formation from methane hydrate were determined by the Avrami model within each region and activation energies, Ea, were determined by the Arrhenius plot. Ea determined from the data for 180 200 K was 42 kJ/mol and for 230 260 K was 22 kJ/mol. The higher Ea in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.

  19. Convergent Beam Electron Diffraction Study of Bi-BASED High Temperature Superconducting Layered Compounds

    NASA Astrophysics Data System (ADS)

    Zhang, X. F.; Yan, Y. F.; Fung, K. K.

    Cleaved specimens of layered compounds Bi2Sr2(CaCuO2)nCuO6, n = 0, 1 and 2 phases have been studied by convergent beam electron diffraction. The identity and the symmetry of the phases have been determined from the higher order Laue zone (HOLZ) rings and the symmetry of their [001] patterns. In the case of Bi2Sr2CuO6, the [001] axial periodicity corresponds to the component of the wave vector of the monoclinic modulation along the c axis. Widely different axial periodicities have been obtained. This is interpreted as the manifestation of the variation of the monoclinic modulation. The presence of basal stacking fault lowers the symmetry of the [001] pattern.

  20. X-ray diffraction, FTIR, UV-VIS and SEM studies on chromium (III) complexes

    SciTech Connect

    Mishra, Ashutosh; Dwivedi, Jagrati Shukla, Kritika

    2015-06-24

    Five Chromium (III) complexes have been prepared using Schiff base ligands which derived from benzoin and five different amino acids (H{sub 2}N-R). Samples were characterized by XRD, FTIR, UV-VIS and SEM method. X-Ray diffraction pattern analyzed that all chromium (III) complexes have hexagonal structure and crystalline, in nature, using Bruker D8 Advance instrument. Using VERTAX 70, FTIR spectroscopy reveals that Samples have (C=N), (C-O), (M-N) and (M-O) bonds in the range of 4000-400cm{sup −1}. UV-VIS spectroscopy give information that samples absorb the visible light which is in the range of 380-780nm. For this, Lambda 960 spectrometer used. SEM is designed for studying of the solid objects, using JEOL JSM 5600 instrument.

  1. Microstructure evolution of tin under electromigration studied bysynchrotron X-Ray micro-diffraction

    SciTech Connect

    Wu, Albert T.; Lloyd, J.R.; Tamura, N.; Tu, K.-N.

    2005-05-05

    Under constant current electromigration, white tin(?-Sn)exhibited a resistance drop of up to 10 percent. It has a body centertetragonal (BCT) structure, and the resistivity along the aand b axes is35 percent smaller than that along the c axis.Microstructure evolutionunder electromigration could be responsible for the resistance drop.Synchrotron radiation white beam x-ray microdiffraction was used to studythis evolution. Both stress and grain orientation was studied.Grain-by-grain analysis was obtained from the diffracted Laue patternsabout the changes of grain orientation during electromigration testing inex-situ and in-situ samples. We observed that high resistance grainsreorient with respect to the neighboring low resistance grains, mostlikely by grain rotation of the latter. A different mechanism ofmicrostructure evolution under electromigration from the normal graingrowth is proposed and discussed.

  2. Accurate X-ray diffraction studies of KTiOPO4 single crystals doped with niobium

    NASA Astrophysics Data System (ADS)

    Novikova, N. E.; Sorokina, N. I.; Alekseeva, O. A.; Verin, I. A.; Kharitonova, E. P.; Orlova, E. I.; Voronkova, V. I.

    2017-01-01

    Single crystals of potassium titanyl phosphate doped with 4% of niobium (KTP:4%Nb) and 6% of niobium (KTP:6%Nb) are studied by accurate X-ray diffraction at room temperature. The niobium atoms are localized near the Ti1 and Ti2 atomic positions, and their positions are for the first time refined independent of the titanium atomic positions. Maps of difference electron density in the vicinity of K1 and K2 atomic positions are analyzed. It is found that in the structure of crystal KTP:4%Nb, additional positions of K atoms are located farther from the main positions and from each other than in KTP and KTP:6%Nb crystals. The nonuniform distribution of electron density found in the channels of the KTP:4%Nb structure is responsible for 20% increase in the signal of second harmonic generation.

  3. In situ synchrotron X-ray diffraction study of hydrides in Zircaloy-4 during thermomechanical cycling

    NASA Astrophysics Data System (ADS)

    Cinbiz, Mahmut N.; Koss, Donald A.; Motta, Arthur T.; Park, Jun-Sang; Almer, Jonathan D.

    2017-04-01

    The d-spacing evolution of both in-plane and out-of-plane hydrides has been studied using in situ synchrotron radiation X-ray diffraction during thermo-mechanical cycling of cold-worked stress-relieved Zircaloy-4. The structure of the hydride precipitates is such that the δ{111} d-spacing of the planes aligned with the hydride platelet face is greater than the d-spacing of the 111 planes aligned with the platelet edges. Upon heating from room temperature, the δ{111} planes aligned with hydride plate edges exhibit bi-linear thermally-induced expansion. In contrast, the d-spacing of the (111) plane aligned with the hydride plate face initially contracts upon heating. These experimental results can be understood in terms of a reversal of stress state associated with precipitating or dissolving hydride platelets within the α-zirconium matrix.

  4. Hydride precipitation kinetics in Zircaloy-4 studied using synchrotron X-ray diffraction

    SciTech Connect

    Courty, Olivier Fabrice; Motta, Arthur T.; Piotrowski, Christopher J.; Almer, Jonathan D.

    2015-01-01

    As a result of in-reactor corrosion during operation in nuclear reactors, hydrogen can enter the zirconium fuel cladding and precipitate as brittle hydride particles, which may reduce cladding ductility. Dissolved hydrogen responds to temperature gradients, resulting in transport and precipitation into cold spots so that the distribution of hydrides in the cladding is inhomogeneous. The hydrogen precipitation kinetics plays a strong role in the spatial distribution of the hydrides in the cladding. The precipitation rate is normally described as proportional to the supersaturation of hydrogen in solid solution. The proportionality constant, α2, for hydride precipitation in Zircaloy-4 is measured directly using in situ synchrotron X-Ray diffraction, at different temperatures and with three different initial hydrogen concentrations. The results validate the linear approximation of the phenomenological model and a near constant value of α2 = 4.5 × 10-4 s-1 was determined for the temperature range studied.

  5. Realizing in-plane surface diffraction by x-ray multiple-beam diffraction with large incidence angle

    SciTech Connect

    Huang, Xian-Rong Gog, Thomas; Assoufid, Lahsen; Peng, Ru-Wen; Siddons, D. P.

    2014-11-03

    Based on rigorous dynamical-theory calculations, we demonstrate the principle of an x-ray multiple-beam diffraction (MBD) scheme that overcomes the long-lasting difficulties of high-resolution in-plane diffraction from crystal surfaces. This scheme only utilizes symmetric reflection geometry with large incident angles but activates the out-of-plane and in-plane diffraction processes simultaneously and separately in the continuous MBD planes. The in-plane diffraction is realized by detoured MBD, where the intermediate diffracted waves propagate parallel to the surface, which corresponds to an absolute Bragg surface diffraction configuration that is extremely sensitive to surface structures. A series of MBD diffraction and imaging techniques may be developed from this principle to study surface/interface (misfit) strains, lateral nanostructures, and phase transitions of a wide range of (pseudo)cubic crystal structures, including ultrathin epitaxial films and multilayers, quantum dots, strain-engineered semiconductor or (multi)ferroic materials, etc.

  6. A high temperature diffraction-resistance study of chalcopyrite, CuFeS{sub 2}

    SciTech Connect

    Engin, T.E.; Powell, A.V.; Hull, S.

    2011-08-15

    The electrical, magnetic and structural properties of synthetic chalcopyrite, CuFeS{sub 2}, have been studied up to 873 K using DC resistance measurements performed in-situ during neutron powder diffraction experiments. Under ambient conditions the material adopts the accepted structural model for CuFeS{sub 2} in the space group I4-bar 2d, with the magnetic moment of the Fe{sup 3+} cations aligned along [001]. The electrical resistivity is around 0.3 {Omega} cm under ambient conditions, consistent with semiconductor character, and decreases slightly with increase in temperature until a more abrupt fall occurs in the region 750-800 K. This abrupt change in resistivity is accompanied by a structural transition to a cubic zinc blende structured phase (space group F4-bar 3m) in which Cu{sup +} and Fe{sup 3+} cations are disordered over the same tetrahedral crystallographic sites and by a simultaneous loss of long-range magnetic order. The implications of these results are discussed in the context of previous studies of the chalcopyrite system. - Graphical abstract: Structural, magnetic and electrical properties of CuFeS{sub 2} to 873 K have been investigated using DC resistance measurements, performed in-situ during the collection of powder neutron diffraction data. Highlights: > Structural, magnetic and electronic properties are probed simultaneously. > A fall in resistivity at high temperatures is associated with cation disorder. > The order-disorder transition is accompanied by the loss of magnetic order. > The structural and magnetic phase transition is preceded by a 2-phase region. > Sulphur loss at high temperatures causes the phase transitions to be irreversible.

  7. Fast in situ x-ray-diffraction studies of chemical reactions: A synchrotron view of the hydration of tricalcium aluminate

    NASA Astrophysics Data System (ADS)

    Jupe, A. C.; Turrillas, X.; Barnes, P.; Colston, S. L.; Hall, C.; Häusermann, D.; Hanfland, M.

    1996-06-01

    We report observations on the early hydration of tricalcium aluminate, the most reactive component of Portland cement, using rapid-energy dispersive diffraction on a high brilliance synchrotron source. In situ observations of the hydration process over short time scales, and through bulk samples, reveal an intermediate calcium aluminate hydrate appearing just prior to the formation of the final stable hydrate, demonstrating the nucleating role of this intermediate. The superior quality of the data is sufficient to yield concentration versus time plots for each phase over the whole hydration sequence. This improvement derives from being able to use smaller diffracting volumes and consequent removal of time smearing due to inhomogenetics, and thus now offers the possibility of extending the technique in terms of time resolution and diversity of system.

  8. Crystallization and preliminary X-ray diffraction study of recombinant ribokinase from Thermus Species 2.9

    NASA Astrophysics Data System (ADS)

    Abramchik, Yu. A.; Timofeev, V. I.; Muravieva, T. I.; Esipov, R. S.; Kuranova, I. P.

    2016-11-01

    Ribokinase from a thermophilic strain of Thermus species 2.9 belonging to the carbohydrate ribokinase family (EC 2.7.1.15) was isolated, purified, and crystallized. The crystallization conditions were found by the vapor-diffusion technique and were then optimized to apply the capillary counter-diffusion technique. The X-ray diffraction data set was collected from the crystals, which were grown by the counter-diffusion technique, at the SPring-8 synchrotron radiation facility to 2.87 Å resolution. The crystals belong to sp. gr. P1211 and have the following unit-cell parameters: a = 81.613 Å, b = 156.132 Å, c = 87.714 Å, α = γ = 90°, β = 103.819°. The X-ray diffraction data set is suitable for determining the three-dimensional structure of the protein by the molecular-replacement method.

  9. Study of Saturn electrostatic discharges with high time resolution

    NASA Astrophysics Data System (ADS)

    Zakharenko, V.; Mylostna, K.; Konovalenko, A.; Kolyadin, V.; Zarka, P.; Griessmeier, J.-M.; Litvinenko, G.; Sidorchuk, M.; Rucker, H.; Fischer, G.; Cecconi, B.; Coffre, A.; Denis, L.; Shevchenko, V.; Nikolaenko, V.

    2013-09-01

    Ground-based observations of SED (Saturn Electrostatic Discharges) with high time resolution are the next stage of extraterrestrial atmospheric processes study. Due to extremely high intensity of Saturn's storm J (2010) [1] we have obtained the records with high signal-to-noise (S/N) ratio with the time resolution of 15 ns. It permitted us to investigate the microsecond structure of lightning and clearly distinguish SED in the presence of local interference in virtue of a dispersive delay of extraterrestrial planetary signals.

  10. Resolution study of imaging in nanoparticle optical phantoms

    NASA Astrophysics Data System (ADS)

    Ortiz-Rascón, E.; Bruce, N. C.; Flores-Flores, J. O.; Sato-Berru, R.

    2011-08-01

    We present results of resolution and optical characterization studies of silicon dioxide nanoparticle solutions. These phantoms consist of spherical particles with a mean controlled diameter of 168 and 429 nm. The importance of this work lies in using these solutions to develop phantoms with optical properties that closely match those of human breast tissue at near-IR wavelengths, and also to compare different resolution criteria for imaging studies at these wavelengths. Characterization involves illuminating the solution with a laser beam transmitted through a recipient of known width containing the solution. Resulting intensity profiles from the light spot are measured as function of the detector position. Measured intensity profiles were fitted to the calculated profiles obtained from diffusion theory, using the method of images. Fitting results give us the absorption and transport scattering coefficients. These coefficients can be modified by changing the particle concentration of the solution. We found that these coefficients are the same order of magnitude as those of human tissue reported in published studies. The resolution study involves measuring the edge response function (ERF) for a mask embedded on the nanoparticle solutions and fitting it to the calculated ERF, obtaining the resolution for the Hebden, Sparrow and Bentzen criteria.

  11. A novel technique combining high-resolution synchrotron x-ray microtomography and x-ray diffraction for characterization of micro particulates

    NASA Astrophysics Data System (ADS)

    Merrifield, David R.; Ramachandran, Vasuki; Roberts, Kevin J.; Armour, Wesley; Axford, Danny; Basham, Mark; Connolley, Thomas; Evans, Gwyndaf; McAuley, Katherine E.; Owen, Robin L.; Sandy, James

    2011-11-01

    The processing of solids, such as crystals, is strongly influenced by the surface properties of the material. In recent years the pharmaceutical industry has shown great interest in identifying, or chemically speciating, the molecular components of crystal faces. Formerly, characterization of the molecular identity of crystal faces was restricted to the study of large single crystals. This would have been primarily for structure determination as part of the drug registration process. Diamond Light Source in Oxfordshire is a new synchrotron facility in the UK, having 18 operational beamlines with 4 more in the construction phase. Beamlines at this medium energy light source enable the study of micron-sized objects in great detail. It is well known that x-ray microtomography (XMT) can be used to investigate the external morphology of a crystal whereas x-ray diffraction (XRD) is used to study the molecular orientation, structure and packing within the crystal. The objective of this research is to assess the feasibility of, and thereby develop a new methodology for, characterizing the molecular identity of a particular face of a crystalline particle at a scale of scrutiny of 20-50 µm by combining these two powerful techniques. This work demonstrates the application of XMT and XRD to investigate respectively the shape and crystalline phase/orientation of relevant test crystals. This research has applications in the pharmaceutical industry in that when the exact molecular nature of a particular face is known, the important physico-pharmaceutical properties stemming from that can be better understood. Some initial data are presented and discussed.

  12. High-resolution x-ray absorption spectroscopy studies of metal compounds in neurodegenerative brain tissue

    NASA Astrophysics Data System (ADS)

    Collingwood, J. F.; Mikhaylova, A.; Davidson, M. R.; Batich, C.; Streit, W. J.; Eskin, T.; Terry, J.; Barrea, R.; Underhill, R. S.; Dobson, J.

    2005-01-01

    Fluorescence mapping and microfocus X-ray absorption spectroscopy are used to detect, locate and identify iron biominerals and other inorganic metal accumulations in neurodegenerative brain tissue at sub-cellular resolution (<5 microns). Recent progress in developing the technique is reviewed. Synchrotron X-rays are used to map tissue sections for metals of interest, and XANES and XAFS are used to characterise anomalous concentrations of the metals in-situ so that they can be correlated with tissue structures and disease pathology. Iron anomalies associated with biogenic magnetite, ferritin and haemoglobin are located and identified in an avian tissue model with a pixel resolution ~5 microns. Subsequent studies include brain tissue sections from transgenic Huntington's mice, and the first high-resolution mapping and identification of iron biominerals in human Alzheimer's and control autopsy brain tissue. Technical developments include use of microfocus diffraction to obtain structural information about biominerals in-situ, and depositing sample location grids by lithography for the location of anomalies by conventional microscopy. The combined techniques provide a breakthrough in the study of both intra- and extra-cellular iron compounds and related metals in tissue. The information to be gained from this approach has implications for future diagnosis and treatment of neurodegeneration, and for our understanding of the mechanisms involved.

  13. High-resolution x-ray absorption spectroscopy studies of metal compounds in neurodegenerative brain tissue

    SciTech Connect

    Collingwood, J.F.; Mikhaylova, A.; Davidson, M.R.; Batich, C.; Streit, W.J.; Eskin, T.; Terry, J.; Barrea, R.; Underhill, R.S.; Dobson, J.

    2008-06-16

    Fluorescence mapping and microfocus X-ray absorption spectroscopy are used to detect, locate and identify iron biominerals and other inorganic metal accumulations in neurodegenerative brain tissue at sub-cellular resolution (< 5 microns). Recent progress in developing the technique is reviewed. Synchrotron X-rays are used to map tissue sections for metals of interest, and XANES and XAFS are used to characterize anomalous concentrations of the metals in-situ so that they can be correlated with tissue structures and disease pathology. Iron anomalies associated with biogenic magnetite, ferritin and haemoglobin are located and identified in an avian tissue model with a pixel resolution {approx} 5 microns. Subsequent studies include brain tissue sections from transgenic Huntington's mice, and the first high-resolution mapping and identification of iron biominerals in human Alzheimer's and control autopsy brain tissue. Technical developments include use of microfocus diffraction to obtain structural information about biominerals in-situ, and depositing sample location grids by lithography for the location of anomalies by conventional microscopy. The combined techniques provide a breakthrough in the study of both intra- and extra-cellular iron compounds and related metals in tissue. The information to be gained from this approach has implications for future diagnosis and treatment of neurodegeneration, and for our understanding of the mechanisms involved.

  14. Revisit: High resolution charge density study of α-rhombohedral boron using third-generation SR data at SPring-8

    NASA Astrophysics Data System (ADS)

    Nishibori, Eiji; Hyodo, Hiroshi; Kimura, Kaoru; Takata, Masaki

    2015-09-01

    Experimental charge density of α-rhombohedral boron (α-B12) by a Maximum entropy method (MEM) has been re-investigated using the high resolution powder diffraction data measured at third-generation synchrotron radiation (SR) source, SPring-8. The present MEM charge density has many discrepancies from the previous MEM charge densities reported by Fujimori et al. and Hosoi et al. The data-resolution dependence of the MEM charge density was investigated using the present data. We found that diffraction data with d > 0.4 Å resolution range were needed to reveal qualitative bonding nature of α-B12 at 100 K. The peculiar bonding natures, such as a bend B-B bond and a propeller-shaped bond, which were found in the previous studies have disappeared by using d > 0.4 Å data. The bonding nature of MEM charge density using the full data with d > 0.327 Å d-spacing range is well agreed with those of theoretical calculations. The present study suggests that resolution test is important for an accurate charge density study of boron related materials.

  15. Nanostructures of Mg0.65Ti0.35Dx studied with x-ray diffraction, neutron diffraction, and magic-angle-spinning H2 NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Srinivasan, S.; Magusin, P. C. M. M.; Kalisvaart, W. P.; Notten, P. H. L.; Cuevas, F.; Latroche, M.; van Santen, R. A.

    2010-02-01

    Magnesium transition-metal alloys have a high hydrogen-storage capacity and show improved hydrogen-uptake and -release kinetics compared to magnesium alone. In the present study we have investigated the structure of bulk magnesium-titanium deuteride Mg0.65Ti0.35Dx prepared via mechanical alloying and gas-phase deuterium absorption by combined use of x-ray diffraction (XRD), neutron diffraction, and magic-angle-spinning H2 nuclear magnetic resonance (NMR). The initial ball-milled alloy has two XRD-distinct Mg and Ti fcc phases. Even after prolonged exposure to deuterium gas at 75 bar and 175°C the materials with and without palladium catalyst are only partly deuterated. Deuterium loading causes the formation of, on the one hand, bct (rutile) MgD2 nanodomains with interdispersed TiDy layers and, on the other hand, a separate fcc (fluorite) TiDz phase. The TiDy phase is XRD invisible, but shows clearly up at a H2 NMR shift of -43ppm between the shift of MgD2 (3 ppm) and the Knight shift of the TiDz phase (-143ppm) . Exchange NMR indicates complete deuterium exchange at 25°C between the MgD2 and TiDy phase within 1 s, as consistent with intimate contacts between these phases. Combined analysis of the XRD and NMR peak areas suggests that the deuterium concentrations y and z in the TiDy and TiDz domains are about 1.5 and 2.0, respectively. Comparing the intrinsic cell parameters of rutile MgH2 and fluorite TiH2 , we propose that stabilization of the mixed nanocomposite may arise from a coherent coupling between the crystal structures of the rutile MgD2 nanodomains and the thin layers of fcc TiDy .

  16. Optical and resonant X-ray diffraction studies of molecular arrangements in several liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, Suntao

    Using optical and x-ray techniques, we have studied several selected liquid crystal compounds formed by three types of molecules: rod-like; hockey-stick-shaped and bent-core-shaped molecules. This thesis describes four research projects. The first one is a study of the molecular arrangements in freestanding films of three chiral compounds showing no-layer-shrinkage behavior above their bulk SmA-SmC* transition temperatures. Upon cooling under a proper electric field, novel nonplanar-anticlinic-synclinic and nonplanar-synclinic transitions have been observed in two compounds. Increasing electric field can induce a rare transition from a synclinic to an anticlinic structure. Results from both x-ray diffraction and optical studies indicate that different molecular packing arrangements exist within the Sm A phase window. The second project is to investigate three achiral meta-substituted three-ring compounds. These compounds exhibit two different tilted smectic phases, Sm C1 and SmC2. A recent paper has reported that mirror symmetry is broken in one of these compounds. However, no mirror symmetry breaking has been observed in our studies of the same compound. Our studies of another two compounds confirmed previous results that the Sm C1 and SmC2 phases are Sm C and SmCA, respectively. Thirdly, we confirmed the SM C*FI2 -SmC* phase sequence reversal in one liquid crystal compound and specially prepared binary mixtures. This phase sequence reversal was predicted by a recent phenomenological model. Moreover, the temperature range for the SM C*FI2 phase increases significantly in the mixture suggesting that such a phase sequence may exist in other compounds. The last project is to study the B2 phase formed by bent-core molecules using polarization-analyzed resonant x-ray diffraction. The B2 phase has three possible arrangements which show a two-layer unit cell. We analyzed the polarization of the resonant peaks at different Bragg orders. By comparing a theoretical

  17. Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001)

    NASA Astrophysics Data System (ADS)

    Hsu, Min-Hsiang Mark; Merckling, Clement; El Kazzi, Salim; Pantouvaki, Marianna; Richard, Oliver; Bender, Hugo; Meersschaut, Johan; Van Campenhout, Joris; Absil, Philippe; Van Thourhout, Dries

    2016-12-01

    In this work, we present a systematic study of the effect of the stoichiometry of BaTiO3 (BTO) films grown on the Ge(001) substrate by molecular-beam-epitaxy using different characterization methods relying on beam diffraction, including reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and selected-area electron diffraction in transmission electron microscopy. Surprisingly, over a wide range of [Ba]/[Ti] ratios, as measured by the Rutherford backscattering spectrometry, all the BTO layers exhibit the same epitaxial relationship <100>BTO(001)//<110>Ge(001) with the substrate, describing a 45° lattice rotation of the BTO lattice with respect to the Ge lattice. However, varying the [Ba]/[Ti] ratio does change the diffraction behavior. From RHEED patterns, we can derive that excessive [Ba] and [Ti] generate twinning planes and a rougher surface in the non-stoichiometric BTO layers. XRD allows us to follow the evolution of the lattice constants as a function of the [Ba]/[Ti] ratio, providing an option for tuning the tetragonality of the BTO layer. In addition, we found that the intensity ratio of the 3 lowest-order Bragg peaks I(001)/I(002), I(101)/I(002), and I(111)/I(002) derived from ω - 2θ scans characteristically depend on the BTO stoichiometry. To explain the relation between observed diffraction patterns and the stoichiometry of the BTO films, we propose a model based on diffraction theory explaining how excess [Ba] or [Ti] in the layer influences the diffraction response.

  18. Sucrose lyophiles: a semi-quantitative study of residual water content by total X-ray diffraction analysis.

    PubMed

    Bates, S; Jonaitis, D; Nail, S

    2013-10-01

    Total X-ray Powder Diffraction Analysis (TXRPD) using transmission geometry was able to observe significant variance in measured powder patterns for sucrose lyophilizates with differing residual water contents. Integrated diffraction intensity corresponding to the observed variances was found to be linearly correlated to residual water content as measured by an independent technique. The observed variance was concentrated in two distinct regions of the lyophilizate powder pattern, corresponding to the characteristic sucrose matrix double halo and the high angle diffuse region normally associated with free-water. Full pattern fitting of the lyophilizate powder patterns suggested that the high angle variance was better described by the characteristic diffraction profile of a concentrated sucrose/water system rather than by the free-water diffraction profile. This suggests that the residual water in the sucrose lyophilizates is intimately mixed at the molecular level with sucrose molecules forming a liquid/solid solution. The bound nature of the residual water and its impact on the sucrose matrix gives an enhanced diffraction response between 3.0 and 3.5 beyond that expected for free-water. The enhanced diffraction response allows semi-quantitative analysis of residual water contents within the studied sucrose lyophilizates to levels below 1% by weight.

  19. STEM Electron Diffraction and High Resolution Images Used in the Determination of the Crystal Structure of Au144(SR)60 Cluster

    PubMed Central

    Bahena, Daniel; Bhattarai, Nabraj; Santiago, Ulises; Tlahuice, Alfredo; Ponce, Arturo; Bach, Stephan B. H.; Yoon, Bokwon; Whetten, Robert L.; Landman, Uzi; Jose-Yacaman, Miguel

    2013-01-01

    Determination of the total structure of molecular nanocrystals is an outstanding experimental challenge that has been met, in only a few cases, by single-crystal X-ray diffraction. Described here is an alternative approach that is of most general applicability and does not require the fabrication of a single crystal. The method is based on rapid, time-resolved nanobeam electron diffraction (NBD) combined with high-angle annular dark field scanning/transmission electron microscopy (HAADF-STEM) images in a probe corrected STEM microscope, operated at reduced voltages. The results are compared with theoretical simulations of images and diffraction patterns obtained from atomistic structural models derived through first-principles density functional theory (DFT) calculations. The method is demonstrated by application to determination of the structure of the Au144(SCH2CH2Ph)60 cluster. PMID:23687562

  20. High-resolution thermal imaging with a combination of nano-focus X-ray diffraction and ultra-fast chip calorimetry.

    PubMed

    Rosenthal, Martin; Doblas, David; Hernandez, Jaime J; Odarchenko, Yaroslav I; Burghammer, Manfred; Di Cola, Emanuela; Spitzer, Denis; Antipov, A E; Aldoshin, L S; Ivanov, Dimitri A

    2014-01-01

    A microelectromechanical-systems-based calorimeter designed for use on a synchrotron nano-focused X-ray beamline is described. This instrument allows quantitative DC and AC calorimetric measurements over a broad range of heating/cooling rates (≤100000 K s(-1)) and temperature modulation frequencies (≤1 kHz). The calorimeter was used for high-resolution thermal imaging of nanogram-sized samples subjected to X-ray-induced heating. For a 46 ng indium particle, the measured temperature rise reaches ∼0.2 K, and is directly correlated to the X-ray absorption. Thermal imaging can be useful for studies of heterogeneous materials exhibiting physical and/or chemical transformations. Moreover, the technique can be extended to three-dimensional thermal nanotomography.

  1. Theoretical study of the properties of X-ray diffraction moiré fringes. I

    SciTech Connect

    Yoshimura, Jun-ichi

    2015-05-14

    A detailed and comprehensive theoretical description of X-ray diffraction moiré fringes for a bicrystal specimen is given on the basis of a calculation by plane-wave dynamical diffraction theory, where the effect of the Pendellösung intensity oscillation on the moiré pattern is explained in detail. A detailed and comprehensive theoretical description of X-ray diffraction moiré fringes for a bicrystal specimen is given on the basis of a calculation by plane-wave dynamical diffraction theory. Firstly, prior to discussing the main subject of the paper, a previous article [Yoshimura (1997 ▸). Acta Cryst. A53, 810–812] on the two-dimensionality of diffraction moiré patterns is restated on a thorough calculation of the moiré interference phase. Then, the properties of moiré fringes derived from the above theory are explained for the case of a plane-wave diffraction image, where the significant effect of Pendellösung intensity oscillation on the moiré pattern when the crystal is strained is described in detail with theoretically simulated moiré images. Although such plane-wave moiré images are not widely observed in a nearly pure form, knowledge of their properties is essential for the understanding of diffraction moiré fringes in general.

  2. Picowatt Resolution Calorimetry for Micro and Nanoscale Energy Transport Studies

    NASA Astrophysics Data System (ADS)

    Sadat, Seid H.

    Precise quantification of energy transport is key to obtaining insights into a wide range of phenomena across various disciplines including physics, chemistry, biology and engineering. This thesis describes technical advancements into heat-flow calorimetry which enable measurement of energy transport at micro and nanoscales with picowatt resolution. I have developed two types of microfabricated calorimeter devices and demonstrated single digit picowatt resolution at room temperature. Both devices incorporate two distinct features; an active area isolated by a thermal conductance (GTh) of less than 1 microW/K and a high resolution thermometer with temperature resolution (DeltaTres) in the micro kelvin regime. These features enable measurements of heat currents (q) with picowatt resolution (q= Th xDeltaTres). In the first device the active area is suspended via silicon nitride beams with excellent thermal isolation (~600 nW/K) and a bimaterial cantilever (BMC) thermometer with temperature resolution of ~6 microK. Taken together this design enabled calorimetric measurements with 4 pW resolution. In the second device, the BMC thermometry technique is replaced by a high-resolution resistance thermometry scheme. A detailed noise analysis of resistance thermometers, confirmed by experimental data, enabled me to correctly predict the resolution of different measurement schemes and propose techniques to achieve an order of magnitude improvement in the resolution of resistive thermometers. By incorporating resistance thermometers with temperature resolution of ~30 microK, combined with a thermal isolation of ~150 nW/K, I demonstrated an all-electrical calorimeter device with a resolution of ~ 5 pW. Finally, I used these calorimeters to study Near-Field Radiative Heat Transfer (NF-RHT). Using these devices, we studied--for the first time--the effect of film thickness on the NF-RHT between two dielectric surfaces. We showed that even a very thin film (~50 nm) of silicon

  3. Study on quasiperiodic Ta/Al multilayer films by x-ray diffraction

    SciTech Connect

    Peng, R.W.; Hu, A.; Jiang, S.S. )

    1991-11-11

    Quasiperiodic (Fibonacci) Ta/Al multilayer films with Ta(110) and Al(111) textures were fabricated by magnetron sputtering. The structure of the multilayers was characterized in detail by x-ray diffraction. The diffraction peaks at low and high angles can be indexed by the projection method from the high-dimension periodic structure. The experimental results were in good agreement with the numerical calculation using the model for the compositionally modulated multilayers. The diffraction spectrum of the quasiperiodic Ta/Al multilayers is totally different from that of periodic structure, and the possible application of Fibonacci films as optical elements in a soft x-ray region is discussed.

  4. Simulation and study of Fresnel diffraction for arbitrary two-dimensional apertures

    SciTech Connect

    Dauger, D.E.

    1996-11-01

    A stable, efficient algorithm to calculate numerically a Fresnel diffraction image, given any two-dimensional aperture or obstacle, is introduced. The algorithm predicts both the intensity and relative phase of the image. An alternate faster algorithm is presented for a limited class of apertures. Also examined are images formed from a variety of aperture shapes. Using this computational technique, plots on the complex plane are shown to give insight into Fresnel diffraction. With additional modifications to accept parameters from an experimental apparatus, the algorithms model Fresnel diffraction for laboratory situations. In addition, the algorithms are suitable for numerical implementation on personal computers. {copyright} {ital 1996 American Institute of Physics.}

  5. X-Ray Diffraction Study of the Internal Structure of Supercooled Water

    NASA Technical Reports Server (NTRS)

    Dorsch, Robert G.; Boyd, Bemrose

    1951-01-01

    A Bragg X-ray spectrometer equipped with a volume-sensitive Geiger counter and Soller slits and employing filtered molybdenum Ka radiation was used to obtain a set of diffracted intensity curves as a Punction of angle for supercooled water. Diffracted intensity curves in the temperature region of 21 to -16 C were obtained. The minimum between the two main diffraction peaks deepened continuously with lowering temperature, indicating a gradual change in the internal structure of the water. No discontinuity in this trend was noted at the melting point. The internal structure of supercooled water was concluded to become progressively more ice-like as the temperature is lowered.

  6. Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging

    DOE PAGES

    Coughlan, H. D.; Darmanin, C.; Phillips, N. W.; ...

    2015-04-29

    For laboratory and synchrotron based X-ray sources, radiation damage has posed a significant barrier to obtaining high-resolution structural data from biological macromolecules. The problem is particularly acute for micron-sized crystals where the weaker signal often necessitates the use of higher intensity beams to obtain the relevant data. Here, we employ a combination of techniques, including Bragg coherent diffractive imaging to characterise the radiation induced damage in a micron-sized protein crystal over time. The approach we adopt here could help screen for potential protein crystal candidates for measurement at X-ray free election laser sources.

  7. Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging

    PubMed Central

    Coughlan, H. D.; Darmanin, C.; Phillips, N. W.; Hofmann, F.; Clark, J. N.; Harder, R. J.; Vine, D. J.; Abbey, B.

    2015-01-01

    For laboratory and synchrotron based X-ray sources, radiation damage has posed a significant barrier to obtaining high-resolution structural data from biological macromolecules. The problem is particularly acute for micron-sized crystals where the weaker signal often necessitates the use of higher intensity beams to obtain the relevant data. Here, we employ a combination of techniques, including Bragg coherent diffractive imaging to characterise the radiation induced damage in a micron-sized protein crystal over time. The approach we adopt here could help screen for potential protein crystal candidates for measurement at X-ray free election laser sources. PMID:26798804

  8. InSitu X-Ray Diffraction Studies on Lithium-Ion Battery Cathodes

    SciTech Connect

    Doughty, Daniel H.; Ingersoll, David; Rodriguez, Mark A.

    1999-07-13

    In this paper numerical simulations of Mach 10 air flow over a hollow cylinder flare are presented in comparison with recent experimental results. The numerical study is performed using a Direct Simulation Monte Carlo code and the experimental results were obtained in the ONERA R5Ch wind tunnel. The flow phenomena involved include shock wave boundary layer interaction in hypersonic laminar flow. An analysis of the requirements on the grid resolution, number of particle simulators and run time is performed. Measured and calculated surface properties including pressure and heat transfer are compared.

  9. X-ray diffraction from rectangular slits.

    PubMed

    Le Bolloc'h, D; Livet, F; Bley, F; Schulli, T; Veron, M; Metzger, T H

    2002-07-01

    It is shown that for micrometre-sized beams the X-ray diffraction from slits is a source of strong parasitic background, even for slits of high quality. In order to illustrate this effect, the coherent diffraction from rectangular slits has been studied in detail. A large number of interference fringes with strong visibility have been observed using a single set of slits made of polished cylinders. For very small apertures, asymmetrical slits generate asymmetrical patterns. This pattern is calculated from the theory of electromagnetic field propagation and compared with experiment in the far-field regime. The use of guard slits to remove Fraunhofer diffraction from the beam-defining slits is treated theoretically. Numerical simulations yield the optimum aperture of the guard slits with respect to the distance to the primary slits. Diffraction theory is shown to be essential to understand how to reduce the background-to-signal ratio in high-resolution experiments.

  10. Accuracy and Resolution in Micro-earthquake Tomographic Inversion Studies

    NASA Astrophysics Data System (ADS)

    Hutchings, L. J.; Ryan, J.

    2010-12-01

    Accuracy and resolution are complimentary properties necessary to interpret the results of earthquake location and tomography studies. Accuracy is the how close an answer is to the “real world”, and resolution is who small of node spacing or earthquake error ellipse one can achieve. We have modified SimulPS (Thurber, 1986) in several ways to provide a tool for evaluating accuracy and resolution of potential micro-earthquake networks. First, we provide synthetic travel times from synthetic three-dimensional geologic models and earthquake locations. We use this to calculate errors in earthquake location and velocity inversion results when we perturb these models and try to invert to obtain these models. We create as many stations as desired and can create a synthetic velocity model with any desired node spacing. We apply this study to SimulPS and TomoDD inversion studies. “Real” travel times are perturbed with noise and hypocenters are perturbed to replicate a starting location away from the “true” location, and inversion is performed by each program. We establish travel times with the pseudo-bending ray tracer and use the same ray tracer in the inversion codes. This, of course, limits our ability to test the accuracy of the ray tracer. We developed relationships for the accuracy and resolution expected as a function of the number of earthquakes and recording stations for typical tomographic inversion studies. Velocity grid spacing started at 1km, then was decreased to 500m, 100m, 50m and finally 10m to see if resolution with decent accuracy at that scale was possible. We considered accuracy to be good when we could invert a velocity model perturbed by 50% back to within 5% of the original model, and resolution to be the size of the grid spacing. We found that 100 m resolution could obtained by using 120 stations with 500 events, bu this is our current limit. The limiting factors are the size of computers needed for the large arrays in the inversion and a

  11. Legitimation processes in environmental dispute resolution: A case study

    SciTech Connect

    Lach, D.H.

    1992-01-01

    Expense, limited access, delay, and hesitancy to get involved in substantive decisions hamper the legal system's effectiveness in creating stable environmental dispute settlements. Parties involved in environmental disputes increasingly turn to alternative forums of dispute resolution. Alternative dispute resolution (ADR) includes mediation, arbitration, negotiation, and a growing number of hybrids such as regulated negotiation (reg-neg). While ADR offers disputants considerable flexibility in developing solutions, it does not provide the public any assurances that decisions about public resources made in ADR forums are fair or legitimate. This study examines how environmental dispute resolution participants construct legitimacy for the decisions they make in ADR forums. The author has developed a case study of the 1989 Oregon Timber Summit. Data sources included a complete Summit transcript, eleven in-depth interviews with participants, and 166 newspaper articles related to the Summit. To sort and analyze these textual data, a discourse analysis technique was used. The results suggest that (1) procedural and distributive justice issues influence participants' behavior even in the absence of dispute professionals, and (2) the structure of environmental dispute resolution provides disputants with ways to resist possible manipulation and exploitation by other participants.

  12. Neutron diffraction as a tool in the study of reinforced concrete. Compilation of some cases

    NASA Astrophysics Data System (ADS)

    Castellote, M.

    2014-11-01

    Cementitious materials are much more complex than it seems at a first sight. On one hand, due to the excess of water needed to make the mix workable, a network of pores is generated, that puts in contact the material with the environment and allows their attack by aggressive agents that can be physical of chemical agents, producing the deterioration of the concrete itself and corrosion of the rebars. Then, it is necessary to study the transport properties and the chemical and physical interaction of aggressive agents with the solid and liquid phases of the cement paste the corrosion of the rebars, and the reparation processes. This is an approach concerning the service life of structures, however, we cannot forget an important chapter which is gaining much relevance in the last time: that of the special uses of concrete, for which, tailored concretes have to be designed. In order to undertake these problems, we need new analysis tools, different that the traditionally ones applied to study concrete, that allows the understanding of the mechanisms regulating the processes. One of these analysis tools is neutron diffraction that gives us the possibility of study the bulk of materials using a quite big specimen. In this work, 4 different problems undertaken with the help of neutrons in experiments carried out by the group of the author at the ILL, at the D1B and D20 instruments are presented.

  13. Aptamers provide superior stainings of cellular receptors studied under super-resolution microscopy

    PubMed Central

    Höbartner, Claudia

    2017-01-01

    Continuous improvements in imaging techniques are challenging biologists to search for more accurate methods to label cellular elements. This is particularly relevant for diffraction-unlimited fluorescence imaging, where the perceived resolution is affected by the size of the affinity probes. This is evident when antibodies, which are 10–15 nm in size, are used. Previously it has been suggested that RNA aptamers (~3 nm) can be used to detect cellular proteins under super-resolution imaging. However, a direct comparison between several aptamers and antibodies is needed, to clearly show the advantages and/or disadvantages of the different probes. Here we have conducted such a comparative study, by testing several aptamers and antibodies using stimulated emission depletion microscopy (STED). We have targeted three membrane receptors, EGFR, ErbB2 and Epha2, which are relevant to human health, and recycle between plasma membrane and intracellular organelles. Our results suggest that the aptamers can reveal more epitopes than most antibodies, thus providing a denser labeling of the stained structures. Moreover, this improves the overall quality of the information that can be extracted from the images. We conclude that aptamers could become useful fluorescent labeling tools for light microscopy and super-resolution imaging, and that their development for novel targets is imperative. PMID:28235049

  14. A Neutron and X-Ray Diffraction Study of Ca-Mg-Cu Metallic Glasses (Postprint)

    DTIC Science & Technology

    2014-04-01

    copper has a total of 6.5 neighbours which are in close contact, but has a total coordination number of about 12-13, when atoms which are almost in...contact are included. 15. SUBJECT TERMS ternary alloy systems, glasses, metallic rapid solidification processing, diffraction 16. SECURITY...online 16 March 2011 Keywords: A. Ternary alloy systems B. Glasses, metallic C. Rapid solidification processing F. Diffraction a b s t r a c t The

  15. Crystallization and preliminary X-ray diffraction study of phosphopantetheine adenylyltransferase from M. tuberculosis crystallizing in space group P32

    NASA Astrophysics Data System (ADS)

    Timofeev, V. I.; Chupova, L. A.; Esipov, R. S.; Kuranova, I. P.

    2015-09-01

    Crystals of M. tuberculosis phosphopantetheine adenylyltransferase were grown in microgravity by the capillary counter-diffusion method through a gel layer. The X-ray diffraction data set suitable for the determination of the three-dimensional structure at atomic resolution was collected from one crystal at the Spring-8 synchrotron facility to 2.00-Å resolution. The crystals belong to sp. gr. P32 and have the following unit-cell parameters: a = b = 106.47 Å, c = 71.32 Å, α = γ = 90°, β = 120°. The structure was solved by the molecular-replacement method. There are six subunits of the enzyme comprising a hexamer per asymmetric unit. The hexamer is a biologically active form of phosphopantetheine adenylyltransferase from M. tuberculosis.

  16. Electron backscatter diffraction study of hexagonal boron nitride growth on Cu single-crystal substrates.

    PubMed

    Hite, Jennifer K; Robinson, Zachary R; Eddy, Charles R; Feigelson, Boris N

    2015-07-22

    Hexagonal boron nitride (h-BN) is an important material for the development of new 2D heterostructures. To enable this development, the relationship between crystal growth and the substrate orientation must be explored and understood. In this study, we simultaneously grew h-BN on different orientations of Cu substrates to establish the impact of substrate structure on the growth habit of thin h-BN layers. The substrates studied were a polycrystalline Cu foil, Cu(100), Cu(110), and Cu(111). Fourier transform grazing-incidence infrared reflection absorption spectroscopy (FT-IRRAS) was used to identify h-BN on copper substrates. X-ray photoelectron spectroscopy (XPS) was used to determine the effective thickness of the h-BN. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to measure the morphology of the films and postgrowth crystal structure of the Cu substrates, respectively. Combining the SEM and EBSD images allowed for the correlation between h-BN film coverage and the crystal structure of Cu. It was found that the growth rate was inversely proportional to the surface free energy of the Cu surface, with Cu(111) having the most h-BN surface coverage. The Cu foil predominately crystallized with a (100) surface orientation, and likewise had a film coverage very close to the Cu(100).

  17. Collagen organization in canine myxomatous mitral valve disease: an x-ray diffraction study.

    PubMed

    Hadian, Mojtaba; Corcoran, Brendan M; Han, Richard I; Grossmann, J Günter; Bradshaw, Jeremy P

    2007-10-01

    Collagen fibrils, a major component of mitral valve leaflets, play an important role in defining shape and providing mechanical strength and flexibility. Histopathological studies show that collagen fibrils undergo dramatic changes in the course of myxomatous mitral valve disease in both dogs and humans. However, little is known about the detailed organization of collagen in this disease. This study was designed to analyze and compare collagen fibril organization in healthy and lesional areas of myxomatous mitral valves of dogs, using synchrotron small-angle x-ray diffraction. The orientation, density, and alignment of collagen fibrils were mapped across six different valves. The findings reveal a preferred collagen alignment in the main body of the leaflets between two commissures. Qualitative and quantitative analysis of the data showed significant differences between affected and lesion-free areas in terms of collagen content, fibril alignment, and total tissue volume. Regression analysis of the amount of collagen compared to the total tissue content at each point revealed a significant relationship between these two parameters in lesion-free but not in affected areas. This is the first time this technique has been used to map collagen fibrils in cardiac tissue; the findings have important applications to human cardiology.

  18. In-situ early-age hydration study of sulfobelite cements by synchrotron powder diffraction

    SciTech Connect

    Álvarez-Pinazo, G.; Cuesta, A.; García-Maté, M.; Santacruz, I.; Losilla, E.R.; Fauth, F.; Aranda, M.A.G.; De la Torre, A.G.

    2014-02-15

    Eco-friendly belite calcium sulfoaluminate (BCSA) cement hydration behavior is not yet well understood. Here, we report an in-situ synchrotron X-ray powder diffraction study for the first hours of hydration of BCSA cements. Rietveld quantitative phase analysis has been used to establish the degree of reaction (α). The hydration of a mixture of ye'elimite and gypsum revealed that ettringite formation (α ∼ 70% at 50 h) is limited by ye'elimite dissolution. Two laboratory-prepared BCSA cements were also studied: non-active-BCSA and active-BCSA cements, with β- and α′{sub H}-belite as main phases, respectively. Ye'elimite, in the non-active-BCSA system, dissolves at higher pace (α ∼ 25% at 1 h) than in the active-BCSA one (α ∼ 10% at 1 h), with differences in the crystallization of ettringite (α ∼ 30% and α ∼ 5%, respectively). This behavior has strongly affected subsequent belite and ferrite reactivities, yielding stratlingite and other layered phases in non-active-BCSA. The dissolution and crystallization processes are reported and discussed in detail. -- Highlights: •Belite calcium sulfoaluminate cements early hydration mechanism has been determined. •Belite hydration strongly depends on availability of aluminum hydroxide. •Orthorhombic ye’elimite dissolved at a higher pace than cubic one. •Ye’elimite larger reaction degree yields stratlingite formation by belite reaction. •Rietveld method quantified gypsum, anhydrite and bassanite dissolution rates.

  19. Interactions of fatty acids with phosphatidylethanolamine membranes: X-ray diffraction and molecular dynamics studies

    PubMed Central

    Cordomí, Arnau; Prades, Jesús; Frau, Juan; Vögler, Oliver; Funari, Sérgio S.; Perez, Juan J.; Escribá, Pablo V.; Barceló, Francisca

    2010-01-01

    An experimental and theoretical study on 1,2-dielaidoyl-sn-glycero-3-phosphoethanolamine (DEPE) membranes containing fatty acids (FAs) was performed by means of X-ray diffraction analysis and molecular dynamics (MD) simulations. The study was aimed at understanding the interactions of several structurally related FAs with biomembranes, which is necessary for further rational lipid drug design in membrane-lipid therapy. The main effect of FAs was to promote the formation of a HII phase, despite a stabilization of the coexisting Lα + HII phases. Derivatives of OA exhibited a specific density profile in the direction perpendicular to the bilayer that reflects differences in the relative localization of the carboxylate group within the polar region of the membrane as well as in the degree of membrane penetration of the FA acyl chain. Hydroxyl and methyl substituents at carbon-2 in the FA acyl chain were identified as effective modulators of the position of carboxylate group in the lipid bilayer. Our data highlight the specific potential of each FA in modulating the membrane structure properties. PMID:19965616

  20. X-Ray diffraction study of KTiOPO{sub 4} single crystals doped with hafnium

    SciTech Connect

    Novikova, N. E. Verin, I. A.; Sorokina, N. I.; Alekseeva, O. A.; Orlova, E. I.; Voronkova, V. I.

    2011-05-15

    Single crystals of KTi{sub 1-x}Hf{sub x}OPO{sub 4} (x = 0.015(2), 0.035(1), and 0.128(1) are reinvestigated by precision X-ray diffraction at room temperature. It is found that the implantation of hafnium atoms in the crystal structure of KTiOPO{sub 4} does not lead to significant changes in the framework and affects only the positions of the potassium atoms in the channel. Our studies reveal the displacements of the potassium atoms from their main and additional positions in the structure of pure KTP in all three structures studied. The largest displacements from the K1 Prime and K1 Double-Prime additional positions are observed in the structure with x = 0.035. At this hafnium concentration, the occupancy of the main positions of potassium atoms decreases and the occupancy of the additional positions increases in relation to those in KTP. This redistribution of potassium atoms enhances the nonuniformity of distribution of the electron density in the vicinity of their positions, which is probably responsible for the increase in the nonlinear susceptibility of KTP crystals that contain 3.5% hafnium in relation to crystals of pure KTP.

  1. Elastic deformations in hexagonal phases studied by small-angle X-ray diffraction and simulations.

    PubMed

    Perutková, Šárka; Daniel, Matej; Rappolt, Michael; Pabst, Georg; Dolinar, Gregor; Kralj-Iglič, Veronika; Iglič, Aleš

    2011-02-28

    In this study we present experimental and theoretical results which concern the deviations from circularity of the pivotal plane in the inverse hexagonal phases (H(II)) of phospholipid self-assemblies. Due to packing constraints, the cross-section of the polar/apolar interface deviates from a circle, which we studied in minute detail by analysing small-angle X-ray diffraction data of dioleoyl-phosphatidylethanolamine (DOPE) and stearoyl-oleoyl-phosphatidylethanolamine (SOPE), respectively. On this structural basis, Monte Carlo (MC) simulated annealing variations of the free energy were carried out, both on the formation of the H(II)-phase and on the particular shape of the cross-section in the H(II)-phase. The equilibrium of the H(II)-phase pivotal plane contour and the corresponding values of the mean intrinsic curvature, H(m), and the hydrocarbon chain stiffness, τ, were determined from MC calculations. The results of these calculations were tested by solving the corresponding system of non-linear differential equations derived using variational calculus. Here our main aim is to predict the range of possible values of H(m) and τ. Comparing the measured structural data with predictions from MC calculations including lipid anisotropy, and accounting for the elastic deformations of the pivotal plane allowed us to determine a relationship between the bending deformation and stretching of hydrocarbon chains.

  2. Preliminayr Study on Diffraction Enhanced Radiographic Imaging for a Canine Model of Cartilage Damage

    SciTech Connect

    Muehleman,C.; Li, J.; Zhong, Z.

    2006-01-01

    Objective: To demonstrate the ability of a novel radiographic technique, Diffraction Enhanced Radiographic Imaging (DEI), to render high contrast images of canine knee joints for identification of cartilage lesions in situ. Methods: DEI was carried out at the X-15A beamline at Brookhaven National Laboratory on intact canine knee joints with varying levels of cartilage damage. Two independent observers graded the DE images for lesions and these grades were correlated to the gross morphological grade. Results: The correlation of gross visual grades with DEI grades for the 18 canine knee joints as determined by observer 1 (r2=0.8856, P=0.001) and observer 2 (r2=0.8818, P=0.001) was high. The overall weighted ? value for inter-observer agreement was 0.93, thus considered high agreement. Conclusion: The present study is the first study for the efficacy of DEI for cartilage lesions in an animal joint, from very early signs through erosion down to subchondral bone, representing the spectrum of cartilage changes occurring in human osteoarthritis (OA). Here we show that DEI allows the visualization of cartilage lesions in intact canine knee joints with good accuracy. Hence, DEI may be applicable for following joint degeneration in animal models of OA.

  3. Time-resolved x-ray diffraction and calorimetric studies at low scan rates

    PubMed Central

    Tenchov, Boris G.; Yao, Haruhiko; Hatta, Ichiro

    1989-01-01

    The phase transitions in fully hydrated dipalmitoylphosphatidylcholine (DPPC) and DPPC/water/ethanol phases have been studied by lowangle time-resolved x-ray diffraction under conditions similar to those employed in calorimetry (scan rates 0.05-0.5°C/min and uniform temperature throughout the samples). This approach provides more adequate characterization of the equilibrium transition pathways and allows for close correlations between structural and thermodynamic data. No coexistence of the rippled gel (Pβ') and liquid-crystalline (Lα) phases was found in the main transition of DPPC; rather, a loss of correlation in the lamellar structure, observed as broadening of the lamellar reflections, takes place in a narrow temperature range of ∼100 mK at the transition midpoint. Formation of a long-living metastable phase, denoted by Pβ'(mst), differing from the initial Pβ' was observed in cooling direction by both x-ray diffraction and calorimetry. No direct conversion of Pβ'(mst) into Pβ' occurs for over 24 h but only by way of the phase sequence Pβ'(mst) → Lβ' → Pβ'. According to differential scanning calorimetry (DSC), the enthalpy of the Pβ'(mst)-Lα transition is by ∼5% lower than that of the Pβ'-Lα transition. The effects of ethanol (Rowe, E. S. 1983. Biochemistry. 22:3299-3305; Simon, S. A., and T. J. McIntosh. 1984. Biochim. Biophys. Acta 773:169-172) on the mechanism and reversibility of the DPPC main transition were clearly visualized. At ethanol concentrations inducing formation of interdigitated gel phase, the main transition proceeds through a coexistence of the initial and final phases over a finite temperature range. During the subtransition in DPPC recorded at scan rate 0.3°C/min, a smooth monotonic increase of the lamellar spacing from its subgel (Lc) to its gel (Lβ') phase value takes place. The width of the lamellar reflections remains unchanged during this transformation. This provides grounds to propose a

  4. A high-resolution study of isotopic compositions of precipitation

    NASA Astrophysics Data System (ADS)

    Lee, Jeonghoon; Kim, Songyi; Han, Yeongcheol; Oh, Yoon Seok; Kim, Young-Hee; Kim, Hyerin; Ham, Ji-Young; Choi, Hye-Bin; Na, Un-Sung; Koh, Dong-Chan

    2015-04-01

    Isotopic compositions of precipitation have been used to understand moisture transport in the atmosphere and interactions between precipitation and groundwater. Isotopic compositions of speleothems and ice cores, so called, "paleoarchives", can be utilized to interpret climate of the past and global circulation models (GCMs), which are able to explain the paleoarchives, can be validated by the precipitation isotopes. The developments of stable isotope analyzers make high-resolution isotopic studies feasible and a high-resolution study of precipitation isotopes is needed. For this study, precipitation samples were collected for every 5 to 15 minutes, depending on precipitation rates, using an auto-sampler for precipitation isotopes near coastal area. The isotopic compositions of precipitation range from -5.7‰ (-40.1‰)) to -10.8‰ (-74.3‰)) for oxygen (hydrogen). The slope of δ18O-δD diagram for the whole period is 6.8, but that of each storm is 5.1, 4.2, 7.9 and 7.7, respectively. It indicates that evaporation occurred during the first two storms, while the latter two storms did not experience any evaporation. The isotopic fractionations of precipitation has significant implications for the water cycle and high-resolution data of precipitation isotopes will be needed for the future studies related to the precipitation isotopes.

  5. X-Ray Diffraction and Imaging Study of Imperfections of Crystallized Lysozyme with Coherent X-Rays

    NASA Technical Reports Server (NTRS)

    Hu, Zheng-Wei; Chu, Y. S.; Lai, B.; Cai, Z.; Thomas, B. R.; Chernov, A. A.

    2003-01-01

    Phase-sensitive x-ray diffraction imaging and high angular-resolution diffraction combined with phase contrast radiographic imaging are employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme crystal in symmetric Laue case. The fill width at half-maximum (FWHM) of a 4 4 0 rocking curve measured from the original crystal is approximately 16.7 arcseconds, and defects, which include point defects, line defects, and microscopic domains, have been clearly observed in the diffraction images of the crystal. The observed line defects carry distinct dislocation features running approximately along the <110> growth front, and they have been found to originate mostly at a central growth area and occasionally at outer growth regions. Individual point defects trapped at a crystal nucleus are resolved in the images of high sensitivity to defects. Slow dehydration has led to the broadening of the 4 4 0 rocking curve by a factor of approximately 2.4. A significant change of the defect structure and configuration with drying has been revealed, which suggests the dehydration induced migration and evolution of dislocations and lattice rearrangements to reduce overall strain energy. The sufficient details of the observed defects shed light upon perfection, nucleation and growth, and properties of protein crystals.

  6. Phase development in the hardening process of two calcium phosphate bone cements: an energy dispersive X-ray diffraction study

    SciTech Connect

    Generosi, A.; Smirnov, V.V.; Rau, J.V.; Albertini, V. Rossi; Ferro, D.; Barinov, S.M.

    2008-03-04

    This work was aimed at the application of an energy dispersive X-ray diffraction technique to study the kinetics of phase development during the setting and hardening reactions in two calcium phosphate bone cements. The cements under study are based on either tricalcium phosphate or tetracalcium phosphate initial solid phase, and a magnesium carbonate-phosphoric acid liquid phase as the hardening liquid. The application of the energy dispersive X-ray diffraction method allowed to collect the diffraction patterns from the cement pastes in situ starting from 1 min of the setting and hardening process. The only crystallized phase in both cements was apatite-like phase, the primary crystallization process proceeds during a few seconds of the setting reaction. Both the compressive strength and the pH value changes during the hardening period can be attributed to the transformations occurring in the intergranular X-ray amorphous phase.

  7. The use of time-resolved X-ray diffraction and sample techniques for studying the muscle structure during relaxation

    NASA Astrophysics Data System (ADS)

    Vazina, A. A.; Gadzhiev, A. M.; Gerasimov, V. S.; Gorbunova, N. P.; Sergienko, P. M.; Korneev, V. N.; Aulchenko, V. M.; Baru, S. E.

    1995-02-01

    The use of the modern time-resolved X-ray diffraction and sample technique has played an important role in studying muscle structures during contraction at various physiological conditions. We represent time-resolved X-ray data on equatorial diffraction and tension response of the frog sartorius muscle during relaxation. The measurements of the time-course of the intensity change of reflections (1,0), (1,1) and the background under them give a possibility to study the effect of potentiation of contraction by repetitive stimulation in fresh and tired muscles. Model calculations of meridional diffraction patterns for various configurations of cross-bridges in the relaxation phase were carried out.

  8. Pain Duration and Resolution Following Surgery: An Inception Cohort Study

    PubMed Central

    Carroll, Ian R.; Hah, Jennifer M.; Barelka, Peter L.; Wang, Charlie KM.; Wang, Bing M.; Gillespie, Matthew J.; McCue, Rebecca; Younger, Jarred W.; Trafton, Jodie; Humphreys, Keith; Goodman, Stuart B.; Dirbas, Fredrick M.; Mackey, Sean C.

    2015-01-01

    Objective Preoperative determinants of pain duration following surgery are poorly understood. We identified preoperative predictors of prolonged pain after surgery in a mixed surgical cohort. Methods We conducted a prospective longitudinal study of patients undergoing mastectomy, lumpectomy, thoracotomy, total knee replacement, or total hip replacement. We measured preoperative psychological distress and substance use, and then measured pain and opioid use after surgery until patients reported the cessation of both opioid consumption and pain. The primary endpoint was time to opioid cessation, and those results have been previously reported. Here we report preoperative determinants of time to pain resolution following surgery in Cox proportional hazards regression. Results Between January 2007 and April 2009 we enrolled 107 of 134 consecutively approached patients undergoing the aforementioned surgical procedures. In the final multivariate model, preoperative self-perceived risk of addiction predicted more prolonged pain. Unexpectedly, anxiety sensitivity predicted more rapid pain resolution after surgery. Each one-point increase (on a four point scale) of self-perceived risk of addiction was associated with a 38% (95% CI 3 - 61) reduction in the rate of pain resolution (p= 0.04). Furthermore, higher anxiety sensitivity was associated with an 89% (95% CI 23–190) increased rate of pain resolution (p=0.004). Conclusions Greater preoperative self-perceived risk of addiction, and lower anxiety sensitivity predicted a slower rate of pain resolution following surgery. Each of these factors was a better predictor of pain duration than preoperative depressive symptoms, PTSD symptoms, past substance use, fear of pain, gender, age, preoperative pain, or preoperative opioid use. PMID:26179223

  9. Si Nanoribbons on Ag(110) Studied by Grazing-Incidence X-Ray Diffraction, Scanning Tunneling Microscopy, and Density-Functional Theory: Evidence of a Pentamer Chain Structure.

    PubMed

    Prévot, Geoffroy; Hogan, Conor; Leoni, Thomas; Bernard, Romain; Moyen, Eric; Masson, Laurence

    2016-12-30

    We report a combined grazing incidence x-ray diffraction (GIXD), scanning tunneling microscopy (STM), and density-functional theory (DFT) study which clearly elucidates the atomic structure of the Si nanoribbons grown on the missing-row reconstructed Ag(110) surface. Our study allows us to discriminate between the theoretical models published in the literature, including the most stable atomic configurations and those based on a missing-row reconstructed Ag(110) surface. GIXD measurements unambiguously validate the pentamer model grown on the reconstructed surface, obtained from DFT. This pentamer atomistic model accurately matches the high-resolution STM images of the Si nanoribbons adsorbed on Ag(110). Our study closes the long-debated atomic structure of the Si nanoribbons grown on Ag(110) and definitively excludes a honeycomb structure similar to that of freestanding silicene.

  10. Si Nanoribbons on Ag(110) Studied by Grazing-Incidence X-Ray Diffraction, Scanning Tunneling Microscopy, and Density-Functional Theory: Evidence of a Pentamer Chain Structure

    NASA Astrophysics Data System (ADS)

    Prévot, Geoffroy; Hogan, Conor; Leoni, Thomas; Bernard, Romain; Moyen, Eric; Masson, Laurence

    2016-12-01

    We report a combined grazing incidence x-ray diffraction (GIXD), scanning tunneling microscopy (STM), and density-functional theory (DFT) study which clearly elucidates the atomic structure of the Si nanoribbons grown on the missing-row reconstructed Ag(110) surface. Our study allows us to discriminate between the theoretical models published in the literature, including the most stable atomic configurations and those based on a missing-row reconstructed Ag(110) surface. GIXD measurements unambiguously validate the pentamer model grown on the reconstructed surface, obtained from DFT. This pentamer atomistic model accurately matches the high-resolution STM images of the Si nanoribbons adsorbed on Ag(110). Our study closes the long-debated atomic structure of the Si nanoribbons grown on Ag(110) and definitively excludes a honeycomb structure similar to that of freestanding silicene.

  11. High-temperature X-ray diffraction study of uranium-neptunium mixed oxides.

    PubMed

    Chollet, Mélanie; Belin, Renaud C; Richaud, Jean-Christophe; Reynaud, Muriel; Adenot, Frédéric

    2013-03-04

    Incorporating minor actinides (MAs = Am, Np, Cm) in UO2 fertile blankets is a viable option to recycle them. Despite this applied interest, phase equilibria between uranium and MAs still need to be thoroughly investigated, especially at elevated temperatures. In particular, few reports on the U-Np-O system are available. In the present work, we provide for the first time in situ high-temperature X-ray diffraction results obtained during the oxidation of (U1-yNpy)O2 uranium-neptunium mixed oxides up to 1373 K and discuss subsequent phase transformations. We show that (i) neptunium stabilizes the UO2-type fluorite structure at high temperature and that (ii) the U3O8-type orthorhombic structure is observed in a wide range of compositions. We clearly demonstrate the incorporation of neptunium in this phase, which was a controversial question in previous studies up to now. We believe it is the particular stability of the tetravalent state of neptunium that is responsible for the observed phase relationships.

  12. X-ray diffraction, Raman, and photoacoustic studies of ZnTe nanocrystals

    NASA Astrophysics Data System (ADS)

    Ersching, K.; Campos, C. E. M.; de Lima, J. C.; Grandi, T. A.; Souza, S. M.; da Silva, D. L.; Pizani, P. S.

    2009-06-01

    Nanocrystalline ZnTe was prepared by mechanical alloying. X-ray diffraction (XRD), energy dispersive spectroscopy, Raman spectroscopy, and photoacoustic absorption spectroscopy techniques were used to study the structural, chemical, optical, and thermal properties of the as-milled powder. An annealing of the mechanical alloyed sample at 590 °C for 6 h was done to investigate the optical properties in a defect-free sample (close to bulk form). The main crystalline phase formed was the zinc-blende ZnTe, but residual trigonal tellurium and hexagonal ZnO phases were also observed for both as-milled and annealed samples. The structural parameters, phase fractions, average crystallite sizes, and microstrains of all crystalline phases were obtained from Rietveld analyses of the X-ray patterns. Raman results corroborate the XRD results, showing the longitudinal optical phonons of ZnTe (even at third order) and those modes of trigonal Te. Nonradiative surface recombination and thermal bending heat transfer mechanisms were proposed from photoacoustic analysis. An increase in effective thermal diffusivity coefficient was observed after annealing and the carrier diffusion coefficient, the surface recombination velocity, and the recombination time parameters remained the same.

  13. Spin and orbital ordering in TlMnO3: Neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Khalyavin, Dmitry D.; Manuel, Pascal; Yi, Wei; Belik, Alexei A.

    2016-10-01

    Crystal and magnetic structures of the high-pressure stabilized perovskite phase of TlMnO3 have been studied by neutron powder diffraction. The crystal structure involves two types of primary structural distortions: a+b-b- octahedral tilting and antiferrodistortive type of orbital ordering, whose common action reduces the symmetry down to triclinic P 1 ¯ . The orbital pattern and the way it is combined with the octahedral tilting are different from the family of LnMnO3 (Ln = lanthanide or Y) manganites who share with TlMnO3 the same tilting scheme. The experimentally determined magnetic structure with the k =(1 /2 ,0 ,1 /2 ) propagation vector and PS1 ¯ symmetry implies anisotropic exchange interactions with a ferromagnetic coupling within the (1 ,0 ,1 ¯) planes and an antiferromagnetic one between them (A type). The spins in the primary magnetic mode were found to be confined close to the (1 ,0 ,1 ¯) plane, which underlines the predominant role of the single ion anisotropy with the local easy axes of Mn3 + following the Jahn-Teller distortions of the octahedra. In spite of the same octahedral tilting scheme in the perovskite structures of both LnMnO3 and TlMnO3 manganites, a coupling of the secondary ferromagnetic component to the primary A-type spin configuration through antisymmetric exchange interaction is allowed in the former and forbidden in the latter cases.

  14. Synthesis and X-ray diffraction study of new uranyl malonate and oxalate complexes with carbamide

    NASA Astrophysics Data System (ADS)

    Medvedkov, Ya. A.; Serezhkina, L. B.; Grigor'ev, M. S.; Serezhkin, V. N.

    2016-05-01

    Two new malonate-containing uranyl complexes with carbamide of the formulas [UO2(C3H2O4)( Urea)2] ( I) and [UO2(C3H2O4)( Urea)3] ( II), where Urea is carbamide, and one uranyl oxalate complex of the formula [UO2(C2O4)( Urea)3] ( III) were synthesized, and their crystals were studied by X-ray diffraction. The main structural units in crystals I are the electroneutral chains [UO2(C3H2O4)( Urea)2]∞ belonging to the crystal-chemical group AT 11 M 2 1 ( A = UO 2 2+ , T 11 = C3H2O 4 2- , M 1 = Urea) of uranyl complexes. Crystals II and III are composed of the molecular complexes [UO2( L)( Urea)3], where L = C3H2O 4 2- or C2O 4 2- , belonging to the crystal-chemical group AB 01 M 3 1 ( A = UO 2 2+ , B 01 = C3H2O 4 2- or C2O 4 2- , M 1 = Urea). The characteristic features of the packing of the uranium-containing complexes are discussed in terms of molecular Voronoi-Dirichlet polyhedra. The effect of the Urea: U ratio on the structure of uranium-containing structural units is considered.

  15. On an electron diffraction study of the structures of anthraquinone and anthracene

    NASA Astrophysics Data System (ADS)

    Ketker, S. N.; Kelley, M.; Fink, M.; Ivey, R. Charles

    1981-11-01

    The molecular structures of gaseous anthraquinone and anthracene have been studied by electron diffraction at nozzle tip temperatures of about 160°C and 135°C, respectively. Each molecule has D 2h symmetry to within experimental error. Anthraquinone resembles two benzene rings linked by ketone bridges with the bond distances ( ra) and bond angle given by r(CH) = 1.087(4) Å, r(CO) = 1.220(2) Å, r(C 9C 11)= 1.499(2) A, r(C 1C 11) = r(C 1 C 2) = r(C 2C 3) = r(C 11C 12)= 1.400(2) Å, ∠C 12C 10C 13 = 117.4(4)°, ∠C1C11C12= 120.1(2)°. For anthracene the bond lengths (r a) and the bond angles are r(CH) = 1.085 A (assumed), r(C 9C 11) = 1.392(6) Å, r(C 11C 1) = 1.437(4) Å, r(C 1C 2) = 1.397(4) Å, r(C 2C 3) = 1.422(16) Å, r(C 11C 12.)= 1.437(4) Å, ∠C 12.C 10C 13= 112(1)°, ∠C 1, C 11C 12 = 118.8(6)°.

  16. X-ray diffraction study of amorphous lithium disilicate glass processed under high pressure

    NASA Astrophysics Data System (ADS)

    Soria Pereira, Altair; Buchner, Silvio; de Lima, Joao; Balzaretti, Naira

    2013-06-01

    Lithium disilicate glass (Li2O.2SiO2) is a very interesting vitreous material, because, besides several important technological applications (e.g. biomaterial to produce prostheses and implants), shows a large difference between the Tg and Tc values. This is important for the investigation of the crystallization mechanism on vitreous phases, as it allows the independent study of the nucleation and growth stages. In this work, we have investigated the effect of high-pressure processing in the induction of structural changes in the amorphous phase. This can give place to polyamorphism and/or to the generation of possible seeds for a crystalline phase nucleation. Using toroidal type high-pressure chambers, glass samples were processed at 2.5 GPa, 4 GPa, 6 GPa and 7.7 GPa at room temperature. Synchrotron X-ray diffraction was used to obtain the radial distribution functions (RDF), in order to follow the structural changes at different ranges. Compared to a pristine sample, the main change observed for the samples processed up to 6 GPa was associated to the distortion of the SiO4 tetrahedra, as already observed in the literature. However, for the sample processed at 7.7 GPa, we have identified a drastic change in the RDF which points for the production of a different amorphous phase with a local structure closer to that observed for the Li2SiO3 crystalline phase.

  17. Neutron Powder Diffraction Study on the Magnetic Structure of NdPd5Al2

    NASA Astrophysics Data System (ADS)

    Metoki, Naoto; Yamauchi, Hiroki; Kitazawa, Hideaki; Suzuki, Hiroyuki S.; Hagihala, Masato; Frontzek, Matthias D.; Matsuda, Masaaki; Fernandez-Baca, Jaime A.

    2017-03-01

    The magnetic structure of NdPd5Al2 has been studied by neutron powder diffraction. We observed the magnetic reflections with the modulation vector q = (1/2,0,0) below the ordering temperature TN. We found a collinear magnetic structure with a Nd moment of 2.7(3) μB at 0.5 K parallel to the c-axis, where the ferromagnetically ordered a-planes stack with a four-Nd-layer period having a ++- sequence along the a-direction with the distance between adjacent Nd layers equal to a/2 (magnetic space group Panma). This "stripe"-like modulation is very similar to that in CePd5Al2 with q = (0.235,0.235,0) with the Ce moment parallel to the c-axis. These structures with in-plane modulation are a consequence of the two-dimensional nature of the Fermi surface topology in this family, originating from the unique crystal structure with a very long tetragonal unit cell and a large distance of >7 Å between the rare-earth layers separated by two Pd and one Al layers.

  18. Neutron diffraction studies of the interaction between amphotericin B and lipid-sterol model membranes

    NASA Astrophysics Data System (ADS)

    Foglia, Fabrizia; Lawrence, M. Jayne; Demeė, Bruno; Fragneto, Giovanna; Barlow, David

    2012-10-01

    Over the last 50 years or so, amphotericin has been widely employed in treating life-threatening systemic fungal infections. Its usefulness in the clinic, however, has always been circumscribed by its dose-limiting side-effects, and it is also now compromised by an increasing incidence of pathogen resistance. Combating these problems through development of new anti-fungal agents requires detailed knowledge of the drug's molecular mechanism, but unfortunately this is far from clear. Neutron diffraction studies of the drug's incorporation within lipid-sterol membranes have here been performed to shed light on this problem. The drug is shown to disturb the structures of both fungal and mammalian membranes, and co-localises with the membrane sterols in a manner consistent with trans-membrane pore formation. The differences seen in the membrane lipid ordering and in the distributions of the drug-ergosterol and drug-cholesterol complexes within the membranes are consistent with the drug's selectivity for fungal vs. human cells.

  19. In Situ Neutron Diffraction Studies of Large Monotonic Deformations of Superelastic Nitinol

    NASA Astrophysics Data System (ADS)

    Stebner, Aaron P.; Paranjape, Harshad M.; Clausen, Bjørn; Brinson, L. Catherine; Pelton, Alan R.

    2015-06-01

    Superelastic Nitinol micromechanics are studied well into plastic deformation regimes using neutron diffraction. Insights are made into the nature of initial transformation, bulk transformation, plastic deformation, and unloading. Schmid factor predictions based on habit plane variants are found to best describe the very first grains that transform, prior to the transformation plateaus. However, the bulk transformation behavior that gives rise to transformation plateaus violates single crystal Schmid factor analyses, indicating that in bulk polycrystals, it is the effect of grain neighborhoods, not the orientations of individual grains, that drives transformation behaviors. Beyond the plateaus, a sudden shift in micromechanical deformation mechanisms is observed at ~8.50 %/4.75 % tension/compression engineering strain. This mechanism results in reverse-phase transformation in both cases, indicating a strong relaxation in internal stresses of the samples. It is inferred that this mechanism is most likely initial bulk plastic flow, and postulated that it is the reason for a transition from fatigue life enhancement to detriment when pre-straining superelastic Nitinol. The data presented in this work provide critical datasets for development and verification of both phenomenological internal variable-driven and micromechanical theories of transformation-plasticity coupling in shape memory alloys.

  20. Optical modulation study of repaired damage morphologies of fused silica by scalar diffraction theory

    NASA Astrophysics Data System (ADS)

    Li, Bo; Zhou, Qingyan; Jiang, Yong; Xiang, Xia; Liao, Wei; Jiang, Xiaolong; Wang, Haijun; Luan, Xiaoyu; Zheng, Wanguo; Yuan, Xiaodong

    2017-01-01

    The cone and Gaussian repaired damage craters are two typical morphologies induced by CO2 laser evaporation and nonevaporation technologies. The mathematical models are built for these two types of repaired craters, and the light modulation at 355 nm induced by the millimeter-scale repaired damage morphology is studied by scalar diffraction theory. The results show that the modulation of the Gaussian repaired morphology has one peak and then decreases with the increasing distance from 0 to 30 cm. While the modulation for cone repaired morphology remains stable after decreasing quickly with the increasing distance. When the horizontal radius increases, the modulation looks like a saw-tooth. However, the modulation has irregular variations for two kinds of morphologies with the increasing vertical depth. The simulated results agree well with experimental results. The horizontal and vertical dimensions, and downstream distance have different influences on the modulation. The risk of damage to downstream optical components can be suppressed to improve the stability of the optical system if the shape and size of repaired craters are well controlled and the positions of downstream optical components are selected appropriately.

  1. Neutron diffraction study of δ-alloy Pu242-Ga aging

    NASA Astrophysics Data System (ADS)

    Somenkov, V. A.; Blanter, M. S.; Glazkov, V. P.; Laushkin, A. V.; Orlov, V. K.

    2014-09-01

    In this paper, we report on a continuing neutron diffraction study of the mean-square atom displacements occurring during the long-term self-irradiation of a Pu-Ga alloy. The measurements were performed at room temperature using the sample based on the isotope Pu242 with low neutron absorption cross-section to which the short-lived isotope Pu238 (1.4 wt.%) was added to accelerate self-irradiation. We obtain the maximum self-irradiation equivalent time of 35.5 years, 12 years longer than in our previous papers. In the entire range of self-irradiation time a single fcc phase is preserved. It was found that after the two stages of change in the mean-square displacements we observed earlier (rapid growth up to ∼5-6 equivalent years and a slow decline in the range of ∼6-25 years), comes a stage of stabilization (after ∼25 years). The stabilization can be explained by the emergence of a balance between the formation of point defects and their absorption by helium bubbles and dislocation loops which accumulated over time.

  2. In situ study of the goethite-hematite phase transformation by real time synchrotron powder diffraction

    SciTech Connect

    Gualtieri, A.F.; Venturelli, P.

    1999-05-01

    The temperature induced goethite-hematite phase transformation that occurs at about 250 C was studied using in situ synchrotron X-ray powder diffraction with a capillary Debye-Scherrer geometry and a translating image plate system (TIPS). This is the first time the goethite-hematite transformation has been investigated in real time. The sample was a pure, synthetic, stoichiometric goethite with 2 {micro}m long needle-shaped crystals. The microstructural characterization showed that the sample was well crystallized. The Rietveld refinement of 30 powder patterns extracted from the image in the range 25--800 C demonstrates that an intermediate phase with non-stoichiometric composition (protohematite) forms after the decomposition of goethite. The cell parameter b of goethite dramatically decreased during the phase transformation while a and c instead continued to increase. Protohematite is iron-deficient and retains residual hydrolysis for charge balance. With temperature protohematite progressively transforms into hematite. Empty layers (pores) are consequently formed about the hematite clusters. The distribution of iron vacancies was modeled in the powder patterns with stacking faults that were simulated using anisotropic broadening coefficients of the pseudo-Voigt profile function. Its disappearance with temperature was effectively followed with a decrease of the density of stacking faults.

  3. Neutron Diffraction Study of 1,2,3-Trichlorobenzene-d3

    NASA Astrophysics Data System (ADS)

    Groke, Dirk; Heger, Gernot; Schweiss, Bernd Peter; Weiss, Alarich

    1994-05-01

    In order to explain the observed 35Cl-NQR anomaly of the title compound, a neutron diffraction study on single crystals was carried out at 295 K and 158 K. No significant structural changes concerning phase transitions or molecular disorder between the two experiments were observed. The space group is P21/c = C2h5 with 8 molecules per unit cell. The asymmetric unit contains 2 molecules. The cell parameters were determined to a = 1264(4) pm, b = 825(2) pm, c = 1503(3) pm, ß = 14.3(3)° at 295 K and a = 1243(2)pm, b = 815(1) pm, c = 1494(2) pm, ß = 114.3(1)° at 158 K. The molecules show rigid-body behaviour. No significant changes of the molecular geometry were observed. A strong variation of the temperature factors as function of the temperature was detected. An anharmonicity of the librational potential of the molecules was found by evaluation of the thermal parameters as function of temperature. For verifying the existence of dynamic processes which lead to a bleaching out of the 35Cl-NQR lines difference, Fourier syntheses were calculated. A reorientation or an order-disorder process as suggested by 35Cl-NQR spectroscopy above 230 K could not be confirmed within the error of the experiments. The degree of deuteration of the samples was determined by refinement of the occupation factors of the deuterium sites.

  4. Deformation in metallic glasses studied by synchrotron x-ray diffraction

    SciTech Connect

    Dmowski, Wojciech; Egami, Takeshi; Tong, Yang

    2016-01-11

    In this study, high mechanical strength is one of the superior properties of metallic glasses which render them promising as a structural material. However, understanding the process of mechanical deformation in strongly disordered matter, such as metallic glass, is exceedingly difficult because even an effort to describe the structure qualitatively is hampered by the absence of crystalline periodicity. In spite of such challenges, we demonstrate that high-energy synchrotron X-ray diffraction measurement under stress, using a two-dimensional detector coupled with the anisotropic pair-density function (PDF) analysis, has greatly facilitated the effort of unraveling complex atomic rearrangements involved in the elastic, anelastic, and plastic deformation of metallic glasses. Even though PDF only provides information on the correlation between two atoms and not on many-body correlations, which are often necessary in elucidating various properties, by using stress as means of exciting the system we can garner rich information on the nature of the atomic structure and local atomic rearrangements during deformation in glasses.

  5. An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading

    SciTech Connect

    Oswald, Benjamin B.; Pagan, Darren C.; Miller, Matthew P.; Schuren, Jay C.

    2013-03-15

    An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 Degree-Sign C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic processing and operating conditions of engineering components. The loaded specimen is reoriented with respect to the incident beam of x-rays using two rotational axes to increase the number of crystal orientations interrogated. The system was used at the Cornell High Energy Synchrotron Source to conduct experiments on single crystal silicon and polycrystalline Low Solvus High Refractory nickel-based superalloy. The data from these experiments provide new insights into how stresses evolve at the crystal scale during thermomechanical loading and complement the development of high-fidelity material models.

  6. An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading

    PubMed Central

    Oswald, Benjamin B.; Schuren, Jay C.; Pagan, Darren C.; Miller, Matthew P.

    2013-01-01

    An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 °C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic processing and operating conditions of engineering components. The loaded specimen is reoriented with respect to the incident beam of x-rays using two rotational axes to increase the number of crystal orientations interrogated. The system was used at the Cornell High Energy Synchrotron Source to conduct experiments on single crystal silicon and polycrystalline Low Solvus High Refractory nickel-based superalloy. The data from these experiments provide new insights into how stresses evolve at the crystal scale during thermomechanical loading and complement the development of high-fidelity material models. PMID:23556825

  7. Identifications studies of Lauha Bhasma by X-ray diffraction and X-ray fluorescence.

    PubMed

    Bhargava, S C; Reddy, K R C; Sastry, G V S

    2012-01-01

    Procedures for preparation of Lauha Bhasma are described in ancient texts of Ayurveda. These procedures also begin with different source material for iron such as Teekshna Lauha and Kanta Lauha etc. In the present study, we have selected different source materials viz. magnetite iron ore for Kanta Lauha and pure (Armco grade) iron turnings for Teekshna Lauha. The standard procedures of preparation of Lauha Bhasma are carried out in identical conditions for these two raw materials. The final product from the Puta are characterized by using X-ray diffraction and X-ray fluorescence spectroscopy to understanding the crystallographic form or forms of iron oxides and their composition at the end of each Puta. The iron content at the end of repeated Putas (18 for Kanta Lauha and 20 for Teekshna Lauha) have shown a decrease in case of Teekshna Lauha since the starting material is pure iron while it showed only marginal decreases in the case of Kanta Lauha because the Fe(3)O(4) of magnetite is undergoing oxidation to Fe(2)O(3). The trace elements remain within the Bhasma in the form of various oxides of Si, Al, Ca, etc.

  8. Interaction of substance P with phospholipid bilayers: A neutron diffraction study.

    PubMed Central

    Bradshaw, J P; Davies, S M; Hauss, T

    1998-01-01

    Neutron diffraction has been used to study the membrane-bound structure of substance P (SP), a member of the tachykinin family of neuropeptides. The depth of penetration of its C-terminus in zwitterionic and anionic phospholipid bilayers was probed by specific deuteration of leucine 10, the penultimate amino acid residue. The results show that the interaction of SP with bilayers, composed of either dioleoylphosphatidylcholine (DOPC), or a 50:50 mixture of DOPC and the anionic phospholipid dioleoylphosphatidylglycerol (DOPG), takes place at two locations. One requires insertion of the peptide into the hydrophobic region of the bilayer, the other is much more peripheral. The penetration of the peptide into the hydrophobic region of the bilayer is reflected in a marked difference in the water distribution profiles. SP is seen to insert into DOPC bilayers, but a larger proportion of the peptide is found at the surface when compared to the anionic bilayers. The positions of the two label populations show only minor differences between the two types of bilayer. PMID:9675189

  9. Deformation in metallic glasses studied by synchrotron x-ray diffraction

    DOE PAGES

    Dmowski, Wojciech; Egami, Takeshi; Tong, Yang

    2016-01-11

    In this study, high mechanical strength is one of the superior properties of metallic glasses which render them promising as a structural material. However, understanding the process of mechanical deformation in strongly disordered matter, such as metallic glass, is exceedingly difficult because even an effort to describe the structure qualitatively is hampered by the absence of crystalline periodicity. In spite of such challenges, we demonstrate that high-energy synchrotron X-ray diffraction measurement under stress, using a two-dimensional detector coupled with the anisotropic pair-density function (PDF) analysis, has greatly facilitated the effort of unraveling complex atomic rearrangements involved in the elastic, anelastic,more » and plastic deformation of metallic glasses. Even though PDF only provides information on the correlation between two atoms and not on many-body correlations, which are often necessary in elucidating various properties, by using stress as means of exciting the system we can garner rich information on the nature of the atomic structure and local atomic rearrangements during deformation in glasses.« less

  10. Neutron-diffraction study up to 1600 °C of 3:2 mullite

    NASA Astrophysics Data System (ADS)

    Brunauer, G.; Frey, F.; Boysen, H.; Schneider, H.; Fischer, P.; Hansen, Th.; Többens, D.; Ehrenberg, H.

    Neutron-diffraction studies were carried out on pure and Cr-doped 3:2 (`sinter') mullite. To learn about structure-property relationships of this refractory material, thermal expansion coefficients and structural parameters were determined by in situ high-temperature investigations. Neutron experiments were performed at the powder diffractometers D2B/ILL, E9/HMI, and HRPT/PSI. All data gave a rather uniform picture of the thermal expansion coefficients: a linear behaviour below 1000 °C and significantly increased (mean) expansion between 1000 and 1600 °C. There is a marked anisotropy of the highest values along the b-axis of the orthorhombic mullite structure. Concerning the structural parameters and the derived bond lengths, there is an expansion of the Al1O6 octahedra, whereas the cross-linking Al2SiO4 tetrahedra stay more or less rigid, but may slightly rotate. Thus a major expansion along the b direction may be qualitatively understood. A structural discussion, however, is affected by the presence of disorder in mullite, in particular in Cr-doped mullite, as it is also reflected by the presence of a modulated diffuse background in the powder patterns.

  11. Boron phosphide under pressure: In situ study by Raman scattering and X-ray diffraction

    SciTech Connect

    Solozhenko, Vladimir L.; Kurakevych, Oleksandr O.; Le Godec, Yann; Kurnosov, Aleksandr V.; Oganov, Artem R.

    2014-07-21

    Cubic boron phosphide, BP, has been studied in situ by X-ray diffraction and Raman scattering up to 55 GPa at 300 K in a diamond anvil cell. The bulk modulus of B{sub 0} = 174(2) GPa has been established, which is in excellent agreement with our ab initio calculations. The data on Raman shift as a function of pressure, combined with equation-of-state (EOS) data, allowed us to estimate the Grüneisen parameters of the TO and LO modes of zinc-blende structure, γ{sub G}{sup TO }= 1.26 and γ{sub G}{sup LO }= 1.13, just like in the case of other A{sup III}B{sup V} diamond-like phases, for which γ{sub G}{sup TO }> γ{sub G}{sup LO }≅ 1. We also established that the pressure dependence of the effective electro-optical constant α is responsible for a strong change in relative intensities of the TO and LO modes from I{sub TO}/I{sub LO} ∼ 0.25 at 0.1 MPa to I{sub TO}/I{sub LO} ∼ 2.5 at 45 GPa, for which we also find excellent agreement between experiment and theory.

  12. Thermal stability of nanocrystalline Cu studied by positron annihilation lifetime spectroscopy and X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Zhou, Kai; Li, Hui; Pang, JinBiao; Wang, Zhu

    2012-06-01

    Thermal stability of nanocrystalline Cu prepared by compacting nanoparticles (mean grain size about 50 nm) under high pressure has been studied by means of positron annihilation lifetime spectroscopy and X-ray diffraction. A gradual increase of mean grain size in the sample is observed with an increase in ageing time at 180°C, indicating an increase of volume fraction of the ordered regions. Furthermore, during the ageing, the increase in average size of the vacancy clusters in grain boundaries is confirmed by the positron lifetime results. The recrystallization is observed at the temperature of about 180°C, and becomes significant above 650°C. Three annealing stages, which are at the intervals 180-400°C, 400-650°C and 650-900°C have been characterized by positron average lifetime. The average volume of the defects almost remains constant in the interval 400-650°C but becomes considerably smaller in the interval 650-900°C.

  13. Diffraction studies of order-disorder at high pressures and temperatures

    SciTech Connect

    Parise, John B; Antao, Sytle M; Martin, Charles D; Crichton, Wilson

    2008-06-18

    Recent developments at synchrotron X-ray beamlines now allow collection of data suitable for structure determination and Rietveld structure refinement at high pressures and temperatures on challenging materials. These include materials, such as dolomite (CaMg(CO{sub 3}){sub 2}) that tends to calcine at high temperatures, and Fe-containing materials, such as the spinel MgFe{sub 2}O{sub 4}, which tend to undergo changes in oxidation state. Careful consideration of encapsulation along with the use of radial collimation produced powder diffraction patterns virtually free of parasitic scattering from the cell in the case of large volume high-pressure experiments. These features have been used to study a number of phase transitions, especially those where superior signal-to-noise discrimination is required to distinguish weak ordering reflections. The structures adopted by dolomite, and CaSO4, anhydrite, were determined from 298 to 1466 K at high pressures. Using laser-heated diamond-anvil cells to achieve simultaneous high pressure and temperature conditions, we have observed CaSO{sub 4} undergo phase transitions to the monazite type and at highest pressure and temperature to crystallize in the barite-type structure. On cooling, the barite structure distorts, from an orthorhombic to a monoclinic lattice, to produce the AgMnO{sub 4}-type structure.

  14. Purification, crystallization and preliminary X-ray diffraction studies of UDP-N-acetylglucosamine pyrophosphorylase from Candida albicans

    SciTech Connect

    Maruyama, Daisuke; Nishitani, Yuichi; Nonaka, Tsuyoshi; Kita, Akiko; Fukami, Takaaki A.; Mio, Toshiyuki; Yamada-Okabe, Hisafumi; Yamada-Okabe, Toshiko; Miki, Kunio

    2006-12-01

    UDP-N-acetylglucosamine pyrophosphorylase was purified and crystallized and X-ray diffraction data were collected to 2.3 Å resolution. UDP-N-acetylglucosamine pyrophosphorylase (UAP) is an essential enzyme in the synthesis of UDP-N-acetylglucosamine. UAP from Candida albicans was purified and crystallized by the sitting-drop vapour-diffusion method. The crystals of the substrate and product complexes both diffract X-rays to beyond 2.3 Å resolution using synchrotron radiation. The crystals of the substrate complex belong to the triclinic space group P1, with unit-cell parameters a = 47.77, b = 62.89, c = 90.60 Å, α = 90.01, β = 97.72, γ = 92.88°, whereas those of the product complex belong to the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 61.95, b = 90.87, c = 94.88 Å.

  15. High resolution studies of atoms and small molecules

    SciTech Connect

    Bushaw, B.A.; Tonkyn, R.G.; Miller, R.J.

    1992-10-01

    High resolution, continuous wave lasers have been utilized successfully in studies of small molecules. Examples of two-photon excitation schemes and of multiple resonance excitation sequences will be discussed within the framework of the spectroscopy and dynamics of selected Rydberg states of nitric oxide. Initial results on the circular dichroism of angular distributions in photoelectron spectra of individual hyperfine states of cesium will also be discussed, but no data given.

  16. Structure resolution by electron diffraction tomography of the complex layered iron-rich Fe-2234-type Sr5Fe6O15.4

    NASA Astrophysics Data System (ADS)

    Lepoittevin, Christophe

    2016-10-01

    The crystal structure of the strontium ferrite Sr5Fe6O15.4, was solved by direct methods on electron diffraction tomography data acquired on a transmission electron microscope. The refined cell parameters are a=27.4047(3) Å, b=5.48590(7) Å and c=42.7442(4) Å in Fm2m symmetry. Its structure is built up from the intergrowth sequence between a quadruple perovskite-type layer with a complex rock-salt (RS)-type block. In the latter iron atoms are found in two different environments : tetragonal pyramid and tetrahedron. The structural model was refined by Rietveld method based on the powder X-ray diffraction pattern.

  17. A combined approach for characterisation of fresh and brined vine leaves by X-ray powder diffraction, NMR spectroscopy and direct infusion high resolution mass spectrometry.

    PubMed

    Rizzuti, Antonino; Caliandro, Rocco; Gallo, Vito; Mastrorilli, Piero; Chita, Giuseppe; Latronico, Mario

    2013-12-01

    X-ray powder diffraction was combined, for the first time, with Nuclear Magnetic Resonance spectroscopy and direct infusion mass spectrometry to characterise fresh and brined grape leaves. Covariance analysis of data generated by the three techniques was performed with the aim to correlate information deriving from the solid part with those obtained for soluble metabolites. The results obtained indicate that crystalline components can be correlated to the metabolites contained in the grape leaves, paving the way to the use of X-ray diffraction analysis for food fingerprinting purposes. Moreover it was ascertained that, differently from most of the metabolites present in the fresh vine leaves, linolenic acid (an omega-3-fatty acid) and quercetin-3-O-glucuronide (a polyphenol metabolite) do not undergo sensible degradation during the brining process, which is used as preservative method for the grape leaves.

  18. Theoretical study of the properties of X-ray diffraction moiré fringes. I.

    PubMed

    Yoshimura, Jun-ichi

    2015-07-01

    A detailed and comprehensive theoretical description of X-ray diffraction moiré fringes for a bicrystal specimen is given on the basis of a calculation by plane-wave dynamical diffraction theory. Firstly, prior to discussing the main subject of the paper, a previous article [Yoshimura (1997). Acta Cryst. A53, 810-812] on the two-dimensionality of diffraction moiré patterns is restated on a thorough calculation of the moiré interference phase. Then, the properties of moiré fringes derived from the above theory are explained for the case of a plane-wave diffraction image, where the significant effect of Pendellösung intensity oscillation on the moiré pattern when the crystal is strained is described in detail with theoretically simulated moiré images. Although such plane-wave moiré images are not widely observed in a nearly pure form, knowledge of their properties is essential for the understanding of diffraction moiré fringes in general.

  19. In-Situ Neutron Diffraction Studies of Complex Hydrogen Storage Materials

    SciTech Connect

    Yelon, William B.

    2013-05-13

    The thrust of this project was to investigate the structures of important materials with potential application to hydrogen storage, in an effort to meet the DOE goals for 2010 and 2015, namely 9% (wt) and 15% (wt) respectively. Unfortunately, no material has been found, despite the efforts of many laboratories, including our own, that achieves these goals in a reversible complex hydride such as ammonia borane (NH{sub 4}BH{sub 4}), and other ammonia based compounds, or with light hydrides such as LiBH{sub 4}, due either to their irreversibility or to the high decomposition temperatures and residual simple hydrides such as LiH from the decomposition of the last named compound. Nevertheless, several important technical goals have been accomplished that could be valuable to other DOE programs and would be available for collaborative research. These include the development of a high quality glove box with controlled (low) oxygen and water content, which we continue to employ for the synthesis of potential new materials (unfunded research) and the development of a high quality neutron diffraction furnace with controlled gas environment for studies of hydrogen uptake and loss as well as for studies with other gasses. This furnace was initially constructed with an alumina (Al{sub 2}O{sub 3}) center tube to contain the sample and the flowing gas. The heaters are located in the vacuum space outside the tube and it was found that, for the low temperatures required for the study of hydrogen storage materials, the heat transfer was too poor to allow good control. At temperatures in excess of about 400C (and up to more than 1200C) the heat transfer and control are excellent. For the lower temperatures, however, the center tube was replaced by stainless steel and temperature control to 1C became possible. The paired heaters, above and below the neutron beam window allowed control of the temperature gradient to a similar precision. The high temperature capability of the furnace

  20. Best Technology Practices of Conflict Resolution Specialists: A Case Study of Online Dispute Resolution at United States Universities

    ERIC Educational Resources Information Center

    Law, Kimberli Marie

    2013-01-01

    The purpose of this study was to remedy the paucity of knowledge about higher education's conflict resolution practice of online dispute resolution by providing an in-depth description of mediator and instructor online practices. Telephone interviews were used as the primary data collection method. Eleven interview questions were relied upon to…

  1. A Weather climate change Impact Study at Extreme Resolution (WISER)

    NASA Astrophysics Data System (ADS)

    Gadian, A.; Burton, R.; Bruyere, C. L.; Done, J.; Tye, M. R.; Holland, G. J.; Thielen, J.; Blyth, A. M.

    2014-12-01

    Understanding and simulation of weather scale processes is required to understand extremes in the rapidly changing climate. The resolution required to include meso-scale features, is still out of the reach of climate model resolution, and this project attempts to include the important meso-scale features. WISER (Weather climate change Impact Study at Extreme Resolution) is a regional climate study to use a numerical weather model (WRF), in a channel formulation (+/- 68 degrees latitude) at a resolution of 20 km at the equator reducing to 9 km at the Northern and Southern boundaries. The inner domain nested regional model at a resolution of 3-4 km over Western Europe aims at resolving the larger convective scale precipitation events statistically. (see figure for geometrical domain set up). The outer domain is driven by ERA interim climate reanalysis global fields for recent decades 1989-2001; the nested inner domain d02 is driven by the outer domain. The inner model climatological statistics are compared with observations and with those from the outer domain, with particular reference for the statistical convective precipitation extremes. The extremes of the pdfs are shown to be better represented by the increase in resolution and suggest that this could be a tool useful in examining the likely extremes in future climates. The data also provides an assessment of the uncertainty in the precipitation extremes and an alternative approach to ownscaling. The overall aim is to examine statistical changes in(a) general precipitation over western Europe and the UK,(b) in quantity and frequency of severe and hazardous convective rainfall events. The future work-plan is(i) to complete simulations for the decade 1989-2000 driven by ERA-Interim reanalysis data(ii) to complete simulations for the same decade with boundary CESM/CAM climate model data to compute offset and bias corrections(iii) to complete climate scenarios for decadal periods, 2020-2030 initially and later 2050

  2. Synchrotron x-ray powder diffraction studies in pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Frings, P.; Vanacken, J.; Detlefs, C.; Duc, F.; Lorenzo, J. E.; Nardone, M.; Billette, J.; Zitouni, A.; Bras, W.; Rikken, G. L. J. A.

    2006-06-01

    X-ray powder diffraction experiments under pulsed magnetic fields were carried out at the DUBBLE beamline (BM26B) at the ESRF. A mobile generator delivered 110kJ to the magnet coil, which was sufficient to generate peak fields of 30T. A liquid He flow cryostat allowed us to vary the sample temperature accurately between 8 and 300K. Powder diffraction patterns of several samples were recorded using 21keV monochromatic x-rays and an on-line image plate detector. Here we present the first results on the suppression of the Jahn-Teller structural distortion in TbVO4 by magnetic field. These data clearly demonstrate the feasibility of x-ray powder diffraction experiments under pulsed magnetic fields with relatively inexpensive instrumentation.

  3. Influence of neutron irradiation on the microstructure of nuclear graphite: An X-ray diffraction study

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Bouwman, W. G.; Schut, H.; van Staveren, T. O.; Heijna, M. C. R.; Pappas, C.

    2017-04-01

    Neutron irradiation effects on the microstructure of nuclear graphite have been investigated by X-ray diffraction on virgin and low doses (∼ 1.3 and ∼ 2.2 dpa), high temperature (750° C) irradiated samples. The diffraction patterns were interpreted using a model, which takes into account the turbostratic disorder. Besides the lattice constants, the model introduces two distinct coherent lengths in the c-axis and the basal plane, that characterise the volumes from which X-rays are scattered coherently. The methodology used in this work allows to quantify the effect of irradiation damage on the microstructure of nuclear graphite seen by X-ray diffraction. The results show that the changes of the deduced structural parameters are in agreement with previous observations from electron microscopy, but not directly related to macroscopic changes.

  4. Advanced sample environments for in situ neutron diffraction studies of nuclear materials

    NASA Astrophysics Data System (ADS)

    Reiche, Helmut Matthias

    Generation IV nuclear reactor concepts, such as the supercritical-water-cooled nuclear reactor (SCWR), are actively researched internationally. Operating conditions above the critical point of water (374°C, 22.1 MPa) and fuel core temperature that potentially exceed 1850°C put a high demand on the surrounding materials. For their safe application, it is essential to characterize and understand the material properties on an atomic scale such as crystal structure and grain orientation (texture) changes as a function of temperature and stress. This permits the refinement of models predicting the macroscopic behavior of the material. Neutron diffraction is a powerful tool in characterizing such crystallographic properties due to their deep penetration depth into condensed matter. This leads to the ability to study bulk material properties, as opposed to surface effects, and allows for complex sample environments to study e.g. the individual contributions of thermo-mechanical processing steps during manufacturing, operating or accident scenarios. I present three sample environments for in situ neutron diffraction studies that provide such crystallographic information and have been successfully commissioned and integrated into the user program of the High Pressure -- Preferred Orientation (HIPPO) diffractometer at the Los Alamos Neutron Science Center (LANSCE) user facility. I adapted a sample changer for reliable and fast automated texture measurements of multiple specimens. I built a creep furnace combining a 2700 N load frame with a resistive vanadium furnace, capable of temperatures up to 1000°C, and manipulated by a pair of synchronized rotation stages. This combination allows following deformation and temperature dependent texture and strain evolutions in situ. Utilizing the presented sample changer and creep furnace we studied pressure tubes made of Zr-2.5wt%Nb currently employed in CANDURTM nuclear reactors and proposed for future SCWRs, acting as the primary

  5. Study of archaeological iron objects by PGAA, Mössbauer spectroscopy and X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Wagner, F. E.; Gebhard, R.; Häusler, W.; Wagner, U.; Albert, P.; Hess, H.; Révay, Z.; Kudejová, P.; Kleszcz, K.

    2016-12-01

    Archaeological iron objects often corrode rapidly after their excavation, even though they have survived long times of burial in the ground. Chlorine that accumulates during burial is thought to play a major role in this destructive post-excavation corrosion. It is therefore important for the conservation of such objects to determine the chlorine content in a non-destructive manner and, if necessary, to remove the chlorine from the artefacts by appropriate methods. Such methods are leaching in alkaline solutions or heating in a reducing atmosphere at temperatures up to 800 ∘C. We have studied the efficiency of the heating method using prompt gamma activation analysis (PGAA) for monitoring the Cl content and Mössbauer spectroscopy at room temperature (RT) and 4.2 K as well as X-ray diffraction to study the mineralogical transformations of the rust layers. The heat treatments were performed a N2/H2 (90/10) mixture at temperatures up to 750 ∘C. As test specimens sections of iron rods from the Celtic oppidum of Manching (Bavaria) were used. The initial Cl contents of the pieces varied in the range of several hundred ppm, referring to the iron mass. Annealing for 24 h at 350, 550 and 750 ∘C was found to reduce the Cl contents of the specimens, to about 70, 30 and 15 % of the original values, respectively. The rust consists mainly of goethite with admixtures of magnetite, lepidocrocite and akaganeite, which is thought to be a major carrier of chlorine, probably together with iron chlorides. Much of the goethite is so fine-grained that it does not split magnetically at RT. Annealing converts the rust mainly to maghemite at 350 ∘C, to magnetite at 550 ∘C and to wüstite plus magnetite and metallic iron at 750 ∘C. Pure akaganeite behaves in nearly the same manner.

  6. High-pressure single-crystal X-ray diffraction study of jadeite and kosmochlor

    NASA Astrophysics Data System (ADS)

    Posner, Esther S.; Dera, Przemyslaw; Downs, Robert T.; Lazarz, John D.; Irmen, Peyton

    2014-10-01

    The crystal structures of natural jadeite, NaAlSi2O6, and synthetic kosmochlor, NaCrSi2O6, were studied at room temperature, under hydrostatic conditions, up to pressures of 30.4 (1) and 40.2 (1) GPa, respectively, using single-crystal synchrotron X-ray diffraction. Pressure-volume data have been fit to a third-order Birch-Murnaghan equation of state yielding V 0 = 402.5 (4) Å3, K 0 = 136 (3) GPa, and K {0/'} = 3.3 (2) for jadeite and V 0 = 420.0 (3) Å3, K 0 = 123 (2) GPa and K {0/'} = 3.61 (9) for kosmochlor. Both phases exhibit anisotropic compression with unit-strain axial ratios of 1.00:1.95:2.09 for jadeite at 30.4 (1) GPa and 1:00:2.15:2.43 for kosmochlor at 40.2 (1) GPa. Analysis of procrystal electron density distribution shows that the coordination of Na changes from 6 to 8 between 9.28 (Origlieri et al. in Am Mineral 88:1025-1032, 2003) and 18.5 (1) GPa in kosmochlor, which is also marked by a decrease in unit-strain anisotropy. Na in jadeite remains six-coordinated at 21.5 (1) GPa. Structure refinements indicate a change in the compression mechanism of kosmochlor at about 31 GPa in both the kinking of SiO4 tetrahedral chains and rate of tetrahedral compression. Below 31 GPa, the O3-O3-O3 chain extension angle and Si tetrahedral volume in kosmochlor decrease linearly with pressure, whereas above 31 GPa the kinking ceases and the rate of Si tetrahedral compression increases by greater than a factor of two. No evidence of phase transitions was observed over the studied pressure ranges.

  7. Synchrotron diffraction studies of TiC/FeTi cermets obtained by SHS

    SciTech Connect

    Contreras, L.; Turrillas, X.; Mas-Guindal, M.J.; Vaughan, G.B.M.; Kvick, A.; Rodriguez, M.A. . E-mail: mar@icv.csic.es

    2005-05-15

    TiC/FeTi composites have been obtained in situ by Self-propagating High-temperature Synthesis (SHS) of an intimate mixture of compacted powders of elemental carbon, titanium and iron. The reaction has been followed in real time by X-ray diffraction at the ESRF. The mechanism of the reaction is discussed in terms of the formation of a liquid phase corresponding to the eutectic of the Fe/Ti system prior to the TiC synthesis. Temperatures of reaction have been estimated by correlating thermal expansion coefficients with diffraction peaks shifts. The microstructures obtained by this method, suitable for cutting tools and wear resistant applications, are presented.

  8. Two-dimensional time-resolved X-ray diffraction study of liquid/solid fraction and solid particle size in Fe-C binary system with an electrostatic levitator furnace

    NASA Astrophysics Data System (ADS)

    Yonemura, M.; Okada, J.; Watanabe, Y.; Ishikawa, T.; Nanao, S.; Shobu, T.; Toyokawa, H.

    2013-03-01

    Liquid state provides functions such as matter transport or a reaction field and plays an important role in manufacturing processes such as refining, forging or welding. However, experimental procedures are significantly difficult for an observation of solidification process of iron and iron-based alloys in order to identify rapid transformations subjected to fast temperature evolution. Therefore, in order to study the solidification in iron and iron-based alloys, we considered a combination of high energy X-ray diffraction measurements and an electrostatic levitation method (ESL). In order to analyze the liquid/solid fraction, the solidification of melted spherical specimens was measured at a time resolution of 0.1 seconds during rapid cooling using the two-dimensional time-resolved X-ray diffraction. Furthermore, the observation of particle sizes and phase identification was performed on a trial basis using X-ray small angle scattering with X-ray diffraction.

  9. High-precision measurements of the groove spacing of diffraction gratings using the interference diffractometer and study of the quality of diffraction gratings

    SciTech Connect

    Vitushkin, L.F.; Zeilikovich, I.S.; Korotkov, V.I.

    1994-07-01

    An interference-diffractometric method for measuring the groove spacing of diffraction gratings (periodical standards of small length) and a method for examining the quality of diffraction gratings are developed and investigated. They are based on the holographic method of controlling the sensitivity of the interference measurements using the repeat recording of holograms with compensation for the aberrations of the optical system. Measurements of the groove spacing (398 nm) of the holographic grating were performed with an error of 5 nm. 4 refs., 4 figs.

  10. A dynamic x-ray diffraction study of anesthesia action. Thickening of the myelin membrane by n-pentane.

    PubMed

    Padron, R; Mateu, L; Requena, J

    1979-04-19

    The structural changes induced in the myelin sheath by n-pentane nerve impulse blockage were studied by small-angle X-ray diffraction using a linear position-sensitive detector. The results show that the thickness of the myelin period lattice increases from 170 to 180 A during n-pentane treatment.

  11. A High Resolution Microprobe Study of EETA79001 Lithology C

    NASA Technical Reports Server (NTRS)

    Schrader, Christian M.; Cohen, B. A.; Donovan, J. J.; Vicenzi, E. P.

    2010-01-01

    Antarctic meteorite EETA79001 has received substantial attention for possibly containing a component of Martian soil in its impact glass (Lithology C) [1]. The composition of Martian soil can illuminate near-surface processes such as impact gardening [2] and hydrothermal and volcanic activity [3,4]. Impact melts in meteorites represent our most direct samples of Martian regolith. We present the initial findings from a high-resolution electron microprobe study of Lithology C from Martian meteorite EETA79001. As this study develops we aim to extract details of a potential soil composition and to examine Martian surface processes using elemental ratios and correlations.

  12. Spatial and spectral resolution necessary for remotely sensed vegetation studies

    NASA Technical Reports Server (NTRS)

    Rock, B. N.

    1982-01-01

    An outline is presented of the required spatial and spectral resolution needed for accurate vegetation discrimination and mapping studies as well as for determination of state of health (i.e., detection of stress symptoms) of actively growing vegetation. Good success was achieved in vegetation discrimination and mapping of a heterogeneous forest cover in the ridge and valley portion of the Appalachians using multispectral data acquired with a spatial resolution of 15 m (IFOV). A sensor system delivering 10 to 15 m spatial resolution is needed for both vegetation mapping and detection of stress symptoms. Based on the vegetation discrimination and mapping exercises conducted at the Lost River site, accurate products (vegetation maps) are produced using broad-band spectral data ranging from the .500 to 2.500 micron portion of the spectrum. In order of decreasing utility for vegetation discrimination, the four most valuable TM simulator VNIR bands are: 6 (1.55 to 1.75 microns), 3 (0.63 to 0.69 microns), 5 (1.00 to 1.30 microns) and 4 (0.76 to 0.90 microns).

  13. Studies of exotic nuclear reactions at the RESOLUT facility

    NASA Astrophysics Data System (ADS)

    Wiedenhoever, Ingo

    2016-09-01

    The RESOLUT facility at Florida State University's accelerator laboratory produces beams of short-lived nuclei using the in-flight method. Beams such as 6He, 7Be, 8Li, 8B, 17F, 19O, 18Ne and 25Al have been successfully used in experiments. The facility has been used to develop innovative experimental techniques, such as the low-energy neutron detector RESONEUT, and the active-target detector ANASEN, which has been developed as a collaboration between FSU and LSU. These detectors have been employed in direct and indirect reaction measurements with impact on astrophysics. An Indiana-University led campaign studying fusion cross sections of exotic nuclei at RESOLUT has also been successful. The results from these three recent RIB campaigns at RESOLUT will be summarized. This work was supported by NSF under Grants Nos. PHY-1401574, PHY-0820941 and PHY-1126345 and by DOE under Grant Nos. DE-FG02-02ER41220, DE-FG02-88ER-40404 and DE-FG02-96ER40978.

  14. Copper phosphonatoethanesulfonates: temperature dependent in situ energy dispersive X-ray diffraction study and influence of the pH on the crystal structures.

    PubMed

    Feyand, Mark; Hübner, Annika; Rothkirch, André; Wragg, David S; Stock, Norbert

    2012-11-19

    The system Cu(2+)/H2O3P-C2H4-SO3H/NaOH was investigated using in situ energy dispersive X-ray diffraction (EDXRD) to study the formation and temperature induced phase transformation of previously described copper phosphonosulfonates. Thus, the formation of [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·3H2O (4) at 90 °C is shown to proceed via a previously unknown intermediate [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·4H2O (6), which could be structurally characterized from high resolution powder diffraction data. Increase of the reaction temperature to 150 °C led to a rapid phase transformation to [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·H2O (1), which was also studied by in situ EDXRD. The comparison of the structures of 1, 4, and 6 allowed us to establish a possible reaction mechanism. In addition to the in situ crystallization studies, microwave assisted heating for the synthesis of the copper phosphonosulfonates was employed, which allowed the growth of larger crystals of [NaCu(O3P-C2H4-SO3)(H2O)2] (5) suitable for single crystal X-ray diffraction. Through the combination of force field calculations and Rietveld refinement we were able to determine the crystal structure of [Cu1.5(O3P-C2H4-SO3)] 2H2O (3) and thus structurally characterize all compounds known up to now in this well investigated system. With the additional structural data we are now able to describe the influence of the pH on the structure formation.

  15. Molecular structure of gaseous isatin as studied by electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Belyakov, Alexander V.; Nikolaenko, Kirill O.; Davidovich, Pavel B.; Ivanov, Anatolii D.; Garabadzhiu, Alexander V.; Rykov, Anatolii N.; Shishkov, Igor F.

    2017-03-01

    The molecular structure of isatin, indole-2,3-dione, was studied by gas-phase electron diffraction (GED) and quantum chemical calculations (M062X and MP2 methods with aug-cc-pVTZ basis set). The best fit of the experimental scattering intensities (R-factor = 4.4%) was obtained for a molecular model of Cs symmetry. The structure of the benzene ring deviates from a regular hexagon due to the adjacent pyrrole heterocycle. The small differences between similar geometric parameters were constrained at the values calculated at the M062X level. The experimental structural parameters agree well with the results of theoretical calculations. The bonds in the benzene moiety are in agreement with their standard values. The (Odbnd)Csbnd C(dbnd O) carbon-carbon bond of the pyrrole moiety (1.573(7) Å) is remarkably lengthened in comparison with standard C(sp2)sbnd C(sp2) value, 1.425(11) Å for N-methylpyrrole. According to NBO analysis of isatin, glyoxal and pyrrole-2,3-dione molecules this lengthening cannot be attributed to the steric interactions of Cdbnd O bonds alone and is, mainly, due to the electrostatic repulsion and hyperconjugation that is delocalization of oxygen lone pairs of π-type into the corresponding carbon-carbon antibonding orbital, nπ(O) → σ∗(Csbnd C). Deletion of σ∗(Csbnd C) orbital followed by subsequent geometry optimization led to shortening of the corresponding Csbnd C bond by 0.06 Å. According to different aromaticity descriptors, aromaticity of benzene moiety of isatin is smaller in comparison with benzene molecule. External magnetic field induces diatropic ring current in benzene moiety of isatin.

  16. Neutron diffraction study of the beta' and gamma phases of LiFeO{sub 2}

    SciTech Connect

    Barre, Maud; Catti, Michele

    2009-09-15

    The beta, beta', gamma and alpha phases of LiFeO{sub 2}, synthesized as powders, were annealed at different temperatures and characterized by X-ray measurements. The beta' and gamma modifications were also studied by time-of-flight neutron diffraction (ISIS Facility, UK). The structure of the beta' phase was refined in the monoclinic C2/c space group (a=8.566(1), b=11.574(2), c=5.1970(5) A, beta=146.064(5){sup o}) to wR{sub p}=0.071-0.080 (data from four counter banks). Fe and Li atoms are ordered over two of the four independent sites, and partially disordered over the other two. The ordered Li has a distorted tetrahedral coordination. The gamma structure was refined at RT (a=4.047(1), c=8.746(2) A) and at 570 deg. C (a=4.082(3), c=8.822(6) A) in the I4{sub 1}/amd symmetry, showing full order with Li in octahedral coordination at RT, and in a split-atom configuration at high temperature. On annealing, the beta' polymorph was found to transform to gamma at 550 deg. C, thus suggesting that it is a metastable phase. Electrostatics is discussed as the driving force for the alpha->beta'->gamma ordering process of LiFeO{sub 2}. - Graphical abstract: Crystal structure of beta'-LiFeO{sub 2} (monoclinic C2/c). Lithium and iron atoms are both ordered (blue and yellow balls) and partially disordered (green balls) over four independent sites. The beta' phase transforms to fully ordered gamma (tetragonal I4{sub 1}/amd) at 550 deg. C.

  17. Synchrotron X-ray Powder Diffraction Studies in Pulsed Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Detlefs, C.; Frings, P.; Vanacken, J.; Duc, F.; Lorenzo, J. E.; Nardone, M.; Billette, J.; Zitouni, A.; Bras, W.; Rikken, G. L. J. A.

    2007-01-01

    X-ray powder diffraction experiments under pulsed magnetic fields were carried out at the DUBBLE beamline (BM26B) at the ESRF. A mobile generator delivered 110kJ to the magnet coil, which was sufficient to generate peak fields of 30T. A liquid He flow cryostat allowed us to vary the sample temperature accurately between 8K and 300K.

  18. Optical diffraction studies of crystalline structures in electron micrographs. I. Theoretical considerations.

    PubMed

    Berger, J E

    1969-12-01

    Determination of the unit cell of crystalline particles by optical diffraction analysis of electron micrographs may establish the identity and help in approximating the molecular weight of the substances contained in the crystal. This technique may be particularly helpful when isolation and purification of the crystalline material cannot be accomplished.

  19. Synchrotron X-Ray Diffraction Studies of Olivine from Comet Wild 2

    NASA Technical Reports Server (NTRS)

    2008-01-01

    We have analyzed a collection of the Comet Wild 2 coma grains returned by the NASA Stardust Mission, using micro-area Laue diffraction equipment. The purpose of the diffraction experiment is to permit the structure refinement of olivine including site occupancies. In addition to the intrinsic importance of the olivine structures for revealing the thermal history of Wild 2 materials, we wish to test reports that olivine recovered after hypervelocity capture in silica aerogel has undergone a basic structural change due to capture heating [1]. The diffraction equipment placed at beam line BL- 4B1 of PF, KEK was developed with a micropinhole and an imaging plate (Fuji Co. Ltd.) using the Laue method combined with polychromatic X-ray of synchrotron radiation operated at energy of 2.5 GeV. The incident beam is limited to 1.6 m in diameter by a micropinhole set just upstream of the sample [2, 3]. It is essential to apply a microbeam to obtain diffracted intensities with high signal to noise ratios. This equipment has been successfully applied to various extraterrestrial materials, including meteorites and interplanetary dust particles [4]. The Laue pattern of the sample C2067,1,111,4 (Fig. 1) was successfully taken on an imaging plate after a 120 minute exposure (Fig. 2).

  20. Formation of optical fields of stimulated Raman scattering with a resolution beyond the Abbe diffraction limit by spherical microlens cavities with whispering gallery modes: Near-field approximation

    NASA Astrophysics Data System (ADS)

    Jouravlev, M. V.

    2012-04-01

    We consider a significant lowering of the threshold of stimulated Raman scattering in solid fused silica spherical microlenses cavities that is caused by an increase in the integral overlap factor of whispering gallery modes. The structure of focal regions of a microlens is shown to have the shape of honeycombs, forming a photonic crystal or a photonic nanojet. We show that, at comparatively small numerical apertures NA = 0.7-0.8, which correspond to hemispherical microlenses, a spherical microlens cavity exhibits the possibility of focusing laser radiation beyond the Abbe diffraction limit. This enables the possibility of wide practical applications of microspheres as a focusing element the resolving power of which exceeds the Abbe diffraction limit in the near field. The whispering-gallery-mode spherical microlens cavity makes it possible to perform laser generation with a duration of a coherent pulse in the subfemtosecond range and to form a subwavelength focal region of the near field. This ensures the possibility of detecting single molecules of a substance in the subwavelength range in the near field and can be used to increase the sensitivity of intracavity spectroscopy methods and as microlasers for excitation of molecules in metal molecular nanoswitches and semiconductor heterostructures. From an array of microlens cavities, metamaterials with a negative refractive index can be formed.

  1. Crystallization and preliminary X-ray diffraction studies of an RNA aptamer in complex with the human IgG Fc fragment

    PubMed Central

    Sugiyama, Shigeru; Nomura, Yusuke; Sakamoto, Taiichi; Kitatani, Tomoya; Kobayashi, Asako; Miyakawa, Shin; Takahashi, Yoshinori; Adachi, Hiroaki; Takano, Kazufumi; Murakami, Satoshi; Inoue, Tsuyoshi; Mori, Yusuke; Nakamura, Yoshikazu; Matsumura, Hiroyoshi

    2008-01-01

    Aptamers, which are folded DNA or RNA molecules, bind to target molecules with high affinity and specificity. An RNA aptamer specific for the Fc fragment of human immunoglobulin G (IgG) has recently been identified and it has been demonstrated that an optimized 24-nucleotide RNA aptamer binds to the Fc fragment of human IgG and not to other species. In order to clarify the structural basis of the high specificity of the RNA aptamer, it was crystallized in complex with the Fc fragment of human IgG1. Preliminary X-ray diffraction studies revealed that the crystals belonged to the orthorhombic space group P21212, with unit-cell parameters a = 83.7, b = 107.2, c = 79.0 Å. A data set has been collected to 2.2 Å resolution. PMID:18931441

  2. Electron diffraction study of La{sub 2}Li{sub O.5}Cu{sub O.5}O{sub 4}

    SciTech Connect

    Moshopoulou, E.; Thompson, J.D.; Sarrao, J.L.; Fisk, Z. |

    1998-03-01

    La{sub 2}Li{sub 0.5}Cu{sub 0.5}O{sub 4} has been investigated by electron diffraction and high resolution electron microscopy at room temperature. Ordering between Li and Cu cations is fairly perfect within the ({anti a}, {anti c}) plane but there is disorder between Cu and Li cations along the {anti b} axis. The detection of weak reflections which violate the C centering of the Cmmm space group (initially proposed for this compound), indicates that the crystal symmetry allows lattice distortions. The evolution of the structure as a function of the temperature may lead to determine whether the low energy singlet-triplet excitation, found in NMR/NQR studies, is coupled with lattice distortions.

  3. A study of monochromatic x-ray area beam for application in diffraction enhanced imaging

    NASA Astrophysics Data System (ADS)

    Kim, Chang Hyeuk

    Synchrotron-based Diffraction Enhanced Imaging (DEI) system has shown improved contrast images on low attenuation material. In a previous DEI study great potential to detect earlier stage breast cancer was reported. However, to apply DEI technique at the clinical level, a synchrotron source is not feasible for clinically-approved systems due to the size of the accelerator, and hence a compact x-ray source that can replace synchrotron is desirable. Development of an x-ray source compatible to synchrotron radiation is an essential part for a clinical DEI system. Some important features for the design of an x-ray source, based on synchrotron radiation, are the photon flux and beam collimation. The NCSU research group suggested a wide-beam x-ray source, which consists of concentric circular filaments producing electron flux onto a cylindrically-shaped oxygen-free copper stationary target with a thin layer of Molybdenum for x-ray production. This source design emphasizes large field of view, which can eliminate the line by line scanning process experienced in a DEI experimental setup. In this study, the proof of principle model of a wide beam x-ray source was used to study for control electron trajectory of the concentric filaments design, calculations of the produced x-ray flux, simulation of the DEI imaging, and estimation of the operation time with target's active cooling system. The DEI images from the electron distribution were computationally generated by adopting a monochromator and an analyzer with a computationally generated dual cylindrical object. The image simulation showed that the wide-beam x-ray source based DEI images are highly dependent on the electron distribution at the target. Uniform electron distribution by electron trajectory optimization is carried out through independent powering of the filaments inside the focusing cup. For higher electron beam current the x-ray flux satisfies obtaining a successful DEI image scan, but such high current

  4. High resolution electron microscopy study of amorphous calcium phosphate

    NASA Astrophysics Data System (ADS)

    Brès, E. F.; Moebus, G.; Kleebe, H.-J.; Pourroy, G.; Werkmann, J.; Ehret, G.

    1993-03-01

    "Amorphous" calcium phosphate (ACP) from human tooth enamel and different synthetic materials has been analysed by high resolution electron microscopy (HREM). All the materials studied showed, in addition to a "truly" amorphous phase, other calcium phosphate phases such as poorly crystalline hydroxyapatite (OHAP), well crystallized OHAP and poorly crystalline CaO type phase. Such structural heterogeneities have not been observed before in ACP, and are only possible to be detected by HREM as this is the only technique able to analyse nanometre size materials in the real space.

  5. Study of radar pulse compression for high resolution satellite altimetry

    NASA Technical Reports Server (NTRS)

    Dooley, R. P.; Nathanson, F. E.; Brooks, L. W.

    1974-01-01

    Pulse compression techniques are studied which are applicable to a satellite altimeter having a topographic resolution of + 10 cm. A systematic design procedure is used to determine the system parameters. The performance of an optimum, maximum likelihood processor is analysed, which provides the basis for modifying the standard split-gate tracker to achieve improved performance. Bandwidth considerations lead to the recommendation of a full deramp STRETCH pulse compression technique followed by an analog filter bank to separate range returns. The implementation of the recommended technique is examined.

  6. High resolution study of magnetic ordering at absolute zero.

    PubMed

    Lee, M; Husmann, A; Rosenbaum, T F; Aeppli, G

    2004-05-07

    High resolution pressure measurements in the zero-temperature limit provide a unique opportunity to study the behavior of strongly interacting, itinerant electrons with coupled spin and charge degrees of freedom. Approaching the precision that has become the hallmark of experiments on classical critical phenomena, we characterize the quantum critical behavior of the model, elemental antiferromagnet chromium, lightly doped with vanadium. We resolve the sharp doubling of the Hall coefficient at the quantum critical point and trace the dominating effects of quantum fluctuations up to surprisingly high temperatures.

  7. Phononic crystal diffraction gratings

    NASA Astrophysics Data System (ADS)

    Moiseyenko, Rayisa P.; Herbison, Sarah; Declercq, Nico F.; Laude, Vincent

    2012-02-01

    When a phononic crystal is interrogated by an external source of acoustic waves, there is necessarily a phenomenon of diffraction occurring on the external enclosing surfaces. Indeed, these external surfaces are periodic and the resulting acoustic diffraction grating has a periodicity that depends on the orientation of the phononic crystal. This work presents a combined experimental and theoretical study on the diffraction of bulk ultrasonic waves on the external surfaces of a 2D phononic crystal that consists of a triangular lattice of steel rods in a water matrix. The results of transmission experiments are compared with theoretical band structures obtained with the finite-element method. Angular spectrograms (showing frequency as a function of angle) determined from diffraction experiments are then compared with finite-element simulations of diffraction occurring on the surfaces of the crystal. The experimental results show that the diffraction that occurs on its external surfaces is highly frequency-dependent and has a definite relation with the Bloch modes of the phononic crystal. In particular, a strong influence of the presence of bandgaps and deaf bands on the diffraction efficiency is found. This observation opens perspectives for the design of efficient phononic crystal diffraction gratings.

  8. High-pressure behavior and thermoelastic properties of niobium studied by in situ x-ray diffraction

    SciTech Connect

    Zou, Yongtao E-mail: yongtaozou6@gmail.com; Li, Baosheng; Qi, Xintong; Wang, Xuebing; Chen, Ting; Li, Xuefei; Welch, David

    2014-07-07

    In situ synchrotron energy dispersive x-ray diffraction (XRD) experiments on Nb have been conducted at pressures up to 6.4 GPa and temperatures up to 1073 K. From the pressure-volume-temperature measurements, thermoelastic parameters were derived for the first time for Nb based on the thermal pressure (ΔP{sub th}) equation of state (EOS), modified high-T Birch-Murnaghan EOS, and Mie-Grüneisen-Debye EOS. With the pressure derivative of the bulk modulus K{sub T}{sup ´} fixed at 4.0, we obtained the ambient isothermal bulk modulus K{sub T0}=174(5) GPa, the temperature derivative of bulk modulus at constant pressure (∂K{sub T}/∂T){sub P}=-0.060(8) GPa K⁻¹ and at constant volume (∂K{sub T}/∂T){sub V}=-0.046(8) GPa K⁻¹, the volumetric thermal expansivity α{sub T}(T)=2.3(3)×10⁻⁵+0.3(2)×10⁻⁸T (K⁻¹), as well as the pressure dependence of thermal expansion (∂α/∂P){sub T}=(₋2.0±0.4)×10⁻⁶ K⁻¹ GPa⁻¹. Fitting the present data to the Mie-Grüneisen-Debye EOS with Debye temperature Θ₀=276.6 K gives γ₀=1.27(8) and K{sub T0}=171(3) GPa at a fixed value of q=3.0. The ambient isothermal bulk modulus and Grüneisen parameter derived from this work are comparable to previously reported values from both experimental and theoretical studies. An in situ high-resolution, angle dispersive XRD study on Nb did not indicate any anomalous behavior related to pressure-induced electronic topological transitions at ~5 GPa as has been reported previously.

  9. Diffraction encoded position measuring apparatus

    DOEpatents

    Tansey, Richard J.

    1991-01-01

    When a lightwave passes through a transmission grating, diffracted beams appear at the output or opposite side of the grating that are effectively Doppler shifted in frequency (phase) whereby a detector system can compare the phase of the zero order and higher order beams to obtain an indication of position. Multiple passes through the grating increase resolution for a given wavelength of a laser signal. The resolution can be improved further by using a smaller wavelength laser to generate the grating itself. Since the grating must only have a pitch sufficient to produce diffracted orders, inexpensive, ultraviolet wavelength lasers can be utilized and still obtain high resolution detection.

  10. Diffraction encoded position measuring apparatus

    DOEpatents

    Tansey, R.J.

    1991-09-24

    When a lightwave passes through a transmission grating, diffracted beams appear at the output or opposite side of the grating that are effectively Doppler shifted in frequency (phase) whereby a detector system can compare the phase of the zero order and higher order beams to obtain an indication of position. Multiple passes through the grating increase resolution for a given wavelength of a laser signal. The resolution can be improved further by using a smaller wavelength laser to generate the grating itself. Since the grating must only have a pitch sufficient to produce diffracted orders, inexpensive, ultraviolet wavelength lasers can be utilized and still obtain high resolution detection. 3 figures.

  11. Neutron and X-ray Microbeam Diffraction Studies around a Fatigue-Crack Tip after Overload

    SciTech Connect

    Lee, Sooyeol; Barabash, Rozaliya; Chung, Jin-Seok; Liaw, Peter K; Choo, Hahn; Sun, Yinan; Fan, C; Li, Li; Brown, Donald; Ice, Gene E

    2008-01-01

    An in-situ neutron diffraction technique was used to investigate the lattice-strain distributions and plastic deformation around a crack tip after overload. The lattice-strain profiles around a crack tip were measured as a function of the applied load during the tensile loading cycles after overload. Dislocation densities calculated from the diffraction peak broadening were presented as a function of the distance from the crack tip. Furthermore, the crystallographic orientation variations were examined near a crack tip using polychromatic X-ray microdiffraction combined with differential aperture microscopy. Crystallographic tilts are considerably observed beneath the surface around a crack tip, and these are consistent with the high dislocation densities near the crack tip measured by neutron peak broadening.

  12. X-ray diffraction study of thermotropic liquid crystalline polyesters and diester model compounds

    NASA Astrophysics Data System (ADS)

    Chin, H. H.; Azaroff, L. V.; Griffin, A. C.

    1987-10-01

    Two nematic liquid crystalline polyesters were examined by X-ray diffraction following quenching from the nematic temperature in a magnetic field of 15 tesla. It was not possible to quench an aligned nematic glass; instead a polycrystalline phase showing some preferred orientation or an unoriented nematic melt yielded monodomain nematic diffraction patterns with one resembling that of a fiber (crystalline) photograph while the other showed good nematic alignment which could be enhanced slightly by annealing. A series of Siamese-twin diester model compounds also examined at their respective nematic temperatures in a magnetic field of compounds also were examined at their crystalline phase at room temperature. All displayed well-aligned nematic monodomains above the crystallization point.

  13. A numerical study of shock wave diffraction by a circular cylinder

    NASA Technical Reports Server (NTRS)

    Yang, J.-Y.; Liu, Y.; Lomax, H.

    1986-01-01

    The nonstationary shock wave diffraction patterns generated by a blast wave impinging on a circular cylinder are numerically simulated using a second-order hybrid upwind method for solving the two-dimensional inviscid compressible Euler equations of gasdynamics. The complete diffraction patterns, including the transition from regular to Mach reflection, trajectory of the Mach triple point and the complex shock-on-shock interaction at the wake region resulting from the Mach shocks collision behind the cylinder are reported in detail. Pressure-time history and various contour plots are also included. Comparison between the work of Bryson and Gross (1961) which included both experimental schlieren pictures and theoretical calculations using Whitham's ray-shock theory and results of the present finite difference computation indicate good agreement in every aspect except for some nonideal gas and viscous effects which are not accounted for by the Euler equations.

  14. Epitaxy of Fe/Cu/Si(1 1 1) ultrathin films: an Auger electron diffraction study

    NASA Astrophysics Data System (ADS)

    Castrucci, P.; Gunnella, R.; Bernardini, R.; Montecchiari, A.; Carboni, R.; De Crescenzi, M.

    2001-06-01

    Epitaxial Fe films, with thickness in the range between 1 and 50 ML (monolayer, ML), were grown in ultrahigh vacuum conditions on the 7×7 reconstructed (1 1 1)-Si surface. The films were evaporated on a Cu thick buffer layer to avoid iron silicides formation. Auger electron diffraction (AED) technique has been used to investigate the growth of the pseudomorphic film of fcc γ-Fe(1 1 1) and the successive growth of bcc Fe(1 1 0) domains in the Kurdjumov-Sachs orientation. The early stages of growth have been carefully investigated through AED to assess the pseudomorphism of iron γ-phase. AED patterns clearly show the presence of diffraction features that are fingerprints of the existence of a few bcc arranged atomic structures even for 1 ML iron coverage.

  15. Diffraction and coherence in breast ultrasound tomography: a study with a toroidal array

    SciTech Connect

    Huang, Lianjie; Simonetti, Francesco; Duric, Neb; Littrup, Peter

    2008-01-01

    Ultrasound is commonly used as an adjunct to mammography for diagnostic evaluation of suspicions arising from breast cancer screening. As an alternative to conventional sonography that uses hand-held transducers, toroidal array probes that encircle the breast immersed in a water bath have been investigated for ultrasound tomography. In this paper, two sets of experiments performed with a prototype ultrasound scanner on a phantom and a human breast in vivo are used to investigate the effects of diffraction and coherence in ultrasound tomography. Reconstructions obtained with transmission diffraction tomography (TDT) are compared with conventional reflection imaging and computerized ultrasound tomography showing a substantial improvement. The in vivo tests demonstrate that TDT can image the complex boundary of a cancer mass and suggest that it can reveal the anatomy of milk ducts and Cooper's ligaments.

  16. Circularly polarized soft x-ray diffraction study of helical magnetism in hexaferrite

    NASA Astrophysics Data System (ADS)

    Mulders, A. M.; Lawrence, S. M.; Princep, A. J.; Staub, U.; Bodenthin, Y.; García-Fernández, M.; Garganourakis, M.; Hester, J.; Macquart, R.; Ling, C. D.

    2010-03-01

    Magnetic spiral structures can exhibit ferroelectric moments as recently demonstrated in various multiferroic materials. In such cases the helicity of the magnetic spiral is directly correlated with the direction of the ferroelectric moment and measurement of the helicity of magnetic structures is of current interest. Soft x-ray resonant diffraction is particularly advantageous because it combines element selectivity with a large magnetic cross-section. We calculate the polarization dependence of the resonant magnetic x-ray cross-section (electric dipole transition) for the basal plane magnetic spiral in hexaferrite Ba0.8Sr1.2Zn2Fe12O22 and deduce its domain population using circular polarized incident radiation. We demonstrate there is a direct correlation between the diffracted radiation and the helicity of the magnetic spiral.

  17. X-ray diffraction and Raman studies on Ho: Eu2O3

    NASA Astrophysics Data System (ADS)

    Irshad, K. A.; Chandra Shekar, N. V.; Ravindran, T. R.; Srihari, V.; Pandey, K. K.

    2017-01-01

    In this paper the structural parameters of mixed rare earth sesquioxides (Eu1-xHox)2O3 (0 ≤ x ≤ 1) is reported for the first time. The oxide samples are characterized by angle dispersive X-ray diffraction (ADXRD) and Raman scattering techniques. ADXRD measurements confirmed the formation of single phase in the cubic bixbyite structure with space group Ia-3. Complete miscibility of the two components is confirmed by the Vegard's law. A random distribution of the two cations in the two rare earth (RE) ion sites is observed. Symmetry modes are assigned for the observed 13 out of 22 expected Raman bands and the dependency of average cationic radii, RRE, is discussed. A low frequency band shows an anomalous mode softening with decrease in Eu content. This mode disappears above x = 0.8, which coincides with a distinct slope change observed in the RE(24d) positional coordinate estimated from refined x-ray diffraction data.

  18. X-ray diffraction study of nanocrystalline and amorphous structure within major and minor ampullate dragline spider silks

    SciTech Connect

    Sampath, Sujatha; Isdebski, Thomas; Jenkins, Janelle E.; Ayon, Joel V.; Henning, Robert W.; Orgel, Joseph P.R.O.; Antipoa, Olga; Yarger, Jeffery L.

    2012-07-25

    Synchrotron X-ray micro-diffraction experiments were carried out on Nephila clavipes (NC) and Argiope aurantia (AA) major (MA) and minor ampullate (MiA) fibers that make up dragline spider silk. The diffraction patterns show a semi-crystalline structure with {beta}-poly(L-alanine) nanocrystallites embedded in a partially oriented amorphous matrix. A superlattice reflection 'S' diffraction ring is observed, which corresponds to a crystalline component larger in size and is poorly oriented, when compared to the {beta}-poly(L-alanine) nanocrystallites that are commonly observed in dragline spider silks. Crystallite size, crystallinity and orientation about the fiber axis have been determined from the wide-angle X-ray diffraction (WAXD) patterns. In both NC and AA, the MiA silks are found to be more highly crystalline, when compared with the corresponding MA silks. Detailed analysis on the amorphous matrix shows considerable differences in the degree of order of the oriented amorphous component between the different silks studied and may play a crucial role in determining the mechanical properties of the silks.

  19. High-precision neutron spectrometry, using diffraction focusing. Test experiment

    NASA Astrophysics Data System (ADS)

    Kuznetsov, I. A.; Berdnikov, Ya. A.; Berdnikov, A. Ya.; Borisov, Yu. V.; Braginetz, Yu. P.; Fedorov, V. V.; Lasitsa, M. V.; Semenikhin, S. Yu.; Khorina, M. L.; Voronin, V. V.

    2016-09-01

    The effect of double-crystal neutron focusing, using Laue diffraction in large perfect crystals was studied. The observed effect allows reach the angular resolution better than 0.03", that is ~ 10-2 of the Bragg reflection width. This fact makes it possible to create a new ultraprecise method for neutron spectrometry combining the spin-echo small angle neutron scattering with Laue diffraction.

  20. X-ray diffraction study of gold nitride films: Observation of a solid solution phase

    NASA Astrophysics Data System (ADS)

    Alves, L.; Hase, T. P. A.; Hunt, M. R. C.; Brieva, A. C.; Šiller, L.

    2008-12-01

    The structure of nitride containing gold films produced by reactive ion sputtering and nitrogen plasma etching is investigated using x-ray photoelectron spectroscopy and x-ray diffraction. It is found that gold nitride is a solid solution of nitrogen atoms dissolved in a fcc gold matrix. Differences between the strain and lattice parameters of gold and gold nitride films were observed and are explained by interstitial nitrogen present in the latter.